Quick collection, several common methods of using helium mass spectrometer leak detection to teach you

At present, electronic product supervision and inspection departments, manufacturers widely use helium mass spectrometry leak detector for product quality supervision, and have established their own standards and methods. In the electrical and electronic industry, according to the requirements of different products for sealing, spray method, suction method and pressure method and other leak detection methods are used.

Quick collection, several common methods of using helium mass spectrometer leak detection to teach you

1, blowing method leak detection

The leak detection method is to connect the tested part to the detection port of the leak detector, and use the spray gun to continuously spray tracer gas into the suspected leak hole, and the tracer gas enters the leak detector through the leak hole and is detected. The shell of electronic device, high voltage switch tube, zinc oxide, lightning arrester, etc., should adopt this method for leak detection.

Depending on the product, it is necessary to choose different sizes of fixtures or auxiliary tools such as tube shell leak detection. After the leak detector works normally, the leakage rate can be calibrated with the standard leak hole, and the tube shell can be sprayed for leak detection. The fixture is fixed at the leak detection port first, and the tube shell to be measured is placed on the rubber plate above the fixture. The auxiliary pumping system will pump it to the predetermined vacuum and then automatically connect it to the measuring system of the instrument. Then, a spray gun is used to continuously spray helium into the shell, usually for 1 to 3 seconds. When there is a leak hole in the shell, helium will enter the mass spectrometry part of the instrument through the leak hole, and the leakage amount will be directly displayed on the leakage rate meter. This method can not only determine the position of the leak hole but also measure the size of the leak hole. The entire inspection cycle takes only one minute.

Quick collection, several common methods of using helium mass spectrometer leak detection to teach you

2, suction method leak detection

The suction leak detection method is contrary to the injection leak detection method. The suction gun is connected to the detection port of the leak detector, and the tested part is filled with the tracer gas under the specified pressure. The helium leaking out of the leak hole is detected by the suction gun leak detector.

It is not economical for large containers or containers with large internal discharge pipes to do spray gun leak detection, and the leak detection speed is slow, generally adopt suction gun leak detection. At present, there is no mature method and standard for leak detection of large containers in the electronic watch industry. For large containers such as high-voltage capacitors, the key to quality control depends on welding technology, and the supervision means of air tightness adopts bubble leak detection, so the rejection rate is controlled in a few thousand.

Before leak detection, it is necessary to calibrate the suction gun sensitivity of the instrument, and then fill the container with helium gas higher than one atmosphere. Some containers are thin-plate structures, it is recommended to make fixtures outside the container to prevent deformation and damage to the device during high pressure. When the suction gun moves along the weld, the speed should not be too fast, leaving about 1mm from the surface to ensure the suction sensitivity, and the probe will be better shaped into a horn mouth. At present, the leak detection results of such large electrical devices show that their leakage rate is generally in the range of 10-6 ~ 10-7Pa.m3/S.

We believe that with the widespread and in-depth use of helium mass spectrometry leak detectors in this field, the industry’s leak detection standards and methods will soon be established.

Quick collection, several common methods of using helium mass spectrometer leak detection to teach you

3, back pressure method leak detection

Back pressure leak detection method is to put the tracer gas under a certain pressure into the leak detection fixture, and then connect to the leak detector to pump it out, the tracer gas leaks out through the leak hole, and the total leakage is detected by the leak detector.

Small electronic devices should adopt this leak detection method. First, the instrument is adjusted well, and then the device is put into a pressurized tank and pressed into helium. Helium enters the device with a leak hole, and the device without a leak hole only absorbs helium on the surface. The device pressure and time are determined according to GB2423, 2328 documents. After the device is removed from the pressurized tank, the helium attached to the surface is blown off and then pumped into the leak detection fixture. After the vacuum is pumped to the set value, the fixture is automatically connected to the measuring system of the instrument. At this time, the helium gas pressed into the inside of the device with a leak hole leaks out and is detected, and its leakage rate is shown on the leakage rate meter.

Helium test by back pressure

Quick collection, several common methods of using helium mass spectrometer leak detection to teach you

Generally, the back pressure method is used to detect leaks. Put a certain number of devices in the fixture, the total leakage rate of this batch does not exceed the predetermined value of scrap, indicating that this batch is qualified; If the total leakage rate exceeds the predetermined value of scrap, half can be taken out, and the remaining half will continue to detect the leak. The qualification of this half indicates that the device with leakage is in the half that is taken out, and the leak is detected until the device with leakage is detected.

This method of leak detection can sometimes be missed. This is because those devices with large leaky holes are drained of helium before being placed in the leak detector fixture, so a rough inspection of the device is usually required before the back pressure method is used for leak detection.

No matter which method of leak detection is used, the operator is required to have the ability to observe carefully and a high sense of responsibility, because false detection and missing detection will cause losses, and the operator’s alertness and proficiency in discovering unknown things is also very important.