Thick-film resistor body

Abstract

The present invention relates to a thick-film resistor comprising ruthenium oxide and glass, the ruthenium oxide having a rutile-type crystal structure, and having Lc / La of 0.6885 or more and a crystallite diameter of 10 nm to 80 nm (inclusive) when the lattice constant of the a-axis as measured by X-ray diffraction is La and the lattice constant of the c-axis as measured by X-ray diffraction is Lc.

Description

Technical Field

[0001] This invention relates to thick film resistors. Background Technology

[0002] Chip resistors, hybrid ICs, or resistor networks are generally thick-film resistors formed by coating a thick-film resistive paste onto a ceramic substrate and then firing it.

[0003] As a composition for thick-film resistors, conductive particles containing ruthenium-based conductive powders, represented by ruthenium oxide powder, and glass powder as main components are widely used as conductive particles.

[0004] The reasons for using ruthenium-based conductive powders and glass powders in thick-film resistors include their ability to be sintered in air, which brings the temperature coefficient of resistance (TCR) close to 0, and the ability to form resistors with a wide range of resistance values.

[0005] In a composition for a thick-film resistor comprising ruthenium-based conductive powder and glass powder, the resistance value of the thick-film resistor varies depending on its proportions. Specifically, increasing the proportion of ruthenium-based conductive powder decreases the resistance value of the thick-film resistor, while decreasing the proportion increases it. Utilizing this, the desired resistance value can be achieved by adjusting the proportion of ruthenium-based conductive powder to glass powder in the thick-film resistor.

[0006] In recent years, the number of resistor mounting points in electrical / electronic equipment has increased, and there is a growing demand for high precision in the resistance values ​​of individual resistors, with a resistance temperature coefficient (TCR) close to 0.

[0007] As described above, in the composition for thick-film resistors comprising ruthenium-based conductive powder and glass powder, when a low resistance value is desired, the amount of ruthenium-based conductive powder is increased, and the amount of glass powder is decreased. Conversely, when a high resistance value is desired, the amount of ruthenium-based conductive powder is decreased, and the amount of glass powder is increased to adjust the resistance value.

[0008] However, it exhibits the characteristic that in the low-resistivity region with a large amount of ruthenium-based conductive powder, the temperature coefficient of resistance (TCR) tends to become positive, while in the high-resistivity region with less ruthenium-based conductive powder, the TCR tends to become negative. The temperature coefficient of resistance (TCR) reflects the change in resistance due to temperature variations, and is therefore one of the important characteristics of thick-film resistors. The temperature coefficient of resistance can be adjusted by adding metal oxides, primarily called modifiers, to the composition. It is relatively easy to adjust the temperature coefficient of resistance to be negative; examples of modifiers include manganese oxide, niobium oxide, tantalum oxide, and titanium oxide. However, it is difficult to adjust the temperature coefficient of resistance to be positive. Therefore, when conductive particles are used in thick-film resistors, a temperature coefficient of resistance close to 0 or greater than a positive number is desired.

[0009] The temperature coefficient of resistance (TCR) of thick film resistors is evaluated using room temperature as a reference, with the low-temperature resistance temperature coefficient (COLD-TCR) on the low-temperature side and the high-temperature resistance temperature coefficient (HOT-TCR) on the high-temperature side.

[0010] In recent years, the requirements for high precision in electronic components have been gradually increasing, requiring both the low-temperature resistance temperature coefficient (COLD-TCR) and the high-temperature resistance temperature coefficient (HOT-TCR) to be close to 0.

[0011] In thick-film resistors manufactured using a composition comprising ruthenium-based conductive powder and glass powder, it is generally difficult to make the low-temperature resistance temperature coefficient (COLD-TCR) on the low-temperature side and the high-temperature resistance temperature coefficient (HOT-TCR) on the high-temperature side the same. Furthermore, it is difficult to make either the COLD-TCR or the HOT-TCR close to 0.

[0012] Patent Document 1 discloses a thick-film resistor, characterized in that it contains a glass composition that is at least substantially lead-free and a conductive material that is substantially lead-free, which are mixed with an organic colorant to form a resistor paste, wherein the average particle size of the conductive material is 5 μm to 50 μm. Furthermore, the resistor paste is coated or printed and then fired to form the resistor.

[0013] According to Patent Document 1, it is possible to make the average particle size of the conductive material between 5 μm and 50 μm, thereby achieving a high resistance value of 10 kΩ / □ or higher, while having a small resistance deviation, a small absolute value of temperature characteristic (TCR), and good voltage withstand characteristic (STOL).

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: Japanese Patent Application Publication No. 2005-129806

[0017] Patent Document 2: Japanese Patent Application Publication No. 2005-209742 Summary of the Invention

[0018] The problem that the invention aims to solve

[0019] In recent years, it has become increasingly important for thick-film resistors to have both the low-temperature resistance temperature coefficient (COLD-TCR) on the low-temperature side and the high-temperature resistance temperature coefficient (HOT-TCR) on the high-temperature side close to zero, and to minimize the difference between the two. However, Patent Document 1 does not evaluate the difference between the low-temperature resistance temperature coefficient and the high-temperature resistance temperature coefficient on the low-temperature side.

[0020] In view of the problems of the prior art, one aspect of the present invention aims to provide a thick film resistor that makes it possible to make the temperature coefficient of resistance close to 0 and to reduce the difference between the temperature coefficient of resistance at low temperatures and the temperature coefficient of resistance at high temperatures.

[0021] Methods for solving problems

[0022] To address the aforementioned issues, the present invention provides a thick-film resistor.

[0023] It contains ruthenium oxide and glass.

[0024] The aforementioned ruthenium oxide has a rutile crystal structure.

[0025] When the lattice constant of the a-axis, determined by X-ray diffraction, is set as La, and the lattice constant of the c-axis is set as Lc, the Lc / La ratio is greater than 0.6885.

[0026] The crystallite diameter is between 10 nm and 80 nm.

[0027] Invention Effects

[0028] According to one aspect of the present invention, it is possible to provide a thick film resistor that makes the temperature coefficient of resistance close to 0 and reduces the difference between the temperature coefficient of resistance at low temperatures and the temperature coefficient of resistance at high temperatures. Attached Figure Description

[0029] Figure 1 This is an explanatory diagram showing the relationship between the lattice constants of the a-axis and c-axis of the ruthenium oxide powder used in the examples and comparative examples. Detailed Implementation

[0030] [Thick film resistor]

[0031] Hereinafter, one embodiment of the thick-film resistor of the present invention will be described.

[0032] The inventors of this invention have studied thick-film resistivity that can make the temperature coefficient of resistance close to 0 and reduce the difference between the temperature coefficient of resistance at low temperature and the temperature coefficient of resistance at high temperature, i.e., suppress it.

[0033] The results showed that by making the ratio of the lattice constant of the a-axis to the lattice constant of the ruthenium oxide constituting the thick-film resistor to a predetermined value or higher, the temperature coefficient of resistance (TCR) of the thick-film resistor approached 0. That is, it was found that the temperature coefficient of resistance at low temperature and high temperature of the thick-film resistor approached 0, and the difference between the two could also be reduced.

