Tips for making PCBs with photosensitive boards!

[davepedals]

Not really going to consider this to be a tutorial per se, but rather a few tips for people making PCBs with photosensitive boards, and not having a lot of success. I recently changed my method altogether and could not be more pleased with the outcome which has been 100%!

Developing:
Like many people out there, I used to develop my boards with what basically amounts to Drano. It worked ok but only about 50% of the time, which can get very expensive! I have recently switched to using Mega Electronics 600-009 Seno 4007 Photoresist Universal Developer Crystals. This works with presensitized boards and boards done with photosensitive paint. I'm in the USA and have to order it from England however it arrives to me in about eight days and not that expensive either.  2 packs makes one liter and can be reused many times I've found. With shipping it cost (corrected) $12.67 USD per two packs. Not bad considering how well this stuff works.

I normally use about 8 gms (half a pack) to 8 oz. warm water. Mix thoroughly and outdoors, as these fumes are extremely harmful but dissipate after only a few minutes.  Even using the small amount allows me to develop at least seven boards , I haven't tried any more than that but my guess it would probably do up to 10 boards 4x6 inches since all of the boards developed within the same time. This stuff is very forgiving as for developing time. On my first test, a 4x6" board was fully developed in about 120 seconds I purposely left it in there another 2 minutes with absolutely no damage to the traces at all. If anyone would like the address where I order this stuff please PM me.

Etching:
I have always used Ferric chloride which works just fine however takes a long time, it can make horrible stains on your clothing, and it is environmentally tough to get rid of! I have recently switched to the muriatic acid and hydrogen peroxide method.  Couldn't be more pleased with the results! This stuff actually smokes when you open the bottle, do not breathe fumes, do not use this indoors!

I use two parts hydrogen peroxide to one part acid. Please do not add the peroxide to the acid! Repeat and listen... pour the hydrogen peroxide into your container first , then carefully pour the acid into that second. I cannot stress this enough, do not mix it the other way around or you may end up with a shocking surprise that is very nasty... so peroxide first then pour the acid into that mixture. Do not use any type of metal container, use a thick plastic, glass, or ceramic container!

After you develop your board wash it off with water then dry thoroughly.  Place it into the acid/peroxide mixture. Agitating will speed up the process of course. Depending on how big your board is and how many ounces of copper it contains, you're looking at between 60 seconds to 4 minutes for complete etching of one oz copper pcb, dependent on board size and the temperature being at least 60 to 70°F.

I have developed and etched seven boards now using this method and even with the smallest of traces, I have had nothing but 100% success! These boards almost look like they were ordered from a professional company!  So there you have it, hopefully these tips will be helpful to someone!
- Cheers!
Dave