What is stencil, how is it used in SMT process, Shenzhen PCB factory
What is stencil, how is it used in SMT process

SMT stencil is a very thin piece of steel. The size of the stencil is usually fixed to match the solder paste printer, like 370*470mm, 420*520mm etc., The thickness of the stencil can be 0.08mm, 0.10mm, 0.12mm, 0.15mm, 0.18mm etc., determined by PCB components used.
The SMT stencil is designed for printing solder paste onto the circuit board. Therefore, the stencil surface will be engraved with many openings. When printing the solder paste, the solder paste should be applied on the stencil. The board will be placed under the stencil, and then a scraper (usually a scraper, because the solder paste is similar to a toothpaste-like viscous material) is brushed over the stencil surface with the solder paste, and the solder paste is squeezed. It will flow down from the opening of the stencil and stick it to the top of PCB board. When the stencil is removed, it will be found that the solder paste has been printed on the board.
To put it simply, the stencil is like a hood to be prepared when painting, and the solder paste is equivalent to lacquer. The hood is engraved with the pattern you want. When you spray the lacquer on the hood, the desired pattern appears.
Since stencil is used to print solder paste on the circuit board, the first step of the SMT process is to use the stencil to print the solder paste, then can place the components on boards. The purpose of the solder paste is to solder components onto the PCB board, so a new stencil must be re-made as long as the position of components on the board changes.