Homebrew PCBs

On 09/12/2010 11:36 AM, Malcolm Parker-Lisberg wrote:
> It does deposit tin on the FR4 surface, and will prove problematic if you have high impedance circuits, it also causes problems when the board is conformally coated, with tin migration under the coating.
> Conformally coating the board first and then applying the tin is a better solution for high impedace or low leakage PCB requirements.
> It should not be a roblem with normal home PCB CMOS circuits.

Do you have more data on this? This is chemistry, I am not qualified to 
understand the process for which the tin may deposit on the board, but:
- is this measurable?
- how much it changes a board? Can one see it with a multimeter?
- do you have any kind of number or data?

bye
as