KR102341611B1 - Composition for positive temperature coefficient resistor, paste for positive temperature coefficient resistor, positive temperature coefficient resistor and method for producing positive temperature coefficient resistor - Google Patents

Abstract

The present invention relates to a composition for a positive temperature coefficient resistor with little limitation in element shape, a wide adjustable specific resistance range, and high reliability at high temperature that switches in the range of 250°C to 400°C, and a resistor using the composition An object of the present invention is to provide a paste, a resistor formed from the resistor paste, and a method for manufacturing the same.
A composition for a positive temperature coefficient resistor comprising metal oxide conductive particles and a glass powder having a glass transition point of 400° C. or less, wherein the metal oxide conductive particles are ruthenium oxide particles, and further, ruthenium oxide particles It is a composition for a positive temperature coefficient resistor, characterized in that

Description

A composition for a positive temperature coefficient resistor, a paste for a positive temperature coefficient resistor, a positive temperature coefficient resistor, and a method for manufacturing a positive temperature coefficient resistor TEMPERATURE COEFFICIENT RESISTOR}

The present invention relates to a composition and a resistance paste used in the production of a positive temperature coefficient resistor. Furthermore, it relates to a positive temperature coefficient resistor formed using this resistance paste.

A positive temperature coefficient resistor is a resistor whose specific resistance increases with a rise in temperature. In particular, those whose specific resistance increases rapidly at a certain temperature are called "PTC thermistors" and are widely applied as temperature control elements, overcurrent control elements, low-temperature heating elements, and the like.

This "PTC thermistor" is roughly _{classified into one using an inorganic material represented by BaTiO 3 type} ceramics and one using an organic material in which a conductive filler such as carbon black is dispersed in a thermoplastic polymer.

BaTiO ₃ -based ceramics are produced by uniformly mixing raw materials such as Ba and Ti, then calcining to proceed with crystallization of the composite oxide, and firing a molded body formed by pressurizing the crystallized composite oxide.

For this reason, there is a limit to the shape of the element, and it is difficult to reduce the size. Further, the temperature at which a drastic change of the specific resistance is called switching temperature, BaTiO ₃ based ceramic is, in general, a temperature of about 120 ℃ Curie point.

Patent Document 1 discloses _{a thermistor ceramic composition in which a part of Ba of BaTiO 3 type} ceramic is substituted with an alkali metal element or part of Ti is substituted with a group 5 element such as Nb. There is no indication, and it is very difficult to make this into a higher temperature. Moreover, the range of the specific resistance of ceramics which can be adjusted is small.

On the other hand, a "PTC thermistor" using an organic material has advantages in that there are few restrictions on device shape, the specific resistance can be changed according to the type or content of the conductive filler, and the range of adjustable specific resistance is wide. However, there is a limit to the switching temperature obtained from the temperature at which the thermoplastic polymer softens, and it is not possible to make an element whose resistance value changes rapidly at high temperature. Moreover, the polymer which is a matrix has the fault that the decomposition advances in long-term use in high temperature or in the environment which becomes high temperature repeatedly, there exists a fault that reliability is insufficient.

In addition, a "PTC thermistor" in which conductive particles such as Ag are dispersed in glass is also proposed in Patent Document 2, but it is limited to a low specific resistance, and the switching temperature is too high to be 400° C. or less, and is lower than the switching temperature. Temperature WHEREIN: There exists a fault, such as becoming a high positive temperature coefficient.

Therefore, in the temperature range of 250 °C or more and 400 °C or less, development of a resistor that enables a switching operation is demanded.

[Patent Document 1] WO2014-141814 International Publication [Patent Document 2] Japanese Patent Laid-Open No. Hei 11-97207

Under these circumstances, the present invention provides a composition for a resistor with high reliability at high temperatures, which has few limitations in element shape, has a wide adjustable specific resistance range, and is switched in the range of 250°C to 400°C, and the To provide a resistor paste using a composition, a resistor formed from the resistor paste, and a method for manufacturing the same.

