Microstructure And Properties Of SiCp/Cu Composites For Electronic Packaging

The electronic packaging technology in modern ICs and other electrical components has a specification-advanced demand for packaging materials. Copper matrix composite is an ideal candidate for electronic packaging materials, because copper matrix shows higher thermal conductivity (TC) but lower coefficient of thermal expansion (CTE) than aluminum matrix. Further, SiCp/Cu composites have a promising potential in future application due to their good combination of TC, electric conductivity (EC) and tailorable CTE. But previous research of SiCp/Cu system is still not satisfied both in the theories and engineering aspects.The commercial SiCp powder was used in present work, and a part of the powder was coated with Cu by Electroless copper plating process, then the composition and morphology of Cu-coated powder were also analyzed. SiCp/Cu composites were fabricated by vacuum and non-vacuum hot pressing process for the coated and uncoated powder, the volume fraction of SiCp in the composites was of 30vol.%, 40vol.% and 50vol.% respectively. The microstructure and interface structure of the SiCp/Cu composites were observed by SEM and TEM methods. The thermophysical properties of the composites were measured such as TC, EC and CTE. And the effect of the volume fraction of reinforcements, powder size and annealing process on the thermophysical properties of SiCp/Cu composites were also discussed. Finally, the Brinell hardness and three-point bending strength of SiCp/Cu composites were also measured. The fracture morphology of the composites was observed then the fracture mechanism of the composites was finally analyzed.It was shown that the copper coating distributed uniformly on the surface of SiCp particles, with the coating thickness of about 1μm. DSC analysis showed that the Cu-coated SiC_p powder began to be melted at 990℃. The Cu-coated and uncoated SiCp particles were also found a uniform distribution in the composites. For the Cu-coated SiC_p powder or uncoated powder, the densification of the composite was decreased with the increasing of reinforcement amount. In same volume fraction of SiCp, the density of the Cu-coated SiCp/Cu composites was improved, compared to uncoated SiCp/Cu composites. The interface between SiCp particles and Cu matrix is bonded well with a little inter-diffusion of Cu and Si elements, and fewer Cu₃Si phase was observed at the interface. The fabricated SiCp/Cu composites showed good thermophysical properties. With the increasing of SiCp content, the CTE, TC and EC of the composites decreased. But more SiCp addition can increase all those properties in same volume fraction of SiCp. The Cu-coated layer improved the interfacial bonding between SiCp particles and Cu matrix, then increased the TC and EC of the composites but degraded the CTE of the composites. A good combination of TC (or EC) with CTE could be obtained as CTE 10.27×l0^-6/℃, TC 236.2 W·m^-1·K^-1 and EC 41.6%IACS. Suitable annealing process can increase the TC and EC but reduce the CTE of the composites due to remove the residual stress.With the increasing of SiCp volume fraction, the Brinell hardness of the composites increased firstly and arrived a peak value then decreased, while the bending strength degraded continuously. In the same volume fraction and size of SiCp, the Brinell hardness and bending strength of the Cu-coated SiCp/Cu composites were higher than that of the uncoated SiCp/Cu composites. The annealing treatment lowered the Brinell hardness and bending strength of the composites. When the volume fraction of SiCp was 30vol.%, the fracture mechanism of the composites showed a mixed manner of dimple and quasi-cleavage fracture. For the composites with the volume fraction of SiCp of 50vol.%, the fracture behavior of the composites dominated in quasi-cleavage manner with a seldom dimples.