High-sheet-resistance resistor paste, preparation method and thick film circuit

Abstract

The invention relates to the technical field of thick-film resistors, and discloses a high-sheet-resistance resistor paste, a preparation method thereof and a thick-film circuit. The resistance paste comprises 6%-24% of a composite conductive phase, 33%-57% of an inorganic binding phase, 2%-6% of a modifier and 22%-38% of an organic carrier. The conductive phase comprises nano-scale / submicron-scale ruthenium dioxide powder and submicron-scale flake silver powder, and the conductivity and the stability are cooperatively guaranteed. According to the preparation method, a secondary dispersing and grinding process is adopted, and a finished product is obtained through coarse grinding, vacuumizing fine grinding and 800-mesh filtering. The thick film circuit adopts an N-group parallel architecture, so that the use amount of conductive phases can be greatly reduced. The problem that traditional slurry is poor in stability under high sheet resistance is solved, TCR is smaller than or equal to 100 ppm / DEG C, resistance precision is within + / -5%, temperature and humidity stability is excellent, cost is low, and the slurry is suitable for high-precision heating scenes such as a new energy automobile heating system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thick film resistance, in particular to a high sheet resistance resistance paste, a preparation method and a thick film circuit. BACKGROUND

[0002] With the continuous rise of global precious metal raw material prices, the production cost of thick film heating products is under great pressure, and the demand for high sheet resistance resistance paste is increasingly urgent. High sheet resistance resistance paste can reduce the amount of conductive phase (mostly precious metal material) under the premise of meeting the heating power demand, thereby significantly reducing the raw material cost of the product, and has important industrial value. At the same time, the application scenarios of thick film heating products are constantly expanding, especially in the fields of new energy vehicles and precision industrial heating, which puts forward more stringent requirements on the performance of resistance paste: not only need to maintain stable resistance value in a wide temperature range (such as -55℃ to 125℃), but also need to resist the erosion of high humidity environment, and have high precision resistance control ability to ensure the reliability and consistency of product operation.

[0003] However, the resistance paste in the prior art mostly uses a single conductive phase (such as pure ruthenium dioxide), which is difficult to balance the conductivity and stability under the conditions of high sheet resistance and low conductive phase content. Although ruthenium dioxide has excellent conductivity, the content is highly sensitive to resistance value, resulting in a resistance temperature coefficient (TCR) of 300-600ppm / ℃, and high noise, which cannot meet the demand of stable work in a wide temperature range.

[0004] In summary, the prior art still has deficiencies in meeting the increasing demand for high performance of high sheet resistance resistance paste for thick film heating products. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned shortcomings, and to provide a high sheet resistance resistance paste, a preparation method and a thick film circuit.

[0006] To achieve the above-mentioned purpose, the specific scheme of the present application is as follows: The first aspect of the present application provides a high sheet resistance resistance paste, which comprises the following components by mass percentage: Conductive phase 6%-24% Inorganic bonding phase 33%-57% Modifier 2%-6% Organic carrier 22%-38%; The conductive phase is a composite system conductive phase, which comprises the following components by total mass percentage of conductive phase: Nano-sized ruthenium dioxide powder 45%-58% Sub-micron-sized ruthenium dioxide powder 25%-38% Sub-micron-sized silver flake powder 6%-17%.

[0007] The nano-sized ruthenium dioxide powder has extremely high specific surface area, and can construct a dense conductive network; the sub-micron-sized ruthenium dioxide powder is supplemented to enhance the continuity of the conductive network; and a small amount of sub-micron-sized silver flake powder can reduce the electron transmission resistance; the three synergistically act together to make the conductive phase of the composite system have extremely high specific surface area and excellent electron conduction capacity; after being mixed with the inorganic adhesive phase glass powder, a more efficient conductive network can be formed in the slurry, the electron transmission efficiency is significantly improved, and the problem of insufficient conductive capacity of the traditional single conductive phase at high sheet resistance is solved.

[0008] Further, the inorganic adhesive phase is a low-melting-point glass powder system, and comprises the following components in terms of total mass percentage of the inorganic adhesive phase: Bismuth oxide 25%-38% Silicon dioxide 30%-52% Boron oxide 6%-12% Aluminum oxide 6%-12%.

