"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."
FULL STORY @ RNTFOIL (http://www.rntfoil.com/technology/documents/RNT-2003-IMAPS.pdf)