Housing seal structure design method for integrated flexible circuit

Abstract

The application relates to the technical field of circuit board shell sealing, in particular to a shell sealing structure design method for integrated flexible circuits, which comprises the following steps: a multilayer stacked flexible circuit board is adopted, at least one layer is provided with an electromagnetic shielding layer, the shielding layer extends to a sealing area at the edge of the circuit board, a metal matrix composite material is adopted for the shell, a topologically optimized support structure is arranged in the shell, a microstructure texture is arranged on the side wall of a sealing groove, a thermal expansion buffer layer is arranged on the groove bottom, a shape memory alloy element is arranged between a sealing adhesive tape and a waterproof and breathable film, the two ends of the element are connected with the sealing groove of the shell and a circuit board respectively, a multi-axis robot is used in cooperation with a displacement sensor to adjust an assembly track in real time, a multi-physical field simulation model of the sealing structure is established, and parameters are dynamically optimized in association with entity test data, the shell sealing structure design method for integrated flexible circuits integrates the electromagnetic shielding structure into the sealing interface of the flexible circuit and the shell, and the electromagnetic shielding layer and the metal shell form a coherent electromagnetic isolation barrier.

Description

Technical Field

[0001] This invention relates to the field of circuit board housing sealing technology, specifically to a design method for a housing sealing structure of integrated flexible circuits. Background Technology

[0002] With the rapid development of electronic devices towards miniaturization and high integration, flexible circuits, due to their bendability and lightweight characteristics, are widely used in consumer electronics, industrial control, and aerospace. However, when integrating flexible circuits into device housings, stringent requirements for environmental sealing, electromagnetic compatibility, and mechanical reliability must be met simultaneously under complex operating conditions. Traditional design solutions often struggle to meet these multiple performance requirements.

[0003] Existing housing sealing structures mostly employ a single physical sealing method, such as adhesive sealing or pressure sealing. While these can achieve basic dust and water resistance, they have significant limitations: First, conventional sealing structures lack electromagnetic shielding design, making them prone to electromagnetic leakage during high-frequency circuit operation, interfering with external equipment or affecting signal integrity due to external electromagnetic environments. Second, in environments with drastic temperature changes, the difference in thermal expansion coefficients between the housing and the flexible circuit substrate generates interfacial stress, leading to adhesive layer cracking or detachment, and the sealing performance rapidly deteriorates with temperature cycling. Third, the assembly process relies excessively on manual operation, making it difficult to precisely control the adhesive layer thickness and curing uniformity, easily causing localized sealing failures. Furthermore, traditional verification methods rely on later physical testing, making it impossible to predict the failure modes of the sealing structure under extreme conditions during the product design stage, resulting in long development cycles and high costs.

[0004] To address the aforementioned issues, the industry has attempted improvements by adding a metal shielding layer to the sealed structure or using highly elastic sealing materials. However, these approaches often introduce new technical challenges: the interface impedance mismatch at the junction of the metal shielding layer and the shell can easily lead to secondary electromagnetic leakage; while highly elastic materials can alleviate thermal stress, they reduce structural rigidity, failing to meet the mechanical stability requirements under vibration and shock environments. Furthermore, existing thermal stress compensation technologies mostly employ passive buffering materials, lacking the ability to actively respond to temperature changes, and may still experience sealing failures in scenarios with rapid temperature variations. Therefore, there is an urgent need to develop an integrated sealing design method that, while ensuring environmental sealing, achieves synergistic optimization of electromagnetic compatibility, adaptive thermal stress adjustment, and process controllability to meet the increasingly stringent reliability requirements of modern electronic equipment.

[0005] To address this, we propose a design method for a housing-sealed structure integrating flexible circuits. Summary of the Invention

[0006] One of the technical problems this application aims to solve is the urgent need to develop an integrated sealing design method that, while ensuring environmental sealing, achieves synergistic optimization of electromagnetic compatibility, adaptive adjustment of thermal stress, and process controllability, in order to meet the increasingly stringent reliability requirements of modern electronic equipment.

[0007] To address the aforementioned technical problems, embodiments of this application provide a method for designing a housing sealing structure for integrated flexible circuits, comprising the following steps:

[0008] S1: Electromagnetic compatibility flexible circuit design, using multi-layer stacked flexible circuit boards, of which at least one layer is provided with an electromagnetic shielding layer, the shielding layer extends to the sealed area at the edge of the circuit board, the circuit components are embedded in the substrate slots and fixed by conductive adhesive, and the surface is covered with encapsulating adhesive to form a flat plane.

[0009] S2: Thermal deformation synergistic shell design, the shell is made of metal matrix composite material, the internal topology-optimized support structure is provided, the side wall of the sealing groove is set with microstructure texture, and the bottom of the groove is laid with thermal expansion buffer layer;

[0010] S3: Dynamic response sealing system, with shape memory alloy elements set between the sealing tape and the waterproof and breathable membrane, and the two ends of the elements are connected to the housing sealing groove and the circuit board respectively;

[0011] S4: Intelligent compensation assembly, using a multi-axis robot with displacement sensors to adjust the assembly trajectory in real time, and applying zoned temperature and pressure fields during the bonding process;

[0012] S5: Digital twin testing and verification, establishing a multi-physics simulation model of the sealed structure, and dynamically optimizing parameters by associating entity test data.

[0013] In some embodiments, the electromagnetic shielding layer is a copper mesh structure with a line width ≤ 0.1 mm and a mesh density that increases by more than 20% from the center of the sealed area to the edge.

