Litz wire

Abstract

The invention relates to the technical field of electrical parts, in particular to a litz wire, and the litz wire comprises a plurality of circuit layers which are arranged layer by layer; the circuit layer comprises an insulating main body and a conductor, and the conductor is arranged on the insulating main body; the electric conductor comprises a plurality of electric leads which are arranged at intervals; the conductors of two adjacent circuit layers are electrically connected; the top layer is arranged on the first circuit layer; and the bottom layer is arranged on the last circuit layer. According to the Litz wire provided by the invention, the winding is etched on the insulating main body through the etching process, so that the copper consumption is reduced, the overall weight of the Litz wire is greatly reduced, additional wiring or welding is not needed, the fixing step is reduced, and the overall weight and size are further reduced; the integrated design of the electric conductor and the insulating main body enables the cable to have better mechanical resistance, and can meet the reliability requirements of strict scenes such as a vehicle gauge grade and an industrial grade.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical components, in particular to a Litz wire. BACKGROUND

[0002] Traditional Litz wire, as the core material in the field of high-frequency transformers, wireless power transmission, etc., can reduce high-frequency eddy current loss by twisting multiple insulated copper wires, but its inherent technical limitations gradually become prominent under the demand of modern high-power density and high-integration devices: relying on pure copper material leads to high material cost and heavy wire harness weight, and the complex structure is difficult to achieve miniaturization and integration, especially significantly increasing the system burden in high-power scenarios. Secondly, the skin effect and proximity effect under high-frequency working conditions still cause uneven current distribution, and the wiring end is prone to local overheating risk, affecting system stability. In terms of installation and maintenance, the traditional cable tie fixing method is easy to damage the insulation layer, and there are safety hazards in the disassembly process. Moreover, the flexible structure of twisted wires is prone to insulation layer wear in a vibrating environment, making it difficult to meet the reliability requirements of harsh scenarios such as automotive and industrial levels. SUMMARY

[0003] The purpose of the present application is to provide a Litz wire to solve the technical problem of the existing Litz wire in the prior art, which has a large wire harness weight and volume, and is difficult to integrate.

[0004] The present application provides a Litz wire, comprising: a plurality of wire layers, the plurality of wire layers are arranged layer by layer;

[0005] The wire layer comprises: an insulating body and a conductive body, the conductive body is arranged on the insulating body; the conductive body comprises a plurality of spaced conductive wires; the conductive bodies of two adjacent wire layers are electrically connected;

[0006] a top layer, the top layer is arranged on the first layer of the wire layer;

[0007] a bottom layer, the bottom layer is arranged on the last layer of the wire layer.

[0008] In the above technical solution, further, the number of conductive bodies in each wire layer is a plurality, and the plurality of conductive bodies are sequentially arranged on the same surface of the insulating body along the length of the insulating body.

[0009] In any of the above technical solutions, further, the insulating body is provided with a plurality of through holes, the end of each conductive wire is provided with a through hole, and the conductive bodies of two adjacent wire layers are electrically connected through the through holes.

[0010] In any of the above technical solutions, further, the Litz wire further comprises an isolation ring, and part of the plurality of through holes is provided with the isolation ring.

[0011] In any of the above technical solutions, further, the top layer comprises:

[0012] An incoming line connecting line, the incoming line connecting line being electrically connected with a part of the through holes, the incoming line connecting line being provided with an incoming line pad;

[0013] An outgoing line connecting line, the outgoing line connecting line being electrically connected with another part of the through holes, the outgoing line connecting line being provided with an outgoing line pad.

[0014] In any of the above technical solutions, further, the bottom layer comprises a body part, the body part being provided with a connecting pad.

[0015] In any of the above technical solutions, further, the width of the conductive line is 5 mm, and the length of the conductive line is 24 mm.

[0016] In any of the above technical solutions, further, the insulating body is annular, and the conductive line is arranged at an angle with the diameter of the insulating body.

[0017] In any of the above technical solutions, further, the Litz wire further comprises an insulating sheet, the insulating sheet being arranged between adjacent two of the circuit layers.

