A preparation method of thick film low resistance resistor based on Ts gradient and three simultaneous principles

Abstract

The application provides a preparation method of a thick film low resistance resistor based on Ts gradient and three simultaneous principles, and is particularly applied to the field of low resistance (0.01-5 ohms / square). In view of the technical problems of high cost, narrow process window and poor interface reliability of the Ag-Pd-RuO2 ternary noble metal system in the prior art, the application adopts an Ag / Pd porous conductive network to replace the traditional ternary system, designs a gradient temperature sintering process based on the glass softening point gradient matching principle (Ts_G1<Ts_C1<Ts_R), constructs a three-dimensional porous conductive structure through high-length-diameter-ratio flaky silver, and realizes precise regulation and control of the temperature coefficient by combining a nano-palladium surface modification technology. On the premise of completely abandoning the high-cost noble metal RuO2, the application improves the interface matching, improves the device reliability, and realizes the cost reduction and performance improvement of the low resistance end thick film resistor paste.

Description

Technical Field

[0001] This invention relates to the field of electronic materials and component manufacturing technology, specifically to a low-resistivity thick-film resistor paste for use in thick-film resistor pastes, chip resistors (wafer resistors) and other fields, and its preparation method. In particular, it relates to a method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three simultaneous principles, with a target sheet resistance range of 0.01Ω / square to 5Ω / square. Background Technology

[0002] Thick-film resistor paste is a functional material formed by screen printing and high-temperature sintering onto a ceramic substrate to create a resistive film. In the low-resistance range (<5Ω / square), the industry has long relied on the Ag-Pd-RuO2 ternary noble metal system (such as the traditional R9000M paste). This technical approach suffers from the following technical problems: First, the material cost is high. It contains a high proportion of precious metals (especially palladium and ruthenium), and the traditional dense sintered structure results in a large amount of precious metals being encased in the glass phase, which cannot effectively participate in electrical conduction, resulting in low utilization.

[0003] Second, the process window is narrow and the electrical properties vary greatly. The compatibility of multi-component systems is complex, and they are extremely sensitive to the sintering process, which can easily lead to drift in the temperature coefficient of resistance (TCR) and dispersion in the resistance distribution.

[0004] Third, poor interface reliability. Due to the mismatch in thermal expansion coefficients and interdiffusion of elements (Kirkendall effect), microcracks are prone to form at the interface between the resistive element and the terminal conductor, posing a risk of failure with long-term use.

[0005] Fourth, the protective effect is limited and the reliability is poor. There is a lack of effective process design principles for matching the glass protective layer (G1 paste) with the functional layer. During the sintering process, the G1 layer often damages the conductive network of the functional layer it is protecting rather than effectively protecting it, and there is a risk of performance degradation in the long term.

[0006] To address the aforementioned issues, although some studies have attempted to adjust the formulation, none have fundamentally altered the underlying design logic of the dense conductive network and the high load of precious metals. Summary of the Invention

[0007] This invention employs the Ts gradient and the three-simultaneity principle to design a method for fabricating a thick-film low-resistivity resistor, achieving the following technical effects at the low-resistivity end (0.01~5Ω / square): 1) A three-dimensional porous conductive network is constructed using high aspect ratio sheet-like silver to replace the noble metal ruthenium oxide (RuO2) as the core conductive phase, thereby reducing material costs; 2) Nano-palladium surface modification technology is used to replace traditional palladium-silver alloying (spherical silver particles), achieving precise control of the temperature coefficient (TCR) with relatively less palladium. 3) Based on the principle of glass softening point gradient matching (Ts_G1 < Ts_C1 < Ts_R), a gradient temperature sintering process is designed to improve the interfacial stress matching between the resistor body, the end conductor, and the protective layer, and reduce the interdiffusion of elements.

[0008] The overall technical solution of the present invention is centered around the "R-C-G three-layer composite system", where R is the resistor layer, C1 is the end conductive layer, whose main function is to establish an ohmic contact between the resistor network and the end and conduct the resistance, and G1 is the glass protective layer. The core lies in the collaborative design of the materials of each layer and the strict implementation of the gradient temperature sintering process.

