WO2012111386A1 - Positive temperature-coefficient thermistor - Google Patents

Positive temperature-coefficient thermistor Download PDF

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Publication number
WO2012111386A1
WO2012111386A1 PCT/JP2012/051332 JP2012051332W WO2012111386A1 WO 2012111386 A1 WO2012111386 A1 WO 2012111386A1 JP 2012051332 W JP2012051332 W JP 2012051332W WO 2012111386 A1 WO2012111386 A1 WO 2012111386A1
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thick film
thermistor
ceramic
positive temperature
temperature coefficient
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PCT/JP2012/051332
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French (fr)
Japanese (ja)
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朗人 内藤
新見　秀明
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株式会社村田製作所
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
    • H01C7/022—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient mainly consisting of non-metallic substances
    • H01C7/023—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient mainly consisting of non-metallic substances containing oxides or oxidic compounds, e.g. ferrites
    • H01C7/025—Perovskites, e.g. titanates
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
    • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
    • C04B35/465—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates
    • C04B35/468—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates
    • C04B35/4682—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates based on BaTiO3 perovskite phase
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
    • H01C1/1406—Terminals or electrodes formed on resistive elements having positive temperature coefficient
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
    • H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
    • H05B3/141—Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds
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    • C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
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Definitions

  • the present invention relates to a positive temperature coefficient thermistor, and more particularly to a positive temperature coefficient thermistor suitable for use as a heating element through which a large current flows.
  • a thermistor composed of a semiconductor ceramic having a positive resistance temperature characteristic (PTC characteristic), that is, a positive temperature coefficient thermistor is widely used as a heating element, for example.
  • a heating element using a positive temperature coefficient thermistor is advantageous in that it has a self-control function and thus does not require an external control circuit.
  • a positive temperature coefficient thermistor used as a heating element is usually provided with an element body made of a single-plate-shaped semiconductor ceramic obtained by pressure-molding and firing a barium titanate-based semiconductor powder.
  • the semiconductor ceramic exhibiting the thermistor characteristics is preferably in the form of a film.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 55-130101
  • Patent Document 2 Japanese Patent Application Laid-Open No. 61-101007
  • Patent Document 1 Ni, Al and / or RuO 2 powder and glass frit are added to barium titanate semiconductor ceramic powder, and a paste-like mixture using an organic binder is applied onto an insulating substrate.
  • a thick film type positive characteristic semiconductor element obtained by firing at 600 to 1000 ° C. after being formed into a thick film is described.
  • the area resistance at room temperature of the obtained thick film type positive characteristic semiconductor element is in the range of 150 to 700 ⁇ / cm 2 .
  • the resistivity is 15 k ⁇ ⁇ cm to 70 k ⁇ ⁇ cm, which is a considerably high resistivity.
  • the thickness is less than 0.1 mm, a higher resistivity is exhibited.
  • Patent Document 1 suggests that the sheet resistance can be controlled by changing the addition amount of the conductive particles.
  • the addition amount of the conductive particles is variable. The range is limited. Therefore, the suppression of resistivity by increasing the amount of conductive particles added cannot be expected so much.
  • Patent Document 2 Ti 2 B is added to a BaTiO 3 based semiconductor ceramic powder in an amount of 1 to 60% by weight based on the total weight, and a paste-like mixture is applied onto a substrate to obtain a thickness.
  • a thick film type positive characteristic semiconductor element obtained by firing after forming into a film is described.
  • Patent Document 2 since Ti 2 B serves as a conductive particle and at the same time generates a liquid phase of B 2 O 3 at a high temperature, adhesion between BaTiO 3 particles and Ti 2 B particles is prevented. It is possible. Therefore, like the one described in Patent Document 1, according to the thick film type positive characteristic semiconductor element described in Patent Document 2, BaTiO 3 particles and Ti 2 B particles are not sintered but simply B 2. Since it is only a state pasted with O 3 phase, only a very high resistivity can be obtained, and a large current cannot be applied.
  • Example 2 described in Patent Document 2 it is disclosed that the area resistance at room temperature is 1.3 k ⁇ / cm 2. From this area resistance 1.3 k ⁇ / cm 2 , the thickness is When calculated at 0.1 mm, only a very high resistivity thick film of 130 k ⁇ ⁇ cm is obtained.
  • Patent Document 3 a semiconductor ceramic element used not as a film-like heating element but as a single-plate heating element is described in, for example, Japanese Patent Application Laid-Open No. 11-246268 (Patent Document 3).
  • Patent Document 3 contains a boron oxide in a barium titanate-based semiconductor sintered body, and an oxide composed of at least one selected from barium, strontium, calcium, yttrium, and a rare earth element.
  • boron element (assumed to be B) is in an atomic ratio of 0.005 ⁇ B / ⁇ ⁇ 0.50, 1 ⁇ B / ( ⁇ ) ⁇ 4 (where ⁇ is in the semiconductor ceramic)
  • the total amount of barium, strontium, calcium, yttrium, and rare earth elements contained in the semiconductor; ⁇ : the total amount of titanium, tin, zirconium, niobium, tungsten, and antimony contained in the semiconductor ceramic) is disclosed. Has been.
  • Patent Document 3 discloses a single-plate semiconductor ceramic element obtained by firing at a temperature of 1000 ° C. or lower.
  • Patent Document 3 only discloses a single-plate semiconductor ceramic element, and does not disclose any film-like heating element. That is, Patent Document 3 does not demonstrate whether a thick film can be sintered after forming a thick film serving as a heating element on an insulating ceramic substrate such as an alumina substrate.
  • the thick film as a sintered body can have low resistance, or no peeling or the like occurs between the insulator ceramic substrate and high
  • adhesion can be secured.
  • JP-A-55-130101 JP-A-61-101007 Japanese Patent Laid-Open No. 11-246268
  • an object of the present invention is to achieve a low resistance while having a form in which a thick film serving as a heat source is formed on an insulating ceramic substrate, and thus it is possible to energize a large current.
  • An object of the present invention is to provide a positive temperature coefficient thermistor having excellent adhesion between a ceramic substrate and a thick film.
  • the present invention has been made by paying attention to the fact that the semiconductor ceramic described in Patent Document 3 can be sintered at a temperature of about 1000 ° C. or lower.
  • a positive temperature coefficient thermistor according to the present invention is in contact with an insulating ceramic substrate, a thermistor thick film having a positive resistance temperature characteristic formed of a semiconductor ceramic sintered body formed on the insulating ceramic substrate, and the thermistor thick film. And at least one pair of electrodes facing each other with at least a portion of the thermistor thick film interposed therebetween, and the resistivity of the thermistor thick film at room temperature is less than 10 k ⁇ ⁇ cm.
  • the thermistor thick film includes ABO 3 (A always contains barium and may further contain at least one selected from strontium, calcium, lead and rare earth elements. B necessarily contains titanium, and further includes tin, zirconium.
  • a sintered body of a semiconductor ceramic comprising as a main component a barium titanate system represented by (ii) niobium, tungsten and antimony), and containing at least boron element as a subcomponent,
  • the A content is ⁇ in atomic ratio
  • the B content is ⁇ in atomic ratio
  • the boron element content is y in atomic ratio, 0.05 ⁇ y / ⁇ ⁇ 1.5, and 1 ⁇ y / ( ⁇ ) ⁇ 4
  • ⁇ is the total amount of all elements that can be Ba sites contained in the barium titanate (BaTiO 3 ) -based semiconductor ceramic, that is, the Ba sites of BaTiO 3 and .
  • the molar ratio of Ba and Ti is the sum of the oxides present as an excess of the Ba site in order to obtain BaTiO 3 having a non-stoichiometric ratio.
  • the content ⁇ of B is the total amount of all elements that can be Ti sites contained in the semiconductor ceramic, that is, the sum of the Ti sites of BaTiO 3 and the oxides present as the excess Ti sites.
  • the thickness of the thermistor thick film is t and the average particle diameter of crystals in the sintered ceramic of the semiconductor ceramic constituting the thermistor thick film is ⁇
  • the condition of t / ⁇ ⁇ 10 It is preferable to satisfy.
  • the insulator ceramic substrate is preferably an alumina substrate.
  • a positive temperature coefficient thermistor having a structure in which a thermistor thick film made of a semiconductor ceramic sintered body is formed on an insulating ceramic substrate, that is, a form suitable as a heating element for large current.
  • the semiconductor ceramic constituting the thermistor thick film is in a state where the crystal grains are in surface contact with each other by sintering, the contact area between the grains can be widened. Therefore, the resistance can be reduced as compared with the case where the semiconductor powder particles and the conductive particles are simply glued so as to be in point contact, as in the above-described Patent Documents 1 and 2. it can.
  • the semiconductor ceramic constituting the thermistor thick film can be sintered at a temperature of about 1000 ° C. or lower.
