I forgot to mention, that I have seen how the solder balls elongate during pull or prey test. They change from a flatted ball to a barrel. That means that the volume between the BGA and the board nearly doubles! I was very surprised. Didn't think solder was like chewing gum. Does the coating or underfiller really expand that much? I'm very interested in this, as we produce boards with a lot of largest available BGAs. Inge PS. Will see if I still have the amazing photos from the test. ----- Original Message ----- From: "Inge" <[log in to unmask]> To: "TechNet E-Mail Forum" <[log in to unmask]>; <[log in to unmask]> Sent: Monday, November 30, 2009 10:15 PM Subject: Re: [TN] BGAs & Conformal Coating > Doug, > > how can that be possible? When temperature rises, the coating ought to > soften and should expand even horisontally, and when at lower > temperatures, the coating should crimp. The only way I can see is if you > have the situation of a closed in liquid, which one cannot be compressed. > BGAs use to be very hard to rip from the board. I measured some 350 kg > force necessary to pull off a very large BGA. > > Inge > > > > ----- Original Message ----- > From: "Douglas Pauls" <[log in to unmask]> > To: <[log in to unmask]> > Sent: Monday, November 30, 2009 2:29 PM > Subject: Re: [TN] BGAs & Conformal Coating > > > Good morning Juan, > I suspect that Xilinx wants you do do a thermal cycle study on solder > joint reliability when conformal coating gets under the BGA. The stresses > brought about by a mismatches in the coefficient of thermal expansion > (CTE) can rip a BGA off the board and can severely deform the balls. > Hillman and I did such a study here a few years ago. I can share a few > pictures of what happens, if Steve Gregory would be kind enough to forward > his present e-mail address for the photos. Not sure I have the right one. > > Doug Pauls > > > > "Juan T. Marugán" <[log in to unmask]> > Sent by: TechNet <[log in to unmask]> > 11/26/2009 11:53 AM > Please respond to > TechNet E-Mail Forum <[log in to unmask]>; Please respond to > "Juan T. Marugán" <[log in to unmask]> > > > To > [log in to unmask] > cc > > Subject > [TN] BGAs & Conformal Coating > > > > > > > Hi, > > I've read in a Xilinx guide that: "Xilinx has no experience or reliability > data on > flip-chip BGA packages on board after exposure to conformal coating. It is > > recommended that the end-user should characterize the board level > reliability > performance of Xilinx packages before production use." > > Does anybody know any infomation or study related with this topic? > > Thank you. > > Juan T. Marugán > Indra Sistemas SA > Espańa > > --------------------------------------------------- > 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 > ----------------------------------------------------- > > > --------------------------------------------------- > 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 > ----------------------------------------------------- > --------------------------------------------------- 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 -----------------------------------------------------