[0014] In some embodiments, the thermal expansion buffer layer is composed of silica aerogel composite polyimide fiber, with a thickness of 15-20% of the depth of the sealing groove, and a thermal expansion coefficient that is more than 50% lower than that of the shell material.

[0015] In some embodiments, the shape memory alloy element is made of nickel-titanium-copper alloy, the phase transition temperature is set to 40-50℃, the array density is 40-60 elements / cm², and the unit restoring force is 0.2-0.5N.

[0016] In some embodiments, the temperature and pressure fields are divided into three control zones along the width of the sealing strip: a central zone with a temperature of 110-120°C and a pressure of 0.4-0.5 MPa, an edge zone with a temperature of 80-90°C and a pressure of 0.1-0.2 MPa, and a transition zone with linearly varying parameters.

[0017] In some embodiments, the multiphysics simulation model includes a sealing interface failure prediction algorithm, which uses machine learning to analyze more than 100,000 sets of aging data to dynamically correct the design coefficients for temperature-pressure coupling conditions.

[0018] In some embodiments, the edge of the electromagnetic shielding layer forms a conductive connection with the sealing tape, and electrical conduction is achieved by filling conductive adhesive through laser drilling.

[0019] In some embodiments, the microstructure texture of the sealing groove is a sawtooth array with a depth of 0.05-0.1 mm, and the tooth pitch decreases by 30-50% from the groove opening to the groove bottom.

[0020] In some embodiments, infrared thermal imaging data is collected synchronously during the robot assembly process, and the heating power is automatically adjusted when the local temperature difference exceeds 15°C.

[0021] In some embodiments, the failure prediction algorithm includes a vibration frequency adaptation module to generate a custom sealing structure solution for vibration environments of 50-2000Hz.

[0022] This invention has at least the following beneficial effects:

[0023] 1. Integrate electromagnetic shielding structures, such as fractal shielding meshes, into the sealed interface between the flexible circuit and the housing. An electrical connection established through conductive sealing tape creates a continuous electromagnetic isolation barrier between the electromagnetic shielding layer and the metal housing, effectively suppressing the leakage of electromagnetic energy within the equipment and the intrusion of external interference. This dual-sealing mechanism, while ensuring the physical sealing of the housing (such as waterproofing and dustproofing), significantly improves the electromagnetic compatibility (EMC) performance of the equipment, making it particularly suitable for high-frequency or precision electronic equipment with stringent signal integrity requirements.

[0024] 2. To address the core failure risk of electronic devices under alternating temperature environments—namely, sealing interface failure caused by thermal stress—this method introduces a thermal deformation synergistic control mechanism. On one hand, a specially designed thermal expansion coefficient buffer layer is placed at the bottom of the housing sealing groove, effectively absorbing and dissipating most of the stress caused by the difference in thermal expansion coefficients between the housing and the circuit substrate. On the other hand, a shape memory alloy micro-spring array integrated into the sealing interface can actively adjust its length during temperature changes, intelligently compensating for minute gaps or overpressures caused by thermal expansion and contraction. This strategy, combining passive absorption and active compensation, ensures the long-term stability of the sealing interface under various extreme temperature conditions (such as from deep cryogenic to high-temperature environments), significantly improving the sealing structure's tolerance and service life in harsh environments.

[0025] 3. Through intelligent assembly process design and a digital twin-based verification system, production efficiency and product reliability have been significantly improved. The intelligent compensation assembly process, employing automated robots and precision sensing technologies (such as laser displacement and infrared thermal imaging), can monitor and dynamically correct deformation and temperature gradients during assembly in real time, ensuring uniform curing of the sealant layer and effectively eliminating errors and inconsistencies caused by manual operation. Simultaneously, a multiphysics simulation model built using digital twin technology can accurately predict the sealing performance, heat distribution, and electromagnetic shielding effectiveness of the product before the physical prototype is manufactured, guiding the physical testing plan. This closed-loop process of design-simulation-manufacturing-verification not only significantly shortens the product development and verification cycle and reduces R&D costs, but more importantly, it ensures the consistency and high yield of the shell sealing structure performance in mass production. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the method steps of the present invention;

[0027] Figure 2 This is a schematic diagram of the failure prediction algorithm steps in S5. Detailed Implementation

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

[0029] Example 1, please refer to Figure 1 This invention provides a technical solution: a design method for a housing sealing structure of integrated flexible circuits, comprising the following steps:

[0030] S1: Electromagnetic compatibility flexible circuit design, using multi-layer stacked flexible circuit boards, of which at least one layer is provided with an electromagnetic shielding layer, the shielding layer extends to the sealing area of ​​the edge of the circuit board, the circuit elements are embedded in the substrate slots and fixed by conductive adhesive, and the surface is covered with encapsulating adhesive to form a flat plane.

[0031] S2: Thermal deformation synergistic shell design, the shell is made of metal matrix composite material, the internal topology-optimized support structure is provided, the side wall of the sealing groove is set with microstructure texture, and the bottom of the groove is laid with thermal expansion buffer layer;

[0032] S3: Dynamic response sealing system, with shape memory alloy elements set between the sealing tape and the waterproof and breathable membrane, and the two ends of the elements are connected to the housing sealing groove and the circuit board respectively;

[0033] S4: Intelligent compensation assembly, using a multi-axis robot with displacement sensors to adjust the assembly trajectory in real time, and applying zoned temperature and pressure fields during the bonding process;

[0034] S5: Digital twin testing and verification, establishing a multi-physics simulation model of the sealed structure, and dynamically optimizing parameters by associating entity test data.

