High-frequency signal transmission line and electronic device

Abstract

A high-frequency signal transmission line (101) comprises: a resin laminate part in which a first resin layer and a second resin layer are laminated; a signal conductor pattern formed on the first resin layer; and a ground conductor layer formed on the first resin layer. In the resin laminate part, a first opening portion is formed in the first resin layer at a position along the signal conductor pattern, and a second opening portion overlapping the first opening portion is formed in the second resin layer. Thus, a hollow portion is formed in the resin laminate part at the first opening portion or the second opening portion. The opening width of the second opening portion is smaller than the opening width of the first opening portion. The second opening portion has a part where the opening width thereof is larger than the line width of the signal conductor pattern. The second resin layer has a lower dielectric constant or a lower dielectric loss tangent than the first resin layer.

Description

High-frequency signal transmission lines and electronic devices

[0001] The present invention relates to a high-frequency signal transmission line and an electronic device including the same.

[0002] Patent Document 1 discloses a transmission line with a suspended structure in which a signal line is formed in a resin layer and hollow portions are formed above and below the signal line, and the side of the adhesive layer in contact with the hollow portion is configured to have a concave shape.

[0003] International Publication No. 2022 / 113591

[0004] In the high-frequency signal transmission line described in Patent Document 1, the through-hole (hollow portion) in the adhesive layer and the through-hole (hollow portion) in the base layer are the same size, so if the adhesive layer and the base layer are misaligned, a partial non-overlapping portion will occur, resulting in a decrease in the strength and electrical characteristics of the high-frequency signal transmission line. Furthermore, it is difficult to process them into a high-frequency signal transmission line of the same dimensions.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a high-frequency signal transmission line that maintains high strength in the resin laminated portion and the hollow portion and has stable electrical characteristics, and an electronic device equipped with the same.

[0006] a signal conductor pattern disposed so as to be in contact with at least one of the first resin layers; and a ground conductor layer disposed so as to be in contact with at least one of the first resin layers; wherein a first opening is formed in at least one of the first resin layers at a position along the signal conductor pattern, and a second opening overlapping the first opening is formed in at least one of the second resin layers, so that a hollow portion is formed in the resin laminate portion by the first opening or the second opening; an opening width of the second opening is smaller than that of the first opening; and a portion of the opening width of the second opening is wider than the line width of the signal conductor pattern; and the second resin layer has a lower dielectric constant or a lower dielectric tangent than the first resin layer.

[0007] According to the present invention, even if there is misalignment between the adhesive layer and the base material layer, a decrease in the bonding area between them can be suppressed, and a decrease in the bonding strength between them can be prevented. As a result, the strength of the resin laminate portion and the hollow portion can be maintained high, and a high-frequency signal transmission line with stable electrical characteristics and an electronic device equipped with the same can be obtained.

[0008] FIG. 1 is a plan view of a high-frequency signal transmission line 101 according to the first embodiment. The upper part of FIG. 2 is a vertical cross-sectional view taken along dashed-dotted line A-A in FIG. 2, and the lower part of FIG. 2 is a vertical cross-sectional view taken along dashed-dotted line B-B in FIG. 1. FIG. 3 is an exploded plan view of the layers of the high-frequency signal transmission line 101 shown in FIG. 1 before pressure and heat pressing during manufacturing. FIG. 4 is a cross-sectional view showing a state of lamination misalignment of the resin layers in the high-frequency signal transmission line according to the first embodiment. FIG. 5 is a cross-sectional view of a high-frequency signal transmission line 102A according to the second embodiment. FIG. 6 is a cross-sectional view of another high-frequency signal transmission line 102B according to the second embodiment. FIG. 7 is a cross-sectional view of a high-frequency signal transmission line 103 according to the third embodiment. FIG. 8 is a cross-sectional view of a high-frequency signal transmission line 104 according to the fourth embodiment. FIG. 9 is a cross-sectional view of a high-frequency signal transmission line 105 according to the fifth embodiment. FIG. 10 is a vertical cross-sectional view of a high-frequency signal transmission line 106 according to the sixth embodiment. FIG. 11 is a longitudinal sectional view of a high-frequency signal transmission line 107 according to the seventh preferred embodiment. The upper part of FIG. 12 is a sectional view of a high-frequency signal transmission line 108A according to the eighth preferred embodiment. The lower part of FIG. 12 is a sectional view of a high-frequency signal transmission line 108B according to the eighth preferred embodiment. The upper part of FIG. 13 is a longitudinal sectional view of a high-frequency signal transmission line 109A according to the ninth preferred embodiment. The lower part of FIG. 13 is a longitudinal sectional view of a high-frequency signal transmission line 109B according to the ninth preferred embodiment. FIG. 14 is a plan view of high-frequency signal transmission lines 110A, 110B, and 110C according to the tenth preferred embodiment. The upper part of FIG. 15 is a sectional view of a high-frequency signal transmission line 111 according to the eleventh preferred embodiment. The lower part of FIG. 15 is a sectional view of the high-frequency signal transmission line 110 showing the electric field distribution due to electric force lines. FIG. 16 is a longitudinal sectional view of a high-frequency signal transmission line 112 according to the twelfth preferred embodiment.

