Laser micro welding with fiber lasers for battery and fuel cell based electromobility

Abstract

New challenges are arising within the joining processes in the field of electromobility. Joining highly reflective metals and dissimilar materials such as copper and aluminum – often encountered in battery electrical vehicles – is viewed as a challenging task. Additionally, the use of thin sheets of stainless steel is gaining importance in applications with PEM fuel cells, where the welding length is sometimes up to and even more than five meters long, yet the process speed remains limited.Laser micro welding offers in comparison to conventional joining methods several advantages regarding process speed, parts accessibility, potential of automation, and particularly localized heat input. There are different types of lasers available on the market ranging from the visible to the infrared range, yet choosing the right laser depending on the task can be challenging. Several characteristics are considered when comparing weld quality such as surface finish, reproducibility and mechanical stability. Recently, the possibility of tuning the parameters of a nanosecond pulsed fiber laser to achieve welding is being examined. On another topic, using a novel welding strategy with spatial power modulation – by applying a new geometry – is also being investigated. In this paper, the welding process with the nanosecond pulsed fiber laser is evaluated based on mechanical stability and surface finish, which allows further insight into the suitability of such a method for welding particularly copper and aluminum materials. Additionally, some initial results from the here introduced spatial power modulation technique – used to weld stainless steel sheets – are presented.