[0009] The bismuth oxide is used as a low-melting-point core component to ensure that the glass powder melts and flows at a relatively low temperature; the silicon dioxide forms a glass skeleton to improve the mechanical strength of the resistance film; and the boron oxide and the aluminum oxide synergistically adjust the chemical stability and the thermal expansion coefficient of the glass powder, so that the glass powder system has a unique softening temperature range and good chemical stability; in the sintering process, the softening temperature of the glass powder matches the reaction temperature of the conductive phase and other additives, the glass powder can melt and flow uniformly at a relatively low temperature, uniformly wrap the conductive phase particles, form a stable adhesive structure, and enhance the adhesion between the resistance film and the substrate, while avoiding the damage to the structure and performance of the conductive phase caused by high-temperature sintering, and avoiding the damage to the structure of the conductive phase, while enhancing the adhesion between the resistance film and the substrate.

[0010] Further, the modifier is a composite system, and comprises the following components in terms of total mass of the slurry: Manganese dioxide 1%-3% Cobalt trioxide 0.5%-3% Yttrium oxide 1%-5%.

[0011] The manganese dioxide and the cobalt trioxide are used as transition metal oxides to interact with the conductive phase and the inorganic adhesive phase, compensate for the resistance fluctuation caused by temperature change, reduce the TCR, and make the slurry maintain stable resistance performance in a relatively wide temperature range; the yttrium oxide is used as a rare earth compound to refine the grains formed in the sintering process, improve the density of the resistance film, enhance the mechanical strength and the anti-aging performance, and reduce the aging and performance degradation of the resistance film in the use process.

[0012] Furthermore, the organic carrier is an environmentally friendly multi-element solvent system, comprising the following components by weight percentage of the total organic carrier: Dodecyl alcohol esters 37%-45% Alcohol ester hexadecyl 42%-52% Ethyl cellulose 5%-10% Surfactants 1.5%-4%.

[0013] The dodecyl and hexadecyl alcohol esters possess excellent solubility and slow volatility, providing suitable fluidity for the paste during the printing process and ensuring uniform screen printing onto the substrate. Ethyl cellulose imparts a certain degree of viscosity and thixotropy to the paste, enabling it to maintain a stable shape after printing and preventing the paste from flowing or deforming. The addition of surfactants reduces the interfacial tension between the organic carrier and the solid components, improving the uniformity of the solid components' dispersion in the organic carrier and ensuring the stability of the paste during storage and use.

[0014] Furthermore, the nano-sized ruthenium dioxide powder has a particle size of 50-200 nm, and the submicron-sized ruthenium dioxide powder and submicron-sized silver powder have a particle size of 0.3-1 μm.

[0015] Furthermore, the softening temperature range of the low melting point glass powder system is 450-600℃.

[0016] A second aspect of the present invention provides a method for preparing a high sheet resistance slurry as described above, specifically comprising the following steps: Step S1: Take the conductive phase, inorganic binder, modifier and 80%-90% organic carrier in proportion and put them into a planetary disperser and disperse them evenly at low speed. Then, use a three-roll mill for coarse grinding. The speed of low-speed dispersion is 300-600 r / min. Coarse grinding under high viscosity can effectively break up solid particle agglomerates and lay the foundation for subsequent fine dispersion.

[0017] Step S2: Add the remaining 10%-20% organic carrier to the coarsely ground slurry, adjust the slurry viscosity to 100 Pa·s ± 20 Pa·s, and then place it in a planetary disperser to disperse evenly under medium speed and vacuum conditions. Then, use a three-roll mill for fine grinding. The medium speed is 800-1200 r / min; the vacuum degree is -0.08 to -0.1 MPa. Vacuum dispersion can release air in agglomerated particles, medium speed stirring ensures that the organic carrier fully coats each powder particle, and fine grinding further reduces particle fineness and improves component uniformity.

[0018] Step S3: Filter the finely ground paste using a filter to obtain a high sheet resistance paste with a fineness of less than 5 μm; the filter removes large particles of impurities that are not thoroughly ground, so as to avoid affecting the printing effect and resistance performance.

