Thermistor element and manufacturing method thereof

Abstract

Provided are: a thermistor element which is provided with a conductive intermediate layer that can be stably present even at high temperatures; and a method for manufacturing the thermistor element. A thermistor element according to the present invention is provided with: a thermistor substrate (2) containing an oxide thermistor material having a perovskite crystal structure; a conductive intermediate layer (3) formed on the thermistor substrate; and an electrode layer (4) formed on the conductive intermediate layer, the conductive intermediate layer being a composite oxide containing Mn. The method for manufacturing a thermistor element includes: an intermediate layer forming step of forming a conductive intermediate layer of a composite oxide containing Mn on a thermistor substrate; and an electrode layer forming step in which an electrode layer is formed on the conductive intermediate layer, in which an Mn-containing dispersion liquid is applied to the thermistor substrate and dried to form a temporary intermediate layer, and in which a Pt paste containing Pt is applied to the temporary intermediate layer and fired to form the electrode layer. And using the temporary intermediate layer as a conductive intermediate layer.

Description

Technical Field

[0001] The present invention relates to a thermistor element suitable for a temperature sensor or a protection circuit of an electronic device, and a method for manufacturing the thermistor element. Background Art

[0002] As part of the global warming countermeasures, the EV market has expanded rapidly in recent years. As a result, the IGBT power module drive temperature has increased with the rapid charging speed and higher engine output. Thermistors that monitor the temperature are also required to operate at higher temperatures.

[0003] Among the thermistor materials that are currently the most commonly used, namely the spinel thermistor materials based on Mn, Co, etc., the temperature coefficient of the thermistor, namely the B constant, is relatively large, at about 3000 to 4000.

[0004] Therefore, in the thermistor material with a spinel structure, the resistance value changes too much with respect to temperature. Under the characteristic of adapting to low temperatures, the resistance value at high temperatures is too low, resulting in the inability to detect accurate temperature. In addition, there is still the problem that under the characteristic of adapting to high temperatures, the resistance value at low temperatures is too high, resulting in the inability to detect accurate temperature.

[0005] Therefore, as in Patent Document 1, a technology has been proposed in which a perovskite-based thermistor material having a small B constant is used to form a composite structure with an insulating material, thereby achieving a low B constant and being able to adjust the resistance value.

[0006] However, due to the composite structure of the insulating material and the thermistor material, there is a problem that less thermistor material is exposed at the electrode interface and the electrical contact with the electrode is reduced.

[0007] In particular, in the commonly used method of printing and sintering a noble metal paste, glass frit is used. The molten glass frit exists between the thermistor substrate and the electrode to ensure adhesion, but the direct contact points between the electrode and the thermistor substrate are very few.

[0008] Therefore, when structures with few electrical contacts are joined together, good electrical properties cannot be obtained. In view of this problem, it is believed that it is effective to form a conductive intermediate layer at the interface between the thermistor substrate and the electrode as in Patent Document 2. In the thermistor element of Patent Document 2, the conductive intermediate layer has a cohesive structure composed of RuO2 particles that are in electrical contact with each other, and SiO2 exists in the gaps of the cohesive structure.

[0009] Patent Document 1: Japanese Patent No. 4183666

[0010] Patent Document 2: Japanese Patent No. 6365603

[0011] The above-mentioned conventional technology has the following problems.

[0012] That is, in the thermistor element described in Patent Document 2, RuO 2 sublimates at about 900° C., and therefore it is difficult to use RuO 2 in a noble metal electrode such as a Pt electrode that uses a noble metal paste such as a Pt paste and must be sintered at a high temperature. Summary of the invention

[0013] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a thermistor element including a conductive intermediate layer that can exist stably even at high temperatures, and a method for manufacturing the thermistor element.

[0014] The present invention adopts the following structure to solve the above-mentioned problems. That is, the thermistor element involved in the first invention is characterized by comprising: a thermistor substrate including an oxide thermistor material having a perovskite crystal structure; a conductive intermediate layer formed on the thermistor substrate; and an electrode layer formed on the conductive intermediate layer, wherein the conductive intermediate layer is a composite oxide including Mn.

[0015] In the thermistor element, since the conductive intermediate layer is a composite oxide containing Mn (manganese), the crystal structure of the composite oxide containing Mn is close to the perovskite type thermistor matrix, thereby improving the adhesion of the conductive intermediate layer, and the conductive intermediate layer can still exist stably even at high temperatures. In particular, the conductive intermediate layer can obtain high adhesion with the electrode layer formed by precious metals by containing Mn, and can also exist stably after sintering when the electrode layer is formed by precious metals that must be sintered at high temperatures. In addition, when the oxide thermistor material constituting the thermistor matrix contains an oxide containing Mn, the adhesion with the conductive intermediate layer as a composite oxide containing Mn will be further improved.

