An insulation film space charge in-situ measurement platform and test method

Abstract

The application discloses an insulation film space charge in-situ measurement platform and a test method, and the measurement platform comprises a test module, an optical loading module, a mechanical loading module, a voltage loading module and a signal acquisition module; the test module comprises a glass prism, a target electrode and a lower electrode which are sequentially and layerwisely arranged along a first direction; the optical loading module is used for inputting pulse laser to the glass prism; the pulse laser is shot into the glass prism along a second direction, and then propagates to the target electrode along the first direction after being folded by the glass prism; the first direction is not parallel to the second direction; the mechanical loading module is used for applying mechanical load to the glass prism, and the application direction of the mechanical load is parallel to the first direction; the voltage loading module is used for establishing a direct current electric field in the insulation film; and the signal acquisition module is used for collecting displacement current signals generated by the insulation film, so as to realize the in-situ measurement of the space charge of the insulation film under the combined action of the mechanical load and the electric field.

Description

Technical Field

[0001] This invention relates to the field of high voltage and insulation testing technology, specifically to an in-situ measurement platform and test method for the space charge of insulating thin films. Background Technology

[0002] As high-voltage power equipment and power electronic devices develop towards higher power density and miniaturization, insulating film materials are typically affected not only by external electric fields during actual operation but also by mechanical factors such as encapsulation pressure, mechanical loads, and residual stress within the material. Mechanical stress alters the migration process of charge carriers within the insulating material, as well as the accumulation and transport behavior of space charge, thereby affecting the internal electric field distribution and potentially leading to problems such as localized electric field distortion, insulation aging, and even breakdown. Therefore, accurate measurement of the space charge distribution within the insulating film is crucial for analyzing the failure mechanisms of insulating materials under complex operating conditions, evaluating material performance, and improving the operational reliability of power equipment.

[0003] Currently, the Laser-Induced Pressure Pulse (LIPP) method is a widely used non-destructive testing method for measuring the space charge distribution inside solid dielectrics. However, existing LIPP measurement platforms are typically designed for single electric field environments. When further mechanical stress loading is required, traditional mechanical loading structures usually employ metal blocks or rigid loading components. These structures can obstruct the laser propagation path, preventing the laser from effectively acting on the target surface, thus making it difficult to simultaneously meet the requirements of mechanical loading and optical detection.

[0004] Therefore, existing LIPP space charge measurement devices cannot simultaneously meet the requirements of laser optical path transmission and mechanical stress loading, and cannot realize in-situ space charge measurement of insulating films under electromechanical coupling conditions. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose an in-situ measurement platform and test method for space charge of insulating thin films, thereby solving the technical problem that the existing LIPP space charge measurement device cannot realize in-situ space charge measurement of insulating thin films under electromechanical coupling conditions.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an in-situ measurement platform for space charge of an insulating thin film, comprising: a testing module, including a glass prism, a target electrode, and a lower electrode stacked sequentially along a first direction, with the thin film to be tested placed between the target electrode and the lower electrode; an optical loading module disposed on one side of the glass prism, for inputting pulsed laser light into the glass prism, the pulsed laser light entering the glass prism along a second direction and propagating to the target electrode along the first direction after being refracted by the glass prism, the first direction being non-parallel to the second direction; a mechanical loading module connected to the glass prism, for applying a mechanical load to the glass prism, so that the mechanical load is transmitted to the thin film to be tested through the glass prism and the target electrode, and the direction of application of the mechanical load is parallel to the first direction; a voltage loading module connected to the target electrode, for applying a DC voltage to the target electrode to establish a DC electric field inside the thin film to be tested; and a signal acquisition module electrically connected to the lower electrode, for acquiring the displacement current signal generated when a pressure wave acts on the thin film to be tested, so as to obtain the space charge distribution inside the thin film to be tested.

[0007] In some embodiments, the inner reflecting surface of the glass prism includes a pressure-bearing section and a reflecting section. The pressure-bearing section is arranged perpendicular to the first direction and is used to bear the mechanical load applied by the mechanical loading module. The reflecting section is arranged at an angle relative to the second direction and is used to reflect the pulsed laser propagating along the second direction back to propagating along the first direction.

[0008] In some embodiments, the pressure-bearing section includes a first pressure-bearing section and a second pressure-bearing section, which are respectively disposed on both sides of the reflective section, and the total length of the pressure-bearing section accounts for 20% to 40% of the total length of the inner reflective surface.

[0009] In some embodiments, the target electrode includes a conductive part and a light-absorbing part. The conductive part is disposed in contact with the thin film under test to establish an electric field inside the thin film under test. The light-absorbing part is disposed on the side of the conductive part away from the thin film under test to absorb pulsed laser light and generate pressure waves.

[0010] In some embodiments, the optical loading module includes a pulsed laser, a mirror, and an aperture. The pulsed laser is used to generate pulsed laser light, the mirror is used to adjust the pulsed laser light to propagate along a second direction, and the aperture is used to adjust the beam size of the pulsed laser light.

