JPH06314601A - Ntc thermistor - Google Patents

Abstract

PURPOSE:To provide an NTC thermistor which can ensure stable electric characteristics, when the surface crystal state of a ceramic element is changed by the influence of outer atmosphere, heat, etc., and the distance between outer terminal electrodes is changed. CONSTITUTION:One ends of inner electrodes 21, 31 face each other so as to keep an interval in the length direction. An intermediate electrode 41 is arranged in a ceramic layer 11 so as to keep intervals from the inner electrodes 21, 31. Auxiliary electrodes 51, 61 are arranged in the ceramic layer 11 so as to keep intervals in the thickness direction from the inner electrodes 21, 31, and one ends of the electrodes 51, 61 are positioned to be more inside than one ends of the inner electrodes 21, 31. Outer terminal electrodes 71, 81 are fixed to the side surfaces of both ends in the length direction of the ceramic base body 1. The inner electrodes 21, 31 and the auxiliary electrodes 51, 61 are connected with the outer electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an NTC thermistor having a negative resistance temperature characteristic.

[0002]

2. Description of the Related Art In a conventionally well-known NTC thermistor, external terminal electrodes are provided at opposite ends of a ceramic substrate, and a required negative resistance temperature characteristic is obtained by utilizing the ceramic substrate between the external terminal electrodes. It was a single plate type. Since the single plate type NTC thermistor obtains the necessary negative resistance temperature characteristic by utilizing the ceramic substrate between the external terminal electrodes, it can be obtained when the distance between the external terminal electrodes changes in the external terminal electrode forming step. The electrical characteristics, such as the resistance value, change. Also, when the surface crystal state of the ceramic substrate changes under the influence of the external atmosphere, heat, etc., the obtained negative resistance temperature characteristic also changes.

Techniques for solving such a problem include, for example, Japanese Patent Laid-Open No. 62-137805 and Japanese Patent Laid-Open No. 4-13.
An NTC thermistor having an internal electrode structure disclosed in, for example, Japanese Patent No. 0702 or Japanese Patent Application Laid-Open No. 4-283902 is known.

The NTC thermistors described in these publicly known documents are provided with an internal electrode consisting of a single layer or a plurality of layers in the thickness direction of a ceramic substrate having a negative resistance temperature characteristic. The electrodes are electrically connected to external terminal electrodes provided on both ends of the wiring. The internal electrodes had a flat area determined by the dimensions in the width direction and the length direction, and were arranged at intervals in the length direction, or were arranged so as to face each other at intervals in the thickness direction. .

[0005]

However, even in the technique described in the above-mentioned publicly known document, the resistance value fluctuates under the influence of the relative ratio of the distance between the internal electrodes and the distance between the external terminal electrodes.

Therefore, an object of the present invention is to ensure a stable negative resistance-temperature characteristic even if the surface crystal state of the ceramic substrate changes under the influence of the external atmosphere or heat.
To provide a thermistor.

Another object of the present invention is to provide an NTC thermistor which can secure a stable negative resistance temperature characteristic even if the distance between the external terminal electrodes changes.

[0008]

In order to solve the above problems, the present invention provides an NTC thermistor including a ceramic substrate, an internal electrode, an intermediate electrode, an auxiliary electrode, and an external terminal electrode. The substrate has a ceramic layer exhibiting a negative temperature coefficient of resistance, and the internal electrode is
At least one pair is provided, and when the thickness direction and the length direction are hypothesized on the ceramic base, one end of each end faces each other at intervals in the length direction, and the other ends of both end faces face each other in the length direction. The intermediate electrode is disposed in the ceramic layer at a distance from the internal electrodes between the internal electrodes, and the auxiliary electrode is spaced from the internal electrodes in a thickness direction. Is disposed in the ceramic layer, one end is located inside the one end of the internal electrode, and the other end is guided to the side end face in the longitudinal direction. Attached to both end faces in the length direction, the other end of the internal electrode and the other end of the auxiliary electrode are connected.

