A power type negative temperature coefficient thermistor and method for suppressing inrush current

Abstract

The application discloses a power type negative temperature coefficient thermistor for inhibiting inrush current and a method, and relates to the technical field of negative temperature coefficient thermistors. The thermistor comprises a core body and pins. The pins are arranged on the electrodes on the two sides of the core body in a multi-contact surface structure. The core body is made of Mn-Co-Ni-La oxide with a nano composite gradient structure. The nano composite gradient structure Mn-Co-Ni-La oxide determines the upper limit of the core capabilities of the thermistor, such as inrush current inhibition, wide temperature stability and low power consumption. The redesign of the pins is a key to performance transmission, which ensures that the electrical properties (low contact resistance and high inrush current bearing) of the nano composite gradient structure Mn-Co-Ni-La oxide are not offset by structural defects. The setting of the support avoids the loss of effect of the nano composite gradient structure Mn-Co-Ni-La oxide due to heat accumulation and physical damage through heat management and mechanical protection. The three parts complement and cooperate with each other, thereby guaranteeing the performance of the thermistor with the nano composite gradient structure Mn-Co-Ni-La oxide.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of negative temperature coefficient thermistor, in particular, to a power type negative temperature coefficient thermistor for suppressing surge current. BACKGROUND

[0002] NTC thermistor is a kind of thermistor element with negative temperature coefficient, whose resistance decreases exponentially with temperature rise. The core characteristic of NTC thermistor is derived from the electron conduction mechanism of semiconductor material. When the temperature rises, the concentration of carriers (electrons or holes) in the material increases significantly, which leads to an exponential decrease in resistance. As an important branch of semiconductor ceramic elements, NTC thermistor is usually made of two or more transition metal oxides such as manganese, copper, cobalt, and nickel. The key performance such as resistivity and material constant (B value, a core parameter representing temperature coefficient) will change significantly with the proportion of material composition (such as the difference in the proportion of manganese, cobalt, and nickel oxides), sintering atmosphere (air, inert gas, etc.), sintering temperature (usually 800-1200℃), and microstructure state (grain size, porosity, and grain boundary characteristics). Therefore, different application scenarios can be adapted through process control. NTC thermistor is currently widely used in surge suppression, temperature compensation, temperature measurement, and other fields.

[0003] In the field of electronic circuits, surge current far exceeding the rated current by several times to dozens of times is easily generated during the startup moment due to effects such as capacitor charging and inductance excitation. This current can cause instantaneous impact on elements such as backend chips, capacitors, and rectifier bridges, and can directly lead to element burnout or significantly shorten the service life. To solve this problem, power type NTC thermistors are generally connected in series in the power circuit. The core principle of surge suppression is based on the dynamic adaptation of the negative temperature coefficient characteristics and working state of the NTC thermistor:

[0004] Surge suppression stage during startup: Before startup, the NTC thermistor is in a room temperature (or low temperature) environment. According to the negative temperature coefficient characteristics, the resistance value is maintained at a high level at this time (i.e., "room temperature high resistance state"). When the circuit is powered on, the high resistance value of the NTC can limit the loop current through voltage division, effectively intercepting the surge current and preventing damage to the backend devices.

[0005] Steady state working stage: After completing surge suppression, the circuit enters a stable running state. The continuous working current through the NTC generates Joule heat, causing the temperature of the NTC to gradually rise. Based on the negative temperature coefficient characteristics, the resistance value of the NTC rapidly decreases from the room temperature high resistance state to a very low "high temperature low resistance state". At this time, the power consumption of the NTC is negligible compared to the total power consumption of the circuit, and the power voltage is almost entirely loaded to the backend devices, ensuring normal operation of the circuit.

[0006] Therefore, applying the power type NTC thermistor in the power supply circuit is a simple and efficient technical solution to realize the compatibility of "power-on surge suppression-steady-state low power consumption" and protect electronic devices.

[0007] However, the traditional power type NTC thermistor material has been limited by the inherent contradiction between "surge suppression capability" and "temperature stability" for a long time, and it is difficult to meet the stringent requirements of high-end electronic devices (such as new energy inverters, automotive electronics, and industrial high-power power supplies) for reliability. The specific pain points are reflected in two aspects:

[0008] Conflict between room temperature resistance (25℃) and functional requirements: If a higher room temperature resistance is designed to strengthen the surge suppression capability, although it can effectively limit the current during power-on, the "high-temperature residual resistance" of the NTC will also increase (the room temperature resistance and the high-temperature residual resistance are positively correlated in traditional materials) during steady-state operation of the circuit, resulting in a significant increase in its own power consumption, not only causing waste of electrical energy, but also causing the NTC to run at high temperature for a long time, accelerating material aging and pin loosening; if a lower room temperature resistance is designed to reduce high-temperature power consumption, although it can reduce steady-state loss, it cannot provide sufficient current limiting capability during power-on, and the surge current is easy to break through the safety threshold, resulting in damage to the downstream equipment;

[0009] High-temperature B value drift destroys performance stability: B value (temperature coefficient) is a core parameter that characterizes the NTC resistance-temperature relationship, and its stability directly determines the performance reliability of the NTC in a wide temperature range. In a high-temperature environment (> 150℃), the traditional NTC material (such as single manganese-cobalt-nickel spinel system) is prone to B value drift (usually fluctuates by ±15% or more) due to problems such as cation migration and increased lattice defects (vacancies, dislocations), which makes the resistance-temperature curve deviate from the design expectation, resulting in attenuation of surge suppression effect, decrease of temperature compensation accuracy, and even causing circuit overcurrent protection failure and safety hazards.

