Method of forming fine-pitch interconnections employing a standoff mask
First Claim
1. A method for forming a pattern of adhesive on a substrate, the pattern of adhesive having a height greater than a given height, comprising:
- obtaining a substrate having a pattern of sites thereon on which adhesive is to be deposited;
obtaining a standoff mask including a metal sheet of thickness substantially the given height having a pattern of openings corresponding to the pattern of sites and having standoff features thereon, wherein the standoff features are spaced away laterally from the openings and with said metal sheet define a thickness greater than the given height;
positioning said substrate and said standoff mask proximate each other with the standoff features proximate the substrate so that the pattern of sites and the pattern of openings correspond;
applying adhesive to substantially fill and pass through the openings of said standoff mask and to contact the sites on the substrate; and
removing said standoff mask to leave said adhesive on said pattern of sites, whereby a pattern of adhesive having a height greater than the given height is formed on the substrate.
1 Assignment
0 Petitions
Accused Products
Abstract
In the construction of electronic devices with one or more flip chips and, in some cases, one or more leadless components, mounted on a substrate, the interconnections are made with conductive adhesive or solder paste deposited using specialized stencils or masks, including suitable snap-back stencils and direct-contact masks without snap back. A metal stencil (or mask) is placed temporarily onto the face of a substrate, such as a semiconductor wafer, circuit board or other substrate, and is spaced apart therefrom by standoff features. When the stencil is properly positioned with respect to the wafer or substrate, as by relational alignment holes or optical alignment methods, conductive adhesive material is deposited onto the substrate through holes or openings in the stencil. The metal stencil includes on the side thereof facing the substrate a flexible standoff layer having standoff features to space the stencil apart from the substrate. The flexible standoff features are spaced away from the openings of the stencil so as to facilitate the forming of fine features of the conductive paste that have a height that is substantially greater than the thickness of the metal stencil, while avoiding smearing of the conductive adhesive paste and avoiding the conductive adhesive paste adhering to the openings of the stencil rather than to the substrate. Standoff features are formed by depositing suitable adhesive or metal materials or by etching the metal stencil. Openings in the metal stencil are formed by suitable means such as laser cutting, electroforming or photo-etching. The stencil may be fabricated of a membrane of magnetic material and be held in place by the magnetic forces produced by an electromagnet included in the assembly tooling.
111 Citations
40 Claims
-
1. A method for forming a pattern of adhesive on a substrate, the pattern of adhesive having a height greater than a given height, comprising:
-
obtaining a substrate having a pattern of sites thereon on which adhesive is to be deposited;
obtaining a standoff mask including a metal sheet of thickness substantially the given height having a pattern of openings corresponding to the pattern of sites and having standoff features thereon, wherein the standoff features are spaced away laterally from the openings and with said metal sheet define a thickness greater than the given height;
positioning said substrate and said standoff mask proximate each other with the standoff features proximate the substrate so that the pattern of sites and the pattern of openings correspond;
applying adhesive to substantially fill and pass through the openings of said standoff mask and to contact the sites on the substrate; and
removing said standoff mask to leave said adhesive on said pattern of sites, whereby a pattern of adhesive having a height greater than the given height is formed on the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
-
- 29. A standoff mask comprising a metal membrane of thickness substantially a given dimension having a pattern of openings therethrough and a patterned layer of flexible material on at least one side of said metal membrane, said patterned layer having a pattern of openings therethrough corresponding to the pattern of openings in said metal membrane, wherein said flexible material is spaced away laterally from at least one of the openings in said metal membrane, and wherein said metal membrane with said patterned layer defines a thickness greater than the given dimension, whereby material deposited through the pattern of openings of said metal membrane has a height greater than the given dimension.
Specification