Stock material or miscellaneous articles – All metal or with adjacent metals – Foil or filament smaller than 6 mils
Reexamination Certificate
2002-07-11
2003-10-28
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Foil or filament smaller than 6 mils
C428S596000, C428S637000, C428S674000, C427S098300, C427S554000
Reexamination Certificate
active
06638642
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a copper foil excellent in laser punchability with which an copper layer connection hole (through hole and via hole) of a printed circuit board can efficiently be formed and also relates to a method for manufacturing such a copper foil.
The copper foil of the present invention includes not only a copper foil alone but also all kinds of copper-laminated boards and build-up laminated board on which copper is directly formed (including electroplated and electroless plated ones)
BACKGROUND OF THE INVENTION
A drill has been employed for forming a small diameter hole (through hole) for copper layer connection of a printed circuit board. Since burrs have easily been formed in the processing (forming holes) by a drill and opening of a hole with an ultra small diameter has been limited, however, a method for forming a hole by laser has been employed recently.
However, a copper foil has a disadvantageous point that the surface of the copper foil conventionally employed for a printed circuit board has a high reflectance to result in inferior processibility with laser beams. Therefore, a method for forming a hole by removing a prescribed copper foil part by etching and then forming a hole by radiating laser beams to the part or a method for forming a hole by thinning a copper foil by chemical polishing and then processing with laser beams have been employed.
In these cases, however, since a step of removing a copper foil by etching or of chemical processing is employed, efficiency has been deteriorated and also since strict control is required for operation of such processing procedures, productivity is lowered and the cost is heightened.
OBJECTS OF THE INVENTION
The present invention has been achieved while taking the foregoing problems into consideration. The purposes of the present invention are to provide a copper foil excellent in drilling property by laser and suitable for forming through hole and via hole with a small diameter and also to provide a method for manufacturing such a copper foil by improving the surface of a copper foil at the time of manufacturing a printed circuit board.
SUMMARY OF THE INVENTION
As described above, the present invention provides the following copper foils:
1. A copper foil excellent in drilling property by laser, having a layer containing any one or more substances selected from indium, tin, cobalt, zinc, cobalt alloys, and nickel alloys on the face to be radiated with laser beams;
2. a copper foil excellent in drilling property by laser as set forth in the above described item 1, having cobalt alloys layer containing at least one of nickel, phosphorus, zinc and copper;
3. a copper foil excellent in drilling property by laser as set forth in the above described item 1, having nickel alloys layer containing at least one of copper, zinc, and phosphorus;
4. a copper foil excellent in drilling property by laser as respectively set forth in the above described items 1 to 3, in which content of cobalt, nickel, tin, zinc, or indium is independently 0.1 to 100 mg/dm
2
(provided that, zinc content is 0.5 to 100 mg/dm
2
); and
5. a copper foil excellent in drilling property by laser as respectively set forth in the above described items 1 to 4, in which thickness of the copper foil is 18 &mgr;m or thinner.
The present invention further provides the following methods for manufacturing a copper foil excellent in drilling property by laser:
6. A method for manufacturing a copper foil excellent in drilling property by laser, in which a layer containing any one or more substances selected from indium, tin, cobalt, zinc, cobalt alloys, and nickel alloys is formed on the face to be radiated with laser beams;
7. a method for manufacturing a copper foil excellent in drilling property by laser as set forth in the above described item 6, in which cobalt alloys layer containing at least one of nickel, phosphorus, zinc and copper is formed;
8. a method for manufacturing a copper foil excellent in drilling property by laser as set forth in the above described item 6, in which nickel alloys layer containing at least one of copper, zinc, and phosphorus is formed;
9. a method for manufacturing a copper foil excellent in drilling property by laser as respectively set forth in the above described items 6 to 8, in which the layer is formed by plating;
10. a method for manufacturing a copper foil excellent in drilling property by laser as respectively set forth in the above described items 6 to 9, in which content of cobalt, nickel, tin, zinc, or indium is independently 0.1 to 100 mg/dm
2
(provided that zinc content is 0.5 to 100 mg/dm
2
);
11. a method for manufacturing a copper foil excellent in drilling property by laser as respectively set forth in the above described items 6 to 10, in which thickness of the copper foil is 18 &mgr;m or thinner;
12. a method for manufacturing a copper foil excellent in drilling property by laser as respectively set forth in the above described items 6 to 11, in which stabilizer treatment is carried out after the layer formation; and
13. a method for manufacturing a copper foil excellent in drilling property by laser as set forth in the above described item 12, in which the surface treated by the stabilizer treatment contains chromium and/or zinc.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention includes formation of a layer containing any one or more of substances selected from indium, tin, cobalt, zinc, cobalt alloys and nickel alloys in a position of a copper foil of a printed circuit board where through hole and via hole is to be formed by radiating laser beams thereto, and thereby drilling property by laser is significantly improved as compared with that of a conventional copper foil.
A copper foil used in the present invention may be an electrodeposited copper foil and a rolled copper foil. Further, the thickness of the copper foil is desirably 18 &mgr;m or thinner for the use in high density wiring.
Nevertheless, the thickness of a copper foil of the present invention with improved laser drilling property is not necessarily restricted within the defined thickness and may, of course, be thicker than the defined thickness.
A layer containing any one or more of substances selected from indium, tin, cobalt, zinc, cobalt alloys and nickel alloys is formed on the face of a copper foil to which laser beams is radiated.
Such a layer can be produced by plating treatment. However, the method is not limited to plating, but vapor deposition, sputtering, or other coating methods may be employed for the layer formation.
Further, even in the case plating treatment is employed, the plating treatment method is not at all restricted to a specified plating method. The layer formation by such a plating method can be carried out either partly on the face of a copper foil to be radiated with laser beams thereto or fully on the copper foil. Such a plating treatment is naturally required to be carried out without deteriorating the characteristic properties of a copper foil usable for a circuit board and any treatment of the present invention sufficiently satisfies such conditions.
In the foregoing alloy layers to be formed on a copper foil, cobalt alloys layer containing at least one of nickel, phosphorus, zinc, and copper is superior in drilling property by laser.
In the case of a nickel layer alone, the laser drilling rate is low as compared with that by the present invention, and even if the amount of nickel is increased, the drilling rate cannot be improved. The layer is thus unsuitable as a layer (coating layer) for improving the laser drilling property.
Incidentally, the drilling rates were 0%, 2%, 67%, 73%, 68%, and 71% in the case where the nickel deposition amount at 32 mJ/pulse was 3,400 &mgr;g/dm
2
, 6,100 &mgr;g/dm
2
, 13,400 &mgr;g/dm
2
, 20,333 &mgr;g/dm
2
, 53,600 &mgr;g/dm
2
, and 81, 333 &mgr;g/dm
2
, respectively, and even when the nickel deposition amount was increased further, the drilling rate was hardly increased.
However, in the case where a nickel layer cont
Hanafusa Mikio
Kitano Kouji
Howson and Howson
Nikko Materials Company Limited
Savage Jason
Zimmerman John J.
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