Reflow soldering is the soldering of the mechanical and electrical connections between the terminations or pins of surface mount components and the printed board pads by remelting the paste-loaded solder pre-distributed on the printed board pads. Share the principle and purpose of reflow soldering here.
Reflow soldering principle:
The circuit board with the mounted smt components is transported through the reflow oven guide rail, and passes through the preheating zone, heat preservation zone, welding zone and cooling zone of the reflow oven respectively. point.
A. When the PCB enters the 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 terminals and pins, and the solder paste softens, collapses, and covers the solder paste. plate to isolate pads and component pins from oxygen.
B. When the PCB enters the heat preservation 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.
C. When the PCB enters the welding area, the temperature rises rapidly so that the solder paste reaches a molten state, and the liquid solder wets, diffuses, diffuses, or reflows the pads, component ends and pins of the PCB to form solder joints.
D. The PCB enters the cooling zone to solidify the solder joints; when the reflow soldering is completed.
Purpose of reflow soldering:
Reflow soldering is because the gas circulates in the welding machine to generate high temperature to achieve the purpose of soldering. It is to send the circuit board with the SMD components installed into the SMT reflow soldering chamber, and then melt the solder paste used to solder the SMD components through the high-temperature hot air to form a process of reflow temperature change, so that the SMT components and the circuit board are melted. Bond on the pads, then cool and solder them together. Overall Summary The purpose of reflow soldering is to solder SMT components with passive pins to the circuit board through solder paste to form a finished PCBA circuit board with certain electrical properties.
