Microfabrication by hot embossing and injection molding at LASTI

Abstract

LIGA process includes three processes as X-ray lithography, electroforming to fabricate metalic molds and replication, and can be fabricated nano and micro parts for various devices that it is difficult to product by conventional machining methods. A key technology which gathers mass-production efficiency in the LIGA process is micro-replication technology.We choiced hot embossing and injection molding methods for replication. For a demonstration, two kinds of Ni molds, a mesh pattern within a line width of 100 lm, and an aspect ratio of 1.0 and a mesh pattern within a line width of 40 lm, and an aspect ratio of 2.5, were prepared. These were produced with X-ray lithography and nickel electrofoming technique. In hot embossing, an experiment of micro-replication using polymethyl methacrylate (PMMA) and polycarbonate (PC) sheets succeeded. At injection molding, it could not transfer well with PMMA and PC, but injection temperature was set up highly, and it succeeded by cycloolefin polymer. Furthermore, we measured sidewall's surface roughness of microstructures produced at each steppes of the LIGA process, and it checked that the LIGA process had processing accuracy higher than a conventional machining method.

Injection molding micro patterns with high aspect ratio using a polymeric flexible stamper

“…After pressing the mold onto the polymer melt, the system that consists of the tool and part is cooled down, after which the part is demolded. The hot embossing process is suitable for replicating complex or high aspect ratio (> 2) microstructures [2,3]. However, a major inconvenience encountered through this process is the need of long cycle times for heating and cooling both the mold and the material [4].…”

Modelling and Simulation for Micro Injection Molding Process

“…The fabrication of high aspect ratio micro features can be realized by using a mold temperature close to the softening temperature of polymer or even higher. In this way, some special structure sizes in the nano meter range also are able to be replicated [Mekaru H et al 2004;Schift H et al 2000;Yao D. & Kim B. 2002;Liou A. C. & Chen R. H. 2006; Despa M. S., Kelly K. W. & Collier J. R. 1999).…”

Development of precision transfer technology of atmospheric hot embossing by ultrasonic vibration

“…Molding of PC was comparatively easier than PMMA in the preliminary experiment (Mekaru et al 2004). The glass transition temperature Tg of PC is 150°C.…”

“…We newly developed this device (Yamada et al 2002). From a result of a preliminary experiment (Mekaru et al 2004) before developing this device, the contact force of 5 kN was necessary to transcribe the precise pattern that a pattern width was 40 lm, an aspect ratio was 2.5 and a pattern area size was 20 · 20 mm 2 on polymethylmethacrylate (PMMA) and polycarbonate (PC) sheets. When the maximum pattern size of the metallic mold was assumed to be 50 · 50 mm 2 , a necessary contact force was calculated with 31 kN (6.25 times 5 kN) from the ratio of the metallic mold pattern area.…”