In modern electronic assembly welding, the distance of cold welding is ≤ 0.5mm μ High incidence of reflow soldering defects in CSP packaging chips of BGA. In BGA, CSP and other devices with a distance of less than 0.5mm, it is difficult to transfer heat to the solder ball joint due to the hidden welding position of the component components on the pcb circuit board, so the welding on the pcb board that is easily cooled is higher than the actual welding. The false soldering on the pcb board is even higher.

However, the cold soldering of pcb circuit board is very similar to the false soldering in defect phenomenon, so it is often mistaken for false soldering and covered up. When dealing with the problem of circuit function failure caused by cold welding, it is often treated as faulty welding, which results in great effort and little effect. The quality consequences of cold welding and faulty welding are similar in form, but the formation mechanism is different. Without visual image screening, it is difficult to distinguish between faulty welding and cold welding.

They are difficult to be completely exposed in the production process of the smt technology workshop of the pcb board manufacturer, and often require users to use them for a period of time. In some cases, they will expose undesirable phenomena one year later. Therefore, not only the impact is extremely bad, but also the consequences are very serious. In the actual judgment, due to the similarities between the phenomenon of false welding and cold welding, it often leads to false judgment. Therefore, it is necessary to accurately identify the similarity between false welding and cold welding. Gender and dissimilarity are very important for quality control in electronic product manufacturing.

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

Formation mechanism of pcb plate cold welding: the main reason for cold welding is that the heat supply is not sufficient during welding, and the welding temperature does not reach the wetting temperature of 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 is attached to the pad surface, sometimes without connection strength. be split. Then, after the components on the pcb circuit board are separated from the pcb pad, the pad surface is clean and metallized, which is completely different from the pad surface of the separated virtual solder joint.