Ca-nb-ti based ltcc material co-fired with copper electrode and preparation method thereof

Abstract

The application belongs to the technical field of low temperature co-fired ceramic and relates to a Ca-Nb-Ti based LTCC material co-fired with a copper electrode and a preparation method. The material comprises CaNb2O6 powder, CaTiO3 powder, a glass sintering aid and a Mn series additive; the mass ratio of the CaNb2O6 powder to the CaTiO3 powder is 96-98:2-4; the glass sintering aid accounts for 3-5 wt% of the total mass of the material; the Mn series additive accounts for 0.5-2.5 wt% of the total mass of the material; the Mn series additive comprises MnO, MnCO3 and MnNb2O6; the glass sintering aid comprises BaO-CuO-Al2O3-B2O3-SiO2 system glass or CaO-CuO-Al2O3-B2O3-SiO2 system glass; and the material has high dielectric constant, high thermal conductivity, near-zero resonance frequency temperature coefficient and moderate dielectric constant. Qf The application effectively solves the problems of performance deterioration and insufficient thermal conductivity of the existing system under a low-oxygen protective atmosphere.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature co-fired ceramics technology, specifically relating to a Ca-Nb-Ti based LTCC material co-fired with a copper electrode and its preparation method. This material possesses high Q value, high thermal conductivity, and a near-zero temperature coefficient of resonant frequency. It can achieve non-reactive, crack-free, and shrinkage-matched co-firing with a copper electrode under low-oxygen partial pressure atmospheres such as argon. It is suitable for packaging and integrating high-reliability LTCC devices such as 5G / 6G communication base stations, microwave filters, high-frequency power modules, and satellite communications. Background Technology

[0002] With the rapid development of high-frequency microwave communication, power electronics, and high-density integration technologies, low-temperature co-fired ceramics (LTCC) have become a core carrier technology for multilayer substrates, filters, antennas, and power modules. LTCC requires the substrate material to be densified at ≤1050 ℃ and co-fired in compatibility with the internal electrode material, while simultaneously meeting requirements such as high-frequency low loss, high thermal conductivity, and structural stability. Currently, commercially available LTCC internal electrodes are mainly silver (Ag), but silver electrodes suffer from high cost, poor migration resistance, and relatively high high-frequency loss, making them unsuitable for high-power, high-frequency, and high-reliability applications. Copper (Cu) electrodes offer advantages such as high conductivity, lower cost, and superior high-frequency performance, making them ideal electrode materials for next-generation high-frequency power LTCCs. However, copper is highly susceptible to high-temperature oxidation in air, necessitating co-firing under a low-oxygen partial pressure protective atmosphere such as argon or argon-hydrogen, which places stringent requirements on the ceramic matrix. Niobium / titanium salt systems (such as CaNb2O6-CaTiO3) offer advantages due to their moderate dielectric constant, tunable temperature coefficient of resonant frequency, and high-frequency performance. Qf It has a high value and is a preferred system for high-performance microwave dielectric ceramics, making it very suitable for high-frequency LTCC.

[0003] However, in the prior art, the dielectric constant (ε) of pure-phase CaNb2O6 ceramics is... r The quality factor is 13.3~18.1. Q× f The GHz frequency can reach 12200~50000 GHz, but its densification sintering temperature is as high as 1300~1500 ℃, and the temperature coefficient of resonant frequency (τ) is high. f The concentration is approximately -74 ppm / ℃. Although some studies have shown that introducing TiO2 or CaTiO3 into the composite can regulate τ... f The value approaches zero, but this also leads to a further increase in sintering temperature and quality factor. QConsequently, the sintering temperature deteriorates. Current literature reports that adding sintering aids such as CuV₂O₆ can lower the sintering temperature of CaNb₂O₆-based ceramics to around 1000 °C. However, this research was only conducted in an air atmosphere and did not address the sintering behavior under a low-oxygen protective atmosphere or compatibility with co-firing with copper electrodes. No studies have yet been found on the sintering behavior of CaNb₂O₆ materials under a low-oxygen atmosphere while simultaneously maintaining high sintering temperature. Qf The report highlights four core properties: high thermal conductivity, near-zero resonant frequency temperature coefficient, and compatibility with copper co-firing.

