Flexible circuit board and method of making the same

Abstract

The application provides a flexible circuit board and a preparation method thereof. The application can effectively save the process flow by continuously manufacturing a substrate, bending the substrate after completing inner layer circuit manufacturing and fixing electronic elements, aligning and pressing, and finally cutting the bent part to form the flexible circuit board. The electric connection part (copper column) is manufactured on the second circuit layer of the inner layer to connect the electronic elements, and the increased height of the electric connection part can make the metal groove exactly accommodate the covered electronic elements after the substrate is bent, thereby protecting the electronic elements and realizing the electromagnetic shielding effect. In addition, the accommodation groove is arranged at the position corresponding to the metal groove and filled with the phase change material, and the phase change material can absorb the heat generated by the electronic elements during the phase transition and transfer the heat out, thereby quickly realizing the longitudinal heat dissipation and improving the heat dissipation performance of the flexible circuit board.

Description

Technical Field

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

[0002] Flexible printed circuit boards (FPCs) are printed circuit boards made of flexible insulating substrates. They can be freely bent, rolled, and folded, and can withstand millions of dynamic bends without damaging the conductors. Therefore, FPCs can be arbitrarily set up according to spatial layout requirements, which helps to reduce the size and weight of electronic products and meets the needs of electronic products to develop towards high density, miniaturization, and high reliability.

[0003] Currently, flexible circuit boards (FPCs) used for signal transmission are prone to electromagnetic interference, affecting signal transmission rates. On the other hand, with the development of electronic products, the requirements for the heat dissipation performance of FPCs are becoming increasingly stringent. Current FPC heat dissipation technologies mainly include embedded metal blocks and the use of heat dissipation films. However, these technologies may increase the overall thickness of the FPC or result in poor heat dissipation performance. Summary of the Invention

[0004] In view of this, this application proposes a flexible circuit board and a method for manufacturing the same, in order to improve the heat dissipation performance and electromagnetic shielding function of the flexible circuit board.

[0005] One embodiment of this application provides a method for fabricating a flexible circuit board, comprising the following steps:

[0006] A substrate is fabricated, the substrate comprising a substrate layer, a first circuit layer, a dielectric layer and a second circuit layer stacked sequentially, the dielectric layer comprising a metal trench, the opening of the metal trench facing the second circuit layer and exposed from the second circuit layer;

[0007] An electrical connection is formed on the second circuit layer;

[0008] Electronic components are electrically connected to the electrical connection portion, and conductive adhesive is provided on the second circuit layer;

[0009] A receiving groove is formed in the substrate, and the metal groove is exposed from the receiving groove;

[0010] A phase change material is placed in the receiving tank;

[0011] A third circuit layer is formed on the surface of the substrate layer opposite to the first circuit layer to obtain an intermediate body, wherein the third circuit layer covers the receiving groove and the phase change material;

[0012] The intermediate body is bent so that the electronic component is housed in the metal groove, and an adhesive layer is placed in the gap of the bent intermediate body and the bent intermediate body is pressed together.

[0013] The flexible circuit board is obtained by cutting off the bent portion of the intermediate body after bending.

[0014] In one embodiment, fabricating the substrate includes the following steps:

[0015] A copper-clad laminate is provided, the copper-clad laminate including the substrate layer and a first copper foil layer disposed on the surface of the substrate layer, wherein the first copper foil layer is fabricated to form a first circuit layer;

[0016] The dielectric layer is laminated onto the surface of the first circuit layer opposite to the substrate layer, the dielectric layer covering the first circuit layer and the surface of the substrate layer exposed from the first circuit layer;

[0017] Conductive holes and metal trenches are formed in the dielectric layer, and a second circuit layer is formed. The conductive holes electrically connect the first circuit layer and the second circuit layer to obtain the substrate.

[0018] In one embodiment, the step of forming a conductive via and a metal trench in the dielectric layer and forming a second circuit layer includes: forming a blind via and a groove in the dielectric layer, wherein the blind via exposes a portion of the surface of the first circuit layer; disposing metal in the blind via and the groove and on the surface of the dielectric layer; etching the metal on the surface of the dielectric layer to form the second circuit layer; etching the metal in the groove to form the metal trench; and forming the conductive via with the blind via and the metal disposed in the blind via.

[0019] In one embodiment, the metal includes copper.

[0020] In one embodiment, the phase change material includes one or more of paraffin wax, higher fatty acids, polyolefins, and inorganic salt hydrates.

