高压SiC器件封装用有机硅弹性体高温宽频介电特性分析

Analysis of High Temperature Wide Band Dielectric Properties of Organic Silicone Elastomer for High Voltage SiC Device Packaging

有机硅弹性体因具有良好的绝缘性与耐高温的特性,广泛应用于高频、高压、高温工况下的SiC器件中。在宽频率、宽温度范围内,有机硅弹性体材料的介电性能对SiC器件内部电场分布产生极大影响,因此该文采用频域介电谱分析方法获得了宽频(10^(-2)-10^(7)Hz)、宽温度(20280℃)范围内的有机硅弹性体介电特性数据,掌握有机硅弹性体在不同频率、温度条件下的介电弛豫过程,在此基础上,采用改进Cole-Cole模型对有机硅弹性体的弛豫特性进行分析,获得温度对有机硅弹性体介电响应过程与介电特征参数的影响规律。研究结果表明,随频率上升,复介电常数实部明显下降并趋于稳定,复介电常数虚部呈现先下降后上升到达峰值的趋势。在高温低频条件(160℃以上,100Hz以下)下,有机硅弹性体材料出现明显的低频弥散现象,280℃下观测到了电荷扩散过程的出现;不同温度下Cole-Cole模型特征参数中直流电导率σ_(dc)、弛豫强度△ε与低频弥散强度ξ与温度的关系满足Arrhenius方程规律;高频介电常数ε_(∞)随温度升高而降低,与温度近似呈线性变化;弛豫时间τ在高温下随温度上升具有明显指数型下降趋势,其机理可利用双势阱模型描述。该文获得的有机硅弹性体宽频、宽温度范围内的介电特性可以为SiC器件封装绝缘设计提供数据支撑。

Because of their good insulation and high temperature resistance,organic silicone elastomers are widely used in SiC devices under high frequency,high pressure and high temperature working conditions.In a wide range of frequency and temperature,the dielectric properties of silicone elastomer materials have a great impact on the electric field distribution in SiC devices.Therefore,the dielectric properties of organic silicone elastomers with wide broadband(10^(-2)-10^(7) Hz)range and wide temperature(20-280℃)range were obtained by frequency-domain dielectric spectrum analysis in this paper.The dielectric process of silicon elastomers at different frequencies and temperatures was revealed,the method of distinguishing low-frequency dispersion process from relaxation polarization process was improved,and an improved Cole-Cole model was introduced.Finally,the influence of temperature on the dielectric response process and dielectric characteristic parameters of organic silicone elastomers was obtained.The results show that with the increase of frequency,the real part of the complex dielectric constant decreases and tends to be stable,while the imaginary part of the complex dielectric constant decreases first and then rises to the peak value.Temperature and frequency have great influence on the dielectric properties of the organic silicone elastomer.Under the condition of high temperature and low frequency,the organic silicone elastomer material has obvious phenomena of low frequency dispersion and charge diffusion.The characteristic parameters of Cole-Cole model at different temperatures are extracted.The relationship of the DC conductivity σ_(dc),the relaxation intensity △ε and the low frequency dispersion strength ξ with temperature satisfies the Arrhenius equation law.The high frequency dielectric constant ε_(∞) shows an approximate first-order function relationship with temperature and decreases with the increase of temperature;the relaxation time t decreases with the increase of temperature at high temperature,and its mechanism can be revealed by the double well model.The characteristic parameters obtained in this paper provide data support for insulating design of SiC device package.