An aluminum nitride copper-clad ceramic substrate for suppressing partial discharge, its preparation method and application

Abstract

The present invention belongs to the technical field of copper-clad laminate manufacturing, and particularly relates to an aluminum nitride copper-clad ceramic substrate for suppressing partial discharge, its preparation method and application. The aluminum nitride copper-clad ceramic substrate includes an aluminum nitride ceramic substrate and a metal conductive layer compounded on the surface of the substrate. The metal conductive layer is patterned and etched to form interconnected conductive lines, and an etching gap exposing the aluminum nitride ceramic substrate is formed between the interconnected conductive lines. The surface of the aluminum nitride ceramic substrate at the etching gap is covered with a functional oxide layer. The functional oxide layer includes a porous matrix with nanoscale Al<subgt;2< / subgt;O<subgt;3< / subgt> particles as the main phase and a silicon-aluminum oxide network structure embedded inside the porous matrix. By forming a functional oxide layer on the surface of the aluminum nitride ceramic substrate, the present application suppresses the accumulation of charges, makes the electric field distribution on the surface of the aluminum nitride ceramic more uniform, and achieves the purpose of improving the partial discharge of the aluminum nitride copper-clad ceramic substrate under high voltage.

Description

Technical Field

[0001] The present invention belongs to the technical field of copper-clad laminate manufacturing, and particularly relates to an aluminum nitride copper-clad ceramic substrate for suppressing partial discharge, a preparation method thereof, and an application thereof. Background Art

[0002] An aluminum nitride copper-clad ceramic substrate is an electronic packaging material formed by compounding an aluminum nitride (AlN) ceramic substrate and a surface copper-clad layer through a high-temperature bonding process. Aluminum nitride ceramics have become ideal substrate materials for power semiconductor devices due to their excellent thermal conductivity (theoretical value is about 170 - 200 W / m·K) and high insulation (volume resistivity > 10 14 Ω·cm). The surface copper-clad layer can form conductive circuits through photolithography and etching processes to achieve chip electrical interconnection and heat dissipation functions. Such substrates are widely used in high-power insulated gate bipolar transistors (IGBTs), silicon carbide (SiC) modules and other devices in the fields of new energy vehicles, high-speed railways, photovoltaic inverters, etc. Their core role is to achieve high-voltage electrical isolation while efficiently conducting the heat generated by the devices, thereby ensuring the long-term reliability of the system under high-frequency and high-temperature conditions.

[0003] However, with the development of power electronic devices towards higher voltage levels (such as above 10 kV), the existing aluminum nitride copper-clad ceramic substrates face the problem of serious deterioration of partial discharge performance. Taking industry standards as an example, the partial discharge amount (PD value) of most products can be controlled below 10 pC under a test voltage of 8.3 kV, but when the voltage is increased to 10.5 kV, the PD value will rise sharply to 50 pC or even higher, resulting in deterioration of insulation performance and a sharp increase in the risk of device failure. This problem stems from multiple constraints of material properties, structural design, and manufacturing processes.

[0004] Physically, the essence of partial discharge is the violent release of charges caused by electric field distortion. When the etched area between the metal conductive circuit and the ceramic substrate is exposed, an interface with a sudden change in dielectric constant is formed between aluminum nitride with a high dielectric constant (dielectric constant ε≈8.8) and air (ε≈1), resulting in a high concentration of the electric field at the edge of the etched groove. Especially when the voltage rises above 10 kV, the edge electric field strength can exceed 30% of the intrinsic breakdown field strength of aluminum nitride, triggering an electron avalanche effect. In addition, the stepped etching profile of the metal cladding (such as insufficient sidewall inclination angle) will further exacerbate the tip discharge phenomenon, forming an initial channel for partial discharge.

[0005] From the perspective of material microdefects, the surface of aluminum nitride ceramic substrates exposed after etching is not ideally smooth and homogeneous. Chemical corrosion or plasma bombardment during the etching process can introduce submicron pits, grain boundary microcracks, and nitrogen vacancy defects into the ceramic surface. These defects lead to uneven surface charge mobility and, under the action of high electric fields, form regions of heterogeneous conductivity. Furthermore, the covalent nature of aluminum nitride makes it difficult for its surface dangling bonds to spontaneously passivate. These active sites readily adsorb and ionize water molecules from the environment, triggering a chain reaction of electrochemical corrosion. Experiments have shown that at a voltage of 10.5 kV, the local current density in such defective regions can be 2-3 orders of magnitude higher than that in normal areas, becoming a precursor to discharge breakdown.

[0006] The limitations of existing surface treatment processes further exacerbate these issues. Current mainstream surface modification technologies include pickling and activation, anodizing, and vapor deposition coating. While pickling processes (such as hydrochloric acid or phosphoric acid treatment) can remove surface contaminants and form a rough aluminum oxide layer, the resulting oxide layer is often amorphous with a porosity exceeding 20%. Its insulation properties plummet after absorbing moisture in high humidity environments. Anodizing can produce a dense Al2O3 film on ceramic surfaces, but this process requires the application of hundreds of volts of DC voltage, making it difficult to uniformly deposit the film on substrates with complex patterned circuits. This leads to interfacial stress accumulation during thermal cycling, ultimately causing cracking and delamination of the film. While vapor deposition (such as ALD deposition of Al2O3) can achieve nanometer-scale thickness control, it is expensive, has low production rates, and lacks adhesion to the copper layer, making it unable to withstand the high-temperature soldering stresses of the packaging process.

[0007] Some improvements attempt to enhance performance through composite coating designs. For example, a sol-gel method is used to prepare a SiO2 / Al2O3 hybrid coating on the ceramic surface to balance dielectric properties and mechanical strength. However, volume shrinkage during the sol drying process can lead to the formation of a microcrack network. Other studies have proposed the introduction of a fluorocarbon resin coating to reduce surface charge affinity, but the resin has poor thermal stability (long-term operating temperature <200°C) and cannot meet the heat dissipation requirements of power modules. For applications requiring higher voltage levels, achieving deep control of surface charge dynamics in the etched area without sacrificing thermal conductivity remains a technical bottleneck that the industry urgently needs to overcome. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings of the aluminum nitride copper-clad ceramic lining in the prior art, such as the lack of resistance to high voltage and the susceptibility to discharge in local areas. Therefore, an aluminum nitride copper-clad ceramic lining for suppressing local discharge and its preparation method and application are provided to overcome the above shortcomings.