[0009] Hereinafter, several specific examples will be given with reference to the drawings to illustrate multiple embodiments for carrying out the present invention. The same reference numerals are used for the same parts in each drawing. For ease of explanation and understanding of the main points, the embodiments are shown divided into multiple embodiments for convenience of explanation, but partial substitution or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, a description of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0010] First Embodiment In the first embodiment, an example of a strip line type high frequency signal transmission line will be described.

[0011] Fig. 1 is a plan view of a high-frequency signal transmission line 101 according to a first embodiment. The upper part of Fig. 2 is a vertical cross-sectional view taken along dashed-dotted line A-A in Fig. 2, and the lower part of Fig. 2 is a vertical cross-sectional view taken along dashed-dotted line B-B in Fig. 1. Note that in the cross-sectional view, lines that appear in the cross section (appearing due to cutting) are depicted, and lines that exist behind the cross section are not shown. This also applies to each embodiment described later.

[0012] 1 shows a single high-frequency signal transmission line 101, a large number of continuous high-frequency signal transmission lines are manufactured in the planar direction up to the final manufacturing process, and are then separated into individual high-frequency signal transmission lines in the final manufacturing process. This also applies to the following embodiments.

[0013] The high-frequency signal transmission line 101 includes an upper resin laminate portion 31, a lower resin laminate portion 32, a signal conductor pattern 4, a first ground conductor layer 51, a second ground conductor layer 52, and a ground conductor pattern 5C. The ground conductor pattern 5C is electrically connected to the first ground conductor layer 51 and the second ground conductor layer 52 via an interlayer connection conductor 5V.

[0014] The upper resin laminate portion 31 is a portion where the first resin layers 11, 12, and 13 and the second resin layers 21 and 22 are laminated. The lower resin laminate portion 32 is a portion where the first resin layer 13 and the second resin layer 22 are laminated. The signal conductor pattern 4 and the ground conductor pattern 5C are formed on the upper surface of the first resin layer 11. A first ground conductor layer 51 is laminated on the upper surface of the upper first resin layer 13. A second ground conductor layer 52 is laminated on the lower surface of the lower first resin layer 13. That is, the signal conductor pattern 4 is disposed between the first ground conductor layer 51 and the second ground conductor layer 52, with the resin laminate portions 31 and 32 sandwiched between them.

[0015] 2, the second resin layer 22 located at the top of the hollow portion HP has an opening that is continuous with the opening of the first resin layer 12. Similarly, the second resin layer 22 located at the bottom of the hollow portion HP has an opening that is continuous with the opening of the first resin layer 11.

[0016] FIG. 3 is an exploded plan view of the layers of the high-frequency signal transmission line 101 shown in FIG. 1 before pressure and heat pressing during manufacturing.

[0017] A first opening OH1 is formed in the first resin layers 11 and 12. A second opening OH2 is formed in the second resin layers 21 and 22. A second opening OH2 is also formed in the lower second resin layer 22. In terms of shape in the drawing, these openings are circular when viewed in the stacking direction of the first resin layers 11, 12, and 13 and the second resin layers 21 and 22.

[0018] In this way, a circular first opening OH1 is formed in the first resin layers 11, 12, and 13, and a circular second opening OH2 is formed in the upper second resin layers 21 and 22 and the lower second resin layer 22, thereby providing a hollow portion HP at these openings.

[0019] The opening width of the second opening OH2 formed in the second resin layers 21 and 22 is smaller than the opening width of the first opening OH1 formed in the first resin layer 12, and the opening width of the second opening OH2 has a portion wider than the line width of the signal conductor pattern 4. That is, in this embodiment, the diameter of the second opening OH2 is larger than the line width of the signal conductor pattern 4.

[0020] In this invention, not limited to this embodiment, the term "stacking direction" does not refer to the direction of the stacking order of the layers during manufacturing, but rather refers to the direction of stacking of the layers in the state shown in the drawing.

[0021] 1 , the high-frequency signal transmission line 101 has six hollow portions HP. That is, the signal conductor pattern 4 passes through the hollow portions HP at six locations. The high-frequency signal transmission line 101 functions as a strip line consisting of the signal conductor pattern 4, the first ground conductor layer 51, the second ground conductor layer 52, the upper resin laminate portion 31, the lower resin laminate portion 32, and the hollow portions HP.

[0022] If the distance between adjacent hollow portions HP is less than 1 / 4 wavelength of the transmission signal, the periodic change in characteristic impedance caused by the change in relative dielectric constant around the signal conductor pattern 4 does not pose a problem.

