Method for manufacturing ceramic substrate for high-frequency thermal compensation type ceramic dielectric capacitor

Abstract

The present application relates to the technical field of ceramic dielectric material, and particularly relates to a preparation method of a high-frequency thermal compensation type ceramic substrate for porcelain dielectric capacitors, which comprises the following steps: after mixing porcelain powder I and porcelain powder II according to a proportion, the mixture is put into a ball mill for secondary ball milling to obtain a casting slurry, the casting slurry is made into a green porcelain tape, the green porcelain tape is made into a blank, is subjected to static pressure, and is cut to form a green porcelain sheet; and the green porcelain sheet is stacked on a supporting plate and is sent into a high-temperature furnace for sintering to obtain the high-frequency thermal compensation type ceramic substrate for porcelain dielectric capacitors. Compared with the prior art, the high-frequency thermal compensation type ceramic substrate for porcelain dielectric capacitors prepared by the present application has a dielectric constant of 210-230, a dielectric loss of <2.5%, an insulation resistance of >10 6 Ω, and a dielectric-temperature coefficient of (-500±200)×10 ‑6 / ℃, and the comprehensive performance index meets the requirements; the preparation process adopts simple raw material components, does not need pre-sintering and separate glue removal in the sintering process, simplifies the process flow, has a high qualified rate, can be mass-produced, helps to break the monopoly, and promotes the miniaturization development of domestic electronic components.

Description

Technical Field

[0001] This invention relates to the field of ceramic dielectric materials technology, and in particular to a method for preparing a ceramic substrate for a high-frequency thermally compensated ceramic capacitor. Background Technology

[0002] In high-frequency oscillation circuits, inductors and resistors often exhibit positive temperature coefficients. High-frequency ceramic capacitor dielectrics typically use non-ferroelectric (paraelectric) formulations, or by adding small amounts of other (ferroelectric) oxides, such as CaTiO3 or SrTiO3, to create "extended" temperature-compensating ceramics. This results in an approximately linear temperature coefficient and increases the dielectric constant. When used in high-frequency ceramic capacitors, this dielectric compensates for the positive temperature coefficients of the inductors and resistors in the circuit, thereby maintaining a stable resonant frequency. The market demands not only low dielectric loss and high insulation resistance for ceramics used in high-frequency thermally compensated ceramic capacitors, but also stringent requirements for temperature characteristics and other specifications.

[0003] Currently, the market demands dielectric constant 220, dielectric loss <2.5%, and insulation resistance >10. 6 There is a significant demand for ceramic substrates with a dielectric constant of (-500±200)×10-6 / ℃. However, current technologies for preparing ceramic substrates for high-frequency thermal compensation ceramic capacitors suffer from complex compositions, high firing temperatures, and difficult process control, resulting in low yield rates. Consequently, it is virtually impossible to mass-produce products that simultaneously meet the requirements of this type of high-frequency ceramic capacitor for capacitance, dielectric constant, and temperature characteristics. Therefore, there is an urgent need to develop a ceramic substrate that can meet the performance requirements of high-frequency thermal compensation ceramic capacitors. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, this invention provides a method for preparing a ceramic substrate for a high-frequency thermal compensation ceramic capacitor, which solves the problems of complex composition, high firing temperature, difficult process control, low yield, inability to mass produce, and failure to meet comprehensive performance requirements for the ceramic substrate of a high-frequency thermal compensation ceramic capacitor.

[0005] A method for preparing a ceramic substrate for a high-frequency thermally compensated ceramic capacitor, the key steps of which are:

[0006] S1. Mix porcelain powder I and porcelain powder II in a certain proportion; wherein, by mass fraction, porcelain powder I includes the following components: 10% to 20% CaCO3, 21% to 34% TiO2, 6% to 14% Li2CO3, and 44% to 57% Nd2O3;

[0007] S2. The mixed powder from S1 is fed into a ball mill for secondary ball milling to obtain a cast slurry;

[0008] S3. The casting slurry from S2 is used to make a green ceramic tape;

[0009] S4. The raw porcelain strip from S3 is shaped, statically pressed, and cut into raw porcelain pieces;

[0010] S5. Stack the raw ceramic pieces from S4 onto the firing plate and sinter them in a high-temperature furnace to obtain the finished product.

