CN117641756A

CN117641756A - Buried flexible circuit board and preparation method thereof

Info

Publication number: CN117641756A
Application number: CN202210978420.1A
Authority: CN
Inventors: 李成佳
Original assignee: Hongqisheng Precision Electronics Qinhuangdao Co Ltd; Avary Holding Shenzhen Co Ltd
Current assignee: Hongqisheng Precision Electronics Qinhuangdao Co Ltd; Avary Holding Shenzhen Co Ltd
Priority date: 2022-08-16
Filing date: 2022-08-16
Publication date: 2024-03-01
Also published as: TW202410762A; TWI846089B

Abstract

The application provides an embedded circuit board and a preparation method thereof. This application is through burying electronic component in to phase change material to set up liquid metal in the circuit board is inside, both can realize heat phase transition heat dissipation, conduction heat dissipation and three kinds of heat dissipation modes of air convection heat dissipation, thereby improve radiating efficiency and improve the radiating effect, can realize the arbitrary angle and the arbitrary direction of circuit board through liquid metal again and buckle, reduce the stress influence of buckling after buckling, thereby can promote the application the bending and shaping precision of embedded flexible circuit board, the stability of buckling after the shaping and flexibility of buckling.

Description

Buried flexible circuit board and preparation method thereof

Technical Field

The application relates to the technical field of Printed Circuit Boards (PCBs), in particular to a preparation method of an embedded flexible circuit board and the embedded flexible circuit board prepared by the preparation method.

Background

The electrical energy consumed by the electronic device during operation is largely converted to heat emissions, in addition to useful work. The heat generated by the electronic equipment can quickly raise the internal temperature, and if the heat is not timely emitted, the device can fail due to overheating, and finally the function and the service life of the electronic equipment are affected. Particularly, in the trend of high density of circuit boards, how to realize heat dissipation of embedded parts becomes a big hot spot and difficulty in the field.

Meanwhile, with the reduction of the packaging space of electronic parts, new requirements are put on the bending angle, the bending radius and the like of the circuit board. Currently, SUS (stainless steel) is commonly used for bending and shaping, but due to the limitation of the thickness and bending precision of SUS, the development requirement of future circuit boards is difficult to meet.

Disclosure of Invention

In view of this, the present application provides a method for manufacturing an embedded flexible circuit board, so as to improve the heat dissipation effect of the existing circuit board and improve the bending precision, stability and flexibility.

An embodiment of the present application provides a method for manufacturing an embedded flexible circuit board, including the following steps:

providing an inner-layer circuit substrate, wherein the inner-layer circuit substrate comprises a first conductive plate, a first bonding layer, a second conductive plate, a second bonding layer and a third conductive plate which are stacked, and the inner-layer circuit substrate is also provided with a blind groove penetrating through the third conductive plate, the second bonding layer, the second conductive plate and the first bonding layer; a welding pad is arranged on the surface, close to the second conductive plate, of the first conductive plate, and the blind groove exposes the welding pad; the second conductive plate, the second bonding layer and the third conductive plate on one side of the blind groove are surrounded to form a cavity;

placing an electronic element in the blind groove and electrically connecting the electronic element with the welding pad;

filling phase change materials into the blind grooves, enabling the phase change materials to cover the electronic elements, and filling gaps between the electronic elements and the side walls and the bottom walls of the blind grooves;

a third bonding layer and a fourth conductive plate are sequentially arranged on the surface, away from the second conductive plate, of the third conductive plate to obtain an intermediate, wherein the third bonding layer covers the third conductive plate and the phase change material;

forming a through hole and a blind hole on the intermediate body, wherein the through hole penetrates through the intermediate body and is communicated with the cavity; the blind holes comprise first blind holes and second blind holes, and the first blind holes penetrate through the fourth conductive plate and the third bonding layer and expose part of the surface of the phase change material; the second blind hole penetrates through the fourth conductive plate, the third bonding layer, the third conductive plate, the second bonding layer, the second conductive plate, the first bonding layer and part of the first conductive plate, and exposes part of the surface of the first conductive plate;

and arranging liquid metal in the through hole, the cavity and the second blind hole to obtain the embedded flexible circuit board.

