JP2004340726A - Leakage detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage detecting device in which a gas exhaust pipe is branched and the branched gas feed pipe line is connected to a position having a different compression ratio of a main pipe with an evacuation means, enabling switching the gas feed pipe line not to affect a leakage test without providing a vacuum meter for high-vacuum area measuring when connecting the gas feed pipe line to a position having a smaller compression ratio. <P>SOLUTION: Each of on-off valves 7 controls switching of the gas feed pipe line 6 based on a background value of a noble gas measured by an analyzer tube 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is used as a tracer gas of helium, which is a rare gas, for example, to detect gas leaks in airtight equipment such as a thin film forming apparatus such as a compressor, a CVD, and a sputtering apparatus used in a refrigerator. The present invention relates to a leak detection device.
[0002]
[Prior art]
In this type of leak detection device, it is desired that the leak detection of a large volume test object can be started in a short time, the detection sensitivity is high, and the reaction speed is high. From this, a main pipe line provided with a composite molecular pump composed of a turbo molecular pump and a drag pump and a rotary pump on the back pressure side is connected to an analysis tube capable of detecting helium, and a test port connected to a device under test is connected. , And the exhaust pipe is branched at three points, and the first, second, and third branched gas introduction pipes are connected to first, second, and third on-off valves. Is known in which a composite molecular pump is connected to a portion having a different compression ratio via a pressure sensor (Patent Document 1).
[0003]
In this case, the first gas introduction pipe is connected to an intermediate position between the turbo molecular pump and the drag pump where a low compression ratio can be obtained, and high-sensitivity leak detection can be performed. The third gas introduction line is connected to the highest compression ratio of the composite molecular pump via a fore valve, and the second gas introduction line is connected to the intermediate compression ratio position. I have. In order to control the opening and closing of the fore-valve and the respective on-off valves provided in each gas introduction pipe, a Pirani vacuum gauge is provided in the exhaust pipe, and the gas introduction pipes of each gas introduction pipe are provided in accordance with the detection pressure of the Pirani vacuum gauge. Controls the opening and closing of each on-off valve, and sequentially switches from a gas introduction line with a high compression ratio to a gas introduction line with a low compression ratio in the main line, and detects leakage from low to high sensitivity using the principle of back diffusion. I can do it.
[0004]
By the way, in recent leak tests, there are many demands for detecting a minute leak of a device under test. In the above configuration, the compression ratio of the on-off valve to air is about 10 ^4, and almost all of the helium introduced from the first gas introduction pipe does not reach the analysis pipe. Helium may not be detected by the analysis tube when the leakage of the gas is very small. To increase the sensitivity of helium detection and to detect minute leaks, connect a gas inlet line for high sensitivity at a position where the compression ratio of the composite molecular pump is lower, for example, between the analysis tube and the composite molecular pump. Is proposed.
[0005]
[Patent Document 1]
Japanese Patent No. 2655315 (for example, description of claims)
[0006]
[Problems to be solved by the invention]
Here, since the Pirani vacuum gauge can stably measure the pressure up to a range of several Pa, as described above, when a gas introduction pipe for high sensitivity is connected to a position with a lower compression ratio, The pressure for switching to the gas introduction line may deviate from the measurement range of the Pirani gauge. If the pressure in the analysis tube rises when switching to a high-sensitivity gas introduction tube, the leak test will be affected, so it is necessary to accurately grasp the pressure in the exhaust line. In this case, in addition to the Pirani vacuum gauge, a vacuum gauge such as an ionization vacuum gauge capable of measuring the pressure in a high vacuum region may be separately provided in the exhaust pipe, but this increases the number of parts and increases the cost. This causes a problem of inviting.
