Epas 11 4th Quarter Las 2921

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 1 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 1 Layout Planning and design Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________  I.   Learning Competency:   Acquir Acquire e manuals and service service information TLE_IAEPAS9-

12SCEP-AVPIVf-g-57 II. Key Conce Concept pt READING DRAWING AND BLOCK DIAGRAM Block Diagram

All All elec electr tron onic ic eq equi uipm pmen entt can can be co cons nsid ider ered ed as sy syst stem emss co comp mpri risi sing ng a se sett of  interacting elements responding to inputs to produce outputs. It is quite possible that a system may be too complex to be analyzed in detail. It is therefore, necessary to divide div ide it into sub-syst sub-systems ems and then then integ integrate rate them. them. Each Each sub-sy sub-system stem would would then then represent a functional block, and the combination of all the blocks would constitute the functional ‘Block Diagram’ of the equipment. A block is only a ‘black box’ with cert certai ain n in inp puts uts and and outpu utputs ts,, but per erfo form rmin ing g a def efin init itee fu fun nct ctio ion n. Th Thee lin lines interconnecting these blocks indicate the signal flow from block to block or circuit to circuit.

 

Schematic  Diagram A schematic diagram is a graphical representation of interconnections of various elect ele ctron ronic, ic, elec electri trical cal an and d elec electro trome mecha chani nica call co comp mpon onen ents ts of an eq equi uipm pmen ent. t. The The schem sch emati aticc is the the fi firs rstt step step in an elec electro troni nicc circ circui uitt de desig sign n be becau cause se it di disp spla lays ys an and d id iden entif tifie iess th thee co comp mpon onen ents ts th that at make make up th thee eq equi uipm pmen ent. t. Furth Further er,, th thee firs firstt step step in designing a printed circuit is to convert the schematic diagram in to an art master. Therefore, for any printed circuit designer, it is important to learn to read and interpret the schematic diagram. However, the schematic diagram does not show any of the mechanical details of the printed circuit board,

The schematic provides the most broadly used view of the design and includes all components: 1. It gives visibility visibility into the status status of all parts parts of the design process; process; 2. Sche Schema matic ticss ar aree th thee pr prim imar ary y sour source ce fo forr de deve velo lopi ping ng de deliv liver erab ables les to pr prod oduc uctt design and manufacturing groups; 3. Design varian variants ts are built around around slightly slightly differing differing schemati schematics; cs; 4. Test departments departments rely on schemat schematics; ics; 5. Field Field service service relies on schema schematics tics;; and Bills-o Bills-of-m f-mate aterial rialss are generate generated d from from schematics. In short, a schematic is the focal point for a product’s electronic data and can be viewed as a set of crucial business documents that capture the decisions affecting all aspects of the product. In a schematic diagram, the symbol represents either what the component does in th thee circ circui uitt or ho how w it is ph phys ysica ically lly co cons nstr truc ucte ted. d. For For examp example le,, a ca capa pacit citor or ca can n be

 

charged to store electricity similar to a battery. A picture of two parallel plates of  equal length and separated by a given space has thus been adopted as the symbol of  capacitor. In most cases, electronic symbols have been evolved logically from their  circuit application, their construction, or from a combination of both. All electronic components have been designated when represented on a schematic diagra dia gram. m. The common common classifi classificati cation on from ANSI ANSI (Ameri (American can Nation National al Standa Standards rds In Inst stit itut ute) e),, IE IEEE EE (I (Ins nsti titu tute te of Elec Electr tric ical al an and d Elec Electr tron onic ic Engi Engine neer ers) s) an and d IE IEC C (International Electrotechnical Commission). A typical schematic diagram and demonstrates its basic parts. Each component is repr repres esen ente ted d as a symb symbol ol in the the diag diagra ram m alon along g with with it itss re refe fere renc ncee de desi sign gnat atio ion. n. Electronic components shown on the circuit diagram are generally in the following units unless mentioned otherwise: Capacitors Capaci tors = Values Values one or greater are in the picofarads picofarads (pF) = Values less than one are in microfarads (mF) Resistors = Ohms ( W)

General PCB Designed Designed The basic function of a printed circuit is to provide support for circuit components and to interconnect the components electrically. In order to achieve these objectives, va vari riou ouss prin printed ted wiring wiring ty type pess ha have ve be been en de deve velo lope ped. d. They They va vary ry in ba base se mate materia riall (laminate), conductor type, number of conductor planes, rigidity, etc. It is therefore expected that the printed circuit designers are adequately familiar with the variations and their effect on cost, component placement, wiring density, delivery cycles and functional performance. No finished product is ever better than its original design or  the material from which it is made. The manufacturing process, at best, can reproduce the design. The same is true with printed circuit boards. The need for formalizing design and layout methods and procedures thus assumes critical importance. Design and layout broadly includes includes the perspective perspective of total system hardware, hardware, which includes not only the printed circuit but each and every component in its final form. Desig De sign n an and d layou layoutt co cons nsid ider erati ation onss must must also also ad addr dress ess th thee re rela latio tions ns be betw twee een n an and d interactions of the components and assemblies throughout the system. Board design is an extrem extremely ely import important ant aspect aspect of printe printed d circuit circuit board board techno technolog logy. y. Quite Quite often, often, designers underestimate the time and effort required to do a good job. This can cause delay in production start-up and much hidden cost during the life of the product (Ross and Leonida, 1996d). The technical requirements that are likely to affect the design of  electrical equipment are mechanical, electrical, functional and environmental.  Mechanical   

design desi gn requ requir irem emen ents ts incl includ udee si size ze,, sh shap apee an and d weig weight ht;; lo loca cati tion on of 

component compon entss and their their mounti mounting ng,, dimens dimension ional al toleran tolerances, ces, shield shielding ing and equipm equipment ent marking.

 

 Electrical   design

requirements have such parameters as circuit function and wiring distribution, component selection with respect to electrical ratings, size and tolerance, internal and external interconnections. design Functional   design

parameters parameters include include reliability, reliability, maintainabili maintainability, ty, accessibility accessibility,, and human engineering (displays, controls).  Environmental 

  desig de sign takes takremes, es es, into intosalt ac accou count fa ctors rs su ch as ofing mech me chan anica ical l shoc sh ock k san and d vibration vibrat ion,, temper temperatur ature en extrem ext spray sprnt ay facto and fungu funsuch gus s proofi pro ng and operat ope ration ions in space or underwater. All the above above factors are not necessarily necessarily inherent in printed printed circuit boards, but by careful design, proper selection of materials and manufacturing techniques, it is  possible to t o optimize most of the t he above parameters. The following factors fact ors should s hould be taken into consideration while designing printed circuit boards including multi-layer   boards. Many factors influence the design of PCBs.

Importantt Design Elements Importan The design inputs which should be provided by the equipment designer to the PCB designer are called design elements. They are: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Type of circuit circuit (analog (analog or or digital, digital, etc.); Boar Board d size size Number Number of layers layers Pad stack stack sizes sizes Hole Hole siz sizes es Layer Layer thickn thickness ess Board Board thickn thickness ess External External connections connections Mounti Mounting ng holes holes

Conductor Shape While deciding the layout, sharp covers and acute angle bends in conductors should  be avoided as far as possible. The rounded contours will not only minimize conductor  crack crackin ing, g, foil foil lifti lifting ng an and d elec electri trica call br brea eakd kdow own, n, bu butt also also gr great eatly ly fa facil cilita itate te sold solder  er  distr distrib ibut utio ion. n. The The pr proc ocess ess may may be more more ex expe pens nsiv ivee from from th thee dr draf afti ting ng stand standpo poin int. t. Rounded corners at conductor bends and smooth fillets at the junction of conductors and terminal areas are desirable.

 

Conductor Shape

Layout Sketch Designed Designed The printed circuit layout sketch is the end-product of the layout design depicting components and the interconnecting conductors. It provides all information for the  preparation of the final artwork. Besides this, the layout sketch also includes inform inf ormatio ation n on compon component ent holes, holes, conduc conductor tor width, width, minimu minimum m spacin spacing g betwee between n the conductors, etc. Before the designer Before designer starts working working on the layout for the design of a printed printed circuit  board, it is advisable to prepare a trial layout drawing keeping the following factors in mind: 1. 2. 3.

4. 5.

Board size — dictated dictated by by equipmen equipmentt enclosure enclosure or the the modular modular design design concepts; Component Component outline outliness — available available from data data books; books; Component Component mounting mounting data — in case of special special mountings mountings,, data data books books may may have to be consulted, consulted, thermal limitation limitation may require require heat sinking or large size de-coupling capacitors; Interconnecti Interconnecting ng patterns; patterns; Conductor Conductor width width and spacing, spacing, depending depending upon the functional functional requirement requirement of  the conductor;

Components Placement Rule Following are the rules for component placement: 1. In a highly highly sensitive sensitive circuit, circuit, the critical critical components components are placed placed first and in such a manner manner as to require minimum length length for the critical conductors. conductors. 2. In a less critical critical circuit, the the components components are arranged arranged exactly exactly in the order order of  signal flow. This will result in a minimum minimum overall conductor conductor length. length. 3. In a circuit circuit where a few components components have have considerabl considerably y more connecting connecting  points than the others, these key components have to be placed first and the remaining ones are grouped around them. 4. The general general rule is to place place first componen components, ts, whose positio position n is fixed for the the final fitting and interconnections, e.g. connectors, heat sinks, etc. Then place the components which are connected to these fixed components.

 

5. Components Components should should be placed placed on the grid grid of 2.5 2.5 mm. 6. Among Among the componen components, ts, larger compon components ents are placed placed first and the the space in  between is filled with smaller small er ones. 7. All the componen components ts should be be placed in such such a manner manner that disordering disordering of  of  other components components is not necessary if they have to be replaced. replaced. 8. Components Components should should be placed placed in a row or a column, column, so that that it gives a good good overview. PCB Design Rules III. Guided Guided practice practice Self-Test Activity 1

Direction: Enumerate at least least 5 important design elements. elements. 1. 2. 3. 4. 5.

________________ ____________________ ____ ________________ ____________________ ____ ________________ ____________________ ____ ________________ ____________________ ____ ________________ ____________________ ____

IV. Independent Independent practice practice

Activity No. 2 Title: Conductor Shape Direction: Draw the conductor shape inside the box. Rubric Neatness 8

Not Acceptable

Clarity 7

Total 15

Acceptable

 

V.

