Low-temperature sintered ceramic material

Abstract

The invention belongs to the technical field of electronic ceramic materials and manufacturing, and particularly relates to a low-temperature sintered ceramic material and a preparation method thereof. 10) and a low dielectric constant (epsilon rlt; 4) and the coefficient of thermal expansion is small (lt; according to the preparation method, Al2O3 and SiO2 composite ceramic is used as a main phase, and SiO2-Al2O3-B2O3-Li2O glass and SiO2-Al2O3-MgO-CaO glass are used as sintering aids for doping, so that the sintering temperature of the Al2O3 and SiO2 composite ceramic is reduced to 900 DEG C or below, and low-temperature sintering is realized. The material has the advantages of low dielectric constant, low thermal expansion coefficient, high strength and the like, and the sintering temperature is relatively low; and the low-resistivity low-dielectric-constant-temperature dielectric ceramic material can be well co-fired with a low-resistivity silver electrode, so that the low-dielectric-constant-temperature dielectric ceramic material is suitable for microelectronic packaging, LTCC passive integrated devices and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic ceramic materials and manufacturing, and relates to a low-temperature sintered ceramic material and a preparation method thereof. Background Art

[0002] With the continuous development of wireless communication technology and microelectronic integration technology, how to further improve packaging density and reduce signal delay on interconnection lines has become a key basic problem that modern electronic technology urgently needs to solve. To solve these problems, on the one hand, it is necessary to develop substrate materials with low dielectric constant and low dielectric loss, and on the other hand, it is necessary to place passive devices and components with high-frequency functions inside the substrate to improve device integration and reduce the distance of interconnection lines. Low Temperature Co-fired Ceramic (LTCC) technology is an advanced passive integration and hybrid circuit packaging technology. LTCC integration technology has many technical advantages such as high processing freedom, high space utilization, high wiring density, good high-frequency characteristics, high reliability and suitability for large-scale production. It is widely used in microwave multi-chip module (MCM) devices, microwave modular circuits, radar T / R components, miniaturized integrated antennas, frequency control and power amplifier devices, etc.

[0003] Dielectric constant, dielectric loss, thermal expansion coefficient, bending strength, etc. are the main technical parameters of LTCC substrate materials. In the microwave millimeter wave communication frequency range, if the LTCC device wants to increase the transmission rate, its ceramic substrate needs to have a lower dielectric constant. Generally speaking, the dielectric constant of the LTCC substrate is generally less than 10, but only when the dielectric constant is less than 5 can it meet the low latency requirements of millimeter wave applications. In addition, in the LTCC three-dimensional packaging structure, the ceramic substrate plays a supporting role, and the high reliability of the package requires that the substrate material has a certain bending strength. In addition, based on the integrated design of millimeter wave active and passive devices based on microwave monolithic integrated circuits and MCM technology, if the thermal expansion coefficient of the substrate material can match the thermal expansion coefficient of the semiconductor material (3-5ppm / ℃), the high reliability of the integrated components can be guaranteed.

