Composite binder for dielectric filter ceramic, preparation method of composite binder and ceramic compounding method

Abstract

The embodiment of the invention provides a composite binder for dielectric filter ceramic, a preparation method of the composite binder and a ceramic compounding method, and the composite binder comprises bonding slurry which realizes compounding of first dielectric ceramic and second dielectric ceramic of a silver-containing electrode; the bonding slurry comprises 90 to 95 weight percent of binder powder, 2 to 10 weight percent of organic binder and 1 to 4 weight percent of surfactant; the binder powder comprises sintering aid powder and composite raw powder, and the composite raw powder is first dielectric ceramic powder or / and second dielectric ceramic powder. The problem that two high-Q ceramic materials containing silver electrodes cannot be directly co-fired is solved, and high bonding strength, low insertion loss and high reliability after compounding are achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ceramic filter material processing, in particular to a composite binder for dielectric filter ceramic, a preparation method thereof and a ceramic compounding method. BACKGROUND

[0002] With the maturity of 5G commercial landing, wireless communication systems have put forward strict requirements for filters, such as low insertion loss, high suppression, high power bearing capacity, low cost and miniaturization. Ceramic dielectric filters, which have significantly lower size and weight than traditional metal waveguide filters, have become the core choice of 5G radio frequency modules. They are usually made of ceramic dielectric materials, and the surface is metalized to achieve electromagnetic shielding.

[0003] Ceramic dielectric filters have become the core choice of 5G radio frequency front ends due to their excellent dielectric properties, high quality factor and good temperature stability, and are widely used in base station radio frequency units, small and micro base stations and terminal equipment (such as satellite communication terminals). The mainstream ceramic dielectric filters are currently made of single dielectric constant ceramic blocks. Silver layers are sputtered or printed on the surface of the ceramic to form an electromagnetic shielding structure, but its performance has been difficult to improve. If further improvement of the suppression performance is needed, the size of the ceramic block is usually increased or a more complex resonant cavity structure is designed, which contradicts the demand for miniaturization. If the size is reduced by reducing the dielectric constant, the Q value will decrease, thereby increasing the insertion loss, making it difficult to balance the dual demands of performance and size.

[0004] To further improve the filter performance, reduce the size and reduce the cost, the industry gradually adopts the innovative design of high Q ceramic composite with different dielectric constants. That is, by using high dielectric constant ceramic material as the core area of the resonant cavity, and low dielectric constant ceramic material as the peripheral matching area, the out-of-band rejection of the filter can be improved without increasing the overall size, and the material cost can be reduced through the differentiated function division of the two types of ceramics. But this design faces key technical bottlenecks: 1) Composite filter needs to use high Q value dielectric material to meet the low insertion loss and high power requirements, such materials are mostly high fired dielectric ceramics, with a sintering temperature as high as 1100-1500℃; while the surface metallization of the filter commonly uses silver with the highest conductivity, whose melting point is only 961℃, the difference between the two sintering temperatures is too large to co-fire; 2) The composite interface of the two different dielectric constant ceramics needs to be provided with a silver electrode to realize the signal coupling between the resonant cavities, and the thickness of the silver layer is usually 5-10μm. The existence of the silver layer prevents the two types of ceramics from directly contacting, and at high temperatures, the silver layer will also chemically react with the ceramic surface, directly hindering the diffusion and combination between the ceramic particles. It is difficult to use direct co-firing or high-temperature melting and bonding process, resulting in the long-term unsolvable problem of high Q ceramic composite containing silver electrodes, which limits the research and application of new type of dielectric filters. In addition, if copper (Cu) or gold (Au) is used to replace the silver electrode, the electrode loss will increase, resulting in the increase of the insertion loss of the filter. Therefore, there is an urgent need for a composite material that is compatible with silver electrodes, has low loss, high bonding strength, and strong process adaptability for the composite of different dielectric constant ceramics. SUMMARY

[0005] In order to overcome the defects of the prior art, the main purpose of the present application is to provide a composite binder for dielectric filter ceramics to solve the problem that two types of high Q ceramic materials containing silver electrodes cannot be directly co-fired, and to realize high bonding strength, low insertion loss and high reliability after compounding.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] The embodiment of the present application provides a composite binder for dielectric filter ceramics, which comprises a binding slurry to realize the compounding of the first dielectric ceramic and the second dielectric ceramic containing silver electrodes; the binding slurry comprises 90-95wt% of binder powder, 2-10wt% of organic binder and 1-4wt% of surfactant; the binder powder comprises sintering aid powder and composite raw powder, and the composite raw powder is first dielectric ceramic powder or / and second dielectric ceramic powder.

[0008] As a further preferred scheme, the mass percentage of the sintering aid powder and the composite raw powder in the binder powder of the embodiment of the present application is 90-95wt% and 5-10wt% respectively.

[0009] As a further preferred embodiment, the sintering aid powder described in this application is a B2O3-SiO2-ZnO-X system powder, where X is one or more of nano-sized Li2O, Al2O3, and ZrO2 powder; wherein, the mass percentage of X in the sintering aid powder is 25-45 wt%; and the mass ratio of B2O3, SiO2, and ZnO is 1:(0.6-1.2):(1.5-2.5).

