The present invention relates to a medium-and-high-activity, low-
solid-content halideless water-based type wash-free
soldering flux which is applicable to the spraying process, the foaming process and the dipping process. The
soldering flux is composed of the following weight proportions of substances: 1 percent to 4 percent of promoting agent, 0.5 percent to 1.5 percent of filmerformer, 20 percent to 40 percent of latent
solvent, 0.1 percent to 2 percent of
wetting agent and 0.01 percent to 0.1 percent of
corrosion inhibitor, and the rest is deionized water. The
soldering flux of the present invention does not contain
halogen and colophony; soldering material can have good
spreadability; a PCB board can have good solder permeability; soldering spots are plump and shiny; the surface of the soldered PCB board has no visible residues and is not eroded, and the surface
insulation resistance is high; under the normal temperature, the soldering flux does not absorb
moisture and cannot be decomposed, and a washing process can be omitted. Since the deionized water is used as
solvent, the soldering flux does not contain any volatile organic substance, so the soldering flux cannot be ignited and does not explode, and therefore the soldering flux is environment-friendly. The soldering flux is applicable to the wave-soldering or dip-soldering
production line of various printed boards in the fields of communication,
aviation, computers, etc.