Product Code: ICA13_M605

Laser Joining of Charge-Collection Tapes Onto Cigs Photovoltaics Modules
Authors:
Ralf Nett, Ruhr-Universitaet Bochum, Applied Laser Technolgy; Bochum Germany
Kerstin Kowalick, Ruhr-Universitaet Bochum, Applied Laser Technology; Bochum Germany
Manuel Joop, Ruhr-Universitaet Bochum, Applied Laser Technology; Bochum Germany
Benjamin Schoeps, Ruhr-Universitaet Bochum, Applied Laser Technology; Bochum Germany
Andreas Ostendorf, Ruhr-Universitaet Bochum, Applied Laser Technology; Bochum Germany
Christoph Ruettimann, Rofin-Lasag AG; Thun Switzerland
David Bremaud, FLISOM AG; Duebendorf Switzerland
Presented at ICALEO 2013

Charge-collection tapes, known as busbars in photovoltaic technology, need to be connected to photovoltaic (PV) modules to discharge the current from the module. The common way for joining is the use of pressure-sensitive adhesive.
We demonstrate connecting the busbars onto a silver grid applied on top of a PV module by laser spot joining. The thicknesses of the PV layers are: Polyimide substrate 25 µm, CIGS stack 5 µm and Ag grid 8 µm. The busbars with a copper core of 150 µm has a tin coating of approx. 17 µm. The tin plating resists oxidation and corrosion. Trials are conducted with a Rofin Lasag SLS GX 1500 laser and a scanner system by Scanlab equipped with optics from Sill optics. Laser joins are evaluated by preparing cross sections of each welded spot and microscopic imaging.
The analysis of these microscope images show molten connections between the tin coating and the silver grid on the PV module with the same value of electric conductivity like the silver grid itself and just a small area of delamination. The laser beam neither damages the CIGS stack nor the polyimide substrate. Additional experiments are conducted joining two busbar to each other.
We show a well suitable remote laser joining process for operation in a roll-to-roll production line.