Printed circuit board and method of manufacturing the same

Abstract

A printed circuit board includes an uncured substrate material with closed voids which are disposed with a through-hole. When the through-hole is formed, voids which exist in the substrate material open from inner wall of the through-hole to form a hollow-shaped part. By filling the through-hole and the hollow-shaped part with conductive paste, the adhesion improves by the increased holding effect between the conductive paste and the wall surface of the through-hole.

What is claimed is:  
     
         1 . A printed circuit board comprising a resin impregnate fiber sheet substrate with through-holes formed in a thickness direction and a conductive resin compound comprising a resin filled in said through-holes in the thickness direction for electrical connection, wherein said substrate and said conductive resin compound are bonded to each other.  
     
     
         2 . The printed circuit board as in    claim 1   , wherein said substrate and said conductive resin compound are bonded to each other such that said conductive resin compound penetrates into said substrate.  
     
     
         3 . The printed circuit board as in    claim 1   , wherein said conductive resin compound comprises metallic particulates and resin, and wherein said substrate and said conductive resin compound are bonded to each other through impregnation of the resin of said conductive resin compound into said substrate.  
     
     
         4 . The printed circuit board as in    claim 1   , wherein said substrate and said conductive resin compound are bonded to each other through covalent bonding, or self-adhesion between the resin of said conductive resin compound and the impregnate resin in said substrate.  
     
     
         5 . The printed circuit board as in    claim 1   , wherein said substrate and said conductive resin compound are bonded to each other such that the fiber of said fiber sheet substrate penetrates into said conductive resin compound.  
     
     
         6 . The printed circuit board as in    claim 1   , wherein the impregnate resin of said substrate and the resin of said conductive resin compound are both thermosetting resin.  
     
     
         7 . The printed circuit board as in    claim 6   , wherein said thermosetting resin comprises at least one resin selected from the group consisting of epoxy resin, thermosetting polybutadiene resin, phenol resin, and polyimide resin.  
     
     
         8 . The printed circuit board as in    claim 1   , wherein said resin impregnate fiber sheet of the substrate comprises at least one fiber selected from the group consisting of heat-resisting synthetic fiber and glass fiber.  
     
     
         9 . The printed circuit board as in    claim 8   , wherein said heat-resisting synthetic fiber comprises at least one fiber selected from the group consisting of aromatic polyamide fiber and polyimide fiber.  
     
     
         10 . The printed circuit board as in    claim 1   , wherein said resin impregnate fiber sheet of the substrate is a nonwoven fabric.  
     
     
         11 . The printed circuit board as claimed in    claim 3   , wherein said metallic particulate in the conductive resin compound is at least one metal selected from the group consisting of gold, silver, copper, palladium, nickel, gold alloy, silver alloy, copper alloy, palladium alloy, and nickel alloy.  
     
     
         12 . The printed circuit board as in    claim 3   , wherein said metallic particulates are present in the conductive resin compound in an amount of from 80 to 92.5 percent by weight.  
     
     
         13 . The printed circuit board as in    claim 3   , wherein each metallic particulate in said conductive resin compound has an average diameter of from 0.2 to 20 μm.  
     
     
         14 . The printed circuit board as in    claim 1   , wherein the through-hole filled with said conductive resin compound has an average diameter of from 50 to 300 μm.  
     
     
         15 . The printed circuit board as in    claim 1   , wherein a circuit is formed on the surface of said substrate, and also formed at a terminal of said conductive resin compound.  
     
     
         16 . The printed circuit board as in    claim 1   , wherein said substrate is either one sheet or a plurality of sheets.  
     
     
         17 . A method of manufacturing a printed circuit board, comprising the steps of: 
 (a) laminating both sides of an uncured resin impregnate fiber sheet substrate material having voids with cover films;    (b) forming through-holes in said substrate material in a thickness direction by laser irradiation;    (c) filling said through-holes with conductive paste;    (d) removing said cover films and applying a metal foil on at least one side of said substrate material;    (e) bonding said substrate material with said conductive paste by compressing and hardening said substrate material through heating and pressurization; and    (f) forming predetermined patterns on said metal foil.    
     
     
         18 . The method of manufacturing a printed circuit board as claimed in    claim 17   , wherein metal foils are applied on both sides of said substrate material.  
     
