Measurement of high-frequency conductivity affected by conductor surface roughness using dielectric rod resonator method

In recent years, high-end interconnects have enabled signal transmission rates of tens of gigabits per second (Gbps) in printed circuit boards (PCB). Reducing the transmission losses induced by conductor surface roughness in a PCB is important from the standpoint of signal integrity. In this study, we measured the effects of surface roughness in a PCB using a dielectric rod resonator method. Then, we derived a relative power dissipation Ksr approximation from the measurement results for the firs time. The dielectric rod resonator method makes it possible to measure only the effects of surface roughness because conductivity is analyzed in a characteristics equation using TE0mn (m; n is the integer) modes which the dielectric rod does not influence The results showed that the Ksr factor was seven times greater than that of the smooth surface. This result is higher than the previous results of measuring the effects of surface roughness. We applied the measurement results to the Ksr approximation equation and verifie the transmission line of a microstrip. We confirme that the insertion loss of the transmission line was successfully measured and simulated. This method can be applied to any copper wiring in a PCB because it can include not only the effects of surface profil but also the effects of a surface treatment agent.