JPWO2015002197A1 - PTC element and heating module - Google Patents

Abstract

A PTC element in which a base metal electrode is formed by baking on a semiconductor ceramic composition, the semiconductor ceramic composition has a perovskite structure made of a BaTiO3 type oxide, and the base metal electrode has Al as a metal component, A low resistance layer having at least one of Ni as a main component and containing at least B and having a lower resistance than the parent phase of the semiconductor ceramic composition is formed on the base metal electrode side of the semiconductor ceramic composition. PTC element.

Description

  The present invention relates to a PTC element and a heat generating module in which electrodes are formed on a semiconductor ceramic composition having a positive resistance temperature coefficient.

Conventionally, a semiconductor porcelain composition in which various semiconducting elements are added to a perovskite-based composition represented by BaTiO ₃ has been proposed as a material exhibiting PTC characteristics (Positive Temperature Coefficient of resiliency). . The PTC characteristic is a characteristic in which the resistance value increases rapidly when the temperature becomes higher than the Curie point. A semiconductor ceramic composition having PTC characteristics is used as a PTC element in which an electrode is formed.

Patent Document 1 discloses a PTC element using a lead-free semiconductor ceramic composition and an electrode. As the semiconductor ceramic composition, BaTiO ₃ 50 to 85%, CaTiO _{3 3 to} 15%, SrTiO ₃ to 50%, SiO ₂ 1 to 1 are used. 2% is preferred (see paragraph 0006). As a method for forming the electrode, the electrode or the partial layer of the electrode is preferably produced by a metal deposition method. Examples of metal deposition methods include sputtering, vapor deposition, electrolytic deposition, and chemical deposition. However, it is described that the electrode may be produced by baking a metal paste (see paragraph 0007).

In Patent Document 2, a Ba _m TiO ₃ composition having a perovskite structure represented by the general formula A _m BO ₃ is a main component, and a part of Ba constituting the A site is at least an alkali metal element, Bi And a rare earth element, and the molar ratio m between the A site and the B site is 0.990 ≦ m ≦ 0.999, and a semiconductor ceramic having a good rise characteristic is described (see paragraph 0026). ). In addition, there is a description that an external electrode is formed by plating, sputtering, electrode baking, or the like, thereby obtaining a PTC thermistor (see paragraph 0069). In the examples, dry plating is performed to form an external electrode having a three-layer structure of NiCr / NiCu / Ag (see paragraph 0079).

In the PTC element, the material cost of the electrode and the cost for the manufacturing process for forming the electrode occupy a very large proportion of the entire manufacturing cost.
The metal deposition method, which is one of the electrode forming methods, has the advantages that it is easy to improve the adhesion between the semiconductor ceramic composition and the electrode, and to easily reduce the resistance at the interface between them (hereinafter referred to as interface resistance). If the interface resistance decreases, the resistance of the PTC element (hereinafter referred to as element resistance) also decreases, and the current efficiency of the PTC element can be improved. On the other hand, however, the metal deposition method has a problem of high production costs.

  A baking method may be employed as a means for forming the electrode at a low cost. Baking is an electrode paste in which metal powder is dispersed in a glass component or organic component, which is applied to a semiconductor ceramic composition by printing or the like, and heated to evaporate the glass component or organic component from the electrode paste. Thus, the metal component is left to form an electrode.

In Patent Document 3, a PTC element having at least two ohmic electrodes and a semiconductor ceramic composition in which a part of BaTiO ₃ disposed between the electrodes is substituted with Bi-Na, the semiconductor ceramic composition things, a composition formula _{[(Bi-Na) x (} Ba 1-y-θ R y a θ) 1-x] Ti 1-z M z O 3 ( provided that at least one of R is a rare earth element, a Represents at least one of Ca and Sr, and M represents at least one of Nb, Ta, and Sb), and x, y, z, and θ are 0 <x ≦ 0.30, 0 ≦ y ≦ 0.020, 0 ≦ z ≦ 0.010, 0 ≦ θ ≦ 0.20 is satisfied, and the proportion of the area where the ohmic component of the electrode and the semiconductor ceramic composition are not in contact at the interface between the electrode and the semiconductor ceramic composition is 25% or less A PTC element is disclosed. In the examples, it is described that this electrode is mainly composed of Ag as a metal component.

  By the way, the electrode uses a noble metal electrode paste mainly composed of elements such as Ag, Au and Pt as a metal component and a base metal electrode paste mainly composed of elements such as Al and Ni. There is. If a noble metal electrode paste is used, it is difficult to oxidize, so that the electrode can be baked in the atmosphere. However, since the noble metal element is expensive, it hinders the cost reduction of the PTC element.

On the other hand, the base metal electrode paste is very inexpensive because it contains Al, Ni or the like as a metal component as a main component. However, it tends to oxidize and hinders a reduction in resistance.
Patent Document 4 discloses an electrode of an electronic component comprising metal aluminum, boron nitride 0.1 to 10% by weight, and glass frit (lead borosilicate glass) 0.01 to 5% by weight. This electrode material can be made into an electrode having ohmic properties with respect to a ceramic element by firing at 850 to 900 ° C. in air.

Japan Special Table 2010-501988 International Publication No. WO2010 / 067866 Japanese Unexamined Patent Publication No. 2012-169515 Japanese Unexamined Patent Publication No. 3-233805

However, when a base metal electrode using Al or Ni (hereinafter simply referred to as an electrode) is baked on a BaTiO ₃ based semiconductor ceramic composition, a gap is formed at the interface between the semiconductor ceramic composition and the electrode. , Both will not make ohmic contact. Therefore, the problem that the interface resistance per unit area (1 cm < ² >) in the interface of a semiconductor ceramic composition and an electrode becomes large exceeding 10 (ohm), for example occurred. When the interface resistance increases, the current efficiency of the PTC element decreases. Hereinafter, description of “around the unit area (1 cm ² )” is omitted, and simply referred to as interface resistance.

An object of the present invention is to provide a PTC element and a heating module having a sufficiently low interface resistance when a base metal electrode is formed by baking on a semiconductor ceramic composition having a perovskite structure made of a BaTiO ₃ type oxide.

The present invention is a PTC element formed by baking a base metal electrode on a semiconductor ceramic composition, wherein the semiconductor ceramic composition has a perovskite structure made of a BaTiO ₃ type oxide, A low-resistance layer containing at least one of Al and Ni as a metal component as a main component and containing at least B, and having a lower resistance than the parent phase of the semiconductor ceramic composition on the base metal electrode side of the semiconductor ceramic composition Is a PTC element formed.

  In the PTC element of the present invention, the thickness of the low resistance layer is preferably 0.1 μm or more.

The present invention can provide a PTC element in which the thickness of the low resistance layer is 0.4 μm or more and the interface resistance of the element per unit area (1 cm ² ) is 5Ω or less.

In the present invention, a PTC element having an element resistance of 10Ω or less per unit area (1 cm ² ) can be obtained.

  The present invention can provide a PTC element having a surface resistance of 10 mΩcm or less.

  In the PTC element of the present invention, it is preferable that a reaction phase mainly composed of Ba oxide exists on the semiconductor ceramic composition side of the base metal electrode.

  The base metal electrode of the present invention may include B in an amount of 3% by mass to 25% by mass with the total of Al, Ni, and B being 100% by mass.

