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Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Epoxy free fiducials improve stencil performance
Keywords Chepaume, Fiducials, Solder paste
Fiducials are a critical component of a solder paste stencil/mask, ensuring accurate alignment and allowing optimum positioning and application of the paste. Traditionally, fiducials have been filled with a black epoxy, enabling machine vision systems to easily identify location and orientation. Unfortunately, as the stencil is used and cleaned, the epoxy fill has a tendency to "pop out", shortening the useful life of the stencil.
Chepaume Industries specializes in electroformed stencils ranging in thicknesses of 1mil to 8mil. Owing to the smooth walled apertures achieved during the forming process, electroformed stencils offer distinct advantages in performance. However, adhering epoxy to the smooth walls in the fiducial area of an electroformed stencil has been problematic. Also, as the thickness of a stencil decreases, it becomes increasingly difficult to create satisfactory epoxy filled fiducials. As a result, Chepaume has developed a proprietary method of blackening fiducials on electroformed stencils without the use of an epoxy fill. The absence of epoxy filled fiducials eliminates the potential problem of the epoxy popping out, thus increasing the useful life of the stencil. The new method has proven to be especially beneficial on electroformed stencils ranging from 1-2mils in thickness, since traditional methods are difficult and yield unsatisfactory results.