Method of reducing defects in I/C card and resulting card

Abstract

A technique is provided for forming a circuitized substrate which substantially reduces defects in a circuit board formed of multiple layers of dielectric material on each of which layers electrical circuitry is formed. Each layer of dielectric material is formed of two distinct and separate coatings or sheets or films of a photopatternable dielectric material which is photoformed to provide through openings to the layer of circuitry below and then plated with the desired circuitry including plating in the photoformed openings to form vias. In this way if there is a pin hole type defect in either coating or sheet of dielectric material, in all probability it will not align with a similar defect in the other sheet or coating of the dielectric layer, thus preventing unwanted plating extending from one layer of circuitry to the underlying layer of circuitry.

What is claimed is:  
     
         1 . A method or forming a circuitized substrate comprising the steps of; 
 providing a dielectric substrate having a layer of circuitry on at least one side thereof;    applying a first film of photoimagable dielectric material over said layer of circuitry on said substrate;    photoforming at least one opening in said first film of photoimagable dielectric material to expose a selected portion of the circuitry on said substrate,    applying a second film of photoimagable dielectric material over said first film of said photoimagable dielectric material,    photoforming at least one opening in said second film of said photoimagable dielectric material in alignment with said at least one opening in said first film of photoimagable dielectric material to thereby form a continuous opening through both films of photoformable material communicating with said selected portion of said circuitry on said substrate; and    forming a pattern of conductive material on said second film of said photoimagable dielectric material and within said continuous opening in both of said films of photoimagable dielectric material and on said selected portion of said circuitry on said substrate.    
     
     
         2 . The invention as defined in    claim 1    wherein said first film of photopatternable material is applied in a dry form and the second film is applied in a liquid form.  
     
     
         3 . The invention as defined in    claim 1    wherein each of the films of photopatternable material are curable, and wherein they are applied in a less than fully cured state, and wherein said films are cured before the forming of the circuitization pattern.  
     
     
         4 . The invention as defined in    claim 3    wherein the first film is fully cured before the second film is applied.  
     
     
         5 . The invention as defined in    claim 1    wherein the pattern of conductive material formed on the second film is formed by a plating process.  
     
     
         6 . The invention as defined in    claim 5    wherein the plating process is an additive plating process.  
     
     
         7 . The invention as defined in    claim 1    wherein each of the films is from about 1 mil to about 3 mils thick.  
     
     
         8 . The invention as defined in    claim 1    wherein said first film has at least one pin hole defect extending through said first film and being free of conductive material.  
     
     
         9 . The invention as defined in    claim 1    wherein said second film has at least one pin hole defect extending through said second film and terminating at the surface of said first film abutting said second film and having conducting material therein.  
     
     
         10 . The invention as defined in    claim 9    wherein said first film has at least one pin hole defect extending through said first film and being free of conductive material, and wherein each pin hole defect in said first film is offset with respect to each pin hole defect in said second film.  
     
     
         11 . A circuitized substrate comprising; 
 a dielectric substrate having a layer of circuitry on at least one side thereof;    a first film of photoimagable dielectric material overlying said layer of circuitry on said substrate;    at least one photoformed opening in said first film of photoimagable dielectric material revealing a selected portion of the circuitry on said substrate,    a second film of photoimagable dielectric material over said first film of said photoimagable dielectric material,    at least one photoformed opening in, said second film of said photoimagable dielectric material in alignment with said at least one opening in said first film of photoimagable dielectric material thereby forming a continuous opening through both films of photoformable material communicating with said selected portion of said circuitry on said substrate; and    a pattern of conductive material on said second film of said photoimagable dielectric material and within said continuous opening in both of said films of photoimagable dielectric material and on said selected portion, of said circuitry on said substrate.    
     
     
         12 . The invention as defined in    claim 11    wherein each of the films of photopatternable material is curable, and wherein said films are cured.  
     
     
         13 . The invention as defined in    claim 12    wherein each of the films is from about 1 mil to about 3 mils thick.  
     
     
         14 . The invention as defined in    claim 11    wherein said first film has at least one pin hole defect extending through said first film and being free of conductive material.  
     
     
         15 . The invention as defined in    claim 11    wherein said second film has at least one pin hole defect extending through said second film and terminating at the surface of said first film abutting said second film and having conducting material therein.  
     
     
         16 . The invention as defined in    claim 15    wherein said first film has at least one pin hole defect extending through said first film and being free of conductive material, and wherein each pin hole defect in said first film is offset with respect to each pin hole defect in said second film.