[0009]

The ceramic substrate has a ceramic layer having a required negative resistance-temperature characteristic, and at least one pair of internal electrodes are opposed to each other in the ceramic layer at intervals in the longitudinal direction. Since the other end of the internal electrode is connected to the external terminal electrode, the negative resistance temperature characteristic of the ceramic layer between the internal electrodes is directly extracted via the external terminal electrode. The negative resistance temperature characteristic of the ceramic layer between the internal electrodes does not change even if the surface crystal state of the ceramic substrate changes under the influence of the external atmosphere or heat. Therefore, even if the surface crystal state of the ceramic substrate changes under the influence of the external atmosphere, heat, etc., a stable negative resistance temperature characteristic can be secured.

Since the intermediate electrodes are arranged in the ceramic layer at a distance from the internal electrodes between the internal electrodes, an electric field is concentrated between the internal electrodes via the intermediate electrodes, and the intermediate electrodes are provided at both ends in the longitudinal direction. The electric field between the external terminal electrodes located is relaxed. Therefore, the resistance value seen between the external terminal electrodes is dominated by the resistance value seen between the internal electrode and the intermediate electrode, and the change in the resistance value due to the variation in the distance between the external terminal electrodes becomes small, and the stable negative Resistance temperature characteristics can be obtained.

The auxiliary electrode is arranged in the ceramic layer at a distance from the internal electrode in the thickness direction, one end is located inside one end of the internal electrode, and the other end is guided to the side end face in the length direction. There is. With this structure, the electric field is further concentrated between the internal electrodes via the intermediate electrode, the resistance value seen between the external terminal electrodes is controlled by the resistance value seen between the internal electrode and the intermediate electrode, and the external terminal electrode is It was found that the change of the resistance value due to the change of the distance between the two became smaller, and a stable negative resistance temperature characteristic was obtained.

[0012]

1 is a front sectional view of an NTC thermistor according to the present invention. 1 is a ceramic substrate, 21 and 31 are internal electrodes, 41 is an intermediate electrode, 51 and 61 are auxiliary electrodes, 71,
81 is an external terminal electrode.

The ceramic substrate 1 has a ceramic layer 11 having a required negative resistance temperature characteristic. The ceramic layer 11 is made of a ceramic material having a negative resistance temperature characteristic. Specifically, the ceramic layer 11 is Mn,
A ceramic material or the like which is a compound containing at least two kinds of Ni, Co, Cu, Al, Fe, Cr or Zr.

At least one pair of internal electrodes 21 and 31 are provided. When the thickness direction T and the length direction L are hypothesized on the ceramic substrate 1, the internal electrodes 21 and 31 respectively,
One end of the ceramic layer 11 faces the lengthwise direction L in the ceramic layer 11 with a space L1 between them, and the other ends of the ceramic layer 11 are guided to opposite side faces of the lengthwise direction. Internal electrodes 21, 3
No. 1 can be formed using a noble metal such as Ag, Ag-Pd, Pd, Au, or Pt or a base metal such as Cu or Ni as a main component.

The intermediate electrode 41 is arranged in the ceramic layer 11 between the internal electrodes 21 and 31 at a distance from the internal electrodes 21 and 31. The intermediate electrode 41, like the internal electrodes 21 and 31, is made of Ag, Ag-Pd, Pd, A.
A noble metal such as u or Pt or a base metal such as Cu or Ni can be formed as a main component.

The auxiliary electrodes 51, 61 are the internal electrodes 21, 3
It is arranged in the ceramic layer 11 at a distance from the thickness direction T in the ceramic layer 11. One end of each of the auxiliary electrodes 51 and 61 is located inside one end of each of the internal electrodes 21 and 31, and the other end is guided to the side end surface in the length direction L. The auxiliary electrodes 51 and 61 are also
Similarly to the internal electrodes 21, 31 and the intermediate electrode 41, Ag,
Noble metal such as Ag-Pd, Pd, Au, Pt or Cu,
A base metal such as Ni can be formed as a main component.

