Circuit board and method of manufacturing the same

Abstract

A circuit board and a manufacturing method thereof are disclosed. The circuit board has a bending area, and includes a flexible substrate, a heat conductive layer, a coil, and a cover layer. The heat conductive layer is disposed on the flexible substrate. The coil is disposed on the heat conductive layer and exposes the heat conductive layer in the bending area. The cover layer covers the coil and exposes the heat conductive layer in the bending area. The coil is between the heat conductive layer and the cover layer. The circuit board is conducive to bending and fast heat dissipation.

Description

Technical Field

[0001] This application relates to a circuit board and a method for manufacturing the same. Background Technology

[0002] With its convenience, wireless charging technology is becoming increasingly widespread. For example, wearable devices and flexible electronic devices can be charged using wireless charging. Therefore, wearable devices and flexible electronic devices equipped with wireless charging technology not only need to be flexible but also need to consider how to achieve multiple goals such as rapid heat dissipation, efficient charging, and miniaturization. Summary of the Invention

[0003] At least one embodiment of this application provides a circuit board and a method for manufacturing the same, which facilitates bending and rapid heat dissipation.

[0004] At least one embodiment of this application provides a circuit board with a bending region, and the circuit board includes a flexible substrate, a thermally conductive layer, a coil, and a cover layer. The thermally conductive layer is disposed on the flexible substrate. The coil is disposed on the thermally conductive layer and exposes the thermally conductive layer within the bending region. The cover layer covers the coil and exposes the thermally conductive layer within the bending region. The coil is located between the thermally conductive layer and the cover layer.

[0005] The method for manufacturing a circuit board provided in at least one embodiment of this application includes: providing a flexible substrate and a composite substrate, wherein the flexible substrate includes a flexible substrate, and the composite substrate includes a metal layer and a thermally conductive layer, wherein the metal layer and the thermally conductive layer are stacked; bonding the flexible substrate and the composite substrate, wherein the flexible substrate and the thermally conductive layer face each other; after bonding the flexible substrate and the composite substrate, partially disposing a thickened metal layer on the metal layer; after disposing the thickened metal layer, patterning the metal layer to expose a portion of the thermally conductive layer, and a portion of the metal layer and the thickened metal layer forming a coil; and disposing a cover layer on the flexible substrate, the thermally conductive layer, and the coil, wherein the cover layer exposes a portion of the thermally conductive layer.

[0006] Based on the above, in the circuit board disclosed in the above embodiments, the circuit board is easier to bend because the thickness in the bending area is relatively thin, and it is easier to dissipate heat quickly because the heat-conducting layer is exposed in the bending area. Attached Figure Description

[0007] To gain a more complete understanding of the embodiments and their advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein:

[0008] Figure 1 This is a partial cross-sectional schematic diagram of a circuit board according to at least one embodiment of this application;

[0009] Figure 2 yes Figure 1 A partial top view of the circuit board;

[0010] Figure 3 This is a partial cross-sectional schematic diagram of a circuit board according to another embodiment of this application;

[0011] Figure 4 yes Figure 3 A partial top view of the circuit board; and

[0012] Figures 5 to 14 This is a partial cross-sectional schematic diagram of the manufacturing process of a circuit board according to at least one embodiment of this application. Detailed Implementation

[0013] In the following text, to clearly present the technical features of this application, the dimensions (e.g., length, width, thickness, and depth) of elements (e.g., layers, films, substrates, and regions) in the accompanying drawings will be enlarged proportionally, and the number of some elements may be reduced. Therefore, the description and explanation of the embodiments below are not limited to the number of elements in the accompanying drawings and the size and shape of the elements, but should cover the dimensions, shapes, and deviations thereof caused by actual manufacturing processes and / or tolerances. Furthermore, for clarity in illustrating the following embodiments, elements with the same or similar functions are designated by the same number.

