Reflow soldering is the soldering of mechanical and electrical connections between the solder ends or pins of surface assembled components and the solder pads of printed boards by remelting the paste solders pre allocated to the solder pads of printed boards.
When the PCB enters the preheating temperature zone of 140 ℃ ~ 160 ℃, the solvent and gas in the solder paste evaporate. At the same time, the flux in the solder paste moistens the pads, component terminals and pins, and the solder paste softens and collapses, covering the pads, isolating the pads and component pins from oxygen; The surface mounted components are fully preheated, and then when entering the welding area, the temperature rises rapidly at the international standard heating rate of 2-3 ℃ per second to make the solder paste reach the melting state, and the liquid solder is mixed with wetting, diffusion, overflow and reflow on the PCB pad, component terminals and pins to generate metal compounds on the welding interface to form the solder joints; Finally, the PCB enters the cooling zone to solidify the solder joint.
