Enhanced investigation on the low-pressure RF discharge of high-power microstrip circuits under different process conditions

Multipactor-induced low-pressure Radio Frequency (RF) discharge has become increasingly critical in high-power planar integrated circuits under vacuum conditions, driven by the gradual increase in operating frequency, power, and system integration. However, the key factors determining the discharge threshold remain ambiguous due to the complexity of RF systems and convergence challenges in semi-open structure calculations. In this study, a planar circuit research model was constructed considering core factors including connection structure, bonding conditions, packaging, and substrate properties. To address the unique boundaries of semi-open structures, finite truncated boundaries were adopted for electron motion and electromagnetic field simulations, resolving issues of calculation accuracy and convergence. Using the particle-in-cell method, the discharge thresholds of models with different bonding structures and package boxes were numerically investigated, revealing a threshold discrepancy exceeding 6 dB. Experiments validate that when the package box is sufficiently large, the tightness and position of connection structures are the dominant factors affecting the discharge threshold. Conversely, when the package box is extremely small (only covering the planar circuit), it becomes the decisive factor. Secondary electron yield (SEY) measurements and microscopic composition analysis indicate that surface cleaning methods (atomization cleaning, ultrasonic cleaning, and hand scrubbing) exert a minor influence on SEY but barely alter the substrate composition. This work is the first to establish a threshold analysis framework for multipactor-induced low-pressure RF discharge in microwave planar circuits with practical processing states, providing actionable design guidelines for engineering applications.