Solder Bond vs. Epoxy Bond as Thermal Interface Materials (TIM)

Thermal interface materials are materials used in creating heat conductive paths at interfaces between components and thus reduce thermal interface resistance. These materials permit more effective heat flow between separate components where heat is being generated to a heat dissipation components such as solid state transistors to heat sink or a high frequency device connected to a heat spreader. Thermal interface materials’ purpose is to fill the air gap that occurs at contact interfaces with more thermally conductive compounds to permit more effective heat flow than poorly conductive air.

There is a wide variety of thermal interface materials (TIM’s); thermal greases, phase change polymers, thermal tapes, gap filling pads, filled epoxies and solders. All having various costs, performance and manufacturing challenges.

S-Bond Thermal Interface
Figure 1. Illustration of thermal grease filling an interface
between a heat generating device and a heat sink.

Thermal greases are viscous fluid substance which increase the thermal conductivity of a thermal interface “gap by filling microscopic air-gaps present due to the imperfectly flat and smooth surfaces of the components as seen in Figure 1.

Thermal grease compounds have far greater thermal conductivity than air (but far less than metals). They are used in electronics, as depicted in Figure 2, to improve the heat flow from lower power electronic devices thus lowering the components temperature and increasing its life.