Asse Assess ssme ment nt

Direction: Give at least 5 components placement rule. 1. _______________ _______________ 2. _______________ _______________ 3. _______________ _______________ 4. _______________ _______________ 5. _______________ _______________

VI. Answer Answer key

Activity 1

1. Type of circu circuit it (analog or digital, digital, etc.); etc.); 2. Board size 3. Number of layers 4. Pad stack sizes 5. Hole sizes 6. Layer thickness 7. Board thickness 8. External connections 9. Mounting holes VII. Reference

Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM

Writer: Benjunly Benjunly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  [email protected] eped.gov.ph Contact information:  information:   benjunly.gengone@d

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 2 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 2 Artwork Generation Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________  I. Learning Competency: Competency:   Verif Verify y PCB layout layout for conformity with the schematic diagram diagram in accordance with the layout rules. Code:  TLE_IAEPAS9- 12AEP-IVb-c-28

II. Key Concept

Artwork Generation Basic Approach to Manual Artwork 

Artwork Artwor k generat generation ion for single-s single-sided ided boards boards is a straigh straightfo tforwa rward rd exercis exercise, e, whereas whereas  preparing artwork for double-sided printed circuit boards, leads to a problem in securing accurate registration between the two sides. Correct and accura Correct accurate te registr registratio ation n is of great great import importanc ancee in multi-l multi-lay ayer er bo board ardss also where shorting between layers may occur because of improper alignment when the  board assembly is drilled for plated-through holes. Ink Drawing on White Card Board Sheet

This is the simplest and earliest method used for PCB artwork design. The materials required are a white cardboard paper, good quality Indian ink and an ink pen. A paper  with blue lines grid is usually preferred as these lines do not get reproduced in the  photographic process for film master production. Suitable polyester foil, which is dimensionally more stable than cardboard paper, can also be used for drawing the ink   pattern. However, the one side of the foil should have a rough or mat surface so that ink will stick to it. In this technique, circumferences of the solder pads and the center holes are drawn with a drawing compass and the spaces in between are filled with ink. Conductors are drawn with an ink pen either by directly providing the desired width or as double lines, which are thereafter filled with ink.

 

Black Taping on Transparent Base Foil

Manual artwork Manual artwork generat generation ion has become become very very conven convenien ientt since since the advent advent of selfselfadhesive or transfer type pads and precision tapes, and no longer relies on the high drawing skills and patience of the draftsman.

Self-Adhesive Tapes They are available in a wide range of widths, which can be selected depending upon the application. They are supplied in rolls with standard widths of 0.5 mm, 1 mm, 2 mm, 4 mm and 8 mm; etc.

Transfer Pads They Th ey are are prin printe ted d on a th thin in ad adhe hesiv sivee fil film m of ty typic picall ally y 10 mm th thic ickn knes ess, s, which which is mounted on the top side against a transparent carrier strip. The pad can be transferred from the carrier strip onto the artwork base (polyester base sheet) by just rubbing with a wooden stick end or pencil. The carrier strip can then be lifted from the artwork   base leaving behind the pad.

 

Type of Pads

Polyesterr Films Polyeste They are They are us usua ually lly empl employ oyed ed as th thee ar artw twor ork k ba base se fo foil il as th they ey pr prov ovid idee an ex exce celle llent nt dimensional stability. The typical values are 17 ppm§°C with respect to temperature changes and 11 ppm§%RH with respect to changes in relative humidity (ppm = parts  per million). Polyester films are available inmany thicknesses. However, the minimu min imum m thickn thickness ess should should be 100 100 mm to facilit facilitate ate suffic sufficien ientt mechan mechanical ical stabilit stability y against wrinkles. Polyester films are available with pre-printed grids.

Conductor Orientation It is a usual practice to run the conductors basically on one side in the direction of the X-coordinate and on the other side in the direction of the Y-coordinate. This provides a fairly regularly regularly distributed distributed pattern with a minimum minimum number of via holes.

 

Conductor Orientation

Solder Pad Diameter Pads are the entities that interface the part pins to the copper traces of the board. The hole in the pad must be big enough to allow for variations in the pin size, in the hole size, in the hole location and in the pin location. The pad must be big enough to ensure that the hole always has some copper around it on the surfaces of the board. Therefore, the diameter of the solder pad with respect to the finished hole diameter is very important for reliable solder joints. Generally, Generally, in PCBs with plated through-holes, through-holes, th thee wi widt dths hs of th thee an annu nula larr ring ring shou should ld be be betw twee een n 0. 0.3 3 to 0. 0.6 6 mm. mm. For For no nonn-pl plate ated d through-hole PCBs, the solder pad size must be bigger because there is no through plating to give mechanical strength to the solder pads. It is however, essential to  provide a sufficient solder pad size in order to avoid broken annular rings because of  drill position tolerances. In addition, another important consideration is the size of the solder pad and width of the joining conductor,

 

III. Guided Practice Self-Test

Activity 1 Direction: Enumerate the 10 type of pads. 1. ____ ________ ________ _____ _ 2. ____ ________ ________ _____ _ 3. ____ ________ ________ _____ _ 4. ____ ________ ________ _____ _ 5. ____ ________ ________ _____ _ 6. ____ ________ ________ _____ _ 7. ____ ________ ________ _____ _ 8. ____ ________ ________ _____ _ 9. ____ ________ ________ _____ _ 10. ____ ________ ________ _____ _

IV. Independent Practice Activity no. 2 Title: Conductor Orientation

Direction: Draw the conductor orientation inside the box. Rubric Neatness 8

Clarity 7

Low voltage nonpreferred

Total 15

Low voltage preferred

 

V. Assessment Direction: Answer the question below. What is artwork generation?

VI. Answer key Activity 1 1. Donut 2. Square 3. Hexagonal 4. Oval one hole 5. Oval two holes 6. Donut solid 7. Square solid 8. Teardrop double end 9. Teardrop with filet radius 10. Teardrop straight side

VII. Reference

Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM

Writer: Benjunly Benjunly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  [email protected] eped.gov.ph Contact information:  information:   benjunly.gengone@d

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 3 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 3 Conductor Routing Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________  I. Learning Competency:  Verify PCB layout for conformity with the schematic diagram in accordance with the layout rules. Code:  TLE_IAEPAS9- 12AEP-IVb-c-28

II. Key Concept

Conductor Routing Guidelines Guidelines The following guidelines are suggested in respect of conductor routing:

Guide 1

The minimum angle that any trace should be placed at is 60 degrees. Angles of less than 60 degrees create a situation during the manufacturing process which could allow the etching solution to build upon the inside angle and etch away excess material as illustrated.

 

Guide 2

The conductor routing must generally avoid passing in between pads resulting in narrow gaps between the pad and the trace, if an alternative path can be worked out. This minimizes the rejection at the manufacturing stage.

Guide 3

 

Conductor and Solder Pad Joints For ensuring reliability of the solder joint, it is important that the pattern around hole should be maintained as uniform and as small as possible to enable symmetrical solder joints. The overlap should be such that even if the tape creeps, there is no gap between the pad and the condition.

Schematic

Design no. 1

PCB Layout Board

Pad

Lllallllll

 

Layout

Component Pictorial

Conductor

 

Schematic

Design no. 2

PCB Layout Board

Pad

 

Conductor Conductor Layout Layout

Component Pictorial

Film Master Preparatio Preparation n The components and the various connections according to circuit design are done in the artwork. Film master is prepared from the artwork. It is the film negative or film  positive, which is finally used for the direct exposure of the photo-resist coated PCB or the light-sensitized screen. In order to ensure PCBs of high quality, the film master  must mu st ha have ve high high dime dimens nsio iona nall ac accu curac racy, y, sh shar arpn pnes esss an and d wearwear-ou outt re resis sistan tance. ce. The The imperfections of the film master get materially reflected in each PCB made with it after afterwa wards rds.. The The fi fina nall qu qual ality ity of th thee fil film m maste master, r, in ge gene neral ral,, de depe pend ndss up upon on th thee chemicals, chemic als, the film emulsion and exposure units such as cameras. cameras.

Photographic Film The material of the base can be acetate, polyester or glass and has thickness of 100250 mm. The dimensional dimensional stability stability of the film is primarily decided decided by the material of  the base. The photographic films are available in rolls, sheets, strips or cards, mounted or unmounted without dimensional limitation. Polyester-based films are popularly used in PCB technology as they offer the best co comp mpro romi mise se be betw tween een dime dimens nsio iona nall stabi stabili lity ty an and d co conv nven enien ience ce in ha hand ndlin ling g an and d  processing. For highest dimensional stability, such as in microelectronics applications,

 

glass base film is used. If the dimensional stability is not much of a concern, acetate based film fi lm can be employed.

Automated Artwork Design Thee ch Th chall allen enge gess po pose sed d by mode modern rn tech techno nolo logi gies es an and d th thee re resu sulti lting ng co comp mple lexi xity ty of  in inter terco conn nnect ectio ion n ne netw twor orks ks make make th thee us usee of th thee co comp mput uter er a pr pref eferr erred ed de desig sign n to tool ol.. Computer-based PCB design systems facilitate the generation of the required artwork  an and d do docu cume ment ntat atio ion n fo forr th thee PCB PCB manu manufa fact ctur urer er such such as a set of maste masterr film filmss th that at represent represe nt the circuit circuit connectivity connectivity;; and drilling information information which gives different different types types of drill sizes used in the PCB, soldermask films and component marking master films, which are present-day standard requirements. The computer-based design process is both faster and more accurate than the manual  process. It also provides the flexibility that is imperative in the development phase of  the product when changes in the PCB sometimes become frequent in the circuit till it is stabilized. If we make a time-analysis of the manual layout design and artwork preparation, the total time spent for these two operations is typically 40 per cent for the layout sketch design; while 60 per cent is spent on the artwork preparation. It is therefore, natural that the first step in automation is the elimination of the manual artwork preparation. The layout layout sketch sketch is digitiz digitized ed and the inform informatio ation n fed to a plotter plotter which directly directly  produces the 1:1 artwork on film. The next step in automation is the use of a co comp mput uter erize ized d layo layout ut de desig sign n whic which h may may sti still ll ne need ed th thee ac activ tivee in invo volv lvem emen entt of th thee desi design gner er.. The The last last st step ep in auto automa mati tion on is to make make ev even en th thee la lay you outt de desi sign gn fu full lly y automatic automa tic and independen independentt of any major involvement involvement of the designer. The availability availability of high-performance personal computers today has changed the scenario drastically. Low-cost PCB design software has made the manual methods of artwork generation almost obsolete.

Computer-Aided Design (CAD) ComputerComput er-aid aided ed design design provid provides es an interf interface ace betwee between n the PCB design designer er and the computer. compu ter. The combination combination of a graphic graphic terminal terminal (video display unit), an input device and a functio functional nal keyboa keyboard rd gives gives the design designer er an automa automated ted drawin drawing g board, board, which which  brings about a significant improvement in productivity. In recent years, there has  been a phenomenal growth in the availability of software for the design of printed circuit boards. Early software programs were simple geometric editors allowing only the placement and routing of tracks. However, they were interactive and it was, therefore, easy to erase, shift and replicate thecomponents and blocks of the circuitry. They had some severe limitations as they did not allow grids other than 100mil or components on

 

 both sides of the board. With the developments in software, schematic entry was added add ed to the geometr geometric ic editor editor,, which, which, in turn, turn, allowed allowed automa automatic tic routing. routing. Today Today,, automatic placement and routing is possible, as the software library now contains not on only ly stand standar ard d fo foot otpr prin ints ts of in indi divi vidu dual al de devi vice cess an and d inte integr grate ated d ci circ rcui uits, ts, bu butt fu full ll electricall data on standard product electrica product lines (such as TTL and CMOS packages packages), ), so that simulation can be undertaken easily on digital circuits. In addition, net lists, drill sizes and other relevant data are automatically generated.

Basic Cad Operation The CAD design process is usually started with a schematic or logic diagram. This can be either in the sketch form or an electronic transfer from a Capture system. It is followed by the merging of the netlist with the physical layout design. The board outlin out linee is then then created created in accord accordanc ancee with the input input requir requireme ements nts.. The The placem placement ent technique techni que is then selected for placing the component components. s. Once the placement placement process is complete, comple te, the routing routing phase of the design is applied. applied. During the design process and on completion of the layout, the system can check  de desig sign n erro errors rs like like sp spac acee viol violat atio ions ns,, land land-t -too-ho hole le size size ra ratio tios, s, an and d cl clea earan rance ce fo for  r  automated insertions, among other things. This is perhaps the most significant benefit of CAD systems in their ability to check the design in real-time.

