Design, Simulation, and Experimental Characterization of a Three-Electrode Planar Spark-Gap Microswitch

This paper presents the design, simulation, fabrication, and testing of a three-electrode planar spark-gap switch for pulsed-power applications. By employing thin-film microfabrication, the discharge gap is precisely controlled at the micrometer scale, enabling a significant reduction in trigger voltage while maintaining a hold-off capability of 2.4 kV. A dual-trigger-electrode configuration is introduced to achieve a symmetric electric-field distribution and to promote rapid plasma formation. A plasma model incorporating Poisson's equation, electron continuity, and drift-diffusion transport is established in COMSOL. The simulation results show that, based on the surface flashover mechanism of the trigger electrode, electron avalanches can be initiated at a lower trigger voltage and rapidly evolve into conductive streamers that bridge the main gap. The device is fabricated on a ceramic substrate using Ti/Cu thin-film metallization and photolithography, resulting in a compact prototype with dimensions of 13 mm ×7 mm. The switch is then integrated into a custom-designed test circuit for experimental evaluation. Under a charging voltage of 1500 V, the switch delivers a peak current of approximately 2830 A with a rise time of about 25 ns. The experimentally observed triggering and conduction sequence is qualitatively consistent with the discharge mechanism revealed by the simulation. These results demonstrate that the proposed structure achieves a relatively low trigger-voltage requirement while maintaining fast response and high current capability, thereby confirming the effectiveness of the simulation-guided design approach for planar spark-gap switch optimization.