[0034] Furthermore, it was discovered that by keeping the crystallite diameter of ruthenium oxide constituting the thick film resistor within a predetermined range, the resistance value deviation can be reduced, thereby forming a thick film resistor with good electrical properties.

[0035] Based on the above understanding, the present invention was completed. The thick-film resistor of this embodiment will be described below.

[0036] Furthermore, here, we consider the variation in the composition of the thick-film resistor composition during the process of forming the thick-film resistor from the composition for the thick-film resistor. The composition for the thick-film resistor comprises glass powder and ruthenium-based conductive powder. In the composition for the thick-film resistor before firing, ruthenium-based conductive particles constituting the ruthenium conductive powder exist around the glass particles constituting the glass powder. Through heating during firing, the glass particles fuse together, and the ruthenium-based conductive particles approach each other to form a conductive path. Moreover, the resulting thick-film resistor comprises: a conductive path provided by the ruthenium-based conductive material formed by the ruthenium-based conductive particles, and glass as a matrix for maintaining the conductive path. That is, the composition of the thick-film resistor comprises a ruthenium-based conductive material and glass. In the thick-film resistor of this embodiment, ruthenium oxide is used as the ruthenium-based conductive material. Therefore, the thick-film resistor of this embodiment comprises ruthenium oxide and glass.

[0037] (1) Regarding the composition of thick film resistors

[0038] The components contained in the thick film resistor of this embodiment are described.

[0039] (1-1) Ruthenium oxide

[0040] (The ratio of the lattice constant Lc of the c-axis to the lattice constant La of the a-axis)

[0041] The inventors of this invention discovered that in a thick-film resistor containing ruthenium oxide and glass, the lattice constant of ruthenium oxide affects the properties of the thick-film resistor, thus completing this invention.

[0042] According to the inventors' research, ruthenium oxide preferably has a rutile crystal structure. Furthermore, when the lattice constant of the a-axis, determined by X-ray diffraction, is set as La, and the lattice constant of the c-axis is set as Lc, the ratio (Lc / La) of the c-axis lattice constant of ruthenium oxide to the a-axis lattice constant is important from the viewpoint of suppressing the temperature coefficient of resistance of the thick-film resistive body. Specifically, by making the Lc / La of ruthenium oxide 0.6885 or higher, and more preferably 0.6886 or higher, it is possible to bring the temperature coefficient of resistance (TCR) of the thick-film resistive body close to 0.

[0043] Furthermore, for example, ruthenium oxide with a tetragonal ruthenium-type crystal structure, crystallized in a sufficiently large mass state, has a lattice constant of 4.499 on its a-axis. The lattice constant of the c-axis is 3.107. Furthermore, the Lc / La ratio of the a-axis lattice constant La and the c-axis lattice constant Lc of a large number of ruthenium oxide states is 0.6906. The lattice constants of these large numbers of ruthenium oxide states are based on the International Diffraction Data Center.

[0044] In contrast, in the thick-film resistive body of this embodiment, which contains ruthenium oxide and glass, the lattice constant of ruthenium oxide with respect to the a-axis, c-axis, and further Lc / La is smaller compared to the bulk state. This is believed to be because the ruthenium oxide contained in the thick-film resistive body consists of fine ruthenium oxide particles.

[0045] According to the inventors' research, in thick-film resistives containing ruthenium oxide with an Lc / La ratio less than 0.6885, the low-temperature temperature coefficient of resistance (COLD-TCR) and the high-temperature temperature coefficient of resistance (HOT-TCR) differ significantly. Therefore, in thick-film resistives containing ruthenium oxide with an Lc / La ratio less than 0.6885, reducing the difference between the low-temperature temperature coefficient of resistance (COLD-TCR) and the high-temperature temperature coefficient of resistance (HOT-TCR) cannot bring them close to 0.

[0046] Furthermore, there is no particular upper limit to the ratio of the c-axis lattice constant Lc to the a-axis lattice constant La of the ruthenium oxide contained in the thick-film resistor of this embodiment, namely Lc / La. For example, when the crystallite diameter is 10 nm or more and 80 nm or less, Lc / La can be 0.690 or less.

[0047] The ratio Lc / La, the lattice constant of the c-axis, increases if the lattice constant of the c-axis increases and the lattice constant of the a-axis decreases. However, according to the inventors' research, no clear correlation has been observed between the lattice constants of the a-axis and c-axis of ruthenium oxide; for example, suppressing only the lattice constants of the a-axis or c-axis does not suppress the aforementioned Lc / La ratio.

[0048] Patent Document 2 focuses on the a-axis and b-axis of ruthenium oxide, disclosing that they are within a predetermined range. However, according to the inventors' research based on the present invention, simply having the lattice constants of the a-axis and b-axis of the ruthenium oxide powder within the predetermined range does not make the low-temperature resistance temperature coefficient (COLD-TCR) and high-temperature resistance temperature coefficient (HOT-TCR) of the thick-film resistor using the ruthenium oxide powder close to 0. Furthermore, even if the lattice constants of the a-axis and b-axis of the ruthenium oxide powder are within the predetermined range, the difference between the high-temperature resistance temperature coefficient and the low-temperature resistance temperature coefficient cannot be reduced.

[0049] Therefore, in thick film resistors, it is important to ensure that the low-temperature resistance temperature coefficient (COLD-TCR) and high-temperature resistance temperature coefficient (HOT-TCR) are close to 0, and to reduce the difference between the high-temperature resistance temperature coefficient and the low-temperature resistance temperature coefficient, so that Lc / La is above a predetermined value.

[0050] (Crystal diameter)

[0051] By making the crystallite diameter of ruthenium oxide contained in the thick film resistor of this embodiment 10 nm or more and 80 nm or less (100 nm or less), Above 800 (The following) thereby improves the resistance accuracy of the thick-film resistor. That is, it can suppress resistance deviations. Furthermore, by using ruthenium oxide containing a crystallite-to-lattice constant ratio Lc / La within a predetermined range, the difference between the low-temperature and high-temperature resistance coefficients of the thick-film resistor can be reduced, making both particularly close to 0. Furthermore, by satisfying the range of ruthenium oxide crystallite diameters, a thick-film resistor with excellent electrical properties can be formed.

[0052] To achieve an Lc / La ratio of 0.6885 or higher for ruthenium oxide in a thick-film resistor, the Lc / La ratio of the ruthenium oxide powder used as a raw material in the thick-film resistor composition and the resistive paste can be adjusted. According to the inventors' research, if a resistive paste containing ruthenium oxide powder with an Lc / La ratio ≥ 0.6913 is printed, dried, and fired, a thick-film resistor with an Lc / La ratio ≥ 0.6885 can be formed.

