Printed circuit board and method for manufacturing printed circuit board

Abstract

An insulating layer made of an insulator film or the like is prepared. Then, a thin metal film and a thin copper film are formed in sequence on the insulating layer. The thin copper film is subsequently laminated with a dry film or the like, and exposed and developed to form a plating resist thereon that have patterns opposite to conductor patterns which are formed in a subsequent step. This is followed by forming conductor patterns made of copper, by electrolytic plating using an electrolytic copper sulfate plating solution, on the surfaces of the thin copper film where the plating resist is not formed. The plating resist is then removed by, for example, stripping. After this, the thin copper film is held at a temperature of not less than 200° C. and not more than 300° C. for approximately an hour to be thermally treated. Then, the thin copper film and the thin metal film are removed by chemical etching except the portions under the conductor patterns.

1 . A printed circuit board comprising, in sequence, an insulating layer, a thin copper film, and a conductor layer, wherein 
 said conductor layer and said thin copper film have prescribed patterns, and    said thin copper film has a first surface in contact with said insulating layer and a second surface in contact with said conductor layer, and contains a grain of a size that extends between said first surface and said second surface.    
     
     
         2 . The printed circuit board according to  claim 1 , wherein said thin copper film has a thickness of not less than 50 nm and not more than 300 nm.  
     
     
         3 . The printed circuit board according to  claim 1 , wherein said conductor layer includes copper.  
     
     
         4 . The printed circuit board according to  claim 1 , further comprising a thin metal film between said insulating layer and said thin copper film.  
     
     
         5 . The printed circuit board according to  claim 4 , wherein said thin metal film includes at least one of chromium and nickel.  
     
     
         6 . The printed circuit board according to  claim 4 , wherein said thin metal film has a thickness of not less than 5 nm and not more than 50 nm.  
     
     
         7 . The printed circuit board according to  claim 1 , wherein said insulating layer includes a flexible substrate.  
     
     
         8 . A method for manufacturing a printed circuit board by a semi-additive method, comprising the steps of: 
 forming a thin copper film on an insulating layer;    forming a conductor layer having prescribed patterns on said thin copper film;    removing said thin copper film except portions on which said conductor layer is formed; and    applying a thermal treatment to said thin copper film between said step of forming said thin copper film and said step of forming said conductor layer or between said step of forming said conductor layer and said step of removing said thin copper film.    
     
     
         9 . The method for manufacturing a printed circuit board according to  claim 8 , wherein 
 a temperature during said thermal treatment of said thin copper film is not less than 200° C. and not more than 300° C.    
     
     
         10 . The method for manufacturing a printed circuit board according to  claim 8 , wherein 
 said step of forming said conductor layer includes the steps of:    forming a resist on said thin copper film that has patterns opposite to said prescribed patterns;    forming a conductor layer on said thin copper film except portions on which said resist is formed; and    removing said resist after forming said conductor layer, and wherein    said step of applying said thermal treatment to said thin copper film is provided between said step of forming said thin copper film and said step of forming said resist or between said step of removing said resist and said step of removing said thin copper film.    
     
     
         11 . The method for manufacturing a printed circuit board according to  claim 8 , further comprising the step of forming a thin metal film between said insulating film and said thin copper film.  
     
     
         12 . The method for manufacturing a printed circuit board according to  claim 11 , wherein 
 said step of forming said thin metal film includes the step of forming at least one of chromium and nickel as said thin metal film.    
     
     
         13 . The method for manufacturing a printed circuit board according to  claim 11 , wherein 
 said step of forming said thin metal film includes the step of forming said thin metal film having a thickness of not less than 5 nm and not more than 50 nm.    
     
     
         14 . The method for manufacturing a printed circuit board according to  claim 8 , wherein 
 said step of forming said thin copper film on said insulating layer includes the step of forming said thin copper film on a flexible substrate that serves as said insulating layer.