Flexible substrate analysis method, device, computer equipment and storage medium

Abstract

The application relates to a flexible substrate analysis method and device, computer equipment and a storage medium. The method comprises the following steps: obtaining a plurality of to-be-analyzed data of a to-be-analyzed flexible substrate in a preset time range; the plurality of to-be-analyzed data comprises load data, displacement data, contact resistance data and topography data; determining a resistance change amount of the to-be-analyzed flexible substrate according to the topography data and the contact resistance data; determining a non-elastic dissipation energy of the to-be-analyzed flexible substrate according to the load data and the displacement data; determining a damage index of the to-be-analyzed flexible substrate according to a preset index determination rule, the resistance change amount of the to-be-analyzed flexible substrate and the non-elastic dissipation energy of the to-be-analyzed flexible substrate; and determining a damage stage of the to-be-analyzed flexible substrate according to the damage index. The method can efficiently detect the damage stage of the flexible circuit board.

Description

Technical Field

[0001] This application relates to the field of flexible circuit board technology, and in particular to a flexible substrate analysis method, apparatus, computer equipment, and storage medium. Background Technology

[0002] In the field of flexible circuit boards, flexible circuit boards are generally made of polyimide or polyester film. Polyimide and polyester film have low elastic modulus, and the bending stiffness of flexible circuit boards is inversely proportional to the elastic modulus of the materials they are made of. Therefore, flexible circuit boards have extremely low bending stiffness. Under repeated bending loads, they will produce significant strain energy release, which will cause microcracks to initiate at the interface where they intersect with solder balls, thereby reducing the reliability of flexible circuit boards.

[0003] In related technologies, the detection of damage stages of flexible circuit boards typically relies on slice observation and pure resistance monitoring. Although this method can detect damage stages of flexible circuit boards, it is inefficient.

[0004] Therefore, there is an urgent need for a solution that can efficiently detect the damage stages of flexible circuit boards. Summary of the Invention

[0005] Therefore, it is necessary to provide a flexible substrate analysis method, apparatus, computer equipment, and storage medium that can efficiently detect the damage stage of flexible circuit boards, addressing the aforementioned technical problems.

[0006] In a first aspect, this application provides a method for analyzing flexible substrates. The method includes: acquiring multiple data sets of the flexible substrate to be analyzed within a preset time range; the multiple data sets include load data, displacement data, contact resistance data, and morphology data, wherein the load data, displacement data, contact resistance data, and morphology data correspond one-to-one in time; determining the change in resistance of the flexible substrate to be analyzed based on the morphology data and contact resistance data; determining the inelastic dissipation energy of the flexible substrate to be analyzed based on the load data and displacement data; determining a damage index of the flexible substrate to be analyzed based on preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed; and determining the damage stage of the flexible substrate to be analyzed based on the damage index.

[0007] In one embodiment, determining the resistance change of the flexible substrate to be analyzed based on the topography data and contact resistance data includes: taking the contact resistance data corresponding to the last topography image in the topography data as the target resistance; and determining the resistance change of the flexible substrate to be analyzed based on the target resistance and a preset reference resistance.

[0008] In one embodiment, determining the inelastic dissipation energy of the flexible substrate to be analyzed based on the load data and displacement data includes: performing curve fitting based on the load data and displacement data to determine a loaded load displacement curve and an unloaded load displacement curve; the starting point and ending point of the loaded load displacement curve and the unloaded load displacement curve are the same; integrating the loaded load displacement curve and the unloaded load displacement curve to determine the inelastic dissipation energy of the flexible substrate to be analyzed.

[0009] In one embodiment, determining the damage index of the flexible substrate to be analyzed based on preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed includes:

[0010] Based on the inelastic dissipation energy and the preset critical release rate, the mechanical energy parameters are determined; based on the resistance change and the preset critical failure resistance, the electrical feedback parameters are determined; based on the first preset weight, the second preset weight, the mechanical energy parameters, and the electrical feedback parameters, the damage index of the flexible substrate to be analyzed is determined.

[0011] In one embodiment, determining the mechanical energy parameter based on the inelastic dissipation energy and the preset critical release rate includes: dividing the inelastic dissipation energy by the preset critical release rate to determine the mechanical energy parameter.

[0012] In one embodiment, determining the electrical feedback parameters based on the resistance change and the preset critical failure resistance includes: dividing the resistance change by the preset critical failure resistance to determine the electrical feedback parameters.

[0013] In one embodiment, determining the damage index of the flexible substrate to be analyzed based on the first preset weight, the second preset weight, the mechanical energy parameter, and the electrical feedback parameter includes: multiplying the first preset weight and the mechanical energy parameter to determine the mechanical damage parameter; multiplying the second preset weight and the electrical feedback parameter to determine the electrical damage parameter; and adding the mechanical damage parameter and the electrical damage parameter to determine the damage index of the flexible substrate to be analyzed.

[0014] Secondly, this application also provides a flexible substrate analysis apparatus. The apparatus includes:

[0015] The acquisition module is used to acquire multiple data to be analyzed for the flexible substrate to be analyzed within a preset time range; the multiple data to be analyzed include load data, displacement data, contact resistance data and morphology data, and the load data, displacement data, contact resistance data and morphology data correspond one-to-one in time;

[0016] An electrical determination module is used to determine the change in resistance of the flexible substrate to be analyzed based on the morphology data and contact resistance data.

[0017] An energy determination module is used to determine the inelastic dissipation energy of the flexible substrate to be analyzed based on the load data and displacement data.

[0018] The damage determination module is used to determine the damage index of the flexible substrate to be analyzed based on preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed.

[0019] The stage determination module is used to determine the damage stage of the flexible substrate to be analyzed based on the damage index.

[0020] Thirdly, this application also provides a computer device, the computer device including a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement any of the methods in the first aspect above.

[0021] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the methods in the first aspect described above.

[0022] The aforementioned flexible substrate analysis method, apparatus, computer equipment, and storage medium acquire multiple data points of the flexible substrate to be analyzed within a preset time range. These multiple data points include load data, displacement data, contact resistance data, and morphology data, which correspond one-to-one in time. Then, based on the morphology data and contact resistance data, the resistance change of the flexible substrate to be analyzed is determined. Next, based on the load data and displacement data, the inelastic dissipation energy of the flexible substrate to be analyzed is determined. Then, based on preset index determination rules, the resistance change of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed, a damage index of the flexible substrate to be analyzed is determined. Finally, based on the damage index, the damage stage of the flexible substrate to be analyzed is determined, thereby efficiently detecting the damage stage of the flexible circuit board. Attached Figure Description

[0023] Figure 1 This is a diagram illustrating the application environment of a flexible substrate analysis method in one embodiment.

[0024] Figure 2 This is a flowchart illustrating a flexible substrate analysis method in one embodiment;

[0025] Figure 3This is a flowchart illustrating the process of determining the damage index of a flexible substrate to be analyzed in one embodiment.

