Glenn,
        Yes, some flex adhesive layers can be susceptible to copper
migration under T&H conditions with bias.  Look for dendrites within the
adhesive layer bonding the poly.
        What do your flex vendors say in terms of their THB REL data? Do
they offer flex products with different adhesive materials?


        Jeff Perkins
        Epitaxx

-----Original Message-----
From: Glenn Pelkey [mailto:[log in to unmask]]
Sent: Wednesday, August 04, 1999 1:34 PM
To: [log in to unmask]
Subject: [TN] Copper Migration


Hello Technetters not on vacation,

Has anyone seen copper migration within a flex?

I have a test running where I believe this has occurred, but until I get
some
SEM and EDX work done, nobody seems to believe me.  The conditions are just
right for electrochemical migration, 85 C/85 %RH, 20 volt bias on 60-mil
space, ionic contaminate (maybe, residual etch chemistry?).  I see dendrites
after 168 hours under test.  The traces are fully covered by the polyimide
cover layers, but I know that the adhesive has an affinity for moisture.

Besides my calls to the fab house and material supplier, I thought I'd ask
the
knowledge base here.  How about it?  Any experience you can share?  I have
photos of the affected area (although not very good) that I can share.

Thanks for your help,
Glenn

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