A ruthenium oxide-based thick film resistor paste with ultra-low temperature measurement performance, and a preparation method and application thereof

Abstract

The application discloses a ruthenium oxide-based thick film resistor paste with super-low temperature measuring performance and a preparation method and application thereof, and belongs to the technical field of super-low temperature measurement. The ruthenium oxide-based thick film resistor paste comprises 15-25 wt% of ruthenium oxide, 50-62 wt% of glass phase powder, 0-1 wt% of a modifier, and the balance of an organic carrier. The glass phase powder is prepared from at least two of PbO, Al2O3, B2O3 and SiO2. The organic carrier comprises an organic solvent, a thickening agent and a surfactant. The thick film resistor paste can stabilize the room temperature resistance of a thick film resistor bare chip in the range of 600-2000 ohms, and can realize the sensitivity of 30-120 ohms / K at 4.2K super-low temperature. Meanwhile, the paste has excellent stability in the super-low temperature range of 10mK-45K, and provides reliable material guarantee for millikelvin-level accurate temperature measurement in a super-low temperature environment.

Description

Technical Field

[0001] This invention relates to the field of cryogenic temperature measurement technology, and in particular to a ruthenium oxide-based thick film resistive paste with cryogenic temperature measurement performance, its preparation method, and its application. Background Technology

[0002] In cutting-edge fields such as deep space exploration, quantum computing, and low-temperature physics experiments, there is an increasing demand for temperature sensors that can operate stably for extended periods at liquid helium temperatures (4.2 K) and even lower temperatures (such as the 10 mK range). Ruthenium oxide-based thick-film resistive pastes are considered ideal materials for fabricating sensitive elements of ultra-low temperature sensors due to their adjustable sheet resistance, negative temperature coefficient of resistance in the low-temperature region, and good process adaptability.

[0003] However, existing ruthenium oxide-based thick-film resistive pastes are mainly geared towards conventional temperature ranges such as automotive electronics and industrial control, and their application in the field of ultra-low temperature precision measurement is not yet mature. Ruthenium oxide-based thick-film resistive pastes capable of achieving precise temperature measurement at ultra-low temperatures of 4.2K or even 10 mK are particularly scarce. The few studies involving low-temperature measurement have failed to provide complete temperature measurement performance data in the ultra-low temperature range (especially near 10 mK), including key indicators such as the temperature coefficient of resistance (TCR), sensitivity, thermal response time, long-term and short-term stability, and temperature control accuracy at ultra-low temperatures.

[0004] The current technological bottleneck for accurate temperature measurement at ultra-low temperatures of 4.2K or even 10 mK lies in the following: To achieve accurate temperature measurement at ultra-low temperatures, the cryogenic sensor must possess sufficient temperature sensitivity. This often requires a high resistance value. However, excessively high resistance can lead to a series of adverse consequences. For example, excessively high resistance can generate a significant self-heating effect at extremely low temperatures, interfering with the measured temperature field and causing a decrease in measurement accuracy. Excessively high resistance also easily introduces noise and errors, placing more stringent requirements on the temperature measurement circuit. Conversely, if a low-resistance design is used to reduce self-heating, the sensitivity will be insufficient, making it impossible to distinguish temperature changes at the mK level. Therefore, it is necessary to carefully adjust the resistance and sensitivity of the ultra-low temperature sensor to achieve a balance between appropriate temperature sensitivity, low self-heating effect, and low noise.

[0005] Controlling the formulation of ruthenium oxide-based thick film resistive paste, the core sensing element in cryogenic sensors, is a key technique for rationally controlling the sensor's resistance and sensitivity. However, the impact of changes in the ruthenium oxide-based thick film resistive paste formulation on the sensor's resistance, sensitivity, and key temperature measurement data is still unclear, and the lack of systematic control methods severely restricts the development of high-precision cryogenic sensors. Summary of the Invention

[0006] In view of this, the present invention provides a ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance, its preparation method and application, aiming to solve the technical problem that existing ruthenium oxide-based thick film resistive pastes are unable to achieve suitable temperature measurement sensitivity, low self-heating effect and low noise at ultra-low temperatures, and cannot achieve mK-level accurate temperature measurement.