[0009] The applicant proposes a design method for a thick film resistor system based on the "glass softening point (Ts) gradient matching and three-simultaneity principle". By controlling the gradient relationship of the glass phase softening points of the resistor layer R, the end conductive layer C1, and the protective layer G1 (Ts_G1 < Ts_C1 < Ts_R), combined with the gradient temperature sintering process, the collaborative design and performance optimization of the multi-layer structure are achieved. However, the applicant has found that although the above related application has established a Ts gradient design framework, in the low-resistance range (0.01 - 5 Ω / square), the noble metal ratio of the traditional Ag-Pd-RuO2 ternary system is further increased, the space for regulating the conductive phase is limited, and it is difficult to balance the resistance value accuracy and TCR stability.

[0010] In view of the above technical problems, the present invention innovatively adopts an Ag / Pd porous conductive network, follows the Ts gradient matching design principle established by the related application, and effectively improves the resistance value accuracy and TCR stability of the traditional system in the low-resistance range by constructing a porous conductive phase structure and adjusting the microstructure, on the premise of completely abandoning the high-cost noble metal (RuO2), verifying the applicability (universality and effectiveness) of the Ts gradient matching principle in the low-resistance domain (0.01 - 5 Ω / square).

[0011] The core design idea of this solution: The realization of the three-simultaneity principle in the low-resistance range: As Figure 5 shown, the technical solution of the present invention strictly follows the "Ts gradient and three-simultaneity principle" proposed by the related application: Design simultaneity: The resistor paste, the end paste, and the protective paste must follow the Ts gradient matching principle (Ts_G1 < Ts_C1 < Ts_R) during the design stage. The three are designed as an overall system and cannot be independently designed and then pieced together.

[0012] Sintering simultaneity: The three layers of the resistor layer R, the end conductive layer C1, and the protective layer G1 must be applied in sequence according to a specific sintering temperature window: The first-stage sintering (shaping of the resistor layer R): T1 > Ts_R + 50 °C (superheat of more than 50 °C to ensure complete densification of the glass phase in the R layer), where T1 is the first temperature of the first-stage sintering. Second-stage sintering (construction of the end conductive layer C1): Ts_C1 + 50°C < T2 < Ts_R (superheat of more than 50°C to ensure densification of the end conductive layer C1 while protecting the resistance layer R), where T2 is the second temperature of the second-stage sintering; Third-stage sintering (encapsulation of the protective layer G1): Ts_G1 + 50°C < T3 < Ts_C1 (superheat of more than 50°C to ensure densification of the protective layer G1 while protecting the lower layer), where T3 is the third temperature of the third-stage sintering.

[0013] During application: The three layers of the resistance layer R, the end conductive layer C1, and the protective layer G1 work together as an integrated system, and any design adjustment of any layer needs to evaluate the impact on the overall performance.

[0014] In response to the specific challenges at the low-resistance end, under the framework of the three-simultaneity principle, the present invention has made the following key material innovations: <C The Ts ranges of the typical glass phases of each layer are as follows: Ts of the R layer (resistance layer): 610 - 630°C Ts of the C1 layer (end conductive layer): 510 - 530°C Ts of the G1 layer (protective layer): 350 - 370°C.

[0015] Based on the Ts gradient principle, the sintering temperature window of the end conductive layer C is set as Ts_C1 ≤ T2 ≤ Ts_R, ensuring densification of the glass phase of the end conductive layer C1 while protecting the integrity of the conductive network of the R layer.

[0016] In addition, innovation in the formulation and microstructure of the resistance paste: The resistance paste is the core of the present invention, and its innovation lies in constructing a new Ag / Pd porous conductive network: 1. Innovation in the conductive phase: High aspect ratio flaky silver porous framework: [[ID=二十八]] Flaky silver powder with an aspect ratio of 100 - 200 is used as the conductive framework. As Figure 4 shown, the high aspect ratio structure forms a three-dimensional porous structure with mutual overlap during sintering, replacing the traditional dense packing structure.

