Circuit board and method of manufacturing the same

Abstract

The application discloses a circuit board and a manufacturing method thereof. The manufacturing method of the circuit board comprises the following steps: providing a first circuit board, wherein the first circuit board comprises a first base material, a first circuit layer and a second circuit layer, the first circuit layer comprises a signal transmission line, and the second circuit layer is provided with a first opening; stacking and pressing a second circuit board, a first adhesive layer, the first circuit board, a second adhesive layer and a third circuit board in sequence, wherein the third circuit board is provided with a second opening, the second opening and the first opening are communicated to form an opening; cutting from a surface of the second circuit board to form a first cavity penetrating through a part of the second circuit board and the first adhesive layer; cutting from a bottom wall of the opening to form a second cavity penetrating through a part of the first base material layer, wherein a normal projection of the signal transmission line is located in the first cavity and the second cavity in a thickness direction of the circuit board; a first electromagnetic shielding film is arranged to close the first cavity; and a second electromagnetic shielding film is arranged to fill the first opening and close the second cavity.

Description

Technical Field

[0001] This application relates to the field of circuit board technology, and in particular to a circuit board and a method for manufacturing the same. Background Technology

[0002] With the advancement of technology, the market demand for thinner electronic products is becoming increasingly apparent, while high-frequency, high-speed data transmission is becoming the standard. Consequently, the requirements for circuit boards are also increasing, particularly regarding their thinness and high-frequency signal transmission performance. Summary of the Invention

[0003] In view of this, it is necessary to provide a circuit board that can solve the above-mentioned technical problems and a method for manufacturing the same.

[0004] This application provides a method for manufacturing a circuit board, comprising: providing a first circuit board, the first circuit board including a first substrate layer and a first circuit layer and a second circuit layer disposed on opposite sides of the first substrate layer, the first circuit layer including a signal transmission line and two ground lines spaced apart on both sides of the signal transmission line, the second circuit layer having a first opening exposing a portion of the first substrate layer; providing a second circuit board, a third circuit board, a first adhesive layer and a second adhesive layer, and sequentially stacking and pressing the second circuit board, the first adhesive layer, the first circuit board, the second adhesive layer and the third circuit board to obtain an intermediate body, wherein the first adhesive layer is sandwiched between the first circuit layer and the second circuit board, the second adhesive layer is sandwiched between the second circuit layer and the third circuit board, the third circuit board has a second opening, the second... An opening is formed by connecting with the first opening, and a portion of the first substrate layer is exposed in the opening. A first cavity is formed by cutting from the surface of the second circuit board away from the first circuit board, which penetrates the second circuit board and the first adhesive layer. In the thickness direction of the circuit board, the orthogonal projection of the signal transmission line is located in the first cavity. A second cavity is formed by cutting from the bottom wall of the opening, which penetrates the portion of the first substrate layer. In the thickness direction of the circuit board, the orthogonal projection of the signal transmission line is located in the second cavity. A first electromagnetic shielding film is provided on the surface of the second circuit board away from the first circuit board, which closes the first cavity. A second electromagnetic shielding film is provided on the surface of the third circuit board away from the first circuit board, which fills the first opening and closes the second cavity.

[0005] A second aspect of this application provides a circuit board including a first circuit board, a second circuit board, a third circuit board, a first adhesive layer, a second adhesive layer, a first electromagnetic shielding film, and a second electromagnetic shielding film. The first circuit board includes a first substrate layer and a first and a second circuit layer disposed on opposite sides of the first substrate layer. The first circuit layer includes signal transmission lines and two ground lines spaced apart on either side of the signal transmission lines. The second circuit board is bonded to the surface of the first circuit layer by the first adhesive layer. The circuit board has a first cavity penetrating the second circuit board and a portion of the first adhesive layer. The third circuit board is bonded to the surface of the second circuit layer by the second adhesive layer. The circuit board has an opening penetrating the third circuit board, the second adhesive layer, and the second circuit layer, and a second cavity penetrating the bottom wall of the opening and a portion of the first substrate layer. The first electromagnetic shielding film is disposed on the surface of the second circuit board facing away from the first circuit board and seals the first cavity. The second electromagnetic shielding film is disposed on the surface of the third circuit board facing away from the first circuit board and on the bottom wall of the opening, and seals the second cavity.

