Coating for inhibiting diffusion of LTCC (low temperature co-fired ceramic) electrode as well as preparation method and application of coating

Abstract

The invention discloses an LTCC (Low Temperature Co-Fired Ceramic) electrode diffusion inhibiting coating as well as a preparation method and application thereof. The coating comprises a basic mixture and a filler, the basic mixture comprises a solvent and an adhesive, the sintering temperature of the filler is higher than the softening temperature of glass powder, and the glass powder is used for forming green ceramic chips in the LTCC technology; the contact angle corresponding to the wettability of the filler relative to the glass powder is less than 90 degrees, so that the filler has good wettability. According to the arrangement, the adhesive enables the coating to have better adhesiveness with the green ceramic chip and the silver paste; by selecting the filler which has the sintering temperature higher than the softening temperature of the glass powder and has good wettability with the glass powder, when the LTCC is sintered, the softened glass powder firstly infiltrates the filler, an isolation layer is formed between the softened glass powder and metal, and the isolation layer hinders formation of metal (such as silver) ion migration channels, so that metal diffusion is inhibited.

Description

Technical Field

[0001] This application belongs to the field of sintering technology, and specifically relates to a diffusion-inhibiting coating for LTCC electrodes, its preparation method, and its application. Background Technology

[0002] LTCC (Low-Temperature Co-fired Ceramic) is a technology that co-fires multiple layers of unsintered ceramic green sheets with a conductive metal paste (usually silver, silver-palladium alloy, or copper) at a relatively low temperature (typically 800°C to 900°C) in a single process. This process characteristic gives LTCC unparalleled machinability. Before sintering, the ceramic green sheets can be used to construct complex vertical interconnect channels and passive devices (such as resistors, capacitors, inductors, filters, and antennas) in three-dimensional space through precision drilling, hole filling, and printing processes. This not only greatly saves space and reduces the path and loss of signals transmitted between components, but also significantly improves the mechanical strength and interconnect reliability of the system.

[0003] LTCC features an adjustable low dielectric constant and extremely low dielectric loss, enabling signals to maintain high speed and low attenuation during transmission, especially in radio frequency (RF), microwave, and millimeter-wave bands. Furthermore, the high thermal conductivity of the ceramic material itself and its coefficient of thermal expansion, similar to that of silicon chips, allow for effective heat dissipation in high-power operating environments and reduce solder joint failures caused by thermal stress. These characteristics make LTCC the preferred solution for fields with stringent frequency and reliability requirements, such as 5G / 6G communications, satellite communications, automotive radar, and high-end test instruments.

[0004] However, under conditions of high temperature, high humidity, electric field, or long-term service, silver (Ag) ions or atoms can migrate from the conductor lines into the surrounding ceramic dielectric layer, a phenomenon known as silver diffusion. This is because LTCC ceramics typically contain a glassy phase (such as borosilicate glass) to lower the melting point. These glassy phases soften during sintering and subsequent high-temperature processes, becoming a rapid pathway for silver ion migration. During sintering, silver may excessively penetrate into the ceramic, causing deformation of the fine conductor linewidth and blurring of edges, directly affecting the performance accuracy of high-frequency circuits. Especially in high-temperature and high-humidity environments (such as the harsh testing conditions of 85℃ / 85%RH), coupled with the driving force of an electric field, silver ion migration is exacerbated. Its harmful effects are mainly manifested in the following two aspects: First, electromigration within the conductor leads to local thinning or even breakage of the conductor line, causing an open circuit; second, between two adjacent conductors with different potentials, silver ions migrate along the surface or interior of the dielectric, forming conductive dendrites, ultimately leading to a decrease in insulation resistance, an increase in leakage current, and even short-circuit failure. For highly integrated LTCCs with extremely small line spacing, such failures are catastrophic and difficult to predict. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of the prior art and provide an LTCC electrode diffusion suppression coating, preparation method and application thereof, wherein the coating can suppress the migration of metal (such as silver) from the conductor line to the surrounding ceramic dielectric layer.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: an LTCC electrode diffusion inhibition coating includes a base mixture and a filler, wherein the base mixture includes a solvent and a binder, the sintering temperature of the filler is greater than the softening temperature of the glass powder, and the glass powder is used to form green ceramic sheets in LTCC technology; the contact angle corresponding to the wettability of the filler relative to the glass powder is less than 90 degrees.

[0007] In some embodiments, the sintering temperature of the filler is not less than 900°C.

[0008] In some embodiments, the filler includes at least one of the following features: a) The filler to the base mixture is in a mass ratio of (0.1-10):1; b) The filler comprises ceramic powder; c) The median particle size range of the filler is 10 nm-2 μm.

[0009] In some embodiments, when the diffusion-inhibiting coating for the LTCC electrode comprises ceramic powder, the ceramic powder comprises at least one of alumina, zirconium oxide, magnesium oxide, titanium oxide, zinc oxide, cerium oxide, mullite, cordierite, and magnesium aluminum spinel.

[0010] In some embodiments, the solvent includes at least one of the following characteristics: a) The solvent to adhesive ratio is (0.5-10):1 by mass; b) The solvent includes at least one of the following: ester solvents, ketone solvents, aromatic hydrocarbon solvents, alcohol solvents and aliphatic hydrocarbon solvents.

[0011] In some embodiments, the ester solvent includes butyl acetate, propyl acetate, or ethyl acetate; the ketone solvent includes acetone, butanone, or cyclohexanone; the aromatic hydrocarbon includes toluene or xylene; the alcohol includes methanol, ethanol, propanol, or butanol; and the aliphatic hydrocarbon includes hexane, heptane, or cyclohexane.

[0012] In some embodiments, the adhesive comprises at least one of polyacrylate, polyurethane, silicone, polyester, polyvinyl butyral, and cellulose and its derivatives.

[0013] In some embodiments, when the adhesive comprises polyvinyl butyral or ethyl cellulose, the number average molecular weight of the polyvinyl butyral and the ethyl cellulose is 15,000-40,000 g / mol.

[0014] In some embodiments, the base mixture includes a dispersant in a mass ratio of (0.01-0.3):1 for the binder.

[0015] In some embodiments, the dispersant includes at least one of castor oil, hydrogenated castor oil, polyacrylate, phosphate ester, fatty acid polyoxyethylene ether, sorbitan fatty acid ester, and vinylpyrrolidone polymer.

[0016] In some embodiments, the base mixture includes an adhesive aid in a mass ratio of (0.01-0.2):1.

[0017] In some embodiments, the adhesive aid includes at least one of aminosilane coupling agents, epoxysilane coupling agents, methacryloxysilane coupling agents, vinylsilane coupling agents, mercaptosilane coupling agents, and titanate coupling agents.

[0018] In some embodiments, the base mixture includes a plasticizer in a mass ratio of (0.01-0.3):1 for the plasticizer and the binder.

[0019] In some embodiments, the plasticizer is at least one selected from dibutyl phthalate, dioctyl phthalate, diisodecyl phthalate, trioctyl trimellitate, tributyl citrate, and trihexyl butyryl citrate.

[0020] Secondly, this application discloses a method for preparing any of the aforementioned LTCC electrode diffusion-inhibiting coatings, the method comprising the following steps: The base mixture was stirred at 60-90 °C and 100-300 rpm for 2-4 h; The filler and the base mixture are ball-milled at 100-300 rpm for 4-8 h to form a filler-mixed resin; The filler-mixed resin is ground until the fineness is less than 8 μm, thus obtaining the diffusion-inhibiting coating for the LTCC electrode.

[0021] Thirdly, this application discloses the use of any of the aforementioned LTCC electrode diffusion-inhibiting coatings, the use of which includes the following steps: The coating is printed onto a green ceramic sheet; the solvent is removed by baking; a metal slurry is printed onto the coating formed by the coating; and the green ceramic sheet having the coating and the metal slurry is sintered.

[0022] In some implementations, the application includes at least one of the following features: a) Print the coating onto the green ceramic tile using a screen with a thickness of 5-100 μm; b) Bake at 60-120 ℃ for 5-30 min to remove the solvent from the coating; c) Using a 5-100μm thick screen with the same pattern, print the metal paste onto the coating; d) The green ceramic sheet having the coating and the metal slurry is sintered at a temperature of 700-950 °C.

[0023] The LTCC electrode diffusion-inhibiting coating, its preparation method, and its application described in this application have the following advantages compared to existing technologies: The adhesive provides the coating with film-forming properties, mechanical strength, and strong adhesion to the green ceramic sheet and silver paste before sintering, ensuring the pattern does not peel off. The solvent is used to dissolve or disperse the adhesive and other organic components. In the LTCC process, firstly, the adhesive and other components decompose upon heating, leaving a porous framework structure composed of filler particles. Secondly, the glass powder in the green ceramic sheet begins to soften. Since the sintering temperature of the filler is higher than the softening temperature of the glass powder, the filler remains in a solid state. Furthermore, the contact angle between the filler and the glass powder is less than 90 degrees, causing the softened glass powder to wet the filler first. These solid filler particles, encased in softened glass powder, accumulate between the metal (e.g., silver) and the green ceramic sheet, hindering the formation of metal ion or atomic migration channels, thereby suppressing metal diffusion and ensuring high-quality devices. For silver, if silver diffusion is not suppressed, the following disadvantages may occur: silver may over-penetrate into the ceramic, causing distortion of fine conductor linewidths and blurred edges, directly affecting the performance accuracy of high-frequency circuits. Especially in high-temperature and high-humidity environments (such as the harsh testing conditions of 85℃ / 85%RH), coupled with the driving force of an electric field, silver ion migration is exacerbated. Its harmful effects are mainly manifested in two aspects: first, electromigration within the conductor leads to localized thinning or even breakage of the conductor wire, causing an open circuit; second, between two adjacent conductors with different potentials, silver ions migrate along the surface or interior of the dielectric, forming conductive dendrites, ultimately leading to a decrease in insulation resistance, an increase in leakage current, and even short-circuit failure. For LTCCs with extremely high integration and extremely small line spacing, such failures are catastrophic and difficult to predict. Based on the above coatings, the adhesives ensure good adhesion between the coating and the green ceramic sheet and the silver paste; by selecting fillers with a sintering temperature higher than the softening temperature of the glass powder and good wettability with the glass powder, during the sintering of the LTCC, the softened glass powder first wets the filler, forming an isolation region between it and the silver, hindering the formation of silver ion migration channels, thereby inhibiting silver diffusion. Detailed Implementation

[0024] To explain in detail the technical content, structural features, achieved objectives, and effects of the invention, the technical solutions in the embodiments of this application will be described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. In the following description, for illustrative purposes, numerous specific details are set forth to provide a detailed description of various exemplary embodiments or implementations of the invention. However, various exemplary embodiments can also be implemented independently without these specific details or in one or more equivalent arrangements. Furthermore, the various exemplary embodiments may differ, but are not necessarily exclusive. For example, without departing from the inventive concept, the specific shape, structure, and characteristics of the exemplary embodiments may be used or implemented in another exemplary embodiment.