The present invention uses a composition for a positive temperature coefficient resistor and a resistor paste obtained by mixing ruthenium oxide particles as conductive particles and a glass powder having a glass transition point of 250°C to 400°C as means for solving the problems.

1st invention of this invention contains metal oxide type electroconductive particle and the glass powder which has a glass transition point of 400 degrees C or less, The composition for positive temperature coefficient resistors characterized by the above-mentioned.

The second invention of the present invention is a composition for a positive temperature coefficient resistor characterized in that the metal oxide conductive particles in the first invention are ruthenium oxide particles.

A third invention of the present invention is a composition for a positive temperature coefficient resistor, wherein the ruthenium-based oxide particles according to the second invention are ruthenium oxide particles.

A fourth invention of the present invention is a paste for a positive temperature coefficient resistor comprising an organic vehicle and the composition for a positive temperature coefficient resistor according to any one of the first to third inventions.

5th invention of this invention is a positive temperature coefficient resistor characterized by the metal oxide type electroconductive particle being contained in the glass which has a glass transition point of 400 degrees C or less.

A 6th invention of this invention is a positive temperature coefficient resistor characterized by the metal oxide type electroconductive particle in 5th invention being a ruthenium type oxide particle.

A seventh invention of the present invention is a positive temperature coefficient resistor characterized in that the ruthenium oxide particles according to the sixth invention are ruthenium oxide particles.

According to the eighth invention of the present invention, the positive temperature coefficient resistor paste according to the fourth invention is coated and fired on an insulating substrate to dissipate the organic solvent and the organic resin, soften the glass powder, and thus for the positive temperature coefficient resistor. Manufacturing of a positive temperature coefficient resistor, characterized in that the metal oxide conductive particles contained in the paste are blown into a glass matrix formed by the glass powder contained in the positive temperature coefficient resistor paste, dried and solidified. way.

Advantageous Effects of Invention According to the present invention, a composition for a positive temperature coefficient resistor with low element shape restrictions, a wide adjustable specific resistance range, and high reliability at high temperatures switching in the range of 250°C to 400°C, and the composition A resistor paste and a resistor formed from the resistor paste can be easily obtained.

1 is a diagram showing "temperature dependence of electrical resistance" of a resistor according to Example 1. FIG.
Fig. 2 is a diagram showing "temperature dependence of electrical resistance" of the resistor according to the second embodiment.
3 is a diagram showing "temperature dependence of electrical resistance" of the resistor according to Example 3;
Fig. 4 is a diagram showing "temperature dependence of electrical resistance" of the resistor according to the fourth embodiment.
5 is a diagram showing "temperature dependence of electrical resistance" of the resistor according to Example 5;
6 is a diagram showing “temperature dependence of electrical resistance” of the resistor according to Comparative Example 1. FIG.
7 is a diagram showing "temperature dependence of electrical resistance" of the resistor according to Comparative Example 2. FIG.

The present invention relates to a composition for positive temperature coefficient resistors comprising metal oxide conductive particles such as ruthenium oxide particles and glass powder. As a result of finding a phenomenon in which the resistance value changes rapidly with the boundary of the set temperature within the temperature range of 400 ° C. or less as described above, and as a result of further development, the combination of the glass powder and the metal oxide-based conductive particles having such a glass transition point, the temperature It has reached the completion of a positive temperature coefficient resistor in which the switching temperature, which is the temperature at which the rise ratio of the specific resistance with respect to the rise changes, is controllable in the range of 250°C to 400°C.

In general, in a thick-film resistor in which conductive particles are dispersed in a glass matrix, the contact between the conductive particles is weakened due to volume expansion of the glass matrix, resulting in an increase in specific resistance.

By the way, glass has a property that the volume expansion rate changes greatly with the glass transition point as a boundary, and the volume expansion rate is higher on the high temperature side of a glass transition point than the low temperature side.

Even in the positive temperature coefficient resistor according to the present invention, since the volume expansion rate increases on the high temperature side of the glass transition point, the increase rate of the specific resistance also changes with the glass transition point as a boundary. That is, at a temperature above the glass transition point, it was expected that the increase rate of the resistance value would be sharply higher than at a temperature below the glass transition point.