[0006] The circuit board and its manufacturing method provided in this application reduce the thickness of the circuit board at the opening by providing an opening that penetrates the third circuit board, the second adhesive layer, and the first circuit board, which is beneficial for meeting the requirements of miniaturization. Furthermore, by providing a first cavity and a second cavity on both sides of the signal transmission line, the overall dielectric constant is reduced, which is beneficial for meeting the requirements of high-frequency signal transmission. In addition, the first cavity only penetrates the first adhesive layer, separating the signal transmission line from the first cavity through the first adhesive layer, and the second cavity only penetrates the first substrate layer, separating the signal transmission line from the second cavity through the first substrate layer. This eliminates the need for surface treatment of the signal transmission line, thus reducing costs. Moreover, the step of sealing the first and second cavities is performed after the hot-pressing step, which avoids the problem of board bursting at the cavity due to internal gas expansion during hot-pressing. Attached Figure Description

[0007] Figure 1 This is a cross-sectional schematic diagram of a substrate provided in one embodiment of this application.

[0008] Figure 2 In order to be in Figure 1 The diagram shows a cross-sectional view of the substrate after the circuit layer has been formed.

[0009] Figure 3 This is a cross-sectional schematic diagram of a first circuit board provided in one embodiment of this application.

[0010] Figure 4 A cross-sectional schematic diagram of the second and third circuit boards provided in one embodiment of this application.

[0011] Figure 5 To be Figure 3 The first circuit board shown and Figure 4The diagram shows a cross-sectional view of the second and third circuit boards after they have been laminated together.

[0012] Figure 6 In order to be in Figure 5 A schematic diagram of the cross-section after the second and third conductive structures are formed on the structure shown.

[0013] Figure 7 In order to be in Figure 6 The diagram shows a cross-section of the structure after the first slot is formed.

[0014] Figure 8 In order to be in Figure 7 The diagram shows a cross-section of the structure after the second slot and the second cavity are formed.

[0015] Figure 9 In order to be in Figure 8 The diagram shows a cross-sectional view of the structure after the first electromagnetic shielding film and the second electromagnetic shielding film are installed.

[0016] Figure 10 In order to be in Figure 9 The diagram shows a cross-section of the structure after the first and second through holes are formed.

[0017] Figure 11 This is a cross-sectional schematic diagram of a circuit board provided in one embodiment of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] The first embodiment of this application provides a method for manufacturing a circuit board, which includes the following steps:

[0020] Step S1, please refer to Figure 3 A first circuit board 10 is provided. The first circuit board 10 includes a first substrate layer 11, a first circuit layer 12, and a second circuit layer 13. The first circuit layer 12 and the second circuit layer 13 are disposed on opposite sides of the first substrate layer 11 in its thickness direction. The first circuit layer 12 includes a signal transmission line 121 and two ground lines 122 spaced apart on both sides of the signal transmission line 121. The second circuit layer 13 has a first opening 130, which penetrates the second circuit layer 13 along the thickness direction of the first substrate layer 11 and exposes a portion of the first substrate layer 11. The second circuit layer 13 includes two first connection pads 131 (see figure). Figure 2The two first connecting pads 131 are separated by a first opening 130. The orthographic projection of the signal transmission line 121 is located within the first opening 130 along the thickness direction of the first substrate layer 11.

[0021] In some embodiments, the first opening 130 and the signal transmission line 121 are separated by a first substrate layer 11 in the thickness direction of the first substrate layer 11.

[0022] In some implementations, step S1 includes the following steps:

[0023] Step S11, please refer to Figure 1 A first substrate 101 is provided, which includes a first substrate layer 11, a first metal layer 102, and a second metal layer 103. The first metal layer 102 and the second metal layer 103 are disposed on two opposing surfaces of the first substrate layer 11 in its thickness direction.