[0053] When the resistive paste is printed and dried below 150°C, and when the ruthenium oxide powder used as the raw material for the resistive paste is in its original state, the lattice constant and crystallite diameter of ruthenium oxide show almost no difference. This indicates that the lattice constant and crystallite diameter of the ruthenium oxide powder remain almost unchanged during the process of dispersing and mixing ruthenium oxide powder and glass powder in an organic color carrier. However, the lattice constant and crystallite diameter of ruthenium oxide measured in a thick-film resistor formed by sintering the dried resistive paste at a temperature above 800°C begin to change from the dried state. Specifically, the lattice constant La and crystallite diameter of ruthenium oxide along the a-axis increase, while the lattice constant Lc along the c-axis decreases. Therefore, by sintering the resistive paste, Lc / La decreases, and the crystallite diameter increases.

[0054] The lattice constant and crystallite diameter of ruthenium oxide can be determined by analyzing the diffraction patterns obtained from powder X-ray diffraction. In recent years, Rietveld analysis in powder X-ray diffraction has enabled the accurate determination and calculation of the lattice constant and crystallite diameter of the powder.

[0055] (1-2) Glass

[0056] Regardless of the glass composition, the thick-film resistor of this embodiment can achieve a resistance temperature coefficient close to 0, and the difference between the low-temperature resistance temperature coefficient and the high-temperature resistance temperature coefficient is reduced. That is, even if either lead-containing glass, which has been used conventionally, or lead-free glass that reduces the impact on human health and pollution, is used, a thick-film resistor with a resistance temperature coefficient close to 0 and high precision can be manufactured. Furthermore, the difference between the low-temperature resistance temperature coefficient and the high-temperature resistance temperature coefficient can be reduced.

[0057] Generally speaking, glass containing lead, which is used in thick-film resistors, can be used. However, due to concerns about environmental issues, there has been a growing desire in recent years to use lead-free glass.

[0058] In this embodiment, when the thick-film resistor contains lead-free glass, the lead-free glass preferably contains, for example, SiO2, B2O3, and RO (R represents one or more alkaline earth metal elements selected from Ca, Sr, and Ba). In this case, when the total amount of SiO2, B2O3, and RO is set to 100 parts by mass, it is preferable that SiO2 is contained in a proportion of 18 to 50 parts by mass, B2O3 in a proportion of 10 to 30 parts by mass, and RO in a proportion of 35 to 70 parts by mass.

[0059] The thick-film resistor of this embodiment contains the aforementioned glass, thereby enabling the temperature coefficient of resistance to approach 0 particularly easily.

[0060] The glass contained in the thick-film resistor of this embodiment is derived from glass powder used in thick-film resistor compositions, etc. Therefore, the reasons for the suitable range of each component are the same as those explained in the description of glass powder in thick-film resistor compositions, and therefore the explanation is omitted.

[0061] In the case of lead-free glass, the thick-film resistor preferably contains SiO2, B2O3, and RO as essential components. The glass can also be composed solely of SiO2, B2O3, and RO, and may further contain other components. Examples of other components include Al2O3, ZrO2, TiO2, SnO2, ZnO, Li2O, Na2O, and K2O. The presence of Al2O3 suppresses phase separation in the glass, ZrO2 and TiO2 improve its weather resistance, and SnO2, ZnO, Li2O, Na2O, and K2O enhance its fluidity.

[0062] (2) The ratio of ruthenium oxide to glass

[0063] Depending on the desired resistance value, the ratio of ruthenium oxide to glass in the thick-film resistor can vary. Therefore, the mass ratio of ruthenium oxide to glass in the thick-film resistor of this embodiment is not particularly limited.

[0064] However, in this embodiment, the mass ratio of ruthenium oxide to glass is preferably in the range of 60:40 to 5:95. That is, when the total mass of ruthenium oxide and glass is 100%, the mass ratio of ruthenium oxide is preferably 5% to 60%.

[0065] By ensuring that the total mass of ruthenium oxide and glass is 100%, and by keeping the mass ratio of ruthenium oxide below 60%, it is possible to suppress the embrittlement of thick film resistors and prevent the occurrence of cracks.

[0066] Furthermore, by ensuring that the total mass of ruthenium oxide and glass is 100%, and by making the mass ratio of ruthenium oxide 5% or more, the resistance value of the thick film resistor is prevented from becoming excessively high, thereby improving stability.

[0067] In the thick-film resistor of this embodiment, various additives may be included in addition to ruthenium oxide and glass. That is, the thick-film resistor of this embodiment may contain ruthenium oxide, glass, and additives. Such additives will be described in the composition for thick-film resistors.

[0068] Furthermore, the thick-film resistor of this embodiment can also be composed solely of ruthenium oxide and glass. Additionally, the thick-film resistor of this embodiment can also be composed solely of ruthenium oxide, glass, and additives. However, even in any of the above cases, the presence of unavoidable impurities cannot be ruled out.

[0069] (3) Characteristics of thick film resistors

[0070] Regarding the low-temperature resistance temperature coefficient and high-temperature resistance temperature coefficient of the thick-film resistor in this embodiment, they can approach 0, and the difference between them is also reduced. In the thick-film resistor of this embodiment, the resistance temperature coefficient is preferably -50ppm / ℃ or higher and +50ppm / ℃ or lower, more preferably -40ppm / ℃ or higher and +40ppm / ℃ or lower, and even more preferably -30ppm / ℃ or higher and +30ppm / ℃ or lower. Furthermore, the above ranges are suitable for either the high-temperature resistance temperature coefficient or the low-temperature resistance temperature coefficient.

[0071] Furthermore, regarding the thick-film resistor, the difference between the high-temperature resistance temperature coefficient and the low-temperature resistance temperature coefficient is preferably 70 ppm / ℃ or less, more preferably 60 ppm / ℃ or less. As shown in the embodiments described later, in the thick-film resistor of this embodiment, the low-temperature resistance temperature coefficient and the high-temperature resistance temperature coefficient can be within the above-mentioned range, for example, they can be -30 ppm / ℃ or more and +30 ppm / ℃ or less. Furthermore, according to this thick-film resistor, the difference between the high-temperature resistance temperature coefficient and the low-temperature resistance temperature coefficient is reduced.

[0072] Furthermore, the thick-film resistor of this embodiment can achieve a high-precision temperature coefficient of resistance and resistance value. In addition, it can also achieve excellent characteristics even under current noise, short-time overload test (STOL), etc.

[0073] In addition, the COLD-TCR, which is the temperature coefficient of resistance at low temperatures, can be calculated using the following equation (1).

[0074] Furthermore, the HOT-TCR, which is the temperature coefficient of high temperature resistance, can be calculated using the following equation (2).

[0075]

[0076]

[0077] Here, R -55 R is the resistance value at a temperature of -55℃. 25 R is the resistance value at 25℃. 125 This is the resistance value at a temperature of 125℃.

[0078] Thus, the thick-film resistor according to this embodiment can achieve excellent characteristics in terms of resistance temperature coefficient, resistance value accuracy, current noise, and short-time overload test.

[0079] [Composition for thick film resistors]

[0080] Next, an example of the composition for thick-film resistors according to this embodiment will be described.