[0023] As shown in the upper part of Figure 1, a signal conductor pattern terminal 4T, which is separated from the first ground conductor layer 51, is formed on the upper surface of the upper resin laminate portion 31. The end of the signal conductor pattern 4 is connected to the signal conductor pattern terminal 4T via an interlayer connection conductor. A coaxial connector 61 is mounted on the upper signal conductor pattern terminal 4T, and a coaxial connector 62 is mounted on the lower signal conductor pattern terminal 4T. In this way, the high-frequency signal transmission line 101 is used as a transmission line with coaxial connectors on both ends. The coaxial connectors 61 and 62 in Figure 1 indicate their mounting positions.

[0024] The signal conductor pattern 4, the first ground conductor layer 51, and the second ground conductor layer 52 are all made of, for example, copper foil. The first resin layers 11, 12, and 13 are made of, for example, polyimide, liquid crystal polymer, or epoxy resin. The second resin layers 21 and 22 are made of, for example, thermoplastic polyimide, fluorine-based resin, or polyolefin-based resin. Examples of polyolefin-based resins include styrene, polyethylene, and polypropylene. The second resin layers 21 and 22 act as adhesive layers that bond adjacent first resin layers of the first resin layers 11, 12, and 13 together.

[0025] The flexibility of the second resin layers 21 and 22 at room temperature is greater than the flexibility of the first resin layers 11, 12, and 13. Here, room temperature is, for example, 25° C. or room temperature.

[0026] For example, the Young's modulus of the second resin layers 21 and 22 is 1 MPa or less, and the Young's modulus of the first resin layers 11, 12, and 13 is 2 MPa or more.

[0027] It is also preferable that the second resin layers 21, 22 have high fluidity during processing. They may be fluid, bond part of the end face (inner end face) of the opening, and then harden. The second resin layers 21, 22 may be made of a prepreg material used for interlayer bonding, for example.

[0028] The second resin layer has a lower dielectric constant than the first resin layer. For example, the second resin layers 21 and 22 have a dielectric constant of 2.2 to 2.8, and the first resin layers 11, 12, and 13 have a dielectric constant of 2.8 to 4.0.

[0029] The dielectric loss tangent of the second resin layer is lower than that of the first resin layer. For example, the dielectric loss tangent of the second resin layers 21 and 22 is 0.0005 to 0.003, and the dielectric loss tangent of the first resin layers 11, 12, and 13 is 0.002 to 0.01.

[0030] It is to be noted that either the relative dielectric constant or the dielectric loss tangent may satisfy the above relationship.

[0031] 4 is a cross-sectional view showing a state in which the resin layers are misaligned in the high-frequency signal transmission line of this embodiment, the cross-sectional position of which corresponds to the cross-sectional position shown in the upper part of FIG.

[0032] As shown in FIG. 4, even if the lamination positions of the resin layers are shifted, the probability of there being a portion where the first resin layers 11 and 12 do not overlap with the second resin layers 21, 22, and 22 is reduced.

[0033] According to this embodiment, even if there is a misalignment between the second resin layers 21 and 22 as adhesive layers and the first resin layers 11, 12, and 13 as base layers, a decrease in the adhesive area between them is suppressed, and a decrease in adhesive strength between them can be prevented. This results in a high-frequency signal transmission line 101 that maintains high strength in the resin laminate portion and the hollow portion. Furthermore, the electrical characteristics of the high-frequency signal transmission line are stably maintained.

[0034] Furthermore, since the opening width of the second opening formed in the second resin layer 21 in contact with the upper part of the first resin layer 11 is wider than the line width of the signal conductor pattern 4, the signal conductor pattern 4 is less affected by the second resin layer 21.

[0035] Since a predetermined amount of misalignment of the lamination positions of the resin layers is permitted, processing into a high-frequency signal transmission line is easy.

[0036] Furthermore, since the second resin layers 21 and 22 have a lower dielectric constant or a lower dielectric loss tangent than the first resin layers 11, 12, and 13, the dielectric loss due to the second resin layers is small even if the second resin layers 21 and 22 protrude from the openings OH by a large amount. Furthermore, although the protrusion amount of the second resin layers 21 and 22 from the openings OH is not necessarily constant, the change in the dielectric loss due to the change in the protrusion amount is small.

[0037] In the example shown in Figure 1, the upper resin laminate portion 31 is formed by laminating three first resin layers 11, 12, and 13 and two second resin layers 21 and 22, and the lower resin laminate portion 32 is formed by laminating one lower first resin layer 13 and one lower second resin layer 22, but the number of first resin layers and second resin layers is not limited to this.

[0038] Second Embodiment In a second embodiment, a high-frequency signal transmission line will be illustrated in which the positions of the openings of the resin layers forming the hollow portion HP are different from those in the example shown in the first embodiment.

[0039] 5 is a cross-sectional view of a high-frequency signal transmission line 102A according to the second preferred embodiment of the present invention, taken at a position corresponding to the upper portion of FIG.

[0040] The high-frequency signal transmission line 102A of the second embodiment includes an upper resin laminate portion 31, a lower resin laminate portion 32, a signal conductor pattern 4, a first ground conductor layer 51, a second ground conductor layer 52, and a ground conductor pattern 5C. The ground conductor pattern 5C is electrically connected to the first ground conductor layer 51 and the second ground conductor layer 52 via an interlayer connection conductor (the interlayer connection conductor 5V shown in the first embodiment).

