Hi, Marie,
One thing that has always concerned me, but which doesn't seem to have
panned out as a big issue so far, is the question of what happens to
absorbed moisture in components at temperatures below zero when the
equipment is unpowered. Does it freeze, expand and delaminate the host
component?
To answer your question directly, though, I haven't generally found that
taking components outside their stated operating temperature range actually
causes them any physical damage. That is, no damage unless you exceed the
temperatures at which the constituent materials degrade, but even with
commercial devices, I doubt you're doing that in a -40 to +70 range.
Commercial components are only rated from 0 deg C to +70 deg C, but what
this means is that the functional performace is only guaranteed within this
temperature range. Above or below that, functionality and/or performance
may drift, and normally, that's about all. Components should come back into
spec when they re-enter their given temperture range.
What is the nature of the failures you're experiencing? Are they "hard"
failures (no electrical contact, or intermittent contact), or are they just
drifting out of spec? You could conceivably have solder joint cracking,
depending on the quality of the processes you used to assemble the boards
and the number of temperature cycles cmpleted before failure occurs.
There are probably more questions than answers with your problem, which may
spark off another grand thread.
Good luck
Peter
ME Magnin <[log in to unmask]> 11/02/2003 12:14 AM
Sent by: TechNet <[log in to unmask]>
Please respond to me.magnin
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: [TN] Dammage on components at low temperatures
Dear Technetters,
we have build PCB's with a commercial range processor (and a few other
components), and tried to have it work at -40¡ãC.
of course, it failed, this could be predictable.
our concern is that the board failed too when tested during raising
temperature to +40¡ãC (via a low temperature gradiant), because of several
dammaged components.
our R&D engineer is investigating to determine the cause of the failure,
but
it brought me to the following question : is there any risk to destroy a
component when using it at a temperature lower than the lower limit ?
if yes, which process does dammage the component ?
thanks for sharing your experience
kind regards
Marie Magnin
QA Manager
FIRSTEC SA
Rue du Grand Pr¨¦ 70
CH 1211 Gen¨¨ve 2
T¨¦l. : +41(0)22 918 36 85
Fax : +41(0)22 918 36 93
mailto:[log in to unmask]
http://www.firstec.ch
---------------------------------------------------
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
-----------------------------------------------------
[This e-mail is confidential and may also be privileged. If you are not the
intended recipient, please delete it and notify us immediately; you should
not copy or use it for any purpose, nor disclose its contents to any other
person. Thank you.]
|
