A high thermal conductivity film capacitor made of graphite material and preparation method thereof

Abstract

The present invention relates to the technical field of capacitors, and in particular to a high thermal conductivity film capacitor of graphite material and a preparation method thereof, comprising spraying a graphene dispersion on a film surface, judging a conductive state of a coating, adjusting winding parameters to control movement of a spraying device; judging whether a graphene layer is evenly distributed, checking a dispersion concentration, or checking an actual layer thickness; judging a dispersion state of a graphene dispersion, determining a cause of an uneven distribution of a graphene layer, adjusting an ultrasonic treatment duration, or adjusting spraying parameters; adjusting spraying parameters according to whether an actual layer thickness meets a curing requirement, or drying and curing; determining a curing degree of a graphene coating, winding a film coil into a capacitor core package, or conducting a thermal stability test on the capacitor core package, adjusting a criterion for judging a conductive state of a coating and a distribution of a graphene layer, and adjusting an initial detection length; the present invention reduces a temperature of a capacitor during operation by coating a high thermal conductivity graphene material.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and in particular to a high thermal conductivity film capacitor made of graphite material and a preparation method thereof. Background Art

[0002] New energy vehicles have higher requirements for the reliability of capacitors, and the heat dissipation capacity of capacitors needs to be further improved, so the development of a high thermal conductivity film capacitor can better meet application needs.

[0003] Chinese patent application publication number: CN119381166A discloses a thin film capacitor and a method for preparing the same. When heat setting the capacitor core, an inert gas is used as a heat-conducting gas, and the space between the film layers of the thin film capacitor is filled with the inert gas, thereby being able to remove the water vapor between the film layers of the thin film capacitor. Since the inert gas is relatively stable, it is not easy to be ionized under the action of electrical stress and thermal stress, thereby being able to reduce the loss of the thin film capacitor. In addition, in the final stage of heat setting heating in the embodiment of the present invention, multiple cooling-heating treatments are performed within a certain temperature range, so that the metallized film in the capacitor core repeatedly expands and contracts, which is beneficial to remove the water vapor inside the metallized film material, thereby further reducing the loss of the thin film capacitor. It can be seen that the thin film capacitor and its preparation method have the following problems:

[0004] The existing core package process does not have a high heat dissipation capacity when the heat generated by the current is passed due to material limitations. Summary of the invention

[0005] To this end, the present invention provides a high thermal conductivity film capacitor of graphite material and a preparation method thereof, so as to overcome the problem that the existing core package process in the prior art does not have a high heat dissipation capacity due to material limitations when the heat generated when current passes through the core package process.

[0006] To achieve the above object, the present invention provides a high thermal conductivity film capacitor of graphite material and a preparation method thereof, comprising:

[0007] Using a spraying device to spray a graphene dispersion onto the surface of the film according to spraying parameters, and limiting the spraying area of ​​the graphene dispersion by a spraying jig to form a graphene layer on the surface of the film;

[0008] During the spraying process, the winding process at the tail end of the film coil is inspected, the surface resistance of the film coil in the capacitor core package is measured according to the initial inspection length, the conductive state of the coating is determined, the winding parameters are adjusted and the movement of the spraying equipment is controlled accordingly;

[0009] The coated film coil is tested according to the conductive state of the coating, the color difference between the graphene layer and the adjacent film surface is tested according to the initial test length, whether the graphene layer is evenly distributed, and the dispersion concentration or actual layer thickness is tested;

[0010] By analyzing the absorbance change of the graphene dispersion sample solution, the dispersion state of the graphene dispersion is judged, and the cause of the uneven distribution of the graphene layer is judged according to the dispersion state, so as to adjust the ultrasonic treatment time or spraying parameters;

[0011] Adjust the spraying parameters according to whether the actual layer thickness meets the curing requirements, or dry and cure the sprayed film roll according to the curing parameters;

[0012] Detect the adhesion between the coating and the film surface, determine the degree of curing of the graphene coating on the film, wind the film roll into a round capacitor core package and flatten the core package to shape it, or detect the thermal stability of the capacitor core package, adjust the evaluation criteria for the conductive state of the coating and whether the graphene layer is evenly distributed and adjust the initial detection length;

[0013] After shaping, gold spraying, heat treatment, welding and assembly are performed on both sides of the capacitor core package to form a high thermal conductivity film capacitor.

[0014] Further, the process of determining the conductive state of the coating includes,

[0015] Directly measure the surface resistance of the film coil in the capacitor core package according to the initial detection length, and calculate the resistance difference between the actual surface resistance of the current initial detection length and the historical surface resistance of the previous initial detection length;

[0016] Compare several resistance differences with the product of the historical surface resistance and the error ratio. Based on the comparison results,

[0017] It is judged that the coating is in the first conductive state, the coating is not uniformly conductive, and the pressure between the capacitor core layers is not uniform, and the winding speed is adjusted;

[0018] Or it is judged that the coating is in the second conductive state and the coating is uniformly conductive.

