基于光热法的热界面材料接触热阻研究

       随着电子产品不断向集成化、小型化、智能化发展，其工作时的热流密度急剧增加， 这些热量将严重影响电子元器件的使用性能、寿命和可靠性。相关研究表明，温度每升高 10℃，电子产品的失效概率将增加 50%，电子封装领域的热管理问题日益突出。热界面材料在热管理中起着重要的作用，其可以填充接触面间不能紧密贴合而产生的空隙。聚合物基热界面材料是目前广泛使用的热界面材料，具有易加工、密度小，成本低等优点。面对日益增长的散热需求，提高聚合物基热界面材料的热导率以及降低热界面材料应用时的接触热阻是学术界和产业界的研究热点。采用高导热填料填充的方式来提升聚合物基热界面材料的热导率时，聚合物基体与高导热填料之间的接触热阻是制约其热导率提升的关键。 因此，准确地表征热界面材料应用中所涉及的接触热阻并对其进行调控，明晰界面热阻的产生机理和影响因素，对热界面材料的设计、加工和应用有重要意义。
       针对填料与聚合物基体间的界面热阻，本文搭建时域热反射法实验装置，采用光热反射法对铝和有机硅基体间的界面热阻进行研究，依据双向热流模型，利用磁控溅射，旋转涂膜等制备工艺，制作 SiO₂/Al/Silicone 多层结构样品，对铝和有机硅之间的界面热导（界面热阻的倒数）进行了准确表征，测得 G_Al-ilicone 为~60 (MW/m²·K)。随后采用表面改性的方法对界面热导进行调控，接枝不同硅烷偶联剂后 G_Al-Silicone 最大为~140 (MW/m²·K)，实现了界面热导约三倍的提升。
      针对热界面材料实际应用时与热源或热沉的接触热阻，本文搭建光热辐射法实验装置，对碳纤维导热垫、相变材料、液态金属、导热凝胶等常见热界面材料与硅之间的接触热阻进行测量，设计了满足光热辐射法测试要求并能施加压力的夹具，研究了不同压力下接触热阻的变化。测试结果表明选定热界面材料与硅的接触热阻在 10^-5~10^-6 量级，其中液态金属与硅的接触热阻最小，为~0.5× 10^-6 (m²·K/W)。导热凝胶与硅的接触热阻最大，为~1.5× 10^-5 (m²·K/W)。不同热界面材料与硅的接触热阻随压力加载的变化趋势各异，这与其自身的相态、粘弹性等物理性质直接相关。

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