Solder-Joint Reliability of a 0.65mm Pitch Molded Array Package for Automotive ApplicationsAuthors: Burton Carpenter, Mollie Benson, A. R. Nazmus Sakib, Andrew Mawer, Paul Galles, Abdullah Fahim
Company: NXP Semiconductors, Inc.
Date Published: 9/22/2019 Conference: SMTA International
The paper reports experimental board level temperature cycle results of a 0.65 pitch, 10x10mm MAPBGA (molded array plastic BGA) package test vehicle that could be used as an automotive radar microprocessor. Thermal fatigue life was assessed per IPC-9701A using AATS (air-to-air thermal shock) between -40ºC and +125ºC.
A 13 cell DOE (design of experiments) examined various combinations of package BGA pad surface finishes (electroplated Ni/Au and OSP [organic solderability preservative]) and five package solder ball alloys (SnAg, SAC105, SAC105N, SAC405, and SAC-Bi [a Bi containing SAC derivative]). NanoIndentation on solder-joint cross-sections were used to correlate localized hardness and microstructure to the solder-joint lifetimes.
Good wetting occurred on the BGA pad OSP surface. The solder-joint lifetimes followed clear trends. The Ni/Au BGA pad surface finish outperformed OSP. SAC-Bi was the best performing alloy, followed by SnAg, SAC405 and SAC105/SAC105N, in that order. No differences were observed for the OSP surface finish provide by different substrate suppliers.
Solder-joint reliability, SnAg, SAC, temperature cycle, thermal fatigue, NanoIndentation, OSP
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