JPH0732537U - Leak detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a leak detector provided with a liquid nitrogen trap that does not malfunction when replenishing liquid nitrogen. [Structure] A tubular liquid nitrogen trap is attached in an inclined manner, and an expiration sensor is attached to its tip via an elastic tube, and the elastic tube is bent to the upper side of the inclined liquid nitrogen trap. , Do not touch the liquid nitrogen supplied by the expiration sensor.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a leak detector that detects the presence or absence of a leak by detecting a probe gas leaking from the DUT in a vacuum pipe to which the DUT is connected.

[0002]

[Prior art]

 Leak detectors that use helium gas as a probe gas are used as an effective means when searching for small holes in various items and for performing sealing inspections of containers that require high airtightness such as semiconductor devices. Has been done.

As a conventional example of such a leak detector, there is one having a piping circuit as shown in FIG. In this device, an object to be measured is connected via a valve RV to an exhaust system path L formed by an oil rotary vacuum pump RP1 as a roughing pump. A high vacuum exhaust system path M connected to the intake port of a turbo molecular pump TMP as a high vacuum pump is connected to the exhaust system path L via a second valve TV and a liquid nitrogen trap TR. An oil rotary pump RP2 as an auxiliary pump is connected to the exhaust port side of the turbo molecular pump TMP. An analysis tube AN (for example, a mass spectroscope) that branches off from the high-vacuum exhaust system path M or branches off at the liquid nitrogen trap TR as shown in FIG. It is attached.

When performing a leak test with this apparatus, first, the valve RV is opened and vacuum exhaust is performed by the roughing pump RP1, and when a predetermined pressure is reached, the valve RV is closed and the valve TV is opened instead. High-vacuum exhaust is performed by the turbo molecular pump TMP. When high vacuum evacuation is completed, the valve AV is opened and the analysis tube AN is communicated. Then, for example, by blowing helium gas around the object to be measured, if there is a hole (leak) in which helium enters the object to be measured, helium will enter through this hole, and the invading helium molecule will be detected by the analysis tube AN. It is detected and the existence of leak can be determined.

In order to improve the sensitivity of such a leak detector, it is effective to increase the ultimate vacuum of the pipe. In other words, the high vacuum makes it possible to reduce the absolute number of various gas molecules that are noise sources, and it becomes possible to measure the leak signal in a state where the background level is low. Therefore, as a means to raise the ultimate vacuum, a liquid nitrogen trap is connected to the pipe to adsorb water molecules and the like existing in the pipe.

As the liquid nitrogen trap used for the leak detector, a double metal tube having a bottomed inner cylinder and an outer bottomed cylinder sealed by a lid portion opposite to the bottom is used. In this, the space between the inner cylinder and the outer cylinder has a sealed structure, and the exhaust system passage of the leak detector is connected by a flange so as to communicate with this sealed space portion. There is a liquid nitrogen introduction hole in the lid part, and by pouring liquid nitrogen into the inside of the bottomed cylinder from here, the inner cylinder surface is cooled to the liquid nitrogen temperature so that an adsorption action occurs.

This liquid nitrogen trap is installed in the leak detector so that the axial line of the tubular shape is vertical so that the liquid nitrogen can be stored in the inner cylinder as much as possible.

[0008]

[Problems to be solved by the device]

 The liquid nitrogen trap used for the conventional leak detector is equipped with a liquid nitrogen empty sensor that indicates that the remaining amount of liquid nitrogen is low, and displays or alerts the operator when it is empty to alert the operator. There are things I do.

When the measurer knows that the remaining amount of liquid nitrogen is small by such a sensor, the liquid nitrogen is replenished. How much liquid nitrogen is in the liquid nitrogen trap during this replenishment work? I couldn't understand it, so it sometimes overflowed, and the liquid nitrogen that overflowed could cause burns.

In order to prevent the liquid nitrogen from overflowing, it is effective to provide a full amount sensor in the liquid nitrogen trap for notifying the full state of the liquid nitrogen. It was difficult to always operate correctly because the nitrogen would come into contact with the full sensor and malfunction.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a leak detector provided with a full sensor that does not malfunction when replenishing liquid nitrogen.

[0012]

[Means for Solving the Problems]

 The leak detector of the present invention, which has been made to solve the above problems, has a pipe to be evacuated by an exhaust system, in which the DUT and the analysis tube are connected, and the probe gas leaking from the DUT is transferred to the analysis tube. In the leak detector to be detected by inserting it into the liquid nitrogen trap through the liquid nitrogen trap connected to the pipe with the axis inclined at a predetermined angle from the vertical line, and the liquid nitrogen inlet provided on the upper side of the liquid nitrogen trap. An elastic tube tube and a liquid nitrogen sensor attached near the tip of the elastic tube tube are provided to detect the full state of liquid nitrogen.

Hereinafter, how the present invention works will be described.