[0011] Preferably, the ceramic powder II mentioned in S1 is at least one of barium titanate ceramic powder and alumina ceramic powder.

[0012] Preferably, S2 specifically involves: adding the mixed powder, anhydrous ethanol, xylene, defoamer, and dispersant into a ball mill, using zirconia balls as the milling medium, and milling for the first time for 23–26 hours; then adding a binder and continuing milling for the second time for 5–7 hours at a speed of 400–700 r / min.

[0013] Preferably, in S1, the mixed powder comprises 25% to 45% ceramic powder I and 55% to 75% ceramic powder II by mass fraction.

[0014] Preferably, in S2, the components, by mass fraction, consist of: 30-70% mixed powder, 15-35% anhydrous ethanol, 15-35% xylene, 0.1-0.9% defoamer, and 0.3-1.4% dispersant.

[0015] In the preferred embodiment, the dispersant is selected from at least one of Nippon Oil's G700, Nippon Oil's AKM-0531, Nippon Oil's RE-610, Sekisui's NK-1, Sekisui's NK-3, Sekisui's NK01, and Sekisui's GTO; the defoamer is selected from at least one of polyether-modified silicone oil defoamers, mineral oil defoamers, mixed silicone oil defoamers, phenyl silicone oil defoamers, and dimethyl silicone oil defoamers.

[0016] Preferably, S3 specifically involves using a casting machine to form a green ceramic tape from the slurry, with a casting speed of 2.0 m / min and temperature control at 23℃, 25℃, 28℃, 29℃, 33℃, 36℃, 45℃, and 55℃.

[0017] Preferably, in S4, the static pressing process is as follows: after the green ceramic strip is cut into film, the film is stacked into green blocks by a stacking machine, and then vacuum-packed in the manner of polyethylene board-PE film-green block-PE film-polyethylene board-steel plate before static pressing.

[0018] Preferably, in S5, the stacking method is as follows: place the raw ceramic pieces flat on the zirconia plate, then place four zirconia plates on the alumina firing plate, and stack them in 15 layers.

[0019] Preferably, in S5, the sintering curves are as follows: 20-400℃, heating time controlled at 80 min; 400-600℃, heating time controlled at 300 min; 600℃, holding time controlled at 180 min; 600-1160℃, heating time controlled at 180 min; 1160-1240℃, heating time controlled at 120 min; 1240℃, holding time controlled at 40 min; 1240-1150℃, cooling time controlled at 5 min; 1150℃, holding time controlled at 10 min; 1150-850℃, cooling time controlled at 60 min.

[0020] Preferably, the blanking conditions in S4 are: under a pressure of 80MPa, the blank is pressed into a square green block with a length and width of 48mm×48mm and a thickness of 210um~220um.

[0021] Beneficial effects: Compared with the prior art, the ceramic substrate for high-frequency thermally compensated ceramic capacitors prepared by this invention has a dielectric constant of 210-230, dielectric loss <2.5%, and insulation resistance >10. 6 Ω, dielectric temperature coefficient is (-500±200)×10 -6 The overall performance indicators meet the requirements at / ℃. The preparation process uses relatively simple raw material components. The sintering process does not require pre-firing or separate debinding, which simplifies the process flow. The pass rate is high, and it can be mass-produced. This will help break the foreign monopoly and promote the miniaturization of domestic electronic components. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0023] Example 1: Fabrication of a ceramic substrate for a high-frequency thermally compensated ceramic capacitor

[0024] S1. Mix 375g of porcelain powder I and 1125g of porcelain powder II evenly; wherein, porcelain powder I is made by calcining the following components in mass fraction: 10% CaCO3, 34% TiO2, 12% Li2CO3, and 44% Nd2O3;

[0025] S2. Add 1500g of mixed powder, 1770g of anhydrous ethanol, 1770g of xylene, 5g of defoamer, and 15g of dispersant to a ball mill, using zirconia balls as the milling medium. The first milling time is 23h. Then add the binder and continue milling. The second milling time is 5h, and the speed is 400r / min to obtain the cast slurry.

