Hermeticity Testing or Hermetic Seal test

Hermetic seal testing is a crucial requirement for military, space, as well as commercial hermetically sealed devices. A lack of hermeticity is a reliability concern and may allow moisture and contaminants to enter the internal cavity, which could lead to premature failure. Seal testing per Mil-Std 883 method 1014 conditions A1 and B1 & B2, Mil-Std 750 method 1071 conditions H1 and G1 & G2, Mil-Std 202 Method 112 conditions C, D, A and E, and client specific requirements. Testing is also performed per Telcordia GR1221-CORE and GR-468-CORE for passive and active devices.

Fluorescent Dye Impregnation

Fluorescent dye impregnation is utilized to identify leak site regions and characterize the physical attributes of the ingress pathways to improve package sealing processes. This technique also eliminates the problem of misinterpretation when cross-sectioning fragile materials.

Helium or Krypton 85 Fine Leak

Devices are typically preconditioned in a pressurized chamber and, after the required conditions are met, the leak rate is measured and recorded, applying pass/fail criteria. Devices sealed with helium and undergoing helium leak testing need not be pressurized if requested.

Expanded Fine Leak for Other Gases and Compounds

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 specialized mass spectrometer tuned for the particular substance of interest. Applicable standards are normally available in a wide range of leak rates.
Helium Gross Leak
A device with a gross leak could theoretically pass the fine leak test. Therefore, this test is typically performed after fine leak. Depending on the requirement of the specification being followed, gross leak may be performed by two different methods.

1. The device is submerged in an indicator fluid tank at a specified high temperature of 125° C, and observed for evidence of bubble stream emanating from a gross leak site. A lower temperature may be used depending on device material constraints.

2. The test may require preconditioning in a pressurized chamber filled with an inert detector fluid that characteristically has a low boiling point. After preconditioning, the devices are submerged in an inert indicator fluid with a higher boiling point. In theory, any detector fluid located within the internal cavity of the package would boil when exposed to the high temperature of the indicator fluid, thus creating a bubble stream from the gross leak site.

Kr85 Gross Leak

A device with a gross leak could theoretically pass the fine leak test. Therefore, this test is typically performed prior to Fine Leak testing as a method of eliminating failures that would other wise trap large amounts of radioactive Kr85 through longer term Fine leak pressurization.