In the PCBA processing process, if the PCBA has poor tin penetration, it will easily lead to the problem of virtual soldering, thereby increasing the cost of repair. Especially in the through-hole plug-in process, if the PCBA has poor tin penetration, it is easy to cause problems such as virtual soldering, tin cracking, and even dropped parts. It can be seen that the choice of PCAB tin penetration is very important.

According to the IPC standard, the PCBA tin penetration between 75% and 100% is more appropriate, and the PCBA requirement of the through-hole solder joints is generally above 75%, that is, the tin penetration standard for the appearance inspection of the soldering board surface is not less than 75% of the aperture height (board thickness) If the through hole is connected to the heat dissipation layer or the heat conduction layer for heat dissipation, the PCBA tin penetration requirement is more than 50%. However, PCBA tin penetration is also susceptible to some factors. The following Sanjing will introduce to you.

PCBA tin penetration is not only affected by the material itself, but also by the welding process (wave soldering, manual soldering), flux, etc. Let's take a look at them in turn.

The first is material influence. We know that tin melted at high temperature has strong permeability, but not all metals to be welded (PCB boards, components) can penetrate in, such as aluminum metal, which automatically forms a dense protective layer on the surface, and the internal molecular structure is different. It is difficult for other molecules to penetrate. In addition, if there is an oxide layer on the surface of the welded metal, it will also prevent the penetration of molecules. In this case, it is generally treated with flux or cleaned with gauze.

The second is the influence of welding process. Let us first talk about ① wave soldering: poor PCBA tin penetration is directly related to some soldering parameters of the soldering process, such as wave height, temperature, soldering time or moving speed. Therefore, what we have to do is to re-adjust some welding parameters, such as reducing the orbital angle, increasing the height of the wave crest, increasing the amount of contact between the liquid tin and the soldering end, and increasing the temperature of the wave soldering. But it should be noted that the higher the temperature, the stronger the permeability of tin, so the temperature resistance of the components should also be considered. In addition, you can also reduce the speed of the conveyor belt, infiltrate the solder end, increase the preheating time, so that the flux can fully remove oxides, thereby increasing the amount of soldering tin.

②Manual welding. In the actual plug-in welding quality inspection, a large part of the weldment only has a taper on the surface after soldering, and there is no tin infiltration in the hole. This situation is generally judged as a virtual solder in the functional test, and the main reason for this situation In the manual plug-in welding process, the soldering iron temperature is not appropriate or the welding time is too short.

Third, flux. Flux is also an important factor affecting PCBA's poor tin penetration. Its main function is to remove surface oxides on PCBs and components, and to prevent re-oxidation during soldering. If the flux selection is not good, the application is uneven, the amount is too small, etc., it will lead to poor tin penetration. The solution is to use good quality and good wetting effect to ensure that the flux is applied evenly on the PCB board. At the same time, the flux nozzle should be checked regularly. If damage is found, it needs to be replaced in time.

The above content is about the factors that affect PCBA tin penetration, I hope it can be helpful to everyone!