Preparation method of radial glass packaged NTC (Negative Temperature Coefficient) thermistor with ceramic base

Abstract

The invention discloses a preparation method of a radial glass packaged NTC thermistor with a ceramic base, and the method comprises the steps of prefabricating a chip-lead assembly, sleeving a glass shell and carrying out preliminary melting wrapping, carrying out high-temperature mutual melting, processing a lead, assembling an insulating sleeve, and detecting and screening, and has the capability of industrial mass production. The core process is as follows: firstly, a chip-lead semi-finished product penetrates into a glass shell and is sintered to form a glass packaging body, and then a lead of the glass packaging body penetrates into a ceramic base and is fused with the ceramic base at high temperature to form a product with a gapless integrated combination structure of the glass packaging body and the ceramic base. According to the NTC thermistor prepared by the method, the ceramic base becomes a strong support of a glass-lead combination part, stress is dispersed fundamentally, and the NTC thermistor can stably work under complex working conditions such as stretching, vibration, collision and thermal shock in a wide temperature range of-55 DEG C to 350 DEG C, and has high reliability and long service life.

Description

Technical Field

[0001] This invention belongs to the field of NTC thermistor packaging technology, and relates to the preparation of radial glass-encapsulated NTC thermistors, specifically to a method for preparing a radial glass-encapsulated NTC thermistor with a ceramic base. Background Technology

[0002] Radial glass-encapsulated NTC thermistors are core temperature measurement and control components in high-end equipment (such as new energy vehicles and robots), and their packaging reliability directly determines the operational stability and safety of the terminal equipment. However, the junction between the glass and the metal leads has long been a core technical bottleneck in the industry: this junction is a stress concentration area where dissimilar materials (metal / glass) meet, and it is particularly prone to microcracks, fissures, or even breakage under tension, vibration, impact, and thermal shock in a wide temperature range of -55 ℃ to 350 ℃. This allows external moisture to seep into the package, causing silver ion migration in the chip's silver electrodes, ultimately resulting in resistance drift and temperature measurement failure, becoming a key bottleneck restricting the application of NTC thermistors in high-end fields.

[0003] In existing technologies, conventional glass encapsulation processes only achieve basic sealing and lack reinforcement design for the glass-lead interface, failing to fundamentally solve the aforementioned failure problems. A few technologies attempt to add a ceramic base for structural reinforcement, but these are mostly simple nesting or stacking, resulting in weak interface bonding, poor stress dispersion, and limited reinforcement. For example, CN108109792B discloses a thermistor with a base and its preparation method. It first prepares a glass head semi-finished product using glass slurry and places it on a base with lead grooves; then, leads are passed through the lead grooves, which are filled with glass slurry; finally, the thermistor product is formed by curing the glass slurry. Structurally, this only fixes the leads to the base; the glass head and base are merely attached, with no interfacial fusion. Under tension, vibration, or impact, the base and glass head are prone to cracking along the interface, leading to product failure. For example, CN112038029B discloses an ultra-small radial glass-encapsulated thermistor and its manufacturing method. First, the lead wire is passed through the ceramic pillar and the chip is welded to form a semi-finished product. Then, a glass glaze slurry is coated and cured to form a semi-finished product. Finally, a PI tube is assembled to obtain the finished thermistor. It adopts a layered molding method of ceramic pillar and glass glaze slurry. The ceramic pillar and glass head also lack material fusion and transition, and the resistance to mechanical shock and thermal shock is insufficient.

[0004] Furthermore, existing improved processes suffer from cumbersome procedures, low assembly precision, and poor product consistency, making it difficult to meet the demands of the high-end market for large-scale mass production. More importantly, existing technologies struggle to balance product miniaturization with structural strength requirements, rendering them unsuitable for extreme conditions such as tension, vibration, collision, and thermal shock. This hinders their ability to meet the miniaturization and high reliability design requirements of equipment such as new energy vehicles and robots.