[0011] In some embodiments, the lower electrode includes a measuring electrode, a grounding protection ring, and a metal shielding shell. The grounding protection ring is disposed around the periphery of the measuring electrode, and the metal shielding shell is disposed on the outside of the measuring electrode and the grounding protection ring.

[0012] In some embodiments, an acoustic coupling layer is provided on the side of the lower electrode that contacts the film under test, and the acoustic coupling layer is formed by coating with an acoustic coupling agent.

[0013] In some embodiments, the mechanical loading module further includes a tensile loading component, which includes a clamp and a drive member. The clamp is disposed in a plane perpendicular to the first direction and is used to clamp the film to be tested. The drive member is connected to the clamp and is used to drive the clamp to apply a lateral tensile load to the film to be tested.

[0014] In some embodiments, the voltage loading module includes a high-voltage output terminal, a protective resistor is connected in series at the high-voltage output terminal, and a bypass capacitor is connected in parallel between the high-voltage output terminal and ground.

[0015] Secondly, the present invention also provides a test method based on the above-mentioned in-situ measurement platform for space charge of insulating thin film, comprising the following steps: attaching or coating a target electrode to one side surface of the film to be tested, and placing the film to be tested above the lower electrode, such that the film to be tested is located between the target electrode and the lower electrode; applying a mechanical load to the film to be tested through a mechanical loading module, the mechanical load including a mechanical load applied along a first direction and / or a mechanical load applied perpendicular to the first direction; applying a preset high voltage DC current to the target electrode through a voltage loading module to establish a DC electric field inside the film to be tested bearing the mechanical load; inputting a pulsed laser to a glass prism through an optical loading module, so that the pulsed laser enters the glass prism along a second direction, and after being refracted by the glass prism, propagates along the first direction to act on the target electrode and generate a pressure wave acting on the film to be tested; acquiring the displacement current signal generated when the pressure wave acts on the film to be tested through a signal acquisition module, and obtaining the space charge distribution inside the film to be tested based on the displacement current signal.

[0016] Compared with existing technologies, the in-situ space charge measurement platform and experimental method for insulating thin films provided by this invention, by setting up a glass prism with an internal reflection structure, enables the glass prism to simultaneously adjust the laser propagation direction and transfer mechanical load. The glass prism deflects the pulsed laser, ensuring that the laser's direction of action is consistent with the mechanical loading direction, thereby avoiding interference from the mechanical loading structure on the optical path and achieving in-situ measurement of the space charge of the insulating thin film under mechanical load. Furthermore, this application establishes a DC electric field on top of the mechanical load, placing the film under test in a test environment where mechanical stress and an electric field act together, more closely resembling actual working conditions and improving the authenticity and reference value of the space charge detection results. Attached Figure Description

[0017] Figure 1 This is a structural block diagram of an in-situ space charge measurement platform for insulating thin films provided in an embodiment of the present invention; Figure 2 This is an equivalent circuit diagram of an in-situ space charge measurement platform for insulating thin films provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the test module provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the lower electrode provided in an embodiment of the present invention; Figure 5 This is a space charge distribution diagram provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 10. Test module; 11. Glass prism; 111. Pressure-bearing section; 112. Reflection section; 12. Target electrode; 13. Lower electrode; 131. Measuring electrode; 132. Grounding protection ring; 133. Metal shielding shell; 20. Optical loading module; 21. Pulsed laser; 22. Reflector; 23. Aperture; 30. Mechanical loading module; 31. Tensile loading assembly; 311. Fixture; 312. Drive component; 40. Voltage loading module; 41. High voltage output terminal; 42. Protection resistor; 43. Bypass capacitor; 50. Signal acquisition module; 51. Coaxial signal interface; 52. Signal amplifier; 53. Oscilloscope; 60. Thin film under test. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] To address the technical problem that existing LIPP space charge measurement devices cannot achieve in-situ space charge measurement of insulating films under electromechanical coupling conditions, this invention provides an in-situ space charge measurement platform and experimental method for insulating films, which can realize in-situ space charge distribution measurement of insulating films under electromechanical coupling conditions, thereby improving the accuracy and reliability of the measurement results.

[0021] It should be noted that the in-situ space charge measurement platform and test method for insulating thin films described in this invention are used for, but not limited to, high voltage and insulation testing. For ease of explanation, this invention will only use the application of the in-situ space charge measurement platform and test method for insulating thin films in high voltage and insulation testing equipment as an example. The principle of the in-situ space charge measurement platform and test method for insulating thin films in other types of equipment is essentially the same as that in high voltage and insulation testing equipment, and will not be described in detail here.

[0022] Please see Figures 1 to 3 , Figure 1 This is a structural block diagram of an in-situ space charge measurement platform for insulating thin films according to one embodiment of the present invention. Figure 2 This is an equivalent circuit diagram of an in-situ space charge measurement platform for insulating thin films provided in an embodiment of the present invention. Figure 3This is a schematic diagram of the structure of the test module 10 provided in an embodiment of the present invention. The measurement platform includes the test module 10, the optical loading module 20, the mechanical loading module 30, the voltage loading module 40, and the signal acquisition module 50, aiming to realize in-situ measurement of space charge of the insulating film under the combined action of mechanical load and electric field.

