Increasingly powerful electronic devices generate more heat. Unless that heat is dissipated efficiently, the device performance suffers. To accomplish this, a thermal interface material is required between the hot component and the heat sink.
The main function of TIMs is to transfer the generated heat from the conductive surface to the heat sink, thus preventing electronics from reaching dangerous temperatures. TIMs come in a variety of forms, including pads, pastes, tapes and gels, and they use various fillers that provide differing inherent and wet out thermal conductivities.
As such, selecting the right TIM for your assembly application is critical. The inherent thermal conductivity of the TIM—measured in Watts per meter-Kelvin—determines how much heat it can disperse over time. The wet out property—how well the TIM fills gaps and eliminates air between mating surfaces—is also an important attribute to consider.
A TIM is composed of a soft resin that serves as the base material, as well as fillers that have been chosen for their high thermal conductivity, as well as their physical properties and density. Some of the most popular TIM fillers are boron nitride (BN), aluminum nitride (AlN) and alumina (Al2O3).
Another key attribute to consider is the temperature at which the TIM experiences a phase change, as this determines how easily it flows onto the mating surfaces and expel any remaining air. For best results, the selected TIM should experience a phase change at a lower temperature than the maximum operating temperature of the assembled product.