Preparation method of patch type platinum resistor thin-film resistor temperature sensor

Abstract

The invention provides a preparation method of a patch type platinum resistor thin film resistor temperature sensor, and relates to the technical field of temperature measurement, and the method comprises the following steps: S1, substrate pretreatment and platinum resistor thin film deposition; s2, high-temperature stabilization treatment; s3, photoetching and etching an electrode pattern; s4, laser precise resistance trimming; s5, printing and sintering the protective layer; s6, scribing and cracking particles; s7, forming a terminal electrode; and S8, carrying out surface coating treatment on the end electrode. The invention provides a complete and ordered patch type platinum resistor preparation process with clear parameters. According to the invention, the protection layer can continuously and completely cover the fragile platinum resistor pattern, the problems of uneven protection layer coverage and insufficient edge protection caused by independent processing of the microchip after scribing are avoided, the environmental reliability of the product is greatly improved, and the manufacturing cost is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of temperature measurement technology, and more specifically, to a method for fabricating a patch-type platinum resistance thin-film resistance temperature sensor. Background Technology

[0002] Platinum resistance temperature sensors are widely used for precision temperature measurement in industrial control, automotive electronics, high-end medical devices, aerospace, and consumer electronics due to their excellent accuracy, long-term stability, wide temperature range, and good linearity. With the rapid development of electronic devices towards intelligence, integration, and miniaturization, the market demands smaller size, higher accuracy, better consistency, and suitability for surface mount technology in temperature sensors. Traditional platinum resistance thin-film temperature sensors mostly employ a leaded structure. Their fabrication process typically involves depositing a platinum resistance film on a ceramic substrate, patterning, resistance adjustment, soldering platinum leads, and finally encapsulating with glass or resin. This structure has the following inherent disadvantages: Miniaturization is difficult: the soldered leads increase the overall size and space requirements of the product, hindering high-density integration. Complex processes and high costs: the lead soldering and subsequent hermetic encapsulation steps are cumbersome, increasing manufacturing costs and time. Reliability risks: the lead solder joints may become concentration points of mechanical and thermal stress, making them prone to failure under vibration or thermal cycling conditions. Consistency challenges: the lead soldering and encapsulation processes may introduce additional resistance drift and thermal stress, affecting the consistency of batch products.

[0003] To adapt to SMT technology, surface-mount platinum resistance thermometers (SRTs) have emerged. However, some surface-mount SRTs, in pursuit of miniaturization, often sacrifice precision and long-term stability, or suffer from unreasonable processes and insufficient protection in their manufacturing, resulting in poor performance in high-precision, high-reliability applications. For example, insufficient density of the protective layer may lead to corrosion of the film by environmental moisture and corrosive gases; insufficient reliability of the electrode structure may affect soldering quality and current transmission stability; and improper control of complex processes can affect product consistency and yield.

[0004] Therefore, developing a method for fabricating a patch-type platinum resistance thin-film resistance temperature sensor with a scientific process flow, clearly defined parameters, and the ability to systematically ensure high precision, high stability, good consistency, and suitability for mass production is of significant industrial value. Summary of the Invention

[0005] The present invention aims to solve the problems of existing surface-mount platinum resistance thin-film resistance temperature sensors, which sacrifice accuracy and long-term stability, and have unreasonable processes and insufficient protection in the manufacturing process, resulting in poor performance of the products in high-precision and high-reliability applications.

[0006] To address the above problems, this invention provides a method for fabricating a patch-type platinum resistance thin-film resistance temperature sensor, the steps of which are as follows: S1. Substrate pretreatment and platinum resistance film deposition: depositing a platinum resistance film on the surface of an alumina ceramic substrate; S2. High-temperature stabilization treatment: The deposited platinum resistance film is sintered at high temperature; S3. Electrode pattern photolithography and etching: Using photolithography and etching processes, platinum resistance thin films are processed into preset resistance patterns; S4. Laser Precision Rating: Using laser rating equipment, the resistor pattern is micro-cut to precisely adjust the resistance value; S5. Protective layer printing and sintering: On the surface of the resistor pattern after resistance adjustment, a protective paste is screen-printed and sintered to form a protective layer; S6. Dicing and splitting: Cutting a whole ceramic substrate into individual sensor chips; S7. End electrode formation: End electrodes are formed at both ends of the sensor chip; S8. Terminal electrode surface plating treatment: A nickel layer and a tin or tin alloy layer are formed on the surface of the terminal electrode.

