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Hi Kevin,
It is the latter—trace connections to lands only becomes an issue in connection with BGA pad cratering.
Werner
-----Original Message-----
From: Glidden, Kevin <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Oct 5, 2010 3:02 pm
Subject: [TN] PTH reliability - pad to surface trace
I've been reading about PTH reliability, mainly through Paul Reid's articles and
old TN posts from Werner....
If you have a PTH with a surface trace attached to the top side pad, would there
be more stress (and thus propensity for cracking / separation between the pad
and joining trace) at the pad / trace interface area with a smaller or larger
pad size?
The "pad rotation" pivots about the knee. A larger pad dia puts the
pad-to-trace connection further away from the pivot point and thus the interface
area would be subjected to greater deflection. Alternately, a smaller pad area
(I believe 6012 requires .002" min) would have less connecting surface area ???
Or is the pad to trace interconnection not a primary failure mode when compared
to barrel or corner cracks?
Thanks!
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