RE>Conformal Coating of BGA's                3/26/96

Steve,

We've been conformally coating our ceramic BGAs for a couple of years now with a sprayed acrylic conformal coating.  35 mil diameter balls at 50 mil pitch on a 1 inch square package.  Haven't seen any problems with it, but it's impossible to verify that the entire underside is coated.

In addition, we've found no compatibility problems between the acrylic coating and an epoxy underfill that we're using.

Feel free to call me if you have any specific questions.

Regards,
Greg Bartlett
Mercury Computer Systems
Chelmsford, MA  
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508-256-1300
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Happy Monday!

Does anyone have any experience with conformal coating of
BGAs and, in particular, what performance standards are used? 
We are using a silicone coating 3-5 mils thick (sprayed), and we
are not using a BGA underfill.  We are uncertain whether the
edges should be sealed or not.  It's not bad for plastic BGAs (as
the balls collapse), but the ceramics can be near impossible.

This is a military (avionics) application.  I appreciate any advice/
experience that you may have.

Thanks,
Steve Murphy
TRW Automotive Electronics Group
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