Lead-free low-Curie-temperature PTC (Positive Temperature Coefficient) thermistor, formula and manufacturing method thereof

Abstract

The invention discloses a lead-free low-Curie-temperature PTC thermistor and a manufacturing method thereof, the lead-free low-Curie-temperature PTC thermistor comprises a main material, an auxiliary material and a sintering aid, on the basis of 1 mol of TiO2, the main material comprises 1 mol of TiO2 and 0.6551-0.8817 mol of BaCO3; the molar ratio of CaCO3 to CaCO3 is 0.1145 mol to 0.3339 mol; the molar ratio of SrCO3 to SrCO3 is 0.0010 mol to 0.0038 mol; the molar composition of the auxiliary material is as follows: 0.0020 mol to 0.0060 mol of Y2O3; and the molar composition of the sintering aid is as follows: 0.010 mol to 0.0450 mol of SiO2 and 0.0050 mol to 0.030 mol of TiO2. The preparation of the PTC thermistor with the Curie temperature of 125 DEG C, the resistance value R25 of 4.5 omega + / -20% and the Curie temperature Tc25 of about 125 + / -5 DEG C can be smoothly realized by combining the formula proportion of the lead-free ceramic material with the existing tunnel furnace sintering process. Meanwhile, due to the advantage of low resistivity of the formula, tunnel furnace sintering and post-processing technologies are stable, and the material is suitable for mass production.

Description

Technical Field

[0001] The present invention belongs to the technical field of PTC thermistors, and particularly relates to a lead-free low Curie temperature PTC thermistor, a formulation thereof, and a manufacturing method therefor. Background Art

[0002] PTC thermistors have functions such as overcurrent protection, overheat protection, and constant temperature heating, and are mainly applied to fields such as transformers, micro-motors, switching power supplies, chargers, instruments, meters, electronic coils, home appliance control boards, program-controlled switches, main distribution frames, communication base stations, user terminal communication devices, motor coils, power devices, start-up circuits of refrigerators and air conditioners, and thermal management systems of new energy vehicles.

[0003] Currently, PTC starter chips for domestic appliances and new energy vehicles in China contain lead. Due to the toxicity and volatility of lead, lead-containing PTCs are harmful to human health and cause environmental pollution throughout the processes of manufacturing, production, use, and recycling. With the development of society and the requirements of environmental protection, lead-containing PTCs are no longer suitable for the market. Therefore, lead-free is the future development trend.

[0004] Currently, the Curie temperature of PTC thermistor devices based on barium titanate for starting is between 100°C and 130°C, and all contain lead (PTC thermistors with a Curie temperature above 100°C contain lead). Due to the volatilization of lead during the preparation process of lead-containing thermistor devices, not only does it cause a deviation in the stoichiometry of ceramic products during the production process, reducing the performance consistency and repeatability of products and making recycling difficult; moreover, lead pollutes the environment and harms the human body. At the same time, with the increasingly urgent requirements for lead-free of electronic materials and components, the development of high-performance lead-free PTC ceramic materials is an inevitable trend. Here, a lead-free low Curie temperature PTC thermistor is proposed. Summary of the Invention

[0005] To overcome the above deficiencies, a lead-free low Curie temperature PTC thermistor, a formulation thereof, and a manufacturing method therefor are proposed. The lead-free porcelain material formulation ratio of the present invention, combined with the existing tunnel furnace sintering process, can successfully achieve the preparation of a PTC thermistor with a Curie temperature of 125°C, a resistance value of R25 = 4.5Ω ± 20%, and a Curie temperature of Tc25 = 125 ± 5°C. At the same time, due to the low resistivity advantage of the formulation, the tunnel furnace sintering and post-processing processes are stable and suitable for mass production.

[0006] The technical solution adopted by the present invention to achieve the above object is: to provide a lead-free low Curie temperature PTC thermistor formulation. It consists of a main material, an auxiliary material, and a sintering aid. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.6551 mol to 0.8817 mol; CaCO3: 0.1145 mol to 0.3339 mol; SrCO3: 0.0010 mol to 0.0038 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0020 mol to 0.0060 mol; The molar composition of the sintering aids is: SiO2: 0.010 mol to 0.0450 mol, TiO2: 0.0050 mol to 0.030 mol.