[0016] In addition, the composite oxide refers to a substance indicated as an oxide of two or more elements (or the same element with different oxidation numbers).

[0017] The thermistor element according to the second invention is characterized in that, in the first invention, the composite oxide further contains Y.

[0018] That is, in the thermistor element, since the composite oxide also contains Y (yttrium), higher conductivity can be obtained by reacting Mn and Y to form a composite oxide. In addition, when the oxide thermistor material constituting the thermistor matrix contains an oxide containing Y, the adhesion with the conductive intermediate layer containing Y is further improved.

[0019] The thermistor element according to the third invention is characterized in that, in the first invention or the second invention, the composite oxide further contains one or two or more of Ca, Sr, Ba and La.

[0020] That is, in this thermistor element, since the composite oxide also contains one or more of Ca (calcium), Sr (strontium), Ba (barium) and La (lanthanum), Y in the composite oxide is substituted with at least one element of Ca, Sr, Ba and La. If La is substituted, the electron mobility is improved due to the reduction of lattice distortion, and if Ca, Sr, Ba is substituted, high conductivity can be obtained due to the increase of carriers.

[0021] A thermistor element according to a fourth invention is characterized in that, in any one of the first to third inventions, the electrode layer contains Pt.

[0022] That is, in this thermistor element, even if the electrode layer is a Pt electrode containing Pt, that is, a Pt electrode layer formed by sintering at a high temperature, good adhesion with the conductive intermediate layer can be obtained. In addition, since the electrode layer formed of Pt is difficult to diffuse, the change in thermistor characteristics is small and the solder erosion is small, the adhesion of the electrode is maintained even if soldering is performed.

[0023] The thermistor element according to the fifth invention is characterized in that, in any one of the first to fourth inventions, the content ratio of the Mn in the conductive intermediate layer relative to all metal atoms in the conductive intermediate layer is C Mn When 0at.%<C Mn ≤60at.%.

[0024] That is, in this thermistor element, since the content ratio of Mn in the conductive intermediate layer to all metal atoms in the conductive intermediate layer is C Mn When 0at.%<C Mn ≤60at.%, so good adhesion can be obtained.

[0025] The thermistor element according to the sixth invention is characterized in that, in the second invention, the content ratio of the Y in the conductive intermediate layer relative to all metal atoms in the conductive intermediate layer is C Y When 0at.%<C Y ≤60at.%.

[0026] That is, in this thermistor element, the content ratio of the Y in the conductive intermediate layer to all metal atoms in the conductive intermediate layer is C Y When 0at.%<C Y≤60at.%, so it can form a composite oxide with Mn and obtain good conductivity.

[0027] The thermistor element according to the seventh invention is characterized in that, in the third invention, the conductive intermediate layer contains one or two or more of Ca, Sr, Ba and La in an amount of 0.1 at. % or more relative to all metal atoms.

[0028] That is, in this thermistor element, since the conductive intermediate layer contains 0.1 at. % or more of one or two or more of Ca, Sr, Ba and La in terms of the content ratio relative to all metal atoms, good conductivity can be obtained.

[0029] The manufacturing method of the thermistor element involved in the eighth invention is characterized by comprising: an intermediate layer forming step of forming a conductive intermediate layer containing a composite oxide of Mn on a thermistor substrate containing a thermistor material having a perovskite crystal structure; and an electrode layer forming step of forming an electrode layer on the conductive intermediate layer, wherein in the intermediate layer forming step, a dispersion containing Mn is applied to the thermistor substrate, and the dispersion containing Mn is dried to form a temporary intermediate layer, the dispersion containing Mn containing a powder containing Mn, an organic solvent and a dispersant, and in the electrode layer forming step, a Pt paste containing Pt is applied to the temporary intermediate layer, and the Pt paste is fired to form the electrode layer, and the temporary intermediate layer is used as the conductive intermediate layer.

[0030] That is, in the method for manufacturing the thermistor element, in the intermediate layer forming step, a dispersion containing Mn is applied to the thermistor substrate, and the dispersion containing Mn is dried to form a temporary intermediate layer, and the dispersion containing Mn contains a powder containing Mn, an organic solvent, and a dispersant, and in the electrode layer forming step, a Pt paste containing Pt is applied to the temporary intermediate layer, and the Pt paste is fired to form an electrode layer, and the temporary intermediate layer is used as a conductive intermediate layer, so that the Mn of the temporary intermediate layer and the thermistor material of the thermistor substrate can react at a high temperature during firing to form a conductive intermediate layer of a composite oxide containing Mn.

