What is the welding principle of an electric soldering iron
Welding principle of electric soldering iron
Electric soldering iron uses tin for welding operations. Its working principle is to heat and melt the solid solder wire through the heated soldering iron, and with the help of soldering flux, it flows into the metal to be welded. After cooling, it forms a solid and reliable welding point.
When the solder is made of tin lead alloy and the welding surface is made of copper, the solder first wets the welding surface. With the occurrence of wetting phenomenon, the solder gradually diffuses towards the metal copper, forming an adhesion layer on the contact surface between the solder and the metal copper, making the two firmly bonded.
Therefore, soldering is accomplished through three physical and Chemical process: wetting, diffusion and metallurgy.
1. Wetting
The wetting process refers to the diffusion of melted solder along the fine concave convex and crystalline gaps on the surface of the base metal using capillary force, forming an adhesion layer on the surface of the welded base metal, making the atoms of the solder and the base metal close to each other, reaching the distance where atomic gravity acts.
Environmental conditions that cause wetting: The surface of the welded base material must be clean and free from oxides or pollutants.
Image metaphor: Dropping water onto lotus leaves to form water droplets means that water cannot moisten the lotus. Drop water onto the cotton and it will penetrate into the cotton, which means that water can moisten the cotton.
2. Diffusion
With the wetting process, the mutual diffusion phenomenon between the solder and the base metal atoms begins to occur.
Usually, atoms are in a thermal vibrational state in the lattice lattice, once the temperature increases. The intensification of atomic activity causes the atoms in the melted solder and base metal to cross the contact surface and enter the lattice of each other. The speed and number of atoms' movement depend on the heating temperature and time.
3. Metallurgical bonding
Due to the mutual diffusion between the solder and the base metal, an intermediate layer~metal compound is formed between the two metals. In order to obtain a good solder joint, a metal compound must be formed between the welded base metal and the solder to achieve a strong metallurgical bonding state of the base metal.