[0026] S3. Use a casting machine to make green ceramic tape from the slurry. The casting speed is 2.0 m / min, and the temperature range is controlled at 23℃, 25℃, 28℃, 29℃, 33℃, 36℃, 45℃, and 55℃.

[0027] S4. After the green ceramic tape is cut into film sheets using a cutting machine, the film sheets are stacked into green blocks using a stacking machine. Then, the film is vacuum-packed using a polyethylene board-PE film-green block-PE film-polyethylene board-steel plate method and statically pressed into a higher density film block. The statically pressed film block is then cut into 48*48um green ceramic sheets using a hot cutting machine.

[0028] S5. Place the raw ceramic pieces flat on a zirconia plate, then place four zirconia plates on an alumina firing plate, stacking them in 15-layer stacks, and sinter them in a high-temperature furnace to obtain the finished product. The sintering curves are as follows: 20-400℃, heating time controlled at 80 min; 400-600℃, heating time controlled at 300 min; 600℃, hold for 180 min; 600-1160℃, heating time controlled at 180 min; 1160-1240℃, heating time controlled at 120 min; 1240℃, hold for 40 min; 1240-1150℃, cooling time controlled at 5 min; 1150℃, hold for 10 min; 1150-850℃, cooling time controlled at 60 min.

[0029] Example 2: Fabrication of ceramic substrate for high-frequency thermally compensated ceramic capacitors

[0030] S1. Mix 675g of porcelain powder I and 825g of porcelain powder II evenly; wherein, porcelain powder I is made by calcining the following components in mass fraction: 20% CaCO3, 21% TiO2, 2% Li2CO3, and 57% Nd2O3;

[0031] S2. Add 1500g of mixed powder, 330g of anhydrous ethanol, 330g of xylene, 20g of defoamer, and 31g of dispersant to a ball mill, using zirconia balls as the milling medium. The first milling time is 26 hours. Then, add the binder and continue milling. The second milling time is 7 hours, and the speed is 700 r / min to obtain a cast slurry.

[0032] S3. Use a casting machine to make green ceramic tape from the slurry. The casting speed is 2.0 m / min, and the temperature range is controlled at 23℃, 25℃, 28℃, 29℃, 33℃, 36℃, 45℃, and 55℃.

[0033] S4. After the green ceramic tape is cut into film sheets using a cutting machine, the film sheets are stacked into green blocks using a stacking machine. Then, the film is vacuum-packed using a polyethylene board-PE film-green block-PE film-polyethylene board-steel plate method and statically pressed into a higher density film block. The statically pressed film block is then cut into 48*48um green ceramic sheets using a hot cutting machine.

[0034] S5. Place the raw ceramic pieces flat on a zirconia plate, then place four zirconia plates on an alumina firing plate, stacking them in 15-layer stacks, and sinter them in a high-temperature furnace to obtain the finished product. The sintering curves are as follows: 20-400℃, heating time controlled at 80 min; 400-600℃, heating time controlled at 300 min; 600℃, hold for 180 min; 600-1160℃, heating time controlled at 180 min; 1160-1240℃, heating time controlled at 120 min; 1240℃, hold for 40 min; 1240-1150℃, cooling time controlled at 5 min; 1150℃, hold for 10 min; 1150-850℃, cooling time controlled at 60 min.

[0035] Example 3: Preparation of ceramic substrate for high-frequency thermally compensated ceramic capacitors

[0036] S1. Mix 450g of porcelain powder I and 1050g of porcelain powder II evenly; wherein, porcelain powder I is made by calcining the following components in mass fraction: 16% CaCO3, 23% TiO2, 7% Li2CO3, and 54% Nd2O3.

[0037] S2. Add 1500g of mixed powder, 450g of anhydrous ethanol, 450g of xylene, 12g of defoamer, and 9g of dispersant to a ball mill, using zirconia balls as the ball milling medium, and ball mill for 26 hours for the first time; then add 450g of binder and continue grinding for 6 hours at a speed of 600r / min to obtain a cast slurry;

[0038] S3. Use a casting machine to make green ceramic tape from the slurry. The casting speed is 2.0 m / min, and the temperature range is controlled at 23℃, 25℃, 28℃, 29℃, 33℃, 36℃, 45℃, and 55℃.