[0009] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions:

[0010] In a first aspect, the present invention first provides an aluminum nitride copper-clad ceramic substrate for suppressing partial discharge,

[0011] comprising an aluminum nitride ceramic substrate and a metal conductive layer compounded on the surface of the substrate,

[0012] the metal conductive layer is formed into interconnected conductive lines through patterning etching, and an etching gap exposing the aluminum nitride ceramic substrate is formed between the interconnected conductive lines;

[0013] the surface of the aluminum nitride ceramic substrate at the etching gap is covered with a functional oxide layer;

[0014] the functional oxide layer comprises a porous matrix with nanoscale Al2O3 particles as the main phase and a silicon-aluminum oxide network structure embedded inside the porous matrix.

[0015] As clearly pointed out in the background art, when the working voltage is increased to more than 10 kV, the core contradiction of the sharp increase in the partial discharge of the existing substrate comes from the mutual coupling of two levels: one is the electric field distortion and charge accumulation caused by the sudden change of the dielectric constant in the etching gap area; the other is the conductivity heterogeneity caused by the surface defects of the material itself. Traditional surface treatment technologies such as pickling activation, anodic oxidation, and vapor deposition all belong to the "post-remedial type" in terms of their improvement logic, that is, they attempt to cover or repair the defects introduced by etching processing in the material surface treatment link, but the common limitation of these methods is that they do not fundamentally change the interfacial dielectric response characteristics of the etching area. The innovation origin of the aluminum nitride copper-clad ceramic substrate for suppressing partial discharge provided in this application precisely breaks this one-way repair thinking and instead starts from the intrinsic properties of the aluminum nitride ceramic substrate, transforming its surface defects into the starting point of functional regulation through process reconstruction.

[0016] Specifically, the functional oxide layer (porous matrix with nanoscale Al2O3 as the main phase + silicon-aluminum oxide network) generated in the middle of the etching gap in this application is not simply a coating coverage, but realizes the directional release, transport, and reconstruction of aluminum elements on the aluminum nitride surface layer, thereby finally forming a gradient interface structure matching the crystal orientation of the matrix.

[0017] More specifically, this application first converts the surface defects (such as grain boundary microcracks and nitrogen vacancy defects) that originally caused charge accumulation into preferential channels for aluminum ion migration through chemical treatment, enabling the oxide layer to have self-healing properties during the formation process; secondly, the three-dimensional interpenetration of the silicon-aluminum oxide network in the porous matrix changes the response mode of the aluminum nitride surface layer to the electric field. In the traditional process, the surface oxide layer only serves as a passive barrier layer, while the composite structure of this solution actively guides the charge distribution through the space polarization effect on the inner wall of the pores, effectively weakening the electric field gradient difference at the dielectric interface.

[0018] In the functional oxide layer, the nanoscale size of Al2O3 particles matches the lattice parameters of aluminum nitride. This lattice coupling makes the oxide layer naturally compatible with the substrate in terms of thermal expansion behavior, avoiding the cracking and spalling problems of the anodic oxide layer caused by crystal orientation mismatch. Secondly, in terms of dielectric response regulation, a multi-scale composite structure is creatively introduced to achieve dynamic charge management. Traditional solutions attempt to block charge migration by reducing surface conductivity, but the polarization effect under high-voltage electric fields still causes charge accumulation under the insulating layer. The porous substrate and the silicon-aluminum network structure in this solution actually provide a directional dissipation path for charges, that is, a micro-capacitor array is formed through the nanoscale pores of the porous substrate to absorb transient charges through the plate effect; while the continuous silicon-aluminum oxide network in the pores forms a low-impedance channel to slowly release the accumulated charges. This mechanism successfully solves the dilemma of "incompatibility between dielectric insulation and charge dissipation" in the background technology, achieving an order-of-magnitude reduction in the partial discharge amount while maintaining a high volume resistivity (as shown by the data in the examples, the PD value after treatment is still below 1.5 pC at 12 kV).

[0019] In addition, in the prior art, there is also a solution of first depositing an alumina layer and then copper plating. Although this method can theoretically form an insulating layer between the aluminum nitride substrate and the copper layer, this architecture has multiple inherent defects: First, the low thermal conductivity of the alumina layer significantly weakens the heat dissipation ability of the aluminum nitride substrate, forming a thermal management bottleneck. Although the theoretical thermal conductivity of aluminum nitride can reach 200 W / m·K, in this traditional sandwich structure, the vast majority of the heat needs to be conducted through the alumina layer to the copper layer, which means that the heat dissipation efficiency will decrease significantly. In this application, the aluminum nitride layer is directly in contact with the metal copper layer, so there is no heat blocking effect of the functional oxide layer. The oxide layer in the etched gap is directly formed by the transformation of the aluminum nitride surface layer. The Al2O3 particles in its porous structure are dispersed at the nanoscale and maintain lattice continuity with the matrix. Combining the advantages of interface lattice matching that does not exist in chemical vapor deposition, the effective thermal conductivity of the oxide layer can be significantly improved, maximizing the retention of the high thermal conductivity characteristics of aluminum nitride. Second, the outer alumina layer faces the fatal defect of interface stress mismatch. The thermal expansion coefficient of alumina is significantly different from that of aluminum nitride and the copper layer. Under the start-stop conditions of the power module, repeated thermal cycling causes the alumina layer to bear huge shear stress. When the stress exceeds the film layer bonding strength, interface peeling or even substrate cracking occurs. The core mechanism of this solution avoids this interface contradiction: the in-situ formed functional oxide layer has an atomic-level transition interface with the matrix aluminum nitride, and its thermal expansion coefficient can be adjusted by doping the silicon-aluminum network, making its difference from aluminum nitride much smaller than that of alumina. At the same time, with the stress buffering effect of the nanoscale pores, the overall interface bonding strength is significantly improved. More importantly, although the dense alumina layer in the existing alumina deposition solution can block charge migration, a polarization electric double layer will be formed at the interface between the insulating layer and aluminum nitride under high-voltage electric fields. Therefore, when the voltage exceeds the critical value, the accumulation of polarized charges triggers dielectric breakdown, which is the deep reason for the out-of-control high-voltage PD value in the background technology. Through the design of the porous composite structure in this application, the polarized charges are dissipated in a gradient manner through the three-dimensional network in the pores. This is equivalent to installing a "pressure regulating valve" at the charge accumulation end: when the electric field strength increases, the conductive path of the silicon-aluminum network is activated, and the charge dissipation rate is positively correlated with the field strength, thus breaking the vicious cycle of "accumulation → breakdown" of the traditional insulating layer under high field strength.

[0020] Therefore, compared with the existing solutions in the background technology, this application not only realizes the synergistic optimization of interface performance in the specific oxide layer components and morphology (such as the synergy of nano-Al2O3 and the silicon-aluminum network), but also redefines the dielectric thermodynamics behavior of the material system through the in-situ transformed functional layer (neither a purely dissipative structure, such as a conductive coating; nor a passive blocking structure, such as a traditional oxide layer), but a composite dielectric with field-strength controlled intelligent response. This innovation enables the product to exhibit improved stability under high-voltage conditions, creating a new paradigm for the performance improvement of high-voltage ceramic liners.