Photoplotter The processed processed digital digital data data from from CAD systems systems are conver converted ted back back to graphi graphics cs by  photographic means with the help of an equipment called a ‘photoplotter’. In this eq equi uipm pmen ent, t, the the dr draw awin ing g he head ad which which is a light light spot spot pr proj ojec ecto torr ch chan ange gess its re relat lativ ivee  position towards the drawing medium which is the photographic film. Depending upon the design of the photoplotter, the drawing head or drawing table or both of  them are moving parts. There are two major types of photoplotters, ‘vector’ and ‘raster’ (or laser). Each of  these the se types types handle handless the apertu apertures res differ different ently ly.. The vector vector photop photoplot lotter ter has become become almost obsolete and is being replaced by the laser photoplotter. Laser plotters operate much quicker than vector machines. For example, a complex plot that required hours. on a ve vect ctor or mach machin inee ca can n us usua ually lly be pe perf rfor ormed med in ten minutes minutes or le less ss on a laser  laser   photoplotter. This decrease in turnaround time has also brought down the  photoplotting cost considerably. The photoplotter includes three main features 1. A photoplotti photoplotting ng head, which comes with a set of apertures; apertures; 2. Film plotter; plotter; and 3. Software. Software.

 

Computer-Aided Manufacturing Computer-aided manufacturing takes the output of the design system and applies it to the manufacturing process. Broadly, the hardware and its operation are very similar to the CAD system. While the CAD system has placement and routing programs, the CAM CA M statio station n ha hass pr prog ogra rams ms suita suitabl blee fo forr th thee manu manufa factu cturin ring g pr proc ocess ess.. CAD/ CAD/CA CAM M systems can be integrated through a common database. All the necessary data to operate numerically controlled (N/C) Printed Circuit Board fabr fabrica icatio tion n mach machin iner ery y ca can n be de deri rive ved d en entir tirel ely y from from th thee co comm mmon on da datab tabase ase af after  ter  converting the same to the equipment’s required data format. The data can also be optimized by the computer to take advantage of the actual machine characteristics, such as drill speed, routing capabilities, tool selection speeds etc. In addition, the data obtain obt ained ed from from the CAD/CA CAD/CAM M databa database se can be used used for the contro controll of compon component ent assembl asse mbly y equipm equipment ent in sequen sequence ce that that provid provides es the maximu maximum m use of automa automation tion.. CAD/ CAM systems can also provide the necessary necessary inputs for testing equipment. equipment.

III. Guided Practice Activity1

Direction: Draw the conductor conductor routing in guide 1 inside the box. Rubric Neatness 8

Not recommended

Clarity 7

Total 15

Recommended

 

IV. Independent Practice Practice

Activity no 2 Title: Layout designing Direction: Make a layout design design base of schematic given. given. (Review design no1 and design no.2) Rubric Neatness 10

Clarity 10

Total 20

Layout Board Schematic Diagram

V. Assessme Assessment nt

Why that we need to follow the conductor routing guidelines? Ans.

VI. Reference

Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM Writer: Benjunly Benjunly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  [email protected] eped.gov.ph Contact information:  information:   benjunly.gengone@d

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 4 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 4

Image Transfer Techniques

Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________ 

I.  Learning Competency:  Transfer PCB layout to copper copper-clad -clad board following acceptable acceptable methodss and standards. method standards. Code: TLE_IAEPAS9- 12AEP-IVb-c-2 II. Key Concept

Image Transfer Techniques What is image transfer?

Image transfer basically involves the transfer of the conductor pattern from the film master on to the copper clad base material or any other metal clad laminate. In the fabrication fabrica tion of the PCB, the two methods common for image transfer are: 1. Photo printing printing method; method; and 2. Screen printing printing method. method. Photo Printing Printing:: This is an extremely accurate accurate process, which which is generally applied applied to the fabrica fabricatio tion n of semicon semiconduc ductor torss and integr integrated ated circui circuits ts wherein wherein the conduc conductor  tor  widt widths hs are are ty typic picall ally y in th thee regi region on of a fe few w micr micron ons. s. Al Alth thou ough gh such such a pr prec ecisi ision on techn tec hniq ique ue is no nott re requ quire ired d in th thee pr prod oduc uctio tion n of ge gene neral ral pu purp rpos osee PCBs PCBs,, ye yett wher wheree conductor widths of 100 mm are required and for PCBs for professional applications, the photo printing process is resorted to. Scre Screen en Prin Printin ting: g: Al Alth thou ough gh less less pr preci ecise se th than an th thee ph phot oto o pr prin intin ting g pr proc ocess ess,, scree screen n  printing is a comparatively cheap and simple method. The majority of PCBs produced worldwide are screen printed.

Laminate Surface Preparation Copper surface plays a major role in the success or yield of the image transfer process. It demands that the surface should be carefully inspected for pits, drilling burns and

 

any other other types types of irregu irregulari larities ties.. If unaccep unacceptab table le defects defects are observ observed, ed, the image image transfer process should not be carried out further and the defective material should be rejected straightaway. So, for the image transfer to take place, the cleaning of the copper surface prior to resist application is an essential step for any type of PCB  process. The difficulties most often encountered in PCB fabrication arise due to insufficient cleaning of the laminate surface. Therefore, the laminate should be free from fro m oil, grease grease,, dust, dust, finger fingerpri prints nts and foreig foreign n particl particles. es. Possib Possible le source sourcess causin causing g contami con taminat nation ion could could be the equipm equipment ent used used for shearin shearing, g, drillin drilling, g, punchi punching ng or air  from from th thee air air co comp mpre resso ssor. r. Any Any co cont ntam amin inati ation on on th thee surf surface ace of th thee lamin laminate ate may may impair imp air the adhesio adhesion n of the photop photopoly olymer mer or decreas decreasee the bonding bonding of the electro electro-deposit dep osited ed copper. copper. Hence, Hence, very very go good od cleanin cleaning g method methodss are requir required ed to prepar preparee the laminatee surface. The methods laminat methods commonly commonly used are: (i) Manual Manual Cleaning Cleaning Process Process — This includes: includes: a. Chemica Chemicall Clea Cleanin ning; g; and  b. De-greasing (vapour or aqueous) (ii) Mechanical Cleaning.

Manual Cleaning Process Chemic Chem ical al Clean Cleanin ing g or Cold Cold Clean Cleanin ing g Chem Chemica icall cl clea eani ning ng en enta tails ils th thee us usee of  concentrated alkali chemicals to remove the oil, grease and soil particles on the surface of the laminate. The concentration of the alkali chemical which is between 80-100 per cent at a temperature range between 60 °C and 70 °C is used for  twenty to thirty minutes for cleaning the laminates. After this process of alkaline soak, the laminate is effectively rinsed with filtered tap water which is oilfree. Water immersion, followed by strong water spray, ensures complete removal of  cleaners. Neutral or acidic cleaners are sometimes preferred because of the attack  of hot alkaline solutions on exposed epoxy or polyamide substrates.

Chemical cleaning process: 1. 2. 3. 4. 5. 6. 7. 8.  

De-grease De-grease with with hot hot soak soak cleaner; cleaner; Water rinse rinse (using pressuri pressurized zed water of more more than 4 bar or 60psi); 60psi); Water Water spray spray;; Micro-etch Micro-etch copper copper (optional); (optional); Water Water rinse; rinse; Inspection Inspection (of (of oil and grease grease complete complete removal); removal); Acid dip (neutralization (neutralization); ); and Water rinse.

Mechanical Cleaning In th thee mech mechan anica icall clea cleani ning ng pr proc ocess ess,, th thee la lamin minat ates es ar aree ty typi pical cally ly clean cleaned ed by abrasivee brush abrasiv brush cleani cleaning ng un units its employ employing ing abrasiv abrasives es such such as emery emery,, corun corundum dum,, aluminium oxide and silicone carbide. These abrasive materials are impregnated

 

into a ny into nylon lon or similar similar plastic plastic matrix. matrix. The resultin resulting g brush brush construc constructio tion n can be eith either er a co comp mpre resse ssed d lamell lamellaa or a fi filam lamen entt ty type. pe. The The silic silicon on ca carb rbid idee 32 3200-gr grid id abrasive filament brush is generally used for cleaning the copper surface prior to lamination lamina tion of the dry film resist. Type of Mechanical Cleaning

a.  b. c. d. e.

Polish Polishing ing;; Brushing; Buffin Buffing g or or ssand anding ing;; Deburring Deburring or scrubb scrubbing; ing; and Scru Scrubb bbin ing g

Screen Printing The ph The phot otog ograp raphi hicc image image is tr tran ansf sferr erred ed to co copp pper er cl clad ad lamin laminat atee by th thee sc scre reen en  printing technique. This technique has been used for a long time t ime for printing cloth, cl oth,  panels and so on, and reaches its maximum degree of accuracy when applied to PCB manufacture. The technique is particularly adopted for low cost print and etches and plated printed boards, when the ultimate resolution and definition are not very exacting. A screen comprises an aluminium frame, mesh, emulsion and adhesive bonding. The emulsion is removed by a photochemical process where deposition is required. A specification of 1:1 ratio of open area to board pad area is typical, but ±10 % variations are not uncommon. The flexibility of the emulsion creates a good good gasket against the PCB and aids print definition. definition. Screen Preparation The screen is prepared by considering various factors such as the image transfer  line and space requirement, panel size, fabrication process, run length, etc. It is followed by properly selecting the fabric type, mesh size, frame stencil and ink. Once this is done, the fabric is cut several cm longer than the frame moulded into the the rails rails of th thee fr fram amee wi with th stapl staples es an and d ad adhe hesiv sives es,, un unde derr maxi maximu mum m tensio tension n uniformly applied by hand. III. Guided Practice

Self-test Activity 1 Direction: Enumerate at least 5 chemical cleaning process. 1. ____ ________ ________ ________ ______ __ 2. .____ .________ ________ ________ _____ _ 3. ____ ________ ________ ________ ______ __ 4. .____ .________ ________ ________ _____ _ 5. ____ ________ ________ ________ ______ __

 

I. Independent Practice

Activity no 2 Title: Mechanical Cleaning Direction : Enumerate the the five mechanical cleaning cleaning process. 1. 2. 3. 4. 5.

