Barium titanate-based thermistor and method for manufacturing the same

Abstract

The application provides a barium titanate-based thermistor and a preparation method thereof. The preparation method comprises the following steps: 1) mixing ceramic powder and sintering aids to obtain mixed powder, dispersing the mixed powder, a dispersing agent, a binder and a release agent in a dispersing medium to obtain a mixed slurry; the ceramic powder comprises main materials and additives, and the main materials comprise BaCO3 and TiO2; 2) spray granulating the mixed slurry to obtain granulated materials; 3) dry pressing and forming the granulated materials, sintering, plating electrodes, and obtaining the barium titanate-based thermistor. The application combines the ceramic powder with other aids, adopts spray granulation and dry pressing forming process, reduces the sintering temperature of the ceramic from 1300 DEG C generally recognized in the industry to 800-1200 DEG C, realizes low-temperature sintering preparation of the barium titanate-based thermistor, greatly reduces the sintering cost, and is simple in process, low in energy consumption and suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic ceramics, in particular to a barium titanate-based thermistor and a preparation method thereof. BACKGROUND

[0002] The barium titanate-based thermistor is a positive temperature coefficient thermistor ceramic material, which is widely used in overcurrent and overheat protection in electronic circuits. The existing production process of the barium titanate-based thermistor adopts a two-step method: first, a blank is prepared and then sintered, and then silver paste or oxide is coated on the surface of the sintered ceramic sheet to obtain the barium titanate-based thermistor. The blank needs to be sintered at a temperature higher than 1200℃, which has high energy consumption and does not conform to the trend of integration of various electronic components in the microelectronic technology field. Therefore, it is of great significance to explore a low-energy barium titanate-based thermistor preparation process. SUMMARY

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a barium titanate-based thermistor and a preparation method thereof, which can solve the problems of high energy consumption and high production cost in the production process of the barium titanate-based thermistor in the prior art.

[0004] To achieve the above-mentioned purposes and other related purposes, the present application is obtained by including the following technical solutions.

[0005] The present application provides a preparation method of a barium titanate-based thermistor, which comprises the following steps:

[0006] 1) mixing ceramic powder and sintering aids to obtain mixed powder, dispersing the mixed powder, dispersing agent, binder and release agent in a dispersion medium to obtain a mixed slurry; the ceramic powder comprises main materials and additives, and the main materials comprise BaCO3 and TiO2;

[0007] 2) spray granulating the mixed slurry to obtain granular material;

[0008] 3) dry pressing the granular material, sintering, and plating electrodes to obtain the barium titanate-based thermistor.

[0009] Preferably, the weight percentage of the main materials is 80-99wt% based on the total weight of the mixed powder, and the sum of the weight percentages of the additives and sintering aids is 1-20wt%.

[0010] Preferably, the additives are selected from one or more of SrCO3, PbO, Y2O3, Nb2O5, Sb2O3, La2O3, Bi2O3, MnCO3 and CuO.

[0011] Preferably, the sintering aid is selected from one or more of the group consisting of blast furnace slag, MgO, SiO2, CaCO3, Al2O3, Na2O, TiO2and ZnO.

[0012] Preferably, the dispersant is ammonium polyacrylate, and the amount of the dispersant added is 0.5-5wt% based on the total weight of the mixed powder.

[0013] Preferably, the binder is polyvinyl alcohol, and the amount of the binder added is 0.5-5wt% based on the total weight of the mixed powder.

[0014] Preferably, the release agent is emulsified paraffin, and the amount of the release agent added is 0.1-2wt% based on the total weight of the mixed powder.

[0015] Preferably, the dispersing medium is water, and the amount of the dispersing medium added is 35-100wt% based on the total weight of the mixed powder.

[0016] The present application also provides a barium titanate-based thermistor prepared by the above preparation method.

[0017] As described above, the barium titanate-based thermistor and the preparation method thereof have the following beneficial effects: by combining the ceramic powder with other aids, and using the spray granulation and dry pressing forming process, the sintering temperature of the ceramic is reduced from the generally recognized 1300℃ in the industry to 800-1200℃, the barium titanate-based thermistor is prepared by low-temperature sintering, the sintering cost is greatly reduced, the process is simple, the energy consumption is low, and the method is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0018] The embodiments of the present application will be described in detail below with specific reference being made to certain embodiments. As would be obvious to one skilled in the art, other advantages and benefits of the present application can be readily ascertained from the disclosure. The present application can be practiced in other embodiments and by using different methods than those described herein without departing from the spirit of the present application. The specifics in the present description can be modified or changed based on different viewpoints and applications without departing from the spirit of the present application.

