Spacecraft force bearing and multi-layer flexible circuit integrated structure based on 3D printing

Abstract

The invention discloses a spacecraft force bearing and multi-layer flexible circuit integrated structure based on 3D printing. The spacecraft force bearing and multi-layer flexible circuit integrated structure is integrally formed by a metal force bearing layer, an electric insulation coating layer and a multi-layer flexible circuit functional layer through an in-situ continuous printing process, wherein the metal force bearing layer is made of metal additive materials. The metal bearing layer is a lightweight metal gradient dot matrix shell with complex internal functional channels; the electric insulation coating layer is sprayed or printed on the surface of the metal bearing layer in a surface modification binding force enhancing mode. And the multi-layer flexible circuit function layer is directly printed on the insulating layer across the curved surface and the edge. Physical and functional deep integration of a spacecraft main force bearing structure, a thermal management path, an electromagnetic compatibility substrate, electrical insulation and a high-low frequency circuit is realized, and the systematic problems of large size, heavy weight, multiple interfaces and low reliability of a traditional discrete design are solved. And the method is particularly suitable for platforms with strict requirements on space, weight and reliability, such as micro-nano satellites and the like.

Description

Technical Field

[0001] This invention belongs to the technical field of spacecraft structures, and particularly relates to an integrated structure based on 3D printing that combines load-bearing capacity and multi-layer flexible circuitry in spacecraft. Background Technology

[0002] With the development of miniaturized spacecraft such as microsatellites and CubeSats, higher demands are being placed on the functional density, lightweight design, and reliability of the platforms. Traditional spacecraft structures and electrical systems, which employ a separate design, independent manufacturing, and subsequent assembly approach, have numerous drawbacks: System redundancy and high weight: The numerous independent metal structural components, plastic insulating components, circuit boards, cables and connectors result in a large number of system parts, complex connection interfaces, and high overall weight.

[0003] Low space utilization: Separate components and wiring harnesses occupy a large amount of valuable cabin space, which contradicts the trend of flattened and modular configuration of spacecraft.

[0004] Reliability risks: Numerous mechanical connections (screws, crimping) and electrical connections (solder joints, connectors) are potential failure points, and reliability challenges are significant in harsh environments such as mechanical vibration and thermal cycling.

[0005] Complex manufacturing and assembly: Multiple processing steps, coordination with multiple suppliers, and cumbersome assembly and testing procedures result in long development cycles and high costs.

[0006] Existing circuit integration solutions mostly involve bonding flexible printed circuit boards (FPCs) to the surface of a structure or performing simple screen printing on flat areas. These methods cannot adapt to complex three-dimensional curved surfaces and suffer from weak interface bonding and poor environmental resistance. Therefore, there is an urgent need for a new technical solution that can achieve true integrated design and manufacturing of structure, insulation, and circuitry. Summary of the Invention

[0007] The purpose of this invention is to provide a method for designing and fabricating an integrated structure combining load-bearing and multi-layer flexible circuitry for spacecraft based on 3D printing. This method aims to achieve integrated continuous molding from the metal load-bearing substrate to the final circuit function through top-level multiphysics collaborative design and multi-material in-situ additive manufacturing processes. This significantly improves the integration and lightweighting of spacecraft systems while systematically optimizing their thermal management capabilities, electromagnetic compatibility, environmental adaptability, and long-term reliability.

[0008] To solve the above problems, the technical solution of the present invention is as follows: A 3D-printed integrated structure for spacecraft load-bearing and multi-layer flexible circuitry, comprising a three-layer integrally formed structure from the inside out: The metal load-bearing layer is a lightweight metal shell integrally formed using metal additive manufacturing technology. The metal shell adopts a variable density gradient lattice topology structure, and its density gradient configuration is optimized in coordination according to the mechanical load-bearing and thermal management requirements: a high fill rate is used under the installation area of ​​key electronic equipment that requires enhanced heat dissipation in high stress concentration areas or areas where heat dissipation needs to be strengthened, and a low fill rate is used in low stress or low heat flow areas. An electrically insulating coating layer is tightly bonded to all or part of the outer surface of the metal shell; the electrically insulating coating layer is pretreated by surface modification of the metal shell to enhance interfacial bonding and environmental durability, and is formed in situ using fused deposition modeling or controlled spraying processes; The multi-layer flexible circuit functional layer is directly printed on the surface of the electrical insulation coating layer, and includes multi-layer conductive patterns of power, signal and radio frequency lines. The multi-layer flexible circuit functional layer uses conductive ink or metal paste and achieves uninterrupted continuous wiring across curved surfaces and edges through multi-axis collaborative direct writing printing technology.

