Sintered high-stability low-resistance temperature coefficient resistor paste

Abstract

This invention discloses a sintering-type high-stability, low-resistance temperature coefficient resistive paste, belonging to the field of electronic materials technology. The resistive paste comprises ZnO-B2O3-La2O3 glass powder, an in-situ doped and modified conductive phase, an organic carrier, organic additives, inorganic additives, and an organic solvent. The in-situ doped and modified conductive phase is formed by dispersing an inorganic composite dopant and conductive phase powder in an organic modifier, followed by thermosetting at 175–220℃ to achieve in-situ bonding between the inorganic composite dopant and the conductive phase powder interface. The inorganic composite dopant is a mixture of rare earth oxides and traditional inorganic oxides, with the rare earth oxides accounting for 30%–80% by weight. This invention achieves precise modification of the conductive phase lattice and interface through the synergistic effect of rare earth doping and thermosetting in-situ bonding, resulting in a stable temperature coefficient of resistance within ±25 ppm / ℃. It can be fully sintered over a wide temperature range of 750–900℃, making it suitable for thick-film circuits, chip resistors, automotive electronics, and high-precision sensors.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials technology, specifically relating to a rare earth-doped modified resistive paste with a wide sintering temperature range, high stability, and low temperature coefficient of resistance, which is suitable for the manufacture of thick film circuits, chip resistors, and automotive electronic components. Background Technology

[0002] Resistive pastes are core functional materials for electronic components such as thick-film circuits, chip resistors, automotive electronics, and high-precision sensors. Their temperature coefficient of resistance (TCR) is one of the key indicators for evaluating paste performance. In high-end applications such as electric motor control units (MCUs) for new energy vehicles, high-precision current sensors, and 5G power amplifiers, the TCR of resistive elements must be strictly controlled within ±25ppm / ℃ to avoid signal distortion and reduced control accuracy caused by temperature drift.

[0003] Traditional resistive pastes often employ a system combining a ruthenium-based conductive phase and a glass phase, with electrical properties improved by adding inorganic oxide dopants. In existing technologies, rare earth oxides have been explored for modifying resistive pastes. For example, the 2002 article "Research Progress on the Application of Rare Earth Oxides in Thick Film Resistive Pastes," published in *Electronic Components and Materials*, reviewed the application of rare earth oxides in resistive pastes, pointing out that adding an appropriate amount of rare earth oxides can reduce the temperature coefficient of resistance of the resistive paste. However, this review only indicated the role of rare earth oxides in principle, without addressing specific doping processes, optimization of doping amounts, and synergistic design with the glass system.

[0004] In terms of doping processes, existing technologies mostly employ simple physical mixing methods to mix dopants with conductive phase powders. However, the dopants are difficult to disperse uniformly and embed into the conductive phase lattice, resulting in limited modification effects. The TCR of finished products is generally in the range of ±60 to ±100 ppm / ℃, with the optimal solution only reaching around ±60 ppm / ℃, which is insufficient to meet the application requirements of high-end electronic components. Furthermore, traditional resistive pastes suffer from reliability issues such as nonlinear temperature drift and abrupt changes in resistance values. Additionally, sintering temperatures are mostly above 800℃, resulting in a narrow sintering window and high energy consumption during production.

[0005] Therefore, developing a resistance paste that can achieve stable TCR control within ±25ppm / ℃, has a wide sintering window, and high stability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention addresses the technical problems of existing resistor pastes where rare earth doping is limited to the theoretical level, the doping method is mainly simple physical mixing, and the temperature coefficient of resistance (TCR) is generally only ±60 to ±100 ppm / ℃, which is insufficient to meet the requirements of high-end electronic components. It provides a resistor paste with a wide sintering temperature range, high stability, and low resistance temperature coefficient. This paste achieves stable TCR control within ±25 ppm / ℃ and full sintering in a wide temperature range of 750 to 900℃ through quantitative optimization of rare earth doping, synergistic effects of thermosetting in-situ bonding process, and the ZnO-B2O3-La2O3 glass system.

[0007] To achieve the above objectives, the present invention provides a sintered, high-stability, low-temperature-coefficient resistive slurry, comprising, by weight percentage (100%): 5%–35% lead-free glass powder, 15%–45% in-situ doped and modified conductive phase, 5%–25% organic carrier, 0.1%–2% organic additives, 0.1%–2% inorganic additives, and 5%–25% organic solvent. A preferred composition is: 8%–20% lead-free glass powder, 30%–45% in-situ doped and modified conductive phase, 15%–25% organic carrier, 1%–1.5% organic additives, 0.5%–1% inorganic additives, and 15%–25% organic solvent.

