JPH08215648A - Descending flow-straightening type immersion cleaning device - Google Patents

Abstract

PURPOSE: To perform a minute cleaning in which cleanness is high in a short time by a small amount of cleaning water by forming the overflow part of cleaning liquid on one wall surface of an outer tank and attaching the liquid level controlling means of cleaning liquid on the inside wall except the overflow part and connecting a plurality of flow parts in which flow rate is different to the pouring port of cleaning liquid. CONSTITUTION: In a double tank consisting of an inner tank 1 and an outer tank 2 surrounding it, an overflow part 3 is formed by setting up the upper edge of one wall surface of the outer tank 2 lower than the other wall surface. Further, an overflow tank 4 is installed in the outside of the overflow part 3. Furthermore, a plurality of pouring ports 6 of cleaning liquid are arranged in the base of a clearance formed between the inner tank 1 and the outer tank 2. On one side, a discharge port 9 for discharging polluted cleaning liquid is formed in the bottom of the inner tank 1. By the way, the respectiv flow paths A, B consisting of stop valves V6, V7, needle valves V8, V9 for controlling each flow rate, flow meters M1, M2 and filters F1, F2 are connected to the respective pouring ports 6 through the respective stop valves V1-V4. Flow rate of the respective flow paths A, B is controlled respectively according to a liquid level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a descending rectification type immersion cleaning apparatus capable of removing suspended particles on the liquid surface of a cleaning tank and controlling the liquid surface against fluctuations in the flow rate of the supplied liquid.

[0002]

2. Description of the Related Art Conventionally, the cleaning of semiconductor wafers and glass substrates for liquid crystals has mainly been carried out by immersion chemical cleaning in which an object to be cleaned is immersed in a cleaning liquid for cleaning. Cleaning is a step of removing stains adhering to the object to be cleaned by treating it in a cleaning chemical solution,
It comprises a step of rinsing the cleaning chemical liquid remaining on the cleaned object after the treatment with pure water and a step of drying the cleaned object after the rinsing.

In the case of immersion cleaning with a cleaning chemical, the contaminant particles liberated from the object to be cleaned are dispersed in the cleaning solution, and if the number of objects to be cleaned increases, the concentration of the contaminant particles accumulated in the cleaning tank increases and There is a problem that re-contamination of the cleaned object with the above particles occurs, a portion of the cleaning liquid in the cleaning tank is continuously withdrawn and passed through a filter to remove dispersed contaminating particles, and then the original again. It is indispensable to carry out so-called circulation filtration, which is returned to the tank. As described above, the overflow type cleaning tank has been conventionally used for the method of extracting the cleaning liquid from the cleaning tank and returning it to the cleaning tank again.

On the other hand, in the case of pure water rinsing for rinsing, fresh pure water is continuously supplied from the lower part of the rinse tank,
Even if the cleaning liquid is mixed with the cleaning liquid that has overflowed from the top of the rinse tank and overflowed from the rinse tank to the outside of the rinse tank, the water quality of the pure water in the rinse tank is supplied. The practice is to continue until the quality of the water matches.

In both cases of circulating filtration of the cleaning liquid and rinsing with pure water, the higher the ability to completely discharge the chemical liquid components and dirt brought into the cleaning tank or the rinse tank in a short time, that is, the higher the discharge displacement efficiency is. The high cleaning quality of immersion cleaning can be obtained economically in a short time. However, the conventional immersion cleaning bath supplies cleaning liquid or pure water from the bottom side of the bath,
The overflow method, which overflows from the upper end of the tank, is mainly used.