[0031] The method for producing a thermistor element according to a ninth invention is characterized in that, in the eighth invention, the Mn-containing dispersion further contains Y.

[0032] That is, in this method for producing a thermistor element, since the dispersion containing Mn also contains Y, Mn and Y can be sintered while reacting during firing, or a conductive intermediate layer of a composite oxide obtained by sintering composite oxide particles of Mn and Y can be obtained.

[0033] The method for producing a thermistor element according to the tenth invention is characterized in that, in the eighth invention or the ninth invention, the Mn-containing dispersion further contains one or more of Ca, Sr, Ba and La.

[0034] That is, in the method for manufacturing thermistor element, since the dispersion containing Mn further contains one or more of Ca, Sr, Ba and La, Mn and one or more of Ca, Sr, Ba and La or Mn, Y and one or more of Ca, Sr, Ba and La can react with each other during firing, and sintering can be performed simultaneously, or a conductive intermediate layer of a composite oxide obtained by sintering composite oxide particles of Mn and one or more of Ca, Sr, Ba and La or Mn, Y and one or more of Ca, Sr, Ba and La can be obtained.

[0035] The manufacturing method of the thermistor element involved in the eleventh invention is characterized in that it includes: an intermediate layer electrode layer forming step, forming a conductive intermediate layer containing a composite oxide of Mn on a thermistor substrate containing a thermistor material having a perovskite crystal structure, and forming an electrode layer on the conductive intermediate layer, in which a Mn-containing Pt paste containing Mn and Pt is applied to the thermistor substrate, and the Mn-containing Pt paste is fired to form the conductive intermediate layer and the electrode layer.

[0036] That is, in the manufacturing method of the thermistor element, since in the intermediate layer electrode layer forming step, a Mn-containing Pt paste containing Mn and Pt is applied to the thermistor substrate, and the Mn-containing Pt paste is fired to form a conductive intermediate layer and an electrode layer, the Mn in the Mn-containing Pt paste can diffuse toward the thermistor substrate side at a high temperature during firing to form a conductive intermediate layer, and the remaining Pt can form an electrode layer.

[0037] According to the present invention, the following effects are achieved.

[0038] That is, according to the thermistor element and the method for manufacturing the same involved in the present invention, since the conductive intermediate layer is a composite oxide containing Mn, the crystal structure of the composite oxide containing Mn is close to the perovskite type thermistor matrix, thereby improving the adhesion of the conductive intermediate layer, and the conductive intermediate layer can still exist stably even at high temperatures.

[0039] Therefore, an electrode layer of Pt or the like that must be sintered at a high temperature can be used, and a thermistor element having good adhesion and high reliability can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 11 is a cross-sectional view showing a thermistor element according to one embodiment of the thermistor element and a method for manufacturing the thermistor element according to the present invention.

[0041] Figure 2 1 is a cross-sectional view showing a method for manufacturing a thermistor element in the present embodiment in order of steps.

[0042] Figure 3 This is a cross-sectional view showing another method of manufacturing thermistor element in this embodiment in order of steps.

[0043] Figure 4 : is a SEM image showing a cross section of the thermistor element in Example 4 of the thermistor element and the method for manufacturing the thermistor element according to the present invention.

[0044] Figure 5 This is a composition distribution image of La in a cross section of the thermistor element in Example 4 of the present invention.

[0045] Figure 6 1 is a composition distribution image of Y in a cross section of a thermistor element in Example 4 of the present invention.

[0046] Figure 7 This is a composition distribution image of Mn in a cross section of the thermistor element in Example 4 of the present invention.

[0047] Figure 8 This is a composition distribution image of Ca in a cross section of the thermistor element in Example 4 of the present invention.

[0048] Fig. 9 : is a SEM image showing a cross section of the thermistor element in Example 5 of the thermistor element and the method for manufacturing the thermistor element according to the present invention.

[0049] Fig.10 This is a composition distribution image of Mn in a cross section of the thermistor element in Example 5 of the present invention.

[0050] Fig.11 This is a composition distribution image of La in a cross section of the thermistor element in Example 5 of the present invention.

[0051] Fig.12 1 is a composition distribution image of Y in a cross section of a thermistor element in Example 5 of the present invention.

[0052] Fig.13 This is a composition distribution image of Ca in a cross section of the thermistor element in Example 5 of the present invention. DETAILED DESCRIPTION

[0053] Below, refer to Figures 1 to 3, an embodiment of the thermistor element and the manufacturing method thereof according to the present invention will be described. In addition, in the drawings used in the following description, the scale is appropriately changed as needed in order to make each component a recognizable or easily recognizable size.

