A thin film material breakdown voltage test electrode system under multiple stress

Abstract

The application discloses a thin film material breakdown test electrode system under multiple stress actions, which comprises a polyimide sheet II, wherein an annealed aluminum foil ground electrode, an annealed aluminum foil high-voltage electrode, a polyimide sheet I, a rubber pad and a pressure bearing block are sequentially arranged on the polyimide sheet II. The application solves the problems that the test data is affected by breakdown caused by air gap, the multiple stress cannot be effectively applied, the thin film sample and the aluminum foil electrode are easily damaged during the application process and heat transfer is poor in the existing electrode system.

Description

Technical Field

[0001] This invention belongs to the field of insulation material breakdown testing technology, and relates to an electrode system for testing the breakdown voltage of thin film materials under multiple stresses. Background Technology

[0002] Thin film materials are widely used in the field of thin film capacitors. The main insulating film material in capacitors is subjected to multiple stresses such as high temperature, AC and DC superimposed voltage, winding tension, and huge interlayer pressure. The breakdown voltage of the main insulating film material under multiple stresses determines the operating voltage level and insulation margin design of the capacitor device. Therefore, it is of great significance to accurately evaluate the breakdown voltage under multiple stresses related to the operating conditions, such as electrical, thermal, pressure, and tensile stresses.

[0003] Currently, there are two types of electrodes used in methods for testing the breakdown voltage of thin film materials, and the following situations exist:

[0004] Type 1 electrodes: The scheme uses brass or stainless steel electrodes as high-voltage and ground electrodes on both the high-voltage and ground sides. When a large pressure is applied to the thin film sample through the electrodes, the pressure distribution in the contact surface between the hard electrode and the thin film sample is uneven. The pressure is greatest at the electrode edge contour. Therefore, the thin film sample at the corresponding position of the electrode edge contour area will be damaged due to the very uneven force, resulting in indentation. As a result, the breakdown usually occurs in the indentation area, and incorrect breakdown test results are obtained. This type of electrode will damage the sample under pressure and affect the breakdown test results. Therefore, it cannot realize the breakdown test of thin film samples under multiple stresses.

[0005] The second type of electrode uses a brass pillar as the high-voltage electrode, an aluminum foil as the ground electrode, and a 3mm thick rubber pad under the aluminum foil. The problem with this type of electrode system is that the thermal conductivity of the 3mm rubber pad is too low. At the same time, the 3mm rubber pad deforms greatly under high pressure, which can easily cause the aluminum foil electrode to tear, thus making it unable to conduct electricity effectively.

[0006] Therefore, there is currently no suitable electrode system for testing the breakdown voltage of thin film materials under multiple stresses. Summary of the Invention

[0007] The purpose of this invention is to provide an electrode system for testing the breakdown voltage of thin film materials under multiple stresses, which solves the problems of current electrode systems, such as the reduction in breakdown voltage due to air gaps affecting test data, damage to thin film samples and aluminum foil electrodes during the application of multiple stresses, and poor heat transfer.

[0008] The technical solution adopted in this invention is a thin film material breakdown voltage test electrode system under multiple stresses, including a polyimide sheet II, on which an annealed aluminum foil ground electrode, an annealed aluminum foil high voltage electrode, a polyimide sheet I, a rubber pad, and a pressure block are sequentially laid.

[0009] The invention is further characterized by:

[0010] The annealed aluminum foil ground electrode and the annealed aluminum foil high voltage electrode are set at 180° relative to each other.

[0011] The annealed aluminum foil high-voltage electrode is located above the thin film sample, and the annealed aluminum foil ground electrode is located below the thin film sample.

[0012] A thin film sample in contact with the matte surface of an annealed aluminum foil ground electrode and an annealed aluminum foil high-voltage electrode.

[0013] The annealed aluminum foil ground electrode has the same structure as the annealed aluminum foil high voltage electrode. The annealed aluminum foil ground electrode is circular in shape, and the lead wire part is designed with chamfers.

[0014] The shape and size of the bottom surface of the pressure block are completely consistent with the shape and size of the electric field-bearing area between the annealed aluminum foil ground electrode and the annealed aluminum foil high-voltage electrode.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. This invention uses 6µm annealed aluminum foil as the electrode, which eliminates the air gap between the aluminum foil electrode and the sample, preventing the air gap from affecting the breakdown process and causing a drop in breakdown voltage. Simultaneously, the shape of the aluminum foil electrode is designed to ensure that the electric field between the high-voltage electrode and the ground electrode is as uniform as possible, preventing electric field distortion from affecting the breakdown voltage.

