WO2024180817A1

WO2024180817A1 - Joint printed wiring board, printed wiring board, and manufacturing method for joint printed wiring board

Info

Publication number: WO2024180817A1
Application number: PCT/JP2023/039897
Authority: WO
Inventors: 赳志重岡
Original assignee: 日本メクトロン株式会社
Priority date: 2023-03-02
Filing date: 2023-11-06
Publication date: 2024-09-06
Also published as: JP2024124227A

Abstract

[Problem] To provide a joint printed wiring board capable of reducing transmission loss with a simple configuration. [Solution] In one embodiment, a joint printed wiring board 1 includes printed wiring boards 10, 20 joined to each other, and a shield portion 30 having a conductive layer provided across the printed wiring boards 10, 20. The printed wiring board 10 includes a first insulating layer, a signal line 11, a second insulating layer laminated on the first insulating layer so that at least a part of the signal line 11 is embedded therein, and a ground layer 14 provided so as to encompass the signal line 11 when the printed wiring board 10 is viewed in the thickness direction. The printed wiring board 20 includes a third insulating layer and a signal line 21 electrically connected to the signal line 11. The conductive layer of the shield portion 30 includes a first conductive portion provided so as to encompass the signal line 21 when the printed wiring board 20 is viewed in the thickness direction, and a second conductive portion integrated with the first conductive portion and joined to the ground layer 14.

Description

Bonded printed wiring board, printed wiring board, and method for manufacturing bonded printed wiring board

The present invention relates to a bonded printed wiring board, a printed wiring board, and a method for manufacturing a bonded printed wiring board, and more specifically, to a bonded printed wiring board, a printed wiring board, and a method for manufacturing a bonded printed wiring board that can improve transmission characteristics with a simple configuration.

Printed wiring boards are used inside smartphones and other information and communication devices as antenna boards that receive radio waves, cable boards that contain signal lines that transmit signals, and main boards on which semiconductor chips are mounted.

In order to achieve both a compact board size and high transmission characteristics even for high-frequency signals used in 5G and other applications, the material of the antenna board is often not the same as the material of the cable board or main board. For example, a high-dielectric material (such as polyimide) is used for the antenna board to reduce size, while a low-dielectric material (such as liquid crystal polymer) is used for the cable board or main board to reduce transmission loss.

Therefore, it is necessary to bond the antenna board and the cable board or main board via a conductive material or the like. Patent Document 1 describes a bonded printed wiring board in which two printed wiring boards made of different materials are bonded via a conductive material.

Patent No. 4685614

　A bonded printed wiring board that transmits high-frequency band signals has a microstrip line structure or a strip line structure. In these structures, a signal line and a ground layer are provided with an insulating layer sandwiched between them. In a bonded printed wiring board, if the ground layer of one printed wiring board is not electrically connected to the ground layer of the other printed wiring board, the return current induced in the ground layer by the signal flowing through the signal line is blocked at the joint, generating noise and degrading the transmission characteristics. In the bonded printed wiring board of Patent Document 1, the ground layers of both boards are not electrically connected, and the blocking of the return current degrades the transmission characteristics.

The present invention has been made based on the above technical recognition, and its purpose is to provide a bonded printed wiring board and a manufacturing method thereof that can improve transmission characteristics with a simple configuration. However, the present invention is not limited to this purpose, and the purpose of the present invention may be an object corresponding to each effect of the configuration of each embodiment described below.

The bonded printed wiring board according to the first aspect of the present invention comprises:
A first printed wiring board;
a second printed wiring board joined to the first printed wiring board;
a shield portion having a conductive layer provided across the first printed wiring board and the second printed wiring board;
A bonded printed wiring board comprising:
The first printed wiring board includes:
a first insulating layer having a first major surface and a second major surface opposite the first major surface;
a first signal line provided on the first main surface;
a second insulating layer having a third main surface facing the first main surface and a fourth main surface opposite the third main surface, the second insulating layer being laminated on the first insulating layer so as to bury at least a portion of the first signal line;
a ground layer provided on the fourth main surface so as to include the first signal line when viewed in a thickness direction of the first printed wiring board;
Equipped with
The second printed wiring board includes:
a third insulating layer having a fifth main surface joined to the first printed wiring board and a sixth main surface opposite the fifth main surface;
a second signal line electrically connected to the first signal line;
Equipped with
The conductive layer of the shield portion is
a first conductive portion provided to include the second signal line when viewed in a thickness direction of the second printed wiring board;
a second conductive portion integral with the first conductive portion and joined to the ground layer;
The present invention is characterized by comprising:

In addition, in the bonded printed wiring board,
the second printed wiring board is an antenna substrate provided with an antenna that is connected to the second signal line and receives a wireless signal;
The first printed wiring board may be a cable board in which the first signal line is connected to another board, or a main board on which a semiconductor chip for processing radio signals received by the antenna is mounted.

In addition, in the bonded printed wiring board,
the first insulating layer of the first printed wiring board includes a first insulating base material made of a liquid crystal polymer, a fluorine-based material, a polyimide-based material, or a cycloolefin polymer;
the second insulating layer of the first printed wiring board includes a second insulating base material made of a liquid crystal polymer, a fluorine-based material, a polyimide-based material, or a cycloolefin polymer;
The third insulating layer of the second printed wiring board may include a third insulating base material made of a polyimide-based material, a liquid crystal polymer, a fluorine-based material, epoxy glass, a cycloolefin polymer, ceramics, or polyphenylene ether.

In addition, in the bonded printed wiring board,
The conductive layer of the shield portion may include a metal foil, a conductive paste layer, a solder layer, an isotropic conductive adhesive layer, or a conductive film layer.

In addition, in the bonded printed wiring board,
the conductive layer of the shield portion is a metal foil,
The shielding portion may further include an anisotropic conductive adhesive layer for adhering the metal foil to the first printed wiring board and the second printed wiring board.

In addition, in the bonded printed wiring board,
the conductive layer of the shield portion is a conductive paste layer,
The shield portion may further include an isotropic conductive adhesive layer for adhering the conductive paste layer to the first printed wiring board and the second printed wiring board.

In addition, in the bonded printed wiring board,
the conductive layer of the shield portion is a conductive paste layer or a solder layer,
The shield portion may further include an anisotropic conductive adhesive layer for adhering the conductive paste layer or the solder layer to the first printed wiring board and the second printed wiring board.

In addition, in the bonded printed wiring board,
The conductive layer of the shield portion may be an isotropically conductive adhesive layer.

In addition, in the bonded printed wiring board,
the conductive layer of the shield portion is a metal foil,
The shield portion is
a first insulating adhesive layer provided on the second printed wiring board and adhering the first conductive portion of the conductive layer to the second printed wiring board;
a second insulating adhesive layer provided on the first printed wiring board and adhering the second conductive portion of the conductive layer to the first printed wiring board;
and
The second conductive portion may be electrically connected to the ground layer via a conductive material.

In addition, in the bonded printed wiring board,
the second insulating layer of the first printed wiring board is laminated on the first insulating layer such that the first main surface and an end of the first signal line are locally exposed;
the second signal line of the second printed wiring board is provided on the fifth main surface,
the first conductive portion of the shield portion is joined to the sixth main surface,
the fifth main surface is joined to a locally exposed portion of the first main surface of the first printed wiring board via a second conductive material;
An end of the first signal line and the second signal line may be electrically connected via the second conductive material.

In addition, in the bonded printed wiring board,
the first printed wiring board further includes an interlayer connection portion that penetrates the second insulating layer and electrically connects the first signal line and a land provided on the fourth main surface;
the fifth main surface of the second printed wiring board is joined to the fourth main surface of the first printed wiring board;
The first signal line and the second signal line may be electrically connected via the interlayer connection portion and the land.

In addition, in the bonded printed wiring board,
the second signal line of the second printed wiring board is provided on the fifth main surface,
the first conductive portion of the shield portion is joined to the sixth main surface,
The land of the interlayer connection portion and the second signal line may be electrically connected via a second conductive material.

In addition, in the bonded printed wiring board,
the second printed wiring board further includes a third signal line provided in the third insulating layer and different from the second signal line;
The land of the interlayer connection portion and the third signal line may be electrically connected via a third conductive material.

In addition, in the bonded printed wiring board,
the second signal line of the second printed wiring board is provided on the sixth main surface,
The second printed wiring board includes:
an insulating protective layer covering the second signal line;
a third conductive material that fills a through hole penetrating the third insulating layer and electrically connects the land of the first printed wiring board and the second signal line;
Further equipped with
The first conductive portion of the shield portion may be joined to the insulating protective layer.

In addition, in the bonded printed wiring board,
the second printed wiring board further includes a second ground layer provided on the fifth main surface,
The ground layer and the second ground layer may be electrically connected via a second conductive material.

In addition, in the bonded printed wiring board,
A third insulating adhesive layer, a second insulating protective layer, and a fourth insulating adhesive layer may be laminated in this order between the fourth main surface and the fifth main surface.

In addition, in the bonded printed wiring board,
The first printed wiring board and/or the second printed wiring board may be a flexible printed wiring board.

In addition, in the bonded printed wiring board,
The first printed wiring board may have two to five circuit layers.

