Homebrew PCBs

An acid sulfate electroplating tin bath is very safe, as it only 
contains sulfuric acid and tin(II) sulfate, plus some proprietary 
non-toxic organic plating additives. Let me know if you want the 
exact bath makeup described on the additive data sheet

There many other tin electroplating baths, which as you say 
contain nasty stuff. This is the reason I chose the sulfuric acid 
tin(II) sulfate bath for plating my PCBs. But of course 
electroplating is not suitable for your application unless you 
can connect every PCB trace to the negative terminal of the power 
supply.

Electroplating solutions are almost everlasting, so there is 
much less disposal than immersion tin. Electroplating also is 
highly predictable and reliable because the quantity of tin 
deposited is directly related to the total electrical charge from 
the power supply. The finish of electroplated tin is much easier 
to control than immersion tin, making it possible to obtain 
bright mirror like finish. In addition, the chemical running 
costs are only tiny fraction, even considering initial bath makeup.
Use immersion only when you cannot make electrical contact with 
the metal.

mpdickens wrote:

>  Wouldn't this
> 
>>allow for less 
>>dangerous chemicals
>>than electroless plating?
> 
> 
> Your kidding, right? 
> 
> The Metal Finishing Guidebook lists three formulations
> for immersion deposits of tin onto copper, only one
> formula is free of really nasty stuff. Here is that
> formula:
> 
> 
> Stannous chloride 3.8 g/L
> Thiourea 49.5 g/L 
> Sulfuric acid 12 ml/L
> 
> Combine the compounds at a temperature of 80-120
> degrees Fahrenheit.
> 
> 
> The TINNIT crystals are more than likey a solid
> formulation of the above because this is the only
> formula that is not deadly poisionous. Electroplating
> ANYTHING. produces nasty stuff that has to be disposed
> of. 
> 
> If I were going to plate tin onto a pcb, I'd use the
> TINNIT crystals: They are premixed, cheap and not as
> hard on the environment as the by-products produced by
> electroplating.
> 
> 
> Best regards
> 
> 
> Marvin Dickens
> Alpharetta, Georgia  USA
> 
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