[0008] The lead-free glass powder is a ZnO-B2O3-La2O3 series glass powder with a particle size of 500 nm to 5 μm. Further, the preferred weight percentage composition of the ZnO-B2O3-La2O3 series glass powder is: ZnO 40%–55%, B2O3 20%–35%, La2O3 5%–15%, with the balance being a flux selected from one or more of bismuth oxide, sodium oxide, potassium oxide, and lithium oxide. This glass system forms a synergistic sintering system with the in-situ doped and modified conductive phase, and the La in the glass phase... 3+ With similar ionic radii to the doped rare earth ions in the conductive phase, the two form stable chemical bonds at the interface (such as La-O-Ce, La-O-Nd, etc.). On the one hand, this lowers the glass softening point, allowing the slurry to be fully sintered at 750℃. On the other hand, it strengthens the bonding strength at the conductive phase-glass phase interface, ensuring the stability of TCR in a wide temperature range.

[0009] The in-situ doped modified conductive phase is a conductive powder prepared by the following method: dispersing an inorganic composite dopant and a conductive phase powder in an organic modifier, followed by thermosetting at 175–220°C, to achieve in-situ bonding between the inorganic composite dopant and the conductive phase powder to form the conductive powder. More preferably, the thermosetting temperature is 190–200°C. The amount of inorganic composite dopant added is 2%–8% of the weight of the in-situ doped modified conductive phase, the amount of organic modifier added is 5%–20% of the weight of the in-situ doped modified conductive phase, and the amount of conductive phase powder added is 75%–90% of the weight of the in-situ doped modified conductive phase; preferably, the amount of inorganic composite dopant added is 3%–5% of the weight of the in-situ doped modified conductive phase, the amount of organic modifier added is 8%–15% of the weight of the in-situ doped modified conductive phase, and the amount of conductive phase powder added is 80%–88% of the weight of the in-situ doped modified conductive phase.

[0010] The conductive phase powder is selected from one or more of silver powder, palladium powder, ruthenium dioxide powder, lead ruthenate powder, bismuth ruthenate powder, and copper ruthenate powder. The particle size of the conductive phase powder is 0.2–3 μm, the moisture content is ≤0.2%, and the loss on ignition is ≤0.2%.

[0011] The inorganic composite dopant is a mixture of rare earth oxides and conventional inorganic oxides. The rare earth oxides are selected from one or more of lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, yttrium oxide, ytterbium oxide, lanthanum-cerium composite oxide, and yttrium-zirconium composite oxide, and the amount of a single rare earth oxide added to the inorganic composite dopant does not exceed 5% of the weight of the conductive phase powder. The conventional inorganic oxides are selected from one or more of zirconium dioxide, zirconium silicate, tin dioxide, tantalum pentoxide, manganese tetroxide, manganese trioxide, strontium oxide, niobium trioxide, and titanium dioxide; and the weight percentage of the rare earth oxides in the inorganic composite dopant is 30%–80%, preferably 50%–60%.

[0012] The organic modifier is selected from one or more of dipropylene glycol methyl ether, propylene glycol monobutyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether acetate, and ethylene glycol hexyl ether.

[0013] The organic carrier, by weight percentage (100%), comprises: 1%–15% hydroxypropyl cellulose, 1%–5% polyvinyl butyral, 1%–5% coupling agent, 20%–75% terpineol, and 20%–70% diethylene glycol ethyl ether acetate. The coupling agent is selected from one or more of titanate coupling agents, aluminate coupling agents, silane coupling agents, and aluminum borate coupling agents.

[0014] The organic additive is selected from one or more of the following: rosin, hydrogenated castor oil, polyamide wax, organosilicon resin, epoxy silane coupling agent, titanate coupling agent, aluminum zirconium coupling agent, polyphosphate dispersant, polyamide dispersant, alicyclic amine curing agent, and polyether amine curing agent.

[0015] The inorganic additive is selected from one or more of the following: carbon black, copper oxide, nickel powder, carbon nanotubes, α-alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, crystalline silicon dioxide, and silicon carbide.

[0016] The organic solvent is selected from one or more of terpineol, dibutyl phthalate, methyl amyl acetate, isobutyl isobutyrate, glycol diacetate, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, and egg yolk lecithin.