[0019] In the preparation of this invention, the resistive slurry is dispersed and ground twice. This is mainly because the viscosity of the slurry is relatively high during the first grinding, and the grinding effect of a three-roll mill is better. The second dispersion is carried out at medium speed under vacuum to ensure that the components of the slurry are fully and evenly dispersed. The air that is agglomerated in the material is released again under negative pressure, allowing the organic phase to encapsulate each powder particle.

[0020] Furthermore, in step S1, the material is coarsely ground 3-5 times using a three-roll mill; in step S2, it is finely ground 3-5 times using a three-roll mill.

[0021] Furthermore, in step S3, the finely ground slurry is filtered using an 800-mesh filter.

[0022] A third aspect of this invention provides a thick-film circuit fabricated using the high sheet resistance paste described above. The thick-film circuit employs an N-group parallel architecture, where N is a positive integer greater than or equal to 1. This multi-parallel design enables high-power heating under the same voltage and heating area, meeting the power requirements of thick-film heating products. Simultaneously, the sheet resistance of the paste used is N² times that of a single parallel group (e.g., 49 times that of a single group when seven groups are in parallel). Higher sheet resistance requires less conductive phase, significantly reducing costs.

[0023] Compared with the prior art, the present invention has the following beneficial effects: Significantly improved stability: After 1000 temperature cycle tests within the range of -55℃ to 125℃, the resistance value change rate is only within ±0.5%, which is far better than the ±1.5% to ±3% level of existing products; Humidity stability: After being placed in an environment of 85%RH and 85℃ for 1000 hours, the resistance value change rate is less than ±1%, which is lower than the fluctuation range of ±2%~±5% of existing products, and can effectively resist the impact of humid environment on performance.

[0024] Excellent temperature adaptability: Through precise control of the modifier, the temperature coefficient of resistance (TCR) is controlled within 100ppm / ℃. Compared with the TCR of 300-600ppm / ℃ of traditional high sheet resistance slurry, it can maintain a stable resistance value over a wider operating temperature range, making it suitable for extreme temperature scenarios such as heating systems for new energy vehicles.

[0025] High resistance accuracy: Through the composite conductive phase system and secondary dispersion and grinding process, the resistance accuracy of the slurry is controlled within ±5%, which is a significant improvement over the ±10% accuracy of existing products. This greatly reduces the resistance defect rate at the production end and improves production efficiency.

[0026] Significant cost advantages: Combined with a multi-parallel circuit architecture, the amount of conductive phase (precious metal) used in high sheet resistance slurry is greatly reduced. For example, when 7 groups are connected in parallel, the sheet resistance of the slurry is only 49 times that of 1 group in parallel. The higher the sheet resistance of the slurry, the less conductive phase is used, which significantly reduces the cost of raw materials and has considerable economic benefits.

[0027] The process is highly feasible: the preparation process uses conventional equipment such as planetary dispersers, three-roll mills, and 800-mesh filters, without the need for special customization. The process parameters are clear, the operation is simple, and it is suitable for industrial mass production. Attached Figure Description

[0028] Figure 1 This is a comparative schematic diagram of the thick film circuit with 1, 3, 5, and 7 parallel architectures provided in Embodiment 6 of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this is not to limit the scope of the invention to this.

[0030] Example 1

[0031] The high sheet resistance slurry described in this embodiment has the following formulation and preparation method: The high square resistance slurry comprises the following raw materials by mass percentage: 15% conductive phase, 45% inorganic binder phase, 4% modifier and 36% organic carrier.

[0032] The conductive phase, by total mass, comprises the following components in the following mass percentages: 55% nano-sized ruthenium dioxide powder, 32% submicron-sized ruthenium dioxide powder, and 13% submicron-sized flake silver powder; the nano-sized ruthenium dioxide powder has a particle size of 100 nm, the submicron-sized ruthenium dioxide powder has a particle size of 0.5 μm, and the submicron-sized flake silver powder has a particle size of 0.8 μm; all these components of the conductive phase are commercially available. Based on the total mass of the inorganic binder phase, the inorganic binder phase comprises the following components by mass percentage: bismuth oxide 32%, silicon dioxide 41%, boron oxide 9%, and aluminum oxide 8%. The inorganic binder phase is a low-melting-point glass powder system with a softening temperature controlled at 450℃. The preparation process is a conventional glass powder preparation process, such as mixing bismuth oxide, silicon dioxide, boron oxide, and aluminum oxide powders evenly in a three-dimensional mixer, melting the mixture in a furnace to obtain molten glass, then quenching the molten glass in water to obtain glass slag, and finally using distilled water as a medium, ball milling the glass slag in a planetary ball mill for 4-6 hours to obtain glass powder with an average particle size of 1μm-3μm.

