JPH0453558Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a rapid leak detection device for checking for leaks in articles that require airtightness, such as ICs, crystal oscillators, and water thermometers.

(Prior Art) Conventionally, as shown in Fig. 1, a rapid leak detection device has been used, for example, as shown in Fig. 1. It is known that the device is composed of a vacuum pump b consisting of a rotary pump and a helium leak detector c that detects helium gas released from a helium leak test product in a vacuum chamber a evacuated by the vacuum pump b. .

The helium leak detector c includes a vacuum pump e consisting of an oil rotary pump connected to the vacuum chamber a via a roughing valve d, and a throttle valve f, a liquid nitrogen trap g, and an oil diffusion pump connected to the vacuum chamber a. It is constructed by providing a vacuum pump i consisting of an oil rotary pump connected via h, and a mass spectrometry tube j connected to the liquid nitrogen trap g. k, k are Penning vacuum gauges, l, l are vent valves, m is standard helium leak valve, n
indicates a main drawing valve, and O indicates a rough drawing valve.

In the apparatus shown in FIG. 1, first, the inside of a vacuum chamber a containing a leak test product is evacuated by a vacuum pump b by opening a roughing valve O. The exhaust pressure is detected by a Penning vacuum gauge k, and when the inside of the vacuum chamber a is sufficiently exhausted, the rough evacuation valve O is closed and the main evacuation valve n is opened. As a result, part of the gas in the vacuum chamber a is exhausted by the oil diffusion pump h via the slot valve f and the liquid nitrogen trap g, and the remaining gas is used for detection of helium gas in the analysis tube j. be done.

The airtightness of the leak test product is determined by the amount of helium gas detected in the analysis tube j, and since the test product is placed in a vacuum, the determination can be made in a short time.

(Problems to be solved by the invention) The conventional rapid leak detection device described above detects a helium leak amount ranging from several Torr·l/sec to 10 ^-8 ~
Although it has become a wide range of 10 ^-11 Torr・l/sec,
If there is a leakage amount exceeding this range, the helium gas sealed or pressurized into the test product may escape during rough evacuation, and the remaining amount may be small at the time of the leak test. Even though there was a large amount of leakage, it was determined that there was only a small amount of leakage, or that there was almost no leakage, and a defective product was sometimes mistakenly determined to be a non-defective product.

The object of the present invention is to provide a rapid leak detection device that detects helium gas during rough evacuation and eliminates the above-mentioned erroneous determination.

(Means for solving the problem) In the present invention, a vacuum chamber containing a leak test product is provided with a vacuum pump that roughly evacuates the inside of the chamber, and a vacuum pump that roughly evacuates the inside of the vacuum chamber, and a vacuum pump that roughly evacuates the inside of the chamber and a vacuum chamber that contains the leak test product. In a device that is connected to a leak detector for detecting gas, the vacuum chamber is further provided with an oil rotary pump for rough evacuation of the inside thereof, and an oil rotary pump is connected to the leak detector at the exhaust port of the oil rotary pump. The above problem was solved by attaching a sniffer gun and a vacuum pump for differential evacuation that were connected to each other.

(Function) A leak test product is placed in a vacuum chamber, and its interior is first roughly evacuated using an oil rotary pump and a vacuum pump for differential pumping, and then connected to another vacuum pump for sufficient rough evacuation. Exhaust. Then, the inside of the vacuum chamber is connected to a leak detector to detect leakage of gas such as helium gas from the leak test product. In this case, if there is a large gas leak from the leak test product, most of the gas will be exhausted during rough evacuation and no gas leak will be detected during the leak test. Since the leak detector can detect the leak during rough evacuation using the sniffer gun, there is no misunderstanding whether the leak test product is good or bad.

(Example) An example of the present invention will be described with reference to Fig. 2. In the figure, reference numeral 1 denotes a vacuum chamber for accommodating a leak test product such as an IC molded with helium gas sealed therein. The vacuum chamber 1 is composed of a cover 1a which is moved up and down by an air cylinder 2 for lifting and a fixed base 1b, and an O-ring is attached to the pressing surface of the cover 1a so as to press the cover 1a against the base 1b in an airtight manner. 3 denotes a vacuum pump consisting of an oil rotary pump connected to the vacuum chamber 1 via a roughing valve 4, 5 denotes a helium leak detector connected to the vacuum chamber 1 via a main evacuation valve 6, and 7 denotes a Pirani vacuum gauge. The leak detector 5 has the same structure as that shown in Fig. 1, and is equipped with a mass spectrometer tube for detecting gas leaking from the leak test product.

