Stress self-adaptive interconnection method and device of thin film battery array based on flexible PCB (Printed Circuit Board)

Abstract

The invention relates to the technical field of battery manufacturing, in particular to a stress self-adaptive interconnection method and device for a thin film battery array based on a flexible PCB, and the method comprises the steps: processing and forming a micro-groove array on the surface of the PCB, and preparing a composite solder structure; collecting a real-time deformation field and a bonding pad position of the PCB, and generating a compensation mounting path of the thin film battery; the contact force between the thin film battery and the bonding pad is controlled to be smoothly increased; performing local thermal ultrasonic solid-phase bonding on the electrode on the thin film battery and the corresponding bonding point on the PCB; performing laser irradiation on the lower electrode of the battery and the PCB bonding pad to form a high-melting-point intermetallic compound; collecting three-dimensional shape geometric parameters of the welding spots, extracting efficiency distribution and defect characteristics of the battery, and dynamically adjusting process parameters of the upflow according to the efficiency distribution and defect characteristics; and calculating residual stress distribution, and dynamically adjusting pressure applied to different areas by a hot pressing roller in a subsequent packaging process. According to the invention, the large-scale and high-reliability manufacturing of the flexible PCB-based thin film solar wing can be effectively realized.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and in particular to a stress-adaptive interconnection method and apparatus for thin-film battery arrays based on flexible PCBs. Background Technology

[0002] As satellite technology evolves, the functional requirements for solar panels are also increasing. Using flexible PCBs to replace traditional rigid glass fiber composite substrates or simple polyimide films is an ideal solution for integrating the electrical functions, thermal management functions, and lightweight structure of solar panels. However, achieving high-density, high-reliability interconnects for thin-film gallium arsenide and other batteries on flexible PCBs faces a series of unique challenges that traditional electronic assembly processes cannot solve: 1. Thermomechanical mismatch: There is an order of magnitude difference in the coefficient of thermal expansion between flexible PCBs (such as polyimide) and thin-film gallium arsenide batteries. When the solar array is in operation, it will experience extreme temperature cycles from -120°C to +120°C. The huge thermal stress is repeatedly applied to the interconnect points. Traditional solder joints are very prone to cracking and failure due to thermal fatigue. This is the primary factor affecting lifespan.

[0003] 2. High risk of damage during mounting: Thin-film batteries are only tens to hundreds of micrometers thick, making them extremely fragile. The surface of flexible PCBs has uneven lines, and during mounting, the batteries are prone to breakage due to uneven contact pressure, scratching against the edges of the lines, or being subjected to bending moments.

[0004] 3. High coupling requirements, unsuitable for mass production: The solder mask layer on the PCB surface and the oxidation tendency of copper require meticulous pre-soldering treatment. The mounting accuracy directly affects the soldering quality, and the soldering thermal stress affects the package reliability. The various process parameters are highly coupled, and traditional production models are difficult to adapt to the needs of large-scale production. Summary of the Invention

[0005] This invention provides a stress-adaptive interconnection method and device for thin-film battery arrays based on flexible PCBs, and a complete set of technologies from structural design innovation to process principle innovation and equipment control innovation, to achieve large-scale and high-reliability manufacturing of flexible PCB-based thin-film solar panels.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs, comprising the following steps: S1: A micro-groove array surrounding the pads is formed in the soldering area of ​​the flexible PCB. Then, the surface of the pads is laser-cleaned and roughened, and a composite solder structure containing low-melting-point metal layers and high-melting-point metal layers is prepared on the pads. S2: The real-time deformation field and pad position of the PCB are collected by the vision system, and the PCB deformation during the mounting process is predicted by the deep learning model to generate the compensation mounting path for the thin-film battery. S3: Mount the thin-film battery and control the contact force between the thin-film battery and the pads, so that the contact force smoothly transitions from the initial value to the steady-state value; S4: Perform local thermo-ultrasonic solid-state bonding on the bonding points between the upper electrode of the thin-film battery and the corresponding bonding points on the PCB; then, at the junction of the lower electrode of the battery and the PCB pad, use laser irradiation to melt the low-melting-point metal layer of the composite solder structure and allow it to diffuse and react with the high-melting-point metal layer and the copper pad to form a high-melting-point intermetallic compound. S5: Collect the three-dimensional morphological geometric parameters of the solder joint; simultaneously perform electroluminescence and photoluminescence imaging to extract the efficiency distribution and defect characteristics of the battery; then dynamically adjust the process parameters in step S4 through a preset process mapping model. S6: Calculate the residual stress distribution based on the defect characteristics of the battery, dynamically adjust the pressure applied by the hot press roller in different areas during the subsequent packaging process, and complete the interconnection of the thin-film battery array.

