A C0G dielectric ceramic material with high dielectric constant and high temperature stability and its preparation method and application

Abstract

The present invention relates to the field of dielectric material technology, and specifically to a C0G dielectric ceramic material with high dielectric constant and high temperature stability, its preparation method, and application. The material comprises the following raw materials in parts by mass: 100 parts by mass of a powder system, 0.5-3 parts by mass of a dispersant, 18-25 parts by mass of a solvent, and 20-25 parts by mass of a binder. The powder system is prepared from 98 parts by mass of a main powder and 2 parts by mass of a formula powder system; the main powder comprises the following components in percentage by mass: 40-58% SrTiO3 powder and 40-58% CaTiO3 powder. The dielectric ceramic material provided by the present invention has a dielectric constant of up to 110, and a capacitance-temperature characteristic of up to (±20) ppm / °C in the range of -55°C to 125°C. Based on this dielectric ceramic material, a finished MLCC is obtained through our company's related preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric materials, and in particular to a COG dielectric ceramic material with high dielectric constant and high temperature stability, and a preparation method and application thereof. Background Art

[0002] Multilayer ceramic capacitors (MLCCs), composed of dielectric layers, interlaced inner and outer electrodes, are an important passive component used in virtually all electronic fields. The latest trends in MLCCs are high capacitance, miniaturization, high-frequency applications, high reliability, and low cost. The rapid development of mobile and satellite communications systems, in particular, has placed higher demands on microwave-band MLCCs. With the advancement of millimeter-wave technology, the application frequency range of RF MLCCs has gradually shifted from a few hundred kHz to a few hundred MHz, and their use in both military and civilian fields will become increasingly prominent. C0G ceramic material, with its low loss, excellent frequency and temperature stability, and superior insulation properties, is a key foundational material for achieving high reliability in RF MLCCs.

[0003] At present, the dielectric constant of C0G ceramic capacitors is relatively small, generally not exceeding 100. A higher dielectric constant can achieve a more certain capacitance value with a thinner dielectric layer, so as to meet the increasing functional density requirements of complex electronic products in the current small volume context. Among the dielectric materials with a dielectric constant exceeding 100, some are based on the bismuth-based pyrochlore system. The intrinsic dielectric loss of pyrochlore materials is high, and they contain too much bismuth elements, which has the problem of element volatilization and alloying; some are ceramic materials based on the BaO-Ln2O3-TiO2 system (referred to as BLT system) with a tungsten bronze structure, in which Ln2O3 is mainly La2O3, Sm2O3, and Nd2O3; and some are CaTiO3 and its modified ceramics and CaO-Li2O-Ln2O3-TiO2 and its modified ceramics. Although there are literature reports of 0.4CaTiO3–0.6(Li2O3) with a dielectric constant as high as 245 and a frequency temperature coefficient close to zero, the dielectric constant of 0.4CaTiO3–0.6(Li2O3) is not as high as 245. 0.5 La 0.5 )TiO3 ceramics, but the dielectric temperature coefficient of this ceramic is relatively high, reaching ±70ppm / ℃, which does not meet the C0G standard.

[0004] In the actual use environment of MLCC products, changes in capacitance often lead to changes in the state of the electronic system in which they are used. With the rapidly developing millimeter-wave technology, whose signal frequencies can reach tens of GHz, signal deviations of tens of ppm can cause changes in the overall operating frequency band of the system. A common example is the large temperature difference between day and night in northwest my country, which can reach 60°C. Microwave dielectric ceramic materials with a capacitance-temperature characteristic of C0G can have a capacitance-temperature characteristic extreme of up to 60ppm / °C within the operating temperature range. However, this is not suitable for current use environments and will significantly challenge the lifespan of communication systems.

[0005] Therefore, it makes sense to develop dielectric ceramic materials with better temperature stability by changing the material properties on the basis of improving the dielectric constant of C0G materials. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a COG dielectric ceramic material with high dielectric constant and high temperature stability, as well as its preparation method and application, to solve the problem of increasing the dielectric constant in high-frequency microwave dielectric ceramic materials while failing to further maintain or reduce the dielectric loss of the ceramic.

