Microstructural Changes of the Ag-Epoxy ICA/Sn Interface in a High-Humidity Environment

Abstract

In the present study, the degradation of the Ag-epoxy conductive adhesive/Sn interface at 85°C and 85% relative humidity was investigated through a variety of microstructural analyses. After the humidity test, the interfacial electrical resistance increased, and the interface was easily separated by external stress. Transmission electron microscopic (TEM) analyses indicated that two different Sn oxides, namely SnO and SnO 2 , were formed inhomogeneously at the interface in the humidity test. In addition, many voids were formed at the interface between Sn oxides and Sn plating. These Sn oxides and voids were the cause of the interfacial degradation.

Electrical Resistance and Microstructural Changes of Silver–Epoxy Isotropic Conductive Adhesive Joints Under High Humidity and Heat

“…The formation of these two oxides corresponds well with the findings of our previous work using a model specimen. 17 Through the galvanic reaction, the surface of the Sn plating near the Ag fillers became corroded. 6,7 The formation of these Sn oxide layers can interfere with the electrical contact between the Ag filler and the Sn plating.…”

“…[18][19][20] It has been reported that oxides with poor electrical conductivity such as Cu, Pb, and Sn oxide on Cu, Pb-Sn, and Sn plating, respectively, cause a decrease in the electrical conductivities of ICA joints in humid conditions. 6,7,17 Thus, the Sn oxide layers formed on the Sn plating undoubtedly cause the increase of electrical resistance.…”