Optimization method for sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics

Abstract

This invention relates to a method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics, and pertains to the field of low-temperature co-fired ceramic material preparation technology. The method includes: placing boron-containing microcrystalline glass powder in a treatment atmosphere containing boron oxide vapor for gas-phase diffusion treatment, allowing boron oxide species to diffuse into the outer surface layer of the powder particles and combine with the outer surface glass network to form a boron-oxygen-enriched surface layer; subjecting the treated powder to dehydration heat treatment, causing the boron-oxygen-enriched surface layer to condense and form a surface glass network with a softening temperature lower than that of the internal glass phase of the particles; during the low-temperature co-firing heating process, causing the surface glass network to undergo viscous flow before the internal glass phase of the particles, and forming sintering necks at the contact points of adjacent powder particles, thereby improving the sintering activity of the boron-containing microcrystalline glass powder, improving the uniformity of sintering neck growth and densification efficiency, reducing performance fluctuations caused by the overall reduction in glass softening temperature, and obtaining a structurally stable powder suitable for LTCC process applications.

Description

Technical Field

[0001] This invention relates to the field of low-temperature co-fired ceramic material preparation technology, specifically to a method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics. Background Technology

[0002] In existing technologies, low-temperature co-fired ceramic materials typically rely on the viscous flow of a low-softening-point glass phase or microcrystalline glass phase during sintering heating to achieve liquid-phase mass transfer, particle rearrangement, and sintering densification among ceramic powders. With the increasing demands for low dielectric loss, low sintering temperature, and high reliability in high-frequency communication, microelectronic packaging, and multilayer integrated devices, the particle size, surface state, glass network structure, and wetting and interfacial bonding properties of the glass powder directly affect the sintering shrinkage, porosity residue, and dielectric stability of LTCC materials. Patent application CN114394768A discloses a modified calcium boron lanthanum glass powder, green ceramic tape, an LTCC substrate with controllable dielectric constant, packaging materials, and their preparation method. This method modifies the calcium boron lanthanum glass powder with a surface modifier to improve the powder's dispersibility in the casting slurry, reduce the slurry viscosity, and increase the densification degree of the sintered substrate. This scheme demonstrates that the surface properties of the glass powder have a significant impact on the subsequent molding and sintering quality of LTCC.

[0003] However, the aforementioned techniques for improving dispersibility through organic surface modification primarily affect the preparation of cast slurry and the control of green ceramic belt uniformity. The modified layer undergoes decomposition, volatilization, or residual changes during binder removal and sintering, making it difficult to controllably adjust the glass network structure of the microcrystalline glass powder particles themselves. Furthermore, it is difficult to achieve higher early sintering activity on the outer surface of individual powder particles compared to the particle interior without introducing a continuously added liquid film or organic residue. Patent application CN118324497A discloses a low-dielectric-loss, low-temperature co-fired ceramic / glass composite material. By using CaO-B2O3-SiO2 microcrystalline glass as the glass phase and incorporating components such as K2O, LiF, and Nb2O5, the material's sintering temperature is lowered and dielectric properties are improved. This approach demonstrates the important role of borosilicate or calcium borosilicate glass phases in reducing the sintering temperature of LTCC.

[0004] However, during the preparation, storage, pulverization, and heat treatment of boron-containing glass-ceramic powder, the surface layer of the powder particles is prone to variations in composition and structure due to boron volatilization, surface hydrolysis, local network breakage, or uneven recondensation. This leads to a mismatch between the surface softening behavior and the internal glass phase. Simply lowering the glass softening temperature through overall formulation may cause simultaneous changes in the crystal phase precipitation window, dielectric properties, and thermal stability. Adding low-melting-point sintering aids to increase sintering activity may result in excessive grain boundary glass phase, localized liquid phase segregation, or increased dielectric loss. Therefore, existing technologies still require a selective control method for the outer surface layer of boron-containing glass-ceramic powder particles. This method should maintain the basic composition of the powder matrix and the characteristics of the glass-ceramic phase while enabling the powder particle surface to form an active structure more prone to early viscous flow, thereby improving the sintering neck formation ability and sintering uniformity during low-temperature co-firing. Summary of the Invention

[0005] The purpose of this invention is to provide a method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics, thereby addressing some of the drawbacks and shortcomings pointed out in the background art.

[0006] The present invention adopts the following technical solution to solve the above-mentioned technical problems:

[0007] Boron-containing microcrystalline glass powder is placed in a treatment atmosphere containing boron oxide vapor for gas phase diffusion treatment, so that the boron oxide species in the boron oxide vapor diffuse into the outer surface of the boron-containing microcrystalline glass powder particles and combine with the glass network of the outer surface of the powder particles to form a boron-oxygen enriched surface layer.

[0008] The boron-containing microcrystalline glass powder after vapor-phase diffusion treatment is subjected to dehydration heat treatment, so that the boron-oxygen enriched surface layer is condensed to form a surface glass network, and the surface glass network has a softening temperature that is lower than that of the glass phase inside the particles.

[0009] During the low-temperature co-firing heating process, the surface glass network undergoes viscous flow before the glass phase inside the particles, and a sintering neck is formed at the contact point of adjacent powder particles, thereby improving the sintering activity of the boron-containing microcrystalline glass powder.