In addition, in the bonded printed wiring board,
The second printed wiring board may have 1 to 5 circuit layers.

The bonded printed wiring board according to the second aspect of the present invention comprises:
A first printed wiring board;
a second printed wiring board joined to the first printed wiring board;
a shield portion having a conductive layer provided across the first printed wiring board and the second printed wiring board;
A bonded printed wiring board comprising:
The first printed wiring board includes:
a first insulating layer having a first major surface and a second major surface opposite the first major surface;
a first signal line provided on the first main surface;
a ground line provided on the first main surface so as to sandwich the first signal line;
Equipped with
The second printed wiring board includes:
a second insulating layer having a third main surface bonded to the first main surface and a fourth main surface opposite the third main surface;
a second signal line provided on the third main surface and electrically connected to the first signal line via a conductive material;
Equipped with
The conductive layer of the shield portion is
a first conductive portion provided on the fourth main surface so as to include the second signal line when viewed in a thickness direction of the second printed wiring board;
a second conductive portion integral with the first conductive portion and joined to the ground line;
The present invention is characterized by comprising:

The printed wiring board according to the present invention comprises:
a first insulating layer having a first major surface and a second major surface opposite the first major surface;
a first signal line provided on the first main surface;
a second insulating layer having a third main surface facing the first main surface and a fourth main surface opposite the third main surface, the second insulating layer including a laminated portion laminated on the first insulating layer and an extending portion extending in a longitudinal direction from the laminated portion;
a second signal line provided on the fourth main surface in the laminated portion and the extending portion of the second insulating layer;
a ground layer provided on the fourth main surface of the laminated portion of the second insulating layer at a distance from the second signal line;
an interlayer connection portion that penetrates the second insulating layer and electrically connects the first signal line and the second signal line;
an insulating protective layer provided so as to cover the second signal line;
a shielding section having a conductive layer including a first conductive section provided to include the second signal line when viewed in a thickness direction of the second insulating layer, and a second conductive section integral with the first conductive section and joined to the ground layer;
The present invention is characterized by comprising:

The method for producing a bonded printed wiring board according to the present invention includes the steps of:
a step of preparing a first printed wiring board including: a first insulating layer having a first main surface and a second main surface opposite to the first main surface; a first signal line provided on the first main surface; a second insulating layer having a third main surface facing the first main surface and a fourth main surface opposite to the third main surface, the second insulating layer being laminated on the first insulating layer so as to embed at least a portion of the first main surface and the first signal line; and a ground layer provided on the fourth main surface so as to encompass the first signal line when viewed in a thickness direction of the second insulating layer;
preparing a second printed wiring board including a third insulating layer having a fifth main surface and a sixth main surface opposite to the fifth main surface, and a second signal line provided in the third insulating layer;
a step of joining the first printed wiring board and the second printed wiring board via a conductive material, the step being to join the fifth main surface of the second printed wiring board to the first printed wiring board and electrically connect the first signal line and the second signal line;
a step of providing a shielding portion having a conductive layer including a first conductive portion and a second conductive portion integral with the first conductive portion, the step of joining the first conductive portion to the second printed wiring board so as to include the second signal line when viewed in a thickness direction of the second printed wiring board, and joining the second conductive portion to the ground layer;
The present invention is characterized by comprising:

Further, in the method for producing the bonded printed wiring board,
The step of joining the first printed wiring board and the second printed wiring board and the step of providing the shielding portion may be performed simultaneously.

The bonded printed wiring board of the present invention has a shielding section with a conductive layer provided across the first and second printed wiring boards, making it possible to improve transmission characteristics with a simple configuration.

1A is a plan view of a bonded printed wiring board according to a first embodiment before bonding, and FIG. 1B is a vertical cross-sectional view taken along a signal line of the bonded printed wiring board according to the first embodiment. 2 is a longitudinal sectional view taken along a ground line of the joint printed wiring board according to the first embodiment; FIG. 3A to 3C are cross-sectional process diagrams illustrating a method for manufacturing a bonded printed wiring board according to the first embodiment. 3B is a process cross-sectional view illustrating the method for manufacturing the bonded printed wiring board according to the first embodiment, following FIG. 3A. 3C is a process cross-sectional view illustrating the method for manufacturing a bonded printed wiring board according to the first embodiment, following FIG. 3B. 3D is a cross-sectional view illustrating a process of the method for manufacturing a bonded printed wiring board according to the first embodiment, following FIG. 3C. 1A is a longitudinal cross-sectional view taken along a signal line of a bonded printed wiring board according to a first modified example of the first embodiment, and FIG. 1B is a longitudinal cross-sectional view taken along a signal line of a bonded printed wiring board according to a second modified example of the first embodiment. 1A is a longitudinal cross-sectional view taken along a signal line of a bonded printed wiring board according to a third modified example of the first embodiment, and FIG. 1B is a longitudinal cross-sectional view taken along a signal line of a bonded printed wiring board according to a fourth modified example of the first embodiment. FIG. 13 is a longitudinal sectional view taken along a signal line of a joint printed wiring board according to a fifth modified example of the first embodiment. FIG. 11 is a longitudinal sectional view taken along a signal line of a bonded printed wiring board according to a second embodiment. FIG. 11 is a longitudinal sectional view taken along a signal line of a bonded printed wiring board according to a modified example of the second embodiment. FIG. 11 is a longitudinal sectional view taken along a signal line of a bonded printed wiring board according to a third embodiment. FIG. 10 is a longitudinal sectional view taken along a signal line of a bonded printed wiring board according to a fourth embodiment. 13A is a plan view of a bonded printed wiring board according to a fifth embodiment before bonding, and FIG. 13B is a vertical cross-sectional view taken along a ground line of the bonded printed wiring board according to the fifth embodiment. FIG. 13 is a longitudinal sectional view taken along a signal line of a printed wiring board according to a sixth embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings. In each drawing, components having equivalent functions are given the same reference numerals.

The scale ratio of each component has been changed appropriately to make it recognizable on the drawings. The drawings are schematic and mainly show the characteristic parts of each embodiment, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc. differ from the actual ones.

In addition, in the following explanation, unless otherwise specified, "joining" includes both bonding via an adhesive and direct contact. When bonding via an adhesive, there are no limitations on whether the material is conductive or insulating, or anisotropic or isotropic.

First Embodiment
A bonded printed wiring board 1 according to a first embodiment will be described with reference to Figures 1 and 2. Figure 1(a) is a plan view of the bonded printed wiring board 1 according to the present embodiment before bonding. Figure 1(b) is a vertical cross-sectional view along the signal lines 11 and 21 of the bonded printed wiring board 1 according to the present embodiment. Figure 2 is a vertical cross-sectional view along the ground line 12 of the bonded printed wiring board 1 according to the present embodiment. Note that the ground layer 14, the insulating protective layer 19, and the shield portion 30 are omitted in Figure 1(a).

As shown in Figures 1 and 2, the bonded printed wiring board 1 according to this embodiment includes a printed wiring board 10, a printed wiring board 20, and a shielding portion 30.

In this embodiment, the printed wiring board 20 is an antenna board provided with an antenna 22 that receives wireless signals. The printed wiring board 10 is also, for example, a cable board for transmitting wireless signals received by the antenna 22. The cable board is connected to another board, for example, a main board on which a semiconductor chip for processing the wireless signals is mounted. Note that by mounting a semiconductor chip on the printed wiring board 10, the printed wiring board 10 itself may be used as the main board.

The printed wiring board 10 includes a signal line 11, a ground line (guard ground) 12, ground layers 13 and 14, insulating substrates 15 and 16, an insulating adhesive layer 17, and insulating protective layers 18 and 19. The insulating substrate 15 is an example of a first insulating layer. The insulating substrate 16 and the insulating adhesive layer 17 form an example of a second insulating layer.

The insulating substrate 15 (first insulating layer) has an upper surface (first main surface) and a lower surface (second main surface) opposite the upper surface. The signal line 11 is provided on the upper surface of the insulating substrate 15. In addition, a pair of ground lines 12 (guard grounds) are provided on the upper surface of the insulating substrate 15 so as to sandwich the signal line 11. The ground layer 13 is provided on the lower surface of the insulating substrate 15. The ground layer 13 is provided so as to encompass the signal line 11 when viewed in the thickness direction of the insulating substrate 15.

As shown in FIG. 2, the ground line 12 and the ground layer 13 are electrically connected by a plurality of ground vias 51. The plurality of ground vias 51 may be provided at intervals of ¼ or less of a wavelength (electrical length) determined by the frequency of the signal transmitted through the signal line 11 and the dielectric constant of the insulating substrate 15. In this embodiment, the signal frequency is 6 GHz, and liquid crystal polymer (LCP) is used as the insulating substrate 15, so the intervals between the ground vias 51 are set to 1.5 mm. This can improve the transmission characteristics of the signal propagating through the signal line 11.

The insulating substrate 16 and the insulating adhesive layer 17 (second insulating layer) have a bottom surface (third main surface) and a top surface (fourth main surface) opposite the bottom surface. In this embodiment, the bottom surface of the second insulating layer is the bottom surface of the insulating adhesive layer 17. Also, the top surface of the second insulating layer is the top surface of the insulating substrate 16.