[0021] In one embodiment, the step of forming an electrical connection on the second circuit layer includes: covering the second circuit layer with a dry film, covering the dry film with a film and exposing and developing it, and then electroplating to form the electrical connection.

[0022] One embodiment of this application provides a flexible circuit board, which includes a first substrate layer, a first dielectric layer, an adhesive layer, a second dielectric layer, and a second substrate layer disposed sequentially. A first circuit layer is disposed on the surface of the first substrate layer near the first dielectric layer, a second circuit layer is disposed on the surface of the first dielectric layer near the adhesive layer, and a third circuit layer is disposed on the surface of the first substrate layer away from the first dielectric layer and the surface of the second substrate layer away from the second dielectric layer.

[0023] The flexible circuit board also includes electronic components, and the second dielectric layer includes a metal trench, in which the electronic components are housed;

[0024] The flexible circuit board further includes a receiving groove, which corresponds to the metal groove. The receiving groove is filled with a phase change material, and the third circuit layer on the surface of the second substrate layer covers the receiving groove and the phase change material.

[0025] In one embodiment, the flexible circuit board further includes conductive vias formed in the first dielectric layer and the second dielectric layer, the conductive vias being electrically connected to the first circuit layer and the second circuit layer.

[0026] In one embodiment, the flexible circuit board further includes an electrical connection portion that electrically connects the electronic component to the second circuit layer.

[0027] In one embodiment, the flexible circuit board further includes a fourth circuit layer formed on the surface of the second dielectric layer near the adhesive layer, the fourth circuit layer being electrically connected to the second circuit layer via conductive adhesive.

[0028] This application utilizes a continuous fabrication process on a single substrate. After completing the inner layer circuitry (first and second circuit layers), fixing electronic components, the substrate is bent, aligned, and laminated. Finally, the bent portion is cut to form a flexible circuit board, effectively saving process steps. Electrical connections (copper pillars) are fabricated on the second circuit layer to connect the electronic components. The increased height of these connections allows the metal channels after substrate bending to precisely accommodate and enclose the electronic components, providing both protection and electromagnetic shielding. Furthermore, receiving grooves are formed at corresponding positions on the metal channels and filled with phase change material. During phase transition, the phase change material absorbs and dissipates heat generated by the electronic components, enabling rapid vertical heat dissipation and improving the heat dissipation performance of the flexible circuit board. Attached Figure Description

[0029] Figures 1 to 5 This is a schematic cross-sectional view of the process for fabricating a substrate according to one embodiment of this application.

[0030] Figure 6 In order to be in Figure 5 A cross-sectional view of the electrical connection portion formed on the substrate shown.

[0031] Figure 7 In order to be in Figure 6 The diagram shows a cross-sectional view of the structure on which electronic components and conductive adhesive are arranged.

[0032] Figure 8 In order to be in Figure 7 The diagram shows a cross-sectional view of the structure forming a receiving groove.

[0033] Figure 9 In order to be in Figure 8 A cross-sectional schematic diagram of the structure shown, in which a phase change material is placed inside the receiving tank.

[0034] Figure 10 In order to be in Figure 9 A cross-sectional schematic diagram of the intermediate obtained by forming the third circuit layer on the structure shown.

[0035] Figure 11 For bending Figure 10 A cross-sectional schematic diagram of the intermediate body with an adhesive layer shown.

[0036] Figure 12 For cutting Figure 11 A cross-sectional view of the flexible circuit board obtained after bending the structure shown.

[0037] Explanation of main component symbols

[0038] Flexible circuit board 100

[0039] Substrate 10

[0040] Copper Clad Laminate 11

[0041] Substrate layer 12

[0042] First copper foil layer 13

[0043] Peelable adhesive layer 14

[0044] Bearing plate 15

[0045] First line layer 16

[0046] Dielectric layer 17

[0047] Blind hole 17a

[0048] Groove 17b

[0049] Conductive hole 101

[0050] Metal trough 102

[0051] Second line layer 18

[0052] Electrical connection part 20

[0053] Electronic Components 30

[0054] Conductive adhesive 40

[0055] Storage slot 50

[0056] Phase change materials 60

[0057] Third line layer 70, 71, 72

[0058] Fourth line layer 73

[0059] Fifth line layer 74

[0060] Intermediate 80

[0061] Adhesive layer 90

[0062] Bending section 81

[0063] First substrate layer 121

[0064] First dielectric layer 171

[0065] Second substrate layer 122

[0066] Second dielectric layer 172

[0067] The following detailed description, in conjunction with the accompanying drawings, further illustrates the embodiments of this application. Detailed Implementation

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of this application belong. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application.

