GB684083A - Improvements in or relating to soldering fluxes - Google Patents

Abstract

The activity of a soldering flux containing at least one heavy metal fluoborate and at least one acidic inorganic non-metallic boro-fluoride compound and at least one aliphatic polyamine or aliphatic amino alcohol is increased by introducing an amount of ammonia which is at least 0.5 per cent but preferably not more than 3 per cent by weight of the total flux, or an equivalent weight of decomposable ammonium salt, into the flux and thereafter heating the flux above 50 DEG C, but below the decomposition temperature of any portion of the amine component until the desired increase in activity is effected, the heating period being in general between 3 and 30 minutes per pound of flux. The flux which may contain other ingredients, e.g. plasticizers, is intended for use in soft soldering of aluminium and its alloys. Specified heavy metal fluoborates are those of cadmium, zinc, tin and lead. The acidic inorganic non-metallic boro-fluoridic compounds include BF3, hydrofluoboric acid, dihydroxy fluoboric acid and like acids; these may be present in the proportion of one or more moles or fraction of a mole per mole amine. The metal fluoborates are normally present in amounts up to 25 per cent by weight of the flux. The activating ammonia may be added to the prepared flux or supplied with the components making up the flux. When a decomposable ammonium salt is used it must be decomposable at the activating temperature and must not yield substances interfering with the action of the flux. The ammonia may be introduced by using the acidic inorganic non-metallic boro-fluoride compound in the form of its ammonium salt. Preferably, the ammonia is introduced in combination with boron and fluorine as in ammonium fluoborate, a heavy metal salt such as cadmium fluoborate hexammine, and in such mixtures as NH4F or NH4HF2 with boric acid, boric oxide, an organic borate or boron-tri-fluoride-ammonia. Examples are given illustrating the activation of fluxes prepared from triethanolamine, hydroxyethyl ethylene diamine and tetraethylene pentamine respectively and cadmium fluoborate and hydrofluoboric acid, the ammonia being introduced as the gas or in combination with the acid or the fluoborate. The activities of some of these are compared with those of similar fluxes which are either not ammoniated or are ammoniated but not heated. Specifications 684,081 and 684,082 are referred to.