WO1995024046A1

WO1995024046A1 - Positive temperature coefficient thermistor and thermistor device using it

Info

Publication number: WO1995024046A1
Application number: PCT/JP1995/000334
Authority: WO
Inventors: Hiroshi Sasaki; Shu-Ichi Takeda
Original assignee: Komatsu Ltd.
Priority date: 1994-03-04
Filing date: 1995-03-02
Publication date: 1995-09-08

Abstract

A highly reliable positive temperature coefficient thermistor in which no silver migration occurs even under a high-temperature, high-humidity condition. The main feature of this invention is that the thermistor has first electrode layers (2a, 2b, 3a and 3b) including a silver layer formed on both main surfaces of a positive temperature coefficient thermistor body (1) in such a way that their ends are inside the outer periphery of the blank body (1) and second electrode layers (4a and 4b) formed of aluminum and covering the surfaces and side faces of the first electrode layers.

Description

Description Positive characteristics summaries and summaries using the same

The present invention relates to a positive temperature coefficient thermistor and a thermistor device using the same, and more particularly to a structure of an electrode thereof.

Background art

B a T i 0 ₃ in Y, an oxide semiconductor added with N d like 0. 1 ~ 0. 3 at%, since having a large Juna positive temperature coefficient, referred to as PTC thermistor evening.

This PTC thermistor can adjust the temperature range with a large positive temperature coefficient by adding Sr, Pb, etc., so that it can measure temperature and prevent overcurrent, It is indispensable in a wide variety of fields, such as circuit elements such as and low-temperature heaters.

As shown in Fig. 23 (a), this type of thermal sintering sinters oxides, carbonates, nitrates, and chlorides of metals such as Ba, Ti, and Nd. A thin silicon body 11 formed into a thin cylindrical shape or the like, and first electrode layers 12a and 12b formed of N i -metal layers formed on the upper and lower surfaces thereof, Second electrode layers 13a and 13b mainly formed of silver and formed in the upper layer.

By the way, such a positive characteristic thermistor is usually used by applying a voltage between the second electrode layers 13a and 13b. A so-called migration phenomenon occurs in which silver migrates and precipitates. In particular, when the outer peripheral edge of the second electrode layer is formed so as to reach the outer peripheral end of the positive temperature coefficient thermistor element 1, silver moves in the direction of the electric field on the outer peripheral surface of the positive temperature coefficient thermistor element 1 There was a problem that they precipitated and eventually caused a short circuit.

In order to solve this problem, a positive temperature coefficient thermistor has been proposed in which the outer diameter of the second electrode layer is smaller than the outer diameter of the first electrode layer as shown in FIG. 23 (b).

However, in this structure, the outer shape of the second electrode layer is larger than the outer shape of the first electrode layer. The first electrode layer, which is not covered by the second electrode layer, is directly exposed to the atmosphere, so it is easily oxidized and gradually increases the connection resistance. There was a problem.

Also, silver migration is a phenomenon that moves along the direction of the electric field, so even if only the second electrode layer is provided inside the outer periphery as in the conventional example, silver in the second electrode layer is exposed. As a result, migration occurred, albeit slightly, and the short-circuit problem was mitigated but could not be completely prevented.

In addition, since the electrodes are formed using the conventional positive temperature coefficient thermistor mounting method, in this method, the plating solution permeates into the sintered body when performing Ni plating when forming the electrodes, The characteristics of the sintered body may change, such as a decrease in the resistance value. _C This may appear as a characteristic change immediately after formation, or may gradually appear over time. As mentioned above, the thermistor applications all require high-precision resistance control, such as temperature measurement and control, compensation, gain adjustment, power measurement, overcurrent prevention, motor startup, color TV degaussing, etc. It is necessary to use those that are within the range of R ± α%. Therefore, the problem of the change in the resistance value due to the penetration of the plating liquid is becoming more serious.

Further, in order to avoid such infiltration of the plating solution, a method has been proposed in which a low melting point metal such as aluminum is formed by metal spraying and used as an electrode. However, this method also involves an abrupt temperature change at the time of electrode formation, and thus cannot avoid the problem that cracks occur in the thermistor body or the electrode itself. In order to solve this problem, the present inventors have proposed a thermistor electrode structure using a printed electrode or a vapor-deposited film containing aluminum as a main component in Japanese Patent Application Laid-Open No. 6-5403. I have. According to such a structure, since aluminum is a main component, migration is completely prevented. In addition, since a printed or vapor-deposited film is used, the element body does not crack and the durability is improved. However, since the first electrode is made of aluminum or the like, the resistance of the electrode itself becomes large, and there is a serious problem that it is not suitable for a circuit in which a relatively large current flows.