[0010] As a further preferred embodiment, the particle size of the composite raw powder described in this application embodiment is 0.5-2μm, and the first dielectric ceramic powder and the second dielectric ceramic powder are ceramic powders with a dielectric constant K of 9-21.

[0011] As a further preferred embodiment, the adhesive slurry described in this application also includes a solvent, the amount of which is 10-40% of the total amount of adhesive powder, and the viscosity of the adhesive slurry is in the range of 10000-50000 mPa·s (25℃).

[0012] As a further preferred embodiment, the organic adhesive described in this application is ethyl cellulose or acrylic resin, the solvent is one or more of terpineol, ethylene glycol butyl ether, and ethyl acetate; and the surfactant is one or a mixture of two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol octylphenyl ether, and polyoxyethylene castor oil.

[0013] As a further preferred embodiment, the adhesive slurry described in this application also includes a vapor-phase SiO2 thixotropic agent, with an amount of 0.5 to 1 wt%.

[0014] This application also provides a method for preparing a composite binder for dielectric filter ceramics, including...

[0015] Obtaining the adhesive solution: Heat the organic adhesive with half the amount of solvent in the formula until completely dissolved and homogeneous to obtain the adhesive solution;

[0016] To obtain the mixed slurry: Mix the binder powder, surfactant and the remaining half of the solvent evenly, and then ball mill once in a ball mill to obtain the mixed slurry;

[0017] Obtaining the binder slurry: Mix the above-mentioned slurry with the binder solution, and then perform a second ball milling at room temperature. After the ball milling is completed, sieve the mixture to obtain the binder slurry.

[0018] As a further preferred embodiment, the preparation method described in this application also includes the step of preparing binder powder: mixing B2O3, SiO2, and ZnO in the sintering aid powder with the composite raw powder according to the formula amount and ball milling, then adding component X and mixing and ball milling again.

[0019] This application also provides a ceramic composite method, including...

[0020] The adhesive paste described in the embodiments of this application is applied to the surface of a first dielectric ceramic containing silver electrodes by means of printing, dotting, or spraying processes to form a predetermined pattern.

[0021] A second dielectric ceramic with silver electrodes on its surface is pressed onto a patterned layer of a dielectric ceramic, and after being fixed by a fixture, it is dried at 80-120℃ to evaporate the solvent, thus obtaining a composite ceramic body.

[0022] The dried composite ceramic body is sintered in stages: in the first stage, the temperature is increased to 320-380℃ at 3-5℃ / min to decompose organic matter, and the temperature is held for 5-15min; in the second stage, the temperature is increased to 850-910℃ at 5-8℃ / min to sinter, and the temperature is held for 10-15min to achieve interfacial diffusion; thus, the composite ceramic is obtained.

[0023] Compared to existing technologies, the beneficial effects of this application are as follows:

[0024] 1. The composite adhesive described in this application embodiment is used for bonding high-Q ceramics containing silver electrodes. It is compatible with the performance of silver electrodes and high-Q ceramics. The sintering temperature of the adhesive slurry is precisely matched with the heat resistance of the silver electrodes. It does not affect the silver electrodes on the two ceramics before bonding, and can withstand the process of silvering and burning again after bonding. It avoids the melting, diffusion or erosion of silver electrodes, ensures the conductivity retention of silver electrodes, and does not affect the low insertion loss foundation of the filter. The bonding process does not damage the high-Q characteristics of the first and second dielectric ceramics, and the Q value of the filter remains basically unchanged after bonding.

[0025] 2. In the composite binder described in this application embodiment, the composite raw powder is the ceramic powder of the medium to be composited, which forms a homologous and compatible structure with the binder powder and the ceramic matrix, greatly improving the interfacial chemical compatibility and physical bonding force; and the ceramic body can be prevented from cracking by adjusting the composition of the binder powder to match the thermal expansion coefficient of the two ceramics.

[0026] 3. The composite binder powder described in the embodiments of this application can be selected from first dielectric ceramic powder, second dielectric ceramic powder or a mixture of both, depending on the requirements. The proportion and composition of the sintering aid powder can be flexibly adjusted to achieve precise control of the dielectric constant.

[0027] 4. The composite adhesive described in this application is used in slurry form, which is suitable for screen printing, dotting, and spraying to prepare different design patterns; the slurry has good fluidity and the slurry system can be adjusted. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0030] Figure 1 This is a 2K electron microscope image of the composite ceramic bonding area obtained in Example 1.