[0007] In a first aspect, the present invention provides a ruthenium oxide-based thick-film resistive paste with ultra-low temperature measurement performance, comprising: Ruthenium oxide 15~25wt%; glassy phase powder 50~62wt%; modifier 0~1wt%; balance organic carrier; The glass phase powder is prepared from at least two of PbO, Al2O3, B2O3 and SiO2; the organic carrier includes an organic solvent, a thickener and a surfactant.

[0008] Preferably, the glass phase powder is prepared from PbO, Al2O3, B2O3 and SiO2, and the mass ratio of PbO, Al2O3, B2O3 and SiO2 is (3.5~5.5): (0.5~1.5): (2~3): (0.5~1.5).

[0009] Preferably, the ruthenium oxide has a particle size of 30~500 nm; the glass phase powder has a particle size of 0.3~50 μm.

[0010] Preferably, the organic solvent is at least two of terpineol, diethylene glycol butyl ether, and diethylene glycol butyl ether acetate; the thickener is ethyl cellulose or hydroxycellulose; and the surfactant is lecithin or oleic acid.

[0011] Preferably, in the organic carrier, the mass fraction of the organic solvent is 85-98 wt%, the mass fraction of the thickener is 1.5-10 wt%, and the mass fraction of the surfactant is 0.5-5 wt%.

[0012] Preferably, the modifier includes one or more of MnO2, CuO, and Nb2O5.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance, comprising the following steps: Ruthenium oxide, glass phase powder, and modifier are mixed evenly to obtain slurry powder; The slurry powder and organic carrier are mixed and rolled to obtain the ruthenium oxide-based thick film resistive slurry with ultra-low temperature measurement performance.

[0014] Preferably, the glass phase powder is prepared as follows: at least two of PbO, Al2O3, B2O3 and SiO2 are mixed and melted, and water-quenched to obtain glass slag. The glass slag is then ball-milled, dried and sieved to obtain glass phase powder.

[0015] Thirdly, the present invention provides the application of the ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance or the ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance prepared by the above preparation method in the preparation of ultra-low temperature sensors or ultra-low temperature sensing elements.

[0016] Preferably, the operating temperature of the ultra-low temperature sensor or ultra-low temperature sensing element is 10mK~45K.

[0017] Compared with the prior art, the present invention has achieved the following beneficial effects: This invention precisely controls the ruthenium oxide content within the range of 15-25 wt%, combines it with glass phase powders prepared from at least two of PbO, Al2O3, B2O3, and SiO2, and an organic carrier containing organic solvents, thickeners, and surfactants, and selectively adds modifiers. This allows the room temperature resistance of the thick-film resistor wafer obtained by screen printing and sintering using the aforementioned slurry to be stable in the range of 600-2000 Ω, while simultaneously achieving a sensitivity of 30-120 Ω / K at an ultra-low temperature of 4.2 K. While ensuring sufficient temperature resolution, the self-heating effect at extremely low temperatures is effectively suppressed, resolving the technical contradiction between high sensitivity and low self-heating. At the same time, the slurry exhibits excellent stability in the ultra-low temperature range of 10mK to 45K, with short-term stability reaching ±15mK and long-term stability reaching ±30mK. The temperature control accuracy at 4.2K can reach ±1mK, and it is fully compatible with standard thick-film screen printing and sintering processes, providing a reliable material guarantee for milliKelvin-level accurate temperature measurement in ultra-low temperature environments. Attached Figure Description

