CN114477961A - Low-temperature co-fired ceramic material and preparation method thereof - Google Patents

Low-temperature co-fired ceramic material and preparation method thereof Download PDF

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CN114477961A
CN114477961A CN202210111665.4A CN202210111665A CN114477961A CN 114477961 A CN114477961 A CN 114477961A CN 202210111665 A CN202210111665 A CN 202210111665A CN 114477961 A CN114477961 A CN 114477961A
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ceramic material
fired ceramic
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岳振星
卢雨田
郭蔚嘉
陈雨谷
马志宇
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Tsinghua University
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Abstract

The application provides a low-temperature co-fired ceramic material and a preparation method thereof, wherein the low-temperature co-fired ceramic material comprises the following raw material components in percentage by mass: 27% -30% Li2O, 17-44 percent of SrO, 7-29 percent of CaO and 22-25 percent of SiO2. The low-temperature co-fired ceramic material generates Li with low melting point4SrCaSi2O8Structural phases, and therefore reduced sintering temperatures without the need for additional addition of a glass phase. In addition, the dielectric constant of the low-temperature co-fired ceramic material can be 8.4-9.5 by regulating and controlling the contents of strontium oxide and calcium oxide in the raw materials; the Qxf value is 41300-64000 GHz; the temperature coefficient of resonance frequency is-140 to-60 ppm/DEG C, and the ceramic material is expected to be used for manufacturing microwave devices such as low-temperature co-fired ceramic substrates, microwave integrated circuit substrates, resonators, electronic product packages and the like.

Description

Low-temperature co-fired ceramic material and preparation method thereof
Technical Field
The application relates to the field of electronic functional materials and devices, in particular to a low-temperature co-fired ceramic material and a preparation method thereof.
Background
The low-temperature co-fired ceramic is a ceramic material which can be co-sintered with common metals of electronic wiring such as silver, copper and the like below the melting point of the ceramic material, has the characteristics of low sintering temperature, low dielectric constant, low loss, high chemical compatibility and the like, and is applied to the fields of integrated packaging of electronic elements and the like. With the development of 5G, 6G and other communication technologies, the mobile communication technology shows the development trend of high frequency and miniaturization, which puts higher requirements on components of communication equipment, and the low-temperature co-fired ceramic technology becomes one of the key technologies for preparing high-frequency communication devices by virtue of the characteristics of high integration, low dielectric and low loss.
Silicate is a commonly used low-temperature co-fired ceramic material, and because of its strong covalent property of silicon-oxygen bond in crystal structure, it tends to have a low dielectric constant and low loss. In order to meet the application conditions of low-temperature co-fired ceramics, researchers usually adopt a method of doping low-melting-point phases such as glass into a silicate ceramic system to reduce the sintering temperature of the silicate ceramic, but the loss of materials is greatly increased, and the application of the silicate ceramic at higher frequency is limited.
Disclosure of Invention
The application provides a low-temperature co-fired ceramic material and a preparation method thereof, aiming at providing a silicate low-temperature co-fired ceramic with low sintering temperature, low loss and low dielectric constant.
On one hand, the embodiment of the application provides a low-temperature co-fired ceramic material, which comprises the following raw material components in percentage by mass: 27% -30% Li2O, 17-44 percent of SrO, 7-29 percent of CaO and 22-25 percent of SiO2The dielectric constant of the low-temperature co-fired ceramic material is 8.4-9.5; the Qxf value is 41300-64000 GHz; the temperature coefficient of the resonance frequency is-140 to-60 ppm/DEG C.
On the other hand, the embodiment of the application provides a preparation method of a low-temperature co-fired ceramic material, which comprises the following steps:
(1) weighing raw material powder according to a ratio, and performing first ball milling to obtain a mixture;
(2) carrying out primary drying, primary screening and pre-burning treatment on the mixture to obtain a pre-burning material, wherein the pre-burning temperature is 800-900 ℃;
(3) carrying out secondary ball milling, secondary drying, secondary screening, granulation and dry pressing forming treatment on the pre-sintered material to obtain a green body;
(4) and sintering the green body to obtain the low-temperature co-fired ceramic material, wherein the sintering temperature is 850-950 ℃.
Preferably, the raw material powder in step (1) includes lithium carbonate, strontium carbonate, calcium carbonate, and silica.
Preferably, the rotation speed of the first ball milling in the step (1) is 250-350 r/min, and the time is 4-8 hours.