[0031] Figure 2 The image shown is a 5K electron microscope image of the composite ceramic bonding area obtained in Example 1. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0033] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0034] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0035] This application provides a composite binder for dielectric filter ceramics, comprising a binder slurry to achieve the composite bonding of a first dielectric ceramic and a second dielectric ceramic containing a silver electrode. The binder slurry comprises 85-90 wt% binder powder, 2-10 wt% organic binder, 1-4 wt% surfactant, and 5-40 wt% solvent. In this application, the binder powder is the core bonding phase, determining the interfacial bonding strength and dielectric properties, and consists of two parts: sintering aid powder and composite raw powder. The sintering aid powder adopts a low-melting-point glass phase system, melting at a low temperature (850-910℃) to form a fluid glass phase, which achieves physical-chemical bonding of the first dielectric ceramic, the second dielectric ceramic, and the silver electrode surface by wetting them. The composite raw powder consists of the powders of the first and second dielectric ceramics to be composited. Its function is to utilize the chemical compatibility of homologous materials to reduce the interfacial stress between the binder and the ceramic matrix, while simultaneously adjusting the dielectric properties and thermal matching of the bonding layer. The proportions of the sintering aid and the composite raw powder significantly affect the strength of the ceramic composite bonding. When the amount of sintering aid is insufficient, the total amount of glass phase is inadequate. After melting, it cannot fully fill the interface gaps between the ceramic and the silver electrode, resulting in discontinuous bonding layer, decreased shear strength, and increased dielectric loss due to interfacial porosity. Excessive sintering aid and glass phase lead to excessive fluidity during sintering, potentially causing over-penetration into the micropores of the ceramic or the grain boundaries of the silver electrode, compromising the density of the ceramic or the conductivity of the silver electrode. Insufficient composite powder results in a large compositional difference from the ceramic matrix, leading to stress concentration at the interface due to chemical heterogeneity. This can cause microcracks during temperature shocks, reducing reliability. Furthermore, the significant deviation between the dielectric constant and coefficient of thermal expansion (CTE) of the bonding layer and the ceramic matrix further exacerbates interfacial stress. Excessive composite powder, being a high-melting-point ceramic powder, increases the melting temperature of the binder, approaching or exceeding the melting point of silver, causing the silver electrode to melt or diffuse. Simultaneously, excessive ceramic powder reduces the fluidity of the glass phase, hindering interfacial wetting and consequently reducing bonding strength. Therefore, in some embodiments of this application, in order to achieve low-temperature sintering, high strength, and low loss, and to solve the problem of silver-containing electrode dielectric ceramic composites, the mass percentages of the sintering aid powder and the composite raw powder in the binder powder are 90-95 wt% and 5-10 wt%, respectively.

[0036] Furthermore, as a preferred embodiment, the sintering aid powder described in this application is a B2O3-SiO2-ZnO-X system powder, wherein the B2O3-SiO2-ZnO ternary system is the base phase of the sintering aid powder, determining the melting temperature, fluidity, and dielectric stability of the glass phase; X, as a nanoscale additive, has a particle size selected from 50-200 nm, and X is selected from one or more of nanoscale Li2O, Al2O3, and ZrO2 powders; this addresses the performance defects of the base glass phase. B2O3 has a low melting point, which is key to reducing the melting temperature of the glass phase; SiO2 is a network forgery, constructing the glass phase framework through Si-O bonds. ZnO, through Zn... 2+ Adjusting the coefficient of thermal expansion (CTE) and polarity of the glass phase. Nano-Li₂O can further lower the melting temperature of the glass phase while enhancing its wettability with ceramics containing high Al₂O₃ content (such as Al₂O₃-based ceramics). Nano-Al₂O₃ can act as a reinforcing phase, dispersed within the glass phase, improving the mechanical strength of the bonding layer through dispersion strengthening. The low dielectric loss of Al₂O₃ reduces the overall loss of the glass phase, ensuring low dielectric loss in the bonding layer. Nano-ZrO₂ can improve the impact toughness of the bonding layer through phase transformation toughening, while its high hardness enhances the wear resistance of the bonding layer. The dispersion strengthening of nano-Al₂O₃ and the phase transformation toughening of nano-ZrO₂ need to reach 25 wt% to improve the shear strength of the bonding layer from the base glass phase; if the dosage is too low, the nanoparticles are sparsely dispersed, resulting in a weak strengthening effect that cannot meet the mechanical requirements of long-term filter use. Furthermore, the total amount of Li2O, Al2O3, and ZrO2 in X needs to reach 25wt% to precisely control the CTE of the binder layer and improve the wettability to high-Al2O3-based ceramics. However, to ensure sufficient melting of the glass phase, avoid runaway sintering temperature and imbalance of thermal expansion coefficients, and prevent deterioration of binder layer uniformity, the proportion of the X phase cannot be too high. Therefore, in the preferred embodiment, the mass percentage of X in the sintering aid powder is 25-45wt%. Experiments show that within this range, the proportion of X in the sintering aid ensures that nano-X can fully exert its functions of mechanical strengthening, thermal matching optimization, and wettability improvement, without diluting the basic glass phase, increasing the sintering temperature, or damaging the interface wetting and uniformity. Ultimately, this allows the composite ceramic to protect the silver electrode during low-temperature sintering while ensuring high-strength bonding for reliability and low-loss adaptation to filter performance.

