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Hermeticity Testing
(Fine and Gross Leak)


Hermeticity Testing (also known as Fine and Gross Leak) is used to determine the effectiveness of the seal in microelectronic component packages. If the package seal is damaged or defective, moisture and other contaminants can enter into the package freely and degrade the long-term reliability.

To determine the size of the leak, the volume of air that passes through the leak each second under a pressure difference of 1 atmosphere is obtained. Leak rates greater than 1x10-5 atm-cc/sec are considered gross leak rates;  those smaller than 1x10-5 atm-cc/sec are considered fine leak rates [1]. Liquids are typically  used to detect gross leaks, while tracer gases are used for fine leak detection. SIX SIGMA performs gross leak test using a perfluorocarbon fluid bubble detection system. Fine leak detection is performed with industry-standard mass spectrometer helium leak detectors. The methods used for gross leak test cannot be used for fine leak test and vice versa.

Components cannot be  constructed of organic materials to pass hermetically tested. With the exception of ink marking, nearly all organic materials will absorb enough helium to fail this test. Even bumper tape or part number labels can cause a false failure, so they must be removed prior to testing.



Applicable Specifications & Standards:

1] H. Greenhouse, Hermeticity of Electronic Packages (William Andrew Publishing, LLC, New York, USA), p. 269 (2000).