[0023] The test module 10, serving as the main structure for space charge detection of the insulating film under test, includes a glass prism 11, a target electrode 12, and a lower electrode 13 stacked sequentially along a first direction. The film under test 60 is placed between the target electrode 12 and the lower electrode 13, such that the target electrode 12 and the lower electrode 13 are in contact with both sides of the film under test 60, respectively. During the test, the target electrode 12 receives pulsed laser light and generates a pressure wave, while also serving as part of the electric field loading structure to create the electric field environment required for detection within the film under test 60. The lower electrode 13 outputs a corresponding displacement current signal under the action of the pressure wave, thereby providing a detection signal for subsequent space charge distribution analysis.

[0024] The glass prism 11 is positioned on the side of the target electrode 12 away from the film 60 under test. It serves not only as the optical path transmission structure for the pulsed laser but also as the structure for transmitting mechanical loads. An internal reflecting surface is formed inside the glass prism 11. After the pulsed laser enters the glass prism 11, its direction is changed by the internal reflecting surface, causing the pulsed laser, originally propagating in the second direction, to be deflected and propagate in the first direction, acting on the target electrode 12. Since the propagation direction of the deflected laser is consistent with the stacking direction of the test module 10, the pulsed laser can act on the target electrode 12 along the direction of the target electrode 12, thus meeting the optical path requirements in the laser-induced pressure wave detection process.

[0025] An optical loading module 20 is disposed on one side of the glass prism 11 and is used to input pulsed laser light into the glass prism 11. During operation, the pulsed laser light generated by the optical loading module 20 enters the glass prism 11 along a second direction and propagates inside the glass prism 11. When the pulsed laser light reaches the inner reflecting surface, the reflection effect inside the glass prism 11 changes the direction of laser propagation, converting the pulsed laser light from the second direction to the first direction, and further acting on the target electrode 12. Through this optical path design, the laser input direction does not need to coincide with the mechanical loading direction, avoiding the problem of interference between the optical path and the mechanical loading path in traditional detection structures, and improving the flexibility of the measurement platform's structural layout.

[0026] The mechanical loading module 30 is configured in conjunction with the glass prism 11 to apply a mechanical load to the glass prism 11. During space charge testing, the mechanical loading module 30 applies a load to the glass prism 11 along a first direction. After receiving the mechanical load, the glass prism 11 sequentially transfers the load to the target electrode 12 and the film under test 60, placing the film under test 60 in a preset mechanical stress state. Since the mechanical loading direction is consistent with the laser propagation direction after folding, the glass prism 11 does not obstruct or interfere with the laser propagation path while bearing the mechanical load, achieving a compatible arrangement between the mechanical loading structure and the optical detection structure.

[0027] The voltage loading module 40 is connected to the target electrode 12 and is used to apply a DC voltage to the target electrode 12 to establish a DC electric field inside the film under test 60. After the mechanical load is applied, a preset voltage is applied to the target electrode 12 through the voltage loading module 40, so that the film under test 60 is in a state under the combined action of mechanical load and DC electric field. In this way, the working state of the insulating film under the combined influence of mechanical and electric field factors in the actual operating environment can be simulated, thereby improving the correspondence between the space charge detection results and the actual application environment.

[0028] The signal acquisition module 50 is connected to the lower electrode 13 and is used to acquire the displacement current signal generated when a pressure wave acts on the film under test 60. During the measurement process, after the pulsed laser acts on the target electrode 12, the target electrode 12 generates a pressure wave. The pressure wave further acts on the film under test 60, causing the space charge inside the film under test 60 to respond and generate a corresponding displacement current signal. The signal acquisition module 50 acquires this displacement current signal and analyzes the acquired signal to obtain the space charge distribution inside the film under test 60.

[0029] In this embodiment, by setting a glass prism 11 with an internal reflection structure, the glass prism 11 simultaneously possesses the functions of optical path deflection and mechanical load transfer. This ensures that the laser can act on the target electrode 12 while maintaining the mechanical loading direction consistent with the laser propagation direction after deflection, thus solving the problem of easy interference of the optical path by the mechanical loading structure in traditional space charge measurement. Simultaneously, this measurement platform can perform space charge detection under the condition that the insulating film is subjected to mechanical load and a DC electric field is established, realizing in-situ measurement under electromechanical coupling conditions and improving the applicability and reliability of space charge testing of insulating films.

[0030] In one embodiment, the inner reflecting surface of the glass prism 11 includes a pressure-bearing section 111 and a reflecting section 112, which are interconnected. The pressure-bearing section 111 bears the mechanical load applied by the mechanical loading module 30 and transmits the mechanical load to the target electrode 12 and the thin film 60 under test. The reflecting section 112 reflects the pulsed laser entering the glass prism 11 to change the propagation direction of the pulsed laser, causing it to propagate along a first direction and act on the target electrode 12.

