CUVAR-a new controlled expansion, high conductivity material for electronic thermal management

The increasing level of integration and operating speed of integrated circuit chips is leading to larger chip sizes with higher power dissipation. Electronic packages incorporating such devices require low cost and highly efficient thermal management materials for reliable performance of the device. W/Cu and Mo/Cu materials are often used as heat sinks or substrates for direct bonding the Si devices. While W and Mo based materials possess the required thermal expansion and thermal conductivity for electronic packages, they are difficult to machine and fabricate into intricate shapes. This report describes a new thermal management material, called CUVAR, which possesses low thermal expansion and high thermal conductivity. CUVAR is an extruded composite of copper and Invar powders, where Invar restrains thermal expansion while copper provides thermal conductivity. Most importantly, CUVAR is easily machined, enabling high speed and efficient fabrication of components. It is readily plated with copper, nickel, silver or gold for joining and finishing. CUVAR is an alternative to low thermal expansion materials such as Kovar and Alloy 42 with a much higher thermal conductivity. CUVAR can also be a replacement for the conventional W and Mo based thermal management materials with the advantages of low cost and excellent fabricability for high volume applications.