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Beginner looking for advice

Hello All,

Please excuse the beginner questions; this is my first attempt at etching a PCB.

I bought some 2oz dbl sided boards, and will be etching them using Sodium Persulphate. I've done the traces using press-n-peal blue. I do not yet have an elaborate set up, and I'm looking for any advice your willing to share.

I've read that I should add 1/2lb Sodium Persulphate crystals to 1 gallon of warm water. The board should be submerged until the copper that is not protected is dissolved. Am I missing anything? Any tips or tricks that would be helpful? will this solution be strong enough? How does one dispose of the remaining etching solution?

Lastly the board is a breakout of sorts, taking a db25 and directing the individual wires to terminal connectors. The board will be exposed to short pulses (1-3 seconds) of 24VDC @ up to 5 amps. The traces are

1/16th of an inch thick and separated by only 1/32th of an inch in many places. This board will not be used for transferring signals, just on or off for short durations. Does this sound ok?

Thanks, Brian

Reply to
Cat
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sounds fine how ever, I think for the 5 amps you're using, you may want to consider using wider traces for that path.

And as far as the etching goes, warming up the solution makes it etch faster.

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Reply to
Jamie

According to my trace width calculator, 5 amps on a 62 mil trace with standard 1 ounce copper will only cause a temperature rise of about 25 C, so 1/16 wide is fine, especially for short pulses. I found the calculator (an Excel spreadsheet) on an internet search. I can send it to you if you wish. Try

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When I etched my own boards many moons ago, I found that it was very important to clean the copper very thoroughly before applying resist. ScotchBrite with soap and water worked well. Just a little bit of oil or oxide on the exposed copper made for slow etching in those areas, and overetching under the resist.

Also, I found it better to drill the holes before etching. Otherwise, sometimes the drill would catch the pad and pull it loose.

Good luck.

Paul

Reply to
Paul E. Schoen

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Are you sure it wasn't Ammonium Persulphate you bought? That's what I use and it is mixed at 200gm per litre of water.

Reply to
Ross Herbert

Use in a ventilated area, and follow all precautions for this chemical. Sodium Persulphate is a strong oxidizer and will combine with many things to make it dangerous. Read the MSDS. You mentioned double sided boards, DS boards are a little tricky for a beginner and you will be putting a lot of unused copper in the mix.

Good luck, Tom

Reply to
Tom Biasi

I was most worried about the closeness of traces (only 1/32th of an inch) glad no one points this out as a problem.

This is good advice I'd not seen anyone recommend this yet. I will give it a go before etching.

How about that green lacquer that is on a commercial board. Does anyone here have any experience applying this to a home etched board?

Reply to
Cat

That green coating is the solder mask. It keeps the wave-soldering process from coating all of the copper, conserving solder. A hand-soldered board doesn't really need it.

Reply to
Stephen J. Rush

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