  The base metal electrode of the present invention contains Si as a metal component, the total of Al, Ni, B, and Si is 100% by mass, B is 3% by mass to 25% by mass, and Si is more than 0% by mass 26 It can be included at mass% or less.

  The base metal electrode of the present invention may include Al at 50% by mass or more, with the total of Al, Ni, B, and Si being 100% by mass.

  The base metal electrode according to the present invention may include 5 to 40% by mass of Ni with the total of Al, Ni, B and Si being 100% by mass.

  In the base metal electrode of the present invention, Al particles having an average particle diameter of 1.2 μm or more and 10 μm or less may be dispersed.

The semiconductor ceramic composition of the present invention, the composition formula _{[(BiA) x (Ba 1} -y R y) 1-x] [Ti 1-z M z] O 3 (A is Na, Li, among the K At least one, R is at least one of rare earth elements including Y, M is at least one of Nb, Ta, and Sb), and x, y, and z are 0 <x ≦ 0.25, 0 ≦ y. It can be set as the composition which satisfies the range of <= 0.052, 0 <= z <= 0.01 (however, y + z> 0).

  The base metal electrode of the present invention can be baked at a temperature of 720 ° C. or higher and 850 ° C. or lower in an air atmosphere.

  The present invention is a heating module comprising any one of the above PTC elements and generating heat from the semiconductor ceramic composition.

  According to the present invention, it is possible to provide a PTC element having a low interface resistance even when a base metal electrode is formed by baking. The PTC element can also be a PTC element having a low element resistance. And the heat generating module excellent in current efficiency can be provided using this PTC element.

It is a SEM observation photograph of the section of the PTC element by one embodiment of the present invention. It is a schematic diagram of FIG. It is Al mapping screen by EDX analysis in the same visual field as FIG. FIG. 4 is a schematic diagram of FIG. 3. It is a Ba mapping screen by EDX analysis in the same visual field as FIG. It is a schematic diagram of FIG. It is a SSRM observation photograph of the section of the PTC element by another embodiment of the present invention. It is a schematic diagram of FIG. It is a schematic diagram which shows an example of the heat generating module by one Embodiment of this invention. It is a figure for demonstrating the measuring method of interface resistance.

  The present inventors include a low-resistance auxiliary agent such as B (boron) as a metal component of a base metal electrode using Al or Ni, so that the base metal electrode side of the semiconductor ceramic composition is compared with the parent phase. It has been found that a low resistance layer having a low resistance is formed, which improves the ohmic contact, and thus the interface resistance and the like can be reduced. Hereinafter, the reduction in resistance of the PTC element of the present invention will be described.

FIG. 1 is a SEM observation photograph of a cross section of a PTC element showing an example of the present invention, and FIG. 2 is a schematic diagram thereof. FIG. 7 is an observation photograph of a cross section of a PTC element similarly by a scanning spread resistance microscope (SSRM), and FIG. 8 is a schematic view thereof.
1 and 2, reference numeral 1 denotes a base metal electrode, and 2 denotes a semiconductor ceramic composition having a perovskite structure made of a BaTiO ₃ type oxide. The interface between the base metal electrode 1 and the semiconductor ceramic composition 2 is a broken line portion 7 drawn to the left and right in the figure, and the low resistance layer 3 is formed on the base metal electrode side of the semiconductor ceramic composition 2. I understand. 7 and 8, it can be seen that the color tone of the low resistance layer 3 is darker than the others, and is lower in resistance than the mother phase. That is, in this specification, the low resistance layer refers to a layer that forms a portion having a smaller resistance compared to the parent phase of the semiconductor ceramic composition, and its resistance value is, for example, 1 Ω · cm or less. Details will be described later.

  Since the low-resistance layer 3 has low electrical resistance and a large number of carriers as a semiconductor, the Schottky barrier between the low-resistance layer 3 and the base metal electrode 1 is lowered, and ohmic contact is made to reduce the interface resistance. The low resistance layer 3 is not necessarily a continuous layer, but is preferably formed so as to spread over the entire interface, and its thickness is preferably 0.1 μm or more. If it is 0.2 μm or more, it is more preferable because resistance reduction is promoted, more preferably 0.4 μm or more, and most preferably 0.5 μm or more. The upper limit of the thickness is influenced by the amount of B and the baking temperature, but even if the thickness exceeds 3 μm, the effect of reducing the interface resistance cannot be expected so much. This is because the low resistance auxiliary agent such as B itself has a high resistance, and if the amount added is excessive, there are problems such as a decrease in insulation resistance and thermal conductivity.

  When the low resistance layer 3 is formed, the base metal electrode 1 is formed with a thicker reaction phase 4 formed by diffusion of Ba to the electrode side than in the prior art. This reaction phase 4 is made of an oxide containing Ba as a main component. Moreover, since the reaction phase 4 is formed so as to fill a gap at the interface between the low-resistance layer 3 and the electrode 1 and a gap between the Al particles, the contact area between the two increases and the interface resistance decreases. doing. Further, when the reaction phase 4 becomes thick, there is an effect that the adhesion strength between the semiconductor ceramic composition and the electrode is increased. The presence or absence of the reaction phase can be discriminated from the SEM observation photograph but is not quantitatively defined because the shape is indefinite and the size is difficult to specify. However, if a low resistance layer is formed, a reaction phase is also formed. The thicker the low resistance layer, the thicker the reaction phase.

  The mechanism by which the low resistance layer is formed is not clear, but is considered as follows. When an easily oxidizable element such as B is introduced into the base metal electrode, B or the like takes oxygen from the semiconductor porcelain composition during baking and creates an oxygen defect in the crystal structure. The emitted electrons are generated near the interface, and this is considered to form a low resistance layer. In addition, all oxygen defects generated at this time do not emit electrons, and some of the oxygen defects move out of the semiconductor ceramic composition together with cations such as Ba and move to the electrode side to maintain electrical neutrality. It is considered that Ba moved at this time reacts with the electrode side to form a reaction phase. As the low resistance auxiliary agent having such an action, B is most preferable, but any element that exhibits the above mechanism may be used. For example, at least one of Zn, Ca, Sb, and Sn may be used together with B or independently. It may be used.

  In the present invention, the base metal-based electrode is one having as a main component at least one of Al and Ni as a whole metal component. The phrase “having at least one of Al and Ni as a main component” means that the content of Al or Ni is 50% by mass or more, or the sum of the contents of Al and Ni is 50% by mass or more. However, since Al is cheaper than Ni, it is preferable to use an electrode with more Al than Ni, and Al is chemically stable and highly reliable because the vicinity of the metal surface is covered with an oxide layer. Oxidation hardly proceeds to the inside, so that baking in an air atmosphere is easy. In this respect, the cost can be reduced.