[0014] Figure 1 This is a partial cross-sectional schematic diagram of a circuit board 100A according to at least one embodiment of this application, and Figure 2 yes Figure 1 A partial top view of circuit board 100A. (See attached diagram.) Figure 1 and Figure 2 The circuit board 100A includes a flexible substrate 110, a thermally conductive layer 120, multilayer circuit layers 131 and 132, a conductive structure 133, multilayer coils 141 and 142, multiple thermally conductive insulating materials 151 and 152, multilayer cover layers 161 and 162, and multilayer adhesive layers 171, 172, and 173. The circuit board 100A can be applied to any wearable device and flexible electronic device using wireless charging technology. It should be noted that... Figure 1 and Figure 2 In the diagram, the number of turns of each layer of coil 141 and 142 is for illustrative purposes only, so... Figure 1 The number of turns of coil 142 in the middle and Figure 2 The number of turns in coil 142 is different. Furthermore, in... Figure 2 In order to clearly illustrate the configuration of coil 142 and thermally conductive insulating material 152, Figure 2 The circuit layer 132, adhesive layer 173, and cover layer 162 are not shown.

[0015] The circuit board 100A may have a bending region 101 and a wireless charging region 102. The circuit board 100A is thinner in the bending region 101, making it easier to bend. The circuit board 100A has a groove 101a in the bending region 101, which facilitates bending on both sides of the groove 101a. The circuit board 100A can sense a time-varying magnetic field in the wireless charging region 102, thereby enabling wireless charging. Furthermore, the circuit board 100A can perform signal processing and signal transmission in other regions. The flexible substrate 110 has surfaces 111 and 112 facing each other. The material of the flexible substrate 110 may be polyimide (PI) or other suitable materials.

[0016] A thermally conductive layer 120 is disposed on the surface 111 of the flexible substrate 110. The material of the thermally conductive layer 120 may contain hexagonal boron nitride (hBN). Hexagonal boron nitride has many advantages, such as high thermal conductivity, low dielectric constant (e.g., in the range of 3 to 5), and low dielectric loss (e.g., 2*10). -4 Up to 8*10 -4 (Within a certain range), it can be made into a thin and lightweight structure and retain chemical stability under high temperature and harsh environments. For example, the thermal conductivity of the thermally conductive layer 120 in the XY plane formed by the X and Y directions can reach 300 W / mK (watts per meter kelvin). The thermal conductivity of the thermally conductive layer 120 in the Z direction can reach 30 W / mK.

[0017] A circuit layer 131 is disposed on the surface 111 of the flexible substrate 110 and the thermally conductive layer 120. Further, the circuit layer 131 does not cover the thermally conductive layer 120 within the bending region 101 and the wireless charging region 102. In other words, the circuit layer 131 exposes the thermally conductive layer 120 within the bending region 101 and the wireless charging region 102. On the other hand, a circuit layer 132 is disposed on the surface 112 of the flexible substrate 110, and the circuit layer 132 also does not cover the surface 112 within the wireless charging region 102. Electronic components (not shown) can be mounted on the circuit layers 131 and 132. The circuit layers 131 and 132 can be used for signal transmission. The material of the circuit layers 131 and 132 can be copper. A conductive structure 133 can be located between the circuit layers 131 and 132 to electrically connect the circuit layers 131 and 132. The material of the conductive structure 133 can also be copper.

[0018] A coil 141 is disposed on the surface 111 of the flexible substrate 110 and the thermally conductive layer 120. Further, the coil 141 is located within the wireless charging region 102. In other words, the coil 141 does not cover the thermally conductive layer 120 within the bending region 101, thus exposing the thermally conductive layer 120 within the bending region 101. Furthermore, the vertical projection (projection in direction Z) of the coil 141 onto the flexible substrate 110 does not overlap with the vertical projection (projection in direction Z) of the circuit layer 131 onto the flexible substrate 110. On the other hand, a coil 142 is disposed on the surface 112 of the flexible substrate 110 and is also located within the wireless charging region 102. The vertical projection (projection in direction Z) of the coil 142 onto the flexible substrate 110 does not overlap with the vertical projection (projection in direction Z) of the circuit layer 132 onto the flexible substrate 110. The coil 141 can be electrically connected to the circuit layer 131, and the coil 142 can be electrically connected to the circuit layer 132 (not shown).