[0009] According to one embodiment of the present invention, the metal casing integrates a cooling channel for conformal propellant / coolant, the cooling channel passing below the high-fill area to facilitate active heat dissipation.

[0010] According to one embodiment of the present invention, the surface modification pretreatment of the metal shell includes laser microtexturing, chemical oxidation, or a combination thereof, to form micro / nano rough structures or active groups.

[0011] According to one embodiment of the present invention, the electrically insulating coating layer is a polymer insulating material layer of polyetheretherketone (PEEK) or its composite material.

[0012] According to an embodiment of the present invention, the circuit design of the multilayer flexible circuit functional layer follows the three-dimensional layout system-level optimization principle, including: Zoning layout and three-dimensional path planning: Based on the overall satellite configuration, electrical connection relationship, pin attributes and circuit power consumption, priority areas and safety boundaries are delineated in the non-load-bearing areas on the surface of the metal load-bearing structure to avoid high stress concentration areas and critical equipment installation interference areas. Layered routing and customized interconnects: Regional signal connections are completed within horizontal layers, and cross-connections between different planes or different functional blocks are achieved by using vertical vias between layers or specially designed customized three-dimensional pin structures adapted to complex geometries. Electromagnetic and shielding integrated design: For critical and sensitive lines, an encircling shielding point or mesh strip design is adopted around them, and the circuit line width, line spacing, shielding point size and spacing are optimized collaboratively through electromagnetic simulation tools. Thermal-mechanical synergistic wiring iterative optimization: Based on the circuit thermal distribution characteristics obtained from multiphysics simulation, the wiring path of high-risk heat-generating units and connection points is iteratively optimized to actively avoid or adapt to areas of thermal stress concentration caused by the difference in thermal expansion coefficients of metal substrate, insulating layer and circuit layer materials.

[0013] According to one embodiment of the present invention, the multilayer flexible circuit functional layer includes a cross-stacking multilayer structure, with the layers isolated by printed insulating dielectric layers.

[0014] A method for fabricating an integrated structure combining load-bearing and multilayer flexible circuitry for spacecraft based on 3D printing includes the following steps: Based on the spacecraft mission profile, we carried out structural-thermal-fluid-electric strong coupling topology optimization and collaborative design for the target components. In a unified digital model, we simultaneously determined the gradient lattice configuration of the metal shell, the layout of internal functional flow channels, the thickness distribution of the insulation layer, and the refined three-dimensional layout of each layer of circuits. Selective laser melting (SLM) or electron beam melting (EBM) technology is used to integrally print a metal gradient lattice structure with internal channels. After printing, stress-relieving heat treatment is performed, and the internal flow channels are finished by abrasive flow finishing. The outer surface of the printed metal shell is cleaned and the interface is strengthened and modified. Then, a uniform and dense insulating coating layer is formed in situ on the metal surface by high temperature melt deposition printing or precision spraying process. The curing process curve is precisely controlled to reduce interlayer residual stress. On the surface of the cured insulation layer, a multi-axis linkage direct writing printing system is used to print conductive circuits and interlayer insulating media layer by layer according to three-dimensional path planning. The conductive filler is quickly cured using an online laser or infrared sintering device. The printing process adapts to complex geometric features, ensuring the continuity of conductors across edges and areas with high curvature, the consistency of line width, and the strength of interface bonding.

[0015] According to one embodiment of the present invention, the preparation method further includes: conducting comprehensive performance testing and reliability evaluation on the prepared integrated structural component, including mechanical environment testing, insulation withstand voltage and resistance testing, circuit function and signal integrity testing, high and low temperature cycling testing, and post-test interface bonding strength comparison testing, to evaluate its long-term performance retention capability in a simulated space environment.

