PURPOSE: To improve the maintenance and operability of a device by simultaneously controlling the ascent and descent of the liquid level and the control of the level of a flux wetting prohibitor with the air pressure inside an air tank.
CONSTITUTION: An operation switch is closed after covering a coating tank 1 by placing a printed circuit board 7 on a coating base by putting it in a gasket 6. With the actuation of a solenoid valve an air feeding pipe is connected to an open port 3, a compressed air is charged into an air tank 2, the air pushes up the inhibitor and raises its liquid level. The printed circuit board 7 is uniformly immersed according to the ascent of the inhibitor and when the liquid level of the inhibitor comes to the prescribed position the power source is cut off with the actuation of a float switch 5, so the air feeding pipe 3 is connected to an exhaust return pipe 8 with the solenoid valve being de-energized. In this way the air in the air tank 2 is returned to the upper face of the inhibitor, which is stored into the air tank again.