Fluxing compositions containing compounds that generate acids upon photoinitiation from a light source such as Hg/Xe ultraviolet (UV) light sources are described. The acids clean oxides from the printed circuit boards (PCBs) under assembly and then volatilize with little or no need for a cleaning step, or cleaning only with water. The compounds that release an oxide removing agent, sometimes called a "photoacid" include metal and organic onium salts and furyl compounds bearing a carbonyl group. Such fluxing compositions can be used mixed with typical solder formulations, such as lead/tin solders, or applied topically thereto; both techniques permit the assembly of PCBs more easily and with high quality bonds.