| Summary: | 碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 99 === In this study, boron nitride and aluminum nitride were used as fillers with different volum ratio in the polyimide matices. The polyimide matrix was synthesized with 2,2-Bis(3-amino-4-hydroxy-phenyl)hexafluoropropane and 4,4’-Oxydiphthalic Anhydride monomers by one-step method. Microstructure and thermal and dielectic properties of the thermally conductive (BN, AlN)/PI composites were investigated.
According to the published reports, most of the ceramic filler/polyimide composites were synthesized by a two-step method, with which the filler/xxx(PAA) mixed solution was molded with pressure at 300oC. However, the problem of the two-step method is the lower molecular weight of the polymized polyimide. In our research, the matrix was synethesized by a one-step method. Our synthesized PI could be dissolved by non-proton solvents such as DMAC and THF. Our fabrication procedure of the filler/PI composite could be made without pressing. The (BN, AlN)/PI composite layers are flexible and thermal conductive.
From results of our research, the stacking states of boron nitride in composite had an effect on the thermal conductivity. With the increase in the BN volum ratio, the contact points among BN plates increase. Therefore, the thermal conductivity increase with volum ratio of BN. In this study, we also blended different ratios of AlN into BN/PI composites and investigate the effect of stack state on the thermal conductivity of composites. From SEM analyses, we can apparently found that the BN stacking was interrupted by AlN due to its irregular shapes, larger particle size etc. Therefore, a decrease of thermal conductivity with the AlN content was observed. Our 60% BN/polyimide compostes after drying at 250oC had shown thermal conductivity of 2.33 W/m‧k and a dielectric constant of 3.8.
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