Thank-you Ingemar, My suspicions is that far to many variables on this problem are undocumented. The actual force required to pull the BGA off the board, any pattern to the non-wetted pads, the dewetted pads and the lands pulled of the laminate, the effect of a second reflow for the back-side BGAs, how quick the switch-over from the HASL boards, which one of 6 SMT lines did the defects show up on, no DOE experimentation on either the creation of the 'Backward RoHS soldering process or looking for the factors on the defect causes (the defects are at a 2% to 5% fallout, 95+ % are good boards), how much handling while doing the 'cut & jumpers' on the bare boards before assembly, how much 'optimization' to the paste and reflow profile to handle a SAC305 balled FP BGA using tin-lead paste on an ENIG board that has been reworked. If I lined all the experts up, I would get a multitude of opinions. Happy Holden Hfjord <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 08/02/2006 03:42 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Hfjord <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] SAC-BGAs on ENIG Using SnPb solder paste Understand you are not happy, despite your forename. Agree with other guys, not easy to help via email only. However, I just wonder if your subcontractor is giving you all facts. I suspect (may be wrong, of course) that they had a primary problem with the wetting, which is not so unusual. What to do then? Run the boards a second time, maybe in combination with increased temperature to get better activation and wetting. The result may be better wetting, but also defective Cu-epoxy joints and unexpected IMCs, as was mentioned by other Technetters. I have learnt after many years in the game, not to rely too much on information given by subcontractors. Not that people mislead on purpose, but rather lack of disciplin and care. As your situation is also a economical disaster, I would doublecheck too see if there is some hidden facts before spending days and nights with sample examinations. Ingemar Hernefjord Ericsson Microwave Systems ----- Original Message ----- From: "Happy Holden" <[log in to unmask]> To: <[log in to unmask]> Sent: Monday, July 31, 2006 8:18 PM Subject: [TN] SAC-BGAs on ENIG Using SnPb solder paste > Greetings Assembly Experts, > This is the first time I have asked a question of this robust group of > technologists, but I am way beyond my knowledge of what can happen. > > We have many thousands of ENIG multilayers (8 and 10 layer-0.062") that an > assembler has returned as "Contaminated or Defective BGA pads". These > boards are smaller (3.0" x 4.25") but they have 3 to 5 fine-pitch BGAs > (0.8mm pitch with 0.3 mm lands) on the Primary side and some have an > additional FP BGA on the Secondary side. > The problem is that after reflow, if the BGAs are pulled, they come right > off the board. Some BGA pads are still gold, some pads come off from the > laminate, some solder joints just break. They returned the boards because > they said that the boards exhibited "non-wetting and de-wetting". > We have finally collected all the facts that we can about the assembly > process, and this is where I don't know what to expect, since the assembly > process seems to be a "Hybrid-RoHS Backward Compatible" assembly. Here is > what we know about the assembly process: > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 -----------------------------------------------------