However, general thick-film resistors are fired at around 850°C, but if glass with a low glass transition point is used, the glass becomes excessively softened and the shape of the thick-film resistor cannot be maintained. It is common to use glass that shows

By the way, when glass powder with a glass transition point of 500°C or higher and metal oxide conductive particles are used, it is considered that a positive temperature coefficient resistor with a switching temperature of 500°C or higher is possible, but a positive temperature coefficient resistor with a switching temperature of 500°C or higher is obtained. If possible, this positive temperature coefficient resistor will operate at a temperature of 500°C or higher. For this reason, not only the positive temperature coefficient resistor but also peripheral parts such as a terminal electrode incorporated in the thick film resistor are exposed to a temperature of 500° C. or higher, and problems such as deterioration of the terminal electrode occur.

In addition, when it was desired to suppress the switching temperature lower than 500 degreeC, these combinations could not be used.

In view of such a problem, when a positive temperature coefficient resistor is formed from a thick film resistor, when a resistor whose switching temperature is 400° C. or less is required, it cannot be met, and a corresponding product is required.

Then, for the glass powder used by this invention, a glass transition point is 400 degreeC or less, Preferably the glass powder of the component composition which has a glass transition point in the range of 250 degreeC or more and 400 degrees C or less is used.

The composition of the glass powder having the above glass transition point is not limited, but examples thereof include lead borate-based glass, tin-phosphate-based glass, and tellurium vanadate glass.

Although the lower limit of the glass transition point of the glass powder in this invention is not limited, Since it is not found that it is below 240 degreeC substantially in oxide glass at the present time, it is set as 250 degreeC or more and 400 degrees C or less as a preferable range. In addition, the glass transition point and softening point of the glass powder used by this invention can be adjusted with the composition of a glass powder. Specifically, what is necessary is just to adjust the mixing|blending ratio of each element, such as silicon, boron, aluminum, zinc, lead, and bismuth which comprises glass.

Here, the glass transition point is measured in the atmosphere by thermomechanical analysis (TMA) of a rod-shaped sample obtained by re-melting glass powder or the like, and is measured as a temperature at which the inflection point of the thermal expansion curve is indicated.

Moreover, it is preferable that the softening point of the glass powder used by this invention is temperature 50 degreeC or more higher than a glass transition point.

The softening point of glass powder is the lowest temperature at which softening of glass occurs, and the shape of the positive temperature coefficient resistor cannot be maintained at a temperature significantly exceeding the softening point. The positive temperature coefficient resistor according to the present invention needs to maintain the positive temperature coefficient resistor even at a temperature exceeding the glass transition point. Therefore, the softening point of the glass powder used by this invention is a temperature 50 degreeC or more higher than a glass transition point, and the temperature below the upper limit of the calcination temperature mentioned later is preferable.

Here, the softening point is the temperature of the peak at which the glass powder is measured in the atmosphere by differential thermal analysis (TG-DTA), and the next differential thermal curve on the high temperature side decreases than the temperature at which the decrease of the differential thermal curve on the lowest side is expressed.

In addition, the glass transition point and softening point of the glass powder used by this invention are adjusted according to the component composition of a glass powder.

The particle size of the glass powder is not particularly limited, but in consideration of the resistance value variation and stability, the median value (D ₅₀ ) of the volume distribution diameter of the laser diffraction scattering particle size distribution meter is preferably 10 µm or less, more preferably 3 µm or less to be.

Metal oxide-type electroconductive particle is used for the electroconductive particle in this invention.

Examples of the metal oxide-based conductive particles include tin oxide-based particles such as ruthenium-based oxide particles, iridium oxide particles, tin oxide particles and antimony-added tin oxide particles, and tin-added indium oxide particles.

The method for producing these metal oxide conductive particles can be obtained by, for example, obtaining precipitation of a hydroxide of a metal element in an aqueous solution, and heating and roasting the compound of the additive element and an air atmosphere or an inert atmosphere, etc. appropriately selected. .

