JPH05311474A - Optical washing method - Google Patents

Abstract

PURPOSE:To provide the washing method for electronic materials, more particularly the method for washing lead frames after silver plating and washing shadow masks, photomask blanks, silicon wafers, substrate glass for liquid crystal display devices, glass formed with transparent electrodes, etc. CONSTITUTION:The org. matter sticking to the lead frames, shadow masks, photomask blanks, silicon wafers, substrate glass for liquid crystal display devices, glass formed with transparent electrodes, etc., is irradiated with UV rays in the state of providing base materials in water or forming the films of water on the surfaces to be treated, by which the org. matter sticking to the base materials is decomposed and the wettability is improved. As a result, the org. matter is removed and the wettability is improved without generating the oxidation, etc., of the base materials.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of cleaning various solid materials, and more particularly, cleaning of lead frames after silver plating, shadow masks, photomask blanks, silicon wafers, substrate glass for liquid crystal display devices, transparent electrodes. The present invention relates to a method for cleaning electronic materials such as glass, which have been formed.

[0002]

2. Description of the Related Art If an organic material or the like adheres to the surface of an electronic material made of various solid materials, the performance of the device is adversely affected. Therefore, the surface can be cleaned by various methods to remove the adhered material. Has been done. For example, in the case of a lead frame or the like obtained by etching a thin metal plate, after neutralizing the residue of the etching solution with an alkali,
Washing is repeated by washing with water. Further, in cleaning photomask blanks, silicon wafers, glass such as glass substrates for liquid crystal display devices, ceramics, etc., physical cleaning such as scrub cleaning, ultrasonic cleaning, high pressure water cleaning is performed.

[0003]

DISCLOSURE OF THE INVENTION Glass, ceramic,
Prior to cleaning a silicon wafer or the like with water, the surface to be cleaned is irradiated with ultraviolet rays in the atmosphere, and the organic matter adhering to the surface is decomposed by ultraviolet rays and ozone generated from oxygen in the air excited by the ultraviolet rays. It was a very useful method because it did not require the use of chemicals, the treatment of washing water was easy, the handling was simple, and a great washing effect was obtained.

However, when the organic matter attached to the surface of the metal is treated by such a method, the organic matter on the metal surface is removed, but an oxide is formed on the metal surface. For example, when a metallic material having a connection portion or the like plated with silver is irradiated with ultraviolet rays in the atmosphere, silver on the surface is oxidized in a short time. The oxide film has a problem in that it interferes with the joining of conductors and the like, and the oxide peels off from the substrate. In a shadow mask whose surface is oxidized, blackening may not be performed or unevenness may occur during blackening treatment in the surface treatment process. Further, other iron, copper, copper alloys and the like have a problem that they have a bad influence on the conductive connection and are discolored by oxidation.

Further, in etching processing of plate materials of iron, copper, iron-based alloys, and copper-based alloys, resist coating properties,
In order to improve the adhesiveness, treatment with an alkali or an acid has been conventionally performed prior to the coating of the resist, but the roughness and gloss of the surface may change, which may cause a problem. In addition, discoloration was observed during drying after washing. However, when a light beam of a low-pressure mercury lamp is irradiated in a dry state, the surface is oxidized and discolored, resist wetting due to the formation of an oxide film is deteriorated, adhesion is lowered, and etching characteristics are changed, which is a problem.

An object of the present invention is to remove an organic film and the like by washing without adversely affecting the base material, improve the wettability of the base material, and prevent the formation of a watermark during drying after cleaning. It is a thing.

[0007]

The present invention is a method for removing organic substances and the like on a surface to be cleaned by placing the surface to be cleaned in water or irradiating with ultraviolet rays in a state of being covered with water. When the method of the present invention is used for cleaning a metal surface, an undesired oxide is not formed on the metal surface, organic substances on the surface can be removed, and glass, ceramics, silicon wafers, etc. can be removed. When used for cleaning the surface, it enhances the wettability of the surface, and as a result, it becomes possible to improve the cleaning performance.Stains due to redeposition of trace organic substances in the cleaning water on the object to be cleaned and water marks when drying Can be prevented.

The ultraviolet rays which can be used in the present invention have a wavelength of 253 to 255n obtained from a low pressure mercury lamp.
UV with a peak at m, and 180 to 185 nm
Both of the UV rays having a peak at 2 can be used, but it is preferable to use the UV rays having a peak at at least 253 to 255 m. Further, the surface of silver, iron, chromium, a waveguide type optical device evaluation device, nickel, glass, a silicon wafer, ITO or the like is directly activated by the method of the present invention, and the wettability with water is improved. In addition, when thin organic matter is attached to these surfaces, the organic matter is removed and the surfaces are cleaned.