[0007] Based on the above objectives, the present invention provides a C0G dielectric ceramic material with high dielectric constant and high temperature stability, comprising the following raw materials in parts by mass: 100 parts by mass of a powder system, 0.5-3 parts by mass of a dispersant, 18-25 parts by mass of a solvent, and 20-25 parts by mass of a binder, wherein the powder system is prepared from 98 parts by mass of a main powder and 2 parts by mass of a formula powder system; the main powder comprises the following components in percentage by mass: 40-58% SrTiO3 powder and 40-58% CaTiO3 powder; the formula powder system comprises the following components in percentage by mass: 0.1-0.4% ZrO2 powder, 0.2-0.8% MgO powder, 0.2-0.6% Bi2O3 powder, 0.2-0.8% MnO powder, 0.2-0.4% SiO2 powder, and 0.05-0.15% B2O3 powder 。

[0008] The main powder is obtained by pre-sintering SrCO3, CaCO3 and TiO2 in a mass ratio of 1:1:2, the pre-sintering temperature is 1100-1200°C, and the pre-sintering time is 3-6h.

[0009] The dielectric constant temperature coefficient of the C0G type dielectric ceramic material is -20 to 20 ppm / °C.

[0010] The present invention also provides a method for preparing the COG dielectric ceramic material having high dielectric constant and high temperature stability, comprising the following steps:

[0011] S1. SrCO3, CaCO3 and TiO2 are taken in a proportion, synthesized by a solid phase method, and pre-sintered into a SrTiO3 matrix and a CaTiO3 matrix with an average particle size of 200nm to 400nm, thereby obtaining a main powder. The pre-sintering temperature is 1100-1200°C, and the pre-sintering time is 3-6h.

[0012] S2. Mix the main powder and the formula powder according to the proportion, and then ball mill and dry to obtain a mixture;

[0013] S3, mixing the mixture with a binder, granulating to obtain a semi-finished product, and then tableting and debinding to obtain a ceramic green body;

[0014] S4. Sintering the ceramic green body to obtain a COG dielectric ceramic material.

[0015] The ball milling in S2 is wet ball milling, the rotation speed of the ball milling is 40 to 60 r / min, and the time is 6 hours to 24 hours.

[0016] The dispersant used in the wet ball milling includes polyethylene oxide resin, and the solvent includes ethanol, toluene and isopropanol; the grinding balls used are 1mm zirconium balls. The dispersant is used to disperse the ceramic powder particles to prevent agglomeration. The dispersant of the present invention is for the purpose of achieving the above-mentioned dispersion. The dispersant can be polyethylene oxide resin and other resins. Based on the main powder + formula powder as 100 parts by mass, the amount of dispersant added is 0.5 to 3wt%. The solvent of the present invention includes but is not limited to ethanol, toluene and isopropanol. Based on the main powder + formula powder as 100 parts by mass, the amount of solvent added is 18-25wt%. Grinding is carried out using a ball mill.

[0017] The drying temperature in S2 is 90-200°C.

[0018] The binder in S3 is an alcohol solution of PVB, and the mass concentration of the binder is 20-25 wt %. The invention has no particular limitation on the source of the binder, and commercially available products known to those skilled in the art can be used.

[0019] In the above-mentioned S3, the binder removal temperature is 300-400° C., the time is 24-30 hours, and the heating rate of the binder removal is 0.5-2° C. / min; thereby, the binder in the ceramic green body can be removed.

[0020] The sintering in S4 is performed in a reducing atmosphere using 2% volume fraction H2-N2, at a temperature of 1200-1350°C, for 24-36 hours, and at a heating rate of 2-10°C / min. Sintering the ceramic green body under these sintering conditions can impart good density, a suitable core-shell structure, and a narrow particle size distribution to the capacitor ceramic body, thereby achieving excellent dielectric properties and capacitance-temperature characteristics in the prepared MLCC.

[0021] The present invention also provides an application of the COG dielectric ceramic material having high dielectric constant and high temperature stability in a multilayer ceramic capacitor.

[0022] Based on this high-dielectric-constant and high-temperature-stability C0G ceramic material, a coating machine is used to create a ceramic film of appropriate thickness. The corresponding internal electrodes are then printed on this ceramic film. A staggered stacking design of the internal electrodes and ceramic film is then used to create a ceramic capacitor green body. This is then sintered into porcelain and copper-plated on the external electrodes to create the corresponding ceramic MLCC. Compared to ceramic capacitors made from existing materials, MLCCs made from this dielectric material not only meet the requirements of general C0G MLCCs, but also possess a relatively high dielectric constant and superior temperature stability.

[0023] Beneficial effects of the present invention: The present invention designs a C0G ceramic powder with high dielectric constant and high temperature stability based on the main powder SrTiO3-CaTiO3 and the formula powder including the system of ZrO2-MgO-Bi2O3-MnO-SiO2-B2O3. After pre-sintering, ball milling, granulation, tableting, debinding, sintering and other steps, a C0G ceramic material with a dielectric constant of 110, a dielectric loss of less than 0.0001, and a temperature coefficient of -20 to +20 ppm / °C is finally obtained.