[0019] It is worth mentioning that coils 141 and 142 can be distributed along a vortex trajectory on surfaces 111 and 112, forming multiple coil portions 141' and 142', respectively, and creating vortex-shaped gaps 141a and 142a. The shape of coils 141 and 142 on surfaces 111 and 112 can resemble a mosquito coil. The shape of each coil portion 141' and 142' can resemble a circle, an ellipse, or other suitable shape. The material of coils 141 and 142 can also be copper. It should be noted that the circuit board 100A of this application includes circuit layers 131 and 132 and coils 141 and 142, but is not limited thereto. In other embodiments, the circuit board may only include circuit layer 131 and coil 141.

[0020] Furthermore, the thickness t1 of coils 141 and 142 can be different from the thickness t2 of circuit layers 131 and 132. For example, the thickness t1 of coils 141 and 142 can be greater than the thickness t2 of circuit layers 131 and 132. In this way, the skin effect of coils 141 and 142 can be reduced, thereby improving the quality factor Q of coils 141 and 142, and the overall volume of circuit board 100A can be reduced due to the thinner thickness of circuit layers 131 and 132.

[0021] Circuit board 100A can be wirelessly charged using coils 141 and 142. For example, when circuit board 100A is placed on a wireless charging pad for charging, a voltage source within the wireless charging pad generates a time-varying current, which in turn generates a time-varying magnetic field via the coils within the wireless charging pad. Then, coils 141 and 142 of circuit board 100A can sense this time-varying magnetic field and generate a voltage difference, enabling circuit board 100A to perform wireless charging. Specifically, since coil 141 is disposed on a thermally conductive layer 120 with a low dielectric constant, the attenuation of the electromagnetic signal generated by coil 141 is reduced, thereby improving the charging efficiency of circuit board 100A.

[0022] Thermally conductive insulating material 151 is disposed on the surface 111 of the flexible substrate 110 and fills the vortex-shaped gap 141a. The thermally conductive insulating material 151 can contact the thermally conductive layer 120 and the coil 141. Similarly, thermally conductive insulating material 152 is disposed on the surface 112 of the flexible substrate 110 and fills the vortex-shaped gap 142a. The thermally conductive insulating material 152 can contact the coil 142.

[0023] Furthermore, the thermally conductive insulating materials 151 and 152 may comprise epoxy resin and boron nitride nanosheets (BNNS). Specifically, the thermally conductive insulating materials 151 and 152 are three-dimensional thermally conductive resin materials, constituting a composite material. For example, the boron nitride nanosheets can be filled into the epoxy resin using a template method or 3D printing, and the volume fraction of the boron nitride nanosheets can be 15%. The inward and outward thermal conductivity of the thermally conductive insulating materials 151 and 152 can reach 4.02 W / mK and 3.87 W / mK, respectively, thereby facilitating the dissipation of heat from the coils 141 and 142 along the XY plane, thus improving the overall thermal conductivity of the circuit board 100A.

[0024] Furthermore, thermally conductive and insulating materials 151 and 152 possess excellent electrical insulation properties. The maximum volume resistivity of boron nitride nanosheets can reach 10⁻⁶. 16 Ω / cm (ohm·cm) to 10 18 The volume resistivity of boron nitride nanosheets is Ω / cm, and even at a high temperature of 1000℃, the volume resistivity is still 10 Ω / cm. 4 Ω / cm to 10 6 Ω / cm. For example, the thickness t1 of coils 141 and 142 can be in the range of 60 micrometers to 150 micrometers, and the spacing d of the spiral gaps 141a and 142a can be in the range of 30 micrometers to 100 micrometers. In this way, the thermally conductive insulating material 151 can prevent short circuits from forming between coil portions 141', and the thermally conductive insulating material 152 can prevent short circuits from forming between coil portions 142', thereby ensuring that the current flows completely through coils 141 and 142.

