True, I was talking about appearance of the BGAs prior to mounting.

We just did a blind installation test with the same packages from an earlier lot that did not exhibit "wrinkles."   The result show a significantly greater voiding joints from the "wrinkled" BGAs, given the same paste, place and reflow processing parameters.  Given that the same things that cause voiding can cause shorting, we have a process problem that appears to be caused by a supplier process.

The packaging vendor claims the bad balls saw a normal process.  I need to tell them we suspect they are .....


Larry Jindra
Mfg Engr Group Lead
TRW Radio Systems
[log in to unmask]
w) 858-592-3424
f)  858-592-3940



-----Original Message-----
From: Guy Ramsey [mailto:[log in to unmask]]
Sent: Friday, March 29, 2002 1:13 PM
To: TechNet E-Mail Forum.; Jindra, Larry
Subject: RE: [TN] Solder Ball Wrinkles


As I read your message, we are not talking about BGAs that were mounted on
boards. These are the packages before they were installed? It this true?

Yes, I would be worried. Sound like something was wrong in the solder ball
attach process. I am not very familiar with commercial methods. Reballing
processes that produce wrinkled balls can be caused by excessive heat and
excessive convection.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Jindra, Larry
> Sent: Friday, March 29, 2002 12:59 PM
> To: [log in to unmask]
> Subject: [TN] Solder Ball Wrinkles
>
>
> 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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