A Tenfold Reduction in Interface Thermal Resistance for Heat Sink Mounting

Reactive NanoTechnologies (RNT) has developed a new platform joining technology that can form a metallic bond between a chip package and a heat sink and thereby offer a thermal interface resistance that is ten times lower than current thermal interface materials (TIM). The joining process is based on the use of reactive multilayer foils as local heat sources. The foils are a new class of nano-engineered materials, in which self-propagating exothermic reactions can be initiated at room temperature with a hot filament or laser. By inserting a multilayer foil between two solder layers and a chip package and heat sink, heat generated by a chemical reaction in the foil heats the solder to melting and consequently bonds the components. The joining process can be completed in air, argon or vacuum in approximately one second. The resulting metallic joints exhibit thermal conductivities two orders of magnitude higher, and thermal resistivities an order of magnitude lower, than current commercial TIMs. We also demonstrate, using numerical modeling, that the thermal exposure of microelectronic packages during joining is very limited. Finally we show numerically that reactive joining can be used to solder Si dies directly to heat sinks without thermally damaging the chip.