[0017] The method for preparing the resistive paste of the present invention includes the following steps:

[0018] Step 1: Preparation of in-situ doped modified conductive phase powder

[0019] Inorganic composite dopant and conductive phase powder are added to organic modifier and dispersed at high speed of 3000-5000 rpm for 30-60 min. After dispersion, the mixture is subjected to low-temperature thermosetting treatment at 175-220℃ for 60-120 min to enable in-situ bonding between inorganic composite dopant and conductive phase powder. The mixture is then purified with anhydrous ethanol to remove impurities and vacuum dried at 60-80℃ for 10-12 h to obtain in-situ doped and modified conductive phase powder.

[0020] Step 2: Preparation of organic carrier

[0021] Hydroxypropyl cellulose, polyvinyl butyral, coupling agent, terpineol, and diethylene glycol ethyl ether acetate were placed in a homogenizer and homogenized at 60–80°C for 4–6 hours until completely dissolved. The organic carrier was then obtained by filtration.

[0022] Step 3: Preparation of resistive paste

[0023] In-situ doped modified conductive phase powder, lead-free glass powder, organic carrier, organic additives, inorganic additives, and organic solvent are homogenized in a high-shear mixer for 1-2 hours, and then finely ground in a three-roll mill to a fineness of ≤10μm to obtain a crude slurry. The crude slurry is then subjected to 300-350 mesh precision filtration and high vacuum degassing treatment (vacuum degree ≥-0.095MPa, degassing for 20-40 minutes) to obtain the finished resistor slurry.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention employs a composite of rare earth oxides and traditional inorganic oxides for in-situ doping modification of the conductive phase. Through liquid-phase dispersion and low-temperature thermal curing processes, rare earth ions are precisely embedded into the conductive phase lattice to form a stable solid solution, effectively suppressing lattice distortion under temperature changes. Traditional inorganic oxides provide precise compensation for interface defects, while organic modifiers ensure doping uniformity, further suppressing lattice distortion under temperature variations. Through synergistic optimization of the process and proportions, in-situ bonding between the dopant elements and the conductive phase is achieved, forming a dense interface modification layer on the conductive phase surface. The synergistic effect of these three components ensures that the temperature coefficient of resistance is stably controlled within ±25ppm / ℃, with an optimal range of ±16ppm / ℃. This meets the stringent requirements of high-end applications such as automotive-grade electronics and high-precision sensors, solving the industry problems of large temperature drift and easily abrupt changes in resistance values ​​in traditional resistive pastes. This invention further optimizes the weight ratio of rare earth oxides in the inorganic composite dopant to 30%–80%. When the proportion of rare earth oxides is less than 30%, the lattice modification effect is insufficient, and the temperature dependence of carrier transport cannot be effectively suppressed, resulting in a significant increase in the temperature coefficient of resistance. When the proportion of rare earth oxides is greater than 80%, the excess rare earth ions exceed the solid solution limit of the conductive phase, causing lattice distortion and precipitation of the second phase, which in turn worsens the temperature coefficient of resistance.

[0026] 2. This invention uses ZnO-B2O3-La2O3 series lead-free glass powder as the binder phase, and the La in the glass phase... 3+ (Ionic radius 1.06 Å) and Ce-doped in the conductive phase 3+ (1.02Å), Nd 3+ (0.98Å), Y 3+ Rare earth ions such as (0.90 Å) form characteristic chemical bonds such as La-O-Ce and Ce-O-Ru at the conductive phase-glass phase interface due to their similar ionic radii. Furthermore, the lattice fringes at the conductive phase-glass phase interface are continuous, and the interface transition region width reaches 20–30 nm. This interface structure simultaneously achieves the triple effects of conductive phase lattice modification, three-phase (conductive phase, glass phase, and dopant phase) interface strengthening, and reduction of the glass phase softening point. This allows the slurry to be fully sintered in a wide temperature range of 750–900℃, with a sintering window of up to 150℃. The wide sintering window and good process compatibility make it highly adaptable to different production processes and equipment, reducing production energy consumption while improving production yield. It balances low-energy sintering with high reliability, effectively solving the industry problems of high sintering temperature and poor stability in traditional resistance slurries.

[0027] 3. This invention achieves a stable temperature coefficient of resistance of ≤±25ppm / ℃ across the entire range from 1Ω / □ to 10MΩ / □ by precisely controlling the particle size, moisture content, and loss on ignition of the conductive phase powder and by using multiple conductive phases in combination to construct a continuous and stable conductive network. Rare earth doping enhances the stability of the crystal phase and interface, completely eliminating nonlinear temperature drift and resistance step changes. Under short-term overload and electrostatic discharge tests, the resistance drift is ≤±0.7%, ensuring excellent long-term reliability and eliminating the risk of sudden resistance changes.