[0024] Among them, SrTiO3 material has a high dielectric constant, but has the problem of poor temperature stability. CaTiO3 material has good temperature stability, but its dielectric constant is small. By doping the two in a certain proportion, a main powder material with excellent dielectric constant and temperature stability is obtained. Zr ions partially replace Ti in the titanium oxide octahedron to play a pinning role, and fill the vacancies in the crystal structure of the material, improve the orderliness inside the material, increase the atomic packing density, and ensure the stability of the capacity coefficient of the material in a wide temperature working range. Mg ions can inhibit excessive grain growth, improve the high-temperature insulation resistance of the material, and improve the dielectric temperature stability within the temperature range. Mn ions will prevent Ti from 4+ The reduction product Ti 3+The production of SiO2-B2O3 effectively reduces the dielectric loss of porcelain powder and improves insulation resistance. SiO2-B2O3 can effectively reduce the sintering temperature of porcelain powder, improve the density of the material, ensure that the grain size of the material is more uniform after sintering, and help reduce dielectric loss and improve the temperature stability of the material. 3+ Will Sr in SrTiO3 2+ The substitution leads to the relaxation of the lattice structure, which is beneficial to the Ti 4+ The movement of the dipoles increases the internal electric field, leading to an increase in the dielectric constant. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a process flow chart for preparing C0G dielectric ceramic materials according to the present invention. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0028] It should be noted that, unless otherwise defined, technical or scientific terms used in the present invention should have the same ordinary meaning as those understood by persons of ordinary skill in the art to which the present invention belongs. The words "include" or "comprise" and similar expressions used in the present invention mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects.

[0029] Example 1

[0030] like Figure 1 As shown, the method for preparing the COG dielectric ceramic material with high dielectric constant and high temperature stability in this embodiment includes the following steps:

[0031] 1. SrCO3, CaCO3 and TiO2 are taken in proportion, synthesized by solid phase method, and pre-sintered into SrTiO3 matrix and CaTiO3 matrix with an average particle size of 200nm to 400nm. The pre-sintering temperature is 1120℃ and the time is 3h.

[0032] 2. The main powder SrTiO3-CaTiO3 and the formula powder ZrO2-MgO-Bi2O3-MnO-SiO2-B2O3 system are mixed evenly in proportion (100% by mass of calcined SrTiO3-CaTiO3 particles with an average particle size of 200nm to 400nm and the formula powder by mass percentage are mixed, and the composition is shown in Table 1), and then added to a ball mill for wet ball milling. The speed of the ball mill is 40r / min and the ball milling time is 6h to obtain a uniformly mixed powder, wherein the dispersant is 2.5% by mass of polyethylene oxide resin and the solvent is 20% by mass of toluene / ethanol mixed solvent. The powder is then dried at a temperature of 150°C to obtain a mixed ceramic slurry.

[0033] 3. Add 25% by mass of PVB binder to the mixed ceramic slurry and granulate, press, and debind. The debinding temperature is set to 350°C, with a heating rate of 1°C / min for 24 hours to remove the binder from the ceramic green body.

[0034] 4. The debinded green ceramic was placed in a sintering furnace at a temperature of 1260°C, a heating rate of 3°C / min, and a sintering duration of 32 hours. The cooked ceramic was subjected to the relevant evaluation tests described below, and the test results are listed in Table 1 below.

[0035] Example 2

[0036] The difference between this embodiment and embodiment 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0037] Example 3

[0038] The difference between this embodiment and embodiment 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0039] Example 4

[0040] The difference between this embodiment and embodiment 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0041] Example 5

[0042] The difference between this embodiment and embodiment 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0043] Example 6

[0044] The difference between this embodiment and embodiment 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0045] Example 7

[0046] The difference between this embodiment and embodiment 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0047] Example 8

[0048] The difference between this embodiment and embodiment 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0051] Comparative Example 2

[0052] The difference between this comparative example and Example 1 is that the mass percentages of the various powder materials in the main powder and formula powder systems are different. The composition and test results are shown in Table 1.