[0039] S4. After the green ceramic tape is cut into film sheets using a cutting machine, the film sheets are stacked into green blocks using a stacking machine. Then, the film is vacuum-packed using a polyethylene board-PE film-green block-PE film-polyethylene board-steel plate method and statically pressed into a higher density film block. The statically pressed film block is then cut into 48*48um green ceramic sheets using a hot cutting machine.

[0040] S5. Place the raw ceramic pieces flat on a zirconia plate, then place four zirconia plates on an alumina firing plate, stacking them in 15-layer stacks, and sinter them in a high-temperature furnace to obtain the finished product. The sintering curves are as follows: 20-400℃, heating time controlled at 80 min; 400-600℃, heating time controlled at 300 min; 600℃, hold for 180 min; 600-1160℃, heating time controlled at 180 min; 1160-1240℃, heating time controlled at 120 min; 1240℃, hold for 40 min; 1240-1150℃, cooling time controlled at 5 min; 1150℃, hold for 10 min; 1150-850℃, cooling time controlled at 60 min.

[0041] Taking Example 3 as an example, 100 samples were randomly selected from the same batch of products for performance testing, and the results are shown in the table below.

[0042]

[0043] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing a ceramic substrate for a high-frequency thermally compensated ceramic capacitor, characterized in that, Includes the following steps: S1. Mix porcelain powder I and porcelain powder II in a certain proportion; wherein, by mass fraction, porcelain powder I includes the following components: 10% to 20% CaCO3, 21% to 34% TiO2, 6% to 14% Li2CO3, and 44% to 57% Nd2O3; The ceramic powder II is at least one of barium titanate ceramic powder and alumina ceramic powder; By mass fraction, the mixed powder includes 25%–45% ceramic powder I and 55%–75% ceramic powder II; S2. The mixed powder from S1 is fed into a ball mill for secondary ball milling to obtain a cast slurry; The mixed powder, anhydrous ethanol, xylene, defoamer, and dispersant are put into a ball mill, using zirconia balls as the ball milling medium. The first ball milling time is 23-26 hours. Then, a binder is added and grinding is continued. The second ball milling time is 5-7 hours, and the speed is 400-700 r / min. S3. The casting slurry from S2 is used to make a green ceramic tape; S4. The raw porcelain strip from S3 is shaped, statically pressed, and cut into raw porcelain pieces; S5. Stack the raw ceramic pieces from S4 onto the firing plate and sinter them in a high-temperature furnace to obtain the finished product; The sintering curves are as follows: 20-400℃, heating time controlled at 80 min; 400-600℃, heating time controlled at 300 min; 600℃, hold for 180 min; 600-1160℃, heating time controlled at 180 min; 1160-1240℃, heating time controlled at 120 min; 1240℃, hold for 40 min; 1240-1150℃, cooling time controlled at 5 min; 1150℃, hold for 10 min; 1150-850℃, cooling time controlled at 60 min. The stacking method is as follows: place the raw ceramic pieces flat on the zirconia plate, then place four zirconia plates on the alumina firing plate, and stack them in 15 layers.

2. The method for preparing a ceramic substrate for a high-frequency thermally compensated ceramic capacitor according to claim 1, characterized in that... S3 specifically involves using a casting machine to form green ceramic tape from the slurry, with a casting speed of 2.0 m / min and temperature control at 23℃, 25℃, 28℃, 29℃, 33℃, 36℃, 45℃, and 55℃.

3. The method for preparing a ceramic substrate for a high-frequency thermally compensated ceramic capacitor according to claim 1, characterized in that... In S4, the static pressing process is as follows: after the green ceramic strip is cut into film, the film is stacked into green blocks by a stacking machine, and then vacuum-packed in the manner of polyethylene board-PE film-green block-PE film-polyethylene board-steel plate before static pressing.

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