Material and process optimization screen printing carbon graphite pastes for mass production of heating elements

• Creation of new product utilising novel high conductivity carbon paste printing technology tracked from invention to pilot manufacturing.
• Identification of interactions between film thickness, deposition method, surface topology and curing.
• Source of process drift in screen printing identified and quantified.

An experimental development programme has been carried out for the production of resistive heated panels to be used in raised access flooring. Screen printing was used as the means of depositing the heating element and the paper examines the means by which the process is optimised from assessment of material formulations through to a pilot production run of 300 tiles. A material with a sheet resistance of 35 Ω/sq, when printed through a 77-48 polyester mesh was selected by examining its rheological and drying behaviour. Higher film thickness with coarser screens was not possible as this incurred topological variations in the printed film and required excessive drying times. During a pilot manufacturing run of 300 panels, process drift was observed and this was attributed to squeegee softening due to solvent absorption. The generic findings of the study are applicable to many applications where screen printing is used for the continuous deposition of materials where the characteristics of the deposit and its subsequent curing is paramount such as sensor, third generation PV and circuit boards.