The prediction of the dimensional resolution, depending on viscosity, shrinkage and crystallization of engineering plastics is essential for the production of molded microstructures. Conventional test structures like 'flow spirals' cannot be used in microscale molding due to insufficient stability. Hence, new micro test structures realized by means of the LIGA techniques were designed to investigate these effects. On the one hand stand-alone circle-shaped structures were produced to compare the filling of microstructures with different aspect ratios at one structure height. Therefore, the wall thickness is varied in steps from 2.5 micrometers to 20 micrometers . Furthermore 'wedge' structures with radius at the tips of 0.5 micrometers and 5 micrometers are arranged in circles at critical locations of the insert in order to investigate the influence of the flow path length and the orientation towards the direction of flow. All structures were mounted to a ground plate with a spacing of 500 micrometers to eliminate all influences among the structures. First results revealed different filling behavior for critical sections of the part. Even circle structures with 5 micrometers wall thickness can be filled and demolded. Wedge structures with sub-micron tip radii are observed and the filling of 5 micrometers radii can be achieved. Very small tips with less than one micro radii cannot be filled yet. The structure's position towards the direction of flow does not seem to play an important role on the filling behavior of those micro structures.

Date Published: 10 March 1999
PDF: 8 pages
Proc. SPIE 3680, Design, Test, and Microfabrication of MEMS and MOEMS, (10 March 1999); doi: 10.1117/12.341235

Published in SPIE Proceedings Vol. 3680:
Design, Test, and Microfabrication of MEMS and MOEMS
Bernard Courtois; Wolfgang Ehrfeld; Selden B. Crary; Wolfgang Ehrfeld; Hiroyuki Fujita; Jean Michel Karam; Karen W. Markus, Editor(s)