FIG. 6A shows a visual observation of a water flow in a cleaning tank in which overflow cleaning is performed in order to clean an object to be cleaned such as wafers and substrates arranged at relatively narrow intervals. The cleaning liquid supplied from the bottom of the cleaning tank 11 as shown in FIG. 3B and passed through the saw-toothed cleaning object support plate 12 shown in (b) does not pass through the narrow gaps between the cleaning objects, but around the cleaning object 13. Flows mainly in a wide area between the inner wall of the tank and the inner wall of the tank. Then, although it overflows from the upper edge of the tank, part of the upward flow moves toward the center of the tank along the liquid surface, and further passes through the narrow gap created by the wafer, substrate, etc. from the upper portion of the object to be cleaned 13. It changes to a downward flow. This gentle downward flow is attracted to and mixed with the upward flow of the supply liquid in the lower part of the object to be cleaned. That is, a circulating flow is generated in the cleaning tank from the wall side of the tank toward the center of the tank. This circulating flow is important in the following two points.

The first problem is that when an object to be cleaned such as a wafer or a substrate is batch-processed, the flow of the cleaning liquid on the surface of the object to be cleaned becomes very slow as compared with the magnitude of the flow rate of the supply liquid. The action of removing the contaminants from the surface of the wash-target and the action of removing the detached contaminants from the vicinity of the wash-target are not sufficiently exerted, and most of the supplied cleaning liquid flows out without contributing to the cleaning action. Further, in No. 2, the contaminants separated from the object to be cleaned stay in the cleaning tank for a long time on the circulating flow. Therefore, the clean object to be cleaned after the cleaning is contaminated again, and it takes a considerably long time to be completely cleaned.

As a measure against the above problems, FIG.
As shown in (b), it is considered that only the portion directly below the object to be cleaned is shielded and the other supporting plate portions are shielded so that the cleaning liquid injected from the bottom of the tank rises directly between the objects to be cleaned. There is. When the flow is visualized and examined in the above case, the upward flow reaching the liquid surface through the gap of the object to be cleaned becomes a horizontal flow toward the tank wall and overflows from the upper edge of the cleaning tank. A substantial part of the above collides with the tank wall, then becomes a downward flow along the tank wall, hits the support plate in the cleaning tank, and is attracted to the upward flow toward the center to be mixed. That is, a circulation flow opposite to the circulation flow is generated toward the tank wall. Although the problem described in No. 1 above is improved, the problem of No. 2 is not solved, and a long-time cleaning process is required to obtain sufficient cleaning quality.

As a solution to the drawbacks of the overflow system, the contaminated cleaning liquid that has passed through the object to be cleaned is forcibly discharged from the bottom of the cleaning tank through a perforated plate having pores, and a cleaning liquid suitable for the discharged flow rate is obtained. We applied for a new cleaning tank using a method of uniformly raising and supplying along the inner wall of the cleaning tank (Japanese Patent Application No. 5-260505).

FIG. 8 shows the result of observing the flow of the cleaning liquid by visualizing the state of cleaning the object to be cleaned in the cleaning tank. Since the cleaning liquid is sucked downward by the pump through the perforated plate 14 below the article to be cleaned 13, the suction flow velocity of the plurality of fine holes appropriately dispersed in the perforated plate is substantially uniform. Therefore, in the cleaning object installation part of the cleaning tank,
A downward flow is formed that has a uniform flow velocity. Therefore, a biased flow that selectively flows in the large gap between the periphery of the object to be cleaned and the tank wall is unlikely to occur, and the cleaning liquid flows well even in the narrow gap between the wafer and the substrate, which is the object to be cleaned. The flow velocity is uniform at.

There are various methods of supplying the cleaning liquid to the object to be cleaned, but in order to properly rectify the downward flow, the way of supplying the cleaning liquid to the object to be cleaned is important, and the method of supplying the cleaning liquid to the object to be cleaned is important. On the other hand, the best condition is that the flow rate of the cleaning liquid flowing from the surroundings is uniform. Therefore, the cleaning tank has a double tank structure composed of an outer tank and an inner tank, and a new cleaning liquid is supplied by using the gap between the outer tank wall and the inner tank wall as an upward flow from the lower part. In this case, it is desirable that four injection ports for the cleaning liquid be provided symmetrically in the front-rear direction, and at least two injection ports be provided at symmetrical positions. The upward flow of the injection cleaning liquid cannot prevent the flow velocity distribution from centering around the injection port. As a method for relaxing this flow velocity distribution as much as possible, for example, an obstacle that disperses the flow is provided near the inlet, or as another method, a porous plate for rectifying is provided in the wall gap between the outer tank and the inner tank. It is to provide.

