JP2005150289A - Composition for thermistor, and thermistor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for a thermistor which has a small change in resistance under the use in high temperature and high humidity environment and can be adjusted for a B constant over a wide range on the low temperature side (for example, 25° to -40°C). <P>SOLUTION: The composition for a thermistor comprises a manganese oxide, a nickel oxide, an iron oxide, and a zirconium oxide. The composite for a thermistor is mainly made of (a) mol %. The reference symbol ((a) is a number between 45 and 95 excluding 45 and 95) of the manganese oxide in terms of Mn and (100-a) mol % of the nickel oxide in terms of Ni, and contains the iron oxide of 0-55 wt.% (excluding 0 wt.% and 55 wt.%) in terms of Fe<SB>2</SB>O<SB>3</SB>and the zirconium oxide of 0-15 wt.% (excluding 0 wt.% and 15 wt.%) in terms of ZrO<SB>2</SB>, with respect to the main components being 100 wt.%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermistor composition used as a thermistor layer or the like, and a thermistor element having a thermistor layer composed of the composition.

  Conventionally, as a composition for a thermistor composed of an oxide semiconductor mainly composed of manganese oxide, resistance before and after being placed in a high-temperature and high-humidity atmosphere by adding a small amount of zirconium oxide to an oxide containing manganese, nickel, and copper. There has been proposed a technique for reducing a change in value (hereinafter referred to as resistance change rate under use of high temperature and high humidity) (see Patent Document 1).

However, with the technique described in Patent Document 1, although the rate of change in resistance under the use of high temperature and high humidity can be reduced, the value of the B constant on the low temperature side such as 25 ° C. to −40 ° C. cannot be adjusted over a wide range. . If the value of the B constant can be adjusted in a wide range, there is a merit that it is possible to cope with a wide range of circuit designs.
JP-A-5-82313

  An object of the present invention is a composition for a thermistor that has a small resistance change rate under the use of high temperature and high humidity and that can adjust a B constant on a low temperature side (for example, 25 ° C. to −40 ° C.) over a wide range, and the composition. And a thermistor element having a thermistor layer.

In order to achieve the above object, according to the present invention,
A thermistor composition comprising manganese oxide, nickel oxide, iron oxide and zirconium oxide,
The main component is manganese oxide of a mol% (where a is 45 to 95 and excluding 45 and 95) in terms of Mn, and (100-a) mol% of nickel oxide in terms of Ni,
The ratio of each component when the main component is 100% by weight,
Iron oxide: _Fe 2 _{O 3} in terms of at 0 to 55 wt% (excluding 0 wt% and 55 wt%),
There is provided a thermistor composition that is zirconium oxide: 0 to 15 wt% (excluding 0 wt% and 15 wt%) in terms of ZrO ₂ .

  Preferably, it further has a copper oxide as an additive component, and the ratio of the copper oxide is less than 45% by weight in terms of CuO with respect to 100% by weight of the main component.

  According to this invention, the thermistor element which has the thermistor layer comprised with the composition for any of the above-mentioned thermistors is provided.

  According to the present invention, there is provided a thermistor element having an element body in which a plurality of thermistor layers and internal electrodes composed of any of the above thermistor compositions are alternately arranged.

  Examples of the thermistor element include a single-layer thermistor and a laminated thermistor, and are used for temperature sensing of battery packs and temperature compensation of RF module circuits, for example.

  According to the present invention, a composition for the thermistor having a small resistance change rate under use at high temperature and high humidity and capable of adjusting a B constant on a low temperature side (for example, 25 ° C. to −40 ° C.) over a wide range, and the composition And a thermistor element having a thermistor layer.

  Embodiments of the present invention will be described below with reference to the drawings. Here, FIG. 1 is a schematic sectional view showing a laminated thermistor element according to an embodiment of the present invention.

  In the present embodiment, as a thermistor element having a thermistor layer, a laminated thermistor in which thermistor layers are formed in multiple layers will be described as an example.

  As shown in FIG. 1, the laminated thermistor 2 according to this embodiment has an element body 4. Although there is no restriction | limiting in particular in the shape of the element main body 4, Usually, it is set as a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use. Usually, it is about vertical (0.4-2 mm) × horizontal (0.2-1.25 mm) × height (0.2-1 mm).

  A first external terminal electrode 6 is formed outside one end of the element body 4, and a second external terminal electrode 8 is formed outside the other end of the element body 4.

  The element body 4 has a multilayer structure in which a thermistor layer 10, a plurality of first internal electrode layers 12 and second internal electrode layers 14 are alternately arranged.