[0031] Specifically, the pressure-bearing section 111 is arranged perpendicular to the first direction so that the mechanical load applied by the mechanical loading module 30 can act on the pressure-bearing section 111 along the first direction. When the mechanical loading module 30 applies a load to the glass prism 11, the mechanical load can be stably applied to the glass prism 11 through the pressure-bearing section 111, and further transferred to the target electrode 12 and the film under test 60 through the glass prism 11, so that the film under test 60 is in a preset mechanical stress state. By setting the pressure-bearing section 111 to a structural form perpendicular to the mechanical loading direction, the effective interaction area between the mechanical load and the pressure-bearing section 111 can be increased, and the stability during the mechanical load transfer process can be improved.

[0032] The reflecting section 112 is inclined relative to the second direction so that the pulsed laser light incident on the glass prism 11 along the second direction is reflected by the reflecting section 112 and changes its propagation direction, then propagates along the first direction to the target electrode 12. In one specific embodiment, the first direction is perpendicular to the second direction, that is, the incident direction of the pulsed laser light is perpendicular to the mechanical loading direction. In this case, to achieve the propagation of the pulsed laser light from the second direction to the first direction, the reflecting section 112 can be set as an inclined surface at a 45° angle to the first direction, so that the pulsed laser light incident along the second direction is reflected by the reflecting section 112 and then propagates along the first direction.

[0033] It should be noted that the angle between the first direction and the second direction, as well as the tilt angle of the reflector 112, can be adjusted according to the optical path arrangement requirements. It is not limited to the above-mentioned vertical setting and 45° angle implementation method. As long as the pulsed laser can be reflected by the reflector 112 and propagate along the first direction, and the coordination requirements of the mechanical loading path and the optical detection path are met, it is acceptable.

[0034] In this embodiment, through the above-described structural configuration, the inner reflecting surface of the glass prism 11 can simultaneously achieve the functions of mechanical load bearing and pulsed laser direction conversion, so that the mechanical loading direction is consistent with the pulsed laser action direction. This avoids the problem of mechanical loading structure interfering with the laser propagation path in traditional measurement devices, improves the flexibility of the measurement platform structure layout, and ensures the reliability of space charge detection of the insulating film under mechanical load.

[0035] Furthermore, in some embodiments, the pressure-bearing section 111 includes a first pressure-bearing section 111 and a second pressure-bearing section 111. The first pressure-bearing section 111 and the second pressure-bearing section 111 are respectively disposed on both sides of the reflecting section 112. By distributing the pressure-bearing sections 111 on both sides of the reflecting section 112, the inner reflecting surface can achieve the function of light path reflection while forming symmetrical or approximately symmetrical load-bearing areas on both sides of the reflecting section 112. When the mechanical loading module 30 applies a mechanical load to the glass prism 11, the first pressure-bearing section 111 and the second pressure-bearing section 111 can jointly bear the external load and uniformly transfer the load to the interior of the glass prism 11, reducing structural deformation caused by localized stress concentration and improving the stability of the glass prism 11 when bearing mechanical loads.

[0036] Meanwhile, by controlling the total length of the pressure-bearing section 111 within the range of 20% to 40% of the total length of the inner reflecting surface, sufficient reflective area can be reserved for the reflecting section 112 while ensuring effective transmission of mechanical load, enabling the pulsed laser to stably complete direction conversion via the reflecting section 112. When the proportion of the pressure-bearing section 111 is too small, the pressure-bearing area is limited, and the mechanical load is easily concentrated near the reflecting section 112, which may affect the structural stability of the glass prism 11 and the stability of the laser reflection path. When the proportion of the pressure-bearing section 111 is too large, it will compress the effective area of ​​the reflecting section 112, reduce the optical path adjustment space, and is not conducive to the efficient reflection of the pulsed laser. Therefore, by reasonably setting the size ratio between the pressure-bearing section 111 and the reflecting section 112, the mechanical load-bearing capacity and optical reflection performance of the glass prism 11 can be balanced.

[0037] In one embodiment, the target electrode 12 includes a conductive portion and a light-absorbing portion, which simultaneously realizes the functions of electric field loading and photoacoustic conversion. The conductive portion is disposed in contact with the film under test 60 to transmit DC voltage, thereby forming the electric field required for detection inside the film under test 60; the light-absorbing portion is disposed on the side of the conductive portion away from the film under test 60 to absorb pulsed laser energy and convert the laser energy into a pressure wave acting on the film under test 60.

[0038] In specific implementation, the target electrode 12 can adopt a single-layer structure or a composite structure. When the target electrode 12 adopts a single-layer structure, the target electrode 12 as a whole serves as both a conductive electrode and a light-absorbing target material, and its material can be metal, polymer, or semi-conductive material. When the target electrode 12 adopts a composite structure, it includes an electrode layer and a light-absorbing target material layer, with the light-absorbing target material layer disposed on the side of the electrode layer away from the film 60 under test. The electrode layer can be a metal foil attached to the surface of the film 60 under test, a metallization layer attached to the surface of the film 60 under test, or a conductive paste layer coated on the surface of the film 60 under test; the light-absorbing target material layer can be formed by coating or spraying, and can be made of carbon-based materials, photoacoustic conversion polymers, or semi-conductive materials.

