It has been discussed in the solder wave crest dynamic phenomenon that when the PCB enters the wave peak working area, since the movement direction of the PCB is opposite to the flow direction of the liquid solder, there is a surface layer close to the PCB below. The thickness of the surface layer is related to the pinching speed of the PCB and the flow velocity of the fluid against the direction of the PCB movement.

Wave soldering work video

For example, when the PCB pinch speed is constant and the reverse flow speed is increased, the thickness of the surface layer will become thinner, the reflow phenomenon will be significantly weakened, and the reverse scrubbing effect of the solder fluid on the PCB will be significantly enhanced. It is not easy to produce tipping and bridging, but it is possible that the amount of solder needed to form the normal contour of the solder joint will be excessively scrubbed, resulting in insufficient tin consumption, dryness, and asymmetric outline of the solder joint. . Conversely, if the fluid velocity is too low, the scrubbing effect is reduced, and the solder joints are plumped, but the probability of sharpening and bridging is also increased. Therefore, for a specific PCB and its clamping speed, it corresponds to an optimal liquid solder fluid velocity.

A large pressurized cavity is used to press the molten solder into the nozzle, and a smooth laminar bidirectional liquid flow is obtained through the nozzle. The liquid solder flow passes through the nozzle flange to form a wave crest of the solder. The shape of the nozzle controls the shape of the wave crest of the solder, and therefore also controls the effect of the wave crest dynamics. A buffer net is set in the pressure chamber to ensure the formation of laminar flow to ensure the smoothness of the wave crest. In order to reduce the generation of solder slag, the solder pouring down from the wave crest shall not have excessive turbulence when it returns to the solder tank. The adjustable side plates arranged on the front and rear outer sides of the nozzle constitute the solder return channel and help to form the best wave crest. It forces the wave crest solder to return to the solder tank from a position far below the liquid level. Thereby, the area of the solder tank liquid remains undisturbed.

Adjusting the inclination angle of the side plate can make the solder continue to slow down during the process of gradually returning to the solder trough along the inclined surface, so as to achieve the purpose of controlling the flow rate of the solder and reduce the turbulence on the surface to a minimum. Adjusting the side plate in front of the nozzle can control the shape of the wave crest entering the working area, thereby controlling the velocity characteristics of the fluid in this area. In the same way, in the PCB exit section, there is also the problem of matching the transfer speed of the PCB with the fluid speed to obtain the best separation condition. At this time, it can be achieved by adjusting the side plate behind the nozzle.