[0019] It should be noted that the process equipment or devices not specifically mentioned in the following examples are all conventional equipment or devices in the art.

[0020] Furthermore, it should be understood that any steps of the methods mentioned in the present application do not exclude that further method steps can be present before and / or after the mentioned steps or that further method steps can be inserted between the mentioned steps, unless otherwise indicated; it should also be understood that any combination of one or more devices / apparatuses mentioned in the present application does not exclude that further devices / apparatuses can be present before and / or after the mentioned devices / apparatuses or that further devices / apparatuses can be inserted between the mentioned two devices / apparatuses, unless otherwise indicated. Moreover, the numbering of the method steps is merely intended to identify various method steps for an easy reference and does not constitute a limitation for the sequence of the method steps or define the scope of the present application, and any change and / or adjustment of the relative arrangement of the method steps, without changing or altering the technical content of the present application, is deemed to be within the scope of the present application.

[0021] The present application provides a specific preparation method of barium titanate-based thermistor, comprising the following steps:

[0022] 1) mixing ceramic powder and sintering aid to obtain mixed powder, dispersing the mixed powder, dispersing agent, binder and release agent in a dispersion medium to obtain mixed slurry; the ceramic powder comprises main material and additive, and the main material comprises BaCO3 and TiO2;

[0023] 2) spray granulating the mixed slurry to obtain granulated material;

[0024] 3) dry pressing the granulated material, sintering and plating electrode to obtain the barium titanate-based thermistor.

[0025] In a more specific embodiment, the mixing of the mixed slurry adopts a wet ball milling method.

[0026] In a specific embodiment, the weight percentage of the main material is 80-99wt% based on the total weight of the mixed powder, and the sum of the weight percentage of the additive and the sintering aid is 1-20wt%, such as 1-5wt%, 5-10wt%, 10-15wt% and 15-20wt%.

[0027] In a more specific embodiment, the weight percentage of BaCO3 is 55-61wt% and the weight percentage of TiO2 is 25-30wt% based on the total weight of the mixed powder.

[0028] In a specific embodiment, the additive is selected from one or more of SrCO3, PbO, Y2O3, Nb2O5, Sb2O3, La2O3, Bi2O3, MnCO3 and CuO.

[0029] In a more specific embodiment, the additives include the following components in the following weight percentages, based on the total weight of the mixed powder: 0-7.5wt% SrCO3, 0-6wt% PbO, 0-1wt% Y2O3, 0-1wt% Nb2O5, 0-0.5wt% Sb2O3, 0-1wt% La2O3, 0-0.5wt% Bi2O3, 0-1wt% MnCO3, and 0-1wt% CuO.

[0030] In a specific embodiment, the sintering aid is selected from one or more of blast furnace slag, MgO, SiO2, CaCO3, Al2O3, Na2O, TiO2, and ZnO.

[0031] In a more specific embodiment, the sintering aid includes the following components in the following weight percentages, based on the total weight of the mixed powder: 0-5wt% blast furnace slag, 0-2.5wt% MgO, 0.5-2.5wt% SiO2, 0-3wt% CaCO3, 0-1.5wt% Al2O3, 0-1wt% TiO2, 0-0.1wt% Na2O, and 0-2wt% ZnO.

[0032] In the above technical solution, the blast furnace slag is an industrial byproduct produced during the blast furnace iron-making process, and the main components are silicates and aluminosilicates, with a production amount of about 30-50% of pig iron. The main chemical components are as follows (%): CaO: 32-49%, SiO2: 32-41%, Al2O3: 6-17%, MgO: 2-13%, TiO2: 0.1-4%, Fe2O3: 0.2-4%, and S: 0.2-2.5%.

[0033] In a specific embodiment, the dispersant is ammonium polyacrylate, and the amount of the dispersant added is 0.5-5wt%, such as specifically 0.5-1wt%, 1-1.5wt%, 1.5-2wt%, 2.5-3wt%, 3.5-4wt%, or 4.5-5wt%, based on the total weight of the mixed powder.

[0034] In a specific embodiment, the binder is polyvinyl alcohol, such as specifically type 1788 or 2488, and the amount of the binder added is 0.5-5wt%, such as specifically 0.5-1wt%, 1-1.5wt%, 1.5-2wt%, 2.5-3wt%, 3.5-4wt%, or 4.5-5wt%, based on the total weight of the mixed powder.