[0016] According to an embodiment of the present invention, the density gradient configuration of the gradient lattice structure of the metal shell is determined according to the following principles: High fill ratios are used below the mounting areas of critical electronic devices that require enhanced heat dissipation in areas of high stress concentration to improve local stiffness and heat conduction paths. Low filler ratios are used in low-stress or low-heat-flux regions to achieve lightweighting under safe load-bearing conditions.

[0017] According to one embodiment of the present invention, the three-dimensional path planning follows the three-dimensional layout system-level optimization principle of one embodiment.

[0018] Because of the above technical solutions, this invention has the following advantages and positive effects compared with the prior art: In one embodiment of the present invention, a spacecraft load-bearing and multi-layer flexible circuit integrated structure based on 3D printing is presented. Through multi-material in-situ additive manufacturing technology, the metal load-bearing structure, polymer insulating layer and multi-layer flexible circuit are truly integrated and continuously formed. Combined with multi-physics field collaborative design method, the structural load-bearing capacity, thermal management, electromagnetic compatibility and electrical performance are optimized simultaneously. As a result, while reducing the weight by more than 40%, the system integration, space utilization, thermal management capability and long-term reliability of the spacecraft are significantly improved, and it can adapt to the requirements of complex three-dimensional curved surface configuration and rapid iterative development. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an integrated structure of spacecraft load-bearing and multi-layer flexible circuit based on 3D printing, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a metal gradient lattice structure (high / low fill rate region) in one embodiment of the present invention; Figure 3 This is a partial microscopic schematic diagram of a spacecraft load-bearing and multi-layer flexible circuit integrated structure based on 3D printing in one embodiment of the present invention. Figure 4 This is a flowchart illustrating the fabrication method of an integrated structure combining 3D printing for spacecraft load-bearing and multilayer flexible circuitry, according to one embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1: Metal load-bearing layer; 2: Electrical insulation coating layer; 3: Multi-layer flexible circuit functional layer; 4: High fill area; 5: Low fill area; 6: Cooling channel. Detailed Implementation

[0021] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further explanation of the integrated structure for spacecraft load-bearing and multi-layer flexible circuitry based on 3D printing proposed in this invention.

[0022] This embodiment provides an integrated structure for spacecraft load-bearing and multi-layer flexible circuitry based on 3D printing. It aims to achieve integrated continuous molding from the metal load-bearing substrate to the final circuit function through top-level multi-physics field collaborative design and multi-material in-situ additive manufacturing process. This significantly improves the integration and lightweighting of spacecraft systems while systematically optimizing their thermal management capabilities, electromagnetic compatibility, environmental adaptability, and long-term reliability.

[0023] For details, please refer to Figures 1 to 3 This 3D-printed integrated structure for spacecraft load-bearing and multi-layer flexible circuitry comprises a three-layer integrated structure from the inside out: Metal Load-Bearing Layer 1: A lightweight metal shell integrally formed using metal additive manufacturing technology, capable of integrating complex internal functional channels (such as conformal propellant / coolant flow channels). Please refer to [link / reference]. Figure 2 The housing adopts a variable density gradient lattice topology (such as a body-centered cubic (BCC) lattice), and its density gradient configuration is simultaneously optimized according to the requirements of mechanical load-bearing and thermal management: in areas of high stress concentration (such as connection parts, curvature abrupt changes) or under the installation area of ​​critical electronic equipment that requires enhanced heat dissipation, a high fill rate is used to enhance local stiffness and heat conduction path, forming a high fill area 4; in areas of low stress / low heat flux, a low fill rate is used to form a low fill area 5, achieving extreme lightweighting under safe load-bearing conditions.

[0024] The metal load-bearing layer 1, made of titanium alloy and printed using SLM (Selective Laser Melting) technology, serves as the main load-bearing structure, propellant tank, and thermal management component. Its lattice design incorporates thermo-mechanical optimization: the lattice fill rate is increased below areas planned for high-power devices to create efficient heat conduction paths leading to the heat dissipation area at the side plate edges; the lattice fill rate is reduced in the remaining main areas. Cooling channels 6 are integrated inside the shell, flowing beneath the high-fill area 4 for active heat dissipation; the inner walls of these channels are polished using abrasive flow technology.

