A Mg-Ti-O based high Q high thermal conductivity microwave dielectric ceramic material and its preparation method

Abstract

The present invention belongs to the technical field of electronic materials, specifically a Mg-Ti-O-based high-Q high thermal conductivity microwave dielectric ceramic material and a preparation method thereof. The ceramic material of the present invention adopts a solid-phase reaction method, and generates a subcrystalline phase MgTiO3 with a high Q value and a high thermal conductivity by doping Mg2TiO4 with TiO2. The microstructure and density of the overall material are improved by the composite ceramic system, thereby improving the thermal conductivity and Q×f value of the ceramic material; the (1-y)Mg2TiO4+yMgTiO3 ceramic material prepared by the present invention, 0<y<0.5, has a thermal conductivity of 8.0~10.5W / (m·K), a Q×f value of 100000~150000GHz, and a relative dielectric constant of 14~16. The Mg-Ti-O-based high-Q high thermal conductivity microwave dielectric ceramic material of the present invention has a simple preparation process, high thermal conductivity and Q×f value and an appropriate dielectric constant, and can be used as a multilayer ceramic component material and a circuit substrate material in the field of electronic packaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and specifically relates to a Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material and a preparation method thereof, which can be used as a multilayer ceramic component material and circuit substrate material in the field of electronic packaging. Background Art

[0002] Microwave dielectric ceramic materials are widely used in the manufacture of high-frequency, miniaturized ceramic components and high-reliability multilayer ceramic circuit substrates in the communications and information industries. In recent years, with the continuous increase in communication frequencies and the miniaturization and integration of electronic components and complete systems, the comprehensive performance requirements for these materials have become increasingly stringent. In particular, they are expected to maintain a high Q value (ultra-low dielectric loss) while also possessing an appropriate dielectric constant (to meet device miniaturization and signal transmission delay requirements) and a high thermal conductivity (to meet the high power and heat dissipation requirements of components and complete systems).

[0003] At present, there are many types of high-Q microwave dielectric ceramic material systems, such as silicates, phosphates, niobates, molybdates, etc., but the thermal conductivity of the materials is basically only in the range of 3 to 5 W / (m·K). For example, Ba(Zn) prepared by Rui Da Shi et al. at 1350℃ 1 / 3 Nb 2 / 3 )O3 ceramics have a Q×f value of up to 111400 GHz, but their thermal conductivity is only 3.72 W / (m·K). Widely used high thermal conductivity microwave ceramic materials such as AlN, Si3N4, and BeO, although they have thermal conductivities exceeding 100, generally have dielectric constants below 10, making it difficult to miniaturize devices. In particular, to ensure the low loss characteristics of the material, high-purity raw materials and relatively complex process flows are often required to match the grain and grain boundary growth of the ceramic material. Therefore, the preparation methods and preparation processes are very demanding and strict, such as the synthesis temperature exceeding 1600°C and the need for a special atmosphere sintering environment. Even so, it is difficult to obtain the expected material properties. For example, the AlN ceramics prepared by Xiangrong Zang et al. in a nitrogen atmosphere have a thermal conductivity of 41.41 W / (m·K), but their dielectric loss in the 8-13 GHz frequency band is as high as 0.25, which cannot meet the application requirements in the microwave frequency band.

[0004] To this end, developing a microwave ceramic material that can simultaneously meet the needs of high-frequency miniaturization of ceramic components and multi-layer ceramic circuit substrates, with a relatively simple preparation process, high thermal conductivity, high quality factor and appropriate dielectric constant (within 10-20) has become an urgent problem to be solved in the field of microwave material engineering, and is bound to have great application value in many technical fields. Summary of the Invention

[0005] To address these issues and shortcomings, the present invention provides a Mg-Ti-O-based microwave dielectric ceramic material with high Q and high thermal conductivity, and its preparation method. The key concept is to dope TiO2 into a Mg2TiO4 microwave ceramic material, utilizing the MgTiO3 secondary crystalline phase with high Q and high thermal conductivity produced during the solid-phase reaction to form a composite ceramic system. Within the appropriate doping range, this can effectively improve the material's sintering characteristics, control grain size, and composite ceramic composition, thereby increasing the material's thermal conductivity and Q×f value.

