Making circuit boards

Last Updated on July 22, 2024 by Mutiara

Required tools & parts

• Computer with a PostScript laser printer.
• Laser Overhead transparency film (5-10 sheets). Available at any office supply store.
• Clothes Iron & ironing board.
• If a PostScript laser printer is unavailable, download Ghostscript from the internet. A PDf file of a circuit board layout can also be used, however Adobe Acrobat occasionally makes the scale incorrect upon printing. The accuracy of the scale is very important.
• Dremel tool, necessary for drilling holes in the board. A common cheap drill press can also work.
• Dremel drill press attachment. It is fairly inexpensive and works well. Drilling holes without this by hand is not recommended, and will likely create poor results.
• Drill bits, #64 or #70, carbide preferred. Available from any hobby shop, seerious electronic parts stores, or Mirco Mark. Buying several is recommended as they have a tendency to break. If wider ones at the end are available, that can fit in a drill, then they should be purchased instead, otherwise electrical tape will have to be used to make them thick enough to go into the tool. The average cost is $ 1 per bit.
• Copper-clad circuit boards. Available from Radio Shack. Smaller boards with copper cladding one side are recommended, usually in packs of 2-3, the boards should not be pre-drilled!
• Ferric Chloride (Etchant). Available at Radio Shack, only a small bottle is required.
• Silicone sealant spray (optional). It will protect the device from oxidation when you’re done. You can get this at a serious electronics store.
• Sharpie brand fine-tip permanent marker.
• A timer or a watch.
• A small plastic container. Should be large enough to fit a couple circuit boards and 1-1.5 cups of liquid. Must have a tight fitting, waterproof lid, cannot be made of metal, and can never be used for food again.
• Magnifying glass

Procedure

1. Print out the circuit board layout onto a sheet of paper. Verify that the scale is correct.
2. Set the laser printer to its darkest (or least economical) setting. If the printer allows you to specify transparency film as a paper type, do so.
3. Print out the board layout again, this time on transparency film.
4. Empty all water from the clothes iron.
5. Heat up the clothes iron to a high heat range, an 8 on a scale of 10.
6. Clean one of the copper clad boards with soap an water. If any tarnish is present, remove it with light scrubbing with a sponge until the board is clean.
7. Dry the board on a clean towel. Do not touch the copper with bare fingers, to avoid contaminating it with oil.
8. Line up the transparency on the copper, toner side down. Find something heavy and heat resistant to hold the edges of the transparency film in place.
9. For 10-15 minutes, iron the transparency film onto the copper clad board. Keep an eye on the plastic and do not allow it to melt. Transparency film is designed to withstand high heat, but all irons are different and can potentially be too hot, thus ruining it. Use firm but not overbearing pressure with the iron.
10. Remove the iron but do not touch the transparency film on the board for at least another 5-10 minutes. This is going to re-fuse the toner to the copper clad board.
11. While running cold water, carefully move the transparency film with the board over to the sink. Do not try to peel them apart yet. Put it under the cold water until it is all cold. Carefully and slowly, peel the film away from the board. Most of the toner should remain on the board. If not, clean the board with a solvent (acetone works good) and repeat the process with the iron until successful results are achieved. What this part of the process accomplishes is creating an etch resistant mask on the copper.
12. Dry the circuit board and inspect it carefully. Make sure the toner covers the traces completely. If it doesn’t, use the Sharpie to darken the light spots.
13. Heat some water. Not to boiling or steaming, just very hot. You may also want to put on some rubber gloves.
14. Add a solution of 50% hot water and 50% ferric chloride to the plastic container.
    • Avoid getting Ferric Chloride on anything metal. If any does get in contact with metal wash it off very quickly and completely in cold water. It will also permanently stain clothes.
    • Radio Shack states not to use hot water with Ferric Chloride. This is incorrect, because without heat the etching will take a really long time and it won’t be nearly as accurate. Try to avoid breathing in any vapors.
15. Place the circuit board in the container, and seal it with the lid.
16. Agitate the container for 5 minutes.
17. Open the container and remove the board with something non-metallic.
18. Rinse the board under cold water. Keep the water running long enough to flush the chemicals fully from the sink. If the board is fully etched, go on to the next step.
19. If you aren’t sure whether the etching is complete, check the resistance of the board with a volt/ohm-meter. If it has less than infinite resistance between two areas that do *not* contain traces, it needs more etch time.
20. Etch the board in the Ferric Chloride solution for 1 or 1.5 minute intervals until it is fully etched. Remember to agitate.
21. What you should have now is a bare board with black traces on it. Rinse the board again. The etching solution can be disregarded or saved for later use.
22. Use a solvent (such as acetone) to clean the board. This will remove the toner and permanent ink.
23. Rinse and dry the board, and remember to avoid touching the copper.
24. If your resist mask was good, the traces on your board will be solid and without breaks. If there are any minor visible problems they can be fixed with a conductive pen. CircuitWorks makes these pens, they can usually be found in Radio Shack. It will probably be cheaper, however, to just make another board. Depending on the nature of your problem, it can also be repaired with a solder bridge or small bits of wire.
25. Install the tiny drill bits in the dremel tool. If they don’t fit, build them up at the base with some electrical tape. Set the tool to its slowest setting and make a few test drills in one of the spare circuit boards before working on the real one. Remember to do this slowly and hold the board steady while drilling to achieve the best results.
26. Assemble your project.
27. Once everything works, remove the solder flux if you like (Radio Shack sells something for this). Then spray the sealant on the circuit side of board. This will protect the copper from oxidation.

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The original article prior to being cleaned up is provided courtesy of Jefferson Noxon.