High Strength Electrodeposited Au-Cu Alloys Evaluated by Bending Test toward Movable Micro-Components

Au-Cu alloy micro-cantilevers are fabricated from Au-Cu alloy films electrodeposited at different current density. Bending deformation behaviors of the Au-Cu alloy micro-cantilevers are evaluated for applications as components in MEMS devices. Au-Cu alloy films with smaller grain size and higher copper content are obtained when a higher current density is used. The Au-Cu alloy film electrodeposited at 5 mA/cm2 has the finest average grain size among films prepared in this work, which the grain size is 4.76 nm. Bending test of a micro-cantilever prepared from this film shows a high yield stress at 1826 MPa. The high strength is contributed by synergetic effects of the grain boundary strengthening and the solid solution strengthening mechanisms. The deformation behavior changes from ductile to brittle as the copper content increased. The capability to control the grain size and copper concentration simply by adjusting the current density and the high strength are both advantageous in fabrication of MEMS components.