JPH1022104A - Positive temperature coefficient thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize resistance value and to raise reliability by providing a positive temperature coefficient thermistor element body, an electrode layer which, whose main component is silver, is formed on a main flat surface of the positive temperature coefficient thermistor element body and a coating layer which, while the center part of the electrode layer is left out, coats the end part of the electrode layer. SOLUTION: A positive temperature coefficient thermistor element body 2 has a disk-like structure, and is constructed of ceramics material such as BaTiO3 . Relating to a positive temperature coefficient thermistor 1, in addition to ohm-contact plating layers 4a and 4b formed by electroless plating with such as Ni, Cu, Au, In, electrode layers 3a and 3b whose main component is silver are formed on the surfaces of them, on both upper and lower surfaces of the positive temperature coefficient thermistor element body 2. In addition, with the use of glass material or resin of both heat- resistance and water-resistance, a coating layer 6 is stuck by spraying method and screen printing method, etc. The coating layer 6 coats end parts 3a1 and 3b1 of the electrode layers 3a and 3b and the entire part of a side surface 5 of the positive temperature coefficient thermistor element body 2 and such entire part of it where the plate layers 4a and 4b are exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive temperature coefficient thermistor.

[0002]

2. Description of the Related Art Conventionally, for example, warm air heaters, waterproof heaters, etc.
2. Description of the Related Art Semiconductor ceramic heating elements having a positive temperature coefficient of resistance (hereinafter, referred to as positive temperature coefficient thermistors) are widely used for demagnetizing circuits of television receivers or television receivers.

As the structure of this positive temperature coefficient thermistor, there are known elements as shown in FIGS. 9A is a schematic perspective view, FIG. 9B is a vertical sectional view, and FIG. 10 is a vertical sectional view.

A positive temperature coefficient thermistor 1 shown in FIG.
The upper and lower surfaces of a metal oxide semiconductor ceramic body 2 (hereinafter referred to as a positive temperature coefficient thermistor body) mainly composed of iO ₃ are mainly made of an ohmic contact made of Ag—Zn, Ag—Sb or the like. Electrode layers 3a and 3b are formed.

A positive temperature coefficient thermistor 1 shown in FIG.
Are Ni, Cu, A on the upper and lower surfaces of the PTC thermistor body 2.
In addition to the ohmic contact plating layers 4a and 4b formed by electroless plating of u, In or the like, electrode layers 3a and 3b mainly composed of Ag are formed on the surface thereof.

The reason for using Ag as the main component for the electrode layers 3a and 3b is that lead terminals and the like are easily soldered,
This is because there are advantages such as excellent contact characteristics of the battery and low electric resistance of itself.

However, when Ag is used as the electrode layer, when a voltage difference is applied between the electrode layers 3a and 3b under high temperature and high humidity,
The silver in the electrode layers 3a and 3b is ionized and moves to a lower potential, and a phenomenon occurs in which electrons are received from the semiconductor ceramic on the side surface 5 of the positive temperature coefficient thermistor body 2 and silver is precipitated. This phenomenon is called a silver migration phenomenon, and may cause a short circuit between the electrodes. Further, the silver migration phenomenon is promoted by an atmosphere such as a compound of sulfur or halogen under high temperature and high humidity conditions.

In the positive temperature coefficient thermistor and its manufacturing method described in JP-A-3-245501, as shown in FIG. 4, FIG. 9, FIG. 10, and FIG.
A glass coating film is formed on the portion excluding the g film or the electrode containing Ag as a main component. It is stated that such a glass coating film has insulating properties, so that even if silver is ionized by moisture in air or chlorine dissolved in moisture, ions on the insulating film cannot move, so that migration can be prevented.

Further, in the PTC heater described in Japanese Patent Application Laid-Open No. 61-211981, the electrode portion and the conductive portion are coated with a glass film, as shown in FIGS. 1, 2 and 3. ing. It is described that such a coating suppresses silver migration and also prevents the adverse effect of poor adhesion due to silver sulfide formed by reaction of a small amount of hydrogen sulfide in the air with silver.

Furthermore, in the positive temperature coefficient thermistor described in JP-A-57-17105, a metal coating is exposed on the surface by partially providing a silver coating. It is stated that if oxidation and corrosion of the exposed metal film do not occur, even if silver is ionized, it cannot move on the exposed portion of the metal film having no potential difference, thereby preventing the occurrence of silver migration.