Preferably, the ball milling medium for the first ball milling in the step (1) is alcohol, and the ball-to-material ratio is (8-12): 1.
Preferably, the pre-firing treatment in the step (2) is performed for 4 to 8 hours.
Preferably, the granulating in the step (3) includes adding an adhesive to the dried pre-sintered material after the second drying, and mixing to prepare the dried pre-sintered material into particles with an average particle size of 0.1-0.5 mm.
Preferably, the pressure of the dry pressing in the step (3) is 100 to 200 MPa.
Preferably, the step (3) further comprises a rubber discharge treatment after the dry pressing treatment, wherein the rubber discharge temperature is 550-650 ℃, and the time is 4-8 hours.
Preferably, the time of the sintering treatment in the step (4) is 4-8 hours.
The silicate crystal structure is composed of silicon-oxygen tetrahedron, wherein silicon-oxygen bonds are composed of semi-covalent bonds and semi-ionic bonds, the bonding strength is strong, and the sintering temperature is high, so that the silicate ceramic to be used for the low-temperature co-fired ceramic substrate generally needs to increase a glass phase to reduce the sintering temperature to be lower than the melting point of silver, but the material loss is greatly increased. The low-temperature co-fired ceramic material provided by the invention has excellent sintering performance and microwave dielectric property, and compared with the current mainstream low-temperature co-fired ceramic material, the low-temperature co-fired ceramic material generates Li with low melting point4SrCaSi2O8The phase of the structure, so the sintering temperature is reduced without adding additional glass phase, and the microwave dielectric property is better and the component adjusting space is larger. The dielectric property of the ceramic can be improved by regulating the contents of strontium oxide and calcium oxide in the raw materialsThe constant is varied from 8.4 to 9.5, the Qxf value can be 64000GHz at most, and the microwave dielectric ceramic material is expected to be used for manufacturing microwave devices such as low-temperature co-fired ceramic substrates, microwave integrated circuit substrates, resonators, electronic product packages and the like.
Drawings
Features, advantages and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.
FIG. 1 is a surface microtopography of a low temperature co-fired ceramic material of example 1;
FIG. 2 is an X-ray diffraction (XRD) spectrum of the low temperature co-fired ceramic material of example 1;
FIG. 3 is a surface microtopography of the low temperature co-fired ceramic material of example 2;
FIG. 4 is a surface microtopography of the LTCC material of example 3.
Detailed Description
In order to make the objects, technical solutions and advantageous technical effects of the present invention more clear, the present invention is further described in detail with reference to the following embodiments. It should be understood that the embodiments described in this specification are only for the purpose of explaining the present invention and are not intended to limit the present invention.
For the sake of brevity, only some numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Also, although not explicitly recited, each point or individual value between endpoints of a range is encompassed within the range. Thus, each point or individual value can form a range not explicitly recited as its own lower or upper limit in combination with any other point or individual value or in combination with other lower or upper limits.
In the description herein, it is to be noted that, unless otherwise specified, "above" and "below" are inclusive, and "a plurality" of "one or more" means two or more.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The following description more particularly exemplifies illustrative embodiments. At various points throughout this application, guidance is provided through a list of embodiments that can be used in various combinations. In various embodiments, the lists are provided as representative groups and should not be construed as exhaustive.
Low-temperature co-fired ceramic material
The embodiment of the first aspect of the invention provides a low-temperature co-fired ceramic material, which comprises the following raw material components in percentage by mass: 27% -30% Li2O, 17-44 percent of SrO, 7-29 percent of CaO and 22-25 percent of SiO2The dielectric constant of the low-temperature co-fired ceramic material is 8.4-9.5; the Qxf value is 41300-64000 GHz; the temperature coefficient of the resonance frequency is-140 to-60 ppm/DEG C.
The low-temperature co-fired ceramic material provided by the invention has excellent sintering performance and microwave dielectric property, and compared with the current mainstream low-temperature co-fired ceramic material, the low-temperature co-fired ceramic material generates Li with low melting point4SrCaSi2O8The phase of the structure, so the sintering temperature is reduced without adding additional glass phase, and the microwave dielectric property is better and the component adjusting space is larger. In addition, by regulating the content of strontium oxide and calcium oxide in the raw materials, the dielectric constant of the ceramic can be changed within 8.4-9.5, the Qxf value can be as high as 64000GHz, and the ceramic is expected to be used for manufacturing microwave devices such as low-temperature co-fired ceramic substrates, microwave integrated circuit substrates, resonators, electronic product packages and the like.
