SMT007 Magazine

SMT-Feb2014

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February 2014 • SMT Magazine 41 TeSTING INTerMeTaLLIC FraGILITy ON eNIG uPON aDDITION OF LIMITLeSS Cu continues FEATUrE More research must be conducted to com- pare the intermetallic morphologies created in these tests with those observed in standard component attach. Since individual solder joints cannot be mechanical tested in a BGA the only comparison that can be made is through intermetallic morphological comparison. An improved HBP test method may provide pull testing results that vary based upon ball at- tach method and solder alloy. Current equipment offerings can mimic pin temperatures that are in- dicative of a mass reflow as shown in Figure 22. Future research Further testing of the HBP test is required to better mimic a surface mount process. Research is being developed to test a standard ramp, soak, reflow soldering profile as well as pins of vari- ous alloys. Test methods for HBP testing may only be applicable for devices attached to cir- cuit boards with Ni substrates since intermetal- lic formation rates are far slower and the system is less elementally complex. acknowledgements Universal Instruments Corporation's Ad- vanced Process Lab would like to thank Indium for supplying materials and Nordson Dage for assisting with equipment setup. SMT references 1. D.Q. Yu, C.M.L. Wu, D.P. He, N. Zhao, L. Wang, J.K.L. Lai,. "Effects of Cu contents in Sn– Cu solder on the composition and morphology of IMCs at a older/Ni interface," J. Mater. Res., Vol. 20, No. 8, Aug 2005. 2. R.C. Kao, "Cross-Interaction Between Cu and Ni in Lead-Free Solder Joints" APEX Presen- tation March 12, 2006. 3. R. Pandher, and A. Pachamuthu, "Effect of Multiple Reflow Cycles On Solder Joint For- mation And Reliability" SMTAi 2010 Confer- ence Proceedings. 4. B. Roggeman, and W. Jones, "Character- izing the Lead-Free Impact on PCB Pad Craters", APEX 2010 Conference Proceedings. 5. G. Milad, D. Gudeczauskas, G. O'Brien, and A. Gruenwald, "A Study of the ENEPIG IMC for Eutectic and LF Solders" SMTAi 2010 Con- ference Proceedings. 6. JEDEC JESD22-B115A, "Solder Ball Pull" JEDEC Solid State Technology Association, Au- gust 2010. Martin Anselm is manager of the ArEA Consortium at Universal Instruments and SMTA Training Committee chair. Figure 22: hbP reflow pin temperature profile used for current research into this test method.

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