Surface analysis of outgassing contamination from edgebond epoxy adhesives on ImAg pads

This paper details the outgassing process during epoxy degradation and evaluates the corresponding influence on adjacent PWB pads for immersion Ag (ImAg) plated circuit boards. Three commercial epoxy adhesives used for edge-bonding of surface-mount (SMT) components were investigated. Scanning electron microscope (SEM) analysis and electron dispersive spectroscopy (EDS) was carried out to investigate the surface of the contaminated ImAg pads. Chemical states of the elements transferred to the pads were analyzed by X-ray Photoelectron Spectroscopy (XPS). The results from the present study showed some ingredients in the adhesives may be thermo-oxidized to gaseous by-products in the presence of oxygen and migrate out from the epoxy body, contaminating the adjacent ImAg pads. Further research will be needed to verify whether these gaseous by-products also contaminate surrounding components, and result in corrosion-related reliability failures.