Edited CBLM Epas

November 9, 2017 | Author: Celeste Licuanan Ching | Category: Printed Circuit Board, Etching, Drill, Electronics, Electricity
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module in electronic product assembly and servicing learning outcome number 2...

Description

ELECTRONIC PRODUCTS ASSEMBLY AND SERVICING NCII COMPETENCY-BASED LEARNING MATERIALS List of Competencies

No.

Unit of Competency

Module Title

Code

1

Assemble Electronic Products

Assembling Electronic Products

ELC724335

2

Service consumer electronic products and systems

Servicing consumer electronic products and systems

ELC724336

3

Service industrial electronic modules, products and systems

Servicing industrial electronic modules, products and systems

ELC724337

LEARNING OUTCOME # 2

PREPARE/MAKE PCB MODULE

CONTENTS: 1. Procedure in PCB Designing. 2. Procedure in PCB Layouting. 3. Procedure in PCB Etching 4. Procedure in PCB Drilling ASSESSMENT CRITERIA: 1. PCB layout is verified for conformity with the schematic diagram in accordance with the layout rules 2. PCB layout is transferred to copper-cladded board following acceptable CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 1 of 36

methods and standards 3. Visual inspection is performed based on standards procedures. 4. Thru-hole is drilled based on standards procedures 5. PCB is cleaned based on standards procedures 6. Functionality of PCB is tested and visual inspection is performed based on standards procedures CONDITION: Students/trainees must be provided with the following: 1. WORKPLACE LOCATION 2. EQUIPMENT - Desktop Computer - Laptop Computer - LCD Projector - Television - DVD player - Multitester (VOM) 3. TOOLS, ACCESSORIES AND SUPPLIES - White board - Set of screw drivers - Set of Pliers 4. TRAINING MATERIALS - Whiteboard marker - Ball pens - Log book/bond papers - Information sheet - Task sheet - Assembled variable regulated power supply. ASSESSMENT METHOD:  Written examination  Demonstration  Interview  Portfolio. Learning Guide Learning Outcome 2 PREPARE/MAKE PCB MODULE CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 2 of 36

Learning Steps

Special Instructions/References

Read the information sheet 1.2-1 on Procedure in PCB designing Answer Self-check 1.2-1 on Procedure in PCB designing. Compare to answer key 1.2-1. Perform activity sheet 1.2-1 Evaluate students’ performance using performance checklist 1.2-1 Read the information sheet 1.2-2 Procedure in PCB lay outing Answer Self-check 1.2-2 on Procedure in PCB lay outing

Read Information Sheet and answer the self-check. After answering, compare your answer from the answer key. Perform the activity required in the task sheet and evaluate your work according to the performance criteria checklist. Make the necessary corrections or improvements. Secure the evaluation of the trainer and let him/her record your accomplishment.

Compare to answer key 1.2-2 Perform activity sheet 1.2-2 Evaluate students’ performance using performance checklist 1.2-2 Read the information sheet 1.2-3 Procedure in PCB Etching Answer Self-check 1.2-3 on Procedure in PCB Etching Compare to answer key 1.2-3 Perform activity sheet 1.2-3 Evaluate students’ performance using performance checklist 1.2-3 Read the information sheet 1.2-4 Procedure in PCB drilling

CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 3 of 36

Answer Self-check 1.2-4 on Procedure in PCB drilling Compare to answer key 1.2-4 Perform activity sheet 1.2-4 Evaluate students’ performance using performance checklist 1.2-4

CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 4 of 36

Information Sheet 1.2.1 CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 5 of 36

Procedure in PCB Designing Learning Objectives: After reading this INFORMATION SHEET, YOU MUST be able to: 1. Acquire knowledge how to design printed circuit board. 2. Perform Printed circuit board designing using the circuit diagram of variable regulated AC/DC power supply. 3. Understand the importance of printed circuit board designing in making PCB module

A printed circuit board (PCB) has components inserted into the hole and soldered to form its circuit connection. Its main purpose is to reduce the space and to troubleshoot easily when problem arises. The printed circuit board (PCB) has conductors that are thin strip of copper, usually bonded to a baseboard called substrate. There are two very common substrate materials used in printed circuit, the phenolic and epoxy plastic.