[0019] Further, when the coating is in the first conductive state, the winding speed after adjustment is compared with the winding speed before adjustment, and the speed difference before and after adjustment is calculated;

[0020] According to the comparison result, the spraying equipment is controlled to start moving toward the front end of the film coil according to the speed difference;

[0021] After the spraying parameters are adjusted or when the coating is in the second conductive state, the film coil that has been sprayed is inspected.

[0022] Furthermore, the process of testing the film coil after spraying includes:

[0023] Detect the color difference between the graphene layer and the adjacent film layer according to the initial detection length, calculate the average value of several color differences, and compare the average color difference with the difference evaluation value;

[0024] Whether the graphene layer is evenly distributed is determined based on the comparison results to check the concentration of the graphene dispersion or to check whether the actual thickness of the graphene layer reaches the required thickness for curing.

[0025] Further, the process of checking the concentration of the graphene dispersion includes,

[0026] When the graphene layer is unevenly distributed, the actual variance values ​​of the absorbance of several sample solutions are calculated and compared with the standard variance values;

[0027] According to the comparison results, the graphene dispersion is in the first dispersion state. The reason for the uneven distribution of the graphene layer is that the concentration of the dispersion does not meet the standard, and the ultrasonic treatment time is increased;

[0028] Or it is judged that the graphene dispersion is in the second dispersion state. The reason for the uneven distribution of the graphene layer is that the concentration of the dispersion does not match the spraying parameters, and the distance between the nozzle and the substrate is reduced.

[0029] Further, the process of verifying the actual layer thickness of the graphene layer includes,

[0030] When the graphene layer is evenly distributed, the required thickness for curing is calculated according to the standard curing thickness and the characteristics of the dispersion, the actual thickness of the graphene layer is detected, and the actual thickness is compared with the required thickness for curing;

[0031] According to the comparison result, it is judged that the actual layer thickness meets the curing requirements, and the film roll material that has been sprayed is cured;

[0032] Or if the actual layer thickness does not meet the curing requirements, increase the spraying air pressure.

[0033] Further, the process of determining the degree of curing of the graphene coating on the film includes:

[0034] Test the adhesion between the coating and the film surface according to the initial test length, and pull the coating according to the standard tensile force value;

[0035] The curing degree of the graphene coating on the film is judged to be at the first curing degree according to whether the coating is pulled away from the film;

[0036] Or the curing degree of the graphene coating on the film is at the second curing degree, and the curing temperature of the curing process is increased.

[0037] Further, when the graphene coating is in the first degree of solidification, the film roll is assembled on a winder and is normally wound into a circular capacitor core package according to the winding parameters designed for the capacitor;

[0038] When the graphene coating is in the second degree of curing, the capacitor core package is tested. The thermal expansion coefficient is calculated by measuring the dimensional change of the coating at different temperatures, and the thermal expansion performance is evaluated. The actual thermal conductivity of the capacitor core package is measured by a thermal conductivity tester.

[0039] Further, if the ratio of the difference in thermal expansion coefficients between the two sprayed areas of the capacitor core package to the average thermal expansion coefficient is greater than the error value, it is determined that the winding parameter fluctuation is large and the thickness of the capacitor core package is different, and the winding tension of the sprayed area of ​​the film roll is adjusted;

[0040] If the actual thermal conductivity is less than the standard thermal conductivity, the capacitor core package is judged to be unable to meet the thermal conductivity requirements, the evaluation criteria for the conductive state of the coating and the uniform distribution of the graphene layer are adjusted, and the initial detection length is adjusted.

[0041] A high thermal conductivity film capacitor made of graphite material,

[0042] The inner film of the capacitor core package of the high thermal conductivity film capacitor is coated with graphene material;

[0043] The inner envelope comprises a thin film layer and a graphene layer, and the graphene layer is located on both sides of the surface of the thin film layer.

[0044] Compared with the prior art, the beneficial effect of the present invention is that a large amount of heat is generated in the film capacitor during the power-on process. If the accumulated heat is not discharged, it will cause high-temperature damage to the capacitor core and affect the overall performance of the capacitor. When the method performs a spraying process on the film, a spraying jig is used during the spraying process to limit the graphene spraying area to a certain extent. A graphene coating is formed on the surface of the film coil after spraying. The graphene coating can significantly improve the conductivity, wear resistance and thermal conductivity of the polypropylene film, and improve the heat dissipation capacity of the heat generated when the core package passes the current. The heat dissipation of the graphene coating reduces the temperature of the capacitor during operation, and extends the service life and reliability of the capacitor. The color difference between the graphene layer and the adjacent film layer is used to judge whether the spraying is uniform, and the corresponding dispersion concentration is tested, or the actual layer thickness is tested to see whether it meets the standard, which increases the comprehensiveness and pertinence of the error test of the spraying process added by the method in the preparation process of the film capacitor.

