| The epoxy-based composites are prepared by both mechanical disperse and ultrasonic disperse. After filling the ultra-fine aluminum nitride, the composites'properties become better. The filler is modified by different content of coupling agent, the influence of combination ability of interphase is studied, and the properties of the composite modified by different filler's content are also studied. The results of viscosity test indicate that viscosity of the epoxy system do not increase after low content filler's adding, but the trend appears decrease. When adding high content filler into the epoxy system, the viscosity of epoxy system increase, and the system added the filler which is modified with coupling agent is lower, while the filler which is not modified make the viscosity increase much more. Impact toughness of the composite filled with AlN powder is increased, while the reagent content is 3%, the effect is most evident , the best improve more than 35% of epoxy resin. Analysis of fracture show that when impact toughness of the composite is better, there are more small rivers and more density and more small steps in the fracture area which can absorb much impact energy to improve the impact toughness of the composite. The idea of interphase regarding as the third phase of the composite is brought forward; the formula of composite's thermal conductibility is concluded after consider some supposes such as factor of thermal conductibility, which is related with thickness of interphase and energy of interphase's combination. The most important factor to affect thermal conductibility is effect of filler's surface modification. The test results indicate that thermal conductibility of composite is improved effectively by filling AlN powder. Samples modified by filler improved thermal conductibility for 2.8 times, reach 1.07W/m·K. Main contributive factors are filler content and property of interphase. When filler content is higher, property of interphase is better, thermal conductibility is better while filler content is the same, there is much difference between the samples with good interphase property and not good interphase property or without modification. To study the interphase combination between filler and epoxy, the XRD and DMA tests are carried out. Analysis show that when the sample is cooled after cured, lattice distance is the biggest when coupling agent content is 3%, the stress from epoxy to filler is also the largest , AlN crystal is expanded. But the bad property of interphase can not transfer the stress to filler effectively, expansion of AlN filler and its lattice distance is little. DMA results indicate that status of composite's tanδmax can be a symbol of composite's interphase combination intensity. When coupling agent content is 3%, tanδmax is the least, intensity of combination is better. In addition, other properties of the composite such as resistivity and coefficient of linear thermal expansion can reach the requirement of electronic package material.
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