[0004] From a defect chemistry perspective, during the formation of the CaNb2O6–CaTiO3 solid solution, Ti... 4+ For Nb 5+ The heterovalent substitution inevitably creates oxygen vacancies to maintain electroneutrality, and the reaction is as follows:

[0005] The above process becomes further complicated when sintering in a reducing atmosphere (such as Ar). First, the low oxygen partial pressure environment promotes the generation of additional oxygen vacancies:

[0006] The generated free electrons ( ) will be surrounded by Ti 4+ or Nb 5+ Capture, resulting in some Ti 4+ Restore to Ti 3+ (and Nb) 5+ Restored to Nb 4+ The Ti produced by these reduction reactions 3+ (and Nb) 4+ ) and oxygen vacancies with two positive charges ( This introduces deep-level defect states into the energy band. These defect states can form strong dipole relaxation polarization in the microwave band, significantly enhancing the dielectric relaxation process. The result is a positive dielectric loss tangent. Increase by orders of magnitude Q×f The GHz value typically drops sharply from over 50,000 GHz when sintered in air to less than 1,000 GHz in a reducing atmosphere.

[0007] Regarding glass sintering aids, low-softening-point borosilicate glass systems (such as Li₂O–MgO–B₂O₃–SiO₂, CaO–B₂O₃–SiO₂, etc.) are widely used in LTCC materials to lower the sintering temperature of the ceramic phase. However, traditional glass systems are difficult to effectively wet CaNb₂O₆–CaTiO₃ ceramic particles with sintering temperatures above 1300℃ at 900–1050℃. Typically, a glass content >15 wt.% is required to cool the CaNb₂O₆ material below 1100℃, and the presence of a large amount of glass phase drastically deteriorates the material's performance. Furthermore, under low-oxygen partial pressure protective atmospheres such as argon, some high-content B₂O₃ glass components are prone to glass crystallization and abrupt viscosity changes, thus affecting the densification process and dielectric properties of the matrix. In addition, the bottleneck in thermal conductivity stems from the phonon transport mechanism. CaNb₂O₆ has a columbite structure, with a theoretical upper limit for its lattice thermal conductivity of approximately 6–8 W / (m·K). However, after introducing a glass phase (with a thermal conductivity typically <1 W / (m·K)), the thermal conductivity of the composite material, as predicted by the Maxwel–Eucken model, will be below 3 W / (m·K) when the glass content exceeds 30 vol%. Current techniques often add up to 40–50 wt% glass to lower the sintering temperature. While this achieves low-temperature sintering, it sacrifices thermal conductivity.

[0008] Therefore, existing LTCC materials generally suffer from the difficulty of achieving a balance between performance and performance during low-temperature sintering under protective atmospheres. This is especially true when Nb-Ti based materials are co-fired with copper electrodes; under protective atmospheres such as argon or hydrogen, Ti oxidation is prone to occur. 4+ Local reduction, accompanied by lattice oxygen loss, leads to a surge in the material's dielectric loss. Qf The significant degradation of the Nb-Ti based LTCC material value has become a core bottleneck restricting its industrial application. Summary of the Invention

[0009] This invention provides the following technical solution: a Ca-Nb-Ti based LTCC material co-fired with a copper electrode, comprising the following components: CaNb2O6 powder, CaTiO3 powder, glass sintering aid, and Mn-based additives; the mass ratio of CaNb2O6 powder to CaTiO3 powder is 96~98:2~4, the glass sintering aid accounts for 3~5 wt% of the total material mass, and the Mn-based additives account for 0.5~2.5 wt% of the total material mass. The Mn-based additives are at least one of MnO, MnCO3, and MnNb2O6. The glass sintering aid is at least one of a BaO-CuO-Al2O3-B2O3-SiO2 glass system or a CaO-CuO-Al2O3-B2O3-SiO2 glass system.

[0010] Preferably, in the BaO-CuO-Al2O3-B2O3-SiO2 glass system, the molar ratio of each oxide is: BaO:CuO:Al2O3:B2O3:SiO2 = 15~25:1~5:5~15:10~25:40~55. In the CaO-CuO-Al2O3-B2O3-SiO2 glass system, the molar ratio of each oxide is: CaO:CuO:Al2O3:B2O3:SiO2 = 15~25:1~5:5~15:10~25:40~55.

[0011] More preferably, in the BaO-CuO-Al2O3-B2O3-SiO2 glass system, the molar ratio of each oxide is: BaO:CuO:Al2O3:B2O3:SiO2 = 20:3:10:17.5:49.5. In the CaO-CuO-Al2O3-B2O3-SiO2 glass system, the molar ratio of each oxide is: CaO:CuO:Al2O3:B2O3:SiO2 = 20:3:10:17.5:49.5.

