Identifying Leakage Pathway with a Penetrant Dye Gross Leak Test

The fluorescent dye penetrant test provides the means to identify failures caused by packaging faults or assembly problems, particularly cracks or voids in the package body with no internal cavities where they can nevertheless lead to deterioration and reliability issues as a result of, for example, exposition to humidity. This method allows detecting such defects being also dedicated to the research of leak origins and mechanisms.

For example, if performed in accordance with MIL-STD-750 method 1071, this test allows detecting the presence of leaks or cracks in glass diodes. The method consists in dipping the samples into a fluorescent dye solution (rhodamine) while being placed in a hermetic chamber and pressurized in order to force the liquid to penetrate the possible cracks, voids or gaps between the glass diode body and the leads. After the cleaning process, the tested samples are examined under high magnification using a UV light source for evidence of rhodamine. Before the inspection, the device can be encapsulated in a transparent resin for cross-sectioning.

This test is performed onto transparent glass encapsulated devices or for destructive verification of opaque devices. Any evidence of dye in the device constitutes a failure and the device is rejected.