JP7298416B2 - Composition for thick film resistor, paste for thick film resistor, and thick film resistor - Google Patents

Description

The present invention relates to a composition for thick film resistors, a paste for thick film resistors, and a thick film resistor.

Thick-film resistors such as chip resistors, hybrid ICs, and resistor networks are generally formed by printing a thick-film resistor paste on a ceramic substrate and firing the printed paste. Compositions for thick-film resistors are widely used that mainly contain ruthenium-based conductive particles, typically ruthenium oxide, and glass as conductive particles.

The reason why ruthenium conductive particles and glass are used for thick film resistors is that they can be fired in air and the temperature coefficient of resistance (TCR) can be brought close to zero. For example, a resistor can be formed.

Here, the temperature coefficient of resistance is a temperature coefficient obtained from resistance values at -55°C and 125°C with respect to a resistance value at 25°C, and is obtained by the following formula. In the following formulas, R _-55 means the resistance value at -55°C, R ₂₅ means the resistance value at 25°C, and R ₁₂₅ means the resistance value at 125°C. The temperature coefficient of resistance obtained from the resistance values at -55°C and 25°C is called the cold side TCR (COLD-TCR), and the temperature coefficient of resistance obtained from the resistance values at 25°C and 125°C is called the high temperature side TCR (HOT-TCR). It says.

COLD-TCR (ppm/°C) = (R ₋₅₅ −R ₂₅ )/R ₂₅ /(−80)×10 ⁶
HOT-TCR (ppm/° C.)=(R ₁₂₅ −R ₂₅ )/R ₂₅ /(100)×10 ⁶
Thick film resistors are required to have both COLD-TCR and HOT-TCR close to zero.

Ruthenium-based conductive particles most commonly used in thick film resistors include ruthenium oxide (RuO ₂ ) having a rutile crystal structure and lead ruthenate (Pb ₂ Ru ₂ O _{6 )} having a pyrochlore crystal structure. _.5 ). All of these are oxides exhibiting metallic conductive properties.

As the thick film resistor glass, glass having a softening point lower than the firing temperature of the thick film resistor paste is generally used, and glass containing lead oxide (PbO) has been conventionally used. The reason for this is that lead oxide (PbO) has the effect of lowering the softening point of glass, and by changing the content rate, the softening point can be changed over a wide range, and that glass with relatively high chemical durability can be produced. and high insulation and excellent withstand voltage.

In the thick-film resistor composition containing ruthenium-based conductive particles and glass, when a low resistance value is desired, a large amount of ruthenium-based conductive particles and a small amount of glass are blended, and when a high resistance value is desired, ruthenium The resistance value is adjusted by adding less conductive particles and more glass. The temperature coefficient of resistance tends to be positive in the low resistance region where a large amount of ruthenium-based conductive particles are blended, and the temperature coefficient of resistance tends to be negative in the high-resistance region where the ruthenium-based conductive particles are less blended.

As is clear from the above formula, the temperature coefficient of resistance expresses the change in resistance value due to temperature change, and is one of the important characteristics of a thick film resistor. The temperature coefficient of resistance can be adjusted by adding additives, mainly metal oxides, to the composition for thick film resistors. It is relatively easy to reduce the temperature coefficient of resistance, that is, to adjust it in the negative direction, and examples of additives include manganese oxide, niobium oxide, and titanium oxide. However, it is difficult to increase the temperature coefficient of resistance, that is, to adjust it in the positive direction. Therefore, in a high resistance region where the temperature coefficient of resistance tends to be negative, it is desirable to combine conductive particles and glass in which the temperature coefficient of resistance is large and positive.

Lead ruthenate (Pb ₂ Ru ₂ O _6.5 ) has a higher specific resistance than ruthenium oxide (RuO ₂ ), and is characterized by a high temperature coefficient of resistance of the thick film resistor. For this reason, lead ruthenate (Pb ₂ Ru ₂ O _6.5 ) has been used as the conductive particles in areas of high resistance.

As described above, in conventional compositions for thick film resistors, materials containing a lead component were used for both the conductive particles and the glass. However, the lead component is undesirable from the viewpoint of its effect on the human body and pollution, and there is a strong demand for the development of lead-free compositions for thick film resistors.

Therefore, conventionally, lead-free compositions for thick film resistors have been proposed (Patent Documents 1 to 4).

Patent Document 1 discloses a resistor paste containing at least a substantially lead-free glass composition and a substantially lead-free conductive material having a predetermined average particle size, which are mixed with an organic vehicle. disclosed. Calcium ruthenate, strontium ruthenate, and barium ruthenate are mentioned as conductive materials.

According to Patent Document 1, the particle size of the conductive material used is within a predetermined range, and the desired effect is obtained by ensuring the substantial particle size of the conductive material excluding the reaction phase.

In Patent Document 2, a step of obtaining a glass material by previously dissolving a first conductive material containing a metal element for imparting conductivity to a glass composition; and a step of kneading a conductive material and a vehicle, wherein the glass composition and the first and second conductive materials do not contain lead. Proposed. RuO ₂ and the like are mentioned as the first and second conductive materials.

Patent Document 3 contains a base solid of (a) a ruthenium-based conductive material and (b) a lead- and cadmium-free glass composition having a predetermined composition, and all of (a) and (b) are organic. A thick film paste composition has been proposed, characterized in that it is dispersed in a medium. Bismuth ruthenate is mentioned as a ruthenium-based conductive material.

In Patent Document 4, a resistor containing a ruthenium-based conductive component that does not contain a lead component, a glass that does not contain a lead component and has a glass basicity (Po value) of 0.4 to 0.9, and an organic vehicle A resistor composition characterized in that MSi ₂ Al ₂ O ₈ crystals (M: Ba and/or Sr) are present in a thick film resistor obtained by firing the composition at a high temperature Proposed.
According to Patent Document 4, the basicity of the glass is close to the basicity of the ruthenium composite oxide, so that the effect of suppressing the decomposition of the ruthenium composite oxide is large. Further, it is said that a conductive network can be formed by precipitating a predetermined crystal phase in the glass.