[0007] Furthermore, in step S1, the shape pattern of the microgroove array is concentric rings, radial stripes, or a grid.

[0008] Furthermore, in step S2, the deep learning model is a convolutional neural network model, and the specific method for generating the compensation mounting path for the thin-film battery is as follows: The PCB is scanned using a global camera, and the three-dimensional deformation field of the PCB under the current tension state is calculated in real time by combining the original dimensions of the PCB. Use a local camera to obtain the three-dimensional coordinates of the target pad; Input the 3D deformation field of the PCB and the pad positioning data into the convolutional neural network model, and calculate the deformation prediction vectors of the PCB in three mutually orthogonal directions under the action of mounting force, with the mounting point on the current pad as the center. Based on the calculated deformation prediction vector in three dimensions, the original mounting path of the thin-film battery is adjusted to form the final compensated mounting path.

[0009] Furthermore, in step S3, when attaching the thin-film battery, the forces on the attachment point in three mutually orthogonal directions and the torque in the direction perpendicular to the surface of the pad are measured simultaneously; the combination of forces in the three mutually orthogonal directions forms the contact force.

[0010] Furthermore, in step S4, when performing local thermo-ultrasonic solid-state bonding between the upper electrode of the thin-film battery and the corresponding bonding point on the PCB, the ultrasonic vibration direction is made parallel to the length direction of the PCB.

[0011] Furthermore, in step S4, when irradiating the low-melting-point metal layer of the composite solder structure, a pulsed laser is used for irradiation. The wavelength of the pulsed laser corresponds to the absorption peak of the low-melting-point metal layer of the composite solder, and the spot diameter D of the pulsed laser is greater than 1.2 times the width W of the solder pad.

[0012] Furthermore, in step S5, the three-dimensional morphological geometric parameters of the weld joint include height H, volume V, and contact angle θ; The process mapping model is a machine learning model trained on a large amount of experimental data. It establishes a quantitative fitting relationship between the three-dimensional morphological geometric parameters of the solder joint, thermo-ultrasonic solid-state bonding pressure, thermo-ultrasonic solid-state bonding time, and laser energy density irradiating the low-melting-point metal layer.

[0013] This invention also provides a stress-adaptive interconnection device for a thin-film battery array based on a flexible PCB, comprising, in sequence along the material flow direction: The processing module includes an ultraviolet laser for fabricating microgroove arrays; The vision force control mounting module includes an end effector that grips a thin-film battery with a suction cup, a robot for moving the end effector, and a vision system for capturing images of the PCB. The interconnect module includes a thermo-ultrasonic solid-phase bonding unit and a laser transient liquid-phase diffusion welding unit, which are arranged side by side in space; The feedback module includes a laser scanner for acquiring the three-dimensional morphological geometry parameters of the solder joints, and an imaging unit for performing electroluminescence and photoluminescence imaging. The encapsulation module includes a multi-temperature zone hot press roller assembly with independent temperature and pressure control, and an encapsulation film unwinding mechanism; It also includes a storage unit and a processor. The storage unit is used to store one or more program instructions, and the processor is used to run one or more program instructions to control the above-mentioned modules and perform the steps of the stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs as described above.

[0014] Furthermore, the thermo-ultrasonic solid-phase bonding unit includes a high-frequency power supply, a piezoelectric transducer, a heating device, and a coaxial infrared thermometer; the selective laser transient liquid phase diffusion bonding unit includes a fiber pulse laser, a two-dimensional galvanometer, a coaxial CCD monitoring lens, and a protective chamber.