A nickel electrode is formed as the first electrode on both surfaces of the thermistor body. Then, a second electrode mainly composed of silver is formed around the gap region, and a third electrode made of aluminum-silicon is formed to cover the gap region. An electrode structure for preventing the cross section has also been proposed (JP-A-5-109503). However, in this structure, unevenness is formed on the surface, and when two elements are used in an overlapping manner, sufficient thermal contact cannot be obtained, so that there is a problem that the residual current is large.

In order to reduce the residual current, a method has been proposed in which a two-element type is used and the positive temperature coefficient thermistor for the heater is heated at the time of the positive temperature coefficient thermistor for the heater. There is a problem that the thermal contact between the elements deteriorates and the residual current cannot be reduced.

As described above, in the conventional electrode structure, there is a problem that the contact resistance increases when aluminum is used instead of silver to prevent migration.

Furthermore, in a structure in which an electrode containing silver as a main component is formed while leaving a gap region at an outer edge portion, and the gap region is covered with an electrode made of aluminum silicon, there is a portion where silver is exposed. However, there is a problem that the residual current is large because sufficient protection cannot be obtained when two elements are used in an overlapping manner. Disclosure of the invention

The present invention has been made in view of the above circumstances, and provides a positive-characteristic thermistor that has good assembling workability, is stable, has high reliability, can completely prevent migration, and is suitable for a circuit with a large current. The purpose is to do.

Therefore, a first feature of the present invention is that a first layer including a silver layer formed on both main surfaces of the positive temperature coefficient thermistor body so that an end thereof is formed inside the outer peripheral edge of the positive temperature coefficient thermistor body is provided. And a second electrode layer made of a layer mainly composed of aluminum and formed so as to cover the surface and side surfaces of the first electrode layer. Desirably, the second electrode layer is formed of a thick print layer containing conductive boron compound ceramic of 5 to 60 Vo 1% and aluminum. Incidentally addition to T i B ₂ as conductive boron compound used _{here, Z r B 2, H f} B 2, V b B Q, T _{_{a B 2, C r B 2}} , M o 2 borides such as _{B 2, T i B, Z} r B, H f B, VBN b B, T a B, C r B, Mo B, WB, N i B 1-element boride or V ₃ B ₄ ,

^{^{^{V 3 B 2, N b 2}}} B 3, N b 3 B 4, T a 3 B 2, T a 3 B 2, C r 3 B 4, M o 3 B 2, M o 2 B 5, W 2 B _{_{_{5, N i 4 B 3,}}} B 4 C compound group from at least Bareru selected one or more or their compounds of the like.

A second feature of the present invention is that a single layer including a silver layer is formed on both main surfaces of the positive temperature coefficient thermistor body so as to have an end inside the outer peripheral edge of the positive temperature coefficient thermistor body. Or a plurality of first electrode layers, and a second electrode layer formed of aluminum as a main component and formed so as to cover a side surface from near an edge of the first electrode layer. That is.

A third feature of the present invention is that a single layer including a silver layer is formed on both main surfaces of the positive temperature coefficient thermistor body so that an end is formed inside an outer peripheral edge of the positive temperature coefficient thermistor body. Or a plurality of first electrode layers, a second electrode layer mainly composed of silver formed so as to cover a surface and side surfaces of the first electrode layer, and a second electrode layer. An aluminum layer formed so as to cover the side surface from the vicinity of the edge portion, or a third electrode layer made of a layer containing 5 to 6 Ovol% of a conductive boron compound and aluminum is provided.

A fourth feature of the present invention is that a first electrode layer formed on both main surfaces of the positive temperature coefficient thermistor body and an edge formed inside the edge of the first electrode layer are formed. A second electrode layer made of a silver layer, and a third electrode layer made of an aluminum layer formed so as to cover the second electrode layer.

A fifth characteristic of the present invention is that a positive temperature coefficient thermistor and a positive temperature coefficient thermistor formed on both main surfaces of the thermistor body and composed of an electrode whose outermost layer is formed of an aluminum layer are provided. And a terminal that is in contact with the positive temperature coefficient thermistor and is formed of a material that does not form an alloy having a melting point of 300 ° C. or less with aluminum.

