A ceramic dielectric material and a COG type multilayer ceramic capacitor

Abstract

The present invention provides a ceramic dielectric material and a COG type multilayer ceramic capacitor. The ceramic dielectric material includes a main crystal phase component, a modifying additive, and a sintering aid. The main crystal phase component is xCaZrO3 + ySrZrO3, where 1 ≤ x / y ≤ 20. The modifying additive includes Re2O3, and one or more of MnCO3, Al2O3, SrCO3, MgTiO3, and CaTiO3. Re is at least one rare earth element selected from Y, Ho, Yb, Gd, Dy, Sm, Nd, and Er. By selecting the material components, the present invention ensures that the material has excellent dielectric properties and reliability, and enables the material to match with nickel electrodes, sinter in a reducing atmosphere and at a low temperature, effectively inhibits grain growth, makes the grains fine, uniform, and dense, is beneficial to improving the reliability and thinning of products, and finally obtains a ceramic dielectric material that can be used for COG type multilayer ceramic capacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-layer ceramic capacitors, and particularly to a ceramic dielectric material and a COG type multi-layer ceramic capacitor. Background Art

[0002] Capacitors are one of the electronic components widely used in electronic devices, with a wide range of applications, large usage amounts, and irreplaceability. With the rapid development of electronic technology, the emergence and development of new electronic products represented by mobile phones, flat panel displays, automotive electronics, etc. have brought good opportunities for the development of capacitors. As an important part of capacitors, multi-layer ceramic capacitors (abbreviated as MLCC) are favored due to many advantages such as small volume, high insulation resistance, and low inductance, and are particularly suitable for improving circuit assembly density and reducing the volume of the whole machine, which makes MLCC one of the components with the largest usage amount and relatively fast development. With the rapid development of the miniaturization and high performance of electrical and electronic devices, the multi-layer ceramic capacitors used in these devices also face requirements for small size and high reliability. That is, it is required that the dielectric layer thickness of the multi-layer ceramic capacitor becomes thinner and thinner while maintaining other performance undiminished, which is undoubtedly a greater challenge.

[0003] In order to achieve a large capacitance, on the one hand, the dielectric material is required to have a high dielectric constant, and on the other hand, the sintered crystal grains need to be small, thereby reducing the thickness of the MLCC dielectric layer and increasing the number of dielectric layers. CN105174947A discloses a COG dielectric ceramic material for low-temperature sintering thin dielectric multi-layer ceramic capacitors, which contains a main component and additives. The main component is: (Ca 1-x Sr x ) z Zr y O3, where 0.2 ≤ x ≤ 0.4, 0.90 ≤ y ≤ 1.0, 0.985 ≤ z ≤ 1.003; the additive components: at least two or several compounds among Al2O3, MnCO3, MgO, TiO2, SiO2, BaCO3, ZnO; it can be seen from the SEM picture of the fired ceramic body surface that the average grain size of the fired ceramic body is about 700nm, and the maximum grain size < 2μm. After firing, the grain size is large, and it is impossible to prepare an MLCC with a thickness below 3μm, the dielectric layer cannot be thinned, and a large capacitance cannot be achieved. CN102964122A discloses a dielectric ceramic composition and a method for manufacturing electronic components thereof. The dielectric ceramic composition includes a main crystal phase, a modifying additive, and a sintering aid. The structural formula of the main crystal phase is (Mg γ Sr α Ca (1-α-γ) ) m (Ti β Zr 1-β)O3, where 0 ≤ α ≤ 1, 0 ≤ γ ≤ 1, 0 ≤ β ≤ 0.1, 0.9 ≤ m ≤ 1.1, the modifying additive is one or more of MnCO3, MgCO3, Re2O3, where Re2O3 is a rare earth oxide, and the sintering aids include one or more of BaCO3, CaCO3, SiO2, Li2CO3, B2O3, Al2O3, but its dielectric constant is only 20 - 30, which is relatively low and cannot achieve a large capacitance. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a ceramic dielectric material and a COG type multilayer ceramic capacitor.