  In the present embodiment, the first internal electrode layer 12 includes a first lead electrode portion 122 having one end electrically connected to the inside of the first external terminal electrode 6, and the first lead electrode portion 122. The second lead electrode portion 124 is insulated on the same plane and has one end electrically connected to the inside of the second external terminal electrode 8.

  The second internal electrode layer 14 is electrically connected to the first auxiliary electrode part 142 having one end electrically connected to the inside of the first external terminal electrode 6 and the inside of the second external terminal electrode 8. A second auxiliary electrode part 144 having one end connected to each other, insulated from the first auxiliary electrode part 142 and the second auxiliary electrode part 144 on the same plane, and the first external terminal electrode 6 and The intermediate electrode portion 146 is arranged in a state where it is not electrically connected to any inner side of the second external terminal electrode 8.

  One end of the first auxiliary electrode portion 142 is disposed closer to the first external terminal electrode 6 side than one end of the first lead electrode portion 122. One end of the second auxiliary electrode portion 144 is disposed closer to the second external terminal electrode 8 than one end of the second lead electrode portion 124.

  The thermistor layer 10 is composed of the thermistor composition of the present invention. The thermistor composition of the present invention comprises manganese oxide, nickel oxide, iron oxide, and zirconium oxide.

  In the present embodiment, manganese oxide and nickel oxide are the main components, and other components may be referred to as additives.

  The ratio of manganese oxide to nickel oxide in the main component is 45 to 95 mol% (except 45 mol% and 95 mol%), preferably 50 to 90 mol%, in terms of Mn. Yes, nickel oxide is 5 to 55 mol% (except 5 mol% and 55 mol%), preferably 10 to 50 mol% in terms of Ni. The total of both is adjusted to 100 mol%. If the manganese oxide is too much and the nickel oxide is too little, or if the former is too little and the latter is too much, the rate of resistance change under high temperature and high humidity use is large and the practicality becomes poor.

The content of iron oxide and zirconium oxide as additives is a ratio when the main component is 100% by weight, and is 0 to 55% by weight in terms of iron oxide: Fe ₂ O ₃ (however, 0% by weight) % And 55% by weight), preferably 0.1 to 50% by weight, zirconium oxide: 0 to 15% by weight in terms of ZrO ₂ (except 0% and 15% by weight), preferably 0.005 to 10% by weight. If the content of iron oxide is too much or too little, the rate of change in resistance under high-temperature and high-humidity use is large, making it impractical. If the content of zirconium oxide is too much or too little, the rate of change in resistance under high temperature and high humidity use is large and the practicality becomes poor.

  In the present invention, a copper oxide may be further added as an additive. By including this copper oxide, there are merits such as greatly changing the B constant. In this case, the ratio of the copper oxide is preferably less than 45% by weight and more preferably less than 40% by weight in terms of CuO with respect to 100% by weight of the main component (total of manganese oxide and nickel oxide). . If the copper oxide content is too high, the resistance change rate under high temperature and high humidity use tends to increase.

  The first internal electrode layer 12 and the second internal electrode layer 14 are made of, for example, a noble metal such as Ag, Ag-Pd, Pd, Au, or Pt, or a base metal such as Cu or Ni.

  The first external terminal electrode 6 and the second external terminal electrode 8 are made of, for example, a noble metal such as Ag, Ag-Pd, Pd, Au, or Pt, a base metal such as Cu or Ni, or a metal that is a combination thereof. The Furthermore, the above various metal plating layers may be formed on the outside.

  Next, an example of a method for manufacturing the laminated thermistor 2 according to this embodiment will be described. In the following description, a case where the sheet method is used will be exemplified.

  First, a green sheet on which an electrode paste having a predetermined pattern for forming the first internal electrode layer 12 is formed on one surface, and an electrode paste having a predetermined pattern for forming the second internal electrode layer 14 on the one surface. And a green sheet not having the first and second internal electrode layers 12 and 14 are prepared.

A green sheet is comprised with the material which will form the composition for the thermistors mentioned above. Note that this type of material may contain inevitable impurities such as Si, Na, and Ca in an amount of about 0.1% by weight or less.
And a green sheet is manufactured by a well-known technique using such a material. Specifically, for example, after first uniformly mixing the material that will form the thermistor composition described above by means of wet mixing or the like, it is dried, and further calcined under appropriately selected firing conditions, The calcined powder is wet pulverized. Next, a binder is added to the pulverized calcined powder to form a slurry. Next, the slurry is formed into a sheet by means such as a doctor blade method or a screen printing method, and then dried to obtain a green sheet.

  The electrode paste includes the various metals described above. By applying this electrode paste onto the green sheet by means such as a printing method, a green sheet on which an electrode paste having a predetermined pattern is formed is obtained.

