Why is reflow soldering called “reflow”? The reflow of reflow soldering means that after the solder paste reaches the melting point of the solder paste, under the action of the surface tension of the liquid tin and the flux, the liquid tin reflows to the component pins to form solder joints, allowing the circuit A process in which the board pads and components are soldered into a whole is also called the “reflow” process.
1. When the PCB board enters the reflow heating zone, the solvent and gas in the solder paste evaporate. At the same time, the flux in the solder paste wets the pads, component ends and pins, and the solder paste softens and collapses. , Covering the pad, isolating the pad and component pins from 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 high temperature area of welding and damaging the PCB and components.
3. When the PCB enters the reflow soldering area, the temperature rises rapidly so that the solder paste reaches a molten state, and the liquid solder wets and diffuses the pads, 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 zone, and the liquid tin is reflowed to solidify the solder joints by the cold air of the reflow soldering; at this time, the reflow soldering is completed.
The entire working process of reflow soldering is inseparable from the hot air in the reflow furnace. Reflow soldering relies on the action of hot air flow on the solder joints. The jelly-like flux undergoes physical reaction under a certain high temperature air flow to achieve SMD soldering; reflow soldering ” “Reflow” is because the gas circulates back and forth in the welding machine to generate high temperature to achieve the purpose of welding, so it is called reflow soldering.
Post time: Nov-03-2022