Multilayer ceramic capacitor dielectric material and method of making same

Abstract

The application relates to the technical field of capacitors, in particular to a dielectric material for a multilayer ceramic capacitor and a preparation method thereof. The preparation method comprises the following steps: preparing a BaTiO3 suspension; adding Mg(Ac)2 into the BaTiO3 suspension first, then adding Mn(Ac)2, and then adding one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3 and Dy(Ac)3, and then mixing and roller grinding to obtain a mixed suspension; adjusting the pH value of the mixed suspension to 9-11 to obtain a precursor; drying the precursor, and then pre-sintering to obtain modified barium titanate powder; adding the modified barium titanate powder into water, and then adding other additives, and then stirring and dispersing to obtain the dielectric material. Through modification of the main dielectric material and optimization of the adding mode of the other additives, the dielectric material has high dielectric performance and high reliability.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, and in particular to a dielectric material for multilayer ceramic capacitors and its preparation method. Background Technology

[0002] Capacitors, along with inductors and resistors, are known as the three major passive components in electronic circuits. The main types of capacitors include multilayer ceramic capacitors, aluminum electrolytic capacitors, tantalum electrolytic capacitors, and film capacitors, with multilayer ceramic capacitors accounting for the largest share, approximately 80% of the total capacitor market. Multilayer ceramic capacitors (MLCCs), also known as monolithic capacitors, are currently the most widely used and abundant new type of surface-mount electronic component in the world. They feature high specific capacitance, high reliability, and good frequency characteristics, and are widely used in modern high-tech fields such as consumer electronics, industrial communications, and automotive applications. The performance requirements for MLCCs vary depending on the application scenario. With the rapid development of MLCC applications in industrial communications and automotive fields, the demand for high-performance, high-reliability MLCCs is becoming increasingly strong.

[0003] MLCCs are used in the communications industry and automotive systems, many of which operate at high temperatures (around 150°C). For example, in automotive control systems, components such as anti-lock braking systems (ABS), engine electronic control units (ECUs), crank angle sensors, air / fuel ratio control modules, and fuel injection program control (PGMFI) modules installed in the engine compartment all require MLCCs to operate within a temperature range of approximately 150°C. Simultaneously, many fields such as avionics, environmental monitoring, and automatic electronics require electronic systems to operate in extremely harsh environments. Electronic systems are used in various harsh environments. Under such demanding operating conditions, the reliability of electronic components determines the overall reliability of the electronic system; therefore, the requirements for the reliability of MLCCs are becoming increasingly stringent.

[0004] Many patented materials propose methods for preparing X8R-type dielectric materials that meet certain dielectric standards, but these methods suffer from problems such as low dielectric constants and low reliability, failing to meet the requirements of industrial and automotive-grade MLCC applications. For example, CN201710239911.3 describes obtaining a "core-shell" structure through surface coating with additives; this patent only indicates that the dielectric properties meet X8R characteristics but does not conduct reliability testing. CN202110915422.1 describes achieving a high dielectric constant that meets X8R characteristics by adding a eutectic of oxides of tantalum, cobalt, magnesium, nickel, and zirconium, but the insulation resistance of the resulting wafers is found to be low. Summary of the Invention

[0005] This invention provides a dielectric material for multilayer ceramic capacitors and its preparation method, addressing the shortcomings of existing X8R type dielectric materials, such as low dielectric constant and low reliability, which prevent them from meeting the requirements of industrial and automotive MLCC applications. To improve the dielectric constant of the X8R type dielectric material while meeting the reliability requirements of automotive MLCCs, this invention modifies the main dielectric material and optimizes the addition of other additives, achieving both high dielectric performance and high reliability.

[0006] This invention provides a method for preparing a dielectric material for multilayer ceramic capacitors, comprising the following steps:

[0007] Step S1: Prepare BaTiO3 suspension;

[0008] Step S2: First add Mg(Ac)2 to the BaTiO3 suspension, then add Mn(Ac)2, then add one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3, then mix and roll mill to obtain a mixed suspension;

[0009] Step S3: Add ammonia to the mixed suspension and adjust the pH to 9-11 to obtain the precursor;

[0010] Step S4: After drying the precursor, pre-sinter it to obtain modified barium titanate powder;

[0011] Step S5: Add the modified barium titanate powder to water, then add SiO2, Al2O3, BaCO3, one or more compounds selected from CaZrO3, ZrO2, and CaCO3, and one or more compounds selected from WO3, MoO3, and V2O5. After stirring the mixture, disperse it evenly with zirconia balls to obtain the medium material.