[0017] 2. When applying thermal stress to a sample using the electrode system provided by this invention, to ensure that the heat from the external heat source can be efficiently transferred to the thin film sample, the heat loss between the sample and the heat source should be minimized. To meet the above requirements, the electrode system uses a thin medium as much as possible and a "pressure-bearing block" is provided. The pressure-bearing block itself provides pressure, reduces the air gap between the sample and other media, improves the thermal conductivity, and facilitates the rapid and uniform application of thermal stress.

[0018] 3. This invention adopts a multi-layer structure design, and innovative work has been done in terms of multi-layer structure arrangement, material selection, shape and size. The electrode system provided by this invention achieves the effects of pressure transmission, pressure uniformity, and integrity of thin film sample and aluminum foil electrode when a pressure of at least 20MPa is applied to the sample, thereby ensuring good breakdown effect.

[0019] 4. This electrode system is designed to be small and compact, with the electrode orientation at 180°, which facilitates the application of mechanical tension in the vertical direction.

[0020] 5. The application of multiple stresses often damages the electrodes or thin film samples, thus requiring highly sophisticated electrode system design. This invention ensures the sample remains intact after multiple stresses are applied, and can simultaneously apply complex voltages, high temperatures, tensile forces, and compressive forces to achieve breakdown voltage testing with excellent results. This invention enables breakdown voltage measurement under simultaneous multiple stresses. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a thin film material breakdown voltage testing electrode system under multiple stress conditions according to the present invention;

[0022] Figure 2 This is a top view of a thin film material breakdown voltage testing electrode system under multiple stress conditions according to the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of the annealed aluminum foil high-voltage electrode in the electrode system for testing the breakdown voltage of thin film materials under multiple stresses according to the present invention.

[0024] Figure 4 This is a comparison diagram of the electrode system for testing thin film material breakdown under stress-free conditions and the existing electrode system.

[0025] Figures 5(a) to 5(b) This is a comparison diagram of the pressure distribution of the electrode system for testing the breakdown voltage of thin film materials under multiple stresses according to the present invention and the existing electrode system using pressure-sensitive test paper.

[0026] Figures 6(a) to 6(b) This is a comparison chart of the statistical distribution of 10 breakdown locations between the electrode system for testing the breakdown voltage of thin film materials under multiple stresses according to the present invention and the existing electrode system.

[0027] In the figure, 1. pressure block, 2. rubber pad, 3. polyimide sheet I, 4. annealed aluminum foil high-voltage electrode, 5. thin film sample, 6. annealed aluminum foil ground electrode, 7. polyimide sheet II. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0029] This invention discloses a breakdown voltage testing electrode system for thin film materials under multiple stresses, which is used to test the breakdown voltage of thin film materials under the simultaneous application of multiple stresses, including complex voltage stress, thermal stress, tensile force, and pressure. The simultaneous application of multiple stresses can ensure the integrity of the thin film and not affect the breakdown voltage test.

[0030] This invention provides an electrode system for testing the breakdown voltage of thin film materials under multiple stresses, such as... Figure 1 , 2As shown, it includes a polyimide sheet II7, on which an annealed aluminum foil ground electrode 6, a thin film sample 5, an annealed aluminum foil high voltage electrode 4, a polyimide sheet I3, a rubber pad 2, and a pressure block 1 are sequentially laid, and a pressure P is applied to the pressure block 1.

[0031] The function of the polyimide sheet II7 is to provide a smooth lower surface, preventing the ground electrode aluminum foil from contacting surfaces that are not smooth enough, such as the operating table or heating plate. Direct contact with rough surfaces may cause unevenness in the lower aluminum foil, affecting the flatness and adsorption of the upper and lower aluminum foil electrodes, and thus introducing air gaps that affect the accuracy of the breakdown voltage test. In addition, because the aluminum foil and film are very thin, it is difficult to transfer them together without deformation or relative displacement when they are arranged in multiple layers. The lower and upper polyimide layers together hold the film and aluminum foil sample, making it easier for the operator to transfer the multi-layer structure together. For example, a double layer of polyimide can be used to hold the sample and aluminum foil electrodes, and then transfer them to the pressure application and heat application device.

[0032] The annealed aluminum foil ground electrode 6 and the annealed aluminum foil high voltage electrode 4 are arranged opposite each other at a 180° angle, and the thin film sample 5 is located between the annealed aluminum foil ground electrode 6 and the annealed aluminum foil high voltage electrode 4.

