JP2023183753A - Junction printed wiring board and method for manufacturing junction printed wiring board - Google Patents

Abstract

To provide a junction printed wiring board having a structure in which transmission characteristics are enhanced and a junction portion is space-saved.SOLUTION: A junction printed wiring board 1 includes a printed wiring board 10 having a signal line 11, a pair of ground lines 12 sandwiching the signal line 11 therebetween, and an insulating substrate 13, and a printed wiring board 20 having a signal line 21, a pair of ground lines 22 sandwiching the signal line 21 therebetween, and an insulating substrate 23. The signal line 11 is provided in the insulating substrate 13, and an end portion thereof is exposed at an exposed surface 14a of a portion where the insulating substrate 13 is locally thinned, and/or the signal line 21 is provided in the insulating substrate 23, and an end portion thereof is exposed at an exposed surface 24a of a portion where the insulating substrate 23 is locally thinned. The printed wiring board 10 and the printed wiring board 20 are joined together such that the end portion of the signal line 11 and the end portion of the signal line 21 face each other and are electrically connected to each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to a bonded printed wiring board and a method for manufacturing a bonded printed wiring board.

Information communication devices such as smartphones, tablets, and mobile phones include an antenna module for communicating with other devices and a main board on which electronic components such as semiconductor chips are mounted. A bonded printed wiring board is used to electrically connect the antenna module and the main board. Some bonded printed wiring boards include two printed wiring boards connected via a connector such as a small coaxial connector or a board-to-board connector.

International Publication No. 2020/158810 pamphlet

In recent years, as communication speeds have further increased, high-frequency signals are being used to increase the speed of digital signals. When using a bonded printed wiring board connected via a connector, a minute stub structure existing at the terminal of the connector poses a problem. That is, in high-frequency signal transmission, signal resonance occurs in the stub structure, significantly deteriorating the transmission characteristics.

Further, as information communication equipment becomes smaller, bonded printed wiring boards are required to be space-saving.

The present invention has been made based on the above technical recognition, and an object thereof is to provide a bonded printed wiring board having improved transmission characteristics and a structure in which the bonded portion saves space.

The bonded printed wiring board according to the first aspect of the present invention includes:
a first printed wiring board having a first signal line, a pair of first ground lines sandwiching the first signal line, and a first insulating substrate;
a second printed wiring board having a second signal line, a pair of second ground lines sandwiching the second signal line, and a second insulating substrate;
The first signal line is provided in the first insulating substrate, and has an end exposed at a first exposed surface of a locally thinned portion of the first insulating substrate, and/or , the second signal line is provided in the second insulating substrate, and an end portion thereof is exposed on a second exposed surface of a locally thinned portion of the second insulating substrate;
The first printed wiring board and the second printed wiring board are joined such that an end of the first signal line and an end of the second signal line face each other and are electrically connected. It is characterized by

Further, in the bonded printed wiring board,
The first insulating substrate of the first printed wiring board is
a first insulating layer having a first main surface on which the first signal line is provided and a second main surface opposite to the first main surface;
a third main surface opposite to the first main surface; and a fourth main surface opposite to the third main surface, the first insulating surface except for the first exposed surface. a second insulating layer laminated in layers;
including;
a first ground layer is provided on the second main surface,
a second ground layer is provided on the fourth main surface,
The second insulating substrate of the second printed wiring board is
a third insulating layer having a fifth main surface on which the second signal line is provided, and a sixth main surface opposite to the fifth main surface;
a seventh main surface opposite to the fifth main surface; and an eighth main surface opposite to the seventh main surface, and the third insulating surface except for the second exposed surface a fourth insulating layer stacked in layers;
including;
a third ground layer is provided on the sixth main surface,
a fourth ground layer is provided on the eighth main surface,
The first ground line is provided on the first main surface and electrically connected to the first ground layer and/or the second ground layer,
The second ground line may be provided on the fifth main surface and electrically connected to the third ground layer and/or the fourth ground layer.

Further, in the bonded printed wiring board,
a first connection part that electrically connects the first ground layer and the fourth ground layer; and/or a second connection part that electrically connects the second ground layer and the third ground layer. The device may further include a connecting portion.

Further, in the bonded printed wiring board,
A first ground layer that covers the first ground layer and the fourth ground layer and has a first opening through which the first ground layer is exposed and a second opening through which the fourth ground layer is exposed. a protective layer of
A second ground layer that covers the second ground layer and the third ground layer and has a third opening through which the second ground layer is exposed and a fourth opening through which the third ground layer is exposed. a protective layer of
Equipped with
The first connection portion includes a conductive material that electrically connects the first ground layer exposed in the first opening and the fourth ground layer exposed in the second opening. ,
The second connection portion includes a conductive material that electrically connects the second ground layer exposed in the third opening and the third ground layer exposed in the fourth opening. You can also do this.

Further, in the bonded printed wiring board,
The first connection portion includes a first metal foil and a first anisotropic layer that is supported by the first metal foil and electrically connects the first ground layer and the fourth ground layer. having a conductive material;
The second connection portion includes a second metal foil and a second anisotropic layer that is supported by the second metal foil and electrically connects the second ground layer and the third ground layer. It may also include a conductive material.

Further, in the bonded printed wiring board,
The first signal line and the second signal line may be electrically connected through the same material as the first and second anisotropic conductive materials.

Further, in the bonded printed wiring board,
The first signal line is provided in the first insulating substrate, includes a first signal line portion whose end portion is exposed on the first exposed surface, and a first signal line portion provided on the first exposed surface, and includes a first signal line portion whose end portion is exposed on the first exposed surface, has an exposed second signal line portion,
The first signal line portion and the second signal line portion may be electrically connected via a chip component.

Further, in the bonded printed wiring board,
On the first exposed surface, the first signal line and the first ground line may be electrically connected via a chip component.

The bonded printed wiring board according to the second aspect of the present invention includes:
a first printed wiring board having a first signal line, a pair of first ground lines sandwiching the first signal line, and a first insulating substrate;
a second printed wiring board having a second signal line, a pair of second ground lines sandwiching the second signal line, and a second insulating substrate;
The first printed wiring board and the second printed wiring board have a first joint surface where the end of the first signal line is located and a second joint surface where the end of the second signal line is located. the first signal line and the second signal line are electrically connected,
The first ground line is characterized in that the distance from the first signal line increases toward the end of the first printed wiring board.

Further, in the bonded printed wiring board,
The first ground line may have a shape that partially approaches the first signal line.

Further, in the bonded printed wiring board,
The first ground line extends longer than the first signal line toward the end of the first insulating substrate, and connects the end of the first ground line with the first insulating substrate. An interlayer connection portion may be provided that electrically connects the first ground layer provided on the outside.

Further, 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.

Further, in the bonded printed wiring board,
The insulating layer of the flexible printed wiring board may contain a liquid crystal polymer, a fluorine-based material, or a polyimide-based material.

Further, in the bonded printed wiring board,
One of the first printed wiring board and the second printed wiring board is connected to an antenna module including an antenna and an antenna board, and the other is mounted with a semiconductor chip that performs information processing based on a signal received by the antenna. It may also be connected to a main board that has been installed.

The method for manufacturing a bonded printed wiring board according to the present invention includes:
preparing a first printed wiring board having a first signal line, a pair of first ground lines sandwiching the first signal line, and a first insulating substrate;
preparing a second printed wiring board having a second signal line, a pair of second ground lines sandwiching the second signal line, and a second insulating substrate;
The first signal line is provided in the first insulating substrate, and has an end exposed at a first exposed surface of a locally thinned portion of the first insulating substrate, and/or , the second signal line is provided in the second insulating substrate, and an end portion thereof is exposed on a second exposed surface of a locally thinned portion of the second insulating substrate;
The first printed wiring board and the second printed wiring board are joined such that the end of the first signal line and the end of the second signal line face each other and are electrically connected. It is characterized by comprising a process.