JP-A-2005-129806 JP 2003-7517 A JP-A-8-253342 JP 2007-103594 A

Report of Interdisciplinary Graduate School of Science and Engineering, Kyushu University, September 1992, Vol. 14, No. 2, pp. 173-179

However, it cannot be said that the technology disclosed in Patent Document 1 can improve the temperature coefficient of resistance. In addition, when conductive particles having a large particle size are used, there is a problem that current noise in the formed resistor is large and good load characteristics cannot be obtained.

The technique disclosed in Patent Document 2 has a problem that the amount of ruthenium oxide dissolved in the glass fluctuates greatly depending on the manufacturing conditions, and the resistance value is not stable.

In the thick-film paste composition disclosed in Patent Document 3, the temperature coefficient of resistance increased negatively, and the temperature coefficient of resistance could not be brought close to zero.

The technique disclosed in Patent Document 4 is based on the premise that ruthenium composite oxide is used as the conductive particles, and ruthenium oxide, which is industrially easier to obtain than ruthenium composite oxide, has not been specifically studied. rice field. Further, according to investigations by the inventors of the present invention, glass having a basicity of 0.4 to 0.9 is used, and MSi ₂ Al ₂ O ₈ (M: Ba and/or Sr) is used for the thick film resistor. Even with the resistor that generated the TCR, it sometimes became less than −100 ppm/° C. in the middle to high resistance range (1 k to 10 MΩ range).

In view of the problems of the prior art, it is an object of one aspect of the present invention to provide a lead-free composition for thick film resistors, which is capable of forming a thick film resistor having an excellent temperature coefficient of resistance.

In order to solve the above problems, the present invention
A composition for a thick film resistor containing a lead-free ruthenium-based conductive powder and a lead-free glass powder,
The glass powder contains Si, B, and R ( the R represents one or more alkaline earth elements selected from Ca, Sr, and Ba), and the Si is 10% by mass or more and 50% by mass as SiO ₂ Hereinafter, the B is 8% by mass or more and 19% by mass or less as B 2 O 3, and the R is 40% by mass or more and 65% by mass or less as RO, and at least Al ₂ O _{3 is} included _as an additive component. ,
The glass powder provides a composition for a thick film resistor in which the amount of defects detected as E' centers by electron spin resonance spectroscopy is 0 or more and 5.0×10 ¹⁵ spins/g or less.

According to one aspect of the present invention, it is possible to provide a lead-free composition for a thick film resistor, which can form a thick film resistor having an excellent temperature coefficient of resistance.

An embodiment of the composition for a thick film resistor, the paste for a thick film resistor, and the thick film resistor of the present invention will be described below.
[Composition for thick film resistor]
The composition for a thick film resistor according to the present embodiment can contain a lead-free ruthenium-based conductive powder and a lead-free glass powder. The glass powder contains Si (silicon), B (boron), and R, and the amount of defects detected as E′ centers by electron spin resonance spectroscopy is 0 or more and 5.0×10 ¹⁵ spins/g or less. can be In addition, said R represents one or more alkaline earth elements selected from Ca, Sr and Ba.

The inventors of the present invention have found that if the amount of defects caused by unpaired electrons of Si atoms in the glass powder containing a predetermined component is 0 or more and 5.0 × 10 ¹⁵ spins/g or less, the thickness of the glass powder containing the glass powder The inventors have found that the temperature coefficient of resistance of a thick film resistor obtained by firing a composition for a film resistor can be set to −100 ppm/° C. or more, which is the lower limit of the specification, and can be approached to 0, and have completed the present invention.

Each component contained in the composition for a thick film resistor of this embodiment will be described below.
(Ruthenium-based conductive powder)
As the ruthenium-based conductive powder, various conductive powders containing ruthenium and containing no lead component can be used. In this specification, "not containing a lead component" means that lead is not intentionally added, and means that the lead content is zero. However, it does not exclude the contamination as an impurity component or an unavoidable component in the manufacturing process or the like.

Ruthenium-based conductive powders include, for example, ruthenium oxide (RuO ₂ ); neodymium ruthenate (Nd ₂ Ru ₂ O ₇ ), samarium ruthenate (Sm ₂ Ru ₂ O ₇ ), neodymium calcium ruthenate (NdCaRu ₂ O ₇ ), Ruthenium composite oxides having a pyrochlore structure such as samarium strontium ruthenate ( _SmSrRu2O7 ) and related oxides thereof _; calcium ruthenate ( _CaRuO3 ), strontium ruthenate ( _SrRuO3 ), barium ruthenate ( _BaRuO3) ), cobalt ruthenate (Co ₂ RuO ₄ ), strontium ruthenate (Sr ₂ RuO ₄ ), and other ruthenium composite oxides; For example, a mixture of two or more selected from the above oxides can also be used.

As described above, it is difficult to increase the temperature coefficient of resistance, that is, to adjust it in the positive direction even if an additive is used. For this reason, if the temperature coefficient of resistance becomes too negative, it is difficult to adjust it to around 0, for example, within ±100 ppm/°C. However, if the temperature coefficient of resistance is positive, even if the value is high, it is possible to adjust the temperature coefficient of resistance to around 0 with an additive such as a modifier.

As the conductive material of the composition for thick film resistors that does not contain lead, ruthenium-based conductive powder is preferably used because the resistance value of the thick film resistor obtained by firing the composition for thick film resistors is stable. In particular, ruthenium oxide powder and ruthenium-containing oxide powder such as ruthenium composite oxide powder can be used more preferably. Among these, ruthenium oxide can be easily used industrially. Therefore, ruthenium oxide powder can be more preferably used as the ruthenium-based conductive powder. In particular, according to the composition for a thick film resistor of the present embodiment, conventionally, when using, for example, ruthenium oxide powder as the ruthenium-based conductive powder, the temperature coefficient of resistance becomes significantly negative in the resistance value region. Also, it is possible to provide a thick film resistor having a temperature coefficient of resistance close to 0 by adjusting the amount of the additive, for example, as required. For this reason, it is preferable to use ruthenium oxide powder as the ruthenium-based conductive powder because it can exhibit a particularly high effect.