[0037] Since the melting point of silver electrodes is 961℃ and thermal diffusion easily occurs above 800℃, the melting temperature of the glass phase of the sintering aid powder must be lower than the melting point of silver, but it can still form an effective bond. The fluidity of the glass phase directly determines its wetting effect on the ceramic surface and the silver electrode; otherwise, the bonding strength will decrease due to interfacial gaps. If the glass phase has a loose structure, it easily absorbs environmental moisture, leading to fluctuations in dielectric constant and a decrease in bonding strength. Therefore, it is necessary to improve its density through composition control. In the embodiments of this application, by adjusting the mass ratio of B2O3, SiO2, and ZnO, multi-dimensional synergistic control of the glass phase melting temperature, fluidity, chemical stability, thermal matching, and dielectric properties can be achieved. Therefore, in some embodiments, the mass ratio of B2O3, SiO2, and ZnO is 1:(0.6-1.2):(1.5-2.5).

[0038] In the binder slurry, the composite powder, as a homologous component, directly affects the interfacial contact area and diffusion effect through its particle size selection. If the composite powder particles are too large, the contact area with the sintering aid and ceramic matrix surface is small, making it difficult to form sufficient physical diffusion and chemical bonding during high-temperature sintering. Gaps easily appear at the interface, leading to insufficient bond strength. Conversely, if the composite powder particles are too fine, the particle specific surface area is too large, making them prone to agglomeration due to van der Waals forces, forming localized clumps, which also prevents uniform contact with the ceramic matrix. Since the density of the binder layer directly affects dielectric loss and mechanical reliability, improper selection of the composite powder particle size can also lead to increased porosity. If the gaps between particles are too large, the sintering aid cannot completely fill the gaps after melting, leaving micropores in the binder layer. These micropores introduce additional dielectric loss and reduce impact resistance. The CTE matching between the binder layer and the ceramic matrix depends on the uniform dispersion of the composite powder. The particle size of the composite powder also affects the CTE. When the particle size is too large, the composite powder particles form hard spots in the binder layer. The CTE of these areas differs significantly from the surrounding glass phase, making them prone to local stress concentration and microcracks during temperature shock. Furthermore, as the core solid component of the binder slurry, the particle size of the composite powder directly affects the slurry's fluidity and molding effect. Excessively large particle sizes can clog the screen printing mesh, leading to incomplete printing patterns and uneven binder layer thickness. It also increases slurry viscosity fluctuations, affecting the uniformity of dotting and spraying. Conversely, excessively small particle sizes can lead to particle agglomeration and the formation of pseudo-particles, similarly disrupting slurry uniformity and causing localized component segregation in the binder layer after molding. In some embodiments of this application, the particle size of the composite powder is controlled to be 0.5-2 μm. This avoids particle agglomeration, ensuring the composite powder is uniformly dispersed in the sintering aid powder, forming a microscale interlocking structure with the ceramic matrix during sintering, improving interfacial bonding, and ensuring stable shear strength. On the other hand, a particle size of 0.5-2μm allows for gradient filling: the composite powder particles can be uniformly distributed in the glass phase of the sintering aid powder, and after sintering, they are tightly packed, reducing the porosity of the binder layer and avoiding fluctuations in dielectric properties and a decrease in strength caused by porosity. Furthermore, this particle size range allows for uniform dispersion of the composite powder, making the overall CTE of the binder layer more consistent, avoiding localized stress superposition, and completely solving the problem of cracking under temperature cycling. Both the first and second dielectric ceramic powders use ceramic powders with a dielectric constant K of 9-21.

[0039] Furthermore, the organic binder described in this application embodiment is ethyl cellulose or acrylic resin. Ethyl cellulose has advantages such as good solubility, excellent film-forming properties, wide decomposition temperature range, and precise viscosity adjustment. As a binder in the adhesive slurry, it can ensure the stability of the slurry, avoid delamination, leave no residue after sintering, and avoid additional dielectric loss. It also does not react with the silver electrode, thus not affecting the electrode conductivity. Acrylic resin has a wide viscosity range, which can effectively adjust the viscosity of the adhesive slurry. Acrylic resin can form a film quickly at room temperature, has strong encapsulation of powder, and good dispersion effect. As an organic binder, it is not only suitable for dotting and spraying processes, but also inhibits the agglomeration of composite powder, ensuring uniform composition of the adhesive layer. The amount of organic binder is an important factor in balancing the slurry's formability and post-sintering performance. The appropriate amount not only gives the slurry suitable viscosity and thixotropy to meet the forming requirements of printing, dotting, and spraying, making printing free of bleeding edges, dotting free of dripping, and spraying uniformly atomized, but also allows the adhesive layer thickness to be controlled to fix the ceramic block, prevent displacement during sintering, and ensure complete decomposition of organic components without residue during sintering. In the embodiments of this application, the amount of organic adhesive is controlled in the range of 2 to 10 wt%; the preferred range is 2-8%.

