Electrical Workshop - Quia

Electrical Workshop

Module 5: PCB Fabrication

PREPARED BY

Academic Services Unit

August 2012

© Applied Technology High Schools, 2012

ATE210- Electrical Workshop

Module 5: PCB Fabrication 2

Module 5: PCB Fabrication Module Objectives Learners who successfully complete this module will be able to:

1. Define a PCB.

2. State the basic functions of a PCB.

3. Describe the PCB fabrication steps.

4. Use Tina PCB Design software to produce the artwork and a layout for a simple circuit diagram.

5. Develop the PCB for a simple circuit.

Module Contents:

Topic Page No.

5.1 Introduction to PCB 3

5.2 PCB Fabrication Steps 4

5.3 PCB Equipment 6

5.4 Practical Task: Preparing a PCB for a simple circuit 8

5.5 Review Exercise 18

ATE210 – Electrical Workshop


1 Introduction to PCB PCB stands for Printed Circuit board. PCBs

are used in many applications such as

radios, televisions, mobile phones…….etc

(see figure 5.1)

Basic functions of a PCB

The basic functions of a printed circuit board are (see Figure 5.2):

1. To provide electrical connection between the points those need to be interconnected;

2. To provide insulation between the tracks and other points that need to be isolated;

3. To provide necessary mechanical support to the components

mounted on the board;

4. To reduce size and cost, provide better performance and reliability.

Figure 5.2: PCB Basic Functions

PCB basic func-ons

provide electrical connec-on

provide insola-on

mechanical support

smaller size

be9er performane

less cost

reliable

Figure5.1: PCB example



5.2 PCB Fabrication Steps PCB Fabrication can be divided into six stages:





5.3 PCB Equipment The PCB Workshop is equipped with the following equipments:

1. Mega PCB Lab Station 2. Exposure Unit 3. PCB Cutter 4. Drill 5. Edge Rounder

Mega PCB Lab Station:

This unit has separate tanks and can be used for the following sequential process: Develop-Wash-Etch-Wash-Immerse tin



UV Exposure Unit

The UV-exposure unit is used to expose the laminate to ultra violet light through the artwork.

PCB Cutter The PCB Cutter is used to cut the PCB to required size

Drill

Drill bits are used to drill holes on the PCB for mounting components.

Edge Rounder The Edge Rounder is used to round the edges of the PCB

Figure5.3: PCB Equipment



5.4 Practical Task: Preparing a PCB for a simple circuit Prepare a PCB for the circuit shown below:

Step 1: Artwork preparation using Tina software:

• Login to Citrix and Click on the Tina icon under Applications.

• After start-up, the following screen appears on your monitor:

Note the parts marked on the screen:

1 Menu Bar 5 Component Bar 2 Pointer 6 Find Component Tool 3 Schematic Window 7 Open Files tab 4 Tool Bar 8 Tina Task bar 9 Help line



• Select Components: Insert the following components from the

Component bar. Components are arranged in groups, named by the tabs on the Component bar.

1 Resistor and 1 Battery from Basic Tab

1 Switch (SPDT) from Switches Tab (2nd switch from the left)

2 LEDs from the semiconductor Tab

• Connect Components: Connect the components with wires using the click and drag method.The final schematic diagram is shown in figure 5.4

Figure 5.4: Circuit Diagram



• Set footprints: Every part in the schematic must have a physical representation with exact physical size. This is done by setting footprints. To set footprints double-click on each part and view the

footprint Name. Then, click the button in the Footprint Name line and see the “PCB information” dialog where you can select from the available footprint names.

• •

• •

Figure 5.5: Footprint Name settings for a battery



• Set the Footprint Name for each component in the circuit according to the following table:

Components Footprint Name Battery Battery 9V

Resistor R_AX200_W100 (R)

Switch SW_SPDT_TS01-C (SW-SPDT)

LED-Green LED_100_D200 (CQX36A)

LED-Red LED_100_D200 (CQX35A)

• 3D view: Click on 2D/3D view button or the F6 key to get a 3D view of the circuit (see Figure 5.6).

Figure 5.6: 3D view of electric circuit in figure 5.4

• PCB Layout Design: Press the button on TINA’s toolbar (the last icon on the right) or select the “PCB Design” command on the Tools menu.



• Set the items in the PCB Design dialog as shown below:

Select “Start New Project”, “Autoplacement” and “Use board template”.

With the Browse button, find and select the 1layer_A.tpt template files from TINA’s Template. The settings are appropriate for a single-sided PCB.

You can set the size of the PCB board in inches or mm depending on the measurement unit settings in the View Options (see figure 5.7)

Figure 5.7: Editor options in Tina

Set the board width to 50mm and board height to 30mm Click OK when done.



Figure 5.8: PCB layout

• If the components are out of the borders of the PCB, place them

within the borders. • Press F4 to invoke the Net Editor and set nets routing width. Click

on “Modify all” and enter 12.5 into the “Track width” field (see figure 5.9)

Figure 5.9: Routing width options

• To automatically route the netlist, press the F5 button or select

“Autoroute board” command from the Tools menu. The following screen will appear:



• To do a final check, press F7 or select DRC (Design Rule Check) from the Tools menu. The following message will appear:

• To add a text box to the silkscreen/assembly layer, click the T button on the toolbar. The following message box will appear:



• Enter the text into the empty upper field and press the OK button. The text will be attached to the cursor. Move it to the place shown on the picture below and press the left mouse button:

• Press F3 or select 3D View from the View menu to get a 3D view of the design.



• To print the PCB design layout, select the bottom layer from the popup menu in the toolbar

• Print the PCB design layout on a transparency paper using file print

• Set the printing options to the following: Printing size : Actual size Printing mode : black and white (current layer only) Scale 1 to 1



Step 2: Transferring the artwork pattern to the PCB

• Keep the UV exposure unit ready for use. • Cut an unexposed board in to the size of your developed

artwork. • Slowly remove the plastic protection film from the PCB. • Place the transparent sheet on top of the PCB. Make sure that

the circuit trace is oriented correctly and not upside down. • Close the UV exposure unit and turn the unit ON. • After 2 minutes, turn off the UV unit and open the UV exposure. • Remove the transparent sheet and take the board for developing • Place the board after exposing to UV rays in the first plastic

container of the PCB machine. • Immerse the plastic container in to the developer solution. • Keep it inside developer tank for 1 minute. • Remove the board after one minute and wash under fresh water.

Step 3: Etching

• Immerse the board in the second plastic container of the PCB

(etching tank). • Check the board from time to time. This is necessary because

over etching may lead to broken copper traces. • When all unwanted copper is removed, wash the board under

fresh running water. Step 4: Tinning

• Immerse the board in the Immerse Tin Tank (in the third plastic container of the PCB)

• Wait for 20 to 30 minutes. Keep checking the board for a clear coating of tin on the copper track.

• Remove the board when the tin coating is completed. • Wash the board under running water and dry it.

Step 5: Drilling

• Drill holes on the PCB using the 1mm drill bit for mounting components.



5.5 Review Exercise Exercise 1 State four functions of the PCB. __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ Exercise 2 Write the PCB fabrication steps in their proper order in the boxes given below:



Exercise 3 Match the following pictures with their appropriate titles:

_______ A. Drill

_______ B. LED

_______ C. Resistor

_______ D. PCB Layout



_______ E. PCB Mega Station

_______ F. Battery

_______ G. PCB Cutter

_______ H. 3 D View

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