Circuit Board Etching

This page is under construction.

These are the instructions for making a printed circuit board in the classroom.

1. Cut copper-clad board to size.

The next few steps are a variation of the "Toner Transfer method". Several Youtube videos show this process. The general idea is to "burn" your layout onto the copper clad board by melting the laser printer toner into the copper. The toner will act to "resist" etching the copper away.

2. Clean the copper surface:

a. Sand the edges

b. Buff surface using a scouring pad, buff it again. Buff it until your fingers hurt. Make it super shiny. From here on in do not touch the copper surface with your fingers. Grease from your hands will prevent the toner from sticking.

c. Clean the copper surface, first with water then with acetone on a cotton swab. Let it dry.

d. Rinse your board with 99% isopropyl alcohol. Let it dry.

3. Print the mirror of your layout onto photo-paper using a laser printer.

4. Cut out your layout from the printout to match the size of your copper clad board.

5. Preheat a laminator using the 5 mil setting.

(Other heat sources like a clothes iron can be used. We want enough heat to melt the toner off of the paper and into the copper. Too much heat could delaminate the copper from the fibreglass backing or burn the paper.)

6. Place your layout, toner down, onto the copper clad board and carefully feed it into the laminator. Be sure the paper does not shift.

7. Keep passing the board and paper though the laminator for 20 consecutive passes. The paper should "stick" after a couple of passes. After a few passes you may need to use pliers to handle your hot circuit board.

8. Let the board cool for 10 minutes.

9. Soak the board for 10 to 20 minutes.

10. Use your nails to carefully separate the top layer of paper from the layer stuck to your board.

11. Soak the board overnight.

12. Preheat the etchant for 2 or 3 hours. We use Ammonium Persulphate in a bubbler tank.

NOTE. This etchant dissolves exposed copper producing Copper sulphate and ammonia gas. The gas can burn your eyes and throat. Never hold your head above the tank. Operate the tank under a fume extractor or power vent.

13. After a good soaking (overnight or over the weekend) you should be able to carefully rub the rest of the photo-paper from your board.

b. If a white film develops as it dries you may need to wet it and rub a little more. Be gentle so as not to disturb the toner.

14. If any of the traces did not transfer fully: wait for the PCB to dry, redraw the traces with a black sharpie, let sharpie dry for at least 30 min before etching.

An ATTiny85Duino board after steps 14 and 16.

15. Drill a small hole in an unused corner.

16. Feed a string through the hole and tie it securely. Tie the other end of the string to a popsicle stick. The board should hang 4 to 6 inches below the stick.

17. Hang your board in the tank. It will take 15 to 30 minutes for all of the exposed copper to be dissolved.

This is the setup I use. The powered vent draws fumes outside. The fish tank bubbler connects to a bubbler hose held at the bottom of the tank with a small ceramic tile. The heater warms the Ammonium Persulphate solution to speed etching.

18. When all of the unwanted copper is removed take your board to the sink. (Do not drip on the floor.)

19. Rinse your board with plenty of cool water.

20. Once dried you can use acetone to wash away the toner.

21. Your PC board is ready for drilling, component mounting and soldering.