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Hot embossing is currently applied to replicate microstructures only on one side or two opposite sides of a polymer substrate. If microstructure replication on two perpendicular sides of the substrate is necessary, closed-die hot embossing can be applied. In this study, polymethyl methacrylate (PMMA) was used as the polymer substrate. A closed die with three mold inserts was used to compress a heated PMMA substrate. Effects of related process parameters on the replication accuracy were studied. Closed-die hot embossing was compared with injection molding and injection compression molding. Results show that closed-die hot embossing can provide better replication accuracy. Optical anisotropy induced by the molding-related stresses can also be reduced.

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Microstructures were formed on low temperature co-fired ceramic (LTCC) green substrates with high fidelity using micro embossing. The impact of embossing temperature and pattern density against the embossed profiles was investigated. The increase in pattern density resulted in a macro deformation in addition to embossed micro-depth. The macro deformation can be decreased by careful management of pattern density as well as pressure ramp and temperature ramp. The embossed ceramic green substrates were debinded and co-fired with a supplier-recommended process; the dimension shrinkage of embossed channels after co-firing ranges from 20 to 22% in depth and from 10 to 13% in width. The achievements of this investigation demonstrated that micro embossing is a promising process for fabricating ceramic-based microstructures and devices, including embedded cavities and channels.