It's interesting and logic in the explanation below. But more
     important is how to prevent it. Any suggestion?

     Regards,
     KenF


______________________________ Reply Separator _________________________________
Subject: Re: [TN] Electromigration of Tin Lead?
Author:  "TechNet E-Mail Forum." <[log in to unmask]>  [log in to unmask] at
Internet
Date:    5/26/99 2:26 PM


Hi Phil,
The "feathery migration tracks" you are describing are most likely dendritic
growth, sometimes called 'Conductive Anodic Filaments (CAF)'. Dendritic
growth starts as the migration of metal, and other salts, along paths created
by structural imperfections. This migration requires moisture, water in most
cases, but the presence of an electrical potential is not necessary. When
electrical potential is applied, the migration is more rapid and organizes
itself into CAF.  CAF leads to a reduction in insulation resistance, and
depending on the currents present can create localized shorts and burn-out.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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