Vacuum leak detector and method with spray-on membrane test leak

Abstract

A vacuum leak detector with improved test leak and corresponding leak detection method is provided. The vacuum leak detector 10 of the present invention comprises a housing 14 containing a suction space 12, a vacuum pump 20 for evacuating the suction space 12, and a gas detector 18 connected to the suction space 12. The housing 14 is provided with a test leak 26 that includes a membrane 32 having selective gas permeability and connects the outside air of the housing 14 to the suction space 12.

Description

[Technical field]

[0001] The present invention relates to a vacuum leak detector with a test leak and a method for testing the functionality of the leak detector. [Background technology]

[0002] Leak detectors capable of detecting leaks using test gases are used to check the tightness of test objects and to detect leaks in test objects using the test gas vacuum method. Examples of test objects include vacuum furnaces, semiconductor industry manufacturing systems equipped with vacuum chambers, various pipelines and other chambers.

[0003] For leak testing, the test specimen is evacuated. This can be done by an exhaust system connected to the test specimen or by a separate exhaust system at the leak detector. The leak detector has a built-in test gas detector, e.g. a mass spectrometer, capable of detecting the test gas. Examples of test gases are helium, forming gas (95% nitrogen + 5% hydrogen), etc.

[0004] During a leak test, a test gas is sprayed onto the area to be tested (e.g., flange seal, weld seam, etc.) from the outside air side of the test specimen. If a leakage path exists at the sprayed area, the test gas will flow through the leakage path together with the outside air into the vacuum chamber and then into the vacuum system. At this time, the test gas can be detected by a detection system (e.g., a mass spectrometer, etc.). The signal strength is a measure of the leak rate, and the location of the leak can be determined from the sprayed area, time, and the temporal correlation of the signal response.

[0005] If a leak exists, a signal response occurs when the leak point is sprayed. If no signal occurs when the test gas is sprayed, the test object is tight.

[0006] In the above leak inspection method, when various types of failures occur, no signal response occurs, making it impossible to distinguish between a test object that is actually sealed and a test object that is not sealed. When there is an abnormality in the sensitivity of the detection system, no signal response occurs. In addition, when the valve of the spray gas source is operating but the test gas does not flow from the spray gas source, no signal response occurs even if there is a leak.

[0007] Typically, the vacuum system is flanged with a known leak point for checking the functionality of the test system. Typically, such a predefined leak point is provided by a so-called capillary leak. This test leak as capillary leak is dimensioned such that when it is sprayed, it gives a clear signal response from the detection system. However, the capillary must be small enough so that the vacuum system and the test specimen are not adversely affected by the constant inflow of air. For this reason, such a capillary leak is dimensioned with a flow path diameter of only a few micrometers. As a result, this test leak point can become clogged by particles or condensed air moisture. As a result, a functional test system appears to fail due to a blocked spray capillary leak.

[0008] WO 2006 / 120122 A1 (Patent Document 1) describes a sniffer leak detector with a quartz window sensor at the test gas inlet. No test leak is provided in this document. Typically, in sniffer leak detectors of the type described in WO 2006 / 120122 A1, a capillary leak is used as the test leak, and a reference gas or test gas that flows out from the test leak into the outside air is sucked in and detected by a so-called sniffer probe. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2006 / 120122 Summary of the Invention [Problem to be solved by the invention]

[0010] Against this background, it is an object of the present invention to provide a vacuum leak detector with an improved test leak and enable a corresponding leak detection method. [Means for solving the problem]

[0011] The vacuum leak detector of the present invention is defined by the features of claim 1. The leak detection method of the present invention is defined by the features of claim 11.

[0012] In the present invention, a housing containing a suction space of a vacuum leak detector, the housing being connected to a vacuum pump for evacuating the suction space and a gas detector connected to the suction space, is provided with a test leak including a membrane having selective gas permeability and connecting the suction space with the outside air of the housing. When a test gas is sprayed onto the test leak after the suction space is evacuated by the vacuum pump, the test gas selectively passes through the membrane into the suction space, while air or outside air from the outside of the vacuum leak detector is blocked by the membrane. The test gas that has entered the suction space through the membrane is detected by the gas detector. The membrane of the present invention makes it possible to determine whether the measurement signal of the test gas measured by the gas detector corresponds to the measurement signal expected if the vacuum leak detector is functioning without restrictions. In this way, the functionality of the vacuum leak detector can be easily tested by the present invention. Additionally, the blowing gas source used to apply the test gas is checked to ensure that it is functioning properly, i.e., providing sufficient amounts of the desired type of test gas.

