Hot embossing in microfabrication. Part II: Rheological characterization and process analysis
Hot embossing in microfabrication. Part II: Rheological characterization and process analysis
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DOI：
10.1002/pen.10971
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发表时间：
2002-03-01
影响因子：
3.2
通讯作者：
Koelling, KW
中科院分区：
文献类型：
--
作者：
Juang, YJ;Lee, LJ;Koelling, KW
测定了聚碳酸酯（PC）、聚甲基丙烯酸甲酯（PMMA）和聚乙烯醇（PVB）在玻璃化转变温度附近和远高于玻璃化转变温度时的动态剪切粘度和瞬态拉伸粘度。用流变特性的温度敏感性来解释压花过程中的位移曲线。对压花过程进行了数值模拟，并与观察到的聚合物流动模式进行了比较。结果表明，等温压花过程的模拟流态与实验结果吻合较好。在压花后期，模拟结果与实验结果之间的偏差可能是由于模具特征和聚合物基材之间的空气夹持造成的。对于非等温压花，也可以合理地模拟观察到的流动模式，即聚合物沿着加热模具特征的壁面向上流动，然后向下压缩并向外挤压。三种聚合物的动态剪切粘度和瞬态拉伸粘度的温度敏感性相似。这与等温压印的初始位移曲线有很好的相关性。在较长时间内，瞬态拉伸黏度的应变硬化效应似乎在位移曲线中起主要作用。
The dynamic shear viscosity and the transient extensional viscosity of polycarbonate (PC), polymethyl methacrylate (PMMA), and polyvinyl butyral (PVB) were measured at temperatures near and far above their glass transition temperatures. The temperature sensitivity of rheological properties was used to explain the displacement curves during embossing. Numerical simulation of the embossing process was also carried out to compare with the observed polymer flow patterns. It was found that the simulated flow pattern during isothermal embossing agrees fairly well with the experimental observation. The deviation between the simulated and experimental results at the late stage of embossing may be due to air entrapment between the mold feature and the polymer substrate. For non-isothermal embossing, the observed flow pattern can also be reasonably simulated, i.e. the polymer flows upward along the wall of the heated mold feature, and then compresses downward and squeezes outward. Temperature sensitivity of the dynamic shear viscosity and the transient extensional viscosity is similar for all three polymers. This correlates well with the initial displacement curves in isothermal embossing. Over a longer time, the strain hardening effect of the transient extensional viscosity seem to play a major role in the displacement curves.