Hi Ian:
        Conformal coating under BAG is a tricky business. You have to
squirt ( not spray) first around the edges of the BAG in a special way
to avoid creating air bubbles ( no coating ) under the component. There
are products that are made for under fill of components that can be
injected after spray coating. These products will cover all the area
under a BAG and prevent dendrites growth much better than a spray
coating can. They will give the component mechanical strength.
        What kind of equipment are you using to spray?  
        Regards,
        Ramon

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Fox, Ian
Sent: Tuesday, July 19, 2005 12:23 PM
To: [log in to unmask]
Subject: [TN] Coating under BGA's

Fellow techies, a BGA related question. We're just starting to design
BGA's into some new designs which are class 3 high rel assemblies and I
am asking myself questions about the ability to adequately conformally
coat under the packages. Our standard coating is a solvent based acrylic
and we are using a 456PBGA device and a 429CBGA device, both on 1.27mm
pitch, as the maximum sizes so far and I'd be interested to hear what
other class 3 builders have experienced when applying the coating.

Regards
Ian Fox
Goodrich ECS
Birmingham
UK

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