The particle size of the ruthenium-based conductive powder used in the thick film resistor composition of the present embodiment is not particularly limited. However, the ruthenium-based conductive powder used in the thick film resistor composition of the present embodiment preferably has an average particle size of 20 nm or more and 115 nm or less in terms of specific surface area. Assuming that the particle size of the ruthenium-based conductive powder is D1 (nm), the density is ρ (g/cm ³ ), the specific surface area is S (m ² /g), and the powder is regarded as a true sphere, the average particle size in terms of specific surface area is , the following relational expression (1) holds. The particle size calculated by D1 is defined as the average particle size in terms of specific surface area, that is, the specific surface area.

D1 (nm)=6×10 ³ /(ρ·S) (1)
When the ruthenium-based conductive powder is ruthenium oxide powder, the density of the ruthenium oxide is preferably 7.05 g/cm ³ and the specific surface area calculated by the formula (1) is preferably 20 nm or more and 115 nm or less, more preferably 25 nm or more and 115 nm or less. is more preferable. Even when the ruthenium-based conductive powder is other than ruthenium oxide powder, the specific surface area calculated by the above formula (1) is preferably 20 nm or more and 115 nm or less from the density and specific surface area corresponding to the materials used in the same manner. More preferably, the thickness is 25 nm or more and 115 nm or less.

By setting the specific surface area diameter of the ruthenium-based conductive powder to 20 nm or more, the temperature coefficient of resistance of the thick-film resistor composition containing the ruthenium-based conductive powder can be more reliably made positive. On the other hand, by setting the specific surface area diameter of the ruthenium-based conductive powder to 115 nm or less, the withstand voltage characteristics can be enhanced.

The method for preparing the ruthenium-based conductive powder used in the composition for thick film resistors of the present embodiment is not particularly limited, and it can be prepared by any method.

Here, a method for preparing a ruthenium-based conductive powder will be described, taking the case of producing a ruthenium oxide powder as an example.

As a method for producing ruthenium oxide powder, for example, a method of producing by heat-treating ruthenium oxide hydrate synthesized in a wet process is desirable. In such a production method, the specific surface area diameter and the crystallite diameter can be changed depending on the synthesis method, heat treatment conditions, and the like.

A method for producing ruthenium oxide powder can have, for example, the following steps.
A ruthenium oxide hydrate production step for synthesizing ruthenium oxide hydrate by a wet method.
A ruthenium oxide hydrate recovery step for separating and recovering ruthenium oxide hydrate in the solution.
A drying step for drying the ruthenium oxide hydrate.
A heat treatment step of heat-treating the ruthenium oxide hydrate.

In the conventional method of producing ruthenium oxide powder in which ruthenium oxide having a large particle size is produced and then the ruthenium oxide is pulverized, it is difficult to reduce the particle size and the variation in particle size is large. Therefore, as a method for producing the ruthenium oxide powder used in the composition for a thick film resistor of the present embodiment, it is preferable to employ a production method in which the ruthenium oxide hydrate is produced by heat treatment.

In the ruthenium oxide hydrate production step, the method for synthesizing ruthenium oxide hydrate is not particularly limited, but examples thereof include a method of precipitating and precipitating ruthenium oxide hydrate in a ruthenium-containing aqueous solution. Specifically, for example, ethanol is added to an aqueous K ₂ RuO ₄ solution to obtain a precipitate of ruthenium oxide hydrate, and an aqueous RuCl ₃ solution is neutralized with KOH or the like to obtain a precipitate of ruthenium oxide hydrate. methods and the like.

Then, as described above, in the ruthenium oxide hydrate recovery step and the drying step, the precipitate of ruthenium oxide hydrate is solid-liquid separated, washed as necessary, and then dried to obtain ruthenium oxide water. A powder of hydrates can be obtained.

The conditions of the heat treatment step for heat-treating the ruthenium oxide hydrate obtained in the drying step are not particularly limited. Thus, a highly crystalline ruthenium oxide powder can be obtained. Here, the oxidizing atmosphere is a gas containing 10% by volume or more of oxygen, and for example, air can be used.

By setting the temperature for heat-treating the ruthenium oxide hydrate powder in the heat treatment step to 400° C. or higher as described above, it is possible to obtain a ruthenium oxide (RuO ₂ ) powder having particularly excellent crystallinity, which is preferable. The upper limit of the heat treatment temperature of the ruthenium oxide hydrate powder in the heat treatment step is not particularly limited. In some cases, the rate of volatilization as octavalent oxides (RuO ₃ and RuO ₄ ) increases. Therefore, it is preferable to perform the heat treatment at a temperature of 1000° C. or less, for example.

In particular, the temperature for heat-treating the ruthenium oxide hydrate powder is more preferably 500° C. or higher and 1000° C. or lower.

As described above, the specific surface area and crystallinity of the resulting ruthenium oxide powder can be changed by changing the synthesis conditions, heat treatment conditions, and the like when producing the ruthenium oxide hydrate. Therefore, it is preferable to conduct a preliminary test, for example, and select conditions so that a ruthenium oxide powder having a desired crystallite size and specific surface area can be obtained.

The method for producing ruthenium oxide powder can also have arbitrary steps in addition to the steps described above.

As described above, the precipitate of ruthenium oxide hydrate is solid-liquid separated in the ruthenium oxide hydrate recovery step, dried in the drying step, and then mechanically separated before the heat treatment step. It is also possible to obtain a pulverized ruthenium oxide hydrate powder (pulverization step).

