Power type high temperature eutectic linear PTC thermistor and preparation method thereof

Abstract

The application provides a power type high-temperature eutectic linear PTC thermistor, which comprises a mixed eutectic core chip pressed by core chip material, an electrode leading part made of guide electrode material and an encapsulation protective layer made of encapsulation material, the electrode leading part comprises a chip coating film and an electrode lead wire, the chip coating film is wrapped outside the mixed eutectic core chip, the electrode lead wire is welded with the chip coating film, the encapsulation protective layer is wrapped outside the chip coating film, the core chip material comprises a shaping material, a conductive material and an auxiliary material, and the shaping material comprises any one or any combination of high-density polyethylene, nylon and polyvinylidene fluoride. The application further provides a preparation method of the power type high-temperature eutectic linear PTC thermistor. The application has the advantages of temperature control after over-high temperature, current control after over-large current, small volume, low cost and high reliability.

Description

Technical Field

[0001] This invention relates to PTC thermistors, and more particularly to a power-type high-temperature synthetic linear PTC thermistor and its preparation method. Background Technology

[0002] In various electronic devices and products, including small household appliances, white goods, and large appliances, topologies can be divided into two types: those containing small motors and those containing power devices. Both types of circuit topologies share a common characteristic: they generate heat and high temperatures during operation. Designers must carefully design temperature control circuits for local circuitry and implement product safety protection measures.

[0003] For products containing small motors: When these motors operate under heavy loads for extended periods, the temperature of their winding coils will continuously rise, potentially leading to carbonization of the insulating varnish, short circuits, and burnout. More seriously, this can cause power line burnout or even a fire. Similarly, in products containing power components, the temperature of these components will also rise under high current. The negative resistance of the PN junction increases the current, and without control circuitry, a vicious cycle occurs (switching power supplies can also cause magnetic saturation of the high-frequency transformer, leading to increased current). This can cause a sharp increase in power transistor current, resulting in breakdown, short circuits, and even explosions. In severe cases, this can also lead to power line burnout or a fire. Addressing these issues has always been a major bottleneck in the design process for solution providers and manufacturers. In the control design of products including small motors, the main consideration is the control of the temperature rise of the motor under heavy load. However, there is a temperature requirement in the safety certification test, namely that the temperature rise of the motor after stalling should not exceed 180°C. This safety requirement causes engineers to encounter many unexpected problems when designing control circuits, because the current will increase to 4-6 times the normal operating current after the motor stalls, and the motor temperature will rise or exceed 180°C or even 200°C or above in about 10-20 seconds. Therefore, a temperature control circuit must be designed. Several common solutions in traditional temperature control circuit designs are as follows: ① Some applications use bimetallic thermostats mounted on the motor casing (which cannot be installed inside the motor). In this application, the temperature control point is designed to be 160℃-170℃. However, in safety testing, the temperature sensor is inserted into the motor. When the internal temperature of the motor reaches 180℃, the temperature of the motor casing has not reached 160℃ or 170℃. The bimetallic thermostat itself has a 3-5℃ delay in sensing temperature, making it difficult for certified products to pass the temperature rise test. This is a simplified control solution. With repeated debugging, testing, and multiple trials, a suitable thermostat can be found to achieve good control. However, the thermal resistance error of the bimetallic thermostat itself and the error in the installation process will lead to less than ideal consistency and stability of the final product; ② Some applications use disposable thermal fuses for over-temperature protection.However, a lot of work still needs to be done in the design, debugging, and selection of specific temperature points, current values, current carrying capacity, and current redundancy of the selected components. This is an unavoidable workload for engineers, and the entire process is the same as ① above. However, the result is a one-time event. This is safe for the product and the manufacturer, but it is a fatal one-time product for the end user. Therefore, this solution is rarely used. ③ A more common solution is to use an NTC temperature sensor to sample the motor temperature signal, send it to a signal amplifier for amplification, and then input it to an operational amplifier comparator. The output comparison result signal is then amplified by a MOSFET amplifier and used as the control signal for the MOSFET switch that controls the motor power supply. ④ A better temperature control design involves using an NTC temperature probe to sample the motor temperature, amplifying the signal, and then sending it to an MCU or DSP for processing. The MCU or DSP then outputs a control signal, which is amplified again and sent to the motor's power switch MOSFET. By controlling the MOSFET's on / off state, the motor current is controlled. This temperature control is achieved through software programming, directly changing the software's temperature control point without altering the hardware design. This method offers high accuracy, timely control, and ease of correction and debugging. To date, the above three temperature control schemes (technically also called measurement and control system circuits) are still widely used options. From the perspective of achieving temperature control, they are all excellent. However, their implementation process is not only very complex, but their inherent drawbacks cannot be adequately addressed. Specifically, the application involves numerous components, occupies a large space, has a large PCB area, and the installation process of the wires and the distribution parameters of the PCB circuit can affect or interfere with the accuracy of temperature control. Production and debugging become more complex, requiring dedicated testing positions. Costs are high (due to the large number of components and the fact that chip costs have increased more than 10 times due to the trade war), resulting in high failure rates in the early and mid-stages of the product (many components, many failures), high return and replacement rates (a reality that is difficult for manufacturers to accept), limited service life (multiple repairs may lead to premature scrapping), and lower reliability (many components, many failures). Software may also crash, stall, or fail due to induced lightning voltage or strong pulse interference, or damage the MCU and DSP chips. Once this function fails, the motor may run away at high temperature, especially in a stalled state, or the temperature of its winding coils may rise continuously and become uncontrollable, even leading to carbonization of the insulation varnish of the motor windings, short circuits in the coils, and burnout. In more serious cases, it may lead to burnout of the power supply line or fire, etc. These are design and control challenges that are difficult to avoid.

[0004] For power devices that generate heat and require heat sinks, such as high-power MOSFETs, IGBTs, rectifier bridges, and switching transistors in switching power supplies, temperature detection and control follow the same principle as the aforementioned motor heating control. To ensure stable, reliable, and safe operation of the equipment circuitry, additional circuits are needed for real-time control. These circuits begin monitoring from startup, increasing power consumption, complicating equipment maintenance, and causing frequent returns and replacements, creating significant headaches for manufacturers. The above explanation focuses on temperature control and over-temperature protection, without addressing overload, short circuit, or partial short circuit monitoring and control. Adding descriptions of current monitoring and control, overcurrent protection, and short circuit protection would be largely the same, differing only in the sampling method. Instead of using an NTC temperature sensor, a precision resistor would be connected in series with the motor circuit, and the voltage drop across the resistor would be used as the sampling signal. Other circuits, functional modules, signal conversion, processing, and control would follow the same principle and will not be elaborated upon here.

[0005] As can be seen from the above process control and required results, in addition to achieving basic functions, the aforementioned products and equipment require timely control of current and temperature, and extension of product lifespan, resulting in higher safety, reliability, and lower costs. However, because consumers prefer high-quality, low-priced products, the idealized design becomes less than ideal in the market. In particular, the short lifespan of products caused by mid-to-late-stage component failures is unacceptable to consumers, leading to quality disputes and significantly impacting the manufacturer's reputation and competitiveness. To date, there is no single component that is few in number, highly reliable, durable, and capable of both current and temperature control, effectively extending the lifespan of the aforementioned system equipment, thus achieving an ideal control scheme and circuit. This has been a major challenge for design engineers and a bottleneck for related equipment manufacturers. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a power-type high-temperature synthetic linear PTC thermistor and its preparation method.