[0005] Therefore, there is an urgent need for a new manufacturing method to achieve a dense and integrated bonding between the thermistor glass and the ceramic base, fundamentally solving the reliability bottleneck of radial glass-encapsulated NTC thermistors and realizing independent control of high-end NTC thermistor packaging technology. Summary of the Invention

[0006] To address the aforementioned problems, the main objective of this invention is to design a method for preparing a radially encapsulated NTC thermistor with a ceramic base. This method achieves a dense, integrated bond by melting and fusing the glass and ceramic base at high temperatures. The ceramic base serves as a reinforcing support for the glass-lead bonding joint, thus solving the problem of glass breakage and failure under tension, vibration, collision, and thermal shock.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for fabricating a radially glass-encapsulated NTC thermistor with a ceramic base includes the following steps: Step 1, Chip-lead assembly prefabrication: Cut two leads to the preset length and clean the cut surfaces; Solder is applied to the cut surface of the lead wire and the chip electrode surface. After the cut surface is aligned and attached to the chip electrode surface, it is soldered and cured to form a chip-lead semi-finished product. Step 2, Glass shell assembly and preliminary melting and wrapping: Insert the chip-lead semi-finished product into the glass shell, with the chip placed inside the glass shell and the lead wires leading out from one end of the glass shell, forming an assembly in which the glass shell, chip, and lead wires are coaxial; The assembly is placed in a sintering furnace for sintering, which initially melts the glass shell, seamlessly wrapping the chip and lead roots. After cooling in the furnace, it forms a glass package. Step 3, High-temperature fusion: The free ends of the two leads are inserted into the through holes of the ceramic base, the two leads are flush and exposed on the ceramic base, and the ceramic base is attached to the glass package to form an assembly of ceramic base-glass packaged thermistor. The assembly is placed in a sintering furnace for sintering, causing the glass encapsulation and the ceramic base to undergo a high-temperature melting and mutual fusion reaction, forming a finished product with a seamless integrated structure. Step 4, lead wire treatment: Immerse the lead wire in the pickling solution to remove sintering residue, rinse the lead wire with deionized water to remove pickling residue, and then dry with hot air; Step 5, Insulating sleeve assembly: Insert two polyimide insulating sleeves into the two leads respectively, and push one end of the insulating sleeve into the through hole of the ceramic base along the lead until it reaches the root of the glass encapsulation. At the contact point between the insulating sleeve and the through hole of the ceramic base, sealant is applied for fixation, and the integrated finished product is placed in an oven to cure and form a highly insulating protective finished product, thus completing the preparation; Step 6, Inspection and Screening: Use visual inspection equipment to inspect the product's dimensions, appearance, and the tightness of the ceramic base-glass joint; Electrical performance and insulation strength were tested using a constant temperature oil bath and an insulation resistance tester. Reliability verification was conducted through temperature shock testing, lead wire tensile testing, steady-state damp heat testing, vibration testing, impact testing, and high-temperature aging testing to obtain qualified products.

[0008] In the application of NTC thermistors, the application scenarios typically include both normal temperature range and high temperature range environments. Therefore, as a further description of the present invention, in step 1, the application scenario is a normal temperature range of -55 ℃ to 200 ℃, where the chip electrodes are silver electrodes, and silver paste is applied to the chip electrode surface and the lead cut surface; the application scenario is a high temperature range of -55 ℃ to 350 ℃, where the chip electrodes are gold electrodes, and gold paste is applied to the chip electrode surface and the lead cut surface. Furthermore, the components can be pressed together using a constant temperature hot press welding machine, and the pressed components are placed in a 150 ℃ oven for 40 minutes to complete the solder curing.

[0009] As a further description of the present invention, in step 2, the glass shell is set as a cylinder with openings at both ends. The chip-lead semi-finished product is inserted into the glass shell through either opening, and the two leads are led out from either opening and fixed by positioning fixtures to avoid subsequent thermal stress concentration due to eccentricity. Further, the assembly is placed in a sintering furnace, which heats the material to 450-500°C at a heating rate of 50-80°C / min and holds it at that temperature for 15-20 minutes to allow the glass shell to initially melt. The assembly is then cooled to 400°C in the furnace at a cooling rate of 3-5°C / min, and then naturally cooled to room temperature to obtain the glass encapsulation. Slow cooling avoids the generation of internal stress in the glass encapsulation.