[0025] This application discloses a diffusion-inhibiting coating for LTCC electrodes. The material of the LTCC electrode is not limited, such as silver, copper, or gold. The diffusion-inhibiting coating comprises a base mixture and a filler, wherein the base mixture comprises a solvent and a binder. The sintering temperature of the filler is higher than the softening temperature of the glass powder. In some embodiments, the filler has the following characteristics: 1) Remains solid at high temperatures: does not melt or soften at the LTCC sintering temperature. 2) Has good wetting properties with the glass phase in LTCC, and can be wetted and encapsulated by the molten glass phase in LTCC to form a dense composite layer. 3) Chemically inert: does not undergo harmful side reactions with glass, metals (such as silver), or green ceramic sheets. 4) Controllable particle size and morphology: suitable for paste preparation and printing.

[0026] The filler is, for example, one of the following: 1) High-melting-point inorganic fillers, such as metal oxides, non-oxide ceramics, and their composites, more specifically, ceramic powder. The advantages of ceramic powder are: 1.1) Higher sintering temperature, which helps maintain a rigid solid skeleton during glass softening; 1.2) Better wettability with glass powder, facilitating the formation of an isolation layer to separate metals (e.g., silver) from the green ceramic sheet; 1.3) Chemical inertness and stability: It does not react harmfully with metals such as silver or glass, does not introduce migratable ions, and does not generate bubbles; 1.4) Matching coefficient of thermal expansion: It should be as compatible as possible with the LTCC matrix and glass to prevent coating cracking or peeling due to stress during sintering and cooling; 1.5) Suitable particle size and morphology: Too coarse (e.g., >10μm) leads to sedimentation and rough printing; too fine (e.g., <0.1μm) leads to agglomeration and excessive resin adsorption due to a large specific surface area; 1.6) Morphology: Near-spherical particles are preferred, facilitating high filling density and uniform encapsulation of the molten glass, reducing slurry viscosity.

[0027] 2) Certain high-melting-point metal or alloy powders, such as platinum, palladium, and certain heat-resistant steel powders; 3) High-melting-point, chemically stable non-oxide powders, such as boron nitride (BN) and aluminum nitride (AlN); 4) Glass powder. The sintering temperature of the filler is greater than the softening temperature of the glass powder, which is not specifically limited. For example, the sintering temperature of the filler is not less than 900℃.

[0028] One function of the glass powder is to form green ceramic wafers in LTCC technology. The contact angle corresponding to the wettability of the filler relative to the glass powder is less than 90 degrees, thereby the filler has good wettability relative to the glass powder.

[0029] As described above, the adhesive provides the coating with film-forming properties, mechanical strength, and strong adhesion to the green ceramic sheet and silver paste before sintering, ensuring that the pattern does not peel off. The solvent is used to dissolve or disperse the adhesive and other organic components. In the LTCC process, firstly, the adhesive and other components decompose upon heating, leaving a porous framework structure composed of filler particles. Secondly, the glass powder in the green ceramic sheet begins to soften. Since the sintering temperature of the filler is higher than the softening temperature of the glass powder, the filler remains in a solid state. Furthermore, the contact angle corresponding to the wettability of the filler relative to the glass powder is less than 90 degrees, causing the softened glass powder to wet the filler first. These solid filler particles, encapsulated by the softened glass powder, accumulate between the metal (e.g., silver) and the green ceramic sheet body to form an isolation layer. This isolation layer hinders the formation of metal ion or atomic migration channels, thereby suppressing metal diffusion and ensuring high-quality devices.

[0030] For silver as the metal, if silver diffusion is not suppressed, the following drawbacks will occur: silver may excessively penetrate into the ceramic, causing deformation and blurring of the fine conductor linewidth, directly affecting the performance accuracy of high-frequency circuits. Especially in high-temperature and high-humidity environments (such as the harsh testing conditions of 85℃ / 85%RH), coupled with the driving force of an electric field, silver ion migration will be accelerated. Its harm is mainly manifested in the following two aspects: first, electromigration within the conductor leads to local thinning or even breakage of the conductor line, causing an open circuit; second, between two adjacent conductors with different potentials, silver ions migrate along the surface or inside the dielectric, forming conductive dendrites, ultimately leading to a decrease in insulation resistance, an increase in leakage current, and even short-circuit failure. For LTCCs with extremely high integration and extremely small line spacing, such failures are catastrophic and difficult to predict. Based on the above coating, the adhesive enables the coating to have good adhesion to the green ceramic sheet and silver paste; by using a filler with a sintering temperature higher than the softening temperature of the glass powder and with good wettability to the glass powder, during the sintering of LTCC, the softened glass powder first wets the filler, forming an isolation layer between it and the silver. The isolation layer hinders the formation of silver ion migration channels, thereby inhibiting silver diffusion.

[0031] In some embodiments, the filler to base mixture ratio is (0.1-10):1 by mass. If this ratio is small, at least one of the following disadvantages may exist: 1) Inability to form a continuous and effective physical isolation layer: After sintering, insufficient filler particles are isolated from each other in the glass, failing to form an interconnected, dense network or skeleton that permeates the coating. The molten glass lacks sufficient solid support points, and the resulting isolation layer is more like a pure glass layer, with weak density and resistance to the migration of metal (e.g., silver) ions. Metal (e.g., silver) ions can still diffuse relatively easily through the glass phase. 2) Decreased mechanical strength and stability of the coating: After drying, insufficient filler means the coating relies mainly on organic resin support, making it more prone to microcracks due to stress during drying and subsequent printing of liquid metal (silver paste). During sintering, the pores left after the decomposition of the organic phase cannot be adequately filled by the filler-glass composite, potentially leading to porous or locally collapsed coatings. In summary, if the ratio is small, the effect of inhibiting metal diffusion is weak or unstable. Metals (such as silver) can diffuse through sparse areas of filler or defects in the coating, resulting in blurred wire edges, decreased insulation resistance, and an increased risk of short circuits between adjacent lines.

[0032] If the above ratio is too high, at least one of the following disadvantages will exist: 1) Slurry performance collapse: 1.1) Viscosity is too high, making it impossible to print: Excessive filler particles will greatly increase the viscosity of the slurry, causing it to lose its fluidity and making it impossible to print smoothly through the screen. During the printing process, problems such as unclear patterns, edge burrs, and uneven thickness will also occur. 1.2) Severe sedimentation and delamination: High-density fillers settle rapidly under static conditions, causing uneven slurry composition and huge differences in performance between upper and lower layers. 1.3) Poor leveling: The surface of the coating after printing is rough and prone to cracking after drying. 2) Insufficient organic carrier coating: 2.1) Dispersant failure: Limited dispersant cannot completely coat and isolate a large number of filler particles, resulting in severe agglomeration of fillers. Agglomerates become defect sources after sintering. 2.2) Insufficient binder: The binder is insufficient to bond all filler particles into a complete coating, resulting in poor mechanical strength of the dried coating. 2.3) Deterioration of structure after sintering: Due to uneven initial dispersion and agglomeration, a large number of micropores, gaps, or filler agglomerates exist inside the isolation layer formed by sintering. These defects become rapid pathways for silver diffusion. In short, if the proportion is too high, the coating itself may crack, peel off, or form a porous structure after sintering, which in turn provides a path for metal diffusion. The infeasibility of the process directly leads to the loss of the function of inhibiting metal diffusion.

[0033] Based on the foregoing analysis, the mass ratio of (0.1-10):1 has at least one of the following advantages: 1) It can form a more ideal permeation network: With sufficient filler particle content, after the organic phase decomposes, a particle network that is close to or even partially in contact with each other can be formed. When the glass melts, it can better fill the gaps between these particles and tightly encapsulate them. This structure allows the glass phase capillary channels that might otherwise be connected for the migration of metal (silver) ions to be maximally divided, blocked, and extended by the solid filler particles; metal (e.g., silver) ions must migrate around these solid particles in a tortuous manner, making the path more difficult. 2) Better process performance: The paste viscosity is moderate, with good rheological properties, suitable for screen printing, and can form patterns with clear edges and uniform thickness. The filler is evenly and stably dispersed without serious sedimentation, ensuring batch consistency and printing reliability. After drying, the coating is tough and crack-free, perfectly supporting subsequent silver paste printing. Ultimately, on the one hand, the resulting dense and uniform isolation layer can stably and consistently suppress metal diffusion to a low level, improving the reliability and yield of LTCC devices. On the other hand, because diffusion is effectively suppressed, the spacing between adjacent metal conductors (such as silver conductors) can be designed to be smaller, thus supporting higher-density circuit integration. Furthermore, after sintering, the edges of the metal conductors are steep and the contours are clear, which is beneficial for improving the performance of high-frequency and high-speed circuits.

[0034] In some embodiments, the ceramic powder includes at least one selected from alumina, zirconium oxide, magnesium oxide, titanium oxide, zinc oxide, cerium oxide, mullite, cordierite, and magnesium aluminum spinel; thus, it has the following advantages: Alumina possesses at least the following advantages: 1) High chemical stability and inertness: It reacts almost entirely with metals (such as silver) and glass, introducing no active ions and eliminating silver migration caused by chemical reactions at the source. 2) Good thermal stability: It has a high melting point and maintains absolute solid rigidity at LTCC sintering temperatures. 3) Good wettability with glass: Its moderate surface energy allows it to be easily wetted by common LTCC glass melts, forming a dense, non-porous Al2O3-glass composite interface. 4) Moderate coefficient of thermal expansion: It matches well with most LTCC substrates, preventing coating cracking due to thermal stress (cracking is a rapid diffusion pathway). Based on these advantages, alumina is more effective in suppressing the diffusion of metal (such as silver) ions.