[0041] A circular first opening is formed in the first resin layers 11 and 12, and a circular second opening is formed in the second resin layer 21, whereby a hollow portion HP is provided by these openings.

[0042] The opening width of the second opening formed in the second resin layer 21 is smaller than the opening width of the first opening formed in the first resin layers 11 and 12, and the opening width of the second opening has a portion wider than the line width of the signal conductor pattern 4.

[0043] 5 , non-penetrating portions NTP are formed in the upper and lower second resin layers 22. In other words, the second resin layer 22 at the top of the hollow portion HP does not have an opening that is continuous with the opening of the first resin layer 12. Similarly, the second resin layer 22 located at the bottom of the hollow portion HP does not have an opening that is continuous with the opening of the first resin layer 11.

[0044] According to this embodiment, the second resin layers 22, 22 serving as adhesive layers are disposed above and below the hollow portion HP, so there is no reduction in the adhesive surface due to misalignment between the second resin layers 22, 22 and the first resin layers 13, 13 serving as base layers. In other words, the second resin layers 22, 22 and the outer first resin layers 13, 13 are always bonded over a wide area, so there is no reduction in strength due to misalignment of the resin layers.

[0045] Fig. 6 is a cross-sectional view of another high-frequency signal transmission line 102B according to the second embodiment. In the high-frequency signal transmission line 102A shown in Fig. 5, the layers above and below the hollow portion HP are both second resin layers 22, 22, but in the high-frequency signal transmission line 102B shown in Fig. 6, the second resin layer 22 is disposed as an adhesive layer above the hollow portion HP, and the second resin layer 22 below the hollow portion HP has an opening that is continuous with the opening of the first resin layer 11.

[0046] In this way, the upper and lower portions of the hollow portion HP may have openings formed in the second resin layer, which ensures the volume of the hollow portion HP and prevents a decrease in the adhesive strength between the second resin layer and the first resin layer due to misalignment between the two layers.

[0047] Third Embodiment In a third embodiment, a high-frequency signal transmission line in which the shape of the second resin layer formed by processing is different from that of the embodiments described so far will be described.

[0048] FIG. 7 is a cross-sectional view of a high-frequency signal transmission line 103 according to the third preferred embodiment.

[0049] The high-frequency signal transmission line 103 of the third embodiment includes an upper resin laminate portion 31, a lower resin laminate portion 32, a signal conductor pattern 4, a first ground conductor layer 51, a second ground conductor layer 52, and a ground conductor pattern 5C. The ground conductor pattern 5C is electrically connected to the first ground conductor layer 51 and the second ground conductor layer 52 via an interlayer connection conductor (the interlayer connection conductor 5V shown in the first embodiment).

[0050] A circular first opening is formed in the first resin layers 11 and 12, and a circular second opening is formed in the second resin layer 21, whereby a hollow portion HP is provided by these openings.

[0051] The opening width of the second opening formed in the second resin layer 21 is smaller than the opening width of the first opening formed in the first resin layers 11 and 12, and the opening width of the second opening has a portion wider than the line width of the signal conductor pattern 4.

[0052] In this embodiment, as shown in FIG. 7, the second resin layer 21 protrudes into the openings of the first resin layers 11 and 12, so that the second resin layer 21 and the second resin layer 22 are continuous within the hollow portion HP.

[0053] According to this embodiment, the second resin layer 21 and the upper second resin layer 22, which are adhesive layers, are bonded to the entire end face (inner surface) of the opening of the first resin layer 12 in the thickness direction, thereby increasing the adhesive strength between the second resin layers 21 and 22 and the first resin layer 12. This more effectively increases the strength of the hollow portion HP.

[0054] Fourth Embodiment In a fourth embodiment, a high-frequency signal transmission line will be illustrated in which the shape of a first resin layer supporting a signal conductor pattern is different from that of the embodiments described so far.

[0055] FIG. 8 is a cross-sectional view of a high-frequency signal transmission line 104 according to the fourth preferred embodiment.

[0056] The high-frequency signal transmission line 104 includes an upper resin laminate portion 31, a lower resin laminate portion 32, a signal conductor pattern 4, a first ground conductor layer 51, a second ground conductor layer 52, and a ground conductor pattern 5C.

[0057] The upper resin laminate portion 31 is a portion where the first resin layers 11, 12, and 13 and the second resin layers 21 and 22 are laminated. The lower resin laminate portion 32 is a portion where the first resin layers 12 and 13 and the second resin layers 22 and 23 are laminated.

[0058] The signal conductor pattern 4 and the ground conductor pattern 5C are formed on the upper surface of the first resin layer 11. A first ground conductor layer 51 is laminated on the upper surface of the upper first resin layer 13. Furthermore, a second ground conductor layer 52 is laminated on the lower surface of the lower first resin layer 13.

[0059] Circular openings are formed in the upper first resin layer 12 and the upper second resin layers 21 and 22. Circular openings are also formed in the lower first resin layer 12 and the lower second resin layers 22 and 23.

