>Please understand, I have trouble understanding most stuff. However, what happened to silver
>migration and all the attendant issues? I mean it's so widely published, no one comes near
>the stuff without some type polish.

In the "thick-film" world, we use silver for circuit traces- typically, but ironically because there is more potential for a problem, with lower cost commercial circuits- bond pads on such circuits are gold.  For military, in hermetically sealed packages, we use all gold.  I learned this morning, from a TechNetter, that most semiconductors are packaged onto lead frames which have been plated with silver for wirebonding (don't know if this is gold or aluminum- I suspect aluminum because it's cheaper).  As far as I know, most ceramic chip capacitors use silver thickfilm for both plates and end terminations- which are often but not always covered with nickel/solder.
 
So I think silver is probably ok if it is covered in some way to prevent exposure to moisture.  I have started looking in MIL-SPEC's to see if they prohibit it for use as a wire bond pad, but so far I haven't found anything.
 
I'm not sure what the effect of tarnish would be on wire bonding (it's probably easily removed?). I have a call into Alpha Metals- they evidently have an immersion silver bath for PCB's which is gold ball bondable- I"ll find out!


Resp.
Phil Hersey, Carson City Nevada USA