Three-dimensional circuit structure and method for manufacturing the same

Abstract

The application relates to a three-dimensional circuit structure and a preparation method thereof, and relates to the technical field of circuit manufacturing. The method comprises the following steps: laying an insulating powder layer in a forming cavity; spraying a binder to a first predetermined area by a first spraying unit to form an insulating profile; spraying a conductive material to a second predetermined area by a second spraying unit to form a conductive path according to a predetermined circuit pattern; repeating the above steps to form a forming green body containing a three-dimensional insulating base body and a three-dimensional conductive network prearranged in the three-dimensional insulating base body; and performing post-processing on the forming green body to make the densification of the three-dimensional insulating base body and the transformation of the three-dimensional conductive network into a continuous conductive network carried out in processing stages with different processing temperatures. The method prearranges the conductive path in the green body according to the circuit pattern in the forming stage, and makes the insulating densification and the conductive phase formation carried out in different temperatures, so that the three-dimensional insulating structure and the three-dimensional conductive network can be formed in the same component at one time and reliably combined.

Description

Technical Field

[0001] This application relates to the field of circuit manufacturing technology, and in particular to a three-dimensional circuit structure and its fabrication method. Background Technology

[0002] Circuit structure is the fundamental carrier for signal transmission and device interconnection in electronic devices. As electronic devices evolve towards miniaturization, high integration, and functional integration, three-dimensional circuit structures—integrating wiring, heat dissipation structures, and antennas into a single component and arranging conductive networks in three-dimensional space—are increasingly becoming a requirement for applications such as radio frequency (RF), high-frequency communication, and high-density packaging. Traditional printed circuit boards (PCBs) primarily use planar stacked structures, which cannot directly meet the aforementioned requirements for three-dimensional wiring and multi-faceted interconnection.

[0003] Traditional printed circuit board (PCB) manufacturing typically involves removing most of the copper foil on a copper-clad insulating substrate through exposure, development, and etching to retain the desired circuitry. Multilayer substrates are then laminated under high temperature and pressure with prepreg, and interlayer conductivity is achieved through mechanical drilling or laser drilling combined with hole metallization. In this process, most of the copper foil is removed during etching, resulting in material waste. Etching and electroplating also generate chemical waste. Furthermore, the planar stacking and drilling-based copper deposition method limits the finished product to a planar structure, resulting in numerous processes and making it difficult to integrally form a three-dimensional conductive network within a single component. To directly construct three-dimensional circuits within a single component, additive manufacturing, which builds circuit structures layer by layer, has become a promising development direction.

[0004] However, forming a three-dimensional insulating structure and a three-dimensional conductive network in the same component requires the coexistence and separate phases of the insulating material, which needs high-temperature densification, and the conductive metal, which is susceptible to high-temperature oxidation and melting, during the same manufacturing process. Existing additive manufacturing solutions struggle to meet this requirement. On one hand, when using a hot-melt method for layer-by-layer forming, the insulating material and conductive metal are incompatible due to their melting temperatures and process temperature windows, making it difficult to simultaneously construct the insulating and conductive structures during the same forming process. On the other hand, some solutions first form or sinter the insulating substrate layer by layer, and then introduce the metal through methods such as impregnation, chemical plating, or first depositing the conductive material on the entire surface and then etching. The conductive material is not embedded into the component according to the circuit pattern during the forming stage, making it difficult to form a truly embedded conductive network that penetrates three-dimensional space. Furthermore, the densification of the insulating substrate and the formation of the conductive metal phase are disconnected, and the temperature and atmosphere conditions required for both cannot be coordinated in the same post-processing, ultimately leading to a reliable integral bonding between the conductive network and the insulating substrate. Summary of the Invention

[0005] In order to form a three-dimensional insulating structure and a three-dimensional conductive network in the same component in one step, and to coordinate the phase formation and reliable bonding of the insulating material that needs to be densified at high temperature and the conductive metal that is susceptible to high temperature oxidation and melting in the same manufacturing process, this application provides a three-dimensional circuit structure and its preparation method.

[0006] Firstly, this application provides a method for fabricating a three-dimensional circuit structure, which employs the following technical solution:

[0007] A method for fabricating a three-dimensional circuit structure includes the following steps:

[0008] S1. Lay an insulating powder layer inside the forming cavity;

[0009] S2. The adhesive is selectively sprayed into a first predetermined area of ​​the insulating powder layer by the first spraying unit, so that the insulating powder in the first predetermined area is bonded to form an insulating profile;

[0010] S3. Conductive material is selectively sprayed into the second predetermined area of ​​the insulating powder layer or the preceding layer through the second spraying unit, and the sprayed conductive material forms a conductive path according to a predetermined circuit pattern;

[0011] S4. Repeat S1 to S3, layer by layer, to form a shaped green body. The shaped green body includes a three-dimensional insulating matrix and a three-dimensional conductive network pre-placed within the shaped green body. The three-dimensional insulating matrix is ​​formed by layering insulating contours, and the three-dimensional conductive network is formed by connecting conductive paths formed layer by layer.

[0012] S5. Perform post-processing on the formed green body. The post-processing includes multiple processing stages with different processing temperatures. The densification of the three-dimensional insulating matrix and the conversion of the three-dimensional conductive network pre-placed in the formed green body into a continuous conductive network are carried out in different processing stages, and the continuous conductive network is combined with the three-dimensional insulating matrix.

[0013] By adopting the above technical solution, the first spraying unit and the second spraying unit operate layer by layer in the same powder bed, so that the insulation contour and the conductive path are pre-placed in the same forming green body according to the circuit pattern during the forming stage. The conductive path does not need to be introduced after the insulation substrate is formed, thereby constructing an embedded conductive network that runs through three-dimensional space inside the green body. On this basis, the post-processing separates the densification of the three-dimensional insulation substrate and the conversion of the pre-placed conductive network into a continuous conductive network in processing stages with different processing temperatures. This allows the densification of the insulation substrate and the continuity of the conductive network to be carried out in their respective processing stages during the post-processing process, and their processing conditions to be controlled separately. As a result, the continuous conductive network and the three-dimensional insulation substrate are integrally formed in the same component.

