CN112010649A - Low-cost ceramic substrate large-scale preparation method for filter - Google Patents
Low-cost ceramic substrate large-scale preparation method for filter Download PDFInfo
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Abstract
The invention provides a low-cost large-scale preparation method of a ceramic substrate for a 5G base station filter, which comprises the following steps of: ba5Nb4O1555-65 parts of microwave dielectric ceramic powder, 0.3-0.8 part of dispersant, 25 ℃ water base36 parts of binder 5-10 parts, plasticizer 3-8 parts and defoaming agent 0.05-0.2 part; preparing casting slurry with the viscosity of 2.5-4 Pa.S by step ball milling and mixing, and preparing the ceramic substrate for the filter by continuous casting molding, drying and tunnel kiln sintering. The invention is based on the water-based casting and continuous molding sintering process, not only avoids high pollution, high risk and high cost caused by the casting by an organic solvent method, but also greatly realizes continuous large-scale preparation, the obtained ceramic substrate has no warpage, smooth and uniform appearance structure and high density, and the mass production can meet the large demand of the medium ceramic substrate for the current filter, thereby being suitable for industrial production.
Description
Technical Field
The invention relates to a large-scale preparation method of a ceramic substrate for a low-cost filter, belongs to the field of microwave dielectric ceramic application, and particularly relates to Ba5Nb4O15Is a method for mass production by tape casting, sintering and sintering of microwave dielectric ceramics;
background
The filter for the base station is an extremely important radio frequency front-end component in network communication, and can ensure the information integrity and eliminate interference factors in transmission. The microwave dielectric ceramic for the 5G base station filter is a novel functional electronic ceramic material applied to microwave frequency band (ultrahigh frequency UHF, ultrahigh frequency SHF) circuits, and is widely applied to modern communication such as communication, radar, positioning and the like. At present in the 5G era, global 5G users have broken through 1 hundred million, and more than 70 million 5G base stations have been built; within 5 years, over 500 million 5G base stations are built in China, the number of the 5G base stations is estimated according to 3 antennas of each base station and 64 filters of each antenna, the demand of the dielectric filters reaches 10 hundred million, and the 5G base station filters have huge demand.
The main parts of the filter are a microwave dielectric ceramic resonant cavity and/or a microwave dielectric ceramic substrate, the main preparation methods of the microwave dielectric ceramic for the current 5G base station filter are dry pressing and box furnace sintering, the preparation of the microwave dielectric ceramic substrate with excellent performance such as low temperature drift, high Q value and the like can be realized, and the microwave dielectric ceramic substrate has good application value; however, the methods generally have the phenomena of more process flows, low production efficiency, high cost and the like, are not suitable for large-scale production, and are more difficult to meet the huge requirements of the current filter ceramics. The medium ceramics mainly used by the current 5G base station filter (frequency bands of 2.6G and 3.5G) belong to medium and low dielectric constant materials, and comprise MgTiO3Is BaO-TiO2Systems, perovskite systems, composite systems, and the like; the ceramic material is mostly prepared by a traditional solid phase method, in order to ensure the electrical property of a material system, the sintering temperature is usually more than 1400 ℃, the sintering is difficult, and the preparation cost is high. Ratheesh R et al (Matter)Lett,2000,45:279-258) and Jupiter et al in Ba doped with glass promoter5Nb4O15The article of ceramic sintering characteristic and dielectric property discloses that Ba is proved5Nb4O15The ceramic has low sintering temperature (1300 ℃, can be as low as 1100 ℃ after being doped) and medium dielectric constant (r39-40), the quality factor can reach 12214-53000 GHz, and the frequency temperature coefficient is adjustable, which makes it a microwave dielectric ceramic with great development prospect.
Disclosure of Invention
The invention provides a large-scale preparation method of a ceramic substrate for a low-cost filter, which has the advantages of low cost, high density, large-scale production and the like, and is suitable for industrial production of the ceramic substrate of the 5G base station filter.