[0081] The aforementioned thick-film resistor can be manufactured using a thick-film resistor composition comprising ruthenium oxide powder as conductive particles and glass powder.

[0082] The following describes the components contained in the thick-film resistor composition suitable for use in manufacturing the thick-film resistor of this embodiment.

[0083] (1) Ruthenium oxide powder

[0084] As previously described, the ruthenium oxide powder has a rutile crystal structure. When the lattice constant of the a-axis, determined by X-ray diffraction, is set as La and the lattice constant of the c-axis is set as Lc, it is preferable that Lc / La is 0.6913 or higher and the crystallite diameter is 10 nm or higher and 80 nm or lower.

[0085] The particle size of ruthenium oxide powder is not particularly limited, but the specific surface area diameter of the ruthenium oxide powder contained in the thick film resistor composition of this embodiment is preferably, for example, 10 nm or more and 115 nm or less.

[0086] The specific surface area diameter of ruthenium oxide powder can be calculated from its specific surface area. Specifically, if the particle size, which is the specific surface area diameter of ruthenium oxide powder, is set as D (nm), and the density is set as ρ (g / cm³), then... 3 Let the specific surface area be S(m). 2 If the particles contained in the g are considered to be spheres, then the following relationship (3) holds true.

[0087]

[0088] In this embodiment, the density ρ of ruthenium oxide can be set to 7.05 g / cm³. 3 The particle size, which is the specific surface area, is calculated by equation (3).

[0089] (2) Glass powder

[0090] There are no particular limitations on the glass powder used; for example, the glass powder with the composition used in thick film resistor compositions can be used.

[0091] (Example of the composition of glass powder)

[0092] As for the glass powder that can be used in the composition for the thick film resistor of this embodiment, for example, in addition to lead aluminoborosilicate glass, one or more can be selected from lead-free zinc borosilicate glass, calcium borosilicate glass, and barium borosilicate glass.

[0093] Glass is generally manufactured by simultaneously mixing ingredients or their precursors with a predetermined purpose, melting the resulting mixture, and then quenching it. The melting temperature is not particularly limited, but may be around 1400°C. Furthermore, quenching is often performed by immersing the molten material in cold water or by flowing it on a cold belt. To prepare the paste raw material for forming thick-film resistors, the glass is pulverized. Pulverization is carried out using ball mills, vibratory mills, planetary mills, or bead mills until the target particle size is achieved.

[0094] Generally speaking, compositions using glass powder containing lead, which is used in thick-film resistors, can be used. However, due to concerns about environmental issues, in recent years, there has been a desire to use compositions using lead-free glass powder.

[0095] In the composition of the lead-free thick-film resistor, the fluidity during firing is adjusted by incorporating metal oxides other than SiO2, which serve as the framework. Metal oxides other than SiO2 include B2O3, RO (where R represents one or more alkaline earth metal elements selected from Ca, Sr, and Ba), etc. Therefore, the glass powder used in the thick-film resistor composition of this embodiment preferably contains SiO2, B2O3, and RO. Furthermore, when the total amount of SiO2, B2O3, and RO in the glass composition is set to 100 parts by mass, the glass powder preferably contains SiO2 in a proportion of 18 to 50 parts by mass, B2O3 in a proportion of 10 to 30 parts by mass, and RO in a proportion of 35 to 70 parts by mass. By using such glass powder, the temperature coefficient of resistance of the resulting thick-film resistor can be made particularly easy to approach 0.

[0096] When the total amount of SiO2, B2O3, and RO in the glass composition of the glass powder is set to 100 parts by mass, by making SiO2 18 parts by mass or more, glass can be easily manufactured and weather resistance can be improved. Furthermore, by making SiO2 50 parts by mass or less, the softening temperature of the glass can be suppressed and the fluidity can be improved.

[0097] In the glass composition of glass powder, by making B2O3 10 parts by mass or more, the softening temperature of the glass powder can be suppressed and its fluidity improved. Furthermore, by making B2O3 30 parts by mass or less, weather resistance is improved.

[0098] In the glass composition of glass powder, by setting RO to 35 parts by mass or more, the softening temperature of the glass can be suppressed, and the fluidity can be improved. Furthermore, by setting RO to 70 parts by mass or less, crystallization can be suppressed, making it easier to manufacture glass.

[0099] The glass powder used in the lead-free thick-film resistor composition preferably contains SiO2, B2O3, and RO as essential components. This glass powder can also consist solely of SiO2, B2O3, and RO, and other components can be included to adjust the weather resistance and flowability during firing. Examples of other components include Al2O3, ZrO2, TiO2, SnO2, ZnO, Li2O, Na2O, and K2O. The presence of Al2O3 suppresses phase separation in the glass, ZrO2 and TiO2 improve the weather resistance of the glass, and SnO2, ZnO, Li2O, Na2O, and K2O improve the flowability of the glass.

[0100] (Softening point)

[0101] The softening point is a measure that affects the flowability of glass during the firing of compositions for thick-film resistors.

[0102] Generally speaking, the temperature for manufacturing thick film resistors, the composition for thick film resistors, and the paste for firing thick film resistors is between 800°C and 900°C.

[0103] Thus, when the firing temperature of the thick film resistor composition, etc., used in manufacturing the thick film resistor is 800°C or higher and 900°C or lower, the softening point of the glass used in the thick film resistor composition of this embodiment is preferably 600°C or higher and 800°C or lower, and more preferably 600°C or higher and 750°C or lower.

[0104] Here, the softening point is the temperature at which the next peak of the differential thermal analysis curve on the high-temperature side decreases, compared to the temperature at which the glass is heated in the atmosphere at a rate of 10 °C / min using differential thermal analysis (TG-DTA).

[0105] (particle size)

[0106] There is no particular limitation on the particle size of the glass powder used in the paste for thick-film resistors. However, if the particle size is too large, it will increase the resistance deviation and reduce the load characteristics of the thick-film resistor. To avoid these issues, the cumulative particle size of the glass powder at 50% volume is preferably below 5 μm, more preferably below 3 μm, and even more preferably below 1.5 μm. Glass can be pulverized using ball mills, planetary mills, bead mills, etc., and wet pulverization is preferred to achieve a sharp particle size.

[0107] Furthermore, if the particle size of the glass powder is made too small, there is a concern that productivity will decrease and the mixing of impurities will increase. Therefore, the cumulative particle size of the glass powder at 50% volume is preferably 0.5 μm or more.

[0108] The 50% volumetric cumulative particle size refers to the particle size at which the cumulative volumetric value of the particle size distribution, obtained through laser diffraction and scattering methods, reaches 50%.

[0109] (3) Mixing ratio of ruthenium oxide powder to glass powder

[0110] The ratio of ruthenium oxide powder to glass powder in the composition for thick-film resistors can be changed by the desired resistance value, etc. Therefore, the mass ratio of ruthenium oxide powder to glass powder in the composition for thick-film resistors in this embodiment is not particularly limited.