[0021] Preferably, the surface roughness Sa of the functional oxide layer is ≤ 0.24 μm, and the roughness Sz is ≤ 4.5 μm.

[0022] In a second aspect, a method for suppressing partial discharge of an aluminum nitride copper-clad ceramic substrate includes the following steps:

[0023] (S.1) Etch the aluminum nitride copper-clad ceramic substrate without pattern transfer to obtain interconnecting conductive lines and etching gaps that completely expose the aluminum nitride ceramic plate between the interconnecting conductive lines;

[0024] (S.2) Perform a film coating treatment on the surface of the interconnecting conductive lines, and in-situ activate the exposed aluminum nitride ceramic plate at the etching gap under alkaline conditions to form a hydrophilic reaction interface with a rough structure on the surface of the aluminum nitride ceramic plate;

[0025] (S.3) Place the hydrophilic reaction interface with a rough structure in an acidic environment so that aluminum ions on the surface of the aluminum nitride ceramic plate are released and enriched on its surface;

[0026] (S.4) Generate a uniform passivation layer containing aluminum oxide, aluminum silicate, and organoaluminum complex on the surface of the aluminum nitride ceramic plate through the synergistic action of aluminum ions with silicate and organic ligands;

[0027] (S.5) Perform high-temperature heat treatment on the substrate in a protective atmosphere to convert the passivation layer into a dense composite oxide layer capable of suppressing charge accumulation, thereby obtaining the aluminum nitride copper-clad ceramic substrate for suppressing partial discharge.

[0028] The process flow of this method for suppressing partial discharge of the aluminum nitride copper-clad ceramic substrate in this application has significant creativity compared with traditional surface treatment methods. Its fundamental breakthrough lies in constructing an in-situ construction route of the functional layer based on the intrinsic reaction path of the material, rather than simply surface coating or mechanical improvement.

[0029] As highlighted in the background art, the core defect of preparing a composite coating by the sol-gel method lies in the formation of a microcrack network caused by drying shrinkage. This fundamental problem stems from the sudden volume change of the solution precursor during the curing process and the mismatch of the thermodynamic behavior of the matrix material. And this method dynamically correlates the growth of the oxide layer with the response of the matrix structure through staged chemical and thermodynamic regulation to form an adaptive gradient interface system.

[0030] Specifically, the in-situ alkaline activation in step (S.2) is not simply a surface roughening treatment. Instead, a transition layer of amorphous alumina rich in reactive hydroxyl groups is formed on the surface of aluminum nitride through topochemical etching of hydroxides. This transition layer has a dual-functional role: First, it provides a reaction path for the controllable release of aluminum ions in the subsequent acidic environment; Second, the nanoscale pore array (rough structure) formed on its surface becomes the preferential channel for the penetration of silicate and organic ligands, which fundamentally differentiates from the thin-film epitaxial growth mode of the sol-gel method.

[0031] In the acidic treatment of step (S.3), the aluminum element in the activation layer is released in the form of a hydrolysis reaction, rather than the over-etching of traditional pickling processes. The key to controlling this process lies in the enrichment of aluminum ions on its surface rather than a large amount of loss. Its regulation mechanism depends on the precise balance of the mixed acid solution, enabling the release rate of aluminum ions to form a dynamic equilibrium with the formation of silicate precipitation in step (S.4). When silicate and organic ligands (such as ammonium citrate) enter the reaction system, the carboxyl groups of the ligands form a multi-dentate coordination structure with aluminum ions. This synergistic effect breaks the multi-phase coexistence state with only physical mixing in the traditional sol-gel method and instead forms an organic-inorganic hybrid structure based on a chemical bonding network.

[0032] This intermediate undergoes ordered decarboxylation and crystallization transformation during the high-temperature heat treatment in step (S.5). In the finally formed composite oxide layer, alumina particles are connected to the silicon-aluminum network through oxygen bridges, and the remaining organic carbon skeleton is embedded in the pores in the form of nano-carbon chains to form conductive microchannels. This structural feature exhibits unique advantages at the dielectric response level: When the externally applied electric field strength exceeds the critical value, the microchannels guide the directional migration of charges to the substrate, avoiding the accumulation of charges on the surface of the oxide layer. At the same time, the semiconductor properties of the carbon network enable the current to be released in a non-avalanche mode, which directly solves the pain point of the sudden breakdown of the sol-gel coating in the background technology under high field strength.

[0033] In addition, another significant and creative improvement of this method compared with the sol-gel method lies in the essential difference in the management of material interface stress: the shrinkage stress of the sol-gel coating stems from the volume mutation during the transformation from liquid to solid, while in this process, through staged reaction control (such as pre-forming a chemical cross-linking network in the passivation layer before high-temperature heat treatment), the stress can be released through the three-dimensional interpenetrating structure of the silicon-aluminum network when the oxide layer shrinks during sintering. At the microscopic morphology level, the SiO2 / Al2O3 hybrid coating formed by the sol-gel method often exhibits a disordered glassy structure, while the composite oxide layer prepared by this method forms a duplex structure with nano-Al2O3 grains embedded in an amorphous silicon-aluminum matrix through a directional crystallization process. This multi-scale arrangement significantly enhances the anti-cyclic fatigue performance of the coating. More importantly, the compatibility of the entire process chain with the existing production line reflects the creative design concept: steps (S.2)-(S.5) can all be completed using conventional wet processing equipment, without the need to introduce vacuum equipment or high-energy beam devices, and the thickness of the oxide layer can be controlled at the nanoscale by adjusting the concentration of the treatment solution, which is in sharp contrast to the high operation complexity of the sol-gel method that requires precise adjustment in multiple links such as spin coating and sintering. At the functional orientation level, the traditional method only makes a single breakthrough in the dimension of improving surface insulation, while this method constructs multi-level protection starting from charge dynamics regulation, that is: the rough interface reduces the field strength concentration coefficient, the silicon-aluminum network balances the dielectric constant gradient, and the carbon skeleton guides the orderly migration of charges. The three steps work together to enable the treated sample to maintain a low PC-level discharge level during the 12 kV-level test.

[0034] Preferably, in step (S.2), the alkaline condition is provided by an alkali solution with a concentration of 5-20%, the in-situ activation temperature is 50-60 °C, and the in-situ activation time is 5-30 min.

[0035] Preferably, the alkali is one or a combination of sodium hydroxide, potassium hydroxide, sodium ethoxide, and tetramethylammonium hydroxide.

