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August 2003

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Subject:
From:
Francois Monette <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 12 Aug 2003 11:47:25 -0400
Content-Type:
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Hi Ted,

Out of curiosity, what kind of bake cycle did you use ? It should have been
something like 48 hours at 125C or 10 days at 90C to remove all the moisture
from the components.

If you are interested, there is a very interesting paper on the subject of
moisture-induced BGA warpage that was recently presented at ECTC by Agere
Systems (former Lucent component division). You can download this document
from the MSD Knowledge base at www.cogiscan.com, click on MSD Knowledge
Base, then select "List of publications and other references", it is the
first paper in the list by chronological order.

Regards,
Francois Monette
Cogiscan Inc.


Date:    Mon, 11 Aug 2003 16:55:33 -0700
From:    Ted Kong <[log in to unmask]>
Subject: Re: BGA bridging on corner pins only

Hi Joe,

Only one corner has a slight warp downward.  I had
bridging at three corner, so I am not sure how much
did the warpage contribute to the bridging.  There is
soldermask damage on the board, but not at the
location where bridgings occured.  As I mentioned
before, the same board with the same chip going
through reflow oven has no bridging.  To avoid out
gasing, I had the board and chip baked before doing
the rework, and it didn't seem to help at all.

I agree.  Without paste, the standoff height is lower.
 Since the unit that I am working on is for R&D only,
I am not worried about long term reliability.

Ted

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