The above configuration is similar to the conventional rapid leak detection device shown in FIG. A sniffer gun 10 such as a needle type sniffer gun 10 connected to a helium leak detector 5 and a vacuum pump 11 such as an oil rotary pump for differential pumping are attached to the exhaust port of the leak test product. Now detected. 12 is a variable leak valve provided in the circuit 13 connecting the sniffer gun 10 and the helium leak detector 5;
4 and 15 are a Pirani vacuum gauge and a test valve provided in the circuit 13. Further, 16 and 17 are vent valves. The helium leak detector 5 has a detection configuration that checks for leakage by ionizing He gas using thermionic electrons from the filament and detecting this ion current, and this detection part has a temperature of 10 ^-4 to ^{10 -5} Torr. If you don't operate it, the filament will burn out. Since the exhaust side of the vacuum chamber 1 and the oil rotary pump 9 are at atmospheric pressure to 10 ^-2 Torr, the leak detector 5 cannot be directly connected to these. Therefore, the front stage of the variable leak valve 12 provided in the circuit 13 is connected to the leak detector 5 by lowering the pressure of this part with a vacuum pump 11 for differential pumping. If only the vacuum pressure inside the leak detector 5 is to be maintained, the variable leak valve 12 may be throttled down, but this will reduce the amount of gas passing through the valve 12 and reduce the amount of gas inside the vacuum chamber 1.
It is undesirable that it takes too much time for the He gas to reach the leak detector 5, so if the differential pumping is performed using the vacuum pump 11 as described above, the gas reaches the leak detector 5 in a short time. Differential evacuation here refers to evacuation using multiple evacuation lines to maintain different pressures in each part of the vacuum system.
The vacuum pump 11 is used for differential pumping to maintain the pressure in the circuit 13 lower than the pressure in the vacuum chamber 1 evacuated by the oil rotary pump 9.

To explain its operation, the leak test product is placed in the vacuum chamber 1, the oil rotary pump 9 and the vacuum pump 11 are operated, and the roughing valve 8 is opened. When a large amount of helium gas leaks from the leak test product, helium is ejected from the exhaust port of the oil rotary pump 9, and a portion of it is further pumped into the sniffer gun 1 by the action of the vacuum pump 11 for differential pumping.
0 through the variable leak valve 12 and the test valve 15 to the helium leak detector 5, where leakage of helium gas is detected. During this time, the suction pressure of the sniffer gun 10 is monitored with the Pirani vacuum gauge 14, and the suction pressure of the sniffer gun 10 is monitored.
Make sure that a constant flow rate is always being drawn into the 0.

If no major gas leakage is found from the test product in the above steps, close the roughing valve 8, open the roughing valve 4, and exhaust the air with the vacuum pump 3.
When the pressure of the Pirani vacuum gauge 7 reaches the predetermined pressure, the roughing valve 4 is closed and the main pulling valve 6 is opened.
The helium leak detector 5 detects minute leaks from the test product in the same way as conventional ones.

When the test is completed, the main pull valve 6 is closed, the vent valve 16 is opened to introduce the atmosphere into the vacuum chamber 1, the cover 1a is raised by the cylinder 2, and the leak test product is taken out. Note that when Ar gas or H ₂ gas is sealed in the leak test product, an Ar gas or H ₂ gas leak detector is used.

(Effects of the invention) As described above, according to the invention, an oil rotary pump is provided in the vacuum chamber of the rapid leak detection device in addition to the conventional vacuum pump for rough evacuation, and the oil rotary pump is connected to the exhaust port of the oil rotary pump. By installing a sniffer gun connected to the leak detector and a vacuum pump for differential pumping, it is possible to reliably detect large gas leaks in leak test products, eliminating the conventional inconvenience of misidentifying defective products as non-defective products. There are effects such as being able to do it.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional example, and FIG. 2 is an explanatory diagram of an embodiment of the present invention. 1... Vacuum chamber, 4... Vacuum pump, 5
... Helium leak detector, 9 ... Oil rotary pump, 10 ... Sniffer gun, 11 ... Vacuum pump.

Claims (1)

[Scope of utility model registration request] A vacuum chamber containing a leak test product is connected to a vacuum pump that roughly evacuates the inside of the chamber, and a leak detector that detects gas released from the leak test product after the vacuum pump roughly evacuates the chamber. In the vacuum chamber, an oil rotary pump for rough evacuation of the inside of the vacuum chamber is further provided, and a sniffer gun connected to the leak detector and a vacuum pump for differential pumping are connected to the exhaust port of the oil rotary pump. A rapid leak detection device characterized by being installed.