WO2013065441A1 - Ptcサーミスタおよびptcサーミスタの製造方法 - Google Patents
Ptcサーミスタおよびptcサーミスタの製造方法 Download PDFInfo
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- WO2013065441A1 WO2013065441A1 PCT/JP2012/075644 JP2012075644W WO2013065441A1 WO 2013065441 A1 WO2013065441 A1 WO 2013065441A1 JP 2012075644 W JP2012075644 W JP 2012075644W WO 2013065441 A1 WO2013065441 A1 WO 2013065441A1
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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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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- 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
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
- H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
- H01C17/06506—Precursor compositions therefor, e.g. pastes, inks, glass frits
- H01C17/06513—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component
- H01C17/06533—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component composed of oxides
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/30—Apparatus or processes specially adapted for manufacturing resistors adapted for baking
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
- C04B2235/3208—Calcium oxide or oxide-forming salts thereof, e.g. lime
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
- C04B2235/3213—Strontium oxides or oxide-forming salts thereof
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3262—Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
Definitions
- the present invention relates to a PTC thermistor using a barium titanate semiconductor ceramic having a positive resistance temperature characteristic.
- a barium titanate-based semiconductor ceramic composition having positive resistance temperature characteristics for example, a semiconductor ceramic composition as shown in Patent Document 1 is known.
- the semiconductor ceramic composition of this Patent Document 1 is a semiconductor ceramic composition having a positive resistance temperature characteristic mainly composed of barium titanate.
- barium titanate is 100 mol
- strontium titanate is added to 20: 30 mol
- calcium titanate 0.05 to 0.20 mol
- manganese oxide 0.05 to 0.15 mol
- silicon oxide 2.5 to 3.5 mol
- rare earth element oxide 0
- Patent Document 1 The semiconductor ceramic composition of Patent Document 1 can be suitably used for a PTC thermistor having a low resistance and a high withstand voltage, which can be used for a large load such as an OA device or an overcurrent protection element for a motor. It is said that.
- Patent Document 1 Although the semiconductor ceramic composition of Patent Document 1 can obtain low resistance and high withstand voltage characteristics, it is required to have a PTC characteristic (resistance change with temperature change) required to enable highly accurate temperature detection for overheat detection. There is a problem that it is not always possible to realize a sufficient characteristic with respect to the size of the above-mentioned characteristic, and the larger the resistance change with respect to the temperature change, the better.
- PTC characteristic resistance change with temperature change
- Patent Document 1 when the semiconductor ceramic composition of Patent Document 1 is used, it is a fact that a PTC thermistor with desirable characteristics cannot be obtained.
- the present invention solves the above-described problems, and an object thereof is to provide a PTC thermistor having a low room temperature resistance, sufficient PTC characteristics for detecting overheat, and capable of detecting overheat near room temperature.
- the PTC thermistor of the present invention is A PTC thermistor comprising a semiconductor ceramic body and an external electrode formed on the outer surface of the semiconductor ceramic body,
- the semiconductor ceramic body contains a perovskite type compound containing Ba, Ti, Sr and Ca, Mn, and a semiconducting agent,
- the content mol part a of Sr and the content mol part b of Ca are: When 20.0 ⁇ a ⁇ 22.5, 12.5 ⁇ b ⁇ 17.5, When 22.5 ⁇ a ⁇ 25.0, 12.5 ⁇ b ⁇ 15.0
- the content mole part c of Mn is 0.030 ⁇ c ⁇ 0.045 It is characterized by that.
- the semiconductor ceramic body includes a plurality of semiconductor ceramic layers and a plurality of internal electrodes, and the semiconductor ceramic layers and the internal electrodes are alternately stacked.
- the laminated body which has a part may be sufficient.
- the PTC thermistor of the present invention is preferably used as an overheat detection element.
- the PTC thermistor of the present invention as an overheat detection element, it is possible to provide a PTC thermistor that can reliably detect overheat near room temperature.
