Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Reexamination Certificate
2001-07-02
2002-05-07
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
C148S269000, C148S272000, C216S020000, C216S034000, C216S105000, C252S079100, C252S188200
Reexamination Certificate
active
06383254
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a treatment solution and a treatment method for reducing a copper oxide having enhanced adhesion to resins and, particularly, to a treatment solution and a treatment method for enhancing the adhesion of copper wires for an internal layer to a resin layer in the production of a multilayer printed-wiring board and enhancing the acid resistance of the copper wires for an internal layer.
In the production of the multilayer printed-wiring board, since the adhesion of the copper wires for an internal layer which are laminated on and bonded to the resin layer is weak when the surface of the copper wire is smooth, a layer of copper oxide such as copper (I) oxide or copper (II) oxide has been heretofore formed on the surface of the copper wire. Since this copper oxide layer has roughness on the surface, it exhibits a mechanical anchoring effect to the resin layer, and since the copper oxide layer has large chemical affinity for the resin layer, it exhibits significantly excellent adhesion to the resin layer.
However, the above copper oxide layer has poor acid resistance. For example, there occurs the phenomenon that the copper oxide layer bonded to the resin layer is dissolved by a hydrochloric acid solution for feeding a catalyst for electroless plating in the through hole plating step after the lamination and bonding step.
To prevent this phenomenon from occurring, copper wires for an internal layer which have adhesion and acid resistance are produced by reducing the copper oxide layer to copper. As the method for reducing the copper oxide layer, there are known a method in which the copper oxide layer is brought into contact with an alkali aqueous solution containing a reducing agent such as sodium borohydride or formalin (Japanese Patent Publication No. 8479/1989), a two-step method in which the copper oxide layer is dipped in sodium boroalkali and formalin successively (Japanese Patent Application Laid-Open No. 156479/1989), a method using dimethylamine borane as a reducing agent (Japanese Patent Application Laid-Open No. 176192/1986 and Japanese Patent Publication No. 50431/1991), a two-step method in which the copper oxide layer is dipped in dimethylamine borane and formalin successively (Japanese Patent Application Laid-Open No. 160564/1993) and the like.
However, the methods disclosed in Japanese Patent Publication No. 8479/1989 and Japanese Patent Application Laid-Open No. 156479/1989 have such problems that it is difficult to reduce the copper oxide layer to copper to a sufficient degree and that the treatment time and the treatment temperature must be severely restricted. The method using dimethylamine borane has the problem that a life of the treatment solution is not long because dimethylamine borane is easily decomposed. Further, reducing agents such as sodium borohydride and dimethylamine borane are expensive and interfere with a reduction in the costs for the reduction treatment.
SUMMARY OF THE INVENTION
The present invention has been invented under the above circumstances. It is the object of the present invention to provide a treatment solution and a treatment method for obtaining a copper material having excellent adhesion to resins and acid resistance.
The present invention has been completed by studying a treatment solution which can still reduce a copper oxide to copper despite a decrease in the concentration of dimethylamine borane and finding that there is a special relationship between an area to be treated (area of copper material having a copper oxide dipped in the treatment solution) and the minimum required amount of dimethylamine borane.
That is, the treatment solution of the present invention for reducing a copper oxide is a treatment solution for reducing a copper oxide formed on the surface of copper to copper, in which dimethylamine borane is contained in an amount of 0.3 to 2.0 g/L and the relationship y≧0.232x
−0.185
holds between the concentration y (g/L) of dimethylamine borane and an area x (dm
2
/L) to be treated per unit solution amount.
Further, the treatment solution of the present invention for reducing a copper oxide is also a treatment solution for reducing a copper oxide formed on the surface of copper to copper, in which dimethylamine borane is contained in an amount of 0.15 to 2.0 g/L, 37% formalin is contained in an amount of 0.5 to 100 mL/L, the pH is 12 or more, and the relationship y≧0.215x
−0.168
holds between the concentration y (g/L) of dimethylamine borane and an area x (dm
2
/L) to be treated per unit solution amount. A preferable embodiment of the treatment solution of the present invention is such that the relationship y≧−0.106z+1.57 holds between the concentration y (g/L) of dimethylamine borane and the value z of the pH of the treatment solution.
The treatment method of the present invention for reducing a copper oxide is a treatment method for reducing a copper oxide formed on the surface of a copper material by oxidation to copper by dipping the copper material in the treatment solution, in which the treatment solution is prepared by adding dimethylamine borane to water in such a manner that the concentration of dimethylamine borane is 0.3 to 2.0 g/L and that the relationship y≧0.232x
−0.185
holds between the concentration y (g/L) of dimethylamine borane and an area x (dm
2
/L) to be treated of the copper material per unit solution amount, and the addition of dimethylamine borane to water is carried out within 10 minutes before the dipping of the copper material having the copper oxide on the surface or after the dipping of the copper material.
Further, the treatment method of the present invention for reducing a copper oxide is also a treatment method for reducing a copper oxide formed on the surface of a copper material by oxidation to copper by dipping the copper material in the treatment solution, in which the treatment solution is prepared by adding dimethylamine borane to a base bath in such a manner that the concentration of dimethylamine borane is 0.15 to 2.0 g/L and that the relationship y≧0.215x
−0.168
holds between the concentration y (g/L) of dimethylamine borane and an area x (dm
2
/L) to be treated of the copper material per unit solution amount; the base bath contains 0.5 to 100 mL/L of 37% formalin; the pH is 12 or more; the addition of dimethylamine borane to the base bath is carried out within 10 minutes before the dipping of the copper material having the copper oxide on the surface or after the dipping of the copper material; and the relationship y≧−0.106z+1.57 holds between the concentration y (g/L) of dimethylamine borane and the value z of the pH of the treatment solution.
The treatment solution of the present invention contains expensive dimethylamine borane in a less amount than conventional treatment solutions. Particularly, since the minimum required amount of dimethylamine borane decreases along with an increase in the area to be treated, the costs required for reducing the copper oxide to copper can be decreased. Further, in the treatment method for reducing the copper oxide to copper, a decrease in the costs for the treatment by decreasing the amount of expensive dimethylamine borane to be added can be achieved, and an increase in the costs for the treatment can be prevented by preventing a reduction in the useful life of the treatment solution by decomposition of dimethylamine borane.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[First Embodiment of Treatment Solution]
The treatment solution of the present invention for reducing a copper oxide is an aqueous solution which contains dimethylamine borane in an amount of 0.3 to 2.0 g/L and for which the relationship y≧0.232x
−0.185
holds between the concentration y (g/L) of dimethylamine borane and an area x (dm
2
/L) to be treated per unit treatment solution amount. Thus, the treatment solution of the present invention is based on the special relationship that the minimum required amount of di
Fujita Yasuji
Ikeshima Kenji
Andrews Melvyn
Meltex Inc.
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