Electronic components

Details Electronic components Electronic components

1999-01-08

2001-04-17

Gellner, Michael L. (Department: 2832)

Inductor devices

Coil or coil turn supports or spacers

Printed circuit-type coil

C336S083000, C336S232000

Reexamination Certificate

active

06218925

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention elates to an electronic component comprising one or more coils buried in a chip.
2. Description of the Related Art
FIG. 2
shows a side sectional view of a laminated inductor as a conventional electronic component on this head.
In
FIG. 2
,
20
is a laminated inductor comprising a rectangular-parallelepiped-shaped chip
21
of a magnetic substance material, a spiral coil
22
buried in the chip
21
, and a pair of terminal electrodes
23
provided at the longitudinal ends of the chip
21
. The winding center line, i.e., longitudinal axis, Y of the coil
22
is orthogonal to a line joining the terminal electrodes
23
together (extending in the longitudinal direction of the chip), and the end of the coil
22
is guided out to the end surface of the chip where it is connected to the respective terminal electrode
23
.
To mount the laminated inductor
20
on a conductor pattern on a circuit board, two orientations are available in which the winding center line (Y) of the coil
22
is perpendicular to the mounting surface of the circuit board (Z) as shown in FIG.
3
and in which winding the center line (Y) of the coil
22
is parallel with the mounting surface of the circuit board (Z) as shown in FIG.
4
.
There is a difference in inductance between the mounting orientations in
FIGS. 3 and 4
due to the different locational relationship between the coil
22
and the circuit board (Z) resulting in a difference in magnetic reluctance to magnetic fluxes outside the chip. In particular, in a laminated inductor using a chip material of a lower relative magnetic permeability, the difference in mounting orientation causes a significant difference in magnetic reluctance and thus a relatively large difference in inductance.
To solve such a problem, a laminated inductor has been proposed in which the orientation of the winding center line of the coil relative to the surface of the circuit board remains unchanged regardless of the mounting orientation (Japanese Patent Application Laid-Open No. 8-55726).
This laminated inductor is generally called a vertically laminated inductor wherein a laminated structure is formed in the direction of a line joining the terminal electrodes together as shown in
FIGS. 5
to
7
.
A chip
31
in a vertically laminated inductor
30
, which is shown in
FIGS. 5
to
7
, is formed by laminating a top-layer sheet (A) of a magnetic material, coil-layer sheets (B
1
) to (B
4
) of a magnetic material, and a bottom-layer sheet (C) of a magnetic material. A leadout conductor (Pa) is formed in the top layer-sheet (A) of a magnetic material in such a way as to overlap a via hole (h). Four types of approximately-U-shaped coil conductors (Pb
1
) to (Pb
4
) are formed in the coil-layer sheets (B
1
) to (B
4
) of a magnetic material in such a way that their ends overlap the via hole (h). In addition, a rectangular leadout conductor (Pc) is formed in the bottom-layer sheet (C) of a magnetic material in such a way as to overlap the via hole (h). Furthermore, terminal electrodes
33
are formed at the respective ends of the chip
31
in the lamination direction to constitute the vertically laminated inductor
30
.
The coil conductors (Pb
1
) to (Pb
4
) are connected together via the via hole (h) to form the coil
32
, and the respective ends of the coil
32
are connected to the terminal electrodes
33
via leadout conductors
34
a
and
34
b
consisting of leadout conductors (Pa) and (Pc) formed in the top- and bottom-layer sheets (A) and (C) of a magnetic material.
In the vertically laminated inductor
30
of the configuration shown in
FIGS. 5
to
7
, when a current flows through the inductor, two fluxes are generated; one of them is parallel with the winding center line (Y) of the coil
32
, while the other rotates around the leadout conductors
34
a
and
34
b.
These magnetic fluxes form the inductance of the chip.
When, however, the laminated inductor
30
is mounted on the circuit board (Z), there is a difference in distance between the leadout conductor
34
a
or
34
b
and the circuit board (Z), between the mounting orientation shown in FIG.
8
and the mounting orientation shown in
FIG. 9
in which the inductor is vertically revered. Consequently, there is a difference in magnetic reluctance to magnetic fluxes generated around the leadout conductors
34
a
and
34
b,
resulting in a difference in inductance depending on the mounting orientation.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electronic component including a coil that avoids a difference in inductance depending on the mounting orientation.
The present invention provides an electronic component comprising a coil buried in a rectangular-parallelepiped-shaped chip and terminal electrodes located at the respective ends of the chip and connected to the respective ends of the coil, wherein the winding center line of the coil, i.e., the coil axis, is set on a straight line joining the central points of a pair of opposed end surfaces of the chip at which terminal electrodes are formed and wherein the winding locus of the coil as seen in the direction of the winding center line and leadout conductors each joining the end of the coil and the terminal electrode together are arranged at positions and/or in conditions such that when the electronic component is mounted on a circuit board, the winding locus of the coil and the distance between the leadout conductor and the circuit board remains unchanged at least despite the reversal of the electronic component.
In the electronic component of this configuration, the distances between the coil and the circuit board and between the leadout conductor and the circuit board remain unchanged whichever of the four surfaces of the chip different from its end surfaces is opposed to the circuit board, as long as, for example, a cross section of the chip perpendicular to the winding center line of the coil is square. Thus, the magnetic reluctance remains the same in each mounting orientation, thereby preventing the inductance provided by the coil and leadout conductors from being changed by the mounting orientation. Consequently, this electronic component precludes a difference in inductance depending on the mounting orientation. In addition, when the chip is shaped like a rectangular parallelepiped and the cross section of the chip perpendicular to the winding center line of the coil is not square, the distance between the leadout conductor and the circuit board remains unchanged despite the vertical reversal of the chip in mounting it on the circuit board. As a result, when the cross section of the chip perpendicular to the winding center line of the coil has a shape other than a square, the inductance remains unchanged despite the vertical reversal of the chip in mounting it on the circuit board.
Moreover, the present invention provides an electronic component wherein the inductance remains unchanged regardless of the mounting orientation even if the chip is shaped like a cylinder as described above. For example, the present invention provides an electronic component comprising a coil buried in a cylinder-shaped chip and terminal electrodes located at the respective ends of the chip and connected to the respective ends of the coil, wherein the winding center line of the coil is set on a straight line joining the central points of a pair of opposed end surfaces of the chip at which terminal electrodes are formed, wherein the distance between the winding locus of the coil as seen in the direction of the winding center line and the central point through which the winding center line of the coil passes remains constant in any cross section of the chip which the winding center line of the coil crosses perpendicularly, and wherein at either end of the chip, a leadout conductor joining the end of the coil and the terminal electrode together is located on the winding center line of the coil.


REFERENCES:
patent: 3765082 (1973-10-01), Zyetz
patent: 3812442 (1974

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