Development of a laser-assisted drop-on demand brazing process to extend the process limits of conventional wire bonding processes for electronics assembly and packaging (T04#)

拟议研究项目的目的是对水滴钎焊工艺进行鉴定，该工艺是在SFB/Transregio 39 PT-PIESA子项目A04框架内开发的，作为电子组装和互连技术（AIT）的替代连接工艺。超声波焊线和焊接目前代表了电子AIT的最新技术。在超声线键合中，必须在硅半导体上应用铜缓冲层，以防止在键合过程中对硅半导体造成机械损伤。在焊接中，被焊接头的低热稳定性约为。230°C对其适用性提出了越来越多的问题，例如在电力电子领域。喷射钎焊工艺有望避免上述标准工艺的缺点。在这个过程中，一个球形的钎焊预制体被引入毛细管，用激光脉冲熔化，然后用惰性气体超压将其排出毛细管。可以加工钎焊合金，其熔化温度约为。比焊料合金高700°C，与焊接接头相比，钎焊接头的热稳定性提高了三到四倍。由于与超声波线键合相比，该工艺的非接触性质，因此高温稳定接触也可以应用于厚度仅为几微米的箔，金属化或电极结构。然而，为了使电子AIT的工艺符合批量生产的要求，必须确保基体和钎焊合金之间的冶金相容性，特别是考虑到电子AIT中常用的钝化层。因此，这项工作的重点是将迄今为止获得的基础知识扩展到更广泛的材料范围。假设钎焊预制坯的体积、基体材料、钝化层及其几何形状对钎焊效果都有影响。为了能够谨慎地量化这些影响，研究还辅以数值模拟。所产生的触点进行了冶金、机械和电学表征，并对其与AIT的相关性进行了评估。这种连接技术的潜在应用领域包括电力电子、汽车工业和航空航天。例如，珀尔帖元素的效率也可以通过高温稳定的键合方法来提高。此外，该技术对于在恶劣环境中使用的封装电路载体也很有前景。

The aim of the proposed research project is the qualification of the drop-jet brazing process - developed within the framework of subproject A04 of the SFB/Transregio 39 PT-PIESA - as an alternative joining process for electronic assembly and interconnection technology (AIT). Ultrasonic wire bonding and soldering currently represent the state of the art in electronic AIT. In ultrasonic wire bonding, copper buffer layers must be applied to silicon semiconductors to prevent mechanical damage to the Si semiconductor during the bonding process. In soldering, the low thermal stability of the soldered joints of approx. 230 °C is increasingly posing a problem for their applicability, for example in power electronics. The drop-jet brazing process promises to avoid the disadvantages of the mentioned standard processes. In this process, a spherical, braze preform is introduced into a capillary, melted by a laser pulse and then expelled from the capillary by inert gas overpressure. Brazing alloys can be processed, which have a melting temperature of approx. 700 °C higher than the solder alloys, which increases the thermal stability of the brazed joint by a factor of three to four compared to soldered joints. Due to the non-contact nature of the process compared to ultrasonic wire bonding, high-temperature stable contacts can also be applied to foils, metallizations or electrode structures with a thickness of only a few micrometers. However, in order to qualify the process for series production in the electronic AIT, metallurgical compatibility between the base and brazing alloy must be ensured, taking into account in particular the passivation layers commonly used in the electronic AIT. The focus of the work is therefore to expand the fundamental knowledge acquired to date to a broader range of materials. It is assumed that both the solder alloy used and the volume of the braze preform as well as the base material, its passivation layer and its geometry have an influence on the process result. In order to be able to quantify these influences discreetly, the investigations are supplemented by numerical simulations. The contacts generated are characterized metallurgically, mechanically and electrically and evaluated with regard to their relevance for AIT. The potential fields of application for such a joining technology range from power electronics to the automotive industry and aerospace. The efficiency of Peltier elements, for example, can also be increased by high-temperature-stable bonding methods. In addition, the technology is also promising for packaging circuit carriers used in harsh environments.