[0007] The present invention provides a method for fabricating a patch-type platinum resistance thin-film resistance temperature sensor, which, compared with the prior art, has the following beneficial effects, but is not limited to: This invention provides a complete, orderly, and parameter-defined fabrication process for surface-mount platinum resistance thermometers. By placing the "protective layer printing and sintering" step before "dicing and splitting" and "terminal electrode formation," it ensures that the protective layer can continuously and completely cover the fragile platinum resistance pattern, avoiding the problems of uneven protective layer coverage and insufficient edge protection caused by processing the microchip separately after dicing, and greatly improving the environmental reliability of the product.

[0008] This invention ensures precision and stability by combining and precisely controlling three core processes: magnetron sputtering to prepare high-quality platinum resistance thin films, high-temperature stabilization treatment, and laser precision trimming. This ensures high purity and stability of the resistor from the material source, optimizes the microstructure through post-processing, and achieves precise digital trimming of the resistance value in the final stage. As a result, the prepared sensor can achieve a precision standard of Class A or even higher, and the temperature coefficient (TCR) is highly consistent.

[0009] The invention offers structural reliability and solderability: the innovative process of first protecting the entire structure, then dividing it into particles, and finally forming the end electrodes, combined with the optimized end electrode structure, ensures sufficient protection for the internal resistive elements and provides external electrodes with high mechanical strength, good conductivity, excellent solderability, and corrosion resistance, fully compatible with standard SMT reflow soldering processes.

[0010] This invention is suitable for mass production and miniaturization: the entire process draws upon and integrates mature semiconductor micromachining and chip component manufacturing technologies, making it suitable for large-scale, parallel production on a single substrate, resulting in high production efficiency and good consistency. Simultaneously, by eliminating the leads and bulk packaging of traditional leaded structures, product sizes can be made very small (such as 0603, 0402, or even smaller packages), meeting the urgent needs of modern electronic products for miniaturization and integration.

[0011] This invention offers significant cost-effectiveness: compared to traditional leaded platinum resistance thermometers, this method eliminates the need for precious metal leads, manual or semi-automatic soldering, and complex metal or glass encapsulation processes. It employs more efficient planar batch processing technology, effectively reducing manufacturing costs while ensuring high performance.

[0012] Furthermore, in step S1, the alumina ceramic substrate has a purity ≥96%, a thickness of 0.25-0.5 mm, and a surface roughness Ra ≤0.05 μm; the platinum resistance film is deposited by magnetron sputtering and has a thickness of 1-3 μm; before deposition, the alumina ceramic substrate is pretreated by ultrasonic cleaning with isopropanol, ethanol, and deionized water.

[0013] Furthermore, in step S2, the high-temperature sintering is carried out in a protective atmosphere or air, with a sintering temperature of 900-1200℃ and a holding time of 1-3 hours.

[0014] Furthermore, step S3 specifically includes coating photoresist, exposure, development, etching the platinum resistance film, and photoresist removal steps, wherein the etching process is ion beam etching or wet chemical etching.

[0015] Furthermore, in step S4, the laser trimming device uses a laser with a wavelength of 355nm or 532nm.

[0016] Furthermore, in step S5, the protective slurry is a glass slurry or a low-temperature co-fired ceramic slurry; the wet film thickness is 15-25 μm; and the sintering conditions are: heating to 800-900℃ and holding for 5-15 minutes.

[0017] Furthermore, step S6 is performed using a diamond wheel scribing machine or a laser scribing machine, with the cutting width controlled at 30-50μm.