[0060] The other structures are the same as those of the high-frequency signal transmission line shown in the first embodiment.

[0061] According to this embodiment, the presence of the first resin layer 11 that continuously supports the signal conductor traces 4 makes it possible to easily increase the strength of the signal conductor traces 4 .

[0062] Fifth Embodiment In a fifth embodiment, a high-frequency signal transmission line having a hollow portion HP only on either the top or bottom of a signal conductor pattern will be exemplified.

[0063] FIG. 9 is a cross-sectional view of a high-frequency signal transmission line 105 according to the fifth preferred embodiment.

[0064] The high-frequency signal transmission line 105 includes an upper resin laminate portion 31, a lower resin laminate portion 32, a signal conductor pattern 4, a first ground conductor layer 51, a second ground conductor layer 52, and a ground conductor pattern 5C.

[0065] The signal conductor pattern 4 and the ground conductor pattern 5C are formed on the upper surface of the first resin layer 11. A first ground conductor layer 51 is laminated on the upper surface of the upper first resin layer 13. Furthermore, a second ground conductor layer 52 is laminated on the lower surface of the lower first resin layer 13.

[0066] Circular openings are formed in the upper first resin layer 12 and the upper second resin layers 21 and 22. No openings are formed in the lower first resin layer 13 and the lower second resin layer 22.

[0067] According to this embodiment, since there is no hollow portion above or below the signal conductor pattern 4, a high-strength high-frequency signal transmission line can be obtained in the hollow portion HP and in the entire high-frequency signal transmission line 105.

[0068] Sixth Embodiment In a sixth embodiment, a high-frequency signal transmission line including a single ground conductor layer will be illustrated.

[0069] FIG. 10 is a vertical cross-sectional view of a high-frequency signal transmission line 106 according to the sixth preferred embodiment.

[0070] The high-frequency signal transmission line 106 includes a resin laminate portion 3 , a signal conductor pattern 4 , and a ground conductor layer 5 .

[0071] The resin laminated portion 3 is a portion where the first resin layers 11, 12, and 13 and the second resin layers 21 and 22 are laminated. The signal conductor pattern 4 is formed on the upper surface of the first resin layer 11. The ground conductor layer 5 is laminated on the upper surface of the first resin layer 13. That is, the signal conductor pattern 4 and the ground conductor layer 5 face each other with part of the resin laminated portion 3 sandwiched therebetween.

[0072] Circular openings are formed in the first resin layer 12 and the second resin layers 21 and 22. In terms of shape in the drawing, these openings are circular when viewed in the stacking direction of the first resin layers 11, 12, and 13 and the second resin layers 21 and 22.

[0073] A circular first opening is formed in the first resin layer 12, and circular second openings are formed in the second resin layers 21 and 22, so that a hollow portion HP is provided by these openings.

[0074] The opening width of the second opening formed in the second resin layers (21, 22) is smaller than the opening width of the first opening formed in the first resin layer (12), and the opening width of the second opening has a portion wider than the line width of the signal conductor pattern (4).

[0075] As exemplified in this embodiment, the present invention can also be applied to a microstrip line type high frequency signal transmission line.

[0076] Seventh Embodiment In a seventh embodiment, another high-frequency signal transmission line including a single ground conductor layer will be illustrated.

[0077] FIG. 11 is a vertical cross-sectional view of a high-frequency signal transmission line 107 according to the seventh preferred embodiment.

[0078] The high-frequency signal transmission line 107 includes a resin laminate portion 3 , a signal conductor pattern 4 , and ground conductor layers 52 and 53 .

[0079] The resin laminate portion 3 is a portion where first resin layers 11, 12, and 13 and second resin layers 21, 22, and 23 are laminated. A signal conductor pattern 4 is formed on the upper surface of the first resin layer 11. A third ground conductor layer 53 is also formed on the upper surface of the first resin layer 11 along the signal conductor pattern 4. A second ground conductor layer 52 is laminated on the lower surface of the first resin layer 13. That is, the signal conductor pattern 4 and the second ground conductor layer 52 face each other with part of the resin laminate portion 3 in between, and the third ground conductor layers 53 are arranged on both sides of the signal conductor pattern 4.

[0080] A circular first opening is formed in the first resin layer 12, and circular second openings are formed in the second resin layers 22 and 23, so that a hollow portion HP is provided by these openings.

[0081] The opening width of the second opening formed in the second resin layer (22, 23) is smaller than the opening width of the first opening formed in the first resin layer (12), and the opening width of the second opening has a portion wider than the line width of the signal conductor pattern (4).

[0082] The present invention can also be applied to a high-frequency signal transmission line of the type exemplified in this embodiment.

[0083] Eighth Embodiment In an eighth embodiment, a high-frequency signal transmission line will be illustrated in which the positional relationship between the hollow portion and the interlayer connection conductor and the structure of the interlayer connection conductor are different from those of the examples shown so far.