________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________

II. Assessm Assessment ent

What is image transfer? Ans. Al

III. Answer key

Activity 1 1. De-grease with hot soak cleaner; 2. Water rinse (using pressurized water of more than 4 bar or 60psi); 3. Water spray; 4. Micro-etch copper (optional); 5. Water rinse; 6. Inspection (of oil and grease complete removal); 7. Acid dip (neutralization); and 8. Water rinse. Activity 2 1. Polishing; 2. Brushing; 3. Buffing or sanding; 4. Deburring or scrubbing; and 5. Scrubbing

 

VII. Reference

Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM

Writer: Benjunly Benjunly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  [email protected] eped.gov.ph Contact information:  information:   benjunly.gengone@d

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 5 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 5

Image Transfer Techniques

Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________ 

I.  Learning Competency:  Transfer PCB layout to copper copper-clad -clad board following acceptable acceptable methodss and standards. method standards. Code: TLE_IAEPAS9- 12AEP-IVb-c-2 II. Key Concept

Pattern Transferring Technique Type of Pattern Transferring technique

1. Screen Stencil Method Method 2. Knife-cut or Hand cut Film Process 3.  Photographic Techniques 4. Photo Printing 5. Plating Process

1. Screen Stencil Method In this method, a photographic emulsion is coated directly on to the screen fabric and is exposed to light, thereby establishing a direct contact with the film master. When Wh en the the sc scre reen en is deve develo lope ped, d, the the me mesh sh op open enss at th thee pa patt tter ern n ar area eas. s. The The  photographic emulsion used is polyvinyl alcohol, polyvinyl acetate or polyvinyl chloride, and they contain some dye to make the pattern visible while processing. Thee sens Th sensit itiz ized ed emul emulsi sion on-c -coa oate ted d sc scre reen en is ex expo pose sed d to ul ultr trav avio iole lett or ot othe her  r  fluorescent light sources. The exposure time depends upon the light intensity and the distance between the bulb and the screen. Normally the distance between the  bulb and the screen is 1.5 feet. During the process of exposing, the positive or  negative film is placed on the printing side of the emulsion-coated screen. The exposure brings about a polymerization in the exposed areas, which makes them insoluble in the developer. If any air gap is present between the photo-tool and screen, it must be removed by using a vacuum system. The air gaps can lead to

 

incomplete incomp lete pattern pattern formin forming g and insuff insufficie icient nt half-t half-tone one work. work. Vacuum Vacuum printi printing ng facilitates sharp details of line, half-tone work and no pin holes. Vacuum printing machines with light source and all the other regulating facilities are available in the market. The suppliers of the emulsion also specify exposure calculations that ensure the correct exposing time.

2. Knife-cut or Hand cut Film Process For electronic circuit printing, the manually prepared screens are usually of the knife-cut film types. This consists of a transparent or translucent film coating. The emulsio emu lsions ns on the knifeknife-cut cut film are either either coated coated or adhered adhered semi-pe semi-perma rmanen nently tly wi with th an ad adhe hesiv sivee or by mean meanss of th thee elec electro trosta static tic pr proc ocess ess to a trans transpa paren rentt or  translucent plastic or paper backing sheet. The film may be either of the lacquer or  of water soluble type; water soluble film may be softened or dissolved, or adhered with water, water and alcohol, or with an adhering liquid recommended by the manufacturer of the film. The film or coating used for the printing screen must be one that will not get dissolved by the inks.

3. Photographic Techniques For electronic circuit printing, the most commonly used and practical method is the one that has plastic type backing sheet. Since this type holds the pattern better and is least affected by atmospheric conditions, there is a tendency to eliminate shrinkage or  expans exp ansion ion of film, especially especially larger larger screens. screens. The knife-c knife-cut ut film is adhered adhered to the screen fabric with the correct adhering liquid only. Each type of film uses a different type of adhering liquid. But water alone may be used for adhering water soluble film. A mixture of water and alcohol in the ratio of 3:1 is recommended for some soluble films. While adhering film to the fabric, it is advisable to make a build-up layer on which the film is placed so that perfect contact is obtained with fabric. The build-up layer may be glass or cardboard. cardboard.

4. Photo Printing Photo printing of PCBs basically means applying photo-sensitive material having the ability to form a continuous film, which is sensitive to light or other radiation so that th thee expos exposed ed (or (or un unex expo pose sed) d) ar areas eas of th thee fi film lm ca can n be fu furt rthe herr pr proc ocess essed ed wi with thou outt affecti aff ecting ng the unexpo unexposed sed (or expose exposed) d) areas. areas. This This photophoto-sen sensiti sitive ve materia materiall is called called ‘photo-resist’. The essential property of a photo-resist is that an exposure to proper  radi radiat atio ion n must must pr prod oduc ucee a ch chan ange ge in it to en enab able le a cl clea earr di dist stin inct ctio ion n in th thee la late ter  r  operations operati ons between the exposed exposed and unexposed unexposed areas. Usually, in all the photo-resis photo-resists, ts, a light light-indu -induced ced change in solution solution forms the basis of their action. action.

 

5. Plating Process Need for Plating

They are organic organic lacquer lacquer coating, oxide coating and plating. plating. In printed circuit boards, copper is used for interconnecting the components on the substrate. Although it is a good conducting material on the PCB to form the conducting track pattern, it is liable to tarnish due to oxidation, if exposed to atmosphere over a long period of time. It undergoes under goes corrosion and thus loses its solderability solderability.. Therefore, Therefore, various various techniques techniques are used for the protection of the copper tracks, and via holes and printed through-holes (PTH Organic lacquer coating, though simple in application, is not suitable for long term usage due to variations in thickness, composition and curing cycles. It can also bring about unpredictable deviation in solderability. Oxide coating can be used to protect the circuit from corrosion, but it fails to preserve the solderability. Plating or the metal coating process is a standard practice to ensure solderability and protect the circuit from corrosion. So it plays an important role in the PCB manufacturing of singlesided, double-sided and multi-layer (PTH) boards. In particular, plating a solderable metal me tal ov over er th thee tr trac acks ks ha hass no now w be beco come me a stand standar ard d pr pract actic icee to af affo ford rd sold solder erab able le  protection to t o the copper tracks.

Electroplating Electroplating Electroplatin g is the process by which a metal is deposited on a conductive conductive surface by  passing a direct current through an electrolytic solution containing a soluble salt sal t of the t he metal. When a uni-directional current is passed through a solution, it results in movement of  the charged charged particles particles through through it. These These particl particles es are called called ions ions and the termina terminals ls which wh ich are are us used ed to pa pass ss th thee cu curr rren entt in into to the the solu solutio tion n ar aree ca calle lled d elect electro rodes des.. The The combination of the two electrodes and the solution form what is known as electrolytic cell. Electrochemical terms associated with electroplating

1. Anode: Anode: The pole or electrode electrode at which the chemical chemical reaction of oxidatio oxidation n takes  place is called cal led the anode. It is a positively posit ively charged electrode. During electrolysis, positive ions are formed at this electrode. 2. Anion: Anion: This is a negatively negatively charged radical radical which, which, on electrolysis, electrolysis, is attracted towards the anode. 3. Cathod Cathode: e: The electro electrode de or pole pole at which the chemical chemical reaction reaction of reduct reduction ion takes place is called the cathode. It is a negatively charged electrode. During electrolysis, negative ions are formed at this electrode. 4. Cation: Cation : This is a positively charged charged radical radical which, on electroly electrolysis, sis, is attracted towards the cathode.

 

5.   Elec Electr trol olyt yte: e: This This is a co cond nduc ucti ting ng medi medium um in which which th thee flow flow of cu curr rren entt is accompanied accomp anied by the movement of ions. For electroplatin electroplating, g, the electrolyte must contain dissolved salt of the metal that is to be deposited.

III.  Guided Practice Self-Test Activity 1 Direction: Enumerate the 5 Pattern Transferring Technique. 1. ____________________  ____________________  2. ____________________  ____________________  3. ____________________  ____________________  4. ____________________  ____________________  5. ____________________  ____________________ 

IV  Independent Practice Activity no. 2 Title. Electrochemical Direction: Enumerate the 5 electrochemical associated with electroplating. 1. _____________  _____________  2. _____________  _____________  3. _____________  _____________  4. _____________  _____________  5. _____________  _____________ 

IV. Assessment

What is electroplating? Ans.

 

V. Answer key

Activity 1 1. Screen Stencil Method 2. Knife-cut or Hand cut Film Process 3.  Photographic Techniques Techniques 4. Photo Printing 5. Plating Process

Activity 2 1. Anode 2. Anion 3. Cathode 4. Cation 5. Electrolyte

VI. Reference

Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM

Writer: Benjunly Benjunly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  [email protected] eped.gov.ph Contact information:  information:   benjunly.gengone@d

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 6 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 6

Image Transfer using Photo Paper Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________  I. Learning Competency: 1.  Transfer PCB layout to copper copper-clad -clad board following following acceptable acceptable methods and standards. 2. Clean PCB based on standards procedures Code:  TLE_IAEPAS9- 12AEP-IVb-c-2

II. Key Concept Image Transfer using Photo Paper

Materials need in Image Transfer  1. PCB PCB 2.  Layout printed in photo paper

P CB

Photo paper with prin inte ted d layout

The smallest trace-thickness that is 4/300ths of an inch (about 0.0133 inch, or 0.338 mm). And, at the top of the photo, some of the traces are separated by only 2/300ths of an inch. (It doesn't show up very well in this photo. But it works well in actuality.).

 

And: the drill-holes' location-markers, on the solder pads, were made by drawing squares, square s, with sides with lengths of 6/300 of an inch (i.e. 1/50th of an inch). inch). There is also an 8-Pin DIP IC location, slightly above and to the left of the center of  the photo, where the distance distance between between adjacent holes' centers centers is exactly 0.10 inch. Process of Image Transfer 1. PCB Cleaning Cleaning Proc Process ess

Scrub the board   with a Scotchbrite or "artificial steel wool" pad (nylon abrasive  pad), equivalent to '0' steel wool, usually in two orthogonal directions (with a lighter   pass or '000' equivalent at the end, so s o it's not too rough). The "scotchbrite" step does two things: 1) It removes oxidation, stains, scratches, etc, so the copper surface of the PCB is all uniformly nice and shiny. (You might have to  press very hard, for this part.) And, 2) It makes the copper surface somewhat LESS than tha n perfect perfectly ly smooth smooth.. The nylon abrasive abrasive pad makes many many tiny scratche scratchess in the copper. This apparently helps the toner to stick to the copper. (Press very lightly, near  the end of this part.) Surface after cleaning

Scrub the board with a paper towel soaked with ACETONE solvent. Keep doing it until (almost) (almost) no more discoloration discoloration is seen on the paper towel. Press hard! And keep switching switchi ng to clean parts of the towel. Lay the board (with the copper side facing up) on a rigid, flat, heat-resistant surface, such as a smooth piece of wood or plywood. Blow any dust, etc, off of it, if necessary, very carefully, and off of the pattern paper. Lay the paper pattern face down on the copper, lining it up exactly right 2. Applying Applying Heat

Procedure of applying heat with Electric Flat Iron. Usee a regu Us regula larr hand handhe held ld hous househ ehol old d elec electr tric ic CLOT CLOTHE HES S IR IRON ON,, se sett as HOT HOT as MAXIMUM temperature setting LINEN or COTTON.

 

Place the iron on the back of the pattern.  Pre-heat the whole board.  i.e. Hold the iron on the whole pattern, if possible (unless the pattern is too large), for at least 1/2 minute or more, pressing firmly (see addendum, below, for pounds of force used). I usually am standing next to a 30-inch-high table that the pcboard is on, and just "lean on" the iron, somewhat, during this step. After the board is well-heated (after the 1/2 minute or more, in the previous step),  place rear of the iron along edge of the board (withI the restthe of iron the iron the  board),theand press hard near the an rear of the iron's handle. move 1/4 on to 1/2 inch away from the edge and press hard again, for about a half-second to a second, and continue that way until I'm near the other side of the board (with the rear of the iron), and it gets hard to keep the iron flat against the board, go back the other way (starting from the opposite edge), doing the same thing, over the same part of the  board. If there are board-edges that are wider than the iron's rear edge, make overlapping passes, with the iron's side being along the outer edge of the board, on  both sides of the wide edge. Usually do this whole procedure starting from each of  the four edges of the board. If you see the pattern starting to show, through the paper, then you have probably done it well-enough. (Or is that just some kind of black stuff from the bottom of my iron rubbing off onto the areas over the slightly-raised pattern?) 3. Removing Removing of Photo Photo Paper Paper

After heated heated with flat iron, immerse immerse PCB to the water, water, after 10 minutes, minutes, Peel off the  paper, or at least the TOP layer or two. If the paper underneath is still a little dryish,  put the board back into the t he water, for another ten minutes or more.