The external terminal electrodes 71, 81 are attached to both end surfaces of the ceramic substrate 1 in the length direction L independently of each other, and the other ends of the internal electrodes 21, 31 and the auxiliary electrodes 51, 61 are attached.
The other ends of are connected. External terminal electrode 71,
Reference numeral 81 is a noble metal, a base metal, or a combination of these metals, and can be formed as a thick film, a thin film by sputtering or vapor deposition, or a plated film.

FIG. 2 is an equivalent circuit diagram of the NTC thermistor shown in FIG. RH1 is an internal electrode 21 and an intermediate electrode 41
The RH2 is an NTC thermistor element generated between and, and RH2 is an NTC thermistor element generated between the intermediate electrode 41 and the internal electrode 31.

Here, the ceramic substrate 1 has a ceramic layer 11 having a negative resistance-temperature characteristic, and at least a pair of internal electrodes 21 and 31 respectively provided in the ceramic layer 11 in the lengthwise direction L. Interval L1
Since the other ends of the internal electrodes 21 and 31 are connected to the external terminal electrodes 71 and 81, the negative resistance temperature characteristic of the ceramic layer 11 between the internal electrodes 21 and 31 is It is directly drawn out via the terminal electrodes 71 and 81. The negative resistance-temperature characteristic of the ceramic layer 11 between the internal electrodes 21-31 does not change even if the surface crystal state of the ceramic substrate 1 changes under the influence of the external atmosphere, heat, or the like.
Therefore, even if the surface crystal state of the ceramic substrate 1 changes due to the influence of the external atmosphere, heat, etc., a stable negative resistance temperature characteristic can be secured.

The intermediate electrode 41 is composed of the internal electrodes 21, 3
1 is disposed in the ceramic layer 11 at a distance from the internal electrodes 21 and 31, the intermediate electrode 4
1, the electric field is concentrated between the internal electrodes 21-31, and the electric field between the external terminal electrodes 71-81 located at both ends in the length direction L is relaxed. Therefore, the external terminal electrodes 71-81
The resistance value seen between the inner electrodes 21 and 31 and the intermediate electrode 41 is
Controlled by the resistance value seen between the external terminal electrode 71
The change in the resistance value with respect to the change in the distance between -81 becomes small, and a stable negative resistance temperature characteristic is obtained.

Further, the auxiliary electrodes 51 and 61 are the internal electrodes 2
1, 31 are arranged in the ceramic layer 11 at intervals in the thickness direction T, one end is located inside one end of the internal electrodes 21, 31, and the other end is guided to the side end face in the length direction. There is. With this structure, the electric field is further concentrated between the intermediate electrode 41 and the internal electrodes 21 and 31, and the external terminal electrode 7
The resistance value seen between 1-81 is dominated by the resistance value seen between the internal electrodes 21, 31 and the intermediate electrode 41, and the change of the resistance value due to the change of the distance between the external terminal electrodes 71-81 becomes smaller. It was found that a stable negative resistance temperature characteristic was obtained.

Further, as shown in FIG. 1, the internal electrodes 21 and 31 are arranged substantially the same in the thickness direction T in the ceramic layer 11. With such a structure, the internal electrodes 21 and 31 can be simultaneously formed in the same step. With respect to the arrangement of the internal electrodes 21 and 31,
The intermediate electrode 41 is arranged at a distance from the internal electrodes 21, 31 in the thickness direction T of the ceramic substrate 1. The intermediate electrode 41 has a length that substantially fills the interval L1.
Therefore, the NTC thermistor elements RH1 and RH2 in FIG. 2 are generated in the thickness direction of the ceramic layer 11.

The external terminal electrodes 71, 81 have end portions 711, 811 extending in the lengthwise direction L from the side end surfaces, and the internal electrodes 21, 3 have their ends.
It ends outside 1. Specifically, a space L2 is formed between the end 711 and the internal electrode 21, and a space L3 is formed between the end 811 and the internal electrode 22. This structure is effective in suppressing the resistance value variation due to the distance variation between the external terminal electrodes 71-81 when the surface specific resistance of the ceramic substrate 1 is small.

