JPH0656798B2 - Electrode for generating air ions - Google Patents

Description

TECHNICAL FIELD The present invention relates to the structure of a discharge electrode of a static eliminator used in a clean room of a semiconductor manufacturing factory.

<Prior Art> Conventionally, this type of static eliminator has been disclosed in JP-A-60-197.
As described in Japanese Patent No. 254, a large number of indoor air ionization discharge electrode needles ranging from tens to hundreds are attached to the ceiling of a clean room at intervals of about 2 m, and the air from the electrodes is used to ionize air. There are those that neutralize the static electricity of charged objects and those that use wire electrodes instead of the electrode needles, and the electrode material is often a tungsten alloy.

This type of device focuses on the fact that minute dust floating in the air easily adheres to electrostatically charged objects, and ionizes the indoor air to remove the electrostatic charge from the charged particles. It reduces the adhesion rate of.

By the way, recent miniaturization of semiconductors is remarkable, and naturally, higher cleanliness of air in a clean room is also required. More specifically, the air cleanliness required in the past was class 100 (less than 100 dust particles with a diameter of 0.5 μm or more per cubic foot), but in the near future class 100 (dust particles with a diameter of 0.1 μm or more will be generated). 100 or less per cubic foot) or Class 10 (0.01 μm)
(10 dust particles with a diameter of 0.01 μm or more per cubic foot
It is conceivable that a numerical value such as (less than or equal to the number of pieces) is within the allowable range.

However, in the conventional static eliminator, a part of the discharge electrode is inevitably decomposed along with corona discharge and is scattered as fine powder that is invisible to the naked eye, resulting in extremely high air cleanliness. In that case, the air in the clean room will be contaminated.

<Problem to be Solved by the Invention> Therefore, an object of the present invention is to provide a discharge electrode in which fine powder of the discharge electrode which is inevitably scattered during corona discharge does not diffuse into a clean room.

<Means for Solving the Problems> In order to achieve such an object, the air ion generating electrode of the present invention has a magnetic force generating means disposed in the vicinity of the discharge electrode,
The magnetic force generating means is composed of a permanent magnet, a cylindrical sheath surrounding the discharge electrode is provided, and the permanent magnet is mounted inside the sheath so that both poles face each other.

<Operation> A part of the electrode, which becomes fine powder and scatters when corona discharge is performed by the discharge electrode, is guided to the magnetic force of the magnetic force generating means immediately after the scatter and is adsorbed thereto.

<Example> Hereinafter, a preferred example of the present invention will be described with reference to the drawings.

In the figure, reference numeral 1 denotes a plastic discharge needle holding base for holding the discharge needle 2, which is fixed to the ceiling of a clean room by any means such as screwing. The discharge needle 2 is preferably made of a tungsten alloy, and is fixed to the discharge needle holding base by any means so that the needle tip faces the floor. Preferably. As shown in FIG. 1, the discharge electrode of this embodiment performs corona discharge by using two discharge needles 2. The high voltage to be applied may be AC or DC. But it's okay.

More specifically, the discharge needle 2 has a total length of about 2 cm, of which about 1 cm is projected from the discharge needle holder 1. The diameter of the discharge needle 2 is about 1 mm,
In order to obtain a uniform corona discharge, the tip of the tip is gently tapered (not shown) so that the diameter of the tip is about 50 μm.

A plastic sheath 3 is detachably attached to the discharge needle holding base 1 so as to surround the discharge needle 2 by means such as screwing. In this embodiment, a cylinder having an inner diameter of about 2 cm and a thickness of about 1 mm is used as the sheath 3.
The lowermost end of the discharge needle 2 was separated from the tip of the discharge needle 2 by about 1.5 cm.

Permanent magnets 4 are fixed to the inside of the sheath 3 with an adhesive or the like so that both poles of different magnets are spaced from the discharge needle 2 at substantially equal intervals and face each other.

When corona discharge is performed at the tip of the discharge needle 2 as shown in FIG. 1, the air near the tip is ionized and a very small part of the tip of the discharge needle 2 is decomposed, so that the fine powder 5 Then, the scattered fine powder 5 of the discharge needle 2 is attracted to the surface of the magnet 4 by the magnetic force of the magnet 4 surrounding the discharge needle 2 immediately after the scattering.

Further, in this case, since the discharge needle 2 is surrounded by the sheath 3, the scattered fine powder 5 of the discharge needle 2 collides with the sheath 3,
This also prevents diffusion. Furthermore, since the fine powder 5 is prevented from scattering by the sheath 3, the fine powder 5 is reliably captured by the magnet 4.

It has been confirmed by the inventor of the present invention that magnetism does not affect the ion balance and the charge removal rate, and the inventor can achieve the intended purpose with a simple structure by utilizing this magnetic property. The present invention capable of achieving the above is completed.

Needless to say, the present invention can be similarly applied to an air ionization device using a wire-type discharge electrode.

<Operation> Since the air ion generating electrode according to the present invention is configured as described above, the fine particles of the electrode that are inevitably scattered when performing corona discharge at the discharge electrode generate magnetic force in the vicinity of the discharge electrode. It can be adsorbed by means and can prevent the fine powder from diffusing. Further, since the discharge electrode is surrounded by the sheath, the scattered fine powder of the discharge electrode can be blocked by the sheath, which also prevents diffusion.
Furthermore, since the scattering of the fine powder can be prevented by the sheath, the fine powder can be reliably captured by the magnet, and the diffusion can be reliably prevented. As a result, the inside of the clean room is not contaminated by the diffusion of the fine powder, and it has an excellent technical effect that the air cleanliness can be kept extremely high.

[Brief description of drawings]

FIG. 1 is a schematic end view showing an embodiment of the present invention, and FIG. 2 is an end view taken along the line AA in FIG. 1 ... Discharge needle holder, 2 ... Discharge needle, 3 ... Sheath body, 4 ... Magnet, 5 ... Discharge needle fine powder

Claims (1)

[Claims] 1. A magnetic force generating means (4) is arranged in the vicinity of the discharge electrode (2), the magnetic force generating means (4) is composed of a permanent magnet, and a cylindrical shape surrounding the discharge electrode (2). Sheath body (3)
An air ion generating electrode, comprising: the sheath (3), the permanent magnet (4) being mounted so that its two poles face each other.