[0010] Therefore, the traditional power type NTC thermistor has a technical bottleneck in the balance of "surge suppression-temperature stability-low power consumption", and it is necessary to break through the above inherent contradictions through material composition optimization and structural innovation to meet the application requirements of high-end electronic devices for high reliability and wide temperature adaptability. SUMMARY

[0011] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a power type negative temperature coefficient thermistor that can overcome the above problems or at least partially solve the above problems.

[0012] To solve the above technical problems, the basic idea of the technical scheme of the present application is: a power type negative temperature coefficient thermistor for suppressing inrush current, comprising a core body and a pin, the pin is arranged on the electrodes on both sides of the core body in a multi-contact surface structure, the core body is an Mn-Co-Ni-La oxide with a nano-composite gradient structure, composed of a core layer, an intermediate layer and an outer layer, the composition and weight percentage range of each layer are:

[0013] The core layer: Mn3O440-50wt%, Co3O420-30wt%, NiO 15-25wt%, La2O33-7wt%, ZnO 1-5wt%, Nb2O51-3wt%;

[0014] The intermediate layer: Mn3O435-45wt%, Co3O425-35wt%, NiO 10-20wt%, CuO 5-10wt%, ZrO25-10wt%;

[0015] The outer layer: Mn3O430-40wt%, Co3O425-35wt%, NiO 5-15wt%, Al2O33-7wt%, SiO215-25wt%;

[0016] The preparation method of the core body comprises the following steps:

[0017] S1, the raw materials of the core layer, the intermediate layer and the outer layer are prepared into sols by sol-gel method at 60-80℃ and PH 6-7, dried at 80-100℃ and calcined at 400-500℃, to obtain core layer, intermediate layer and outer layer nano precursors with a particle size of 20-50nm;

[0018] S2, the core layer, the intermediate layer and the outer layer nano precursors are stacked and pressure formed in sequence to obtain a gradient structure blank;

[0019] S3, pulse field assisted sintering process is adopted to sinter at 1000-1100℃ in air atmosphere for 8-12 minutes.

[0020] Preferably, the composition and weight percentage range of the core layer are: Mn3O445wt%, Co3O425wt%, NiO 20wt%, La2O35wt%, ZnO 3wt%, Nb2O52wt%;

[0021] The composition and weight percentage range of the intermediate layer are: Mn3O440wt%, Co3O430wt%, NiO 15wt%, CuO 8wt%, ZrO27wt%;

[0022] The outer layer component and weight percentage range are: Mn3O435wt%, Co3O430wt%, NiO 10wt%, Al2O35wt%, SiO220wt%.

[0023] Preferably, the inner core layer component and weight percentage range are: Mn3O442wt%, Co3O428wt%, NiO 22wt%, La2O36wt%, ZnO 2wt%, Nb2O52wt%;

[0024] The intermediate layer component and weight percentage range are: Mn3O438wt%, Co3O432wt%, NiO 17wt%, CuO7wt%, ZrO28wt%;

[0025] The outer layer component and weight percentage range are: Mn3O433wt%, Co3O432wt%, NiO 12wt%, Al2O36wt%, SiO218wt%.

[0026] Preferably, the inner core layer component and weight percentage range are: Mn3O448wt%, Co3O422wt%, NiO 18wt%, La2O34wt%, ZnO 4wt%, Nb2O52wt%;

[0027] The intermediate layer component and weight percentage range are: Mn3O443wt%, Co3O427wt%, NiO 13wt%, CuO9wt%, ZrO28wt%;

[0028] The outer layer component and weight percentage range are: Mn3O438wt%, Co3O426wt%, NiO 8wt%, Al2O34wt%, SiO224wt%.

[0029] Preferably, the multi-contact surface structure includes that the contact section of the pin and the core electrode is provided with a continuous polyline contact part, and the polyline contact part is formed with a triangular area on both sides of the core electrode.

[0030] Preferably, the multi-contact surface structure includes that the contact section of the pin and the core electrode is provided with a semicircular arc contact part, and the semicircular area of the semicircular arc contact part faces the core axis.

[0031] Preferably, the semicircular area of the semicircular arc contact part faces the outside.

[0032] Preferably, it further includes a support provided on the core, the support includes two symmetrical supporting legs, the core is located between the two supporting legs, supporting arms are provided on both sides of the support, a clamping groove is provided on the supporting arm, the pin is located in the clamping groove, and the two supporting arms and the two supporting legs form a package for the core.

[0033] Further, a heat dissipation channel is arranged in the leg, and the heat dissipation channel is communicated with the opening section on the support.

[0034] Preferably, the two legs are provided with heat conduction blocks on the opposite sides, and the heat conduction blocks form an arch-shaped area on the leg.

