A low-viscousity, highly thermally conductive epoxy molding compound (EMC)

Abstract

Advanced epoxy molding compounds (EMCs) should be considered to alleviate the thermal stress problems caused by low thermal conductivity and high elastic modulus of an EMC and by the mismatch of the coefficient of thermal expansion (CTE) between an EMC and the Si-wafer. Though AlN has some advantages, such as high thermal conductivity and mechanical strength, an AlN-filled EMC could not be applied to commercial products because of its low fluidity and high modulus. To solve this problem, we used 2-μm fused silica, which has low porosity and spherical shape, as a small size filler in the binary mixture of fillers. When the composition of the silica in the binary filler system reached 0.3, the fluidity of EMC was improved more than twofold and the mechanical strength was improved 1.5 times, relative to the 23-μm AlN-filled EMC. In addition, the values of the elastic modulus and the dielectric constant were reduced to 90%, although the thermal conductivity of EMC was reduced from 4.3 to 2.5W/m-K, when compared with the 23μm AlN-filled EMC. Thus, the AlN/silica (7/3)-filled EMC effectively meets the requirements of an advanced electronic packaging material for commercial products, such as high thermal conductivity (more than 2W/m-K), high fluidity, low elastic modulus, low dielectric constant, and low CTE.