An electrolytic capacitor separator esr testing device and detection method

Abstract

This invention relates to the technical field of electrolytic capacitor diaphragm testing equipment, and more particularly to an ESR testing device and method for electrolytic capacitor diaphragms. The device includes a sealed test chamber, a wet electrode test fixture with an electrolyte tank and a flow ramp, a servo-controlled closed-loop constant force pressurization mechanism, a temperature, humidity, and pressure environment simulation system, a four-terminal impedance measurement module, and a parasitic compensation and ESR component extraction module. During testing, the diaphragm sample undergoes vacuum-backpressure degassing and wetting. Open-circuit / short-circuit calibration and frequency sweep measurement are performed under controllable temperature, humidity, and pressure and constant clamping pressure. After parasitic compensation, the ESR spectrum and judgment report are output. This scheme can realistically simulate the working state of the diaphragm, reduce the influence of leads and contacts, improve high-frequency testing accuracy, repeatability, and cross-batch comparability, and is suitable for diaphragm R&D and quality control.

Description

Technical Field

[0001] This invention relates to the field of electrolytic capacitor diaphragm testing equipment, and in particular to an electrolytic capacitor diaphragm ESR testing equipment and testing method. Background Technology

[0002] Electrolytic capacitors, as one of the most widely used passive devices in electronic circuits, are extensively used in power supply filtering, decoupling, energy buffering, and ripple suppression. Electrolytic capacitors typically consist of an anode aluminum foil, a cathode aluminum foil, an electrolyte, and a separator. The separator, located between the positive and negative electrodes and completely immersed in the electrolyte, needs to stably isolate the electrodes during long-term operation, preventing micro-short circuits or breakdown; it also serves as an electrolyte storage and ion transport channel. Factors such as the separator's pore structure, wetting uniformity, compression deformation, and electrolyte retention capacity significantly affect the capacitor's resistive loss under AC conditions, ultimately reflected in the equivalent series resistance (ESR). Especially in high-frequency, miniaturized, and high-ripple current applications, ESR is closely related to temperature rise, lifespan decay, and ripple suppression capability. Therefore, the research and development of separator materials and the quality control of incoming materials urgently require a dedicated device capable of rapid, repeatable, and comparable testing of the separator's ESR contribution under near-real-world operating conditions (controllable electrolyte wetting, pressure, and temperature, humidity, and pressure boundary conditions).

[0003] However, according to common industry practices, the electrical properties of the separator are often indirectly evaluated through the ESR of the entire electrolytic capacitor, or by manually measuring the wetted sample at room temperature and atmospheric pressure using simplified fixtures. These methods have at least three limitations: First, the ESR of the entire capacitor is affected by multiple factors, including the electrode foil, leads, winding structure, and electrolyte state, making it difficult to separate the contribution of the separator itself to the ESR. Second, manual fixtures have poor consistency in electrode contact pressure, wetted area, and wetted degree, resulting in insufficient repeatability. Third, the testing conditions lack standardized environmental control and parasitic parameter compensation, leading to weak comparability of data from different laboratories and batches, thus making it difficult to support formulation screening, structural optimization, and quality assessment during the separator R&D stage.

[0004] One of the prior art technologies most closely related to the technical subject of this invention is Chinese patent CN101576607A, which discloses a "method and apparatus for detecting the wet resistance of a nickel-metal hydride battery separator". This document proposes applying a certain pressure to the separator sample using porous electrodes and performing wet resistance detection in an electrolyte environment. It also includes a reservoir for injecting electrolyte to wet the separator, thus simulating, to some extent, the pressure- and wetting state of the separator within the battery structure. This approach offers valuable insights into the "wet state + pressure" testing concept. However, CN101576607A focuses on the wet resistance testing of battery separators, and its test objects and evaluation indicators are not entirely consistent with the ESR characteristics of electrolytic capacitor separators. Furthermore, its scheme is more inclined towards a structured clamping platform, which is usually difficult to cover the measurement requirements of the impedance spectrum of electrolytic capacitor separators under wide frequency conditions (e.g., from low frequency to MHz level). It also does not emphasize closed-loop control of temperature, humidity and air pressure in a sealed cavity, and lacks open-circuit / short-circuit calibration and compensation mechanisms for the parasitic impedance of clamps in high-humidity electrolyte environments. Therefore, it is difficult to directly solve the problems of high-frequency accuracy and cross-laboratory comparability in the ESR testing of electrolytic capacitor separators.

[0005] Another similar prior art is CN104678173A, which discloses a "test method for the surface resistance of lithium battery separators". This document proposes to clamp the separator between upper and lower electrode plates, control the applied pressure, and measure the resistance between the electrodes at a specific frequency (such as 100kHz) using the AC impedance method. At the same time, the blank resistance of the electrolyte is obtained first and then subtracted to reduce the error and obtain the surface resistance of the separator. While this approach offers insights into "pressure control," "electrolyte blank subtraction," and "AC impedance measurement," it primarily focuses on evaluating the single-point frequency resistance / surface resistance of lithium-ion battery separators. It serves more as a macroscopic resistance characterization tool for separator ion channels and does not prioritize the ESR spectrum of electrolytic capacitor separators. Furthermore, this method does not establish a repeatable wet wetting interface at the equipment level (e.g., a stable liquid supply structure, defoaming wetting procedure) or propose standardized control of temperature, humidity, and pressure in a sealed environment. Additionally, regarding common issues in high-frequency impedance measurements such as clamp lead resistance, contact resistance, and parasitic capacitance / inductance, this literature does not provide a systematic implementation method for "open-circuit / short-circuit calibration under wet conditions and establishing parasitic compensation parameters." Therefore, there is still room for improvement in the accuracy and stability of high-frequency ESR.

