Surface Mount International Conference Proceedings


EFFECT OF THERMAL AGING ON THE MICROSTRUCTURE AND RELIABILITY OF BALL GRID ARRAY (BGA) SOLDER JOINTS

Author: Edwin Bradley
Company: Motorola
Date Published: 9/10/1996   Conference: Surface Mount International


Abstract: Plastic Ball Grid Array (PBGA) packages are used in Motorola’s wireless two-way radio products due to their improved electrical performance and space savings on the PCB relative to leaded packages. One of the causes of solder joint failures in assemblies with PBGAs is due to PC board bending. Solder joint failures caused by board bending induced solder joint deformation are often located at the interfaces where the solder has wetted to the PCB metallization. The formation and growth of interrnetallics at these interfaces can substantially impact assembly-level reliability. This study investigated the solder joint reliability of BGA packages under three point bending as a function of aging (100 to 170°C for up to 1500 hours) before the package is reflowed onto the PCB. The failure modes in three point bending and tension are related to the development of intermetallics at the BGA solder joint interfaces. Finite element analysis of the assembly deformation in tension and three-point bending was validated with the test results. This validation allows calculation of the local stresses at the interface for various package/board geometries. KEYWORDS: BGA, solder joint reliability, intermetallic, FEA modeling



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