High Efficiency Heat Sinks from Polycrystalline Diamond Grown by CVD Method
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0956-J08-04
High Efficiency Heat Sinks from Polycrystalline Diamond Grown by CVD Method Oleg A. Voronov, Gary S. Tompa, and Veronika Veress Diamond Materials Inc., 120 Centennial Ave., Piscataway, NJ, 08854 ABSTRACT While absolute power levels in microelectronic devices are relatively modest (a few tens to a few hundred watts), heat fluxes can be significant (through 50 W/cm2 in current electronic chips and up to 2000 W/cm2 in semiconductor lasers). Diamond heat sinks enable heat transfer rates well above what is possible with standard thermal management devices. We have fabricated heat sinks using diamond, which has the highest temperature thermal conductivity of any known material. Polycrystalline diamonds manufactured by chemical vapor deposition (CVD) are machined by laser and combined with metallic or ceramic tiles. Cooling by fluid flow through micro-channels enhances heat removal. These unique attributes make diamond based heat sinks prime contenders for the next generation of high heat load sinks. Such devices could be utilized for efficient cooling in a variety of applications requiring high heat transfer capability, including semiconductor lasers, microprocessors, multi-chip modules in computers, laser-diode arrays, radar systems, and high-flux optics, among other applications. This paper will review test designs, heat flux measuring system, and measured heat removal values. INTRODUCTION Thermal loads of electronics continue to increase due to increased device densities and/or power loading. Predictions for the heat generated by high-end devices such as microprocessors and microcontrollers are predicted to exceed 200 Watts by the end of the decade [1]. Therefore, more efficient heat exchangers are needed for the next generation electronics. Recent developments in micro-manufacturing, such as lithography, electroplating, and modeling (LIGA), have enabled micro-channel heat exchangers that are lighter, more compact, and provide better heat transfer to pressure drop ratios than traditional plate-fin heat exchangers. Diamond Materials Inc. has developed and characterized a micro-channel diamond based heat sink system which was formed utilizing micro-fabrication technologies. The heat sink has highstrength and is lightweight, compact, and offers a superior heat-transfer solution. Table I: Thermal conductivity of heat transfer materials at ambient temperature. Material Property Thermal Conductivity ⎛ W ⎞ ⎜ ⎟ ⎝m⋅K ⎠
at 300 K
Polycrystal Monocrystal
Cu
Ag
401
429
Graphitic Carbon 1.6 (am.) 50200 (cer.) 400-1000 fibers 5.7 ||c 2000⊥c
SiC
Al2O3
31
30
490 ||c
47||c, sapphire
GaN/ GaAs
~60/
58
BeO
Diamond
230
200-600
370
6002300
Heatsinks with tiny flow channels (micro-channels) make it possible to boost heat transfer rates well above what is possible with ordinary cooling devices. The enabling process is the physical movement of heat “collected” in addition to heat conduction. The range of heat transfer coefficients attainable varies with different fluids and cooling schemes. Air is the most
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