[0018] Furthermore, in step S7, the terminal electrode is formed by printing or coating conductive silver paste and sintering, with a silver paste layer thickness of 80-120μm, a sintering temperature of 550-650℃, and a holding time of 5-15 minutes.

[0019] Furthermore, in step S8, the nickel layer is formed by electroplating or chemical plating, with a thickness of 3-5 μm; the tin or tin alloy layer is formed on the nickel layer by electroplating, with a thickness of 5-8 μm.

[0020] Furthermore, the protective layer printing and sintering in step S5 are performed simultaneously on all sensor units on the entire substrate, and the dicing and splitting in step S6 are performed after the protective layer is formed. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the patch-type platinum resistance thin-film resistance temperature sensor according to an embodiment of the present invention; Explanation of reference numerals in the attached figures: 1. Terminal electrode; 2. Alumina ceramic substrate; 3. Platinum resistance film; 4. Slurry protective layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings showing multiple embodiments according to this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," etc., in the description, claims, and accompanying drawings of this application are open-ended terms. Therefore, "comprising," "including," or "having" refers to, for example, a method or apparatus having one or more steps or elements, but is not limited to having only these one or more elements. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] It should be emphasized that when the term "comprising / including" is used in this specification, it is used to explicitly indicate the presence of the stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, parts, or groups of features, integers, steps, or parts.

[0027] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0028] See Figure 1 The present invention discloses a method for fabricating a patch-type platinum resistance thin-film resistance temperature sensor, the method steps of which are as follows: S1. Substrate pretreatment and platinum resistance film deposition: depositing a platinum resistance film on the surface of an alumina ceramic substrate; A high-purity alumina ceramic substrate with high surface flatness is selected. After cleaning and drying, a dense platinum resistance film is deposited on its surface using physical vapor deposition, preferably magnetron sputtering. Magnetron sputtering uses high-purity platinum targets and forms films in a vacuum environment with minimal impurity introduction, ensuring that the temperature coefficient of resistance (TCR) approaches the theoretical value of 3850 ppm / ℃ for bulk platinum, with high batch-to-batch consistency. The high energy of the platinum atoms generated by sputtering results in films with high density, fine and uniform grains, and strong adhesion to the alumina ceramic substrate.

[0029] S2. High-temperature stabilization treatment: The deposited platinum resistance film is sintered at high temperature; The deposited platinum resistance film is subjected to high-temperature sintering to eliminate internal stress and stabilize the crystal structure and resistance characteristics of the film. The TCR value of the platinum resistance film is stabilized at approximately 3850 ppm / ℃, close to the ideal value of bulk platinum, with high batch-to-batch consistency. Newly deposited films typically contain numerous lattice defects, internal stresses, and non-equilibrium structures. High-temperature treatment at 900-1200℃ drives atomic diffusion, promoting grain growth, defect annihilation, and structural relaxation. Through this process, the electron scattering mechanism of the film more closely resembles that of a perfect crystal, and its resistance-temperature change (TCR) becomes more linear, predictable, and closer to the theoretical value. This is the material physics basis for achieving high precision and good linearity in sensors. Without this step, even with high film purity, its TCR may be low or unstable.

[0030] S3. Electrode pattern photolithography and etching: Using photolithography and etching processes, platinum resistance thin films are processed into preset resistance patterns; Photolithography, a micro-nano fabrication technology, allows for the design and precise fabrication of long, meandering resistance strips within an extremely small area. To achieve a sufficiently high nominal resistance, such as 100Ω, the longest possible conductive path needs to be accommodated on a limited ceramic alumina substrate. Photolithography enables fine linewidths of 10-30 micrometers and precise line spacing, allowing for densely packed resistance paths. This allows for achieving the designed resistance value even in extremely small chip sizes, such as the 0402 package (1.0mm x 0.5mm). This is the fundamental technological prerequisite for the miniaturization of surface-mount sensors.

