High-frequency signal transmission line and electronic device

Abstract

A high-frequency signal transmission line (101) comprises: a resin laminate part (3) in which first resin layers (11, 12, 13) and second resin layers (21, 22) are laminated; a signal conductor pattern (4) formed on the first resin layer (11); and a ground conductor layer (5) that faces the signal conductor pattern (4) across part or all of the resin laminate part (3). The Young's modulus of the second resin layers (21, 22) is lower than the Young's modulus of the first resin layers (11, 12, 13). In the resin laminate part (3), an opening is formed at least in the first resin layer (12) at a position along the signal conductor pattern (4), so that a hollow part (HP) is provided in the resin laminate part (3) at said opening.

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. It also discloses a structure in which a resin layer is disposed between the upper hollow portion and an upper ground conductor layer, and a resin layer is disposed between the lower hollow portion and the lower ground conductor layer.

[0003] International Publication No. 2022 / 114092

[0004] In the high-frequency signal transmission line described in Patent Document 1, the hollow portion not filled with resin is easily deformed when stress is applied from the outside. This can cause deformation of the ground conductor layer near the hollow portion. For example, when stress exceeding a specified value is applied from the outside of the high-frequency signal transmission line toward the hollow portion, the ground conductor layer recesses toward the hollow portion. Such deformation of the ground conductor layer near the hollow portion can degrade electrical characteristics.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a high-frequency signal transmission line having improved resistance to externally applied stress and stable electrical characteristics, and an electronic device equipped with the same.

[0006] As an example of a high-frequency signal transmission line disclosed herein, the high-frequency signal transmission line includes a ground conductor layer, a first resin layer, a second resin layer, and a signal conductor pattern, wherein the ground conductor layer, the first resin layer, the second resin layer, and the signal conductor pattern are stacked in this order, a hollow space is present between the signal conductor pattern and the second resin layer in the stacking direction, the first resin layer and the second resin layer are made of different materials, and the Young's modulus of the second resin layer is lower than the Young's modulus of the first resin layer.

[0007] According to the present invention, a high-frequency signal transmission line having high resistance to externally applied stress and stable electrical characteristics, and an electronic device including the same, can be obtained.

[0008] The upper part of Fig. 1 is a plan view of the high-frequency signal transmission line 101 according to the first embodiment, and the lower part of Fig. 1 is a vertical cross-sectional view of the dashed-dotted line portion in the upper part of Fig. 1. Fig. 2 is a diagram showing stress near the hollow portion HP when stress is applied from outside the high-frequency signal transmission line 101. The upper part of Fig. 3 is a partial plan view of the high-frequency signal transmission line 102 according to the second embodiment, and the lower part of Fig. 3 is a vertical cross-sectional view of the dashed-dotted line portion in the upper part of Fig. 3. The upper part of Fig. 4 is a plan view of the high-frequency signal transmission line 103 according to the third embodiment, and the lower part of Fig. 4 is a vertical cross-sectional view of the dashed-dotted line portion in the upper part of Fig. 4. The upper part of Fig. 5 is a plan view of the high-frequency signal transmission line 104 according to the fourth embodiment, and the lower part of Fig. 5 is a vertical cross-sectional view of the dashed-dotted line portion in the upper part of Fig. 5. Fig. 6 is a plan view of the high-frequency signal transmission line 104 before the layers constituting the line are stacked. FIG. 7 is a cross-sectional view of the high-frequency signal transmission line 104 taken along the dashed-dotted line in FIG. 6 before the layers constituting the line are laminated. FIG. 8 is a diagram showing stress in the vicinity of the hollow portion HP when stress is applied from outside the line. The upper part of FIG. 9 is a partial plan view of the high-frequency signal transmission line 104 according to the fourth embodiment during the manufacturing process, and the lower part of FIG. 9 is a vertical cross-sectional view of the dashed-dotted line in the upper part of FIG. 9. FIG. 10 is a cross-sectional view of the high-frequency signal transmission line 104. FIG. 11 is a vertical cross-sectional view of the high-frequency signal transmission line 105 according to the fifth embodiment. FIG. 12 is a vertical cross-sectional view of the high-frequency signal transmission line 106 according to the sixth embodiment. FIG. 13 is a vertical cross-sectional view of the high-frequency signal transmission line 107 according to the seventh embodiment. FIG. 14 is a vertical cross-sectional view of the high-frequency signal transmission line 108 according to the eighth embodiment. FIG. 15 is a cross-sectional view showing a manufacturing process of the high-frequency signal transmission line 108. Fig. 16 is a longitudinal sectional view of a high-frequency signal transmission line 108A configured by forming a resist film on the high-frequency signal transmission line 108 shown in Fig. 14. Fig. 17 is a longitudinal sectional view of a high-frequency signal transmission line 109 according to the ninth 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 microstrip line type high-frequency signal transmission line will be described.

[0011] The upper part of Fig. 1 is a plan view of the high-frequency signal transmission line 101 according to the first embodiment, and the lower part of Fig. 1 is a vertical cross-sectional view of the dashed line portion in the upper part of Fig. 1. Note that in the cross-sectional view, lines that appear in the cross section (appearing due to cutting) are drawn, 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 a resin laminate portion 3 , a signal conductor pattern 4 , and a ground conductor layer 5 .

[0014] 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.

[0015] A circular opening is formed in the first resin layer 12 and the second resin layer 21. In terms of shape in the drawing, this opening is circular when viewed in the stacking direction of the first resin layers 11, 12, and 13 and the second resin layers 21 and 22.

