A room-temperature colloidal encapsulation method and encapsulation structure for multi-heterogeneous module smart cards

Abstract

This application relates to the field of smart card manufacturing technology, and discloses a room-temperature encapsulation method and encapsulation structure for multi-heterogeneous module smart cards. The method includes: machining a cavity for a first cover plate, an intermediate layer, and a second cover plate to obtain a three-layer carrier structure; placing a PCBA and heterogeneous modules into the cavity and positioning them using positioning pins and vacuum adsorption to form a first bonding layer; stacking and assembling the three-layer structure to form a first stacked space; injecting a two-component epoxy resin under vacuum to wet the electrical connection points; segmented pressing to remove excess resin; and curing at room temperature to form a sealing and protective layer. This application solves the problem of thermal damage to temperature-sensitive components caused by traditional high-temperature processes, as well as the problems of incomplete resin filling and inaccurate pressure control in existing room-temperature methods.

Description

Technical Field

[0001] This application relates to the field of smart card manufacturing technology, and in particular to a room temperature colloidal encapsulation method and encapsulation structure for multi-heterogeneous module smart cards. Background Technology

[0002] Traditional smart card packaging technology mainly uses high-temperature hot pressing, which melts PVC or other plastic materials at 130-200°C to laminate the card body. This process is suitable for traditional smart cards that only integrate simple chips. With the development of smart card functional requirements, modern smart cards have evolved from early contact or contactless chip cards to complex electronic devices that integrate multiple functions such as display screens, fingerprint sensors, and touch buttons. These internally integrated electronic modules are composed of components with different materials, structures, and thermal expansion coefficients, forming heterogeneous modules. In particular, precision electronic components such as OLED screens, electronic paper screens, and fingerprint sensors are extremely sensitive to temperature. Traditional high-temperature processes can cause irreversible thermal damage to these temperature-sensitive components during manufacturing, leading to problems such as component failure, screen burn-in, and solder joint desoldering. At the same time, the difference in thermal expansion coefficients of different materials during high-temperature processes can cause internal stress concentration inside the card body, affecting the flatness of the card and its long-term reliability.

[0003] Existing technologies for encapsulating temperature-sensitive components typically employ a process where a base card is first fabricated using high-temperature lamination, followed by subsequent steps such as slotting, embedding, and secondary encapsulation to install the heat-sensitive electronic module. While this method avoids the electronic module directly enduring high temperatures to some extent, the process is cumbersome and complex. The slotting operation disrupts the overall structural integrity of the card, and the cuts and slots formed on the card become stress concentration points, making them prone to crack propagation during use. The localized dispensing or pre-formed adhesive film methods used for embedding and secondary encapsulation cannot achieve complete filling of all micro-gaps by the adhesive, leading to issues at the bottom of PCBA solder joints and cores. Residual air in areas such as between pins and component side seams creates potential moisture channels, leading to electrochemical corrosion of solder joints in high-humidity environments. This reduces the reliability of data transmission. Existing improvement solutions, such as local low-temperature lamination, step-by-step lamination, or adding a heat insulation layer, still require local heating and have complex process parameter control, resulting in low yield and difficulty in achieving mass production. In addition, the UV-curable adhesives or hot melt adhesives used in existing packaging methods are mostly single-component systems with large curing shrinkage rates. The volume shrinkage during the curing process generates tensile stress around the module, causing brittle components such as OLED screen edges to crack or fingerprint sensors to shift, affecting data reading accuracy. Summary of the Invention

[0004] This application provides a room-temperature encapsulation method and structure for multi-heterogeneous module smart cards. It uses a three-layer carrier structure with a pre-formed cavity to replace the post-grooving process. At room temperature, the encapsulant completely fills and evenly distributes all micro gaps through vacuum-assisted injection and segmented controllable pressing. This solves the problem of thermal damage to temperature-sensitive components caused by traditional high-temperature processes, as well as the problems of incomplete encapsulant filling and inaccurate pressing stress control in existing room-temperature methods. This improves the encapsulation yield and long-term reliability of multi-heterogeneous module smart cards.

[0005] In a first aspect, this application provides a room-temperature gel encapsulation method for a multi-heterogeneous module smart card, the room-temperature gel encapsulation method for the multi-heterogeneous module smart card comprising:

[0006] Step S1: The first cover plate, the intermediate layer and the second cover plate are shaped into cavities, wherein the intermediate layer forms a second cavity for accommodating the PCBA and heterogeneous modules, resulting in a three-layer carrier structure;

[0007] Step S2: Place the PCBA and heterogeneous module into the second cavity, and spatially position them by using positioning pins and vacuum adsorption to obtain the first bonding layer after assembly;

[0008] Step S3: Assemble the three-layer carrier structure with the first bonding layer to form a first stacked space including the bottom of the PCBA, the area around the heterogeneous module, and the interlayer gaps;

[0009] Step S4: In a vacuum environment, inject two-component epoxy adhesive into the first stacked space, so that the adhesive wets the PCBA solder joints and the electrical connection points of the heterogeneous modules, and obtain the encapsulation structure after the adhesive is injected.

[0010] Step S5: The encapsulation structure is segmented and pressed together, with low pressure, medium pressure and constant pressure applied sequentially to remove excess colloid and make the colloid layer thickness uniformly distributed, thus obtaining the pressed smart card body. The smart card body is then left to stand and cure at room temperature to allow the colloid to cross-link and form a sealing protective layer.

[0011] Secondly, this application provides a room-temperature gel encapsulation structure for a multi-heterogeneous module smart card, the room-temperature gel encapsulation structure for the multi-heterogeneous module smart card comprising:

[0012] The three-layer carrier structure consists of a first cover plate, an intermediate layer, and a second cover plate. The inner surface of the first cover plate is provided with a rectangular first cavity for accommodating the display screen module. The inner surface of the second cover plate is provided with a circular first cavity for accommodating the fingerprint recognition sensor. The intermediate layer is provided with a second cavity for accommodating the PCBA and heterogeneous modules.

[0013] The PCBA, display screen module, fingerprint recognition sensor and lithium battery are located in the second cavity, and the bottom of the intermediate layer has an NFC antenna coil with a rectangular spiral structure printed on it.

[0014] A room-temperature curable colloid layer is filled in the bottom of the PCBA, around the heterogeneous modules and in the interlayer gaps. The colloid layer is formed by cross-linking and curing a two-component epoxy adhesive at room temperature. The colloid layer encapsulates the NFC antenna coil, PCBA solder joints, display screen connection points, fingerprint recognition sensor solder joints and lithium battery electrode connection points.

[0015] The colloid layer forms a sealing protective layer, the thickness of which is uniformly distributed and forms an integrated encapsulation structure with the three-layer carrier structure.

[0016] In the technical solution provided in this application, a three-layer carrier structure is formed by pre-machining the first cover plate, the intermediate layer, and the second cover plate. The second cavity of the intermediate layer is directly machined while the material is in a layered state, avoiding the structural integrity damage caused by the traditional method of first preparing a complete card body and then slotting. The precise matching of the cavity shape with the geometric parameters of the PCBA and heterogeneous modules eliminates the embedding gap. During the assembly stage, spatial positioning is achieved through the engagement of positioning pins and vacuum adsorption. The matching accuracy of the positioning pins and positioning through holes controls the positional deviation of the PCBA and heterogeneous modules to the micrometer level, significantly improving assembly accuracy compared to the millimeter-level accuracy of traditional manual embedding. The CCD vision inspection and fine-tuning platform correction mechanism further ensures the accuracy of the module position. Vacuum adsorption... The fixed attachment eliminates the risk of module displacement during subsequent operations. During the stacking assembly stage, the three-layer carrier structure is precisely stacked with the first bonding layer. Precise alignment of the cavities on the first and second cover plates with the corresponding heterogeneous modules is achieved through positioning pin guidance and pre-pressing with a flexible pressing head. The resulting first stacked space comprises a complete interconnected network structure encompassing the bottom of the PCBA, the area around the heterogeneous modules, and the interlayer gaps. Reserved injection ports and venting holes provide channels for subsequent full filling of the adhesive. Two-component epoxy adhesive is injected under a vacuum environment at room temperature. The vacuum negative pressure eliminates residual air in the space, preventing air bubble retention. Driven by both capillary pressure and vacuum differential pressure, the adhesive spreads laterally along the bottom surface of the PCBA and rises longitudinally along the interlayer gaps, actively penetrating into the NF (fiber optic interface). The process addresses minute gaps that manual dispensing cannot reach, such as those for the C-antenna coil, PCBA solder joints, display screen connection points, fingerprint sensor solder joints, and lithium battery electrode connections. It achieves complete encapsulation and sealing of all electrical connections. A segmented pressing process applies low, medium, and constant pressure sequentially. The low-pressure stage eliminates residual air bubbles and initially homogenizes the adhesive distribution. The medium-pressure stage uses a pressure sensor array to monitor the pressure distribution in real time and dynamically adjusts the pressure plate position using a PID control algorithm, ensuring uniform pressure and consistent adhesive thickness across all areas. A silicone rubber buffer layer on the bottom of the flexible pressure plate effectively disperses pressure, preventing cracking damage to brittle components such as the OLED screen and fingerprint sensor. The constant-pressure holding stage maintains stable pressure until the adhesive flow stops, and then the adhesive is slowly unloaded. The compression process gradually releases the internal compressive stress of the colloid, avoiding rebound and delamination caused by sudden unloading. During the room-temperature static curing stage, the two-component epoxy adhesive undergoes a cross-linking curing reaction at 25°C, with the system temperature only rising to 38°C, far below the 65°C tolerance temperature of OLED screens and the 60°C safety temperature of lithium batteries. This completely eliminates the risk of thermal damage to temperature-sensitive components caused by traditional high-temperature processes. The uniform formation of the cross-linked network during slow curing allows the internal stress to be fully released through the creep movement of molecular chain segments. The residual stress after curing is significantly lower than that of high-temperature rapid curing methods. The resulting sealing protective layer has excellent dielectric properties and low-loss characteristics, minimizing the impact on the electromagnetic field distribution around the NFC antenna and ensuring that data communication functions are not affected by encapsulation.The low curing shrinkage and excellent interfacial adhesion of the colloid enable the smart card to maintain structural integrity and functional stability during reliability tests such as temperature cycling and mechanical bending.

