Design optimization and reliability of PWB level electronic package

Abstract

As the Electronic Packaging industry develops technologies for fabrication of smaller, faster, economical and reliable products; thermal management and design play an important role. The major part of the failures of the electronic components is temperature related. During thermal cycling, fatigue failures are caused due to mismatch of coefficient of thermal expansion (CTE) of different materials present in the components. Increased power dissipation and density in modern electronics system require efficient and intelligent design and thermal management strategies to ensure the reliability of electronic products. This paper discusses the reliability and design optimization of a generic Printed Wiring Board (PWB) level electronic package under thermal cycle loading. 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 ANSYS for providing the details on determining optimal design parameters which affect the product reliability. Combining finite element analysis with optimization would significantly reduce the design time and increases the product reliability. Four model characteristics: PWB core in-plane Young's Modulus, PWB core in-plane coefficient of thermal expansion, PWB core thickness and the stand-off solder joint height are chosen as the optimization inputs (design variables) that ensure higher reliability and improved performance of the assembled product. The objective of the optimization is to improve the fatigue life of solder joints of the package. Sub approximation, Design of Experiment (DoE) and Central Composite Design based Response Surface Modeling Methodology are used to study the effects of each design variables on the fatigue life.