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Hi Roger;
I also agree with Jon Moylan of Delsen Laboratories. The only other thing
that I could add is that you might also want to check the elongation and
thickness of the copper in the via hole wall. If the copper properties are
not optimal, anything under .0007" thickness could start to show increased
rates of failure at the test parameters you are using.
Hope this helps.
Greg Schroeder
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: FAB: Barrel Cracking due to Air Entrapment
Author: [log in to unmask] at SMTPLINK-HADCO
Date: 6/6/96 6:34 PM
To TechNet,
I have had a problem with a sample PCB evaluation and I hope someone
can help me with some supporting data.
The problem is that the evaluation board had a shear crack in the
barrel of a 12mil small via hole after 100 cycles of thermal shock.
What we discovered is that the hole had been plugged on both sides
with soldermask (not my idea). We feel like the expansion of the
trapped air eventually caused the barrel to shear. What I need is
some confirming data to show that the theory is correct.
In the past, we had some boards which were plugged on both sides with
mask (but not thermal shocked). The resultant after reflow was that
one side of the plug popped (outgassing) and that the barrel did not
crack. Was the difference in resultants due to the cycling at lower
temperature (-65C ~ +125C) vs. short term exposure at high temp (270C
for ~7 secs.)?
Any opinions or sources of data would be greatly appreciated. Thanks
in advance for all your responses.
Roger Held
Hitachi Computer Products (America), Inc.
[log in to unmask]
(405) 360-5500 x142
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