Copper foil having glossy surface with excellent oxidation...

Details Copper foil having glossy surface with excellent oxidation... Copper foil having glossy surface with excellent oxidation...

1999-11-30

2001-11-20

Koehler, Robert R. (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

C205S152000, C205S154000, C205S155000, C205S156000, C205S243000, C205S244000, C205S246000, C205S255000, C205S258000, C428S607000, C428S647000, C428S648000, C428S656000, C428S666000, C428S667000, C428S674000, C428S675000, C428S680000, C428S687000

Reexamination Certificate

active

06319621

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a copper foil having a glossy surface with excellent oxidation resistance and also to a method of manufacturing the same and, more particularly, relates to a copper foil for printed wiring having excellent oxidation resistance characterized by a composite layer containing chromium, zinc, phosphorus, and nickel formed on the glossy copper foil surface and also to a method of manufacturing the same.
2. Prior Art
Copper foils that have hitherto been used for printed wiring purposes are those whose glossy surfaces are chromated or otherwise treated, as by chelation with copper using an organic agent such as benzotriazole, for enhanced corrosion resistance.
Those treated copper foils are improved in corrosion resistance as well as oxidation-tarnishing resistance during the course of lamination to insulation substrates. Nevertheless, they are unsatisfactory in other properties such as solder wettability and oxidation resistance at the time of heating.
Under the circumstances Japanese Patent Application Kokai No. 5-299834 discloses an electrolytic copper foil characterized by a composite layer containing chromium, zinc, and phosphorus formed on the glossy surface of the foil. Advantages claimed of the foil are good resistance to heating and oxidation tarnishing during and after lamination to insulation substrates, corrosion resistance, solder wettability, and ease of black oxidation treatment.
However, the copper foil provided with a composite layer containing chromium, zinc, and phosphorus as taught in the Patent Application Kokai No. 5-299834 has an oxidation resistance problem. It has been observed to undergo serious oxidation tarnishing of the entire surface under certain heating conditions (e.g., at 180° C. for 30 minutes).
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to establish a technique of further improving the oxidation resistance of the glossy surface of a copper foil that has a composite layer containing chromium, zinc, and phosphorus on its glossy surface.
It has now been found that the addition of nickel to the composite layer that contains chromium, zinc, and phosphorus further enhances the oxidation resistance of the glossy surface of the copper foil.
Thus the invention provides a copper foil having a glossy surface with excellent oxidation resistance characterized by a composite layer containing chromium, zinc, phosphorus, and nickel formed on the glossy surface.
The copper foil may have the composite layer formed with an intermediate layer of a material selected from the group consisting of zinc, nickel, chromium, tin, and their alloys on the glossy surface.
It is desirable that the amounts of the components deposited in the composite layer be:
deposited amount of Cr: 10-50 &mgr;g/dm
2
deposited amount of Zn: 30-300 &mgr;g/dm
2
deposited amount of Ni: 5-50 &mgr;g/dm
2
deposited amount of P: 1-50 &mgr;g/dm
2
.
The invention further provides a method of manufacturing a copper foil having a glossy surface with excellent oxidation resistance characterized by an anti-corrosive treatment of the glossy copper foil surface with a bath of a composition comprising
Cr: 0.1-2.0 g/L
Zn: 0.1-3.0 g/L
P: 0.01-1.0 g/L
Nit: 0.1-0.5 g/L,
whereby a composite layer containing chromium, zinc, phosphorus, and nickel is formed on the glossy copper foil surface.
Oxidation resistance increases as the Ni concentration in copper foil rises. In an ordinary composite layer containing chromium, zinc, and phosphorus, zinc is present in the form of metallic zinc that readily diffuses with heat. The addition of Ni in accordance with the present invention forms a Zn—Ni alloy that is less diffusible on heating. This presumably combines with an increase in the amount of Zn deposition with a change in deposition potential to achieve a favorable effect upon the oxidation resistance.


REFERENCES:
patent: 4935310 (1990-06-01), Nakatsugawa
patent: 5389446 (1995-02-01), Yamanishi et al.
patent: 5-299834 (1993-11-01), None

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