[0035] In one specific embodiment, the releasing agent is emulsified paraffin wax, and the amount of the releasing agent added is 0.1-2 wt%, such as 0.1-0.5 wt%, 0.5-1.0 wt%, 1.5-2 wt%, based on the total weight of the mixed powder.

[0036] In one specific embodiment, the dispersing medium is water, and the amount of the dispersing medium added is 35-100 wt%, such as 35-45 wt%, 45-55 wt%, 55-60 wt%, 60-70 wt%, 70-80 wt%, 80-90 wt%, 90-100 wt%, based on the total weight of the mixed powder.

[0037] In one specific embodiment, the particle size of the main material is 1-4 μm, such as 1-2 μm, 2-3 μm, 3-4 μm.

[0038] In one specific embodiment, in step 2), the particle size of the granular material is -40-+320 mesh.

[0039] In one specific embodiment, in step 2), before the spray granulation, the method further comprises a slurry impurity removal process.

[0040] In one specific embodiment, in step 3), the tonnage of the dry pressing forming is 5-10 T, such as 5-6 T, 6-7 T, 7-8 T, 8-9 T, 9-10 T.

[0041] In one specific embodiment, in step 3), the sintering temperature is 800-1200 °C, such as 800-850 °C, 850-900 °C, 900-1000 °C, 1000-1200 °C, and the holding time is 0.5-4 h.

[0042] In one specific embodiment, the slurry impurity removal process comprises a slurry filtration process and a slurry iron removal process; the slurry filtration process is to filter the mixed slurry by using a 40-mesh sieve or an 80-mesh sieve to remove the bulk impurities in the mixed slurry.

[0043] In one specific embodiment, the impurity removal process is iron removal.

[0044] The application also provides a specific barium titanate-based thermistor.

[0045] In one specific embodiment, the density of the barium titanate-based thermistor is ≥5.1 g / cm 3 .

[0046] In one specific embodiment, the Curie temperature of the barium titanate-based thermistor is 80-160°C, such as specifically 80-100°C, 100-120°C, 120-140°C, 140-160°C.

[0047] In one specific embodiment, the maximum voltage resistance of the barium titanate-based thermistor is 100-700V, such as specifically 100-200V, 200-400V, 400-600V, 600-700V.

[0048] The following specific examples illustrate the embodiments of the present application, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure of the present specification.

[0049] Example 1

[0050] The present example provides a preparation method of a barium titanate-based thermistor, comprising the following steps:

[0051] 1) Referring to the formula shown in Table 1, ceramic powder and sintering aid are mixed to obtain mixed powder, and the mixed powder, dispersant, binder and release agent are dispersed in a dispersion medium, wet ball-milled to obtain a mixed slurry; the ceramic powder comprises main material and additives, and the main material comprises BaCO3 and TiO2;

[0052] 2) The ball-milled slurry is passed through a 40-mesh screen to remove bulk impurities in the mixed slurry and remove iron; the mixed slurry after iron removal is spray granulated, and the obtained granulated powder is passed through 40-mesh and 320-mesh screens, and the powder between the two screens is collected to obtain granulated material;

[0053] 3) The granulated material is dry-pressed and formed, sintered (sintered size: diameter 16 mm, thickness 2 mm), and plated with electrodes to obtain a barium titanate-based thermistor.

[0054] Examples 2-5

[0055] Examples 2-5 differ from Example 1 in that the raw material component formula and part of the process conditions are different, and the specific see Table 1.

[0056] The properties of the barium titanate-based thermistors prepared in Examples 1-5 were detected, and the test method was as follows:

[0057] The density was determined according to the principle of Archimedes drainage method:

[0058] First, the fired thermistor substrate is placed in boiling water for 6 hours to open the internal pores, then the sample is removed and the float weight, wet weight and dry weight are measured separately. Finally, the density is calculated according to the formula listed below: p = m1*mliquid / m3-m2, where m1 is the dry weight of the sample; m3 is the saturated wet weight of the ceramic sample; m2 is the float weight of the sample in the test liquid, and mliquid is deionized water with a specific gravity of 1 g / cm 3 .

[0059] Room temperature resistance test conditions: Ta = 25 ± 0.5 °C Test voltage ≤ 1.5 V DC .

[0060] After standing for 1-2 hours at room temperature, the room temperature resistance is measured in the test temperature range.