[0018] In any of the above technical solutions, further, the Litz wire further comprises a protective layer, the protective layer covering the top layer, the circuit layers and the bottom layer.

[0019] Compared with the prior art, the Litz wire has the following beneficial effects:

[0020] The Litz wire provided by the application comprises: a circuit layer, the number of the circuit layers being multiple, the multiple circuit layers being arranged layer by layer; the circuit layer comprising: an insulating body and a conductive body, the conductive body being arranged on the insulating body; the conductive body comprising multiple conductive lines arranged at intervals; the conductive bodies of adjacent two of the circuit layers being electrically connected; a top layer, the top layer being arranged on the first circuit layer; and a bottom layer, the bottom layer being arranged on the last circuit layer.

[0021] The Litz wire provided by the application has the following beneficial effects: the winding is etched on the insulating body through an etching process, the amount of copper is reduced, the overall weight of the Litz wire is greatly reduced, no additional wiring or welding is needed, the fixing step is reduced, the overall weight and volume are further reduced, the conductive body and the insulating body are designed in an integrated manner, the mechanical resistance is better, and the reliability requirements of harsh scenes such as vehicle-grade and industrial-grade can be met. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the drawings needed to be used in the description of the specific embodiments or the prior art will be briefly introduced. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 A structure diagram of a first circuit layer of a Litz wire provided by an embodiment of the present application is shown in the figure.

[0024] Figure 2 A partial structure diagram of the first circuit layer of the Litz wire provided by the embodiment of the present application is shown in the figure.

[0025] Figure 3 A structure diagram of a second circuit layer of a Litz wire provided by an embodiment of the present application is shown in the figure.

[0026] Figure 4 A partial structure diagram of the second circuit layer of the Litz wire provided by the embodiment of the present application is shown in the figure.

[0027] Figure 5 A structure diagram of a top layer of a Litz wire provided by an embodiment of the present application is shown in the figure.

[0028] Figure 6 A partial structure diagram of the top layer of the Litz wire provided by the embodiment of the present application is shown in the figure.

[0029] Figure 7 A structure diagram of a bottom layer of a Litz wire provided by an embodiment of the present application is shown in the figure.

[0030] Reference signs:

[0031] 100-first circuit layer, 200-second circuit layer, 1-first via hole, 2-second via hole, 3-third via hole, 4-fourth via hole, 1a-fifth via hole, 2a-sixth via hole, 3a-seventh via hole, 4a-eighth via hole, 5-isolation ring, 6-insulation groove, 7-conductive wire, 8-incoming wire connecting line, 9-outgoing wire connecting line, 10-incoming wire pad, 11-outgoing wire pad, 12-top layer, 13-bottom layer, 1301-body part, 1302-connection pad. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be described in detail below with reference to the drawings. Obviously, the described embodiments are some embodiments of the present application, and not all embodiments.

[0033] The components of the application embodiments described and illustrated herein can be arranged and designed in a wide variety of different configurations. Therefore, the following detailed description of the embodiments of the application, as provided in the accompanying drawings, is not intended to limit the scope of the application, but is merely representative of selected embodiments of the application.

[0034] All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present application without creative work are within the scope of protection of the present application.

[0035] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and 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 particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0036] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] The following refers to Figures 1 to 7 The description of the embodiments of the present application describes the Litz wire.

[0038] Referring to Figures 1 to 7As shown, the embodiment of the present application provides a Litz wire, the Litz wire comprises: a plurality of circuit layers, a top layer 12 and a bottom layer 13, wherein the plurality of circuit layers are stacked layer by layer, along the stacking direction of the plurality of circuit layers, the top layer 12 is arranged on the side of the first circuit layer away from other circuit layers, and the bottom layer 13 is arranged on the side of the last circuit layer away from other circuit layers, and the top layer 12, the plurality of circuit layers and the bottom layer 13 are integrated. Each adjacent two circuit layers are connected and conductive, so that the plurality of circuit layers are sequentially connected in series. The circuit layer comprises an insulating body and a conductor, preferably, the insulating body and the conductor are both plate-shaped, the conductor is attached to one side surface of the insulating body, the conductor comprises a plurality of spaced conductive wires 7, the number of conductive wires 7 included in the conductor of each circuit layer is the same, and the conductive wires 7 of each circuit layer are connected in parallel and then connected in series with the conductive wires 7 connected in parallel of the next circuit layer, so as to connect the adjacent two circuit layers and form a loop.