[0035] Compared with the prior art, the application has the following beneficial effects:

[0036] 1. The power type negative temperature coefficient thermistor for suppressing surge current, the "pinning effect" of the intermediate layer ZrO2 enables the thermistor to withstand 8-9A surge current, and the fold line / semicircular arc structure of the pin increases the contact area, the triangular area / semicircular area stores solder, and mechanical engagement + solder anchoring is formed to avoid pin soldering from the surge impact.

[0037] 2. The power type negative temperature coefficient thermistor for suppressing surge current, the La-O bond of the core layer enables the resistance drift of the thermistor to be less than ±10% at a wide temperature of-40-200℃, the bending area of the pin can absorb thermal stress to avoid the soldering crack caused by the difference in thermal expansion between the pin and the core body when the temperature changes suddenly; and the high-temperature resistant epoxy resin material (temperature resistance > 150℃) of the support is suitable for a wide temperature environment, the heat conduction block and the heat dissipation channel can reduce the steady-state temperature of the core body, prevent the local overheating from breaking through the upper limit of 200℃, and avoid the B value drift.

[0038] 3. The power type negative temperature coefficient thermistor for suppressing surge current, the arch-shaped heat conduction block of the support is attached to the core body to accelerate heat transfer and avoid heat concentration of the core body, and the close attachment design of the pin also assists heat conduction to the outside, and the two together guarantee that the rapid thermal response is not weakened by heat accumulation and ensure that the surge suppression state is quickly entered at the moment of starting.

[0039] 4. The power type negative temperature coefficient thermistor for suppressing surge current, the nano-composite gradient structure Mn-Co-Ni-La oxide determines the upper limit of the core capabilities of the thermistor such as surge suppression, wide temperature stability, and low power consumption, and the redesign of the pin is the "key to performance transmission", which ensures that the electrical properties (low contact resistance and high surge withstand) of the nano-composite gradient structure Mn-Co-Ni-La oxide are not offset by structural defects; the support is provided to avoid the nano-composite gradient structure Mn-Co-Ni-La oxide from losing effect due to heat accumulation and physical damage through heat management and mechanical protection, and the three complement each other and cooperate to guarantee the performance of the nano-composite gradient structure Mn-Co-Ni-La oxide thermistor. BRIEF DESCRIPTION OF DRAWINGS

[0040] In the drawings:

[0041] Figure 1 Perspective view of the pin with straight contact portion;

[0042] Figure 2 Schematic view of the pin with straight contact portion on the holder;

[0043] Figure 3 Schematic view of the bending area of the pin with straight contact portion;

[0044] Figure 4 Schematic view of the pin with broken line contact portion;

[0045] Figure 5 Schematic view of the pin with broken line contact portion on the holder Figure 1 ;

[0046] Figure 6 Schematic view of the pin with broken line contact portion on the holder Figure 2 ;

[0047] Figure 7 Schematic view of the bending area of the pin with broken line contact portion;

[0048] Figure 8 Schematic view of the semicircular area of the pin with semicircular contact portion facing the axis of the core;

[0049] Figure 9 Schematic view of the pin with semicircular contact portion on the holder Figure 1 ;

[0050] Figure 10 Schematic view of the pin with semicircular contact portion on the holder Figure 2 ;

[0051] Figure 11 Schematic view of the bending area of the pin with semicircular contact portion;

[0052] Figure 12 Schematic view of the semicircular area of the pin with semicircular contact portion facing outward;

[0053] Figure 13 Schematic view of the structure of the leg, arm, clamping groove and arch-shaped area;

[0054] Figure 14 Perspective view of the holder;

[0055] Figure 15 Schematic view of the structure of the heat dissipation channel and opening section.

[0056] In the figure: 1, core; 11, pin; 111, straight contact portion;

[0057] 112, broken line contact portion; 1121, triangular area;

[0058] 113, semicircular contact portion; 1131, semicircular area;

[0059] 12, bending area;

[0060] 2, support; 21, leg; 22, arm; 23, clamping groove; 24, buckle; 25, heat-conducting bump; 26, arch-shaped area; 27, heat dissipation channel; 28, opening section. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application but not to limit the scope of the present application.

[0062] Embodiment 1: A power type negative temperature coefficient thermistor for suppressing inrush current, the core 1 adopts a nano-composite gradient structure Mn-Co-Ni-La oxide, which is composed of a core layer, an intermediate layer and an outer layer, and the composition and weight percentage of each layer are as follows:

[0063] The composition and weight percentage of the core layer are as follows: Mn3O445wt%, Co3O425wt%, NiO 20wt%, La2O35wt%, ZnO 3wt%, Nb2O52wt%;

[0064] The composition and weight percentage of the intermediate layer are as follows: Mn3O440wt%, Co3O430wt%, NiO 15wt%, CuO 8wt%, ZrO27wt%;

[0065] The composition and weight percentage of the outer layer are as follows: Mn3O435wt%, Co3O430wt%, NiO 10wt%, Al2O35wt%, SiO220wt%.