[0025] Electrical insulation coating layer 2: A polymer insulating material layer (preferably polyetheretherketone (PEEK) or its composite material) tightly bonded to all or part of the outer surface of the metal shell. This electrical insulation coating layer 2 is pretreated by surface modification of the metal shell (such as laser microtexturing, chemical oxidation to form micro-nano rough structures or active groups) to significantly enhance interfacial bonding and long-term environmental durability. It is formed by fused deposition modeling or controlled spraying processes to ensure uniform and dense coating in complex curved surfaces and grooved areas, meeting the requirements of high-voltage insulation and space environment tolerance.

[0026] Multilayer Flexible Circuit Functional Layer 3: A multilayer conductive pattern containing power, signal, and radio frequency lines, directly printed on the surface of the electrical insulation coating layer. This multilayer flexible circuit functional layer 3 uses conductive ink or metal paste and achieves uninterrupted continuous wiring across curved surfaces and edges through multi-axis collaborative direct-write printing technology. Multi-axis collaborative direct-write printing technology refers to additive manufacturing technology that utilizes multi-axis motion platforms such as robots or machine tools, in conjunction with end effectors such as printheads or lasers, to directly deposit materials or energy onto complex three-dimensional curved surfaces or suspended structures. In practical applications, existing equipment can be used, and this will not be described further.

[0027] Its circuit design must follow the principle of three-dimensional layout system-level optimization: Zoning layout and three-dimensional path planning: First, based on the overall satellite configuration, electrical connection relationship, pin attributes and circuit power consumption, priority areas and safety boundaries that can be used for high-reliability wiring are delineated in the non-load-bearing areas on the surface of the metal load-bearing structure (metal shell), avoiding high stress concentration areas and critical equipment installation interference areas.

[0028] Layered routing and customized interconnects: Regional signal connections are completed within horizontal layers, and cross-connections between different planes or different functional blocks are achieved by using interlayer vertical vias (implemented by printing) or specially designed customized 3D pin structures adapted to complex geometries, ensuring the electrical accessibility of unreachable connection points.

[0029] Integrated electromagnetic and shielding design: For critical sensitive lines (such as RF and clock lines), an encircling shielding point or mesh design is used (e.g., printing a grounding copper dot matrix around the sensitive line). Electromagnetic simulation tools are used to collaboratively optimize circuit linewidth, line spacing, and shielding point size and spacing to achieve optimal electromagnetic shielding and signal integrity in three-dimensional space. In practical applications, this can be achieved using ANSYS HFSS + SIwave, CST EM Studio + Design Studio, or RDSim electromagnetic simulation tools.

[0030] Thermal-Mechanical Co-location Iterative Optimization of Routing: Based on the circuit thermal distribution characteristics obtained from multiphysics simulation, the routing paths of high-risk heat-generating units (such as those below power devices) and connection points are iteratively optimized. Path planning must proactively avoid or adapt to areas of thermal stress concentration that may be caused by differences in the thermal expansion coefficients of metal casing, insulation layers, and circuit layer materials, preventing defects such as breakage, warping, or poor contact caused by thermal cycling at the root of the routing. In practical applications, the circuit thermal distribution characteristics obtained from multiphysics simulation can be simulated using ANSYS Icepak or COMSOL Multiphysics, and verified using experimental methods such as thermal imaging. This allows for a limited number of experimental iterative optimizations of the routing paths of high-risk heat-generating units (such as those below power devices) and connection points.

[0031] The multilayer flexible circuit functional layer 3 can contain a cross- and stacked multilayer structure, with reliable isolation between layers through printed insulating dielectric layers.

