Introduction to the principle and process of reflow soldering

Reflow solderingIt is a widely used process for soldering electronic components, especially in surface mount technology（SMT）In the middle. It is mainly used for surface mount components（SMD）Solder to printed circuit board（PCB）Up there. The following is an introduction to the principle and process of reflow soldering.

principle

The basic principle of reflow soldering is to use the melting and solidification process of solder to achieve the connection between components and circuit boards. The core steps include:

1. Solder paste printing: inPCBPrint solder paste on the solder pads, which is usually composed of solder powder, flux, and solvent.

2. Component placement: Place surface mount components on solder paste, which will adhere to the pins of the components under gravity.

3. Heating: willPCBPut it into a reflow soldering furnace, heat it to evaporate the flux in the solder paste, melt the solder powder, and form liquid solder.

4. Cooling solidification: After heating, the solder re solidifies during the cooling process, forming a strong welding connection.

Process steps

The process steps of reflow soldering generally include the following stages:

1. Solder paste printing

   - Use a screen printing machine to accurately print solder paste ontoPCBOn the solder pad.

2. Component mounting

   - Use a surface mount machine to place surface mount components onto solder paste, ensuring accurate positioning of the components.

3. Preheating stage

   - PCBAfter entering the reflow soldering furnace, it first passes through the preheating zone, where the solvent in the solder paste evaporates, the flux is activated, and the solder begins to heat up.

4. Reflux stage

   - In the reflow zone, the temperature reaches the melting temperature of the solder (usually220°Cto250°C）The solder completely melts, forming a liquid solder joint.

5. Cooling stage

   - PCBEntering the cooling zone, the solder rapidly cools and solidifies, forming a stable welding connection.

equipment

Reflow soldering usually uses specialized reflow soldering furnaces, which are mainly divided into the following types:

- Hot air reflow soldering furnace: using hot air heating, suitable for most applications.

- Infrared reflow soldering furnace: using infrared heating, suitable for temperature sensitive components.

- Laser reflow soldering furnace: using laser precise heating, suitable for high-precision welding.

advantage

- High efficiency: can simultaneously solder multiple components, suitable for large-scale production.

- High quality: Uniform welding connection, high reliability.

- Strong adaptability: suitable for different types of components andPCBDesign.

shortcoming

- Large equipment investment: The cost of reflow soldering furnaces is relatively high.

- Challenge for temperature sensitive components: It is necessary to control the heating process to avoid damage to sensitive components.

summary

Reflow soldering is an efficient and reliable soldering process widely used in modern electronic manufacturing. Through reasonable process control, high-quality welding connections can be achieved to ensure the performance and reliability of electronic products.