Vacuum coating equipment back pressure leak detection method
The back pressure leak detection method is a combination of pressure leak detection and vacuum leak detection. Vacuum coating equipment is mostly used in the non-destructive leak detection technology of sealed electronic devices, semiconductor devices and other sealing parts.
The leak detection process can basically be divided into three steps: charging, purification and leak detection.
(1) The charging process is to store the tested part in a container filled with high-pressure leaking gas for a certain period of time. If the tested part has a leak, the leaking gas can enter the inside of the tested part through the leak. And as the immersion time increases and the inflation pressure increases, the partial pressure of the leaking gas inside the test piece will inevitably increase gradually.
(2) The purification process is to use dry nitrogen flow or dry air flow to spray the inspected part outside or inside the pressurized container.
If there is no gas source, the test piece can also be allowed to stand still in order to remove the leaking gas adsorbed on the outer surface of the test piece.
During the purification process, a part of the gas will inevitably be lost from the inside of the inspected part through the leak, which will cause the partial pressure of the leaking gas inside the inspected part to gradually decrease, and the longer the purification time, the partial pressure of the leaked gas The greater the drop.
(3) The leak detection process is to put the cleaned test piece into the vacuum chamber, connect the leak detector to the vacuum chamber, and perform leak detection.
After vacuuming, due to the pressure difference, the leaking gas can flow out from the inside of the tested part through the leak hole, and then enter the leak detector through the vacuum chamber, and determine the existence and leak rate of the leak according to the output instructions of the leak detector The size.