In such a cleaning tank, the chemicals and contaminants brought into the tank by the object to be cleaned are separated from the surface of the object to be cleaned by quick downward rectification, and are quickly transferred and discharged from the bottom of the tank. Since the object to be cleaned is installed in the descending rectifier that occurs in the tank, there is no retention of released contaminants, and the cleaning liquid is replaced in a short time in the cleaning tank to be cleaned. That is, high quality cleaning can be completed in a shorter time than that of the overflow type cleaning tank, which is economically advantageous.

Using an overflow tank having the same tank volume and a descending straightening tank, rinsing with pure water having the same flow rate, that is, pure rinsing was performed. FIG. 9A shows a comparison of the substitution and ejection characteristics of the ions carried in the tank at this time. The conductivity of pure water flowing out from each tank is taken on a logarithmic scale on the vertical axis, and the elapsed time of rinsing is based on when the wafer cassette immersed in saline solution is pulled up and placed in the rinse tank. It is on the horizontal axis on the minute scale. However, the conductivity value at each time is shown as a ratio with the highest value immediately after the cassette was placed in the tank. As is clear from FIG. 9 (a), the solid line showing the case of the downflow rectification tank shows a faster decrease in the ion concentration in the tank, and the rinse time until it decreases to the same concentration is the case of the overflow tank shown by the broken line. It is about 1/2. Since the flow rate of pure water supplied is the same,
By using the descending rectification tank, the amount of expensive pure water used can be halved, and the running cost can be significantly reduced.

As for the decreasing rate of the particle concentration in the cleaning tank in which the circulation filtration is carried out, the descending rectifying tank has a value about twice that of the overflow tank as shown in FIG. 9 (b). . In other words, the contaminant particles brought into the tank by the object to be cleaned are filtered and removed in about half the time in the descending rectification tank as if they were circulated and filtered under the same conditions, and the contaminant particles on the object to be cleaned are removed. It is expected that the chance of recontamination will be significantly reduced and a highly clean cleaning surface will be obtained. As described above, by using the descending rectifying tank, a circulating flow in the tank is not generated, and even in a narrow gap between the objects to be cleaned, such as when cleaning a wafer or a glass substrate, the flow velocity is fairly high and evenly pure. To be able to drain water,
High-quality cleaning can be performed quickly and economically as compared with the overflow tank.

[0015]

However, when the cleaning liquid or the rinse is actually performed by using the above-mentioned descending rectification type cleaning tank, there are the following problems. That is, if the supply flow rate and the discharge flow rate do not match, the liquid level changes. If there are contaminant particles floating on the surface of the liquid, they will continue to stay on the surface of the liquid as they are, and when the object to be cleaned is taken out of the tank after cleaning, the above-mentioned suspended particles adhere to the object to be cleaned and cause recontamination. become.

When the liquid level changes and the liquid level approaches the upper edge of the inner tank, the flow of the cleaning liquid into the inner tank is disturbed, the rectification of the cleaning liquid in the tank is impaired, and the replacement efficiency of the cleaning liquid is deteriorated. Is reduced.

An object of the present invention is to solve these problems and to obtain a descending rectification type immersion cleaning apparatus which can perform high quality cleaning in a short time with a small flow rate of cleaning liquid or pure water.