[0039] Furthermore, when the electrode layer uses a metal foil, to reduce the electric field concentration in the edge region under high voltage conditions, the edge of the metal foil can be configured as an arc-shaped transition structure, and / or an insulating encapsulating medium can be wrapped around the junction of the metal foil edge and the film under test 60 to suppress tip discharge and improve the stability of the test process. Through the above configuration, the target electrode 12 can meet the requirements of DC electric field loading and pressure wave generation, and by separating the functions of the conductive and light-absorbing parts, it improves the laser energy conversion efficiency and the reliability of space charge measurement.

[0040] In one embodiment, the optical loading module 20 includes a pulsed laser 21, a reflector 22, and an aperture 23. The pulsed laser 21 is used to generate pulsed laser light, the reflector 22 is used to adjust the propagation direction of the pulsed laser light so that the pulsed laser light enters the glass prism 11 along a second direction, and the aperture 23 is used to adjust the beam size of the pulsed laser light so that the pulsed laser light acts on the target electrode 12 with a preset spot size.

[0041] In this embodiment, a pulsed laser 21 serves as the light source, outputting a pulsed laser with a high peak power to enable the target electrode 12 to absorb laser energy and generate a pressure wave. In one specific implementation, the pulsed laser 21 can be a picosecond pulsed laser with a center wavelength of 1064 nm and a pulse width of less than 10 ps, ​​its output power can be set to 70 W, and its repetition frequency can be set to 20 kHz. By employing a short-pulse-width laser source, the laser energy can act on the target electrode 12 in a shorter time, which is beneficial for generating a transient pressure wave, thereby meeting the requirements for pressure wave response speed during space charge measurement.

[0042] A reflector 22 is positioned between the pulsed laser 21 and the glass prism 11 to alter the propagation path of the pulsed laser, ensuring it enters the glass prism 11 in a preset direction. Since the installation position between the optical loading module 20 and the glass prism 11 may be limited by the overall structure of the test platform, the reflector 22 allows for flexible adjustment of the laser propagation path, enabling the pulsed laser to enter the glass prism 11 in a second direction. This, combined with the internal reflective surface of the glass prism 11, completes the subsequent direction conversion, thus meeting the optical path arrangement requirements.

[0043] An aperture 23 is positioned along the pulsed laser propagation path to shape and adjust the size of the pulsed laser beam, thereby controlling the laser irradiation area acting on the surface of the target electrode 12. In one specific embodiment, the aperture 23 can shape the laser beam into a spot with a diameter of approximately 2 mm, concentrating the laser energy onto the corresponding area of ​​the target electrode 12 and improving the consistency of the pressure wave generation process. Simultaneously, by adjusting the opening size of the aperture 23, the laser action area can be adjusted according to different sizes of target electrodes 12 and different testing requirements, improving the adaptability of the measurement platform.

[0044] In this embodiment, through the above-mentioned settings, the optical loading module 20 can realize the generation, direction adjustment and beam shaping of pulsed laser, so that the pulsed laser can stably enter the glass prism 11 along the predetermined direction, and after being folded by the glass prism 11, it acts on the target electrode 12, providing stable pressure wave excitation conditions for in-situ measurement of space charge of insulating thin film.

[0045] In one embodiment, please refer to Figure 4 , Figure 4 This is a schematic diagram of the lower electrode 13 provided in an embodiment of the present invention. The lower electrode 13 includes a measuring electrode 131, a grounding protection ring 132, and a metal shielding shell 133. The measuring electrode 131 is used to contact the film under test 60 and collect the displacement current signal generated under the action of pressure wave. The grounding protection ring 132 is disposed around the measuring electrode 131 and connected to the grounding terminal. It is used to improve the electric field distribution around the measuring electrode 131, reduce the electric field concentration phenomenon in the electrode edge region, and thus reduce the influence of edge effect on the space charge measurement result.

[0046] A metal shielding shell 133 is disposed outside the measuring electrode 131 and the grounding protection ring 132 and connected to the grounding terminal to form electromagnetic shielding for the measuring electrode 131, reducing the interference of external electromagnetic noise on the weak detection signal. In one specific embodiment, the lower electrode 13 can be made of a metal material with good conductivity, such as brass. The diameter of the measuring electrode 131 can be set to 4 mm, the inner diameter of the grounding protection ring 132 can be set to 8 mm, and the outer diameter can be set to 10 mm. The edge height of the metal shielding shell 133 can be lower than the upper surface of the measuring electrode 131 and the grounding protection ring 132 to avoid affecting the contact state between the measuring electrode 131 and the film 60 under test.

[0047] Furthermore, the displacement current signal output by the measuring electrode 131 can be transmitted to the signal amplifier 52 via the coaxial signal interface 51, and after processing by the signal amplifier 52, it is input to the oscilloscope 53 for acquisition and display. By adopting a coaxial transmission method, external interference during signal transmission can be reduced, and the fidelity of high-frequency transient signals can be improved.