[0018] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0019] Figure 1 These are microscopic images of the surface microstructure of a bare wafer prepared by screen printing using the ruthenium oxide-based thick film resistor paste described in Embodiment 1 of this invention. Figure 2 The resistance-temperature (RT) curve (4.2-100K temperature range) of the ultra-low temperature sensor prepared by the ruthenium oxide-based thick film resistive paste described in Example 1 of this invention is shown. Figure 3 This is the temperature sensitivity curve (4.2-100K temperature range) of the ultra-low temperature sensor prepared by the resistive paste described in Embodiment 1 of the present invention. Figure 4 This is the resistance-temperature (RT) curve (10mK-45K temperature range) of the ultra-low temperature sensor prepared by the ruthenium oxide-based thick film resistive paste described in Example 1 of the present invention. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] This invention provides a ruthenium oxide-based thick-film resistor paste with ultra-low temperature measurement performance, suitable for preparing temperature sensor sensitive elements capable of precise temperature measurement in the ultra-low temperature range of 10 mK to 45 K. By precisely controlling the content of ruthenium oxide (conductive phase), combined with specific glass phase powder, organic carrier, and selectively added modifiers, the prepared thick-film resistor wafer can simultaneously maintain sufficient sensitivity and controllable self-heating effect at ultra-low temperatures.

[0022] This invention provides a ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance, comprising: 15~25 wt% ruthenium oxide; 50~62 wt% glass phase powder; 0~1 wt% modifier; and the balance being an organic carrier.

[0023] Ruthenium oxide, as the conductive phase, is the core functional component of this invention. Ruthenium oxide possesses a negative temperature coefficient of resistance (TCR), meaning its resistance increases with decreasing temperature at low temperatures. This characteristic makes it an ideal sensitive material for ultra-low temperature sensors. Extensive experiments have revealed that the ruthenium oxide content has a decisive influence on the room temperature resistance, ultra-low temperature sensitivity, and self-heating effect of the thick-film resistor wafer after sintering the slurry. When the ruthenium oxide content is too high, the room temperature resistance is too low, resulting in insufficient sensitivity at ultra-low temperatures (below 30 Ω / K at 4.2 K), with only a weak change in resistance with temperature, leading to a loss of temperature resolution. When the ruthenium oxide content is too low, the room temperature resistance is too high (above 10 kΩ). Although the absolute sensitivity increases, a significant self-heating effect occurs at ultra-low temperatures of 10 mK to 45 K, interfering with the measured temperature field and causing a decrease in temperature measurement accuracy. This invention limits the ruthenium oxide content to the range of 15-25 wt%, for example, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 25 wt%, and more preferably 15-23 wt%. Within this range, the room temperature resistance can be stably controlled at 600-2000 Ω, and the sensitivity at 4.2 K can reach 30-120 Ω / K, thereby effectively suppressing the self-heating effect while ensuring sufficient temperature resolution.

[0024] Glass phase powder, acting as a binder phase, provides mechanical support for thick-film resistors, regulates sintering density, and influences the dispersion state of the conductive phase within the glass matrix, thereby affecting the resistance stability at ultra-low temperatures. In this invention, the glass phase powder is prepared from at least two of PbO, Al2O3, B2O3, and SiO2. Preferably, the glass phase powder is prepared from all four components: PbO, Al2O3, B2O3, and SiO2. The glass system formed by these four oxides exhibits good thermal expansion matching and sintering density at ultra-low temperatures, ensuring the stability of the thick-film resistor wafer and contributing to its long-term stability.

[0025] In a preferred embodiment of the present invention, the mass ratio of PbO, Al2O3, B2O3 and SiO2 in the glass phase powder is (3.5~5.5): (0.5~1.5): (2~3): (0.5~1.5).

[0026] The particle size of the glass phase powder affects the printing performance of the paste and the density of the sintered film. Excessively large particle sizes may lead to uneven sintered film, while excessively small particle sizes can easily cause agglomeration. In this invention, the particle size of the glass phase powder is 0.3~50 μm, preferably 0.5~10 μm, more preferably 0.5~5 μm, for example, it can be 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 20 μm, or 50 μm. Further preferably, it is 0.5~2 μm.

[0027] Modifiers are used to control the resistance, sensitivity, and TCR value of thick-film resistor wafers based on semiconductor doping principles, without altering the ruthenium oxide as the primary conductive phase. The amount of modifier added is 0-1 wt%, meaning it can be omitted or added at no more than 1 wt%. Different modifiers have different effects on resistance at ultra-low temperatures: doping with n-type semiconductors such as CuO reduces wafer resistance, decreases sensitivity at ultra-low temperatures, and positively shifts the TCR value; doping with p-type semiconductors such as MnO2 increases wafer resistance, improves sensitivity at ultra-low temperatures, and negatively shifts the TCR value. The preferred amount of modifier added is 0.1-0.9 wt%, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, or 0.9 wt%. More preferably, it is 0.1-0.8 wt%. Excessive addition of modifiers may lead to abnormal sintering behavior or deterioration of the temperature coefficient of resistance.