[0040] Furthermore, in the embodiments of this application, the solvent is used to adjust the viscosity of the slurry to suit the molding process. Improper use will directly lead to slurry failure or process abnormalities. Some embodiments use solvents selected from, but not limited to, one or more of terpineol, ethylene glycol butyl ether, and ethyl acetate; the selection can be combined with the coating process of the slurry; for example, terpineol is preferred for screen printing, ethyl acetate for spraying, and ethylene glycol butyl ether for dot coating. The amount of solvent mainly affects the viscosity of the binder slurry. If the amount of solvent is too small, the powder will be unevenly dispersed and prone to agglomeration, the organic binder will not dissolve sufficiently, and the slurry will lack fluidity; if the amount is too large, the fluidity will be too strong, causing sagging and easy powder settling. In the embodiments of this application, the amount of organic binder is 10-40 wt% of the total binder powder. Preferably, some embodiments use a mixture of two of the above solvents, for example, a mixture of terpineol and ethyl acetate can be used to ensure stability and shorten drying time, and the volume ratio of the two can be controlled at 7:3.

[0041] In this application, the core role of surfactants in the binder slurry is to solve the compatibility problem between inorganic powders and organic / inorganic systems. They are used to disperse powders and break up agglomerates; simultaneously, they improve multiphase compatibility and prevent stratification; and they can also regulate surface tension and optimize the slurry's molding performance. The amount of surfactant used is mainly determined by factors such as dispersion efficiency, residual effects, and cost balance. In some embodiments of this application, the amount of surfactant used is 1–4 wt%. In some embodiments, the surfactant used is one or a mixture of two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol octylphenyl ether, and polyoxyethylene castor oil.

[0042] In this application, viscosity is a key factor in controlling the shape stability and thickness consistency of the binder layer, and it also directly affects the wettability of the slurry to the ceramic matrix and silver electrode. A suitable viscosity allows the slurry to possess both fluidity and thixotropy, enabling it to quickly recover its consistency after molding and preventing excessive thickness deviation in the binder layer. It also allows the slurry to form a uniformly spread and impermeable film at the interface, reducing the contact angle and ensuring that the glassy phase of the sintering aid powder fully wets the interface during sintering, forming a continuous and dense binder layer and guaranteeing shear strength. Adjusting the viscosity of the binder slurry can also prevent powder sedimentation. To avoid process failures and performance degradation due to excessive thinning or thickening, and to ensure the stability of the binder slurry throughout the entire process from production to application, as a further preferred embodiment, the viscosity range of the binder slurry described in this application is 10000–50000 mPa·s (25°C).

[0043] Furthermore, the adhesive slurry described in this application embodiment also includes a fumed SiO2 thixotropic agent. The thixotropic agent can adjust the thixotropy and structural stability of the adhesive slurry, solving the problems of molding process adaptation, storage dispersion, and microstructure optimization of the adhesive layer. In the static state of the adhesive slurry, the nanoparticles of fumed SiO2 form a three-dimensional network structure through hydrogen bonds, causing the slurry viscosity to increase instantaneously, preventing sagging after molding and ensuring controllable thickness and pattern accuracy of the adhesive layer. Under the scraping of the printing squeegee and the pressure of spraying, the three-dimensional network structure is destroyed, the slurry viscosity decreases rapidly, and the fluidity increases, allowing it to pass smoothly through the mesh of screen printing, the needle of dotting, or the nozzle of spraying, avoiding process defects such as clogging and ink breakage. Furthermore, the high specific surface area of ​​fumed SiO2 allows it to adsorb onto the surface of solid particles, forming steric hindrance and preventing particle aggregation, thus ensuring the slurry's storage time. During sintering, fumed SiO2 fills the tiny gaps not completely covered by the melted glass phase of the sintering aid, reducing the porosity of the binder layer and minimizing dielectric loss fluctuations caused by porosity. The high hardness of fumed SiO2 enhances the wear resistance of the binder layer, preventing damage to the bonding interface due to friction during filter assembly and indirectly ensuring shear strength stability. Additionally, the high-temperature resistance of fumed SiO2 ensures it does not decompose or volatilize during sintering at 850–910℃ and will not chemically react with the glass phase of the sintering aid, silver electrodes, or ceramic matrix, leaving no impurities. The dosage of the thixotropic agent is controlled at 0.5–1 wt% to avoid an excessively strong three-dimensional network structure of fumed SiO2, which could increase the slurry's shear viscosity and affect molding fluidity; it also avoids insufficient thixotropic effect due to insufficient dosage, which would fail to effectively prevent sagging and sedimentation.

[0044] This application also provides a method for preparing a composite binder for dielectric filter ceramics, including...

[0045] To obtain the adhesive solution: Heat the organic adhesive and half the amount of solvent in the formula to 85-95°C until completely dissolved and homogeneous to obtain the adhesive solution;

[0046] To obtain the mixed slurry: Mix the binder powder, surfactant and the remaining half of the solvent evenly, and then ball mill in a ball mill at room temperature for 12-24 hours to obtain the mixed slurry;

[0047] Obtaining the binder slurry: Mix the above-mentioned slurry with the binder solution, and then perform a second ball milling at room temperature. After ball milling for 24-48 hours, sieve the mixture to obtain the binder slurry.

[0048] As a further preferred embodiment, the preparation method described in this application also includes the step of preparing binder powder: mixing B2O3, SiO2, and ZnO in the sintering aid powder with the composite raw powder according to the formula amount and ball milling, then adding component X and mixing and ball milling again.

[0049] This application also provides a ceramic composite method, including...