In order to comprehensively improve the sintering property and the microwave dielectric property of the silicate system low-temperature co-fired ceramic material, Li2The mass percentage of O is 27-30%, and the sintering temperature is reduced without adding extra glass phase into the silicate system ceramic, so that the loss is lower and the dielectric constant is higher. Li2The content of O may be 27%, 28%, 29%, 30% or the like by mass.
In order to comprehensively improve the sintering performance and the microwave dielectric performance of the silicate system low-temperature co-fired ceramic material, the mass percentage of SrO is selected to be 17-44%, for example, 17%, 20%, 25%, 30%, 35%, 40% and 44%.
In order to comprehensively improve the sintering performance and the microwave dielectric performance of the silicate system low-temperature co-fired ceramic material, the mass percentage of CaO is selected to be 7-29%, for example, 7%, 12%, 15%, 20%, 22%, 25%, 27% or 29%.
The mass percent of SrO is adjusted to be 17-44%, and the mass percent of CaO is adjusted to be 7-29%, so that Li can be formed by the ceramic4SrCaSi2O8The Sr ions in the solid solution are gradually replaced by Ca ions along with the reduction of SrO and the increase of CaO, so that the dielectric constant of the low-temperature co-fired ceramic material is changed within 8.4-9.5, and the Qxf value can reach 64000GHz at most. If the contents of CaO and SrO are outside the above ranges, the solid solution limit of the solid solution is exceeded, and Li is formed2CaSiO4And (Ca, Sr)2SiO4And the like, increase the sintering temperature of the ceramic, and deteriorate the dielectric properties of the ceramic.
In order to comprehensively improve the sintering property and the microwave dielectric property of the silicate system low-temperature co-fired ceramic material, SiO2The content of (b) is selected from 22 to 25% by mass, for example, 22%, 23%, 24%, 25% by mass or the like.
Preparation method of low-temperature co-fired ceramic material
The embodiment of the second aspect of the invention provides a preparation method of a low-temperature co-fired ceramic material, which comprises the following steps:
(1) weighing raw material powder according to a ratio, and performing first ball milling to obtain a mixture;
(2) carrying out primary drying, primary screening and pre-burning treatment on the mixture to obtain a pre-burning material, wherein the pre-burning temperature is 800-900 ℃;
(3) carrying out secondary ball milling, secondary drying, secondary screening, granulation and dry pressing forming treatment on the pre-sintered material to obtain a green body;
(4) and sintering the green body to obtain the low-temperature co-fired ceramic material, wherein the sintering temperature is 850-950 ℃.
In the examples of the present application, the raw material powder in step (1) includes lithium carbonate, strontium carbonate, calcium carbonate, and silica. The first ball milling can reduce the particle size of the raw material powder and mix the raw material powder uniformly.
In the embodiment of the application, the rotation speed of the first ball milling in the step (1) is 250-350 r/min, and the time is 4-8 hours. The first ball milling may be planetary ball milling, for example, the rotational speed may be 250 revolutions per minute, 280 revolutions per minute, 300 revolutions per minute, 320 revolutions per minute, 350 revolutions per minute, or the like; the time may be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or the like.
In the embodiment of the application, the ball milling medium for the first ball milling is alcohol, and the ball-to-material ratio is (8-12): 1. For example, the ball to feed ratio may be 8:1, 9:1, 10:1, 11:1, or 12: 1.
In the ball milling process, the impact force when the zirconium balls do centrifugal motion and the friction force between the zirconium balls and the inner wall of the ball milling tank are utilized to crush the raw materials to achieve the effect of refining the raw materials, alcohol is added to serve as a ball milling medium, and a mixture is obtained after ball milling.
In some embodiments, the mixture is dried and sieved before pre-sintering at 800-900 deg.C, for example, 800 deg.C, 820 deg.C, 850 deg.C, 880 deg.C or 900 deg.C.
According to the embodiment of the application, the pre-sintering temperature is 800-900 ℃, and the pre-sintered powder in the temperature range can generate the decomposition of carbonate and the synthesis reaction of oxide to generate Li with low melting point4SrCaSi2O8The powder with the structure ensures that the subsequent sintering can be carried out at low temperature.
In some embodiments, the burn-in time is 4 to 8 hours. For example, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or the like.
A series of physical and chemical reactions occur in the pre-sintering process to synthesize the required crystal form and phase, the pre-sintering can also remove internal stress in the mixture to cause volume shrinkage, and partial impurities can be removed at high temperature, so that the purity of the mixture is improved.