[0016] In this way, an opening is formed in the first resin layer 12 of the resin laminate portion 3 at a position along the signal conductor pattern 4, and this opening provides a hollow portion HP in the resin laminate portion 3. In particular, in this embodiment, a hollow portion HP is formed in which the first resin layer 12 and the second resin layer 22 do not contact the signal conductor pattern 4.

[0017] In this way, the high-frequency signal transmission line 101 includes a ground conductor layer 5, a first resin layer 13, a second resin layer 22, and a signal conductor pattern 4, and the ground conductor layer 5, the first resin layer 13, the second resin layer 22, and the signal conductor pattern 4 are stacked in this order, and a hollow portion HP exists between the signal conductor pattern 4 and the second resin layer 22 in this stacking direction.

[0018] 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.

[0019] 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 microstrip line consisting of the signal conductor pattern 4, the ground conductor layer 5, a part of the resin laminate portion 3, and the hollow portions HP.

[0020] If the spacing between the hollow portions HP is less than a quarter wavelength of the transmission signal, the periodic change in the characteristic impedance caused by the change in the relative dielectric constant around the signal conductor pattern 4 does not pose a problem.

[0021] 1, a signal conductor pattern terminal 4T, which is separated from the ground conductor layer 5, is formed on the upper surface of the resin laminate portion 3. 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.

[0022] The signal conductor pattern 4 and the ground conductor layer 5 are both made of, for example, copper foil. 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 resin include styrene, polyethylene, and polypropylene. 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 act as adhesive layers that bond adjacent first resin layers 11, 12, and 13 together. That is, the first resin layer 13 and the second resin layer 22 are made of different materials.

[0023] The Young's modulus of the second resin layers 21 and 22 is lower than that of the first resin layers 11, 12, and 13. For example, the Young's modulus of the second resin layers 21 and 22 is 1 GPa or less, and the Young's modulus of the first resin layers 11, 12, and 13 is 2 to 5 GPa. In other words, the Young's modulus of the second resin layer 22 is lower than that of the first resin layer 13.

[0024] "Young's modulus" is the ratio of stress to strain and is also expressed as "Young's modulus" or "modulus of longitudinal elasticity."

[0025] 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 2.0 to 2.5, and the first resin layers 11, 12, and 13 have a dielectric constant of 2.5 to 3.5. That is, the second resin layer 22 has a lower dielectric constant than the first resin layer 13.

[0026] 2 is a diagram showing stress near the hollow portion HP when stress is applied from outside the high-frequency signal transmission line 101. When stress EF is applied from outside the high-frequency signal transmission line 101 toward the hollow portion HP, the first resin layer 13, which is located outward from the hollow portion and has a relatively high Young's modulus, distributes the stress over a wide area. The first resin layer 12 located below the second resin layer 22 receives weak stress distributed by the second resin layer 22. As a result, the second resin layer 22 absorbs the stress, thereby suppressing deformation such as bending or denting of the ground conductor layer 5. Therefore, the distance between the ground conductor layer 5 and the signal conductor pattern 4 remains stable.

[0027] To put it simply, the above-mentioned effect is that the stress received by the ground conductor layer 5 is dispersed by the first resin layer 13 having a high Young's modulus and absorbed by the second resin layer 22 having a low Young's modulus, thereby suppressing deformation of the ground conductor layer 5.

[0028] Furthermore, according to this embodiment, the dielectric loss is reduced due to the presence of the hollow portion HP around the signal conductor pattern of the high-frequency signal transmission line. That is, since the hollow portion HP is made of air, both the dielectric loss tangent and the dielectric constant are smaller than those of the resin of the resin laminate portion 3, and the dielectric loss of the high-frequency signal transmission line is reduced. This effect is the same in each of the embodiments described below.

[0029] For example, the signal conductor pattern 4 may be provided on the lower surface of the first resin layer 11 instead of the upper surface, so that the entire resin laminate portion 3 is sandwiched between the signal conductor pattern 4 and the ground conductor layer.

[0030] Second Embodiment In a second embodiment, an example of a high-frequency signal transmission line in which a ground conductor exists on the side of a signal conductor pattern will be described.

[0031] The upper part of FIG. 3 is a partial plan view of the high-frequency signal transmission line 102 according to the second preferred embodiment, and the lower part of FIG. 3 is a vertical cross-sectional view of the portion enclosed by the dashed dotted line in the upper part of FIG.

[0032] The high-frequency signal transmission line 102 includes a resin laminate portion 3, a signal conductor pattern 4, a ground conductor layer 5, a ground conductor pattern 5C, and an interlayer connection conductor 5V.

[0033] The resin laminate 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 and the ground conductor pattern 5C are 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 laminate portion 3 in between. In addition, interlayer connection conductors 5V are formed in the resin laminate portion 3. These interlayer connection conductors 5V electrically connect the ground conductor layer 5 and the ground conductor pattern 5C.

[0034] The first resin layer 12 and the second resin layer 21 have circular openings formed therein when viewed in the stacking direction of the first resin layers 11 , 12 , 13 and the second resin layers 21 , 22 .

[0035] In this way, an opening is formed in the first resin layer 12 of the resin laminate portion 3 at a position along the signal conductor pattern 4, and this opening provides a hollow portion HP in the resin laminate portion 3. In particular, in this embodiment, a hollow portion HP is formed in which the first resin layer 12 and the second resin layer 22 do not contact the signal conductor pattern 4.

