Hi Amol,
There is something happening that you have not observer/mentioned.
You say: "LF laminate subjected to Pb-Free processing exhibited mixed-mode
failures; both cratering and IMC fracture was observed. The IMC fractures were
secondary failures occurring after the pad had failed."
So what is different? What is different is the much higher LF-soldering T—
thus, whatever is happening is most likely related to the high T's.
What I do not understand is, how you can get IMC fractures after the pad
cratering has occurred—if the SJ is no longer attached to the PCB, where are the
loads coming from? When you say IMC failures, what exactly do you mean? IMC
layers very rarely, if ever fail as such—they may be on one side of the
separation with the other side being somethiing other than IMC.
The PCB thickness is not the issue, fixturing should avoid problems—there are
other underlying root causes. How fast are you cooling from reflow?
At the end you say that "our SnPb variant of the same product...works without
any issues", but earlier yoou said you got pad cratering. Which is it?
Werner Engelmaier
Future workshops:
Solder Joint Reliability: Parts 1 through 4, July 17/18, Thal, Switzerland
Pb-Free Soldering Processes—Survival, Quality, Reliability, August 18,
Orlando
Reliability Issues with Lead-Free Soldering Processes, September 22,
Schaumburg
Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture,
ENIG), September 22, Schaumburg
**************
Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.
(http://autos.aol.com/used?ncid=aolaut00050000000007)
---------------------------------------------------
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
-----------------------------------------------------
|