[0066] The preparation method of the core 1 includes the following steps: weighing the raw material powders of the core layer, the intermediate layer and the outer layer respectively, and preparing nano-sized precursors respectively;

[0067] The weighed raw material powders of each layer are added into a “citric acid-ethylene glycol mixed solvent” (citric acid is a chelating agent and ethylene glycol is a cosolvent) in proportion, the solid-liquid ratio is controlled to be 1:6, stirring is carried out in a 65℃ constant temperature water bath for 2-4h, while ammonia water is added dropwise to adjust the PH to 6.5, so that the metal ions form stable chelates with citric acid to form a sol;

[0068] The sol of each layer is transferred to a constant temperature drying oven and dried at 85℃ for 10h to form a xerogel;

[0069] The dried layers of xerogel were placed in a muffle furnace and calcined at 450°C for 4h (heating rate 5°C / min, to avoid particle agglomeration caused by sudden temperature rise), and after complete combustion of the organic components, each layer of nano-oxide precursor powder with a particle size of 30nm was obtained, with a specific surface area of 30m2 / g. ;

[0070] Each layer of precursor was granulated with 5wt% PVA and sieved through an 80 mesh sieve.

[0071] The outer layer, intermediate layer and core layer were sequentially laid in the mold, and the pressure was gradually increased to 25MPa in steps, and the pressure was maintained for 30s.

[0072] Process parameters: air atmosphere, 1050°C for 10min, pressure 12MPa, pulse voltage 600V, frequency 80Hz.

[0073] Cooling rate: 50°C / min to room temperature, to obtain the core 1 with interlayer-bonded nano-composite gradient structure.

[0074] In subsequent processing, silver paste was printed and sintered at 620°C for 30min to form an electrode with a contact resistance of 4mΩ; epoxy resin was used for packaging; the final performance: B value 3450K, room temperature resistance (room temperature resistance refers to rated resistance, specifically at 25°C) 45Ω, thermal response time 0.6s, inrush current 8.5A, 1000h / 200°C resistance drift ±9.2%.

[0075] Example 2: A power type negative temperature coefficient thermistor that suppresses inrush current, the core 1 adopts a nano-composite gradient structure of Mn-Co-Ni-La oxide, which is composed of a core layer, an intermediate layer and an outer layer, and the components and weight percentages of each layer are as follows:

[0076] The components and weight percentages of the core layer are: Mn3O442wt%, Co3O428wt%, NiO 22wt%, La2O36wt%, ZnO 2wt%, Nb2O52wt%;

[0077] The components and weight percentages of the intermediate layer are: Mn3O438wt%, Co3O432wt%, NiO 17wt%, CuO 7wt%, ZrO28wt%;

[0078] The components and weight percentages of the outer layer are: Mn3O433wt%, Co3O432wt%, NiO 12wt%, Al2O36wt%, SiO218wt%;

[0079] The core 1 preparation method comprises the following steps: additional addition of 0.5wt% citric acid (enhancing La 3+ chelation) to the core layer, 70°C water bath stirring for 4h, pH=6.0, to ensure La 3+uniformly dispersed;

[0080] 90℃ drying for 8h, avoiding segregation of La element, forming xerogel;

[0081] 480℃ calcination for 3.5h (heating rate 8℃ / min), obtaining precursor with particle size 25nm, specific surface area ;

[0082] Each layer precursor added 4wt% PVA (for reducing organic residues), passing 100 mesh sieve;

[0083] Layered pressurization 30MPa, pressure maintaining 40s, ensuring no gap between layers;

[0084] Pulse electric field sintering process parameters: air atmosphere, 1080℃ for 9min (high temperature and short holding time for strengthening and densification), pressure 15MPa, pulse voltage 700V, frequency 100Hz;

[0085] Cooling rate: 30℃ / min for the first 200℃ to reduce thermal stress, and then 50℃ / min to obtain the core 1 with interlayer-bonded nano-composite gradient structure;

[0086] In subsequent processing, silver paste is printed, with silver content 90wt%, sintering at 650℃ for 25min, contact resistance 3mΩ; high-temperature resistant epoxy resin is used for packaging, and the final performance is: B value 3550K, room temperature resistance 48Ω, thermal response time 0.5s, inrush current 9.0A, 1000h / 200℃ resistance drift ±8.8%.

[0087] Example 3: A power type negative temperature coefficient thermistor for suppressing inrush current, the core 1 adopts Mn-Co-Ni-La oxide with nano-composite gradient structure, composed of core layer, intermediate layer and outer layer, the composition and weight percentage of each layer are:

[0088] The composition and weight percentage of the core layer are: Mn3O448wt%, Co3O422wt%, NiO 18wt%, La2O34wt%, ZnO 4wt%, Nb2O52wt%;

[0089] The composition and weight percentage of the intermediate layer are: Mn3O443wt%, Co3O427wt%, NiO 13wt%, CuO 9wt%, ZrO28wt%;

[0090] The composition and weight percentage of the outer layer are: Mn3O438wt%, Co3O426wt%, NiO 8wt%, Al2O34wt%, SiO224wt%;

[0091] Single citric acid solvent, solid-liquid ratio 1:5, 60℃ water bath stirring 2h, PH=7.0;

[0092] 80℃ dry 12h, make it gel;

[0093] 420℃ calcination 5h, get particle size 40nm precursor, specific surface area 31m² / g;

[0094] Each layer of precursor added 6wt% PVA, through 60 mesh sieve;

[0095] Layered pressure 20MPa, pressure 20s;

[0096] Pulse field sintering process parameters: air atmosphere, 1020℃ heat preservation 11min, pressure 10MPa, pulse voltage 500V, frequency 50Hz;

[0097] Natural cooling as the main, auxiliary air cooling, get the interlayer binding of nano composite gradient structure of core 1;

[0098] Subsequent processing, using conventional silver paste, silver content 85wt%, 600℃ sintering 35min, contact resistance 5mΩ; using epoxy resin packaging; the final performance: B value 3350K, room temperature resistance 42Ω, thermal response time 0.7s, inrush current 8.0A, 1000h / 200℃ resistance drift ±9.8%.

