JP2000241289A - Helium leak tester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a helium leak tester which can perform test in a short time even when the member of a specimen itself discharges a gas significantly. SOLUTION: A specimen W composed of a resin part Wa and a non-resin part Wb and previously encapsulating helium gas as a probe gas is held while vacuum sealing the side face of the resin part Wa having high gas discharge rate with upper and lower O-rings 10. Since the resin part Wa of the specimen W separated by two O-rings 10 is not exposed to vacuum in a chamber 2, gas is not discharged from that part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helium leak test apparatus and, more particularly, to a mechanism for preventing the release of gas other than gas leaking from a test object set in a chamber during a sealing test.

[0002]

2. Description of the Related Art As a method of searching for leaks in a container or the like, there is a method in which a container to be checked is pressurized or depressurized to check whether gas actually blows out from the container or enters the container. As one of the methods, a method in which a probe gas is sealed in a test object in advance and a leak of the probe gas is detected from outside by a detector has been widely used. Helium is used as the probe gas, and only the probe gas is sensitive,
A helium leak detector is a device that incorporates a helium-specific mass spectrometer that is completely insensitive to other gases. The main reason for using helium as a probe gas is that helium is an ion with a mass number of 4 and is easy to identify, and because of its small molecular diameter it is easy to penetrate leaks, it is inert without toxic or flammable, The energy of the air is small and the exhaust is gentle even if it enters once,
It has a feature that it quickly reaches a distant place and its background is small because its content in the atmosphere is minute. FIGS. 2 and 3 show a conventional leak test apparatus using a helium leak detector. FIG. 2 shows a state in which the test object W in which helium gas has been sealed in advance is held by the O-ring 10 of the holder 16 in the vacuum vessel 14, sealed with the O-ring 11 of the lid 13, and set inside. . The test object W is only held by the O-ring 10, and the entire surface of the test object W is set in the container 14 so as to be exposed to vacuum. Then, evacuation is performed from the opening 15 of the container 14. FIG. 3 is a system diagram of a device that includes the mass spectrometer 1 and evacuates the chamber 2 to perform a leak test of the test object W set in the chamber 2. This apparatus comprises a mass spectrometer 1 for detecting only helium, a chamber 2 for accommodating a test object W, an oil rotary pump RP3 and a turbo molecular pump TMP4 for evacuating the mass spectrometer 1 and the chamber 2, and a chamber. An atmosphere opening section 5 for bringing the inside of the chamber 2 to atmospheric pressure, a Pirani vacuum gauge 8 for detecting the degree of vacuum of the vacuum system, a mass analysis section 1, a chamber 2,
A switching pipe (leak valve LV, test valve TV,
It comprises exhaust valves BV and FV and their pipes) and a control microcomputer unit (not shown) for controlling this switching pipe. Next, an outline of the operation of the above-described device will be described. Helium gas is sealed in the test object W in advance. Then, it is set in the chamber 2. The leak valve LV, the exhaust valve BV, and the test valve TV are closed, the exhaust valve FV is opened, and the power supply of the RP3 is turned on. After a predetermined time, the power of the TMP 4 is turned on, and the vacuum circuit of the mass spectrometer 1 is evacuated. It is confirmed that the mass spectrometric unit 1 is evacuated to a predetermined degree of vacuum and the indicated value falls below a certain background value. Next, close the exhaust valve FV,
The evacuation valve BV is opened, and the evacuation of the chamber 2 is started while the mass spectrometric unit 1 is kept in a vacuum. Thereafter, when the detected pressure of the Pirani vacuum gauge 8 reaches a predetermined set pressure, the exhaust valve BV is closed, the exhaust valve FV is opened, and the test valve TV is opened. As a result, the line from the chamber 2 to the mass spectrometer 1 is
And RP3, a vacuum is drawn. At this time, if there is a leak of helium from the test object W, the mass spectrometric unit 1 detects the helium and indicates the leak amount. The microcomputer unit makes a determination based on the stability of the measured value and the like, and when it is determined that the process is completed, the test valve TV is closed, and then the leak valve LV is opened. Thereby, the inside of the chamber 2 is brought to the atmospheric pressure.

[0003]

The conventional helium leak test apparatus is configured as described above. However, when a resin is adhered or molded to the test object W, the gas released from the resin is In addition, there is a problem that it takes a long time to evacuate, and it takes time to lower the background at the time of measurement after evacuation. When a resin material is used on the surface of the test object W, a large amount of gas is released therefrom, and further, it becomes a source of organic molecules and contaminates the vacuum system. Above all, those containing a plasticizer are generally a major source of pollution. For example, vinyl chloride, bakelite, acrylic, and the like must be avoided in a vacuum system for obtaining a pressure lower than 10 ⁻³ Pa. For example, in acrylic and styrene, the main component of gas release at room temperature is water vapor. In Teflon, nitrogen, carbon monoxide, carbon dioxide, and oxygen become smaller in that order. Acrylic is only carbon monoxide next to water vapor, while styrene is nitrogen, carbon monoxide, oxygen and carbon dioxide in that order. The main component of the gas emitted from the resin material is water vapor.
When the analysis is performed up to 1% or less, organic molecules are found in addition to the above-mentioned gas. Due to the release of gas from these resin materials, there is a problem that it takes a long time to evacuate and that the background does not drop easily during measurement.

The present invention has been made in view of such circumstances, and even if a resin is bonded or molded to a test object W, the helium leak is prevented from being affected by the gas released from the portion. It is intended to provide a test device.