[0039] Specifically, the insulating body has a ring structure, preferably a circular ring structure, of course, not limited to this, but also rectangular ring and the like. One side surface of the insulating body is provided with a conductive layer for forming the conductor, preferably a copper layer, more preferably a 40z copper foil. Each circuit layer comprises a plurality of conductors, and the plurality of conductors of each circuit layer are sequentially arranged on the same side surface of the insulating body along the circumference of the insulating body. It should be noted that the circuit layer is a common PCB in the prior art, the insulating body is the core plate of the PCB, and the conductive layer is the copper foil of the PCB. The Litz wire takes the PCB as the substrate, processes the PCB, and etches the copper foil on the PCB to form the conductive wire 7 pattern as the winding wire. The winding wire group is interconnected through the through hole to form a loop. In this way, each circuit layer of the Litz wire is obtained, and the Litz wire is obtained. Compared with the traditional enameled wire type Litz wire, the overall volume and weight are greatly reduced, the fixing steps of the enameled wire are also reduced, the manufacturing process is simple, the production efficiency is significantly improved, and the Litz wire made in this way realizes the integration of the copper wire and the substrate, thereby significantly improving the mechanical strength.

[0040] In the embodiment, each of the conductive bodies includes six conductive wires 7 connected in parallel, and the number of the conductive wires 7 is not limited to six. Part of the conductive bodies is removed by an etching process, and the removed positions form the insulating grooves 6. The insulating grooves 6 separate any two adjacent conductive wires 7, thereby reducing the influence of eddy current and effectively reducing the influence of eddy current caused by excessively wide line width and excessively close distance between adjacent conductive wires 7 when the conductive bodies are used at high frequency. Preferably, the width of the conductive wires 7 is 5 mm, and the length of the conductive wires 7 is 24 mm. The width of the insulating grooves 6 is preferably 0.25 mm. It should be noted that the thickness of the insulating grooves 6 is affected by the amount of copper foil used in the copper layer. In actual production, the line width, line length and thickness of the conductive wires 7 are determined according to the size and current carrying capacity of the produced litz wire.

[0041] Further, the litz wire also includes a plurality of through holes. The through holes are arranged at the end portions of the conductive wires 7. The plurality of conductive wires 7 are connected in parallel to form an extension portion (not shown in the figure). The extension portion extends towards the through holes. The extension portion is used to electrically connect with the extension portion of the next circuit layer, so that the conductive wires 7 of the two circuit layers are respectively connected in parallel and then electrically connected at the through holes.

[0042] Further, the litz wire also includes a plurality of insulating sheets (not shown in the figure). The number of the insulating sheets is multiple. One insulating sheet is arranged between every two circuit layers. The insulating sheet separates the two circuit layers. The insulating sheet is specifically a semi-cured sheet commonly used in the prior art, which can play the role of insulation and bonding between the two circuit layers.

[0043] Further, the litz wire also includes an isolation ring 5. The shape of the isolation ring 5 is matched with the shape of the through hole. In the actual connection process, there may be some through holes that do not need to be used. The isolation ring 5 is arranged in these unused through holes, which can avoid short circuit caused by the connection of the two circuit layers at the positions that need to be insulated. The specific arrangement of the isolation ring 5 is described below.

