Development of the thin film with high thermal conductivity for power devices

In recent years, heat generation and heat density of electronic devices have been increasing due to highly integrated and high working frequency of semiconductors. Power devices have a cooling system to release its generated heat efficiently. For cooling system low thermal resistance material is required in order to conduct generated heat from semiconductor to the heat sink. This paper reports a very low thermal resistive film material developed for thin, high thermal conductive, good compliance to the surface to reduce thermal contact resistance and high resistance for dielectric-breakdown material for power devices. High thermal conductive films have been promoted in the market. However they have limitations of 1) thermal contact resistance due to low compliance to the surface caused by high modulus as a result of high loading volume of inorganic fillers, and 2) thickness to ensure the dielectric-breakdown resistance. For these challenges we have applied a low modulus resin to satisfy both high filler loading and compliance to the surface. We also have tried optimizing particle size and loading volume of inorganic filler. As a result of development we achieved to have a film material which can suppress corona discharge, has high dielectric-breakdown resistance even thickness is less than 100 um, and has more than 5 W/m-K of thermal conductivity. To confirm the heat dissipation performance of this material we performed to measure thermal resistance which has to be a key factor for the thermal design of power devices. The thermal resistance was 0.86 K/W when 50 μm compare to 1.45 K/W with conventional 125 um film in the market. It demonstrates that this material has very low thermal resistance. It is expected that using this film material may reduce the joint temperature of semiconductor and also improve thermo-mechanical reliability of the power device by a good stress relaxation performance given by low modulus.