Non-halogen cleaning-free soldering flux

The invention provides a non-halogen cleaning-free soldering flux, which comprises the following compositions in percentage by weight: 0.5 to 5 percent of stannous oxalate, 0.5 to 20 percent of organic acid activator, 0.1 to 1 percent of surfactant, 0 to 3 percent of cosolvent, and the balance of solvent. Because of adopting the stannous oxalate as an activator, and having synergistic action withthe organic acid activator and no halogen, the soldering flux has the advantages of no irritant odour, less smoke, no environmental pollution, strong wetting power and excellent weldability. When thesoldering flux is used for welding, a printed package board has less solid residue, clean layout and low ionic contamination, and needs no cleaning after the welding; and the printed package board has high insulation resistance after the welding, which can meet the cleaning-free requirement of the printing package board.