[0099] Table 1 is the B value, room temperature resistance, thermal response time, inrush current parameter comparison of example 1-3:

[0100]

[0101] The core 1 uses nano composite gradient structure Mn-Co-Ni-La oxide technology, through three layer gradient structure design to solve the contradiction between surge suppression and temperature stability; the inner core layer, the middle layer and the outer layer respectively use different proportion of metal oxide, realize the optimization of resistance gradient and heat diffusion;

[0102] Inner core layer: anchor basic NTC characteristics and high temperature stability, in component design, take Mn3O4, Co3O4, NiO as spinel structure main body, ensure the core carrier (Mn 3+ / Mn 2+ Valence electron conduction) of NTC effect;

[0103] La2O3 as rare earth dopant, La 3+ (Ion radius ) by replacing part of the octahedral position of Mn 3+ , form high bond energy La-O bond (bond energy ), inhibit the migration and diffusion of cations at high temperature (> 150℃), reduce lattice defects (such as vacancies, dislocations), and reduce the resistance drift rate from the root;

[0104] Zn of ZnO 2+ ( ) fill the tetrahedral gap, refine the grain, and inhibit overgrowth; Nb of Nb2O5 5+ ( ) stabilize the lattice charge through electric charge compensation (balance the low electric charge of La 3+ ), and avoid fluctuations in carrier concentration;

[0105] Therefore, it can provide a stable B value basis and high temperature structural support, and ensure that the resistance drift is less than ± 10% during long-term operation.

[0106] Intermediate layer: build a resistance gradient buffer zone to solve the "inhibition-power consumption" mutation problem. In this component design, the proportion of Mn3O4 is reduced, Co3O4 is increased, CuO and ZrO2 are introduced, and the performance transition zone between the core and the outer layer is formed;

[0107] In the resistance gradient adjustment mechanism, Cu of CuO 2+ / Cu + Variable valence characteristics can dynamically adjust the carrier concentration, so that the room temperature resistance of the intermediate layer is between the core (high resistance) and the outer layer (low resistance), avoiding the local electric field concentration caused by resistance mutation at the moment of starting; Co3O4 proportion increase enhances the structural stability at high temperature (Co 3+ / Co 2+ Redox buffer effect);

[0108] Zr of ZrO2 4+ ( ) forms a dispersed distribution of ZrO2 nanoparticles, which hinders grain boundary sliding through the "pinning effect", and cooperates with the stress dispersion design of the gradient structure, so that the material can withstand 8.5A surge current;

[0109] Therefore, the design of the intermediate layer realizes the smooth transition of resistance from the core to the outer layer, which not only ensures the surge suppression effect at startup, but also avoids the surge of power consumption caused by resistance mutation at high temperature.

[0110] Outer layer: in the component design, the proportion of Mn3O4 and NiO is greatly reduced, high proportion of SiO2 and Al2O3 is introduced, and a dense surface structure is formed;

[0111] SiO2 and Al2O3 form an amorphous-microcrystalline composite layer with low thermal conductivity (k) ), which on the one hand accelerates the heat diffusion to the outside during surge impact (avoiding overheating of the core), and on the other hand reduces the heat accumulation during operation;

[0112] The glass phase characteristic of SiO2 improves the wettability of the silver electrode, reduces the contact resistance to <5 mΩ, and Al2O3 enhances the surface hardness to improve the mechanical wear resistance and corrosion resistance.

[0113] Therefore, the outer layer effectively balances the heat management by building a "thermal barrier and protective layer".

[0114] The 20-50 nm precursor prepared by the sol-gel method has a high specific surface area (SSA) ), and the pulse electric field sintering can retain the nanocrystalline structure, with a heat response time of <0.8 s, ensuring that the surge suppression state is quickly entered in the instant start-up.

[0115] The pulse electric field sintering method used in the above embodiment has the following advantages over traditional sintering (such as air atmosphere sintering):

[0116] Short-time high-temperature sintering (traditional 1200℃ / 2h) can inhibit excessive grain growth (maintaining 50-100nm grains) while realizing atomic diffusion between layers to avoid interlayer cracking.

[0117] The directional effect of the pulse electric field can inhibit excessive mixing of different components between layers, ensuring the composition gradient of the core layer-middle layer-outer layer and the effectiveness of the functional zones.

[0118] Compared with traditional sintering, the energy consumption is reduced, and there is no need for complex atmosphere control (air atmosphere can be used), greatly reducing the industrialization cost.