[0084] 12 is a cross-sectional view of a high-frequency signal transmission line 108A according to the eighth embodiment. In this example, the cross-sectional view is taken along a line passing through the hollow portion HP and two interlayer connection conductors 5V sandwiching the hollow portion HP. The high-frequency signal transmission line 108A includes an upper resin laminate portion 31, a lower resin laminate portion 32, a signal conductor pattern 4, a first ground conductor layer 51, a second ground conductor layer 52, a ground conductor pattern 5C, and an interlayer connection conductor 5V.

[0085] The interlayer connection conductor 5V is formed by forming an opening that exposes the ground conductor pattern 5C on the outer surface of the laminate formed by laminating the above-mentioned resin layers using laser processing, and then depositing a copper plating film inside this opening.

[0086] 12 shows a cross-sectional view of a high-frequency signal transmission line 108B according to the eighth embodiment. This example also shows a cross-sectional view taken along a line passing through two interlayer connection conductors 5V sandwiching a hollow portion HP and the hollow portion HP. In this high-frequency signal transmission line 108B, the interlayer connection conductor 5V is formed by filling with a conductor openings formed in the resin layers between the first ground conductor layer 51 and the ground conductor pattern 5C of the high-frequency signal transmission line 107A, and the interlayer connection conductor 5V is formed by filling with a conductor openings formed in the resin layers between the second ground conductor layer 52 and the ground conductor pattern 5C.

[0087] Ninth Embodiment In a ninth embodiment, a high-frequency signal transmission line having a protective film on its outer surface will be exemplified.

[0088] 13 is a longitudinal sectional view of a high-frequency signal transmission line 109A according to the ninth embodiment. The high-frequency signal transmission line 109A is configured by forming a resist film on the high-frequency signal transmission line 104 shown in FIG.

[0089] 13 is a longitudinal sectional view of a high-frequency signal transmission line 109B according to the ninth embodiment, which is configured by forming a resist film on the high-frequency signal transmission line 104 shown in FIG.

[0090] The resist film RF shown in FIG. 13 is a resist film obtained by applying a resist resin to the front and back surfaces of the high-frequency signal transmission line 104 shown in FIG. 8 and then hardening it.

[0091] In this way, by providing the resist film RF on the outer surface, the stress applied to the high-frequency signal transmission lines 109A and 109B from the outside is alleviated by the resist film RF, and a decrease in strength of the high-frequency signal transmission lines due to the presence of the hollow portion HP is suppressed.

[0092] In particular, in the high-frequency signal transmission line 109B, even if some external object abuts against it, the stress received by the resist film RF is concentrated on the interlayer connection conductor 5V, so that the hollow portion HP is effectively protected.

[0093] Tenth Embodiment In a tenth embodiment, a high-frequency signal transmission line will be illustrated in which the positional relationship between the hollow portion and the interlayer connection conductor and the structure of the interlayer connection conductor are different from those of the examples shown so far.

[0094] 14 is a plan view of high-frequency signal transmission lines 110A, 110B, and 110C according to the tenth embodiment. Each of the high-frequency signal transmission lines 110A, 110B, and 110C includes a first ground conductor layer 51, a ground conductor pattern 51C, a signal conductor pattern terminal 4T, multiple hollow portions HP, and multiple interlayer connection conductors 5V. The internal structure is the same as that shown in the first embodiment. The second ground conductor layer 52 overlaps the first ground conductor layer 51 in the plan view. When viewed in the stacking direction of the resin layers, the interlayer connection conductors 5V adjacent to the hollow portions HP are positioned to straddle the hollow portions HP, so that the interlayer connection conductors 5V are located adjacent to the hollow portions HP.

[0095] The high-frequency signal transmission lines 110A, 110B, and 110C differ in the arrangement of the interlayer connection conductors 5V. Both the high-frequency signal transmission lines 110B and 110C have fewer interlayer connection conductors than the example shown in FIG. 1. In the high-frequency signal transmission line 110A, the interlayer connection conductors 5V are arranged on both sides of the hollow portion HP when viewed in the stacking direction of the resins. In the high-frequency signal transmission line 110A, the interlayer connection conductors 5V are located in close proximity to each hollow portion HP, so the strength of the hollow portion HP can be effectively increased by the interlayer connection conductors 5V.

[0096] Eleventh Embodiment In an eleventh embodiment, a high-frequency signal transmission line in which the top and bottom of a resin laminate are recessed will be exemplified.

[0097] The upper part of Fig. 15 is a cross-sectional view of a high-frequency signal transmission line 111 according to the eleventh embodiment. The lower part of Fig. 15 is a cross-sectional view of the high-frequency signal transmission line 111, showing the electric field distribution caused by electric field lines. This high-frequency signal transmission line 111 includes an upper resin laminate portion 31, a lower resin laminate portion 32, a signal conductor pattern 4, a first ground conductor layer 51, a second ground conductor layer 52, and a ground conductor pattern 5C. The other basic structure is similar to that of the high-frequency signal transmission line 104 shown in Fig. 8.