[0026] Figure 4 This is a flowchart illustrating the flexible substrate analysis method in another embodiment;

[0027] Figure 5 Normal contact stiffness in one embodiment Contact conductivity at the interface A schematic diagram of the analogy mapping model;

[0028] Figure 6 This is a DIC extraction algorithm model for crack tip opening displacement (CTOD) in one embodiment;

[0029] Figure 7 This is a schematic diagram of the load-displacement hysteresis loop and the Wdiss calculation model of inelastic dissipated energy in one embodiment;

[0030] Figure 8 D represents the interface damage index under different bending strain levels in one embodiment. index Evolutionary curve;

[0031] Figure 9 This is a structural block diagram of a flexible substrate analysis device in one embodiment;

[0032] Figure 10 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] With the widespread application of flexible electronics technology in wearable devices, medical brain-computer interfaces, and foldable screen terminals, the mechanical reliability of the interface between flexible circuit boards and chip packaging, such as the interface where they intersect with BGA solder balls, has become a bottleneck limiting product lifespan. Due to the extremely low bending stiffness of flexible circuit boards, significant strain energy release occurs under repeated bending loads, making the solder ball interface highly susceptible to microcrack initiation. Currently, failure analysis of packaging interfaces mainly relies on cross-sectional observation and pure resistance monitoring. Cross-sectional observation is a destructive testing method and cannot capture the dynamic evolution of damage; while pure resistance monitoring, although performed in situ, suffers from extremely small impedance signal fluctuations in the early stages of failure (typically on the order of mΩ) and is easily affected by environmental noise, making it difficult to establish a direct physical correspondence between resistance changes and the geometric parameters of microcracks, thus hindering early failure warning.

[0035] Existing theoretical research attempts to explain package interface failure through contact mechanics. However, due to the complex residual stress, material nonlinearity, and geometric singularities at the BGA solder ball interface, simple constitutive models are insufficient to accurately describe the causes of package interface failure. In particular, while Barber's analogy between contact stiffness and conductivity has been validated in ideal planar contacts, an effective mapping calibration method is lacking in flexible circuit board systems with micron-level roughness and viscoelastic substrates. Related technologies lack an evaluation system that can simultaneously integrate experimentally observed microscopic morphology evolution, mechanical load response, and weak electrical fluctuations. This keeps the reliability evaluation of flexible electronic devices at the qualitative descriptive stage, unable to achieve quantitative prediction.

[0036] The flexible substrate analysis method provided in this application embodiment can be applied to, for example... Figure 1 In the application environment shown, terminal 102 communicates with server 104 via a network. A data storage system can store the data that server 104 needs to process. The data storage system can be integrated onto server 104 or placed in the cloud or on other network servers. Terminal 102 is used to execute the flexible substrate analysis method. Terminal 102 can be, but is not limited to, various personal computers, laptops, smartphones, tablets, IoT devices, and portable wearable devices. IoT devices can include smart speakers, smart TVs, smart air conditioners, smart vehicle devices, etc. Portable wearable devices can include smartwatches, smart bracelets, head-mounted devices, etc. Server 104 can be implemented using a standalone server or a server cluster consisting of multiple servers.

[0037] To address the aforementioned problems, in one embodiment of this application, such as Figure 2 As shown, a method for analyzing flexible substrates is provided, including the following steps:

[0038] Step 201: Obtain multiple data points of the flexible substrate to be analyzed within a preset time range.

[0039] The flexible substrate to be analyzed is the flexible substrate that needs to be analyzed.

[0040] The multiple data to be analyzed include load data, displacement data, contact resistance data, and morphology data, which correspond one-to-one in time.

[0041] The preset time range is a pre-defined time period. The load data is the bending load borne by the interface between the flexible substrate and the solder ball at a specific time point within the preset time range. This is the physical quantity applied to the flexible substrate and can be preset as needed. The displacement data is the macroscopic displacement of the flexible substrate at a specific time point within the preset time range, which can be obtained by sampling using a displacement sensor embedded in the flexible substrate. The contact resistance data is the contact resistance of the interface between the flexible substrate and the solder ball at a specific time point within the preset time range, which can be obtained by sampling using a resistance sensor embedded in the flexible substrate. The morphology data consists of morphological images of the interface between the flexible substrate and the solder ball at multiple time points within the preset time range. These images are in the form of SEM micrographs and can be obtained by scanning the interface between the flexible substrate and the solder ball.

[0042] It should be noted that within a preset time range, a bending load is applied to the flexible substrate to be analyzed, and then the bending load is unloaded. In other words, the preset time range includes the process of applying a bending load to the flexible substrate to be analyzed and then unloading the bending load. Unloading the bending load refers to gradually removing the bending load applied to the flexible substrate to be analyzed after it has been applied.

[0043] It should be noted that, because the current needs to flow from one side to the other when the flexible substrate and the solder balls are pressed together, and because the interface between the flexible substrate and the solder balls has microscopic roughness, oxide film, and contaminants, the actual conductive contact only occurs on a few scattered microscopic contact spots at the interface between the flexible substrate and the solder balls. The current must contract as it passes through these spots, thus generating additional resistance, which is the contact resistance.

[0044] In this embodiment, the preset time range includes multiple time points, and the time interval between each time point is equal. According to the time order of each time point, the displacement data, contact resistance data and morphology data of the flexible substrate to be analyzed are sampled in sequence. Combined with the pre-set load data of the flexible substrate to be analyzed, the load data, displacement data, contact resistance data and morphology data corresponding to each time point are obtained, that is, multiple data to be analyzed of the flexible substrate to be analyzed within the preset time range are obtained.

[0045] Step 202: Determine the change in resistance of the flexible substrate to be analyzed based on the morphology data and contact resistance data.

[0046] The change in resistance of the flexible substrate to be analyzed is the difference between the target resistance and the preset reference resistance. The target resistance is the contact resistance data corresponding to the last time point within the preset time range. The preset reference resistance is the contact resistance at the interface between the flexible substrate to be analyzed and the solder ball when the flexible substrate to be analyzed has not been subjected to a load.

[0047] In this embodiment, the contact resistance data corresponding to the last time point within a preset time range is determined based on the morphology data and contact resistance data. Then, the contact resistance data is subtracted from the preset reference resistance, and the result of the subtraction is used as the resistance change of the flexible substrate to be analyzed.

[0048] Step 203: Determine the inelastic dissipation energy of the flexible substrate to be analyzed based on the load data and displacement data.

[0049] Inelastic dissipation energy is a parameter characterizing the energy loss of the flexible substrate under analysis within a preset time range.

[0050] In this embodiment, curve fitting is performed based on load data and displacement data to obtain loaded load displacement curve and unloaded load displacement curve. Then, based on the loaded load displacement curve and unloaded load displacement curve, the inelastic dissipation energy of the flexible substrate to be analyzed is determined.

[0051] The load-displacement curve is used to characterize the relationship between load data and displacement data when a load is applied to the flexible substrate under analysis. The load-unloaded displacement curve is used to characterize the relationship between load data and displacement data when a load is unloaded from the flexible substrate under analysis.

[0052] Step 204: Determine the damage index of the flexible substrate to be analyzed based on the preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed.

[0053] The preset index determination rules are pre-defined rules used to determine the damage indices of the flexible substrate to be analyzed. The damage indices of the flexible substrate to be analyzed are parameters used to characterize the damage of the flexible substrate at the last time point within the preset time range.

[0054] In this embodiment, mechanical energy parameters are determined based on inelastic dissipation energy and a preset critical release rate. Then, electrical feedback parameters are determined based on the change in resistance and a preset critical failure resistance. Finally, the damage index of the flexible substrate to be analyzed is determined based on preset index determination rules, mechanical energy parameters, and electrical feedback parameters.

[0055] The preset critical release rate is the energy release rate of the flexible substrate under analysis at the critical moment, which is a pre-set value. The preset critical failure resistance is the contact resistance of the interface between the flexible substrate under analysis and the solder ball at the critical moment, which is a pre-set value. The critical moment is the time point at which a microcrack with a length greater than or equal to a preset length first appears on the flexible substrate under analysis, and the preset length can be 1 μm.

