What is reflow soldering?

PCB Reflow soldering is a process that electrically and mechanically connects electronic components to a printed circuit board (PCB).

The process begins by applying solder paste on the PCB in a specific pattern using a specialized stencil printer.

The solder paste consists of a metal alloy suspended in a mixture of solvents and other materials. Then, the circuit board is heated using a reflow oven.

The reflow oven is a sealed box with a heater, fan, and temperature sensor inside.

The circuit board is placed in a furnace, where the temperature gradually increases.

When the temperature reaches the melting point of the solder paste, the solder paste melts and fills the gap between the component and the PCB. Then, the temperature gradually decreases, and the solder paste cools and solidifies.

Reflow soldering is one of the most commonly used PCB soldering processes. It has the following advantages:

• High welding quality, low empty welding, and false welding rate;

• High production efficiency, suitable for high-volume PCB production;

• The process is simple and easy to control;

• Little impact on the environment.

There are two main types of reflow: single-sided reflow and double-sided reflow.

Single-sided reflow only requires a one-time solder reflow oven, while double-sided reflow requires two times reflow ovens.

In double-sided reflow soldering, need to consider the following factors :

• Parts temperature resistance: The first side parts need to go through the reflow oven twice, so their temperature resistance must be able to withstand the temperature of two reflows;

• Part size: It is recommended that smaller parts be placed on the first side of the reflow oven because they are lighter and will not fall off during the second reflow oven.

• Parts layout: Parts layout should be as even as possible to avoid too many parts in certain areas leading to warping.

PCB Reflow soldering is a significant process in electronic manufacturing. Understanding the principles and methods of reflow soldering can improve PCB soldering quality and production efficiency.