What is reflow soldering and what is the working principle of reflow soldering

What is reflow soldering and what is the working principle of reflow soldering

In electronic component mounting, soldering techniques such as reflow soldering and wave soldering are often used.

1.What is reflow soldering?

Reflow Soldering is a technology for installing electronic components. It is a method of connecting components to the PCB by heating the entire PCB in a heater after pre coating with solder paste and installing the components, allowing the solder paste to melt within an appropriate temperature and time range. Because the entire board is being heated, this method is called reflow soldering.

During the reflow soldering process, the position of components on the PCB is limited because it is necessary to ensure that all parts of the board can be heated to the appropriate temperature to melt the solder paste. One advantage of reflow soldering is that it can be used on high-speed production lines for mass production. It is also suitable for using high-density arrangements on SMT components.

However, reflow soldering also has some drawbacks, such as high temperatures may damage sensitive components, and high or low temperatures can also lead to welding quality issues. In addition, reflow soldering requires a high level of technical expertise and experience to ensure quality and reliability.

2.So what exactly is reflow soldering?

Reflow soldering is the process of remelting the paste like solder that has been pre allocated to the printed circuit board solder pads to achieve mechanical and electrical bonding between the solder ends or pins of surface assembled components and the printed circuit board solder pads.

Reflow soldering is the process of soldering components onto a PCB board, which involves surface mount devices.

By relying on the action of hot air flow on the solder joints, the adhesive solder undergoes physical reactions under a certain high-temperature airflow to achieve SMD (surface mount device) welding.

The reason why it is called "reflow welding" is because the gas (nitrogen) circulates in the welding machine to generate high temperature and achieve the welding purpose.

3.Reflow soldering principle

Reflow soldering is generally divided into four working areas: heating area, insulation area, welding area, and cooling area.

(1) 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 solder pads, component ends, and pins. The solder paste softens, collapses, and covers the solder pads, isolating them from oxygen.

(2) The PCB enters the insulation area to provide sufficient preheating for the PCB and components, in order to prevent the PCB from suddenly entering the high-temperature welding area and damaging the PCB and components.

(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 ends, and pins of the PCB to form solder joints.

(4) The PCB enters the cooling zone, causing the solder joints to solidify and completing the entire reflow soldering process.