[0015] Furthermore, the bottom surface of the suction cup of the end effector is a micro-convex surface that matches the curvature of the thin-film battery, and the material is a low thermal conductivity material.

[0016] The technical solution of this invention can achieve the following technical effects: 1. This process introduces a laser-processed micro-groove stress buffer structure into the PCB interconnect area. This structure acts as a "mechanical fuse" and "stress damper," effectively absorbing, redistributing, and limiting the transmission of thermal stress. From a physical design perspective, this enhances the fatigue resistance of the interconnect area and effectively extends its service life.

[0017] 2. This process, based on deep learning-based visual compensation, can effectively predict and compensate for PCB deformation. Combined with multi-dimensional force feedback "soft landing" mounting technology, the system can automatically adapt to material batch fluctuations and environmental changes, effectively improving the mounting yield of brittle thin-film batteries.

[0018] 3. This process proposes a closed-loop intelligent control flow of "multimodal perception - process mapping model - real-time feedforward / feedback". High-precision 3D topography measurement and electro / photoluminescence imaging are used to acquire multi-dimensional information reflecting welding quality and battery performance. A pre-trained machine learning model is used to infer the mechanical properties and long-term reliability of interconnect joints in real time, and to dynamically adjust upstream mounting or welding process parameters, shifting quality control from "post-inspection" to "in-process control" and even "pre-prediction".

[0019] 4. The core innovation at the equipment level lies in the construction of a deeply coupled "information-physical" production system. Each physical execution module (laser processing, mounting, welding, testing, and packaging) is no longer an isolated workstation, but rather integrated into a unified intelligent entity capable of real-time sensing, autonomous analysis, intelligent decision-making, and precise execution. The equipment can adaptively adjust according to the real-time status of each product during the process, ensuring it always operates within the optimal process window, achieving a high degree of flexibility and intelligence in the manufacturing process. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating a stress-adaptive interconnection method for a thin-film battery array based on a flexible PCB. Figure 2 A flowchart illustrating the compensation mounting path for generating thin-film batteries. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] This invention relates to a stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs, the main steps of which are: S1: Flexible PCB pretreatment and stress buffer structure fabrication; S2: Obtain the compensation mounting path based on deep learning vision; S3: Force feedback soft landing patch; S4: Time-space coordinated composite interconnect; S5: Online multimodal fusion detection and process feedback; S6: Stress-matched roll-to-roll packaging.

[0025] The specific steps are as follows: S1 (Flexible PCB Pre-processing and Stress Buffer Structure Preparation): In the soldering area of ​​the flexible PCB, a micro-trench array surrounding the solder pads is rapidly formed using ultraviolet laser processing. The depth of the micro-trench is 20%-80% of the copper layer thickness, and the width is 10-50μm. The ultraviolet laser has a short wavelength and high energy per photon, and removes materials mainly through photochemical ablation rather than thermal effects, generating almost no thermal stress. This avoids PCB warping or damage during processing and can produce micro-trenches with steep sidewalls and clear contours. After fabricating the microgroove array, the surface of the pads is laser-cleaned and roughened. Laser cleaning is used to remove oxide layers and organic contaminants, while laser roughening is used to increase surface roughness and improve the bonding strength of the solder joints. A composite solder structure containing low-melting-point metal layers and high-melting-point metal layers is also prepared on the pads.

[0026] S2 (Deep Learning Vision-Based Compensated Mounting Path): Flexible PCBs inevitably experience microscopic warping, wrinkles, and other non-uniform deformations during transport and pre-processing. By acquiring the real-time deformation field and pad positions of the PCB through a vision system, and using a deep learning model to predict the PCB deformation during the mounting process, a compensated mounting path for the thin-film battery is generated, ensuring that the thin-film battery can be mounted in the correct position on the deformed PCB.

[0027] S3 (Force Feedback Soft Landing Mount): This method mounts the thin-film battery and controls the contact force Fc between the battery and the pads. The contact force smoothly transitions from an initial value F0 (0.1-0.3N) to a steady-state value Fs (0.5-1.5N), with the force change rate dF / dt controlled between 10-50N / s. The initial value F0 (0.1-0.3N) is used only to sense the contact, ensuring a stable contact surface between the battery and the PCB. The steady-state value Fs (0.5-1.5N) ensures tight contact between the battery and the pads, providing good thermal conductivity and mechanical stability for subsequent soldering. This smooth transition achieves a "soft landing" for the battery, allowing it to effectively adapt to uneven PCB surfaces and preventing damage to the battery and PCB due to impact.