[0025] Furthermore, the coefficient of linear expansion of boron nitride nanosheets is in the low range of 2.0 / ℃ to 6.5 / ℃, and boron nitride nanosheets possess good mechanical properties. Therefore, when the circuit board 100A is heated or subjected to stress, the thermally conductive insulating materials 151 and 152 can still maintain volume stability, thereby reducing the stress on the coils 141 and 142 caused by thermal expansion or stress, or causing deformation of the coils 141 and 142. Thus, the thermally conductive insulating materials 151 and 152 can maintain the spacing d of the vortex gaps 141a and 142a, thereby maintaining the charging efficiency and reliability of the circuit board 100A.

[0026] Cover layer 161 covers circuit layer 131 and coil 141 to protect them from oxidation and short circuits. That is, cover layer 161 also covers flexible substrate 110 and thermally conductive layer 120, with coil 141 located between thermally conductive layer 120 and cover layer 161. Furthermore, cover layer 161 exposes thermally conductive layer 120 within bending region 101. In other words, thermally conductive layer 120 is completely uncovered within bending region 101. Therefore, circuit board 100A is not only thinner in bending region 101, making it easier to bend, but also benefits from better heat dissipation due to the exposed thermally conductive layer 120 in bending region 101. On the other hand, cover layer 162 covers circuit layer 132 and coil 142 to protect them from oxidation and short circuits. The materials of cover layers 161 and 162 can be polyimide or other suitable materials.

[0027] It should be noted that the thermally conductive layer 120 can be connected to the flexible substrate 110 via the adhesive layer 171. The cover layers 161 and 162 can be connected to the circuit layers 131 and 132 and the coils 141 and 142 via adhesive layers 172 and 173, respectively. The adhesive layers 171, 172, and 173 can be made of glass fiber and epoxy resin, or other suitable materials. It is worth mentioning that filling the vortex gaps 141a and 142a with thermally conductive and insulating materials 151 and 152 can reduce the required thickness of the adhesive layers 172 and 173, and avoid gaps and unevenness caused by unevenness in the adhesive layers 172 and 173, thereby preventing the circuit board 100A from denting.

[0028] As described above, the circuit board 100A is easier to bend due to its thinner thickness in the bending region 101, and the thermally conductive layer 120 is directly exposed in the bending region 101 without being covered by the circuit layer 131, coil 141, adhesive layer 172, and cover layer 161, thus facilitating rapid heat dissipation. The thermally conductive layer 120 has a low dielectric constant, and the coils 141 and 142 have a relatively thick thickness t1, both of which contribute to improved wireless charging efficiency. Secondly, the circuit layers 131 and 132 have a relatively thin thickness t2, which helps to reduce the size of the circuit board 100A. Furthermore, the thermally conductive and insulating materials 151 and 152 within the vortex gaps 141a and 142a can help dissipate heat from the coils 141 and 142, ensure the electrical insulation of the vortex gaps 141a and 142a, and prevent gaps and unevenness caused by the unevenness of the adhesive layers 172 and 173. In addition, the thermally conductive insulating materials 151 and 152 can maintain volume stability, thereby reducing the impact on the volume of coils 141 and 142.

[0029] Figure 3 This is a partial cross-sectional schematic diagram of a circuit board 100B according to another embodiment of this application, and Figure 4 yes Figure 3A partial top view of circuit board 100B. (See attached diagram.) Figure 3 and Figure 4 Circuit board 100B is similar to Figure 1 Circuit board 100A is different from circuit board 100B in that circuit board 100B also includes multilayer thermally conductive and wave-absorbing films 181 and 182 and soft magnetic composite material 190. It should be noted that... Figure 3 and Figure 4 In the diagram, the number of turns of each layer of coil 141 and 142 is for illustrative purposes only, so... Figure 3 The number of turns of coil 142 in the middle and Figure 4 The number of turns in coil 142 is different. Furthermore, in... Figure 4 In order to clearly illustrate the configuration of coil 142, thermally conductive insulating material 152 and thermally conductive absorbing film 182, Figure 4 The circuit layer 132, adhesive layer 173, cover layer 162, and soft magnetic composite material 190 are not shown.

