Novel heatsink for power semiconductor module using high thermal conductivity graphite

The thermal properties and reliability of novel heatsinks that use high thermal conductivity graphite were investigated. Graphite plates with different high-thermal-conductivity directions were laminated together using an Ag-based brazing material, with thin Cu plates on their outer surfaces. The heatsinks were bonded to Si heater chips using Sn-3Ag-0.5Cu solder. Samples with conventional Cu or Cu-65Mo heatsinks were also fabricated as references. The samples were attached to an active cooling plate subjected to a constant water flow, and thermal and reliability measurements were conducted. The experimental results were also compared with the results of a finite element analysis. The novel laminated heatsinks exhibited a lower thermal resistance than the Cu or Cu-65Mo heatsinks, and the experimental results were in reasonable agreement with those of the finite element analysis. The graphite-based heatsinks had better power cycle reliability than Cu-based heatsinks. Therefore, these novel graphite heatsinks have potential for application to power semiconductor modules, it seems to be useful for applications with high heat flux of power semiconductor devices.