[0098] The lower part of Fig. 15 is a cross-sectional view of the high-frequency signal transmission line 111 according to this embodiment, taken at the same location as the upper part of Fig. 15. The arrows protruding from the signal conductor pattern 4 in the lower part of Fig. 15 are noteworthy electric field lines. As such, an electric field is generated between the signal conductor pattern 4 and the first ground conductor layer 51, and between the signal conductor pattern 4 and the second ground conductor layer 52. As shown in this figure, the electric field lines from the signal conductor pattern 4 to the first ground conductor layer 51 and the second ground conductor layer 52 become longer as they approach both ends of the signal conductor pattern 4, i.e., as they move away from the center of the signal conductor pattern 4.

[0099] Although the current density of the signal conductor pattern 4 increases closer to both ends due to the edge effect (skin effect) of the conductor, the above-described configuration reduces the electric field strength closer to both ends of the signal conductor pattern 4, averaging the current distribution in the signal conductor pattern 4. As a result, the conductor loss due to the signal conductor pattern 4 is mitigated.

[0100] Twelfth Embodiment In a twelfth embodiment, a high-frequency signal transmission line having a structure on the upper and lower outer surfaces of a hollow portion different from the examples shown so far will be described.

[0101] 16 is a longitudinal cross-sectional view of a high-frequency signal transmission line 112 according to a twelfth embodiment. In this example, when viewed in the stacking direction of the layers, the plating thickness of the first ground conductor layer 51 and the second ground conductor layer 52 is increased in regions that overlap the hollow portion HP to form thickened portions TF. The plating of these regions may be performed simultaneously with the plating for forming the interlayer connection conductors 5V.

[0102] According to this embodiment, the strength of the laminate above and below the hollow portion HP is effectively increased, which makes it possible to more effectively suppress deformation of the hollow portion HP.

[0103] Thirteenth Embodiment In the thirteenth embodiment, an electronic device will be exemplified.

[0104] The high-frequency signal transmission line of the present invention can be used as a high-frequency signal transmission line in various electronic devices. For example, connectors are provided on high-frequency circuits formed on two circuit boards, and coaxial connectors 61 and 62 of the high-frequency signal transmission line 101 shown in Figure 1 are connected to each other. The circuit boards and high-frequency signal transmission line 101 are housed in a housing of a predetermined shape. In this way, an electronic device is constructed.

[0105] Finally, the present invention is not limited to the above-described embodiments. Those skilled in the art can make appropriate modifications and variations. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention includes modifications and variations from the embodiments within the scope of the claims and their equivalents.

[0106] For example, in each of the above-described embodiments, examples have been formed in which both the first resin layer and the second resin layer have a plurality of layers, but the first resin layer or the second resin layer may be a single layer.

[0107] Although the high-frequency signal transmission line has been described in each embodiment as having a single signal conductor pattern, it may also have a plurality of signal conductor patterns, which may be arranged in the layer direction of the resin layers or in the stacking direction of the resin layers.

[0108] In addition, in each embodiment, the high-frequency signal transmission line has a rectangular shape when viewed from the lamination direction of the resin layers, but this shape is arbitrary.

[0109] In addition, in each embodiment, a high-frequency signal transmission line having a linear signal conductor pattern is shown, but when viewed from the stacking direction of each resin layer, the signal conductor pattern may be curved or partially curved.

[0110] In addition, although the high-frequency signal transmission line has been illustrated as being planar in each embodiment, the lamination surface of each resin layer may be a curved surface such as a cylindrical surface, or a partially curved surface.Furthermore, for example, the entire surface or a portion thereof may be a twisted curved surface.

[0111] The high-frequency signal transmission line and electronic device of the present invention may be provided in the following aspects.

[0112] <1> A high-frequency signal transmission line comprising: a resin laminate portion in which one or more first resin layers and one or more second resin layers are laminated; a signal conductor pattern arranged to be in contact with at least one of the first resin layers; and a ground conductor layer arranged to be in contact with at least one of the first resin layers; wherein a first opening is formed in at least one of the first resin layers in the resin laminate portion at a position along the signal conductor pattern, and a second opening overlapping the first opening is formed in at least one of the second resin layers, so that a hollow portion is formed in the resin laminate portion by the first opening or the second opening; an opening width of the second opening is smaller than that of the first opening; and a width of the second opening has a portion wider than the line width of the signal conductor pattern; and the second resin layer has a lower dielectric constant or a lower dielectric loss tangent than the first resin layer.

[0113] <2> The high-frequency signal transmission line according to <1>, wherein the ground conductor layer is composed of at least two ground conductor layers facing the signal conductor pattern with a part or all of the resin laminate portion sandwiched therebetween.

[0114] <3> The high-frequency signal transmission line according to <1> or <2>, wherein the second resin layers at the top and bottom of the hollow portion have the second openings that are continuous with the first openings of the first resin layer.

[0115] <4> The high-frequency signal transmission line according to <1> or <2>, wherein the second resin layers at the top and bottom of the hollow portion do not have openings that are continuous with the first opening of the first resin layer.

