JP7347056B2 - Composition for thick film resistor and method for producing the same, paste for thick film resistor and method for producing the same - Google Patents

Description

The present invention relates to a method for producing a composition for a thick film resistor and a method for producing a paste for a thick film resistor. The present invention also relates to a composition for a thick film resistor and a paste for a thick film resistor obtained by these manufacturing methods.

Thick film resistors used in chip resistors, hybrid ICs, resistance networks, etc. are generally formed by printing a thick film resistor paste on a ceramic substrate and firing it. As a composition for a thick film resistor used in a paste for a thick film resistor, a composition whose main components are ruthenium-based conductive particles, typified by ruthenium oxide, which are conductive particles, and glass powder is widely used.

The reason why such a composition is used as a material for thick film resistors is that it can be fired in air at a temperature range of 800°C to 900°C, and the temperature coefficient of resistance can be made close to 0. can be mentioned. Furthermore, when a thick film resistor is produced using such a composition, the resistance value may be adjustable by adjusting the mixing ratio of the ruthenium-based conductive particles and the glass powder. In other words, in a composition for a thick film resistor mainly composed of ruthenium-based conductive particles and glass powder, the resistance value can be lowered by increasing the mixing ratio of the ruthenium-based conductive particles. The resistance value can be increased by lowering the mixing ratio.

Ruthenium-based conductive particles used in the composition for thick film resistors include ruthenium oxide (RuO ₂ ) having a rutile crystal structure and lead ruthenate (Pb ₂ Ru ₂ O _6.5 ) having a pyrochlore crystal structure. can be mentioned. These conductive particles are all oxides that exhibit metallic conductivity.

Here, one of the important characteristics of the thick film resistor is the resistance temperature coefficient, which represents a change in the resistance value of the thick film resistor due to temperature change. It is relatively easy to adjust the temperature coefficient of resistance to the negative side, and it is common practice to add metal oxides called adjusting agents, such as manganese oxide, niobium oxide, and titanium oxide. On the other hand, it is difficult to adjust the temperature coefficient of resistance to the positive side, and in particular, when the thick film resistor has a negative temperature coefficient of resistance, it is substantially impossible to bring it close to zero. Therefore, in a high resistance region where the temperature coefficient of resistance tends to be negative, it is necessary to combine conductive particles with a positive temperature coefficient of resistance and glass powder.

Among ruthenium-based conductive particles, lead ruthenate (Pb ₂ Ru ₂ O _6.5 ) has a resistance about one order of magnitude higher than that of ruthenium oxide (RuO ₂ ), and a thick film resistor using lead ruthenate has a high resistance. The temperature coefficient can be increased. For this reason, lead ruthenate has conventionally been used as conductive particles in thick film resistors used in a high resistance region of 10 kΩ or more.

On the other hand, glass powder containing lead oxide (PbO) has conventionally been used as a glass powder used in a composition for a thick film resistor. The reasons for this are that lead oxide has a softening point lower than the firing temperature of paste for thick film resistors, lead oxide has the effect of lowering the softening point of glass, and that changing the content of lead oxide The softening point can be adjusted over a wide range, the glass can be manufactured with high chemical durability, and it has high insulation properties and excellent pressure resistance.

As described above, conventionally, the ruthenium-based conductive particles and the glass powder that constitute the composition for a thick film resistor both contain lead. However, in recent years, there has been a strong demand for lead-free compositions for thick film resistors from the viewpoint of the impact on the human body and environmental protection.

For example, in Japanese Patent Application Laid-Open No. 2005-129806, in order to improve resistance values, variations in resistance values, temperature characteristics, withstand voltage characteristics, etc., the average particle size is 5 μm to 50 μm, and calcium ruthenate, strontium ruthenate, ruthenium A lead-free thick-film resistor paste using at least one selected from barium oxide as a conductive material has been proposed.

In JP-A No. 2003-007517, a first conductive material containing a metal element for imparting conductivity to a glass composition is melted in advance to obtain a glass material, and then this glass material and the above-mentioned metal material are melted in advance. A method has been proposed for producing a lead-free thick film resistor paste by kneading a second conductive material containing a vehicle. This document mentions ruthenium oxide and ruthenium composite oxide as the first or second conductive material. In addition, the paste for thick film resistors produced by this method can form thick film resistors with high resistance values without adding various kinds of metal oxides in large quantities. It is said that it can be obtained.

JP-A No. 2007-103594 discloses a thick film obtained after high-temperature firing, which contains a lead-free ruthenium-based conductive component, a lead-free glass with a basicity of 0.4 to 0.9, and an organic vehicle. A composition for a thick film resistor has been proposed in which MSi ₂ Al ₂ O ₈ crystals (M is Ba and/or Sr) are present in the resistor. It is said that by using this composition for a thick film resistor, it is possible to form a thick film resistor with excellent TCR characteristics, noise characteristics, withstand voltage characteristics, heat cycle characteristics, etc. over a wide resistance range.

Japanese Patent Application Publication No. 2005-129806 Japanese Patent Application Publication No. 2003-007517 Japanese Patent Application Publication No. 2007-103594

However, although JP-A-2005-129806 proposes a lead-free paste for thick film resistors, it is difficult to adjust the temperature coefficient of resistance to the positive side. It cannot be said that it can be improved sufficiently.

