Hi Marryin'

Is that Quail, as in Quayle ??    :-))

--
Thx & best regards . . .
------------------------------------------------------------------------
Norman S. Robinson      Tel. No.: (44) 1355 355349
Snr. Assy. Engr.        Fax. No.: (44) 13552 65201
TSG BE/OS PE            Email: [log in to unmask]
MOTOROLA EKB, SCOTLAND, U.K.
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Marion A. Graybeal wrote:
"Marion A. Graybeal" <[log in to unmask]>To: [log in to unmask]

Werner,

I see that you and Dan Quail attended the same school (potatoe).

Marion Graybeal
----- Original Message -----
From: Werner Engelmaier <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, July 28, 1999 10:07 AM
Subject: Re: [TN] Freeze Spray and BGAs

>Hi Darrelt,
>What happened to your BGA is pretty obvious. Just consider what is
physically
>happening when you hit iot with the freeze spray.
>You hit the BGA with the freeze spry from the top, I am sure. This quickly
>cools the top layer of the BGA, the rest of the BGA to a lesser degree.
That
>sets up differential thermal shrinking (the opposite of thermal expansion
on
>heating), which causes the BGA to warp like a potatoe chip with the top
>surface being concave. This puts tremendous tensile stresses on the solder
>joints, as well as on other parts in the BGA depending on construction. On
>top of which, the PCB does not cool very much at all (the BGA shields it
from
>the freeze spray) and sets up shear stresses between the BGA and the PCB.
>I would not at all be surprised if failure analysis shows fractured solder
>joints. likely in combination of soldering pads ripped out of the polymer
>matrix.

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