[0005]

In order to achieve the above object, a helium leak test apparatus according to the present invention comprises: a device under test in which helium gas is previously sealed; a chamber accommodating the device under test; In a helium leak test apparatus comprising a vacuum evacuation device for evacuating the chamber and a mass spectrometer for detecting helium leaking from the device under test, sealing means for vacuum-sealing a part of the device under test in the chamber Is provided so that the sealed portion is not evacuated.

The helium leak test apparatus of the present invention is configured as described above, and a part of the test object, that is, a part which is considered to emit a large amount of gas from the member itself, for example, a resin is bonded or molded. By enclosing the part with a vacuum seal material and setting the DUT so that only that part is not evacuated, the chamber can be evacuated in a short time without being affected by gas release from that part. The background during measurement can be reduced in a short time.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a helium leak test apparatus according to the present invention will be described with reference to FIG. This apparatus is provided with a vacuum exhaust system and a mass spectrometer 1 similar to the conventional helium leak test apparatus shown in FIG. 3, but as apparent from a comparison between FIG. 1 and FIG. The method of setting the test object W set inside the device 2 is greatly different. The chamber 2 of the apparatus is a container 1 for vacuum.
4, an O-ring 11, a lid 13, a holder 12 for holding the DUT W therein, and upper and lower O-rings 10 for vacuum-sealing the side surface of the resin portion Wa of the DUT W to the holder 12. And the test object W.

The test object W shown in FIG. 1 is composed of a resin part Wa and a non-resin part Wb, and helium is sealed in advance therein as a probe gas. Since the material of the resin portion Wa of the test object W is resin, the amount of gas released from this portion is large. Therefore, in the conventional method of holding the resin portion Wa shown in FIG. 2, the surface of the resin portion Wa is exposed to the vacuum in the chamber 2, so that it takes time to evacuate due to the gas released from the portion, and the background is reduced. Level does not drop easily. On the other hand, the holding method of the device under test W of the present apparatus has a structure in which the side surfaces of the resin portion Wa are vacuum-sealed with upper and lower O-rings 10 as shown in FIG. The resin portion Wa of the device under test W separated by the two O-rings 10 is no longer exposed to the vacuum in the chamber 2, and no gas is released from this portion.

Next, a method of setting the device under test W in the chamber 2 and a leak test operation will be described with reference to FIGS. First, helium is sealed in the device under test W as a probe gas outside. Next, it is confirmed that the exhaust valve BV and the test valve TV shown in FIG.
Then, air is introduced into the chamber 2 to bring the pressure inside the chamber 2 to atmospheric pressure. Then, the lid 13 on the upper part of the chamber 2 is opened, the test object W is inserted into the holder 12 from above, and the resin portions Wa on the side surfaces of the test object W are evenly positioned on the upper and lower O-rings 10 of the holder 12. Make sure you are. Then, the lid 13 of the chamber 2 is closed via the O-ring 11.
Next, the leak valve LV is closed, the exhaust valve FV is opened, and the power of the RP3 is turned on. After a predetermined time TM
The power of P4 is turned on, and the vacuum circuit of the mass spectrometry unit 1 is evacuated. It is confirmed that the mass spectrometric unit 1 is evacuated to a predetermined degree of vacuum and the indicated value falls below a certain background value. Next, the exhaust valve FV is closed, the exhaust valve BV is opened, and the exhaust of the chamber 2 is started while the mass spectrometric unit 1 is kept in a vacuum. Thereafter, when the detected pressure of the Pirani vacuum gauge 8 reaches a predetermined set pressure, the exhaust valve BV is closed, the exhaust valve FV is opened, and the test valve TV is opened. As a result, a line from the chamber 2 to the mass spectrometry unit 1 is evacuated by the TMP 4 and the RP 3. Show. The microcomputer unit determines based on the stability of the measured value and the like, and when it is determined that the measurement is completed, the test valve TV is closed, and then the leak valve LV is opened. Thereby, the inside of the chamber 2 is brought to the atmospheric pressure.

In the above embodiment, the resin portion W of the test object W
Although the shape of “a” has been described as a cylindrical shape, the shape and the sealing method should be variously changed depending on the shape of the test object W, and the shape of the resin portion Wa and the entire shape of the test object W are taken into consideration. And then vacuum seal.

In the above embodiment, the resin portion Wa has been described. However, the present invention is not limited to the resin portion Wa. Good.

[0012]

The helium leak test apparatus of the present invention is constructed as described above, and surrounds a part of the test object, that is, a part which is considered to emit a large amount of gas from the member itself, with a vacuum sealing material. Since the device under test is set so that only that part is not evacuated, the chamber can be evacuated in a short time without being affected by outgassing from that part, and the background during measurement is short. Can be lowered in time. Therefore, the processing amount of the leak test can be increased.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a helium leak test apparatus of the present invention.

FIG. 2 is a diagram showing a conventional helium leak test device.

FIG. 3 shows a system diagram of a helium leak test apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Mass analysis part 2 ... Chamber 3 ... RP (oil rotary pump) 4 ... TMP (turbo molecular pump) 5 ... Atmosphere opening part 8 ... Pirani vacuum gauge 10 ... O-ring 11 ... O-ring 12 ... Holder 13 ... Lid 14 ... Container 15: Opening 16: Holder W: Test piece Wa: Resin part Wb: Non-resin part LV: Leak valve TV: Test valve BV: Exhaust valve BV: Exhaust valve

Claims (1)

[Claims] 1. A test object in which helium gas is previously sealed, a chamber accommodating the test object, a vacuum exhaust device for evacuating the chamber, and a helium leaking from the test object. A helium leak test apparatus comprising a mass spectrometer for detecting, wherein a sealing means for vacuum-sealing a part of the test object is provided in the chamber so that the sealed part is not evacuated. Leak test equipment.