Development of a Fluxless Soldering Process for Surface Mount Technology Available to Purchase

In the surface mount industry, microelectronic devices are reflow soldered to printed circuit boards with the benefit of mildly activated rosin (RMA) based fluxes. The residues from these fluxes, when not properly cleaned from the component boards, have been cited for decreased circuit life due to corrosion of the solder joints and loss of insulating resistance. Post‐solder cleaning operations with CFC (chlorofluorocarbon) solvents have been deemed environmentally harmful. Hence, there is a great need in the surface mount community for a no‐clean or fluxless solder reflow process. The BOC Group has developed a novel, proprietary process, by which circuit boards and their components are attached with a solder paste under a reactive fluxing atmosphere. The post‐solder residue is non‐corrosive and so minimal that it does not require a post‐solder cleaning operation. The solder joints exhibit good wetting, excellent joint strength and are essentially void‐free. Assembled circuits processed in this way meet all the criteria for ionic cleanliness and surface insulation resistance without post‐solder cleaning.