Hi all, especially the Indi-man,
We have soldered IRC's power MOSFET (100-250  W) dice for a decade without 
problems. They use to be vacuum soldered to a solderable gold thickfilm 
Al2O3 substrate with AuSn 50 micrometer preforms. Now there is a production 
stop because of Al heavy wire wedge bonding problems. My analysis of this 
case points at the presence of large voids in the solder joints  or maybe 
partly dewetting (FineFocus is good but the resolution is not sufficient to 
make me sure), something the US mechanical waves don't like. The die 
backside is plated with something that I don't recognize: Cadmium over 
Silver over Nickel. What the heck is that? Anyone who can figure out if AuSn 
is the best preforms for that plating?
Thanks
/Inge 

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