[0010] Furthermore, before entering the powder processing area, the boron-containing oxide vapor passes through a glass buffer layer containing a network-regulating oxide consistent with the boron-containing microcrystalline glass powder. This allows the boron-containing oxide vapor to replenish boron-depleted regions on the outer surface of the powder particles with boron-oxygen species, and prevents the formation of a continuous free boron oxide deposition layer on the outer surface of the powder particles.

[0011] Furthermore, the gas-phase diffusion treatment is performed alternately with water-containing boron-oxygen vapor treatment and low-dew-point gas desorption treatment. The water-containing boron-oxygen vapor treatment causes discontinuous hydrolysis and chain opening on the outer surface of the powder particles, while the low-dew-point gas desorption treatment causes the hydrolyzed and chain-opened outer surface of the powder particles to condense and form a boron-oxygen enriched surface layer, thus avoiding the formation of a continuous liquid wetting film.

[0012] Furthermore, the gas-phase diffusion treatment causes the boron-containing microcrystalline glass powder to be in a state of agitation, suspension, or pulsed fluidization, and the boron-containing oxide vapor is introduced into the powder treatment area in an intermittent manner, so that a boron-oxygen enriched surface layer is formed on the outer surface of individual powder particles.

[0013] Furthermore, in two consecutive aqueous boron-oxygen vapor treatments, the partial pressure of boron and oxygen in the latter aqueous boron-oxygen vapor treatment is higher than that in the former aqueous boron-oxygen vapor treatment, and the temperature of the latter low dew point gas desorption treatment is higher or equal to that of the former low dew point gas desorption treatment, so that boron and oxygen species are added to the outer surface of the powder particles in stages after hydrolysis and chain opening.

[0014] Furthermore, the water vapor content in the water-containing boron-oxygen vapor treatment is controlled to a level that prevents the formation of a continuous adsorbed water layer on the outer surface of the powder particles, causing discontinuous hydrolysis and chain opening on the outer surface of the powder particles, and transforming them into a discontinuous boron-oxygen bridging structure after the low dew point gas desorption treatment.

[0015] Furthermore, the low dew point gas desorption treatment, as the final step of the last alternating treatment, reduces the residual hydroxyl content in the boron-oxygen enriched surface through a condensation reaction and keeps the boron-oxygen enriched surface in an amorphous glassy state.

[0016] Furthermore, the intermittent introduction method includes alternately introducing boron-containing oxide vapor and boron-free dry gas into the powder processing area, so that the boron-containing microcrystalline glass powder in the agitated, suspended or pulsed fluidized state undergoes an alternating process of surface adsorption and surface condensation stabilization.

[0017] Furthermore, the pulsed fluidization state is controlled by at least one of the parameters of gas pulse pressure, apparent gas velocity, pulse frequency, and pulse duration to disperse the powder agglomerates and keep the powder particles of the boron-containing microcrystalline glass powder intact, so that the boron-oxygen enriched surface layer is formed on the outer peripheral surface of individual powder particles.

[0018] Furthermore, after each introduction of the boron-containing oxide vapor, the boron-free drying gas first passes through the powder processing area in the opposite direction to the direction of introduction of the boron-containing oxide vapor, and then passes through the powder processing area in the direction of introduction of the boron-containing oxide vapor, so as to remove the residual boron-containing oxide vapor in the gaps between powder agglomerations and reduce the desorption loss of boron oxygen species adsorbed on the surface of powder particles.

[0019] This invention involves subjecting boron-containing glass-ceramic powder to a vapor-phase diffusion treatment atmosphere containing boron oxides. This allows boron and oxide species to diffuse into the outer surface of the powder particles and combine with the surface glass network, forming a boron-oxygen-enriched surface layer. This method does not involve simply depositing sintering aids on the powder surface; instead, it compensates for and activates the structure of the glass network on the outer surface of the particles. This approach helps to improve the sintering response of the powder surface layer while maintaining the bulk properties of the glass-ceramic material within the particles.

[0020] This invention further utilizes dehydration heat treatment to condense the boron-oxygen-enriched surface layer into a surface glass network, which has a lower softening temperature compared to the internal glass phase of the particles. Therefore, during the low-temperature co-firing heating process, the surface layer of the powder particles can undergo viscous flow before the internal glass phase, and preferentially form sintering necks at the contact points of adjacent powder particles, thereby promoting inter-particle bonding, reducing the difficulty of sintering initiation, and improving sintering activity.

[0021] The present invention focuses on the outer surface of individual powder particles, which can reduce the problems of uncontrolled crystal phase precipitation, dielectric property degradation and liquid phase segregation that may be caused by lowering the overall glass softening temperature. At the same time, through the sintering behavior of surface flow first and internal response later, the uniformity of neck growth and densification efficiency during the sintering process of low temperature co-fired ceramic materials can be improved, which is conducive to obtaining boron-containing microcrystalline glass powder with stable structure, high sintering activity and suitable for LTCC process application. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the optimization process for the sintering activity of microcrystalline glass powder used in low-temperature co-fired ceramics according to the present invention.

[0023] Figure 2 This is a flowchart of the alternating gas-phase diffusion process in Embodiment 1 of the present invention.

[0024] Figure 3 This is a graph showing the increasing relationship between boron-oxygen partial pressure and desorption temperature in Example 1 of the present invention.

[0025] Figure 4 This is a verification diagram showing the relationship between the boron-oxygen replenishment ratio and the decrease in softening temperature in Example 1 of the present invention.

