JP3089180B2 - Cleaning equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a supercritical fluid,
The present invention relates to a cleaning apparatus for performing precision cleaning of semiconductors, liquid crystals and the like, and more particularly to a cleaning apparatus capable of quickly discharging a cleaning medium after cleaning.

[0002]

2. Description of the Related Art The supercritical state is a state in which a liquid does not become a liquid even when sufficiently pressurized. The substance in a supercritical state (supercritical fluid) has a viscosity, a diffusion coefficient, a density, and a dissolving power between gas and liquid. In addition, since the gas is originally in a compressed state, it has many advantages such as behaving as a gas if the pressure is returned to the normal pressure.

[0003] The above-mentioned properties of supercritical fluids have been known for a long time, but in 1955 a research presentation was made that they could be used industrially. Later, in the 1970s, a decaffeinating plant for coffee started operating in West Germany, and supercritical fluids began to be used as a full-scale industrial separation operation. The use of supercritical fluids is actively performed in so-called extraction methods. In the extraction method, first, a target substance is dissolved from a raw material in a supercritical fluid, and the supercritical fluid in which the target component is dissolved is transferred to another container by utilizing a difference in specific gravity, and the pressure is reduced. Then, by changing the supercritical fluid into a gas, the dissolving power of the target component is eliminated, and only the target component is finally taken out. This operation (the operation of dissolving the target substance from the raw material in the supercritical fluid and using a difference in specific gravity to transfer the supercritical fluid in which the target component is dissolved to another container)
In recent years, the use of a supercritical fluid in a cleaning apparatus has been attracting attention because of the cleaning of raw materials.

[0004] Cleaning using a supercritical fluid is easier to cope with miniaturization, does not require a drying step, can be performed quickly, is non-toxic, and produces no waste liquid, as compared with conventional wet cleaning. There is an advantage that the dissolving power can be freely controlled by adding an additive solvent, and the apparatus is small in size and the like. The washing of the supercritical fluid has the same mechanism as the conventionally used supercritical fluid extraction and supercritical fluid chromatography.

FIG. 4 shows a conventional supercritical fluid cleaning apparatus. Here, 51 is a tank for holding a cleaning medium to be turned into a supercritical fluid, 52 is a high-pressure generating pump that pressurizes the cleaning medium and turns it into a supercritical fluid, 53 is a pressure-resistant washing tank for putting a work to be washed, and 54 is a washing tank Heater for heating the medium, 55
Is a pressure adjusting valve or needle valve, 56 is a separation tank for separating dirt from the work after cleaning, 57 is a dirt discharging valve, 58 is a pressure adjusting valve or needle valve, and 59 is a work. For cleaning, a work to be cleaned is put inside the pressure-resistant cleaning tank 53, and the high-pressure generating pump 5 is used.
The supercritical fluid whose temperature and pressure are appropriately controlled by the heater 2 and the heater 54 is sent out, and the supercritical fluid and the work 59 are brought into contact with each other.

[0006]

However, in a cleaning apparatus using a supercritical fluid, it takes a long time to pressurize and discharge the supercritical fluid, and the tact time is reduced under conditions such as processing in a closed tank. There was a problem that shortening was very difficult.

When a supercritical fluid is discharged, a rapid adiabatic expansion occurs because the compressed gas is released to the atmosphere. Since the adiabatic expansion increases in proportion to the internal pressure and the volume of the container, it takes more time to discharge in a large-sized and high-pressure apparatus. This adiabatic expansion is very large,
When carbon dioxide gas at 100 atm, 40 ° C. and 1 ml is released into the atmosphere, the volume becomes about 100 times, and the carbon dioxide gas immediately changes to solid (dry ice). The phenomenon that a solid is formed in the pipe is called a liquid ring, which is a very dangerous state because the pipe may break and cause an explosion. In order to prevent the liquid seal caused by this rapid adiabatic expansion, in the conventional cleaning device, the pipe used for discharging the gas is made extremely thin, and the needle valve and the pressure regulating valve are used very slowly. Had been discharged. This was the main cause of the difficulty in shortening the tact time in the past.

