Preparation And Properties Of Low Expansion, High Thermal Conductivity Copper Matrix Composites For Electronic Packaging

The integration of electronic components increased rapidly due to the requirements of small,light and fast.Correspondingly,the chip heat and heat deformation of the materials increase dramatically.The thermal performance of conventional packaging materials,such as Al and Cu,can not meet the application requirements,and the research of materials with low expansion and high thermal conductivity has become an urgent need.In this paper,Cu/Sc₂W₃O₁₂ and Cu/SiC/Sc₂W₃O₁₂ composites were prepared by powder metallurgy method with Cu as the matrix and the negative thermal expansion material Sc₂W₃O₁₂ and low thermal expansion material SiC as the reinforced materialss.The microstructures and thermal properties of the composites were characterized in detail.The main research contents and results are as follows:?1?Homogeneous mixtures of plake-Sc₂W₃O₁₂ powders prepared by solid-state method and Cu powders were mixed homogeneously with different ratios and then pressed into wafers??10mm×1.5mm?and pressureless sintered under reduction atmosphere.The microstructures of the obtained composites were characterized by scanning electron microscopy?SEM?and X-ray diffractometer?XRD?,the coefficients of thermal expansion?CTEs?were measured by thermomechanical analyzer and thermal conductivities were measured by laser flasher?LFA?.The results show that the minimum CTEs of the composite is 2.1×10^-6/K.When the temperature is higher than 600?,the Cu_0.4W_0.6 alloy phase appeared inside the composites.In order to avoid alloying,600? was set as the sintering temperature,which is lower than the sintering temperature of Cu with high density.So the relative density and thermal conductivities of composites were poor.The maximum value of thermal conductivity is 77.5W/?m?K?.?2?Cu/Sc₂W₃O₁₂ composites were prepared by vacuum hot-sintering to improve the relative density.The effects of the particle morphology of Sc₂W₃O₁₂ and the sintering temperature on the microstructure,thermal properties of composites were investigated.The results show that the relative density of ^*Cu60 composite prepared at 700? with the nano-Sc₂W₃O₁₂ powder as raw material is 92.44%,and the Cu matrix form complete network structure,which is favorable for heat conduction.Thermal conductivity and CTEs of ^*Cu60 composite is respectively 243.99W/?m?K?and 9.02×10^-6/K,and the hardness reach to 234.32 HV.When the sintering temperature increased to 800?,nano-Sc₂W₃O₁₂ particles recrystallized to large particles and the CTEs of ^*Cu60 composite further reduced to 7.27×10^-6/K,which closes to the CTEs of the Si/GaAs or other chip materials.The corresponding thermal conductivity also decreased to 208.64W/?m?K?,and the hardness decreased to 205.4HV.So the optimum vacuum hot-pressing sintering temperature of composites is 800?,to match the application requirements.?3?Cu/SiC/Sc₂W₃O₁₂ composites were prepared by vacuum hot-pressing using nano-SiC particles as the second reinforced phase.The effects of SiC content and sintering temperature on the microstructure and thermal properties of composites were studied.The results show that the addition of SiC improves the sintering temperature of composites.When the sintering temperature increased to 1000?,there is dimple fracture when composites were broken,and the reinforced particles uniformly distributed inside the composites.Besides,because of the addition of nano-SiC,the sintering activation energy was improved and the fluidity of molten Cu was accelerated.The maximum relative density of composites reach to 92.86%,and the corresponding CTEs and thermal conductivity is 13.33×10^-6/K and 251.18W/?m?K?,respectively.Besides,The CTEs of the 60%Cu10%SiC30%Sc₂W₃O₁₂ composite sintered at 1000? is 7.12×10^-6/K,and the corresponding thermal conductivity is230.60W/?m?K?,which meet the practical application of packaging materials.