A new approach to control a deflection of an electroplated microstructure: dual current electroplating methods

Abstract

We propose and demonstrate a simple and novel method to control the deflection in a suspended microstructure by using a dual current electroplating (DuCE) method. The key concept of this method is to divide the structure into two layers-a bottom layer and a top layer-and then apply respective current densities in electroplating to those two layers while all other conditions are kept the same. In addition to a flat structure, the direction of structure bending is freely controlled by virtue of the DuCE method. Cantilever Ni beams with a length of 400 μm, which were electroplated by the conventional single current electroplating method, bent downward with a deflection of 3.4 μm. On the contrary, by the DuCE method, cantilever beams with a length of 400 μm showed an almost flat structure as desired. (The current densities of the bottom layer, the top layer, and the ratio of the two current densities, are 0.15, 1.24 A dm -2 , and 8.3, respectively.) Consequently, a nickel electroplated spiral structure with a length of 8600 μm was suspended flat with an end deflection of less than 0.7 μm (the ratio between the deflection and length is 0.007%). This work therefore represents the unprecedented ultra-long suspended microstructure with submicrometer deflection.

Magnetically-actuated micromechanical nickel patches for a monolithically integrated reconfigurable antenna on printed circuit board

“…Therefore, the stress gradient of the structural beam was controlled by varying the current density used for plating. This technique was previously reported in [27][28][29]. We calibrated the current density of the plating step by performing a set of experiments first on silicon wafers since it is easier to work with than the Duroid substrate.…”

Residual stress gradients in electroplated nickel thin films

“…The assumption of linear stress distribution, i.e. constant stress gradient, is frequently employed in the literature [10,14,[16][17][18], which is especially proper for very thin films such as the 1-lm-thick nickel film of this study:…”

“…However, residual stress gradients in thin metallic films remain mostly unstudied. Among the limited number of accounts one can mention the recent study on strain-gradient-free 4.5-lm-thick Ni cantilevers obtained through multiple electroplating steps [14]. A few other studies [10,11,15] determined residual stress gradients for metallic materials under some specific deposition conditions with fairly limited fabrication parameter range.…”

Signal Power-Insensitive Analog MEMS Tunable Capacitor by Immobilizing the Movable Plates

“…6(f)), respectively. In these Ni electroplating steps, we used the dual current electroplating (DuCE) method to control the stress gradient of the suspended Ni structure [30]. Then, the upper part of the rivet-shaped dielectric bridge made of 15 μm-thick SU-8 layer was then formed (Fig.…”