[0054] like Figures 1 to 3 As shown, the thermistor element 1 of the present embodiment includes a thermistor base 2 made of an oxide thermistor material having a perovskite crystal structure, a conductive intermediate layer 3 formed on the thermistor base 2 , and an electrode layer 4 formed on the conductive intermediate layer 3 .

[0055] The conductive intermediate layer 3 is a composite oxide containing Mn.

[0056] Furthermore, it is preferred that the composite oxide further contains Y (yttrium).

[0057] Furthermore, it is more preferable that the composite oxide further contains one or two or more of Ca, Sr, Ba and La.

[0058] The electrode layer 4 contains Pt. That is, the electrode layer 4 is a Pt electrode formed by sintering a Pt paste.

[0059] In addition, the content ratio of Mn in the conductive intermediate layer 3 to all metal atoms in the conductive intermediate layer 3 is denoted as C Mn When 0 at.% < C Mn ≤60at.%.

[0060] Furthermore, the content ratio of Y in the conductive intermediate layer 3 to all metal atoms in the conductive intermediate layer 3 is denoted as C Y When 0 at.% < C Y ≤60at.%.

[0061] Furthermore, the conductive intermediate layer 3 preferably contains 0.1 at.% or more of one or two or more of Ca, Sr, Ba and La in terms of the content ratio relative to all metal atoms. The content ratio of Ca, Sr, Ba and La is not particularly limited and may be 10 at.% or less.

[0062] In addition, the conductive intermediate layer 3 may be disposed on the entire surface between the thermistor base 2 and the electrode layer 4, or the conductive intermediate layer 3 may be disposed discontinuously at a plurality of locations.

[0063] Furthermore, the thickness of the conductive intermediate layer 3 is preferably 0.1 to 3 μm.

[0064] Furthermore, the B constant of the thermistor element 1 of the present embodiment is within a range of 1500 to 4000K, for example.

[0065] The resistivity of the thermistor element 1 of the present embodiment is, for example, 10 0 ~10 6 In the range of Ωcm.

[0066] like Figure 2 As shown, the manufacturing method of the thermistor element 1 of the present embodiment includes: an intermediate layer forming step of forming a conductive intermediate layer 3 containing a composite oxide of Mn on a thermistor substrate 2 containing a thermistor material having a perovskite crystal structure; and an electrode layer forming step of forming an electrode layer 4 on the conductive intermediate layer 3.

[0067] In the intermediate layer forming step, a Mn-containing dispersion liquid containing a Mn-containing powder, an organic solvent and a dispersant is coated on the thermistor substrate 2. Figure 2 As shown in (a), the Mn-containing dispersion is dried to form a temporary intermediate layer 3a.

[0068] In the above-mentioned electrode layer forming step, Figure 2 As shown in (b), a Pt paste containing Pt is applied on the temporary intermediate layer 3a, and the Pt paste is fired, as shown in FIG. Figure 2 As shown in (c), the electrode layer 4 is formed and the temporary intermediate layer 3a is used as the conductive intermediate layer 3.

[0069] In addition, it is preferred that the Mn-containing dispersion further contains Y.

[0070] Furthermore, it is more preferred that the Mn-containing dispersion further contains one or more of Ca, Sr, Ba and La. Since these react with the Mn compound to form a composite oxide with Mn, they may be respective oxides or carbonates, etc., but since abnormal particle growth may occur during the reaction, they are preferably composite oxides with Mn.

[0071] The above-mentioned thermistor substrate 2 is obtained, for example, by the following method: a substrate formed of various metal oxides and calcium carbonate (CaCO3) as a sintering promoter and electrical property adjuster are used as starting materials, and each material is weighed in a manner so that each metal has a specified molar ratio, and these materials are mixed, dried, and then temporarily fired, and then the material mixed with the binder is formed into a plate shape and fired.

[0072] The Mn-containing dispersion is prepared, for example, by weighing materials containing at least Mn at a predetermined molar ratio, mixing the calcined powder with an organic solvent such as ethanol and a dispersant, and dispersing the mixture with a disperser such as a paint shaker.

[0073] That is, in the case of powders containing one or more of Y, Ca, Sr, Ba and La in addition to Mn, these various metals are weighed in a manner to form a prescribed molar ratio, and the powders obtained by calcining are mixed and dispersed with an organic solvent and a dispersant to produce the powder.

[0074] The electrode layer 4 is produced by, for example, applying a Pt paste by printing and firing. The higher the firing temperature, the smaller the voids generated at the interface between the electrode layer 4 and the conductive intermediate layer 3.

