Conductor-loss reduction for high-frequency transmission lines based on the magnetorheological-fluid polishing method

In this paper, a novel polishing method using magnetorheological (MR) fluid is presented in order to improve conductor-surface roughness and achieve high-frequency performance of the electroplated three-dimensional (3D) CPW, where the MR fluid is utilized to efficiently polish uneven and imperfect conductor surfaces resulting from the widely used MEMS process. For the purpose of comparison, two 50Ω CPW lines on glass substrate are fabricated in order to validate the performance of the proposed polishing scheme. From the measurement, the polished CPW lines using the MR fluid show much lower attenuation constants up to a maximum of 0.3-0.54 dB/cm than unpolished CPW lines, according to the geometries used. Thus, it is clear that the proposed MR fluid-based polishing scheme is very effective when used to smooth 3D high-frequency structures and can dramatically improve conductor-loss characteristics.