What is the use of stencil for processing PCBA, How to use them

The stencil of PCBA processing patch is used to print red glue or solder paste on the PCB. The steel mesh generally has a solder paste net and a red plastic net. At the beginning, the stencil and the PCB are required to be aligned and then printed. Solder paste or red glue, the process will be different after this. The solder paste net is made of a solder paste process. The holes opened correspond to the pads of the parts on the PCB, so that the solder paste is printed on the pads, and then the parts are pasted and reflowed. The red plastic mesh is the middle position corresponding to the parts on the PCB board (need to avoid the tin solder pad), then the parts are attached, heated to cure the red glue, and then soldered on the tin furnace.