[0012] This invention discloses a method for preparing dielectric materials for multilayer ceramic capacitors. First, a BaBaTiO3 suspension is prepared. Then, Mg(Ac)2, Mn(Ac)2, and one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3 are sequentially added to the BaTiO3 suspension to prepare a mixed suspension. This feeding method is more conducive to obtaining highly reliable dielectric materials. Mg 2+ With Y 3+ Ho 3+ Rare earth ions can be synergistically doped to create a core-shell structure in BaTiO3, which is more conducive to product reliability. Firstly, Mg... 2+The rare earth ions do not diffuse into the interior of BaTiO3. Instead, they react with BaTiO3 at low temperatures to form a shell of Ba(TiMg)O3. The rare earth ions then react with this shell, preventing their diffusion into the interior of BaTiO3. This ensures the tetragonality of the product and is beneficial to the TCC characteristics of the dielectric material. Additionally, Mg... 2+ As a grain suppressant, doping with an appropriate amount of rare earth elements can yield fine-grained barium titanate ceramics, which possess a high dielectric constant and a gentle dielectric temperature profile. Mn 2+ As an acceptor dopant, it also helps to improve resistance to reduction, therefore, it is compatible with Mg. 2+ Rare earth ions are added together. The selection of these three elements first plays a crucial role in improving the reliability of the material while ensuring a high dielectric constant. The resulting mixed suspension is adjusted to pH 9-11, dried, and then pre-sintered to obtain modified barium titanate powder coated with MgO, MnO2, and rare earth oxides. Finally, the modified barium titanate powder is mixed with SiO2, Al2O3, BaCO3, one or more compounds selected from CaZrO3, ZrO2, and CaCO3, and one or more compounds selected from WO3, MoO3, and V2O5, stirred together, and then dispersed uniformly using zirconia balls to obtain the dielectric material. In this invention, adding SiO2 to the dielectric material can lower and broaden the sintering temperature range, while adding Al2O3 can improve sintering characteristics and insulation resistance. Adding one or more compounds selected from CaZrO3, ZrO2, and CaCO3 to the dielectric material can improve its high-temperature performance, enabling it to operate at temperatures above 150°C. The present invention adds one or more compounds selected from WO3, MoO3, and V2O5 to the dielectric material, which can increase the Curie temperature of the dielectric material and flatten the temperature coefficient of the capacitor, thereby improving the insulation resistance and average life.

[0013] According to the preparation method of the present invention, in step S2, Mg(Ac)2 is first added to the BaTiO3 suspension and stirred for more than 0.5 h, then Mn(Ac)2 is added and stirred for more than 0.5 h, then one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3 are added and stirred for more than 0.5 h, and then mixed and milled; the time for mixing and milling is 1 h to 3 h.

[0014] Optionally, the time of 0.5h or more can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, etc. The time of the mixing roller mill can be 1h, 1.5h, 2h, 2.5h or 3h, etc., and preferably, the time of the mixing roller mill is 2h.

[0015] In the above scheme, after each acetate is added to the BaTiO3 suspension, it is necessary to stir for more than 0.5 hours to ensure that the added acetate can be fully doped into BaTiO3 and participate in the reaction. If the stirring time after adding Mg(Ac)2 to BaTiO3 suspension is not sufficient, an effective Ba(TiMg)O3 shell may not be formed, which will not effectively block the subsequent diffusion of rare earth metal particles into the interior of BaTiO3, and thus cannot effectively guarantee the tetragonality of the product, which is not conducive to the TCC characteristics of the dielectric material.

[0016] According to the preparation method of the present invention, the molar proportions of each raw material used to prepare the dielectric material are as follows:

[0017] BaTiO3: 100 moles;

[0018] Mn(Ac)2: 0.01-0.6 molar parts;

[0019] Mg(Ac)2: 0.1-2.0 molar parts;

[0020] SiO2: 1.5-5.5 moles;

[0021] Al2O3: 0.1-1.5 moles;

[0022] One or more compounds selected from CaZrO3, ZrO2, and CaCO3: 0.7-4.0 molar parts;

[0023] BaCO3: 1.0-2.0 moles;

[0024] One or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, Dy(Ac)3: 0.1-4.5 molar parts;

[0025] One or more compounds selected from WO3, MoO3, and V2O5: 0.01-0.5 molar parts.

[0026] In the above scheme, the present invention reasonably limits the molar ratio of each raw material in the preparation of the dielectric material, and the raw materials work together to ensure that the obtained dielectric material has high reliability (4 times the working voltage, 150°C, 240h test with zero failure) while meeting the requirements of high dielectric constant (dielectric constant is 2200-2420).