[0028] The organic carrier, as a functional medium, serves to uniformly disperse the conductive phase, glassy phase, and modifier powder, forming a paste with suitable viscosity and rheological properties to meet the requirements of screen printing. In this invention, the organic carrier includes an organic solvent, a thickener, and a surfactant.

[0029] The organic solvent is responsible for dissolving the thickener and adjusting the viscosity of the slurry. In this invention, the organic solvent is at least two of terpineol, diethylene glycol butyl ether, and diethylene glycol butyl ether acetate. For example, a combination of terpineol and diethylene glycol butyl ether, a combination of terpineol and diethylene glycol butyl ether acetate, a combination of diethylene glycol butyl ether and diethylene glycol butyl ether acetate, or all three can be used simultaneously. Compared to a single solvent system, a compound solvent can achieve a better balance of evaporation rates and screen printing suitability. The mass fraction of the organic solvent in the organic carrier is 85-98 wt%, preferably 90-96 wt%, and more preferably 92-96 wt%.

[0030] Thickeners are used to adjust the viscosity and rheological behavior of the paste, ensuring the thickness and shape retention of the printed film. In this invention, the thickener is ethyl cellulose or hydroxycellulose. Ethyl cellulose has excellent thermoplasticity and film-forming properties, while hydroxycellulose provides better hydrophilicity adjustment capabilities. Hydroxycellulose may further include one or more of hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose. The mass fraction of the thickener in the organic carrier is 1.5~10 wt%, preferably 3~8 wt%, more preferably 3~5 wt%.

[0031] Surfactants are used to improve the wettability and dispersibility of powders in organic carriers and prevent particle agglomeration. In this invention, the surfactant is lecithin or oleic acid. Lecithin has good emulsifying and dispersing properties, while oleic acid can effectively reduce solid-liquid interfacial tension. The mass fraction of the surfactant in the organic carrier is 0.5~5 wt%, preferably 0.5~3 wt%, more preferably 0.5~1.5 wt%.

[0032] This invention also provides a method for preparing the aforementioned ruthenium oxide-based thick-film resistor paste with ultra-low temperature measurement performance. This method is simple and fully compatible with standard thick-film processes.

[0033] In one embodiment, the preparation method includes the following steps: mixing ruthenium oxide, glass phase powder and modifier evenly to obtain slurry powder; mixing the slurry powder with an organic carrier and rolling it to obtain the ruthenium oxide-based thick film resistor slurry with ultra-low temperature measurement performance.

[0034] Specifically, ruthenium oxide powder, glass phase powder, and selectively added modifiers are first weighed according to the specified ratio. The particle size of the ruthenium oxide powder is preferably 30–500 nm, more preferably 30–100 nm, for example, 30 nm, 50 nm, 100 nm, 150 nm, 200 nm, 300 nm, or 500 nm. Nanoscale to submicron-scale ruthenium oxide powder helps form a more uniform conductive network and improves the consistency of the resistance-temperature response at ultra-low temperatures. The particle size of the glass phase powder is preferably 0.3–10 μm. The particle size of the modifier powder is preferably 30–100 nm.

[0035] The above solid powders are thoroughly mixed in a mixing device to obtain a slurry powder. Mixing can be performed using equipment such as a V-type mixer, a three-dimensional mixer, or a ball mill. The mixing time is generally 1 to 4 hours to ensure that the components are evenly distributed.

[0036] Then, the prepared organic carrier is added to the slurry powder and premixed using a mixer or kneader to ensure the powder is fully wetted by the organic carrier. The premixed paste is then transferred to a three-roll mill for repeated rolling. The purpose of rolling is to break up agglomerated particles through high shear force and to uniformly disperse the powder in the organic carrier, while simultaneously grinding the slurry to a fineness of less than 5 μm (e.g., 3-5 μm). The preferred number of rolling cycles is 3-6 times, for example, 3, 4, 5, or 6 times. During the rolling process, the gap of the three-roll mill can be gradually reduced, such as 30-50 μm for the first pass, 15-25 μm for the second pass, and 5-10 μm for the third pass.

