Analysis of the Effect of UV-LIGA Fabrication Error on the Microspring Elastic Coefficient

Yu Qin,Liangyu Chen,Yongping Hao,Xianlong Hu,Shuangjie Liu

doi:10.1109/access.2019.2949386

Abstract

The manufacturing process of planar microsprings by the UV-LIGA process was introduced; the mechanism of fabrication error was analyzed from three process stages of exposure, SU-8 swelling, and corrosion; and the corresponding improvement measures were proposed. The line width of two groups of microsprings after the exposure, SU-8 swelling, and debonding was measured, and the elastic coefficients in three coordinate directions were accurately measured. The results show that the factors that affect the line width error are stable. The effects of the exposure diffraction, swelling of SU-8 glue, and debonding corrosion process on the line width size follow the order: corrosion error > swelling error > exposure error. When the line width is small, the aspect ratio of the microspring is large, and the direction of machining error is generally negative. The relative error of the elastic coefficient of microsprings in three coordinate directions is larger. The influence rule of the line width error on the elastic coefficient follows the order: k error y > k error x > k error z.

Highlights

With the rapid development of MEMS technology, more attention has been paid to the application of MEMS devices in micromechanical structures [1], [2]
Shao et al [19] performed an accurate measurement of the linewidths of two groups of different microsprings processed by the LIGA process, calculated the longitudinal elastic coefficients by theoretical formulas, and VOLUME 7, 2019
PREPARATION OF PLANAR MICROSPRINGS Planar microsprings were prepared by the UV-LIGA process, which is a quasi-LIGA process that is based on the SU-8 glue

Summary

INTRODUCTION

With the rapid development of MEMS technology, more attention has been paid to the application of MEMS devices in micromechanical structures [1], [2]. Li et al [18] designed and manufactured an S-shaped nickel microspring by the LIGA process, deduced the calculation formula of its elastic coefficient in three coordinate directions, analyzed the effect of the fabrication error of each structural parameter of the microspring on its mechanical properties, and pointed out that the linewidth error considerably affects its mechanical properties. Deng et al [20] measured the microspring size and response threshold of a MEMS inertial universal switch with flexible electrodes, analyzed the effect of processing error on the switch response threshold, and concluded that the microspring line width error was the main factor that affected the switch response threshold. The influence of diffraction effect, swelling effect of the SU-8 glue and debonding corrosion process on the linewidth size was studied, and the influence of linewidth error on the elastic coefficient of microsprings in three coordinate directions was analyzed using the self-designed testing system of the elastic coefficient of microsprings to optimize the design and improve the process, to ensure the consistency of the actual mechanical properties of microsprings with the design requirements to the greatest extent, and to facilitate the mass standardized production of microsprings

PREPARATION OF PLANAR MICROSPRINGS

ELASTIC COEFFICIENT TEST

CONCLUSION