[0012] Preferably, the performance parameters of the sintered Ca-Nb-Ti based LTCC material are: relative density 97.3%–97.8%, dielectric property ε r =14.9~15.3, quality factor Q×f =26800~30500 GHz, thermal conductivity λ=4.8~5.3 W / (m·K), temperature coefficient of resonant frequency τ f = -1.8~+1.5ppm / ℃.

[0013] This invention also discloses a method for preparing Ca-Nb-Ti based LTCC materials co-fired with copper electrodes. This method, used to prepare the aforementioned Ca-Nb-Ti based LTCC materials, includes the following steps: Step 1: Synthesis of CaNb2O6 powder: Weigh calcium carbonate and niobium pentoxide, mix them by ball milling, pre-calcine at 900~1050℃ for 2~4 hours, pulverize and sieve to obtain CaNb2O6 powder with D50=1~2 μm.

[0014] Step 2: Preparation of low-temperature glass sintering aid: Weigh the oxide raw material, melt it at 1250~1350℃ for 1.5~2.5 hours, quench it in water, and then ball mill it to D50=2~3 μm.

[0015] Step 3, Mixing: Weigh CaNb2O6 powder, CaTiO3 powder, low-temperature glass sintering aid, and Mn-based additives according to the mass ratio, ball mill them with anhydrous ethanol for 6-10 hours, and dry them for later use.

[0016] Step 4, Granulation and Molding: Add 5% to 8% of PVA or PVB binder by weight of powder for granulation, dry press molding, and obtain ceramic green body.

[0017] Step 5, Adhesive Removal: Keep the temperature at 550~600℃ for no less than 2 hours in an argon atmosphere to remove the adhesive.

[0018] Step 6, Sintering: Under an argon protective atmosphere, heat to 950-1050℃ at a rate of 2-5℃ / min, hold for 2-4 hours, and then cool to room temperature with the furnace.

[0019] Preferably, in step 6, the green blank with printed copper electrodes and the green blank without printed copper electrodes are stacked and then sintered together, and the shrinkage deviation between the copper electrodes and the substrate material is ≤2%.

[0020] Preferably, in step 6, the oxygen partial pressure of the argon atmosphere is less than 10 ppm, and the argon gas flow rate is 1~3 L / min.

[0021] Preferably, the CaTiO3 powder used in step 3 is synthesized by pre-calcining a mixture of calcium carbonate and titanium dioxide at 1100~1150℃, and the particle size D50 of the CaTiO3 powder is 1~1.5μm.

[0022] Preferably, in step 1, the pre-calcination temperature of the CaNb2O6 powder is 950~1000℃.

[0023] The beneficial effects of this invention are: 1. This invention introduces MnO variable-valence ions as acceptor dopant to capture oxygen vacancies in the system. Utilizing Mn... 2+ / Mn 3 + / Mn 4+ Due to its multi-valence transition characteristics, under low oxygen partial pressure, manganese ions can preferentially react with Ti ions. 4+ It undergoes a reduction reaction, acting as an oxygen vacancy scavenger and reduction sacrificial agent, effectively consuming free electrons and oxygen vacancies in the system, thus inhibiting Ti at its source. 4+ / Nb 5+ Restored to low-valence Ti 3+ / Nb 4+ This significantly improves the problem of dielectric loss degradation under reducing atmosphere.

[0024] 2. This invention pre-synthesizes a highly stable perovskite phase, CaTiO3, and uses it in combination with CaNb2O6 powder. The pre-synthesis process ensures the stoichiometry and lattice integrity of the CaTiO3 phase, reduces the formation of impurity phases such as free CaO or TiO2, and effectively reduces the concentration of Ti in a low-oxygen atmosphere. 4+ The reduction active sites enhance the overall structural stability and reduction resistance of the material.

[0025] 3. This invention regulates the mass ratio of CaNb₂O₆ to CaTiO₃ to 96~98:2~4, achieving a stable dielectric constant of approximately 15 and obtaining a near-zero resonant frequency temperature coefficient, meeting the required temperature. By using highly active CaNb₂O₆ powder pre-calcined at 900~1050℃, combined with the composite calcination aid effect of MnO, the glass phase addition can be controlled within a low content range of 3~5 wt%. Based on achieving low-temperature densification sintering at 950~1050℃, the thermal conductivity of the composite material is increased to 5 W / (m²). K) and above.