[0007] This invention provides a power-type high-temperature hybrid linear PTC thermistor, comprising a hybrid core chip pressed from a core chip material, an electrode lead portion made of a guiding electrode material, and an encapsulation protective layer made of an encapsulation material. The electrode lead portion includes a chip coating and electrode leads. The chip coating covers the hybrid core chip, and the electrode leads are soldered to the chip coating. The encapsulation protective layer covers the chip coating. The core chip material includes a shaping material, a conductive material, and auxiliary materials. The shaping material includes any one or any combination of high-density polyethylene, nylon, and polyvinylidene fluoride.

[0008] As a further improvement of the present invention, the mass percentage of high-density polyethylene is 22-26%, the mass percentage of nylon is 7-9%, and the mass percentage of polyvinylidene fluoride is 10-12%.

[0009] As a further improvement of the present invention, the conductive material includes any one or any combination of rubber carbon black, silicon dioxide, metallic nickel powder, and semiconductor ceramic powder.

[0010] As a further improvement of the present invention, the mass percentage of rubber carbon black is 24-28%, the mass percentage of metallic nickel powder is 0.8-1.2%, and the mass percentage of semiconductor ceramic powder is 7.5-9.5%.

[0011] As a further improvement of the present invention, the auxiliary materials include any one or any combination of antioxidants, flame retardants, dispersants, reinforcing agents, sensitizers, and lubricants.

[0012] As a further improvement of the present invention, the antioxidant is 0.15-0.3% by mass, the flame retardant is 19-22% by mass, the dispersant is 0.3-0.5% by mass, and the reinforcing agent is 0.3-0.5% by mass.

[0013] As a further improvement of the present invention, the chip coating includes a single-sided rough nickel-plated copper film, the electrode leads include tin-plated copper wires, the tin-plated copper wires are connected to the single-sided rough nickel-plated copper film by welding, and the encapsulation material includes pressure-sensitive adhesive and epoxy resin encapsulation powder, the pressure-sensitive adhesive and epoxy resin encapsulation powder are used to form an epoxy resin insulating encapsulation protective layer.

[0014] This invention also provides a method for preparing a power-type high-temperature synthetic linear PTC thermistor, comprising the following steps: S1. Raw material drying and preheating treatment; S2. Weighing and dispensing ingredients; S3, the first secret refining; S4, First granulation; S5, Second Intensive Refining; S6, Second granulation; S7, High-temperature and high-pressure extruded black sheet; S8. Double-sided copper plating is completed simultaneously under high temperature and high pressure. S9, Vacuum multilayer tableting; S10, irradiation; S11, chip punching; S12, insert plate; S13, solder; S14, resin impregnation; S15, Encapsulation; S16, Curing; S17. Conduct aging tests, then perform resistance testing to screen out defective products; finally, inspect and approve products before shipping.

[0015] As a further improvement of the present invention, in step S1, the raw materials are pretreated under vacuum at 150°C for 48 to 52 hours, with material turning over midway to ensure a vacuum degree of -0.10 MPa; in step S3, the raw materials are mixed and plasticized in a mixer at 165-180°C; in step S5, the raw materials are mixed and plasticized in a mixer at 165-180°C; in step S7, black sheets are extruded using an extruder; in step S8, nickel-plated copper films are coated on both sides of the black sheets to form coated chips; in step S9, the coated chips are vacuum multilayer pressed using a vacuum vulcanizing machine to obtain large coated sheet plates. The vacuum vulcanization molding process is as follows: preheating for 5 minutes, vacuum vulcanization hot pressing time for 10 minutes, hot pressing pressure for 15 MPa, hot pressing temperature for 180°C to 190°C, and the thickness of the sheet is 2.1 mm. The thickness is from 0.5 mm to 4.5 mm; in step S10, cross-linking is performed by irradiation with gamma rays or an electron accelerator. The irradiation process is as follows: cross-linking is performed 1 to 5 times, with an irradiation dose of 5 to 15 KGY each time; in step S11, the large coated sheet is punched and cut into the required small-sized semi-finished products by punching at room temperature; in step S13, soldering is performed, followed by heat treatment at 190°C for 20 minutes in an oven; in step S14, the semi-finished products are immersed in water-soluble insulating pressure-sensitive adhesive; in step S15, the surface of the semi-finished products is encapsulated with epoxy resin or coated with insulating varnish.

[0016] As a further improvement of the present invention, the semiconductor ceramic powder, also known as the synthetic barium titanate ferroelectric material crystal powder, is made by uniformly mixing BaCO3, Al2O3, SrCO3, TiO2, CaCO3, Tc2O5, Pm2O3, MnO2, SiO2, and LiCO3 through ball milling, followed by high-temperature sintering at 1200℃, granulation, crushing, and grinding to produce powder crystals. As a further improvement of the present invention, in step S17, the product is subjected to heat treatment at 190°C for 20 minutes and aging with an electric current of 5 times the working current. After cooling at room temperature for 2 hours, the resistance value is tested using a high-precision low-resistance tester. Products with different resistance value ranges are grouped by resistance value, and the parts exceeding the upper limit of the specified resistance value and the parts exceeding the lower limit of the specified resistance value are regarded as unqualified products. Unqualified products are discarded and qualified products are retained.

[0017] The beneficial effects of this invention are: it provides a power-type high-temperature synthetic linear PTC thermistor that can control temperature after excessive high temperature and current after excessive current, and has the advantages of small size, low cost and high reliability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other solutions can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a power-type high-temperature synthetic linear PTC thermistor according to the present invention.

[0020] Figure 2 This is a characteristic curve of a power-type high-temperature synthetic linear PTC thermistor according to the present invention. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 limiting the scope of protection of this invention. Furthermore, the terms "first," "second," etc., 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 with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] like Figures 1 to 2As shown, a power-type high-temperature synthetic linear PTC thermistor is mainly made of non-conductive high-density polymer materials and nanocrystals of conductors and semiconductor compounds through a special process. Its composition includes: high-temperature high-density polyethylene, high-temperature nylon, polyvinylidene fluoride, carbon black, metal powder, conductive ceramic powder, antioxidants, flame retardants, dispersants, reinforcing agents, copper film, tin-plated copper wire leads, and encapsulating epoxy resin, etc. Because it is a homogeneous mixture of physical grains produced by physical methods and is a flat-plate pressing product at high temperature, its essence is a homogeneous grain mixture, hence the abbreviation "synthetic" or "mixed crystal".

[0026] like Figure 1 As shown, the power-type high-temperature hybrid crystal linear PTC thermistor mainly includes a hybrid crystal core chip 1 pressed from a core chip material, an electrode lead-out portion made of a guiding electrode material, and an encapsulation protective layer 3 made of an encapsulation material. The electrode lead-out portion includes a chip film 21 and electrode leads 22. The chip film 21 wraps around the hybrid crystal core chip 1, and the electrode leads 22 are soldered to the chip film 21. The encapsulation protective layer 3 wraps around the chip film 21.

[0027] The materials used in this power-type high-temperature synthetic linear PTC thermistor include: core chip material, guiding electrode material, and encapsulation material.