- the manufacturing method of the PTC thermistor according to the present invention is as follows: A method of manufacturing a PTC thermistor comprising a semiconductor ceramic body and an external electrode formed on the outer surface of the semiconductor ceramic body, Step A for producing an unsintered semiconductor ceramic body, Step B for firing the unsintered semiconductor ceramic body to obtain a semiconductor ceramic body; Forming an external electrode on the outer surface of the semiconductor ceramic body; and A method of manufacturing a PTC thermistor comprising:
- the unsintered semiconductor ceramic body contains a perovskite type compound containing Ba, Ti, Sr and Ca, Mn, and a semiconducting agent, When the total content mol part of Ba, Sr, Ca and the semiconducting agent is 100, the content mol part a of Sr and the content mol part b of Ca are: When 20.0 ⁇ a ⁇ 22.5, 12.5 ⁇ b ⁇ 17.5, When 22.5 ⁇ a ⁇ 25.0, 12.5 ⁇ b ⁇ 15.0 And When the total content mo
- the unfired semiconductor ceramic body produced in the step A includes a plurality of semiconductor ceramic green sheets and a plurality of unfired internal electrode patterns, It may be an unfired laminate having a laminated structure in which ceramic green sheets and the unfired internal electrode patterns are alternately laminated.
- the room temperature resistance which has been conventionally difficult to realize, is sufficient for detecting overheat. It is possible to detect overheating near room temperature. It should be noted that overheat detection using a PTC thermistor means that the resistance value of the PTC thermistor suddenly increases from a specific temperature and the temperature of the circuit reaches a predetermined temperature (an overheating state that is an abnormal situation).
- the PTC thermistor for preventing overheating is a PTC thermistor that functions to shut off a circuit by utilizing a rapid increase in resistance.
- a semiconductor ceramic used as a thermistor element having a positive resistance temperature characteristic has a low resistance near room temperature, can be operated at a low temperature, and has an excellent resistance temperature characteristic.
- it can be suitably used as a protective element for a personal computer or the like.
- a PTC thermistor using a barium titanate-based semiconductor ceramic that does not contain lead has hitherto been difficult to realize, and has a low room temperature resistance and is used for overheat detection.
- a PTC thermistor having sufficient PTC characteristics can be efficiently manufactured.
- FIG. 3 is a diagram showing a temperature detection (overheat detection) circuit using the PTC thermistor of the present invention.
- FIG. 1 is a perspective view showing a PTC thermistor (positive characteristic thermistor) according to the present invention.
- This PTC thermistor 1 is provided with a pair of electrodes 3a and 3b on the front and back surfaces of a semiconductor ceramic body (thermistor body having positive resistance temperature characteristics) 2.
- This PTC thermistor is, for example, (A) a step of producing an unsintered semiconductor ceramic body; (B) firing the unsintered semiconductor ceramic body to obtain the semiconductor ceramic body 2 as shown in FIG. (C)
- the semiconductor ceramic body 2 can be manufactured through a process of forming a pair of electrodes 3a and 3b on the front and back surfaces.
- the ceramic material constituting the semiconductor ceramic body is a barium titanate semiconductor ceramic containing a perovskite type compound containing Ba, Ti, Sr and Ca, Mn, and a semiconducting agent.
- a basis for content ratio limitation will be described along with operation of the present invention.
- the main component of the barium titanate semiconductor ceramic (hereinafter also simply referred to as “semiconductor ceramic”), which is a constituent material of the PTC thermistor, is a perovskite type compound.
- the semiconductor ceramic fired body can be dissolved and quantitatively analyzed by, for example, ICP (Emission Spectroscopic Plasma Analysis).
- Sr is added to shift the Curie point of the barium titanate-based semiconductor ceramic to the low temperature side.
- the content of Sr is less than 20.0 (20.0 mol%) when the total content of Ba, Sr, Ca and the semiconducting agent (Er in this embodiment) is 100. Even if the relationship with other components is adjusted, the Curie point is not sufficiently lowered in temperature and becomes unsuitable for operation near room temperature. On the other hand, when the content molar part of Sr exceeds 25.0 (25.0 mol%), a remarkable increase in specific resistance occurs even if the relationship with other components is adjusted.
- Ca is added to control the particle size of the barium titanate semiconductor ceramic.