[0026] 4. This invention, through a low-glass content formulation design, low-temperature pre-calcination modification of highly active niobium-based powder, and the synergistic effect of manganese-based additives, produces a high-performance LTCC material that can be co-fired with copper electrodes under an argon protective atmosphere. This material possesses both high... Qf With its high thermal conductivity, near-zero resonant frequency temperature coefficient, and suitable dielectric constant, it effectively solves the technical bottlenecks of existing systems such as performance degradation and insufficient thermal conductivity under low-oxygen protective atmospheres, and has good application prospects in fields such as high-frequency high-power communication devices and copper co-fired LTCC functional modules. Attached Figure Description

[0027] Figure 1 This is an example of the X-ray diffraction pattern of the LTCC material after sintering under an argon atmosphere, which is a Ca-Nb-Ti based LTCC material co-fired with a copper electrode and its preparation method according to the present invention. Figure 2 This is a scanning electron microscope image of the LTCC material after sintering under an argon atmosphere according to an embodiment of the present invention. Figure 3 This is an X-ray diffraction pattern of the interface between the LTCC material and the copper electrode after co-firing in an embodiment of the present invention. Figure 4 This is a scanning electron microscope image of the interface between the LTCC material and the copper electrode after co-firing according to an embodiment of the present invention. Detailed Implementation

[0028] The relevant technologies of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] like Figures 1-4 As shown, the preparation method of Ca-Nb-Ti based LTCC material co-fired with copper electrode in this embodiment is as follows: Preparation of composite powders: First, highly active CaNb₂O₆ powder was prepared. Calcium carbonate (CaCO₃) and niobium pentoxide (Nb₂O₅) were weighed according to stoichiometric ratio, ball-milled and mixed with anhydrous ethanol for 6–12 hours, dried, and then pre-calcined at 900–1050℃ for 2–4 hours to obtain CaNb₂O₆ powder with a D50 of 1–2 μm. This pre-calcination temperature is significantly lower than the conventional synthesis temperature (usually 1200–1300℃), and the obtained powder exhibits higher sintering activity. Simultaneously, CaTiO₃ powder was synthesized separately: CaCO₃ and TiO₂ were weighed according to stoichiometric ratio, ball-milled and mixed, dried, and then pre-calcined at 1100–1150℃ for 2–4 hours to obtain pure-phase CaTiO₃ powder with a D50 of 1–3 μm. The two powders were mixed in a mass ratio of CaNb2O6:CaTiO3 = 96~98:2~4. 3~5 wt% of glass sintering aid and 0.5~2 wt% of MnO additive were added based on the total mass of the powders. The mixture was then ball-milled with anhydrous ethanol as the medium for 4~8 hours and dried to obtain the composite powder.

[0030] Glass phase design: The glass sintering aid used is either a BaO-CuO-Al2O3-B2O3-SiO2 system or a CaO–CuO–Al2O3–B2O3–SiO2 system. Taking CaO–CuO–Al2O3–B2O3–SiO2 as an example, its molar ratio is CaO:CuO:Al2O3:B2O3:SiO2 = (15~25):(1~5):(5~15):(10~25):(40~55). The softening point of this glass is controlled at 600~700℃, and the coefficient of thermal expansion is 6~9 ppm / ℃, which is compatible with niobium-based ceramic fillers. The glass preparation method is as follows: weigh CaCO3, CuO, Al2O3, B2O3, SiO2 and other raw materials according to the proportion, mix them evenly and place them in a corundum crucible, melt them at 1250~1350℃ for 2 hours, pour the molten glass liquid into deionized water for water quenching, obtain glass fragments, and then pulverize them to D50=2~3 μm by planetary ball milling.

