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In this paper, the two-flume method was used to study the change laws of the thermal conductivity and thermal expansion coefficient of diamond/Cu composite materials with 100, 300, and 500 cycle numbers, under the action of thermal shock load between −196 and 85 °C; the X-ray diffraction method (XRD) was used to study the change of the residual stress in the thermal shock process of the diamond/Cu composite materials; and the evolution of the fracture microstructure with different thermal shock cycle numbers was observed through scanning electron microscopy (SEM). The results of the study show that the increase of the binder residue at the interface reduces the thermal shock stability of the diamond/Cu composite materials. In addition, under the thermal shock load between −196 and 85 °C, the residual stress of the diamond/Cu composite materials increases continuously with the increase of the cycle numbers, the increase of residual stress leads to a small amount of interface debonding, an increase of the interfacial thermal resistances, and a decrease of the constraints of low-expansion component on material deformation, thus the thermal conductivity decreases slightly and the thermal expansion coefficient increases slightly.

The thermal conductivity of diamond hybrid SiC/Cu, diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper. The effects of the particle volume fraction, the particle size and the volume ratio of the diamond particles to the total particles on the thermal conductivity of the composite were studied. The DEM theoretical calculation results show that, for the diamond hybrid SiC/Cu composite, when the particle volume fraction is above 46% and the volume ratio of the diamond particles to the SiC particles is above 13:12, the thermal conductivity of the composite can reach 500 W·m−1·K−1. The thermal conductivity of the composite has little change when the particle size is above 200 μm. The experimental results show that Ti can improve the wettability of the SiC and Cu. The thermal conductivity of the diamond hybrid SiCTi/Cu is almost two times better than that of the diamond hybrid SiC/Cu. It is feasible to predict the thermal conductivity of the composite by DEM theoretical model.

The package and system level temperature and thermal stress distributions of 10 W light emitting diode (LED) with 4 chips and 100 W LED with 100 chips were investigated using finite element analysis. The chips were arranged on a Si sheet which is soldered on the copper/diamond composite slug with very high conductivity. The experimental results show that the maximal temperature appears in the chips of both two high power LEDs packages. Compared with the 10 W LEDs package with 4 chips array, the heat issue caused by stacking and coupling of the heat in 100 W LEDs package with 100 chips array is more serious. The chip temperature in the center of the array is much higher, and it decreases with the distance between the chip and the center of LEDs increases. Great thermal stress lies between the chips and the solder, which will reduce the reliability of the package.

The thermal conductivity of diamond/copper composites with bimodal particle sizes was studied. The composites were prepared through pressure infiltration of liquid copper into diamond preforms with a mixture of 40 and 100 μm-size diamonds. The permeability of the preforms with different coarse-to-fine volume ratios of diamonds was investigated. The thermal conductivity of the diamond/copper composites with bimodal size distribution was compared to the theoretical value derived from an analytical model developed by Chu. It is predicted that the diamond/copper composites could reach a higher thermal conductivity and their surface roughness could be improved by applying bimodal diamond particle sizes.

Diamond reinforced copper (Cu/diamond) composites were prepared by a pressure infiltration technique. The composites show a super high conductivity of 713 W·m−1·K−1 in combination with an extremely low coefficient of thermal expansion (CTE) of 7.72 × 10−6 K−1 (25–100°C), which are achieved by modifying the copper matrix with adding 0.3 wt.% of boron to get a good thermal contact between the matrix and the diamond particles. By adopting a series of postmachining techniques the composites were made into near-net-shape parts, and an electroless silver coating was also successfully plated on the composites. Finally, their potential applications in the thermal management of light emitting diodes (LED) were illustrated via prototype examples.

Diamond/Cu-xCr composites were fabricated by pressure infiltration process. The thermal conductivities of diamond/Cu-xCr (x = 0.1, 0.5, 0.8) composites were above 650 W/mK, higher than that of diamond/Cu composites. The tensile strengths ranged from 186 to 225 MPa, and the bonding strengths ranged from 400 to 525 MPa. Influences of Cr element on the thermo-physical properties and interface structures were analyzed. The intermediate layer was confirmed as Cr3C2 and the amount of Cr3C2 increased with the increase of Cr concentration in Cu-xCr alloys. When the Cr concentration was up to 0.5 wt.%, the content of the Cr3C2 layer was constant. As the thickness of the Cr3C2 layer became larger, the composites showed a lower thermal conductivity but higher mechanical properties. The coefficients of thermal expansion (CTE) of diamond/Cu-xCr (x = 0.1, 0.5, 0.8) composites were in good agreement with the predictions of the Kerner’ model.

The thermal conductivity of SiCp/Al composites with high volume fractions of 46 to 68% has been investigated. The composites were fabricated by pressureless infiltrating liquid aluminum into SiC preforms with monomodal and bimodal size distributions. The density measurement indicates that a small amount of pores is presented for the composites approaching their maximum volume fractions. An analytical model with an explicit expression is proposed for describing the thermal conductive behavior of the composites with multimodal-reinforced mixtures in terms of an effective medium approach taking into account the porosity effect. Predictions of the developed effective medium expression reveal good correspondence with the experimental results, and explore how each of the considered factors (i.e., particle size ratio, volume fraction ratio, and porosity) can have a significant effect on the thermal conductivity of the composites with bimodal mixtures.

AlSiCp (65 vol.% SiC) electronic packaging materials were manufactured by powder injection molding (PIM) and pressure infiltration process in order to obtain near net-shaped parts. SiCp preformed compacts obtained by pre-sintering process at 1150 K have high strength and good appearance, and the ratio of open porosity to total porosity is nearly 98%. The relative density of composites is bigger than 99%. The thermal conductivity of AlSiCp composites fabricated by this method is 198 W.m −1 .K −1 , and the coefficient of thermal expansion (CTE) is 8.0 x 10 −6 /K (298 K).

Carbon nanotube–copper (CNT/Cu) composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS) technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.