[0004] There are some typical application materials on the market, such as Ferro's A6M material, which has a dielectric constant of about 5.9 and a thermal expansion coefficient of about 7ppm / ℃; Dupont's 951 substrate material, which has a dielectric constant of about 7.8 and a thermal expansion coefficient of about 6.5ppm / ℃. Compared with the target dielectric constant of less than 5 and thermal expansion coefficient of less than 5ppm / ℃ required for millimeter wave and component packaging, there is still a big gap. The dielectric constant of the composite substrate material is closely related to the dielectric constant of the filled ceramic material and the sintering glass. Since Al2O3 and SiO2 have relatively low dielectric constants, for the low dielectric constant LTCC material system, Al2O3, SiO2, etc. are generally used as ceramic phases, and glass with a low softening point temperature that can be wetted with the ceramic phase is developed as a sintering aid to promote densification sintering at low temperatures. Liu Ming et al. composited 45wt.% Al2O3 with 55wt.% CaO-Al2O3-B2O3-SiO2 glass and sintered it at 875℃. The LTCC material prepared had a dielectric constant of 7.82 and a dielectric loss of 5.3×10 -4 Luo XF et al. composited 50wt.% Al2O3 with 50wt.% CaO-B2O3-SiO2 glass and sintered them at 875℃. The dielectric constant of the prepared LTCC material was 8.06 and the dielectric loss was 1.2×10 -3 , flexural strength 204MPa, thermal expansion coefficient 5.47ppm / ℃. Chen XY et al. studied the composite of 40wt.% Al2O3 and 60wt.% La2O3-B2O3-Al2O3 glass, and obtained LTCC material after sintering at 875℃, with a dielectric constant of 7.91 and a dielectric loss of 2.12×10 -3. A large number of studies have found that the dielectric constant and thermal expansion coefficient of LTCC materials with glass and ceramic system filled with Al2O3 are relatively high. Compared with Al2O3, the dielectric constant of SiO2 is lower (about 3.8), but there are relatively few studies on LTCC materials with SiO2 as ceramic filler at home and abroad. Xin Yu et al. studied SiO2 as ceramic filler, sintered with CuO-ZnO-B2O3-Li2O glass composite, and prepared LTCC materials with a dielectric constant of 4.6 at 900°C. However, this study focused more on microwave dielectric properties and did not study thermal expansion properties and flexural strength. Xia GB et al. studied the composite of 70wt.%CaO-Al2O3-SiO2 glass and 30wt.%fused quartz. Due to the precipitation of a large amount of quartz during the sintering process of CAS glass and fused quartz, different sintering systems will result in different thermal expansion coefficients (ranging from 4.7 to 16.96ppm / ℃), which also increases its instability in application. Xia Qin et al. studied the use of K2O-B2O3-SiO2-Al2O3 glass to reduce the sintering temperature of Al2O3 and partially replaced Al2O3 with SiO2. However, as the amount of substitution increased, the ceramic properties deteriorated, and the dielectric constant and thermal expansion coefficient were relatively large. When the ratio of glass: Al2O3: SiO2 was 60:30:10, the dielectric constant of the material was 6.1 and the dielectric loss was 2.1×10 -3 (@1MHz), flexural strength of 168MPa, and thermal expansion coefficient of 8.62ppm / ℃. Therefore, finding a low-temperature sintered ceramic material with low dielectric constant (<5), low thermal expansion coefficient (<5ppm / ℃), and high strength (>180MPa) has become a difficult problem that needs to be overcome in this research field. Summary of the invention

[0005] The object of the present invention is to provide a low-temperature sintered ceramic material with low dielectric constant (<5), low thermal expansion coefficient (<5ppm / °C) and high strength (>180MPa).

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A low-temperature sintered ceramic material, whose components include: α-Al2O3: 27-45wt.%, crystalline SiO2: 15-33wt.%, SiO2-Al2O3-B2O3-Li2O glass: 7-25wt.%, SiO2-Al2O3-MgO-CaO glass: 15-33wt.%; wherein α-Al2O3 and crystalline SiO2 are main crystal phases, and SiO2-Al2O3-B2O3-Li2O glass and SiO2-Al2O3-MgO-CaO glass are sintering aids.

[0008] Furthermore, the SiO2-Al2O3-B2O3-Li2O glass comprises the following components: SiO2: 30-55wt.%, Al2O3: 10-30wt.%, B2O3: 5-10wt.%, Li2O: 0.5-6wt.%, P2O5: 0-0.5wt.%, ZrO2: 0-0.5wt.%, CeO2: 0-0.5wt.%, K2O: 0-0.5wt.%.

[0009] Furthermore, the SiO2-Al2O3-MgO-CaO glass comprises the following components: SiO2: 10-40wt.%, Al2O3: 4-12wt.%, MgO: 3-8wt.%, B2O3: 10-20wt.%, CaO: 25-40wt.%, P2O5: 0.2-0.5wt.%, ZrO2: 0-0.5wt.%, TiO2: 0-0.5wt.%, Na2O: 0-0.5wt.%, K2O: 0-0.5wt.%.

