SMTA International Conference Proceedings


IDENTIFYING THE CHEMICALS RESPONSIBLE FOR CONDUCTIVE ANODIC FILAMENT (CAF) ENHANCEMENT

Author: Westin R. Bent
Company: Georgia Institute of Tech.
Date Published: 9/12/1999   Conference: SMTA International


Abstract: In recent years, field failures of critical electrical equipment have been reported as being associated with the soldering chemicals. Certain water-soluble fluxes, in particular those containing polyglycols and/or polyglycol surfactants have been shown to enhance conductive anodic filament (CAF) formation. CAF is an electrochemical failure mode of electronic substrates, which involves the growth of a copper-containing filament subsurface along the epoxy-glass fiber interface from anode to cathode. The objective of this study was to evaluate a series of water soluble flux vehicles for their propensity to enhance CAF. These flux vehicles were also studied along with chloride or bromide activators to determine if the presence of halide increases CAF enhancement. Flux formulations containing the different flux vehicles were tested with and without HBr and HCl activators, to see what effects the presence of the halide had on CAF formation. Key Words: Water-soluble flux, SIR, CAF, corrosion,



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