[0007]
In view of the above, an object of the present invention is to provide a leak detection device capable of performing a leak test with high sensitivity at low cost without increasing the number of parts.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the leak detection device of the present invention includes an analysis tube capable of analyzing a rare gas as a tracer gas, connects a main line to the analysis tube, and connects a high vacuum exhaust means to the main line. And an auxiliary evacuation means on the back pressure side of the high evacuation means, connecting an evacuation line to a test port connected to the device under test, branching the evacuation line at a plurality of locations, and branching out. The gas introduction pipelines are connected to each other at different compression ratios of the main pipeline via on / off valves, and each on / off valve is controlled to open and close to compress from the gas introduction pipeline with a high compression ratio of the main pipeline. In the leak detection device, which sequentially switches to a gas introduction pipe having a low ratio and analyzes a rare gas in the analysis pipe to detect a leak of a test object, gas introduction by controlling opening and closing of each of the on-off valves is provided. Switch the pipeline by the analysis tube And performing on the basis of the background value of the definitive noble gases.
[0009]
According to the present invention, the switching of the gas introduction pipe by controlling each of the on-off valves is performed based on the background value of the rare gas measured in the analysis pipe, so that the pressure in the exhaust pipe is detected. Even if it is not necessary, it is possible to switch to a gas introduction line for high sensitivity so that the pressure in the analysis tube does not increase. This prevents an increase in the number of parts and an increase in cost.
[0010]
Note that the background value may be, for example, the partial pressure of the rare gas being analyzed in the analysis tube.
[0011]
In addition, a fore valve is provided between the high vacuum evacuation means and the auxiliary evacuation means, and a low-sensitivity gas introduction pipe is connected between the fore valve and the auxiliary evacuation means. If a vacuum gauge that controls the opening and closing of the on-off valve and the opening and closing of the fore valve provided in the pipeline is provided in the exhaust pipeline, the gas pipeline with the high compression ratio of the main pipeline can be changed to the gas pipeline with the low compression ratio. While switching sequentially, leakage detection from low sensitivity to high sensitivity can be performed using the principle of despreading.
[0012]
In this case, if a high-sensitivity gas introduction line having a low compression ratio of the main line is connected between the analysis tube and the high-vacuum evacuation means, a high-pressure detecting device for detecting an extremely small leak of the DUT is provided. Leak test of sensitivity becomes possible.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to FIG. 1, reference numeral 1 denotes a leak detection device of the present invention that can detect leaks of instruments using, for example, helium as a tracer gas. The leak detection device 1 has a mass analysis tube 2. This mass spectrometer tube 2 is of a known quadrupole type or a magnetic field deflection type, and detects helium ions. The mass spectrometer tube 2 is connected to a main molecular line 3 provided with a compound molecular pump 31 as a high vacuum evacuation means and a rotary pump 33 as an auxiliary evacuation means on the back pressure side via a fore valve 32. The inside of the tube 2 is maintained at a predetermined pressure or less (≦ ¹⁰⁻² Pa). The composite molecular pump 31 has a known structure, and includes a turbo molecular pump and a drag pump built in a pump casing having a connection to the main pipeline 3. The auxiliary evacuation unit may be a membrane pump or the like.
[0014]
On the other hand, an exhaust pipe 5 is connected to a test port 41 of a device under test 4 which is a device requiring airtightness such as a compressor used in a refrigerator or a thin film forming device such as a CVD or sputtering device. The pipe 5 is branched at three places, and the first, second and third gas introduction pipes 6a, 6b and 6c are connected to the first, second and third on-off valves 7a, 7b and 7c. The pumps are respectively connected to the composite molecular pumps 31 at different compression ratios. In the present embodiment, the first gas introduction pipe line 6a is located at a position where a compression ratio of 100 to 1000 (N ₂ ) of the composite molecular pump 31 is obtained so that a minute leak of the test object 4 can be detected. It is connected. The third gas introduction pipe 6c is connected between the fore valve 32 and the rotary pump 33 at a position where a compression ratio of 150,000 (N ₂ ) is obtained. The second gas introduction pipe line 6b is connected to an intermediate position where a compression ratio of 10,000 (N ₂ ) of the composite molecular pump 31 is obtained. This enables leak detection to very small leak because the counter flow is obtained with the pressure in the mass spectrometer tube 2 can be accurately mass spectrometry can be held below 10 ^{@ 3} Pa.