[0018]

The above object is composed of a double tank having an inner tank and an outer tank formed in a rectangular shape, and the cleaning liquid is injected from a lower portion of a gap provided between the inner tank and the outer tank. , A cleaning liquid is poured from the upper edge of the inner tank to the object to be cleaned, and a contaminated cleaning liquid containing contaminated fine particles released from the object to be cleaned is discharged from the bottom of the inner tank through a perforated plate in a descending rectification type immersion cleaning device, An overflow portion of the cleaning liquid is provided on the upper edge of one side surface of the outer tank,
A cleaning liquid level control means is installed in the inner wall of the outer tub other than the above-mentioned overflow portion, and the flow rates are different from each other.
This is achieved by providing one flow path at the cleaning liquid injection port and providing a means for controlling the flow rate. Further, it is achieved by providing a perforated plate above the gap between the inner tank and the outer tank and pouring the cleaning liquid that has permeated through the perforated plate onto the object to be cleaned from the upper edge of the inner tank. Further, it is achieved by controlling the liquid level with a level sensor provided on the inner wall of the tank. That is, the liquid level control and the overflow portion are provided to eliminate the floating particles, and the flow rate control means has a function of reducing the cleaning liquid in a state where the cleaning is not performed.

[0019]

[Function] A double tank is composed of an inner tank formed in a rectangular shape and an outer tank provided so as to surround the inner tank, and the upper edge of one of the four wall surfaces of the outer tank is higher than the upper edges of the other three wall surfaces. The cleaning liquid is made low to form an overflow portion, and an overflow tank for receiving the overflowing cleaning liquid and a drain pipe are provided on the outer wall of the overflow portion. An inlet for the cleaning liquid is provided at the bottom of the gap formed between the inner wall of the outer tank and the outer wall of the inner tank, and a perforated plate for rectifying the injected cleaning liquid is provided around the outer periphery of the inner tank at the upper part of the gap. ing. The inner tank whose upper edge is set at a position lower than the overflow portion is provided with a perforated plate at a position where the object to be cleaned is sufficiently immersed in the cleaning liquid, and serves as an installation table for the object to be cleaned. A discharge port is provided on the bottom surface, and the contaminated cleaning liquid that has passed through the porous plate is sucked and discharged by a pump provided outside the tank. The shape of the overflow portion and the edge of the upper edge of the inner tank where the cleaning liquid or pure water overflows is formed in a sawtooth shape so that the overflow can be performed uniformly.

The above structure is the basic structure of the descending rectification type immersion cleaning tank, and in order to inject the cleaning liquid into the object to be cleaned at a flow velocity as uniform as possible, a porous plate is provided in the gap between the inner tank and the outer tank. Although the injected cleaning liquid is rectified, in order to further improve the rectification degree, at least two symmetrical positions are provided in the cleaning liquid injection port on the bottom surface of the outer tank around the inner tank.

A level sensor is installed at a position above the upper edge of the inner tank so that the average liquid surface can be kept within a certain range. In the cleaning apparatus of the present invention, the liquid surface is installed above the upper edge of the inner tank in advance. However, if the flow rate of the cleaning liquid to be injected and the discharge flow rate of the pump match, the initially set liquid surface is maintained. However, in practice, it is inevitable that the flow rate slightly fluctuates, so if the flow rate difference between the injection flow rate and the discharge flow rate is positive, the liquid level rises, and if it is negative, the liquid level falls. If the liquid level rises above the level above the set liquid level and reaches the edge of the overflow, it naturally overflows and is discharged, so there is no problem. When approaching to (5), the flow of the cleaning liquid flowing into the object to be cleaned from the upper edge is significantly disturbed, and as a result, the rectifying property in the inner tank is disturbed and the cleaning liquid replacement efficiency is reduced. Therefore, it is important to control the liquid level within a relatively narrow range in order to keep the performance of the cleaning device stable.For this reason, level sensors are installed at the upper and lower limits to control the liquid level. Try to keep it.

The inlet of the cleaning liquid is provided with a flow path A for a flow rate slightly smaller than the suction flow rate of the discharge port and a flow path B for a flow rate slightly larger than the suction flow rate.
Install a flow rate adjusting needle valve, a flow meter, and a filter so that the flow rate can be selected independently. When operating in the flow path A, the liquid level lowers and reaches a low level level sensor, which opens the valve of the flow path B to raise the liquid level and reach the high level liquid level sensor, The valve closes and the liquid level descends again.