In the paste for thick film resistors described in JP-A No. 2003-7517, the amount of ruthenium oxide dissolved in the glass varies greatly depending on the manufacturing conditions, so the characteristics such as the resistance value and temperature coefficient of resistance of the thick film resistor are difficult to stabilize.

The composition for a thick film resistor described in JP-A No. 2007-103594 is based on the premise that a high-cost ruthenium composite oxide is used as the conductive particles. Sufficient consideration has not been given to the application of

In view of the above problems, the present invention provides a lead-free composition for thick film resistors that can improve the resistance temperature coefficient of thick film resistors with excellent noise characteristics by an industrially simple method. The present invention also aims to provide a method for producing a paste for thick film resistors. The present invention also provides a lead-free thick film resistor composition and a thick film resistor composition, which can be obtained by these manufacturing methods and have a temperature coefficient of resistance close to 0. The purpose of the present invention is to provide a paste for film resistors.

The method for producing the composition for thick film resistors of the present invention includes:
a dipping step of immersing lead-free glass powder in a solution containing an organosilicon compound in which oxygen is bonded to silicon atoms;
a drying step of drying the glass powder after the dipping step to obtain a silica component-attached glass powder with a silica component attached to the surface;
a mixing step of mixing the silica component-attached glass powder and lead-free ruthenium oxide powder to obtain a lead-free thick film resistor composition;
Equipped with

The dipping step is performed such that the content of the silica component contained in the silica component-attached glass powder is 0.5% by mass or more and 20% by mass or less based on the total amount of the glass powder and the ruthenium oxide powder. It is preferable to do so.

The organosilicon compounds include ether compounds represented by the general formula (A): (RO) ₄ Si (where R is an alkyl group), polyalkylene oxide-modified silicones, polyalkylene oxide-modified siloxane compounds, and silane coupling compounds. It is preferable that it is at least one selected from the group of.

Among these, an ether compound represented by the general formula (A): (RO) ₄ Si (where R is an alkyl group) is preferable, and R in the general formula (A) has 1 carbon number. More preferably, it is an ether compound having ~10 alkyl groups. Particularly preferred is at least one selected from the group of methyl silicate, ethyl silicate, propyl silicate, and butyl silicate.

The ruthenium oxide powder is preferably at least one selected from the group of ruthenium oxide powder, calcium ruthenate powder, strontium ruthenate powder, and barium ruthenate powder, and is more preferably ruthenium oxide powder. .

The BET specific surface area diameter of the ruthenium oxide powder is preferably 10 nm or more and 120 nm or less.

The glass powder contains SiO ₂ , B ₂ O ₃ , RO (where R is at least one alkaline earth metal selected from the group of Ca, Sr, and Ba), R ₂ O (where R is At least one alkali metal element selected from Li, Na, K, and Cs), ZnO, and at least one selected from the group Bi ₂ O ₃ is preferably included.

The glass powder contains SiO ₂ , B ₂ O ₃ and RO (where R is at least one alkaline earth metal selected from the group of Ca, Sr, and Ba), and contains SiO ₂ and B 2 O 3 . When the total amount of ₂ O ₃ and RO is 100 parts by mass, the proportion of SiO ₂ is 10 parts by mass or more and 50 parts by mass or less, the proportion of B ₂ O ₃ is 8 parts by mass or more and 30 parts by mass or less, and the proportion of RO is 10 parts by mass or more and 50 parts by mass or less. The proportion is more preferably 40 parts by mass or more and 65 parts by mass or less.

The 50% volume cumulative particle size of the glass powder is preferably 0.1 μm or more and 5 μm or less.

In the mixing step, the proportion of the ruthenium oxide powder is preferably 5% by mass or more and 50% by mass or less based on the total of the silica component-attached glass powder and the ruthenium oxide powder.

The method for producing a paste for a thick film resistor of the present invention includes a step of kneading the composition for a thick film resistor produced by the above production method and an organic vehicle.

When the content of the thick film resistor composition is 100 parts by mass, the proportion of the organic vehicle is preferably 20 parts by mass or more and 200 parts by mass or less.

The composition for a thick film resistor of the present invention is characterized in that it contains a lead-free glass powder and a lead-free ruthenium oxide powder, and a silica component is attached to the surface of the glass powder.

The silica component is attached to the surface of the glass powder, and the content of the silica component contained in the silica component-adhered glass powder is 0.5% by mass or more and 20% by mass based on the total amount of the glass powder and the ruthenium oxide powder. % or less.

The ruthenium oxide powder is preferably at least one selected from the group of ruthenium oxide powder, calcium ruthenate powder, strontium ruthenate powder, and barium ruthenate powder, and is more preferably ruthenium oxide powder. .

The BET specific surface area diameter of the ruthenium oxide powder is preferably 10 nm or more and 120 nm or less.

