HOW TO MAKE PRINTED CIRCUIT BOARD (PCB) AT HOME ~ Electro aRK

There are many software for PCB designing i.e. Express PCB, OrCAD, Zenit PCB, Free PCB, Tiny CAD, Osmond PCB, BSch3V, Kicad, gEDA, Score, Eagle etc. but in this tutorial we will use Eagle which is good and easy to use. We can easily download the eagle software from link http://www.cadsoftusa.com/download-eagle/?language=en

To make the PCB, following stuffs are required

1. PCB design software

2. Laser Printer

3. Over Head Projector sheet(OHP sheet) or butter paper

4. Electric Iron

5. Back permanent marker

6. Copper clad board

7. Ferric chloride solution

8. Hand held PCB drill and drill bits

Steps to PCB design

1. Draw the schematic of the circuit

2. Transfer schematic to the layout editor

3. Design the PCB(Route the circuit or make the tracks)

4. Print the designed layout of PCB using laser printer

5. Take the impression of the circuit on a copper clad board of required size

6. Remove the excess copper by etching process

Drawing the schematic

First of all we need to draw the schematic for the circuit which has to be designed.

Function of schematic commands are described below with figure

1. INFO-Provides all information about the object/component to be selected.

2. SHOW-Highlights the object/component to be selected.

3. DISPLAY-Select and deselect the layers to be displayed. This is used specially at the time of printing PCB layout.

4. MARK-Place mark to display relative coordinates.

5. MOVE-Move any objects. At move command, the right mouse button rotates the object.

6. COPY-Copy the objects.

7. MIRROR-Mirror the objects.

8. ROTATE -Rotate objects by 90 degrees.

9. GROUP-Used to define a group which can then be moved, rotated, or copied, deleted.

10. CHANGE-Used to change parameters i.e. the width of a line, the package variant or the size of text.

11. PASTE- Paste previously cut and copy object to a drawing.

12. DELETE-Delete the objects.

13. ADD-Used to add library components to the schematic.

14. PINSWAP- The PINSWAP command is used to swap pins within the same symbol which have been allocated the same swaplevel.

15. GATESWAP- Using this command two gates may be swapped within a schematic. Both gates must be identical with the same number of pins and must be allocated the same Swap level in the device definition.

16. Replace-Replace the components.

17. NAME-Used to write names to components, nets, or buses.

18. VALUE- Used to define values for components.

19. SMASH-Separate name and value texts from a device, so that they can be moved and placed individually.

20. MITER-Round off or bevel wire joints. The grade of mitering is determined by the miter radius. Positive sign results in a rounded joint, negative sign in a bevel.

21. SPLIT- Used to split a wire or a polygon edge into two segments in order.

22. INVOKE-Fetch a particular gate from a device. This command allows you also to add a gate from a device which is located on another sheet.

23. WIRE-Draw line, and used to define electrical connections, i.e. wires, in the Layout Editor.

24. TEXT-Used to place text.

25. CIRCLE-Draw a circle.

26. ARC-Draw an arc.

27. RECT-Draw a rectangle.

28. POLYGON-Draw a polygon.

29. BUS-Draw a bus line.

30. NET-Used to draw a net.

31. JUNCTION-Place the symbol for a net/wire connection to show nets/wires are connected together.

32. LABEL-Used to place the name of a bus or net as a label.

33. ATTRIBUTES-Define attributes.

34. DIMENSION-Draw dimensions.

35. ERC-Stands for Electrical Rule Check and perform an Electrical Rule Check and a consistency check for schematic and board.

36. Errors-Show errors found by ERC (Electrical Rule Check) or DRC (Design Rule Check).

Transfer Schematics to the Layout editor

We can transfer schematic of the circuit into layout editor just by clicking board command as indicated on the figure by circle.

Designing the PCB

Most of the commands in Layout editor are same as that of the schematic which is already explained in the schematic section. Here we will discuss the Layout editor commands which is only available in Layout editor

1. LOCK- Locks the position and orientation of a part in the board.

2. OPTIMIZE- joins wire segments which lie in one straight line.

3. MEANDER- Balance lengths of differential pairs and increase the length of a signal segment.

4. ROUTE- Used to route signals manually i.e. convert airwires (unrouted connections) into real wires.

5. RIPUP-Converts routed wires (tracks) into unrouted wires (airwires).

6. VIA-Place a via-hole.

7. SIGNAL- Define signals.

8. HOLE-Used to add drill holes to a board.

9. RATSNEST- Used to view the shortest possible airwires and polygons.

10. AUTO- This command starts the auto router.

11. DRC-Stands for Design Rule Check and performs the DRC.

Printing the PCB Layout

Now we have to utilize our laser printer to print PCB design. First of all go to the command Display and select only number 16(Bottom) and 17(Pads) and apply this setting and click on the ok. Now PCB is ready to print and print the PCB on butter paper.

Go to file and click on the Print (we can also use shortcut to print command by clicking Ctrl+P to print the PCB) and then make the suitable settings and checkmark the option Mirror.

Etching process

First of all cut the copper clad board to the required size using hacksaw blade. Place the printout on the board with the printed side facing the copper side and affix the paper to the board using cello tape so that it prevents the movement while heating with iron. Now take the electric iron and set it to maximum temperature and start heating by pressing and moving over the paper for few minutes (say 5minutes) until the complete impression of the circuit prints on the copper side of the board.

Now after heating as you remove the paper you get circuit printed on the copper side. Check whether the any lines are missing and dark enough or not, if lines are missing or not dark then redraw the lines on the board using a black permanent marker and keep it for few minutes(say 6 minutes) to dry the ink then wash the board in normal water. Now drill holes using appropriate drill bits as given in the table.

Drill-bit size	Used for
1mm	IC pins
1.2mm	Resistor, capacitor, transistor etc.
1.5mm	diode, LED pins, presets etc.
5mm	LED, nuts, screws etc.
8mm	switches, pots etc.

Now its time to make ferric chloride solution for etching so that mix some ferric chloride (FeCl₃) powder in hot water. The reaction is vigorous, so take safety precautions and use hand gloves during this process. Now drop the board into ferric chloride solution and constantly tilt the container from side to side and continues until excess copper washes away. Now take the board away from ferric chloride solution and clean it using acetone or normal tap water and scrub the board with scrubber till it shines. Now PCB is ready to use

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