The bottom surface of the insulating adhesive layer 17 faces the top surface of the insulating substrate 15. The insulating adhesive layer 17 is laminated on the insulating substrate 15 so as to bury at least a portion of the signal line 11 and the ground line 12. In this embodiment, the insulating adhesive layer 17 is laminated on the insulating substrate 15 so that the top surface of the insulating substrate 15 and the ends of the signal line 11 and the ground line 12 are locally exposed.

If the insulating substrate 15 and the insulating substrate 16 can be joined without adhesive, the insulating adhesive layer 17 does not need to be provided. In this case, the bottom surface of the second insulating layer is the bottom surface of the insulating substrate 16. In addition, in this case, the insulating substrate 16 may be laminated on the insulating substrate 15 so as to embed at least a portion of the signal line 11 and the ground line 12.

In this embodiment, the material of the insulating substrates 15 and 16 is a liquid crystal polymer (LCP) having a relatively low dielectric constant. The material of the insulating substrates 15 and 16 is not limited to this, and may be polyether ether ketone (PEEK), polyethylene naphthalate (PEN), or the like. Alternatively, the material of the insulating substrates 15 and 16 may be a fluorine-based material such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or a material in which epoxy glass is embedded in a fluorine material, a polyimide-based material such as modified polyimide (MPI) or polyimide (PI), or a material with a low dielectric constant and low dielectric tangent such as cycloolefin polymer (COP). The LCP used in this embodiment is included in the material with a low dielectric constant and low dielectric tangent. By using a material with a low dielectric constant and low dielectric tangent as the material of the insulating substrates 15 and 16, the transmission characteristics of the printed wiring board 10 can be improved.

The materials of insulating substrate 15 and insulating substrate 16 may be the same or different.

The ground layer 14 is provided on the upper surface of the insulating substrate 16. The ground layer 14 is provided so as to encompass the signal line 11 when viewed in the thickness direction of the printed wiring board 10. As shown in FIG. 2, the ground line 12 and the ground layer 14 are electrically connected by a plurality of ground vias 52. The spacing between the plurality of ground vias 52 is determined in the same manner as the spacing between the plurality of ground vias 51.

The insulating protective layer 18 is provided so as to cover the ground layer 13. The insulating protective layer 19 is provided so as to cover the ground layer 14 except for the portion where the anisotropic conductive adhesive layer 34 described below is bonded. Note that the insulating protective layers 18 and 19 may be provided with openings for connection, etc.

In this embodiment, the insulating protective layers 18 and 19 are polyimide films. Note that the insulating protective layers 18 and 19 may be made of a photosensitive photoresist. The same applies to the insulating protective layer 29 described below.

The printed wiring board 20 includes a signal line 21, an antenna 22, an insulating substrate 25, and an insulating protective layer 29. The insulating substrate 25 is an example of a third insulating layer.

The insulating substrate 25 (third insulating layer) has a bottom surface (fifth main surface) and a top surface (sixth main surface) opposite the bottom surface. In this embodiment, the material of the insulating substrate 25 is polyimide (PI), which has a higher dielectric constant than LCP. By using a material with a high dielectric constant and low dielectric tangent as the material of the insulating substrate 25, a smaller antenna can be provided when the printed wiring board 20 is used as an antenna substrate. The material of the insulating substrate 25 may be a fluorine-based material, a polyimide-based material other than PI, LCP, epoxy glass such as FR4, or COP. Alternatively, the material of the insulating substrate 25 may be a material with a high dielectric constant and low dielectric tangent, such as ceramic or polyphenylene ether.

The printed wiring board 20 is bonded to the printed wiring board 10 via an anisotropic conductive adhesive 41. In this embodiment, the lower surface of the insulating substrate 25 of the printed wiring board 20 is bonded to a locally exposed portion of the upper surface of the insulating substrate 15 of the printed wiring board 10 via the anisotropic conductive adhesive 41. In this embodiment, the anisotropic conductive adhesive 41 is an anisotropic conductive film (ACF). The anisotropic conductive adhesive 41 is an example of a second conductive material.

The anisotropic conductive adhesive 41 may be an anisotropic conductive paste (ACP). Also, instead of the anisotropic conductive adhesive 41, an isotropic conductive adhesive such as an isotropic conductive film or an isotropic conductive paste, or solder such as cream solder may be used. When an isotropic conductive adhesive or solder is used, an insulating material such as a non-conductive film (NCF), a non-conductive paste (NCP), or an insulating adhesive may be used to achieve insulation between the isotropic conductive adhesive or solder.

Signal line 21 is electrically connected to signal line 11. In this embodiment, signal line 21 is provided on the lower surface of insulating substrate 25. In this embodiment, the end of signal line 11 and the end of signal line 21 face each other and are electrically connected via anisotropic conductive adhesive 41. Note that if an isotropic conductive adhesive, isotropic conductive paste, or solder such as cream solder is used instead of anisotropic conductive adhesive 41, signal line 11 and signal line 21 may not face each other and may be misaligned in plan view. Alternatively, signal line 11 and signal line 21 may be in direct contact with each other and printed wiring boards 10, 20 may be joined using an insulating material.

The antenna 22 receives or transmits, for example, a wireless signal. In this embodiment, the antenna 22 is provided on the lower surface of the insulating substrate 25, is formed integrally with the signal line 21, and is electrically connected to the signal line 21. In this embodiment, since a PI having a thickness of 25 μm is used as the insulating substrate 25, the width W of the antenna 22 shown in FIG. 1(a) is, for example, 16 mm, and the length L is, for example, 13 mm.

The insulating protective layer 29 is provided to cover a portion of the signal line 21 and the antenna 22.

As shown in Figs. 1(b) and 2, the shielding portion 30 is provided across the printed wiring board 10 and the printed wiring board 20. The shielding portion 30 has a metal foil 31 provided across the printed wiring board 10 and the printed wiring board 20, an anisotropic conductive adhesive layer 34, and an insulating protective layer 39. The metal foil 31 is an example of a conductive layer.

In this embodiment, the metal foil 31 is provided over the entire upper surface of the insulating substrate 25 and over a portion of the ground layer 14. More specifically, the metal foil 31 includes metal foil 31a (first conductive portion) bonded to the upper surface of the insulating substrate 25, and metal foil 31b (second conductive portion) extending from an end of the printed wiring board 20 and bonded to the ground layer 14. In this embodiment, the metal foil 31 is a 3 μm copper foil.

The metal foil 31a is arranged to encompass the signal line 21 and the antenna 22 when viewed in the thickness direction of the printed wiring board 20. As a result, the metal foil 31a functions as a ground for the signal line 21 and the antenna 22. Note that in FIG. 1, the metal foil 31a is arranged over the entire upper surface of the insulating substrate 25 and is arranged to encompass the signal line 21 and the antenna 22 when viewed in the thickness direction of the printed wiring board 20, but it is sufficient that the metal foil 31a is arranged to encompass at least the signal line 21 when viewed in the thickness direction of the printed wiring board 20.

Metal foil 31b is integral with metal foil 31a and is bonded to ground layer 14 via an anisotropic conductive adhesive layer 34. This electrically connects metal foil 31 to ground layer 14.

The anisotropic conductive adhesive layer 34 is provided between the metal foil 31 and the printed wiring boards 10, 20, and adheres the metal foil 31 to the printed wiring boards 10, 20. The anisotropic conductive adhesive layer 34 may be divided into two or more parts. For example, the anisotropic conductive adhesive layer 34 may be divided into a first anisotropic conductive adhesive that bonds the metal foil 31a to the upper surface of the insulating substrate 25, and a second anisotropic conductive adhesive that bonds the metal foil 31b to the ground layer 14.

The insulating protective layer 39 is provided on the metal foil 31 and covers the metal foil 31. Note that the insulating protective layer 39 does not necessarily have to be provided.

In the bonded printed wiring board 1 described above, the shielding portion 30 is provided across the printed wiring board 10 and the printed wiring board 20. The metal foil 31 of the shielding portion 30 has metal foil 31a and metal foil 31b. The metal foil 31a functions as the ground of the signal line 21. The metal foil 31b is integrated with the metal foil 31a and is electrically connected to the ground layer 14 of the printed wiring board 10. Because of this configuration, the return current is not blocked at the joint. For example, when a wireless signal is received by the antenna 22 and the current flows from the signal line 21 to the signal line 11, the return current induced in the ground layer 14 by the current flowing through the signal line 11 flows through the metal foil 31b to the metal foil 31a and is not blocked at the joint. This makes it possible to improve the transmission characteristics of the signal propagating through the signal lines 11 and 21 with a simple configuration.

<Method of manufacturing bonded printed wiring board>
Next, a method for manufacturing the junction printed wiring board 1 according to the first embodiment will be described with reference to Figures 3A to 3D. Figures 3A to 3D are cross-sectional views illustrating steps in the method for manufacturing the junction printed wiring board 1 according to the present embodiment.

As shown in FIG. 3A (1), a double-sided metal-clad laminate 100 is prepared having a metal foil 110, a metal foil 120, and an insulating substrate 130. The metal foil 110 is provided on the upper surface of the insulating substrate 130, and the metal foil 120 is provided on the lower surface of the insulating substrate 130.