[0015]
The exhaust pipe 5 is provided with a Pirani vacuum gauge 51 for detecting the pressure of the test port 41. The Pirani vacuum gauge 51 opens and closes the second and third on-off valves 7b and 7c and opens and closes the fore valve 32. Used to control and. In addition, a standard leak 71 is connected to the exhaust pipe 5 via an on-off valve 71a, and a vent valve 72 is provided. The operation of these devices is controlled by control means (not shown) provided in the leak detection device 1. The control means activates the composite molecular pump 31 and the rotary pump 33, and the gas introduction pipes 6a, 6b, The opening and closing of each of the on-off valves 7a, 7b, 7c of 6c is controlled to sequentially switch from the gas introduction line 6c having a high compression ratio to the gas introduction line 6a having a low compression ratio, and from the low sensitivity using the principle of reverse diffusion. Leak detection up to high sensitivity is possible.
[0016]
By the way, when the first gas introduction line 6a is connected to the position where the compression ratio is small as described above, the second opening / closing valve 7b is closed and the first opening / closing is performed from the second gas introduction line 6b. When the valve 7a is opened to switch to the first gas introduction pipe line 6a, the pressure at the test port 4 deviates from the range that can be accurately measured by the Pirani vacuum gauge 51. In this case, if the pressure in the mass spectrometer tube 2 rises when switching to the first gas introduction pipe line 6a, a leak test with high sensitivity is affected.
[0017]
By the way, when the leak detection is performed from low sensitivity to high sensitivity by sequentially switching from the gas introduction line 6c having a high compression ratio to the gas introduction line 6a having a low compression ratio, as shown in FIG. The background value, which is the partial pressure of helium analyzed in the above, decreases almost in proportion to the pressure decrease in the exhaust pipe 5. For this reason, in the present embodiment, this background value is used as a threshold when switching from the second gas introduction pipe 6b to the first gas introduction pipe 6a, and this background value becomes a predetermined value. In this case, it is decided to switch to the first gas introduction pipe line 6a. As a result, the control means can automatically switch to the first gas introduction line 6a so that the pressure of the mass spectrometer tube 2 does not increase, and can switch to the first gas introduction line 6a. Other high vacuum gauges such as a vacuum gauge are not required, and the cost can be reduced.
[0018]
Next, the operation of the leak detection device 1 of the present invention will be described. The rotary pump 33 and the composite molecular pump 31 are operated by the control means. In this case, the fore valve 32 and the vent valve 72 are opened, and the other valves are closed. When the start of the leak detection is instructed by the control means, the fore valve 32 and the vent valve 72 are closed, the third on-off valve 7c is opened, and the inside of the test object 4 is evacuated by the rotary pump 33. Is done. When the pressure detected by the Pirani vacuum gauge 51 reaches 1000 Pa, the fore valve 32 is opened, and a low-sensitivity leak test for detecting a large leak is started. In this case, the tester sprays helium on the test object 4 with a spray gun or the like, and when there is a leak point in the test object 4, helium that has entered through the leak point passes from the test port 41 to the third gas. The helium is introduced into the portion of the highest compression ratio of the composite molecular pump 31 through the introduction line 6c, and this helium is back-diffused through the fore valve 32 and the composite molecular pump 31 and is captured by the mass spectrometer tube 2, and leakage is confirmed. .
[0019]
When helium is not captured by the mass spectrometer tube 2 and no leakage is confirmed, the evacuation is continued as it is, and when the detection pressure of the Pirani vacuum gauge 51 reaches 100 Pa, the third opening / closing valve 7c is closed by the control means. The second on-off valve 7b is opened to switch from the third gas introduction line 6c to the second gas introduction line 6b, and a leak test with medium sensitivity is started. In this case, as described above, the tester sprays helium on the DUT 4 and, if there is a leak in the DUT 4, the helium that has entered from the leak is passed from the test port 41 to the second gas introduction pipe. The helium introduced into the composite molecular pump 31 through the passage 6b at an intermediate compression ratio is captured by the mass spectrometer tube 2, and leakage is confirmed.