[0033] Based on the total mass of the slurry, the modifier comprises the following components by mass percentage: 1.5% manganese dioxide, 1.0% cobalt trioxide, and 1.5% yttrium oxide; all of these modifiers are commercially available. Based on the total mass of the organic carrier, the organic carrier comprises the following components by mass percentage: 41% dodecyl alcohol ester, 47% hexadecyl alcohol ester, 8% ethyl cellulose, and 3% surfactant. The surfactant is polyethylene glycol fatty acid ester. The organic carrier is prepared using a conventional oil bath dispersion process. For example, organic solvent and ethyl cellulose are added to a reaction vessel and reacted for 5-10 hours, with the temperature controlled at 70-80℃ and the disperser speed at 100 rpm, to obtain an ethyl cellulose mixture. Then, the temperature in the reaction vessel is lowered to 60-70℃, the disperser speed is reduced to 80 rpm, and the surfactant is added, reacting for 1-5 hours to obtain the organic carrier.

[0034] The preparation method of the above-mentioned high square resistance slurry includes the following steps: Step S1: Take the above proportion of conductive phase, inorganic binder, modifier and 85% organic carrier, put them into a planetary disperser and disperse them at a low speed of 450r / min for 20 minutes, and then coarsely grind them 4 times with a three-roll mill. Step S2: Add the remaining 15% organic carrier to the coarsely ground slurry, adjust the slurry viscosity to 100 Pa·s, put it into a planetary disperser and disperse it under vacuum at a speed of 1000 r / min and a vacuum degree of -0.09 MPa for 30 minutes, and then grind it finely 4 times with a three-roll mill. Step S3: Filter the finely ground slurry using an 800-mesh filter to remove large particle impurities and obtain a high sheet resistance slurry with a fineness of 4.2μm.

[0035] Example 2

[0036] The high sheet resistance slurry described in this embodiment has the following formulation and preparation method: The high square resistance slurry comprises the following raw materials in weight percentages: 6% conductive phase, 56.5% inorganic binder phase, 2.5% modifier, and 35% organic carrier.

[0037] The conductive phase, by total mass, comprises the following components in the following mass percentages: 58% nano-sized ruthenium dioxide powder, 36% submicron-sized ruthenium dioxide powder, and 6% submicron-sized flake silver powder; the nano-sized ruthenium dioxide powder has a particle size of 150 nm, the submicron-sized ruthenium dioxide powder has a particle size of 0.7 μm, and the submicron-sized flake silver powder has a particle size of 0.6 μm; all these components of the conductive phase are commercially available. Based on the total mass of the inorganic binder phase, the inorganic binder phase comprises the following components by mass percentage: bismuth oxide 38%, silicon dioxide 44%, boron oxide 9%, and aluminum oxide 9%. The inorganic binder phase is a low-melting-point glass powder system with a softening temperature controlled at 500℃. The preparation process is a conventional glass powder preparation process, such as mixing bismuth oxide, silicon dioxide, boron oxide, and aluminum oxide powders evenly in a three-dimensional mixer, melting them in a furnace to obtain molten glass, then quenching the molten glass in water to obtain glass slag, and finally using distilled water as a medium, placing the glass slag into a planetary ball mill for ball milling for 4-6 hours to obtain glass powder with an average particle size of 1μm-3μm. Based on the total mass of the slurry, the modifier comprises the following components by mass percentage: 1.0% manganese dioxide, 0.5% cobalt trioxide, and 1.0% yttrium oxide; all of these modifiers are commercially available. Based on the total mass of the organic carrier, the organic carrier comprises the following components by mass percentage: 42% dodecyl alcohol ester, 48% hexadecyl alcohol ester, 7% ethyl cellulose, and 3% surfactant. The surfactant is sorbitan fatty acid ester. The organic carrier is prepared using a conventional oil bath dispersion process. For example, organic solvent and ethyl cellulose are added to a reaction vessel and reacted for 5-10 hours, with the temperature controlled at 70-80℃ and the disperser speed at 100 rpm, to obtain an ethyl cellulose mixture. Then, the temperature in the reaction vessel is lowered to 60-70℃, the disperser speed is reduced to 80 rpm, and the surfactant is added, reacting for 1-5 hours to obtain the organic carrier.