In one embodiment, the method for preparing the inner layer circuit substrate comprises the following steps:

providing a first copper-clad plate, wherein the first copper-clad plate comprises a first substrate layer, and a first copper foil layer and a second copper foil layer which are respectively arranged on two opposite surfaces of the first substrate layer; manufacturing the first copper foil layer to form a first circuit layer, so as to obtain the first conductive plate, wherein the first circuit layer comprises the welding pad;

providing a second copper-clad plate, wherein the second copper-clad plate comprises a second substrate layer and a third copper foil layer arranged on the second substrate layer; bonding the first conductive plate and the second copper-clad plate by using the first bonding layer, wherein the first bonding layer is positioned between the first circuit layer and the second substrate layer; removing the first bonding layer and the second copper-clad plate in the corresponding region of the welding pad to form a first groove, wherein part of the surfaces of the welding pad and the first substrate layer are exposed by the first groove; manufacturing the third copper foil layer to form a second circuit layer to obtain the second conductive plate;

providing a third conductive plate, wherein the third conductive plate comprises a third substrate layer and a fourth copper foil layer arranged on the third substrate layer; bonding the second conductive plate and the third conductive plate by using the second bonding layer, wherein the second bonding layer is positioned between the second circuit layer and the third substrate layer; removing the second bonding layer and the third conductive plate in the corresponding area of the first groove to form a second groove, wherein the second groove and the first groove are communicated to form a blind groove, and the blind groove exposes part of the surfaces of the welding pad and the first substrate layer; and the second circuit layer, the second bonding layer and the third substrate layer which are positioned at one side of the blind groove are laminated to form a cavity.

In one embodiment, the method for preparing the inner layer circuit substrate further includes: and forming a gold layer on the welding pad.

In one embodiment, the method for preparing the inner layer circuit substrate further includes: a first conductive material is disposed on sidewalls of the blind trench.

In one embodiment, after the step of filling the blind trench with the phase change material, the preparation method further includes: and manufacturing the fourth copper foil layer of the third conductive plate to form a third circuit layer.

In one embodiment, after the step of forming the through holes and the blind holes on the intermediate body, the preparation method further includes: and a second conductive material is arranged in the through hole, a third conductive material is arranged in the first blind hole, and a fourth conductive material is arranged in the second blind hole.

In one embodiment, the fourth conductive plate includes a fourth substrate layer and a fifth copper foil layer disposed on the fourth substrate layer, and the manufacturing method further includes: and manufacturing the fifth copper foil layer to form a fourth circuit layer, and manufacturing the second copper foil layer to form a fifth circuit layer.

In one embodiment, before the step of disposing the liquid metal into the through hole, the chamber, and the blind hole, the preparation method further includes: and a protective layer is arranged on one side, away from the first substrate layer, of the fifth circuit layer, and the protective layer is arranged on one side, away from the fourth substrate layer, of the fourth circuit layer.

Another aspect of the present application also provides an embedded flexible circuit board, comprising:

the inner-layer circuit substrate comprises a first conductive plate, a first bonding layer, a second conductive plate, a second bonding layer and a third conductive plate which are arranged in a stacked manner, and the inner-layer circuit substrate is also provided with a blind groove penetrating through the third conductive plate, the second bonding layer, the second conductive plate and the first bonding layer; a welding pad is arranged on the surface, close to the second conductive plate, of the first conductive plate, and the blind groove exposes the welding pad; the second conductive plate, the second bonding layer and the third conductive plate on one side of the blind groove are surrounded to form a cavity;

the electronic element is arranged in the blind groove and is electrically connected with the welding pad;

the phase change material is used for coating the electronic element and filling gaps between the electronic element and the side wall and the bottom wall of the blind groove;