Metal foils 110 and 120 are, for example, copper foils having a thickness of 12 μm. Note that the material of metal foils 110 and 120 is not limited to copper, and may be metals such as silver or aluminum. The same applies to metal foils 210 and 310, which will be described later.

The insulating substrate 130 is, for example, an LCP having a thickness of 100 μm. The material of the insulating substrate 130 may be PEEK, PEN, a fluorine-based material, a polyimide-based material, or COP, etc.

Next, as shown in FIG. 3A (2), the metal foils 110 and 120 are patterned using a known photofabrication method. As a result, the metal foil 110 is patterned to form the signal line 11 and the ground line 12. In addition, the metal foil 120 is patterned to form the ground layer 13. At this time, an opening (not shown) for a conformal mask is formed in the ground layer 13. Note that the opening may be formed in a separate process.

Next, as shown in FIG. 3A (3), a single-sided metal-clad laminate 200 is prepared having a metal foil 210 and an insulating substrate 220. The metal foil 210 is provided on the upper surface of the insulating substrate 220.

The insulating substrate 220 is, for example, an LCP having a thickness of 50 μm. The material of the insulating substrate 220 may be PEEK, PEN, a fluorine-based material, a polyimide-based material, or COP, etc.

Next, as shown in FIG. 3A(4), the metal foil 210 is patterned using a known photofabrication method to form the ground layer 14 and the metal foil 210a. At this time, an opening (not shown) for a conformal mask is formed in the ground layer 14. The opening may be formed in a separate process. Since the end shape of the insulating base material 220 is stabilized by forming the metal foil 210a, the process of removing a part of the insulating base material 220 later becomes easier. The metal foil 210a does not have to be formed. Also, an insulating adhesive layer 17 is provided on the lower surface of the insulating base material 220. As shown in FIG. 3A(4), the insulating adhesive layer 17 is not provided in the end region of the insulating base material 220. This makes it easier to remove a part of the insulating base material 220 in a later step. In this embodiment, the thickness of the insulating adhesive layer 17 is 50 μm. The material of the insulating adhesive layer 17 may be a material with a low dielectric constant and a low dielectric loss tangent.

Next, as shown in FIG. 3B(1), the substrate obtained in FIG. 3A(4) is laminated on the substrate obtained in FIG. 3A(2). More specifically, the signal line 11 of the substrate in FIG. 3A(2) and the insulating adhesive layer 17 of the substrate in FIG. 3A(4) are aligned so that they face each other. At this time, the substrate is laminated so that the upper surface of the insulating substrate 130 and the ends of the signal line 11 and ground line 12 are locally exposed. After that, the substrate is heated and pressed by a heat press to be integrated. In the heat press process, the substrate is pressed at a temperature (e.g., 170°C) higher than the floating point of the insulating adhesive layer 17. If the heat curing is insufficient, a heating process using an oven cure may be added.

Next, the insulating substrate 220 is cut along the dotted line CL shown in FIG. 3B (2) to remove a portion of the insulating substrate 220 and the metal foil 210a. In this embodiment, a portion of the insulating substrate 220 is removed by tearing it with a clamp. Note that the insulating substrate 220 may also be cut and removed using a CO2 laser or the like. Also, instead of cutting the insulating substrate 220, an insulating substrate 220 that is already shorter than the insulating substrate 130 may be used.

Next, a laser pulse is applied to the openings in the ground layers 13 and 14 to form conductive holes for forming ground vias 51 and 52 (see FIG. 2) in the insulating substrate 130 and 220. More specifically, a laser pulse is applied to the metal foil (part of the ground layers 13 and 14) around the openings as a conformal mask to remove the insulating substrate 130 and 220 and the insulating adhesive layer 17 in the openings. In this embodiment, a carbon dioxide laser is used as the laser, but a UV-YAG laser or the like may also be used. The diameter of the conductive hole is, for example, 150 μm. The ground line 12 is exposed at the bottom of the conductive hole. After the conductive hole is formed, a desmear process may be performed.

Next, the ground vias 51 and 52 are formed by forming metal plating in the conductive holes. In this embodiment, copper plating is performed. In this embodiment, a dry film is laminated on the ground layers 13 and 14, and then the dry film is exposed and developed to form openings in the areas where the conductive holes are formed, and then a button plating method (pattern plating method) is used to perform plating. Note that instead of the button plating method, a panel plating method in which metal plating is performed on the entire board may be used. Through these steps, the insulating substrates 130 and 220 become the insulating substrates 15 and 16 described above. Note that after the metal plating, the ground layers 13 and 14 may be patterned by a known photofabrication method.

Next, as shown in FIG. 3B (3), the ground layer 13 is covered with an insulating protective layer 18, and the ground layer 14 is covered with an insulating protective layer 19. In this embodiment, the ground layers 13 and 14 are laminated with a polyimide film, but a photosensitive photoresist may also be used. At this time, at least a part of the ground layer 14 is exposed for later electrical connection to the shielding section. In addition, the exposed ground layers 13 and 14 may be subjected to a surface treatment such as gold plating. In this embodiment, gold plating is performed, but a water-based preflux may also be applied.

The above steps result in the printed wiring board 10 shown in Figure 3B (3).

Next, as shown in FIG. 3C (1), a single-sided metal-clad laminate 300 is prepared having a metal foil 310 and an insulating substrate 320. The metal foil 310 is provided on the lower surface of the insulating substrate 320.

In this embodiment, the insulating substrate 320 is, for example, polyimide having a thickness of 25 μm. The material of the insulating substrate 320 may be a fluorine-based material, a polyimide-based material other than polyimide, LCP, epoxy glass, COP, ceramic, polyphenylene ether, or the like.

Next, as shown in FIG. 3C (2), the metal foil 310 is patterned using a known photofabrication method to form the signal line 21 and the antenna 22. Note that in this embodiment, no interlayer connections such as vias are formed in the insulating substrate 320, so at this stage it becomes the insulating substrate 25.

Next, as shown in FIG. 3C (3), the signal line 21 and the antenna 22 are covered with an insulating protective layer 29. At this time, at least the end of the signal line 21 is exposed for later electrical connection with the signal line 11. In this embodiment, a polyimide film is laminated to the signal line 21 and the antenna 22, but a photosensitive photoresist may also be used. In addition, the exposed end of the signal line 21 may be subjected to a surface treatment such as gold plating. In this embodiment, gold plating is performed, but a water-based preflux may also be applied.

The above steps result in the printed wiring board 20 shown in Figure 3C (3).

Next, as shown in FIG. 3D (1), printed wiring board 10 and printed wiring board 20 are bonded via anisotropic conductive adhesive 41. In this embodiment, ACF is used as anisotropic conductive adhesive 41, and printed wiring board 10 and printed wiring board 20 are bonded by the following process.

First, to position the ACF, it is temporarily bonded at a temperature below the curing temperature of the ACF. For example, when using an ACF made of an epoxy-based material that cures at 170°C, the heating temperature is set to 100°C, and the ACF is temporarily bonded to the upper surface of the insulating base material 15 and the signal line 11 that are locally exposed at the end of the printed wiring board 10. The ACF may also be temporarily bonded to the lower surface of the insulating base material 25 and the signal line 21 of the printed wiring board 20.

Next, the printed wiring board 10 and the printed wiring board 20 are aligned. In this embodiment, the alignment is performed using the external shapes of the printed wiring boards 10 and 20 as a reference. Note that a transparent material or through-holes may be provided on the printed wiring boards 10 and 20, and the alignment may be performed using the transparent material or through-holes as a reference.

Next, the actual bonding process is carried out at a temperature of 170°C and a pressure of 4 MPa.

By carrying out the above steps, printed wiring board 10 and printed wiring board 20 are joined.

In this embodiment, the bottom surface of insulating substrate 25 is joined to the locally exposed portion of the top surface of insulating substrate 15. This electrically connects signal line 11 and signal line 21.

Next, as shown in FIG. 3D (2), a shielding portion 30 is provided across the printed wiring board 10 and the printed wiring board 20. More specifically, the metal foil 31a is bonded to the upper surface of the insulating substrate 25 so as to encompass the signal line 21 when viewed in the thickness direction of the printed wiring board 20. The metal foil 31b is also bonded to the ground layer 14. In this process, for example, an anisotropic conductive adhesive layer 34, a metal foil 31, and an insulating protective layer 39 are bonded together. Alternatively, after applying or placing the anisotropic conductive adhesive layer 34, a shielding material having the metal foil 31 and the insulating protective layer 39 is bonded. As a result, the metal foil 31a functions as a ground for the signal line 21 and the antenna 22. The metal foil 31 is electrically connected to the ground layer 14 via the anisotropic conductive adhesive layer 34.

The above steps result in the bonded printed wiring board 1 according to this embodiment.

As described above, according to the manufacturing method of the bonded printed wiring board 1 of the first embodiment, after bonding the printed wiring boards 10, 20, the shield section 30 is provided, and the metal foil 31 (conductive layer) of the shield section 30 functions as the ground (ground layer) for the signal line 21 and the antenna 22. This allows a single-sided metal-clad laminate to be used as the starting material for the printed wiring board 20, and the bonded printed wiring board 1 can be manufactured easily and inexpensively. In addition, a material with good properties, such as a material with a low dielectric constant and transparency, can be used.