  • a positive temperature coefficient thermistor having a structure in which a thermistor thick film made of a sintered body is formed on an insulating ceramic substrate, that is, a form suitable as a heating element for large current can be realized.
  • the thickness t of the thermistor thick film and the average particle diameter ⁇ of the crystals in the sintered ceramic of the semiconductor ceramic constituting the thermistor thick film satisfy the condition of t / ⁇ ⁇ 10. Then, as will be clarified by an experimental example described later, the resistance can be further increased. This is because by setting t / ⁇ ⁇ 10 so that more crystal grains exist in the thermistor thick film, the number of contacts between the crystal grains increases, which contributes to the reduction in resistance. Presumed to be.
  • FIG. 2 is an enlarged sectional view taken along line II-II in FIG. It is a top view which shows the positive temperature coefficient thermistor 11 as a sample produced in the experiment example.
  • a positive temperature coefficient thermistor 1 according to an embodiment of the present invention will be described with reference to FIGS.
  • the positive temperature coefficient thermistor 1 is, for example, an insulating ceramic substrate 2 made of alumina, a thermistor thick film 3 having PTC characteristics formed on the insulating ceramic substrate 2, and in contact with the thermistor thick film 3 and the thermistor thick film 3 And at least one pair of electrodes 4 and 5 which are opposed to each other with at least a part thereof. Further, although not shown, a protective film may be formed on the insulator ceramic substrate 2 so as to cover the thermistor thick film 3 and the electrodes 4 and 5.
  • the thermistor thick film 3 is preferably ABO 3 (A necessarily contains barium and may further contain at least one selected from strontium, calcium, lead and rare earth elements. B necessarily contains titanium, and A sintered body of a semiconductor ceramic containing a barium titanate system as a main component and a subcomponent containing at least a boron element. Consists of. Boron element acts to enable low temperature firing.
  • ABO 3 A necessarily contains barium and may further contain at least one selected from strontium, calcium, lead and rare earth elements.
  • B necessarily contains titanium
  • the content of A is ⁇ by atomic ratio
  • the content of B is ⁇ by atomic ratio
  • the content of boron element is y by atomic ratio, 0.05 ⁇ y / ⁇ ⁇ 1.5, and 1 ⁇ y / ( ⁇ ) ⁇ 4
  • the thermistor thick film 3 can be satisfactorily sintered on the insulator ceramic substrate 2, and a low resistivity of, for example, less than 10 k ⁇ ⁇ cm can be realized at room temperature. Further, high adhesion can be obtained between the insulator ceramic substrate 2 and the thermistor thick film 3.
  • the thermistor thick film 3 after firing has poor adhesion to the insulator ceramic substrate 2 and may peel off after firing.
  • y / ⁇ exceeds 1.5, As a result, a large amount of insulating B—Ba—O-based liquid phase component is generated, and the thermistor thick film 3 is increased in resistance.
  • the thermistor thick film 3 is not sintered by firing at a temperature of about 1000 ° C. or lower. Although it is possible to sinter at a higher temperature, in this case, as described above, a reaction with the insulator ceramic substrate 2 occurs, and the resistance of the thermistor thick film 3 as a sintered film is increased. It is fully predicted.
  • the boron element contained in the semiconductor ceramic having the above-described composition exists in the form of an oxide represented by B 2 BaO 4 or B 2 O 3 dissolved in a main component represented by a BaTiO 3 ceramic. As long as it contains a boron element, it is not limited to the above form.
  • the thermistor thick film 3 has a thickness of 1 ⁇ m or more, for example.
  • a semiconductor ceramic paste formed by mixing semiconductor ceramic powder with varnish is prepared, and this semiconductor ceramic paste is applied on the insulator ceramic substrate 2, or the insulator ceramic substrate 2.
  • the baking process may be performed after applying the doctor blade method or the like to form a sheet.
  • T / ⁇ ⁇ 10 is preferably satisfied. Therefore, for example, the calcination temperature in the calcination step and / or the calcination temperature in the calcination step for obtaining a semiconductor ceramic are changed, or the thickness of the thermistor thick film 3 is adjusted.
  • the average particle diameter ⁇ is based on a value obtained by ASTM (intersection point cutting method).
  • the electrodes 4 and 5 have a portion located on the thermistor thick film 3 as well shown in FIG. As shown well in FIG. 1, the first electrode 4 is formed along the longitudinal direction of the thermistor thick film 3 having a rectangular planar shape. On the other hand, the second electrode 5 is positioned so as to face the first electrode 4 with a predetermined distance from the first electrode 4. Further, the electrodes 4 and 5 respectively form wide lead portions 6 and 7 at respective end portions, and these lead portions 6 and 7 are located on one end side of the insulating ceramic substrate 2. .
  • the electrodes 4 and 5 are made of a material capable of making ohmic contact with the thermistor thick film 3.
  • a material of the electrodes 4 and 5 for example, a base metal such as Ni, Cu, or Al or an alloy thereof, or ohmic Ag that is ohmicized by addition of a base metal is used.
  • a thin film forming method such as sputtering or vapor deposition, or a thick film method in which a conductive paste is applied and baked can be applied.
  • the positive temperature coefficient thermistor 1 shown in FIG. 1 has a structure in which a thermistor thick film 3 is formed in a long pattern on an elongated ceramic substrate 2 (that is, a large aspect ratio). have. For this reason, there is a problem that peeling is likely to occur between the insulator ceramic substrate 2 and the thermistor thick film 3 due to differences in the respective linear expansion coefficients.
  • the present invention it is possible to ensure high adhesion between the insulating ceramic substrate 2 and the thermistor thick film 3, and thus it is possible to prevent peeling. Accordingly, the present invention becomes more significant particularly when the positive temperature coefficient thermistor has a form in which a long thermistor thick film is formed on a long insulator ceramic substrate as shown in FIG.
  • varnish is added to the above mixture to form a paste, which is then coated on an alumina substrate and baked at a temperature of 1050 ° C. for 2 hours to form a thermistor thick film made of a sintered ceramic ceramic having the following composition Obtained.
  • a pair of electrodes 14 is formed on the alumina substrate 12 so as to cover each end of the thermistor thick film 13 formed on the alumina substrate 12. And a positive temperature coefficient thermistor 11 as a sample was obtained.
  • ⁇ indicates the content of the A site element (here, Ba and Sm) in the BaTiO 3 series compound represented by ABO 3 in terms of atomic ratio
  • ⁇ is also the B site.
  • the content of the element (here, Ti) is indicated by an atomic ratio
  • “y” indicates the content of the added boron element B by an atomic ratio, as can be seen from the above-described composition formula. Is.
  • Table 1 various "y / beta” and shown in obtaining the “y / ( ⁇ - ⁇ )", as described above, (Ba 0.998 Sm 0.002) BaCO 3 added to TiO 3 The amount x and the BN amount y were changed, thereby adjusting by changing the BaO amount and the B 2 O 3 amount.
  • room temperature resistivity was measured for each of the obtained samples.
  • Room temperature resistivity is measured by the two-terminal method when a DC voltage of 1 V is applied at a room temperature of 25 ° C.
  • room temperature resistivity when it was 10 k ⁇ ⁇ cm or more, it was determined to be defective.
  • the “room temperature resistivity” can be lowered to less than 10 k ⁇ ⁇ cm.
  • the thermistor thick film does not peel off from the alumina substrate and can sufficiently function as a thick film type positive temperature coefficient thermistor.
  • the same result was obtained even when a part of Ti at the B site of ABO 3 , that is, the Ti site was replaced with at least one selected from Sn, Zr, Nb, W and Sb. It has been confirmed that it can be obtained.

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Abstract

The present invention enables the passage of a large current and increases the adhesiveness of a thermistor thick film in a positive temperature-coefficient thermistor having an embodiment wherein the thermistor thick film that is a heat source is formed on an insulating ceramic substrate. The positive temperature-coefficient thermistor (1) is provided with: an insulating ceramic substrate (2); a thermistor thick film (3) exhibiting PTC characteristics, comprising a semiconductor ceramic sintered body, and formed on the insulating ceramic substrate (2); and a pair of electrodes (4, 5) that face each other sandwiching at least a portion of the thermistor thick film (3). The electrical resistivity at room temperature of the thermistor thick film (3) is less than 10 kΩ·cm.

Description

正特性サーミスタPositive temperature coefficient thermistor
　この発明は、正特性サーミスタに関するもので、特に、大電流が流れる発熱体としての用途に適した正特性サーミスタに関するものである。 The present invention relates to a positive temperature coefficient thermistor, and more particularly to a positive temperature coefficient thermistor suitable for use as a heating element through which a large current flows.