[0069] It will be understood that when a layer is referred to as being "on" another layer, it can be directly on that other layer or there can be intermediate layers in between. Conversely, when a layer is referred to as being "directly" on another layer, there are no intermediate layers.

[0070] Embodiments of this application are described herein with reference to cross-sectional views, which are schematic diagrams of idealized embodiments (and intermediate configurations) of this application. Therefore, variations in the shapes illustrated due to manufacturing processes and / or tolerances are foreseeable. Consequently, embodiments of this application should not be construed as limited to the specific shapes of the areas illustrated herein, but should include, for example, deviations in shape due to manufacturing processes. The areas shown in the figures are merely illustrative, and their shapes are not intended to represent the actual shapes of the illustrated devices, nor are they intended to limit the scope of this application.

[0071] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0072] Please see Figures 1 to 12 This application provides a method for preparing a flexible circuit board 100, which includes steps S10 to S80.

[0073] Step S10, please refer to Figures 1 to 6 , Fabricate substrate 10.

[0074] like Figure 1As shown, a copper-clad laminate 11 is provided, the copper-clad laminate 11 including a substrate layer 12 and a first copper foil layer 13 disposed on the surface of the substrate layer 12. The substrate layer 12 is flexible, and its material is typically selected from one or more polymer materials such as polyimide (PI), thermoplastic polyimide (TPI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), and polyvinyl chloride polymer (PVC).

[0075] In some embodiments, the copper-clad laminate 11 is disposed on the surface of a carrier plate 15 via a peelable adhesive layer 14, the peelable adhesive layer 14 being located between the substrate layer 12 and the carrier plate 15. The carrier plate 15 can be a steel plate or the like, and this application is not limited thereto. The carrier plate 15 supports the copper-clad laminate 11 to enhance its rigidity and mechanical strength, preventing breakage during subsequent drilling and other processes. In some embodiments, the carrier plate 15 and the peelable adhesive layer 14 may also be omitted.

[0076] Please see Figure 2 The first copper foil layer 13 is then used to form the first circuit layer 16. The first circuit layer 16 can be formed using image transfer and etching processes, including steps such as lamination, exposure, development, etching, and film removal. These processes are commonly used techniques in the field and will not be described in detail here.

[0077] Please see Figure 3 A dielectric layer 17 is laminated onto the surface of the first circuit layer 16 opposite to the substrate layer 12. The dielectric layer 17 covers the first circuit layer 16 and the surface of the substrate layer 12 exposed from the first circuit layer 16. The dielectric layer 17 is made of a flexible insulating material, such as polyimide, polypropylene, liquid crystal polymer, polyetheretherketone, polyethylene terephthalate, and polyethylene naphthalate.

[0078] Please see Figure 4 and Figure 5 Conductive holes 101 and metal trenches 102 are formed in the dielectric layer 17, and a second circuit layer 18 is formed.

[0079] Specifically, firstly, such as Figure 4As shown, blind vias 17a and grooves 17b can be formed in the dielectric layer 17 by laser drilling or mechanical drilling. The number of blind vias 17a and grooves 17b can be set as needed, and this application does not impose any limitation. The blind via 17a exposes a portion of the surface of the first circuit layer 16. The groove 17b can penetrate a portion of the dielectric layer 17 along the thickness direction (i.e., the sidewalls and bottom walls of the groove 17b are both dielectric layer 17), or the groove 17b can also penetrate the entire dielectric layer 17 along the thickness direction (i.e., a portion of the surface of the substrate layer 12 can be exposed from the groove 17b). The depth of the groove 17b is sufficient to accommodate subsequent electronic components.

[0080] Then, as Figure 5 As shown, metal can be filled into the blind via 17a and the groove 17b by means of, but not limited to, sputtering and electroplating. It is understood that when metal is filled into the blind via 17a and the groove 17b by sputtering and electroplating, a metal layer (not shown) will also be formed on the surface of the dielectric layer 17 facing away from the substrate layer 12. The metal layer on the surface of the dielectric layer 17 is etched to form the second circuit layer 18, while a portion of the metal in the groove 17b is etched away to form a metal trench 102. The blind via 17a and the metal filled in the blind via 17a form a conductive via 101. The conductive via 101 electrically connects the first circuit layer 16 and the second circuit layer 18 to obtain the substrate 10.