[0036] 3, a plurality of hollow portions HP are formed in the high-frequency signal transmission line 102. In other words, the signal conductor pattern 4 passes through these hollow portions HP.

[0037] The signal conductor pattern 4, the ground conductor pattern 5C, and the ground conductor layer 5 are all made of, for example, copper foil. The materials of the first resin layers 11, 12, and 13 and the second resin layers 21 and 22 are the same as those in the first embodiment. The second resin layers 21 and 22 act as adhesive layers that bond adjacent first resin layers 11, 12, and 13 together.

[0038] As in the example shown in the first embodiment, the Young's modulus of the second resin layers 21 and 22 is lower than the Young's modulus of the first resin layers 11 , 12 , and 13 .

[0039] In the high-frequency signal transmission line 102 of this embodiment, similarly to the high-frequency signal transmission line 101 shown in the first embodiment, the ground conductor layer 5, the first resin layer 13, the second resin layer 22, and the signal conductor pattern 4 are stacked in this order, with a hollow portion HP being present between the signal conductor pattern 4 and the second resin layer 22 in this stacking direction, the first resin layer 13 and the second resin layer 22 being made of different materials, and the Young's modulus of the second resin layer 22 being lower than the Young's modulus of the first resin layer 13.

[0040] As described in the first embodiment, when stress is applied from outside the high-frequency signal transmission line 102, the stress near the hollow portion is suppressed, and deformation such as bending or denting of the ground conductor layer 5 is suppressed. Therefore, the gap between the ground conductor layer 5 and the signal conductor pattern 4 remains stable, and the electrical characteristics of the high-frequency signal transmission line can be kept constant.

[0041] Like the high-frequency signal transmission line 102 shown in this embodiment, the high-frequency signal transmission line of the present invention may further include a ground conductor layer (5C) in the line width direction of the signal conductor pattern (4).

[0042] Third Embodiment In a third embodiment, an example of a triplate stripline type high-frequency signal transmission line in which a hollow portion HP exists above a signal conductor pattern 4 will be described.

[0043] The upper part of FIG. 4 is a plan view of the high-frequency signal transmission line 103 according to the third embodiment, and the lower part of FIG. 4 is a vertical cross-sectional view of the portion enclosed by the dashed dotted line in the upper part of FIG.

[0044] The high-frequency signal transmission line 103 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.

[0045] The upper resin laminate portion 31 is a portion where the upper first resin layers 11, 12, 13 and the second resin layers 21, 22 are laminated. The lower resin laminate portion 32 is a portion where the lower first resin layer 13 and the lower second resin layer 22 are laminated. That is, the resin laminate portion is composed of the upper resin laminate portion 31 laminated in a first stacking direction SD1 of the stacking directions of the first resin layers and the second resin layers, and the lower resin laminate portion 32 configured in a second stacking direction SD2 that is the opposite direction to the first stacking direction SD1.

[0046] The signal conductor pattern 4 is 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 faces the first ground conductor layer 51 and the second ground conductor layer 52, with the upper resin laminate part 31 and the lower resin laminate part 32 sandwiched therebetween.

[0047] A circular opening is formed in the first resin layer 12 and the second resin layer 21. In terms of shape in the drawing, this opening is circular when viewed in the stacking direction of the first resin layers 11, 12, and 13 and the second resin layers 21 and 22.

[0048] In this way, an opening is formed in the first resin layer 12 of the upper resin laminate portion 31 at a position along the signal conductor pattern 4, and this opening provides a hollow portion HP in the upper resin laminate portion 31. In particular, in this embodiment, a hollow portion HP is formed in which the first resin layer 12 and the second resin layer 22 do not contact the signal conductor pattern 4.

[0049] In the high-frequency signal transmission line 103 of this embodiment, the first ground conductor layer 51, the upper first resin layer 13, the upper second resin layer 22, and the signal conductor pattern 4 are stacked in this order, and a hollow portion HP is present between the signal conductor pattern 4 and the upper second resin layer 22 in this stacking direction, the upper first resin layer 13 and the upper second resin layer 22 are made of different materials, and the Young's modulus of the upper second resin layer 22 is lower than the Young's modulus of the upper first resin layer 13.

[0050] 4 , the high-frequency signal transmission line 103 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 103 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.

[0051] In this embodiment, as in the first and second embodiments, when stress is applied from the outside of the high-frequency signal transmission line 103 toward the hollow portion HP, the first resin layer 13 on the outside, which has a relatively high Young's modulus, disperses the stress over a wide range, thereby suppressing deformation such as bending or denting of the first ground conductor layer 51. Therefore, the distance between the first ground conductor layer 51 and the signal conductor pattern 4 remains stable.

[0052] Fourth Embodiment In a fourth embodiment, an example of a stripline-type high-frequency signal transmission line in which hollow portions HP exist above and below a signal conductor pattern 4 will be described.

[0053] The upper part of Fig. 5 is a plan view of the high-frequency signal transmission line 104 according to the fourth embodiment, and the lower part of Fig. 5 is a vertical cross-sectional view of the dashed-dotted line portion in the upper part of Fig. 5. Fig. 6 is a plan view of the high-frequency signal transmission line 104 before the layers constituting the line are laminated. Fig. 7 is a cross-sectional view of the dashed-dotted line portion in Fig. 6 before the layers constituting the line 104 are laminated. Since Figs. 6 and 7 show the state before lamination, the interlayer connection conductor 5V described below does not appear in these figures.

