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High thermal conductive epoxy molding compound with thermal conductive pathway



The epoxy molding compound (EMC) with thermal conductive pathways was developed by structure designing. Three kinds of EMCs with different thermal conductivities were used in this investigation, specifically epoxy filled with Si3N4, filled with hybrid Si3N4/SiO2, and filled with SiO2. Improved thermal conductivity was achieved by constructing thermal conductive pathways using high thermal conductivity EMC (Si3N4) in low thermal conductivity EMC (SiO2). The morphology and microstructure of the top of EMC indicate that continuous network is formed by the filler which anticipates heat conductivity. The highest thermal conductivity of the EMC was 2.5 W/m K, reached when the volume fraction of EMC (Si3N4) is 80% (to compare with hybrid Si3N4/SiO2 filled-EMC, the content of total fillers in the EMC was kept at 60 vol %). For a given volume fraction of EMC (Si3N4) in the EMC system, thermal conductivity values increase according to the order EMC (Si3N4) particles filled-EMC, hybrid Si3N4/SiO2 filled-EMC, and EMC(SiO2) particles filled-EMC. The coefficient of thermal expansion (CTE) decreases with increasing Si3N4 content in the whole filler. The values of CTE ranged between 23 × 10−6 and 30 × 10−6 K−1. The investigated EMC samples have a flexural strength of about 36–39 MPa. The dielectric constant increases with Si3N4 content but generally remains at a low level (<6, at 1 MHz). The average electrical volume resistivity of the EMC samples are higher than 1.4 × 1010 Ω m, the average electrical surface resistivity of the EMC samples are higher than 6.7 × 1014 Ω. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009