B contained in the base metal electrode is preferably 3% by mass or more and 25% by mass or less, with the total of Al, Ni, and B being 100% by mass. By including B, a low resistance layer having a thickness of 0.1 μm or more can be formed. Further, when the content is 3% by mass or more, the thickness of the low resistance layer is 0.4 μm or more, and the PTC element having an interface resistance of 5Ω or less can be obtained by sufficiently forming the low resistance layer and the reaction phase. . Note that Si may be contained as described below.
When B exceeds 25% by mass, B oozes out to the surface layer of the electrode, and an oxide layer starts to form on the surface, so that the surface resistance of the electrode tends to increase. Further, since the element resistance tends to increase, the upper limit is preferably 25% by mass or less. More preferably, the PTC element has an interface resistance of 1.5Ω or less, an element resistance of about 5Ω or less, and a surface resistance of 10 mΩcm or less. Furthermore, if it is 5 mass% or more and less than 10 mass%, in addition, the PTC element whose surface resistance is 2 mΩcm or less can be obtained. Here, the surface resistance is a value obtained by measuring the resistance of the base metal electrode itself. By reducing the surface resistance, there is an effect that an electric field can be uniformly applied to the PTC element.

  The base metal electrode contains Si as a metal component, the total of Al, Ni, B, and Si is 100% by mass, B is 3% by mass to 25% by mass, Si is more than 0% by mass and 26% by mass. Can be included below. By containing Si in the above range, the moisture resistance can be improved, and the change over time of the element resistance, particularly the change over time of the PTC element under a high temperature and high humidity environment can be reduced. In addition, the inclusion of Si makes it difficult to melt Al particles that are difficult to melt, increasing the ratio of the contact area of the interface between the Al particles and reducing the interface resistance. The Si content is preferably 5.0% by mass or more and 20.0% by mass or less, and more preferably 5.0% by mass or more and 15.0% by mass or less.

  B is preferably added in the form of a single metal rather than an oxide. If B is a stable compound such as an oxide or nitride, the ability to deprive oxygen from the semiconductor porcelain composition cannot be exhibited, or the ability to deprive oxygen is weak, making it difficult to form a low resistance layer. Further, if the low resistance layer is not formed, Ba of the semiconductor ceramic composition is difficult to move to the electrode side, so that the reaction phase is hardly formed.

  The base metal electrode preferably contains Si, and the total of Al, Ni, B, and Si is 100% by mass, and Al is 50% by mass or more. The cost of the electrode can be further reduced.

  Further, the base metal electrode may contain 5 mass% or more and 40 mass% or less of Ni, with the total of Al, Ni, B, and Si being 100 mass%. Preferably, when Al is contained in an amount of 50% by mass or more and Ni is contained in the above range, the Ni particles remove the oxide layer on the surface of the Al particles at a low temperature to facilitate the alloying of the Al particles and the Ni particles. Electrode baking temperature can be lowered. However, it is desirable to adjust the baking time so that an excessive sintering reaction does not occur. If the amount of Ni is 5% by mass or more, the above effect can be sufficiently obtained. Further, if the amount of Ni does not exceed 40% by mass, it is easy to avoid an increase in the resistance of the electrode itself, and it is possible to suppress an increase in the material cost of the electrode. If the amount of Ni is 20% by mass or more, the baking temperature can be further lowered, and specifically, baking at 700 ° C. becomes possible.

  If Ni is 20% by mass or less, B is 5% by mass or more and 10% by mass or less, Si is 5.0% by mass or more and 15.0% by mass or less and the remaining Al is a base metal electrode, the interface resistance is 1.5Ω or less. A PTC element having an element resistance of 10Ω or less and a surface resistance of 2.0 mΩcm or less can be obtained.

As the Al powder used for the base metal electrode, those having an average particle diameter of 1.2 μm or more and 10 μm or less can be suitably used. In addition, it is more preferable to use one having a particle size distribution with a median diameter d30 of 0.1 μm or more and less than 1.2 μm.
The Al particles in the base metal electrode are difficult to melt because of the presence of an oxide film on the surface, and as shown in FIG. 2, the Al particles remain approximately the same size as when included in the electrode paste before firing. Therefore, the gap 6 is easily formed between the Al particles, the contact area between the semiconductor ceramic composition and the electrode is reduced, and the interface resistance is easily increased. Therefore, it is preferable to use Al particles having an average particle size of 1.2 μm or more and 10 μm or less, and further by using an electrode structure having a particle size distribution including about 20 to 40% of small particles less than 1.2 μm. A small Al particle of 0.1 μm or more and less than 1.2 μm is filled between 2 μm or more and 10 μm or less of Al particles, and the gap at the interface is reduced. In addition, since the ratio of the contact area between the semiconductor ceramic composition and the electrode increases due to the presence of the reaction phase 4 formed to be relatively thick, the interface of the PTC element can be formed even when an electrode in which relatively large Al particles are dispersed is formed. It is easy to reduce the resistance. At the same time, the adhesion strength of the electrode is increased.

When the base metal electrode has Al particles and Ni particles dispersed therein, it is preferable to use Ni particles having an average particle size smaller than that of the Al particles. The gap between the Al particles and the semiconductor ceramic composition is easily filled with Ni particles, which contributes to reducing the interface resistance. For example, if the average particle diameter of Al particles is 1.2 μm or more and 10 μm or less, the average particle diameter of Ni particles is preferably 0.1 μm or more and 5 μm or less.
In addition, the risk of dust explosion increases as the particle size of Al particles decreases, and handling becomes difficult. On the other hand, when it exceeds 10 μm, the ratio of the contact area tends to be small, and it is difficult to reduce the interface resistance.

Next, the preferable manufacturing method for obtaining the PTC element of this invention is demonstrated.
First, a semiconductor porcelain composition having a perovskite structure made of a BaTiO ₃ type oxide is prepared, and a base metal containing at least one of Al and Ni as a main component and containing at least B as a metal component in the semiconductor porcelain composition. A production method can be employed in which a system electrode paste is applied to a desired thickness by printing or the like, heated in an air atmosphere at a temperature of 720 ° C. or more and 850 ° C. or less, and a base metal electrode is baked.

Even if the baking temperature is as low as about 720 ° C., the base metal electrode is less likely to have insufficient bonding between the semiconductor ceramic composition and the electrode and can easily suppress an increase in interface resistance.
Since B also has an effect as an oxidation inhibitor, the use of a base metal electrode paste to which B is added suppresses the oxidation of the semiconductor ceramic composition and the base metal electrode even when the baking temperature is as high as about 850 ° C. This makes it easy to obtain a PTC element having a low element resistance.
The baking temperature is preferably 750 ° C. or more and 830 ° C. or less, and a PTC element having an interface resistance of 5Ω or less and an element resistance of 10Ω or less can be obtained. By reducing the element resistance, a PTC element excellent in current efficiency can be obtained. More preferably, it is 750 degreeC or more and 800 degrees C or less.

  As for the baking time of the base metal electrode, the time of exposure to a temperature of 720 ° C. or more and 850 ° C. or less is preferably 10 minutes or more and 5 hours or less. If the baking time is longer than 10 minutes, it is easy to suppress an increase in the interface resistance due to insufficient bonding between the semiconductor ceramic composition and the electrode. If the baking time exceeds 5 hours, the oxidation suppressing effect tends to be reduced. If the baking time is shorter than this, oxidation of the semiconductor ceramic composition is suppressed, and a PTC element having a low element resistance can be easily obtained. The baking time is preferably 15 minutes to 1 hour, more preferably 20 minutes to 50 minutes.

