Hi Jim,
I think it was understood by everybody that manual--and therefore
uncontrolled--soldering processes, be they production or rework, are the
worst temperature excursions seen by the PCB, and thus will produce the most
PTV failures.
I am intrigued by you making laminate choice as important as Cu
thickness--are you referring to low-Tg vs. high-Tg materials? That certainly
would make sense particularly in combination with manual soldering processes.
You say: "The Z axis expansion of the laminate after several thermal
excursions is remarkable." What happens in most cases that the first cycle
brings crack initiation, which propagates to completion on subsequent cycles.
The z-expansion is essentially the same for each cycle as long as Tmax is the
same.

Werner Engelmaier

---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/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
-----------------------------------------------------