[0056] It should be noted that the preset critical release rate is an intrinsic physical quantity characterizing the fracture resistance of a specific flexible packaging interface, and its value can be obtained based on Griffith's fracture theory. The specific flexible packaging interface, for example, can be the interface between the flexible substrate to be analyzed and the solder balls, such as the interface between the SAC305 solder balls and the copper pads in the flexible substrate. In some exemplary embodiments, the preset critical release rate can range from 10 J / m². 2 Up to 80 J / m 2 Furthermore, the preset critical release rate of the flexible substrate to be analyzed can be calibrated through a micro double cantilever beam DCB experiment. Specifically, the interface between the flexible substrate to be analyzed and the solder ball is subjected to in-situ tension or bending using a micro-displacement loading stage. The relationship curve between load and displacement is recorded, and then the formula is used to determine the release rate. Calculate the preset critical release rate, where P is the load at the critical moment, b is the thickness of the interface between the flexible substrate to be analyzed and the solder ball at the critical moment; C is the compliance at the critical moment, which is the quotient of the displacement at the critical moment and the load at the critical moment, and a is the length of the crack at the interface between the flexible substrate to be analyzed and the solder ball at the critical moment.

[0057] It should be noted that the preset critical release rate, preset critical failure resistance, and critical time are obtained by calibrating the flexible substrate to be analyzed in advance.

[0058] The mechanical energy parameter is used to correct the mechanical energy calculation deviation caused by the viscoelasticity of the flexible substrate, while the electrical feedback parameter is a parameter that characterizes the electrical capability of the flexible substrate to be analyzed at the last time point within the preset time range.

[0059] Step 205: Determine the damage stage of the flexible substrate to be analyzed based on the damage index.

[0060] In this embodiment, the damage stage of the flexible substrate to be analyzed is determined based on the first preset damage threshold, the second preset damage threshold, and the damage index.

[0061] The first preset damage threshold and the second preset damage threshold are preset damage index thresholds, with the first preset damage threshold being less than the second preset damage threshold.

[0062] In this embodiment, both the first preset damage threshold and the second preset damage threshold correspond to the flexible substrate to be analyzed. That is, one flexible substrate to be analyzed corresponds to one first preset damage threshold and one second preset damage threshold.

[0063] In other embodiments of this application, different flexible substrates to be analyzed correspond to the same first preset damage threshold and the same second preset damage threshold.

[0064] In this embodiment, if the damage index of the flexible substrate to be analyzed is less than or equal to a first preset damage threshold, the flexible substrate to be analyzed is in the initial adaptation period. If the damage index of the flexible substrate to be analyzed is greater than the first preset damage threshold and less than or equal to a second preset damage threshold, the flexible substrate to be analyzed is in the steady-state accumulation period. If the damage index of the flexible substrate to be analyzed is greater than the second preset damage threshold, the flexible substrate to be analyzed is in the unstable failure period.

[0065] The initial adaptation period is the time when the damage index of the flexible substrate under analysis is at a low level and exhibits minor fluctuations. The steady-state accumulation period is the period during which the damage index of the flexible substrate under analysis increases synchronously with the increase of the applied bending load time. The instability failure period is the period during which the rate of change of the damage index of the flexible substrate under analysis undergoes a drastic change.

[0066] In the aforementioned flexible substrate analysis method, multiple data points of the flexible substrate to be analyzed are acquired within a preset time range. These multiple data points include load data, displacement data, contact resistance data, and morphology data, which correspond one-to-one in time. Then, based on the morphology data and contact resistance data, the resistance change of the flexible substrate to be analyzed is determined. Next, based on the load data and displacement data, the inelastic dissipation energy of the flexible substrate to be analyzed is determined. Then, based on preset index determination rules, the resistance change of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed, the damage index of the flexible substrate to be analyzed is determined. Finally, based on the damage index, the damage stage of the flexible substrate to be analyzed is determined, thereby efficiently detecting the damage stage of the flexible circuit board.

[0067] In other embodiments of this application, determining the change in resistance of the flexible substrate to be analyzed based on morphology data and contact resistance data includes:

[0068] Step 1: Based on the topography data and contact resistance data, take the contact resistance data corresponding to the last topography image in the topography data as the target resistance.

[0069] The target resistance is the contact resistance data corresponding to the last time point within the preset time range.

[0070] In this embodiment, the contact resistance data corresponding to the time point of the last topographic image in the topographic data will be used as the target resistance.

[0071] Step 2: Determine the change in resistance of the flexible substrate to be analyzed based on the target resistance and the preset reference resistance.

[0072] In this embodiment, the difference between the target resistance and the preset reference resistance is calculated, and the result of the difference is used as the resistance change of the flexible substrate to be analyzed.

[0073] The change in resistance is the difference between the target resistance and the preset reference resistance.

[0074] It should be noted that, in this embodiment, based on the morphology data and contact resistance data, the contact resistance data corresponding to the last morphology data in the morphology data will be used as the target resistance. Then, based on the target resistance and the preset reference resistance, the resistance change of the flexible substrate to be analyzed will be determined, laying the foundation for the subsequent determination of the damage index of the flexible substrate to be analyzed.

[0075] In other embodiments of this application, determining the inelastic dissipation energy of the flexible substrate to be analyzed based on load data and displacement data includes:

[0076] Step 1: Perform curve fitting based on load and displacement data to determine the loaded load displacement curve and the unloaded load displacement curve.

[0077] In this embodiment, curve fitting is performed based on the load data and displacement data to obtain the loaded load displacement curve and the unloaded load displacement curve.

[0078] In this embodiment, the load data is the load data sampled during the process of continuously applying bending loads to the flexible substrate under analysis within a preset time range and then unloading the bending loads. Therefore, curve fitting is performed on the load data and displacement data. Specifically, based on the time points of the load data and displacement data, load data and displacement data at the same time are matched, and multiple points are determined on the displacement-load coordinate system based on the corresponding load data and displacement data. Then, adjacent points are connected to obtain two different curves, namely the loaded load-displacement curve and the unloaded load-displacement curve. It should be noted that both the loaded load-displacement curve and the unloaded load-displacement curve have displacement on the horizontal axis and load on the vertical axis.

[0079] The loading-displacement curve and the unloading-displacement curve share the same starting and ending points. The loading-displacement curve characterizes the relationship between load and displacement data when a load is applied to the flexible substrate being analyzed. The unloading-displacement curve characterizes the relationship between load and displacement data when a load is unloaded from the flexible substrate being analyzed. Both loading-displacement and unloading-displacement curves are curves showing displacement data with respect to load data.

[0080] Step 2: Integrate the loaded load displacement curve and the unloaded load displacement curve to determine the inelastic dissipation energy of the flexible substrate to be analyzed.

[0081] Inelastic dissipation energy is a parameter characterizing the energy loss of the flexible substrate under analysis within a preset time range.

[0082] In this embodiment, the loaded load displacement curve and the unloaded load displacement curve are integrated, and the result of the integration is used as the inelastic dissipation energy of the flexible substrate to be analyzed.

[0083] For example, the process of integrating the loaded load displacement curve and the unloaded load displacement curve is as follows:

[0084] .

[0085] in, For inelastic dissipated energy, D represents displacement data, and F represents load data. For the load displacement curve, For the unloaded load displacement curve, Displacement data at the starting points of the loaded load displacement curve and the unloaded load displacement curve. Displacement data for the termination points of the loaded load displacement curve and the unloaded load displacement curve.

[0086] It should be noted that in this embodiment, the loaded load displacement curve and the unloaded load displacement curve are determined by curve fitting based on the load data and displacement data. Then, the loaded load displacement curve and the unloaded load displacement curve are integrated to determine the inelastic dissipation energy of the flexible substrate to be analyzed, which lays the foundation for the subsequent determination of the damage index of the flexible substrate to be analyzed.

[0087] In other embodiments of this application, such as Figure 3 As shown, based on the preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed, the damage indices of the flexible substrate to be analyzed are determined as follows:

[0088] Step 301: Determine the mechanical energy parameters based on the inelastic dissipation energy and the preset critical release rate.

