Solder joint attachment reliability evaluation and failure analysis of the 244 I/O pre-molded PolyHIC package

The analyses and tests used to evaluate the long-term surface mount attachment reliability of the PolyHIC (polymer hybrid integrated circuit) package are described. Mechanical shock resistance was predicted by analysis and verified by mechanical shock testing. The PolyHIC has a large thermal expansion mismatch with the bare printed circuit board due to the ceramic substrate and heat sink metals. The combination of this mismatch and the PolyHIC´s large size resulted in significantly higher solder joint strains during thermal cycling than in smaller plastic quad flat pack and plastic leaded chip carrier packages. Thermal cycling life predictions made using the figure of merit model predicted that failures would occur very early in the design life due to environmental stress testing, transportation, and storage environments. Preliminary small sample thermal cycling tests showed much greater solder joint fatigue life than predicted. A complete thermal cycling test was then performed to characterize the long-term attachment reliability. The experimental results were extrapolated to design use conditions and failure rates were predicted. The PolyHIC was found to have adequate attachment reliability for its intended application