Salve!
What about this: Murphy has had his finger in our chip soldering
process. We have bougt a wonderful vacuum soldering equipment and we buy
perfect 80Au/20Sn preforms. And we solder large MMIC chips on perfectly
gold plated carriers. And suddenly there is no wetting at all! You look
at the chip and it jumps off the carrier! You pick up the chip and the
backside is virgin gold, never touched by any Gold/Tin! And you
experiment with the process window, just to find that Murphy is one step
in advance. My experience is that failure analysis in order to find thin
oxides or superthin lubricants etc. is not an easy task. You try Auger,
get a lot of spectras, which confuse you still more. You look with
ordinary SEM and sees nothing. And you have Murphy hanging around.
My question to you is as follows:  Is there anyone with experience from
Failure Analysis of perfect non-wetting who I can speed with? Normally,
Gold/Tin soldering use to bee rather problem free. / Ingemar Hernefjord
/ Ericsson Microwave Systems.