Further, in the etching process, the formation of an oxide film can be suppressed and the wettability can be improved by irradiating with light of a low-pressure mercury lamp in the state where the object to be cleaned is installed in the same manner as above. It is possible to eliminate coating unevenness during coating.

[0010]

[Function] The problem such as the oxidation of the metal surface which occurs during the treatment of organic substances by ultraviolet irradiation, which is an effective method for cleaning the surface, is caused by placing the substance to be treated in water or by applying water on the treated surface. It has become possible to solve this problem by forming a film and irradiating it with ultraviolet rays, and improve the wettability of many materials.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining one embodiment of the present invention. An object to be treated 1 of a lead frame is placed in water 2, and a low pressure mercury lamp 3 is provided on the water surface. A water layer 4 or a water film is formed on the surface of the object to be processed. The water layer may be thick as long as the intensity of the ultraviolet rays applied is high.
On the other hand, when the water layer is thin, it is preferable to replenish the water during the treatment so that the water does not evaporate during the treatment and the treated surface does not come into direct contact with the atmosphere. The distance between the surface to be treated and the mercury lamp can be appropriately set depending on the emission intensity of the low-pressure mercury lamp, but it is generally preferably 10 to 30 mm.

FIG. 2 shows another embodiment.
In (a), the object to be treated 21 and the low-pressure mercury lamp 22 are provided in a treatment tank 24 filled with water 23. The tube wall of the mercury lamp may come into direct contact with the water in the treatment tank, but in order to keep the temperature of the tube wall of the low-pressure mercury lamp at a temperature at which stable output can be obtained, the mercury lamp is transparent such as synthetic quartz that does not block the transmission of ultraviolet rays. It is preferable that the protective tube 25 is provided in the protective tube 25 and the space between the protective tube and the wall of the mercury lamp is filled with nitrogen or the like that does not react with vacuum or ultraviolet rays.

Further, FIG. 2 (b) shows a low pressure mercury lamp 22 provided in a protective tube 25 below the object to be treated 21,
While attached to the transfer device 26 to move the object to be processed,
A method is shown in which water is continuously jetted from a jet nozzle 27 provided in the lower part of the object to be treated onto the surface to be treated, and ultraviolet rays are irradiated in a state where a water film 28 is formed on the surface to be treated. Further, the positional relationship between the object to be treated and the mercury lamp may be various arrangements other than the above-mentioned ones. For example, it is possible to take an arbitrary arrangement such as forming a water film on the surface to be processed and irradiating with ultraviolet rays while moving the object to be processed in the vertical direction.

Example 1 Iron-based alloy (42 alloy containing 42% nickel, nickel 5
50 alloy containing 0%, Kovar containing 13% cobalt and 29% nickel), copper alloy (Orin 194 made by Yamaha,
0.05 to 0.25 m that was partially silver-plated using Kobe Steel KLF5 and Furukawa Electric F-Tech 764) as a base material.
Prepare lead frames with various thicknesses of m and set the distance between the lead frame and the low-pressure mercury lamp to 3 by the method shown in FIG.
After irradiation with 0 mm, water depth of 5 mm and light intensity on the lead frame of 30 mW / cm ² , irradiation time was changed, washing with ultrapure water and drying in an oven were performed.
The contact angle of water droplets was measured, and the sample was washed with ultrapure water without being irradiated with ultraviolet rays and used as a comparative sample.

The contact angle of each of the 10 samples with water was measured after irradiation, and the minimum and maximum values are shown. Contact angle of sample water Minimum Maximum Maximum dried product after plating only 85 ° 92 ° Irradiation with low pressure mercury lamp in water for 10 seconds 30 60 〃 30 seconds 30 45 1 minute 30 40 5 minutes 16 17 Also contact due to difference in base material No difference in horn was observed. Furthermore, the amount of oxide on the silver surface after irradiation for 5 minutes was E
The surface analysis by SCA showed almost no difference from the product dried only by washing with water.

Example 2 Before the washing process of the lead frame continuous plating apparatus with pure water, a 500 W low-pressure mercury lamp was attached, and ultraviolet rays were irradiated while the substrate surface was covered with pure water. The distance between the surface of the mercury lamp and the product was 30 mm, and the feed rate of the lead frame was 15 mm / sec.