[0010] As a further description of the invention, in step 3, the gap between the ceramic base and the glass encapsulation body after bonding is ≤0.1mm, ensuring the tightness of the high-temperature fusion. Furthermore, the sintering furnace is heated to 650℃~800℃ at a heating rate of 50~100℃ / min and held for 5~10 min, allowing the glass encapsulation body and the ceramic base to fuse together at high temperature; the assembly is then cooled to 550℃ in the furnace at a cooling rate of 3~5℃ / min, and then naturally cooled to room temperature. This eliminates thermal stress at the glass-ceramic interface, avoids cracks caused by differences in thermal shrinkage, and ensures the stability of the integrated structure.

[0011] As a further description of the present invention, in step 4, the lead wire is immersed in an acid pickling solution for 3-5 minutes to remove the borate coating and trace oxide layer remaining after sintering; after repeatedly rinsing with deionized water to remove acid pickling residue, it is placed in a 100°C hot air drying oven for 30 minutes to expose a bright copper layer on the surface of the Dummex wire, thereby improving the conductivity and solderability of the lead wire. Furthermore, the lead wire is also tin-plated with a thickness of 5-10 μm to improve its oxidation resistance and solderability.

[0012] A radial glass-encapsulated NTC thermistor with a ceramic base, prepared using the above-mentioned method, includes an NTC thermistor chip, leads, a glass shell, a ceramic base, and an insulating sleeve. The lead wire is provided in two parts, and one end of each lead wire is welded to the electrode surface of the NTC thermistor chip to form a welding end. The glass shell is fitted over the NTC thermistor chip and the lead bonding end, and is sintered to form a glass package. The ceramic base has two parallel through holes, the free ends of two leads are inserted into the through holes, and the ceramic base is bonded to the glass encapsulation body and sintered together to form an integrated product. Two insulating sleeves are provided, which are respectively fitted outside the two leads and inserted into the through holes, reaching the root of the glass encapsulation body.

[0013] As a further description of the present invention, the ceramic base is configured as a column with parallel upper and lower planes, the through hole is vertically opened from the two parallel planes, and the root of the glass encapsulation body is attached to the upper plane of the ceramic base.

[0014] Compared with the prior art, the technical advantages of the present invention are as follows: This invention provides a method for fabricating a radially glass-encapsulated NTC thermistor with a ceramic base. The method includes steps such as chip-lead assembly prefabrication, glass shell assembly and initial melting, high-temperature fusion, lead processing, insulating sleeve assembly, and testing and screening, enabling large-scale mass production of NTC thermistors. The core process involves first inserting the chip-lead semi-finished product into a glass shell, sintering it to form a glass encapsulation, and then inserting the leads of the glass encapsulation into a ceramic base and performing high-temperature fusion to form the final product. The overall fabrication process employs a two-step sintering process: the first step involves initial melting and encapsulating the glass shell to form the glass encapsulation; the second step involves high-temperature fusion to achieve a seamless, integrated bond between the glass encapsulation and the ceramic base. The NTC thermistor produced by this method provides strong support for the glass-lead junction through the ceramic base, fundamentally dispersing stress in this area and improving product reliability. Simultaneously, this structure prevents moisture penetration into the glass encapsulation and prevents silver ion migration from the chip's silver electrodes, achieving high reliability, long lifespan, and zero defects.

[0015] The NTC thermistors prepared by this method are suitable for fields such as new energy vehicles, robots, energy storage equipment, and high-end industrial control that have stringent requirements for high reliability, long life and resistance to harsh working conditions. They can work stably under complex working conditions such as tension, vibration, impact, and thermal shock in a wide temperature range of -55℃ to 350℃. Moreover, this method has the capability for large-scale mass production, enabling industrial mass production and meeting the performance requirements of high-end markets for components in extreme environments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation method of the present invention; Figure 2 This is a structural view of the NTC thermistor of the present invention; Figure 3 The table shows the resistance change rate of the NTC thermistor with dual 85 diodes obtained in this invention after 1000 hours of testing.