[0014] Optionally, the multiple processing stages include an insulation densification stage and a conductive phase formation stage. The densification of the three-dimensional insulating matrix is ​​carried out in the insulation densification stage, and the transformation of the three-dimensional conductive network into a continuous conductive network is carried out in the conductive phase formation stage.

[0015] By adopting the above technical solution, the two types of transformation are respectively implemented in the insulation densification stage and the conductive phase formation stage, so that the conditions for the phase formation of the insulating matrix and the phase formation of the conductive network in the post-processing can be controlled separately.

[0016] Optionally, the processing temperature of the conductive phase formation stage is lower than that of the insulation densification stage; and / or, the insulation densification stage is carried out in an inert atmosphere, and the conductive phase formation stage is carried out in a reducing atmosphere; and / or, the conductive material contains silver particles, and the post-processing also includes a silver network formation stage prior to the insulation densification stage, in which the silver particles are sintered to form a continuous silver network; and / or, the multiple processing stages sequentially include a low-temperature curing stage, a degreasing stage, an insulation densification stage, and a conductive phase formation stage; the low-temperature curing stage cures the binder, and the processing temperature of the low-temperature curing stage is 80℃~150℃; the degreasing stage removes organic components from the formed green body, and the processing temperature of the degreasing stage is 200℃~400℃; the processing temperature of the insulation densification stage is 700℃~850℃; and the processing temperature of the conductive phase formation stage is 300℃~400℃.

[0017] By adopting the above technical solution, the conductive phase is formed at a temperature lower than that of insulation densification and the oxidation of conductive metal is suppressed by a reducing atmosphere. The silver particles can also be sintered in advance to maintain the continuity of the conductive path, providing support for the maintenance of the conductive network during the high-temperature densification stage.

[0018] Optionally, in S3, the sprayed conductive material forms conductive lines within the layer and via segments extending along the stacking direction in the same spraying step; in S4, the via segments of adjacent layers are aligned and connected during layer stacking to form a vertical conductive path that runs through multiple layers. The vertical conductive path and conductive lines are transformed into a continuous conductive network after post-processing; the via segments are formed without drilling, cutting, or hole metallization.

[0019] By adopting the above technical solution, the vertical conduction between layers is generated in the same position by the through-hole segment along with the conductive line segment in the same spraying step, without the need for additional drilling, cutting or hole metallization, so that the interlayer connection and the wiring within the layer are completed at the same time in the forming stage.

[0020] Optionally, the three-dimensional conductive network includes conductive patterns distributed on at least five faces of the three-dimensional circuit structure, and the conductive patterns on different faces are electrically connected through vertical conductive paths.

[0021] By adopting the above technical solution, conductive patterns are distributed on at least five sides of the structure and interconnected through vertical conductive paths, providing a structural basis for realizing multi-faceted wiring and multi-faceted device interconnection in three-dimensional space.

[0022] Optionally, in S2, the layer-by-layer insulating contour forms a heat dissipation channel inside the three-dimensional insulating substrate, and the heat dissipation channel is defined by the cavity wall of the insulating contour; and / or, in S3, the sprayed conductive material forms an antenna radiator and a feed line, which constitute part of a three-dimensional conductive network and are located at least at one location on the outer surface and the inner cavity wall of the three-dimensional circuit structure.

[0023] By adopting the above technical solution, the heat dissipation channel is directly formed by the insulating contour during the forming stage, and the antenna radiator and feed line are printed together with the conductive network, so that the heat dissipation structure and the antenna are integrally formed with the circuit in the same manufacturing process.

[0024] Optionally, the conductive material includes at least one of a nano-copper dispersion, a nano-silver dispersion, and a reducible metal precursor solution; the copper particles in the nano-copper dispersion have a particle size of 5 nm to 100 nm; the silver particles in the nano-silver dispersion have a particle size of 5 nm to 50 nm; when the conductive material includes a reducible metal precursor solution, the reducible metal precursor solution contains at least one of a copper salt, a silver salt, and a metal-organic compound, the reducible metal precursor solution is sprayed by a second spraying unit to form a conductive path according to a predetermined circuit pattern, and the metal elements in the reducible metal precursor solution are in compound form during spraying and are reduced in situ to a metallic conductive phase under a reducing atmosphere in the post-treatment.

[0025] By adopting the above technical solution, the metal precursor can be reduced to be deposited in the form of a compound according to the circuit pattern during spraying and then converted into a conductive metal phase in situ in the reducing atmosphere of post-processing, thereby reducing the requirements of the conductive material for oxidation resistance during spraying and printing.

[0026] Optionally, in S3, the amount of conductive material sprayed at the via segment is greater than the amount of conductive material sprayed at the conductive line segment, so that the deposition thickness of the via segment along the stacking direction is greater than the layer thickness of the insulating powder layer, and the upper end of the via segment protrudes from the upper surface of the current insulating powder layer; in S4, the protruding upper end extends into the next insulating powder layer after the next insulating powder layer is laid, and contacts and overlaps with the conductive material sprayed in that layer.

[0027] Optionally, the linewidth of the conductive path is not greater than 50 μm; and / or, the insulating powder includes at least one of borosilicate glass powder, alumina powder, zirconium oxide powder and calcium oxide ceramic powder; the thickness of the insulating powder layer is 20 μm to 100 μm; and the particle size distribution of the insulating powder satisfies D99 ≤ 50 μm.

[0028] By adopting the above technical solution, the conductive path linewidth and the type, layer thickness and particle size distribution of insulating powder are limited, so that the wiring precision and the quality of the layer-by-layer forming insulating substrate are matched.

[0029] Optionally, the conductive phase formation stage is performed after the insulation densification stage is completed; after the insulation densification stage is completed, the temperature is lowered to the processing temperature of the conductive phase formation stage, and the conductive paths pre-placed in the forming green body are converted into a continuous conductive network in situ under a reducing atmosphere.

[0030] By adopting the above technical solution, after the insulating substrate is densified, it is cooled to a lower temperature and then transformed into a continuous conductive network in situ in a reducing atmosphere. This allows the formation of the conductive network to proceed in a predetermined sequence after the insulation densification is completed.

[0031] Optionally, the conductive material is a mixed dispersion of nano-silver and nano-copper, with a mass ratio of silver to copper of 1:1 to 4:1.

