Fabrication and thermal properties of hot press sintered Cr-coated carbon fiber/Cu composites
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摘要: 采用热压法将拥有超高导热率和负热膨胀系数（CTE）的中间相沥青基短碳纤维（CFs）与Cu复合，并利用化学气相沉积技术对CFs镀Cr以改善其与Cu的结合状况，研究了所制备的镀Cr CFs/Cu复合材料的显微结构与热性能。结果表明：在制备中Cr层的大部分与CFs表层的C反应形成连续、均匀的界面薄层Cr7C3，少量的扩散于Cu基体中，使CFs与Cu之间的界面由结合极差的机械结合转化成良好的冶金结合，有效提升了复合材料的热性能。CFs含量为40vol%~55vol%时，镀Cr CFs/Cu复合材料致密度高于97.5%，平面方向上的热导率达393~419 W（mK）-1，平面方向的CTE在5.1×10-6~8.4×10-6 K-1之间。高的热导率、低的CTE以及优良的可加工性能使其成为极有潜力的电子封装材料。Abstract: The mesophase pitch-based short carbon fibers (CFs) with ultra-high thermal conductivity and negative coefficient of thermal expansion (CTE) were compounded with Cu via hot press sintering. In order to improve the bonding state between CFs and Cu, Cr was pre-coated on CFs by chemical vapor deposition technique. The microstructure and thermal properties of the Cr-coated CFs/Cu composites were studied. The results show that most of Cr coating reacts with C forming to a thin, continuous and uniform Cr7C3 interfacial layer, and small amount of them diffuses into Cu matrix during the preparation process, which causes the interface structure between CFs and Cu to change from week mechanical bonding into good metallurgical bonding. Consequently, the thermal properties of the composites are improved effectively. The Cr-coated CFs/Cu composites with 40vol%-55vol% CFs achieve the relative densities higher than 97.5%, the in-plane thermal conductivities to 393-419 W(mK)-1 and the in-plane CTE ranging of 5.1×10-6-8.4×10-6 K-1. The composites are promising materials for electronic packaging applications due to their high thermal conductivities, low CTE and good machinabilities.
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Keywords:
- carbon fiber/Cu /
- composites /
- hot press sintering /
- microstructure /
- thermal conductivity /
- thermal expansion
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