[0017] In the diagram, 1. NTC thermistor chip, 2. Lead wire, 3. Glass shell, 4. Ceramic base, 5. Insulating sleeve. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings: Example 1

[0019] A method for fabricating a radially encapsulated NTC thermistor with a ceramic base, such as... Figure 1As shown, the process includes five steps: chip-lead assembly prefabrication, glass shell assembly and initial fusion wrapping, high-temperature interlocking, lead wire treatment, and insulating sleeve assembly. Combined with testing and screening, qualified products are obtained. Qualified products effectively prevent moisture penetration and silver ion migration, achieving high reliability, long lifespan, and zero defects in the components. It not only enables standardized, automated, and continuous mass production but also balances product miniaturization and structural strength.

[0020] Before this preparation method begins, tooling and material preparation are also required: Tooling and fixtures: Custom-made high-temperature resistant positioning fixtures, including glass shell positioning, ceramic base positioning, and lead wire positioning. The glass shell positioning is used to ensure the glass shell and chip-lead assembly are coaxial; the ceramic base positioning is used to ensure the ceramic base and lead wires are aligned, with a hole spacing error ≤0.02 mm; the lead wire positioning is used to ensure the two leads are parallel, with a parallelism error ≤0.05 mm.

[0021] Material preparation: Prepare ceramic base, glass shell, Dummes wire leads, NTC thermistor chip, and auxiliary materials such as polyimide insulating tube, high-temperature sealant, pickling solution, and tin plating solution; the difference between the thermal expansion coefficient of the glass shell and that of the ceramic base, Dummes wire leads, and NTC thermistor chip should be ≤1.5×10⁻⁶. -6 / ℃, the diameter of the Dumex wire leads and the diameter of the through hole in the ceramic base form a clearance fit.

[0022] Specifically, this embodiment provides a detailed explanation of the steps involved in the preparation method described above, as follows: Step 1: Chip-lead assembly prefabrication: Lead wire pretreatment: Cut two leads to a preset length and clean the cut surfaces to remove impurities and burrs. In this embodiment, the preset length is set to 50~80 mm and the diameter to 0.35 mm.

[0023] Electrode connection: Solder is applied to the cut surface of the lead wire and the electrode surface of the chip. After aligning and bonding the cut surface with the electrode surface of the chip, the two are soldered and cured to form a chip-lead semi-finished product. Specifically, in this embodiment, in the conventional temperature range of -55℃ to 200℃, the chip electrode is a silver electrode, and silver paste is applied to the chip electrode surface and the cut surface of the lead wire; in the high temperature range of -55℃ to 350℃, the chip electrode is a gold electrode, and gold paste is applied to the chip electrode surface and the cut surface of the lead wire, thereby preventing the diffusion of silver ions at high temperatures. Further pressing can be performed using a constant temperature thermocompression welding machine with the following process parameters: pressure 0.8~1.0 N, temperature 180~200℃, time 5~8 s. Conductive connection is achieved directly through silver / gold paste, and the pressing parameters ensure connection reliability.

[0024] Initial curing and inspection: The crimped components are placed in a 150 ℃ oven for 40 min to complete solder curing. Microscopic visual inspection is used to ensure there are no loose connections or desoldering, and the lead parallelism error is ≤0.05 mm. Defective products are discarded, yielding a chip-lead semi-finished product.

[0025] Step 2, Glass shell assembly and initial molten encapsulation: Glass Shell Assembly: The chip-lead semi-finished product is inserted into the glass shell, with the chip placed inside the glass shell. The leads are led out from one end of the glass shell, forming an assembly in which the glass shell, chip, and leads are coaxial. Specifically, in this embodiment, the glass shell is set as a cylinder with openings at both ends. The chip-lead semi-finished product is inserted into the glass shell from either end, and the two leads are led out from either end. They are fixed by positioning fixtures to ensure that the glass shell, chip, and leads are coaxial, avoiding subsequent thermal stress concentration due to eccentricity.