[0054] The high-frequency signal transmission line 104 according to this 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, a ground conductor pattern 5C, and an interlayer connection conductor 5V.

[0055] The upper resin laminate portion 31 is a portion where the upper first resin layers 11, 12, 13 and the second resin layers 21, 22 are laminated. The lower resin laminate portion 32 is a portion where the lower first resin layer 13 and the lower second resin layer 22 are laminated. That is, the resin laminate portion is composed of the upper resin laminate portion 31 laminated in a first stacking direction SD1 of the stacking directions of the first resin layers and the second resin layers, and the lower resin laminate portion 32 laminated in a second stacking direction SD2 that is the opposite direction to the first stacking direction SD1.

[0056] The signal conductor pattern 4 is 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.

[0057] 6 and 7 , a first ground conductor layer 51 is formed on the upper first resin layer 13, and a second ground conductor layer 52 is formed on the lower first resin layer 13. A signal conductor pattern 4 and a ground conductor pattern 5C are formed on the first resin layer 11. Openings OH are formed in the upper first resin layer 12, the second resin layer 21, and the first resin layer 11.

[0058] By laminating the openings OH, hollow portions HP are formed in the signal conductor pattern 4, where the first resin layers 11, 12 and the second resin layer 22 do not come into contact with each other. As is clear from a comparison with the example shown in Fig. 4, there are portions of the signal conductor pattern 4 that do not come into contact with the first resin layer 11 either.

[0059] In the high-frequency signal transmission line 104 of this embodiment, the first ground conductor layer 51, the upper first resin layer 13, the upper second resin layer 22, and the signal conductor pattern 4 are laminated in this order, with a hollow portion HP between the signal conductor pattern 4 and the upper second resin layer 22 in the lamination direction. Similarly, the second ground conductor layer 52, the lower first resin layer 13, the lower second resin layer 22, and the signal conductor pattern 4 are laminated in this order, with a hollow portion HP between the signal conductor pattern 4 and the lower second resin layer 22 in the lamination direction. Furthermore, the upper first resin layer 13 and the upper second resin layer 22 are made of different materials, and the Young's modulus of the upper second resin layer 22 is lower than that of the upper first resin layer 13. Similarly, the lower first resin layer 13 and the lower second resin layer 22 are made of different materials, and the Young's modulus of the lower second resin layer 22 is lower than that of the lower first resin layer 13.

[0060] 5 , the high-frequency signal transmission line 104 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 104 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.

[0061] FIG. 8 is a diagram showing stress in the vicinity of the hollow portion HP when stress is applied from the outside of the high-frequency signal transmission line 104.

[0062] When stress EF is applied from the outside of the high-frequency signal transmission line 104 toward the hollow portion HP, the first resin layer 13, which has a relatively high Young's modulus and is located above and outside the hollow portion, distributes the stress over a wide area. The upper second resin layer 22 absorbs the stress. By absorbing the stress in this way, deformation such as bending and denting of the first ground conductor layer 51 is suppressed.

[0063] Similarly, the first resin layer 13, which is located on the lower outer side of the hollow portion HP and has a relatively high Young's modulus, distributes the stress over a wide area. The lower second resin layer 22 absorbs the stress. By absorbing the stress in this way, deformation such as bending or denting of the second ground conductor layer 52 is suppressed. Therefore, the distances between the first ground conductor layer 51 and the second ground conductor layer 52 and the signal conductor pattern 4 are kept stable.

[0064] The upper part of FIG. 9 is a partial plan view of the high-frequency signal transmission line 104 according to this embodiment at an intermediate stage of manufacture, and the lower part of FIG. 9 is a vertical cross-sectional view of the portion indicated by the dashed dotted line in the upper part of FIG.

[0065] 5 shows a single high-frequency signal transmission line 104, but in the intermediate stage of manufacturing such a single high-frequency signal transmission line 104, it is a continuation of a plurality of high-frequency signal transmission lines. The configuration of the high-frequency signal transmission line 104 unit is as already shown in FIG.

[0066] In FIG. 9, a laminate of resin layers, conductor layers, etc. is cut vertically and horizontally along chain double-dashed lines to separate it into a plurality of high-frequency signal transmission lines 104 .

[0067] 10 is a cross-sectional view showing the difference in electric field between the high-frequency signal transmission line 104 and a high-frequency signal transmission line as a comparative example. FIG. 10 is a cross-sectional view of the high-frequency signal transmission line 104 according to this embodiment.

[0068] In the high-frequency signal transmission line 104, the second resin layer 22, which has a lower relative dielectric constant than the first resin layer 13, is exposed over a wide area in the hollow portion HP. That is, the relative dielectric constant of the second resin layers 22, 22 located closer to the signal conductor pattern 4 in the stacking direction is lower than that of the first resin layers 13, 13, so that the dielectric loss due to the dielectric in areas with high electric field strength is reduced, thereby preventing deterioration of the transmission characteristics.

[0069] Fifth Embodiment In a fifth embodiment, an example of a stripline-type high-frequency signal transmission line in which hollow portions HP exist above and below the signal conductor pattern 4 will be described.

[0070] FIG. 11 is a vertical cross-sectional view of a high-frequency signal transmission line 105 according to the fifth preferred embodiment.

