Etching solution, method of etching and printed wiring board
There is provided an etching solution comprised of a cupric chloride solution and a high-concentration triazole type compound added to the cupric chloride solution and capable of forming an etching-inhibiting coating. In a process of forming a circuit pattern by etching with the etching solution, an etching-inhibiting coating is selected formed on parts of a copper foil laid under the edge of an etching resist to effectively inhibit horizontal side-etching of the copper foil from the edge of the etching resist. Also, nonuniform irregularities formed on the side wall of the circuit pattern by the etching improves the adhesion between the circuit pattern and an insulating resin layer covering the circuit pattern.
1. An etching solution comprising:
a solution of cupric chloride and at least one triazole type compound added to the cupric chloride solution; and
at least one amphoteric surface active agent selected from the group consisting of alkyldimethyl betaine aminoacetate, alkyldimethyl betaine acetate, alkyldimetyl carboxymethyl betaine, alkyldimethyl carboxymethylene ammonium betaine, alklydimethyl ammoniumacetate, fatty amide propyl dimethyl betaine aminoacetate, alkyl amide propyl betaine, alkyloyl amide propyl dimethyl glycine, alkanoyl aminopropyl dimethyl ammonium acetate, palm oil fatty amide propyl betaine and palm oil fatty amide propyl dimethyl betaine aminoacetate.
2. The etching solution of claim 1 , wherein the at least one triazole type compound is selected from the group consisting of benzotriazole, benzotriazole-COOH and tolyl triazole.
3. The etching solution according to claim 1 , wherein the concentration of the at least one triazole type compound is over 1000 ppm and under 3000 ppm.
4. The etching solution according to claim 1 , wherein the concentration of the at least one triazole type compound is in a range of from 1200 to 2500 ppm.
5. The etching solution according to claim 1 , wherein the concentration of the at least one amphoteric surface active agent ranges from 2000 to 11000 ppm.
6. The etching solution of claim 1 , wherein the concentration of the at least one amphoteric surface active agent ranges from 4000 to 9700 ppm.
7. A method of etching exposed parts of a copper layer, wherein parts of the copper layer are coated with an etching resist having a predetermined pattern, wherein the parts of the copper layer not coated with the etching resist are exposed, using an etching solution, comprising:
applying, to parts of the copper layer exposed between traces of the etching resist pattern, an etching solution comprising a solution comprising cupric chloride and at least one triazole type compound to etch the exposed parts of the copper layer;
wherein an inhibiting coating is selectively formed on the parts of the copper layer coated with the etching resist; and
wherein the etching solution comprises at least one amphoteric surface active agent selected from the group consisting of alkyldimethyl betaine aminoacetate, alkyldimethyl betaine acetate, alkyldimetyl carboxymethyl betaine, alkyldimethyl carboxymethylene ammonium betaine, alklydimethyl ammoniumacetate, fatty amide propyl dimethyl betaine aminoacetate, alkyl amide propyl betaine, alkyloyl amide propyl dimethyl glycine, alkanoyl aminopropyl dimethyl ammonium acetate, palm oil fatty amide propyl betaine and palm oil fatty amide propyl dimethyl betaine aminoacetate.
8. The method of claim 7 , wherein the etching solution further comprises at least one anionic surface active agent.
9. The etching method according to claim 7 , wherein the at least one triazole type compound is selected from the group consisting of benzotriazole, benzotriazole-COOH and tolyl triazole.
10. The etching method according to claim 7 , wherein the concentration of the at least one triazole type compound is over 1000 ppm and under 3000 ppm.
11. The etching method according to claim 7 , wherein the concentration of the at least one triazole type compound is in a range of 1200 to 2500 ppm.
12. The etching method of claim 7 , wherein the concentration of the at least one amphoteric surface active agent ranges from 2000 to 11000 ppm.
13. The etching solution according to claim 7 , wherein the concentration of the at least one amphoteric surface active agent ranges from 4000 to 9700 ppm.
14. A printed wiring board having a circuit pattern formed by the etching method of claim 7 , wherein on the side wall of the circuit pattern, there are formed nonuniform irregularities having a shape and size that depend upon the concentration of the at least one triazole type compound added to the etching solution, the concentration of the surface active agent or spray pressure of the etching solution.
15. The printed wiring board according to claim 14 , wherein the nonuniform irregularities are comprised of primary depressions including convexities extending irregularly from the surface of the circuit pattern toward the surface of a substrate and concavities existing between the convexities, and secondary depressions including smaller irregularities existing between the concavities and convexities included in the primary depressions.
16. The printed wiring board according to claim 15 , wherein:
the primary depressions comprise a pitch of from 5 to 20 μm; and
wherein the primary depressions comprise a depth of from 5 to 15 μm.
17. The printed wiring board according to claim 15 , wherein the primary and secondary depressions comprise a depth, and wherein the depth of the secondary depressions is 1/10 to ½ of the depth of the primary depressions.