Laser Welding of Fuel Cells (Bipolar Plates)

The use of fuel cells offers a flexible option to generate electrical energy directly at the consuming device. Hydrogen and the oxygen of the ambient air are used to produce electrical energy, water and waste heat. 

This process takes place between bipolar plates. Several of these plates must be connected to each other to generate the high voltages required for the automotive application. Fuel cells for electrical vehicles can include, therefore, 200 or more bipolar plates. 

Bipolar plates are also used to guide a cooling medium and therefore they must be tight. They consist of two stainless steel films, which are welded together by using a laser. 

Process Requirement: Productivity

Bipolar plates include one or more circumferential seal welds as well as many short welding seams for the electrical contacting between the plates. Welding seams with a total length of 1 to 2 m - or even more - may be required for each plate. This and the high quantity requires welding at high speeds to guarantee an economic operation.

The scanner based remote laser welding is outstandingly qualified to successively weld the circumferential seam and the contacts without interruption. If several scan systems are used at the same time, then seams can be welded simultaneously, and this increases the throughput.

Process Requirement: Precision

Another relevant system requirement is the use of single-mode lasers to generate especially narrow seams. The intelliSCAN FT and fiberSYS scan systems are especially qualified for this purpose.

The intelliSCAN FT is especially qualified for the process evaluation in connection with the diffractive optical elements (DEO) for the generation of an adapted beam profile. This optimization permits a flawless joining even for feed rates of more than 60 m/min. 

fiberSYS scanner are characterized by their compactness and the very precise seam guidance. Several scanners can process a bipolar plate in the same processing field. Based on state-of-the-art galvanometer technology, the seam can be set with high precision as it is required for the delicate structure of the cooling channels. 

Typical System Configurations for High Quantities