A method for testing the corrosion behavior of copper foil based on an electrochemical workstation

Abstract

This invention relates to the field of electrochemical testing and material corrosion protection technology, and discloses a method for testing the corrosion behavior of copper foil based on an electrochemical workstation. The method includes: placing a copper foil sample in a custom electrolytic cell integrating a micro-strain sensing unit and an optical window; simultaneously applying electrochemical excitation while acquiring strain time-series data and high-speed microscopic images, and aligning the timestamps to form a ternary dataset; establishing a quantitative mapping between corrosion current density and local strain based on this dataset; identifying the initiation time and location of cracks, voids, or peeling; and determining the corrosion-mechanical coupling failure threshold. This invention achieves in-situ, real-time, multi-physics joint characterization of copper foil corrosion behavior, improving the accuracy and engineering applicability of corrosion assessment.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical testing and material corrosion protection technology, specifically relating to a method for testing the corrosion behavior of copper foil based on an electrochemical workstation. Background Technology

[0002] With the rapid development of electronic devices towards high density, flexibility, and miniaturization, copper foil, as the core conductive layer of printed circuit boards and flexible electronic substrates, faces increasingly prominent corrosion reliability issues under complex service environments. Electrochemical testing methods, with their high sensitivity and quantitative analysis capabilities, have become the standard means of assessing metal corrosion behavior and are widely used in material corrosion resistance evaluation and mechanism research. These methods, by monitoring electrochemical response signals such as current and potential, can effectively reflect the thermodynamic tendency and kinetic rate of corrosion reactions, providing macroscopic electrochemical characterization of the corrosion process.

[0003] Electrochemical workstation-based techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy, and constant potential step analysis are widely used to simulate the corrosion behavior of copper foil in different electrolyte environments. These methods can reveal key parameters such as corrosion current density, passivation characteristics, and interfacial charge transfer resistance, thus providing a preliminary assessment of whether the material is prone to uniform or localized corrosion. However, such electrochemical signals essentially only reflect charge exchange processes at the electronic or ionic level and cannot directly capture the microstructural evolution and mechanical damage events that accompany the corrosion process.

[0004] In existing technologies, electrochemical testing and mechanical performance monitoring have long been disconnected: traditional electrochemical workstations lack the ability to perceive physical damage to the material itself, making it difficult to distinguish between mass loss caused by pure electrochemical dissolution and sudden fracture caused by stress corrosion cracking (SCC) or fatigue-corrosion coupling; although some studies have attempted to introduce optical microscopy or scanning probe technology to assist in observation, they are limited by the airtightness of the electrolytic cell, solution interference, and insufficient time resolution, and cannot achieve in-situ, real-time, and highly sensitive mechanical damage tracking.

[0005] Especially in scenarios where repeated bending of flexible copper foil is combined with electrochemical corrosion, the transient stress wave signals released by the initiation and propagation of microcracks are easily overlooked, leading to misjudgment of the failure mechanism. Therefore, there is an urgent need for an in-situ testing method that can simultaneously integrate electrochemical response and mechanical damage characteristics to achieve multi-dimensional and accurate diagnosis of copper foil corrosion behavior. Summary of the Invention

[0006] This invention provides a copper foil corrosion behavior testing method based on an electrochemical workstation, aiming to solve the technical problem that existing electrochemical testing technologies can only acquire current or potential signals and cannot directly monitor the mechanical damage that occurs during corrosion. This method constructs a multi-physics synchronous sensing architecture, introducing a high-precision mechanical response and microstructure evolution monitoring mechanism simultaneously with electrochemical excitation, thereby achieving joint characterization of the electrochemical activity and mechanical integrity degradation of copper foil during corrosion.

[0007] This invention provides a method for testing the corrosion behavior of copper foil based on an electrochemical workstation, comprising: The copper foil sample to be tested is fixed in a customized electrolytic cell fixture, which integrates a micro-strain sensing unit, an optical observation window, and a reference or auxiliary electrode interface. A preset electrochemical excitation signal is applied to the copper foil using an electrochemical workstation. The electrochemical excitation signal includes a potentiostatic polarization, potentiodynamic scanning, or electrochemical impedance spectroscopy test waveform. While applying electrochemical excitation, the micro-strain sensing unit collects local strain time-series data on the copper foil surface in real time. Simultaneously, a high-speed microscopic imaging system positioned outside the optical observation window continuously captures a dynamic image sequence of the microscopic morphology of the copper foil surface; The electrochemical response signal, strain time series data and micromorphology image sequence are time-stamped to form a ternary synchronous dataset. Based on the aforementioned ternary synchronous dataset, a quantitative mapping relationship between corrosion current density and local strain amplitude is established, and the starting time and spatial location of crack initiation, pore expansion, or lamellar peeling in the microscopic morphology image are identified. Based on the quantitative mapping relationship and damage initiation characteristics, the corrosion-mechanical coupling failure threshold of copper foil under a specific electrochemical environment is determined.

