TELOK, Tampereen Elektroniikan Opiskelijoiden Kerho
CEST, Club of Electronics Students in Tampere
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TELOKilla on uusi levyjen valmistusprosessi, lisätietoa tulossa nettiinkin lähiaikoina.
Quick guide how to make PCBs at TELOK
This is short guide with pictures how to make printed circuit boards at TELOK.1) Copy your layouts to transparencies. Attach transparencies to each other to make a 'pocket'. If you have narrow traces or you need sharp images remember to put the ink side closest to copper surface.
2) Choose right PCB material, one or two layers. Cut PCB to right shape using guillotine. Leave small edges, about 1-5mm per side.
3) Remove impurities from PCB by using steel wool. You can add some dish washing liquid, if you want to be sure that all grease will be removed.
4) Rinse.
5) Add photo resist layer to PCB. Use Positiv photocopying lacquer. Make sure that your PCB is on horizontal position. Spray from a distance of approximately 20cm. Let lacquer layer to smooth at least 2 min. before proceeding to next step.
6) Dry up photo resist layer using hot air gun. About 1 min. Apply heat to back side of PCB. If you can't keep PCB on your fingertips, then there is too much heat and a risk of destroying photo resist layer.
7) Let PCB to cool down. Now you should have smooth and thin layer of photo resist at the top of copper surface.
8) Repeat process to another side. Go back to step 5. On step 6 use less heat and apply it to the same side on which you have sprayed the lacquer.
9) Put PCB to 'pocket' and expose it to UV-light. 140-200 seconds.
10) Remove 'pocket'. You should see light shades of green and blue on PCB.
11) Develop PCB using NaOH (5,8g/l). Just put PCB to liquid and you should see purple 'smoke' loosen from PCB. Image comes visible.
12) After all unnecessary photoresist has been removed from PCB, rinse it.
13) Etch PCB by using ferrichloride in bubble etch tank.
14) After all unnecessary copper has been removed, rinse PCB.
15) Drill holes.
16) Just before soldering remove photoresist layer using solvent (e.g. IPA).
I have achieved best results using quite thin layer of photo resist lacquer. With thin lacquer layer you can use short exposure times (140sec.) and your transparencies ink quality is not so important. If you have thicker layer, you have to use longer exposure times and ink quality has more important role. You can avoid this problem using another transparency on top of the other, but it needs more work. It is also good idea to turn on etch tank when you start making PCBs. By doing this, liquid in etch tank has time to warm up and etching process works faster when liquid is warmer.
R. Soukkala / TELOK 2003