- the total molar content of Ba, Sr, Ca, and the semiconducting agent (Er in this embodiment) is 100, when the molar content of Ca is less than 12.5 (12.5 mol%), other components Even if the relationship is adjusted, the resistance-temperature characteristics are not improved due to the acceptor effect of Ca which is one of the effects of the present invention. Moreover, when the content molar part of Ca exceeds 17.5 (17.5 mol%), a remarkable increase in specific resistance occurs even if the relationship with other components is adjusted.
- Rare earth elements are added mainly as a semiconducting agent to reduce the resistance of barium titanate semiconductor ceramics.
- the content is affected by the type of semiconducting element and the content of other elements such as Sr and Ca.
- the total content of Ba, Sr, Ca and a semiconducting agent Er in this embodiment
- the content molar part of the semiconducting agent exceeds 1.0 (1.0 mol%) when the part is 100, a significant increase in specific resistance occurs.
- Mn element is mainly added as an acceptor to improve the resistance-temperature characteristics of barium titanate semiconductor ceramics.
- the total molar content of Ti and Mn is 100, if the molar content of Mn is less than 0.03 (0.03 mol%), the resistance-temperature characteristics are not significantly improved.
- the molar part of Mn exceeds 0.045 (0.045 mol%), a significant increase in specific resistance occurs.
- the present invention has the above effects.
- the semiconductor ceramic constituting the semiconductor ceramic body 2 is manufactured by the method described below using the above-described barium titanate-based semiconductor ceramic.
- the electrodes 3a and 3b are electrodes having a two-layer structure in which an Ni layer is formed on both the front and back main surfaces of the semiconductor ceramic body 2, and then an Ag layer is further formed on the Ni layer as an outermost electrode layer. is there.
- the following raw materials were prepared as raw materials for the barium titanate semiconductor ceramic for the semiconductor ceramic body 2.
- BaCO 3 , TiO 2 , SrCO 3 , and CaCO 3 were prepared as main component materials, and Er 2 O 3 was prepared as a semiconducting agent.
- Er 2 O 3 was prepared as a semiconducting agent.
- rare earth such as Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu instead of Er (Er 2 O 3 )
- an element or an oxide of at least one element selected from pentavalent elements such as Sb, Nb, Ta, W, and Bi.
- MnCO 3 resistance-temperature coefficient improver
- SiO 2 sining aid
- Each of the raw materials described above was prepared at a desired ratio shown in Tables 1A to 1E, and wet pulverized and mixed with pure water and zirconia balls in a polyethylene pot to obtain a mixture slurry. Next, the obtained mixture slurry was dehydrated and dried, and calcined at 1200 ° C.
- the binder was mixed and granulated, and the resulting granulated particles were molded by uniaxial pressing to obtain a disk-shaped molded body having a thickness of 2 mm and a diameter of 14 mm.
- the obtained molded body is placed in a sheath made of a material mainly composed of Al 2 O 3 , SiO 2 , and ZrO, and fired at 1350 ° C. for 2 hours (main firing) in the atmosphere.
- a semiconductor ceramic body (a thermistor body having positive resistance temperature characteristics) was obtained.
- Ni-Ag electrodes 3a and 3b were formed on the front and back surfaces of the semiconductor ceramic body.
- the Ni—Ag electrodes 3a and 3b were formed through a process of forming an Ni layer as an ohmic electrode layer and then forming an Ag layer as an outermost electrode layer on the Ni layer.
- the current value at the time of voltage application at room temperature (25 ° C.) was measured using a multimeter (Agilent 334401A), and the specific resistance ( ⁇ 25 ° C. ) was calculated. Calculated.
- the specific resistance was calculated in the same manner while changing the temperature from 20 ° C. to 250 ° C. in a state where each of the above samples was placed in a thermostat, and a resistance-temperature curve was obtained. Then, from the resistance-temperature curve, the temperature (double point) at which the specific resistance is twice the specific resistance at room temperature (25 ° C.) was obtained.
- the double point is a phase transition temperature at which the PTC characteristic starts to appear, and is supposed to indicate a value substantially close to the Curie point.
- the specific resistance value of the material varies greatly by changing the addition amount of Er, which is a donor
- various donor amounts with different donor amounts can be used to enable comparison based on the same standard.