[0038] The preparation method of the above-mentioned high square resistance slurry includes the following steps: Step S1: Take the above proportion of conductive phase, inorganic binder, modifier and 90% organic carrier, put them into a planetary disperser and disperse them at a low speed of 500r / min for 25 minutes, and then coarsely grind them 5 times with a three-roll mill. Step S2: Add the remaining 10% organic carrier to the coarsely ground slurry, adjust the slurry viscosity to 90 Pa·s, put it into a planetary disperser and disperse it under vacuum at a speed of 1100 r / min and a vacuum degree of -0.1 MPa for 25 minutes, and then grind it finely 5 times with a three-roll mill. Step S3: Filter the finely ground slurry using an 800-mesh filter to remove large particle impurities and obtain a high sheet resistance slurry with a fineness of 3.8μm.

[0039] Example 3

[0040] The high sheet resistance slurry described in this embodiment has the following formulation and preparation method: The high square resistance slurry comprises the following raw materials by weight percentage: 24% conductive phase, 33% inorganic binder phase, 5% modifier and 38% organic carrier.

[0041] The conductive phase, by total mass, comprises the following components in the following mass percentages: 45% nano-sized ruthenium dioxide powder, 38% submicron-sized ruthenium dioxide powder, and 17% submicron-sized flake silver powder; the nano-sized ruthenium dioxide powder has a particle size of 80 nm, the submicron-sized ruthenium dioxide powder has a particle size of 0.6 μm, and the submicron-sized flake silver powder has a particle size of 0.7 μm; all these components of the conductive phase are commercially available. Based on the total mass of the inorganic binder phase, the inorganic binder phase comprises the following components by mass percentage: bismuth oxide 25%, silicon dioxide 52%, boron oxide 11%, and aluminum oxide 12%. The inorganic binder phase is a low-melting-point glass powder system with a softening temperature controlled at 600℃. The preparation process is a conventional glass powder preparation process, such as mixing bismuth oxide, silicon dioxide, boron oxide, and aluminum oxide powders evenly in a three-dimensional mixer, melting the mixture in a furnace to obtain molten glass, then quenching the molten glass in water to obtain glass slag, and finally using distilled water as a medium, ball milling the glass slag in a planetary ball mill for 4-6 hours to obtain glass powder with an average particle size of 1μm-3μm.

[0042] Based on the total mass of the slurry, the modifier comprises the following components by mass percentage: 2% manganese dioxide, 1.5% cobalt trioxide, and 1.5% yttrium oxide; all of these modifiers are commercially available. Based on the total mass of the organic carrier, the organic carrier comprises the following components by mass percentage: 37% dodecyl alcohol ester, 52% hexadecyl alcohol ester, 8% ethyl cellulose, and 3% surfactant. The surfactant used is sorbitan fatty acid ester. The organic carrier is prepared using a conventional oil bath dispersion process. For example, organic solvent and ethyl cellulose are added to a reaction vessel and reacted for 5-10 hours, with the temperature controlled at 70-80℃ and the disperser speed at 100 rpm, to obtain an ethyl cellulose mixture. Then, the temperature in the reaction vessel is lowered to 60-70℃, the disperser speed is reduced to 80 rpm, and the surfactant is added, reacting for 1-5 hours to obtain the organic carrier.

[0043] The preparation method of the above-mentioned high square resistance slurry includes the following steps: Step S1: Take the above proportion of conductive phase, inorganic binder, modifier and 80% organic carrier, put them into a planetary disperser and disperse them at a low speed of 350r / min for 18 minutes, and then coarsely grind them 3 times with a three-roll mill. Step S2: Add the remaining 20% ​​organic carrier to the coarsely ground slurry, adjust the slurry viscosity to 110 Pa·s, put it into a planetary disperser and disperse it under vacuum at a speed of 900 r / min and a vacuum degree of -0.085 MPa for 28 minutes, and then grind it three times with a three-roll mill. Step S3: Filter the finely ground slurry using an 800-mesh filter to remove large particle impurities and obtain a high sheet resistance slurry with a fineness of 4.5μm.