According to the present invention, the signal lines of at least one of the first printed wiring board and the second printed wiring board are locally exposed in a thin bonding region, and the signal lines of the first and second printed wiring boards are connected to each other. are directly electrically connected without interlayer connections. Therefore, it is possible to provide a bonded printed wiring board having improved transmission characteristics and a structure in which the bonded portion saves space.

FIG. 2 is a longitudinal cross-sectional view along a signal line of the bonded printed wiring board according to the first embodiment. (1) is a plan view of the bonded printed wiring board according to the first embodiment before bonding, and (2) is a plan view of the bonded printed wiring board after bonding. FIG. 3 is a process cross-sectional view illustrating a method for manufacturing a bonded printed wiring board according to the first embodiment. FIG. 4 is a process cross-sectional view following FIG. 3 to explain the method for manufacturing the bonded printed wiring board according to the first embodiment. FIG. 5 is a process cross-sectional view following FIG. 4 and explaining the method for manufacturing the bonded printed wiring board according to the first embodiment. FIG. 6 is a process sectional view following FIG. 5 illustrating the method for manufacturing the bonded printed wiring board according to the first embodiment. FIG. 3 is a diagram for explaining a return current flowing through a ground layer. FIG. 3 is a diagram showing simulation results of transmission characteristics (characteristic impedance) of bonded printed wiring boards according to the first and second embodiments. FIG. 7 is a longitudinal cross-sectional view along a signal line of a bonded printed wiring board according to a second embodiment. FIG. 7 is a process cross-sectional view illustrating a method for manufacturing a bonded printed wiring board according to a second embodiment. FIG. 7 is a longitudinal cross-sectional view taken along a signal line of a bonded printed wiring board according to a modification of the second embodiment. FIG. 7 is a cross-sectional view illustrating a method for manufacturing a bonded printed wiring board according to a modification of the second embodiment. (a) is a partial vertical cross-sectional view along a signal line of a bonded printed wiring board according to a third embodiment, and (b) is a plan view of the bonded printed wiring board. FIG. 7 is a partial vertical cross-sectional view illustrating a method of manufacturing a bonded printed wiring board according to a third embodiment. FIG. 7 is a partial vertical cross-sectional view along a signal line of a bonded printed wiring board according to a modification of the third embodiment. (1) is a plan view of a bonded printed wiring board according to a fourth embodiment before bonding, and (2) is a plan view of the bonded printed wiring board after bonding. FIG. 7 is a plan view of a bonded printed wiring board according to Modification 1 of the fourth embodiment before bonding; FIG. 7 is a plan view of one printed wiring board of a bonded printed wiring board according to Modification 2 of the fourth embodiment.

Embodiments according to the present invention will be described below with reference to the drawings. Note that in each figure, the same reference numerals are given to components having the same function. In addition, the scale ratio of each component is changed appropriately in order to make it recognizable on the drawing, so it does not necessarily match the actual one. In addition, terms such as "parallel," "orthogonal," "equal," etc., dimensions, and physical property values used in this specification are not limited to strict meanings, and are used to the extent that similar functions can be expected. shall be interpreted to include the scope of

(First embodiment)
A bonded printed wiring board 1 according to a first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal cross-sectional view along signal lines 11 and 21 of a bonded printed wiring board 1 according to this embodiment. FIG. 2(1) is a plan view of the bonded printed wiring board 1 before bonding, and FIG. 2(2) is a plan view of the bonded printed wiring board 1 after bonding. In addition, in FIG. 2(2), the printed wiring board 10 and the printed wiring board 20 are shown slightly shifted from each other in order to make it easier to understand the state of bonding.

As shown in FIGS. 1 and 2, the bonded printed wiring board 1 includes a printed wiring board 10 and a printed wiring board 20. Printed wiring board 10 and printed wiring board 20 are joined at bonding areas 14 and 24. In this embodiment, printed wiring boards 10 and 20 are flexible printed wiring boards. Note that at least one of printed wiring boards 10 and 20 may be a rigid printed wiring board.

The bonded printed wiring board 1 is used, for example, in an information communication device, and connects an antenna module including an antenna and an antenna board, and a main board on which a semiconductor chip is mounted that performs information processing based on a signal received by the antenna. used to connect to In this case, one of the printed wiring boards 10 and 20 is connected to the antenna module, and the other is connected to the main board. Note that the printed wiring boards 10 and 20 themselves may be an antenna board or a main board.

As shown in FIGS. 1 and 2, the printed wiring board 10 includes a signal line 11, a pair of ground lines (guard grounds) 12 sandwiching the signal line, and an insulating substrate 13. The signal line 11 and the ground line 12 are provided in the insulating substrate 13, and their ends are exposed at the exposed surface 14a of the bonding region 14 where the insulating substrate 13 is locally thinned.

Similarly, the printed wiring board 20 includes a signal line 21, a pair of ground lines 22 sandwiching the signal line, and an insulating substrate 23. The signal line 21 and the ground line 22 are provided in the insulating substrate 23, and their ends are exposed at the exposed surface 24a of the bonding region 24 where the insulating substrate 23 is locally thinned.

The signal line 11 and the signal line 21 are arranged such that their exposed ends face each other.

The distance between the signal line 11 (21) and the ground line 12 (22) is, for example, 150 μm. Furthermore, in this embodiment, the signal currents input to the signal lines 11 and 21 have a frequency in the GHz band. Furthermore, the characteristic impedances of printed wiring boards 10 and 20 are matched to 50Ω.

Note that the numbers of signal lines 11, 21 and ground lines 12, 22 are not limited to those shown in FIG. For example, two signal lines 11 may be provided sandwiched between two ground lines 12 as differential transmission lines. Further, a plurality of pairs of signal lines and ground lines may be provided. Further, the signal line 11 is not limited to a straight line, and may be bent or curved in the middle as necessary. The same applies to the signal line 21 and the ground lines 12 and 22. The same applies to subsequent embodiments and modifications.

Printed wiring board 10 and printed wiring board 20 are arranged such that exposed surface 14a of bonding region 14 and exposed surface 24a of bonding region 24 face each other. The signal line 11 and the signal line 21 are electrically connected via the anisotropic conductive material 31. Further, the ground line 12 and the ground line 22 are also electrically connected via an anisotropic conductive material 31.

In this embodiment, the anisotropic conductive material 31 is an anisotropic conductive film (ACF). Note that instead of the anisotropic conductive film, an anisotropic conductive paste (ACP), a conductive adhesive, solder such as cream solder, a conductive paste, or a conductive film may be used. When using a conductive adhesive, solder, conductive paste, or conductive film, a non-conductive material may be used to provide insulation between the conductive adhesive, solder, conductive paste, or conductive film. Alternatively, the printed wiring boards 10 and 20 may be bonded using a non-conductive material by bringing the signal line 11 and the signal line 21 into direct contact with each other, and between the ground line 12 and the ground line 22, respectively. In both cases, the non-conductive material used is, for example, a non-conductive film (NCF), a non-conductive paste (NCP) or an adhesive (including a slight adhesive).

In this embodiment, printed wiring boards 10 and 20 have a stripline structure. As shown in FIG. 1, insulating substrate 13 of printed wiring board 10 includes insulating layers 13a, 13b and adhesive layer 13c. A signal line 11 and a ground line 12 are provided on the upper surface of the insulating layer 13a, and a ground layer 16 is provided on the lower surface of the insulating layer 13a. The lower surface of the ground layer 16 is covered with a protective layer 18.

Further, the insulating layer 13b is stacked on the insulating layer 13a except for the exposed surface 14a of the bonding region 14. An adhesive layer 13c is provided on the lower surface of the insulating layer 13b, and the signal line 11 and the ground line 12 are embedded in the adhesive layer 13c. A ground layer 17 is provided on the upper surface of the insulating layer 13b. The upper surface of the ground layer 17 is covered with a protective layer 19.

