Fellow technetters,
I still need your help.  I am trying to prove that many of the board related
BGA failures are being caused by poor solderability (insufficient wetting)
on the BGA component pads.  So far I have received only a couple of
responses from people who are seeing the same thing I am.  I have also heard
some reasonable arguments as to why I may be completly off-base here.  I
have included a link to a page that has the pictures and an explanation of
what we are seeing.

http://www.sixsigmaservices.com/defectivebga

Please check out the picture then check some board pulls and tell us (on
Technet) what you see and what you believe is causing it.  I'd really like
to hear what you intermetalic experts think.  Is this some strange
intermetalic crack caused by pulling the component off the board while it is
nearing the solder melting point or is it simply bad ball attach in
assembly?  Either way how do we prove it?

Regards,  Russ

-----Original Message-----
From:   Russ Winslow [mailto:[log in to unmask]]
Sent:   Sunday, February 07, 1999 1:37 PM
To:     'TechNet E-Mail Forum. (E-mail)'
Subject:        Defective BGAs?

Technetters,
In our BGA reballing services we are finding a high percentage of components
with serious dewetting and/or non-wetting on the component pads after board
removal.  These components have not been deballed with vacuum tools or
solderwick as evidenced by the large icicles on pads surrounding some of the
defective pads.

We are seeing this problem on BGA's from many different sources and are
beginning to see a trend which concerns us.  Our evidence suggests that the
failure mechanism is between the solder ball and the component rather than
between the ball and the board.

My question's are:

1.  If you have removed BGA's from the board do you see the same phenomenon?
2.  Upon removal from the board, do you believe that a component should ever
be left with a "bare pad" (no solder bump and no icicle) ?
3.  If a component can exhibit this effect and not be a "defective
component" then what mechanism would cause such an effect?
4.  Do you see "bare pads" on the board after desoldering the BGA from the
board?

Please help!

Russ Winslow
Six Sigma

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