[0044] The litz wire is described by taking two circuit layers as an example. The two circuit layers are the first two circuit layers in the stacking direction of all the circuit layers, which are defined as the first circuit layer 100 and the second circuit layer 200. The first circuit layer 100 includes a first insulating body, and the second circuit layer 200 includes a second insulating body. The first insulating body and the second insulating body have the same structure and are coaxially arranged in a ring shape. The side surface of the first insulating body opposite to the second insulating body is provided with a plurality of first conductive bodies along the circumferential direction. Each of the first conductive bodies includes a plurality of first conductive wires.

[0045] The second insulating body is provided with a plurality of second conductive bodies on the side surface facing the first insulating body in the circumferential direction, each of the second conductive bodies comprising a plurality of second conductive wires, and the number of the first conductive wires and the number of the second conductive wires can both be six, six first conductive wires are connected in parallel to form a first extension, and six second conductive wires are connected in parallel to form a second extension, the first extension and the second extension extending towards and electrically connecting the mutually facing through holes.

[0046] The number of the through holes is matched with the number of the circuit layers, and in the embodiment, the number of the through holes on each circuit layer is specifically eight, four of the through holes on each circuit layer are arranged at intervals at the position close to the outer ring of the insulating body at one end of the conductive wire 7, and the four through holes are respectively the first through hole 1, the second through hole 2, the third through hole 3, and the fourth through hole 4; the other four through holes are arranged at intervals at the position close to the inner ring of the insulating body at the other end of the conductive wire 7, and the four through holes are respectively the fifth through hole 1a, the sixth through hole 2a, the seventh through hole 3a, and the eighth through hole 4a, each circuit layer is provided with eight through holes according to the above rule, and the first through holes 1 of all the circuit layers are coaxially arranged, all the second through holes 2 are coaxially arranged, and so on.

[0047] On the first circuit layer 100 and the second circuit layer 200, the first through hole 1 of the first circuit layer 100 and the first through hole 1 of the second circuit layer are both not provided with the isolation ring 5, and the rest of the through holes are all provided with the isolation ring 5, one end of all the first conductive wires connected in parallel forms a first extension part extending towards the first through hole 1, and the other end of all the first conductive wires connected in parallel forms another first extension part extending towards the fifth through hole 1a; one end of all the second conductive wires connected in parallel forms a second extension part extending towards the first through hole 1, and the other end of all the second conductive wires connected in parallel forms another second extension part extending towards the fifth through hole 1a, and the first through hole 1 and the fifth through hole 1a are both provided with a conductive medium, so that the first circuit layer 100 and the second circuit layer 200 can be electrically connected through the conductive medium at the first through hole 1, the current direction of the first conductive wire is opposite to that of the second conductive wire, so that the first circuit layer 100 and the second circuit layer 200 form a series loop. The conductive medium can be copper or other conductive substances. The through holes other than the first through hole 1 are all provided with the isolation ring 5, which can avoid the first circuit layer 100 and the second circuit layer 200 from being connected with other circuit layers.

[0048] Further, the third circuit layer is arranged on the side of the second circuit layer 200 away from the first circuit layer 100. In the same way as above, the second circuit layer 200 and the third circuit layer are connected at the fifth through hole 1a, and the current direction of the conductive wire 7 of the third circuit layer is opposite to that of the second circuit layer 200, so as to connect the first circuit layer 100, the second circuit layer 200 and the third circuit layer in series.

[0049] It should be noted that the through holes of the second circuit layer 200 except the first through hole 1 and the fifth through hole 1a, and the through holes of the third circuit layer except the fifth through hole 1a and the second through hole 2 are all provided with isolation rings 5.

[0050] In the embodiment, the number of circuit layers is preferably 8, of course, not limited to this, and the arrangement rules of other circuit layers are the same as above. The 8 circuit layers are respectively the first circuit layer 100, the second circuit layer 200, the third circuit layer, the fourth circuit layer, the fifth circuit layer, the sixth circuit layer, the seventh circuit layer and the eighth circuit layer. In the same way as above, the first circuit layer 100 and the second circuit layer 200 are connected at the first through hole 1, the second circuit layer 200 and the third circuit layer are connected at the fifth through hole 1a, the third circuit layer and the fourth circuit layer are connected at the second through hole 2, the fourth circuit layer and the fifth circuit layer are connected at the sixth through hole 2a, the fifth circuit layer and the sixth circuit layer are connected at the third through hole 3, the sixth circuit layer and the seventh circuit layer are connected at the seventh through hole 3a, the seventh circuit layer and the eighth circuit layer are connected at the fourth through hole 4, and the eighth circuit layer and the connection pad 1302 of the bottom layer 13 are connected at the eighth through hole 4a, so as to realize the series connection of all the circuit layers layer by layer.