[0008] To solve this problem, the present applicant has proposed FIG.
(Japanese Patent Application No. Hei 6-2375) has been proposed.
88, filing date: September 30, 1994, title of invention: cleaning device). In FIG. 5, 1 is a tank, 2 is a high pressure generating pump, 3
Denotes a washing tank, 4 denotes a heater, 16 denotes an exhaust tank, 20 denotes a spare tank, 5, 9, 21, and 22 denote valves, and 23 denotes a liquid feed pump. Hereinafter, the operation of the cleaning device will be described with reference to FIG.

First, a work (not shown) to which dirt has adhered
To the washing tank 3. Thereafter, the cleaning medium in the tank 1 is pressurized to a critical pressure or higher by the high-pressure generating pump 23, heated to a critical temperature or higher by the heater 4, and introduced into the cleaning tank 3. Here, the cleaning medium enters a supercritical state.

Next, the work is washed. At this time, the cleaning tank 3 is in a state of being filled with the high-pressure gas.

Next, the above-described high-pressure gas discharging step will be described. The valve 5 is released at a predetermined speed, and a part of the gas is released into the exhaust tank 16 having a volume calculated in advance by using van der Waals equation of state or the like. At this time, adiabatic expansion occurs that takes away heat that can change gas and supercritical fluid into liquid. The adiabatic expansion removes the heat given by the heater 4, and the gas inside the cleaning tank 3 undergoes a phase change to become liquid.

Next, the liquid in the washing tank 3 is supplied to the liquid sending pump 23.
To the exhaust tank 16. At this time, the valve 22 is opened so as not to apply an excessive load to the liquid sending pump 23. When the volume of the liquid is larger than the volume of the exhaust tank 16, the valve 21 is opened and the spare tank 20 is used.

Finally, the residual pressure in the cleaning tank 3 is released from the valve 9, and the discharge of the cleaning medium from the cleaning tank 3 is completed.

With the use of the above-described cleaning apparatus, the supercritical fluid can be rapidly discharged, so that the tact time can be reduced.

However, in the above-described cleaning apparatus, when the spare tank 20 is used, liquid sealing may occur, which is very dangerous. Further, there is a problem that it takes time to discharge the liquid from the cleaning tank 3 to the exhaust tank 6 by the liquid sending pump 23.

The present invention has been made in order to solve the above-mentioned problems, and provides a cleaning apparatus capable of discharging a supercritical fluid at a high speed without causing a liquid seal after cleaning. The purpose is to do.

[0017]

In order to achieve the above object, a cleaning apparatus according to the present invention includes a cleaning tank for cleaning a workpiece by introducing a supercritical cleaning medium, and a cleaning medium for cleaning the workpiece after cleaning the workpiece. By introducing a part of the cleaning medium, the cleaning medium is adiabatically expanded to liquefy the cleaning medium in the cleaning tank.
A discharge tank, a second discharge tank for introducing a liquefied cleaning medium in the cleaning tank by a pressure difference between the cleaning tank, and a pressure in the second discharge tank when the liquefied cleaning medium is introduced. Pressure regulating means for adjusting the pressure so as not to cause liquid sealing.

Further, the invention is characterized in that the inside of the second discharge tank and the washing tank are connected so that the liquefied washing medium in the washing tank can flow into the second washing tank with a difference in height.

[0019]

According to the present invention, the volume of the first discharge tank is set in advance by calculation or the like, and when the cleaning medium in the supercritical state is discharged, the volume of the cleaning medium changes to a solid which cannot be rapidly controlled. Avoid adiabatic expansion and cause adiabatic expansion that takes away enough heat to change into liquid. In addition, the pressure of the second discharge tank is set to a pressure lower than the pressure of the cleaning tank after liquefaction, and the discharge of the liquid from the cleaning tank to the second discharge tank is performed by the cleaning tank and the second discharge tank. This is done by the pressure difference. For this reason, discharge can be performed at high speed.

Further, the pressure of the second discharge tank is set to a pressure which is set in advance by a calculation or the like so as not to generate a liquid seal when the cleaning tank discharges the liquid. It can be carried out.