[0028] Core chip materials include: 1. Shaping materials: High-density polyethylene, nylon, polyvinylidene fluoride; 2. Conductive materials: rubber carbon black, silicon dioxide, nickel powder, semiconductor ceramic powder; 3. Auxiliary materials: antioxidants, flame retardants, dispersants, reinforcing agents, sensitizers, lubricants, etc.

[0029] The guiding electrode materials include: 1. Chip coating: Single-sided rough nickel-copper plated film, 35um thick; 2. Electrode leads: Tinned copper wire (φ0.5mm, φ0.6mm, φ0.8mm, 1.2mm). The specifications of the copper wire will be determined according to the current carrying capacity of the chip. The connection between the lead and the copper film is made with lead-free environmentally friendly solder (soldering temperature 260℃).

[0030] Encapsulation materials include: 1. Pressure-sensitive adhesive (acrylic resin); 2. Epoxy resin encapsulation powder.

[0031] Product Name High-density polyethylene nylon polyvinylidene fluoride carbon black Nickel metal powder Semiconductor ceramic powder antioxidants Flame retardant Dispersants, reinforcing agents Quality percentage 22-26% 7-9% 10-12% 24-28% 0.8-1.2 % 7.5-9.5% 0.15-0.3 % 19-22% 0.3-0.5 % The fabrication process of this power-type high-temperature synthetic linear PTC thermistor is as follows: Raw material drying and preheating treatment → weighing and batching → first internal mixing (physical mixing) → granulation → second internal mixing (to make the components more uniform) → re-granulation → high temperature and high pressure extrusion of black sheets → double-sided copper plating (nickel-copper film) completed under high temperature and high pressure → vacuum multilayer pressing → irradiation → chip punching → insertion → soldering → impregnation → encapsulation → curing → resistance division → marking → packaging → inspection and delivery.

[0032] Process and flow description: High-density polyethylene, a specific grade of rubber carbon black (N550), ethylene propylene rubber, semiconductive materials, and other processing aids are pretreated under vacuum at 150℃ for 48–52 hours (with material turning during the process to maintain a vacuum level of -0.10 MPa). After weighing and proportioning, the raw materials are mixed and plasticized in a Banbury mixer at 165–180℃. After exiting the mixer, the mixture is cut into small pieces, cooled, and crushed into small granules (granulation). These granules are then mixed and plasticized at 165–180℃ and simultaneously extruded to form rectangular coated chips (double-sided coated with nickel-plated copper film). An appropriate proportion of ethylene-tetrafluoroethylene copolymer ETFE (F-40) fluoroplastic is added to the formulation to improve the adhesion strength between the copper foil and the core material, ensuring a strong bond between the electrode core material. The addition of ethylene propylene rubber (a copolymer of ethylene and propylene) to the formulation increases the mechanical impact elasticity and weather resistance of the chip material, enhancing the pressure resistance and heat resistance of the PTC product. Oxide ceramic powder can also be added in appropriate amounts to enhance chip performance. The finished chips are then pressed using a multi-layer vacuum vulcanizing machine. This involves placing the chips into multi-compartment, multi-layer specialized chip clamps and pressing them in a 25t vacuum vulcanizing machine mold. Vacuum vulcanizing differs from ordinary presses; under vacuum conditions, gases in the electrode copper foil and chip are easily and completely removed, while preventing oxidation of the electrode copper foil and chip materials at high temperatures. This increases bonding strength and improves the chip's PTC effect, enabling the product to withstand high intensity, high current, and high voltage without cracking or burning, and to withstand high-power impacts. Vacuum vulcanization molding process: preheating for 5 minutes, vacuum vulcanization hot pressing time for 10 minutes, hot pressing pressure 15MPa, hot pressing temperature 180–190℃, and sheet thickness of 2.1–4.5mm. The finished sheets are then cross-linked using gamma rays (Co60) or electron accelerator irradiation. Irradiation process: 1 to 5 cross-linkings, each irradiation dose is 5 to 15 kGy.By using low-dose, multiple irradiations, the resin cross-linking is improved, enabling the chip material to form a stable conductive network structure, ensuring the stability and reliability of the product's resistance and withstand voltage characteristics. The irradiated coated sheet is then punched and cut into the required semi-finished products (square or round) using a room-temperature punch press. The square or round chip is then inserted into the pre-formed, 45° bent, overlapping position of two parallel tin-plated copper wires fixed to a paper tape. The copper wires clamp the chip at the overlapping position, ensuring the bending point is at the chip's edge, thus maintaining the 45° bend. The overlapping sections are in close contact with the copper films on both sides of the chip for easy soldering, while the parallel lines connecting the outside are the lead electrodes of the product, thus completing the die insertion. After soldering, the chip is heat-treated at 190℃ for 20 minutes in an oven (to eliminate internal stress in the chip and improve the soldering effect). The small-sized semi-finished product after soldering is impregnated with a water-soluble insulating pressure-sensitive adhesive (acrylic resin) to ensure the thermosetting properties of the encapsulation material, improve the problem of asynchronous thermal expansion and contraction between the chip and the encapsulation material, avoid the risk of electric arcing between the two electrodes of the chip, and improve the product's voltage withstand capability by ≥50% and its ability to withstand high current surges. The PTC element is encapsulated with epoxy resin or coated with insulating varnish. The encapsulation material is selected for its good flexibility and heat dissipation. The encapsulation powder manufacturer was coordinated to adjust the traditional formula, selecting functional resin materials and flame retardant materials that meet the new characteristics of this product. This allows the product to have a thermal power of 3-5KW or more, and to withstand high current and high voltage surges of 10A and 600V or more, as well as low voltage surges of 220V-40A or 60V-100A, improving the product's electrical performance. Then, the product undergoes heat treatment at 190℃ for 20 minutes and aging with an appropriate voltage and current of 5 times the operating current. After aging and cooling to room temperature for 2 hours, it is then subjected to high... A precision low-resistance tester is used to test resistance values. Products with different resistance value ranges are grouped into three groups (usually high, medium, and low). Products exceeding the upper and lower limits of the specified resistance value are considered unqualified. Unqualified products are discarded, and qualified products are retained to ensure improved product quality and performance. Finally, products with electrical performance and resistance values ​​that meet customer circuit requirements are stored together and labeled. The qualified products are then marked with their brand logo and model number using a laser marking machine. After packaging according to the specified packaging requirements, they are randomly sampled and inspected again before being shipped out.

