In the electrical and electronic industries, leak detection methods such as blowing, suction, and pressurization are often used according to the sealing requirements of different products.

1. Spray method for leak detection

Spray method leak detection is to connect the tested part to the detection port of the leak detector, and use a spray gun to continuously spray tracer gas into the suspicious leak hole. The tracer gas enters the leak detector through the leak hole and is detected. This method should be used for leak detection of electronic device casings, high-voltage switch tubes, zinc oxide, lightning arresters, etc.

Depending on the product, different sizes of fixtures or auxiliary tools such as leak detection for pipe shells need to be selected. After the leak detector works normally, the leakage rate can be calibrated using standard leak holes to perform spray leak detection on the pipe shell. First, fix the fixture at the leak detection port, and place the tested pipe shell on the rubber plate on top of the fixture. The auxiliary suction system will draw it to the predetermined vacuum and automatically connect it to the measurement system of the instrument. Then use a spray gun to continuously spray helium gas onto the casing for 1-3 seconds. When there is a leak in the casing, the helium gas will enter the mass spectrometry analysis section of the instrument through the leak, and the leak amount will be directly displayed on the leak rate table. This method can determine the location of the leak and measure its size. The entire testing cycle only takes one minute.

2. Inhalation method for leak detection

Inhalation leak detection is the opposite of spray leak detection. The suction gun is connected to the detection port of the leak detector, and the tested object is filled with tracer gas at a specified pressure. Helium gas leaked from the leak hole is sucked into the leak detector by the suction gun for detection. It is not economical to use a spray gun for leak detection in large containers or containers with large internal vent pipes, and the leak detection speed is slow. Generally, a suction gun is used for leak detection. At present, there is no mature method and standard for leak detection of large containers in the electronic watch industry. For example, for large containers such as high-voltage capacitors, the key to quality control relies on welding technology, and the supervision of airtightness uses bubble leak detection, so the scrap rate is controlled at a few thousandths.

Before leak detection, it is necessary to calibrate the sensitivity of the suction gun of the instrument, and then fill the container with helium gas at a pressure higher than one atmosphere. Some containers are thin plate structures, and it is recommended to use fixtures outside the container to prevent deformation and damage to the components under high pressure. When the suction gun moves along the weld seam, the speed should not be too fast and should be about 1mm away from the surface to ensure suction sensitivity. It is better to make the probe into a horn shape for better effect. At present, the leak detection results of such large electrical components indicate that their leakage rate is generally within the range of 10-6 to 10-7Pa.m3/S.

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

3. Back pressure method for leak detection

The back pressure method for leak detection is to place the tested object under a certain pressure of tracer gas into a leak detection fixture, and then connect it to a leak detector to evacuate it. The tracer gas leaks out through the leak hole, and the total leakage amount is detected by the leak detector.

This leak detection method is suitable for small electronic devices. Firstly, adjust the instrument, then place the device into a pressurized tank and inject helium gas. Helium gas enters the interior of the device with leaks, while the device without leaks only absorbs helium gas on the surface. The pressurization pressure and time of the device are determined according to the GB24232328 document. After the device is removed from the pressurization tank, the helium gas adsorbed on the surface is blown off and then placed in the leak detection fixture for vacuuming. After the vacuum is drawn to the set value, the fixture is automatically connected to the measurement system of the instrument. At this point, the helium gas inside the leak hole device leaked out and was detected, and its leakage rate was displayed on the leakage rate meter. The exclusion method is generally used for back pressure leak detection. Place a certain number of components in the fixture, and if the total leakage rate of this batch does not exceed the predetermined scrap value, it indicates that this batch is qualified; If the total leakage rate exceeds the predetermined scrap value, half of it can be taken out, and the remaining half can continue to be checked for leaks. If this half is qualified, it indicates that there are leaking devices in the taken out half. Repeat the leak detection process until the devices with leakage holes are detected.

This leak detection method sometimes results in missed detections. This is because devices with large leakage holes have already been purged of helium gas before being placed in the leak detection fixture, so a rough inspection of the device is usually required before back pressure leak detection.

At present, electronic product supervision and inspection departments and manufacturers widely use helium mass spectrometer leak detectors for product quality supervision, and have established their own standards and methods.

Regardless of which leak detection method is used, the operator is required to have careful observation ability and a high sense of responsibility, as false or missed detections will cause losses. In addition, the operator's alertness and proficiency in discovering unknown things are also important.

1. Helium and nitrogen fluorine oil leak detection platform

The helium nitrogen fluorine oil leak detection platform is a specialized equipment for sealing and reliability rough leak detection of semiconductor devices. It is used in conjunction with a helium mass spectrometer leak detector to meet the requirements of helium pressure precision leak detection and high-pressure fluorine oil rough leak detection for semiconductor device parts in the GJBI128A-97 national standard and GJB548-96 military standard.

The working process of this platform is:

(1) Helium leak detection experiment involves placing semiconductor components or devices in a high-pressure container, applying different pressures and helium gas according to the volume size of the inspected part, maintaining them for different times, and then removing the inspected part from the container after decompression. The leak is then detected on a helium mass spectrometer leak detector, and the qualification is judged based on the leakage rate value.

(2) Rough leak detection experiment involves placing the inspected item after precision leak detection into a vacuum pressurized tank, vacuuming it, injecting a certain amount of fluorine oil, and holding it under pressure for a certain period of time. After emptying and removing it, it is placed in specially heated fluorine oil and judged for qualification based on the presence of bubbles. The whole process is coherent, easy to operate, safe and reliable, and the working environment is clean.

2. Multi station high vacuum exhaust leak detection table

The multi station helium mass spectrometer leak detection high vacuum exhaust leak detection device is suitable for leak detection equipment in industrial fields that require large quantities, multiple varieties, high sensitivity, and fast leak detection of high-pressure switch tubes, microwave emission tubes, and other products.

The system consists of two parts: a leak detector and a leak detection platform. The leak detector is used to determine whether the workpiece is leaking; The leak detection platform performs vacuum pre pumping on the workpiece, and has two independent detection stations on the left and right sides. Each station is equipped with 1-3 detection interfaces; While one set of workstations is vacuuming, another set of workstations is conducting inspections or loading/unloading of workpieces, shortening the inspection cycle and improving work efficiency. The entire detection process is automatically controlled by a programmable industrial controller (PLC), ensuring the stability and reliability of the system. The operation is very simple and convenient for users.

Main technical indicators and parameters:

1. Power supply: 220V 12A

2. Vacuum degree: 5 × 10-3 Pa · m3/S

3. Work cycle without load: 20S/beat

4. Start time:<10 minutes 5. Response time:<5 seconds

6. Compressed air: 5-6kg

7. Environmental temperature: 5-35 ℃

8. Relative humidity of the air: ＜ 80

9. There is no strong magnetic field, severe vibration, or corrosive gas near the working environment; Ensure good indoor ventilation to prevent helium gas from drying up.