A Helium Leak Detector for Small Components

A helium leak detection method has been developed to leak check small hermetically sealed components with leak rates from 2 to 2 × 10-12 atm cc/s. Equivalent leak rates from 2 to 10-6 atm cc/s can be measured in a 0.4-cc volume component filled only with atmospheric air. Use of a 1% helium tracer in a 0.4-cc component can measure leak rates from 2 to 10-8 atm cc/s. A leak checking cycle requires less than 30 seconds. The inlet presently being used has a volume of 80 cc with an inside diameter of 1 ½ in. An optimum number of 12 components may be tested in each cycle. This number is based on both the chamber size and the assumption of a failure for one part in two hundred. Conservatively, 1000 to 1200 components can be tested in an hour in a semiautomatic system. For leaks greater than 1 × 10-6 atm cc/s, components can be leak checked from the shelf without a helium backfill. With a 1% helium tracer in a 0.4-cc component, equivalent leak rates from 2 to 1 × 10-8 atm cc/s can be made thus eliminating the helium purge program. This system provides a measurement of a leak size and a simple rapid method for leak checking hermetically sealed components.