A low-temperature sinterable ceramic material, a method for producing the same, and a laminate

Abstract

The application discloses a low-temperature sinterable ceramic material, a preparation method thereof and a laminated body. The ceramic material comprises a ceramic base material and a filler, the ceramic base material comprises CaO, SiO2, MgO, Li2CO3 and TiO2, and the filler comprises quartz, B2O3, ZnO and Y2O3, wherein the ceramic material comprises the following components in percentage by weight: 50wt%-70wt% of the ceramic base material, 25wt%-45wt% of quartz in the filler, 0.8wt%-4.2wt% of B2O3 in the filler, 1wt%-5wt% of ZnO in the filler and 0.1wt%-2wt% of Y2O3 in the filler. The ceramic material has low dielectric constant, low dielectric loss, high thermal expansion coefficient and high mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic ceramic packaging materials, in particular to a low-temperature sinterable ceramic material, a preparation method thereof and a laminate. BACKGROUND

[0002] The sintered body composed of a multilayer ceramic substrate in an electronic packaging material is generally required to have a low dielectric constant and a low dielectric loss to cope with the high frequency of the electrical signal, a high thermal expansion coefficient to improve the reliability when the ceramic substrate is mounted, and a high mechanical strength to be applied to large electronic components. However, the ceramic material for preparing the ceramic substrate in the prior art cannot simultaneously satisfy the low dielectric constant, the low dielectric loss, the high thermal expansion coefficient and the high mechanical strength.

[0003] It should be noted that the information disclosed in the above background section is only for understanding the background of the present application, and therefore can include information that does not constitute the prior art known to those of ordinary skill in the art. SUMMARY

[0004] In order to make up for the deficiencies of the prior art, the present application provides a low-temperature sinterable ceramic material, a preparation method thereof and a laminate, which can simultaneously have a low dielectric constant, a low dielectric loss, a high thermal expansion coefficient and a high mechanical strength.

[0005] The present application adopts the following technical solutions:

[0006] In a first aspect, a low-temperature sinterable ceramic material is provided, which comprises a ceramic base and a filler, the ceramic base comprising CaO, SiO2, MgO, Li2CO3 and TiO2, and the filler comprising quartz, B2O3, ZnO and Y2O3, wherein the ceramic material comprises the following weight percentages of each component: 50wt%-70wt% of the ceramic base, 25wt%-45wt% of quartz in the filler, 0.8wt%-4.2wt% of B2O3 in the filler, 1wt%-5wt% of ZnO in the filler and 0.1wt%-2wt% of Y2O3 in the filler.

[0007] In a second aspect, a preparation method of the ceramic material of the first aspect is provided, which comprises the following steps:

[0008] S1: mixing the components in the ceramic base, then ball milling, drying and sieving to obtain a uniformly dispersed main powder;

[0009] S2: pre-sintering the main powder obtained in step S1 to obtain a ceramic base;

[0010] S3: weighing and uniformly mixing the ceramic base obtained in step S2 and the filler according to the formula, and adding a binder to obtain a ceramic slurry;

[0011] S4: sintering the material obtained in S3 after degreasing, to obtain the ceramic material.

[0012] In a third aspect, a laminate is provided, which comprises a plurality of ceramic layers, and the ceramic layers are sintered bodies of the ceramic material according to the first aspect.

[0013] The present application has the following advantages or benefits: the present application realizes low dielectric constant, low dielectric loss, high mechanical strength and high thermal expansion coefficient through the combined action of the components in the ceramic material, and the insulation reliability of the obtained device is excellent. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is an XRD diffraction analysis diagram of the ceramic material obtained in Example 4, Example 7 and Comparative Example 3 of the present application.

[0015] Figure 2 is a TMA curve of the ceramic material obtained in Example 1, 4, 6 and 10 of the present application.

[0016] Figure 3 is a cross-sectional schematic diagram of a laminated ceramic capacitor prepared in the process of preparing a sample for insulation reliability evaluation. DETAILED DESCRIPTION

[0017] The embodiments of the present application are described in detail below. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present application and its applications, and the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0018] The embodiments of the present application provide a low-temperature sinterable ceramic material, which comprises a ceramic base and a filler, the ceramic base comprises CaO, SiO2, MgO, Li2CO3 and TiO2, and the filler comprises quartz, B2O3, ZnO and Y2O3, wherein the ceramic material comprises the following components in the following weight percentages: 50wt%-70wt% of the ceramic base, 25wt%-45wt% of quartz in the filler, 0.8wt%-4.2wt% of B2O3 in the filler, 1wt%-5wt% of ZnO in the filler and 0.1wt%-2wt% of Y2O3 in the filler.