[0005] The present invention provides a ceramic dielectric material, including a main crystal phase component, a modifying additive, and a sintering aid. The main crystal phase component is xCaZrO3 + ySrZrO3, where 1 ≤ x / y ≤ 20; the modifying additive includes Re2O3, and one or more of MnCO3, Al2O3, SrCO3, MgTiO3, CaTiO3, where Re is at least one rare earth element selected from Y, Ho, Yb, Gd, Dy, Sm, Nd, and Er.

[0006] The ceramic dielectric material of the present invention uses xCaZrO3 + ySrZrO3 as the main crystal phase component, adds specific modifying additives and sintering aids, and through the selection of the main crystal phase component and the composition of the additive material, ensures that the dielectric constant of the ceramic dielectric material is maintained between 32 and 40, and the dielectric loss is less than 4×10 -4 , the insulation resistance at 25°C > 10×10 11 Ω, the insulation resistance at 125°C > 1×10 10 Ω, and the temperature characteristics in the temperature range of -55°C to 125°C meet the COG characteristics of the EIA standard. By mixing the main crystal phase, the modifying additive, and the sintering aid and then performing wet mixing and dispersion, drying, and then adopting a calcination treatment method, it is beneficial to improve the mixing uniformity of the main crystal phase and the additive, and is beneficial to improving the dielectric properties and reliability of the product, so as to be applicable to the ceramic dielectric material of the COG type multilayer ceramic capacitor.

[0007] Further, 10 ≤ x / y ≤ 15 in the main crystal phase component.

[0008] Further, the modifying additive is composed of MnCO3, Al2O3, SrCO3, MgTiO3, CaTiO3, and Re2O3, and the molar ratio of each component is (1.5 - 3.5):(0.3 - 0.7):(0.2 - 1.0):(0.1 - 0.3):(0.5 - 2.5):(0.2 - 0.66).

[0009] Further preferably, the Re2O3 is Y2O3.

[0010] Further, the sintering aid is a mixture of SiO2, H3BO3 and ZnO. By adding the above sintering aid, the ceramic dielectric material can be matched with the nickel electrode, sintered in a reducing atmosphere and at a low temperature, effectively inhibiting grain growth, making the grains fine, uniform and dense, and having a high dielectric strength, which is beneficial to improving the reliability and thinning of the product.

[0011] Further, the molar ratio of SiO2, H3BO3, ZnO in the sintering aid is (0.5 - 3.0):(0.2 - 0.7):(0.5 - 3.5).

[0012] Further, the molar ratio of the main crystal phase component, the modification additive and the sintering aid is 100:(2.5 - 6.5):(1.0 - 3.5). That is, calculated by the amount of substance, the main crystal phase is 100 mol, the modification additive is 2.5 - 6.5 mol, and the addition amount of the sintering aid is 1.0 - 3.5 mol. Within the above dosage range, the effective dosage of the main crystal phase can be guaranteed, and thus the overall performance of the material can be guaranteed.

[0013] Further, the main crystal phase component is obtained by a solid-phase method.

[0014] In a preferred embodiment of the present invention, the solid-phase method specifically includes the following steps:

[0015] Select CaCO3 and ZrO2 with a purity of more than 99.5%, weigh according to the composition ratio of CaZrO3, and the calcination temperature is 1000 - 1080 °C to obtain 100 - 200 nm CaZrO3; select SrCO3 and ZrO2 with a purity of more than 99.5%, weigh according to the composition ratio of SrZrO3, and the calcination temperature is 1000 - 1100 °C to obtain 100 - 200 nm SrZrO3; then weigh these two main crystal phases according to x / y in xCaZrO3 + ySrZrO3, and add the corresponding additives for subsequent operations.

[0016] Further, the average particle size of the main crystal phase component is 100 - 200 nm.

[0017] The present invention also provides a preparation method of the above ceramic dielectric material, including: wet-mixing and dispersing the main crystal phase component, the modification additive and the sintering aid, drying, and calcining.