Preferably, the material is nickel, silver, copper, aluminum, titanium, or an alloy thereof.

According to the above configuration, a silver electrode having good electrical conductivity is used, and the silver electrode is Since it is completely covered by the miniature electrode, there is no danger of short circuit due to migration.

In the above configuration, the electrodes are formed by a dry process such as a vapor deposition method or a thick film printing method. Therefore, it is possible to form an electrode having high adhesion and low contact resistance without causing a change in characteristics due to contamination of the exposed portions of the front and back surfaces of the thermistor body by a solution or the like at the time of electrode formation.

According to the first configuration, the first electrode layer including the silver layer formed so as to have an end inside the outer peripheral edge of the positive temperature coefficient thermistor element body is formed, and the first electrode layer is formed. Since the second electrode layer made of the aluminum layer is formed so as to cover the surface and the side surfaces of the semiconductor device, it is possible to maintain good electric conductivity and completely prevent the occurrence of migration. Desirably, if the second electrode layer is constituted by a thick film print layer containing a conductive boron compound of 5 to 60 Vo 1% and aluminum, the electrode firing step can be performed. Even if oxygen is trapped, the conductivity does not decrease, so that good electrical contact can be maintained even in a region where the second electrode directly contacts the thermistor body.

According to the second configuration of the present invention, a contact can be formed on most of the surface of the thermistor body, so that the contact resistance can be further reduced. In addition, since the edges of the first and second electrode layers are covered with the third electrode layer, the occurrence of cracks and cracks in the phosphor body is further reduced.

According to the third configuration of the present invention, the third electrode layer is formed so as to cover the edges and side surfaces except for a part of the second electrode layer but not the entire surface. As with the configuration, migration can be prevented.

According to the fourth configuration of the present invention, the entire surface of the thermistor body is covered with the first electrode layer, and the second electrode layer is formed thereover. However, the occurrence of cracks and cracks in the thermistor body is further reduced.

According to the fifth configuration of the present invention, at the point where the terminal and the electrode come into contact, that is, at the contact point, heat is generated by a large current every time the voltage is turned on. The force that will rise to about C; 'The surface of the area where at least the terminal comes into contact with the positive temperature coefficient thermistor is made of aluminum and a material that does not form an alloy of 300 ° C or less. Therefore, it can be maintained well without peeling. Desirably, the elastic terminal uses, as a surface layer, any of nickel, silver, copper, aluminum, titanium, or an alloy thereof, which is a substance having a high melting point of an alloy with aluminum. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a thermistor according to the first embodiment of the present invention.

Figures 2 (a) and (b) show the manufacturing process of the same summit.

FIG. 3 is a diagram showing a thermistor according to the second embodiment of the present invention.

Fig. 4 shows a conventional thermistor (comparative example).

Fig. 5 shows a conventional example of a thermistor (comparative example).

Figure 6 shows the test equipment for the middaring test

Fig. 7 shows the results of a migration test performed using the device shown in Fig. 6. Fig. 8 shows a test device for performing a low-temperature intermittent load test.

Fig. 9 is a diagram showing the results of a low-temperature intermittent load test performed using the device shown in Fig. 8. Fig. 10 is a diagram showing a test device for performing a surge current test.

Fig. 11 shows the results of a surge current test performed using the device shown in Fig. 10. Fig. 12 shows a test device for measuring the dependence of the low-temperature intermittent load test results on the terminal material. Figure

Fig. 13 shows the results of a low-temperature intermittent load test performed using the device shown in Fig. 12 Fig. 14 shows the state of peeling by a low-temperature intermittent load test using the device shown in Fig. 12 Figure

Fig. 15 shows the melting point of the alloy of aluminum and nickel, silver, and tin. Fig. 16 shows the relationship between the composition and melting point of the aluminum alloy tin base metal.

Figure 17 shows the relationship between the composition of silver-aluminum alloy and the melting point.

Fig. 18 shows the relationship between the composition of aluminum-nickel and the melting point. Fig. 19 shows an example of the terminal structure.

FIG. 20 is a diagram showing the result of measuring the relationship between the element resistance and the maximum surge voltage. FIG. 21 is a diagram showing the thermistor of the third embodiment of the present invention.

FIG. 22 is a diagram showing a thermistor according to the fourth embodiment of the present invention. FIGS. 23 (a) and 23 (b) are diagrams showing a thermistor of a conventional example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1

FIG. 1 is a diagram showing a PTC thermistor according to a first embodiment of the present invention.