[0116] <5> The high-frequency signal transmission line according to any one of <1> to <4>, wherein the signal conductor pattern has a portion in the second opening that does not contact the first resin layer and the second resin layer in a direction perpendicular to the stacking direction.

[0117] <6> The high-frequency signal transmission line according to any one of <1> to <5>, further comprising an interlayer connection conductor formed in the resin laminate portion and electrically connected to the ground conductor layer, the interlayer connection conductor having a protruding portion that protrudes from the ground conductor layer to an outside of the resin laminate portion.

[0118] <7> The high-frequency signal transmission line according to <6>, further comprising a third resin layer on an outer surface of the resin laminated portion, the third resin layer covering the protruding portion.

[0119] <8> The high-frequency signal transmission line according to any one of <1> to <7>, wherein the resin laminated portion is recessed in the direction of lamination in the vicinity of the hollow portion compared to a distant portion.

[0120] <9> The high-frequency signal transmission line according to any one of <1> to <8>, wherein the first resin layer is polyimide, a liquid crystal polymer, or an epoxy resin, and the second resin layer is thermoplastic polyimide, a fluorine-based resin, or a polyolefin-based resin.

[0121] <10> The high-frequency signal transmission line according to any one of <1> to <9>, wherein the resin laminated portion is configured in a first lamination direction relative to the signal conductor pattern and a second lamination direction opposite to the first lamination direction.

[0122] <11> An electronic device comprising the high-frequency signal transmission line according to any one of <1> to <10>.

[0123] HP...hollow portion NTP...non-penetrating portion OH...opening OH1...first opening OH2...second opening RF...resist film TF...thickened portion 3...resin laminated portion 4...signal conductor pattern 4T...signal conductor pattern terminal 5...ground conductor layer 5C...ground conductor pattern 5V...interlayer connecting conductor 11, 12, 13...first resin layer 21, 22, 22...second resin layer 31...upper resin laminated portion 32...lower resin laminated portion 51...first ground conductor layer 51C...ground conductor pattern 52...second ground conductor layer 53...ground conductor layer 61, 62...coaxial connector 101, 102A, 102B, 103 to 107, 108A, 108B, 109A, 109B, 110A, 110B, 110C, 111, 112...high frequency signal transmission line

Claims

1. A high-frequency signal transmission line comprising: a resin laminate section in which a single or multiple first resin layers and a single or multiple second resin layers are laminated; a signal conductor pattern arranged so as to be in contact with at least a single first resin layer of the first resin layers; and a ground conductor layer arranged so as to be in contact with at least a single first resin layer of the first resin layers, wherein a first opening is formed in at least a single first resin layer of the first resin layers at a position along the signal conductor pattern in the resin laminate section, and a second opening overlapping the first opening is formed in at least a single second resin layer of the second resin layers, thereby forming a hollow section in the resin laminate section at the first opening or the second opening, an opening width of the second opening is smaller than that of the first opening, and a width of the second opening has a portion wider than the line width of the signal conductor pattern, and the second resin layer has a lower dielectric constant or a lower dielectric tangent than the first resin layer.

2. The high-frequency signal transmission line according to claim 1, wherein the ground conductor layer is composed of at least two ground conductor layers facing the signal conductor pattern with part or all of the resin laminate portion sandwiched therebetween.

3. The high-frequency signal transmission line according to claim 1 or 2, wherein the second resin layer at the top and bottom of the hollow portion has the second opening that is continuous with the first opening of the first resin layer.

4. The high-frequency signal transmission line according to claim 1 or 2, wherein the second resin layer at the top and bottom of the hollow portion does not have an opening that is continuous with the first opening of the first resin layer.

5. A high-frequency signal transmission line as described in any one of claims 1 to 4, wherein the signal conductor pattern has a portion in the second opening that does not contact the first resin layer and the second resin layer in a direction perpendicular to the stacking direction.

6. A high-frequency signal transmission line as claimed in any one of claims 1 to 5, further comprising an interlayer connection conductor formed in the resin laminate portion and electrically connected to the ground conductor layer, the interlayer connection conductor having a protruding portion protruding from the ground conductor layer to an outside of the resin laminate portion.

7. The high-frequency signal transmission line according to claim 6, further comprising a third resin layer on an outer surface of the resin laminate portion to cover the protruding portion.

8. The high-frequency signal transmission line according to claim 1, wherein the resin laminate portion is recessed in the direction of lamination in the vicinity of the hollow portion compared to the distant portion.

9. The high-frequency signal transmission line according to any one of claims 1 to 8, wherein the first resin layer is a polyimide, a liquid crystal polymer or an epoxy resin, and the second resin layer is a thermoplastic polyimide, a fluorine-based resin or a polyolefin-based resin.

10. A high-frequency signal transmission line as claimed in any one of claims 1 to 9, wherein the resin laminated portion is configured in a first lamination direction relative to the signal conductor pattern and a second lamination direction that is opposite to the first lamination direction.

11. An electronic device comprising the high-frequency signal transmission line according to any one of claims 1 to 10.

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