[0008] Preferably, the copper foil sample to be tested is fixed in a customized electrolytic cell fixture, including: The customized electrolytic cell fixture is made of polytetrafluoroethylene and has a central test chamber inside. The copper foil sample is flattened and adhered to the bottom of the test chamber by vacuum adsorption, ensuring that its working surface is fully exposed to the electrolyte and its back side is in close contact with the micro-strain sensing unit. The bottom of the central test chamber is provided with a circular light-transmitting hole with a diameter of 8 mm as the optical observation window; The reference electrode and auxiliary electrode are introduced through the threaded interface on the side wall of the fixture, and together with the copper foil working electrode, they form a three-electrode system.

[0009] Preferably, the micro-strain sensing unit is a distributed strain sensor based on the fiber grating principle, encapsulated on a flexible polyimide substrate, with three parallel sensing lines arranged along the length of the copper foil. The fiber optic grating sensor reads the reflection spectral shift using a wavelength demodulator and converts the spectral shift into a strain value according to the Bragg wavelength shift formula.

[0010] Preferably, the high-speed microscopic imaging system includes a confocal microscope lens, a high quantum efficiency CMOS image sensor, and a ring-shaped LED coaxial illumination source; During the test, the illumination source operated in pulse mode, with the pulse width strictly synchronized with the CMOS exposure window.

[0011] Preferably, the electrochemical response signal, strain time series data, and microstructure image sequence are time-stamped and aligned, including: The electrochemical workstation, wavelength demodulator, and high-speed microscopic imaging system are all connected to the same high-precision clock source. At the start of the test, the electrochemical workstation sends a synchronous trigger pulse, which simultaneously starts the data acquisition of the wavelength demodulator and the frame capture of the high-speed microscopic imaging system. All acquisition devices record the time offset of their respective data, with the rising edge of the trigger pulse as time 0. Linear interpolation is used to unify data with different sampling rates onto a common time axis.

[0012] Preferably, establishing a quantitative mapping relationship between corrosion current density and local strain amplitude includes: The instantaneous corrosion current value is extracted from the electrochemical response signal and divided by the exposed area of ​​the copper foil to obtain the corrosion current density. Extract the maximum principal strain value at the corresponding moment from the strain time series data; A two-dimensional scatter plot was constructed with corrosion current density as the abscissa and maximum principal strain as the ordinate; Piecewise linear fitting was performed on the scatter plot to identify the critical corrosion current density corresponding to the abrupt slope change point; When the corrosion current density exceeds this critical value, the copper foil is determined to have entered the mechanical instability stage.

[0013] Preferably, identifying the initiation time and spatial location of crack initiation, hole propagation, or lamellar delamination in a microscopic morphology image includes: Background subtraction is performed on consecutive frames of images to generate a dynamically changing mask; In the dynamically changing mask, the area growth rate of connected regions is detected; When the area growth rate of a certain connected region is greater than 5% per frame for three consecutive frames, and its shape conforms to linear characteristics, that is, the aspect ratio is greater than 5, it is marked as a crack initiation event. When a connected region is circular or elliptical and its area continues to expand, it is marked as a hole expansion event; When a large-area sheet-like region is detected to have shifted as a whole and separated from the substrate, it is marked as a layered peeling event; Record the frame number of the first occurrence of the above event, and combine it with the timestamp to determine its absolute occurrence time. At the same time, record the center pixel coordinates of the event and convert them into the actual spatial location.