  Next, these green sheets are superposed, pressure is applied and pressure-bonded, and after necessary steps such as a drying step, the green sheets are cut and the green element body 4 is taken out. Cutting can be performed using a dicing saw or the like.

  Next, after the green element body 4 taken out is fired under a predetermined condition, the first and second external terminal electrodes 6 and 8 are formed on the end surface of the element body 4, so that the laminated thermistor 2 shown in FIG. Is obtained.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects. .

  Next, the present invention will be described in more detail with reference to examples that further embody the embodiment of the present invention. However, the present invention is not limited to these examples.

First, as a starting material, commercially available trimanganese tetroxide (Mn ₃ O ₄ ), nickel oxide, iron oxide, copper oxide, and zirconium oxide, the composition ratio after firing shown in sample numbers 1 to 51 in Table 1 ( In Table 1, mol% of Mn oxide and Ni oxide constituting the main component indicates mol% in terms of Mn and Ni, respectively, and iron oxide, copper oxide and zirconium oxide as additives. Shows the added amount (wt%) in terms of Fe ₂ O ₃ , CuO and ZrO ₂ when the main component is 100% by weight.) Wet mixed for 16 hours. These starting materials contain about 0.1% by weight of inevitable impurities.

  Next, the starting material after the wet mixing was dehydrated and dried, and powdered using a mortar and pestle.

  Next, the obtained powder was put into an alumina pot and pre-baked at 800 to 1200 ° C. for 2 hours.

  Next, the obtained calcined powder was finely pulverized by a ball mill and then dehydrated and dried to obtain a composition material for the thermistor.

  Next, 1.5 parts by weight (solid content) of polyvinyl alcohol is added to 100 parts by weight of the obtained composition material for thermistor, and the mixture is granulated into granules with a mortar and pestle. A molded body was obtained by pressure forming into a 5 mm disk shape.

  Next, this molded body was heated in air at 600 ° C. for 2 hours to remove the binder, and then sintered in the air at 900 to 1300 ° C. for 2 hours to obtain a sintered body.

  Next, a silver paste was screen-printed on both surfaces of the obtained sintered body and baked at 800 ° C. to form electrodes, whereby a thermistor sample was obtained.

The obtained thermistor sample was measured for the resistance value (R ₂₅ ) at ₂₅ ° C., the resistance value (R ₋₄₀ ) at ₋₄₀ ° C., and the resistance value (R ₈₅ ) at 85 ° C. using the direct current four-terminal method. The following formula 1 was used to calculate the B constant (B _{25 / -40} ) Y, and the following formula 2 was used to calculate the B constant (B _25/85 ) X (whether the B constant can be adjusted over a wide range). Evaluation). In this example, the case where the difference (X−Y) between the (B _25/85 ) value X and the (B _{25 / −40} ) value Y was 100 or more was considered good.

Further, a thermistor samples obtained, placed in boiling pure water of 100 ° C., the resistance value after boiling 50 hours (R _{25 ')} is measured, the initial resistance at 25 ° C. using the following equation 3 (R ₂₅ ) And the resistance change rate (ΔR ₂₅ ) was calculated (evaluation of the resistance change rate under high temperature and high humidity use). In this example, the case where the value of ΔR ₂₅ was 5.0% or less was considered good. The results are shown in Table 1.

Formula 1
B _{25 / −40} (K) = (2.3026 × log (R ₂₅ / R ₋₄₀ )) / ((1 / (273.15 + 25)) − (1 / (273.15-40)))

However, in Equation _{1, B 25 / -40: B} constant _{(K), R} 25: the resistance value at _{25 ℃ (Ω), R -40} : the resistance value at -40 ℃ (Ω).

Formula 2
B _25/85 (K) = (2.3026 × log (R ₂₅ / R ₈₅ )) / ((1 / (273.15 + 25)) − (1 / (273.15 + 85)))

However, in Formula 2, B _25/85 : B constant (K), R ₂₅ : Resistance value (Ω) at 25 ° C., R ₈₅ : Resistance value (Ω) at 85 ° C.

Formula 3
ΔR ₂₅ = ((R _{25 ′} −R ₂₅ ) / R ₂₅ ) × 100

However, in Formula 3, ΔR ₂₅ : resistance change rate (%) after boiling test, R _{25 ′} : resistance value (Ω) after boiling test, R ₂₅ : resistance value (Ω) before boiling test.

  From Table 1, the following can be understood.