[0111] However, in this embodiment, the composition for thick-film resistors is preferably in the range of ruthenium oxide powder to glass powder mass ratio of 60:40 to 5:95. That is, when the total mass of ruthenium oxide powder and glass powder is set to 100%, the mass ratio of ruthenium oxide powder is preferably 5% to 60%. The ratio of ruthenium oxide powder to glass powder in the composition for thick-film resistors is also maintained during the formation of the thick-film resistor, becoming the ratio of ruthenium oxide to glass in the thick-film resistor.

[0112] When the total mass of ruthenium oxide powder and glass powder is set to 100%, by keeping the mass ratio of ruthenium oxide powder below 60%, it is possible to suppress the brittleness of the sintered film and prevent the occurrence of cracks.

[0113] Furthermore, when the total mass of ruthenium oxide powder and glass powder is set to 100%, the mass ratio of ruthenium oxide powder is 5% or more, thereby preventing the resistance value of the thick film resistor from becoming excessively high and improving its stability.

[0114] (4) About additives

[0115] The thick-film resistor composition of this embodiment can also be composed solely of ruthenium oxide powder and glass powder, and may further contain additives. That is, the thick-film resistor composition of this embodiment can contain ruthenium oxide powder, glass powder, and additives. The thick-film resistor composition of this embodiment can also be composed solely of ruthenium oxide powder, glass powder, and additives. Furthermore, even in the above cases, it is not ruled out that the thick-film resistor composition may contain unavoidable impurities.

[0116] In cases where a thick-film resistor with a lower desired resistance value is desired, the thick-film resistor of this embodiment may also contain Ag and Pd.

[0117] The composition for thick-film resistors according to this embodiment includes ruthenium oxide powder and glass powder as described above, and contains Ag and Pd, so that even when manufacturing a thick-film resistor with reduced resistance, the low-temperature resistance temperature coefficient and the high-temperature resistance temperature coefficient can be close to 0.

[0118] The composition for thick-film resistors in this embodiment aims to improve and adjust the resistance value, temperature coefficient of resistance, voltage load characteristics, and tailorability of thick-film resistors. Generally, it may also contain additives.

[0119] Representative additives include powders selected from one or more of the following: Nb2O5, Ta2O5, TiO2, MnO2, CuO, ZrO2, Al2O3, SiO2, and ZrSiO4.

[0120] Nb₂O₅, Ta₂O₅, TiO₂, and MnO₂ reduce the resistance variation when a voltage load is applied to a thick-film resistive body, but they shift the temperature coefficient of resistance negatively. CuO reduces the resistance of the thick-film resistive body and shifts the temperature coefficient of resistance positively. ZrO₂, Al₂O₃, SiO₂, and ZrSiO₄ suppress the elongation of microcracks that are easily generated by laser trimming of the resistance of the thick-film resistive body.

[0121] The thick-film resistor composition of this embodiment, by containing these additives, enables the production of thick-film resistors with superior properties. Furthermore, when the thick-film resistor composition of this embodiment contains the aforementioned additives, the thick-film resistor manufactured using this composition also contains the corresponding additives.

[0122] The content of the additives in the composition for the thick-film resistor of this embodiment is adjusted according to the purpose. When the total amount of ruthenium oxide powder and glass powder is set to 100 parts by mass, it is preferable to contain more than 0 and less than 20 parts by mass. In the thick-film resistor, it is preferable to contain additives within the same range.

[0123] [Paste for thick film resistors]

[0124] Next, the paste for forming the thick film resistor in this embodiment will be described.

[0125] The paste for forming the thick-film resistor of this embodiment can contain ruthenium oxide powder, glass powder, and an organic colorant. The paste for the thick-film resistor of this embodiment can also consist solely of ruthenium oxide powder, glass powder, and an organic colorant; even in this case, the presence of unavoidable impurities is not excluded.

[0126] In order to make both ruthenium oxide powder and glass powder into pastes for thick-film resistors used in printing, they can be mixed and dispersed in an organic color carrier.

[0127] Furthermore, the thick-film resistor paste of this embodiment may further contain the additives described in the thick-film resistor composition. In this case, the ruthenium oxide powder, glass powder, and additives contained in the thick-film resistor paste of this embodiment are preferably mixed and dispersed in an organic color carrier in order to produce a thick-film resistor paste for printing.

[0128] The paste for the thick film resistor in this embodiment can also be composed of only ruthenium oxide powder, glass powder, additives, and organic color carriers. Even in this case, it is not excluded that it contains unavoidable impurities.

[0129] The following describes the components contained in the paste for forming the thick-film resistor of this embodiment.

[0130] (1) Regarding the composition of the paste used for thick film resistors

[0131] (1-1) Ruthenium oxide powder

[0132] As the ruthenium oxide powder, the ruthenium oxide powder described in the thick-film resistor composition can be used. That is, the ruthenium oxide powder contained in the thick-film resistor paste of this embodiment preferably has a rutile crystal structure. Moreover, when the lattice constant of the a-axis, as determined by X-ray diffraction, is set to La and the lattice constant of the c-axis is set to Lc, the ruthenium oxide powder preferably has an Lc / La ratio of 0.6913 or higher and a crystallite diameter of 10 nm or more and 80 nm or less.

[0133] (1-2) Glass powder

[0134] As the glass powder, the glass powder that has been used in thick film resistor pastes can be used.

[0135] The glass powder can, for example, contain SiO2, B2O3, and RO (R represents one or more alkaline earth metal elements selected from Ca, Sr, and Ba). Furthermore, when the total amount of SiO2, B2O3, and RO is set to 100 parts by mass, the glass powder preferably contains SiO2 in a proportion of 18 to 50 parts by mass, B2O3 in a proportion of 10 to 30 parts by mass, and RO in a proportion of 35 to 70 parts by mass. By using such a glass powder, the temperature coefficient of resistance of the resulting thick-film resistor can be made particularly easy to approach 0.

[0136] (1-3) Mixing ratio of ruthenium oxide powder to glass powder

[0137] Depending on the desired resistance value, the ratio of ruthenium oxide powder to glass powder in the thick-film resistor paste can be varied. Therefore, the mass ratio of ruthenium oxide powder to glass powder in the thick-film resistor paste of this embodiment is not particularly limited.

[0138] However, in this embodiment, the paste for the thick-film resistor is preferably in the range of ruthenium oxide powder to glass powder mass ratio of 60:40 to 5:95. That is, when the total mass of ruthenium oxide powder and glass powder is set to 100%, the mass ratio of ruthenium oxide powder is preferably 5% to 60%.

[0139] (1-4) Organic color carriers

[0140] The organic colorant contained in the thick film resistor paste of this embodiment is not particularly limited, and various organic colorants can be used.

[0141] Organic color carriers, for example, are suitable for use in solutions containing resins such as ethyl cellulose, acrylate, methacrylate, rosin, and maleate in solvents such as terpineol, butyl carbitol, and butyl carbitol acetate.

[0142] Dispersants, plasticizers, etc. can also be added to organic color carriers as needed.

[0143] (1-5) Additives

[0144] In the thick-film resistor paste of this embodiment, in addition to the dispersant and plasticizer described above as organic color carriers, it may also contain various additives described in the thick-film resistor composition.