III.  Guided Practice Self-Test Activity 1

Direction: Enumerate the following: Two materials need in Image Transfer. Transfer. 1. ____ ________ ________ _______  ___  2. ____ ________ ________ _______  ___  Three Process of Image Transfer  3. ____ ________ ________ _______  ___  4. ____ ________ ________ _______  ___  5. ____ ________ ________ _______  ___ 

 

V  Independent Practice Activity no. 2 Title: Removing of Photo Paper  Direction: Directio n: Write the procedure procedure of removing removing photo paper. paper.

VI  Assessment When applying applying heat, What is the maximum temperatur temperaturee setting of Electric Electric Flat Iron?

VII. Answer Answer key

Activity 1 1. PCB PCB printed in photo paper 2.  Layout 3. PCB cleanin cleaning g process process 4. Applying Applying heat heat 5. Removing Removing of Photo Photo Paper  Paper  VIII. Reference Reference

Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM Writer: Benjunly Benjunly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  [email protected] eped.gov.ph Contact information:  information:   benjunly.gengone@d

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 7 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 7 Etching Process Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________ 

I.  Learning Competency:  Perform Etching procedure. Co Code de::  TLE_IAEPAS9- 12AEPIVb-c-2 II. Key Concept Etching Etching is one of the major steps in the chemical processing of the subtractive PCB  process. By this process, the final copper pattern is achieved by selective removal of  all the unwanted copper to retain the desired circuit patterns. The copper which is not  protected by an etch resist is removed by the etching process. Etching Method •

 

Chemical etching or chemical machining;

•

 

Electrochemical etching or chemical milling; and

•

 

Mechanical etching (by milling).

Etching Solutions and Chemistry

Several chemicals chemicals are used for etching. The most common etchants are: •

 

Ferric chloride;

•

 

Ammonium persulphate;

•

 

Chromic acid;

•

 

Cupric chloride; and

•

 

Alkaline ammonia.

 

The follow following ing section sectionss give give charact characteris eristics tics,, chemist chemistry ry and process process details details of these these etching methods.

Ferric Chloride Ferric chloride etching solutions are widely used in the ‘print’ and ‘etch’ process in the PCB indust industry ry.. Ferric Ferric chlori chloride de has a high high etch etch rate rate and high copper copper dissolv dissolving ing capacity. It is used with screen inks, photo-resist (wet film and dry film) and gold  plated boards. As the ferric chloride etchant attacks tin, this is not suitable for tin or  tin-lead plated boards. This etchant is an aqueous solution of 28 to 42 per cent by weight of ferric chloride. The solution has a specific gravity of 1.353 to 1.402. It operates over a wide range of  co conc ncent entra ratio tion, n, bu butt is most most wi wide dely ly us used ed at ab abou outt 35 pe perr ce cent nt.. The The fe ferri rricc ch chlo lori ride de solution has free acid due to the following hydrolysis reaction: FeCl3 + 3 H2O

> Fe( e(O OH)3 + 3 HCl

In orde orderr to pr prev even entt th thee fo form rmat atio ion n of inso insolu lubl blee fe ferr rric ic hy hydr drox oxid ide, e, an ex exce cess ss of  hydrochloric acid, upto 5 per cent by weight is usually added, which prevents the spontaneouss hydrolysis spontaneou hydrolysis of FeCl3 as per the above equation. equation. Commercial Commercial formulations formulations also contain wetting and anti-foam agents. At the initial stage of the etching process, the concentration of copper dissolved is high due to the high concentration of ferric chloride. As the ferric chloride in the solution solu tion gradu gradually ally gets gets deplete depleted, d, the etching etching time corres correspon pondin dingly gly increas increases es to the extent that after some time, the solution has to be discarded and replaced by a fresh so solu luti tion on.. Bette etterr dis isso solu luti tio on of cop copper per occu occurs rs whe hen n th thee etch etchan antt is sp spra ray yed  perpendicular to the copper surface and the board is moved. The rate of dissolution of  copper depends upon the ferric chloride concentration, temperature and agitation rate. Ferric chloride is the oldest and perhaps the most common etchant. It normally comes in crystal form. The crystals are dissolved in de-ionized water to achieve its desired concentration in the solution. This is typically 500 gm of ferric chloride in one litre of  water. In practice, when a solution contains 8 oz./gal (60 g/l) or more of dissolved copper, the etch time becomes longer than desired. However, the ferric chloride can dissolve copper even upto 120 g/l if the prolonged etching time can be tolerated. In order to increase the copper dissolving capacity and to bring down the etching time slightly, hydrochloric acid (upto 10 per cent of the etchant volume) is added after the copper  content has reached 80 g/l. The acid also helps to control excessive sludge formation. Fi Figu gure re 9.1 9.1 sh show owss th thee de depe pend nden ence ce of etch etchin ing g time time ve versu rsuss co copp pper er co cont nten entt in th thee etchant.  For monitoring purposes and to know the exact copper concentration in the etchant, a chemical analysis has to be done. A less accurate but practical solution is to use the

 

colorimetric method of color comparison with standard solutions of known copper  co cont nten ent. t. On an av avera erage ge,, to etch etch 1k 1kg g of co copp pper, er, 5.1 kg of fe ferri rricc ch chlo lori ride de wi will ll be consumed, with etching temperature in the range of 20-45 °C.

Etching Arrangements Simple Batch Production Etching

Batch etching is applied in laboratories and small industries wherein small series of  PCBs have to be etched occasionally. This simple arrangement for etching of PCBs involves the use of the etchant until saturation or until the etching speed becomes too slow. The etchant is then dispose disposed d and fresh solution is filled into the etching etching machine. When the etching of a new batch of PCBs is started, the optimum etching time must  be initially determined. The typical etchant used in this method is ferric chloride.

Continuous Continu ous Feed Etching In this this meth method od,, a smal smalll st stea eady dy st stre ream am of fres fresh h et etch chan antt ei eith ther er co cont ntin inuo uous usly ly or   periodically flows into the etchant sump while an equal quantity of partially saturated etchant is simultaneously removed.  In order to utilize the full copper solving capacity of the etchant, it is necessary to have etching with a very slow etching speed (conveyor speed). This, however, would result in a low productivity rate. The system is therefore operated in a mode with only  partially saturated etchant which gives, more or less, constant results at a reasonable etching speed. However, the copper-solving capacity of the etchant is not optimally utilized. The typical etchant used in the continuous feed etching system is generally ferric chloride. The etch The etchan antt ec econ onom omy y in co cont ntin inuo uous us fe feed ed etchi etching ng syste systems ms ca can n be impro improve ved d by cascading several etching modules. In such a system, the first module contains almost saturat satu rated ed etchan etchant, t, wherea whereass the follow following ing interco interconne nnected cted module moduless have have decreas decreasing ing copper content in the etchant and the last module operates with nearly fresh etchant. Usua Us ually lly,, th thre reee or fo four ur modu module less ar aree ca casc scad aded ed an and d th thee etcha etchant nt flow flow be betw tween een th thee module mod uless go goes es via the sump sump overflo overflows. ws. This This arrang arrangeme ement nt gives gives reasona reasonable ble etchin etching g speed obtained in combination with a practically full utilization of the etchant copperdissolving capacity. A typical problem with cascaded etching systems is the need to maintain maintai n the copper copper content within certain limits in each one of the modules.

Open Loop Regeneration The methods described in the previous section depend upon utilization of the addition of prepre-mi mixed xed fu full ll str stren engt gth h etch etchan ant, t, wher whereas eas th thee op open en lo loop op re regen gener erati ation on syste systems ms empl em ploy oy th thee ad addi ditio tion n of ch chem emica icall ad addi ditiv tives es like like re repl plen enis ishe hers rs an and d re regen gener erati ation on chemicals chemic als in order to maintain the etching performance performance at a constant constant level.

 

In such such syste systems ms,, whic which h ar aree mostl mostly y au auto toma matic tic,, th thee co comp mpos ositi ition on of th thee et etch chan antt is monitor mon itored ed via a sensor sensor for the pH value, value, the oxidat oxidation ion-re -reduc ductio tion n potent potential ial (redo (redox x  potential), specific gravity or colour. The most typical etchant used in open loop regeneration is cupric chloride which permits the dissolution of typically 130 g cu per  litre litre of etch etchan antt spen spent. t. Open Open lo loop op re rege gene nerat ratio ion n ca can n also also be ca carri rried ed ou outt manu manual ally ly,, especi esp ecial ally ly for for smal smaller ler pr prod oduc uctio tion n vo volu lume mes, s, bu butt it ne need edss ca caref reful ul an and d co cont ntin inuo uous us monitoring of the etchant composition.

Closed Loop Regeneration The closed loop regeneration involves the removal of copper containing by-product from fro m the etchan etchantt mainst mainstrea ream m while while the copper copper-pu -purifi rified ed etchan etchantt is returne returned d to the etchant sump. Although the investment in equipment is high, it offers efficiency and ec econ onom omy y in re resp spec ectt of etch etchin ing g chem chemic ical als, s, co cons nsta tant nt et etch chin ing g perf perfor orma manc ncee an and d environmental pollution. Among the etchants economically suited for closed loop regeneration, we find that cupric cup ric chlori chloride, de, ammoni ammonium um persul persulpha phate te and alkali alkali etchan etchants ts are qu quite ite suitab suitable. le. For  each one of these these etchan etchants, ts, the reactor reactor/sep /separa arator tor sy system stem is comple completely tely different different in terms of how it suits the particular particular chemistry. chemistry. The conditioning conditioning chemicals promote the formation of copper salts in the reactor which is, in certain cases, further supported by chilling chillin g of the etchant. The copper salts are then filtered out in the  separator and stored as a by-product in a special tank. This by-product with its high co copp pper er co cont nten entt ca can n us usua uall lly y be sold sold wi with thou outt ca caus usin ing g an any y pr prob oble lems ms to ch chem emica icall industries indust ries in terms of its further further use. The high high comple complexity xity of the sy system stem needs needs meticu meticulou louss mainte maintenan nance ce for achiev achieving ing a constant etching quality in the presence of widely variable chemical compositions.

Etching Parameters Etching Rate: The rate of etching is determined by the amount of material removed  per unit time. t ime. Etch Factor: The etch factor is the ratio between the depth of etching (d) and the under-etching (b) (under-cut) d Etch factor = b.

 

Equipment and Techniques of Etching •

Immersion etching;

•

Bubble etching;

•

Splash etching; and

•

Spray etching.

Spray etching is the most commonly used technique due to its high productivity and fine line definitions.

Immersion Etching Immersion etching is the semi-plast technique which requires only a tank containing etching solution into which the boards are immersed. The boards are kept immersed until the etching is complete. This requires a long process time and the etch rate is thereby low. The solution can be heated to speed up the etching process. This method is suitabl suitablee for small small boards boards or protot prototyp yping ing.. Normal Normally ly ammoni ammonium um persul persulpha phate te or  hydrogen hydro gen peroxide with sulphuric acid etching etching medium is used for immersion etching, etching, suggested to use magnetic wire no. 18 to hold PCB to avoid touching chemical when removing PCB.