- the samples were evaluated, and the characteristics of the samples were compared at the Er amount (Er- ⁇ min ) at which the specific resistance was the minimum value.
- Table 1A, Table 1B, Table 1C, Table 1D, and Table 1E show the measurement results for each of the above samples.
- the molar part of Ba is the value of the molar part of Ba when the total molar part of Ba, Sr, Ca, and the semiconducting agent (Er in this embodiment) is 100. is there.
- the molar part of Ti is the value of the molar part of Ti when the total molar part of Ti and Mn is 100.
- the respective molar parts of Sr, Ca and the semiconducting agent (Er in this embodiment) in Tables 1A to 1E are the total containing molar parts of Ba, Sr, Ca and the semiconducting agent (Er in this embodiment).
- the molar part of Mn is the value of the molar part of Mn when the total molar part of Ti and Mn is 100.
- Tables 1A to 1E showing the characteristics of the samples having the respective compositions, the following can be understood.
- Table 1A when the total content mole part of Sr in the semiconductor ceramic constituting the semiconductor ceramic body (Ba, Sr, Ca and semiconducting agent (Er in this embodiment) is 100, In the case of the samples Nos. 107 to 124 whose Sr content mole part) is 17.5 (17.5 mol%), the resistance double temperature (2) which shows a value almost close to the Curie temperature because the Sr content is too small. Double point) is considerably higher than room temperature, and the detection temperature of overheat detection becomes too high, which is not preferable.
- the content mole part of Sr is 27.5 (27.5 mol%) when the total content mole part of Ba, Sr, Ca and the semiconducting agent (Er in this embodiment) is 100.
- the Sr content is too high, the double point is lower than room temperature, and the specific resistance ⁇ 25 ° C. is high, which is not preferable.
- the content mole part of Sr is 20.0 to 25.0 (20.0 to 25.0 mol%) when the total content mole part of Ba, Sr, Ca and the semiconducting agent (Er in this embodiment) is 100.
- Sample numbers 208 to 211, 214 to 217, 220 to 223 in Table 1B Sample numbers 308 to 311, 314 to 317, 320 to 323 in Table 1C
- Sample numbers 408 to 411 and 414 to 417 in Table 1D In the case of each sample, a low specific resistance of ⁇ 25 ° C. ⁇ 120 ⁇ ⁇ cm can be realized, and a high resistance-temperature characteristic improvement effect can be obtained. Specifically, 10.0 ⁇ ⁇ 10-100 / Log ( ⁇ 25 ° C. ) ⁇ ⁇ 12.0 can be realized.
- the Sr-containing molar part satisfies the requirement of 20.0 ⁇ Sr ⁇ 22.5 (20.0 mol% ⁇ Sr ⁇ 22.5 mol%).
- the semiconductor ceramic used in the PTC thermistor of the present invention simultaneously achieves the low curie point, the low room temperature resistance, and the high resistance-temperature coefficient (ie, excellent PTC characteristics).
- the semiconductor ceramic it is possible to realize a PTC thermistor with excellent characteristics, in particular, a temperature detection element.
- the barium titanate semiconductor ceramic used in the PTC thermistor of the present invention it is possible to change the type and amount of donor within a general range, and in that case, the same effect can be obtained. Can do.
- the electrode constituting the PTC thermistor is a Ni—Ag electrode
- the electrode configuration is not particularly limited, and electrodes having various configurations can be applied. is there.
- the shape of the PTC thermistor body formed using the above-described barium titanate-based semiconductor ceramic is a disk shape, but is not limited to this, for example, a rectangular shape. It is also possible.
- a PTC thermistor having a structure in which electrodes are formed on both main surfaces of a disk-shaped semiconductor ceramic body has been described as an example.
- a stacked type as shown in FIG. A PTC thermistor is also possible.
- external electrodes 14a and 14b are arranged on both ends of a multilayer semiconductor ceramic body 13 having a structure in which semiconductor ceramic layers 11 and internal electrodes 12a and 12b are alternately stacked. It has an established structure.