Further, when the floating dust drops on the surface of the cleaning liquid and stays on the liquid surface for some reason, it is inevitable that the floating dust adheres when the object to be cleaned is pulled out from the tank. In this case, when all the valves except the cleaning liquid inlet valve are closed, the liquid level rises and the outlet is also closed, so that it flows over the upper liquid level sensor and flows out from the overflow part. Dust floating at that time is discharged together with the overflow cleaning liquid. When the above dust is discharged, open the closed valve to restore normal operation. Furthermore, when only the flow path A having a small flow rate is opened at the time of rinsing pure water and the suction pump connected to the discharge port is stopped, pure water is discharged by natural flow and the flow rate of pure water can be reduced. When performing circulation filtration, the destination of the suction pump is connected to the above flow path instead of the drain.
Due to these effects, high-quality cleaning can be performed with a small flow rate of the cleaning liquid. Although the above description mainly describes the cleaning tank and the cleaning liquid, the same applies to pure water in the rinse tank.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the descending rectifying type immersion cleaning apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a cross section of a cleaning tank of a descending rectification type immersion cleaning apparatus according to the present invention, FIG. 2 is a perspective view showing the appearance of the cleaning tank, FIG. 3 is a top view of the cleaning tank, and FIG. FIG. 5 is a diagram showing an example of piping of the immersion cleaning device.

As shown in FIG. 1, the cleaning tank for the descending rectifying type immersion cleaning apparatus of the present invention is a double tank in which an inner tank 1 and an outer tank 2 surrounding the inner tank 1 are formed in a rectangular shape, and the outer tank 2 has a wall surface. Of the short side, the upper edge of one surface is made lower than the height of the other wall of the outer tank, and the overflow portion 3
Further, an overflow tank 4 and a drain pipe 5 for receiving the overflowed cleaning liquid are provided outside the tank. A cleaning liquid inlet 6 is provided on the bottom surface of the gap formed between the inner tank 1 and the outer tank 2, and a perforated plate 7 having a plurality of holes at the upper portion of the gap.
Are provided along the outer wall of the inner tank 1 for rectifying the injected cleaning liquid. The inner tank 1 has its upper edge at the overflow portion 3
The setting table 8 is set at a lower position, and the setting table 8 for the cleaning object is provided at a position where the cleaning object is sufficiently immersed in the cleaning liquid in the inner tank. It is composed of a plate, passes the contaminated cleaning liquid after cleaning the object to be cleaned, rectifies the flow of the cleaning liquid in the inner tank 1, and uses the discharge port 9 provided at the bottom of the inner tank 1 directly below the installation table 8. , A pump provided outside the tank sucks and discharges the contaminated cleaning liquid. In the above configuration, the cleaning liquid injected from the injection port 6 is used as the inner tank 1
The gap formed by the outer tank 2 and the outer tank 2 is raised, and the perforated plate 7 provided at the upper portion of the gap is passed to clean the rectified cleaning liquid from the upper edge of the inner tank 1 at a uniform flow rate in the inner tank. In order to make the flow rate of the cleaning liquid uniform and to further rectify the flow of the cleaning liquid, it is necessary to arrange the cleaning liquid inlets 6 on the bottom surface of the gap as symmetrically as possible. The symmetrical arrangement as shown in FIG. 3 is performed.