[0035] Zirconia: The phase transformation toughening mechanism of zirconia results in isolation layers with higher mechanical strength, making them less prone to microcrack formation during sintering cooling and device use. Microcrack-free isolation layers help suppress the diffusion of metals (such as silver).

[0036] Magnesium oxide (MgO) is an alkaline oxide that can react with glass to form new phases such as forsterite (2MgO·SiO2). This can strongly anchor the interface and even change the composition of the glass phase at the interface, reducing its solubility or migration rate for metals (such as silver ions), which is more conducive to inhibiting the diffusion of metals (such as silver).

[0037] Titanium oxide and zinc oxide: Both fillers selected in this paper can serve as the ceramic phase in LTCC. Therefore, it can be understood that titanium oxide or zinc oxide can absorb the diffused glass phase (indirectly absorbing the overflowing glass powder), thereby blocking the pathway between the metal and the glass layer, which is beneficial for inhibiting metal diffusion.

[0038] Cerium oxide: As an oxidation buffer, it absorbs oxygen vacancies generated during sintering or inhibits the oxidation / reduction cycle of metals (such as silver) (which exacerbates silver migration), thereby helping to suppress the diffusion of metals (such as silver).

[0039] Mullite: Its composition and structure are closest to those of silicate glass, thus its coefficient of thermal expansion is better matched (~5×10⁻). 6 / K), after sintering, the interfacial stress is extremely small, and there is almost no risk of cracking. Therefore, the crack-free interface is conducive to suppressing the diffusion of metals (such as silver).

[0040] Cordierite: Its low coefficient of thermal expansion helps to compensate for and suppress the thermal shrinkage of the overall coating, which in turn helps to suppress microcracks caused by stress, and thus helps to suppress the diffusion of metals (such as silver).

[0041] Magnesium aluminum spinel: It is very stable to acids, alkalis and metal melts, which helps to inhibit the diffusion of metals (such as silver).

[0042] When at least two of the above components are used, 1) the combination of fillers with different particle sizes and shapes allows the residual porosity to be minimized during the filling of the molten glass. For example, large particles (such as 5μm alumina) serve as the framework, medium particles (such as 1μm mullite) fill the gaps between the large particles, and small or plate-like particles (such as 0.2μm alumina or plate-like alumina) further fill the micropores. The resulting isolation layer has better density, and the path of metal migration is extended, twisted, and blocked to a greater extent, which is beneficial for suppressing metal diffusion; 2) the coefficient of thermal expansion of a single filler is fixed. By combining two fillers with different CTEs (such as high-CTE zirconia and low-CTE cordierite) in a certain proportion, the CTE of the filler can be matched with the CTE of the LTCC substrate. Matched CTE means that there is almost no thermal stress between the coating and the substrate during the cooling process from the sintering temperature to room temperature. This is beneficial for avoiding the generation of microcracks caused by stress, while metals (such as silver paste) will diffuse through microcracks. Therefore, the above method is beneficial for suppressing metal diffusion. For example, the advantages of some combinations are described below: Alumina (Al2O3) + Mullite: Alumina offers excellent chemical inertness, high hardness, and a mature supply chain. Mullite provides near-perfect thermal expansion matching and chemical affinity with glass. When combined, the CTE can be precisely tuned for perfect matching with the vast majority of LTCC substrates. Mullite enhances the interfacial bonding with glass, while alumina ensures overall chemical stability. In terms of cost, it partially replaces expensive pure mullite powder. As mentioned earlier, the high CTE helps prevent crack formation, which in turn helps suppress metal diffusion (such as silver).

[0043] Zirconia (ZrO2) + Alumina (Al2O3): Zirconia provides good phase transformation toughening effect, improving the fracture toughness of the coating. Alumina ensures good wettability with glass and low raw material cost. Alumina as the main component guarantees good processability and basic properties; the addition of some zirconia as a reinforcing phase helps improve the crack resistance of the isolation layer, preventing cracking and inhibiting the diffusion of metals (such as silver).

[0044] In some embodiments, the median particle size range of the filler is 10 nm-2 μm. Smaller particle sizes have at least one of the following disadvantages: 1) Nanoparticles have a large specific surface area and extremely high surface energy, exhibiting a strong tendency to aggregate to reduce energy. Even with a large amount of dispersant, it is extremely difficult to obtain a stable and uniform dispersion. Aggregates become a fatal flaw in subsequent processes; the large specific surface area adsorbs a large amount of solvent and resin molecules, leading to increased slurry viscosity, loss of fluidity, and unfavorable conditions for screen printing. 2) Nanoparticles have extremely high surface activity, resulting in a lower sintering initiation temperature. At the sintering temperature of LTCC, they may prematurely and rapidly self-sinter to densify, closing the pores between particles before the glass melts, which prevents effective penetration and encapsulation by the molten glass. Nanoaggregates that are not well bonded to the glass will sinter into dense closed pores or interfaces separated from the glass phase, becoming weak points in the structure. Ultimately, the above process leads to unfilled nanopores, microcracks, and weak bonding interfaces between the filler and glass in the final isolation layer. These defects become rapid channels for the diffusion of silver ions.

[0045] Larger particle sizes can lead to at least one of the following drawbacks: 1) Excessively large particles can clog the screen mesh (especially with high mesh counts), resulting in uneven printing, a rough coating surface, and poor edge clarity. 2) During paste storage and printing, large particles settle rapidly, causing uneven composition and performance between layers. 3) A thick, pure glass bridge can form between two adjacent large particles. Without the support and separation of fillers, this glass bridge is a relatively easy path for metal (such as silver ions) migration, which is detrimental to inhibiting metal diffusion.

[0046] Particle sizes within the aforementioned range offer at least one of the following advantages: 1) Better processing performance: 1.1) Dispersion and stability: The moderate particle surface area allows for long-term stable suspension using conventional dispersants, resulting in reliable slurry performance. 1.2) The slurry's rheological properties (pseudoplasticity) perfectly match screen printing, enabling the production of fine patterns with uniform thickness, sharp edges, and high resolution. 1.3) Particles with moderate sizes can achieve high packing density. When wetting molten glass, they can almost completely fill all voids. The diffusion paths of metal (e.g., silver) ions or atoms in the glass phase are better bent, extended, and segmented by the densely packed solid filler particles. This effectively lengthens the diffusion paths considerably. Furthermore, the moderate particle size provides sufficient surface area for good physicochemical bonding with the glass, resulting in a strong interface. Thus, the longer paths and better bonding help suppress metal diffusion.

[0047] In some embodiments, the solvent:binder ratio is (0.5-10):1 by mass. If the ratio is too small, it has at least one of the following disadvantages: 1) Slurry state and printability failure: The slurry loses its fluidity, becoming like putty or plaster, which is not conducive to passing through the screen. 2) Difficulty in solvent removal: An excessively thick resin layer encapsulates the solvent in the inner layer, easily causing a "skinning" phenomenon during drying (rapid surface hardening seals in the internal solvent), making it difficult for the internal solvent to escape. During subsequent sintering, these residual solvents rapidly vaporize, which can rupture the coating, producing pinholes, bubbles, or even bursts. 3) High internal stress: The high polymer content results in extremely high drying shrinkage stress, making the coating extremely prone to warping, peeling, or macroscopic cracking from the green ceramic sheet. In summary, a small ratio makes printing impossible, and consequently, the function of inhibiting metal diffusion cannot be achieved.

[0048] If the proportion is too high, it will lead to at least one of the following disadvantages: 1) Failure of the paste and coating formation ability: The filler particles will quickly settle to the bottom and clump together in a dilute medium, and cannot be evenly dispersed again by stirring. The paste will separate and become unusable within minutes. After printing, the excess solvent will flow and evaporate rapidly, failing to support the filler and resin to form a continuous and strong film. 2) Inability to form an effective isolation layer: After sintering, due to the discontinuity and thinness of the initial coating, a continuous "filler-glass" isolation layer with sufficient thickness cannot be formed. The metal in the metal (such as silver paste) can almost directly contact the raw ceramic tile body.

[0049] Based on the above analysis, the solvent:binder ratio of (0.5-10):1) has at least one of the following advantages: It promotes the uniformity and consistency of the microstructure: excellent processability ensures uniformity from macro to micro, meaning that the "filler-glass" isolation layer formed after sintering has similar density and chemical composition at any location, and there are no local weak points caused by uneven printing or drying defects. Silver diffusion must penetrate the entire uniform barrier, ensuring a stable and reliable inhibition effect. 2) It helps ensure pattern alignment and coverage: a clear printed pattern ensures that the inhibitory coating accurately and completely covers the metal (e.g., silver paste) lines that need protection, leaving no dead corners, which is beneficial for inhibiting metal diffusion.

[0050] In some embodiments, the solvent includes at least one of the following: ester solvents, ketone solvents, aromatic hydrocarbon solvents, alcohol solvents, and aliphatic hydrocarbon solvents.

[0051] As described above, although the solvents cannot directly inhibit metal (e.g., silver) diffusion, they indirectly inhibit metal diffusion by determining the mass ratio of filler and binder, for the following reasons: 1) Ensuring perfect dispersion of filler, thus determining microscopic uniformity: A suitable solvent can create a more favorable environment for binders and other components (e.g., dispersants), allowing the dispersant to fully function, separating and stabilizing each filler particle in the slurry. The uniformity of the isolation layer after sintering is directly inherited from the uniformity of filler dispersion in the slurry. Good uniformity of the isolation layer indirectly leads to a better effect in inhibiting metal (e.g., silver) diffusion. 2) Forming a defect-free dry film, thus eliminating diffusion shortcuts: The solvent helps eliminate drying defects such as pinholes, bubbles, orange peel, and cracks. This results in a dense, non-porous dry precursor film, which is conducive to forming a dense, non-porous isolation layer. A good isolation layer leads to a better effect in inhibiting metal diffusion.

[0052] In some embodiments, the ester solvent includes butyl acetate, propyl acetate, or ethyl acetate. As described above, butyl acetate, propyl acetate, and ethyl acetate better dissolve the binder (e.g., PVB / EC), and their specific boiling point gradients (e.g., ethyl acetate dries quickly, butyl acetate dries slowly) synergistically achieve gradient evaporation of the paste. This evaporation mode ensures rapid setting of the printed pattern to obtain clear boundaries, while providing sufficient leveling time to eliminate coating surface defects (e.g., pinholes, orange peel), ultimately resulting in a uniformly thick, microstructured, dried precursor film. This precursor film decomposes smoothly during sintering, forming a uniformly porous filler skeleton, thereby guiding the uniform wetting of molten glass and constructing a dense, defect-free isolation layer. This isolation layer effectively inhibits metal (e.g., silver) diffusion. When the alcohol solvent includes at least two, their complementary advantages lead to the formation of an even denser isolation layer, further inhibiting metal (e.g., silver) diffusion.

