Soldering iron welding principle
It is a science to solder. Electric soldering iron welding works by heating and melting the solid solder wire with a heated soldering iron, causing it to flow into the metal to be welded, and then, after cooling, forming a solid and trustworthy solder joint.
When the solder is a tin-lead alloy and the soldering surface is copper, the solder first wets the soldering surface, and with the occurrence of wetting, the solder slowly diffuses to the copper metal, forming an adhesion layer on the contact surface between the solder and the copper metal, so that The two are firmly combined. Therefore, soldering is accomplished through three physical and chemical processes of wetting, diffusion and metallurgy.
1. Wetting: In the wetting process, the melted solder flows by capillary force along the small bumps and crystallized gaps on the metal surface of the base metal, forming an adhesion layer on the surface of the base metal to be welded. The metal's atoms are in close proximity to one another, getting to the point where their gravitational pull is active.
Conditions in the environment that lead to wetting: The base metal surface that is being welded must be free of contaminants and oxides.
Picture metaphor Water cannot moisten the lotus if it is dropped onto its leaves to generate water droplets. If you drop water on cotton, it will seep inside the fibers, allowing the cotton to be moistened.
2. Diffusion: Mutual diffusion between solder and base metal atoms starts to happen as wetting progresses. Once the temperature rises, the atoms in the lattice are typically in a condition of thermal vibration. Atomic activity increases to the point where molten base metal and solder atoms cross the contact surface and enter each other's lattices. The heating temperature and duration determine the atoms' rate of movement and number.
3. Metallurgical combination: An intermediary layer —- metal compound is formed between the two metals as a result of mutual diffusion between the solder and the base metal. A metal compound must form between the base material to be welded and the solder in order to achieve a good solder joint. in order to achieve a strong metallurgical bond with the base metal.