[0006] In addition, there are some general-purpose clamp solutions in the field of impedance measurement. For example, CN201716338U discloses a "test clamp for impedance analyzer". It uses a clamp and a bent metal sheet to form an elastic gripper, which holds the upper and lower electrode surfaces of the sample and connects to the impedance analyzer to achieve measurement. Its advantages are easy clamping, simplified process, and suitability for devices with a metal layer on the sample surface but no leads. However, this type of clamp is essentially a "general-purpose electrical connection clamp under normal temperature and pressure". Its design focuses on the convenience of mechanical clamping and wire connection. It usually does not consider the testing requirements of electrolytic capacitor diaphragms in electrolyte immersion and sealed high humidity environments. It also lacks closed-loop control and drift compensation of electrode clamping pressure, and does not address key issues such as vacuum-backpressure cyclic degassing immersion, the formation of a stable immersion interface by the flow guide ramp, and open / short circuit calibration to compensate for the parasitic impedance of wet clamps. Therefore, when this type of general-purpose fixture is directly used for wet ESR testing of diaphragms, it is easily affected by inconsistent contact conditions, fluctuations in wetting state, and drift of parasitic parameters, resulting in scattered test results that are difficult to standardize and compare.

[0007] In summary, while existing technologies have made valuable explorations in areas such as "diaphragm wet pressure testing platform," "diaphragm resistance subtraction method under AC impedance," and "universal fixture connection for impedance analyzer," significant gaps remain: First, there is a lack of dedicated testing equipment and standardized procedures for the specific ESR index of electrolytic capacitor diaphragms, especially the ability to stably acquire wideband ESR spectra; second, there is a lack of environmental simulation capabilities to achieve closed-loop control of temperature, humidity, and chamber pressure within the same equipment, in conjunction with the diaphragm wet immersion state; third, there is a lack of servo closed-loop constant force control of electrode clamping pressure and pressure drift compensation mechanisms during frequency sweeps; fourth, there is a lack of a systematic solution for performing open / short circuit calibration and establishing parasitic compensation parameters under electrolyte immersion and high humidity environments, thereby achieving fixture parasitic impedance de-embedding and diaphragm ESR component extraction; and fifth, there is a lack of structural design to ensure the consistency of the immersion interface through the electrolyte tank and flow guiding structure, making it difficult to guarantee data consistency across different batches and laboratories. Based on the above situation, the industry urgently needs a dedicated testing device and method that can perform four-terminal impedance measurements in wet immersion, pressurized, and temperature-controlled wet-pressure environments, and combine open-circuit / short-circuit calibration to complete parasitic compensation and extract diaphragm ESR components, so as to meet the requirements of diaphragm R&D and quality control for accuracy, repeatability, and comparability. Summary of the Invention

[0008] The technical objective of this invention is to provide an electrolytic capacitor separator ESR testing device and method. By constructing the electrolyte wet wetting interface of the separator sample within a sealed test chamber, controlling the simulation of temperature, humidity, and pressure environment, and controlling the closed-loop constant force of electrode clamping pressure, and combining it with a parasitic compensation algorithm for four-terminal impedance measurement and open / short circuit calibration, the contribution of the separator to ESR is accurately extracted and repeatable ESR spectrum data is obtained. This solves the problems of insufficient accuracy, unrealistic environmental simulation, poor repeatability, and poor cross-laboratory comparability in existing separator ESR testing.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] An electrolytic capacitor separator ESR testing device, the device comprising:

[0011] A) A sealing test chamber, wherein the sealing test chamber is provided with a transparent sealing cover, a sealing cover hinge, and a sealing cover door lock;

[0012] B) A wet electrode test fixture is disposed in the sealed test chamber. The wet electrode test fixture includes an upper electrode and a lower electrode disposed opposite to each other, and the lower electrode is provided with a lower electrode electrolyte tank in the circumferential direction. A guide ramp is provided between the lower electrode electrolyte tank and the effective test area of ​​the lower electrode to guide the electrolyte to the effective test area to form a wet wetting interface of the diaphragm sample.

[0013] C) A pressure closed-loop electrode pressurization mechanism is connected to the upper electrode via a transmission. The pressure closed-loop electrode pressurization mechanism includes a servo motor and an upper electrode lead screw, and has a pressure detection unit. The servo motor performs closed-loop control based on the feedback from the pressure detection unit, so that the upper electrode applies and maintains a preset clamping pressure on the diaphragm sample.

[0014] D) Temperature, humidity and pressure environment simulation system, connected to the sealed test chamber, the temperature, humidity and pressure environment simulation system includes a temperature, humidity and pressure control unit, atomizing spray nozzle, positive pressure air port, negative pressure air port and temperature and humidity probe, and includes a vacuum generator with pressure detection and a pressure regulating valve with pressure detection, used to switch the chamber air pressure to vacuum / micro positive pressure and maintain the preset air pressure in a closed loop during the test;

[0015] E) A four-terminal impedance measurement and low parasitic connection assembly, including an analysis module, the analysis module being used to perform four-terminal impedance measurement on the upper and lower electrodes within a preset frequency range.

[0016] F) Parasitic compensation and diaphragm ESR component extraction module, wherein the parasitic compensation and diaphragm ESR component extraction module is set in the data processing system or connected to the data processing system by signal, and is used to perform at least open-circuit calibration and short-circuit calibration under wet conditions, and to compensate for the parasitic impedance of the fixture based on the calibration results, and output the ESR test results of the diaphragm sample.

[0017] The temperature, humidity and pressure environment simulation system, the pressure closed-loop electrode pressurization mechanism, and the parasitic compensation and diaphragm ESR component extraction module work together to obtain repeatable ESR spectrum data under the wet conditions of the diaphragm sample being immersed in electrolyte.

[0018] Preferably, the temperature, humidity and pressure environment simulation system also includes a humidifier, and the vacuum generator with pressure detection and the pressure regulating valve with pressure detection are configured to perform a vacuum-backpressure cycle to defoam and wet the diaphragm sample before testing, and to stabilize the cavity pressure within a preset range after backpressure.

[0019] Preferably, the pressure closed-loop electrode pressurization mechanism further includes a servo motor driver, which drives the servo motor and compensates for clamping pressure drift during frequency sweep to maintain constant clamping pressure.