The glass powder contains SiO ₂ , B ₂ O ₃ , RO (where R is at least one alkaline earth metal selected from the group of Ca, Sr, and Ba), R ₂ O (where R is At least one alkali metal element selected from Li, Na, K, and Cs), ZnO, and at least one selected from the group Bi ₂ O ₃ is preferably included.

The glass powder contains SiO ₂ , B ₂ O ₃ and RO (where R is at least one alkaline earth metal selected from the group of Ca, Sr, and Ba), and contains SiO ₂ and B 2 O 3 . ₂ When the total amount of O ₃ and RO is 100 parts by mass, SiO ₂ is 10 parts by mass or more and 50 parts by mass or less, B ₂ O ₃ is 8 parts by mass or more and 30 parts by mass or less, and RO is 40 parts by mass. More preferably, the amount is 65 parts by mass or less.

The 50% volume cumulative particle size of the glass powder is preferably 0.1 μm or more and 5 μm or less.

The proportion of the ruthenium oxide powder is preferably 5% by mass or more and 50% by mass or less based on the total of the silica component-attached glass powder and the lead-free ruthenium oxide powder.

Further, the paste for thick film resistors of the present invention includes a composition for thick film resistors and an organic vehicle, and the composition for thick film resistors is composed of the composition for thick film resistors of the present invention. It is characterized by being

When the content of the thick film resistor composition is 100 parts by mass, the proportion of the organic vehicle is preferably 20 parts by mass or more and 200 parts by mass or less.

The present invention provides a lead-free thick film resistor composition that can be used as a material for thick film resistors that have a resistance temperature coefficient close to 0 and excellent noise characteristics by an industrially simple method. It becomes possible to provide a paste for thick film resistors.

In view of the above-mentioned problems, the present inventor has developed a lead-free thick-film resistor that makes it possible to improve the resistance temperature coefficient of a thick-film resistor with excellent noise characteristics using an industrially simple method. We have conducted extensive research into methods for producing the composition. As a result, the lead-free glass powder to be mixed with the lead-free ruthenium oxide powder is immersed in a solution containing an organic silicon compound in which oxygen is bonded to silicon atoms to obtain a glass powder with silica components attached. By doing so, we have found that the temperature coefficient of resistance of the ultimately obtained thick film resistor can be improved while maintaining excellent noise characteristics. The present invention was completed based on this knowledge.

In this specification, "lead-free" means that lead is not intentionally added, and does not apply to thick-film resistors that contain trace amounts of lead mixed in as impurities or unavoidable components during the manufacturing process. Compositions or pastes for thick film resistors are not excluded. The lead content in the thick film resistor composition is preferably 0.10% by mass or less, more preferably 0.05% by mass or less. Note that this definition also applies to glass powder and ruthenium oxide powder.

Hereinafter, a composition for a thick film resistor, a method for producing the same, a paste for a thick film resistor, and a method for producing the same, according to an example of an embodiment of the present invention, will be described in detail. However, the present invention is not limited to the following example embodiment.

1. Composition for Thick Film Resistor and Method for Producing the Same The method for producing the composition for thick film resistor of the present invention includes a dipping step, a drying step, and a mixing step.

(1) Immersion process In the dipping process, lead-free glass powder (hereinafter referred to as "glass powder") is immersed in a solution containing an organosilicon compound in which oxygen is bonded to silicon atoms (hereinafter referred to as "organosilicon compound"). It is a process.

In this dipping step, the organosilicon compound is hydrolyzed in the solution, and the Si--O moiety contained in the organosilicon compound physically adheres to the surface of the glass powder. The Si—O portions attached to the surface of the glass powder remain attached as silica components after the drying process described below. That is, the glass powder constituting the composition for a thick film resistor of the present invention is composed of a silica component-attached glass powder with a silica component attached to the surface thereof. As a result, in the thick film resistor, a silica component (SiO ₂ ), which is a silicon oxide substance derived from the firing residue of an insulating organosilicon compound, is present in the conductive network of ruthenium oxide formed around the glass powder. That will happen. For this reason, it is necessary to adjust the resulting thick film resistor to have high resistance and to increase the temperature coefficient of resistance, including when additives are added to the composition for thick film resistors to improve noise characteristics. Therefore, it is possible to easily bring the temperature coefficient of resistance close to 0.

[Solution containing organosilicon compound]
A solution containing an organosilicon compound in which oxygen is bonded to a silicon atom can be obtained by dissolving a specific organosilicon compound in a solvent.

a) Organosilicon compound An organosilicon compound in which oxygen is bonded to a silicon atom, that is, an organosilicon compound having a Si-O bond, has the general formula (A): (RO) ₄ Si (where R represents an alkyl group). At least one selected from the group of ether compounds represented by the following formulas, polyalkylene oxide-modified silicones, polyalkylene oxide-modified siloxane compounds, and silane coupling compounds can be used.

Polyalkylene oxide-modified silicone has a polyalkylene oxide residue of the general formula (B): (EO) _n (PO) _m (where EO is ethoxy, PO is propoxy, and n and m represent natural numbers). It is made of silicone. The polyalkylene oxide modified silicones also include linear methyltrisiloxanes in which polyethers are grafted onto silicones by hydrosilation.