[0024] The material of the first substrate layer 11 may include one or more of the following: glass fiber epoxy resin (FR-4), polyethylene naphthalate (PEN), polyimide (PI), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), liquid crystal polymer (LCP), and polytetrafluoroethylene (PTFE). The material of the first metal layer 102 and the second metal layer 103 may include one or more of the following: gold, silver, and copper. In some embodiments, the first substrate 101 is a double-sided copper-clad laminate.

[0025] Step S12, please refer to Figure 2 The first metal layer 102 and the second metal layer 103 are respectively fabricated to pattern the first metal layer 102 and the second metal layer 103 to form the first circuit layer 12 and the second circuit layer 13.

[0026] In some embodiments, the first metal layer 102 and the second metal layer 103 are fabricated by lamination, exposure, development, and line etching.

[0027] Step S13, please refer to Figure 3 A first conductive structure 14 is formed to electrically connect the first circuit layer 12 and the second circuit layer 13, thereby obtaining the first circuit board 10.

[0028] The first conductive structure 14 penetrates the first substrate layer 11. The first conductive structure 14 can be an electroplated hole formed by electroplating a blind via. Specifically, step S13 includes: drilling a hole from the surface of the first circuit layer 12 to form a blind via penetrating the first circuit layer 12 and the first substrate layer 11, and electroplating the blind via to form the first conductive structure 14. The first conductive structure 14 can also be a conductive pillar formed by filling the blind via with a conductive material (e.g., conductive paste).

[0029] In some embodiments, there are two first conductive structures 14, each first conductive structure 14 being connected between a ground wire 122 and a corresponding first connecting pad 131.

[0030] For step S2, please refer to [link / reference]. Figure 4 and Figure 5 A second circuit board 20, a third circuit board 30, a first adhesive layer 41, and a second adhesive layer 42 are provided. The second circuit board 20, the first adhesive layer 41, the first circuit board 10, the second adhesive layer 42, and the third circuit board 30 are stacked and pressed together in sequence to obtain an intermediate body.

[0031] The second circuit board 20 includes a second substrate layer 21 and a third circuit layer 22. A first adhesive layer 41 is sandwiched between the first circuit layer 12 and the second substrate layer 21, and fills the gaps between the circuits in the first circuit layer 12. The third circuit layer 22 is located on the surface of the second substrate layer 21 that faces away from the first adhesive layer 41 in its thickness direction.

[0032] The third circuit board 30 includes a third substrate layer 31 and a fourth circuit layer 32 disposed on the surface of the third substrate layer 31. The third circuit board 30 has a second opening 310 extending through the third substrate layer 31 and the fourth circuit layer 32 along its thickness direction. A second adhesive layer 42 is sandwiched between the second circuit layer 13 and the third substrate layer 31, filling the gaps in the circuits within the second circuit layer 13. The fourth circuit layer 32 is located on the surface of the third substrate layer 31 facing away from the second adhesive layer 42 in its thickness direction. The fourth circuit layer 32 includes a third connecting pad 321. The second opening 310 communicates with the first opening 130 to form an opening, and a portion of the first substrate layer 11 is exposed in the opening. That is, the bottom wall of the opening is formed by the first substrate layer 11. In the thickness direction of the first substrate layer 11, the orthographic projection of the signal transmission line 121 is located within the opening, and the orthographic projection of the grounding line 122 is at least partially located within the opening.

[0033] In some embodiments, the second opening 310 is aligned with the first opening 130 in the thickness direction of the third substrate layer 31.

[0034] The materials of the second substrate layer 21 and the third substrate layer 31 can each independently include one or more of the following: glass fiber epoxy resin (FR-4), polyethylene naphthalate (PEN), polyimide (PI), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), liquid crystal polymer (LCP), and polytetrafluoroethylene (PTFE). The materials of the third circuit layer 22 and the fourth circuit layer 32 can include one or more of the following: gold, silver, and copper.

[0035] The first adhesive layer 41 and the second adhesive layer 42 can each be a prepreg or a resin. The resin may include phenolic resin, polyvinyl chloride resin, polyester resin, epoxy resin, polyurethane, polyvinyl ester, polyfluorinated resin, polyfluorocarbon resin, polybismaleimide resin, polymatriazine resin, polyimide resin, polycyanate resin, or epoxy polyphenylene ether.