[0020] Preferably, the low parasitic connection assembly further includes an upper electrode sheath and an anti-interference base plate. The upper electrode sheath is used to reduce the leakage path around the upper electrode, and the anti-interference base plate is used to reduce the parasitic coupling between the electrode and the analysis module.

[0021] Preferably, the lower electrode electrolyte tank is provided with an electrolyte tank fixing frame to fix the relative position of the lower electrode electrolyte tank and the guide slope, so as to ensure the consistency of the wetting interface.

[0022] Preferably, a heating plate is provided below the lower electrode, and the heating plate is thermally connected to the temperature, humidity and pressure control unit for local temperature control of the electrode area; and the device also includes a cooling fan.

[0023] A method for testing the ESR of an electrolytic capacitor separator using the apparatus described in any one of claims, characterized in that it comprises:

[0024] S1, Place the diaphragm sample in the effective test area of ​​the lower electrode, so that the guide ramp area connecting the diaphragm sample and the electrolyte tank of the lower electrode forms a wettable interface.

[0025] S2 controls the vacuum generator with pressure detection and the pressure regulating valve with pressure detection to perform vacuum-back pressure cycle, degas and impregnate the diaphragm sample, and controls the temperature, humidity and pressure control unit to stabilize the temperature, humidity and air pressure of the test chamber to the preset test conditions.

[0026] S3 drives the servo motor to press down the upper electrode via the upper electrode lead screw, and performs closed-loop control based on the pressure detection unit to make the clamping pressure reach and maintain the preset value;

[0027] S4, the control and analysis module performs four-end calibration and establishes fixture parasitic compensation parameters;

[0028] S5, the control and analysis module performs a four-terminal impedance frequency sweep, and the data processing system calculates the ESR spectrum of the diaphragm sample based on the parasitic compensation parameters of the fixture and outputs the results.

[0029] Preferably, S3 includes: monitoring the clamping pressure drift during frequency sweep, and when the drift exceeds a preset threshold, triggering a compensation displacement of the servo motor to restore the clamping pressure to the preset value.

[0030] Preferably, S4 includes at least open-circuit calibration and short-circuit calibration, and S includes: the data processing system performs equivalent circuit fitting on the measured impedance spectrum, and outputs the membrane ESR contribution value after stripping the electrode-electrolyte interface component.

[0031] Preferably, S2 to S5 are repeated at at least two temperature setpoints according to a preset test sequence, and the ESR spectrum under each condition is normalized and stored, while a test report is printed out.

[0032] This invention, through a collaborative design of "sealed temperature, humidity, and pressure environment simulation, vacuum-backpressure degassing and wetting, servo closed-loop constant force clamping, four-terminal broadband impedance measurement, open-circuit / short-circuit calibration parasitic compensation, and component extraction," enables diaphragm samples to obtain stable and reliable ESR spectrum data under conditions close to the actual working state of electrolytic capacitors (fully wetted electrolyte, stable pressure, and controllable temperature, humidity, and chamber pressure). On the one hand, the four-terminal measurement combined with open-circuit / short-circuit calibration effectively suppresses interference from lead resistance, contact resistance, clamp parasitic capacitance / inductance, and high-humidity leakage channels, achieving higher precision extraction of the diaphragm's ESR contribution, especially improving the reliability of high-frequency ESR assessment; on the other hand... On the other hand, servo constant force control and pressure drift compensation during frequency sweep ensure that the electrode contact state is consistent with the diaphragm compression ratio. Vacuum-backpressure circulation and flow guiding structure ensure uniform wetting of diaphragm pores and significantly reduce bubbles, reducing the dispersion caused by sample state fluctuations from the source, thereby significantly improving test repeatability and batch / cross-laboratory comparability. At the same time, the equipment can automatically execute standardized test sequences and output ESR-frequency / temperature curves and pass / fail judgment reports at different temperature, humidity and air pressure setpoints. It can support the formulation screening and structural optimization in diaphragm material research and development, and can also be used for incoming materials and process quality control in production, reducing reliance on manual labor and the risk of misjudgment, and improving testing efficiency and data value. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of the electrolytic capacitor separator ESR testing equipment of the present invention.

[0034] Figure 2 This is a front structural schematic diagram of the electrolytic capacitor separator ESR testing equipment of the present invention.

[0035] Figure 3 This is a side cross-sectional view of the electrolytic capacitor separator ESR testing equipment of the present invention.

[0036] Figure 4 This is a schematic diagram of the back structure of the electrolytic capacitor separator ESR testing equipment of the present invention.

[0037] Figure 5 This is a schematic diagram of the structure of the wet electrode testing fixture of the present invention.

[0038] Figure 6 This is a schematic diagram of the electrolyte simulation and supply structure of the present invention.

[0039] Figure 7 for Figure 6 The diagram shows a cross-sectional view of the electrolyte simulation and the electrolyte supply structure.

[0040] Figure 8 This is a schematic diagram of the test sample for the present invention. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0042] I. Terminology Explanation and Test Subjects

[0043] 1. Separator Samples: Refers to paper-based or fiber-based separator materials used in electrolytic capacitors, and may also include surface-modified separators, composite separators, or functionalized separators. For example... Figure 8 As shown, the diaphragm sample can be cut into a circle 132 or a square 133, with a typical size of 35mm × 35mm (the specific size can be adjusted according to the effective area of ​​the device electrode).

[0044] 2. Wet interface: This refers to the stable wetting region formed by the diaphragm sample under the action of the electrolyte, including the liquid-filled state of the diaphragm pores, the liquid film state on the diaphragm surface, and the three-phase contact state of the electrode-electrolyte-diaphragm. The consistency of this interface has a significant impact on the repeatability of ESR tests.

[0045] 3. Clamping pressure: refers to the normal clamping force applied by the upper electrode 109 and the lower electrode 111 to the diaphragm sample. The clamping pressure determines the changes in contact resistance, diaphragm compressibility, and porosity, thus affecting the high-frequency ESR performance.

[0046] 4. Four-terminal impedance measurement (4TP): This refers to reducing the influence of lead and contact resistance by separating the current excitation terminal and the voltage sampling terminal. In this invention, the analysis module 120 performs four-terminal measurement.

