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58 SMT007 MAGAZINE I APRIL 2018 mismatched by 2ppm/°C, versus 7ppm/°C for the standard material. Therefore, at low temper- atures the package using a low CTE substrate material should warp less. Though it was not manifest in the room temperature coplanarity data, the TherMoire results clearly show a tran - sition to temperature range where the standard material package is significantly more warped. Results of the electrical tests were clear: the lower CTE added over 950 cycles to the char- acteristic life, and nearly 1,200 cycles to the first failure. Cross-section and dye-and-pry did not show clear trends. The inconclusiveness of the crack growth data likely resulted from the small sample sizes. Based on the strength of the electrical test and warpage data, the low CTE substrate dielectric material did perform better. Verification will be needed to confirm the results, ensure it scales across different package types, and to better analyze the crack growth mechanics. Conclusions The conclusions are: • A hybrid design, mixing SMD and NSMD pads on the same package is feasible for manufacturing, and was demonstrated to improve the solder joint characteristic life of a 512TEPBGA package by 30%. • Lowering the package substrate dielectric CTE from 16ppm/°C to 11ppm/°C was demonstrated to improve the solder joint characteristic life of a 512TEPBGA package by 22% • Greater than 3000 cycles to first failures for the 512TEPBGA package solder joint lifetime in -40°C to +125°C TCoB testing. Acknowledgements The author wishes to recognize the support and contribution of Andrew Mawer, Paul Galles, John Arthur, Alvin Youngblood, Roy Arldt, Betty Yeung, Eli Trevino, and B.Y. Low. SMT007 References 1. A. Mawer, D. Cho and R. Darveaux, "The Effect of PBGA Solder Pad Geometry on Solder Joint Reliability," Surface Mount International, September 1996. 2. J. Suhling, et al., "Reliability of Small BGAs in the Automotive Environment," SPIE Proceedings, 2002. 3. B. Carpenter, T. Koschmieder, B. Wilker- son, T. Hauck, J. Arthur, "Design and Material Parameter Effects on BGA Solder joint Reliabil- ity for Automotive Applications," SMTAI 2014, Rosemont, Illinois. 4. "Performance Test Methods and Qualifi- cation Requirements for Surface Mount Solder Attachments," IPC-9701, February 2006. 5. "Coplanarity Test for Surface-Mount Semi- conductor Devices," JEDEC JESD22-B108A, January 2003. 6. "Package Warpage Measurement of Surface-Mount Integrated Circuits at Elevated Temperature," JEDEC JESD22-B112A, October 2009. 7. T. Burnette and T. Koschmieder, "Solder joint failure analysis: Dye penetrant technique," electroiq.com. 8.B. Carpenter and T. Koschmieder, "Solder joint Reliability of 0.8 mm BGA Packages for Automotive Applications," SMTAI 2015, Rose- mont, Illinois. Editor's Note: This article was originally published in the proceedings of SMTA International 2016. Burton Carpenter is a senior principal engineer at NXP Semiconductors Inc. Cross-section and dye-and-pry did not show clear trends. The inconclusiveness of the crack growth data likely resulted from the small sample sizes.