Then, the pulverized ruthenium oxide hydrate powder is subjected to a heat treatment step and heat treated at a temperature of 400 ° C. or higher in an oxidizing atmosphere to remove water of crystallization as described above and improve the crystallinity of the ruthenium oxide powder. can be enhanced. By performing the pulverization step as described above, the degree of aggregation of the ruthenium oxide hydrate powder to be subjected to the heat treatment step can be suppressed or reduced. By heat-treating the pulverized ruthenium oxide hydrate powder, it is possible to suppress the generation of coarse particles and connected particles due to the heat treatment. Therefore, ruthenium oxide powder having a desired crystallite size and specific surface area can be obtained by selecting conditions in the pulverization step.

The crushing conditions in the crushing step are not particularly limited, and can be arbitrarily selected through preliminary tests and the like so as to obtain the desired ruthenium oxide powder.

Further, in the method for producing ruthenium oxide powder, the obtained ruthenium oxide powder can be classified after the heat treatment step (classification step). By performing the classification step in this manner, ruthenium oxide powder having a desired specific surface area can be selectively recovered.

So far, the case of ruthenium oxide powder has been described as an example, but a ruthenium composite oxide can also be prepared in substantially the same manner. For example, in the ruthenium oxide hydrate production step, in addition to ruthenium, a predetermined metal component other than ruthenium is added to prepare a hydrate of the ruthenium composite oxide, and by using the hydrate, ruthenium composite oxide can also be prepared.
(glass powder)
The composition for a thick film resistor of the present embodiment can contain glass powder (glass) containing no lead component. The glass powder containing no lead component means that lead is not intentionally added, and means that the lead content is zero. However, it does not exclude the contamination as an impurity component or an unavoidable component in the manufacturing process or the like.

In the lead-free thick-film resistor composition glass powder, the fluidity at the time of firing can be adjusted by adding a metal oxide in addition to SiO ₂ as the skeleton. B ₂ O ₃ and RO can be used as metal oxides other than SiO ₂ . Element R of RO represents one or more alkaline earth elements selected from Ca, Sr, and Ba. Therefore, glass powder containing Si, B and R, for example, can be suitably used as the glass powder used in the thick film resistor composition of the present embodiment. R represents one or more alkaline earth elements selected from Ca, Sr and Ba as described above.

The glass contained in the thick film resistor has an electrical action with the ruthenium-based conductive powder, which is conductive particles. Most of the physical properties related to the electrons that make up the glass, such as the electrical action and optical action of the glass, are calculated from the Morinaga formula disclosed in Non-Patent Document 1. It is known that there is a relationship between For example, when the content of Ba in a glass containing Si, B, and Ba (also referred to as Si—B—Ba glass) is changed, the basicity of the glass is changed.

As disclosed in Non-Patent Document 1, the basicity pO of the glass can be evaluated as the oxygen ion supplying ability of the glass based on the Coulomb attractive force _Ai between the cations of the oxide components constituting the glass and the oxygen ions. This indicates that the higher the value of the basicity pO, the stronger the basicity.

Here, the Coulomb attractive force A _i between cations and oxygen ions is obtained by the following equation (2).

A _i =Z _i ×2/(r _i +1.40) ² (2)
In the above formula (2), Z _i is the cation valence, r _i is the cation radius (Å), 1.40 is the oxygen ion radius (Å), and 2 is the oxygen ion valence. each means.

Then, the reciprocal of A _i represented by the following equation (3) can be evaluated as the oxygen ion supply capability of the oxide.

pO _i '=1/A _i (3)
The oxygen ion supply capacity of multi-component glass can be expanded using the cation molar fraction _ni , and can be expressed as in the following equation (4).

pO′=Σ( _ni × _pOi ′) (4)
pO _i ' in the formula (4) means the basicity of each oxide constituting the glass.

The basicity pO is normalized by setting the basicity of CaO to 1 and the basicity of SiO ₂ to 0, and is expressed by the following formula (5).

pO=(pO'-0.405)/1.023 (5)
By the way, even with Si--B--Ba-based glasses, if the constituent elements of the glass other than Si, B, and Ba are changed, the temperature coefficient of resistance may differ even if the basicity of the glass has almost the same value. . In view of the relationship between the basicity of glass and the temperature coefficient of resistance, the glass powder of the composition for thick film resistors for producing a thick film resistor having an excellent temperature coefficient of resistance is appropriately You will not be able to choose. Therefore, the inventors of the present invention conducted further studies on the glass powder.

Unpaired electrons can occur in the Si atoms of the glass, and these unpaired electrons manifest as magnetic center activity and the E′ center (E prime center).

Considering the conduction mechanism of thick film resistors, electron conduction passes through the glass skeleton, so the inventor of the present invention presumes that Si, which is the main skeleton of glass, also has some factor related to conduction. As a result, it was presumed that the amount of E' centers, which are glass defects having unpaired electrons, is particularly involved. That is, it was presumed that a large amount of E' centers promotes electron conduction in the glass, resulting in a negative temperature coefficient of resistance.

Therefore, the amount of E' centers of the glass powder whose particle size distribution is adjusted to the extent that it is used for paste for thick film resistors was measured by electron spin resonance spectroscopy. In addition, thick film resistors were manufactured by using only the glass powder for which the E' center amount was evaluated and the ruthenium oxide powder, and having the same composition other than the glass powder used, and the temperature coefficient of resistance was measured. As a result, it was confirmed that even if the basicity of the glass is high, when the temperature coefficient of resistance decreases as the resistance value increases and the negative value increases, the E′ center amount tends to increase.

In addition, a plurality of thick film resistors using only fumed silica fine powder and ruthenium oxide powder in which no defects detected as E′ centers as measured by electron spin resonance spectroscopy can be confirmed, and changing the ratio of ruthenium oxide powder A body was fabricated and the temperature coefficient of resistance was confirmed. As a result, although the temperature coefficient of resistance decreased as the resistance of the thick film resistor increased, it was confirmed that the temperature coefficient of resistance was about 600 ppm/° C. at 1 MΩ and the temperature coefficient of resistance did not become negative.

However, if fumed silica is used as the glass powder, the adhesion between the thick film resistor and the ceramic substrate is insufficient, which is not practical. The number of defects detected as E' centers measured by electron spin resonance spectroscopy of fumed silica is zero.