the fourth conducting plate is arranged on one side, away from the second conducting plate, of the third conducting plate through a third bonding layer;

the through hole penetrates through the inner-layer circuit substrate and the fourth conductive plate and is communicated with the cavity;

the blind holes comprise first blind holes and second blind holes, the first blind holes penetrate through the fourth conductive plate and the third bonding layer, and part of the surface of the phase change material is exposed; the second blind hole penetrates through the fourth conductive plate, the third bonding layer, the third conductive plate, the second bonding layer, the second conductive plate, the first bonding layer and part of the first conductive plate, and exposes part of the surface of the first conductive plate; and

and the liquid metal is arranged in the through hole, the cavity and the second blind hole.

In one embodiment, a first conductive material is arranged in the blind groove, a second conductive material is arranged in the through hole, a third conductive material is arranged in the first blind hole, and a fourth conductive material is arranged in the second blind hole.

This application is through burying electronic component in to phase change material to set up liquid metal in the circuit board is inside, both can realize heat phase transition heat dissipation, conduction heat dissipation and three kinds of heat dissipation modes of air convection heat dissipation, thereby improve radiating efficiency and improve the radiating effect, can realize the arbitrary angle and the arbitrary direction of circuit board through liquid metal again and buckle, reduce the stress influence of buckling after buckling, thereby can promote the application the bending and shaping precision of embedded flexible circuit board, the stability of buckling after the shaping and flexibility of buckling.

Drawings

Fig. 1 to 6 are schematic cross-sectional views of an embodiment of the present application for preparing an inner circuit substrate.

Fig. 7 is a schematic cross-sectional view of an electronic component placed in the blind recess shown in fig. 6.

Fig. 8 is a schematic cross-sectional view of filling the blind trench shown in fig. 7 with a phase change material.

Fig. 9 is a schematic cross-sectional view of a third circuit layer formed by fabricating a fourth copper foil layer of the third conductive plate shown in fig. 8.

Fig. 10 is a schematic cross-sectional view showing the arrangement of a third adhesive layer and a fourth conductive plate on the surface of the structure shown in fig. 9.

Fig. 11 to 12 are schematic cross-sectional views illustrating the formation of through holes and blind holes in the intermediate body shown in fig. 10.

Fig. 13 is a schematic cross-sectional view of the conductive material disposed within the through holes and blind holes shown in fig. 12.

Fig. 14 is a schematic cross-sectional view of the second copper foil layer and the fifth copper foil layer shown in fig. 12, respectively, to form a circuit layer.

Fig. 15 is a schematic cross-sectional view of the structure of fig. 14 with a protective layer disposed on the outside.

Fig. 16 is a schematic cross-sectional view of an embodiment of the embedded flexible circuit board obtained after disposing liquid metal in the through holes and blind holes shown in fig. 15.

Fig. 17 is a schematic cross-sectional view of an embedded flexible circuit board according to another embodiment of the present application.

Description of the main reference signs

Embedded flexible circuit board 100

Inner layer circuit board 10

First copper-clad plate 11

First substrate layer 110

First copper foil layer 111

Second copper foil layer 112

First circuit layer 113

First conductive plate 101

Bond pad 114

Second copper-clad plate 12

Second substrate layer 120

Third copper foil layer 121

First adhesive layer 102

First slot 1061

Second circuit layer 122

Second conductive plate 103

Second adhesive layer 104

Third conductive plate 105

Third substrate layer 1051

Fourth copper foil layer 1052

Third wiring layer 1053

Blind groove 106

Chamber 1041

First conductive material 107

Electronic component 20

Phase change material 30

Third adhesive layer 108

Fourth conductive plate 40

Fourth substrate layer 401

Fifth copper foil layer 402

Intermediate 50

Through hole 60

Blind hole 70

First hole 61

Second hole 62

Third hole 63

First blind hole 71

Second blind hole 72

Second conductive material 64

Third conductive material 711

Fourth conductive material 721

Fourth wiring layer 403

Fifth wiring layer 115

Protective layer 116

First hollow groove 801

Second hollowed-out groove 802

The following detailed description will further illustrate embodiments of the present application in conjunction with the above-described figures.

