TECHNET Archives

January 2003

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 23 Jan 2003 10:11:35 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (66 lines)
Werner,

Well said!
Now is anyone listening!

David A. Douthit
Manager
LoCan LLC

Werner Engelmaier wrote:

> Hi Howard,
> I have never seen: Spec Number TSC7514g, section 5.4, reference specification
> TSC 7010g, or anything like it, and I have been involved in SMT reliability
> for almost 25 years.
> >The first question is: is this customer using their own test or is there an
> >IPC test for thermal cycling of a completely assembled circuit board?
> ANSWER: The test (Ts, dwell times) is reasonable, except for its use of
> thermal shock--T-shock will give you totally misleading results, because the
> high T-gradients cause component and PWB warpage, and thus create tensile
> loads not seen in product. Further, a different damage mechanism in the
> solder [see Günter's response] occurs due to the much higher stress levels
> occurring with T-shock. For test guidelines and a standard go to IPC-SM-785
> and IPC-9701.
>
> >The second question is: is the customer's temperature range too extreme,
> >which is causing severe thermal shock, which is then causing joint failures
> >due to different co-efficients of expansion and contraction  (board, solder,
> >lead)?
> ANSWER: For T-cycling, the Ts are not extreme. For T-shock the differences in
> CTEs are not as much of a factor as are the T-gradients.
>
> >The third question is: is the use of 3,500 hours of thermal cycling realistic
> >and/or too long?
> ANSWER: For T-cycling no--all bets are off for T-shock.
>
> Werner Engelmaier
> Engelmaier Associates, L.C.
> Electronic Packaging, Interconnection and Reliability Consulting
> 7 Jasmine Run
> Ormond Beach, FL  32174  USA
> Phone: 904-437-8747, Fax: 904-437-8737
> E-mail: [log in to unmask], Website: www.engelmaier.com
>
> ---------------------------------------------------
> 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
> -----------------------------------------------------

---------------------------------------------------
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
-----------------------------------------------------

ATOM RSS1 RSS2