wirebonding Au-Ag
Yes, thank you. I ran across it yesterday, and found it to be one of the more helpful documents in the limited information available on the net. A few key statements from the paper confirmed this is not a common procedure (yet).
"While this work provided data that shows evidence that this coating (silver immersion) will bond with aluminum wire, another course of study has been engaged to evaluate gold wire bond effectiveness. As of this paper's publication, no data is available to report and will be published in a later paper." The paper goes on to say "Silver has been used as a substitute for gold wire for ball bonding integrated circuits. It has shown to be effective providing strong bonds with both gold and aluminum (pads)." This describes a reverse usage of the bonding materials (Ag wire/Au pads), but is helpful in prodding me to explore the idea a little further. As noted in the first post, our simple experiments showed good results, but I'd like to see some long-term reliablity data, if any exists.
I'll try to contact a few technical gurus from these companies and see what they have to say, but it sounds like immersion silver isn't well tested for this application. Thanks again for the link - Claude