Detailed Description

Unless defined otherwise, 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 the present application belong. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the examples of the application.

It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present application are merely used to explain the relative positional relationship, movement, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is correspondingly changed.

In addition, descriptions such as those related to "first," "second," and the like in this application are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise.

Embodiments of the present application are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate configurations) of the present application. Thus, differences in the shapes of the illustrations as a result, of manufacturing processes and/or tolerances, are to be expected. Thus, embodiments of the present application should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. The regions illustrated in the figures are merely schematic in nature and their shapes are not intended to illustrate the actual shape of a device and are not intended to limit the scope of the present application.

Some embodiments of the present application are described in detail below with reference to the accompanying drawings. The following embodiments and features of the embodiments may be combined with each other without collision.

Referring to fig. 1 to 16, an embodiment of the present application provides a method for manufacturing an embedded flexible circuit board, which includes the following steps.

Step S10, please refer to fig. 1 to 6, which illustrate a method for manufacturing the inner circuit substrate 10 according to an embodiment of the present application.

As shown in fig. 1, in step S11, a first copper-clad plate 11 is provided. The first copper-clad laminate 11 includes a first substrate layer 110, and a first copper foil layer 111 and a second copper foil layer 112 respectively disposed on two opposite surfaces of the first substrate layer 110.

The material of the first substrate layer 110 includes, but is not limited to, polyimide (PI), polyester resin (Polyethylene terephthalate, PET), polyethylene naphthalate (Polyethylene naphthalate two formic acid glycol ester, PEN), liquid crystal polymer (liquid crystal polymer, LCP), modified Polyimide (modified Polyimide, MPI), and the like. In this embodiment, the material of the first substrate layer 110 is PI.

As shown in fig. 2, in step S12, the first copper foil layer 111 is fabricated to form a first circuit layer 113, so as to obtain the first conductive board 101. The first circuit layer 113 includes a pad 114, and the pad 114 is used for connection with an electronic component or the like. The first circuit layer 113 may be formed using, but not limited to, an image transfer process and an etching process.

As shown in fig. 3, in step S13, a second copper-clad plate 12 is provided. The second copper-clad laminate 12 includes a second substrate layer 120 and a third copper foil layer 121 disposed on the second substrate layer 120. The second copper-clad plate 12 is bonded to the first conductive plate 101 by using a first bonding layer 102, and the first bonding layer 102 is located between the first circuit layer 113 and the second substrate layer 120. The first adhesive layer 102 covers the first wiring layer 113 and the surface of the first base material layer 110 exposed from the gap of the first wiring layer 113.

The material of the second substrate layer 120 includes, but is not limited to, PI, PET, PEN, LCP, MPI, etc., and the material of the second substrate layer 120 may be the same as or different from the material of the first substrate layer 110. In this embodiment, the material of the first substrate layer 110 is PI. The first adhesive layer 102 may be, but is not limited to, a prepreg or the like.

As shown in fig. 4, in step S14, the first adhesive layer 102 and the second copper-clad plate 12 in the corresponding region of the bonding pad 114 are removed to form a first groove 1061. The first groove 1061 exposes the bonding pad 114 and a portion of the surface of the first substrate layer 110. And manufacturing the third copper foil layer 121 to form a second circuit layer 122, thereby obtaining the second conductive plate 103. The second circuit layer 122 may be formed using, but not limited to, an image transfer process and an etching process.

As shown in fig. 5, in step S15, the third conductive plate 105 is provided. The third conductive plate 105 includes a third substrate layer 1051 and a fourth copper foil layer 1052 disposed on the third substrate layer 1051. The second conductive plate 103 and the third conductive plate 105 are bonded by a second bonding layer 104, and the second bonding layer 104 is located between the second wiring layer 122 and the third base material layer 1051. The second adhesive layer 104 may be, but is not limited to, a prepreg or the like. In this embodiment, the third base material layer 1051 is PI.

