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SMT reflow soldering principle introduction

  • Time:2020-01-23
  • Visits:436

SMT reflow soldering principle introduction


I believe many friends have heard of the term "SMT reflow soldering", but there are not many who can truly explain the principle of SMT reflow soldering. SMT reflow soldering is the process of remelting the pre allocated paste solder paste on the printed circuit board solder pads, achieving the mechanical and electrical connection between the surface assembled component solder joints or pins and the printed circuit board solder pads through soft soldering. 


SMT reflow soldering is the process of soldering components onto a PCB board, which involves surface mounted components. SMT reflow soldering relies on the action of hot air flow on the solder joint, and the adhesive flux undergoes physical reactions under a fixed high-temperature air flow to achieve SMD soldering; So it is called "SMT reflow soldering" because the gas circulates in the soldering machine to generate high temperature and achieve the soldering purpose.


1.When the PCB enters the heating zone, the solvents and gases in the solder paste evaporate. At the same time, the flux in the solder paste wets the solder pads, component terminals, and pins. The solder paste softens, collapses, and covers the solder pads, isolating them from oxygen.


2.When the PCB enters the insulation area, sufficient preheating is provided to the PCB and components to prevent them from suddenly entering the high-temperature soldering area and damaging them.


3.When the PCB enters the soldering area, the temperature rapidly rises, causing the solder paste to reach a molten state. Liquid solder wets, diffuses, diffuses, or mixes with the solder pads, component terminals, and pins of the PCB to form solder joints.


4. PCB enters the cooling zone to solidify the solder joints; At this point, SMT reflow soldering has been completed.