Similarly, as shown in FIG. 1, insulating substrate 23 of printed wiring board 20 includes insulating layers 23a, 23b and adhesive layer 23c. A signal line 21 and a ground line 22 are provided on the lower surface of the insulating layer 23a, and a ground layer 26 is provided on the upper surface of the insulating layer 23a. The upper surface of the ground layer 26 is covered with a protective layer 28.

Further, the insulating layer 23b is stacked on the insulating layer 23a except for the exposed surface 24a of the bonding region 24. An adhesive layer 23c is provided on the upper surface of the insulating layer 23b, and the signal line 21 and the ground line 22 are embedded in the adhesive layer 23c. A ground layer 27 is provided on the lower surface of the insulating layer 23b. The lower surface of the ground layer 27 is covered with a protective layer 29.

In this embodiment, the material of the insulating layers 13a, 13b, 23a, and 23b is liquid crystal polymer (LCP). Note that the material of the insulating layers 13a, 13b, 23a, and 23b is not limited to LCP, but includes, for example, fluorine-based materials such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) and PTFE (polytetrafluoroethylene); It may be a polyimide material such as modified polyimide (MPI) or polyimide (PI), PEEK (polyetheretherketone), or PEN (polyethylene naphthalate). Moreover, the materials of the insulating layers 13a, 13b, 23a, and 23b can be independently selected arbitrarily.

In order to ensure high frequency signal transmission characteristics, it is desirable to use a material with a low dielectric constant and a low dielectric loss tangent as the material for the insulating layers 13a, 13b, 23a, and 23b. Furthermore, it is desirable to use a material with a low dielectric constant and a low dielectric loss tangent for the adhesive layers 13c and 23c as well.

From FIG. 7 onwards, the adhesive layers 13c and 23c are omitted. In addition, when the insulating layer is made of LCP, PEEK material, thermoplastic polyimide, etc., when laminating the insulating layers 13a and 13b, a method of pressing at a temperature higher than the melting point of the material of the insulating layers 13a and 13b may be used. In this case, the insulating layers 13a and 13b are directly bonded without using the adhesive layer 13c. Similarly, the insulating layers 23a and 23b may be directly bonded without using the adhesive layer 23c.

In this embodiment, the protective layers 18, 19, 28, and 29 are protective films using a PI-based material. Note that a photosensitive photoresist may be used as the protective layer.

Further, the protective layers 18, 29 and the protective layers 19, 28 may be integrated, respectively (see protective layers 41, 42 in FIG. 13(a), which will be described later).

As shown in FIGS. 2(1) and 2(2), interlayer connection portions 15 and 25 are provided at the ends of the ground lines 12 and 22 exposed on the exposed surfaces 14a and 24a, respectively. Interlayer connection portion 15 electrically connects ground line 12 and ground layer 16 . Further, the interlayer connection portion 25 electrically connects the ground line 22 and the ground layer 26. This prevents the ground lines 12 and 22 from having a stub structure and stabilizes the transmission characteristics. In order to avoid the stub structure as much as possible, the interlayer connections 15 and 25 are preferably provided within 1 mm from the ends of the ground lines 12 and 22.

In this embodiment, the interlayer connections 15 and 25 are plated vias in which the inner walls of bottomed via holes are plated. Note that the interlayer connections 15 and 25 may be filled vias, through holes, or the like.

Further, the interlayer connecting portions 15 and 25 are generally called ground vias, and as shown in FIG. 7, which will be described later, a plurality of interlayer connecting portions 15 and 25 are provided in order to electrically connect the ground line and the upper and lower ground layers. For example, the interlayer connection section 15 may be provided to electrically connect the ground line 12 and the ground layer 17. Moreover, as the interlayer connection part 15, one that electrically connects the ground line 12, the ground layer 16, and the ground layer 17 may be provided. In FIG. 2 and later-described FIGS. 13 and 16 to 18, interlayer connections 15 and 25 are omitted except for the parts necessary for explanation.

As shown in FIG. 2(1), the anisotropic conductive material 31 electrically connects the signal line 11 exposed on the exposed surface 14a of the printed wiring board 10 and the signal line 21 exposed on the exposed surface 24a of the printed wiring board 20. provided for connection to. Further, the anisotropic conductive material 31 also electrically connects the ground wire 12 exposed on the exposed surface 14a of the printed wiring board 10 and the ground wire 22 exposed on the exposed surface 24a of the printed wiring board 20.

As shown in FIG. 2(1), the ends of the signal lines 11 and 21 are covered with an anisotropic conductive material 31. This can prevent the ends of the signal lines 11 and 21 from forming a stub structure.

In FIG. 2(1), the ends of the ground lines 12 and 22, more specifically, the portions of the ground lines 12 and 22 where the interlayer connections 15 and 25 are provided, are not covered with the anisotropic conductive material 31. . This is because the interlayer connection parts 15 and 25 are provided at the ends of the ground lines 12 and 22, so even if they are not covered with the anisotropic conductive material 31, they do not form a stub structure.

Note that the ground lines 12 and 22 may be covered with an anisotropic conductive material 31. However, if the anisotropic conductive material 31 is thin, or if the interlayer connections are not bottomed, such as through holes, it is preferable to arrange the interlayer connections 15 and 25 so as to avoid the anisotropic conductive material 31.

Note that the lengths of the signal lines 11, 21 and the ground lines 12, 22 exposed on the exposed surfaces 14a, 24a are not limited to those shown in FIG. 2(1). For example, the ground lines 12 and 22 may be exposed at the same length as the signal lines 11 and 21, or the ground lines 12 and 22 may be exposed at a portion shorter than the signal lines 11 and 21.

Preferably, as shown in FIG. 2(1), the ground line 12 extends longer than the signal line 11 toward the end of the insulating substrate 13, and connects the end of the ground line 12 and the ground layer 16 with electricity. An interlayer connection portion is provided to connect the two layers. Thereby, the transmission characteristics of the signal line 11 can be improved, and the stub structure of the signal line 11 can be eliminated.

Among the printed wiring boards 10 and 20 shown in FIG. 2(1), the printed wiring board 20 is turned upside down and bonded with the anisotropic conductive material 31, thereby forming the bonded printed wiring board 1 shown in FIG. 2(2). get. Note that in FIG. 2(2), the anisotropic conductive material 31 is omitted.

In this embodiment, the printed wiring boards 10 and 20 are joined such that the longitudinal direction of the printed wiring boards 10 and the longitudinal direction of the printed wiring boards 20 are parallel to each other. Note that the joining form is not limited to this, and the printed wiring boards 10 and 20 may be joined such that the longitudinal direction of the printed wiring board 10 and the longitudinal direction of the printed wiring board 20 are perpendicular or oblique to each other. . In this case, the signal line and the ground line exposed on the exposed surface may be bent or curved on the exposed surface depending on the joining angle.

Note that the printed wiring boards 10 and 20 are not limited to the stripline structure shown in FIG. For example, one of the printed wiring boards 10 and 20 may have a microstrip line structure.

For example, when the printed wiring board 10 has a microstrip line structure, among the components of the printed wiring board 10 shown in FIG. is provided with a protective layer. The same applies when the printed wiring board 20 has a microstrip line structure.

As for the other number of layers, for example, one printed wiring board has 3 to 10 layers, and the other printed wiring board has 2 to 10 layers. According to the bonded printed wiring board 1 according to the present embodiment, at least one of the signal lines of the printed wiring board 10 and the printed wiring board 20 is exposed in the locally formed thin bonding area, and the signal line 11 and the signal line 21 are directly electrically connected without using an interlayer connection part. Therefore, it is possible to provide a bonded printed wiring board having improved transmission characteristics and a structure in which the bonded portion saves space.

(Method for manufacturing bonded printed wiring board)
Next, an example of a method for manufacturing printed wiring board 10 constituting bonded printed wiring board 1 will be described with reference to FIGS. 3 to 6. Note that the bonded printed wiring board according to this embodiment is not limited to a bonded printed wiring board manufactured by the following manufacturing method.