[0044] Example 4

[0045] The high sheet resistance slurry described in this embodiment has the following formulation and preparation method: The high square resistance slurry comprises the following raw materials by mass percentage: 20% conductive phase, 52% inorganic binder phase, 6% modifier and 22% organic carrier.

[0046] The conductive phase, by total mass, comprises the following components in the following mass percentages: 48% nano-sized ruthenium dioxide powder, 37% submicron-sized ruthenium dioxide powder, and 15% submicron-sized flake silver powder; the nano-sized ruthenium dioxide powder has a particle size of 100 nm, the submicron-sized ruthenium dioxide powder has a particle size of 0.5 μm, and the submicron-sized flake silver powder has a particle size of 0.8 μm; all these components of the conductive phase are commercially available. Based on the total mass of the inorganic binder phase, the inorganic binder phase comprises the following components by mass percentage: 35% bismuth oxide, 45% silicon dioxide, 10% boron oxide, and 10% aluminum oxide. The inorganic binder phase is a low-melting-point glass powder system with a softening temperature controlled at 550℃. The preparation process is a conventional glass powder preparation process, such as mixing bismuth oxide, silicon dioxide, boron oxide, and aluminum oxide powders evenly in a three-dimensional mixer, melting the mixture in a furnace to obtain molten glass, then quenching the molten glass in water to obtain glass slag, and finally using distilled water as a medium, ball milling the glass slag in a planetary ball mill for 4-6 hours to obtain glass powder with an average particle size of 1μm-3μm.

[0047] Based on the total mass of the slurry, the modifier comprises the following components by mass percentage: 2.5% manganese dioxide, 2.0% cobalt trioxide, and 1.5% yttrium oxide; all of these modifiers are commercially available. Based on the total mass of the organic carrier, the organic carrier comprises the following components by mass percentage: 37% dodecyl alcohol ester, 52% hexadecyl alcohol ester, 8% ethyl cellulose, and 3% surfactant. The surfactant is polyethylene glycol fatty acid ester. The organic carrier is prepared using a conventional oil bath dispersion process. For example, organic solvent and ethyl cellulose are added to a reaction vessel and reacted for 5-10 hours, with the temperature controlled at 70-80℃ and the disperser speed at 100 rpm, to obtain an ethyl cellulose mixture. Then, the temperature in the reaction vessel is lowered to 60-70℃, the disperser speed is reduced to 80 rpm, and the surfactant is added, reacting for 1-5 hours to obtain the organic carrier.

[0048] The preparation method of the above-mentioned high square resistance slurry includes the following steps: Step S1: Take the above proportion of conductive phase, inorganic binder, modifier and 85% organic carrier, put them into a planetary disperser and disperse them at a low speed of 400r / min for 25 minutes, and then coarsely grind them 5 times with a three-roll mill. Step S2: Add the remaining 15% organic carrier to the coarsely ground slurry, adjust the slurry viscosity to 110 Pa·s, put it into a planetary disperser and disperse it under vacuum at a speed of 1200 r / min and a vacuum degree of -0.095 MPa for 30 minutes, and then grind it five times with a three-roll mill. Step S3: Filter the finely ground slurry using an 800-mesh filter to remove large particle impurities and obtain a high sheet resistance slurry with a fineness of 4.6μm.

[0049] Example 5

[0050] The high sheet resistance slurry described in this embodiment has the following formulation and preparation method: The high square resistance slurry comprises the following raw materials by weight percentage: 10% conductive phase, 57% inorganic binder phase, 5% modifier and 28% organic carrier.

