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March 2002

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Subject:
From:
"Edward S. Wheeler" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 29 Mar 2002 13:37:06 -0500
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We have noticed that on BGA devices that undergo warp during the reflow
cycle (shadow moire results showed the parts would warp up at the ends,
then down, then up) can cause this if the joint is moving during the
transition back to solid. The joint looks similar to wrinkled tin foil.
When we have parts that don't warp with all of the same parameters, the
joint is smooth and shiny.
Our main failure with these warping parts has been a head in pillow open.


Ed


At 09:59 AM 3/29/2002 -0800, you wrote:
>We have a lot of BGA packages from a custom package house with a
>"wrinkled" appearance to the ball surface, most pronounced on top of the
>ball, where they will interface with the PCB.  These packages are prone to
>shorting.
>
>Does anyone out there have an idea of what might cause that "wrinkled"
>appearance, and why it might make the package succeptible to shorting?
>
>
>Larry Jindra
>Mfg Engr Group Lead
>TRW Radio Systems
>[log in to unmask]
>w) 858-592-3424
>f)  858-592-3940
>
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