How does reflow soldering work?

Reflow soldering is a surface assembly technology commonly used in electronic manufacturing, which is used to solder surface mount components to PCBs (Printed Circuit Boards). The working principle of reflow soldering mainly includes three stages: preheating, soldering and cooling. The working principle of reflow soldering will be introduced in detail below.

1. Warm-up stage:

1. Purpose: The purpose of the preheating stage is to evenly heat the entire PCB and surface mount components to the soldering temperature, making the soldering process more uniform and stable.

2. Process: The PCB is fed into the reflow oven via a conveyor belt and first passes through the preheating area, which is usually set at around 150°C. During this stage, the PCB gradually heats up to remove moisture and volatile substances in preparation for subsequent soldering.

3. Note: The preheating temperature and time need to be adjusted according to the specific components and PCB requirements to ensure welding quality and stability.

2. Welding stage:

1. Purpose: The soldering stage is the core part of reflow soldering, which mainly connects components firmly to the pads of the PCB by melting the solder.

2. Process: After the PCB passes through the preheating area, it enters the soldering area, which is set at a higher temperature, usually around 220°C. At this time, the solder will be heated to the melting point, and the solder applied to the PCB pad will melt into liquid, contact with the pad of the component and form a reliable solder connection.

3. Soldering form: Reflow soldering is usually divided into two forms: wave soldering and lead-free reflow soldering. Lead-free reflow soldering is more environmentally friendly and is the trend of future development.

4. Solder selection: According to the requirements of different components and PCBs, choose the appropriate solder, usually solder alloy, common ones are Sn63Pb37, SnAgCu, etc.

3. Cooling stage:

1. Purpose: The cooling stage is to allow the solder to solidify quickly, making the soldered connection strong and stable.

2. Process: After the PCB passes through the soldering area, it enters the cooling area, where the temperature is usually room temperature or slightly higher. During the cooling stage, the solder temperature drops rapidly, changing from liquid to solid, and the soldering connection is formed.

3. Cooling method: Cooling can be accelerated by natural cooling or by cooling fans and other equipment to speed up the welding process.

The working principle of reflow soldering is to firmly connect surface mount components to PCB through a three-stage process of preheating, soldering and cooling to achieve high-quality and efficient soldering. The quality and stability of the soldering connection can be ensured by precisely controlling the temperature and time of each stage. With the continuous development of electronic manufacturing technology, reflow soldering technology is also constantly improving and innovating to meet the more complex and sophisticated electronic manufacturing needs.