Dewey, Marion, Hey, be easy on Werner our res expert on reliability. If I knew half as much German as he knows English I would be happy! :) regards, Bev Nortel Networks > -----Original Message----- > From: Marion A. Graybeal [SMTP:[log in to unmask]] > Sent: Wednesday, July 28, 1999 11:44 AM > To: [log in to unmask] > Subject: Re: [TN] Freeze Spray and BGAs > > Werner, > > I see that you and Dan Quail attended the same school (potatoe). > > Marion Graybeal > ----- Original Message ----- > From: Werner Engelmaier <[log in to unmask]> > To: <[log in to unmask]> > Sent: Wednesday, July 28, 1999 10:07 AM > Subject: Re: [TN] Freeze Spray and BGAs > > > >Hi Darrelt, > >What happened to your BGA is pretty obvious. Just consider what is > physically > >happening when you hit iot with the freeze spray. > >You hit the BGA with the freeze spry from the top, I am sure. This > quickly > >cools the top layer of the BGA, the rest of the BGA to a lesser degree. > That > >sets up differential thermal shrinking (the opposite of thermal expansion > on > >heating), which causes the BGA to warp like a potatoe chip with the top > >surface being concave. This puts tremendous tensile stresses on the > solder > >joints, as well as on other parts in the BGA depending on construction. > On > >top of which, the PCB does not cool very much at all (the BGA shields it > from > >the freeze spray) and sets up shear stresses between the BGA and the PCB. > >I would not at all be surprised if failure analysis shows fractured > solder > >joints. likely in combination of soldering pads ripped out of the polymer > >matrix. > > > >Werner Engelmaier > >Engelmaier Associates, L.C. > >Electronic Packaging, Interconnection and Reliability Consulting > >7 Jasmine Run > >Ormond Beach, FL 32174 USA > >Phone: 904-437-8747, Fax: 904-437-8737 > >E-mail: [log in to unmask], Website: www.engelmaier.com > > > >############################################################## > >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c > >############################################################## > >To subscribe/unsubscribe, send a message to [log in to unmask] with > following > text in > >the body: > >To subscribe: SUBSCRIBE TECHNET <your full name> > >To unsubscribe: SIGNOFF TECHNET > >############################################################## > >Please visit IPC web site (http://www.ipc.org/html/forum.htm) for > additional > >information. > >If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] > or > >847-509-9700 ext.5365 > >############################################################## > > > > ############################################################## > TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c > ############################################################## > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in > the body: > To subscribe: SUBSCRIBE TECHNET <your full name> > To unsubscribe: SIGNOFF TECHNET > ############################################################## > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for > additional > information. > If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or > 847-509-9700 ext.5365 > ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################