[0030] A thermally conductive absorbing film 181 is disposed on the outer wall of coil 141 and surrounds coil 141. A cover layer 161 covers the thermally conductive absorbing film 181. A thermally conductive absorbing film 182 is disposed on the outer wall of coil 142 and surrounds coil 142. A cover layer 162 covers the thermally conductive absorbing film 182. Furthermore, the thermally conductive absorbing films 181 and 182 may extend onto the flexible substrate 110, adhesive layer 171, and / or thermally conductive layer 120, but are not limited thereto. In this way, the thermally conductive absorbing films 181 and 182 can also reduce the required thickness of adhesive layers 172 and 173. It should be noted that the thermally conductive absorbing films 181 and 182 may completely or partially surround coils 141 and 142, respectively, without limitation.

[0031] It is worth mentioning that the thermally conductive and absorbing films 181 and 182 can be made of magnetic powder, thermally conductive powder, and hydrogen-containing silicone oil. Therefore, the thermally conductive and absorbing films 181 and 182 can absorb the electromagnetic waves generated during wireless charging, reducing electromagnetic wave reflection and scattering, allowing magnetic field lines to stably surround the thermally conductive and absorbing films 181 and 182, thereby reducing magnetic flux leakage. Furthermore, the thermally conductive and absorbing films 181 and 182 can also isolate the mutual interference between the metal structures (such as the circuit layers 131 and 132 and the metal surrounding the circuit board 100B) and the coils 141 and 142, thereby improving the efficiency of wireless charging. Further, the thermally conductive and absorbing films 181 and 182 also have good thermal conductivity. Therefore, the thermally conductive and absorbing films 181 and 182 can increase the heat transfer contact area of ​​the circuit board 100B, accelerating heat dissipation and reducing the charging temperature of the coils 141 and 142, thereby improving the stability and safety of wireless charging.

[0032] The soft magnetic composite material 190 can be disposed on the capping layer 162, and the vertical projection (projection in direction Z) of the soft magnetic composite material 190 onto the flexible substrate 110 overlaps with the vertical projection (projection in direction Z) of the coil 142 onto the flexible substrate 110, wherein the capping layer 162 is located between the coil 142 and the soft magnetic composite material 190. In other embodiments, the soft magnetic composite material 190 can also be disposed on the capping layer 161, and the vertical projection of the soft magnetic composite material 190 onto the flexible substrate 110 overlaps with the vertical projection of the coil 141 onto the flexible substrate 110, without limitation.

[0033] It is worth mentioning that the soft magnetic composite material 190 can be made of magnetic powder and an insulating binder. Therefore, the soft magnetic composite material 190 has high magnetic permeability and good insulation properties. The insulating binder can be a silicon solution or an aluminum dihydrogen phosphate solution. The soft magnetic composite material 190 can enhance the magnetic field strength to improve the coupling efficiency of coils 141 and 142, thereby improving the conversion efficiency of wireless charging. Furthermore, the soft magnetic composite material 190 can reduce magnetic flux leakage and prevent coils 141 and 142 and surrounding metal from interfering with each other, thereby improving the stability and safety of wireless charging. In addition, the soft magnetic composite material 190 can also prevent metal overheating to protect circuit board 100B.

[0034] It should be noted that the circuit board 100B of this application includes multilayer thermally conductive and wave-absorbing films 181 and 182 and a soft magnetic composite material 190, but is not limited thereto. In other embodiments, the circuit board may only include multilayer thermally conductive and wave-absorbing films 181 and 182, without including the soft magnetic composite material 190. In other embodiments, the circuit board may only include the soft magnetic composite material 190, without including the multilayer thermally conductive and wave-absorbing films 181 and 182.

