Three principles of electric soldering iron welding
1. Wetting: The wetting process means that the melted solder flows around along the fine bumps and crystallized gaps on the metal surface of the base metal by means 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 the material metal are close to each other, reaching the distance at which the gravitational force of the atoms works.
Environmental conditions that cause wetting: The surface of the base metal to be welded must be clean and free from oxides or contaminants.
Image metaphor: Drop water on the lotus leaves to form water droplets, that is, 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: With the progress of wetting, mutual diffusion between solder and base metal atoms begins to occur. Usually the atoms are in a state of thermal vibration in the lattice lattice, once the temperature rises. The atomic activity is intensified, so that the atoms in the molten solder and the base metal cross the contact surface and enter the lattice lattice of each other. The moving speed and quantity of the atoms are determined by the heating temperature and time.
3. Metallurgical combination: Due to mutual diffusion between the solder and the base metal, an intermediate layer --- metal compound is formed between the two metals. To obtain a good solder joint, a metal compound must be formed between the base material to be welded and the solder. So that the base metal achieves a firm metallurgical bond.
