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验证在SFB/TransRegio 39 PT-PIESA子项目A04框架内开发的滴注钎焊工艺作为电子组装和互连技术(AIT)的替代连接工艺的资格。超声波引线键合和焊接目前代表了电子AIT的技术水平。在超声引线键合中，必须在硅半导体上施加铜缓冲层，以防止键合过程中对硅半导体的机械损伤。在焊接过程中，焊点的热稳定性较低。230摄氏度对它们的适用性提出了越来越多的问题，例如在电力电子领域。滴注钎焊工艺可以避免上述标准工艺的缺点。在这一过程中，将球形的铜焊预制件引入毛细管，通过激光脉冲熔化，然后通过惰性气体超压从毛细管中排出。铜焊合金可以加工，其熔化温度约为。焊接温度比焊料高700℃，与焊点相比，焊点的热稳定性提高了三到四倍。与超声波引线键合相比，由于该工艺的非接触性，高温稳定的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，为了使该工艺符合电子AIT中批量生产的要求，必须确保基材和钎料之间的冶金兼容性，特别是要考虑电子AIT中常用的钝化层。因此，工作的重点是将迄今获得的基本知识扩大到更广泛的材料范围。假设使用的焊料、预制件的体积以及母材、钝化层和几何形状都对工艺结果有影响。为了能够谨慎地量化这些影响，这些研究辅之以数值模拟。对产生的触点进行了冶金、机械和电气方面的表征，并根据它们与AIT的相关性进行了评估。这种连接技术的潜在应用领域从电力电子到汽车工业和航空航天。例如，Peltier元件的效率也可以通过高温稳定的结合方法来提高。此外，该技术还有望用于恶劣环境中的电路载体封装。

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.