Conductivity Improvement of Microdispensed Microstrip Lines and Grounded Coplanar Waveguides Using Laser Micromachining

Microdispensed transmission lines (TLs) show high conductor losses at microwave frequencies. Recently, laser micromachining has been introduced as a technique to form the slots of the coplanar waveguide (CPW). Smoother and highly conductive signal trace and ground plane edges have been obtained to enhance the CPW's effective conductivity. Since conductor loss depends on the TL type and geometry, it is important to investigate the effect of laser micromachining on other TL types. Therefore, this letter investigates laser micromachining for microstrip line (ML) and grounded CPW (GCPW) for the first time and reports improvements in their conductivities within the 1-30-GHz frequency range. Specifically, laser micromachining is shown to decrease insertion loss at 30 GHz by 0.18 and 0.29 dB/cm for the microstrip and GCPW, respectively, when the TLs are over a 254-μm-thick ε
_r
= 3.6 substrate. Effective conductivity of laser micromachined ML and GCPW is extracted as 5 and 12.5 MS/m at 30 GHz, respectively. It is shown that GCPW benefits from laser micromachining the most due to higher current concentration at the signal trace edges. Narrower lines are also shown to improve the most with the employment of laser micromachining.