Among the metal oxide-based conductive particles, ruthenium-based oxide particles are preferable from the viewpoint of high electrical conductivity, and as the ruthenium-based oxide particles, pyro such as lead ruthenate and bismuth ruthenate in addition to ruthenium dioxide (hereinafter referred to as ruthenium oxide). Those having a clad crystal structure and oxide particles having a perovskite crystal structure such as strontium ruthenate or calcium ruthenate are suitable.

Moreover, ruthenium oxide can cover a wide resistance value area|region by changing the compounding ratio with glass, Furthermore, the resistance temperature coefficient can be adjusted by adding a specific metal oxide etc. in a small amount.

As for the mixing ratio of a glass powder and a ruthenium-type oxide particle, the electroconductive particle is 10 mass % - 50 mass % with respect to the sum total of a glass powder and electroconductive particle. When electroconductive particle is smaller than 10 mass %, a resistance value will become high, and when more than 50 mass %, a film|membrane becomes too weak.

If the mixing ratio of the glass powder and the ruthenium-based oxide particles is, the surface of the positive temperature coefficient resistor obtained from the composition for a positive temperature coefficient resistor according to the present invention becomes smooth, and the film structure is maintained, and the positive temperature coefficient resistor is subjected to temperature changes or the like. is not damaged.

Moreover, although the particle diameter of electroconductive particle is not limited from a viewpoint of adjusting a resistance value gently with the compounding ratio with glass, 0.1 micrometer or less is preferable. The measuring method of the particle diameter of electroconductive particle may measure a specific surface area by BET method, it may convert to a granular form, and may calculate|require a particle diameter.

By the way, it is known that metal particles such as silver-palladium alloy particles are used for the conductive particles of a resistor composition containing glass powder and conductive particles in addition to metal oxide particles. It is not preferable to use the composition for a positive temperature coefficient resistor according to the present invention because there is a fear that the desired resistance value cannot be obtained due to oxidation or sintering, or the positive temperature coefficient resistor may be damaged due to temperature change or the like.

So, in the constant-temperature composition coefficient resistor of the present invention, the resistance value to the improvement, the adjustment of the temperature coefficient of resistance for the purpose may be to add an _{additive, MnO 2, Nb 2 O 5} , Ta 2 O 5, TiO 2, CuO , ZrO ₂ , Al ₂ O ₃ , SiO ₂ , Mg ₂ SiO ₄ , ZrSiO ₄ .

By adding these additives, a positive temperature coefficient resistor having more excellent properties can be produced. Although the quantity to add is adjusted according to the objective, it is 20 weight part or less normally with respect to a total of 100 weight part of a ruthenium oxide electrically-conductive particle and a glass powder.

In addition, the additive may be in the _{form of a powder of 3 µm or less with a median value (D 50} ) of the number average diameter, or organometallic compounds may be decomposed in the process of firing the positive temperature coefficient resistor paste to generate compounds of these additives. .

The ruthenium oxide conductive particles and glass powder are mixed and dispersed in an organic vehicle to form a printing paste together with an additive, if necessary.

The organic vehicle to be used is not particularly limited, and an organic vehicle in which a resin such as ethyl cellulose, acrylic acid ester, methacrylic acid ester, rosin, and maleic acid ester is dissolved in a solvent such as tapineol, butylcarbitol, butylcarbitol acetate is used. do. Moreover, a dispersing agent, a plasticizer, etc. can be added as needed.

The dispersion method is not particularly limited, either, but it is common to use a three roll mill, a bead mill, a planetary mill, or the like for dispersing fine particles. Although the blending ratio of the organic vehicle is appropriately adjusted depending on the printing or coating method, it is about 20 to 200 parts by weight based on 100 parts by weight in total of the ruthenium oxide conductive particles, glass powder, and additives.

[Method for producing resistors]

An example of the method for manufacturing a positive temperature coefficient resistor according to the present invention is a printing process in which a positive temperature coefficient resistor paste is applied on an insulating substrate such as ceramic by a known screen printing method, etc., which is included in the positive temperature coefficient resistor paste. It is manufactured through each process of the drying process which heat-removes a solvent and obtains a dry film, and the baking process of baking the obtained dry film in order.