[0010] A method for preparing a low-temperature sintered ceramic material comprises the following steps:

[0011] (1) Prepare SiO2-Al2O3-B2O3-Li2O glass powder and SiO2-Al2O3-MgO-CaO glass powder respectively:

[0012] SiO2, Al2O3, H3BO3, Li2CO3, H3PO4, ZrO2, CeO2, K2CO3 and other ingredients are mixed according to the proportion, ball-milled and mixed, dried, and then melted at 1100°C to 1300°C for 1 to 5 hours, quenched with water to form glass slag, and the prepared glass slag is crushed and ball-milled to form SiO2-Al2O3-B2O3-Li2O glass powder with a particle size (D50) of 1 to 5 μm;

[0013] SiO2, Al2O3, MgO, H3BO3, CaCO3, H3PO4, ZrO2, TiO2, Na2CO3, K2CO3 and other ingredients are mixed according to the proportion, ball-milled and mixed, dried, and then melted at 1300°C to 1500°C for 1 to 5 hours, quenched with water to form glass slag, and the prepared glass slag is crushed and ball-milled to prepare SiO2-Al2O3-MgO-CaO glass powder with a particle size (D50) of 1 to 5 μm;

[0014] (2) Weigh α-Al2O3, crystalline SiO2, and SiO2-Al2O3-B2O3-Li2O glass powder and SiO2-Al2O3-MgO-CaO glass powder prepared in step (1) according to a predetermined formula, put the mixture into a ball mill, add zirconium balls, add deionized water at a material-water mass ratio of 1:1-1.5, and ball mill on a planetary ball mill for 4-8 hours at a rotation speed of 250-400 rpm; by controlling the ball milling material-water ratio, ball milling time and rotation speed, the porcelain-forming properties are improved according to the powder particle size.

[0015] (3) drying the ball-milled material in step (2) in an oven at 80-120°C, passing through a 100-mesh sieve, adding 10-15 wt.% of an acrylic emulsion binder for granulation, and then manually dry pressing the material; then heating the material to 450°C at 1-2°C / min and keeping the temperature for 2 hours to remove the binder, heating the material to 850-900°C at 5-8°C / min, keeping the temperature for 0.5-2 hours, and sintering the material to obtain a low-temperature sintered ceramic material. The low-temperature sintered ceramic material of the present invention is a low-dielectric-constant α-Al2O3 (ε r <10) and low dielectric constant (ε r <4) and a crystalline SiO2 ceramic with a small thermal expansion coefficient (<1ppm / ℃) as the main phase, and homemade SiO2-Al2O3-B2O3-Li2O glass and SiO2-Al2O3-MgO-CaO glass as sintering aids for doping, so that the sintering temperature of Al2O3 and SiO2 composite ceramics is reduced to below 900℃, thereby achieving low-temperature sintering. The softening points of homemade SiO2-Al2O3-B2O3-Li2O glass-ceramics and SiO2-Al2O3-MgO-CaO glass-ceramics are 617℃ and 693℃ respectively. During the sintering process, on the one hand, glasses with different softening points fill the ceramic phase gaps at different temperatures, promote the ceramic liquid phase mass transfer, and achieve low-temperature sintering. In addition, during the sintering process, SiO2-Al2O3-B2O3-Li2O glass-ceramics and SiO2-Al2O3-MgO-CaO glass-ceramics will partially analyze Li2SiO3, Li2SiO4, LiAlSi2O6, CaSiO3, Ca2BO4 and other crystalline phases, which are beneficial to improve the bonding strength of the ceramic phase interface. Therefore, by gradient doping of glass with different softening points and adjusting the relative content of Al2O3 and SiO2, the obtained ceramic material can be sintered at low temperature and obtain low dielectric constant, low thermal expansion coefficient and high strength characteristics.