In the above manufacturing method, the process of joining the printed wiring board 10 and the printed wiring board 20 and the process of providing the shield portion 30 may be performed simultaneously. More specifically, the anisotropic conductive adhesive 41, the printed wiring boards 10 and 20, and the shield portion 30 are aligned and then joined by flat pressing. Under the conditions of this embodiment, for example, pressing is performed at 170°C for 60 seconds. This shortens the process and allows the joined printed wiring board 1 to be manufactured more inexpensively.

Furthermore, in the joined printed wiring board 1 according to the first embodiment, the metal foil 31 (conductive layer) of the shielding portion 30 is electrically connected to the ground layer 14. This allows a return current induced in the ground layer of one printed wiring board by a signal flowing through the signal line to flow to the ground layer of the other printed wiring board without being blocked at the joint. This improves the transmission characteristics.

In addition, in the conductive layer of the shield section 30, the first conductive layer and the second conductive layer are formed as a single unit. This reduces the number of points on the path along which the ground return current flows where the electrical characteristics change, further improving the transmission characteristics.

Furthermore, a material with a low dielectric constant and low dielectric tangent can be applied to printed wiring board 10, and a material with a high dielectric constant and low dielectric tangent can be applied to printed wiring board 20. In this way, different materials can be applied to printed wiring boards 10 and 20, allowing a cable board with high transmission characteristics and a space-saving antenna board to coexist.

Note that printed wiring board 10 may be a flexible printed wiring board or a rigid printed wiring board. The same applies to printed wiring board 20. Also, by making one of printed wiring boards 10, 20 a flexible printed wiring board and the other a rigid printed wiring board, a rigid-flex structure can be provided at low cost.

In the above description, the printed wiring board 10 has two circuit layers (layers including signal lines, ground lines, and/or ground layers). This is not limited to the above, and the printed wiring board 10 may have any number of circuit layers. The printed wiring board 10 may also have one to five circuit layers.

Similarly, in the above description, the printed wiring board 20 has two circuit layers. However, the present invention is not limited to this, and the printed wiring board 20 may have any number of circuit layers. Furthermore, the printed wiring board 20 may have one to five circuit layers. Regardless of the number of circuit layers used for the printed wiring board 20, the shield portion 30 forms a ground layer, so that the number of circuit layers can be reduced by one. More specifically, in the manufacture of the printed wiring board 20, a board having fewer circuit layers than those normally used can be used. This allows the bonded printed wiring board 1 to be manufactured more inexpensively.

In the above description, the printed wiring board 10 is a cable board or main board connected to an antenna board. However, the printed wiring board 10 may be a cable board that connects main boards to each other. In this case, a shield section that functions as a ground for a signal line provided on the cable board may be provided. For example, the shield section has a conductive layer that includes the signal line of the cable board when viewed in the thickness direction of the cable board. The conductive layer may be electrically connected to the ground layer of the main board. This allows the width of the signal line to be made larger than when, for example, coplanar wiring is used, and a cable board with high transmission characteristics for signals in the high frequency band can be provided. Furthermore, since the etching process can be omitted, the cable board can be produced at low cost.

In the above description, the printed wiring board 20 is an antenna board. However, the present invention is not limited to this, and the printed wiring board 20 may be a cable board or a main board. Furthermore, both printed wiring boards 10 and 20 may be cable boards. This allows a long cable to be produced. Furthermore, the longitudinal directions of the printed wiring boards may be different. For example, the printed wiring boards 10 and 20 may be joined so that the longitudinal directions of the boards intersect at right angles or at another angle in the joint area. This allows cables of various shapes to be produced using multiple printed wiring boards.

In the above description, the signal lines 11, 21 of the printed wiring board 10 and the printed wiring board 20 are parallel to each other. However, the present invention is not limited to this, and the signal lines 11, 21 may be bent at a right angle, at another angle, or in an arc shape near the joint area of the printed wiring boards 10, 20 in the insulating substrate 15.

The structure of this embodiment can also be applied to the joint between a cable board having a power line and a main board having an IC. In this case, for example, the cable board can be regarded as a printed wiring board 10, and the main board can be regarded as a printed wiring board 20, and a shield section 30 can be provided as in this embodiment. The power line of the cable board may be provided in place of or together with the signal line 11. A cable board having a power line has a problem in that power integrity is impaired by IR drop caused by an IC. Therefore, the number of conductor layers is increased by providing a shield section 30 as described above. This makes it possible to reduce the impedance of the cable (PDN: Power Delivery Network) and to easily and inexpensively route the power line directly below the IC, thereby improving power integrity.

The conductive layer of the shield section 30 is not limited to the metal foil 31. For example, the conductive layer may have a metal foil, a conductive paste layer, a solder layer (e.g., a cream solder layer), an isotropic conductive adhesive layer, or a conductive film layer. Here, the conductive film is, for example, a transparent resin with fine wiring formed in a mesh shape to form a pseudo-transparent material. Also, an isotropic conductive adhesive layer may be used instead of the anisotropic conductive adhesive layer 34 of the shield section 30. Alternatively, the conductive layer of the shield section 30 may be joined to the ground layer 14 via a conductive paste or solder, and joined to the upper surface of the insulating substrate 25 and the insulating protective layer 19 via a conductive adhesive or an insulating adhesive.

Below, we will explain variants 1 to 4 of the first embodiment as examples in which the configuration of the shielding section is different from that of the first embodiment. Note that in explaining each variant, we will focus on the parts that are different from the first embodiment, and will omit explanations of parts that are common to the first embodiment.

(Modification 1 of the first embodiment)
A bonded printed wiring board according to a first modified example of the first embodiment will be described with reference to Fig. 4(a) , which is a vertical cross-sectional view taken along signal lines 11 and 21 of the bonded printed wiring board according to this modified example.

The shield part 30A of this modification has a conductive paste layer 32 instead of the metal foil 31 in the shield part 30 of the first embodiment, and has an isotropic conductive adhesive layer 33 instead of the anisotropic conductive adhesive layer 34. That is, as shown in FIG. 4(a), the shield part 30A of this modification has a conductive paste layer 32, an isotropic conductive adhesive layer 33, and an insulating protective layer 39. The conductive paste layer 32 is an example of a conductive layer.

In addition, "isotropic conductive adhesive" refers to conductive adhesives that have electrical conductivity, excluding anisotropic conductive adhesives.

In this way, with the shield section 30A of this modified example, it is possible to configure a shield section having different characteristics from, for example, the shield section 30 of the first embodiment.

(Modification 2 of the First Embodiment)
A bonded printed wiring board according to the second modification of the first embodiment will be described with reference to Fig. 4(b) . Fig. 4(b) is a vertical cross-sectional view taken along signal lines 11 and 21 of the bonded printed wiring board according to this modification.

The shield part 30B of this modified example has a conductive paste layer 32 instead of the metal foil 31 in the shield part 30 of the first embodiment. That is, the shield part 30B has a conductive paste layer 32, an anisotropic conductive adhesive layer 34, and an insulating protective layer 39. Note that a solder layer may be provided instead of the conductive paste layer 32. The conductive paste layer 32 or the solder layer is an example of a conductive layer.

The shield section 30 of the first embodiment and the shield section 30A of the first modified example of the first embodiment are cases where a ready-made product is used in which, for example, a conductive layer, a conductive adhesive layer, and an insulating protective layer are integrated. In contrast, the shield section 30B of this modified example is manufactured by a process in which, for example, an anisotropic conductive adhesive layer 34 is provided, and then a conductive paste layer 32 or a solder layer is applied.

More specifically, first, the anisotropic conductive adhesive layer 34 is disposed and compressed. Next, a conductive paste or solder is provided on the anisotropic conductive adhesive layer 34 by inkjet or screen printing. Next, the insulating protective layer 39 is disposed and compressed. Through the above steps, the shield section 30B is provided.

When an insulating protective layer 39 is provided, the pressing step after disposing the anisotropic conductive adhesive layer 34 may be omitted, and the anisotropic conductive adhesive layer 34 and the insulating protective layer 39 may be pressed simultaneously in the pressing step after disposing the insulating protective layer 39.

In this way, with the shield section 30A of this modified example, the shield section can be provided using different manufacturing methods.

(Modification 3 of the first embodiment)
A bonded printed wiring board according to a third modification of the first embodiment will be described with reference to Fig. 5(a) . Fig. 5(a) is a vertical cross-sectional view taken along signal lines 11 and 21 of the bonded printed wiring board according to this modification.

In this modified example, the shield section 30C has an isotropic conductive adhesive layer 33 and an insulating protective layer 39. The isotropic conductive adhesive layer 33 is an example of a conductive layer.

The isotropic conductive adhesive layer 33 includes an isotropic conductive adhesive layer 33a (first conductive portion) bonded to the upper surface of the insulating substrate 25, and an isotropic conductive adhesive layer 33b (second conductive portion) extending from the end of the printed wiring board 20 and bonded to the ground layer 14.