[0028] S4 (Time-Spatial Collaborative Composite Interconnect): Local thermo-ultrasonic solid-state bonding is performed on the bonding points of the upper electrode of the thin-film battery and the corresponding bonding points on the PCB. The bonding parameters are: temperature T1=180-220℃, ultrasonic frequency f1=60-120kHz, pressure P1=2-4N, and time t1=80-200ms. Then, at the junction of the lower electrode of the battery and the PCB pad, the low-melting-point metal layer of the composite solder structure is irradiated with a laser. The laser energy density E satisfies: Emin (melting threshold) < E < Emax (battery damage threshold) to melt it and allow it to diffuse and react with the high-melting-point metal layer and copper pad to form a high-melting-point intermetallic compound.

[0029] S5 (Online Multimodal Fusion Detection and Process Feedback): Uses laser to scan the weld joint and collect the three-dimensional morphological geometric parameters of the weld joint, extracting the height H, volume V, and contact angle θ parameters; Simultaneous electroluminescence and photoluminescence imaging are performed. Electroluminescence imaging involves passing current through the battery and capturing its emitted infrared light image, which is used to detect electrical defects such as series resistance, microcracks, and broken grids. Photoluminescence imaging involves exciting the battery with a laser of a specific wavelength and capturing the fluorescence image emitted by the recombination of photogenerated carriers, which is used to quantitatively evaluate the uniformity of conversion efficiency in different regions of the battery. The principle is existing technology and will not be elaborated here. After imaging, the efficiency distribution and defect characteristics of the battery can be extracted. Then, the process parameters (time T1, pressure P1, laser energy density E) in step S4 are dynamically adjusted using a preset process mapping model.

[0030] S6 (Stress-Matched Roll-to-Roll Packaging): Based on the defect characteristics of the battery, the residual stress distribution is calculated, and the pressure applied by the hot press roller in different areas during the subsequent packaging process is dynamically adjusted. For areas with high residual stress, the pressure is reduced by 10%-30%, and stress buffer adhesive dots are pre-placed at the corresponding positions to finally complete the interconnection of the thin-film battery array.

[0031] In preferred step S1, the shape and pattern of the microgroove array are concentric rings, radial stripes, or grids. Its function is to disperse and confine thermomechanical stress locally, preventing cracks from propagating to the active area of ​​the battery. The composite solder structure is a Sn-Bi-In / Ag stacked structure or an In-Ag / Cu stacked structure.

[0032] In the preferred step S2, the deep learning model is a convolutional neural network model, and the specific method for generating the compensation mounting path for the thin-film battery is as follows: The PCB is scanned using a global camera, and the three-dimensional deformation field of the PCB under the current tension state is calculated in real time by combining the original dimensions of the PCB. Use a local camera to obtain the three-dimensional coordinates of the target pad; Input the 3D deformation field of the PCB and the positioning data of the pads into the convolutional neural network model. Taking the mounting point on the current pad as the center, calculate the deformation prediction vectors of the PCB in three mutually orthogonal directions under the action of mounting force. With the length direction of the PCB as the x-axis, the width direction as the y-axis, and the thickness direction as the z-axis, the three deformation prediction vectors are △x, △y, and △z, respectively. Based on the calculated deformation prediction vector in three dimensions, the original mounting path of the thin-film battery is adjusted to form the final compensated mounting path.

[0033] In preferred step S3, when mounting the thin-film battery, the forces Fx, Fy, and Fz at the mounting point in three mutually orthogonal directions, as well as the torque Mz in the direction perpendicular to the pad surface, are measured simultaneously; the combination of forces in the three mutually orthogonal directions forms the contact force.

