Characteristics and application of PCBA circuit board welding materials
2022-11-18
With the continuous progress of science and technology, human's exploration of the unknown world is deepening gradually. A variety of advanced equipment, along with the human desire for the unknown, for us to uncover one mystery after another. But the only constant is that these devices must use PCBA circuit boards.
So when it comes to printed circuit boards, we can't forget the important role of auxiliary materials. At present, the most commonly used tin lead solder and lead - free solder. The most famous is 63Sn-37Pb eutectic tin-lead solder, which has been the most important electronic welding material for nearly a century. Tin is a low-melting metal with a soft texture and good ductility due to its good oxidation resistance at room temperature. Lead is not only a kind of soft metal, has stable chemical properties, oxidation resistance, and corrosion resistance, but also has good formability, and casting, easy to process molding. Lead and tin are well miscible. High, medium, and low temperature solders can be formed by adding different proportions of lead to tin. Especially 63Sn-37Pb eutectic solder has excellent electrical conductivity, chemical stability, mechanical properties and technology, low melting point and high solder joint strength, it is an ideal electronic welding material. Therefore, tin can be combined with lead, silver, bismuth, indium and other metallic elements to form high, medium and low temperature solder for various purposes.
Basic physical and chemical properties of tin
Tin is a silvery-white glossy metal with good oxidation resistance at room temperature and can retain its luster when exposed to air: with a density of 7.298 g/cm2 (15) and a melting point of 232, it is a low-melting metal with a soft texture and good ductility.
1. Phase transition of tin
The phase transition point of tin is 13.2. White borotin at temperatures higher than the phase transition point; When the temperature is below the phase transition point, it begins to become a powder. When a phase transition occurs, the volume will increase by about 26%. The low temperature tin phase transition will make the solder brittle and the strength almost disappear. The rate of phase transition is fastest around -40, when the temperature is below -50, the metallic tin changes to a powdered gray tin. Therefore, pure tin cannot be used for electronic assembly.
2. Chemical properties of tin
(1) Tin has good corrosion resistance in the atmosphere, is not easy to lose luster, is not affected by water, oxygen, carbon dioxide.
(2) Tin can resist the corrosion of organic acids, and has high corrosion resistance to neutral substances.
(3) Tin is an amphoteric metal that reacts with strong acids and bases, but is not resistant to chlorine, iodine, caustic soda and bases.
Corrosion. Therefore, for the assembly plate used in acidic, alkaline, salt spray environment, the need for a three-proof coating to protect the solder joints.
There are advantages and disadvantages, which are two sides of the coin. For PCBA manufacturing, quality control must consider how to select suitable solder solder or even lead-free solder for different products.
So when it comes to printed circuit boards, we can't forget the important role of auxiliary materials. At present, the most commonly used tin lead solder and lead - free solder. The most famous is 63Sn-37Pb eutectic tin-lead solder, which has been the most important electronic welding material for nearly a century. Tin is a low-melting metal with a soft texture and good ductility due to its good oxidation resistance at room temperature. Lead is not only a kind of soft metal, has stable chemical properties, oxidation resistance, and corrosion resistance, but also has good formability, and casting, easy to process molding. Lead and tin are well miscible. High, medium, and low temperature solders can be formed by adding different proportions of lead to tin. Especially 63Sn-37Pb eutectic solder has excellent electrical conductivity, chemical stability, mechanical properties and technology, low melting point and high solder joint strength, it is an ideal electronic welding material. Therefore, tin can be combined with lead, silver, bismuth, indium and other metallic elements to form high, medium and low temperature solder for various purposes.
Basic physical and chemical properties of tin
Tin is a silvery-white glossy metal with good oxidation resistance at room temperature and can retain its luster when exposed to air: with a density of 7.298 g/cm2 (15) and a melting point of 232, it is a low-melting metal with a soft texture and good ductility.
1. Phase transition of tin
The phase transition point of tin is 13.2. White borotin at temperatures higher than the phase transition point; When the temperature is below the phase transition point, it begins to become a powder. When a phase transition occurs, the volume will increase by about 26%. The low temperature tin phase transition will make the solder brittle and the strength almost disappear. The rate of phase transition is fastest around -40, when the temperature is below -50, the metallic tin changes to a powdered gray tin. Therefore, pure tin cannot be used for electronic assembly.
2. Chemical properties of tin
(1) Tin has good corrosion resistance in the atmosphere, is not easy to lose luster, is not affected by water, oxygen, carbon dioxide.
(2) Tin can resist the corrosion of organic acids, and has high corrosion resistance to neutral substances.
(3) Tin is an amphoteric metal that reacts with strong acids and bases, but is not resistant to chlorine, iodine, caustic soda and bases.
Corrosion. Therefore, for the assembly plate used in acidic, alkaline, salt spray environment, the need for a three-proof coating to protect the solder joints.
There are advantages and disadvantages, which are two sides of the coin. For PCBA manufacturing, quality control must consider how to select suitable solder solder or even lead-free solder for different products.
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