When the flow rate of the cleaning liquid injected from the cleaning liquid injection port 6 and the flow rate of the contaminated cleaning liquid discharged from the discharge port 9 are equal, the cleaning liquid surface in the cleaning tank maintains a constant state. When the balance between the above two flow rates is lost, the amount of cleaning liquid increases or decreases. That is, when the difference between the injection flow rate and the discharge flow rate becomes positive, the liquid level rises, and when it becomes negative, the liquid level falls. Actually, it is unavoidable that the flow rate slightly fluctuates, and if it continues to rise, it will reach the upper edge of the overflow portion 3 and will be overflowed and discharged. When the water drops and approaches the upper edge of the inner tank 1, the rectifying property of the cleaning liquid injected over the upper edge into the object to be cleaned is disturbed, and the replacement efficiency of the cleaning liquid decreases.
Therefore, the fluctuation of the liquid level of the cleaning liquid in the tank must be controlled within a relatively narrow range, but the allowable fluctuation range is about ± 10 mm with respect to a predetermined average liquid level as shown in FIG. Is desirable. Therefore, the liquid level sensor 10 (LH and L
L) is installed to keep the fluctuation of the cleaning liquid level within a certain range. An example of the relationship between the height of the inner tank 1 and the outer tank 2, the height of the overflow portion 3, and the average liquid level is shown in FIG.

The four cleaning solution inlets 6 provided at the bottom of the gap between the inner tank 1 and the outer tank 2 of the main cleaning tank are respectively opened and closed via valves V ₁ , V ₂ , V ₃ and V ₄ . The flow path for the cleaning liquid is connected to the discharge port 9 as shown in FIG.
Flow rate A slightly lower than the suction flow rate Ql / min, for example, a flow rate A set to a flow rate (Q-2) 1 / min reduced by about 2 l / min and a flow path B set to a flow rate of about 3 l / min. Each flow path is composed of opening / closing valves V ₆ and V ₇ , needle valves V ₈ and V ₉ for flow rate adjustment, and flow meters M ₁ and M ₂ and filters F ₁ and F ₂ , respectively. The flow rate can be selected independently by switching. When operating with the flow path A, the supply flow rate is smaller than the suction flow rate, so the level of the cleaning liquid decreases,
Eventually, the liquid level sensor LL is reached. The valve V ₇ of the flow path B is opened by the operation of the sensor LL, and the flow rate (Q-2 + 3) l
/ Min, that is, about 1 l / min, which is larger than the suction flow rate and the liquid level rises. When the rise continues, the cleaning liquid level eventually reaches the liquid level sensor LH. However, if the level sensor LH closes the valve V ₇ of the flow path B, the cleaning liquid surface can be lowered. With such a control method,
The level of the cleaning liquid in the cleaning tank is centered around the level at the start of operation ±
The washing treatment can be carried out by moving up and down within a range of 10 mm. The flow rate setting values of the flow paths A and B are not fixed to the above exemplified values, but it is necessary to appropriately set the flow rate setting values based on the flow rate fluctuation value on the cleaning liquid injection side.

In order to carry out precision cleaning, a cleaning device is installed in a clean booth or the like in order to avoid contamination such as suspended dust. However, in the unlikely event that the airborne dust settles on the cleaning liquid surface, it remains in the cleaning liquid surface, and the floating dust is attached when the object to be cleaned after cleaning is pulled out from the cleaning tank, Will be polluted again. When there is floating dust on the surface of the cleaning liquid, the valve V in FIG.
Inlet valves V ₂ , V ₃ , V ₄ other than ₁ and outlet valve V ₅
When the valve is closed, the cleaning liquid level rises and the liquid level sensor LH works to close the valve of the flow path B, but since the outlet valve V ₅ is closed, the cleaning liquid level continues to rise and reaches the overflow portion 3. And drains from the drain pipe 5. At this time, a horizontal surface flow is formed from one of the cleaning tanks toward the overflow portion 3,
The dust floating on the surface is discharged in a relatively short time together with the above flow. When the suspended dust is removed, the closed valves V ₂ , V ₃ , V ₄ and V ₅ are opened, and the pump discharge port 9
When the suction from is restarted, the cleaning liquid level is lowered because the cleaning liquid injection flow rate is smaller than the suction flow rate. In addition, in order to quickly return the cleaning liquid level to a predetermined level, the injection port valves V _{1 to} V ₄ may be temporarily closed.