[0017] From the perspective of data processing function protection, the method of this application provides comprehensive protection for the core functions of smart cards, such as data reading, data storage, data processing, and data communication, throughout the entire packaging process. Precise positioning of the pre-formed cavity ensures the shortest electrical connection path and impedance matching between the NFC antenna coil and the chip. Vacuum-assisted potting completely wets the antenna printed circuitry, eliminating moisture corrosion paths and maintaining the stability of the antenna inductance and Q value. Room-temperature packaging avoids oxidation and increased resistance of the antenna circuitry caused by high temperatures, keeping the NFC communication distance and data transmission rate within the design specifications. For OLED displays, the complete filling of the FPC cable contact gaps with the adhesive forms a high-insulation-resistance isolation layer, preventing leakage and signal crosstalk between adjacent contacts, ensuring accurate transmission of screen display data and image quality. For fingerprint sensors, the sealing protection of the bump solder joints with the adhesive prevents increased contact resistance due to solder joint oxidation, maintaining the integrity of the I²C bus signal and the high signal-to-noise ratio of fingerprint image data acquisition. For lithium batteries, the improved insulation and thermal conductivity of the colloid at the positive and negative electrode connection points keep the temperature rise within a safe range during charging and discharging, extending battery cycle life and smart card standby time. Uniform pressure control during segmented lamination avoids PCBA warping caused by localized stress, maintaining the integrity of the chip package and the reliability of circuit connections. The low-stress sealing layer formed by room temperature curing acts as a buffer when the smart card is subjected to mechanical stresses such as bending and torsion, preventing stress transmission to brittle components and causing functional failure. The low dielectric loss characteristics of the colloid reduce the impact on data signal transmission, especially in high-frequency data communication scenarios, maintaining signal quality and transmission rate. Overall, the method of this application achieves high-precision positioning, complete filling and sealing, and stress control under room temperature conditions, solving the thermal damage problem of traditional high-temperature processes and overcoming the defects of incomplete filling and inaccurate stress control in existing room temperature methods. This significantly improves the manufacturing yield and long-term reliability of multi-heterogeneous module smart cards as data recording carriers and data processing devices. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a schematic diagram of an embodiment of the room temperature colloidal encapsulation method for multi-heterogeneous module smart cards in this application;

[0020] Figure 2 This is an exploded view of the three-layer carrier structure in an embodiment of this application;

[0021] Figure 3 This is a top-down exploded view of the three-layer carrier structure assembled with various heterogeneous modules in the embodiments of this application;

[0022] Figure 4 This is a schematic diagram of the positioning worktable in the embodiments of this application;

[0023] Figure 5 This is a schematic diagram of the two-component epoxy resin mixing and dispensing device in the embodiments of this application;

[0024] Figure 6 This is a schematic diagram of the segmented pressing unit in an embodiment of this application. Detailed Implementation

[0025] This application provides a room-temperature gel encapsulation method and encapsulation structure for a multi-heterogeneous module smart card. The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. Furthermore, the terms "comprising" or "having" and any variations thereof are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0026] For ease of understanding, the specific process of the embodiments of this application is described below. Please refer to [link / reference]. Figure 1 One embodiment of the room-temperature colloidal encapsulation method for multi-heterogeneous module smart cards in this application includes:

[0027] Step S1: The first cover plate, the intermediate layer and the second cover plate are shaped into cavities, wherein the intermediate layer forms a second cavity to accommodate the PCBA and heterogeneous modules, resulting in a three-layer carrier structure;

[0028] Step S2: Place the PCBA and heterogeneous modules into the second cavity, and spatially position them by using positioning pins and vacuum adsorption to obtain the first bonding layer after assembly.

[0029] Step S3: Assemble the three-layer carrier structure with the first bonding layer to form a first stacked space including the bottom of the PCBA, the area around the heterogeneous module, and the interlayer gaps;

[0030] Step S4: In a vacuum environment, inject two-component epoxy adhesive into the first stack space, so that the adhesive wets the PCBA solder joints and the electrical connection points of the heterogeneous modules, and obtain the encapsulation structure after the adhesive is injected.

[0031] Step S5: Perform segmented pressing of the encapsulation structure, applying low pressure, medium pressure and constant pressure in sequence to remove excess colloid and make the colloid layer thickness uniformly distributed, to obtain the pressed smart card body. Let the smart card body stand and cure at room temperature to allow the colloid to cross-link and form a sealing protective layer.

[0032] Specifically, this invention constructs a three-layer carrier structure by machining cavities in the first cover plate, the intermediate layer, and the second cover plate. The inner surface of the first cover plate is machined using precision die-cutting equipment to form a rectangular first cavity to accommodate the display screen module. The cavity depth is set according to the screen thickness, with residual thickness retained at the bottom to ensure light transmittance. The inner surface of the second cover plate is machined with a circular first cavity to accommodate the sensing surface of the fingerprint sensor. The cavity diameter is slightly smaller than the sensor sensing surface diameter to create an interference fit, ensuring the sensor sensing surface is flush with the outer surface of the cover plate. The intermediate layer is machined using laser cutting technology to create a through-type second cavity. This cavity includes a PCBA main mounting area to accommodate a printed circuit board integrating the main control chip and memory chip. The recessed groove accommodates the OLED display screen module, the fingerprint module mounting hole accommodates the capacitive fingerprint sensor chip, and the battery mounting slot accommodates the polymer lithium battery. The dimensions of each cavity are precisely matched with the geometric parameters of the corresponding module to form a mating relationship. An NFC antenna coil is printed at the bottom of the intermediate layer using screen printing. The coil has a rectangular spiral structure, is printed with silver conductive ink, and cured in an oven. After curing, the inductance value of the NFC antenna reaches the design value at the operating frequency, forming an LC resonant circuit with the internal capacitor of the NFC chip on the PCBA to achieve contactless data communication with the card reader. After the PCBA is placed into the main mounting area of ​​the second cavity, radial positioning is achieved through the engagement of positioning pins and positioning through-holes in the intermediate layer. The insertion depth and fit tolerance of the positioning pins ensure that the positional deviation of the PCBA in the XY plane is controlled within the micrometer level. The display screen module, fingerprint recognition sensor, and lithium battery are sequentially placed into the corresponding screen mounting groove, fingerprint module mounting hole, and battery mounting slot. The heterogeneous modules are pushed to the cavity wall by a side-pushing mechanism. The side-pushing mechanism is driven by a stepper motor to push the module gently against the cavity wall with a constant thrust. The thrust is monitored in real time by a force sensor to avoid excessive thrust and damage to brittle components. When performing CCD vision inspection on the module assembly, the industrial camera captures the entire middle layer from directly above. The image processing algorithm performs edge detection to extract the contours of each module, shape matching to identify the module type, and calculates the geometric center coordinates and theoretical position coordinates of each module. When the deviation value exceeds a threshold, the servo-driven XY fine-tuning platform automatically performs a correction operation. During correction, the vacuum suction cup at the bottom of the platform adsorbs the bottom of the offset module, and the platform moves in the opposite direction according to the deviation to push the module to the correct position. After correction, a vacuum negative pressure is applied to the module assembly. The negative pressure is applied through the micro-pore channels reserved on the bottom surface of the intermediate layer to firmly adsorb the back of each module to the bottom of the cavity. The adsorption force is sufficient to resist the inertial force generated by the module's own weight and the acceleration of handling during subsequent stacking operations. When aligning and bonding the bottom surface of the intermediate layer of the first cover plate with the first bonding layer, the positioning pin guides the display screen cavity on the first cover plate to align with the display screen module. The coaxiality of the first cover plate and the intermediate layer in the horizontal direction is controlled by the fitting tolerance.After the first cover plate and the intermediate layer are initially bonded together, a lower semi-closed cavity is formed between them, including the bottom surface of the PCBA, the bottom of each module, and the cavity space. The volume of this cavity is calculated geometrically to include the sum of the volumes of the micro-gap between the bottom surface of the PCBA and the silicone pad, the peripheral gap between the side surface of the PCBA and the cavity wall, the gap between the bottom surface of the OLED screen and the bottom of the recess, and the annular sealing gap between the screen and the cavity of the first cover plate. When the second cover plate is aligned and bonded to the top surface of the intermediate layer, a pre-pressure is applied by a flexible pressing head to align the fingerprint sensor cavity on the second cover plate with the fingerprint recognition sensor. After the second cover plate is bonded, an upper semi-closed cavity is formed between the intermediate layer and the second cover plate, including the top of each module and the cavity space. The enclosed cavity, with the lower and upper semi-enclosed cavities connected, forms a continuous mesh structure around the PCBA, along with the side gaps of the heterogeneous modules and the interlayer gaps. A glue inlet and a vent are pre-reserved at the edge of the middle layer of the package. The glue inlet connects to the bottom of the first stacked space, and the vent connects to the top of the first stacked space. When epoxy resin component A and polyamide curing agent component B are mixed according to a mass ratio, component A (epoxy resin with added nano-silica thixotropic agent and silane coupling agent) and component B (curing agent with added accelerator and defoamer) are mixed. After mixing, the mixture is stirred in a planetary mixer to fully disperse the nanoparticles. The prepared two-component adhesive solution is transferred to a vacuum degassing machine for high-speed stirring and degassing under vacuum. After degassing, the viscosity and thixotropic index of the adhesive solution are measured to ensure the adhesive solution remains stable under static conditions. To maintain high viscosity under certain conditions to prevent flow and rapidly reduce viscosity under shear to facilitate flow, the first layer space is placed in a vacuum chamber and the vacuum degree is controlled within the negative pressure range during evacuation. The negative pressure causes residual air in the space to be discharged through the exhaust port. When the two-component epoxy adhesive is injected into the injection port through the injection needle for constant flow, the adhesive first spreads laterally along the bottom surface of the PCBA under the combined action of the vacuum negative pressure difference and its own viscosity. Due to the capillary effect formed by the micro gap between the bottom surface of the PCBA and the silicone pad, capillary pressure is generated to drive the adhesive to spread rapidly. The superposition of capillary pressure and driving pressure generated by the vacuum pressure difference causes the adhesive to advance towards the center area of ​​the PCBA at a certain speed. After reaching the edge of the PCBA, the adhesive begins to climb longitudinally along the interlayer gap between the middle layer and the first cover plate. During the climbing process, the adhesive simultaneously penetrates the bottom of each heterogeneous module. When the adhesive reaches the edge of the OLED screen, it seeps in along the gap between the bottom surface of the screen and the bottom of the recess, as well as the annular gap between the side surface of the screen and the side wall of the recess. The capillary pressure in the gap drives the adhesive to fill. After filling the bottom of the screen, the adhesive continues to flow through the FPC cable channel to the FPC connector position on the PCBA. After filling, the adhesive wraps around the FPC contacts to form an insulating layer to prevent leakage between adjacent contacts. When the adhesive wets the NFC antenna coil, it seeps into the rough gap between the side of the circuit and the substrate. The complete wrapping of the antenna circuit by the adhesive forms an insulating layer to protect the antenna from moisture corrosion. At the same time, the influence of the low dielectric loss adhesive on the electromagnetic field distribution around the antenna is controlled within the allowable range.When the adhesive wets the PCBA solder joints, it fills the gaps at the bottom of the solder joints, the roots of the solder feet, and the bottom surface of the chip. When the adhesive wets the contact points of the display screen, it fills the contact gaps to form an insulating wall. When the adhesive wets the fingerprint recognition sensor solder joints, it wraps around the bump solder joints at the bottom of the sensor to form a sealing protective layer to prevent solder joint oxidation. When the adhesive wets the lithium battery electrode connection points, it wraps around the positive and negative electrode solder joints to form an insulating layer to isolate the positive and negative electrodes and prevent short circuits. When the adhesive overflows from the vent, it indicates that the first layer space has been basically filled and the air has been expelled. When applying low pressure to the encapsulated structure after adhesive application for initial pressing, the pressure plate descends at an initial speed to a certain distance from the surface of the encapsulated structure, then decelerates to a lower speed and continues to descend until contact. The control system sets the target pressure to a low pressure value, and the pressure plate descends at a constant speed. The loading rate is slowly applied, and under this low pressure, the colloid in the first layer space begins to be compressed. Due to the incompressibility of the colloid, it flows from the higher-pressure central area to the edge area, fully filling the tiny gaps between PCBA pads and chip pins during the flow. The colloid propels from the center to the edge at a certain speed, and some excess colloid slowly overflows from the overflow groove at the edge of the intermediate layer and flows into the collection groove of the base. When applying medium pressure to the initially pressed package structure for molding and pressing, the pressure plate is driven to descend by a servo motor, and the target pressure is controlled to increase from the low-pressure stage to the medium-pressure stage. The loading rate is reduced to achieve more precise pressure control. Under this medium pressure, the gap between each layer is further reduced, and the interlayer gap between the first cover plate and the intermediate layer decreases from the initial pressing stage. The thickness continues to be compressed, and the gap between the second cover plate and the intermediate layer is also compressed simultaneously. During the compression process, the extruded glue is discharged from the overflow grooves around the perimeter. After collecting the real-time pressure values ​​of each measuring point through a pressure sensor array, the standard deviation and coefficient of variation of the pressure distribution are calculated to obtain the pressure distribution parameters. The standard deviation reflects the dispersion of the pressure value of each measuring point relative to the average value, and the coefficient of variation is the ratio of the standard deviation to the average value, reflecting the relative uniformity of the pressure distribution. After inputting the pressure distribution parameters into the PID control system, when the pressure deviation is detected to exceed the set threshold, the position of the pressure plate is finely adjusted by the servo motor for compensation. The PID control algorithm calculates the adjustment amount based on the current deviation, the integral of the historical deviation, and the derivative of the deviation change rate. The servo motor finely adjusts the position of the pressure plate according to the adjustment amount to adjust the pressure at each measuring point. As the pressure approaches the target value, the medium-pressure driven colloid continues to flow from the interlayer gap into the overflow tank. The gap thickness between the first cover plate and the intermediate layer, and the gap thickness between the second cover plate and the intermediate layer decrease simultaneously. When applying constant pressure to the molded and pressed encapsulated structure for pressure holding, the control system maintains the target pressure at a constant medium pressure value. Under constant pressure, the flow of the colloid gradually slows down until it stops. The mechanism for stopping the flow is that the colloid flows under shear stress. As the colloid flows from the center to the edge, the colloid decreases in the central region, leading to a decrease in pressure, while the colloid increases in the edge region, gradually reducing the pressure gradient. At the same time, during the pressure holding process, the colloid gradually crosslinks due to the two-component reaction, increasing viscosity and flow resistance. When the driving force equals the resistance, the flow stops, reaching an equilibrium state, and the interlayer gap thickness tends to stabilize.During the pressure holding process, the control system continuously monitors the pressure sensor values. When pressure fluctuations exceed the threshold, the servo motor automatically fine-tunes the pressure plate position to compensate for the shrinkage, ensuring that the pressure remains within the set range. After the pressure holding is completed, when the pressure release program is started, the servo motor gradually unloads the pressure from the set value at a slow rate. This slow pressure release allows the internal compressive stress of the colloid to be released gradually, preventing the colloid layer from rebounding and delaminating due to sudden unloading. During the pressure release process, the colloid is in a gel state, with a certain degree of curing and viscosity that has essentially lost its fluidity. The cross-linked network has initially formed, but the molecular chain segments still have the ability to move. When the pressure is slowly released, the cross-linked network has enough time to release the internal stress through the creep movement of the molecular chain segments, allowing the smart card to be stored at room temperature. When left to stand, the two-component epoxy adhesive undergoes a cross-linking and curing reaction. The reaction mechanism involves the reaction of epoxy groups with amine groups to generate hydroxyl groups and secondary amines. The secondary amines then react with epoxy groups to generate tertiary amines and hydroxyl groups, forming a three-dimensional network cross-linked structure. Under isothermal curing conditions at room temperature, the curing curve is divided into four stages: induction period, rapid curing period, post-curing period, and complete curing period. During the induction period, the accelerator slowly dissociates and releases the catalyst, the epoxy-amine reaction rate is low, the cross-linked network has not yet formed, and the liquid remains fluid. The rapid curing period is the main stage of the cross-linking reaction, with a rapid increase in epoxy group conversion rate, molecular weight growth, sol-gel transition, and cross-linking density reaching a critical value, forming an infinite molecular network. The system transforms from a flowable sol state to a non-flowing gel state. During the curing period, the crosslinking reaction continues but at a significantly reduced rate. Residual epoxy groups and residual amine groups continue to react, further increasing the crosslinking density and raising the glass transition temperature. During the complete curing period, the reaction rate is extremely slow, primarily due to the diffusion-controlled stage. High curing degree and high crosslinking network density restrict molecular chain movement, hindering reactant diffusion and becoming the rate-controlling step. During the phase transition from liquid to gel to solid, the colloid undergoes volume shrinkage. The curing volume shrinkage rate is determined by the density method, calculated as the difference between the liquid and solid colloid densities divided by the solid colloid density. The change in card thickness caused by the effective volume shrinkage of the colloid is equal to the shrinkage volume divided by the effective encapsulation area of ​​the card. After curing, the colloid forms a sealing protective layer. This sealing protective layer is formed by the complete curing process... The cross-linked epoxy resin network possesses excellent mechanical and electrical properties. Mechanical properties include tensile strength, flexural strength, elongation at break, glass transition temperature, and elastic modulus. Electrical properties include volume resistivity, surface resistivity, breakdown strength, dielectric constant, and loss tangent. The sealing protective layer encapsulates all critical electrical connection points for data functions, including the NFC antenna pads, OLED screen FPC contacts, fingerprint sensor bump solder joints, and lithium battery solder pad connections, forming insulation to prevent leakage between adjacent connection points. Simultaneously, the sealing protective layer fills all micro-gaps, forming a dense barrier to prevent external moisture intrusion, electrochemical corrosion of solder joints, and increased leakage current.