[0014] Preferably, determining the corrosion-mechanical coupling failure threshold of copper foil under a specific electrochemical environment includes: A triple failure criterion is defined by combining the critical corrosion current density, the potential value corresponding to the crack initiation moment, and the test duration when the maximum principal strain reaches 0.3%. When any criterion is met, the copper foil is considered to have suffered corrosion-mechanical coupling failure. The failure threshold is represented in three-dimensional coordinates, including electrochemical parameters, mechanical parameters, and time parameters.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By integrating the electrochemical workstation with micro-strain sensing and high-speed microscopic imaging at the hardware level, the first in-situ, real-time, and quantitative joint monitoring of mechanical damage caused by copper foil corrosion during standard electrochemical testing was achieved. 2. The constructed ternary synchronous dataset breaks through the limitations of traditional electrochemical methods that rely solely on electrical signals to infer the degree of corrosion. It directly establishes a causal relationship between corrosion current density and local strain and micromorphological evolution. Based on this relationship, it can accurately identify the critical point of corrosion-mechanical coupling failure, providing a new technical means and quantitative basis for the life prediction, process optimization and service safety assessment of copper foil materials for high-reliability electronic devices. 3. This method does not require interruption of the testing process, maintaining the continuity and authenticity of the electrochemical environment, and significantly improving the scientific rigor and engineering applicability of corrosion behavior characterization. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall technical solution architecture of the present invention; Figure 2 This is a schematic diagram of the core principle framework of the electrochemical-mechanical-morphology ternary synchronous sensing and data fusion in this invention; Figure 3 This is a logical structure framework diagram of the customized electrolytic cell fixture and multi-physics field sensing integration in this invention; Figure 4This is a flowchart illustrating the synchronous triggering and data acquisition logic of the high-speed microscopic imaging and microstrain monitoring subsystem in this invention. Figure 5 This is a schematic diagram of the multi-level interaction relationship and data flow of the construction of the ternary synchronization dataset and timestamp alignment in this invention; Figure 6 This is a decision analysis logic framework diagram for determining the corrosion-mechanical coupling failure threshold in this invention. Detailed Implementation

[0017] refer to Figures 1 to 6 This invention provides a copper foil corrosion behavior testing method based on an electrochemical workstation. Its core lies in constructing a multi-physics field joint monitoring system that simultaneously senses electrochemical excitation, mechanical response, and micromorphological evolution, in order to solve the technical defects of traditional electrochemical testing that can only obtain current or potential signals and cannot directly observe the mechanical damage that occurs during the corrosion process.

[0018] This method integrates a high-precision micro-strain sensing unit and a high-speed microscopic imaging system into a standard electrochemical testing process, and achieves strict time alignment of three types of heterogeneous data. This establishes a quantitative mapping relationship between corrosion current density and local strain amplitude, identifies the initiation time and spatial location of typical mechanical damage events such as crack initiation, hole propagation, or lamellar peeling, and ultimately determines the corrosion-mechanical coupling failure threshold of copper foil under a specific electrochemical environment.

[0019] The method includes the following steps: S1, the copper foil sample to be tested is fixed in a customized electrolytic cell fixture, which integrates a micro-strain sensing unit, an optical observation window and a reference or auxiliary electrode interface; S2, apply a preset electrochemical excitation signal to the copper foil through an electrochemical workstation. The excitation signal includes constant potential polarization, potentiodynamic scanning or electrochemical impedance spectroscopy test waveform. S3, while applying electrochemical excitation, the local strain time series data of the copper foil surface are collected in real time through the micro-strain sensing unit; S4. Simultaneously, a high-speed microscopic imaging system located outside the optical observation window continuously captures a sequence of dynamic images of the microstructure of the copper foil surface at a sampling frequency of more than 1000 frames per second. S5, the electrochemical response signal, strain time series data and micromorphology image sequence are time-stamped to form a ternary synchronous dataset; S6. Based on the ternary synchronous dataset, establish a quantitative mapping relationship between corrosion current density and local strain amplitude, and identify the starting time and spatial location of crack initiation, hole expansion or lamellar peeling in the micro-morphology image. S7. Based on the quantitative mapping relationship and damage initiation characteristics, determine the corrosion-mechanical coupling failure threshold of the copper foil under a specific electrochemical environment.

[0020] In step S1, the customized electrolytic cell fixture is made of polytetrafluoroethylene and has a central test chamber inside. The copper foil sample is flattened and attached to the bottom of the test chamber by vacuum adsorption, ensuring that its working surface is completely exposed to the electrolyte and its back side is in close contact with the micro-strain sensing unit.

