Komax Solar has developed a new, fully automatic stringer for 6-inch back contact cells. The contactless soldering technology as well as the ribbon handling technology was designed to minimize the thermo mechanical stress introduced into the solar cell. In addition, this back contact stringer adds the electrical isolation between the cells and the ribbons.

Problem

Typically, 5-inch back contact cells are contacted at the edges and interconnected with tabs. However 6-inch back contact cells (MWT, EWT as well as IBC) need to be connected over the whole area in order to minimize resistive losses. One possibility is to use a foil based approach (like a flexible PCB), but this solution is expensive in terms of material cost and CapEx. A ribbon based approach is a cost efficient solution in terms of material cost as well as CapEx, but the thermo mechanical stress introduced into the solar cell must be minimized and the electrical isolation needs to be established.

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Solution

Komax Solar has developed a low stress cell interconnection technology for back contact cells by further optimizing their contactless soldering technology, in combination with a special treatment of the ribbon which minimizes the thermo mechanical stress introduced into the cell. In addition, the back contact stringer from Komax adds the electrical isolation between the ribbons and the cell. For high aesthetic values, the electrical isolation material is available transparent or white or black colored. The newly developed interconnection technology takes care of environmental aspects, since it also works with lead free solder.

Applications

Ribbon based interconnection of 5 and 6-inch MWT, EWT and IBC solar cells.

Platform

The new back contact stringer is based on back contact technology from Komax Solar with more than 1GW of back contact stringers (Xcell 3000 platform) installed in the market. The new back contact stringer uses the same key technologies (closed loop induction soldering, ribbon handling and handling of the isolating materials) as the Xcell 3000.