As shown in FIG. 3(1), a single-sided metal foil-clad laminate 100 having an insulating layer 110 and a metal foil 120 provided on the upper surface of the insulating layer 110 is prepared. The insulating layer 110 corresponds to the above-mentioned insulating layer 13b. The insulating layer 110 is an insulating film (for example, 100 μm thick) made of liquid crystal polymer (LCP) or the like. Note that the insulating layer 110 may be made of a fluorine-based material such as PFA or PTFE, a polyimide material such as MPI or PI, PEEK, PEN, or the like. The metal foil 120 is a copper foil (for example, 12 μm thick). Note that a metal foil made of a metal other than copper (silver, aluminum, etc.) may also be used.

Next, as shown in FIG. 3(2), an adhesive layer 130 is partially formed on the lower surface of the insulating layer 110. The adhesive layer 130 corresponds to the adhesive layer 13c described above. The reason why the adhesive layer 130 is partially formed is to make it easier to remove a portion of the insulating layer 110 later. Note that in this embodiment, after the adhesive layer 130 was formed on the entire lower surface of the insulating layer 110, a part of the adhesive layer 130 was removed by cutting, but it could also be removed by applying a laser or die cutting process. You can. Alternatively, the adhesive layer 130 may be formed by forming the adhesive layer only on a predetermined region of the insulating layer 110 from the beginning.

To form the adhesive layer 130, a method of bonding adhesive films is used. Note that a method of applying an adhesive or a method of laminating a protective film with an adhesive layer and then peeling the protective film may be used.

As shown in FIG. 3(3), a double-sided metal foil-clad laminate having an insulating layer 210, a metal foil 220 provided on the upper surface of the insulating layer 210, and a metal foil 230 provided on the lower surface of the insulating layer 210. Prepare 200. The insulating layer 210 corresponds to the above-mentioned insulating layer 13a. The insulating layer 210 is an insulating film (for example, 100 μm thick) made of LCP or the like. Note that the insulating layer 210 may be made of a fluorine-based material such as PFA or PTFE, a polyimide-based material such as MPI or PI, PEEK, PEN, or the like. The metal foil 230 corresponds to the ground layer 16 described above. The metal foils 220 and 230 are copper foils (for example, 12 μm thick). Note that a metal foil made of a metal other than copper (silver, aluminum, etc.) may be used.

Next, as shown in FIG. 3(4), the metal foil 220 is patterned on the double-sided metal foil-clad laminate 200 using a known photofabrication method, and the signal line 220a and ground lines 220b, 220c are formed. Form. The signal line 220a corresponds to the signal line 11 described above. Further, the ground lines 220b and 220c correspond to the ground line 12 described above. The distance between the signal line 220a and the ground line 220b (220c) is, for example, 150 μm.

Next, the second wiring base material obtained in the step of FIG. 3(2) is laminated on the first wiring base material obtained in the step of FIG. 3(4). ) Fabricate the laminate shown in (). More specifically, a first wiring base material and a second wiring base material are laminated so that the signal line 220a and the ground line 220c are embedded in the adhesive layer 130, and the adhesive layer 130 is cured by heat pressing. A laminate is produced using the following steps. The temperature of the hot press is higher than the floating point of the adhesive layer 130 (for example, 170° C.). In addition, if curing is insufficient, oven curing may be performed. In this embodiment, oven curing was performed at 170° C. for 2 hours to complete the curing reaction of the adhesive layer 130.

In this step, the first wiring base material and the second wiring base material are laminated so that a portion of the signal line 220a is buried in the adhesive layer 130. Similarly, the first wiring base material and the second wiring base material are laminated so that the ground lines 220b and 220c are partially buried in the adhesive layer 130.

Next, as shown in FIG. 4(2), a predetermined region is irradiated with a laser pulse to form via holes H1 and H2. The diameter of the via holes H1 and H2 is, for example, φ150 μm. For laser processing, for example, an infrared laser such as a carbon dioxide laser, a UV-YAG laser, or the like is used. Note that the metal foils 120 and 230 may be partially removed in advance to form a comfort mask. Further, a through hole H3 is formed using a drill or the like. Note that the via holes H1, H2 and the through hole H3 may be formed first.

Next, as shown in FIG. 5(1), via holes H1, H2 and through hole H3 are subjected to metal plating treatment (for example, copper plating treatment) to form vias 310, 320 and plated through hole 330. Vias 310 and plated through holes 330 correspond to interlayer connections 15. In this embodiment, a button plating (pattern plating) method was used in which a dry film is laminated on the surface of a multilayer substrate, the dry film is exposed and developed, and the open areas of the dry film are plated. Note that a panel plating method in which the entire substrate is plated may be used.

Next, as shown in FIG. 5(2), the metal foil 120 is patterned by a known photofabrication technique to form a pad 120a and a ground layer 120b. The ground layer 120b corresponds to the ground layer 17 described above. At this time, an opening line 410 for cutting is formed in the metal foil 120 directly above the end surface of the adhesive layer 130. This makes it easier to remove the insulating layer 110 in a later step.

Next, as shown in FIG. 6(1), protective layers 140, 240 are laminated on the surface of the laminated substrate, and openings 140a, 240a are formed in the protective layers 140, 240. The protective layer 140 corresponds to the protective layer 19 described above. Furthermore, the protective layer 240 corresponds to the protective layer 18 described above. In this embodiment, the protective layers 140 and 240 are protective films using a PI-based material. Note that a photosensitive photoresist may also be applied. Further, the metal foil exposed on the surface may be surface-treated with gold plating, water-based preflux, or the like. In this embodiment, gold plating treatment was performed to form a gold plating layer (not shown) on the metal foil.

Next, a portion of the insulating layer 110 is removed along the cutting line L in FIG. 6(1). In this embodiment, a portion of the insulating layer 110 was removed by tearing it with a clamp. Note that it may be removed using a CO ₂ laser or the like. Further, as the insulating layer 110, a layer shorter than the insulating layer 210 may be used in advance.

Through the above steps, a printed wiring board 300 shown in FIG. 6(2) can be obtained. Printed wiring board 300 corresponds to printed wiring board 10. Note that the printed wiring board 20 can also be manufactured by the same method as described above.

The two printed wiring boards 300 obtained as described above are electrically connected so that the ends of the signal lines on one printed wiring board and the ends of the signal lines on the other printed wiring board face each other. Connect so that the A conductive material such as an anisotropic conductive film (ACF) is used for electrical connection between signal lines.

In this embodiment, a bonded printed wiring board 1 is obtained by bonding two printed wiring boards via an anisotropic conductive film (ACF). Specifically, first, for positioning, temporary adhesion is performed at a temperature below the curing temperature of the ACF, and then the main pressure bonding is performed by heating to a temperature above the curing temperature. When using ACF, which is an epoxy material with a curing temperature of 170°C, for example, temporary adhesion is performed at 100°C, and then the ACF joint is heated to the curing temperature of 170°C for final pressure bonding.

In addition, when using conductive adhesive, solder such as cream solder, conductive paste or conductive film as the conductive material, conductive adhesive, solder such as cream solder, conductive paste or conductive film may be printed on the predetermined connection position. After that, a non-conductive film, a non-conductive paste, an adhesive (a slight adhesive may be used), etc. are applied. Thereafter, the printed wiring boards 10 and 20 are aligned and stacked, and the joint portion is heated with a pulse heater to melt the conductive material.

Note that the two printed wiring boards 300 may be joined together using a non-conductive material by directly connecting the signal line of one of the two printed wiring boards 300 to the signal line of the other. Similarly, the ground line of one of the two printed wiring boards 300 may be directly connected to the ground line of the other.