As a result, the contact angle showing the wettability of the silver surface after drying to water is 25 to 35 degrees, which is much higher than the contact angle of 60 to 95 degrees when the silver is not irradiated. .. Further, the lead frame irradiated with ultraviolet rays was tested for the wire bonding property of the gold wire and the aluminum wire, but there was no difference from the ordinary product. In the measurement of the amount of carbon on the surface by ESCA, the amount of pure water only 50 to 10 against silver strength of 100.
While the intensity ratio was 0, in the lead frame irradiated with ultraviolet rays, the amount of organic substances on the surface was 0 to 30 per 100 of silver intensity, which was also reduced.

Example 3 Similar to Examples 1 and 2, a lead frame partially plated with silver was exposed to ultraviolet rays by placing a low pressure mercury lamp in water as shown in FIG. 2 (a). When the irradiation time was 10 seconds, the contact angle decreased only to 60 to 70 degrees. It has been found that this is because the lamp is water-cooled and the temperature of the tube wall is lowered, so that the luminous efficiency is lowered.

Example 4 A low-pressure mercury lamp was provided in a synthetic quartz cover, which was placed in water, nitrogen was sealed inside the cover, and a silver-plated lead frame was irradiated with ultraviolet rays. As in Examples 1 and 2, the contact angle to water could be lowered to 25 to 30 degrees by irradiation for 10 seconds. In this embodiment, the space between the mercury lamp and the quartz cover may be vacuum.

Example 5 Based on the result of Example 4, cleaning was performed in the line shown in FIG. 3 with the plated surface facing downward. The processing object 21 sent by the processing object transport roll 29 forms a wet state on the surface of the processing object by the overflow water 31 in the upper part of the overflow tank 30. The low-pressure mercury lamp 2 covered with the protective tube 25 is provided on the plated portion 32 of the object to be processed.
It was irradiated with ultraviolet rays from 2. Water that wets the object to be processed is received by the water receiving tank 33 and collected in the water storing tank 34. From the water storage tank, it is sent to the overflow tank by the water supply pump 35 and used for wetting the surface of the object to be treated.

The lead frame was moved by the object-conveying roll at a feed rate of 15 mm / sec for processing.
As a result, the contact angle of water on the silver surface after drying was 20.
It was as good as ~ 25 degrees. Further, the wire bondability was not different from that of the normal product, and the surface analysis result by ESCA was the same as in Example 2, indicating that the strength ratio of carbon was 50 or less with respect to the strength of silver of 100, and that there was no organic contamination. ..

[0022]

INDUSTRIAL APPLICABILITY According to the method of the present invention, the object to be treated such as silver is oxidized by irradiating with ultraviolet rays while the object to be treated is placed in water or a water film is formed on the surface to be treated. The surface can be cleaned and wettability can be improved in the state of being prevented, and the formation of the watermark can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating Examples 2 to 4 of the present invention.

FIG. 3 is a diagram illustrating a fifth embodiment of the present invention.

[Explanation of symbols]

1 ... Object to be treated, 2 ... Water, 3 ... Low-pressure mercury lamp, 4 ... Water layer,
21 ... Object to be treated, 22 ... Low-pressure mercury lamp, 23 ... Water, 24 ...
Processing tank, 25 ... Protective tube, 26 ... Conveying device, 27 ... Injection nozzle, 28 ... Water film, 29 ... Conveying object conveying roll, 30
… Overflow tank, 31… Overflow water, 32…
Plating section, 33 ... Water receiving tank, 34 ... Water storage tank, 35 ... Water pump

Claims (5)

[Claims] 1. An optical cleaning method for cleaning an object to be cleaned by using ultraviolet rays, wherein the object to be cleaned is provided in water, or the surface of the object to be cleaned is irradiated with ultraviolet rays while being covered with water. And light cleaning method. 2. The photocleaning method according to claim 1, wherein ultraviolet rays having a peak in a wavelength range of 260 nm or less are used. 3. A low pressure mercury lamp, an excimer laser,
Irradiation with a YAG laser is carried out, The optical cleaning method of Claim 1 or 2 characterized by the above-mentioned. 4. The ultraviolet luminous tube is covered with a protective tube through which ultraviolet rays are transmitted, and a gas that does not absorb ultraviolet rays is filled or vacuumed between the protective tube and the ultraviolet luminous tube. Light cleaning method. 5. The photo-cleaning method according to claim 1, wherein the UV-irradiation is performed in a state where the object to be cleaned is continuously transferred.