Patent ID: 7818133

Claim:
A leak inspection method for applying gas to a device under inspection and a reference tank and for determining whether or not the device has a leak based on whether the device and the reference tank have a pressure difference equal to or larger than a predetermined value when a predetermined period of time elapses, the leak inspection method comprising: in a calibration mode, (a-1) a step of applying a predetermined gas pressure to the device and the reference tank only for a pressure applying period of a predetermined length and then stopping application thereof; (a-2) a step of measuring a first pressure-difference change ΔP 1 between pressure differences generated between the device and the reference tank in a first equilibrium period after the end of the pressure applying period; (a-3) a step of measuring a second pressure-difference change ΔP 2 between pressure differences generated between the device and the reference tank in a second equilibrium period after the end of the first equilibrium period; (a-4) a step of measuring a third pressure-difference change ΔP 3 between pressure differences generated between the device and the reference tank in a first inspection period after the end of the second equilibrium period; (a-5) a step of measuring a fourth pressure-difference change ΔP 4 between pressure differences generated between the device and the reference tank in a second inspection period after the end of the first inspection period; and (a-6) a step of calculating and storing a drift correction coefficient K corresponding to a drift included in the third pressure-difference change ΔP 3 , from the difference (ΔP 3 −ΔP 4 ) between the third and fourth pressure-difference changes and the difference (ΔP 1 −ΔP 2 ) between the first and second pressure-difference changes, and of discharging the gas from the device and the reference tank; and in an inspection mode, (b-1) a step of applying the predetermined gas pressure to the device and the reference tank only for the pressure applying period and then stopping application thereof; (b-2) a step of measuring a first pressure-difference change ΔP 1 ′ between pressure differences generated between the device and the reference tank in the first equilibrium period; (b-3) a step of measuring a second pressure-difference change ΔP 2 ′ between pressure differences generated between the device and the reference tank in the second equilibrium period; (b-4) a step of measuring a third pressure-difference change ΔP 3 ′ between pressure differences generated between the device and the reference tank in the first inspection period; (b-5) a step of estimating a drift included in the third pressure-difference change ΔP 3 ′, from the difference (ΔP 1 ′−ΔP 2 ′) between the first and second pressure-difference changes and the drift correction coefficient K, and (b-6) a step of estimating a leak of the device by subtracting the drift from the third pressure-difference change ΔP 3 ′, and of discharging the gas from the device and the reference tank.