In the BMWi-funded project KAluS50, a consortium consisting of the Fraunhofer Institute for Solar Energy Systems ISE, KSG Leiterplatten GmbH and Christian Koenen GmbH is working on an innovative alternative to the currently complex and expensive structuring of metal layers with paint masks and the chemical etching of the metal. At present, this process is mainly being used for the production of highly efficient interdigitated-back-contact (IBC) solar cells.
The project is investigating the electrochemical structuring of larger surfaces using screen printing and dispensing processes. The necessary medium is transferred to the metal surface to be structured and is also used to locally close the circuit. This process offers the advantage that the etch rate can be directly adjusted by the electrical parameters, which in turn enables good control and short processing times. The structures can also be galvanically strengthened if, as in the case of IBC solar cells, a high lateral conductivity of the generated metal pattern is needed.
The successful generation of meander structures on an area of 125 x 125 mm² from a 100nm-thick aluminium layer using electrochemical screen printing demonstrates that the project partners are on the right track. Furthermore, in the case of a layer stack, the selective removal of a 50 nm-thick copper layer from the underlying 100 nm-thick aluminum layer was achieved. This structure was then galvanically strengthened with copper and the aluminium layer was selectively removed in the intermediate area. The copper areas created can then be used as electrically isolated conductor tracks for solar cells, printed circuit boards and other electrical components.
KAluS50 is expected to be completed in May 2019 after the construction of an advanced demonstrator and subsequent evaluation.