[0033] In one specific embodiment, step S1 includes:

[0034] A rectangular first cavity is machined on the inner surface of the first cover plate. The first cavity is used to accommodate the display screen module, thus obtaining the machined first cover plate.

[0035] A circular first cavity is machined on the inner surface of the second cover plate. The first cavity is used to accommodate the fingerprint recognition sensor, thus obtaining the machined second cover plate.

[0036] The intermediate layer is processed with a through-type second cavity, which includes the PCBA main mounting area, screen mounting groove, fingerprint module mounting hole and battery mounting groove, to obtain an intermediate layer with functional partitions;

[0037] An NFC antenna coil is printed at the bottom of the middle layer. The NFC antenna coil has a rectangular spiral structure, resulting in a three-layer carrier structure that integrates NFC communication function.

[0038] Specifically, when machining the rectangular first cavity on the inner surface of the first cover plate, a precision die-cutting device is used to cut the transparent PET material. The die-cutting tool cuts into the inner surface of the first cover plate according to the preset rectangular contour path to form a recessed area. The length and width of the cavity are determined according to the effective display area size of the display screen module to be accommodated. The cavity depth is achieved by controlling the cutting depth of the die-cutting tool. The cutting depth is equal to the original thickness of the first cover plate minus the residual thickness. The residual thickness, i.e., the thickness of the material layer retained at the bottom of the cavity, must ensure sufficient light transmittance so that users can clearly see the screen display content. The cavity edges are eliminated by precision chamfering. The chamfer radius must be selected to avoid stress concentration that could cause cracks in the PET material during subsequent assembly and use. After the cavity is machined, the rectangular groove formed on the inner surface of the first cover plate matches the outer contour of the display screen module. The width of the annular gap reserved between the cavity edge and the screen edge is used for subsequent adhesive sealing. When machining the circular first cavity on the inner surface of the second cover plate, CNC drilling or milling equipment is used to process the opaque PC material. The spindle of the machining equipment drives the tool to rotate and feeds along the Z-axis to cut the inner surface of the second cover plate. The cutting depth is controlled by the Z-axis feed amount. The diameter of the circular cavity is determined according to the diameter of the sensing surface of the fingerprint recognition sensor. The cavity diameter is designed to be slightly smaller than the sensor sensing surface diameter to form an interference fit. The interference amount, i.e., the difference between the cavity diameter and the sensor diameter, needs to be controlled within a reasonable range. The interference fit ensures that the sensor sensing surface can remain flush with the outer surface of the second cover plate after being installed in the cavity. The sensor sensing surface and the outer surface of the cover plate are separated only by the residual thickness of the PC material. This residual thickness is the thickness of the dielectric layer that the capacitive fingerprint recognition sensor needs to penetrate when detecting a finger fingerprint. The dielectric layer thickness directly affects the amount of capacitance change detected by the sensor. The amount of capacitance change is inversely proportional to the dielectric layer thickness. The platform area reserved around the cavity and the bottom of the cavity form a stepped structure for the subsequent formation of a sealing ring by the colloid.When processing the through-type second cavity of the intermediate layer, laser cutting technology is used to precisely cut the PVC material. The diameter of the laser spot after focusing determines the kerf width, while the laser power and cutting speed together determine the cutting depth and cutting quality. The laser moves along a preset cutting path to complete the cavity processing that penetrates the entire thickness of the intermediate layer. The second cavity includes multiple functional areas. The PCBA main mounting area is a rectangular region in the center, and its length and width are determined according to the PCBA's external dimensions. The gap width reserved around the main mounting area is used to accommodate the subsequently injected adhesive. The screen mounting groove is a rectangular recessed area, and its length and width are determined according to the display screen module's external dimensions. The groove depth is equal to the center... The thickness of the layer minus the residual thickness at the bottom of the groove leaves a gap between the light-emitting surface of the screen module and the top surface of the middle layer after installation. The fingerprint module mounting hole is a circular through hole with a diameter determined by the outer diameter of the fingerprint sensor chip. The hole diameter is larger than the outer diameter of the sensor to form a clearance fit. The gap is used to accommodate the colloid to form a radial seal. The battery mounting groove is a rectangular recessed area with a length, width and depth determined by the external dimensions of the lithium battery. The position layout of each functional area is determined by the overall circuit design and functional requirements of the smart card. The positioning through holes machined at the four corners of the middle layer are circular through holes with a diameter determined by the diameter of the positioning pins used in subsequent assembly. The coordinate accuracy of the through hole position directly affects the positioning accuracy during subsequent assembly.When printing the NFC antenna coil at the bottom of the intermediate layer, the screen printing process is adopted. First, a screen template is made. The screen is a grid structure woven from stainless steel material, and the mesh count determines the printing accuracy. The ink-permeating holes are opened on the template according to the pattern of the NFC antenna coil. The area of the ink-permeating holes corresponds to the positions where the conductive lines need to be printed. Pour the silver paste conductive ink on the screen template, and the squeegee scrapes along the surface of the template to transfer the ink through the ink-permeating holes to the surface of the bottom of the intermediate layer. The silver particles in the ink pass through the grid under the action of the squeegee pressure and deposit on the surface of the intermediate layer to form a conductive line pattern. The NFC antenna coil is a rectangular spiral structure, which means that the conductive line starts from the outer starting point and winds inward along the rectangular contour to form multiple concentric rectangular coils. The outer diameter size of the coil is determined according to the available area of the intermediate layer, and the inner diameter size is calculated based on the line width, line pitch, and total number of turns. The line width, that is, the width of a single conductive line, affects the resistance value of the line. The line pitch, that is, the gap width between two adjacent turns of conductive lines, needs to ensure insulation to avoid short circuits. The number of turns, that is, the number of turns of the coil winding, determines the inductance value of the coil. The inductance value is calculated according to the formula, where it is related to the geometric size and number of turns of the coil. After printing, the intermediate layer is placed in an oven for curing treatment. The curing temperature and curing time are set according to the technical parameters of the silver paste ink. During the curing process, the solvent in the ink volatilizes and the silver particles are connected to each other to form a continuous conductive path. The inductance value of the cured NFC antenna coil needs to be measured by an LCR tester at the operating frequency. The measured inductance value is compared with the designed target value. If the inductance value deviation is within the allowable tolerance range, it is qualified. The NFC antenna coil is connected to the NFC chip pins on the surface of the PCBA through the metallized vias on the intermediate layer. The metallized vias are through holes with copper plating on the inner wall to form a conductive channel. The antenna coil and the internal capacitance of the NFC chip form an LC resonance circuit. When the resonance frequency is equal to the operating frequency, the impedance of the resonance circuit is the smallest, and efficient electromagnetic coupling can be achieved with an external card reader for non-contact data communication.

[0039] In a specific embodiment, step S2 includes:

[0040] Place the PCBA into the PCBA main installation area of the second cavity, and perform radial positioning through the cooperation of the positioning pin columns and the positioning through holes of the intermediate layer to obtain the positioned PCBA;

[0041] Place the display screen module, fingerprint recognition sensor, and lithium battery into the screen installation groove, fingerprint module installation hole, and battery installation groove in sequence, and push the heterogeneous modules to the cavity wall surface to be tightly attached through the side push mechanism to obtain the assembled module combination;

[0042] Perform CCD vision inspection on the module combination, calculate the deviation value between the actual position coordinates and the designed position coordinates of the heterogeneous modules, and when the deviation value exceeds the threshold, perform deviation correction through the fine adjustment platform to obtain the module combination with position calibration;

[0043] A vacuum negative pressure is applied to the module assembly after position calibration, and the heterogeneous modules are adsorbed and fixed through the microporous channels on the bottom surface of the intermediate layer to obtain the first bonding layer after assembly.

