Dear Techneter:

I recently experienced customer return of corner crack. The PCB is 50 mil
thick, 10 mil via, OSP finish and corner crack is over the 4 corners of top
and bottom
of hole. Crack is started from the bottom of external foil and crack through

the entire plating. You can see the photo (file: crack through) of actual
failure. Plating is unusual column type crystal on the surface. In the hole
barrel, the plating crystal is regular. We also performed many in-procss WIP

cross section (refer to the file "crack 9X IR") and we could only find the
crack after 6X IR reflow and its crack is started from external foil top
corner. I have sucessfuly duplicated similar failire with very high plating
current density of 30ASF with very low brighter (0.15cc/l), but its failure
mode is crack on ehe top of external foil not the same as customer return.
 My questions are:

1. Are these two failre modes with the same root cause? What is the reason
one crack is started from the foil top corner and the other is from the
bottom?
2.Is there any non-destructive method able screening the cracked plating?


http://tw.pg.photos.yahoo.com/ph/minalong2003/album?.dir=/5c32scd

Thank you very much.

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