The difference between PCB solder mask layer and solder flux layer?
The solder mask layer and solder paste layer play vital roles in the PCB assembly and soldering process. People often mistakenly believe that the solder mask layer is a coating that prevents soldering, while the solder paste layer is a coating that promotes soldering. However, the actual meanings of the solder mask layer and solder paste layer are different.
Solder mask layer:
The solder mask layer on a PCB is divided into the top solder mask layer and the bottom solder mask layer. It is used to cover the areas on the top or bottom of the PCB where soldering is not intended, that is, the areas that require the application of solder mask, commonly referred to as the "green mask" layer. Positive image output is used during the design of the solder mask layer. Positive image output means that the intended areas to be coated with solder mask are indeed the solder mask regions. Therefore, the true meaning of the solder mask layer is to create openings on the entire solder mask coating, allowing for soldering in the designated areas.
Solder paste layer:
The solder paste layer is divided into the top solder paste layer and the bottom solder paste layer, referring to the areas on the PCB that are not covered with solder mask. The main purpose of the solder paste layer is not to promote soldering but to assist in component placement. The solder paste layer corresponds to the PCB's solder pads. During the manufacturing of the SMT stencil, the solder paste layer is used to create openings on the stencil, ensuring that solder paste is accurately deposited onto the PCB's solder pads. Therefore, the solder paste layer is also referred to as the "solder paste layer" or the "solder stencil layer."
The difference between the solder mask layer and solder paste layer lies in the following aspects: The solder mask layer primarily protects the areas where soldering is not intended, providing an additional protective layer to prevent unnecessary coverage with soldering materials. On the other hand, the solder paste layer is mainly used for assisting component placement by providing a meltable soldering material for achieving reliable connections between components and the PCB. Although both are related to soldering, the ultimate purpose of the solder mask layer is to prevent soldering, while the purpose of the solder paste layer is to assist soldering operations.