Under What Circumstances Will PCBA Processing Cause False Soldering?

False soldering, also known as false soldering, is a state in which it is not connected at all times. It belongs to a kind of poor welding and is a very important reason for the high PCBA repair rate in the early stage.

The reasons for PCBA soldering are as follows:

1, pad and component pins oxidation

Oxidation of the pads and component pins can easily lead to the solder paste being liquefied during reflow soldering, and the pads cannot be fully wetted, and the solder can be crawled, resulting in soldering.

2.Shao tin

In the solder paste printing process, the stencil opening is too small or the scraper pressure is too small, which results in less tin. When soldering, the amount of solder paste is insufficient, and the components cannot be fully soldered, resulting in virtual soldering.

3.The temperature is too high or too low

In addition to the low temperature, it will cause false soldering, and the temperature should not be too high. Because the temperature is too high, not only the solder flows, but also the surface oxidation rate is accelerated. It may also cause false soldering or not soldering.

4. Low melting point of solder paste

For some low-temperature solder pastes, the melting point is relatively low, and the component pins and the board material of the fixed component are different, and their thermal expansion coefficients are different. After a long time, with the change of the component operating temperature, under the force of thermal expansion and contraction, Will cause false soldering.

5, solder paste quality problems

The quality of solder paste is not good. The solder paste is easily oxidized and the flux is lost, which will directly affect the soldering performance of the solder paste and lead to false soldering.

In general, the situation of PCB soldering is complex, and strict process control is needed in production to optimize the process flow.