Good Morning,

I need some opinions on a flexible soldermask problem but I need to post the
pictures to Steve's web site.

The picture will show the flexible soldermask has separated apart
(separation is approx .0002 wide). In our opinion it is not a crack or a
conventional crack. The separation only occurs on top of the acrylic
adhesive in the frame which surrounds the part which is free of copper. It
never occurs on top of the copper. The separation occurs in approx. 10-15%
of the parts we are building in the same batch built at the same time. The
separation is there after "tack cure" and does not get worse after full cure
or HASL.  When we solder float the part without baking the separation does
not propagate - get any larger or do anything. The IPC-SM-840 really does
not address flexible soldermasks well so my questions are 1)  any thoughts
on what is causing this 2) reliability issues - part goes into a super
computer which will be in a controlled environment - application is not
dynamic. 

Thanks in advance.

Regards Steve Kelly


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