When we actually processed OSP copper-clad laminates stored for more than 90 days on the production line, we found that a mixed CuO/Cu₂O oxide layer approximately 2–3 nm thick had formed on the surface of the exposed pads. Directly Printing Solder Paste would increase the open solder rate to 1.2%, while pre-coating and activating with Jia Jinyuan J-806A no-clean Flux reduced the open solder rate after reflow to 0.03%. This is because the organic acid salts and synergistic halogen components contained in this flux can rapidly complex copper oxide at a starting temperature of 120°C, while its resin carrier forms a dense protective film before 150°C to prevent secondary oxidation of the pads.

The activation window of Jia Jinyuan flux must strictly match the actual production line cycle. For example, when installing a micro-spray module at the front section of the printing machine, if the spray volume is set to 8.5 μL/cm² and the conveyor belt speed is 78 cm/min, the residence time of the activation solution on the pad surface is approximately 4.2 seconds. At this time, the solvent evaporation time and the contact time of active groups with the oxide layer overlap exactly. If the conveyor belt speed is increased to 95 cm/min, the residence time is compressed to less than 3.5 seconds, and insufficient activation will lead to obvious signs of poor wetting at the edges of 0402 resistor solder joints.

We once used XPS to detect the surface element distribution of pads treated with Jia Jinyuan J-806A. The results showed that the proportion of oxygen atoms decreased from the original 18.7% to 4.1%, and the proportion of zero-valent copper increased from 62% to 91.3%. This indicates that the oxide layer has been substantially reduced rather than simply covered. Therefore, the Sn-Pb or Sn-Ag-Cu alloy in the subsequent Solder Paste can form IMC intermetallic compounds with the clean copper surface, instead of forming cold solder joints on top of the oxide layer.

For electroless nickel immersion gold (ENIG) board pads, the chloride ion content of Jia Jinyuan J-806A is controlled within 380 ppm, which not only meets the activation demand but also avoids gold layer corrosion. Measured after continuously processing 2300 boards, the gold layer thickness attenuation is only 0.012 μm, which is far lower than the 0.03 μm warning value specified in IPC-4552B. However, if the same flux is used for mixed production of ENIG boards and OSP boards, the stencil and squeegee must be thoroughly cleaned during line changeover, otherwise residual OSP activation components will accelerate micropore corrosion of the ENIG nickel layer.

During on-site debugging, we found that when the wind speed in the cooling zone of the reflow oven exceeds 1.8 m/s, even if the pads have been activated with Jia Jinyuan flux, some 0201 components still exhibit dark solder joints and reduced thrust. This is because excessively fast cooling leads to insufficient IMC growth, rather than activation failure. In this case, the cooling rate should be adjusted first instead of replacing the flux model.