有机硅改性环氧导热绝缘胶的研究

【作者】 张宪国；

【导师】 张一烽；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2004， 硕士

【摘要】 随着电子工业中集成技术和组装技术的发展，电子元器件和逻辑电路的体积趋向小型化，对于粘接和封装材料的导热、绝缘、耐热等性能的要求越来越高。本文以有机硅改性环氧树脂为胶粘剂的主体材料，开发导热、绝缘、抗冲击等综合性能优良的粘接材料，用于机载设备电源组件的粘接灌封。 以有机硅改性双酚A型环氧树脂（E—44或E—51）为基胶，系统研究了接枝共聚改性的催化剂、聚二甲基硅氧烷的分子量、用量、接枝反应条件等因素对改性反应的影响。结果表明采用端羟基聚二甲基硅氧烷（简称羟油）为改性剂的最优化条件为：以W-3为催化剂，羟油的动力粘度为3000cs，用量为9wt％左右，120℃—150℃反应4—6h。改性环氧树脂无漂油现象发生。红外光谱图显示属于环氧树脂的羟基吸收峰明显降低，用盐酸—丙酮法测得改性环氧树脂的环氧值降低，其降低值的大小与羟油的分子量、用量及催化剂的种类、反应条件等有关。改性环氧胶以甲基四氢苯酐为固化剂，DMP—30为促进剂在适当条件下所得固化物的玻璃化转变温度（Tg）为119℃，高于未改性环氧树脂的Tg，表明有机硅改性环氧树脂的耐热性较好。采用扫描电镜（SEM）观察固化产物的断面形貌表明，有机硅在环氧树脂相中分散较均匀，界面模糊，表明接枝反应效果较好。 在有机硅改性环氧树脂中添加适宜的无机填料组成A组份胶，固化剂和促进剂为B组份，两者组成双组份环氧导热绝缘胶（EG—201）。为提高其热导率，研究了在A组份中填充导热性较好的不同填料，如Al粉、AlN、Al₂O₃、BeO、SiC等。结果表明采用铝粉作填料时固化物的击穿电压和体积电阻率比纯改性环氧固化物有较大降低，添加其余填料的固化物电绝缘性能较好。另外BeO虽然导热绝缘性能良好，但毒性较大，因此Al粉和BeO不宜使用。系统研究固化物的热导率表明填料的种类、填充量、粒径及粒径分布、测试温度等对固化物的热导率等有重要影响。填充50—80 wt％的Al₂O₃、AlN、BeO、SiC，其室温热导率为0.8—1.2 W／mK。测试温度升高时热导率相应明显提高，如填充33.3％氧化铝固化物的热导率在223K测试时为0.21W／m·K，298K测试时为0.35 W／m·K，373K测试时为0.52W/m·K。填料粒径对热导率也有影响，如填充75%SIC，当D:。二lpln时热导率为O.SOw加·K，I)s。=愁时热导率为1.2卿m·K，表明粒径较大时有利于提高固化物热导率。 双组份环氧导热绝缘胶的固化物耐热性能优良，在一60—150℃可长期使用，拉伸剪切强度在13即a以上，弯曲强度达82抑a，电击穿强度>20 KV/InIn，体积电阻率3x1012Q·Cm以上，耐湿热性、耐汽油、耐盐雾等优良。 将上述双组份环氧导热绝缘胶应用于电源典型件中，与进口实样的全面对照试验表明:预期要求，其导热、绝缘、电抗、抗共振、抗冲等性能优良，线性加速试验达到是一类综合性能优良的导热绝缘胶。更多还原

【Abstract】 Current trends in encapsulating heating dissipating electronic components with epoxy resins have stimulated interest in the thermal conductivity of particulate-filled epoxy resins. By the careful selection of filler, the thermal properties of the epoxy system can be influenced. It is important also in many of these applications that the fillers chosen exhibit a high electrical resistance in order to maintain low leakage currents and high dielectric strength. When developing such epoxy system ,it is equally important that the processing ability and mechanical end properties be given high consideration.A copolymer was synthesized through the copolycondensation of a hydroxyl terminated polydimethylsiloxane(PDMS), bisphenol A epoxy resin(EP). The copolymerization of polysiloxane and EP was confirmed by the decrease of the hydroxyl group absorption at 3500 cm-1 and the appearance of the absorption of Si-O-C and Si-O-Si at 806 cm-1, 1090-1020 cm-1. The effect of reaction conditions and the quantity of catalyst and organosilicon has been explored. As a result, the best conditions for copolymerization of organosilicon and EP are 120℃ -150℃/4-6h, with W-3 as catalyst. A stable dispersion of polysiloxane particles in an epoxy resin matrix was achieved. The copolymer was characterized by IR, DSC, TEM. Upon cure the glass transition temperature is 119℃. A "sea-island" structure ("island" of silicon rubber dispersed in the "sea" of an epoxy resin) was observed in cured rubber-modified epoxy networks via SEM.With the modified epoxy resin as the matrix, different fillers (Al powder AIN A1203 BeO SiC) are presented. The results showed that adhesive filled with Al powder shows very low electrical resistance. The effects of particle size and distribution, temperature on thermal conductivity were studied. The thermal conductivities increased from 223K to 373K. A thermal conductivity of 0.80 W/m.K is achieved for SiC at its loading of 75% by weight with an average size of ca.lum, 1.0 W/m-K with an average size of ca.10um and 1.2 W/m-K with an average size ofca. 76um.The adhesive is employed for long time at -60-350℃.and the shear strength could reach over 13 MPa, flexural strengths at room temperature are 82 MPa. Upon cure the adhesive exhibit a high electrical resistance.更多还原