Thermal Conductivity of Diamond Composites

Abstract

A major problem challenging specialists in present-day materials sciences is the development of compact, cheap to fabricate heat sinks for electronic devices, primarily for computer processors, semiconductor lasers, high-power microchips, and electronics components. The materials currently used for heat sinks of such devices are aluminum and copper, with thermal conductivities of about 250 W/(m·K) and 400 W/(m·K), respectively. Significantly, the thermal expansion coefficient of metals differs markedly from those of the materials employed in semiconductor electronics (mostly silicon); one should add here the low electrical resistivity metals possess. By contrast, natural single-crystal diamond is known to feature the highest thermal conductivity of all the bulk materials studied thus far, as high as 2,200 W/(m·K). Needless to say, it cannot be applied in heat removal technology because of high cost. Recently, SiC- and AlN-based ceramics have started enjoying wide use as heat sink materials; the thermal conductivity of such composites, however, is inferior to that of metals by nearly a factor two. This prompts a challenging scientific problem to develop diamond-based composites with thermal characteristics superior to those of aluminum and copper, adjustable thermal expansion coefficient, low electrical conductivity and a moderate cost, below that of the natural single-crystal diamond. The present review addresses this problem and appraises the results reached by now in studying the possibility of developing composites in diamond-containing systems with a view of obtaining materials with a high thermal conductivity.

On critical aspects of infiltrated Al/diamond composites for thermal management: Diamond quality versus processing conditions

“…These composites, which are preferentially fabricated via gas pressure-assisted liquid metal infiltration, are known to exhibit excellent thermal properties [1][2][3][4][5][6][7][8][9]. Their thermal expansion coefficient, which is mainly determined by the volume fraction of present phases, can be tailored to desired values (4-5 ppm/K) for many metal-diamond combinations.…”

Graphene quilts for thermal management of high-power GaN transistors

“…Average temperature rise and non-uniform distribution of dissipated power in GaN transistors, leading to the formation of hotspots near device channels, result in degradation of the drain current, gain and output power, as well as an increase in the gate-leakage current and poor reliability 1 . Various thermal management solutions, for example, flip-chip bonding 4 or diamond composite substrates 5, have been attempted. However, the hotspots, which appear due to the non-uniform dissipation of the high-power densities and relatively high thermal resistance of the substrates 6,7 , still limit practical applications of the nitride-based technology [1][2][3] .…”

“…However, even in GaN transistors on SiC substrate, self-heating can lead to temperature rises, ∆T, above 180 °C. The composite substrates 5 and flip-chip bonding 4 were utilized to improve the heat removal by reducing the thermal resistance on the scale of the whole wafer. Despite these efforts, the problems of the hotspots that develop near the downscaled device channels-at the nanometre and micrometre-scale-still persist.…”

Phonon transmission across an interface between two crystals

“…The Kapitza resistance is a crucial parameter for calculating the heat conductivity of nanocomposite materials. These materials are needed for the development of compact, inexpensive, easily-fabricated heat sinks for electronic devices, primarily for computer processors [1,2]. The study of thermal transmission across the crystal interface, on in its own, attracts the attention to the problem of phonon transmission across the crystal interface since, in the majority of cases, the phonons are responsible for the energy transfer across the interface.…”