The isotropic conductive adhesive layer 33a is provided so as to encompass the signal line 21 and the antenna 22 when viewed in the thickness direction of the printed wiring board 20. This allows the metal foil 31a to function as a ground for the signal line 21 and the antenna 22.

The isotropic conductive adhesive layer 33b is integral with the isotropic conductive adhesive layer 33a and is bonded to the ground layer 14. This electrically connects the isotropic conductive adhesive layer 33 to the ground layer 14.

In this modified example, the isotropic conductive adhesive layer 33 serving as a conductive layer is directly bonded to the printed wiring board 10 and the printed wiring board 20. This makes it possible to further simplify the configuration of the shielding section.

(Fourth Modification of the First Embodiment)
A bonded printed wiring board according to the fourth modified example of the first embodiment will be described with reference to Fig. 5(b) . Fig. 5(b) is a vertical cross-sectional view taken along signal lines 11 and 21 of the bonded printed wiring board according to this modified example.

In this modified example, the shield section 30D has a metal foil 31, an insulating adhesive layer 35a, and an insulating adhesive layer 35b. The metal foil 31 is an example of a conductive layer.

The metal foil 31 is provided across the upper surface of the insulating substrate 25 and the ground layer 14. More specifically, the metal foil 31 includes metal foil 31a (first conductive portion) adhered to the upper surface of the insulating substrate 25 via an insulating adhesive layer 35a, and metal foil 31b (second conductive portion) adhered to the insulating protective layer 19 via an insulating adhesive layer 35b. The insulating adhesive layers 35a and 35b are, for example, NCF, NCP, or an insulating adhesive.

A portion of the metal foil 31b is electrically connected to the ground layer 14 via a conductive material 36 at position A in the figure. The conductive material 36 is, for example, solder, a conductive paste, or a conductive adhesive.

Note that a portion of the metal foil 31b may be in direct contact with the ground layer 14 at position A in the figure without using the conductive material 36. In this case, the metal foil 31b may be pressed from above using an insulating adhesive or the like.

In addition, an insulating protective layer may be provided on the metal foil 31.

In this way, with the shield section 30D of this modified example, the shield section can be constructed using metal foil as the starting material.

Fifth Modification of the First Embodiment
Modification 5 of the first embodiment will be described with reference to Fig. 6. One of the differences between this modification and the first embodiment is the number of layers of printed wiring board 10. Fig. 6 is a vertical cross-sectional view taken along signal lines 11, 21 of a bonded printed wiring board according to this modification. Hereinafter, the present embodiment will be described with a focus on the differences from the first embodiment, and a description of the parts common to the first embodiment will be omitted.

The printed wiring board 10 of this embodiment includes a signal line 11A, an insulating substrate 16A, an insulating adhesive layer 17A, and a signal via 53 in addition to the components of the printed wiring board 10 of the first embodiment.

Signal line 11A is a signal line provided in a layer different from signal line 11, and is provided on the lower surface of insulating substrate 15. Signal line 11A is also electrically connected to signal line 11 via signal via 53. Signal via 53 is provided so as to penetrate insulating substrate 15. Note that a pair of ground wires may be provided on the lower surface of insulating substrate 15 so as to sandwich signal line 11A therebetween. The ground wires may also be electrically connected to ground layer 13 and/or ground line 12 via ground vias.

The insulating adhesive layer 17A is provided on the lower surface of the insulating substrate 15 so as to bury the signal line 11A. The insulating substrate 16A is provided on the lower surface of the insulating adhesive layer 17A. Note that the insulating adhesive layer 17A does not necessarily have to be provided. In this case, the insulating substrate 16A may be provided so as to bury the signal line 11A.

A ground layer 13 is provided on the underside of the insulating substrate 16A. An insulating protective layer 18 is provided to cover the ground layer 13.

As described above, according to the bonded printed wiring board of the fifth modified example of the first embodiment, a multilayer substrate having four circuit layers can be used as the printed wiring board 10. This makes it possible to improve the transmission characteristics with a simple configuration, for example, in a bonded printed wiring board in which a multilayer substrate and an antenna substrate are integrated.

Second Embodiment
The second embodiment will be described with reference to Fig. 7. One of the differences between the present embodiment and the first embodiment is, for example, the shape of the end portion of the printed wiring board 10. Fig. 7 is a vertical cross-sectional view taken along the signal lines 11 and 21 of the bonded printed wiring board according to the present embodiment.

In this embodiment, unlike the first embodiment, the insulating substrate 16 and the insulating adhesive layer 17 (second insulating layer) are laminated on the insulating substrate 15 so as to completely bury the signal line 11 and the ground line 12. In other words, the insulating adhesive layer 17 is laminated on the insulating substrate 15 so that the top surface of the insulating substrate 15 and the signal line 11 and the ground line 12 are not exposed.

Therefore, in order to electrically connect signal line 11 and signal line 21, printed wiring board 10 further includes signal via 54. Signal via 54 penetrates insulating substrate 16 and insulating adhesive layer 17, and electrically connects signal line 11 and land 55 provided on the upper surface of insulating substrate 16. Signal via 54 is an example of an interlayer connection.

The lower surface (fifth main surface) of the insulating substrate 25 is joined to the upper surface (fourth main surface) of the insulating substrate 16 via an anisotropic conductive adhesive 41.

The land 55 and the end of the signal line 21 are electrically connected via anisotropic conductive adhesive 41.

The bonded printed wiring board according to the second embodiment can improve transmission characteristics with a simple configuration in a structure in which the signal line 11 is not exposed at the end.

The thickness of the insulating substrate 25 in this embodiment may be thinner than that of the insulating substrate 25 in the first embodiment. This makes it possible to reduce the overall thickness of the bonded printed wiring board 1.

(Modification of the second embodiment)
A modified example of the second embodiment will be described with reference to Fig. 8. The difference between this modified example and the second embodiment is the number of layers of printed wiring board 10. Fig. 8 is a vertical cross-sectional view taken along signal lines 11 and 21 of a bonded printed wiring board according to this modified example.

The printed wiring board 10 of this embodiment is configured to include a signal line 11A, an insulating adhesive layer 17A, an insulating substrate 16A, and a signal via 53 in addition to the components of the printed wiring board 10 of the first embodiment.

Note that the signal line 11A, insulating adhesive layer 17A, insulating substrate 16A, and signal via 53 are the same as those in variant 5 of the first embodiment, and therefore will not be described here.

According to the bonded printed wiring board according to the modified example of the second embodiment, a multilayer board having four circuit layers can be used as the printed wiring board 10. This makes it possible to improve the transmission characteristics with a simple configuration, for example, in a multilayer board in which the signal lines 11 are not exposed at the ends.

Next, we will explain the third and fourth embodiments in which an interlayer connection is provided on the printed wiring board 20.

Third Embodiment
A bonded printed wiring board according to a third embodiment will be described with reference to Fig. 9. Fig. 9 is a vertical cross-sectional view taken along signal lines 11 and 21 of a bonded printed wiring board according to this embodiment. Hereinafter, this embodiment will be described with a focus on differences from the second embodiment, and descriptions of parts common to the second embodiment will be omitted.

The printed wiring board 20 of this embodiment includes a signal line 21, a ground layer 24, an insulating substrate 25, an insulating protective layer 28, and a conductive paste 61. The conductive paste 61 is an example of a third conductive material.

The signal line 21 is provided on the upper surface (sixth main surface) of the insulating substrate 25. The signal line 21 is covered with an insulating protective layer 28. The signal line 21 is electrically connected to the land 55 via a conductive paste 61. Note that a part of the signal line 21 may be an antenna.

The ground layer 24 is provided on the lower surface (fifth main surface) of the insulating substrate 25. The ground layer 24 is provided so as to encompass the signal line 21 when viewed in the thickness direction of the printed wiring board 20. The ground layer 14 and the ground layer 24 are electrically connected via an anisotropic conductive adhesive 41.

In this embodiment, an insulating adhesive layer 71, an insulating protective layer 73, and an insulating adhesive layer 72 are laminated in this order between the upper surface of the insulating substrate 16 and the lower surface of the insulating substrate 25. This improves the insulation between the ground layer 14 and the ground layer 24.

As shown in FIG. 9, the insulating adhesive layer 71, the insulating protective layer 73, and the insulating adhesive layer 72 each have openings for filling with the anisotropic conductive adhesive 41 and the conductive paste 61.

The insulating protective layer 28 is provided to cover the signal line 21. The material of the insulating protective layer 28 is the same as that of the insulating protective layer 29.

The conductive paste 61 fills the through holes in the insulating substrate 25, the insulating adhesive layer 71, the insulating protective layer 73, and the insulating adhesive layer 72, and electrically connects the signal line 21 and the land 55.

The conductive paste 61 is formed using, for example, the method described in Patent No. 6177639. Note that the conductive paste 61 may be one that forms an alloy at a temperature close to the hardening temperature of the anisotropic conductive adhesive 41 (for example, 170°C). This allows the formation of the conductive paste 61 and bonding with the anisotropic conductive adhesive 41 to be performed simultaneously. This makes it possible to provide the bonded printed wiring board according to this embodiment at a lower cost.