[0011]

However, the conventional positive temperature coefficient thermistor has the following problems. (1) In the case of the positive temperature coefficient thermistor and its manufacturing method described in Japanese Patent Application Laid-Open No. 3-245501, the electrode containing Ag as a main component is not coated with glass. Ag is easily ionized by the attachment of compounds such as Cl and Br. Since the ionized Ag moves in the direction of the electric field, there is a high possibility that the migration phenomenon occurs by permeating into the interface between the element and the glass coating film or inside the element.

(2) In the case of the PTC heater described in Japanese Patent Application Laid-Open No. 61-211981, a glass film is coated on the entire surface of the electrode portion or conductive portion using silver as an electrode material, and on the entire heater. ing. However, the glass coating is sufficiently effective if it is limited only to the portion where the electric field is concentrated. It is advantageous to coat only the necessary portion in terms of cost, and the strain stress of the PTC element due to a rapid temperature change. This is advantageous in terms of quality deterioration due to reduction of the quality.

(3) In the case of the positive temperature coefficient thermistor described in Japanese Patent Application Laid-Open No. 57-17105, oxidation and corrosion of the exposed metal film occur depending on the use environment, and the interface between the silver film and the metal film is In some cases, a potential difference occurs between the metal film and the interface of the positive temperature coefficient thermistor body. At this time, when silver is ionized, silver ions move on the metal film and reach the side surface of the positive temperature coefficient thermistor body, and there is a high possibility that silver migration occurs.

An object of the present invention is to improve the reliability of a positive temperature coefficient thermistor by stabilizing the resistance value of the positive temperature coefficient thermistor by focusing on a coating layer which covers an electrode layer containing silver as a main component. is there.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above objects. The positive temperature coefficient thermistor of the present invention is a positive temperature coefficient thermistor body, an electrode layer containing silver as a main component and formed on a main plane of said positive temperature coefficient thermistor body, and said electrode layer leaving a central portion of said electrode layer. And a coating layer covering the edge of the layer.

Further, the positive temperature coefficient thermistor of the present invention comprises a positive temperature coefficient thermistor body, a plating layer formed on a main plane of the positive temperature coefficient thermistor body, and silver as a main component. And a coating layer formed by covering an end of the electrode layer except for a central portion of the electrode layer.

Further, in the positive temperature coefficient thermistor of the present invention, the coating layer may cover an end of the electrode layer and a part of a side surface of the positive temperature coefficient thermistor body.

Further, in the positive temperature coefficient thermistor of the present invention, the coating layer covers an end portion of the electrode layer, a part of a side surface of the positive temperature coefficient thermistor body, and an exposed part of the plating layer. May be.

Further, in the positive temperature coefficient thermistor of the present invention, the coating layer may cover an end portion of the electrode layer and the entire side surface of the positive temperature coefficient thermistor body.

Further, in the positive temperature coefficient thermistor of the present invention, the coating layer covers an end portion of the electrode layer, the entire side surface of the positive temperature coefficient thermistor body, and an exposed part of the plating layer. It may be something.

Further, in the positive temperature coefficient thermistor of the present invention, the coating layer covers an end portion of the electrode layer, a whole side surface of the positive temperature coefficient thermistor body, and a whole exposed portion of the plating layer. It may be.

Further, in the positive temperature coefficient thermistor of the present invention, the width of the end portion of the electrode layer covered with the coating layer is preferably 100 μm or more.

In the PTC thermistor according to the present invention, the coating layer is made of B, Si, Bi, Zn, P
It is preferable that the glass is composed of at least two of the compositions of b and Ba, and the softening point of the glass is 250 ° C. or higher.

In the PTC thermistor according to the present invention, the coating layer is a resin having a water absorption of 1.0% or less and a deflection temperature under load equal to or higher than the heat generation temperature of the PTC thermistor body. Is preferred.

In the positive temperature coefficient thermistor of the present invention, the coating layer preferably has a total content of sulfur, chlorine or bromine of 100 ppm or less.