[0020]
If no further leakage can be confirmed, the vacuum evacuation is continued as it is, and the background value of helium in the mass spectrometer tube 2 is set to a value at which the pressure of the mass spectrometer tube 2 does not increase even if the background gas is switched to the first gas introduction line 6a. For example, when the pressure becomes 1 × 10 ⁻¹⁰ Pa · m ³ / s, the second on-off valve 7b is closed by the control means to open the first on-off valve 7a, and the second gas introduction pipe is opened. The line 6b is switched to the first gas introduction line 6a, and a highly sensitive leak test for detecting an extremely small leak is started. In this case, in the same manner as above, the tester sprays helium on the test object 4, and if there is a leak point in the test object 4, helium that has entered from the leak point passes from the test port 41 to the first gas introduction pipe. The helium that has been introduced into the portion of the composite molecular pump 31 having the lowest compression ratio via the passage 6a and is back-diffused is captured by the mass spectrometer tube 2, and leakage is confirmed.
[0021]
In the present embodiment, a compression ratio of 100 to 1000 (N ₂ ) of the composite molecular pump 31 is obtained in the first gas introduction pipe 6 a so that a minute leak of the device under test 4 can be detected. Although connected to the position, the present invention is not limited to this. The first gas is connected to a position where a compression ratio of 100 (N ₂ ) or less is obtained, for example, as shown in FIG. The introduction conduit 6a may be connected. In this case, an extremely small leak can be detected.
[0022]
【The invention's effect】
As described above, the leak detection device of the present invention has an effect that a low-cost and high-sensitivity leak test can be performed without increasing the number of components.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating the configuration of a leak test apparatus of the present invention. FIG. 2 is a graph showing the relationship between the background value of a mass spectrometer tube and the pressure of a test port. FIG. 3 is a leak test of the present invention. FIG. 3 is a diagram schematically illustrating a modification of the configuration of the apparatus.
DESCRIPTION OF SYMBOLS 1 Leak detection device 2 Mass spectrometer tube 3 Main line 31 High vacuum exhaust unit 33 Auxiliary evacuation unit 4 DUT 41 Test port 5 Exhaust line 51 Vacuum gauge 6 Gas introduction line 7 Open / close valve

Claims (4)

An analysis tube capable of analyzing a rare gas that is a tracer gas is provided, and a main line is connected to the analysis tube, and a high vacuum exhaust unit and an auxiliary vacuum exhaust unit are provided on the back pressure side of the high vacuum exhaust unit. And
An exhaust pipe is connected to a test port connected to the device under test, and the exhaust pipe is branched at a plurality of locations. The branched gas introduction pipes have different compression ratios of a main pipe via an on-off valve. Connected to each part and configured,
By controlling the opening and closing of each on-off valve, the compression ratio of the main line is sequentially switched from the gas introduction line having a high compression ratio to the gas introduction line having a low compression ratio, and the rare gas is analyzed by the analysis tube. In a leak detection device that can detect leaks,
A leakage detection device, wherein switching of a gas introduction pipe line by controlling opening and closing of each of said on-off valves is performed based on a background value of a rare gas in said analysis pipe. The leak detection device according to claim 1, wherein the background value is a partial pressure of a rare gas being analyzed in an analysis tube. A fore valve is interposed between the high vacuum evacuation means and the auxiliary evacuation means, and a low-sensitivity gas introduction pipe is connected between the fore valve and the auxiliary evacuation means. 3. The leak detecting device according to claim 1, wherein a vacuum gauge for controlling the opening and closing of the on-off valve and the opening and closing of the fore valve provided in the exhaust pipe is provided. 4. The high-sensitivity gas introduction line having a low compression ratio of the main line is connected between the analysis tube and the high vacuum evacuation means. The leak detection device according to claim 1.

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