Capacitor for wireless charging

Abstract

The invention provides a capacitor for wireless charging, and belongs to the technical field of wireless charging. In order to solve the problems that a capacitor for wireless charging is large in weight and high in cost, the capacitor for wireless charging comprises a capacitor body, and the capacitor body comprises a plurality of first electrode plates and second electrode plates which are alternately arranged in a stacked mode in the first direction. An insulating sheet is arranged between the adjacent first electrode plate and second electrode plate; the insulation sheet is made of single crystal aluminum oxide, metal layers are arranged on the opposite surfaces of the insulation sheet and are in contact conduction with the first electrode sheet and the second electrode sheet respectively, and orthographic projections of the two metal layers in the first direction are overlapped; isolation cavities are formed in the circumferential directions of the first electrode plate and the second electrode plate, and the isolation cavities are filled with insulating materials. According to the invention, the light weight and low cost of the capacitor are realized, and the capacitance value precision of the capacitor can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of wireless charging, and in particular to a capacitor for wireless charging. Background Art

[0002] In recent years, with the continuous development of artificial intelligence and control technology, various mobile service platforms such as intelligent robots, large drones, and unmanned express delivery vehicles have received more and more attention and applications in various industries. The traditional wired charging mode mainly relies on manual intervention, resulting in low availability of unmanned equipment distributed throughout the geographical area. The magnetic resonance wireless power transmission technology has a high degree of power supply flexibility and safety. Since 2007, it has received extensive attention and research in academia and industry. This type of mobile service platform (such as the above-mentioned unmanned equipment) uses magnetic resonance wireless charging, which can significantly improve the availability of the equipment.

[0003] However, the medium-power wireless charging devices suitable for these devices are still large in size and weight. Currently, the weight of wireless power transmission receivers with a power of 500-3000 watts on the market is generally 3-10 kilograms, and the weight gradually increases with the increase of charging power, resulting in increased power consumption of the equipment, low actual energy efficiency, and unfavorable integration. For example, for battery-driven drone equipment, the introduction of wireless charging is convenient to use, but it greatly increases the power consumption of the equipment, shortens the battery charging cycle, and reduces the operating energy efficiency.

[0004] Therefore, the lightweight and low cost of medium and high power wireless charging equipment is an important improvement direction for the popularization and application of wireless charging technology.

[0005] There are also some lightweight methods in the existing technology. For example, in terms of circuit design, the E or EF2 type circuit topology is used to reduce the number of electronic components used; in terms of heat dissipation, the coil is connected to the metal shell base to increase the surface area of ​​the material used; in terms of shell design, low-density and high-thermal conductivity engineering plastics or composite materials are used. These methods can reduce weight to a certain extent. However, these methods cannot fundamentally optimize the core components of magnetic resonance wireless charging, that is, the resonant body composed of coils and capacitors, which is the main body of wireless charging and determines the size and weight of the device.

[0006] Furthermore, it is difficult to balance the cost and performance of capacitor optimization at this stage. Common organic dielectric materials such as PP, PTFE, PE, PS, etc., although simple to prepare and relatively stable in nature, have a small dielectric constant, and have a higher volume and weight under the same capacitor withstand voltage and capacity requirements; common inorganic dielectric materials such as barium titanate, niobium oxide, tantalum oxide, etc., these materials have large dielectric losses at high frequencies, and the capacitance is easily affected by the DC bias voltage, and the temperature characteristics are general; and other special inorganic materials such as magnesium, zinc doped titanium dioxide, niobium oxide, tantalum oxide and natural mica, etc., have relatively complex preparation processes and high costs, which are not conducive to the popularization of wireless charging systems. In addition, the capacity error of commercial capacitors is usually between 2% and 20%, which makes it difficult to accurately control the capacity, which is not conducive to commercial debugging. Summary of the invention

[0007] The purpose of the present application is to solve the problem of heavy weight and high cost of capacitors used for wireless charging in the prior art. Therefore, the present application provides a capacitor for wireless charging, which achieves lightness and low cost of the capacitor by adopting an insulating sheet made of single crystal alumina, and improves the accuracy of the capacitance value of the capacitor by adjusting the overlapping area ratio of the metal layers on both sides of the insulating sheet.