The technical method of the invention is as follows:
a large-scale preparation method of a ceramic substrate for a low-cost filter comprises the following steps:
s1, mixing Ba according to mass fraction5Nb4O15The microwave dielectric ceramic powder material, a dispersing agent and deionized water are mixed, and are ground and mixed for the first time under the condition of 200r/min to obtain dispersed slurry, wherein the dispersed slurry comprises the following components in parts by weight: ba5Nb4O1555-65 parts of microwave dielectric ceramic powder, 0.3-0.8 part of dispersant and 25-36 parts of water base;
s2, adding a binder, a plasticizer and a defoaming agent into the dispersed slurry prepared in the step S1, mixing, performing secondary ball milling mixing under the condition of 180r/min, and removing bubbles in vacuum to prepare casting slurry, wherein the components in parts by mass comprise: 5-10 parts of binder, 3-8 parts of plasticizer and 0.05-0.2 part of defoaming agent;
s3, placing the casting slurry obtained in the step S2 into a casting forming machine to form a diaphragm in a casting mode, and performing gradient drying by adopting an integrated drying channel to obtain a ceramic green body;
and S4, conveying the ceramic green blank obtained by drying in the step S3 to a film rolling working section through a crawler belt for punching and forming, removing residual leftover materials, and conveying to a tunnel kiln for drying, binder removal and sintering.
Wherein, theAbove Ba5Nb4O15The particle size of the ceramic powder raw material is 1.0-5.0 um;
wherein the dispersant is one of polyacrylic acid, polymethacrylic acid and ammonium salt thereof;
the dispersant is polyacrylic acid, polymethacrylic acid and ammonium salts thereof. The dispersant and the powder are ground and mixed in advance, which is beneficial to more completely forming an adsorption layer with nano-scale thickness on the surface of the particles by the dispersant, thereby generating a steric hindrance effect which can effectively prevent mutual aggregation among the particles; in addition, the dispersant groups can be dissociated to increase the surface potential, so that electrostatic stabilization is generated among particles.
Wherein the binder is one or two of ethyl cellulose, acrylic acid copolymer, PVA, PVB, PVC and polyvinyl butyral;
wherein the plasticizer is one of dibutyl phthalate and polyethylene glycol;
wherein the defoaming agent is an emulsion type organic silicon defoaming agent;
the defoaming agent is an emulsion type organic silicon defoaming agent, the components of the defoaming agent are 30-40% of polysiloxane, 10-20% of emulsifier, 40-60% of water and 1-3% of other additives, the defoaming agent is prepared by emulsifying through a colloid grinding homogenizer, and the defoaming agent is widely used for defoaming in a water system, and can reduce the local surface tension and viscosity of bubbles by adsorbing the surfaces of the bubbles, destroy the stability of the bubbles and promote the bubbles to be discharged out of the liquid surface;
wherein the ball mill is a horizontal tank mill; step S1, performing ball milling for the first time for 24-36 hours to obtain ceramic dispersion slurry with the fineness of 0.5-1.5 um; step S2, performing secondary ball milling for 6-10 hours to obtain ceramic tape casting slurry;
wherein the vacuum defoaming time is 0.5-1 hour, the stirring speed is 60-100 r/min, and the vacuum degree is-0.075-0.095 MPa;
in the present invention, step S3 is a tape casting and integrated drying method, including the following steps:
pouring the casting slurry obtained in the step S2 into a feeding funnel of a casting machine, controlling the casting speed to be 0.2-0.5 m/min, and controlling the thickness of the ceramic substrate to be 5-10um by adjusting the height of a scraper;
in step S3, the setting of the parameters of the integrated drying channel mainly includes: the moving speed of the channel crawler is 0.1-0.2 m/min, the temperature of the front section is 40-55 ℃, and the time is 15-30 min; the temperature of the middle section is 70-90 ℃, and the time is 10-20 min; the temperature of the last section is 30-45 ℃, and the time is 10-20 min;
in the invention, the tunnel kiln in the step S4 is a push plate type medium temperature electric heating tunnel kiln;
the drying, binder removal and sintering parameters are as follows: the conveying speed of the caterpillar band of the tunnel kiln is 0.2-0.6 m/min, the temperature inside the tunnel kiln is divided into a plurality of stages, the slow glue discharging process is guaranteed at the front stage, the temperature is increased to 500-650 ℃, and the temperature is kept for 10-35 min; the highest temperature of the high-temperature section is 1250-1310 ℃, and the temperature is kept for 20-60 min; the cooling period is 15-40 min.
