SMTA International Conference Proceedings

Design And Material Parameter Effects on BGA Solder-Joint Reliability for Automotive Applications

Authors: Burton Carpenter, Thomas Koschmieder, Brett Wilkerson, Torsten Hauck Ph.D., John Arthur
Company: Freescale Semiconductor, Inc.
Date Published: 9/28/2014   Conference: SMTA International

Abstract: In recent years, under-the-hood automotive applications have increasingly had stringent board level reliability (BLR) requirements. 3000 cycles without failure for components mounted on boards and cycled between -40?C and +125?C is common. This paper describes experimental and modeling work to improve the board level reliability of BGA (Ball Grid Array) packages.

Two package types were studied: 292 I/O 0.8mm pitch 17mm x 17mm MAPBGA (292MAP), and 416 I/O 1.0mm pitch 27mm x 27mm TEPBGA (416PBGA). FEM (finite element modeling) simulations were completed on the 17mm package, and empirical studies were complete on both packages. A DOE (design of experiments) approach was used for both simulation and experimentation to understand the impact of a variety of design and material parameters. These included package pad diameter, solder sphere diameter, solder alloy, die thickness, substrate core CTE, substrate thickness, mold compound CTE, and mold thickness. Cross-section and dye-and-pry analyses were used to measure crack sizes at various cycle readpoints, and also to map failure locations.

Experimental results showed that increasing the package pad and sphere diameters had the greatest impact. Increasing from 0.4mm to 0.5mm for the 292MAP increased solder-joint life 33%. Similarly, increasing the diameter from 0.5mm to 0.6mm increased joint life 41% on the 416PBGA.

Failure analysis using both cross-section and dye-and-pry revealed that the BGA spheres directly under the die edge had the highest propensity to fail in the 17mm package. As a result, thinning the die from 279?m (11 mils) to 178?m (7 mils) improved reliability 22% 292MAP. However, die thickness was not a significant factor in the 416PBGA, which did not have spheres under the die edge. Solder alloy also had a significant effect.

Key Words: 

SJR (solder-joint reliability), SRO (solder resist opening), solder alloy, automotive, board-level reliability, ball grid array (BGA)

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