[0017] Advantages of the porous structure: ① The conductive silver framework is fully exposed, and the utilization rate of precious metals is maximized; ② The pore structure can absorb and buffer internal stress, fundamentally suppressing interface cracking; ③ The extremely low percolation threshold enables the formation of a continuous conductive path even when the silver content is reduced by 20 - 30%.

[0018] 2. Innovation in the modification technology: High-efficiency surface modification with nano-palladium: Palladium nanoparticles with a specific surface area of ​​2-4 m² / g and an average particle size of 100-200 nm were uniformly adhered to the surface of flake silver using a resonant milling process.

[0019] The essence of technology: This process involves physical surface modification, replacing the traditional three-dimensional (bulk) alloying of palladium and silver with two-dimensional (surface) alloying. Nano-palladium acts as an "anchor" to suppress the high-temperature migration of silver atoms, thereby stabilizing the TCR (transient chromatogram). This technology reduces palladium usage by more than 30%, achieving maximum efficiency in Pd applications.

[0020] 3. Glass phase system, glass mixed powder: Taking the R5000M slurry designed in this scheme as an example, its glass mixture powder is composed of four different Ts glass powders, which play the roles of inhibiting diffusion (Ts: 700-800°C), supporting the skeleton (Ts: 500-600°C), and promoting sintering (Ts: 450-550°C). Its precise ratio is the key to achieving the target Ts and performance.

[0021] Based on the total mass percentage of the first glass being 100%, the first glass contains 26-32% SiO2, 6-10% Al2O3, 2-4% ZrO2, 5-9% CaO, 10-16% ZnO, 21-27% BaO, and 13-19% SrO, with the sum of the mass percentages of each component being 100%.

[0022] Based on the total mass percentage of the second glass being 100%, the second glass comprises 27-33% SiO2, 12-18% B2O3, 14-20% Al2O3, and 35-41% PbO, with the sum of the mass percentages of each component being 100%.

[0023] Based on the total mass percentage of the third glass being 100%, the third glass includes 17-23% SiO2, 17-23% B2O3, 3-7% Al2O3, 35-41% PbO, and 14-20% MnO, with the sum of the mass percentages of each component being 100%.

[0024] Based on the total mass percentage of the fourth glass being 100%, the fourth glass comprises 18-24% SiO2, 18-24% B2O3, 3-7% Al2O3, 3-5% PbO, and 8-12% MnO, with the sum of the mass percentages of each component being 100%.

[0025] In some embodiments, the glass mixture powder comprises, by weight percentage (100%), 18-22% first glass, 20-24% second glass, 25-29% third glass, and 29-33% fourth glass, with the sum of the weight percentages of each component being 100%. That is, the glass mixture powder includes a first glass that inhibits diffusion, a second glass that acts as a framework, and a third and fourth glass that promote sintering. The glass transition point of the first glass is 700-800°C, the glass transition point of the second glass is 500-600°C, and the glass transition points of the third and fourth glasses are 450-550°C.

[0026] The softening temperature of the glass phase in the glass mixture powder is as follows: Ts=(w1% Ts1+w2% Ts2+w3% Ts3+w4% Ts4) / (w1%+w2%+w3%+w4%); Where Ts1 is the glass phase softening temperature of the first glass, w1 is the mass fraction of the first glass, Ts2 is the glass phase softening temperature of the second glass, w2 is the mass fraction of the second glass, Ts3 is the glass phase softening temperature of the third glass, w3 is the mass fraction of the third glass, Ts4 is the glass phase softening temperature of the first glass, and w4 is the mass fraction of the first glass.

[0027] That is, in some embodiments, the glass phase softening temperature of the glass mixture is obtained by summing the glass phase softening temperatures of each glass phase in the glass mixture using a mass-weighted average method.