[0037] After rolling, the ruthenium oxide-based thick-film resistive paste with ultra-low temperature measurement performance is obtained. The preferred viscosity of the paste in this invention is 150~400 Pa·s (measured using a rotational viscometer at 25°C and 10 rpm), more preferably 200~300 Pa·s. Excessive viscosity will result in poor screen transmission and incomplete film layers during printing; excessively low viscosity will result in pattern diffusion and unclear boundaries after printing.

[0038] In this invention, the glass phase powder is preferably prepared by the following steps: at least two of PbO, Al2O3, B2O3 and SiO2 are mixed evenly in proportion; the mixed raw materials are melted at 800~1300℃; the melted raw materials are water-quenched to obtain glass slag; the glass slag is ball-milled, dried and sieved to obtain glass phase powder.

[0039] Specifically, each oxide raw material (PbO, Al2O3, B2O3, SiO2) is accurately weighed according to the designed composition and mixed evenly in a ball mill jar. The mixed raw material is then transferred to a corundum crucible or platinum crucible and placed in a high-temperature electric furnace to be heated to 800~1300℃ for melting. The preferred melting temperature is 1000~1200℃, more preferably 1100~1150℃. The holding time is generally 0.5~2 hours. After melting, the molten glass is quickly poured into deionized water for water quenching to obtain loose glass slag. The glass slag is dried in an oven (e.g., 100~120℃, 12~24 hours) and then ball-milled in a planetary ball mill. This invention does not impose any special limitations on the specific ball milling method; any ball milling method commonly used in the art can be used. The ball-milled glass powder is sieved (e.g., a 200 mesh, 300 mesh, or 400 mesh standard sieve), and the undersize material is collected to obtain the glass phase powder.

[0040] The organic carrier is prepared as follows: Organic solvent, thickener, and surfactant are mixed in a specific ratio and heated and stirred until fully dissolved. For example, at least two of the organic solvents (such as terpineol, diethylene glycol butyl ether, and diethylene glycol butyl ether acetate) can be weighed and placed in a beaker or reaction vessel, and heated to 60-80°C; then, a thickener (such as ethyl cellulose or hydroxycellulose) is added, and stirring continues until completely dissolved (usually requiring 0.5-2 hours); finally, a surfactant (such as lecithin or oleic acid) is added, stirred evenly, and cooled to room temperature to obtain the organic carrier. During the preparation process, vacuum stirring or vacuum degassing can further reduce air bubbles and improve the uniformity of the organic carrier. The prepared organic carrier is sealed and stored in a brown reagent bottle for later use.

[0041] The present invention also provides the application of the above-mentioned ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance or the ruthenium oxide-based thick film resistive paste prepared by the above preparation method in the preparation of ultra-low temperature sensors or ultra-low temperature sensing elements.

[0042] The preferred operating temperature range for the ultra-low temperature sensor or ultra-low temperature sensing element is 10 mK to 45 K. Within this temperature range, the sensing element prepared using the slurry of this invention exhibits a negative temperature coefficient, high sensitivity, high stability, and high temperature control accuracy.

[0043] In practical applications, the paste of this invention can be printed onto an insulating ceramic substrate (such as 96% alumina ceramic, sapphire, or aluminum nitride ceramic) using a standard screen printing process to form the designed resistor pattern. The printed substrate is then leveled (e.g., allowed to stand at room temperature for 5-15 minutes), dried (e.g., at 80-150°C for 10-20 minutes), and then sintered in a belt sintering furnace or box furnace. The peak sintering temperature is preferably 800-900°C, more preferably 830-870°C, and the peak holding time is 5-15 minutes. The sintering atmosphere can be air or oxygen. After sintering, a thick-film resistor die is obtained, which can be used as the sensitive element of an ultra-low temperature sensor.

