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 -----------------------------------------------------