[0089] In this embodiment, determining the mechanical energy parameters based on the inelastic dissipation energy and the preset critical release rate includes: dividing the inelastic dissipation energy by the preset critical release rate to determine the mechanical energy parameters. That is, the result of dividing the inelastic dissipation energy by the preset critical release rate is calculated, and then the calculated result is used as the mechanical energy parameters.

[0090] The preset critical release rate is the energy release rate of the flexible substrate to be analyzed at the critical moment, which is a pre-defined value. The mechanical energy parameter is used to correct for the mechanical energy calculation deviation caused by the viscoelasticity of the flexible substrate.

[0091] The critical moment is the time point at which a microcrack with a length greater than or equal to a preset length first appears on the flexible substrate to be analyzed. The preset length can be 1 μm.

[0092] Step 302: Determine the electrical feedback parameters based on the change in resistance and the preset critical failure resistance.

[0093] In this embodiment, determining the electrical feedback parameters based on the resistance change and the preset critical failure resistance includes: dividing the resistance change by the preset critical failure resistance to determine the electrical feedback parameters. That is, calculating the result of dividing the resistance change by the preset critical failure resistance and using the calculated result as the electrical feedback parameters.

[0094] The preset critical failure resistance is the contact resistance at the interface between the flexible substrate under analysis and the solder ball at the critical moment, as predetermined. The electrical feedback parameters characterize the electrical capabilities of the flexible substrate under analysis at the last time point within the preset time range.

[0095] Step 303: Determine the damage index of the flexible substrate to be analyzed based on the first preset weight, the second preset weight, the mechanical energy parameter, and the electrical feedback parameter.

[0096] In this embodiment, the damage indicators of the flexible substrate to be analyzed are determined based on the first preset weight, the second preset weight, the mechanical energy parameter, and the electrical feedback parameter, including:

[0097] Step 1: Multiply the first preset weight and the mechanical energy parameter to determine the mechanical damage parameter.

[0098] In this embodiment, the first preset weight and the mechanical energy parameter are multiplied together, and the result of the multiplication is used as the mechanical damage parameter.

[0099] The first preset weight is a pre-defined mechanical weight. The mechanical damage parameter is a parameter used to characterize the contribution of the mechanical energy parameter to the overall damage of the flexible substrate being analyzed.

[0100] Step 2: Multiply the second preset weight and the electrical feedback parameter to determine the electrical damage parameter.

[0101] In this embodiment, the second preset weight and the electrical feedback parameter are multiplied together, and the result of the multiplication is used as the electrical damage parameter.

[0102] The second preset weight is a pre-defined electrical weight. Electrical damage parameters are parameters used to characterize the contribution of electrical feedback parameters to the overall damage of the flexible substrate being analyzed.

[0103] Step 3: Add the mechanical damage parameters and the electrical damage parameters to determine the damage index of the flexible substrate to be analyzed.

[0104] The damage index of the flexible substrate to be analyzed is a parameter used to characterize the damage of the flexible substrate to be analyzed at the last time point within a preset time range.

[0105] In this embodiment, the mechanical damage parameters and the electrical damage parameters are added together, and the result of the addition is used as the damage index of the flexible substrate to be analyzed.

[0106] In other embodiments of this application, a method for simultaneous force-electrical-morphology calibration and damage evaluation of flexible packaging interfaces is provided, belonging to the field of microelectronic packaging reliability evaluation technology. This method is based on in-situ scanning electron microscopy loading experiments, simultaneously acquiring load data, contact resistance data, and morphology data of the interface between the flexible substrate and solder balls under bending loads; utilizing an improved Barber contact stiffness-conductivity analogy theory, a mapping model between the effective contact area and conductivity of the interface is established; and combining the digital image correlation (DIC) algorithm, crack tip opening displacement (CTOD) and crack propagation length are extracted. The innovation of this invention lies in proposing a quantitative evaluation index for interface damage based on the real-time interface force-electrical mapping factor α(t). By calculating the inelastic dissipation energy, a non-destructive digital characterization of the entire process of the packaging interface from crack initiation to final failure is achieved. This method solves the problem that related technologies cannot quantitatively describe the microscopic damage state without destroying the sample, and is of great significance for the lifetime prediction of flexible electronic devices.

[0107] like Figure 4 As shown, the above-mentioned method for simultaneous calibration and damage evaluation of the force-electricity-morphology interface of flexible packaging is a flexible substrate analysis method, including:

[0108] S1: Multi-source data loading and spatiotemporal alignment. During in-situ loading, timestamp marking technology is used to simultaneously acquire the load, contact resistance, macroscopic displacement, and SEM microscopic image sequence of the BGA solder ball interface, thereby obtaining the original dataset of the in-situ experiment. The load represents the load data of the flexible substrate to be analyzed, the contact resistance represents the contact resistance data of the flexible substrate to be analyzed, the macroscopic displacement represents the displacement data of the flexible substrate to be analyzed, and the SEM microscopic image sequence represents the morphological data of the flexible substrate to be analyzed. Furthermore, signal preprocessing and denoising are performed, including EMD decomposition, sliding filtering, and image sharpening.

[0109] S2: Interface morphology feature extraction: Subpixel-level edge detection and DIC processing are performed on the microscopic image sequence to extract the microcrack extension length a and crack tip opening displacement CTOD.

[0110] S3: Establishing a force-electricity mapping model: Based on the Barber stiffness-conductivity analogy theory, the interface contact conductivity is... Converted to normal contact stiffness Furthermore, a real-time interface force-electric mapping factor α(t) is introduced to dynamically calibrate the interface contact state. The dynamic calibration is based on the non-destructive mapping factor α0 and is performed according to the damage drift Δα.

[0111] S4: Quantitative Calculation of Damage Indicators: Calculate the inelastic dissipation energy W based on the obtained data. diss And based on this, a damage evaluation D for the encapsulation interface is established. index .

[0112] S5: Health Status Classification and Life Prediction: Based on D index The evolution rate is used to classify the service health status of flexible substrates in real time, including stable regions characterized as healthy, metastable regions characterized as damage initiation, and failure regions characterized as severe damage. Finally, a real-time report on interface health status and lifetime prediction are output.

[0113] The formula for calculating the real-time interface force-electric mapping factor α(t) is as follows:

[0114] = .

[0115] To account for the microscopic normal contact stiffness after modulus compensation of the flexible substrate, For interface contact conductivity.

[0116] It should be noted that the formula for calculating the real-time interface force-electric mapping factor α(t) is based on Barber's Analogy. Furthermore, it can be dimensionlessly or constant-corrected using the intrinsic material properties to reflect the microscopic morphology of the force-electric coupling interface. Specifically, based on the analogy between contact mechanics and electricity, for an ideal, clean, atomically flat contact surface, its contact conductivity is... ,in For interface contact conductivity, Let be the electrical conductivity, r be the contact radius of the contact surface, and the normal contact stiffness be... ,in, For normal contact stiffness, Let r be the equivalent elastic modulus and r be the contact radius of the contact surface. In this case, the relationship between the interfacial contact conductivity and the normal contact stiffness is: That is, there is a fixed linear proportional relationship between the two.

[0117] The real-time interface force-electric mapping factor α(t) physically refers to the correction coefficient of the apparent force-electric transfer characteristics of a real, non-ideal contact interface relative to an ideal contact interface, or the combined influence factor of interface roughness and oxide layer, and is a dimensionless parameter. It is understandable that, due to the presence of micro-roughness and oxide layer at the interface between the flexible substrate and the solder ball, the actual ratio between interface contact conductivity and normal contact stiffness will deviate from the ideal linear relationship. Therefore, this embodiment proposes a further calculation formula for the real-time interface force-electric mapping factor α(t). ,in, For interface contact conductivity, For electrical conductivity, For normal contact stiffness, It is the equivalent elastic modulus.

