Coated stencil with reduced surface tension

摘要

A stencil used for printing solder paste on a contact pad of a printed wiring board has interior surfaces that define one or more apertures through the stencil. Those interior surfaces are coated with a material, such as parylene, having a lower surface tension than the interior surfaces absent the coating. The stencil can also have one or more reverse-tapered apertures passing there through, wherein the apertures have a variable cross-section that is larger at the fill side of the stencil (i.e., where solder paste enters the apertures) than at the board side of the stencil (i.e., where the stencil contacts the contact pad of the printed wiring board). Solder paste can be printed through the aperture(s) of the stencil onto contact pads on a printed wiring board.