[0044] Specifically, when placing the PCBA into the main PCBA mounting area of ​​the second cavity, the intermediate layer is first laid flat on the positioning worktable. The worktable surface is equipped with positioning pins that mate with the positioning through holes at the four corners of the intermediate layer. The positioning pins are cylindrical metal rods whose outer diameter is determined according to the inner diameter of the positioning through holes. The insertion depth of the pins is controlled by the height of the worktable surface. The PCBA board is pre-set with positioning holes or slots corresponding to the positions of the positioning through holes in the intermediate layer. The PCBA is laid flat at the bottom of the main PCBA mounting area along the guide corner marks marked on the intermediate layer. The slots at the four corners of the PCBA board and the elastic grooves on the cavity wall... The limiting pins are used in conjunction with the elastic limiting pins, which are made of thin sheet spring steel and apply preload inward. Under the dual constraints of the positioning pins and the limiting pins, the positional deviation of the PCBA in the horizontal XY plane is controlled. The positioning accuracy is determined by the size of the fit clearance between the positioning pin and the positioning through hole. The fit clearance is equal to the inner diameter of the through hole minus the outer diameter of the pin. The smaller the clearance, the higher the positioning accuracy, but the more difficult the assembly becomes. After radial positioning, the deviation between the PCBA center position and the cavity center position is calculated through geometric relationships. The deviation is equal to the distance from the pin center to the through hole center multiplied by the magnification factor from the pin to the PCBA center. When placing the display module into the screen mounting recess, first confirm the front and back orientation of the screen module, with the light-emitting side facing up and the back side facing down. Use a vacuum pen to adhere the screen module to the center of the back. The vacuum applied by the pen creates suction force to overcome the screen's own weight. Move the screen horizontally to the top of the recess and then lower it vertically into the recess. The gap width between the screen edge and the recess edge should be pre-designed. The gap height between the bottom of the screen and the bottom of the recess should be equal to the recess depth minus the screen thickness. When placing the fingerprint sensor into the fingerprint module mounting hole, the sensor chip is cylindrically packaged, with a diameter slightly smaller than the mounting hole diameter to create a gap fit for easy installation. The pins or pads on the bottom of the sensor need to be aligned with the corresponding pads on the PCBA surface. Alignment is achieved by aligning the positioning marks on the sensor with the silkscreen marks on the PCBA. After the sensor is placed into the mounting hole, its top sensing surface should be flush with or slightly lower than the hole opening. Place the lithium battery into the battery holder. When the battery is installed in the slot, it is packaged as a rectangular thin sheet, with its length and width slightly smaller than the dimensions of the mounting slot. The positions of the positive and negative terminal solder pads of the battery must correspond to the positions of the battery connection pads on the PCBA. After the battery is placed in the mounting slot, a gap is left between the bottom surface of the battery and the bottom of the slot. When the heterogeneous modules are pushed to the cavity wall by the side pushing mechanism, the side pushing mechanism includes a push rod device driven by a stepper motor. The end of the push rod is equipped with a flexible contact head that matches the shape of the side of the module. The contact head is made of silicone and has a certain degree of elasticity. After receiving the control signal, the stepper motor rotates according to the set step angle. The rotational motion is converted into the linear motion of the push rod through the lead screw mechanism. The push rod moves towards the inside of the cavity at a constant speed. After the contact head contacts the side of the module, it continues to apply a pushing force. The magnitude of the pushing force is measured in real time by a force sensor installed at the end of the push rod. The sensor output voltage signal is proportional to the pushing force. The controller reads the voltage signal and converts it into a pushing force value. When the pushing force reaches the set value, the stepper motor stops rotating.The thrust value must be less than the module's destructive strength to prevent damage. Under the thrust, the module moves towards the cavity wall until it is flush against the wall. After flushing, there is no gap between the module and the wall, or the gap is less than a set threshold. When performing CCD vision inspection on the module assembly, the industrial camera is installed directly above the worktable, with the camera lens optical axis perpendicular to the worktable surface. The camera's field of view covers the entire intermediate layer area. An LED ring light source provides uniform illumination. The camera acquires grayscale images of the intermediate layer. In the image, each heterogeneous module presents different grayscale values ​​and texture features. The image processing algorithm first binarizes the original image, sets a grayscale threshold to divide the image into foreground and background, with the foreground being the module area and the background being a blank area. Then, edge detection is performed on the binary image using Canny. Edge detection algorithms or the Sobel operator extract the module's edge contour, which is a series of continuous pixel coordinate points. Shape matching is performed on the edge contour to identify the module type. Shape matching is achieved by calculating the similarity between the contour to be identified and the template contour. Similarity is measured using shape features such as Hu moments or Fourier descriptors. After identifying the module type, the geometric center coordinates of the module are calculated. The geometric center coordinates are the average of the coordinates of all pixels in the contour. The actually measured geometric center coordinates are compared with the theoretical design position coordinates read from the CAD design file, and the deviation between the two is calculated. The deviation includes X-direction deviation and Y-direction deviation. The X-direction deviation equals the actual X-coordinate minus the designed X-coordinate, and the Y-direction deviation equals the actual Y-coordinate minus the designed Y-coordinate. The Y-coordinate, with the sign of the deviation value indicating the offset direction, compares the calculated deviation value with a preset threshold, set according to assembly accuracy requirements. When the absolute value of the X-axis deviation exceeds the threshold, or the absolute value of the Y-axis deviation exceeds the threshold, it is determined to be out of position and requires correction. Correction is performed using a fine-tuning platform, a two-axis servo-driven platform with a vacuum suction cup at its bottom. The controller generates correction commands based on the calculated deviation value, including X-axis and Y-axis movement. The X-axis movement equals the negative value of the X-axis deviation, and the Y-axis movement equals the negative value of the Y-axis deviation. The servo motor drives the platform to move the corresponding distance along the X and Y axes. As the platform moves, the suction cup adheres to the bottom of the offset module, and the module moves with the platform to the correct position. After the position is moved and the vacuum suction force is released, the camera is restarted to collect images and recalculate the position coordinates to verify the correction effect. When applying vacuum negative pressure to the module assembly after position calibration, a vacuum pump connected to the bottom of the workbench is used. The vacuum pump evacuates air to create a negative pressure environment inside the workbench. The negative pressure is transmitted to the bottom of the module through micro-pore channels reserved on the bottom surface of the intermediate layer. The micro-pore channels are fine pores with a diameter of sub-millimeter that penetrate the thickness of the intermediate layer. The pores are distributed in the corresponding areas on the bottom of each module. The negative pressure acts on the gap space between the bottom surface of the module and the bottom surface of the intermediate layer. The air in the gap is extracted, causing the pressure in the gap to be lower than atmospheric pressure. The top surface of the module is subjected to atmospheric pressure. The pressure difference between the atmospheric pressure on the top surface and the negative pressure on the bottom surface generates a downward suction force. The magnitude of the suction force is equal to the pressure difference multiplied by the bottom area of ​​the module.The pressure difference equals atmospheric pressure minus the absolute pressure within the gap. The absolute pressure within the gap is determined by the vacuum pump's pumping capacity; the higher the vacuum level, the lower the absolute pressure, and the greater the pressure difference, the stronger the adsorption force. The adsorption force must be greater than the sum of the module's own weight and any external forces that may be applied during subsequent operations. After adsorption and fixation, each heterogeneous module is firmly attached to its corresponding position in the intermediate layer, forming a stable assembly state.

[0045] In one specific embodiment, step S3 includes:

[0046] The first cover plate and the bottom surface of the intermediate layer of the first bonding layer are aligned and bonded together. The display screen cavity on the first cover plate is guided by the positioning pin to align with the display screen module, forming a lower semi-closed cavity including the bottom surface of the PCBA and the bottom of the heterogeneous module.

[0047] The second cover plate is aligned and bonded to the top surface of the intermediate layer. Pre-pressure is applied by a flexible pressing head to align the fingerprint sensor cavity on the second cover plate with the fingerprint recognition sensor, forming an upper semi-closed cavity containing the top of each heterogeneous module.

[0048] The lower semi-enclosed cavity is connected to the upper semi-enclosed cavity, and the gaps around the PCBA, the side gaps of the heterogeneous modules, and the interlayer gaps form a continuous mesh structure, resulting in a three-layer stacked package.

[0049] A glue injection port and an vent are reserved at the edge of the middle layer of the package. The glue injection port is connected to the bottom of the first stacked space, and the vent is connected to the top of the first stacked space, thus forming a three-layer carrier structure that forms the first stacked space.