Note that the timing for removing a portion of the insulating layer 110 may be immediately after the step of FIG. 5(2). In this case, the protective layers 140, 240 may be formed immediately after removing a portion of the insulating layer 110, or the two printed wiring boards 300 may be bonded first, and then the protective layers 140, 240 may be formed. may be formed. In the latter case, the protective layer may be formed across two printed wiring boards.

In the above manufacturing method, the insulating layer 110 and the insulating layer 210 are bonded together using an adhesive. The insulating layer 110 and the insulating layer 210 may be directly bonded by heating and pressurizing. In this case, a part of the insulating layer 110 is removed before lamination, or a single-sided metal foil-clad laminate 100 having a different length from the double-sided metal foil-clad laminate 200 is used from the beginning.

Other embodiments and modifications will be described below. In the following description, parts that are different from the first embodiment will be mainly described, and descriptions of similar parts will be omitted.

(Second embodiment)
Next, a bonded printed wiring board 1 according to a second embodiment will be described with reference to FIGS. 7 to 10. FIG. 7 is a diagram for explaining the return current flowing through the ground layers 16 and 26 in the first embodiment. FIG. 8 is a diagram showing simulation results of transmission characteristics (characteristic impedance Z0) of the bonded printed wiring board. FIG. 9 is a longitudinal cross-sectional view along signal lines 11 and 21 of the bonded printed wiring board according to this embodiment. FIG. 10 is a process sectional view illustrating a method for manufacturing a bonded printed wiring board according to this embodiment.

First, it will be explained that the inductance component of the characteristic impedance of the bonded printed wiring board 1 changes at the bonded portion due to the return current. As shown in FIG. 7, consider the case in which the signal current S flows in the direction of the arrow in the signal lines 11 and 21 of the bonded printed wiring board 1 in the first embodiment. More specifically, FIG. 7 shows a situation in which the signal current S flows through the signal line 11, the conductive material, and the signal line 21 in this order. Note that, in order to make the state of the current easier to understand, the dashed-dotted line representing the signal current S is shown slightly shifted from the signal lines 11 and 21.

At this time, a return current flows in a direction opposite to the signal current S. The return current mainly flows through the portion of the ground line and ground layer that is closest to the signal line. In FIG. 7, the return current flowing through the ground layers 16 and 26 of the bonded printed wiring board 1 is indicated by the symbol R. In addition, in FIG. 7, the protective layers 18, 19, 28, and 29 are omitted.

As shown in FIG. 7, the return current R flowing in the portion of the ground layer 26 directly above the signal line 21 spreads toward the interlayer connection portion 25 as it approaches the junction region. The return current R flows through the interlayer connection 25, the ground line 22, the conductive material, the ground line 12, and the interlayer connection 15 in this order, and then flows to the ground layer 16. That is, the return current R flows from the upper ground layer 26 of the printed wiring board 20 to the lower ground layer 16 of the printed wiring board 10 through the interlayer connections 15 and 25 and the ground lines 12 and 22. In this way, since the return current takes a route (detour route) passing through the inside of the printed wiring boards 10 and 20, the inductance component of the characteristic impedance increases at the joint portion of the joined printed wiring board 1. As shown by the broken line in FIG. 8, a characteristic impedance mismatch occurs.

Therefore, in order to prevent the return current from detouring, in this embodiment, the return current flows from the ground layer 26 of the printed wiring board 20 to the ground layer 17 of the printed wiring board 10 (that is, inside the printed wiring boards 10, 20). The ground layer 17 and the ground layer 26 are connected by a connecting portion so that the ground layer 17 and the ground layer 26 do not pass through the ground layer. Similarly, the ground layer 16 and the ground layer 27 are connected by a connecting portion.

In this embodiment, a bypass path for the return current is provided by a first connection part that electrically connects the ground layer 16 and the ground layer 27 and a second connection part that electrically connects the ground layer 17 and the ground layer 26. will be established. By providing such a bypass path, the return current does not pass through the inside of the printed wiring boards 10, 20, so that an increase in characteristic impedance can be prevented, as shown by the solid line in the graph of FIG.

As shown in FIG. 9, the bonded printed wiring board according to this embodiment includes a protective layer 41 that is provided across printed wiring boards 10 and 20 and covers ground layer 16 and ground layer 27. This protective layer 41 has an opening 41a through which the ground layer 16 is exposed and an opening 41b through which the ground layer 27 is exposed. In this embodiment, a conductive material 34 is provided as the first connection portion to electrically connect the ground layer 16 exposed in the opening 41a and the ground layer 27 exposed in the opening 41b.

Similarly, the bonded printed wiring board according to this embodiment includes a protective layer 42 that is provided across printed wiring boards 10 and 20 and covers ground layer 17 and ground layer 26 . This protective layer 42 has an opening 42a through which the ground layer 17 is exposed and an opening 42b through which the ground layer 26 is exposed. In this embodiment, a conductive material 35 is provided as the second connection portion to electrically connect the ground layer 17 exposed in the opening 42a and the ground layer 26 exposed in the opening 42b.

In this embodiment, the conductive materials 34, 35 are copper shields. Here, the copper shield includes a conductive layer made of copper and a conductive adhesive formed on the conductive layer. The conductive layer may be a metal other than copper. Note that solder, conductive paste, or conductive adhesive film may be used as the conductive materials 34 and 35.

In addition, when using a copper shield or a conductive adhesive film for the conductive materials 34 and 35, the bonding of the printed wiring board 10 and the printed wiring board 20, the formation of the first connection part, and the formation of the second connection part are performed all at once. You can go.

Note that only one of the first connection part and the second connection part may be provided. The same applies to other embodiments and modifications.

Further, similarly to the first embodiment, protective layers 18, 19, 28, and 29 may be provided on the printed wiring boards 10 and 20, and openings may be provided in each of the protective layers 18, 20, and the protective layers may be connected using a conductive material. Alternatively, the ends of the protective layers 18, 19, 28, and 29 on the bonding region side may be cut to expose the ground layer, and the cut portions may be connected using a conductive material. In these cases, a non-conductive material such as a molding material may be inserted into the gap between the printed wiring board 10 and the printed wiring board 20 in order to prevent a short circuit between the conductive material and the signal line or ground line exposed on the exposed surface. good. The same applies to other embodiments and modified examples.

Next, with reference to FIG. 10, a method for manufacturing a bonded printed wiring board according to this embodiment will be described.

First, as shown in FIG. 10(1), a bonded printed wiring board is prepared in which printed wiring boards 10 and 20 whose bonding regions are locally thinned are bonded together using an anisotropic conductive material 31. The printed wiring boards 10 and 20 are obtained by cutting the laminate obtained in FIG. 5(2) above along the cutting line L.

Next, as shown in FIG. 10(2), a protective layer 41 is laminated on the lower surface of the printed wiring boards 10, 20 so as to cover the ground layers 16, 27, and openings 41a, 41b are formed. Similarly, a protective layer 42 is laminated on the upper surface of the printed wiring boards 10, 20 so as to cover the ground layers 17, 26, and openings 42a, 42b are formed.

Thereafter, as shown in FIG. 9, the opening 42a where the ground layer 17 is exposed and the opening 42b where the ground layer 26 is exposed are electrically connected by the conductive material 35, and the ground exposed in the opening 41a is connected by the conductive material 34. The layer 16 and the ground layer 27 exposed in the opening 41b are electrically connected. Thereby, the bonded printed wiring board according to this embodiment can be obtained.

According to this embodiment, impedance mismatch due to return current can be avoided. Furthermore, since the ground layers are bonded to each other using a conductive material, the thickness of the bonded portion can be reduced compared to the case where the ground layers are connected using a connector or the like.

(Modified example of second embodiment)
A modification of the second embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a longitudinal cross-sectional view along signal lines 11 and 21 of a bonded printed wiring board according to this modification. FIG. 12 is a process sectional view illustrating a method for manufacturing a bonded printed wiring board according to a modification.

