Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2000-11-09
2003-02-25
Talbott, David L. (Department: 2841)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C174S264000, C361S313000, C361S328000, C361S301400
Reexamination Certificate
active
06525921
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a capacitor-mounted metal foil and a circuit board using the same, and a method for producing them.
2. Description of the Related Art
In recent years, with the demand for high performance and miniaturization of electronic equipment, there is an increasing demand for high density and high function of a semiconductor device. This results in a demand for a miniaturized high-density circuit board for mounting a semiconductor device.
Furthermore, when semiconductor devices are mounted at high density, heat and noise are generated by components. Thus, in order to mount semiconductor devices at high density, a circuit board is required that allows high-density mounting and is excellent in a thermal dissipation property and noise resistance.
As a technique of improving the thermal dissipation property of a circuit board, a heat-conductive substrate using a thermosetting resin and an inorganic filler has been proposed (see JP 10-173097 A). Furthermore, JP 11-168112 A has proposed a method for heating and pressurizing a sheet-shaped material containing a mixture of an inorganic filler and a thermosetting resin, thereby performing mounting and sealing of semiconductor devices simultaneously.
As a general method for enhancing the noise resistance of a circuit board, capacitors for removing noise are mounted on a circuit board so as to absorb high-frequency noise and ripple. However, in the case where capacitors are mounted on a circuit board, the size of the circuit board is enlarged so as to ensure a mounting area for the capacitors. Therefore, there has been an attempt in which capacitors are embedded in a circuit board.
For example, methods for forming a capacitor in a ceramic substrate have been proposed (JP 62-131411 A, JP 1-152688 A, and JP 2-305490 A). According to these methods, a ceramic substrate material and a ceramic dielectric material capable of being sintered under the same conditions as those of the substrate material are layered on one another, and both the materials are sintered simultaneously, whereby capacitors are formed in a ceramic substrate.
However, a conventional ceramic substrate with capacitors embedded therein entails a high cost. Furthermore, it takes a long period of time to produce a prototype of and to change the design of such a substrate. On the other hand, according to the method for embedding ceramic capacitors made of a sintered body in an inexpensive resin substrate, the sintered body may be broken when the substrate is layered to form a multi-layer structure.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is an object of the present invention to provide a capacitor-mounted metal foil, which allows high-density mounting and allows an inexpensive circuit board excellent in noise resistance and a thermal dissipation property to be formed, and a method for producing the same. It is another object of the present invention to provide an inexpensive circuit board, which allows high-density mounting and is excellent in noise resistance and a thermal dissipation property, and a method for producing the same.
In order to achieve the above-mentioned object, the capacitor-mounted metal foil of the present invention is provided with a metal foil and a plurality of capacitors formed on the metal foil, and each of the capacitors includes: a conductive layer disposed above the metal foil; and a dielectric layer disposed between the metal foil and the conductive layer. Since the above-mentioned capacitor-mounted metal foil includes capacitors, a circuit board excellent in noise resistance can be produced. Furthermore, the capacitor-mounted metal foil is flexible, so that a circuit board can be produced using a resin. Also, an inexpensive circuit board can be produced, which allows high-density mounting and is excellent in a thermal dissipation property.
In the present specification, the term “metal foil” refers to a film, a layer, a sheet, and the like. Furthermore, in the present specification, for easy understanding, the terms “metal foil” and “metal film” are used for another member; however, there is no difference in meaning therebetween.
In the above-mentioned capacitor-mounted metal foil, the capacitor further may include a metal layer disposed between the metal foil and the dielectric layer, and a surface of the metal layer that is in contact with the dielectric layer may be roughened. According to this structure, a capacitor with a large capacitance can be formed. Furthermore, by controlling the degree of roughness, the capacitance of a capacitor can be regulated.
In the above-mentioned capacitor-mounted metal foil, the dielectric layer may be made of an oxide of the metal forming the metal layer. According to this structure, production becomes easy.
In the above-mentioned capacitor-mounted metal foil, the metal layer may be made of a material selected from the group consisting of aluminum, tantalum, and niobium. According to this structure, an aluminum electrolytic capacitor and a tantalum electrolytic capacitor can be formed.
In the above-mentioned capacitor-mounted metal foil, the metal foil and the metal layer may be bonded to each other via a metallic bond. According to this structure, a capacitor-mounted metal foil can be produced, which enables a highly reliable circuit board to be produced.
In the above-mentioned capacitor-mounted metal foil, a thickness of the metal layer may be in a range of 10 &mgr;m to 100 &mgr;m. By prescribing the thickness of the metal layer to be 10 &mgr;m or more, the surface of the metal layer can be roughened easily.
In the above-mentioned capacitor-mounted metal foil, the metal foil may be made of a material selected from the group consisting of copper and nickel. According to this structure, a wiring pattern that is soldered easily at a low resistance can be formed.
In the above-mentioned capacitor-mounted metal foil, a thickness of the metal foil may be in a range of 3 &mgr;m to 70 &mgr;m. It is preferable that the thickness of the metal foil is in a range of about 3 &mgr;m to about 18 &mgr;m for forming a fine wiring pattern. It is preferable that the thickness of the metal foil is 18 &mgr;m or more for mounting a component by soldering. Furthermore, it is preferable that the thickness of the metal foil is in a range of about 35 &mgr;m to about 70 &mgr;m for forming a wiring pattern through which a large current flows. Furthermore, it is preferable that the thickness of the metal foil is in a range of about 18 &mgr;m to about 70 &mgr;m for facilitating handling. Furthermore, it is preferable that the metal foil is thinner for producing a thin circuit board.
In the above-mentioned capacitor-mounted metal foil, the conductive layer may include a conductive polymer layer and an electrode made of metal that are layered successively from the metal foil side. According to this structure, a capacitor having a small equivalent series resistance (hereinafter, it may be referred to as an “ESR”) can be produced.
In the above-mentioned capacitor-mounted metal foil, the electrode may be made of at least one metal selected from the group consisting of silver, copper, nickel, and aluminum. According to this structure, since an Ohmic contact can be formed, a capacitor having a small ESR can be produced.
In the above-mentioned capacitor-mounted metal foil, the conductive layer may include a conductive polymer layer and a carbon layer that are layered successively from the metal foil side. According to this structure, since an Ohmic contact can be formed, a capacitor having a particularly small ESR can be produced.
In the above-mentioned capacitor-mounted metal foil, the dielectric layer may be made of a nonconductive polymer. The nonconductive polymer has a low dielectric constant; however, it is easily handled due to its high mechanical strength and is unlikely to be damaged during layering on a substrate.
The above-mentioned capacitor-mounted metal foil further may include a resistor formed on the metal foil. According to this
Hirano Koichi
Nakatani Seiichi
Shimada Mikinari
Sugaya Yasuhiro
Alcala José H.
Matsushita Electric Industrial Co. LTD
Merchant & Gould P.C.
Talbott David L.
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