[0034] In preferred step S4, when performing local thermo-ultrasonic solid-state bonding between the electrode on the thin-film battery and the corresponding bonding point on the PCB, the ultrasonic vibration direction is parallel to the length direction of the PCB. This is because the flexible PCB has the greatest degree of freedom along its length when the temperature changes, resulting in the greatest thermal expansion / contraction strain. Therefore, the main shear stress direction is along the length direction. Aligning the ultrasonic vibration direction with the principal stress direction allows the ultrasonic energy to act most effectively on the atoms in that direction, giving the formed bonding joint better ductility and stress relaxation capability in that direction. Furthermore, during the connection formation process, the direction of the maximum stress that may occur in the future is "pre-compensated" or "stress-shaped," making the residual stress distribution inside the joint more conducive to resisting subsequent thermal cycling loads. Preferably, the transducer used for local thermo-ultrasonic solid-state bonding has a non-circular working end face that matches the shape of the electrode on the battery, ensuring accurate bonding connections.

[0035] In the preferred step S4, when irradiating the low-melting-point metal layer of the composite solder structure, pulsed laser irradiation is used. The pulsed laser irradiation time is in the millisecond range, achieving dual spatial and temporal localization of energy. This concentrates heat only on the solder joints that need to be connected, minimizing the thermal impact on adjacent batteries and PCB substrates. The pulsed laser wavelength corresponds to the absorption peak of the low-melting-point metal layer of the composite solder, ensuring that as much energy as possible is absorbed by the low-melting-point metal layer. The laser spot diameter D is greater than 1.2 times the pad width W, ensuring that the entire pad width is uniformly irradiated and preventing incomplete or cold solder joints at the edges due to insufficient energy. During laser-induced transient liquid phase diffusion soldering, a protective gas containing active gas is introduced during the welding process to isolate air and prevent the molten solder from oxidizing and forming slag, which would affect the connection quality.

[0036] In the preferred step S5, the three-dimensional morphological geometric parameters of the solder joint include height H, volume V, and contact angle θ; the process mapping model is a machine learning model trained based on a large amount of experimental data, which establishes a quantitative fitting relationship between the three-dimensional morphological geometric parameters of the solder joint (height H, volume V, contact angle θ), thermo-ultrasonic solid-state bonding pressure P1, thermo-ultrasonic solid-state bonding time T1, and laser energy density E irradiating the low-melting-point metal layer.

[0037] This invention also relates to a stress-adaptive interconnection device for a thin-film battery array based on a flexible PCB. The device is a linear, fully automated production line, and the fully automated production line includes, in sequence along the material flow direction: The processing module includes an ultraviolet laser for fabricating microgroove arrays; The vision force control mounting module includes an end effector that grips a thin-film battery with a suction cup, a robot for driving the end effector, and a vision system (containing a dual camera system with a global camera and a local camera) for capturing PCB images. The interconnect module includes a thermo-ultrasonic solid-phase bonding unit and a laser transient liquid-phase diffusion welding unit, which are arranged side by side in space; The feedback module includes a laser scanner for acquiring the three-dimensional morphological geometry parameters of the solder joints, and an imaging unit for performing electroluminescence and photoluminescence imaging. The encapsulation module includes a multi-temperature zone hot press roller assembly with independent temperature and pressure control, and an encapsulation film unwinding mechanism; It also includes a storage unit and a processor. The storage unit is used to store one or more program instructions, and the processor is used to run one or more program instructions to control the above-mentioned modules and execute the steps of the aforementioned stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs.

[0038] The preferred thermal ultrasonic solid-phase bonding unit includes a high-frequency power supply, a piezoelectric transducer, a heating device, and a coaxial infrared thermometer; the selective laser transient liquid phase diffusion bonding unit includes a fiber pulse laser, a two-dimensional galvanometer, a coaxial CCD monitoring lens, and a protective chamber.

[0039] Preferably, the bottom surface of the suction cup of the end effector is a micro-convex surface that matches the curvature of the thin-film battery, and the material is a low thermal conductivity material, with an atmosphere-protected chamber.

[0040] The preferred multi-temperature zone hot press roller assembly has at least three independent temperature and pressure control zones, with each zone having a temperature control accuracy of ±2℃ and a linear pressure control accuracy of ±0.5N / cm; the encapsulation film is a composite structure of polyimide / silicone / atomic-resistant coating.

