【作者】 杨勇；

【导师】 田无边；

【作者基本信息】 东南大学 ， 材料学， 2023， 硕士

【摘要】 氮化铝直接覆铜板（AlN-DBC）具有优良的高频特性、导热性质和电流承载能力,是下一代功率电子封装基板的理想候选材料。探索并优化DBC技术中AlN片和Cu箔的预处理工艺,是改善AlN-DBC性能的有效途径之一。本论文重点研究AlN片的新型表面预处理工艺。通过对AlN片进行水化处理并优化热处理工艺,利用AlN水化特性及其表面产物Al₂O₃晶型转变,可在AlN片表面引入厚度可控（约2μm）且产物可调（θ-Al₂O₃、θ/α-Al₂O₃、α-Al₂O₃）的微米-纳米多级结构氧化层,继而分析了其水化热处理的转化机制。而传统高温热氧化处理的AlN片表面产物为单一结构α-Al₂O₃。此外,采用预氧化工艺处理Cu箔,探究了氧分压、温度和时间等参数对预氧化产物和形貌的影响。最后,将预氧化Cu箔和不同工艺的预处理AlN片进行高温连接,成功制备了AlN覆铜基板。通过测试上述AlN-DBC的导热性能,发现AlN片表面Al₂O₃的形貌和晶型对基板导热性有显著影响。基于界面观察和高温润湿实验（Cu/Cu₂O混合物在不同预处理AlN片表面）,研究了AlN表面产物对界面润湿性和导热性能的影响规律,并探究了其影响机制与界面连接机理。结果表明,Al₂O₃形貌对Cu/Cu₂O共晶液相与基板的润湿性起主导作用,共晶液相在具有微米-纳米多级结构的Al₂O₃膜表面呈Cassie-Baxter型接触,最终表现为不润湿,同时润湿性随着低表面能α-Al₂O₃相的增多而降低。AlN-DBC导热性质与界面结合、界面陶瓷层和界面处弥散颗粒（Cu₂O、Cu-Al-O）密切相关。孤岛状分布于Al₂O₃上的Cu-Al-O颗粒以及析出并镶嵌于Cu箔的Cu₂O颗粒,分别通过化学键合和物理键合锚定界面,从而实现AlN与铜箔的连接,因此调控界面物相的数量和分布对于优化AlN-DBC的界面结合和导热性能至关重要。上述研究成果,从AlN片表面产物Al₂O₃的晶型和形貌角度,为开发AlN-DBC提供了新思路,并为优化AlN直接覆铜技术提供了实验基础与理论支撑。更多还原

【Abstract】 Aluminum Nitride Direct Bonded Copper（AlN-DBC）has excellent high frequency characteristics,thermal conductivity and current carrying capacity,making it an ideal candidate material for next-generation power electronics packaging substrate.Exploring and optimizing the pretreatment process of AlN substrates and Cu foils during DBC technique is one of the effective ways to improve the performance of AlN-DBC.This thesis focuses on the study of new surface pretreatment process for AlN substrates.By conducting hydrolysis treatment and optimizing the following heat treatment process of AlN substrates,utilizing the hydrolysis characteristics of AlN and the crystal transition of its surface product Al₂O₃,it is possible to introduce a micro-nanometer multiscale structured oxide layer with a controllable thickness（about 2μm）and adjustable products（θ-Al₂O₃,θ/α-Al₂O₃,α-Al₂O₃）on the surface of AlN substrates,and then analyze the transition mechanism during the hydrolysis and heat treatment process.In contrast,the surface product of AlN substrates using conventional high-temperature oxidation treatment is single structuredα-Al₂O₃.In addition,the effects of oxygen partial pressure,temperature,and time on the products and morphology of Cu foils during the pretreatment process were investigated.Finally,the AlN-DBC substrates were successfully prepared by joining the pre-oxidized Cu foils and the pretreated AlN substrates of different processes at high temperature.By testing the thermal conductivity of the above AlN-DBC,it is found that the morphology and crystal structure of Al₂O₃ on the surface of AlN substrates has a significant impact on the thermal conductivity of the substrate.Based on interface observation and high-temperature wetting experiments（Cu/Cu₂O mixture on the surface of AlN substrates pretreated differently）,the effects of AlN surface products on the interfacial wettability and thermal conductivity was investigated,and the influencing mechanism and interfacial bonding mechanism were explored.The results show that the Al₂O₃ morphology plays a dominant role in the wettability of the Cu/Cu₂O eutectic liquid phase with the substrate.The eutectic liquid phase presents a Cassie-Baxter type contact on the hydrolyzed and heat treated AlN surface that consists of Al₂O₃ layer with a micron-nanometer multiscale structure,ultimately exhibiting nonwetting.At the same time,the wettability decreases with the increase ofα-Al₂O₃ phase with low surface energy.The thermal conductivity of AlN-DBC is closely related to the interfacial bonding,interfacial ceramic layer and dispersed particles（Cu₂O,Cu-Al-O）at the interface.The Cu-Al-O particles distributed as islands on Al₂O₃ surface and the Cu₂O particles precipitated and embedded in Cu foil anchor the interface through chemical bonding and physical bonding respectively,thereby realizing the joining between AlN and Cu foil.Therefore,controlling the amount and distribution of interfacial phases is crucial for optimizing the interfacial bonding and thermal conductivity of AlN-DBC.The above results provide new strategies for the development of AlN-DBC substrates from the perspective of the crystal structure and morphology of Al₂O₃ on the surface of AlN substrates,and establish an experimental basis and theoretical support for the optimization of AlN-DBC technique.更多还原