[0026]

Embodiments of the present invention will be described below. The positive temperature coefficient thermistor of the present invention includes a positive temperature coefficient thermistor body, an electrode layer mainly composed of silver and formed on a main plane of the positive temperature coefficient thermistor body, and an end of the electrode layer except for a central portion of the electrode layer. And a coating layer covering the portion. With such a configuration, the resistance value of the positive temperature coefficient thermistor can be stabilized, and the reliability of the positive temperature coefficient thermistor can be improved.

That is, when a voltage is applied between both electrode layers of the positive temperature coefficient thermistor, the electric field concentrates at the end of the electrode layer. By covering and protecting this portion with a coating layer, adhesion of water, sulfur, a halogen compound, or the like, which is a substance causing ionization of the electrode layer, is prevented, and as a result, generation of silver ions is suppressed. Although an electric field for moving silver ions is generated, silver migration does not occur because silver ions are not generated. Even if water, sulfur, or a halogen compound adheres to the other electrode portions, no silver ion migration occurs because no potential difference for moving silver ions is generated.

Further, the positive temperature coefficient thermistor of the present invention is formed on a positive temperature coefficient thermistor body, a plating layer formed on the main plane of the positive temperature coefficient thermistor body, and a plating layer containing silver as a main component. It comprises an electrode layer, and a coating layer formed by covering an end of the electrode layer except for a central portion of the electrode layer. With such a configuration, it is possible to prevent silver migration of the electrode layer in the same manner as described above.

The edge of the electrode layer is a portion excluding a region around the center of the electrode layer. There is no particular relationship between the area of the center and the edge of the electrode layer. In view of the formation of the electrode layer, the surface of the electrode layer has a coated portion and an uncoated portion, and the peripheral portion of the electrode layer which needs to be coated for the above-described reason is an end.

Here, the portion covered by the coating layer may be any other coating, such as coating on the side surface of the positive temperature coefficient thermistor element, or plating, as long as the end of the electrode layer is necessarily coated as described above. There is no particular limitation on coating the exposed portion of the layer. Whether the side surface of the positive temperature coefficient thermistor body or the plating layer is partially covered or entirely covered may be simplified by, for example, considering the manufacturing process if the whole is covered, or considering the manufacturing cost. For example, partial coating is more advantageous in terms of cost, or considering partial characteristics, partial coating has better heat exchange than full coating, and has less influence such as distortion during processing of the coating layer, In some cases, cracks are prevented from occurring. Therefore, for other parts of the coating shape,
Various shapes are conceivable depending on the purpose.

In the method of forming the plating layer, various plating processes can be performed. As a specific example,
Examples include an electroless plating method, an evaporation method, and a sputtering method.

Further, in the positive temperature coefficient thermistor of the present invention, the width of the end of the electrode layer covered with the coating layer is preferably 100 μm or more. When the coating width is as small as less than 100 μm, silver migration caused by adhesion of moisture, sulfur, or a halogen compound is caused by jumping over the coating layer depending on electric field concentration. It is considered something. The electric field strength varies depending on the voltage, the electrode structure, or the processing accuracy of the electrode, but the coating width is 100 μm with a normal thermistor operating at 50 to 300 V.
By doing so, the effect of suppressing silver migration increases. In the present invention, since the coating is performed so as to leave the central portion of the electrode layer, it goes without saying that the upper limit is limited thereby.

In the PTC thermistor of the present invention, the coating layer is made of B, Si, Bi, Zn, Pb,
It is preferable that the glass is composed of at least two kinds of Ba compositions, and that the glass has a softening point of 250 ° C. or higher.

In a positive temperature coefficient thermistor operating at a high temperature, when the softening temperature of the glass material to be coated is low, silver as a silver migration substance easily penetrates between the coating material and the thermistor body. There is a danger of becoming. This is because when glass having a high softening point is used as the coating material, the bonding strength with the thermistor body is maintained even at a high temperature, and the effect of suppressing silver migration is enhanced. If the softening point is lower than 250 ° C., the resistance of the positive temperature coefficient thermistor, which is considered to be caused by the occurrence of silver migration, is undesirably reduced.

Further, among the above glass compositions, Pb-Si-based and Si-Bi-based glasses are more preferred.