[0033] The technological principle is as follows: High-density polyethylene (HDPE) with high-strength PTC effect (-:[C2H4]n-, melt index 0.25~0.35g / 10min), nylon ([-NH-(CH2)5-CO]n-, melting point 180-240℃), polyvinylidene fluoride (PVDF) (-(C2H2F2)n-, melting point 180-240℃), rubber carbon black (-CC-), metallic nickel powder (Ni), and semiconductor ceramic powder, namely barium titanate ferroelectric material crystal powder (a product made from specially formulated μm-level powder with a grain boundary phase transition point of 140℃, composed of BaCO3, Al2O3, SrCO3, TiO2, CaCO3, etc.). Tc2O5, Pm2O3, MnO2, SiO2, LiCO3, etc. are uniformly mixed in a specific ratio through ball milling, then sintered at 1200℃ to granulate, crush, and grind to produce powder crystals (custom-made products); antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]); antioxidant 168 (1,4-di-tert-butylphenyl) phosphite); antioxidant 618 (bis(octadecyl)pentaerythritol diphosphite); flame retardants (antimony trioxide, magnesium hydroxide prepared by mineral method); dispersants; reinforcing agents, etc. The mixture is thoroughly mixed and stirred in a 180℃ internal mixer until homogeneous. After thorough and uniform mixing, it undergoes a multi-layer pressing process in a vacuum vulcanizing machine, followed by double-sided high-temperature 180℃ coating and pressing to produce a low-resistivity and high-strength PTC chip substrate of power-type eutectic crystal. This substrate is then cross-linked by gamma-ray (Co60) electron accelerator irradiation, forming a stable conductive network in the composite chip material. The finished products feature a series of specifications: maximum withstand voltage 600V, high current 10A; low voltage 220V, high current 20A; 60V, high current 40A, etc. These products are characterized by small size and low internal resistance (down to the mΩ level). Figure 2The characteristic test curve for commonly used products with 0.3-0.5Ω resistance without power-on operation shows that the inflection point of 120℃ represents the Curie point. In practical circuit applications, due to the balance between heat generation and heat dissipation, it is difficult to reach this temperature. Moreover, after heat dissipation is hindered and the internal temperature reaches the Curie point, the outer surface temperature of the PTC remains at 90-100℃ due to the thermal resistance of the encapsulation layer. This indicates the product's high-strength PTC effect achieved with high-density polyethylene using a special high-density material with a Curie point of 110-120℃. This ensures that the product's resistance remains stable in well-ventilated environments below 85℃. When the internal junction temperature approaches or exceeds 120℃ (when heat dissipation is hindered above 85℃), the PTC material enters a low-elasticity state (state density begins to decrease), causing some conductive links to break and increasing the resistance. The internal temperature is determined by the resistance value of a uniformly mixed semiconductor and conductor mixture (carbon black, nickel powder, semiconductor ceramic powder, etc.) in a specific ratio, and is generated according to the Q=I²RT rule. The Curie point of the barium titanate ceramic and other semiconductor grains is selected at 130-140℃. The resistivity only increases when the internal temperature rises to 130-140℃, and the combined effect of high-temperature nylon (melting point 180℃) and high-temperature polyvinylidene fluoride (melting point 240℃) is utilized. This selection causes the RT curve of the finished PTC product to slow down after the inflection point (see...). Figure 2This is the main driving force behind the design, and the electrical characteristics of the product are exhibited by the entire device during operation. In all the manufacturing processes of this product, there are no chemical reactions; it is a completely homogeneous blend crystal of various materials at the micrometer / nm level. Furthermore, its resistance change only occurs after the ambient temperature exceeds 85°C, making it a high-temperature variable-resistivity hybrid crystal product. This specially designed and manufactured product cannot be expressed or described using algebraic equations, electrochemical reaction equations, vector diagrams, or functional expressions, nor can its laws be deduced based on assumptions. Therefore, it can only undergo various electrical performance tests on the finished product, using different formulation combinations to obtain its actual electrical characteristic change patterns, and then its practicality and reliability are assessed and verified through practical applications. The barium titanate ferroelectric ceramic semiconductor used above inherently possesses PTC characteristics. The resistance change of its fabricated product before the Curie point on the T-axis is a linear decrease at approximately 13° below the horizontal line, and after exceeding the Curie point, the resistance exhibits a near 90° abrupt change. When this material is removed, the PTC RT curve shows a linear increase in resistance before the Curie point on the T-axis, again at approximately 13° above the horizontal line, and again exhibits a near 90° abrupt change after exceeding the Curie point. Therefore, adding this material is equivalent to superimposing the two curves, resulting in a completely new PTC characteristic curve. This new electrical characteristic (RT) curve becomes a horizontal straight line before the Curie point on the T-axis, exhibiting electrical characteristics that do not change with temperature. Furthermore, after the Curie point on the R-axis, it does not exhibit a near 90° abrupt change, but rather a new, sloping linear curve with a gradient of approximately 40°-60°. This characteristic represents a novel device with broad prospects for further development into new application areas.

[0034] As can be seen from the above process and technology, HDPE is used as the high-temperature, high-density molecular matrix, combined with different types of resins, rubber carbon black, polyvinylidene fluoride copolymer plastics, semiconductor materials, and additives. By adjusting the proportions of the formulation, the final product performance and resistance value are achieved. Its special process lies in the following: the material is granulated and then extruded after being discharged in a closed, high-speed mixing process at 185°C. The duration of this mixing process affects the aging of the chip composite material, the uniformity of grain mixing, and the final electrical characteristic stability, reliability, and product consistency. The granulation process serves as an additional layer of uniformity assurance after granulation, ensuring consistent product performance and resistance values. Furthermore, the pressure and temperature of the vacuum pressing process also require multiple experiments and tensile tests to accurately determine the adhesion between the copper foil and the chip. This data cannot be obtained through modeling or calculation; it can only be derived after multiple experiments. Suitable data includes a vacuum level of -0.10 MPa, a pressure of 15 MPa, a hot-pressing temperature of 180-190°C, and a hot-pressing time of 10 minutes. Research on the impact of irradiation processes on product performance revealed that only through small irradiation doses and multiple irradiations can resin cross-linking be improved, enabling the chip material to form a stable conductive network structure, ensuring product resistance, withstand voltage, electrical stress adaptability, and stability. This conclusion was drawn through repeated crystal phase analysis of product cross-sections, final electrical characteristic testing, and practical application analysis. Simultaneously, the potential for thermal aging in plastic materials needs to be studied. Repeated experiments using special thermal and electrical aging processes have been conducted to study the impact on product performance and the overall performance stability under different service conditions, such as withstand voltage, withstand current surges, and anti-aging properties. Based on years of R&D experience, a series of methods have been developed to improve overall performance and screen for substandard products through special thermal and electrical aging processes, along with improvement measures for various problems in large-scale, automated production operations.

[0035] The barium titanate semiconductor ferroelectric ceramics used above have PTC characteristics. The resistance value of the manufactured product before the Curie point on the T-axis changes linearly downwards at an angle of 13° below the horizontal line. Moreover, the resistance value after exceeding the Curie point exhibits a near 90° abrupt change. When this material is removed, the resistance value of the PTC before the Curie point on the T-axis changes linearly upwards at an angle of nearly 13° above the horizontal line. Moreover, the resistance value after exceeding the Curie point also exhibits a near 90° abrupt change. Therefore, the addition of this substance completely changes the characteristics of the original formulation product. It is equivalent to the mechanical superposition of two PTC characteristic curves, resulting in a completely new PTC characteristic curve. This new electrical characteristic (RT) curve becomes a horizontal straight line before the Curie point on the T axis and exhibits electrical characteristics that do not change with temperature. After the Curie point on the R axis, it does not change abruptly by nearly 90°, but becomes a new slope-like linear curve with a slope of approximately 40°-60°. This characteristic is a device with completely new characteristics and has broad prospects for further development of new applications.

