JP3897860B2 - Sealed leak test method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leak test method for testing a sealing effect or hermeticity of a sealed product such as a crystal resonator or a package IC.
[0002]
[Prior art]
Conventionally, a submerging method, a bombing method (dipping method), and the like are known as methods for testing the sealing effect or hermeticity of a sealed product such as a crystal resonator. In the submerged method, hot water or a heated fluorocarbon liquid is put in a water tank, the sealed product is submerged in it, the gas inside the sealed product is warmed and expanded by the liquid temperature, and it is observed that bubbles emerge from the leak location. Testing. Further, the bombing method is a leak test method using a helium leak detector also in JIS-Z2331, and a sealed product b to be tested on a bombing tank a in which a helium gas cylinder c and an exhaust device d are connected as shown in FIG. After evacuating the inside of the tank a, helium gas is filled from the cylinder c and pressurized to 5.1 × 10 ⁵ Pa for 2 hours or more. If a leak location exists in the sealed product b, helium gas enters the sealed product. Then, the pressure is released, the sealed product b is taken out, air is blown onto the surface thereof, and then it is put into the vacuum container e of the leak test apparatus provided with the exhaust device f and the helium leak detector g shown in FIG. After exhausting the inside of the vacuum vessel e by roughing by the exhaust device f, the helium gas leaking from the sealed product b is detected by the helium leak detector g to detect the leak.
[0003]
[Problems to be solved by the invention]
The leak test using the submerged method observes air bubbles coming out of the sealed product by human eyes, so it has the disadvantage of being easily overlooked and misjudged, requiring experience and a process for drying the sealed product after submersion. Become. The bombing method is mainly a method for measuring minute leaks (fine leaks), and it is difficult to manage the time for which the sealed product is left after pressurization, and there is a large leak (gross leak). In this case, the helium gas that has entered the sealed product returns to atmospheric pressure immediately after releasing the pressure, and is removed while the sealed product is left in the atmosphere or in the roughing process in the leak test device. Therefore, the gross leak product may be determined as a product that has passed the inspection.
[0004]
The present invention was created to solve the above-described disadvantages of the prior art, and an object thereof is to provide a novel test method capable of determining the presence or absence of gross leak of a sealed product using the tracer gas method. is there.
[0005]
[Means for Solving the Problems]
In the present invention, the test chamber containing the sealed product is evacuated to a vacuum, and then the tracer gas is introduced into the test chamber so as to be at or above atmospheric pressure. Gas is then infiltrated, the interior is then communicated to the atmosphere, a cleanup gas is introduced and flushed to expel the tracer gas in the room, the interior is shut off from the atmosphere, and then the cleanup gas is While exhausting the chamber from the atmospheric pressure to a vacuum, a part of the exhaust is introduced into the leak detector via the on-off valve and the orifice, and the tracer gas released from the sealed product mixed in the cleanup gas. by detecting the presence or absence of at the leak detector, by detecting the presence or absence of gross leaks of the sealed product, and so as to achieve the above object. Argon gas or helium gas is preferably used as the tracer gas, and nitrogen gas or dry air is preferably used as the cleanup gas.
Further, on the basis of the ratio of the inner volume and the test chamber of the chamber volume of the sealed products, by selecting the tracer gas in accordance with the leak level detected by the leak detector, it is possible to improve the S / N ratio.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. In the figure, reference numeral 1 denotes an airtight test chamber for containing a sealed product 2 such as a crystal resonator or a package IC and testing its sealing performance. In the test chamber 1, an atmosphere communication pipe 4 provided with a vent valve 3, a flushing valve 5, a cleanup gas introduction circuit 7 connected to a cleanup gas source 6 of nitrogen gas or dry air, and a tracer gas valve 8, helium and A tracer gas introduction circuit 10 connected to an argon tracer gas source 9, a cleanup circuit 13 connected to a cleanup pump 12 such as an oil rotary pump via a pressure reducing valve 11, and a test circuit connected to a sweep pump 15 via a test valve 14 16 were connected. A leak detector 17 is connected in the middle of the test circuit 16.