- This laminated PTC thermistor is, for example, (A) A plurality of semiconductor ceramic green sheets and a plurality of internal electrode patterns are provided by alternately laminating semiconductor ceramic green sheets and unfired internal electrode patterns. Forming an unsintered semiconductor ceramic body made of a laminate having an alternately laminated structure; (B) firing an unsintered semiconductor ceramic body to obtain a semiconductor ceramic body 13 as shown in FIG. (C) The semiconductor ceramic body 13 can be manufactured through a process of forming the external electrodes 14a and 14b on the outer surface.
- FIG. 3 is a diagram showing a temperature detection (overheat detection) circuit using the PTC thermistor of the present invention.
- This temperature detection (overheat detection) circuit is a control circuit that receives a voltage supply from a resistor 101, a PTC thermistor 102, a transistor 111 having a base terminal connected between the resistor 101 and the PTC thermistor 102, and outputs a control signal.
- the integrated circuit 112 includes a power control integrated circuit 113 that receives a control signal and shuts down the system.
- a PTC thermistor 102 having a characteristic that the electrical resistance is low at room temperature and the electrical resistance rapidly increases when reaching a predetermined temperature is used.
- the transistor 111 is turned on, and the specified voltage is supplied to the control integrated circuit 112.
- the temperature at which the transistor 111 is turned on is the detected temperature.
- control integrated circuit 112 receives a voltage supply and outputs a control signal.
- the power control integrated circuit 113 receives the control signal and shuts down the system.
- a device for example, a personal computer
- a temperature detection (overheat detection) circuit is protected from overheating.
- the PTC thermistor and the manufacturing method thereof according to the present invention are not limited to the above embodiment in other points, and various applications and modifications can be added within the scope of the present invention.
Abstract
Description
半導体セラミック素体と、前記半導体セラミック素体の外表面に形成された外部電極とを備えるPTCサーミスタであって、
前記半導体セラミック素体が、Ba、Ti、SrおよびCaを含むペロブスカイト型化合物と、Mnと、半導体化剤とを含有し、
