Thermal conductivity and fire resistance of epoxy molding compounds filled with Si3N4 and Al(OH)3

The production of composites of epoxy molding compounds (EMCs), which can feature a good balance between thermal conductivity and flame-retardant behavior in terms of flammability and burning behavior, was achieved by incorporating high thermal conductivity Si3N4 and flame retardant Al(OH)3 (ATH) fillers in the epoxy matrix. The experimental results were obtained from thermal conductivity measurements and limiting oxygen index (LOI) and UL-94 tests. These results showed that the Si3N4 filler has a great influence on thermal conductivity, which markedly increased for Si3N4 volume fractions >40%, whereas the ATH filler greatly improved the flame resistance of EMCs. The simultaneous presence of both Si3N4 and ATH fillers in the EMCs positively influenced both properties. The aim of this study was to produce composites suitable for electronic packaging applications: an optimum combination of the two fillers was determined for a total volume fraction of fillers in EMC of 60 vol.% and a volume ratio of Si3N4:ATH at 3:2; this composite had a thermal conductivity of 2.15 W/m K, an LOI of 53.5, and a UL-94 vertical burning test ranking of V-0.