[0032] By adopting the above technical solution, the sintering characteristics and phase formation temperature of the conductive phase are adjusted by using a silver-copper hybrid system, thus ensuring both the continuity and reliability of the conductive network.

[0033] Optionally, the processing temperature for the insulation densification stage is 600℃~900℃.

[0034] By adopting the above technical solutions, a wider temperature range can be selected for densification of the insulating matrix to adapt to the softening and sintering characteristics of different insulating powder systems.

[0035] Optionally, a wave-transparent window is formed in a predetermined area of ​​the three-dimensional circuit structure, and the antenna radiator is arranged around or inside the wave-transparent window.

[0036] By adopting the above technical solution, the antenna radiator and the wave-transmitting window are arranged in the same component, providing a low-loss transmission area for the transmission and reception of electromagnetic waves.

[0037] Optionally, the inert atmosphere is nitrogen or argon, and the reducing atmosphere is a mixture of nitrogen and hydrogen.

[0038] By adopting the above technical solutions, specific atmosphere selection is provided for each stage of post-processing, respectively meeting the oxygen isolation requirements for insulation densification and the reduction requirements for the formation of conductive phases.

[0039] Optionally, the linewidth of the conductive path is no greater than 20 μm.

[0040] By adopting the above technical solution, the line width of the conductive path can be further reduced, providing support for high-density wiring.

[0041] Optionally, the thickness of the insulating powder layer is 30μm~60μm.

[0042] By adopting the above technical solution, the thickness of the powder layer is limited to a narrower range, taking into account both the resolution and efficiency of layer-by-layer forming.

[0043] Optionally, the particle size distribution of the insulating powder satisfies D99≤38μm and D50 is 7μm~30μm, the particle morphology of the insulating powder is near-spherical or equiaxed, and the moisture content of the insulating powder is not greater than 0.2wt%.

[0044] By adopting the above technical solutions, the uniformity and packing density of the insulating powder are improved, thus ensuring the forming quality of the insulating profile.

[0045] Optionally, in S1, the insulating powder layer is laid by a roller-type powder spreading mechanism or a scraper-type powder spreading mechanism.

[0046] By adopting the above technical solution, a specific powder laying method is provided for the laying of the insulating powder layer, so that the powder bed thickness is uniform.

[0047] Optionally, the adhesive may be a water-based adhesive or an alcohol-based adhesive.

[0048] By adopting the above technical solution, a specific adhesive system is provided for the bonding and forming of the insulation profile, which is easy to remove in post-processing.

[0049] Optionally, the heating rate of the degreasing stage is 2℃ / min to 5℃ / min, and the holding time of the low-temperature curing stage, the insulation densification stage and the conductive phase formation stage is 1h to 2h respectively.

[0050] By adopting the above technical solution, and by controlling the degreasing heating rate and the holding time at each stage, the risk of cracking and deformation of the formed green body in post-processing can be reduced.

[0051] Optionally, the conductive material may also include at least one of a binder resin, a dispersant, a solvent, and a sintering accelerator.

[0052] By adopting the above technical solution and adjusting the rheological properties and spraying precision of the conductive material with the help of the above components, the forming quality of the conductive path can be improved.

[0053] Optionally, the insulating powder is a composite powder, and at least one of a flow aid and a sintering aid is added to the composite powder.

[0054] By adopting the above technical solutions, the spreadability and sintering densification behavior of composite powders can be improved with the help of flow aids and sintering aids.

[0055] Optionally, the post-processing is carried out in at least one of an inert atmosphere, a reducing atmosphere, and a vacuum environment.

[0056] By adopting the above technical solutions, multiple environmental options, including vacuum, are provided for post-processing to adapt to the phase formation requirements of different conductive materials.

[0057] Secondly, this application provides a three-dimensional circuit structure, which adopts the following technical solution:

[0058] A three-dimensional circuit structure includes a three-dimensional insulating substrate and a continuous conductive network, wherein the continuous conductive network is located at least once inside and on the surface of the three-dimensional insulating substrate; the continuous conductive network includes a solid vertical conductive path located inside the three-dimensional insulating substrate, the solid vertical conductive path being integrally continuous with the rest of the continuous conductive network, and its peripheral wall not having an independent hole wall metallization layer; the three-dimensional circuit structure is prepared by the aforementioned method for preparing a three-dimensional circuit structure.

[0059] By adopting the above technical solution, the interlayer vertical conduction is achieved by a solid vertical conductive path that is integrated with the continuous conductive network. The peripheral wall of the solid vertical conductive path does not have an independent hole wall metallization layer, so that the interlayer connection is structurally manifested as a continuous solid conductor.

[0060] In summary, this application includes at least one of the following beneficial technical effects:

[0061] 1. By pre-setting the insulation profile and the conductive path according to the circuit pattern in the same forming body by the first spraying unit and the second spraying unit in the forming stage, and by performing the densification of the insulation substrate and the continuity of the conductive network in the processing stages with different processing temperatures, the three-dimensional insulation structure and the three-dimensional conductive network can be formed in the same component at one time, and the conductive network and the insulation substrate can be reliably integrated.

[0062] 2. By dividing the post-processing into an insulation densification stage and a conductive phase formation stage, and by forming the conductive phase at a temperature lower than that of insulation densification and in a reducing atmosphere, the densification of the insulating matrix and the formation of the conductive phase are carried out under their respective temperature and atmospheric conditions, and the processing conditions of the two are controlled separately.

[0063] 3. By generating vertical conductive paths in the layer-by-layer spraying process with through-hole segments aligned with conductive lines and distributing conductive patterns on at least five surfaces of the structure, interlayer and multi-surface interconnection can be achieved without drilling or hole metallization. At the same time, heat dissipation channels and antenna structures can be integrally formed in the same manufacturing process. Attached Figure Description

[0064] Figure 1 A flowchart illustrating the method for fabricating a three-dimensional circuit structure provided in this application embodiment.

