JP2015213116A - Ptc device and exothermic module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PTC (positive temperature coefficient of resistance) device which offers a solution to the problem of the increase in surface specific resistance for forming a base metal electrode on BaTiObased semiconductor ceramic composition by baking.SOLUTION: A PTC device comprises: a semiconductor ceramic composition 1 having a perovskite structure and composed of a BaTiOtype oxide; and a base metal electrode including at least one of Al and Ni as a primary component and formed on the semiconductor ceramic composition by baking. In the base metal electrode, an amount of carbon remaining therein is 90 ppm or less. The base metal electrode includes: a first electrode layer 2a forming the first layer in contact with the semiconductor ceramic composition; and a second electrode layer 2b forming the second layer covering the first electrode layer 2a.

Description

  The present invention relates to a PTC element in which an electrode is formed on a semiconductor ceramic composition having a positive temperature coefficient of resistance, and a heat generating module using the PTC element.

Conventionally, as a material exhibiting PTC characteristics (Positive Temperature Coefficient of Resistivity), a semiconductor ceramic composition in which various semiconducting elements are added to the composition represented by BaTiO ₃ has been proposed. 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. This PTC element is used in a heat generating module configured so that the semiconductor ceramic composition generates heat by contacting the electrode with an external electrode.

Patent Document 1 discloses a PTC element in which an electrode is formed on a lead-free semiconductor ceramic composition. As the semiconductor ceramic composition, BaTiO ₃ is 50 to 85%, CaTiO ₃ is ₃ to 15%, SrTiO ₃ is 50%, SiO 2 it ₂ 1-2% of each containing composition preferably have been described (see paragraph 0006). In addition, as a method for forming an electrode, it is described that an electrode or an electrode partial layer is preferably formed by a metal deposition method. Examples of this metal deposition method include sputtering, vapor deposition, electrolytic deposition, and chemical deposition. Patent Document 1 also describes that the electrode may be produced by baking an electrode 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 electrode is formed by plating, sputtering, baking, or the like, thereby obtaining a PTC thermistor (see paragraph 0069). In the examples, dry plating is performed to form an 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 advantage 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 an organic component, and this is applied to a semiconductor ceramic composition by printing, etc., and heated to evaporate the organic component from the electrode paste to form a metal component. Is used as 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 the electrode is formed by baking and that the main component is Ag.

Special table 2010-501988 International Publication WO2010 / 067866 JP2012-169515

The electrodes used for the semiconductor porcelain composition are those using a noble metal electrode paste mainly composed of elements such as Ag, Au and Pt, and a base metal electrode paste mainly composed of elements such as Al and Ni. There was something that was there. If a noble metal electrode paste is used, it is difficult to oxidize, so that the resistance can be prevented from increasing, and 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, base metal electrode paste is very inexpensive because it contains Al, Ni, or the like as a main component.

  However, when the base metal electrode is baked on the semiconductor porcelain composition, a discharge occurs between the external electrode of the heat generating module and the base metal electrode of the PTC element while the power is repeatedly turned ON / OFF, and the element resistance is reduced. It was found that it changed (hereinafter referred to as change over time).

Accordingly, an object of the present invention is to use a PTC element in which an increase in change over time is eliminated even if a base metal electrode is formed by baking a lead-free BaTiO ₃ based semiconductor ceramic composition, and this PTC element is used. Was to provide a heat generation module.

The present invention is a PTC element in which a base metal electrode mainly composed of at least one of Al and Ni is formed by baking on a semiconductor ceramic composition having a perovskite structure made of a BaTiO ₃ type oxide, the base metal electrode The amount of carbon remaining inside is 90 ppm or less.
The base metal electrode includes a first electrode layer that is in contact with the semiconductor ceramic composition, and a second electrode layer that is a second layer that covers the first electrode layer. The first electrode layer includes Al, The total of Ni, B, and Si is 100% by mass, the sum of the contents of Al and Ni is 50% by mass or more and less than 95% by mass, and includes at least one of B and Si. The second electrode layer is made of Al, Ni , B, and Si may be 100% by mass, and the Al content may be 90% by mass or higher and higher than the sum of the Al and Ni content of the first electrode layer.
The first electrode has a Si content exceeding 0 and not more than 14% by mass, the second electrode layer has a Si content exceeding 0 and not more than 10% by mass, and the second electrode layer is a first electrode layer. The Si content can be lower than that.
These PTC elements are characterized by a surface resistance of 0.1 mΩcm or less.
This semiconductor ceramic composition has a composition formula of [(BiA) _x (Ba _1-y R _y ) _1-x ] [Ti _1-z M _z ] O ₃ (A is at least one of Na, Li, and K, 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 ≦ 0. It is preferable to use a composition that satisfies the range of 052, 0 ≦ z ≦ 0.01 (where y + z> 0).
A heat generating module that includes these PTC elements and generates heat from the semiconductor ceramic composition can be obtained.

  According to the present invention, a PTC element having a small change with time and high durability can be obtained. 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 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.