[0071] 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, a ground conductor pattern 5C, and an interlayer connection conductor 5V.

[0072] The upper resin laminate portion 31 is a portion where the upper first resin layers 11, 12, 13, 14 and the second resin layers 21, 22, 23 are laminated. The lower resin laminate portion 32 is a portion where the lower first resin layers 13, 14 and the lower second resin layers 22, 23 are laminated. That is, the resin laminate portion is composed of the upper resin laminate portion 31 laminated in a first stacking direction SD1 of the stacking directions of the first resin layers and the second resin layers, and the lower resin laminate portion 32 laminated in a second stacking direction SD2 that is the opposite direction to the first stacking direction SD1.

[0073] This high-frequency signal transmission line 105 is obtained by adding an upper first resin layer 14, a lower first resin layer 14, an upper second resin layer 23, and a lower second resin layer 23 to the high-frequency signal transmission line 104 shown in FIG. 5 in the fourth embodiment.

[0074] Circular openings are formed in the upper first resin layers 11, 12, and 13, the upper second resin layers 21 and 22, and the lower first resin layer 13 and second resin layer 22. These openings form hollow portions HP where the first resin layers 11, 12, and 13 and the second resin layer 22 do not contact the signal conductor pattern 4. As is clear from a comparison with the example shown in Fig. 4, there are portions of the signal conductor pattern 4 that do not contact the first resin layer 11 either.

[0075] The second resin layers 21, 22, and 23 act as adhesive layers that bond adjacent first resin layers among the first resin layers 11, 12, 13, and 14 to each other.

[0076] The Young's modulus of the second resin layers 21 , 22 , and 23 is lower than the Young's modulus of the first resin layers 11 , 12 , 13 , and 14 .

[0077] As described above, in the high-frequency signal transmission line 105 of this embodiment, the first ground conductor layer 51, the upper first resin layer 14, the upper second resin layer 23, and the signal conductor pattern 4 are laminated in this order, with a hollow portion HP between the signal conductor pattern 4 and the upper second resin layer 23 in the lamination direction. Similarly, the second ground conductor layer 52, the lower first resin layer 14, the lower second resin layer 23, and the signal conductor pattern 4 are laminated in this order, with a hollow portion HP between the signal conductor pattern 4 and the lower second resin layer 23 in the lamination direction. This hollow portion HP is continuous with the hollow portion HP. Furthermore, the upper first resin layer 14 and the upper second resin layer 23 are made of different materials, and the Young's modulus of the upper second resin layer 23 is lower than that of the upper first resin layer 14. Similarly, the lower first resin layer 14 and the lower second resin layer 23 are made of different materials, and the Young's modulus of the lower second resin layer 23 is lower than the Young's modulus of the lower first resin layer 14 .

[0078] According to the present embodiment, the stress acting on the first ground conductor layer 51 is dispersed by the upper first resin layer 14 having a high Young's modulus and absorbed by the upper second resin layer 23 having a low Young's modulus, thereby suppressing deformation of the first ground conductor layer 51. Similarly, the stress acting on the second ground conductor layer 52 is dispersed by the lower first resin layer 14 having a high Young's modulus and absorbed by the lower second resin layer 23 having a low Young's modulus, thereby suppressing deformation of the second ground conductor layer 52.

[0079] The present invention can also be applied to a high-frequency signal transmission line having three or more upper second resin layers 21, 22, 23 and two or more lower second resin layers 22, 23, as in this embodiment.

[0080] Sixth Embodiment In a sixth embodiment, an example of a stripline-type high-frequency signal transmission line in which a hollow portion HP exists above a signal conductor pattern 4 will be described.

[0081] FIG. 12 is a vertical cross-sectional view of a high-frequency signal transmission line 106 according to the sixth preferred embodiment.

[0082] The high-frequency signal transmission line 106 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.

[0083] The upper resin laminate portion 31 is a portion where the upper first resin layers 11, 12, 13, 14 and the second resin layers 21, 22, 23 are laminated. The lower resin laminate portion 32 is a portion where the lower first resin layers 13, 14 and the lower second resin layers 22, 23 are laminated. That is, the resin laminate portion is composed of the upper resin laminate portion 31 laminated in a first stacking direction SD1 of the stacking directions of the first resin layers and the second resin layers, and the lower resin laminate portion 32 configured in a second stacking direction SD2 that is the opposite direction to the first stacking direction SD1.

[0084] The upper first resin layers 12 and 13 and the upper second resin layer 22 each have a circular opening formed therein.

[0085] In this way, openings are formed in the first resin layers 12, 13 of the upper resin laminate portion 31 at positions along the signal conductor pattern 4, and these openings provide hollow portions HP in the upper resin laminate portion 31. In particular, in this embodiment, hollow portions HP are formed in which the first resin layer 12, the second resin layer 22, and the first resin layer 13 do not contact the signal conductor pattern 4.

[0086] The second resin layers 21, 22, and 23 act as adhesive layers that bond adjacent first resin layers among the first resin layers 11, 12, 13, and 14 to each other.

[0087] The Young's modulus of the second resin layers 21 , 22 , and 23 is lower than the Young's modulus of the first resin layers 11 , 12 , 13 , and 14 .

