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Tapered LIGA HARMs

Ryan Turner1, Yohannes Desta2, Kevin Kelly1, Jian Zhang1, Emil Geiger1, Steve Cortez1 and Derrick C Mancini3

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The standard LIGA process takes advantage of the use of x-ray lithography to produce mold inserts with nearly vertical sidewall; the typical slope of patterns produced by x-ray lithography of polymethylmethacrylate is 0.1%. This lack of significant taper (draft angle) greatly increases the difficulty associated with ejecting parts during demolding. In this paper, a procedure is described to fabricate a mold insert with tapered features having a height of approximately 1 mm and lateral dimensions of approximately 300 μm. A set of six oblique exposures of a thick layer of SU-8 (an EPON epoxy based negative tone resist) is used to create hexagonal posts with a 3° draft angle. An electroforming process is used to fabricate a nickel mold insert with the tapered features. This mold insert is used to injection mold tapered polymer high aspect ratio microstructures. The dimensions of the SU-8 tapered structures (as well as the mold insert) are within 4 μm of desired/predicted values.


PACS

81.20.Hy Forming; molding, extrusion etc.

81.16.Nd Nanolithography

81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

81.20.Wk Machining, milling

85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Subjects

Soft matter, liquids and polymers

Electronics and devices

Nanoscale science and low-D systems

Condensed matter: structural, mechanical & thermal

Dates

Issue 3 (May 2003)

Received 11 November 2002, in final form 28 January 2003

Published 24 February 2003



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