[0036] The present invention provides a power-type high-temperature synthetic linear PTC thermistor, the working principle of which is as follows: This high-power, high-temperature, linear polycrystalline PTC thermistor is manufactured using a special process from a crystalline mixture of the aforementioned non-conductive, high-temperature, high-density polymer material, conductors, semiconductors, and modifiers. At ambient pressure below 85°C, its zero-power resistance value (adjustable from 0.01Ω to 10.0Ω) remains constant (parallel to the T-axis on the resistance-temperature curve, i.e., the RT curve, before 85°C, as shown in the measured curve). Figure 2 As shown), this is the linear characteristic of the first linear segment (as shown in the measured curve). Figure 2 (as shown) Figure 2This is an application curve obtained from actual product testing. As can be seen from the graph, the inflection point of the curve is 120℃ (this test was conducted in a precisely temperature-controlled chamber when no current was flowing through the PTC; this 120℃ represents the internal accumulated temperature of the product; the PTC will only reach 120℃ when the external environment exceeds 85℃ and normal or high current is flowing through it). When the PTC generates heat due to factors such as additional heating from local components, motor overload, short circuit, momentary circuit mismatch, or software interference causing a system crash, causing the temperature around the PTC to rise above 85℃ (which is easily observed during malfunctions), the internal heat of the PTC dissipates outwards. Thermal resistance occurs; simultaneously, the large current generated under the above conditions passes through the PTC, causing the PTC to heat up according to the law Q=I²RT. Due to the obstructed heat dissipation, the internal temperature rises rapidly and exceeds the Curie point of the high-density polymer (around 120°C). Its surface temperature reaches 90°C to 100°C (measured). At this point, the polymer undergoes a small expansion and becomes in a low-elasticity state, causing a small part of the conductive path to break. At the same time, the semiconductor ceramic grains undergo a grain boundary phase transition, and the resistance value increases. Under these dual effects, the resistance value of the PTC has a near-linear increase, but this increase only goes from 0.55Ω to 1 ohm, which is about 40%.If the ambient temperature of the PTC continues to rise and internal heat continues to accumulate, the phase transition elastic state of the internal polymer will be enhanced, the conductive grains will be further separated, and the grain boundary phase transition of the ceramic grains will also be enhanced. At this time, the resistance value of the PTC increases linearly along a 40-60° slope. When the circuit current decreases and the temperature decreases, the resistance value of the PTC will decrease linearly along a 40-60° slope until an equilibrium state is reached. This process is a dynamic equilibrium process. It can be seen that the application has unique advantages in circuit environments where the requirements for high temperature control and high current control are not strict. Because the PTC is connected in series with the main working current circuit, it directly controls (or limits) the current and temperature state of the main circuit. The Curie point of the PTC is selected from high-temperature, high-density polymers with a matrix of around 120°C. Its characteristic changes from solid state to high-density, low-elasticity state, to medium-density, elastic state, and then to low-density, high-elasticity state. This process of change is a continuous process. The electrical characteristics exhibited during this process are that the resistance value rises and falls linearly along a 40-60° slope. For ease of description, several densities of states are used to illustrate this. Its external characteristics are as follows: When the ambient temperature is below 80-85°C, the PTC dissipates heat well under normal operating current, with heat generation and dissipation balanced. The internal accumulated temperature rarely reaches or exceeds the Curie point, so the resistance value of the PTC does not change (this is the essence of choosing a high-temperature, high-density polymer as the matrix material). This is also the essence of the PTC's temperature and current control capabilities. When there is a severe short circuit, motor stall, or excessively high temperature in the circuit containing the PTC, the resistance value of the PTC will linearly increase to tens or hundreds of ohms under the combined effect of high internal current and high external junction temperature. This can greatly limit the circuit current, causing the product equipment to stop working. This is the over-temperature and over-current protection function, or control function, of the PTC. Therefore, this power-type high-temperature synthetic linear PTC thermistor is a unique resistive device capable of controlling temperature after excessive temperature and current after excessive current. Furthermore, the specific temperature control components in the products and equipment listed in the above application areas all require resistors with these characteristics. The application of this power-type high-temperature synthetic linear PTC thermistor not only achieves timely circuit control but also fulfills the ultimate protection of design parameters. This makes products or equipment using this power-type high-temperature synthetic linear PTC thermistor safer and more reliable. All the problems and potential risks mentioned in point 6 above will be handled by this single PTC component, fulfilling all the functions that would otherwise require many components or MCU / DSP functional blocks (in terms of installation, it can be placed close to or near heat-generating elements such as motors, MOSFETs, and IGBT devices). Therefore, its reliability is predictable and the highest, as the PTC controls problems promptly when they occur and protects against catastrophic issues long before they arise. To date, we have applied multiple control schemes and simulated catastrophic problems through extreme and destructive testing, which has proven impossible to replicate in a laboratory and has not been observed in actual user experience.Therefore, no similar phenomena or problems have occurred in market applications. Furthermore, the substrate material, donor material, acceptor material, and auxiliary materials of this device all meet the requirements for long-term high-temperature operation, so its service life is very long, making it a long-life device.

[0037] This high-temperature linear PTC thermistor, with its ingenious design, manufacturing, and unique electrical characteristics, is unlike anything seen on the market today. It is widely needed in motor equipment (for stall protection), and not only solves various problems and potential hazards associated with multiple components and equipment, but also uses far fewer components. A single component addresses the problems and hazards that previously required multiple components. It also solves design challenges for equipment manufacturers and engineers, minimizing component usage, space requirements, cost, and reliability. This makes the product safer, does not alter the overall appearance of the equipment, provides genuine safety assurance, and directly enhances the manufacturer's market competitiveness.

[0038] This power-type high-temperature synthetic linear PTC thermistor can perform the following functions in practical applications: 1. Pure resistive function: This high-temperature high-temperature synthetic linear PTC thermistor is a pure resistor, conforming to Ohm's law (I=U / R) regarding the relationship between parameters. In electronic circuits, it performs functions such as voltage division, current limiting, and current shunting. (When the ambient temperature of the circuit surrounding the PTC is below 85℃, its resistance value will not change with temperature, acting like a fixed resistor; its resistance change with temperature will always be a straight line on the curve.) Figure 2 ).

