Many relationships are described, one of which is a Curtiss-Wright report. They have exposed identical boards to SnPb soldering/repair and compared with same for SACs, and found a significant difference in time to failure. 

                  
                                       1st thermal cycle to failure

					As Received				6 x 230 Celcius			6 x 260 Celcius

Mean						788					443					4



That is a dramatic change in via failures.  We have seen some failures recently on ordinary double sided FR-4 boards, which were exposed to several heat exposures in conjunction with electrical testing. Far from 260 Celcius, think only 125 Celcius. If we got microvia issues with only 125 C, what if we use 260 C (e.g. repeated repair)?

Has anyone seen any signs of via failure due to increased heat exposure in practice?


Inge
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------