[0019] The terms in the present application are explained as follows:

[0020] Low-temperature sinterable ceramic material: refers to a ceramic material that can be sintered at a sintering temperature of 950°C or lower.

[0021] Filler: refers to an inorganic additive not included in the ceramic base.

[0022] Dielectric constant: The ratio of the electric field in a dielectric material to the applied electric field (in vacuum) when the dielectric is subjected to an applied electric field. The dielectric constant is a measure of the ability of a material to store electric energy.

[0023] Tan delta: Tan delta is the dielectric loss, defined as the energy dissipated per unit time by a dielectric material. The smaller the tan delta, the better the material performance.

[0024] Thermal expansion coefficient: The ability of an object to change in size in response to a change in temperature, measured by the change in dimension per degree of temperature change at constant pressure (p).

[0025] [Ceramic base]

[0026] The Ca / Si molar ratio in the ceramic base is preferably between 1.0 and 1.5.

[0027] CaO in the ceramic base helps to improve the chemical stability of the ceramic. The ceramic base preferably contains 40wt% to 60wt% CaO, more preferably 45wt% to 55wt% CaO.

[0028] SiO2 in the ceramic base helps to reduce the dielectric constant when the ceramic material is sintered, allowing the reduction of stray capacitance with the high frequency of the electrical signal. The ceramic base preferably contains 30wt% to 50wt% SiO2, more preferably 35wt% to 47wt% SiO2.

[0029] MgO in the ceramic base can significantly reduce the solid phase reaction temperature, increase the grain boundary migration speed, expel pores, and promote densification. The ceramic base preferably contains 1wt% to 10wt% MgO, more preferably 2.5wt% to 6wt% MgO.

[0030] Li2CO3 in the ceramic base helps to reduce the viscosity of the system when sintering, allowing the sintered body of the ceramic material to become dense. The ceramic base preferably contains 0.5wt% to 5wt% Li2CO3, more preferably 1.5wt% to 4.2wt% Li2CO3.

[0031] TiO2 in the ceramic base helps to improve the temperature properties of the material system, allowing the temperature drift of the material to approach zero. The ceramic base preferably contains 0.5wt% to 5wt% TiO2, more preferably 1.5wt% to 3wt% TiO2.

[0032] In the preferred embodiment, the content of the ceramic base is 55wt% to 67wt%.

[0033] Preferably, the ceramic base material further comprises rare earth oxides, such as CeO2, and the like, to further refine the grain and improve the mechanical properties of the material. More preferably, the content of rare earth oxides in the ceramic material is less than 2wt%.

[0034] In addition, the ceramic material can also contain other impurities. In the case of containing impurities, the preferred content of impurities is less than 5wt%, and preferably the content of impurities is less than 3wt%.

[0035] [Filler]

[0036] The filler comprises quartz, B2O3, ZnO and Y2O3, which helps to improve the mechanical strength of the ceramic material during sintering.

[0037] The quartz in the filler helps to increase the thermal expansion coefficient of the system during sintering of the ceramic material. The thermal expansion coefficient of quartz is about 15 ppm / K, while the thermal expansion coefficient of the ceramic base material is about 4-5 ppm / K. Therefore, by adding quartz with a high thermal expansion coefficient to the ceramic base material, a material with a high thermal expansion coefficient can be obtained. The ceramic material contains 25wt%-45wt% of quartz in the filler, and preferably contains 27wt%-38% of quartz.

[0038] Cristobalite is a type of SiO2 crystal, with a thermal expansion coefficient of about 50 ppm / K, and a phase transition occurs at 200-300°C, resulting in a large change in volume and poor thermal stability (temperature has a large effect on deformation). Therefore:

[0039] By adding 0.1wt%-2wt% of Y2O3 as a filler to the ceramic material, the precipitation of SiO2 cristobalite crystals in the entire ceramic material can be prevented during sintering. Preferably, 0.2wt%-1.5wt% of Y2O3 is contained.

[0040] By adding 1wt%-5wt% of ZnO as a filler to the ceramic material, the precipitation of SiO2 quartz crystal phase in the entire ceramic material can be promoted without being converted into other phases (such as cristobalite crystals) during sintering. Preferably, 1.7wt%-2.7wt% of ZnO is contained.

