Dave-
Thanks for your interest. My "wrinkles" are irregular. The "wrinkles" do not appear to be mechanically made. However, the balls were probed by the BGA supplier (different company than the BGA packager) during test at temperature (95C). These probe (prong) marks are evident on the sides of the balls, at the 4 quadrants. I don't believe they are causing any trouble.
I am sending samples of the wrinkled balls to Mr. Ramsey, to see what he thinks of the metallurgy.
Larry Jindra
Mfg Engr Group Lead
TRW Radio Systems
[log in to unmask]
w) 858-592-3424
f) 858-592-3940
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, April 01, 2002 9:07 AM
To: [log in to unmask]; Jindra, Larry
Subject: Re: [TN] Solder Ball Wrinkles
Hi Larry. Is it possible that the "wrinkles" are not a reflection of
solderball metallurgical microstructure but witness marks from test probing
of the BGA by the component fabricator?
Dave Hillman
Rockwell Collins
[log in to unmask]
"Jindra, Larry" <[log in to unmask]>@ipc.org> on 03/29/2002 04:19:24 PM
Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
to "Jindra, Larry" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
To: [log in to unmask]
cc:
Subject: Re: [TN] Solder Ball Wrinkles
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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