Copper Substrat e Printed Circuit Board In PCB designing, we should not focus only on the size of the pathways linking to the other component, but also on the types, kinds, and characteristics of component. Here are the other design factors needed: 1. PCB size and shape. The PCB must be big enough for the entire component to be mounted where it is anticipated. CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 6 of 36

2. Position of the Terminal. Input, output and supply voltage if possible should be placed near the border for easier way during troubleshooting or minor repair. 3. High Temperature Dissipation. Too much heat is the number one problem of all components. Bigger space is needed so that heat sink can be provided to the component. This will protect the component from burning up. 4. Accessibility of Components. This component that is adjustable or variable (example: potentiometer, trimmer resistor or capacitor) should be placed near the border to make the troubleshooting or minor repair easier. 5. Space for Bolt and Nut. The designer should place an allowance for mounting the PCB with bolt and nut in securing the entire board to the chassis. 6. Different Types of Circuit Should be grouped according to its Application. This will enhance the circuit operation and will prevent it from distortion generated by other circuit. This is the reason why the circuit of the power supply is far from the audio circuit.

Procedure in PCB designing

1. Prepare the tools and materials needed in lay outing and designing a PCB

Tools and materials needed:  Ruler CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

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 Utility cutter  Permanent marker  Pencil and Eraser  Graphing paper and a piece of bond paper (short)  Masking Tape

2. Prepare the schematic diagram of the circuit.

Schematic diagram of Variable regulated AC/DC power supply

3. Make the PCB design. Arrange the components terminals on a graphing paper or a piece of paper to show/illustrate the interconnection of the components based on the schematic diagram given.

CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 8 of 36

Example position of the pads or terminals of the components

4. Interconnect the traces to the pads/terminals of the components depending on the connections of the components to one another. Make sure that the traces will be the same as the connection of the schematic diagram.

5. Finalized your design with the actual size of the component, terminals and size of the PCB (1 ½ ” x 2”) to check the spacing of the components. It should not be on top of the other components.

6. Let your work check by the trainer.

CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 9 of 36

SELF-CHECK 1.2-1 Direction: Identify the following items. 1. A board that is open mounted and soldered.

with

electronic

components

is

2. A conductor where the component’s terminal lead is soldered. 3. It consists of a thin copper layer which is firmly bonded to an insulating base material. It is sometimes called as a component side. 4 -5. The two types of substrate materials used in a present circuit.

CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 10 of 36

ANSWER KEY 1. 2-1

1. 2. 3. 4. 5.

PCB Substrate Copper foil side Epoxy Phenolic

CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

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ACTIVITY SHEET 1.2-1 Title: Procedure in PCB Designing Performance Objective: Given the ACTIVITY SHEET 1.2-1, you should be able to perform procedure in PCB designing for variable regulated AC/DC power supply circuit diagram Supplies/Materials : Activity Sheet 1.2-1, piece of paper pencil or ball pen, circuit diagram of variable regulated AC/DC power supply Equipment

:

N/A

Steps/Procedure: Procedure in PCB designing 1.