[0033] The annealed aluminum foil high-voltage electrode 4 is located above the thin film sample 5, and the annealed aluminum foil ground electrode 6 is located below the thin film sample 5.

[0034] Both the annealed aluminum foil ground electrode 6 and the annealed aluminum foil high-voltage electrode 4 have a thickness of 6 μm. 6 μm annealed aluminum foil is used as the electrode, and the matte surfaces of the annealed aluminum foil ground electrode 6 and the annealed aluminum foil high-voltage electrode 4 contact the thin film sample 5. The 6 μm annealed aluminum foil ground electrode 6 and the annealed aluminum foil high-voltage electrode 4 are lightweight. When voltage is applied, the high-voltage electrode and the ground electrode attract each other due to electrostatic forces, achieving mutual adsorption between the aluminum foil electrode, the thin film sample, and the aluminum foil electrode. Simultaneously, the annealed aluminum foil ground electrode 6 and the annealed aluminum foil high-voltage electrode 4 have a certain degree of ductility, and the roughness of the matte surface is smaller than that of the other side. Therefore, using 6 μm annealed aluminum foil as the electrode can eliminate the air gap between the aluminum foil electrode and the sample, preventing the air gap from affecting the breakdown process and causing a decrease in breakdown voltage.

[0035] Meanwhile, to ensure the electric field between the high-voltage electrode and the ground electrode is as uniform as possible and to prevent electric field distortion from affecting the breakdown voltage, the shape of the aluminum foil electrode was also designed. The annealed aluminum foil ground electrode 6 has the same structure as the annealed aluminum foil high-voltage electrode 4. Taking the annealed aluminum foil ground electrode 6 as an example, the following explanation is provided: Figure 3 As shown, the annealed aluminum foil ground electrode 6 is circular in shape, and the lead wire part is also chamfered with a radius of 10mm to generate a more uniform electric field between the aluminum foil electrodes and prevent electric field distortion from affecting the breakdown voltage.

[0036] The thickness of both polyimide sheet I3 and polyimide sheet II7 is 100um. The reason for designing the thickness to be 100um is that if it is too thin, the polyimide itself will be damaged, and if it is too thick, it will affect heat transfer. The thickness of rubber pad 2 is 1mm. If it is too thin, rubber pad 2 itself will be torn and damaged.

[0037] When applying thermal stress to the sample, in order to ensure that the heat from the external heat source can be efficiently transferred to the thin film sample 5, the heat loss between the sample and the heat source should be minimized. To meet the above requirements, a thin dielectric material should be selected as much as possible in the electrode system, and a pressure block 1 should be set up. The pressure block 1 itself provides a pressure P, which reduces the air gap between the thin film sample 5 and other dielectric materials, improves the thermal conductivity, and facilitates the rapid and uniform application of thermal stress.

[0038] A metal cylinder with a diameter of 20mm and a height of 20mm is selected as the pressure-bearing block 1, which serves to transmit pressure. The required pressure can be applied to the top of the pressure-bearing block 1. Since its base area is fixed, the pressure on the lower surface of the block can be calculated based on the applied pressure. In actual multi-stress breakdown tests, the applied pressure is usually determined based on the pressure required for the test sample. Furthermore, the shape and size of the bottom surface of the pressure-bearing block 1 are designed to perfectly match the shape and size of the electric field borne by the aluminum foil electrode. This ensures the overlap between the effective electric field region and the effective pressure region. This overlap ensures that the film in the area where breakdown may occur does indeed bear the expected pressure, thus ensuring the validity of the stress test data.

[0039] A 1mm thick rubber pad 2 is placed under the pressure block 1. The rubber pad 2 can play a role in uniform pressure. Without the rubber pad 2, in the multilayer electrode system, the pressure in the edge area of ​​the bottom surface of the pressure block 1 is significantly greater than that in the center area, resulting in uneven pressure stress on the thin film sample 5, which affects the breakdown voltage test results under multiple stresses.