[0036] Step S3, please refer to Figure 6 This forms a second conductive structure 210 that electrically connects the first circuit layer 12 and the third circuit layer 22, and a third conductive structure 320 that electrically connects the second circuit layer 13 and the fourth circuit layer 32.

[0037] The second conductive structure 210 penetrates the second substrate layer 21 and the first adhesive layer 41, and the third conductive structure 220 penetrates the third substrate layer 31 and the second adhesive layer 42. The second conductive structure 210 and the third conductive structure 220 can each be an electroplated hole formed by electroplating blind holes, or a conductive pillar formed by filling blind holes with conductive material.

[0038] In some embodiments, there are two second conductive structures 210 and two third conductive structures 320. The two second conductive structures 210 are respectively connected to two grounding wires 122, and each third conductive structure 320 is connected to a third connecting pad 321 and a first connecting pad 131 located on the same side of the second opening 310.

[0039] Step S3: Cut from the surface of the third circuit layer 22 to form a first cavity that penetrates the second circuit board 20 and part of the first adhesive layer 41. The orthographic projection of the signal transmission line 121 is located within the first cavity in the thickness direction of the first substrate layer 11.

[0040] The bottom wall of the first cavity is formed by a first adhesive layer 41, which separates the signal transmission line 121 from the first cavity and prevents the signal transmission line 121 from being oxidized by the air inside the first cavity. In some embodiments, the thickness of the first adhesive layer 41 covering the signal transmission layer 121 is 1μm-2μm.

[0041] In some embodiments, the projection of the grounding wire 122 is located outside the first cavity in the thickness direction of the first substrate layer 11.

[0042] In some implementations, step S3 includes the following steps:

[0043] Step S31, please refer to Figure 7The third circuit layer 22 is cut away from the surface of the first circuit board 10, removing the third circuit layer 22 to form a first slot 220 and two second connecting pads 221 located on both sides of the first slot 220. A portion of the second substrate layer 21 is exposed in the first slot 220. The two second connecting pads 221 are separated by the first slot 220, and each second connecting pad 221 is connected to a corresponding ground wire 122 via a second conductive structure 210. The bottom wall of the first slot 220 is partially formed by the second substrate layer 21. Along the thickness direction of the second substrate layer 21, the orthographic projection of the signal transmission line 121 lies within the first slot 220.

[0044] In some embodiments, the first slot 220 is formed by laser cutting.

[0045] Step S32, please refer to Figure 8 A second groove 410 is formed by cutting from the bottom wall of the first groove 220 to remove portions of the second substrate layer 21 and the first adhesive layer 41. The second groove 410 penetrates portions of the second substrate layer 21 and the first adhesive layer 41. The second groove 410 and the first groove 220 together constitute the first cavity. The bottom wall of the second groove 410 is formed by the first adhesive layer 41. In the thickness direction of the first substrate layer 11, the orthographic projection of the signal transmission line 121 is located within the second groove 410.

[0046] In some implementations, the second slot 410 is formed by mechanical depth-fixed scooping and cutting.

[0047] In some embodiments, a step is formed between the bottom wall of the first slot 410 and the side wall of the second slot 420, which supports the subsequently installed first electromagnetic shielding film. In some embodiments, the side wall of the first slot 410 is aligned with the side wall of the second slot 420, so that the subsequently installed first electromagnetic shielding film can be supported on the second circuit layer 22.

[0048] In some embodiments, the orthographic projection of the grounding wire 122 is located outside the second slot 410 in the thickness direction of the first substrate layer 11.

[0049] For step S4, please refer to [link / reference]. Figure 8 The bottom wall of the opening is cut to remove a portion of the first substrate layer, forming a second cavity 420. The orthographic projection of the signal transmission line 121 is located within the second cavity 420 in the thickness direction of the first substrate layer 11.

[0050] In some embodiments, the orthographic projection of the grounding wire 122 is located outside the second cavity 420 in the thickness direction of the first substrate layer 11. In some embodiments, the second slot 410 is aligned with the second cavity 420 in the thickness direction of the first substrate layer 11.

