JP2001050852A - Sniffer probe and gas leak testing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sniffer probe and gas leak testing method using the same whereby, if the scan speed varies or the defect-probe distance is long, the detecting limit (min. detectable value) of He leakage can be improved. SOLUTION: The sniffer probe 11a has a gas intake hole 12 at the top of a gas intake pipe and a handle 13 at the base. The gas intake pipe has a cylindrical cover 15 surrounding the gas intake 12 hole with its closed base end fixed to the gas intake pipe and its open base end surrounding the gas intake hole 12. The top end of the cylindrical cover 15 is made flush with the gas intake hole end whereby, if the gap between a sample under test and the gas intake hole 12 is about 10 mm, a leaking gas can be detected accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sniffer probe and a gas leak test method using the same.

[0002]

2. Description of the Related Art A gas leak test by a sniffer method is often employed for defect inspection of a device requiring airtightness (hereinafter referred to as a "test object") such as a compressor of a refrigerator and a radiator of an automobile.

In the sniffer method (suction method), a probe gas is introduced into a test object and pressurized. Almost only helium gas is used as the probe gas. Generally, a mixed gas of helium gas and air or the like is used, but hereinafter, it will be described as helium gas for convenience.

The helium gas leaked outside from the leak location of the test object is sucked by a sniffer probe, and helium is detected by a helium leak detector (JIS Z2).
331 "Helium leak test method").

FIG. 6 is a configuration diagram showing an example of a conventional leak detector. The inside of the DUT 1 is pressurized with helium gas. Since the helium gas leaks to the outside if there is a leak portion 1a, the helium gas is sucked by the sniffer probe 2, and the helium gas is detected by the leak detector 3a connected to the sniffer probe 2.

The leak detector 3 a reversely diffuses the helium gas sucked by the sniffer probe 2 so as to flow to the mass spectrometer tube 4.

That is, most of the helium gas sucked by the sniffer probe 2 is exhausted by the rotary pump 6 and a part of the helium gas is diffused back into the mass analysis tube 4 from the exhaust port of the turbo molecular pump 5 as a secondary pump. . Mass spectrometer tube 4
A magnetic deflection type mass spectrometer or a quadrupole type mass spectrometer is used. Reference numeral 8 is a roughing valve, reference numeral 9 is a fore valve, and reference numeral 10 is a test valve.

The helium gas that reaches the mass spectrometer tube 4 by back-diffusing the turbo molecular pump 5 is ionized by an electron beam from a filament in the ion chamber.
The released helium ions fly in a circular orbit determined by mass, magnetic intensity, and flight speed. In the ion collector installed according to the trajectory of helium ions,
Only helium ions are collected and amplified by an ion current amplifier and detected in the form of current.

However, the sniffer method has the following problems. A test object for detecting a gas leak by the sniffer method generally has a complicated shape. When the outer surface of the DUT has irregularities, it is difficult to bring the sniffer probe close to the outer surface of the DUT, and the leak cannot be detected unless the suction amount is increased. However, when detecting minute gas leaks, high sensitivity cannot be detected unless the suction amount is reduced.

As described above, the suction amount of the sniffer probe and the minimum detectable value (sensitivity) are mutually contradictory items.
Increasing the suction amount increases the minimum detectable value. If it is desired to reduce the minimum detectable value, the suction amount must be reduced.

As one of such measures, Japanese Patent Laid-Open No.
JP-A-145835 proposes, as shown in FIG. 7, a sniffer helium leak detector 3b provided with a pressure gauge 7 for measuring a pressure in a connection pipe between a turbo molecular pump 5 and a rotary pump 6. ing. According to the publication, such a helium leak detector 3b
Then, the foreline pressure Pf of the turbo-molecular pump 5 is measured by the pressure gauge 7 and the helium ion current I _He is measured, whereby the output of the pressure gauge 7 and the ions detected by the mass spectrometer tube 4 of the helium leak detector 3b are measured. It is described that the amount of leakage can be calculated by means for calculating the amount of leakage from the current value irrespective of the amount of suction of the sniffer probe.

[0012]

However, the technology disclosed in Japanese Patent Application Laid-Open No. 8-145835 has the following problems.

The sniffer helium leak detector 3b is configured such that the pumping speed of the rotary pump, the sensitivity of the mass spectrometer tube, and the compression ratio of the turbo molecular pump to helium gas are substantially constant within the range used by the helium leak detector 3b. The amount of leakage is calculated from the output of the pressure gauge 7 and the ion current value detected by the mass spectrometer tube 4 of the helium leak detector 3b using a relational expression.