[0040] Based on the stress-strain characteristics of the rubber pad 2, it is known that under vertical pressure, as the rubber pad 2 shortens in the vertical direction, it will undergo corresponding elongation deformation in the horizontal direction. If the rubber pad 2 directly contacts the thin film sample 5, the annealed aluminum foil ground electrode 6, and the annealed aluminum foil high-voltage electrode 4, the horizontal elongation deformation of the rubber pad 2 will lead to the destruction of the thin film sample 5, the annealed aluminum foil ground electrode 6, and the annealed aluminum foil high-voltage electrode 4. Therefore, the polyimide sheet I3 placed below the rubber pad 2 has very small horizontal deformation when transmitting vertical pressure, thus protecting the thin film sample 5, the annealed aluminum foil ground electrode 6, and the annealed aluminum foil high-voltage electrode 4 from damage. At the same time, the 100µm thickness of the polyimide sheet I3 is small enough to meet the heat transfer efficiency requirements of the system after the heating plate is placed below the multilayer electrode system.

[0041] In other words, this system can apply multiple stresses while ensuring that the sample itself is not affected by the application of multiple stresses, and will not negatively impact the breakdown voltage test. It is mainly suitable for conditions with multiple stresses.

[0042] Compared with other electrode systems, the present invention has excellent breakdown results without stress and can successfully carry out breakdown tests under various expected stresses. Therefore, it can obtain breakdown test data with and without stress and under different degrees of external stress, which is convenient for forming a comparison.

[0043] like Figure 4 As shown, electrode 1 corresponds to Clause 21.3 of GB / T13542.2-2021 Thin Films for Electrical Insulation - Part 2: Test Methods, electrode 2 corresponds to Clause 18.2.2.2 of GB / T13542.2-2009 Thin Films for Electrical Insulation - Part 2: Test Methods, and electrode 3 corresponds to the DC breakdown test results of the method of the present invention without the application of multiple stress.

[0044] The electrode system provided by the invention corresponds to Figure 4 Electrode 3 in the model exhibits high breakdown strength and low dispersion in breakdown data, demonstrating the effectiveness of the method and its independence from factors such as air gaps and sample damage. For details on how this invention achieves good breakdown voltage testing results without applying multiple stresses, please refer to [link to details]. Figure 4 .

[0045] Figure 4 This is a statistical graph of the data after the breakdown test. The data was fitted using a Weibull distribution and quantitatively analyzed. α is called the Weibull distribution scale factor, reflecting the characteristic value (similar to the mean in a normal distribution) when the breakdown voltage probability of a data set is 63.2%. The higher the overall breakdown voltage, the larger the scale factor. β is called the Weibull distribution shape factor, reflecting the dispersion of the data set (similar to the standard deviation in a normal distribution). The more concentrated the data set, the better. Various adverse factors such as air gap introduction, field distortion, and sample damage can lead to a decrease in both the scale factor and shape factor.

[0046] Electrode 3 of the electrode system provided by this invention, when no stress is applied, has high breakdown strength and low dispersion in breakdown data, proving the effectiveness of the method.

[0047] The electrode 3 corresponding to the electrode system provided by this invention has the advantage of being able to withstand multiple stresses without affecting the sample itself or the breakdown results. Other existing electrode systems have their own problems to varying degrees and cannot be used under multiple stresses. Therefore, its specific effect is not reflected in the breakdown data, but rather in the state of the sample after applying multiple stresses (for example, obvious sample damage can be observed) and the unreasonable breakdown location (the breakdown occurs at the weak insulation location of the sample).

[0048] The performance of the electrode system provided by this invention is compared with that of existing electrode systems, and the results are as follows:

[0049] Figure 5(a) shows the pressure distribution of the electrode system of the present invention under a pressure of 20 MPa when tested with pressure-sensitive paper. The darker the color, the greater the pressure. It can be seen that the pressure distribution is very uniform within the preset circular pressure area.

[0050] Figure 5(b) shows an existing electrode system tested using pressure-sensitive paper. Figure 4 The pressure distribution of the middle electrode 1) under 20MPa pressure shows that the pressure at the edge of the electrode is significantly greater than that in the center.

[0051] Figure 6(a) shows the statistical distribution of breakdown positions in 10 breakdown tests within the pressure region of the electrode system of the present invention. The breakdown positions are relatively evenly distributed in the overlapping regions of the pressure and electric fields.

[0052] Figure 6(b) shows the existing electrode system ( Figure 4 The statistical distribution of breakdown locations in 10 breakdown tests within the pressure area of ​​the middle electrode 1) shows that the breakdown points are mainly concentrated at the indentation location on the electrode edge (the area between the dashed line and the solid line of the outer contour is the indentation width area).

