Lawrence-

In step 4), beware of bowing, twisting of assy, especially if BGA substrate
is not square (i.e., rectangular MCM PBGA, if you have multiple die placed
in an asymmetric pattern (MCM again), and if substrate layer stack-up is not
symmetric (especially high % Cu planes). Others may be able to explain
encapsulant cure schedules and warp avoidance. I may also have heard that
heat spreader plates in PBGA can cause warpage (?)

Good luck.

Michael Alderete



You wrote...
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Date:    Wed, 7 Apr 1999 11:03:27 +0800
From:    [log in to unmask]
Subject: Question: Problems in BGA assembly process...

     Dear Technetters,

     Calling all you experts out there, can anyone tell me in which area of
     the BGA/CSP assembly process does manufacturers experience
     defects/faults.What are the common faults which BGA manufacturers
     concerns?

     Thank you all for your kind attention.

     example of a BGA assembly process:

     1)substrate__2)die-attach__3)wirebonding__4)encapsulation__5)marking__
     6)singulation__7)flux-print__8)ballplacement__9)reflow/ballattach__10)
     cleaning__11)packaging.

     Best Regards,
     Lawrence Yeo

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