[0028] 4. The coupling agent in the organic carrier of this invention can form a strong chemical bond with the surface of the conductive phase after rare earth doping, thereby improving the printability and film-forming properties of the slurry. At the same time, combined with precision filtration and high vacuum degassing processes, large particles and bubbles in the slurry are effectively removed, avoiding fluctuations in the temperature coefficient of resistance due to film defects.

[0029] 5. This invention uses a ZnO-B2O3-La2O3 lead-free glass system throughout, which is lead-free and environmentally friendly, complies with RoHS environmental directives and automotive electronics industry requirements, and is suitable for high-reliability application scenarios such as automotive electronics, high-precision sensors, and 5G devices. Attached Figure Description

[0030] Figure 1 This is the O1s XPS peak spectrum of the interface region between the conductive phase and the glass phase in the sample sintered from the resistive slurry of Example 2.

[0031] Figure 2 This is a TEM characterization image of the interface region between the conductive phase and the glass phase in the sample sintered from the resistive paste of Example 3. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0033] The silver powder, palladium powder, ruthenium dioxide powder, lead ruthenate powder, bismuth ruthenate powder, and copper ruthenate powder used in the examples each have a particle size independently ranging from 0.2 to 3 μm, a moisture content ≤0.2%, and a loss on ignition ≤0.2%. The ZnO-B2O3-La2O3 glass powder used has a particle size of 500 nm to 5 μm, and its weight percentage composition is: ZnO 50%, B2O3 30%, La2O3 10%, Bi2O3 10%. Preparation method: The raw materials are mixed in proportion, melted and kept at 1250℃ for 2 hours, water quenched, ball-milled to a particle size of 500 nm to 5 μm, dried, and crushed for later use.

[0034] Example 1

[0035] Step 1: Preparation of in-situ doped modified conductive phase powder

[0036] Weigh out 60g of silver powder, 28g of palladium powder, 1.5g of lanthanum oxide, 1.5g of strontium oxide, and 9g of dipropylene glycol methyl ether, mix them, and disperse them at 4500rpm for 30min. After dispersion, heat-cur them at 200℃ for 90min, then purify them with anhydrous ethanol to remove impurities, and vacuum dry them at 70℃ for 12h to obtain in-situ doped modified conductive phase powder.

[0037] Step 2: Preparation of organic carrier

[0038] Weigh 4g of hydroxypropyl cellulose, 1g of polyvinyl butyral, 1g of silane coupling agent KH550, 60g of terpineol, and 34g of diethylene glycol ethyl ether acetate. Place them in a homogenizer and homogenize at 70℃ for 6 hours until completely dissolved. After filtration, the organic carrier is obtained.

[0039] Step 3: Preparation of resistive paste

[0040] Weigh out 23g of organic carrier, 42g of in-situ doped modified conductive phase powder, 25g of terpineol, 8g of ZnO-B2O3-La2O3 lead-free glass powder, 1.5g of Dow Corning 6040, and 0.5g of zinc oxide. Homogenize the mixture in a high-shear mixer for 1 hour, then finely grind it to a fineness of ≤10μm using a three-roll mill to obtain a crude slurry. The crude slurry is then subjected to 325-mesh precision filtration and high-vacuum degassing treatment (vacuum degree ≥-0.095MPa, degassing for 30min) to obtain the finished resistor slurry.

[0041] Example 2

[0042] The difference between this embodiment and Embodiment 1 is as follows: In step 1, 33g of silver powder, 14g of palladium powder, 41g of ruthenium dioxide powder, 1.5g of cerium oxide, 1g of zirconium silicate, and 9.5g of ethylene glycol butyl ether acetate are weighed and mixed, dispersed at 4500rpm for 30min, and then heat-cured at 220℃ for 60min. After purification with anhydrous ethanol, the powder is vacuum-dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Embodiment 1.

[0043] Example 3

[0044] The difference between this embodiment and Embodiment 1 is as follows: In step 1, 21g of ruthenium dioxide powder, 60g of lead ruthenate powder, 3g of yttrium oxide, 2g of titanium dioxide, and 14g of ethylene glycol hexyl ether are weighed and mixed, dispersed at 4000rpm for 40min, and then heat-cured at 190℃ for 90min. After purification with anhydrous ethanol, the mixture is vacuum dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Embodiment 1.

