Fuzan W-1 is a water-based, no-clean flux for wave soldering of surface-mount and through-hole components, classified ORL0 under J-STD-004C with 4.5% solids and 0.0% halogen content. Testing confirms it passes the surface insulation resistance (SIR) test and the copper-mirror corrosion test, and it delivers excellent wetting across a range of metallizations along with outstanding penetration into plated through-holes, minimizing bridging and icicles for a virtually defect-free joint. It is compatible with tin-copper, tin-silver-copper, and tin-lead alloys, supports both lead-free and standard SnPb processes, and is applied by spray for even coverage with reduced flux consumption on single- or dual-wave systems. Recommended process parameters include board preheat up to 149 °C, 5 seconds of wave contact time, a flux solids deposit of 155–400 mg/cm², and a standard conveyor speed of 0.91–1.83 m/min. Supplied in 5 L and 10 L plastic canisters, it should be stored between 5–25 °C, away from sunlight and heat, and never frozen; shelf life is 1 year.