[0047] 5. Parasitic Impedance / Parasitic Admittance: This refers to the equivalent impedance or admittance introduced by the clamp conductor, connection structure, environmental leakage path, parasitic capacitance / inductance, etc., excluding the diaphragm itself under test. This invention establishes parasitic compensation parameters through open-circuit calibration and short-circuit calibration.

[0048] 6. ESR Spectrum Data: Refers to the curve or set of discrete points showing the change of the diaphragm's equivalent series resistance with frequency. Outputtable. or target frequency It can also output the change with temperature. .

[0049] II. Overall Equipment Structure

[0050] 2.1 Sealing Test Chamber

[0051] like Figure 1 , Figure 2 As shown, the entire device of this invention is installed inside the frame, with the key testing components located within the sealed testing chamber. The sealed testing chamber comprises a transparent sealing cover 101, a sealing cover hinge 102, and a sealing cover door lock 103, forming an openable and closable sealed space. The transparent sealing cover 101 can be made of a temperature- and corrosion-resistant transparent material (e.g., tempered glass, chemical-resistant PC, or PMMA composite structure), the purpose of which is:

[0052] This facilitates observation of sample placement, electrode contact status, and electrolyte level in electrolyte tank 112.

[0053] When used in conjunction with the door lock 103, it forms an airtight space, enabling the temperature, humidity, and pressure environment simulation system to establish stable boundary conditions within the cavity;

[0054] By designing the cavity structure to reserve cable / air passage sealing ports, external electromagnetic and moisture disturbances are reduced.

[0055] The sealing cover hinge 102 ensures that the opening angle of the sealing cover 101 is controllable. The door lock 103 can adopt a mechanical lock + compression sealing strip structure to ensure that the leakage rate of the cavity meets environmental control requirements after closure. In this embodiment, a sealing ring and a compression strip can be installed in the sealing cavity, preferably using fluororubber sealing material that is resistant to electrolyte corrosion.

[0056] 2.2 Human-computer interaction and status display

[0057] A touchscreen 104 can be installed on the front of the device for:

[0058] Set the test parameters (temperature, humidity, air pressure, clamping pressure, frequency range, number of sweep points, signal level, etc.);

[0059] Displays real-time status (current temperature and humidity, air pressure, pressure, impedance curve, ESR curve, stability criteria, etc.);

[0060] Trigger automated processes (defoaming and wetting, calibration, measurement, report generation and printing, etc.).

[0061] The touchscreen 104 communicates with the data processing system 121 via serial port, Ethernet, or industrial bus protocol. The touchscreen 104 can also serve as an access point, supporting different permissions for administrators and operators.

[0062] 2.3 Heat dissipation and rear interface

[0063] road Figure 3 , Figure 4 As shown, a cooling fan 124 can be installed inside the device to reduce the thermal drift effects on the analysis module 120 and control drive components. A power switch 128, a socket 129, a fuse 130, and a communication interface 131 can be installed on the back. The communication interface 131 can be used to export test data to a host computer or MES system, or for remote maintenance and software upgrades.

[0064] III. Wet Electrode Testing Fixture and Electrolyte System

[0065] 3.1 Upper electrode 109 and lower electrode 111

[0066] like Figure 5 As shown, the wet electrode test fixture includes an upper electrode 109 and a lower electrode 111. The upper electrode 109 and lower electrode 111 can be made of corrosion-resistant conductive materials (such as a stainless steel substrate with a gold plating layer) to reduce electrolyte corrosion and contact resistance changes. The electrode end faces are preferably mirror-polished or finely textured to obtain repeatable contact conditions; alternatively, annular electrodes, planar electrodes, or microporous permeable electrodes can be selected based on the characteristics of the diaphragm material.

[0067] like Figure 2 , Figure 3 As shown, to avoid leakage paths in humid environments, an upper electrode sheath 110 can be installed around the upper electrode. The upper electrode sheath 110 can be made of an insulating electrolyte-resistant material (such as PTFE, PPS, PEEK, etc.), and its functions include:

[0068] 1) Limit the electrolyte creep path to reduce parallel leakage current channels formed around the electrode;

[0069] 2) Reduce parasitic capacitive coupling between the electrode and the surrounding metal structure;

[0070] 3) It forms a stable electric field boundary in a high humidity environment, improving the stability of high-frequency measurements.

[0071] 3.2 Lower electrode electrolyte tank 112 and guide ramp 113

[0072] like Figure 6 and Figure 7 As shown, a lower electrode electrolyte tank 112 is circumferentially arranged on the lower electrode 111. The lower electrode electrolyte tank 112 is used to contain the test electrolyte and provide continuous wet conditions for the diaphragm sample. A flow guide ramp 113 is provided between the lower electrode electrolyte tank 112 and the effective test area of ​​the lower electrode 111. The structure of the flow guide ramp 113 can be an inclined surface, a stepped surface, or a capillary flow guide groove. Its core purpose is:

[0073] 1) Stable and controllable guidance of the electrolyte from the electrolyte tank 112 to the effective testing area of ​​the lower electrode;

[0074] 2) To form repeatable liquid film thickness and wetting front position, avoiding measurement discrepancies caused by random seepage;

[0075] 3) During the vacuum / backpressure cycle degassing process, it provides channels for bubble escape and liquid backfilling, improving the adequacy of wetting.

[0076] The lower electrode electrolyte tank 112 can be fixed by an electrolyte tank fixing bracket 114. The electrolyte tank fixing bracket 114 is used to ensure the long-term stability of the relative position between the tank and the guide ramp 113, and to reduce the difference in the wetting interface caused by assembly errors. The electrolyte tank fixing bracket 114 can adopt a detachable structure to facilitate cleaning and replacement of different electrolyte systems.

[0077] In this embodiment, for ease of maintenance, the electrolyte tank 112 may be equipped with a liquid level scale or a liquid level sensing structure (optional). When the liquid level is lower than the threshold, it will prompt for liquid replenishment to avoid changes in immersion conditions during the test.