[0045] Example 4

[0046] The difference between this embodiment and Embodiment 1 is as follows: In step 1, 5g of ruthenium dioxide powder, 80g of bismuth ruthenate powder, 3g of lanthanum-cerium composite oxide, 2g of manganese trioxide, and 10g of dipropylene glycol methyl ether are weighed and mixed, dispersed at 4000rpm for 40min, and then heat-cured at 190℃ for 90min. After purification with anhydrous ethanol, the mixture is vacuum dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Embodiment 1.

[0047] Example 5

[0048] The difference between this embodiment and Embodiment 1 is as follows: In step 1, 31g of lead ruthenate powder, 54g of copper ruthenate powder, 4g of yttrium zirconium composite oxide, 1g of manganese tetroxide, and 10g of dipropylene glycol methyl ether are weighed and mixed, dispersed at 4000 rpm for 40 minutes, and then heat-cured at 200℃ for 90 minutes. After purification with anhydrous ethanol, the powder is vacuum-dried at 70℃ for 12 hours to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Embodiment 1.

[0049] Comparative Example 1

[0050] According to the weight proportions, weigh 23g of organic carrier (preparation method is the same as step 2 of Example 1), 28.6g of silver powder, 1.4g of palladium powder, 25g of terpineol, 8g of ZnO-B2O3-La2O3 lead-free glass powder, 1.5g of Dow Corning 6040, and 0.5g of zinc oxide. Homogenize and mix them in a high-shear mixer for 1 hour, and then grind them into fine powder with a three-roll mill until the fineness is ≤10μm to obtain a crude slurry. The crude slurry is then subjected to 325-mesh precision filtration and high-vacuum degassing treatment (vacuum degree ≥-0.095MPa, degassing for 30min) to obtain the finished resistor slurry.

[0051] Comparative Example 2

[0052] The difference between this comparative example and Example 1 is as follows: In step 1, 60g of silver powder, 28g of palladium powder, and 9g of dipropylene glycol methyl ether were weighed and mixed, dispersed at 4500rpm for 30min, and then heat-cured at 200℃ for 90min. After purification with anhydrous ethanol, the mixture was vacuum dried at 70℃ for 12h to obtain the modified conductive phase powder. The other steps are the same as in Example 1.

[0053] Comparative Example 3

[0054] The difference between this comparative example and Example 1 is as follows: In step 1, 60g of silver powder, 28g of palladium powder, 3g of strontium oxide, and 9g of dipropylene glycol methyl ether were weighed and mixed, dispersed at 4000rpm for 40min, and then heat-cured at 175℃ for 90min. After purification with anhydrous ethanol, the mixture was vacuum dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Example 1.

[0055] Comparative Example 4

[0056] The difference between this comparative example and Example 2 is as follows: In step 1, 33g of silver powder, 14g of palladium powder, 41g of ruthenium dioxide powder, 2.5g of zirconium silicate, and 9.5g of ethylene glycol butyl ether acetate were weighed and mixed, dispersed at 4000rpm for 40min, and then heat-cured at 200℃ for 90min. After purification with anhydrous ethanol, the powder was vacuum dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Example 2.

[0057] Comparative Example 5

[0058] The difference between this comparative example and Example 3 is as follows: In step 1, 21g of ruthenium dioxide powder, 60g of lead ruthenate powder, 5g of titanium dioxide, and 14g of ethylene glycol hexyl ether were weighed and mixed, dispersed at 3500rpm for 50min, and then heat-cured at 180℃ for 120min. After purification with anhydrous ethanol, the powder was vacuum dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Example 3.

[0059] Comparative Example 6

[0060] The difference between this comparative example and Example 4 is as follows: In step 1, 5g of ruthenium dioxide powder, 80g of bismuth ruthenate powder, 5g of manganese trioxide, and 10g of dipropylene glycol methyl ether were weighed and mixed, dispersed at 3500rpm for 50min, and then heat-cured at 180℃ for 120min. After purification with anhydrous ethanol, the mixture was vacuum dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Example 4.

[0061] Comparative Example 7

[0062] The difference between this comparative example and Example 4 is as follows: In step 1, 31g of lead ruthenate powder, 54g of copper ruthenate powder, 5g of manganese tetroxide, and 10g of dipropylene glycol methyl ether were weighed and mixed, dispersed at 3500rpm for 50min, and then heat-cured at 180℃ for 120min. After purification with anhydrous ethanol, the powder was vacuum-dried at 70℃ for 12h to obtain in-situ doped modified conductive phase powder. Other steps are the same as in Example 5.

