And to re-inforce the points being made, those lessons that Werner
mentions will be very costly.
For "proper" testing of lead free PWB materials the only real decision
is not whether to IST test the materials, but actually should be "how
many 260 C excursions shall I put the test coupons through BEFORE IST
testing, as a preconditioning?" and also be prepared to carry out CSAM
on your testing of materials to ensure that there is no delamination
taking place.
By the way Werner, how is Hans?, I have not seen him for 20 years...
John Burke
Senior Manager - Operations , Optichron
[log in to unmask]
W: 510 249 5233
M: 408 515 4992
http://www.optichron.com
Profile: https://www.linkedin.com/e/fps/2665502/
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, December 12, 2005 4:16 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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