[0065] Figure 2 is a schematic diagram of the temperature and processing atmosphere at each processing stage in the post-processing provided in the embodiments of this application. Detailed Implementation

[0066] The present application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. The present application discloses a method for preparing a three-dimensional circuit structure. In the same powder bed, a first spraying unit first bonds insulating powder according to a cross-sectional contour to form an insulating contour, and then a second spraying unit sprays conductive material according to a predetermined circuit pattern to form a conductive path. The two are layered and pre-placed together in the same forming body. Finally, through staged post-processing, the densification of the three-dimensional insulating substrate and the transformation of the three-dimensional conductive network into a continuous conductive network are completed in their respective processing stages. Thus, the three-dimensional insulating structure and the three-dimensional conductive network can be integrally formed in the same component. The present application embodiments will be described in detail below regarding terminology, raw materials and equipment, main process flow, characterization of intermediate and finished products, alternative process routes, and the obtained three-dimensional circuit structure.

[0067] The following section will first explain some of the technical terms involved in the embodiments of this application.

[0068] Binder jetting is a powder bed additive manufacturing method in which powder is laid layer by layer in a forming cavity, and liquid material is selectively sprayed onto predetermined areas of the powder layer through a jetting unit, causing the powder in the predetermined area to bond together, and layer by layer to obtain a three-dimensional solid. In this embodiment, two types of jetting units are set on the powder bed, respectively responsible for insulating forming and conductive pattern formation.

[0069] A shaped green body refers to a shaped body that has been sprayed with adhesive and conductive material and layered on top of each other, but has not yet been sintered or fully cured.

[0070] A three-dimensional insulating substrate refers to a three-dimensional insulating structure formed by the stacking of insulating contours layer by layer, which constitutes the main body supporting a three-dimensional circuit structure.

[0071] A three-dimensional conductive network refers to a conductive structure distributed in three-dimensional space, consisting of interconnected conductive paths formed layer by layer. The three-dimensional conductive network exists in a pre-defined form during the green body formation stage and is transformed into a continuous conductive network through post-processing.

[0072] A continuous conductive network refers to a conductive network in which the metallic conductive phases are continuously connected after post-processing and possess electrical conduction capabilities.

[0073] Pre-setting refers to the conductive path being formed and embedded in the interior or surface of the green body according to a predetermined circuit pattern during the layer-by-layer forming stage of the green body, rather than being introduced after the insulating substrate has been formed.

[0074] Conductive phase formation treatment refers to the process of transforming conductive materials into a continuous metallic phase, including low-temperature sintering, reduction treatment, and laser-assisted or hot-press-assisted treatment methods.

[0075] Multifaceted circuits refer to conductive patterns and their interconnections that have electrical connections on at least five or six faces of a structure.

[0076] An inert atmosphere refers to a gaseous environment, such as nitrogen or argon, that does not chemically react with conductive metals.

[0077] A reducing atmosphere refers to a gaseous environment composed of a nitrogen-hydrogen mixture containing hydrogen or pure hydrogen, used to prevent or eliminate metal oxidation. For example, the nitrogen-hydrogen mixture contains 5% hydrogen by volume and 95% nitrogen by volume.

[0078] D10, D50, D90, and D99 are powder particle size distribution parameters. Dxx indicates that xx% of the particles by volume have a particle size smaller than this value. For example, D99≤38μm means that 99% of the particles have a particle size of no more than 38μm.

[0079] The terms “first”, “second”, etc., used in the specification and claims of this application are used to distinguish similar objects, not to describe a specific order or sequence; “comprising”, “having”, and any variations thereof are intended to cover non-exclusive inclusion.

[0080] After clarifying the above terminology, the raw materials and forming equipment used in the embodiments of this application will be introduced first. The insulating powder includes at least one of borosilicate glass powder, alumina powder, zirconia powder, and calcium oxide ceramic powder. Among them, borosilicate glass powder has a low softening temperature range, which is suitable for matching with the heat treatment window of conductive materials; alumina powder is suitable for applications requiring high strength and high temperature resistance; zirconia powder is suitable for applications requiring high toughness and precise dimensional control; and calcium oxide ceramic powder is suitable for applications with specific dielectric property requirements. In some embodiments, the insulating powder is a composite powder, and at least one of a flow aid and a sintering aid is added to the composite powder to improve the spreadability and sintering densification behavior of the powder.

[0081] Taking borosilicate glass powder as an example, the particle size distribution of the insulating powder satisfies D99 ≤ 50 μm. Further, the particle size distribution of the insulating powder satisfies D99 ≤ 38 μm and D50 is 7 μm to 30 μm. The particle morphology of the insulating powder is nearly spherical or equiaxed, and the moisture content of the insulating powder is no more than 0.2 wt%. Particle size distribution, particle morphology, and moisture content collectively affect the powder's flowability, spreading uniformity, and bulk density. Powders with excessively large particle sizes or irregular morphologies are prone to producing voids and streaks during spreading, while excessively high moisture content easily leads to powder agglomeration. For example, the insulating powder selected is nearly spherical borosilicate glass powder with a D50 of 10 μm to 20 μm.

[0082] The binder is a water-based or alcohol-based binder with a viscosity that is compatible with the nozzle of the spraying unit. It can be cured at room temperature or low temperature and removed by degreasing during post-treatment.

[0083] The forming equipment includes a forming cavity, a forming cylinder, a powder spreading mechanism, a first spraying unit, a second spraying unit, and a post-processing module. The forming cylinder can precisely descend along the stacking direction with a minimum step of no more than 50 μm to match the thickness of the powder spreading layer. The powder spreading mechanism is either a roller-type powder spreading mechanism or a scraper-type powder spreading mechanism. The first and second spraying units perform selective spraying based on the slicing data of the 3D model. The slicing data defines a first predetermined area for spraying binder and a second predetermined area for spraying conductive material in each layer, and determines the formation logic of powder spreading, spraying sequence, spraying amount, and interlayer conductive paths. It should be understood that the number of spraying units is not limited to two; more spraying units can be set to spray different functional materials separately, and this is not a limitation here. The post-processing module includes a built-in or external curing oven, debinding oven, and sintering oven, and is equipped with an atmosphere control system to provide an inert atmosphere, reducing atmosphere, or vacuum environment. The composition and selection of conductive materials will be described in detail in step S3.

[0084] Based on the aforementioned raw materials and equipment, the overall process of this method is described in detail below. This method includes steps S1 to S5. In the overall process, S1 involves laying an insulating powder layer inside the forming cavity; S2 involves bonding a first predetermined area of ​​this layer to form an insulating outline; S3 involves spraying conductive material onto this layer or a previous layer according to a predetermined circuit pattern to form a conductive path; S4 involves repeating S1 to S3 layer by layer to obtain the formed green body; and S5 involves performing phased post-processing on the formed green body. Each step is described in turn below, with particular emphasis on S3 and S5.