[0044] This sensor can be used in fields requiring precise temperature measurement at extremely low temperatures, such as deep space exploration (e.g., cosmic microwave background radiation detection), quantum computing (e.g., temperature monitoring of dilution refrigerators), superconducting magnet systems, and low-temperature physics experiments.

[0045] The thick-film resistor blank prepared using the slurry of this invention can have its resistance stably controlled within the range of 600~2000 Ω at room temperature. At an ultra-low temperature of 4.2 K, the sensitivity (S = dR / dT) can reach 30~120 Ω / K, and the dimensionless sensitivity (SD = S / R) can reach 0.17~0.24. Within the ultra-low temperature range of 10 mK~45 K, the short-term stability (repeatability) can reach ±15 mK, the long-term stability (over one year) can reach ±30 mK, and the temperature control accuracy at 4.2 K can reach ±1 mK.

[0046] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention does not impose any special restrictions on the source of reagents used in the following embodiments; commercially available products well known to those skilled in the art can be used.

[0047] Example 1 This embodiment provides a ruthenium oxide-based thick-film resistive paste with ultra-low temperature measurement performance. Its composition is: 24.5 wt% ruthenium oxide, 50.5 wt% glass phase powder, 25 wt% organic carrier, and no modifier added. The ruthenium oxide powder has a particle size of 30~100 nm and a purity of over 95%.

[0048] The glass phase powder was prepared from four components—PbO, Al2O3, B2O3, and SiO2—in a mass ratio of 4.5:1:2.5:1, with a particle size of 0.5–2 μm. The preparation method is as follows: Each oxide raw material was weighed according to the designed composition, mixed thoroughly, and placed in a corundum crucible; melted at 1000℃ for 2 hours; quickly poured into deionized water for quenching to obtain glass slag; after ball milling and drying, it was passed through a 300-mesh sieve for later use.

[0049] The organic carrier is composed of terpineol, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, ethyl cellulose, and oleic acid. The organic solvent (terpineol + diethylene glycol butyl ether + diethylene glycol butyl ether acetate, in a mass ratio of 7:2:1) accounts for 95 wt% of the total organic carrier mass, the thickener (ethyl cellulose) accounts for 4 wt%, and the surfactant (oleic acid) accounts for 1 wt%. The preparation method is as follows: Weigh each organic solvent, thickener, and surfactant according to the designed composition; mix them and place them in a round-bottom flask; heat and stir until all components are fully dissolved and uniformly mixed; pour into a brown reagent bottle for later use.

[0050] The preparation method of the ruthenium oxide-based thick film resistor slurry in this embodiment is as follows: (1) Ruthenium oxide powder and glass phase powder are mixed evenly according to the weight ratio to obtain slurry powder; (2) The slurry powder is mixed evenly with an organic carrier; (3) The slurry is repeatedly rolled 4 times using a three-roll mill until the fineness of the slurry is less than 5 μm, and the viscosity of the slurry is about 300 Pa·s (rotational viscometer, 25℃, 10 rpm).

[0051] Example 2 Compared with Example 1, the difference in this embodiment is that the slurry composition of this embodiment is as follows: 23 wt% ruthenium oxide, 52 wt% glass phase powder, and 25 wt% organic carrier.

[0052] The specifications and preparation methods of ruthenium oxide powder and glass phase powder are the same as in Example 1.

[0053] The organic carrier is composed of terpineol, diethylene glycol butyl ether acetate, ethyl cellulose, and oleic acid, wherein the organic solvent (terpineol + diethylene glycol butyl ether acetate, mass ratio 7:3) accounts for 95 wt% of the total mass of the organic carrier, the thickener (ethyl cellulose) accounts for 4 wt%, and the surfactant (oleic acid) accounts for 1 wt%. The preparation method is the same as in Example 1.

[0054] The preparation method of the ruthenium oxide-based thick film resistor paste in this embodiment is the same as that in Embodiment 1.

[0055] Example 3 Compared with Example 1, the difference in this embodiment is that the slurry composition of this embodiment is as follows: 17.6 wt% ruthenium oxide, 56.6 wt% glass phase powder, 25 wt% organic carrier, and 0.8 wt% modifier.