[0088] As described above, in the high-frequency signal transmission line 106 of this embodiment, the first ground conductor layer 51, the upper first resin layer 14, the upper second resin layer 23, and the signal conductor pattern 4 are stacked in this order, and a hollow portion HP is present between the signal conductor pattern 4 and the upper second resin layer 23 in this stacking direction, the upper first resin layer 14 and the upper second resin layer 23 are made of different materials, and the Young's modulus of the upper second resin layer 23 is lower than the Young's modulus of the upper first resin layer 14.

[0089] In this embodiment, the lower portion of the signal conductor pattern 4 is supported by the plurality of resin layers thereunder, so that the distance between the signal conductor pattern 4 and the second ground conductor layer 52 can be kept more stable.

[0090] The present invention can also be applied to a high-frequency signal transmission line having three or more second resin layers 21, 22, 23 and two or more second resin layers 22, 23, as in this embodiment.

[0091] Seventh Embodiment In the seventh embodiment, an example of a strip line type high-frequency signal transmission line is shown in which a hollow portion HP exists above the signal conductor pattern 4 and a hollow portion HP exists below the first resin layer 11 on which the signal conductor pattern is formed.

[0092] FIG. 13 is a vertical cross-sectional view of a high-frequency signal transmission line 107 according to the seventh preferred embodiment.

[0093] The high-frequency signal transmission line 107 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.

[0094] Circular openings are formed in the upper first resin layers 12 and 13 and the upper second resin layers 21 and 22. In this manner, openings are formed in the first resin layers 12 and 13 at positions along the signal conductor pattern 4 in the upper resin laminate portion 31, and thus hollow portions HP are provided in the upper resin laminate portion 31 at these openings.

[0095] Furthermore, circular openings are formed in the lower first resin layer 13 and the lower second resin layer 22. In this manner, openings are formed in the first resin layer 13 at lower positions along the signal conductor pattern 4 in the lower resin laminate portion 32, and thus hollow portions HP are provided in the lower resin laminate portion 32 at these openings.

[0096] The second resin layers 21, 22, and 23 act as adhesive layers that bond adjacent first resin layers among the first resin layers 11, 12, 13, and 14 to each other.

[0097] The Young's modulus of the second resin layers 21 , 22 , and 23 is lower than the Young's modulus of the first resin layers 11 , 12 , 13 , and 14 .

[0098] As described above, in the high-frequency signal transmission line 107 of this embodiment, the first ground conductor layer 51, the upper first resin layer 14, the upper second resin layer 23, and the signal conductor pattern 4 are laminated in this order, with a hollow portion HP between the signal conductor pattern 4 and the upper second resin layer 23 in the lamination direction. Similarly, the second ground conductor layer 52, the lower first resin layer 14, the lower second resin layer 23, and the signal conductor pattern 4 are laminated in this order, with a hollow portion HP between the signal conductor pattern 4 and the lower second resin layer 23 in the lamination direction. Furthermore, the upper first resin layer 14 and the upper second resin layer 23 are made of different materials, and the Young's modulus of the upper second resin layer 23 is lower than that of the upper first resin layer 14. Similarly, the lower first resin layer 14 and the lower second resin layer 23 are made of different materials, and the Young's modulus of the lower second resin layer 23 is lower than that of the lower first resin layer 14.

[0099] According to the present embodiment, the stress acting on the first ground conductor layer 51 is dispersed by the upper first resin layer 14 having a high Young's modulus and absorbed by the upper second resin layer 23 having a low Young's modulus, thereby suppressing deformation of the first ground conductor layer 51. Similarly, the stress acting on the second ground conductor layer 52 is dispersed by the lower first resin layer 14 having a high Young's modulus and absorbed by the lower second resin layer 23 having a low Young's modulus, thereby suppressing deformation of the second ground conductor layer 52.

[0100] Even if a hollow portion (the lower hollow portion HP in FIG. 13 ) is provided in which the signal conductor pattern 4 is not exposed as in this embodiment, deformation such as bending or denting of the second ground conductor layer 52 near the hollow portion due to external stress is suppressed.

[0101] Furthermore, in this embodiment, the signal conductor pattern 4 is supported by the first resin layer 11 even in areas where there is a hollow portion below, so the first resin layer 11 acts as a rigid layer, and the distance between the signal conductor pattern 4 and the first ground conductor layer 51 and the second ground conductor layer 52 can be kept more stable.

[0102] Eighth Embodiment In an eighth embodiment, a high-frequency signal transmission line having a protrusion on an interlayer connection conductor that electrically connects a first ground conductor layer and a second ground conductor layer will be described as an example.

[0103] 14 is a longitudinal sectional view of a high-frequency signal transmission line 108 according to the eighth preferred embodiment. The high-frequency signal transmission line 108 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.

[0104] In the high-frequency signal transmission line 104 shown in FIG. 5 , the interlayer connection conductor 5V is formed by forming a conductor plating film on the inner surface of an opening formed in each resin layer between the first ground conductor layer 51 and the ground conductor pattern 5C. However, in the high-frequency signal transmission line 108 shown in FIG. 14 , the interlayer connection conductor 5V is formed by filling with a conductor the opening formed in each resin layer between the first ground conductor layer 51 and the ground conductor pattern 5C, and the interlayer connection conductor 5V is formed by filling with a conductor the opening formed in each resin layer between the second ground conductor layer 52 and the ground conductor pattern 5C.

[0105] The upper interlayer connection conductor 5V that is electrically connected to the first ground conductor layer 51 has a protruding portion 5P that protrudes outward from the first ground conductor layer 51 in the first stacking direction SD1. The lower interlayer connection conductor 5V that is electrically connected to the second ground conductor layer 52 has a protruding portion 5P that protrudes outward from the second ground conductor layer 52 in the second stacking direction SD2.

