1. Oxidation of pads and component pins

The oxidation of the pads and component pins can easily cause the solder paste to liquefy during reflow soldering, the pads cannot be wetted sufficiently, and the solder will creep and form a false solder.

2. Tin less

In the solder paste printing process, the stencil opening is too small or the squeegee pressure is too small, resulting in a small amount of tin. When soldering, the amount of solder paste is lacking, and the components cannot be completely soldered, resulting in virtual soldering.

3. The temperature is too high or too low

Except that the temperature is too low, it will also form false welding, so the temperature should not be too high. Due to the high temperature, not only the soldering tin moves, but also the surface oxidation speed increases. It is also possible to form a solder joint or no solder.

4. Low melting point of solder paste

Regarding some low-temperature solder pastes, the melting point is relatively low, the component pins and the plate materials of the fixed component are different, and the thermal shrinkage coefficient is also different. Over time, as the operating temperature of the component changes, under the action of thermal expansion and contraction, virtual solder will form.

5. The quality of solder paste

The solder paste is of poor quality. The solder paste is easy to oxidize and the flux is lost, which directly affects the soldering performance of the solder paste and leads to false soldering.

Generally speaking, the status of PCB soldering is more complicated, and strict process control is required to optimize the process flow during consumption.

The above is what is the virtual solder? PCBA processing shows the reason of the virtual solder, I hope to help everyone.