[0026] Figure 5 This is a flowchart of the dynamic distributed alternating feed process in Embodiment 2 of the present invention.

[0027] Figure 6 This is a graph showing the relationship between the alternating flow duty cycle and the apparent flow rate in Embodiment 2 of the present invention.

[0028] Figure 7 This is a verification diagram of the dispersion and densification effect of aggregates in Example 2 of the present invention. Detailed Implementation

[0029] As attached Figure 1 As shown, in one specific embodiment, boron-containing microcrystalline glass powder is first added to a processing device through which boron-containing oxide vapor can be introduced, allowing the powder to fully contact the boron-containing oxide vapor. The processing device may include a boron-containing oxide vapor generation area, a powder processing area, a gas introduction channel, and a gas discharge channel, with the boron-containing microcrystalline glass powder located within the powder processing area. The boron-containing oxide vapor can be formed by boric acid, metaboric acid, boron oxides, or boron-containing precursors capable of releasing boron oxide species, carried by a carrier gas. The carrier gas is a gas that does not adversely react with the boron-containing microcrystalline glass powder. During the processing, the boron oxide species in the boron oxide vapor diffuse along the outer peripheral surface of the powder particles and combine with the existing glass network in the outer peripheral surface, thereby forming a boron-oxygen-enriched surface layer on the powder particle surface. This boron-oxygen-enriched surface layer is not a simple deposit attached to the particle surface, but rather a surface structure formed after boron oxide species enter the outer peripheral surface of the particles and participate in the reconstruction of the glass network.

[0030] After vapor-phase diffusion treatment, the boron-containing glass-ceramic powder undergoes a dehydration heat treatment. This treatment causes condensation reactions of hydroxyl groups or other hydrated groups in the boron-oxygen enriched surface layer, further stabilizing the surface structure and forming a surface glass network. The dehydration heat treatment is conducted under conditions that prevent overall sintering and significant agglomeration of the boron-containing glass-ceramic powder, ensuring that dehydration condensation primarily occurs on the outer surface of the powder particles. Because boron-oxygen species are introduced into the surface glass network, its network structure is more prone to thermal softening compared to the internal glass phase; therefore, the softening temperature of the surface glass network is lower than that of the internal glass phase.

[0031] During the subsequent low-temperature co-firing process, the surface glass network on the outer periphery of the powder particles undergoes viscous flow before the internal glass phase. Adjacent powder particles migrate and bond at the contact points through this viscous flow, gradually forming sintering necks. This enhances the interparticle bonding at lower sintering temperatures, improves the sintering activity of boron-containing microcrystalline glass powder, and enhances its densification effect during low-temperature co-firing.

[0032] In this embodiment, boron-containing oxide vapors are guided through a glass buffer layer before entering the powder processing zone. The glass buffer layer can be formed using glass particles or glass fragments whose composition matches that of the boron-containing microcrystalline glass powder, and contains network-regulating oxides consistent with the boron-containing microcrystalline glass powder. Composition matching means that the glass buffer layer and the boron-containing microcrystalline glass powder belong to the same or similar glass system, and that no impurities that would impair the low-temperature co-firing performance are introduced into the boron-containing microcrystalline glass powder. The glass particles or glass fragments in the glass buffer layer can be pre-dried and set to a particle size that is not easily carried into the powder processing zone by the airflow. When the boron-containing oxide vapors pass through the glass buffer layer, their vapor composition and activity state are buffered and regulated, thereby reducing the tendency for the boron-containing oxide vapors to directly condense or accumulate and deposit on the powder surface.

[0033] After the boron-containing oxide vapor, conditioned by the glass buffer layer, enters the powder treatment area, it primarily replenishes boron-oxygen species to the boron-depleted regions on the outer surface of the powder particles. Since the network-regulating oxides in the glass buffer layer are consistent with those in the boron-containing microcrystalline glass powder, unfavorable deviations between the powder surface composition and the particle interior composition during vapor treatment are reduced. This allows boron-oxygen species to more easily diffuse and bind into the outer surface of the powder particles, rather than forming a continuous free boron oxide deposition layer. This method improves the uniformity of boron-oxygen replenishment and maintains compositional harmony between the glass network on the powder particle surface and the glass phase inside the particles.

[0034] In this embodiment, the gas-phase diffusion treatment alternates between water-containing boron-oxygen vapor treatment and low-dew-point gas desorption treatment. The water-containing boron-oxygen vapor is a vapor containing boron oxide compounds and is a water-containing form of boron oxide vapor. During the water-containing boron-oxygen vapor treatment stage, the vapor contacts the outer surface of the powder particles. The moisture participates in the localized bond breaking of the surface glass network, causing discontinuous hydrolysis and chain opening on the outer surface of the powder particles. This hydrolysis and chain opening mainly occurs on the outer surface of the powder particles, and the water vapor content is controlled to be insufficient to form a continuous adsorbed water layer on the outer surface of the powder particles. This results in dispersed active sites on the surface network, preventing the formation of a continuous liquid wetting film on the outer surface of the powder particles.

