Micro-bending testing of electrodeposited gold for applications as movable components in MEMS devices

Abstract

This study reports micro-bending testing results of electrodeposited gold for applications as movable components in MEMS accelerometers. Cold-rolled gold was also evaluated to be used as a comparison with the electrodeposited gold. The specimens evaluated were micro-cantilevers having dimensions of 10×10×50μm3, which were fabricated by focused ion beam system. The bending test was conducted using a displacement controlled micro-mechanical testing machine developed in our group. Engineering stress-engineering strain curves generated from the micro-bending tests showed there are two types of enhanced mechanism involved during the deformation. One was the sample size effect, which yield stresses of the two micro-cantilevers evaluated in this study were both higher than that of the bulk gold material. Yield stresses of the cold-rolled and electrodeposited gold were 260 and 369MPa, respectively. The other was the Hall-Petch relationship, which the electrodeposited gold showed a higher yield stress than that of the cold-rolled gold, because the electrodeposited gold has a finer average grain size. Average grain sizes of the cold-rolled and electrodeposited gold were 1.95 and 0.918μm, respectively.