[0018] The present invention conducts wet mixing and dispersion on the main crystal phase, modified additive, and sintering aid, followed by drying, and then adopts a calcination treatment method, which is beneficial to improving the mixing uniformity of the main crystal phase and the additive, and is beneficial to improving the dielectric properties and reliability of the product, thus being applicable to the ceramic dielectric material of COG type multilayer ceramic capacitors.

[0019] Further, the temperature of the calcination is 800 - 1000 °C.

[0020] The present invention also provides a COG type multilayer ceramic capacitor, including the above-mentioned ceramic dielectric material. Preferably, the inner electrode of the COG type multilayer ceramic capacitor is a nickel electrode.

[0021] The dielectric material of the present invention conforms to the COG characteristics of the EIA standard, with uniform material particles, narrow particle size distribution, and excellent dielectric properties. Applying this dielectric material to manufacture MLCC, matching with nickel inner electrodes, after sintering, the grains on the surface of the porcelain body are small, with an average grain size of about 250 nm. The cross-section of the porcelain body is uniform and dense, suitable for manufacturing thin dielectric, large-capacity, and high-reliability MLCC products.

[0022] The present invention provides a ceramic dielectric material and a COG type multilayer ceramic capacitor. By selecting the main crystal phase composition and adding modified additives and sintering aids, it is ensured that the material has excellent dielectric properties and the grain size of the grains on the surface of the porcelain body is superior to the prior art level (average grain size 250 nm, prior grain level 600 - 700 nm). Through the powder preparation process and calcination process treatment, the material has high reliability. The material can be matched with nickel electrodes, sintered in a reducing atmosphere and at a low temperature, effectively inhibiting grain growth, making the grains small, uniform, and dense, with high dielectric strength, which is beneficial to improving the reliability and thin-layerization of the product. Finally, a ceramic dielectric material applicable to COG type multilayer ceramic capacitors is obtained, and the material of the present invention does not contain harmful elements such as Pd, meeting the requirements of EU ROHS. Description of the Drawings

[0023] Figure 1 It is the SEM image of the ceramic dielectric material obtained in Example 10 of the present invention;

[0024] Figure 2 It is the SEM image of the surface of the MLCC made of the ceramic dielectric material in Example 10 of the present invention;

[0025] Figure 3 It is the SEM image of the cross-section of the MLCC made of the ceramic dielectric material in Example 10 of the present invention. Detailed Embodiments

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following describes the technical solutions in the embodiments of the present invention clearly and completely. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0027] For the raw materials and auxiliary materials involved in the following embodiments, unless otherwise specified, they can all be purchased commercially.

[0028] Examples 1 to 32

[0029] This embodiment provides a ceramic dielectric material, which is composed of a main crystal phase (xCaZrO3 + ySrZrO3, x / y = 10), a modification additive, and a sintering aid. The specific formula is shown in Table 1.

[0030] Table 1 Composition Table of Main Crystal Phase, Modification Additive, and Sintering Aid

[0031]

[0032]

[0033] The preparation methods of the ceramic dielectric materials in the above embodiments are as follows:

[0034] (1) Preparation of the main crystal phase components: Select raw materials of CaCO3, SrCO3, and ZrO2 with a purity of more than 99.5%, weigh them according to the composition ratios of CaZrO3 and SrZrO3 respectively, calcine them separately to obtain CaZrO3 and SrZrO3, and then weigh CaZrO3 and SrZrO3 according to the molar ratio of x / y and set aside.

[0035] (2) Preparation of the ceramic dielectric material: Wet-mix and disperse the main crystal phase, modification additive, and sintering aid obtained in the previous step, dry them, and then calcine the dried mixture at 900°C to obtain the ceramic dielectric material.