[0078] IV. Pressure Closed-Loop Electrode Pressurization Mechanism

[0079] like Figure 3 As shown, the upper electrode 109 achieves vertical displacement via the upper electrode lead screw 116. The servo motor 115 drives the upper electrode lead screw 116 to rotate, causing the upper electrode 109 to move up and down, thereby applying clamping pressure to the diaphragm sample. The servo motor 115 is controlled by the servo motor driver 117, which receives the pressure setpoint and closed-loop control commands from the data processing system 121.

[0080] 4.1 Implementation of the pressure detection unit

[0081] The pressure detection unit can be implemented using any of the following methods or combinations thereof:

[0082] Method 1: Direct measurement using force sensor

[0083] A force sensor is arranged between the upper electrode 109 and the transmission structure or in the support structure of the lower electrode 111 to directly measure the clamping force. This method offers high accuracy and good linearity, making it suitable for research and development as well as high-consistency testing.

[0084] Method 2: Servo Motor Current Estimation

[0085] Based on the direct proportionality between the output torque and current of the servo motor 115, and considering the transmission efficiency and pitch of the lead screw 116, the current is converted into axial force. This method is less expensive, but it requires calibration under different temperatures and lubrication conditions.

[0086] Method 3: Displacement-Stiffness Model Estimation

[0087] When the equivalent stiffness models of the clamp and diaphragm materials are known, electrode displacement can be used to determine the stiffness. computing power This method is suitable for stable material systems, but it is sensitive to diaphragm compression nonlinearity.

[0088] This embodiment preferably uses method one. If method two or three is used, the calibration process and error compensation strategy should be given in the specification.

[0089] 4.2 Pressure Closed-Loop Control and Drift Compensation

[0090] During frequency sweep measurement, the clamping pressure may drift due to factors such as temperature changes, material creep, and lead screw hysteresis. The data processing system 121 periodically reads the pressure feedback and performs closed-loop compensation to maintain the pressure at the set value. nearby.

[0091] The following control strategies can be adopted:

[0092] 1) Set the allowable error band ;when At that time, servo compensation displacement is triggered;

[0093] 2) Update the pressure control at a fixed period (e.g., 100ms to 500ms) during the frequency sweep period;

[0094] 3) Low-pass filtering is applied to the pressure feedback to prevent motor vibration.

[0095] This closed-loop constant force mechanism, together with subsequent parasitic compensation and ESR component extraction, ensures data repeatability.

[0096] V. Temperature, Humidity and Pressure Environment Simulation System

[0097] like Figure 2 As shown, the temperature, humidity and pressure environment simulation system is connected to the sealed test chamber and includes a temperature, humidity and pressure control unit 118, an atomizing spray nozzle 105, a positive pressure air port 106, a negative pressure air port 107 and a temperature and humidity probe 108, as well as a vacuum generator 125 with pressure detection, a pressure regulating valve 126 with pressure detection, and a humidifier 127.

[0098] 5.1 Temperature control (including local temperature control)

[0099] The temperature, humidity, and pressure control unit 118 can employ a heating / cooling integrated module (such as a combination of thermoelectric cooling, compressor cooling, and electric heating) to create a set temperature within the cavity. To improve temperature uniformity in the electrode area, a heating plate 119 is installed below the lower electrode 111. The heating plate 119 is thermally connected to the temperature control unit to control the local temperature of the electrode area and reduce the lag and gradient between the cavity temperature and the electrode temperature.

[0100] 5.2 Humidity control and atomized spraying

[0101] Humidity control can be achieved by humidifier 127 providing basic humidification capacity, while atomizing spray nozzle 105 is used for rapid humidification or to create a specific humid atmosphere. Temperature and humidity probe 108 provides real-time feedback of relative humidity. With temperature The data processing system 121 adjusts the duty cycle of the humidifier 127 or the spray nozzle 105 accordingly to maintain the humidity at a certain level. .

[0102] 5.3 Pressure control, vacuum / backpressure circulation and defoaming impregnation

[0103] The vacuum generator 125 with pressure detection and the pressure regulating valve 126 with pressure detection work together to achieve chamber air pressure. Closed-loop control. Before testing, a vacuum-backpressure cycle can be performed to degas and wet the membrane. The specific mechanism is as follows: vacuuming reduces the partial pressure of gas in the pores of the diaphragm, causing bubbles to precipitate; during backpressure, the electrolyte is forced into the pores, thereby forming a more complete and consistent wetting state.

[0104] The vacuum-backpressure cycle can be performed with the following parameters:

[0105] 1) Draw to (Negative or low pressure state) and maintain ;

[0106] 2) Back pressure to (Atmospheric pressure or slightly positive pressure) and maintain ;

[0107] 3) Number of loops The number of cycles is 1 to 10, depending on the membrane thickness and porosity.

[0108] VI. Analysis Module and Data Processing

[0109] 6.1 Four-terminal impedance measurement

[0110] Analysis module 120 is used to perform four-terminal impedance measurement within a preset frequency range to obtain the measured impedance. The measurement signal level can be set to... (e.g., 10mV to 100mV) to avoid nonlinear polarization effects on the electrolyte system.

[0111] Impedance can be expressed in complex form:

[0112] ;

[0113] in: For testing frequency; To measure the real part of the impedance; To measure the imaginary part of the impedance; It is the imaginary unit.

[0114] 6.2 Parasitic Compensation and Extraction of ESR Components from the Diaphragm

[0115] The parasitic compensation and diaphragm ESR component extraction module is located in or connected to the data processing system 121. It is used to perform at least open-circuit and short-circuit calibrations under humid conditions, compensate for the parasitic impedance of the fixture based on the calibration results, and output the ESR test results of the diaphragm sample. Its implementation consists of three sub-processes: "calibration - compensation - extraction".

[0116] 6.2.1 Implementation of Open Circuit Calibration and Short Circuit Calibration

[0117] Open circuit calibration: while maintaining the same environmental conditions ( , , ) with the same clamping pressure This creates an "electrically open circuit" state between the electrodes. This open circuit state can be achieved by placing a highly insulating spacer or by separating the electrodes to the calibration gap. Analysis module 120 performs a frequency sweep to obtain... .