[0008] The embodiment of the present application provides a capacitor for wireless charging, comprising a capacitor body, wherein the capacitor body comprises a plurality of first electrode sheets and second electrode sheets alternately and stacked along a first direction, and an insulating sheet is arranged between adjacent first electrode sheets and second electrode sheets;

[0009] The plurality of first electrode sheets are electrically connected to each other, and the plurality of second electrode sheets are electrically connected to each other;

[0010] The insulating sheet is made of single crystal aluminum oxide, and metal layers are provided on opposite surfaces of the insulating sheet, and are respectively in contact and conductive with the first electrode sheet and the second electrode sheet, and the orthographic projections of the two metal layers in the first direction overlap;

[0011] An isolation cavity is disposed in the circumferential direction of the first electrode sheet and the second electrode sheet, and the isolation cavity is filled with insulating material.

[0012] By adopting the above technical scheme, by using an insulating sheet made of single crystal alumina, and utilizing the higher dielectric constant, lower dielectric loss rate, stable chemical properties and lower cost of alumina, the capacitor can be lightweight and low-cost while maintaining relatively excellent performance; at the same time, by arranging metal layers with projected overlapping areas on the surfaces of both sides of the insulating sheet, the capacitance value of the capacitor can be accurately adjusted by adjusting the overlapping area ratio, thereby improving the commercial quality of the capacitor; and the process for preparing insulating sheets from single crystal alumina is relatively mature, which ensures the quality of the capacitor and effectively controls the manufacturing cost of the capacitor.

[0013] In some embodiments, the metal layer overlapping area ratio of a part of the insulating sheets in the capacitor body is 4-96%, and varies in multiples of 4%; the metal layer overlapping area ratio of another part of the insulating sheets is 100%.

[0014] By adopting the above technical solution, the capacity adjustment is achieved by adjusting the overlapping area ratio of the metal layer of part of the insulating sheet, while the other part is 100%, which can further ensure the accuracy of capacity adjustment, reduce manufacturing difficulty and control costs; and, by controlling the adjustment ratio range and the change amount, the capacity error requirements and cost control can be taken into account, which is convenient for manufacturing.

[0015] In some embodiments, the insulating sheet is obtained by forming the metal layer on the front and back surfaces of an aluminum oxide wafer respectively through photolithography and thin film processing, and then cutting.

[0016] By adopting the above technical solution and through a relatively mature semiconductor manufacturing process, the quality of the capacitor is further ensured and the cost is controlled.

[0017] In some embodiments, the metal layer is located in the central area of ​​the surface of the insulating sheet, and a conductive glue coating is disposed between the metal layer and the first electrode sheet or the second electrode sheet.

[0018] In some embodiments, the capacitor further comprises a first receiving electrode and a second receiving electrode, wherein the first receiving electrode and the second receiving electrode are respectively located on opposite sides of the capacitor body along the first direction, and the first receiving electrode and the second receiving electrode are both provided with a plurality of receiving grooves spaced apart along the first direction;

[0019] The first electrode sheet has a first connecting portion extending toward the first receiving electrode, and the first connecting portion protrudes from the edge of the insulating sheet and is inserted into the corresponding receiving groove of the first receiving electrode, so that the plurality of first electrode sheets are mutually conductive through the first receiving electrode;

[0020] The second electrode sheet has a second connecting portion extending toward the second receiving electrode, and the second connecting portion protrudes from the edge of the insulating sheet and is inserted into the corresponding receiving groove of the second receiving electrode, so that the plurality of second electrode sheets are electrically connected to each other through the second receiving electrode.

[0021] By adopting the above technical solution, through the cooperation of the first receiving electrode and the first connecting part, as well as the cooperation of the second receiving electrode and the second connecting part, regular connection and conduction of multiple first electrode sheets and multiple second electrode sheets are achieved, thereby improving the overall regularity of the capacitor; and avoiding the unstable connection between a single first electrode sheet or a second electrode sheet and the corresponding first receiving electrode or a second receiving electrode, resulting in the inability to connect and conduct the whole; at the same time, it is also convenient to increase or decrease the first electrode sheet and the second electrode sheet gradually according to the capacitance requirements, and to achieve conduction respectively.