  The thickness of the electrode is preferably 5 μm or more and 50 μm or less. If it is 5 micrometers or more, it will become easy to suppress generation | occurrence | production of application | coating nonuniformity and peeling of an electrode. If the thickness is 50 μm or less, the cost of the electrode can be reduced. Preferably they are 10 micrometers or more and 35 micrometers or less, More preferably, they are 12 micrometers or more and 30 micrometers or less.

  The base metal electrode paste can lower the baking temperature to 700 ° C. by setting Ni to 20% by mass or more.

  In order to prevent oxidation of the base metal electrode and improve the wettability of the solder, a noble metal electrode such as an Ag-based electrode can be formed on the base metal electrode as the second layer electrode. Furthermore, it is possible to have a three-layer or more electrode structure in which another electrode is formed on the noble metal-based electrode.

Next, the preferable form of a semiconductor ceramic composition is demonstrated.
The semiconductor ceramic composition may have a perovskite structure made of a BaTiO ₃ type oxide, and among them, a lead-free semiconductor ceramic composition is preferable. For example, at least one of the composition formula _{[(BiA) x (Ba 1} -y R y) 1-x] [Ti 1-z M z] O 3 (A is Na, Li, K, R comprises Y At least one of rare earth elements, M is at least one of Nb, Ta, and Sb), and x, y, and z are 0 <x ≦ 0.25, 0 ≦ y ≦ 0.052, and 0 ≦ z. It is preferable that the composition satisfies a range of ≦ 0.01 (provided that y + z> 0).

By using the above-mentioned semiconductor ceramic composition, it becomes easier to obtain a PTC element having a higher resistance temperature coefficient α than using a semiconductor ceramic composition containing Pb as a dopant. Specifically, even a PTC element having a low element resistance (10Ω or less) can be obtained with a resistance temperature coefficient α of 2.5% / ° C. or more, preferably 3.5% / ° C. or more.
A semiconductor ceramic composition containing Pb as a dopant tends to have a low temperature coefficient of resistance α. This is an estimate, but during baking, the base metal electrode paste deprives the grain boundary layer oxygen in the semiconductor porcelain composition, thereby easily losing the Schottky barrier formed inside the composition. It is assumed that α tends to be small. On the other hand, the semiconductor porcelain composition having the above composition is only deprived of oxygen in the surface layer in contact with the electrodes in the semiconductor porcelain composition, and is deprived of oxygen in the grain boundary phase inside the composition exhibiting jump characteristics. As a result, a high resistance temperature coefficient α can be maintained. For these reasons, it is more preferable to use a semiconductor ceramic composition having the above composition, which is one of the new findings obtained in the course of studying the present invention.

The reasons for limiting each element in the composition formula of the semiconductor ceramic composition will be described below.
The addition amount x of Bi or A is more than 0 and not more than 0.25. By setting x to more than 0, the Curie temperature can be increased to 130 ° C. or higher.
If x exceeds 0.25, the element resistance increases. In addition, since Bi and A elements are easily evaporated during sintering, the number of moles of Ba site elements is smaller than that of Ti sites. As a result, since the semiconductor ceramic composition becomes Ti-rich, the Ti-rich phase is deposited as a different phase. Since part of the Ti-rich phase melts during sintering, the yield may deteriorate and a semiconductor ceramic composition having a desired shape may not be obtained.

  At least one of the addition amount y of R and the addition amount z of M is essential, that is, y + z> 0. The resistance temperature coefficient α can be increased by adding R element and M element. However, both R and M are not necessarily required, and at least one of them may be used.

  The range of the addition amount y of R is 0 or more and 0.052 or less (provided that y + z> 0). If y exceeds 0.052, the temperature coefficient of resistance, which is a PTC characteristic, is small, and the semiconductor ceramic composition does not have good heat resistance. Moreover, since the temperature required for sintering becomes high and this temperature may exceed the heat resistance of the sintering furnace, it is not preferable in production. R is at least one element selected from rare earths containing La (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). La is preferable because an excellent PTC characteristic can be obtained.

  The range of the addition amount z of M is 0 or more and 0.01 or less (provided that y + z> 0). When z exceeds 0.01, the element resistance increases. Further, since the mechanical strength of the semiconductor ceramic composition is lowered and cracking is likely to occur when the PTC element is formed, it is not preferable in production. M is particularly preferable because Nb can provide excellent PTC characteristics.

  The ratio of Bi to A may be 1: 1, but when the materials are blended, even if the ratio is 1: 1, Bi is volatilized by the calcination or sintering process, causing a deviation in the ratio of Bi to A and sintering. This includes cases where the body is not 1: 1. In other words, Bi: A = 0.78 to 1.55: 1 is acceptable, and if it is within this range, an increase in heterogeneous phase can be suppressed, so that an increase in room temperature resistivity and a change with time can be suppressed. A more preferable range is Bi: A = 0.90 to 1.2: 1. By setting this range, the effect of improving the Curie temperature can be obtained.

  In addition, in this specification, the evaluation method of each characteristic value is as follows.

(Element resistance per unit area)
A base metal electrode is formed on both main surfaces of the semiconductor ceramic composition to form a PTC element, and an ammeter / voltmeter probe is brought into contact with the base metal electrode on both sides, and the element resistance is measured at room temperature (25 ° C.) by a four-terminal method. Was measured.
This element resistance is the element resistance of the entire PTC element, and the element resistance per unit area (1 cm ² ) can be calculated by dividing the area (cm ² ) of the range covered with the electrodes.
In the following examples, the thickness of the semiconductor porcelain composition is evaluated at 1 mm and the area is 1 cm ^2. Therefore, the element resistance value can be converted to room temperature specific resistance (Ωcm) by multiplying by 10.

(Interface resistance per unit area)
First, a base metal electrode is provided on the semiconductor ceramic composition, and the element resistance is measured. Thereafter, the electrode is peeled off once, the thickness of the semiconductor ceramic composition is reduced to 3/4 from the initial thickness, a base metal electrode is provided again, and the element resistance is measured. Similarly, the thickness of the semiconductor ceramic composition is reduced to 2/4 and 1/4 of the initial thickness, and the element resistance is measured each time. As shown in FIG. 10, the horizontal axis represents the thickness of the semiconductor ceramic composition, and the vertical axis represents the element resistance plotted. From this data, an approximate straight line between the thickness of the semiconductor ceramic composition and the element resistance is obtained. When this approximate straight line is expressed as R = a · Δt + R ₀ (Δt: thickness, R: element resistance, a: resistivity of the semiconductor ceramic composition), the resistance value R ₀ when the thickness Δt is 0 on the graph is convenient. Can be calculated automatically. In the present invention, this resistance value R ₀ is regarded as the interface resistance. This interface resistance is the interface resistance of the entire PTC element, and the interface resistance per unit area (1 cm ² ) can be calculated by dividing the area (cm ² ) in the range covered with the electrodes.

(Low resistance layer thickness)
The thickness of the low resistance layer was measured from a SEM observation photograph (magnification 3000 times) as shown in FIG. 1 and a mapping (Al) of EDX analysis of the same visual field as shown in FIG. In mapping (Al) of EDX analysis, a boundary part where Al is not detected is defined as an interface between the semiconductor ceramic composition and the electrode (indicated by a dotted line 7 in FIG. 2). Ten points of widths with different color tones were measured arbitrarily on the matrix side, and the average value was taken as the thickness of the low resistance layer. In the SEM observation photograph, the low resistance layer appears darker than the matrix and has a different color tone. The reaction phase can also be discriminated by the similar shades of shade and different color tone. Since the low-resistance layer and the reaction phase are formed almost simultaneously, if the layer that appears darker than the parent phase is visible on the electrode side of the semiconductor ceramic composition in the SEM observation photograph, the presence of both the low-resistance layer and the reaction phase is confirmed. It will be possible.