[0118] Short-circuit calibration: Under the same environmental and pressure conditions, the electrodes are brought into an "electrical short-circuit" state. This short-circuit state can be achieved by placing a low-resistance short-circuit plate (e.g., a gold-plated metal plate), which is then obtained by frequency sweep analysis module 120. .

[0119] To improve traceability, load calibration (optional) can also be set: measuring standard impedance components under the same conditions. It is used to verify the compensation effect and long-term drift monitoring.

[0120] 6.2.2 Implementation of Parasitic Compensation Algorithm

[0121] Common parasitic behaviors in wet conditions include parallel leakage admittance and parasitic capacitance; therefore, compensation in the admittance domain can improve stability. Admittance is defined as follows:

[0122] ,

[0123] in For admittance. Then:

[0124] ,

[0125] First, deduct open-circuit parasitism:

[0126] ,

[0127] Then, short-circuit calibration is used to normalize and correct the residual series error:

[0128] ,

[0129] ,

[0130] Finally, the compensated impedance is obtained:

[0131] ,

[0132] in: The equivalent impedance after de-embedding; The admittance after de-embedding;

[0133] The above is an implementable engineering algorithm. Those skilled in the art can use equivalent one-port error models, open-short load correction models, or network analysis de-embedding methods to achieve the same purpose.

[0134] 6.2.3 Extraction of ESR components from the diaphragm

[0135] In obtaining Then, two types of extraction methods can be used:

[0136] Method 1: Target Frequency Point ESR (Suitable for quality inspection and rapid screening)

[0137] ,

[0138] in: The target frequency (e.g., 100kHz or 1MHz); This indicates taking the real part. (It can be used in this context.) Take several frequency points in the vicinity and perform mean / median filtering to improve noise immunity.

[0139] Method 2: Equivalent circuit fitting to remove interface components (suitable for R&D and mechanism analysis)

[0140] Data processing system 121 pairs Equivalent circuit fitting is performed, and the electrode-electrolyte interface component is stripped away to output the membrane ESR contribution value. An example equivalent model could be: series resistance. (Representing the conductive channels of the diaphragm and residual series losses) and parallel / interface branches (representing polarization, electric double layers, etc.). Fitting yields... It later became a contributor to or a major component of membrane ESR.

[0141] VII. Specific Implementation Process of the Testing Method

[0142] The test sample of this invention can be circular or square. The testing procedure can be implemented according to the following steps:

[0143] 7.1 Preparations before testing

[0144] 1) Sample cutting: Cut the diaphragm material into samples of the specified size. The edges of the samples should be neat and free of burrs to avoid fiber scattering that could affect wetting and contact.

[0145] 2) Electrolyte preparation: Select an electrolyte that is consistent with the target electrolytic capacitor system (e.g., a system containing solvent and salt), and record information such as batch number, ratio, and viscosity.

[0146] 3) Fixture cleaning: Clean the upper electrode 109, lower electrode 111, electrolyte tank 112 and flow guide ramp 113 with an appropriate solvent and dry them to avoid residual contamination that could cause leakage or interface changes.

[0147] 4) Equipment preheating and self-test: Turn on the equipment, the data processing system 121 performs a self-test, the analysis module 120 completes the status check; the temperature, humidity and pressure control unit 118 enters the standby stable state.

[0148] 7.2 Sample mounting and wetting interface construction

[0149] Place the diaphragm sample in the effective testing area of ​​the lower electrode 111, ensuring that the center of the sample is aligned with the center of the electrode. Add a predetermined volume of electrolyte to the lower electrode electrolyte tank 112, allowing the electrolyte to form a wettable interface through the guide ramp 113. The wetting front can be observed through the transparent sealing cover 101. If necessary, allow a certain settling time to allow the liquid to initially spread.

[0150] 7.3 Vacuum-backpressure cycle degassing and wetting and environmental stability

[0151] Close the sealing cover 101 and lock the door lock 103. Start the vacuum generator 125 and pressure regulating valve 126 to perform a vacuum-backpressure cycle. After the cycle is completed, control the temperature, humidity and pressure control unit 118 to maintain the chamber temperature. ,humidity With air pressure Stabilize to the set value.

[0152] To ensure repeatability, the data processing system 121 can set a stability criterion: for example, when , , In continuous The fluctuations within the time period were all less than the threshold. , , If the above thresholds are not met, proceed to the next step. These thresholds can be set according to application requirements.

[0153] 7.4 Closed-loop constant force compression

[0154] Data processing system 121 issues clamping pressure setting The servo motor 115 drives the upper electrode 109 to press down via the lead screw 116, and the pressure detection unit feeds back the actual pressure. Servo closed-loop control enables Converge and maintain at Nearby. If pressure drift occurs during frequency sweep, compensation displacement is triggered according to claim 8 to restore pressure.

[0155] 7.5 Four-terminal calibration and parasitic compensation parameter establishment

[0156] Perform open-circuit and short-circuit calibrations (with optional load calibration) under humid, stable environmental, and constant-force compression conditions to obtain... and Based on this, parasitic compensation parameters are established. To avoid human error, the calibration process is preferably guided by the touchscreen 104 and automatically records the calibration fixture number and execution time.

[0157] 7.6 Frequency sweep measurement, ESR spectrum output and report generation

[0158] Analysis module 120 performs a four-terminal impedance sweep frequency to obtain... The data processing system 121 obtains data based on the parasitic compensation algorithm. , and then output or .

[0159] This invention can be repeatedly executed at at least two temperature setpoints (e.g., 25°C and 105°C) according to a test sequence to form The curve or temperature coefficient index. After the test, the data processing system 121 generates a report, which can be printed out as a paper report via printer 123 and exported as electronic data via communication interface 131.

[0160] VIII. Experimental Examples

[0161] 1. Experimental Objective

[0162] The invention verifies that the electrolytic capacitor diaphragm ESR testing equipment and method described in this invention can achieve high-precision extraction of the diaphragm ESR contribution and high-repeatability ESR spectrum output under the conditions of "wet immersion, pressure, and controllable temperature, humidity, and pressure" through four-terminal impedance measurement combined with open / short circuit calibration and parasitic compensation; and compared with existing conventional methods, it has significant improvements in data dispersion, cross-batch comparability, and testing efficiency.