[0050] The adhesive paste described in the embodiments of this application is applied to the surface of a first dielectric ceramic containing a silver electrode by means of printing, dotting, or spraying processes to form a predetermined pattern.

[0051] A second dielectric ceramic with a silver electrode on its surface is pressed (by mechanical pressure of 0.1–0.5 MPa) onto a patterned layer of a dielectric ceramic, so that the bonding layers of the first and second dielectric ceramics are tightly bonded together, eliminating air gaps between layers and preventing the formation of bubbles after sintering. The ceramic is fixed by a fixture to prevent misalignment caused by thermal expansion during high-temperature drying or sintering. The solvent is slowly dried at a low temperature of 80–120°C to evaporate, avoiding boiling caused by rapid evaporation at high temperatures. This allows the organic adhesive to initially cure, enhancing the temporary strength of the bonding layer and preventing pattern deformation, thus obtaining a composite ceramic body.

[0052] The dried composite ceramic body is sintered in a stepwise manner: the organic binders, surfactants and other components in the bonding slurry must be completely removed before the sintering aid powder melts, otherwise the residual organic matter will carbonize or volatilize at high temperature, causing pores and cracks in the bonding layer, and even affecting the dielectric properties; moreover, the sintering aid powder must be melted to form a glass phase within the upper temperature limit that does not damage the silver electrode (melting point 961℃), and then diffuse at the interface with the ceramic and the silver electrode to achieve a reliable bond. This application employs a two-stage heating process. In the first stage, the temperature is increased to 320-380°C at a rate of 3-5°C / min to decompose organic matter, and then held for 5-15 minutes. During this stage, the organic adhesive and surfactant are slowly decomposed. The heating rate is controlled at 3-5°C / min to avoid excessively rapid heating that could lead to explosive decomposition of the organic matter. The temperature is set at 320-380°C, which is the efficient decomposition temperature for organic components. This ensures complete decomposition of the organic matter without causing premature slight oxidation or diffusion of the silver electrode due to excessively high temperatures. Holding for 5-15 minutes allows sufficient time for the decomposition of the organic matter, preventing local residues (such as at the edges of the adhesive layer or in thick film areas) and ensuring that the entire adhesive layer is free of organic impurities. The second stage involves heating at 5-8℃ / min to 850-910℃ for sintering, followed by holding at that temperature for 10-15 minutes to achieve interfacial diffusion. Since organic matter has been removed in the first stage, slow heating is unnecessary. A rate of 5-8℃ / min allows for rapid attainment of the sintering temperature, reducing thermal stress accumulation between the ceramic and the binder layer and preventing microcracks caused by CTE mismatch due to prolonged high temperatures. Temperature control at 850-910℃ precisely matches the melting requirements of the sintering aid powder (below the silver melting point of 961℃), ensuring complete melting of the aid powder to form a fluid glass phase while preventing the silver electrode from melting and diffusing. This ensures that the silver electrodes on the first two ceramic pieces are not affected, while also allowing the composite device to withstand the silvering and sintering process again. Holding at that temperature for 10-15 minutes provides sufficient time for interfacial diffusion to obtain the composite ceramic, allowing the glass phase to fully wet the ceramic and silver electrode surfaces, physically diffusing with the ceramic particles and chemically adsorbing with the silver electrode. Simultaneously, the composite powder and the ceramic matrix undergo homologous fusion, further strengthening the interfacial bonding.

[0053] The following are some of the embodiments listed in this invention.

[0054] Example 1

[0055] This embodiment provides a composite binder for dielectric filter ceramics, comprising:

[0056] Binder powder (90g, 90wt%): 56.67g of B2O3-SiO2-ZnO ternary system, B2O3:SiO:ZnO = 1:1.0:2.3, 18.38g of Al2O3, 1.61g of nano ZrO2, 3.30g of Li2O; 6.73g of Al2O3-based ceramic powder, 3.31g of K21 (MgTiO3 55wt%, CaTiO3 45wt%) ceramic powder;

[0057] Organic binder: 2.5g ethyl cellulose + 2.5g acrylic resin (mass ratio 1:1), accounting for 5wt%;

[0058] Surfactant: 4g of polyethylene glycol octylphenyl ether, accounting for 4wt%;

[0059] 1.0 g of vapor-phase SiO2 thixotropic agent, accounting for 1.0 wt%;

[0060] Solvent: terpineol 32.48g, accounting for 35wt% of the binder powder;

[0061] The preparation method of the composite adhesive is as follows:

[0062] To obtain the adhesive solution: Ethyl cellulose and half of the formulated amount of a mixed solvent of terpineol and ethyl acetate are heated to 90°C and completely dissolved to obtain the adhesive solution.

[0063] To obtain the mixed slurry: Mix the binder powder, sodium dodecylbenzenesulfonate, and half of the remaining mixed solvent evenly, and then ball mill them in a ball mill at room temperature for 12 hours to obtain the mixed slurry;

[0064] Obtaining the binder slurry: Mix the above-mentioned mixed slurry with the binder solution, and ball mill it in a ball mill at room temperature for 24 hours. After ball milling, sieve it to obtain the binder slurry.

