At 11:12 AM 10/6/99 -0700, you wrote:
>Phil- DON'T
>
Amen.

>right. Also, why the big heat sink?  ...
>Sounds like a 'special' application...

yep.  it's a case of mondo watts in a box.  basically it's a box on a stick
outdoors with no active cooling available and frequently with addition of
solar load.   we're having fun, you betcha.

dwight
"for the RF designer the ultimate abstraction is the physical design"

>
>-----Original Message-----
>From: Phil Bavaro [mailto:[log in to unmask]]
>Sent: Monday, October 04, 1999 6:08 PM
>To: [log in to unmask]
>Subject: [TN] BGA Solder joint compression
>
>
>Ok, before I get hammered for posing this question, let me say that
>my answer is  "Don't do it, solder will creep and it will short out".
>Anyways, here is the question:
>
>Some of our designers have come up with a design using about eight
>560 BGAs as well as many other SMT packages on a board which will be
>pressed up against a sheet of thermal tranfer type spongy material
>which is then pressing against a solid metal chassis.
>
>They are worried about dissipating 6 watts per BGA and therefore need
>to envelope the thermal pad around the BGA by applying 30 psi
>according to the spec sheet.  This part is only 1.5" square so I
>calculate that we need to apply approx 65 pounds of pressure to the
>component.
>
>I take this to mean that they want to compress the solid tin lead
>solderballs with this huge amount of force and believe that this will
>definitely cause the solder to deform/creep.
>
>Any comments (please be nice....).
>
>
>Phil
>
>Phillip A. Bavaro
>QUALCO/\/\/\/\  Incorporated
>Manufacturing Engineer, Staff
>[log in to unmask]
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>
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