Further, in the positive temperature coefficient thermistor of the present invention, the coating layer has a water absorption of 1.0% or less,
Further, it is preferable that the resin is a resin whose deflection temperature under load is equal to or higher than the heat generation temperature of the positive temperature coefficient thermistor body.

When a resin having a high deflection temperature under load is used as the coating material, the bonding strength with the thermistor body is maintained even at a high temperature, and the effect of suppressing silver migration is enhanced. Further, by using a coating material that does not absorb water, which is one of the substances causing silver migration, the effect of suppressing silver migration is further enhanced. When the water absorption exceeds 1.0%, silver migration occurs, which is not preferable. If the deflection temperature under load is lower than the heat generation temperature of the thermistor body, silver migration occurs, which is not preferable.

[0038] In the PTC thermistor of the present invention, the total content of sulfur, chlorine or bromine in the coating layer is preferably 100 ppm or less.

One of the causes of silver migration occurring in a high temperature load test is a reaction between silver and a sulfur compound or a halide present in a trace amount in the atmosphere. When these adhere to the electrode layer mainly composed of silver of the positive temperature coefficient thermistor, ionized silver can be present in the electrode. For example, in the case of silver and a sulfur compound, silver sulfide which is an ionic bond is formed, and silver ions easily enter between lattices. In the case of silver and halide, silver halide, which is an ionic bond, is formed, and silver ions easily enter between lattices. This is because silver migration is a phenomenon in which silver ions move under the influence of an electric field, and the effect of preventing silver migration is further enhanced by eliminating sulfur and halides that are the causes of ionization. It is considered that this is also effective in preventing silver ionization by other halogen elements such as iodine. Also, sulfur,
When the content of chlorine or bromine exceeds 100 ppm, silver migration occurs, which is not preferable.

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to only these examples.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A PTC thermistor 1 according to an embodiment of the present invention.
Will be described. 1 to 6 are vertical sectional views of a positive temperature coefficient thermistor.

The positive temperature coefficient thermistor body 2 has a disk-like structure and is made of a ceramic material such as BaTiO ₃ . In the positive temperature coefficient thermistor 1 shown in FIG. 1, electrode layers 3a and 3b mainly composed of ohmic silver composed of Ag-Zn, Ag-Sb and the like are formed on the upper and lower surfaces of the positive temperature coefficient thermistor body 2. ing. The positive temperature coefficient thermistor 1 shown in FIG.
An ohmic contact plating layer 4 formed by electroless plating of Ni, Cu, Au, In, etc. on the upper and lower surfaces of the myster body 2.
a, an electrode layer 3 containing silver as a main component on its surface
a, 3b are formed.

Further, using a glass material or a resin having both heat resistance and water resistance, a coating layer 6 formed by means such as spraying or screen printing is adhered. When a glass material is used, about 500 ° C. to 90 ° C.
When a baking process is performed at a temperature of 0 ° C. and a resin material is used, a curing agent is added, and a heating and drying process is performed according to the type.

After such processing, the coating layer 6
Are formed in the following state. (1) The electrode layers 3a, 3b, except for the central portions of the electrode layers 3a, 3b,
End 3a ₁ of 3b, 3b ₁ only covers (5, 6). (2) The ends 3a ₁ , 3b _{1 of the} electrode layers 3a, 3b and a part of the side surface 5 of the positive temperature coefficient thermistor body 2 are covered (FIG. 3). (3) End portions 3a ₁ , 3b _{1 of} electrode layers 3a, 3b, part of side surface 5 of positive temperature coefficient thermistor body 2, and plating layer 4
Cover the exposed portions of a, 4b (FIG. 4). (4) The end portions 3a ₁ and 3b _{1 of the} electrode layers 3a and 3b and the entire side surface 5 of the positive temperature coefficient thermistor body 2 are covered (FIG. 1). (5) The end portions 3a ₁ , 3b _{1 of the} electrode layers 3a, 3b, the entire side surface 5 of the positive temperature coefficient thermistor body 2, and the plating layer 4
Cover the exposed portions of a and 4b (FIGS. 7 and 8). (6) The end portions 3a ₁ , 3b _{1 of the} electrode layers 3a, 3b, the entire side surface 5 of the positive temperature coefficient thermistor body 2, and the plating layer 4
Cover all exposed portions of a and 4b (FIG. 2).