[0031] The additive contains one or more of the following components: MnO, MnCO3, or MnNb2O6, with an addition amount of 0.5~2.5 wt% based on the total mass of the powder. The mechanism of action of MnO and MnCO3 utilizes the variable valence characteristic of Mn ions (Mn... 2+ / Mn 3+ / Mn 4+ Under low oxygen partial pressure, it preferentially consumes Ti. 4+ The reduction reaction occurs, effectively consuming free electrons and oxygen vacancies in the system and inhibiting Ti. 4+ Reduced to Ti 3+ MnNb2O6 acts as a nucleating agent or sintering aid, promoting uniform grain growth and improving... QfThe composite powder was granulated by adding 5%–8% polyvinyl alcohol (PVA) binder (by weight of 5%–8% of the total powder). After passing through a 40-mesh sieve, it was dry-pressed under 100–200 MPa pressure to obtain a green body. The green body was placed in an atmosphere sintering furnace and first heated to 550–600°C at 1–2°C / min under an argon atmosphere, and held for 2 hours for debinding. Subsequently, the temperature was increased to 950–1050°C at 2–5°C / min and held for 2–4 hours for sintering. Throughout the sintering process, high-purity argon (Ar ≥ 99%) was continuously introduced at a flow rate of 1–3 L / min, and the oxygen partial pressure in the furnace was controlled below 10 ppm. After sintering, the sample was cooled to room temperature with the furnace. Under these conditions, the linear shrinkage rate of the sample was 10%–15%, and the relative density reached over 97%. Since the glass content is only 3~5 wt%, the densification mainly relies on the solid-phase sintering of highly active niobium-based fillers and the transient liquid-phase assisted sintering mechanism induced by additives, thereby avoiding the problems of thermal conductivity degradation and dielectric loss increase of traditional high glass content LTCC materials.

[0032] Performance Achievement and Advantage Comparison: (a) Stable High Q Value: This invention, by adding 0.5~2.5 wt% MnO, MnCO3 or MgNb2O6 as a variable valence additive, achieves superior performance compared to Ti under an argon protective atmosphere. 4+ The reduction reaction occurs, effectively consuming free electrons and oxygen vacancies in the system, thereby inhibiting the Ti... 4+ Restore to Ti 3+ This avoids the formation of deep-level defect states. Compared to traditional low-oxygen atmospheres... Qf Compared to CaNb2O6–CaTiO3 materials with a GHz value of less than 1000 GHz, this invention will... Qf The value has been steadily increased to over 25000 GHz, and the dielectric loss tanδ has been reduced to 3×10⁻⁶. -4The following features meet the requirements of high-frequency, low-loss applications. (b) Extremely low glass content design: This invention controls the amount of glass sintering aid added to an ultra-low level of 3~5 wt%, far lower than conventional LTCC materials (usually 10~30 wt%). The main crystalline phase CaNb2O6 has a niobite structure, and its intrinsic lattice thermal conductivity theoretical value can reach 6~8 W / (m·K). By combining highly active powders (CaNb2O6 pre-sintering temperature 900~1050℃ and CaTiO3 pre-sintering temperature 1100~1150℃) with a very small amount of glass phase, phonon scattering at the glass / ceramic interface is reduced, while achieving high densification (relative density ≥97%) at 950~1050℃. Ultimately, the thermal conductivity of the composite material is increased to 4.5~5.0 W / (m·K), which is significantly better than traditional LTCC materials (usually <4 W / (m·K)) and most microcrystalline glass systems (<2 W / (m·K)). (d) Adjustable temperature coefficient and dielectric constant of near-zero resonant frequency: This invention utilizes the positive τ of CaTiO3 to adjust the ratio of CaNb2O6 to CaTiO3 (96~98 wt% niobium-based filler, 2~4 wt% adjustment phase). f (≈+800 ppm / ℃) Compensation for the negative τ of CaNb2O6 f (≈-74 ppm / ℃), at a dielectric constant ε r A near-zero temperature coefficient (|τ) was achieved in the range of 14.5~15.5. f (≤5 ppm / ℃), meeting the stringent frequency stability requirements of 5G / 6G communication base stations, filters, and other devices.

[0033] Compared with existing technologies: Compared with using Mn additives to suppress Ti 4+ Compared with existing reduction techniques, this invention precisely controls the addition amount of MnO / MnCO3 / MnNb2O6 in the niobium-based system to 0.5–2.5 wt%, and synergizes with an extremely low glass content (3–5 wt%) to suppress Ti 4+ reduction( Q×f While achieving ≥25000 GHz, it avoids the formation of a high-loss second phase. Compared to existing LTCC technologies that co-fire CuO glass with copper, this invention achieves simultaneous low-temperature sintering, copper co-firing compatibility, and Ti... 4+ Reduction inhibition and high thermal conductivity (4.5–5.0 W / (m·K)).

[0034] Example Example 1 Prepare CaO–CuO–Al2O3–B2O3–SiO2 glass powder according to the following mass percentages (corresponding molar ratio CaO:CuO:Al2O3:B2O3:SiO2 = 20:3:10:17.5:49.5): CaO 17.1 wt%, CuO 3.6 wt%, A2O3 15.5 wt%, B2O3 18.5 wt%, SiO2 45.3 wt%. Accurately weigh the raw materials (CaCO3, CuO, Al2O3, H3BO3, SiO2), ball mill them together with anhydrous ethanol and zirconium balls as the medium for 4 hours, and then dry them in an oven at 90℃.

