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RoHS question
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I never tried tin plating PCBs, from memory the stuff was expensive, hard to
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get and went "off" quickly. Seemed like a lot of hassle for little reward, I just sprayed boards with clear lacquer. Out of curiosity I looked up chemical tin plating, and of course ENIG comes up. The 'N' is nickel, and the 'G' is gold. Explains why it's expensive I guess. The other type of chemical nickel plating is a nickel phosphor coating, not good for PCBs but ok for machinery parts. It's occurred to me that if you were into milling PCBs you could electroplate the copper board beforehand. I wonder if anyone does that. Tony -----Original Message-----boards I ordered are of the ENIG variety. No rocket science comes out of myhobby. :) |
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It may have gotten more expensive over time.? It was about 30 USD for a pint the last time I bought it, and it does have some nasty stuff in it.? It does work well on a clean board, though.
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One method of making PC boards was to put down a layer of positive photoresist over a bare board, expose it with a positive of the artwork so that when developed, copper would be exposed where you wanted there to be a track.? You'd then electroplate tin on the board, strip the resist and etch it.? You would have to use something like ammonium persulphate, which does not attack tin. Regular Ferric chloride and CuCl etchants will not work. If you were making double sided boards with plated through holes you'd drill the holes first, dunk the board in a graphite solution, plate one ounce of copper over that, then add resist and etch as normal.? The tin plating would also cover the inside of the plated through holes. Haven't used any of these, I did toner transfer for double sided boards, stitched top and bottom together, with the top and bottom boards being half thickness and produced separately. Harvey On 11/1/2020 4:57 AM, Tony Smith wrote:
I never tried tin plating PCBs, from memory the stuff was expensive, hard to |
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Electroplating after applying a resist is a good idea. That'd work just fine.
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I was never keen on ammonium persulphate, as a cheapskate hobbyist the mixture didn't last, unlike ferric chloride that lasts for ages, or even better (& cheaper!) cupric chloride that you can regenerate. And it doesn't stain everything brown either. I have used graphite to electroplate non-conductive things, that's pretty simple. Vias might be a bit fiddly. Tony -----Original Message----- |
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When I made double sided boards, I didn't do electroplating, but did epoxy the top and bottom boards together.? The registration holes need to be exact, which is why I made an upside down drill press, which is far more accurate (no parallax).
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The electroplating/positive resist, (they reversed the negatives photographically, I think they used kodalith and KPR, it was a long time ago), well, they did tin plated boards with the persulphate. My preferred etchant was cupric chloride once I discovered it. But then again, I was using toner transfer and immersion tin plating of the boards. Harvey On 11/6/2020 6:41 AM, Tony Smith wrote:
Electroplating after applying a resist is a good idea. That'd work just fine. |
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