[0075] And, if Figure 3 As shown, another method for manufacturing thermistor element 1 of the present embodiment includes: an intermediate layer electrode layer forming step, forming a conductive intermediate layer 3 containing a composite oxide of Mn on a thermistor substrate 2 containing a thermistor material having a perovskite crystal structure, and forming an electrode layer 4 on the conductive intermediate layer 3.

[0076] In the intermediate electrode layer forming step, a Mn-containing Pt paste 4 b containing Mn and Pt is applied onto the thermistor base 2 , and the Mn-containing Pt paste 4 b is fired to form the conductive intermediate layer 3 and the electrode layer 4 .

[0077] The Mn-containing Pt paste 4b is produced by, for example, adding Mn 2 O 3 to Pt paste.

[0078] Thus, in the thermistor element 1 of the present embodiment, since the conductive intermediate layer 3 is a composite oxide containing Mn, the crystal structure of the composite oxide containing Mn is close to the perovskite type thermistor substrate 2, so that the adhesion between the conductive intermediate layer 3 and the thermistor substrate can be improved, and the conductive intermediate layer 3 can still exist stably even at high temperatures. In particular, the conductive intermediate layer 3 can obtain high adhesion with the electrode layer 4 formed of a noble metal by containing Mn, and in the case where the electrode layer 4 is formed of a noble metal that must be sintered at a high temperature, it can also exist stably after sintering. In addition, by the oxide thermistor material constituting the thermistor substrate 2 containing an oxide containing Mn, the adhesion with the conductive intermediate layer 3 as a composite oxide containing Mn will be further improved.

[0079] Therefore, even if the electrode layer 4 made of Pt is formed by sintering at a high temperature, good adhesion can be obtained with the conductive intermediate layer 3. In addition, since the electrode layer 4 made of Pt is difficult to diffuse, the change in thermistor characteristics is small, and the solder erosion is small, the adhesion of the electrode is maintained even if soldering is performed.

[0080] Furthermore, since the formed intermediate layer contains Y, Mn and Y react during heat treatment to form a composite oxide and are sintered at the same time, or a Mn compound that becomes a composite oxide with Y is sintered, thereby achieving higher conductivity. In addition, the oxide thermistor material constituting the thermistor substrate 2 contains an oxide containing Y, thereby further improving the adhesion with the conductive intermediate layer 3 containing Y.

[0081] Moreover, since the composite oxide also contains one or more of Ca, Sr, Ba and La, Y in the composite oxide is substituted with at least one element of Ca, Sr, Ba and La. If La is substituted, the electron mobility is improved due to the reduction of lattice distortion, and if Ca, Sr, Ba is substituted, high conductivity can be obtained due to the increase of carriers.

[0082] In addition, since the content ratio of Mn in the conductive intermediate layer 3 to all metal atoms in the conductive intermediate layer 3 is C Mn When 0at.%<C Mn ≤60at.%, so good adhesion can be obtained.

[0083] Furthermore, since the content ratio of Y in the conductive intermediate layer 3 to all metal atoms in the conductive intermediate layer 3 is C Y When 0at.%<C Y ≤60at.%, so it can form a composite oxide with Mn and obtain good conductivity.

[0084] Furthermore, since the conductive intermediate layer 3 contains one or two or more of Ca, Sr, Ba, and La at a content ratio of 0.1 at. % or more relative to all metal atoms, good conductivity can be obtained.

[0085] In the method for manufacturing thermistor element 1 of the present embodiment, in the intermediate layer forming step, a dispersion containing Mn is applied to the thermistor substrate 2, and the dispersion containing Mn is dried to form a temporary intermediate layer 3a, and the dispersion containing Mn contains a powder containing Mn, an organic solvent, and a dispersant, and in the electrode layer forming step, a Pt paste containing Pt is applied to the temporary intermediate layer 3a, and the Pt paste is fired to form an electrode layer 4, and the temporary intermediate layer 3a is used as the conductive intermediate layer 3, so that the Mn of the temporary intermediate layer 3a and the thermistor material of the thermistor substrate 2 can react at a high temperature during firing to form the conductive intermediate layer 3 of a composite oxide containing Mn.

[0086] Furthermore, since the dispersion containing Mn also contains Y, the conductive intermediate layer 3 of a composite oxide obtained by the reaction of Mn and Y can be obtained during firing.

[0087] Moreover, since the Mn-containing dispersion also contains one or more of Ca, Sr, Ba and La, Mn and one or more of Ca, Sr, Ba and La or Mn, Y and one or more of Ca, Sr, Ba and La can react and sinter simultaneously during sintering, or a conductive intermediate layer 3 of a composite oxide obtained by sintering composite oxide particles of Mn and one or more of Ca, Sr, Ba and La or Mn, Y and one or more of Ca, Sr, Ba and La can be obtained.