Furthermore, the formation of the conductive paste 61, the bonding with the anisotropic conductive adhesive 41, and the bonding of the shield section 30 may be performed simultaneously. This allows the bonded printed wiring board according to this embodiment to be provided at even lower cost. When the formation of the conductive paste 61, the bonding with the anisotropic conductive adhesive 41, and the bonding of the shield section 30 are performed simultaneously, for example, a flat plate press is used.

As shown in FIG. 9, the metal foil 31a (first conductive portion) of the shield portion 30 is bonded to the insulating protective layer 28. The metal foil 31a is disposed so as to sandwich the insulating protective layer 28 together with the signal line 21, and functions as the ground of the signal line 21.

In this way, the printed wiring board 20 of this embodiment can form a stripline structure having the signal line 21, the ground layer 24, and the metal foil 31a. In other words, a double-sided metal-clad laminate can be used as the starting material for the printed wiring board 20, and a stripline structure can be provided at a lower cost than when a three-layer board is used as the starting material.

In addition, by using the signal line 21 as an antenna, a stripline antenna with high transmission characteristics can be provided with a simple configuration.

The ground layer 24 does not necessarily have to be provided. Alternatively, as in the fourth embodiment described below, a signal line separate from the signal line 21 or an antenna may be provided on the underside of the insulating substrate 25 instead of the ground layer 24.

The printed wiring board 10 of this embodiment has the same structure as that of the second embodiment, but a printed wiring board 10 having the same structure as that of the first embodiment may also be used.

Fourth Embodiment
A bonded printed wiring board according to the fourth embodiment will be described with reference to Fig. 10. Fig. 10 is a vertical cross-sectional view taken along signal lines 11 and 21 of a bonded printed wiring board according to this embodiment. Hereinafter, this embodiment will be described with a focus on differences from the second and third embodiments, and descriptions of parts common to the second and third embodiments will be omitted.

The printed wiring board 20 of this embodiment includes a signal line 21, a signal line 21A, and an insulating substrate 25.

The signal line 21 is provided on the lower surface (fifth main surface) of the insulating substrate 25. The signal line 21 is electrically connected to the land 55 via the anisotropic conductive adhesive 41.

Signal line 21A is provided on the lower surface of insulating substrate 25 with a gap between it and signal line 21. Signal line 21A is electrically connected to land 55 via conductive paste 62. Note that signal line 21A may be provided on a layer different from signal line 21, such as on the upper surface of insulating substrate 25.

The conductive paste 62 fills the insulating adhesive layer 71, the insulating protective layer 73, and the insulating adhesive layer 72, and electrically connects the signal line 21 and the land 55. The conductive paste 62 is an example of a third conductive material.

The conductive paste 62 and the anisotropic conductive adhesive 41 can be used when the signal line 21 and the signal line 21A have different electrical characteristics (e.g., current capacity). For example, when a large current does not flow through both the signal line 21 and the signal line 21A, an anisotropic conductive adhesive may be used instead of the conductive paste 62 in FIG. 9.

The printed wiring board 20 of this embodiment also includes multiple signal lines 21, 21A. This allows, for example, the production of an ultra-wideband (UWB) antenna when the printed wiring board 20 is used as an antenna substrate.

In this embodiment, the signal lines 21 and 21A are electrically connected to the same land 55. However, this is not limited to the above, and the signal lines 21 and 21A may be electrically connected to different lands.

Fifth Embodiment
A bonded printed wiring board 1A according to the fifth embodiment will be described with reference to Fig. 11. Fig. 11(a) is a plan view of the bonded printed wiring board 1A according to the present embodiment before bonding. Fig. 11(b) is a vertical cross-sectional view along the ground line 12A of the bonded printed wiring board 1A according to the present embodiment. Note that the ground layer 14, the insulating protective layer 19, and the shield part 30 are omitted in Fig. 1(a).

In this embodiment, the printed wiring board 10 has one circuit layer (coplanar structure). Below, the present embodiment will be described, focusing on the differences from the first embodiment, and a description of the parts common to the first embodiment will be omitted.

As shown in FIG. 11, the printed wiring board 10 according to this embodiment includes a signal line 11, a ground line 12, an insulating substrate 15, and an insulating protective layer 19.

The signal line 11 is provided on the upper surface of the insulating substrate 15. In addition, a pair of ground lines 12A are provided on the upper surface of the insulating substrate 15 so as to sandwich the signal line 11.

An insulating protective layer 19 is provided to cover the signal line 11 and the ground line 12A. The insulating protective layer 19 is provided so that the upper surface of the insulating substrate 15, the signal line 11, and the ends of the ground line 12A are exposed. An opening 19a is provided in the insulating protective layer 19, and the ground line 12A is exposed inside the opening 19a.

Of the metal foil 31 of the shielding portion 30, the metal foil 31b is bonded to the ground wire 12A exposed inside the opening 19a via an anisotropic conductive adhesive layer 34. This electrically connects the metal foil 31 to the ground wire 12A.

In this way, according to the bonded printed wiring board 1A of the fifth embodiment, the transmission characteristics can be improved with a simple configuration by providing a shielding section 30 even for a printed wiring board 10 having a coplanar structure.

Sixth Embodiment
A printed wiring board 10A according to the sixth embodiment will be described with reference to Fig. 12. Fig. 12 is a longitudinal cross-sectional view taken along the signal lines 11 and 21 of the printed wiring board 10A according to the present embodiment. In this embodiment, instead of joining two printed wiring boards as in the first to fifth embodiments, a part of the insulating base material of the printed wiring board 10A extends out.

The printed wiring board 10A includes signal lines 11, 11A, and 21, ground layers 13 and 14, insulating substrates 15, 16, and 16A, insulating protective layers 18, 19, and 29, a signal via 54, and a shield portion 30.

The signal lines 11, 11A, ground layer 13, insulating substrates 15, 16A, and insulating protective layers 18, 19 are the same as those in the modified example of the second embodiment shown in FIG. 8, and therefore will not be described. Note that the insulating adhesive layers 17, 17A are omitted in FIG. 12.

The insulating substrate 16 is laminated on the insulating substrate 15 and includes a laminated portion in which the signal line 11 is embedded, and an extension portion that extends in the longitudinal direction (to the right) from the laminated portion.

The signal line 21 is provided on the upper surface of the insulating substrate 16 in the laminated portion and the extending portion of the insulating substrate 16. The signal line 21 is electrically connected to the signal line 11 through a signal via 54 provided so as to penetrate the insulating substrate 16. The signal line 21 may be an antenna. In this case, the portion of the signal line 21 provided on the extending portion of the insulating substrate 16 may be shaped like the antenna 22 in FIG. 1(a).

The ground layer 14 is spaced apart from the signal line 21 in the laminated portion of the insulating substrate 16.

The insulating protective layer 29 is provided to cover the signal line 21 and a part of the ground layer 14. Note that the insulating protective layer 29 may be integrated with the insulating protective layer 19.

The shielding portion 30 is provided across the laminated portion and the extended portion of the insulating substrate 16, and has a metal foil 31, an anisotropic conductive adhesive layer 34, and an insulating protective layer 39.

The metal foil 31 (conductive layer) is provided across the laminated portion and the extended portion of the insulating substrate 16. More specifically, the metal foil 31 includes metal foil 31a (first conductive portion) bonded to the insulating protective layer 29, and metal foil 31b (second conductive portion) bonded to the ground layer 14.

The metal foil 31a is arranged to encompass the signal line 21 when viewed in the thickness direction of the insulating substrate 16. As a result, the metal foil 31a functions as a ground for the signal line 21.

In this way, with the printed wiring board 10A according to the sixth embodiment, by providing the shielding portion 30, it is possible to improve the transmission characteristics with a simple configuration, not limited to cases where two printed wiring boards are joined.

Based on the above description, a person skilled in the art may be able to conceive of additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. Components from different embodiments may be combined as appropriate. For example, in the second to sixth embodiments, shield portions 30A to 30D may be used in place of shield portion 30. Various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and intent of the present invention derived from the contents defined in the claims and their equivalents.