[0028] Accordingly, this solution provides a method for fabricating thick-film low-resistivity resistors based on the Ts gradient and the principle of three simultaneities, including the following steps: First, an R conductive network structure is printed on the substrate, in which a mixture of nano-palladium powder, sheet-like silver with an aspect ratio greater than 1, glass mixed powder and organic carrier phase are used as a resistive paste. The resistive paste is printed on the substrate and sintered at 850~860°C for 5~10 min to form a porous conductive network structure. An end conductive layer is printed at the end position of the conductive network structure. The end paste is obtained by mixing flake silver powder, inorganic powder, glass powder and organic carrier. The end paste is printed at the end position of the porous conductive network structure and sintered at 600~620°C for 5~10 minutes.

[0029] Furthermore, regarding the sintering of the protective layer: In some embodiments, a protective layer is printed on the end and the conductive network structure. The protective layer paste is printed directly above the porous conductive network structure and sintered at 500~520°C for 3~5 minutes.

[0030] In some embodiments, this solution provides a typical formulation of the resistance paste as follows: Special glass mixing powder: 16~40%; Ts: 620.5°C; Nano-palladium powder: 10~24%; Flake silver powder (aspect ratio 50~200): 10~20%; Organic carriers (ethyl cellulose, terpineol, etc.): 37~41%; Total: The sum of the mass percentages of all components is 100%, and it contains no RuO2 at all.

[0031] That is, the resistive paste of this scheme includes 10~24% nano-palladium powder, 10~20% flake silver with an aspect ratio greater than 1, 16~40% glass mixed powder and 37~41% organic carrier phase, and the sum of the mass percentages of each component is 100%.

[0032] In some embodiments, a typical formulation of the conductive paste for the end caps provided in this solution is as follows: T7065: Special glass phase: 13~15%; Ts: 521°C, B1 1~2%, B2 11~13%; Inorganic powder: 0.7~1.0%; Flake silver powder: 62~66%; Organic carriers (ethyl cellulose, terpineol, etc.): 22~24%.

[0033] Total: The sum of the mass percentages of all components is 100%.

[0034] That is, the present solution is to mix 62-66% flake silver powder, 0.7-1.0% inorganic powder, 13-15% glass fraction, and 22-24% organic carrier to obtain end slurry, and the sum of the mass percentages of each component is 100%.

[0035] In some embodiments, regarding the protective layer slurry of this solution: G1 solution: TJ730: Special glass phase: 62~66%; Ts: 361°C; Inorganic powder: 8~12%; Organic powder: 0.1~0.5%; Organic carriers (ethyl cellulose, terpineol, etc.): 13-17%; Total: The sum of the mass percentages of all components is 100%.

[0036] That is, this method mixes a special glass phase, inorganic powder, organic powder, and organic carrier to obtain a protective layer slurry. In some preferred embodiments, this method mixes 62-66% special glass phase, 8-12% inorganic powder, 0.1-0.5% organic powder, and 13-17% organic carrier to obtain a protective layer slurry.

[0037] Regarding the sintering system of this scheme: Gradient temperature sintering process flow: The key to the preparation method lies in the gradient temperature sintering process, which strictly follows the aforementioned Ts gradient principle: The first stage of high-temperature sintering of the resistive layer: The resistive paste is printed on the substrate and sintered at 850~860°C for 5~10 minutes. At this time, the glass phase of the resistive layer R is completely melted, the sheet silver forms a stable porous framework, and the nano-palladium completes the surface modification.

[0038] The second stage of the conductive layer C1 is sintered at medium temperature: the end paste is printed on the resistive layer and sintered at 600~620°C for 5~10 minutes. This temperature is lower than the glass Ts of the resistive layer, ensuring that the structure of the resistive layer is not damaged, while the conductive layer at the end is well sintered.

[0039] The third protective layer G1 is sintered at low temperature: Finally, the protective paste (protective glass) is printed and sintered at 500~520°C to form a protective layer. This temperature is lower than the glass Ts of the end conductive layer.

[0040] In some embodiments, the glass phase softening point temperature Ts of the protective layer slurry is in the range of 350-500°C, the glass phase softening point temperature Ts of the end slurry is in the range of 500-600°C, and the glass phase softening point temperature Ts of the resistance slurry is in the range of 600-650°C.