[0063] The resistance pastes prepared in Examples 1-5 and Comparative Examples 1-7 were screen-printed once on a 96% alumina substrate using a 325-mesh screen, and the sintered film thickness was controlled to be 8-10 μm. The pastes were then dried at 180°C for 10-15 min, sintered at 850°C and held at that temperature for 10 min. The performance of the fired samples was tested according to the following standards: appearance and color were visually inspected; viscosity was measured using a Brookfield HBT viscometer (14# rotor, 10 rpm, constant temperature at 25℃±1℃ for 30 min); sheet resistance was tested according to YS / T 607-2006 standard, with ≥10 samples; temperature coefficient of resistance (TCR) was tested according to YS / T 607-2006 standard within the temperature range of -55℃ to +125℃, with ≥10 samples; short-term overload (STOL) and electrostatic discharge (ESD) were tested according to YS / T 607-2006 standard; adhesion of the dried film was tested according to GB / T 9286-1998 standard; resistance drift after 100 temperature cycles was conducted within the temperature range of -55℃ to +125℃ (heating and cooling at 10℃ / min, with 15 min of holding time at both high and low temperatures). The test results are shown in Table 1.

[0064] Table 1

[0065]

[0066] As shown in Table 1, the resistive pastes in Examples 1-5, using a composite doping of rare earth oxides and traditional inorganic oxides to modify the conductive phase, all achieved stable TCRs within ±16 to ±23 ppm / ℃. Comparative Example 1, using an unmodified conductive phase, and Comparative Example 2, using only an organic modifier, achieved TCRs as high as ±190 to ±200 ppm / ℃. Comparative Examples 3-7, using only traditional inorganic oxides to modify the conductive phase, had TCRs between ±35 and ±48 ppm / ℃, which, while better than Comparative Examples 1 and 2, still fell short of ±25 ppm / ℃. This indicates that the modification effect of traditional single oxide doping is limited and cannot meet the stringent requirements of high-end applications. Comparing Examples 1-5 with Comparative Examples 3-7, both used the same thermosetting in-situ bonding process; the only difference was the addition of rare earth oxides. Experimental results showed that after adding rare earth oxides, the TCR significantly decreased from ±35 to ±48 ppm / ℃ to ±16 to ±23 ppm / ℃, a reduction of over 50%. This fully demonstrates the crucial and irreplaceable role of rare earth oxides in reducing the temperature coefficient of resistance. Furthermore, the STOL, ESD, and temperature cycling drift of the resistance pastes in Examples 1-5 are significantly better than those in Comparative Examples 3-7, proving that rare earth doping effectively improves the long-term stability of the film. The resistance paste of this invention can be fully sintered over a wide temperature range of 750-900℃, with TCR fluctuations not exceeding ±5ppm / ℃ across the entire temperature range, far superior to the narrow sintering window of existing technologies.

[0067] To determine the optimal weight ratio of rare earth oxides in the inorganic composite dopant, this invention designed a single-factor comparative experiment: using lanthanum oxide and strontium oxide as composite dopant (total doping amount fixed at 3g, relative to the weight ratio of the conductive phase powder), other raw materials, preparation process, and testing conditions were completely consistent with Example 1. The TCR and resistance drift after 100 temperature cycles were tested. Temperature cycle test conditions: -55℃ to +125℃ temperature range, heating and cooling rate 10℃ / min, holding at both high and low temperatures for 15min, 100 cycles. The results are shown in Table 2.

[0068] Table 2. Experimental Results of Rare Earth Doping Ratio Optimization

[0069]

[0070] As shown in Table 2, when the weight percentage of rare earth oxides in the inorganic composite dopant is 30%–80%, the TCR of the resulting resistive paste is stably controlled between ±16 and ±24 ppm / ℃, and the resistance drift after 100 temperature cycles is ≤ ±0.7%, with no abrupt change in resistance. When the weight percentage of rare earth oxides in the inorganic composite dopant is less than 30%, the lattice modification effect of rare earth ions is insufficient, and the temperature dependence of carrier transport cannot be effectively suppressed, resulting in a significant increase in TCR. When the weight percentage of rare earth oxides in the inorganic composite dopant is greater than 80%, the excess rare earth ions exceed the solid solution limit of the conductive phase, causing severe lattice distortion and second phase precipitation, which in turn leads to a deterioration in TCR and a decrease in system stability. Under the same test conditions, the TCR of single rare earth oxide doping or single traditional inorganic oxide doping (100% percentage) is ±110 ppm / ℃ and ±185 ppm / ℃, respectively, which are far inferior to the composite doping of the present invention.