[0045] Furthermore, when the winding speed in the winding process changes, the moving speed of the film on the production line will change, which will correspondingly affect the front-end spraying process and curing process. During the spraying process of the first section of the film, the present invention performs electrical testing on the capacitor core package in the winding process of the tail end of the film, and determines whether the pressure between the layers of the capacitor core package is uniform by the conductive state of the coating. The spraying process parameters are adjusted accordingly according to the changes in the winding process parameters to avoid the corresponding spraying process parameters not matching the changes in the winding process parameters. The degree of automation of the preparation process of the thin film capacitor is improved, and the conductivity of the graphene coating is evaluated by the conductivity test, thereby improving the applicability of high thermal conductivity thin film capacitors in conductive coatings, sensors and other fields.

[0046] Furthermore, the dispersion effect of graphene in the graphene solution directly affects the coating quality. When the graphene layer is unevenly distributed, the method first analyzes and judges the concentration of the dispersion liquid according to the absorbance variance of the sample solution to judge the dispersion state of the graphene dispersion liquid, and determines that the reason for the uneven distribution of the graphene layer is that the concentration of the dispersion liquid does not meet the standard, or the concentration of the dispersion liquid does not match the spraying parameters. Correspondingly, the ultrasonic treatment time is increased or the spraying parameters are adjusted, which improves the reaction speed of problems in the film capacitor preparation process and further increases the degree of automation of the preparation process.

[0047] Furthermore, after the solvent in the graphene coating of the film coil evaporates, the coating thickness will decrease, affecting the coverage and uniformity of the coating. As the solvent evaporates, the coating will shrink, which may cause cracks or wrinkles on the coating surface. Therefore, the thickness of the sprayed graphite layer needs to meet the required thickness for curing. In the previous steps, the method adjusts the spraying parameters accordingly according to the adjusted winding speed. After the spraying equipment drives the nozzle to start moving, it may affect the process of the spray liquid falling on the film and combining, resulting in a decrease in the amount of spray liquid per unit area of ​​the film, causing the actual layer thickness to become smaller. The method predicts whether the thickness of the sprayed graphite layer meets the required thickness for curing before curing, and adjusts the spraying parameters accordingly, thereby avoiding the reduction in coating thickness and causing cracks or wrinkles on the coating surface, increasing the coverage and uniformity of the coating, and improving the intelligence level of the spraying link in the preparation process and the adaptability of the preparation parameters to this method.

[0048] Furthermore, controlling the curing temperature and time is the key to avoiding defects in the coating. The method determines the degree of curing of the graphene coating on the film by detecting the adhesion between the coating and the surface of the object, and correspondingly increases the curing temperature to increase the degree of curing; at the same time, the method only sprays part of the film, and the strength of the sprayed area and the non-sprayed area of ​​the film roll is inconsistent. The winding tension needs to take into account that the non-sprayed area is subjected to a smaller tension. The thickness of the capacitor core package is judged by the thermal expansion coefficient. Increasing the winding tension in the sprayed area when winding the film roll reduces the thickness difference of the capacitor core package, avoids uneven winding in the non-sprayed area during winding, and improves the degree of automation and adaptability of the winding process in the preparation method; judging whether the capacitor core package can meet the thermal conductivity requirements based on the thermal conductivity coefficient, reducing the error ratio and the difference evaluation value, thereby lowering the evaluation criteria for the conductive state of the coating and whether the graphene layer is evenly distributed, and reducing the initial detection length to increase the detection accuracy, and ensuring that the graphene coating still maintains good performance under high temperature or extreme environment through thermal stability testing.

[0049] Furthermore, the method adds a graphite material coating process to the inner-rolled film production process, and the graphite is evenly coated on both sides of the film according to the required thickness, and a 10mm electrical distance is reserved in the middle. The capacitor made in this way has excellent thermal conductivity and reliability, improves the heat dissipation capacity of the core package when current passes through, improves the current capacity of the overall capacitor, and reduces the temperature of the capacitor during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the process of preparing a high thermal conductivity film capacitor made of graphite material in an embodiment of the present invention;

[0051] Figure 2 Schematic diagram of a device for preparing a high thermal conductivity film capacitor made of graphite material in an embodiment of the present invention;

[0052] Figure 3 Schematic diagram of a spraying process device in an embodiment of the present invention;

[0053] Figure 4 Schematic diagram of a film roll according to an embodiment of the present invention;