  As a result of studies by the present inventors, this change over time is caused by the fact that the carbon remaining in the base metal electrode is deposited on the electrode surface, and the resistance of the surface of the base metal electrode (hereinafter referred to as surface resistance) increases. It was found that a discharge occurred between the external electrode and the external electrode, which caused the base metal electrode to oxidize and increase with time.

That is, the present invention is a PTC element in which a base metal electrode mainly composed of at least one of Al and Ni is formed on a semiconductor ceramic composition having a perovskite structure made of a BaTiO ₃ type oxide, and the base metal electrode Is characterized in that the amount of carbon remaining inside (hereinafter referred to as residual carbon amount) is 90 ppm or less.

The remaining carbon is mixed from an organic binder or an organic solvent mixed in the electrode paste for forming the base metal electrode. The organic binder is used to dissolve the electrode powder in an organic solvent, and the organic solvent is necessary for making the powder into a paste (hereinafter, the organic binder and the organic solvent may be collectively referred to as an organic component). This organic component is used together with an inorganic component (a metal component responsible for the conductive portion of the electrode, a glass component, and other additive elements such as Si and B that are not bonded to carbon). Therefore, when the electrode paste is baked, carbon remains in the formed electrode.
By setting the residual carbon amount to 90 ppm or less, an electrode having a small surface resistance can be obtained. If the amount of residual carbon exceeds 90 ppm, the surface resistance exceeds 0.10 mΩcm and the change with time increases. A preferable residual carbon amount is 80 ppm or less, and more preferably 60 ppm or less.
The residual carbon content is preferably as small as possible to reduce the surface resistance, and there is no particular lower limit. However, an electrode paste cannot be produced without using an organic binder. It is also impossible to completely remove carbon after electrode formation. Therefore, although the residual carbon amount does not become 0 ppm, the lower limit as an actual residual carbon amount remaining in forming the electrode is about 10 ppm.

In order to set it as said residual carbon amount, it can carry out by making the carbon amount in an electrode paste into a predetermined range, for example. At this time, it is preferable to adjust the amounts of the organic component and the inorganic component so that the electrode paste contains 10% to 24% carbon by mass.
However, even if the amount of carbon in the electrode paste exceeds 24%, the residual carbon can be increased by increasing the baking temperature of the electrode, increasing the baking time, or performing a separate heat treatment after baking. The amount can also be adjusted to 90 ppm or less.
A preferred production method will be described later.

  The base metal electrode in the present invention has at least one of Al and Ni as a main component. The sum of Al and Ni is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more with respect to the total weight of the electrode. In addition to Al and Ni, B and Si may also be included, but in addition to these elements, another composition may be included from a glass component or the like. Inevitable impurities may also be included.

As the base metal electrode, a multilayer electrode structure may be used. Below, the preferable form in the case of setting it as a two-layer electrode structure as a multilayer base metal electrode is demonstrated.
Of the two layers, the electrode layer on the semiconductor porcelain composition side (hereinafter referred to as the first electrode layer) has a total of Al, Ni, B, and Si as 100% by mass, and the sum of the contents of Al and Ni is 50%. % Or more and less than 95% by mass. By making the sum of the contents of Al and Ni 50% by mass or more, an inexpensive electrode can be obtained. In addition, when the sum of the content ratios of Al and Ni is less than 95% by mass and includes at least one of B and Si, the interface resistance can be reduced as described later.
As an element to be used, since Al is cheaper than Ni, it is preferable to use an electrode having more Al than Ni.

The first electrode layer includes a Si content exceeding 0 and not more than 14% by mass, the second electrode layer includes a Si content exceeding 0 and not more than 10% by mass, and the second electrode layer is more than the first electrode layer. It is preferable that the Si content is low.
The following effects can be obtained by adding Si to the first electrode layer. The first effect is that the ohmic connection with the semiconductor porcelain composition is increased to reduce the interface resistance between the semiconductor porcelain composition and the electrode, thereby reducing the element resistance. The second effect is that the Al used for the electrode is in the form of particles, but the Al particles (hereinafter referred to as Al particles) are likely to melt, increasing the contact area between the Al particles and the semiconductor ceramic composition and increasing the interface. It can contribute to the reduction of resistance. The third effect is that 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.
However, while these effects can be obtained, there is a demerit that the resistance of the electrode increases and as a result the surface resistance increases.
Therefore, the PTC element having a small surface resistance can be obtained by setting the Si content of the first electrode layer and the second electrode layer in the above range and the second electrode layer having a composition having a lower Si content than the first electrode layer. Can be.

  Moreover, it is preferable that the first electrode layer contains 5 mass% or more and 40 mass% or less of Ni, and the sum of Al and Ni is 50 mass% or more. If the amount of Ni is 5% by mass or more, the baking temperature can be lowered. Further, if the amount of Ni does not exceed 40% by mass, it is possible to suppress an increase in the resistance of the electrode itself and an increase in the material cost of the electrode. The amount of Ni is preferably 35% by mass or less. Preferably, when Al is contained in an amount of 50% by mass or more and Ni is contained in this range, Ni removes the oxide layer on the surface of the Al particles at a low temperature to facilitate alloying of Al and Ni. Can be lowered. However, it is desirable to adjust the baking time so that an excessive sintering reaction does not occur.