(Confirmation of low resistance)
Moreover, the confirmation means that the low-resistance layer is reducing in resistance was evaluated using a scanning spreading resistance microscope (manufactured by Bruker AXS: NanoScope IVa AFM Dimension 3100). According to this method, by scanning the interface between the semiconductor ceramic composition and the electrode with a conductive probe, the resistance value distribution can be measured two-dimensionally and the resistance can be visualized. Specifically, a mapping image is obtained in which the electrical resistance value is represented by the color shading, and the dark portion has a low resistance, so that the parent phase (at least 5 μm from the surface when viewed in the thickness direction). It can be visually recognized by the difference in color tone (shading) of the low resistance layer.

(Surface resistance)
The surface resistance is a value obtained by measuring the resistance of the base metal electrode itself. The resistance Rw in the planar direction of the formed electrode is measured by the four-terminal method, and the resistivity (= Rw × (W × T) / L) from the length L, the electrode width W, and the electrode thickness T measured by SEM observation. ). In this embodiment, W is 1 cm, L is 1 cm, and T is 0.0025 cm. However, since it was difficult to make the electrode thickness T constant, it was measured each time. The first m of the unit mΩcm represents millimeter (10 ⁻³ ).

(Curie temperature)
The temperature showing a resistance twice the room temperature specific resistance at room temperature was defined as the Curie temperature.

(Resistance temperature coefficient α)
The temperature coefficient of resistance α was calculated by measuring resistance-temperature characteristics while raising the temperature to 260 ° C.
The resistance temperature coefficient α is defined by the following equation.
α = (lnR ₁ −lnR _c ) × 100 / (T ₁ −T _c )
R ₁ is a room temperature specific resistance at 260 ° C., T ₁ is a temperature indicating R ₁ , T _c is a Curie temperature, and R _c is a room temperature specific resistance at T _c .
The change with time is preferably 15% or less, more preferably 10% or less.

(change over time)
The reliability test of the electrode was evaluated by a high temperature and high humidity test. The change in element resistance before and after leaving for 1000 hours at 80 ° C. and 95% RH was measured.

(Metal component ratio of electrode)
The sum of Al, Ni, B, and Si was set to 100% by mass, and the ratio of each element was determined. For the measurement, an electron beam microanalyzer (manufactured by Shimadzu Corporation: EPMA1610) was used. As measurement conditions, the acceleration voltage was 15 kV, the current was 100 nA, the beam diameter was 10 μm, and an average value of five points was obtained.

  Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Example 1: No. 1-1)
100 parts by mass of spherical Al particles having an average particle diameter of 5 μm were added, 10 parts by mass of glass frit and 10 parts by mass of B were added thereto, and an organic binder and an organic solvent were added to obtain a base metal electrode paste.
B was not an oxide but a single metal B particle. B particles having an average particle diameter of 1 μm or less were used.
The Al ratio and B ratio in the base metal electrode paste are No. 1 in Table 1. As shown in 1-1.
A semiconductor ceramic composition used as a substrate was processed into a plate shape of 10 mm × 10 mm (plate surface dimension) × 1.00 mm (thickness dimension).
The base metal electrode paste was applied to both sides of the semiconductor ceramic composition by screen printing. After drying the applied electrode paste at 150 ° C., the temperature was raised in air at 30 ° C./min and maintained at 775 ° C. for 10 minutes, and the temperature was lowered at 30 ° C./min to obtain a PTC element on which a baked electrode was formed. The area covered by the electrode was 1 cm ² , and the electrode thickness was about 25 μm.

The semiconductor ceramic composition used in the examples was produced as follows.
Raw material powders of BaCO ₃ , TiO ₂ , and La ₂ O ₃ were prepared, blended so as to be (Ba _0.994 La _0.006 ) TiO _3, and mixed with pure water. The obtained mixed raw material powder was calcined in the atmosphere at 900 ° C. for 4 hours to prepare a first calcined powder.

Raw material powders of Na ₂ CO ₃ , Bi ₂ O ₃ and TiO ₂ were prepared, weighed and blended so as to be Bi _0.5 Na _0.5 TiO _3, and mixed in ethanol. The obtained mixed raw material powder was calcined in the atmosphere at 800 ° C. for 2 hours to prepare a second calcined powder.

The prepared first calcined powder (Ba _0.994 La _0.006 ) TiO ₃ and the second calcined powder Bi _0.5 Na _0.5 TiO ₃ are mixed at a molar ratio of 73: 7. [(Bi _0.5 Na _0.5 ) _0.0875 (Ba _0.994 La _0.006 ) _0.9125 ] TiO ₃ , and this is mixed and calcined by a pot mill using pure water as a medium. The powder was mixed and pulverized until the average particle size of the powder became 1.0 μm to 2.0 μm, and then dried. Subsequently, it heat-processed at 1150 degreeC for 4 hours, and obtained the 3rd calcined powder. After adding 1.0 mol% of Y ₂ O ₃ to the obtained calcined powder, mixing and pulverizing it with a pot mill using pure water as a medium until the average particle diameter becomes 1.0 μm to 2.0 μm, and then drying it. A mixed calcined powder was obtained. 10% by mass of PVA was added to the pulverized powder of the mixed calcined powder, mixed, and granulated by a granulator. The obtained granulated powder was molded with a uniaxial press machine to obtain a molded body. After debinding the molded body at 700 ° C., it was held at 1400 ° C. for 4 hours in a nitrogen atmosphere having an oxygen concentration of 0.01% (100 ppm) and then gradually cooled to obtain a sintered body of 50 mm × 25 mm × 4 mm. It was.

In addition, the said manufacturing method is an example and is not caught by this. For example, the raw material powders are mixed at once without obtaining the first and second calcined powders, pulverized, dried and then heat treated to obtain a calcined powder (corresponding to the third calcined powder above). Y ₂ O ₃ may be added and then manufactured in the same manner as described above.

  In addition, in order to measure the interface resistance, the above sintered body is processed into a plate shape having a plate surface size of 10 mm × 10 mm and a thickness of 1.00 mm, 0.75 mm, 0.50 mm, and 0.25 mm. Each sintered body of the prepared semiconductor ceramic composition was prepared, and a PTC element was produced in the same manner.

FIG. 1 shows the result of observing the boundary between the semiconductor ceramic composition of the PTC element and the electrode by SEM. FIG. 2 is a schematic diagram thereof. 3 is a mapping image of Al by EDX (energy dispersive X-ray spectroscopy) having the same field of view as FIG. 1, FIG. 4 is a schematic diagram of FIG. 3, FIG. 5 is an EDX mapping image of Ba having the same field of view as FIG. 6 is a schematic diagram of FIG.
A portion where Al is not detected is defined as an interface between the base metal electrode 1 and the semiconductor ceramic composition 2 (indicated by a dotted line 7 in FIGS. 2 and 4), and the low resistance layer 3 having a different color tone on the semiconductor ceramic composition 2 side from this interface. However, it can be seen that the reaction phase 4 is formed on the base metal electrode 1 side. The degree of penetration of Ba is not clear, but is considered to have occurred to the extent indicated by dots in FIG.