[0088] In another method for manufacturing thermistor element 1 of the present embodiment, in the intermediate layer electrode layer forming step, a Mn-containing Pt paste 3b containing Mn and Pt is applied to the thermistor substrate 2, and the Mn-containing Pt paste 3b is fired to form a conductive intermediate layer 3 and an electrode layer 4. Therefore, Mn in the Mn-containing Pt paste 3b can be diffused toward the thermistor substrate 2 side at a high temperature during firing to form a conductive intermediate layer 3, and the remaining Pt forms the electrode layer 4.

[0089] Example

[0090] <Example 1>

[0091] First, a substrate consisting of commercially available yttrium oxide (Y2O3), chromium oxide (Cr2O3) and manganese carbonate (MnCO3) and calcium carbonate (CaCO3) as a sintering promoter and electrical property adjuster are used as starting materials, and each material is weighed in a manner such that the molar ratio of Y:Cr:Mn:Ca becomes 79.5:8.5:8.5:3.5. After mixing and drying these weighed materials in a wet ball mill and temporarily sintering them at 1000°C for 5 hours, polyvinyl alcohol as a binder is added and mixed so that the powder is 1.5wt.%. The powder is formed into a plate with a thickness of 1mm by uniaxial pressure molding. The plate obtained by sintering it at 1500°C for 24 hours is double-sided polished to produce a wafer with a thickness of 0.4mm that becomes the thermistor substrate.

[0092] Secondly, as a conductive intermediate layer material, each material is weighed in such a way that the molar ratio of Y:La:Sr:Mn becomes 3:6:1:10, and is fired at 1200°C for 5 hours. After the obtained powder is coarsely crushed in a mortar, SC-0505K manufactured by NOFCORPORATION is used as a dispersant, and a 20wt.% ethanol dispersion (containing Mn) is prepared by a paint stirrer. The dispersion is applied to both sides of the produced wafer by deep coating, and dried to form a conductive intermediate layer. In addition, the conductive intermediate layer becomes a composite oxide of Mn, Y, La, and Sr. Thereafter, Pt paste is applied by printing, and fired at 1300°C to form an electrode layer. Moreover, a 0.5mm×0.5mm chip-shaped thermistor element is obtained by cutting.

[0093] In Example 1, 3CV (coefficient of variation) indicating the deviation of the resistance values ​​of 20 thermistor elements measured at 25° C. was 4.4%. As a result of observing the cross section of the thermistor element using TEM-EDS, an average conductive intermediate layer of 0.1 μm was observed in five observed fields of view, and the composition was Mn: 48 at.%, Y: 17 at.%, La: 31 at.%, and Sr: 5 at.%.

[0094] <Example 2>

[0095] On both sides of the wafer (thermistor substrate) prepared in Example 1, a Pt paste (Pt paste containing Mn) obtained by adding 5 wt.% of Mn2O3 to Pt (platinum) was applied by printing, and the electrode layer and the conductive intermediate layer were formed by firing at 1400°C. In addition, the conductive intermediate layer became a composite oxide containing elements Y and Ca diffused from the thermistor substrate in addition to Mn. Thereafter, a 0.5 mm×0.5 mm chip-shaped thermistor element was obtained by dicing.

[0096] In Example 2, 3CV, which indicates the variation in resistance values ​​of 20 thermistor elements measured at 25° C., was 4.9%. When the element cross section was observed using TEM-EDS, a conductive intermediate layer of 3 μm on average was observed in five observed fields of view, and the composition was Mn: 44 at.%, Y: 54 at.%, and Ca: 2 at.%.

[0097] <Example 3>

[0098] A substrate consisting of commercially available lanthanum oxide (La2O3), chromium oxide (Cr2O3) and manganese carbonate (MnCO3) and calcium carbonate (CaCO3) as a sintering accelerator and electrical property adjuster are used as starting materials, and each material is weighed in a manner that the molar ratio of La:Cr:Mn:Ca becomes 7:6:4:3. The weighed materials are mixed and dried in a wet ball mill and then temporarily calcined at 1300°C for 5 hours. Since La2O3 reacts with moisture in the atmosphere and easily changes into hydroxide, it is weighed within 3 hours after heating at 1000°C for 2 hours. After the powder after temporary calcination is coarsely crushed in a mortar, for commercially available yttrium oxide (Y2O3), Y is weighed in a manner that is twice the amount of La in terms of molar ratio and mixed with a wet ball mill. Thereafter, it is dried, and polyvinyl alcohol as a binder is added and mixed so that the powder is 1.5wt.%. The powder is formed into a plate with a thickness of 1mm by uniaxial press molding. The plate obtained by sintering at 1600° C. for 24 hours was double-sided polished to produce a wafer having a thickness of 0.4 mm, which would serve as a thermistor base.

