JPS60120219A - Flow-rate measuring device for clean draft - Google Patents

Abstract

PURPOSE:To enhance reliability and to reduce cost, by providing a measuring part comprising a specified resistance bridge between a blower discharge port and an exhaust duct, detecting static pressure and total pressure in the exhaust duct and the discharge pressure of the blower, and guiding the values to the measuring part. CONSTITUTION:A blower-discharge-pressure detecting pipe 12 is connected to one end of a fluid resistance bridge 11 and attached in the vicinity of a discharge port 10 of an upper blower (not shown) of an air filter 2 of an etching tank 1 in a clean draft 9. The pipe 12 is branched into pipes 15 and 16 through the bridge 11. The end parts thereof are coupled to static pressure and total pressure detecting pipes 13 and 14 which are arranged in an exhaust duct 4. Fluid resistors ra, rc, rb and rd are provided in the pipes 15 and 16, respectively. A point A between the resistors ra and rc and a point B between the resistors rb and rd are connected by a branch pipe 17 having a fluid resistor rg. A flow speed sensor 18 is provided in the pipe 17. Thus mixing of corrosive vapor and mist into the bridge 11 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a clean draft flow rate measuring device for managing the exhaust state of a clean draft.

[Background of the invention]

In the manufacturing process of semiconductor devices, chemical etching using chemicals such as strong acids, strong alkalis, or hydrofluoric acid is often used. Since these processing steps naturally involve the emission of intense corrosive vapor and mist, the corrosive vapor and mist must be safely and reliably discharged. Moreover, since the work space must be filled with extremely clean air, a so-called clean draft is usually used.

As shown in the block diagram of FIG. 1, the clean draft is equipped with a high-performance air filter 2 above an etching tank 1, and constantly supplies clean air that is sent by a clean air blower 3 and passed through the air filter 2. At the same time, corrosive steam and mist are generated from the cooling tank 1 and the exhaust duct 4 on the rear surface of the gee/draft to the damper 5 and the filtration device 6.
After that, the air is forcibly exhausted by an exhaust blower. When the exhaust flow rate of the clean draft is appropriate, a part of the clean air that has passed through the air filter 2 forms an air curtain 8 in front of the clean draft, as shown in FIG. All of the generated corrosive vapor and mist (indicated by broken lines in the figure) are exhausted from the exhaust duct 4.

If the exhaust flow rate is too small, some of the corrosive vapor and mist from the etching bath 1 will mix with the clean air flow and spread into the factory, as shown in FIG. 3, which is extremely dangerous. In addition, if the exhaust flow rate of the clean draft is excessive, as shown in Figure 4, the dusty air from inside the factory is introduced through the front opening of the clean draft, and the clean air mixed with this dusty air is used for etching. Since it flows into the tank 1, it causes defects in the product and significantly reduces productivity.

As mentioned above, optimization of the exhaust flow rate is most important when using a clean draft, but conventionally reliable and inexpensive equipment has been used to measure the exhaust flow rate when handling large amounts of highly corrosive steam and mist. I couldn't.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lean draft flow rate measuring device that is highly reliable and inexpensive in order to maintain and manage appropriate exhaust conditions.

[Summary of the invention]

In order to achieve the above object, the clean draft flow rate measuring device according to the present invention detects the static pressure and total pressure in the exhaust duct of the clean draft, and the discharge pressure of the clean air blower, and leads the piping to the measuring section. and a measuring section consisting of a fluid resistance bridge constituted by a fluid resistance and a flow rate sensor provided between the discharge port of the clean air blower and the exhaust duct.

[Embodiments of the invention]

Next, an embodiment of the present invention will be explained with drawings. Figure 5 is a diagram showing the configuration of an embodiment of the clean draft flow rate measuring device according to the present invention, and Figure 6 is a diagram showing the aspiration suction pressure (negative Dynamic pressure) A high-performance air filter 2 is provided above the etching tank 1 in the lean draft 9, and a blower (not shown) is located above the air filter 2.
A blower discharge pressure detection tube 12 connected to one end of the fluid resistance bridge 11 is installed near the air discharge port 10 from the fluid resistance bridge 11.The other end of the fluid resistance bridge 11 is connected to a static pressure detection tube 13 and a total pressure detection tube 14, respectively. and is introduced into the exhaust duct 4 led from the rear of the clean draft 9.

The fluid resistance bridge 11 is the blower discharge pressure detection tube 1
2, the fluid resistances rlL and r connected to the static pressure detection tube 13
. and a pipe 16 having fluid resistances rb and rd connected to the total pressure detection pipe 14.
A point A between fluid resistances ra and ro and a point B between fluid resistances rb and rd in the two pipes 15 and 16 are connected by a branch pipe 17 having a fluid resistance rg. A flow rate sensor 18 is provided.

In the flow measuring device of the clean draft 9, the highest air pressure (・ is the blower discharge pressure of the blower discharge pressure detection tube 12. Therefore, the air flow is from the blower detection tube 12 to the fluid resistance pre-noise. to the static pressure detection tube 13 and the total pressure detection tube 14. When the fluid resistance ra is equal to rb, the fluid resistance r is equal to rd, and the exhaust flow rate is zero, the pressure in the static pressure detection tube 13 is and the pressure in the total pressure detection tube 14 become equal, the fluid resistance bridge 11 becomes in an equilibrium state, and there is no air flow in the branch pipe 17, and the air that has passed through the discharge pressure detection tube 12 reaches the static pressure detection tube 13 and the total pressure. It flows from the pressure detection pipe 14 into the exhaust duct 4.