  From the mapping of Al in FIG. 3, it can be seen that the portion (the portion indicated by 5 in FIG. 2) that looks mainly spherical in the base metal electrode 1 in FIG. 1 is Al. Al particles keep almost the same shape in the electrode after firing when they are contained in the electrode paste, but relatively small particles have entered between the large particles, and there are particles in the vicinity of the interface. Yes. In FIG. 1, the portions that appear black between the Al particles (portion 6 in FIG. 2) are voids inside the electrodes.

  FIG. 7 is a resistance mapping image of SSRM. A dark portion indicates a low resistance, and a light portion indicates a high resistance. FIG. 7 clearly shows that a deep color layer is formed on the semiconductor ceramic composition 2 side from the interface 7 between the base metal electrode 1 and the semiconductor ceramic composition 2. That is, this layer has a darker tone than the internal matrix and can be said to be a low-resistance layer 3 with reduced resistance. In addition, it confirmed that this low resistance layer 3 was in agreement with the low resistance layer 3 seen by the SEM observation image of FIG.

  Next, for the obtained PTC element, the Al ratio (mass%), Ni ratio (mass%), B ratio (mass%), Si ratio (mass%) in the metal component of the electrode, the thickness of the low resistance layer (μm) ), Interface resistance (Ω), element resistance (Ω), surface resistance (mΩ · cm), Curie temperature (° C.), resistance temperature coefficient α (% / ° C.), and change with time (%). The properties other than the interface resistance were measured using a semiconductor ceramic composition having a thickness of 1.00 mm. The obtained evaluation results are shown in Table 1.

In this example, the thickness of the low resistance layer is 0.5 μm, and there is a reaction phase, the interface resistance is 1.1Ω, the element resistance is 4.9Ω, the surface resistance is 0.9 mΩ · cm, and the Curie temperature is 160. The resistance temperature coefficient α was 4.1% / ° C., and the change with time was 12.5%. Therefore, the effect of lowering the resistance as well as the interface resistance and the element resistance was observed, and the PTC characteristics were also satisfied.
When the composition of the base metal electrode was measured by EPMA, the ratio (mass%) of Al, Ni, B, and Si shown in Table 1 was obtained. Also in the following examples and comparative examples, the ratios of Al, Ni, B, and Si in the tables indicate measured values by EPMA. This value was the same as each content ratio in the electrode paste.

(Example 2: No. 1-2 to 1-9)
No. In 1-2 to 1-9, no. With respect to 1-1, an electrode was formed in which a part of Al was replaced with Si, and the addition amount of B was changed.
Spherical Al particles having an average particle diameter of 5 μm and Si particles having an average particle diameter of 5 μm are mixed at a mass ratio of 92: 8, and the total value is 100 parts by mass. Mass parts and B were added as 3 parts by mass, 5 parts by mass, 7.5 parts by mass, 10 parts by mass, 12.5 parts by mass, 15 parts by mass, 20 parts by mass, and 25 parts by mass, respectively.
When the metal component after the base metal electrode was measured, the Al ratio, B ratio, and Si ratio were No. 1 in Table 1. As shown in 1-2 to 1-9. As described above, the Al ratio, B ratio, and Si ratio in the base metal electrode paste were the same as the values shown in Table 1.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
According to Table 1, the B ratio is 3% by mass or more. In the PTC elements 1-3 to 1-9, the low resistance layer had a thickness of 0.4 μm or more, and the interface resistance was 5Ω or less.
Moreover, No. B ratio is 5 mass% or more and 17 mass% or less. The PTC elements of 1-4 to 1-8 had an interface resistance of 1.5Ω or less and an element resistance of about 5Ω or less. The PTC element has a surface resistance of 10 mΩcm or less. Furthermore, the B ratio is 5% by mass or more and 10% by mass or less. The surface resistance of the PTC elements 1-4 to 1-5 was 2 mΩcm or less.

(Comparative Example 1: No. 1-10)
A base metal electrode to which B was not added was formed.
Si particles were added at a rate of 8 parts by mass with respect to 92 parts by mass of Al particles as in Example 1 to give 100 parts by mass, and 10 parts by mass of glass frit was added thereto to obtain a base metal electrode paste.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.
In this example, the low resistance layer could not be confirmed. Although the reaction phase was confirmed, the thickness of the reaction phase was about 1/5 or less as compared with the case where B was added. Further, the interface resistance was as large as 12Ω and the element resistance was as large as 15.5Ω.

(Comparative Example 2: No. 1-11, 1-12)
Base metal electrodes were formed using B ₂ O ₃ and H ₃ BO ₃ as additives for B.
Si was added at a rate of 8 parts by mass to 92 parts by mass of Al particles as in Example 1 to make 100 parts by mass, and there were 10 parts by mass of B ₂ O ₃ or H ₃ BO ₃ and 10 parts by mass of glass frit. To make a paste.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained results are shown in Table 1.
In this example, no. 1-11, No. 1 A low resistance layer could not be confirmed in both 1-12. However, the reaction phase was confirmed. However, the interfacial resistances were very large, 23.4Ω and 13.7Ω, respectively, and the element resistances were also large, 26.2Ω and 16.9Ω.

(Example 3: No. 2-1 to 2-5)
Base metal electrodes were formed by changing the baking temperature.
Spherical Al particles having an average particle diameter of 5 μm and Si particles having an average particle diameter of 5 μm are mixed at a mass ratio of 92: 8, and the total value is 100 parts by mass. Part by mass and B were added as 10 parts by mass.
A semiconductor ceramic composition processed into a plate shape of 10 mm × 10 mm (plate surface dimension) × 1.00 mm (thickness dimension) was used. Further, in order to measure the interface resistance, a semiconductor ceramic composition processed into a plate shape of 10 mm × 10 mm × 0.75 mm, 10 mm × 10 mm × 0.50 mm, 10 mm × 10 mm × 0.25 mm was also prepared.
The base metal electrode paste was applied to both sides of the semiconductor ceramic composition by screen printing. After the applied base metal electrode paste is dried at 150 ° C., the temperature is raised in the air at 30 ° C./min, and the holding temperature is changed to 725 ° C., 750 ° C., 775 ° C., 800 ° C., 825 ° C., 850 ° C. and held for 10 minutes Then, the temperature was lowered at 30 ° C./min and baked to obtain a PTC element in which an electrode was formed. The area covered by the electrode was 1 cm ² , and the electrode thickness was about 25 μm. Each of the above-mentioned semiconductor ceramic compositions having a plate thickness was similarly made into a PTC element.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
According to Table 2, the baking temperature was 725 ° C. 2-1 has a low resistance layer as thin as 0.2 μm and an interface resistance of 6.8Ω. The baking temperature is 750 ° C. or higher. In 2-2 to 2-5, the thickness of the low resistance layer was 0.4 μm or more, and the interface resistance was 5Ω or less. In addition, no. In 2-2 to 2-4, the element resistance was 10Ω or less.
From the above, it can be said that the baking temperature is more preferably 750 ° C. or higher and 830 ° C. or lower. It has been found that if the baking temperature exceeds 850 ° C., the semiconductor ceramic composition itself is oxidized and becomes high resistance.