[0027] According to the preparation method of the present invention, the molar proportions of each raw material used to prepare the dielectric material are as follows:

[0028] BaTiO3: 100 moles;

[0029] Mn(Ac)2: 0.1-0.6 moles;

[0030] Mg(Ac)2: 0.1-2.0 molar parts;

[0031] SiO2: 1.5-5.5 moles;

[0032] Al2O3: 0.1-1.5 moles;

[0033] One or more compounds selected from CaZrO3, ZrO2, and CaCO3: 1.0-4.0 molar parts;

[0034] BaCO3: 1.0-2.0 moles;

[0035] One or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, Dy(Ac)3: 2-4.5 molar parts;

[0036] One or more compounds selected from WO3, MoO3, and V2O5: 0.15-0.5 molar parts.

[0037] According to the preparation method of the present invention, the BaTiO3 is produced by hydrothermal method, and the particle size is 300nm-600nm.

[0038] In the above-described scheme, this invention specifies that BaTiO3 is produced using a hydrothermal method. BaTiO3 produced by the hydrothermal method has well-developed grains, minimal agglomeration, and no pores. Furthermore, the powder does not require high-temperature calcination, avoiding grain growth, defect formation, and impurity introduction caused during sintering. The absence of pores and fewer defects in the BaTiO3 grains contributes to the high reliability of the dielectric material. Selecting BaTiO3 with a particle size of 300nm-600nm can significantly improve the electrical performance and reliability of MLCC products.

[0039] According to the preparation method of the present invention, in step S1, the method for preparing the BaTiO3 suspension is as follows: dispersing BaTiO3 powder in a mixed solvent of ethanol and toluene.

[0040] In the above scheme, the method for preparing BaTiO3 suspension is to disperse BaTiO3 powder in a mixed solvent of ethanol and toluene. Ethanol and toluene can effectively disperse the agglomerated barium titanate, thereby obtaining a suspension with good dispersibility, which is beneficial to the subsequent dispersion of acetate.

[0041] According to the preparation method of the present invention, the volume ratio of ethanol to toluene in the mixed solvent is 1:1.

[0042] In the above scheme, limiting the volume ratio of ethanol to toluene in the mixed solvent to 1:1 can yield a suspension with better dispersibility.

[0043] According to the preparation method of the present invention, in step S4, the pre-sintering temperature is 400℃-800℃ and the time is 1.5h-3h.

[0044] Optionally, the pre-sintering temperature can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, etc., and the time can be 1.5h, 2h, 2.5h or 3h, etc.

[0045] In the above scheme, by limiting the pre-sintering temperature and time within a reasonable range, the obtained modified barium titanate powder can have excellent porosity, density, strength and hardness, thereby improving the performance of the modified barium titanate powder.

[0046] According to the preparation method of the present invention, in step S5, the dispersion rate of the zirconia spheres is 100 r / min-300 r / min, and the time is 1 h-3 h.

[0047] Optionally, the dispersion speed of the zirconia balls can be 100 r / min, 150 r / min, 200 r / min, 250 r / min or 300 r / min, etc., and the time can be 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc., preferably, the time is 2 h.

[0048] In the above scheme, by limiting the dispersion speed and time of zirconia balls within a reasonable range, it is possible to ensure that the powders are fully mixed, improve the dispersion efficiency, and make the resulting medium material have good uniformity.

[0049] The present invention also provides a dielectric material for multilayer ceramic capacitors, which is prepared by the above-described preparation method.

[0050] This invention provides a dielectric material for multilayer ceramic capacitors and its preparation method. By modifying the main dielectric material and optimizing the addition of other additives, the material achieves both high dielectric performance and high reliability requirements. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0052] Example

[0053] Prepare the raw materials according to the molar proportions of each raw material in Table 1 to prepare the media materials of Examples 1-24.

[0054] The preparation method of the dielectric material in Examples 1-24 specifically includes the following steps:

[0055] Step S1: Disperse BaTiO3 powder in a mixed solvent of ethanol and toluene with a volume ratio of 1:1 to obtain BaTiO3 suspension; BaTiO3 is produced by hydrothermal method and has a particle size of 400nm.

[0056] Step S2: First, add Mg(Ac)2 to the BaTiO3 suspension and stir for 1.5 h, then add Mn(Ac)2 and stir for 1.5 h, then add one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3 and stir for 1.5 h, then mix and roll mill for 2 h to obtain a mixed suspension.

