Henry and all,
An associated issue I've experienced is the inability to accept solder due
to degraded solderability of the surface after multiple thermal excursions.
Depending on plating materials, processes, thermal duration, aging, etc. the
surface may not accept solder at all when the IM approaches the surface.
Basically it is nonsolderable and aggressive fluxes are not the solution.
Common consideration in the provision of 55110 and the supporting assembly
process standards was 5 thermal cycles including the fabrication and
production process. That does not leave many rework cycles before expected
degradation.

Best of luck,
Mel

Mel Parrish
Director of Training
Soldering Technology International
102 Tribble Drive
Madison, AL 35758
256 705 5530
256 705 5538 Fax
[log in to unmask]
www.solderingtech.com

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Werner Engelmaier
Sent: Wednesday, June 19, 2002 7:48 AM
To: [log in to unmask]
Subject: Re: [TN] Intermetallic Joint Failure


Hi Henry,
The problem with "rework" is not IMC layers getting too thick, but the
damage
done to the solder joints of neighboring components and the PWB. In all my
years in reliability, I have never seen an "Intermetallic Joint Failure."

Best regards,
Werner Engelmaier

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