[0085] S1. Laying an insulating powder layer in the forming cavity. The thickness of the insulating powder layer is 20μm~100μm. The insulating powder includes at least one of borosilicate glass powder, alumina powder, zirconium oxide powder, and calcium oxide ceramic powder. The particle size distribution of the insulating powder satisfies D99≤50μm. In specific implementation, the insulating powder layer is laid by a roller-type powder laying mechanism or a scraper-type powder laying mechanism. The powder laying mechanism pushes the insulating powder in the horizontal direction, laying a thin layer with a thickness H on top of the previous layer. After each powder laying, the forming surface rises by a layer thickness H in the stacking direction. The insulating powder particles are loosely packed in this thin layer, with gaps between the particles. The uniformity of powder laying directly affects the forming quality of the subsequent insulation profile and conductive path. The layer thickness is generally 20μm~100μm, preferably 30μm~60μm. The smaller the layer thickness, the higher the forming resolution in the stacking direction; the larger the layer thickness, the higher the forming efficiency. For example, the powder layer thickness is 50μm.

[0086] On the insulating powder layer laid in S1, in S2, adhesive is selectively sprayed onto a first predetermined area of ​​the insulating powder layer by a first spraying unit, causing the insulating powder in the first predetermined area to bond together and form an insulating profile. In a specific implementation, the first predetermined area is determined by the slice data of the current layer of the 3D model, corresponding to the cross-sectional profile of the 3D insulating substrate in that layer. After the adhesive is sprayed, it is cured at room temperature or low temperature, bonding the insulating powder particles in the first predetermined area into an insulating profile with a certain strength. The insulating powder in areas where no adhesive is sprayed remains in a loose state, playing a supporting role in the layer-by-layer forming process, and is removed by powder cleaning after the formed body is completed.

[0087] In some embodiments, during S2, the layer-by-layer forming insulating contours enclose heat dissipation channels within the three-dimensional insulating substrate, with the cavity walls defined by the insulating contours. For example, the heat dissipation channel may be a cavity channel without adhesive spraying, where loose insulating powder is removed during powder cleaning, forming a continuous cavity mesh or thermal diffusion channel; or, for another example, a heat dissipation channel filled with highly thermally conductive powder, where a thermally conductive filling structure is formed by laying highly thermally conductive powder in this area. The heat dissipation channel is constructed along with the layer-by-layer forming process, requiring no additional processing steps.

[0088] After the insulation profile of this layer is formed, the method proceeds to the formation of the conductive pattern. S3. Conductive material is selectively sprayed onto a second predetermined region of the insulating powder layer or the preceding layer by a second spraying unit. The sprayed conductive material forms a conductive path according to a predetermined circuit pattern. In a specific implementation, the second predetermined region is defined by slice data according to a predetermined circuit pattern. The second spraying unit sprays conductive material along the direction of the circuit pattern to form the conductive pattern of this layer. In S3, the sprayed conductive material forms conductive lines within the layer and vias extending along the stacking direction in the same spraying step. The conductive lines carry out wiring within the layer, and the vias provide connections for interlayer conduction. The amount of conductive material sprayed at the vias is greater than that at the conductive lines, resulting in a via deposition thickness in the stacking direction greater than the layer thickness H of the insulating powder layer. The upper end of the via protrudes from the upper surface of the current insulating powder layer. For example, when the layer thickness H is 50 μm, the deposition thickness of the via is greater than 50 μm, and its upper end protrudes from the upper surface of the current insulating powder layer. The linewidth of the conductive path formed by the second spraying unit is no greater than 50 μm; in some embodiments, the linewidth of the conductive path is no greater than 20 μm to support high-density wiring.

[0089] Since the conductive path is embedded in the interior or surface of the green body according to the predetermined circuit pattern during the layer-by-layer forming stage of the green body, the insulating contour and the conductive path coexist as two types of objects in the same formed green body. The post-processing can set up processing stages for these two types of objects respectively, so that the densification of the insulating substrate and the continuity of the conductive network are completed in their respective stages under control.

[0090] The conductive materials used in S3 include at least one of nano-copper dispersion, nano-silver dispersion, and reducible metal precursor solution. The following describes each type of conductive material separately.

[0091] The copper particles in the nano-copper dispersion have a particle size of 5 nm to 100 nm, and the dispersion contains a sintering accelerator. For example, the nano-copper dispersion uses copper particles with a particle size of 10 nm to 50 nm and a solid content of 10 wt% to 30 wt%. In some embodiments, the conductive material further includes at least one of a binding resin, a dispersant, a solvent, and a sintering accelerator to adjust the rheological properties, spraying accuracy, and phase formation quality of the conductive material.

[0092] The silver particles in the nano-silver dispersion have a particle size of 5nm to 50nm. The sintering temperature window of silver particles is lower than that of copper particles, allowing for sintering and interconnection at lower temperatures, which helps reduce the thermal impact of the conductive phase formation process on the interface. Nano-copper and nano-silver can also be used in combination; corresponding implementation methods will be described in the alternative process route section.

[0093] When the conductive material includes a reducible metal precursor solution, the reducible metal precursor solution contains at least one of copper salt, silver salt, and organometallic compounds. The reducible metal precursor solution is sprayed by a second spraying unit to form a conductive path according to a predetermined circuit pattern. The metal elements in the reducible metal precursor solution are in compound form during spraying and are reduced in situ to a conductive metallic phase under a reducing atmosphere during post-processing. The metal elements undergo spraying and layer-by-layer forming in compound form, reducing the requirements for oxidation resistance of the conductive material during printing.

[0094] In some embodiments, in S3, the sprayed conductive material forms an antenna radiator and a feed line, which constitute part of a three-dimensional conductive network and are located at least once on the outer surface and inner cavity wall of the three-dimensional circuit structure. For example, the antenna radiator is a conductive patch pattern or a helical antenna pattern, which is sprayed together with the conductive pattern.