[0031] S4. Laser Precision Rating: Using laser rating equipment, the resistor pattern is micro-cut to precisely adjust the resistance value; It can adjust the resistance value accuracy to ±0.1%, ±0.05%, or even higher levels.

[0032] While the preceding thin-film deposition (S1) and patterning (S3) processes are highly precise, they are still limited by material uniformity and equipment fluctuations, making it impossible to ensure that the resistance value of each resistor is absolutely equal to the target value, such as 100.00Ω. Laser trimming, as an active, closed-loop correction process, uses non-contact laser micro-cutting, much like micro-sculpting, to precisely and controllably remove minute amounts of platinum material, thereby increasing the effective length of the resistance path and achieving an increase in resistance value. This is a clever way to achieve a precise target through subtraction.

[0033] S5. Protective layer printing and sintering: On the surface of the resistor pattern after resistance adjustment, a protective paste is screen-printed and sintered to form a protective layer; It forms a dense, non-porous ceramic or glassy protective layer, ensuring complete physical isolation between the intricate platinum resistance pattern and the external environment, such as water vapor, oxygen, sulfides, chloride ions, and other corrosive gases.

[0034] While platinum resistance films are chemically stable, prolonged exposure to humid or polluted environments can lead to slow oxidation or adsorption on their surface, causing resistance drift. Protective layers, especially high-temperature sintered glass / ceramic layers, are the best barriers against moisture and ions, ensuring long-term resistance stability and significantly extended lifespan for sensors in harsh environments such as automotive engine compartments, outdoor industrial equipment, and medical sterilization environments. This is the most crucial measure for achieving high product stability.

[0035] S6. Dicing and splitting: Cutting a whole ceramic substrate into individual sensor chips; The entire ceramic substrate, which carries multiple sensor units, is cut along a pre-set cutting path to separate it into independent sensor chips. Through precision cutting, a single substrate integrating hundreds or even thousands of sensor units is separated into individual chips of uniform size and neat edges, such as standard package sizes like 0603 and 0402. This is the final forming process to achieve the surface-mount physical form of the product. Precise size control ensures that the chips are compatible with standard SMT mounting equipment and processes, meeting the fundamental requirements of the electronics industry for standardized and miniaturized component shapes.

[0036] S7. End electrode formation: End electrodes are formed at both ends of the sensor chip; Solderable terminal electrodes are formed at both ends of the sensor chip; Low-resistance, high-adhesion conductive channels are formed at both ends of the chip, reliably connecting the micron-scale platinum resistance film pattern to the subsequent surface-processed metal layer S8 for soldering. While the internal platinum resistance pattern, i.e., the electrode contact pad, is conductive, its small area and thin thickness prevent direct soldering. By printing and sintering a thick layer of conductive silver paste, a landing platform with strong current carrying capacity and a large contact area is constructed, allowing weak resistance change signals to be extracted without loss. This is the physical prerequisite for the sensor to achieve its temperature measurement function.

[0037] S8. Terminal electrode surface plating treatment: A nickel layer and a tin or tin alloy layer are formed on the surface of the terminal electrode.

[0038] A layer of pure tin (Sn) or a tin alloy such as Sn-Ag-Cu, with a moderate melting point, good fluidity, and oxidation resistance, is formed on the outermost layer. This tin layer is an industry-standard SMT soldering material. It ensures that the sensor chip is perfectly compatible with standard electronic assembly processes such as lead-free reflow soldering. Excellent solderability means good wetting during soldering, resulting in smooth, full solder joints, reducing defects such as cold solder joints and improving first-pass yield.

[0039] This invention provides a complete, orderly, and parameter-defined fabrication process for surface-mount platinum resistance thermometers. By placing the "protective layer printing and sintering" step before "dicing and splitting" and "terminal electrode formation," it ensures that the protective layer can continuously and completely cover the fragile platinum resistance pattern, avoiding the problems of uneven protective layer coverage and insufficient edge protection caused by processing the microchip separately after dicing, and greatly improving the environmental reliability of the product.

