Author: Stephen M. Bobbio Company: University of NC at Charlotte Date Published: 11/1/2000
Abstract: A gas treatment process has been developed to replace the use of fluxes used for soldering printed circuit board assemblies. One of the main reasons for using flux is to dissolve the high melting point oxide that covers the solder surface. This layer prohibits solder flow and wetting of the component leads or circuit board contacts. Chemically, the flux process is a reduction step. The FST (Fluorinated Soldering Technology) approach is a radical departure. It is a pure gas pretreatment that quickly permeates the smallest crevices and converts a part of the oxide to an oxyfluoride - this is actually an oxidation and not a reduction. The conversion film is stable for some months in dry air or nitrogen, allowing for later solder joining, if desired, without flux, using existing equipment, wave solder or oven reflow. There is no residue left from this process. Because the chemistry is very specific only a very small amount of gas is needed to perform the process.