A low dielectric, low loss and high strength LTCC material and preparation method thereof

Abstract

A low-dielectric, low-loss and high-strength LTCC material and its preparation method. The present invention belongs to the field of electronic ceramics and their manufacturing, and relates to a low-dielectric, low-loss and high-strength LTCC material and its preparation method. The material of the present invention is a Li2O-Ca0-MgO-CoO-SiO2-based micro LTCC material, and its material chemical formula is xLi2O-Ca0-(1-x-y)MgO-yCoO-2SiO2 (x = 0-0.2 mol, y = 0-0.5), which is prepared by the solid-phase reaction method; the crystal phase after sintering is a mixed phase of CaMg(SiO3)2 (JCPDS#00-019-0239), Ca2CoSi2O7 (JCPDS#01-070-5361), CaSiO3 (JCPDS#00-027-1064) and Co2SiO4 (JCPDS#00-025-0254). The sintering temperature of the present invention is 880°C to 925°C, the dielectric constant is 5 to 8, and the loss is as low as 2.8×10 ‑4 (f = 12 GHz), and the flexural strength exceeds 200 MPa. The ceramic of this composition has a high quality factor and a high flexural strength, and can be applied in the fields of LTCC filters, microwave antennas, inductors, etc. The preparation process of the present invention is simple and the performance is excellent.

Description

Technical Field

[0001] The invention belongs to the field of electronic ceramics and their manufacturing, and relates to a low temperature sintered Li 2 O-Ca0-MgO-CoO-SiO 2 Micro-LTCC materials and preparation methods thereof. Background Art

[0002] With the development of national communication technology, radio mobile communication equipment is frequently updated, and miniaturization, more powerful functions and low cost have become its development trend. Low Temperature Co-fired Ceramic (LTCC) technology can integrate multiple passive components of different types and performances in one package, which can effectively reduce the volume of various communication RF devices and is the mainstream technology of passive integration. The emergence and development of low temperature co-firing technology makes it possible to miniaturize, increase frequency and increase reliability of microwave components.

[0003] Since LTCC technology requires co-firing with Ag, Cu and other electrodes used in current production, LTCC materials must have a low sintering temperature (≤950°C) and good chemical compatibility with electrodes. For LTCC materials, the most important performance requirement is a low relative dielectric constant ε r , high quality factor Q×f, near-zero resonant frequency temperature coefficient τ f And high bending strength. Among them, the relative dielectric constant ε r Usually used to characterize the polarization and dielectric properties of dielectric materials; the quality factor Q×f is a quality indicator that represents the ratio of the energy stored in an energy storage device (such as an inductor, capacitor, etc.) and the energy lost per cycle in a resonant circuit. The higher the Q×f value, the smaller the loss; the resonant frequency temperature coefficient τ f It is expressed as the sensitivity of the resonant frequency to temperature changes; high bending strength means that the device is not easily damaged during assembly and use.

[0004] In particular, the low latency and low loss required by 5G technology are very important for low-medium (ε r<10) LTCC materials have higher requirements. However, the current low-dielectric LTCC materials are mainly glass-ceramic composite systems. The strength of this material can be very high, but due to the high glass content, the loss is generally greater than 0.001, which greatly limits the development of high-performance filters. For example, the document "Li Zaiying, Li Qiang, Yan Jian, et al. Research on high-bending strength microwave dielectric LTCC substrate materials [J]. Electronic Components and Materials, 2020, 39(1):4." reported that the Ca-Mg-Zr-Zn-B-Si ceramic material has a dielectric constant of 7.96 and a bending strength of up to 400MPa, but the loss exceeds 0.003. If you want to obtain a low-loss LTCC material, you have to reduce the glass content, but it will generally increase the sintering temperature and cannot meet the LTCC application. Therefore, it is a very difficult task to obtain a low-loss, high-strength low-dielectric LTCC material that does not contain glass. Summary of the invention

[0005] In view of the above problems, the present invention provides a glass-free, low-dielectric, low-loss, high-strength Li 2 O-Ca0-MgO-CoO-SiO 2 Based LTCC material and preparation method thereof.

[0006] The low dielectric ceramic material can be sintered at low temperature (<950℃) to form a compact structure with low loss and high bending strength. 3 ) 2 , Ca 2 CoSiO 7 、CaSiO 3 and Co 2 SiO 4 phase, the sintering temperature can be as low as 910℃, the dielectric constant is 5-8, and the loss is as low as 2.8×10 -4 (f = 12GHz), the bending strength exceeds 200MPa, so it can be used in the LTCC field, the preparation process is simple, and the performance is excellent. The raw material composition is Li 2 CO 3 、CaCO 3 、MgO、Co 2 O 3 、SiO 2 , according to xLi 2 O-Ca0-(1-xy)MgO-yCoO-2SiO 2 (x=0-0.2mol, y=0-0.5) is used for preparing ingredients and synthesizing by solid phase reaction method.

[0007] The preparation method is as follows:

[0008] Step 1: Li2 CO 3 、 CaCO 3 、 MgO, Co 2 O 3 、 SiO 2 The original powder materials of 2 xLi 2 O-CaO-(1-x-y)MgO-yCoO-2SiO

[0009] (0 < x ≤ 0.2 mol, 0 < y ≤ 0.5) are proportioned according to the chemical formula;

[0010] Step 2: Load the proportioned materials prepared in Step 1 into a ball milling tank, use zirconium balls and deionized water as the grinding media, perform planetary ball milling for 4 - 10 hours according to the ratio of powder:zirconium balls:deionized water = 1:3 - 7:2 - 4 (mass ratio), then dry at 80 - 120 °C. The dried powder is sieved through a 40 - 60 mesh sieve, and then pre-fired in an air atmosphere at 850 - 950 °C for 2 - 4 hours;

[0011] Step 3: Perform secondary ball milling on the pre-fired powder, with a ratio of powder:zirconium balls:deionized water = 1:2 - 7:1 - 3 (mass ratio), perform planetary ball milling for 2 - 6 hours. After taking out and drying the wet material after ball milling, granulate the powder with an acrylic acid solution with a concentration of 2 - 6 wt% as the binder; 2 O-CaO-MgO-CoO-SiO 2 based low-temperature sintering microwave dielectric ceramics can be obtained.