[0040] This invention ensures precision and stability by combining and precisely controlling three core processes: magnetron sputtering to prepare high-quality platinum resistance thin films, high-temperature stabilization treatment, and laser precision trimming. This ensures high purity and stability of the resistor from the material source, optimizes the microstructure through post-processing, and achieves precise digital trimming of the resistance value in the final stage. As a result, the prepared sensor can achieve a precision standard of Class A or even higher, and the temperature coefficient (TCR) is highly consistent.

[0041] The invention offers structural reliability and solderability: the innovative process of first protecting the entire structure, then dividing it into particles, and finally forming the end electrodes, combined with the optimized end electrode structure, ensures sufficient protection for the internal resistive elements and provides external electrodes with high mechanical strength, good conductivity, excellent solderability, and corrosion resistance, fully compatible with standard SMT reflow soldering processes.

[0042] This invention is suitable for mass production and miniaturization: the entire process draws upon and integrates mature semiconductor micromachining and chip component manufacturing technologies, making it suitable for large-scale, parallel production on a single substrate, resulting in high production efficiency and good consistency. Simultaneously, by eliminating the leads and bulk packaging of traditional leaded structures, product sizes can be made very small (such as 0603, 0402, or even smaller packages), meeting the urgent needs of modern electronic products for miniaturization and integration.

[0043] This invention offers significant cost-effectiveness: compared to traditional leaded platinum resistance thermometers, this method eliminates the need for precious metal leads, manual or semi-automatic soldering, and complex metal or glass encapsulation processes. It employs more efficient planar batch processing technology, effectively reducing manufacturing costs while ensuring high performance.

[0044] Furthermore, in step S1, the alumina ceramic substrate has a purity ≥96%, a thickness of 0.25-0.5 mm, and a surface roughness Ra ≤0.05 μm; the platinum resistance film is deposited using magnetron sputtering and has a thickness of 1-3 μm; before deposition, the alumina ceramic substrate undergoes pretreatment including ultrasonic cleaning with isopropanol, ethanol, and deionized water.

[0045] Ensuring excellent and stable insulation, high thermal conductivity, and chemical inertness. High purity means extremely low levels of impurities such as alkali metal ions and transition metal ions. Guaranteeing excellent electrical insulation, preventing substrate leakage, and ensuring the purity of the temperature measurement signal. Improving thermal conductivity, as impurities scatter phonons and reduce thermal conductivity. A high-purity substrate can quickly and uniformly conduct heat from the mounting surface to the platinum film, improving the sensor's response speed and measurement accuracy. Ensuring high-temperature stability and chemical inertness: It is less prone to phase transitions or contaminant release during subsequent high-temperature processes such as S2: sintering at 900-1200℃, avoiding adverse interfacial reactions with the platinum film and ensuring long-term reliability.

[0046] Furthermore, in step S2, the high-temperature sintering is carried out in a protective atmosphere or air, with a sintering temperature of 900-1200℃ and a holding time of 1-3 hours.

[0047] Ensuring sufficient recrystallization and defect repair in platinum thin films is crucial for stabilizing the temperature coefficient of resistance (TCR) and reducing resistivity. Platinum has a high recrystallization temperature. Below 900℃, insufficient atomic diffusion energy is necessary to effectively eliminate lattice distortions and grain boundary defects introduced by deposition, preventing the film's TCR and stability from reaching their optimal state. 900℃ is the critical temperature for initiating effective bulk diffusion and grain growth; above this temperature, the film can transition from the "deposited state" to a stable "annealed state."

[0048] Furthermore, step S3 specifically includes coating photoresist, exposure, development, etching the platinum resistance film, and photoresist removal steps, wherein the etching process is ion beam etching or wet chemical etching.

[0049] This technology enables the high-fidelity and high-reproducibility replication of complex, meandering resistor patterns designed on a photomask, sometimes only 10-25 micrometers wide, onto a platinum thin film. The photoresist acts as a temporary, high-resolution "prototype template," patterned through optical exposure. This offers significantly higher resolution and edge sharpness compared to direct printing or laser writing. This is a crucial technology for achieving sensor miniaturization and high initial consistency. Precise linewidth control directly determines the concentration of the initial resistance value.