[0163] 2. Experimental Materials and Equipment

[0164] 2.1 Diaphragm Sample

[0165] Select electrolytic capacitor separators of the same manufacturer and specifications, according to Figure 8 Cut into square samples, measuring 35 mm × 35 mm. The samples are divided into three groups:

[0166] Sample A: Cuttings at different locations on the same roll of material (A1~A10);

[0167] Sample Group B: Another roll of material from the same batch (B1~B10);

[0168] Sample Group C: Different batches (C1~C10).

[0169] 1.2 Electrolyte

[0170] Select an electrolyte that is consistent with the target electrolytic capacitor system (denoted as E1), keep it at a constant temperature of 25 ℃ before testing, and keep it sealed to reduce compositional drift caused by water absorption.

[0171] 1.3 Test Equipment and Comparison Methods

[0172] Example Equipment (Invention): Electrolytic Capacitor Separator ESR Testing Equipment.

[0173] Comparative Example 1 (Traditional Manual Fixture Method): Conventional two-end measurement, manual fixture (no sealed cavity, no constant force, no vacuum back pressure wetting, no open / close calibration compensation).

[0174] Comparative Example 2 (Four-terminal pair but no wet calibration): Four-terminal impedance measurement, but without performing wet open / short circuit calibration, only dry calibration parameters are used (cannot follow wet leakage and parasitic changes).

[0175] Comparative Example 3 (Indirect ESR method for the whole capacitor): The ESR was measured after the diaphragm was wound into the structure of the test capacitor as an indirect evaluation (affected by electrode foil, winding and leads).

[0176] 3. Test conditions and procedures

[0177] 3.1 Example 1: Standardized testing procedure under the equipment of the present invention

[0178] Follow these steps as follows:

[0179] 1) Sample placement and electrolyte supply: The sample is placed in the effective test area of ​​the lower electrode 111, and a fixed volume of electrolyte is added to the electrolyte tank 112 of the lower electrode. The electrolyte forms a stable wetting interface through the guide ramp 113.

[0180] 2) Vacuum-backpressure degassing and impregnation: Control the vacuum generator 125 and pressure regulating valve 126 to perform vacuum-backpressure cycle 3 times (each time vacuum is maintained for 60 s, backpressure is maintained for 60 s);

[0181] 3) Stable environment: Temperature 25 ℃, humidity 60%RH, chamber air pressure at normal pressure (or slightly positive pressure), and the temperature and humidity probe 108 shows stability before entering the test;

[0182] 4) Constant force clamping: Servo motor 115 drives upper electrode 109 to clamp, and the pressure closed loop is stabilized at 1.0 N;

[0183] 5) Wet calibration: Perform open-circuit and short-circuit calibrations to establish parasitic compensation parameters;

[0184] 6) Frequency sweep test: Sweep the frequency from 100 Hz to 1 MHz and record the results. Curve extraction and ;

[0185] 7) Repeated measurements: The same sample was measured 5 times, with an interval of 2 minutes between each measurement (without reloading the sample), to assess short-term repeatability.

[0186] 2. Comparative Example 1: Measurement at both ends of the hand clamp

[0187] After the sample was immersed in the electrolyte, it was held in a hand clamp at room temperature and atmospheric pressure, and the equivalent resistance was read at 100 kHz using the two-end method as “ESR”.

[0188] 3. Comparative Example 2: Four-terminal pair but without wet calibration

[0189] The same frequency sweep and constant force conditions as in the example were used, but only dry calibration was used, and wet open-short calibration was not performed, and ESR was directly output.

[0190] 4. Comparative Example 3: Indirect Measurement of ESR of the Entire Capacitor

[0191] The sample diaphragm was used to make a test capacitor, and the ESR was measured according to the standard method for capacitor ESR, which served as an indirect evaluation of the diaphragm performance.

[0192] IV. Experimental Data and Comparative Analysis

[0193] Table 1. Comparison of repeatability of the same sample (A1) at 25 ℃ and 1.0 N (n=5)

[0194]

[0195] Conclusion 1: This invention, through "constant force compression, vacuum backpressure wetting, and wet-state short-circuit calibration parasitic compensation," enables the same sample to... The coefficient of variation decreased significantly, demonstrating a significant improvement in test repeatability.

[0196] Table 2. Comparability comparison of different samples / batches (n=10, 25 ℃, 1.0 N), with... Using this as an indicator, we compare the mean differences and dispersion between the same batch and different batches.

[0197]

[0198] Conclusion 2: The data dispersion of the present invention is significantly less than that of the comparative example (CV approximately 3% vs 9%), and it can clearly distinguish the ESR differences between the same volume, the same batch, and different batches, indicating that it has stronger quality discrimination ability and cross-batch comparability.

[0199] Table 3. Temperature simulation accuracy: ESR variation trends at different temperatures (sample A1, n=3)

[0200]

[0201] Conclusion 3: This invention, relying on a sealed cavity and temperature, humidity and air pressure control, can stably measure the ESR spectrum under high temperature conditions and show a reasonable trend; while conventional manual methods are not stable enough in high temperature and MHz-level tests and cannot reflect the high-frequency ESR characteristics of the diaphragm under real working conditions.

