1. Field of the Invention
The present invention relates to a static electricity removing apparatus and method thereof for neutralizing an object charged with static electricity by means of ionized air generated by corona discharge.
2. Description of Related Art
In manufacturing and assembling an electronic part such as a semiconductor substrate, if the electronic part or a tool for handling the electronic part is charged with static electricity, the electronic part is likely to suffer from adhesion of contaminants such as dusts and a circuit in the electric part is possibly broken by discharging. In order to prevent such problems, a static electricity removing apparatus called an ionizer has been used for neutralizing an object, or removing static electricity of the object, by spraying ionized air on the object charged with static electricity (see JP 2007-287368 A, JP 2006-196380 A, JP 52-30440 A, and JP04-206378 A).
DC or AC corona discharge is generally used for generating ionized air. Ionized air generated by corona discharge may be sprayed on an object by using compressed air or a fan in general.
Static electricity removing apparatuses using AC corona discharge are disclosed in JP 52-30440 A and JP 04-206378 A.
These documents disclose techniques for controlling disparity in balance of ions generated by AC corona discharge and preventing an object to be neutralized from being incompletely neutralized and being charged negatively or positively. For example, FIG. 4 of JP 52-30440 A discloses a configuration in which a grid electrode having a grid shape is installed between an AC corona discharge electrode and the object to be neutralized on a plate electrode grounded. The grid electrode is grounded through a diode and a resistor. In addition, JP 04-206378 A discloses a structure which controls to vary a resistance value between a ground electrode opposite to the discharge electrode and a ground potential, according to a charge potential of a charged object.