[0081] The metal may be, but is not limited to, copper. In this embodiment, the metal is copper.

[0082] like Figure 5 As shown, the substrate 10 includes a substrate layer 12, a first circuit layer 16, a dielectric layer 17, and a second circuit layer 18. The first circuit layer 16 is formed on one surface of the substrate layer 12, and the dielectric layer 17 is located between the first circuit layer 16 and the second circuit layer 18, covering the surface of the substrate layer 12 exposed from the first circuit layer 16. The dielectric layer 17 includes a metal trench 102, the inner wall of which is provided with metal, and the opening of the metal trench 102 faces the second circuit layer 18.

[0083] For step S20, please refer to... Figure 6 An electrical connection portion 20 is formed on the second circuit layer 18.

[0084] Specifically, a dry film (not shown) can be coated onto the second circuit layer 18, and a film (not shown) can be coated onto the dry film and exposed. The dry film corresponding to the light-transmitting areas of the film softens, while the dry film corresponding to the non-light-transmitting areas of the film does not soften. Afterwards, development is performed, such as washing away the softened dry film in a sodium carbonate solution, forming a pattern corresponding to the electrical connection portion. Then, the patterned semi-finished product is immersed in an electrolyte for electroplating. After electroplating to a certain thickness, it is removed and the remaining dry film is peeled off, forming the electrical connection portion 20. The electrical connection portion 20 can be a copper pillar.

[0085] The electrical connection portion 20 and the metal channel 102 are located on different sides of the extending direction of the substrate 10. In this embodiment, along the extending direction of the substrate 10, the electrical connection portion 20 is approximately located in the left half, and the metal channel 102 is approximately located in the right half.

[0086] For step S30, please refer to... Figure 7 The electronic component 30 is electrically connected to the electrical connection part 20, and conductive adhesive 40 is provided on the second circuit layer 18.

[0087] In some embodiments, the electronic component 30 is electrically connected to the electrical connection portion 20 by soldering, and the conductive adhesive 40 is applied to a portion of the circuit pattern on the second circuit layer 18 by coating. In this embodiment, the conductive adhesive 40 is located approximately on the circuit pattern at the left end of the second circuit layer 18.

[0088] For step S40, please refer to... Figure 8 A receiving groove 50 is formed in the substrate layer 12 and the dielectric layer 17. The receiving groove 50 can be formed by means of, but not limited to, laser drilling or mechanical drilling. The receiving groove 50 corresponds to the metal groove 102, and the metal groove 102 is exposed from the receiving groove 50. The receiving groove 50 may penetrate the substrate layer 12 and part of the dielectric layer 17 in the thickness direction, or the receiving groove 50 may only penetrate the substrate layer 12 in the thickness direction, as long as the metal groove 102 is exposed from the receiving groove 50.

[0089] It is understandable that if the peelable adhesive layer 14 and the carrier plate 15 are used in the step of preparing the substrate 10, the peelable adhesive layer 14 and the carrier plate 15 need to be removed before the step of forming the receiving groove 50.

[0090] For step S50, please refer to... Figure 9 A phase change material (PCM) 60 is disposed in the receiving groove 50, and the phase change material 60 fills the receiving groove 50 completely. The phase change material 60 can absorb a large amount of heat during the phase change process, thereby improving the heat dissipation efficiency and heat dissipation effect of the flexible circuit board.

[0091] In some embodiments, the phase change material 60 can be a solid-solid phase change material such as paraffin, higher fatty acids, or polyolefins, or a solid-liquid phase change material such as inorganic salt hydrates.

[0092] For step S60, please refer to... Figure 10 A third circuit layer 70 is formed on the surface of the substrate layer 12 opposite to the first circuit layer 16 to obtain an intermediate body 80.

[0093] Specifically, a copper foil layer (not shown) can be laminated onto the surface of the substrate layer 12 opposite to the first circuit layer 16. A resist film is then laminated onto the outside of the copper foil layer. After exposure, development, etching, and film removal, the third circuit layer 70 is formed. The circuit pattern of the third circuit layer 70 covers the receiving groove 50 and the phase change material 60, so that the phase change material 60 is located in a sealed space.