Examples of polyalkylene oxide-modified silicones include ADVALON FA33, FLUID L03, FLUID L033, FLUID L051, FLUID L053, FLUID L060, FLUID L066, IM22, WACKER-Belsil DMC 6038 (and above). , Asahi Kasei Wacker Silicone Co., Ltd.), KF -352A, KF-353, KF-615A, KP-112, KP-341, X-22-4515, KF-354L, KF-355A, KF-6004, KF-6011, KF-6011P, KF-6012, KF -6013, KF-6015, KF-6016, KF-6017, KF-6017P, KF-6020, KF-6028, KF-6028P, KF-6038, KF-6043, KF-6048, KF-6123, KF-6204 , KF-640, KF-642, KF-643, KF-644, KF-945, KP-110, KP-355, KP-369, KS-604, Polon SR-Conc, X-22-4272, X- 22-4952 (manufactured by Shin-Etsu Chemical Co., Ltd.), 8526 ADDITIVE, FZ-2203, FZ-5609, L-7001, SF 8410, 2501 COSMETIC WAX, 5200 FORMULATION AID, 57 ADDITIVE, 801 9 ADDITIVE, 8029 ADDITIVE, 8054 ADDITIVE, BY16-036, BY16-201, ES-5612 FORMULATION AID, FZ-2104, FZ-2108, FZ-2110, FZ-2123, FZ-2162, FZ-2164, FZ-2191, FZ-2207, FZ- 2208, FZ-2222, FZ-7001, FZ-77, L-7002, L-7604, SF8427, SF8428, SH 28 PAINR ADDITIVE, SH3749, SH3773M, SH8400, SH8700 (all manufactured by Dow Corning Toray Co., Ltd. ), BYK-333, BYK-378, BYK-302, BYK-307, BYK-331, BYK-345, BYK-3455, BYK-347, BYK-348, BYK-349, BYK-377 (BIK-Chemie Japan stock) company), Silwet L-7001, Silwet L-7002, Silwet L-720, Silwet L-7200, Silwet L-7210, Silwet L-7220, Silwet L-7230, Silwet L-7605, TSF444 0, TSF4441, TSF4445, TSF4446, TSF4450, TSF4452, TSF4460, Silwet Hydrostable 68, Silwet L-722, Silwet L-7280, Silwet L-7500, Silwet L-7550, Silwet L-760 0, Silwet L-7602, Silwet L-7604, Silwet L- 7607, Silwet L-7608, Silwet L-7622, Silwet L-7650, Silwet L-7657, Silwet L-77, Silwet L-8500, Silwet L-8610, (Momentive Performance Materials Japan LLC (manufactured by).

The polyalkylene oxide modified siloxane compound has the general formula (C): (EO) _n (PO) _m (where EO is ethoxy, PO is propoxy, n and m represent natural numbers, and satisfy m<n≦3). ) is a siloxane compound having a polyalkylene oxide residue.

Among these organosilicon compounds, ether compounds represented by the general formula (A): (RO) ₄ Si (wherein R is an alkyl group) are preferred. In particular, from the viewpoint of hydrolyzability, R in the general formula (A) is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. That is, at least one selected from the group of methyl silicate, ethyl silicate, propyl silicate, and butyl silicate can be suitably used.

The content of the silica component contained in the silica component-attached glass powder obtained after the drying step is 0.5% by mass or more and 20% by mass or less based on the total amount of the glass powder and ruthenium oxide powder, as described below. It is preferably 0.5% by mass to 10% by mass, and even more preferably 0.5% by mass to 5% by mass. By setting the content of the silica component that adheres to the surface of the glass powder to 0.5% by mass or more, the temperature coefficient of resistance in the thick film resistor is suppressed from becoming negative, and the effect of improving the electrical characteristics is sufficiently achieved. Demonstrated. On the other hand, if the content of the silica component adhering to the surface of the glass powder exceeds 20% by mass, the denseness of the film in the thick film resistor may decrease.

The content of the silica component attached to the surface of the glass powder through the dipping process and the drying process can be confirmed by the change in mass of the glass powder before the dipping process and after the drying process. Furthermore, the amount of silica component adhering to the surface of the glass powder can be controlled by adjusting the concentration of the solution containing the organic silicon compound and the immersion time of the glass powder.

b) Solvent From the viewpoint of hydrolyzability, it is preferable to use alcohol as a solvent for forming a solution containing an organosilicon compound in which oxygen is bonded to a silicon atom. In particular, from the viewpoint of handling, it is preferable to use methanol, ethanol, or the like. By using these, the organosilicon compound is easily hydrolyzed, so that the Si 2 -O moieties that constitute the organosilicon compound can be easily attached to the surface of the glass powder.

[Glass powder]
As the lead-free glass powder, it is possible to use a powder in which a metal oxide other than SiO ₂ is blended with SiO ₂ serving as the skeleton to adjust the fluidity during firing. The metal oxide other than SiO ₂ preferably contains B ₂ O ₃ and RO (where R is at least one alkaline earth metal selected from the group of Ca, Sr, and Ba). . Further, for the purpose of adjusting fluidity, R ₂ O (where R is at least one alkali metal element selected from Li, Na, K, and Cs), ZnO, and Bi ₂ O ₃ may be included. can.

