Electronic Packaging Sicp / Al Composite Thermal Conductivity Study

For the purpose of electronic packaging applications, SiC_p/Al composites which include different SiC particle diameter(220μm,90μm,63μm),different SiC particle shape(irregularity and sphericity), different Si element content(5%,9%,12%),Mg element content(3.5%,6.3%,10.2%)in matrix, different heat treatments(the annealing treatment,the solution aging ) were fabricated by pressureless infiltration without preforms ; SiC_p/Al composites which include different volume fractions (38.4%,48.93%,52%,62%) , different hole coefficient (3.7%,3.0%,2.4%,1.7%)were fabricated by pressureless infiltration with performs.The microstructure,phase and interface characteristic of SiC_p/Al composites were observed and analyzed by OM, XRD, SEM and TEM; The thermal conductivity were tested by laser flash thermal conductivity apparatus. The relation between thermal conductivity of SiC_p/Al composites and diameter,shape,volume fractions of SiC particle, interface characteristic were discussed,and the rule and characteristic of changes on thermal conductivity of composites were analyzed from view point of the proportion and states of interface. Besides, based on the Maxwell and micromechanics models, the theoretical model for protecting thermal conductivity of SiC_p/Al composites is constructed.The main results can be summarized as follows: (1)With increasing of SiC particle diameter, the thermal conductivity of SiC_p/Al composites increase gradually; The thermal conductivity of composites with spherical SiC particles is higher than that of with irregular SiC particles; With increasing of SiC volume fractions, the thermal conductivity of SiC_p/Al composites decrease, when volume fraction is less to 50%, thermal conductivity declines markedly ,the better boundary scope of volume fraction is about 50% to meet the demand of high thermal conductivity and low coefficient of thermal expansion together in electronic packaging applications; when composites contain tiny hole, thermal conductivity of them decrease but not evidently; The reason for these difference of their thermal conductivity above is that surface areas of SiC particles in composites is different. (2) When appropriate Si elements content are contained in matrix, the detrimental interface reaction during the fabrication of composites will be controlled, with the increasing of Si element content in matrix, thermal conductivity of composites decrease but not linear; When Mg element is merely contained in matrix, interface reactions will be not controlled and A14C3 is found at the interface as a detrimental reaction product, with the increasing of Mg element content in matrix, the extent of interface reaction during the fabrication of composites will become small, and it is found that Mg element has an obvious effect on the interface wet ability between molten aluminum and SiC particles,thermal conductivity of composites increase as Mg element content in matrix increases, but Mg element content is up to in excess of 6.3%,the increasing of thermal conductivity is not obviously; The oxidation of SiC particles can control the detrimental interface reaction and improve wet ability between Al and SiC particles, but it is better to improve thermal conductivity of composites with SiC particles under the oxidation of (800℃×4h) than that of (1100℃×4h); The thermal conductivity of composites for solution aging treatment are higher than that of for annealing treatment , and the thermal conductivity is highest in the condition of solution aging treatment (495℃×3h , cold-water-quenched + 200℃×3h, air-cooled). (3) The theoretical model for protecting thermal conductivity of SiC_p/Al composites is constructed, in which interfacial shells and the shapes of particles are considered, and the calculations of the model are close to the experiment results.