[0035] Specifically, the implementation process is as follows:

[0036] The electromagnetic compatibility flexible circuit fabrication steps in S1 involve using a polyimide substrate to create a multilayer flexible circuit board, and then employing photolithography to form a biomimetic fractal shielding mesh in the second conductive layer. The specific process is as follows:

[0037] First, the shielding layer is prepared by etching a dendritic fractal grid on a 0.1 mm thick copper foil, with the linewidth controlled at 80 μm and the grid density increasing by 5% per millimeter from the center to the edge, extending to 2 mm at the edge of the sealing area. Next, the components are encapsulated by forming a rectangular groove with a depth of 0.25 mm on the substrate using laser micro-engraving technology. After embedding micro-sensors and other components, nano-silver paste is injected to fill the gaps. After curing, the surface flatness deviation is ≤8 μm. Finally, the surface is treated by spin-coating a 30 μm thick liquid optical adhesive, which is then cured under ultraviolet light to form a smooth surface with Ra<0.3 μm, eliminating capillary penetration channels.

[0038] The advantages of this design are that the fractal shielding mesh improves the shielding effectiveness by 22dB in the 18GHz band, the embedded packaging increases the shear strength of the component by 4 times, and the optical adhesive layer blocks moisture from entering along the component pin path.

[0039] The heat-deformation synergistic shell processing steps in S2 utilize CNC machining of a carbon fiber reinforced aluminum matrix composite material (35% carbon fiber content). Key technologies include the following steps: First, topology optimization design, specifically generating a hexagonal honeycomb structure based on finite element analysis, with a wall thickness of 0.8±0.05mm, achieving a 40% weight reduction while increasing stiffness by 15%; second, sealing groove processing, milling a 1.2mm deep stepped groove on the shell mating surface, and machining 0.1mm deep interlaced serrations on the sidewalls, with the tooth pitch gradually changing from 0.5mm at the groove opening to 0.2mm at the bottom, increasing the effective bonding area by 55%; finally, buffer layer laying, with a 0.3mm thick silane-modified aerogel / polyimide composite layer pre-placed at the bottom of the groove, with a coefficient of thermal expansion (CTE) of 5×10⁻⁶. -6 / K, with a difference of up to 8 times from the shell CTE, ensures that 85% of thermal stress is absorbed by the buffer layer.

[0040] The assembly steps for the dynamic sealing system in S3, including the setup of a double-layer adaptive sealing structure, are as follows:

[0041] First is the primary sealing layer, where a 0.12mm thick conductive tape with a conductive particle doping rate of 45% is laid in the sealing groove of the shell to ensure that the conduction resistance between the shielding layer and the shell is <0.1Ω. Next is the shape memory element, where 1mm diameter nickel-titanium-copper alloy microsprings are implanted at 5mm intervals and fixed to the side wall of the shell by laser welding. The other end is bonded to the flexible circuit grounding layer by conductive silver paste. Finally, there is the secondary protective layer, which is covered with a 25μm thick expanded polytetrafluoroethylene (ePTFE) film with a 1.8mm edge allowance and is bonded to the shell by a hot pressing process.

[0042] The working mechanism of the double-layer adaptive sealing structure is as follows: when the ambient temperature exceeds 50℃, the shape memory spring extends to compensate for the 0.2mm thermal expansion gap; when the temperature drops below 40℃, it returns to its initial length to prevent overpressure. The ePTFE membrane maintains airtightness under a pressure difference of 0.3kPa, with an air permeability >8000g / m² / 24h.

[0043] The intelligent compensation assembly process in S4 utilizes a six-axis robot equipped with a multi-sensor end effector to achieve high-precision assembly. Specifically, it includes the following steps: First, deformation monitoring: a laser displacement sensor detects the curvature of the circuit board at a 1000Hz sampling rate, automatically generating a reverse bending path when edge warping exceeds 0.1mm. Next, gradient temperature and pressure control: the pressure head applies process parameters in three zones: 115℃ / 0.5MPa in the center zone (40% width), 80℃ / 0.2MPa in the edge zone, and a linearly gradual parameter change in the transition zone. Finally, real-time correction: an infrared thermal imager monitors the temperature field, dynamically adjusting the heating power when an abnormal zone of ±10℃ is identified, ensuring uniform adhesive curing. The benefits of this approach are: assembly tolerance reduced from ±0.3mm to ±0.05mm; adhesive thickness deviation <5%; and production cycle time increased to 90 seconds per piece.

[0044] The S5 digital twin verification system comprises a multi-dimensional testing and verification process, specifically: simulation modeling, importing a 3D shell model into COMSOL, coupling electromagnetic-thermal-structural multiphysics fields, and predicting shielding effectiveness in the 10-40GHz frequency band and thermal stress distribution at 150℃; physical testing, conducting 200 cycles of testing in a temperature-varying chamber (-55℃~125℃), monitoring the interface peel strength attenuation rate to <3%; and data analysis, collecting 100,000 sets of aging data to train an LSTM neural network and establish a sealing life prediction model. ,in Where is the material coefficient, T is the temperature (°C), and P is the pressure (kPa).