[0099] Secondly, as a conductive intermediate layer material, each material is weighed in a manner such that the molar ratio of Y:La:Ca:Mn becomes 1:7:2:10, and is fired at 1200°C for 5 hours. After the obtained powder is coarsely crushed in a mortar, SC-0505K manufactured by NOFCORPORATION is used as a dispersant, and a 20wt.% ethanol dispersion (dispersion containing Mn) is prepared by a paint stirrer. The dispersion is applied to both sides of the produced wafer (thermistor substrate) by dip coating, and dried to form a conductive intermediate layer. In addition, the conductive intermediate layer becomes a composite oxide of Mn, Y, La, and Ca. Thereafter, Pt paste is applied by printing, and fired at 1300°C to form an electrode layer. And, a 0.5mm×0.5mm chip-shaped thermistor element is obtained by cutting.

[0100] In Example 3, 3CV, which indicates the variation in resistance values ​​of 20 thermistor elements measured at 25° C., was 1.3%. When the element cross section was observed using TEM-EDS, an intermediate layer with an average thickness of 1.2 μm was observed in five observed fields of view, and the composition was Mn: 50 at.%, Y: 6 at.%, La: 35 at.%, and Ca: 9 at.%.

[0101] <Example 4>

[0102] On both sides of the wafer (thermistor substrate) prepared in Example 3, a Pt paste (Pt paste containing Mn) obtained by adding 1wt.% of Mn2O3 to Pt was applied by printing, and the electrode layer was formed by firing at 1300°C, and a conductive intermediate layer was formed. In addition, the conductive intermediate layer became a composite oxide containing elements Y, La, and Ca diffused from the thermistor substrate in addition to Mn. Thereafter, a 0.5mm×0.5mm chip-shaped thermistor element was obtained by dicing.

[0103] In Example 4, 3CV indicating the variation in resistance values ​​of 20 thermistor elements measured at 25° C. was 3.8%. When the element cross section was observed using TEM-EDS, an average conductive intermediate layer of 0.5 μm was observed in five observed fields of view, and the composition was Mn: 47 at.%, Y: 52 at.%, and La: 1 at.%.

[0104] In this Example 4, a SEM image showing a cross section of the thermistor element is shown in FIG. Figure 4 .

[0105] Furthermore, the composition distribution images of La, Y, Mn, and Ca in the cross section of the thermistor element in Example 4 are shown in FIG. Figures 5 to 8 .

[0106] <Example 5>

[0107] On both sides of the wafer produced in Example 3, a Pt paste (Pt paste containing Mn) obtained by adding 1wt.% Mn2O3 to Pt was applied by printing, and the electrode layer was formed by firing at 1400°C. The conductive intermediate layer was formed into a composite oxide containing elements Y, La, and Ca diffused from the thermistor matrix in addition to Mn. Thereafter, a 0.5mm×0.5mm chip-shaped thermistor element was obtained by dicing.

[0108] In Example 5, 3CV indicating the variation of the resistance values ​​of 20 thermistor elements measured at 25° C. was 2.5%. When the element cross section was observed using TEM-EDS, an intermediate layer of 0.7 μm on average was observed in five observed fields of view, and the composition was Mn: 43 at.%, Y: 46 at.%, La: 6 at.%, Ca: 1 at.%, and Cr: 4 at.%.

[0109] In this Example 5, a SEM image showing a cross section of the thermistor element is shown in FIG. Fig. 9 .

[0110] Furthermore, the composition distribution images of Mn, La, Y, and Ca in the cross section of the thermistor element in Example 5 are shown in FIG. Figure 10 to Figure 13 .

[0111] <Example 6>

[0112] As a conductive intermediate layer material, each material is weighed in such a way that the molar ratio of Y:La:Ba:Mn becomes 2:7:1:10, and is fired at 1200°C for 5 hours. After the obtained powder is coarsely crushed in a mortar, SC-0505K manufactured by NOF CORPORATION is used as a dispersant, and a 20wt.% ethanol dispersion (containing Mn) is prepared by a paint stirrer. The dispersion is applied to both sides of the wafer prepared in Example 3 by dip coating, and dried to form a conductive intermediate layer. In addition, the conductive intermediate layer becomes a composite oxide of Mn, Y, La, and Ca. Thereafter, Pt paste is applied by printing, and fired at 1300°C to form an electrode layer. And, thereafter, a 0.5mm×0.5mm chip-shaped thermistor element is obtained by cutting.