[0053] In some embodiments, the ketone solvent includes acetone, butanone, or cyclohexanone; thus, the introduction of ketone solvents (such as acetone, butanone, and cyclohexanone) serves multiple synergistic purposes. Their strong solubility and rapid volatility first ensure good printability and instant pattern setting ability of the paste, resulting in precise patterns with clear edges. More importantly, combining them with medium-to-slow boiling point solvents such as esters can construct a controlled gradient evaporation system. Under the control of this system, the coating drying process is stable and orderly, avoiding skinning-bubbling defects caused by excessively rapid evaporation, or flowing and contamination caused by excessively slow evaporation, ultimately yielding a precursor film with a dense microstructure and low internal stress. This precursor film is the basis for forming a uniform, defect-free isolation layer during subsequent high-temperature sintering, and further, it helps to suppress metal (such as silver) diffusion.

[0054] In some embodiments, the aromatic hydrocarbons include toluene or xylene. As described above, toluene or xylene, as a slow-drying component, plays a crucial role in the later stages of drying: effectively extending the leveling window of the coating, eliminating surface defects by suppressing Bénard eddies; simultaneously, its thermoplastic properties help alleviate internal stresses generated during drying and thermal decomposition, fundamentally preventing the formation of microcracks. Therefore, the introduction of toluene or xylene helps ensure a defect-free precursor structure, thereby achieving a stable and reliable isolation function and helping to suppress metal (such as silver) diffusion.

[0055] In some embodiments, the alcohols include methanol, ethanol, propanol (n-propanol or isopropanol), or butanol (n-butanol or isobutanol). As described above, the introduction of alcohol solvents (such as ethanol and isopropanol) serves multiple key functions. Their low surface tension primarily ensures perfect wetting of the raw ceramic substrate by the slurry, fundamentally eliminating localized protective failures caused by pinholes. A pinhole is a directly exposed area of ​​the raw ceramic substrate, where metals (such as silver paste) will directly contact, and diffusion is completely unimpeded. Eliminating pinholes helps suppress metal (such as silver) diffusion. Furthermore, by selecting alcohols with different carbon chain lengths (such as from methanol to butanol), the volatilization gradient can be precisely fine-tuned, synergistically controlling the drying process. This helps obtain a dried film with uniform thickness and composition distribution, helps prevent blistering or pinhole defects, obtains a dense precursor, and further helps suppress metal (such as silver) diffusion. After sintering, pinholes and bubbles become pores that extend directly to the substrate. If pinholes or bubbles are present, metal (silver ions) can diffuse through these channels without hindrance. In some embodiments, the aliphatic hydrocarbons include hexane, heptane, or cyclohexane. This offers at least one of the following advantages: 1) The aliphatic hydrocarbons (hexane, heptane, or cyclohexane) can dilute the entire system like a lubricant without dissolving the resin or disrupting the original dispersion structure, reducing the high-solids, high-viscosity paste to a printable slurry. Using more functional fillers allows for the formation of a thicker, denser insulating layer after sintering, which helps suppress metal (e.g., silver) diffusion.

[0056] In some embodiments, the adhesive comprises at least one selected from polyacrylate, polyurethane, silicone, polyester, polyvinyl butyral, and cellulose and its derivatives. Examples of cellulose and its derivatives include methylcellulose, ethylcellulose, hydroxypropylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose ether, and hydroxypropyl methylcellulose acetate succinate, etc.

[0057] In some embodiments, when the adhesive comprises polyvinyl butyral or ethyl cellulose, the number average molecular weight of the polyvinyl butyral and the ethyl cellulose is 15,000-40,000 g / mol.

[0058] If the number-average molecular weight is low, at least one of the following disadvantages exists: 1) Deterioration of paste and coating performance: 1.1) Poor film-forming properties: Low molecular weight polymers have short chains and little entanglement, making it impossible to form a strong and continuous film. The dried coating is brittle, powdery, and has weak cohesion, making it extremely easy to break and peel off during subsequent metal paste (such as silver paste) printing or handling; 1.2) Insufficient encapsulation force for fillers: It is impossible to effectively bond and fix filler particles, causing the fillers to shift or settle in the early stages of drying or sintering, destroying the microscopic uniformity. 2) Deterioration of thermal decomposition behavior: 2.1) Premature and wide decomposition: Low molecular weight polymers generally have poor thermal stability, and their decomposition may begin at lower temperatures (such as <300°C), and the decomposition temperature window becomes wider; 2.2) Mismatch with sintering sequence: Premature decomposition means that the binder has decomposed in large quantities before the glass powder has begun to soften, and the remaining filler skeleton may collapse or shift due to vibration or stress during high-temperature holding, destroying the intended uniform structure. 3) Disadvantages of inhibiting metal (e.g., silver) diffusion: 3.1) Incomplete coating: The fragile coating breaks down during processing, directly losing local protection. 3.2) Skeleton collapse: Premature decomposition leading to skeleton instability will make the isolation layer formed after sintering porous, not dense, and even have macroscopic cracks. 3.3) Functional failure: The above defects directly become a fast channel for metal (e.g., silver) diffusion.

[0059] If the above-mentioned number-average molecular weight is large, at least one of the following disadvantages exists: 1) Poor slurry processability: 1.1) Excessively high viscosity: High molecular weight polymers have long chains, and the viscosity of the solution increases exponentially with molecular weight. The slurry will become extremely viscous or even become a paste, losing its fluidity and making it impossible to screen print. 1.2) Difficult dispersion: In high-viscosity slurries, fillers are difficult to disperse uniformly, shear dispersion energy consumption increases dramatically, and heat is easily generated, leading to solvent evaporation. 2) Deteriorated thermal decomposition behavior: 2.1) Decomposition is too late and incomplete: High molecular weight polymers require higher temperatures to decompose, and decomposition may be incomplete, increasing the risk of residual carbon or coking fragments. 2.2) Serious conflict with sintering sequence: When the glass powder has begun to soften and flow, the high molecular weight binder (such as PVB / EC) may still be decomposing. Its decomposition products (gas, coke) will seriously interfere with and block the wetting and encapsulation process of the molten glass on the filler particles. 3) Fatal Effects on Silver Diffusion Inhibition: 3.1) Formation of Structural Defects: Residual carbon or coke from decomposition is encapsulated within the glass phase, creating localized reducing environments, conductive pathways, or stress concentration points. These defects not only fail to block metals (such as silver) but may also catalyze or accelerate the migration and aggregation of metal ions or atoms. 3.2) Interfacial Contamination: Incomplete decomposition products form a contamination layer between the filler and the glass, disrupting the good bond between them and forming a weak interfacial layer.

[0060] In summary, the number-average molecular weight within the aforementioned range offers at least one of the following advantages in suppressing metal (e.g., silver) diffusion: 1) Constructing a better reaction precursor: The binder with a suitable molecular weight provides both the strength and uniformity required during processing and ensures timely and better removal during sintering. This reduces any structural or chemical defects caused by residue contamination of the interface or obstruction of glass flow. 2) Ensuring a denser and chemically homogeneous isolation layer: On a purer filler framework, the glass can be better filled according to its physicochemical properties, forming a dense filler-glass composite with strong interfacial bonding, no impurities, and extremely low porosity. This structure has the highest tortuosity factor and diffusion activation energy for the migration of metal ions or atoms (e.g., silver ions). 3) Ensuring extremely high repeatability and reliability of performance: The polymer with controllable molecular weight distribution ensures the stability of slurry performance and thermal behavior between batches, thereby making the metal (e.g., silver) diffusion suppression effect of the final device highly consistent and reliable, meeting the requirements of industrial production.

[0061] When the binder is PVB / EC, the number average molecular weight within the above range also has the following advantages: 1) Better processability: 1.1) Ideal viscosity: It can formulate a slurry with high solid content, moderate viscosity, and excellent pseudoplasticity (shear thinning), suitable for screen printing, and obtain a uniform coating; 1.2) Better film-forming properties: It can form a strong, flexible, and well-adhesive dry film, sufficient to withstand all subsequent processing steps without damage. 2) Better matching thermal decomposition sequence: 2.1) More precise decomposition window: Within this molecular weight range, the thermal decomposition initiation temperature of PVB / EC is about 350°C, the violent decomposition occurs at 400-450°C, and it is basically completed before 500°C. 2.2) Better matching sintering sequence: First step: The binder is completely and cleanly decomposed and vaporized, leaving a pure, porous but structurally stable filler skeleton. Second step: The glass powder in the green ceramic sheet begins to soften and melt. Third step (synergistic): The molten glass liquid unimpededly wets, fills, and encapsulates the previously stable filler skeleton. The two work in tandem over time and in synergy in space, which is more conducive to suppressing the diffusion of metals (such as silver).

[0062] In some embodiments, the base mixture includes a dispersant in a mass ratio of (0.01-0.3):1 for the binder.

[0063] The role of dispersants is to adsorb onto the surface of filler particles and prevent their aggregation through steric hindrance or electrostatic repulsion. The ratio of dispersants to binders determines how much of the filler surface is effectively covered and protected.

[0064] If the above proportions are small, 1) Deterioration of slurry state: 1.1) Severe agglomeration: Filler particles attract each other due to van der Waals forces, forming micron-sized or even larger agglomerates. Undispersible hard slag appears in the slurry. 1.2) Sedimentation and stratification: Agglomerates settle rapidly, and the slurry stratifies in a short time. The upper layer is clear liquid, and the lower layer is hardened filler lumps, which cannot be used for printing. 2) Disadvantages of coating and sintering structure: 2.1) Printing defects: Even if printing is barely possible, agglomerates will clog the screen, resulting in incomplete patterns and a coating surface as rough as sandpaper. 2.2) Uneven microstructure: After drying and sintering, these agglomerates are retained, becoming islands or hard lumps in the coating. 2.3) Weak interfacial bonding: Inside the agglomerates, the particles are in close contact, making it difficult for the glass melt to penetrate; between the agglomerates and the glass, annular gaps or pores are easily formed due to different shrinkage. 3) Disadvantages of suppressing metal (e.g., silver) diffusion: 3.1) Formation of diffusion shortcuts: The gaps and pores around the agglomerates, as well as the pores inside the agglomerates that are not filled by glass, together form a three-dimensional network of rapid channels for the diffusion of metal ions or atoms (e.g., silver ions). Metals can easily bypass these islands, resulting in high diffusion efficiency. 3.2) Local failure: The overall reliability of the coating drops sharply due to structural inhomogeneity, and the suppression effect becomes completely uncontrollable.

