Foil Treatment
Subtractive foil finishing is a category of surface treatment designed to eliminate physical imperfections on stencil apertures. Utilizing an electro-polished stencil removes these burrs by dissolving microscopic peaks through an electrochemical bath. This chemical treatment smooths the inner walls of the stainless steel sheet to a mirror-like finish.
The stainless steel sheet is submerged in an acid electrolyte while an electric current is applied, which selectively targets surface irregularities. This process reduces the surface roughness of the aperture walls to a sub-micron finish without altering the overall thickness of the foil.
Release Performance
High-density boards require extremely small deposit areas that demand optimal paste transfer efficiency. Using an electro-polished stencil ensures that the paste slides easily from the aperture during the separation phase. This action results in clean paste deposits with vertical walls and consistent height.
Printed volumes remain uniform even on fine-pitch grid arrays and small chip scale packages.
Aperture Cleaning
Cleaning cycles during automated inline printing can be spaced further apart when the aperture walls do not retain residue. Since the electro-polished stencil surface is highly uniform, fewer paste particles cling to the metal after each print stroke. This reduction in build-up lowers the risk of bridging and saves solvent consumption.
Smooth aperture walls define the primary line of defense against print defects on sub-millimeter pitches.