[0051] The conductive phase, by total mass, comprises the following components in the following mass percentages: 52% nano-sized ruthenium dioxide powder, 38% submicron-sized ruthenium dioxide powder, and 10% submicron-sized flake silver powder; the nano-sized ruthenium dioxide powder has a particle size of 100 nm, the submicron-sized ruthenium dioxide powder has a particle size of 0.5 μm, and the submicron-sized flake silver powder has a particle size of 0.8 μm; all these components of the conductive phase are commercially available. Based on the total mass of the inorganic binder phase, the inorganic binder phase comprises the following components by mass percentage: bismuth oxide 38%, silicon dioxide 44%, boron oxide 9%, and aluminum oxide 9%. The inorganic binder phase is a low-melting-point glass powder system with a softening temperature controlled at 500℃. The preparation process is a conventional glass powder preparation process, such as mixing bismuth oxide, silicon dioxide, boron oxide, and aluminum oxide powders evenly in a three-dimensional mixer, melting the mixture in a furnace to obtain molten glass, then quenching the molten glass in water to obtain glass slag, and finally using distilled water as a medium, ball milling the glass slag in a planetary ball mill for 4-6 hours to obtain glass powder with an average particle size of 1μm-3μm.

[0052] Based on the total mass of the slurry, the modifier comprises the following components by mass percentage: 1.8% manganese dioxide, 1.2% cobalt trioxide, and 2.0% yttrium oxide; all of these modifiers are commercially available. Based on the total mass of the organic carrier, the organic carrier comprises the following components by mass percentage: 45% dodecyl alcohol ester, 45% hexadecyl alcohol ester, 7% ethyl cellulose, and 3% surfactant. The surfactant is polyethylene glycol fatty acid ester. The organic carrier is prepared using a conventional oil bath dispersion process. For example, organic solvent and ethyl cellulose are added to a reaction vessel and reacted for 5-10 hours, with the temperature controlled at 70-80℃ and the disperser speed at 100 rpm, to obtain an ethyl cellulose mixture. Then, the temperature in the reaction vessel is lowered to 60-70℃, the disperser speed is reduced to 80 rpm, and the surfactant is added, reacting for 1-5 hours to obtain the organic carrier.

[0053] The preparation method of the above-mentioned high square resistance slurry includes the following steps: Step S1: Take the above proportion of conductive phase, inorganic binder, modifier and 90% organic carrier, put them into a planetary disperser and disperse them at a low speed of 600r / min for 25 minutes, and then coarsely grind them 3 times with a three-roll mill. Step S2: Add the remaining 10% organic carrier to the coarsely ground slurry, adjust the slurry viscosity to 120 Pa·s, put it into a planetary disperser and disperse it under vacuum at a speed of 900 r / min and a vacuum degree of -0.1 MPa for 30 minutes, and then grind it five times with a three-roll mill. Step S3: Filter the finely ground slurry using an 800-mesh filter to remove large particle impurities and obtain a high sheet resistance slurry with a fineness of 3.8μm.

[0054] High sheet resistance resistive paste samples 1, 2, and 3 prepared according to Examples 1, 2, and 3, as well as commercially available competitor products 1 and 2, were printed onto alumina ceramic substrates. After sintering at 850℃±20℃, resistance samples were prepared and their performance was tested according to the same testing standards. The results are as follows: In the temperature cycling test, as shown in Table 1, the resistance sample prepared in this embodiment underwent 1000 cycles from -55℃ to 125℃, and the resistance value change rate was only ±0.5%, while the resistance value change rate of existing competing products was between ±1.5% and ±3%.

[0055] Table 1

[0056] In the humidity environment test, as shown in Table 2, the resistance sample prepared in this embodiment was placed in an environment of 85%RH and 85℃ for 1000 hours, and the resistance value change rate was less than ±1%, which is much lower than the resistance change rate of existing competing products, which is within the range of ±2% to ±5%. This shows good moisture resistance and can effectively resist the influence of humid environment on resistance performance.

[0057] Table 2

[0058] Regarding the temperature coefficient of resistance, as shown in Table 3, through precise control of the modifier, the resistance slurry of this embodiment achieves a temperature coefficient of resistance (TCR) of less than 100 ppm / ℃ within the temperature range of 25℃ to 125℃. Compared with the existing competing products with a TCR of 300 ppm / ℃ to 600 ppm / ℃, it can maintain a stable resistance value over a wider operating temperature range, meeting the needs of application fields such as heating systems for new energy vehicles that have extremely high requirements for temperature stability.