As shown in FIG. 11, in this modification, the ground layers are connected using an anisotropic conductive material and metal foil. That is, the bonded printed wiring board according to this modification is supported by the metal foil 36 and the metal foil 36 as a first connection part that electrically connects the ground layer 16 and the ground layer 27, and connects the ground layer 16 and the ground. It has an anisotropic conductive material 32 electrically connecting layers 27. Further, as a second connection portion that electrically connects the ground layer 17 and the ground layer 26, a metal foil 37 and an anisotropic structure that is supported by the metal foil 37 and that electrically connects the ground layer 17 and the ground layer 26 are provided. It has a conductive material 33. The anisotropic conductive materials 32 and 33 are, for example, anisotropic conductive films or anisotropic conductive pastes.

In this modification, the material of the metal foils 36 and 37 is copper. Note that other metals such as silver and aluminum may be used as the material for the metal foils 36 and 37.

Note that a combination of the anisotropic conductive material 32 (33) and the metal foil 36 (37) may be used, for example (a copper shield in which the conductive adhesive is an anisotropic conductive material).

Next, with reference to FIG. 12, a method for manufacturing a bonded printed wiring board according to this modification will be described.

First, as shown in FIG. 12, printed wiring boards 10 and 20 are prepared in which the bonding area is locally thinned and the signal line is exposed in the bonding area. The printed wiring boards 10 and 20 are obtained by cutting the laminate obtained in FIG. 5(2) above along the cutting line L.

Next, as shown in FIG. 12, printed wiring boards 10 and 20 are bonded together using an anisotropic conductive material 31. Further, a first connection portion is formed by joining the metal foil 36 and the ground layers 16 and 27 using the anisotropic conductive material 32. Furthermore, a second connection portion is formed by joining the metal foil 37 and the ground layers 17 and 26 using the anisotropic conductive material 33.

By the above method, the bonded printed wiring board according to the present modification shown in FIG. 11 can be obtained.

Note that the bonding of the printed wiring board 10 and the printed wiring board 20, the formation of the first connection part, and the formation of the second connection part may be performed all at once. Anisotropic conductive materials 32 and 33 are covered with metal foils 36 and 37, respectively. Therefore, as shown in FIG. 12, printed wiring board 10 and printed wiring board 20 are stacked so that their exposed surfaces face each other, and anisotropic conductive material 33 and metal foil 37 are placed on printed wiring board 10 and printed wiring board 20. By applying heat and pressure treatment to the parts arranged so as to straddle the boundary line of the printed wiring boards 10 and 20, the bonding of the printed wiring boards 10 and the printed wiring boards 20 and the formation of the first and second connection parts are simultaneously performed. It can be carried out. Thereby, the manufacturing process can be shortened.

Note that a protective layer covering the ground layers 16 and 27 and the metal foil 36 may be provided, or a protective layer covering the ground layers 17 and 26 and the metal foil 37 may be provided. At this time, formation of a protective layer covering the ground layers 16, 27 and the metal foil 36, formation of a protective layer covering the ground layers 17, 26 and the metal foil 37, bonding of the printed wiring board 10 and the printed wiring board 20, and The formation of the connection portion and the formation of the second connection portion may be performed at once.

Note that the anisotropic conductive materials 31, 32, and 33 may all be made of the same material. In this case, the signal lines 11 and 21 are electrically connected through the same material as the anisotropic conductive material 32 and the anisotropic conductive material 33. This makes it possible to unify the curing conditions, etc., and to easily perform the bonding of the printed wiring board 10 and the printed wiring board 20, the formation of the first connection part, and the formation of the second connection part all at once. can do.

Note that after forming the protective layers 18, 19, 28, and 29 as shown in FIG. 1, openings may be provided in each protective layer, and the openings may be connected to each other with an anisotropic conductive material and metal foil. In this case, the printed wiring board 300 obtained as shown in FIG. 6(2) may be used instead of the laminate obtained as shown in FIG. 5(2).

(Third embodiment)
A bonded printed wiring board according to a third embodiment will be described with reference to FIGS. 13 and 14. This embodiment differs from the first embodiment in that a cavity (indentation) is provided in the bonding region, and a chip component constituting an impedance matching circuit (matching circuit) is provided in the cavity for antenna connection. Here, the antenna connection refers to a usage pattern in which an antenna module is connected to one printed wiring board of the bonded printed wiring board, and a main board is connected to the other printed wiring board. By configuring the matching circuit, the impedance of the antenna and the impedance of the semiconductor chip (LSI) of the main board are matched, and reflection of signals flowing through the signal line can be suppressed.

FIG. 13(a) is a partial longitudinal sectional view along signal lines 11 and 21 of the bonded printed wiring board according to this embodiment, and FIG. 13(b) is a plan view of the bonded printed wiring board. Note that, in order to make it easier to understand the state of bonding, the printed wiring board 10 and the printed wiring board 20 are shown slightly shifted from each other in FIG. 13(b). FIG. 14 is a partial vertical cross-sectional view illustrating the method for manufacturing a bonded printed wiring board according to this embodiment.

As shown in FIG. 13A, in the bonded printed wiring board according to this embodiment, since the bonding area of the printed wiring board 20 is narrow, a cavity is formed in the bonding area of the printed wiring board 10.

The signal line 11 has a signal line portion 11a and a signal line portion 11b. The signal line portion 11a is provided in the insulating substrate 13, and its end portion is exposed on the exposed surface 14a. The signal line portion 11b is provided on the exposed surface 14a and is entirely exposed. The signal line portion 11a and the signal line portion 11b are electrically connected via a chip component 51.

Furthermore, as shown in FIG. 13(b), the signal line 11 and the ground line 12 are electrically connected via the chip component 52 on the exposed surface 14a of the printed wiring board 10. More specifically, the signal line portion 11b and the ground line 12 are electrically connected via the chip component 52.

Chip components 51 and 52 are chip capacitors or chip inductors. For example, the chip component 51 is a chip capacitor, the chip component 52 is a chip inductor, and a so-called L-type matching circuit is configured.

Note that the form shown in FIG. 13(b) is only an example. Whether to use a chip capacitor or a chip inductor for the chip components 51, 52, how to electrically connect the signal line 11 and the ground line 12 via the chip components 51, 52, or whether to use the chip components 51, 52 The number of chips (for example, whether to omit the chip component 51 or the chip component 52) is determined depending on the purpose of impedance matching, and is selected as appropriate.

For example, unlike the L-type matching circuit shown in FIG. Alternatively, a bandpass circuit in which the chip component 51 is not provided may be configured. Further, a plurality of matching circuits may be provided.

Note that the chip component 52 may be provided to electrically connect the signal line and the ground layer. For example, it may be provided to electrically connect the signal line 11 and the ground layer 17 or the signal line 11 and the ground layer 26.

Next, with reference to FIG. 14, a method for manufacturing a bonded printed wiring board according to this embodiment will be described.

First, as shown in FIG. 14(1), printed wiring boards 10 and 20 having locally thinned bonding areas are prepared. A printed wiring board 20 having a bonding area narrower than that of the printed wiring board 10 is prepared.

Next, as shown in FIG. 14(1), an anisotropic conductive material 31 is temporarily pressed onto the exposed surface 14a of the printed wiring board 10.

Next, as shown in FIG. 14(2), the chip components 51 and 52 are aligned using a mounter, and the printed wiring board 20 is aligned using a pin guide or the like. Thereafter, as shown in FIG. 13(a), the protective layers 41 and 42 are laminated onto the printed wiring boards 10 and 20, and the anisotropic conductive material 31 is finally crimped. As a result, a bonded printed wiring board shown in FIG. 13(a) is obtained.

Note that the anisotropic conductive material 31 may be permanently crimped before laminating the protective layers 41 and 42.

In addition, in the above description, the chip components 51 and 52 and the printed wiring board 20 are crimped together, but they may be crimped separately. For example, after the chip components 51 and 52 are crimped, the printed wiring board 20 is crimped. Further, the chip component 51 and the chip component 52 may be crimped together or separately.