[0032] Please refer to Figure 4 The above-mentioned method for fabricating an integrated structure combining spacecraft load-bearing and multilayer flexible circuitry based on 3D printing includes the following steps: Multiphysics Collaborative Forward Integrated Design: Based on spacecraft mission profiles, this approach involves strong coupling topology optimization and collaborative design of target components across structure, heat, fluidity, and electricity (including electromagnetic compatibility). Within a unified digital simulation model, the gradient lattice configuration of the metal shell, the layout of internal functional channels, the thickness distribution of the insulating layer, and the refined three-dimensional layout of each circuit layer are simultaneously determined, ensuring that the design meets comprehensive performance indicators such as mechanical properties, heat dissipation, insulation, signal integrity, and electromagnetic shielding from the outset.

[0033] Metal load-bearing layer printing and post-processing: Based on the design documents from the previous step, selective laser melting (SLM) or electron beam melting (EBM) techniques are used to integrally print a metal gradient lattice structure with internal functional flow channels (such as cooling channels). After printing, stress-relieving heat treatment is performed. For the internal functional flow channels, abrasive flow finishing and other finishing processes are required to ensure that the surface roughness of the inner wall meets the requirements of the corresponding fluid, thereby guaranteeing fluid performance.

[0034] Metal surface pretreatment and insulation layer preparation: The outer surface of the printed metal shell is cleaned and subjected to interface strengthening modification treatments (such as laser texturing and plasma treatment). Subsequently, a uniform and dense insulating coating layer (such as PEEK) is formed in situ on the metal surface using high-temperature fused deposition modeling (FDM) or precision spraying, and the curing process curve is precisely controlled to reduce interlayer residual stress. Alternatively, PEEK powder can be precisely sprayed onto the pretreated surface using a high-temperature spray gun and then subjected to crystallization heat treatment to form a dense insulating layer.

[0035] Printing of complex curved multilayer flexible circuits: On the surface of the cured insulating layer, a multi-axis linkage direct-write printing system is used to print conductive circuits and interlayer insulating media layer by layer according to three-dimensional path planning. In-line laser or infrared sintering devices are used to rapidly cure the conductive filler. The printing process must adapt to complex geometric features, ensuring the continuity, linewidth consistency, and interface bonding strength of conductors across edges and areas of high curvature. The circuit can integrate simple status monitoring nodes (such as thermistor patterns). For example, a power distribution network layer is first printed using nano-silver conductive paste, which is closest to the metal substrate to facilitate heat dissipation. Next, a polyimide dielectric layer is printed, followed by a signal layer and a continuous grounding grid layer. Finally, the RF circuit layer is printed, where the sensitive S-band receiver link is located away from the power layer, with a complete grounding grid below it to enhance shielding. All high-speed LVDS signal lines are printed adjacently in differential pairs of equal length. At the folded edges connecting the side panels and adjacent panels, precise attitude adjustment of the five-axis print head achieves uninterrupted continuous circuit connections across edges.

[0036] When designing the layout, the following points should be noted: 1. Divide the wiring area: Based on the satellite configuration, divide the circuit surface into "high reliability wiring area" (avoiding load-bearing and assembly interference areas such as screw holes and equipment mounting groove edges) and "normal wiring area".

[0037] 2. Application of Shielding Design: For S-band receiving links, a grounding shielding grid consisting of tiny squares is continuously printed on both sides and above the adjacent circuit layers along the trace path, instead of a simple single ground wire. The grid size and linewidth are determined through simulation to achieve optimal shielding effectiveness in the target frequency band.

[0038] 3. Thermal stress consideration: When configuring power supply lines for high-power devices, simulations predicted the local high-temperature distribution during operation. We designed the power supply routing path to pass through a low-stress elastic bending section after leaving the high-power device mounting point before connecting to the main power network, rather than the shortest straight path. This buffers and disperses the shear stress between different material interfaces caused by periodic temperature rises, avoiding fatigue failure of solder joints (in this case, the printed connection point).

[0039] Despite the high degree of physical integration, the electrical architecture still needs to be divided into logical functional blocks such as integrated electronics, power management, attitude control interface, and RF front end. Each block has a standardized group of boundary scan test points reserved on the edge of the board to facilitate independent testing and fault diagnosis.

