Question: We found an article online about solder pot maintenance and the removal of dross, specifically there is an interest to us in the “changing bar solder” Section. Does turning up the solder pot too high cause impurities to collect on parts? Can you comment on this?
https://www.aimsolder.com/technical-articles/bar-solder-drossing-characteristics-and-wave-contamination
Answer: The article from AIM Solder is one of many regarding how solder bars are made and the type of elemental materials used to create them.
If this is a wave solder machine, the solder pot temperature should be fixed and the product temperature is controlled by the conveyor speed and the time the product is in the wave. The amount of dross generated in a wave solder system can be enormous due to the turbulence of the wave from wave generation and from the amount of surface area of the exposed molted metal within the system.
If the use is in a tinning solder pot the only dross build up will be on the exposed surface of the molten solder. The amount of dross can change depending upon the set temperature of the solder in the pot as well. Any soldering done using a tinning pot should require wiping of the surface of the pot to remove the dross prior to inserting the component leads or wires into the pot. As there is mention of dross collecting on parts, this could be because there is tinning through the dross on the surface of the solder pot.
As a quick note, solder dross does not build up too quickly in a static pot, so there is enough time to tin after cleaning off the oxides (dross) from the surface of the pot, whereas in the wave solder system, the solder is being pumped and there is a lot of surface area being exposed to the air, creating this dross.
Another issue to consider, is the amount of solder in the wave machine pot. If the solder is too low, then the dross will be pulled into the pump and end up in the solder joints, which is not a good thing. Larger machines tend to generate more dross, so solder levels should continue to be monitored.