[0041] In addition, this solution provides a method for preparing a thick-film low-resistance resistor based on the Ts gradient and the three simultaneous principles. The resistor has a resistance range of 0.01~5Ω / square. The specific surface area of ​​the flake silver powder in the thick-film low-resistance resistor is 0.5-1.3 m² / g, the Fisher particle size is 0.5-1.0 μm, the tap density is 3.0-4.2 g / mL, and the aspect ratio of the flake silver is 50~200. The specific surface area of ​​the palladium nanoparticles modified on the flake silver powder is 2-4 m² / g, and the average particle size is 100-200 nm.

[0042] Beneficial effects: Traditional co-firing processes for conductors and resistors have several drawbacks: 1. Traditional processes require sintering the conductor, resistor, and terminal paste at temperatures above 850℃ in a single operation. Prolonged high-temperature holding leads to high energy consumption, rapid equipment wear, and significantly increased production and maintenance costs. 2. High-temperature co-firing results in large shrinkage of the resistor film, poor microstructure uniformity, and severe fluctuations and drift in the G1 characteristic parameters of the resistor film. Subsequent laser trimming can easily lead to problems such as film edge chipping, overcutting, and uncontrolled resistance values, resulting in low laser cutting yield and difficulty in improving overall product qualification rates. 3. Traditional silver-palladium-ruthenium resistive pastes are highly sensitive to product size. Chip resistors with the same design resistance value but different package sizes exhibit significant differences in temperature coefficient (TCR). A single resistive paste formulation cannot be compatible with all sizes, such as 0402, 0603, 0805, and 1206, requiring multiple formulations in parallel, which complicates process debugging and material management. 4. Due to the size effect of film thickness, shrinkage rate, and interfacial contact area, the actual resistance value of the same resistive paste deviates from the design value after sintering on substrates of different sizes, making it impossible to achieve "one paste for multiple uses" and doubling the workload of formula development and mass production debugging. 5. During high-temperature co-firing at 850℃, the mismatch between resistor and terminal shrinkage, element interdiffusion, and uneven local stress lead to large differences in resistance between wafers and poor uniformity of individual wafer resistors, making it difficult to meet the high consistency requirements of automotive electronics, industrial control, and other fields.

[0043] This solution effectively overcomes the problems existing in traditional one-piece sintering by adopting a step-by-step sintering method for the terminal and conductive network structure. This solution is completely different from the conventional process of "printing the terminal first and then the resistor" or "printing the resistor and terminal simultaneously and sintering at one time". First, the resistor paste is firmly fixed on the substrate by high-temperature sintering, and then the terminal paste is printed and sintered at high temperature for a second time. This completely avoids the performance degradation caused by the shrinkage difference between the resistor and the terminal and the interdiffusion of elements during co-firing at 850 degrees Celsius.

[0044] Compared with existing technologies (using the traditional R9000M system as a comparison example), the beneficial effects of this invention are as follows: 1) Significant reduction in precious metal usage: The porous structure of sheet silver reduces silver usage by about 20-30%; the nano-palladium surface modification technology reduces palladium usage by more than 30%; RuO2 is completely eliminated.

[0045] 2) Reduced overall cost: The cost of raw materials for the slurry is reduced by approximately 30-40% compared to the R9000M system.

[0046] Improved electrical performance and reliability.

[0047] 3) TCR stability: Gradient sintering and interface design keep TCR drift within ±200 ppm.

[0048] 4) Interface bonding strength: The porous structure buffers stress, enhancing the interface bonding strength and completely eliminating microcracks.

[0049] 5) Process tolerance: The gradient temperature sintering process has a wide process window, and the first-pass yield of the product is increased to >90%. Brief Description of the Drawings

[0050] Figure 1 It is a schematic diagram of the porous structure of Example 2.

[0051] Figure 2 It is a schematic diagram of the dense structure of Comparative Example 2.

[0052] Figure 3 It is the fracture phenomenon observed in Comparative Example 3.

[0053] Figure 4 It is a comparison schematic diagram of a three-dimensional porous conductive network (left) constructed by high aspect ratio flaky silver and a traditional dense structure (right).

