Design Optimization and Reliability of PWB Level Electronic Package

摘要

As the electronic packaging industry develops technologies for fabrication of smaller, faster, economical and reliable products, thermal management and design play an important role. Temperature fluctuations caused by either power consumption or environmental changes, along with the resulting thermal expansion mismatch between the various packages materials result in deformation stresses in packages/assemblies especially in solder interconnects. Increased power dissipation and density in modern electronics system requires efficient and intelligent design and thermal management strategies to ensure the reliability of electronic products. In the past reliability issues related to optimization of electronic packages were dealt with by coupling analysis tools with optimization solvers. In this paper, ANSYS APDL code is used with a built-in optimization tool for optimization of electronic packages, and for improving the solder joint life and arriving at optimal design. It has been shown that, design optimization would enormously decrease the lead time. The finite element tool ANSYS is used to estimate the cycles to fatigue failure of solder joint of the package coupled with optimization module present in the solver for providing the details on determining optimal design parameters that affect the product reliability. Four model characteristics: printed wiring board (PWB) core in-plane Young's modulus, PWB core in-plane coefficient of thermal expansion, PWB core thickness, and the standoff solder joint height are chosen as the optimization inputs (design variables) that ensure higher reliability and improved performance of the assembled product. The objective junction of the paper is to minimize average plastic work to improve the fatigue life of solder joints of the package. Subapproximation, design of experiment and central composite design based response surface modeling methodologies are used to study the effects of each design variables on the fatigue life.