In this page I am documenting the steps involved in creating PCBs (Printed Circuit Boards) at home. It is mainly to help myself to remember the process as it involves few easy to forget steps!
- Copper cladding board
- OHP sheets
- Photoresist dryfilm
- Sodium Carbonate
- Ferric Chloride
- Sodium Hydroxide
- Solder mask paint (optional)
Step 1: Create PCB Design then Print¶
- Create PCB using KiCAD.
- Create the negative image of the copper layer using "File -> Plot" menu, then print it on an OHP sheet.
- You can print Front Copper layer mirrored and Back Copper layer as is. However it is not essential since we will be printing to OHP sheet, which can be flipped as required.
- Each layer to be printed twice. I do it on same sheet by copying circuit diagram in Pcbnew view before printing.
- Ensure "Drill marks" selected with "Actual size" option.
- Print solder mask layer in OHP sheet. This also needs to be two print per layer
- Cut the copper cladding board in required size. Scrub copper coating with water paper just to ensure the uniformity of the copper. Clean it with detergent then dry it.
- Cut photoresist dryfilm to a required size, usually bit more extra than the PCB. Remove the protective sheet of dryfilm from one side. Then carefully paste it on copper cladding board. Dryfilm side to be inside touching the copper on board. Make sure no bubbles are trapped when pasting.
- Put printed negative images of circuit above to dryfilm. As mentioned above, we had printed two copies, need to place both well aligned. We can use cello tape to fix them in position once aligned.
- Now take two sheet of glass and place the board between them. It is to ensure the printed layout to stay close enough on board.
- Now expose the set up in sunlight or ultraviolet light source for 4-10 minutes.
- Remove glass sheets. Then remove circuit layout. Then carefully remove the protective cover over dryfilm.
- Take a cup of water and mix half teaspoon of Sodium Carbonate. Immerse the board within the solution. You will see the unexposed dryfilm parts going off. Take the board out of solution and clean in fresh water.
- Immerse the board within Ferric Chloride solution or mix of Copper Chloride. Stir the solution well until the copper under exposed regions gone off. It will take longer unless you stir it well. Make sure copper on exposed region are completely removed. Take board out of solution and clean in fresh water.
- Now put the board in Sodium Hydroxide solution. The dryfilm will go off. Take board out of solution and clean well with water.
This part is not necessary but it will protect board from corrosion. Also gives some good look.
- Put solder mask paint over board and place piece of OHP sheet over the paint. Then spread the pain over board uniformly to form a thin layer completely covering the board.
- Now put two copies of printed solder mask one over another over board. Align it with solder pads in board. Now, put it between two sheets of glass. Then expose in sunlight or ultraviolet light source for 5-8 minutes. Remove glass sheet, solder mask print, and the OHP sheet. Wipe out the solder mask paint from unexposed pads. You may use some alcohol or thinner to make it clean.