　正の抵抗温度特性（ＰＴＣ特性）を有する半導体セラミックをもって構成されたサーミスタ、すなわち正特性サーミスタは、たとえば発熱体として広く利用されている。正特性サーミスタを利用した発熱体は、自己制御機能を有し、よって外部の制御回路を必要としない点で有利である。 A thermistor composed of a semiconductor ceramic having a positive resistance temperature characteristic (PTC characteristic), that is, a positive temperature coefficient thermistor is widely used as a heating element, for example. A heating element using a positive temperature coefficient thermistor is advantageous in that it has a self-control function and thus does not require an external control circuit.
　発熱体として用いられる正特性サーミスタは、通常、チタン酸バリウム系半導体粉末を加圧成形した後、焼成することによって得られた、単板形状の半導体セラミックからなる素子本体を備えている。しかし、正特性サーミスタが大面積の発熱体として用いられる場合には、サーミスタ特性を示す半導体セラミックは膜状の形態とされることが好ましい。 A positive temperature coefficient thermistor used as a heating element is usually provided with an element body made of a single-plate-shaped semiconductor ceramic obtained by pressure-molding and firing a barium titanate-based semiconductor powder. However, when the positive temperature coefficient thermistor is used as a large-area heating element, the semiconductor ceramic exhibiting the thermistor characteristics is preferably in the form of a film.
　このような膜状の発熱源を有する半導体素子としては、たとえば、特開昭５５－１３０１０１号公報（特許文献１）または特開昭６１－１０１００７号公報（特許文献２）に記載されたものがある。 As the semiconductor element having such a film-like heat generation source, for example, those described in Japanese Patent Application Laid-Open No. 55-130101 (Patent Document 1) or Japanese Patent Application Laid-Open No. 61-101007 (Patent Document 2). is there.
　特許文献１には、チタン酸バリウム系半導体セラミック粉末に、Ｎｉ、Ａｌおよび／またはＲｕＯ２粉末とガラスフリットとを加え、有機結合剤を用いてペースト状にした混合物を絶縁性基板上に塗布して厚膜状に成形した後、６００～１０００℃で焼成することによって得られた、厚膜型正特性半導体素子が記載されている。 In Patent Document 1, Ni, Al and / or RuO 2 powder and glass frit are added to barium titanate semiconductor ceramic powder, and a paste-like mixture using an organic binder is applied onto an insulating substrate. A thick film type positive characteristic semiconductor element obtained by firing at 600 to 1000 ° C. after being formed into a thick film is described.
　しかしながら、特許文献１に記載の厚膜型正特性半導体素子では、チタン酸バリウム系半導体セラミック粉末粒子とＮｉ粉末等の導電性粒子とは、焼結するのではなく、単にガラスで糊付けされた状態にすぎないため、個々の粒子の結合が点接触となり、低抵抗化が困難である。このため、発熱体などに使用される場合において、大電流を通電できず、極めて狭い範囲での実用化しかできない。 However, in the thick film type positive characteristic semiconductor element described in Patent Document 1, the barium titanate-based semiconductor ceramic powder particles and the conductive particles such as Ni powder are not sintered but are simply glued with glass. Therefore, the bonding of individual particles becomes point contact, and it is difficult to reduce resistance. For this reason, when it is used for a heating element or the like, a large current cannot be applied, and it can only be put into practical use within an extremely narrow range.
　事実、特許文献１に記載の実施例では、得られた厚膜型正特性半導体素子の室温における面積抵抗は１５０～７００Ω／ｃｍ２の範囲にあり、同文献第３頁左上欄第１６～１７行の「厚さが０．１ｍｍ以下」という文言を根拠に、厚さ０．１ｍｍで計算すると、抵抗率が１５ｋΩ・ｃｍ～７０ｋΩ・ｃｍとなり、かなりの高抵抗率となる。ここで、もし、厚みが０．１ｍｍより薄い場合は、さらに高い抵抗率を示すことになる。 In fact, in the example described in Patent Document 1, the area resistance at room temperature of the obtained thick film type positive characteristic semiconductor element is in the range of 150 to 700 Ω / cm 2 . Based on the phrase “thickness is 0.1 mm or less” in the row, when the calculation is performed with a thickness of 0.1 mm, the resistivity is 15 kΩ · cm to 70 kΩ · cm, which is a considerably high resistivity. Here, if the thickness is less than 0.1 mm, a higher resistivity is exhibited.
　なお、特許文献１は、導電性粒子の添加量を変えることによって面積抵抗の制御が可能であることを示唆しているが、良好なＰＴＣ特性を維持するため、導電性粒子の添加量の可変範囲は限られている。よって、導電性粒子の添加量を増やすことによる抵抗率の抑制はそれほど望めない。 Note that Patent Document 1 suggests that the sheet resistance can be controlled by changing the addition amount of the conductive particles. However, in order to maintain good PTC characteristics, the addition amount of the conductive particles is variable. The range is limited. Therefore, the suppression of resistivity by increasing the amount of conductive particles added cannot be expected so much.
　次に、特許文献２には、ＢａＴｉＯ３系半導体セラミック粉末に、Ｔｉ２Ｂをその混合量が全重量に対して１～６０重量％加え、ペースト状にした混合物を基板上に塗布して厚膜状とした後、焼成することによって得られた、厚膜型正特性半導体素子が記載されている。 Next, in Patent Document 2, Ti 2 B is added to a BaTiO 3 based semiconductor ceramic powder in an amount of 1 to 60% by weight based on the total weight, and a paste-like mixture is applied onto a substrate to obtain a thickness. A thick film type positive characteristic semiconductor element obtained by firing after forming into a film is described.
　特許文献２の記載に従えば、Ｔｉ２Ｂが導電性粒子としての役目を果たすと同時に、高温でＢ２Ｏ３の液相を生成するため、ＢａＴｉＯ３粒子とＴｉ２Ｂ粒子との接着が可能であるとしている。したがって、上記特許文献１に記載のものと同様、特許文献２に記載の厚膜型正特性半導体素子によれば、ＢａＴｉＯ３粒子およびＴｉ２Ｂ粒子は、焼結するのではなく、単にＢ２Ｏ３相で糊付けされた状態にすぎないため、極めて高い抵抗率しか得られず、大電流を通電することができない。 According to the description in Patent Document 2, since Ti 2 B serves as a conductive particle and at the same time generates a liquid phase of B 2 O 3 at a high temperature, adhesion between BaTiO 3 particles and Ti 2 B particles is prevented. It is possible. Therefore, like the one described in Patent Document 1, according to the thick film type positive characteristic semiconductor element described in Patent Document 2, BaTiO 3 particles and Ti 2 B particles are not sintered but simply B 2. Since it is only a state pasted with O 3 phase, only a very high resistivity can be obtained, and a large current cannot be applied.
　すなわち、特許文献２に記載の実施例２について検証すると、実施例２では、室温での面積抵抗が１．３ｋΩ／ｃｍ２であると開示され、この面積抵抗１．３ｋΩ／ｃｍ２から、厚み０．１ｍｍで計算すると、やはり１３０ｋΩ・ｃｍといった極めて高抵抗率の厚膜しか得られていない。 That is, when Example 2 described in Patent Document 2 is verified, in Example 2, it is disclosed that the area resistance at room temperature is 1.3 kΩ / cm 2. From this area resistance 1.3 kΩ / cm 2 , the thickness is When calculated at 0.1 mm, only a very high resistivity thick film of 130 kΩ · cm is obtained.
　他方、膜状の発熱体ではなく、単板形状の発熱体として用いられる半導体セラミック素子が、たとえば特開平１１－２４６２６８号公報（特許文献３）に記載されている。 On the other hand, a semiconductor ceramic element used not as a film-like heating element but as a single-plate heating element is described in, for example, Japanese Patent Application Laid-Open No. 11-246268 (Patent Document 3).
　特許文献３には、チタン酸バリウム系の半導体焼結体中に、ホウ素酸化物を含有し、バリウム、ストロンチウム、カルシウム、イットリウム、希土類元素の中から選ばれる少なくとも１種類からなる酸化物を含有しした半導体セラミックであって、ホウ素元素（Ｂとする）が原子比で、０．００５≦Ｂ／β≦０．５０、１≦Ｂ／（α－β）≦４（ただし、α：半導体セラミック中に含まれるバリウム、ストロンチウム、カルシウム、イットリウム、希土類元素の総量；β：半導体セラミック中に含まれるチタン、錫、ジルコニウム、ニオブ、タングステン、アンチモンの総量）となるように添加されている半導体セラミックが開示されている。 Patent Document 3 contains a boron oxide in a barium titanate-based semiconductor sintered body, and an oxide composed of at least one selected from barium, strontium, calcium, yttrium, and a rare earth element. In the semiconductor ceramic, boron element (assumed to be B) is in an atomic ratio of 0.005 ≦ B / β ≦ 0.50, 1 ≦ B / (α−β) ≦ 4 (where α is in the semiconductor ceramic) The total amount of barium, strontium, calcium, yttrium, and rare earth elements contained in the semiconductor; β: the total amount of titanium, tin, zirconium, niobium, tungsten, and antimony contained in the semiconductor ceramic) is disclosed. Has been.
