Once the solder bath surface for pin Dip Soldering is exposed to air, it oxidizes rapidly. After the oxide film ruptures, the exposed fresh solder liquid immediately undergoes secondary oxidation. This cyclic superposition effect directly causes the amount of solder dross to grow non-linearly with operating time, which is especially pronounced when wave height fluctuates or pins enter the solder bath densely.

Coupling Mechanism of Solder Surface Oxidation and Solder Dross Formation

The surface tension of molten solder decreases as temperature rises, while the diffusion rate of oxygen molecules increases simultaneously. When pin dip soldering actions disturb the liquid surface, SnO and SnO? particles originally floating on the surface layer are drawn into the bulk molten solder. These oxides cannot be reduced by conventional Flux, and instead act as nucleation sites for new solder dross, further adsorbing free solder ash and PCB residue, and eventually agglomerating into lumpy solder dross at the edges of the solder pot.

On-site Adaptation Logic of JJY Anti-oxidation Flux

This flux does not simply increase the rosin ratio, but is formulated by compounding palmitamide derivatives with trace bismuth salts at a mass ratio of 3.8:1. It can spontaneously spread into a dynamic protective film with a thickness of approximately 8–12 μm within the temperature range of 195℃ to 255℃. This film not only allows pins to penetrate and wet, but also instantly repairs local damage caused by puncturing. Actual measurements show that after 4 hours of continuous operation, the thickness of the oxide layer on the solder surface remains below 0.3 μm, which is far better than the 1.7 μm observed without the additive.

Hard Matching Requirements for Equipment Parameters and Process Windows

When using this solution, the nitrogen flow rate of the wave generator must be synchronously adjusted to 2.4L/min ± 0.3L/min, and the nitrogen inlet must be directly facing the main recirculation zone of the molten solder. Otherwise, the protective film will be torn apart by the high-speed solder flow. Meanwhile, the pin dip soldering angle must be controlled between 72° and 78°. An excessively small angle will cause the pins to drag an overly thick liquid film, exacerbating oxidation, while an excessively large angle will easily lead to solder joint spikes and an increased void rate.

Production Line Verification Data for Solder Dross Reduction

After an automotive ECU production line switched to the JJY solution, the average weight of solder dross per shift decreased from 3.6kg to 2.4kg, and the solder pot cleaning cycle was extended from once per shift to once every two shifts. More importantly, the standard deviation of the solder climb height dispersion in AOI inspection narrowed from 0.13mm to 0.07mm, indicating that thermal disturbance and oxidation interference during the pin dip soldering process have been substantially suppressed.

Three Key Actions in Daily Maintenance

Before each shift starts, the dross accumulation area at the edge of the solder pot must be wiped with non-woven fabric dipped in the same model of flux to prevent dried oxide from flaking off and mixing into the main solder bath. After the solder temperature exceeds 245℃ and operates continuously for more than 2.5 hours, an anti-oxidation mother liquor with a volume ratio of 0.8% must be manually added. At the same time, PCBs with residual halogen-containing cleaning agent are strictly prohibited from being directly put into the pin dip soldering process, otherwise the protective film will be instantly destroyed and a chain oxidation reaction will be induced.