Patent ID: 6427587
Filing Date: 2002-08-06
Classification: B41F,B41M,B41N,H01L,H05K

Abstract:
A stencil for applying a paste to a wafer comprising:a stencil, comprised of plastic, having a top surface, a bottom surface, a thickness, and a plurality of apertures passing from said top surface to said bottom surface, at least one aperture of said plurality of apertures, including: a first portion of said at least one aperture formed by a first wall portion extending generally vertically from said top surface of said stencil into said at least one aperture of said plurality of apertures and having a first diameter forming a first cross-sectional area; a second portion of the at least one aperture of the plurality of apertures formed by a second wall portion extending generally vertically from said bottom surface of said stencil into said at least one aperture of said plurality of apertures and having a second diameter forming a second cross-sectional area; at least one sloped annular shoulder intermediate said first wall portion and said second wall portion of said at least one aperture of said plurality of apertures, said at least one sloped annular shoulder having a shape; and said second cross-sectional area in said at least one aperture of said plurality of apertures larger than said first cross-sectional area of said first portion of said at least one aperture of said plurality of apertures for providing a location of said second wall portion of said at least one aperture of said plurality of apertures free of contact by said paste during use of said stencil, said thickness of said stencil ranging from about 0.1 to 10 times the first diameter of said at least one aperture of said plurality of apertures adjacent said top surface of said stencil.