As Al used for the first electrode layer, Al particles having an average particle diameter of 1.2 μm or more and 10 μm or less can be used.
The Al particles in the base metal electrode are hardly melted due to the presence of an oxide film on the surface, and remain almost as large as the particle size at the time of the electrode paste. Therefore, as shown in FIG. 1 and FIG. 2, a gap 6 is easily formed between the Al particles 5, and the contact area between the semiconductor ceramic composition and the electrode is reduced, and the interface resistance is likely to be increased. Therefore, by using Al particles having an average particle diameter of 1.2 μm or more and 10 μm or less, small Al particles are filled in the gap 6 and the gap at the interface can be reduced. As a result, it becomes easy to reduce the interface resistance of the PTC element. Moreover, the adhesion strength of the electrodes can be increased.
If the average particle size is 1.2 μm or more, the occurrence of a dust explosion or the like can be suppressed. Small Al particles of less than 1.2 μm can be included if they are 30% or less of the total Al particles. On the other hand, when the average particle diameter exceeds 10 μm, the ratio of the contact area becomes small, and it becomes difficult to reduce the interface resistance.

  In the case where both the Al particles and the Ni particles are dispersed in the first electrode layer, it is preferable to use Ni particles having an average particle size smaller than that of the Al particles. Ni particles are easily filled in the gaps between the Al particles and the semiconductor ceramic composition, and the interface resistance can be reduced. 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.

An electrode layer (hereinafter referred to as a second electrode layer) provided on the first electrode layer will be described.
In the second electrode layer, the total content of Al, Ni, B, and Si may be 100% by mass, and the Al content may be 90% by mass or higher and higher than the sum of the Al and Ni content of the first electrode layer. preferable. By doing so, the resistance of the second electrode layer is reduced, so that the surface resistance can be reduced. In addition, since the surface of the particles is covered with an oxide layer, Al is chemically stable and excellent in reliability, and the oxidation is difficult to proceed inside. Therefore, if the Al content of the second electrode layer is increased, it is baked in the air atmosphere. Also, the oxidation of the first electrode layer can be suppressed, and the element resistance can be reduced.
B or Si may be contained as an element other than Al. B and Si may be mixed by diffusion from the first electrode layer as will be described later. In addition, preferable Al content rate is 95 mass% or more.

  The thickness of the base metal electrode is preferably 5 μm or more and 70 μm or less. However, in the case of a multilayer structure such as a two-layer structure, each layer is preferably 5 μm to 70 μm. If it is 5 micrometers or more, generation | occurrence | production of application | coating nonuniformity and peeling of an electrode can be suppressed. If the thickness is 70 μm or less, the cost of the electrode can be reduced. A preferred thickness is 10 μm or more and 50 μm or less, and a more preferred thickness is 12 μm or more and 40 μm or less.

Even when Si is not added at the stage of the electrode paste, the second electrode layer may contain Si diffused from the first electrode layer during electrode baking. The Si content of the second electrode layer includes Si due to this diffusion.
When the Si content of the second electrode layer is less than 10% by mass, a PTC element having a surface resistance of 0.1 mΩcm or less can be obtained. The Si content is preferably 5% by mass or less, and more preferably 3% by mass or less.

Al used for the second electrode layer may have Al particles having an average particle diameter of 1.2 μm or more and 10 μm or less dispersed in the same manner as Al used for the first electrode layer.
A particle having a particle size larger than that of the Al particles used for the first electrode layer can be used.

Next, a first manufacturing method will be described as a specific example for obtaining the PTC element of the present invention.
First, a semiconductor ceramic composition having a perovskite structure made of a BaTiO ₃ type oxide is prepared, and an electrode paste containing at least one of Al and Ni as a main component is applied to the semiconductor ceramic composition. The electrode paste is a mixture of the electrode metal component, glass component, Si raw material, B raw material, organic binder, and organic solvent so as to contain 10% to 24% carbon by mass. A manufacturing method in which this electrode paste is applied and formed by screen printing and a base metal electrode is baked in an air atmosphere can be employed. In addition, after baking a base metal-type electrode, you may give the below-mentioned heat processing.

A second manufacturing method will be described as another specific example for obtaining the PTC element of the present invention.
First, a semiconductor ceramic composition having a perovskite structure made of a BaTiO ₃ type oxide is prepared, and an electrode paste containing at least one of Al and Ni as a main component is applied to the semiconductor ceramic composition. As the electrode paste, a mixture of the electrode metal component, glass component, Si raw material, B raw material, organic binder, and organic solvent can be used. However, unlike the first manufacturing method, the electrode paste exceeds 24% by mass. Carbon may be included. This electrode paste is applied and formed by screen printing, and a base metal electrode is baked in an air atmosphere.
Thereafter, the amount of residual carbon in the electrode can be reduced by heat-treating the PTC element.