[0040] Integrated Performance Verification and Reliability Assessment: A comprehensive performance test and reliability assessment is conducted on the fabricated integrated structural component. Tests should include: mechanical environment testing (vibration, shock), insulation withstand voltage and resistance testing, circuit function and signal integrity testing, high and low temperature cycling testing, and post-test interface bonding strength comparison testing. The long-term performance retention capability in a simulated space environment is evaluated. If, after testing, the interface bonding strength retention rate exceeds 85%, and all electrical performance parameters meet design requirements, this test can be performed using existing equipment and will not be described here.

[0041] Finally, protective coatings are selectively applied to critical areas of the circuitry as needed. This 3D-printed integrated structure, combining spacecraft load-bearing capacity with multi-layered flexible circuitry, replaces traditional designs with aluminum honeycomb panels, individual wiring harnesses, connectors, and multiple circuit boards, achieving a weight reduction of over 40% while providing higher structural stiffness, better thermal management, and superior electrical performance.

[0042] In summary, this 3D-printed integrated structure and fabrication method for spacecraft load-bearing and multi-layer flexible circuits integrates a metal load-bearing layer, an electrically insulating coating layer, and a multi-layer flexible circuit functional layer through in-situ continuous printing. The metal load-bearing layer is a lightweight metal gradient lattice shell with complex internal functional channels; the electrically insulating coating layer is sprayed or printed onto the metal shell surface through surface modification to enhance adhesion; the multi-layer flexible circuit functional layer is directly printed across curved surfaces and edges on the electrically insulating coating layer, enabling strong / weak current partitioning and complete high-speed signal wiring. This achieves deep physical and functional integration of the spacecraft's main load-bearing structure, thermal management path, electromagnetic compatibility substrate, electrical insulation, and high / low frequency circuits. Through top-level multi-physics collaborative design, it ensures optimal overall performance in terms of lightweighting, heat dissipation, electromagnetic compatibility, and long-term reliability from the source, solving the systemic problems of large size, heavy weight, numerous interfaces, and low reliability inherent in traditional discrete designs. It is particularly suitable for platforms such as micro- and nano-satellites with stringent requirements for space, weight, and reliability.

[0043] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A 3D-printed integrated structure for spacecraft load-bearing and multi-layer flexible circuitry, characterized in that, It consists of a three-layer integrated structure from the inside out: The metal load-bearing layer is a lightweight metal shell integrally formed using metal additive manufacturing technology. The metal shell adopts a variable density gradient lattice topology structure, and its density gradient configuration is optimized in coordination according to the mechanical load-bearing and thermal management requirements: a high fill rate is used under the installation area of ​​key electronic equipment that requires enhanced heat dissipation in high stress concentration areas or areas where heat dissipation needs to be strengthened, and a low fill rate is used in low stress or low heat flow areas. An electrically insulating coating layer is tightly bonded to all or part of the outer surface of the metal shell; the electrically insulating coating layer is pretreated by surface modification of the metal shell to enhance interfacial bonding and environmental durability, and is formed in situ using fused deposition modeling or controlled spraying processes; The multi-layer flexible circuit functional layer is directly printed on the surface of the electrical insulation coating layer, and includes multi-layer conductive patterns of power, signal and radio frequency lines. The multi-layer flexible circuit functional layer uses conductive ink or metal paste and achieves uninterrupted continuous wiring across curved surfaces and edges through multi-axis collaborative direct writing printing technology.

2. The integrated structure of spacecraft load-bearing and multi-layer flexible circuit based on 3D printing according to claim 1, characterized in that, The metal casing integrates conformal propellant / coolant cooling channels that pass below the high-fill area for active heat dissipation.

3. The integrated structure of spacecraft load-bearing and multi-layer flexible circuit based on 3D printing according to claim 1, characterized in that, The surface modification pretreatment of the metal shell includes laser microtexturing, chemical oxidation, or a combination thereof, to form micro / nano rough structures or active groups.

4. The integrated structure of spacecraft load-bearing and multi-layer flexible circuit based on 3D printing according to claim 1, characterized in that, The electrical insulation coating layer is a polymeric insulating material layer of polyetheretherketone (PEEK) or its composite material.