It should be noted that the sintering process parameters have a good repairing effect on subsequent ceramic formation, the temperature change inside the tunnel kiln has gradient transition, the sintering process is important for controlling temperature partition and time in a channel, the electrical property and toughness of the ceramic material are deteriorated due to too fast temperature distribution change, deformation, fracture, incomplete sintering and the like are caused due to improper sintering time distribution, and the filter dielectric ceramic with extremely high quality factor and proper dielectric constant cannot be obtained. Experiments show that the optimal sintering temperature and the optimal sintering time of the high-temperature section are 1290-1310 ℃ and 20-35 min respectively, and under the condition, the obtained ceramic substrate has high density, low cost, proper dielectric constant and near-zero resonant frequency temperature coefficient.
The invention has the advantages that:
the water-based tape casting system has low cost and no toxic risk, and the prepared slurry has proper viscosity, stable dispersion and large substrate yield; the continuous sintering of the tunnel kiln can realize large-scale and industrial production; temperature subareas in the tunnel kiln channel are reasonably controlled, the surface of the prepared ceramic membrane is flat and has no warpage, powder particles and air holes are uniformly distributed, the strength is high, the dielectric constant is 39.1-39.7, the density reaches more than 93% of the theoretical density, and the requirement of the dielectric ceramic for the 5G base station filter can be met.
Detailed Description
The invention will be further illustrated with reference to specific examples.
Example 1
1 kilogram of slurry is prepared at a time, 600g of barium niobate ceramic powder raw material with the grain diameter of 4um, 5g of polymethacrylic acid and 298g of deionized water are added into a nylon grinding tank for primary grinding and mixing, the ball milling speed is 200r/min, the grinding time is 36 hours, the obtained dispersed slurry has good dispersibility, and the median grain diameter of the slurry powder is reduced to 1.2 um;
adding 60g of polyvinyl butyral as a binder, 3.6g of polyethylene glycol 400 as a plasticizer and 1g of an emulsion type organic silicon defoaming agent into the obtained dispersion slurry, and performing ball milling mixing for the second time, wherein the ball milling speed is 180r/min, the grinding time is 6 hours, and the obtained casting slurry has good viscosity and stability, and the viscosity value is 3.5 Pa.S;
carrying out vacuum defoaming treatment on the casting slurry for 0.5 hour, wherein the stirring speed is 80r/min, and the vacuum degree is-0.08 MPa;
pouring the casting slurry into a feeding funnel of a casting machine, controlling the casting speed to be 0.15m/min, and controlling the thickness of the ceramic substrate to be 8um by adjusting the height of a scraper;
the integral drying channel parameter setting comprises: the moving speed of the channel crawler is 0.15m/min, the temperature of the front section is 40 ℃, and the time is 15 min; the temperature of the middle section is 85 ℃, and the time is 15 min; the temperature of the last stage is 45 ℃ and the time is 10 min;
the drying, binder removal and sintering parameters of the tunnel kiln are as follows: the conveying speed of the caterpillar band is 0.3m/min, the temperature inside the tunnel kiln is divided into a plurality of stages, the slow glue discharging process is ensured at the front stage, the temperature is 600 ℃, and the temperature is kept for 28 min; the highest temperature of the high-temperature section is 1300 ℃, and the temperature is kept for 35 min; cooling for 25 min; thus obtaining the barium niobate dielectric ceramic substrate material, and the performance detection is shown in table 1.