[0035] After completing one aqueous boron-oxygen vapor treatment, a low dew point gas is introduced into the powder treatment area for desorption. The low dew point gas can be air, nitrogen, argon, or a mixture thereof, and its water content is lower than that of the atmosphere during the aqueous boron-oxygen vapor treatment stage. The low dew point gas removes adsorbed moisture and some volatile residues from the outer surface of the powder particles, causing a condensation reaction in the hydrolyzed, open-chain outer surface and allowing the introduced boron-oxygen species to combine with the surface glass network. Through alternating aqueous boron-oxygen vapor treatment and low dew point gas desorption treatment, the outer surface of the powder particles can cycle between open-chain activation and condensation stabilization, gradually forming a boron-oxygen-enriched surface layer. During the treatment, the partial pressure of boron-oxygen in the subsequent aqueous boron-oxygen vapor treatment is higher than that in the previous aqueous boron-oxygen vapor treatment, and the temperature of the subsequent low dew point gas desorption treatment is higher or equal to that of the previous low dew point gas desorption treatment. The increase in boron-oxygen partial pressure can be achieved by increasing the intensity of boron-containing oxide vapor generation, prolonging the contact time between boron-containing oxide vapor and the carrier gas, or increasing the supply of boron-containing precursors. The low dew point gas desorption treatment temperature should be set to promote surface dehydration and condensation without causing powder particle softening and adhesion. This allows for the phased replenishment of boron-oxygen species onto the outer surface of the powder particles based on the already formed hydrolytic open-chain structure, preventing excessive enrichment of boron-oxygen species in a single treatment.

[0036] In the aforementioned alternating treatment process, the water vapor content in the aqueous boron-oxygen vapor treatment is controlled to prevent the formation of a continuous adsorbed water layer on the outer surface of the powder particles, thus creating a discontinuous hydrolytic open-chain structure on the outer surface of the powder particles. Subsequently, a low-dew-point gas desorption treatment transforms the discontinuous hydrolytic open-chain structure into a discontinuous boron-oxygen bridging structure through dehydration condensation. As the final step in the alternating treatment, a low-dew-point gas desorption treatment is used to reduce the residual hydroxyl content in the boron-oxygen enriched surface layer through condensation reactions, and to maintain the boron-oxygen enriched surface layer in an amorphous glassy state, thereby obtaining a stable surface glass network. The amorphous glassy state refers to the boron-oxygen enriched surface layer not forming independent crystalline boron oxide particles or a continuous crystalline deposition layer, but rather forming a continuous or discontinuous glassy surface structure together with the glass network on the outer surface of the powder particles.

[0037] In this embodiment, the vapor-phase diffusion treatment is carried out in a processing apparatus capable of maintaining the dynamic dispersion of boron-containing microcrystalline glass powder. During the treatment, the powder particles can be continuously changed in position and contact state through mechanical agitation, airflow suspension, or pulsed fluidization, reducing the obstruction of boron-containing oxide vapor diffusion by powder agglomerates. Dynamic dispersion is achieved when the powder particles can separate from each other or periodically loosen without significant breakage or abnormal wear. Boron-containing oxide vapor is introduced into the powder processing area intermittently, allowing the outer surface of individual powder particles to periodically contact the boron-containing oxide vapor and form a boron-oxygen-enriched surface layer on the outer surface of the particles. This dynamic dispersion treatment reduces the concentration of boron-oxygen species on the outer side of powder agglomerates, resulting in a more uniform formation of the boron-oxygen-enriched surface layer on the outer surface of individual powder particles.

[0038] During the intermittent induction process, boron-containing oxide vapor and boron-free dry gas are alternately introduced into the powder treatment zone. The boron-free dry gas is a dry gas that does not contain boron-oxygen species that can be introduced into the powder particles; it can be air, nitrogen, argon, or a mixture thereof. The boron-containing oxide vapor induction stage is used to adsorb and diffuse boron-oxygen species into the outer surface layer of the powder particles, while the boron-free dry gas induction stage is used to remove residual vapor that has not participated in surface bonding and promote condensation stabilization of the outer surface layer of the powder particles. The boron-containing microcrystalline glass powder, in a state of agitation, suspension, or pulsed fluidization, sequentially undergoes surface adsorption and surface condensation stabilization processes in the alternating atmosphere, thereby inhibiting the formation of continuous deposition layers and improving the uniformity of surface modification.

[0039] When pulsed fluidization is employed, control can be achieved through one or more parameters selected from gas pulse pressure, apparent gas velocity, pulse frequency, and pulse duration. These parameters are set to disperse powder agglomerates while maintaining the integrity of the boron-containing microcrystalline glass powder particles. Particle integrity means that the powder particles do not exhibit significant breakage, flaking, or severe adhesion after processing, which would affect the uniformity of low-temperature co-firing and sintering. Consequently, boron-containing oxide vapors can penetrate the gaps between powder agglomerates and around individual powder particles, causing a boron-oxygen enriched surface layer to form on the outer periphery of individual powder particles, rather than primarily on the outer surface of the agglomerates.

[0040] After each introduction of boron-containing oxide vapor, boron-free drying gas is first passed through the powder processing area in the opposite direction to the direction of introduction of the boron-containing oxide vapor to dislodge residual boron-containing oxide vapor from the gaps between powder agglomerates. Subsequently, boron-free drying gas is passed through the powder processing area in the direction of introduction of the boron-containing oxide vapor to further remove residual vapor and stabilize the airflow distribution. Through the continuous action of reverse and forward airflows, the retention of residual boron-containing oxide vapor within the gaps between powder agglomerates can be reduced, while simultaneously decreasing the likelihood of excessive removal of boron and oxide species already adsorbed on the surface of powder particles.

