Development of the RF plasma source at atmospheric pressure

A radio frequency (RF) plasma source operates by feeding helium or argon gas through two coaxial electrodes driven by a 13.56 MHz RF source. In order to prevent an arc discharge, a dielectric material is loaded outside the center electrode. A stable, arc-free discharge is produced at a flow rate of 1.5 l/min of helium gas. The temperature of the gas flame varies from 100 to 150 °C depending on the RF power. The breakdown voltage also changes when the flow rate varies. The plasma generation in a hot chamber is much more efficient than that in a cold chamber. The plasma characteristics are diagnosed by using optical emission spectroscopy. One of the applications of the RF plasma source is the printed circuit board (PCB) cleaning process, needed for environmental protection. The PCB cleaning device forms an asymmetric biaxial reactor.