[0051] Further, as shown in Figures 1 to 4 the first conductive wire is arranged at an angle with the straight line where the diameter of the first insulating body is located, and the angle between the two is α, preferably 0°<α≤90°, when α=90 degrees, the first conductive wire extends along the radial direction of the first insulating body, more preferably α=60°, so that the first conductive wire is inclined relative to the diameter of the first insulating body, and the loss value is low at this angle. Preferably, the first conductive wire is inclined relative to the diameter of the first insulating body in the clockwise direction.

[0052] Similarly, the second conductive wire and the diameter of the second insulating body form an included angle β between the straight lines, 0°<β≤90°, preferably β=30 degrees, so that the second conductive wire is inclined relative to the diameter of the second insulating body, and the second conductive wire is inclined relative to the diameter of the second insulating body in the counterclockwise direction. In addition, it should be noted that the first conductive wire and the second conductive wire can be straight lines or arcs.

[0053] It should be noted that in the present embodiment, the conductive wires 7 of the circuit layer located at the odd layers have the same inclination direction and inclination angle, and the conductive wires 7 of the circuit layer located at the even layers have the same inclination direction and inclination angle.

[0054] Further, the present Litz wire further comprises a top layer 12, wherein the top layer 12 is arranged on the side of the first circuit layer 100 away from the second circuit layer 200, the top layer 12 comprises an incoming wire connecting line 8 and an incoming wire pad 10 arranged at one end of the incoming wire connecting line 8, the incoming wire connecting line 8 is electrically connected with the conductive body of the first circuit layer 100, preferably, each first through hole 1 of the first circuit layer 100 is electrically connected. The top layer 12 further comprises an outgoing wire connecting line 9 and an outgoing wire pad 11 arranged at one end of the outgoing wire connecting line 9, preferably, the outgoing wire connecting line 9 is connected with each fifth through hole 1a of the first circuit layer 100, and the outgoing wire pad 11 is used for connecting the Litz wire externally.

[0055] Further, the present Litz wire further comprises a bottom layer 13 arranged on the outer side of the last circuit layer. The bottom layer 13 comprises a body part 1301, which is annular, and the shape of the body part 1301 is the same as that of the insulating body, and the body part 1301 is not provided with a conductive body, and the body part 1301 is additionally provided with a plurality of connecting pads 1302, which are arranged along the circumferences of the outer ring and the inner ring of the bottom layer 13, and the connecting pads 1302 are used for welding wires to electrically connect the Litz wire with other devices.

[0056] Further, the present Litz wire further comprises a protective layer (not shown in the figure), which has insulation and is arranged on the outer side of the bottom layer and each circuit layer to achieve the insulation protection of the Litz wire. Preferably, the protective layer can be made by the way of solder mask through ink coating, and has significantly better temperature resistance and chemical corrosion resistance than traditional enameled wires, thereby greatly prolonging the service life.

[0057] In summary, the Litz wire provided by the present application has the conductive body and the insulating body integrally designed, which has better mechanical resistance and can meet the reliability requirements of harsh scenes such as vehicle-grade and industrial-grade.

[0058] The embodiments of the present application also provide a Litz wire manufacturing method for manufacturing the Litz wire described in any of the above embodiments, thus having all the beneficial technical effects of the Litz wire, which will not be described here again.