[0016] Compared with the prior art, the present invention has the advantages of low dielectric constant, low thermal expansion coefficient, high strength, etc., and has a low sintering temperature (<900°C), and can be well co-fired with low-resistivity silver electrodes, so it is suitable for microelectronic packaging and LTCC passive integrated devices, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the SEM of the cross-section of the low-temperature sintered ceramic material of Example 6 co-fired with silver. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0019] In this embodiment, α-Al2O3 with a purity greater than 99.5%, crystalline SiO2 with a purity greater than 99.5%, and analytically pure MgO, H3BO3, Li2CO3, CaCO3, H3PO4, ZrO2, CeO2, TiO2, Na2CO3, K2CO3, etc. are used to melt glass. The specific preparation steps and formula are consistent with the above steps and formula, and are specifically implemented as follows:

[0020] (1) Prepare SiO2-Al2O3-B2O3-Li2O glass powder and SiO2-Al2O3-MgO-CaO glass powder respectively:

[0021] The components of SiO2-Al2O3-B2O3-Li2O glass include: SiO2: 30~55wt.%, Al2O3: 10~30wt.%, B2O3: 5~10wt.%, Li2O: 0.5~6wt.%, P2O5: 0~0.5wt.%, ZrO2: 0~0.5wt.%, CeO2: 0~0.5wt.%, K2O: 0~0.5wt.%. SiO2, Al2O3, H3BO3, Li2CO3, H3PO4, ZrO2, CeO2, K2CO3 and other ingredients are mixed according to the proportion, ball-milled and dried, and then melted at 1100°C to 1300°C for 1 to 5 hours, and quenched with water to form glass slag. The prepared glass slag is crushed and ball-milled into powder to make SiO2-Al2O3-B2O3-Li2O glass powder with a particle size (D50) of 1 to 5 μm.

[0022] SiO2-Al2O3-MgO-CaO glass, its components include: SiO2: 10~40wt.%, Al2O3: 4~12wt.%, MgO: 3~8wt.%, B2O3: 10~20wt.%, CaO: 25~40wt.%, P2O5: 0.2~0.5wt.%, ZrO2: 0~0.5wt.%, TiO2: 0~0.5wt.%, Na2O: 0~0.5wt.%, K2O: 0~0.5wt.%. SiO2, Al2O3, MgO, H3BO3, CaCO3, H3PO4, ZrO2, TiO2, Na2CO3, K2CO3 and other ingredients are mixed in proportion, ball-milled and dried, then melted at 1300°C to 1500°C for 1 to 5 hours, and quenched with water to form glass slag. The prepared glass slag is crushed and ball-milled to prepare SiO2-Al2O3-MgO-CaO glass powder with a particle size (D50) of 1 to 5 μm.

[0023] (2) α-Al2O3, crystalline SiO2, SiO2-Al2O3-B2O3-Li2O glass powder, and SiO2-Al2O3-MgO-CaO glass powder were weighed and prepared according to Table 1. The mixture was placed in a ball mill, zirconium balls were added, and deionized water was added at a material-water mass ratio of 1:1.2. The mixture was ball milled on a planetary ball mill for 6 hours at a speed of 300 rpm. The ball milled mixture was placed in an oven at 100°C and dried, and passed through a 100 mesh sieve. 10 wt.% acrylic emulsion binder was added to granulate the mixture, and dry pressed with a manual press to form a Φ15 mm×7 mm cylinder and a 4.8 mm×4.0 mm×55 mm strip. The green sample was placed in a sintering furnace, heated to 450°C at 2°C / min and kept warm for 2 hours for debinding, then heated to 850-900°C at 6°C / min, kept warm for 0.5-2 hours and sintered to make a low-temperature sintered ceramic material. The dielectric, thermal and mechanical properties of the sample were tested.

[0024] Table 1 is a table of technical parameters used in preparing samples from Examples 1 to 13

[0025]

[0026] The test methods and test equipment used to test the dielectric properties, thermal properties and mechanical properties of the samples obtained in Examples 1 to 13 are as follows:

[0027] 1. Use Agilent network analyzer and closed cavity method to test the microwave dielectric properties of cylindrical samples in the test frequency range of 1 GHz to 20 GHz;

[0028] 2. Use NETZSCH thermal expansion instrument to measure the thermal expansion coefficient, the temperature range is 25~300℃;

[0029] 3. Use SANS universal testing machine and three-point bending method to test the bending strength of strips.

[0030] The test results of each sample are shown in Table 2.