The temperature of this heat treatment is preferably 420 ° C. or higher and 600 ° C. or lower. If the temperature is less than 420 ° C., the amount of residual carbon cannot be reduced, and if it exceeds 600 ° C., the electrode is oxidized and the surface resistance becomes high. The heat treatment time is preferably 0.5 h or more and 12 h or less. If it is less than 0.5 h, the amount of residual carbon cannot be reduced, and if it exceeds 12 h, the electrode is oxidized and the surface resistance becomes high. The heat treatment may be repeated multiple times at a temperature of 420 ° C. or higher. In short, it is preferable that the total time required for the temperature of 420 ° C. or higher is 0.5 h or more and 12 h or less.
If there is no oxygen in the atmosphere in which the heat treatment is performed, oxygen in the electrode is not lost, so it is necessary to perform in an atmosphere containing oxygen. The atmosphere is most convenient and preferable.

  Known organic components can be used. For example, as an organic binder, an acrylic acid ester of a water-soluble polycopolymer, a cellulose derivative (carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, etc.), polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, polyolefin, polyurethane, polystyrene, or Any known copolymer or the like can be used. Any known organic solvents such as toluene, xylene, diethylene ether, terpineol, butyl carbitol, kerosene, etc. can be used.

  If the baking temperature is 700 ° C. or higher, the base metal electrode can suppress insufficient bonding between the semiconductor ceramic composition and the electrode, and as a result, the interface resistance can be easily reduced. It also has the effect of reducing the amount of residual carbon in the electrode paste. However, when the baking temperature exceeds 850 ° C., the semiconductor ceramic composition is likely to be oxidized, and the element resistance may be increased. Therefore, the baking temperature is preferably 850 ° C. or lower.

As for the baking time of the base metal electrode, the time of exposure to a temperature of 700 ° C. or more and 850 ° C. or less is preferably 1 minute or more and 5 hours or less. If the baking time is longer than 1 minute, it is easy to suppress an increase in the interface resistance due to insufficient bonding between the semiconductor ceramic composition and the electrode. In addition, an effect of reducing the amount of carbon remaining in the base metal electrode is obtained.
However, if the baking time exceeds 5 hours, the semiconductor ceramic composition is likely to be oxidized, and the device resistance may be increased. The baking time is preferably 3 minutes or more and 3 hours or less, more preferably 5 minutes or more and 1 hour or less.

  The electrode paste can be applied using known means such as screen printing or bar coder.

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 semiconductor ceramic composition having the above composition, it is easier to obtain a PTC element having a higher temperature coefficient of resistance α than using a semiconductor ceramic composition containing Pb as a dopant. Specifically, even a PTC element having a low element resistance (12Ω or less) can be obtained with a resistance temperature coefficient α of 2.5% / ° C. or more, preferably 3.5% / ° C. or more.
In a semiconductor ceramic composition containing Pb as a dopant, the base metal electrode paste deprives the grain boundary phase oxygen in the semiconductor ceramic composition during baking, thereby losing the Schottky barrier formed inside the composition. The resistance temperature coefficient 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, it is difficult to maintain a high temperature coefficient of resistance α.

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 elements of Bi and A easily evaporate during sintering, the Ba site ([(BiA) _x (Ba _1-y R _y ) _{1- 1} is compared to the Ti site ([Ti _1-z M _z ]). _The number of moles of the element _x ]) is reduced. 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 (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) containing Y. 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.

The ratio of Bi to A may be 1: 1, and (Bi _0.5 A _0.5 ) may be used in the above composition formula. Volatilization causes a shift in the ratio of Bi and A, and thus may shift within the range of significant figures. From the above formula (Bi _0.45 A _0.54 ) to (Bi _0.54 A _0.45 ) This range is also included.

As a method for producing a semiconductor porcelain composition, the first calcined powder represented by (Ba · R) TiO ₃ or Ba (Ti · M) O ₃ and the first represented by (Bi · Na) TiO ₃ It is possible to employ a method in which the two calcined powders are calcined and prepared at different calcining temperatures, and then the first and second calcined powders are mixed and sintered. By calcining the first and second calcined powders at different calcining temperatures, the volatilization of the components, particularly the volatilization of Bi and Na in the second calcined powder, can be suppressed, and the Curie temperature is set to a desired value. It becomes easy to control.
The calcining temperature of the second calcined powder is preferably lower than the calcining temperature of the first calcined powder. The calcining temperature of the first calcined powder is preferably 900 ° C. or higher and 1300 ° C. or lower, and the calcining temperature of the second calcined powder is preferably 600 ° C. or higher and 950 ° C. or lower.

  The semiconductor ceramic composition used in the present invention is obtained by mixing the first calcined powder and the second calcined powder to form a third calcined powder, and molding and sintering. The sintering temperature is preferably 1200 ° C. or higher and 1450 ° C. or lower.

  In addition, the said manufacturing method is an example and is not caught by this. For example, the raw material powders are mixed together 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), and thereafter You may manufacture similarly to the above.