In the firing step, the resin is heated and removed, and the resin is fired at a temperature higher than the softening point of the used glass powder. adhered to the substrate.

Moreover, when electroconductive particle exists around a glass powder and bakes a dry film, it adheres in the glass matrix formed by fusion|fusion of a glass powder.

As a result, a positive temperature coefficient resistor is obtained as a sintered body in which conductive particles are introduced into a glass matrix formed by fusion of glass powder.

The firing temperature in the firing step is determined in consideration of the glass transition point and softening point of the glass powder to be used, and when the firing temperature is too high, the fired body cannot be formed in a predetermined shape, and the firing temperature is too low. This becomes insufficient, a sintered body of a predetermined shape cannot be obtained, and the introduction into the sintered body of electroconductive particles becomes insufficient.

As the temperature range, softening point +50 degreeC - 150 degreeC is preferable, and softening point +60 degreeC - 130 degreeC is more preferable.

In addition, as for the drying temperature and drying time of a drying process, conditions sufficient for the solvent in a paste to volatilize can be selected in a timely manner.

Ceramic substrates, such as alumina, are used for an insulating substrate. Further, terminal electrodes are provided on the obtained positive temperature coefficient resistor to be connected to an electric circuit. The terminal electrode may be formed in advance on an insulating substrate using a known thick-film silver paste or the like.

Heretofore, although the present invention has been described, the resistor obtained by firing the composition for a positive temperature coefficient resistor according to the present invention is the positive temperature coefficient resistor according to the present invention, and by dispersing the positive temperature coefficient resistor composition according to the present invention in an organic vehicle A paste for positive temperature coefficient resistors can be obtained.

Example

Although the present invention will be specifically described, the present invention is not limited to these Examples.

Table 1 shows the component composition of the glass powder used in the Examples and Comparative Examples of the present invention, the median value (D ₅₀ ) of the number average diameter, and the glass transition point.

^{For the conductive particles, ruthenium oxide particles having a specific surface area of 20 m 2} /g and a particle diameter of 40 nm determined from the specific surface area measurement by the BET method are used, and for the glass powder, the median value of the number average diameter of a laser diffraction scattering type particle size distribution meter. Each glass powder shown in Table 1 having a (D _{50 ) of 1.5 µm was used.}

Let the said electroconductive particle and the glass powder be the mixing ratio shown in Table 2, with respect to the total 100 weight part, in 43 weight part organic vehicle, after addition and mixing, it is disperse|distributed by 3 roll mill, The resistance which is a test material A paste was prepared.

Next, the produced resistance paste is printed on the Ag electrode formed by baking on an alumina substrate in advance, dried under the conditions of 150°C x 5 minutes, and then to a temperature matching the softening degree of each glass powder shown in Table 2 After raising the temperature, it was fired under the condition of holding for 10 minutes, and lowered to room temperature to form a resistor.

As for the size of the resistor as a test material, the width of the resistor was set to 1.0 mm, and the length (between electrodes) of the resistor was set to be 1.0 mm.

Using an oven capable of temperature control, the "temperature dependence of the resistance value" exhibited by the produced resistor is placed in the oven as a potential resistance measurement sample of the four-terminal method, and the above-mentioned test material is placed, while changing the oven temperature, the four-terminal method The electrical resistance was measured with a digital multimeter.

The measurement results are shown in Figs. 1 to 5 (Examples 1 to 5), Fig. 6 (Comparative Example 1), and Fig. 7 (Comparative Example 2).

Examples 1 and 2 are resistors composed of glass powder having a glass transition point of 240° C. and ruthenium oxide particles. From the temperature characteristics of the resistance values shown in Figs. 1 and 2, it can be seen that the resistance value change (temperature coefficient of resistance) with respect to temperature is changing at about 250°C. This inflection point of the temperature coefficient of resistance almost coincides with the glass transition point of the glass as a raw material.