[0095] After S3 completes the formation of the conductive path for this layer, S4 repeats S1 to S3, layer by layer, to form a shaped green body. The shaped green body includes a three-dimensional insulating substrate and a three-dimensional conductive network pre-placed within it. The three-dimensional insulating substrate is formed by stacking insulating contours layer by layer, and the three-dimensional conductive network is formed by connecting conductive paths layer by layer. In specific implementation, in S4, during layer-by-layer stacking, the via segments of adjacent layers are aligned and connected along the stacking direction to form a vertical conductive path that runs through multiple layers. The vertical conductive path and conductive segments are transformed into a continuous conductive network after post-processing. The via segments are formed without drilling, cutting, or metallization. The via segments of adjacent layers are generated layer by layer from slice data at the same planar position and aligned sequentially in the stacking direction.

[0096] Specifically, the upper end of the via segment in the preceding layer protrudes from the upper surface of the preceding layer, with a protrusion height less than the layer thickness H. In step S1, when a new insulating powder layer is laid on top of the preceding layer, the upper end of the protruding via segment extends into the insulating powder layer. In step S3, when conductive material is sprayed onto this layer, the conductive material sprayed into the second predetermined area penetrates into the gaps between the insulating powder particles and extends downwards to the upper end of the via segment in the preceding layer, contacting that upper end. The via segments of adjacent layers overlap at the contact point. This process is repeated layer by layer, with the via segments of each layer overlapping sequentially along the stacking direction, forming a continuous vertical conductive path. Thus, interlayer conductivity and intralayer wiring are completed simultaneously during the forming stage, eliminating the need for post-forming interlayer connection structures.

[0097] In some embodiments, the three-dimensional conductive network includes conductive patterns distributed on at least five faces of the three-dimensional circuit structure, with the conductive patterns on different faces electrically connected by vertical conductive paths. The conductive patterns on multiple faces and the internal vertical conductive paths belong to the same three-dimensional conductive network defined by slice data, and are integrally constructed as layers are formed, thereby realizing the structural basis for multi-faceted wiring and multi-faceted device interconnection.

[0098] Based on the shaped green body obtained in S4, S5. Post-processing is performed on the shaped green body. This post-processing includes multiple processing stages at different temperatures. The densification of the three-dimensional insulating matrix and the transformation of the three-dimensional conductive network pre-placed within the shaped green body into a continuous conductive network are carried out in different processing stages, thereby bonding the continuous conductive network with the three-dimensional insulating matrix. The densification of the insulating powder and the phase formation of the conductive material require different temperature conditions, and the post-processing is therefore divided into multiple processing stages for separate control. In some embodiments, the multiple processing stages include an insulation densification stage and a conductive phase formation stage. The densification of the three-dimensional insulating matrix is ​​carried out in the insulation densification stage, and the transformation of the three-dimensional conductive network into a continuous conductive network is carried out in the conductive phase formation stage. Further, the processing temperature of the conductive phase formation stage is lower than that of the insulation densification stage; the insulation densification stage is carried out in an inert atmosphere, and the conductive phase formation stage is carried out in a reducing atmosphere. The inert atmosphere is nitrogen or argon, and the reducing atmosphere is a mixture of nitrogen and hydrogen.

[0099] In some embodiments, the multiple processing stages sequentially include a low-temperature curing stage, a degreasing stage, an insulating densification stage, and a conductive phase formation stage. Specifically, S5 includes the following sub-steps.

[0100] S51. Perform low-temperature curing on the formed green body. The low-temperature curing stage cures the adhesive, which then stably maintains the insulating contours and conductive paths in the formed position, improving the overall strength of the green body and providing structural support for subsequent handling and degreasing. The processing temperature for the low-temperature curing stage is 80℃~150℃, the holding time is 1h~2h, and the processing atmosphere is air. For example, the processing temperature for the low-temperature curing stage is 100℃.

[0101] S52. Degreasing is performed on the molded green body that has been cured at low temperature. The degreasing stage removes organic components from the molded green body, including binders and dispersants in conductive materials, thus removing obstacles to the densification of the insulating matrix. The processing temperature for the degreasing stage is 200°C to 400°C, and the processing atmosphere is an air atmosphere or a nitrogen atmosphere. In some embodiments, the heating rate for the degreasing stage is 2°C / min to 5°C / min. An excessively rapid heating rate can easily cause the organic components to decompose violently, generating internal stress and leading to cracking or deformation of the green body. For example, the processing temperature for the degreasing stage is 300°C.

[0102] S53. Perform insulation densification on the degreased shaped green body. During the insulation densification stage, the borosilicate glass powder softens and sinters, the interparticle pores shrink and close, the three-dimensional insulating matrix densifies, and a stable glass phase is formed. The treatment temperature for the insulation densification stage is 700℃~850℃, the holding time is 1h~2h, and the treatment atmosphere is a nitrogen atmosphere. In some embodiments, the treatment temperature for the insulation densification stage is 600℃~900℃ to adapt to the softening and sintering characteristics of different insulating powder systems. For example, the treatment temperature for the insulation densification stage is 780℃, and a nitrogen atmosphere is used to isolate oxygen.

[0103] S54. Perform a conductive phase formation process on the formed green body after the insulation densification is completed. The conductive phase formation stage is performed after the insulation densification stage is completed; after the insulation densification stage is completed, the temperature is lowered to the processing temperature of the conductive phase formation stage, and the conductive paths pre-placed in the formed green body are transformed into a continuous conductive network in situ under a reducing atmosphere. The processing temperature of the conductive phase formation stage is 300℃~400℃, the holding time is 1h~2h, and the processing atmosphere is a nitrogen-hydrogen mixed reducing atmosphere with a hydrogen gas fraction of 5%. For example, the processing temperature of the conductive phase formation stage is 350℃. The reducing atmosphere prevents and eliminates oxidation on the surface of the copper particles, and the copper particles are sintered and connected at this temperature to form a continuous conductive network that bonds with the densified three-dimensional insulating matrix. In addition to in-furnace heat treatment, the conductive phase formation process can also be supplemented by laser-assisted or hot-pressing assisted processing methods. Laser-assisted and hot-pressing assisted processing are also implementation methods of conductive phase formation.