In the glass powder of the present invention, when the total content of metal oxides in the glass composition is 100 parts by mass, the proportion of SiO ₂ is preferably 10 parts by mass or more and 50 parts by mass or less. By setting the proportion of SiO ₂ to 50 parts by mass or less, the fluidity of the glass powder during firing can be sufficiently increased. If the proportion of SiO ₂ is less than 10 parts by mass, it may become difficult to form glass in the thick film resistor.

The glass powder of the present invention contains SiO ₂ , B ₂ O ₃ and RO, and when the total content of metal oxides in the glass composition is 100 parts by mass, the proportion of B ₂ O ₃ is 8 parts by mass. Parts by weight or more and 30 parts by weight or less, and the proportion of RO is preferably 40 parts by weight or more and 65 parts by weight or less. By using a glass powder containing SiO ₂ , B ₂ O ₃ and RO in such proportions, the temperature coefficient of resistance of the thick film resistor can be made less likely to become negative.

By setting the proportion of B ₂ O ₃ to 8 parts by mass or more, the fluidity of the glass powder during firing can be sufficiently increased. By setting the proportion of B ₂ O ₃ to 30 parts by mass or less, the weather resistance of the thick film resistor can be improved.

By setting the content of RO to 40 parts by mass or more, it is possible to sufficiently suppress the temperature coefficient of resistance of the obtained thick film resistor from becoming negative. By controlling the content of RO to 65 parts by mass or less, crystallization can be suppressed and glass can be formed more easily.

In addition to SiO ₂ , B ₂ O ₃ and RO, the glass powder of the present invention can also contain other components from the viewpoint of adjusting the fluidity during firing of the glass and the weather resistance of the glass. 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, etc., and one type selected from these compounds. The above can also be added to glass.

Al ₂ O ₃ can be added for the purpose of suppressing phase separation of the glass, and at least one selected from ZrO ₂ and TiO ₂ can also be added for the purpose of adjusting weather resistance and chemical resistance. For the purpose of improving fluidity during firing, at least one member selected from the group consisting of Bi ₂ O ₃ , SnO ₂ , ZnO, Li ₂ O, Na ₂ O, and K ₂ O may be added.

Softening point is a measure that affects the fluidity of glass powder during firing. When the firing temperature of the thick film resistor composition is 800°C or more and 900°C or less, the softening point of the glass powder is preferably 600°C or more and 800°C or less, more preferably 600°C or more and 750°C or less. When the softening point of the glass powder is within this range, the fluidity of the glass is ensured during firing, making it easier to form glass into a thick film resistor. Here, the softening point is measured by heating glass powder at a rate of 10°C/min in the atmosphere using differential thermal analysis (TG-DTA), and the decrease in the differential thermal curve at the lowest temperature is This is the peak temperature at which the next differential thermal curve on the higher temperature side than the temperature at which it occurs decreases.

Although the particle size of the glass powder is not particularly limited, the 50% volume cumulative particle size measured by a particle size distribution analyzer using laser diffraction is preferably 5 μm or less, more preferably 3 μm or less. If the 50% volume cumulative particle size of the glass powder exceeds 5 μm, it will cause increased variation in the resistance value of the thick film resistor and decreased load characteristics. On the other hand, if the particle size of the glass powder becomes too small, there is a risk that productivity will decrease and impurities may be mixed in. For this reason, the 50% volume cumulative particle size of the glass powder is preferably 0.1 μm or more.

The 50% volume cumulative particle size is determined from particle size distribution measurements. More specifically, the particle size is defined as the particle size at which the cumulative volume calculated from the volume integrated value measured with a laser diffraction scattering particle size analyzer is 50% of the total volume of all particles (the cumulative curve of particle size distribution with the total volume as 100%). (particle size at the point where this cumulative curve becomes 50%).

Glass powder can generally be produced by mixing predetermined components or precursors of predetermined components in a desired composition ratio, melting the mixture, quenching it, and then pulverizing it. The melting temperature is appropriately set depending on the composition ratio, but can be approximately 1400°C. Moreover, the quenching can be carried out by known means, for example, by bringing the melt into contact with cold water or by flowing it on a cooling belt.

Glass can also be pulverized using known means such as a ball mill, a planetary mill, and a bead mill. In order to sharpen the particle size distribution of the resulting glass powder, wet pulverization is preferably performed.

(2) Drying process In the drying process, the glass powder after the dipping process, that is, the glass powder with Si -O moieties attached to its surface, is dried, water is removed from the glass powder, and the Si -O moieties are replaced with a silica component ( This is a step of obtaining a silica component-attached glass powder with a silica component attached to the surface by converting it into SiO ₂ ).

The drying temperature in the drying step is not particularly limited, but is preferably 80° C. or higher. Further, the drying time is not particularly limited, and may be appropriately selected depending on the type of solvent, the amount of drying, and the like.