[0113] In Example 6, 3CV indicating the variation in resistance values ​​of 20 thermistor elements measured at 25° C. was 1.8%. When the element cross section was observed using TEM-EDS, an intermediate layer of 0.8 μm on average was observed in five observed fields of view, and the composition was Mn: 48 at.%, Y: 11 at.%, La: 34 at.%, Ba: 4 at.%, and Cr: 4 at.%.

[0114] <Comparative Example 1>

[0115] A thermistor element was produced in the same manner as in Example 1, except that no intermediate layer was formed on the wafer (thermistor substrate) produced in Example 1.

[0116] In Comparative Example 1, 3CV indicating the variation in resistance values ​​of 20 thermistor chips measured at 25° C. was 7.8%.

[0117] Table 1 shows the results of evaluation of the intermediate layer composition, the intermediate layer formation method, and the resistance value variation (3CV) of each of these examples and comparative examples of the present invention.

[0118] [Table 1]

[0119]

[0120] From these evaluation results, it can be seen that in Comparative Example 1, the resistance value deviation (3CV) is large, 7.8%, while the resistance value deviation (3CV) of the examples of the present invention is small, 4.9% or less. As can be seen, in the examples of the present invention, Pt paste or Pt paste containing Mn can be sintered, and the adhesion of the conductive intermediate layer is improved to have high conductivity.

[0121] In Examples 2, 4, and 5, the conductive intermediate layer composition contains Y, La, and Ca. This is because Y, La, and Ca thermally diffuse from the thermistor base to the conductive intermediate layer during firing.

[0122] The technical scope of the present invention is not limited to the above-described embodiment and examples, and various modifications can be made without departing from the gist of the present invention.

[0123] Explanation of symbols

[0124] 1-thermistor element; 2-thermistor substrate; 3-conductive intermediate layer; 3a-temporary intermediate layer; 4-electrode layer; 4a-Pt paste; 4b-Pt paste containing Mn.

Claims

1. A thermistor element, characterized in that: have: A thermistor substrate comprising an oxide thermistor material having a perovskite-type crystal structure; a conductive intermediate layer formed on the thermistor substrate; and an electrode layer formed on the conductive intermediate layer, The conductive intermediate layer is a composite oxide containing Mn.

2. The thermistor element according to claim 1, characterized in that: The composite oxide further contains Y.

3. The thermistor element according to claim 1, characterized in that: The composite oxide further includes one or two or more of Ca, Sr, Ba and La.

4. The thermistor element according to claim 1, characterized in that: The electrode layer contains Pt.

5. The thermistor element according to claim 1, characterized in that: The content ratio of the Mn in the conductive intermediate layer to all metal atoms in the conductive intermediate layer is denoted as C Mn When 0at.%<C Mn ≤60at.%.

6. The thermistor element according to claim 2, characterized in that: The content ratio of Y in the conductive intermediate layer relative to all metal atoms in the conductive intermediate layer is denoted as C. Y When 0at.%<C Y ≤60at.%.

7. The thermistor element according to claim 3, characterized in that: The conductive intermediate layer contains one or two or more of Ca, Sr, Ba and La in an amount of 0.1 at. % or more relative to all metal atoms.

8. A method for manufacturing a thermistor element, characterized in that: include: An intermediate layer forming step of forming a conductive intermediate layer containing a composite oxide of Mn on a thermistor substrate containing a thermistor material having a perovskite crystal structure; as well as an electrode layer forming step of forming an electrode layer on the conductive intermediate layer, In the intermediate layer forming step, a dispersion containing Mn is applied on the thermistor substrate, and the dispersion containing Mn is dried to form a temporary intermediate layer, wherein the dispersion containing Mn contains a powder containing Mn, an organic solvent, and a dispersant. In the electrode layer forming step, a Pt paste containing Pt is applied on the temporary intermediate layer, and the Pt paste is fired to form the electrode layer, and the temporary intermediate layer serves as the conductive intermediate layer.

9. The method for manufacturing a thermistor element according to claim 8, characterized in that: The Mn-containing dispersion further contains Y.

10. The method for manufacturing a thermistor element according to claim 8, characterized in that: The Mn-containing dispersion further includes one or more of Ca, Sr, Ba and La.

11. A method for manufacturing a thermistor element, characterized in that: include: The intermediate electrode layer forming step is to form a conductive intermediate layer containing a composite oxide of Mn on a thermistor substrate containing a thermistor material having a perovskite crystal structure, and to form an electrode layer on the conductive intermediate layer. In the intermediate electrode layer forming step, a Mn-containing Pt paste containing Mn and Pt is applied on the thermistor substrate, and the Mn-containing Pt paste is fired to form the conductive intermediate layer and the electrode layer.

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