Surface Mount International Conference Proceedings


Author: Roger Rorgren
Company: IVF
Date Published: 4/28/1997   Conference: Surface Mount International

Abstract: This paper addresses reliability aspects that users of BGA packages may be concerned with. Results from reliability tests under harsh automotive-like environmental conditions are presente4 involving a number of different BGA packages, including OMPACS, Super BGAs and Tape BGAs, as well as fine-pitch quad flatpacks serving as a reference. All packages were mounted to standard gold-plated FR-4 test boards, specifically designed for the tests. Parameters such as pad design BGA substrate thickness, and use of underfill or conformal coating, were varied in order to study their influence on the reliability. Daisy chain packages were used to check the electrical performance of the solder joints whereas micro-sectioning and the use of a dye penetrant were employed to study the joint quality. The environmental tests comprised temperature cycling from -40 to 100”C, with and without simultaneous exposure to vibration (8 G, 10-500 Hz) during the high temperature phase, as well as humidity cycling from 25 to 65 “Cat 93 % RH. The results show that non-soldermask defined (NSMD) pads on both board and package gives superior performance for the PBGA361, compared to when solder mask defined (SMD) pads are used. The PBGA256, as well as the QFP reference samples, all pass at least 4000 cycles from -40 to 100 “C without failure. Cross-section analysis, performed after 6000 temperature cycles, shows extensive cracking, which however can be avoided if an underfill is used. A dye penetrant was successfully employed as a complementary technique, giving added value when combined with cross-sectioning.

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