When the exhaust blower (not shown) operates and a flow exists in the exhaust duct 4 in the direction indicated by the arrow in FIG. The pressure increases, causing an air flow in the branch pipe 17 from point B to point A, and the normal air flow rate related to the flow rate in the exhaust duct 4 is detected by the flow rate sensor 18.

If the total exhaust pressure in the exhaust duct 4 becomes higher than the pressure in the blower discharge pressure detection tube 12, air flows from the total pressure detection tube I4 toward the static pressure detection tube 3. However, in the fluid resistance bridge 110 branch pipe 17, there is a possibility that air may flow from point A to point B. If there is such a possibility, bend the tip of the total pressure detection tube 14' in the exhaust duct 4 in the downstream direction of the exhaust duct 4 as shown in FIG. ), it is possible to prevent the fluid resistance bridge 11 from sucking in air mixed with corrosive vapor or mist generated in the etching tank 1 in the clean draft 9. When using the above-mentioned asvilation suction pressure, normal air flows through the branch pipe 17 of the fluid resistance bridge 11 in the opposite direction from point A to point B during proper operation.

Note that FIG. 7 is a sectional view showing a specific example of the fluid resistance bridge 11 in the measurement section, and each fluid resistance ra, rb
, r0, and r6 each use a needle valve so that the resistance value can be adjusted. (Fluid resistance rg of branch pipe 17
is omitted. ) Reference numerals 19, 21, and 21 in the figure are connection ports for the discharge pressure detection tube, static pressure detection tube, and total pressure detection tube, respectively.

As described above, in the clean draft 9 fluid measuring device shown in the embodiment, there is no risk of air mixed with corrosive vapor or mist flowing into the fluid resistance bridge 11 of the measurement section. There is no need to consider the corrosion resistance of the flow rate sensor 18 inserted into the exhaust duct 4, and it is sufficient to make only the exhaust duct 4 and the piping inserted into the exhaust duct 4 corrosion resistant.

Note that if the total pressure of the exhaust duct 4 is always negative than atmospheric pressure (this condition holds in most cases), the blower discharge pressure detection pipe 12 in FIGS. 5 and 6 is connected to the blower. It may be opened to the atmosphere without being connected to the vicinity of the discharge port 10.

〔Effect of the invention〕

As described above, the clean draft flow rate measuring device according to the present invention includes a piping system that detects the static pressure and total pressure in the exhaust duct of the clean draft, and the discharge pressure of the clean air blower and guides them to the measurement section. By providing a measuring section consisting of a fluid resistance bridge consisting of a fluid resistance and a flow velocity sensor provided between the discharge port of the clean air blower and the exhaust duct, corrosive vapor and mist can be mixed in. In order to prevent this air from flowing into the fluid resistance bridge, if only the exhaust duct and the piping inserted into the exhaust duct are made corrosion-resistant, the exhaust condition can be maintained and managed using a normal flow rate sensor. It is possible to obtain a lean draft flow rate measuring device that is extremely reliable and inexpensive.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional clean draft, Figure 2 is an explanatory diagram showing the air flow when the exhaust flow rate of the clean draft is appropriate, and Figure 3 is an illustration of the air flow when the exhaust flow rate is too low. FIG. 4 is an explanatory diagram showing the air flow when the exhaust flow rate is excessive, FIG. 5 is a diagram showing the configuration of an embodiment of the clean draft flow rate measuring device according to the present invention, and FIG. 7 is a configuration diagram showing a piping system and a measuring section that utilize aspiration suction pressure in the exhaust duct in the above embodiment, and FIG. 7 is a sectional view showing a specific example of the measuring section. 4°・Exhaust duct, 9.・Clean draft, 10.
Clean air blower discharge port, 11... Fluid resistance bridge, 12... Blower discharge pressure detection tube, 13...
Static pressure detection tube, 14... Total pressure detection tube, 17... Branch pipe, 1
8...Flow rate sensor, ra, rb, re, r
(1, rg ”'Fluid resistance agent patent attorney Junnosuke Nakamura 1st figure 2nd figure 3rd figure 4th figure 5th figure

Claims (5)

[Claims] (1) A piping system that detects the static pressure and total pressure in the exhaust duct of the clean draft and the discharge pressure of the clean air blower and leads them to the measurement unit, and the discharge port of the clean air blower and the exhaust duct. A clean draft flow rate measurement device comprising a measurement section consisting of a fluid resistance bridge, which is provided between fluid resistance and a flow velocity sensor. (2) The fluid resistance bridge has fluid resistances ra and rb.
, rc, rd, rg and a flow rate sensor, and ra
-rb,,ro:=rd, and ra and r. and r.b.
and rd are connected in series, and the other end of the above ra and rb
Connect the other end to the outlet of a clean air blower, and
The other ends of and rd are connected to the static pressure side and the total pressure side of the exhaust duct, respectively, and ra and r. A patent characterized in that a branch pipe having a fluid resistance r connects between (rI) and rd, and a flow velocity sensor for measuring the flow rate in the branch pipe is provided in the branch pipe. A clean draft flow rate measuring device according to claim 1. (3) The clean draft flow measuring device according to claim 1 or 2, wherein the fluid resistance is fluid resistance of a connecting pipe. (4) The clean draft flow rate measuring device according to any one of claims 1 to 3, wherein the flow rate sensor is a thermally conductive type wind speed sensor using a thermistor. . (5) Claims 1 to 4, characterized in that the total pressure is an aspiration pressure detected by a pressure detection tube opened toward the downstream direction of the exhaust duct.
A clean draft flow rate measuring device described in any of the paragraphs.