[0007]
The leak detector 17 is, for example, a reverse diffusion type in which an intake port of a turbo molecular pump 19 is connected to an analysis tube 18 for detecting tracer gas, and an exhaust port thereof is connected to an auxiliary exhaust pump 20 comprising a dry pump. Then, the middle of the test circuit 16 was connected to the turbo molecular pump 19 via a filter 21 and branched exhaust pipes 22a and 22b. One exhaust pipe 22a is provided with an open / close valve 23, and the other exhaust pipe 22b is provided with two open / close valves 24 and an orifice 25 in the middle thereof. When the test circuit 16 is at atmospheric pressure or higher, the two on-off valves 24 are opened and the orifices are opened. A leak test is performed using the other exhaust pipe 22 b having 25. When the tracer gas is present in the cleanup gas exhausted from the test chamber 1, the gas is back-diffused through the turbo molecular pump 19 and detected by the analysis tube 18, and the presence of the leak of the sealed product 2 is detected. The setting of the analysis tube 18 differs depending on the type of tracer gas, and by measuring the voltage of a voltmeter connected to the analysis tube 18, the concentration of the tracer gas diffused into the analysis tube, that is, the amount of leakage can be measured. .
[0008]
In order to perform a leak test on the sealed product 2, the sealed product 2 is placed in the test chamber 1, and first, the decompression valve 11 is opened and the cleanup pump 12 is evacuated to a vacuum of about 10 Pa. If there is a leak in the sealed product 2, the inside of the sealed product is also evacuated. Next, the pressure reducing valve 11 is closed, the tracer gas valve 8 is opened, and the inside of the test chamber 1 is filled with the tracer gas from the tracer gas source 9 of, for example, 1 atm of helium pressure or higher. If there is a leak in the sealed product 2, the inside of the sealed product 2 is depressurized to a vacuum, so that the tracer gas enters the inside. After maintaining this state for several seconds, the tracer gas valve 8 is closed, the vent valve 3 and the flushing valve 5 are opened, and the tracer gas in the test chamber 1 is flushed with a clean-up gas such as nitrogen gas or dry air. Then, these valves 3 and 5 are closed and the test valve 14 is opened. The auxiliary exhaust pump 20 and the turbo molecular pump 19 of the leak detector 17 are operated before the test valve 14 is opened, and the inside of the analysis tube 18 is previously exhausted to a high vacuum so that the tracer gas in the cleanup gas can be detected. When the test valve 14 is opened and the sweep pump 15 is operated to evacuate the test chamber 1 at atmospheric pressure to a vacuum, a part of the exhaust is turbocharged through the two on-off valves 24 and the orifice 25. When the tracer gas is introduced into the molecular pump 19 and exhausted, the turbo molecular pump 19 is back-diffused and detected in the analysis tube 18. As described above, when there is a gross leak in the sealed product 2, the tracer gas that has entered the inside is released when the inside of the test chamber 1 is at atmospheric pressure or slightly lower than that, but in the method of the present invention, Since the tracer gas can be detected from the atmospheric pressure state after the flushing while the sealed product 2 is stored in the test chamber 1, the gross leak can be accurately checked. After the test is completed, the test valve 14 is closed, the vent valve 3 is opened, the inside of the test chamber 1 is brought to atmospheric pressure, and the sealed product 2 is taken out.
[0009]
Specific leak test results according to the method of the present invention are shown in FIGS. The sealed product 2 in this case was a quartz resonator having a volume of 5 c.c, and helium was used as a tracer gas and maintained at atmospheric pressure for 2 seconds. Also, dry air was used as the cleanup gas. As a result, in the non-defective product with no leak, as shown in FIG. 4, the helium concentration measured by the analysis tube 18 gradually decreased and became constant after ten seconds, but in the defective product having a gross leak of a hole with a diameter of 0.1 mm. The concentration increased all at once when the sweep pump 15 started to generate a differential pressure due to the pressure reduction after about 3 seconds in the test chamber 1, and the gross leak was reliably detected.