[0036] Preferably, the acidic environment in step (S.3) is provided by a mixed acid solution containing an aluminum salt;

[0037] The mixed acid solution contains nitric acid and hydrochloric acid. The nitric acid accounts for 3-10% of the total volume of the mixed acid solution, the hydrochloric acid accounts for 8-12% of the total volume of the mixed acid solution, and the aluminum salt accounts for 10-30% of the total mass of the mixed acid solution, with the balance being water;

[0038] In step (S.3), the treatment temperature is 30-50 °C, and the treatment time is 5-30 min.

[0039] Preferably, the aluminum salt is any one of aluminum nitrate, aluminum chloride, and aluminum sulfate.

[0040] Preferably, the step (S.4) is carried out in a reaction solution containing silicate, sodium citrate and ammonia water, and the reaction temperature is 40-50 °C and the treatment time is 15-30 min;

[0041] The silicate is any one of sodium silicate and potassium silicate, and its addition amount is 25-35% of the total mass of the reaction solution;

[0042] The addition amount of sodium citrate is 15-25% of the total mass of the reaction solution;

[0043] The addition amount of ammonia water is 5-20% of the total volume of the reaction solution;

[0044] The chemical treatment temperature is 40-50 °C and the treatment time is 15-30 min.

[0045] Preferably, the heat treatment in the step (S.4) is carried out in a nitrogen-oxygen mixed atmosphere, and the oxygen content is 500-2000 ppm.

[0046] Preferably, the heat treatment time in the step (S.4) is 20-40 min, and the heat treatment temperature is 800-850 °C.

[0047] In a third aspect, the present application also provides an application of the aluminum nitride copper-clad ceramic substrate for suppressing partial discharge in a high-power insulated gate bipolar transistor, a silicon carbide module, and an intelligent power module.

[0048] Therefore, the present application has the following beneficial effects compared with the prior art:

[0049] In the present application, a functional oxide layer is formed on the surface of the aluminum nitride ceramic substrate between the interconnection conductive lines on the aluminum nitride copper-clad ceramic substrate, thereby suppressing the accumulation of charges, making the electric field distribution on the surface of the aluminum nitride ceramic more uniform, and achieving the purpose of improving the partial discharge of the aluminum nitride copper-clad ceramic substrate under high voltage. Description of the Drawings

[0050] Figure 1 is a flowchart of the present application.

[0051] Figure 2 is a topographic photo of the unprocessed etching gap.

[0052] Figure 3 is a SEM photo of the unprocessed etching gap.

[0053] Figure 4 is a topographic photo of the functional oxide layer obtained after treatment.

[0054] Figure 5 is a SEM photo of the functional oxide layer obtained after treatment.

[0055] Figure 6 It is an enlarged electron microscope photograph of the functional oxide layer obtained after processing. Specific Embodiments

[0056] The present invention will be further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0057] Embodiment 1

[0058] A method for suppressing partial discharge of an aluminum nitride copper-clad ceramic substrate, as Figure 1 shown, includes the following steps:

[0059] (S.1) Etch the aluminum nitride copper-clad ceramic substrate without pattern transfer to obtain interconnecting conductive lines and etching gaps that completely expose the aluminum nitride ceramic plate between the interconnecting conductive lines. At this time, the topographic photograph and electron microscope photograph of the etching gap are respectively as Figure 2 and Figure 3 shown.

[0060] (S.2) Perform a film coating treatment on the surface of the interconnecting conductive lines, and place the film-coated aluminum nitride copper-clad ceramic substrate in a potassium hydroxide solution with a concentration of 10% to in-situ activate the exposed aluminum nitride ceramic plate at the etching gap for 20 minutes at 55 °C, so as to form a hydrophilic reaction interface with a rough structure on the surface of the aluminum nitride ceramic plate, and then clean the hydrophilic reaction interface.

[0061] (S.3) Place the hydrophilic reaction interface with a rough structure in a mixed acid solution containing aluminum nitrate to provide an acidic environment, and treat it at 40 °C for 20 minutes to release and enrich aluminum ions on the surface of the aluminum nitride ceramic plate;

[0062] Among them, the mixed acid solution contains nitric acid and hydrochloric acid. The nitric acid accounts for 5% of the total volume of the mixed acid solution, the hydrochloric acid accounts for 10% of the total volume of the mixed acid solution, the aluminum salt accounts for 20% of the total mass of the mixed acid solution, and the balance is water. After the treatment, it is washed with water.

[0063] (S.4) Immerse the surface of the aluminum nitride ceramic plate into a reaction solution containing sodium silicate, sodium citrate, and ammonia water, and treat it at 45 °C for 20 min, so that aluminum ions generate a uniform passivation layer containing alumina, aluminum silicate, and organoaluminum complex through the synergistic effect with sodium citrate and ammonia water. Subsequently, wash the uniform passivation layer with clear water and then with hot water at 55 °C in sequence, and dry it after the washing is completed; wherein,

[0064] The addition amount of the sodium silicate is 30% of the total mass of the reaction solution;

[0065] The addition amount of the sodium citrate is 20% of the total mass of the reaction solution;

[0066] The addition amount of the ammonia water is 10% of the total volume of the reaction solution.

[0067] (S.5) Perform high-temperature heat treatment on the lining plate in a nitrogen-oxygen mixed atmosphere. The oxygen content in the nitrogen-oxygen mixed atmosphere is 1000 ppm, the heat treatment temperature is 820 °C, and the heat treatment time is 30 min, so as to convert the passivation layer into a dense functional oxide layer capable of inhibiting charge accumulation, and finally obtain an aluminum nitride copper-clad ceramic lining plate capable of inhibiting partial discharge. Among them, the morphology photo of the functional oxide layer is as Figure 4 shown, and the electron microscope photos of the functional oxide layer at different magnification ratios are as Figure 5 and Figure 6 shown.

[0068] Example 2

[0069] A method for inhibiting partial discharge of an aluminum nitride copper-clad ceramic lining plate, as Figure 1 shown, which includes the following steps:

[0070] (S.1) Perform etching treatment on the aluminum nitride copper-clad ceramic lining plate without pattern transfer, so as to obtain interconnected conductive lines and etching gaps that completely expose the aluminum nitride ceramic plate between the interconnected conductive lines.

[0071] (S.2) Perform film coating treatment on the surface of the interconnected conductive lines, and place the aluminum nitride copper-clad ceramic lining plate after film coating in a potassium hydroxide solution with a concentration of 5%, so that the aluminum nitride ceramic plate exposed at the etching gap is in-situ activated at 60 °C for 30 min, thereby forming a hydrophilic reaction interface with a rough structure on the surface of the aluminum nitride ceramic plate, and then wash the hydrophilic reaction interface.