[0054] Figure 5 It is a schematic diagram of the sintering principle of the preparation method of a thick film low-resistance resistor based on the Ts gradient and the three-simultaneity principle. Detailed Embodiments

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0056] The present invention will be further described below by way of examples, but not limited thereto. All "parts" in the examples are parts by mass.

[0057] Example 1: Preparation of a resistor with a level of 0.1 Ω / square Adopt the nano-palladium surface modification technology to replace the traditional palladium-silver alloying; Ts gradient design: Based on the glass softening point (Ts_G1 < Ts_C1 < Ts_R), design the resistor paste, end paste, and protection paste simultaneously: Preparation of the resistor paste: Take 23.5 parts of nano-palladium powder (specific surface area 3 m² / g), 20 parts of flaky silver powder (aspect ratio 80, SA 0.50), 16.5 parts of glass mixed powder, and 40 parts of organic carrier, mix and disperse evenly; Preparation of the end paste: Take 14.8 parts of this glass phase, 62 parts of compounded silver powder, and 23.2 parts of organic carrier, mix and disperse evenly; Preparation of the protection paste: Take 74 parts of this glass phase and 26 parts of organic carrier, mix and disperse evenly; Sintering process: First, the resistance layer R is sintered at 850°C for 10 minutes, then the end conductive layer is sintered at 620°C for 10 minutes, and finally the protective layer is sintered at 520°C for 3 minutes; Test results: Sheet resistance is 0.24 Ω / square, HTCR is 159 ppm / °C, CTCR is 183 ppm / °C, and the change rate of G1 is 0.15%.

[0058] Comparative Example 1 (same resistance paste + traditional blind matching + traditional sintering): Preparation of the resistance paste: Take 23.5 parts of nano-palladium powder (specific surface area 3 m² / g), 20 parts of flaky silver powder (aspect ratio 80, SA 0.50), 16.5 parts of glass mixed powder, and 40 parts of organic carrier, mix and disperse evenly; Preparation of the paste from the end to the resistance layer: Blind matching; Preparation of the protective paste: Blind matching.

[0059] Sintering process: First, the end conductive layer is sintered at 850°C for 10 minutes, then the resistance layer R is sintered at 850°C for 10 minutes, and finally the protective layer is sintered at 600°C for 3 minutes Test results: Sheet resistance is 0.22 Ω / square, HTCR is 230.5 ppm / °C, CTCR is 264.9 ppm / °C, and the change rate of G1 is 0.3%.

[0060] The comparison of the test data of Example 1 and Comparative Example 1 is shown in Table 1 below: Table 1 Test data of Example 1 and Comparative Example 1

[0061] Conclusion: In Example 1, the use of nano-palladium surface modification to replace traditional palladium-silver alloying, combined with the Ts gradient matching and gradient temperature sintering process, shows excellent performance in resistors at the 0.1 Ω / square level: the temperature coefficients HTCR and CTCR are reduced by 31% respectively, both are better than the traditional process and closer to the target value of 0, indicating that the nano-palladium modification technology combined with gradient design can effectively improve the comprehensive performance of low-resistance thick-film resistors.

[0062] Example 2: Preparation of a 1 Ω / square level resistor: Adjustment key points: Ts gradient design: Synchronously design the resistance paste, end paste, and protective paste based on the glass softening point (Ts_G1 < Ts_C1 < Ts_R); Preparation of the resistance paste: Take 13.8 parts of nano-palladium powder (specific surface area 3 m² / g), 11.8 parts of flaky silver powder (aspect ratio 80, SA 0.50), 21.5 parts of glass mixed powder, and 40 parts of organic carrier, and mix evenly.

[0063] Preparation of the end paste: Take 14.8 parts of this glass phase, 62 parts of compounded silver powder, and 23.2 parts of organic carrier, mix and disperse evenly.

[0064] Preparation of the protective paste: Take 74 parts of this glass phase and 26 parts of organic carrier, mix and disperse evenly.