[0054] In the figure: 1-polypropylene film, 2-graphene coating, 3-spraying equipment, 4-spray gun, 5-spraying jig, 6-curing equipment, 7-winding equipment, 8-film roll. DETAILED DESCRIPTION

[0055] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0057] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0058] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] See also Figure 1-Figure 4 As shown, Figure 1 Schematic diagram of the process of preparing a high thermal conductivity film capacitor made of graphite material in an embodiment of the present invention; Figure 2 Schematic diagram of a device for preparing a high thermal conductivity film capacitor made of graphite material in an embodiment of the present invention; Figure 3 Schematic diagram of a spraying process device in an embodiment of the present invention; Figure 4 Schematic diagram of a film roll in an embodiment of the present invention.

[0060] The present invention provides a high thermal conductivity film capacitor of graphite material and a preparation method thereof, comprising:

[0061] Step S1, producing a large amount of carbon-containing gas through a high-temperature reaction chamber, preparing graphene by chemical vapor deposition, preparing a graphene dispersion, and placing the prepared graphene dispersion in a spraying device 3;

[0062] Step S2, using a spraying device 3 to spray graphene on the surface of the film according to spraying parameters, and limiting the graphene spraying area by a spraying jig 5 to form a graphene layer on the surface of the film;

[0063] Step S3, during the spraying process, the winding process of the tail end of the film coil 8 is detected, the surface resistance of the film coil 8 in the capacitor core package is directly measured according to the initial detection length, the conductive state of the coating is determined, the winding parameters are adjusted and the movement of the spraying device 3 is controlled accordingly;

[0064] Step S4, detecting the film coil 8 after spraying according to the conductive state of the coating, detecting the color difference between the graphene layer and the adjacent film layer according to the initial detection length, judging whether the graphene layer is evenly distributed, checking the concentration of the dispersion, or checking the actual layer thickness;

[0065] Step S5, by analyzing the absorbance change of the sample solution, judging the dispersion state of the graphene dispersion liquid, judging the cause of the uneven distribution of the graphene layer according to the dispersion state, adjusting the ultrasonic treatment time, or adjusting the spraying parameters;

[0066] Step S6, adjusting the spraying parameters according to whether the actual layer thickness meets the curing requirements, or drying and curing the sprayed film coil 8 according to the curing parameters, so that the sprayed film and the graphene layer can be fully cooled and attached;

[0067] Step S7, testing the cured film roll 8, determining the degree of curing of the graphene coating 2 on the film, and adjusting the curing parameters;

[0068] Step S8, according to the curing degree and the winding parameters, the film roll 8 is wound into a circular capacitor core package, the core package is flattened and shaped, or the capacitor core package is subjected to a thermal stability test, the conductive state of the coating and the judgment criteria of whether the graphene layer is evenly distributed are adjusted, and the initial detection length is adjusted;

[0069] Step S9, after finalization, both sides of the capacitor core package are sprayed with gold, heat treated, welded, assembled and packaged for storage.

[0070] In this embodiment, the preparation method uses a preparation device including:

[0071] The spraying device 3 is located above the first section of the film, with two spray guns 4 arranged at the bottom and a hanging moving device connected to the top, which can be moved above the film through the hanging moving device, and the height of the spraying device 3 can be changed by telescopic movement to adjust the relative distance between the spray gun 4 and the film;

[0072] A spraying tool 5, which is located in the middle above the film and at the bottom ends of the two spray guns 4, and is used to limit the film area where graphene is sprayed when the spraying device 3 sprays the film;

[0073] A curing device 6, which is located above the film and is used to dry and cure the film coil 8 after spraying according to the curing process parameters;

[0074] The winding device 7 is located at the tail end of the film coil 8 and is used to wind the solidified film coil 8 into a capacitor core package according to the winding process parameters.

[0075] The process of preparing graphene dispersion includes:

[0076] The graphene powder is mixed with a solvent (such as water or ethanol) to prepare a graphene dispersion, and the mixed graphene dispersion is treated with an ultrasonic treatment technique (frequency of 30kHz-1000kHz) to prevent agglomeration;

[0077] The spraying parameters set in this embodiment are: the distance between the nozzle and the substrate is 15-30cm, the spraying air pressure is 2-3kgf / cm², the substrate preheating temperature is 35-40°C, and the graphene dispersion is evenly sprayed on both sides of the surface of the polypropylene film 1 according to the required thickness, and an electrical distance of 10mm is reserved in the middle;

[0078] After spraying is completed, the film roll 8 is dried and cured using a curing device 6 to ensure that the graphene coating 2 is completely cured.

[0079] In this embodiment, the material of the film is a polypropylene film 1.

