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

Abstract

In this report, authors have discussed the effect of the chemical displacement reaction between metal chloride added to ZnC1₂ flux and Sn-Pb solder on the spreadability of the solder.
The spreadability of solder is measured by spread area of the solder for sessile drop method. The chemical displacement reaction between solder and flux is examined by X-ray diffraction of the solder, and by value of free energy of formation of metal chloride (ΔG°Mcln).
When ΔG°MCIn of metal chloride added to ZnCl₂ is greater than ΔG°snCl₂ or ΔG°pbCl₂, the remarkable chemical displacement reaction between solder and the added metal chloride may take place and it may lead to a increase in spread area of the solder (BiC₃, SbC1₃, AgCl, NiC1₂⋅6H₂O).
Nevertheless, when ΔG°MCIn of added metal chloride is pretty small than ΔG°SnCl₂ or ΔG°pbC1₂, the chemical displacement reaction does not almost take place and the spread area of solder is similar to the spread area with pure ZnC1₂ flux (CdC1₂.51/ZH₂O, LiCI, KC1, NaCI, CrC1₃⋅6H₂O).
Though ΔG°MCin of added metal chloride is smaller than ΔG°snC1₂ or Δ°Gpbc1₂, when remarkable difference between ΔG°MCIn and ΔG°snC1₂ or ΔG°pbCl is not recognized, the chemical displacement reaction takes place and the spread area of solder may change (FeCl₂⋅nH₂O).