[0048] In some embodiments, the signal acquisition process can also be configured with a triggering unit to achieve synchronous control of the laser excitation process and the signal acquisition process. The triggering signal of the triggering unit can be selected according to the test requirements, such as the synchronous electrical signal output by the pulsed laser 21, the photoelectric detection signal used to detect the laser scattered light pulse, or a threshold triggering signal set based on the amplitude of the displacement current signal, thereby improving the accuracy of transient displacement current signal acquisition.

[0049] Furthermore, since the lower electrode 13 and the test film 60 are made of different materials, there is a certain difference in acoustic impedance between them. When pressure waves propagate at their interface, interface reflection is easily generated, thereby reducing the effective transmission efficiency of the pressure waves and affecting the intensity of the detection signal. Therefore, in some embodiments, an acoustic coupling layer is provided on the side of the lower electrode 13 that contacts the test film 60, so that a continuous acoustic transmission interface is formed between the lower electrode 13 and the test film 60. The acoustic coupling agent can fill the tiny gaps that may exist between the contact surfaces of the lower electrode 13 and the test film 60, reducing the influence of low acoustic impedance media such as air on the propagation of pressure waves, thereby reducing acoustic wave reflection at the interface and improving the transmission efficiency of pressure waves towards the lower electrode 13.

[0050] In this embodiment, the above settings can improve the response intensity of the displacement current signal during the action of the pressure wave, enabling the signal acquisition module 50 to more accurately acquire the detection signal generated by the change of space charge inside the film under test 60, thereby improving the accuracy and reliability of the space charge measurement results.

[0051] In one embodiment, the mechanical loading module 30 further includes a tensile loading component 31, which applies an in-plane tensile load perpendicular to a first direction to the film 60 under test to simulate the transverse mechanical stress experienced by the insulating film in practical applications. The tensile loading component 31 includes a clamp 311 and a drive member 312. The clamp 311 is disposed in a plane perpendicular to the first direction and clamps opposite sides of the film 60 under test, ensuring the film 60 remains stably fixed and preventing slippage or localized stress concentration during the stretching process. The drive member 312 is connected to the clamp 311 and drives the clamp 311 to move in mutually distancing directions, thereby causing transverse tensile deformation of the film 60 clamped between the clamps 311. During the test, by adjusting the movement distance or output load of the drive member 312, the degree of stretching applied to the film 60 under test can be changed, allowing the film 60 to be subjected to different mechanical stress states for space charge measurement.

[0052] In this embodiment, by setting up the tensile loading component 31, the film under test 60 can be subjected to both the normal mechanical load transmitted by the glass prism 11 and the transverse tensile load, thereby forming a multi-directional mechanical stress loading environment. Combined with the DC electric field established by the voltage loading module 40, the measurement platform can more closely approximate the electromechanical coupling state of the insulating film during actual operation, improving the authenticity and reference value of the space charge measurement results.

[0053] In one embodiment, the voltage loading module 40 includes a high-voltage output terminal 41 for applying a DC high voltage to the target electrode 12 to establish a stable DC electric field inside the film under test 60. During space charge measurement, since the displacement current signal generated by the space charge response inside the film under test 60 is a transient and weak signal, and a relatively high voltage exists in the test environment, it is necessary to ensure the stability of the high-voltage loading process while avoiding the influence of the high-voltage power supply on the detection signal. Therefore, a protective resistor 42 is connected in series with the high-voltage output terminal 41, and a bypass capacitor 43 is connected in parallel between the high-voltage output terminal 41 and ground.

[0054] The protective resistor 42 is connected in series at the high-voltage output terminal 41 to limit current changes during high-voltage loading. When transient current fluctuations or abnormal discharges occur during testing, the protective resistor 42 can reduce current surges and prevent damage to the test film 60, target electrode 12, and signal acquisition circuit at the high-voltage output terminal 41, thereby improving the safety and stability of the test platform during operation.

[0055] A bypass capacitor 43 is connected in parallel between the high-voltage output terminal 41 and ground to provide a low-impedance return path for high-frequency transient signals. When a pressure wave acts on the film under test 60 and generates a displacement current signal, the bypass capacitor 43 can reduce the transmission impedance of the high-frequency signal in the high-voltage power supply circuit, reduce the interference of the high-voltage power supply on the transient detection signal, and enable the signal acquisition module 50 to acquire the space charge response signal more accurately.

[0056] On the other hand, this application also provides a test method based on the above-mentioned in-situ space charge measurement platform for insulating thin films, including the following steps: First, the sample to be tested is prepared and the test module 10 is assembled. The target electrode 12 is attached or coated on one side surface of the film to be tested 60, and the film to be tested 60 is placed above the lower electrode 13, so that the film to be tested 60 is located between the target electrode 12 and the lower electrode 13, thereby forming the test structure required for space charge detection.

