JP3116830B2 - Helium leak detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helium leak detector used for performing a sealing inspection, a sealing inspection, and the like.

[0002]

2. Description of the Related Art A helium leak detector using a helium bombing method is one of the powerful means for performing a sealing test or a sealing test. Above all, the so-called reverse diffusion leak test method, in which only high-vacuum pump back-diffused helium is introduced into the analysis tube, can be leak-tested by introducing the minimum necessary helium into the analysis tube, and the background value of the analysis tube Is expected to be rapidly reduced, which can greatly contribute to shortening the tact time of the leak test.

A conventional apparatus for this purpose can induce a helium leak from an exhaust port of a turbo molecular pump (TMP) which is a high vacuum pump connected to an analysis tube 3 and a test object W, as shown in FIG. Test chamber 5 configured as follows
Are connected to a common oil rotary vacuum pump (RP) via valves FV and RV. With this RP, the valve RV is first closed and the valve FV is opened to exhaust the analysis tube 3. Thereafter, when a predetermined background value is obtained, the valve FV
Is closed, the valve RV is opened, and the test chamber 5 is roughed to induce a helium leak, and finally, both valves FV, RV are opened to shift to the test mode, thereby despreading the leaked helium into the TMP. Then, it is introduced into the analysis tube 3 so that the amount of helium leak from the test object W can be measured indirectly.

[0004]

However, according to the above configuration, the response time of the measured value at the time of switching from the roughing to the test does not matter, but during roughing, the exhaust port side of the TMP is in a vacuum-sealed state. Therefore, there is a concern that the background value increases due to the analysis tube 3 picking up the residual helium in the surroundings, and the contamination of the analysis tube 3 also progresses.

In order to solve such a problem, RP
A back pump for exhausting the exhaust port of the TMP,
Two roughing pumps having the same performance as that of the back pump for exhausting the test chamber 5 are provided in parallel, and the exhaust to the exhaust port of the TMP can be continued by the back pump even during the roughing. It is considered. However, in such a configuration, when the test is switched from the roughing to the test, the pumping speed is doubled by the parallel pumping of the two pumps. There is a drawback that the response time of the measured value in is extended at least twice or more.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a helium leak detector capable of effectively preventing an increase in response time of a measured value when switching from roughing to test, while having two vacuum pumps. And

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a high vacuum pump connected to an analysis tube and an exhaust port of the high vacuum pump exhausted through a first exhaust line. A back pump, a test chamber for inducing helium leak from the device under test, and a roughing pump for exhausting the test chamber through a second exhaust line, the analysis tube and the test chamber being paralleled by each of these pumps. After evacuating, the first and second exhaust lines are connected to each other so that the high vacuum pump is back-diffused from the test chamber and the amount of helium leaking into the analysis tube can be measured. The speed is set to be lower than the exhaust speed of the roughing pump.

As described above, when the test chamber and the analysis tube can be evacuated in parallel, the exhaust port side of the high vacuum pump does not become in a vacuum-sealed state during evacuation of the test chamber. An increase in the background value due to picking up and contamination of the analysis tube can be effectively avoided. Moreover, if the pumping speed of the back pump is set to a certain value and the pumping speed of the roughing pump is set to a certain value, the change in the pumping speed when switching from the roughing to the test can be suppressed to a negligible range. In addition, it is possible to prevent the response time of the measured value from increasing.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the helium leak detector includes a turbo-molecular pump (TMP) 4 as a high vacuum pump connected to the analysis tube 3 and a first oil rotary as a back pump for exhausting an exhaust port 4b of the TMP 4. The apparatus includes a vacuum pump (RP) 1, a test chamber 5 into which the device under test W is loaded, and a second oil rotary vacuum pump (RP) 2 as a roughing pump for exhausting the test chamber 5.

More specifically, the analysis tube 3 is a general one configured so that only helium can be selected from the gas existing therein and its amount can be measured.
The intake port 4a of MP4 is connected. The exhaust port 4b of the TMP 4 is connected to the intake port 1a of the RP1 disposed at the end via a first exhaust line L1 having a valve FV on the way. The test chamber 5 is configured such that a test object W filled with He is loaded therein, and helium leak can be induced from the test object W. The test chamber 5 includes a second exhaust line L2. Is detachably attached to the starting end of the connector so that the connection portion is airtight. The test chamber 5 is connected to an intake port 2a of RP2 via a second exhaust line L2 having a valve RV. Further, a portion of the second exhaust line L2 upstream of the valve RV and the first exhaust line L2
1 is connected to a portion downstream of the valve FV via an intermediate passage LM having a valve BV. Further, a valve LV for releasing the test chamber 5 to the atmosphere is provided in the intermediate system path LM. In the drawing, reference numeral 6 indicates a Pirani vacuum gauge.