[0050] Specifically, when aligning and bonding the first cover plate with the bottom surface of the intermediate layer of the first bonding layer, the first cover plate is first flipped so that the inner surface with the display screen cavity faces upward. A six-axis robotic arm holds the edge of the first cover plate and moves it horizontally to directly below the intermediate layer. The pre-machined positioning holes on the first cover plate precisely engage with the positioning pins of the worktable. The fit tolerance is that the gap between the hole diameter and the shaft diameter is controlled within the micrometer range. The size of the gap determines the coaxiality of the first cover plate and the intermediate layer in the horizontal XY plane. Coaxiality is the offset between their central axes. The lifting mechanism under the worktable is activated to lift the first cover plate upward along the Z-axis. A faster lifting speed is used when the distance from the bottom surface of the intermediate layer is relatively large. When the photoelectric sensor detects… When the inner surface of the first cover plate reaches a preset distance from the bottom surface of the intermediate layer, it automatically decelerates to a slower speed to enter the precision docking stage. Simultaneously, the local vacuum suction cups on the upper surface of the first cover plate are activated. The suction cups are arrayed in the non-cavity area of ​​the first cover plate. The vacuum negative pressure applied by a single suction cup generates an adsorption force. The total adsorption force of multiple suction cups is balanced by the downward force of the intermediate layer's own weight and the vacuum adsorption force at the bottom, allowing the first cover plate to gently adhere to the bottom surface of the intermediate layer, avoiding rigid impact. Guided by the positioning pin, when the display screen cavity on the first cover plate is aligned with the display screen module, the cylindrical outer surface of the pin contacts the cylindrical inner surface of the positioning hole on the first cover plate. The optimal alignment is achieved when the central axis of the pin coincides with the central axis of the hole. The display screen cavity on the inner surface of the first cover plate is a rectangular groove. The geometric center of the groove and the geometric center of the display screen module already installed in the intermediate layer must coincide in the horizontal plane. The coincidence accuracy is ensured by the fit accuracy of the positioning pins and positioning holes. The width of the annular gap formed between the edge of the cavity and the edge of the screen is the difference between the side length of the cavity and the side length of the screen divided by two. This gap width must be evenly distributed around the perimeter. The uniformity is ensured by both the cavity machining accuracy and the module positioning accuracy. After the first cover plate and the intermediate layer are initially attached, a lower semi-closed cavity is formed between them, including the bottom surface of the PCBA and the bottom of the heterogeneous module. This cavity is a three-dimensional space. The bottom boundary of the cavity is the inner surface of the first cover plate, and the top edge is the inner surface of the first cover plate. The boundary is the bottom surface of the intermediate layer, and the side boundary is the side wall of the intermediate layer cavity. The space included in the cavity includes a flat gap space between the bottom surface of the PCBA and the first cover plate. The height of this gap is equal to the thickness of the intermediate layer minus the thickness of the PCBA. It also includes a gap space between the bottom surface of the display screen module and the bottom of the screen mounting groove. The height of this gap is equal to the groove depth minus the screen thickness. It also includes a gap space between the bottom of the fingerprint recognition sensor and the bottom of the mounting hole. It also includes a gap space between the bottom surface of the lithium battery and the bottom of the battery mounting groove. It also includes a gap space between the side surfaces of each module and the side wall of the cavity. The total volume of the lower semi-enclosed cavity is the sum of the volumes of each part of the space. The volume is calculated by multiplying and summing the geometric dimensions.When aligning and bonding the second cover plate with the top surface of the intermediate layer, remove the second cover plate with its inner surface (where the fingerprint sensor cavity is machined) facing down. A robotic arm then horizontally places the second cover plate directly above the intermediate layer. The positioning holes and pins on the second cover plate have the same tolerance as the first cover plate. The upper flexible pressing head descends and lightly touches the outer surface of the second cover plate. The bottom surface of the flexible pressing head is covered with a silicone rubber buffer layer. The thickness and hardness parameters of the buffer layer determine the stress distribution when the pressing head contacts the second cover plate. The hardness is expressed using Shore hardness; the smaller the value, the softer the material and the greater the elastic deformation. The pressing head's descent speed and applied pressure are controlled by a servo motor. The applied pre-pressure is measured by a pressure sensor built into the pressing head. The sensor's output signal is converted into a digital signal by an amplifier and an AD converter and input to the controller. The controller adjusts the servo motor's output torque based on the deviation between the target pressure value and the actual measured value, achieving closed-loop pressure control. The pre-pressure ensures a tight fit between the second cover plate and the top surface of the intermediate layer. The two covers are joined without causing significant compression deformation. After joining, the fingerprint sensor cavity on the second cover aligns with the fingerprint recognition sensor. The alignment mechanism is similar to that of the first cover, relying on positioning pins for guidance. The cavity is a circular hole, and the center of the hole coincides with the center of the sensor chip in the horizontal plane. The gap height between the bottom of the cavity and the sensor sensing surface is equal to the residual thickness of the second cover. This gap height is the thickness of the medium layer when touched. After the second cover is joined, an upper semi-closed cavity containing the tops of each heterogeneous module is formed between the middle layer and the second cover. The bottom boundary of this cavity is the top surface of the middle layer, and the top boundary is the inner surface of the second cover. The cavity contains the gap between the top surface of the display screen module and the top surface of the middle layer. This gap height is equal to the thickness of the middle layer minus the groove depth minus the screen thickness. It also contains the gap between the top surface of the fingerprint sensor and the bottom of the second cover cavity, as well as the gap between the top surface of the battery and the top surface of the middle layer. The total volume of the upper semi-closed cavity is also the sum of the volumes of each part.When the lower and upper semi-enclosed cavities are connected, the two cavities are connected through the through-area of ​​the intermediate layer cavity. The PCBA perimeter gap refers to the annular gap between the outer edge of the PCBA and the sidewall of the intermediate layer cavity. This gap extends from the bottom of the lower cavity to the top of the upper cavity. The gap width is the difference between the inner edge dimension of the cavity and the outer edge dimension of the PCBA, divided by two. The gap extends vertically through the entire thickness of the intermediate layer. The heterogeneous module side gaps refer to the gaps between the sides of each module and the sidewall of the cavity. Examples include the circumferential gap between the rectangular side of the display screen module and the sidewall of the screen mounting recess, and the annular gap between the cylindrical side of the fingerprint sensor and the inner wall of the fingerprint module mounting hole. (Lithium battery...) The rectangular sides of the battery compartment and the sidewalls of the battery mounting slot have surrounding gaps. These side gaps connect vertically to the gaps around the PCBA. The interlayer gaps refer to the gaps between the first cover plate and the intermediate layer, and the gaps between the second cover plate and the intermediate layer. These two interlayer gaps connect to the gaps around the PCBA through the edge region of the intermediate layer. All gaps and seams are interconnected in three-dimensional space to form a continuous mesh structure. The mesh structure means that there is at least one connecting path formed by gaps between any two points. After fluid is injected at any point in the mesh structure, it can flow to any other point in the mesh structure, resulting in a three-layer stacked package, namely the first cover plate, the intermediate layer, the second cover plate, and the third layer. The structure is completely integrated to form a whole. When pre-reserving injection ports and venting holes at the edge of the intermediate layer of the package, the injection ports are rectangular or trapezoidal grooves machined at the edge of the intermediate layer. The bottom of the injection port penetrates the intermediate layer and directly connects to the first cover plate, while the top penetrates the intermediate layer and directly connects to the second cover plate. The cross-sectional area of ​​the injection port determines the flow rate of the adhesive during injection; the flow rate equals the cross-sectional area multiplied by the flow velocity. Multiple injection ports are distributed at different edge positions of the intermediate layer, allowing for multi-point injection and shortening the adhesive filling time. The injection port connecting to the bottom of the first stacked space means that after the injection needle is inserted into the injection port, the injected adhesive first enters the bottom area of ​​the lower semi-enclosed cavity, i.e., the area between the bottom surface of the PCBA and the first cover plate. The gaps between the layers are filled with vent holes, which are circular holes machined on the sidewall of the intermediate layer. The vent holes penetrate from the sidewall of the intermediate layer into the cavity. The diameter of the vent holes determines the venting rate. The vent holes are connected to the top of the first layer space, which means that the vent hole opening is close to the top area of ​​the upper semi-closed cavity. When the colloid is injected from the bottom and rises upward, it squeezes the air out of the vent holes. The first layer space is a complete three-dimensional space consisting of the lower semi-closed cavity, the upper semi-closed cavity, and all the gaps and seams connecting the two. The boundary of this space is formed by the inner surface of the first cover plate, the inner surface of the second cover plate, the sidewall of the intermediate layer cavity, and the surfaces of each module. Any position in the space can reach the injection port or vent hole through the gap mesh structure.

[0051] In one specific embodiment, step S4 includes:

[0052] Epoxy resin component A and polyamide curing agent component B are mixed in a certain mass ratio and then subjected to vacuum degassing treatment to obtain a two-component epoxy adhesive with controlled viscosity.

[0053] The first stacked space is placed in a vacuum chamber and a vacuum is drawn. The residual air in the space is discharged from the exhaust port by negative pressure to obtain a package under vacuum environment.

[0054] Two-component epoxy adhesive is injected into the dispensing port through a dispensing needle under constant flow. The adhesive spreads laterally along the bottom surface of the PCBA and rises longitudinally along the interlayer gap under the drive of capillary pressure and vacuum pressure difference, resulting in an adhesive-filled encapsulation.

[0055] The colloid sequentially wets the NFC antenna coil, PCBA solder joints, display screen connection points, fingerprint sensor solder joints, and lithium battery electrode connection points. The colloid injection is stopped when it overflows from the vent, resulting in a fully encapsulated structure.

[0056] Specifically, when epoxy resin component A and polyamide curing agent component B are mixed in a certain mass ratio, component A includes epoxy resin matrix material and additives. The epoxy resin selected is bisphenol A type, and its epoxy equivalent is the molar mass of the epoxy groups. The additives include nano-silica thixotropic agents to adjust the thixotropic properties of the adhesive. Thixotropy refers to the ability of the adhesive to maintain high viscosity under static conditions to prevent flow and to rapidly reduce viscosity under shear to facilitate flow. It also includes silane coupling agents to enhance the adhesion strength between the adhesive and the substrate interface. Component B includes an aliphatic polyamide curing agent as the active component of the curing reaction and an accelerator to accelerate the curing reaction. The mass ratio is the ratio of the mass of component A to the mass of component B. This ratio is calculated based on the epoxy equivalent and amine value. The amine value indicates the curing... The active hydrogen content in the agent is controlled by a stoichiometric ratio, requiring a specific ratio between the molar number of epoxy groups and the molar number of active hydrogen. Component A is poured into a planetary mixer in the mixing chamber. The mixer's rotation and revolution ensure thorough mixing. After adding nano-silica, stirring further disperses the nanoparticles uniformly in the matrix. The dispersion effect is assessed using a Malvern laser particle size analyzer, which measures the particle size distribution of agglomerates in the adhesive. The particle size distribution is represented by the D90 parameter, which is the particle size value corresponding to a volumetric cumulative distribution of 90%. Component B is then added to component A at the specified mass ratio, and stirring continues to ensure uniform mixing at the molecular level. The mixed two-component adhesive is immediately transferred to a vacuum degassing machine. The degassing machine rotates at high speed under vacuum, generating centrifugal force to remove dissolved oxygen from the adhesive. Air bubbles entrained during mixing rise to the liquid surface and burst under the combined action of centrifugal force and vacuum negative pressure. Vacuum degree is the difference between the absolute pressure inside the chamber and atmospheric pressure. Degassing time is determined based on the volume and viscosity of the adhesive. After degassing, visual inspection confirms that no visible bubbles remain inside the adhesive. The viscosity of the adhesive is measured using a rotational viscometer. The rotor of the viscometer is immersed in the adhesive and rotates. The torque experienced by the rotor is proportional to the viscosity of the adhesive. The viscosity value is calculated by measuring the torque. The thixotropic index is the ratio of the viscosity measured at low rotation speed to the viscosity measured at high rotation speed. A larger ratio indicates stronger thixotropy. Controlled viscosity means the viscosity value is within a preset target range. Excessive viscosity makes it difficult for the adhesive to flow and fully fill micro-gaps, while excessively low viscosity causes the adhesive to fall due to gravity in vertical gaps. When the first stacked space is placed in the vacuum chamber, the packaged body assembled in the aforementioned steps is transferred from the positioning worktable to the vacuum dispensing chamber. The chamber is a sealed container equipped with a mechanical pump to evacuate the vacuum. The mechanical pump uses piston or vane movement to expel the gas inside the chamber. The vacuuming process is carried out in stages. The first stage quickly evacuates to a medium vacuum level, and the second stage continues to evacuate to a high vacuum level. The selection of the vacuum level needs to comprehensively consider the effect of residual air removal and the pressure impact on brittle components. If the vacuum level is too high, the sealed cavity inside the OLED screen will fail due to the excessive pressure difference between the inside and outside. When the residual air in the space is discharged through the exhaust port by negative pressure, the space is initially filled with atmospheric pressure air. After vacuuming, the absolute pressure in the space decreases, the air density decreases, and the air flows out of the chamber through the exhaust port.The mass of exhaust air is calculated based on the ideal gas law. The initial air mass is related to the space volume, initial pressure, and temperature. The residual air mass is related to the space volume, residual pressure, and temperature. The exhaust air mass equals the initial mass minus the residual mass. The residual air ratio equals the residual mass divided by the initial mass. A vacuum environment encapsulation refers to a state where the encapsulation is in a low-pressure environment and most of the air in the first stack space has been exhausted. When injecting two-component epoxy resin through a dispensing needle inserted into the dispensing port for constant flow, the two-component resin is loaded into the storage cylinder of the dispensing device. The device is equipped with a precision metering pump to control the resin flow rate. The flow rate is the volume of resin flowing per unit time. Constant flow means that the flow rate remains constant and does not change over time. The dispensing needle is a stainless steel tubular structure. The inner diameter determines the resistance to the flow of the adhesive. The depth to which the needle is inserted into the dispensing port ensures that the needle tip reaches the interior of the first stacked space. After the metering pump is started, the adhesive flows out from the needle tip into the space at a constant flow rate. When the adhesive flows under the drive of capillary pressure and vacuum pressure difference, the capillary pressure is generated by the surface tension effect of the adhesive in the tiny gaps. Surface tension causes the adhesive surface to tend towards the minimum area, forming a meniscus in the gap. The pressure difference on both sides of the meniscus is the capillary pressure. The capillary pressure is directly proportional to the surface tension and inversely proportional to the gap radius. The smaller the gap, the greater the capillary pressure. The vacuum pressure difference is the difference between the pressure at the dispensing port and the pressure inside the space. The pressure at the dispensing port includes the pressure applied by the dispensing pump and atmospheric pressure. The pressure inside the space is the low pressure drawn by the vacuum pump. The pressure difference generates a driving force to propel the adhesive. As the adhesive flows and spreads laterally along the bottom surface of the PCBA, it first enters the flat gap between the PCBA bottom surface and the first cover plate from the injection port. The small gap height results in high capillary pressure, driving the adhesive to diffuse laterally along the gap. The diffusion rate is directly proportional to the capillary pressure and inversely proportional to the adhesive viscosity. Lateral spreading progresses from the injection port towards the center of the PCBA, with the adhesive front gradually expanding in a circular or elliptical shape. Once the adhesive reaches the edge of the PCBA, it begins to rise longitudinally along the interlayer gaps (between the first cover plate and the intermediate layer, and between the second cover plate and the intermediate layer). This longitudinal rise is the adhesive flowing upwards vertically. The rising speed is affected by gravity, which creates downward resistance. The rising speed equals the driving pressure minus the gravitational resistance. Dividing the net pressure by the viscous resistance yields the encapsulated body filled with adhesive. This refers to the gaps and crevices within the first layer being filled with adhesive. As the adhesive sequentially wets the NFC antenna coil, it flows to the NFC antenna area printed at the bottom of the intermediate layer. The antenna is a silver paste conductive circuit with microscopic roughness on its surface, with roughness gaps at the micrometer level. Under capillary action, the adhesive penetrates into the roughness gaps between the side of the circuit and the PVC substrate. Wetting refers to the adhesive fully contacting and wetting the solid surface. After wetting the NFC antenna, the adhesive continues to flow towards the PCBA solder joints. PCBA solder joints are solder points formed by connecting chip pins to PCB pads with solder. There are tiny gaps between the bottom of the solder joint and the PCB. The adhesive penetrates the bottom of the solder joint and coats its surface.When the adhesive is applied to the contact points of the display screen, it flows to the contact points of the FPC (Flexible Printed Circuit) cable. The FPC is a flexible printed circuit, and the contacts on the cable are made of gold-plated copper foil. The spacing between adjacent contacts forms gaps, and the adhesive fills these gaps to form an insulating layer. When the adhesive is applied to the solder joints of the fingerprint sensor, it flows to the bump solder joints at the bottom of the sensor. Bumps are tiny solder bumps, and the solder joints are connected to the PCBA pads via solder. There are radial gaps between the solder joints and the cavity walls, and the adhesive seeps into these gaps to coat the solder joints. When the adhesive is applied to the lithium battery electrode connection points, it flows to the locations where the battery positive and negative electrode solder pads connect to the PCBA pads. The solder pads are then soldered to the pads. The process begins with gaps around the connection points. Adhesive fills these gaps and encapsulates the connection points. When adhesive overflows from the vent, it indicates that the adhesive has flowed from the injection port through the entire first-layer space to the vent. The vent is located at the top of the space. The adhesive reaching the top means that all areas below the vent are filled. The adhesive then flows out of the vent and into the outside of the chamber. The operator stops injection when adhesive overflows from the vent through the transparent chamber observation window. Stopping injection means turning off the metering pump to stop the adhesive flow. A completed encapsulation structure means that all gaps and seams within the first-layer space are filled with adhesive, and the adhesive has permeated all critical electrical connection points.

