Hello,
In general, BGA's and micro-BGA's do not need underfill to survive thermal
cycle requirements. They are designed to perform as well, in this regard,
as any other surface mount component. Problems arise when these components
are subjected to vibration and mechanical shock, like a misste launch. For
this, use of underfill is helpful. For missile electronics, and many other
applications, a reworkable underfill is best.
Reworkable underfill encapsulants designed for CSP's and BGA's are
available from Zymet, [log in to unmask]
Karl
On Wed, 5 Feb 2003 21:01:13 EST, Steve Gregory <[log in to unmask]> wrote:
>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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