Effect Of Salt Bath Plating Ti On Diamond Particles On The Microstructure And Properties Of Diamond/Al Composites

With the development of electronic information technology,electronic devices are developing towards high temperature,high frequency and high power density.The requirements of heat dissipation for electronic devices are getting higher and higher.Diamond/Al composites have become a new promising electronic packaging material due to their excellent thermal physical properties.In this paper,the surface of diamond was coated with titanium by salt bath plating method.The optimum process parameters of diamond surface treatment were investigated.Diamond/Al composites were prepared by pressure infiltration method,and the effects of Ti coating on relative density,thermal conductivity and thermal expansion coefficient of Diamond/Al composites were studied.At the same time,the stability of Diamond/Al composites in thermal cycling and dry-wet alternating environments was studied.The main results are as follows:A thin coating can be plated on the diamond surface by holding at 780?for 90 min.The coating consists of a TiC layer and a small amount of Ti particles.As the holding time increases,the thickness of the coating increases,uniformity and compactness of the coating improves.According to the weight gain of diamond plating and the loss of corrosion of diamond plating,the theoretical calculation model of coating thickness is established.The error is analyzed and compared with the results of XPS test,which can ensure that the coating thickness is controllable.Ti-coated diamond particles are not peeled after baking at 800?for 1 h,which shows that the coating has good adhesion.When the coating thickness increases from 180 to 550 nm,the thermal conductivity of Ti-coated Diamond/Al composites increases first and then decreases.When the thickness of the coating is 320nm,the thermal conductivity of the composites is 502W/?m·K?,and the average thermal expansion coefficient is 8.25×10^-6/K at 25?300?,which meets the requirements of electronic packaging materials.The titanium surface of the diamond can eliminate the selective interface between the diamond and the aluminum matrix,effectively improve the interface wettability,thereby increasing the relative density of the composite,reducing the thermal expansion coefficient,and suppressing the formation of Al₄C₃ at the interface.Since the titanium coating layer introduces a new interface thermal resistance,the thermal conductivity of the composite material is somewhat reduced,which is in agreement with the calculation result of the AMM model.A large amount of Al₄C₃ is formed at the interface of the Diamond/Al composites,and its deliquescence will lead to deterioration of properties.After 30 days in a dry-wet alternating environment,the thermal conductivity of the bare diamond/aluminum composite decreased from558W/?m·K?to 507W/?m·K?,and the thermal conductivity decreased by 9.1%,while the Ti-coated Diamond/Al composites decreased from 458 W/?m·K?to 446W/?m·K?,and the thermal conductivity only declined by 2.6%.The thermal conductivity of Diamond/Al composites decreased from 564W/?m·K?to 509W/?m·K?by 9.8%after 100 thermal cycles at 25?125?.However,the thermal conductivity of Ti-coated Diamond/Al composites remained unchanged after100 thermal cycles.The reason is that Ti plating on diamond surface can effectively inhibit the formation of interfacial product Al₄C₃,thus improving the stability of composites in thermal cycling and dry-wet alternating environments.