[0022] In some embodiments, a conductive connection seat is integrally formed on a side of the first receiving electrode away from the capacitor body, and the connection seat includes a circular limiting space adapted to a coil for wireless charging;

[0023] The second receiving electrode is connected to a conductive flexible connector, and the flexible connector is used to connect the second receiving electrode and a circuit board.

[0024] By adopting the above technical solution, the connecting seat and the flexible connector are connected to the coil and the circuit board respectively, which can reduce parasitic capacitance, inductance and resistance; and the flexible connector avoids the mechanical stress caused by thermal expansion and contraction between the capacitor and the circuit board, thereby ensuring the connection stability.

[0025] In some embodiments, a heat-resistant insulating plate is provided between the capacitor body and the first receiving electrode, and between the capacitor body and the second receiving electrode;

[0026] One side of the heat-resistant insulating plate is attached to the first receiving electrode or the second receiving electrode and bonded by insulating glue, and the other side is spaced apart from the corresponding side of the capacitor body to form a buffer cavity;

[0027] The first connecting portion of the first electrode sheet or the second connecting portion of the second electrode sheet sequentially passes through the corresponding buffer cavity and the heat-resistant insulating plate to be connected to the first receiving electrode or the second electrode sheet.

[0028] In some embodiments, the buffer cavity is filled with a high thermal conductivity insulating resin.

[0029] In some embodiments, a shell is further included, the shell covers the outside of the capacitor body that is not covered by the first receiving electrode or the second receiving electrode, and the shell is made of single crystal aluminum oxide.

[0030] By adopting the above technical solution, the shell of the capacitor is prepared by single crystal alumina, and the high thermal conductivity of single crystal alumina is utilized to significantly improve the heat dissipation and load-carrying capacity of the capacitor.

[0031] In some embodiments, a high thermal conductivity insulating resin is filled between the housing and the capacitor body.

[0032] Other features and corresponding beneficial effects of the present application are described in the latter part of the specification, and it should be understood that at least some of the beneficial effects become obvious from the records in the specification of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the structure of an embodiment of the present application;

[0034] Figure 2 It is a schematic cross-sectional structure diagram of an embodiment of the present application;

[0035] Figure 3 This is a schematic diagram of the structure of the capacitor body according to an embodiment of the present application;

[0036] FIG4( a ) is a schematic diagram of the connection state of the embodiment of the present application with the coil and the circuit board;

[0037] FIG4( b ) is a schematic diagram of the connection state of the embodiment of the present application and the circuit board at another angle;

[0038] Figure 5 A schematic diagram of the manufacturing process of an embodiment of the present application;

[0039] FIG6( a ) is a schematic diagram of a process of wafer selection in a manufacturing step of an embodiment of the present application;

[0040] FIG6( b ) is a schematic diagram of the process of photolithography, thin film deposition and wafer cutting in the manufacturing steps of an embodiment of the present application;

[0041] FIG6( c ) is a schematic diagram of the assembly process in the manufacturing steps of an embodiment of the present application;

[0042] FIG. 7( a ) is a schematic diagram of wafer front-side photolithography in an embodiment of the present application;

[0043] FIG7( b ) is a schematic diagram of wafer backside photolithography in an embodiment of the present application;

[0044] FIG. 7( c ) is a schematic diagram showing the superposition of the front and back lithography areas of the wafer in an embodiment of the present application.