[0021] The key to this customized electrolytic cell fixture design lies in simultaneously satisfying the requirements of sealing for electrochemical testing, fit for mechanical sensing, and transparency for optical observation. Polytetrafluoroethylene (PTFE) material possesses excellent chemical inertness, tolerating common corrosive electrolytes such as sodium chloride, sulfuric acid, or nitric acid solutions, thus preventing the fixture itself from participating in the electrochemical reaction and interfering with the test results.

[0022] The central test chamber has a diameter of 10 mm and a depth of 5 mm, with an 8 mm diameter circular aperture at the bottom serving as an optical observation window. The copper foil sample, 12 micrometers thick, is cut into a 9 mm diameter circular sheet. Negative pressure is applied through a micro-vacuum channel at the bottom of the fixture to ensure it adheres tightly to the surface of the micro-strain sensing unit, eliminating strain measurement errors caused by sample warping.

[0023] The reference electrode and the auxiliary electrode are introduced through the threaded interface on the side wall of the fixture. The reference electrode is a saturated calomel electrode, and the auxiliary electrode is a platinum mesh electrode. Together with the copper foil working electrode, they form a three-electrode system and are connected to an external electrochemical workstation.

[0024] The micro-strain sensing unit is a distributed strain sensor based on the fiber Bragg grating principle. Its grating period is 532 nanometers, and it is encapsulated on a 10-micrometer-thick flexible polyimide substrate. Three parallel sensing lines are arranged along the length of the copper foil, each containing no fewer than 10 discrete measurement points, with a spatial resolution of 0.5% millimeters. The distributed strain sensor is in direct contact with the back of the copper foil via an adhesive layer. The adhesive layer uses a UV-curable acrylate adhesive with a thickness of less than 1 micrometer to ensure a strain transfer efficiency greater than 95%.

[0025] The fiber Bragg grating sensor is connected to an external wavelength demodulator via single-mode fiber. The demodulator has a sampling frequency of 2000 Hz and a wavelength resolution of 1.5 picometers. During the test, the copper foil undergoes localized deformation due to corrosion product formation, grain boundary slip, or stress concentration. This localized deformation is transmitted to the polyimide substrate through the adhesive layer, causing a change in the fiber Bragg grating period, which in turn leads to a shift in the Bragg reflection wavelength. The wavelength demodulator records the shift in real time and converts the spectral shift into a strain value according to the Bragg wavelength shift formula. The Bragg wavelength shift formula is expressed as: ; This is the Bragg wavelength shift. The initial Bragg wavelength, The effective photoelastic coefficient is set to 0.22. For axial strain. Based on this formula, and combined with the conversion coefficient of 1.2 picometers per microstrain obtained from experimental calibration, the wavelength drift at each measurement point can be accurately converted into a local strain value, forming a two-dimensional strain field matrix, where the rows correspond to spatial locations and the columns correspond to time series.

[0026] In step S2, the electrochemical workstation applies a preset electrochemical excitation signal to the copper foil.

[0027] The excitation signal is selected according to the test target: If the stability of copper foil in a static corrosion environment is to be evaluated, constant potential polarization is used, with the polarization potential set to be 500 mV positively biased relative to the open circuit potential for 30 minutes. If the passivation-activation behavior of copper foil under dynamic potential scanning is to be studied, then dynamic potential scanning is used with a scanning rate of 1 mV per second and a potential range from -800 mV to +600 mV. If the charge transfer impedance characteristics of the copper foil / electrolyte interface are analyzed, electrochemical impedance spectroscopy is used, with a perturbation voltage amplitude of 10 mV and a frequency range from 100 kHz to 10 mHz, taking 10 data points for every 10 octaves.

[0028] The electrochemical workstation records current and potential response signals at a sampling rate of 5000 Hz to ensure the capture of key features such as transient current spikes or potential jumps.

[0029] In step S3, the micro-strain sensing unit continuously acquires strain data during the application of electrochemical excitation. Since the corrosion process is typically accompanied by volume expansion, lattice distortion, or localized peeling, tensile or compressive strain will occur on the copper foil surface. The three parallel sensing lines are located at the center line of the copper foil and 1.5 mm on each side, respectively, covering the main stress concentration areas.

[0030] Each measurement point independently outputs strain time-series data, forming a 30-channel raw strain signal stream. In subsequent processing, principal component analysis is performed on the 30 strain values ​​at each time step, and the maximum principal strain is extracted as the representative mechanical response index for that time step. The maximum principal strain reflects the maximum tensile strength that the copper foil withstands at that time step and is a key parameter for judging mechanical instability.

