On 2007-09-13 13:59, Ian Hanna wrote:
> Mike -- are these cracks always associated with similar
> geography? Looks like there is could be an association
> between the copper plane layer topography and this defect --
> the cracks appear in regions around the thermals and
> knock-outs where there is a step down from copper to bare
> laminate...is this always true?

I noticed that, and it often seems to be true.

> could be stressing the 
> copper -- anything unusual in the build/lay-up -- heavy
> copper, thin dielectrics, brittle base material or low t&e of
> the foil?

I originally thought that, but it's looking like a defect is
initially there before fracture (?) occurs.  Any stress may
cause the latter, but not the former?

The part is RoHS and the areas involved see heavy uptake
from the solder wave; thermal stress may be a factor in the
final outcome.

Mike

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