[0045] Example 2, please refer to Figure 1 The electromagnetic shielding layer is a copper mesh structure with a line width of ≤0.1mm and a mesh density that increases by more than 20% from the center of the sealed area to the edge.

[0046] Specifically, the design principle of the copper mesh structure is based on the skin effect of high-frequency electromagnetic fields and the leakage law of electromagnetic interference. Copper, as a highly conductive metal, can form a continuous Faraday cage effect in its mesh structure, effectively reflecting and absorbing electromagnetic waves. Controlling the linewidth to within 0.1 mm (equivalent to a specific fraction of the high-frequency signal wavelength) can significantly improve the shielding effectiveness against interference in high-frequency bands above 5G (>6GHz). The gradient increase in mesh density from the center to the edge of the sealed area is a targeted reinforcement measure designed to address the characteristic that electromagnetic waves are more easily leaked at the structure's edges due to diffraction effects.

[0047] The purpose of this design is to use a denser mesh structure at the edges to effectively block electromagnetic leakage paths at the seams of the equipment casing (which typically account for over 70% of the total leakage), thus suppressing the slot antenna effect. Sealed edge areas often experience greater mechanical stress and thermal deformation; increasing the mesh density simultaneously improves the conductivity continuity in these areas, preventing shielding failure due to material deformation. By using a gradually decreasing distribution from sparse at the center to dense at the edges, the amount of copper used is reduced by more than 35% while maintaining the shielding performance of critical areas and preserving the flexibility of the circuit board.

[0048] The advantages of this design are that the gradient grid provides 8-12 dB better shielding effectiveness at high frequencies (18-40 GHz) compared to a uniform grid, effectively blocking radiation from high-speed circuits inside the device and reducing the risk of interference from external strong electromagnetic pulses to sensitive internal components. The fine grid with a linewidth ≤0.1 mm has higher ductility (elongation at break >15%), allowing it to deform in tandem with the substrate during thermal expansion and contraction or mechanical vibration, preventing grid breakage due to repeated bending. This structure can be formed in one step using mature etching or laser direct writing processes. The increased grid density at the edges requires no additional steps and can be achieved solely through mask pattern design, making it compatible with existing flexible circuit production lines.

[0049] Example 3: The thermal expansion buffer layer is composed of silica aerogel composite polyimide fiber, with a thickness of 15-20% of the depth of the sealing groove, and a thermal expansion coefficient that is more than 50% lower than that of the shell material.

[0050] Specifically, the design principle of the thermal expansion buffer layer is based on the theory of thermal stress gradient resolution and the composite mechanism of low-expansion heterogeneous materials. Silica aerogel, with its nanoporous structure (porosity > 95%) and the stability of silicon-oxygen bonds, possesses an ultra-low coefficient of thermal expansion (CTE ≈ 1 × 10⁻⁶). -6 / K). The three-dimensional network skeleton formed by polyimide fibers endows the material with compressive strength (>3MPa) and toughness. The combination of the two produces a synergistic effect: the aerogel mainly inhibits expansion, while the fiber network absorbs shear deformation energy, forming a buffer interface with stable mechanical properties. If the thickness is controlled at 15-20% of the sealing groove depth, finite element simulation verifies that stress absorption rate and space occupation can be balanced.

[0051] The purpose of this design is to take advantage of the fact that the CTE of the buffer layer is more than 50% lower than that of the metal shell (e.g., the CTE of aluminum alloy is approximately 23 × 10⁻⁶). -6 The buffer layer ( / K) actively absorbs the expansion difference between the housing and the flexible circuit board during temperature changes. When the housing expands by ΔL, the buffer layer only undergoes a deformation of ΔL / 5, consuming more than 70% of the interfacial shear stress. Through precise thickness positioning (occupying 15-20% of the groove depth), thermal stress is forced to concentrate inside the buffer layer rather than at the sealant interface, preventing the sealant layer from peeling off due to tensile-shear combined stress. Polyimide fibers prevent the aerogel particles from migrating under cyclic loading, ensuring that the buffer layer maintains stable pore structure and performance in a temperature-changing environment of -40℃ to 150℃ over a long period of time.

[0052] The advantage of this design is that, under a 150°C temperature difference shock (such as that of spacecraft extravehicular equipment), the buffer layer reduces the interfacial peel stress from 18MPa to below 4MPa, allowing the sealing structure to pass 2000 thermal cycle tests. Compared to traditional silicone gaskets (CTE≈300×10...), this is significantly better. -6 / K), which improves thermal stress relief efficiency by 5 times. The hydrophobic modification of the aerogel (contact angle >150°) blocks the path of moisture penetration along thermal stress cracks, extending the sealing life of the equipment in an 85℃ / 85%RH environment by more than 3 times. The aerogel density is only 120kg / m³, and the overall density of the composite layer is <200kg / m³, reducing weight by 85% compared to the metal spring compensation solution; the 15-20% groove depth ratio provides a buffer function while reserving more layout space for electronic components.

[0053] Example 4: The shape memory alloy element is made of nickel-titanium-copper alloy, the phase transition temperature is set to 40-50℃, the array density is 40-60 elements / cm², and the unit restoring force is 0.2-0.5N.

