Inductor devices – Core forms casing
Reexamination Certificate
2001-11-01
2003-06-10
Mai, Anh (Department: 2832)
Inductor devices
Core forms casing
C336S083000
Reexamination Certificate
active
06577218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic component and a manufacturing method for the electronic component, and more particularly to an electronic component having including external electrodes connected to an internal conductor and provided on the surface of a molded body having the internal conductor embedded therein and a manufacturing method for the electronic component.
2. Description of the Related Art
One electronic component, as shown in
FIG. 10
, is a surface mounting type inductor in which a pair of external electrodes
54
a
and
54
b
are electrically connected to end portions
52
a
and
52
b
of a conductor coil
52
, on the surface of a molded body
53
arranged such that the coil conductor (internal conductor)
52
is embedded in a magnetic material
51
having a resin or rubber mixed with a magnetic powder and kneaded such that they are configured in a fixed shape. Conventionally, such an inductor is manufactured by a method described below.
Step 1
First, a molded body is formed, in which an air-core coil (internal conductor) defined by a wound copper wire is embedded in a resin or rubber mixed with a magnetic powder and kneaded such that both end portions of the air-core coil are exposed.
Step 2
Next, the surface of the molded body including the exposed portions of the air-core coil (internal conductor) is cleaned with alcohol or a neutral degreasing agent, and then etched to roughen the surface using an acidic or alkaline solution.
Step 3
Then, after the molded body has been immersed in a solution containing palladium ions, the palladium ions are reduced with a reducing agent to cause the metal palladium nuclei to precipitate onto the surface of the molded body.
Step 4
Next, electroless nickel plating is performed to form a metal film on the entire surface of the molded body.
Step 5
Then, after a necessary portion of the metal film has been coated with a resist, etching is performed to remove unnecessary portions of the metal film.
Step 6
Next, the resist is removed and various electroplating processes are performed on the metal film to form the external electrodes.
In this way, a surface mounting type inductor as shown in
FIG. 10
is obtained.
However, when a metal film is formed by electroless plating, after the molded body is immersed in a solution containing palladium ions, the palladium ions on the molded body are reduced with a reducing agent, and then a palladium catalyst is provided on the surface of the molded body by precipitating the metal palladium nuclei, the adherence of a metal film provided on the surface of the molded body is affected by the adhesion of palladium nuclei, and thus, it is difficult to form a metal film having good adherence to both the surface of the molded body, which is made of a magnetic material having a resin or rubber as the main component, and is hereinafter, simply referred to as the molded body's surface and the exposed surface of the internal conductor, which is hereinafter, simply referred to as the internal conductor's exposed surface. Accordingly, to improve the adherence to both the molded body's surface and the internal conductor's exposed surface, strict control of the concentration and viscosity of a solution containing palladium ions and the conditions for electroless plating is required, which greatly increases to cost of producing the surface mounting type inductor.
SUMMARY OF THE INVENTION
To overcome the above-described problems, preferred embodiments of the present invention provide an electronic component including external electrodes having excellent adherence to both the molded body's surface and the internal conductor's exposed surface and having a greatly improved reliability and a manufacturing method for the electronic component.
The inventors have researched and investigated the relationship between the density of palladium deposited on the surface of the molded body and the adhesion of the electroless plating films. It was discovered that, in the method of electroless plating using palladium as a catalyst, 1) when palladium is densely deposited, the adhesion between a metal film formed by electroless plating and a molded body, preferably made of magnetic material including a resin or rubber as the main component, is good, but the adhesion between a metal film and the exposed portion of an internal conductor, preferably made of metal, is insufficient, and 2) on the contrary, when palladium is thinly deposited, the adhesion between a metal film formed by electroless plating and the exposed portion of an internal conductor, preferably made of metal, is good, but the adhesion between a metal film and a molded body, preferably made of magnetic material containing a resin or rubber as the main component, is insufficient. Furthermore, the inventors have conducted experiments on and investigated the relationship between the density of palladium deposited on the surface of a molded body preferably made of a magnetic material containing a resin or rubber as the main component, referred to as the molded body's surface, and on the surface of the internal conductor exposed at the molded body, referred to as the internal conductor's exposed surface, and the adhesion of an electroless plating film, which led the inventors to the present invention.
An electronic component according to preferred embodiments of the present invention includes an internal conductor made of a metal embedded in a molded body formed by molding an insulative material including a resin or rubber as the main component into a desired shape such that at least a portion of the internal conductor is exposed on the surface of the molded body, and external electrodes are connected to the internal conductor and are provided in a desired area, including the area where the internal conductor is exposed, on the surface of the molded body, and palladium is deposited at a deposition density of about 0.5 &mgr;g/cm
2
to about 1.5 &mgr;g/cm
2
on the surface of the molded body where the external electrodes are provided except at the area the internal conductor is exposed, palladium is deposited at a deposition density of about 0.05 &mgr;g/cm
2
to about 0.3 &mgr;g/cm
2
on the internal conductor exposed at the surface of the molded body, and a metal film, that defines at least a portion of the external electrode, is formed by electroless plating in the area where the palladium is deposited.
In the electronic component according to preferred embodiments of the present invention, palladium is deposited at a deposition density of about 0.5 &mgr;g/cm
2
to about 1.5 &mgr;g/cm
2
in the area where the internal conductor is not exposed within the area where the external electrodes are provided on the surface of the molded body, palladium is deposited at a density of about 0.05 &mgr;g/cm
2
to about 0.3 &mgr;g/cm
2
on the internal conductor exposed at the surface of the molded body, and a metal film, defining at least a portion of the external electrodes, is provided in the area where the palladium is deposited at a fixed density, which includes the molded body's surface and internal conductor's exposed surface. Accordingly, an electronic component having excellent adhesion between the metal film and both the molded body's surface and the internal conductor's exposed surface is provided, and a greatly improved external connection via the external electrodes is obtained.
That is, although the adhesion of a metal film to the molded body's surface and the internal conductor's exposed surface is affected by the density of deposited palladium (deposition per unit area), when the density of deposited palladium is within the above-described range, that is, a density of about 0.5 &mgr;g/cm
2
to about 1.5 &mgr;g/cm
2
on the molded body's surface, and a density of about 0.05 &mgr;g/cm
2
to about 0.3 &mgr;g/cm
2
on the internal conductor's exposed surface, it is possible to form a metal film which has excellent adhesion to
Hamatani Junichi
Oshima Hisato
Keating & Bennett LLP
Mai Anh
Murata Manufacturing Co. Ltd.
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