[0041] Example 1:

[0042] A certain organization used boron-containing microcrystalline glass powder for sintering activity optimization treatment before preparing a low-temperature co-fired ceramic dielectric layer. The boron-containing microcrystalline glass powder is a borosilicate-based microcrystalline glass powder with a particle size... for Take the powder mass before processing for The boron-containing microcrystalline glass powder is placed in the powder processing area of ​​the gas phase diffusion treatment device. The powder processing area is connected to the area where boron-containing oxide vapor is generated, and a gas inlet channel and a gas outlet channel are provided so that the boron-containing oxide vapor can pass through the powder layer and make full contact with the outer surface of the powder particles. Figure 2 The diagram illustrates the connection between powder loading, glass buffering, water-containing boron-oxygen vapor incremental treatment, low dew point gas desorption treatment, and dehydration heat treatment in this embodiment. This is used to explain the processing path in which boron-oxygen species enter the outer peripheral surface of powder particles from the vapor atmosphere and are stabilized by condensation to form a surface glass network.

[0043] Before the boron-containing oxide vapors enter the powder processing area, they are first passed through a glass buffer layer. This buffer layer is formed from glass fragments of the same system as the boron-containing microcrystalline glass powder, containing network-regulating oxides identical to those in the powder. Passing through the buffer layer, the active state of the boron-containing oxide vapors is buffered, allowing them to primarily replenish boron-oxygen species in the boron-depleted regions on the outer surface of the powder particles, rather than forming a continuous free boron oxide deposition layer on the outer surface of the powder particles. Figure 2 The glass buffer layer is located before the water-containing boron and oxygen vapor treatment. Its function is to enable the boron and oxygen species that subsequently enter the powder treatment area to participate in the surface network reconstruction through diffusion and bonding.

[0044] The gas-phase diffusion treatment employs an alternating process of water-containing boron-oxygen vapor treatment and low-dew-point gas desorption treatment. The water-containing boron-oxygen vapor is a vapor containing boron oxide compounds with moisture content, while the low-dew-point gas is dry nitrogen with a dew point of [missing information]. During the aqueous boron-oxygen vapor treatment stage, the aqueous boron-oxygen vapor comes into contact with the outer surface of the powder particles. The moisture causes localized bond breakage in the glass network of the outer surface of the powder particles, forming a discontinuous hydrolytic open-chain structure. The water vapor content is controlled to be insufficient to form a continuous adsorbed water layer on the outer surface of the powder particles, ensuring that the hydrolytic open-chain structure mainly occurs on the outer surface of the powder particles, thus avoiding the formation of a continuous liquid wetting film on the outer surface of the powder particles.

[0045] In this embodiment, the water-containing boron-oxygen vapor treatment is performed three times, and the partial pressures of boron and oxygen in the three treatments are, respectively, as follows: , and After each treatment with water-containing boron-oxygen vapor, a low-dew-point gas was introduced for desorption. The desorption temperatures of the low-dew-point gas were as follows: , and The partial pressure of boron and oxygen in the subsequent water-containing boron and oxygen vapor treatment is higher than that in the previous water-containing boron and oxygen vapor treatment, and the temperature of the subsequent low dew point gas desorption treatment is higher or equal to that of the previous low dew point gas desorption treatment. As a result, boron and oxygen species are added to the outer surface of the powder particles in stages on the basis of the already formed hydrolytic open-chain structure. Figure 3 The synchronous increasing relationship between boron-oxygen partial pressure and low dew point gas desorption temperature during three alternating treatments is shown. The increase in boron-oxygen partial pressure corresponds to the staged replenishment of boron-oxygen species, and the increase in desorption temperature corresponds to the gradual removal of surface adsorbed moisture and volatile residues.

[0046] During the low dew point gas desorption treatment stage, the low dew point gas removes adsorbed moisture and some volatile residues from the outer surface of the powder particles, causing a condensation reaction in the hydrolyzed, open-chain outer surface and allowing the newly added boron-oxygen species to combine with the glass network of the outer surface of the powder particles. The final alternating treatment uses low dew point gas desorption as a terminating step to reduce the residual hydroxyl content in the boron-oxygen enriched surface through condensation reactions and to maintain the boron-oxygen enriched surface in an amorphous glassy state. Figure 2 The connection between the low-dew-point gas treatment and the dehydration heat treatment and the surface glass network state indicates that the treatment is not simply a purge of residual vapors, but rather works with subsequent heat treatments to stabilize the surface network.

[0047] After completing the above vapor-phase diffusion treatment, the boron-containing microcrystalline glass powder is subjected to a dehydration heat treatment at a temperature of [temperature missing]. This dehydration heat treatment further condenses the hydroxyl groups or other hydrated groups in the boron-oxygen enriched surface layer, forming a stable surface glass network. After the dehydration heat treatment, the mass of the boron-containing microcrystalline glass powder... for No obvious sintering or agglomeration was observed between the powder particles, and the powder remained in a dispersible state. Figure 4 The left side shows a slight increase in powder mass by comparing the mass before and after treatment. This change in mass corresponds to the entry of boron and oxygen species into the outer surface of the powder particles and their retention after dehydration heat treatment.