The second adhesive layer 104 and the third conductive plate 105 in the corresponding region of the first groove 1061 are removed to form a second groove 1062. The second grooves 1062 and the first grooves 1061 communicate and form blind grooves 106, and the blind grooves 106 expose portions of the surfaces of the pads 114 and the first substrate layer 110.

The second adhesive layer 104 located on the blind groove 106 side (left side in fig. 5) is discontinuous in the extending direction of the second adhesive layer 104, that is, a gap is provided between the third base material layer 1051 and the second wiring layer 122 without filling the second adhesive layer 104 in a portion on the blind groove 106 side. Therefore, the second circuit layer 122, the second adhesive layer 104 and the third substrate layer 1051 located at the left side of the blind via 106 jointly enclose a cavity 1041. The second adhesive layer 104 located on the other side (right side in fig. 5) of the blind groove 106 is continuous, and the second adhesive layer 104 on the right side covers the second wiring layer 122 and the surface of the second base material layer 120 exposed from the gap of the second wiring layer 122.

Further, a gold layer 1141 may be formed on the pad 114.

As shown in fig. 6, in step S16, a first conductive material 107 is disposed on a sidewall of the blind via 106, to obtain the inner circuit substrate 10. In this embodiment, a layer of copper is electroplated on the sidewalls of the blind via 106 by electroplating.

In step S20, referring to fig. 7, the electronic component 20 is disposed in the blind via 106 and electrically connected to the bonding pad 114.

In step S30, referring to fig. 8, the blind trench 106 is filled with the phase change material 30, so that the phase change material 30 encapsulates the electronic element 20, and fills the gap between the electronic element 20 and the side wall and the bottom wall of the blind trench 106. That is, the electronic component 20 is completely embedded within the phase change material 30. The surface of the phase change material 30 facing away from the first conductive plate 101 (upper surface in fig. 8) is flush with the surface of the third conductive plate 105 facing away from the second conductive plate 103. The phase change material 30 is an insulating material, and can perform an insulating function without affecting the electrical property of the product. The phase change material 30 may be in contact with the first conductive material 107.

The phase change material 30 may be filled in the blind via 106 by, but not limited to, printing. In this embodiment, the phase change material 30 is a phase change solder paste. Phase change materials (Phase Change Material, PCM) are substances that change state of matter and provide latent heat without changing temperature. The process of transforming physical properties is known as the phase change process, where the phase change material will absorb or release a significant amount of latent heat. The electronic element 20 is embedded in the phase change material 30, heat generated in the working process of the electronic element 20 is transferred to the phase change material 30, and after the phase change temperature of the phase change material 30 is reached, the phase change material 30 is changed from a solid state to a liquid state, so that a large amount of heat generated by the electronic element 20 is absorbed, and the heat dissipation effect is improved.

In step S40, referring to fig. 9, a third circuit layer 1053 is formed by fabricating a fourth copper foil layer 1052 of the third conductive plate 105. The third line layer 1053 may be formed using, but not limited to, an image transfer process and an etching process.

In step S50, referring to fig. 10, a third bonding layer 108 and a fourth conductive plate 40 are sequentially disposed on a surface of the third circuit layer 1053 facing away from the second conductive plate 103, so as to obtain an intermediate 50. The third adhesive layer 108 covers the phase change material 30, the third wiring layer 1053, and the surface of the third base material layer 1051 exposed from the gap of the third wiring layer 1053.

The fourth conductive plate 40 includes a fourth base material layer 401 and a fifth copper foil layer 402 provided on the fourth base material layer 401. In this embodiment, the material of the fourth substrate layer 401 is PI. The third adhesive layer 108 may be, but is not limited to, a prepreg or the like.

In step S60, referring to fig. 11 and 12, a through hole 60 and a blind hole 70 are formed in the intermediate body 50. The through hole 60 penetrates the intermediate body 50 and communicates with the chamber 1041, and the blind hole 70 includes a first blind hole 71 and a second blind hole 72.