[0031] In step S4, the high-speed microscopic imaging system simultaneously captures a dynamic image sequence of the microscopic morphology of the copper foil surface. The system includes a confocal microscope lens, a high-quantum-efficiency CMOS image sensor, and a ring-shaped LED coaxial illumination source. The confocal microscope lens has a numerical aperture of 0.75, a working distance of 2 mm, and a magnification of 50x, enabling clear resolution of sub-micron level surface features. The CMOS image sensor has a pixel size of 6.5 micrometers, and its global shutter exposure time is adjustable from 1 microsecond to 10 milliseconds, ensuring no motion blur during high-speed imaging.

[0032] The ring-shaped LED coaxial illumination source has a center wavelength of 470 nm and a light intensity stability better than 0.5%. Its pulsed operating mode is strictly synchronized with the CMOS exposure window: before each frame of image acquisition, the LED emits a 50-microsecond-wide light pulse to illuminate the copper foil surface, and the CMOS opens the global shutter for exposure during the pulse duration. This synchronization mechanism effectively suppresses dynamic blur caused by electrolyte convection or bubble movement, ensuring the sharpness and temporal consistency of the image sequence. The image acquisition frequency is set to 1200 frames per second, with each frame having a resolution of 1280×1024 pixels and a single frame data size of 1.2 megabytes.

[0033] In step S5, the electrochemical response signal, strain time-series data, and microscopic morphology image sequence are timestamped to form a ternary synchronous dataset. This timestamping alignment is achieved through a hardware trigger signal. The electrochemical workstation, wavelength demodulator, and high-speed microscopic imaging system are all connected to the same high-precision clock source, which outputs a square wave signal with a frequency of 10 MHz. At the start of the test, the electrochemical workstation sends a synchronous trigger pulse, which simultaneously activates the data acquisition of the wavelength demodulator and the frame capture of the high-speed microscopic imaging system.

[0034] All acquisition devices recorded the time offset of their respective data, with the rising edge of the trigger pulse as time 0. The original sampling rate of the electrochemical workstation was 5000 Hz, the micro-strain data was 2000 Hz, and the image frame rate was 1200 Hz. Subsequently, linear interpolation was used to unify the three types of data to a common time axis, with a reference sampling frequency of 1000 Hz for the common time axis.

[0035] For any common time point Seconds, the electrochemical signal is taken from the current value of the nearest sampling point. The strain data were obtained by two-point linear interpolation to obtain the maximum principal strain. The image sequence is selected from the closest ones. The frames are used as morphological representations at that moment. The resulting ternary synchronization dataset contains three parallel time series: and , This represents the total number of sampling points. Indicates a public time point The corresponding electrochemical voltage signal value, Indicates a public time point The corresponding morphological image.

[0036] In step S6, based on the ternary synchronous dataset, two core analysis tasks are performed. The first task is to establish a quantitative mapping relationship between corrosion current density and local strain amplitude.

[0037] Specifically, this includes: extracting instantaneous corrosion current values ​​from electrochemical response signals. Divide by the exposed area of ​​the copper foil Obtain corrosion current density Extract the maximum principal strain value at the corresponding time from the strain time series data. ;by x-axis A two-dimensional scatter plot is constructed with the vertical axis as the ordinate; piecewise linear fitting is performed on the scatter plot to identify the critical corrosion current density corresponding to the abrupt slope changes. .

[0038] When the corrosion current density is greater than At this point, the rate of increase of the maximum principal strain accelerates significantly, indicating that the copper foil has entered the mechanical instability stage. The second task is to identify the initiation time and spatial location of crack initiation, void propagation, or lamellar delamination in the microscopic morphology images. Specifically, this includes: Background subtraction processing is performed on consecutive frame images, that is, the pixel grayscale difference between the current frame and the previous frame is calculated to generate a dynamic change mask; in the dynamic change mask, the area growth rate of connected regions is detected. When the area growth rate of a certain connected region is greater than 5% per frame for 3 consecutive frames, and its shape conforms to linear characteristics (aspect ratio greater than 5), it is marked as a crack initiation event. When a connected region is circular or elliptical and its area continues to expand, it is marked as a hole expansion event; When a large-area sheet-like region is detected to have shifted as a whole and separated from the substrate, it is marked as a layered peeling event; Record the frame number of the first occurrence of the above event, and combine it with the timestamp to determine its absolute occurrence time. Simultaneously record the pixel coordinates of the event center. The calibration parameters of the microscope lens are converted into actual spatial positions. .

