Fineline stencil chemistry
By Katrin Oehrle, Screen and Textile Printing Applications Technology, Kissel + Wolf GmbH
The primary goals of crystalline photovoltaics are to lower cell costs while increasing their efficiency. Screen printing makes a considerable contribution here, as it enables ever-narrower conductive fingers to be achieved at high process speeds on the front side of the solar cell. This and also the miniaturisation of functional prints, for example in electronics, place very high demands on the screen printing stencil. So that the resolution of such fine lines not only occurs in the stencil but is also able to subsequently function in print, all the stencil production parameters must be perfectly coordinated with each other. The stencil chemistry used plays a decisive role in the first place. Merely coating with an emulsion is often no longer sufficient. First, a base coating with a high-resolution emulsion should be done. Following the emulsion coating, a top-coat, i.e. a special coating medium for screen printing emulsions, can be post-coated on the printing side, which further improves the Rz value and protects the screen printing stencil from mechanical attacks during the printing process. Especially in the solar sector, a uniform topography of the printed line is important so that electricity can flow unhindered.
Kissel + Wolf GmbH, D-69168 Wiesloch, www.kiwo.de