[0041] During sintering of the ceramic material, the specific contents of quartz, B2O3, ZnO and Y2O3 in the filler work together to help obtain a material with low dielectric constant, low dielectric loss, high density, high thermal expansion coefficient and high mechanical strength.

[0042] In the preferred embodiment, the ceramic material contains 2wt%-3.2wt% of B2O3.

[0043] In a preferred embodiment, the ceramic material does not contain cristobalite crystals. In this context, "does not contain cristobalite crystals" means that the content of cristobalite crystals is below the detection limit, and whether or not cristobalite crystals are present can be confirmed by X-ray diffraction (XRD) analysis.

[0044] Embodiments of the present application also provide a method for preparing the ceramic material, comprising the following steps:

[0045] S1: After mixing the components of the ceramic base, the mixture is ball milled, dried, and sieved to obtain a uniformly dispersed main powder;

[0046] S2: The main powder obtained in step S1 is pre-fired to obtain a ceramic base;

[0047] S3: The ceramic base obtained in step S2 and the filler are weighed and mixed according to the formula, and a binder is added to obtain a ceramic slurry;

[0048] S4: The material obtained in S3 is degassed and sintered to obtain the ceramic material.

[0049] In a preferred embodiment, in step S2, pre-firing is carried out at 800-900°C for 2-4h; in step S4, the degassing temperature is 200-400°C; in step S4, sintering is carried out at 840-950°C for 1-3h.

[0050] In some embodiments, after obtaining the ceramic slurry in step S3, the ceramic slurry is granulated and press-formed to obtain a green body, and the green body is degassed and sintered in step S4 to obtain a sample of the desired shape. In other embodiments, after obtaining the ceramic slurry in step S3, the ceramic slurry is subjected to flow casting, drying, etc. to obtain a green sheet, and the green sheet is cut after being stacked to obtain a green body of the desired shape, and the green body is degassed and sintered in step S4 to obtain a sample of the desired shape.

[0051] Embodiments of the present application also provide a laminate comprising a plurality of ceramic layers, wherein the ceramic layers are sintered bodies of the ceramic material.

[0052] As an example of a laminate, for example Figure 3 The cross-sectional view of the laminated ceramic capacitor shown in the figure is a laminated ceramic capacitor made during the process of making a sample for insulation reliability evaluation. The laminated ceramic capacitor comprises a structure body in which dielectric layers 1 (the dielectric layers are sintered from the ceramic material of the above-mentioned embodiments of the present application) and internal electrode layers 2 are alternately laminated, and a pair of external electrodes 3 in electrical communication with the internal electrode layers at both ends of the structure body. The shape of the laminated ceramic capacitor of the present application is not particularly limited, and is usually cuboid.

[0053] The present application is further described below by way of examples and comparative examples.

[0054] <Manufacture of green sheets>

[0055] Ceramic bases C1 to C6 (all in powder form) having the compositions shown in Table 1 were manufactured by the following method. The ceramic base manufacture included the following steps:

[0056] S1 : Analytically pure CaO, SiO2, MgO, Li2CO3, and TiO2were used as raw materials, and the proportions of the formulation were calculated, weighed, and mixed uniformly to obtain a mixture;

[0057] S2: The mixture in S1 was ball-milled, dried, and sieved to obtain a uniformly dispersed main powder;

[0058] S3: The main powder in S2 was loaded into a crucible and pre-fired at a temperature of 800 to 900°C for 2 to 4 hours in a sintering furnace to obtain a ceramic base;

[0059] Table 1

[0060]

[0061] S4: Next, the ceramic base, quartz, B2O3, ZnO, and Y2O3 having the compositions shown in Table 2 were mixed uniformly in a ball mill, and mixed with a binder liquid of acrylic resin dissolved in an organic solvent and a liquid of dibutyl phthalate as a plasticizer to manufacture a ceramic slurry. Then, the ceramic slurry was flow-cast and dried to manufacture green sheets S1 to S14 having a thickness of about 30 μm, as shown in Table 2 below.

