JPH0653199A - Surface cleaning method using dry ice stick - Google Patents

Abstract

PURPOSE:To effectively remove a pollutant stuck to the surface of an article by contact moving a dry ice stick along the surface to be cleaned in a state where the dry ice stick is made to contact with the surface of a cleaned part of an article to be cleaned. CONSTITUTION:A columnar dry ice stick 3 is tightly held by a retainer 2 of a head, for instance, of a device of a jig for electrostatic coating. Then, the head 1 is set up, for instance, on a rotary polisher. In case of removing the stuck coating, the under face, that is the sliding surface 4 of the dry stick 3 is pressure welded with the coating surface of the part to be removed so as to turn and move it. Then, the coating gets a low temperature for being fragile, broken so as to be peeled off and removed by a rapid gas flow due to sublimation of dry ice.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cleaning of silicon substrates, cleaning of magnetic disk substrates in the field of electronic component manufacturing, cleaning of lenses and other parts in the field of optical component manufacturing,
The present invention relates to a surface cleaning method using a dry ice stick for removing contaminants adhering to the surface of an article, such as cleaning the conductive part of an electrodeposition coating jig in the field of manufacturing automobiles, home appliances, building materials and the like.

[0002]

2. Description of the Related Art In the field of precision cleaning such as in the field of electronic parts manufacturing and optical parts manufacturing, it is necessary to rotate a brush as a wet cleaning and sprinkle pure water or a detergent solution on it, and optionally include an abrasive such as silica gel. There is also scrubbing that presses against the surface to be cleaned, 20-200 kg
High-pressure liquid jet cleaning that sprays pure water, detergent liquid, CFCs pressurized to / cm ² from the nozzle, and uses straight flow, cavitation, and vibration acceleration of medium obtained by irradiating ultrasonic waves into the liquid Ultrasonic cleaning, immersion of the object to be cleaned in a cleaning treatment liquid, and chemical cleaning utilizing the chemical action of the cleaning liquid such as dissolution / oxidative decomposition of contaminants or surface layer dissolution are performed.

Further, as a dry cleaning method, a high-speed jet gas or a mixed gas of dry ice particles is used to scatter adhering particles. Laser cleaning to vaporize substances, plasma cleaning to react radicals of active chemical species generated by high-frequency discharge with contaminants and convert them into volatile substances, and UV irradiation under an atmosphere containing O ₂ or 0 _3. Ultraviolet ozone cleaning, which decomposes and removes organic pollutants by photoexcitation and the action of generated O ₃ and oxygen radicals, is performed.

On the other hand, in electro-deposition coating, in order to remove the coating film adhering to the conductive portion of a coating jig such as a hanger made of a conductive material, a mechanical cleaning and coating in which polishing is performed manually with a file or the like is performed. Chemical cleaning is performed by cleaning the jigs with a strong alkaline solution such as caustic soda.

[0005]

In precision cleaning performed in the fields of electronic component manufacturing, optical component manufacturing, etc., the equipment cost in the conventional cleaning method is expensive, and the solution and gas used for cleaning are recovered. There are problems such as difficulty in processing. Further, wet cleaning in the semiconductor process has problems such as deterioration of the atmosphere in the process and generation of bacteria, and a drying process is also required. In cleaning the coating jig, in order to remove the coating film that has adhered to the current-carrying part of the jig, you have to grind the hooks of the jig one by one using a file etc. It has the disadvantage that the cost becomes huge and it is not suitable for mass production. Further, in the method of cleaning with a strong alkali such as caustic soda, in the cationic type electrodeposition coating, a small amount of the alkali content remaining on the jig has a significant adverse effect on the electrodeposition coating. Even if an alkaline component remains in the coating jig by containing it, the electrodeposition coating is not adversely affected.

However, if the solvent contains an organic alkali or an organic acid, the tank and the jig must be made of acid-resistant stainless steel, which increases the cost of the coating equipment.
Further, it takes a long time to remove the coating film, and since the coating film is not subdivided, it is not easy to remove the residual coating film during washing with water.

It is an object of the present invention to provide a dry surface cleaning method using a dry ice stick which effectively removes contaminants adhering to the surface of an article.