(Example 4: Nos. 3-1 to 3-8)
A base metal electrode having a different amount of Si was prepared.
The same Al particles and Si particles as in the above example were used, and the mass ratios of Al and Si were 98: 2, 96: 4, 94: 6, 88:12, 84:16, 80:20, and 76:24, respectively. 72:28. The total value was 100 parts by mass, and 10 parts by mass of glass frit and 10 parts by mass of B were added thereto.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
According to Table 3, No. with Si ratio of 1.8-21.8 mass%. In 3-1 to 3-7, an interface resistance of 5Ω or less, an element resistance of 10Ω or less, and a surface resistance of 10 mΩcm or less were obtained. In addition, No. having a Si ratio of 5.5% by mass to 21.8% by mass. In 3-3 to 3-7, the change with time is 10% or less, and the effect of reducing the change with time is seen even with a small amount of Si.
In addition, No. whose Si ratio is 25.5 mass%. In 3-8, although the surface resistance exceeded 10 mΩcm, a PTC element with small element resistance and interface resistance was obtained.
From the above, it can be said that Si also has an effect of suppressing change with time, and is preferably 5.0% by mass or more and 15.0% by mass or less in consideration of lowering resistance.

(Example 5: No. 4-1 to 4-6)
A base metal electrode added with Ni was prepared.
Spherical Al particles having an average particle diameter of 5 μm, Si particles having an average particle diameter of 5 μm, and Ni particles having an average particle diameter of 0.2 μm are 82.8: 7.2: 10, 73 by mass ratio, respectively. 6: 6.4: 20, 64.4: 5.6: 30, 55.2: 4.8: 40, 27.6: 2.4: 70, 9.2: 0.8: 90 And the total value was made into 100 mass parts, and B was added as 10 mass parts with respect to it. The glass frit was 0 part by mass.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained evaluation results are shown in Table 4.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
According to Table 4, the interface resistance of all PTC elements was a small value of 2.5Ω or less. No. 4-1 showed the lowest resistance value. In particular, the Ni ratio is 5 mass% or more and 20 mass% or less. In 4-1 and 4-2, PTC elements having an interface resistance of 1Ω or less, an element resistance of 5Ω or less, and a surface resistance of 2.0 mΩcm or less were obtained.
From the above, it can be said that the Ni ratio is more preferably 20% by mass or less because the effect of lowering the interface resistance is increased by adding a small amount of Ni.
Further, from this example, it is considered that glass frit is not necessarily added, and it is desirable to add it when the baking temperature exceeds 800 ° C.

(No. 4-7 to 4-9)
As a base metal electrode, Ni was added and the amount of B was changed.
No. 4-7 to 4-12 are 55.2 in terms of mass ratio of spherical Al particles having an average particle diameter of 5 μm, Si particles having an average particle diameter of 5 μm, and Ni particles having an average particle diameter of 0.2 μm. : 4.8: 40, the total value was 100 parts by mass, and B was added thereto as 5.0, 7.5, and 12.5 parts by mass, respectively. The glass frit was 0 part by mass.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained evaluation results are also shown in Table 4.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
According to Table 4, with any PTC element, a PTC element having a low interface resistance of 1.0Ω or less and an element resistance of 5Ω or less was obtained.

(No. 4-10 to 4-12)
No. Using the base metal electrode paste prepared in 4-9, the baking temperature was changed. The obtained evaluation results are also shown in Table 4.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
According to Table 4, with any PTC element, a PTC element having a low interface resistance of 1.0Ω or less and an element resistance of 5Ω or less was obtained. The baking temperature was lowered to 700 ° C. 4-12 PTC elements have equivalent interface resistance and element resistance.

(Example 6: No. 5-1 to 5-8)
What changed the ratio of x and y about the composition of the semiconductor ceramic composition was produced.
No. In 5-1 to 5-4, y = 0.006 and z = 0. The values of x with respect to 1-5 are 0.02, 0.14, 0.18, and 0.2, respectively. In 5-5 to 5-7, x = 0.0875, z = 0, and the value of y was 0.003, 0.048, 0.05. The electrode is no. The same as 1-5 was formed. The same applies to the following examples. Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. The obtained evaluation results are shown in Table 5.

No. No. 5-8 is No.5. In contrast to 1-5, a rare earth element was not used as a semiconducting element (y = 0), a part of the Ti site was Ta, and the value of z in the composition formula was 0.009.
In this example, BaCO ₃ , TiO ₂ , and Ta ₂ O ₅ raw material powders were prepared, blended so as to be Ba (Ti _0.991 Ta _0.009 ) O _3, and mixed with pure water. The obtained mixed raw material powder was calcined in the atmosphere at 900 ° C. for 4 hours to prepare a first calcined powder.
The second calcined powder was produced in the same manner as in Example 1. Moreover, the manufacturing and evaluation method of the PTC element by the subsequent mixing, molding, sintering, and electrode formation of the first calcined powder and the second calcined powder were performed in the same manner as in Example 1. The obtained evaluation results are shown in Table 5.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
From the results shown in Table 5, the interface resistances of all the PTC elements were all 5Ω or less. A PTC element having a surface resistance of 2.0 mΩcm or less and a temperature coefficient of resistance α of 2.5% / ° C. or more is obtained.

(Example 7: No. 6-1 to 6-4)
What changed the particle diameter of the Al particle used with a base metal system electrode was produced.
No. In Example 6-1, Al particles having an average particle diameter of 3.8 μm are designated as No. 6-1. In No. 6-2, Al particles having an average particle size of 2.5 μm were obtained as In 6-3 and 6-4, Al particles having an average particle diameter of 1.5 μm were used. These Al particles and Si particles were mixed at a mass ratio of 92: 8, and the total value was 100 parts by mass, and 10 parts by mass of glass frit and 10 parts by mass of B were added thereto. No. 6-4 changed baking temperature to 750 degreeC.
Other methods for producing and evaluating the PTC element were performed in the same manner as in Example 1. Table 6 shows the obtained evaluation results.

It was confirmed that any PTC element had a low resistance layer having a resistance smaller than that of the parent phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed.
According to Table 6, both PTC elements having an interface resistance of 1Ω or less, an element resistance of 5Ω or less, and a surface resistance of 10.0 mΩcm or less are obtained.
By reducing the Al particles, the surface resistance tends to increase.

（実施例８：Ｎｏ．７−１）
半導体磁器組成物としてＰｂ入りの半導体磁器組成物を用いた。
Ｐｂ入りの半導体磁器組成物として、組成式が（Ｂａ_０．８３Ｐｂ_０．１７）ＴｉＯ_３で表されるものとした。それ以外のＰＴＣ素子の作製方法や評価方法は、Ｎｏ．１−５と同様の方法で行った。得られた評価結果を表７に示す。
母相よりも抵抗が小さい低抵抗層があることを確認できた。また、低抵抗層の厚さに相応する反応相の存在も確認された。抵抗温度係数が小さいという難点があるものの、素子抵抗、界面抵抗、表面抵抗は全て低い値を示した。

(Example 8: No. 7-1)
A semiconductor ceramic composition containing Pb was used as the semiconductor ceramic composition.
As a semiconductor ceramic composition containing Pb, the composition formula is represented by (Ba _0.83 Pb _0.17 ) TiO ₃ . Other methods for producing and evaluating the PTC element are described in No. The same method as in 1-5 was performed. Table 7 shows the obtained evaluation results.
It was confirmed that there was a low resistance layer having a lower resistance than that of the mother phase. The presence of a reaction phase corresponding to the thickness of the low resistance layer was also confirmed. Although there was a problem that the temperature coefficient of resistance was small, the element resistance, interface resistance, and surface resistance all showed low values.

