In modern electronic assembly and soldering, cold soldering is a high-occurrence defect in reflow soldering of CSP packaged chips with pitch ≤ 0.5mm μ BGA. In BGA, CSP and other devices with a distance of less than 0.5mm, because the soldering parts of the components on the pcb circuit board are concealed, it is difficult to transfer heat to the solder ball joints, so it is easy to be cold. The soldering on the pcb board is higher than the actual soldering . The virtual soldering situation on the pcb board is even higher.

However, because the cold welding of the PCB circuit board is very similar to the virtual welding in defect phenomenon, it is often misjudged as a virtual welding and covered up. When dealing with the problem of circuit function failure caused by cold welding, it is often treated as a false welding, and the result is that it takes a lot of effort and has little effect. The quality consequences of cold welding and virtual welding are similar in form, but the formation mechanism is different. Without visual image screening, it is difficult to distinguish between wet and cold welds.

It is difficult for them to be completely exposed during the production process of the smt technical workshop of the pcb board manufacturer, and they often need to be used by the user for a period of time. Therefore, not only the impact is extremely bad, but the consequences are also very serious. In actual judgment, due to the fact that there are many similarities between the phenomenon of virtual welding and cold welding, misjudgment is often caused. Therefore, it is necessary to accurately identify the similarity between virtual welds and cold welds. Gender and dissimilarity are important for quality control in electronics manufacturing.

Features of cold welding: There is no problem with the solderability of PCB boards and components. The root cause of this phenomenon is that the temperature conditions of welding are not suitable.

The formation mechanism of pcb board cold welding: the main reason for cold welding is that the heating is not strict enough during welding, and the welding temperature does not reach the wetting temperature of the solder, so there is no IMC or IMC is too thin on the bonding interface. The interface is also cracked. In this type of solder joint, the solder adheres to the surface of the pad, sometimes without connection strength. Torn apart. Then, after the components on the pcb circuit board are separated from the pcb pad, the surface of the pad is clean and metallized, which is completely different from the surface of the pad of the separated virtual solder joint.