[0039] In step S7, based on the quantitative mapping relationship and damage initiation characteristics, the corrosion-mechanical coupling failure threshold of the copper foil under a specific electrochemical environment is determined.

[0040] This determination uses a triple failure criterion: The first criterion is that the corrosion current density reaches a critical value. ; The second criterion is the electrical potential value at the moment of crack initiation. ; The third criterion is the test duration when the maximum principal strain reaches 0.3%. .

[0041] When any criterion is met, the copper foil is considered to have suffered corrosion-mechanical coupling failure.

[0042] The failure threshold is expressed in three-dimensional coordinate form as follows: It comprehensively covers electrochemical parameters, mechanical parameters, and time parameters, providing a quantitative basis for predicting the service life of materials.

[0043] The testing system underlying the method includes a customized electrolytic cell fixture, an electrochemical workstation, a microstrain monitoring subsystem, a high-speed microscopic imaging subsystem, a synchronous control and data fusion unit, and a corrosion-mechanical coupling analysis module. The customized electrolytic cell fixture, as described above, enables sample fixation and multi-physics field integration. The electrochemical workstation uses a commercially available model and features constant potential, potentiodynamic scanning, and electrochemical impedance spectroscopy (EIS) testing capabilities. The microstrain monitoring subsystem consists of a fiber Bragg grating sensor and a wavelength demodulator, the latter possessing multi-channel parallel demodulation capabilities.

[0044] The high-speed microscopic imaging subsystem consists of a confocal microscope lens, a CMOS camera, and an LED light source, and supports external triggering synchronization. The synchronization control and data fusion unit is implemented using a field-programmable gate array (FPGA) chip, which is internally equipped with a timestamp generator, a multi-channel data buffer, and a gigabit Ethernet interface.

[0045] The timestamp generator receives an external 10 MHz clock signal with a counting accuracy of 100 nanoseconds; the multi-channel data buffer is a dual-port static random access memory with a capacity of 16 megabytes, supporting parallel writing by electrochemical workstations, wavelength demodulators, and high-speed microscopic imaging systems via independent buses; the gigabit Ethernet interface transmits structured data streams to the host computer.

[0046] The corrosion-mechanical coupling analysis module is deployed on the host computer, and its software architecture includes a data parsing layer, a feature extraction layer, and a decision-making layer. The data parsing layer reads the structured data stream and separates the electrochemical signals, strain matrix, and image sequence; the feature extraction layer performs corrosion current density calculation, principal strain field reconstruction, and dynamic mask generation; the decision-making layer runs a preset failure logic rule engine and outputs failure state flags and corresponding threshold parameters.

[0047] This method maintains the continuity and authenticity of the electrochemical environment during implementation, enabling in-situ acquisition of multiphysics data without interrupting testing, significantly improving the scientific rigor and engineering applicability of corrosion behavior characterization. Through the construction of a ternary synchronous dataset, the causal relationship between the surge in corrosion current density and abrupt changes in local strain and microscopic damage events is directly revealed, providing a novel technical approach for process optimization, lifetime prediction, and safety assessment of copper foil materials for high-reliability electronic devices.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for testing the corrosion behavior of copper foil based on an electrochemical workstation, characterized in that, include: The copper foil sample to be tested is fixed in a customized electrolytic cell fixture, which integrates a micro-strain sensing unit, an optical observation window, and a reference or auxiliary electrode interface. A preset electrochemical excitation signal is applied to the copper foil using an electrochemical workstation. The electrochemical excitation signal includes a potentiostatic polarization, potentiodynamic scanning, or electrochemical impedance spectroscopy test waveform. While applying electrochemical excitation, the micro-strain sensing unit collects local strain time-series data on the copper foil surface in real time. Simultaneously, a high-speed microscopic imaging system positioned outside the optical observation window continuously captures a dynamic image sequence of the microscopic morphology of the copper foil surface; The electrochemical response signal, strain time series data and micromorphology image sequence are time-stamped to form a ternary synchronous dataset. Based on the aforementioned ternary synchronous dataset, a quantitative mapping relationship between corrosion current density and local strain amplitude is established, and the initiation time and spatial location of crack initiation, void propagation, or lamellar delamination in the microscopic morphology images are identified, including: Background subtraction is performed on consecutive frames of images to generate a dynamically changing mask; In the dynamically changing mask, the area growth rate of connected regions is detected; When the area growth rate of a certain connected region is greater than 5% per frame for three consecutive frames, and its shape conforms to linear characteristics, that is, the aspect ratio is greater than 5, it is marked as a crack initiation event. When a connected region is circular or elliptical and its area continues to expand, it is marked as a hole expansion event; When a large-area sheet-like region is detected to have shifted as a whole and separated from the substrate, it is marked as a layered peeling event; Record the frame number of the first occurrence of the above event, and combine it with the timestamp to determine its absolute occurrence time. At the same time, record the center pixel coordinates of the event and convert them into the actual spatial location. Based on the quantitative mapping relationship and damage initiation characteristics, the corrosion-mechanical coupling failure threshold of copper foil under a specific electrochemical environment is determined, including: A triple failure criterion is defined by combining the critical corrosion current density, the potential value corresponding to the crack initiation moment, and the test duration when the maximum principal strain reaches 0.3%. When any criterion is met, the copper foil is considered to have suffered corrosion-mechanical coupling failure. The failure threshold is represented in three-dimensional coordinates, including electrochemical parameters, mechanical parameters, and time parameters.