     
         19 . The method of manufacturing a printed circuit board as claimed in    claim 17   , comprising the steps of: 
 (a) laminating both sides of an uncured resin impregnate fiber sheet substrate material having voids with cover films;    (b) forming through-holes in said substrate material in the thickness direction by laser irradiation;    (c) filling said through-holes with conductive paste;    (d) removing said cover films and applying a metal foil on one side of each sheet, thereby forming two sheets of intermediate;    (e) disposing said intermediates such that sides with metal foils face outside;    (f) holding at least two layers of circuit substrates having circuit patterns in a core;    (f) bonding said substrate material with said conductive paste by compressing and hardening through heating and pressurization; and    (g) forming predetermined patterns on said metal foil.    
     
     
         20 . The method of manufacturing a printed circuit board as claimed in    claim 17   , comprising the steps of: 
 (a) laminating both sides of an uncured resin impregnate fiber sheet substrate material having voids with cover films;    (b) forming through-holes in said substrate material in the thickness direction by laser irradiation;    (c) filling said through-holes with conductive paste;    (d) removing said cover films, thereby forming an intermediate connecting member;    (e) positioning said intermediate connecting member between a plurality of double sided printed circuit boards; and    (f) bonding said substrate material with said conductive paste by compressing and hardening through heating and pressurization.    
     
     
         21 . The method of manufacturing a printed circuit board as in    claim 17   , wherein said voids in the uncured resin impregnate fiber sheet substrate material are closed holes.  
     
     
         22 . The method of manufacturing a printed circuit board as in    claim 21   , wherein said closed hole has a diameter of 5 to 20 μm in said uncured substrate material.  
     
     
         23 . The method of manufacturing a printed circuit board as in    claim 17   , wherein said uncured substrate material with holes has a porosity of from 2 to 35%.  
     
     
         24 . The method of manufacturing a printed circuit board as in    claim 17   , wherein the heating is carried out at a temperature of said substrate material of from 170 and 260° C.  
     
     
         25 . The method of manufacturing a printed circuit board as in    claim 17   , wherein the pressurization is carried out at a pressure on said substrate material of from 20 to 80 kg/cm 2 .  
     
     
         26 . The method of manufacturing a printed circuit board as in    claim 17   , wherein a part of fiber in said substrate material is allowed to remain in said through-holes by laser irradiation.  
     
     
         27 . The method of manufacturing a printed circuit board as in    claim 17   , wherein a compound of metallic particulates and resin is used as said conductive resin compound to fill said through-holes, and the resin of said conductive resin compound is bonded to said substrate through impregnation.  
     
     
         28 . A method of manufacturing a printed circuit board as claimed in    claim 17   , wherein the resin of said conductive resin compound and the impregnate resin of said substrate belong to the resin having the same functional group, and are bonded to each other through covalent bonding, or self-adhesion.  
     
     
         29 . The method of manufacturing a printed circuit board as in    claim 17   , wherein the impregnate resin in said substrate and the resin of said conductive resin compound are both thermosetting resins, and each comprises at least one resin selected from the group consisting of epoxy resin, thermosetting polybutadiene resin, phenol resin, and polyimide resin.  
     
     
         30 . The method of manufacturing a printed circuit board as in    claim 17   , wherein said filling is carried out using a roll coating method.  
     
     
         31 . The method of manufacturing a printed circuit board as in    claim 17   , wherein said resin impregnate fiber sheet of the substrate comprises at least one fiber selected from the group consisting of heat-resisting synthetic fiber and glass fiber.  
     
     
         32 . The method of manufacturing a printed circuit board as in    claim 31   , wherein said heat-resisting synthetic fiber comprises at least one fiber selected from the group consisting of aromatic polyamide fiber and polyimide fiber.  
     
     
         33 . The method of manufacturing a printed circuit board as in    claim 17   , wherein said resin impregnate fiber sheet of the substrate is a nonwoven fabric.  
     
     
         34 . The method of manufacturing a printed circuit board as in    claim 27   , wherein said metallic particulate in the conductive resin compound comprises at least one element selected from the group consisting of gold, silver, copper, palladium, nickel, gold alloy, silver alloy, copper alloy, palladium alloy, and nickel alloy.  
     
     
         35 . The method of manufacturing a printed circuit board as in    claim 27   , wherein said metallic particulates are present in the conductive resin compound in an amount of from 80 to 92.5 percent by weight.  
     
     
         36 . The method of manufacturing a printed circuit board as in    claim 27   , wherein each metallic particulate in said conductive resin compound has an average diameter of from 0.2 to 20 μm.  
     
     
         37 . The method of manufacturing a printed circuit board as in    claim 17   , wherein the through-hole filled with said conductive resin compound has an average diameter of from 50 to 300 μm.  
     
     
         38 . The method of manufacturing a printed circuit board as in    claim 17   , wherein said laser beam is selected from the group consisting of carbon dioxide laser, YAG laser, and excimer laser.