[0010]
When nitrogen gas that does not contain components of the tracer gas such as helium or argon is used as the cleanup gas, it is possible to detect with a good S / N ratio with a sharp detection peak. Further, the S / N ratio becomes better as the sweep pump having a higher ultimate vacuum is used. The level of measurement varies greatly depending on the relationship between the internal volume of the sealed product 2 and the chamber volume of the test chamber 1, and helium is used when the internal volume / chamber volume value is 1% or less, and argon is used when the value is higher. It is advantageous. Helium may be used for all leak tests if the running cost allows. The S / N ratio can also be improved by reducing the dead volume of the test chamber 1. For example, when the internal volume is 5 c.c and the chamber volume is 100 c.c, the concentration of the tracer gas released into the test chamber 1 is about 5%. The S / N ratio at that time is a comparison with air-containing components. Since helium is 5 ppm and argon is 1% in the atmosphere, it is approximately 10,000 for helium and 5 for argon. Therefore, the tracer gas may be selected in accordance with the level of leak to be detected. In addition, as a sealed product that needs to be tested for gross leak, there are a fishing lure, a package of food and medicine, a battery, etc., and the method of the present invention can test these sealed products in a short time without missing the gross leak. .
[0011]
【The invention's effect】
According to the present invention as described above, by a test chamber that contains the sealed product by introducing a tracer gas into the test chamber after evacuating to a vacuum to above atmospheric pressure, when there is a leak in the sealed product Then , tracer gas is allowed to enter the sealed product, and then the room is communicated with the atmosphere to introduce a cleanup gas, flushing is performed, the tracer gas in the room is expelled, and the room is shut off from the atmosphere. From the atmospheric state after the upgas introduction, the interior of the chamber is evacuated to a part of the exhaust through the on-off valve and the orifice to the leak detector, and the sealed product mixed in the cleanup gas since the presence or absence of tracer gas emitted detected by said leak detector, perform a reliable leak test, not miss gross leaks of the sealed product in one test chamber, a short period of time To complete the test, the effect of such that can improve the test can productivity without requiring experience leak test.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a conventional bombing method bombing apparatus. FIG. 2 is an explanatory diagram of a leak test apparatus used in the conventional bombing method. FIG. 3 is an explanatory diagram of an embodiment of the present invention. Fig. 5 is a measurement diagram of a leak test of a normal sealed product according to the method of the invention.
1 Test chamber 2 Sealed product 6 Cleanup gas source 9 Tracer gas source 15 Sweep pump 16 Test circuit 17 Leak detector 18 Analysis tube 25 Orifice

Claims (3)

The test chamber that contains the sealed product by introducing a tracer gas into the test chamber after evacuating to a vacuum by the above atmospheric pressure, is entering the tracer gas in the enclosed article when there is a leak in the sealed product ,
Next, the room is communicated with the atmosphere, a cleanup gas is introduced and flushed to expel the tracer gas in the room, and then the room is shut off from the atmosphere.
Subsequently, from the atmospheric pressure state after the introduction of the cleanup gas, while exhausting the chamber to a vacuum, a part of the exhaust is introduced to the leak detector via the on-off valve and the orifice,
A leak test of a sealed product characterized by detecting the presence or absence of a gross leak in the sealed product by detecting the presence or absence of a tracer gas released from the sealed product mixed in the cleanup gas with the leak detector Method. Before SL using argon gas or helium gas as a tracer gas, before Symbol leak testing method of sealing article of claim 1 wherein the clean-up gas, characterized in that using nitrogen gas or dry air. The leak of the sealed product according to claim 1, wherein the tracer gas is selected in accordance with a leak level detected by the leak detector based on a ratio between an internal volume of the sealed product and a chamber volume of the test chamber. Test method.

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