Production of Micro-Molding Tooling by Hot Embossing

Tooling is especially critical for micro-molding of polymers because the tool defines the geometry of the finished part. Various tool materials and processes have been demonstrated, including etched silicon, machined or electroformed metal, and molded polymers. Adhesion of the part to the tool and differential thermal contraction are frequently cited problems related to micro-molding tooling. Brittle silicon tools are particularly vulnerable to failure during demolding because of adhesion and thermal stress. The current work demonstrates the production of micro-molding tools by hot embossing of thermoplastics. Polymer materials for working tools are selected on the basis of high heat deflection temperature and high interfacial tension with the polymer being embossed. The high thermal resistance of the working tool material enables its use in hot embossing of materials with lower glass transition temperature such as polymethyl-methacrylate and cyclo-olefin-polymer, as well as other micro-molding processes. The high interfacial tension reduces adhesion between the master mold and the final part, reducing loads on the tools and facilitating demolding. Embossing parameters for a variety of working tool materials, as well as replication fidelity of the working tools and parts and tool-part adhesion are explored. Polymer working tools produced by hot embossing show great promise for manufacturing polymer micro-devices.