This positive temperature coefficient thermistor is composed of a thermistor element body 1 mainly composed of barium titanate, and silver formed on the upper and lower surfaces by a printing method so that the edge is slightly intruded from the outer peripheral edge. —The first electrode layers 2a and 2b composed of a zinc (Ag—Zn) layer, and the silver layer (A) formed by printing to cover the first electrode layers 2a and 2b. g), and aluminum-titanium boride (A 1-) formed by a printing method so as to cover the second electrode layers 3 a and 3 b and the second electrode layers 3 a and 3 b. and a T i B ₂₎ and the third electrode layer 4 a, 4 b made of layers. The thickness of each electrode layer was about 1 °. Next, a manufacturing process of the positive characteristic thermistor will be described.

2 (a) and 2 (b) are process diagrams showing the process of manufacturing a thermistor according to the embodiment of the present invention.

First, as shown in Fig. 2 (a), T i O. _{, B a C 0 3, N} d 2 0. The powder is mixed at a specified ratio, calcined at a temperature in the range of 700 ° C to 10000 ° C, pulverized, pressed into a disk by cold pressing, and then pressurized to 130 CTC. To form a disc-shaped thermistor body 1 having a diameter of 4.47 mm.

Subsequently, as shown in FIG. 2 (b), first to third electrode layers are sequentially applied to the end surface (electrode formation surface) of the thermistor body 1 by a screen printing method. Here, screen printing was first performed using an Ag-Zn paste, followed by a drying process at 18 CTC for 10 minutes, followed by screen printing using an Ag paste at 180 ° C for 10 minutes. Drying, and finally, screen printing using A 1 -TiB 、 paste, drying at 180 ° C for 10 minutes, and baking at 550 ° C for 10 minutes are performed.

Here, A 1 — Ti B ₂ paste is a mixture of aluminum powder having an average particle diameter of about 5 m and Ti B „ceramic powder having an average particle diameter of 3 m in a mixing ratio of 7: 3. It is prepared by mixing a binder, forming a paste, and then adjusting the viscosity. The thermistor obtained in this way can be used for a long time in a high-temperature and high-humidity environment because the electrode layer mainly composed of A1 that does not ionize in dew condensation water completely covers the electrode layer containing Ag. However, reliability can be maintained without silver migration. The electrical contact between the thermistor body and the electrode is good.

In addition, since aluminum does not cause migration, an electrode can be applied to the entire main surface of the element. Therefore, the flow of the rush current to the element becomes uniform, and it is less likely that a surge current or a voltage is applied when a voltage is applied than in the past.

Example 2

FIG. 3 is a diagram showing a positive temperature coefficient thermistor according to a second embodiment of the present invention.

This positive temperature coefficient thermistor is composed of a thermistor body 1 mainly composed of titanium titanate and nickel (Ni) having a thickness of 0.3 to 2 formed by a vacuum evaporation method so as to cover the entire upper and lower surfaces thereof. The first electrode layer 2 m, 2 m ′ and the silver layer (A g) formed by the screen printing method so that the edge is at a position slightly entering from the outer peripheral edge. The second electrode layer 3a, 3b and the aluminum-titanium boride (A 1 —TiB ₂ ) layer formed by printing so as to cover the second electrode layer 3a, 3b. And three electrode layers 4a and 4b. The thickness of each of the second and third electrode layers was set to about 1 m.

At the time of formation, it is formed in the same manner as in the first embodiment.

The thermistor thus obtained also exhibits the above-mentioned effects, similarly to the first embodiment.

For comparison, the same lamination as that used in the first and second embodiments of the present invention was successively laminated by a printing method such that the edge was slightly intruded from the outer peripheral edge of the phosphor body 1. The electrode structure in which the first electrode layers 2a, b made of the silver-zinc layer and the second electrode layers 3a, b made of the silver layer were formed as Comparative Example 1 (FIG. 4).

Further, as Comparative Example 2, the third electrode layer of Example 2 was omitted, and the other electrode layers were formed in the same manner. (Figure 5).

Next, in order to perform a migration test, using a test device as shown in the explanatory diagram in Fig. 6, a voltage of 250 V was applied at an ambient temperature of 120 and a humidity of 95 RH%. It was turned off for 30 minutes, turned off for 30 minutes, and applied for 100 cycles. After the test, the element side is EP MA analysis was performed to detect silver migration. The results are shown in a table in FIG. As is apparent from this table, no migration was observed in the structures of Examples 1 and 2 of the present invention, whereas silver was slightly detected on the side in Comparative Examples 1 and 2. Was done.