[0106] Even if an external force is applied to this high-frequency signal transmission line 108 over a wide surface, the external force is received by the protrusion 5P, so that stress is not applied directly above the hollow portion HP, and deformation of the first ground conductor layer 51 above the hollow portion HP and the second ground conductor layer 52 below the hollow portion HP is effectively suppressed.

[0107] 15 is a cross-sectional view showing a manufacturing process of the high-frequency signal transmission line 108. In the process indicated by (1) in Fig. 15, a laminate of the first resin layers 11, 12, and 13, the second resin layers 21 and 22, the signal conductor pattern 4, the ground conductor pattern 5C, the first ground conductor layer 51, and the second ground conductor layer 52 is formed.

[0108] The first ground conductor layer 51 is attached to the upper first resin layer 13. The second ground conductor layer 52 is attached to the lower first resin layer 13. Openings for forming the hollow portion HP are formed in the first resin layers 11 and 12. The second resin layer 21 is applied to the upper surface of the first resin layer 11. The upper second resin layer 22 is applied to the lower surface of the upper first resin layer 13. The lower second resin layer 22 is applied to the upper surface of the lower first resin layer 13. These layers are stacked and heated and pressurized to form the laminate.

[0109] In the step indicated by (2) in FIG. 15, an opening H is formed on the outer surface of the laminate by laser processing to expose the ground conductor pattern 5C.

[0110] In the step indicated by (3) in FIG. 15, dry films DF are attached to both sides of the laminate, and openings larger in diameter than the openings H are formed in the dry films DF.

[0111] In the step shown in FIG. 15(4), copper filling plating (via fill plating) is applied to the inside of the opening H, filling the entire opening with copper.

[0112] In a subsequent step, the dry film DF is peeled off, thereby obtaining the high-frequency signal transmission line 108 shown in Fig. 14. Thereafter, the high-frequency signal transmission line 108 is separated into individual high-frequency signal transmission lines 108.

[0113] According to the present embodiment, even if an external force is applied to the high-frequency signal transmission line 108 over a wide area, no stress is applied directly above the hollow portion HP, and deformation of the first ground conductor layer 51 above the hollow portion HP and the second ground conductor layer 52 below the hollow portion HP is effectively suppressed.

[0114] Fig. 16 is a longitudinal cross-sectional view of a high-frequency signal transmission line 108A formed by forming a resist film on the high-frequency signal transmission line 108 shown in Fig. 14. The resist film RF shown in Fig. 16 is a resist film that is applied to the front and back surfaces of the high-frequency signal transmission line 108 shown in Fig. 14 and then hardened. Because the resist film RF protrudes at the protruding portions 5P of the interlayer connection conductor in this manner, even if an external force is applied to the high-frequency signal transmission line 108A over a wide area, no stress is applied directly above the hollow portion HP, and deformation of the first ground conductor layer 51 above the hollow portion HP and the second ground conductor layer 52 below the hollow portion HP is effectively suppressed.

[0115] Ninth Embodiment In a ninth embodiment, a high-frequency signal transmission line including a plurality of transmission lines will be illustrated.

[0116] 17 is a longitudinal sectional view of a high-frequency signal transmission line 109 according to the ninth preferred embodiment. The high-frequency signal transmission line 109 includes a resin laminate portion 3, signal conductor patterns 4 and 4A, a power supply conductor pattern 4B, a first ground conductor layer 51, a second ground conductor layer 52, and an interlayer connection conductor 5V.

[0117] 17 , two signal conductor patterns 4, 4A and a power supply conductor pattern 4B are arranged side by side in an area separated by a plurality of interlayer connection conductors 5V arranged in the Y direction. The signal conductor pattern 4, the first ground conductor layer 51, the second ground conductor layer 52, and the interlayer connection conductor 5V form a first high-frequency signal transmission line. The signal conductor pattern 4A, the first ground conductor layer 51, the second ground conductor layer 52, and the interlayer connection conductor 5V form a second high-frequency signal transmission line. The power supply conductor pattern 4B, the first ground conductor layer 51, the second ground conductor layer 52, and the interlayer connection conductor 5V form a power line.

[0118] For example, the first high-frequency signal transmission line is a line for transmitting RF signals in the 5G millimeter wave band, and the second high-frequency signal transmission line is a line for transmitting RF signals in the 5G Sub6 band. The power supply line is a DC power supply line for driving an IC. The power supply line may also be a low-frequency signal transmission line for transmitting, for example, near field communication (NFC) signals.

[0119] In this way, a high-frequency signal transmission line including a plurality of transmission lines or a high-frequency signal transmission line including a line for a direct current line may be configured.

[0120] Tenth Embodiment In a tenth embodiment, an electronic device will be exemplified.

[0121] 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 103 shown in Figure 4 are connected to each other. The circuit boards and high-frequency signal transmission line 103 are housed in a housing of a predetermined shape. In this way, an electronic device is constructed.

[0122] 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.

[0123] For example, in each embodiment, an example has been shown in which the hollow portion HP extends in both the up-down and left-right directions (X and Z directions) perpendicular to the direction in which the signal conductor pattern 4 extends (e.g., the Y direction in FIG. 1 ), but the present invention is not limited to this. For example, the hollow portion HP may extend only in the up-down direction (Z direction). Also, the hollow portion HP may extend only in the left-right direction (X direction).