[0006] A Mg-Ti-O-based microwave dielectric ceramic material with high Q and high thermal conductivity has a general chemical formula of (1-y)Mg2TiO4+yMgTiO3, where 0<y<0.5, a thermal conductivity of 8.0-10.5 W / (m·K), a Q×f value of 100,000-150,000 GHz, and a relative dielectric constant of 14-16. A Mg2TiO4 pre-sintered material is first prepared using TiO2 and MgO by a solid-phase method. The material is then mixed by ball milling, granulated, formed, and sintered to produce a Mg-Ti-O-based microwave dielectric ceramic material with a primary crystalline phase of Mg2TiO4 and a secondary crystalline phase of MgTiO3.

[0007] The preparation method of the above-mentioned Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material comprises the following specific steps:

[0008] Step 1: Use MgO and TiO2 as raw materials, weigh the materials according to the molar ratio of MgO:TiO2 of 2:1 (the chemical formula molar ratio of Mg2TiO4) to obtain the main powder.

[0009] Step 2: ball mill the main powder prepared in step 1 to mix it evenly, and then take it out and dry it.

[0010] Step 3: Keep the powder dried in step 2 at 1100-1300° C. until the powder reacts completely to obtain Mg2TiO4 pre-sintered material.

[0011] Step 4: Add TiO2 dopant to the Mg2TiO4 pre-sintered material obtained in step 3 to obtain powder A; the total amount of the two by mass ratio is 1, and the respective proportions are: 85% ≤ Mg2TiO4 pre-sintered material < 100%, 0% < TiO2 dopant ≤ 15%.

[0012] Step 5: ball-mill the powder A prepared in step 4 for a second time to mix it evenly, take it out and dry it; then add PVA glue to granulate the dried powder and press it into a green embryo.

[0013] Step 6: Place the green body obtained in step 5 into a sintering furnace, raise the temperature to 1300-1500° C. at a heating rate of 1-5° C. / min, and keep the temperature until the reaction inside the green body is complete and sintered. Then, reduce the temperature to 300-700° C. at a cooling rate of 1-5° C. / min, and then naturally cool to room temperature to obtain a (1-y)Mg2TiO4+yMgTiO3 ceramic material, where 0<y<0.5.

[0014] Furthermore, in step 2 and step 5, the ball milling time is 8 to 12 hours, the rotation speed is 200 to 400 r / min, and the drying temperature is 100 to 120°C.

[0015] In summary, the present invention first synthesizes a Mg2TiO4 pre-sintered material and then dopes the Mg2TiO4 with TiO2 at varying mass ratios. During the sintering process in step 6, the doped TiO2 reacts with Mg2TiO4 at 900°C as follows: TiO2 + Mg2TiO4 → MgTiO3, completely converting the TiO2 doped in step 4 into MgTiO3. The appearance of the secondary crystalline MgTiO3 phase controls grain growth, making the ceramic material denser and improving thermal conductivity and Q value. By varying the doping amount of TiO2, Mg-Ti-O-based high-Q, high-thermal conductivity dielectric ceramics with thermal conductivity of 8.0 to 10.5 W / (m·K), Q×f values of 100,000 to 150,000 GHz, and relative dielectric constants of 14 to 16 are obtained. These ceramics can be used as multilayer ceramic component materials and circuit substrate materials in the field of electronic packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 XRD patterns of (1-y)Mg2TiO4+yMgTiO3 ceramics in Examples 3, 7, 9, 10 and 11;

[0017] Figure 2 MgTiO3 phase ratio diagram of (1-y)Mg2TiO4+yMgTiO3 ceramics in Examples 3, 7, 9, 10 and 11;

[0018] Figure 3 The SEM images and grain size distribution diagrams of (1-y)Mg2TiO4+yMgTiO3 ceramics in Examples 3, 7 and 11 are shown;

[0019] Figure 4 Figures 3, 7, 9, 10, and 11 show the bulk density and relative density of (1-y)Mg2TiO4+yMgTiO3 ceramics;

[0020] Figure 5 is the thermal conductivity value of the (1-y)Mg2TiO4+yMgTiO3 ceramic in Example 1-11;

[0021] Figure 6 is the Q×f value of the (1-y)Mg2TiO4+yMgTiO3 ceramic in Examples 1-8;

[0022] Figure 7 is the dielectric constant of the (1-y)Mg2TiO4+yMgTiO3 ceramics in Examples 3, 7, 9, 10 and 11. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] A method for preparing a Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material comprises the following steps:

[0025] Step 1: Use MgO and TiO2 as raw materials, weigh the materials according to the molar ratio of MgO:TiO2 of 2:1, and prepare the main powder.