  First, in Samples 1 and 51 in which the ratio of manganese oxide and nickel oxide in the main component is outside the range of the present invention, the resistance change rate under high temperature and high humidity use is large. Samples 2, 7, 18, 24, 35, and 40 in which the ratio of iron oxide as an additive falls outside the scope of the present invention, and samples 13 and 17 in which the ratio of zirconium oxide as an additive falls outside the scope of the present invention. , 30, 34, 46, 50 are the same. Moreover, when the ratio of the copper oxide as an additive is too large at 45% by weight as in Samples 12, 19, 29, and 45, the resistance change rate under use at high temperature and high humidity tends to deteriorate.

  On the other hand, for the remaining samples in which the ratio of manganese oxide and nickel oxide in the main component and the ratio of iron oxide and zirconium oxide as additives are within the scope of the present invention, the low temperature side (25 / -40) Even if the temperature characteristic of the B constant is arbitrarily changed, the resistance change rate under the use of high temperature and high humidity is small, and a stable thermistor composition is obtained. As a result, it is possible to meet various requirements such as ease of circuit design and cost reduction.

Further, in the samples 2, 18, and 35 in which the ratio of iron oxide as an additive is outside the scope of the present invention, the difference between the B constant (B _25/85 ) X and the B constant (B _{25 / -40} ) Y (X -Y) is as small as about 50, and is hardly different from the temperature characteristics of -85 ° C to 25 ° C. For this reason, it is difficult to adjust the temperature characteristic of the B constant on the low temperature side (25 ° C. to −40 ° C.) over a wide range.

  On the other hand, for samples within the scope of the present invention, the value of XY is 100 or more. For example, as the proportion of iron oxide as an additive increases as in samples 20 to 23, XY The value of can be increased. For this reason, it is easy to appropriately change and select the temperature characteristic of the B constant on the low temperature side (25 to -40 ° C.). As a result, it is possible to cope with a wide range of circuit designs and is extremely useful.

FIG. 1 is a schematic sectional view showing a laminated thermistor according to an embodiment of the present invention.

Explanation of sign

DESCRIPTION OF SYMBOLS 2 ... Stack type thermistor 4 ... Element main body 6 ... 1st external terminal electrode 8 ... 2nd external terminal electrode 10 ... Thermistor layer 12 ... 1st internal electrode layer 122 ... 1st extraction electrode part 124 ... 2nd extraction electrode part 14 ... 2nd internal electrode layer 142 ... 1st auxiliary electrode part 144 ... 2nd auxiliary electrode part 146 ... Intermediate electrode part

Claims (4)

A thermistor composition comprising manganese oxide, nickel oxide, iron oxide and zirconium oxide,
The main component is manganese oxide of a mol% (where a is 45 to 95 and excluding 45 and 95) in terms of Mn, and (100-a) mol% of nickel oxide in terms of Ni,
The ratio of each component when the main component is 100% by weight,
Iron oxide: _Fe 2 _{O 3} in terms of at 0 to 55 wt% (excluding 0 wt% and 55 wt%),
Zirconium oxide: A thermistor composition that is 0 to 15 wt% (excluding 0 wt% and 15 wt%) in terms of ZrO ₂ . The thermistor composition according to claim 1, further comprising a copper oxide as an additive component, wherein the ratio of the copper oxide is less than 45% by weight in terms of CuO with respect to 100% by weight of the main component. A thermistor element having a thermistor layer,
The thermistor layer is composed of a thermistor composition;
The thermistor composition includes manganese oxide, nickel oxide, iron oxide and zirconium oxide,
The main component is manganese oxide of a mol% (where a is 45 to 95 and excluding 45 and 95) in terms of Mn, and (100-a) mol% of nickel oxide in terms of Ni,
The ratio of each component when the main component is 100% by weight,
Iron oxide: _Fe 2 _{O 3} in terms of at 0 to 55 wt% (excluding 0 wt% and 55 wt%),
Zirconium oxide: a thermistor element of 0 to 15% by weight (excluding 0% and 15% by weight) in terms of ZrO ₂ . A thermistor element having an element body in which a plurality of thermistor layers and internal electrodes are alternately arranged,
The thermistor layer is composed of a thermistor composition;
The thermistor composition includes manganese oxide, nickel oxide, iron oxide and zirconium oxide,
The main component is manganese oxide of a mol% (where a is 45 to 95 and excluding 45 and 95) in terms of Mn, and (100-a) mol% of nickel oxide in terms of Ni,
The ratio of each component when the main component is 100% by weight,
Iron oxide: _Fe 2 _{O 3} in terms of at 0 to 55 wt% (excluding 0 wt% and 55 wt%),
Zirconium oxide: a thermistor element of 0 to 15% by weight (excluding 0% by weight and 15% by weight) in terms of ZrO ₂ .

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