　特許文献３に記載の半導体セラミックによれば、１０００℃以下の温度での焼結が可能である。よって、特許文献３には、１０００℃以下の温度で焼成して得られた単板形状の半導体セラミック素子が開示されている。 According to the semiconductor ceramic described in Patent Document 3, sintering at a temperature of 1000 ° C. or lower is possible. Therefore, Patent Document 3 discloses a single-plate semiconductor ceramic element obtained by firing at a temperature of 1000 ° C. or lower.
　しかしながら、特許文献３では、単板形状の半導体セラミック素子が開示されているのみで、膜状の発熱体については一切開示されていない。すなわち、特許文献３では、アルミナ基板などの絶縁体セラミック基板上に発熱体となる厚膜を形成した後、この厚膜を焼結できるかどうかは実証されていない。また、半導体セラミックを絶縁体セラミック基板上において厚膜状態で焼成したとき、焼結体としての厚膜が低抵抗となり得るか、あるいは、絶縁体セラミック基板との間で剥離等が生じず、高い密着性を確保できるか、など、さらに追求すべき課題がある。 However, Patent Document 3 only discloses a single-plate semiconductor ceramic element, and does not disclose any film-like heating element. That is, Patent Document 3 does not demonstrate whether a thick film can be sintered after forming a thick film serving as a heating element on an insulating ceramic substrate such as an alumina substrate. In addition, when a semiconductor ceramic is fired in a thick film state on an insulator ceramic substrate, the thick film as a sintered body can have low resistance, or no peeling or the like occurs between the insulator ceramic substrate and high There are further issues to be pursued, such as whether adhesion can be secured.
特開昭５５－１３０１０１号公報JP-A-55-130101 特開昭６１－１０１００７号公報JP-A-61-101007 特開平１１－２４６２６８号公報Japanese Patent Laid-Open No. 11-246268
　そこで、この発明の目的は、絶縁体セラミック基板上に発熱源となる厚膜が形成された形態を有しながら、低抵抗化が図られ、よって大電流の通電が可能であり、しかも絶縁体セラミック基板と厚膜との間での密着性に優れた、正特性サーミスタを提供しようとすることである。 Accordingly, an object of the present invention is to achieve a low resistance while having a form in which a thick film serving as a heat source is formed on an insulating ceramic substrate, and thus it is possible to energize a large current. An object of the present invention is to provide a positive temperature coefficient thermistor having excellent adhesion between a ceramic substrate and a thick film.
　膜状の半導体素子を構成する場合、たとえばアルミナ基板上に半導体セラミック材料を含む厚膜を形成した後、厚膜をアルミナ基板とともに焼成することが考えられる。この場合、従来から正特性サーミスタ用として通常用いられているチタン酸バリウム系半導体セラミックは、約１３５０℃の温度で焼成されるものであるので、当然のことながら、チタン酸バリウム系半導体セラミックを焼結させるためには、約１３５０℃といった高温を付与しなければならない。しかし、焼成工程において、このような高温を適用すると、半導体セラミック材料とアルミナとの間で不所望な反応が生じ、良好な状態で厚膜型の正特性サーミスタを到底得られるような状況ではないことを、本件発明者等は見出した。 In the case of forming a film-like semiconductor element, for example, it is conceivable to form a thick film containing a semiconductor ceramic material on an alumina substrate and then to fire the thick film together with the alumina substrate. In this case, since the barium titanate-based semiconductor ceramic that has been conventionally used for a positive temperature coefficient thermistor is fired at a temperature of about 1350 ° C., naturally, the barium titanate-based semiconductor ceramic is fired. In order to bind, a high temperature of about 1350 ° C. must be applied. However, when such a high temperature is applied in the firing process, an undesired reaction occurs between the semiconductor ceramic material and alumina, and a thick film type positive temperature coefficient thermistor cannot be obtained in a good state. The present inventors have found that.
　そこで、前述の特許文献３に記載の半導体セラミックが１０００℃程度またはそれより低い温度で焼結させることができることに注目し、この発明をなすに至ったものである。 Therefore, the present invention has been made by paying attention to the fact that the semiconductor ceramic described in Patent Document 3 can be sintered at a temperature of about 1000 ° C. or lower.
　この発明に係る正特性サーミスタは、絶縁体セラミック基板と、絶縁体セラミック基板上に形成された、半導体セラミック焼結体からなる正の抵抗温度特性を示すサーミスタ厚膜と、サーミスタ厚膜に接し、かつサーミスタ厚膜の少なくとも一部を挟んで対向する、少なくとも１対の電極とを備え、サーミスタ厚膜の室温での抵抗率は１０ｋΩ・ｃｍ未満であることを特徴としている。 A positive temperature coefficient thermistor according to the present invention is in contact with an insulating ceramic substrate, a thermistor thick film having a positive resistance temperature characteristic formed of a semiconductor ceramic sintered body formed on the insulating ceramic substrate, and the thermistor thick film. And at least one pair of electrodes facing each other with at least a portion of the thermistor thick film interposed therebetween, and the resistivity of the thermistor thick film at room temperature is less than 10 kΩ · cm.
　上記サーミスタ厚膜は、ＡＢＯ３（Ａは、バリウムを必ず含み、さらにストロンチウム、カルシウム、鉛および希土類元素から選ばれる少なくとも１種を含むことがある。Ｂは、チタンを必ず含み、さらに錫、ジルコニウム、ニオブ、タングステンおよびアンチモンから選ばれる少なくとも１種を含むことがある。）で表わされるチタン酸バリウム系を主成分とし、かつ副成分として少なくともホウ素元素を含む、半導体セラミックの焼結体からなり、この半導体セラミックにおける、Ａの含有量を原子比でα、Ｂの含有量を原子比でβ、およびホウ素元素の含有量を原子比でｙとしたとき、
　０．０５≦ｙ／β≦１．５、および
　１≦ｙ／（α－β）≦４
の条件を満たす、半導体セラミック焼結体からなることが好ましい。 The thermistor thick film includes ABO 3 (A always contains barium and may further contain at least one selected from strontium, calcium, lead and rare earth elements. B necessarily contains titanium, and further includes tin, zirconium. A sintered body of a semiconductor ceramic, comprising as a main component a barium titanate system represented by (ii) niobium, tungsten and antimony), and containing at least boron element as a subcomponent, In this semiconductor ceramic, when the A content is α in atomic ratio, the B content is β in atomic ratio, and the boron element content is y in atomic ratio,
0.05 ≦ y / β ≦ 1.5, and 1 ≦ y / (α−β) ≦ 4
It is preferable that it consists of a semiconductor ceramic sintered body that satisfies the above condition.
　ここで、Ａの含有量αについて説明を加えると、αは、チタン酸バリウム（ＢａＴｉＯ３）系の半導体セラミック中に含まれるＢａサイトとなり得るすべての元素の総量、すなわち、ＢａＴｉＯ３のＢａサイトと、ＢａとＴｉのモル比が非化学量論比のＢａＴｉＯ３とするためにＢａサイト過剰分として存在する酸化物との和である。同様に、Ｂの含有量βは、半導体セラミック中に含まれるＴｉサイトとなり得るすべての元素の総量、すなわち、ＢａＴｉＯ３のＴｉサイトとＴｉサイト過剰分として存在する酸化物の和である。 Here, when the content α of A is described, α is the total amount of all elements that can be Ba sites contained in the barium titanate (BaTiO 3 ) -based semiconductor ceramic, that is, the Ba sites of BaTiO 3 and , The molar ratio of Ba and Ti is the sum of the oxides present as an excess of the Ba site in order to obtain BaTiO 3 having a non-stoichiometric ratio. Similarly, the content β of B is the total amount of all elements that can be Ti sites contained in the semiconductor ceramic, that is, the sum of the Ti sites of BaTiO 3 and the oxides present as the excess Ti sites.
　この発明に係る正特性サーミスタにおいて、サーミスタ厚膜の厚みをｔとし、サーミスタ厚膜を構成する半導体セラミックの焼結体中の結晶の平均粒子径をφとしたとき、ｔ／φ≧１０の条件を満たすことが好ましい。 In the positive temperature coefficient thermistor according to the present invention, when the thickness of the thermistor thick film is t and the average particle diameter of crystals in the sintered ceramic of the semiconductor ceramic constituting the thermistor thick film is φ, the condition of t / φ ≧ 10 It is preferable to satisfy.
　絶縁体セラミック基板はアルミナ基板であることが好ましい。 The insulator ceramic substrate is preferably an alumina substrate.