Prepare the tools and materials needed in lay outing and designing a PCB

     

Tools and materials needed: Ruler Utility cutter Permanent marker Pencil and Eraser Graphing paper and a piece of bond paper (short) Masking Tape

Prepare the schematic diagram of the circuit. 3. Make the PCB design. Arrange the components terminals on a graphing paper or a piece of paper to show/illustrate the interconnection of the components based on the schematic diagram given. 4. Interconnect the traces to the pads/terminals of the components depending on the connections of the components to one another. Make sure that the traces will be the same as the connection of the schematic diagram. 5. Finalized your design with the actual size of the component, terminals and size of the PCB (1 ½ ” x 2”) to check the spacing of the components. It should not be on top of the other components. 6. Let your work by the trainer. Date Developed: CBLM check on Document No. 1 7. Discuss Electronic your answers with the trainer Issued by: Page 12 of 8. Apply theProducts safety precautions following theCMRHS OH&S policies 36 and Assembly and Procedures Developed By: Revision No. 0 Servicing NCII Assessment Method: Ariel M. Medina 2.

(Assemble

Electronic Products)

Written - Oral Questioning Performance Criteria checklist

Performance criteria checklist 1.2-1 CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

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CRITERIA

Did you…. 1. Interconnect base on the schematic diagram?

YES

NO

2. Used appropriate tools and materials in PCB designing? 3. Position the terminals not overlapping to each components? 4. Used correct PCB size? 5. Position the terminal of the input , output and auxialliary components accessible? 6. Provide space for the bolts and nuts? 7. Provide proper grounding on your design?

CBLM on

Electronic Products Assembly and Servicing NCII

Date Developed:

CMRHS Developed By: Ariel M. Medina

(Assemble

Electronic Products)

Document No. 1 Issued by: Revision No. 0

Page 14 of 36

INFORMATION SHEET 1.2-2 Procedure in PCB Layouting Learning Objectives: After reading this INFORMATION SHEET, YOU MUST be able to: 1. Acquire knowledge how to layout printed circuit board. 2. Perform Printed circuit board layout using the circuit diagram of variable regulated AC/DC power supply. 3. Understand the importance of printed circuit board layout in making PCB module In every electronic activity specially PCB layout can be performed (using CAD ) or in combination with an Autorouter, The results are usually still achieved using at least some manual routing – simply because the design engineer has a far better judgement of how arrange circuitry.Surprisingly, many autorouted boards are often illogical in track routing – the program has optimized the connections an sacrificed any small amount of order that may have been put in place by manual routing. Generally autorouted boards are somewhat harder for a technician to repair debug; for this reason. Historically, PCBs used to be laid out by using stick on paper shapes and ape on mylar drafting film, - that really WAS manual routing. Procedure in Lay outing 1. Using a permanent marker, art transfer or masking tape for layout the design on the PCB. Follow the procedure on how to trace the path of the connection traces from the schematic diagram.

2. Be wise on positioning the terminals or the pads of the components and avoid shorting the traces of the connections.

3. Double check your design, make sure that all of the connections are the same as the connections on the schematic diagram.

4. Make sure that the components size are seized so the components will not be on top of the other in mounting procedure.

5. Let your trainer check your design work before the etching process. SELF – CHECK 1.2- 2 Direction : Answer the following questions and write your answers in separate sheet of paper. 1. What should be consider in PCB layout? 2. This will protect the component from burning up? 3. The _______ layout must be accessible to all Components? 4. The layout should place an allowance for mounting the PCB? 5. What do you call the status where excessive heat is the number one problem of all components?

ANSWER KEY 1.2-2 1. Size 2. Space 3. PCB 4. Bolts and Nuts 5. High Temperature Dissipation

ACTIVITY SHEET 1.2-2 Title: Procedure in PCB Layouting Performance Objective: Given the ACTIVITY SHEET 1.2-2, you should be able to perform procedure in PCB lay outing for variable regulated AC/DC power supply circuit diagram Supplies/Materials : Activity Sheet 1.2-2, piece of paper pencil or ball pen, circuit diagram of variable regulated AC/DC power supply Equipment

:

N/A

Steps/Procedure: Procedure in PCB Layouting

1. 1 Using a permanent marker, art transfer or masking tape for layout the design on the PCB. Follow the procedure on how to trace the path of the connection traces from the schematic diagram. 1. 2 Be wise on positioning the terminals or the pads of the components and avoid shorting the traces of the connections. 1. 3 Double check your design, make sure that all of the connections are the same as the connections on the schematic diagram. 1. 4 Make sure that the components size are seized so the components will not be on top of the other in mounting procedure. 1. 5 Let your trainer check your design work before the etching process.

