Reflow soldering machine is one of the core equipment in SMT production line. It melts the solder paste and secures the electronic components and the PCB pad soldering well through different temperature curve. So the temperature curve and temperature control of the reflow soldering have a great influence on the soldering quality of the PCBA. Generally, the reflow soldering is divided into four temperature zones. Each temperature zone has the different functions, so what is the role of each temperature zone in reflow soldering?
What are the four temperature zones for reflow soldering?
Reflow soldering is generally divided into four temperature zones, which are preheating zone, heating zone, soldering zone and cooling zone. Each temperature zone correspond to different reflow effects.
Reflow soldering preheating zone
The function of preheating is to activate the solder paste, make the solder paste moving, the soldering material reaches thermal equilibrium, and the flux will volatilize in an appropriate amount as the temperature rises. The heating rate of the preheating zone should be controlled within an appropriate range. If it is too slow, the flux will not volatilize enough, which will affect the soldering quality.
Reflow soldering heating zone
The heat-absorbing zone is to stabilize the temperature of various components in the reflow furnace. Because the components on the board are in different sizes, small components heat up quickly, while large components heat up slowly. In order to make the temperature of each component reach a balance, the The flux is fully volatilized, reducing the rate of soldering bubbles.
Reflow soldering zone
The temperature in the reflow soldering zone should be raised to the highest level to fully melt the tin powder metal substance in the solder paste, and the flux should be fully volatilized. The residence time in the reflow soldering zone should not be too long, so as not to cause damage to electronic components and PCB boards due to excessive temperature.
Reflow soldering cooling zone
To make sure best soldering quality, the temperature should be cooled below the freezing point of the solder paste. If it is too slow, the solder paste will oxidize with the moisture in the air, resulting in poor soldering quality.