Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
2000-07-28
2002-12-24
Donovan, Lincoln (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C336S083000
Reexamination Certificate
active
06498555
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monolithic inductor used as, for example, an inductor or coil and, more specifically, the present invention relates to a monolithic inductor having a greatly improved connecting structure between coil conductors in a sintered ceramic body.
2. Description of the Related Art
Various monolithic inductors having a coil conductor embedded in magnetic ceramics are known (See for example, Japanese Patent No. 2655657, Japanese Unexamined Patent Application Publication No. 62-189707, Japanese Unexamined Patent Application Publication No. 59-152605).
Such a conventional monolithic inductor is manufactured by printing a conductor pattern on a ceramic green sheet which is composed almost exclusively of magnetic ceramics, laminating a plurality of such ceramic green sheets, and sintering the ceramic green sheets as a unit to obtain a sintered ceramic body, whereby a plurality of conductor patterns printed on a plurality of ceramic green sheets are connected through via-hole electrodes so that a coil is constructed in a sintered ceramic body.
FIGS. 6
to
9
are explanatory schematic plan views of the above described conductor pattern in a conventional monolithic inductor. While there are shown only the coil conductor sections in
FIGS. 6
to
9
, a coil conductor section is printed on each ceramic green sheet by screen printing or other suitable process.
In a structure shown in
FIG. 6
, several ¾-turn coil conductor sections
51
-
53
are electrically connected via electrodes
54
and
55
. Each coil conductor section
51
to
53
is printed on the respective ceramic green sheet and has a ¾-turn. In other words, when viewed from the top, it appears to be a coil having a rectangular shape, however the coil conductor sections
51
-
53
each constituting a ¾-turn of a rectangular coil are printed on the respective ceramic green sheets.
In a structure shown in
FIG. 7
, the coil conductor sections
56
-
58
are connected through via-hole electrodes
59
and
60
. Each of the coil conductor sections
56
-
58
constitutes a turn of a rectangular coil.
In a structure shown in
FIG. 8
, the coil conductor sections
61
and
62
are electrically connected through a via-hole electrode
63
. Each of the coil conductor sections
61
and
62
constitutes 2.25 turns of a coil composed of coil conductors.
In a structure shown in
FIG. 9
, the coil conductor sections
64
,
65
are connected through a via-hole electrode
66
. Each of the coil conductor sections
64
and
65
constitutes 2.25 turns of a coil composed of coil conductors.
In the coil conductor sections
64
and
65
shown in
FIG. 9
, by increasing the number of turns of a coil conductor section printed on a green sheet, miniaturization of a monolithic inductor may be realized.
As described above, by increasing the number of turns of each coil conductor section to be printed on each ceramic green sheet, miniaturization of a monolithic inductor may be achieved. However, there is a recognized disadvantage that if a coil conductor section of more than one turn is formed on a ceramic green sheet as in the structures shown in
FIGS. 7
to
9
, even if the number of turns is increased, a large inductance corresponding to the increased turns cannot be obtained. This will be explained referring to FIG.
10
and FIG.
11
.
FIG. 10A
is a cross-sectional view illustrating a portion of a monolithic inductor having coil conductor sections
56
-
58
of
FIG. 7
taken along the line A—A in FIG.
7
. In the monolithic inductor
71
, upper and lower coil conductor sections, that is, the coil conductor section
56
and the coil inductor section
57
, for example, are arranged in such a manner that the upper and lower coil conductor sections
56
and
57
overlap one on another in the direction of thickness via a ceramic layer on the side opposed to the side where the via-hole electrodes are provided. However, in the vicinity of the portion where the via-hole
59
is provided, in other words, in the vicinity of the extremity
56
a
of the coil conductor section
56
and the extremity
57
a
of the coil conductor section
57
, as will be apparent from FIG.
10
A and
FIG. 7
, the upper and lower coil conductor sections
56
and
57
do not overlap one another in the direction of thickness.
Likewise,
FIG. 10B
is a cross-sectional view illustrating a monolithic inductor having coil conductor sections
61
and
62
of
FIG. 8
taken along the line B—B of FIG.
8
. In this case as well, in the vicinity of the extremity
61
a
of the coil conductor section
61
and in the vicinity of the extremity
62
a
of the coil conductor section
62
, the upper and lower coil conductor sections
61
and
62
do not overlap one another in the direction of thickness and are not aligned.
FIGS. 11A and 11B
are cross-sectional views illustrating the monolithic inductor using the coil conductor sections
64
and
65
of
FIG. 9
taken along the lines C—C and D—D of
FIG. 9
respectively. When the coil conductor sections
64
and
65
of 2.25 turns are laminated alternately, non-alignment portions between the upper and lower coil conductor sections
64
and
65
are present in the vicinity of the extremity
64
a
of the coil conductor section
64
and in the vicinity of the beginning end
65
a
of the coil conductor section
65
.
In other words, while the upper and lower coil conductor sections
51
-
53
can be overlapped precisely on one another in the case of coil conductor sections
51
to
53
of ¾-turn shown in
FIG. 6
, there is a portion where the upper and lower coil conductor do not align in the direction of thickness when the number of turns is increased. When the portion where the upper and lower coil conductor sections are not aligned via the ceramic layer in the direction of thickness is formed, the magnetic path in that portion is hindered, thus lowering the efficiency of inductance which is obtained by the inductor component. Since the coil conductor sections shown in
FIG. 6
are ¾-turn sections, when these coil conductor sections are laminated, the distances between the coil conductor sections in the direction of lamination becomes wider in some portions. As a result, deterioration of the characteristics associated with the leakage of magnetic flux occurs.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a monolithic inductor wherein the formation of portions where the upper and lower coil conductor sections do not overlap on one another is reduced even when the number of turns of a coil conductor section provided on a ceramic green sheet is selected to be 1 or more to achieve miniaturization, and thereby a large inductance is obtained.
According to one preferred embodiment of the present invention, a monolithic inductor includes a sintered ceramic body, and a plurality of coil conductor sections in which each coil conductor is wound by at least one turn, wherein the plurality of the coil conductor sections are located at vertical positions in the sintered ceramic body, and the upper and lower conductor sections are electrically connected through via-hole electrodes to define a coil, a terminal end of the upper coil conductor section and a beginning end of the lower coil conductor section are bent inwardly from the innermost portion of the coil such that a connecting portion of the coil where the upper and lower coil conductor sections are electrically connected through a via-hole electrode is located within the innermost portion of the coil defined by the upper and lower coil conductor sections.
According to at least one preferred embodiment of the present invention, a coil is preferably a substantially rectangular coil in a plan view, and the terminal end of the upper coil conductor section and the beginning end of the lower coil conductor sections are respectively bent in a direction that is substantially perpendicular to the innermost substantially rectang
Donovan Lincoln
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Nguyen Tuyen T.
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