(3) Crushing process Although the particle size distribution of the glass powder does not change before and after the dipping process, the silica component-adhered glass powder after the drying process may aggregate. In this case, the aggregated glass powder adhering to the silica component can be crushed by mechanical treatment. Here, crushing refers to an operation in which mechanical energy is applied to aggregates of glass powder to which silica components are attached to loosen the aggregates without destroying the shape of the powder.

As a crushing method, a known means can be used, for example, a pin mill, a hammer mill, etc. can be used.

(4) Mixing process In the mixing process, the silica component-adhered glass powder obtained in the drying process is mixed with lead-free ruthenium oxide powder (hereinafter referred to as "ruthenium oxide powder") to form a lead-free thick film. This is a step of obtaining a composition for a resistor.

A common mixer can be used for mixing. For example, a shaker mixer, Loedige mixer, Julia mixer, V-blender, etc. can be used.

[Ruthenium oxide powder]
The lead-free ruthenium oxide powder includes at least one selected from the group of ruthenium oxide (RuO ₂ ) powder, calcium ruthenate (CaRuO ₃ ), strontium ruthenate (SrRuO ₃ ), and barium ruthenate (BaRuO ₃ ). Seeds can be used. Among these, ruthenium oxide is preferred because it can form a thick film resistor with excellent resistance temperature coefficient and noise characteristics.

The particle size of the ruthenium oxide powder is preferably a BET specific surface area diameter calculated from the BET specific surface area, and is preferably 10 nm to 120 nm, more preferably 10 nm to 110 nm.

By setting the BET specific surface area diameter of the ruthenium oxide powder to 10 nm or more, it is possible to control the network structure of the ruthenium oxide powder and glass powder when firing the paste for thick film resistors. It becomes possible to suppress the temperature coefficient of resistance from becoming negative. If the BET specific surface area diameter of the ruthenium oxide powder is less than 10 nm, the ruthenium oxide powder may not be sufficiently dispersed in the composition for a thick film resistor. On the other hand, when the BET specific surface area diameter of the ruthenium oxide powder exceeds 120 μm, the number of contact points between the ruthenium oxide particles, which are conductive particles, decreases, which may deteriorate the noise characteristics of the thick film resistor.

The BET specific surface area diameter can be calculated from the BET specific surface area and the density of ruthenium oxide. The BET specific surface area is measured by the BET method using nitrogen gas adsorption. The BET one-point method, which determines the specific surface area from the amount of adsorption at one point where the relative pressure (saturated vapor pressure and adsorption equilibrium pressure) is 0.25, allows for easy measurement. If the BET specific surface area diameter is D (nm), the density of ruthenium oxide is ρ (g/cm ³ ), the BET specific surface area is S (m ² /g), and the powder is regarded as a true sphere, then the formula: D (nm )=6×10 ³ /(ρ·S) holds true. Using this formula, the BET specific surface area diameter can be calculated from the BET specific surface area (measured value) of the ruthenium oxide powder.

[Mixing ratio]
In the mixing step, the mixing ratio of the ruthenium oxide powder is preferably 5% by mass or more and 50% by mass or less, and 5% by mass or more and 40% by mass, based on the total of the silica component-attached glass powder and the ruthenium oxide powder. It is more preferable that By setting the mixing ratio of lead-free ruthenium oxide powder to 50% by mass or less, sufficient strength of the thick film resistor can be ensured.

[Additive]
In the mixing step, a known metal compound may be mixed as an additive for the purpose of improving or adjusting the resistance value, temperature coefficient of resistance, load characteristics, or trimmability of the thick film resistor. Specifically, at least one metal compound powder selected from the group of Nb ₂ O ₅ , Ta ₂ O ₅ , TiO ₂ , CuO, MnO ₂ , ZrO ₂ , Al ₂ O ₃ , and ZrSiO ₄ is added as an additive. May be mixed as

The mixing ratio of these additives should be adjusted depending on the characteristics of the target thick film resistor, but it should be 20 parts by mass, assuming the total content of the silica-attached glass composition and ruthenium oxide to be 100 parts by mass. It is preferable that the amount is less than parts by mass.

According to the method for producing a composition for a thick film resistor according to an example of the embodiment of the present invention, the composition includes a lead-free glass powder and a lead-free ruthenium oxide powder, and a silica component is formed on the surface of the lead-free glass powder. A composition for a thick film resistor is obtained, which is characterized in that:

By combining such a glass powder to which a silica component is attached and a ruthenium oxide powder, the temperature coefficient of resistance of a thick film resistor can be easily controlled to around 0 or to a positive value. That is, it is possible to improve electrical characteristics such as current noise while maintaining the temperature coefficient of resistance of the finally obtained thick film resistor at -100 ppm/°C or higher.

In particular, by using ruthenium oxide powder as the ruthenium oxide powder and combining it with silica component-adhered glass powder, the resistance temperature of the thick film resistor can be improved even in the resistance range where the area resistance value is higher than 80 kΩ, which was previously difficult. It becomes possible to perform control to bring the coefficient close to 0.

Note that the composition of the composition for a thick film resistor of the present invention and the characteristics of the individual elements are the same as those described for the manufacturing method above, and therefore the description thereof will be omitted.

