1. Classification of tin bars

Tin bars are classified according to their composition and can be divided into leaded tin bars and lead-free tin bars.

At present, the commonly used lead-free tin bars are: tin-copper lead-free tin bars (Sn99. /Pb40 etc.)

In addition to the main elements tin, lead, copper, and silver, tin bars often contain a small amount of other elements, such as nickel, antimony, bismuth, In, and rare earths. These trace alloy elements in the tin bar have a great influence on the physical and mechanical properties of the tin bar: bismuth can reduce the melting temperature of the tin bar and improve the wettability and spreadability, but if the amount added is too large, it will reduce the fatigue life and plasticity of the solder joint. Among the systematically designed chemical components, the designer obviously hopes to achieve an optimal balance in all aspects of the performance of the tin bar, such as soldering performance, melting temperature, strength, plasticity and fatigue life.

2. Reuse of tin bars

Tin is a silver-white metal. A golden oxide film is often formed on the surface of a newly poured tin ingot. When the tin bar is bent hard, it will make a rustling sound due to the effect of tin twin crystals. It feels like biting and rustling, which is called tinming. Tin bars have many advantages, such as smooth surface; good fluidity and wettability during welding; good mechanical properties; bright solder joints; less oxidation residue. In the electronic manufacturing process, there are also many discarded tin bars. These need to be recycled for tin bars to avoid waste. For example, there is no scraping surface during manufacturing, the cooling system is not good, the mold is not smooth, etc. will cause the above problems. Production workers should not use their hands directly when holding tin bars. Generally speaking, these defects of tin bars do not affect the welding effect. However, if the defect is relatively large, it will have some impact on the welding effect. In order to solve this adverse effect, we can recycle the tin bars and sell them after reprocessing, which can ensure the effect of the tin bars during welding.