[0061] Thermistors are prepared by plating electrodes on the surfaces of the thermistor substrates prepared in Examples 1-5, and the performance is tested:

[0062] Curie temperature: temperature point corresponding to 2*R25

[0063] Curie temperature experiment: (1) The thermistor is connected in series and welded on a PCB, and leads are connected to both ends of each thermistor;

[0064] (2) The thermistor is placed in an oven, and the leads are placed outside the oven;

[0065] (3) The temperature of the oven is raised to the lower limit of the Curie temperature minus 1 °C and maintained for 30 minutes, and the resistance of the thermistor is measured with a multimeter;

[0066] (4) The temperature of the oven is raised to the upper limit of the Curie temperature and maintained for 30 minutes, and the resistance of the thermistor is measured with a multimeter;

[0067] (5) Determine whether the initial resistance multiplied by 2 is within the range of resistance values measured at the upper and lower limit temperatures;

[0068] Note: During the test, the influence of air flow should be minimized.

[0069] Maximum voltage test

[0070] Before testing, measure the resistance of the thermistor. First, apply 220V AC voltage to both ends of the thermistor at room temperature for 3 seconds, then increase the voltage to its maximum withstand voltage value and maintain it for 30 seconds, without appearing to break down and arc, then disconnect the voltage, and measure the resistance of the thermistor after 3 hours, with a change in resistance within 5%.

[0071] The test results are shown in Table 1:

[0072] Table 1. Raw material component formulation and thermistor test results of Examples 1-5

[0073]

[0074]

[0075] In Table 1, PTC log (R250 / R25) represents the logarithm of the resistance of the PTC thermistor sample at 250°C divided by the resistance of the sample at 25°C.

[0076] In summary, the present application combines ceramic powder with other additives, and uses spray granulation and dry pressing forming process, reduces the sintering temperature of ceramic from 1300°C generally recognized in the industry to 800-1200°C, realizes low-temperature sintering to prepare barium titanate-based thermistor, greatly reduces the sintering cost, the process is simple, the energy consumption is low, and it is suitable for large-scale industrial production. Therefore, the present application effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0077] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

Claims

1. A method for producing a barium titanate-based thermistor, characterized by comprising the steps of: 3 ​ 1) mixing ceramic powder and sintering aids to obtain mixed powder, dispersing the mixed powder, dispersing agent, binder and release agent in a dispersion medium to obtain mixed slurry; the ceramic powder comprises main material and additives, and the main material comprises BaCO3 and TiO2; 2) spray granulating the mixed slurry to obtain granular material; 3) dry pressing the granular material, sintering, plating electrode, and obtaining barium titanate-based thermistor; The weight percentage of the main material is 80-99wt% based on the total weight of the mixed powder, and the sum of the weight percentage of the additives and sintering aids is 1-20wt%; The dispersing agent is polyacrylammonium, and the addition amount of the dispersing agent is 0.5-5wt% based on the total weight of the mixed powder; The binder is polyvinyl alcohol, and the addition amount of the binder is 0.5-5wt% based on the total weight of the mixed powder; The release agent is emulsified paraffin, and the addition amount of the release agent is 0.1-2wt% based on the total weight of the mixed powder; The dispersion medium is water, and the addition amount of the dispersion medium is 35-100wt% based on the total weight of the mixed powder; The additives are selected from one or more of SrCO3, PbO, Y2O3, Nb2O5, Sb2O3, MnCO3 and CuO; The sintering aids are selected from one or more of blast furnace slag, MgO, SiO2, CaCO3, Na2O, TiO2 and ZnO; The sintering temperature is 800-850℃.

2. The method of claim 1, wherein: The particle size of the main material is 1-4μm.

3. The method of claim 1, wherein: In step 2), the particle size of the granular material is-40-+320 mesh; and / or, before the spray granulation, the method further comprises a slurry impurity removal process; And / or, in step 3), the tonnage of dry pressing is 5-10T; And / or, the holding time is 0.5-4h.

4. The method of claim 3, wherein: The slurry impurity removal process comprises a slurry filtration process and a slurry iron removal process; the slurry filtration process is to filter the mixed slurry by using a 40-mesh or 80-mesh sieve.

5. A barium titanate-based thermistor prepared by the preparation method of any one of claims 1-4.

6. The barium titanate-based thermistor according to claim 5, characterized by: The density of the barium titanate-based thermistor is ≥ 5.1 g / cm 3 ; And / or, the Curie temperature of the barium titanate-based thermistor is 80-160℃; And / or, the maximum voltage resistance of the barium titanate-based thermistor is 100-700V.

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