According to the embodiment of the application, the presintering material is subjected to secondary ball milling (can be planetary ball milling) after the presintering, so that the particle size of the presintering material is further reduced, and the particles are distributed more uniformly.
According to the embodiment of the application, the pre-sintered material after the second ball milling is subjected to second drying, second sieving, granulation and dry pressing, the flowability of the material can be improved after granulation, and subsequent dry pressing is facilitated.
In an embodiment of the application, the granulating in the step (3) includes adding an adhesive to the dried pre-sintered material after the second drying, and mixing to prepare the dried pre-sintered material into particles with an average particle size of 0.1-0.5 mm.
In some embodiments, the adhesive may be selected from an aqueous solution of polyvinyl alcohol at a concentration of 5 wt%.
In the embodiment of the application, the pressure of the dry pressing in the step (3) is 100-200 MPa, and the pressure is applied in an axial direction. For example, the pressure may be 100 megapascals, 120 megapascals, 150 megapascals, 180 megapascals, or 200 megapascals. After the pressure dry pressing molding, the pre-sintering material particles become more compact green bodies.
In some embodiments, the green body further comprises a binder removal treatment before the sintering treatment, wherein the binder removal treatment is performed to remove the binder added in the granulation process. The glue discharging temperature is 550-650 ℃, and the time is 4-8 hours. For example, the degumming temperature is 550 ℃, 580 ℃, 600 ℃, 620 ℃ or 650 ℃; the gel removal time may be 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours.
In the embodiment of the application, the temperature for sintering the green body is 850-950 ℃. For example, the temperature of the sintering treatment may be 850 ℃, 880 ℃, 900 ℃, 920 ℃ or 950 ℃.
According to the embodiment of the application, the temperature for sintering the green body is 850-950 ℃, at the sintering temperature, because Li4SrCaSi2O8The melting point of the structural powder is low, so that the structural powder is sinteredThe liquid phase sintering exists in the process, so that the ceramic blank can be sintered at a lower temperature. This means that the ceramic can be co-sintered with the common electrode materials silver (melting point 961 ℃) and copper (melting point 1083 ℃), i.e. can be used as substrate material in the integration of circuits.
In some embodiments, the sintering treatment time is 4 to 8 hours. For example, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours. In the sintering process, crystal grains fully grow, the size of air holes is reduced, the porosity is reduced, the volume is shrunk, and the density is further improved.
Examples
The present disclosure is more particularly described in the following examples that are intended as illustrative only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the equipment used in the examples is commercially available.
Example 1
(1) 29% by mass of Li2O, 29% SrO, 19% CaO and 23% SiO2Weighing lithium carbonate, strontium carbonate, calcium carbonate and silicon dioxide, adding alcohol with proper content, and carrying out planetary ball milling for 4 hours;
(2) drying the slurry, sieving, and presintering at 850 deg.C for 4 hr;
(3) and ball-milling the obtained powder for 4 hours, drying, sieving, adding a proper amount of polyvinyl alcohol (PVA) aqueous solution, grinding, granulating, and performing dry pressing and molding.
(4) Finally, the green body is glued for 4 hours at 600 ℃, and then sintered for 4 hours at 950 ℃ to obtain the ceramic material with the required chemical component proportion.
The SEM surface morphology of the ceramic is shown in FIG. 1, which shows that the ceramic has high density, less pores and a volume density of 3.1g/cm3The average crystal grain size was 4 μm. The XRD spectrum of the ceramic is shown in figure 2, and the ceramic is Li4SrCaSi2O8Structure, no significant second phase is present. The dielectric constant was 8.6, the Qxf value was 51700GHz, and the temperature coefficient of the resonant frequency was-95 ppm/deg.C as measured by a network analyzer.
Example 2
(1) 27% by mass of Li2O, 44% SrO, 7% CaO and 22% SiO2Weighing lithium carbonate, strontium carbonate, calcium carbonate and silicon dioxide, adding alcohol with proper content, and carrying out planetary ball milling for 4 hours;
(2) drying the slurry, sieving, and presintering at 850 deg.C for 4 hr;
(3) and ball-milling the obtained powder for 4 hours, drying, sieving, adding a proper amount of polyvinyl alcohol (PVA) aqueous solution, grinding, granulating, and performing dry pressing and molding.
(4) Finally, the green body is degummed for 4 hours at 600 ℃, and then sintered for 4 hours at 950 ℃ to obtain the ceramic material with the required chemical component ratio.