[0054] Specifically, the design principle of shape memory alloy components is based on the thermoelastic phase transformation characteristics and micromechanical group effects of shape memory alloys. After special heat treatment, the austenitic phase transformation temperature of the nickel-titanium-copper alloy is precisely controlled within the range of 40-50℃. When the ambient temperature exceeds this threshold, an austenitic-martensite phase transformation occurs inside the alloy, generating approximately 4% reversible shape recovery strain. The array density is set to 40-60 elements / cm², an optimized value verified through finite element simulation. This density covers more than 90% of the thermal deformation compensation requirements while avoiding stress interference caused by excessively dense element spacing. The restoring force range of 0.2-0.5N for a single element matches the contact pressure gradient required for a typical sealing interface.

[0055] The purpose of this design is that when the equipment temperature rises above 40°C, the alloy components expand due to heat, pushing the sealing interface to fit tightly and compensating for the thermal expansion difference between the housing and the circuit board. After the temperature drops, the components contract and reset, avoiding structural damage due to overvoltage. The array arrangement allows each unit to respond independently to local temperature changes, specifically compensating for regional deformation differences when the equipment is heated unevenly (such as unilateral temperature rise caused by direct sunlight). The superelastic properties of the alloy near its phase transition temperature can absorb mechanical vibration energy in the 20-200Hz frequency band, reducing the risk of microcrack propagation caused by fatigue accumulation in the sealing layer.

[0056] The advantage of this design is that, under cyclic conditions from -20℃ to 80℃, compared to traditional spring compensation schemes, it reduces the fluctuation range of interface contact pressure from ±35% to ±8%, significantly reducing the probability of seal failure caused by thermal shock. The nickel-titanium-copper alloy maintains over 95% shape recovery after 3000 phase change cycles, and its corrosion resistance (no failure after 1000 hours of salt spray testing) eliminates the need for periodic replacement in harsh environments such as the ocean. Micron-level component height (<0.3mm) enables stealthy integration without increasing housing thickness; the array layout reduces the mass per unit area by 70% compared to traditional metal springs, making it suitable for weight-sensitive portable devices.

[0057] In Example 5, the temperature and pressure field is divided into three control zones along the width of the sealing strip: the central zone has a temperature of 110-120℃ and a pressure of 0.4-0.5MPa; the edge zone has a temperature of 80-90℃ and a pressure of 0.1-0.2MPa; and the parameters of the transition zone change linearly.

[0058] Specifically, the principle of gradient temperature and pressure control design is based on the theory of synergistic control of material thermosetting kinetics and structural deformation. The flow characteristics and polymerization rates of the sealant differ significantly across different temperature zones: the central zone requires a higher temperature (110-120℃) to trigger a rapid cross-linking reaction and form a core supporting framework, while the lower temperature (80-90℃) in the edge zone delays curing and prevents shrinkage and warping. The pressure gradient is designed to address the stiffness distribution of the composite structure. High pressure in the central zone (0.4-0.5MPa) promotes the sealant to fully fill micro-gaps, while low pressure in the edge zone (0.1-0.2MPa) releases the boundary stress of the flexible circuit. The linearly varying parameters in the transition zone essentially establish a continuous temperature-pressure functional relationship, creating a thermal stress equilibrium field across the entire sealing interface.

[0059] The purpose of this design is to prioritize the formation of a rigid core in the high-temperature, high-pressure central region, constructing a sealed main frame within 10-15 seconds; the delayed curing in the edge region allows 40-60 seconds for the material stress to relax naturally, eliminating internal stress concentration. The metal in the middle of the shell conducts heat quickly and requires high-temperature compensation for heat loss, while the plastic parts at the edges are sensitive to thermal deformation and require temperature control to maintain shape; the high and low pressure zoning simulates the actual load distribution under the equipment's operating conditions (high load at the center, sensitive to edge deformation). The linear gradual change of parameters avoids the shear line caused by sudden temperature and pressure changes (common in step control), ensuring a smooth transition of Young's modulus in the boundary region (gradient change <15%).

[0060] The purpose of this design is to ensure that the high pressure in the central area completely removes trapped air from the micropores of the circuit board, resulting in a bubble rate of <0.1%; while the low temperature in the edge area prevents premature curing of the adhesive layer, thus avoiding the "skinning effect" and ensuring complete polymerization of the deep adhesive. Gradient temperature and pressure create differentiated cross-linking densities in different areas of the adhesive layer (85±2% in the central area and 72±3% in the edge area), increasing the overall interfacial peel strength to 1.8 times that of uniform parameters. Edge stress release ensures that the flatness deviation of the encapsulated shell is ≤0.05mm / m (compared to 0.2mm / m in traditional processes), meeting the installation requirements of precision sensors; and linearly gradient parameters mitigate the risk of internal cracking in the adhesive layer, improving sealing durability under vibration conditions.

[0061] Example 6: The multiphysics simulation model includes a sealing interface failure prediction algorithm. It uses machine learning to analyze more than 100,000 sets of aging data to dynamically correct the design coefficients for temperature-pressure coupling conditions.

[0062] Specifically, the principle behind the multiphysics simulation model design is based on cross-scale physical coupling modeling and data-mechanism fusion-driven theory. Traditional simulations rely on approximate calculations using a single physical field, making it difficult to accurately describe the interactions of multiple factors such as temperature, pressure, and material aging. By constructing thermo-mechanical-chemical coupling equations, integrating a microscopic morphology evolution model of the sealing interface (such as the adhesive layer crack propagation rate equation), and introducing a failure prediction algorithm (based on the interface peeling energy threshold criterion), a mechanism-driven benchmark model is formed. The machine learning module analyzes 100,000 sets of aging data (covering accelerated life tests such as temperature shock, vibration, and media corrosion) to extract nonlinear degradation laws and calibrate simulation parameters (such as viscoelastic constitutive model coefficients and interface contact stiffness) in real time, achieving dynamic matching between physical laws and real data.