Ba、Sr、Caおよび半導体化剤の合計含有モル部を100としたときの、Srの含有モル部aおよびCaの含有モル部bが、
20.0≦a≦22.5のとき、12.5≦b≦17.5、
22.5≦a≦25.0のとき、12.5≦b≦15.0
であり、
TiおよびMnの合計含有モル部を100としたときの、Mnの含有モル部cが、
0.030≦c≦0.045
であること
を特徴としている。
半導体セラミック素体と、前記半導体セラミック素体の外表面に形成されている外部電極とを備えるPTCサーミスタの製造方法であって、
未焼成半導体セラミック素体を作製する工程Aと、
前記未焼成半導体セラミック素体を焼成して半導体セラミック素体を得る工程Bと、
前記半導体セラミック素体の外表面に外部電極を形成する工程Cと、
を備えるPTCサーミスタの製造方法であって、
前記未焼成半導体セラミック素体が、Ba、Ti、SrおよびCaを含むペロブスカイト型化合物と、Mnと、半導体化剤とを含有し、
Ba、Sr、Caおよび半導体化剤の合計含有モル部を100としたときの、Srの含有モル部aおよびCaの含有モル部bが、
20.0≦a≦22.5のとき、12.5≦b≦17.5、
22.5≦a≦25.0のとき、12.5≦b≦15.0
であり、
TiおよびMnの合計含有モル部を100としたときの、Mnの含有モル部cが、
0.030≦c≦0.045
であること
を特徴としている。
なお、PTCサーミスタを用いた過熱検知とは、PTCサーミスタの抵抗値が、特定の温度から急激に大きくなる性質を利用して、回路の温度が所定温度に達した場合(異常事態である過熱状態に至った場合)に、それを検知することを意味するものであり、過熱防止用PTCサーミスタとは、抵抗の急上昇を利用して回路を遮断する機能を果たすPTCサーミスタをいう。
図1は、本発明にかかるPTCサーミスタ(正特性サーミスタ)を示す斜視図である。
このPTCサーミスタ1は、半導体セラミック素体(正の抵抗温度特性を有するサーミスタ素体)2の表裏面に一対の電極3a,3bを設けたものである。
このPTCサーミスタは、例えば、
(a)未焼成半導体セラミック素体を作製する工程、
(b)未焼成半導体セラミック素体を焼成して、図1に示すような半導体セラミック素体2を得る工程、
(c)半導体セラミック素体2の表裏面に一対の電極3a,3bを形成する工程
などを経て製造することができる。
以下に、半導体セラミック素体を構成するセラミック材料(BaTiO3を基本組成とするチタン酸バリウム系半導体セラミック)の各成分について、含有比率限定の根拠を本発明の作用とともに説明する。
(a)イオン半径の関係により、本来Ba元素の存在するサイトを置換すべきCa元素が、Ti元素の存在するサイトを置換することにより、その電価バランスからアクセプター効果を発現すること、および、
(b)結晶格子定数を詳細に調整することを意図した組成の設計を行うことにより、Ba元素の存在するサイトとTi元素の存在するサイトのどちらをも、Ca元素で自己制御的に置換することができる領域とすることにより、室温における抵抗の著しい上昇が抑制されること
などによるものと推測される。
まず、半導体セラミック素体2用のチタン酸バリウム系半導体セラミックの原料として、以下の原料を用意した。
主成分原料として、BaCO3、TiO2、SrCO3、CaCO3を用意するとともに、半導体化剤として、Er2O3を用意した。
ただし、半導体化剤としては、Er(Er2O3)の代わりにY、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Luなどの希土類元素、あるいはSb、Nb、Ta、W、Bi等の5価元素より選ばれる少なくとも一種の元素の酸化物を用いることも可能である。
次に、得られた混合物スラリーを脱水、乾燥した後、1200℃で仮焼した。
なお、Ni-Ag電極3a,3bは、オーミック電極層としてNi層を形成した後、Ni層の上にさらに最外電極層としてAg層を形成する工程を経て形成した。
次に、上記の各試料を恒温槽に入れた状態で温度を20℃から250℃に変えながら、同様に比抵抗を算出し、抵抗-温度曲線を求めた。そして、抵抗-温度曲線から、比抵抗が室温(25℃)での比抵抗の2倍となる温度(2倍点)を求めた。なお、2倍点とは、PTC特性が発現し始める相転移温度であり、ほぼキュリー点に近い値を示すとされている。
づいて抵抗-温度係数α10-100を計算し、これを指標とした。
α10-100={In10×(LogR2-LogR1)/(T2-T1)×100}
また、表1A~表1EにおけるTiのモル部は、TiおよびMnの合計含有モル部を100としたときの、Tiの含有モル部の値である。
また、表1A~表1EにおけるSr、Caおよび半導体化剤(この実施形態ではEr)のそれぞれのモル部は、Ba、Sr、Caおよび半導体化剤(この実施形態ではEr)の合計含有モル部を100としたときの、Sr、Caおよび半導体化剤(この実施形態ではEr)の含有モル部の値である。
また、表1A~表1EにおけるMnのモル部は、TiおよびMnの合計含有モル部を100としたときの、Mnの含有モル部の値である。
また、表1A、表1B、表1C、表1D、表1Eにおいて、試料番号に“*”を付した試料は、本発明の要件を備えていない比較例の試料である。