As shown in FIG. 3, the SEM surface morphology of the ceramic shows that the ceramic has high density, less pores and a volume density of 3.2g/cm3. The XRD spectrum of the ceramic is similar to that of figure 1, which shows that the ceramic is Li4SrCaSi2O8Structure, no significant second phase is present. The dielectric constant was 9.0, the Qxf value was 41300GHz, and the temperature coefficient of the resonant frequency was-140 ppm/deg.C as measured by a network analyzer.
Example 3
(1) 30% by mass of Li2O, 18% SrO, 28% CaO and 24% SiO2Weighing lithium carbonate, strontium carbonate, calcium carbonate and silicon dioxide, adding alcohol with proper content, and performing planetary ball milling for 4 hours;
(2) drying the slurry, sieving, and presintering at 850 deg.C for 4 hr;
(3) and ball-milling the obtained powder for 4 hours, drying, sieving, adding a proper amount of polyvinyl alcohol (PVA) aqueous solution, grinding, granulating, and performing dry pressing and molding.
(4) Finally, the green body is degummed for 4 hours at 600 ℃, and then sintered for 4 hours at 950 ℃ to obtain the ceramic material with the required chemical component ratio.
The SEM surface topography of the ceramic is shown in FIG. 4, which shows that the ceramic has high density and few pores, and the volume density is 3.0g/cm3. The XRD spectrum of the ceramic is similar to that of figure 1, which shows that the ceramic is Li4SrCaSi2O8Structure, no significant second phase is present. The dielectric constant was 9.4, the Qxf value was 45000GHz, and the temperature coefficient of the resonance frequency was-60 ppm/deg.C as measured by a network analyzer.
While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and those skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the invention. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. The low-temperature co-fired ceramic material is characterized by comprising the following raw material components in percentage by mass: 27% -30% Li2O, 17-44 percent of SrO, 7-29 percent of CaO and 22-25 percent of SiO2The dielectric constant of the low-temperature co-fired ceramic material is 8.4-9.5; the Qxf value is 41300-64000 GHz; the temperature coefficient of the resonance frequency is-140 to-60 ppm/DEG C.
2. A method for preparing a low temperature co-fired ceramic material as claimed in claim 1, comprising the steps of:
(1) weighing raw material powder according to a ratio, and performing first ball milling to obtain a mixture;
(2) carrying out primary drying, primary screening and pre-burning treatment on the mixture to obtain a pre-burning material, wherein the pre-burning temperature is 800-900 ℃;
(3) carrying out secondary ball milling, secondary drying, secondary screening, granulation and dry pressing forming treatment on the pre-sintered material to obtain a green body;
(4) and sintering the green body to obtain the low-temperature co-fired ceramic material, wherein the sintering temperature is 850-950 ℃.
3. The method for preparing the low-temperature co-fired ceramic material as claimed in claim 2, wherein the raw material powder in the step (1) comprises lithium carbonate, strontium carbonate, calcium carbonate and silicon dioxide.
4. The preparation method of the low-temperature co-fired ceramic material as claimed in claim 2, wherein the rotation speed of the first ball milling in the step (1) is 250-350 r/min, and the time is 4-8 hours.
5. The preparation method of the low-temperature co-fired ceramic material according to claim 2, wherein the ball milling medium for the first ball milling in the step (1) is alcohol, and the ball-to-material ratio is (8-12): 1.
6. The preparation method of the low-temperature co-fired ceramic material as claimed in claim 2, wherein the pre-sintering treatment time in the step (2) is 4-8 hours.
7. The preparation method of the low-temperature co-fired ceramic material according to claim 2, wherein the granulating in the step (3) comprises adding an adhesive into the dried pre-sintered material after the secondary drying, and mixing to prepare the dried pre-sintered material into particles with an average particle size of 0.1-0.5 mm.
8. The preparation method of the low-temperature co-fired ceramic material as claimed in claim 2, wherein the pressure of the dry pressing in the step (3) is 100-200 MPa.
9. The preparation method of the low-temperature co-fired ceramic material according to claim 2, wherein the dry pressing treatment in the step (3) further comprises a glue removing treatment, wherein the glue removing temperature is 550-650 ℃, and the time is 4-8 hours.
10. The preparation method of the low-temperature co-fired ceramic material as claimed in claim 2, wherein the sintering time in the step (4) is 4-8 hours.
CN202210111665.4A 2022-01-29 2022-01-29 Low-temperature co-fired ceramic material and preparation method thereof Pending CN114477961A (en)

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