[0035] In addition to the advantages of circuit board 100A, circuit board 100B also has advantages such as improved charging efficiency, avoidance of mutual interference with surrounding metals, and accelerated heat conduction and dissipation to improve the stability and safety of wireless charging due to the thermally conductive and wave-absorbing films 181 and 182 and the soft magnetic composite material 190.

[0036] Figure 1 The manufacturing method of the circuit board 100A is as follows. Figures 5 to 10 yes Figure 1 A partial cross-sectional view of the manufacturing process of circuit board 100A. (See attached image.) Figure 5 and Figure 6First, a flexible substrate 200 and a composite substrate 300 are provided. The flexible substrate 200 includes a metal layer 210 and a flexible substrate 110, wherein the metal layer 210 and the flexible substrate 110 are stacked. The composite substrate 300 includes a metal layer 310 and a thermally conductive layer 120, wherein the metal layer 310 and the thermally conductive layer 120 are stacked. The material of the metal layers 210 and 310 can be copper. Specifically, in the composite substrate 300, the thermally conductive layer 120 can be formed on the metal layer 310 by chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0037] Next, the flexible substrate 200 and the composite substrate 300 are combined. The flexible substrate 110 and the thermally conductive layer 120 can face each other and are bonded together via the adhesive layer 171. The flexible substrate 200 and the composite substrate 300 can be bonded by thermoforming. Then, a blind via 410 is formed, wherein the blind via 410 extends from the metal layer 210 to the metal layer 310 and exposes the metal layer 310. Next, a photoresist layer 420 is formed on the metal layers 210 and 310, and the photoresist layer 420 is patterned using a photolithography process.

[0038] See Figure 6 and Figure 7 Since patterned photoresist layers 420 are already provided on metal layers 210 and 310, thickened metal layers 430 and 440 can be locally provided on metal layers 210 and 310 respectively, and conductive structures 133 can be formed within blind vias 410. The thickened metal layers 430 and 440 and the conductive structures 133 can be formed by electroplating.

[0039] Next, after removing the photoresist layer 420, a resist coating 450 can be applied to the metal layers 210, 310 and the thickened metal layers 430, 440. The resist coating 450 can be a polymer, such as an electron resist. Electron resists can be applied using electron beam lithography. The thickness t3 of the resist coating 450 can range from 1 micrometer to 8 micrometers.

[0040] See Figure 7 and Figure 8 Then, a patterned resist coating 450 is applied. The patterned resist coating 450 can be achieved using a laser process. Next, metal layers 210 and 310 are etched, such that a portion of metal layer 210 forms circuit layer 132, and another portion of metal layer 210 and thickened metal layer 430 form coil 142; a portion of metal layer 310 forms circuit layer 131, and another portion of metal layer 310 and thickened metal layer 440 form coil 141. See reference. Figure 8 and Figure 9Next, the resist coating 450 is removed. Then, photolithography and etching processes are used to remove a portion of the metal layer 310. Figure 7 This exposes a portion of the heat-conducting layer 120. Thus, the patterned metal layers 210 and 310 are completed.

[0041] It is worth mentioning that the resist coating 450, with its relatively thin thickness, can form vortex-like gaps 141a and 142a in the coils 141 and 142, thus replacing the need for a thicker or high-resolution photoresist layer. Therefore, using the resist coating 450 can save costs. Furthermore, the thinner resist coating 450 allows for the formation of a greater number of coil portions 141' and 142' within a limited area, thereby improving the transmission efficiency of wireless charging. Further, when etching the metal layers 210 and 310, the resist coating 450 can cover the thickened metal layers 430 and 440 to reduce lateral etching, thereby improving the smoothness and reliability of the coil surfaces 141 and 142 and reducing the skin effect. In particular, using a laser process to pattern the resist coating 450 can create a keyhole effect in the metal layers 210 and 310, thereby increasing the contact area between the metal layers 210 and 310 and the etching solution. This allows for faster formation of the circuit layers 131 and 132 and the coils 141 and 142.

