High frequency circuit

Abstract

The present invention provides a high-frequency circuit, comprising: a first dielectric layer; a circuit layer, arranged on the first dielectric layer, comprising a transmission path for high-frequency signals and a ground pattern arranged around the transmission path; a second dielectric layer, arranged so that the circuit layer is located between the second dielectric layer and the first dielectric layer; and an electromagnetic wave shielding device, arranged on the first dielectric layer and the second dielectric layer around the transmission path, the electromagnetic wave shielding device comprising: a first grounding conductor, formed on the inner surface of one or more first holes formed to penetrate the first dielectric layer without penetrating the ground pattern; and a second grounding conductor, formed on the inner surface of one or more second holes formed to penetrate the second dielectric layer without penetrating the ground pattern, the first grounding conductor and the second grounding conductor being electrically connected to the ground pattern, respectively.

Description

Technical Field

[0001] The present disclosure relates to high frequency circuits.

[0002] This application claims the benefit of priority based on Japanese patent application No. 2020-084546 filed on May 13, 2020, and all the contents described in the aforementioned Japanese application are incorporated herein by reference. Background Art

[0003] Patent Document 1 discloses a structure including a plurality of shielded vias electrically connected to a front surface ground and a back surface ground of a dielectric substrate.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 8-274513 Summary of the invention

[0007] One aspect of the present disclosure is a high-frequency circuit. The high-frequency circuit of the present disclosure comprises: a first dielectric layer; a circuit layer, which is arranged on the first dielectric layer, and has a transmission path for high-frequency signals and a ground pattern arranged around the transmission path; a second dielectric layer, which is arranged so that the circuit layer is located between the second dielectric layer and the first dielectric layer; and an electromagnetic wave shielding member, which is arranged on the first dielectric layer and the second dielectric layer around the transmission path, and the electromagnetic wave shielding member comprises: a first grounding conductor, which is formed on the inner surface of one or more first holes, and the one or more first holes are formed to penetrate the first dielectric layer without penetrating the ground pattern; and a second grounding conductor, which is formed on the inner surface of one or more second holes, and the one or more second holes are formed to penetrate the second dielectric layer without penetrating the ground pattern, and the first grounding conductor and the second grounding conductor are electrically connected to the ground pattern, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a top view of the high-frequency circuit according to the embodiment.

[0009] Figure 2 yes Figure 1 AA cross-section diagram.

[0010] Figure 3 It is an exploded perspective view of the first conductive layer, the circuit layer, and the second conductive layer.

[0011] Figure 4 It is a diagram showing the first half of the manufacturing process of the high-frequency circuit according to the embodiment.

[0012] Figure 5It is a diagram showing the second half of the manufacturing process of the high-frequency circuit according to the embodiment.

[0013] Figure 6 This is an explanatory diagram of a plating completion inspection for discovering a plating defect.

[0014] Figure 7 It is a top view of a high-frequency circuit according to a comparative example. DETAILED DESCRIPTION

[0015] [Technical Problems to be Solved by the Present Disclosure]

[0016] The shielding via is formed by forming a plurality of circular through holes in a dielectric substrate in a thickness direction of the dielectric substrate when viewed from above and placing a conductor such as copper in the through holes. The shielding via is used as an electromagnetic wave shield to prevent leakage of electromagnetic waves in the dielectric substrate.

[0017] Figure 7 The present invention shows an example of a structure in which a plurality of shield vias 102 are formed in a high-frequency circuit 100 having a signal transmission path 101 so as to surround the signal transmission path 101. Unnecessary electromagnetic waves are radiated from the high-frequency signal transmission path 101. The electromagnetic waves become noise to the surrounding circuits, degrading the characteristics of the surrounding circuits.

[0018] When a plurality of shielding vias 102 are provided around the signal transmission path 101 , the plurality of shielding vias 102 function as an electromagnetic wave shield. The electromagnetic wave shield can shield electromagnetic waves leaking from the signal transmission path 101 .

[0019] In order to form the shielding via 102, it is necessary to form a hole in the high-frequency circuit 100. When the hole passes through the high-frequency circuit 100, the strength of the area where the shielding via 102 exists decreases. As a result, when the area of ​​the hole is increased, the area surrounded by the shielding via 102, that is, the area where the signal transmission path 101 exists, and the area outside the shielding via 102 may become easily separated.

[0020] Therefore, it is desirable to prevent leakage of electromagnetic waves and suppress reduction in strength of the circuit caused by formation of the hole.

[0021] [Effects of the present disclosure]

[0022] According to the present disclosure, it is possible to prevent leakage of electromagnetic waves and suppress reduction in strength of a circuit caused by formation of a hole.