[0065] Sintering process: First, sinter the resistance layer R at 850°C for 10 minutes, then sinter the end conductive layer C1 at 620°C for 10 minutes, and finally sinter the protective layer G1 at 520°C for 3 minutes.

[0066] Test results: Sheet resistance is 0.94 Ω / square, HTCR is 101.9 ppm / °C, CTCR is 130.7 ppm / °C, and the change rate of G1 is 0.42%. A porous conductive network structure can be seen through interface microscopic observation. See attachment Figure 1 。

[0067] Comparative Example 2 (prepared by traditional process R9000M + traditional blind mating + traditional process sintering): Preparation of the resistance paste: Take 18 parts of palladium powder, 15.3 parts of silver powder, 3.5 parts of ruthenium oxide, 23.2 parts of glass mixed powder, and 40 parts of organic carrier, and mix evenly.

[0068] Preparation of the end paste: Blind mating; Preparation of the protective paste: Blind mating.

[0069] Sintering process: First, sinter the end conductive layer C1 at 850°C for 10 minutes, then sinter the resistance layer R at 850°C for 10 minutes, and finally sinter the protective layer G1 at 600°C for 3 minutes.

[0070] Test results: Sheet resistance is 1.19 Ω / square, HTCR is 133.2 ppm / °C; CTCR is 152 ppm / °C, and the change rate of G1 is 0.51%. A dense structure can be seen through interface microscopic observation. See attachment Figure 2 。

[0071] The comparison of the test data of Example 2 and Comparative Example 2 is shown in Table 2 below: Table 2 Test data of Example 2 and Comparative Example 2

[0072] Combination: Example 2 adopts the Ts gradient matching and gradient temperature sintering process. Compared with the traditional formula (containing ruthenium dioxide) for blind mating C1 G1 and traditional temperature sintering, it shows excellent performance in terms of temperature coefficient: HTCR is reduced by 57%, CTCR is reduced by 39%, indicating that the gradient design based on Ts_G1<Ts_C1<Ts_R can effectively improve the temperature stability and reliability of thick film resistors, and the cost is reduced by 35%.

[0073] Example 3: Preparation of a resistor with a sheet resistance of 5 Ω / square: Adjustment key points: Further increase the proportion of the glass mixed powder in the resistor paste, and use flaky silver with a higher aspect ratio (aspect ratio 200) to achieve percolation of the conductive network at a lower w%, so as to further reduce costs. Synchronously design the resistor paste, end paste, and protection paste based on the glass softening point (Ts_G1<Ts_C1<Ts_R); Preparation of the resistor paste: Take 10.5 parts of nano palladium powder (specific surface area 3 m² / g), 10.5 parts of flaky silver powder (aspect ratio 200, SA 0.98), 39 parts of glass mixed powder, and 40 parts of organic carrier, mix and disperse evenly.

[0074] Preparation of the end paste: Take 14.8 parts of this glass phase, 62 parts of compounded silver powder, and 23.2 parts of organic carrier, mix and disperse evenly Preparation of the protection paste: Take 74 parts of this glass phase and 26 parts of organic carrier, mix and disperse evenly.

[0075] Sintering process: First, sinter the resistor layer at 860°C for 10 minutes, then sinter the end conductive layer at 620°C for 10 minutes, and finally sinter the protection layer at 520°C for 3 minutes.

[0076] Test results: Sheet resistance 6.02 Ω / square, HCR 49.6 ppm / °C, CTCR 94.4 ppm / °C, G1 change rate 0.14%.

[0077] Comparative example 3 (same R paste + traditional blind matching + traditional sintering): Preparation of the resistor paste: Take 10.5 parts of nano palladium powder (specific surface area 3 m² / g), 10.5 parts of flaky silver powder (aspect ratio 200, SA 0.98), 39 parts of glass mixed powder, and 40 parts of organic carrier, mix and disperse evenly; End paste and protection paste: Blind matching Sintering process: First, sinter the end conductive layer paste at 850°C for 10 minutes, then sinter the resistor layer at 850°C for 10 minutes, and finally sinter the protection layer at 600°C for 3 minutes.