[0094] For step S70, please refer to... Figure 11 The intermediate body 80 is bent and pressed together.

[0095] In this embodiment, the right half of the intermediate body 80 is bent towards the left half, allowing the electronic component 30 to be housed within the metal groove 102. An adhesive layer 90 is then placed within the gaps in the intermediate body 80 and pressed together; the gap between the electronic component 30 and the metal groove 102 can also be filled with the adhesive layer 90. The conductive adhesive 40 electrically connects the second circuit layer 18 at the right end of the intermediate body 80 to the second circuit layer 18 at the left end of the intermediate body 80. The metal groove 102 perfectly covers the electronic component 30, protecting it while effectively preventing electromagnetic interference and achieving electromagnetic shielding.

[0096] It is understandable that after bending, the intermediate body 80 will form a generally arc-shaped bent portion 81.

[0097] For step S80, please refer to... Figure 12 The bent portion 81 is cut to obtain the flexible circuit board 100.

[0098] Please see Figure 12 In another aspect, this application also provides a flexible circuit board 100 prepared by the above-described preparation method.

[0099] The flexible circuit board 100 includes a first substrate layer 121, a first dielectric layer 171, an adhesive layer 90, a second dielectric layer 172, and a second substrate layer 122, arranged sequentially. A first circuit layer 16 is provided on the surface of the first substrate layer 121 near the first dielectric layer 171; a second circuit layer 18 is provided on the surface of the first dielectric layer 171 near the adhesive layer 90; a third circuit layer 71 is provided on the surface of the first substrate layer 121 opposite to the first dielectric layer 171; and a third circuit layer 72 is provided on the surface of the second substrate layer 122 opposite to the second dielectric layer 172. The adhesive layer 90 is used to bond the first dielectric layer 171 and the second dielectric layer 172. The flexible circuit board 100 also includes an electronic component 30, which is electrically connected to the second circuit layer 18 via an electrical connection portion 20. The second dielectric layer 172 includes a metal groove 102, and the electronic component 30 is housed within the metal groove 102. The gap between the electronic component 30 and the metal groove 102 can be filled with the adhesive layer 90.

[0100] The flexible circuit board 100 also includes a receiving groove 50, which corresponds to the metal groove 102. The receiving groove 50 is filled with a phase change material 60, and the third circuit layer 72 covers the receiving groove 50 and the phase change material 60.

[0101] In some embodiments, such as Figure 12 As shown, the flexible circuit board 100 further includes a conductive hole 101 formed in the first dielectric layer 171 and the second dielectric layer 172, and the conductive hole 101 is electrically connected to the first circuit layer 16 and the second circuit layer 18.

[0102] In some embodiments, such as Figure 12 As shown, the flexible circuit board 100 also includes an electrical connection portion 20, which electrically connects the electronic component 30 to the second circuit layer 18.

[0103] In some embodiments, such as Figure 12 As shown, the flexible circuit board 100 further includes a fourth circuit layer 73 formed on the surface of the second dielectric layer 172 near the adhesive layer 90, and the fourth circuit layer 73 is electrically connected to the second circuit layer 18 through conductive adhesive 40.

[0104] In some embodiments, such as Figure 12 As shown, the flexible circuit board 100 further includes a fifth circuit layer 74 formed on the surface of the second substrate layer 122 near the second dielectric layer 172, and the fifth circuit layer 74 is electrically connected to the fourth circuit layer 73 through a conductive hole 101.

[0105] This application achieves a flexible circuit board 100 by continuously fabricating the substrate 10, completing the inner layer circuitry (first circuit layer 16 and second circuit layer 18), fixing the electronic components 30, bending the substrate 10, aligning and pressing it, and finally cutting off the bent portion. This effectively saves on process steps. Electrical connection portions 20 (copper pillars) are fabricated on the second circuit layer 18 to connect the electronic components 30. The increased height of the electrical connection portions 20 allows the metal groove 102 to precisely accommodate and cover the electronic components 30 after the substrate 10 is bent, protecting the electronic components 30 while also achieving electromagnetic shielding. Furthermore, a receiving groove 50 is formed at the corresponding position of the metal groove 102 and filled with phase change material 60. During the phase transition process, the phase change material 60 absorbs and transfers the heat generated by the electronic components 30, enabling rapid vertical heat dissipation and improving the heat dissipation performance of the flexible circuit board 100.