[0119] Therefore, the core 1 can adapt to the start-up impact of new energy inverters and industrial power supplies (500-2000W), solving the problem of easy burning of traditional power NTCs in high-power scenarios; in wide temperature environment applications, combined with low resistance drift rate, it can meet the temperature compensation needs of automotive electronics (engine compartment), aerospace, and other extreme environments.

[0120] In summary, the core advantage of the thermistor is that it realizes functional zoning through gradient structure, solves parameter contradictions through multi-element doping, and improves performance boundaries through nanotechnology, retaining the NTC basic characteristics of the Mn-Co-Ni spinel system, and breaking through the traditional material "surge suppression-temperature stability-response speed" triangle restriction through La / Cu / Zr doping and SiO2 / Al2O3 surface optimization, suitable for high-end electronic equipment fields with strict reliability requirements.

[0121] Example 4: Refer to Figure 1 , Figure 3 , Figure 4 , Figure 7, the thermistor includes a core 1, a pin 11, the pin 11 is arranged on the electrodes on both sides of the core 1 in a multi-contact surface structure, the multi-contact surface structure includes a continuous zigzag contact part 112 provided on the contact section of the pin 11 and the electrode of the core 1, and the zigzag contact part 112 is formed with a triangular area 1121 on both sides of the electrode of the core 1;

[0122] With reference to Figure 1 The linear contact part 111 of the pin 11 is a design structure of a traditional pin 11, and the linear design is in linear contact with the core 1, the contact area is small, and when the temperature of the core 1 suddenly changes, such as surge impact and environmental temperature fluctuation, the thermal shrinkage of the two is inconsistent, thermal stress is generated, and looseness or falling off is caused;

[0123] The zigzag contact part 112 designed in a continuous "Z" shape, the folding angle is 60-70°, preferably 65°, effectively improves the contact area of the pin 11 and the electrode of the core 1;

[0124] And a triangular area 1121 is naturally formed on one side of the electrode of the core 1, and then when the solder is filled, the triangular area 1121 can be filled, forming a double fixation of mechanical engagement and solder anchoring between the core 1 and the pin 11, avoiding the soldering caused by the insufficient amount of solder in the traditional linear contact;

[0125] At the same time, when the epoxy resin is encapsulated or immersed in the epoxy resin, the epoxy resin will also be filled into the triangular area 1121, further enhancing the bonding force between the core 1 and the pin 11, avoiding the looseness between the pin 11 and the core 1 caused by the pulling force generated by the cutting process in the subsequent cutting process of the pin 11, and further reducing the risk of looseness and falling off of the pin 11.

[0126] Embodiment 5, with reference to Figure 8 The multi-contact surface structure includes a semicircular arc contact part 113 provided on the contact section of the pin 11 and the electrode of the core 1, and the semicircular area 1131 of the semicircular arc contact part 113 faces the axis of the core 1;

[0127] With reference to Figure 12 The semicircular area 1131 of the semicircular arc contact part 113 faces the outside;

[0128] The design of the semicircular arc contact part 113 can increase the contact area with the electrode of the core 1 compared with the traditional linear contact part 111, and the semicircular arc contact part 113 can make the solder flow more easily during welding, completely cover the contact arc surface, avoid the problem of uneven solder accumulation in the traditional linear contact, and the design of the semicircular area 1131 facing the outside and the axis of the core 1 can store more solder and enhance the welding strength.

[0129] Therefore, by designing the pin 11, the soldering-off rate can be reduced, and under the impact of the surge current, the contact resistance fluctuation of the pin 11 can be reduced, and the current limiting failure caused by the sudden change of the contact resistance can be avoided.

[0130] In some embodiments, with reference to Figure 3 , Figure 7 , Figure 11 The straight line contact part 111, the broken line contact part 112, and the semicircular arc contact part 113 are bent to form a bending area 12 at the center of the core 1. This design can increase the contact area of the pin 11 with the core 1 while extending the pin 11. In addition, during subsequent packaging, the pin 11 covers the core 1 in a semi-enclosed manner, which increases the bonding force between the epoxy resin and the core 1 and the pin 11, further improving the tensile resistance of the pin 11 and preventing the pin 11 from loosening.

[0131] In example 6, with reference to Figure 2 , Figure 5 , Figure 6 , Figure 9 , Figure 10 , Figures 12-15 The support 2 is arranged on the core 1, and the support 2 includes two symmetrical legs 21. The core 1 is located between the two legs 21, and the support 2 is provided with an arm 22 on both sides. The arm 22 is provided with a clamping groove 23, and the pin 11 is located in the clamping groove 23. The two arms 22 and the two legs 21 form a package for the core 1.

[0132] The pin 11 is placed in the clamping groove 23 of the arm 22, which can limit the pin 11 and separate the pins 11. In addition, the clamping groove 23 is provided with a buckle 24 on the side wall, which can limit the position of the pin 11 in the clamping groove 23, and can prevent the pin 11 from separating from the clamping groove 23.

[0133] In addition, during the manufacturing process of the thermistor, the core 1 is inserted between the front and back of the pin 11 by automatic equipment. Therefore, by limiting the pin 11 with the support 2, the position of the pin 11 can be fixed before the core 1 is inserted between the pins 11, which can prevent the core 1 from falling due to the excessive separation distance between the pins 11.