[0026] In this embodiment, nitrogen protection is used for initial melting. Specifically, the assembly is placed in a nitrogen-protected sintering furnace with a nitrogen purity of ≥99.99%. The sintering furnace is heated to 450℃-550℃ at a heating rate of 50~80℃ / min and held for 15~20min to allow the glass shell to initially melt, seamlessly encapsulating the chip and lead root. Nitrogen protection prevents the leads and chip from oxidizing during the melting process.

[0027] Cooling and shaping: The glass encapsulation is cooled to 400 ℃ at a cooling rate of 3~5 ℃ / min in the furnace, and then naturally cooled to room temperature to obtain the glass encapsulation. Slow cooling avoids the generation of internal stress in the glass encapsulation.

[0028] Step 3, High-Temperature Fusion: Ceramic base installation: The free ends of the two leads are inserted into the through holes of the ceramic base. The two leads are flush and exposed on the ceramic base. The ceramic base is then bonded to the glass package using a positioning fixture. The bonding gap is ≤0.1 mm to ensure the high-temperature fusion and tightness, forming an assembly of ceramic base-glass packaged thermistor. Nitrogen-protected fusion sintering: The assembly is placed in a nitrogen-protected sintering furnace with nitrogen purity ≥99.99%. The furnace is heated to 650℃~800℃ at a heating rate of 50~100℃ / min and held for 5~10 min, causing the glass encapsulation and ceramic base to undergo a high-temperature melting and fusion reaction, forming a seamless integrated structure. This makes the ceramic base a structural reinforcement support for the glass-lead bonding section.

[0029] Gradient cooling: The temperature is reduced to 550℃ in the furnace at a cooling rate of 3~5℃ / min, and then naturally cooled to room temperature. This eliminates thermal stress at the glass-ceramic base joint, avoids cracks caused by thermal shrinkage differences, and ensures the stability of the integrated structure.

[0030] It should also be noted that for silver electrode products, aging at 200 ℃ under nitrogen protection for 96 hours followed by natural cooling is also included; for gold electrode products, aging at 300 ℃ under nitrogen protection for 96 hours followed by natural cooling is also included. This reduces thermal stress after gradient cooling and improves the consistency of product resistance and stability in high-temperature applications.

[0031] Step 4, Lead wire treatment: Pickling to remove impurities: Immerse the lead wire in the pickling solution for 3-5 minutes to remove the borate coating and trace oxide layer remaining after sintering of the lead wire; during the pickling process, the ratio of the pickling solution can be adjusted to remove impurities while avoiding corrosion of the copper layer of the lead wire.

[0032] Cleaning and drying: Rinse the leads repeatedly with deionized water to remove acid residue, and then dry them in a 100 ℃ hot air drying oven for 30 min to expose a bright copper layer on the surface of the Dumex wire, thereby improving the conductivity and solderability of the leads.

[0033] Tin plating (optional): This also includes chemical tin plating or hot-dip tin plating of the leads according to the application requirements. The tin plating thickness is controlled at 5~10 μm to improve the oxidation resistance and solderability of the leads. The tin plating process is optional and can be adapted to different application scenarios.

[0034] Step 5, Insulating sleeve assembly: Sleeve installation: Insert two polyimide insulating sleeves into the two leads respectively, and push one end of the insulating sleeve into the through hole of the ceramic base along the lead. Using the gap between the through hole of the ceramic base and the lead, push the insulating sleeve to the root of the glass encapsulation; ensure that the insulating sleeve completely covers the insulation requirement section of the lead, and eliminate the risk of short circuit of the lead from the source.

[0035] Fixed sealing: At the contact point between the insulating sleeve and the through hole of the ceramic base, a high-temperature sealant is applied for fixation. This not only fixes the insulating sleeve but also enhances the sealing performance between the insulating sleeve and the ceramic base, preventing moisture from seeping in along the gap.

[0036] Curing treatment: Place the assembled insulating sleeve in an oven at 120~150 ℃ for 20~40 min to cure the sealant and form a highly insulating and protective finished product, thus completing the preparation.

