Thanks for the thoughtful response. One of the other MEs here is thinking that this is a normal appearance, that the SAC305 solder uniformly separated from the intermetallic when we reflowed and pulled the BGA. I wish this was the case but it seems unlikely. Isn't the affinity of the bulk solder to the intermetallic higher than its surface tension? On Thu, Dec 21, 2017 at 4:26 PM, Yuan-chia Joyce Koo <[log in to unmask]> wrote: > Steve, your friend might need cross section and see if UBM is done > correctly, besides, the solder mask looks extra thick for a device... > didn't look like std BT substrate... cross section of good vs after reflow > one might give you some clue what is wrong... the color of the pad look > like poor adhesion of the nickel layer... it might be poorly done either > possiviation layer prior to balling (either ImAg, ImAu or ImTin), or > missing etchant step (or pH adjustment not done properly) prior to last > immersion plating step...IMHO. > On Dec 21, 2017, at 2:39 PM, Steve Gregory wrote: > > Hi all, >> >> I've been asked to post this to the Technet by a dear friend: >> >> *We installed this little processor. At test we identified opens on the >> device. When we removed it we saw a number of pads that were matte gray >> with no evidence of solder adhered to the pad. * >> *We attempted to bump the pads with solder, they did not wet easily. In >> some cases we had to scrape through the matte finish to a shiny metal. >> But, we did get all the pads to appear wetted.* >> >> *We cleaned the site well and then fluxed the bumps with a tacky flux ROLO >> designed for POP, placed the BGA and reflowed it on a rework station.* >> >> *The assembly failed test with similar result, opens under the processor.* >> >> *The attached photo shows that the bump process only appeared to wet the >> pads. The condition returned when we removed the BGA second time.* >> >> * http://stevezeva.homestead.com/2017-12-21_11.21.17.jpg >> <http://stevezeva.homestead.com/2017-12-21_11.21.17.jpg>* >> >> *Have you seen this before? Is there any recovery? This assembly is worth >> about $45K. * >> >> Thanks, >> >> Steve >> >> -- >> Steve Gregory >> Kimco Design and Manufacturing >> Process Engineer >> (208) 322-0500 Ext. -3133 >> >> -- >> >> >> This email and any attachments are only for use by the intended >> recipient(s) and may contain legally privileged, confidential, proprietary >> or otherwise private information. Any unauthorized use, reproduction, >> dissemination, distribution or other disclosure of the contents of this >> e-mail or its attachments is strictly prohibited. If you have received >> this >> email in error, please notify the sender immediately and delete the >> original. >> >