Combining humidity testing and static bending with flip chip test structures

Humidity testing in 8585-test conditions has been carried out with different test structures. The behavior of substrates, thin chips and conformal coatings and the reliability of the structures in comparison with non-coated bended structures are reported in this paper. Furthermore, both thick and thin structures are tested without bending and with and without conformal coating. Thick and thin FR-4 substrates were used with thick and thin Si test chips, which were joined using anisotropically conductive adhesive film (ACF). Half of the test structures were coated using parylene C as the conformal coating material. Part of the test samples were bent on a radius of 3.25 cm and placed into 85/85 - constant temperature and humidity test. During testing the daisy chain resistance of the samples was measured real time to see the behaviour of the contact resistance in humid environment. After testing failure analysis was carried out; cross sectioning and analysis with optical and scanning electronic microscopy (SEM).