Bubble Etching This technique is a modified form of immersion etching with the difference that air is  bubbled through the etching solution. Air, passing through the solution, has two functions: • To ensu ensure re fre fresh sh etc etcha hant nt con conta tact ct at at the the surf surfac acee and and to rin rinse se awa away y diss dissol olve ved d metal; and •

To en enha hanc ncee the the ox oxid idati ation on po powe werr an and d to re rege gene nerat ratee th thee et etch chan ant. t.

The rate of etching, to a certain extent, depends upon the air pressure (normally up to 2 psi) psi) to obtain obtain go good od qu qualit ality y of etchin etching. g. Chromi Chromicc sulphur sulphuric ic acid and ammoni ammonium um

 

 persulphate etchants are used in this technique. The primary disadvantage of bubble etching, when used with hydrogen peroxide- sulphuric acid etchant, is that it generates a signif significan icantt quantit quantity y of corros corrosive ive aeroso aerosol. l. Effecti Effective ve fume fume collec collecting ting with active scrubbing scrubb ing must be implemented implemented if a bubbler bubbler is used.

Splash Etching The principle of splash etching involves a paddle or cup attached to a motor-driven shaft. When the motor rotates, the etchant is thrown by centrifugal force towards the boards  being etched. The contact of the solution with the boards depends upon the shaft rotation and paddle design, Splash etching or paddle etching is better than bubble. etching with regard to even etching and mini-Drive motor mum undercut. But, only a limited number of for paddles boards can be etched at a time. Ferric chloride and chromic/sulp chrom ic/sulphuric huric acid solutions are commonly commonly used in this type of technique. A large volu volume me rese reserv rvoi oirr is pr prov ovid ided ed at the the bott bottom om of th thee ta tank nk to mini minimi mize ze so solu luti tion on replace rep lacemen ment. t. The techniqu techniquee has become become obsole obsolete te because because of the low etch etch rates rates as compared to automatic spray etch machines.

Spray Etching In its simplest form, a spray etching machine consists of a box type chamber having a sump below. The etching solution is pumped under pressure from the sump through a  pipe network to the nozzles and splashed onto the board surface. This allows the fresh solution to be sprayed, giving a high etching rate. The factors which determine the evenness evenn ess of etch are: •

Unifor Uniformity mity of spray spray patter pattern, n, force, force, draina drainage ge and pattern pattern config configura uratio tion; n;

• Etchan Etchantt chemist chemistry ry,, the pump pump pressur pressure, e, and nozzle nozzle configu configurati ration on and placeme placement, nt, which wh ich de dete term rmin inee th thee ra rate te of etch etchin ing; g; an and d • The The spra spray, y, whi which ch is is don donee on bot both h side sidess of the the PCB PCB in cas casee of dou doubl blee-si side ded d  boards. The boards are etched continuously in this closed loop system. The etch rate is high in this system with minimum under cut and fine-line definition. Ammonium chloride etcha etc hant nt is co comm mmon only ly us used ed in this this techn techniq ique ue fo forr do doub uble le-si -side ded d PTH PTH bo boar ards ds.. The The fabrica fab ricated ted equipm equipment ent should be made made of acid acid and alkali resist materia materiall like like PVC. PVC. However, Howev er, equipment equipment for sulphuric sulphuric acid/hydrog acid/hydrogen en peroxide peroxide etchant etchant system requires stainlesss steel, poly-carbon stainles poly-carbonate ate or polypropy polypropylene lene material, of spray machine.

 

There are two types of spray etching techniques, techniques, which are: •   Horizontal this techni technique que,, etching etching is done done from from indepe independe ndently ntly Horizontal Sprayin Spraying g: In this

controlled spray nozzle banks at the top and bottom. Double-sided horizontal etches are generally preferred in PC manufacturing as a majority of the PCBs are doublesided. The design of a horizo horizontal ntal spray etcher is shown in Figure. •  Vertical Spraying:  Figure 9.8 shows the design of a vertical spray etcher. In this technique, the etching is carried out by placing panels in a rack, which is lowered into the spray box area. A combination of nozzle movement and nozzle oscillation up and down or sideways, with a large number of nozzles, provides optimum results. Spray etchin Spray etching g machin machines es are availab available le in automa automatic tic and semi-a semi-auto utomat matic ic modes modes for  vertical or horizontal type of spray. The automation contains pressure control, heating, specific gravity indicator and automatic solution regeneration. Automatic machines are designed for high production rates. The boards are loaded on a rack, which is passed through the etch chamber, where it is sprayed on one or both sides by an oscillating bank of spray nozzles. The rack is then used to spray rinse with water and neutralizing chambers. The pressure to each  bank of spray nozzle can be easily easi ly controlled. For the manufacture of prototype and small batch quantities of PCBs, rotary etching machines prove useful. In this machine, the etching solution is contained in a tank at the base of the machine. It is heated by a quartz heater, which provides a short warmup time and constant temperature that is controlled electronically. Machines have the capacity to handle 300 x 500 mm boards. In the PCBs, the board holder is rotated 180° before the second etching cycle. A provision is made to have a wash tank for the rinsing of the etched boards. This machine facilitates line resolution of better than 0.1 mm and an etching speed of only 90 seconds with fresh ferric chloride.

 

Etching Equipment Selection The foll The follow owin ing g fa fact ctor orss ar aree gener eneral ally ly take taken n in into to co cons nsid ider erat atio ion n whil whilee se sele lect ctin ing g equipment for etching: • Maxi Maximu mum m Boa Board rd Siz Size: e: The The max maxim imum um bo boar ard d size size det deter ermi mine ness the the size size of of the the tanks for etching, rinsing, cleaning and neutralizing, as well as the size of the holding rack or conveyor. • Quan Quantit titie iess of of Boa Board rd:: Thi Thiss det deter ermi mine ness the the typ typee of of etch etchin ing g equ equip ipme ment nt re requ quir ired ed to meet the production needs. The equipment should be able to complete the normal dail daily y prod produc ucti tion on targ target et whil whilee allo allowi wing ng fo forr so solu luti tion on ad adju just stin ing g time time,, mach machin inee maintenance and actual hours of operation. • Space Space Availab Available le for Etchin Etching: g: This This is needed needed to allow allow genero generous us amount amountss of of walk  walk  around space with extra room for easy loading and unloading. Storage racks, bins, tables and shelves should be provided in each area where boards are stacked, which are regained from plating, screening, photo-resist coating and etching.  •

Types Types of Etchin Etching: g: This This includ includes es fine fine line, line, wide wide line or printprint-and and-etc -etch h only. only.

•

Types Types of Boards Boards:: These These are metal metal resist resist plated plated,, printprint-and and-etc -etch, h, etc.

Optimiz imiziing

Etc Etchant

Economy

In PCB etching on an industrial scale, the following are the various desirable features which, in practice, can only be partially fulfilled: •

High etching speed;

•

High High copp copper er diss dissol olvi ving ng capa capaci city ty;;

•

No atta attack ck on the the re resi sist stss use sed d;

•

Constan tant etchin ing g sp speeed;

•

Easy Easy disp dispos osal al of sp spen entt etch etchan antt or by by-pr -prod oduc ucts; ts;

•

Littl ittlee toxi toxici city ty an and d fume fumes; s;

•

Easy regeneration;

•

Low cost costss fo forr ch chem emic ical als; s; an and d

•

Littl Littlee po postst-et etch ch clea cleani ning ng re requ quire ireme ment nts, s, etc. etc.

The response to this challenge in terms of equipment selection, and the availability of  conveyorized spray etching machines is now considered as a standard approach.

 

Problems in Etching The etching process is one of the most important steps in PCB fabrication. It looks simple, but, in practice, several problems are encountered during this stage, which affect the quality of the final boards, especially in the production of fine line and high  precision PCBs. The two commonly encountered problems are under-etching and overhang.

Under-etching or Under-cut During the etching process, it is expected that the etching would progress vertically. However, corrosive action of the etchant works in all directions, and in practice, there is usually an etching action sideways which attacks the pattern below the etch resist. Sidee corros Sid corrosion ion is promot promoted ed by the moveme movement nt of the liquid and the dissoluti dissolution on of  copper takes place gradually. The final wall of the conductor becomes an inclined line instead of a vertical one at one end. This can lead to a considerable reduction of  conductor line widths. The simplest approach to minimize under-etching is by keeping the etching time as short as possible. This is achieved by using fast working etchant and exercising exact control on the etching time. PCB after soaking, with all but one layer of paper peeled off:

Rub the remaining paper off , with thumb pressure (or a toothbrush or other soft  brush). It's ok to rub fairly hard. But your thumbs' skin may get sore. Usually, almost all of the paper residue residue comes off, even off of the toner itself itself.. You could could see if there were any pinholes, etc, in the toner.

 

PCB after final soak, with most of the paper rubbed off:

PCB after removing enough paper; ready for etching:

Rinse the board and wipe the board dry with a clean paper towel.

III. Guided Practice Self-Test Activity 1

Direction: Enumerate the five etching solutions. 1. 2. 3. 4. 5.

____ ________ ________ ________ _______ ___ ____ ________ ________ ________ _______ ___ ____ ________ ________ ________ _______ ___ ____ ________ ________ ________ _______ ___ ____ ________ ________ ________ _______ ___

 

IV  Independent Practice Activity no. 2 Title: Etching Etching Method and equipme equipment nt Direction: Write the following method and equipment. Etching Method

 

Equipment and Techniques of Etching

1.___________ 

1. ________ ____________  ____ 

2.___________ 

2. ________ ____________  ____ 

3.___________ 

3. ________ ____________  ____  4. ________ ____________  ____  5. ________ ____________  ____ 

V   Assessment What is etching?

VI.  Answer key Activity 1 1. 2. 3. 4. 5.

Ferric chloride chloride Ammonium persulphate; Chromi Chromicc acid; acid; Cupri Cupricc chloride; chloride; and Alkalin Alkaline e ammonia. ammonia.

VII Reference Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM Writer: Benju Benjunly nly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  Contact information: [email protected] information:  [email protected]

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 QUARTER 4 WEEK 8 LEARNING LEARN ING ACTIVITY ACTIVITY SHEET SHEET NO. 8 Cutting and Drilling Name of Learner :______________________________ :________________________________ __ Section:_____________ Section:______________  _  School :___________ :______________________ ______________________ ___________________ ________ Date : ______________  ______________ 

I.  Learning Competency:   Drill Drill thruthru-hole hole . Code: TLE_IAEPAS9- 12AEP-IVb-c-2 II. Key Concept

Mechanical Operation Mechanical operation in an important when fabricating PCB, The PCB fabrication  process involves a number of mechanical operations to prepare the circuit boards for  the chemical processes of image transfer, plating, and etching. The process starts with the acquisition of laminate sheets which may be as big as 2 m ¥ 2 m or bigger. Therefore, the mechanical process such as cutting to size, drilling holes and shaping  play an important role in the final quality of the printed circuit board. Unlikee othe Unlik otherr PCB PCB pr proc ocess essin ing g steps steps,, most most of th thee mech mechan anica icall op oper erati ation onss re requ quir iree considerable manual handling of the board. Such operations do not form part of the transfer-line equipment, and would therefore, have a major impact on the costing of  the final product. Each mechanical operation has its own set of requirements in terms of tolerance and accuracy. In general, tolerances should be made as narrow as they are functionally really needed. Proper choice of tools and their sharpness are very important in each of  the mechanical operations for obtaining an acceptable machining finish. Blunt and du dull ll to tool olss resu result lt in ch chip ippi ping ng be beca caus usee of re resin sin br britt ittlen leness ess of th thee lamin laminat ate. e. Prop Proper  er  application of machining forces must be kept low. Excessive machining forces may ca caus usee pa part rtial ial de de-l -lam amin inati ation on be becau cause se of th thee in inhe here rent nt la lamin minate ate struc structu ture re,, th ther ereb eby y weakening the interlaminar bond strength. A good knowledge of the base material compos com positio ition, n, equipm equipment ent and tools tools comple complemen mented ted with with go good od operato operatorr habits habits can facilitate good mechanical operations resulting in higher quality PCB yield.

