Helium mass spectrometry leak detector Helium pressure method leak detection steps and precautions (all)
Back pressure helium mass spectrometry leak detection method, also known as helium pressure leak detection method, is a leak detection method suitable for small volume of the tested part, such as semiconductor a vacuum seal device non-destructive leak detection. Its leak detection process is the same as other back pressure methods, including 3 steps: pressure, purification, leak detection.
Helium 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 amount is detected by the leak detector.
Generally small electronic devices should adopt this leak detection method.
First of all, the helium mass spectrum leak detector is adjusted, and then the device is put into a pressurized tank to press helium into 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 device with a leak hole leaks out and is detected, and its leakage rate is shown on the leakage rate meter.
Back pressure leak detection – Pressure helium tank
In general, the elimination method is used when the pressure helium method is used for leak detection. 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.
Pressurized tank helium device: external switching sequence of pressurized tank helium device:
Write the turn-on sequence of the external conditions of the equipment, the operation method, the specific parameters, etc.
1. Connect the pressurized tank, resistance vacuum gauge, vacuum pump and helium cylinder as required.
2. Check whether the sealing ring of the pressurized tank is damaged, and whether the inlet and outlet valve of the pressurized tank can not be closed; Whether the vacuum pump has enough pump oil, and whether the gas ballast valve knob is in the closed position; Helium cylinder pressure reducing valve leakage phenomenon.
3, confirm that all matters that should be paid attention to have no problems can be connected to the power supply.
Helium mass spectrometry leak detector back pressure method leak detection process description:
- Pressure helium
1. Put the workpiece into the pressurized helium tank and make sure that the tank is clean.
2. After the workpiece is placed, place the cover of the helium pressure tank on the helium pressure tank and secure it with screws.
3. Connect the helium tank ball valve port to the helium cylinder.
4. After confirming that the connection is OK, first open the ball valve of the helium tank, then open the reducing valve of the helium cylinder, and control the outlet pressure of the inspection valve. After the pressure gauge on the helium tank indicates the specified pressure, close the ball valve of the helium tank, and then close the valve and reducing valve of the helium cylinder.
5. Disconnect the pipeline between the gas cylinder and the pressurized helium tank. (Note: there is pressure in the pipeline.) Place the pressurized helium tank in a safe area for a specified time.
6. After the pressure holding time is up, release the ground helium in the pressurized helium tank to the outside atmosphere or use a helium bag to recover.
- Clear helium
7. Remove the screws fixing the lid of the helium tank, and then open the lid.
8. Remove the workpiece and use air or nitrogen to remove the remaining helium on the surface of the workpiece.
9. Place the workpiece for use.
- Leak detection
10. Assemble the leak detection tank to the leak detection port of the leak detector, use the leak detector to evacuate, and the background value is minimum.
11. “Stop” the leak detector, open the leak detection tank, and place the workpiece in batches into the leak detection tank. “Start” the leak detector again.
12. The leak detector press “Start” to start timing and observe the leakage rate value of the leak detector.
13. Record the leakage rate of 10 seconds, 20 seconds, 30 seconds and 60 seconds after the start of the leak detector.
14. After the end of the record, “stop” the leak detector and remove the workpiece.
15. Repeat items 11-14 again to check other workpieces. Helium mass spectrometry leak detector – Precautions for leak detection by back pressure method The leak detection process will have the following phenomena:
1. Helium mass spectrometer leak detector can only detect micro leakage of the workpiece; In the process of helium cleaning, the helium pressed into the workpiece may leak out, and the helium leak can not be detected during helium detection.
2. After the workpiece is cleared of helium, the time for inspection should not exceed 1 hour to prevent the compressed helium from leaking out.
3. The workpiece is detected separately during the experimental test; The background value of the leak detector during batch inspection will be exponentially greater than the background value of the single inspection.
4. When the batch test is conducted, it is found that there are missing parts, which can be gradually halved to find the specific missing parts.
5. During each test, you can empty the leak detection tank and record the corresponding leak rate value as the comparison parameter of the test.
Remind everyone that no matter what kind of leak detection method is used, it requires the operator to have the ability to observe carefully and a high sense of responsibility, because false detection and missing detection will cause losses, and the alertness and proficiency of the operator to find unknown things is also very important.