[0037] Step 6, Detection and Screening: Size and appearance inspection: The size and appearance of the product are inspected using visual inspection equipment, as well as the tightness of the ceramic base-glass joint, the surface condition of the lead wires, and the assembly position of the insulating sleeve, to ensure that the finished product is free from defects such as cracks, damage, bubbles, and chip or insulating sleeve misalignment.

[0038] Electrical performance and insulation testing: (1) Place the finished product in a constant temperature oil bath and test the resistance at each temperature point of -55 ℃, 25 ℃, 50 ℃, 85 ℃, 125 ℃ and 350 ℃. The resistance and B value deviations should meet the standards, such as ±0.5%, ±1%, and ±2%. (2) The insulation strength of the product is tested by an insulation resistance tester. The insulation resistance is ≥100 MΩ at 300 ℃ and 500 V DC.

[0039] Reliability verification: (1) Temperature shock test, test conditions: temperature -55 ℃~350 ℃, heat preservation for 30 min, switching time ≤10 s, shock 100 times; performance requirements: no visible damage, resistance change rate ≤±2.0%, B value change rate ≤±1.0%; (2) Lead wire tensile test. Test method: Fix the resistor end, separate the two radially parallel leads to 180° and apply a tensile force ≥ 5 N for 10 s. Performance requirements: No visible damage, resistance change rate ≤ ±2.0%, B value change rate ≤ ±1.0%. (3) Steady-state damp heat test, test method: temperature 85±2 ℃, humidity 85±5% RH, for 1000 h; performance requirements: no visible damage, resistance change rate ≤±2.0%, B value change rate ≤±1.0%; (4) Vibration test, test conditions: frequency range 10~500 Hz, amplitude 0.75 mm or acceleration 98 m / s 2 Orientation upright, duration 2 hours, recovery time 2 hours, total time 1000 hours; Performance requirements: no visible damage, resistance change rate ≤ ±2.0%, B-value change rate ≤ ±1.0%; (5) Collision test, test conditions: acceleration 250 m / s 2 The pulse duration is 6 ms, the direction is upright, the number of collisions is 4000, and the recovery time is 2 h; performance requirements: no visible damage, resistance change rate ≤ ±2.0%, B value change rate ≤ ±1.0%; (6) High temperature aging test, test conditions: temperature 350 ℃, time 1000 h; performance requirements: no visible damage, resistance change rate ≤ ±2.0%, B value change rate ≤ ±1.0%.

[0040] The aforementioned visible damage includes, but is not limited to, glass cracking, ceramic breakage, loose leads, and detached insulating sleeves. Products that pass the above tests are then vacuum-packed to complete the qualified product processing and adapt to mass production requirements. Example 2

[0041] A radially encapsulated NTC thermistor with a ceramic base, the NTC thermistor being fabricated using the method described above, such as... Figure 2 As shown, it includes an NTC thermistor chip 1, leads 2, a glass shell 3, a ceramic base 4, and an insulating sleeve 5; The lead wire 2 is provided in two parts, and one end of the two lead wires 2 is respectively welded to the electrode surface of the NTC thermistor chip 1 to form a welding end; The glass shell 3 is fitted outside the welding end of the NTC thermistor chip 1 and the lead wire 2, and is sintered to form a glass encapsulation body; The ceramic base 4 has two parallel through holes, the free ends of the two leads 2 are inserted into the through holes, and the ceramic base 4 is bonded to the glass encapsulation body and sintered together to form an integrated product. Two insulating sleeves 5 are provided, which are respectively fitted outside the two leads 2 and inserted into the through holes to reach the root of the glass encapsulation body.

[0042] Specifically, in this embodiment, the ceramic base 4 is configured as a column with parallel upper and lower planes, the through hole is vertically opened from the two parallel planes, and the root of the glass encapsulation body is attached to the upper plane of the ceramic base 4.

