This paper introduces and analyzes selective reflow welding from two aspects of equipment and technology. In terms of equipment, the main structure of the machine is described, and in terms of reflow welding technology, the process of selective welding is introduced. Finally, several defects that are most likely to occur in selective wave soldering are analyzed. The special wind wheel for reflow soldering is designed with stable wind speed; each temperature zone adopts forced independent circulation, independent PID control, up and down independent heating mode, so as to make the temperature of furnace chamber accurate, uniform and large heat capacity; the temperature rises fast, from room temperature to working temperature ≤ 20min; the imported high-quality high-speed high-temperature motor has stable wind, small reflow soldering vibration and noise; the furnace body adopts cylinder jacking and safety rod support (electric optional); chain Bar,

The reflow welding adopts stepless speed change, imported power; special high-quality aluminum alloy guide rail, reflow welding automatic oil filling system; Chinese and English Windows operating system, with powerful functions and convenient operation; routine or predetermined monitoring functions, such as temperature detection, adjustment and control, transmission speed, direction detection and control, etc. Automatic detection function, reflow welding can automatically ultra-high and low temperature acoustooptic alarm function. After reflow welding for a certain year, it has a certain wavelength of square wave or sine wave magnetic track signal. The magnetic head moves and reads the magnetic stick on the magnetic grid ruler, and converts it into an electrical signal to be input to the control circuit, and finally controls the operation of the AC servo motor.

The advantages of reflow welding are simple manufacture, convenient installation, high stability, wide range, measuring accuracy up to 1-5um, and generally 0.02mm. This kind of measurement needs to go through tens of millions of times to achieve the best reflow welding positioning accuracy which is 1-2 orders of magnitude higher than the magnetic grid scale. When the turret structure is moving, the maximum allowable value of radial acceleration on the vacuum nozzle is limited, so the mounting speed is limited. Directly and quickly achieve the control and analysis functions. Reflow soldering system adopts double-sided temperature supply technology, which reduces the bending deformation of PCB and requires high temperature control accuracy. Input channel of switching value feedback (signal acquisition), output channel of switching value of reflow soldering (control SSR), serial port output control frequency converter (control the speed of transmission belt), analog output (control the hot air blower, realize temperature control), analog input (thermocouple signal input)