From the above examination results, the glass powder used for the thick film resistor of the present embodiment contains Si, B and R, and the amount of defects detected as E' centers by electron spin resonance spectroscopy is 0 or more. It is preferably 0×10 ¹⁵ spins/g or less. In addition, R represents one or more alkaline earth elements selected from Ca, Sr, and Ba as described above.

As described above, according to the studies of the inventors of the present invention, by suppressing the amount of defects detected as the E' center of the glass powder used, that is, the contained glass, the medium to high resistance of the thick film resistor It is possible to suppress the temperature coefficient of resistance from increasing to the negative side in the region (1 kΩ to 10 MΩ region). In particular, when the amount of defects detected as the E' center of the glass powder used in the composition for a thick film resistor is 5.0 × 10 ¹⁵ spins/g or less, the resistance in the medium to high resistance range (1 kΩ to 10 MΩ region) The temperature coefficient can be suppressed from increasing to the negative side, and can be set to -100 ppm/°C or higher, for example.

As described above, according to the study of the inventors of the present invention, the temperature coefficient of resistance of the thick film resistor is larger than the defect amount detected as the E' center of the glass powder used in the composition for the thick film resistor. to be influenced. The effect of the glass basicity of the glass powder on the temperature coefficient of resistance of the thick film resistor is small compared to the amount of defects. However, the higher the glass basicity of the glass powder contained in the composition for a thick film resistor of the present embodiment, the more likely the temperature coefficient of resistance will shift from the negative side to near zero. Therefore, it is preferable that the glass basicity of the glass powder contained in the composition for a thick film resistor of the present embodiment is high. The glass basicity of the glass powder contained in the composition for a thick film resistor of the present embodiment is preferably, for example, 0.4 or more and 0.7 or less.

The particle size of the glass powder contained in the composition for a thick film resistor of the present embodiment is not limited, but if the particle size of the glass powder is too large, it may cause an increase in variation in the resistance value of the thick film resistor and a decrease in load characteristics. Become. Therefore, the glass powder contained in the composition for a thick film resistor of the present embodiment preferably has a 50% volume cumulative particle size of 2.0 μm or less as measured by a particle size distribution meter using laser diffraction.

On the other hand, if the particle size of the glass powder is excessively small, the productivity will be lowered, and there is a possibility that the contamination of impurities and the like will increase. Therefore, the 50% volume cumulative particle size of the glass powder contained in the thick film resistor composition of the present embodiment is preferably 0.7 μm or more.

Therefore, the glass powder contained in the thick film resistor composition of the present embodiment preferably has a 50% volume cumulative particle size of 0.7 μm or more and 2.0 μm or less.

The glass powder contained in the composition for a thick film resistor of the present embodiment may contain Si, B and R as described above, and its specific composition is not particularly limited. For example, from the viewpoint of enhancing fluidity, the glass powder preferably contains 50 parts by mass or less of SiO ₂ . However, if the content of SiO ₂ is less than 10 parts by mass, it may become difficult to form glass. Therefore, the glass powder contained in the composition for a thick film resistor of the present embodiment preferably contains SiO ₂ in a proportion of 10 parts by mass or more and 50 parts by mass or less.

Further, the glass powder of the composition for thick film resistors of the present embodiment preferably contains B ₂ O ₃ in a proportion of 8 parts by mass or more and 30 parts by mass or less. This is because when the content of B ₂ O ₃ is 8 parts by mass or more, fluidity can be sufficiently improved, and when it is 30 parts by mass or less, weather resistance can be improved.

The glass powder of the composition for thick film resistors of the present embodiment preferably contains RO in a proportion of 40 parts by mass or more and 65 parts by mass or less. This is because when the RO content is 40 parts by mass or more, the temperature coefficient of resistance of the thick film resistor obtained using the composition for a thick film resistor can be particularly suppressed from becoming negative. . Further, by setting the content of RO to 65 parts by mass or less, crystallization of the glass component can be suppressed and glass can be easily formed. In addition, when the glass powder contains a plurality of types of RO, the total preferably satisfies the above range.

In addition to SiO ₂ , B ₂ O ₃ and RO described above, the glass powder contained in the composition for a thick film resistor of the present embodiment includes other powders for the purpose of adjusting the weather resistance of the glass and fluidity during firing. can also contain the components of Examples of optional additive components include Al ₂ O ₃ , ZrO ₂ , TiO ₂ , SnO ₂ , ZnO, Li ₂ O, Na ₂ O, K ₂ O and the like, and one selected from these compounds The above can also be added to the glass.

Among the above compounds, Al ₂ O ₃ tends to suppress the phase separation of the glass, and ZrO ₂ and TiO ₂ work to improve the weather resistance of the glass. Also, SnO ₂ , ZnO, Li ₂ O, Na ₂ O, K ₂ O, etc. have the function of increasing the fluidity of the glass. Therefore, additional components can be added depending on the performance required for the composition for thick film resistors.

The softening point is a measure that affects the fluidity of glass during firing. In general, the temperature for baking the composition for thick film resistors is 800° C. or higher and 900° C. or lower when manufacturing thick film resistors.

As described above, when the baking temperature of the composition for a thick film resistor is 800° C. or more and 900° C. or less when manufacturing a thick film resistor, the glass used for the composition for a thick film resistor according to the present embodiment softens. The point is preferably 600° C. or higher and 800° C. or lower, more preferably 600° C. or higher and 750° C. or lower.

Here, the softening point is the differential thermal curve on the lowest temperature side of the differential thermal curve obtained by heating and heating the glass at 10 ° C./min in the atmosphere by differential thermal analysis (TG-DTA). It is the peak temperature at which the next differential thermal curve decreases, which is higher than the temperature at which the decrease occurs.

The method for preparing the glass powder of the present embodiment is not particularly limited, and it can be prepared so as to have the desired composition and properties. Glass powders can be produced, for example, by mixing predetermined components or their precursors in a desired formulation, melting and quenching the resulting mixture. Although the melting temperature is not particularly limited, it can be around 1400°C, for example. Also, the method of quenching is not particularly limited, but it can be carried out by placing the melt in cold water or flowing it on a cooling belt.

