Introduction to soldering using an electric soldering iron
Tin welding is a science, and the principle of electric soldering is to heat and melt the solid solder wire through a heated soldering iron. With the help of flux, it flows into the metal to be soldered, and 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 slowly 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. So soldering is completed through three physical and chemical processes: wetting, diffusion, and metallurgical combination.
1. Wetting: The wetting process refers to the use of capillary force to diffuse molten solder along the fine bumps and crystalline gaps on the surface of the base metal, forming an attachment layer on the surface of the welded base metal, making the atoms of the solder and the base metal close to each other, and achieving the distance at which atomic gravity acts.
Environmental conditions that cause wetting: The surface of the welded base material must be clean and free of oxides or pollutants.
Image metaphor: Dropping water onto lotus leaves to form water droplets means that water cannot wet the lotus. Dropping water onto cotton allows it to seep into the cotton, making it moist.
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, and once the temperature rises. Atomic activity intensifies, causing the melted solder and atoms in the base material to cross the contact surface and enter each other's lattice lattice. The speed and number of atomic movement are determined by the temperature and time of heating.
3. Metallurgical bonding: Due to the mutual diffusion between the solder and the base metal, an intermediate layer - a metal compound - is formed between the two metals. In order to obtain good solder joints, 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.