In this embodiment, the evaluation method is as follows.
(Residual carbon content)
The amount of residual carbon was determined by analyzing the surface of the base electrode system electrode in the depth direction within a range of 10 × 10 mm by glow discharge emission analysis (GD-OES analysis), and the average value of the analyzed carbon amount was defined as the residual carbon amount. .

(Surface resistance)
The resistance Rw of the formed base metal 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 Converted into In this example, W was 1 cm and L was 1 cm. Since it was difficult to make the electrode thickness T constant, it was measured each time. The first m in the unit mΩcm represents millimeters.

(Change with time by ON / OFF)
As an electrode reliability test, an ON / OFF test of energization was used for evaluation. An external electrode made of Al was disposed on the electrode surface of the PTC element. Further, a cooling panel was disposed outside the external electrode. A cycle of holding a non-voltage state for 1 minute after applying a voltage of 13 V for 1 minute was repeated for 1000 hours, and the change in element resistance before and after 1000 hours was measured. The temperature was adjusted with a cooling panel so that the PTC element did not exceed 140 ° C. while the voltage was applied.

(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. In addition, the 1st electrode layer took out the joining cross section of the electrode by CP process, and made the inside of the range of 1 micrometer-10 micrometers from the low resistance layer made into the material component of an electrode part into the measurement part. Moreover, the surface after baking was analyzed for the 2nd electrode layer.

(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 is evaluated as 1 mm and the area is evaluated as 1 cm ^2. Therefore, the element resistance can be converted to room temperature specific resistance (Ωcm) by multiplying the value by 10 times.

(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. 4, 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.

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

(Resistance temperature coefficient α)
The resistance temperature coefficient α was calculated by measuring the resistance-temperature characteristics while raising the temperature to 260 ° C. in a thermostatic bath.
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 .

(Example 1: No. 1-1 to 1-2, Comparative Example 1: No. 1-3)
The effect of the amount of residual carbon on the surface resistance of the base metal electrode was investigated. A PTC element in which a base metal electrode having a two-layer structure was formed was used.

The used semiconductor ceramic composition was manufactured 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 1200 ° 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. 1.0 mol% of Y ₂ O ₃ was further added to the obtained _third calcined powder, and the obtained mixed calcined powder was subjected to a pot mill using pure water as a medium, and the average particle size was 1.0 μm to 2.0 μm. After mixing and pulverizing until dry, it was dried. 10% by mass of PVA was added to the pulverized powder of the mixed calcined powder, mixed, and then 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.

  A semiconductor ceramic composition processed into a plate shape of 10 mm × 10 mm (plate surface dimension) × 1.00 mm (thickness dimension) was used. 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.

In order to form the first electrode layer, the following preparation was made. Spherical Al particles having an average particle diameter of 5 μm and Si particles having an average particle diameter of 5 μm were used. They were mixed such that the mass ratio of Al and Si was 94: 6, respectively. 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. B was not an oxide, but B alone (particulate). Further, the organic binder and the organic solvent are in a ratio of 3: 5 (mass ratio, the same applies hereinafter), and the organic component (organic binder and organic solvent) and the inorganic component (Al particles, Si particles, glass frit, and B). It added so that it might become a ratio 25:75, 30:70, and 40:60, and it mixed with the kneader, and was set as three types of 1st electrode paste. The amount of carbon in the first electrode paste was 15.5% by mass, 18.6% by mass, and 24.8% by mass, respectively.
In order to form the second electrode layer, the following preparation was made. The spherical Al particles having an average particle diameter of 5 μm were taken as 100 parts by mass. Further, the ratio of the organic binder to the organic solvent is 3: 5, and the ratio of the organic component (organic binder and organic solvent) to the inorganic component (Al particles) is 25:75, 30:70, and 40:60. The mixture was added and mixed with a kneader to obtain three types of second electrode pastes. The amount of carbon in the second electrode paste was 15.5% by mass, 18.6% by mass, and 24.8% by mass, respectively.
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 first electrode paste was applied to both sides of the semiconductor ceramic composition by screen printing. After the applied first electrode paste was dried at 150 ° C., a second electrode paste having the same ratio of the organic component and the inorganic component was further applied and dried under the same conditions. Thereafter, the temperature was raised at 30 ° C./min and 775 ° C. for 10 minutes in the atmosphere, the temperature was lowered at 30 ° C./min, and an electrode was formed by baking to obtain a PTC element. The area covered by the electrode was 1 cm ² , and the electrode thickness was about 30 μm for both the first electrode layer and the second electrode layer.

  About the obtained PTC element, the Al ratio (mass%), Ni ratio (mass%), B ratio (mass%), Si ratio (mass%) of the first electrode layer and the second electrode layer, the ratio of organic components ( Ratio of organic component occupying the sum of organic component and inorganic component as 100. The same applies hereinafter), residual carbon content, surface resistance (mΩ · cm), change with time (%), interface resistance (Ω), element resistance (Ω), Curie temperature (° C.), and resistance temperature coefficient α (% / ° C.) were measured. For measurements other than the interface resistance, a semiconductor ceramic composition having a thickness of 1.00 mm was used. The obtained evaluation results are shown in Table 1 for the ratio of the metal component and the ratio of the organic component, and in Table 2 otherwise.

