JP4130968B2 - Leak detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses rare gas helium as a tracer gas, for example, to detect gas leaks in devices requiring airtightness such as compressors used in refrigerators, thin film forming devices such as CVD and sputtering devices, etc. The present invention relates to a leak detection device.
[0002]
[Prior art]
In this type of leakage detection device, it is desired that leakage detection of a large volume of a test object can be started in a short time, that detection sensitivity is high, and that the reaction rate is high. Therefore, a test port connected to the device under test is connected to the analysis tube capable of detecting helium with a main pipeline with a composite molecular pump composed of a turbo molecular pump and a drag pump and a rotary pump on the back pressure side. An exhaust pipe is connected to the pipe, the exhaust pipe is branched at three locations, and the branched first, second, and third gas introduction pipes are connected to the first, second, and third on-off valves. There is known a structure in which the composite molecular pump is connected to a portion having a different compression ratio via the above (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 that can obtain a low compression ratio, and can detect leaks with high sensitivity. Further, the third gas introduction line is connected to the position of the highest compression ratio of the complex molecular pump via the fore valve, and the second gas introduction line is connected to the position of the intermediate compression ratio. Yes. And in order to control opening and closing of each on-off valve provided in this fore valve and each gas introduction pipe line, a Pirani vacuum gauge is provided in the exhaust pipe line, and according to the detected pressure of the Pirani vacuum gauge, each gas introduction pipe line Leak detection from low sensitivity to high sensitivity using the principle of reverse diffusion while controlling the opening and closing of each on-off valve and switching sequentially from gas introduction pipe with high compression ratio of main pipe to gas introduction pipe with low compression ratio To be able to.
[0004]
By the way, in recent leak tests, there are many requests for detecting minute leaks in the device under test. In the above-described structure is located approximately 10 ⁴ compression ratio to air on-off valve, also for substantially the entire helium introduced from the first gas inlet pipe is not intended to reach the analyzer tube, the test object If the leakage of water is very small, helium may not be detected by the analysis tube. In order to detect helium leaks by increasing the sensitivity of detection of helium, a high-sensitivity gas introduction line should be connected between a position where the compression ratio of the complex molecular pump is lower, for example, between the analysis tube and the complex 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 it is in the range up to several Pa that the Pirani gauge can stably measure the pressure, as described above, when a high-sensitivity gas introduction conduit is connected to a position where the compression ratio is lower, this 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 inlet tube, the leak test will be affected, so it is necessary to accurately grasp the pressure in the exhaust pipe. In this case, it may be possible to separately provide a vacuum gauge such as an ionization vacuum gauge that can measure the pressure in the high vacuum region in addition to the Pirani vacuum gauge, but this increases the number of parts and increases the cost. The problem of inviting arises.
[0007]
In view of the above, the present invention has an object to provide a leak detection apparatus that can perform a leak test with high sensitivity at low cost without increasing the number of components.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, a leak detection apparatus of the present invention includes an analysis tube capable of analyzing a rare gas that is a tracer gas, and a main line is connected to the analysis pipe, and a high vacuum exhaust is provided to the main line. And an auxiliary vacuum exhaust means on the back pressure side of the high vacuum exhaust means, 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 gas introduction pipelines are connected to the locations where the compression ratios of the main pipelines are different via the on-off valves, respectively, and the on-off valves are controlled to open and close, so that the gas introduction pipelines with a high compression ratio of the main pipelines In a leak detection device that can detect a leak of a device under test by sequentially switching to a gas introduction pipe having a low compression ratio and analyzing a rare gas in the analysis pipe, the gas by controlling the opening and closing of each on-off valve The introduction pipe is switched by the analysis pipe. And performing based on the partial pressure of the definitive noble gas.
[0009]
According to the present invention, since the switching of the gas introduction line by the control of each on-off valve is performed based on the background value of the rare gas measured in the analysis pipe, the pressure in the exhaust line is detected. Even without this, it is possible to switch to a high-sensitivity gas introduction line 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]
The background value may be, for example, the partial pressure of a rare gas analyzed by an analysis tube.
