Studies on the Flux Action of Soldering (V)

Inorganic Metal Salts

Abstract

In previous papers, on aniline hydrochloride flux action of soldering, it has been shown that molten aniline hydrochloride reacts with copper to give CuCl₂ and copper complex, which react with molten solder to give metallic copper.
Successively, this copper dissolves into the molten solder and a thin Cu-rich layer is formed on the surface of molten solder. The wetting of the solder on copper plate is improved through the reaction and the dissolution of Cu into molten solder.
In this report, the flux action of various inorganic metal salts (chloride, sulfate and nitrate) on soldering was studied in the relation between the reaction of flux with Sn and wettability of Sn solder on Cu plate.
The results of flux action of various inorganic metal salts are summarized as follows:
1) The reaction of molten Sn with metal salt and the effect of metal salt on spreading are dependent mainly on an electrochemical series.
2) The improvement of spreading by inorganic metal salts may be ascribed to the reaction of molten Sn with metal salt and the dissolution of the metal into molten Sn from the flux.
3) The difference in effect on spreading by inorganic metal salts is acknowledged to some degree.