[0014]

[Action]

 In the leak detector of the present invention, the cylindrical liquid nitrogen trap is installed with an inclination, and the full sensor is inserted into the liquid nitrogen trap by the elastic tube tube. At this time, the elastic tube is bent at a predetermined angle so that it will not come into contact with liquid nitrogen when supplying liquid nitrogen. That is, since the cylindrical liquid nitrogen trap is installed with an inclination, when liquid nitrogen is replenished, the liquid nitrogen that flows in flows along the surface directly below the side surface of the liquid nitrogen trap. By bending it right above the other side, it is possible to prevent the liquid nitrogen from hitting the sensor during liquid nitrogen replenishment. Therefore, it can be made to work properly when the liquid nitrogen is really full. Also, since the liquid nitrogen sensor is supported by the elastic tube, when inserting the sensor into the liquid nitrogen trap from the liquid nitrogen introduction hole, make sure that the vicinity of the tip where the sensor is attached is folded back 180 degrees. After being inserted into the liquid nitrogen trap by passing through the introduction hole, it is bent at an appropriate angle (about 90 degrees) by the elastic restoring force of the tube and can be easily installed at the intended position.

[0015]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a leak detector showing an embodiment according to the present invention, and FIG. 2 is a sectional view of a liquid nitrogen trap which is a main part thereof. In the figure, 10 is a leak detector, which is connected to the object to be measured at a connection port 11. The pipe 12 and subsequent pipes connected to the connection port 11 are similar to the pipe circuit shown in the conventional example of FIG. However, as shown in FIG. 1, the liquid nitrogen trap 13 has a bottomed cylindrical shape including an inner cylinder 13a, an outer cylinder 13b, and a lid 13c, and its axial direction is inclined at about 45 degrees from the vertical direction. There is. The lid portion 13c is provided with a liquid nitrogen introduction hole 14, and liquid nitrogen is supplied from this hole. Further, two elastic tube pipes 16 are inserted into the liquid nitrogen trap from the liquid nitrogen introduction hole 14, one of which has a full sensor 17 at the tip and the other has an empty sensor 18 at the tip. Is attached. The full-volume sensor 17 and the empty-volume sensor 18 are connected to an external control device via the connector 15 by wiring that passes through the elastic tube tube 16.

Next, the operation of this configuration will be described. When the empty volume sensor 18 informs that the remaining amount of liquid nitrogen is low or has disappeared, the measurer replenishes the liquid nitrogen through the liquid nitrogen introduction hole 14 in order to replenish the liquid nitrogen. The liquid nitrogen is poured from the liquid nitrogen introducing hole 14 by, for example, a funnel, but the liquid nitrogen that has passed through the liquid nitrogen introducing hole 14 flows and accumulates on the lower surface (D) side of the inner cylinder 13a due to gravity. At this time, since it is attached on the lower surface (D) side of the space sensor 18 and near the bottom surface, the liquid nitrogen is immediately touched to inform that the space is no longer empty.

On the other hand, since the full amount sensor 17 is bent toward the upper surface (U) side of the inner cylinder 13a, it does not touch the liquid nitrogen at the time of replenishing the liquid nitrogen, so it does not emit a signal indicating the full amount. Absent. Only when the liquid nitrogen is sufficiently replenished and the liquid surface actually reaches the position of the full sensor 17, the full signal is issued. Therefore, liquid nitrogen will not come into contact with the full sensor and malfunction. By stopping the replenishment when the full sensor issues a signal, the work can be performed safely without causing the liquid nitrogen to overflow.

When the full sensor 17 is mounted in the liquid nitrogen trap, the elastic tube 16 is folded back and passed through the liquid nitrogen introducing hole 14 so that it is not inserted into the liquid nitrogen trap. The elastic tube returns to an appropriate angle (about 90 degrees) by its elastic restoring force, and the full quantity sensor 17 can be easily installed at a desired position.

[0020]

[Effect of device]

 As described above, according to the present invention, since the full sensor can be installed at a position where liquid nitrogen is not touched when introducing liquid nitrogen, malfunction does not occur due to touching liquid nitrogen during introduction, It is possible to accurately determine the full state.

Further, since the elastic tube can be easily installed toward the upper side of the inner cylinder by simply folding back the elastic tube at the time of mounting, it is not necessary to use a special jig.

[Brief description of drawings]

FIG. 1 is a perspective view of a leak detector according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a liquid nitrogen trap which is an essential part of the present invention.

FIG. 3 is a piping circuit diagram of a conventional leak detector and a leak detector of the present invention.

[Explanation of symbols]

 10: Leak Detector 12: Piping 13: Liquid Nitrogen Trap 13a: Inner Cylinder 13b: Outer Cylinder 13c: Lid 14: Liquid Nitrogen Inlet 16: Elastic Tube 17: Full Sensor

Claims (1)

[Scope of utility model registration request] 1. In a leak detector in which an object to be measured and an analysis tube are connected to a pipe which is evacuated by an exhaust system, and a probe gas leaking from the object to be measured is detected by the analysis tube, an axis line is determined from a vertical line. A liquid nitrogen trap connected to the pipe in a tilted state, an elastic tube pipe inserted into the liquid nitrogen trap through a liquid nitrogen introduction hole provided on the upper side of the liquid nitrogen trap, and a tip end of the elastic tube pipe A leak detector, comprising a liquid nitrogen sensor attached to, and a liquid nitrogen sensor for detecting a full state of liquid nitrogen.