2. The method for testing the corrosion behavior of copper foil based on an electrochemical workstation according to claim 1, characterized in that, The copper foil sample to be tested is fixed in a customized electrolytic cell fixture, including: The customized electrolytic cell fixture is made of polytetrafluoroethylene and has a central test chamber inside. The copper foil sample is flattened and adhered to the bottom of the test chamber by vacuum adsorption, ensuring that its working surface is fully exposed to the electrolyte and its back side is in close contact with the micro-strain sensing unit. The bottom of the central test chamber is provided with a circular light-transmitting hole with a diameter of 8 mm as the optical observation window; The reference electrode and auxiliary electrode are introduced through the threaded interface on the side wall of the fixture, and together with the copper foil working electrode, they form a three-electrode system.

3. The method for testing the corrosion behavior of copper foil based on an electrochemical workstation according to claim 2, characterized in that, The micro-strain sensing unit is a distributed strain sensor based on the fiber optic grating principle, encapsulated on a flexible polyimide substrate, with three parallel sensing lines arranged along the length of the copper foil. The strain sensor reads the reflection spectral shift using a wavelength demodulator and converts the spectral shift into a strain value according to the Bragg wavelength shift formula.

4. The method for testing the corrosion behavior of copper foil based on an electrochemical workstation according to claim 3, characterized in that, The high-speed microscopic imaging system includes a confocal microscope lens, a high quantum efficiency CMOS image sensor, and a ring-shaped LED coaxial illumination source. During the test, the illumination source operated in pulse mode, with the pulse width strictly synchronized with the CMOS exposure window.

5. The method for testing the corrosion behavior of copper foil based on an electrochemical workstation according to claim 4, characterized in that, The electrochemical response signal, strain time series data, and microstructure image sequence are time-stamped and aligned, including: The electrochemical workstation, wavelength demodulator, and high-speed microscopic imaging system are all connected to the same high-precision clock source. At the start of the test, the electrochemical workstation sends a synchronous trigger pulse, which simultaneously starts the data acquisition of the wavelength demodulator and the frame capture of the high-speed microscopic imaging system. All acquisition devices record the time offset of their respective data, with the rising edge of the trigger pulse as time 0. Linear interpolation is used to unify data with different sampling rates onto a common time axis.

6. The method for testing the corrosion behavior of copper foil based on an electrochemical workstation according to claim 5, characterized in that, Establish a quantitative mapping relationship between corrosion current density and local strain amplitude, including: The instantaneous corrosion current value is extracted from the electrochemical response signal and divided by the exposed area of ​​the copper foil to obtain the corrosion current density. Extract the maximum principal strain value at the corresponding moment from the strain time series data; A two-dimensional scatter plot was constructed with corrosion current density as the abscissa and maximum principal strain as the ordinate; Piecewise linear fitting was performed on the scatter plot to identify the critical corrosion current density corresponding to the abrupt slope change point; When the corrosion current density exceeds this critical value, the copper foil is determined to have entered the mechanical instability stage.

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