Wave Soldering Machine Theory

- Mar 16, 2018 -

Wave Soldering Machine Theory

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Wave soldering is a kind of soldering wave formed on the surface of molten liquid solder by means of pump pressure. When the components of components are inserted to pass the solder wave at a fixed angle, the solder joint technology is formed in the pin welding area. The components are preheated at the preheating area of the welding machine during the transmission process from the chain conveyor belt, and the preheating and preheating temperature of the components are still controlled by the predetermined temperature curve. In actual welding, the preheating temperature of the component surface is usually controlled, so many devices have added the corresponding temperature detection devices (such as infrared detectors). After preheating, the component enters the lead slot for welding. Tin bath is filled with molten liquid solder. The bottom nozzle of the steel slot will solder the solder to form the wave shape with fixed shape, so that when the component surface is passed through the wave, it will be heated by the solder wave. Meanwhile, the solder wave will also moisten the welding area and expand and fill up, so as to achieve the final welding process.

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It is obvious that the wave soldering is heated by the principle of convection heat transfer. The molten solder wave acts as a heat source. It flows to scour the pin welding area and heat conduction on the other hand. The pin welding area is heated under this action. When using silver lead solder, the temperature of the molten solder is usually controlled at about 245 degrees C. In order to ensure the heating of the welding area, the solder wave usually has a fixed width, so that when the welding surface of the component passes through the wave, it has sufficient heating and wetting time. In the traditional wave soldering, a wave is used, and the wave is flat. With the use of lead solder, more and more two wave forms are adopted at present.

The pin of the component provides a way for the liquid solder immersing into the metallized through hole. When the pin contacts the solder wave, the liquid solder rises up along the pin and the hole wall with the help of the surface tension. The progress in capillary action of metallized holes promotes the climbing of solder. The solder arrives at the PCB plate and spreads under the surface tension of the pad. The welding flux gas and air in the through hole are discharged from the rising solder, and the through hole is filled, and the solder joint is formed after the cooling.

The main difference between the wave soldering and reflow is that the heating source and the material supply in the welding are different.

In the wave soldering, the solder is heated and melted in the groove in advance. The welding wave of the pump plays the dual role of heat source and solder. The solsoled solder waves heat the PcB's through holes, pads, and component pins, and also provide the required solder for the formation of solder joints. In reflow soldering, the solder paste (solder paste) is pre assigned to the welding area of PCB in advance. The effect of the heat source on the reflux is to remelt the solder.


Main components and working principle of wave soldering


The wave soldering machine is mainly composed of conveyor belt, heater, tin slot, pump, flux foaming (or spray) device. It is mainly divided into flux adding area, preheating area and welding area.

The solder in tin bath gradually melts under the heating of heater. Molten liquid solder forms a specific shape solder wave on the surface of solder tank under the action of mechanical pump or electromagnetic pump. The PCB installed with the components is placed on the transmission device. After a certain angle and the depth of penetration, the solder joint is welded through the solder wave, so it is called wave soldering.

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For a single wave, only a wave, called flat wave. The double wave, the wave is called interference wave, the second wave is called flat wave (Ping Huabo).

Wave disturbance effect: the SMT element and prevent the leakage of welding, which ensures the proper distribution through the circuit board solder. The solder is penetrated through the slit at high speed, so that the narrow gap is penetrated. The direction of the injection is the same as that of the circuit board. The SMT element, disturbance wave can complete welding. But for through hole components, disturbance wave itself is not appropriate for welding components, solder joints left on the uneven and excess solder, thus requiring second wave - flat wave.

Flat wave function: eliminate the disturbance wave generated by the burrs and welding bridge. Flat wave is actually a single wave soldering machine used by the wave, therefore, when the traditional through-hole components in double wave welding machine, you can put off the flat wave interference wave, you can complete the welding. The flat wave wave basically maintain the level as a mirror. At first, it seems that the tin wave is static. In fact, the solder is flowing constantly, but the wave is very stable.

Wave soldering machine joint formation: when PCB entered the wave front end, substrate and pin is heated, and not leave before the PCB wave, which is dipped in solder, solder bridging, but in the end the moment left wave, a small amount of solder wetting force effects due to the adhesion on the pad, and the reasons the surface tension, will appear to lead to the center small contraction state, the cohesive force between the solder and the wetting force is greater than two between the solder pads. So a full, round solder will be formed, and the excess solder, leaving the tail of the wave, falls back to the tin trough because of the gravity.

HB Automation specializes in  research and development, manufacturing, and sales of wave soldering, reflow soldering, selective wave soldering, vertical curing oven, SMT peripheral equipment and so on. Welcome to our company to visit and discuss.