In a message dated 12/16/99 6:25:30 PM Central Standard Time, [log in to unmask] writes: > Hi everyone ... I have been looking at solder joint failures for quite a > while and have stumbled on something new to me. I hope someone has seen > this and can give me some insights. Here it is ... > > * the failures occur on a number of different component types including > SOICs, QFPs, SMT caps (not chip caps) > * the failure is complete interfacial failure of the mounting pad at > the copper/IMC interface (i.e the solder, Cu6Sn5 and Cu3Sn layers stay > with the component lead) > * the board finish was HASL and the IMC layer appears normal (i.e. ~ > 1-2 microns total thickness) > * the copper is heavily oxidized. However, I believe this is because > the crack existed for a long period of time (perhaps?) > * I see no convincing evidence of contamination at the failed interface > > * the failure does not appear to be related to an electroplated copper > interface > > Based on past experience, this type of thing seems to be caused by gross > thermal shock!?! Have any of you seen the type of failure I have > described? If so, what was the conclusion as to cause? > > Best regards, > Ed Hare > VP SEM Lab, Inc. Hi Ed, I'm just guessing a bit, but there maybe a problem with the design of the boards. I've run acoss problems in the past (as many other technetters have) that there are via's that have been laid-out very close to surface mount pads, no thermals and very little trace length to a surface mount pad. During wave soldering, they provide very good thermal transfer to re-reflow SMT solder joints and actually cause the solder fillets to separate from the pads with the fillets intact to the leads...one could inspect the joints under a microscope and you wouldn't know there was a problem unless you actually put some side-ways force to the leads and see that there was observed movement...there maybe enough contact to pass ICT, but fail shortly...which may explain the heavily oxidized copper... Just guessing... -Steve Gregory- ############################################################## 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 ##############################################################