[0043] In this embodiment, the ceramic base 4 is set as a cylinder, with two through holes running parallel through the upper and lower planes of the cylinder. The thermal expansion coefficients of the ceramic base 4, lead wire 2, and glass shell 3 are matched to achieve high-temperature melting and fusion with the glass encapsulation. The lead wire 2 is an iron-nickel alloy core + copper cladding + surface borate coating, which forms a gap fit with the ceramic base 4, ensuring assembly accuracy and reserving space for the subsequent insulating sleeve 5.

[0044] To verify the performance of the NTC thermistor prepared by this invention, products that met the resistance change rate requirement of ≤±2.0% after lead wire stretching tests were selected. The resistance value of the product after the stretching test was used as the resistance value before the test, and steady-state damp heat tests were performed. Figure 3 As shown in the data, the resistance change rate |(R2-R1) / R1|≤2.0%, indicating that the product can prevent the migration of silver ions caused by water vapor penetration in harsh environments, and has excellent anti-permeability and insulation retention capabilities.

[0045] The above content discloses the method for preparing NTC thermistors of the present invention. Compared with the prior art, the present invention has the following advantages: 1. The present invention includes chip-lead assembly prefabrication, glass shell assembly and preliminary melting and wrapping, high-temperature interweaving, lead wire treatment, insulating sleeve assembly, testing and screening processes. The processes are smoothly connected, the products have high consistency, and large-scale industrial production can be realized. 2. This invention uses a ceramic base and a glass encapsulation body to fuse together at high temperature to form a seamless integrated structure. The ceramic base serves as a reinforcing support for the glass-lead joint, reducing the dispersion of stress under product tension, vibration, collision and thermal shock, fundamentally solving the problem of easy breakage of the glass encapsulation body, and preventing moisture penetration and silver ion migration. 3. This invention can match the glass shell by using a small cylindrical ceramic base, without increasing the overall size of the product, and is suitable for the miniaturization and lightweight requirements of high-end assembly. 4. The Dumex wire of this invention only needs to be cut and cleaned before use, simplifying the traditional wire polishing process and improving production efficiency. At the same time, it is equipped with tin plating treatment and insulating sleeve assembly, which can be flexibly configured according to customer needs and application scenarios, and adapt to the differentiated needs of traditional fuel vehicles, new energy vehicles, robots and other fields.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the direction and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for fabricating a radially encapsulated NTC thermistor with a ceramic base, characterized in that, Includes the following steps: Step 1, Chip-lead assembly prefabrication: Cut two leads to the preset length and clean the cut surfaces; Solder is applied to the cut surface of the lead wire and the chip electrode surface. After the cut surface is aligned and attached to the chip electrode surface, it is soldered and cured to form a chip-lead semi-finished product. Step 2, Glass shell assembly and preliminary melting and wrapping: Insert the chip-lead semi-finished product into the glass shell, with the chip placed inside the glass shell and the lead wires leading out from one end of the glass shell, forming an assembly in which the glass shell, chip, and lead wires are coaxial; The assembly is placed in a sintering furnace for sintering, which initially melts the glass shell, seamlessly wrapping the chip and lead roots. After cooling in the furnace, it forms a glass package. Step 3, High-temperature fusion: The free ends of the two leads are inserted into the through holes of the ceramic base, the two leads are flush and exposed on the ceramic base, and the ceramic base is attached to the glass package to form an assembly of ceramic base-glass packaged thermistor. The assembly is placed in a sintering furnace for sintering, causing the glass encapsulation and the ceramic base to undergo a high-temperature melting and mutual fusion reaction, forming a finished product with a seamless integrated structure. Step 4, lead wire treatment: Immerse the lead wire in the pickling solution to remove sintering residue, rinse the lead wire with deionized water to remove pickling residue, and then dry with hot air; Step 5, Insulating sleeve assembly: Insert two polyimide insulating sleeves into the two leads respectively, and push one end of the insulating sleeve into the through hole of the ceramic base along the lead until it reaches the root of the glass encapsulation. At the contact point between the insulating sleeve and the through hole of the ceramic base, sealant is applied for fixation, and the integrated finished product is placed in an oven to cure and form a highly insulating protective finished product, thus completing the preparation; Step 6, Inspection and Screening: Use visual inspection equipment to inspect the product's dimensions, appearance, and the tightness of the ceramic base-glass joint; Electrical performance and insulation strength were tested using a constant temperature oil bath and an insulation resistance tester. Reliability verification was conducted through temperature shock testing, lead wire tensile testing, steady-state damp heat testing, vibration testing, impact testing, and high-temperature aging testing to obtain qualified products.

