An abnormal increase in wave soldering dross is often not caused by a single factor, but rather the combined effect of excessive copper content in the Solder Bar itself and wave temperatures consistently above 265℃. Especially when using low-cost solder bars with a recycling ratio exceeding 30%, impurity elements in the lead-tin alloy accelerate oxidation at high temperatures. Combined with excessive liquid surface disturbance in the solder pot, this significantly increases the generation rate of tin oxide particles.

We found that over 80% of sudden spikes in production line dross volume occur within the first two hours after switching to a new batch of solder bars. This is because the antioxidant additive ratios vary greatly between solder bars from different manufacturers. Some solder bars have a natural oxidation rate as high as 1.8 g/kg per hour at a constant temperature of 255℃, while high-quality solder bars can keep this rate below 0.3 g/kg. Therefore, suppliers must be required to provide third-party measured oxidation rate reports, rather than only looking at nominal melting point or purity values.

Improper parameter settings for wave soldering equipment also exacerbate dross formation. For example, if the nozzle air velocity exceeds 2.3 m/s, it will entrain a large amount of air into the molten solder, increasing dissolved oxygen concentration. Meanwhile, once the wave height exceeds 12 mm, liquid surface disturbance intensifies, further promoting oxidation reactions. Therefore, the air velocity must be locked within the range of 1.6 to 2.0 m/s, paired with daily morning shift measurements of wave height using a stainless steel ruler.

Flux selection and spray volume control are equally critical. Rosin-based flux begins to carbonize significantly above 180℃. If the end-of-preheat zone temperature reaches 165℃ and the conveyor speed is too slow, incompletely volatilized organic matter will burst and splash the moment it enters the solder pot, entraining molten solder to form black carbonized dross clumps. Therefore, preheat temperature must be adjusted in tandem with chain speed; for example, when the chain speed is 1.2 m/min, the preheat upper limit should be capped at 152℃.

Poor nitrogen protection is an issue overlooked by many factories. When the oxygen content inside the furnace chamber exceeds 200 ppm, dross volume increases by an average of 40%. However, simply increasing nitrogen flow rate does not solve the problem; the key lies in sealing inspections. We once used a smoke pen to conduct segment-by-segment testing and found that the gap in the aged soft curtain at the rail entrance reached as much as 0.8 mm. After replacement, the oxygen content immediately dropped below 85 ppm.

Daily dross removal operations also require attention. Do not wait until dross accumulates to the point of obscuring the viewing window before handling it. It is recommended to shut down the machine every 4 hours and clean it with a dedicated skimming ladle. Move gently to avoid agitating the molten solder at the bottom, otherwise fine particles that have just settled will be re-suspended, which instead accelerates subsequent dross accumulation. Additionally, after each dross removal, an infrared thermometer must be used to recheck whether the temperature deviation across the four corners of the solder pot is less than ±3℃, to prevent local overheating from becoming a new oxidation source.