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Heat has been a significant concern in electronics since the beginning of the electronics age when hot glowing vacuum tubes were first used to receive and transmit data bits. The transistor and integrated circuit effectively solved that basic problem, but increases in integration resulted in increased concentration of heat, exacerbated by relentless increases in operating frequency. While improvements in electronics technology have been able to mitigate many thermal issues at chip level thanks to improved semiconductor designs devised to operate at lower voltages (thus requiring less energy) the thermal management challenge continues to vex electronic product developers. Moreover, with ever denser heterogeneous integration solutions now being introduced, this is expected to remain a concern to be addressed for the foreseeable future. Thermal engineers have long known that thermal energy must ultimately be “returned to the air” but getting it there in an efficient way is of great importance. They know also that there are but three basic ways of removing heat from a system: conduction, convection, and radiation; of these, conduction is by far the most efficient.
In the manufacture of printed circuits, especially those used in high power applications, the board itself becomes an obvious potential means of helping to remove heat. However, the choice must be made carefully to assure that it fits well into the scheme of traditional manufacturing, as the materials required must not only remove heat but must also maintain the high electrical insulation properties that are vitally important to printed circuit designers and the products they develop. This has been a primary focus of Aismalibar for some time and the company has accordingly developed a family of new thermal interface material (TIM) technologies designed specifically for printed circuits. The unique materials the company has developed have thermal conductivities up to 3.2 W/mK (tested according to ASTM D5470) and high electrical insulation properties of up to 6 KV AC. (For comparison, nominal laminate materials have thermal conductivities of 0.25 W/mK.)
Concept Model for Thermal Management Chain in Power Electronics
Thermal interface materials are used by design in power electronics modules to facilitate the transfer and dissipation of the heat generated by the active and passive power components on the printed circuit board by enabling efficient transfer of heat though a cooling chain to a downstream cooling element, such as a heat spreader or heat pipe and cooling fan. The ultimate objective is to ensure that the maximum component temperature specified by the manufacturer is not reached.
In addition to providing high thermal conductivity, the TIM must also provide adequate electrical insulation properties; this is especially and increasingly important in high-voltage environments such as those experienced in modern electric vehicles. The better balanced the compromise between thermal conductivity and electrical insulation capability of the TIM, the higher the performance and reliability of the entire power electronics module over its service life.
To read this entire article, which appeared in the March 2022 issue of PCB007 Magazine, click here.