表1Aに示すように、半導体セラミック素体を構成する半導体セラミックにおけるSrの含有モル部(Ba、Sr、Caおよび半導体化剤(この実施形態ではEr)の合計含有モル部を100としたときのSrの含有モル部)が17.5(17.5mol%)である試料番号107~124の試料の場合、Sr含有量が少なすぎて、ほぼキュリー温度に近い値を示す抵抗2倍温度(2倍点)が室温よりかなり高くなり、過熱検知の検知温度が高くなり過ぎて、好ましくない。
表1Bの試料番号208~211,214~217,220~223,
表1Cの試料番号308~311,314~317,320~323,
表1Dの試料番号408~411,414~417
の各試料の場合、ρ25℃≦120Ω・cmの低比抵抗を実現することが可能になり、かつ、高い抵抗-温度特性向上の効果が得られる。具体的には、10.0≦{α10-100/Log(ρ25℃)}≦12.0を実現することができる。
(a)半導体セラミックグリーンシートと、未焼成内部電極パターンとを交互に積層することにより、複数の半導体セラミックグリーンシートと、複数の内部電極パターンとを備え、半導体セラミックグリーンシートと内部電極パターンとが交互に積層された構造を有する積層体からなる未焼成半導体セラミック素体を形成する工程、
(b)未焼成半導体セラミック素体を焼成して、図2に示すような半導体セラミック素体13を得る工程、
(c)半導体セラミック素体13の外表面に外部電極14a,14bを形成する工程
などを経て製造することができる。
また、図3は、本発明のPTCサーミスタを用いた温度検知(過熱検知)回路を示す図である。
この温度検知(過熱検知)回路は、抵抗101と、PTCサーミスタ102と、抵抗101とPTCサーミスタ102の間にベース端子が接続されたトランジスタ111と、電圧供給を受け、制御信号を出力する制御用集積回路112と、制御信号を受け、システムをシャットダウンする電源制御用集積回路113とを備えている。
2 半導体セラミック素体
3a,3b 電極
10 積層型のPTCサーミスタ
11 半導体セラミック層
12a,12b 内部電極
13 積層型の半導体セラミック素体
14a,14b 外部電極
101 抵抗
102 PTCサーミスタ
111 トランジスタ
112 制御用集積回路
113 電源制御用集積回路
Claims (5)
- 半導体セラミック素体と、前記半導体セラミック素体の外表面に形成された外部電極とを備えるPTCサーミスタであって、
前記半導体セラミック素体が、Ba、Ti、SrおよびCaを含むペロブスカイト型化合物と、Mnと、半導体化剤とを含有し、
Ba、Sr、Caおよび半導体化剤の合計含有モル部を100としたときの、Srの含有モル部aおよびCaの含有モル部bが、
20.0≦a≦22.5のとき、12.5≦b≦17.5、
22.5≦a≦25.0のとき、12.5≦b≦15.0
であり、
TiおよびMnの合計含有モル部を100としたときの、Mnの含有モル部cが、
0.030≦c≦0.045
であること
を特徴とするPTCサーミスタ。 - 前記半導体セラミック素体が、複数の半導体セラミック層と、複数の内部電極とを備え、前記半導体セラミック層と前記内部電極とが交互に積層されてなる積層構造部を有する積層体であることを特徴とする請求項1記載のPTCサーミスタ。
- 過熱検知素子として用いられるものであることを特徴とする請求項1または2記載のPTCサーミスタ。
- 半導体セラミック素体と、前記半導体セラミック素体の外表面に形成されている外部電極とを備えるPTCサーミスタの製造方法であって、
未焼成半導体セラミック素体を作製する工程Aと、
前記未焼成半導体セラミック素体を焼成して半導体セラミック素体を得る工程Bと、
前記半導体セラミック素体の外表面に外部電極を形成する工程Cと、
を備えるPTCサーミスタの製造方法であって、
前記未焼成半導体セラミック素体が、Ba、Ti、SrおよびCaを含むペロブスカイト型化合物と、Mnと、半導体化剤とを含有し、
Ba、Sr、Caおよび半導体化剤の合計含有モル部を100としたときの、Srの含有モル部aおよびCaの含有モル部bが、
20.0≦a≦22.5のとき、12.5≦b≦17.5、
22.5≦a≦25.0のとき、12.5≦b≦15.0
であり、
TiおよびMnの合計含有モル部を100としたときの、Mnの含有モル部cが、
0.030≦c≦0.045
であること
を特徴とするPTCサーミスタの製造方法。 - 前記工程Aで作製される未焼成半導体セラミック素体が、複数の半導体セラミックグリーンシートと、複数の未焼成内部電極パターンとを備え、前記半導体セラミックグリーンシートと前記未焼成内部電極パターンとが交互に積層された積層構造部を有する未焼成積層体であることを特徴とする請求項4記載のPTCサーミスタの製造方法。
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WO2016084562A1 (ja) * | 2014-11-26 | 2016-06-02 | 株式会社村田製作所 | チタン酸バリウム系半導体セラミック、チタン酸バリウム系半導体セラミック組成物および温度検知用正特性サーミスタ |
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