[0071] To visually demonstrate the presence of La in ZnO-B2O3-La2O3 series glass powder 3+ The gradient matching effect with rare earth doped ions reveals the microscopic mechanism for achieving low TCR and wide temperature sintering, which is characterized by XPS interface elemental analysis and TEM lattice imaging.

[0072] (1) Analysis of XPS Interface Elements

[0073] Taking the resistive paste (cerium oxide and zirconium silicate composite doping) from Example 2 as an example, elemental analysis of the conductive phase-glass phase interface was performed by X-ray photoelectron spectroscopy (XPS). The XPS test was conducted using a ThermoFisher ESCALAB 250Xi X-ray photoelectron spectrometer with an excitation source of Al Kα rays (1486.6 eV), a power of 150 W, a pass energy of 20 eV, a step size of 0.1 eV, and a vacuum level better than 1 × 10⁻⁶. -9Pa. Before testing, the sintered sample was etched with argon ions for 30 seconds to remove the surface contamination layer. The binding energy was calibrated using C1s (284.8 eV) as a reference. The results are as follows. Figure 1 As shown in Table 3. The results show that the characteristic binding energies of Ce-O-La and Ce-O-Zn chemical bonds were detected in the interface region, proving that La 3+ (From glass phase) and Ce 3+ (from rare earth oxides), Zn 2+ (From the glass phase) Stable chemical bonds were formed, rather than physical mixing.

[0074] Table 3. Binding Energy Data of XPS Interface Elements

[0075]

[0076] (2) TEM lattice image analysis

[0077] Taking the resistive paste (yttrium oxide and titanium dioxide composite doping) of Example 3 as an example, the lattice structure of the conductive phase-glass phase interface was observed by transmission electron microscopy (TEM). TEM testing was performed using a JEOL JEM-2100F field emission transmission electron microscope with an accelerating voltage of 200 kV and a point resolution of 0.19 nm. Sample preparation method: The sintered resistive film was peeled off from the alumina substrate, embedded in epoxy resin, and then ultra-thinly sliced ​​to a thickness of approximately 50 nm. The slices were then placed on a carbon film supported by a copper mesh for testing. Figure 2 The results showed that La in the glass phase 3+ Y in ions and dopants 3+ The two ions form a continuous ionic radius gradient, and clear ruthenium dioxide (110) crystal lattice fringes are visible in the conductive phase region, while the glass phase region exhibits typical amorphous diffuse scattering contrast. A 20-30 nm wide interfacial transition region exists between the two, with smooth lattice spacing and no obvious lattice fractures, effectively mitigating interfacial thermal mismatch. The simultaneous embedding of rare earth ions into the glass phase lattice lowers the glass softening point by approximately 70°C, enabling the slurry to achieve full sintering at 750°C. This is the core microscopic mechanism for achieving wide-temperature sintering in this invention. The La in the ZnO-B2O3-La2O3 glass powder... 3+ By matching the ionic radius gradient with rare earth doped ions, the invention simultaneously achieves the triple effect of "conductive phase lattice modification + three-phase interface strengthening + glass phase softening point reduction". This is the core reason why the invention can simultaneously obtain low TCR within ±25ppm / ℃ and wide temperature sintering of 750~900℃, which is different from the physical mixing system without synergistic design in the existing technology.

[0078] As can be seen from the above embodiments and comparative examples, the resistive paste of the present invention, through the synergistic effect of rare earth doping quantification optimization, thermosetting in-situ bonding process, and ZnO-B2O3-La2O3 glass, achieves stable TCR control within ±25ppm / ℃ and can be fully sintered in a wide temperature range of 750~900℃, exhibiting excellent stability and reliability. Among these, the optimal overall performance is achieved when the mass ratio of rare earth oxides in the inorganic composite dopant is 50%~60% (Examples 1-2), with a TCR reaching ±16~±18ppm / ℃. Therefore, the resistive paste of the present invention is suitable for thick-film circuits, chip resistors, automotive electronics, and high-precision sensors.