[0057] Step S3: Add ammonia to the mixed suspension and adjust the pH to 9-11 to obtain the precursor;

[0058] Step S4: After drying the precursor, pre-sinter it to obtain modified barium titanate powder; the pre-sintering temperature is 600℃ and the time is 3h.

[0059] Step S5: Add modified barium titanate powder to pure water at a weight ratio of 1:1, then add SiO2, Al2O3, BaCO3, one or more compounds selected from CaZrO3, ZrO2, and CaCO3, and one or more compounds selected from WO3, MoO3, and V2O5. After stirring the mixture, disperse it evenly with zirconia balls at a speed of 100 r / min-300 r / min for 2 hours to obtain the medium material.

[0060] Table 1. Molar proportions of each raw material in preparation examples 1-24

[0061]

[0062]

[0063] The obtained dielectric material was used to fabricate MLCCs of specific specifications according to the commonly used MLCC manufacturing process: paste preparation → casting → screen printing → lamination → cutting → debinding → sintering → chamfering → end sealing → end burning, etc. The product specification is 0805C223J500N, with a dielectric layer thickness of 8μm. Nickel inner paste was used for screen printing. The product was sintered in a reducing atmosphere at 1280℃. After chamfering, copper outer electrodes were sealed at both ends of the product. The copper electrodes were heat-treated in a nitrogen protective atmosphere at 800℃. After that, the relevant electrical properties can be tested.

[0064] Under ambient temperature (25℃) and RH (45-65%), the capacitance (C) and dielectric loss (DF) of MLCCs were tested using an Agilent 4284A bridge at 1kHz and 1Vrm. The dielectric constant was calculated based on the dielectric layer thickness, effective electrode area, wire mesh coefficient, number of dielectric layers, and capacitance. The insulation resistance (IR) of the MLCCs was tested using a TH2683 insulation resistance tester at 50VDC for 60 seconds. The withstand voltage (BDV) of the MLCCs was tested using a CJ2671S withstand voltage tester at a charging current <20mA and a voltage application rate of 200V / 60s. The temperature coefficient (TCC) of the MLCCs was tested using a high and low temperature test chamber between -55℃ and 150℃. The aging performance (HALT) of the MLCCs was tested using an aging test chamber at 150℃ and 4 times the operating voltage for 240 hours. Forty samples were tested in each group, and the IR value was set at 10. 8 Samples with an Ω or lower were considered as failures, and the number of failures in each group of 40 samples was used as the evaluation result of aging performance; Table 2 is a table of MLCC performance parameters made from the dielectric materials of Examples 1-24 above.

[0065] Table 2 Performance parameters of MLCCs made from dielectric materials in Examples 1-24

[0066]

[0067] As can be seen from the experimental data in Table 2, the dielectric material prepared by the preparation method of the present invention has a high dielectric constant and high reliability, and can work under high temperature conditions above 150°C.

[0068] Comparative Example 1

[0069] The preparation method of the dielectric material in this comparative example differs from that in Example 13 in the following ways:

[0070] Step S2: First, add one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3 to the BaTiO3 suspension and stir for 1.5 h. Then add Mg(Ac)2 and stir for 1.5 h. Next, add Mn(Ac)2 and stir for 1.5 h. Finally, mix and roll mill for 2 h to obtain a mixed suspension.

[0071] Comparative Example 2

[0072] The preparation method of the dielectric material in this comparative example differs from that in Example 13 in the following ways:

[0073] Step S2: First, add Mg(Ac)2 to the BaTiO3 suspension and stir for 15 min, then add Mn(Ac)2 and stir for 15 min, then add one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3 and stir for 15 min, then mix and roll mill for 2 h to obtain a mixed suspension.

[0074] Comparative Example 3

[0075] The preparation method of the dielectric material in this comparative example differs from that in Example 13 in the following ways:

[0076] In step S5, the amount of CaZrO3 added is 0.

[0077] Comparative Example 4

[0078] The preparation method of the dielectric material in this comparative example differs from that in Example 13 in the following ways:

[0079] In step S5, the amount of CaZrO3 added is 0.35 mol.

[0080] The dielectric materials obtained in Comparative Examples 1-4 were subjected to relevant electrical performance tests, and the test results are shown in Table 3 below.

[0081] Table 3. Performance parameters of MLCCs made from the dielectric materials obtained in Example 13 and Comparative Examples 1-4.

