Method of forming a metal layer and method of manufacturing a substrate having such metal layer
In a substrate like a printed circuit board comprising an insulator and a copper layer laminated on part of the insulator, said insulator outer surface and said copper layer outer surface are simultaneously subjected to a process (1) comprising treatment with an alkali metal hydroxide solution, a process (2) comprising treatment with an alkaline aqueous solution containing an aliphatic amine, a process (3) comprising treatment with an alkaline aqueous solution having a permanganate concentration of 0.3 to 3.5 wt % and a pH of 8 to 11, a process (4) comprising treatment with an acidic microemulsion aqueous solution containing a thiophene compound and an alkali metal salt of polystyrenesulphonic acid, and a process (5) comprising copper electroplating, which are implemented sequentially.
1. A method of forming a metal layer on an insulator outer surface and on a copper layer outer surface of a substrate comprising an insulator and said copper layer laminated on part of the insulator, characterised in that simultaneously said insulator outer surface and the copper layer outer surface are subjected to a process (1) comprising treatment with an alkali metal hydroxide solution, a process (2) comprising treatment with an alkaline aqueous solution containing an aliphatic amine, a process (3) comprising treatment with an alkaline aqueous solution having a permanganate concentration of 0.3 to 3.5 wt % and a pH of 8 to 11, a process (4) comprising treatment with an acidic microemulsion aqueous solution containing a thiophene compound and an alkali metal salt of polystyrenesulphonic acid, and a process (5) comprising copper electroplating, which are implemented sequentially.
2. The method of forming a metal layer according to claim 1 , characterised in that after the abovementioned process (3), a process (3A) comprising treatment with an acidic aqueous solution is performed, then the processes from (4) onward are implemented sequentially.
3. The method of forming a metal layer according to claim 1 , characterised in that the insulator is a polyimide resin or an epoxy resin.
4. The method of forming a metal layer according to claim 1 , characterised in that the contact angle of the insulator outer surface after the abovementioned (1) treatment with an alkali metal hydroxide solution is 15° to 55°.
5. The method of forming a metal layer according to claim 1 , characterised in that the pH of the alkaline aqueous solution containing an aliphatic amine in the abovementioned process (2) is in the range of 9 to 13.
6. The method of forming a metal layer according to claim 2 , characterised in that the pH of the acidic aqueous solution in the abovementioned (3A) is in the range of 3.0 to 5.5.
7. The method of forming a metal layer according to claim 1 , characterised in that the substrate is an electronic substrate having a metal layer circuitry structure.
8. The method of forming a metal layer according to claim 7 characterised in that the electronic substrate is an IC substrate, a printed circuit board or lead frame.
9. The method of forming a metal layer according to claim 7 characterised in that the electronic substrate is a multilayer printed circuit board.
10. The method of forming a metal layer according to claim 2 , characterised in that the contact angle of the insulator outer surface after the abovementioned (1) treatment with the alkali metal hydroxide solution is 15° to 55°.
11. The method of forming a metal layer according to claim 2 , characterised in that the pH of the alkaline aqueous solution containing an aliphatic amine in the abovementioned (2) is in the range of 9 to 13.
12. The method of forming a metal layer according to claim 4 , characterised in that the pH of the alkaline aqueous solution containing an aliphatic amine in the abovementioned (2) is in the range of 9 to 13.
13. A method of manufacturing a printed circuit board characterised in that a board comprising an insulator sheet and a copper layer laminated onto both sides of said insulator sheet is used, holes penetrating through from the front to the back of said board are provided, an electrically conductive polymer layer is provided on insulator wall surfaces of said through holes by simultaneously subjecting said insulator outer surface and the copper layer outer surface to the following processes (1)-(4) in this sequence: (1) a process comprising treatment with an alkali metal hydroxide solution, (2) a process comprising treatment with an alkaline aqueous solution containing an aliphatic amine, (3) a process comprising treatment with an alkaline aqueous solution having a permanganate concentration of 0.3 to 3.5 wt % and a pH of 8 to 11, (4) a process comprising treatment with an acidic microemulsion aqueous solution containing a thiophene compound and an alkali metal salt of polystyrenesulphonic acid, after which a patterned mask is formed on the copper layer on the insulator sheet outer surface using a photolithographic method, the copper layer not covered by said patterned mask and the insulator wall surfaces in the through holes are subjected to (5) a copper electroplating process after which the patterned mask is removed, and thereafter only the copper layer portion that was covered by the patterned mask is removed by etching, thereby forming a patterned circuit and forming a layer of copper plating on the through hole wall surfaces.
14. The method of manufacturing a printed circuit board according to claim 13 , characterised in that after the patterned circuit has been formed on the copper layer, plating is performed using tin, nickel, palladium, silver, gold, platinum or alloys thereof, individually or in combination.
15. The method of manufacturing a printed circuit board according to claim 13 , characterised in that a metal layer other than copper constituting an adhesion reinforcing layer and a copper layer are laminated by this procedure on at least one surface of the insulator sheet.
16. A method of manufacturing a printed circuit board characterised in that a board comprising an insulator sheet and a copper layer laminated onto both sides of said insulator sheet is used, holes penetrating through from the front to the back of said board are provided, an electrically conductive polymer layer is provided on insulator wall surfaces of said through holes by simultaneously subjecting said insulator outer surface and the copper layer outer surface to the following processes (1)-(4) in this sequence: (1) a process comprising treatment with an alkali metal hydroxide solution, (2) a process comprising treatment with an alkaline aqueous solution containing an aliphatic amine, (3) a process comprising treatment with an alkaline aqueous solution having a permanganate concentration of 0.3 to 3.5 wt % and a pH of 8 to 11, (4) a process comprising treatment with an acidic microemulsion aqueous solution containing a thiophene compound and an alkali metal salt of polystyrenesulphonic acid, after which the through holes and the copper layer provided with the electrically conductive polymer layer are subjected to copper plating by means of a copper electroplating process (5), after which a patterned mask is formed on the layer of copper plating using a photolithographic method, the portion of the layer of copper plating not covered by the patterned mask is removed by etching and the patterned mask is removed, thereby forming a patterned circuit and forming a layer of copper plating on the through hole wall surfaces.
17. The method of manufacturing a printed circuit board according to claim 16 , characterised in that after the patterned circuit has been formed on the copper layer, plating is performed using tin, nickel, palladium, silver, gold, platinum or alloys thereof, individually or in combination.
18. The method of manufacturing a printed circuit board according to claim 16 , characterised in that a metal layer other than copper constituting an adhesion reinforcing layer and a copper layer are laminated by this procedure on at least one surface of the insulator sheet.