Modeling and Experimental Study of Thin Bond Line Thermal Interface Material Failure

Thermal delivery has become an even tougher a challenge with the increasing levels of integration, which drives the demand for low bond line thicknesses of the thermal interface materials (TIM) in electronic packages. The low elongation property of thin bond line thermal interface in turn leads to significant complications for reliable electronic packaging. Package encapsulation needs to be carefully designed to handle the thermal expansion mismatch driven stress engendered during the bond and assembly (BA) process and in field operation. In this paper, special attention is paid to the material characterization of the thin bond line thermal interface. As the thickness of TIM is comparable to its filler particle size, the mechanical behavior of the TIM cannot be described by the material properties determined with traditional testing techniques using bulk specimens. To fill this gap, testing coupons are built with the dimensions of field application. A testing technique developed for characterizing the TIM will be discussed. The material properties obtained will be implemented into the commercial finite element codes ABAQUS through its cohesive zone model. Thermo-mechanical modeling to predict the propagation of TIM delamination and model verification will be presented. The impact of TIM tearing on other risks associated with electronics encapsulation will be discussed.