Investigation on interaction between indium based thermal interface material and copper and silicon substrates

The continuous progress in miniaturization and integration of semiconductor devices have led to increasing heat generated from unit volume in the chip. Consequently, more efficient thermal management on chip and package level is required because the reliability of electronic equipment strongly decreasing with rising the temperature of work. To improve the heat dissipation from chip to package as well as from package to heat sink the thermal interface material (TIM) is applied. One of the most important parameter of TIMs is their thermal conductivity. Example of such high thermal conductive TIM is a composite structure based on an electrospun polyimide structure infiltrated with indium. Nevertheless the thermal conductivity of TIM is not only parameter which influence on the efficiency of thermal management. It is also important their interaction with the joined materials, because the voids or delamination between TIM and chip or substrate would dramatically increase thermal contact resistance and decrease the heat transfer efficiency. Moreover the brittle intermetallic compounds which would be formed in the interface would decrease the reliability of such joints. Therefore in this study the interface between two types of materials (silicon die and copper substrate) and the polymer nanofiber-metal TIM as well as pure indium was examined. The subject of the investigation is the stack consisted of copper substrate, TIM (or pure indium) and silicon. The interfaces between layers after aging process were analyzed experimentally by using the 3D X-Ray computed tomography, metallography and optical microscopy as well as by SEM equipped with EDS (X-ray spectroscope).