remz said:
Hi all,
I have a modest PCB setup at home using photosensitive boards. These are the symptoms of the boards problems.
1. Not all the copper which is to be removed actually gets etched away (see figure attached).
Currently, I use 5min for the UV which I have found works well. Around 2 minutes for the developer and the etchant time varies from around 30min - 1h30 and his highly dependant on ambient conditions.
Rem
Hi Rem:
Reading thru your post and all the good answers by others given, I have a couple good tips. Some already partly answered.
I use the same method like yours for a good 20 years. However, I invested in a good
SunLamp, which is a special lamp (deuteronium I think) of high intensity. I always follow manufacturer's specifications and guidelines at first and then tweek it for my own purpose.
1 - The exposure with the
SunLamp is 90 seconds. Overexposure will result in pitted tracks after etching.
2 - Use fresh developer and more importantly, just the correct water/developer mix, 10 parts water to 1 part developer is common I think.
If the solution is too strong *OR* warm, it will weaken the photosensitive coating (film), so make sure your developer solution is COLD! Rinse excessively with cold water when you're done developing which should be at the most 2 minutes or so. Any longer will indicate your solution is 'over-used' or too old.
3- Purchase an aquarium-heater(thermostat) and a aquarium airpump with a bubbler to circulate the etchant. Preheat your etchant to no more than about 35°C. Any hotter and it will take off the film and etch through the copper.
I recommend swithing to Ammonium Persulphate as an etchant. Works much better (heated to 35°C) and is clear so you can see what's going on. Rinse excessively with cold water after you're done. Very important to stop the etching process.
That's basically it. I use a laserprinter and transparancies to make my boards.
I put the transparancy a couple times through the printer to get a real black image. Can be a bit tricky sometimes to position the sheet at exactly the same location, so make a mark somewhere on the transparency and the printer tray to get as close as possible. This will avoid being 'off' by a pixel or so...
And last, don't touch any part of the pcb with your fingers. It results in being unable to etch that part of the board.
If you have more questions, fire away and I will answer them as good as i can.