Homebrew PCBs

The paper kinda, sorta, gets around to mentioning silver migration at 
the very end.  The is  a very important failure mechanism for silver 
plated traces that have a DC voltage difference between them. The paper 
mentions that this occurs under specific conditions, but does not say 
what those conditions are. The conditions are easily met. A small 
potential difference between the conductors, and moisture. A film of 
water is not necessary, but just plain humidity. If you want to see this 
very dramatically, and quickly, put 5 volts between two silver plated 
conductors and bridge them with a drop of water. Watch under about 10X 
magnification. A fern like (dendritic) structure will grow out from the 
negative side toward the positive trace. If you don't limit the current, 
the the dendritic structure will "explode" when it hits the positive 
trace. If you limit the current enough, the short will be permanent, 
even after the water evaporates.

A good description is available here:

http://www.te.com/documentation/whitepapers/pdf/p313-89.pdf

This is a well known failure mechanism in the aerospace community.

Harvey

On 11/5/2016 8:44 PM, k5ess.nothdurft@... [Homebrew_PCBs] wrote:
>
> I posted a file RE silver vs gold plating for contacts. I probably 
> shouldn't take up file space for this so i will delete the file and 
> just supply the link.
>
>
> The Performance Implications of Silver as a Contact ... - TE 
> Connectivity 
> <https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwiEhubckpPQAhUHbiYKHQfMDY0QFggjMAE&url=http%3A%2F%2Fwww.te.com%2Fdocumentation%2Fwhitepapers%2Fpdf%2FPerformance_implications_Silver_Myers2009.pdf&usg=AFQjCNGVx3zCZqRRKj0FXGcohb0U-lT_Cw&cad=rja>
>
>
>   Mike N.
>
>