As shown in FIG. 13A, in this embodiment, there is a gap between the protective layer 42 and the chip components 51 and 52. Note that a molding material may be provided to fill the gap. Further, the gap may be filled with an adhesive attached to the protective layer 42. The same applies to the modified examples described below.

According to the third embodiment described above, the effects described in the first embodiment can be obtained. In addition, since a matching circuit is provided in the cavity, impedance matching (antenna matching) can be achieved when an antenna is connected to the bonded printed wiring board.

Furthermore, since the chip components constituting the matching circuit are mounted within the cavity, the matching circuit can be provided without increasing the thickness of the bonded portion.

Furthermore, since the matching circuit is provided inside the bonded printed wiring board, physical damage to the matching circuit can be prevented.

(Modification of third embodiment)
A modification of the third embodiment will be described with reference to FIG. 15. FIG. 15 is a longitudinal cross-sectional view along the signal line of the bonded printed wiring board according to this modification. In this modification, the outer ground layers 16 and 27 and the ground layers 17 and 26 are electrically connected to each other in the third embodiment. It can also be said that chip components 51 and 52 are provided in the second embodiment.

The bonded printed wiring board according to this modification further includes a protective layer 41 that is provided across printed wiring boards 10 and 20 and covers ground layer 16 and ground layer 27. This protective layer 41 has an opening 41a through which the ground layer 16 is exposed and an opening 41b through which the ground layer 27 is exposed. In this embodiment, a conductive material 34 is provided as the first connection portion to electrically connect the ground layer 16 exposed in the opening 41a and the ground layer 27 exposed in the opening 41b.

Similarly, the bonded printed wiring board according to the present embodiment further includes a protective layer 42 that is provided across the printed wiring boards 10 and 20 and covers the ground layer 17 and the ground layer 26. This protective layer 42 has an opening 42a through which the ground layer 17 is exposed and an opening 42b through which the ground layer 26 is exposed. In this embodiment, a conductive material 35 is provided as the second connection portion to electrically connect the ground layer 17 exposed in the opening 42a and the ground layer 26 exposed in the opening 42b.

In this embodiment, the conductive materials 34, 35 are copper shields. Note that solder, conductive paste, or conductive adhesive film may be used as the conductive materials 34 and 35.

Note that only one of the first connection part and the second connection part may be provided.

Regarding the lower protective layer, similarly to the first embodiment, protective layers 18 and 29 may be provided on the printed wiring boards 10 and 20, and openings may be provided in each of the protective layers 18 and 29, and these may be connected using a conductive material. . For the upper protective layer, the chip components 51 and 52 are filled with a non-conductive material such as a molding material, the protective layers 19 and 28 are provided on the printed wiring boards 10 and 20, openings are provided in each, and the connections are made with a conductive material. may be done.

Furthermore, similarly to the modification of the second embodiment, the first connection part and the second connection part may be formed of metal foil and an anisotropic conductive material. At this time, in order to prevent a short circuit between the anisotropic conductive material of the second connection part, which is the upper connection part, and the chip parts 51, 52, the chip parts 51, 52 are filled with a non-conductive material such as a molding material. You can.

According to this embodiment, in addition to obtaining the effects of the third embodiment, it is possible to avoid the effects of the second embodiment, that is, impedance mismatch due to return current.

(Fourth embodiment)
A bonded printed wiring board according to a fourth embodiment will be described with reference to FIG. 16. FIG. 16(1) is a plan view of the bonded printed wiring board according to this embodiment before bonding, and FIG. 16(2) is a plan view of the bonded printed wiring board after bonding.

In this embodiment, the inductance component of the characteristic impedance in the junction region is adjusted by adjusting the path (detour path) through which the return current flows.

As shown in FIG. 16(1), in the printed wiring board 10 according to the present embodiment, the distance between the signal line 11 and the ground line 12 becomes smaller toward the end exposed on the exposed surface (joint surface) 14a. It has a spreading shape. Specifically, the interval between the signal line 11 and the ground line 12 is the interval X in most parts, but it widens to the interval Y, which is larger than the interval X, at the end of the printed wiring board 10. For example, the spacing X is 150 μm and the spacing Y is 500 μm. Note that the sizes of the interval X and the interval Y may be adjusted as appropriate so as to obtain desired inductance and capacitance components.

The same applies to the printed wiring board 20. That is, the interval between the signal line 21 and the ground line 22 has a shape in which the interval increases toward the end exposed to the exposed surface (joint surface) 24a.

In this embodiment, the ground lines 12 and 22 are broken lines at the starting point where the width changes, but they may be curved lines. Further, the starting point at which the width changes may be exposed on the exposed surfaces (joint surfaces) 14a, 24a.

As shown in FIG. 16(1), an interlayer connection portion 15 is provided at the end of the ground line 12. Interlayer connection portion 15 electrically connects ground line 12 and ground layer 16 . Similarly, an interlayer connection portion 25 is provided at the end of the ground line 22 . Interlayer connection portion 25 electrically connects ground line 22 and ground layer 26 . In this embodiment, as shown in FIG. 16(2), interlayer connecting portions 15 and 25 are provided facing each other so as to overlap when viewed in the thickness direction of the bonded printed wiring board. Note that the present invention is not limited to this, and the interlayer connection portion 15 and the interlayer connection portion 25 may be provided so as not to overlap.

In this embodiment, both printed wiring boards 10 and 20 have a microstrip line structure. Therefore, instead of the protective layers 19 and 29, protective layers 19A and 29A are provided. More specifically, printed wiring board 10 does not have insulating layer 13b, ground layer 17, and protective layer 19, and instead of adhesive layer 13c, protective layer 19A is provided at the same position as adhesive layer 13c. Similarly, in the case of the printed wiring board 20, a protective layer 29A is provided.

As described above, in this embodiment, by increasing the distance between the signal line 11 and the ground line 12 (the signal line 21 and the ground line 22) in the bonding region, the return current is reduced compared to the first embodiment. The signal lines 10 and 20 are configured to flow at positions relatively far from the signal lines 11 and 21. This increases the inductance component. According to this embodiment, the inductance component can be adjusted without using a chip inductor.

Note that this embodiment is not limited to the case where microstrip line structures are joined together. It may be a connection between a microstripline structure and a stripline structure, or a connection between stripline structures.

(Modification 1 of the fourth embodiment)
Modification 1 of the fourth embodiment will be described with reference to FIG. 17. FIG. 17 is a plan view of the bonded printed wiring board according to this modification before bonding. In this modification, the exposed surface (joint surface) 24a of the printed wiring board 20 is intentionally made larger than that of the fourth embodiment.

As shown in FIG. 17, the exposed surface (joint surface) 24a of the printed wiring board 20 has an overlap portion W where the ends of the signal line 21 and the ground line 22 are not formed. The ground layer 26 is also formed in the overlap portion W.

In this embodiment, the overlap portion W is provided so as to overlap the protective layer 19A of the printed wiring board 10.

According to this embodiment, by providing the overlap portion W, the overlap between the signal line 11 of the printed wiring board 10 and the ground layer 26 becomes large, and as a result, the capacitance component of the characteristic impedance can be increased. Thereby, the capacitance component can be adjusted without using a chip capacitor.

Note that the thickness of the insulating layer 23a of the printed wiring board 20 may be greater than the thickness of the insulating layer 13a of the printed wiring board 10. Thereby, the effect of adjusting the capacitance component by the overlap portion W can be enhanced.

(Modification 2 of the fourth embodiment)
Modification 2 of the fourth embodiment will be described with reference to FIG. 18. FIG. 18 is a plan view of the printed wiring board 10 according to this modification before bonding.

In the printed wiring board 10 of the bonded printed wiring board according to this modification, the ground line 12 has a shape that partially approaches the signal line 11. Specifically, as shown in FIG. 18, it has a region where the interval Z is narrower than the interval X. This increases the capacitance component of the characteristic impedance. Thereby, the capacitance component can be adjusted without using a chip capacitor.