No. in which the ratio of the organic component was 25% by mass. The PTC element of 1-1 had a very small PTC element with a residual carbon amount in the base metal electrode of 53 ppm and a surface resistance of 0.075 mΩ · cm. As a result, the change with time was 12.0%, which was 15% or less of the target. Further, the ratio of the organic component to the inorganic component was set to 30:70. The 1-2 PTC element also had a residual carbon content of 90 ppm or less (72 ppm), and the change with time was 15% or less (14.9%) of the target.
On the other hand, the ratio of the organic component to the inorganic component was 40:60. In the 1-3 PTC element, the amount of residual carbon in the base metal electrode is as large as 212 ppm. As a result, the surface resistance was as large as 0.173 mΩ · cm, and the change with time was as large as 33.2%.

  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.

  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 almost the same as each content ratio in the electrode paste.

(Example 2: No. 2-1 to 2-5)
PTC elements were produced by changing the baking temperature.
In order to form the first electrode layer, the following preparation was made. Spherical Al particles having an average particle diameter of 5 μm, spherical Si particles having an average particle diameter of 5 μm, and Ni particles having an average particle diameter of 0.2 μm were used. They were mixed at a mass ratio of 73.6: 6.4: 20, respectively. The total value of this mixture was 100 parts by mass, and 10 parts by mass of glass frit and 10 parts by mass of B were added. B was not an oxide, but B alone (particulate). Furthermore, the ratio of the organic binder to the organic solvent is 3: 5, and the ratio of the organic component (organic binder and organic solvent) to the inorganic component (Al particles, Si particles, Ni particles, glass frit, B) is 20:80. And mixed with a kneader to obtain a first electrode paste. The amount of carbon in the first electrode paste was 12.4% by mass.
In order to form the second electrode layer, the following preparation was made. The spherical Al particles having an average particle diameter of 5 μm were taken as 100 parts by mass. Furthermore, the organic binder and the organic solvent were added at a ratio of 3: 5, and the organic component (organic binder and organic solvent) and the inorganic component (Al particles) were added so that the ratio was 20:80, and mixed with a kneader. Thus, a second electrode paste was obtained. The amount of carbon in the second electrode paste was 12.4% 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 drying the applied base metal electrode paste at 150 ° C., the temperature is raised in the air at 30 ° C./min, and the holding temperatures are 700 ° C. (No. 2-1), 725 ° C. (No. 2-2), 750 ° C. ( No. 2-3), 825 ° C. (No. 2-4), 850 ° C. (No. 2-5), held for 10 minutes, cooled at 30 ° C./min, and baked to form an electrode An element was obtained. The area covered by the electrode was 1 cm ² , and the thickness was about 30 μm for both the first electrode layer and the second electrode layer. 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 3 and Table 4.

  All the PTC elements had a residual carbon content of 90 ppm or less and a surface resistance of 0.10 mΩcm or less. As a result, the change with time was 15% or less of the target.

(Example 3: No. 3-1, Comparative example 2: No. 3-2)
The PTC element after electrode formation was heat-treated, and the influence of the residual carbon amount on the surface resistance of the base metal electrode was examined.
In order to form the first electrode layer, the following preparation was made. Spherical Al particles having an average particle diameter of 5 μm and Si particles having an average particle diameter of 5 μm were used. They were mixed such that the mass ratio of Al and Si was 94: 6, respectively. 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. B was not an oxide, but B alone (particulate). Furthermore, the ratio of the organic binder to the organic solvent is 3: 5, and the ratio of the organic component (organic binder and organic solvent) to the inorganic component (Al particles, Si particles, glass frit, B) is 40:60. And mixed with a kneader to obtain a first electrode paste. The amount of carbon in the first electrode paste was 24.8% by mass.

In order to form the second electrode layer, the following preparation was made. The spherical Al particles having an average particle diameter of 5 μm are 100 parts by mass, the organic binder and the organic solvent are in a ratio of 3: 5, and the ratio of the organic component (organic binder and organic solvent) to the inorganic component (Al particles) is 40:60 and mixed with a kneader to obtain a second electrode paste. The amount of carbon in the second electrode paste was 24.8% by mass.
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 first and second electrode pastes described above were applied to both sides of the semiconductor ceramic composition by screen printing and baked to obtain a PTC element. Application and baking were performed under the same conditions as in Example 1. The area covered by the electrode was 1 cm ² , and the electrode thickness was about 30 μm for both the first electrode layer and the second electrode layer.

  Thereafter, the PTC element was heat-treated at 600 ° C. (No. 3-1) and 400 ° C. (No. 3-2) for 2 hours, respectively. The evaluation method of the PTC element was performed in the same manner as in Example 1. The obtained results are shown in Tables 5 and 6.

