SOFT SOLDER FLUX

PURPOSE:To obtain a flux by which good joinability is obtd. when used for soft brazing by consisting the flux principally or rosin or hydrogenated rosin and ammonium acetate without contg. halogen. CONSTITUTION:A soft solder flux consists principally of rosin or hydrogenated rosin and ammonium acetate and contains no halogen. Said flux provides good joinability by preventing generation of voids when used for soft soldering of the electrode parts of a semiconductor element. Such flux as well as a suitable solvent and soft solder powder are intimately mixed to a paste ink state and the mixture composed thereof is coated directly to the metallic part of a diode or the electrode part of the element and is subjected to reflow by heating in a protective or reducing atmosphere, by which direct mounting is accomplished. The above-mentioned flux is easily removed by water or an org. solvent. The similar effect is also exhibited by constituting the above-mentioned flux of zinc chloride or ammonium zinc chloride and ammonium acetate or zinc acetate, ammonium chloride, ammonium acetate, etc.