Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-09-17
2001-02-20
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S831000, C156S089120, C336S200000, C336S232000
Reexamination Certificate
active
06189200
ABSTRACT:
This application is based on Japanese Patent Application No. 8-245008, filed on Sep. 17, 1996, which is incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing multi-layered chip inductors, in which a large number of external electrodes can be readily formed.
2. Description of the Related Art
A conventional method for producing chip inductors will be explained with reference to
FIGS. 10
to
12
.
First, a slurry of a magnetic ceramic material is applied to the surface of a base film, dried, and then stripped from the base film to obtain a magnetic green sheet (not shown in the figures). In the ceramic arts, the term “green” generally refers to a ceramic part in its unsintered state, as explained on pages 181-185 of Engineering Materials Handbook: Ceramics and Glasses, Vol. 4, 1991, ASM International. Green sheet pieces
1
b
having a predetermined size are then prepared by cutting the magnetic green sheet. A via hole
2
is made at a predetermined position on each of the green sheet pieces
1
b
. A coil-shaped internal conductor pattern
3
is printed, for example, using a paste essentially consisting of Ag, at a predetermined position on each of the green sheet pieces
1
b
. A predetermined number of the green sheet pieces
1
b
are laminated to form a coil spiralled in the laminating direction, as is shown in FIG.
10
. Electrical continuity between the printed coil-shaped internal conductor patterns
3
of the green sheet pieces
1
b
is achieved through the via holes
2
, as is shown by the dotted lines in
FIG. 10. A
predetermined number of green sheet pieces
1
a
on which no conductor pattern is printed are provided above and below the laminated green sheet pieces
1
b
and are pressed to adhere to one another and to adhere to the green sheet pieces
1
b.
In a practical manufacturing process, large-area green sheet pieces having a plurality of coil-shaped internal conductors are used for preparing a green ceramic laminate
4
comprising a group of chip-shaped laminates, shown in FIG.
11
. The green ceramic laminate
4
is cut along the dotted lines
5
and
6
to obtain chip-shaped green ceramic laminates
7
having a structure shown in FIG.
12
. Each end
3
a
of the coil-shaped internal conductors
103
formed inside the chip-shaped green ceramic laminates
7
is exposed on the corresponding cut face.
Each of the chip-shaped green ceramic laminates
7
is then fired. To obtain a multi-layered chip inductor, external-electrode-paste layers
8
are formed on the cut faces, which are parallel to the lamination direction of the fired chip-shaped ceramic laminate
7
so that the external-electrode-paste layers
8
electrically connect to the corresponding ends
3
a
of the coil-shaped internal conductor
103
, as is shown in FIG.
12
.
However, according to the above structure, the ends
3
a
of the coil-shaped internal conductor
103
are located inside the green ceramic laminate
4
, i.e., exposed on the cut faces of each chip-shaped laminate
7
. Therefore, for producing a multi-layered chip inductor having the above structure, the following procedure is required: the green ceramic laminate
4
is cut into chip-shaped laminates
7
so that each end
3
a
of coil-shaped internal conductors
103
is exposed on a cut face; and the external-electrode-paste layers
8
are formed on the cut faces having the exposed ends
3
a
at chip-shaped laminates
7
. Thus, disadvantageously, a jig, an extra manufacturing step, and longer processing time are required for forming the external-electrode-paste layers
8
on the corresponding cut faces of each chip-shaped laminate
7
.
SUMMARY OF THE INVENTION
To solve the above problems, the present invention is aimed at providing a method for producing a multi-layered chip inductor, in which a large number of external electrodes can be readily formed by applying an external electrode paste to the laminating-direction surfaces of a ceramic laminate that has not yet been cut into chip-shaped laminates. In the following discussion, the term “laminating-direction surface” pertains to a direction parallel to the surfaces of the laminated sheets. The term “laminating direction” pertains to a direction generally perpendicular to the surface of the laminated sheets, which also generally corresponds to the longitudinal axis of an inductor coil within the multi-layered chip inductor.
According to the present invention, a method for producing a multi-layered chip inductor comprises: a step for forming coil-shaped internal conductors inside a green ceramic laminate, each of which coil-shaped internal conductors is spiralled around an axial line in the laminating direction of the green ceramic laminate; a step for applying an external electrode paste onto at least one laminating-direction surface of the green ceramic laminate, which external electrode paste electrically connects to an end of the coil-shaped internal conductors; a step for cutting the green ceramic laminate along the laminating direction into chip-shaped green ceramic laminates each having a coil-shaped internal conductor inside; and a step for firing each of the chip-shaped green ceramic laminates and baking the external electrode paste to form an external electrode.
In addition, another method for producing a multi-layered chip inductor comprises: a step for forming coil-shaped internal conductors inside a green ceramic laminate, each of which coil-shaped internal conductors is spiralled around an axial line in the laminating direction of the green ceramic laminate; a step for applying an external electrode paste onto at least one laminating-direction surface of the green ceramic laminate, which external electrode paste electrically connects to an end of the coil-shaped internal conductors; a step for firing the green ceramic laminate and baking the external electrode paste to form an external electrode; and a step for cutting the fired ceramic laminate along the laminating direction into chip-shaped ceramic laminates each having a coil-shaped internal conductor inside.
Still another method for producing a multi-layered chip inductor comprises: a step for forming coil-shaped internal conductors inside a green ceramic laminate, each of which coil-shaped internal conductors is spiralled around an axial line in the laminating direction of the green ceramic laminate; a step for firing the green ceramic laminate; a step for applying and baking an external electrode paste electrically connected to an end of the coil-shaped internal conductors onto at least one laminating-direction surface of the fired ceramic laminate so as to form an external electrode; and a step for cutting the fired ceramic laminate, on which the external electrode paste has been baked to form an external electrode, along the laminating direction into chip-shaped ceramic laminates each having a coil-shaped internal conductor inside.
Furthermore, for each chip inductor, both ends of the coil-shaped internal conductor are led to one laminating-direction surface of the multi-layered chip inductor and two baked external electrodes are formed on this laminating-direction surface so that the electrodes are electrically connected to the corresponding ends. Preferably, a plating layer is formed on the surface of the baked external electrode.
Another method for producing a multi-layered chip inductor comprises: a step for forming coil-shaped internal conductors inside a green ceramic laminate, each of which coil-shaped internal conductors is spiralled around an axial line in the laminating direction of the green ceramic laminate; a step for firing the green ceramic laminate and forming an external thin-film electrode on at least one laminating-direction surface of the fired ceramic laminate, which external thin-film electrode electrically connects to an end of the coil-shaped internal conductors; and a step for cutting the fired ceramic laminate along the laminating direction into chip-shaped ceramic laminates each having
Hatsuda Yoshiyuki
Nishii Motoi
Nishinaga Yoshihiro
Takeuchi Hiroyuki
Burns Doane , Swecker, Mathis LLP
Murata Manufacturing Co. Ltd.
Tugbung A. Dexter
Young Lee
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