PCB surface tension refers to the interaction force between a liquid or solid material and air that forms on the surface of a PCB circuit board. It is a physical phenomenon that describes the tension of a liquid or solid material on a thin layer that forms on a surface.
Surface tension is caused by intermolecular interactions and mainly involves the forces of attraction and repulsion between molecules. A higher surface tension causes the liquid to form small droplets on the surface, while a lower surface tension makes it easier for the liquid to unfold on the surface.
In PCB fabrication, the following general surface tension standards are typically followed:
1. For PCBs with lead soldering: the most common surface tension standard is determined according to IPC-6012C standard. This standard recommends that the surface tension of leaded soldered PCBs should be between 46-56 dyn cm.
2. For lead-free soldering PCBs: With the wide application of lead-free soldering, new surface tension standards have emerged. According to the IPC-6012D standard, the surface tension of lead-free solder PCBs should be between 38-48 Dyn cm.
In PCB manufacturing, the importance of surface tension is to affect the quality and reliability of processes such as coating, spraying, and soldering. The right surface tension ensures that the material is evenly coated on the PCB surface and helps in the proper joining and soldering of the components. Therefore, controlling and maintaining proper PCB surface tension is one of the key factors in ensuring the success of the manufacturing process and the performance of the final product.