PCBA virtual soldering is also commonly referred to as cold soldering. The surface looks welded, but there is no actual internal connection, or it is in an unstable state when it is connected. This will not only affect the circuit characteristics, but may even cause the PCB quality to be unqualified. Or scrap. Therefore, we have to pay attention to the phenomenon of virtual welding. However, what is the cause of the false welding? And is there a solution? Let’s take a look at the following Sanjing:

The main reasons for the virtual soldering are: 1. Oxidation of pads and component pins: Oxidation of pads and component pins can easily lead to solder reflow, the solder paste cannot fully infiltrate the pads in the liquefied state, but it is easy to climb tin.

2. Less tin: In the solder paste printing process, due to the small opening of the stencil or the excessive pressure of the scraper, the amount of tin is insufficient during soldering, and the components cannot be fully soldered.

3. The temperature is too high or too low: Too high temperature will cause the solder to flow and increase the surface oxidation rate. Too low temperature can not make the solder paste completely melt and adhere to the surface of the solder.

4. Low melting point of solder paste: For some low temperature solder pastes, the melting point is lower, and the component pins and the board material of the fixed component are different, and the thermal expansion coefficient is also different. After a long time, the working temperature of the component will change, and the temperature will expand and cool. Under the action of shrinkage, it is easy to cause false welding.

5. Solder paste quality problem: poor solder paste quality (easy to oxidize) or flux loss will directly affect the soldering performance of solder paste, resulting in false soldering.

Solution to virtual welding: Generally speaking, PCBA virtual welding can reduce the problems of virtual welding through pre-material storage and post-processing. The specific measures are as follows: ①The storage of components should be protected from moisture; ②In-line electrical appliances can be slightly polished; ③Soldering paste and flux can be used when soldering, the best way is to use a reflow soldering machine, manual soldering requires skilled soldering skills ④ Reasonably choose PCB substrate material with good quality.

In short, in the PCBA processing process, virtual soldering is an important reason that affects the quality of the circuit board. Once the virtual soldering phenomenon occurs, it needs to be reworked. This will not only cost more manpower, but also affect production efficiency. Strictly supervise the production quality of each link, and find and solve problems in time.