[0080] During the spraying process, the winding process of the tail end of the film coil 8 is detected, the winding parameters are adjusted, and the movement of the spraying device 3 is adjusted accordingly;

[0081] The capacitor performance test is used to determine whether the winding is uniform, and the surface resistance of the film coil 8 in the capacitor core package is directly measured according to the initial detection length using a surface resistance tester, and the resistance difference between the actual surface resistance of the current initial detection length and the historical surface resistance of the previous initial detection length is calculated;

[0082] The initial detection length is the unit detection length, which can be set according to specific needs.

[0083] If any resistance difference is greater than the product of the historical surface resistance and the error ratio, it is judged that the coating is in the first conductive state, the coating is not uniformly conductive, the pressure between the capacitor core layers is not uniform, and the winding speed is adjusted;

[0084] Specifically, the winding speed is reduced according to the ratio of the product of the historical surface resistance and the error ratio to the resistance difference.

[0085] If any resistance difference is less than or equal to the product of the historical surface resistance and the error ratio, it is determined that the coating is in the second conductive state and the coating is uniformly conductive.

[0086] The error ratio is set according to the ratio of the error value of the surface resistance to the historical data of the surface resistance of the capacitor core package that has passed the qualification test.

[0087] When the coating is in the first conductive state, the spraying parameters are adjusted accordingly according to the adjusted winding speed.

[0088] The adjusted winding speed is less than the winding speed before the adjustment. The speed difference is calculated according to the winding speeds before and after the adjustment, and the spraying device 3 is controlled to move toward the first section of the film coil 8 according to the speed difference.

[0089] Specifically, when the winding speed in the winding process changes, it will cause the moving speed of the film on the production line to change, which will correspondingly affect the front-end spraying process and curing process; the present invention performs electrical testing on the capacitor core package in the winding process of the tail end of the film during the spraying process of the first section of the film, and judges whether the pressure between the layers of the capacitor core package is uniform through the conductive state of the coating, and adjusts the spraying process parameters accordingly according to the changes in the winding process parameters to avoid the corresponding spraying process parameters not matching after the winding process parameters change, thereby improving the degree of automation of the preparation process of the thin film capacitor, evaluating the conductivity of the graphene coating 2 through the conductivity test, and improving the applicability of high thermal conductivity thin film capacitors in conductive coatings, sensors and other fields.

[0090] After adjusting the spraying parameters or when the coating is in the second conductive state, the film coil 8 that has been sprayed is inspected;

[0091] The color difference between the graphene layer and the adjacent film layer is detected by a spectrophotometer according to the initial detection length, and the average value of several color differences is calculated.

[0092] If the average color difference is greater than the difference evaluation value, it is judged that the graphene layer is unevenly distributed, and the concentration of the graphene dispersion is tested;

[0093] If the average color difference is less than or equal to the difference evaluation value, it is judged that the graphene layer is evenly distributed, and it is checked whether the actual layer thickness of the graphene layer reaches the required thickness for curing.

[0094] The difference evaluation value is set according to the historical data of the color difference between the graphene layer and the adjacent thin film layer.

[0095] Specifically, a film capacitor generates a large amount of heat during the power-on process. If the accumulated heat is not discharged, it will cause high-temperature damage to the capacitor core and affect the overall performance of the capacitor. When the method performs a spraying process on the film, a spraying jig 5 is used during the spraying process to limit the graphene spraying area to a certain extent. A graphene coating 2 is formed on the surface of the film roll 8 after spraying. The graphene coating 2 can significantly improve the conductivity, wear resistance and thermal conductivity of the polypropylene film 1, and improve the heat dissipation capacity of the heat generated when the core package passes current. The heat dissipation through the graphene coating 2 reduces the temperature of the capacitor during operation, and extends the service life and reliability of the capacitor; the color difference between the graphene layer and the adjacent film layer is used to judge whether the spraying is uniform, and the corresponding dispersion concentration is tested, or the actual layer thickness is tested to see whether it meets the standard, which increases the comprehensiveness and pertinence of the error inspection of the spraying process added by the method in the preparation process of the film capacitor.

[0096] When the graphene layer is unevenly distributed, several samples of the graphene dispersion are taken for ultraviolet-visible spectroscopy (UV-Vis) detection, and the dispersion state of the graphene dispersion is determined by analyzing the absorbance change of the sample solution, and the cause of the uneven distribution of the graphene layer is determined according to the dispersion state;

[0097] Calculate the actual variance of the absorbance of several sample solutions.

