Werner, Is the epoxy placed before reflow? Before placement? What I'm trying to figure out is how you keep from disturbing the BGA placement during epoxy application. Blair -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Tuesday, April 17, 2007 11:32 AM To: [log in to unmask] Subject: Re: [TN] Tacking corners of BGAs Hi Richard, The improved reliability should not have come as a surprise. Consider what is happening: (1) the solder balls are at their full diameter when BGA is placed, (2) the epoxy fixes the distance between PCB and BGA at that diameter value, (3) during reflow, the epoxy expands opening the solder gap further, (4) on cooling, that solder balls are prevented by the epoxy from collapsing, (5) you have the equivalent reliability of using non-melting 10Sn90 Pb solder balls, and (6) this results in the reliability improvement observed. I have been pushing this for ceramic chipp components for some time. Werner ************************************** See what's free at http://www.aol.com. --------------------------------------------------- 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 ----------------------------------------------------- ******************************************************************* This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept for the presence of computer viruses. www.Hubbell.com - Hubbell Incorporated --------------------------------------------------- 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 -----------------------------------------------------