Preparation Process And Properties Characterization Of High-Temerature Resistant Interconnection Material Based On Porous Cu Infiltrated With Sn-Based Solder

As electronic devices becoming more and more mutifunctional,miniaturized and high-power,the increasing integration of devices will lead to large amount of heat generation on chips.Thus the demands of high reliability of electronic devices in high temperature environments is increasing every year.Traditional silicon-based devices can only work in environments below 150 °C,while the third-generation semiconductor SiC can theoretically serve in high-temperature environments above 300 °C and provide higher power.However,the current die attach methods in electronic devices are mainly for silicon-based devices,which cannot meet the requirements for high-temperature service.In order to give full play to the excellent performance of SiC high-power devices,this dissertation aims to introduce a die attach method for them.At the same time,the bonding temperature should not be too high to avoid residual stress or damage on other components.On the basis of the traditional transient liquid phase soldering method,porous copper sheets filled with tin were used as interlayers during bonding,which had a threedimensional through-pore structure.By utilizing the low melting point of Sn and the large specific surface area of the porous copper sheets,the effective reaction area between Cu and Sn was greatly improved and the welding efficiency was improved,too.The asreflowed joints were composed of high melting-point phases.Thereby the purpose of ‘low temperature rapid reflow and high temperature service’ was achieved.Two preparation methods for porous Cu,electroplating method and chemical dealloying method,were conducted.The electroplated pre-sheets were obtained by alkaline plating of Sn and tableting treatment on porous Cu sheets with micron-scale pore size.The nanometer-scale pore size porous Cu sheets were fabricated by dealloying Cu40Al60 precursor alloy in hydrochloric acid solution.In this dissertation,the two kinds of porous copper sheets above were used for bonding,and the reflow process was optimized to a low temperature of 240 ° C for 10 min.The joints composed of Cu+Cu-Sn intermetallics or Cu-Sn intermetallics,both of which were high melting point phases.Thus those joints can meet the requirements for high temperature service.The shear strength,electrical conductivity and thermal conductivity of the joints were tested.The properties of the joints were excellent and could meet the industrial requirements.Finally,during the 200 °C aging test of the joints,it was confirmed that no defects such as holes or cracks had been found in the joints.The shear strength and Vickers hardness of the joints were stable,and the mechanical properties didn’t decrease significantly,showing an excellent reliability.According to the preparation process parameters and properties of the joints,the joints strictly meets the requirements of ‘low temperature reflow and high temperature service’.