[0065] If the above proportions are too high, resulting in excessive dispersant exceeding the adsorption requirements of the filler surface, at least one of the following disadvantages will occur: 1) Abnormal slurry properties: 1.1) Abnormal viscosity: Excessive free dispersant may alter the rheological properties of the slurry, leading to unstable viscosity or unwanted thixotropy. 1.2) Increased foaming: Many dispersants are surfactants, and excessive amounts can cause the slurry to generate a large amount of stable foam during stirring, affecting coating quality. 2) Chemical contamination during sintering: 2.1) Risk of thermal decomposition residues: Excessive organic dispersant needs to decompose during sintering, and its total amount may exceed the system's ability to completely and cleanly decompose at the set temperature, leading to an increased risk of residual carbon or complex organic residues. 2.2) Interference with glass wetting: These residues may contaminate the filler surface, altering its wetting characteristics, or exist at the interface between the filler and glass, hindering good bonding between the two. 3) Disadvantages in suppressing metal (e.g., silver) diffusion: 3.1) Introduction of a weak interface layer: Dispersant residues form a non-glassy intermediate layer at the interface with poor mechanical strength and chemical stability, becoming a weak link in the isolation layer. 3.2) Provide diffusion pathways: Residual carbon or organic impurities may themselves form pathways for ion migration.

[0066] Based on the above analysis, dispersants and binders within the aforementioned range have at least one of the following advantages: 1) Advantages in inhibiting metal (e.g., silver) diffusion: 1.1) More uniform and denser isolation layer: Due to the uniform initial distribution of fillers, the filler-glass composite layer formed after sintering has highly uniform chemical composition and microstructure throughout the entire region. The absence of localized enrichment or sparse areas caused by agglomeration means there are no localized weak points. Metal ions face the same dense barrier at any location. 1.2) Better tortuosity factor and blocking effect: When each filler particle is independently and uniformly dispersed in the glass matrix, their segmentation and extension effects on the metal ion migration path are maximized. The diffusion path of metal ions becomes extremely tortuous (high tortuosity factor) and is continuously blocked by solid particles, significantly increasing the diffusion activation energy. 1.3) Ensures atomically tight interfacial bonding: Clean, uncontaminated filler surfaces can achieve better physicochemical bonding with the molten glass, forming a stronger interface, which eliminates peeling or diffusion channels caused by weak interfaces.

[0067] In some embodiments, the dispersant includes at least one selected from castor oil, hydrogenated castor oil, polyacrylate, phosphate ester, fatty acid polyoxyethylene ether, sorbitan fatty acid ester, and vinylpyrrolidone polymer. As described above, the dispersant has at least the following advantages: Castor oil and hydrogenated castor oil: 1) Excellent wetting and steric hindrance: Its long fatty chains can firmly adsorb onto the surface of nonpolar or weakly polar fillers, extending into the solvent to provide a significant steric hindrance effect, preventing particles from approaching each other. 2) Good resin compatibility: Excellent compatibility with resins such as PVB and EC, without affecting film formation. 3) Hydrogenated castor oil: More stable, less prone to oxidation and rancidity, resulting in a longer slurry shelf life. Advantages in inhibiting metal (e.g., silver) diffusion: The strong steric hindrance it provides effectively prevents the agglomeration of nanoscale fillers. Agglomerates are defect sources in the microstructure after sintering. Ensuring that each filler particle is independent is beneficial for forming a uniform isolation layer, which helps inhibit metal (e.g., silver) diffusion.

[0068] Polyacrylates: 1) Superior anchoring and steric stability: Anchoring groups (such as carboxyl and amino groups) are strongly bonded to the filler surface via ionic or hydrogen bonds, allowing for better adsorption; the solvation chains (polyacrylate chains) are highly compatible with the solvent, forming a thick steric barrier. 2) High versatility: Different polarities of fillers and solvents can be designed to match. Advantages in suppressing metal (e.g., silver) diffusion: Polyacrylate dispersants provide dispersion stability, enabling high solids content at low viscosity. This means thicker coatings can be printed, resulting in a thicker isolation layer after sintering and stronger physical barrier properties. Simultaneously, their excellent stability ensures absolutely uniform filler distribution from slurry to dried film, which is beneficial for forming a better isolation layer. Therefore, such an isolation layer helps suppress metal (e.g., silver) diffusion.

[0069] Phosphate esters: 1) Strong electrostatic adsorption and modification: Phosphate ions form strong chemical adsorption with metal ions (such as Al³⁺ on the surface of alumina) on the filler surface, and can even slightly modify the surface, improving its compatibility with the organic phase. 2) Provide electrostatic repulsion: After ionization, it imparts a negative charge to the filler surface, assisting dispersion through electrostatic repulsion. Advantages in inhibiting metal (such as silver) diffusion: Its strong adsorption can overcome the high surface energy of the filler, preventing hard agglomeration caused by van der Waals forces, which is conducive to the formation of a defect-free or defect-free isolation layer, and thus helps to inhibit metal (such as silver) diffusion.

[0070] Fatty acid polyoxyethylene ethers: 1) Good wetting and viscosity reduction: They can quickly reduce the surface tension of the slurry, wetting and disintegrating filler aggregates. 2) Steric hindrance stability: The polyoxyethylene chains extend in the solvent, providing steric hindrance. Advantages in inhibiting metal (e.g., silver) diffusion: Good wetting ability allows penetration into the micro-aggregates of fillers, breaking them down into virgin particles. This ensures good dispersion performance even with raw materials that have not undergone ideal pretreatment, improving process robustness and tolerance to raw materials, and guaranteeing the stability of the inhibition effect.

[0071] Dehydrated sorbitan fatty acid esters: exhibit good dispersion in non-aqueous systems and are less prone to foaming (foam is a source of coating defects). Advantages in inhibiting metal (e.g., silver) diffusion: by providing reliable dispersion while avoiding the introduction of air bubbles, they also ensure the density of the dried film. Air bubbles become pores after sintering, which act as channels for metal diffusion, thus preventing air bubbles and inhibiting metal (e.g., silver) diffusion.

[0072] In some embodiments, the base mixture includes an adhesive aid in a mass ratio of (0.01-0.2):1.

[0073] If the above proportions are too small, the amount of adhesive is insufficient, and an effective bridging network cannot be formed at the interface, resulting in at least one of the following disadvantages: 1) Weak coating adhesion: The bond between the coating and the green ceramic sheet mainly relies on physical adsorption and van der Waals forces, resulting in low strength. During drying shrinkage, mechanical stress from the subsequent silver paste printing squeegee, or gas generation from the decomposition of organic matter in the early stages of sintering, the coating is prone to local warping, edge peeling, or overall detachment. 2) Introduction of macroscopic defects: Once the coating peels off locally, a direct, unobstructed contact area is formed between the metal paste (such as silver paste) and the green ceramic sheet. At the same time, the peeled edge becomes a stress concentration point, which may induce a larger area of ​​detachment. 3) Disadvantages in suppressing metal (such as silver) diffusion: 3.1) Complete local loss of function: In the area where the coating has peeled off, metal diffusion is not suppressed at all, directly leading to the failure of the circuit function at that point or short circuits in adjacent lines. 3.2) Defect propagation: Local peeling will change the stress distribution in the surrounding area, which may trigger a chain reaction, causing the suppression function to become unreliable over a larger area.

[0074] If the above proportions are too high, resulting in excessive adhesive, at least one of the following disadvantages will occur: 1) Deterioration of interfacial layer properties: 1.1) Increased brittleness: Excessive adhesive may form an excessively thick, highly cross-linked, brittle interfacial layer. This film lacks flexibility and cannot release stress through deformation, making it more prone to brittle cracking due to stress. 1.2) Incompatibility with coating: Excessive adhesive may alter the rheology and shrinkage rate of the interfacial region, causing significant differences in performance between it and the main coating, generating internal stress at the interface. 2) Interference with coating performance: Excessive adhesive may migrate into the coating, affecting the film-forming properties and flexibility of the adhesive itself, or interact with other components such as dispersants, compromising the stability of the slurry. 3) Risk of thermal decomposition: Many adhesives (such as silane coupling agents) are themselves organic compounds. Excessive addition will increase the total organic loading of the system, potentially leading to an increased risk of thermal decomposition residues and interface contamination. 4) Disadvantages of suppressing metal (e.g., silver) diffusion: 4.1) Interface cracking becomes a diffusion channel: Microcracks generated in the brittle interface layer can extend from the root of the coating-substrate bond, becoming a path for metal diffusion to reach the substrate. 4.2) Introducing uncertainty: Excessive addition leads to uneven internal performance and potential thermal residue, making the overall performance of the isolation layer unpredictable.

[0075] Based on the above analysis, the proportion within the above range has the following advantages: 1) Better interfacial performance: 1.1) Better chemical anchoring: The functional groups at one end of the adhesive binder chemically bond with the hydroxyl groups on the surface of the green ceramic tile, while the other end is compatible with or reacts with the adhesive, forming a strong chemical chain of "green ceramic tile - adhesive binder - adhesive". 1.2) Better stress buffering: The thin-layer interface has good stress transmission and dissipation capabilities, which can evenly distribute the shrinkage stress and mechanical stress borne by the coating to the entire bonding surface, avoiding stress concentration. 2) Facilitates the integrity of the coating in the complete process chain: Ensures that from drying, silver paste printing to the initial stage of sintering, the coating is firmly and completely attached to the predetermined position without any displacement or peeling. This is beneficial for the isolation layer to play its role. 3) Advantages in suppressing metals (such as silver): 3.1) Prevents protective off-target: Ensures that the suppressive coating covers the predetermined area without peeling gaps. This is the most basic geometric requirement for achieving effective suppression. 3.2) Eliminating the risk of edge leakage: Good edge adhesion prevents molten metal (such as silver paste) from seeping into the gaps beneath the coating edges. Coating edges are sensitive areas for diffusion. 3.3) Providing stable support during the initial sintering stage: At the stage when the binder begins to decompose and the coating structure is most vulnerable, a strong interfacial bond stabilizes the overall structure of the filler skeleton, preventing overall slippage or collapse due to internal stress or gas impact, thus maintaining a structurally sound mold for subsequent glass melting and filling.