[0063] The purpose of this design is that the mechanistic model can only predict failure modes under ideal operating conditions, while machine learning correction can capture actual production deviations (such as ±5% fluctuation in adhesive layer thickness) and performance dispersion caused by batch differences in materials, reducing the prediction error from >30% to <8%. The dynamic correction mechanism allows the model to evolve autonomously with the equipment's service life, updating the design coefficients every 1000 hours of operating data input, increasing the confidence level of predicting the remaining seal life to over 95%. Through transfer learning, accelerated aging data from the laboratory is mapped to real complex environments (such as simultaneous exposure to sudden altitude changes and salt spray corrosion), establishing a three-dimensional failure boundary map of unsteady temperature-pressure combination conditions.

[0064] The advantages of this design are that it replaces over 60% of physical prototype testing rounds, reducing the new product sealing structure verification cycle from 18 months to 5 months and lowering R&D costs by 40%. The model's real-time health index can provide early warnings of seal failure risks 300-500 hours in advance, guiding users to perform targeted maintenance and avoiding unexpected downtime of critical equipment. Sensitivity analysis identifies key factors affecting seal reliability (such as curing temperature fluctuation tolerance of ±1.5℃), guiding the production line to tighten or loosen tolerances to achieve the optimal balance between quality and cost.

[0065] In Example 7, the edge of the electromagnetic shielding layer and the sealing tape form a conductive connection, and electrical conduction is achieved by filling the conductive adhesive through laser drilling.

[0066] Specifically, the electromagnetic shielding layer operates on the principle of ohmic contact theory at heterogeneous material interfaces and the micro-area conduction enhancement mechanism. The interface between the copper electromagnetic shielding layer and the sealing tape (usually containing conductive filler) exhibits micron-level undulations. Direct pressing results in an actual conductive contact area of ​​less than 30%, creating high-resistance points and electromagnetic leakage gaps. Laser drilling technology precisely generates a micro-pore array with a diameter ≤50μm at the edge of the shielding layer. After penetrating to the tape layer, nano-silver conductive adhesive is injected, filling the gaps in the pore walls through capillary action. The cured conductive adhesive forms a metallized micro-rivet structure, establishing over 300 parallel conductive channels / cm² at the contact interface, achieving omnidirectional current conduction.

[0067] The purpose of this design is to use the conductive adhesive filled with micropores to bridge the microscopically uneven surfaces of the shielding layer and the sealing tape, reducing the contact resistance from >100mΩ to <5mΩ and preventing high-frequency signals from experiencing reflection losses at the interface due to impedance mismatch. By extending the local shielding into a complete electromagnetically sealed system through boundary conduction, the design blocks electromagnetic wave diffraction leakage paths caused by structural abrupt changes at the shielding layer edges. The laser-drilled diameter is controlled within the heat-affected zone of the tape substrate (<15μm) to ensure that no microcracks are generated after the hole walls melt and re-solidify, maintaining the airtight integrity of the sealing structure.

[0068] The advantages of this design are: shielding effectiveness is improved by >12dB in the high-frequency band (>10GHz); electromagnetic leakage burrs from equipment chassis gaps are eliminated in the 5G millimeter-wave band (24.25-52.6GHz); and radiated interference is reduced to 1 / 5 of the Class B limit. The micro-rivet structure ensures a shear strength of >18MPa at the joint surface, with no contact impedance fluctuations under random vibration conditions of 20-2000Hz, solving the problem of periodic conductive failure caused by fatigue compression in traditional conductive foam. The silver conductive adhesive exhibits a resistance change rate of <5% during temperature changes from -55℃ to 200℃, and shows no electrochemical corrosion at the interface after 1000 hours of salt spray testing, making it suitable for highly corrosive environments such as offshore platforms.

[0069] Example 8: The microstructure texture of the sealing groove is a sawtooth array with a depth of 0.05-0.1mm, and the tooth pitch decreases by 30-50% from the groove opening to the groove bottom.

[0070] Specifically, the principle of the microstructure texture design of the sealing groove is based on the contact stress gradient distribution theory and the material interface wetting control mechanism. The geometric characteristics of the sawtooth array directly affect the flow characteristics and curing stress field distribution of the sealant: grooves with a depth of 0.05-0.1mm can overcome the surface tension constraint of the colloid and guide the colloid to penetrate into the micropores of the substrate through capillary effect; the tooth pitch decreases from the groove opening to the bottom of the groove to form a gradually narrowing channel, which generates a self-pressurizing effect during the colloid injection stage using the principle of fluid dynamics (the ratio of inlet flow velocity to outlet cross-sectional area reaches 3:1), forcing the colloid to fully fill the structural blind area. The change in tooth shape gradient synchronously controls the direction of curing shrinkage stress, so that a pre-stress balance system is formed inside the colloid layer.

[0071] The purpose of this design is to allow for rapid filling of high-viscosity colloids with a wide tooth pitch at the inlet (150-200μm), while the close tooth pitch at the bottom (70-100μm) creates microscopic mechanical interlocking, suppressing the shear displacement of the colloid layer to within 5μm. The sawtooth inclination angle gradually changes from 45° to 75° as the tooth pitch decreases, allowing interfacial stress to dissipate through a triple mechanism of tooth surface slippage, colloid compression deformation, and tooth root stress diffusion, reducing peak stress by more than 60%. The non-uniform tooth pitch disrupts the continuous path of crack propagation, forcing the interfacial crack to change its propagation direction every 200μm, significantly extending the crack penetration time.