The ceramic substrate 1 may have other ceramic layers 12 and 13 on both sides in the thickness direction of the ceramic layer 11. According to this structure, the ceramic layer 12,
13 can be formed of a material having a specific resistance value higher than that of the ceramic layer 11, thereby further reducing the variation of the negative resistance temperature characteristic with respect to the variation of the distance between the external terminal electrodes 71-81. You can

Next, an embodiment of the NTC thermistor according to the present invention will be described with reference to FIGS. In these figures, the same reference numerals as those in FIG. 1 denote the same components.

In the embodiment of FIG. 3, the internal electrodes 21, 31 are
Are arranged at different positions in the ceramic layer 11 in the thickness direction T. Also in the case of this embodiment, the same operational effect as in FIG. 1 can be obtained.

In the embodiment shown in FIG. 4, the internal electrodes 21 and 31 are arranged at substantially the same position in the ceramic layer 11 in the thickness direction T, and the intermediate electrode 41 is arranged at a distance L1 between the internal electrodes 21-31.
It is arranged at intervals inside. According to this electrode structure, the intermediate electrode 41 can be formed simultaneously with the internal electrodes 21 and 31 in the same step.

In the embodiment shown in FIG. 5, a plurality of intermediate electrodes 41 and 42 are provided and are arranged at intervals. There are two intermediate electrodes 41 and 42, and they are divided into two at the same height position. According to this structure,
The electric field concentration between the intermediate electrodes 41, 42 and the internal electrodes 21, 31 can be controlled by the distance between the intermediate electrodes 41-42.

In the embodiment shown in FIG. 6, both ends of the intermediate electrode 41 overlap the end portions of the internal electrodes 21 and 31. With this structure, the electric field concentration between the intermediate electrode 41 and the internal electrodes 21, 31 and the auxiliary electrodes 51, 61 can be controlled.

The embodiment shown in FIG. 7 is provided with a plurality of electrode pairs of the internal electrodes 21, 31 and the internal electrodes 22, 32. These electrode pairs (21, 3
1) and (22, 32) are arranged at intervals in the thickness direction T of the ceramic substrate 1. Auxiliary electrode 5
1, 61 are arranged in the ceramic layer 11 between the electrode pairs (21, 31), (22, 32). FIG. 8 is FIG.
3 is an equivalent circuit diagram of the NTC thermistor shown in FIG. RH1
Is an NTC thermistor element generated between the internal electrode 21 and the intermediate electrode 41, RH2 is an NTC thermistor element generated between the internal electrode 22 and the intermediate electrode 41, and RH3 is an NTC generated between the internal electrode 31 and the intermediate electrode 41. The thermistor element, RH4, represents an NTC thermistor element generated between the internal electrode 21 and the intermediate electrode 41, respectively. As is clear from FIG. 8, in the case of the structure shown in FIG. 7, the combined resistance value seen between the external terminal electrodes 71-81 can be adjusted by selecting the number of pairs of internal electrodes.

In the embodiment of FIG. 9, three internal electrode pairs (2
1, 31), (22, 32) and (23, 33). Two intermediate electrodes 41, 42 are provided between the pair of corner electrodes, and two pairs of auxiliary electrodes (51, 52), (61, 6) are provided.
2) is provided.

The embodiment shown in FIG. 10 has two internal electrode pairs (21, 31) and (22, 32). Between the two internal electrode pairs (21, 31), (22, 32), the intermediate electrodes 41, 42 and the auxiliary electrodes (51, 52, 53),
(61, 62, 63) are provided.

The embodiment of FIG. 11 has two internal electrode pairs (21, 31) and (22, 32). The intermediate electrode 41 is disposed between the internal electrodes 21 and 31, the intermediate electrode 42 is disposed between the internal electrodes 22 and 32, and the auxiliary electrode 51 is disposed between the internal electrode pairs (21, 31) and (22, 32). ,
61 is provided.

