Last lot we lost for innerconnect defects was built in Dec 1994.  GFG 
material, 170-180 Tg.  Name of the Shop available upon request.  Defect 
not caught until assembly final test (Temperature and Vibration).  Opens 
and high resistance.  Very costly assemblies scrapped out.  Not using 
that shop much anymore.  (One "Oh-crap" cancels out 1000 "Atta-boys".)

The coupons had been thermally floated, and the cracks were not visible 
in the cross sections delivered with the order because the cracks were 
lost in the etched e'less line.  The cracks WERE in the cross sections 
delivered by the supplier, as additional grinding to the next set of 
holes proved.  

Root cause was supplier Innerconnect failures.  Why the supplier had 
them was never determined, however all shops will have these defects 
from time to time.  Need to identify supplier who know how to spot the 
defect.

Foster Gray of TI-Austin Tx, tells me there may be a nondestructive 
method of catching the defect at the fab shop.  Foster leads an IPC 
sub-group on the problem.  

Have not seen the problem since 1994.  On the other hand, it is our job 
to buy boards from shops who know how to catch this defect, at least.

George

-- 


George Franck Jr
Raytheon E-Systems
Product Assurance Engineer
Falls Church Va

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