[0036] Example 33

[0037] This embodiment provides a ceramic dielectric material, whose main crystal phase is xCaZrO3 + ySrZrO3, x / y = 1. Its formula is 100 mol of the main crystal phase, 2 mol of MnCO3, 0.7 mol of Al2O3, 0.8 mol of SrCO3, 0.2 mol of MgTiO3, 2.0 mol of CaTiO3, 0.66 mol of Y2O3, and sintering aids ZnO 0.8 mol, H3BO3 0.6 mol, and SiO2 1.7 mol.

[0038] Example 34

[0039] This embodiment provides a ceramic dielectric material, whose main crystal phase is xCaZrO3 + ySrZrO3, x / y = 5. Its formula is 100 mol of the main crystal phase, 2 mol of MnCO3, 0.7 mol of Al2O3, 0.8 mol of SrCO3, 0.2 mol of MgTiO3, 2 mol of CaTiO3, 0.66 mol of Y2O3, and sintering aids ZnO 0.8 mol, H3BO3 0.6 mol, SiO2 1.7 mol..

[0040] Example 35

[0041] This embodiment provides a ceramic dielectric material, whose main crystal phase is xCaZrO3 + ySrZrO3, x / y = 15. Its formula is 100 mol of the main crystal phase, 2 mol of MnCO3, 0.7 mol of Al2O3, 0.8 mol of SrCO3, 0.2 mol of MgTiO3, 2 mol of CaTiO3, 0.66 mol of Y2O3, and sintering aids ZnO 0.8 mol, H3BO3 0.6 mol, SiO2 1.7 mol..

[0042] Example 36

[0043] This embodiment provides a ceramic dielectric material, whose main crystal phase is xCaZrO3 + ySrZrO3, x / y = 20. Its formula is 100 mol of the main crystal phase, 2 mol of MnCO3, 0.7 mol of Al2O3, 0.8 mol of SrCO3, 0.2 mol of MgTiO3, 2 mol of CaTiO3, 0.66 mol of Y2O3, and sintering aids ZnO 0.8 mol, H3BO3 0.6 mol, SiO2 1.7 mol.

[0044] Example 37

[0045] This embodiment provides a ceramic dielectric material, whose main crystal phase is xCaZrO3 + ySrZrO3, x / y = 10. Its formula is 100 mol of the main crystal phase, 2 mol of MnCO3, 0.7 mol of Al2O3, 0.8 mol of SrCO3, 0.2 mol of MgTiO3, 2 mol of CaTiO3, 0.66 mol of Ho2O3, and sintering aids ZnO 0.8 mol, H3BO3 0.6 mol, SiO2 1.7 mol.

[0046] Example 38

[0047] This embodiment provides a ceramic dielectric material, whose main crystal phase is xCaZrO3 + ySrZrO3, where x / y = 10. Its formulation is 100 mol of the main crystal phase, 2 mol of MnCO3, 0.7 mol of Al2O3, 0.8 mol of SrCO3, 0.2 mol of MgTiO3, 2 mol of CaTiO3, 0.7 mol of Dy2O3, and 0.8 mol of sintering aid ZnO, 0.6 mol of H3BO3, and 1.7 mol of SiO2.

[0048] Example 39

[0049] This embodiment provides a ceramic dielectric material, whose main crystal phase is xCaZrO3 + ySrZrO3, where x / y = 10. Its formulation is 100 mol of the main crystal phase, 2 mol of MnCO3, 0.7 mol of Al2O3, 0.8 mol of SrCO3, 0.2 mol of MgTiO3, 2 mol of CaTiO3, 0.7 mol of Er2O3, and 0.8 mol of sintering aid ZnO, 0.6 mol of H3BO3, and 1.7 mol of SiO2.

[0050] Experimental example

[0051] According to the common MLCC preparation process flow: slurry preparation → tape casting → screen printing → lamination → pressing → cutting → debinding → sintering → chamfering → end capping → end firing, etc., MLCC is prepared; the product specification is 0805C223J500N, the thickness of the dielectric layer is 3 μm, nickel internal paste is used for screen printing during screen printing, the product is sintered in a reducing atmosphere at 1160 °C, copper external electrodes are sealed at both ends of the product after chamfering, and the copper electrodes are heat treated in a nitrogen protection atmosphere at 800 °C, and then relevant electrical properties can be detected.

