Each manufacturer in the solder industry has different solder paste formulations, different production processes, and different types. The lead-free solder pastes are roughly divided into low temperature solder pastes, medium temperature solder pastes, and high temperature solder pastes. So what are the characteristics of low temperature, medium temperature, and high temperature solder paste? What are the differences? From the surface we should be able to see why they are so named. The temperature must be different. So what are the specific characteristics and differences? Best Tools summarizes for you as follows:
Low temperature solder paste
Low-temperature solder paste: A solder paste with a melting point of 138 ℃ is called a low-temperature solder paste. When the components of the chip cannot withstand temperatures of 200 ℃ and above and a chip reflow process is required, a low-temperature solder paste is used for the soldering process. It protects the original components and PCB that cannot withstand high temperature reflow soldering. It is very popular with LED patches. Its alloy composition is tin-bismuth alloy. The low-temperature solder paste reflow peak temperature is 135-170 ℃.
Medium temperature solder paste
Medium temperature solder paste: Melting point is 172 ℃ ~ 183 ℃. Its alloy composition is Sn / Pb (lead) or Sn / Ag / Bi (lead-free). The particle size of tin powder is between 25 ~ 45um. It is mainly used for the welding of components that cannot withstand high temperatures. The LED industry is widely used. The characteristics of medium temperature solder paste are mainly imported rosin, which has good adhesion and can effectively prevent slump. The amount of residue after reflow is small, and Transparency, without hindering ICT testing.
High temperature solder paste
High temperature solder paste: High temperature solder paste is composed of metal elements such as tin, silver, copper, etc. The melting point of high temperature solder paste is 210-227 ℃. If the SMD components or lamp beads can withstand high temperatures, LEDs are still recommended to use high temperature lead-free solder paste, which has high reliability and is not easy to desolder and crack. Its high temperature solder paste is more widely used than low temperature and medium temperature solder paste. For example, some BGA, QFN, SMT, and mobile phone precision components are soldered with high temperature solder paste. The characteristics are better, no-clean, low residue, high insulation Resistance, can pass the ICT probe test; good tin crawling effect, long service life; high activity, low void rate, not easy to collapse; full and bright solder joints, high strength, excellent electrical conductivity; excellent printing performance and mold release performance, fine There is no pressure for pin-pitch mounting; the imported flux can be used for long-term printing without affecting the wettability and viscosity of the solder paste.
Only by clearing the respective characteristics of these three types of solder paste can we select the appropriate solder paste according to the actual situation, reduce the defective rate, and improve production efficiency and quality!
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