Laser cut stencils are the most cost effective and the most commonly used in PCB assembly. The new lasers can produce aperture walls that are very smooth. Laser Cutting is a subtractive process where the laser beam completely cuts the aperture out of the metal, one aperture at a time. Electropolish is sometimes used for deburring and nano-coating to improve paste release.
Electroformed stencils are the most expensive, have the longest lead times but have the smoothest aperture walls. Electroforming is an additive process where the stencil is created by electroforming nickel.
Chem-etch stencils are not very commonly used today. They are fabricated using the oldest and least eco-friendly technology. The apertures sidewalls can be rough. Chemical Etching is also a subtractive process where the metal is removed by masking an area with a protectant (photo resist) and then submerging the material into an etchant in order to remove the areas that have not been protected by the photo resist. The stencils created by this process can be of a wide variety of materials.
