Study On Fabrication And Properties Of Diamond/Al Matrix Composites Used In Electronic Packaging

Diamond particles reinforced aluminum matrix composite is new and ideal electronic packaging materials. The composites have higher thermal conductivity and lower coefficient of thermal expansion than that of traditional electronic packaging materials. In this paper, Al and Al-Cu matrix composites used single-crystal diamond particles as reinforcement were fabricated by hot-press method. The density, thermal conductivity and coefficient of thermal expansion of composites were respectively measured by Archimedes’ principle, laser flash method and quartz dilatometer method. Different sintering temperature, varying levels of sintering pressure and different particle size and volume fraction of diamond were applied to investigate the influence on density, thermal conductivity and coefficient of thermal expansion of diamond/Al composite.Research shows as:(1) Diamond/Al and diamond/Al-Cu composite material meeting requirement of electronic packaging materials can be fabricated by hot-press method with choosing reasonable sintering process (60MPa,873K and heat preservation20min).(2) The density and thermal conductivity of diamond/Al composites under60MPa sintering pressure increased with the increase in sintering temperature. And the coefficients of thermal expansion of diamond/Al composites were decrease. As the sintering temperature reached873K, the performance of diamond/Al composites were most superior. In order to ensure that no liquid phase appears in the sintering process, the sintering temperature should not exceed903K.(3)Sintering pressure affect the performance of composites. As the sintering temperature reached837K and the sintering pressure increased from25MPa to65MPa, the density and thermal conductivity values of the50vol.%diamond/Al composites respectively increased from80.1%to96.5%and94W/(m·K) to321W/(m·K) and the coefficient of thermal expansion values of the diamond/Al composite were significantly decreased from (12.5-20.4)×10-6/K to (8.3-13.2)×10-6/K. Due to micro-pore presence in composites, the coefficient of thermal expansion values of50vol.%composites sintered under50MPa ((8.6-11.3)×10-6/K)was lower than the coefficient of thermal expansion under60MPa. As the sintering pressure reached to60MPa, increasing sintering pressure was no long effect on density, thermal conductivity and coefficient of thermal expansion of composites.(4)10vol.%diamond/Al composite as the research object to study that diamond particle size relate with the performance of composites. Research shows that the thermal conductivity and coefficient of thermal expansion values of composites increased with the increase in diamond particles size. The thermal conductivity and coefficient of thermal expansion of composites reinforced by size of5-10μm or55-70μm diamond particles were175W/(m·K),207W/(m·K) and (13.5-17.6)×10-6/K,(15.2-19.2)×10-6/K, respectively.(5)Varying volume fraction (10,30,50,60vol.%) composites reinforced by size of55-70μm diamond particles were fabricated successfully. Research show that the volume fraction of diamond increasing the thermal conductivity of composites increases, the coefficient of thermal expansion is reduced. Due to the reducing binding phase in composite, the density of composite decreased, resulting in a sharp decline in composite performance when the volume fraction of composite increased to60%. The thermal conductivity and coefficient of thermal expansion of50vol.%diamond/Al composite were321W/(m·K) and (8.3-13.2)×10-6/K, respectively.(6)Diamond/Al-Cu composites material meeting requirement of electronic packaging material can be fabricated by reasonable pressing sintering process (60MPa,883K and heat preservation35min). Due to adding a small amount of Cu powder in the mixing process, there will be a small amount of liquid phase during sintering process so that density of Diamond/Al-Cu composites were higher than that of Diamond/Al composites, the coefficient of thermal expansion were more stable.The density, thermal conductivity and coefficient of thermal expansion of50vol.%diamond/Al-Cu respectively were97.4%,325W/(m·K) and (7.3-11.2)×10-6/K.(7) Coefficient of thermal expansion measured value of varying volume fraction (10,30,50,60vol.%) diamond/Al composites in373k temperature and coefficient of thermal expansion measured value of50vol.%diamond/Al composites under different temperature compare with Coefficient of thermal expansion calculated value computed by three theoretical models. Comparative analysis found that the Coefficient of thermal expansion values obtained in the experiment were approximately equal to the coefficient of thermal expansion calculated by the Kerner model. But due to assumed condition, there is a deviation between values calculated by Kerner model and actual measured value.