Overview
Thermal interface materials (TIMs) play a key role in connecting
the heat source with the heat-spreader or the heat sink, ensuring
the efficient transfer of heat. The effective thermal resistance RTIM at the interface has two components: The bulk resistance Rbulk of the TIM arising from its finite thermal conductivity and the
contact resistance Rc between the TIM and the adjoining solids:
where BLT is the bond-line thickness of the TIM, kTIM is the thermal conductivity of the TIM, and Rc1 and Rc2 are the contact resistances of the TIM with the two adjoining surfaces.
The thermal conductivity of a TIM is enhanced by loading a polymeric matrix with conducting solid particles, such as aluminum, alumina and boron nitride. Thermal conductivity of particle-laden TIMs depend on the filler thermal conductivity, and volume fraction, as well as on the contact resistance between the particles and the polymeric matrix.
One of the main problems of particle-filled materials is their limited stability in terms of phase segregation and paste pumping. The latter effect is the interpenetration of a thin paste layer by an air bubble, which can be understood using the Hele-Shaw theory.
Publications
[1] T. Brunschwiler, U. Kloter, H. Rothuizen, and B. Michel, "Hierarchically nested channels for fast squeezing interfaces with reduced thermal resistance," 21st IEEE SEMI-THERM Symposium, San Jose, CA (2000).
[2] T. Brunschwiler, U. Kloter, R. Linderman, H. Rothuizen, and B. Michel, "Hierarchically nested channels for fast squeezing interfaces with reduced thermal resistance," Trans. Comp. Packag. Technol., in press.
