Multilayer board having precise perforations and circuit substrate having precise through-holes

Abstract

A perforation of a multilayer board has a surface-profile precision of 8 μm or less, and the ratio of a diameter or the minimum distance between the opposing edges on the opening surface thereof to the axial length is preferably from about 1:1 to 1:15. The multilayer board is fabricated by a punching machine comprising a punch and a stripper such that a required number of plates are prepared, the first plate is perforated by the punch and is pulled up by closely attaching it to the stripper while leaving the punch in the first bore, the second plate is perforated by the punch and is pulled up together with the first plate while leaving the punch in the second bore, and subsequently, the following plates are perforated by the punch and the perforated plates are stacked along the punch serving as a stacking axis sequentially.

What is claimed is:  
     
         1 . A multilayer board comprising: 
 a plurality of stacked plates; and    a plurality of perforations precisely formed in the stacked plates,    wherein the perforations have a surface-profile precision of 8 μm or less.    
     
     
         2 . The multilayer board according to  claim 1 , wherein the ratio of the diameter of the perforation, or the minimum distance of the opposing edges on the opening surface of the perforation, to an axial length of the perforation lies in the range from about 1:1 to about 1:15.  
     
     
         3 . The multilayer board according to  claim 2 , wherein the ratio of the spacing between the adjacent perforations to an axial length of the perforations lies in the range from about 1:1 to about 1:15.  
     
     
         4 . The multilayer board according to  claim 1 , wherein the diameter of the perforation, or the minimum distance of the opposing edges on the opening surface of the perforation is equal to 100 μm or less.  
     
     
         5 . The multilayer board according to  claim 1 , wherein the spacing between the adjacent perforations is equal to 100 μm or less.  
     
     
         6 . The multilayer board according to  claim 1 , wherein the plates comprise an insulating material comprising a plastic resin or a ceramic, or comprise a compound insulating material of a plastic resin and a ceramic.  
     
     
         7 . The multilayer board according to  claim 1 , wherein the plate has a Yung's modulus of 3000 kgf/mm 2  or less and a tensile strength of 20 kgf/mm 2  or less.  
     
     
         8 . A multilayer board comprising: 
 a plurality of stacked plates; and    a plurality of precise perforations which are formed in the plates by a punching machine comprising a punch, a die, and a stripper, and which have a surface-profile precision of 8 μm or less,    wherein the multilayer board is fabricated by the following steps: 
 preparing a required number of the plates;  
 forming a first bore in the first plate by the punch and pulling up the first plate by closely attaching the first plate to the stripper while leaving the punch in the first bore;  
 forming a second bore in the second plate by the punch and pulling up the second plate together with the first plate while leaving the punch in the second bore; and  
 repeating forming bores in the following plates and stacking the punched plates along the punch serving as a stacking axis sequentially until the predetermined number of plates is stacked.  
   
     
     
         9 . A circuit substrate comprising: 
 a plurality of conductors;    a plurality of insulators for insulating the conductors; and    at least one through-hole passing through all the conductors and insulators,    wherein the conductors and the insulators are stacked and the through-hole has a surface-profile precision of 8 μm or less.    
     
     
         10 . The circuit substrate according to  claim 9 , wherein the ratio of the diameter of the through-hole, or the minimum distance of the opposing edges on the opening surface of the through-hole, to an axial length of the through-hole lies in the range from about 1:1 to about 1:15.  
     
     
         11 . The circuit substrate according to  claim 9 , wherein the ratio of the spacing between the adjacent through-holes to an axial length of the through-holes lies in the range from about 1:1 to about 1:15.  
     
     
         12 . A circuit substrate comprising: 
 a plurality of conductors;    a plurality of insulators for insulating the conductors, stacked together with the conductors; and    at least one through-hole which passes through all the insulators and the conductors, which is formed by a punching machine comprising a punch, a die, and a stripper, and which has a surface-profile precision of 8 μm or less,    wherein the circuit substrate is fabricated in the following steps: 
 preparing a plurality of wiring boards comprising an insulating material and having respective circuits formed thereon;  
 forming a first hole in the first wiring board by the punch and pulling up the first wiring board by closely attaching the first wiring board to the stripper while leaving the punch in the first hole;  
 forming a second hole in the second wiring board by the punch and pulling up the second wiring board together with the first wiring board while leaving the punch in the second hole; and  
 repeating forming holes in the following wiring boards and stacking the formed wiring boards along the punch serving as a stacking axis sequentially until the predetermined number of wiring boards is stacked.  
   
     
     
         13 . A circuit substrate comprising: 
 a base substrate; and    at least one build-up layer formed on at least one side of the base substrate, the base substrate comprising:    a plurality of conductors;    a plurality of insulators for insulating the conductors, stacked together with the conductors; and    at least one through-hole formed therein, passing through all the conductors and insulators, and the build-up layer comprising: 
 at least one conducting layer; and  
 at least one insulating layer stacked together with the conducting layer alternately,  
 wherein the through-hole has a surface-profile precision of 8 μm or less.  
   
     
     
         14 . The circuit substrate according to  claim 13 , 
 wherein the ratio of the diameter of the through-hole, or the minimum distance of the opposing edges on the opening surface of the through-hole, to an axial length of the through-hole lies in the range from about 1:1 to about 1:15.    
     
     
         15 . The circuit substrate according to  claim 13 , wherein the ratio of the spacing between the adjacent through-holes to the axial length of the through-holes lies in the range from about 1:1 to about 1:15.  
     
     
         16 . A circuit substrate comprising: 
 a base substrate; and    at least one build-up layer formed on at least one side of the base substrate, the base substrate comprising: 
 a plurality of conductors;  
 a plurality of insulators for insulating the conductors, stacked together with the conductors; and  
 at least one through-hole formed therein, passing through all the conductors and insulators, and the build-up layer comprising: 
 at least one conducting layer; and  
 at least one insulating layer stacked together with the conducting layer alternately,  
 wherein the through-hole is formed by a punching machine comprising a punch, a die, and a stripper and has a surface-profile precision of 8 μm or less, and  
 wherein the circuit substrate is fabricated in the following steps: 
 preparing a plurality of wiring boards comprising an insulating material and having respective circuits formed thereon;  
 forming a first hole in the first wiring board by the punch and pulling up the first wiring board by closely attaching the wiring board to the stripper while leaving the punch in the first hole;  
 forming a second hole in the second wiring board by the punch and pulling up the second wiring board together with the first wiring board while leaving the punch in the second hole;  
 repeating forming holes in the following wiring boards and stacking the punched wiring boards along the punch serving as a stacking axis sequentially until a predetermined base substrate is stacked; and  
 forming the build-up layer on thus fabricated base substrate.