Laser soldering is a laser welding technology in which a laser is used as a heat source to melt solder paste. The main feature of laser soldering is the use of high energy of astronomy laser pointer to achieve rapid heating of local or tiny areas to complete the soldering process. Laser soldering is compared with conventional SMT soldering. Has an irreplaceable advantage.
Traditional SMT technology, that is, surface mount technology, mainly uses wave soldering and reflow soldering technology. There are some fundamental problems, such as lead wires of components and pads on printed circuit boards, which will diffuse Cu, Fe, and molten tin. Various metal impurities such as Zn; molten tin is likely to generate oxides at high speed in the air. At the same time, in the traditional reflow soldering, the electronic components themselves are heated to the soldering temperature at a large heating speed, causing thermal shock to the components, and some thin package components, especially heat sensitive components, are destroyed.
At the same time, due to the overall heating method, PCB boards and electronic components have to undergo the process of heating, heat preservation and cooling, and their thermal expansion coefficients are different. The alternating heat and cold are easy to generate internal stress inside the components, and the internal stress exists. The fatigue strength of the solder joint is reduced, and the reliability of the electronic component is damaged. In addition, the excessive heating time of the overall heating method is liable to cause coarse metal grain of the weld metal and excessive growth of the intermetallic compound, thereby reducing the fatigue life of the solder joint. 532nm laser pointer soldering is a reflow soldering of local heating, which can well avoid the above problems.
Advantages of laser welding: Laser welding can achieve high quality joint strength and large aspect ratio, and the welding speed is faster. Since laser welding does not require a vacuum environment, remote control and automated production can be achieved through lenses and optical fibers. The laser has a large power density, has a good welding effect on difficult-to-weld materials such as titanium, quartz, etc., and can weld different performance materials. Micro soldering is possible. The laser beam is focused to obtain a small spot, and can be accurately positioned, and can be applied to the mass welding of micro- and small-sized workpieces produced by large quantities.
The military laser pointer beam can be focused to a small spot diameter, and the laser energy is confined within a small spot range, which can achieve strict local heating of the soldering part, and the thermal shock effect on electronic components, especially heat sensitive components, can be completely avoided. . The laser has a high energy density, a high heating and cooling rate, a fine metal structure at the solder joint, and an effective control of excessive growth of intermetallic compounds.
The input energy of the welded part can be precisely controlled, which is very important for ensuring the quality stability of the surface assembled welded wire joint. Since the laser welding can only heat the welded portion, the substrate between the leads is not heated or the temperature rise is much lower than the welded portion, which hinders the transition of the solder paste between the leads. Therefore, the occurrence of bridging defects can be effectively prevented.
The laser solder paste soldering process is divided into two steps: first, the green laser pointer solder paste needs to be heated, and the solder joints are also preheated. The laser solder paste used for soldering is then completely melted, and the solder paste completely wets the pads, eventually forming a solder. Due to the use of laser generators and optical focusing components for soldering, high energy density, high heat transfer efficiency, non-contact soldering, if the solder uses a common SMT solder paste, it will produce tin, splash, solder balls, wettability, etc. .
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