Wiring board, process for producing the same, polyimide film for use in the wiring board, and etchant for use in the process

Abstract

In etching an organic insulating layer made of a polyimide film, a polyimide containing at least a recurrent unit expressed by general formula (1) is used for the polyimide film: ; and an alkaline etchant containing oxyalkylamine, a hydroxide of an alkaline metal compound, water, and preferably an aliphatic alcohol is used as an etchant. The composition enables efficient formation of desirably shaped via holes and through holes through the organic insulating layer on a wiring board.

1 . A method of manufacturing a wiring board, comprising the etching step of etching an organic insulating layer, 
 wherein: 
 the organic insulating layer is a polyimide film made of a polyimide containing at least a recurrent unit expressed by general formula (1)  
                     
  where R1 is an aromatic structure containing a benzene ring or a naphthalene ring and R is an aromatic structure containing a benzene ring; and  
 for the etching, an etchant is used which contains oxyalkylamine, a hydroxide of an alkaline metal compound, and water.  
   
     
     
         2 . The method as defined in  claim 1 , wherein 
 the etchant further contains an aliphatic alcohol.    
     
     
         3 . The method as defined in  claim 1 , wherein: 
 in the polyimide, R1 in general formula (1) is                           where R 2  is any one of —CH 3 , —Cl, —Br, —F., and —CH 3 O; and R is                           where n is, and X is any monovalent substituent selected from the group consisting of hydrogen, halogen, a carboxyl group, a lower alkyl group having 6 or less carbons, and a lower alcoxy group having 6 or less carbons; and/or                           where each of Y and Z is any monovalent substituent selected from the group consisting of hydrogen, halogen, a carboxyl group, a lower alkyl group having 6 or less carbons, and a lower alcoxy group having 6 or less carbons, Y and Z may be either identical or different, and A is any divalent linking group selected from the group consisting of —O—, —S—, —CO—, —SO 2 —, and —CH 2 —.    
     
     
         4 . The method as defined in  claim 1 , wherein 
 the polyimide contains, in addition to the recurrent unit expressed by general formula (1), a recurrent unit expressed by general formula (2)                           where R is identical to R in general formula (1), and R 3  is a tetravalent organic group selected from:                          
     
     
         5 . The method as defined in  claim 1 , wherein 
 in the polyimide, the recurrent unit expressed by general formula (1) is expressed by general formula (3)                           where R 4  is a divalent organic group selected from:                          
     
     
         6 . The method as defined in  claim 4 , wherein 
 in the polyimide, the recurrent unit expressed by general formula (2) is a recurrent unit expressed by general formula (4)                           where R 5  is any one of                           and R 4  is a divalent organic group expressed by                          
     
     
         7 . The method as defined in  claim 4 , wherein 
 the polyimide further contains recurrent units expressed by general formulas (5) to (8).                          
     
     
         8 . The method as defined in  claim 1 , wherein 
 the organic insulating layer has a thickness in a range of not less than 5 μm and not more than 75 μm.    
     
     
         9 . The method as defined in  claim 1 , wherein: 
 the polyimide film is formed using a polyamic-acid solution prepared by using: 
 paraphenylenediamine, as a diamine component, which accounts for not less than 25 mole % of all diamine components; and  
 diaminodiphenylether, as a diamine component, which accounts for not less than 25 mole % of all diamine components.  
   
     
     
         10 . The method as defined in  claim 1 , wherein 
 the polyimide film is formed using a polyamic-acid solution prepared by using pyromellitic acid dianhydride, as an acid dianhydride component, which accounts for not less than 25 wt % of all acid dianhydride components.    
     
     
         11 . The method as defined in  claim 1 , wherein 
 the oxyalkylamine constituting the etchant is a primary amine and/or a secondary amine.    
     
     
         12 . The method as defined in  claim 11 , wherein 
 the primary amine is at least any one of an ethanolamine, a propanolamine, a butanolamine, and an N(a-aminoethyl)ethanolamine.    
     
     
         13 . The method as defined in  claim 11 , wherein 
 the secondary amine is at least any one of a diethanolamine, a dipropanolamine, an N-methylethanolamine, and an N-ethylethanolamine.    
     
     
         14 . The method as defined in  claim 1 , wherein 
 the hydroxide of an alkaline metal compound is at least any one of potassium hydroxide, sodium hydroxide, and lithium hydroxide.    
     
     
         15 . The method as defined in  claim 2 , wherein 
 the aliphatic alcohol is a lower aliphatic alcohol having 5 or less carbon atoms.    
     
     
         16 . The method as defined in  claim 1 , wherein: 
 the oxyalkylamine has a concentration in a range of not less than 10 wt % and not more than 40 wt % to the whole etchant; and    the hydroxide of an alkaline metal compound has a concentration in a range of not less than 10 wt % and not more than 40 wt % to the whole etchant.    
     
     
         17 . The method as defined in  claim 2 , wherein: 
 the oxyalkylamine has a concentration in a range of not less than 10 wt % and not more than 40 wt % to the whole etchant; and    the hydroxide of an alkaline metal compound has a concentration in a range of not less than 10 wt % and not more than 40 wt % to the whole etchant.    
     
