What is the principle of electric soldering iron welding?
Soldering is a science. The principle of soldering iron is to heat and melt the solid solder wire with a heated soldering iron, and then use the action of flux to make it flow between the metals to be welded, and then form a strong and reliable solder joint after cooling. .
When the solder is a tin-lead alloy and the soldering surface is copper, the solder first wets the soldering surface. As the wetting phenomenon occurs, the solder slowly diffuses toward the metal copper, forming an adhesion layer on the contact surface between the solder and the metal copper. The two are firmly combined. Therefore, soldering is completed through three physical and chemical processes of wetting, diffusion and metallurgical bonding.
1. Wetting: The wetting process means that the melted solder flows around along the fine unevenness and crystallization gaps on the surface of the base metal with the help of capillary force, thereby forming an adhesion layer on the surface of the base metal to be welded, so that the solder and the base metal The atoms of a material metal are close to each other, reaching a distance where the atomic gravity takes effect.
Environmental conditions causing wetting: The surface of the base metal to be welded must be clean and free of oxides or contaminants.
Image metaphor: Dropping water onto the lotus leaves to form water droplets means that the water cannot moisten the lotus. Drop water on the cotton, and the water will penetrate into the cotton. That is, the water can moisten the cotton.
2. Diffusion: As wetting proceeds, the mutual diffusion phenomenon between solder and base metal metal atoms begins to occur. Normally the atoms in the crystal lattice are in a state of thermal vibration once the temperature is increased. The atomic activity intensifies, causing the atoms in the molten solder and the base metal to cross the contact surface and enter each other's crystal lattice. The moving speed and number of the atoms are determined by the heating temperature and time.
3. Metallurgical bonding: Due to mutual diffusion between the solder and the base metal, an intermediate layer - a metal compound - is formed between the two metals. To obtain a good solder joint, a metal compound must be formed between the base metal to be welded and the solder. Thus, the base material reaches a strong metallurgical bonding state.
