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September 2009

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Subject:
From:
Larry Dzaugis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Larry Dzaugis <[log in to unmask]>
Date:
Thu, 3 Sep 2009 11:54:14 -0500
Content-Type:
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text/plain (22 lines)
I have a 5-10% void on a bottom side BGA that grows to a 20-40% void when
the top side is assembled and reflowed.
Paste lead free OM338, profile is peak temp is 246 for 60 seconds.
Immersion tin board finish.

Why would the void expand on a second reflow? There are 22 BGA's on this
assembly. Only a few are growing voids, most voids seen are in the 5-10% or
less range.

Two parts are in the process of cross sectioning, to verify where the void
really is. Only have in line x-ray capablility, no angled views.

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