　この発明によれば、半導体セラミック焼結体からなるサーミスタ厚膜を絶縁体セラミック基板上に形成した構造、すなわち大電流用の発熱体として適した形態の正特性サーミスタを実現することができる。特に、サーミスタ厚膜を構成する半導体セラミックは、焼結により、結晶粒子同士が面接触した状態となっているので、粒子間の接触面積を広くすることができる。よって、前述の特許文献１および２に記載のもののように、半導体粉末粒子および導電性粒子が点接触するように単に糊付けされているような状態のものに比べて、低抵抗化を図ることができる。 According to the present invention, it is possible to realize a positive temperature coefficient thermistor having a structure in which a thermistor thick film made of a semiconductor ceramic sintered body is formed on an insulating ceramic substrate, that is, a form suitable as a heating element for large current. In particular, since the semiconductor ceramic constituting the thermistor thick film is in a state where the crystal grains are in surface contact with each other by sintering, the contact area between the grains can be widened. Therefore, the resistance can be reduced as compared with the case where the semiconductor powder particles and the conductive particles are simply glued so as to be in point contact, as in the above-described Patent Documents 1 and 2. it can.
　また、この発明によれば、絶縁体セラミック基板とサーミスタ厚膜との間で高い密着性を得ることができ、よって剥離等の問題を招きにくくすることができる。 In addition, according to the present invention, high adhesion can be obtained between the insulator ceramic substrate and the thermistor thick film, so that it is difficult to cause problems such as peeling.
　また、この発明に係る正特性サーミスタにおいて、上記の特定の組成を用いた場合、サーミスタ厚膜を構成する半導体セラミックが１０００℃程度またはそれより低い温度で焼結可能なものであるので、半導体セラミック焼結体からなるサーミスタ厚膜を絶縁体セラミック基板上に形成した構造、すなわち大電流用の発熱体として適した形態の正特性サーミスタを実現することができる。 In the positive temperature coefficient thermistor according to the present invention, when the above specific composition is used, the semiconductor ceramic constituting the thermistor thick film can be sintered at a temperature of about 1000 ° C. or lower. A positive temperature coefficient thermistor having a structure in which a thermistor thick film made of a sintered body is formed on an insulating ceramic substrate, that is, a form suitable as a heating element for large current can be realized.
　この発明に係る正特性サーミスタにおいて、サーミスタ厚膜の厚みｔ、およびサーミスタ厚膜を構成する半導体セラミックの焼結体中の結晶の平均粒子径φについて、ｔ／φ≧１０の条件を満たすようにすれば、後述する実験例によって明らかにされるように、より抵抗化が図られる。これは、ｔ／φ≧１０とすることによって、サーミスタ厚膜中により多くの結晶粒子が存在するようにすれば、結晶粒子間の接点数がより多くなり、このことが低抵抗化に寄与するものと推測される。 In the positive temperature coefficient thermistor according to the present invention, the thickness t of the thermistor thick film and the average particle diameter φ of the crystals in the sintered ceramic of the semiconductor ceramic constituting the thermistor thick film satisfy the condition of t / φ ≧ 10. Then, as will be clarified by an experimental example described later, the resistance can be further increased. This is because by setting t / φ ≧ 10 so that more crystal grains exist in the thermistor thick film, the number of contacts between the crystal grains increases, which contributes to the reduction in resistance. Presumed to be.
この発明の一実施形態による正特性サーミスタ１を示す平面図である。It is a top view which shows the positive temperature coefficient thermistor 1 by one Embodiment of this invention. 図１の線II－IIに沿う拡大断面図である。FIG. 2 is an enlarged sectional view taken along line II-II in FIG. 実験例において作製した試料としての正特性サーミスタ１１を示す平面図である。It is a top view which shows the positive temperature coefficient thermistor 11 as a sample produced in the experiment example.
　図１および図２を参照して、この発明の一実施形態による正特性サーミスタ１について説明する。 A positive temperature coefficient thermistor 1 according to an embodiment of the present invention will be described with reference to FIGS.
　正特性サーミスタ１は、たとえばアルミナからなる絶縁体セラミック基板２と、絶縁体セラミック基板２上に形成された、ＰＴＣ特性を示すサーミスタ厚膜３と、サーミスタ厚膜３に接し、かつサーミスタ厚膜３の少なくとも一部を挟んで対向する、少なくとも１対の電極４および５とを備えている。さらに、図示しないが、絶縁体セラミック基板２上には、サーミスタ厚膜３ならびに電極４および５を覆うように、保護膜が形成されてもよい。 The positive temperature coefficient thermistor 1 is, for example, an insulating ceramic substrate 2 made of alumina, a thermistor thick film 3 having PTC characteristics formed on the insulating ceramic substrate 2, and in contact with the thermistor thick film 3 and the thermistor thick film 3 And at least one pair of electrodes 4 and 5 which are opposed to each other with at least a part thereof. Further, although not shown, a protective film may be formed on the insulator ceramic substrate 2 so as to cover the thermistor thick film 3 and the electrodes 4 and 5.
　サーミスタ厚膜３は、好ましくは、ＡＢＯ３（Ａは、バリウムを必ず含み、さらにストロンチウム、カルシウム、鉛および希土類元素から選ばれる少なくとも１種を含むことがある。Ｂは、チタンを必ず含み、さらに錫、ジルコニウム、ニオブ、タングステンおよびアンチモンから選ばれる少なくとも１種を含むことがある。）で表わされるチタン酸バリウム系を主成分とし、かつ副成分として少なくともホウ素元素を含む、半導体セラミックの焼結体からなる。ホウ素元素は、低温焼成を可能とするように作用する。 The thermistor thick film 3 is preferably ABO 3 (A necessarily contains barium and may further contain at least one selected from strontium, calcium, lead and rare earth elements. B necessarily contains titanium, and A sintered body of a semiconductor ceramic containing a barium titanate system as a main component and a subcomponent containing at least a boron element. Consists of. Boron element acts to enable low temperature firing.
　そして、半導体セラミックにおける、上記Ａの含有量を原子比でα、上記Ｂの含有量を原子比でβ、および上記ホウ素元素の含有量を原子比でｙとしたとき、
　０．０５≦ｙ／β≦１．５、および
　１≦ｙ／（α－β）≦４
の条件を満たすようにされる。 In the semiconductor ceramic, when the content of A is α by atomic ratio, the content of B is β by atomic ratio, and the content of boron element is y by atomic ratio,
0.05 ≦ y / β ≦ 1.5, and 1 ≦ y / (α−β) ≦ 4
To meet the requirements of
　これらの条件を満たすことによって、絶縁体セラミック基板２上でのサーミスタ厚膜３の良好な焼結が可能となり、また、室温でたとえば１０ｋΩ・ｃｍ未満といった低い抵抗率を実現することができる。さらに、絶縁体セラミック基板２とサーミスタ厚膜３との間で高い密着性を得ることができる。 By satisfying these conditions, the thermistor thick film 3 can be satisfactorily sintered on the insulator ceramic substrate 2, and a low resistivity of, for example, less than 10 kΩ · cm can be realized at room temperature. Further, high adhesion can be obtained between the insulator ceramic substrate 2 and the thermistor thick film 3.
　ｙ／βが０．０５未満では、焼成後のサーミスタ厚膜３の、絶縁体セラミック基板２に対する密着性が悪いため、焼成後に剥がれることがあり、他方、ｙ／βが１．５を超えると、絶縁性のＢ－Ｂａ－Ｏ系液相成分が多量に生成され、サーミスタ厚膜３が高抵抗化してしまう。 If y / β is less than 0.05, the thermistor thick film 3 after firing has poor adhesion to the insulator ceramic substrate 2 and may peel off after firing. On the other hand, if y / β exceeds 1.5, As a result, a large amount of insulating B—Ba—O-based liquid phase component is generated, and the thermistor thick film 3 is increased in resistance.
　また、ｙ／（α－β）が１未満であっても、４を超えても、サーミスタ厚膜３は、１０００℃程度またはそれより低い温度での焼成では焼結が達成されない。なお、さらに高温とすれば焼結可能であるが、この場合には、前述したように、絶縁体セラミック基板２との反応が起きて、焼結膜としてのサーミスタ厚膜３の高抵抗化を引き起こすことが十分に予測される。 Also, if y / (α-β) is less than 1 or exceeds 4, the thermistor thick film 3 is not sintered by firing at a temperature of about 1000 ° C. or lower. Although it is possible to sinter at a higher temperature, in this case, as described above, a reaction with the insulator ceramic substrate 2 occurs, and the resistance of the thermistor thick film 3 as a sintered film is increased. It is fully predicted.
　上述した組成の半導体セラミックに含まれるホウ素元素は、ＢａＴｉＯ３系セラミックで表わされる主成分に固溶しているもの、Ｂ２ＢａＯ４あるいはＢ２Ｏ３で示される酸化物の状態で存在しているものであってもよく、ホウ素元素を含有していれば、上記形態に限定されるものではない。 The boron element contained in the semiconductor ceramic having the above-described composition exists in the form of an oxide represented by B 2 BaO 4 or B 2 O 3 dissolved in a main component represented by a BaTiO 3 ceramic. As long as it contains a boron element, it is not limited to the above form.