The NTC thermistor according to the present invention can be manufactured, for example, by a sheet laminating method. First, a green sheet having a group of internal electrodes formed on one surface is prepared. The green sheet is composed of a ceramic material having a predetermined negative resistance temperature characteristic, for example, a ceramic material which is a compound containing at least two kinds of Mn, Ni, Co, Cu, Al, Fe, Cr or Zr. A green sheet is manufactured by a known technique using these ceramic materials. Specifically, the above-mentioned ceramic materials are uniformly mixed by means such as wet mixing, dried, and then calcined under appropriately selected firing conditions, and the calcined powder is wet-ground. A binder is added to the pulverized calcined powder to form a slurry. The slurry is formed into a sheet by a means such as a doctor blade method or a screen printing method. Then, it is dried to obtain a green sheet.

For the internal electrodes, an electrode paste containing a noble metal such as Ag, Ag-Pd, Pd, Au, or Pt or a base metal such as Cu or Ni as a main component is applied onto the green sheet by a printing method or the like. Can be formed by

Similarly, a green sheet having a group of intermediate electrodes formed on one surface and a green sheet having no electrodes are prepared.

These green sheets are superposed on each other, pressure-bonded to them, and after the necessary steps such as a drying step, they are cut and the NTC thermistor element is taken out. The cutting can be performed using a dicing saw or the like. The desired NTC thermistor is obtained by firing the NTC thermistor element thus taken out and applying external terminal electrodes after the firing.

Next, a concrete example of manufacturing the NTC thermistor and characteristics of the obtained NTC thermistor will be shown. As a starting material, using the Mn ₃ 0 _4, NiO and Al ₂ O _3, were weighed such that the Mn / Ni / Al = 66.7 / 28.6 / 4.7 (mol%), were uniformly mixed by wet mixing, drying Then, the calcined powder is wet-pulverized under the condition of 1100 ° C. for 2 hours. A binder was added to the pulverized calcined powder to obtain a slurry. The slurry was formed into a sheet by the doctor blade method and then dried to obtain a green sheet.

Next, a Pd paste was printed on this green sheet to prepare green sheets for internal electrodes, intermediate electrodes and auxiliary electrodes. This green sheet for electrodes and another green sheet prepared separately were overlapped so as to have a desired electrode pattern, and pressure of 400 kg / cm ² was applied to perform pressure bonding.

Next, after passing through a drying step, a dicing saw was used to cut into 2.3 × 1.43 × 1.14 mm to obtain a chip shape. This chip was fired at 1300 ° C. for 2 hours. The Ag-Pd electrode paste was applied to both ends of the fired chip by the dipping method and baked at 850 ° C. As a result, an NTC thermistor having the structure shown in FIG. 7 is obtained.

Apply the above NTC thermistor to 25 ° C and 85 ° C.
Was immersed in the silicone oil bath and the resistance value was measured by the DC four-terminal method. For comparison, a single plate type NTC thermistor (referred to as a conventional product) in which external terminal electrodes are provided at opposite ends of a ceramic substrate and a ceramic substrate between the external terminal electrodes is used to obtain necessary negative resistance temperature characteristics )
Was manufactured to have the same shape under the same starting material and the same manufacturing condition, and the resistance value was measured under the same measuring condition. The measurement results are shown below.

[0042] However, R25: Average of resistance value at 25 ℃ N = 40 B25 / 85: Calculated from resistance value at 25 ℃ and 85 ℃ N =
40 average B25 / 85 = {ln (R25) ー ln (R85)} / {(1/25 + 273.15) ー (1/85 + 27
3.15)} R25 · CV: Coefficient of variation in resistance value at 25 ° C. CV = (σ / average resistance value of number N) × 100 (%) As apparent from the above test data, NT according to the present invention
The C thermistor has less variation in resistance value than the conventional single-plate type NTC thermistor. Regarding the resistance value and B constant, desired characteristics can be secured by changing the material composition and the internal electrode configuration.

Next, the test results of the resistance change after the high temperature storage test at 125 ° C. for 1000 hours are shown below.

[0044] However: ΔR25 = {(resistance value after high temperature-initial resistance value) / initial resistance value} × 100 (%) △ B25 / 85 = {(B constant value after high temperature storage-initial B constant value)
/ Initial B constant value} × 100 (%) As is clear from the above test data, NT according to the present invention
The C thermistor has a significantly smaller change in resistance after being left at a high temperature than the conventional NTC thermistor.