Examples 3 and 4 are resistors composed of a glass powder having a glass transition point of 270°C and ruthenium oxide particles. From Figs. 3 and 4, the inflection point of the temperature coefficient of resistance appears at approximately 280 DEG C, which almost coincides with the transition point of the glass.

Example 5 is a resistor composed of a glass powder having a glass transition point of 400°C and ruthenium oxide particles. From Fig. 5, the inflection point of the temperature coefficient of resistance appears at approximately 400 DEG C, which almost coincides with the transition point of the glass.

With respect to the above examples, in Comparative Examples 1 and 2 shown in FIGS. 6 and 7, resistance temperature characteristics of a resistor made of glass and ruthenium oxide having glass transition points of 510°C and 550°C were shown. In all of them, in the temperature range of 25 degreeC - 500 degreeC, the inflection point of the resistance temperature characteristic did not appear.

As can be seen from the Examples and Comparative Examples, according to the present invention, it is possible to manufacture a constant temperature coefficient resistor in which the resistance temperature coefficient changes in the temperature range of 250 ° C to 400 ° C, which was difficult in the prior art, and the inflection point of the resistance temperature coefficient is It becomes possible to select by adjusting the glass transition point of raw material glass.

Claims (8)

A composition for a positive temperature coefficient resistor comprising ruthenium-based oxide particles and glass powder, the composition comprising:
The glass powder is a glass powder having a glass transition point of 240° C. or higher and 400° C. or lower, and a glass softening point higher than the glass transition point by 50° C. or higher,
The mixing ratio of the glass powder and the ruthenium-based oxide particles is 10% by mass to 50% by mass of the ruthenium-based oxide particles with respect to the total of the glass powder and the ruthenium-based oxide particles,
The positive temperature coefficient resistor prepared from the composition is switched in a temperature range of 250 °C or higher and 400 °C or lower, the composition for a positive temperature coefficient resistor. A composition for a positive temperature coefficient resistor comprising ruthenium-based oxide particles, glass powder, and an additive, the composition comprising:
The glass powder is a glass powder having a glass transition point of 240° C. or higher and 400° C. or lower, and a glass softening point higher than the glass transition point by 50° C. or higher,
The mixing ratio of the glass powder and the ruthenium-based oxide particles is 10% by mass to 50% by mass of the ruthenium-based oxide particles with respect to the total of the glass powder and the ruthenium-based oxide particles,
The additive is added in an amount of 20 parts by weight or less based on 100 parts by weight of the total of the ruthenium-based oxide particles and the glass powder, MnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , TiO ₂ , CuO, ZrO ₂ , SiO ₂ , Mg ₂ SiO ₄ , ZrSiO _{4 It} is one kind of additive,
The composition for a positive temperature coefficient resistor, characterized in that the positive temperature coefficient resistor made of the composition is switched in a temperature range of 250 °C or higher and 400 °C or lower. The composition for a positive temperature coefficient resistor according to claim 1 or 2, wherein the ruthenium-based oxide particles are ruthenium oxide particles. A paste for a positive temperature coefficient resistor comprising an organic vehicle and the composition for a positive temperature coefficient resistor according to claim 1. A paste for a positive temperature coefficient resistor comprising an organic vehicle and the composition for a positive temperature coefficient resistor according to claim 2. A sintered body using the composition for a positive temperature coefficient resistor according to claim 1 or 2 or the paste for a positive temperature coefficient resistor according to claim 4 or 5, which is switched in a temperature range of 250°C or higher and 400°C or lower. A positive temperature coefficient resistor, characterized in that. The positive temperature coefficient resistor according to claim 6, wherein the ruthenium-based oxide particles are ruthenium oxide particles. The paste for a positive temperature coefficient resistor according to claim 4 or 5 is coated and fired on an insulating substrate to dissipate the organic solvent and organic resin, and soften the glass powder, which is contained in the paste for the positive temperature coefficient resistor. A method for producing a positive temperature coefficient resistor, wherein the ruthenium-based oxide particles are blown into a glass matrix formed of glass powder contained in the positive temperature coefficient resistor paste, dried and solidified.

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