Chip-type resistor element

Details Chip-type resistor element Chip-type resistor element

2001-10-31

2004-04-06

Easthom, Karl D. (Department: 2832)

Electrical resistors

Resistance value responsive to a condition

Current and/or voltage

C338S328000, C338S332000, C338S0220SD

Reexamination Certificate

active

06717506

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chip-type resistor element such as a thermistor, and more particularly, to a laminated chip-type resistor element having a plurality of pairs of first and second inner electrodes, the tips of each of the pairs being mutually opposed with a gap interposed therebetween.
2. Description of the Related Art
Conventional chip-type thermistors have been used for temperature compensation or temperature detection. In conventional chip-type thermistor elements, various laminated chip-type thermistor elements have been proposed in order to prevent the fluctuation of electrical characteristics caused by changes in external environment (for example, see Japanese Unexamined Patent Application Publication No. 8-250307).
Also, in Japanese Patent Application No. 9-49256 (i.e., Japanese Unexamined Patent Application Publication No. 10-247601), a chip-type thermistor element shown in
FIGS. 6A
and
6
B is disclosed.
This chip-type thermistor element
51
has a thermistor body
52
having a rectangular shape. In the thermistor body
52
, a plurality of first inner electrodes
53
a
to
53
g
, and a plurality of second inner electrodes
54
a
to
54
g
are provided. The first inner electrodes
53
a
to
53
g
extend out to a first end surface
52
a
, while the second inner electrodes
54
a
to
54
g
extend out to a second end surface
52
b
. First and second outer electrodes
55
and
56
are disposed on the first and second end surfaces, respectively.
In this chip-type thermistor element
51
, as shown by the inner electrodes
53
a
and
54
a
as an example, the tip of one first inner electrode and that of one second inner electrode are arranged with a gap “a” interposed therebetween. In the case of the chip-type thermistor element
51
, the gaps “a” are formed at positions that are alternately different in the lamination direction. For example, the gap “a” between the first inner electrode
53
a
and the second inner electrode
54
a
defining the uppermost layer is located near the end surface
52
a
, while the gap formed at the next vertical level in the lamination direction, i.e., the gap between the inner electrode
53
b
and the inner electrode
54
b
, is formed near the end surface
52
b.
In this manner, an attempt at reducing the resistance is made by arranging a plurality of gap positions at different locations along the lamination direction.
In addition, as shown in
FIG. 6B
, as compared with the inner electrodes
53
a
and
54
a
located at the uppermost portion, the inner electrodes
53
b
and
54
b
located at the next vertical position have a small dimension in the widthwise direction, thereby reducing the variations in the resistance value caused by a laminate shear that occurs between inner electrodes.
Thus, in the chip-type thermistor element
51
, the positions of gaps between the first and second inner electrodes are mutually different in the longitudinal direction. More specifically, the gap “a” is located near one outer electrode
55
, or near the other outer electrode
56
.
As a result, the distance Z between the inner electrode
54
a
situated in the uppermost layer and the outer electrode
55
having the potential opposite to the potential of the outer electrode
56
, to which the inner electrode
54
a
is connected, becomes small.
Typically, the above-described inner electrodes
53
a
to
54
g
are formed by screen-printing a conductive paste on a ceramic green sheet. The outer electrodes
55
and
56
are formed by applying a conductive paste via a dipping method, and by printing the paste. Therefore, variations of the electrode covering portions of the outer electrodes
55
and
56
in the length E are usually larger than those of the gap “a” in the longitudinal dimension.
Hence, if the distance Z in
FIG. 6
approaches the longitudinal dimension of the gap “a”, or becomes smaller than the longitudinal dimension of the gap “a”, the contribution to the total resistance value from between the outer electrode
55
and the inner electrode
54
a
will become larger than that between the inner electrodes
53
a
and
54
a
. This raises a problem in that, as the distance Z decreases, variations of the chip-type thermistor element
51
in the resistance value increases because of variations of the covering portion of the outer electrode
55
in the longitudinal dimension E.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a chip-type resistor element which minimizes and eliminates variations in the resistance value caused by forming accuracy of the outer electrodes, and which has thereby very low variations in the resistance value, by improving the chip-type resistor element which is, as described above, capable of reducing the resistance value, and minimizing the variations in the resistance value caused by inter-laminate shear.
In accordance with a first preferred embodiment of the present invention, a chip-type resistor element includes a resistor body having first and second end surfaces which are opposite to each other, a plurality of first inner electrodes disposed in the resistor and extending out to the first end surface, a plurality of second inner electrodes disposed in the resistor and extending out to the second end surface, and the tip of each of which is opposed to the tip of a corresponding first inner electrode with a gap interposed therebetween, and first and second outer electrodes which cover the first and second end surfaces, respectively, and each of which has an electrode covering portion reaching the top surface, bottom surface, and a pair of side surfaces of the resistor body. In this chip-type resistor element, the positions of the gaps between the first inner electrodes and the corresponding second inner electrodes are different in the longitudinal direction, where the longitudinal direction is the direction connecting the first and second end surfaces. This chip-type resistor element also includes third inner electrodes which are disposed closer to the outside of the resistor body in the lamination direction than the first and second inner electrodes on the outermost sides in the lamination direction, which are connected to the outer electrode near the gaps between the first and second inner electrodes on the outermost sides, and which are arranged to extend to closer to the inside in the longitudinal direction than the gaps between the first and second inner electrodes on the outermost sides.
In the first preferred embodiment of the present invention, it is preferable that the chip-type resistor element in accordance with the present invention also include fourth inner electrodes, the tip of each of which is opposed to a corresponding third electrode with a gap interposed therebetween, and which are electrically connected to the outer electrode opposite to the outer electrode to which the third inner electrodes are connected.
In accordance with a second preferred embodiment of the present invention, a chip-type resistor element includes a resistor body having first and second end surfaces that are opposite with each other, a plurality of first inner electrodes disposed in the resistor and extending out to the first end surface, a plurality of second inner electrodes disposed in the resistor and extending out to the second end surface, and the tip of each of which is opposed to the tip of a corresponding first inner electrode with a gap interposed therebetween, first and second outer electrodes arranged to cover the first and second end surfaces, respectively, and each of which has an electrode covering portion extending to the top and bottom surfaces of the resistor body and a pair of side surfaces thereof. In this chip-type resistor element, the positions of the gaps between the first inner electrodes and the corresponding second inner electrodes are different in the longitudinal direction, where the longitudinal direction is the direction connecting the first and second end surfac

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