[0048] To characterize the relative amount of boron-oxygen species incorporated into the outer surface of powder particles and retained after dehydration heat treatment, the mass ratio of boron-oxygen incorporation was used. The expression is as follows:

[0049]

[0050] In the formula, This represents the percentage increase in mass corresponding to the formation of a boron-oxygen enriched surface layer after vapor-phase diffusion treatment and dehydration heat treatment, expressed in units of 1. This indicates the mass of boron-containing microcrystalline glass powder before treatment, in units of... ; This indicates the mass of the treated boron-containing microcrystalline glass powder, in units of... The derivation of this formula is based on the fact that the difference in powder mass before and after treatment corresponds to the relative increase in boron and oxygen species that enter the outer surface of the powder particles and are retained after dehydration heat treatment. Dividing this mass difference by the powder mass before treatment yields the boron and oxygen replenishment mass ratio.

[0051] Will , Substituting into the above equation, we get:

[0052]

[0053] Therefore, in this embodiment, after the boron-containing microcrystalline glass powder undergoes vapor-phase diffusion treatment and dehydration heat treatment, the mass ratio of boron to oxygen added is [missing information]. This result indicates that boron-oxygen species do not accumulate on the powder surface as large amounts of free sediments, but rather enter the outer surface layer of powder particles in a low increment and participate in the formation of the surface glass network, thus helping to maintain the compositional harmony between the surface layer of powder particles and the internal glass phase of the particles. Figure 4 The difference between the quality before and after treatment corresponds to the above calculation results, which is used to intuitively show that the amount of boron and oxygen supplementation is within a trace and controllable range.

[0054] The softening temperature of the glass phase inside the boron-containing microcrystalline glass particles in the treated powder. for The softening temperature of the surface glass network for To characterize the prior softening ability of the surface glass network relative to the internal glass phase of the particles, the softening temperature reduction was used. The expression is as follows:

[0055]

[0056] In the formula, This represents the decrease in softening temperature of the surface glass network relative to the internal glass phase of the particles, expressed in units of... ; This indicates the softening temperature of the glassy phase inside the particle, expressed in units of... ; This indicates the softening temperature of the surface glass network, in units of... The derivation of this formula is based on the fact that the difference in softening temperature between the surface glass network and the glass phase inside the particles can reflect the order of softening during the low-temperature co-firing process. The more obvious the difference, the easier it is for the surface glass network to undergo viscous flow before the glass phase inside the particles.

[0057] Will , Substituting into the above equation, we get:

[0058]

[0059] Therefore, in this embodiment, the softening temperature reduction of the surface glass network relative to the internal glass phase of the particles is: . Figure 4 The right side illustrates this temperature difference by comparing the softening temperatures of the internal glass phase and the surface glass network, and... to The interval between these points serves as the surface-pre-softening zone, illustrating that the surface glass network can undergo viscous flow before the internal glass phase of the particles significantly softens. In subsequent... During the low-temperature co-firing process, the surface glass network on the outer periphery of the powder particles undergoes viscous flow before the glass phase inside the particles. Adjacent powder particles achieve interfacial bonding and form sintering necks at the contact points through viscous flow, thereby improving the sintering activity of boron-containing microcrystalline glass powder and enhancing the densification effect of low-temperature co-fired ceramic materials.

[0060] Example 2:

[0061] A certain unit used boron-containing microcrystalline glass powder for sintering activity optimization treatment before the preparation of a low-temperature co-fired ceramic dielectric layer. The amount of boron-containing microcrystalline glass powder processed was... This is added to a powder processing device capable of forming a pulsed fluidization state. The powder processing device includes a powder bed, a gas distribution section, a boron-containing oxide vapor introduction channel, a boron-free drying gas introduction channel, and a gas discharge channel. The cross-sectional area of ​​the powder bed is... for See also Figure 5 After the powder is loaded, it undergoes pulsed fluidized dispersion, introduction of boron-containing oxygen vapor, desorption of boron-free drying gas, reverse purging, forward purging, and surface condensation stabilization in sequence. The bottom pulsed airflow and the cross-sectional area of ​​the powder bed in the figure together indicate that the gas enters from the bottom of the powder bed and acts on the powder layer.

[0062] In the gas-phase diffusion process, boron-containing microcrystalline glass powder is subjected to pulsed fluidization. Pulsed gas enters the bottom of the powder bed from the gas distribution section, causing the powder particles to periodically loosen, agitate, and redistribute, thereby reducing the obstruction of boron-containing oxide vapor diffusion by powder agglomerates. The pulsed fluidization state is controlled by gas pulse pressure, apparent gas velocity, pulse frequency, and pulse duration, where the gas pulse pressure is... The pulse frequency is The duration of a single pulse is . Figure 5 The pulsed fluidization stage in the diagram is located before the boron-containing oxide vapor is introduced, illustrating that the powder particles are first dynamically dispersed and then come into contact with the boron-containing oxide vapor.

[0063] Boron-containing oxide vapor is introduced into the powder processing area intermittently. In each processing cycle, boron-containing oxide vapor is first introduced, causing boron-oxygen species to adsorb onto the outer surface of the powder particles and diffuse outwards. Then, boron-free drying gas is introduced to remove any residual vapor that has not participated in surface bonding and to stabilize the outer surface of the powder particles through condensation. The amount of boron-free drying gas introduced is . Figure 6 The alternation between the boron-containing oxide vapor introduction stage and the boron-free dry gas desorption stage in the four processing cycles is shown in time axis form, which can reflect the cyclical changes of powder particles between repeated adsorption, diffusion and desorption stabilization.

