Hi Steve and All -

There sounds like a high probability that Susan's hit the nail on the head -
I've had several wonderful adventures with electromigration over the years,
mostly in envrionmental test and qualification testing prior to shipment.
I've also gotten some hardware back out of the field that we were able to
pin down to various aspects of the operating environment, such as sea water,
carbonated beverages, spilled coffee and a variety of other items.  One
customer had his hardware operatiing in a relatively uncontrolled, moist
environment in a paper mill -- brutal for unprotected electronics.

Recommend you perform a really thorough examination at 10-20X magnification
under good lighting to see if you can spot any black fernlike structures,
white or green encrustations, etc.  Then ship that hummer off to one of the
labs noted previously.      WHATEVER YOU DO, DON'T LET ANYONE DISTURB THE
EVIDENCE.

Have a fun day - Kelly





-----Original Message-----
From: [log in to unmask] <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, September 10, 1999 5:17 PM
Subject: Re: [TN] Internal fab shorts that happen over time...


>Hi Steve
>What you are describing is exactly what will happen with electromigration.
>Of course after the material migrates and shorts out completely, it will
>work for a while then finally won't at all.
>
>1)  Horizontal microsections will some times be able to let us see the
>dendrites within the board.
>
>2)  If you have the condition in one location it is probably present in
other
>locations across the board.
>
>3)  To get electromigration you have to have moisture and contamination.
>So what kind of environment do these assemblies see?  Conf Coating?
>
>4)  Hind sight would suggest some sort of cleanliness requirements for
>inner layers prior to lamination - Bellcore requires process qualification
>with SIR type tests.  IPC specs and military specs do not.
>
>Susan Mansilla
>Technical Director
>Robisan Lab
>
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