[0045] Description of reference numerals:

[0046] 1. Circuit board; 2. Coil;

[0047] 10. capacitor body; 11. first electrode sheet; 111. first connection portion; 12. second electrode sheet; 121. second connection portion; 13. insulating sheet; 14. isolation cavity;

[0048] 20. First storage electrode; 21. Storage groove; 22. Buffer cavity; 23. Heat-resistant insulating plate; 24. Connecting seat;

[0049] 30. A second receiving electrode; 31. A flexible connecting member;

[0050] 40. Shell. DETAILED DESCRIPTION

[0051] The following specific embodiments illustrate the implementation of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Although the description of the present application will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this application are limited to the implementation. On the contrary, the purpose of introducing the application in conjunction with the implementation is to cover other options or modifications that may be extended based on the claims of the present application. In order to provide a deep understanding of the present application, the following description will include many specific details. The present application can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0052] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0053] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description created by the present application, unless otherwise specified, "multiple" means two or more. 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 directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0054] See also Figure 1-3 , Figure 1 This is a schematic diagram of the structure of an embodiment of the present application; Figure 2 It is a schematic cross-sectional structure diagram of an embodiment of the present application; Figure 3 Schematic diagram of the structure of the capacitor body according to an embodiment of the present application.

[0055] The embodiments of the present application provide a capacitor for wireless charging, which is particularly suitable for medium and high power wireless charging devices.

[0056] The capacitor includes a capacitor body 10, which includes a plurality of first electrode sheets 11 and second electrode sheets 12 alternately and stacked along a first direction, and an insulating sheet 13 is disposed between adjacent first electrode sheets 11 and second electrode sheets 12. The first direction may be a height direction of the capacitor body 10.

[0057] The plurality of first electrode sheets 11 are mutually conductive, and the plurality of second electrode sheets 12 are mutually conductive, thereby forming a positive electrode and a negative electrode of the capacitor. It should be noted that the capacitor is a non-polar capacitor, and the first electrode sheet 11 or the second electrode sheet 12 can be used as a positive electrode or a negative electrode, and one of them is connected to the coil 2 or the inductor, and the other is connected to the circuit board 1 or the connecting cable.

[0058] In a specific embodiment, the plurality of first electrode sheets 11 are electrically connected to each other and connected to the coil 2 . The plurality of second electrode sheets 12 are electrically connected to each other and connected to the circuit board 1 .

[0059] In one embodiment, the insulating sheet 13 is made of single crystal aluminum oxide. By utilizing the higher dielectric constant, lower dielectric loss rate, stable chemical properties and lower cost of aluminum oxide, the capacitor can be lightweight and low-cost at the same capacitance while maintaining relatively excellent performance.

[0060] It should be noted that the process of preparing the insulating sheet 13 from single crystal alumina is relatively mature, thereby ensuring the quality of the capacitor and effectively controlling the manufacturing cost of the capacitor.

[0061] Preferably, the insulating sheet 13 is prepared using alumina wafers instead of the traditional ceramic sintering process, which can maximize the use of the physical properties of the material. Single-crystal alumina is anisotropic, and its dielectric constant is the highest and the dielectric loss is the lowest in the direction parallel to the c-axis, and the dielectric loss hardly changes with frequency. Furthermore, when prepared using c-axis alumina wafers, its dielectric constant is about 11.6, and under the same withstand voltage and capacity requirements, the effective capacitance area is only about one-tenth of that of Teflon material.

[0062] In addition, the chemical properties of aluminum oxide wafers are stable and can be used in different working conditions. In the temperature range of -196 degrees to 250 degrees, the dielectric constant of the material changes little.

[0063] It should be noted that in the prior art, the capacitance value is usually changed by changing the area of ​​the two electrode sheets. However, this method, on the one hand, will cause the overall structure of the capacitor to be irregular, affecting its connection with the positive and negative electrodes, and electrode sheets of different areas are not conducive to mass production and storage; on the other hand, its accuracy in adjusting the capacitance value is poor.

[0064] Therefore, in one embodiment, metal layers are disposed on opposite surfaces of the insulating sheet 13 and are in contact and conduction with the first electrode sheet 11 and the second electrode sheet 12 respectively, and the orthographic projections of the two metal layers in the first direction overlap.