[0035] The above mixture was placed in a corundum crucible and heated to 1300℃ at a rate of 5℃ / min. The temperature was maintained for 1.5 hours. After the temperature maintenance was completed, the glass melt was poured into deionized water for quenching. After crushing, the glass was ball-milled to D50=2.5 ​​μm to obtain glass powder.

[0036] Preparation of niobium-based fillers: CaCO3 and Nb2O5 were weighed according to stoichiometric ratio, ball-milled for 8 hours with anhydrous ethanol as the medium, dried, and pre-calcined at 950℃ for 3 hours to obtain CaNb2O6 powder (D50=1.5 μm). Simultaneously, CaCO3 and TiO2 were weighed according to stoichiometric ratio, ball-milled and mixed, dried, and pre-calcined at 1120℃ for 3 hours to obtain CaTiO3 powder (D50=2 μm).

[0037] Based on a total mass of 100%: 94.5 wt% of CaNb2O6 powder, 2.5 wt% of CaTiO3 powder (mass ratio 97.4:2.6), 3.0 wt% of glass powder, and 1.0 wt% of MnO additive were weighed. The mixture was then planetarily ball-milled for 6 hours using anhydrous ethanol as the medium and dried to obtain the composite powder.

[0038] Add 6 wt% PVA aqueous solution (concentration 10 wt%) as a binder to the composite powder, mix thoroughly and granulate, pass through a 40-mesh sieve, and dry press into φ12 mm×2 mm round blanks under 150 MPa pressure.

[0039] The green compact was placed in an atmosphere sintering furnace and heated to 600℃ at 2℃ / min under an argon atmosphere (purity ≥99%, flow rate 2 L / min), held at that temperature for 2 hours to remove the binder; then the temperature was increased to 1000℃ at 3℃ / min and held at that temperature for 3 hours for sintering, and then cooled to room temperature with the furnace. The sintered sample was grayish-black, dense and without cracks.

[0040] The dielectric properties, thermal conductivity, phase composition (XRD), and microstructure (SEM) of the ceramic samples were tested, see [link to relevant documentation]. Figure 1 and Figure 2XRD patterns showed the main crystalline phase as CaNb₂O₆, with no detected CaTiO₃ phase, indicating solid solution formation. SEM revealed uniform and dense grains with a relative density of 97.5%. The dielectric constant ε₀... r =15.1, Q×f =26800 GHz, thermal conductivity λ=4.8 W / (m·K), temperature coefficient of resonant frequency τ f =+1.5 ppm / ℃.

[0041] The composite powder from Example 1 was co-fired with commercially available copper electrode slurry: copper electrodes were screen-printed on the surface of the green body, and co-fired using the same debinding and sintering process (argon atmosphere, 1000℃ for 3 hours). After co-firing, the copper electrodes maintained a metallic luster, showed no oxidation, and exhibited no interface cracking or delamination, indicating good compatibility between the material and copper.

[0042] Example 2 The glass powder adopted the BaO–CuO–Al2O3–B2O3–SiO2 system, with the following mass percentages (corresponding to a molar ratio of BaO:CuO:Al2O3:B2O3:SiO2 = 20:3:10:17.5:49.5): BaO 36.0 wt%, CuO 2.8 wt%, Al2O3 12.0 wt%, B2O3 14.3 wt%, SiO2 34.9 wt%. The preparation method was the same as in Example 1, and the melting temperature was 1320℃.

[0043] The niobium-based filler uses a (Ca,Mn)Nb2O6 solid solution: CaCO3, MnCO3, and Nb2O5 are weighed according to the stoichiometric ratio (Ca:Mn molar ratio = 95:5) and synthesized by pre-calcination at 980℃ for 3 hours. The dielectric constant adjustment phase uses CaTiO3.

[0044] Based on a total mass of 100%: weigh 92.0 wt% (Ca,Mn)Nb2O6, 4.0 wt% CaTiO3 (mass ratio 96:4), 3.0 wt% glass powder, and 1.0 wt% MnCO3 additive. Mix, ball mill, granulate, form, debind, and sinter (980℃, 4h) as in Example 1.