As shown in fig. 11, the first laser may be performed to form the first hole 61, the second hole 62, and the first blind hole 71.

The first hole 61 penetrates through the fifth copper foil layer 402 and a part of the fourth substrate layer 401, that is, the side wall of the first hole 61 is formed by two parts of the fifth copper foil layer 402 and the fourth substrate layer 401, and the bottom wall is the fourth substrate layer 401. The second hole 62 penetrates through the second copper foil layer 112 and a part of the first substrate layer 110, that is, the sidewall of the second hole 62 is formed by two parts of the second copper foil layer 112 and the first substrate layer 110, and the bottom wall is the first substrate layer 110. The first blind hole 71 penetrates the fourth conductive plate 40 and the third adhesive layer 108 to expose a portion of the surface of the phase change material 30. In this embodiment, the number of the first blind holes 71 is three, and in other embodiments, the number of the first blind holes 71 can be adjusted according to the requirement.

As shown in fig. 12, a second laser is performed to form a third hole 63 and a second blind hole 72.

The third hole 63 penetrates the remaining portion of the fourth substrate layer 401 (the first hole 61 and the third hole 63 penetrate the fourth substrate layer 401 together), the third adhesive layer 108, the third conductive plate 105, the chamber 1041, the second conductive plate 103, the first adhesive layer 102, the first circuit layer 113, and the remaining portion of the first substrate layer 110 (the second hole 62 and the third hole 63 penetrate the first substrate layer 110 together). The diameter of the third hole 63 is smaller than the diameter of the first hole 61 and smaller than the diameter of the second hole 62. The third hole 63 connects the first hole 61 and the second hole 62, thereby forming a through hole 60. And, the through hole 60 communicates with the chamber 1041.

The second blind hole 72 penetrates the fourth conductive plate 40, the third adhesive layer 108, the third conductive plate 105, the second adhesive layer 104, the second conductive plate 103, the first adhesive layer 102 and the first circuit layer 113, and exposes a portion of the surface of the first substrate layer 110.

In step S70, referring to fig. 13, the second conductive material 64 may be disposed in the through hole 60, the third conductive material 711 may be disposed in the first blind hole 71, and the fourth conductive material 721 may be disposed in the second blind hole 72 by plating, but not limited to electroplating. In this embodiment, the second conductive material 64, the third conductive material 711, and the fourth conductive material 721 are all copper.

The second conductive material 64 covers the side walls and the bottom wall of the first hole 61, covers the side walls of the third hole 63 and covers a portion of the surface of the third base material layer 1051 near the second adhesive layer 104, covers a portion of the surface of the second wiring layer 122 near the second adhesive layer 104, and covers the side walls and the bottom wall of the second hole 62.

The second conductive material 64 covers the side walls and the bottom walls of the first hole 61 and the second hole 62, that is, the second conductive material 64 covers a part of the surfaces of the first substrate layer 110 and the fourth substrate layer 401, which corresponds to sinking the second conductive material 64 (copper) into the substrate layer to form a sunk copper plating structure. The insufficient hole covering ability of the dry film (15 μm) may cause a problem of poor ring biting due to the dry film being broken during etching. Under the condition of ensuring the thickness and the height of the copper of the hole ring, the submerged copper plating structure reduces the break difference during film pressing, and further can improve and eliminate the problem of poor etching of the hole ring.

The third conductive material 711 fills the first blind via 71, covers the entire upper surface of the phase change material 30, and is connected to the first conductive material 107. The frame structure formed by connecting the first conductive material 107 and the third conductive material 711 is equivalent to placing the electronic component 20 in a metal cover, and the first conductive material 107 and the third conductive material 711 can realize a shielding function while realizing heat dissipation.

The fourth conductive material 721 covers the sidewalls and bottom wall of the second blind via 72.

