軟ろうのWettabilityに関する研究(第1報)

Abstract

In the fundamental equation for the shape of the surface of a drop resting on a horizontal plane, when the drop is so small that the gravitational term can be neglected, its surface forms part of a sphere.In these circumstances, the area of contact between the drop and the plane depends only on the volume of liquid and the contact angle. An equation of balance in the horizontal direction can be written.γSU=γLS+γLV COSθwhere γsv : Surface tension solid/vaporγLS : Interfacial tension of liquid/solidγLV : Surface tension of liquid/vaporIt is well known that the use of a flux which reduces the γLV, will reduce the contact angle and greater spreading. The term "Wetting" of a solid by a liquid is defined in terms of the contact angle and therefore of the relative adhesions between the liquid for a solid and of the liquid for itself.Experiments were carried out with the object of determing at what temperature, the maxium spreading over a flux-cleaned copper and brass surface. As flux, ammonium-chloride, HNaNH4PO4, NaH2PO4 solution are used beside Zinc-chloride. Organic acids such as stearic acid, palmitic acid and others are also used. Solders used are 5mm dia., 1mm thickness specimen. It is interesting to compare the results obtained in Tin-Lead solder to those obtained in Lead-Cadminum, Cadminum-Zinc, Cadminum-Tin and Zinc-Tin. By the spreading degree of interfacial area, sombinations of fluxes and solders were classified as superior (over 1.0 sq. cm.) excellent (0.8-1.0 sq. cm.), good fair (0.5-0.8sq. cm.) and no-good (below 0.5sq. cm.).The following results may be drawn from the simple experiments described above :(1) The best known flux "Zinc chloride" is effective on copper except No. 5 Zn-Sn solder.(2) No. 2 Pb-Cd solder does not spread on copper but relatively good spread on Brass.(3) NH4Cl flux has little power and low wettability on copper but better results are obtained on brass.