[0065] According to the principle of flat-plate capacitors, the higher the overlapping area ratio a, the larger the effective capacitance area of ​​the layer and the larger the capacitance value. The present application can accurately adjust the capacitance value of the capacitor by adjusting the overlapping area ratio of the metal layer on both sides of the insulating sheet 13, thereby improving the commercial quality of the capacitor and ensuring that each insulating sheet 13 is the same size, which is convenient for assembling the capacitor.

[0066] The overlap area (effective capacitance area) ratio a=2C / (A+B), where A is the area of ​​the first metal layer, B is the area of ​​the second metal layer, and C is the overlap area. Usually, A=B for ease of mass production.

[0067] It should also be noted that leakage current or breakdown may occur at the edge of the alumina insulating sheet 13, which may easily lead to damage to the capacitor.

[0068] Therefore, in one embodiment, an isolation cavity 14 is provided in the circumferential direction of the first electrode sheet 11 and the second electrode sheet 12. The size of the isolation cavity 14 can be determined according to the breakdown voltage of air, the withstand voltage and capacity of the capacitor, and the like.

[0069] Preferably, the isolation cavity 14 is filled with insulating material to further improve the insulation isolation effect. The insulating material may be, but is not limited to, silicone rubber or fluororubber.

[0070] In one embodiment, the metal layer overlap area ratio of a portion of the insulating sheets 13 in the capacitor body 10 is 4-96% and varies in multiples of 4%; the metal layer overlap area ratio of another portion of the insulating sheets 13 is 100%.

[0071] This method adjusts the capacity by adjusting the overlap area ratio of the metal layer of part of the insulating sheet 13, while the other part is 100% and does not need to be adjusted, so that the adjustment amount is small, which can further ensure the accuracy of capacity adjustment, reduce manufacturing difficulty, and control costs. In addition, by controlling the adjustment ratio range and the change amount, the capacity error requirements and cost control can be taken into account, which is convenient for manufacturing.

[0072] That is, the capacitor includes a fixed capacitance layer and a capacitance value adjustment layer. The overlapping area of ​​the insulating sheet 13 in the fixed capacitance layer is 100%, that is, the capacitance value is maximum; the overlapping area of ​​the insulating sheet 13 in the capacitance adjustment layer is determined according to the total capacitance value, and usually 1-3 layers are sufficient.

[0073] In one embodiment, the metal layer is located in the center area of ​​the surface of the insulating sheet 13 to avoid errors caused by discontinuity of the dielectric constant and affect the withstand voltage and leakage current of the capacitor. Generally, the metal layer is 2.5 mm away from the edge of the insulating sheet 13.

[0074] In one embodiment, a conductive adhesive coating is provided between the metal layer and the first electrode sheet 11 or the second electrode sheet 12 to enhance the contact and conductive stability. The conductive adhesive coating may be made of nano silver wire, conductive silver paste, or conductive high polymer.

[0075] In one embodiment, the first receiving electrode 20 and the second receiving electrode 30 are further included, and the first receiving electrode 20 and the second receiving electrode 30 are respectively located on opposite sides of the capacitor body 10 along the first direction, and the first receiving electrode 20 and the second receiving electrode 30 are both provided with a plurality of receiving grooves 21 spaced apart along the first direction. The receiving grooves 21 may be through in a direction perpendicular to the first direction, or may not be through.

[0076] The first electrode sheet 11 has a first connecting portion 111 extending toward the first receiving electrode 20 , and the first connecting portion 111 protrudes from the edge of the insulating sheet 13 and is inserted into the corresponding receiving groove 21 of the first receiving electrode 20 , so that the plurality of first electrode sheets 11 are electrically connected to each other through the first receiving electrode 20 .

[0077] The second electrode sheet 12 has a second connecting portion 121 extending toward the second receiving electrode 30 . The second connecting portion 121 protrudes from the edge of the insulating sheet 13 and is inserted into the corresponding receiving groove 21 of the second receiving electrode 30 , so that the plurality of second electrode sheets 12 are electrically connected to each other through the second receiving electrode 30 .

