控制参数对热压的影响分析

he key control parameters in hot embossing (imprint pressure, embossing temperature, holding time, demolding temperature, horizon of substrate et al.) can significantly influence the pattern quality. Finite element method (FEM) was used to analysis the embossing, cooling and demolding step to get the optimal effect. The simulation results show that imprint pressure, imprint temperature, holding pressure change the polymer flow characteristics and the adhesion force between the polymer and the mold significantly influence the replication accuracy. Because of polymer flow, non-uniform pressure distribution can be observed and this result in the pattern height difference. The hydraulic pressure system was designed to acquire uniform pressure. The difference of the thermal expansion coefficients between the mold and the substrate causes lateral thermal stress can induce the stress concentration at the corner. In demolding step, if the demolding direction isn’t vertical to horizon, another stress concentration will appear. Excessive stress results in defects and causes fracture at the base part of the pattern during the mold releasing step. To eliminate the defects, cooling to a relative high temperature is introduced to reduce the stress concentration and an auto demolding device was used to insure no additional stress was imported at mold releasing stage. The followed experiment shows the successful fabrication of fine patterns with the optimized parameter.