Single-sided circuit board and method for maufacturing the same

Abstract

Holes ( 40 a ) are formed with a laser beam through an insulating substrate ( 40 ) on which a metallic layer ( 42 ) is formed and via holes ( 36 a ) are formed by filling up the holes ( 40 a ) with a metal ( 46 ). After the via holes ( 36 a ) are formed, a conductor circuit ( 32 a ) is formed by etching the metallic layer ( 42 ) and a single-sided circuit board ( 30 A) is formed by forming projecting conductors ( 38 a ) on the surfaces of the via holes ( 36 a ). The projecting conductors ( 38 a ) on the circuit board ( 30 A) are put on the conductor circuit ( 32 b ) of another single-sided circuit board ( 30 B) with adhesive layers ( 50 ) composed of an uncured resin in-between and heated and pressed against the circuit ( 32 b ). The projecting conductors ( 38 a ) get in the uncured resin by pushing aside the resin and are electrically connected to the circuit ( 32 b ). Since single-sided circuit boards ( 30 A, 30 B, 30 C, and 30 D) can be inspected for defective parts before the boards ( 30 A, 30 B, 30 C, and 30 D) are laminated upon one another, only defectless single-sided circuit can be used in the step of lamination.

What is claimed is:  
     
         1 . A single-sided circuit substrate comprising: an insulating base member on either side of which a conductive circuit is formed, wherein said insulating base member has non-penetrating holes which reach said conductive circuit, via holes are formed by enclosing electrolytic plating in said non-penetrating holes, projecting conductors made of conductive paste or metal having a low melting point are formed on the surfaces of said via holes formed on the surface of said insulating base member opposite to the surface on which said conductive circuit has been formed.  
     
     
         2 . A single-sided circuit substrate according to  claim 1 , wherein said non-penetrating holes are completely filled with electrolytic plating.  
     
     
         3 . A single-sided circuit substrate according to  claim 1  or  2 , wherein said non-penetrating holes are filled with the electrolytic plating to an average depth of 50% or higher of the depth of said non-penetrating holes and lower than 100% of the same.  
     
     
         4 . A single-sided circuit substrate according to any one of  claims 1  to  3 , wherein said insulating base member is an organic insulating member.  
     
     
         5 . A single-sided circuit substrate according to any one of  claims 1  to  4 , wherein said electrolytic plating is copper electrolytic plating.  
     
     
         6 . A single-sided circuit substrate according to any one of  claims 1  to  5 , wherein said insulating member is a single-sided copper-clad laminate.  
     
     
         7 . A method of manufacturing a single-sided circuit substrate at least comprising the steps (1) to (4): 
 (1) forming non-penetrating holes which reach a metal layer by a laser process in a insulating base member having said metal layer formed on either side thereof;    (2) enclosing electrolytic plating into said non-penetrating holes formed in step (1) to form via holes;    (3) forming a conductive circuit by etching said metal layer; and    (4) forming projecting conductors made of conductive paste or metal having a low melting point on the surfaces of said via holes formed on the surface of said insulating base member opposite to the surface on which said conductive circuit has been formed so that a single-sided circuit substrate is obtained.    
     
     
         8 . A method of manufacturing a single-sided circuit substrate at least comprising the steps (1) to (3): 
 (1) forming non-penetrating holes which reach a metal layer by a laser process in an insulating base member having said metal layer formed on either side thereof;    (2) enclosing electrolytic plating into said non-penetrating holes formed in step (1) to form via holes and forming projecting conductors made of conductive paste or metal having a low melting point on the surfaces of said via holes formed on the surface of said insulating base member opposite to the surface on which said conductive circuit has been formed; and    (3) etching said metal layer to form a conductive circuit so that a single-sided circuit substrate is obtained.    
     
     
         9 . A method of manufacturing a single-sided circuit substrate according to  claim 7  or  8 , wherein said step (1) is performed such that a film is bonded to said insulating base member having the metal layer formed on either side thereof and non-penetrating holes which penetrate said film and said insulating base member to reach said metal layer are formed by a laser process.  
     
     
         10 . A method of manufacturing a single-sided circuit substrate according to any one of  claims 7  to  9 , wherein said insulating base member is an organic insulating base member.  
     
     
         11 . method of manufacturing a single-sided circuit substrate according to any one of  claims 7  to  10 , wherein said insulating base member is a single-sided copper cladding laminate.  
     
     
         12 . A single-sided circuit substrate according to any one of  claims 7  to  11 , wherein said electrolytic plating is copper electrolytic plating.  
     
     
         13 . A method of manufacturing a single-sided circuit substrate according to any one of  claims 7  to  12 , wherein said projecting conductors are formed by printing conductive paste.  
     
     
         14 . A method of manufacturing a single-sided circuit substrate according to any one of  claims 7  to  13 , wherein said projecting conductor are formed by printing metal paste having a low melting point, plating of metal having a low melting point or immersion of metal having a low melting point into molten solution.