In the above configuration, this embodiment is
The pumping speed of the RP1 is set smaller than the pumping speed of the RP2. As a specific example, a pump having a pumping speed of 36 L / min is used for RP1, and a pump having a pumping speed of 1300 L / min is used for RP2. Next, the procedure of the leak test in this embodiment will be described. In addition, the bold line in FIGS. 2 to 5 indicates a line where the exhaust is progressing. First, during the test standby, the valves RV, BV, LV are closed and the valve FV is opened as shown in FIG.
1, the exhaust port 4b of the TMP 4 is exhausted. TMP4
Operates while being backed up by the RP1, and evacuates the analysis tube 3 to high vacuum. If a predetermined background value is obtained in the analysis tube 3, as shown in FIG.
Only switch to open to start roughing. This allows
In parallel with the exhaust in the first exhaust line L1, R
Exhaust of the test chamber 5 through the second exhaust line L2 by P2 is started. Before starting the evacuation, it is needless to say that the test object W filled with helium is set in the test chamber 5. As the evacuation progresses, if cracks or pinholes are present in the DUT W, He having a high diffusibility leaks into the test chamber 5 through the portion, and the leaked He flows into the second exhaust line L2. Flow out to. After an appropriate time has elapsed, as shown in FIG. 4, only the valve BV is switched to the open state, and the mode shifts to the test mode. As a result, the second exhaust line L2 and the first exhaust line L1 communicate with each other, and part of He leaked to the second exhaust line L2 is reduced to the intermediate passage LM.
Through to the first exhaust line L1. And
Further, a part thereof reverse diffuses the TMP 4 and reaches the analysis tube 3, where He is detected. When the measured value is stabilized, the amount of leak from the test object W is determined based on the measured value at that time. Finally, as shown in FIG. 5, the valves BV and RV are closed and the valve LV is opened to open the test chamber 5 to the atmosphere (vent). After opening to the atmosphere, the LV is closed again to return to the state shown in FIG. At this time,
The test object W in the test chamber 5 is replaced to prepare for the next measurement.

As described above, the helium leak detector according to the present embodiment can successively perform a leak test on the device under test W. In this embodiment, the test chamber 5 is used.
And the analysis tube 3 are evacuated in parallel, so that the exhaust port 4b of the TMP 4 does not become in a vacuum-sealed state during the evacuation of the test chamber 5, and the analysis tube 3 picks up residual helium in the vicinity. An increase in the background value and contamination of the analysis tube can be effectively avoided. And RP
1 is set to be somewhat lower and the exhaust speed of RP2 is set to be higher to some extent, so that the change in the exhaust speed when switching from the roughing state shown in FIG. 3 to the test state shown in FIG. 4 can be ignored. , And the time (response time) from the start of the test to the stabilization of the measured value can be prevented from being extended at the same time. Therefore, when this leak detector is used, an excellent effect of dramatically shortening the tact time, for example, from 9 seconds to 6 seconds as compared with the related art is exerted.

FIG. 6 shows the transition of the measured value in the analysis tube 3 when the pumping speed was changed for each of RP1 and RP2. In FIG. 6, A shows 5 L / min for RP1 and 1300 L / min for RP2. min, B is 3 for RP1
6 L / min, RP2 at 1300 L / min, C: RP1 at 1300 L / min, RP2 at 1
It is the one at 300 L / min. It can be said from these measurements that if RP1 is too large, as shown in FIG. C, the response time until the measured value stabilizes due to the slowing down speed of He flowing into the analysis tube 3 after the start of the test,
Even if RP1 is too small, the amount of He flowing into the analysis tube 3 becomes excessive, so that it is difficult to stabilize the measured value at an early stage as shown in FIG. This is most desirable. As a result of various tests by the present inventors, in order to configure the exhaust system without substantially extending the response time, the exhaust speed of the RP1 was set to 25 to 45.
L / min, pumping speed of RP2 is set to 1000-20.
It became clear that setting the range of 00 L / min was effective.

In the above embodiment, an oil rotary vacuum pump is used for both the back pump and the roughing pump, but one of them may be a dry pump. Similarly, a drag pump can be used instead of the TMP as the high vacuum pump. In addition, the specific configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0015]

The helium leak detector of the present invention has the following features.
With the configuration described above, it is possible to prevent an increase in the background value and contamination of the analysis tube while shortening the tact time. As a result, excellent effects such as improvement of the throughput of the apparatus and extension of the interval time of the apparatus maintenance can be obtained.

[Brief description of the drawings]

FIG. 1 is an exhaust system diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing a procedure of a leak test.

FIG. 3 is a diagram showing a procedure of a leak test.

FIG. 4 is a diagram showing a procedure of a leak test.

FIG. 5 is a diagram showing a procedure of a leak test.

FIG. 6 is a graph showing the results of a response test performed under a plurality of conditions.

FIG. 7 is an exhaust system diagram corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Back pump (1st oil rotary vacuum pump; RP) 2 ... Roughing pump (2nd oil rotary vacuum pump; RP) 3 ... Analysis tube 4 ... High vacuum pump (turbo molecular pump; TMP) 4b ... Exhaust Mouth 5: Test chamber L1: First exhaust line L2: Second exhaust line W: Test object

Claims (1)

(57) [Claims] 1. A high vacuum pump connected to an analysis tube, a back pump for exhausting an exhaust port of the high vacuum pump through a first exhaust line, a test chamber for inducing helium leak from a test object, A roughing pump for evacuating the test chamber through a second exhaust line. The pump evacuates the analysis tube and the test chamber in parallel, and connects the first and second exhaust lines to each other. The structure is designed to measure the amount of helium leaking into the analysis tube by back-diffusion of the high vacuum pump from, and the pumping speed of the back pump is set to be smaller than the pumping speed of the roughing pump. Helium leak detector.