Publication

Nouvelles technologies de microstructuration de type UV-LIGA et fabrication de composants micromécaniques

1998
EPFL thesis
Abstract

This study presents two techniques of structuration of type UV-LIGA (Lithographie, Galvanisierung und Abformung) based on the use of two thick photoresists which are a dry film resist called Riston® from DuPont and the new SU-8 negative-working resist from IBM. The relating processes to the structuration of these photoresists and some applications are presented too. The minimal resolution of the Riston® films has been found to be 30 µm for lines and trenches, and 40 µm for isolated holes in a 50 µm-thick film. A technique for the structuration of multilevel superimposed cavities has been set up. The verticality of the sidewalls (85.5°deg. to 87.5°deg) has been measured on film thicknesses between 25 and 100 µm. The SU-8 process has been studied and is presented. Some optical and mechanical properties have been analysed. We have determined a coefficient of light attenuation of 5.18 [db/mm] at 365 nm, a coefficient of thermal expansion of 52 [ppm/°C] and a biaxial modulus of 5.18 GPa. The verticality of the walls depends on the exposure energy and has been found to be higher than 89°deg. Layers from 750 nm to 2 mm can be exposed in one time, which seems to be the state-of-the art for a UV-photoresist to our knowledge. A specific process for the electroforming in multi-level superimposed cavities has been developed. With an adequate dosage of a leveling agent (coumarin) in the electrolytic Watt bath of nickel, a change in the growth rate of the high and the low level of the mold has been demonstrated. This rate is harmonised to obtain a flat deposition on the top surface of the formed structure. The UV-LIGA techniques developed in this thesis have found applications in the field of the-micromechanics. A flexible gearwheel, whose teeth are bound to the center via three integrated spring, and a multilevel gear system are the main realizations obtained by electroforming. These two structures have been used in a mechanism with a special watch mechanism and in a microreducer based on an electrostatic rotary micromotor. We have experimented with success the plastic injection of a gear system having 1.4 mm in height and 3 mm in diameter. Its mold has been electroformed on a master in SU-8. Theses microparts have demonstrated their functionality and have been mounted in commercialy-available-low-cost watches. All the process step of the LIGA technique have been established. The main advantages of this fabrication method are a better control of the tolerances and an improvement of the rugosity (against the wire electrodischarge machining technology). This technique is also cheaper and easier to start than X-LIGA.

About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Graph Chatbot

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.