[0008]

The method according to the present invention is applied to a surface dry ice stick for cleaning a product such as a silicon substrate, a magnetic disk substrate, an optical component, a jig for electrodeposition coating and other devices and components to be cleaned. The feature is that the dry ice stick is moved in contact with the cleaning surface such as forward, backward, reciprocating, and rotating in a state of being in contact with to clean the surface.

Dry ice sticks, from needle-shaped to large ones like cannons, can be manufactured in various shapes and sizes according to the object to be cleaned, but they are very hard and slightly transparent when pressed with sufficiently high pressure. You can get what you became. And even if it is taken out into the atmosphere at room temperature,
Since it maintains its hardness and does not rapidly sublime, it can be used for surface cleaning as described above.

In order to make the cleaning according to the present invention more effective, it may be used in combination with other methods. For example, when it is desired to remove oily contaminants, the effect of cleaning can be improved by applying a solution of a surfactant on the contaminated surface in advance by brushing.

When the adhered foreign matter is hard and requires a long time to be removed, an abrasive material (for example, SiC or Al) having a hardness and a particle size such that the surface to be cleaned is not scratched.
_By mixing an appropriate amount of ₂ O ₃ ) with dry ice and press-molding it, the function of removing foreign matter that adheres particularly hard is improved. It is also possible to use dry ice sticks mixed with abrasives of various hardness and particle size in advance according to the condition of the object to be cleaned, the required degree of cleaning, surface roughness, etc. .

Further, when cleaning a large area, first, the present invention roughly cleans only a portion where the degree of contamination is severe,
After that, a well-known method of spraying dry ice particles (pellets) with a high-speed injection gas is applied widely and uniformly, whereby the cleaning can be performed more efficiently.

It is also effective to apply a coating film peeling agent (for example, methylene chloride) to the deposits that are very difficult to remove, such as a certain type of baking paint, before applying the present invention. There is.

Laser cleaning of organic contaminants,
Combination with plasma cleaning or ultraviolet ozone cleaning is also effective.

As described above, the present invention can be applied to a wide variety of objects to be cleaned by combining it with one or more of the known cleaning methods as described above, but the degree of contamination is comparatively light. In general, the present invention alone gives sufficiently satisfactory results. Liquefied carbon dioxide gas, which is a raw material of dry ice, usually has a purity of 99.5% or more.

Therefore, according to the present invention alone, when cleaning, there is no fear of new contamination from dry ice,
The washer is completely dry and does not require a drying step. This is particularly advantageous when incorporated in a continuous process in a clean environment such as the semiconductor industry.

[0017]

According to the method of the present invention, dry ice is rapidly gasified by sublimation by bringing dry ice into contact with and moving it against the surface to be cleaned. The contaminants on the surface are removed and cleaned by the force. Further, when dry ice (about -80 ° C) is pressed and moved to the adhered coating film, the temperature of the coating film is rapidly lowered to cause a temperature difference with the metal surface of the jig. Therefore, the coating film is easily peeled off from the metal surface of the jig.
Further, since the coating film becomes brittle due to the temperature decrease, the coating film is easily broken by the pressure contact movement of dry ice. For example, when the adhered substance is a polymer compound such as a coating film, the embrittlement temperature (or glass light transition point) is often −80 ° C. or higher and becomes brittle when cooled. When the object to be cleaned is a metal such as iron and the adherent is a thermosetting polymer, their linear expansion coefficients are 12 × 10 ⁻⁶ / ° C. and 20 to 70 ×, respectively.
It is about 10 ⁻⁶ / ° C., and the polymer has a larger shrinkage due to cooling, which is also considered to promote embrittlement.

The coefficient of linear expansion of thermoplastic polymers is generally 5
It is 0 to 100 × 10 ⁻⁶ / ° C., and a larger effect is expected. Then, once the coating film is torn, the rapid peeling of the coating film is accelerated by the sublimation of dry ice, and the entire coating film is efficiently removed in a short time.

The characteristic feature of dry ice is that it has a hardness that is softer than that of sand and that it gasifies rapidly at the contact surface with the cleaning surface, so that the cleaning surface is not damaged. In addition, the shape and size of dry ice can be manufactured to be most suitable for the shape of the object to be cleaned.