[0145] (2) Regarding the dispersion method

[0146] As described above, ruthenium oxide powder and glass powder, with additives added as needed, are preferably mixed and dispersed in an organic color carrier.

[0147] There are no particular limitations on the dispersion method of ruthenium oxide powder, glass powder, additives, etc. For example, dispersion is conventionally performed using a three-roll mill, bead mill, planetary mill, etc., which disperse fine particles. The proportion of organic colorant can be appropriately adjusted by the printing and coating method of the thick film resistor paste, and therefore is not particularly limited. For example, when the total amount of ruthenium oxide powder, glass powder, and additives is set to 100 parts by mass, the thick film resistor paste preferably contains organic colorant in the range of 20 to 200 parts by mass.

[0148] [Manufacturing method of thick film resistors]

[0149] Next, the method for manufacturing the thick-film resistor according to this embodiment will be described. Furthermore, the method for manufacturing the thick-film resistor according to this embodiment can manufacture the previously described thick-film resistor; therefore, repeated descriptions are omitted.

[0150] The aforementioned thick-film resistors can be manufactured, for example, using the aforementioned thick-film resistor compositions or thick-film resistor pastes.

[0151] Therefore, the aforementioned thick film resistor can contain ruthenium oxide derived from ruthenium oxide powder and glass derived from glass powder.

[0152] The manufacturing method of the thick-film resistor in this embodiment is not particularly limited. For example, the existing thick-film resistor can be formed by firing the composition on a ceramic substrate. In addition, as described above, the existing thick-film resistor can also be formed by coating a paste onto a ceramic substrate, drying, and firing.

[0153] Therefore, the manufacturing method of the thick film resistor in this embodiment can be manufactured using the existing thick film resistor paste, and can include the following printing process, drying process, and firing process.

[0154] In the printing process, for example, the paste for the thick film resistor can be printed between a pair of electrodes formed by a known thick film technology.

[0155] During the drying process, heating and drying can cause the solvents, such as organic colorants, contained in the paste to evaporate from the thick film resistive body that constitutes the printing film printed in the printing process.

[0156] In the firing process, the printed film dried in the drying process can be fired at a temperature condition with a peak temperature of 800℃ to 900℃.

[0157] By performing the above-described firing process, the thick-film resistor of this embodiment can be manufactured.

[0158] It is also possible to form a coated glass on the surface of the obtained thick film resistor using known thick film technology, and adjust the resistance value by known laser trimming.

[0159] Example

[0160] The following specific embodiments and comparative examples are provided for illustration, but the present invention is not limited to these embodiments.

[0161] [Evaluation Method]

[0162] (1) Evaluation methods for ruthenium oxide powder and glass powder used as raw materials

[0163] (1-1) Lattice constant, crystallite diameter

[0164] The lattice constant and crystallite size of ruthenium oxide powder were determined by Rietveld analysis using X-ray diffraction.

[0165] In addition, the lattice constant of the a-axis of the ruthenium oxide powder is set as La, and the lattice constant of the c-axis is set as Lc, and Lc / La is calculated.

[0166] (1-2) Specific surface area diameter

[0167] The specific surface area diameter of ruthenium oxide powder is calculated from its specific surface area and density. The specific surface area was determined using the simple BET1 point method. If the specific surface area diameter is denoted as D (nm) and the density as ρ (g / cm³), then... 3 Let the specific surface area be S(m). 2 If the particles contained in the ruthenium oxide powder are considered to be spheres, then the following equation (A) holds true. The specific surface area diameter calculated using this equation (D) is taken as the specific surface area diameter of the ruthenium oxide powder.

[0168] D(nm) = 6 × 10 3 / (ρ S) (A)

[0169] When the specific surface area is calculated, the density ρ of ruthenium oxide is 7.05 g / cm³. 3 .

[0170] In addition, the ratio of crystal diameter to specific surface area diameter was calculated.

[0171] (1-3) Softening point of glass powder

[0172] The softening point of the glass powder is determined by heating the glass powder in the atmosphere at a rate of 10°C per minute using differential thermal analysis (TG-DTA), and comparing the temperature at which the temperature decreases on the lowest side of the resulting differential thermal curve with the temperature at which the temperature decreases on the next peak on the high-temperature side.

[0173] (2) Evaluation methods for thick film resistors

[0174] (2-1)Film thickness

[0175] The film thickness of the thick-film resistor was first measured using a thickness roughness gauge with a stylus to measure the film thickness of five thick-film resistors manufactured under the same conditions in each embodiment and comparative example. Furthermore, the film thicknesses of the five obtained thick-film resistors were averaged to calculate the film thickness (firing film thickness) of the thick-film resistor in each embodiment and comparative example.

[0176] (2-2) Area resistivity and CVR (coefficient of variation of area resistivity)

[0177] The area resistivity value was calculated by averaging the area resistivity values ​​of 25 thick-film resistors manufactured under the same conditions in each embodiment and comparative example.

[0178] The area resistivity of each thick-film resistor was measured using a digital multimeter (KEITHLEY, No. 2001).

[0179] The coefficient of variation (CVR) of the area resistivity is calculated by dividing the standard deviation of the area resistivity values ​​of 25 thick-film resistors manufactured under the same conditions in each embodiment and comparative example by the average value. CVR represents the deviation of the resistance value, and a small value means a small deviation of the resistance value. Therefore, CVR is preferably, for example, 5% or less.

[0180] (2-3) Temperature coefficient of resistance

[0181] For the five thick-film resistors fabricated under the same conditions in each embodiment and comparative example, their resistance values ​​were measured after being kept at -55°C, 25°C, and 125°C for 15 minutes respectively, and each resistance value was set as R. -55 R 25 R 125 .

[0182] Furthermore, the low-temperature resistance temperature coefficient (COLD-TCR) and high-temperature resistance temperature coefficient (HOT-TCR) of each thick-film resistor are calculated using the following equations (B) and (C), and the average of the five thick-film resistors is obtained. The low-temperature resistance temperature coefficient is shown in the "C-TCR" column in Tables 3 and 4, and the high-temperature resistance temperature coefficient is shown in the "H-TCR" column in Tables 3 and 4.

[0183] The expected temperature coefficient of resistance (COT-TCR) and HOT-TCR are both close to 0. For any temperature coefficient of resistance, -50ppm / ℃ or higher and +50ppm / ℃ or lower are considered to be the standard for high-precision resistors.

[0184] COLD-TCR (ppm / ℃) = (R -55 -R 25 ) / R 25 / (-80)×10 6 (B)

[0185] HOT-TCR (ppm / ℃) = (R 125 -R 25 ) / R 25 / (100)×10 6 (C)

[0186] In addition, in each embodiment and comparative example, the difference between COLD-TCR and HOT-TCR was calculated and displayed in the "Difference between H / C" column of Tables 3 and 4.