However, in the leak test of the DUT by the sniffer helium leak detector 3b, the leak amount is generally suctioned by scanning a defective portion, and when a small gas leak is detected with high sensitivity. In addition, not only the amount of suction but also a change in the scanning speed of the probe and a change in the distance between the defect and the probe are major factors that affect the detection accuracy.

Therefore, in the technique disclosed in Japanese Patent Application Laid-Open No. 8-145835, it may be difficult to detect a small gas leak with high sensitivity in a leak test in which the scanning speed of the probe changes.

The present invention has been made to solve the above-mentioned problems, and the detection limit (for the helium gas leakage) can be obtained even when the scanning speed is changed or the distance between the defective portion and the probe is large. An object of the present invention is to provide a sniffer probe capable of improving the minimum detectable value and a gas leak test method using the same.

[0017]

According to a first aspect of the present invention, there is provided a probe for use in a sniffer method, wherein a cover surrounding a suction port of the probe is attached. Sniffer probe.

Further, the invention of claim 2 of the present application is a gas leak test method using a probe gas leak detector using a sniffer probe, in which a probe gas is introduced into a test object and pressurized, and the test sample is pressurized. A gas leak test method using a sniffer probe, wherein a probe gas leaking outside from a leak location of the probe is sucked by a sniffer probe having a cover surrounding the suction port, and the probe gas is detected by a probe gas leak detector. It is.

According to the present invention, the gas leak detection limit (hereinafter referred to as the minimum detectable value) can be improved by a simple structure in which the suction port of the sniffer probe is simply surrounded by the cover.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the sniffer probe of the present invention. Sniffer probe 1
In 1a, a gas suction port 12 is provided at a distal end of a gas suction pipe, and a handle 13 is provided at a base end side of the gas suction pipe. The gas suction pipe is provided with a cylindrical cover 15 surrounding the gas suction port 12. This cylindrical cover 15
The closed base end is fixed to the gas suction pipe, and the open distal end surrounds the gas suction port 12. A tube 14 connected to the detector body is provided at the base end of the gas suction pipe.
Is attached.

It is preferable that the distance between the test object and the gas inlet 12 of the sniffer probe 11b is 3 mm or less for the test. However, even if the distance cannot be set, the gas inlet 12 is closed by the cylindrical cover 15 in the present invention. Since the gas leaking from the defective portion can be collected inside the cylindrical cover 15, the minimum value at which gas leakage can be detected is improved.

The tip of the cylindrical cover 15 and the gas inlet are located at approximately the same position, and the device under test and the gas inlet 12 are positioned.
The leaked gas can be detected with high accuracy even if the distance between them becomes about 10 mm.

The cylindrical cover 15 is a cylindrical acrylic resin cover (for example, when the diameter of the gas suction port is 5 mm, the inner diameter of the cross section is 3 cm and the length is 5 cm).

The shape of the cover is not limited to a cylindrical shape, and a conical gabber having an enlarged end can be used.

The dimensions such as the cross-sectional diameter can also be appropriately selected. FIG. 2 is a perspective view showing another embodiment according to the present invention. 1 are given the same reference numerals, and a part of the description is omitted.

In this example, instead of the cylindrical cover of FIG.
A conical gabber 19 having an enlarged diameter at the end surrounding the gas inlet 12 is provided.

According to the sniffer probe 11b of this example, even if it is difficult to approach the defect of the test object, the gas leaking from the defect can be collected in the conical gabber 19, so that the gas leakage It is possible to improve the minimum detection value.

Next, a helium gas leak test method using a helium gas leak detector using the sniffer probe of the present invention will be described in detail.

Helium gas leak test method is JIS Z2
331 is performed in accordance with “Helium leak test method”.

Helium gas is introduced into the test object and pressurized. When helium gas leaks from the test object to the outside, a sniffer probe with a cover surrounding the suction port is approached to the leaked location, the leaked helium gas is sucked, and the helium gas is leaked by the helium gas leak detector. To detect.

As for the detection method, as is generally known, helium gas reaching the mass spectrometer tube of the leak detector is ionized by an electron beam from a filament in an ion chamber. The released helium ions fly in a circular orbit determined by mass, magnetic intensity, and flight speed. Only helium ions are collected by an ion collector installed in accordance with the trajectory of the helium ions, and are amplified by an ion current amplifier and detected in the form of current.

The test object is an airtight device such as a compressor of a refrigerator or a radiator of an automobile.