[0057] In one specific embodiment, step S5 includes:

[0058] Apply low pressure to the encapsulation structure after glue injection for preliminary pressing. The glue flows from the center area to the edge area and is discharged from the glue overflow groove to obtain the preliminary pressed encapsulation structure.

[0059] Medium pressure is applied to the pre-pressed encapsulation structure for molding and pressing. The pressure distribution in each area is monitored and adjusted in real time by a pressure sensor array to reduce the interlayer gap thickness and make the adhesive layer thickness more uniform, thus obtaining the molded and pressed encapsulation structure.

[0060] A constant pressure is applied to the molded and pressed packaging structure for pressure holding treatment. When the flow of the colloid stops and the thickness stabilizes, the pressure is slowly released to obtain the pressed smart card body.

[0061] The smart card body is left to stand at room temperature, and the two-component epoxy adhesive undergoes a cross-linking and curing reaction. The adhesive changes from a liquid state to a gel state and then to a solid state, forming a sealing and protective layer, thus obtaining a packaged multi-heterogeneous module smart card.

[0062] Specifically, during the initial pressing of the encapsulated structure after adhesive injection, the encapsulated structure is removed from the vacuum chamber and transferred to the controllable pressing unit. The pressing unit includes a servo motor drive system and a flexible pressure plate. The servo motor converts the rotational motion into the vertical linear motion of the pressure plate via a ball screw. A silicone rubber buffer pad is attached to the bottom surface of the pressure plate, and the surface of the buffer pad is processed with a grid pattern. The pressure plate descends at a set speed to contact the surface of the encapsulated structure. At the moment of contact, a pressure sensor detects the initial contact force and triggers the low-pressure pressing stage. The control system sets a low-pressure target value, and the servo motor slowly increases the pressure to the target value at a constant loading rate. The low pressure acting on the encapsulated structure causes compressive stress on the colloid within the first layer space. Since the colloid is an incompressible fluid, after being compressed, the colloid in the space... An internal pressure gradient is generated, with the pressure in the central region being higher than that in the edge regions. This pressure gradient drives the colloid to flow from the high-pressure zone to the low-pressure zone. As the colloid flows from the central region to the edge, it moves through the gaps around the PCBA and between layers towards the edge of the intermediate layer. The flow velocity is directly proportional to the pressure gradient and inversely proportional to the colloid viscosity. After reaching the edge of the intermediate layer, the colloid enters a pre-processed overflow groove. This overflow groove has a trapezoidal cross-section and its volume is used to temporarily hold the discharged colloid. Once the overflow groove is full, the colloid continues to overflow into a collection groove on the base. An absorbent felt is laid in the collection groove to absorb the overflowing colloid and prevent backflow. The low-pressure stage of compression allows the colloid to fully fill the tiny pores between components, pads, and chip pins on the PCBA surface. These pores are on the micrometer scale. During the pressing stage, the flow distance and outflow volume of the colloid are related to the pressure and holding time. The initial pressed encapsulation structure refers to the state after low-pressure pressing, where the colloid has been partially discharged and initially evenly distributed. When applying medium pressure to the initially pressed encapsulation structure for molding pressing, the control system increases the target pressure from the low pressure value to the medium pressure value. The increase process uses a low loading rate to achieve fine control. The medium pressure being greater than the low pressure means that the compressive stress applied to the encapsulation structure increases. Under the action of medium pressure, the gaps between the layers further decrease. The interlayer gap thickness between the first cover plate and the middle layer continues to compress from the value after the initial pressing, and the interlayer gap thickness between the second cover plate and the middle layer also compresses synchronously. The reduction in gap thickness causes the colloid in the gap to be squeezed out, and the squeezed colloid overflows from the edge. When the pressure is discharged from the tank, the pressure sensor array monitors the pressure distribution in each area. The pressure sensor array consists of multiple thin-film pressure sensors distributed in a matrix on the bottom surface of the pressure plate. The sensing area of ​​the sensors covers the main area of ​​the encapsulation structure. Each sensor independently measures the pressure value at its location, and the measured value is output in the form of a voltage or current signal. The signal is converted into a digital signal by an analog-to-digital converter and input to the controller. The controller collects the pressure data from all sensors to form a pressure distribution matrix. The pressure distribution matrix is ​​a two-dimensional array, with each element corresponding to the pressure value of a sensor. The statistical parameters of the pressure distribution are calculated, including the mean, standard deviation, and coefficient of variation. The mean is the sum of all pressure values ​​divided by the number of sensors, and the standard deviation is the square root of the sum of the squares of the differences between each pressure value and the mean.The coefficient of variation is calculated by dividing the standard deviation by the mean. The standard deviation reflects the dispersion of the pressure distribution, while the coefficient of variation reflects the relative uniformity of the pressure distribution. Real-time adjustment refers to the controller dynamically adjusting the pressure plate position based on the pressure distribution parameters. When the pressure value of a sensor deviates from the target value by more than a set threshold, it is determined that the pressure distribution is uneven. The controller generates a compensation command to drive the servo motor to fine-tune the pressure plate position. The fine-tuning amount is calculated based on the pressure deviation and uses a PID control algorithm. The algorithm input is the pressure deviation value, and the output is the motor adjustment amount. PID includes a proportional term, an integral term, and a derivative term. The proportional term is proportional to the current deviation, the integral term is proportional to the cumulative historical deviation, and the derivative term is proportional to the rate of change of the deviation. The weighted sum of the three terms yields the total adjustment amount. The servo motor adjusts accordingly. The movable pressure plate moves the sensor pressure values ​​towards the target value, reducing the interlayer gap thickness and making the adhesive layer thickness more uniform. This reduction in gap thickness is a result of continuous application of medium pressure. The gap is compressed from its initial thickness to a smaller thickness, with the adhesive continuously being discharged during compression. Adhesive layer thickness refers to the thickness of the adhesive within the gap. Uniform adhesive layer thickness means a reduction in the difference in adhesive layer thickness across different areas. Thickness uniformity is achieved through uniform pressure distribution. When the pressure is uniform, each area experiences the same compressive stress, resulting in the same amount of compression. The molded and pressed encapsulated structure refers to the state where the interlayer gap and adhesive layer thickness meet the design requirements after medium-pressure pressing. When applying constant pressure to the molded and pressed encapsulated structure for pressure holding, the control system maintains the target pressure at the medium-pressure value. This is achieved by stopping the application of additional pressure. Maintaining the current pressure, during the pressure holding phase, the flow of the colloid under constant pressure gradually slows down. This slowdown is due to both a decrease in pressure gradient and an increase in colloid viscosity. The pressure gradient decreases because the colloid volume decreases in the central region as it flows towards the edges, leading to a pressure drop and an increase in colloid volume at the edges. The viscosity increase is due to the curing reaction of the two-component epoxy adhesive at room temperature. This curing reaction is a chemical reaction between epoxy groups and amine groups, forming a cross-linked network. The increased cross-linking density restricts the movement of molecular chain segments, leading to increased viscosity. When the colloid flow stops, the driving pressure equals the flow resistance, reaching an equilibrium state. After flow stops, thickness stability means that the interlayer gap thickness and adhesive layer thickness no longer change over time. Thickness stability is achieved by monitoring the total thickness of the card body using a laser thickness gauge. The thickness is continuously measured. When the change in the measured value is less than a set threshold, the thickness is considered stable. During slow depressurization, the servo motor gradually reduces the pressure from the constant pressure value to zero at a low rate. The depressurization rate is the decrease in pressure per unit time. Slow depressurization allows the compressive stress inside the colloid to be gradually released. At this point, the colloid is in a gel state with a certain degree of curing. The gel state refers to the state where the colloid has lost its fluidity but has not yet completely hardened. The molecular chain segments still have the ability to move. During slow pressure release, the cross-linked network adjusts the internal stress distribution through the creep movement of the molecular chain segments. The stress relaxation time is the ratio of the colloid viscosity to the shear modulus. The depressurization time is much longer than the stress relaxation time to ensure that the stress is fully released. The smart card body after pressing and depressurization refers to the card body after pressing and depressurization.The card body thickness meets the standard requirements. When the smart card body is left to stand at room temperature (temperature and humidity at normal levels), this means the card body is placed flat on a horizontal surface without any external force. During the cross-linking and curing reaction of the two-component epoxy adhesive, the epoxy groups and amine groups react in stoichiometric ratio. The reaction mechanism involves the opening of the three-membered ring of the epoxy group and the addition of active hydrogen from the amine group to generate hydroxyl and secondary amines. The secondary amines further react with the epoxy groups to generate tertiary amines and hydroxyl groups. The reaction proceeds gradually, forming a three-dimensional network cross-linked structure. The nodes of the cross-linked network are the locations where epoxy resin molecules and curing agent molecules are connected by chemical bonds. The network density increases with the reaction progress. The curing reaction is exothermic, releasing heat of reaction, which causes the system temperature to rise. This temperature rise, in turn, accelerates the reaction rate. Under room temperature conditions, the curing curve is divided into an induction period, a rapid curing period, a post-curing period, and a complete curing period. During the induction period, the reaction rate is low and the viscosity increases slowly. During the rapid curing period, the reaction rate increases rapidly, and the viscosity exponential increases, leading to dissolution. The gel-gel transition occurs when the crosslinking density reaches a critical value, forming an infinitely large molecular network. After the transition, the system changes from a liquid to a gel state, losing its fluidity. During the post-curing period, the reaction continues but at a slower rate, and the degree of curing continues to increase. During the complete curing period, the reaction rate is extremely slow, and the degree of curing approaches the final value. The phase transition process of the colloid from a liquid to a gel state to a solid state is accompanied by changes in physical properties. In the liquid state, the colloid is fluid and has low viscosity; in the gel state, the colloid loses its fluidity but still retains elasticity; in the solid state, the colloid is completely hardened and has rigidity. The formation of a sealing and protective layer refers to the continuous and dense solid layer formed by the cured colloid in the first stack space. This layer encapsulates all electrical connection points, fills all gaps and gaps, and provides mechanical support and environmental isolation. The encapsulated multi-heterogeneous module smart card refers to the final product after the colloid is completely cured. The card body has complete structural strength and sealing performance. The internally integrated PCBA and various heterogeneous modules are protected by the colloid layer, and data functions such as NFC communication, display, and fingerprint recognition work normally.

