Tin Plating PCB:s


2004-11-21 10:06 pm
I would often like to have my PCB:s tin-plated, but the ordinary solder/desolder/solderpaste gives a result not satisfying to me, therefore I wonder - is it possible to chemically plate a tin layer, on the un-etched PCB, and then etch it, through both copper and tin? or is the tin more resistant to the etching chemicals?
Or does someone else have a better solution to this?
Have you looked at the products from electronics suppliers which let you brush on the tinning compound? Is this what you're dissatisfied with? Or are you just using solder and an iron?

I suspect that you could electroplate tin (definately silver -- remember the pennies in high school science?) if you tried hard enough. Electroplated tin may, however, form tin whiskers (although at the thickness we're talking about, I don't think it would matter much in the real world).

Another option would be to electroplate a tin alloy... such as solder! You'd want to use flux-free solder for this, however.

Etching this stuff would depend a lot on the etchant used. As a data point, I know that electroplated nickel will be eaten quite effectively by a mixture of salt and vinegar overnight, leaving behind shiny copper underneath. It will also eat copper oxides, I don't know about pure copper.

This kit looks like it might do what you want: http://www.caswellplating.com/kits/tin_plate.htm

If I were trying to produce aesthetically-pleasing silver-coloured traces, I would tie all the traces together electrically somehow (cuttable jumpers? Wires temporarily tacked on?) and do the old science fair silver-plating process after etching. You know, some of your mom's good silverware, a couple of D cells, and some sort of electrolyte. Silver Chloride solution, maybe? AgNO3? Or maybe just NaCl in H2O, let all the silver come from the silverware.

If I were just trying to protect my copper traces from oxidization, I would assemble the board as normal and spray it down with a conformal coating, like this one: http://www.mgchemicals.com/products/419b.html