[0007] According to a lead-free low Curie temperature PTC thermistor formula described in the present invention, a further preferred technical solution is: the molar composition of the main materials is TiO2: 1 mol, BaCO3: 0.7183 mol to 0.8629 mol; CaCO3: 0.1344 mol to 0.2806 mol; SrCO3: 0.0011 mol to 0.0027 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0030 mol to 0.0052 mol; The molar composition of the sintering aids is: SiO2: 0.0150 mol to 0.0350 mol, TiO2: 0.010 mol to 0.020 mol.

[0008] According to a lead-free low Curie temperature PTC thermistor formula described in the present invention, a further preferred technical solution is: the molar composition of the main materials is TiO2: 1 mol, BaCO3: 0.7542 mol to 0.8503 mol; CaCO3: 0.1476 mol to 0.2446 mol; SrCO3: 0.0012 mol to 0.0021 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0040 mol to 0.0048 mol; The molar composition of the sintering aids is: SiO2: 0.020 mol to 0.030 mol, TiO2: 0.0110 mol to 0.0180 mol.

[0009] According to a lead-free low Curie temperature PTC thermistor formula described in the present invention, a further preferred technical solution is: the molar composition of the main materials is TiO2: 1 mol, BaCO3: 0.8003 mol to 0.8277 mol; CaCO3: 0.1706 mol to 0.1984 mol; SrCO3: 0.0013 mol to 0.0017 mol; The molar composition of auxiliary materials is: Y2O3: 0.0042mol~0.0047mol; the molar composition of sintering aids is: SiO2: 0.022mol~0.026mol, TiO2: 0.013mol~0.017mol A method for manufacturing a lead-free low Curie temperature PTC thermistor, comprising the following steps: 1) weighing raw materials according to the required performance of the thermistor and the raw material composition and proportion, and mixing the weighed raw materials by ball milling according to a mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Pressing the powder into a round ceramic green body; 6) The ceramic green body is loaded into the sintering sagger and quickly sintered into a ceramic body at 1280℃~1300℃ in a tunnel furnace; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode is measured and the appearance is sorted to obtain the finished PTC thermistor.

[0010] According to the method for manufacturing a lead-free low Curie temperature PTC thermistor of the present invention, a further preferred technical solution is: in step 5), the circular ceramic green body φ=18.6mm, T=3.06mm.

[0011] A lead-free low Curie temperature PTC thermistor is made by the above method.

[0012] Compared with the prior art, the technical solution of the present invention has the following advantages / benefits: 1. The lead-free porcelain material formula ratio of the present invention combined with the existing tunnel furnace sintering process can smoothly realize the preparation of PTC thermistors with a Curie temperature of 125°C, a resistance value of R25=4.5Ω±20%, and a Curie temperature of about Tc25=125±5°C. At the same time, due to the low resistivity advantage of the formula, the tunnel furnace sintering and post-processing process are stable and suitable for mass production.

[0013] 2. The resistance qualification rate of the product obtained by adopting the formula ratio and processing and manufacturing method of the present invention is high, which can reach more than 95%.

[0014] 3. Due to the stability of the process, the basic characteristics of the PTC thermistor (such as R-T characteristics, V-I characteristics) fluctuate less, and the safety of customers using it on the machine is relatively high. Brief Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0016] Figure 1 It is a flowchart of a method for preparing a lead-free low Curie temperature PTC thermistor of the present invention. Detailed Embodiments

[0017] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention.

[0018] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it may not be further defined and explained in subsequent drawings.

[0019] Example 1: As Figure 1 shown, a lead-free low Curie temperature PTC thermistor formula. It consists of a main material, an auxiliary material and a sintering aid. Based on 1 mol of TiO2, The molar composition of the main material is: TiO2: 1 mol, BaCO3: 0.7011 mol, CaCO3: 0.2951 mol, SrCO3 0.0038 mol; The molar composition of the auxiliary material is: Y2O3: 0.0060 mol; The molar composition of the sintering aid is: SiO2: 0.010 mol, TiO2: 0.0050 mol.

[0020] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1260°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain a finished PTC thermistor with a resistance of 3.8Ω (excluding the influence of silver electrode and other factors, here only refers to the resistance value caused by the material, the same as in the following embodiments), Tc25 (Curie temperature (Tc25) is the temperature corresponding to a step increase in the resistor, generally defined as the temperature corresponding to twice the zero-power resistance at 25°C. Curie temperature (Tc is also Tb in the literature) is the temperature corresponding to a step increase in the resistor, generally defined as the temperature corresponding to twice the minimum resistance (Rmin)) The temperature corresponding to the doubling of the resistance) is 120°C.