1, 1A Bonded printed wiring board 10, 10A, 20 Printed wiring board 11, 11A, 21, 21A Signal line 12, 12A Ground line 13, 14, 24 Ground layer 15, 16, 16A, 25 Insulating substrate 17, 17A Insulating adhesive layer 18, 19, 28, 29 Insulating protective layer 22 Antenna 30, 30A, 30B, 30C, 30D Shielding section 31, 31a, 31b Metal foil 32 Conductive paste layer 33, 33a, 33b Isotropic Conductive adhesive layer 34 Anisotropic conductive adhesive layer 35a, 35b Insulating adhesive layer 36 Conductive material 39 Insulating protective layer 41 Anisotropic conductive adhesive 51, 52 Ground via 53, 54 Signal via 55 Land 61, 62 Conductive paste 71, 72 Insulating adhesive layer 73 Insulating protective layer 100 Double-sided metal-clad laminate 110, 120, 210, 210a, 310 Metal foil 130, 220, 320 Insulating substrate 200, 300 Single-sided metal-clad laminate

Claims

A first printed wiring board;
a second printed wiring board joined to the first printed wiring board;
a shield portion having a conductive layer provided across the first printed wiring board and the second printed wiring board;
A bonded printed wiring board comprising:
The first printed wiring board includes:
a first insulating layer having a first major surface and a second major surface opposite the first major surface;
a first signal line provided on the first main surface;
a second insulating layer having a third main surface facing the first main surface and a fourth main surface opposite the third main surface, the second insulating layer being laminated on the first insulating layer so as to bury at least a portion of the first signal line;
a ground layer provided on the fourth main surface so as to include the first signal line when viewed in a thickness direction of the first printed wiring board;
Equipped with
The second printed wiring board includes:
a third insulating layer having a fifth main surface joined to the first printed wiring board and a sixth main surface opposite the fifth main surface;
a second signal line electrically connected to the first signal line;
Equipped with
The conductive layer of the shield portion is
a first conductive portion provided to include the second signal line when viewed in a thickness direction of the second printed wiring board;
a second conductive portion integral with the first conductive portion and joined to the ground layer;
A bonded printed wiring board comprising:
the second printed wiring board is an antenna substrate provided with an antenna that is connected to the second signal line and receives a wireless signal;
2. The bonded printed wiring board according to claim 1, wherein the first printed wiring board is a cable board in which the first signal line is connected to another board, or a main board on which a semiconductor chip that processes a radio signal received by the antenna is mounted.
the first insulating layer of the first printed wiring board includes a first insulating base material made of a liquid crystal polymer, a fluorine-based material, a polyimide-based material, or a cycloolefin polymer;
the second insulating layer of the first printed wiring board includes a second insulating base material made of a liquid crystal polymer, a fluorine-based material, a polyimide-based material, or a cycloolefin polymer;
3. The bonded printed wiring board according to claim 2, wherein the third insulating layer of the second printed wiring board includes a third insulating substrate made of a polyimide-based material, a liquid crystal polymer, a fluorine-based material, an epoxy glass, a cycloolefin polymer, a ceramic, or a polyphenylene ether.
The bonded printed wiring board according to claim 1, wherein the conductive layer of the shielding portion has a metal foil, a conductive paste layer, a solder layer, an isotropic conductive adhesive layer, or a conductive film layer.
the conductive layer of the shield portion is a metal foil,
The bonded printed wiring board according to claim 4 , wherein the shielding portion further comprises an anisotropic conductive adhesive layer for adhering the metal foil to the first printed wiring board and the second printed wiring board.
the conductive layer of the shield portion is a conductive paste layer,
5. The joined printed wiring board according to claim 4, wherein the shield portion further comprises an isotropic conductive adhesive layer for adhering the conductive paste layer to the first printed wiring board and the second printed wiring board.
the conductive layer of the shield portion is a conductive paste layer or a solder layer,
The bonded printed wiring board according to claim 4 , wherein the shield portion further has an anisotropic conductive adhesive layer for adhering the conductive paste layer or the solder layer to the first printed wiring board and the second printed wiring board.
The bonded printed wiring board according to claim 4, wherein the conductive layer of the shielding portion is an isotropic conductive adhesive layer.
the conductive layer of the shield portion is a metal foil,
The shield portion is
a first insulating adhesive layer provided on the second printed wiring board and adhering the first conductive portion of the conductive layer to the second printed wiring board;
a second insulating adhesive layer provided on the first printed wiring board and adhering the second conductive portion of the conductive layer to the first printed wiring board;
and
The bonded printed wiring board according to claim 4 , wherein the second conductive portion is electrically connected to the ground layer via a conductive material.
the second insulating layer of the first printed wiring board is laminated on the first insulating layer such that the first main surface and an end of the first signal line are locally exposed;
the second signal line of the second printed wiring board is provided on the fifth main surface,
the first conductive portion of the shield portion is joined to the sixth main surface,
the fifth main surface is joined to a locally exposed portion of the first main surface of the first printed wiring board via a second conductive material;
10. The bonded printed wiring board according to claim 1, wherein an end of the first signal line and the second signal line are electrically connected via the second conductive material.
the first printed wiring board further includes an interlayer connection portion that penetrates the second insulating layer and electrically connects the first signal line and a land provided on the fourth main surface;
the fifth main surface of the second printed wiring board is joined to the fourth main surface of the first printed wiring board;
10. The bonded printed wiring board according to claim 1, wherein the first signal line and the second signal line are electrically connected via the interlayer connection portion and the land.
the second signal line of the second printed wiring board is provided on the fifth main surface,
the first conductive portion of the shield portion is joined to the sixth main surface,
12. The bonded printed wiring board according to claim 11, wherein the land of the interlayer connection portion and the second signal line are electrically connected via a second conductive material.
the second printed wiring board further includes a third signal line provided in the third insulating layer and different from the second signal line;
13. The bonded printed wiring board according to claim 12, wherein the land of the interlayer connection portion and the third signal line are electrically connected via a third conductive material.
the second signal line of the second printed wiring board is provided on the sixth main surface,
The second printed wiring board includes:
an insulating protective layer covering the second signal line;
a third conductive material that fills a through hole penetrating the third insulating layer and electrically connects the land of the first printed wiring board and the second signal line;
Further equipped with
The bonded printed wiring board according to claim 11 , wherein the first conductive portion of the shield portion is bonded to the insulating protective layer.
the second printed wiring board further includes a second ground layer provided on the fifth main surface,
15. The bonded printed wiring board according to claim 14, wherein the ground layer and the second ground layer are electrically connected via a second conductive material.
The bonded printed wiring board according to claim 11, wherein a third insulating adhesive layer, a second insulating protective layer, and a fourth insulating adhesive layer are laminated in this order between the fourth main surface and the fifth main surface.
The bonded printed wiring board according to any one of claims 1 to 9, wherein the first printed wiring board and/or the second printed wiring board is a flexible printed wiring board.
The bonded printed wiring board according to any one of claims 1 to 9, wherein the first printed wiring board has 2 to 5 circuit layers.
The bonded printed wiring board according to any one of claims 1 to 9, wherein the second printed wiring board has 1 to 5 circuit layers.
A first printed wiring board;
a second printed wiring board joined to the first printed wiring board;
a shield portion having a conductive layer provided across the first printed wiring board and the second printed wiring board;
A bonded printed wiring board comprising:
The first printed wiring board includes:
a first insulating layer having a first major surface and a second major surface opposite the first major surface;
a first signal line provided on the first main surface;
a ground line provided on the first main surface so as to sandwich the first signal line;
Equipped with
The second printed wiring board includes:
a second insulating layer having a third main surface bonded to the first main surface and a fourth main surface opposite the third main surface;
a second signal line provided on the third main surface and electrically connected to the first signal line via a conductive material;
Equipped with
The conductive layer of the shield portion is
a first conductive portion provided on the fourth main surface so as to include the second signal line when viewed in a thickness direction of the second printed wiring board;
a second conductive portion integral with the first conductive portion and joined to the ground line;
2. A bonded printed wiring board comprising:
a first insulating layer having a first major surface and a second major surface opposite the first major surface;
a first signal line provided on the first main surface;
a second insulating layer having a third main surface facing the first main surface and a fourth main surface opposite the third main surface, the second insulating layer including a laminated portion laminated on the first insulating layer and an extending portion extending in a longitudinal direction from the laminated portion;
a second signal line provided on the fourth main surface in the laminated portion and the extending portion of the second insulating layer;
a ground layer provided on the fourth main surface of the laminated portion of the second insulating layer at a distance from the second signal line;
an interlayer connection portion that penetrates the second insulating layer and electrically connects the first signal line and the second signal line;
an insulating protective layer provided so as to cover the second signal line;
a shielding section having a conductive layer including a first conductive section provided to include the second signal line when viewed in a thickness direction of the second insulating layer, and a second conductive section integral with the first conductive section and joined to the ground layer;
A printed wiring board comprising:
a step of preparing a first printed wiring board including: a first insulating layer having a first main surface and a second main surface opposite to the first main surface; a first signal line provided on the first main surface; a second insulating layer having a third main surface facing the first main surface and a fourth main surface opposite to the third main surface, the second insulating layer being laminated on the first insulating layer so as to embed at least a portion of the first main surface and the first signal line; and a ground layer provided on the fourth main surface so as to encompass the first signal line when viewed in a thickness direction of the second insulating layer;
preparing a second printed wiring board including a third insulating layer having a fifth main surface and a sixth main surface opposite to the fifth main surface, and a second signal line provided in the third insulating layer;
a step of joining the first printed wiring board and the second printed wiring board via a conductive material, the step being to join the fifth main surface of the second printed wiring board to the first printed wiring board and electrically connect the first signal line and the second signal line;
a step of providing a shielding portion having a conductive layer including a first conductive portion and a second conductive portion integral with the first conductive portion, the step of joining the first conductive portion to the second printed wiring board so as to include the second signal line when viewed in a thickness direction of the second printed wiring board, and joining the second conductive portion to the ground layer;
A method for manufacturing a bonded printed wiring board, comprising:
The method for manufacturing a bonded printed wiring board according to claim 22, in which the step of bonding the first printed wiring board and the second printed wiring board and the step of providing the shielding portion are performed simultaneously.