[0056] The specifications and preparation methods of ruthenium oxide powder and glass phase powder are the same as in Example 1.

[0057] The organic carrier is composed of terpineol, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, ethyl cellulose, and lecithin. The organic solvent (terpineol + diethylene glycol butyl ether + diethylene glycol butyl ether acetate, in a mass ratio of 7:2:1) accounts for 95 wt% of the total organic carrier mass, the thickener (hydroxycellulose) accounts for 4 wt%, and the surfactant (lecithin) accounts for 1 wt%. The preparation method is the same as in Example 1.

[0058] The modifier is CuO.

[0059] The preparation method of the ruthenium oxide-based thick film resistor paste in this embodiment is the same as that in Embodiment 1.

[0060] Comparative Example 1 The difference between this comparative example and Example 1 is that the slurry composition of this comparative example is as follows: 22.5 wt% ruthenium oxide, 2 wt% CuO modifier, 50.5 wt% glass phase powder, 25 wt% organic carrier, and the rest of the preparation methods and conditions remain unchanged.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is that the slurry composition of this comparative example is as follows: 12 wt% ruthenium oxide, 63 wt% glass phase powder, and 25 wt% organic carrier, while the other preparation methods and conditions remain unchanged.

[0062] Comparative Example 3 The difference between this comparative example and Example 3 is that the slurry composition of this comparative example is as follows: 17.2 wt% ruthenium oxide, 1.2 wt% CuO modifier, 56.6 wt% glass phase powder, 25 wt% organic carrier, and the rest of the preparation methods and conditions remain unchanged.

[0063] Test case The ruthenium oxide-based thick film resistor pastes from the above embodiments and comparative examples were prepared into thick film resistor blanks, and their performance was tested.

[0064] The test results are shown in Tables 1 and 2.

[0065] Table 1. Cryogenic temperature measurement performance of the thick film resistor blanks prepared from the slurry in the examples.

[0066] Note: Short-term stability is the temperature equivalent deviation calculated from resistance fluctuations after 30 days of repeated testing at 4.2 K; long-term stability is the temperature equivalent deviation calculated from resistance fluctuations after 12 months of repeated testing at 4.2 K. Table 2. Cryogenic temperature measurement performance of thick-film resistor blanks prepared from comparative slurries.

[0067] As shown in Table 1, by adjusting the proportions of each component in the thick-film resistor paste, especially the content of the conductive phase ruthenium oxide and the modifier, examples 1-3 can produce thick-film resistor blanks with negative temperature coefficients. The room temperature resistance of the thick-film resistor blanks is effectively stabilized in the range of 600-2000Ω, and a sensitivity of 30-120Ω / K can be achieved simultaneously at an ultra-low temperature of 4.2K. This effectively suppresses the self-heating effect at extremely low temperatures while ensuring sufficient temperature resolution, thus resolving the technical contradiction between high sensitivity and low self-heating. Furthermore, the paste exhibits excellent stability, with short-term stability reaching approximately ±6mK and long-term stability reaching approximately ±30mK.

[0068] As shown in Table 2, when the content of the conductive phase ruthenium oxide or the modifier CuO in the thick-film resistor paste exceeds the optimal range, it will cause the room temperature resistance of the thick-film resistor die to increase or decrease drastically, resulting in an excessively high or low sensitivity value. When the sensitivity value is too high, it will cause the thick-film resistor die to have a self-heating effect at extremely low temperatures; when the sensitivity value is too low, it will cause a sharp decrease in temperature measurement accuracy and a rapid reduction in the temperature measurement range.

[0069] Figure 1 This is a microscopic image of the surface microstructure of a bare die prepared by screen printing using the ruthenium oxide-based thick film resistor paste described in Example 1 of the present invention. The dark purple area represents the area printed with the prepared thick film resistor paste. It can be seen that the surface of the bare die printed with the prepared thick film resistor paste is very uniform, without any obvious defects such as cracks, gaps, or missing parts.

