A device with a gross leak could theoretically pass the fine leak test. Therefore, this test is usually performed after the fine leak test. In addition, the wet fluorocarbon could block the fine leakage paths.
The gross leak test is an inspection test based on the boiling point differential of two fluorocarbons. It requires preconditioning in a pressurized chamber filled with low-boiling fluorocarbon (80 ° C) [the Detector]. Under pressure, fluid from the detector can enter the device. After preconditioning, the device is immersed in a second higher boiling fluorocarbon fluid (125 ° C) [the indicator]. When exposed to the high temperature, the detector fluid inside the package cavity boils, generating high pressure inside the device causing a flow of bubbles to emanate from the leak site.
Gross leak (simulated bubbles)