Techniques for fabricating high-aspect-ratio microscale structures (HARMS) are being investigated for wide-ranging applications. Microdevices employing metal-based HARMS are of particular interest for mechanical, electro-mechanical, and chemical applications. In many applications, HARMS with two or several distinct heights are necessary, the fabrication of which necessitates two-level or multi-level mold inserts. In addition, tapered mold inserts would help achieving easy insert-part separation. Here we report a process for fabricating two-level, tapered mold inserts by combining UV-lithography on SU-8 resist, one-step metal electrodeposition, polish and level, and SU-8 resist removal. Without tilt and rotation during the lithography process, tapered SU-8 plating molds are obtained by employing light diffraction during lithography and proper development procedures. The SU-8 resist removal process does not reduce its strength. Efficacy of this approach is demonstrated with a two-level insert prototype suitable for fabricating micro heat exchanger parts by compression micromolding.
Embossing of microscale features into Pb and Zn was carried out using LIGA (Lithographie, Galvanoformung, Abformung) fabricated Ni mold inserts with features 100 microns in diameter and 500 microns in height. Molding was carried out at 300 °C with both uncoated Ni inserts and Ni inserts coated with Ti-containing hydrocarbon (Ti-C:H). The coatings were applied using a high-density inductively coupled plasma (ICP) assisted hybrid chemical vapor deposition (CVD)/physical vapor deposition (PVD) technique. This technique is shown to produce coatings conformally onto LIGA fabricated high aspect ratio microstructures (HARMs). The performance of the molding process was characterized using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy both in terms of the features generated and the insert condition after molding. The present results indicate that in molding metals that are not reactive with Ni no coating is necessary to produce the microfeatures. This study also demonstrates that in molding Zn, where significant metal/insert chemical interactions exist, surface engineering of the mold insert is necessary to obtain satisfactory performance. Conformal deposition of engineered ceramic coatings onto Ni microscale mold inserts is an effective means for achieving micromolding of reactive metals.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.