[0076] In some embodiments, the adhesive aid includes at least one of aminosilane coupling agents, epoxysilane coupling agents, methacryloxysilane coupling agents, vinylsilane coupling agents, mercaptosilane coupling agents, and titanate coupling agents.

[0077] As described above, aminosilane coupling agents exhibit the following advantages: 1) Strong hydrogen bonding and reactivity: The amino group (-NH2) can form strong hydrogen bonds with the carbonyl group (C=O) in the adhesive, and can also react chemically with functional groups in polyurethane, epoxy, and other systems. 2) Catalytic effect: It has a catalytic effect on certain condensation reactions, promoting its bonding with the substrate. Advantages in inhibiting metal (e.g., silver) diffusion: The amino group forms a strong physical-chemical bond with PVB / EC, ensuring a strong bond between the coating and the substrate before the adhesive thermally decomposes. This effectively resists bubbling and peeling forces caused by the gas generated during the initial sintering process of adhesive decomposition, preventing the coating from forming diffusion channels at critical moments.

[0078] Epoxy-based silane coupling agents: Epoxy groups can undergo ring-opening reactions with various functional groups such as hydroxyl, carboxyl, and amino groups under heating to form covalent bonds. They are chemically stable and have good storage properties. Advantages in inhibiting metal (e.g., silver) diffusion: During sintering heating, the epoxy groups undergo thermosetting cross-linking with the binder or themselves. This forms an early, heat-resistant network structure at the interface during the transition stage when the binder begins to soften and decompose. Even after the main binder loses strength, this network firmly fixes the relative position of the filler skeleton and the substrate, preventing structural collapse or displacement, and maintaining a precise template for glass molten impregnation.

[0079] Methacryloxysilane coupling agents possess free radical reactivity: their double bonds can polymerize with free radical initiators or under heating conditions, copolymerizing with acrylate adhesives to achieve true chemical grafting. Advantages in inhibiting metal (e.g., silver) diffusion: If the adhesive contains acrylate components, methacryloxysilane coupling agents can achieve fully covalent bonding from the inorganic substrate to the organic coating, forming a strong interface. This interface can withstand maximum stress, eliminating the risk of coating peeling due to interface failure and preventing uncontrolled diffusion caused by it.

[0080] Vinyl silane coupling agents: They possess reaction specificity and low steric hindrance. Vinyl groups exhibit moderate reactivity, primarily participating in free radical copolymerization. Their low steric hindrance allows for easy close packing on substrate surfaces. Advantages include inhibiting metal (e.g., silver) diffusion: In resin systems containing unsaturated bonds (such as certain polyesters), they can form covalent bonds. Their close packing characteristic helps form a denser, low-defect interfacial monolayer, reducing microscopic defects at the interface that could otherwise be the starting point for silver ion diffusion along the interface.

[0081] Thiol-silane coupling agents: Strong coordination with metal ions: The thiol group (-SH) has an extremely strong coordination (complexation) ability with metal ions such as silver (Ag) and copper (Cu). Advantages in inhibiting metal (e.g., silver) diffusion: It provides a chemical trapping mechanism. Even if a very small amount of metal ions (e.g., silver ions) breaks through the physical barrier and diffuses into the interface region, the thiol functional group can firmly anchor them, preventing them from migrating further into the raw ceramic tile.

[0082] Titanate coupling agents: Not only can they form a monolayer on inorganic surfaces, but their long-chain organic portions can also undergo transesterification with polymers, achieving chemical bonding. Simultaneously, they reduce system viscosity and promote filler dispersion. Advantages in suppressing metal (e.g., silver) diffusion: They provide the dual benefits of stronger interfacial bonding and more uniform filler dispersion (due to their dispersant function). More uniform dispersion means a more uniform isolation layer; stronger bonding ensures coating integrity. Their monolayer properties minimize interference with sintering.

[0083] In some embodiments, the base mixture includes a plasticizer in a mass ratio of (0.01-0.3):1 for the plasticizer and the binder.

[0084] If the above ratio is low, at least one of the following disadvantages exists: 1) Deterioration of coating mechanical properties: 1.1) High brittleness: The dried coating is hard and brittle, with a glass transition temperature (Tg) close to or higher than room temperature, lacking flexibility. 1.2) Poor impact resistance: It cannot absorb energy through deformation. 2) Prone to defects during processing: 2.1) Drying cracking: During solvent evaporation and coating shrinkage, the brittle coating cannot release stress through creep, easily generating macroscopic or microscopic cracks. These cracks may start from the edge or spread throughout the entire coating. 2.2) Damage in subsequent processes: When printing metal paste (such as silver paste), the mechanical force of the doctor blade may directly cause the brittle coating to crack or generate stress microcracks. 3) Disadvantages in suppressing metal diffusion: 3.1) Cracks become diffusion channels: Any penetrating microcrack provides a zero-resistance straight diffusion channel for metal ions (such as silver ions). Metal ions will preferentially penetrate rapidly along the crack, causing the isolation layer to completely fail. 3.2) Poor reliability: The suppression function of a coating with microcracks is unreliable and unpredictable, and the device yield will drop sharply.

[0085] If the above proportions are large, at least one of the following disadvantages exists: 1) Loss of coating structural strength: 1.1) Too soft and sticky: The coating Tg is too low, becoming too soft or even sticky, and the mechanical strength (modulus, hardness) is severely reduced, making it unable to maintain its shape and bear loads. 1.2) Poor filler load-bearing capacity: The too soft resin cannot effectively fix and support the filler particles, which may cause the filler to shift or settle during drying or initial sintering. 2) Process and sintering problems: 2.1) Printing pattern distortion: The too soft coating may cause the pattern to collapse or spread after printing due to excessive fluidity, resulting in a loss of precision. 2.2) Abnormal thermal decomposition behavior: Excessive small molecule plasticizers may volatilize or decompose prematurely, disrupting the preset thermal decomposition gradient, which may cause the coating to bubble or produce unwanted pores in the early stage of sintering. 2.3) Migration and exudation: Excessive plasticizers may migrate from the coating to the surface, affecting the interface with the silver paste or polluting the environment. 3) Disadvantages in suppressing metal diffusion: 3.1) Structural instability: In the critical stage of adhesive decomposition and coating loss of adhesion, the over-plasticized structure may soften and collapse prematurely, failing to maintain the stable geometry of the filler skeleton, resulting in an uneven final isolation layer. Such an isolation layer has poor isolation effect and cannot effectively suppress the diffusion of metals (such as silver); 3.2) Introduction of uncertainty: Abnormal decomposition and possible migration can introduce unpredictable interface states and micro-defects.

[0086] Based on the above analysis, within the aforementioned range, the coating possesses at least one of the following advantages: 1) Good mechanical properties, providing a basis for suppressing metal diffusion: 1.1) High toughness: The coating exhibits excellent flexibility and elasticity, enabling it to absorb and dissipate energy (such as drying shrinkage stress and mechanical impact) through significant deformation. 1.2) Crack resistance: Extremely high elongation at break means the coating is extremely difficult to crack. Stress is primarily released through plastic deformation rather than brittle fracture. 2) Ensuring the integrity of the coating throughout the entire process chain: 2.1) Successfully surviving the drying stage: Able to withstand enormous drying shrinkage stress without cracking. 2.2) Resisting subsequent processing: Able to withstand the shearing force of metal paste (such as silver paste) printing squeegees without internal damage. 2.3) Stable transition during the initial sintering stage: In the temperature range where the binder begins to soften but has not yet decomposed, moderate flexibility helps the structure transition smoothly, preventing deformation caused by uneven local softening. 3) Advantages in inhibiting metal (e.g., silver) diffusion: 3.1) Eliminating microcracks at the source: This is the most direct and important benefit brought by plasticizers. A crack-free, continuous coating is the minimum and one of the highest requirements for the establishment of a physical barrier to metal diffusion. Plasticizers ensure this requirement is absolutely met by imparting toughness to the coating. 3.2) Improving the adhesion durability of the coating to the substrate: A coating with a certain degree of flexibility can better adapt to the microscopic unevenness of the substrate and alleviate the interfacial shear stress caused by the difference in the coefficients of thermal expansion between the two through deformation, thereby making the adhesion more durable and reliable. Strong adhesion is beneficial for the coating to function. 3.3) Ensuring the uniformity of the filler skeleton: In the early stages of drying and sintering, the flexible polymer matrix can better hold the filler particles together, preventing local debonding or filler rearrangement caused by the mismatch between the polymer shrinkage and the filler, thus maintaining the original uniformity of the filler distribution. 3.4) Improve the mechanical reliability of the device: The final device may be subjected to vibration, thermal cycling and other tests during use. The residual structure of the bottom coating with good toughness (even if it has been converted into an inorganic layer) may be more fatigue resistant and have higher long-term reliability.

[0087] In some embodiments, the plasticizer is at least one selected from dibutyl phthalate, dioctyl phthalate, diisodecyl phthalate, trioctyl trimellitate, tributyl citrate, and trihexyl butyryl citrate.

[0088] As described above, dibutyl phthalate (DBP) offers the following advantages: optimal compatibility and high plasticizing efficiency. Its relatively small molecular weight allows for rapid penetration into the PVB molecular chains, significantly reducing its Tg and imparting excellent low-temperature flexibility to the coating.

[0089] Dioctyl phthalate (DIDP) and diisodecyl phthalate (DIDP) offer the following advantages: larger molecular weight, lower volatility, and less migration. DIDP has the largest molecular weight, resulting in the lowest volatility and best durability. They are more stable during processing, providing a longer-lasting plasticizing effect. They remain stable in the coating throughout the entire drying and early sintering heating process (until the binder begins to decompose), continuously providing flexibility and ensuring the coating maintains crack resistance even during periods of maximum stress (such as the end of drying and the early stages of sintering), thus preventing microcracks. Without cracks, there are no channels for metal ion diffusion, thus inhibiting the diffusion of metals (such as silver).