[0013] The test leak may be configured as a blow-on leak that selectively guides a test gas blown onto the test leak from the outside into the suction space via the membrane while blocking gases different from the test gas.

[0014] The membrane of the test leak may include or consist of quartz, which is selectively permeable to helium, neon or hydrogen. Alternatively or additionally, the membrane may include or consist of palladium, which is selectively permeable to hydrogen, and / or silver, which is selectively permeable to oxygen.

[0015] The membrane material may be configured as thin-walled closed tubes, for example in the form of Glass fingers.

[0016] A heater may be provided for heating the membrane, and the material of the membrane may be configured to selectively conduct or block the test gas depending on the temperature.

[0017] The membrane may have a layer thickness of a few micrometers, preferably about 100 μm or less.

[0018] The test leak may include a flange-type holder for the membrane, the flange-type holder being inserted into an opening in the housing. Preferably, the outside and / or the inside of the holder may be covered with a protective grid.

[0019] The test leak may have a selective gas permeable membrane or a plurality of flow paths each closed by the membrane. In this case, the membrane may be attached to a membrane chip, preferably a membrane chip having a thickness of less than 1 centimeter, more preferably less than 1 millimeter. The membrane chip has a window configured as a flow path covered by the membrane and penetrating the entire membrane chip, whereby the end of the flow path is covered by the membrane, the flow path having a diameter of about 10 μm to about 1000 μm. In this case, preferably, the membrane seals the outside air side of the flow path so that water vapor or dust particles from the outside do not enter the flow path, i.e., covers the end of the flow path opposite to the suction space.

[0020] In one embodiment, the membrane may be attached to a membrane chip, preferably less than 1 mm thick, with at least one membrane window covered by the membrane, preferably supported by an open pore porous structure such as a grid or porous solid material to support and stabilize the membrane.

[0021] The vacuum system of the leak detector is provided with a selective gas inlet, which is realized by a membrane that is airtight or substantially impermeable to the outside air. In this way, the vacuum system is less susceptible to the absence of test gas. When test gas is sprayed onto the spray-on membrane leak, it penetrates through the membrane into the vacuum system and is detected there by a detection system, thus verifying the functionality of the entire system (detection system) and the spray-on test gas source.

[0022] Depending on the test gas used, a suitable membrane material can be selected: - If helium is to be selectively introduced, quartz is used. ●If hydrogen (a component of forming gas) is to be selectively introduced, palladium is used. ●If oxygen is to be selectively introduced, silver is used.

[0023] The material may be configured as a thin-walled closed tube (glass finger). In such an example, the material must be heated so that the diffusion rate of the gas within the separation layer is fast enough. If configured as a thin membrane, a few micrometers thick, the membrane may be used at room temperature and still provide a fast enough response.

[0024] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 illustrates a first embodiment. [Diagram 2] FIG. 2 is a detailed view of FIG. [Diagram 3] FIG. 3 is a detailed view of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The illustrated vacuum leak detector 10 includes a housing 14 that contains an suction space 12. The suction space 12 is connected in gas communication with a gas detector 18 and a vacuum pump 20 via a vacuum line 16. The housing 14 has a test gas inlet 22. A test gas to be tested is sucked into the suction space 12 from the outside 24 of the housing 14 through the test gas inlet 22 and analyzed by the gas detector 18.

[0027] In order to be able to check the functionality of the vacuum leak detector 10, the housing 14 is provided with a test leak 26 that completely covers the opening of the housing 14. The exploded view of FIG. 2 shows the details of the test leak 26. The test leak 26 includes a flange-type holder 28 that fits over the entire opening of the housing 14 and seals it. In this embodiment, the holder 28 is configured as a disk-shaped body with a recess 30 formed in the center. A hole is formed at the bottom of the recess 30 through the holder 28. A selectively gas-permeable membrane is inserted into the recess 30 as a membrane tip 32 that hermetically seals the entire hole at the bottom of the recess 30. The membrane 32 is selectively gas-permeable to a certain type of gas and blocks all other types of gas.

[0028] Both the upper side of the holder 28 facing the exterior 24 and the lower side of the holder 28 facing the suction space 12 are covered with a protective grid, which completely covers the recess 30 with the membrane 32 and the hole which is closed by the membrane 32. Both protective grids 34 are screwed to the holder 28 by means of a threaded connection.