[0021] Embodiment 2: A lead-free low Curie temperature PTC thermistor formula. It is composed of main materials, auxiliary materials and sintering aids, based on 1 mol of TiO2. The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8817 mol, CaCO3: 0.1173 mol, SrCO3 0.0010 mol; The molar composition of auxiliary materials is: Y2O3: 0.0020 mol; The molar composition of the sintering aid is: SiO2: 0.0450 mol, TiO2: 0.030 mol.

[0022] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1275°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 5.4Ω and a Tc25 of 130℃.

[0023] Embodiment 3: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8817 mol, CaCO3: 0.1145 mol, SrCO3 0.0038 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0025 mol; The molar composition of the sintering aid is: SiO2: 0.0130 mol, TiO2: 0.0080 mol.

[0024] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1285°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 5.2Ω and a Tc25 of 120℃.

[0025] Embodiment 4: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.6651 mol, CaCO3: 0.3339 mol, SrCO3 0.0010 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0055 mol; The molar composition of the sintering aid is: SiO2: 0.040 mol, TiO2: 0.0250 mol.

[0026] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1295°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.1Ω and a Tc25 of 130℃.

[0027] Embodiment 5: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.7183 mol, CaCO3: 0.2790 mol, SrCO3 0.0027 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0030 mol; The molar composition of the sintering aid is: SiO2: 0.0150 mol, TiO2: 0.010 mol.

[0028] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1260°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.9Ω and a Tc25 of 122℃.

[0029] Embodiment 6: A lead-free low Curie temperature PTC thermistor formula. It is composed of main materials, auxiliary materials and sintering aids, based on 1 mol of TiO2. The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8629 mol, CaCO3: 0.1360 mol, SrCO3 0.0011 mol; The molar composition of auxiliary materials is: Y2O3: 0.0052 mol; The molar composition of the sintering aid is: SiO2: 0.0350 mol, TiO2: 0.020 mol.

[0030] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1275°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.2Ω and a Tc25 of 129℃.

[0031] Embodiment 7: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8629 mol, CaCO3: 0.1344 mol, SrCO3 0.0027 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0035 mol; The molar composition of the sintering aid is: SiO2: 0.0180 mol, TiO2: 0.0130 mol.

[0032] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1285°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.8Ω and a Tc25 of 122℃.

[0033] Embodiment 8: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.7183 mol, CaCO3: 0.2806 mol, SrCO3 0.0011 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0050 mol; The molar composition of the sintering aid is: SiO2: 0.0320 mol, TiO2: 0.0180 mol.

[0034] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1295°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.2Ω and a Tc25 of 129℃.

[0035] Embodiment 9: like Figure 1As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.7542 mol, CaCO3: 0.2437 mol, SrCO3 0.0021 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0040 mol; The molar composition of the sintering aid is: SiO2: 0.020 mol, TiO2: 0.0110 mol.

[0036] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1260°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.7Ω and a Tc25 of 124℃.

[0037] Embodiment 10: A lead-free low Curie temperature PTC thermistor formula. It is composed of main materials, auxiliary materials and sintering aids, based on 1 mol of TiO2. The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8503 mol, CaCO3: 0.1485 mol, SrCO3 0.0012 mol; The molar composition of auxiliary materials is: Y2O3: 0.0048 mol; The molar composition of the sintering aid is: SiO2: 0.030 mol, TiO2: 0.0180 mol.

[0038] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1275°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.5Ω and a Tc25 of 127℃.

[0039] Embodiment 11: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8503 mol, CaCO3: 0.1476 mol, SrCO3 0.0021 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0042 mol; The molar composition of the sintering aid is: SiO2: 0.0230 mol, TiO2: 0.0120 mol.

[0040] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1285°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.7Ω and a Tc25 of 124℃.

[0041] Embodiment 12: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.7542 mol, CaCO3: 0.2446 mol, SrCO3 0.0012 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0045 mol; The molar composition of the sintering aid is: SiO2: 0.0270 mol, TiO2: 0.0150 mol.

[0042] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1295°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.6Ω and a Tc25 of 127℃.

[0043] Embodiment 13: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8003 mol, CaCO3: 0.1980 mol, SrCO3 0.0017 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0042 mol; The molar composition of the sintering aid is: SiO2: 0.0220 mol, TiO2: 0.0130 mol.