[0057] In one specific embodiment, the film under test 60 can be a 10μm thick BOPP insulating film, and the conductive part in the target electrode 12 can be formed by copper foil attached to the surface of the film under test 60. To reduce the electric field concentration at the electrode edge during high-voltage loading, the edge of the copper foil can be rounded, and an insulating encapsulation material can be provided at the interface between the edge of the copper foil and the film under test 60 to improve the stability during electric field loading. Furthermore, a light-absorbing layer can be formed on the side of the copper foil away from the film under test 60, for example, by spraying graphite spray to form a light-absorbing target material layer, so that the target electrode 12 simultaneously has the functions of electric field loading and laser energy conversion.

[0058] After the sample preparation is completed, the test film 60 is flatly placed above the lower electrode 13. To improve the transmission efficiency of pressure wave and displacement current signals, an acoustic coupling medium can be placed between the lower electrode 13 and the test film 60. By eliminating air gaps in the contact interface, a good acoustic transmission interface is formed between the test film 60 and the lower electrode 13. Subsequently, the glass prism 11 is placed on the side of the target electrode 12 away from the test film 60, so that the glass prism 11, the target electrode 12, the test film 60, and the lower electrode 13 form a complete detection structure.

[0059] Next, mechanical loads are applied. Mechanical loads are applied to the film under test 60 through the mechanical loading module 30. The mechanical loads include mechanical loads applied along the first direction and / or mechanical loads applied perpendicular to the first direction, in order to simulate the stress state of the insulating film during actual operation.

[0060] In one specific embodiment, an in-plane transverse tensile stress can be applied to the test film 60 by means of a tensile loading component 31. For example, the test film 60 can be clamped on opposite sides by means of an insulating clamp 311, and the clamp 311 can be driven away from each other by means of a driving component 312, so that the test film 60 generates a transverse tensile stress of about 12 MPa to simulate the tension of the film during the operation of the film capacitor. At the same time, a pressure load along a first direction can be applied to the glass prism 11 by means of a mechanical loading module 30, so that the mechanical load is transmitted to the test film 60 through the glass prism 11 and the target electrode 12. For example, a constant longitudinal mechanical pressure of about 0.8 MPa can be applied to simulate the normal stress generated by interlayer extrusion and thermal shrinkage of the film.

[0061] The above method can place the film under test 60 in a preset mechanical stress state, providing a test environment for subsequent space charge measurement under electromechanical coupling conditions.

[0062] Subsequently, an electric field is applied. A preset high-voltage DC current is applied to the target electrode 12 through the voltage loading module 40 to establish a DC electric field inside the test film 60 which is subjected to mechanical load, so that the test film 60 is simultaneously under the combined action of mechanical stress and electric field.

[0063] In one specific embodiment, a 600V DC high voltage can be applied to the target electrode 12 to form a polarized electric field of approximately 50kV / mm inside the 10μm-thick film under test 60, and maintain this field for a preset time, allowing the space charge inside the film under test 60 to reach a relatively stable state under the influence of mechanical load and DC electric field. During this process, the protective structure in the voltage loading module 40 can ensure the stability of the high voltage loading process, while reducing the impact of the high voltage environment on the transient detection signal.

[0064] Next, pulsed laser excitation and pressure wave generation are performed. Pulsed laser is input to the glass prism 11 through the optical loading module 20, so that the pulsed laser enters the glass prism 11 along the second direction, and after being deflected by the internal structure of the glass prism 11, it propagates along the first direction to act on the target electrode 12 and generate a pressure wave.

[0065] In one specific embodiment, the pulsed laser 21 can be a picosecond pulsed laser with a center wavelength of 1064 nm and a pulse width of less than 10 ps. The output pulsed laser is adjusted in propagation direction by the reflector 22 and then enters the glass prism 11. After being refracted by the glass prism 11, it acts perpendicularly on the target electrode 12. The light-absorbing layer in the target electrode 12 absorbs the pulsed laser energy and generates a transient response. Under the constraint of the glass prism 11, a pressure wave is formed that propagates along the first direction. The pressure wave is further transmitted into the interior of the thin film 60 under test.

[0066] Finally, displacement current signal acquisition and space charge distribution analysis are performed. After the pressure wave acts on the test film 60, it causes microscopic displacement of the space charge inside the test film 60, forming a weak transient displacement current signal in the measuring electrode 131 circuit of the lower electrode 13. The signal acquisition module 50 acquires this displacement current signal and analyzes and processes the acquired time-domain signal to obtain the space charge distribution inside the test film 60.

[0067] In one specific embodiment, the displacement current signal can be amplified by signal amplifier 52 and then input to oscilloscope 53 for recording. Oscilloscope 53 can use an external photoelectric detection signal, laser synchronization signal, or other trigger signal as the acquisition trigger source to ensure synchronization between the laser excitation process and the signal acquisition process. By performing mathematical inversion on the acquired displacement current waveform, the internal space charge distribution of the thin film 60 under test can be obtained. Please refer to [link to relevant documentation]. Figure 5 , Figure 5 This is a space charge distribution diagram provided in an embodiment of the present invention.

