Why reflow soldering is called reflow

Why is reflow soldering called "reflow"? Reflow soldering reflow refers to a process in which the liquid tin reflows to the component pins to form solder joints under the action of liquid tin surface tension and flux after the solder paste reaches the melting point of the solder paste, so that the circuit board pad and the component are welded into a whole, which is also called "reflow" process. Jeenoce electronic through reflow soldering process, so that we can more intuitive understanding.

1. When the PCB board enters the reflow soldering temperature rise zone, the solvent and gas in the solder paste evaporate. At the same time, the flux in the solder paste moistens the pads, component ends and pins, and the solder paste softens, collapses and covers the pads, isolating the pads, component pins and oxygen.

2. When the PCB circuit board enters the reflow soldering insulation area, the PCB and components are fully preheated to prevent the PCB from suddenly entering the soldering high temperature area and damaging the PCB and components.

3. When the PCB enters the reflow soldering area, the temperature rises rapidly to make the solder paste reach the melting state, and the liquid solder wets and diffuses the solder pad, component ends and pins of the PCB, and the liquid tin reflows and mixes to form solder joints.

4. The PCB enters the reflow cooling area, and the liquid tin reflows again to solidify the solder joint under the action of reflow cooling air; At this time, reflow soldering is completed.

The whole working process of reflow welding cannot be separated from the hot air in the reflow furnace. Reflow welding depends on the effect of hot air flow on the solder joint, and the colloidal flux reacts physically under a fixed high-temperature air flow to achieve SMD welding; The "reflow" of reflow welding is because the gas circulates back and forth in the welding machine to produce high temperature to achieve the purpose of welding, so it is called reflow welding.