[0078] This method realizes the regular connection and conduction of multiple first electrode sheets 11 and multiple second electrode sheets 12 through the cooperation of the first receiving electrode 20 and the first connecting part 111, and the cooperation of the second receiving electrode 30 and the second connecting part 121, thereby improving the overall regularity of the capacitor. In addition, it avoids the instability of the connection between a single first electrode sheet 11 or a second electrode sheet 12 and the corresponding first receiving electrode 20 or second receiving electrode 30, resulting in the inability to connect and conduct the whole. At the same time, it is also convenient to increase or decrease the first electrode sheet 11 and the second electrode sheet 12 according to the capacitance requirements, and to achieve conduction respectively.

[0079] Please refer to Figures 4(a)-(b), Figure 4(a) is a schematic diagram of the connection status of the embodiment of the present application with the coil 2 and the circuit board 1; Figure 4(b) is a schematic diagram of the connection status of the embodiment of the present application with the circuit board 1 at another angle.

[0080] In one embodiment, a conductive connection seat 24 is integrally formed on the side of the first receiving electrode 20 facing away from the capacitor body 10, and the connection seat 24 includes a circular limiting space adapted to the coil 2 for wireless charging, and is preferably welded to the coil 2 through an indium silver alloy. The coil 2 can be a copper tube, copper foil, or Litz wire, etc.

[0081] The second receiving electrode 30 is connected with a conductive flexible connector 31, and the flexible connector 31 is used to connect the second receiving electrode 30 and the circuit board 1. The flexible connector 31 can be a braided copper tape or copper foil, and is connected by welding.

[0082] This method can reduce parasitic capacitance, inductance and resistance by connecting the coil 2 and the circuit board 1 through the connection base 24 and the flexible connector 31. In addition, the flexible connector 31 avoids the mechanical stress caused by thermal expansion and contraction between the capacitor and the circuit board 1, ensuring the connection stability.

[0083] In one embodiment, a heat-resistant insulating plate 23 is provided between the capacitor body 10 and the first receiving electrode 20, and between the capacitor body 10 and the second receiving electrode 30 to protect the capacitor, prevent electrical breakdown, and adapt to different operating temperatures. The heat-resistant insulating plate 23 can be made of polytetrafluoroethylene, polyimide, or PEEK.

[0084] One side of the heat-resistant insulating plate 23 is attached to the first receiving electrode 20 or the second receiving electrode 30 and bonded by insulating glue, and the other side is spaced apart from the corresponding side of the capacitor body 10 to form a buffer cavity 22. The buffer cavity 22 can provide a certain space for thermal expansion and contraction, and preferably, the buffer cavity 22 is filled with a high thermal conductivity insulating resin to further improve the insulation effect and ensure the structural stability of the buffer cavity 22.

[0085] The first connecting portion 111 of the first electrode sheet 11 or the second connecting portion 121 of the second electrode sheet 12 sequentially passes through the corresponding buffer cavity 22 and the heat-resistant insulating plate 23 to be connected to the first receiving electrode 20 or the second electrode sheet 12 .

[0086] In one embodiment, the capacitor further includes a shell 40, which covers the outside of the capacitor body 10 that is not covered with the first receiving electrode 20 or the second receiving electrode 30. Preferably, the shell 40 is made of single crystal alumina, which is transparent in color. The high thermal conductivity of single crystal alumina can significantly improve the heat dissipation and load carrying capacity of the capacitor.

[0087] In one embodiment, a high thermal conductivity insulating resin is filled between the housing 40 and the capacitor body 10 to further improve the insulation and heat dissipation effects, as well as the connection stability and reliability.

[0088] In one embodiment, the insulating sheet 13 is obtained by forming a metal layer on the front and back sides of an aluminum oxide wafer respectively through photolithography and thin film technology and then cutting. That is, through a relatively mature semiconductor manufacturing process, the quality of the capacitor is further ensured and the cost is controlled.

