Finite element modeling of heat transfer and thermal stresses for three-dimensional packaging of power electronics modules

The state-of-the-art packaging technology for power electronics modules uses wire bonds to interconnect power devices. Emerging 3-D interconnected power package designs have shown their advantages over conventional wire bonding modules in higher power density, reduced interconnect resistance and parasitic oscillations, better thermal management, higher level of system integration and lower cost. The authors attempt to eliminate the use of wire bonds has led to the development of a three-dimensional, stacked-plate technique. With this technique, thick metal posts are directly soldered onto power devices to form an interconnected 'flat-pack' package that potentially offers improved electrical and thermal performance. On the other hand, high-density 3-D power modules experience more stringent environmental conditions such as thermal cycles during the fabrication and operation. Due to different thermal expansion coefficients (CTE) in different materials, cyclic stresses may lead to thermal fatigue and failure of power modules. A study in this respect will help understanding the key issues of thermal management and thermo-mechanical reliability for 3-D power electronic packaging. In this paper, the authors present a finite-element modeling of thermal and thermomechanical behavior in a power module fabricated by this technique.