A Rapid Cycle Method for Gross Leak Testing with the Helium Leak Detector

A new noncontaminating dry gas, quantitative test method has been developed that permits gross leak measurements on hermetic packages. It provides rapid testing with a helium leak detector over the leak size range of less than 1 x 10^-5to more than I atm-cm³/s with a test gas of ~1 percent helium. The present limitation on dry gas procedures results from the rapid depletion of the test gas from the package interior which prevents detection of the larger leaks. The rapid cycle method attacks this limitation by employing either a rapid transfer of the test package or a rapid gas cycling technique for extending the upper range of the helium leak detector procedure. Theoretical relationships have been derived based on viscous flow to correlate the leak detector reading to leak size. Experimental apparatus is described, and test results are given for a test time of about g s, a measurement precision of 15-35 percent, and a correlation coefficient between theory and test of better than 0.99. The rapid transfer mode of operation can be implemented readily with any helium leak detector equipped for fast pump-down and high helium flow rate.