[0050] Furthermore, in step S4, the laser trimming device uses a laser with a wavelength of 355nm or 532nm. The laser cuts specific parts of the resistor pattern through program control, adjusting the resistance accuracy to within ±0.1%.

[0051] Employing short-wavelength lasers of 355nm ultraviolet or 532nm green light, which possess high photon energy and high material absorption, and with extremely short interaction times (nanoseconds or picoseconds), the high absorption rate means that laser energy is rapidly absorbed and converted into heat within a very shallow layer of the material surface. The ultrashort pulse ensures that the interaction ends before the heat can diffuse and conduct to the surrounding area. This results in the removal of the platinum thin film primarily being "photoablation" rather than "thermal melting." The cutting edges are clean and sharp, without burrs or thermal deformation zones formed by melting and resolidification. Thermal damage and stress to the area adjacent to the resistance lines are minimal, maximizing the protection of the stabilized film microstructure and avoiding the introduction of new performance drift sources due to resistance tuning.

[0052] Furthermore, in step S5, the protective slurry is a glass slurry or a low-temperature co-fired ceramic slurry; the wet film thickness is 15-25 μm; and the sintering conditions are: heating to 800-900℃ and holding for 5-15 minutes.

[0053] Both glass paste and LTCC paste, after sintering, form a completely dense, non-porous, and continuous inorganic amorphous or microcrystalline ceramic layer. This dense structure consists of water molecules and ions such as carbon. , S An impermeable physical barrier fundamentally isolates the platinum film from environmental moisture and corrosive media, which is the most effective measure to ensure long-term stability. Extremely high volume resistivity and breakdown field strength ensure reliable electrical isolation. High hardness and abrasion resistance provide a robust mechanical armor for the fragile micron-level resistivity lines beneath.

[0054] Furthermore, step S6 is performed using a diamond wheel scribing machine or a laser scribing machine, with the cutting width controlled at 30-50μm.

[0055] Highly pragmatic and directly impacting the quality of the final product, it precisely addresses the core challenges in the transition from whole-wafer manufacturing to individual chip production, achieving efficient separation while maximizing the integrity and performance consistency of each unit.

[0056] Furthermore, in step S7, the terminal electrode is formed by printing or coating conductive silver paste and sintering, with a silver paste layer thickness of 80-120μm, a sintering temperature of 550-650℃, and a holding time of 5-15 minutes.

[0057] An electrode layer with extremely low resistivity is formed, ensuring that current is efficiently and losslessly drawn from the internal platinum resistance thermometer. Silver, the metal with the highest electrical conductivity, forms a dense conductive network after sintering. Minimizing the voltage drop across the electrodes themselves ensures the integrity of the sensor signal, which is crucial for high-precision measurements.

[0058] Furthermore, in step S8, the nickel layer is formed by electroplating or chemical plating, with a thickness of 3-5 μm; the tin or tin alloy layer is formed on the nickel layer by electroplating, with a thickness of 5-8 μm.

[0059] It completely prevents or greatly delays the diffusion of outer tin to the internal silver electrode during high-temperature soldering and long-term service, as well as the migration of silver to the tin layer. It prevents silver corrosion and the formation of brittle intermetallic compounds (IMCs): Tin and silver react rapidly to form brittle IMC layers such as Ag3Sn. Without a nickel layer, tin continuously consumes the silver electrode, leading to a reduction in the effective cross-section of the electrode, increased resistance, and even porous and pulverized electrodes. The nickel layer acts as an inert barrier, confining this harmful reaction outside the nickel layer, protecting the structural integrity and electrical properties of the silver electrode. It ensures the long-term stability of the composition and mechanical properties of the solder joint.