[0065] The composite adhesive described in Example 1 is used in a ceramic composite method to composite a first K9 ceramic with a second K9 ceramic.

[0066] Coating process: dot coating process, the paste is dotted on the surface of K21 ceramic (size 12mm×12mm×3mm) containing thick silver electrode (15μm) to form 3 discrete dots with a diameter of 1mm, and the adhesive layer thickness is 20μm;

[0067] Pressing and drying: Al2O3-based ceramics (of the same size) are pressed together with a pressure of 0.4 MPa, fixed with a metal fixture, and then dried at 90°C for 3.5 hours.

[0068] Step sintering: First stage: heat up to 350℃ at 3℃ / min and hold for 10min; Second stage: heat up to 900℃ at 6℃ / min and hold for 12min.

[0069] like Figure 1 , Figure 2 As shown, the interface at the joint of the composite ceramics exhibits a continuous and dense structure, with no obvious macroscopic gaps or delamination, indicating that the binder slurry achieved full wetting and bonding of the first and second dielectric ceramics during sintering. Uniform interweaving of ceramic grains and the glassy phase is visible in the interface region, with the ceramic grains and the glassy phase formed by the sintering aid powder tightly interlocked, without obvious grain agglomeration or glassy phase segregation. No excessive diffusion or erosion traces of the silver electrode (such as abnormal agglomeration of silver particles or interface voids) are observed in the interface region.

[0070] Example 2

[0071] This embodiment provides a composite binder for dielectric filter ceramics, comprising:

[0072] Binder powder (93g, 93wt%): 58.59g of B2O3-SiO2-ZnO ternary system, B2O3:SiO:ZnO = 1:0.8:2.0, 24.27g of Al2O3, 0.84g of nano ZrO2; 9.3g of K9 (MgTiO3 25wt%, CaTiO3 5wt%, Mg2SiO4 70wt%) ceramic powder (particle size 1.0μm);

[0073] Organic binder: 4g of ethyl cellulose, accounting for 4wt%;

[0074] Surfactant: 3g of polyethylene glycol octylphenyl ether, accounting for 2wt%;

[0075] Solvent: 16.28g terpineol + 6.97g ethanol (mass ratio 7:3), accounting for 25wt% of the binder powder.

[0076] The preparation method of the composite adhesive is as follows:

[0077] To obtain the adhesive solution: Ethyl cellulose and half of the formulated amount of a mixed solvent of terpineol and ethyl acetate are heated to 90°C and completely dissolved to obtain the adhesive solution.

[0078] To obtain the mixed slurry: Mix the binder powder, sodium dodecylbenzene sulfonate and the remaining half of the mixed solvent evenly, and then ball mill them in a ball mill at room temperature for 15 hours to obtain the mixed slurry;

[0079] Obtaining the binder slurry: Mix the above-mentioned slurry with the binder solution, and ball mill in a ball mill at room temperature for 30 hours. After ball milling, sieve to obtain the binder slurry.

[0080] The composite adhesive described in Example 2 is used in the ceramic composite method to composite the first K9 ceramic with the second K9 ceramic.

[0081] Coating process: Screen printing (200 mesh screen) to coat the surface of the first K9 ceramic (10mm×10mm×2mm) containing silver electrode (thickness 5μm) with paste to form a 2mm×2mm rectangular pattern, with an adhesive layer thickness of 15μm;

[0082] Pressing and drying: Press the second K9 ceramic (the same size as the first K9 ceramic, with the silver electrode face opposite each other) with a pressure of 0.3MPa. After the ceramic fixture is fixed, dry at 100℃ for 3 hours.

[0083] Step sintering: First stage: heat up to 350℃ at 3℃ / min and hold for 10min; Second stage: heat up to 900℃ at 6℃ / min and hold for 12min.

[0084] Example 3

[0085] Binder powder (95g, 95wt%): 60.54g of B2O3-SiO2-ZnO ternary system, B2O3:SiO2:ZnO = 1:1.0:2.2; 23.83g Al2O3, 1.30g nano ZrO2, 1.81g Li2O; 4.51g K21 ceramic powder + 3.01g K9 ceramic (mixed particles 0.8μm).

[0086] Organic adhesive: 3g acrylic resin, accounting for 3wt%;

[0087] Surfactant: Sodium dodecylbenzenesulfonate 2.5g, accounting for 2.5wt%.

[0088] Vaporized SiO2 thixotropic agent: 0.7g, accounting for 0.7wt%;

[0089] Solvent: 28.34 g of ethylene glycol butyl ether, relative to the powder mass of 30 wt%.

[0090] Coating process: Spray coating process, a paste is coated on the surface of K21 ceramic (size 8mm×8mm×1.5mm) containing silver electrode (thickness 8μm) to form a ring pattern (inner diameter 1mm, outer diameter 3mm), and the adhesive layer thickness is 10μm;

[0091] Pressing and drying: K9 ceramic (same size as K21 ceramic, with silver electrode faces opposite each other) is pressed together with a pressure of 0.2MPa, fixed with a quartz fixture, and then dried at 110℃ for 2.5 hours;

[0092] Step sintering: First stage: heat up to 360℃ at 4℃ / min and hold for 8min; Second stage: heat up to 920℃ at 8℃ / min and hold for 10min.