[0062] Table 2

[0063]

[0064] <Manufacture of laminates>

[0065] [Evaluation of bending strength]

[0066] For the green sheets S1 to S14, each green sheet was cut into a square sheet of 140 mm * 140 mm, and 120 sheets were stacked, and then pressure-bonded by hydrostatic pressure press or the like to form a stacked green sheet. The stacked green sheet was cut into a green body of 46 mm * 4.7 mm * 3.5 mm, and subjected to debinding treatment. The debinding treatment conditions were, for example, preferably set to a holding temperature of 200 to 400°C (in this example, the debinding temperature was 380°C, and the treatment time was 12 hours). After the debinding treatment, the stacked green sheet was fired to obtain a laminate. In this embodiment, the atmosphere at the time of firing is not particularly limited, and the firing temperature is preferably 840 to 950°C for 1 to 3 hours (in this example, the firing temperature was 905°C for 2 hours) in air or a reducing atmosphere, to obtain evaluation samples of Examples 1 to 10 and Comparative Examples 1 to 4 shown in Table 3, for use in the evaluation of the bending strength, the evaluation of the density, and the evaluation of the thermal expansion coefficient in the Examples of the present application.

[0067] The width and the thickness of each of the evaluation samples were measured, and the average bending strength of the samples was measured using a universal testing machine (manufacturer: Shenzhen Sanyi Longyan Electronic Universal Testing Machine, model: UTW6104), and the results are shown in Table 3. The criteria for determination were that a case where the average bending strength was 200 MPa or more was determined to be high strength.

[0068] [Insulation reliability evaluation]

[0069] Figure 3 is a cross-sectional view of a laminated ceramic capacitor produced during the process of producing a sample for insulation reliability evaluation. First, for the green sheets S1 to S14, each green sheet was cut into a square sheet of 140 mm * 140 mm, and then a conductor layer was printed onto the square sheet using a screen printing plate and a conductive paste, and the square sheet on which the conductor layer was printed was stacked alternately with 7 sheets, and then 40 sheets on which no conductor layer was printed were stacked thereon, to produce a stacked green body. The stacked green body was pressure-bonded by hydrostatic pressure press or the like to form a stacked green sheet, and cut into a laminate of 2.0 mm * 2.2 mm. The laminate was subjected to debinding treatment, and the debinding treatment conditions were, for example, preferably set to a holding temperature of 200 to 400°C (in this example, the debinding temperature was 380°C, and the treatment time was 12 hours). After the debinding treatment, the laminate was fired to obtain a component main body. In this embodiment, the atmosphere at the time of firing is not particularly limited, and the firing temperature is preferably 840 to 950°C for 1 to 3 hours (in this example, the firing temperature was 905°C for 2 hours).

[0070] The thus obtained element body was subjected to end face polishing, and an external electrode paste was applied and sintered to form an external electrode. Then, as needed, a plating layer was formed on the surface of the external electrode (in this example, the plating layer formed on the surface of the external electrode was composed of a 20-μm-thick inner layer (nickel layer) and a 30-μm-thick outer layer (tin layer)), to obtain an evaluation sample having a stacked capacitor structure.

[0071] Each of the evaluation samples was left in a constant temperature and humidity test chamber at 85°C and 85% humidity for 1000 hours under a state where a voltage of 40V was applied between the two electrodes. After the test, the insulation resistance was measured, and the results are shown in Table 3. The criteria for judgment were as follows:

[0072] √: The insulation resistance was 1.0 x 10 9 Ω or more.

[0073] X: The insulation resistance was less than 1.0 x 10 9 Ω.

[0074] [Compactness Evaluation]

[0075] Each of the evaluation samples was evaluated for sintering compactness by whether or not ink penetrated the cross section and was colored. Specifically, the sintered sample was immersed in black ink for 20 minutes, and after being taken out, it was washed in clean water. If the sample was not colored after being washed, it was judged to be sintered compactly. The results are shown in Table 3. The criteria for judgment were as follows:

[0076] √: Not colored, and the ink did not penetrate.

[0077] X: The ink penetrated and colored.

[0078] [Thermal Expansion Coefficient Evaluation]

[0079] Then, for the evaluation samples that were sintered well, the average thermal expansion coefficient in the temperature range of 30 to 300°C was measured using a thermal mechanical analyzer (NETZSCH thermal expansion analyzer, Model: DIL 402 series). The results are shown in Table 3. The criteria for judgment were that an average thermal expansion coefficient of more than 10 ppm / K was judged to be a high thermal expansion coefficient. Exemplarily, the TMA curves of the ceramic materials obtained in Examples 1, 4, 6, and 10 are shown in FIG. 1. Figure 2

[0080] [Dielectric Property Evaluation]

[0081] The thickness of each of the evaluation samples was measured, and the relative dielectric constant and dielectric loss under the condition of 13 GHz were measured using a network analyzer (Keysight E5071C network analyzer). The results are shown in Table 3.

[0082] ​Criteria for determination: the case where the dielectric constant (i.e. the relative dielectric constant) is lower than 6 is determined as low dielectric constant, and the case where tan δ is less than 1 ‰ is determined as low dielectric loss.