In step S80, referring to fig. 14, a fourth circuit layer 403 is formed by fabricating the fifth copper foil layer 402, and a fifth circuit layer 115 is formed by fabricating the second copper foil layer 112. The fourth wiring layer 403 and the fifth wiring layer 115 may be formed using, but not limited to, an image transfer process and an etching process.

Further, referring to fig. 15, a protective layer 116 may be further disposed on a side of the fifth circuit layer 115 facing away from the first substrate layer 110, and the protective layer 116 may be disposed on a side of the fourth circuit layer 403 facing away from the fourth substrate layer 401. In this embodiment, the protective layer 116 is a cover-lay (CVL), and in other embodiments, the protective layer 116 may be a solder mask. The protective layer 116 is used for protecting the fourth circuit layer 403 and the fifth circuit layer 115 from external moisture or foreign matter scratch, etc.

In step S90, referring to fig. 16, the liquid metal 80 is disposed in the through hole 60, the cavity 1041 and the second blind hole 72, so as to obtain the embedded flexible circuit board 100.

Specifically, a certain amount of the liquid metal to be cast is poured into the through hole 60, the chamber 1041 and the second blind hole 72, and then the liquid metal 80 is crystallized and solidified under pressure by continuously applying mechanical static pressure through a specific mold. Depending on the type of the liquid metal 80, the pressurizing pressure may be varied, for example, 40MPa, 60MPa, 80MPa, or the like.

Because the liquid metal 80 has advantages in metal hardness, tensile strength, ductility and the like, bending at any angle and in any direction can be realized, and the influence of bending stress after bending is reduced, so that the bending and shaping precision of the embedded flexible circuit board and the bending stability after molding can be improved. In addition, the whole thickness of the circuit board can be reduced without adding a reinforcing layer (PI reinforcing sheet, steel sheet and the like).

Referring to fig. 16, the present application further provides a buried flexible circuit board 100, which includes an inner circuit substrate 10, an electronic component 20, a phase change material 30, a fourth conductive plate 40, a through hole 60, a blind hole 70, and a liquid metal 80.

The inner circuit board 10 includes a first conductive plate 101, a first adhesive layer 102, a second conductive plate 103, a second adhesive layer 104, and a third conductive plate 105 that are stacked, and the inner circuit board 10 further includes a blind via 106 that penetrates the third conductive plate 105, the second adhesive layer 104, the second conductive plate 103, and the first adhesive layer 102. The surface of the first conductive plate 101, which is close to the second conductive plate 103, is provided with a bonding pad 114, and the blind groove 106 exposes the bonding pad 114. The second conductive plate 103, the second adhesive layer 104 and the third conductive plate 105 on one side of the blind groove 106 form a cavity 1041.

The electronic component 20 is disposed within the blind via 106 and is electrically connected to the bond pad 114.

The phase change material 30 encapsulates the electronic component 20 and fills the gap between the electronic component 20 and the side and bottom walls of the blind via 106.

The fourth conductive plate 40 is disposed on a side of the third conductive plate 105 facing away from the second conductive plate 103 through a third adhesive layer 108.

The through hole 60 penetrates the inner circuit substrate 10 and the fourth conductive plate 40, and communicates with the chamber 1041.

The blind hole 70 includes a first blind hole 71 and a second blind hole 72, and the first blind hole 71 penetrates the fourth conductive plate 40 and the third adhesive layer 108 to expose a portion of the surface of the phase change material 30. The second blind hole penetrates the fourth conductive plate 40, the third adhesive layer 108, the third conductive plate 105, the second adhesive layer 104, the second conductive plate 103, the first adhesive layer 102 and a part of the first conductive plate 101, and exposes a part of the surface of the first conductive plate 101.

The liquid metal 80 is disposed within the through bore 60, the chamber 1041, and the second blind bore 72. The liquid metal 80 may be, but is not limited to, mercury, gallium, rubidium, cesium, and the like. The liquid metal 80 has characteristics of high strength, high hardness, high tensile strength, excellent corrosion resistance, high recovery coefficient, excellent abrasion resistance, and the like, and has remarkable advantages in terms of performance, process, and cost. In some embodiments, the liquid metal 80 may also be used with a solidified gel to further enhance the above properties.