Hereinafter, more detailed embodiments will be described. (Example 1) First, by molding a material obtained by adding CuO 0.005% by weight of a part of Ba of BaTiO ₃ to that replaced by Ce thickness 3 mm, the disc-shaped 20Fai, 1320
Calcination was carried out at ℃ for 1 hour. Using this thermistor body 2,
The evaluation regarding silver migration was performed.

A conductive paste composed of 50 parts by weight of a metal powder composed of silver and a small amount of zinc, 0.3 parts by weight of a B-Si-Bi-based glass frit, and the remainder being an organic vehicle, on the thermistor body 2 Was screen printed and baked at 700 ° C. to form electrode layers 3a and 3b mainly containing silver.

Similarly, Ni was electrolessly plated on the thermistor body 2, heat-treated at 150 ° C. for 1 hour, and the cylindrical plating layer corresponding to the side surface 5 of the thermistor body 2 was removed by polishing. At the same time, the same processing was also performed on Au which had been subjected to electroless plating.

On each of the plating layers 4a and 4b made of Ni and Au, 50 parts by weight of silver powder and B-Si-Bi
A conductive paste consisting of 0.3 parts by weight of a system glass frit and the remainder of the organic vehicle was screen-printed and baked at 700 ° C. to form electrode layers 3a and 3b. Next, BS
Coating layer 6-1 by i-Bi-based glass, BS
i-Pb-based coating layer 6-2 or polyamide-based heat-resistant resin coating layer 6-2
3 was coated as described above to form a coating layer 6. The glass coating layers 6-1 and 6-2 are 500 to 6 after the glass and the resin are processed into a paste and applied by screen printing.
Baking at 00 ° C, the resin coating layer 6-3 is 150
It was dried and cured at ℃.

These samples were subjected to an applied voltage of 100 V (AC 60 Hz), a temperature of 300 ° C. and 500 hours in an atmosphere of H ₂ S.
After applying a load, the sample was examined for resistance (20 ° C.) and the presence or absence of silver migration. Further, the measurement was performed while changing the coating width of the side surface 5 of the thermistor body 2. Table 1 shows the results. In addition, the mark 正常 indicates normal, and the mark X indicates that silver migration has occurred.

[0050]

[Table 1]

As shown in Table 1, the positive temperature coefficient thermistor of the present invention has a silver migration of an electrode layer containing silver as a main component which is generated by energization under a high-temperature and polluted atmosphere, as compared with the conventional product. Can be prevented. Further, it can be seen that if the coating material covers the edge of the silver electrode layer, it is not necessary to cover the entire side surface of the thermistor body with the coating layer.

In addition, by suppressing the formation of the coating layer to a part, it is possible to reduce the amount of use, and it can be expected to have an advantage that stress strain on the thermistor body can be reduced.

Example 2 Next, the Ag—Zn electrode layer 3
A coating layer 6 was formed on each of the positive temperature coefficient thermistor 1 on which a and 3b were formed and the positive temperature coefficient thermistor 1 on which the Ag electrode layers 3a and 3b were formed on the Ni plating layers 4a and 4b. At this time, the ends 3a ₁ , 3a of the silver electrode layers 3a, 3b
b ₁ covering width 0~500μ (width x shown in FIGS. 1-8)
m. At this time, the coating of the side surface 5 of the thermistor body 2 was performed only on a part as shown in FIGS.

These samples were subjected to an applied voltage of 100 V (AC 60 Hz), a temperature of 300 ° C. and 500 hours in an H ₂ S atmosphere.
After applying a load, the sample was examined for resistance (20 ° C.) and the presence or absence of silver migration. Table 2 shows the results. In addition, the mark 正常 indicates normal, and the mark X indicates that silver migration has occurred.

[0055]

[Table 2]

As shown in Table 2, the product of the present invention was subjected to high temperature,
It is possible to prevent silver migration of an electrode layer containing silver as a main component, which is caused by energization in a polluted atmosphere. However, in order to effectively block market contaminants and air moisture, it is necessary to define the coating width. It can be seen that the effect of preventing silver migration is insufficient unless the coating width of the glass or heat-resistant resin coating the edge of the electrode layer containing silver as a main component is at least 100 μm or more.