[0044] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after secondary ball milling, mix it thoroughly according to the ratio of powder: 13% polyvinyl alcohol solution = 100:17, granulate it, and then dry it; 5) Press the powder into a circular ceramic green body with φ = 18.6 mm and T = 3.06 mm (referring to the diameter and thickness respectively); 6) Place the ceramic green body into a sintering crucible and sinter it into a ceramic body in a tunnel furnace at 1260 °C for 30 min. At this time, the diameter φ = 15.60 ± 0.05 mm and the thickness T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered ceramic body, and sinter and infiltrate at 520 °C for 10 min - 20 min to prepare silver electrodes; 8) Measure the resistance value and perform appearance sorting on the chip with electrodes prepared to obtain the finished PTC thermistor with a resistance of 4.7 Ω and Tc25 of 126 °C.

[0045] Example 14: A lead-free low Curie temperature PTC thermistor formula. It consists of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8277 mol, CaCO3: 0.1710 mol, SrCO3 0.0013 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0047 mol; The molar composition of the sintering aids is: SiO2: 0.0260 mol, TiO2: 0.0170 mol.

[0046] Based on the above formula, a lead-free low Curie temperature PTC thermistor is made by the following manufacturing method. The steps include: 1) According to the required performance of the thermistor, weigh the raw materials according to the above raw material composition and ratio, and perform primary ball milling and mixing on the weighed raw materials according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after primary ball milling and perform pre-sintering at 1100 °C - 1150 °C for 3 h; 3) Perform secondary ball milling and pulverization on the pre-sintered powder according to the mass ratio of powder: grinding balls: deionized water = 1:2:2; 4) Dry the powder after secondary ball milling, mix it thoroughly according to the ratio of powder: 13% polyvinyl alcohol solution = 100:17, granulate it, and then dry it; 5) Press the powder into a circular ceramic green body with φ = 18.6 mm and T = 3.06 mm (referring to the diameter and thickness respectively); 6) The green ceramic body is placed into a sintering crucible and sintered into a ceramic body in a tunnel furnace at 1275 °C for 30 min. At this time, the diameter φ = 15.60 ± 0.05 mm and the thickness T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered ceramic body, and sinter and infiltrate at 520 °C for 10 min to 20 min to prepare silver electrodes; 8) Measure the resistance value and perform appearance sorting on the chip with electrodes prepared, to obtain the finished PTC thermistor, with a resistance of 4.5 Ω and Tc25 of 127 °C.

[0047] Example 15: As Figure 1 shown, a lead-free low Curie temperature PTC thermistor formula. It consists of a main material, an auxiliary material and a sintering aid. Based on 1 mol of TiO2, The molar composition of the main material is: TiO2: 1 mol, BaCO3: 0.8277 mol, CaCO3: 0.1706 mol, SrCO3 0.0017 mol; The molar composition of the auxiliary material is: Y2O3: 0.0043 mol; The molar composition of the sintering aid is: SiO2: 0.0240 mol, TiO2: 0.0140 mol.

[0048] Based on the above formula, a lead-free low Curie temperature PTC thermistor is made by the following manufacturing method. The steps include: 1) According to the required performance of the thermistor, weigh the raw materials according to the above raw material composition and proportion, and perform primary ball milling and mixing on the weighed raw materials according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling, and perform pre-sintering at 1100 °C to 1150 °C for 3 h; 3) Perform secondary ball milling and pulverization on the pre-sintered powder according to the mass ratio of powder: grinding balls: deionized water = 1:2:2; 4) Dry the powder after the second ball milling, fully mix according to the ratio of powder: 13% polyvinyl alcohol solution = 100:17, granulate, and dry; 5) Press the powder into a circular ceramic green body, with the circular ceramic green body φ = 18.6 mm and T = 3.06 mm (referring to the diameter and thickness respectively); 6) Place the ceramic green body into a sintering crucible and sinter it into a ceramic body in a tunnel furnace at 1285 °C for 30 min. At this time, the diameter φ = 15.60 ± 0.05 mm and the thickness T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.7Ω and a Tc25 of 126℃.

[0049] Embodiment 16: like Figure 1 As shown in the figure, a lead-free low Curie temperature PTC thermistor formula is composed of main materials, auxiliary materials and sintering aids. Based on 1 mol of TiO2, The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.8003 mol, CaCO3: 0.1984 mol, SrCO3 0.0013 mol; The molar composition of the auxiliary materials is: Y2O3: 0.0046 mol; The molar composition of the sintering aid is: SiO2: 0.0250 mol, TiO2: 0.0160 mol.