Further, when the cleaning is temporarily suspended, in order to continuously pass water in a state where the flow rate of pure water is reduced so as not to lower the cleanliness of the pure water rinse tank, the flow path B having a small flow rate is used.
The valve V ₁ is opened, the pump connected to the discharge port 9 is stopped, and the valve V ₁₀ is opened to allow natural flow to flow out. In order to adjust the flow rate under the natural flow to be balanced with the flow rate in the flow path B, a needle valve V ₁₁ is provided after the valve V ₁₀ .

Although the above description mainly describes the cleaning liquid, the same applies when pure water is used as the rinse tank. Further, the valve switching operation such as the liquid level adjustment, the elimination of floating dust, and the switching to a small flow rate to save water can be easily automated by sequence control using an automatic valve.

[0031]

As described above, the descending straightening type dipping and cleaning apparatus according to the present invention is composed of a double tank including an inner tank and an outer tank, which are formed in a rectangular shape, and has a gap provided between the inner tank and the outer tank. Inject the cleaning liquid from the lower part of the inner tank, pour the cleaning liquid into the object to be cleaned from the upper edge of the inner tank, and discharge the contaminated cleaning liquid containing contaminated fine particles released from the object to be cleaned from the bottom of the inner tank through the perforated plate. In the rectification type immersion cleaning device, an overflow portion of the cleaning liquid is provided on the upper edge of one side surface of the outer tank, and a liquid level control means for the cleaning liquid is installed in the inner wall of the outer tank other than the overflow portion. By providing two flow paths different from each other in the cleaning liquid inlet and providing the means for controlling the above flow rate, it is possible to perform a precision cleaning with a high cleaning degree in a short time at a used flow rate with a small amount of cleaning liquid or pure water. A down-rectifying immersion cleaning device is obtained.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of a cleaning tank of a descending rectifying type immersion cleaning apparatus according to the present invention.

FIG. 2 is a perspective view showing an appearance of the cleaning tank.

FIG. 3 is a top view of the cleaning tank.

FIG. 4 is an explanatory diagram for liquid level control.

FIG. 5 is a diagram showing an example of piping of the descending rectifying type immersion cleaning device.

FIG. 6 is a diagram showing a flow of a cleaning liquid in a conventional overflow type cleaning tank.

FIG. 7 is a diagram showing a flow of a cleaning liquid in another example of the conventional cleaning tank.

FIG. 8 is a diagram showing a flow of a cleaning liquid in a descending rectification type cleaning tank.

FIG. 9 is a view showing a comparison of cleaning efficiency between an overflow type cleaning tank and a downflow rectification type cleaning tank, wherein (a) is a pure water rinse and (b) is a circulation cleaning.

[Explanation of symbols]

 1 Inner tank 2 Outer tank 3 Overflow part 6 Injection port 7, 8 Perforated plate 9 Discharge port 10 Level sensor

Claims (3)

[Claims] 1. A double tank consisting of an inner tank and an outer tank formed in a rectangular shape, and a cleaning liquid is injected from a lower part of a gap provided between the inner tank and the outer tank, and from the upper edge of the inner tank. In a descending straightening type dip cleaning device in which a cleaning liquid is poured into an object to be cleaned and a contaminated cleaning liquid containing contaminated fine particles released from the object to be cleaned is discharged from the bottom of the inner tank through a perforated plate, on one side surface of the outer tank. An overflow portion of the cleaning liquid is provided at the rim, and a liquid level control means for the cleaning liquid is provided in the inner wall of the outer tank other than the overflow portion.
A descending rectifying type immersion cleaning apparatus, characterized in that two flow paths having different flow rates are provided in a cleaning liquid inlet and a means for controlling the flow rate is provided. 2. A gap provided between the inner tank and the outer tank is provided with a perforated plate on the upper portion, and the cleaning liquid that has permeated through the perforated plate is poured from the upper edge of the inner tank onto the object to be cleaned. Claim 1
The descending rectification type immersion cleaning device described. 3. The descending rectifying immersion cleaning apparatus according to claim 1, wherein the liquid level in the cleaning tank is controlled by a level sensor installed in the cleaning tank.