[0072] (S.3) Place the hydrophilic reaction interface with a rough structure in a mixed acid solution containing aluminum nitrate to provide an acidic environment, and treat it at 30 °C for 30 min, so that the aluminum ions on the surface of the aluminum nitride ceramic plate are released and enriched on its surface;

[0073] Among them, the mixed acid solution contains nitric acid and hydrochloric acid. The nitric acid accounts for 3% of the total volume of the mixed acid solution, the hydrochloric acid accounts for 12% of the total volume of the mixed acid solution, the aluminum salt accounts for 10% of the total mass of the mixed acid solution, and the balance is water. After the treatment, it is washed with water.

[0074] (S.4) Immerse the surface of the aluminum nitride ceramic plate into a reaction solution containing sodium silicate, sodium citrate, and ammonia water, and treat it at 40 °C for 30 min, so that aluminum ions generate a uniform passivation layer containing aluminum oxide, aluminum silicate, and organic aluminum complex through the synergistic effect of sodium citrate and ammonia water. Subsequently, wash the uniform passivation layer with hot water at 60 °C, and dry it after the washing is completed; among them,

[0075] The addition amount of the (sodium silicate, potassium silicate) is 25% of the total mass of the reaction solution;

[0076] The addition amount of sodium citrate is 15% of the total mass of the reaction solution;

[0077] The addition amount of the ammonia water is 5% of the total volume of the reaction solution, and the balance is water.

[0078] (S.5) Perform high-temperature heat treatment on the liner plate in a nitrogen-oxygen mixed atmosphere. The oxygen content in the nitrogen-oxygen mixed atmosphere is 500 ppm, the heat treatment temperature is 850 °C, and the heat treatment time is 40 min, so as to convert the passivation layer into a dense functional oxide layer that can inhibit charge accumulation, and finally obtain an aluminum nitride copper-clad ceramic liner plate that can inhibit partial discharge.

[0079] Example 3

[0080] A method for inhibiting partial discharge of an aluminum nitride copper-clad ceramic liner plate, as Figure 1 shown, which includes the following steps:

[0081] (S.1) Perform etching treatment on the aluminum nitride copper-clad ceramic liner plate without pattern transfer, so as to obtain interconnected conductive lines and etching gaps that completely expose the aluminum nitride ceramic plate between the interconnected conductive lines.

[0082] (S.2) Perform film covering treatment on the surface of the interconnected conductive lines, and place the aluminum nitride copper-clad ceramic liner plate after film covering in a sodium hydroxide solution with a concentration of 5-20%, so that the aluminum nitride ceramic plate exposed at the etching gap is in-situ activated at 60 °C for 5 min, so as to form a hydrophilic reaction interface with a rough structure on the surface of the aluminum nitride ceramic plate. Subsequently, wash the hydrophilic reaction interface.

[0083] (S.3) Place the hydrophilic reaction interface with a rough structure in a mixed acid solution containing aluminum chloride to provide an acidic environment, and at 50 °C, treat it for 5 min, so that the aluminum ions on the surface of the aluminum nitride ceramic plate are released and enriched on its surface;

[0084] Among them, the mixed acid solution contains nitric acid and hydrochloric acid. The nitric acid accounts for 10% of the total volume of the mixed acid solution, the hydrochloric acid accounts for 8% of the total volume of the mixed acid solution, the aluminum salt accounts for 30% of the total mass of the mixed acid solution, and the balance is water. After the treatment, it is washed with water.

[0085] (S.4)Immerse the surface of the aluminum nitride ceramic plate into a reaction solution containing potassium silicate, sodium citrate, and ammonia water, and treat it at 50 °C for 15 min, so that aluminum ions generate a uniform passivation layer containing alumina, aluminum silicate, and organic aluminum complex through the synergistic effect of sodium citrate and ammonia water. Subsequently, the uniform passivation layer is washed with hot water at 50 °C, and dried after the washing is completed; among them,

[0086] The addition amount of the potassium silicate is 35% of the total mass of the reaction solution;

[0087] The addition amount of the sodium citrate is 25% of the total mass of the reaction solution;

[0088] The addition amount of the ammonia water is 20% of the total volume of the reaction solution, and the balance is water.

[0089] (S.5)Perform high-temperature heat treatment on the liner in a nitrogen-oxygen mixed atmosphere. The oxygen content in the nitrogen-oxygen mixed atmosphere is 2000 ppm, the heat treatment temperature is 850 °C, and the heat treatment time is 20 min, so as to convert the passivation layer into a dense functional oxide layer that can inhibit charge accumulation, and finally obtain an aluminum nitride copper-clad ceramic liner that can inhibit partial discharge.

[0090] Example 4

[0091] A method for inhibiting partial discharge of an aluminum nitride copper-clad ceramic liner, as Figure 1 shown, which includes the following steps:

[0092] (S.1)Etch the aluminum nitride copper-clad ceramic liner without pattern transfer to obtain interconnected conductive lines and etching gaps that completely expose the aluminum nitride ceramic plate between the interconnected conductive lines.

[0093] (S.2)Perform a film coating treatment on the surface of the interconnected conductive lines, and place the aluminum nitride copper-clad ceramic liner after film coating in a potassium hydroxide solution with a concentration of 8%, so that the aluminum nitride ceramic plate exposed at the etching gap is in-situ activated at 58 °C for 15 min, thereby forming a hydrophilic reaction interface with a rough structure on the surface of the aluminum nitride ceramic plate, and then washing the hydrophilic reaction interface.

[0094] (S.3) Place the hydrophilic reaction interface with a rough structure in a mixed acid solution containing aluminum sulfate to provide an acidic environment, and treat it at 35 °C for 25 min, so that the aluminum ions on the surface of the aluminum nitride ceramic plate are released and enriched on its surface;

[0095] Among them, the mixed acid solution contains nitric acid and hydrochloric acid. The nitric acid accounts for 8% of the total volume of the mixed acid solution, the hydrochloric acid accounts for 10% of the total volume of the mixed acid solution, the aluminum salt accounts for 15% of the total mass of the mixed acid solution, and the balance is water. After the treatment, wash with water.

[0096] (S.4) Immerse the surface of the aluminum nitride ceramic plate into a reaction solution containing sodium silicate, sodium citrate and ammonia water, and treat it at 45 °C for 25 min, so that the aluminum ions generate a uniform passivation layer containing aluminum oxide, aluminum silicate and organic aluminum complex through the synergistic effect of sodium citrate and ammonia water. Subsequently, wash the uniform passivation layer with hot water at 60 °C, and dry it after the washing; among them,

[0097] The addition amount of the sodium silicate is 30% of the total mass of the reaction solution;

[0098] The addition amount of the sodium citrate is 16% of the total mass of the reaction solution;

[0099] The addition amount of the ammonia water is 14% of the total volume of the reaction solution, and the balance is water.