[0063] In one specific embodiment, medium pressure is applied to the initially pressed encapsulation structure for molding and pressing. A pressure sensor array monitors the pressure distribution in each area and adjusts it in real time to reduce the interlayer gap thickness and make the adhesive layer thickness more uniform, resulting in a molded and pressed encapsulation structure, including:

[0064] Medium pressure is applied to the initially pressed packaging structure. The pressure plate is driven to descend by a servo motor, and the target pressure is controlled to increase from the low pressure stage to the medium pressure stage, thus obtaining the packaging structure under medium pressure.

[0065] Real-time pressure values ​​at each measuring point are collected by a pressure sensor array, and the standard deviation and coefficient of variation of the pressure distribution are calculated to obtain the pressure distribution parameters.

[0066] The pressure distribution parameters are input into the PID control system. When the pressure deviation is detected to exceed the set threshold, the position of the pressure plate is finely adjusted by the servo motor to compensate, so that the pressure at each measuring point tends to the target value, resulting in a packaging structure with uniform pressure distribution.

[0067] Medium-pressure driven colloid continues to flow from the interlayer gap into the overflow groove, and the gap thickness between the first cover plate and the intermediate layer and the gap thickness between the second cover plate and the intermediate layer decrease simultaneously, resulting in a molded and pressed encapsulation structure.

[0068] Specifically, when applying medium pressure to the initially pressed packaging structure, the controller of the controllable pressing unit receives the medium-pressure pressing command. The controller adjusts the operating parameters of the servo motor according to the command. When the servo motor drives the pressure plate to descend, the motor output torque is amplified by the reducer and transmitted to the ball screw. The rotational motion of the screw is converted into the linear motion of the pressure plate. The descending speed of the pressure plate is determined by both the motor speed and the screw pitch. The pitch is the distance the pressure plate moves when the screw rotates one revolution. The target pressure value is preset in the controller program when the target pressure is increased from the low-pressure stage to the medium-pressure stage. The target value for the low-pressure stage is a smaller pressure value, and the target value for the medium-pressure stage is a larger pressure value. The increasing process uses a gradual loading method, with the loading rate being the increase in pressure per unit time. The pressure rate is set to a low value to achieve fine control. As the pressure plate continues to descend, the pressure sensor array on the bottom surface measures the pressure at the contact surface with the encapsulation structure in real time. The measured value is fed back to the controller, which compares the actual pressure with the target pressure. This difference is the control deviation. Based on the control deviation, the motor output torque is adjusted. When the actual pressure is less than the target pressure, the torque is increased to accelerate the descent; when the actual pressure approaches the target pressure, the torque is decreased to reduce the descent speed; when the actual pressure reaches the target pressure, the descent stops and the current position is maintained. This results in the encapsulation structure under medium pressure, meaning the encapsulation structure is subjected to compressive stress of the medium pressure value while the pressure remains stable at the target value. When collecting real-time pressure values ​​at each measuring point through the pressure sensor array, the pressure sensor array includes multiple independent sensors distributed at specific intervals. The pressure sensor is either a thin-film resistive or capacitive pressure sensor. When pressure is applied, the sensor outputs an electrical signal, the amplitude of which is proportional to the pressure magnitude. The output signals from each sensor are amplified and filtered by a signal conditioning circuit before being input to a multiplexer analog-to-digital converter. The converter converts the analog voltage signal into a digital signal, representing a quantified pressure value. The controller sequentially reads the digital signals from each sensor using a scanning method to form a pressure data array. Real-time data acquisition refers to a high acquisition frequency, collecting data multiple times per second. The acquired pressure values ​​contain instantaneous pressure information from each measuring point. To calculate the standard deviation of the pressure distribution, the average pressure value of all measuring points is first calculated. The average value equals the sum of the pressure values ​​at each measuring point divided by the number of measuring points. Then, the ratio of the pressure value at each measuring point to the average value is calculated. The deviation is calculated by subtracting the average pressure value from the measured point. The sum of squared deviations is obtained by squaring each deviation value. Dividing this sum of squared deviations by the number of measured points yields the variance. Taking the square root of the variance gives the standard deviation, which is in the same unit as pressure. A larger standard deviation indicates a more dispersed pressure distribution across measured points. The coefficient of variation (COP) is calculated by dividing the standard deviation by the average value. The COP is a dimensionless parameter; a smaller COP indicates a more uniform pressure distribution. The pressure distribution parameters thus provide a quantitative description of the pressure distribution characteristics: the standard deviation and COP. When these parameters are input into the PID control system, the controller compares the calculated standard deviation and COP with preset thresholds. These thresholds are set based on pressure uniformity requirements, with the standard deviation threshold representing the maximum allowable pressure fluctuation range.The coefficient of variation threshold is the maximum allowable relative fluctuation ratio. When the standard deviation exceeds the threshold or the coefficient of variation exceeds the threshold, it is determined that the pressure distribution is uneven and adjustment is needed. Further analysis of the pressure deviation at each measuring point is conducted. The pressure deviation is the difference between the pressure value at the measuring point and the target pressure value. The location of the measuring point with the largest deviation is identified. A positive deviation indicates that the pressure at that measuring point is too high, and a negative deviation indicates that the pressure at that measuring point is too low. The PID control system calculates the adjustment amount based on the pressure deviation. The proportional term coefficient of the PID algorithm is multiplied by the current deviation to obtain the proportional adjustment amount; the integral term coefficient is multiplied by the time accumulation value of the deviation to obtain the integral adjustment amount; and the derivative term coefficient is multiplied by the rate of change of the deviation to obtain the derivative adjustment amount. The sum of these three adjustment amounts yields the total adjustment amount, which corresponds to the required movement of the pressure plate. When the distance or angle of movement is compensated by fine-tuning the pressure plate position via a servo motor, the controller converts the total adjustment amount into a motion command for the motor. The motor rotates the corresponding angle according to the command, driving the pressure plate to move the corresponding distance via a lead screw. The direction of movement is determined by the sign of the deviation. In areas with excessively high pressure, the pressure plate rises to reduce pressure; in areas with excessively low pressure, the pressure plate falls to increase pressure. Since the pressure plate is a single structure and cannot be adjusted independently for each area, actual adjustment is achieved by tilting the pressure plate or utilizing the deformation of a flexible buffer pad to achieve local pressure adjustment. After fine-tuning, the pressure values ​​at each measuring point are re-acquired, and the pressure distribution parameters are recalculated to determine if the threshold requirements are met. If not, adjustment continues, iterating until the pressure distribution meets the requirements, making the pressure at each measuring point tend towards the target value after multiple iterative adjustments. The deviations between the pressure values ​​at the measuring points and the target pressure values ​​are all less than the allowable deviations. A uniformly pressure-distributed encapsulation structure indicates that the pressure in each area of ​​the encapsulation structure is basically the same and close to the target pressure value. When the medium-pressure driving colloid continues to flow from the interlayer gap to the overflow groove, the medium-pressure is greater than the driving pressure in the low-pressure stage. Under the action of the greater driving pressure, the colloid in the interlayer gap is subjected to greater compressive stress, and the rate at which the colloid is squeezed out of the gap increases. The squeezed colloid flows along the gap to the edge. The flow path is from the interlayer gap between the first cover plate and the middle layer, and the interlayer gap between the second cover plate and the middle layer, to the edge of the middle layer. After the colloid reaches the edge, it enters the reserved overflow groove. The volume of the overflow groove is partially filled in the low-pressure stage, and continues to fill until it overflows in the medium-pressure stage. The overflowed colloid flows into The adhesive is absorbed by the base collection groove. When the gap thickness between the first cover plate and the intermediate layer decreases, the first cover plate moves towards the intermediate layer under medium pressure. The moving distance is equal to the compression of the gap thickness. The compression is related to the applied pressure and the elastic modulus of the material. After the adhesive in the gap is squeezed out, the gap thickness further decreases from the value after initial compression to a smaller value. The synchronous decrease in the gap thickness between the second cover plate and the intermediate layer means that the second cover plate also moves towards the intermediate layer under medium pressure. The compression of the gaps on both sides is basically the same. The synchronous decrease ensures that the card body thickness changes uniformly. The decrease in gap thickness leads to a decrease in the total thickness of the card body. The total thickness is equal to the thickness of the first cover plate plus the thickness of the intermediate layer plus the thickness of the second cover plate plus the thickness of the two interlayer gaps. The decrease in gap thickness makes the total thickness close to the target thickness.A properly formed and pressed encapsulated structure refers to an encapsulated structure that, after medium-pressure pressing and pressure homogenization adjustment, achieves the designed specifications for interlayer gap thickness and adhesive layer thickness, meets the requirements for thickness uniformity in all areas, has good card flatness, stable internal heterogeneous module positions, uniform adhesive distribution, and has had most of the excess adhesive removed.

[0069] The above describes the room-temperature gel encapsulation method for multi-heterogeneous module smart cards in the embodiments of this application. The following describes the room-temperature gel encapsulation structure for multi-heterogeneous module smart cards in the embodiments of this application. One embodiment of the room-temperature gel encapsulation structure for multi-heterogeneous module smart cards in the embodiments of this application includes:

[0070] The three-layer carrier structure consists of a first cover plate, an intermediate layer, and a second cover plate. The inner surface of the first cover plate is provided with a rectangular first cavity for accommodating the display screen module. The inner surface of the second cover plate is provided with a circular first cavity for accommodating the fingerprint recognition sensor. The intermediate layer is provided with a second cavity for accommodating the PCBA and heterogeneous modules.

[0071] The PCBA, display screen module, fingerprint recognition sensor and lithium battery are located in the second cavity, and the bottom of the intermediate layer has an NFC antenna coil with a rectangular spiral structure printed on it.

[0072] A room-temperature curable colloid layer is filled in the bottom of the PCBA, around the heterogeneous modules and in the interlayer gaps. The colloid layer is formed by cross-linking and curing a two-component epoxy adhesive at room temperature. The colloid layer encapsulates the NFC antenna coil, PCBA solder joints, display screen connection points, fingerprint recognition sensor solder joints and lithium battery electrode connection points.

[0073] The colloid layer forms a sealing protective layer, the thickness of which is uniformly distributed and forms an integrated encapsulation structure with the three-layer carrier structure.

[0074] Figure 2 This is an exploded view of the three-layer carrier structure in an embodiment of this application. 1 is the middle layer, 2 is the second cover plate, and 3 is the first cover plate. The figure shows the spatial relationship of the three layers before stacking. The first cover plate 3 and the second cover plate 2 are located on the upper and lower sides of the middle layer 1, respectively. The three layers are assembled into a complete carrier structure through subsequent stacking. The central area of ​​the middle layer 1 is a second cavity for accommodating the PCBA and heterogeneous modules. The inner surfaces of the first cover plate 3 and the second cover plate 2 are respectively machined with first cavities for accommodating the display screen module and the fingerprint recognition sensor.