(Heat generation module)
FIG. 9 is a schematic diagram of a heat generating module (PTC heater) according to an embodiment of the present invention.
As shown in FIG. 9, the heat generating module 20 can be configured by sandwiching and fixing the PTC element described above between metal radiation fins 21 a, 21 b, and 21 c. The PTC element 11 is composed of a base 1a of a semiconductor ceramic composition and base metal electrodes 2a, 2b, 2c, and the electrodes 2a, 2c are in thermal and electrical contact with the positive power supply electrodes 20a, 20c, respectively, The electrode 2b formed on the surface is thermally and electrically in close contact with the power supply electrode 20b on the negative electrode side. Further, the power supply electrodes 20a, 20b, and 20c are thermally connected to the radiation fins 21a, 21b, and 21c, respectively. The insulating layer 2d is provided between the power supply electrode 20a and the power supply electrode 20c, and electrically insulates them. The heat generated in the PTC element 11 is transmitted in the order of the electrodes 2a, 2b, 2c, the power supply electrodes 20a, 20b, 20c, and the radiation fins 21a, 21b, 21c, and is mainly released from the radiation fins 21a, 21b, 21c into the atmosphere. The

  If the power supply 30c is connected between the power supply electrode 20a and the power supply electrode 20b, or between the power supply electrode 20c and the power supply electrode 20b, the power consumption is reduced, and both the power supply electrode 20a and the power supply electrode 20c If it connects between the electric power supply electrodes 20b, power consumption will become large. That is, the power consumption can be changed in two stages. Thus, the heat generating module 20 can switch the heating capacity according to the load condition of the power source 30c and the desired degree of heating. The heating device 30 can be configured by connecting the heating module 20 capable of switching the heating capacity to the power source 30c. The power supply 30c is a DC power supply. The power supply electrode 20a and the power supply electrode 20c of the heat generating module 20 are connected in parallel to one electrode of the power supply 30c via separate switches 30a and 30b, respectively, and the power supply electrode 20b is connected to the other electrode of the power supply 30c as a common terminal. Connected. If only one of the switches 30a and 30b is made conductive, the heating capacity can be reduced to reduce the load of the power source 30c, and if both are made conductive, the heating capacity can be increased.

According to the heating device 30, the PTC element 11 can be maintained at a constant temperature without providing the power supply 30c with a special mechanism. That is, when the substrate 1a having a large resistance temperature coefficient is heated to the vicinity of the Curie temperature, the resistance value of the substrate 1a rapidly increases, the current flowing through the PTC element 11 decreases, and the substrate 1a is not automatically heated any further. Further, when the temperature of the PTC element 11 decreases from around the Curie temperature, a current flows again to the element, and the PTC element 11 is heated. By repeating such a cycle, the temperature of the PTC element 11 and thus the temperature of the heat generating module 20 as a whole can be made constant. Therefore, a circuit for adjusting the phase and amplitude of the power supply 30c, as well as the temperature detection mechanism and the target temperature. A comparison mechanism and a heating power adjustment circuit are also unnecessary.
The heating device 30 may flow air between the radiation fins 21a to 21c to warm the air, or connect a metal tube through which a liquid such as water passes between the radiation fins 21a to 21c to warm the liquid. it can. Also at this time, since the PTC element 11 is maintained at a constant temperature, a safe heating device 30 can be obtained.
Such a heat generating module is an example, and changes and modifications such as simplification with two electrodes can be added.

Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
In addition, this application is based on the Japan patent application (2013-139001) for which it applied on July 2, 2013, The whole is used by reference. Also, all references cited herein are incorporated as a whole.

1: Base metal electrode 2: Semiconductor porcelain composition 3: Low resistance layer 4: Reaction phase 5: Al particles 6: Air gap 11: PTC element 20: Heat generating modules 20a, 20b, 20c: Power supply electrodes 21a, 21b, 21c: Radiating fins 30a, 30b: switch 30c: power supply

Claims (14)

A PTC element in which a base metal electrode is formed on a semiconductor ceramic composition by baking,
The semiconductor ceramic composition has a perovskite structure made of a BaTiO ₃ type oxide,
The base metal electrode includes, as a metal component, at least one of Al and Ni as a main component, and at least B.
A PTC element, wherein a low resistance layer having a resistance smaller than that of a parent phase of the semiconductor ceramic composition is formed on a base metal electrode side of the semiconductor ceramic composition.   The PTC element according to claim 1, wherein the low resistance layer has a thickness of 0.1 μm or more. 3. The PTC element according to claim 1, wherein the thickness of the low resistance layer is 0.4 μm or more, and the interface resistance of the element per unit area (1 cm ² ) is 5Ω or less. The element resistance of the element around unit area (1 cm < ² >) is 10 ohms or less, The PTC element in any one of Claims 1-3 characterized by the above-mentioned.   5. The PTC element according to claim 1, wherein the surface resistance is 10 mΩcm or less.   The PTC element according to claim 1, wherein a reaction phase mainly composed of Ba oxide is present on the semiconductor ceramic composition side of the base metal electrode.   The said base metal type electrode is a composition which contains B in 3 mass% or more and 25 mass% or less by making the sum total of said Al, Ni, and B into 100 mass%. A PTC element according to 1.   The base metal electrode contains Si as a metal component, the total of Al, Ni, B, and Si is 100% by mass, B is 3% by mass to 25% by mass, Si is more than 0% by mass and 26% by mass or less. The PTC element according to claim 7, comprising:   9. The PTC element according to claim 7, wherein the base metal electrode includes Al in an amount of 50 mass% or more, with the total of Al, Ni, B, and Si being 100 mass%.   10. The base metal electrode according to claim 7, wherein the base metal electrode includes 5% by mass to 40% by mass of Ni, with the total of Al, Ni, B, and Si being 100% by mass. The PTC element described.   11. The PTC element according to claim 1, wherein Al particles having an average particle diameter of 1.2 μm to 10 μm are dispersed in the base metal electrode. The semiconductor porcelain composition is
Rare earth elements containing at least one, R represents Y of composition formula _{[(BiA) x (Ba 1} -y R y) 1-x] [Ti 1-z M z] O 3 (A is Na, Li, K At least one of them, M is at least one of Nb, Ta, and Sb), and x, y, and z are 0 <x ≦ 0.25, 0 ≦ y ≦ 0.052, 0 ≦ z ≦ 0. The PTC element according to claim 1, wherein the PTC element has a composition satisfying a range of 0.01 (where y + z> 0).   The PTC element according to any one of claims 1 to 12, wherein the base metal electrode is baked at a temperature of 720 ° C or higher and 850 ° C or lower in an air atmosphere. A heat generating module comprising the PTC element according to claim 1, wherein the semiconductor ceramic composition generates heat.

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