[0059] The Litz wire manufacturing method comprises the following steps:

[0060] S1. Cutting: cutting the copper-clad plate into the required size;

[0061] S2. Inner layer: the cut copper-clad plate is subjected to inner layer wet film, exposure, development, etching, and film removal to obtain a circuit layer, so that each circuit layer forms an inner layer circuit pattern, wherein the patterns are different between different circuit layers, and the width of the insulating groove 6 is ensured to be 0.25 mm after etching to prevent short circuit between two wires due to too small width;

[0062] S3. Pressing: multiple copper-clad plates with circuits are pressed, and a semi-cured sheet is added between two adjacent copper foil plates and stacked in turn according to the rules to achieve interlayer insulation and bonding;

[0063] S4. Drilling: the pressed laminated plate is drilled to facilitate subsequent copper deposition and electroplating to conduct between different circuit layers. Mechanical drilling or laser drilling can be used. In this embodiment, the diameter of the through hole is large, and the thickness of the pressed plate is thin. To save production time and cost, mechanical drilling is selected, and the diameter is preferably 0.2 mm;

[0064] S5. Copper deposition and electroplating: a certain thickness of copper layer is deposited in the through hole by copper deposition and electroplating to conduct between different layers while meeting the current carrying requirement. According to the current carrying requirement, the minimum copper thickness in the through hole is designed to be 25 μm in this embodiment;

[0065] S6. Resin plugging: the metalized hole is plugged with resin to prevent hole copper oxidation and protect the Litz wire plate (i.e. the above-mentioned insulating body) from being corroded by acid and alkali during long-term use;

[0066] S7. Solder resist: coating ink on the surface to prevent circuit oxidation;

[0067] S8. Surface treatment: in this embodiment, the top layer 12 is provided with two square pads for current conduction, i.e. the above-mentioned wire inlet pad 10 and wire outlet pad 11. The two square pads are subjected to surface treatment, such as gold deposition, tin deposition, OSP, lead-free tin spraying, etc. In this embodiment, lead-free tin spraying is preferably used to protect the pads;

[0068] S9. Detection and packaging: the finished plate is subjected to inductance test and appearance detection, and finally packaged.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A type of Leeds wire, characterized in that, include: The circuit layer is a plurality of circuit layers, which are arranged layer by layer. The circuit layer includes: an insulating body and a conductor, the conductor being disposed on the insulating body; the conductor includes multiple spaced-apart conductive lines; the conductors of two adjacent circuit layers are electrically connected; The top layer is located at the first layer, which is the line layer. The bottom layer is located at the last layer, the circuit layer.

2. The Lids line according to claim 1, characterized in that, The number of conductors in each of the circuit layers is multiple, and the multiple conductors are arranged sequentially along the length of the insulating body on the same surface of the insulating body.

3. The Litz wire according to claim 1, characterized in that, The insulating body has multiple through holes, and each end of the conductive wire is provided with a through hole. The conductors of two adjacent circuit layers are electrically connected through the through holes.

4. The Lids line according to claim 3, characterized in that, The Litz wire also includes an isolation ring, and some of the plurality of through holes are provided with the isolation ring.

5. The Litz wire according to claim 3, characterized in that, The top layer includes: An incoming line connection wire is electrically connected to a portion of the through holes, and the incoming line connection wire is provided with an incoming line pad; The outgoing connection wire is electrically connected to another part of the through hole, and the outgoing connection wire is provided with an outgoing pad.

6. The Litz wire according to claim 1, characterized in that, The bottom layer includes a body portion, which is provided with connecting pads.

7. The Lids line according to claim 1, characterized in that, The width of the conductive wire is 5mm and the length of the conductive wire is 24mm.

8. The Litz wire according to claim 1, characterized in that, The insulating body is ring-shaped, and the conductive wire is set at an angle to the diameter of the insulating body.

9. The Lids line according to claim 1, characterized in that, The Litz wire also includes an insulating sheet, which is disposed between two adjacent wire layers.

10. The Lids line according to any one of claims 1 to 9, characterized in that, The Litz line also includes a protective layer that covers the top layer, the circuit layer, and the bottom layer.

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