[0064] In this embodiment, the boron oxide vapor introduction time in each processing cycle for Boron-free drying gas introduction time for The number of processing loops is To characterize the time proportion of powder particles in contact with boron-containing oxide vapor in an alternating treatment cycle, the boron-containing oxide vapor introduction duty cycle was used. The expression is as follows:

[0065]

[0066] In the formula, This indicates the proportion of time that boron-containing oxide vapor is introduced in an alternating treatment cycle, expressed in units of ; This indicates the time for introducing boron-containing oxide vapor in each cycle, in units of... ; This indicates the time of introduction of boron-free drying gas in each cycle, in units of... A cycle consists of a boron-containing oxide vapor introduction stage and a boron-free drying gas introduction stage. Therefore, by dividing the boron-containing oxide vapor introduction time by the total time of the two stages, the proportion of time that the powder particles are in contact with boron-oxygen species in a single cycle can be obtained. Figure 6 The duty cycle calculation area corresponds to the proportion of the time for the introduction of boron oxide vapor in the four cycles in the total processing time. This is used to illustrate that the intermittent introduction is not a continuous gas supply, but a combination of controlled gas supply and desorption stabilization.

[0067] Will , Substituting into the above equation, we get:

[0068]

[0069] Therefore, in this embodiment, the duty cycle for the introduction of boron-containing oxide vapor is: This duty cycle allows sufficient contact time between the boron and oxygen species in the powder particles, while maintaining a longer desorption time for the boron-free drying gas. This reduces the continuous retention of boron-containing oxygen vapors in the gaps between powder agglomerates and inhibits the formation of a continuous free boron oxide deposition layer on the surface of the powder particles. Figure 6 In each loop Boron-containing vapor stage and The fact that the dry gas desorption stages are sequentially connected further illustrates that the gas phase diffusion treatment and the surface condensation stabilization are completed alternately within the same treatment cycle.

[0070] After each introduction of boron-containing oxide vapor, boron-free drying gas is first passed through the powder treatment area in the opposite direction to the direction of introduction of boron-containing oxide vapor. The reverse purging time is [duration missing]. Subsequently, the boron-free drying gas is passed through the powder treatment area in the same direction as the boron-containing oxide vapor, with a forward purging time of [time missing]. Reverse purging is used to push residual boron-containing oxide vapors in the gaps between powder agglomerates out of the processing area, while forward purging is used to further remove residual vapors and stabilize the airflow distribution. Figure 5 Setting the reverse and forward purging after the desorption of the boron-free drying gas indicates that the residual vapor discharge process has both directional switching and airflow stabilization functions.

[0071] To characterize the dispersion ability of boron-free drying gas on powder agglomerates when passing through a powder bed, the apparent gas flow rate was used. The expression is as follows:

[0072]

[0073] In the formula, The apparent velocity of gas passing through the cross section of the powder bed is expressed in units of... ; This indicates the gas volumetric flow rate entering the powder processing area, in units of... ; This represents the cross-sectional area of ​​the powder bed, in units of... Within the powder processing area, the dispersion effect of gas on the powder bed is related to the gas flow rate per unit cross-sectional area. Therefore, the apparent flow rate can be obtained by dividing the gas volumetric flow rate by the cross-sectional area of ​​the powder bed. Figure 6The apparent velocity calculation region in the figure corresponds to the passage state of the boron-free drying gas on the cross section of the powder bed, and is used to represent the intensity of the effect of the airflow on the continuous dispersion and desorption of the powder bed.

[0074] Will , Substituting into the above equation, we get:

[0075]

[0076] Therefore, in this embodiment, the apparent flow velocity of the boron-free drying gas through the powder bed cross-section is: Under the combined effects of the apparent flow rate, pulse pressure, pulse frequency, and pulse duration, the powder agglomerates can be dispersed, and the powder particles remain intact. No significant breakage, flaking, or severe adhesion occurs, which would affect the low-temperature co-firing and sintering uniformity.

[0077] through After alternating treatments, the boron-containing microcrystalline glass powder undergoes a dehydration heat treatment, which further condenses the hydrous groups adsorbed on the outer surface of the powder particles and allows the boron and oxygen species that have entered the outer surface to combine with the glass network, forming a stable boron and oxygen-enriched surface layer. The average particle size of the powder agglomerates after treatment is reduced from [previous value]. Down to This indicates that pulsed fluidization and alternating purging can allow boron-containing oxide vapors to enter the gaps between powder agglomerates and around individual powder particles, causing the boron-oxygen enriched surface layer to form on the outer surface of individual powder particles, rather than mainly on the outer surface of agglomerates. Figure 7 The left side shows the dispersion effect of agglomerates by comparing the average particle size of agglomerates before and after treatment. The average particle size decreased significantly after treatment, indicating that dynamic dispersion treatment is beneficial to improving the exposure of the outer surface of individual powder particles.

