Hi Richard, Just some food for thoughts. I've been looking at perfectly healthy solder joints on ENIG finished boards and measuring the content of P in the layer of electroless Ni layer quite a few times and every time the reading was way above 3%. Atotech has a few publications on the topic. In addition, doing quantification on a fracture surface isn't a very good way of getting some numbers, as the surface is obviously not perfectly flat. Regards, Vladimir -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D. Sent: Wednesday, March 19, 2008 4:22 PM To: [log in to unmask] Subject: Re: [TN] Case of the popping BGAs This analysis reads very similar to lab analysis reports I have had done in the past that turned out to be levels of grey pad or black pad. The key is the widely varying levels of P on different pads on the same board. This can cause anything from flat-out black pad to brittle failure. Anything over a P content of about 3% will begin to cause problems. Be sure to monitor the PWB lot codes. I hate to tell you this, but the problem will probably affect more than 1 assembly. As the assemblies see thermal excursions in their service life, the P barrier will continue to grow, causing more failures. Monitor the failures so you can detect a trend in the PWB lot numbers, this way you can be somewhat proactive in determining which assemblies have potential reliability issues. Where is that guy who told us that Black Pad was no longer a problem? Anybody heard from him lately? -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Gervascio, Thomas Sent: Wednesday, March 19, 2008 2:08 PM To: [log in to unmask] Subject: [TN] Case of the popping BGAs Want to ask the advice of the Learned Forum members. Had an experience where BGAs were falling off CCAs after shipment. Both the solder and the solder balls are Sn63/Pb 37 solder alloy. Had the parts and boards tested by a third party lab. Their results are "The following report is in regards to the failure analysis of the two largest BGA components on failed assembly . The following lists the analyses performed in the attempt to determine the root cause of the separation of the BGA components from the assembly: - SEM/EDS surface analysis of the failed PCB sites -SEM/EDS surface analysis of the corresponding failed BGA component sites -Micro-sectional/SEM evaluation of the failed PCB sites -Micro-sectional/SEM evaluation of the corresponding failed BGA component sites All evaluations were performed with a Camscan MV2300 thermionic emission scanning electron microscope (SEM), fitted with an Oxford EDS system (elementalanalysis). The images obtained during the analysis can be found in the following pages. Note: All micro-section samples were exposed to a chemical tin and copper etch, to better visualize the intermetallic layer (IMC). Results: SEM/EDS surface analysis The following tables show the EDS results (in weight%) of five randomly chosen sites on the failed PCB and failed component site respectively. All analysis was obtained at 10kV acceleration potential (ND = Not Detected): PCB site/small BGA Pad Ni Sn P C O 1 74.5 3.9 6.6 13.8 1.2 2 75.7 3.7 6.9 12.7 1.0 3 78.8 4.0 7.3 9.9 ND 4 77.7 4.1 6.8 11.4 ND 5 81.1 3.6 7.9 7.5 ND PCB site/large BGA Pad Ni Sn P C O 1 80 3 .2 4 .7 11.3 0.9 2 81.1 2.4 5.3 11.3 ND 3 72 4.3 6.7 15.9 1.1 4 77.5 4.9 7.4 10.3 ND 5 78 5.5 7.5 8.9 ND Component site/small BGA Pad Ni Sn Pb C O P 1 42.9 24. 8.1 23.6 7.1 0.6 2 25.1 23 5.1 32.7 13.7 0.3 3 42.8 26 2.4 22.4 5.9 0.5 4 49.8 28.3 1.5 16.5 3.3 0.6 5 35.5 20.7 1.4 31.1 10.8 0.5 Component site/large BGA Pad Ni Sn Pb C O P 1 42.3 27.3 1.7 23.2 5.0 0.4 2 37.9 23.3 1.3 28.6 8.3 0.6 3 40.7 26.4 1.8 25.2 5.4 0.5 4 47.4 29.2 2.4 16 4.3 0.6 5 38.7 25.3 2.8 24.7 8.4 0.2 Small BGA: PCB site; very thin areas of IMC were detected, but too thin to measure. Nickel thickness was measured to be approximately 133 micro-inches. No signs of nickel corrosion were detected. Component site; an average of 2.09um of IMC layer thickness was measured on a total of three BGA solder balls evaluated. All solder balls showed proper ball collapse and IMC formation, indicating a sufficiently hot assembly reflow profile. Large BGA: PCB site; very thin areas of IMC were detected, but too thin to measure. No signs of nickel corrosion were detected. Component site; an average of 1.52um of IMC layer thickness was measured on a total of three BGA solder balls evaluated. All solder balls showed proper ball collapse and IMC formation, indicating a sufficiently hot assembly reflow profile. , What levels of Phosphorus would be expected in a nickel plating that exhibits Black Pad? Any other ideas relating to the failure mechanism and methods to validate them? Thanks Tom --------------------------------------------------- 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 -----------------------------------------------------