[0045]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide an NTC thermistor that can secure stable negative resistance-temperature characteristics even if the surface crystal state of the ceramic substrate changes due to the influence of the external atmosphere, heat, and the like. (B) It is possible to provide an NTC thermistor that can secure a stable negative resistance temperature characteristic even if the distance between the external terminal electrodes changes.

[Brief description of drawings]

FIG. 1 is a front sectional view of an NTC thermistor according to the present invention.

FIG. 2 is an equivalent circuit diagram of the NTC thermistor shown in FIG.

FIG. 3 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

FIG. 4 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

FIG. 5 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

FIG. 6 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

FIG. 7 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

8 is an equivalent circuit diagram of the NTC thermistor shown in FIG.

FIG. 9 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

FIG. 10 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

FIG. 11 is a front sectional view of another embodiment of the NTC thermistor according to the present invention.

[Explanation of symbols]

 1 Ceramic Substrate 21, 22, 23 Internal Electrodes 31, 32, 33 Internal Electrodes 41, 42 Intermediate Electrodes 51, 52, 53 Auxiliary Electrodes 61, 62, 63 Auxiliary Electrodes 71, 81 External Terminal Electrodes

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Numata 1-13-1 Nihonbashi Chuo-ku, Tokyo TDC Corporation (72) Inventor Kiyoshi Ito 1-13-1 Nihonbashi Chuo-ku, Tokyo TDC Within the corporation

Claims (12)

[Claims] 1. An NTC thermistor including a ceramic base, an internal electrode, an intermediate electrode, an auxiliary electrode, and an external terminal electrode, wherein the ceramic base has a ceramic layer exhibiting negative resistance-temperature characteristics. At least one pair of the internal electrodes are provided, and when the thickness direction and the length direction are hypothesized on the ceramic base, one ends of the internal electrodes face each other at intervals in the length direction, and the other ends of the internal electrodes are long. The intermediate electrodes are disposed in the ceramic layer at a distance from the internal electrodes between the internal electrodes, and the auxiliary electrodes are the internal electrodes. It is arranged in the ceramic layer at a distance from the electrode in the thickness direction, one end is located inside the one end of the internal electrode, and the other end is guided to the side end face in the length direction. Ri, the external terminal electrodes, the are attached to both side end surfaces in the length direction of the ceramic base, the other end and the NTC thermistor in which the other end of the auxiliary electrode is connected to the internal electrodes. 2. The NTC thermistor according to claim 1, wherein the internal electrodes are arranged substantially in the same thickness direction in the ceramic layer. 3. The NTC thermistor according to claim 1, wherein the internal electrodes are arranged at different positions in the ceramic layer in the thickness direction. 4. The NTC thermistor according to claim 1, wherein a plurality of pairs of the internal electrodes are provided, and each of the electrode pairs is arranged at intervals in the thickness direction of the ceramic substrate. 5. The NTC thermistor according to claim 1, wherein the intermediate electrode is arranged at a distance from the internal electrode in the thickness direction of the ceramic substrate. 6. The NTC thermistor according to claim 1, wherein the intermediate electrode is arranged at a distance from the internal electrode in the length direction of the ceramic substrate. 7. The NTC thermistor according to claim 1, wherein a plurality of the intermediate electrodes are provided, and the intermediate electrodes are spaced apart from each other. 8. The NTC thermistor according to claim 1, wherein the auxiliary electrode is provided for each of the internal electrodes. 9. The ceramic layer comprises Mn, Ni, Co, Cu,
The NTC thermistor according to claim 1, which is a compound containing at least two kinds of Al, Fe, Cr or Zr. 10. The NTC thermistor according to claim 1, wherein the ceramic substrate has another ceramic layer on both sides in the thickness direction of the ceramic layer. 11. The specific resistance value of the other ceramic layer is equal to or lower than the specific resistance value of the ceramic layer located between the internal electrodes.
The NTC thermistor described in 0. 12. The NTC thermistor according to claim 10, wherein the other ceramic layer has a specific resistance value higher than a specific resistance value of the ceramic layer located between the internal electrodes.