Evaluation of influencing factors on the heavy wire bondability of plasma printed copper structures

Power semiconductor devices and systems enable the efficient conversion and management of electrical energy. Power electronic applications range from fewer watts up to several mega- and gigawatts. Driven by a continuous electrification of society, power electronics are not only found in the automotive and energy sector, but also in industrial and lighting applications, as well as consumer electronics. In power electronic devices wire bonding is the established and predominant top-level interconnect technology due to a high process stability and low production costs. Characterized by a great process flexibility it might also be the predominant interconnection technology of coming additive manufactured devices and structures if wire bonding proves to be capable of connecting printed layers that form the basis of additive functionalized and even three-dimensional power device layouts. This paper will therefore display the influencing factors, as well as the possibilities and challenges that come along with the process combination of cold active atmospheric plasma printing with large wire aluminum bonding. For the investigations, copper layers are additively printed on Al2O3 ceramic substrates. Based on the printing parameters the most influential characteristics of the printed layers are derived. The influence and effectiveness of various steps of post processing such as grinding and cleaning are discussed. Last, a production series of 300 μm aluminum wires is bonded on the generated copper layers. The process stability as well as the interconnection quality is evaluated by destructive pull and shear tests and metallographic cross sections.