There are three situations of virtual welding on the circuit board:
1. Virtual welding between the element foot and solder, press the element foot protruding from solder welding edge with the screwdriver, the ability to move indicates virtual welding;
2. There is virtual welding in the middle of the solder, which occurs in electrical appliances that have been used for a long time. Due to thermal expansion in use and cold shrinkage in use, this kind of solder joint has no luster.
3. As long as you press down on the component, it will become loose.