Partners participating in the RoBE (Robust Bonds in Electric Vehicles) collaborative research project have developed a reliable means of predicting the service life of bonded connections, and an alternative bonding technique based on laser micro welding that is ready for industrial implementation.
Advances in the field of wire bonding technologies are crucial in Germany’s future as a leading provider of electromobility solutions. To encourage this, the German Federal Ministry of Education and Research (BMBF) has set aside €4.96 million in funding to support this collaborative project as part of its ICT 2020 initiative.
In power electronics systems, bonded connections create the central electrical connections between adjoining surfaces. The quality of these bonded connections is one of the main factors that determines the reliability and availability of drive systems in electric vehicles, and hence constitutes a major design challenge for German auto manufacturers aiming to electrify their vehicles.
The new technique opens up a wider range of options for the use of wire bonding, especially in applications requiring the joining of copper. Here, modern laser sources with a very high beam quality ensure precise, reproducible weld joints in copper and aluminium.
The use of oscillation welding, in combination with adapted design of the wire and ribbon joining zones, allows the strength of the joint to be further improved. By comparison with conventional wire bonding, this process offers a higher surface quality and requires less cleaning. Moreover, the process is less dependent on the nature of the underlying surface or the vibration characteristics of the workpiece.
A standard bonding machine was adapted to allow the laser bonding process to be combined with traditional bonding technologies. The new machine now allows the use of a laser in the bonding process. The main applications of this system include ribbon bonding on DCB substrates and copper terminals in the packaging of power electronics assemblies.