Fundamental Investigation into the Mechanisms of Ultrasonic Assisted Single-Component and Multi-Component Low Temperature Sintering for the Assembly of Power Electronic Components

当今对电力电子产品的需求显著增加，特别是由于电子移动性，因此焊接或粘合等成熟工艺的连接特性不再满足未来的要求。特别是电导率和导热性以及工艺温度的升高都是挑战。因此，银复合烧结在近年来变得越来越重要。在这里，衬底和芯片由烧结的银中间层连接。与传统复合材料相比，烧结银复合材料的性能提高了许多倍。为什么这个过程还没有被广泛应用？原因是该工艺所需的压力和温度值很高。处理时间明显长于其他方法，因此目前只有批处理是经济的；然而，这会导致不规则的关节质量。这就是我们研究项目的切入点。我们能够证明，在单芯片组装中，将超声波引入键合层对键合的形成有显著的积极作用，从而降低了工艺温度、压力和时间。此外，合金合作伙伴对该工艺进行了扩展，形成了一种新型的多组分超声辅助烧结工艺，即超声瞬态液相烧结（UTLPS）。在这里，我们也展示了最初的积极影响。本研究项目的指导问题是：当使用超声波时，哪些机制对化合物的形成有积极的影响？超声波加速扩散过程是否类似于金属丝粘合？为此，将首先开发微纳米级烧结浆料。随后，将进行参数对接头质量影响的实验研究，使超声波影响参数分离出来。这些主要是超声的振幅、功率和持续时间。在确定最佳超声方向（水平或垂直）后，分析了该过程的时间分布。通过测量孔隙率和机械强度来评价接头，并辅以其他分析方法。研究在无源测试芯片和有源组件（二极管，IGBT， NTC）上进行。在这里，超声波对连接质量和耐久性的影响以及可能对部件的损坏进行了检查。最后对超声辅助银复合烧结的机理进行了基于模型的描述。通过回答这些关键问题，银复合烧结技术将得到显著改善。这为这种粘合技术开辟了更多的应用领域。

Today's demands on power electronics have increased significantly, especially due to e mobility, so that the connection properties of proven processes such as soldering or bonding no longer meet future requirements. Especially the electrical and thermal conductivity as well as the increased process temperatures are challenges. As a result, silver compound sintering has become increasingly important in recent years. Here, a substrate and a chip are connected by a sintered intermediate layer of silver. Compared to traditional compounds, the properties of silver compound sintering are many times better. Why is this process not yet widely used? The reason are the high values of pressure and temperature required for the process. The process times are significantly longer than with other methods, so that currently only a batch process is economical; however, this leads to irregular joint qualities. This is where our research project comes in. We were able to show that in single chip assembly, the introduction of ultrasound into the bonding layer has a significantly positive effect on the formation of the bond, so that the process temperature, pressure and times were reduced. In addition, the process was extended by an alloying partner to form a new type of multi-component, ultrasonic-assisted process, which is introduced as Ultrasonic Transient Liquid Phase Sintering (UTLPS). Here, we were able to show first positive effects, too. The guiding questions for this research project are: Which mechanisms have a positive effect on the formation of compounds when using ultrasound? Is the diffusion process accelerated by ultrasound analogous to wire bonding? For this purpose, micro- and nanoscale sintering pastes will be developed first. Subsequently, the experimental investigation of the parameter influences on the joint quality will be carried out to enable a separation from the ultrasonic influence parameters. These are mainly the vibration amplitude, the power and the duration of the ultrasound. After the optimal ultrasonic direction (horizontal or vertical) has been determined, the time profile of the process is analyzed. Porosity and mechanical strength are measured to evaluate the joints and supplemented with other analysis methods. The investigations are performed on passive test chips and on active components (diode, IGBT, NTC). Here, the ultrasonic influence on the quality of the connection and the durability as well as possible damage to the components are examined. The research project is concluded with the model-based description of the mechanisms of ultrasonic assisted silver compound sintering. By answering the key questions, silver compound sintering will be significantly improved. This opens up this bonding technology for many more applications.