A ball mill, a planetary mill, a bead mill, or the like can be used for pulverizing the glass, but wet pulverization is preferably used to sharpen the particle size.
(Composition of composition for thick film resistor)
The mixing ratio of the ruthenium-based conductive powder and the glass powder contained in the thick film resistor composition of the present embodiment is not particularly limited. For example, the mixing ratio of the ruthenium-based conductive powder and the glass powder can be changed depending on the desired resistance value. The mass of the ruthenium-based conductive powder: the mass of the glass powder can be, for example, 5:95 or more and 50:50 or less. That is, the ratio of the ruthenium-based conductive powder to the ruthenium-based conductive powder and the glass powder is preferably 5% by mass or more and 50% by mass or less.

This is because, when the total amount of the ruthenium-based conductive powder and the glass powder contained in the composition for a thick film resistor of the present embodiment is 100% by mass, if the ratio of the ruthenium-based conductive powder is less than 5% by mass, This is because the resulting thick film resistor may have an excessively high resistance value and become unstable.

Further, when the total of the ruthenium-based conductive powder and the glass powder contained in the composition for a thick film resistor of the present embodiment is 100% by mass, the proportion of the ruthenium-based conductive powder is set to 50% by mass or less. This is because the strength of the resulting thick film resistor can be sufficiently increased, and brittleness can be particularly reliably prevented.

The mixing ratio of the ruthenium-based conductive powder and the glass powder in the composition for a thick film resistor of the present embodiment is in the range of mass of ruthenium-based conductive powder:mass of glass powder=5:95 or more and 40:60 or less. It is more preferable to have That is, it is more preferable to set the ratio of the ruthenium-based conductive powder to 5% by mass or more and 40% by mass or less in the ruthenium-based conductive powder and the glass powder.

The thick film resistor composition of the present embodiment preferably contains the aforementioned ruthenium-based conductive powder and glass powder as main components, and may be composed only of the ruthenium-based conductive powder and glass powder. can also The composition for a thick film resistor of the present embodiment preferably contains the above-described mixed powder of the ruthenium-based conductive powder and the glass powder at a ratio of, for example, 80% by mass or more and 100% by mass or less, and 85% by mass. It is more preferable to contain at a ratio of 100% by mass or more.

The composition for thick film resistors of the present embodiment may further contain optional components as necessary. Note that a material containing no lead component can also be used for these arbitrary components.

Additives generally used for the purpose of improving and adjusting the resistance value, temperature coefficient of resistance, load characteristics, and trimming properties of the resistor may be added to the thick film resistor composition of the present embodiment. Typical additives include _Nb2O5 , _Ta2O5 , _{TiO2 ,} CuO, _MnO2 , _ZrO2 , _{Al2O3 , SiO2} , _ZrSiO4 and the _like . By adding one or more selected from these additives, a thick film resistor having better characteristics can be produced. Although the amount to be added is adjusted depending on the purpose, it is preferably 20 parts by mass or less with respect to the total of 100 parts by mass of the ruthenium-based conductive powder and the glass powder.

Note that these components may not be added. That is, the composition for a thick film resistor of this embodiment can also be composed of a ruthenium-based conductive powder and a glass powder. Therefore, these additives can be added so as to be 0 or more with respect to a total of 100 parts by mass of the ruthenium-based conductive powder and the glass powder.

According to the composition for a thick film resistor of the present embodiment described above, by using a predetermined glass powder, a thick film resistor having an excellent temperature coefficient of resistance can be produced using the composition for a thick film resistor. can be formed. In addition, materials containing no lead component are used for the ruthenium-based conductive powder and the glass powder. Therefore, the composition for thick film resistors of the present embodiment can also be a composition that does not contain a lead component.
[Paste for thick film resistors]
A configuration example of the thick film resistor paste of the present embodiment will be described.

The thick film resistor paste of the present embodiment can contain the aforementioned thick film resistor composition and an organic vehicle. The thick film resistor paste of the present embodiment preferably has a structure in which the thick film resistor composition described above is dispersed in an organic vehicle.

As described above, the thick-film resistor paste of the present embodiment is prepared by dispersing the above-described thick-film resistor composition in a solvent in which a resin component called an organic vehicle is dissolved. It can be a paste.

There are no particular restrictions on the type and composition of the organic vehicle resin and solvent. As the resin component of the organic vehicle, for example, one or more selected from ethyl cellulose, acrylic acid ester, methacrylic acid ester, rosin, maleic acid ester and the like can be used.

As the solvent, for example, one or more selected from terpineol, butyl carbitol, butyl carbitol acetate and the like can be used. A solvent having a high boiling point may be added for the purpose of delaying the drying of the thick film resistor paste. Moreover, a dispersant, a plasticizer, etc. can also be added as needed.

The compounding ratio of the resin component and the solvent can be adjusted according to the viscosity and the like required for the thick film resistor paste to be obtained. The ratio of the organic vehicle to the composition for thick film resistors is not particularly limited, but when the composition for thick film resistors is 100 parts by mass, the ratio of the organic vehicle is, for example, 20 parts by mass or more and 200 parts by mass or less. can do.

The method for producing the thick film resistor paste of the present embodiment is not particularly limited. The resistor composition can also be dispersed in an organic vehicle. Alternatively, for example, the composition for thick film resistors described above may be mixed in a ball mill or a grinder and then dispersed in an organic vehicle.

In the paste for thick film resistors, it is desirable to break the agglomeration of the inorganic raw material powder such as the ruthenium-based conductive powder and disperse it in a solvent in which the resin component is dissolved, ie, an organic vehicle. In general, the smaller the particle size of the powder, the stronger the agglomeration and the easier the formation of secondary particles. Therefore, the thick film resistor paste of the present embodiment may contain a fatty acid or the like as a dispersant in order to facilitate the disaggregation of the secondary particles and their dispersion into the primary particles.
[Thick film resistor]
A configuration example of the thick film resistor of this embodiment will be described.