[0041] The preferred option also includes a central collaborative control system equipped with digital twin software, which can synchronously simulate and optimize the entire interconnection process in virtual space based on real-time process data, and predict the long-term reliability of the product.

[0042] Example: Fabrication of a flexible gallium arsenide thin-film solar cell string for low-Earth orbit communication satellites: Materials preparation: Flexible PCB substrate: adopts double-sided copper-clad polyimide substrate with a thickness of 50μm and a copper layer thickness of 18μm; Thin-film battery: Gallium arsenide thin-film battery chip, with dimensions of 30mm×40mm and a thickness of 100μm; Encapsulation materials: The upper encapsulation film is a 25μm thick polyimide film with an atomic oxygen resistant coating; the lower encapsulation film is a 50μm thick silicone film. Solder: Sn42-Bi57-In1 alloy powder and Ag powder, used to prepare composite solder.

[0043] The specific manufacturing process of the embodiment is as follows: The flexible PCB substrate first enters the PCB stress buffer processing module. Under program control, an ultraviolet laser (wavelength 355nm, average power 15W) processes a grid-like microgroove array with a width of 20μm and a depth of 12μm within a 0.1mm area around each copper pad. This structure effectively blocks and disperses stress from the solder joints. Subsequently, the same laser scans and cleans the pad surface at a lower energy density to remove oxides and increase the surface roughness Ra from 0.1μm to 0.8μm to enhance adhesion. Finally, Sn-Bi-In / Ag composite solder paste is printed onto the pads using precision screen printing and cured at low temperature to form a composite solder structure, in which Sn-Bi-In is the low-melting-point phase (eutectic point approximately 138℃) and Ag is the high-melting-point phase.

[0044] The processed PCB enters the placement module. A global camera scans four pre-set optical reference points on the PCB, and combined with the PCB's CAD design file, an embedded CNN model calculates the 3D deformation field of the PCB in real time under the current tension state. The model predicts that when a force of 0.8N is applied to the target placement point, the area will produce a deformation of approximately (Δx=+2μm, Δy=-1μm, Δz=-15μm). The six-DOF robot pre-compensates for the standard placement path based on this. Subsequently, a local high-resolution camera performs sub-pixel-level precise positioning of the target pads. The robot controls the end effector to move the thin-film battery above the target position. At the start of placement, the end effector gently contacts the PCB with an initial contact force (F0) of 0.2N, and then smoothly and linearly increases the contact force to 0.8N (Fs) within 50ms through closed-loop control, with the force change rate dF / dt stabilizing at 12N / s, achieving a perfect "soft landing". The multi-dimensional force sensor integrated at the end monitors the entire process to ensure that the contact torque Mz is less than 0.01 N·m, indicating that there is no harmful horizontal shear force.

[0045] The assembled semi-finished products enter the interconnect module. This module consists of thermo-ultrasonic bonding units and laser welding units arranged in parallel, and is switched by a precision gantry.

[0046] Step 1: Thermo-ultrasonic solid-state bonding. The gantry crane moves the thermo-ultrasonic unit to the workstation. Its transducer descends, applying a static pressure of 3N (P1) to the bonding point between the battery electrode and the PCB. Simultaneously, the heating device raises the interface temperature to 200℃ (T1) and starts the ultrasonic generator, vibrating at a frequency of 100kHz (f1) parallel to the length of the PCB (i.e., the main thermal deformation direction) for 150ms (t1). During this process, the gold layer on the electrode surface undergoes plastic flow and solid-state diffusion, forming a strong Au-Au metallic bond, and the direction of ultrasonic energy application is beneficial for optimizing the distribution of residual stress.

[0047] Step 2: Selective laser-induced transient liquid phase diffusion welding. The gantry crane switches to the laser welding unit. A pulsed fiber laser (wavelength 915nm, matched to the Sn-Bi-In absorption peak) emits a single laser pulse (energy density 15J / cm²). 2 With a pulse width of 10ms, a 1.5mm diameter laser spot, controlled by a galvanometer system, precisely covers a 1.0mm wide solder pad. The laser energy is selectively absorbed by the low-melting-point Sn-Bi-In layer of the composite solder, causing it to melt instantaneously. The molten solder rapidly interdiffused with the upper Ag particles and the lower Cu pads, forming high-melting-point intermetallic compounds (IMCs) such as Ag3Sn and Cu6Sn5 at the interface. The entire process is conducted in a formic acid vapor protective atmosphere to remove any trace surface oxides. The heat input of laser welding is highly concentrated, with minimal thermal impact on adjacent cells and the PCB substrate.

