Fine and Gross leak testings are widely used in the Microelectronic Industry. Both techniques provide a valuable information on the size of the leak. The Helium Fine Leak test measures a leak rate in atm.cm3.s-1.
Seal integrity testing is crucial for hermetic packages in military, space, and commercial applications. A loss of hermeticity is a reliability concern and will allow moisture and contaminants to enter the package cavity shortening device lifetime.
ORS performs seal testing per Mil-Std 883 method 1014 conditions A1 and C1, Mil-Std 750 method 1071 conditions H1 and C, Mil-Std 202 Method 112 conditions C, D, A and E, and client specific requirements. Testing is also performed per Telcordia GR-1221-CORE and GR-468-CORE for passive and active devices.
First, devices are preconditioned in a pressurized helium chamber for a given period of time. Then, the helium leak rate is measured and recorded, applying pass/fail criteria. Devices that are sealed with a known concentration of helium don't necessarily need to be pressurized.
Extended Fine Leak for Other Gases
Specialized leak testing is available for determining leak rates for gases other than helium. Leak rates of various gases (i.e. Argon, CO2, Acetic Acid, Ethylene Glycol, etc...) may be measured at low leak rates utilizing a mass spectrometer tuned specifically for the particular substance of interest.
A device presenting a gross leak could theoretically pass the fine leak test. Therefore, this test is typically performed after the fine leak test. The gross leak test is an inspection test based on boiling points differential of two fluorocarbons. It requires a preconditioning in a pressurized chamber filled with a low boiling point fluorocarbon (the Detector). Under the pressure, the Detector fluid may penetrate the device. After the preconditioning, the device is submerged in a second fluorocarbon fluid with a higher boiling point (the Indicator). When exposed to the high temperature, the detector fluid located within the cavity of the package boils, generating an elevated pressure inside the devise causing a bubble stream to emanate from the leak site.
Gross Leak (Simulated Bubbles)