Hi Richard,
In a message dated 02/21/2002 2:04:38, [log in to unmask] writes:
>but then I've heard discussion that a fast cool down can produce a better
solder joint metallurgically....
Yes, this was a bit of red herring in the early 80's. Faster cooling produces
finer grained solder joints which in accelerated testing show about a factor
of 2 longer life. Unfortunately, the grain structure of solder coarsens with
time and temperature and after one year on the shelf you cannot tell the
difference. That is why both IPC-SM-785 and IPC-9701 strongly recommend
artificial aging to coarsen the solder grain structure prior to T-cycling to
prevent unrealistic high test results.

Werner Engelmaier

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------