[0048] The welded components immediately enter the feedback module. A confocal laser scanner rapidly acquires the three-dimensional morphology of the entire battery string using a line scan method. Software analysis extracts the height H=85μm and volume V=0.012mm of the key weld points. 3 The contact angle θ = 25°, both within the preset acceptable range. Simultaneously, the electroluminescence imaging system excites and captures the battery's luminescence image, showing uniform luminescence without dark spots, cracks, or other defects; the photoluminescence imaging system quantitatively measures the battery's average conversion efficiency to be 29.5%. All this data is uploaded to the central control system in real time. The system's preset random forest process mapping model analyzes the current solder joint morphology parameters (H, V, θ) and luminescence uniformity index, inferring that the current thermo-ultrasonic bonding pressure P1 = 3N is slightly high, potentially leading to localized stress concentration. The model output suggests fine-tuning the P1 parameter of the next battery to 2.8N. This adjustment command is immediately sent to the interconnect module's control unit.

[0049] Qualified components that pass inspection enter the final encapsulation module. The module controller receives residual stress distribution analysis results from the inspection module (typically, stress is higher around the battery edges and solder joints). Based on this, it controls the pressure zones of the multi-temperature zone hot press roller assembly: a standard linear pressure of 40 N / cm is applied to the low-stress area in the center of the battery; for the high-stress area at the battery edges, the linear pressure is automatically reduced by 20% to 32 N / cm. The upper layer of atomically oxygen-resistant polyimide encapsulation film and the lower layer of silicone encapsulation film are simultaneously drawn from the unwinding mechanism and fed into the hot press rollers along with the battery substrate. Under precisely controlled temperature (160°C) and differentiated pressure, the films cure and complete lamination, forming the final rollable, lightweight flexible solar panel assembly, which is finally collected into a reel by the winding mechanism.

[0050] All the above steps are seamlessly integrated under the scheduling of the central collaborative control system. The digital twin model on the system runs synchronously with the physical production line in virtual space, simulating material deformation, heat transfer, and stress evolution in real time. When the simulation predicts that material differences in a certain batch of PCBs may lead to long-term reliability risks, the system will issue an early warning and provide suggestions for optimizing process parameters.

[0051] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs, characterized in that the steps include... include: S1: A micro-groove array surrounding the pads is formed in the soldering area of ​​the flexible PCB. Then, the surface of the pads is laser-cleaned and roughened, and a composite solder structure containing low-melting-point metal layers and high-melting-point metal layers is prepared on the pads. S2: The real-time deformation field and pad position of the PCB are collected by the vision system, and the PCB deformation during the mounting process is predicted by the deep learning model to generate the compensation mounting path for the thin-film battery. S3: Mount the thin-film battery and control the contact force between the thin-film battery and the pads, so that the contact force smoothly transitions from the initial value to the steady-state value; S4: Perform local thermo-ultrasonic solid-state bonding on the bonding points between the upper electrode of the thin-film battery and the corresponding bonding points on the PCB; then, at the junction of the lower electrode of the battery and the PCB pad, use laser irradiation to melt the low-melting-point metal layer of the composite solder structure and allow it to diffuse and react with the high-melting-point metal layer and the copper pad to form a high-melting-point intermetallic compound. S5: Collect the three-dimensional morphological geometric parameters of the solder joint; simultaneously perform electroluminescence and photoluminescence imaging to extract the efficiency distribution and defect characteristics of the battery; Then, the process parameters in step S4 are dynamically adjusted using a preset process mapping model. S6: Calculate the residual stress distribution based on the defect characteristics of the battery, dynamically adjust the pressure applied by the hot press roller in different areas during the subsequent packaging process, and complete the interconnection of the thin-film battery array.