[0093] Performance testing: The performance of the composite ceramics obtained in Examples 1-3 above was tested, and the test results are shown in Table 1.

[0094] Table 1: Performance Test Results of Examples 1-3

[0095]

[0096] Furthermore, in order to explore the relationship between the proportion of composite raw powder in the binder powder and the performance of the composite ceramic body, based on the above Example 2, experiments were conducted with different proportions of composite raw powder, and the total amount of the B2O3-SiO2-ZnO ternary system was adjusted according to the amount of composite raw powder. All other steps and parameters were the same as in Example 2. The results of the relationship between the proportion of composite raw powder in the binder powder and the performance are shown in Table 2.

[0097] Table 2: Dosage and Performance of Composite Raw Powder

[0098]

[0099] Furthermore, in order to explore the correlation between the particle size of the composite raw powder and the properties of the composite ceramic body, based on the above Example 2, experiments were conducted using composite raw powders with different particle sizes. All other steps and parameters were the same as in Example 2. The results of the correlation between the particle size and properties of the composite raw powder are shown in Table 3.

[0100] Table 3: Particle size and properties of composite raw powder

[0101]

[0102]

[0103] The above description is merely a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A composite binder for dielectric filter ceramics, characterized in that, The invention includes a binder slurry to achieve the composite of a first dielectric ceramic and a second dielectric ceramic containing a silver electrode; the binder slurry includes 90-95 wt% binder powder, 2-10 wt% organic binder, and 1-4 wt% surfactant; the binder powder includes sintering aid powder and composite raw powder, wherein the composite raw powder is the first dielectric ceramic powder and / or the second dielectric ceramic powder.

2. The composite adhesive according to claim 1, characterized in that, The mass percentages of the sintering aid powder and the composite raw powder in the binder powder are 90-95 wt% and 5-10 wt%, respectively.

3. The composite adhesive according to claim 2, characterized in that, The sintering aid powder is a B2O3-SiO2-ZnO-X system powder, where X is one or more of nano-sized Li2O, Al2O3, and ZrO2 powders; wherein, the mass percentage of X in the sintering aid powder is 25-45 wt%; and the mass ratio of B2O3, SiO2, and ZnO is 1:(0.6-1.2):(1.5-2.5).

4. The composite adhesive according to claim 1, characterized in that, The particle size of the composite raw powder is 0.5-2μm, and the first dielectric ceramic powder and the second dielectric ceramic powder are ceramic powders with a dielectric constant K of 9-21.

5. The composite adhesive according to claim 1, characterized in that, The adhesive slurry also includes a solvent, the amount of which is 10-40% of the total amount of adhesive powder, and the viscosity range of the adhesive slurry is 10000-50000 mPa·s (25℃).

6. The composite adhesive according to claim 5, characterized in that, The organic binder is ethyl cellulose or acrylic resin, the solvent is one or more of terpineol, ethylene glycol butyl ether, and ethyl acetate; the surfactant is one or a mixture of two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyethylene glycol octylphenyl ether, and polyoxyethylene castor oil.

7. The composite adhesive according to any one of claims 1-6, characterized in that, The adhesive slurry also includes a vapor-phase SiO2 thixotropic agent, used in an amount of 0.5–1 wt%.

8. A method for preparing a composite binder for dielectric filter ceramics as described in any one of claims 1-6, characterized in that, include Obtaining the adhesive solution: Heat the organic adhesive with half the amount of solvent in the formula until completely dissolved and homogeneous to obtain the adhesive solution; To obtain the mixed slurry: Mix the binder powder, surfactant and the remaining half of the solvent evenly, and then ball mill once in a ball mill to obtain the mixed slurry; Obtaining the binder slurry: Mix the above-mentioned slurry with the binder solution, and then perform a second ball milling at room temperature. After the ball milling is completed, sieve the mixture to obtain the binder slurry.

9. The preparation method according to claim 8, characterized in that, It also includes the step of preparing binder powder: after mixing B2O3, SiO2 and ZnO in the sintering aid powder with the composite raw powder according to the formula, the X component is added and then mixed and ball-milled again.

10. A ceramic composite method, characterized in that, include The adhesive paste described in any one of claims 1-7 is applied to the surface of a first dielectric ceramic containing a silver electrode by means of printing, dotting, or spraying processes to form a predetermined pattern. A second dielectric ceramic with silver electrodes on its surface is pressed onto a patterned layer of a dielectric ceramic, and after being fixed by a fixture, it is dried at 80-120℃ to evaporate the solvent, thus obtaining a composite ceramic body. The dried composite ceramic body is sintered in stages: in the first stage, the temperature is increased to 320-380℃ at 3-5℃ / min to decompose organic matter, and the temperature is held for 5-15min; in the second stage, the temperature is increased to 850-910℃ at 5-8℃ / min to sinter, and the temperature is held for 10-15min to achieve interfacial diffusion; thus, the composite ceramic is obtained.

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