[0053] Table 1 Powder composition and test results of Examples 1-8 and Comparative Examples 1-2

[0054]

[0055]

[0056] As can be seen from Table 1, the influence of SrTiO3-CaTiO3 main powder on the dielectric constant and temperature stability of ceramic materials is greater than that of the formula powder. The dielectric constant of the C0G dielectric ceramic material prepared by the present invention is between 101-121, and the dielectric loss is between 1.0-2.0×10 -4Within. From Examples 1-5, as the proportion of SrTiO3 material in the main powder increases, its dielectric constant increases, up to 121.0, but its TCC also increases, which is -22.4 to +21.6ppm / ℃. Example 3 When the proportion of SrTiO3-CaTiO3 is 49% each, a suitable dielectric constant and TCC will be obtained. Among them, the formula powder ZrO2-MgO-Bi2O3-MnO-SiO2-B2O3 has a certain influence on the performance system of ceramic powder. When the proportion of ZrO2 and Bi2O3 is 0.1% and 0.5%, the dielectric constant and TCC obtained are better. In Comparative Example 1, when the ZrO2 proportion exceeds the required range and reaches 0.5%, its dielectric constant will become abnormally low, and the original intention of this design cannot be achieved. In Comparative Example 2, when the Bi2O3 ratio exceeds the required range and reaches 0.8%, although the dielectric constant is higher, the TCC condition deteriorates to -23.6 to +19.8 ppm / °C.

[0057] Those skilled in the art will understand that the discussion of any of the above embodiments is merely illustrative and is not intended to limit the scope of the present invention to these examples. Within the spirit and principles of the present invention, the technical features of the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and many other variations exist for the various aspects of the present invention described above, which are not provided in detail for the sake of clarity. Any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A COG dielectric ceramic material with high dielectric constant and high temperature stability, characterized in that: The invention comprises the following raw materials in parts by mass: 100 parts by mass of a powder system, 0.5-3 parts by mass of a dispersant, 18-25 parts by mass of a solvent, and 20-25 parts by mass of a binder. The powder system is prepared from 98 parts by mass of a main powder and 2 parts by mass of a formula powder system. The main powder comprises the following components in percentage by mass: 40-58% SrTiO3 powder and 40-58% CaTiO3 powder. The formula powder system comprises the following components in percentage by mass: 0.1-0.4% ZrO2 powder, 0.2-0.8% MgO powder, 0.2-0.6% Bi2O3 powder, 0.2-0.8% MnO powder, 0.2-0.4% SiO2 powder, and 0.05-0.15% B2O3 powder. The dielectric constant temperature coefficient of the C0G dielectric ceramic material is -20 to 20 ppm / °C.

2. The COG dielectric ceramic material with high dielectric constant and high temperature stability according to claim 1, characterized in that: The main powder is obtained by pre-sintering SrCO3, CaCO3 and TiO2 in a mass ratio of 1:1:2, the pre-sintering temperature is 1100-1200°C, and the pre-sintering time is 3-6h.

3. The method for preparing a COG dielectric ceramic material having high dielectric constant and high temperature stability according to claim 1 or 2, characterized in that: The steps include: S1. SrCO3, CaCO3 and TiO2 are taken in a proportion, synthesized by a solid phase method, and pre-sintered into a SrTiO3 matrix and a CaTiO3 matrix with an average particle size of 200nm to 400nm, thereby obtaining a main powder. The pre-sintering temperature is 1100-1200°C, and the pre-sintering time is 3-6h. S2. Mix the main powder and the formula powder according to the proportion, and then ball mill and dry to obtain a mixture; S3, mixing the mixture with a binder, granulating to obtain a semi-finished product, and then tableting and debinding to obtain a ceramic green body; S4. Sintering the ceramic green body to obtain a COG dielectric ceramic material.

4. The method for preparing a COG dielectric ceramic material having high dielectric constant and high temperature stability according to claim 3, wherein: The ball milling in S2 is wet ball milling, the rotation speed of the ball milling is 40 to 60 r / min, and the time is 6 hours to 24 hours.

5. The method for preparing a COG dielectric ceramic material having high dielectric constant and high temperature stability according to claim 4, wherein: The dispersant used in the wet ball milling includes polyethylene oxide resin, the solvent includes ethanol, toluene and isopropanol; and the grinding balls used are 1 mm zirconium balls.

6. The method for preparing a COG dielectric ceramic material having high dielectric constant and high temperature stability according to claim 3, wherein: The binder in S3 is an alcohol solution of PVB, and the mass concentration of the binder is 20-25wt%.

7. The method for preparing a COG dielectric ceramic material with high dielectric constant and high temperature stability according to claim 3, characterized in that: In the S3, the binder removal temperature is 300-400° C., the time is 24-30 hours, and the binder removal heating rate is 0.5-2° C. / min.

8. The method for preparing a COG dielectric ceramic material with high dielectric constant and high temperature stability according to claim 3, characterized in that: The sintering in S4 is carried out in a reducing atmosphere using 2% volume fraction of H2-N2, the sintering temperature is 1200-1350°C, the sintering time is 24-36h, and the sintering heating rate is 2-10°C / min.

9. Use of the COG dielectric ceramic material having high dielectric constant and high temperature stability according to claim 1 or 2 in multilayer ceramic capacitors.

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