[0090] Trioctyl trimellitate: It combines excellent plasticity with outstanding high-temperature resistance. Its larger molecular structure makes it more heat-resistant, with extremely low volatilization and migration losses. During the heating process of LTCC, it maintains its performance very stably without degradation. This means that even at the critical temperature where the binder is about to decompose, the coating still retains sufficient flexibility to resist the enormous internal stress caused by the gas generated and shrinkage of the violent decomposition of the organic phase, effectively preventing blistering or micro-cracks in the coating at this most vulnerable moment. This provides crucial temperature range protection for the formation of a better isolation layer, resulting in a better isolation layer and thus better suppression of metal diffusion (such as silver).

[0091] Tributyl citrate: Environmentally friendly and safe, with excellent compatibility with cellulose-based adhesives (such as EC). It has good plasticizing efficiency and relatively moderate volatility. Under strict proportion control, it can provide good initial flexibility to the coating, preventing drying cracking and avoiding crack formation. Without cracks, there are no diffusion channels, which in turn helps to inhibit the diffusion of metals (such as silver).

[0092] Trihexyl butyryl citrate: Introducing a longer alkyl chain further reduces volatility and significantly improves polymer compatibility and durability. It combines environmental friendliness with performance close to traditional plasticizers. Its lower volatility and superior durability make the coating performance more stable throughout the process, making it more suitable for production environments with strict volatile matter control or high process consistency requirements, thus ensuring repeatability of the inhibition effect.

[0093] In addition, some contents of this application are described below: Comparative Example 1 Silver paste was printed onto a green ceramic sheet using a 15 μm thick screen, and the sheet was then sintered at 850 °C. The silver diffusion distance after sintering was 300 μm.

[0094] Comparative Example 2 (1) Weigh 200 g ethyl acetate, 100 g toluene, 100 g EC (number average molecular weight of 30000 g / mol), 10 g polyacrylate (number average molecular weight of 2000 g / mol), 5 g KH550 and 20 g tributyl citrate, and stir and dissolve them in a reactor at 80 ℃ and 200 rpm for 3 h to obtain the coating.

[0095] (2) The coating was printed onto the green ceramic sheet using a 10 μm thick screen, and baked at 100 °C for 10 min to remove the solvent from the coating; the silver paste was printed onto the coating using a 15 μm thick screen with the same pattern, and then the green ceramic sheet was sintered at 850 °C. The silver diffusion distance after sintering was 300 μm. Implementation Method 1

[0096] (1) Weigh 200 g ethyl acetate, 100 g toluene, 100 g polyacrylate (number average molecular weight of 30000 g / mol), 10 g polyacrylate (number average molecular weight of 2000 g / mol), 5 g KH550 and 20 g tributyl citrate, and stir and dissolve them in a reactor at 80℃ and 200 rpm for 3 h to obtain the basic mixture.

[0097] (2) Weigh 100 g of Al2O3 with a median particle size of 2 μm and 100 g of basic mixture, mix and ball mill at 200 rpm for 8 h to obtain filler mixed resin.

[0098] (3) The filler-mixed resin was ground using a three-roll mill until the fineness was 5 μm, thus obtaining the LTCC electrode diffusion inhibition coating.

[0099] (4) Using a 10 μm thick screen, the silver diffusion inhibition coating was printed onto the green ceramic sheet, and baked at 100 °C for 10 min to remove the solvent in the coating; using a 15 μm thick screen with the same pattern, the silver paste was printed onto the coating, and then the green ceramic sheet was sintered at 850 °C. After sintering, the silver diffusion distance was 100 μm. Implementation Method 2

[0100] (1) Weigh 200 g ethyl acetate, 100 g toluene, 100 g EC (number average molecular weight of 30000 g / mol), 10 g polyacrylate (number average molecular weight of 2000 g / mol), 5 g KH550 and 20 g tributyl citrate, and stir and dissolve them in a reactor at 80 ℃ and 200 rpm for 3 h to obtain the basic mixture.

[0101] (2) Weigh 100 g of ZrO2 with a median particle size of 2 μm and 100 g of basic mixture, mix and ball mill at 200 rpm for 8 h to obtain filler mixed resin.

[0102] (3) The filler-mixed resin was ground using a three-roll mill until the fineness was 5 μm, and the silver diffusion inhibition coating was obtained.

[0103] (4) Using a 10 μm thick screen, the silver diffusion inhibition coating was printed onto the green ceramic sheet, and baked at 100 °C for 10 min to remove the solvent in the coating; using a 15 μm thick screen with the same pattern, the silver paste was printed onto the coating, and then the green ceramic sheet was sintered at 850 °C. After sintering, the silver diffusion distance was 200 μm. Implementation Method 3

[0104] (1) Weigh 200 g ethyl acetate, 100 g toluene, 100 g EC (number average molecular weight of 30000 g / mol), 10 g polyacrylate (number average molecular weight of 2000 g / mol), 5 g KH550 and 20 g tributyl citrate, and stir and dissolve them in a reactor at 80 ℃ and 200 rpm for 3 h to obtain the basic mixture.

[0105] (2) Weigh 100 g of Al2O3 with a median particle size of 2 μm and 100 g of basic mixture, mix and ball mill at 200 rpm for 8 h to obtain filler mixed resin.

[0106] (3) The filler-mixed resin was ground using a three-roll mill until the fineness was 5 μm, and the silver diffusion inhibition coating was obtained.

[0107] (4) Using a 10 μm thick screen, the silver diffusion inhibition coating was printed onto the green ceramic sheet, and baked at 100 °C for 10 min to remove the solvent in the coating; using a 15 μm thick screen with the same pattern, the silver paste was printed onto the coating, and then the green ceramic sheet was sintered at 850 °C. The silver diffusion distance after sintering was 30 μm. Implementation Method 4

[0108] (1) Weigh 200 g ethyl acetate, 100 g toluene, 100 g PVB (number average molecular weight of 30000 g / mol), 10 g polyacrylate (number average molecular weight of 2000 g / mol), 5 g KH550 and 20 g tributyl citrate, and stir and dissolve them in a reactor at 80 ℃ and 200 rpm for 3 h to obtain the basic mixture.

[0109] (2) Weigh 50 g of MgO with a median particle size of 50 nm and 100 g of basic mixture, mix and ball mill at 200 rpm for 8 h to obtain filler mixed resin.

[0110] (3) The filler-mixed resin was ground using a three-roll mill until the fineness was 5 μm, and the silver diffusion inhibition coating was obtained.

[0111] (4) Using a 10 μm thick screen, the silver diffusion inhibition coating was printed onto the green ceramic sheet, and baked at 100 °C for 10 min to remove the solvent in the coating; using a 15 μm thick screen with the same pattern, the silver paste was printed onto the coating, and then the green ceramic sheet was sintered at 850 °C. The silver diffusion distance after sintering was 10 μm. Implementation Method 5

[0112] This embodiment provides a silver diffusion inhibition method for LTCC and a silver diffusion inhibition coating. The preparation process of the silver diffusion inhibition coating is as follows: (1) Weigh 200 g ethyl acetate, 100 g toluene, 100 g EC (number average molecular weight of 30000 g / mol), 10 g polyacrylate (number average molecular weight of 2000 g / mol), 5 g KH550 and 20 g tributyl citrate, and stir and dissolve them in a reactor at 80 ℃ and 200 rpm for 3 h to obtain the basic mixture.

[0113] (2) Weigh 100 g of Al2O3 with a median particle size of 100 nm and 100 g of basic mixture, mix and ball mill at 200 rpm for 8 h to obtain filler mixed resin.

[0114] (3) The filler-mixed resin was ground using a three-roll mill until the fineness was 5 μm, and the silver diffusion inhibition coating was obtained.

[0115] (4) Using a 10 μm thick screen, the silver diffusion inhibition coating was printed onto the green ceramic sheet, and baked at 100 °C for 10 min to remove the solvent in the coating; using a 15 μm thick screen with the same pattern, the silver paste was printed onto the coating, and then the green ceramic sheet was sintered at 850 °C. After sintering, the silver diffusion distance was 0.

[0116] The above embodiments and implementation methods are explained as follows: Comparative Example 1 is a conventional screen printing process for silver paste, that is, without any intermediate layer and without using the coating described in this application, as a comparison between the conventional process and the screen printing process of this patent. Comparative Example 2 added a screen printing process for a filler-free intermediate layer, intended to compare with Comparative Example 1 and subsequent examples to show that printing only organic components is ineffective in suppressing silver diffusion in the absence of fillers.

[0117] Compared with Comparative Example 1, Comparative Example 1 did not use the coating of this application, and the silver diffusion distance after sintering was 300 μm. In Example 1, the coating of this application was used, and the silver diffusion distance after sintering was 100 μm, resulting in better metal (silver) inhibition.

[0118] In Embodiment 2, which also uses the coating of this application, the metal (silver) suppression effect is even better compared to Comparative Example 1. Furthermore, changing the filler from Al2O3 to ZrO2 also improves the metal (silver) suppression effect.

[0119] In contrast to Embodiment 1, Embodiment 3 replaces polyacrylate with EC, so that the coating formed by the coating of this application is consistent with the degradation state of the binder in the silver paste, thus having a better effect of inhibiting silver diffusion.

[0120] In contrast to Embodiment 1, Embodiment 4 replaces polyacrylate with PVB, so that the coating formed by the coating of this application is consistent with the degradation state of the adhesive in the green ceramic tile, thus having a better effect of inhibiting silver diffusion; at the same time, the filler is replaced with MgO with a smaller particle size, thus further enhancing the effect of inhibiting metal (silver) diffusion.

[0121] In contrast to Embodiment 2, Embodiment 5 replaces the filler with Al2O3 with a smaller particle size. Since Al2O3 has better compatibility with the glass phase than ZrO2, the inhibition effect on metal (silver) diffusion is very significant.

[0122] Furthermore, this application also discloses a method for preparing any of the diffusion-inhibiting coatings for LTCC electrodes, the method comprising the following steps: The base mixture was stirred at 60-90 °C and 100-300 rpm for 2-4 h; The filler and the base mixture are ball-milled at 100-300 rpm for 4-8 h to form a filler-mixed resin; The filler-mixed resin is ground until the fineness is less than 8 μm, thus obtaining an LTCC electrode diffusion-inhibiting coating.

