Heat-Assisted Screen Printing of High-Aspect-Ratio Microstructures

Herein we propose a new screen-printing method called heat-assisted screen printing (HASP). This method uses a local heater located at the squeegee tip. The heater increases the temperature and decreases the viscosity of the ink around the squeegee tip and improves the flow of ink into the mask opening. Subsequently, the ink is cooled by heat conduction to the mask and the substrate, and the viscosity increases, which improves the maintenance of the structure after demolding. We designed a machine for model experiments. The heater temperature was set to 20 °C, 40 °C, 60 °C, 80 °C, and 100 °C. The filling rate increases as the heater temperature increases. The filling rate became constant at approximately 0.75 at temperatures above 60 °C. The thermal fluid of the ink over the mask was also simulated using the particle method, and the temperature of the ink near the squeegee tip was evaluated. When the heater temperature was 60 °C, the temperature of the ink was constant at 39 °C and the viscosity was 1880 mPa·s. It was found that HASP improved the filling of high-viscosity ink and a boundary temperature exists for sufficiently filling the ink.