In my experience, if you want a good electrical connection to the
of a die, you must metallize. I've mounted dice that are not metallized
the back, and I always get a high resistance connection (Kohms). On one
chip that I designed (in a radhard p++ epi process -- very low
substrate), we actually used the substrate to conduct the analog ground
current through the backside to the die pad instead of using bondwires.
order to do this, we had to backgrind and backplate with metal. I was
amazed at the incredibly low resistance contact we were able to achieve
on the order of a few milliohms from die pad to bulk.
If you have p- wafers (higher resistivity substrate), then I think you
to ask if it is of any benefit to ground the backside.
From: Matt Kaufmann [SMTP:firstname.lastname@example.org]
Sent: Friday, September 10, 1999 1:27 PM
Subject: [SI-LIST] : backside metal
Can anyone comment on the necessity of metallizing the backside of the
if we want to ground the backside? In other words, if we want to have
electrical connection between the package substrate and the backside of
die, is backside metallization required or is the presence of
conductive adhesive sufficient (assuming the die sits on a grounded die
Senior Packaging Engineer
Silicon Spice Inc.
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