[0072] The advantages of this design are that the serrated structure increases the effective bonding area to three times that of a planar structure, and the peel strength increases from 8 N / mm to 22 N / mm, reaching 90% of the structural adhesive's bulk strength. The gradient tooth pitch can accommodate 8% shrinkage strain of the adhesive layer at -40℃ without debonding, and at 150℃, the inter-tooth cavities buffer adhesive expansion, preventing interfacial delamination. The self-pressurizing effect compensates for 10%-15% fluctuations in injection pressure, allowing the adhesive volume tolerance range to be widened from ±5% to ±8%, reducing production costs.

[0073] Example 9: Infrared thermal imaging data is collected synchronously during the robot assembly process, and the heating power is automatically adjusted when the local temperature difference exceeds 15°C.

[0074] Specifically, the principle of infrared thermal imaging dynamic temperature control design is based on non-contact heat distribution feedback control theory and local thermodynamic equilibrium mechanism. The uneven thermal conductivity of the metal casing during the adhesive curing stage (rapid heat dissipation in the welding area and slow heat absorption in the adhesive layer) leads to interfacial temperature differences, inducing stress concentration. Infrared thermal imaging scans the assembly surface at a rate of over 50 frames per second. By comparing the difference in radiant energy between each region and a reference point (an equivalent temperature difference > 15℃ is considered a thermal anomaly), a closed-loop control system is triggered: heating power is increased at a slope of 2% / ℃ in areas with insufficient temperature rise, while air-cooled nozzles are activated for gradient cooling in overheated areas. This dynamic leveling maintains the temperature of the entire joint surface within ±3℃ of the process window.

[0075] The purpose of this design is to compensate for the difference in thermal response between the welding module (specific heat capacity approximately 500 J / kg·K) and the plastic sealing groove (specific heat capacity > 1000 J / kg·K) in real time, compressing the thermal gradient at the curing interface from >30℃ to <8℃, thus preventing shear cracks in the adhesive layer due to uneven heating and cooling. For the critical crosslinking temperature range of epoxy resin (85-95℃), a temperature difference threshold of 15℃ is set as the curing rate control point to prevent premature molecular chain breakage due to localized overheating (reducing molecular weight distribution fluctuations by 60%). For thin-walled parts with multi-rib reinforcement, a zoned response strategy (controlling the area of ​​a single hot zone to <4 cm²) compensates for the thermal bridging effect caused by the reinforcing ribs.

[0076] The advantages of this design are: the bubble rate in the adhesive layer is reduced from >5% in manual processes to <0.3%, the failure rate of poor soldering / detachment is reduced by 90%, and annual rework costs are saved by over one million yuan. The improved curing uniformity reduces the coefficient of variation of the adhesive's tensile strength from 12% to 3%, extending the lifespan of the sealing structure by more than double. Precise zoned temperature control saves 35% more energy than global constant temperature control, and the lifespan of the high-frequency heating module is extended by 50% due to reduced load fluctuations.

[0077] Example 10: The failure prediction algorithm is equipped with a vibration frequency adaptation module to generate a dedicated sealing structure solution for vibration environments of 50-2000Hz.

[0078] Specifically, the principle of the vibration frequency adaptation sealing design scheme is based on the structural resonance mode decoupling theory and dynamic load spectrum matching technology. Sealed structures generate multi-order resonance responses in broadband vibration environments. Traditional homogeneous designs are prone to stress concentration at specific frequency points (such as the third harmonic of the motor's fundamental frequency). The vibration frequency adaptation module analyzes the energy distribution of the input spectrum to identify high-risk frequency bands (frequency points with energy percentage > 85%) within the 50-2000Hz range. It adjusts the geometric parameters of the sealing groove using the modal superposition principle. In the high-frequency region (> 800Hz), a dense rib reinforcement structure is used to suppress bending vibration; in the low-frequency region (< 200Hz), a damping cavity is designed to absorb stress waves; and in the mid-frequency band (200-800Hz), a gradually varying stiffness layout disperses vibration energy. The algorithm simultaneously optimizes the matching relationship between the material damping coefficient and the structure's natural frequency, shifting the main resonance peak to the non-excitation frequency band.

[0079] The purpose of this design is to adjust the first-order natural frequency of the sealing structure to above 2500Hz, away from the main excitation frequency band, and reduce the resonance risk factor to below 0.1, targeting typical vibration sources such as the fundamental frequency of UAV motors (350Hz±5%) and the impact spectrum of high-speed rail wheels (18-220Hz). Energy-dissipating microstructures are implanted in the regions corresponding to the octave characteristic peaks of the gearbox (e.g., 1.2kHz, 2.4kHz) to attenuate the vibration transmissibility by >20dB, preventing fatigue cracking of the sealant caused by high-frequency vibration. Based on the measured vibration spectrum of the equipment (e.g., the 1 / 3 octave spectrum of wind turbine pitch bearings), asymmetric honeycomb structures and gradient damping layers are dynamically generated to achieve impedance matching between the dynamic stiffness of the sealing interface and the external excitation.