　サーミスタ厚膜３は、たとえば１μｍ以上の厚みを有している。サーミスタ厚膜３を形成するため、たとえば、半導体セラミック粉末にワニスを混合して形成した半導体セラミックペーストを用意し、この半導体セラミックペーストを絶縁体セラミック基板２上に塗布するか、絶縁体セラミック基板２上でドクターブレード法等を適用してシート状に成形するかした後、焼成工程を実施するようにすればよい。 The thermistor thick film 3 has a thickness of 1 μm or more, for example. In order to form the thermistor thick film 3, for example, a semiconductor ceramic paste formed by mixing semiconductor ceramic powder with varnish is prepared, and this semiconductor ceramic paste is applied on the insulator ceramic substrate 2, or the insulator ceramic substrate 2. The baking process may be performed after applying the doctor blade method or the like to form a sheet.
　サーミスタ厚膜３の一層の低抵抗化のためには、サーミスタ厚膜３の厚みをｔとし、サーミスタ厚膜３を構成する半導体セラミックの焼結体中の結晶の平均粒子径をφとしたとき、ｔ／φ≧１０の条件を満たすようにすることが好ましい。そのため、たとえば、半導体セラミックを得るための仮焼工程における仮焼温度および／または焼成工程における焼成温度を変えたり、サーミスタ厚膜３の厚みを調整したりすることが行なわれる。なお、ここで、平均粒子径φは、ＡＳＴＭ（交点切断法）によって求められた値に基づいている。 In order to further reduce the resistance of the thermistor thick film 3, when the thickness of the thermistor thick film 3 is t and the average particle diameter of crystals in the sintered ceramic of the semiconductor ceramic constituting the thermistor thick film 3 is φ , T / φ ≧ 10 is preferably satisfied. Therefore, for example, the calcination temperature in the calcination step and / or the calcination temperature in the calcination step for obtaining a semiconductor ceramic are changed, or the thickness of the thermistor thick film 3 is adjusted. Here, the average particle diameter φ is based on a value obtained by ASTM (intersection point cutting method).
　電極４および５は、図２によく示されているように、サーミスタ厚膜３上に位置する部分を有している。第１の電極４は、図１によく示されているように、矩形の平面形状を有するサーミスタ厚膜３の長手方向に沿うように形成されている。他方、第２の電極５は、第１の電極４に対して所定の間隔を隔てながら、第１の電極４に対向するように位置している。また、電極４および５は、それぞれ、各々の端部において幅広の引出し部６および７を形成しており、これら引出し部６および７は、絶縁体セラミック基板２の一方端側に位置している。 The electrodes 4 and 5 have a portion located on the thermistor thick film 3 as well shown in FIG. As shown well in FIG. 1, the first electrode 4 is formed along the longitudinal direction of the thermistor thick film 3 having a rectangular planar shape. On the other hand, the second electrode 5 is positioned so as to face the first electrode 4 with a predetermined distance from the first electrode 4. Further, the electrodes 4 and 5 respectively form wide lead portions 6 and 7 at respective end portions, and these lead portions 6 and 7 are located on one end side of the insulating ceramic substrate 2. .
　電極４および５は、サーミスタ厚膜３との間でオーミック接触が取れる材料から構成される。電極４および５の材料としては、たとえば、Ｎｉ、Ｃｕ、Ａｌ等の卑金属またはその合金、あるいは卑金属添加によりオーミック化されたオーミックＡｇ等が用いられる。 The electrodes 4 and 5 are made of a material capable of making ohmic contact with the thermistor thick film 3. As a material of the electrodes 4 and 5, for example, a base metal such as Ni, Cu, or Al or an alloy thereof, or ohmic Ag that is ohmicized by addition of a base metal is used.
　電極４および５を形成するにあたっては、たとえば、スパッタリング、蒸着等の薄膜形成法、または導電性ペーストを塗布して焼き付ける厚膜法を適用することができる。 In forming the electrodes 4 and 5, for example, a thin film forming method such as sputtering or vapor deposition, or a thick film method in which a conductive paste is applied and baked can be applied.
　図示した正特性サーミスタ１は、特に図１からわかるように、長尺状の（すなわち、アスペクト比が大きい）絶縁体セラミック基板２上にサーミスタ厚膜３が長尺状のパターンをもって形成された構造を有している。そのため、絶縁体セラミック基板２とサーミスタ厚膜３との間で、各々の線膨張係数の違い等が原因となって剥がれが生じやすいという課題がある。しかし、この発明によれば、絶縁体セラミック基板２とサーミスタ厚膜３との間で高い密着性を確保でき、よって、剥がれが生じにくくすることができる。したがって、この発明は、特に、正特性サーミスタが図１に示すような長尺の絶縁体セラミック基板上に長尺のサーミスタ厚膜が形成された形態を有するとき、より意義深いものとなる。 As shown in FIG. 1, the positive temperature coefficient thermistor 1 shown in FIG. 1 has a structure in which a thermistor thick film 3 is formed in a long pattern on an elongated ceramic substrate 2 (that is, a large aspect ratio). have. For this reason, there is a problem that peeling is likely to occur between the insulator ceramic substrate 2 and the thermistor thick film 3 due to differences in the respective linear expansion coefficients. However, according to the present invention, it is possible to ensure high adhesion between the insulating ceramic substrate 2 and the thermistor thick film 3, and thus it is possible to prevent peeling. Accordingly, the present invention becomes more significant particularly when the positive temperature coefficient thermistor has a form in which a long thermistor thick film is formed on a long insulator ceramic substrate as shown in FIG.
　次に、この発明の効果を確認するために実施した実験例について説明する。 Next, experimental examples carried out to confirm the effects of the present invention will be described.
　［実験例１］
　まず、ＢａＣＯ３、ＴｉＯ２およびＳｍ２Ｏ３の各粉末を用意し、これら粉末を（Ｂａ０．９９８Ｓｍ０．００２）ＴｉＯ３となるように調合し、次いで、ボールミルを用いて、水中でＰＳＺボールとともに５時間粉砕した後、１０００℃の温度で２時間仮焼した。得られた仮焼粉に、表１の「ＢａＴｉＯ３への添加」における「Ｂａ添加量ｘ」および「Ｂ添加量ｙ」の各欄にそれぞれ示す添加量をもって、ＢａＣＯ３とＢＮとを添加して、以下の組成のような混合物を得た。 [Experimental Example 1]
First, BaCO 3 , TiO 2, and Sm 2 O 3 powders are prepared, and these powders are prepared to be (Ba 0.998 Sm 0.002 ) TiO 3, and then in water using a ball mill. After grinding with PSZ balls for 5 hours, calcining was performed at a temperature of 1000 ° C. for 2 hours. BaCO 3 and BN were added to the obtained calcined powder with the addition amounts shown in the columns “Ba addition amount x” and “B addition amount y” in “Addition to BaTiO 3 ” in Table 1, respectively. Thus, a mixture having the following composition was obtained.
　（Ｂａ０．９９８Ｓｍ０．００２）ＴｉＯ３＋ｘＢａＣＯ３＋ｙＢＮ
　次に、上記混合物にワニスを添加し、ペースト化した後、アルミナ基板上に塗布して１０５０℃の温度で２時間焼成して、以下の組成の半導体セラミックの焼結体からなるサーミスタ厚膜を得た。 (Ba 0.998 Sm 0.002 ) TiO 3 + xBaCO 3 + yBN
Next, varnish is added to the above mixture to form a paste, which is then coated on an alumina substrate and baked at a temperature of 1050 ° C. for 2 hours to form a thermistor thick film made of a sintered ceramic ceramic having the following composition Obtained.
　Ｂａ０．９９８Ｓｍ０．００２ＴｉＯ３＋ｘＢａＯ＋１／２ｙＢ２Ｏ３
　焼成後のサーミスタ厚膜の厚みｔは１００μｍであった。また、半導体セラミックの焼結体中の結晶の平均粒子径φをＡＳＴＭ（交点切断法）で求めたところ、１０μｍであった。よって、ｔ／φ＝１０であった。 Ba 0.998 Sm 0.002 TiO 3 + xBaO + 1 / 2yB 2 O 3
The thickness t of the thermistor thick film after firing was 100 μm. Further, when the average particle diameter φ of the crystals in the sintered body of the semiconductor ceramic was determined by ASTM (intersection cutting method), it was 10 μm. Therefore, t / φ = 10.
　次に、Ｎｉスパッタリングを実施することによって、図３に示すように、アルミナ基板１２上に形成された上記サーミスタ厚膜１３の各端部を覆う状態で、アルミナ基板１２上に１対の電極１４および１５を形成し、試料となる正特性サーミスタ１１を得た。 Next, by performing Ni sputtering, as shown in FIG. 3, a pair of electrodes 14 is formed on the alumina substrate 12 so as to cover each end of the thermistor thick film 13 formed on the alumina substrate 12. And a positive temperature coefficient thermistor 11 as a sample was obtained.