[0100] (S.5) Perform high-temperature heat treatment on the liner plate in a nitrogen-oxygen mixed atmosphere. The oxygen content in the nitrogen-oxygen mixed atmosphere is 1500 ppm, the heat treatment temperature is 820 °C, and the heat treatment time is 35 min, so as to convert the passivation layer into a dense functional oxide layer capable of suppressing charge accumulation, and finally obtain an aluminum nitride copper-clad ceramic liner plate capable of suppressing partial discharge.

[0101] Example 5

[0102] A method for suppressing partial discharge of an aluminum nitride copper-clad ceramic liner plate, as Figure 1 shown, which includes the following steps:

[0103] (S.1) Etch the aluminum nitride copper-clad ceramic liner plate without pattern transfer to obtain interconnecting conductive lines and etching gaps that completely expose the aluminum nitride ceramic plate between the interconnecting conductive lines.

[0104] (S.2) Perform a film coating treatment on the surface of the interconnecting conductive lines, and place the aluminum nitride copper-clad ceramic liner plate after film coating in a potassium hydroxide solution with a concentration of 15%, so that the aluminum nitride ceramic plate exposed at the etching gap is in-situ activated at 50 °C for 20 min, so as to form a hydrophilic reaction interface with a rough structure on the surface of the aluminum nitride ceramic plate, and then wash the hydrophilic reaction interface.

[0105] (S.3) Place the hydrophilic reaction interface with a rough structure in a mixed acid solution containing aluminum nitrate to provide an acidic environment, and treat it at 40 °C for 15 min, so that aluminum ions on the surface of the aluminum nitride ceramic plate are released and enriched on its surface;

[0106] Among them, the mixed acid solution contains nitric acid and hydrochloric acid. The nitric acid accounts for 6% of the total volume of the mixed acid solution, the hydrochloric acid accounts for 10% of the total volume of the mixed acid solution, and the aluminum nitrate accounts for 15% of the total mass of the mixed acid solution. The balance is water. After the treatment, wash it with water.

[0107] (S.4) Immerse the surface of the aluminum nitride ceramic plate into a reaction solution containing sodium silicate, sodium citrate and ammonia water, and treat it at 50 °C for 25 min, so that aluminum ions generate a uniform passivation layer containing aluminum oxide, aluminum silicate and organic aluminum complex through the synergistic action of sodium citrate and ammonia water. Subsequently, wash the uniform passivation layer with hot water at 60 °C, and dry it after the washing; Among them,

[0108] The addition amount of the sodium silicate is 28% of the total mass of the reaction solution;

[0109] The addition amount of the sodium citrate is 20% of the total mass of the reaction solution;

[0110] The addition amount of the ammonia water is 12% of the total volume of the reaction solution, and the balance is water.

[0111] (S.5) Perform high-temperature heat treatment on the lining plate in a nitrogen-oxygen mixed atmosphere. The oxygen content in the nitrogen-oxygen mixed atmosphere is 1800 ppm, the heat treatment temperature is 820 °C, and the heat treatment time is 30 min, so as to convert the passivation layer into a dense functional oxide layer capable of inhibiting charge accumulation, and finally obtain an aluminum nitride copper-clad ceramic lining plate capable of inhibiting partial discharge.

[0112] Comparative Example 1

[0113] The difference between Comparative Example 1 and Example 1 is that steps (S.2)-(S.5) are not carried out.

[0114] Comparative Example 2

[0115] The difference between Comparative Example 2 and Example 1 is that step (S.2) is not carried out, and the other conditions are the same.

[0116] Comparative Example 3

[0117] The difference between Comparative Example 3 and Example 1 is that the reaction solution in step (S.4) only contains ammonia water, without sodium silicate and sodium citrate, so that only an aluminum oxide layer is formed in the etching gap, and the other conditions are the same.

[0118] Comparative Example 4

[0119] The difference between Comparative Example 4 and Example 1 is that step (S.3) is cancelled, and the reaction solution in step (S.4) only contains sodium silicate, so that only a layer of silicon dioxide layer is formed in the etched gap, and the other conditions are the same.

[0120] Comparative Example 5

[0121] The difference between Comparative Example 5 and Example 1 is that step (S.5) is cancelled, and the other conditions are the same.

[0122] The aluminum nitride copper-clad ceramic substrates prepared in Example 1 and Comparative Example 1 were taken respectively, and the roughness of their etched gaps was measured. The test results are shown in Table 1 below.

[0123] Table 1

[0124] ITEM Comparative Example 1 Roughness Sa (μm) Example 1 Roughness Sa (μm) Comparative Example 1 Roughness Sz (μm) Example 1 Roughness Sz (μm) Point 1 0.227 0.224 7.468 4.470 Point 2 0.219 0.239 2.884 4.494 Point 3 0.204 0.204 3.516 3.748 Point 4 0.212 0.197 3.037 2.626 Point 5 0.210 0.199 2.973 3.311 Point 6 0.184 0.212 3.165 2.710 Point 7 0.169 0.173 2.734 3.369 Point 8 0.166 0.210 2.908 3.613 Point 9 0.151 0.180 2.219 2.990 Point 10 0.244 0.197 2.953 10.624 Mean 0.199 0.203 3.386 4.195

[0125] Subsequently, 50 aluminum nitride copper-clad ceramic substrates prepared in Example 1 and Comparative Example 1 were taken respectively, and they were successively subjected to partial discharge tests at voltages of 7 kV, 8.3 kV, 10.5 kV, and 12 kV. The test results are shown in Table 2 below:

[0126] Table 2

[0127] ITEM Comparative Example 1 7KV Measurement 1st Time (pC) Comparative Example 1 7KV Measurement 2nd Time (pC) Comparative Example 1 8.3KV Measurement 1st Time (pC) Comparative Example 1 8.3KV Measurement 2nd Time (pC) Comparative Example 1 10.5KV Measurement 1st Time (pC) Comparative Example 1 10.5KV Measurement 2nd Time (pC) Comparative Example 1 12KV Measurement 1st Time (pC) Example 1 7KV Measurement 1st Time (pC) Example 1 7KV Measurement 2nd Time (pC) Example 1 8.3KV Measurement 1st Time (pC) Example 1 8.3KV Measurement 2nd Time (pC) Example 1 10.5KV Measurement 1st Time (pC) Example 1 10.5KV Measurement 2nd Time (pC) Example 1 12KV Measurement 1st Time (pC) The 1st one 0.9 0.9 1.1 1.8 211.9 110.1 693 0.7 0.7 0.7 0.7 0.7 0.7 0.7 The 2nd one 1.8 1.1 1 1.1 559.5 138.3 753.3 0.8 0.7 0.7 0.7 0.8 0.7 0.7 The 3rd one 0.9 0.9 1 0.8 149.5 196.5 450.7 0.9 0.7 0.7 0.8 0.6 0.7 0.7 The 4th one 0.9 0.9 0.9 0.9 178.7 38.7 949 0.7 0.7 0.7 0.7 0.7 0.7 0.8 The 5th one 0.9 0.9 3.6 0.9 96.6 136.8 536.9 0.7 0.7 0.7 0.7 0.8 0.7 0.7 The 6th one 1 1.1 1 1 137 50.5 465.5 0.6 0.7 0.7 0.7 0.8 0.7 0.7 The 7th one 0.9 0.9 0.9 0.9 325.5 51.5 441 0.7 0.7 0.7 0.7 0.7 0.7 0.7 The 8th one 1.1 1.2 0.9 0.8 76.9 60 888.3 0.7 1.2 0.8 0.7 0.6 0.7 0.6 The 9th one 1.5 1.3 1.3 1 109.1 31.9 1017.3 1.2 0.8 0.7 0.7 0.7 0.8 0.7 The 10th one 1 1.3 4.4 3.2 238.8 88.9 1693.5 0.7 0.7 0.7 0.7 0.7 0.7 0.7 The 11th one 1.1 1 0.9 0.9 268.3 53.9 531.8 0.7 0.7 0.7 0.7 0.7 0.6 0.8 The 12th one 0.9 1 0.9 1 4 26.2 338.2 0.7 0.7 0.7 0.7 0.7 0.7 0.7 The 13th one 0.9 1.1 1 2 193.3 5.5 693.9 0.7 1.8 0.7 0.7 0.7 0.7 0.7 The 14th one 0.9 1.1 1.2 1 28 21 635.5 0.8 1.0 0.7 0.7 0.7 0.7 0.7 The 15th one 1.2 1.2 1 0.9 61 97.8 435.3 0.7 0.7 0.7 1.1 0.7 0.9 0.7 The 16th one 0.9 1 0.9 1 205.4 0.9 605.8 0.7 1.2 0.7 0.7 0.8 0.7 0.6 The 17th one 1.1 0.9 0.9 1 2.6 30.4 402.5 0.7 0.9 0.8 0.7 0.8 1.2 0.7 The 18th one 1 0.9 1 1 11.7 37 420.8 0.7 0.8 0.7 0.7 0.6 0.8 0.6 The 19th one 1 0.9 3.2 1 27.1 7 374.5 0.7 0.7 0.7 0.8 0.7 0.7 0.6 The 20th one 1.6 0.9 3.4 47.2 242 169.4 653.3 0.7 0.8 0.7 0.6 0.7 0.9 0.7 The 21st one 1 0.9 10.6 0.8 94.9 157 830.6 0.7 0.9 0.7 0.8 0.7 0.9 0.7 The 22nd one 0.8 0.8 1.4 1.6 82.7 40.4 452.5 0.9 0.7 0.9 1.0 0.8 0.9 0.6 The 23rd one 0.9 0.8 1.7 0.9 156.6 111.6 610 0.7 0.6 0.7 0.9 0.9 0.9 0.7 The 24th one 0.9 0.8 0.8 2.5 130.8 14.5 544 0.8 0.7 1.0 1.5 0.7 0.9 0.6 The 25th one 1 1.6 4.8 9.5 135 101 499.8 0.7 0.7 0.7 1.2 0.8 0.9 0.8 The 26th one 3.7 0.9 2.6 0.9 190.7 45.5 468.5 1.1 1.0 0.9 0.9 0.9 1.0 0.7 The 27th one 0.9 1.1 0.9 2.4 44.8 5.3 227.1 0.8 0.8 1.9 1.1 0.8 0.8 0.7 The 28th one 0.8 0.8 0.9 2 134.9 72.2 306.7 0.8 0.8 1.0 0.7 0.7 0.7 0.7 The 29th one 0.9 0.9 0.9 1 47.6 17.9 338.2 0.9 0.9 0.9 1.1 0.8 0.9 1.0 The 30th one 0.9 0.8 0.8 0.8 16.5 35 476.1 0.9 0.9 1.0 0.9 0.8 0.8 1.0 The 31st one 0.9 0.8 0.9 1 100.2 23.7 433.1 0.9 0.9 1.0 1.0 0.8 0.9 1.0 The 32nd one 0.9 0.8 1 1 17.2 1 205.1 0.8 0.9 0.9 0.9 0.9 0.9 0.9 The 33rd one 2.1 1 0.9 0.8 231.1 15.5 523.6 1.1 0.8 0.9 1.5 0.7 0.9 0.8 The 34th one 0.9 0.9 0.9 0.9 114.2 4.2 548.9 1.0 0.9 0.9 1.2 0.8 0.9 0.9 The 35th one 0.9 1 1.6 0.9 131.7 38.9 364.4 0.8 0.8 0.8 0.9 0.9 1.0 0.9 The 36th one 0.9 0.8 0.9 0.9 25.6 150.4 320.7 1.1 1.2 1.5 1.1 0.8 0.8 0.9 The 37th one 1 0.9 0.9 0.8 117.8 17.1 532.6 1.5 1.0 1.2 2.0 0.9 0.9 0.9 The 38th one 1.2 0.9 0.9 0.9 115.9 26.3 562.8 1.0 0.9 1.0 1.0 1.8 0.7 0.7 The 39th one 0.9 1.1 0.9 0.9 58 41.4 400.1 0.9 0.8 1.1 1.0 1.0 0.7 0.7 The 40th one 0.9 0.9 1.1 0.9 4.6 120.6 472.3 1.0 0.9 1.1 1.0 0.8 0.7 1.1 The 41st one 0.8 0.8 1 1 29.5 39.4 416.3 0.7 0.7 0.7 0.7 0.7 0.8 0.7 The 42nd one 0.8 0.9 1 1.7 60.4 29.6 493.6 0.8 0.7 0.6 0.7 1.2 0.8 0.7 The 43rd one 3.6 0.9 3 2 121.7 149.1 600.5 0.7 0.7 0.7 1.2 0.8 0.7 0.7 The 44th one 0.8 0.9 6.8 1.1 148.7 130.2 530.4 0.7 0.7 0.9 0.7 0.7 0.7 0.7 The 45th one 0.8 8.9 1.2 11.5 194.1 128.3 575.1 0.7 0.7 0.7 0.7 0.7 0.7 0.7 The 46th one 2.7 0.8 2.2 36.7 191.3 98.7 475.9 0.7 0.7 0.7 0.7 0.7 0.8 0.7 The 47th one 2.4 1 5.1 5.6 153.6 48.9 838.1 0.7 0.7 0.7 0.7 1.8 0.7 0.7 The 48th one 0.9 0.9 2.1 3.2 182.3 47.5 578.8 0.7 0.7 0.7 0.8 1.0 0.7 0.7 The 49th one 0.8 0.8 1 0.9 52.1 116.4 515.7 0.6 0.8 0.6 0.7 0.7 0.8 1.1 The 50th one 0.9 0.9 1 1 53.3 30.7 589.2 0.7 0.7 0.6 0.7 1.2 0.7 0.7