No. of an Example. 3-1 had a low residual carbon content of 54 ppm and a surface resistance of 0.069 mΩcm. As a result, the change with time was 11.7%, which is 15% or less of the target.
On the other hand, the comparative example No. 3-2 had a residual carbon content as high as 91 ppm and a surface resistance of 0.127 mΩcm. As a result, the change with time was 18.6%, exceeding the target of 15%. Carbon deposition was observed on the surface of the electrode after the ON / OFF test, and the portion had increased resistance. Whether carbon has precipitated can be confirmed by analyzing the portion of the electrode surface layer blackened after energization of ON / OFF by SDX EDX analysis and detecting C.

(Example 4: Nos. 4-1 to 4-6)
The influence of the amount of Si in the first electrode layer on the surface resistance was examined.
In order to form the first electrode layer, the following preparation was made. Spherical Al particles having an average particle diameter of 5 μm and Si particles having an average particle diameter of 5 μm were used. The mass ratio of Al and Si is 100: 0 (No. 4-1), 98: 2 (No. 4-2), 96: 4 (No. 4-3), 94: 6 (No. 4- 4), 88:12 (No. 4-5), and 84:16 (No. 4-6). 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. B was not an oxide, but B alone (particulate). Further, the ratio of the organic binder to the organic solvent is set to 3: 5, and the ratio of the organic component (organic binder and organic solvent) to the inorganic component (Al particles, Si particles, glass frit, B) is set to 20:80. It was added and mixed with a kneader to obtain a first electrode paste. The amount of carbon in the first electrode paste was 12.4% by mass.
In order to form the second electrode layer, the following preparation was made. The spherical Al particles having an average particle diameter of 5 μm were taken as 100 parts by mass. Furthermore, the organic binder and the organic solvent were added at a ratio of 3: 5, and the organic component (organic binder and organic solvent) and the inorganic component (Al particles) were added so that the ratio was 20:80, and mixed with a kneader. Thus, a second electrode paste was obtained. The amount of carbon in the second electrode paste was 12.4% 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 7 and Table 8.

No. of an Example. 4-1 had a low residual carbon content of 34 ppm and a small surface resistance of 0.044 mΩcm. As a result, the change with time was 12.5%, which is 15% or less of the target. No. In the 4-2 to 4-4 PTC elements, the residual carbon amount was 90 ppm or less, the surface resistance was 0.10 mΩcm or less, and the change with time was 15% or less of the target.
Moreover, No. of an Example. In the PTC elements 4-5 to 4-6, since the Si in the first electrode layer diffused into the second electrode layer, the Al content of the second electrode layer was No. Although it was lower than the PTC elements of 4-1 to 4-4 and an increase in the surface resistance was confirmed, the surface resistance was 0.10 mΩcm or less and the change over time was as low as 15% or less. there were.

(Example 5: No. 5-1 to 5-8)
PTC elements were produced by changing the composition (B amount) of the first electrode layer.
In order to form the first electrode layer, the following preparation was made. Spherical Al particles having an average particle diameter of 5 μm and Si particles having an average particle diameter of 5 μm were mixed at a mass ratio of 92: 8. The total value is 100 parts by mass, and 10 parts by mass of glass frit and 3 parts by mass of B (No. 5-1), 5 parts by mass (No. 5-2), 7.5 parts by mass (No. .5-3), 10 parts by mass (No. 5-4), 12.5 parts by mass (No. 5-5), 15 parts by mass (No. 5-6), 20 parts by mass (No. 5-7) ), 25 parts by mass (No. 5-8). B was not an oxide, but B alone (particulate). Further, the ratio of the organic binder to the organic solvent is set to 3: 5, and the ratio of the organic component (organic binder and organic solvent) to the inorganic component (Al particles, Si particles, glass frit, B) is set to 20:80. It was added and mixed with a kneader to obtain a first electrode paste.
In order to form the second electrode layer, the following preparation was made. The spherical Al particles having an average particle diameter of 5 μm were taken as 100 parts by mass. Furthermore, the organic binder and the organic solvent were added at a ratio of 3: 5, and the organic component (organic binder and organic solvent) and the inorganic component (Al particles) were added so that the ratio was 20:80, and mixed with a kneader. Thus, a second electrode paste was obtained.
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 9 and Table 10.
In this example, any PTC element had a residual carbon content of 90 ppm or less and a surface resistance of 0.1 mΩ · cm or less. As a result, the change with time was 15% or less of the target.

(Example 6: No. 6-1 to 6-4)
The influence of the amount of Ni in the first electrode layer was examined.
In order to form the first electrode layer, the following preparation was made. Spherical Al particles having an average particle diameter of 5 μm, spherical Si particles having an average particle diameter of 5 μm, and Ni particles having an average particle diameter of 0.2 μm were used. 82.8: 7.2: 10 (No. 6-1), 73.6: 6.4: 20 (No. 6-2), 64.4: 5.6: 30 (No. 6-3), 55.2: 4.8: 40 (No. 6-4). The total value of this mixture was 100 parts by mass, and 10 parts by mass of glass frit and 10 parts by mass of B were added. B was not an oxide, but B alone (particulate). Furthermore, the ratio of the organic binder to the organic solvent is 3: 5, and the ratio of the organic component (organic binder and organic solvent) to the inorganic component (Al particles, Si particles, Ni particles, glass frit, B) is 20:80. And mixed with a kneader to obtain a first electrode paste.
In order to form the second electrode layer, the following preparation was made. The spherical Al particles having an average particle diameter of 5 μm were taken as 100 parts by mass. Furthermore, the organic binder and the organic solvent were added at a ratio of 3: 5, and the organic component (organic binder and organic solvent) and the inorganic component (Al particles) were added so that the ratio was 20:80, and mixed with a kneader. Thus, a second electrode paste was obtained.
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 11 and Table 12.

