Inge,

Is the dielectric used in the die still SiO2 or it is a polymer?

Paul

Paul Edwards
Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, October 09, 2008 9:00 AM
To: [log in to unmask]
Subject: [TN] Need soldering advice ASAP!

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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