[0118] Furthermore, the mathematical relationships between α(t), α0, and Δα are as follows: Where Δα is the damage drift, α0 is the preset baseline value of the initial health stage, which can be obtained in advance by calibrating the flexible substrate to be analyzed in the undamaged state; α(t) is the current interface force-electric mapping factor. When Δα exceeds the preset damage drift threshold, it can be determined that the interface between the flexible substrate to be analyzed and the solder ball has entered the steady-state propagation period of microcracks.

[0119] It should be noted that, Normal contact stiffness refers to the microscopic contact stiffness generated solely by the elastic compression of the microscopic crests of the solder ball; Effective apparent stiffness refers to the comprehensive apparent stiffness measured directly by macroscopic sensors, encompassing the overall bending and sagging flexibility of the flexible substrate under analysis. For example, the conversion relationship can be: It can also be ,in, For normal contact stiffness, For effective apparent stiffness, The substrate flexibility can be preset from the structural layer characteristics of the flexible substrate to be analyzed. Based on the above formula, the effective apparent stiffness can be detected. To calculate normal contact stiffness .

[0120] It should be noted that in this embodiment, multiphysics features are extracted in parallel, and mechanical features, namely the effective apparent stiffness K, are extracted from path A. eff In path B, morphological features are extracted and DIC tracing is performed to extract the crack tip opening displacement (CTOD). In path C, the interface contact conductivity is extracted. The quotient of the change in resistance divided by a preset reference resistance, where the preset reference resistance is the contact resistance of the flexible substrate to be analyzed when it is not subjected to bending load, will be used to extract the inelastic dissipated energy W in path D. diss .

[0121] It should be noted that during the process of extracting interface morphology features, the SEM image is sharpened using the Laplacian operator, and the center coordinates of the crack tip are obtained by Gaussian fitting, with a positioning accuracy of less than 50nm.

[0122] It should be noted that damage assessment D index It is defined as a weighted fusion function based on the ratio of inelastic dissipation energy and the ratio of contact resistance change. The contact resistance change is the change in resistance.

[0123] It should be noted that this application proposes a full-process, digital, and non-destructive calibration and evaluation method. By establishing a three-field synchronous correlation algorithm of force, electricity, and morphology, the complex physical process of interface failure is simplified into a mapping relationship with the real-time interface force-electric mapping factor α(t) as the core. This method can not only visualize cracks but also calculate the crack depth and stress state through electrical fluctuations.

[0124] The difference between this invention and related technologies lies in its shift from qualitative to quantitative analysis. Related technologies rely solely on resistance spikes to determine failure, while this invention can quantitatively infer the CTOD of cracks based on resistance fluctuations. Furthermore, it moves from single-field to multi-field fusion, introducing an improved version of Barber's analogy theory to deeply couple mechanical stiffness and electrical conductivity, eliminating the interference of flexible substrate modulus changes on test results. Non-destructive calibration utilizes in-situ SEM images as the ground truth, employing deep learning or image feature extraction to perform deconvolution calibration on the electrical signals.

[0125] The core innovations include a real-time interface force-electric mapping factor α(t) mapping calibration method based on improved Barber analogy theory. Traditional theory holds that... While the constant is assumed, this method considers the viscoelasticity of the flexible substrate and proposes a real-time interface force-electric mapping factor α(t). A baseline α0 for this specific packaging system is obtained through calibration during the initial crack-free stage of in-situ loading, serving as the initial coordinate for subsequent damage assessment. Subpixel-level microcrack geometric parameters are extracted in real time. The DIC algorithm is used to monitor the relative displacement vector field between the solder ball and the pad. The energy release rate at the crack tip is calculated using J-integral theory and correlated with the synchronously acquired impedance growth rate. Based on the inelastic dissipation energy W... diss The health assessment model extracts the area of ​​the force-displacement hysteresis loop in each loading cycle, subtracts the pure elastic deformation energy, and obtains the dissipated energy W due to interface damage. diss Establish the change in resistance. The empirical formula enables the real-time characterization of mechanical damage by electrical indicators.

[0126] For example, the change in resistance The empirical formula can be derived from the constitutive model of material fatigue damage evolution. In a specific embodiment, the empirical formula can be: ,in, W represents the change in resistance. diss This refers to the energy dissipated due to interface damage. The critical total energy dissipation before material failure can be measured by standard fatigue tests. A and m are pre-calibrated intrinsic constants of the material and are preset values.

[0127] The theoretical basis of this application is an improved Barber contact stiffness-conductivity analogy model. In this embodiment, the core logic of the evaluation method is based on the isomorphism between micromechanics and microelectricity. According to Barber's theory in solid mechanics, for any shape of rough surface contact, its normal contact stiffness... Contact conductivity at the interface The following conditions must be met:

[0128] ;

[0129] Where σ is the electrical conductivity and κ is a material property constant. For the equivalent elastic modulus, For normal contact stiffness, For interface contact conductivity.

[0130] It should be noted that, in this embodiment, based on the isomorphism of micromechanics and microelectricity, an improved Barber contact stiffness-conductivity analogy model was constructed. This not only solves the problem in related technologies where a direct physical correspondence between resistance changes and the geometric parameters of microcracks cannot be established, leading to difficulties in early failure warning, but also addresses the issue that while Barber's contact stiffness-conductivity analogy theory has been verified in ideal planar contacts, it lacks an effective mapping calibration method in flexible circuit board systems with micron-level roughness and viscoelastic substrates.

[0131] In a flexible substrate environment, due to the elastic modulus E of the PI substrate PI Much smaller than the elastic modulus E of tin-lead solder solder Traditional analogy constants will drift. This method introduces a real-time interface force-electric mapping factor α(t):

[0132] ;

[0133] Where σ is the electrical conductivity and κ is a material property constant. K(t) is the real-time equivalent elastic modulus, and K(t) is the real-time normal contact stiffness. G(t) is the real-time interfacial contact conductance. α(t) is the real-time interface force-electric mapping factor.

[0134] Using the synchronization data obtained in the multiphysics data synchronization acquisition step, we can reverse-calibrate the system's fundamental mapping factor α0 within the first 10 preset time ranges, before the interface experiences physical breakage. This step is a crucial setting point to ensure the accuracy of subsequent evaluations, specifically:

[0135] S10: Preprocessing and Denoising Methods for Multiphysics Data. Since the minute strain signals and resistance fluctuations on the flexible substrate are highly susceptible to vibrations from the experimental equipment, this method employs an adaptive denoising algorithm based on EMD (Empirical Mode Decomposition). High-pass filtering is applied to the data from the S-type force sensor to remove the inertial force of the macroscopic loading frame, retaining the perturbation components of interface friction and fracture forces for mechanical signal processing. The raw voltage data acquired through four-wire sampling is smoothed using a 50ms moving average window, focusing on monitoring high-frequency spikes on the resistance curve. These spikes typically correspond to instantaneous jumps in interface microcracks and are then processed as electrical signals.

[0136] S11: A quantitative method for morphological features based on DIC (Digital Image Correlation) is employed. This method utilizes a digital image correlation subroutine, which requires speckle fabrication. Before SEM observation, aerosol spraying technology is used to create a nanoscale speckle field on the side of the BGA solder balls. Displacement tracking is performed by tracing the relative coordinates between the pad and solder ball sides using an algorithm. When the microcrack length 'a' is greater than 5 μm, the algorithm automatically identifies the crack root and tip. The crack tip opening displacement (CTOD) is defined as the vertical separation distance at a specific distance behind the crack tip. This is a key geometric parameter for evaluating brittle or ductile fracture.

