Hypothetical situation...

Just surmising.


-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Tuesday, October 05, 2010 3:09 PM
To: [log in to unmask]; Glidden, Kevin
Cc: [log in to unmask]
Subject: RE: PTH reliability - pad to surface trace

Kevin.

  A photo is worth one thousand words.

"X,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
Sent: Tuesday, October 05, 2010 2:02 PM
To: [log in to unmask]
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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