Note that the shape of the approaching portion is not limited to that shown in FIG. For example, the interval between the signal line 11 and the ground line 12 is narrowed from the interval Y at the end of the printed wiring board 10 to the interval X, and after a region where the interval X is maintained is provided, it is narrowed from the interval X to the interval Z. It's okay to be. Moreover, although the ground lines 12 and 22 are broken lines at the starting point where the width changes, they may also be curved lines.

Based on the above description, those skilled in the art may be able to imagine additional effects and various modifications of the present invention, but aspects of the present invention are not limited to the individual embodiments described above. . Components from different embodiments may be combined as appropriate. Various additions, changes, and partial deletions are possible without departing from the conceptual idea and gist of the present invention derived from the content defined in the claims and equivalents thereof.

1 Bonded printed wiring boards 10, 20 Printed wiring boards 11, 21 Signal lines 12, 22 Ground lines 13, 23 Insulating substrates 13a, 13b, 23a, 23b Insulating layers 13c, 23c Adhesive layers 14, 24 Bonding areas 14a, 24a Exposure Surfaces 15, 25 Interlayer connections 16, 17, 26, 27 Ground layers 18, 19, 19A, 28, 29, 29A Protective layers 18a, 19a, 28a, 29a Openings 31, 32, 33 Anisotropic conductive material 34, 35 Conductive material 36, 37 Metal foil 41, 42 Protective layer 51, 52 Chip component 100 Single-sided metal foil clad laminate 110, 210 Insulating layer 120, 220, 230 Metal foil 120a Pad 120b Ground layer 130 Adhesive layer 140, 240 Protection Layer 140a, 240a Opening 200 Double-sided metal foil clad laminate 220a Signal line 220b Ground line 300 Printed wiring board 310, 320 Via 330 Plated through hole 410 Opening line 420 Opening H1, H2 Via hole H3 Through hole

Claims (15)

a first printed wiring board having a first signal line, a pair of first ground lines sandwiching the first signal line, and a first insulating substrate;
a second printed wiring board having a second signal line, a pair of second ground lines sandwiching the second signal line, and a second insulating substrate;
The first signal line is provided in the first insulating substrate, and has an end exposed at a first exposed surface of a locally thinned portion of the first insulating substrate, and/or , the second signal line is provided in the second insulating substrate, and an end portion thereof is exposed on a second exposed surface of a locally thinned portion of the second insulating substrate;
The first printed wiring board and the second printed wiring board are joined such that an end of the first signal line and an end of the second signal line face each other and are electrically connected. It is a bonded printed wiring board. The first insulating substrate of the first printed wiring board is
a first insulating layer having a first main surface on which the first signal line is provided and a second main surface opposite to the first main surface;
a third main surface opposite to the first main surface; and a fourth main surface opposite to the third main surface, the first insulating surface except for the first exposed surface. a second insulating layer laminated in layers;
including;
a first ground layer is provided on the second main surface,
a second ground layer is provided on the fourth main surface,
The second insulating substrate of the second printed wiring board is
a third insulating layer having a fifth main surface on which the second signal line is provided, and a sixth main surface opposite to the fifth main surface;
a seventh main surface opposite to the fifth main surface; and an eighth main surface opposite to the seventh main surface, and the third insulating surface except for the second exposed surface a fourth insulating layer stacked in layers;
including;
a third ground layer is provided on the sixth main surface,
a fourth ground layer is provided on the eighth main surface,
The first ground line is provided on the first main surface and electrically connected to the first ground layer and/or the second ground layer,
The bonded print according to claim 1, wherein the second ground line is provided on the fifth main surface and electrically connected to the third ground layer and/or the fourth ground layer. wiring board. a first connection part that electrically connects the first ground layer and the fourth ground layer; and/or a second connection part that electrically connects the second ground layer and the third ground layer. The bonded printed wiring board according to claim 2, further comprising a connecting portion. A first ground layer that covers the first ground layer and the fourth ground layer and has a first opening through which the first ground layer is exposed and a second opening through which the fourth ground layer is exposed. a protective layer of
A second ground layer that covers the second ground layer and the third ground layer and has a third opening through which the second ground layer is exposed and a fourth opening through which the third ground layer is exposed. a protective layer of
Equipped with
The first connection portion includes a conductive material that electrically connects the first ground layer exposed in the first opening and the fourth ground layer exposed in the second opening. ,
The second connection portion includes a conductive material that electrically connects the second ground layer exposed in the third opening and the third ground layer exposed in the fourth opening. The bonded printed wiring board according to claim 3. The first connection portion includes a first metal foil and a first anisotropic layer that is supported by the first metal foil and electrically connects the first ground layer and the fourth ground layer. having a conductive material;
The second connection portion includes a second metal foil and a second anisotropic layer that is supported by the second metal foil and electrically connects the second ground layer and the third ground layer. The bonded printed wiring board according to claim 3, comprising a conductive material. The bonded printed wiring according to claim 5, wherein the first signal line and the second signal line are electrically connected through the same material as the first and second anisotropic conductive materials. Board. The first signal line is provided in the first insulating substrate, includes a first signal line portion whose end portion is exposed on the first exposed surface, and a first signal line portion provided on the first exposed surface, and includes a first signal line portion whose end portion is exposed on the first exposed surface, has an exposed second signal line portion,
The bonded printed wiring board according to claim 1, wherein the first signal line portion and the second signal line portion are electrically connected via a chip component. The bonded printed wiring board according to any one of claims 1 to 6, wherein the first signal line and the first ground line are electrically connected via a chip component on the first exposed surface. . a first printed wiring board having a first signal line, a pair of first ground lines sandwiching the first signal line, and a first insulating substrate;
a second printed wiring board having a second signal line, a pair of second ground lines sandwiching the second signal line, and a second insulating substrate;
The first printed wiring board and the second printed wiring board have a first joint surface where the end of the first signal line is located and a second joint surface where the end of the second signal line is located. the first signal line and the second signal line are electrically connected,
In the bonded printed wiring board, the first ground line has a shape in which a distance from the first signal line increases toward an end of the first printed wiring board. 10. The bonded printed wiring board according to claim 9, wherein the first ground line has a shape that partially approaches the first signal line. The first ground line extends longer than the first signal line toward the end of the first insulating substrate, and connects the end of the first ground line with the first insulating substrate. The bonded printed wiring board according to claim 1 or 9, further comprising an interlayer connection portion that electrically connects the first ground layer provided on the outside. The bonded printed wiring board according to claim 1 or 9, wherein the first printed wiring board and/or the second printed wiring board are flexible printed wiring boards. 13. The bonded printed wiring board according to claim 12, wherein the insulating layer of the flexible printed wiring board includes a liquid crystal polymer, a fluorine-based material, or a polyimide-based material. One of the first printed wiring board and the second printed wiring board is connected to an antenna module including an antenna and an antenna board, and the other is mounted with a semiconductor chip that performs information processing based on a signal received by the antenna. The bonded printed wiring board according to claim 1 or 9, wherein the bonded printed wiring board is connected to a main board that is connected to a main board. preparing a first printed wiring board having a first signal line, a pair of first ground lines sandwiching the first signal line, and a first insulating substrate;
preparing a second printed wiring board having a second signal line, a pair of second ground lines sandwiching the second signal line, and a second insulating substrate;
The first signal line is provided in the first insulating substrate, and has an end exposed at a first exposed surface of a locally thinned portion of the first insulating substrate, and/or , the second signal line is provided in the second insulating substrate, and an end thereof is exposed on a second exposed surface of a locally thinned portion of the second insulating substrate;
The first printed wiring board and the second printed wiring board are joined such that the end of the first signal line and the end of the second signal line face each other and are electrically connected. A method for manufacturing a bonded printed wiring board, comprising the steps of:

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