[0029] FIG. 3 shows the construction of the membrane 32 in detail. That is, the membrane 32 is configured as a quartz membrane chip and has about 50 holes 36 in the center formed as channels passing through the entire membrane chip 32, which are arranged in an equally spaced grid. Each hole 36 is closed by a quartz membrane having a thickness of about 10 μm. The membrane chip 32 has a thickness of about 0.6 mm. Each hole 36 constitutes a quartz window that is selectively permeable to helium at a membrane temperature of about 25° C., while not allowing other gases contained in air to pass through the membrane 32. Besides helium, only neon and hydrogen permeate the quartz, but to a much smaller extent than helium. That is, they can basically also be used as test gases when using a blown leak equipped with a quartz membrane.

[0030] The protective grid 34 protects the membrane tip 32 from direct contact with a spray gun 38, for example when the spray gun 38 sprays helium 40 into the test leak 26 in the direction of the arrow in Fig. 1. Furthermore, the protective grid 34 on the underside of the holder 28, i.e. on the side facing the suction space 12, protects the membrane tip 32 and the vacuum system in case of breakage or if individual pieces of the membrane window would be sucked in by the vacuum pump 20.

Claims

1. A vacuum leak detector (10) comprising a housing (14) containing a suction space (12), a vacuum pump (20) for evacuating the suction space (12), and a gas detector (18) connected to the suction space (12), A vacuum leak detector (10), characterized in that the housing (14) is provided with a test leak (26) including a membrane (32) having selective gas permeability and connecting the outside atmosphere of the housing (14) with the suction space (12).

2. 2. A vacuum leak detector (10) as described in claim 1, characterized in that the test leak (26) is configured as a spray leak that selectively guides a test gas sprayed onto the test leak (26) from the outside into the suction space (12) through the membrane (32) while blocking gases other than the test gas.

3. 2. The vacuum leak detector (10) of claim 1, characterized in that the membrane (32) of the test leak (26) is made of quartz, which is selectively permeable to helium, neon or hydrogen, and / or palladium, which is selectively permeable to hydrogen, and / or silver, which is selectively permeable to oxygen.

4. 2. A vacuum leak detector (10) according to claim 1, characterized in that the material of the membrane (32) is formed as a thin-walled closed tube, for example in the form of a glass finger.

5. 2. The vacuum leak detector (10) of claim 1, further comprising a heater for heating the membrane (32), the membrane being made of a material that selectively conducts or blocks electricity depending on temperature.

6. 2. A vacuum leak detector (10) according to claim 1, characterized in that the membrane (32) has a layer thickness of a few micrometers, preferably less than 100 μm.

7. 2. The vacuum leak detector (10) of claim 1, characterized in that the test leak (26) includes a flange-type holder (28) for the membrane (32), the flange-type holder (28) being inserted into an opening in the housing (14), and preferably the outside and / or inside of the holder being covered with a protective grid (34).

8. 2. The vacuum leak detector (10) of claim 1, wherein the test leak (26) has a selectively gas-permeable membrane (32) or a plurality of flow paths closed by the membrane (32).

9. 2. A vacuum leak detector (10) as described in claim 1, characterized in that the membrane (32) is attached to a membrane chip, preferably a membrane chip having a thickness of less than 1 cm or less than 1 mm, and the membrane chip has at least one membrane window configured as a flow path covered by the membrane (32) and each passing through the entire membrane chip, whereby the ends of the flow paths are covered by the membrane (32), the flow path having a diameter of between about 10 μm and about 1000 μm.

10. 2. A vacuum leak detector (10) as described in claim 1, characterized in that the membrane (32) is attached to a membrane chip having at least one membrane window covered by the membrane (32) and supported by an open-pore porous structure, preferably a membrane chip having a thickness of less than 1 mm.

11. A method for testing the functionality of a vacuum leak detector (10) according to any one of claims 1 to 10, comprising: - evacuating the suction space (12) by means of the vacuum pump; - spraying the test leak (26) with a test gas, whereby the test gas selectively passes through the membrane (32) into the inside of the suction space (12), while air or ambient air from the outside (24) of the vacuum leak detector (10) is blocked by the membrane (32); - detecting the test gas that has passed through the membrane (32) into the suction space (12) with the gas detector (18); - determining whether the measurement signal of the gas detector (18) corresponds to the measurement signal expected in the case of a problem-free functioning of the vacuum leak detector (10); A method comprising:

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