The technological characteristics of selective welding can be used to understand the technological characteristics of selective welding by comparing with wave soldering. The most obvious difference between the two is that the lower part of the PCB in wave soldering is completely immersed in liquid solder, and in selective welding, only some specific areas are in contact with solder waves. Because the PCB itself is a bad heat conduction medium, it does not heat the solder joints that melt adjacent components and PCB areas when welded. The flux must also be applied in advance before welding. Compared with wave soldering, the flux is coated only at the part of the PCB to be welded, not the entire PCB. In addition, selective welding is only suitable for the welding of plug-in components. Selective welding is a completely new approach, and a thorough understanding of selective welding processes and equipment is necessary for successful welding.