[0053] This invention provides an electrode system for testing the breakdown voltage of thin film materials under multiple stresses. Addressing the problems of existing electrode systems, the solution adopted is as follows:

[0054] 1. To address the problem that existing commonly used electrode systems introduce air gaps that are not negligible for micron-sized thin film materials, affecting the breakdown voltage test results: The solution adopted in this invention is to use 6µm annealed aluminum foil as the electrode, and to use the matte side of the annealed aluminum foil to contact the sample.

[0055] The technical principle behind the above method is as follows: 6µm aluminum foil is lightweight. When voltage is applied, the high-voltage electrode and the ground electrode attract each other due to electrostatic forces, achieving mutual adsorption between the aluminum foil electrode, the thin film sample, and the aluminum foil electrode. Simultaneously, the annealed aluminum foil has a certain degree of ductility, and its matte surface roughness is smaller than that of the other side. Therefore, using 6µm annealed aluminum foil as the electrode can eliminate air gaps between the aluminum foil electrode and the sample, preventing these gaps from affecting the breakdown process and causing a drop in breakdown voltage. Furthermore, to ensure a uniform electric field between the high-voltage electrode and the ground electrode and to prevent electric field distortion from affecting the breakdown voltage, the aluminum foil electrode is designed in a circular shape, with chamfered edges on the lead wires.

[0056] 2. To address the problem that existing electrode systems cannot effectively apply multiple stresses such as heat, pressure, and tension, the solution proposed in this invention is to design a multi-layered electrode system to address the issues in applying pressure and heat to the electrode system.

[0057] The specific solution is as follows: A 1mm thick rubber pad is placed under the pressure block. The rubber pad can uniformly distribute the pressure. Based on the stress-strain characteristics of the rubber pad, under vertical pressure, as the rubber pad shortens vertically, it will undergo corresponding elongation deformation in the horizontal direction. If the rubber pad directly contacts the sample film and aluminum foil, the horizontal elongation deformation of the rubber pad will lead to damage to the film and aluminum foil electrodes. Therefore, a polyimide sheet is placed under the rubber pad. Due to its high modulus, the polyimide sheet exhibits minimal horizontal deformation when transmitting high vertical pressure, thus protecting the film sample and aluminum foil from damage. This ensures that the film sample and aluminum foil electrodes remain intact and the electric field is uniformly applied even under a pressure of at least 20MPa. When applying thermal stress to the sample, to ensure efficient heat transfer from the external heat source to the film sample, heat loss between the sample and the heat source should be minimized. To meet the above requirements, the electrode system uses a thin dielectric material as much as possible, and a "pressure block" is set up. The pressure block itself provides pressure, reduces the air gap between the sample and other media, improves the thermal conductivity, and facilitates the rapid and uniform application of thermal stress.

[0058] Meanwhile, the shape and size of the bottom surface of the pressure-bearing block are designed to be completely consistent with the shape and size of the electric field borne by the aluminum foil electrode. This ensures the overlap between the effective electric field region and the effective pressure region. The overlap of these two regions ensures that the film at the breakdown location has indeed withstood the expected pressure, thus ensuring the validity of the test data under stress.

Claims

1. A thin film material breakdown test electrode system under multiple stresses, characterized in that: It includes a polyimide sheet II (7), on which an annealed aluminum foil ground electrode (6), an annealed aluminum foil high voltage electrode (4), a polyimide sheet I (3), a rubber pad (2) and a pressure block (1) are sequentially laid; The annealed aluminum foil ground electrode (6) and the annealed aluminum foil high voltage electrode (4) are positioned at 180° relative to each other; The annealed aluminum foil high-voltage electrode (4) is located above the thin film sample (5), and the annealed aluminum foil ground electrode (6) is located below the thin film sample (5). The matte surface of the annealed aluminum foil ground electrode (6) and the annealed aluminum foil high voltage electrode (4) are in contact with the thin film sample (5); The annealed aluminum foil ground electrode (6) has the same structure as the annealed aluminum foil high voltage electrode (4). The annealed aluminum foil ground electrode (6) is circular in shape and has chamfered edges on the lead wire portion. The shape and size of the bottom surface of the pressure block (1) are completely consistent with the shape and size of the annealed aluminum foil ground electrode (6) and the annealed aluminum foil high voltage electrode (4) that bear the electric field; The thickness of the annealed aluminum foil ground electrode (6) and the annealed aluminum foil high voltage electrode (4) is 6 μm; the thickness of the polyimide sheet I (3) and the polyimide sheet II (7) is 100 μm; the thickness of the rubber pad (2) is 1 mm; and a metal cylinder with a diameter of 20 mm and a height of 20 mm is selected as the bearing block (1).

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