[0098] If the actual variance value is greater than the standard variance value, it is judged that the graphene dispersion is in the first dispersion state, the volatility of some sample solutions is large, the reason for the uneven distribution of the graphene layer is that the concentration of the dispersion does not meet the standard and the graphene powder agglomerates, and the ultrasonic treatment time is adjusted;

[0099] Specifically, the ultrasonic treatment time is increased according to the ratio of the actual variance value to the standard variance value;

[0100] If the actual variance value is less than or equal to the standard variance value, it is judged that the graphene dispersion is in the second dispersion state, the dispersion concentration meets the standard, and the reason for the uneven distribution of the graphene layer is that the dispersion concentration does not match the spraying parameters, and the spraying parameters are adjusted;

[0101] Specifically, the distance between the nozzle and the substrate is reduced according to the ratio of the actual variance value to the standard variance value;

[0102] The standard deviation value is set according to the fluctuation of graphene in the dispersion.

[0103] Specifically, the dispersion effect of graphene in the graphene solution directly affects the coating quality. When the graphene layer is unevenly distributed, the method first analyzes and judges the concentration of the dispersion according to the absorbance variance of the sample solution to judge the dispersion state of the graphene dispersion, and determines that the reason for the uneven distribution of the graphene layer is that the concentration of the dispersion does not meet the standard, or the concentration of the dispersion does not match the spraying parameters. Correspondingly, the ultrasonic treatment time is increased or the spraying parameters are adjusted, which improves the reaction speed of problems in the thin film capacitor preparation process and further increases the degree of automation of the preparation process.

[0104] When the graphene layer is evenly distributed, the required curing thickness is calculated according to the standard curing thickness and the dispersion characteristics. The cured thickness of the graphene layer after curing is equal to the product of the actual layer thickness and the dispersion concentration and the curing calculation coefficient. Therefore, the required curing thickness before curing is equal to the ratio of the standard curing thickness to the dispersion concentration and the curing calculation coefficient.

[0105] Detecting the actual thickness of the graphene layer, if the actual thickness is greater than or equal to the required thickness for curing, it is determined that the actual thickness meets the curing requirement, and the sprayed film roll 8 is cured;

[0106] If the actual layer thickness is less than the required curing thickness, it is determined that the actual layer thickness does not meet the curing requirements, and the spraying parameters are adjusted;

[0107] Specifically, the process of adjusting the spraying parameters is to increase the spraying air pressure according to the ratio of the required curing thickness to the actual layer thickness.

[0108] Specifically, after the solvent in the graphene coating 2 of the film roll 8 evaporates, the coating thickness will decrease, affecting the coverage and uniformity of the coating. As the solvent evaporates, the coating will shrink, which may cause cracks or wrinkles on the coating surface. Therefore, the thickness of the sprayed graphite layer needs to meet the required thickness for curing. In the previous steps, the method adjusted the spraying parameters accordingly according to the adjusted winding speed. After the spraying equipment 3 drives the nozzle to start moving, it may affect the process of the spray liquid falling on the film and combining, resulting in a decrease in the amount of spray liquid per unit area of ​​the film, causing the actual layer thickness to become smaller. The method predicts whether the thickness of the sprayed graphite layer meets the required thickness for curing before curing, and adjusts the spraying parameters accordingly, thereby avoiding the reduction in coating thickness and causing cracks or wrinkles on the coating surface, increasing the coverage and uniformity of the coating, and improving the intelligence level of the spraying link in the preparation process and the adaptability of the preparation parameters to this method.

[0109] The cured film roll 8 is tested by using an adhesion tester to test the adhesion between the coating and the film surface according to the initial test length.

[0110] If the coating is not pulled away from the film when the coating is pulled according to the standard pulling force value, it is judged that the curing degree of the graphene coating 2 on the film is at the first curing degree;

[0111] If the coating is pulled away from the film when the coating is pulled according to the standard tensile force value, it is judged that the curing degree of the graphene coating 2 on the film is at the second curing degree, and the curing temperature of the curing process is increased;

[0112] The standard tensile force value is a tester parameter set according to the required adhesion.

[0113] When the graphene coating 2 is in the first degree of solidification, the film roll 8 is assembled on the winding machine and is normally wound into a circular capacitor core package according to the winding parameters designed for the capacitor;

[0114] When the graphene coating 2 is in the second degree of solidification, the capacitor core package is tested, and the thermal expansion coefficient is calculated by measuring the dimensional change of the coating at different temperatures, and its thermal expansion performance is evaluated. The actual thermal conductivity of the capacitor core package is measured by a thermal conductivity tester.

[0115] If the ratio of the difference in thermal expansion coefficients of the two sprayed areas of the capacitor core package to the average thermal expansion coefficient is greater than the error value, it is judged that the winding parameter fluctuation is large and the thickness of the capacitor core package is different, and the winding tension of the sprayed area of ​​the film roll 8 is adjusted;

[0116] Specifically, the winding tension is increased according to the ratio of the difference in thermal expansion coefficient to the average thermal expansion coefficient;

[0117] If the actual thermal conductivity is less than the standard thermal conductivity, the capacitor core package is judged to be unable to meet the thermal conductivity requirements, the evaluation criteria for the conductive state of the coating and the uniform distribution of the graphene layer are adjusted, and the initial detection length is adjusted.