　表１に示すように、試料間では、サーミスタ厚膜を構成する半導体セラミックの組成について、「ｙ／β」および「ｙ／（α－β）」をそれぞれ変動させている。ここで、「α」は、ＡＢＯ３で表わされるＢａＴｉＯ３系化合物におけるＡサイト元素（ここでは、ＢａおよびＳｍ）の含有量を原子比で示したものであり、「β」は、同じくＢサイト元素（ここでは、Ｔｉ）の含有量を原子比で示したものであり、「ｙ」は、前述した組成式からもわかるように、添加されたホウ素元素Ｂの含有量を原子比で表したものである。 As shown in Table 1, “y / β” and “y / (α−β)” are varied between the samples with respect to the composition of the semiconductor ceramic constituting the thermistor thick film. Here, “α” indicates the content of the A site element (here, Ba and Sm) in the BaTiO 3 series compound represented by ABO 3 in terms of atomic ratio, and “β” is also the B site. The content of the element (here, Ti) is indicated by an atomic ratio, and “y” indicates the content of the added boron element B by an atomic ratio, as can be seen from the above-described composition formula. Is.
　表１に示した種々の「ｙ／β」および「ｙ／（α－β）」を得るにあたっては、前述のように、（Ｂａ０．９９８Ｓｍ０．００２）ＴｉＯ３に添加されたＢａＣＯ３量ｘおよびＢＮ量ｙを変え、それによって、ＢａＯ量とＢ２Ｏ３量とを変えることで調整した。 Table 1 various "y / beta" and shown in obtaining the "y / (α-β)", as described above, (Ba 0.998 Sm 0.002) BaCO 3 added to TiO 3 The amount x and the BN amount y were changed, thereby adjusting by changing the BaO amount and the B 2 O 3 amount.
　次に、表１に示すように、得られた各試料について、「室温抵抗率」を測定した。「室温抵抗率」は、室温２５℃において、１Ｖの直流電圧を印加した際の抵抗率を２端子法で測定したものである。この「室温抵抗率」に関して、１０ｋΩ・ｃｍ以上の場合、不良と判定した。 Next, as shown in Table 1, “room temperature resistivity” was measured for each of the obtained samples. “Room temperature resistivity” is measured by the two-terminal method when a DC voltage of 1 V is applied at a room temperature of 25 ° C. Regarding this “room temperature resistivity”, when it was 10 kΩ · cm or more, it was determined to be defective.
　また、得られた各試料について、「基板からの剥がれ」を評価した。「基板からの剥がれ」は、アルミナ基板からサーミスタ厚膜が少しでも剥がれていることが目視で確認されたら不良と判定し、表１において「×」で示し、剥がれが生じていないことが確認されたら良好と判定し、「○」で示した。 Also, for each of the obtained samples, “peeling from the substrate” was evaluated. “Peeling from the substrate” is judged as defective when it is visually confirmed that the thermistor thick film has been peeled off even a little from the alumina substrate, and is indicated by “x” in Table 1, and it is confirmed that no peeling has occurred. It was judged as good and indicated by “◯”.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１において、試料番号に＊を付したものは、この発明の範囲外の比較例である。 In Table 1, the sample number marked with * is a comparative example outside the scope of the present invention.
　表１に示すように、この発明の範囲内の試料７～９、１２～１４、１７～１９、および２２～２４によれば、「室温抵抗率」を１０ｋΩ・ｃｍ未満と低くすることができるとともに、サーミスタ厚膜がアルミナ基板から剥がれることもなく、厚膜型の正特性サーミスタとして十分に機能し得ることがわかる。これらの試料は、０．０５≦ｙ／β≦１．５、および１≦ｙ／（α－β）≦４の条件を満たしている。 As shown in Table 1, according to Samples 7 to 9, 12 to 14, 17 to 19, and 22 to 24 within the scope of the present invention, the “room temperature resistivity” can be lowered to less than 10 kΩ · cm. In addition, it can be seen that the thermistor thick film does not peel off from the alumina substrate and can sufficiently function as a thick film type positive temperature coefficient thermistor. These samples satisfy the conditions of 0.05 ≦ y / β ≦ 1.5 and 1 ≦ y / (α−β) ≦ 4.
　これらに対して、「ｙ／（α－β）」が１未満か、４を超える、試料１、５、６、１０、１１、１５、１６、２０、２１、２５、２６および３０では、「室温抵抗率」が、１０ｋΩ・ｃｍ以上の高抵抗となった。 On the other hand, in samples 1, 5, 6, 10, 11, 15, 16, 20, 21, 25, 26, and 30, where “y / (α−β)” is less than 1 or greater than 4, The “room temperature resistivity” was 10 kΩ · cm or higher.
　また、「ｙ／β」が０．０５未満の試料１～５では、「基板からの剥がれ」が「×」となった。他方、「ｙ／β」が１．５を超える試料２６～３０では、「基板からの剥がれ」が「○」となったものの、「室温抵抗率」が１０ｋΩ・ｃｍ以上と高くなった。 In addition, in samples 1 to 5 where “y / β” was less than 0.05, “peeling from the substrate” was “x”. On the other hand, in samples 26 to 30 in which “y / β” exceeds 1.5, “peeling from the substrate” was “◯”, but “room temperature resistivity” was as high as 10 kΩ · cm or more.
　［実験例２］
　実験例２では、上述の実験例１において作製した仮焼粉の組成（Ｂａ０．９９８Ｓｍ０．００２）ＴｉＯ３におけるＢａサイト（Ａサイト）におけるＢａの一部を、表２の「Ｂａサイト置換元素と置換量」の欄に示す「置換元素Ｄ」により、「Ｔｉ＝１モルに対する置換モル数ｚ」をもって置換し、（Ｂａ０．９９８－ｚＤｚ）Ｓｍ０．００２ＴｉＯ３となるように調整した後、その１モルに対し、０．１モルのＢａＣＯ３と０．１モルのＢ２Ｏ３とを添加したことを除いて、実験例１の場合と同様の操作を経て、試料となる正特性サーミスタを得た。 [Experiment 2]
In Experimental Example 2, a part of Ba at the Ba site (A site) in the composition (Ba 0.998 Sm 0.002 ) TiO 3 of the calcined powder prepared in Experimental Example 1 described above was replaced with “Ba site in Table 2. Substitution with “substitution element D” shown in the column of “substitution element and substitution amount” with “substitution number of moles z with respect to Ti = 1 mol” is (Ba 0.998−z D z ) Sm 0.002 TiO 3. After adjusting as described above, the same operation as in Experimental Example 1 was performed except that 0.1 mol of BaCO 3 and 0.1 mol of B 2 O 3 were added to 1 mol thereof. A positive temperature coefficient thermistor was obtained as a sample.
　なお、実験例２では、作製したすべての試料について、「ｙ／β」を０．２とし、「ｙ／（α－β）」を２とした。また、すべての試料について、焼成後のサーミスタ厚膜の厚みｔは１００μｍであり、ｔ／φは１０であった。 In Experimental Example 2, “y / β” was set to 0.2 and “y / (α−β)” was set to 2 for all the prepared samples. Further, for all the samples, the thickness t of the thermistor thick film after firing was 100 μm, and t / φ was 10.
　次に、表２に示すように、得られた各試料について、実験例１の場合と同様の要領で、「室温抵抗率」および「基板からの剥がれ」を評価した。 Next, as shown in Table 2, “room temperature resistivity” and “peeling from the substrate” were evaluated for each of the obtained samples in the same manner as in Experimental Example 1.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示すように、半導体セラミック組成中のＢａサイトのＢａの一部をＰｂ、ＳｒおよびＣａのいずれに置換しても、実験例１で得られたこの発明の範囲内の試料と同様、１０ｋΩ・ｃｍ以下の低抵抗が得られた。また、すべての試料について、「基板からの剥がれ」が「○」となった。 As shown in Table 2, even if a part of Ba at the Ba site in the semiconductor ceramic composition is replaced with any of Pb, Sr and Ca, as in the sample within the scope of the present invention obtained in Experimental Example 1, A low resistance of 10 kΩ · cm or less was obtained. Moreover, “peeling from the substrate” was “◯” for all the samples.