Further, if the second discharge tank and the cleaning tank are arranged so that the liquid in the cleaning tank can flow into the second discharge tank at a height difference, the above-mentioned pressure difference causes the inflow of the liquid. Even when the size becomes smaller, the liquid in the cleaning tank can be sent to the second discharge tank at high speed to the end.

[0022]

FIG. 1 is a block diagram showing one embodiment of the configuration of the cleaning apparatus of the present invention. Here, the same parts as those in FIG. 5 are denoted by the same reference numerals. In FIG. 1, 1 is a tank, 2 is a high-pressure generating pump, 3 is a washing tank, 4 is a heater,
6 is a first discharge tank, 8 is a second discharge tank, 9 is a pressure release valve, 11 is a pressurizing tank, 5, 7, and 10 are valves, 12
Denotes a pressure relief valve, and 13 denotes a pressure reducing valve.

The washing tank 3 and the second discharge tank 8 are connected by two-system piping, and each piping can be opened and closed by a valve 7 and a pressure relief valve 12. The cleaning tank 3 and the first discharge tank 8 are connected by a pipe via a valve 5. The pressurizing tank 11 and the pressure reducing valve 13 are means for adjusting the pressure in the second discharge tank 8.

FIG. 2 is a flow chart showing a cleaning process in the cleaning apparatus of this embodiment, and FIG. 3 is a flow chart showing details of steps 4 and 5 in FIG. Hereinafter, the operation of the cleaning apparatus of this embodiment will be described with reference to FIGS.

First, a work to which dirt has adhered (not shown)
Is transported to the pressure-resistant cleaning tank 3 (step 1). Here, the dirt attached to the work is dirt that is soluble in the cleaning medium, such as oil impregnation and resist.

After the lid (not shown) of the pressure-resistant cleaning tank 3 is closed, the cleaning medium in the tank 1 is pressurized to a critical pressure or higher by the high-pressure generating pump 2 and heated to a critical temperature or higher by the heater 4 ( Step 2). In this embodiment, carbon dioxide is used as a cleaning medium because a supercritical state is easily obtained and handling is easy.
Oxygen, nitrogen, chlorine, methyl ether and the like can be used.

Next, the work is washed with the supercritical fluid sent into the washing tank 3 (step 3).

When the cleaning is completed, the valve 5 is released at a predetermined speed, and a part of the gas is released to the first discharge tank 6 (step 4). At this time, the supercritical fluid expands adiabatically,
It is deprived of heat and cooled. By this cooling, the supercritical fluid changes into a liquid and a gas, but the liquid and the gas can be obtained at an arbitrary ratio in consideration of the dryness of the gas enthalpy diagram. Here, the volume of the first discharge tank 6 is set to a size calculated in advance, and the cleaning medium in the cleaning tank 3 becomes liquid only in an appropriate amount (an amount that allows the work to be immersed in the liquid). The cleaning medium in the tank 6 becomes gas.

Next, the valve 5 is closed, the valve 7 is opened, and the liquid in the cleaning tank 3 is discharged to the second discharge tank 8 (Step 5). Here, if the pressure difference between the second discharge tank 8 and the cleaning tank 3 is large, the liquid is further cooled, becomes a solid, and may cause liquid sealing. Therefore, in this example, a pressurizing tank 11 is provided, and gaseous carbon dioxide is supplied from the pressurizing tank 11 to the second discharge tank 8 via the valve 10 in advance, and the pressure of the second discharge tank is increased. Is set to a pressure lower by 0 to several atmospheres than the pressure of the washing tank 3 so that liquid sealing does not occur. This pressure is set in advance by calculation or the like.
After the carbon dioxide is supplied by the pressurizing tank 11, the pressure of the second discharge tank 8 is adjusted by the pressure reducing valve 13.

