Chemical_tinning_of_PCB's

[Mike I.]

My old synthesizer (built in 1980) uses homemade glass-epoxy PCB's. 
There is no evidence of corrosion on the copper foil. I thoroughly rinse 
the boards with warm water (several minutes, sometimes a soak for 
several hours) after etching in ferric chloride solution. After 
soldering, I remove the flux by thoroughly rinsing with acetone, 
followed by a rinse with distilled or deionized water if high impedances 
are involved. The board is then dried and sprayed with a film of 
silicone-epoxy conformal coating ( GC Electronics ). This is 
transparent, and has a slightly waxy/rubbery consistency. It may be 
soldered through or scraped off if necessary - or dissolved in acetone. 
This seems to do a good job of protecting the boards. I have not tried 
tin-plating.
Regards, Mike