Analysis the reason and solutions of PCB surface mount welding

1, Bridging

The cause of the bridging is mostly caused by excessive solder, serious solder bumps, PCB pad size is out of tolerance or SMD placement offset, etc.In the SOP, QFP circuit tends to miniaturization stage, the bridging will cause electrical short circuit, it will affect the use of the product.

2, Poor wetting

Poor wetting refers to the welding process of solder and PCB welding area does not produce metal reaction after the infiltration, resulting in leakage welding or virtual welding. The reason is that the surface of the welding is contaminated, or stained with solder mask oil, or caused by a metal compound layer produced by a bond, such as silver surface sulfide, tin surface oxide and so on,these will cause poor welding. In addition, when the residual aluminum, zinc and cadmium in the solder exceeds 0.005%, wetting may occur due to the decrease in the degree of activity by the moisture absorption of the flux. Wave soldering, if the gas exists in the PCB surface, it will also happen the questi. Therefore, in addition to the implementation of the appropriate welding process, the PCB surface and component surface also need to do a good job of anti-fouling measures, select the appropriate solder, and set a reasonable welding temperature and time.

Article from Shenzhen Vip Circuit Co.，Ltd