5. The integrated structure of spacecraft load-bearing and multi-layer flexible circuit based on 3D printing according to claim 1, characterized in that, The circuit design of the multi-layer flexible circuit functional layer follows the three-dimensional layout system-level optimization principle, including: Zoning layout and three-dimensional path planning: Based on the overall satellite configuration, electrical connection relationship, pin attributes and circuit power consumption, priority areas and safety boundaries are delineated in the non-load-bearing areas on the surface of the metal load-bearing structure to avoid high stress concentration areas and critical equipment installation interference areas. Layered routing and customized interconnects: Regional signal connections are completed within horizontal layers, and cross-connections between different planes or different functional blocks are achieved by using vertical vias between layers or customized three-dimensional pin structures. Electromagnetic and shielding integrated design: For critical and sensitive lines, an encircling shielding point or mesh strip design is adopted around them, and the circuit line width, line spacing, shielding point size and spacing are optimized collaboratively through electromagnetic simulation tools. Thermal-mechanical synergistic wiring iterative optimization: Based on the circuit thermal distribution characteristics obtained from multiphysics simulation, the wiring path of high-risk heat-generating units and connection points is iteratively optimized to actively avoid or adapt to areas of thermal stress concentration caused by the difference in thermal expansion coefficients of metal substrate, insulating layer and circuit layer materials.

6. The integrated structure of spacecraft load-bearing and multi-layer flexible circuit based on 3D printing according to claim 1, characterized in that, The multilayer flexible circuit functional layer comprises a cross-stacking, stacked multilayer structure, with the layers isolated by printed insulating dielectric layers.

7. A method for fabricating an integrated structure combining load-bearing and multilayer flexible circuitry for spacecraft based on 3D printing, characterized in that, Includes the following steps: Based on the spacecraft mission profile, we carried out structural-thermal-fluid-electric strong coupling topology optimization and collaborative design for the target components. In a unified digital model, we simultaneously determined the gradient lattice configuration of the metal shell, the layout of internal functional flow channels, the thickness distribution of the insulation layer, and the refined three-dimensional layout of each layer of circuits. Selective laser melting (SLM) or electron beam melting (EBM) technology is used to integrally print a metal gradient lattice structure with internal channels. After printing, stress-relieving heat treatment is performed, and the internal flow channels are finished by abrasive flow finishing. The outer surface of the printed metal shell is cleaned and the interface is strengthened and modified. Then, a uniform and dense insulating coating layer is formed in situ on the metal surface by high temperature melt deposition printing or precision spraying process. The curing process curve is precisely controlled to reduce interlayer residual stress. On the surface of the cured insulation layer, a multi-axis linkage direct writing printing system is used to print conductive circuits and interlayer insulating media layer by layer according to three-dimensional path planning. The conductive filler is quickly cured using an online laser or infrared sintering device. The printing process adapts to complex geometric features, ensuring the continuity of conductors across edges and areas with high curvature, the consistency of line width, and the strength of interface bonding.

8. The method for fabricating an integrated structure of spacecraft load-bearing and multilayer flexible circuit based on 3D printing according to claim 7, characterized in that, It also includes: conducting comprehensive performance testing and reliability assessment on the completed integrated structural components, including mechanical environment testing, insulation withstand voltage and resistance testing, circuit function and signal integrity testing, high and low temperature cycling testing, and post-test interface bonding strength comparison testing, to evaluate its long-term performance retention capability in simulated space environment.

9. The method for fabricating an integrated structure of spacecraft load-bearing and multilayer flexible circuit based on 3D printing according to claim 7, characterized in that, The density gradient configuration of the gradient lattice structure of the metal shell is determined according to the following principles: High fill ratios are used below the mounting areas of critical electronic devices that require enhanced heat dissipation in areas of high stress concentration to improve local stiffness and heat conduction paths. Low filler ratios are used in low-stress or low-heat-flux regions to achieve lightweighting under safe load-bearing conditions.

10. The method for fabricating an integrated structure of spacecraft load-bearing and multilayer flexible circuit based on 3D printing according to claim 7, characterized in that, The three-dimensional path planning follows the three-dimensional layout system-level optimization principle as described in claim 5.

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