High aspect ratio PMMA posts and characterization method for micro coils manufactured with an automatic wire bonder

We present the development of high aspect ratio PMMA posts manufactured in deep X-ray lithography technology. The posts serve as support structures for micro coil windings. The coils are wound around these cores by an automatic wire bonder, and they are fully compatible with MEMS processes. Posts with outer diameters down to 100 μm and minimal sidewall thicknesses of 20 μm have an aspect ratio of up 38, leading to single-layer coils with more than 20 windings. With a flexible software, the winding number is only limited by the post height. We introduce a specially designed structure to determine the forces caused by the winding process. These measured forces are confirmed by shear test data. Electrical measurements show a quality factor of over 50.