Example 2
1 kilogram of slurry is prepared at a time, 550g of barium niobate ceramic powder raw material with the grain diameter of 2um, 4g of polymethacrylic acid and 360g of deionized water are added into a nylon grinding tank for first grinding and mixing, the ball milling speed is 200r/min, the grinding time is 32 hours, the obtained dispersed slurry has good dispersibility, and the median grain diameter of the slurry powder is reduced to 0.7 um;
adding 50g of PVA + PVC as a binder, 35.5g of polyethylene glycol 400 as a plasticizer and 0.5g of emulsion type organic silicon defoamer into the obtained dispersion slurry, and performing ball milling mixing for the second time, wherein the ball milling speed is 180r/min, the grinding time is 8 hours, and the obtained casting slurry has good viscosity and stability, and the viscosity value is 2.7 Pa.S;
carrying out vacuum defoaming treatment on the casting slurry for 0.5 hour, wherein the stirring speed is 60 revolutions per minute, and the vacuum degree is-0.075 MPa;
pouring the casting slurry into a feeding funnel of a casting machine, controlling the casting speed to be 0.2m/min, and controlling the thickness of the ceramic substrate to be 6um by adjusting the height of a scraper;
the integral drying channel parameter setting comprises: the moving speed of the channel crawler is 0.2m/min, the temperature of the front section is 45 ℃, and the time is 10 min; the temperature of the middle section is 90 ℃, and the time is 10 min; the temperature of the last stage is 40 ℃, and the time is 10 min;
the drying, binder removal and sintering parameters of the tunnel kiln are as follows: the conveying speed of the caterpillar track is 0.3m/min, the temperature inside the tunnel kiln is divided into a plurality of stages, the slow glue discharging process is ensured at the front stage, the temperature is 650 ℃, and the temperature is kept for 18 min; the highest temperature of the high-temperature section is 1280 ℃, and the temperature is kept for 40 min; cooling for 25 min; thus obtaining the barium niobate dielectric ceramic substrate material, and the performance detection is shown in table 1.
Example 3
1 kilogram of slurry is prepared at a time, 620g of barium niobate ceramic powder raw material with the grain diameter of 5um, 6.5g of polyacrylic acid and 250g of deionized water are added into a nylon grinding tank for first grinding and mixing, the ball milling speed is 200r/min, the grinding time is 48 hours, the obtained dispersed slurry has good dispersibility, and the median grain diameter of the slurry powder is reduced to 1.4 um;
adding 75g of ethyl cellulose as a binder, 43g of dibutyl phthalate as a plasticizer and 1.5g of an emulsion type organic silicon defoaming agent into the obtained dispersion slurry, and performing ball milling mixing for the second time, wherein the ball milling speed is 180r/min, the grinding time is 8 hours, and the obtained casting slurry has good viscosity and stability, and the viscosity value is 3.8 Pa.S;
carrying out vacuum defoaming treatment on the casting slurry for 0.8 hour, wherein the stirring speed is 120 r/min, and the vacuum degree is-0.095 MPa;
pouring the casting slurry into a feeding funnel of a casting machine, controlling the casting speed to be 0.1m/min, and controlling the thickness of the ceramic substrate to be 10um by adjusting the height of a scraper;
the integral drying channel parameter setting comprises: the moving speed of the channel crawler is 0.1m/min, the temperature of the front section is 40 ℃, and the time is 15 min; the temperature of the middle section is 90 ℃, and the time is 30 min; the temperature of the last stage is 45 ℃ and the time is 15 min;
the drying, binder removal and sintering parameters of the tunnel kiln are as follows: the conveying speed of the caterpillar track is 0.25m/min, the temperature inside the tunnel kiln is divided into a plurality of stages, the slow glue discharging process is ensured at the front stage, the temperature is up to 550 ℃, and the temperature is kept for 25 min; the highest temperature of the high-temperature section is 1290 ℃, and the temperature is kept for 45 min; cooling for 30 min; thus obtaining the barium niobate dielectric ceramic substrate material, and the performance detection is shown in table 1.