[0137] Furthermore, the algorithm for automatically identifying crack roots and tips can be a displacement field strain gradient identification algorithm based on the Digital Image Correlation (DIC) method combined with Canny edge detection and morphological skeleton extraction algorithms. For example, when the microcrack length *a* is greater than 5 μm, the algorithm uses DIC to calculate the discontinuous displacement jumps across the entire field, locking in the local strain concentration region; then, the Canny operator is used to extract the crack boundary, and the morphological thinning operator is used to extract the crack center skeleton line. The endpoint of the skeleton line penetrating into the solder ball is the crack tip, while the starting point near the edge of the solder pad is the crack root. The algorithm for identifying crack roots and tips can also employ other existing algorithms in computer vision and micromechanical image processing; this embodiment does not limit the specific algorithms used.

[0138] S12: This invention uses a synchronous calibration method. The specific calibration process and implementation steps of this method are as follows:

[0139] S120: Initial calibration. During the initial stage of cyclic loading, plot the RF curve of contact resistance R as a function of load F. At this point, since there are no cracks, the curve shows a linear correlation. Calculate its slope and establish α0.

[0140] S121: Evolution monitoring. As the number of preset time ranges increases, hysteresis and nonlinear drift of the slope are observed in the RF curve.

[0141] S122: Mapping calibration, which pairs the crack area Acrack in the synchronously acquired SEM images with the decrease in conductivity ΔG. Using the formula... For calibration, d represents the effective current path length.

[0142] S123: Feature point correlation. When the first microcrack exceeding 1µm in length is observed in the SEM image, the rate of change of resistance ΔR / R0 is recorded. This value is the failure initiation threshold for this specific package structure, i.e., the preset critical failure resistance.

[0143] S13: This application uses damage index D index In terms of construction and lifetime prediction, this method proposes a comprehensive damage index D. index Its mathematical model combines mechanical energy and electrical feedback, as shown in the following equation:

[0144] ;

[0145] Among them, D index As a damage indicator, As the first preset weight, This is inelastic dissipated energy, obtained by integrating the loaded load-displacement curve and the unloaded load-displacement curve, and includes micro-plastic deformation energy and new surface formation energy or fracture energy. The preset critical release rate of the material. As the second preset weight, For the change in resistance, To preset the critical failure resistance, the first preset weight and the second preset weight are adjusted according to different material systems or lead-free solder paste. The material system can be SAC305.

[0146] like Figure 5 As shown, the normal contact stiffness is illustrated. Contact conductivity at the interface Based on the analogy mapping model diagram, this method abstracts the interface between the flexible substrate to be analyzed and the solder ball as a set of multiple randomly distributed contact spots. Figure 5 The left side of the middle section shows the stress field distribution under load, and the density of streamlines represents the normal contact stiffness of the interface. ; Figure 5 The right side of the middle section shows the current contraction field under the same geometric topology, and its streamline distribution represents the interfacial contact conductance. Since the Laplace equations for the stress field and the current field at the microscopic spots are mathematically isomorphic, this embodiment establishes the following analogical mapping constitutive equation:

[0147] ;

[0148] in, K is the interface contact conductance acquired in real time, which is the reciprocal of the contact resistance R; eff The effective apparent stiffness of the macroscopic structure is taken into account after modulus compensation of the flexible substrate; σ is the intrinsic conductivity of the solder material. This refers to the equivalent elastic modulus of the interface. The aforementioned modulus compensation can be achieved by extracting the equivalent elastic modulus. This is achieved by eliminating the softening effect of the PI substrate. In this method, the real-time interfacial force-electric mapping factor α(t) is... Figure 5 The mapping operator shown in the central region is defined as a morphological characteristic factor that corrects the deviation between the actual engineering interface and the ideal Barber contact model. It specifically encompasses several physical variables: surface roughness distribution, which corrects for the contact spot aggregation effect caused by non-ideal smooth surfaces; oxide layer impedance effect, which characterizes the additional obstruction of charge transport by the microscopic oxide layer at the interface, an effect not reflected in the mechanical stiffness field; and field line contraction difference, used to compensate for the nonlinear deviation of the current field and strain field at different damage stages.

[0149] In the actual implementation process, the application of the real-time interface force-electric mapping factor α(t) is divided into two stages:

[0150] S20: Initial Calibration Phase: In the initial, non-destructive phase of loading, the system synchronously acquires the effective apparent stiffness K. eff Contact conductivity at the interface Combining known material parameters σ and The baseline mapping factor α0 is automatically calculated. At this point, the interface is in a force-electric coordination state, and the real-time interface force-electric mapping factor α(t) remains constant.

[0151] S21: Damage Evolution Stage: As the number of preset time ranges increases, such as Figure 5 As microscopic crack initiation occurs, the transmission paths of the mechanical stress field and the current field begin to evolve asymmetrically. At this point, the real-time calculated interfacial force-electric mapping factor α(t) will deviate from the baseline value α0.

[0152] It should be noted that this method determines damage by monitoring the deviation rate of the real-time interfacial force-electric mapping factor α(t), rather than simply by an increase in resistance. If the real-time interfacial force-electric mapping factor α(t) drifts drastically, even if the resistance change ΔR is still small, the interface is determined to have entered the steady-state propagation stage of microcracks. This is achieved by introducing... Figure 5 The real-time interface force-electric mapping factor α(t) value is defined as shown in this embodiment. This embodiment can effectively eliminate the interference of pseudo-stiffness changes caused by the viscoelastic creep of the flexible substrate. The mechanical index is calibrated in real time through electrical feedback, so as to realize the assessment of the microscopic damage state of the encapsulation interface without relying on in-situ microscopic observation.

[0153] like Figure 6 The diagram shows the DIC (Digital Correlation Analysis) algorithm model for extracting the crack tip opening displacement (CTOD) from SEM images. This embodiment uses the digital image correlation (DIC) method to perform non-contact displacement tracking on the morphology data during in-situ loading, aiming to extract the evolutionary geometric parameters of microcracks. For the detailed algorithm flow, please refer to [link / reference]. Figure 6 The implementation steps are as follows:

[0154] S30: Image feature enhancement and edge preprocessing. This preprocesses the original image sequence to address potential electron beam drift noise and low contrast characteristics of flexible substrates during SEM microscopy imaging. For example... Figure 6 As shown, this method employs the Laplacian operator to perform second-order differential sharpening on the image to enhance the grayscale gradient between the BGA solder ball edges and the interface crack region. Subsequently, Gaussian filtering is used to eliminate high-frequency noise, ensuring the robustness of subsequent sub-region matching.

[0155] S31: Selection and search strategy for reference subsets. In the undeformed reference image, reference subsets of 31x31 pixels are selected on the upper and lower sides of the preset crack initiation site on the interface, namely the solder ball side and the solder pad side. These two subsets serve as reference points for displacement tracking, and their initial spacing is defined as δ. initial The algorithm uses a normalized cross-correlation criterion to perform a global search in the deformed image sequence, initially locking down pixel-level matching positions in sub-regions.

[0156] S32: Subpixel-level positioning and Gaussian fitting optimization. To achieve the positioning accuracy below 50nm, this algorithm introduces subpixel interpolation technology based on pixel-level search. By fitting a two-dimensional Gaussian surface to the peak region of the correlation coefficient matrix, the subpixel coordinates x', y' of the sub-region center are calculated. This process eliminates the limitation of discrete pixel grids on displacement calculation, enabling the algorithm to capture the extremely small opening amount in the early stage of microcrack initiation.

[0157] S33: Quantitative calculation and output of CTOD Figure 6 The geometric relationship on the right, the crack tip opening displacement CTOD, is extracted in real time using the following formula:

[0158] ;

[0159] in, To track the obtained vertical subpixel coordinates on the pad side, To track the longitudinal sub-pixel coordinates of the obtained solder ball side sub-region, the crack tip opening displacement (CTOD) characterizes the degree of physical separation caused by tensile forces on the interface under bending load. The initial spacing is used as a reference sub-region.