[0089] Please attend Figure 5 and Figures 6(a)-(c), 7(a)-(c), Figure 5 6(a) is a schematic diagram of the manufacturing process of the embodiment of the present application; FIG. 6(b) is a schematic diagram of the process of wafer selection in the manufacturing steps of the embodiment of the present application; FIG. 6(b) is a schematic diagram of the process of photolithography, thin film deposition and wafer cutting in the manufacturing steps of the embodiment of the present application; FIG. 6(c) is a schematic diagram of the assembly process in the manufacturing steps of the embodiment of the present application; FIG. 7(a) is a schematic diagram of wafer front-side photolithography in the embodiment of the present application; FIG. 7(b) is a schematic diagram of wafer back-side photolithography in the embodiment of the present application; FIG. 7(c) is a schematic diagram of the superposition of wafer front-side and back-side photolithography areas in the embodiment of the present application.

[0090] The manufacturing process of this capacitor can basically include:

[0091] 1) Determine the capacitor requirements, including but not limited to the capacitor's capacity, withstand voltage, operating temperature range and size.

[0092] 2) Wafer selection: select the appropriate alumina wafer diameter and thickness based on the capacitance parameter requirements.

[0093] 3) Use photolithography and thin film technology to prepare specific electrode patterns on the front and back sides of the alumina wafer. The metal materials used for the electrodes include but are not limited to Ti / Au, Pd / Au, Ta / Pt, Ag, etc. Based on this process, the effective capacitance area of ​​different regions can be adjusted on the same wafer.

[0094] 4) Cut the photolithographic alumina wafer according to the design pattern to obtain a coated substrate, namely, an insulating sheet 13. Then, the insulating sheet 13 is classified according to the overlapping area (effective capacitance area).

[0095] 5) Manually / automatically assemble the insulating sheet 13 to prepare the required capacitor.

[0096] Among them, the photolithography process is applicable to the front and back sides of the wafer, and its specific parameters, such as exposure dose, baking time and temperature, are determined by the selected photoresist composition. Thin film deposition processes include but are not limited to physical vapor deposition, chemical vapor deposition, electroplating / electrochemical deposition, etc.

[0097] In the design, by adjusting the photolithography process, the maximum capacitance value can be distributed within a specific range, where the minimum step size of capacitance adjustment depends on the photolithography pattern resolution, and the use of photolithography can make the capacitance value adjustment accuracy reach 0.5~1pF.

[0098] In a specific application, the finished capacitor requirements are: length less than 21mm, width less than 17mm, height less than 17mm, withstand voltage of 15kV and above, capacity 150pF, and capacity error less than 1pF.

[0099] (1) Determine wafer thickness, substrate and wafer size

[0100] The breakdown voltage of alumina material is about 48kV / mm, so the use of single-crystal alumina with a thickness of 0.5mm can meet the withstand voltage requirements. Considering that the width and height of the capacitor must be less than 17mm, the maximum substrate size that can be used here is 15mm, so a 15x 15mm square substrate design is selected. Furthermore, considering that there are scraps that cannot be reused during the cutting process of alumina wafers, the overall cost of choosing a 4-inch diameter is the lowest.

[0101] (2) Determine the maximum effective capacitance value and number of layers

[0102] There is leakage current or breakdown at the edge of the alumina substrate. It is known that the breakdown voltage of air is about 3kV / mm. At least 2.5mm of space, or a total of at least 5mm of space, needs to be reserved at the edge, that is, the isolation cavity 14 is used to isolate the metal electrodes on the upper and lower surfaces of the substrate. The isolation cavity 14 is filled with insulating materials, such as silicone rubber, fluororubber, etc. Therefore, excluding the reserved size, according to the calculation formula of the flat capacitor, the maximum effective capacitance value of each layer is 20.4pF, and 7 layers (total 142.8pF) are required to approach the requirement of 150pF.

[0103] (3) Determine the adjustable capacitance layer

[0104] In order to meet the requirement of capacitance error less than 1pF, the capacitance adjustment step is at least 4% of the maximum effective capacitance value. Therefore, the overlap area (i.e., effective capacitance area) needs to be designed within the range of 4% to 96% of the maximum area, with 4% as the minimum change in the overlap area. Therefore, only one layer of capacitance adjustment layer is needed in this application, and the overlap area is 36% of the maximum area, which can meet the requirement.