[0051] The bottom wall of the second cavity 420 is formed by a first substrate layer 11, which separates the signal transmission line 121 from the second cavity 420 through the first substrate layer 11, preventing the signal transmission line 121 from being oxidized by the air inside the second cavity 420. In some embodiments, the thickness of the first substrate layer 11 covering the signal transmission layer 121 is 1μm-2μm.

[0052] Step S5: Bake the intermediate body after forming the first cavity and the second cavity 420 to fully cure the substrate layer and adhesive layer at the first cavity and the second cavity, so as to facilitate the subsequent installation of the electromagnetic shielding film.

[0053] In step S6, please refer to step 9, a first electromagnetic shielding film 51 is disposed on the surface of the third circuit layer 22 facing away from the first circuit board 10. The first electromagnetic shielding film 51 seals the first cavity. The first electromagnetic shielding film 51 covers the entire surface of the third circuit layer 22 facing away from the first circuit board 10 and fills the circuit gaps within the third circuit layer 22.

[0054] In some embodiments, the first electromagnetic shielding film 51 fills the first slot 220 and is electrically connected to the second connecting pad 221.

[0055] Step S7, please refer to Figure 9 A second electromagnetic shielding film 52 is provided on the surface of the third circuit board 30 opposite to the first circuit board 10. The second electromagnetic shielding film 52 fills the first opening 130, contacts and connects with the second circuit layer 13, and seals the second cavity 420.

[0056] The second electromagnetic shielding film 52 covers the entire surface of the fourth circuit layer 52 away from the first circuit board 10 and fills the gaps between the circuits in the fourth circuit layer 52. The second electromagnetic shielding film 52 covers the sidewalls and bottom wall of the opening, but does not completely fill the second opening 310, which helps to reduce the thickness of the circuit board at the opening and meets the requirements of miniaturization.

[0057] The first electromagnetic shielding film 51 and the second electromagnetic shielding film 52 serve as the grounding layer of the circuit board. The first electromagnetic shielding film 51, the third circuit layer 22, the second conductive structure 210, the first circuit layer 12, the first conductive structure 14, the second circuit layer 13, and the second electromagnetic shielding film 52 constitute the current return path. There is a cavity between the signal transmission line 122 and the electromagnetic shielding film. This cavity may contain air or be a vacuum, which reduces the overall dielectric constant to meet the requirements of high-frequency signal transmission.

[0058] Step S8, please refer to Figure 10 A first through hole 510 is formed, which penetrates the first electromagnetic shielding film 51 and exposes the second connecting pad 221, and a second through hole 520 is formed, which penetrates the second electromagnetic shielding film 51 and exposes the third connecting pad 321.

[0059] The first through hole 510 and the second through hole 520 can be formed by laser etching.

[0060] Step S9, please refer to Figure 11 A first surface treatment layer 61 covering the second connecting pad 221 is formed in the first through hole 510, and a second surface treatment layer 62 covering the third connecting pad 321 is formed in the second through hole 520, thereby obtaining a circuit board 100.

[0061] The first surface treatment layer 61 is used to protect the second connecting pad 221, and the second surface treatment layer 62 is used to protect the third connecting pad 321. The first surface treatment layer 61 and the second surface treatment layer 62 may be formed by, but are not limited to, chemical nickel-gold processing.

[0062] Please see Figure 11 One embodiment of this application provides a circuit board 100, including a first circuit board 10, a second circuit board 20, a third circuit board 30, a first adhesive layer 41, a second adhesive layer 42, a first shielding film 51, and a second shielding film 52.

[0063] The first circuit board 10 includes a first substrate layer 11, a first circuit layer 12, and a second circuit layer 13. The first circuit layer 12 and the second circuit layer 13 are disposed on two opposing surfaces of the first substrate layer 11 in its thickness direction. The first circuit layer 12 includes a signal transmission line 121 and two ground lines 122 spaced apart on both sides of the signal transmission line 121.