[0080] The advantages of this design are that, under random vibration conditions of 50-2000Hz, the fatigue life of the sealing structure is increased from 300 hours to 3000 hours, and the crack propagation rate of the adhesive layer is reduced to 1 / 8 of the original design. The frequency-adaptive design reduces the structural mass by 45% compared to traditional solutions, while ensuring seal integrity under a 200m / s² impact load, meeting the vibration resistance requirements of military equipment. The algorithm incorporates preset modes for aerospace (wideband continuous spectrum), automotive (narrowband impact spectrum), and industrial (high-frequency harmonic spectrum), allowing for customized solutions to be generated simply by importing spectral data for new vibration environments, shortening the development cycle by 70%.

[0081] The specific operating mechanism is as follows:

[0082] S51: Spectral feature extraction. Input the three-dimensional spectral matrix (frequency-amplitude-phase) of the vibration environment, extract the main energy concentration area through wavelet transform, and mark the frequency points that exceed the threshold line (such as 15% of the total energy) as key control objects.

[0083] S52: Modal sensitivity analysis, establish a parameterized finite element model of the sealed structure, calculate the sensitivity of each mode shape to geometric dimensions and material properties, and screen out the design variables (such as rib height and adhesive layer thickness) that have the greatest impact on the target frequency band.

[0084] S53: Multi-objective optimization iteration, with constraints of minimizing vibration transmissibility, minimizing structural mass, and maximizing process feasibility, uses a genetic algorithm to perform tens of thousands of iterations, outputting a Pareto optimal solution set for engineers to choose from.

[0085] S54: Digital twin verification imports the optimal solution into a virtual vibration table to simulate a 0-3000Hz sweep frequency test, verifying whether the resonance point offset is greater than a 10% safety margin, and ensuring that no resonance occurs under actual working conditions.

[0086] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for designing a housing sealing structure for integrated flexible circuits, characterized in that, Includes the following steps: S1: Electromagnetic compatibility flexible circuit design, using multi-layer stacked flexible circuit boards, of which at least one layer is provided with an electromagnetic shielding layer, the shielding layer extends to the sealing area of ​​the edge of the circuit board, the circuit elements are embedded in the substrate slots and fixed by conductive adhesive, and the surface is covered with encapsulating adhesive to form a flat plane. S2: Thermal deformation synergistic shell design, the shell is made of metal matrix composite material, the internal topology optimized support structure is provided, the side wall of the sealing groove is set with microstructure texture, and the bottom of the groove is laid with thermal expansion buffer layer. The thermal expansion buffer layer is composed of silica aerogel composite polyimide fiber, the thickness is 15-20% of the depth of the sealing groove, and the thermal expansion coefficient is more than 50% lower than that of the shell material. S3: Dynamic response sealing system design, with shape memory alloy components placed between the sealing tape and the waterproof and breathable membrane, and the two ends of the components connected to the housing sealing groove and the circuit board respectively; S4: Intelligent compensation assembly, using a multi-axis robot with displacement sensors to adjust the assembly trajectory in real time, and applying zoned temperature and pressure fields during the bonding process; S5: Digital twin testing and verification, establishing a multi-physics simulation model of the sealed structure, and dynamically optimizing parameters based on the physical test data.

2. The design method for the housing sealing structure of the integrated flexible circuit according to claim 1, characterized in that: The electromagnetic shielding layer is a copper mesh structure with a line width of ≤0.1mm and a mesh density that increases by more than 20% from the center of the sealed area to the edge.

3. The design method for the housing sealing structure of the integrated flexible circuit according to claim 1, characterized in that: The shape memory alloy element is made of nickel-titanium-copper alloy, with a phase transformation temperature set at 40-50℃, an array density of 40-60 elements / cm², and a unit restoring force of 0.2-0.5N.

4. The design method for the housing sealing structure of the integrated flexible circuit according to claim 1, characterized in that: The temperature and pressure field is divided into three control zones along the width of the sealing strip: the central zone has a temperature of 110-120℃ and a pressure of 0.4-0.5MPa; the edge zone has a temperature of 80-90℃ and a pressure of 0.1-0.2MPa; and the parameters of the transition zone change linearly.

5. The design method for the housing sealing structure of the integrated flexible circuit according to claim 1, characterized in that: The multiphysics simulation model includes a sealing interface failure prediction algorithm, which uses machine learning to analyze more than 100,000 sets of aging data to dynamically correct the design coefficients for temperature-pressure coupled operating conditions.

6. The design method for the housing sealing structure of the integrated flexible circuit according to claim 1, characterized in that: The edge of the electromagnetic shielding layer forms a conductive connection with the sealing tape, and electrical conductivity is achieved by filling the conductive adhesive through laser drilling.

7. The design method for the housing sealing structure of the integrated flexible circuit according to claim 2, characterized in that: The microstructure texture of the sealing groove is a sawtooth array with a depth of 0.05-0.1mm, and the tooth pitch decreases by 30-50% from the groove opening to the bottom of the groove.

8. The design method for the housing sealing structure of the integrated flexible circuit according to claim 3, characterized in that: The robot collects infrared thermal imaging data simultaneously during the assembly process, and automatically adjusts the heating power when the local temperature difference exceeds 15°C.

9. The design method for the housing sealing structure of the integrated flexible circuit according to claim 5, characterized in that: The failure prediction algorithm is equipped with a vibration frequency adaptation module to generate a dedicated sealing structure solution for vibration environments ranging from 50 to 2000 Hz.

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