Subject: | |
From: | |
Reply To: | |
Date: | Fri, 11 Mar 2005 07:21:49 EST |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
Hi Valerie,
CTE matching comes from the 'old' ceramic leadless chip carrier days.
Exact matching is not a practical idea, because
(1) for active components with power dissipation, it is better that the
component has a CTE about 2 ppm/C [depends on power dissipated] higher than the
PCB;
(2) all of these materials have CTE's in ranges; thus you get the ~CTE +/-
1ppm/C;
(3) how small the delta-CTE needs to be depends on the the attachment method
[balls (diameter), columns, compliant leads], and your reliability goals;
(4) what affects SJ reliability is the effective CTE; thus not all layers
have to be the same.
Second-best advice, get a copy of IPC-D-279; best advice, of course, is
consult me.
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
---------------------------------------------------
Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
|
|