  No. of an Example. Each of 6-1 to 6-4 had a residual carbon content of 90 ppm or less and a surface resistance of 0.10 mΩcm or less. As a result, the change with time was 15% or less of the target.

(Example 7: No. 7-1 to 7-7)
Composition formula of the semiconductor ceramic composition prepared _{[(BiA) x (Ba 1} -y R y) 1-x] [Ti 1-z M z] For _{O 3} x, y, and PTC element with different values of z did.
In Table 13, no. The values of x, y and z in the above composition formulas of 7-1 to 7-7 are shown.
No. In 7-1 to 7-3, y = 0.006, z = 0, and the values of x were 0.02, 0.14, and 0.18, respectively. No. In 7-4 to 7-6, x = 0.0875, z = 0, and the values of y were 0.003, 0.048, 0.050, respectively.
In order to form the first electrode layer and the second electrode layer, no. First electrode paste (Al: B: Si ratio (mass%) = 85.0: 9.1: 5.9) same as 4-4, second electrode paste (Al: B: Si ratio (mass%) ) = 98.6: 0: 1.4).

No. No. 7-7 is No.7. In contrast to 4-4, a rare earth element is not used as a semiconducting element (y = 0), part of the Ti site is Ta, and the value of z in the composition formula is 0.009.
A method for manufacturing the PTC element will be described below.
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. Further, the production of the PTC element by mixing, molding, sintering, and electrode formation of the first calcined powder and the second calcined powder thereafter is No. The same method as in 4-4 was performed.

The evaluation method of the PTC element was performed in the same manner as in Example 1. Table 13 shows the obtained evaluation results.
In all of Examples 7-1 to 7-7, the residual carbon amount was 90 ppm or less, and the surface resistance was 0.10 mΩcm or less. As a result, the change with time was 15% or less of the target.

(Heat generation module)
FIG. 3 is a schematic diagram of a heat generating module (PTC heater) according to an embodiment of the present invention. As shown in FIG. 3, the above-described PTC element can be sandwiched and fixed between metal radiating fins 21 a, 21 b, and 21 c to constitute the heat generating module 20. 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 and 2c, the power supply electrodes (external electrodes) 20a, 20b and 20c, and the radiation fins 21a, 21b and 21c, and the atmosphere mainly from the radiation fins 21a, 21b and 21c. Released into.

Since the PTC element of the present invention has a small surface resistance, since the discharge generated between the base metal electrodes 2a, 2b, 2c and the power supply electrodes 20a, 20b, 20c, which are external electrodes, is suppressed, the element resistance due to the oxidation of the electrodes As a result, a stable heat generating module could be realized.

  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.

1: semiconductor porcelain composition,
2a: first electrode layer,
2b: second electrode layer,
3: Low resistance layer,
5: Al particles,
6: void,
11: PTC element,
20: heating module,
20a, 20b, 20c: power supply electrodes,
21a, 21b, 21c: radiating fins,
30a, 30b: switches,
30c: Power supply

Claims (6)

A PTC element in which a base metal electrode mainly composed of at least one of Al and Ni is formed by baking on a semiconductor ceramic composition having a perovskite structure composed of a BaTiO ₃ type oxide,
The PTC element, wherein the base metal electrode has an amount of carbon remaining in the interior of 90 ppm or less. The base metal-based electrode includes a first electrode layer that is in contact with the semiconductor ceramic composition, and a second electrode layer that is a second layer that covers the first electrode layer,
The first electrode layer includes a total of Al, Ni, B, and Si of 100% by mass, and the sum of the content ratios of Al and Ni is 50% by mass or more and less than 95% by mass, and includes at least one of B and Si.
The second electrode layer has a total content of Al, Ni, B, and Si of 100% by mass, an Al content of 90% by mass or more, and a sum of the Al and Ni content of the first electrode layer. The PTC element according to claim 1, wherein the PTC element is high.   The first electrode has a Si content exceeding 0 and not more than 14% by mass, the second electrode layer has a Si content exceeding 0 and not more than 10% by mass, and the second electrode layer has the first electrode The PTC element according to claim 1, wherein the content of Si is lower than that of one electrode layer.   4. The PTC element according to claim 1, wherein the surface resistance is 0.1 mΩcm or less. 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. 5. The PTC element according to claim 1, wherein the PTC element has a composition satisfying a range of .01 (provided that y + z> 0). A heating module comprising the PTC element according to claim 1, wherein the semiconductor ceramic composition generates heat.

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