As described above, the pressure in the second discharge tank 8 is set, and the delivery of the liquid from the cleaning tank 3 to the second discharge tank 8 is performed between the cleaning tank 3 and the second discharge tank 8. This is done by pressure difference. The cleaning tank 3 and the second discharge tank 8 are delivered by sending the liquid.
When the pressure difference between the cleaning tank 3 and the second discharge tank 8 decreases, the moving speed of the liquid decreases. To the second discharge tank at high speed until the end. When the liquid is sent out due to the height difference, the pressure relief valve 12 is opened to move the gas in the second discharge tank 8 to the cleaning tank 3 so that the pressure in the second discharge tank 8 does not increase. There is a need to.

By the above processing, the cleaning tank 3 and the first discharge tank 6 are filled with gaseous carbon dioxide, and the second discharge tank 8 is filled with liquefied carbon dioxide and gaseous carbon dioxide.

Next, the valve 7 is closed, the pressure release valve 9 is opened, and the work is taken out with the pressure in the cleaning tank 3 at normal pressure (step 6). At this time, since the inside of the cleaning tank 3 is gaseous carbon dioxide and has a somewhat low pressure, even if the carbon dioxide is rapidly released from the pressure release valve 9, solid carbon dioxide (dry ice) Is not formed and liquid sealing does not occur.

Subsequently, gaseous carbon dioxide is discharged from the first discharge tank 6 through a valve (not shown), and the pressure in the second discharge tank 8 is set to the above-mentioned predetermined pressure by the pressure reducing valve 13 (step). 7).

As shown in FIG. 2, in the cleaning apparatus of this embodiment,
The process of Step 7 is replaced with Step 1 at the time of cleaning the next work.
To Step 3 can be performed simultaneously. Therefore, even if the high-pressure carbon dioxide is slowly released from the first discharge tank 6 and the second discharge tank 8 in order to suppress the liquid seal caused by rapid adiabatic expansion, the tact time is increased. There is no.

As described above, in the cleaning apparatus of the present invention, the discharge of the liquid from the cleaning tank 3 to the second discharge tank 8 is performed by the cleaning tank 3.
The cleaning medium can be discharged from the cleaning tank 3 at a high speed, and the tact time can be shortened. Further, by setting the above pressure difference to a value that does not cause liquid sealing, the liquid can be safely discharged from the cleaning tank 3 to the second discharge tank 8. Further, since the high-pressure cleaning medium in the first discharge tank 6 and the second discharge tank 8 can be slowly discharged, liquid sealing at the time of discharging them can be suppressed.
Further, since a liquid feeding pump is not required, it is possible to reduce the cost.

[0036]

As described above, according to the present invention,
Since the liquid in the cleaning tank can be discharged at a high speed, the tact time is reduced. In addition, since it can be constituted by relatively simple parts, the initial cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a cleaning apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a cleaning process of the cleaning device of FIG. 1;

FIG. 3 is a flowchart showing details of steps 4 and 5 of FIG. 2;

FIG. 4 is a block diagram showing a configuration of a conventional cleaning device.

FIG. 5 is a block diagram showing a configuration of a cleaning device proposed by the present applicant previously.

[Explanation of symbols]

 Reference Signs List 1 tank 3 washing tank 6 first discharge tank 8 second discharge tank 9 pressure release valve 11 pressurizing tank 12 pressure relief valve 13 pressure reducing valve

Claims (2)

(57) [Claims] 1. A cleaning apparatus having a cleaning tank for cleaning a workpiece by introducing a cleaning medium in a supercritical state, wherein a part of the cleaning medium is introduced from the cleaning tank after the cleaning of the workpiece. A first discharge tank for adiabatically expanding the cleaning medium to liquefy the cleaning medium in the cleaning tank; and introducing a liquefied cleaning medium in the cleaning tank by a pressure difference between the cleaning tank and the first discharge tank. 2 and a pressure adjusting means for adjusting the pressure of the second discharge tank to a pressure that does not cause liquid sealing when the liquefied cleaning medium is introduced. Cleaning equipment. 2. The cleaning apparatus according to claim 1, wherein the liquefied cleaning medium in the cleaning tank flows into the second discharging tank due to a height difference between the second discharging tank and the cleaning tank. A cleaning device characterized by being connected so as to be capable of being used.