[0052] Under the conditions of room temperature 25 °C and 45 - 65% RH, the capacitance C and dielectric loss DF of the MLCC are tested using an Agilent 4284A bridge at 1 MHz and 1 Vrms. The dielectric constant is calculated based on the thickness of the dielectric layer, the effective electrode area, the screen factor, the number of dielectric layers, and the capacitance; the insulation resistance IR of the MLCC is tested using a TH2683 insulation resistance tester at 50 VDC and 60 S; the breakdown voltage BDV of the MLCC is tested using a CJ2671S breakdown voltage tester under the conditions of charging current < 20 mA and applied voltage speed 200 V / 60 S; the temperature coefficient TCC of the MLCC is tested using a high and low temperature test chamber between -55 °C and 125 °C; the aging performance HALT of the MLCC under 500 H is tested using an aging test chamber at 125 °C and 4 times the working voltage. 40 samples are tested in each group. Samples with an IR value below 106 Ω are set as failed, and the number of failed samples in each group of 40 samples is used as the evaluation result of the aging performance.

[0053] Table 2 shows the performance parameter table of MLCCs prepared from the dielectric materials of Examples 1-39 respectively.

[0054] Figure 1 It is the SEM image of the ceramic dielectric material in Example 10; Figure 2 It is the SEM image of the surface of the MLCC prepared from the dielectric material of Application Example 10; Figure 3 It is the SEM image of the cross-section of the MLCC prepared from the dielectric material of Application Example 10.

[0055] Performance parameter table of MLCCs prepared from the dielectric materials in Table 2

[0056]

[0057]

[0058] From the above results, it can be seen that by controlling the addition amounts of the respective components, dielectric materials with excellent dielectric properties and aging properties can be obtained. Using the dielectric materials of the present invention to manufacture MLCCs and matching with nickel inner electrodes, after sintering, the grains are small, uniform and dense, which are suitable for manufacturing thin dielectric, large-capacity and high-reliability MLCC products.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ceramic dielectric material, characterized in that, It includes a main crystal phase component, a modification additive and a sintering aid. The main crystal phase component is xCaZrO3 + ySrZrO3, where 1 ≤ x / y ≤ 20. The main crystal phase component is obtained by a solid-phase method. The average particle size of the main crystal phase component is 100 - 200 nm. The modification additive consists of MnCO3, Al2O3, SrCO3, MgTiO3, CaTiO3 and Re2O3, and the molar ratio of each component is (1.5 - 3.5):(0.3 - 0.7):(0.2 - 1.0):(0.1 - 0.3):(0.5 - 2.5):(0.2 - 0.66). Among them, Re is at least one rare earth element selected from Y, Ho, Yb, Gd, Dy, Sm, Nd and Er. The sintering aid is a mixture of SiO2, H3BO3 and ZnO. Among them, the molar ratio of SiO2, H3BO3, ZnO is (0.5 - 3.0):(0.2 - 0.7):(0.5 - 3.5).

2. The ceramic dielectric material according to claim 1, characterized in that, The Re2O3 is Y2O3.

3. The ceramic dielectric material according to claim 1 or 2, characterized in that, The molar ratio of the main crystal phase component, the modification additive and the sintering aid is 100:(2.5 - 6.5):(1.0 - 3.5).

4. The preparation method of the ceramic dielectric material according to any one of claims 1-3, characterized in that, It includes: Wet-mix and disperse the main crystal phase component, the modification additive and the sintering aid, dry, and calcine.

5. The preparation method of the ceramic dielectric material according to claim 4, characterized in that, The temperature of the calcination is 800 - 1000 °C.

6. A COG type multilayer ceramic capacitor, characterized in that, It includes the ceramic dielectric material according to any one of claims 1 - 5.

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