Hi, Steve,

I have no requirement specs for using Underfill at all, nor have I come
across any. The equipment we're making has to rattle around in a chopper
for 15 years. Given the immediate failure under mild vibration of the first
boards that were (badly) made for us by the house that designed them, I
decided to use underfill as an insurance policy in addition to making sure
our processes here were as good as possible for subsequent builds. As
mentioned in an earlier reply to Ted Kong, we've had no failures since,
even under much more severe vibration.

If the claims for underfill are true, it's supposed to extend BGA solder
joint life by a factor between 3 and 5. This is too hard to resist for
equipment that has to live a long time under harsh conditions.

Best regards
Peter



Steve Gregory <[log in to unmask]>   06/02/2003 10:01 AM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to SteveZeva

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: [TN] Speaking of Underfilling...








Hi All!

Peters thread about reworking a single ball on a BGA with underfill,
brings-up a question.

Are there any guidelines, or anything that someone would like to share,
when to use an underfill? Is it something that is determined after ESS or
HAST, and upon seeing failures then, which requires it? Or is there some
sort of established guidelines that one can reference that say; "If you
have BGA's on a assembly that will see "X" loads, then underfilling is
necessary..."

Question to the point; BGA's and Micro-BGA's on a missile...underfill these
guys?

-Steve Gregory-
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