Today, we will introduce part of the terms of PCB SMT Stencil.
The terms and definitions we have introduced primarily follow the IPC-T-50. Definitions marked with an asterisk (*) are sourced from the IPC-T-50.
1. Aperture: The opening in the stencil sheet through which the solder paste is deposited onto the PCB pads.
2. Aspect Ratio and Area Ratio: The aspect ratio is the ratio of the aperture width to the stencil thickness, while the area ratio is the ratio of the aperture base area to the aperture wall area.
3. Border: The polymer or stainless steel mesh that is stretched around the periphery of the stencil sheet, serving to keep the sheet in a flat and taut condition. The mesh lies between the stencil sheet and the frame, connecting the two.
4. Solder Paste Sealed Print Head: A stencil printer head that holds, in a single replaceable component, the squeegee blades and a pressurized chamber filled with solder paste.
5. Etch Factor: The etch factor is the ratio of the etch depth to the lateral etch length during the etching process.
6. Fiducials: Reference marks on the stencil (or other standard circuit boards) used by the vision system on the printer to recognize and calibrate the PCB and stencil.
7. Fine-Pitch BGA/Chip Scale Package (CSP): A BGA (Ball Grid Array) with a ball pitch of less than 1 mm [39 mil], also known as CSP (Chip Scale Package) when the BGA package area/bare chip area is ≤1.2.
8. Fine-Pitch Technology (FPT)*: Surface mount technology where the center-to-center distance between component solder terminals is ≤0.625 mm [24.61 mil].
9. Foils: The thin sheets used in the manufacture of stencils.
10. Frame: The device that holds the stencil in place. The frame can be hollow or made of cast aluminum, and the stencil is secured by permanently gluing the mesh to the frame. Some stencils can be directly fixed in frames with tensioning capabilities, characterized by not requiring mesh or a permanent fixture to secure the stencil and frame.
