Studies on the Hot Dip Coating of Pb (Report 2)

Effect of Chemical Displacement Reaction between Cu Chloride and Solder on Spreadability of Sn-Pb Solder

Abstract

As reported in previous paper, the chemical displacement reaction between flux and solder or base metal can be determined by free energy of formation of metal chloride. In this report, authors describe to-behavious of CuCI, CuCl₂ or CuO in ZnCl₂ flux.
CuCl or CuCl₂ existing in molten ZnCl₂ react with Sn-Pb solder to displace Cu. The spread area of Sn-Pb solder on Cu plate is increaded due to Cu produced by this displacement reaction between flux and solder.
The spread area of solder is governed by test temp., composition of Sn-Pb solder and added quantity of CuCl or CuC1₂ to ZnCl₂. In this case, the spreading characteristics may be classified into three different categories. Namely
(1) The marked secondary spreading causes in definite range of test temperature.
(2) The marked secondary spreading causes at all range of test temperature.
(3) The slight secondary spreading causes at all range of test temperature.
When flux added CuO to ZnCl₂ aqu. solution is used, the spreading characteristic of Sn-Pb solder with this flux on Cu plate is similar to ZnCl₂-CUCl or ZnCl₂-CuCl₂ fluxes. Namely, when ZnCl₂ aq. solution is concentrated on heating, HCl is produced. This HCl reacts with CuO to produce CuCl or CuCl₂