Shear Modulus Measurement for Thermal Interface Materials in Flip Chip Packages

During the thermal interface material (TIM) development for flip chip packages, it was found that the shear storage modulus, G', was a key parameter impacting the material processing and the package thermal performance. When the G' was too low, the TIM was pumped out easily after curing. When the G' was too high, delamination occurred at the interfaces between the TIM and die or heat spreader, especially at the die corners. Due to the significant warpage caused by the large die size, the TIM needs to be a soft gel. This will allow the material to maintain its interfacial adhesion at large deformation. In this paper, the shear modulus testing method for TIM's development will be discussed