[0118] Specifically, the error ratio, the difference evaluation value and the initial detection length are reduced according to the ratio of the actual thermal conductivity to the standard thermal conductivity.

[0119] Among them, the winding parameters include winding tension, winding speed, initial thickness and stretching state of the film, the standard thermal conductivity is set according to actual needs, and the error value is ±1%.

[0120] Specifically, controlling the curing temperature and time is the key to avoiding defects in the coating. The method determines the degree of curing of the graphene coating 2 on the film by detecting the adhesion between the coating and the surface of the object, and correspondingly increases the curing temperature to increase the degree of curing; at the same time, the method only sprays part of the film, and the strength of the sprayed area and the non-sprayed area of ​​the film roll 8 are inconsistent. The winding tension needs to take into account that the non-sprayed area is subjected to a smaller tension. The thickness of the capacitor core package is judged by the thermal expansion coefficient. Increasing the winding tension in the sprayed area when winding the film roll 8 reduces the thickness difference of the capacitor core package, avoids uneven winding in the non-sprayed area during winding, and improves the degree of automation and adaptability of the winding process in the preparation method; judging whether the capacitor core package can meet the thermal conductivity requirements based on the thermal conductivity coefficient, reducing the error ratio and the difference evaluation value, thereby lowering the evaluation criteria for the conductive state of the coating and whether the graphene layer is evenly distributed, and reducing the initial detection length to increase the detection accuracy, and ensuring that the graphene coating 2 still maintains good performance under high temperature or extreme environment through thermal stability testing.

[0121] A high thermal conductivity film capacitor made of graphite material,

[0122] The high thermal conductivity film capacitor is prepared by winding a polypropylene film 1 into an inner film of a capacitor core package, coating a high thermal conductivity graphene material, hot pressing, gold spraying, welding, potting, and testing.

[0123] Specifically, the method adds a graphite material coating process to the inner-rolled film production process, and the graphite is evenly coated on both sides of the film according to the required thickness, and a 10mm electrical distance is reserved in the middle. The capacitor made in this way has excellent thermal conductivity and reliability, improves the heat dissipation capacity of the core package when current passes through, improves the current capacity of the overall capacitor, and reduces the temperature of the capacitor during operation.

[0124] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high thermal conductivity film capacitor of graphite material, characterized in that: include: Using a spraying device to spray a graphene dispersion onto the surface of the film according to spraying parameters, and limiting the spraying area of ​​the graphene dispersion by a spraying jig to form a graphene layer on the surface of the film; During the spraying process, the winding process at the tail end of the film coil is inspected, the surface resistance of the film coil in the capacitor core package is measured according to the initial inspection length, the conductive state of the coating is determined, the winding parameters are adjusted and the movement of the spraying equipment is controlled accordingly; The coated film coil is tested according to the conductive state of the coating, the color difference between the graphene layer and the adjacent film surface is tested according to the initial test length, whether the graphene layer is evenly distributed, and the dispersion concentration or actual layer thickness is tested; By analyzing the absorbance change of the graphene dispersion sample solution, the dispersion state of the graphene dispersion is judged, and the cause of the uneven distribution of the graphene layer is judged according to the dispersion state, so as to adjust the ultrasonic treatment time or spraying parameters; Adjust the spraying parameters according to whether the actual layer thickness meets the curing requirements, or dry and cure the sprayed film roll according to the curing parameters; Detect the adhesion between the coating and the film surface, determine the degree of curing of the graphene coating on the film, wind the film roll into a round capacitor core package and flatten the core package to shape it, or detect the thermal stability of the capacitor core package, adjust the evaluation criteria for the conductive state of the coating and whether the graphene layer is evenly distributed and adjust the initial detection length; After finalization, both sides of the capacitor core package are subjected to gold spraying, heat treatment, welding, and assembly to form a high thermal conductivity film capacitor; The process of controlling the movement of the spraying equipment and adjusting the spraying parameters includes: When the coating is in the first conductive state, the coating is not uniformly conductive and the pressure between the capacitor core layers is not uniform. The winding speed is adjusted and the adjusted winding speed is compared with the winding speed before the adjustment. Calculate the speed difference before and after the adjustment, and control the spraying equipment to move toward the front end of the film coil according to the speed difference according to the comparison result; After adjusting the spraying parameters or when the coating is in the second conductive state and the coating is evenly conductive, the film coil that has been sprayed is inspected; During the inspection of the film roll that has been sprayed, the reason for the uneven distribution of the graphene layer is that when the concentration of the dispersion liquid does not match the spraying parameters, the distance between the nozzle and the substrate is reduced.