[0042] See Figure 1 , Figure 9 and Figure 10 Thermally conductive and insulating materials 151 and 152 are filled into the vortex-shaped gaps 141a and 142a, respectively. Then, cover layers 161 and 162 are formed on the flexible substrate 110, the thermally conductive layer 120, the circuit layers 131 and 132, and the coils 141 and 142, respectively. The cover layers 161 and 162 can be bonded to the circuit layers 131 and 132 and the coils 141 and 142 via adhesive layers 172 and 173. Specifically, the cover layer 161 can expose a portion of the thermally conductive layer 120. Thus, the manufacturing of the circuit board 100A is essentially completed.

[0043] Figure 3 The manufacturing method of the circuit board 100B is as follows. Figures 5 to 7 and Figures 11 to 14 yes Figure 3 A partial cross-sectional schematic diagram of the manufacturing process of circuit board 100B. Figures 5 to 7 The process flow is as described above and will not be repeated here. See also... Figure 11 and Figure 12 , Figure 11 The manufacturing process is similar Figure 8In the manufacturing process, specifically, the outer wall of coil 142 can be surrounded by an annular groove 460. Next, after removing the resist coating 450 and exposing the exposed portion of the thermally conductive layer 120, the outer walls of coils 141 and 142 are exposed. Then, thermally conductive and microwave-absorbing films 181 and 182 are respectively provided on the outer walls of coils 141 and 142, wherein the thermally conductive and microwave-absorbing film 182 can be attached within the annular groove 460.

[0044] See Figure 3 , Figure 12 , Figure 13 and Figure 14 Next, thermally conductive insulating materials 151 and 152 are filled into the vortex gaps 141a and 142a, respectively. Then, cover layers 161 and 162 are applied to the circuit layers 131 and 132 and the coils 141 and 142. This essentially completes the manufacturing of the circuit board 100B. It should be noted that the order in which the thermally conductive absorbing films 181 and 182 are applied and the thermally conductive insulating materials 151 and 152 are filled is not limited. In other embodiments, the thermally conductive insulating materials 151 and 152 can be filled first, followed by the application of the thermally conductive absorbing films 181 and 182.

[0045] In summary, the circuit board disclosed in the above embodiments is easier to bend due to its thinner thickness in the bending area, and its exposed thermal conductive layer in the bending area facilitates rapid heat dissipation. Furthermore, the low dielectric constant of the thermal conductive layer and the thicker coil both contribute to improved wireless charging efficiency. Secondly, the thinner circuit layer helps reduce the size of the circuit board. Moreover, the thermally conductive insulating material within the vortex-shaped gap helps dissipate heat from the coil and ensures electrical insulation. The thermally conductive absorbing film and soft magnetic composite material can improve the charging efficiency of the coil and prevent interference between the coil and surrounding metal.

[0046] Although this application has been disclosed above with reference to embodiments, it is not intended to limit this application. Those skilled in the art can make some modifications and refinements without departing from the spirit and scope of this application. Therefore, the scope of protection of this application shall be determined by the appended claims.

[0047] [Symbol Explanation]

[0048] 100A, 100B: Circuit Boards

[0049] 101: Bend Zone

[0050] 101a: Groove

[0051] 102: Wireless Charging Area

[0052] 110: Flexible substrate

[0053] 111,112: Surface

[0054] 120: Thermal conductive layer

[0055] 131, 132: Line Layer

[0056] 133: Conductive Structure

[0057] 141, 142: Coils

[0058] 141', 142': Coil section

[0059] 141a, 142a: Vortex-shaped gaps

[0060] 151, 152: Thermally conductive and insulating materials

[0061] 161, 162: Overlay

[0062] 171, 172, 173: Adhesive layer

[0063] 181, 182: Thermally conductive and microwave absorbing film

[0064] 190: Soft magnetic composite materials

[0065] 200: Flexible substrate

[0066] 210, 310: Metal layer

[0067] 300: Composite substrate

[0068] 410: Blind hole

[0069] 420: Photoresist layer

[0070] 430, 440: Thickened metal layer

[0071] 450: Anti-corrosion coating

[0072] 460: Annular groove

[0073] d: Spacing

[0074] t1, t2, t3: Thickness

[0075] X, Y, Z: Direction.