[0078] Test results: Sheet resistance 3.14 Ω / square, HCR 169 ppm / °C, CTCR 194.7 ppm / °C, the G1 change rate is unstable, and even fractures can be observed microscopically at the lap joints of some resistor bodies R and C1, see attachment Figure 3 .

[0079] The comparison of the test data of Example 3 and Comparative example 3 is shown in Table 3 below: Table 3 Test data of Example 3 and Comparative example 3

[0080] Conclusion: Example 3, employing the R-slurry formulation of this invention combined with Ts gradient matching and gradient temperature sintering, demonstrates excellent performance in the 5Ω / square resistivity range: HTCR is reduced by 71% and CTCR by 52%, both closer to the target value of 0. This indicates that even with the same R-slurry formulation, the gradient temperature sintering process still plays a crucial role in improving electrical performance. Blindly matched G1 has an unstable change rate and severe interface defects, making mass production difficult.

[0081] The designs of the various embodiments and comparative examples of this solution are shown in Table 4 below: Table 4 shows the design of the embodiments and comparative examples. .

[0082] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for fabricating a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle, characterized in that, Includes the following steps: A conductive network structure is printed on a substrate, wherein a mixture of nano-palladium powder, flake silver with an aspect ratio greater than 1, glass mixed powder and organic carrier phase are used as a resistive paste. The resistive paste is printed on the substrate and sintered at 850~860°C for 5~10 min to form a porous conductive network structure. An end conductive layer is printed at the end position of the conductive network structure. The end paste is obtained by mixing flake silver powder, inorganic powder, glass powder and organic carrier. The end paste is printed at the end position of the porous conductive network structure and sintered at 600~620°C for 5~10 minutes.

2. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 1, characterized in that, A protective layer is printed on the end and the conductive network structure. The protective layer paste is printed on the top of the porous conductive network structure and sintered at 500~520°C for 3~5 minutes.

3. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 1, characterized in that, The resistive paste comprises 10-24% nano-palladium powder, 10-20% flake silver with an aspect ratio greater than 1, 16-40% glass mixed powder, and 37-41% organic carrier phase, with the sum of the mass percentages of each component being 100%.

4. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 1, characterized in that, The glass mixture powder includes a first glass that inhibits diffusion, a second glass that acts as a framework, and a third and fourth glass that promote sintering. The glass transition point of the first glass is 700~800°C, the glass transition point of the second glass is 500~600°C, and the glass transition point of the third and fourth glasses is 450~550°C.

5. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 1, characterized in that, The resistive paste does not contain ruthenium dioxide.

6. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 1, characterized in that, The end slurry is prepared by mixing 62-66% flake silver powder, 0.7-1.0% inorganic powder, 13-15% glass fraction, and 22-24% organic carrier, with the sum of the mass percentages of each component being 100%.

7. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 2, characterized in that, A protective layer slurry is obtained by mixing 62-66% of a special glass phase, 8-12% of inorganic powder, 0.1-0.5% of organic powder, and 13-17% of organic carrier, with the sum of the mass percentages of each component being 100%.

8. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 2, characterized in that, The glass phase softening temperature Ts of the protective layer slurry ranges from 350 to 500°C.

9. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 1, characterized in that, The glass phase softening point temperature Ts of the end slurry ranges from 500 to 600°C.

10. The method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to claim 1, characterized in that, The glass phase softening temperature Ts of the resistive paste ranges from 600 to 650°C.

11. A thick-film low-resistivity resistor prepared by the method for preparing a thick-film low-resistivity resistor based on the Ts gradient and the three-simultaneity principle according to any one of claims 1 to 10, characterized in that, The resistance ranges from 0.01 to 5 Ω / square. The specific surface area of ​​the flake silver powder in the thick-film low-resistance resistor is 0.5-1.3 m² / g, the Fisher particle size is 0.5-1.0 μm, the tap density is 3.0-4.2 g / mL, and the aspect ratio of the flake silver is 50-200. The specific surface area of ​​the palladium nanopowder modified on the flake silver powder is 2-4 m² / g, and the average particle size is 100-200 nm.

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