Preparation And Properties Of Insulating Thermal Conductive Epoxy Resin Based Composites

LED is the main choice in many illuminating application due to the merits such assmall size, energy saving, non-pollution, long life expectancy, and also is hot inresearch and applications in recent years. Nowadays, LED is usually packaged in theMCPCB. As the LED chip power increases, the device failure due to poor heatdissipation become increasingly prominent.The epoxy resin （EP）-ceramic powder composites and insulating thermalconductive aluminum plate were fabricated in this thesis to improve the heat transferperfomance of resin-based thermal insulation composites for LED package. Theeffects of filler types and its amounts on the thermal and mechanical properties of thecomposite materials and heat transfer performance of the thermal insulation aluminumplate were investigated. The effects of insulating layer on the heat transferperformance of the aluminum plate were studied by measuring the back surfacetemperature of the aluminum plate loaded in7W LED lights. The main results aregiven as follows:The thermal conductivity of EP material is significantly improved with Si₃N₄addition. As Si₃N₄content increases, thermal conductivity network forms due to thedirectly contacts between the ceramic particles in composites, resulting in asignificantly increasing of the thermal conductivity of Si₃N₄/EP material. When theSi₃N₄content is25vol%, the thermal conductivity of Si₃N₄/EP material is of0.511W/（m·K）,2.5times that of the EP. With increasing Si₃N₄amounts, the thermalexpansion coefficient of Si₃N₄/EP materials decreased and improved the stability ofinsulated aluminum plate. The hardness of composite material increased with thecontent of Si₃N₄increases, due to the improved crosslinking density of epoxy resinwith the addition of Si₃N₄.The thermal conductivity of EP material is improved with AlN addition. As theAlN volume content is25%, the thermal conductivity of AlN/EP material is 0.507W/（m·K）). With the increment of AlN content, the thermal expansion coefficientof AlN/EP declined, and its hardness increased. As AlN content increased, the tensileshear strength of AlN/EP composite firstly increased and then decreased. When thevolume fraction of AlN was up to33.8%, the tensile shear strength was still up to3.16MPa.The more ceramic fillers were added in the dielectric layer, the better the heattransfer of composite performanced. And the steady temperature was also much higherat the same time. The steady temperature of aluminum substrate was101.8°C when thevolume content of Si₃N₄in the insulating layer was50%, while that of was105°Cwhen the volume content of AlN in the insulating layer was50%. According to energyconservation, the heat accumulated of the chip was relatively less and the junctiontemperature was lower. Thus it was better for LED.