[0105] (4) Preparation, assembly and testing

[0106] Use photolithography and thin film deposition processes to complete the coverage of metal electrodes in the designed area, complete wafer cutting based on the design, and then select a suitable substrate for manual or automated assembly and testing.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A capacitor for wireless charging, characterized in that: The capacitor body comprises a plurality of first electrode sheets and second electrode sheets alternately and stacked along a first direction, and an insulating sheet is arranged between adjacent first electrode sheets and second electrode sheets; The plurality of first electrode sheets are electrically connected to each other, and the plurality of second electrode sheets are electrically connected to each other; The insulating sheet is made of single crystal aluminum oxide, and metal layers are provided on opposite surfaces of the insulating sheet, and are respectively in contact and conductive with the first electrode sheet and the second electrode sheet, and the orthographic projections of the two metal layers in the first direction overlap; An isolation cavity is disposed in the circumferential direction of the first electrode sheet and the second electrode sheet, and the isolation cavity is filled with insulating material.

2. The capacitor for wireless charging according to claim 1, characterized in that: The metal layer overlapping area ratio of a part of the insulating sheets in the capacitor body is 4-96%, and changes in multiples of 4%; the metal layer overlapping area ratio of another part of the insulating sheets is 100%.

3. The capacitor for wireless charging according to claim 1, characterized in that: The insulating sheet is obtained by forming the metal layer on the front and back surfaces of an aluminum oxide wafer respectively through photolithography and thin film technology, and then cutting.

4. The capacitor for wireless charging according to claim 1, characterized in that: The metal layer is located in the central area of ​​the surface of the insulating sheet, and a conductive adhesive coating is arranged between the metal layer and the first electrode sheet or the second electrode sheet.

5. The capacitor for wireless charging according to claim 1, characterized in that: Also includes a first receiving electrode and a second receiving electrode, the first receiving electrode and the second receiving electrode are respectively located on opposite sides of the capacitor body along the first direction, and the first receiving electrode and the second receiving electrode are both provided with a plurality of receiving grooves spaced apart along the first direction; The first electrode sheet has a first connecting portion extending toward the first receiving electrode, and the first connecting portion protrudes from the edge of the insulating sheet and is inserted into the corresponding receiving groove of the first receiving electrode, so that the plurality of first electrode sheets are mutually conductive through the first receiving electrode; The second electrode sheet has a second connecting portion extending toward the second receiving electrode, and the second connecting portion protrudes from the edge of the insulating sheet and is inserted into the corresponding receiving groove of the second receiving electrode, so that the plurality of second electrode sheets are electrically connected to each other through the second receiving electrode.

6. The capacitor for wireless charging according to claim 5, characterized in that: A conductive connection seat is integrally formed on a side of the first receiving electrode away from the capacitor body, and the connection seat includes a circular limiting space adapted to a coil for wireless charging; The second receiving electrode is connected to a conductive flexible connector, and the flexible connector is used to connect the second receiving electrode and a circuit board.

7. The capacitor for wireless charging according to claim 5, characterized in that: A heat-resistant insulating plate is provided between the capacitor body and the first receiving electrode, and between the capacitor body and the second receiving electrode; One side of the heat-resistant insulating plate is attached to the first receiving electrode or the second receiving electrode and bonded by insulating glue, and the other side is spaced apart from the corresponding side of the capacitor body to form a buffer cavity; The first connecting portion of the first electrode sheet or the second connecting portion of the second electrode sheet sequentially passes through the corresponding buffer cavity and the heat-resistant insulating plate to be connected to the first receiving electrode or the second electrode sheet.

8. The capacitor for wireless charging according to claim 7, characterized in that: The buffer cavity is filled with high thermal conductivity insulating resin.

9. The capacitor for wireless charging according to claim 5, characterized in that: The device further comprises a shell, wherein the shell covers the outside of the capacitor body which is not covered by the first receiving electrode or the second receiving electrode, and the material of the shell is single crystal aluminum oxide.

10. The capacitor for wireless charging according to claim 9, characterized in that: The space between the housing and the capacitor body is filled with a high thermal conductivity insulating resin.

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