[0026] Step 2: ball mill the main powder prepared in step 1 according to the mass ratio of main powder: deionized water: zirconium ball = 1:2:3. The ball milling time is 12 hours and the ball milling speed is 300r / min. After taking out, dry it at 100°C.

[0027] Step 3: The powder obtained after drying in step 2 is placed in a sintering furnace, heated from room temperature to 1200°C at a heating rate of 2°C / min and kept warm for 6 hours, then cooled to 500°C at a cooling rate of 2°C / min, and then naturally cooled to room temperature to obtain Mg2TiO4 pre-sintered material.

[0028] Step 4: Add TiO2 dopant to the Mg2TiO4 pre-calcined material obtained in step 3 to prepare powder A, wherein the specific contents of Mg2TiO4 and TiO2 in each embodiment are shown in Table 1.

[0029] Step 5: The powder A prepared in step 4 is subjected to secondary ball milling, wherein the mass ratio of powder A: deionized water: zirconium balls is 1:2:3, the ball milling time is 8 hours, and the ball milling speed is 300 r / min; then the secondary ball milled material is taken out and dried at 100° C., and PVA glue with a concentration of 10 wt% (PVA to the total mass ratio of the aqueous solution) is added to granulate and form, and then pressed into a green embryo under a pressure of 10 MPa.

[0030] Step 6: Place the green body obtained in step 5 into a sintering furnace and keep it warm for 6 hours, with the heating and cooling rates both at 2°C / min, to obtain a (1-y)Mg2TiO4+yMgTiO3 ceramic material. The holding temperatures of the various embodiments are shown in Table 1.

[0031] Table 1: Relevant process parameters of Examples 1-11

[0032] Example No. <![CDATA[Content of Mg2TiO4 pre-sintered material]]> <![CDATA[TiO2 dopant content]]> Holding temperature 1 100wt% 0wt% 1350℃ 2 100wt% 0wt% 1400℃ 3 100wt% 0wt% 1450℃ 4 100wt% 0wt% 1500℃ 5 91wt% 9wt% 1350℃ 6 91wt% 9wt% 1400℃ 7 91wt% 9wt% 1450℃ 8 91wt% 9wt% 1500℃ 9 97wt% 3wt% 1450℃ 10 94wt% 6wt% 1450℃ 11 88wt% 12wt% 1450℃

[0033] The materials prepared in the above 11 embodiments were tested, and the results were as follows: Figures 1 to 7 , where x is the mass ratio of added TiO2.

[0034] like Figure 1 As shown, the sample materials of Examples 3, 7, 9, 10 and 11 all generated MgTiO3 secondary crystalline phase; Figure 2 The percentage of MgTiO3 phase in samples of Examples 3, 7, 9, 10 and 11 is shown. As the TiO2 doping content increases, more and more TiO2 reacts with Mg2TiO4 to form MgTiO3. Figure 1 、 Figure 2 It can be seen that when the TiO2 doping amount is 0wt%, MgTiO3 sub-crystalline phase is still produced. This is because when the temperature reaches 1300℃, a small amount of Mg2TiO4 will undergo thermal decomposition to produce MgTiO3; however, at this time, MgTiO3 exists as an impurity phase in the overall material, which will lead to uneven distribution of grain size and affect the ceramic density (such as Figure 3 、 Figure 4 ).

[0035] The SEM test results of Examples 3, 7 and 11 are as follows: Figure 3 As shown in Figure 2, it can be seen that as the grain size of the TiO2 doped material decreases rapidly, the grain size distribution becomes more uniform. Figure 4 As shown in Figure 2, the grain size decreases and the size distribution becomes uniform, resulting in a rapid increase in relative density. The thermal conductivity of Examples 1-11 is shown in Figure 2. Figure 5 As shown, the thermal conductivity of the material after doping with TiO2 is 8.0~10.5W / (m·K), which is higher than that of the material without TiO2, and reaches the optimal thermal conductivity when the TiO2 doping amount is 9wt%; the Q×f value test results of Examples 1-8 are shown in Figure 6 As shown in the figure, the Q×f value (100,000 to 150,000 GHz) is also improved after doping with TiO2. Figure 7 is the dielectric constant of the (1-y)Mg2TiO4+yMgTiO3 ceramics in Examples 3, 7, 9, 10 and 11. The dielectric constant of the ceramics is also maintained in an appropriate range (14 to 16).

