Laser welding process between FPC and PCB connectors

　　As more and more FPC flexible circuit boards are applied to high-end intelligent devices, such as mobile phones, laptops, auto parts, medical equipment and other electronic terminal equipment. Nowadays, with the electronic products into high-density assembly, with the introduction of new electronic equipment, new CHIP parts, new ceramic piezoelectric transformers, new electronic materials and new processes, laser automatic soldering machine is widely used in FPC, electronic components and other fields.

　　Automatic tin welding machine is a laser welding technology in which the solder paste is heated by laser as a heat source. The main feature of laser welding is to use the high energy of laser to quickly heat the welding in local or small areas. Compared with traditional welding, laser welding has irreplaceable advantages.

　　There are some fundamental problems in the application of traditional welding technology in FPC and electronic components, such as the lead of the component and the pad of the printed circuit board will diffuse and melt the solder Cu, Fe, Zn various metal impurities; Molten tin material flows at high speed in the air and is easy to produce oxides. At the same time, in the traditional reflow welding, the electronic components themselves are also heated to the tin welding temperature at a large heating rate, which produces thermal shock to the components. Some thin-packaged components, especially thermal components, can be damaged. At the same time, due to the use of integral heating method, FPC flexible circuit boards and PCB circuit boards, electronic components must go through heating, heat insulation and cooling processes, and their thermal expansion coefficients are different. The alternation of hot and cold is easy to produce internal stress in the element. The existence of internal stress reduces the fatigue strength of solder joints and destroys the reliability of electronic components.

　　Laser welding is a local heating method of reflow welding. The welding process of laser welding paste is divided into two steps: First, the laser welding paste needs to be heated, and the solder joint also needs to be preheated. After that, the laser solder paste used for welding is completely melted, and the solder paste completely wets the pad, finally forming a weld. Due to the use of laser generator and optical focusing components welding, high energy density, high heat transfer efficiency. This is a non-contact welding that can well avoid the above problems.