Preparation And Investigation On The Polyimide/AIN Composite Materials

In the trend of high power, density, integrating, and speed of the electronic, microelectronic, and photoelectron components in modern information industry, it is an urgent demand of new generation microelectronic materials used in substrates, package materials, and interlayer dielectrics with high performance of high thermal conductivity, low dielectric constant and dielectric loss, low thermal expansion coefficient, and excellent insulation. A1N with its very high thermal conductivity, combined with excellent dielectric properties and , low thermal expansion coefficient, is especially useful as substrates in advanced IC. Polyimide which has unique properties of low dielectric constant and loss, low thermal expansion, and high insulation, is one kind of the high strength, thermal stable polymers, and is widely used as interlayer dielectrics, packaging materials, and circuit boards. Polyimide/AIN composite materials are expected to have an attractive combination of properties of polyimide and A1N, and have the advantages of light weight, ease of processing, high chemical stability, and adjustability of properties in polymer composites.The preparation of PI/A1N composite materials is discussed firstly in the dissertation. Two types of PI/A1N composite materials are prepared by in-situ polymerization and PMR method. A series of in-situ polymerized PI/A1N composite materials are prepared with varied in A1N fractions, coupling agents, and polymerizing conditions. A series of PMR PI/A1N composite materials are prepared with varied in A1N fractions, mechanical milling and moulding conditions, and coupling agents. DSC, H-NMR, FTIR, SEM, and TG are used in analysis of monomers, processing, and final composites. Based on the analysis of PMR technique, the PMR PI/A1N composite materials are moulded in normal moulding machine with modified in die and an additional heater. The fully dense PMR PI/A1N composite materials up to 80wt % (62vol %) A1N contents are prepared successfully by the combination of PMR technique and mechanical milling.The thermal conduct behavior of composites is complex. Maxwell equation isoften used in calculation of the thermal conductivity of composite materials composed by particles dispersed in a matrix. However, there are lager divergences by Maxwell equation when the shape of particles is not sphere, the fraction of particles is high, or boundary resistance exists in the interface of composites. Several researchers have modified Maxwell equation in the above effects respectively. A new modified equation, which considers all factors simultaneously and therefore more useful, is proposed and testified in this dissertation.The research on the properties of PMR PI/A1N composite materials reveals: the thermal conductivity is varied by the mechanical milling with the change in particle shape, and by the compress moulding with the change in polyimide matrix and composite interface; coupling agents can increase the thermal conductivity by modifying interface; PMR PI/A1N composite materials is low dielectric constant (about 2~4), low dielectric loss (<3.5xlO?, and low thermal expansion coefficient.The research on the properties of the in-situ PI/A1N composite materials reveals: the thermal conductivity is notably affected by the A1N fractions and coupling agent contents, the dielectric constant is high notably affected by the A1N fractions. The properties of the in-situ PI/A1N composite materials are: high thermal conductivity (increased with the A1N fraction), low dielectric constant, low dielectric loss and excellent insulation.