[0012] In the present invention, by adjusting the proportion of oxides such as Li 2 CO 3 、 MgO, Co 2 O 3 and CaCO 3 、 SiO 2 with the main base materials, it can be sintered densely at a relatively low sintering temperature (≤950 °C), and has excellent dielectric properties and can be applied in the field of high-frequency filters. A low-loss, high-strength, low-dielectric LTCC material without glass is prepared, and its preparation method is a solid-phase sintering method, with a simple process. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the XRD diagram of Example 2, Example 5 and Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be further described in detail below with reference to the drawings and examples.

[0015] Step 1: Li 2 CO 3 、CaCO 3 、MgO、Co 2 O 3 、SiO 2 The original powder is xL i 2 O-Ca0-(1-xy)MgO-yCoO-2S iO 2 (x=0-0.2 mol, y=0-0.5) and the raw powders in different embodiments are shown in Table 1 below.

[0016] Step 2, the ingredients prepared in step 1 are loaded into a ball mill, zirconium balls and deionized water are used as grinding media, and the powder: zirconium balls: deionized water = 1:5:2 (mass ratio) is planetary ball milled for 6 hours, and then dried at 120°C, the dried powder is sieved with a 60-mesh screen, and then pre-calcined in an atmosphere at 880°C for 4 hours;

[0017] Step 3, the pre-sintered powder is subjected to secondary ball milling, with zirconium ball: deionized water = 1:5:2 (mass ratio) planetary ball milling for 2 to 6 hours, the wet material is taken out and dried, and then the powder is granulated using a 3wt% concentration of acrylic acid solution as a binder;

[0018] Step 4: Put the powder granulated in step 3 into a φ12 mold for dry pressing. After the cylindrical block is debinded at 500°C, it is sintered and kept warm at 880°C and 910°C (different embodiments have different sintering temperatures, as shown in Table 1 below) in air atmosphere for 2 hours to obtain Li 2 O-Ca0-MgO-CoO-SiO 2 Based on low temperature sintered microwave dielectric ceramics.

[0019] Figure 1 The XRD diagrams of Example 2, Example 5, and Example 7 show that the embodiment is CaMg(SiO 3 ) 2 (JCPDS#00-019-0239), Ca 2 CoSiO 7 (JCPDS#01-070-5361), CaSiO 3 (JCPDS#00-027-1064) and Co 2 SiO 4 (JCPDS#00-025-0254) mixed phase.

[0020] Table 1 The composition and microwave dielectric properties of each example are as follows

[0021]

[0022]

[0023] The relative dielectric constant εr, quality factor Q×f, resonant frequency temperature coefficient τf and bending strength of the ceramics prepared in the above Examples 1-7 were tested, and the test results are as follows:

[0024]

[0025] The above table includes the results of the example ingredients in the chemical formula and the microwave dielectric properties and flexural strength of the sintered samples. It can be seen from the table that all samples showed excellent microwave dielectric properties and high flexural strength when kept at 880℃ to 910℃ for 2 hours. The low loss indicates that the ceramic is in good condition within this temperature. In particular, the dielectric constant of the sample in Example 7 is 7.65, the loss is as low as 0.00028, and the flexural strength exceeds 200MPa, which can meet the application requirements of most LTCCs.

[0026] In summary, the present invention adjusts the raw material Li 2 CO 3 、CaCO 3 、MgO、Co 2 O 3 、SiO 2 The molar ratio of the final product is the Li i with excellent performance, low dielectric, high quality factor and high strength. 2 O-Ca0-MgO-CoO-Si O 2 Based on LTCC material system, its preparation method is simple and easy to industrialize.

Claims

1. A method for preparing low dielectric, low loss and high strength LTCC material. It is characterized in that The preparation method comprises the following steps: Step 1: Add CaCO 3 、SiO 2 、MgO、Li 2 CO 3 and Co 2 O 3 The original powders are mixed according to mass ratios of 19.358, 69.724, 4.677, 1.429 and 4.812 to obtain powder; Step 2: The powder prepared in step 1 is loaded into a ball mill, and zirconium balls and deionized water are used as grinding media. The mass ratio of powder, zirconium balls and deionized water is 1:5:

2. The powder is planetarily ball milled for 6 hours, and then dried at 120°C. The dried powder is sieved with a 60-mesh screen and then pre-calcined in an atmosphere at 880°C for 4 hours. Step 3: The pre-calcined powder is subjected to secondary ball milling, the mass ratio of the powder, zirconium ball and deionized water is 1:5:2, and the planetary ball milling is performed for 2 to 6 hours. After the wet material after ball milling is taken out and dried, the powder is granulated using a 2 to 6 wt% concentration of acrylic acid solution as a binder; Step 4: Put the powder granulated in step 3 into a mold for dry pressing. After debinding the cylindrical block at 500℃, sinter and keep warm at 910℃ in air atmosphere for 2 hours to obtain Li 2 O-CaO-MgO-CoO-SiO 2 Based on LTCC materials.

2. A low dielectric, low loss, high strength LTCC material, It is characterized in that The LTCC material is prepared by the preparation method as claimed in claim 1.

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