PuHui Presents the Role of Each Stage in a Reflow Soldering Machine

The reflow soldering machine is a device that provides a heating environment to heat the solder paste, allowing the surface-mounted components to be reliably bonded to the PCB pads through the solder paste alloy. Reflow soldering machines can be classified into various types based on technological developments: vapor phase reflow soldering, infrared reflow soldering, far infrared reflow soldering, infrared heating air reflow soldering, full hot air reflow soldering, and water-cooled reflow soldering. Reflow soldering machines have evolved alongside the emergence of miniaturized electronic products and are mainly used for the soldering of various surface-mounted components. The soldering material for this technique is solder paste. An appropriate amount and form of solder paste are pre-coated on the pads of the circuit board, and then the SMT components are placed in the corresponding positions. The solder paste has a certain degree of adhesiveness, which fixes the components, and then the circuit board with mounted components is placed into the reflow soldering machine. The conveying system drives the circuit board through different temperature zones within the equipment, and the solder paste undergoes processes such as drying, preheating, melting, wetting, and cooling, soldering the components to the printed circuit board. The core function of reflow soldering is to utilize an external heat source to heat the solder material, causing it to melt and flow again to complete the soldering process of the circuit board. The conveying system drives the PCB through different zones of the reflow soldering machine for soldering, and each stage plays a different role.

1 Function of the heating zone The heating zone is a stage in the reflow soldering machine process, where the PCB is preheated and the solder paste is activated. Some of the solvents are evaporated, and the moisture on the PCB and components is removed, eliminating stress inside the PCB.

2 Function of the insulation zone When the PCB enters the insulation zone, it reaches a certain temperature to prevent sudden exposure to the high-temperature soldering zone, which could damage the PCB and components. This zone also serves to maintain a stable temperature for the components, ensuring uniform temperature for components of different sizes on the PCB, reducing temperature differences across the entire PCB, and evaporating the flux in the solder paste to remove the oxides from the pads and component leads.

3 Function of the soldering zone When the PCB enters the soldering zone, the temperature rises to a high level. The solder paste changes from a solid to a liquid, fully wetting the solder pads and component leads. The duration of this stage is relatively short to prevent high-temperature damage to the PCB and components.

4 Function of the cooling zone After the solder paste becomes liquid, it can be cooled. The faster the cooling speed, the better. Slow cooling can produce a dark, rough surface. Generally, once the temperature drops to 75℃, the solidification is completed, thereby achieving the soldering of the PCB."