Virtual welding, also known as false welding, is a state of disconnection. It is a kind of poor soldering, which is a very important reason for the high repair rate of PCBA in the early stage. Next, Shenzhen Viasion Electronics, a PCBA processing manufacturer in Shenzhen, will introduce the reasons for the virtual soldering in PCBA processing.
Causes of virtual welding in PCBA processing
1. Oxidation of pads and component pins
The oxidation of pads and component pins can easily cause the solder paste to liquefy during reflow soldering, the pads cannot be fully wetted, and the solder will crawl and cause false soldering.
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 insufficient, and the components cannot be completely soldered, resulting in false soldering.
3. The temperature is too high or too low
In addition to the fact that the temperature is too low, it will cause false welding, so the temperature should not be too high. Because the temperature is too high, not only the solder flows, but also the surface oxidation speed increases. It may also cause false welding or no welding.
4. Low melting point of solder paste
For some low-temperature solder pastes, the melting point is relatively low, the component pins and the plate material of the fixed component are different, and the thermal expansion coefficient is also different. After a long time, as the operating temperature of the component changes, under the action of thermal expansion and contraction, it will cause virtual welding.
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, resulting in false soldering.
Generally speaking, the situation of PCB welding is more complicated, and strict process control is required to optimize the process flow in production.