The invention relates to a preparation method of a flux coated silver solder ring. The method comprises the steps of 1, preparing the following raw materials: 10-50% of Ag, 15-45% of Cu, 17-40% of Zn,1-3% of Sn, 0.1-0.5% of P, 0.5-2% of Ni, 0.1-0.3% of Ge, and 0.1-0.3% of Li; adding the raw materials to an intermediate-frequency
smelting furnace
crucible; performing
smelting,
casting, extruding and drawing to obtain silver solder wires; and preparing multi-
coil spring shaped silver solder ring through the silver solder wires; 2, preparing 1-5% of
boron micro
powder, 5-10% of
sodium borohydride, 15-30% of
potassium fluoborate, 25-40% of boric anhydride, 10-30% of
sodium fluoride, 2-5% of
potassium bifluoride, 1-5% of
copper sulfate, 0.1-2% of
polystyrene, and 0.2-2% of
dibutyl phthalate; mixing the materials; adding 45% of
ethyl acetate; and uniformly stirring to obtain a flux
coating solution for later use; and 3, spraying the flux
coating solution to cover the outer parts of the spring shaped silver solder ring; and
drying to obtain the flux coated silver solder ring. The flux coated silver solder ring prepared by the method is high in wettability, high in flowability, and capable of self-fluxing;
zinc is hard to volatilize; and moreover, the flux
coating is high in activity, low in
moisture absorption capacity, few in carbon residues, high in
ductility and
toughness, and isparticularly applicable to
soldering of pipeline assemblies such as a stainless
steel pipeline assembly and a
manganese brass pipeline
assembly.