2. Paste for thick film resistor and method for producing the same The paste for thick film resistor of the present invention can be produced by kneading the composition for thick film resistor obtained by the above-mentioned production method and an organic vehicle. can. At this time, a dispersant and a plasticizer may be added as necessary.

The organic vehicle is at least one solvent selected from the group of terpineol, butyl carbitol, and butyl carbitol acetate, and selected from the group of ethyl cellulose, acrylic esters, methacrylic esters, rosin, and maleic esters. A solution in which at least one type of resin is dissolved can be used.

The organic vehicle is kneaded so that the content of the thick film resistor composition is preferably 20 parts by mass or more and 200 parts by mass or less, based on 100 parts by mass.

The kneading of the thick film resistor composition and the organic vehicle is not particularly limited, and any known means may be used as long as the thick film resistor composition can be uniformly dispersed in the organic vehicle. I can do it. For example, a three-roll mill, a bead mill, a planetary mill, etc. can be used.

The paste for thick film resistors of the present invention is characterized by using the composition for thick film resistors of the present invention, and the content ratio of the composition for thick film resistors and the organic vehicle is determined by the above manufacturing method. Since the contents are the same as those described in , the explanation thereof will be omitted.

3. Thick film resistor A thick film resistor can be formed by firing a composition for a thick film resistor on a ceramic substrate, or by applying a paste for a thick film resistor on a ceramic substrate and then firing it. I can do it.

In thick film resistors, a conductive network formed from ruthenium oxide is formed around a glass matrix formed from glass powder.

By using the composition for thick film resistor and the paste for thick film resistor of the present invention, it has a structure in which an insulating silica component is interposed in the conductive network of ruthenium oxide formed around the glass powder. A thick film resistor is obtained. Therefore, the electrical characteristics of the thick film resistor can be adjusted to high resistance, even when the thick film resistor contains additives to improve noise characteristics, and the temperature coefficient of resistance can be adjusted to be high. Since the resistance temperature coefficient can be near 0 or plus, it is possible to easily bring the temperature coefficient of resistance close to 0.

Note that in the thick film resistor, the silica component exists in the form of SiO ₂ .

The composition of the thick film resistor other than the silica component is almost the same as the composition for a thick film resistor.

In the thick film resistor obtained according to the present invention, it is desirable that the temperature coefficient of resistance is close to 0, and a criterion for an excellent thick film resistor is that -100 ppm/°C≦temperature coefficient of resistance≦100 ppm/°C.

The sheet resistance value of the thick film resistor is preferably high, and more preferably higher than 80 kΩ, for example.

The current noise of a thick film resistor is related to overload characteristics and reliability, and it can be said that the lower the value, the better the electrical characteristics of the thick film resistor. The thick film resistor obtained by the present invention also has excellent noise characteristics, specifically, preferably -3.0 dB or less, more preferably -4.0 dB or less.

The present invention will be explained in more detail using Examples and Comparative Examples, but the present invention is not limited to these Examples in any way.

(Example 1)
[Preparation of paste for thick film resistor]
A Si-B-Ca-Ba-Zn glass powder was prepared as a lead-free glass powder. The composition _of the glass powder was _SiO2 : 22% by mass, _B2O3 : 13% by mass, CaO: 5% by mass, BaO: 45% by mass, and ZnO: 12% by mass. The softening point of the glass was 700°C.

The glass powder was immersed in an ethanol solution containing hydrolyzed ethyl silicate ((C ₂ H ₅ O) ₄ Si, manufactured by Colcoat Co., Ltd.) (immersion step). In addition, the relationship between the amount of silica component adhering to the glass powder, the concentration of the ethanol solution containing ethyl silicate, and the immersion time of the glass powder was obtained in advance, and the amount of silica component adhering to the glass powder was determined experimentally. The ratio was adjusted to be 2.0% by mass based on the total mass of the glass powder and ruthenium oxide powder (2.35% by mass based on the glass powder).

Aggregates were obtained by vaporizing and removing ethanol and drying (drying step).

Subsequently, the aggregate was crushed using an agate mortar to finally obtain a silica component-attached glass powder (pulverization step). In the crushing step, the 50% volume cumulative particle size of the silica component-attached glass powder determined by particle size distribution measurement was adjusted to 1.2 μm.

On the other hand, a ruthenium oxide powder (manufactured by Sumitomo Metal Mining Co., Ltd.) having a BET specific surface area diameter of 36 nm was prepared as a lead-free ruthenium oxide powder. The ruthenium oxide powder and the silica component-adhered glass powder are weighed so that the amounts are 15% by mass and 85% by mass, respectively, based on the total mass of these powders, and then mixed. A composition was obtained (mixing step).

Next, the organic vehicle was weighed in an amount of 43 parts by mass to 100 parts by mass of this composition for thick film resistors, and mixed in a three-roll mill to obtain a paste for thick film resistors. Ta. The organic vehicle used was 15% by mass of ethyl cellulose dissolved in 85% by mass of terpineol.