[0187] (2-4) Short-duration overload test (STOL)

[0188] The resistance change rate in the Short-Time Overload Test (STOL) is calculated by applying an overload voltage equivalent to 2.5 times the voltage of 0.25W (400V if exceeding 400V) to the thick-film resistors fabricated in each embodiment and comparative example for 5 seconds, and then calculating the resistance change rate after voltage application. The resistance value is measured using the same procedure as for the area resistance value described previously. For the STOL evaluation, for each embodiment and comparative example, the resistance change rate is measured and calculated for 10 thick-film resistors. The resistance change rate in the Short-Time Overload Test (STOL) is preferably within ±1%, more preferably within ±0.5%.

[0189] (2-5) Current noise

[0190] The current noise of five thick-film resistors fabricated under the same conditions in each embodiment and comparative example was measured, and the average value was calculated.

[0191] Current noise was measured using a noise meter (Quan-Tech type: 315c) with a voltage equivalent to 1 / 10W applied. The current noise of a thick-film resistor is related to its overload characteristics and reliability; the lower the value, the better the electrical characteristics of the resistor.

[0192] (2-6) The lattice constant and crystallite diameter of ruthenium oxide contained in the dry film and thick film resistor.

[0193] A composition for thick-film resistors was prepared by combining ruthenium oxide powder, glass powder, and additive powders (MnO2, TiO2, CuO, SiO2) in the proportions listed in Tables 3 and 4. Furthermore, using this composition, a paste for thick-film resistors (described later) was prepared, and this paste was screen-printed onto a ceramic substrate (alumina substrate) containing 96% by mass alumina to obtain a printed film. A dried film and a sintered body were obtained through a drying process and a firing process (described later). In the drying process, the film was dried at a peak temperature of 150°C for a peak time of 5 minutes. In the firing process, the dried film was fired at a peak temperature of 850°C for a peak time of 9 minutes to obtain a sintered body (sintered film). X-ray diffraction measurements were performed on the obtained dried film and sintered body, and the lattice constant and crystallite size of ruthenium oxide contained in the dried film and sintered body were determined by Rietveld analysis in X-ray diffraction. The lattice constant and crystallite size of ruthenium oxide in the dried film are shown in the "Characteristics of Ruthenium Oxide in the Dry Film" column of Tables 3 and 4. Similarly, the lattice constant and crystallite size of ruthenium oxide in the thick-film resistive body are shown in the "Characteristics of Ruthenium Oxide in the Thick-film Resistor" column of Tables 3 and 4.

[0194] Current noise is simply recorded as noise in Tables 3 and 4.

[0195] [Examples 1 to 10]

[0196] (1) Composition for thick film resistors

[0197] In Examples 1 to 10, ruthenium oxide powder, glass powder, and additive powders (MnO2, TiO2, CuO, SiO2) were mixed in the proportions shown in Table 3 to prepare a composition for thick film resistors.

[0198] In addition, in Table 3, "RuO2" indicates the proportion of ruthenium oxide powder, and "glass" indicates the proportion of glass powder. Furthermore, "MnO2", "TiO2", "CuO", and "SiO2" indicate the proportions of each component of the additive.

[0199] For example, in Example 1, as shown in the "Ruthenium Oxide Powder Type" column of Table 3, ruthenium oxide powder of type A in Table 1 is used. Furthermore, in Example 1, as shown in the "Glass Powder Type" column of Table 3, glass powder of type a in Table 2 is used.

[0200] Therefore, in Example 1, 50 parts by weight of ruthenium oxide powder of A, 50 parts by weight of glass powder of a, 1.5 parts by weight of MnO2 as an additive, and 1 part by weight of CuO were mixed to prepare a composition for thick film resistors.

[0201] (Ruthenium oxide powder)

[0202] The specific surface area, crystallite diameter, and lattice constant of the ruthenium oxide powders A to G used in each embodiment are shown in Table 1. The "Characteristics of the Raw Material Ruthenium Oxide Powder" column in Table 3 also shows the crystallite diameter and lattice constant of the ruthenium oxide powders used in each embodiment. In Table 1, "c-axis lattice constant / a-axis lattice constant" corresponds to Lc / La, which represents the ratio of the c-axis lattice constant Lc to the a-axis lattice constant La.

[0203] in addition, Figure 1 This shows the relationship between the lattice constants of the ruthenium oxide powders used in the examples and comparative examples, specifically the lattice constants of the a-axis and c-axis. Figure 1 As shown, it can be confirmed that no clear correlation was observed between the lattice constant of the a-axis and the lattice constant of the c-axis.

[0204] (Glass powder)

[0205] In addition, the composition of the glass powder used in each embodiment and comparative example is shown in Table 2.

[0206] In the examples and comparative examples, from the viewpoint of preventing environmental pollution, glass powders a to c that do not contain lead are used, and it is not a problem to use glass containing lead that has been used all along.

[0207] Furthermore, glass powders a through c are all pulverized using a laser diffraction particle size analyzer, with a median particle size of 1.3 μm to 1.5 μm. That is, the cumulative volume particle size of any one of glass powders a through c is 1.3 μm to 1.5 μm.

[0208] (additive)

[0209] As an additive, one or more selected from MnO2, TiO2, CuO, and SiO2 are used, as described above.

[0210] The particle sizes of the additives are 0.5 μm for MnO2, 0.3 μm for TiO2, 0.5 μm for CuO, and 15 nm for SiO2.

[0211] The particle sizes of MnO2, TiO2, and CuO mentioned above are similar to those of glass powders, referring to the median particle size in the particle size distribution measured using a laser diffraction particle size analyzer. That is, the aforementioned particle sizes refer to the 50% volumetric cumulative particle size.

[0212] The particle size of SiO2 described above is the specific surface area diameter, which is determined using the BET method. Specifically, the specific surface area diameter is calculated in the same manner as that of ruthenium oxide powder. Furthermore, the density ρ of SiO2 is 2.2 g / cm³. 3 .

[0213] (2) Paste for thick film resistors

[0214] For the thick-film resistor composition of each embodiment, an organic colorant in proportion of 43 parts by weight is added relative to 100 parts by weight of ruthenium oxide powder and glass powder additive, and the mixture is dispersed using a three-roll mill to prepare a paste for thick-film resistor.

[0215] Furthermore, as the organic color carrier, a mixture of ethyl cellulose at a ratio of 5% to 25% by mass and terpineol at a ratio of 75% to 95% by mass was used. The proportions of the above-mentioned components in the organic color carrier were adjusted within the above-mentioned ranges so that the viscosity of the thick-film resistor pastes described in Examples 1 to 10 was approximately the same.

[0216] (3) Thick film resistor

[0217] Beforehand, the paste for the thick film resistor prepared in each embodiment is printed on an alumina substrate (alumina substrate) to form a printed film (printing process).

[0218] The printed film obtained from the printing process was dried in a manner that set the peak temperature to 150°C and the holding time at the peak temperature to 5 minutes (drying process).

[0219] Next, the dried film obtained from the drying process is fired to a peak temperature of 850°C and a holding time at the peak temperature of 9 minutes to form a thick film resistor (firing process).