Assessment Method: Written - Oral Questioning Performance Criteria checklist

Performance Criteria Checklist 1.2-2 Did you.... YES 1. Finalized your layout with the actual size of the component, terminals and size of the PCB? 2. use appropriate materials in layouting your design on the PCB? 3. position the terminals or the pads of the components to avoid shorting the traces of the connections? 4. Double check your Layout or make sure that all of the connections are the same as the connections on the schematic diagram? 5. measure the actual size of the component so it will not be on top of each other?

INFORMATION SHEET 1.2-3 Procedure in PCB ETCHING

NO

Learning Objectives: After reading this INFORMATION SHEET, YOU MUST be able to: Acquire knowledge how to etch printed circuit board. 2. Perform Printed circuit board etching using the materials needed in PCB etching. 3. Understand the importance of printed circuit board etching in making PCB module 1.

Printed Circuit Board Etching is where the excess copper is removed to leave the individual tracks or traces as they are sometimes called. Buckets, bubble tanks, and spray machines are tools to do different ways of etching but most firms currently use high pressure conveyors spray equipment. Spray etching is fast Ammoniacal etching solutions when sprayed can etch 55 microns of copper a minute. Less than 40 seconds to etch a standard 1 oz, 35 micron circuit board.

Many different chemical solutions can be used to etch circuit boards ranging from slow controlled speed etches used for surface preparation to the faster etches used for etching the tracks. Some are best used in horizontal spray process equipment while others are best used in tanks. Enchants for PTH work have to be selective and be nonaggressive to tin / tin lead plating, which is used as the etch resists. Copper etching is normally exothermic where high speed etching is carried out solution cooling is normally required. This is normally done by placing titanium water cooling coils into the enchant. Almost all etching solutions liberate toxic corrosive fumes. Extraction is highly recommended. All enchants are corrosive and toxic mainly due to the high metal content. P.P.E. Personal Protection Equipment must always be used. Spent solutions should always be disposed properly and not to be spilled down local drains where they can pollute local sewage works and rivers. Printed Circuit Board Etching

It is the removal of unwanted portion materials (that is copper) bonded to an substrate. By using a chemical reaction to chloride, it liquefies the uncovered surfaces clad board that creates a PCB.

or layer of conductive insulating base called the copper called ferric of the designed copper

Tools and Materials Needed In PCB Etching 1. Designed PCB 2. A bottle of the Ferric Chloride. (The quantity of bottle will depend upon the area of the PCB). 3. Plastic Basin. It is the medium of ferric chloride 4. Popsicle sticks (2 pieces). It is used for hauling the designed PCB. 5. Old newspaper. It is placed under the plastic basin for the prevention of accidental spill of chemical over the table. 6. Apron 7. Piece of Cloth 8. Plastic Varnish 1 bottle 9. Lacquer Thinner 10. Surgical Gloves 11. Knife or Cutter PROCEDURE IN PCB ETCHING

1. Prepare the necessary tools and materials needed in PCB etching. 2. Wear your apron and surgical gloves in order to prevent accidental splash of the solution on your clothes or on your skin.

3. Pour the ferric chloride in the plastic basin.

Ferric chloride

4. Etch the PCB by immersing it in a basin filled with ferric chloride until the uncovered part of the copper clad is totally etched.

Immerse PCB in plastic basin filled with ferric chloride

5. After 10 - 15 minutes, check the PCB if all the parts needed

to be removed are totally etched (using the two Popsicle sticks in hauling). If not yet, return it into the plastic basin filled with ferric chloride. After 3 - 5 minutes check it again.

