Modern microelectronics are perpetually pushing against limitations caused by inadequate heat dissipation. One of the critical bottlenecks is at the interfaces between different materials and components. Thermal interface materials (TIM) are used to improve the heat transfer at these interfaces, and to improve TIMs is one of the critical research areas in order to reduce the total thermal resistance for electronics systems.A TIM requires both high thermal conductivity, ability to conform to mating surfaces, and the ability to absorb stress from thermal expansion mismatch during thermal cycling. Solder based TIMs utilize solder to form a strong connection between the mating surfaces with high thermal conductivity, but their stiffness prevents adequate absorption of thermal expansion mismatch. In this thesis, the solder is combined with a fiber network phase, which modifies the mechanical properties, while maintaining the continuous heat paths within the solder. This solder matrix fiber network composite TIM allows for the tailoring of the mechanical properties of solder based TIM while retaining thermal performance. Another promising TIM candidate is based on arrays of vertically aligned CNTs. CNT arrays can achieve good thermal performance, but the reliability had not previously been investigated experimentally. A thorough investigation of the reliability of CNT array TIM revealed that reliability is not guaranteed, but requires careful matching between CNT array height, bonding method and substrate configuration.Furthermore, we developed a new joule self-heating chemical vapor deposition (CVD) method for the synthesis of double-sided CNT arrays on thin foils, which can be used both as TIM or as supercapacitor electrodes. Double-sided arrays are challenging with conventional CNT array synthesis methods, but the Joule heating CVD method allows for rapid, scalable and uniform synthesis of large area double-sided arrays. Finally, this method was used to study the effect of heat treatment of CNT arrays on graphite. The heat treatment serves to simultaneously improve the CNT crystallinity, eliminate catalyst residues, and form a seamless connection between CNT arrays and graphite