[0059] Table 3

[0060] The high sheet resistance resistive paste of this embodiment can achieve a high resistance accuracy of ±5%, while existing methods typically only achieve ±10%. This significantly reduces the resistance defect rate in the production of heat-generating products with extremely high resistance accuracy requirements.

[0061] Example 6

[0062] like Figure 1 As shown, this embodiment provides a thick-film circuit made from the aforementioned high sheet resistance resistive paste. The thick-film circuit adopts an N-group parallel architecture, where N is a positive integer greater than or equal to 1. Preferably, depending on the sheet resistance of different resistive pastes, N can be designed to be 1, 3, 5, or 7.

[0063] Specifically, thick-film circuits with parallel architectures of 1, 3, 5, and 7 groups were applied to tubes with a diameter of ∮20*140mm, and the sheet resistance values ​​used are shown in Table 4: Table 4

[0064] According to the experimental data in Table 4, the sheet resistance of the resistive slurry used in a design with 7 parallel circuits is 49 times that of a design with 1 parallel circuit. Even with 5 parallel circuits, the sheet resistance of the resistive slurry used is 25 times that of a design with 1 parallel circuit. The higher the sheet resistance of the slurry, the less conductive phase it contains, resulting in a significant reduction in slurry cost and considerable economic benefits.

[0065] The above description is only a preferred embodiment of the present invention. Therefore, any equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included within the protection scope of this patent application.

Claims

1. A high sheet resistance resistor paste, characterized in that, The composition comprises the following mass percentages of components: Conductive phase 6%-24% Inorganic bonding phase 33%-57% Modifier 2%-6% Organic carrier 22%-38%; The conductive phase is a composite system conductive phase, comprising the following components in total mass percentage of the conductive phase: Nano-sized ruthenium dioxide powder 45%-58% Sub-micron-sized ruthenium dioxide powder 25%-38% Sub-micron-sized silver flake powder 6%-17%.

2. The high sheet resistance paste according to claim 1, characterized by, The inorganic bonding phase is a low-melting-point glass powder system, comprising the following components in total mass percentage of the inorganic bonding phase: Bismuth oxide 25%-38% Silicon dioxide 30%-52% Boron oxide 6%-12% Aluminum oxide 6%-12%.

3. The high sheet resistance paste of claim 1, wherein, The modifier is a composite system, comprising the following components in total mass of the slurry: Manganese dioxide 1%-3% Cobalt sesquioxide 0.5%-3% Yttrium oxide 1%-5%.

4. The high sheet resistance paste of claim 1, wherein, The organic carrier is an environmentally friendly multi-solvent system, comprising the following components in total mass percentage of the organic carrier: Alcohol ester twelve 37%-45% Alcohol ester sixteen 42%-52% Ethyl cellulose 5%-10% Surfactant 1.5%-4%.

5. The high sheet resistance paste of claim 1, wherein, The nano-sized ruthenium dioxide powder has a particle size of 50-200 nm, and the sub-micron-sized ruthenium dioxide powder and the sub-micron-sized silver powder have a particle size of 0.3-1 μm.

6. The high sheet resistance paste of claim 2, wherein, The low-melting-point glass powder system has a softening temperature range of 450-600℃.

7. A method of preparing a high sheet resistance resistive paste as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1. Put the conductive phase, inorganic bonding phase, modifier, and 80%-90% of the organic carrier into a planetary disperser and disperse uniformly at low speed, and then coarsely grind with a three-roll mill; S2. Add the remaining 10%-20% of the organic carrier to the coarsely ground slurry, adjust the slurry viscosity to 100 Pa·s±20 Pa·s, and then disperse uniformly in a planetary disperser at medium speed under vacuum, and then finely grind with a three-roll mill; S3. Filter the finely ground slurry with a filter to obtain a high-sheets-resistance resistive paste with a fineness of less than 5 um.

8. The preparation method according to claim 7, characterized in that, In step S1, coarsely grind 3-5 times with a three-roll mill; in step S2, finely grind 3-5 times with a three-roll mill.

9. The preparation method according to claim 7, characterized in that, In step S3, filter the finely ground slurry with an 800-mesh filter.

10. A thick film circuit made from the high sheet resistance paste according to any one of claims 1 to 6, characterized in that The thick film circuit adopts an N-parallel architecture, where N is a positive integer greater than or equal to 1.

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