As shown in fig. 16, the blind via 106 is provided with a first conductive material 107, the through hole 60 is provided with a second conductive material 64, the first blind via 71 is provided with a third conductive material 711, and the second blind via 72 is provided with a fourth conductive material 721.

Referring to fig. 17, the liquid metal 80 in the through hole 60 may be partially hollowed out to form a first hollowed-out groove 801; the second hollow groove 802 may be formed by partially hollow the liquid metal 80 in the second blind hole 72. The first hollow groove 801 and the second hollow groove 802 can further reduce the influence of bending stress, and improve bending precision.

The heat dissipation process of the embedded flexible circuit board 100 described in the present application is as follows: heat is generated during the operation of the electronic component 20, and is continuously generated and transferred to the phase change material 30 in contact with the electronic component, so that the phase change temperature of the phase change material 30 is reached, and the phase change material 30 is changed from a solid state to a liquid state, and absorbs the heat. Heat is also transferred to the first conductive material 107 and the third conductive material 711 in contact with the phase change material 30, and the first conductive material 107 may also conduct heat to the liquid metal 80 through the wiring layer, and dissipate heat through conduction. The third conductive material 711 and the liquid metal 80 may be in contact with air, and dissipate heat by convection. When the heat is radiated, the temperature is reduced to reach the phase transition temperature of the phase change material 30, and the phase change material 30 can be changed from a liquid state to a solid state and returns to the original state.

The foregoing description is of some embodiments of the present application, but is not limited to only those embodiments during actual application. Other variations and modifications of the present application, which are apparent to those of ordinary skill in the art, are intended to be within the scope of the present application.

Claims

1. The preparation method of the embedded flexible circuit board is characterized by comprising the following steps of:

2. The method for manufacturing a buried flexible circuit board according to claim 1, wherein the method for manufacturing a circuit board of an inner layer comprises the steps of:

3. The method for manufacturing a buried flexible circuit board according to claim 2, wherein said method for manufacturing a circuit board of an inner layer further comprises: and forming a gold layer on the welding pad.

4. The method for manufacturing a buried flexible circuit board according to claim 2, wherein said method for manufacturing a circuit board of an inner layer further comprises: a first conductive material is disposed on sidewalls of the blind trench.

5. The method of manufacturing a buried flexible circuit board according to claim 2, wherein after the step of filling the blind trench with the phase change material, the method further comprises: and manufacturing the fourth copper foil layer of the third conductive plate to form a third circuit layer.

6. The method of manufacturing a buried flexible circuit board according to claim 2, wherein after the step of forming the through holes and the blind holes in the intermediate body, the method further comprises: and a second conductive material is arranged in the through hole, a third conductive material is arranged in the first blind hole, and a fourth conductive material is arranged in the second blind hole.

7. The method of manufacturing a buried flexible circuit board according to claim 1, wherein said fourth conductive sheet comprises a fourth base material layer and a fifth copper foil layer provided on said fourth base material layer, said method further comprising: and manufacturing the fifth copper foil layer to form a fourth circuit layer, and manufacturing the second copper foil layer to form a fifth circuit layer.

8. The method of manufacturing a buried flexible circuit board according to claim 7, wherein before the step of disposing liquid metal into said through hole, said chamber and said blind hole, said method further comprises: and a protective layer is arranged on one side, away from the first substrate layer, of the fifth circuit layer, and the protective layer is arranged on one side, away from the fourth substrate layer, of the fourth circuit layer.

9. A buried flexible circuit board, comprising:

10. The embedded flexible circuit board of claim 9, wherein a first conductive material is disposed in the blind via, a second conductive material is disposed in the through via, a third conductive material is disposed in the first blind via, and a fourth conductive material is disposed in the second blind via.