In actual production lines for pin Dip Soldering, the melting temperature of tin bars must be controlled within the range of 195±3℃. Otherwise, when the temperature is below 190℃, the increased viscosity of the molten tin will lead to uneven tin coating on pins, while a temperature above 200℃ will accelerate Flux carbonization and cause black slag to accumulate on the tank walls. We once conducted tests with Jia Jinyuan Sn63/Pb37 tin bars and found that when the heating power fluctuation of the constant temperature bath exceeds ±5%, the dispersion of tin plating thickness on pins of 100 plug-in resistors from the same batch expands from ±0.012mm to ±0.028mm, which directly affects the first-pass yield of subsequent AI plug-in mounting.

Before dip soldering, component pins must undergo double-station treatment. First, 3% concentration no-clean rosin-based flux is applied via atomized spraying, followed by hot air pre-drying at 120℃ for 60 seconds to fully evaporate the solvent. If the pre-drying step is skipped and components are directly immersed in the tin bath, the instantaneous vaporization of flux upon encountering high temperature will cause local tin bead splashing on pins. During a batch processing of 1206 package diodes, this issue led to an increase in the false solder re-inspection rate by 0.8%, while after adopting pre-drying, the defect rate dropped back to below 0.15%.

The addition of Jia Jinyuan tin bars into the tin bath must follow the principle of "small amounts, multiple times". Each replenishment amount shall not exceed 8% of the current liquid level height. After replenishment, the molten tin must be left to stand and stirred for 5 minutes before production resumes. Otherwise, the density difference between new and old molten tin will cause bottom sediments to float upward, leading to uncontrolled dip soldering depth. Once, after 4 hours of continuous operation without timely cleaning of the oxide film, we found that the thickness of floating slag on the bath surface reached 1.2mm, which caused the pin immersion depth deviation of DIP package ICs to exceed the 0.3mm tolerance band, ultimately resulting in solder bridging rework on 32 PCBs.

The vertical lifting speed for pin dip soldering is set to 85mm/s. Too fast a speed will cause molten tin to detach from pins and form pointed burrs, while too slow a speed will trigger excessive tin climbing to cover the component body. For a certain model of relay, when the dip speed was reduced to 60mm/s, 7% of samples suffered internal short circuits after potting. Dissection confirmed that the cause was excessive residual tin at the pin roots. After adjusting the speed back and matching it with a 0.5-second dwell time, this issue was completely eliminated.

Before the end of each shift, stainless steel scrapers must be used to remove accumulated slag from the edges of the tin bath, and nitrogen must be used to purge residual flux vapor from the bath opening. Otherwise, condensed liquid dripping into the molten tin upon next-day startup will induce tin splashing. We compiled three months of data and found that teams adhering to this operation had 11.3% lower tin bar unit consumption than teams that did not implement it, and the bath solution lifespan was extended by over 27%. Under these conditions, Jia Jinyuan tin bars can be used continuously for 18 shifts without full replacement.