6. Haul the PCB from the plastic basin and wash it in a free flowing water to remove the remaining residue in the PCB.

PCB Basin

7. With a clean and dry piece of cloth, wipe the wet PCB. 8. Pour a little amount of lacquer thinner on a clean dry piece of cloth and wipe the markings of the permanent marker pen in the copper clad. (Note: In doing this, you should wear your surgical gloves.)

9. Aided by bright light, inspect the PCB for possible hairline break or short. If there is a hairline path between the copper conductors, cut it by a knife or cutter. And if there is a break between the copper conductors, solder it.

PCB

Light

10.

Apply plastic varnish to the newly etched PCB to prevent corrosion or rust, and let it dry before touching it.

Techniques to correct PCB Hairline Break or Short A. Hairline Break. It is an open copper foil in the Printed Circuit Board. Most of the time this is due to improper PCB designing or etching. To eliminate the hairline break, just place a hook up wire and solder it.

Hairline Break B. Hairline Short in the PCB Conductor. It arises if the printed circuit board designing or etching is done improperly. To eliminate the hairline short, you should cut it with a knife.

Hairline Short in the PCB Conductor

SELF CHECK 1.2-3 Procedure in PCB ETCHING Direction : Answer the following questions and write your answers in separate sheet of paper, 1. What is the method called by removing unwanted copper in the PCB?

2. What material is used, that protects parts of the laminate from the acid and leaves the desired copper layer untouched? 3. At least how many minutes the PCB is in the basin with acid? 4. What is the chemical solution use in PCB Etching? 5. What are the safety equipment and use when we do the process of etching?

ANSWER KEY 1.2-3 1. Etching 2. Masking tape

3. 20 minutes 4. Ferric Chloride 5. Goggles, mask, gloves , apron

ACTIVITY SHEET 1.2-3 Title: Procedure in PCB Etching Performance Objective: Given the ACTIVITY SHEET 1.2-3, you should be able to perform procedure in PCB Etching for variable regulated AC/DC power supply circuit diagram Supplies/Materials : Activity Sheet 1.2-3, ferric chloride, basin, designed PCB, rags, water, popsicle stick, newspaper, utility cutter and PPE. Equipment

:

N/A

Steps/Procedure: Procedure in PCB Etching 1. Prepare the necessary tools and materials needed in PCB etching. 2. Wear your apron and surgical gloves in order to prevent accidental splash of the solution on your clothes or on your skin. 3. Pour the ferric chloride in the plastic basin 4. Etch the PCB by immersing it in a basin filled with ferric chloride until the uncovered part of the copper clad is totally etched. 5. After 10 - 15 minutes, check the PCB if all the parts needed to be removed are totally etched (using the two Popsicle sticks in hauling). If not yet, return it into the plastic basin filled with ferric chloride. After 3 - 5 minutes check it again. 6. Haul the PCB from the plastic basin and wash it in a free flowing water to remove the remaining residue in the PCB. 7. With a clean and dry piece of cloth, wipe the wet PCB. 8. Pour a little amount of lacquer thinner on a clean dry piece of cloth and wipe the markings of the permanent marker pen in the copper clad. (Note: In doing this, you should wear your surgical gloves.) 9.

Aided by bright light, inspect the PCB for possible hairline break or short. If there is a hairline path between the copper conductors, cut it by a knife or

Performance Criteria Checklist 1.2-3 Did you....

Yes

1. Use appropriate PPE while performing the etching activity? 2. Etch your designed PCB following the procedure correctly? 3. Fix any hairline short or hairline break on your PCB? 4. Apply proper safety precaution while performing the activity? 5. Use appropriate tools while performing the activity?