Comparative example 1
The comparative example is a dry pressing and box furnace sintering preparation method of barium niobate powder, and adopts the traditional process methods of ball milling and crushing, drying and granulation, dry pressing and sintering in a high-temperature furnace;
grinding and crushing a barium niobate ceramic powder raw material with the particle size of 4um in a ball mill, wherein the ball milling speed is 200r/min, the time is 36 hours, and the median particle size of the powder also reaches 1.2 um;
drying the powder, adding 0.5 wt% of 0.5 wt% PVA aqueous solution for grinding and granulating, and sieving with a 200-mesh sieve to obtain granulated powder with the particle size of 45 um;
dry pressing the granulated powder with the forming pressure of more than 20t to obtain a flaky ceramic substrate with the thickness of 6 um;
sintering the substrate, wherein the sintering parameters comprise: heating to 600 ℃ at the speed of 2 ℃/min, preserving heat for 40min, heating to 1300 ℃ at the speed of 2 ℃/min, preserving heat for 120min, and finally, firing and forming in a manner of cooling at the speed of 1-2 ℃/min to obtain the barium niobate ceramic substrate material, wherein the performance test is shown in table 1.
The ceramic substrate for the 5G base station filter prepared in the example and the substrate prepared in the comparative example are subjected to performance test, and specific performance test results are shown in table 1;
the performance detection of the microwave dielectric ceramic substrate mainly comprises the following steps: bulk density, dielectric constant, quality factor, etc.
Wherein, the dielectric property of the material is detected and analyzed by a network analyzer;
TABLE 1 ceramic substrate Performance test results and comparison
In the embodiment, the method reduces the molding and sintering time of the ceramic substrate to be within 4-6h, and the whole preparation process has larger scale and process continuity; the dielectric constants of the obtained 3 samples are between 39 and 40, the theoretical density reaches more than 93 percent, and compared with the comparative example 1, the quality factor is slightly reduced, and the temperature drift coefficient is improved (except for the example 2); the obtained sample has good dielectric property, and the feasibility of preparing the ceramic filter substrate in a large scale is proved; the method of the invention is not limited to the scale preparation of the system materials.
Claims (6)
1. A large-scale preparation method of a ceramic substrate for a low-cost filter is characterized by comprising the following steps:
s1, mixing Ba5Nb4O15Carrying out primary ball milling and mixing on microwave dielectric ceramic powder, a dispersing agent and deionized water according to a proportion of 200r/min to obtain dispersed slurry, wherein the slurry comprises the following components in parts by weight: ba5Nb4O1555-65 parts of microwave dielectric ceramic powder, 0.3-0.8 part of dispersant and 25-36 parts of water base;
s2, adding a binder, a plasticizer and a defoaming agent into the dispersed slurry prepared in the step S1, performing ball milling mixing at 180r/min for the second time, and removing bubbles in vacuum to prepare casting slurry, wherein the casting slurry comprises the following components in parts by weight: 5-10 parts of binder, 3-8 parts of plasticizer and 0.05-0.2 part of defoaming agent;
s3, placing the casting slurry obtained in the S2 into a casting forming machine to form a diaphragm in a casting mode, and performing gradient drying by adopting an integrated drying channel to obtain a ceramic green body;
and S4, conveying the ceramic green blank obtained by drying in the step S3 to a film rolling working section through a crawler belt for punching and forming, removing residual leftover materials, and conveying to a tunnel kiln for drying, binder removal and sintering.