Next, in order to perform a low-temperature intermittent load test, using a test device as shown in the explanatory diagram of Fig. 8, at an environmental temperature of −20, a voltage of 250 V was turned on for 1 minute, turned off for 5 minutes, and turned off. After application of 0 cycles, the device after the test was subjected to measurement of cracks, presence / absence of a hook, and a rate of change in resistance. The results are tabulated in FIG. As is evident from this table, none of the examples was flawless, the rate of change in resistance was about 2.6-1.9%, and the judgment was 〇 for all.

Next, in order to conduct a surge current test, using a test apparatus as shown in the explanatory diagram in Fig. 10, the voltage was gradually increased every 250 V from 50 V at an ambient temperature of −20. Figure 11 shows the results of an examination of the device after application and test to determine whether the device is cracked or not. As can be seen from the results, after the test was completed, there was no break in the device.

Next, the thermistor of Example 1 was mounted on a terminal 10 as shown in FIG. 12, and a low-temperature intermittent load test was performed to measure the terminal material. Here, when the surface material of the terminal was composed of a nickel or silver plating layer, the electrode did not peel off after the test as shown in the table in FIG. However, when the terminal was formed of solder or tin, peeling occurred at the terminal contact part. Here, peeling means that peeling R occurs on an electrode surface corresponding to a contact portion with the terminal 10 as shown in FIG. In the low-temperature intermittent load test, heat is generated due to the flow of a large current each time a voltage is applied, so there is a local temperature rise, and it is considered that aluminum and tin or solder were alloyed. These results also indicate that it is desirable to use nickel or silver that does not alloy with aluminum as the material used for the terminal surface.

The melting points of alloys of aluminum with nickel, silver, and tin are shown in the table in Figure 15. FIGS. 16 to 18 show the relationship between the composition and melting point of aluminum-tin alloy and the relationship between the composition and melting point of silver-aluminum alloy, respectively. And relationship. By the way, the contact generates heat due to a large current every time the voltage is turned on, so the temperature locally rises and rises to about 200 ° C. Therefore, considering safety, aluminum and aluminum are required. It is desirable to use a material that does not form the following alloy. Also, as shown in Fig. 19, the structure of the terminal is based on the whole plating method in which the entire surface of the elastic terminal or the central terminal is composed of a plating layer of nickel, copper, silver, aluminum, etc. There is a partial plating method in which only the contact area is formed of a plating layer made of a metal as described above. In addition, a terminal that is usually used and that is made of tin may be used, and at least a portion of the aluminum electrode layer that is in contact with the terminal may be further provided with a layer that is not metalized with tin.

Next, in the first and second embodiments, the example in which Ti B ₂ is added to A 1 has been described.However, the addition amount of Ti B ₂ is changed so that the resistance of the element is not affected. The relationship with the maximum surge voltage was measured. The results are tabulated in FIG.

As is clear from these results, the effect is exhibited when the addition amount is 5 vo 1 ¾; however, calcination becomes difficult when the addition amount is 70 vo 1% or more. This is thought to be because the addition of Ti B ₂ improves the ohmic contact between the thermistor body and the aluminum, thereby increasing the maximum surge voltage. In addition, in the structure shown in Example 2, since the ohmic contact with the thermistor body was obtained by the nickel electrode, the effect on the maximum surge voltage by the addition of TiB „was hardly observed.

From these comparisons, according to the present invention, a highly reliable thermistor having a stable specific resistance can be obtained.

Next, a third embodiment of the present invention will be described.

As shown in Fig. 21, this positive temperature coefficient thermistor has a thermistor body 1 mainly composed of barium titanate, and a top surface having an edge at a position slightly entering from the outer periphery. A first electrode layer 2a, 2b composed of a silver-zinc (Ag-Zn) layer and a second electrode layer 3a composed of a silver layer (Ag) sequentially formed on the lower surface by a printing method. , 3b, and aluminum titanium boride (Al-TiB) formed by printing from the vicinity of the edge of the second electrode layer to cover the side surfaces of the first and second electrode layers. ) The third electrode layers 4a and 4b are composed of layers. The thickness of each electrode layer is about 10 πι. According to this configuration, since the first and second electrode layers are laminated in the same pattern shape, both main surfaces of the positive temperature coefficient thermistor body can be brought into contact with the first electrode layer more. And the contact resistance is reduced. In addition, since it is formed without covering the entire second electrode layer, the material can be reduced and the cost can be reduced.