2. The stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs according to claim 1, characterized in that, In step S1, the shape and pattern of the microgroove array are concentric rings, radial stripes, or grids.

3. The stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs according to claim 1, characterized in that, In step S2, the deep learning model is a convolutional neural network model, and the specific method for generating the compensation mounting path for the thin-film battery is as follows: The PCB is scanned using a global camera, and the three-dimensional deformation field of the PCB under the current tension state is calculated in real time by combining the original dimensions of the PCB. Use a local camera to obtain the three-dimensional coordinates of the target pad; Input the 3D deformation field of the PCB and the pad positioning data into the convolutional neural network model, and calculate the deformation prediction vectors of the PCB in three mutually orthogonal directions under the action of mounting force, with the mounting point on the current pad as the center. Based on the calculated deformation prediction vector in three dimensions, the original mounting path of the thin-film battery is adjusted to form the final compensated mounting path.

4. The stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs according to claim 1, characterized in that, In step S3, when attaching the thin-film battery, the forces on the attachment point in three mutually orthogonal directions and the torque in the direction perpendicular to the surface of the pad are measured simultaneously; the combination of forces in the three mutually orthogonal directions forms the contact force.

5. The stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs according to claim 1, characterized in that, In step S4, when performing local thermo-ultrasonic solid-state bonding between the upper electrode of the thin-film battery and the corresponding bonding point on the PCB, the ultrasonic vibration direction is made parallel to the length direction of the PCB.

6. The stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs according to claim 5, characterized in that, In step S4, when irradiating the low-melting-point metal layer of the composite solder structure, a pulsed laser is used for irradiation. The wavelength of the pulsed laser corresponds to the absorption peak of the low-melting-point metal layer of the composite solder, and the spot diameter D of the pulsed laser is greater than 1.2 times the width W of the solder pad.

7. The stress-adaptive interconnection method for thin-film battery arrays based on flexible PCBs according to claim 1, characterized in that, In step S5, the three-dimensional morphological geometric parameters of the weld joint include height H, volume V, and contact angle θ; The process mapping model is a machine learning model trained on a large amount of experimental data. It establishes a quantitative fitting relationship between the three-dimensional morphological geometric parameters of the solder joint, thermo-ultrasonic solid-state bonding pressure, thermo-ultrasonic solid-state bonding time, and laser energy density irradiating the low-melting-point metal layer.

8. A stress-adaptive interconnection device for a thin-film battery array based on a flexible PCB, characterized in that, Along the material flow direction, the following are included in sequence: The processing module includes an ultraviolet laser for fabricating microgroove arrays; The vision-force control mounting module includes an end effector that grips a thin-film battery with a suction cup, a robot for moving the end effector, and a vision system for capturing PCB images. The interconnect module includes a thermo-ultrasonic solid-phase bonding unit and a laser transient liquid-phase diffusion welding unit, which are arranged side by side in space; The feedback module includes a laser scanner for acquiring the three-dimensional morphological geometry parameters of the solder joints, and an imaging unit for performing electroluminescence and photoluminescence imaging. The encapsulation module includes a multi-temperature zone hot press roller assembly with independent temperature and pressure control, and an encapsulation film unwinding mechanism; It also includes a storage unit and a processor, the storage unit being used to store one or more program instructions; the processor being used to run one or more program instructions for controlling the various modules described above and performing the steps of the stress-adaptive interconnection method for a thin-film battery array based on a flexible PCB as described in any one of claims 1 to 7.

9. The stress-adaptive interconnection device for a thin-film battery array based on a flexible PCB according to claim 1, characterized in that, The thermo-ultrasonic solid-phase bonding unit includes a high-frequency power supply, a piezoelectric transducer, a heating device, and a coaxial infrared thermometer; the selective laser transient liquid phase diffusion welding unit includes a fiber pulse laser, a two-dimensional galvanometer, a coaxial CCD monitoring lens, and a protective chamber.

10. The stress-adaptive interconnection device for a thin-film battery array based on a flexible PCB according to claim 1, characterized in that, The suction cup bottom surface of the end effector is a micro-convex surface that matches the curvature of the thin-film battery, and the material is a low thermal conductivity material.

Images