Example 3 Next, the positive characteristic thermistor body 2 was formed with the Ag-Zn electrode layers 3a and 3b formed on the positive temperature thermistor body 2 at different exothermic temperatures of 150.degree. Ag electrode layers 3a and 3b are formed on the thermistor 1 and the Ni plating layers 4a and 4b, and B is formed on the ends 3a ₁ and 3b ₁ .
The end portions 3 of the silver electrode layers 3a and 3b are formed by using a glass made of a combination of two or more types of Si, Bi, Zn, Pb and Ba.
Positive temperature coefficient thermistors 1 each having a coating layer 6 formed on a ₁ and 3b ₁ with a width of 50 μm were produced. At this time, the coating of the side surface 5 of the thermistor body 2 was performed only on a part as shown in FIGS.

These samples were tested for resistance (20 ° C.) and the presence or absence of silver migration after applying a load of 2,000 hours under an applied voltage of 100 V (AC 60 Hz) in an H ₂ S atmosphere. Table 3 shows the results. In addition, the mark 正常 indicates normal, and the mark X indicates that silver migration has occurred.

[0059]

[Table 3]

As shown in Table 3, the resistance of the positive temperature coefficient thermistor decreases with the occurrence of silver migration at a low glass softening point irrespective of the type of glass constituent elements. The lower the softening temperature is, the more the migration of silver ions cannot be prevented under the conditions of the high temperature load test, and silver migration occurs at the interface between the glass and the thermistor body. It is considered that the softening of the glass makes it easier for silver ions to enter the interface between the coating layer and the thermistor body, or that the Ag ions diffuse into the glass and the glass acts as an ion medium. It can be seen that a glass material having a higher softening point should be used as a material selection criterion in order to stably function as a glass material at a high temperature.

Example 4 Next, two types of positive temperature coefficient thermistor bodies 2 having different heating temperatures were prepared. Subsequently, a positive temperature coefficient thermistor 1 in which Ag-Zn electrode layers 3a and 3b were formed on the thermistor body 2 was produced. Then, coating was performed with a width of 100 μm on the ends 3a ₁ and 3b ₁ of the electrode layers 3a and 3b containing silver as a main component using various heat-resistant resins. At this time, the coating of the side surface 5 of the thermistor body 2 was performed only on a part as shown in FIG.

[0062] The samples H ₂ S atmosphere at an applied voltage 100V (AC60Hz), humidity 70%, 2000 hr
After applying a load, the sample was examined for resistance (20 ° C.) and the presence or absence of silver migration. Table 4 shows the results. In addition, the mark 正常 indicates normal, and the mark X indicates that silver migration has occurred.

[0063]

[Table 4]

As shown in Table 4, the heat generation temperature was 150
With a positive temperature coefficient thermistor at ° C, silver migration was confirmed when the water absorption of the coating resin was 1.20%. Similarly, a positive temperature coefficient thermistor having an exothermic temperature of 200 ° C. has a water absorption of 1.20% and a deflection temperature under load of 234 ° C. or less, and silver migration has been confirmed. For resins with high water absorption, both positive temperature coefficient thermistors use silver migrating.
In addition to the occurrence of the migration, the positive temperature coefficient thermistor having an exothermic temperature of 200 ° C. has a deflection temperature under load lower than the exothermic temperature and causes silver migration. Heat-resistant resin that effectively suppresses silver migration has a water absorption of 1%
It is necessary to select a coating material having a deflection temperature under load lower than the exothermic temperature.

(Example 5) Next, a positive temperature coefficient thermistor 1 having Ag-Zn electrode layers 3a and 3b formed on a positive temperature coefficient thermistor body 2 has a water absorption of 0.50% and a deflection temperature under load of 240.
Electrode layers 3a, 3a containing a phenolic resin of silver
The ends 3a ₁ and 3b ₁ of b were coated with a width of 100 μm. The phenolic resins used were those to which arbitrary amounts of sulfur, chlorine and bromine were added. These samples were applied at an applied voltage of 100 V (AC 60 Hz) and a temperature of
After applying a load of 2000 hours at 00 ° C., the resistance (20 ° C.) of the sample and the presence or absence of silver migration were examined. Table 5 shows the results. In addition, the mark 正常 indicates normal, and the mark X indicates that silver migration has occurred.