[0082]

[0083] Referring to the experimental results in Table 3, it can be seen from the experimental results of Example 13 and Comparative Example 1 that the order of adding each acetate in step S2 of the preparation method of the dielectric material for multilayer ceramic capacitors of the present invention is very important. Strictly following the present invention, adding Mg(Ac)2 first, then Mn(Ac)2, and then adding one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3 results in a dielectric material with high dielectric constant and high reliability. However, changing the order of addition will affect the reliability of the dielectric material. It can also be seen from the experimental results of Example 13 and Comparative Example 2 that the stirring time after adding each acetate in step S2 of the preparation method of the dielectric material for multilayer ceramic capacitors of the present invention is very important. When the stirring time is less than 0.5 h, the dielectric constant and reliability of the obtained dielectric material both decrease. As can be seen from the experimental results of Example 13 and Comparative Examples 3 and 4, adding one or more compounds of CaZrO3, ZrO2, and CaCO3 during the preparation of the dielectric material of the present invention is beneficial to improving the high-temperature working performance of the dielectric material.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a dielectric material for a multilayer ceramic capacitor, characterized by, Includes the following steps: Step S1: Prepare BaTiO3 suspension; Step S2: First add Mg(Ac)2 to the BaTiO3 suspension, then add Mn(Ac)2, then add one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3, then mix and roll mill to obtain a mixed suspension; Step S3: Add ammonia to the mixed suspension and adjust the pH to 9-11 to obtain the precursor; Step S4: After drying the precursor, pre-sinter it to obtain modified barium titanate powder; Step S5: Add the modified barium titanate powder to water, then add SiO2, Al2O3, BaCO3, one or more compounds selected from CaZrO3, ZrO2, and CaCO3, and one or more compounds selected from WO3, MoO3, and V2O5. After stirring the mixture, disperse it evenly with zirconia balls to obtain the medium material. In step S2, Mg(Ac)2 is first added to the BaTiO3 suspension and stirred for more than 0.5 hours, then Mn(Ac)2 is added and stirred for more than 0.5 hours, and then one or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, and Dy(Ac)3 are added and stirred for more than 0.5 hours, and then mixed and milled; the time for mixing and milling is 1 hour to 3 hours.

2. The production method according to claim 1, characterized by, The molar proportions of each raw material used to prepare the dielectric material are as follows: BaTiO3: 100 moles; Mn(Ac)2: 0.01-0.6 molar parts; Mg(Ac)2: 0.1-2.0 molar parts; SiO2: 1.5-5.5 moles; Al2O3: 0.1-1.5 moles; One or more compounds selected from CaZrO3, ZrO2, and CaCO3: 0.7-4.0 molar parts; BaCO3: 1.0-2.0 moles; One or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, Dy(Ac)3: 0.1-4.5 molar parts; One or more compounds selected from WO3, MoO3, and V2O5: 0.01-0.5 molar parts.

3. The preparation method according to claim 1, characterized in that, The molar proportions of each raw material used to prepare the dielectric material are as follows: BaTiO3: 100 moles; Mn(Ac)2: 0.1-0.6 moles; Mg(Ac)2: 0.1-2.0 molar parts; SiO2: 1.5-5.5 moles; Al2O3: 0.1-1.5 moles; One or more compounds selected from CaZrO3, ZrO2, and CaCO3: 1.0-4.0 molar parts; BaCO3: 1.0-2.0 moles; One or more compounds selected from Y(Ac)3, Ho(Ac)3, Er(Ac)3, Yb(Ac)3, Gd(Ac)3, Dy(Ac)3: 2-4.5 molar parts; One or more compounds selected from WO3, MoO3, and V2O5: 0.15-0.5 molar parts.

4. The method of claim 1, wherein, The BaTiO3 is produced by a hydrothermal method, and the particle size is between 300nm and 600nm.

5. The preparation method according to claim 1, characterized in that, In step S1, the method for preparing the BaTiO3 suspension is as follows: disperse the BaTiO3 powder in a mixed solvent of ethanol and toluene.

6. The production method according to claim 5, wherein In the mixed solvent, the volume ratio of ethanol to toluene is 1:

1.

7. The preparation method according to claim 1, characterized in that, In step S4, the pre-sintering temperature is 400℃-800℃ and the time is 1.5h-3h.

8. The method of claim 1, wherein, In step S5, the zirconium oxide spheres are dispersed at a rate of 100 r / min to 300 r / min for a time of 1 h to 3 h.

9. A dielectric material for a multilayer ceramic capacitor, characterized by, It is prepared by the preparation method according to any one of claims 1-8.

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