2. The method for preparing a high thermal conductivity film capacitor of graphite material according to claim 1, characterized in that: The process of determining the conductive state of the coating includes: Directly measure the surface resistance of the film coil in the capacitor core package according to the initial detection length, and calculate the resistance difference between the actual surface resistance of the current initial detection length and the historical surface resistance of the previous initial detection length; Compare several resistance differences with the product of the historical surface resistance and the error ratio. Based on the comparison results, It is judged that the coating is in the first conductive state, the coating conductivity is uneven, and the pressure between the capacitor core layers is uneven. Adjust winding speed; Or it is judged that the coating is in the second conductive state and the coating is uniformly conductive.

3. The method for preparing a high thermal conductivity film capacitor of graphite material according to claim 1, characterized in that: The process of testing the finished film coil includes: Detect the color difference between the graphene layer and the adjacent film layer according to the initial detection length, calculate the average value of several color differences, and compare the average color difference with the difference evaluation value; Whether the graphene layer is evenly distributed is determined based on the comparison results to check the concentration of the graphene dispersion or to check whether the actual thickness of the graphene layer reaches the required thickness for curing.

4. The method for preparing a high thermal conductivity film capacitor of graphite material according to claim 3, characterized in that: The process of checking the concentration of graphene dispersion includes: When the graphene layer is unevenly distributed, the actual variance values ​​of the absorbance of several sample solutions are calculated and compared with the standard variance values; According to the comparison results, the graphene dispersion is in the first dispersion state. The reason for the uneven distribution of the graphene layer is that the concentration of the dispersion does not meet the standard, and the ultrasonic treatment time is increased; Or it is judged that the graphene dispersion is in the second dispersion state. The reason for the uneven distribution of the graphene layer is that the concentration of the dispersion does not match the spraying parameters, and the distance between the nozzle and the substrate is reduced.

5. The method for preparing a high thermal conductivity film capacitor of graphite material according to claim 3, characterized in that: The process of verifying the actual layer thickness of the graphene layer includes, When the graphene layer is evenly distributed, the required thickness for curing is calculated according to the standard curing thickness and the characteristics of the dispersion, the actual thickness of the graphene layer is detected, and the actual thickness is compared with the required thickness for curing; According to the comparison result, it is judged that the actual layer thickness meets the curing requirements, and the film roll material that has been sprayed is cured; Or if the actual layer thickness does not meet the curing requirements, increase the spraying air pressure.

6. The method for preparing a high thermal conductivity film capacitor of graphite material according to claim 1, characterized in that: The process of determining the degree of curing of the graphene coating on the film includes, Test the adhesion between the coating and the film surface according to the initial test length, and pull the coating according to the standard tensile force value; Determining the curing degree of the graphene coating on the film according to whether the coating is pulled away from the film, and determining that the curing degree is at a first curing degree when the coating is not pulled away from the film; The curing degree is determined to be at a second curing degree when the coating is pulled away from the film, and a curing temperature of the curing process is increased.

7. The method for preparing a high thermal conductivity film capacitor of graphite material according to claim 6, characterized in that: When the graphene coating is in the first degree of solidification, the film roll is assembled on the winder and wound into a circular capacitor core package according to the winding parameters designed for the capacitor; When the graphene coating is in the second degree of curing, the capacitor core package is tested. The thermal expansion coefficient is calculated by measuring the dimensional change of the coating at different temperatures, and the thermal expansion performance is evaluated. The actual thermal conductivity of the capacitor core package is measured by a thermal conductivity tester.

8. The method for preparing a high thermal conductivity film capacitor of graphite material according to claim 7, characterized in that: If the ratio of the difference in thermal expansion coefficients of the two sprayed areas of the capacitor core package to the average thermal expansion coefficient is greater than the error value, it is judged that the winding parameter fluctuation is large and the thickness of the capacitor core package is different, and the winding tension of the sprayed area of ​​the film roll is adjusted; If the actual thermal conductivity is less than the standard thermal conductivity, the capacitor core package is judged to be unable to meet the thermal conductivity requirements, the evaluation criteria for the conductive state of the coating and the uniform distribution of the graphene layer are adjusted, and the initial detection length is adjusted.

9. A high thermal conductivity film capacitor of graphite material, characterized in that: The method according to any one of claims 1 to 8 is used to prepare the film, wherein a graphite material coating process is added to the inner roll film production process, and graphite is evenly coated on both sides of the film according to the required thickness, and an electrical distance is reserved in the middle; The inner film of the capacitor core package of the high thermal conductivity film capacitor is coated with a graphene material, and the inner film comprises a film layer and a graphene layer, and the graphene layers are located on both sides of the surface of the film layer.

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