Application of electrical conductors to an electrically insulating substrate

Abstract

A method is disclosed for applying an electrical conductor to an electrically insulating substrate, which comprises providing a flexible membrane with a pattern of groove formed on a first surface thereof, and loading the grooves with a composition comprising conductive particles. The composition is, or may be made, electrically conductive. Once the membrane is loaded, the grooved first surface of the membrane is brought into contact with a front or/and back of the substrate. A pressure is then applied between the substrate and the membrane(s) so that the composition loaded to the grooves adheres to the substrate. The membrane(s) and the substrate are separated and the composition in the groove is left on the surface of the electrically insulating substrate. The electrically conductive particles in the composition are then sintered to form a pattern of electrical conductors on the substrate, the pattern corresponding to the pattern formed in the membrane(s).

1 . An electrically insulating substrate having a pattern comprising a pattern of electrical conductors applied on a first side thereof, wherein at least part of the electrical conductors fulfils two or more of the following features:
 (a) a distance between facing edges of at least one pair of adjacent electrical conductors is less than 15 μm;   (b) the at least part of the electrical conductors consists of sintered electrically conductive particles and of voids between said sintered particles, the voids being present in at least 1% by area in a cross-section of the electrical conductors; and   (c) the at least part of the electrical conductors includes at least one contact pad that is flat on the first side, the at least one contact pad being capped by a solder bump, and wherein the at least one of the solder bumps capping the at least one of the contact pads has a diameter of at most 50 μm.   
     
     
         2 . The electrically insulating substrate of  claim 1 , wherein the electrically insulating substrate is non-planar. 
     
     
         3 . The electrically insulating substrate of  claim 1 , wherein the at least part of the electrical conductors is not entirely surrounded by a polymer and there is no polymer between the at least part of the electrical conductors and the electrically insulating substrate. 
     
     
         4 . The electrically insulating substrate of  claim 1 , wherein the electrical conductors are substantially identical to one another. 
     
     
         5 . The electrically insulating substrate of  claim 1 , wherein a first and a second of the electrical conductors have different cross-sectional dimensions. 
     
     
         6 . The electrically insulating substrate of  claim 1 , wherein a first segment and a second segment of a same electrical conductor have different cross-sectional dimensions. 
     
     
         7 . The electrically insulating substrate of  claim 1 , wherein the pattern of electrical conductors is a first pattern of a first composition, the insulating substrate further comprising a second pattern of a second composition, the second composition differing from the first composition. 
     
     
         8 . The electrically insulating substrate of  claim 7 , wherein the second composition is substantially devoid of electrically conductive particles. 
     
     
         9 . The electrically insulating substrate of  claim 7 , wherein the second composition comprises ferromagnetic particles and an adhesive. 
     
     
         10 . The electrically insulating substrate of  claim 7 , wherein at least part of the second pattern is parallel to at least part of the first pattern. 
     
     
         10 . The electrically insulating substrate of  claim 7 , wherein at least part of the second pattern is interposed with, and/or surrounding, at least part of the first pattern. 
     
     
         12 . The electrically insulating substrate of  claim 1 , wherein the distance between the facing edges of the at least one pair of adjacent electrical conductors is at least 7.5 μm and is no more than 12.5 μm. 
     
     
         13 . The electrically insulating substrate of  claim 1 , wherein at least one of the electrical conductors has an aspect ratio ASP between an orthogonal distance h between a base and a top point of a cross-sectional profile and a width of the base WB (ASP=h/WB) of at least 3:1. 
     
     
         14 . The electrically insulating substrate of  claim 1 , wherein the pattern of electrical conductors spans over an area larger than a field of view of lithographic equipment, the pattern of electrical conductors simultaneously applied having at least one of a width and a length of 70 cm or more. 
     
     
         15 . The electrically insulating substrate of  claim 1 , wherein for at least one of the electrical conductors, electrically conductive particles, blends of electrically conductive particles, and/or electrically conductive particle size vary along a height of the electrical conductor. 
     
     
         16 . The electrically insulating substrate of  claim 1 , wherein the electrical conductors comprise electrically conductive particles made of compounds selected from the group consisting of metals, alloys, organo-metals, conductive polymers, conductive polymers precursors and salts thereof, and combinations thereof. 
     
     
         17 . The electrically insulating substrate of  claim 1 , further comprising an insulating material on top of said pattern of electrical conductors, and another pattern of electrical conductors on top of said insulating material. 
     
     
         18 . A flexible membrane, having a first surface, wherein the first surface has a pattern of grooves formed therein, wherein at least part of the grooves fulfils the following features:
 a) a distance between facing edges of at least one pair of adjacent grooves is less than 15 μm;   b) aspect ratio ASP between an orthogonal distance h between a base and a top point of a cross-sectional profile and a width of the base WB (ASP=h/WB) is at least 3:1.   
     
     
         19 . The flexible membrane of  claim 18 , wherein the pattern of grooves spans over an area larger than a field of view of lithographic equipment, the pattern of grooves having at least one of a width and a length of 70 cm or more. 
     
     
         20 . The flexible membrane of  claim 18 , wherein for at least one of the grooves, the constituents of a composition, relative proportions of constituents of the composition, electrically conductive particles, blends of electrically conductive particles, and/or electrically conductive particle size vary along a depth of the groove.