[0060] Furthermore, the protective layer printing and sintering in step S5 are performed simultaneously on all sensor units on the entire substrate, and the dicing and splitting in step S6 are performed after the protective layer is formed.

[0061] Before dicing, the protective layer covers the entire substrate in a continuous thin film. Therefore, after dicing, the four sidewalls of each individual chip, i.e., the diced surfaces, are naturally covered by the protective layer material. This is something that the "dic-and-seal" process cannot achieve. The latter typically only coats the top surface and part of the end faces of the chip, leaving the diced sidewalls exposed and vulnerable, easily becoming channels for moisture, contaminants, and stress corrosion, thus representing a weak point in long-term reliability. This method fundamentally eliminates this weakness, achieving true all-around, three-dimensional packaging and greatly improving the environmental robustness of the device.

[0062] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

[0063] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method of fabricating a patch platinum resistance thin film resistance temperature sensor, characterized by, The method steps are as follows: S1. Substrate pretreatment and platinum resistance film deposition, depositing a platinum resistance film on the surface of an alumina ceramic substrate; S2. High-temperature stabilization treatment: high-temperature sintering the deposited platinum resistance film; S3. Electrode pattern photolithography and etching: using photolithography and etching processes to process the platinum resistance film into a pre-set resistance pattern; S4. Laser precision resistance adjustment: using a laser resistance adjustment device to micro-cut the resistance pattern to accurately adjust the resistance value; S5. Protective layer printing and sintering: screen printing a dielectric protective paste on the surface of the resistance pattern after resistance adjustment and sintering to form a protective layer; S6. Scribing and breaking: cutting and separating the whole ceramic substrate into independent sensor chips; S7. End electrode formation: forming end electrodes on both ends of the sensor chip; S8. End electrode surface plating treatment: forming a nickel layer and a tin or tin alloy layer on the surface of the end electrode.

2. The method of claim 1, wherein the method further comprises: The purity of the alumina ceramic substrate in step S1 is ≥96%, the thickness is 0.25-0.5mm, and the surface roughness Ra is ≤0.05μm; the platinum resistance film is deposited by magnetron sputtering process, with a thickness of 1-3μm; the alumina ceramic substrate is pretreated by ultrasonic cleaning with isopropyl alcohol, ethanol and deionized water before deposition.

3. The method of claim 2, wherein the method further comprises: The high-temperature sintering in step S2 is carried out in a protective atmosphere or air, with a sintering temperature of 900-1200℃ and a holding time of 1-3 hours.

4. The method of claim 3, wherein the method further comprises: Step S3 specifically includes the steps of coating photoresist, exposure, development, etching the platinum resistance film and removing the photoresist, and the etching process is ion beam etching or wet chemical etching.

5. The method of claim 4, wherein the method further comprises: The laser resistance adjustment device in step S4 uses a laser with a wavelength of 355nm or 532nm.

6. The method of claim 5, wherein the method further comprises: The dielectric protective paste in step S5 is glass paste or low-temperature co-fired ceramic paste; the printed wet film thickness is 15-25μm; the sintering conditions are: heating to 800-900℃ and holding for 5-15 minutes.

7. The method of claim 6, wherein the method further comprises: Step S6 is carried out using a diamond grinding wheel scribe machine or a laser scribe machine, with a cutting width controlled at 30-50μm.

8. The method of claim 7, wherein the method further comprises: In step S7, the end electrode is formed by printing or coating conductive silver paste and sintering, with a silver paste layer thickness of 80-120μm, a sintering temperature of 550-650℃ and a holding time of 5-15 minutes.

9. The method of claim 8, wherein the method further comprises: In step S8, the nickel layer is formed by electroplating or chemical plating, with a thickness of 3-5μm; the tin or tin alloy layer is formed on the nickel layer by electroplating, with a thickness of 5-8μm.

10. The method of claim 9, wherein the method further comprises: The protective layer printing and sintering in step S5 are carried out simultaneously on the whole substrate for all sensor units, and step S6 scribing and breaking is carried out after the protective layer is formed.

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