The thick film resistor of the present embodiment can be manufactured using the thick film resistor composition and the thick film resistor paste described above. Therefore, the thick film resistor of the present embodiment can contain the composition for a thick film resistor described above, and can contain the ruthenium-based conductive powder described above and a glass component.

As described above, in the composition for a thick film resistor, the ratio of the ruthenium-based conductive powder to the ruthenium-based conductive powder and the glass powder is preferably 5% by mass or more and 50% by mass or less. The thick film resistor of the present embodiment can be manufactured using the thick film resistor composition, and the glass component in the resulting thick film resistor is derived from the glass powder of the thick film resistor composition. . Therefore, in the thick film resistor of the present embodiment, similarly to the composition for a thick film resistor, the proportion of the ruthenium conductive powder in the ruthenium conductive powder and the glass component is 5% by mass or more and 50% by mass. It is preferably 5% by mass or more, and more preferably 5% by mass or more and 40% by mass or less.

The method for producing the thick film resistor of the present embodiment is not particularly limited, but for example, the thick film resistor composition described above can be fired on a ceramic substrate. Alternatively, the thick-film resistor paste described above may be applied to a ceramic substrate and then fired to form the ceramic substrate.

Although specific examples and comparative examples will be given below, the present invention is not limited to these examples.
(Evaluation method)
First, evaluation methods in the following reference examples, examples, and comparative examples (also collectively referred to as “experimental examples”) will be described.
(1) Measurement of Defect Amount of Glass Powder Glass powder was filled in a sample tube and measured using an electron spin resonance spectrometer (manufactured by JEOL Ltd.) at liquid nitrogen temperature (77K). The amount of defects in the glass powder was quantified using 2,2,6,6-tetramethyl-4-piperidiol-1-oxyl and ruby of known concentrations as standard samples.
(2) 50% Volume Cumulative Particle Size of Glass Powder The 50% volume cumulative particle size was measured with a particle size distribution meter using laser diffraction.
(3) Measurement of the softening point of the glass powder The softening point of the glass powder is determined by heating the glass powder at 10°C per minute in the atmosphere using the differential thermal analysis method (TG-DTA). The peak temperature at which the next differential heat curve on the high temperature side decreases was taken as the temperature at which the decrease in the differential heat curve on the lowest temperature side appears.
(4) Average particle size (specific surface area diameter) of ruthenium oxide powder in terms of specific surface area
The specific surface area can be calculated from the specific surface area and density. The specific surface area was measured using the BET one-point method, which allows easy measurement. Assuming that the specific surface area diameter is D1 (nm), the density is ρ (g/cm ³ ), the specific surface area is S (m ² /g), and the powder is regarded as a true sphere, the following relational expression (1) is obtained. It holds. The particle diameter calculated by this D1 was taken as the specific surface area diameter.

D1 (nm)=6×10 ³ /(ρ·S) (1)
The specific surface area was calculated assuming that the density of ruthenium oxide was 7.05 g/cm ³ .
(5) Film thickness The film thickness was measured using a stylus thickness and roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., model number: Surfcom 480B) for five thick-film resistors produced in the same manner in each example and comparative example. The thickness of the thick film resistor was calculated by measuring the thickness and averaging the measured values.
(6) Measurement of resistance value The sheet resistance value is the average value of the resistance values of 25 thick film resistors prepared in the same manner in each experimental example measured with a digital multimeter (manufactured by KEITHLEY, No. 2001). It was calculated by
(7) Temperature coefficient of resistance In measuring the temperature coefficient of resistance, five thick-film resistors prepared in the same manner in each experimental example were held at −55° C., 25° C., and 125° C. for 15 minutes, respectively. The resistance value was measured, and the resistance value at −55° C. was defined as R ₋₅₅ , the resistance value at 25° C. as R ₂₅ , and the resistance value at 125° C. as R ₁₂₅ . Then, the temperature coefficient of resistance in each temperature range was calculated for each thick film resistor using the following formulas (A) and (B). Then, the average temperature coefficient of resistance of five thick film resistors in each temperature range was calculated, and the temperature coefficient of resistance (COLD-TCR , HOT-TCR). Both units are ppm/°C. The temperature coefficient of resistance is desirably close to 0, and the temperature coefficient of resistance ≦±100 ppm/° C. is regarded as a standard for an excellent resistor.

COLD-TCR=(R ₋₅₅ −R ₂₅ )/R ₂₅ /(−80)×10 ⁶ (A)
HOT-TCR=(R ₁₂₅ −R ₂₅ )/R ₂₅ /(100)×10 ⁶ (B)
In Table 1, COLD-TCR is written as C-TCR, and HOT-TCR is written as H-TCR.
(Reference example 1)
Ruthenium oxide powder with a specific surface area of 36 nm and fumed silica with a particle size of 15 nm (area average particle size according to TEM image) are used so that thick film resistors with low resistance values to high resistance values can be obtained. mass ratio (ruthenium oxide/glass) is 87.5/12.5, 80/20, 75/25 as shown in Table 1, weighed and mixed, and the thick film resistor composition and bottom.

Next, 40 parts by mass of an organic vehicle was added to 100 parts by mass of the composition for thick film resistors, and the mixture was kneaded in a three-roll mill to prepare a paste for thick film resistors according to Reference Example 1. The organic vehicle was prepared by mixing 85% by mass of terpineol and 15% by mass of ethyl cellulose and dissolving the mixture at 80°C.

The thickness of the thick-film resistor paste after firing is in the range of 6 μm to 8 μm after firing on an electrode containing 1% by mass of Pd and 99% by mass of Ag, which is pre-fired on an alumina substrate. printed to be inside. Next, after drying at 150° C. for 5 minutes, firing was performed at a peak temperature of 850° C. for 9 minutes in total, including heating and cooling times, for a total of 30 minutes to form a thick film resistor. The size of the thick film resistor was such that the resistor width was 1.0 mm and the resistor length (between electrodes) was 1.0 mm.