[0070] Figure 2 The resistance-temperature (RT) curves (4.2-100K temperature range) of the ultra-low temperature sensor prepared by the ruthenium oxide-based thick film resistive paste described in Example 1 of this invention show that, within this temperature range, the shape and trend of the RT curves of the two sets of samples prepared are very close to those of the internationally advanced Lakeshore RX-102A low-temperature sensor, indicating that the prepared ultra-low temperature sensor has approached the international advanced level.

[0071] Figure 3The temperature sensitivity curve (4.2-100K temperature range) of the ultra-low temperature sensor prepared by the resistive paste described in Embodiment 1 of this invention is shown. It can be seen that, in this temperature range, in addition to the RT curve, the shape and trend of the sensitivity curves of the two sets of samples prepared by this invention are very close to the internationally advanced Lakeshore RX-102A low temperature sensor, which is at an internationally advanced level. This further illustrates that the ultra-low temperature sensor prepared by this invention is close to the internationally advanced level.

[0072] Figure 4 The resistance-temperature (RT) curves (10mK-45K temperature range) of the ultra-low temperature sensor prepared by the ruthenium oxide-based thick film resistive paste described in Example 1 of this invention show that when the temperature range is further reduced to around 10 mK, the RT curve of the sample prepared by this invention still exhibits a negative temperature coefficient and good monotonicity, indicating that this sample has the ability to accurately measure temperature at 10 mK. The shape and trend of the RT curve of the prepared sample are also very close to the internationally advanced Lakeshore RX-102B type cryogenic sensor, further demonstrating that the temperature measurement performance of the prepared ultra-low temperature sensor in the ultra-low temperature range around 10 mK is close to the internationally advanced level.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ruthenium oxide-based thick-film resistive paste with ultra-low temperature measurement performance, characterized in that, include: Ruthenium oxide 15~25wt%; glass phase powder 50~62wt%; modifier 0~1wt%; balance organic carrier; The glass phase powder is prepared from at least two of PbO, Al2O3, B2O3 and SiO2; the organic carrier includes an organic solvent, a thickener and a surfactant.

2. The ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance as described in claim 1, characterized in that, The glass phase powder is prepared from PbO, Al2O3, B2O3 and SiO2, and the mass ratio of PbO, Al2O3, B2O3 and SiO2 is (3.5~5.5): (0.5~1.5): (2~3): (0.5~1.5).

3. The ruthenium oxide-based thick-film resistive paste with ultra-low temperature measurement performance as described in claim 1, characterized in that, The ruthenium oxide has a particle size of 30~500 nm; the glass phase powder has a particle size of 0.3~50 μm.

4. The ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance as described in claim 1, characterized in that, The organic solvent is at least two of terpineol, diethylene glycol butyl ether, and diethylene glycol butyl ether acetate; the thickener is ethyl cellulose or hydroxy cellulose; and the surfactant is lecithin or oleic acid.

5. The ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance as described in claim 1, characterized in that, In the organic carrier, the mass fraction of the organic solvent is 85~98wt%, the mass fraction of the thickener is 1.5~10wt%, and the mass fraction of the surfactant is 0.5~5wt%.

6. The ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance as described in claim 1, characterized in that, The modifier includes one or more of MnO2, CuO, and Nb2O5.

7. The method for preparing ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Ruthenium oxide, glass phase powder, and modifier are mixed evenly to obtain slurry powder; The slurry powder and organic carrier are mixed and rolled to obtain the ruthenium oxide-based thick film resistive slurry with ultra-low temperature measurement performance.

8. The preparation method according to claim 1, characterized in that, The glass phase powder is prepared as follows: at least two of PbO, Al2O3, B2O3 and SiO2 are mixed and melted, and water quenched to obtain glass slag. The glass slag is then ball-milled, dried and sieved to obtain glass phase powder.

9. The application of the ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance as described in any one of claims 1 to 6, or the ruthenium oxide-based thick film resistive paste with ultra-low temperature measurement performance prepared by the preparation method described in any one of claims 7 to 8, in the preparation of ultra-low temperature sensors or ultra-low temperature sensing elements.

10. The application as described in claim 9, characterized in that, The operating temperature of the ultra-low temperature sensor or ultra-low temperature sensing element is 10mK~45K.

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