[0068] In this embodiment, the above-described experimental method enables space charge measurement of the insulating film under the combined influence of mechanical load and DC electric field. Compared to traditional methods that only operate under a single electric field, this method better simulates the electromechanical coupling environment of the insulating film during actual operation. Simultaneously, the glass prism 11 facilitates laser propagation direction conversion and mechanical load transfer, ensuring compatibility between the optical detection path and the mechanical loading path. This allows for in-situ measurement of the space charge distribution of the insulating film, improving the accuracy and reliability of the measurement results.

[0069] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An in-situ space charge measurement platform for insulating thin films, characterized in that, include: The test module includes a glass prism, a target electrode, and a lower electrode stacked sequentially along a first direction, with the target electrode and the lower electrode used to place the thin film to be tested. An optical loading module is disposed on one side of the glass prism and is used to input pulsed laser into the glass prism. The pulsed laser enters the glass prism along a second direction, and after being refracted by the glass prism, it propagates to the target electrode along a first direction. The first direction is not parallel to the second direction. A mechanical loading module, connected to the glass prism, is used to apply a mechanical load to the glass prism so that the mechanical load is transferred to the thin film under test through the glass prism and the target electrode, and the direction of application of the mechanical load is parallel to the first direction; A voltage loading module, connected to the target electrode, is used to apply a DC voltage to the target electrode to establish a DC electric field inside the thin film under test. as well as The signal acquisition module is electrically connected to the lower electrode and is used to acquire the displacement current signal generated when the pressure wave acts on the film under test, so as to obtain the space charge distribution inside the film under test.

2. The in-situ space charge measurement platform for insulating thin films according to claim 1, characterized in that, The inner reflecting surface of the glass prism includes a pressure-bearing section and a reflecting section. The pressure-bearing section is arranged perpendicular to the first direction and is used to bear the mechanical load applied by the mechanical loading module. The reflecting section is arranged at an angle relative to the second direction and is used to reflect the pulsed laser propagating along the second direction back to propagating along the first direction.

3. The in-situ space charge measurement platform for insulating thin films according to claim 2, characterized in that, The pressure-bearing section includes a first pressure-bearing section and a second pressure-bearing section, which are respectively disposed on both sides of the reflective section, and the total length of the pressure-bearing section accounts for 20% to 40% of the total length of the inner reflective surface.

4. The in-situ space charge measurement platform for insulating thin films according to claim 1, characterized in that, The target electrode includes a conductive part and a light-absorbing part. The conductive part is disposed in contact with the film under test and is used to establish an electric field inside the film under test. The light-absorbing part is disposed on the side of the conductive part away from the film under test and is used to absorb pulsed laser light and generate pressure waves.

5. The in-situ space charge measurement platform for insulating thin films according to claim 1, characterized in that, The optical loading module includes a pulsed laser, a reflector, and an aperture. The pulsed laser is used to generate pulsed laser light, the reflector is used to adjust the pulsed laser light to propagate along a second direction, and the aperture is used to adjust the beam size of the pulsed laser light.

6. The in-situ space charge measurement platform for insulating thin films according to claim 1, characterized in that, The lower electrode includes a measuring electrode, a grounding protection ring, and a metal shielding shell. The grounding protection ring is arranged around the periphery of the measuring electrode, and the metal shielding shell is covered on the outside of the measuring electrode and the grounding protection ring.

7. The in-situ space charge measurement platform for insulating thin films according to claim 6, characterized in that, An acoustic coupling layer is provided on the side of the lower electrode that contacts the film under test, and the acoustic coupling layer is formed by coating with an acoustic coupling agent.

8. The in-situ space charge measurement platform for insulating thin films according to claim 1, characterized in that, The mechanical loading module further includes a tensile loading component, which includes a clamp and a drive component. The clamp is disposed in a plane perpendicular to the first direction and is used to clamp the film to be tested. The drive component is connected to the clamp and is used to drive the clamp to apply a lateral tensile load to the film to be tested.

9. The in-situ space charge measurement platform for insulating thin films according to claim 1, characterized in that, The voltage loading module includes a high-voltage output terminal, a protective resistor is connected in series with the high-voltage output terminal, and a bypass capacitor is connected in parallel between the high-voltage output terminal and ground.

10. A test method, implemented based on the in-situ space charge measurement platform for insulating thin films according to any one of claims 1 to 9, characterized in that, Includes the following steps: The target electrode is attached or coated on one side surface of the film to be tested, and the film to be tested is placed above the lower electrode, so that the film to be tested is located between the target electrode and the lower electrode; A mechanical load is applied to the film under test by a mechanical loading module, the mechanical load including a mechanical load applied along the first direction and / or a mechanical load applied perpendicular to the first direction; A preset high-voltage DC current is applied to the target electrode through a voltage loading module to establish a DC electric field inside the thin film under test, which is subjected to the mechanical load. A pulsed laser is input to the glass prism through an optical loading module, so that the pulsed laser enters the glass prism along the second direction, and after being refracted by the glass prism, it propagates along the first direction to act on the target electrode and generate a pressure wave acting on the film under test. The displacement current signal generated when the pressure wave acts on the film under test is acquired by the signal acquisition module, and the space charge distribution inside the film under test is obtained based on the displacement current signal.

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