Since dry ice sublimes over time and diffuses into the atmosphere as a gas, it is not necessary to treat waste water and is easy to handle.

[0021]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show a head 1 of, for example, an electrostatic coating jig apparatus for carrying out the present invention.
A cylindrical dry ice stick 3 is tightly held by a cage 2 of the head 1 formed of a heat insulating material. The head 1 is set on, for example, a rotary polishing machine (not shown).

Next, a mode for removing the adhered coating film will be described.

When removing, the lower surface of the dry ice stick 3, that is, the sliding surface 4 is pressed against the surface of the coating film to be removed, and is rotated and moved. Then, since the coating film is in contact with dry ice, it becomes brittle at a low temperature. Further, since the dry ice stick 3 in pressure contact is rotated and moved, the coating film is broken, and the coating film is effectively peeled and removed by a rapid gas flow due to sublimation of dry ice. In this way, dry ice is rotated on the contact surface with the coating film,
Alternatively, the method of sliding the coating back and forth to remove the coating film requires a short time for the treatment (it usually takes several tens of seconds depending on the number of rotations and the pressure contact force, etc.), and after removing the coating film, Since the metal surface is clean, it can be incorporated into the painting line and automated without the need for further cleaning.

3 and 4 show another embodiment of the head for carrying out the present invention, in which the cage 2 of the head 1a has a cross-shaped groove 5 formed on the sliding surface 4a. The dry ice stick 3a is held.

FIGS. 5 and 6 show another embodiment of the head for carrying out the present invention. The holder 2 of the head 1b has a plurality of sliding surfaces 4b (three in the illustrated example). The dry ice stick 3b having the parallel concave grooves 6 is held.

7 and 8 show another embodiment of the head for carrying out the present invention, in which the holder 2 of the head 1c has a plurality of sliding surfaces 4c (three in the illustrated example). The dry ice stick 3c having the annular groove 7 is held.

Although not shown in the drawing, in addition to the above-described grooved head, the simplest cylindrical head without a groove can be used in some cases.

These dry ice sticks 3a-3
The sliding surfaces 4a to 4c of c are selected according to the size of the electrostatic coating jig, the shape of the portion where the coating film is to be removed, and the like.

[0030]

[Embodiment 2] Exactly the same rotary abrasive and cylindrical dry ice as those in Embodiment 1 are used. It can be applied to a wafer in the same manner and almost the same result can be obtained.

[0031]

As described above, according to the present invention, it is possible to effectively remove a coating film, foreign matter such as oil, and contaminants attached to an article.

The surface from which the coating film has been removed is clean and in a dry state, and can be used as it is without being dried.

Further, since no cleaning chemical is used, and since the doira ice stick sublimes to carbon dioxide gas and is diffused into the atmosphere, the cleaning equipment does not need corrosion resistance and the equipment cost is low. Is.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a head of an apparatus for carrying out the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is a side sectional view showing another embodiment of the head.

FIG. 4 is a bottom view of FIG.

FIG. 5 is a side sectional view showing another embodiment of the head.

6 is a bottom view of FIG.

FIG. 7 is a side sectional view showing another embodiment of the head.

FIG. 8 is a bottom view of FIG.

[Explanation of symbols]

 1, 1a to 1c ... Head 2 ... Retainer 3, 3a to 3c ... Dry ice stick 4, 4a to 4c ... Sliding surface 5 ... Cross-shaped concave groove 6 ... Parallel groove 7 ... Annular groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Tsuruoka 1-9-1 Shinonome, Koto-ku, Tokyo Inside Teisan Co., Ltd. (72) Inventor Kyudo Hakaku 3-7-1-10 Tennodai, Abiko, Chiba Prefecture

Claims (1)

[Claims] 1. A dry ice stick is brought into contact with the surface of a cleaning portion of an article to be cleaned such as a silicon substrate, a magnetic disk substrate, an optical component, a jig for electrodeposition coating and other devices, components, and the dry ice stick. A surface cleaning method using a dry ice stick, characterized in that the surface is cleaned by moving the ice stick forward, backward, reciprocating, rotating, etc. to the cleaning surface.