[0160] S34: Synchronous correlation between morphological features and force-electric indices. In this embodiment, through... Figure 6 The algorithm shown extracts the crack tip opening displacement (CTOD) and synchronously acquired interface contact conductivity. Effective apparent stiffness K eff Alignment is performed on the time axis. When the first derivative of the crack tip opening displacement CTOD changes abruptly, the system automatically marks it as the start time of steady-state crack propagation and corrects the dynamic benchmark of the mapping factor accordingly, thereby completing the closed-loop calibration of the force-electric-morphology three fields.

[0161] like Figure 7 As shown, the load-displacement hysteresis loop and the inelastic dissipated energy Wdiss calculation model are illustrated. This embodiment utilizes mechanical sensors and high-precision displacement monitoring data during in-situ loading to construct a force-displacement (FD) response model for the encapsulated interface. By extracting the energy dissipation characteristics under cyclic loading, a quantitative evaluation of the interface fatigue damage state is achieved. The specific steps are as follows:

[0162] S40: Construction and Feature Identification of Force-Displacement Hysteresis Loop. Under bending loads on a flexible substrate, the BGA solder ball interface undergoes periodic stress alternation. Due to the micro-plastic deformation of the solder material and the inherent viscoelastic hysteresis effect of the flexible substrate PI, the trajectories of the loading and unloading segments within a single preset time range do not coincide, thus forming a closed force-displacement hysteresis loop. The vertical axis F represents the real-time acquired normal contact load, and the horizontal axis D represents the macroscopic displacement fed back by the nanoscale displacement stage. The initial slope of the loading segment is defined as the initial effective apparent stiffness K in this method. eff .

[0163] S41: Inelastic dissipation energy W diss Mathematical integral extraction, inelastic dissipation energy W diss Defined as the net work done by the load on the displacement within a preset time range. This method uses edge computing kernels to perform the calculation. Figure 7 Real-time numerical integration of closed curves in the equation:

[0164] .

[0165] in, For inelastic dissipated energy, D represents displacement data, and F represents load data. For the load displacement curve, For the unloaded load displacement curve, Displacement data at the starting points of the loaded load displacement curve and the unloaded load displacement curve. This provides displacement data for the termination points of the loading and unloading load displacement curves. The process of calculating inelastic dissipated energy eliminates the interference of purely elastic deformation energy, directly characterizing the total irreversible energy consumed by the interface in a single cycle.

[0166] S42: Evolution of hysteresis loops under damage accumulation, illustrated by the evolution of the shaded area. As the number of preset time ranges increases, the hysteresis loops exhibit two significant characteristics. Increased area represents the increased new surface formation energy due to the initiation of microcracks within the interface and enhanced local frictional dissipation; decreased slope reflects the reduction in macroscopic stiffness caused by the decrease in the effective contact area of ​​the interface. This embodiment captures the incremental changes in the shaded area in the figure to map the failure process of the interface's micro-topology in real time.

[0167] S43: Based on G c Damage index D index Normalized calculations: The core innovation of this method lies in the deep integration of energy dissipation in the mechanical dimension and impedance fluctuations in the electrical dimension, utilizing... Figure 7 The calculated Wdiss construction damage evaluation index:

[0168] ;

[0169] Among them, D index As a damage indicator, As the first preset weight, This is inelastic dissipated energy, obtained by integrating the loaded load-displacement curve and the unloaded load-displacement curve, and includes micro-plastic deformation energy and new surface formation energy or fracture energy. The preset critical release rate of the material is determined through a synchronous calibration process. As the second preset weight, For the change in resistance, To preset the critical failure resistance, the first and second preset weights are adjusted according to different material systems or lead-free solder pastes. The material system can be SAC305. The damage index normalizes the abstract energy dissipation into a damage degree between [0,1], providing a basis for subsequent active intervention.

[0170] Through the aforementioned calculation model, this application overcomes the drawback of traditional reliability testing that relies solely on resistance mutations as the criterion. Because the mechanical hysteresis loop is extremely sensitive to changes in the interface microstructure, the system can detect changes in resistance before the crack length reaches the micrometer level, i.e., before a significant shift in resistance occurs, by monitoring the inelastic dissipation energy W. diss Abnormal fluctuations enable early warning of damage.

[0171] like Figure 8 The figure shows the interface damage index D under different bending strain levels. indexThe evolution curves are shown in this embodiment. This example illustrates the evolution curves at several different bending strain levels. Under cyclic loading, the damage index D of the interface is calculated using the algorithm provided in this application. index The real-time evolution characteristics increase with the number of preset time ranges. Figure 8 The aim is to verify the evaluation model's ability to linearly identify the damage accumulation process and its universality in failure prediction.

[0172] S50: such as Figure 8 As shown, at all strain energy levels, D index The curves all exhibit three highly consistent physical stages, demonstrating the deep coupling between this index and the microscopic fatigue damage mechanism:

[0173] Phase I Initial Adaptation Period: Initial Loading Stage, D index The value is at a low level, i.e., <0.2, with slight fluctuations. At this point, the interface is in a state of flexible adaptation, and the value of the real-time interface force-electric mapping factor α(t) remains stable, indicating that the encapsulated interface is intact.

[0174] Phase II steady-state accumulation period: As the number of preset time ranges increases, D index It exhibits a stable upward trend. At this point, the inelastic dissipation energy W calculated from the figure... diss The damage accumulates steadily, and a slight increase begins to appear in the monitored crack tip opening displacement (CTOD). The slope of the curve at this stage visually reflects the rate of interface damage propagation.

[0175] Stage III instability failure period: when D index Approaching the critical threshold, approximately between 0.75 and 0.8, the slope of the curve undergoes a drastic change and rapidly approaches 1. At this point, the change in resistance ΔR undergoes an exponential jump, indicating that a through-crack has occurred at the interface.

[0176] S51: The control effect of strain level on damage slope Figure 8 A comparison of several curves shows that, at the highest strain level ε3, D index The curve is steepest, indicating that the larger curvature leads to a greater energy dissipation W per unit cycle. diss This significantly increases and accelerates the drift of the real-time interfacial force-electric mapping factor α(t). At the lowest strain level ε1, the curve exhibits excellent linearity, demonstrating that this method outperforms the traditional criterion that relies solely on abrupt changes in resistance in its ability to detect extremely small damage in its early stages.

[0177] S52: Damage Criterion D index Regarding the convergence and scaling significance, a key point of this embodiment is that although the failure lifetime Nf varies by orders of magnitude under different strain levels, the critical D for entering the stage III instability failure period remains the same.index All converge to the same narrow interval. This phenomenon verifies the scientific validity of normalization using the critical strain energy release rate Gc as the denominator. This indicates that D index It is an intrinsic material-structure index that does not change with the magnitude of external load, and can provide absolute physical coordinates for setting a unified early warning threshold.

[0178] pass Figure 8 The curve model shown in this embodiment demonstrates that the method provided in this application can offer a longer effective early warning window than traditional testing. Before the resistance drifts by more than 10%, D... index The slope prediction of the curve during the steady-state accumulation period in stage II allows for the calculation of the remaining service life of the flexible packaging interface in advance, thereby significantly improving the safety of electronic systems under dynamic bending conditions, such as rehabilitation robots.

[0179] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0180] Based on the same inventive concept, this application also provides a flexible substrate analysis apparatus for implementing the flexible substrate analysis method described above. The solution provided by this apparatus is similar to the implementation described in the above method; therefore, the specific limitations in one or more embodiments of the flexible substrate analysis apparatus provided below can be found in the limitations of the flexible substrate analysis method described above, and will not be repeated here.