[0064] The second circuit board 20 includes a second substrate layer 21 and a third circuit layer 22. The second circuit board 20 is bonded to the surface of the first circuit layer 12 by a first adhesive layer 41, which is sandwiched between the first circuit layer 12 and the second substrate layer 21. The third circuit layer 22 is located on the surface of the second substrate layer 21, facing away from the surface of the first adhesive layer 41 in its thickness direction. The circuit board 100 has a first cavity penetrating the second circuit board 20 and a portion of the first adhesive layer 41. The thickness of the first adhesive layer 41 located on the signal transmission line 121 is less than the thickness of the first adhesive layer 41 located on the ground line 122. A first electromagnetic shielding film 51 is disposed on the surface of the second circuit board 20 facing away from the first circuit board 10 and seals the first cavity.

[0065] In some embodiments, the first cavity includes a first slot 220 and a second slot 410 that are connected. The first slot 220 penetrates a portion of the third circuit layer 22 and exposes a portion of the second substrate layer 21, and the second slot 410 penetrates a portion of the second substrate layer 21 and the first adhesive layer 41. A step is formed between the bottom wall of the first slot 220 and the sidewall of the second slot 410. A first electromagnetic shielding film 51 fills the first slot 410 and is supported on the step.

[0066] The third circuit board 30 is bonded to the surface of the second circuit layer 13 via the second adhesive layer 42. The circuit board 100 has an opening that passes through the third circuit board 30, the second adhesive layer 42, and the second circuit layer 13. The opening includes a first opening 130 and a second opening 310 that are connected. The first opening 130 passes through the second circuit layer 13, and the second opening 310 passes through the third circuit board 30 and the second adhesive layer 42. The bottom wall of the opening is formed by a first substrate layer 11. The circuit board 100 also has a second cavity 420 that passes through the bottom wall of the opening and a portion of the first substrate layer 11. The thickness of the first substrate layer 11 located on the signal transmission line 121 is less than the thickness of the first substrate layer located on the ground line 122. A second electromagnetic shielding film 52 is disposed on the surface of the third circuit board 30 facing away from the first circuit board 10 and the bottom wall of the opening, and seals the second cavity 420.

[0067] In some embodiments, the second circuit layer 13 includes two first connection pads 131 separated by an opening, the third circuit layer 22 includes two second connection pads 221 separated by a first slot 410, and the circuit board 100 also includes two first conductive structures 14 and two second conductive structures 210. Each first conductive structure 14 penetrates the first substrate layer 11 and connects a corresponding ground wire 122 and a first connection pad 131, and each second conductive structure 210 penetrates the second substrate layer 21 and connects a corresponding ground wire 122 and a second connection pad 221.

[0068] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with this application are still within the scope of this application.

Claims

1. A method for manufacturing a circuit board, characterized in that, include: A first circuit board is provided, the first circuit board includes a first substrate layer and a first circuit layer and a second circuit layer disposed on opposite sides of the first substrate layer, the first circuit layer includes a signal transmission line and two ground lines disposed on both sides of the signal transmission line at intervals, and the second circuit layer has a first opening that exposes a portion of the first substrate layer. A second circuit board, a third circuit board, a first adhesive layer, and a second adhesive layer are provided, and the second circuit board, the first adhesive layer, the first circuit board, the second adhesive layer, and the third circuit board are stacked and pressed in sequence to obtain an intermediate body. The first adhesive layer is sandwiched between the first circuit layer and the second circuit board, and the second adhesive layer is sandwiched between the second circuit layer and the third circuit board. The third circuit board has a second opening, which communicates with the first opening to form an opening. A portion of the first substrate layer is exposed in the opening. A first cavity is formed by cutting the surface of the second circuit board away from the first circuit board, which is a portion of the second circuit board and the first adhesive layer. The orthogonal projection of the signal transmission line is located in the first cavity in the thickness direction of the circuit board. A second cavity is formed by cutting through the bottom wall of the opening, extending through a portion of the first substrate layer, wherein the orthographic projection of the signal transmission line is located within the second cavity in the thickness direction of the circuit board; A first electromagnetic shielding film is provided on the surface of the second circuit board opposite to the first circuit board, and the first electromagnetic shielding film seals the first cavity. A second electromagnetic shielding film is disposed on the surface of the third circuit board opposite to the first circuit board. The second electromagnetic shielding film fills the first opening and seals the second cavity.

