In the PCBA processing process, especially the through-hole plug-in process, if the PCB board is not penetrated well, it is easy to cause problems such as virtual soldering, tin cracking and even dropouts, which will increase the cost of repair. Therefore, the choice of PCBA tin penetration is very important. So the question is, what factors will affect PCBA tin penetration? Let's take a look at the following Sanjing:

Before introducing the factors that affect PCBA processing tin penetration, let's first understand the PCBA tin penetration requirements: According to the IPC standard, the PCBA tin penetration requirements of through-hole solder joints are generally more than 75%, that is, the solder penetration standard for the appearance inspection of the panel surface Not less than 75% of the hole height (plate thickness). For plated through holes to connect to the heat dissipation layer or the heat conduction layer for heat dissipation, the PCBA tin penetration requirement is not less than 50%.

PCBA tin penetration is mainly affected by factors such as material, wave soldering process, flux, and manual soldering. The following Sanjing will introduce you in turn:

①Materials. 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. Generally, a dense protective layer is automatically formed on the surface, and the difference in internal molecular structure also makes it difficult for other molecules to penetrate into it. Secondly, if there is an oxide layer on the surface of the welded metal, it will also prevent the penetration of molecules. Generally, it is treated with flux or cleaned with gauze.

② Wave soldering. PCBA poor tin penetration is directly related to the wave soldering process. The welding parameters of poor tin penetration, such as wave height, temperature, soldering time or moving speed, need to be optimized. At this time, the orbit angle should be lowered a bit, the height of the wave crest should be increased, the contact amount of the liquid tin and the soldering end should be increased, and then the temperature of the wave soldering should be increased. Generally speaking, the higher the temperature, the stronger the permeability of tin, but the premise is that the temperature that the components can withstand must be considered. In addition, it can also reduce the speed of the conveyor belt, increase the preheating and soldering time, so that the flux can fully remove oxides, infiltrate the soldering ends, and increase the amount of tin consumed.

③Flux. Flux is also an important factor affecting the poor tin penetration of PCBA. It mainly plays a role in removing oxides on the surface of PCB and components and preventing re-oxidation during soldering. If the flux selection is not good, the application is uneven or the amount is too small, it will lead to poor tin penetration. Therefore, a good quality (high activation and wetting effect) flux should be selected, which can effectively remove difficult-to-remove oxides. In addition, the flux nozzle should be checked, and the damaged nozzle should be replaced in time to ensure that the PCB board surface is coated with an appropriate amount of flux to exert the flux effect of the flux.

④ Manual welding. In the actual plug-in welding quality inspection, there are many weldments that only have a taper on the surface of the solder, and there is no tin penetration in the vias. Most of the functional tests are virtual soldering. This situation usually occurs in manual soldering because the soldering iron temperature is not appropriate. Or the welding time is too short.

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