[0011]
In addition, a fore valve is interposed between the high vacuum evacuation means and the auxiliary vacuum evacuation means, and a low-sensitivity gas introduction conduit is connected between the fore valve and the auxiliary vacuum 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 pipe line is provided in the exhaust pipe line, the gas introduction pipe line with a high compression ratio of the main pipe line is changed to a gas introduction pipe line with a 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 pipe having a low compression ratio of the main pipe is connected between the analysis pipe and the high vacuum evacuation means, it is possible to detect a very small leak of the test object. Sensitivity leakage test is possible.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, reference numeral 1 denotes a leak detection apparatus according to the present invention, which can detect leaks of instruments using, for example, helium as a tracer gas. The leak detection device 1 has a mass spectrometer tube 2. This mass spectrometer tube 2 is of a known quadrupole type or magnetic field deflection type and detects helium ions. The mass analysis tube 2 is connected to a main molecular line 3 provided with a complex molecular pump 31 that is a high vacuum exhaust means and a rotary pump 33 that is an auxiliary vacuum exhaust means on the back pressure side via a forevalve 32. The inside of the tube 2 is maintained at a predetermined pressure or lower (≦ ¹⁰⁻² Pa). The complex molecular pump 31 has a known structure, and has a turbo molecular pump and a drag pump built in a pump casing having a connection portion to the main pipeline 3. The auxiliary vacuum exhaust means may be a membrane pump or the like.
[0014]
On the other hand, for example, 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, a thin film forming apparatus such as a CVD or sputtering apparatus, and the like. The pipe 5 is branched at three locations, and the branched first, second and third gas introduction pipes 6a, 6b and 6c connect the first, second and third on-off valves 7a, 7b and 7c. And are connected to different positions of the composite molecular pump 31 at different compression ratios. In the present embodiment, the first gas introduction pipe 6a is located at a position where a compression ratio of 100 to 1000 (N ₂ ) of the complex molecular pump 31 is obtained so that minute leakage of the DUT 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 150000 (N ₂ ) is obtained. The second gas introduction pipe 6b is connected to an intermediate position where a compression ratio of 10000 (N ₂ ) of the complex molecular pump 31 is obtained. As a result, the pressure in the mass spectrometer tube 2 can be maintained at 10 ⁻³ Pa or less, and mass analysis can be performed accurately, and a counter flow can be obtained, so that even a very small leak can be detected.
[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. In addition, a standard leak 71 is connected to the exhaust pipe line 5 via an on-off valve 71a, and a vent valve 72 is provided. The operation of these devices is controlled by a control means (not shown) provided in the leak detection device 1, and the composite molecular pump 31 and the rotary pump 33 are operated by the control means, and the gas introduction pipes 6 a, 6 b, 6c controls the opening and closing of each on-off valve 7a, 7b, 7c, and switches from the gas introduction pipe 6c having a high compression ratio to the gas introduction pipe 6a having a low compression ratio, while using the principle of reverse diffusion to reduce the sensitivity. 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 gas introduction line 6b is connected to the first opening / closing line. The pressure of the test port 4 when the valve 7 a is opened and switched to the first gas introduction pipe 6 a deviates from the range in which the Pirani vacuum gauge 51 can accurately measure the pressure. In this case, if the pressure in the mass spectrometer tube 2 is increased when switching to the first gas introduction line 6a, a highly sensitive leak test is affected.
[0017]
By the way, when leak detection is performed from low sensitivity to high sensitivity by sequentially switching from the gas introduction pipe 6c having a high compression ratio to the gas introduction pipe 6a having a low compression ratio, for example, as shown in FIG. The background value, which is the partial pressure of helium analyzed in (1), decreases substantially in proportion to the pressure drop in the exhaust pipe 5. Therefore, in the present embodiment, this background value is used as a threshold value when switching from the second gas introduction line 6b to the first gas introduction line 6a, and this background value becomes a predetermined value. In this case, the first gas introduction pipe 6a is switched. 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 the switching to the first gas introduction line 6a is possible. Other high-vacuum gauges such as a vacuum gauge are not necessary and can be made at low cost.
[0018]
Next, the operation of the leak detection apparatus 1 of the present invention will be described. The rotary pump 33 and the complex 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 leakage 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 DUT 4 is evacuated by the rotary pump 33. Is done. When the pressure detected by the Pirani 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 DUT 4 with a spray gun or the like, and if the DUT 4 has a leaked portion, the helium that has entered through the leaked portion passes from the test port 41 to the third gas. The helium is introduced into the portion of the composite molecular pump 31 having the highest compression ratio through the introduction pipe 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 to confirm leakage. .