INFORMATION SHEET 1.2-3

No

Procedure in Drilling Learning Objectives: After reading this INFORMATION SHEET, YOU MUST be able to: 1. Acquire knowledge how to drill printed circuit board. 2. Perform Printed circuit board drill using the Mini – drill. 3. Understand the importance of printed circuit board drill in making PCB module Drilling is a cutting process that uses a drill beat to cut a hole of circular cross section in solid material, the drill beat is rotary cutting tools, often multi point, the beat is pressed against the work piece and rotated at rates from hundreds to thousands of revolution per minute. This forces the cutting edge against the work piece, cutting off chips (swarf) from the hole as it is drilled. Exceptionally, specially-shaped bits can cut holes of non-circular crosssection; a square cross-section is possible,

How to set – up Mini Drill 1. Loosen the chuck by using a long metal tool and change the drill bit. This is done in a counter clockwise movement.

Drill Bit Long Metal Mini Drill

2. Insert the drill bit 1mm diameter in size and attach it to the chuck of the unit. 3. Turn the long metal tool clockwise to tighten the jaw of the unit. Be sure that the drill bit is well secured on the chuck. 4. Before inserting the 12 volts adaptor, you should turn off the unit.

5. Test the rotation of the unit if it is well aligned. If not, align it following the steps no. 1 and 2. How to Use a Mini Drill To control the unit, hold the mini - drill at the lower part and firmly position your arm. Then with the mini drill held perpendicularly to your work surface, lightly press downward to the holes to be drilled in the PCB but be sure that the PCB has a piece of wood under it to avoid damaging the table. With practice, you will be able to get the procedure correctly. MINI DRILL PCB

PIECE OF WOOD

PROCEDURE IN DRILLING 1. Prepare all the materials needed. Mini drill -

Designed etched PCB

2. Mark where the holes are to be drilled. 3. Using the mini drill, bore hole perpendicularly to the surface of the PCB. 4. Clean the surface of the PCB and look for open line or short circuit. 5. Apply varnish on the clad surface to prevent it from corrosion.

SELF CHECK 1.2-4 Direction : Answer the following questions and write your answers in separate sheet of paper. 1. 2. 3. 4. 5.

What is the material use in PCB drilling? What do you called the process of cutting using the drill beat? Mark where the __________ are to be drilled? What should be the position of the hole to the surface of the PCB? What liquid form is used to prevent it from corrosion?

Answer Key 1.2-4 1. 2. 3. 4. 5.

PCB Drilling Hole Perpendicularly Varnish

ACTIVITY SHEET 1.2-4 Title: Procedure in PCB Drilling Performance Objective: Given the ACTIVITY SHEET 1.2-4, you should be able to perform procedure in PCB Drilling for variable regulated AC/DC power supply circuit diagram Supplies/Materials : Activity Sheet 1.2-4, 12v Mini Drill designed etched PCB, and PPE. Equipment

:

N/A

Steps/Procedure: Procedure in PCB Drilling 1. Prepare all the materials needed. Mini drill Designed etched PCB 2. Mark where the holes are to be drilled. 3.

Using the mini drill, bore hole perpendicularly to the surface of the PCB.

4.

Clean the surface of the PCB and look for open line or short circuit.

5.

Apply varnish on the clad surface to prevent it from corrosion.

6.

Apply the safety precautions following the OH&S policies and Procedures

Assessment Method: Written - Oral Questioning Performance Criteria checklist

Performance Criteria Checklist 1.2-4 Did you....

Yes

1. Use appropriate PPE while performing the drilling activity? 2. Drilled your designed etched PCB following the procedure correctly? 3. Clean your PCB after drilling? 4. Apply proper safety precaution while performing the activity? 5. Use appropriate tools while performing the activity?

BIBLIOGRAPHY

No

Tan, Michael Q., Gantalao, Fred T., Lasala, Rommel M. Simple Electronics;

Andes Mountain Printers: 2004

Enriquez, Marcelo T. Electronics Technology IV; Souvenir Publications,Inc. 2003

Online Resources :

https://en.wikipedia.org/wiki/Drilling

https://en.wikipedia.org/wiki/etching

https://en.wikipedia.org/wiki/designing

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