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Advancement in High Thermal Conductive Graphite for Microelectronic Packaging

Abstract:

New electronic devices are constantly becoming more powerful and more compact. High power components, including radio-frequency (RF)/microwave (MW) electronics, diode lasers, light emitting diodes (LED), insulated gate bipolar transistors (IGBT), central processing units (CPU), etc., are utilized in a wide variety of industries such as telecommunications, automotive, aerospace, avionics, medical, illumination, and materials processing. These electronics generate great heat that must be dissipated, or else the electronics can be damaged by heat buildup. New capabilities are constrained by the ability of designers to remove heat in a cost-effective manner. Generally, every 10 °C increase in chip junction temperature decreases the lifespan of the device by half. The U.S. Air Force estimates that 55% of its electronics equipment failures are due to thermal effects.

Conventional thermal management products are typically constructed of either copper or aluminum. In many cases, heat generated by power electronics has exceeded the dissipation capability of aluminum, or even copper. The heavy weight of copper also makes it a less favorable choice for certain applications such as avionics and portable devices. In addition, copper and aluminum have very high coefficients of thermal expansion (CTE), compared with the semiconductor materials from which electronic components are constructed. A mismatch in CTE with electronic components causes thermal stress in the mounted electronic devices at an elevated temperature. This stress can cause unreliable operation and eventually lead to component failure. To combat this problem, heat sinks with direct contact with semiconductor dies have been made from low-CTE materials such as aluminum silicon carbide (AlSiC), molybdenum-copper (MoCu), tungsten-copper (WCu), or copper-molybdenum laminates (CPC or CMC). However, these materials sacrifice thermal performance in exchange for better CTE matching with the electronic components.

In general, materials with high thermal conductivity, lightweight, and/or low thermal expansion are desired for high power thermal management application. In the rest of this chapter, we will discuss a group of advanced thermal management products based on high thermal conductivity and lightweight TPG graphite.