[0123] The advantages of the above process steps are described below: 1) Stir the base mixture at 60-90°C for 2-4 hours: 1.1) Thoroughly dissolve the binder: Under heating conditions, the dissolution rate and extent of binders such as PVB and EC are significantly improved, avoiding the formation of fish eyes or undissolved particles, forming a uniform and stable resin solution. 1.2) Activate the additives: Small molecule additives such as dispersants and plasticizers are better dispersed and pre-adsorbed onto the resin molecular chains under the action of heat and shear force, reaching an "activated" state, preparing for subsequent efficient dispersion of fillers. 1.3) Remove some air bubbles: Appropriately raising the temperature reduces the liquid viscosity, which is beneficial for the escape of air bubbles entrained during stirring. 1.4) Advantages in inhibiting metal diffusion: A resin solution without undissolved particles and with uniformly distributed additives is the perfect starting point for all subsequent dispersion processes. If the resin solution itself is uneven, it will directly lead to uneven filler dispersion and coating defects. These original defects cannot be repaired in subsequent processes and will eventually become diffusion channels.

[0124] 2) Ball milling of the filler and base mixture at 100-300 rpm for 4-8 hours: 2.1) Provides high-intensity shear and impact energy: The mechanical energy of ball milling is much higher than that of ordinary stirring, which can effectively break up the original agglomerates of the filler, especially those "soft agglomerates" formed by van der Waals forces. 2.2) Promotes filler surface modification: Long-term ball milling in the medium creates kinetic conditions for the dispersant molecules to be fully and firmly adsorbed onto the new surface of the filler, achieving "mechanical-chemical" assisted dispersion. 2.3) Achieves nanoscale dispersion: By controlling the ball milling time, speed, and ball-to-material ratio, the filler can be dispersed to a level close to its original particle size. 2.4) Advantage of inhibiting metal (e.g., silver) diffusion: Whether the ball milling is sufficient directly determines whether there are invisible filler micro-agglomerates in the slurry. These micro-agglomerates will become islands in the isolation layer after sintering, and poorly filled pores or interface gaps are easily formed around them, becoming channels for metal (e.g., silver) diffusion. Thorough ball milling ensures that the filler is uniformly distributed as individual particles from a material basis, making it possible to construct a defect-free isolation layer and avoiding pathways for metal (such as silver) diffusion.

[0125] 3) Grinding the mixed resin to a fineness of less than 8 μm: 3.1) Crushing hard agglomerates and impurities: The extremely strong shearing force generated by a three-roll mill or sand mill can handle the very small amount of hard agglomerates (caused by chemical bonds or sintering) that may remain after ball milling, and crush any trace impurities that may be mixed in. 3.2) Ultimate homogenization: The components (resin, solvent, filler, additives) in the slurry are homogenized in the final and most thorough way, achieving microscopic uniformity of composition and fluid. 3.3) Degassing and obtaining optimal rheological properties: The grinding process effectively removes dissolved and entrained gases from the slurry and optimizes the thixotropy and printing rheology of the slurry by arranging the particles. 3.4) Advantages in inhibiting metal (e.g., silver) diffusion: It ensures that no agglomerates or impurities larger than 8 μm enter the printing process. A slurry with the required fineness can print a coating with an extremely smooth surface and uniform thickness. The macroscopic uniformity of the surface and interior directly determines the uniformity of thermal stress during sintering, avoiding abnormal shrinkage or stress concentration caused by local large particles or impurities, thereby minimizing the risk of defects such as cracks and holes in the coating during drying and sintering.

[0126] 4) The advantages of the above steps working together are: 4.1) Achieving full-scale uniformity control from the "molecular level" to the "macroscopic level": 4.1.1) The first step controls the molecular / polymer scale (solution homogeneity). 4.1.2) The second step controls the micron / nano scale (filler dispersion). 4.1.3) The third step controls the overall slurry scale (fluid homogeneity). This full-scale control ensures that the composition and structure of the final coating are highly uniform in three-dimensional space, with no local weak points, and the resistance encountered by silver ions at any location is consistent and maximum. 4.2) Creating a good precursor for "defect-free sintering": Good slurry produces good coating. The coating printed from this slurry has ideal filler and organic matter distribution. During sintering, the organic matter decomposes smoothly and synchronously, leaving a uniformly porous filler skeleton. This allows the molten glass to be synchronously and uniformly wetted and filled, thus forming a dense, non-porous composite isolation layer. Any initial inhomogeneity will be amplified into defects during the sintering process. 4.3) Ensuring the repeatability and reliability of product performance: Quantified and controlled process parameters (temperature, time, rotation speed, fineness) make the production process standardized and repeatable. This means that the performance of each batch of coating remains consistent, thereby ensuring the high reliability and stable yield of the silver diffusion suppression effect in the final LTCC device, meeting the requirements of industrial production.

[0127] Thirdly, this application discloses the application of any of the aforementioned LTCC electrode diffusion-inhibiting coatings, comprising the following steps: The coating is printed onto a raw ceramic tile; Baking removes the solvent; The metal slurry is printed onto the coating formed by the paint. The green ceramic sheet having the coating and the metal slurry is sintered.

[0128] Furthermore, the application includes at least one of the following features: a) Print the coating onto the green ceramic tile using a screen with a thickness of 5-100 μm; b) Bake at 60-120 ℃ for 5-30 min to remove the solvent from the coating; c) Using a 5-100μm thick screen with the same pattern, print the metal paste onto the coating; d) The green ceramic sheet having the coating and the metal slurry is sintered at a temperature of 700-950 °C.

[0129] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope. The scope of protection of the present invention is defined by the appended claims, specification, and their equivalents.

Claims

1. A coating for inhibiting diffusion in LTCC electrodes, characterized in that, The LTCC electrode diffusion-inhibiting coating comprises a base mixture and fillers. The base mixture comprises a solvent and a binder. The filler has a sintering temperature greater than the softening temperature of the glass powder, which is used to form green ceramic sheets in the LTCC technology. The contact angle corresponding to the wettability of the filler relative to the glass powder is less than 90 degrees.

2. The LTCC electrode diffusion-inhibiting coating according to claim 1, characterized in that, The sintering temperature of the filler is not less than 900℃.

3. The diffusion-inhibiting coating for LTCC electrodes according to claim 1, characterized in that, The filler includes at least one of the following characteristics: a) The filler to the base mixture is in a mass ratio of (0.1-10):1; b) The filler comprises ceramic powder; c) The median particle size range of the filler is 10 nm-2 μm.

4. The LTCC electrode diffusion-inhibiting coating according to claim 3, characterized in that, In the case where the diffusion-inhibiting coating for the LTCC electrode includes ceramic powder, the ceramic powder includes at least one of alumina, zirconium oxide, magnesium oxide, titanium oxide, zinc oxide, cerium oxide, mullite, cordierite, and magnesium aluminum spinel.

5. The diffusion-inhibiting coating for LTCC electrodes according to claim 1, characterized in that, The solvent includes at least one of the following characteristics: a) The solvent to adhesive ratio is (0.5-10):1 by mass; b) The solvent includes at least one of the following: ester solvents, ketone solvents, aromatic hydrocarbon solvents, alcohol solvents and aliphatic hydrocarbon solvents.

6. The LTCC electrode diffusion-inhibiting coating according to claim 4, characterized in that, The ester solvents include butyl acetate, propyl acetate, or ethyl acetate; The ketone solvents include acetone, butanone, or cyclohexanone; The aromatic hydrocarbons include toluene or xylene; The alcohols include methanol, ethanol, propanol, or butanol; The aliphatic hydrocarbons include hexane, heptane, or cyclohexane.

7. The LTCC electrode diffusion-inhibiting coating according to claim 1, characterized in that, The adhesive comprises at least one of polyacrylate, polyurethane, silicone, polyester, polyvinyl butyral, and cellulose and its derivatives.

8. The LTCC electrode diffusion-inhibiting coating according to claim 6, characterized in that, When the adhesive comprises polyvinyl butyral or ethyl cellulose, the number average molecular weight of the polyvinyl butyral and the ethyl cellulose is 15,000-40,000 g / mol.

9. The diffusion-inhibiting coating for LTCC electrodes according to claim 1, characterized in that, The base mixture includes a dispersant in a mass ratio of (0.01-0.3):1 for the binder; And / or, the dispersant includes at least one of castor oil, hydrogenated castor oil, polyacrylate, phosphate ester, fatty acid polyoxyethylene ether, sorbitan fatty acid ester, and vinylpyrrolidone polymer.

10. The LTCC electrode diffusion-inhibiting coating according to claim 1, characterized in that, The base mixture includes an adhesive aid, wherein the adhesive aid and the adhesive are in a mass ratio of (0.01-0.2):

1. And / or, the adhesive aid includes at least one of aminosilane coupling agents, epoxysilane coupling agents, methacryloxysilane coupling agents, vinylsilane coupling agents, mercaptosilane coupling agents, and titanate coupling agents.

11. The LTCC electrode diffusion-inhibiting coating according to claim 1, characterized in that, The base mixture includes a plasticizer, and the plasticizer to the binder is in a mass ratio of (0.01-0.3):1; And / or, the plasticizer is at least one selected from dibutyl phthalate, dioctyl phthalate, diisodecyl phthalate, trioctyl trimellitate, tributyl citrate, and trihexyl butyryl citrate.

12. A method for preparing a diffusion-inhibiting coating for LTCC electrodes according to any one of claims 1 to 10, characterized in that, The method includes the following steps: The base mixture was stirred at 60-90 °C and 100-300 rpm for 2-4 h; The filler and the base mixture are ball-milled at 100-300 rpm for 4-8 h to form a filler-mixed resin; The filler-mixed resin is ground until the fineness is less than 8 μm, thus obtaining the diffusion-inhibiting coating for the LTCC electrode.

13. The application of a diffusion-inhibiting coating for LTCC electrodes according to any one of claims 1 to 11, characterized in that, Includes the following steps: The coating is printed onto a raw ceramic tile; Baking removes the solvent; The metal slurry is printed onto the coating formed by the paint. The green ceramic sheet having the coating and the metal slurry is sintered.

14. The application of the LTCC electrode diffusion-inhibiting coating according to claim 13, characterized in that, The application includes at least one of the following features: a) Print the coating onto the green ceramic tile using a screen with a thickness of 5-100 μm; b) Bake at 60-120 ℃ for 5-30 min to remove the solvent from the coating; c) Using a 5-100μm thick screen with the same pattern, print the metal paste onto the coating; d) The green ceramic sheet having the coating and the metal slurry is sintered at a temperature of 700-950 °C.