Method and stencil for extruding material on a substrate
AssigneeMicron Technology, Inc.
InventorsChad Cobbley, Ford B. Grigg
Life of this patent
Estimating the term…
Abstract
A stencil for use in fabricating semiconductor devices is disclosed that has an aperture having a first portion extending from a first side thereof and a second portion extending from a second side thereof to minimize the shear stress between the material extruded therethrough and the stencil. The stencil allows for material to be extruded through the top of the stencil to the surface of the substrate and not contact the wall of the second portion of the aperture of the stencil. Since the material only contacts a small area of the first portion of the aperture near the top of the stencil, the material remains on the substrate and not in the aperture of the stencil.
Claims19
A stencil for applying a solder paste to a wafer, said stencil comprising:
- a stencil 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 nominal diameter defining 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 nominal diameter defining 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 preselected 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 such that said solder paste does not contact said second wall portion of said at least one aperture of said plurality of apertures during use of said stencil, said thickness of said stencil ranging from 0.1 to 10 times the first nominal diameter of said at least one aperture of said plurality of apertures adjacent said top surface of said stencil.
A method for forming substantially vertical elements of solder paste on a wafer comprising:
- providing a stencil having a plurality of apertures formed therethrough from a top surface of said stencil to a bottom surface of said stencil, aperture of said plurality of apertures including a first portion having a first cross-sectional area formed by a first wall portion having a first nominal diameter and extending generally vertically from said top surface of said stencil, a second portion of said at least one aperture of said plurality of apertures adjacent said bottom surface of said stencil and having a second cross-sectional area formed by a second wall portion having a nominal diameter larger than said first nominal diameter of said first wall portion and extending generally vertically from said bottom surface of said stencil, said stencil having a thickness in the range from 0.1 to 10 times the first nominal diameter of the first wall portion of said at least one aperture of said plurality of apertures, and at least one sloped annular shoulder having a preselected shape located between said first wall portion and said second wall portion of said at least one aperture of said plurality of apertures;
- applying said stencil to a surface of said wafer;
- extruding a solder material having a viscosity in the range between 30K to 310K centipoise through said plurality of apertures formed in said stencil;
- preventing contact of said solder material with said second wall portion of said at least one aperture of said plurality of apertures during said extruding of said solder material by said second cross-sectional area of said second portion of said at least one aperture of said plurality of apertures being larger than said first cross-sectional area of said first portion of said aperture of said plurality of apertures;
- and
- removing said stencil and leaving said solder paste in a substantially vertical column.
Dependencies are inferred from the claim text.