Metal-transfer-molding (MTM) technique for micromachined RF components

This dissertation reports a metal-transfer-molding (MTM) technique for simultaneous implementation of air-lifted RF passive components, as well as coplanar waveguide (CPW) structures, in a high performance and potentially cost-effective fashion. A metal transfer mechanism is introduced into the conventional micro-molding process to realize polymer-core RF passive components and integration. A system-on-package (SOP) integration scheme of front-end RF components can be realized by this process. Several air-lifted RF components based on MTM technology have been presented with excellent performance. The first component is a CPW bandstop filter on a flexible organic substrate. The filter comprises a unique air-gap CPW to reduce the dependence of filter performance on substrate non-idealities. The measured characteristic shows a loss of less than 2.5dB in passband and more than 20dB in stopband, with more than 40% lower loss than a conventional planar filter. The second component is an integrated Ka-band monopole antenna array, with resonant frequency ranging from 26GHz to 42GHz in a compact size. 21.5% 10dB bandwidth for the monopole antennas has been achieved. The third component is a reduced-size high-Q cavity resonator based on evanescent-mode operation. An unloaded Q exceeding 500 and more than 40% size reduction have been achieved from micromolded organic materials. As an integration application of the MTM technology, a novel wireless passive airflow sensor based on the RF evanescent-mode cavity resonators has been also presented. The sensor makes use of RF technology to measure wind velocity through changes in the resonant frequency with applied airflow. Compared with reported wireless sensors based on conventional RF cavity resonator, this design has advantages such as compact size and greatly improved sensitivity. The presented airflow sensor shows a 360MHz frequency shift per m/s airflow. By embedding an ultra-wide-bandwidth monopole (UWB) antenna, wireless interrogating has also been demonstrated for the passive sensor. The resonance shift has been successfully detected in wireless measurement.;Overall, the RF components developed in this thesis illustrate the great potential of MTM technology in both wireless communication and sensor areas.