Performance Characterization of Micromachined Inductive Suspensions Based on 3D Wire-Bonded Microcoils

Abstract

We present a comprehensive experimental investigation of a micromachined inductive suspension (MIS) based on 3D wire-bonded microcoils. A theoretical model has been developed to predict the levitation height of the disc-shaped proof mass (PM), which has good agreement with the experimental results. The 3D MIS consists of two coaxial wire-bonded coils, the inner coil being used for levitation, while the outer coil for the stabilization of the PM. The levitation behavior is mapped with respect to the input parameters of the excitation currents applied to the levitation and stabilization coil, respectively: amplitude and frequency. At the same time, the levitation is investigated with respect to various thickness values (12.5 to 50 μm) and two materials (Al and Cu) of the proof mass. An important characteristic of an MIS, which determines its suitability for various applications, such as, e.g., micro-motors, is the dynamics in the lateral direction. We experimentally study the lateral stabilization force acting on the PM as a function of the linear displacement. The analysis of this dependency allows us to define a transition between stable and unstable levitation behavior. From an energetic point of view, this transition corresponds to the local maximum of the MIS potential energy. 2D simulations of the potential energy help us predict the location of this maximum, which is proven to be in good agreement with the experiment. Additionally, we map the temperature distribution for the coils, as well as for the PM levitated at 120 μm, which confirms the significant reduction of the heat dissipation in the MIS based on 3D microcoils compared to the planar topology.

Keywords

• inductive levitation
• suspension
• 3D microcoils
• stability