[0134] At the same time, the support 2 can prevent the position of the pin 11 on the core 1 from shifting greatly (because the two arms 22 on both sides form a package for the core 1 when the core 1 is inserted into the pin 11, and because the two arms 22 on both sides are arc-shaped, the insertion of the core 1 can be self-centered), which can prevent the pin 11 from being skewed or leaking outside the core 1 after welding, and further improve the welding quality of the pin 11.

[0135] Further, the setting of the support leg 21 on the support 2 can cooperate with the bending area 12 of the lead 11 to form a limit for the lead 11, which can further avoid the lead 11 from being pulled by external force and loosened from the core 1.

[0136] In some embodiments, with reference to Figure 13 、 Figure 14 、 Figure 15 , a heat dissipation channel 27 is arranged in the support leg 21, and the heat dissipation channel 27 is in communication with an opening section 28 on the support 2 (wherein it is understood that the length of the opening section 28 can be set according to the actual packaging requirements of the core 1, so as to avoid the packaging body from entering the opening section 28; further, a heat-conducting block with the same cross section as the opening section 28 can be inserted into the opening section 28 to fill and block the opening section 28, so as to avoid moisture from entering while not affecting heat dissipation);

[0137] A part of the core 1 is located between the two support legs 21, and the support legs 21 are close to the middle part of the core 1. The support legs 21 are integrated with the core 1 through packaging, and form a heat dissipation path of the core 1-support leg 21-opening section 28, so that when the core 1 is at high temperature, the core 1 can be promptly cooled through the heat dissipation channel 27;

[0138] The support 2 is made of high-temperature-resistant epoxy resin and is injection molded.

[0139] In some embodiments, with reference to Figure 13 、 Figure 14 、 Figure 15 , the two support legs 21 are each provided with a heat-conducting block 25 on the opposite side, and the heat-conducting block 25 forms an arch-shaped area 26 on the support leg 21;

[0140] The heat-conducting block 25 directly adheres to the side surface of the core, quickly conducts the heat generated by the core during operation (especially the instantaneous heat after surge impact) to the support leg 21, and then conducts the heat to the outside through the heat dissipation channel 27 and the opening section 28, forming an efficient heat dissipation path of the core 1-heat-conducting block 25-heat dissipation channel 27;

[0141] The arch-shaped area 26 can increase the contact area and contact points of the heat-conducting block 25 and the core 1, so as to avoid too few contact surfaces between the support leg 21 and the core 1 due to deformation of the support leg 21;

[0142] In addition, the heat-conducting block 25 of the arch-shaped area 26 forms multi-point support for the core 1, which can limit the left-right and up-down displacement of the core 1 in the vibration or impact scene, avoid mechanical stress generated by the core 1 shaking at the welding position of the core 1 and the lead 11, and prevent the core 1 from being damaged due to direct friction between the core 1 and the inner wall of the support 2;

[0143] In one embodiment, the heat-conducting bump 25 protrudes 1-2mm from the surface of the foot 21, which leaves a gap between the core 1 and the foot 21, and when encapsulating, the epoxy resin fills into the gap, which can further improve the heat dissipation effect of the core 1 through the bracket 2, and improve the bonding force between the bracket 2 and the core 1 after encapsulation, avoid the bracket 2 loose, and further protect the stability of the pin 11, and the arch-shaped area 26 formed by the heat-conducting bump 25 can further improve the bonding force between the bracket 2 and the core 1.

[0144] In one embodiment, the heat-conducting bump 25 extends into the heat dissipation channel 27, further improving the conduction of heat.

[0145] The setting of the arch-shaped area 26 on the bracket 2 can avoid the destruction of the material structure of the core 1 due to heat accumulation.

[0146] In the present application, the nano-composite gradient Mn-Co-Ni-La oxide is the "performance core" of the thermistor, which determines the upper limit of surge suppression (8A-9A), wide temperature stability (-40~200℃), and fast thermal response (<0.8s); the redesigned pin 11 increases the welding area and buffers thermal stress, avoids the surge bearing force of the nano-composite gradient structure being offset by the disassembly, and at the same time guarantees low contact resistance and does not waste the low power consumption advantage of the nano-composite gradient structure;

[0147] And the bracket 2 not only strengthens the heat dissipation to make the nano-composite gradient structure immune to performance degradation caused by overheating, but also fixes the core 1 and the pin 11 to avoid damage to the nano-composite gradient structure due to mechanical impact, and the three work together to make the performance of the thermistor truly translate into reliable protection and stable work in actual application.

[0148] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form, although the present application has been disclosed as above, however, it is not intended to limit the present application, any person skilled in the art can make some changes or modifications to the above-mentioned technical content without departing from the scope of the technical solution of the present application, as long as it does not depart from the technical solution of the present application, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application, all still belong to the scope of the present application.