 

Cutting Method 1. Shear Shearing ing 2. Sawing Sawing 3. Blank Blanking ing 4. Milling 5. Hole Punching Punching 6. Drilli Drilling ng

1. Shearing

Shearing is perhaps the first mechanical operation carried out on PCBs to give them  proper shape or contour. It is basically a cutting method applicable to all kinds of base materials, generally of less than 2 mm thickness. When cutting boards have more than 2 mm thickness, shearing results in the edge finish which is coarse and unclean, and therefore, the method becomes unacceptable. Laminate Lamina te cuttin cutting g by shearin shearing g can be done done either either by manual manually ly operate operated d or motormotordriven dri ven machin machines. es. Both Both types types howeve however, r, have have common common constru constructio ctional nal feature features. s. A shea sheari ring ng mach machin inee norm normal ally ly has has an adju adjust stab able le se sett of sh shea earr bl blad ades es as sh show own n in Figure10.1. The blades are of rectangular shape. The lower blade has a free angle of  about 7°. The cutting length capability is available up to 1000 mm. The lengthwise angle ang le betwee between n the blades blades is general generally ly preferr preferred ed betwee between n 1–1.5° 1–1.5°,, thoug though h for glass glass epoxy materials, upto 4° can be used. The clearance between the cutting edges of the two blades should be limited to less than 0.25 mm. The angle between the shear blades depends upon the thickness of the material to be cut. The thicker the material, the greater will be the angle. If the shear angle is too high or the gap between the plates is too wide, feathered cracks appear while cutting  paper base materials. However, in case of glass epoxy laminates, even though cracks do no nott de deve velo lop p du duee to flexu flexura rall str stren engt gth h of th thee mater materia ial, l, th thee mate materia riall do does es show show de defo form rmati ation on if th thee sh shea eari ring ng an angl glee is to too o wi wide de or th thee bl blad adee ga gap p is to too o large large.. For  For  obtaining a clean edge finish in paper base materials by shearing, heating the material in the range of 30–100 °C is helpful. In order to obtain a clean cut, the board must be firmly pressed down with a springloaded holddown device to prevent the otherwise unavoidable shifting of the board during shearing. Also, parallax errors which may result in errors upto 0.3–0.5 mm, should be minimized and precision stoppers should be used for alignment of the corner marks. Shearing machines are available to handle jobs of various sizes and to offer accurate dimensional dimens ional reproducibility reproducibility.. There are larger machines which can cut several hundred hundred kilograms kilog rams of base material per hour. hour.

 

2. Sawing

Sawing offers another method of cutting the laminates. The method is preferred as it gives giv es a smothe smotherr edge edge finish finish and clean cut, cut, thoug though h the dimens dimension ional al tolera tolerances nces are similar (0.3-0.5 (0.3-0.5 mm) to that of shearing. In the PCB industry, mostly circular sawing machines of the moving table type are  preferred. The saw blade speed is adjustable between 2000-6000 rpm. But once set, the cutting speed should not vary. This is achieved by using heavy pulleys with more than one V-belt. High speed steel blades with a diameter of approximately 3000 mm are used at a speed of 20003000 rpm for paper phenolic materials. They are about 1.2-1.5 tooth per  cm circumference circumference.. For glass epoxy laminates, laminates, tungsten carbide tipped blades are used. Forr sti Fo still ll be bette tterr pe perf rfor orma manc nce, e, diam diamon ond d whee wheels ls ar aree pr pref eferr erred ed.. Al Alth thou ough gh th they ey may may require higher initial investment, they help in future savings due to their long life and improved edge finish. Sawing Machine Precaution

1. The precision precision of the bearing bearingss has a direct impact on the the edge finish. finish. Check the the  bearings for tightness. t ightness. No play should be perceptible when inspected i nspected by hand. 2. For safety, safety, the blade blade should always always be covered covered by a suitable suitable guard guard device. device. 3. The alignment alignment of the the arbor and the the motor mountin mounting g should should be correct. correct. 4. The The clea cleara ranc ncee betw betwee een n the the saw saw blad bladee an and d be benc nch h sh shou ould ld be mini minimu mum m to  provide a good support to the board for the cutting edge. 5. The circula circularr saw should should be so adjusted adjusted that the free height height of the blade blade above above the boards should be in the range of 10-15 mm. 6. A blunt or badly badly sharpene sharpened d blade and too coarse coarse teething teething can result result in a bad edge finish. Proper Proper care should be taken to avoid them. 7. An incorre incorrect ct feed rate can lead to a bad edge edge finish. finish. Adjust Adjust it proper properly. ly. Thick  Thick  materials need a lower feed rate while thin materials can be cut faster. 8. Manufacturer’ Manufacturer’ss recommendation recommendationss pertaining pertaining to speed should be followed. followed. 9. If the saw has a thin blade, blade, a stiffening stiffening collar collar is used to reduce reduce vibration. vibration. 3. Blanking of PCBs

When PCBs When PCBs ar aree de desig signe ned d to ha have ve sh shap apes es othe otherr th than an re rect ctan angu gular lar or ha have ve an od odd d contour, the use of a blanking die is a faster and more economical method. Blanking  basically consists of a clean cutting operation done with a punching tool rather than with a saw or a shearing machine. In some cases, even hole punching and blanking are done with the tool in the same operation. However, when a superior edge finish or  a tight dimensional tolerance is required, blanking may not fully serve the purpose. In PCBs, blanking is very well adopted on paper-based laminates but rarely on glass

 

epoxy laminates. Blanking helps to achieve PCB dimensions within a tolerance of ± (0.1 – 0.2 mm). Blanking Blanki ng a PaperPaper-bas based ed Lamina Laminate te Since Since paper-b paper-based ased lamina laminate te materia materiall is soft soft as compared to glass epoxy laminate, it is a more suitable laminate for blanking. While designing a blanking tool for a paper-based laminate, the resilience or yield of the materia mate riall is taken taken into consider consideratio ation. n. The blank blanked ed part part will will be, in general general,, slightl slightly y larger than the die which produced it because the paper-based laminate tends to spring  back. Hence, the die is made slightly under-sized compared to the print size to compensate for the over-sizing, depending upon the tolerance and the thickness of the  base material. It may be noted that when a hole punching is done, the die is over-sized, whereass when blanking wherea blanking is done, done, the die is under-sized under-sized.. 4. Milling

Milling is a commonly used operation which can be applied for the clean cutting of  PCBs and for obtaining obtaining good edge finish and overall overall dimensions with a high degree of  accuracy. The generally used cutting speeds are in the range of 1000-3000 rpm. They us usua ually lly empl employ oy str strai aigh ghtt or spira spirall to toot oth h HSS HSS (h (hig igh h spee speed d steel steel)) milli milling ng cu cutte tters rs.. However, in the case of glass epoxy laminates, the use of tungsten carbide tools is  preferred due to their long life. In order to avoid de-lamination, the PCB must be given given stron strong g su supp ppor ortt wi with th ba back ckin ing g plate platess du duri ring ng milli milling ng.. For For de detai tails ls of milli milling ng machines, tools and other operational aspects, standard texts on workshop or machine shop equipment may be consulted. Routing of PCBs For ob For obta tain inin ing g su supe perio riorr ed edge ge finish finish an and d high higher er di dime mens nsio iona nall ac accu curac racy y th than an th that at obtainable from shearing or sawing, especially for PCBs with odd contours, routing  becomes a method of choice. The dimensional tolerances within ± (0.1-0.2) mm can  be achieved with a much lower cost than blanking. Therefore, in some cases, blanking with slight over-size over-size is applied applied followed by routing to get a smooth surface finish. The use of present day multi-spindle machines especially ensures that the routing is much faster, and that both the labor cost and total cost much less than that entailed while making a blanking die. the only blanking method that is capable of providing an acceptable quality of boards. When the board has traces close to the board edge, routing is perhaps Routing is basically a machining process similar to milling but done at a much higher  cutter speed and feed rate. In this method, the boards are moved past a vertical side mill with the aid of a routing jig. The routing jig is guided in relation to the mill by holding it against a bushing which is concentric with the mill. The positioning of the PCB on the routing routing jig is determined by the material material registration holes.

 

There are three basic routing systems available. They are: a. Pin routin routing; g;  b. Tracer or stylus s tylus routing; and

c.   NC routing. 5. Hole Punching Punching of holes into PCBs is also one of the machining operations like hole drilling. However, the hole diametrical accuracy, hole wall finish and pad de-lamination from the base material are not as good in case of hole punching as compared to drilling. In general, large holes are easier to punch than small holes. For example, failure in holes made by punching below 0.9 mm for paper-reinforced laminates and 1.2 mm for glass cloth-reinfo clothreinforced rced laminates are quite common. common. So, punching punching is used in the high volume volume  production of consumer type PCBs made of paper phenolic and paper epoxy lamin lam inat ates. es. The The othe otherr disad disadva vant ntag ages es of pu punc nchi hing ng ar aree th thee pa pad d de de-la -lami mina natio tion n an and d laminate cracks on adjacent holes. In addition, punching results in holes of conical shape and rather rough surface. They are thus not compatible with the professional PCB plated through-hole process where high surface smoothness is desirable. Along with the above laminations, hole punching also has some advantages. They are: a. Low operatio operation n cost because because a large large number number of holes holes can be punched punched simultaneously;  b. Very high production rate; and c. High accuracy accuracy and repeatabili repeatability ty of the hole hole position. position.

6. Drilling Drill rillin ing g opera perati tio on is one one of the the impo import rtan antt mecha echan nic ical al pr pro oce cess sses es in th thee manufa man ufactu cture re of printe printed d circui circuitt boards boards.. Its purpos purposee is two fold: (i) To provid providee compon com ponent ent lead lead mountin mounting g precise precisely ly and with with structu structural ral integr integrity ity,, and (ii) To establish establi sh an electri electrical cal interco interconne nnectio ction n between between the top, top, bottom bottom and sometim sometimes es intermediate conductor pathways. After the drilling process, the drilled circuit board undergoes various processes likee platin lik plating, g, imagin imaging, g, etchin etching g and solder solder platin plating. g. Therefo Therefore, re, care is needed needed to ob obta tain in a go good od su surf rface ace on th thee dr drill illed ed ho hole le an and d he henc ncee its qu qual ality ity as assu sume mess gr grea eatt significance. The quality of a drilled hole depends upon various factors such as the quality of the laminate and drills, processes including machine accuracy, drilling techniques and operator skill in control and evaluation of hole quality and drill  bits hole and hence its quality assumes great significance. The quality of a drilled hole depends upon various factors such as the quality of the laminate and drills,  processes including machine accuracy, drilling techniques and operator skill in control contr ol and evaluation evaluation of hole quality and drill bits.

