Circuit board and method for manufacturing the same

Abstract

A circuit board with conductive wiring which is precisely shaped and sized includes a two-part conductive element, namely a first conductive wiring layer and a second conductive wiring layer. The first conductive wiring layer and the second conductive wiring layer are in direct contact to each other. A projection of the first conductive wiring layer along a direction perpendicular to the circuit board and a projection of the second conductive wiring layer totally cover each other.

What is claimed is: 
     
         1 . A method for manufacturing a circuit board comprising:
 providing a metal substrate comprising a first surface and a second surface facing away from the first surface;   electroplating the metal substrate to form a first conductive wiring layer on the first surface; and   completely etching a portion of the metal substrate from the second surface to the first surface, thereby forming a second conductive wiring layer; the first conductive wiring layer and the second conductive wiring layer being direct contact to each other, the first conductive wiring layer and the second conductive wiring layer cooperatively forming a conductive wiring, thereby forming the circuit board;   wherein a projection of the first conductive wiring layer along a direction perpendicular to the circuit board and a projection of the second conductive wiring layer totally cover each other.   
     
     
         2 . The method of  claim 1 , wherein the step of electroplating the metal substrate to form a first conductive wiring layer on the first surface, further comprising:
 forming a first dry film and a second dry film on the first surface and the second surface, respectively;   treating the first dry film and the second dry film by an exposure and development process, thereby forming a hollow pattern in the first dry film towards the first surface;   removing the first dry film and the second dry film; and   electroplating the metal substrate to form the first conductive wiring layer in the hollow pattern.   
     
     
         3 . The method of  claim 2 , wherein the step of treating the first dry film and the second dry film by an exposure and development process, further comprising:
 covering a photo mask on the first dry film facing away from the metal substrate, and exposing the first dry film and the second dry film to ultraviolet radiation, thereby causing the second dry film and an uncovered portion of the first dry film to be exposed under the ultraviolet radiation;   removing the photo mask and etching a remaining unexposed portion of the first dry film, thereby forming the hollow pattern in the first dry film.   
     
     
         4 . The method of  claim 2 , the first dry film has a thickness greater than a thickness of the second dry film. 
     
     
         5 . The method of  claim 4 , wherein the first dry film has a thickness of about 75 μm, and the second dry film has a thickness of about 15 μm. 
     
     
         6 . The method of  claim 1 , wherein the metal substrate has a thickness of about 50 μm to about 80 μm. 
     
     
         7 . The method of  claim 1 , wherein the first conductive wiring layer has a thickness of about 60 μm to about 70 μm, a cross-sectional shape of the first conductive wiring layer is rectangular. 
     
     
         8 . The method of  claim 1 , further comprising:
 covering a first cover film on the first conductive wiring layer and filling the first cover film in gaps of the first conductive wiring layer.   
     
     
         9 . The method of  claim 8 , wherein the first cover film comprises a first cover layer and a first adhesive layer connected to the first cover layer, the first adhesive layer is between the first cover layer and the first conductive wiring layer and fills in the gaps of the first conductive wiring layer. 
     
     
         10 . The method of  claim 1 , wherein the step of completely etching a portion of the metal substrate from the second surface to the first surface, further comprising:
 covering a third dry film on the second surface;   treating the third dry film by an exposure process to form patterns corresponding to the first conductive wiring layer;   treating the metal substrate by a development process through the patterned third dry film, thereby completely etching the portion of the metal substrate from the second surface to the first surface to form the second conductive wiring layer; and   removing the third dry film.   
     
     
         11 . The method of  claim 10 , wherein the second conductive wiring layer has a thickness of about 70 μm, and a cross-sectional shape of the second conductive wiring layer is trapezoidal. 
     
     
         12 . The method of  claim 1 , further comprising:
 covering a second cover film on the second conductive wiring layer which fills in gaps of the second conductive wiring layer.   
     
     
         13 . The method of  claim 12 , wherein the second cover film comprises a second cover layer and a second adhesive layer connected to the second cover layer, the second adhesive layer is positioned between the second cover layer and the second conductive wiring layer and fills in the gaps of the second conductive wiring layer. 
     
     
         14 . A circuit board comprising:
 a conductive wiring comprising:
 a first conductive wiring layer; and 
 a second conductive wiring layer; 
   wherein the first conductive wiring layer and the second conductive wiring layer are in direct contact to each other, a projection of the first conductive wiring layer along a direction perpendicular to the circuit board and a projection of the second conductive wiring layer totally cover each other.   
     
     
         15 . The circuit board of  claim 14 , further comprising a first cover film covering and filling in gaps of the first conductive wiring layer. 
     
     
         16 . The circuit board of  claim 14 , further comprising a second cover film covering and filling in gaps of the second conductive wiring layer.