[0104] In some embodiments, the conductive material comprises silver particles, and the post-processing further includes a silver network formation stage prior to the insulation densification stage, in which the silver particles are sintered to form a continuous silver network. The sintering temperature window for the silver particles is 150°C to 250°C, and the silver network formation stage utilizes this low-temperature window to allow the silver particles to be sintered and connected beforehand. The corresponding complete implementation is described in the alternative process route section.

[0105] In other embodiments, the post-processing is performed in at least one of an inert atmosphere, a reducing atmosphere, and a vacuum environment. For example, oxidation-sensitive processing stages are performed in a vacuum environment to further isolate oxygen.

[0106] After the above post-processing, the formed chloroplast is transformed into a three-dimensional circuit structure with a continuous conductive network. To verify the forming quality and electrical performance, the intermediate product and the finished product can be characterized and tested as follows. After powder removal, the formed chloroplast contains a three-dimensional insulating matrix outline formed by stacking and conductive paths pre-placed inside or on its surface. The conductive paths in the chloroplast stage are not yet connected into a continuous metallic phase. After post-processing, the conductive linewidth is measured by metallographic microscopy or scanning electron microscopy, with a target value not greater than 20 μm; the sheet resistance of the conductive layer is measured by the four-probe method, with a target value less than 50 mΩ / □; the resistivity of the conductive path is measured by the four-probe method, with a target value less than 10 μΩ·cm; and the insulation resistance is measured by the two-terminal method, with a target value greater than 10 μΩ·cm. 9 Ω.

[0107] Regarding structural performance, sintering shrinkage was measured using calipers or a coordinate measuring machine, with target values ​​of less than 5% in the X and Y directions and less than 8% in the Z direction; porosity was measured using the Archimedes method or image analysis, with a target value of less than 15%; the conductive phase composition was analyzed using X-ray diffraction, with the target being the presence of characteristic copper peaks without a copper oxide main peak; the interface bonding was analyzed using scanning electron microscopy and energy dispersive spectroscopy, with the target being a continuous distribution of copper elements without obvious fractures. To verify the effectiveness of each step of this method, the following comparative examples were set up. Comparative Example 1 uses a traditional multilayer printed circuit board with the same wiring density target, which has many layers, a large volume, lacks three-dimensional interconnection, and requires additional components for heat dissipation and antennas. Comparative Example 2 only performs adhesive spraying insulation molding; the conductive pattern is applied to the surface by screen printing after molding, and the conductive path exists only on the surface of the structure, failing to form an internal three-dimensional conductive network, making multi-faceted interconnection difficult. Comparative Example 3 uses the same molding process as this method, but the conductive phase formation process is carried out in an air atmosphere. Copper particles are oxidized by heat in the air, the conductive phase fractures, and the resistivity increases significantly. The only difference between Comparative Example 3 and this method is the atmospheric conditions during the formation of the conductive phase, which is used to separate and verify the effect of the reducing atmosphere on the continuity of the conductive network.

[0108] The above embodiments use a dispersion of borosilicate glass powder and nano-copper as an example. The material system and post-processing route of this method are not limited to this; alternative process routes can also be used. In some embodiments, the conductive material is a mixed dispersion of nano-silver and nano-copper, with a silver-to-copper mass ratio of 1:1 to 4:1. After the mixed dispersion forms a conductive path through spraying, in the silver network formation stage, silver particles are first sintered at a low temperature window of 150°C to 250°C to form a continuous silver network. This continuous silver network maintains the interconnected framework of the conductive path in subsequent processing stages, and a second treatment further enhances its conductive stability. The silver system is less sensitive to oxidation than the copper system, and the post-processing can be carried out under an inert atmosphere, thus widening the process window accordingly. The insulating powder can be a technical glass powder with a low dielectric loss formulation, and the particle size can be selected according to the dielectric performance requirements of the target frequency band. For high-frequency applications, the high-frequency dielectric constant and dielectric loss tangent of the sample can be tested, with the test frequency band being, for example, 1GHz to 10GHz.

[0109] In addition to the aforementioned nanoparticle system, a reducible metal precursor solution can be used as an alternative route for conductive materials. The precursor solution is sprayed according to a predetermined circuit pattern and undergoes various processing stages along with the biomass. During the conductive phase formation stage, the metal elements are reduced in situ in a reducing atmosphere and sintered together. Compared to the nanoparticle system, in the precursor route, the metal elements remain in compound form throughout the spraying and forming process, and their phase formation is entirely controlled by the reduction conditions of the post-processing. The precursor route is also an implementation method for the formation of conductive materials and conductive phases in this approach.

[0110] Regardless of the material system and process route used, the method produces a three-dimensional circuit structure that integrates a three-dimensional insulating substrate and a three-dimensional conductive network within the same component. The structure itself is described below. The three-dimensional circuit structure includes a three-dimensional insulating substrate and a continuous conductive network, which is located at least once inside and on the surface of the three-dimensional insulating substrate. The continuous conductive network includes a solid vertical conductive path located inside the three-dimensional insulating substrate. This solid vertical conductive path is integrally continuous with the rest of the continuous conductive network, and its peripheral walls do not have independent hole-wall metallization layers. That is, the vertical conductive path is a solid conductor formed by spray deposition and post-processing, and it belongs to the same continuous metallic phase as the conductive segments within the layer. Interlayer conductivity does not depend on the hole-wall plating structure.

[0111] In some embodiments, at least five faces of the three-dimensional circuit structure are distributed with conductive patterns, and the conductive patterns on different faces are electrically connected through solid vertical conductive paths to form a multi-faceted circuit. The interior of the three-dimensional circuit structure is provided with heat dissipation channels enclosed by insulating contours; these channels are either through-hole channels or channels filled with highly thermally conductive powder. Antenna radiators and feed lines are provided on the outer surface or internal cavity walls of the three-dimensional circuit structure; the antenna radiators are conductive patch patterns or helical antenna patterns. Furthermore, a wave-transparent window is formed in a predetermined area of ​​the three-dimensional circuit structure, and the antenna radiators are arranged around or inside the wave-transparent window. The wave-transparent window utilizes the low dielectric properties of the borosilicate glass substrate and the structural design to achieve low-loss electromagnetic wave transmission. Thus, the same component integrates three functional structures—electrical connection, thermal management, and wireless radiation and wave transmission—in a single fabrication process.