　［実験例３］
　実験例３では、上述の実験例１において作製した仮焼粉の組成（Ｂａ０．９９８Ｓｍ０．００２）ＴｉＯ３におけるＢａサイト（Ａサイト）における希土類元素Ｓｍを、表３の「Ｓｍに代えた希土類元素Ｌｎ」の欄に示す他の希土類元素に置換し、（Ｂａ０．９９８Ｌｎ０．００２）ＴｉＯ３となるように調整した後、その１モルに対し、０．１モルのＢａＣＯ３と０．１モルのＢ２Ｏ３とを添加したことを除いて、実験例１の場合と同様の操作を経て、試料となる正特性サーミスタを得た。 [Experiment 3]
In Experimental Example 3, the rare earth element Sm at the Ba site (A site) in the composition (Ba 0.998 Sm 0.002 ) TiO 3 of the calcined powder prepared in Experimental Example 1 described above was replaced with “Sm” in Table 3. After replacing with other rare earth elements shown in the column of “rare earth element Ln” and adjusting to be (Ba 0.998 Ln 0.002 ) TiO 3 , 0.1 mol of BaCO 3 with respect to 1 mol thereof. A positive temperature coefficient thermistor as a sample was obtained through the same operation as in Example 1 except that and 0.1 mol of B 2 O 3 were added.
　なお、実験例３では、作製したすべての試料について、「ｙ／β」を０．２とし、「ｙ／（α－β）」を２とした。また、すべての試料について、焼成後のサーミスタ厚膜の厚みｔは１００μｍであり、ｔ／φは１０であった。 In Experimental Example 3, “y / β” was set to 0.2 and “y / (α−β)” was set to 2 for all the prepared samples. Further, for all the samples, the thickness t of the thermistor thick film after firing was 100 μm, and t / φ was 10.
　次に、表３に示すように、得られた各試料について、実験例１の場合と同様の要領で、「室温抵抗率」および「基板からの剥がれ」を評価した。 Next, as shown in Table 3, “room temperature resistivity” and “peeling from the substrate” were evaluated for each of the obtained samples in the same manner as in Experimental Example 1.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表３に示すように、半導体セラミック組成中のＢａサイトにおけるＳｍを他の希土類元素に置換しても、実験例１で得られたこの発明の範囲内の試料と同様、１０ｋΩ・ｃｍ以下の低抵抗が得られた。また、すべての試料について、「基板からの剥がれ」が「○」となった。 As shown in Table 3, even when Sm at the Ba site in the semiconductor ceramic composition was replaced with another rare earth element, as in the sample within the scope of the present invention obtained in Experimental Example 1, a low value of 10 kΩ · cm or less was obtained. Resistance was obtained. Moreover, “peeling from the substrate” was “◯” for all the samples.
　なお、半導体セラミックの組成に関して、ＡＢＯ３のＢサイト、すなわちＴｉサイトにあるＴｉの一部を、Ｓｎ、Ｚｒ、Ｎｂ、ＷおよびＳｂから選ばれる少なくとも１種で置換しても、同様の結果が得られることが確認されている。 Regarding the composition of the semiconductor ceramic, the same result was obtained even when a part of Ti at the B site of ABO 3 , that is, the Ti site was replaced with at least one selected from Sn, Zr, Nb, W and Sb. It has been confirmed that it can be obtained.
　［実験例４］
　実験例４では、半導体セラミックの組成を、実験例１において作製した試料１３と同様、Ｂａ０．９９８Ｓｍ０．００２ＴｉＯ３＋０．１ＢａＯ＋０．１Ｂ２Ｏ３としながら、表４に示すように、仮焼温度を変えることで、焼結後の半導体セラミック中の結晶粒子の「平均粒子径φ」を変化させ、また、半導体セラミック材料ペーストをアルミナ基板上に塗布する際の塗布厚みを変えることで、サーミスタ厚膜の「厚みｔ」を変えたことを除いて、実験例１の場合と同様の操作を経て、試料となる正特性サーミスタを得た。 [Experimental Example 4]
In Experimental Example 4, the composition of the semiconductor ceramic was Ba 0.998 Sm 0.002 TiO 3 + 0.1BaO + 0.1B 2 O 3 as shown in Table 4 as in Sample 13 prepared in Experimental Example 1, By changing the calcining temperature, the “average particle diameter φ” of the crystal particles in the sintered semiconductor ceramic is changed, and the coating thickness when the semiconductor ceramic material paste is applied on the alumina substrate is changed. Except for changing the “thickness t” of the thermistor thick film, a positive temperature coefficient thermistor serving as a sample was obtained through the same operation as in Experimental Example 1.
　次に、表４に示すように、得られた各試料について、実験例１の場合と同様の要領で、「室温抵抗率」および「基板からの剥がれ」を評価した。 Next, as shown in Table 4, “room temperature resistivity” and “peeling from the substrate” were evaluated for each of the obtained samples in the same manner as in Experimental Example 1.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表４に示すように、「ｔ／φ」を１０以上とした試料４２～４４、４６～４８、および５０～５２を、それぞれ、同じ「厚みｔ」の試料と比較したとき、「ｔ／φ」が１０未満の試料４１、４５および４９に比べて、より低抵抗化が図られ得ることがわかった。また、すべての試料について、「基板からの剥がれ」が「○」となった。 As shown in Table 4, when samples 42 to 44, 46 to 48, and 50 to 52 having “t / φ” of 10 or more were compared with samples of the same “thickness t”, “t / φ” It has been found that the resistance can be further reduced as compared with Samples 41, 45, and 49 in which “is less than 10.” Moreover, “peeling from the substrate” was “◯” for all the samples.
１，１１　正特性サーミスタ
２　絶縁体セラミック基板
３，１３　サーミスタ厚膜
４，５，１４，１５　電極
１２　アルミナ基板 1, 11 Positive temperature coefficient thermistor 2 Insulator ceramic substrate 3, 13 Thermistor thick film 4, 5, 14, 15 Electrode 12 Alumina substrate

Claims (4)

  1. 　絶縁体セラミック基板と、
    　前記絶縁体セラミック基板上に形成された、半導体セラミック焼結体からなる正の抵抗温度特性を示すサーミスタ厚膜と、
    　前記サーミスタ厚膜に接し、かつ前記サーミスタ厚膜の少なくとも一部を挟んで対向する、少なくとも１対の電極と
    を備え、
    　サーミスタ厚膜の室温での抵抗率は１０ｋΩ・ｃｍ未満であることを特徴とする、正特性サーミスタ。     An insulating ceramic substrate;
    A thermistor thick film formed on the insulator ceramic substrate and exhibiting positive resistance temperature characteristics made of a sintered ceramic ceramic;
    And at least one pair of electrodes that are in contact with the thermistor thick film and face each other with at least a part of the thermistor thick film interposed therebetween,
    A positive temperature coefficient thermistor characterized in that the thermistor thick film has a resistivity at room temperature of less than 10 kΩ · cm.
  2. 　前記サーミスタ厚膜は、ＡＢＯ３（Ａは、バリウムを必ず含み、さらにストロンチウム、カルシウム、鉛および希土類元素から選ばれる少なくとも１種を含むことがある。Ｂは、チタンを必ず含み、さらに錫、ジルコニウム、ニオブ、タングステンおよびアンチモンから選ばれる少なくとも１種を含むことがある。）で表わされるチタン酸バリウム系を主成分とし、かつ副成分として少なくともホウ素元素を含む、半導体セラミックの焼結体からなり、
    　前記半導体セラミックにおける、前記Ａの含有量を原子比でα、前記Ｂの含有量を原子比でβ、および前記ホウ素元素の含有量を原子比でｙとしたとき、
    　０．０５≦ｙ／β≦１．５、および
    　１≦ｙ／（α－β）≦４
    の条件を満たす、半導体セラミック焼結体からなる、
    請求項１に記載の正特性サーミスタ。     The thermistor thick film may contain ABO 3 (A necessarily contains barium and may further contain at least one selected from strontium, calcium, lead and rare earth elements. B necessarily contains titanium, and further contains tin, zirconium. A sintered body of a semiconductor ceramic, comprising as a main component a barium titanate system represented by (ii) niobium, tungsten and antimony), and containing at least boron element as a subcomponent,
    In the semiconductor ceramic, when the A content is α by atomic ratio, the B content is β by atomic ratio, and the boron element content is y by atomic ratio,
    0.05 ≦ y / β ≦ 1.5, and 1 ≦ y / (α−β) ≦ 4
    It consists of a semiconductor ceramic sintered body that satisfies the following conditions:
    The positive temperature coefficient thermistor according to claim 1.
  3. 　前記サーミスタ厚膜の厚みをｔとし、前記サーミスタ厚膜を構成する前記半導体セラミックの焼結体中の結晶の平均粒子径をφとしたとき、ｔ／φ≧１０の条件を満たす、請求項１または２に記載の正特性サーミスタ。 The condition of t / φ ≧ 10 is satisfied, where t is a thickness of the thermistor thick film and φ is an average particle diameter of crystals in the sintered ceramic of the semiconductor ceramic constituting the thermistor thick film. Or the positive temperature coefficient thermistor according to 2;
  4. 　前記絶縁体セラミック基板はアルミナ基板である、請求項１ないし３のいずれかに記載の正特性サーミスタ。 The positive temperature coefficient thermistor according to any one of claims 1 to 3, wherein the insulator ceramic substrate is an alumina substrate.
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