[0031] Table 2 shows the properties of the sintered samples of Examples 1 to 13

[0032]

[0033] It can be seen from the above embodiments that within the range of Al2O3: 30wt.%, SiO2: 30wt.%, SiO2-Al2O3-B2O3-Li2O glass: 15~25wt.%, SiO2-Al2O3-MgO-CaO glass: 15~25wt.%, the sintering temperature is between 850~900℃, the dielectric constant of the ceramic samples is lower than 5, the thermal expansion coefficient is less than 5ppm / ℃, and the flexural strength is greater than 180MPa. Figure 1 The SEM morphology of the co-fired material of Example 6 and the silver electrode is shown, which meets the LTCC process requirements and is a potential LTCC packaging substrate material.

Claims

1. A low temperature sintered ceramic material, characterized in that: The components of the material include: α-Al2O3: 27-45wt.%, crystalline SiO2: 15-33wt.%, SiO2-Al2O3-B2O3-Li2O glass: 7-25wt.%, SiO2-Al2O3-MgO-CaO glass: 15-33wt.%; wherein, α-Al2O3 and crystalline SiO2 are main crystal phases, and SiO2-Al2O3-B2O3-Li2O glass and SiO2-Al2O3-MgO-CaO glass are sintering aids.

2. A low temperature sintered ceramic material according to claim 1, characterized in that: The SiO2-Al2O3-B2O3-Li2O glass comprises the following components: SiO2: 30-55wt.%, Al2O3: 10-30wt.%, B2O3: 5-10wt.%, Li2O: 0.5-6wt.%, P2O5: 0-0.5wt.%, ZrO2: 0-0.5wt.%, CeO2: 0-0.5wt.%, K2O: 0-0.5wt.%.

3. A low temperature sintered ceramic material according to claim 1, characterized in that: The SiO2-Al2O3-MgO-CaO glass comprises the following components: SiO2: 10-40wt.%, Al2O3: 4-12wt.%, MgO: 3-8wt.%, B2O3: 10-20wt.%, CaO: 25-40wt.%, P2O5: 0.2-0.5wt.%, ZrO2: 0-0.5wt.%, TiO2: 0-0.5wt.%, Na2O: 0-0.5wt.%, K2O: 0-0.5wt.%.

4. A low temperature sintered ceramic material according to claim 4, characterized in that: The low temperature sintered ceramic material is prepared according to the following steps: (1) Prepare SiO2-Al2O3-B2O3-Li2O glass powder and SiO2-Al2O3-MgO-CaO glass powder respectively: The ingredients are prepared according to a ratio, wherein the ingredients include SiO2, Al2O3, H3BO3, Li2CO3, H3PO4, ZrO2, CeO2, and K2CO3, the ingredients are ball-milled and mixed, dried, and then melted at 1100° C. to 1300° C. for 1 to 5 hours, and water-quenched to form glass slag, and the prepared glass slag is crushed and ball-milled to form a SiO2-Al2O3-B2O3-Li2O glass powder with a particle size (D50) of 1 to 5 μm; The ingredients are prepared according to a ratio, wherein the ingredients include SiO2, Al2O3, MgO, H3BO3, CaCO3, H3PO4, ZrO2, TiO2, Na2CO3, and K2CO3; the ingredients are ball-milled and mixed, dried, and then melted at 1300° C. to 1500° C. for 1 to 5 hours, and water-quenched to form glass slag; the prepared glass slag is crushed and ball-milled to prepare SiO2-Al2O3-MgO-CaO glass powder with a particle size (D50) of 1 to 5 μm; (2) accurately weighing α-Al2O3, crystalline SiO2, and the SiO2-Al2O3-B2O3-Li2O glass powder and SiO2-Al2O3-MgO-CaO glass powder prepared in step (1) according to a predetermined formula, ball-milling with deionized water to uniformly mix them; (3) drying the powder ball-milled in step (2), adding 10-15 wt.% of an acrylic emulsion binder to granulate, and then manually dry pressing to form; then heating to 450°C at 1-2°C / min and keeping the temperature for 2 hours to debind, heating to 850-900°C at 5-8°C / min, keeping the temperature for 0.5-2 hours, and sintering to prepare a low-temperature sintered ceramic material.

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