[0112] The same or similar parts in the various embodiments of this application can be referenced to each other, and the technical features in the various embodiments can be combined with each other without conflict to form new embodiments.

[0113] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0114] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for fabricating a three-dimensional circuit structure, characterized in that, The steps are as follows: S1. Lay an insulating powder layer inside the forming cavity; S2. The adhesive is selectively sprayed into a first predetermined area of ​​the insulating powder layer by the first spraying unit, so that the insulating powder in the first predetermined area is bonded to form an insulating profile; S3. Conductive material is selectively sprayed into the second predetermined area of ​​the insulating powder layer or the preceding layer through the second spraying unit, and the sprayed conductive material forms a conductive path according to a predetermined circuit pattern; S4. Repeat S1 to S3, layer by layer, to form a shaped green body. The shaped green body includes a three-dimensional insulating substrate and a three-dimensional conductive network pre-placed in the shaped green body. The three-dimensional insulating substrate is formed by the overlapping of the insulating contours formed layer by layer, and the three-dimensional conductive network is formed by the interconnection of the conductive paths formed layer by layer. S5. Perform post-processing on the shaped green body. The post-processing includes multiple processing stages with different processing temperatures. The densification of the three-dimensional insulating matrix and the conversion of the three-dimensional conductive network pre-placed in the shaped green body into a continuous conductive network are carried out in different processing stages, and the continuous conductive network is combined with the three-dimensional insulating matrix.

2. The method for fabricating a three-dimensional circuit structure according to claim 1, characterized in that, The multiple processing stages include an insulation densification stage and a conductive phase formation stage. The densification of the three-dimensional insulating matrix is ​​carried out in the insulation densification stage, and the transformation of the three-dimensional conductive network into the continuous conductive network is carried out in the conductive phase formation stage.

3. The method for fabricating a three-dimensional circuit structure according to claim 2, characterized in that, The processing temperature of the conductive phase formation stage is lower than the processing temperature of the insulation densification stage. And / or, the insulation densification stage is carried out in an inert atmosphere, and the conductive phase formation stage is carried out in a reducing atmosphere; And / or, the conductive material comprises silver particles, and the post-processing further includes a silver network formation stage prior to the insulation densification stage, in which the silver particles are sintered to form a continuous silver network; And / or, the plurality of processing stages sequentially include a low-temperature curing stage, a degreasing stage, an insulation densification stage, and a conductive phase formation stage; the low-temperature curing stage cures the adhesive, and the processing temperature of the low-temperature curing stage is 80℃~150℃; the degreasing stage removes organic components from the formed green body, and the processing temperature of the degreasing stage is 200℃~400℃; the processing temperature of the insulation densification stage is 700℃~850℃; and the processing temperature of the conductive phase formation stage is 300℃~400℃.

4. The method for fabricating a three-dimensional circuit structure according to claim 1, characterized in that, In S3, the sprayed conductive material forms conductive line segments within the layer and via segments extending along the stacking direction in the same spraying step. In step S4, the via segments of adjacent layers are aligned and connected during the layer-by-layer stacking to form a vertical conductive path that runs through multiple layers. The vertical conductive path and the conductive line segments are transformed into a continuous conductive network after the post-processing. The via segments are formed without drilling, cutting or metallization.

5. The method for fabricating a three-dimensional circuit structure according to claim 4, characterized in that, The three-dimensional conductive network includes conductive patterns distributed on at least five faces of the three-dimensional circuit structure, and the conductive patterns on different faces are electrically connected through the vertical conductive path.

6. The method for fabricating a three-dimensional circuit structure according to claim 1, characterized in that, In S2, the insulating contours formed layer by layer enclose a heat dissipation channel inside the three-dimensional insulating substrate, and the heat dissipation channel is defined by the cavity wall of the insulating contours. And / or, in S3, the sprayed conductive material forms an antenna radiator and a feed line, the antenna radiator and the feed line constituting part of the three-dimensional conductive network and located at least once on the outer surface and the inner cavity wall of the three-dimensional circuit structure.

7. The method for fabricating a three-dimensional circuit structure according to claim 6, characterized in that, The conductive material includes at least one of a nano-copper dispersion, a nano-silver dispersion, and a reducible metal precursor solution; the copper particles in the nano-copper dispersion have a particle size of 5 nm to 100 nm; the silver particles in the nano-silver dispersion have a particle size of 5 nm to 50 nm; when the conductive material includes the reducible metal precursor solution, the reducible metal precursor solution contains at least one of a copper salt, a silver salt, and a metal-organic compound, and the reducible metal precursor solution is sprayed by the second spraying unit to form the conductive path according to the predetermined circuit pattern, and the metal elements in the reducible metal precursor solution are in compound form during spraying and are reduced in situ to a metallic conductive phase under the reducing atmosphere of the post-treatment.

8. The method for fabricating a three-dimensional circuit structure according to claim 4, characterized in that, In step S3, the amount of conductive material sprayed at the via segment is greater than the amount of conductive material sprayed at the conductive line segment, so that the deposition thickness of the via segment along the stacking direction is greater than the layer thickness of the insulating powder layer, and the upper end of the via segment protrudes from the upper surface of the current insulating powder layer; in step S4, the protruding upper end extends into the next insulating powder layer after the next insulating powder layer is laid, and contacts and overlaps with the conductive material sprayed in that layer.

9. The method for fabricating a three-dimensional circuit structure according to claim 2, characterized in that, The conductive phase formation stage is performed after the insulation densification stage is completed; after the insulation densification stage is completed, the temperature is lowered to the processing temperature of the conductive phase formation stage, and the conductive path pre-placed in the shaped green body is transformed in situ into the continuous conductive network under a reducing atmosphere.

10. A three-dimensional circuit structure, characterized in that, The three-dimensional circuit structure includes a three-dimensional insulating substrate and a continuous conductive network, wherein the continuous conductive network is located at least once inside and on the surface of the three-dimensional insulating substrate; the continuous conductive network includes a solid vertical conductive path located inside the three-dimensional insulating substrate, the solid vertical conductive path being integrally continuous with the rest of the continuous conductive network and its peripheral wall not having an independent hole wall metallization layer; the three-dimensional circuit structure is prepared by the method for preparing a three-dimensional circuit structure according to any one of claims 1 to 9.

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