[0083] [Evaluation of crystallization of cristobalite]

[0084] For the sintered evaluation sample, the phase of the sintered sample was determined using an X-ray diffractometer (exemplarily, XRD patterns of Example 4, Example 7 and Comparative Example 3 are provided by the present application, as shown in Figure 1 Table 3, with the following criteria for determination:

[0085] : No crystallization of cristobalite.

[0086] : Crystallization of cristobalite.

[0087] Table 3

[0088]

[0089] As shown in Table 3, in Examples 1-10, low dielectric constant, low dielectric loss, high mechanical strength and high thermal expansion coefficient were achieved. And in Examples 1-10, no crystallization of cristobalite occurred, and the insulation reliability was excellent.

[0090] The thermal expansion coefficient of the ceramic material is 10-15 ppm / K, and the ceramic material has a good thermal expansion curve linearity, as shown in Figure 2 which can reduce the thermal stress between the packaging material and the PCB caused by thermal mismatch, and improve the material packaging reliability

[0091] The above further describes the present application in conjunction with specific / preferred embodiments, and cannot be deemed to limit the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, they can make several substitutions or variations to the described embodiments, and these substitutions or variations shall be deemed to fall within the protection scope of the present application. In the description of the present application, the description of the terms "an embodiment", "some embodiments", "a preferred embodiment", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the case of no mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples. Although the embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A low temperature sinterable ceramic material, characterized in that, The material comprises a ceramic matrix and fillers. The ceramic matrix includes 40wt%~60wt% CaO, 30wt%~50wt% SiO2, 1wt%~10wt% MgO, 0.5wt%~5wt% Li2CO3, and 0.5wt%~5wt% TiO2. The fillers include quartz, B2O3, ZnO, and Y2O3. The ceramic material comprises the following components in weight percentages: 50wt%~70wt% ceramic matrix, 25wt%~45wt% quartz in the fillers, 0.8wt%~4.2wt% B2O3 in the fillers, 1wt%~5wt% ZnO in the fillers, and 0.1wt%~2wt% Y2O3 in the fillers.

2. The ceramic material of claim 1, wherein, The CaO content in the ceramic matrix is ​​45wt%~55wt%.

3. The ceramic material of claim 1, wherein, The SiO2 content in the ceramic matrix is ​​35wt%~47wt%.

4. The ceramic material of claim 1, wherein, The MgO content in the ceramic matrix is ​​2.5wt%~6wt%.

5. The ceramic material of claim 1, wherein, The content of Li2CO3 in the ceramic matrix is ​​1.5wt%~4.2wt%.

6. The ceramic material of claim 1, wherein, The TiO2 content in the ceramic matrix is ​​1.5wt%~3wt%.

7. The ceramic material of claim 1, wherein, The content of the ceramic matrix is ​​55wt%~67wt%.

8. The ceramic material of claim 1, wherein, The quartz content in the ceramic material is 27wt%~38wt%.

9. The ceramic material of claim 1, wherein, The B2O3 content in the ceramic material is 2wt%~3.2wt%.

10. The ceramic material of claim 1, wherein, The ZnO content in the ceramic material is 1.7wt%~2.7wt%.

11. The ceramic material of claim 1, wherein, The Y2O3 content in the ceramic material is 0.2wt%~1.5wt%.

12. The ceramic material according to any one of claims 1 to 11, characterized in that The ceramic material does not contain cristobalite crystals.

13. A method of producing the ceramic material according to any one of claims 1 to 12, characterized in that Includes the following steps: S1: After mixing the components in the ceramic matrix, the mixture is ball-milled, dried, and sieved to obtain a uniformly dispersed main powder. S2: Pre-fire the main powder obtained in step S1 to obtain ceramic matrix; S3: Weigh and mix the ceramic matrix and filler obtained in step S2 according to the formula ratio, and add the binder to obtain the ceramic slurry. S4: After removing the binder from the material obtained in S3, sinter it to obtain the ceramic material.

14. The method of producing a ceramic material according to claim 13, wherein In step S2, the pre-firing temperature is 800~900℃ for 2~4 hours; in step S4, the temperature for removing the binder is 200~400℃; in step S4, the sintering temperature is 840~950℃ for 1~3 hours.

15. A laminate characterized by comprising: It includes multiple ceramic layers, wherein the ceramic layers are sintered bodies of the ceramic material as described in any one of claims 1-12.

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