Next, a fourth embodiment of the present invention will be described.

As shown in Fig. 22, this positive characteristic semiconductor is composed of a thermistor element 1 mainly composed of barium titanate and its upper surface so that the edge is slightly intruded from the outer peripheral edge. And on the lower surface, first electrode layers 2a and 2b made of a silver-zinc (Ag-Zn) layer formed by a printing method, and a printing method formed so as to cover the first electrode layer. Silver layer

(A g), and aluminum titanium boride (A 1 —) formed by a printing method so as to cover the side surface from the vicinity of the edge of the second electrode layer. And a third electrode layer 4a, 4b composed of a T i B ₉ ) layer. The thickness of each electrode layer was about 10 μm.

Even with this configuration, an inexpensive and highly reliable positive characteristic thermistor can be obtained.

In the present invention, the aluminum layer is not limited to pure aluminum but refers to a layer containing aluminum as a main component. Industrial applicability

As described above, according to the present invention, it is possible to obtain a positive temperature coefficient thermistor that is easy to assemble and has stable characteristics without causing a short circuit due to migration.

Claims

The scope of the claims

(1) Positive characteristic noise body and

A single electrode or a plurality of first electrode layers including a silver layer and formed on both main surfaces of the positive temperature coefficient thermistor body so as to have an edge inside an outer peripheral edge of the positive temperature coefficient thermistor body; When,

A positive temperature coefficient thermistor, comprising: a second electrode layer formed of aluminum as a main component and formed to cover the surface and side surfaces of the first electrode layer.

(2) The second electrode layer is formed of a thick-film printing layer containing 5 to 60 Vo 1% of a conductive boride substrate and aluminum. Positive characteristic thermistor described in.

(3) Positive characteristic thermistor body,

A single or multiple first electrode layer formed on both main surfaces of the positive temperature coefficient thermistor body so as to have an edge inside the outer peripheral edge of the positive temperature coefficient thermistor body and including a silver layer; ,

A second electrode layer formed of a layer whose main component is aluminum and formed so as to cover the side surface from the vicinity of the edge of the first electrode layer. .

(4) The second electrode layer according to claim 3, wherein the second electrode layer is formed of a thick-film printing layer containing 5 to 60 Vo 1% of a conductive boron compound and aluminum. Positive thermistor evening.

(5) Positive thermistor body,

A first single-layer or multiple-layer including a silver layer is formed on both main surfaces of the positive-characteristic thermistor body so as to have an end inside the outer peripheral edge of the positive-characteristic thermistor body. An electrode layer;

A second electrode layer mainly composed of silver formed so as to cover the surface and side surfaces of the first electrode layer,

The main component formed so as to cover the side surface from the vicinity of the edge of the second electrode layer is made of aluminum. 3. A positive-characteristics semiconductor device comprising: a third electrode layer formed of a layer to be minimized.

(6) The third electrode layer is constituted by a thick-film printing layer containing a conductive boron compound of 5 to 60 Vo 1% and aluminum. Thermistor with positive characteristics described in 5.

(7) Positive characteristic thermistor element,

A first electrode layer formed on both main surfaces of the positive temperature coefficient thermistor body; and a silver formed such that an edge is formed inside an edge of the first electrode layer. A second electrode layer,

A positive electrode thermistor comprising: a third electrode layer formed of aluminum as a main component and formed so as to cover the second electrode layer.

(8) The third electrode layer is constituted by a thick-film printing layer containing a conductive boron compound of 5 to 60 Vo 1% and aluminum. Positive characteristic thermistor evening described in 7.

(9) Positive characteristics

A positive electrode formed on both main surfaces of the positive temperature coefficient thermistor body, the outermost layer being an aluminum layer or an electrode composed of a layer containing 5 to 6 O vol% of a conductive boron compound and aluminum. Characteristic summaries

And a terminal for holding the PTC thermistor,

At least a region of the terminal, which is in contact with the positive temperature sensor, is made of a material that does not form an alloy with aluminum having a melting point of 300 ° C. or less with respect to aluminum. .

(10) The thermistor device according to claim 9, wherein the substance is any one of nickel, silver, copper, aluminum, titanium, and an alloy of two or more thereof.