Copper Diamond Composites Research Articles

Preparation and Properties of Porous Diamond Preforms

A binder comprising of 60% PW (paraffin wax), 10% HDPE (high-density polyethylene), 12% PS (polystyrene), 13% PPR (random-polypropylene), and 5% SA (stearic acid) has been selected and successfully employed to fabricate the diamond preforms possessing high strength and well shape retention capability. Various effects of processing methods on the properties of the diamond preforms have been investigated. The results indicate that the binder consisting of PW-HDPE-PS-PPR-SA possesses excellent comprehensive rheological properties and is more appropriate as the organic vehicle for fabricating porous diamond preform. It has been evaluated that the mixing of 140m size diamond particles with 20m size diamond particles in the weight proportion of 3:1 provides the best particle size distribution for preparation of diamond preforms. It is also observed that impregnation of preform with 1.7wt (SiO2)% water glass and subsequently heat-treated in vacuum at 800°C for 40min yields in high strength (with the strength of 7.1 MPa) diamond preform for infiltration. The strengthened preforms have been observed to possess an excellent shape maintaining capability. It is concluded that the diamond-copper composites fabricated by utilizing this high strength preform through hot-press infiltration method have high relative density of 96.4% and thermal conductivity of 300W.m-1.K-1.

Effect of carbide formers on microstructure and thermal conductivity of diamond-Cu composites for heat sink materials

Diamond-copper composites were prepared by powder metallurgy, in which the diamond particles were pre-coated by magnetic sputtering with copper alloy containing a small amount of carbide forming elements (including B, Cr, Ti, and Si). The influence of the carbide forming element additives on the microstructure and thermal conductivity of diamond composites was investigated. It is found that the composites fabricated with Cu-0.5B coated diamond particles has a relatively higher density and its thermal conductivity approaches 300 W/(m·K). Addition of 0.5%B improves the interfacial bonding and decreases thermal boundary resistance between diamond and Cu, while addition of 1%Cr makes the interfacial layer break away from diamond surface. The actual interfacial thermal conductivity of the composites with Cu-0.5B alloy coated on diamond is much higher than that of the Cu-1Cr layer, which suggests that the intrinsic thermal conductivity of the interfacial layer is an important factor for improving the thermal conductivity of the diamond composites.

Multiple Fan-Heat Sink Cooling System With Enhanced Evaporator Base: Design, Modeling, and Experiment

A cooling device using stacked centrifugal fans and circular heat sinks was designed for cooling a semiconductor chip with a heat flux near 125 W/cm2. In this device, heat is conducted from the chip to a copper heat distribution block and then distributed to multiple heat sinks via four heat pipes. The copper block with embedded heat pipes or evaporator block was optimized using finite element analysis, and several cases were validated with experimental data. The experiments showed great benefits by having a second fan/heat sink in the device. The copper block by itself was found to contribute more than half of the overall thermal resistance of the cooling device. The thermal spreading resistance of the block can be reduced by about 70% if a piece of high-conductivity material, such as a diamond-copper composite, is inserted into its base. The thermal spreading resistance is generally lower when the thickness of the high-conductivity base piece increases. However, the analysis shows that the benefit of using a high-conductivity base tapers off as the thickness of the base piece nears the diameter of the heat pipes (δ∗=1) and weakly worsens after (δ∗>1). The base will also not have a benefit when the size of the chip approaches that of the copper block (A∗=1).

Interface Design in Copper-Diamond Composite by Using PVD and CVD Coated Diamonds

One of the key problems in copper-diamond composites is the interface between the metal matrix and the diamond reinforcement. In order to take advantage of the high thermal conductive diamond filler in a composite the design of the interface is crucial. One approach to minimize the thermal contact resistance between metal and diamond reinforcement is to coat the diamonds with functional layers, e.g. Mo or W. For coating of diamonds PVD and CVD have been used followed by characterization of coating thickness by different methods. The coated diamonds were used for composite manufacturing and the thermal diffusivity of the compacted materials was measured.

A study on graphitization of diamond in copper–diamond composite materials

The graphitization of diamond particles in the copper–diamond composite materials used for low voltage electro-contacts was investigated by SEM, TEM and X-ray diffraction (XRD) analyses. The results show that although diamond is a metastable allotropic modification of carbon, the diamond particles are not graphitized to an apparent extent after sintering at 1150–1220 K in the copper–diamond composite. The reason for this phenomenon was discussed. The diamond powders prepared by explosion synthetic method are supposed to possess higher resistance to graphitization and thus benefit the performance of the copper–diamond composite used for electro-contacts.