Etching solutions and processes for manufacturing flexible wiring boards

Abstract

An etching solution of the invention includes 3-65% by weight of a diol containing 3 to 6 carbon atoms or a triol containing 4 to 6 carbon atoms, 10-55% by weight of an alkali compound, and water in an amount of 0.75-3.0 times the amount of the alkali compound. Such a solution may be used at 65° C. or higher to rapidly etch a polyimide resin layer having an imidation degree of 50-98% without unfavorably affecting the working atmosphere.

1 . An etching solution suitable for etching a resin layer based on a polyimide, the solution comprising an alcohol, water and an alkali compound, wherein the alcohol is present in a range of from 3 to 65% by weight, the alkali compound is present in a range of from 10 to 55% by weight and the water is present in a range of from 0.75 to 3.0 times a weight of the alkali compound, and wherein the alcohol is based on either one or both of a diol containing from 3 to 6 carbon atoms and a triol containing from 4 to 6 carbon atoms and the alkali compound is based on either one or both of an alkali metal hydroxide and a quaternary ammonium hydroxide.  
   
   
       2 . An etching solution suitable for etching a resin layer based on a polyimide, the solution comprising an alcohol, water and an alkali compound, wherein the alcohol is present in a range of from 3 to 65% by weight, the alkali compound is present in a range of from 10 to 55% by weight and the water is present in a range of from 0.85 to 2.5 times a weight of the alkali compound, and wherein the alcohol is based on either one or both of a diol containing from 3 to 6 carbon atoms and a triol containing from 4 to 6 carbon atoms and the alkali compound is based on either one or both of an alkali metal hydroxide and a quaternary ammonium hydroxide.  
   
   
       3 . The etching solution of  claim 1 , wherein the alkali metal hydroxide is based on at least one compound selected from a group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.  
   
   
       4 . The etching solution of  claim 2 , wherein the alkali metal hydroxide is based on at least one compound selected from a group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.  
   
   
       5 . The etching solution of  claim 1 , wherein the quaternary ammonium hydroxide is based on either one or both of tetramethylammonium hydroxide and tetraethylammonium hydroxide.  
   
   
       6 . The etching solution of  claim 2 , wherein the quaternary ammonium hydroxide is based on either one or both of tetramethylammonium hydroxide and tetraethylammonium hydroxide.  
   
   
       7 . The etching solution of  claim 1 , wherein the diol is based on at least one diol selected from a group consisting of 1,3-propanediol, 2,3-butanediol, 1,4-butanediol and 1,5-pentanediol.  
   
   
       8 . The etching solution of  claim 2 , wherein the diol is based on at least one diol selected from a group consisting of 1,3-propanediol, 2,3-butanediol, 1,4-butanediol and 1,5-pentanediol.  
   
   
       9 .- 18 . (canceled)