[0036] It can be seen from the above embodiments that the ceramic material of the present invention adopts a solid-phase reaction method to generate a subcrystalline phase MgTiO3 with a high Q value and high thermal conductivity by doping Mg2TiO4 with TiO2, effectively improving the grain size and relative density of the composite ceramic within a suitable doping range, improving the microstructure and density of the overall material through the composite ceramic system, and thereby improving the thermal conductivity and Q×f value of the ceramic material, thereby preparing a Mg-Ti-O based microwave dielectric ceramic material with high thermal conductivity, high Q value and appropriate dielectric constant; the (1-y)Mg2TiO4+yMgTiO3 ceramic material prepared by the present invention, 0<y<0.5, has a thermal conductivity of 8.0~10.5W / (m·K), a Q×f value of 100000~150000 GHz, and a relative dielectric constant of 14~16. The Mg-Ti-O-based high-Q and high-thermal conductivity microwave dielectric ceramic material of the present invention has a simple preparation process, high thermal conductivity and Q×f value, and an appropriate dielectric constant, can meet the application requirements of high-frequency and high-integration microwave communication devices, and can be used as a multilayer ceramic component material and circuit substrate material in the field of electronic packaging.

Claims

1. A Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material, characterized by: The invention discloses a microwave dielectric ceramic material having a general chemical formula of (1-y)Mg2TiO4+yMgTiO3, 0<y<0.5, a thermal conductivity of 8.0~10.5W / (m·K), a Q×f value of 100000~150000GHz, and a relative dielectric constant of 14~16. The invention first uses TiO2 and MgO to prepare a Mg2TiO4 pre-sintered material by a solid phase method. Then, a Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material having a main crystal phase of Mg2TiO4 and a secondary crystal phase of MgTiO3 is prepared by ball milling, granulating, forming and sintering a total amount of 85%≤Mg2TiO4 pre-sintered material<100% and 0%<TiO2 dopant≤15%.

2. The Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material according to claim 1, characterized in that: The content of the TiO2 dopant is 3% to 12%.

3. The Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material according to claim 1, characterized in that: The content of the TiO2 dopant is 9%.

4. The method for preparing the Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material according to claim 1, wherein: The specific steps are as follows: Step 1: Using MgO and TiO2 as raw materials, weigh the materials according to the molar ratio of MgO:TiO2 of 2:1 to prepare the main powder; Step 2: ball mill the main powder prepared in step 1 to mix it evenly, and then take it out and dry it; Step 3: keeping the powder dried in step 2 at 1100-1300° C. until the powder reacts completely to obtain Mg2TiO4 pre-sintered material; Step 4: Adding a TiO2 dopant to the Mg2TiO4 pre-calcined material obtained in step 3 to obtain powder A; the total weight of the two is 1, and the respective proportions are: 85% ≤ Mg2TiO4 pre-calcined material < 100%, 0% < TiO2 dopant ≤ 15%; Step 5: ball mill the powder A prepared in step 4 for a second time to mix it evenly, then take it out and dry it; then add PVA glue to granulate the dried powder and press it into a green embryo; Step 6: Place the green body obtained in step 5 into a sintering furnace, raise the temperature to 1300-1500° C. at a heating rate of 1-5° C. / min, and keep the temperature until the reaction inside the green body is complete and sintered. Then, reduce the temperature to 300-700° C. at a cooling rate of 1-5° C. / min, and then naturally cool to room temperature to obtain a (1-y)Mg2TiO4+yMgTiO3 ceramic material, where 0<y<0.

5.

5. The method for preparing the Mg-Ti-O based high Q and high thermal conductivity microwave dielectric ceramic material according to claim 4, characterized in that: In step 2 and step 5, the ball milling time is 8 to 12 hours, the rotation speed is 200 to 400 r / min, and the drying temperature is 100 to 120° C.

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