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To explore alternatives to the use of pure Au in Ohmic contact RF microelectromechanical switches, we have measured changes in the electrical resistivity and nanoindentation hardness of a series of sputter deposited Au–V and Au–V2O5 thin films. Increasing V content in the Au–V alloys increases resistivity and hardness, which is consistent with solid solution strengthening. In the Au–V2O5 films, the increase in resistivity is greatly reduced and the hardness is further increased as expected for dispersion strengthening with V2O5 particles. These two phenomena are explained in terms of solute and particle effects on electron scattering and bowing of dislocations, respectively. [ABSTRACT FROM AUTHOR]

Thin metal films acting as structural components in microelectromechanical systems (MEMS) devices can exhibit viscoelastic mechanical behavior even at small strains, causing time-dependent changes in device performance. In an effort to characterize the temperature dependence of this behavior, stress relaxation experiments using gas pressure bulge testing have been conducted on 1.0-\mu\m-thick Au films at temperatures between 20 ^\circ\C and 80 ^\circ\C. By fitting a Prony series of saturating exponentials to the resulting relaxation curves, a function for the time-dependent elastic modulus was developed for each temperature. The time-dependent elastic moduli were used in an analytical model to demonstrate the impact of viscoelastic stress relaxation on the restoring forces of two different RF MEMS capacitive switch designs. The implications for testing and performance of a cantilever-type contact switch were also assessed. Finally, using time–temperature superposition, a master curve was generated that may enable prediction of room temperature device performance out to times greater than one year.\hfill [2010-0106] [ABSTRACT FROM AUTHOR]

The tin-silver-copper eutectic is a three-phase eutectic consisting of Ag3Sn plates and Cu6Sn5 rods in a (Sn) matrix. It was thought that the two phases would coarsen independently. Directionally solidified ternary eutectic and binary eutectic samples were isothermally annealed. Coarsening of the Cu6Sn5 rods in the binary and ternary eutectics had activation energies of 73 ± 3 and 82 ± 4 kJmol-1, respectively. This indicates volume copper diffusion is the rate controlling mechanism in both. The Ag3Sn plates break down and then coarsen. The activation energies for the plate breakdown process were 35 ± 3 and 38 ± 3 kJmol-1 for the binary and ternary samples respectively. This indicates that tin diffusion along the Ag33Sn/(Sn) interfaces is the most likely the rate-controlling mechanism. The rate-controlling mechanisms for Cu6Sn5 coarsening and Ag3Sn plate breakdown are the same in the ternary and binary systems, indicating that the phases evolve microstructurally independently of one another in the ternary eutectic. [ABSTRACT FROM AUTHOR]

The effect of grain size on viscoelastic relaxation behavior of Au thin films was investigated by using gas pressure bulge testing to measure the changing normalized plane-strain modulus as a function of time. We observed more rapid and extensive relaxation with increasing grain sizes. The normalized modulus of the Au films is shown to be linearly dependent on the square of the in-plane grain size. Transmission electron microscopy suggests that an increase in grain size allows a higher fraction of mobile dislocation segments to bow under an applied stress, resulting in a proportional increase of the relaxation of coarser-grained films. [ABSTRACT FROM AUTHOR]

Abstract: Microtensile tests were performed on a series of free-standing gold and gold–vanadium thin films at 200 °C and 400 °C. At these temperatures, significant strain rate and stress relaxation effects were observed, indicating the presence of substantial inelastic deformation at all compositions. The addition of vanadium was associated with higher proportional limit and reduced stress relaxation. However, despite the formation of a solid solution at all compositions studied, the expected dependence of strength on V concentration was not observed. The primary effect of vanadium alloying in gold films was to reduce the grain size, which was the likely cause of the increased resistance to inelastic deformation. [Copyright &y& Elsevier]