微热压印过程中聚合物流动形貌的研究

Study on polymer flow profile in micro hot embossing

为研究模具结构对聚合物流动形貌的影响,利用Deform-2D对微热压印成型过程进行了有限元模拟。系统地研究了模具占空比、宽厚比、阴模、阳模及不对称结构对聚合物流动形貌的影响。模拟结果显示,随着占空比的减小,聚合物截面流形从单峰过渡到双峰,从陡峭过渡到平坦,当宽厚比>1.5时,截面流形开始表现为双峰形式,其仿真结果和相关实验结果吻合。和阳模压印时没有明显的高度差相比,使用阴模压印时,微结构之间存在较大的高度差。针对压印过程易出现的填充效率不佳,提出了模具拓扑结构优化策略,通过在模具边缘布置一些流动坝,达到降低边界处聚合物流动率,促进聚合物有效填充的目的。仿真结果表明,该优化策略对促进聚合物填充具有很好的效果。

To find the relationship between the mold structure and the flow profile, the Deform-2D code was used to simulate the micro hot embossing process. The effect of the mold duty ratio, Ratio Of the mold Width to the polymer Thickness （ROWT）, concave mold, convex mold and the non-symmetric mold on the polymer flow profile was systematically studied. The numerical simulation results show that the flow profile of the polymer changes from single peak to dual peak, from craggedness to flatness with the decrease of the duty ratio. When ROWT is more than 1.5, the flow profile becomes dual peak. The simulation results are verified by the relative experiments. Compared with the results of nearly no pattern height difference when the convex mold is used, the micro pattern height has distinct difference when the concave mold is used. The strategy of topology optimization of mold struc tures was proposed to improve the polymer filling efficiency. With the help of some flow barriers located at the edge of the mold, the polymer flow speed at the boundary can decrease and the effective filling will be enhanced. The numerical simulation results show that this optimization strategy can accelerate the polymer filling speed in hot embossing.