A fully MEMS-compatible process for 3D high aspect ratio micro coils obtained with an automatic wire bonder

Abstract

We report the fabrication of 3D micro coils made with an automatic wire bonder. Using standard MEMS processes such as spin coating and UV lithography on silicon and Pyrex R wafers results in high aspect ratio SU-8 posts with diameters down to 100 μm that serve as mechanical stabilization yokes for the coils. The wire bonder is employed to wind 25 μm insulated gold wire around the posts in an arbitrary (e.g. solenoidal) path, yielding arrays of micro coils. Each micro coil is bonded directly on-chip, so that loose wire ends are avoided and, compared to other winding methods, coil re-soldering is unnecessary. The manufacturing time for a single coil is about 200 ms, and although the process is serial, it is batch fabrication compatible due to the high throughput of the machine. Despite the speed of manufacture we obtain high manufacturing precision and reliability. The micro air-core solenoids show an RF quality factor of over 50 when tested at 400 MHz. We present a flexible coil making method where the number of windings is only limited by the post height. The coil diameter is restricted by limits defined by lithography and the mechanical strength of the posts. Based on this technique we present coils ranging from 100 μm diameter and 1 winding up to 1000 μm diameter and 20 windings.

Novel concept of a series linear electromagnetic array artificial muscle

“…Furthermore this design particularity raises the fiber density, as the cells have a height to diameter ratio of over 2. Therefore the EMAM fiber surpasses previous attempts [1,3,5] in terms of cell density of a fiber, leading to a more uniform actuation needed for precise positioning.…”

Integrated Magnetic MEMS Relays: Status of the Technology

“…The third option involves the patterning of microcoils, a choice that implies an increased level of complication in terms of both design and fabrication and is being actively pursued by many research groups [118][119][120][121]. The magnetic field generation requires an electrical current flow, which has a dramatic impact on the power dissipation and thermal budget characteristics of the manufactured components.…”

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

“…The parameters of the outer (stabilization) coil, such as position, diameter, number of windings and current intensity, contribute to the stabilization of the proof mass and are reflected in the stiffness of the structure, as shown in [13]. We have previously thoroughly explained the wire bonding process used in the fabrication of the 3D solenoidal coils [14]. Basically, the movement of the head of an automatic wire bonder is controlled via a MATLAB interface where a three-dimensional helical trajectory is defined.…”