[0106] The above description describes some specific embodiments of this application, but in actual applications, the application should not be limited to these embodiments. For those skilled in the art, other modifications and alterations made based on the technical concept of this application should fall within the protection scope of this application.

Claims

1. A method for fabricating a flexible circuit board, characterized in that, Includes the following steps: A substrate is fabricated, the substrate comprising a substrate layer, a first circuit layer, a dielectric layer and a second circuit layer stacked sequentially, the dielectric layer comprising a metal trench, the opening of the metal trench facing the second circuit layer and exposed from the second circuit layer; An electrical connection is formed on the second circuit layer; Electronic components are electrically connected to the electrical connection portion, and conductive adhesive is provided on the second circuit layer; A receiving groove is formed in the substrate, the receiving groove corresponding to the metal groove along the thickness direction of the substrate, and the metal groove is exposed from the receiving groove; A phase change material is placed in the receiving tank; A third circuit layer is formed on the surface of the substrate layer opposite to the first circuit layer to obtain an intermediate body, wherein the third circuit layer covers the receiving groove and the phase change material; The intermediate body is bent so that the electronic component is housed in the metal groove, and an adhesive layer is placed in the gap of the bent intermediate body and the bent intermediate body is pressed together. The flexible circuit board is obtained by cutting off the bent portion of the intermediate body after bending.

2. The preparation method according to claim 1, characterized in that, The fabrication of the substrate includes the following steps: A copper-clad laminate is provided, the copper-clad laminate including the substrate layer and a first copper foil layer disposed on the surface of the substrate layer, wherein the first copper foil layer is fabricated to form a first circuit layer; The dielectric layer is laminated onto the surface of the first circuit layer opposite to the substrate layer, the dielectric layer covering the first circuit layer and the surface of the substrate layer exposed from the first circuit layer; Conductive holes and metal trenches are formed in the dielectric layer, and a second circuit layer is formed. The conductive holes electrically connect the first circuit layer and the second circuit layer to obtain the substrate.

3. The preparation method according to claim 2, characterized in that, The step of forming a conductive via and a metal trench in the dielectric layer and forming the second circuit layer includes: forming a blind via and a groove in the dielectric layer, wherein the blind via exposes a portion of the surface of the first circuit layer; disposing metal in the blind via and the groove and on the surface of the dielectric layer; etching the metal on the surface of the dielectric layer to form the second circuit layer; etching the metal in the groove to form the metal trench; and forming the conductive via with the blind via and the metal disposed in the blind via.

4. The preparation method according to claim 3, characterized in that, The metal includes copper.

5. The preparation method according to claim 1, characterized in that, The phase change material includes one or more of paraffin, higher fatty acids, polyolefins, and inorganic salt hydrates.

6. The preparation method according to claim 1, characterized in that, The step of forming an electrical connection on the second circuit layer includes: covering the second circuit layer with a dry film, covering the dry film with a film and exposing and developing it, and then electroplating it to form the electrical connection.

7. A flexible circuit board, characterized in that, The first substrate layer, the first dielectric layer, the adhesive layer, the second dielectric layer and the second substrate layer are arranged in sequence. The first substrate layer has a first circuit layer on the surface near the first dielectric layer, the first dielectric layer has a second circuit layer on the surface near the adhesive layer, and the first substrate layer and the second substrate layer have a third circuit layer on the surface away from the first dielectric layer and the surface away from the second dielectric layer. The flexible circuit board also includes electronic components, and the second dielectric layer includes a metal trench, in which the electronic components are housed; The flexible circuit board further includes a receiving groove, which corresponds to the metal groove along the thickness direction of the flexible circuit board. The receiving groove is filled with a phase change material, and the third circuit layer on the surface of the second substrate layer covers the receiving groove and the phase change material.

8. The flexible circuit board as described in claim 7, characterized in that, The flexible circuit board further includes conductive vias formed in the first dielectric layer and the second dielectric layer, the conductive vias being electrically connected to the first circuit layer and the second circuit layer.

9. The flexible circuit board as described in claim 7, characterized in that, The flexible circuit board also includes an electrical connection portion that electrically connects the electronic component to the second circuit layer.

10. The flexible circuit board as described in claim 7, characterized in that, The flexible circuit board further includes a fourth circuit layer formed on the surface of the second dielectric layer near the adhesive layer, and the fourth circuit layer is electrically connected to the second circuit layer by conductive adhesive.

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