2. The method for fabricating a radially encapsulated NTC thermistor with a ceramic base according to claim 1, characterized in that: In step 1, the application scenario is a normal temperature range of -55 ℃ to 200 ℃, the chip electrode is a silver electrode, and silver paste is applied to the chip electrode surface and the cut surface of the lead wire; the application scenario is a high temperature range of -55 ℃ to 350 ℃, the chip electrode is a gold electrode, and gold paste is applied to the chip electrode surface and the cut surface of the lead wire.

3. The method for fabricating a radially encapsulated NTC thermistor with a ceramic base according to claim 1, characterized in that: In step 2, the glass shell is set as a cylinder with openings at both ends. The chip-lead semi-finished product is inserted into the glass shell through any one opening, and the two leads are led out from any one opening.

4. The method for fabricating a radially encapsulated NTC thermistor with a ceramic base according to claim 3, characterized in that: In step 2, the sintering furnace is heated to 450 ℃-550 ℃ at a heating rate of 50~80 ℃ / min and held for 15~20 min to allow the glass shell to initially melt; the assembly is cooled to 400 ℃ with the furnace at a cooling rate of 3~5 ℃ / min, and then naturally cooled to room temperature to obtain the glass encapsulation.

5. The method for fabricating a radially encapsulated NTC thermistor with a ceramic base according to claim 1, characterized in that: In step 3, the gap between the ceramic base and the glass encapsulation body after bonding is ≤0.1 mm to ensure the tightness of high-temperature fusion.

6. The method for fabricating a radially encapsulated NTC thermistor with a ceramic base according to claim 5, characterized in that: In step 3, the sintering furnace is heated to 650 ℃~800 ℃ at a heating rate of 50~100 ℃ / min and held at that temperature for 5~10 min, so that the glass encapsulation and the ceramic base can be fused together at high temperature; the assembly is cooled to 550 ℃ with the furnace at a cooling rate of 3~5 ℃ / min, and then naturally cooled to room temperature.

7. The method for fabricating a radially encapsulated NTC thermistor with a ceramic base according to claim 1, characterized in that: In step 4, the lead wire is immersed in the pickling solution for 3-5 minutes to remove the borate coating and trace oxide layer remaining from the sintering of the lead wire. After repeatedly rinsing with deionized water to remove acid residue, the product is dried in a 100 ℃ hot air drying oven for 30 min.

8. The method for fabricating a radially encapsulated NTC thermistor with a ceramic base according to claim 7, characterized in that: Step 4 also includes tin plating the leads, with a tin plating thickness of 5~10 μm.

9. A radially encapsulated NTC thermistor with a ceramic base, prepared by any one of claims 1-8, characterized in that: Includes NTC thermistor chip, leads, glass shell, ceramic base, and insulating sleeve; The lead wire is provided in two parts, and one end of each lead wire is welded to the electrode surface of the NTC thermistor chip to form a welding end. The glass shell is fitted over the NTC thermistor chip and the lead bonding end, and is sintered to form a glass package. The ceramic base has two parallel through holes, the free ends of two leads are inserted into the through holes, and the ceramic base is bonded to the glass encapsulation body and sintered together to form an integrated product. Two insulating sleeves are provided, which are respectively fitted outside the two leads and inserted into the through holes, reaching the root of the glass encapsulation body.

10. The radially encapsulated NTC thermistor with ceramic base according to claim 9, characterized in that: The ceramic base is configured as a column with parallel upper and lower planes, and the through hole is vertically opened from the two parallel planes. The root of the glass encapsulation body is attached to the upper plane of the ceramic base.

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