[0039] 2. Temperature sampling and control function: In control circuits of small household appliances, white goods, large household appliances, and the aforementioned application areas, temperature sampling or direct current limiting control functions are implemented: When the power-type high-temperature synthetic linear PTC thermistor is close to or in close contact with a heat source (such as a heat-generating power component, transistor, MOSFET, IGBT, thyristor, motor, etc.), when the temperature exceeds 85℃, the internal temperature of the PTC rises to the resistance inflection point due to impeded heat dissipation, causing the PTC's resistance value to enter the linear increase region. The voltage drop across the PTC increases linearly and stops at the designed equilibrium point. This facilitates design engineers in accurately designing the required temperature control point; or its... Voltage dividers are directly applied to control circuits to achieve balanced control (because the resistance increases linearly with temperature, the voltage divider causes the circuit current to decrease linearly, achieving stable temperature control) or for MOSFET control: Since this PTC is a power type, applied to the main current line, its linearly increasing resistance voltage divider current limiting can effectively limit the drain-source current of the MOSFET (MOSFET circuits are mostly low-voltage circuits). If the PTC is applied to the gate (G) of the MOSFET, it causes the gate voltage to decrease linearly, narrowing the MOSFET channel width, thereby controlling the controller's conduction, directly or indirectly controlling (or limiting) the linear decrease of the main current. When an MCU, DSP, or CPU participates in device control, this PTC can be applied to sampling applications, and can be used in conjunction with its digital control software design to achieve accurate temperature control. This is because the sampling control point of this PTC can be designed with a wide sampling range between 90℃ and 180℃ (if a small current PTC is selected, the control point can also be moved forward by 70℃), while the resistance value remains basically unchanged below 85℃, exhibiting a horizontal linear state. When the ambient temperature exceeds 85℃ or 90℃, heat dissipation within the PTC is hindered. Once the accumulated temperature exceeds the Curie point of 120℃, its resistance begins to increase linearly, and the temperature rise curve becomes steeper under the influence of internal and external temperatures. The aforementioned temperature sampling and control function involves selecting a PTC whose operating current (defined at 25℃, the current that keeps the PTC's resistance constant until the ambient temperature drops below 85℃) is the same as or greater than the circuit's operating current. If a model with a PTC operating current less than the circuit's operating current is selected, the PTC will reach the resistance change inflection point earlier than the ambient temperature drops below 85℃, entering the linear segment of increasing resistance prematurely. The PTC will then reach equilibrium at another resistance value point. This selection of the PTC model provides flexibility in its application. Therefore, proper selection and application of the PTC offer designers relative flexibility. Furthermore, the temperature control point becomes adjustable across different models, although the control point itself remains fixed depending on the specific PTC model.

[0040] 3. Temperature control and over-temperature protection functions: This high-temperature synthetic linear PTC thermistor, when used in a main circuit, exhibits a essentially constant resistance value at ambient temperatures below 85°C, with its resistance curve remaining horizontal and linear, reaching as low as 0.3-0.5Ω (lower resistance values ​​can be achieved in the mΩ range, depending on circuit requirements). However, when the ambient temperature exceeds 85°C, its resistance increases linearly with temperature, causing a linear decrease in the main circuit current (this linearity is characterized by a slope of approximately 40°-60°). When the ambient temperature around the PTC rises or exceeds 85°C... After reaching a certain temperature, the Joule heat (Q=I²RT) generated by the internal current cannot be dissipated, and the internal junction temperature rises, causing the PTC resistance value to increase to tens of ohms. In low-voltage circuits, this effectively limits current, reducing the current at the heating point or providing constant temperature control. If there is a local circuit short circuit, the large current not only causes the ambient temperature to rise rapidly but also causes the PTC to heat up even faster. As a result, the PTC becomes high-resistance, limiting the main current and causing the main circuit to slowly or stop heating, thus achieving temperature control or over-temperature protection. When the fault is cleared, the PTC and circuit return to normal. This over-temperature protection function is particularly important in the equipment products in the application areas mentioned above, especially in circuits with motors. For example, the motors of soymilk makers, food processors, and juicers heat up quickly, easily burning out the motor and the MOSFET controlling the motor. By using the PTC as a bias resistor for the MOSFET and placing it close to the motor or directly connecting it in series with the motor wires, the motor temperature rise increases the PTC resistance value, directly controlling the current conduction of the MOSFET. This reduces or eliminates the risk of motor overheating and burning out or causing a fire. The aforementioned temperature control and over-temperature protection functions are achieved by selecting a PTC whose operating current (defined at 25°C, the current that keeps the PTC's resistance constant until the ambient temperature drops below 85°C) is the same as or greater than the circuit's operating current. If a model with a PTC operating current less than the circuit's operating current is selected, the PTC will reach the resistance change inflection point earlier than the ambient temperature drops below 85°C, meaning the control point moves forward and it enters the linear segment where the resistance increases earlier. The PTC will then be in a balanced state at another resistance value or temperature point, or enter the current-limiting and temperature-controlling state for over-temperature protection against short-circuit high current. This selection of the PTC model provides flexibility in its application. Therefore, as long as the PTC is correctly selected and applied, it offers designers relative flexibility. Furthermore, the temperature control point and overcurrent protection point are moved forward, becoming adjustable through different models, although the control point or protection point remains fixed depending on the specific PTC model.

[0041] 4. Current control or overcurrent protection function: This high-temperature linear PTC thermistor, a power-type high-temperature synthetic crystal, is used in main current circuits (non-control or signal circuits). When the (main) circuit is operating normally, the PTC's resistance is below 1Ω (actually around 0.3-0.5Ω) at temperatures below 85℃, and remains unchanged with increasing temperature. This ensures that the PTC will not affect the normal operation of the circuit within this temperature range. When there is an overload, increased current, short circuit, or partial short circuit overload, a large or even extremely large current will flow through the PTC. At this time, the PTC will heat up according to Q=I²RT, and its resistance will rapidly increase to tens or hundreds of ohms. This effectively limits the current in the main circuit, allowing the heated device to cool down without interrupting the current, and also sharing most of the power supply voltage. This reduces the voltage received by the load. If the temperature is controlled and decreases, the PTC resistance will decrease and return to normal, allowing the circuit to return to normal operation. If the temperature continues to rise, the resistance value increases accordingly, making its current-limiting effect stronger or allowing it to handle a larger voltage. This prevents the load from operating under voltage and current loss conditions, placing it in a PTC-limited protection state. This protection state is maintained until power is cut off and the system recovers. This protection function ensures that any adverse consequences caused by a short circuit (such as burnt-out circuits, equipment damage, or catastrophic accidents like fires) will no longer exist. This is a unique characteristic of this PTC. The aforementioned current control and overcurrent protection functions are achieved by selecting a PTC whose operating current (defined at 25°C, the current that keeps the PTC's resistance constant until the ambient temperature drops below 85°C) is the same as or greater than the circuit's operating current. If a PTC with a lower operating current than the circuit's operating current is selected, the PTC will reach the resistance change inflection point earlier, before the ambient temperature drops below 85°C. This means the current control point moves forward, entering the linear phase where resistance increases earlier. The PTC will then reach equilibrium at another resistance value point or enter the current-limiting state for short-circuit high-current protection earlier. This selection of the PTC model provides flexibility in its application. Therefore, proper selection and application of the PTC offer designers relative flexibility. Furthermore, the temperature control point and overcurrent protection point are moved forward, becoming adjustable through different models, although the control or protection points remain fixed depending on the specific PTC model.

[0042] 5. Voltage negative feedback control function: This power-type high-temperature synthetic linear PTC thermistor is used in switching power supplies, inverters, MOSFETs, IGBTs, etc., for emitter resistors, source resistors, power amplifier tube emitter resistors, emitter follower emitter resistors, power operational amplifier feed resistors, etc. Previously, fixed resistors were used, which are characterized by large pulse current and small resistance value (Re≤1Ω). If our power-type high-temperature synthetic linear PTC thermistor (R≤1Ω) is used instead, it is better than the above fixed resistors. Because the aforementioned power devices generate significant heat during operation, when a PTC is applied near or in close contact with a heat source, its resistance remains constant under normal operating conditions (below 85°C). However, when the power device experiences excessive load or overload, it heats up further, draws larger currents, and may even cause the switching transformer to become magnetically saturated, leading to a breakdown. In this situation, the PTC resistance rapidly increases due to the increased internal current and external heat buildup. This not only limits the current flowing through the power transistor but also provides voltage feedback to the input, inverting and canceling out the source control signal strength, thus acting as negative feedback. In some circuits, this negative feedback stabilizes the circuit, while in others it weakens the input control voltage or alters the circuit's operating characteristics, such as changing the pulse duty cycle, pulse width, or switching frequency, making the circuit more stable and reliable. If the load is short-circuited, the large current causes the PTC resistance to rapidly rise to the hundreds of ohms, limiting the large switching current of the power transistor and protecting the power transistor and control chip. This is the application of voltage negative feedback. It can effectively prevent the risk of power supply burnout or fire. This is a function that traditional negative feedback resistors cannot achieve.