[0202] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. An ESR testing device for electrolytic capacitor separators, characterized in that, The device includes: A) A sealing test chamber, wherein the sealing test chamber is provided with a transparent sealing cover (101), a sealing cover hinge (102) and a sealing cover door lock (103). B) A wet electrode test fixture is disposed in the sealed test chamber. The wet electrode test fixture includes an upper electrode (109) and a lower electrode (111) disposed opposite to each other, and the lower electrode (111) is provided with a lower electrode electrolyte tank (112) circumferentially. A flow guide ramp (113) is provided between the lower electrode electrolyte tank (112) and the effective test area of ​​the lower electrode (111) to guide the electrolyte to the effective test area to form a wet wetting interface of the diaphragm sample. C) A pressure closed-loop electrode pressurization mechanism is connected to the upper electrode (109) in a transmission manner. The pressure closed-loop electrode pressurization mechanism includes a servo motor (115) and an upper electrode lead screw (116), and has a pressure detection unit. The servo motor (115) performs closed-loop control according to the feedback of the pressure detection unit so that the upper electrode (109) applies and maintains a preset clamping pressure on the diaphragm sample. D) Temperature, humidity and pressure environment simulation system, connected to the sealed test chamber, the temperature, humidity and pressure environment simulation system includes a temperature, humidity and pressure control unit (118), an atomizing spray nozzle (105), a positive pressure air port (106), a negative pressure air port (107) and a temperature and humidity probe (108), and includes a vacuum generator (125) with pressure detection and a pressure regulating valve (126) with pressure detection, used to switch the chamber air pressure to vacuum / micro positive pressure and maintain the preset air pressure in a closed loop during the test; E) Four-terminal impedance measurement and low parasitic connection assembly, including analysis module (120), which is used to perform four-terminal impedance measurement on the upper electrode (109) and the lower electrode (111) within a preset frequency range; F) Parasitic compensation and diaphragm ESR component extraction module, wherein the parasitic compensation and diaphragm ESR component extraction module is set in the data processing system (121) or connected to the data processing system (121) by signal, for performing at least open-circuit calibration and short-circuit calibration under wet conditions, and compensating for the parasitic impedance of the fixture based on the calibration results, and outputting the ESR test results of the diaphragm sample; The temperature, humidity and pressure environment simulation system, the pressure closed-loop electrode pressurization mechanism, and the parasitic compensation and diaphragm ESR component extraction module work together to obtain repeatable ESR spectrum data under the wet conditions of the diaphragm sample being immersed in electrolyte.

2. The electrolytic capacitor separator ESR test apparatus of claim 1, wherein, The temperature, humidity and pressure environment simulation system also includes a humidifier (127), and the vacuum generator (125) with pressure detection and the pressure regulating valve (126) with pressure detection are configured to perform a vacuum-backpressure cycle to defoam and wet the diaphragm sample before testing and stabilize the cavity pressure within a preset range after backpressure.

3. The electrolytic capacitor separator ESR test apparatus of claim 1, wherein, The pressure closed-loop electrode pressurization mechanism also includes a servo motor driver (117), which drives a servo motor (115) and compensates for clamping pressure drift during frequency sweep to maintain constant clamping pressure.

4. The electrolytic capacitor separator ESR test apparatus of claim 1, wherein, The low parasitic connection assembly also includes an upper electrode sheath (110) and an anti-interference base plate (122). The upper electrode sheath (110) is used to reduce the leakage path around the upper electrode (109), and the anti-interference base plate (122) is used to reduce the parasitic coupling between the electrode and the analysis module (120).

5. The electrolytic capacitor separator ESR test apparatus of claim 1, wherein, The lower electrode electrolyte tank (112) is provided with an electrolyte tank fixing frame (114) to fix the relative position of the lower electrode electrolyte tank (112) and the guide ramp (113) to ensure the consistency of the wetting interface.

6. The electrolytic capacitor separator ESR test apparatus of claim 1, wherein, A heating plate (119) is provided below the lower electrode (111). The heating plate (119) is thermally connected to a temperature, humidity and pressure control unit (118) for local temperature control of the electrode area. The device also includes a cooling fan (124).

7. A method for testing the ESR of an electrolytic capacitor separator using the device according to any one of claims 1 to 6, characterized in that, include: S1, place the diaphragm sample in the effective test area of ​​the lower electrode (111), so that the guide ramp (113) area connecting the diaphragm sample and the electrolyte tank (112) of the lower electrode forms a wettable interface; S2, control the vacuum generator (125) with pressure detection and the pressure regulating valve (126) with pressure detection to perform vacuum-backpressure cycle to defoam and wet the diaphragm sample, and control the temperature, humidity and pressure control unit (118) to stabilize the temperature, humidity and air pressure of the test chamber to the preset test conditions. S3, drive the servo motor (115) to press down the upper electrode (109) via the upper electrode lead screw (116), and perform closed-loop control based on the pressure detection unit to make the clamping pressure reach and maintain the preset value; S4, the control analysis module (120) performs four-terminal calibration and establishes clamp parasitic compensation parameters; S5, the control analysis module (120) performs four-terminal impedance frequency sweep, and the data processing system (121) calculates the ESR spectrum of the diaphragm sample based on the clamp parasitic compensation parameters and outputs the results.

8. The test method of claim 7, wherein, S3 includes: monitoring the clamping pressure drift during frequency sweep, and when the drift exceeds a preset threshold, triggering a compensation displacement by the servo motor (115) to restore the clamping pressure to the preset value; and / or, S4 includes at least open-circuit calibration and short-circuit calibration, and S5 includes: the data processing system (121) performing equivalent circuit fitting on the measured impedance spectrum, stripping the electrode-electrolyte interface component, and outputting the membrane ESR contribution value; And / or, repeat S2 to S5 at at least two temperature setpoints according to the preset test sequence, and store the normalized ESR spectrum under each condition, while the printer (123) outputs the test report.

9. The test method of claim 7, wherein, The algorithm implementation method for parasitic compensation is as follows: Define admittance: ,in For admittance; Then: , Subtract open circuit parallel parasitics first: , Then, short-circuit calibration is used to normalize and correct the residual series error: ， ， Finally, the compensated impedance is obtained: ， wherein: is the de-embedded equivalent impedance; is the de-embedded admittance.

10. The test method of claim 9, wherein, obtained After that, two types of extraction methods can be used: Method 1: Target Frequency Point ESR ， wherein: is the target frequency (e.g., 100 kHz or 1 MHz); represents taking the real part; Method 2: Equivalent circuit fitting to remove interface components Data processing system Equivalent circuit fitting is performed, and the electrode-electrolyte interface component is stripped to output the membrane ESR contribution value.

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