[0124] Furthermore, in each embodiment, an example has been shown in which not only the first resin layer has a portion that does not contact the signal conductor pattern 4, but also the second resin layer 21 has a portion that does not contact the signal conductor pattern 4. However, the second resin layer 21 may be in contact with the signal conductor pattern 4. Since the second resin layer has a lower Young's modulus than the first resin layer, deformation of the ground conductor layer and the first resin layer is suppressed even when the second resin layer 21 is in contact with the signal conductor pattern 4. Furthermore, if the second resin layer has a lower relative permittivity than the first resin layer, spreading of the electric field between the signal conductor pattern 4 and the interlayer connection conductor 5V is suppressed even when the second resin layer 21 is in contact with the signal conductor pattern 4.

[0125] Furthermore, as already described, although a single high-frequency signal transmission line is shown in each embodiment, a large number of high-frequency signal transmission lines that are continuous in the planar direction may be manufactured up to the final manufacturing process, and then separated into individual high-frequency signal transmission lines in the final manufacturing process.

[0126] The high-frequency signal transmission line and electronic device of the present invention may be provided in the following aspects.

[0127] <1> A high-frequency signal transmission line comprising: a ground conductor layer, a first resin layer, a second resin layer, and a signal conductor pattern, wherein the ground conductor layer, the first resin layer, the second resin layer, and the signal conductor pattern are laminated in this order, a hollow portion is present between the signal conductor pattern and the second resin layer in the lamination direction, the first resin layer and the second resin layer are made of different materials, and the Young's modulus of the second resin layer is lower than the Young's modulus of the first resin layer.

[0128] <2> The high-frequency signal transmission line according to <1>, wherein the ground conductor layer is composed of a first ground conductor layer and a second ground conductor layer located on both sides of the signal conductor pattern in the stacking direction, and the first resin layer and the second resin layer are located on both sides of the signal conductor pattern in the stacking direction.

[0129] <3> The high-frequency signal transmission line according to <2>, further comprising an interlayer connection conductor that electrically connects the first ground conductor layer and the second ground conductor layer, and configured to include the first ground conductor layer, the second ground conductor layer, the signal conductor pattern, and the interlayer connection conductor.

[0130] <4> The high-frequency signal transmission line according to <3>, wherein the interlayer connection conductor has a protruding portion that protrudes outward from the first ground conductor layer and a protruding portion that protrudes outward from the second ground conductor layer.

[0131] <5> The high-frequency signal transmission line according to any one of <1> to <4>, wherein the hollow portion expands in all directions perpendicular to the direction in which the signal conductor pattern extends.

[0132] <6> The high-frequency signal transmission line according to any one of <1> to <5>, wherein the second resin layer has a lower dielectric constant than the first resin layer.

[0133] <7> The high-frequency signal transmission line according to any one of <1> to <6>, 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.

[0134] <8> An electronic device comprising the high-frequency signal transmission line according to any one of <1> to <7>.

[0135] DF...dry film EF...stress H...opening HP...hollow portion OH...opening RF...resist film SD1...first lamination direction SD2...second lamination direction 3...resin laminated portion 4...signal conductor pattern 5...ground conductor layer 5C...ground conductor pattern 5P...projection portion 5V...interlayer connection conductor 11, 12, 13, 14...first resin layer 21, 22, 23...second resin layer 31...upper resin laminated portion 32...lower resin laminated portion 51...first ground conductor layer 52...second ground conductor layer 61, 62...coaxial connectors 101 to 108, 108A...high-frequency signal transmission line

Claims

1. It comprises a ground conductor layer, a first resin layer, a second resin layer, and a signal conductor pattern. The ground conductor layer, the first resin layer, the second resin layer, and the signal conductor pattern are stacked in this order, and there is a hollow portion between the signal conductor pattern and the second resin layer in the direction of stacking. The first resin layer and the second resin layer are made of different materials, and the Young's modulus of the second resin layer is lower than that of the first resin layer. High-frequency signal transmission line.

2. The ground conductor layer is composed of a first ground conductor layer and a second ground conductor layer located on both sides of the signal conductor pattern in the direction of lamination. The first resin layer and the second resin layer are located on both sides of the signal conductor pattern in the lamination direction, The high-frequency signal transmission line according to claim 1.

3. The first ground conductor layer and the second ground conductor layer are electrically connected by interlayer connecting conductors, The system comprises the first ground conductor layer, the second ground conductor layer, the signal conductor pattern, and the interlayer connecting conductor, The high-frequency signal transmission line according to claim 2.

4. The interlayer connecting conductor has a projection that protrudes outward from the first ground conductor layer and a projection that protrudes outward from the second ground conductor layer. The high-frequency signal transmission line according to claim 3.

5. The hollow portion extends in all directions perpendicular to the direction in which the signal conductor pattern extends, both vertically and horizontally. A high-frequency signal transmission line according to any one of claims 1 to 4.

6. The relative permittivity of the second resin layer is lower than that of the first resin layer. A high-frequency signal transmission line according to any one of claims 1 to 4.

7. The first resin layer is polyimide, liquid crystal polymer, or epoxy resin, and the second resin layer is thermoplastic polyimide, fluororesin, or polyolefin resin. A high-frequency signal transmission line according to any one of claims 1 to 4.

8. An electronic device comprising a high-frequency signal transmission line according to any one of claims 1 to 4.