[0043] As can be seen from the above applications of high-power high-temperature synthetic linear PTC thermistors, this is a revolutionary new type of device that can replace dozens of component unit circuits and modular functional circuits.

[0044] The electrical performance characteristics of this power-type high-temperature synthetic linear PTC thermistor are as follows: 1. This power-type high-temperature synthetic linear PTC thermistor exhibits purely resistive characteristics. Its reactance parameters contain neither capacitive nor inductive reactance, only pure impedance, satisfying the algebraic relationship between parameters defined by Ohm's law (I=U / R). This characteristic allows the product to be applied to high-frequency circuits, low-frequency circuits, and AC / DC circuits. This greatly increases the application range and versatility of the PTC, improving the convenience and flexibility of engineers' designs.

[0045] 2. This PTC device is a power type device and can be used in circuits with AC220V and current below 6A; and in low-voltage circuits with current below 16V35A, 30V30A, and 60V25A, with a maximum of 600V3A.

[0046] 3. The initial zero-power resistance value of this power-type high-temperature synthetic linear PTC thermistor is mostly below 1Ω, but some are greater than 1Ω, and can be customized arbitrarily. This resistance value is defined at an ambient temperature of 25℃±2℃ and is usually called the zero-power resistance value.

[0047] 4. The linearity of this high-temperature synthetic linear PTC thermistor is divided into two segments, which is a unique linearity characteristic of this PTC: horizontal linearity and slope linearity. 4.1. Horizontal linearity: When the PTC is working normally, the current through the PTC is not greater than the normal operating current, and the ambient temperature around the PTC is not higher than 85℃. The horizontal segment of linearity (parallel to the T-axis of the RT curve) belongs to the region where the resistance value remains unchanged. That is, the resistance value will not change due to temperature changes in this region. The PTC is similar to a fixed resistor in this region and satisfies the algebraic relationship of Ohm's law. 4.2. Ramp-Linear Segment: When a normal operating current is applied to the power-type high-temperature synthetic linear PTC thermistor (this current allows the PTC's heat to dissipate promptly without heat accumulation, i.e., heat generation and dissipation are in equilibrium), if the ambient temperature rises above 85°C, the internal heat cannot dissipate and the accumulated temperature exceeds 120°C (measured value). In this case, the PTC's resistance will increase linearly with a slope of approximately 45°-60°, which is the ramp-linear segment. This linear change in resistance can be applied to negative feedback circuits in the aforementioned application areas for functions such as temperature compensation, temperature control, temperature sampling, current limiting, current control, and protection. Once this action occurs, a dynamic current-limiting state is entered, causing the components in the heating circuit to cool down due to current limiting, resulting in a decrease in the PTC resistance. This cycle repeats until thermal equilibrium is reached.

[0048] 5. The high-temperature linearity of this power-type high-temperature synthetic linear PTC thermistor is manifested in two aspects: First, the resistance of the PTC only increases linearly with temperature when the ambient temperature exceeds 85°C; below 85°C, the resistance remains unchanged. Second, when the current flowing through the PTC exceeds the normal operating current, the internal heat generation (Q=I²RT) of the PTC will exceed its external heat dissipation, causing the internal temperature of the PTC to rise. When this temperature causes the surface and surrounding temperature to exceed 85°C, the resistance of the PTC will also increase linearly by approximately 45°C with this temperature increase. This characteristic has a particular advantage in performing functions such as temperature compensation, temperature control, or temperature sampling in negative feedback circuits. This particular advantage refers to the fact that the PTC only exhibits its function above 85°C, which is usually the upper limit of the design temperature for electronic products. Because of the linear change at high temperatures, it is called a high-temperature linear PTC thermistor. This is a unique characteristic that ordinary thermistors or other types of PTCs do not possess.

[0049] 6. Operating temperature of this high-temperature linear PTC thermistor: The operating ambient temperature range of this linear PTC is -20℃ to +200℃. The range of -20℃ to +85℃ is a fixed resistance region; within this range, the PTC's resistance remains essentially unchanged as the ambient temperature varies. However, in the range of +85℃ to +200℃, the PTC's resistance changes linearly with temperature at approximately a 45° slope. Therefore, it is called a high-temperature linear PTC thermistor. This is a unique characteristic not found in ordinary thermistors or other types of PTCs.

[0050] 7. Failure modes of this power-type high-temperature synthetic linear PTC thermistor: When the selection is incorrect, the circuit voltage is much higher than the PTC's withstand voltage, or the inrush current is much higher than the PTC's maximum withstand inrush current, the PTC may crack and fail due to a sudden increase in internal junction temperature and insufficient heat dissipation. This is similar to the cracking failure of other diodes, transistors, and IC chips, resulting in irreversible damage. When its characteristic parameters are used correctly, this PTC has no lifespan limitation.

[0051] 8. Flexibility in Selecting and Applying the Power-Type High-Temperature Synthetic Linear PTC Thermistor: The applications described above are based on selecting a PTC whose operating current (defined at 25°C, the current that keeps the PTC's resistance constant until the ambient temperature drops below 85°C) is the same as or greater than the circuit's operating current. If the selected PTC's operating current is less than the circuit's operating current, the PTC will reach the resistance change inflection point earlier than the ambient temperature drops below 85°C, meaning the control point shifts earlier and it enters the linear segment where the resistance increases earlier. The PTC will then reach equilibrium at another resistance and temperature point. This selection of the PTC model provides flexibility in its application. Therefore, proper selection and application of the PTC offer designers relative flexibility. The control point can be adjusted through different model selections, but the control point or operating point remains fixed depending on the PTC model.

[0052] 9. The electrical performance characteristics of the power-type high-temperature synthetic linear PTC thermistors described above only illustrate the electrical characteristics they exhibit, which are applicable and can be used by engineers for design reference.

[0053] Explanation of the novel performance of this high-temperature high-temperature synthetic linear PTC thermistor: New: This power-type high-temperature synthetic linear PTC thermistor has a brand-new electrical characteristic, as well as flexibility in selection and application. It is a unique new product and device that is not currently available on the market.

[0054] The remarkable feature of this high-temperature high-temperature synthetic linear PTC thermistor lies in its unique synthetic formulation. The combination of two PTC materials with different Curie points gives the new PTC linear and electrical performance characteristics unmatched by any traditional PTC or linear resistor: horizontal linearity and ramp linearity. Furthermore, the horizontal linearity can be further adjusted by selecting different PTC models until the design objective is achieved.

[0055] Special Features: The "special features" of this high-power high-temperature synthetic linear PTC thermistor are manifested in its ability to directly control the current and temperature of the main circuit (without requiring a specially designed sensing and control circuit), while also providing protection against over-temperature and short-circuit overcurrent, all accomplished by a single component. Its control point can be moved forward or backward on the T-axis of the RT curve according to actual needs (i.e., advance control or backward control is selectable), and the resistance value before the control point will not change with temperature, remaining a fixed resistance value. This characteristic is irreplaceable in certain circuit applications.