 

Requirements Require ments of Drilling A good drilling technique must satisfy the following conditions: 1. Consistent Consistent high quality; quality; 2. 3. 4. 5.

Perfect through-h through-hole ole plating; plating; Smaller diameter diameter,, shorter shorter distance distance between between the holes; holes; Greater production production;; and Lower Lower cost and simple simple storekeeping storekeeping..

Drilling Machines Drilling machines are of two types: 1. Manually Manually contro controlled lled machines; machines; and and 2. Numerical Numerical controlled controlled machines. machines. Small quantities of PCBs can be drilled using single head manually controlled machines machin es while while large large volume volumess of PCBs PCBs usually usually requir requiree numeri numerical cal contro controlle lled d drilling machines. The selection of drilling machines depends upon their speed, capacity, accuracy and cost. Manual machines require an operator to position the work piece and initiate the drilling cycle. In Computer Numerical Control (CNC) machines, both  positioning and drilling cycles are controlled by inputs from the computers.

Manually Controlled Machines The PCB or work piece is positioned for drilling in a manual machine by one of  the following two methods: a) Direct sight method; and b) Optical method. Both these methods require the hole location to be defined either by an artwork  overlap or reproduction of the circuit image on the board. Photo-resist is often used when the developed image is sufficient to locate the hole position and the  boards may be stacked or pinned for registration to the template, which is usually made of acrylic material. The stack can then be moved under a stylus controlled  by the operator. Direct Sight Bench Mount Drilling Machines This machine consists of a solid base frame and a column which supports the motor. mot or. For drillin drilling g applica application tions, s, the vertica verticall moveme movement nt of the drillin drilling g head head is controlled by a lever, which is located on the right side of the drill head. The move mo veme ment nt ca can n be lo lock cked ed by mean meanss of a small small ad addi ditio tiona nall lever lever.. The The spin spindl dlee rotation speed is continuously adjustable from 0-45000 rpm. Dust is collected by an exhaust vacuum system.

 

Optical Sight High Speed Drilling Machine This machine is an improvement over a direct sight drilling machine. The drilling spindle spind le whose speed ranges from 15,000 15,000 to 60,000 60,000 rpm is mounted underneath underneath the work table and fed from the bottom through a jig plate. The feed from the bottom and the clamping from the top are controlled and sequenced by a pneumatic time delay circuit. The complete sequence is affected by a foot pedal. The feed, time delay and rpm can be varied by accessing accessing the respective respective controls.

Numerically Controlled Machines In numerically controlled machines, the machine control logic is obtained from software. The computer is programmed to control the machine. The advantages of   NC machine are flexibility, versatility, repeatability and speed The drilling of  PCB production quantities with NC machines is normally done with a multi-head drillin dri lling g machin machine. e. A typica typicall set-up set-up would would includ includee machin machines es with two or more more heads, each simultaneously drilling a stack of cards. Dummy cards are placed at the top and bottom of each stack to ensure constancy of drilling. The numerically controlled drill automatically changes the drill adjustment, drill speed and feed rate rate,, an and d br brin ings gs th thee ca card rd stack stack to th thee co corr rrec ectt X-Y X-Y co co-o -ord rdin inate atess fo forr dr drill illin ing. g. A reco record rd rela relati ting ng to the the usag usagee of the the dr dril ills ls is main mainta tain ined ed so th that at th they ey ca can n be withdrawn withd rawn from service before before they show signs of wear, deteriorating deteriorating cutting edge and the possibility of causing burrs. Usually, smaller and inexpensive drills are discarded while the larger and expensive ones are re-sharpened.

Use of UV Laser Drilling Machines

Four types of lasers are currently in use for making PCB microvias: CO2, YAG, excimer and Cuvapour. CO2 lasers typically produce holes of around 75 mm, but the the be beam am re refl flect ectss ba back ck of offf co copp pper er an and d is th ther eref efor oree on only ly suite suited d fo forr re remo movi ving ng dielectric. CO2 lasers are very stable, inexpensive and maintenance-free.Excimer  lasers are the best for producing high quality, small features. Diameters below 10 mm are typical. The best application for these types is in drilling densely packed arrays in polyimide for use in microBGA devices. Cu-vapour lasers are still in their infancy, yet offer some advantages when high production rates are needed. Cu-v Cu -vap apou ourr ty types pes ca can n re remo move ve diel dielec ectri tricc an and d co copp pper, er, ye yett suff suffer er from from sever severee drawbacks that make their current use in a production environment prohibitive. The most The most po popu pula larr laser laser syste system m us used ed in th thee PCB PCB in indu dustr stry y is th thee Q-sw Q-switc itche hed d  Nd:YAG laser las er with a wavelength of 355 nm which is in the ultraviolet (UV) range. At this wavelength, most of the metals (Cu, Ni, Au, Ag) that are to be ablated in  printed circuit applications, show absorption rates of more than 50 per cent (Meier 

 

and Schmidt, 2002). Organic materials can also be accurately ablated. The high  photon energy of UV lasers at 3.5–7eV cracks the chemical bonding as the ablation process in the UV spectrum is partly photo-chemical and partly photother therma mal. l. Thes Thesee capa capabi bili liti ties es make make a UV la lase serr sy syst stem em th thee firs firstt ch choi oice ce fo for  r  applications in the printed circuit board industry.

Hybrid Laser Drillin Drilling g Proces Processs Two kind Two kindss of laser laser tech techno nolo logi gies es ar aree co comm mmer ercia cially lly av avail ailab able le as la laser ser dr drill illin ing g systems; CO2 laser with wavelength in the far infra-red region of the spectrum, and UV laser with wavelength in the ultraviolet region of the spectrum. The CO2 lasers are widely used for microvia formation in the PCB industry wherein the microvia design calls for larger vias, 100 mm in diameter (Raman, 2001). The CO2 CO 2 lase lasers rs have have high high pr prod oduc ucti tivi vity ty at th thes esee la larg rgee di diam amet eter er vi vias as.. The The hi high gh  productivity is due to the fact that the CO2 lasers can ‘punch’ large vias with very small drill times. The UV laser is widely used when the microvia design calls for  < 100 mm via diameters, with the roadmap shrinking to even smaller vias of < 50 mm diameter. The UV laser technology delivers very high productivity at < 80 mm vias. Therefore, given the everincreasing demand to improve productivity of  microvia formation, many manufacturers have started introducing dual head laser  drilling systems. Three major type of dual head laser drill.

1. Dual Dual head head UV laser laser system system;; 2. Dual head CO2 laser system; system; and 3. Hybrid Hybrid laser laser system system (UV (UV and and CO2). CO2). PCB after drilling

Drilled

 

III. Guided Guided Practice Practice

Self-Test Activity 1 Direction: Directio n: Give at least five cutting method. method. 1. _______________ _______________ 2. _______________ _______________ 3. _______________ _______________ 4. _______________ _______________ 5. _______________ _______________

IV. Independent Practice Activity no. 2

Title: Sawing Machine Precaution Direction Write at least five sawing machine precaution

1. _____________ __________________________ _________________________ ______________ __ 2. _________________________ _____________________________________ ________________ ____ 3. _________________________ _____________________________________ ________________ ____ 4. _________________________ _____________________________________ ________________ ____ 5._________________________ 5.______________ _______________________ ________________ ____

V. Assessme Assessment nt Direction:  Give the three major type of dual head laser drill.

1. 2. 3.

 

_____ ______ ___ ___ ____ ____ ____  __  _____ ______ ___ ___ ____ ____ ____  __  ________________ 

 

VI. Answer Answer key key Activity 1 1. Sheari Shearing ng 2. Sawing 3. Blanki Blanking ng 4 Milli Milling ng 5. Hole Punchi Punching ng 6. Drillin Drilling g

Activity 2 1. The precision of the bearings has a direct impact on the edge finish. Check  the bearings for tightness. No play should be perceptible when inspected by hand. 2. For safety, the blade should always always be covered by a suitable suitable guard device. 3. The alignment of the arbor and the motor mounting should be correct. 4. The clearance between the saw blade and bench should be minimum to  provide a good support to the board for the cutting edge. 5. The circular saw should be so adjusted that the free height of the blade above the boards should be in the range of 10-15 mm. 6. A blunt or badly sharpened blade and too coarse teething can result in a bad edge finish. Proper Proper care should be taken to avoid them. 7. An incorrect feed rate can lead to a bad edge finish. Adjust it properly. Thick materials need a lower feed rate while thin materials can be cut faster. 8. Manufacturer’s recommendations pertaining to speed should be followed. 9. If the saw has a thin blade, a stiffening collar is used to reduce vibration.

VII Reference Microsoft Encarta Premium By: Michael Antonoff  LCD CBLM Writer: Benju Benjunly nly P. Gengone Gengone School: Trento National High School Division: Agusan del Sur  Contact information: [email protected] information:  [email protected]

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 SUMMATIVE NO. 1

Direction:  Enumerate the following:

Five important design elements. 1. _________________ ____________________ ___ 2. _________________ ____________________ ___ 3. _________________ ____________________ ___ 4. _________________ ____________________ ___ 5. _________________ ____________________ ___

Ten type of pads. pads. 6. _____________ _____________ 7. _____________ _____________ 8. _____________ _____________ 9. _____________ _____________ 10. _____________ _____________ 11. _____________ _____________ 12. _____________ _____________ 13. _____________ _____________ 14. _____________ _____________ 15. _____________ _____________

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 SUMMATIVE NO. 2

Direction: Enumerate the following: Five chemical cleaning process. 6. ____ ________ ________ ________ ______ __ 7. .____ .________ ________ ________ _____ _ 8. ____ ________ ________ ________ ______ __ 9. .____ .________ ________ ________ _____ _ 10. ____________ __________________ ______

Five mechanical cleaning process. process. 6. ________________ ________________ 7. ________ 8. ________________ ________________ ________________ ________ 9. ________________ ________________ 10.________________

Five Pattern Transferring Technique. 6. ____________________  ____________________  7. ____________________  ____________________  8. ____________________  ____________________  9. ____________________  ____________________  10. ____________________  ____________________ 

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 SUMMATIVE NO. 3

Direction: Enumerate the following: Five electrochemic electrochemical al associated with electroplating. electroplating. 6. _____________  _____________  7. _____________  _____________  8. _____________  _____________  9. _____________  _____________  10. _____________  _____________  Two materials need in Image Transfer. Transfer. 11. _______________  _______________  _______________  12. __________ _____  Three Process of Image Transfer  13. _______________  _______________  14. _______________  _______________  15. _______________  _______________  Five etching solutions. 16. ___________________ ___________________ 17. ___________________ ___________________ 18. ___________________ ___________________ 14.___________________ 15.___________________

 

ELECTRONIC PRODUCT ASSEMBLY AND SERVICING NC II GRADE 11 SUMMATIVE NO. 4

Direction: Enumerate the following: Nine sawing machine precaution 1. ______________ ______________ 2. ______________ ______________ 3. ______________ ______________ 4. ______________ ______________ 5. ______________ ______________ 6. ______________ ______________ 7. _____________ _____________ 8. _____________ _____________ 9. _____________ _____________ Six cutting method 10. ____________ ____________ 11. ____________ ____________ 12. ____________ ____________ 13. ____________ ____________ 14. ____________ ____________ 15. ____________ ____________