screen mask
A component used for precise printing on devices such as circuit boards.
screen mask: the stencil that shapes your print
A screen mask is a fine mesh screen stretched across a frame, with a photoresist pattern applied to block certain areas while leaving others open. When ink or solder paste is pushed across the screen with a squeegee, material passes only through the open mesh, creating a precise deposit on the substrate below. The mask acts as both a stencil and a barrier, controlling where material lands and how much accumulates.
Screen masks are made from stainless steel or polyester mesh, typically 40 to 400 microns per opening depending on the application. For circuit boards, standard mesh counts range from 120 to 180 threads per inch. The photoresist emulsion is applied to both sides of the mesh, then exposed through a film positive to harden the pattern. The unexposed emulsion washes away, leaving open mesh in the shape of the deposit pattern. Thickness matters: a 10 micron emulsion thickness will deposit less paste than a 25 micron thickness, all else equal.
The name comes directly from the function: the mask controls what the screen reveals. In printing trade language, this is called a stencil, but in electronics manufacturing, screen mask is standard terminology because the screen itself is the critical component. The term distinguishes it from other stencils that are cut from sheet material.
Common failure modes and trade-offs
Wear occurs at the edges where the squeegee blade contacts the screen repeatedly. Emulsion breaks down, creating ragged deposits. Buildup of cured solder paste or ink clogs the mesh openings, reducing flow. This is why masks are cleaned between cycles with solvents appropriate to the paste type, and why production runs include planned screen replacements. A mask worn to 70% of its original line definition is typically rejected.
Screen tension, measured in Newtons per centimeter, directly affects deposit consistency. Low tension causes sagging and uneven contact; high tension risks frame damage. Industrial screens are tensioned to 25 to 35 N/cm for solder paste work. The angle of the squeegee blade, the pressure applied, and the speed of the stroke all interact with the mask design to determine final deposit shape and volume, making screen mask selection integral to process control in electronics assembly.