Hello Werner,
I posted a peripheral question about determining if a peak temperature could
be detected by looking at the microstructure of solder joints.  The answer I
am getting is that intermetallic growth is both time and temperature
dependent.  Thank you to Ryan Grant and others.  I had hoped to find that
there was a way to show that a joint saw much higher temperature than
expected in processing, but that is the board bias.  We also practice
assembly operations.  In that case, show that the boards did not see much
higher temperature than expected in processing.

I fielded the question from an OEM that procures boards and assembly
services from different contractors.  From a practical standpoint we
generated several questions.
1)  Can you look at a board that has failed in a lead free process and see
if the board saw the same thermal experience as other boards in the lot?  By
thermal analysis?  By metallurgical examination?
2)  Within a board, could you look at a BGA for example, near a failure, and
see if it saw more thermal experience (rework) than the surrounding board?

The answer to all the questions is probably "yes", but do you know if an
acceptable procedure has been published that we could reference in support
of an analysis? The answers help direct where to go to find a solution to
prevent a future failure.

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Werner Engelmaier
Sent: Thursday, April 13, 2006 7:46 PM
To: [log in to unmask]
Subject: Re: [LF] Tin Pest + Aging Performance--from Jennie Hwang


Hi Ryan,
And what is the point of this exercise?

Werner

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