The need for faster, smaller, and more reliable and efficient products has resulted in increase of heat generated in microelectronic components. The removal of the heat generated is an important issue in electronic packaging. A novel Nano-TIM was developed to improve the heat dissipation of electronics packaging. This paper aims at studying the heat dissipation performance of a new class of nano-structured polymer-metal composite film (Nano-TIM) after power cycling. The new Nano-TIM uses metal to provide continuous thermal pathways while using nano-polymer to control the elasticity of the TIM. Through semiconductor processing and RTD principle, chips including 5*5, 10*10, 20*20, 30*30 (mm 2), were developed to study different size's influence on heat dissipation effect of the Nano-TIM. Additional parameters studied include power effect. RTD is used respectively to measure the junction temperature, and then the R thJC (Junction-to-Case Thermal Resistance) is calculated afterwards. The Transient thermal resistances of the Nano-TIM were also tested by T3Ster method to further study heat dissipation effect of Nano-TIM. The morphologies and interaction between the Nano-TIM and chips were carefully studied using X-ray Scanning Microscope to analyze heat flow path. The result shows that Nano-TIMs can be used to 30 mm in chip length as the thermal interface material.