Conventionally, a sniffer probe is used to perform a gas leak test on a test object with the distance between the suction port and the test object being 3 mm or less. However, in the present invention, under normal test conditions, at a predetermined scanning speed, Even if the distance between the suction port and the subject is 3 mm or more (for example, 10 mm), a gas leak test can be performed with good detection accuracy.

Therefore, according to the method of the present invention, the detection limit (minimum detectable value) for helium leakage can be improved even when the scanning speed changes or when the distance between the defective portion and the probe is large. .

FIG. 3 is a conceptual diagram showing an experimental example using the sniffer probe of the present invention. In this example, an experiment was performed using the sniffer probe 11a shown in FIG.
In this experiment, a cylindrical experimental vacuum vessel 16 capable of introducing and exhausting helium gas was used as a test object.
The experimental vessel 16 was provided with a pseudo defect portion 16a, a pressure sensor 17 was installed, and the experimental vessel 16 was filled with helium gas at a desired pressure and concentration. Helium gas is a mixture of air and nitrogen.

Thereafter, the sniffer probe 11a is set at a desired distance from the pseudo defect portion 16a, and the pseudo defect portion 16a is scanned at a desired speed.
Helium gas leaked from a was detected by the detector 18. As a comparative example, an experiment was performed using a sniffer probe without a cover, under the same conditions except that the cover was not mounted. The test results are shown in FIGS.

FIG. 4 shows the relationship between the minimum detectable value and the scanning speed of the sniffer probe when the sniffer probe of the present invention and the sniffer probe of the comparative example are used.

The main experimental conditions in this experimental example are as follows. Detector / defect distance = 5 mm, pseudo defect diameter = 5 μm,
Pseudo defect depth = 13 μm, He gas concentration = 20%, He
Gas pressure 150 mbar According to the results of FIG. 4, when the sniffer probe equipped with the cover according to the present invention was used, any scan speed (with respect to the case where the sniffer probe without the cover according to the comparative example was used) was used. m / min), the minimum detectable value could be reduced and improved.

That is, in the present invention, the minimum detectable value was reduced by about 3 × 10 ⁻⁵ [torrl / s] as compared with the comparative example, and the detection accuracy was improved.

FIG. 5 shows the relationship between the minimum detectable value and the scanning speed of the sniffer probe in another example of the sniffer probe according to the present invention and the sniffer probe according to the comparative example.

The detector / defect distance was set to 10 mm, and the other conditions were the same as those in FIG. According to the results of FIG. 5, when the sniffer probe 11a with the cover according to the present invention is used, the minimum detectable value is about 5 × as compared with the case where the sniffer probe without the cover according to the comparative example is used. 10 ^-5 [torr l / s] was reduced, and the detection accuracy was improved.

An experiment as shown in FIG. 3 was performed using the sniffer probe shown in FIG. 2, and as a result, similar to the sniffer probe shown in FIG. 1, the minimum detectable value was lower than that of the comparative example without gabber. About 3-5 × 10 ^-5 [torr
1 / s], and the detection accuracy has improved.

[0044]

According to the present invention, the structure of the sniffer probe can be easily improved so that even if the scanning speed is changed or the distance between the defective portion and the probe is large, the structure can be improved.
The detection limit (minimum detectable value) for helium leakage can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a sniffer probe according to the present invention.

FIG. 2 is a perspective view showing another embodiment of the sniffer probe according to the present invention.

FIG. 3 is a conceptual diagram showing an experimental example using sniffer probes of the present invention and a comparative example.

FIG. 4 is a graph showing a relationship between a minimum detectable value and a scanning speed in one detection example obtained in the experiment of FIG. 3;

FIG. 5 is a graph showing a relationship between a minimum detectable value and a scanning speed in another detection example obtained in the experiment of FIG. 3;

FIG. 6 is a configuration diagram illustrating an example of a conventional leak detector.

FIG. 7 is a configuration diagram showing another example of a conventional leak detector.

[Explanation of symbols]

 11a, 11b Sniffer Probe 12 Gas Inlet 13 Handle 14 Tube 15 Cylindrical Cover 16 Laboratory Vessel 16a Pseudo-Defective Part 17 Pressure Sensor 18 Helium Leak Detector 19 Conical Cover

Claims (2)

[Claims] 1. A sniffer probe for use in the sniffer method, wherein a cover surrounding a suction port of the probe is attached. 2. A gas leak test method using a probe gas leak detector using a sniffer probe, wherein a probe gas is introduced into a test object and pressurized.
A gas using a sniffer probe, wherein a probe gas leaking outside from a leak portion of the test piece is sucked by a sniffer probe provided with a cover surrounding a suction port, and the probe gas is detected by a probe gas leak detector. Leak test method.