[0181] In one embodiment of this application, such as Figure 9 As shown, a flexible substrate analysis apparatus is provided, comprising:

[0182] The acquisition module 100 is used to acquire multiple data to be analyzed of the flexible substrate to be analyzed within a preset time range; the multiple data to be analyzed include load data, displacement data, contact resistance data and morphology data, and the load data, displacement data, contact resistance data and morphology data correspond one-to-one in time;

[0183] The electrical determination module 200 is used to determine the amount of resistance change of the flexible substrate to be analyzed based on the morphology data and contact resistance data.

[0184] The energy determination module 300 is used to determine the inelastic dissipation energy of the flexible substrate to be analyzed based on the load data and displacement data.

[0185] The damage determination module 400 is used to determine the damage index of the flexible substrate to be analyzed based on the preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed.

[0186] The stage determination module 500 is used to determine the damage stage of the flexible substrate to be analyzed based on the damage index.

[0187] In one embodiment of this application, the electrical determination module 200 is further configured to, based on the morphology data and the contact resistance data, take the contact resistance data corresponding to the last morphology data in the morphology data as the target resistance; and determine the resistance change of the flexible substrate to be analyzed based on the target resistance and the preset reference resistance.

[0188] In one embodiment of this application, the energy determination module 300 is further configured to perform curve fitting based on the load data and displacement data to determine the loaded load displacement curve and the unloaded load displacement curve; the starting point and ending point of the loaded load displacement curve and the unloaded load displacement curve are the same; and to integrate the loaded load displacement curve and the unloaded load displacement curve to determine the inelastic dissipation energy of the flexible substrate to be analyzed.

[0189] In one embodiment of this application, the damage determination module 400 is further configured to determine mechanical energy parameters based on the inelastic dissipation energy and a preset critical release rate; determine electrical feedback parameters based on the resistance change and a preset critical failure resistance; and determine the damage index of the flexible substrate to be analyzed based on a first preset weight, a second preset weight, mechanical energy parameters, and electrical feedback parameters.

[0190] In one embodiment of this application, the damage determination module 400 is further configured to divide the inelastic dissipation energy by a preset critical release rate to determine the mechanical energy parameters.

[0191] In one embodiment of this application, the damage determination module 400 is further configured to divide the resistance change by a preset critical failure resistance to determine the electrical feedback parameters.

[0192] In one embodiment of this application, determining the damage index of the flexible substrate to be analyzed based on the first preset weight, the second preset weight, the mechanical energy parameter, and the electrical feedback parameter includes: multiplying the first preset weight and the mechanical energy parameter to determine the mechanical damage parameter; multiplying the second preset weight and the electrical feedback parameter to determine the electrical damage parameter; and adding the mechanical damage parameter and the electrical damage parameter to determine the damage index of the flexible substrate to be analyzed.

[0193] Each module in the aforementioned flexible substrate analysis device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the operations corresponding to each module.

[0194] In one embodiment of this application, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows. Figure 10 As shown, the computer device includes a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a flexible substrate analysis method. The display screen can be a liquid crystal display (LCD) or an e-ink display. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0195] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0196] In one embodiment of this application, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the flexible substrate analysis method in the above embodiment.

[0197] In one embodiment of this application, a computer-readable storage medium is provided, on which a computer program is stored, the computer program being executed by a processor to implement the steps of the flexible substrate analysis method in the above-described method embodiments.

[0198] In one embodiment of this application, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the flexible substrate analysis method in the above-described method embodiments.

[0199] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0200] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0201] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0202] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for analyzing flexible substrates, characterized in that, The method includes: Acquire multiple data points of the flexible substrate to be analyzed within a preset time range; the multiple data points include load data, displacement data, contact resistance data, and morphology data, and the load data, displacement data, contact resistance data, and morphology data correspond one-to-one in time; Based on the morphology data and contact resistance data, the change in resistance of the flexible substrate to be analyzed is determined. Based on the load data and displacement data, the inelastic dissipation energy of the flexible substrate to be analyzed is determined; The damage index of the flexible substrate to be analyzed is determined based on the preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed. Based on the damage index, the damage stage of the flexible substrate to be analyzed is determined; The step of determining the damage index of the flexible substrate to be analyzed based on preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed includes: The mechanical energy parameters are determined based on the inelastic dissipation energy and the preset critical release rate. The electrical feedback parameters are determined based on the change in resistance and the preset critical failure resistance. The damage index of the flexible substrate to be analyzed is determined based on the first preset weight, the second preset weight, the mechanical energy parameter, and the electrical feedback parameter. The determination of the mechanical energy parameters based on the inelastic dissipation energy and the preset critical release rate includes: The mechanical energy parameters are determined by dividing the inelastic dissipation energy by the preset critical release rate.

2. The flexible substrate analysis method according to claim 1, characterized in that, Based on the morphology data and contact resistance data, the resistance change of the flexible substrate to be analyzed is determined as follows: Based on the morphology data and contact resistance data, the contact resistance data corresponding to the last morphology image in the morphology data is taken as the target resistance. The change in resistance of the flexible substrate to be analyzed is determined based on the target resistance and the preset reference resistance.

3. The flexible substrate analysis method according to claim 1, characterized in that, The step of determining the inelastic dissipation energy of the flexible substrate to be analyzed based on the load data and displacement data includes: Based on the load data and displacement data, curve fitting is performed to determine the loaded load displacement curve and the unloaded load displacement curve; the starting point and ending point of the loaded load displacement curve and the unloaded load displacement curve are the same. By integrating the loaded load displacement curve and the unloaded load displacement curve, the inelastic dissipation energy of the flexible substrate to be analyzed is determined.

4. The flexible substrate analysis method according to claim 1, characterized in that, The determination of electrical feedback parameters based on the resistance change and the preset critical failure resistance includes: Divide the change in resistance by the preset critical failure resistance to determine the electrical feedback parameters; the preset critical failure resistance is the contact resistance of the interface between the flexible substrate to be analyzed and the solder ball at the critical moment.

5. The flexible substrate analysis method according to claim 1, characterized in that, The step of determining the damage index of the flexible substrate to be analyzed based on the first preset weight, the second preset weight, the mechanical energy parameter, and the electrical feedback parameter includes: The mechanical damage parameters are determined by multiplying the first preset weight by the mechanical energy parameter. The electrical damage parameters are determined by multiplying the second preset weight and the electrical feedback parameters. The mechanical damage parameters and electrical damage parameters are added together to determine the damage index of the flexible substrate to be analyzed.

6. A flexible substrate analysis device, characterized in that, The device includes: The acquisition module is used to acquire multiple data to be analyzed for the flexible substrate to be analyzed within a preset time range; the multiple data to be analyzed include load data, displacement data, contact resistance data and morphology data, and the load data, displacement data, contact resistance data and morphology data correspond one-to-one in time; An electrical determination module is used to determine the change in resistance of the flexible substrate to be analyzed based on the morphology data and contact resistance data. An energy determination module is used to determine the inelastic dissipation energy of the flexible substrate to be analyzed based on the load data and displacement data. The damage determination module is used to determine the damage index of the flexible substrate to be analyzed based on preset index determination rules, the change in resistance of the flexible substrate to be analyzed, and the inelastic dissipation energy of the flexible substrate to be analyzed. The stage determination module is used to determine the damage stage of the flexible substrate to be analyzed based on the damage index. The damage determination module is also used to determine mechanical energy parameters based on the inelastic dissipation energy and the preset critical release rate; determine electrical feedback parameters based on the resistance change and the preset critical failure resistance; and determine the damage index of the flexible substrate to be analyzed based on the first preset weight, the second preset weight, the mechanical energy parameters, and the electrical feedback parameters. The damage determination module is also used to divide the inelastic dissipation energy by a preset critical release rate to determine the mechanical energy parameters.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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