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March 2001

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Subject:
From:
Craig Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 20 Mar 2001 18:09:05 -0500
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text/plain
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text/plain (55 lines)
Bob,

Was electrical monitoring performed in-situ? If you only monitor before and
after exposure (or only during dwells), you are often missing bad solder
joints, especially in ball grid arrays.

Craig

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bob Perkins
Sent: Tuesday, March 20, 2001 5:10 PM
To: [log in to unmask]
Subject: [TN] BGA Thermal Cycling and cold spray


Hi all,

I have a question regarding thermal cycling, a good pcb that has passed all
pretests and post tests with a typical thermal cycle.  A few PCBs were then
hit with a cold spray of -30c and then tested again, after this test a fall
out of 20%.  Are we introducing a crack by the severe thermal shock of the
cold spray or is it revealing a bad solder joint.

Thanks in advance,

Bob Perkins
SMT Process Manufacturing,
Automation Technician
Aimtronics-Delta

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