[0056] This invention provides a power-type high-temperature synthetic linear PTC thermistor, which exhibits a pure resistive state below 85°C, with a resistance value R ≤ 1Ω (approximately 0.5Ω). This characteristic has no impact on normal operation when applied in the aforementioned products. Only when the circuit experiences abnormal temperature rise, partial short circuit, overload generating large current, or sustained temperature increase exceeding 85°C will the resistance value of the power-type high-temperature synthetic linear PTC thermistor increase proportionally with temperature. This increased resistance effectively and promptly limits the increase in current, thereby limiting the temperature rise. This is easily understood, as the power-type high-temperature synthetic linear PTC thermistor is used in series in a motor or main circuit, and its resistance change directly affects and limits the current.

[0057] This invention provides a power-type high-temperature synthetic linear PTC thermistor and its fabrication process, mainly applied to: various household appliance control circuits (such as: height-adjustable coffee tables, height-adjustable beds, massage beds, massage chairs, foot massagers, electric foot baths, juicers, soy milk makers, noodle makers, bread makers, dough mixers, curtain machines, meat grinders, blenders, ice crushers, food processors, electric kettles, electric frying pans, electric slow cookers, LCD TVs, LED TVs, amplifiers, blowers, vacuum cleaners, air purifiers, refrigerators, air conditioners, washing machines, sweeping robots, LED lighting products, liquid crystal displays, etc.), various frequency converters, switching power supplies, medical devices, security power supplies and system control circuits, automotive electric systems (window lift control circuits, wiper motor control circuits, seat motor control circuits, etc.), various industrial motor control systems, industrial servo motor systems, electric heating baking systems, agricultural greenhouse sprinkler systems, solar inverter systems, etc. It is an essential component with few components, low cost, high reliability, high safety, and long lifespan.

[0058] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A power-type high-temperature synthetic linear PTC thermistor, characterized in that: The device includes a hybrid crystal core chip pressed from core chip material, an electrode lead-out portion made of guiding electrode material, and an encapsulation protective layer made of encapsulation material. The electrode lead-out portion includes a chip film and electrode leads. The chip film wraps around the hybrid crystal core chip, and the electrode leads are soldered to the chip film. The encapsulation protective layer wraps around the chip film. The chip film includes a single-sided rough nickel-plated copper film, and the electrode leads include tin-plated copper wires. The tin-plated copper wires are connected to the single-sided rough nickel-plated copper film by soldering. The encapsulation material includes pressure-sensitive adhesive and epoxy resin encapsulation powder. The pressure-sensitive adhesive and epoxy resin encapsulation powder form an epoxy resin insulating encapsulation protective layer. The core chip materials include shaping materials, conductive materials, and auxiliary materials; The shaping materials include high-density polyethylene, nylon, and polyvinylidene fluoride; the conductive materials include rubber carbon black, nickel powder, and semiconductor ceramic powder; the semiconductor ceramic powder includes BaCO3, Al2O3, SrCO3, TiO2, CaCO3, Tc2O5, and Pm. 2O3, MnO2, SiO2 and Li2CO3; the auxiliary materials include antioxidants, flame retardants, dispersants, reinforcing agents, sensitizers and lubricants; According to the quality formulation, the mass percentage of high-density polyethylene is 22-26%, nylon is 7-9%, and polyvinylidene fluoride is 10-12%; the mass percentage of rubber carbon black is 24-28%, nickel powder is 0.8-1.2%, and semiconductor ceramic powder is 7.5-9.5%; the mass percentage of antioxidant is 0.15-0.3%, flame retardant is 19-22%, dispersant is 0.3-0.5%, and reinforcing agent is 0.3-0.5%. The resistance of this power-type high-temperature synthetic linear PTC thermistor remains basically unchanged in the temperature range of -20℃ to +85℃, and in the temperature range of +85℃ to +200℃, the resistance increases linearly with the temperature in a slope of 40° to 60°.

2. A method for preparing a power-type high-temperature synthetic linear PTC thermistor as described in claim 1, characterized in that, The process includes the following: S1. Raw material drying and preheating treatment; S2. Weighing and dispensing ingredients; S3, the first secret refining; S4, First granulation; S5, Second Intensive Refining; S6, Second granulation; S7, High-temperature and high-pressure extruded black sheet; S8. Double-sided copper plating is completed simultaneously under high temperature and high pressure. S9, Vacuum multilayer tableting; S10, irradiation; S11, chip punching; S12, insert plate; S13, solder; S14, resin impregnation; S15, Encapsulation; S16, Curing; S17. Conduct aging tests, then perform resistance testing to screen out defective products; finally, inspect and approve products before shipping.

3. The method for preparing a power-type high-temperature synthetic linear PTC thermistor according to claim 2, characterized in that: In step S1, the raw materials are pretreated under vacuum at 150°C for 48 to 52 hours, with material turning over midway to ensure a vacuum degree of -0.10 MPa; in step S3, the raw materials are mixed and plasticized in an internal mixer at 165-180°C; in step S5, the raw materials are mixed and plasticized in an internal mixer at 165-180°C; in step S7, the raw materials are extruded as black flakes through an extruder. In step S8, a nickel-plated copper film is coated on both sides of the black sheet to form a coated chip; in step S9, the coated chip is vacuum-pressed into a large coated sheet using a vacuum vulcanizing machine. The vacuum vulcanizing process is as follows: preheating for 5 minutes, vacuum vulcanizing hot pressing time for 10 minutes, hot pressing pressure of 15 MPa, and hot pressing temperature of 180°C to 190°C, resulting in a sheet thickness of 2.1 mm to 4.5 mm; in step S10, cross-linking is performed using gamma rays or an electron accelerator irradiation. The irradiation process is as follows: radiation cross-linking 1 to 5 times, with an irradiation dose of 5 to 15 mg / L each time. KGY; In step S11, the large sheet of film is stamped and cut into the required small-sized semi-finished products by a punch press at room temperature; In step S13, soldering is performed, followed by heat treatment at 190°C for 20 minutes in an oven; In step S14, the semi-finished products are immersed in water-soluble insulating pressure-sensitive adhesive; In step S15, the surface of the semi-finished products is encapsulated with epoxy resin or coated with insulating varnish.

4. The method for preparing a power-type high-temperature synthetic linear PTC thermistor according to claim 2, characterized in that: Semiconductor ceramic powder includes BaCO3, Al2O3, SrCO3, TiO2, CaCO3, Tc2O5, Pm2O3, MnO2, SiO2, and Li2CO3. After being uniformly mixed by ball milling, the powder is sintered at 1200℃, granulated, crushed, and ground to form powder crystals. In step S17, the product is subjected to heat treatment at 190℃ for 20 minutes and current aging at 5 times the working current. After cooling at room temperature for 2 hours, the resistance value is tested using a high-precision low-resistance tester. Products with different resistance value ranges are grouped by resistance value. The parts exceeding the upper limit of the specified resistance value and the parts exceeding the lower limit of the specified resistance value are considered as unqualified products. Unqualified products are discarded and qualified products are retained.

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