軟ろう付用溶剤の電気化学的作用について(第 2 報)

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Authors have reported that both H^+ and Cl^- ions in an aqueous solution of HCl acted well as flux for the spreading of solder on copper base metal. However, the flux action of the individual ion cannot be made clear, because that solution includes simultaneously these ions. So, in the present paper, the aqueous solution of H_2SO_4 was selected as flux not containing Cl^- ions, and particular aqueous solutions including Cl^- ions at various concentrations were prepared by adding NaCl to the aqueous solution of H_2SO_4,and in order to distinguish the electrochemical flux action of each ion, the corrosion potentials of base metal and solder were measured in these solutions and also spreading tests wre made by the same methods described in the previous report. In addition, external cathodic polarization curves of base metal and external anodic polarization curves of the solder were plotted to investigate whether there was a relation between the spreading of solder and the electrode reaction of a galvanic cell formed instantaneously in contact with the base metal and solder in these aqueous solutions. The results obtained from these investigations are summarized as follows : 1) When the concentration of H^+ ions in the particular aqueous solutions was kept constant, the spreading of solder did not increase appreciably with an increasing concentration of Cl^- ions in these solutions. But a significant increasing phenomenon of the spreading occurred at a certain critical concentration of Cl^- ion in both solutions of pH's about 2.5 and 3.0. 2) A correlation between logarithm of the critical Cl^- ion activity and pH of the aqueous solution is shown by following eq. log α_<Cl^->=-4.65+pH(1.0<pH<3.0) As this experimental eq. approximates to a theoretical eq. (10), the flux action of Cl^- ion for the base metal may be expressed by the meaning of eqs. (10) and (13). 3) When the corrosion potential of the galvanic cell had a higher value than the break potential of the cathodic polarization curve, the spreading of solder did not occur because the formation of H_2O_2 or H_2O on cathode (that is base metal) decreased H^+ ion concentration in the aqueous solution. It is concluded that the higher the concentration of H^+ ions in flux solution, the better the spreading of solder becomes.
社団法人溶接学会の論文
1971-02-25

軟ろう付用溶剤の電気化学的作用について(第 2 報)

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