2. The method for large-scale preparation of the ceramic substrate for the low-cost filter according to claim 1, wherein the Ba is added5Nb4O15The particle size of the microwave dielectric ceramic powder is 1.0-5.0 um.
3. The method for large-scale preparation of the ceramic substrate for the low-cost filter according to claim 1, wherein the dispersant is one of polyacrylic acid, polymethacrylic acid and ammonium salt thereof; the binder is one or two of ethyl cellulose, acrylic acid copolymer, PVA, PVB, PVC and polyvinyl butyral; the plasticizer is one of dibutyl phthalate and polyethylene glycol; the defoaming agent is an emulsion type organic silicon defoaming agent.
4. The method for large-scale preparation of the ceramic substrate for the low-cost filter according to claim 1, wherein the ball mill is a horizontal tank mill; the first ball milling time is 24-36 hours, so as to obtain ceramic dispersion slurry with the fineness of 0.5-1.5 um; the second ball milling time is 6-10 hours, so as to obtain ceramic tape casting slurry; the vacuum defoaming time is 0.5-1 hour, the stirring speed is 60-100 r/min, and the vacuum degree is-0.075-0.095 MPa.
5. The large-scale preparation method of the ceramic substrate for the low-cost filter according to claim 1, wherein the tape casting and integrated drying method comprises the following steps:
pouring the casting slurry obtained in the step S2 into a feeding funnel of a casting machine, controlling the casting speed to be 0.2-0.5 m/min, and controlling the thickness of the ceramic substrate to be 5-10um by adjusting the height of a scraper;
in step S3, the setting of the parameters of the integrated drying channel mainly includes: the moving speed of the channel crawler is 0.1-0.2 m/min, the temperature of the front section is 40-55 ℃, and the time is 15-30 min; the temperature of the middle section is 70-90 ℃, and the time is 10-20 min; the temperature of the last stage is 30-45 ℃ and the time is 10-20 min.
6. The method for mass-producing the ceramic substrate for the low-cost filter according to claim 1, wherein the tunnel kiln in the step S4 is a push plate type medium temperature electrothermal tunnel kiln; the drying, binder removal and sintering parameters are as follows: the conveying speed of the caterpillar band of the tunnel kiln is 0.2-0.6 m/min, the temperature inside the tunnel kiln is divided into a plurality of stages, the slow glue discharging process is guaranteed at the front stage, the temperature is increased to 500-650 ℃, and the temperature is kept for 10-35 min; the highest temperature of the high-temperature section is 1250-1310 ℃, and the temperature is kept for 20-60 min; the cooling period is 15-40 min.
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| JP2000319066A (en) * | 1999-05-07 | 2000-11-21 | Selectron | Low temperature simultaneously firing dielectric ceramic composition |
| CN101328069A (en) * | 2008-07-28 | 2008-12-24 | 浙江大学 | Preparation of microwave dielectric ceramic diaphragm by aqueous tape casting forming |
| CN103553610A (en) * | 2013-10-30 | 2014-02-05 | 云南云天化股份有限公司 | Low-temperature sintered microwave dielectric ceramic material, preparation method and microwave device |
| CN111499376A (en) * | 2020-05-08 | 2020-08-07 | 深圳市鑫恒睿电子科技有限公司 | Ceramic powder for 5G communication high-dielectric ceramic filter and preparation method thereof |
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- 2020-09-08 CN CN202010937203.9A patent/CN112010649A/en active Pending
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| JP2000319066A (en) * | 1999-05-07 | 2000-11-21 | Selectron | Low temperature simultaneously firing dielectric ceramic composition |
| CN101328069A (en) * | 2008-07-28 | 2008-12-24 | 浙江大学 | Preparation of microwave dielectric ceramic diaphragm by aqueous tape casting forming |
| CN103553610A (en) * | 2013-10-30 | 2014-02-05 | 云南云天化股份有限公司 | Low-temperature sintered microwave dielectric ceramic material, preparation method and microwave device |
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Application publication date: 20201201 |