[0128] As can be seen from the data in Table 2 above, in the present application, by covering the surface of the aluminum nitride ceramic substrate at the etched gap with a functional oxide layer, the electric field distribution on the surface of the aluminum nitride ceramic is made more uniform, and the partial discharge problem of the aluminum nitride copper-clad ceramic substrate under high voltage can be well improved.

[0129] In addition, the aluminum nitride copper-clad ceramic substrates prepared in Examples 2-5 and Comparative Examples 2-5 were taken respectively, and they were also subjected to partial discharge tests at voltages of 7 kV, 8.3 kV, 10.5 kV, and 12 kV, and their average partial discharge data were recorded. The test results are shown in Table 3 below:

[0130] Table 3

[0131] ITEM 7KV 8.3KV 10.5KV 12KV Example 2 0.9 0.8 0.7 0.9 Example 3 0.7 0.8 0.9 1 Example 4 0.8 0.9 0.8 0.8 Example 5 0.7 0.7 0.7 0.9 Comparative Example 2 1.2 2.3 85 226 Comparative Example 3 1.4 1.9 103 187 Comparative Example 4 1.2 1.1 116 116 Comparative Example 5 2.1 5.5 91 154

[0132] As can be seen from the results in Table 3 above, in the process of preparing the functional oxide layer in the present application, each step has an obvious influence on the performance of the product. Forming only an alumina or silicon dioxide layer on the surface of the etched gap cannot help well in suppressing the partial discharge performance.

[0133] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains may make various modifications or supplements to the described specific embodiments or use similar means for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for suppressing partial discharge of a copper-clad aluminum nitride ceramic substrate, characterized in that The following steps are involved: (S.1) etching the aluminum nitride copper-clad ceramic substrate to which the pattern transfer has not been performed, thereby obtaining interconnected conductive lines and etching gaps between the interconnected conductive lines that completely expose the aluminum nitride ceramic substrate; (S.2) The surfaces of the interconnected conductive circuits are coated, and the aluminum nitride ceramic plates exposed in the etched gaps are in-situ activated under alkaline conditions, thereby forming a hydrophilic reaction interface with a rough structure on the surface of the aluminum nitride ceramic plates; (S.3) Placing the hydrophilic reaction interface with a rough structure in an acidic environment, so that the aluminum ions on the surface of the aluminum nitride ceramic plate are released and enriched on its surface; (S.4) Aluminum ions on the surface of the aluminum nitride ceramic plate react with silicates and organic ligands to form a uniform passivation layer comprising aluminum oxide, aluminum silicate, and an organic aluminum complex; (S.5) Performing a high-temperature heat treatment on the liner in a protective atmosphere to convert the uniform passivation layer located in the etched gap into a functional oxide layer capable of inhibiting charge accumulation, wherein the functional oxide layer comprises a porous matrix with nano-sized Al2O3 particles as a main phase and a silicon aluminum oxide network structure embedded in the porous matrix.

2. The method for suppressing partial discharge of aluminum nitride copper-clad ceramic liner according to claim 1, characterized in that: The alkaline conditions in the step (S.2) are provided by an alkaline solution with a concentration of 5-20%, an in-situ activation temperature of 50-60°C, and an in-situ activation time of 5-30 minutes.

3. The method for suppressing partial discharge of aluminum nitride copper-clad ceramic liner according to claim 2, characterized in that: The alkali is a combination of one or more of sodium hydroxide, potassium hydroxide, sodium ethoxide, and tetramethylammonium hydroxide.

4. The method for suppressing partial discharge of aluminum nitride copper-clad ceramic liner according to claim 1, characterized in that: The acidic environment in the step (S.3) is provided by a mixed acid solution containing aluminum salt; The mixed acid solution contains nitric acid and hydrochloric acid, wherein the nitric acid accounts for 3-10% of the total volume of the mixed acid solution, the hydrochloric acid accounts for 8-12% of the total volume of the mixed acid solution, the aluminum salt accounts for 10-30% of the total mass of the mixed acid solution, and the balance is water; In the step (S.3), the treatment temperature is 30-50°C and the treatment time is 5-30 minutes.

5. The method for suppressing partial discharge of aluminum nitride copper-clad ceramic liner according to claim 4, characterized in that: The aluminum salt is any one of aluminum nitrate, aluminum chloride, and aluminum sulfate.

6. The method for suppressing partial discharge of aluminum nitride copper-clad ceramic liner according to claim 1, characterized in that: The step (S.4) is carried out in a reaction solution containing silicate, sodium citrate and aqueous ammonia, and the reaction temperature is 40-50°C and the treatment time is 15-30 minutes; The silicate is any one of sodium silicate and potassium silicate, and its addition amount is 25-35% of the total mass of the reaction solution; The amount of sodium citrate added is 15-25% of the total mass of the reaction solution; The amount of ammonia added is 5-20% of the total volume of the reaction solution; After the uniform passivation layer is prepared, it is washed with clean water and hot water at 50° C.-60° C. in sequence.

7. The method for suppressing partial discharge of aluminum nitride copper-clad ceramic liner according to claim 1, characterized in that: The heat treatment in step (S.5) is carried out in a nitrogen-oxygen mixed atmosphere with an oxygen content of 500-2000 ppm, a heat treatment time of 20-40 minutes, and a heat treatment temperature of 800-850°C.

8. An aluminum nitride copper-clad ceramic liner for suppressing partial discharge, prepared by the method according to any one of claims 1 to 7.

9. The aluminum nitride copper-clad ceramic liner for suppressing partial discharge according to claim 8, characterized in that: The surface roughness Sa of the functional oxide layer is ≤0.24 μm, and the roughness Sz is ≤4.5 μm.

10. Use of the aluminum nitride copper-clad ceramic liner for suppressing partial discharge according to claim 8 or 9 in high-power insulated gate bipolar transistors, silicon carbide modules, and intelligent power modules.

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