I was wondering if I could get a opinion on some problems
we are having with vias. Built two different types of getek boards
10 layer .062. Both types have over 2000 10 mil vias. One set
of boards went through everything and are doing fine. The other
set went through the same fab shop and same assembly shop.
The second set of boards passed electrical test at the fab house but
after assembly and the start of useage the boards are developing
opens like crazy in the 10 mil holes. I am going over on Monday to
get some cross sections of actual bad vias. I just wanted to
get some ideas of what to look for. If the barrels show cracks
can you tell anything by where the cracks are? If the plating
is too thin will it make the vias much more likely to crack during reflow.
I am just trying to really understand what happened so that it doesn't happen
again. But the vias just continue to open you fix one and the board works
for awhile and then another one opens up.
I am thinking that if there is adequate plating in the bad holes then the assembly
shop either ran the boards to hot or for too long and the z axis expansion killed
me. Is it possible that something in the plating process caused the vias to
be inadeqaute. Doesn't the plating have to have some ductility to it?
any input will really be appreciated
Thanks
John Foster
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