2. The method for manufacturing a circuit board as described in claim 1, characterized in that, The second circuit board includes a second substrate layer and a third circuit layer, with the first adhesive layer sandwiched between the second substrate layer and the first circuit layer. The third circuit layer is located on the surface of the second substrate layer facing away from the first adhesive layer. The step of "cutting from the surface of the second circuit board facing away from the first circuit board to form a first cavity penetrating the second circuit board and the first adhesive layer" includes: A first groove is formed by cutting from the surface of the third circuit layer away from the first circuit board to expose the portion of the second substrate layer. A second groove is formed by cutting from the bottom wall of the first groove, penetrating the second substrate layer and the first adhesive layer. A step is formed between the bottom wall of the first groove and the side wall of the second groove. The first electromagnetic shielding film fills the first groove.

3. The method for manufacturing a circuit board as described in claim 2, characterized in that, The second circuit layer includes two first connection pads separated by the first opening, the third circuit layer includes two second connection pads separated by the first slot, and the circuit board also includes two first conductive structures and two second conductive structures. Each first conductive structure penetrates the first substrate layer and is connected to a corresponding ground wire and a first connection pad, and each second conductive structure penetrates the second substrate layer and is connected to a corresponding ground wire and a second connection pad.

4. The method for manufacturing a circuit board as described in claim 3, characterized in that, Also includes: A first through hole is formed, penetrating the first electromagnetic shielding film and exposing the second connecting pad; A first surface treatment layer is formed within the first through hole to cover the second connecting pad.

5. The method for manufacturing a circuit board as described in claim 2, characterized in that, Along the thickness direction of the circuit board, the orthographic projection of the grounding wire is located outside the second slot, and the orthographic projection of the grounding wire is at least partially located inside the opening.

6. The method for manufacturing a circuit board as described in claim 1, characterized in that, Also includes: The intermediate body formed after the first cavity and the second cavity are baked.

7. A circuit board, characterized in that, include: The first circuit board includes a first substrate layer and a first circuit layer and a second circuit layer disposed on opposite sides of the first substrate layer. The first circuit layer includes a signal transmission line and two ground lines disposed at intervals on both sides of the signal transmission line. The second circuit board is bonded to the surface of the first circuit layer by a first adhesive layer, and the circuit board is provided with a first cavity that passes through the second circuit board and the first adhesive layer. The third circuit board is bonded to the surface of the second circuit layer by a second adhesive layer. The circuit board has an opening that passes through the third circuit board, the second adhesive layer and the second circuit layer, and a second cavity that passes through the bottom wall of the opening and a portion of the first substrate layer. A first electromagnetic shielding film is disposed on the surface of the second circuit board away from the first circuit board and seals the first cavity. The second electromagnetic shielding film is disposed on the surface of the third circuit board away from the first circuit board and the bottom wall of the opening, and seals the second cavity.

8. The circuit board as described in claim 7, characterized in that, The thickness of the first adhesive layer on the signal transmission line is less than the thickness of the first adhesive layer on the grounding line, and the thickness of the first substrate layer on the signal line is less than the thickness of the first substrate layer on the grounding line.

9. The circuit board as described in claim 7, characterized in that, The second circuit board includes a second substrate layer and a third circuit layer. The first adhesive layer is sandwiched between the second substrate layer and the first circuit layer. The third circuit layer is located on the surface of the second substrate layer opposite to the first adhesive layer. The first cavity includes a first slot and a second slot that are connected. The first slot penetrates the third circuit layer and exposes a portion of the second substrate layer. The second slot penetrates a portion of the second substrate layer and the first adhesive layer. A step is formed between the bottom wall of the first slot and the side wall of the second slot. The first electromagnetic shielding film fills the first slot.

10. The circuit board as described in claim 9, characterized in that, The second circuit layer includes two first connection pads separated by the opening, the third circuit layer includes two second connection pads separated by the first slot, and the circuit board also includes two first conductive structures and two second conductive structures. Each first conductive structure penetrates the first substrate layer and is connected to a corresponding ground wire and a first connection pad, and each second conductive structure penetrates the second substrate layer and is connected to a corresponding ground wire and a second connection pad.

Images