Product Code: ICA10_M1103

Concept and Realization of a High-Rate Laser Drilling Process Reaching for Ten Thousand Holes Per Second and Beyond
Authors:
Alexander Olowinsky, PRESENTER NOT AUTHOR, Fraunhofer ILT; Aachen Germany
Malte Schulz-Ruhtenberg, Fraunhofer Institute for Laser Technology; Aachen Germany
Tobias Baier, Manz Automation AG; Reutlingen Germany
Ernst Wilhelm Boeckler, SCANLAB AG; Puchheim Germany
Christof Siebert, TRUMPF Laser- und Systemtechnik GmbH; Ditzingen Germany
Presented at ICALEO 2010

One major breakthrough on the way to cheap sustainable solar electricity generation is the back contact solar cell. One way to move the front contacts to the back side of the cell is to drill vias through the silicon wafer which are either filled with metal or are heavily doped. For the former only up to 100 through-holes are necessary, but some metallization for current collection is still required on the front side. All metallization shadowing losses can be eliminated by applying the emitter wrap-through (EWT) concept, where up to one hole per mm² is needed, i.e. up to 24,000 holes on a 6 wafer.
Since the processing time should remain below one second to allow high throughput in production the goal is to drill 10,000 holes/s and more. In this work this is tackled by developing optical concepts such as beam splitting and the combination of ultra-fast scanning and simultaneous movement of a linear axis. Also the selection of the proper laser source and processing parameters has proven to be crucial to successfully achieve the desired drilling rates. Of course other applications, such as laser drilling of filters can benefit from these developments.