[0050] Based on the above formula, a lead-free low Curie temperature PTC thermistor is prepared according to the following manufacturing method, the steps of which include: 1) weighing raw materials according to the required performance of the thermistor and the above raw material composition and proportion, and mixing the weighed raw materials by ball milling according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Press the powder into a round ceramic green body, the round ceramic green body φ = 18.6 mm, T = 3.06 mm (referring to the diameter and thickness respectively); 6) The ceramic green body is placed in a sintering sagger and sintered in a tunnel furnace at 1295°C for 30 minutes to form a ceramic body with a diameter of φ = 15.60 ± 0.05 mm and a thickness of T = 2.60 ± 0.05 mm; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode was measured and the appearance was sorted to obtain the finished PTC thermistor with a resistance of 4.6Ω and a Tc25 of 127℃.

[0051] The above are only the preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be construed as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art, without departing from the spirit and scope of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A lead-free low Curie temperature PTC thermistor formula, characterized in that: It is composed of main materials, auxiliary materials and sintering aids, based on 1 mol of TiO2. The molar composition of the main materials is: TiO2: 1 mol, BaCO3: 0.6551 mol~0.8817 mol; CaCO3: 0.1145mol~0.3339mol; SrCO3: 0.0010mol~0.0038mol; The molar composition of the auxiliary materials is: Y2O3: 0.0020mol~0.0060mol; The molar composition of the sintering aid is: SiO2: 0.010mol~0.0450mol, TiO2: 0.0050mol~0.030mol.

2. A lead-free low Curie temperature PTC thermistor formulation according to claim 1, characterized in that: The molar composition of the main materials is TiO2: 1 mol, BaCO3: 0.7183 mol~0.8629 mol; CaCO3: 0.1344mol~0.2806mol; SrCO3: 0.0011mol~0.0027mol; The molar composition of the auxiliary materials is: Y2O3: 0.0030mol~0.0052mol; The molar composition of the sintering aid is: SiO2: 0.0150 mol~0.0350 mol, TiO2: 0.010 mol~0.020 mol.

3. A lead-free low Curie temperature PTC thermistor formulation according to claim 2, characterized in that: The molar composition of the main materials is TiO2: 1 mol, BaCO3: 0.7542 mol~0.8503 mol; CaCO3: 0.1476mol~0.2446mol; SrCO3: 0.0012mol~0.0021mol; The molar composition of the auxiliary materials is: Y2O3: 0.0040mol~0.0048mol; The molar composition of the sintering aid is: SiO2: 0.020mol~0.030mol, TiO2: 0.0110mol~0.0180mol.

4. A lead-free low Curie temperature PTC thermistor formulation according to claim 3, characterized in that: The molar composition of the main materials is TiO2: 1 mol, BaCO3: 0.8003 mol~0.8277 mol; CaCO3: 0.1706mol~0.1984mol; SrCO3: 0.0013mol~0.0017mol; The molar composition of auxiliary materials is: Y2O3: 0.0042mol~0.0047mol; The molar composition of sintering aids is: SiO2: 0.022mol~0.026mol, TiO2: 0.013mol~0.017mol.

5. A method for manufacturing a lead-free low Curie temperature PTC thermistor, characterized in that: The steps include: 1) weighing raw materials according to the raw material composition and proportion according to any one of claims 1 to 4 according to the required performance of the thermistor, and ball milling the weighed raw materials according to the mass ratio of raw materials: grinding balls: deionized water = 1:2:2; 2) Dry the powder after the first ball milling and pre-sinter it at 1100℃~1150℃ for 3h; 3) The pre-calcined powder is subjected to secondary ball milling according to the mass ratio of powder: grinding ball: deionized water = 1:2:2; 4) Dry the powder after the secondary ball milling, fully mix the powder and 13% polyvinyl alcohol solution in a ratio of 100:17, granulate and dry; 5) Pressing the powder into a round ceramic green body; 6) The ceramic green body is loaded into the sintering sagger and quickly sintered into a ceramic body at 1280℃~1300℃ in a tunnel furnace; 7) Print silver-zinc ohmic silver paste and surface silver paste on the front and back surfaces of the sintered porcelain body, and sinter and infiltrate at 520°C for 10min~20min to prepare silver electrodes; 8) The resistance value of the chip with the prepared electrode is measured and the appearance is sorted to obtain the finished PTC thermistor.

6. The method for manufacturing a lead-free low Curie temperature PTC thermistor according to claim 5, characterized in that: In step 5), the circular ceramic green body has φ=18.6 mm and T=3.06 mm.

7. A lead-free low Curie temperature PTC thermistor, characterized in that: The method is prepared by any one of claims 5 to 6.

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