After that, after obtaining thick film resistors, which are sintered bodies of thick film resistor pastes having respective mixing ratios, resistance values and temperature coefficients of resistance were determined. Table 1 shows the results.
(Example 1)
In this example, a glass powder having a basicity calculated by Morinaga's formula of 0.60 and an amount of defects detected as E' centers of 4.3×10 ¹⁵ spins/g was used. The glass powder contains _SiO2 : 22% by mass, _B2O3 : 13% by mass, _Al2O3 : ₃ % by mass, CaO: 5% _by mass, BaO: 45% by mass, and ZnO: 12% by mass. Each component was contained in proportion, the softening point was 700° C., and the 50% volume cumulative particle size was 0.95 μm.

A composition for a thick film resistor and a thick film resistor were prepared in the same manner as in Reference Example 1, except that the above glass powder was used instead of fumed silica and mixed with ruthenium oxide powder at the ratio shown in Table 1. A paste and a thick film resistor were prepared and evaluated. Table 1 shows the results.
(Example 2)
In this example, a glass powder having a basicity calculated by Morinaga's formula of 0.60 and an amount of defects detected as E' centers of 4.9×10 ¹⁵ spins/g was used. The glass powder contains SiO ₂ : 19% by mass, B ₂ O ₃ : 19% by mass, Al ₂ O ₃ : 5% by mass, SrO: 1% by mass, and BaO: 56% by mass. It had a softening point of 690° C. and a 50% volume cumulative particle size of 0.95 μm.

A composition for a thick film resistor and a thick film resistor were prepared in the same manner as in Reference Example 1, except that the above glass powder was used instead of fumed silica and mixed with ruthenium oxide powder at the ratio shown in Table 1. A paste and a thick film resistor were prepared and evaluated. Table 1 shows the results.
(Comparative example 1)
In this comparative example, a glass powder having a basicity calculated by Morinaga's formula of 0.39 and an amount of defects detected as E' centers of 5.6×10 ¹⁵ spins/g was used. The glass powder contains SiO ₂ : 42% by mass, B ₂ O ₃ : 6% by mass, Al ₂ O ₃ : 6% by mass, CaO: 5% by mass, BaO: 26% by mass, and ZnO: 15% by mass. Each component was contained in proportion, the softening point was 800° C., and the 50% volume cumulative particle size was 1.3 μm.

A composition for a thick film resistor and a thick film resistor were prepared in the same manner as in Reference Example 1, except that the above glass powder was used instead of fumed silica and mixed with ruthenium oxide powder at the ratio shown in Table 1. A paste and a thick film resistor were prepared and evaluated. Table 1 shows the results.
(Comparative example 2)
In this comparative example, a glass powder having a basicity calculated by Morinaga's formula of 0.62 and an amount of defects detected as E' centers of 8.2×10 ¹⁵ spins/g was used. The glass powder contains SiO ₂ : 22% by mass, B ₂ O ₃ : 13% by mass, CaO: 5% by mass, BaO: 46% by mass, and ZnO: 14% by mass. Point 670° C., 50% volume cumulative particle size 1.3 μm.

A composition for a thick film resistor and a thick film resistor were prepared in the same manner as in Reference Example 1, except that the above glass powder was used instead of fumed silica and mixed with ruthenium oxide powder at the ratio shown in Table 1. A paste and a thick film resistor were prepared and evaluated. Table 1 shows the results.

表１に示した結果によると、実施例１、２で得られた厚膜抵抗体は、抵抗値によらず、抵抗温度係数が、いずれも－１００ｐｐｍ／℃以上となっていることが確認できた。特に、中～高抵抗域（１ｋ～１０ＭΩ領域）においても、－１００ｐｐｍ／℃以上になることを確認できた。なお、一部の試料において、１００ｐｐｍ／℃を超える厚膜抵抗体も確認されたが、既述の様に添加剤を加えることで、抵抗温度係数を±１００ｐｐｍ／℃以内とすることができる。

According to the results shown in Table 1, it can be confirmed that the temperature coefficient of resistance of the thick film resistors obtained in Examples 1 and 2 is -100 ppm/° C. or more regardless of the resistance value. rice field. In particular, it was confirmed that the value was −100 ppm/° C. or higher even in the middle to high resistance region (1 k to 10 MΩ region). In some samples, thick film resistors exceeding 100 ppm/°C were also confirmed, but by adding additives as described above, the temperature coefficient of resistance can be made within ±100 ppm/°C.

On the other hand, in Comparative Examples 1 and 2, it was confirmed that a thick film resistor having a temperature coefficient of resistance of less than −100 ppm/° C. was obtained because glass powder with a large amount of defects was used.

Claims (6)

A composition for a thick film resistor containing a lead-free ruthenium-based conductive powder and a lead-free glass powder,
The glass powder contains Si, B, and R ( the R represents one or more alkaline earth elements selected from Ca, Sr, and Ba), and the Si is 10% by mass or more and 50% by mass as SiO ₂ Hereinafter, the B is 8% by mass or more and 19% by mass or less as B 2 O 3, and the R is 40% by mass or more and 65% by mass or less as RO, and at least Al ₂ O _{3 is} included _as an additive component. ,
The composition for a thick film resistor, wherein the glass powder has a defect amount of 0 or more and 5.0×10 ¹⁵ spins/g or less as E′ centers detected by electron spin resonance spectroscopy. 2. The composition for a thick film resistor according to claim 1, wherein said glass powder has a glass basicity of 0.4 or more and 0.7 or less. 3. The composition for a thick film resistor according to claim 1, wherein the glass powder has a 50% volume cumulative particle size of 0.7 [mu]m or more and 2.0 [mu]m or less. 4. The composition for a thick film resistor according to claim 1, wherein said ruthenium-based conductive powder is ruthenium oxide powder. A paste for thick film resistors, comprising the composition for thick film resistors according to claim 1 and an organic vehicle. A thick film resistor comprising the composition for a thick film resistor according to claim 1 .