In PCB manufacturing, there are also strict requirements for the solder resistance process, mainly reflected in the following three points:
1.Film-forming requirements,
The solder resistance film must have good film formation to ensure that it can be uniformly covered on the PCB wire and pad to form effective protection.
2.Thickness requirements,
At present, the identification is mainly based on the United States civil standard IPC-SM-840C specification. The thickness of the first grade product is not limited, giving greater flexibility; The minimum thickness of the solder resistance film of the grade 2 product is 10μm to meet certain performance requirements; The minimum thickness of Class 3 products should be 18μm, which is usually suitable for applications with higher reliability requirements. Precise control of solder resistance film thickness helps to ensure electrical insulation, prevent short circuits and improve welding quality.
3.Fire resistance requirements,
The flame resistance of welding resistance film is usually based on the specification of the United States UL agency, and must pass the requirements of UL94V-0. This means that the welding resistance film should show very high flame retardant performance in the combustion test, which can effectively prevent fire caused by circuit failure and other reasons to ensure the safety of equipment and personnel.
In addition, in actual production, the solder resistance process is also required to have good adhesion to ensure that the solder resistance film will not easily fall off during the long-term use of the PCB. At the same time, the color of the solder mask should be uniform to facilitate the identification of the circuit and quality inspection. Moreover, the process should be environmentally friendly and reduce pollution to the environment.
