Dynamic determination of Young's modulus of electroplated nickel used in LIGA technique

Mechanical properties of materials involved in the fabrication of new microactuators have to be well characterized in order to be used in CAD and for the simulation of Microsystems. To achieve that goal, we present a study of the Young's modulus E of electroplated nickel used in the LIGA technique. This mechanical parameter was obtained by the analysis of vibration frequencies of free-clamped microcantilevers. The resonant frequencies of in-plane and out-of-plane flexural modes were measured with an optical bench. The experimental results are compared to the frequencies derived from a pure elastic finite element model. The variation of the boundary conditions, in particular the description of the clamped part of the devices, leads to a good agreement between the experimental and the simulation. The correlation between these two methods leads to the determination of the Young's modulus of the device. First results lead to an average value of 195 GPa, which is lower than the data reported for the. bulk material. These results are in good agreement with our previous values obtained by steady-state bending tests and other works reported in the literature. E is insensitive to the direction of the excited mode which is characteristic of an isotropic behaviour of the electroplated metal. (C) 1999 Elsevier Science S.A. All rights reserved.