无压低温烧结纳米银-铜连接SiC器件的高导热、长寿命封装互连方法

This proposal is aimed at developing an innovative die-attach technology for joining SiC power devices to address the need for substantial reduction in volume and weight of space vehicles. We will focus on extending the science and engineering of an emerging die-attach technology based on pressureless low-temperature sintering of metal nanoparticles to enable high-temperature and reliable operation of the power devices. These power devices offer designers of power electronics systems for electric vehicles the advantage of eliminating an extra cooling loop. The technical goal of this project is to develop a pressureless sinter-bonding solution with superior thermal properties for making.SiC power modules that can function reliably at temperatures over 200°C. To achieve the goal， we will focus our efforts to achieve the following objectives:.(1) understand interactions between metal nanoparticles and organic dispersants, binders, and solvents molecules to optimize the formulation of a stable metal nanopaste for ease of printing and or dispensing in a manufacturing process; ⑵ establish processing-microstructures-properties relationships for sintering the nanopaste at temperatures below 250°C;⑶ investigate effects of substrate finish, its metallization composition and thickness on mechanical, thermal, and electrical performeice the sintered joint;⑷ elucidate failure mechanisms of SiC power modules using the pressureless low temperature sinter-bonding solution and develop a failure criterion for guiding the solution. Achieving these.objectives would help identify limitations of existing materials and processes to guide the design and selection of compatible combinations of materials and processes for making reliable high-temperature SiC power modules. The domestic electrical vehicle industry would directly benefit from successful completion of this program by having an innovative high-temperature die-attach material and superior thermal conductivity method for high-temperature power modules and converters.

面向中碳化硅器件的耐高温封装需求，围绕纳米金属的无压低温烧结互连动力学及其高导热形成机理开展研究。包括：（1）澄清纳米金属、分散剂、表面活性剂之间的胶体化学机理，科学描述无压烧结工艺一组织一性能间交互作用，揭示其无压低温烧结致密化动力学，建立碳化硅器件的耐高温无压连接方法；（2）阐明互连表面金属镀层成分、厚度对烧结金属冶金组织和扩散速率的影响，定量描述烧结内应力与接头预缺陷的作用关系，澄清烧结连接层高热导率形成机理，获得连接碳化硅器件的高导热银-铜接头；（3）利用自主开发的快速温差冲击老化手段，定量描述无压烧结互连的热、电、机械性能退化规律，描述其热循环老化失效行为，基于Weibull统计模型，获得失效判据。目标是综合考虑材料化学、电、热、力的多因素交互作用，形成针对碳化硅器件高温封装用高导热芯片互连材料及工艺方法的科学认识，充分发挥碳化硅器件的耐高温优势，提高模块功率密度。

项目针对碳化硅器件的耐高温封装需求，澄清了纳米金属、分散剂、表面活性剂之间的胶体化学机理，建立了碳化硅器件的耐高温无压连接方法，获得了连接碳化硅器件的高导热银-铜接头，形成了无压烧结银-铜以及铜-铜互连的热、电、机械性能退化规律及其热循环老化失效行为。创新成果包括：1、确定了稳定制备的纳米银-铜复合焊膏材料体系，研究了有机添加剂对纳米银-铜颗粒成形过程中的烧结驱动力的影响规律，获得稳定实现低温快速致密化的纳米银-铜复合焊膏的工艺方法，连接孔隙率低于25%，烧结银-铜焊膏，≥350℃条件下芯片的连接材料无分解。2、优化研究了烧结工艺，从而获得可靠的连接接头，实现了烧结连接碳化硅器件的烧结银/铜膜，通过定量/半定量描述烧结银/铜膜导热、机械性能与其微观组织结构的内在关联，综合考虑界面热阻和体热阻效应，实现低温烧结银-铜接头导热调控的科学认识，并完成了双面散热封装的SiC模块的开发。3、研究了铜焊膏烧结工艺及可靠性，揭示了加载速率、平均应力、应力幅值、最大应力和应力比对烧结铜接头棘轮行为和疲劳寿命的影响规律，并对烧结铜互连接头的疲劳寿命进行预测，得到最适合预测烧结铜互连接头疲劳寿命的模型。通过以上研究，项目已在TOP期刊IEEE Transactions on Power Electronics等发表SCI论文16篇，EI收录中文期刊论文1篇，公开发明专利2项。项目形成了针对碳化硅器件高温封装用高导热芯片互连材料及工艺方法的科学认识，推动了电力电子器件封装材料、工艺及可靠性的相关基础理论与关键技术发展。