In the wave soldering process, the through-tin through-hole process refers to PCBA after coating flux to remove the oxide film, the contact with the solder peak and rely on the solder wetting of the substrate metal and capillary phenomenon along the metal hole to climb, to achieve the welding process. Here we say some of the wave soldering tin some of the mechanisms of poor:

(1) Coating flux is the first step to ensure the quality of wave soldering. Its main function is to evenly apply a proper amount of flux, remove the oxide layer on the soldering surface of PCBs and components and prevent reoxidation during soldering. Flux must be evenly coated, be sure to amount, otherwise it will lead to poor tin.

(2) Preheating is preheating the PCB and activating the flux.

(3) Wave soldering commonly used dual-wave soldering. During wave soldering, the PCB touches the first peak and then the second peak. The first peak causes turbulent peaks to flow out of narrow nozzles with high flow rates and high vertical component forces. This is a measure of the solder's good permeability to the soldered ends of surface mount components with small dimensions and high mounting density; Turbulent molten solder scrubs the component surface in all directions, improving solder wettability and overcoming problems with complex shapes and orientations seen in the long term; overcoming solder shadowing. The upward jet force of the turbulent wave is sufficient to discharge the flux gas. Therefore, there is no influence of the flux gas even when the vent plate is not provided on the printed board, so welding defects such as leaky welding, bridging and insufficient weld bead are greatly reduced and increased The reliability of welding. After the first peak of the product, due to a short time immersion tin and parts of its own cooling factor, after immersion tin there are many short circuit, tin, solder joint finish and welding strength is not enough and other undesirable content. So immediately followed by a poor tin-immersion correction, this action is relatively wide jet stream, the crest of a more stable peak smooth, colleagues can also effectively remove excess solder on the solder end, and make all the solder on the feed Run Wet well, the welding surface is amended, eliminating the possible tip and bridge, access to enrich the defect-free solder joints, and ultimately ensure the reliability of component welding. When the PCB enters the front end of a smooth wave soldering surface, the substrate and the pins are heated, and the entire PCB is immersed in the solder before it leaves the end of the wave crest, that is, the solder is bridged. At this point the solder is wicked up to the termination of the solder to form tin. However, at the moment of leaving the end of the wave soldering surface, a small amount of soldering material adheres to the soldering pad due to the wetting force and shrinks to the minimum due to the surface tension, and the soldering and soldering The wetting force between the plates is greater than the cohesion of the solder between the two lands. Therefore, a full, rounded solder joint will be formed. At the same time excess solder due to gravity down to the tin pot to prevent bridging. Dual wave soldering principle shown in Figure 1.

(4) hot air knife. Immediately after the PCBA leaves the weld crest, a narrow, long cavity with an opening is provided beneath the PCBA. The cavity is capable of blowing hot air into the post and routing it like a channel to remove the bridging and reduce thermal stress on the module.

(5) cooling. Proper cooling after tin immersion helps to increase the bond strength of the solder joints and, at the same time, the cooled product is more conducive to the operation of the furnace operator. Therefore, after immersion tin products need to be cooled.