James,

We would normally attach a uBGA with a mimimal amount of tacky flux to hold
in it place during reflow.  Depending on whos uBGA it is, and how it is
constructed, some will also underfill the finished part.

I always try to keep soldering and wirebonding as far apart as possible.
Soldering in a clean room many times makes it an 'un-clean' room unless the
reflow equipment is properly vented and maintained.

Check out Tessera's web page for their uBGA.  You are likely to find
processing guidelines there as well.

Steve




At 09:27 AM 3/30/00 -0500, you wrote:
>I need a little help on a new design that Eng.in coming up with.  They
>would like to take an Alumina substrate and attach a MMIC to it.  The
>substrate is a MicroBGA.  We have a clean room operation in our facility
>and do wire bonding but I do not have enough knowledge on how this would
>be done.  Whether to solder it or use epoxy.  and it either then what
>would the material be.  So if anyone can help with how the mmic should
>be attached to the substrate or direct me to some good literature it
>would be greatly appreciated.
>
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