[0019]
When helium is not captured by the mass spectrometer tube 2 and no leakage can be confirmed, evacuation is continued as it is, and when the detected pressure of the Pirani vacuum gauge 51 reaches 100 Pa, the control unit closes the third on-off valve 7c. The second on-off valve 7b is opened and switched from the third gas introduction line 6c to the second gas introduction line 6b, and a medium sensitivity leak test is started. In this case, in the same manner as described above, when the tester sprays helium on the DUT 4 and there is a leaked part in the DUT 4, helium that has entered from the leaked part passes from the test port 41 to the second gas introduction pipe. Helium introduced into the intermediate compression ratio portion of the complex molecular pump 31 via the path 6b and back-diffused is captured by the mass spectrometer tube 2 and leakage is confirmed.
[0020]
When no further leaks can be confirmed, evacuation is continued as it is, and the background value of helium in the mass spectrometer tube 2 is a value at which the pressure of the mass spectrometer tube 2 does not increase even if the helium background value is switched to the first gas introduction line 6a. For example, when the pressure reaches 1 × ¹⁰⁻¹⁰ Pa · m ³ / s, the control unit closes the second on-off valve 7b to open the first on-off valve 7a, and the second gas introduction pipe The line 6b is switched to the first gas introduction line 6a, and a highly sensitive leak test for detecting extremely small leaks is started. In this case, in the same manner as described above, when the tester sprays helium on the DUT 4 and there is a leaked part in the DUT 4, helium that has entered from the leaked part passes from the test port 41 to the first gas introduction pipe. Helium introduced into the portion of the lowest compression ratio of the complex molecular pump 31 via the path 6a and back-diffused helium 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 complex molecular pump 31 is obtained so that the first gas introduction pipe 6a can detect minute leakage of the DUT 4. However, the present invention is not limited to this, and the first gas is located at a position where a compression ratio of 100 (N ₂ ) or less is obtained, for example, at a position where the compression ratio becomes zero as shown in FIG. The introduction pipe line 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 leak test with high sensitivity can be performed at low cost without increasing the number of parts.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating the configuration of a leak test apparatus according to the present invention. FIG. 2 is a graph showing the relationship between the background value of a mass spectrometer tube and the pressure at a test port. FIG. 6 is a diagram schematically illustrating a modification of the device configuration.
DESCRIPTION OF SYMBOLS 1 Leak detection apparatus 2 Mass spectrometer tube 3 Main pipe 31 High vacuum exhaust means 33 Auxiliary vacuum exhaust means 4 Test object 41 Test port 5 Exhaust pipe 51 Vacuum gauge 6 Gas introduction pipe 7 On-off valve

Claims (3)

An analysis tube capable of analyzing a rare gas which is a tracer gas is provided. A main pipe is connected to the analysis pipe, and a high vacuum evacuation means is connected to the main pipe, and an auxiliary vacuum evacuation means is provided on the back pressure side of the high vacuum evacuation means. Provided,
The exhaust pipe is connected to the test port connected to the device under test, the exhaust pipe is branched at a plurality of locations, and the branched gas introduction pipe is connected to the main pipe through a switching valve with different compression ratios. Connected to each location,
Control the opening and closing of each on-off valve, and sequentially switch from a gas introduction line with a high compression ratio of the main line to a gas introduction line with a low compression ratio, and analyze the noble gas in the analysis tube. In a leak detection device that can detect leaks,
A leak detection apparatus characterized in that switching of a gas introduction line by controlling opening and closing of each on-off valve is performed based on a partial pressure of a rare gas in the analysis pipe. A fore valve is interposed between the high vacuum exhaust means and the auxiliary vacuum exhaust means, and a low-sensitivity gas introduction pipe is connected between the fore valve and the auxiliary vacuum exhaust means. 2. The leak detection 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 is provided in the exhaust pipe. 3. The leak detection device according to claim 1 , wherein a high-sensitivity gas introduction pipe having a low compression ratio of the main pipe is connected between the analysis pipe and the high vacuum exhaust means.

Images