[0066]

[Table 5]

As shown in Table 5, S and C were contained in the resin.
Those containing l and Br in excess of at least 100 ppm cause silver migration. By suppressing the content of these impurities to 100 ppm or less, silver migration is further suppressed.

[0068]

By using the thermistor of the present invention,
By focusing on an electrode layer containing silver as a main component or a coating layer covering the silver electrode layer, it is possible to prevent the occurrence of silver migration, which is likely to occur in a high-temperature, high-humidity market environment, so that positive The resistance value of the characteristic thermistor is stabilized. Therefore, it is possible to further improve the reliability of the positive temperature coefficient thermistor.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a positive temperature coefficient thermistor according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a positive temperature coefficient thermistor according to one embodiment of the present invention.

FIG. 3 is a vertical sectional view of a positive temperature coefficient thermistor according to one embodiment of the present invention.

FIG. 4 is a vertical sectional view of a positive temperature coefficient thermistor according to one embodiment of the present invention.

FIG. 5 is a vertical sectional view of a positive temperature coefficient thermistor according to one embodiment of the present invention.

FIG. 6 is a vertical sectional view of a positive temperature coefficient thermistor according to an embodiment of the present invention.

FIG. 7 is a vertical sectional view of a positive temperature coefficient thermistor according to one embodiment of the present invention.

FIG. 8 is a vertical sectional view of a positive temperature coefficient thermistor according to one embodiment of the present invention.

FIG. 9 is a vertical sectional view of a conventional positive temperature coefficient thermistor.

FIG. 10 is a vertical sectional view of a conventional PTC thermistor.

[Explanation of symbols]

1 PTC thermistor 2 PTC thermistor element 3a, 3b electrode layer 3a _1, 3b ₁ end 4a of the electrode layer, 4b plating layer 5 thermistor sides 6 coating layer of the element body

Claims (11)

[Claims] 1. A positive temperature coefficient thermistor body, an electrode layer containing silver as a main component and formed on a main plane of said positive temperature coefficient thermistor body, and an end of said electrode layer except for a central portion of said electrode layer. And a coating layer covering the portion. 2. A positive temperature coefficient thermistor body, a plating layer formed on a main plane of said positive temperature coefficient thermistor body, an electrode layer containing silver as a main component and formed on said plating layer, and said electrode A coating layer formed by covering an end of the electrode layer except for a central part of the layer. 3. The PTC thermistor according to claim 1, wherein the coating layer covers an end of the electrode layer and a part of a side surface of the PTC thermistor body. . 4. The coating layer according to claim 2, wherein the coating layer covers an end portion of the electrode layer, a part of a side surface of the PTC thermistor element, and an exposed part of the plating layer. Item 3. The positive temperature coefficient thermistor according to Item 3. 5. The coating layer according to claim 1, wherein the coating layer covers an end portion of the electrode layer and the entire side surface of the PTC thermistor body. Positive characteristic thermistor. 6. The coating layer according to claim 2, wherein the coating layer covers an end portion of the electrode layer, a whole side surface of the positive temperature coefficient thermistor body, and an exposed part of the plating layer. A positive temperature coefficient thermistor according to claim 5. 7. The coating layer according to claim 2, wherein the coating layer covers an end portion of the electrode layer, a whole side surface of the positive temperature coefficient thermistor body, and a whole exposed portion of the plating layer. A positive temperature coefficient thermistor according to any one of claims 1 to 6. 8. The positive temperature coefficient thermistor according to claim 1, wherein an end portion of said electrode layer covered with said coating layer has a width of 100 μm or more. 9. The coating layer is made of B, Si, B
The glass is composed of at least two of the compositions of i, Zn, Pb, and Ba, and has a softening point of 2
The positive temperature coefficient thermistor according to any one of claims 1 to 8, wherein the temperature is 50 ° C or higher. 10. The coating layer has a water absorption of 1.
9. The positive temperature coefficient thermistor according to claim 1, wherein the positive temperature coefficient thermistor is a resin having a deflection temperature under load of 0% or less and a heat generation temperature of the positive temperature coefficient thermistor body or higher. 10. 11. The positive temperature coefficient thermistor according to claim 1, wherein the total content of sulfur, chlorine or bromine in said coating layer is 100 ppm or less. .