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Subject:	Re: Antw: [TN] Intermetallic thickness
From:	Earl Moon <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Tue, 26 Feb 2002 08:25:20 -0600
Content-Type:	text/plain
Parts/Attachments:	text/plain (38 lines)

I've been reading IPC-D-279 with great interest. However, I get a little
more confused about thick IMC layers especially after reading the following:

IPC-D-279

A-3.3 CAVEAT 1 ? SOLDER JOINT QUALITY
The solder joint fatigue behavior and the resulting reliability prediction
equations. Eqs. A-1 through A-2, were determined from thermal cycling
results of solder joints that failed as a result of fracture of the solder,
albeit sometimes close to the IMC layers. For solder joints for which
layered structures are interposed between the base material and the solder
joints, these equations could be optimistic upper bounds if the interposed
layered structures become the ?weakest link? in the surface mount solder
attachments. Such layered structures could be: metallization layers that
have weak bonds to the underlying base material, or are weak themselves, or
dissolve essentially completely in the solder; oxide or contamination layers
preventing a proper metallurgical bond of the solder to the underlying
metal; brittle IMC layers TOO THICK due to too many or improperly long high
temperature processing steps.

Guenter, I'm sure you, Werner, and Dave H. and all others on this planet can
end my pain. I'm talking, of course, about the last, very long paragraph in
the caveat.

MoonMan

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