[0075] Figure 3This is a top-down exploded view of the three-layer carrier structure after assembling various heterogeneous modules in an embodiment of this application. In this view, 1 is the middle layer, 2 is the second cover plate, 3 is the first cover plate, 101 is the screen mounting groove for the display screen module, 102 is the PCBA main mounting area, 103 is the battery mounting slot for the lithium battery, 104 is the fingerprint module mounting hole for the fingerprint sensor, and 105 is the positioning through hole. The figure shows the functional partition layout of the middle layer 1 and the assembly position relationship of each heterogeneous module in the second cavity. The positioning through hole 105 is used to cooperate with the positioning pin to achieve precise positioning. The second cover plate 2 and the first cover plate 3 cover the top and bottom surfaces of the middle layer 1 respectively to complete the stacked assembly.

[0076] Figure 4 This is a schematic diagram of the positioning workbench in this application embodiment. The diagram shows a rectangular flat plate structure on the surface of the workbench, with circular positioning pins at the four corners. The positioning pins are cylindrical metal rods perpendicular to the surface of the workbench, and their outer diameter is precisely matched with the inner diameter of the positioning through hole at the bottom of the intermediate layer. The fit gap is controlled at the micrometer level. After the intermediate layer is placed on the surface of the workbench, the positioning pins are inserted into the positioning through hole to achieve radial positioning. A vacuum pump connected to the bottom of the workbench applies a vacuum negative pressure to the intermediate layer placed on the workbench through the microporous channel on the surface, adsorbing and fixing the assembled PCBA and heterogeneous modules in the corresponding positions of the intermediate layer.

[0077] Figure 5 This is a schematic diagram of a two-component epoxy adhesive mixing and dispensing device in an embodiment of this application. In the diagram, A is a storage cylinder for epoxy resin component A, and B is a storage cylinder for polyamide curing agent component B. The two storage cylinders are connected to a vacuum mixing table via proportional control valves. The proportional control valves precisely control the flow rates of components A and B according to a preset mass ratio. After the two components are fully mixed and degassed in the vacuum mixing table, a two-component epoxy adhesive with controlled viscosity is obtained. The mixed adhesive is delivered to the first stacked space to be encapsulated through the dispensing needle at the bottom. The vacuum environment of the vacuum mixing table eliminates air bubbles in the adhesive, ensuring the quality of dispensing.

[0078] Figure 6 This is a schematic diagram of the segmented pressing unit in this embodiment of the application. The diagram shows the upper and lower pressure plate structure of the pressing device. The lower pressure plate fixes the packaging structure to be pressed by positioning pins. The upper pressure plate achieves precise vertical lifting and lowering by a ball screw driven by a servo motor. A pressure sensor is installed on the bottom surface of the upper pressure plate to monitor the pressure distribution in real time during the pressing process. An elastic buffer spring is set between the pressure plates to provide flexible buffering during the pressing process. A bottom force sensor is installed at the bottom of the lower pressure plate to measure the total pressure. During the pressing process, the servo motor precisely adjusts the position of the pressure plates according to the feedback signal of the pressure sensor through a PID control algorithm to achieve segmented pressing control of low pressure, medium pressure and constant pressure.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for room-temperature gel encapsulation of a multi-heterogeneous module smart card, characterized in that, The method includes: Step S1: The first cover plate, the intermediate layer and the second cover plate are shaped into cavities, wherein the intermediate layer forms a second cavity for accommodating the PCBA and heterogeneous modules, resulting in a three-layer carrier structure; Step S2: Place the PCBA and heterogeneous module into the second cavity, and spatially position them by using positioning pins and vacuum adsorption to obtain the first bonding layer after assembly; Step S3: Assemble the three-layer carrier structure with the first bonding layer to form a first stacked space including the bottom of the PCBA, the area around the heterogeneous module and the interlayer gap; Step S4: In a vacuum environment, inject two-component epoxy adhesive into the first stacked space, so that the adhesive wets the PCBA solder joints and the electrical connection points of the heterogeneous modules, and obtain the encapsulation structure after the adhesive is injected. Step S5: Perform segmented pressing on the encapsulation structure, applying low pressure, medium pressure, and constant pressure sequentially to remove excess adhesive and ensure uniform adhesive layer thickness, resulting in a pressed smart card body. Allow the smart card body to cure at room temperature, allowing the adhesive to cross-link and form a sealing protective layer. This includes: applying low pressure to the encapsulation structure for initial pressing, where the adhesive flows from the center to the edge and is discharged from the overflow groove, resulting in an initially pressed encapsulation structure; applying medium pressure to the initially pressed encapsulation structure for final pressing, using pressure... A sensor array monitors the pressure distribution in each area and adjusts it in real time to reduce the thickness of the interlayer gap and make the adhesive layer thickness more uniform, thus obtaining a molded and pressed encapsulation structure. A constant pressure is applied to the molded and pressed encapsulation structure for pressure holding. When the adhesive flow stops and the thickness stabilizes, the pressure is slowly released to obtain a pressed smart card body. The smart card body is left to stand at room temperature, and the two-component epoxy adhesive undergoes a cross-linking and curing reaction. The adhesive changes from a liquid state to a gel state and then to a solid state, forming a sealing and protective layer, thus obtaining a packaged multi-heterogeneous module smart card.

2. The room-temperature colloidal encapsulation method for multi-heterogeneous module smart cards according to claim 1, characterized in that, Step S1 includes: A rectangular first cavity is machined on the inner surface of the first cover plate. The first cavity is used to accommodate the display screen module, thus obtaining the machined first cover plate. A circular first cavity is machined on the inner surface of the second cover plate. The first cavity is used to accommodate the fingerprint recognition sensor, thus obtaining the machined second cover plate. The intermediate layer is processed into a through-type second cavity, which includes a PCBA main mounting area, a screen mounting groove, a fingerprint module mounting hole, and a battery mounting groove, to obtain an intermediate layer with functional partitions. An NFC antenna coil is printed at the bottom of the intermediate layer. The NFC antenna coil has a rectangular spiral structure, resulting in a three-layer carrier structure that integrates NFC communication functions.

3. The room-temperature colloidal encapsulation method for multi-heterogeneous module smart cards according to claim 2, characterized in that, Step S2 includes: The PCBA is placed into the main mounting area of ​​the PCBA in the second cavity, and radial positioning is performed by the positioning pins cooperating with the positioning through holes in the intermediate layer to obtain the positioned PCBA. The display screen module, fingerprint recognition sensor and lithium battery are sequentially placed into the screen mounting groove, fingerprint module mounting hole and battery mounting slot. The heterogeneous modules are pushed to the cavity wall and pressed tightly by the side pushing mechanism to obtain the assembled module assembly. The module assembly is subjected to CCD vision inspection to calculate the deviation between the actual position coordinates and the designed position coordinates of each heterogeneous module. When the deviation exceeds the threshold, the module assembly is corrected through a fine-tuning platform to obtain the module assembly after position calibration. A vacuum negative pressure is applied to the module assembly after position calibration, and the heterogeneous modules are adsorbed and fixed through the microporous channels on the bottom surface of the intermediate layer to obtain the first bonding layer after assembly.

4. The room-temperature colloidal encapsulation method for multi-heterogeneous module smart cards according to claim 3, characterized in that, Step S3 includes: The first cover plate is aligned and bonded to the bottom surface of the intermediate layer of the first bonding layer. The display screen cavity on the first cover plate is aligned with the display screen module by the positioning pin, forming a lower semi-closed cavity including the bottom surface of the PCBA and the bottom of the heterogeneous module. The second cover plate is aligned and bonded to the top surface of the intermediate layer. Pre-pressure is applied by a flexible pressing head to align the fingerprint sensor cavity on the second cover plate with the fingerprint recognition sensor, forming an upper semi-closed cavity containing the top of each heterogeneous module. The lower semi-enclosed cavity is connected to the upper semi-enclosed cavity, and the gaps around the PCBA, the side gaps of the heterogeneous modules, and the interlayer gaps form a continuous mesh structure to obtain a three-layer stacked package. An injection port and an vent are reserved at the edge of the middle layer of the package. The injection port is connected to the bottom of the first stacked space, and the vent is connected to the top of the first stacked space, thus forming a three-layer carrier structure that forms the first stacked space.

5. The room-temperature colloidal encapsulation method for multi-heterogeneous module smart cards according to claim 4, characterized in that, Step S4 includes: Epoxy resin component A and polyamide curing agent component B are mixed in a certain mass ratio and then subjected to vacuum degassing treatment to obtain a two-component epoxy adhesive with controlled viscosity. The first stacked space is placed in a vacuum chamber and a vacuum is drawn. The residual air in the space is discharged from the exhaust port by negative pressure to obtain a package under vacuum. The two-component epoxy adhesive is injected into the injection port through a dispensing needle under constant flow. The adhesive spreads laterally along the bottom surface of the PCBA and rises longitudinally along the interlayer gap under the drive of capillary pressure and vacuum pressure difference, resulting in an adhesive-filled encapsulation. The colloid sequentially wets the NFC antenna coil, PCBA solder joint, display screen connection point, fingerprint recognition sensor solder joint, and lithium battery electrode connection point. The colloid injection stops when it overflows from the vent hole, resulting in a fully encapsulated structure.

6. The room-temperature colloidal encapsulation method for multi-heterogeneous module smart cards according to claim 1, characterized in that, The process involves applying medium pressure to the initially pressed encapsulation structure for molding and pressing, monitoring the pressure distribution in each area using a pressure sensor array and adjusting it in real time to reduce the interlayer gap thickness and make the adhesive layer thickness more uniform, thereby obtaining a molded and pressed encapsulation structure, including: Medium pressure is applied to the initially pressed packaging structure. The pressure plate is driven to descend by a servo motor, and the target pressure is controlled to increase from the low pressure stage to the medium pressure stage, thus obtaining the packaging structure under medium pressure. The pressure sensor array is used to collect real-time pressure values ​​at each measuring point, and the standard deviation and coefficient of variation of the pressure distribution are calculated to obtain the pressure distribution parameters. The pressure distribution parameters are input into the PID control system. When the pressure deviation is detected to exceed the set threshold, the position of the pressure plate is finely adjusted by the servo motor to compensate, so that the pressure at each measuring point tends to the target value, resulting in a packaging structure with uniform pressure distribution. The medium-pressure driven colloid continues to flow from the interlayer gap into the overflow groove, and the gap thickness between the first cover plate and the intermediate layer and the gap thickness between the second cover plate and the intermediate layer decrease simultaneously, resulting in a molded and pressed encapsulation structure.

7. A room-temperature colloidal encapsulation structure for a multi-heterogeneous module smart card, characterized in that, Manufactured based on the room-temperature gel encapsulation method for a multi-heterogeneous module smart card as described in any one of claims 1-6, wherein the room-temperature gel encapsulation structure of the multi-heterogeneous module smart card comprises: The three-layer carrier structure consists of a first cover plate, an intermediate layer, and a second cover plate. The inner surface of the first cover plate is provided with a rectangular first cavity for accommodating the display screen module. The inner surface of the second cover plate is provided with a circular first cavity for accommodating the fingerprint recognition sensor. The intermediate layer is provided with a second cavity for accommodating the PCBA and heterogeneous modules. The PCBA, display screen module, fingerprint recognition sensor and lithium battery are located in the second cavity, and the bottom of the intermediate layer has an NFC antenna coil with a rectangular spiral structure printed on it. A room-temperature curable colloid layer is filled in the bottom of the PCBA, around the heterogeneous modules and in the interlayer gaps. The colloid layer is formed by cross-linking and curing a two-component epoxy adhesive at room temperature. The colloid layer encapsulates the NFC antenna coil, PCBA solder joints, display screen connection points, fingerprint recognition sensor solder joints and lithium battery electrode connection points. The colloid layer forms a sealing protective layer, the thickness of which is uniformly distributed and forms an integrated encapsulation structure with the three-layer carrier structure.

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