[0220] The sample used for measuring the lattice constant and crystallite diameter of ruthenium oxide was fabricated in a square pattern with a resistive element size of 20.0 mm × 20.0 mm.

[0221] For measuring film thickness, area resistivity, CVR, temperature coefficient of resistance, short-time overload test (STOL), and current noise, a thick-film resistive body paste is used between a pair of electrodes pre-cast on an alumina substrate. As the aforementioned pair of electrodes, a thick-film Ag / Pd mixture of 1% Pd and 99% Ag is used. Furthermore, the thick-film resistive body sample used for measuring area resistivity, etc., is formed such that the resistive body width (1.0 mm) and resistive body length (between electrodes) are 1.0 mm between the pair of electrodes.

[0222] The obtained thick-film resistor was evaluated as described above. The evaluation results are shown in Table 3.

[0223] In addition, it can be confirmed that any of the ruthenium oxide contained in the thick film resistors prepared by Examples 1 to 10 has a rutile crystal structure.

[0224] [Table 1]

[0225]

[0226] [Table 2]

[0227]

[0228] [Table 3]

[0229]

[0230] [Comparative Examples 1 to 8]

[0231] The composition for thick-film resistors and the paste for thick-film resistors were prepared using ruthenium oxide powder, glass powder, and additives as shown in Table 4, with the amounts added in the proportions shown in Table 4. Except for this, the same steps as in Examples 1 to 10 were followed. Furthermore, thick-film resistors were prepared using the pastes for thick-film resistors prepared in each comparative example, except for this, using the same steps as in Examples 1 to 10, and then evaluated. The evaluation results are shown in Table 4.

[0232] [Table 4]

[0233]

[0234] According to the results shown in Tables 3 and 4, the lattice constant and crystallite size of ruthenium oxide in the dried film are essentially the same as those of the ruthenium oxide powder used as a raw material for the resistive paste. This indicates that the lattice constant and crystallite size of the ruthenium oxide powder remain essentially unchanged during the process of dispersing and mixing the ruthenium oxide powder and glass powder in an organic colorant.

[0235] However, the lattice constant and crystallite size of ruthenium oxide measured in the thick-film resistor formed by sintering the dried resistive paste changed from the dry state. Specifically, the lattice constant La and crystallite size of ruthenium oxide along the a-axis increased, while the lattice constant Lc along the c-axis decreased. Therefore, by sintering the resistive paste, Lc / La decreased and the crystallite size increased.

[0236] When the Lc / La ratio of ruthenium oxide in a thick-film resistor formed by printing, drying, and firing resistive paste is 0.6885 or higher, both COLD-TCR and HOT-TCR are close to 0. Furthermore, when the crystallite diameter of ruthenium oxide in the thick-film resistor is 10 nm to 80 nm (100 nm),... Above 800 Excellent electrical properties are obtained under the following conditions.

[0237] In the thick film resistors of Examples 1 to 10, COLD-TCR and HOT-TCR are both within ±30ppm / ℃, close to 0, and the H / C difference is as small as below 70ppm / ℃, thus confirming that a high-precision temperature coefficient of resistance can be achieved.

[0238] Furthermore, it can be confirmed that the thick film resistors of Examples 1 to 10 exhibit excellent characteristics, with a resistance change rate within ±0.5% during short-time overload tests (STOL) and sufficiently low current noise.

[0239] As described above, in Examples 1 to 10, ruthenium oxide was obtained as a thick-film resistor (sintered body) with a ruthenium oxide having a ruthenium-type crystal structure, a lattice constant Lc of the c-axis to a lattice constant La of the a-axis ratio Lc / La of 0.6885 or higher, and a crystallite diameter of 10 nm to 80 nm. Furthermore, it can be confirmed that in such thick-film resistors of Examples 1 to 10, both the low-temperature resistance temperature coefficient and the high-temperature resistance temperature coefficient are close to 0, and the difference between the two can be reduced.

[0240] Furthermore, since the crystal size of ruthenium oxide is between 10 nm and 80 nm, it can be confirmed that the rate of change of resistance in the short-time overload test (STOL) is smaller, within ±0.5%.

[0241] On the other hand, in the thick-film resistive bodies (sintered bodies) of Comparative Examples 1 to 7, Lc / La is less than 0.6885. Therefore, in the thick-film resistive bodies obtained in these comparative examples, it can be confirmed that there is a tendency for the difference between the low-temperature temperature coefficient of resistance and the high-temperature temperature coefficient of resistance to increase, and the difference cannot be within ±30ppm / ℃. Furthermore, in Comparative Examples 6 and 7, even without the addition of TiO2 and MnO2, which cause a negative shift in the temperature coefficient of resistance, it can be confirmed that the temperature coefficient of resistance becomes significantly more negative.

[0242] Furthermore, in Comparative Example 8, the Lc / La ratio was 0.68963, and both COLD-TCR and HOT-TCR were within ±30 ppm / ℃. However, the crystallite diameter was as large as 94.1 nm, indicating that the coefficient of variation (CVR) of the resistance value deviation exceeded 5%. In addition, it was confirmed that the resistance value change rate in the short-time overload test (STOL) exceeded ±0.5%.

[0243] Based on the results of the above examples and comparative examples, it can be confirmed that in thick-film resistors using ruthenium oxide as the conductive phase, by suppressing the lattice constant and crystallite size of ruthenium oxide, the previously difficult temperature coefficient of resistance can be easily adjusted to within ±30 ppm / ℃. Furthermore, based on thick-film resistors with suppressed ruthenium oxide lattice constant and crystallite size, it can be confirmed that thick-film resistors with a highly accurate temperature coefficient of resistance can be fabricated.

[0244] The thick-film resistor has been described above using embodiments and examples, but the present invention is not limited to the above embodiments and examples. Various modifications and alterations are possible within the scope of the spirit of the invention as described in the claims.

[0245] This application claims priority based on Japan Patent Application No. 2023-075114 filed with the Japan Patent Office on April 28, 2023, and incorporates the entire contents of Japan Patent Application No. 2023-075114 into this international application.

Claims

1. A thick-film resistor comprising ruthenium oxide and glass, The ruthenium oxide has a rutile crystal structure. When the lattice constant of the a-axis, determined by X-ray diffraction, is set as La, and the lattice constant of the c-axis is set as Lc, the Lc / La ratio is greater than 0.6885. The crystallite diameter is between 10 nm and 80 nm.

2. The thick-film resistor according to claim 1, When the total mass of the ruthenium oxide and the glass is set to 100%, The mass ratio of ruthenium oxide is more than 5% and less than 60%.

3. The thick-film resistor according to claim 1 or 2, The glass contains SiO2, B2O3, and RO, where R represents one or more alkaline earth metal elements selected from Ca, Sr, and Ba. With the total of SiO2, B2O3 and RO set at 100 parts by mass, SiO2 is contained in a proportion of 18 to 50 parts by mass, B2O3 in a proportion of 10 to 30 parts by mass, and RO in a proportion of 35 to 70 parts by mass.

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