Thermal management plays a major role in the electronic and packaging design of power electronic systems. It takes a combination of heat-reducing devices to ensure the reliability of power electronic systems. The primary concern is maintaining the junction temperature of power semiconductors within the manufacturer's limits. Another concern is the operating temperature of passive components where forced-air cooling may be necessary to keep their characteristics within the prescribed limits. In either case, a power electronic system's reliability may hinge on the ability of electronic and mechanical designers to prevent excessive heating of components.
The most visible of the heat-reducing devices are heatsinks. They come in many different shapes, colors, and construction techniques. They are stationary, reliable devices that eliminate heat via condition and radiation. Fin structures can be pins, flat plates, or other variations of the flat plates. Fans are the answer for forced-air convection cooling of the hotter power electronic systems. They consume power, produce audible noise, and can cause EMI if not properly designed, but they may be the only answer for systems that dissipate hundreds or thousands of watts. However, fan system reliability has improved in the last decade, helped in part by motor drive ICs that control fan speed in accordance with the ambient temperature. In some cases, fans combine with heatsinks to provide a more efficient cooling system.
Although you may not notice them within a power electronic system, thermal interface materials have found use in mounting power semiconductors to heatsinks. These materials compete with the “old-fashioned” silicone grease in getting the heat out of power semiconductors. They provide electrical isolation and good thermal conductivity. Articles in this special report cover these important topics and other advances in thermal management.