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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