Process analysis of ultrasonic metal welding by acoustic emission

近年来，超声波金属焊接（USMW）已被证明是连接电子元件的合适技术。电气系统的日益复杂性已经促使该行业广泛部署这项技术。然而，尽管其广泛应用，USMW工艺仍然存在质量波动。这种波动主要源于对工具和连接部件之间的相互依赖性缺乏深刻的科学知识和理解，这在过去的实证研究中基本上被忽视了。申请人最近的研究表明，测量由工具和粘附物组成的整个机械系统的变化的振荡行为，可以提供关于结合界面内的热机械过程的详细状态和顺序的有价值的信息。特别是（结构）声发射似乎可以对复杂的过程进行全面分析，因此可以使用基于科学的模型对其进行描述，从而提供一个有充分依据的基础。因此，本项目计划对使用声发射作为USMW过程分析工具的适用性进行基本调查。为此，将开发和应用广泛的数据采集概念，包括内部和外部传感器技术以及粘附物的预处理和后处理筛选，以捕获必要的测量数据。基于最新的知识和对所获得的特征结构声发射和空气声发射的分析，将描述整个连接过程的基本物理过程。与接头性能相关的特征变量将从声发射中导出，并允许在未来的项目中预测焊接质量。通过对焊接过程中热力学机理的错误案例分析，加深对超声波焊接过程的理解。一旦验证，该项目的结果将引入应用现场可测量的监测标准来实时控制USMW过程的前景。

In recent years, ultrasonic metal welding (USMW) has proven to be a suitable technique for joining electronic components. The increasing complexity of electrical systems already prompted the industry to widely deploy this technology. However, despite its widespread application, the USMW process still suffers from quality fluctuations. The fluctuations largely originate in the lack of profound scientific knowledge and understanding of the interdependency between the tools and joining parts, which was largely ignored in past empirical studies. Recent investigations of the applicants have indicated that measurements of the changing oscillation behavior of the entire mechanical system, comprised of the tools and the adherents, can provide valuable information about the detailed state and sequence of the thermo-mechanical process within the bond interface. The (structural) acoustic emissions in particular appear to allow for a comprehensive analysis of the complex process and thus might provide a well-founded base for its description using a scientifically based model.Therefore, a fundamental investigation of the applicability of using acoustic emission as an analysis tool for the USMW process is planned in this project. For this purpose, an extensive data acquisition concept, encompassing internal and external sensor technology as well as the pre- and post-process screening of the adherents, will be developed and applied for capturing the necessary measurement data. Based on the state-of-the-art knowledge and the analysis of the acquired characteristic structure-borne and airborne acoustic emissions, the underlying physical processes will be described for the entire joining procedure.Characteristic variables which correlate with the properties of the joint, will be derived from acoustic emission and allow the prediction of the weld quality in future projects. By analysis of defined error cases on thermo-mechanical mechanism during welding a more profound understanding of the USMW process should be achieved. Once validated, the results of this project will introduce the prospective to apply on-site measurable monitoring criteria for controlling the USMW process in real-time.