Improved thermal interface materials for cooling high power electronics
Heat has been a major concern in electronics since the beginning of the electronic age, when hot glowing vacuum tubes were first used to receive and transmit bits of data. The transistor and IC effectively solved this basic problem, but increasing integration resulted in increased concentration of heat, exacerbated by relentless increases in operating frequency. While improvements in electronics technology have been able to alleviate many chip-level thermal issues through improved semiconductor designs designed to operate at lower voltages (thereby requiring less power), the management challenge thermal continues to frustrate electronics developers. Additionally, with the introduction of increasingly dense heterogeneous integration solutions, this should remain a concern for the foreseeable future. Thermal engineers have long known that thermal energy must ultimately be “sent back into the air,” but getting it there efficiently is of great importance. They also know that there are only three basic ways of removing heat from a system: conduction, convection, and radiation; of these, conduction is by far the most efficient.
In printed circuit board manufacturing, especially those used in high-power applications, the board itself becomes an obvious potential way to help remove heat. However, the choice must be made carefully to ensure that it fits well into the traditional manufacturing scheme, as the materials required must not only conduct away heat, but must also maintain the high electrical insulation properties. which are of vital importance to PCB and product designers. they develop. This has been a primary focus of Aismalibar for some time and so the company has developed a family of new Thermal Interface Material (TIM) technologies designed specifically for PCBs. The unique materials the company has developed have thermal conductivities of up to 3.2 W/mK (tested to ASTM D5470) and high electrical insulation properties of up to 6 KV AC. (For comparison, nominal laminated materials have thermal conductivities of 0.25 W/mK.)
Conceptual model of thermal management chain in power electronics
Thermal interface materials are used by design in power electronics modules to facilitate the transfer and dissipation of heat generated by active and passive power components on the circuit board by allowing efficient heat transfer. heat through a cooling chain to a downstream cooling element, such as a heat sink or heat pipe and cooling fan. The ultimate goal is to ensure that the maximum component temperature specified by the manufacturer is not reached.
In addition to providing high thermal conductivity, TIM must also provide adequate electrical insulation properties; this is particularly and increasingly important in high voltage environments such as those found in modern electric vehicles. The more balanced the trade-off between thermal conductivity and electrical insulation capability of the TIM, the higher the performance and reliability of the entire power electronics module over its lifetime.
To read the full article, which appeared in the March 2022 issue of PCB007 magazine, click here.