[0045] The sintered sample was dense, with a relative density of 97.3%. (See attached image) Figure 1 XRD analysis revealed that the main crystalline phase was a (Ca, Mn)Nb₂O₆ solid solution, with a small amount of CaTiO₃. Dielectric properties: ε r =14.9, Q×f =27500 GHz, thermal conductivity λ=5.0 W / (m·K), τ f =-1.8ppm / ℃. After co-firing with copper electrodes, the interface is good, with no oxidation or cracking.

[0046] Example 3 The glass powder was the same as the CaO–CuO–Al2O3–B2O3–SiO2 system in Example 1, but the glass content was increased to 5 wt%. The niobium-based filler was CaNb2O6 (pre-calcined at 900°C), and the dielectric constant adjusting phase was CaTiO3 (same as in Example 1). The additive was MnNb2O6 (synthesized separately: MnO and Nb2O5 were pre-calcined at 1100°C for 4 hours in a molar ratio of 1:1 and then pulverized to D50 = 1.5 μm).

[0047] Based on a total mass of 100%: weigh 92.0 wt% CaNb₂O₆, 3.0 wt% CaTiO₃ (mass ratio 96.8:3.2), 4.5 wt% glass powder, and 0.5 wt% MnNb₂O₆ additive. Mixing, ball milling, granulation, molding, and debinding are the same as in Example 1. Sintering temperature is 1020℃, held for 3 hours.

[0048] The relative density after sintering is 97.8%. XRD shows the main crystalline phase as CaNb₂O₆ and a small amount of CaTiO₃, with no impurity phases. Dielectric properties: ε r =15.3, Q×f =30500 GHz, thermal conductivity λ=5.3 W / (m·K), τf=+0.5 ppm / ℃.

[0049] The performance parameters of the LTCC materials in Examples 1–3 are shown in Table 1.

[0050]

[0051] The composite powder from Example 1 was further mixed with 20 wt% metallic copper powder (simulating extreme co-firing conditions), and sintered under an argon atmosphere using the same process. XRD analysis was performed. Figure 3 The results show that copper remains in its elemental state, with no copper oxide formation and no change in the main crystalline phase of the ceramic, proving that the material of this invention has excellent chemical compatibility with copper.

[0052] Clearly, the preparation process of this embodiment is simple and novel. Through the design of extremely low glass content (3~5 wt%), low-temperature pre-calcination of highly active niobium-based fillers, and the synergistic effect of Mn-based additives, an LTCC material with excellent comprehensive performance that can be co-fired with copper electrodes under an argon protective atmosphere was successfully prepared. This solves the problem of the existing CaNb2O6–CaTiO3 system under low oxygen atmosphere. Qf The sharp drop in thermal conductivity is a prominent contradiction with insufficient thermal conductivity.

[0053] In summary, this invention introduces Mn 2+ As an atmosphere-compensating acceptor dopant, Mn² achieves lattice stabilization based on the defect chemical mechanism of perovskite and niobate solid solutions. +Upon entering the ceramic lattice, it can preferentially capture holes and undergo valence state transitions, forming Mn³ + / Mn 4+ Stable at the B site, suppressing Ti at its source. 4+ Reduced to Ti³ + It reduces oxygen vacancy concentration and carrier loss, significantly improving high-frequency performance. Qf The dielectric constant ε was increased and the crystal structure stabilized; simultaneously, the glass composition was optimized to prevent decomposition under argon atmosphere. The resulting LTCC material, after sintering in an argon atmosphere and co-firing with a copper electrode, exhibited a dielectric constant ε. r The value is between 14.0 and 15.5. Qf With a spectral density ≥25000GHz, thermal conductivity of 4.0~5.5 W / (m·K), temperature coefficient of resonant frequency (TCF) of 0±5ppm / ℃, and sintering shrinkage well matched with copper electrodes (11%~15%), the interface is free of oxidation and cracks. This invention solves the key problem of performance degradation of niobium / titanium-based materials when co-fired with copper under a protective atmosphere, and exhibits good compatibility with copper electrodes and excellent thermal stability. It is suitable for high-frequency, high-thermal-conductivity LTCC modules co-fired with copper.

[0054] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A Ca-Nb-Ti based LTCC material co-fired with copper electrodes, characterized in that, It is composed of the following components: CaNb2O6 powder, CaTiO3 powder, glass sintering aid, and Mn-based additives; the mass ratio of CaNb2O6 powder to CaTiO3 powder is 96~98:2~4, the glass sintering aid accounts for 3~5 wt% of the total mass of the material, and the Mn-based additives account for 0.5~2.5 wt% of the total mass of the material. The Mn-based additive is at least one of MnO, MnCO3, and MnNb2O6; The glass sintering aid is at least one of the following: BaO-CuO-Al2O3-B2O3-SiO2 system glass or CaO-CuO-Al2O3-B2O3-SiO2 system glass.

