Werner,
You are absolutely correct, as usual.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, December 12, 2005 6:16 PM
To: [log in to unmask]
Subject: Re: [TN] Qualification of the Pb-free capable manufacturers
Hi Paul,
I certainly concur with you technical assessments--the reliability
bottleneck for LF-soldering will be in the PWB as well as in the
component areas, and less though with the solder joints, where most of
the efforts are concentrated.
There are people that understand these issues--there is you and PWB
Solutions, there is Hans Danielsson in Europe and I give workshops on
these issues. But you are correct, that the industry has not yet grasped
the importance of these issues. Thermal excursions to SnPb soldering
processes cost between 12 and 14% of the life of the PTHs/vias--going to
LF-solders and a 30C increase raises the cost to 18 to 20% of the
life--no wonder you saw what you reported.
The slash sheets for laminate/prepreg materials given in IPC-4101 are so
wide open in the ranges of properties that they are in fact useless. New
slash
sheets IPC-4101B/99, /101, /121, and /124 have been proposed for use
for
LF-soldering--again, the property ranges are much too wide to be useful
for any designer. I proposed a "Soldering Tempreature Impact Index
[STII]" for these slash sheets and was promplty shot down by the
committee consisting of lots of suppliers. The STII incorporates the 3
most important properties in this context, Tg, Td, and CTE.
Yes, there are people out there that understand the issues, the rest of
the industry will have to learn the hard way.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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