[0078] The treated boron-containing microcrystalline glass powder was used to prepare low-temperature co-fired ceramic slurry and then sintered. Compared with the untreated boron-containing microcrystalline glass powder, the relative density of the ceramic body after low-temperature co-firing was increased from [value missing]. Increase to The results indicate that after the outer surface of the powder particles is replenished and stabilized by boron-oxygen species, viscous flow can occur first during the low-temperature co-firing process, and a sintering neck can be formed at the contact area between adjacent powder particles. Figure 7 The right side shows the densification effect by comparing the relative density before and after low-temperature co-firing; the relative density increased to [value missing] after treatment. The results, together with the reduction in the average particle size of agglomerates, indicate that dynamic dispersion treatment and surface modification treatment can synergistically improve powder sintering behavior.

[0079] Through the above methods, the intermittent introduction of boron-containing oxide vapor, the alternating desorption of boron-free dry gas, the reverse and forward purging, and the pulsed fluidized dispersion work together to modify the outer surface of boron-containing microcrystalline glass powder while maintaining the integrity of the particles. This reduces the local enrichment and deposition on the outside of the powder agglomerates, improves the uniformity of the boron-oxygen enriched surface layer, and enhances the sintering activity of boron-containing microcrystalline glass powder for low-temperature co-fired ceramics.

Claims

1. A method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics, characterized in that, include: Boron-containing microcrystalline glass powder is placed in a treatment atmosphere containing boron oxide vapor for gas phase diffusion treatment, so that the boron oxide species in the boron oxide vapor diffuse into the outer surface of the boron-containing microcrystalline glass powder particles and combine with the glass network of the outer surface of the powder particles to form a boron-oxygen enriched surface layer. The boron-containing microcrystalline glass powder after vapor-phase diffusion treatment is subjected to dehydration heat treatment, so that the boron-oxygen enriched surface layer is condensed to form a surface glass network, and the surface glass network has a softening temperature that is lower than that of the glass phase inside the particles. During the low-temperature co-firing heating process, the surface glass network undergoes viscous flow before the glass phase inside the particles, and a sintering neck is formed at the contact point of adjacent powder particles, thereby improving the sintering activity of the boron-containing microcrystalline glass powder.

2. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 1, characterized in that, Before entering the powder processing area, the boron-containing oxide vapor passes through a glass buffer layer containing a network-regulating oxide consistent with the boron-containing microcrystalline glass powder. This allows the boron-containing oxide vapor to replenish boron-depleted regions on the outer surface of the powder particles with boron-oxygen species, and prevents the formation of a continuous free boron oxide deposition layer on the outer surface of the powder particles.

3. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 1, characterized in that, The gas-phase diffusion treatment is performed alternately with water-containing boron-oxygen vapor treatment and low-dew-point gas desorption treatment. The water-containing boron-oxygen vapor treatment causes discontinuous hydrolysis and chain opening on the outer surface of the powder particles, and the low-dew-point gas desorption treatment causes the hydrolyzed and chain-opened outer surface of the powder particles to condense and form a boron-oxygen enriched surface layer.

4. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 1, characterized in that, The gas-phase diffusion treatment causes the boron-containing microcrystalline glass powder to be in a state of agitation, suspension, or pulsed fluidization, and allows the boron-containing oxide vapor to enter the powder treatment area in an intermittent manner.

5. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 3, characterized in that, In two consecutive aqueous boron-oxygen vapor treatments, the partial pressure of boron and oxygen in the latter aqueous boron-oxygen vapor treatment is higher than that in the former aqueous boron-oxygen vapor treatment, and the temperature of the latter low dew point gas desorption treatment is higher or equal to that of the former low dew point gas desorption treatment, so that boron and oxygen species are added to the outer surface of the powder particles in stages after hydrolysis and chain opening.

6. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 3, characterized in that, The water vapor content in the water-containing boron-oxygen vapor treatment is controlled to prevent the formation of a continuous adsorbed water layer on the outer surface of the powder particles, causing discontinuous hydrolysis and chain opening on the outer surface of the powder particles, and transforming them into a discontinuous boron-oxygen bridging structure after the low dew point gas desorption treatment.

7. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 3, characterized in that, The low dew point gas desorption treatment, as the final step of the last alternating treatment, reduces the residual hydroxyl content in the boron-oxygen enriched surface through a condensation reaction and keeps the boron-oxygen enriched surface in an amorphous glassy state.

8. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 4, characterized in that, The intermittent introduction method includes alternately introducing boron-containing oxide vapor and boron-free dry gas into the powder processing area, so that the boron-containing microcrystalline glass powder in the agitated, suspended or pulsed fluidized state undergoes an alternating process of surface adsorption and surface condensation stabilization.

9. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 4, characterized in that, The pulsed fluidization state is controlled by at least one of the parameters of gas pulse pressure, apparent gas velocity, pulse frequency and pulse duration, which disperses the powder agglomerates and keeps the powder particles of the boron-containing microcrystalline glass powder intact, so that the boron-oxygen enriched surface layer is formed on the outer surface of the individual powder particles.

10. The method for optimizing the sintering activity of microcrystalline glass powder for low-temperature co-fired ceramics according to claim 8, characterized in that, After each introduction of the boron-containing oxide vapor, the boron-free drying gas first passes through the powder treatment area in the opposite direction to the direction of introduction of the boron-containing oxide vapor, and then passes through the powder treatment area in the direction of introduction of the boron-containing oxide vapor, so as to remove the residual boron-containing oxide vapor in the gaps between powder agglomerates and reduce the desorption loss of boron and oxygen species adsorbed on the surface of powder particles.

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