2. The Ca-Nb-Ti based LTCC material co-fired with a copper electrode according to claim 1, characterized in that: In the BaO-CuO-Al2O3-B2O3-SiO2 system glass, the molar ratio of each oxide is: BaO:CuO:Al2O3:B2O3:SiO2=15~25:1~5:5~15:10~25:40~55; In the CaO-CuO-Al2O3-B2O3-SiO2 system glass, the molar ratio of each oxide is: CaO:CuO:Al2O3:B2O3:SiO2=15~25:1~5:5~15:10~25:40~55.

3. The Ca-Nb-Ti based LTCC material co-fired with a copper electrode according to claim 2, characterized in that: In the BaO-CuO-Al2O3-B2O3-SiO2 system glass, the molar ratio of each oxide is: BaO:CuO:Al2O3:B2O3:SiO2=20:3:10:17.5:49.5; In the CaO-CuO-Al2O3-B2O3-SiO2 system glass, the molar ratio of each oxide is: CaO:CuO:Al2O3:B2O3:SiO2=20:3:10:17.5:49.

5.

4. The Ca-Nb-Ti based LTCC material co-fired with a copper electrode according to claim 1, characterized in that, The performance parameters of the sintered Ca-Nb-Ti based LTCC material are: relative density 97.3%–97.8%, dielectric property ε r =14.9~15.3, quality factor Q×f =26800~30500 GHz, thermal conductivity λ=4.8~5.3 W / (m·K), temperature coefficient of resonant frequency τ f = -1.8~+1.5ppm / ℃.

5. A method for preparing Ca-Nb-Ti based LTCC material co-fired with copper electrode, characterized in that, The preparation method is used to prepare the Ca-Nb-Ti based LTCC material according to any one of claims 1 to 4, and the preparation method includes the following steps: Step 1: Synthesis of CaNb2O6 powder: Weigh calcium carbonate and niobium pentoxide, mix them by ball milling, pre-calcine at 900~1050℃ for 2~4 hours, pulverize and sieve to obtain CaNb2O6 powder with D50=1~2 μm; Step 2, Preparation of low-temperature glass sintering aid: Weigh the oxide raw material, melt it at 1250~1350℃ for 1.5~2.5 hours, quench it with water, and then ball mill it to D50=2~3 μm; Step 3, Mixing: Weigh CaNb2O6 powder, CaTiO3 powder, low-temperature glass sintering aid, and Mn-based additives according to the mass ratio, ball mill them with anhydrous ethanol as the medium for 6-10 hours, and dry them for later use. Step 4, Granulation and Molding: Add 5% to 8% of PVA or PVB binder by weight of powder for granulation, dry press molding, and obtain ceramic green body; Step 5, Adhesive Removal: In an argon atmosphere, maintain the temperature at 550~600℃ for no less than 2 hours to remove the adhesive; Step 6, Sintering: Under an argon protective atmosphere, heat to 950-1050℃ at a rate of 2-5℃ / min, hold for 2-4 hours, and then cool to room temperature with the furnace.

6. The method for preparing a Ca-Nb-Ti based LTCC material co-fired with a copper electrode according to claim 5, characterized in that, In step 6, the green blank with printed copper electrodes and the green blank without printed copper electrodes are stacked and then sintered together.

7. The method for preparing a Ca-Nb-Ti based LTCC material co-fired with a copper electrode according to claim 5, characterized in that, In step 6, the oxygen partial pressure of the argon atmosphere is less than 10 ppm, and the argon gas flow rate is 1~3 L / min.

8. The method for preparing a Ca-Nb-Ti based LTCC material co-fired with a copper electrode according to claim 5, characterized in that, The CaTiO3 powder used in step 3 is synthesized by pre-calcining a mixture of calcium carbonate and titanium dioxide at 1100~1150℃, and the particle size D50 of the CaTiO3 powder is 1~1.5μm.

9. The method for preparing a Ca-Nb-Ti based LTCC material co-fired with a copper electrode according to claim 5, characterized in that, In step 1, the pre-calcination temperature of the CaNb2O6 powder is 950~1000℃.

10. The application of the Ca-Nb-Ti based LTCC material as described in any one of claims 1-4 in the preparation of high-frequency, high-thermal-conductivity LTCC substrates and copper internal electrode co-fired electronic modules.

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