Claims

1. A circuit board, characterized in that, The circuit board has a bending area, and the circuit board includes: Flexible substrate; A thermally conductive layer is disposed on the flexible substrate; A coil, disposed on the thermally conductive layer, and exposing the thermally conductive layer within the bending region; and A cover layer covers the coil and exposes the thermally conductive layer within the bending area, wherein the coil is located between the thermally conductive layer and the cover layer.

2. The circuit board according to claim 1, characterized in that, The thermally conductive layer is made of hexagonal boron nitride.

3. The circuit board according to claim 1, characterized in that, Also includes: A circuit layer is disposed on the thermally conductive layer and exposes the thermally conductive layer within the bending area, wherein the vertical projection of the circuit layer on the flexible substrate does not overlap with the vertical projection of the coil on the flexible substrate, and the cover layer covers the circuit layer. The thickness of the coil is greater than the thickness of the circuit layer.

4. The circuit board according to claim 1, characterized in that, The coils are distributed along a vortex trajectory on the flexible substrate, forming vortex-shaped gaps; The circuit board also includes: A thermally conductive insulating material is filled within the vortex-shaped gap, wherein the covering layer covers the thermally conductive insulating material.

5. The circuit board according to claim 4, characterized in that, The thermally conductive and insulating material comprises epoxy resin and boron nitride nanosheets.

6. The circuit board according to claim 1, characterized in that, Also includes: A thermally conductive and microwave-absorbing film is disposed on the outer wall of the coil and surrounds the coil, wherein the covering layer covers the thermally conductive and microwave-absorbing film.

7. The circuit board according to claim 1, characterized in that, Also includes: A soft magnetic composite material is disposed on the cover layer, and the vertical projection of the soft magnetic composite material on the flexible substrate overlaps with the vertical projection of the coil on the flexible substrate, wherein the cover layer is located between the coil and the soft magnetic composite material.

8. A method for manufacturing a circuit board, characterized in that, Include: A flexible substrate and a composite substrate are provided, wherein the flexible substrate includes a flexible substrate, and the composite substrate includes a metal layer and a thermally conductive layer, wherein the metal layer and the thermally conductive layer are stacked. Combining the flexible substrate and the composite substrate, wherein the flexible substrate and the thermally conductive layer face each other; After combining the flexible substrate and the composite substrate, a thickened metal layer is locally formed on the metal layer. After the thickened metal layer is applied, the metal layer is patterned to expose a portion of the heat-conducting layer, and a portion of the metal layer and the thickened metal layer form a coil. as well as A cover layer is provided on the flexible substrate, the thermally conductive layer, and the coil, wherein the cover layer exposes a portion of the thermally conductive layer.

9. The manufacturing method according to claim 8, characterized in that, Patterning the metal layer includes: An anti-corrosion coating is provided on the metal layer and the thickened metal layer; Pattern the corrosion-resistant coating; After patterning the resist coating, the metal layer is etched such that the portion of the metal layer and the thickened metal layer form the coil; After the coil is formed, the anti-corrosion coating is removed; as well as After removing the anti-corrosion coating, the metal layer is etched to expose the thermally conductive layer in the specified portion.

10. The manufacturing method according to claim 8, characterized in that, Also includes: Before the covering layer is applied, a thermally conductive insulating material is filled into the vortex-shaped gap formed by the coil, wherein the covering layer covers the thermally conductive insulating material. Before setting the covering layer, a thermally conductive and wave-absorbing film is set on the outer wall of the coil, wherein the thermally conductive and wave-absorbing film surrounds the coil, and the covering layer covers the thermally conductive and wave-absorbing film; as well as After the cover layer is set, a soft magnetic composite material is set on the cover layer, wherein the vertical projection of the soft magnetic composite material on the flexible substrate overlaps with the vertical projection of the coil on the flexible substrate, and the cover layer is located between the coil and the soft magnetic composite material.

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