Back pressure leak detection method of vacuum coating equipment

Back pressure leak detection method is a combination of pressurized leak detection and vacuum leak detection. Vacuum coating equipment is mostly used in nondestructive leak detection technology of sealed electronic devices, semiconductor devices and other seals.

The leak detection process can basically be divided into three steps: pressurization, purification and leak detection.

(1) The charging process is to store the tested piece in a container filled with high-pressure leak gas for a certain period of time. If there is a leak in the tested piece, the leak gas can enter the tested piece through the leak hole, and the partial pressure of the leak gas inside the tested piece will inevitably increase with the increase of soaking time and inflation pressure.

(2) In the purification process, dry nitrogen flow or dry air flow is used to blow the tested object outside or inside the pressurized container.

If there is no air source, the tested piece can be left standing to remove the leakage gas adsorbed on the outer surface of the tested piece.

In the process of purification, because a part of the gas will inevitably be lost from the inside of the tested piece through the leak hole, the partial pressure of the leakage gas in the tested piece will gradually decrease, and the longer the purification time, the greater the partial pressure drop of the leakage gas.

(3) In the process of leak detection, the purified tested piece is put into the vacuum chamber, and the leak detector is connected with the vacuum chamber for leak detection.

After vacuumizing, due to the pressure difference, the leak gas can flow out from the inside of the tested piece through the leak hole, then enter the leak detector through the vacuum chamber, and judge the existence of the leak hole and its leak rate according to the output indication of the leak detector.