[Formation of thick film resistor]
The obtained paste for a thick film resistor was printed on an electrode (Pd: 1% by mass, Ag: 99% by mass) that had been previously formed by firing on an alumina substrate, and dried at 150° C. for 5 minutes. Next, it was fired under conditions such that the peak temperature was 850° C., the holding time at this temperature was 9 minutes, and the total firing time was 30 minutes to obtain a thick film resistor. When printing the thick film resistor paste, make sure that the thickness of the thick film resistor after firing is 7 μm, the resistor width is 1.0 mm, and the resistor length (length between electrodes) is 1.0 mm. Adjusted to.

[evaluation]
The electrical characteristics of the obtained thick film resistor were evaluated by measuring a) sheet resistance value, b) resistance temperature coefficient, and c) current noise using the following method. These results are shown in Table 1.

a) Area resistance value The area resistance value is calculated by measuring the resistance values of the obtained 25 thick film resistors with a digital multimeter (manufactured by KEITHLEY, No. 2001) and taking the average (arithmetic mean). did.

b) Temperature coefficient of resistance The five thick film resistors obtained were held in environments of -55°C, 25°C, and 125°C for 15 minutes, respectively. Next, for each thick film resistor, the resistance values R _-55, R ₂₅ , and R ₁₂₅ of the thick film resistor held at each temperature were measured using a digital multimeter. Finally, for each thick film resistor, calculate the COLD-TCR and HOT-TCR based on the following formulas (A) and (B), and take the average (arithmetic mean) to obtain the temperature coefficient of resistance (COLD-TCR). TCR, HOT-TCR) were calculated.

COLD-TCR (ppm/°C)=(R _-55 - _R25 )/ _R25 /(-80)× ¹⁰⁶ ...(A)
HOT-TCR (ppm/°C) = (R ₁₂₅ - R ₂₅ )/R ₂₅ / (100) x 10 ⁶ ... (B)
c) Current noise Current noise is measured by applying a voltage equivalent to 1/10W to each thick film resistor using a noise meter (manufactured by Quan-Tech, 315c), and taking the average (arithmetic mean). It was calculated by

(Example 2)
In the dipping process, the amount of silica component on the surface of the glass powder was adjusted to be 4.0% by mass relative to the total mass of the ruthenium oxide powder and glass powder (4.7% by mass relative to the glass powder). A thick film resistor was formed in the same manner as in Example 1 except for the above. Further, in the same manner as in Example 1, the electrical characteristics of the obtained thick film resistor were evaluated. These results are shown in Table 1.

(Comparative example 1)
A thick film resistor was formed in the same manner as in Example 1 except that the dipping step was not performed. Further, in the same manner as in Example 1, the electrical characteristics of the obtained thick film resistor were evaluated. These results are shown in Table 1.

From Table 1, in Examples 1 and 2, the presence of silica components on the surface of the glass powder resulted in higher resistance and lower current noise in the thick film resistor compared to Comparative Example 1. be understood. Furthermore, it is understood that in Example 1 and Example 2, the temperature coefficient of resistance (TCR) of the thick film resistor is closer to 0 than in Comparative Example 1.

Claims (8)

a dipping step of immersing lead-free glass powder in a solution containing an organosilicon compound in which oxygen is bonded to silicon atoms;
a drying step of drying the glass powder after the dipping step to obtain a silica component-attached glass powder with a silica component attached to the surface;
a mixing step of mixing the silica component-attached glass powder and lead-free ruthenium oxide powder to obtain a lead-free thick film resistor composition;
Equipped with
The organosilicon compound is an ether compound represented by the general formula (A): (RO) ₄ Si (wherein R is an alkyl group),
A method for producing a composition for a thick film resistor. The method for producing a composition for a thick film resistor according to claim 1 , wherein the R is an alkyl group having 1 to 10 carbon atoms. 3. The method for producing a composition for a thick film resistor according to claim 2 , wherein the organosilicon compound is at least one selected from the group consisting of methyl silicate, ethyl silicate, propyl silicate, and butyl silicate. The dipping step is performed such that the content of the silica component contained in the silica component-attached glass powder is 0.5% by mass or more and 20% by mass or less based on the total amount of the glass powder and the ruthenium oxide powder. A method for producing a composition for a thick film resistor according to any one of claims 1 to 3 . The lead-free thick-film resistor composition is produced by the production method according to any one of claims 1 to 4 , comprising the step of kneading a lead-free thick-film resistor composition and an organic vehicle. A method for producing a paste for a thick film resistor using the produced lead-free composition for a thick film resistor. Containing lead-free glass powder and lead-free ruthenium oxide powder, on the surface of the lead-free glass powder, a compound represented by the general formula (A): (RO) ₄ Si (where R is an alkyl group) A composition for a thick film resistor, to which a silica component (SiO ₂ ) derived from an ether compound is attached. The silica component (SiO ₂ ) is attached to the surface of the glass powder, and the content of the silica component (SiO ₂ ) contained in the silica component-attached glass powder is relative to the total amount of the glass powder and the ruthenium oxide powder. The composition for a thick film resistor according to claim 6 , wherein the content is 0.5% by mass or more and 20% by mass or less. A paste for a thick film resistor, comprising a composition for a thick film resistor and an organic vehicle, wherein the composition for a thick film resistor is the composition for a thick film resistor according to claim 6 or 7 .