     
         18 . The method as defined in  claim 1 , wherein: 
 the oxyalkylamine constituting the etchant is 2-ethanolamine; and    the hydroxide of an alkaline metal compound constituting the etchant is potassium hydroxide.    
     
     
         19 . The method as defined in  claim 18 , wherein: 
 the 2-ethanolamine has a concentration in a range of not less than 55 wt % and not more than 75 wt % to the whole etchant; and    the potassium hydroxide has a concentration in a range of not less than 20 wt % and not more than 30 wt %-to the whole etchant.    
     
     
         20 . The method as defined in  claim 1 , wherein 
 in the etching step, etching temperature is in a range of not less than 50° C. and not more than 90° C.    
     
     
         21 . The method as defined in  claim 1 , wherein 
 the polyimide film is subjected to corona processing and/or plasma processing.    
     
     
         22 . The method as defined in  claim 2 , wherein: 
 the polyimide film is subjected to corona processing and/or plasma processing.    
     
     
         23 . A method of manufacturing a wiring board, comprising the etching step of etching an organic insulating layer, 
 wherein: 
 the organic insulating layer is a polyimide film;  
 the polyimide film has at least any one of following properties: a water absorbency of not more than 2.0%, a linear swelling coefficient of not more than 20 ppm/° C. in a temperature range of 100° C. to 200° C., a moisture-absorption swelling coefficient of not more than 10 ppm/% RH, an elastic modulus of not less than 4.0 GPa and not more than 8.0 GPa, and a tension elongation ratio of not less than 20%; and  
 for the etching, an etchant is used which contains oxyalkylamine, a hydroxide of an alkaline metal compound, and water.  
   
     
     
         24 . The method as defined in  claim 23 , wherein 
 the etchant further contains an aliphatic alcohol.    
     
     
         25 . The method as defined in  claim 23 , wherein 
 the organic insulating layer is a polyimide film; and    the polyimide film has a thickness in a range of not less than 5 μm and not more than 75 μm.    
     
     
         26 . The method as defined in  claim 23 , wherein 
 the polyimide film is subjected to corona processing and/or plasma processing.    
     
     
         27 . The method as defined in  claim 24 , wherein: 
 the polyimide film is subjected to corona processing and/or plasma processing.    
     
     
         28 . A method of manufacturing a wiring board, comprising the etching step of etching an organic insulating layer, 
 wherein: 
 the organic insulating layer is a polyimide film;  
 for the etching, an etchant is used which contains oxyalkylamine, a hydroxide of an alkaline metal compound, and water; and  
 a metal layer made of at least any one of copper, chromium, and nickel is used as a mask in the etching.  
   
     
     
         29 . The method as defined in  claim 28 , wherein 
 the metal layer used as the mask is formed directly on a surface of the polyimide film.    
     
     
         30 . The method as defined in  claim 29 , wherein 
 the polyimide film and the metal layer are attached with an adhesive in between.    
     
     
         31 . A wiring board, comprising at least organic an insulating layer and a metal wiring layer, 
 wherein the organic insulating layer has an opening with a wall having a taper angle of not more than 45° with respect-to an axis of the opening.    
     
     
         32 . The wiring board as defined in  claim 31 , wherein 
 the taper angle is not more than 5°.    
     
     
         33 . The wiring board as defined in  claim 31 , wherein 
 the organic insulating layer is made of a polyimide.    
     
     
         34 . A method of manufacturing a wiring board, comprising the step of forming an opening through an organic insulating layer of a wiring board which is made of at least the organic insulating layer and a metal wiring layer by alkaline etching, so that a wall of the opening wall has a taper angle of not more than 45° with respect to an axis of the opening.  
     
     
         35 . A wiring board for flexible printing, prepared by etching a polyimide film using an etchant containing at least, water, an aliphatic alcohol, 2-ethanolamine, and an alkaline metal compound, 
 said wiring board meeting following conditions: 
 (1) a wall of an opening formed has a taper angle of not more than 45° with respect to an axis of the opening;  
 (2) in the opening, an edge profile deformation is not as long as the polyimide film is thick; and  
 (3) when two or more of the opening are formed in a circular shape measuring 0.5 mm in diameter, in not more than 5 of the openings, an edge profile deformation is not less than 10% as long as the polyimide film is thick.  
   
     
     
         36 . An etchant for etching a polyimide, provided on a board as an organic insulating layer, containing at least a recurrent unit expressed by general formula (1),  
       
         
           
           
               
               
           
         
       
       where R1 is an aromatic structure containing a benzene ring or a naphthalene ring and R is an aromatic structure containing a benzene ring, 
 said etchant comprising oxyalkylamine, a hydroxide of an alkaline metal compound, and water.  
 
     
     
         37 . The etchant as defined in  claim 36 , further comprising an aliphatic alcohol.  
     
     
         38 . The etchant as defined in  claim 36 , wherein: 
 the oxyalkylamine is 2-ethanolamine and has a concentration in a range of not less than 55 wt % and not more than 75 wt % to the whole etchant;    the hydroxide of an alkaline metal compound is potassium hydroxide and has a concentration in a range of not less than 20 wt % and not more than 30 wt % to the whole etchant.