The molten solder (lead-tin alloy) is sprayed into a solder wave required by the design by an electric pump or an electromagnetic pump. It can also be formed by injecting nitrogen into the solder pool to pass the printed board containing components in advance. Solder crest, to achieve the soldering of the mechanical and electrical connection between the component soldering end or pin and the printed circuit board pad. The wave soldering machine is mainly composed of a conveyor belt, a flux adding area, a preheating area and a wave soldering furnace.
definition:
Wave soldering is to make the soldering surface of the plug-in board directly contact the high-temperature liquid tin to achieve the purpose of welding. The high-temperature liquid tin maintains an inclined surface and the special device makes the liquid tin form a wave-like phenomenon.
work process:
1. Spray no-clean flux to the circuit board
The circuit board with inserted components is embedded into the fixture, and the connection device at the entrance of the machine is fed into the wave soldering machine at a certain inclination and transmission speed, and then held by the continuously running claws, which is sensed by the sensor. The spray head sprays uniformly back and forth along the starting position of the fixture, so that a thin layer of flux is evenly coated on the exposed pad surface of the circuit board, the pad vias and the surface of the component pins.
2.Preheat the PCB board
Into the preheating area, the soldering part of the PCB is heated to the wetting temperature. At the same time, due to the rise of the component temperature, large thermal shocks are avoided when immersed in the molten solder. In the preheating stage, the temperature of the PCB surface should be between 75 ~ 110 ℃.
1) The role of preheating:
①The solvent in the flux is volatilized, which can reduce the gas generated during soldering;
② Rosin and activator in the flux begin to decompose and activate, which can remove the oxide film and other pollutants on the surface of printed circuit board pads, component terminals and pins, and also protect the metal surface from high temperature reoxidation. effect;
