Ultrahigh-thermal-conductivity packaging materials

Thermal management problems are now critical in microelectronic and optoelectronic packaging. In response to the serious limitations of traditional packaging materials, material suppliers are developing an increasing number of new thermal management materials with low coefficients of thermal expansion (CTEs), ultrahigh thermal conductivities , and low densities. There are now fifteen low-CTE materials with thermal conductivities between that of copper (400 W/m-K) and four times that of copper (1600 W/m-K), several of which are being used in production applications like servers, ultra-lightweight notebook computers, printed circuit board cold plates, optoelectronic packages and plasma displays. Thermally conductive carbon fibers are being used to reduce the CTEs and increase the thermal conductivities of printed circuit boards. These materials greatly expand the options of the packaging engineer, making it possible to eliminate heat pipes and fans. This paper provides an overview of the state of the art of advanced packaging materials, including their key properties, state of maturity, applications, manufacturing, cost and lessons learned. We also look at likely future directions, including nanocomposites.