PCB News - Talk about the importance of tin-lead solder to pcba

Talk about the importance of tin-lead solder to PCBA
Today's electronic devices are becoming more and more intelligent and more diverse, which can bring people a different experience. Human beings are curious about the unknown world, and are also exploring the unknown world, so various advanced and intelligent devices are introduced to people's eyes, and they have also uncovered one unsolved mystery for mankind. Then these devices can't leave one thing, that is the PCBA circuit board. The following editor will talk about the importance of tin-lead solder to PCBA.

Talk about the importance of tin-lead solder to PCBA

When the editor talks about PCBA circuit board, we will talk about auxiliary materials, because it is very important for PCBA circuit board. The most commonly used auxiliary materials for PCBA circuit boards are tin-lead solder and lead-free solder. The more famous among them is 63Sn-37Pb eutectic tin-lead solder, which is the most critical electronic soldering material in the past century.

Because tin has good oxidation resistance at room temperature, it is a low melting point metal with soft texture and good ductility: lead is not only chemically stable, oxidation and corrosion resistance, but also a soft metal with moldability, castability, and lubricity. Good, it is easy to process and shape: Lead and tin have good mutual solubility. Adding different proportions of lead to tin can form high, medium and low temperature solders for various purposes, so as to meet the requirements of various difficult SMT patches. In particular, 63Sn-37Pb eutectic solder has excellent electrical conductivity, chemical stability, mechanical properties and manufacturability, low melting point, high solder joint strength, and is an extremely ideal electronic soldering material. Therefore, Sn can be combined with Pb, Ag, Bi, In and other metal elements to form high, medium and low temperature solders for various applications.

1. The basic physical and chemical properties of tin
Tin is a silver-white shiny metal with good oxidation resistance at room temperature. It can maintain gloss even when exposed to the air: its density is 7.298g/cm2 (15°C), and its melting point is 232°C. It is a soft and extensible texture. Low melting point metal with good properties.
(1) Phase transition phenomenon of tin
The phase transition point of tin is 13.2°C. When the temperature is higher than the phase transition point, it is white B-Sn; when the temperature is lower than the phase transition point, it becomes powdery. When the phase change occurs, the volume will increase by about 26%. The low-temperature tin phase change will make the solder brittle and almost lose its strength. The phase transition rate is the fastest near -40°C, and when it is lower than -50°C, metallic tin becomes powdery gray tin. Therefore, pure tin cannot be used for electronic assembly.
(2) The chemical properties of tin
1. Tin has good corrosion resistance in the atmosphere, is not easy to lose its luster, and is not affected by water, oxygen, and carbon dioxide.
2. Tin can resist the corrosion of organic acids, and for neutral substances, it has higher corrosion resistance.
3. Sn is an amphoteric metal, which can react chemically with strong acids and alkalis, and cannot resist chlorine, iodine, caustic soda and alkalis.
corrosion. Therefore, for those assembled boards that are used in acidic, alkaline, and salt spray environments, three-proof coating is required to protect the solder joints.
Every thing has two sides, that is, it has its advantages and its disadvantages, and how to choose your own suitable tin-lead solder inPCBA production, or even choose lead-free solder according to different products, must be planned to quality Go in control.