Ultra-soft wires for direct soldering on finger grids of solar cells. (September 2017)

• Record Type: Journal Article
• Authors: Rendler, Li C.; Walter, Johann; Kraft, Achim; Ebert, Christian; Wiese, Steffen; Eitner, Ulrich
• Is Part Of: Energy procedia. Volume 124(2017)
• Page Start: 478
• Page End: 483
• Publication Date: 2017-09
• Subjects: Wire interconnection -- wave-shaped wires -- reliability -- contact fingers -- thermomechanical stress -- stress relief -- Multi Busbar -- SmartWire -- temperature cycling -- electroluminescence; Power resources -- Congresses; Power resources -- Periodicals; Power resources; Conference proceedings; Periodicals; 333.7905
• DOI: 10.1016/j.egypro.2017.09.284
• Languages: English
• ISSNs: 1876-6102

Abstract

Abstract: We propose an interconnection concept for solar cells that enables the soldering of solder coated copper wires directly on the contact fingers of the front side metallization without the need of busbars or contact pads. By reshaping the copper wires we realize a wave-shaped stress relief structure. This reduces the yield force, the force value where plastic deformation of the wire starts, up to 90 % compared to straight wires and therefore minimizes mechanical stresses in the joint after the soldering process essentially. Our experimental analysis demonstrates the mechanical long-term stability of the interconnection (ΔP < 2 % after TC 370). The method enables a significant silver reduction by omitting solder pads or busbars on the front side and is especially suitable for the interconnection of exceptionally thin, stress sensitive solar cells or back contact solar cells with a minimized cell bow.