Claims

1. A sintering-type high-stability, low-resistivity temperature coefficient resistive paste, characterized in that, The resistive paste, by weight percentage (100%), comprises: 5%–35% lead-free glass powder, 15%–45% in-situ doped modified conductive phase, 5%–25% organic carrier, 0.1%–2% organic additives, 0.1%–2% inorganic additives, and 5%–25% organic solvent; The in-situ doped modified conductive phase is a conductive powder prepared by the following method: dispersing an inorganic composite dopant and a conductive phase powder in an organic modifier, followed by thermosetting at 175–220°C to achieve in-situ bonding between the inorganic composite dopant and the conductive phase powder to form the conductive powder; wherein the amount of the inorganic composite dopant added is 2%–8% of the weight of the in-situ doped modified conductive phase, the amount of the organic modifier added is 5%–20% of the weight of the in-situ doped modified conductive phase, and the amount of the conductive phase powder added is 75%–90% of the weight of the in-situ doped modified conductive phase; The inorganic composite dopant is a mixture of rare earth oxides and traditional inorganic oxides. The rare earth oxides are selected from one or more of lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, yttrium oxide, ytterbium oxide, lanthanum-cerium composite oxide, and yttrium-zirconium composite oxide, and the amount of a single rare earth oxide added to the inorganic composite dopant does not exceed 5% of the weight of the conductive phase powder. The traditional inorganic oxides are selected from one or more of zirconium dioxide, zirconium silicate, tin dioxide, tantalum pentoxide, manganese tetroxide, manganese trioxide, strontium oxide, niobium trioxide, and titanium dioxide; and the weight percentage of the rare earth oxides in the inorganic composite dopant is 30% to 80%. The conductive phase powder is selected from one or more of silver powder, palladium powder, ruthenium dioxide powder, lead ruthenate powder, bismuth ruthenate powder, and copper ruthenate powder; its particle size is 0.2-3 μm, moisture content is ≤0.2%, and loss on ignition is ≤0.2%; The organic modifier is selected from one or more of dipropylene glycol methyl ether, propylene glycol monobutyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether acetate, and ethylene glycol hexyl ether; The lead-free glass powder is a ZnO-B2O3-La2O3 series glass powder with a particle size of 500nm to 5μm.

2. The sintered high-stability, low-resistivity temperature coefficient resistive slurry according to claim 1, characterized in that, The resistive paste, by weight percentage (100%), comprises: 8%–20% lead-free glass powder, 30%–45% in-situ doped modified conductive phase, 15%–25% organic carrier, 1%–1.5% organic additives, 0.5%–1% inorganic additives, and 15%–25% organic solvent.

3. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 1 or 2, characterized in that, The rare earth oxides account for 50% to 60% of the weight of the inorganic composite dopant.

4. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 1 or 2, characterized in that, The temperature for the thermosetting treatment is 190–200°C.

5. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 1 or 2, characterized in that, The amount of inorganic composite dopant added is 3% to 5% of the weight of the in-situ doped and modified conductive phase, the amount of organic modifier added is 8% to 15% of the weight of the in-situ doped and modified conductive phase, and the amount of conductive phase powder added is 80% to 88% of the weight of the in-situ doped and modified conductive phase.

6. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 1 or 2, characterized in that, The ZnO-B2O3-La2O3 series glass powder, by weight percentage (100%), has the following composition: ZnO 40%–55%, B2O3 20%–35%, La2O3 5%–15%, with the balance being flux. The flux is selected from one or more of bismuth oxide, sodium oxide, potassium oxide, and lithium oxide.

7. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 1 or 2, characterized in that, The organic carrier, by weight percentage (100%), comprises: 1%–15% hydroxypropyl cellulose, 1%–5% polyvinyl butyral, 1%–5% coupling agent, 20%–75% terpineol, and 20%–70% diethylene glycol ethyl ether acetate; the coupling agent is selected from one or more of titanate coupling agents, aluminate coupling agents, silane coupling agents, and aluminum borate coupling agents.

8. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 7, characterized in that, The organic solvent is selected from one or more of terpineol, dibutyl phthalate, methyl amyl acetate, isobutyl isobutyrate, glycol diacetate, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, and egg yolk lecithin.

9. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 1 or 2, characterized in that, The organic additive is selected from one or more of the following: rosin, hydrogenated castor oil, polyamide wax, organosilicon resin, epoxy silane coupling agent, titanate coupling agent, aluminum zirconium coupling agent, polyphosphate dispersant, polyamide dispersant, alicyclic amine curing agent, and polyether amine curing agent.

10. The sintered high-stability, low-resistivity temperature coefficient resistive paste according to claim 1 or 2, characterized in that, The inorganic additive is selected from one or more of the following: carbon black, copper oxide, nickel powder, carbon nanotubes, α-alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, crystalline silicon dioxide, and silicon carbide.

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