Claims

1. A power type negative temperature coefficient thermistor for suppressing inrush current, characterized by, The thermistor comprises a core (1) and a pin (11), the pin (11) is arranged on the electrodes on both sides of the core (1) in a multi-contact surface structure, the core (1) adopts a Mn-Co-Ni-La oxide with a nano-composite gradient structure and is composed of a core layer, an intermediate layer and an outer layer, the component and weight percentage range of each layer are as follows: The core layer: Mn3O4 40-50wt%, Co3O4 20-30wt%, NiO 15-25wt%, La2O3 3-7wt%, ZnO 1-5wt%, Nb2O5 1-3wt%; The intermediate layer: Mn3O4 35-45wt%, Co3O4 25-35wt%, NiO 10-20wt%, CuO 5-10wt%, ZrO2 5-10wt%; The outer layer: Mn3O4 30-40wt%, Co3O4 25-35wt%, NiO 5-15wt%, Al2O3 3-7wt%, SiO2 15-25wt%; The preparation method of the core (1) comprises the following steps: S1, the raw materials of the core layer, the intermediate layer and the outer layer are prepared into sols by sol-gel method at 60-80℃ and PH 6-7, and then the core layer, the intermediate layer and the outer layer nano precursors with a particle size of 20-50nm are obtained by drying at 80-100℃ and calcining at 400-500℃; S2, the core layer, the intermediate layer and the outer layer nano precursors are stacked and pressure-formed in sequence to obtain a gradient structure blank; S3, the gradient structure blank is sintered at 1000-1100℃ for 8-12 minutes in air atmosphere by using a pulse electric field assisted sintering process.

2. A power NTC thermistor for suppressing inrush current according to claim 1, wherein The component and weight percentage of the core layer are as follows: Mn3O4 45wt%, Co3O4 25wt%, NiO 20wt%, La2O3 5wt%, ZnO 3wt%, Nb2O5 2wt%; The component and weight percentage of the intermediate layer are as follows: Mn3O4 40wt%, Co3O4 30wt%, NiO 15wt%, CuO 8wt%, ZrO2 7wt%; The component and weight percentage of the outer layer are as follows: Mn3O4 35wt%, Co3O4 30wt%, NiO 10wt%, Al2O3 5wt%, SiO2 20wt%.

3. The power NTC thermistor for suppressing inrush current according to claim 1, wherein The component and weight percentage of the core layer are as follows: Mn3O4 42wt%, Co3O4 28wt%, NiO 22wt%, La2O3 6wt%, ZnO 2wt%, Nb2O5 2wt%; The component and weight percentage of the intermediate layer are as follows: Mn3O4 38wt%, Co3O4 32wt%, NiO 17wt%, CuO 7wt%, ZrO2 8wt%; The component and weight percentage of the outer layer are as follows: Mn3O4 33wt%, Co3O4 32wt%, NiO 12wt%, Al2O3 6wt%, SiO2 18wt%.

4. The power NTC thermistor for suppressing inrush current according to claim 1, wherein The inner core layer component and weight percentage are: Mn3O448wt%, Co3O422wt%, NiO 18wt%, La2O34wt%, ZnO 4wt%, Nb2O52wt%; The middle layer component and weight percentage are: Mn3O443wt%, Co3O427wt%, NiO 13wt%, CuO 9wt%, ZrO28wt%; The outer layer component and weight percentage are: Mn3O438wt%, Co3O426wt%, NiO 8wt%, Al2O34wt%, SiO224wt%.

5. A power NTC thermistor for suppressing inrush current according to claim 2 or 3 or 4, characterized in that, The multi-contact surface structure comprises a contact section of a pin (11) and an electrode of a core body (1), and a continuous broken line contact part (112) is arranged on the contact section, and the broken line contact part (112) is formed with a triangular area (1121) on both sides of the electrode of the core body (1).

6. A power NTC thermistor for suppressing inrush current according to claim 2 or 3 or 4, characterized in that, The multi-contact surface structure comprises a contact section of a pin (11) and an electrode of a core body (1), and a semicircular arc contact part (113) is arranged on the contact section, and a semicircular area (1131) of the semicircular arc contact part (113) faces the axis of the core body (1).

7. A power NTC thermistor for suppressing inrush current according to claim 2 or 3 or 4, characterized in that, The multi-contact surface structure comprises a contact section of a pin (11) and an electrode of a core body (1), and a semicircular arc contact part (113) is arranged on the contact section, and a semicircular area (1131) of the semicircular arc contact part (113) faces the axis of the core body (1).

8. The power NTC thermistor for suppressing inrush current according to claim 1, wherein A support (2) is further arranged on the core body (1), the support (2) comprises two symmetrical supporting legs (21), the core body (1) is located between the two supporting legs (21), supporting arms (22) are arranged on both sides of the support (2), clamping grooves (23) are arranged on the supporting arms (22), the pin (11) is located in the clamping grooves (23), and the two supporting arms (22) and the two supporting legs (21) form a package for the core body (1).

9. A power NTC thermistor for suppressing inrush current according to claim 8, wherein A heat dissipation channel (27) is arranged in the supporting leg (21), and the heat dissipation channel (27) is in communication with an opening section (28) on the support (2).

10. A power NTC thermistor for suppressing inrush current according to claim 9, wherein Heat conduction blocks (25) are arranged on the two supporting legs (21) and face each other, and the heat conduction blocks (25) form a bow-shaped area (26) on the supporting legs (21).

Images