[0023] [1. Description of embodiments of the present disclosure]

[0024] (1) The high-frequency circuit involved in the embodiment includes: a first dielectric layer; a circuit layer provided on the first dielectric layer, and including a transmission path of a high-frequency signal and a ground pattern arranged around the transmission path; a second dielectric layer provided so that the circuit layer is located between the second dielectric layer and the first dielectric layer; and an electromagnetic wave shield provided on the first dielectric layer and the second dielectric layer around the transmission path. By providing the high-frequency circuit with the electromagnetic wave shield, it is possible to prevent leakage of electromagnetic waves propagating in the first dielectric layer and the second dielectric layer existing on both sides of the transmission path. The electromagnetic wave shield includes: a first ground conductor formed on the inner surface of one or more first holes, the one or more first holes being formed so as not to penetrate the ground pattern but to penetrate the first dielectric layer; and a second ground conductor formed on the inner surface of one or more second holes, the one or more second holes being formed so as not to penetrate the ground pattern but to penetrate the second dielectric layer, the first ground conductor and the second ground conductor being electrically connected to the ground pattern, respectively. By not penetrating the ground pattern around the transmission path, the first hole and the second hole that penetrate the first dielectric layer and the second dielectric layer can suppress the reduction in strength of the high-frequency circuit. Therefore, according to the electromagnetic wave shielding member involved in the embodiment, it is possible to prevent the leakage of electromagnetic waves and suppress the reduction in strength of the high-frequency circuit caused by the formation of the hole.

[0025] (2) The one or more first holes may include one or more first long holes whose length dimension along the direction surrounding the transmission path is greater than the width dimension. Since the area of ​​the long hole is easy to increase, it is easy to cause the strength of the high-frequency circuit to decrease. However, since the first hole does not penetrate the ground pattern, the strength reduction of the high-frequency circuit can be effectively suppressed.

[0026] (3) The one or more second holes may include one or more second long holes whose length dimension along the direction surrounding the transmission path is greater than the width dimension. Since the area of ​​the long hole is easy to increase, it is easy to cause the strength of the high-frequency circuit to decrease. However, since the second hole does not penetrate the ground pattern, the strength reduction of the high-frequency circuit can be effectively suppressed.

[0027] (4) The one or more first holes may include one or more first long holes whose length dimension in the direction surrounding the transmission path is greater than the width dimension, and the one or more second holes may include one or more second long holes whose length dimension in the direction surrounding the transmission path is greater than the width dimension. The first long hole and the second long hole may respectively include: a first hole portion extending along the length direction of the transmission path on one side in the width direction of the transmission path; a second hole portion extending along the length direction of the transmission path on the other side in the width direction of the transmission path; and a third hole portion connecting the first hole portion and the second hole portion. In this case, the transmission path can be surrounded by a smaller number of long holes.

[0028] (5) The first hole and the second hole can each have a shape in which the opening becomes larger as the hole is further away from the circuit layer. In this case, a shape that is preferred for the completion inspection of the ground conductor formed inside the first hole and the second hole can be obtained. That is, during the completion inspection, the inside of the hole can be observed from the front and back sides of the high-frequency circuit.

[0029] (6) It is preferred that the device further comprises: a first conductor layer, which is arranged so that the first dielectric layer is located between the first conductor layer and the circuit layer; and a second conductor layer, which is arranged so that the second dielectric layer is located between the second conductor layer and the circuit layer, wherein the first hole is formed to penetrate the first conductor layer, and the second hole is formed to penetrate the second conductor layer. In this case, the first conductor layer can prevent the electromagnetic waves radiated from the transmission path from radiating in the circuit thickness direction through the first dielectric layer. In addition, the second conductor layer can prevent the electromagnetic waves radiated from the transmission path from radiating in the circuit thickness direction through the second dielectric layer.

[0030] (7) Preferably, the first conductor layer is electrically connected to the first ground conductor, and the second conductor layer is electrically connected to the second ground conductor. In this case, it is easy to set the first conductor layer and the second conductor layer to the ground potential.

[0031] (8) It is preferable to further include a cover film adhered to the surface of at least one of the first conductive layer and the second conductive layer. In this case, even if the first hole and the second hole are elongated holes, the cover film can ensure the strength of the high-frequency circuit formed with these elongated holes.

[0032] [2. Details of the embodiments of the present disclosure]

[0033] Hereinafter, the same reference numerals in the drawings represent the same items.

[0034] Figures 1 to 6The high-frequency circuit 10 involved in the embodiment is shown. The high-frequency circuit 10 involved in the embodiment is configured as a flexible printed circuit (FPC) for high-frequency signal transmission. The FPC has a structure in which a conductor such as copper foil is attached to a thin and soft insulating base film. It should be noted that the high-frequency circuit 10 is not limited to the FPC, and can also be a circuit formed on a rigid substrate.

[0035] like Figure 2 As shown, the high-frequency circuit 10 involved in the embodiment includes a first dielectric layer 11, a circuit layer 21, a second dielectric layer 12 and an electromagnetic wave shielding member 50. The high-frequency circuit 10 also includes a first conductive layer 31 and a second conductive layer 32. The high-frequency circuit 10 involved in the embodiment has a multi-layer structure, and the multi-layer structure has three conductive layers. It should be noted that the number of conductive layers is not particularly limited, and can also be two, four, five or more layers. Figure 2 In the embodiment, the conductor layer arranged in the middle of the three conductor layers is a circuit layer 21 having a high-frequency transmission path 21A. Figure 2 On the lower side of the circuit layer 21, a first conductive layer 31 is disposed as one of the three conductive layers. Figure 2 On the upper side of the 3D image layer, a second conductive layer 32 is arranged as the remaining layer of the three conductive layers.

[0036] like Figure 3 As shown, the circuit layer 21 has a transmission path 21A and a ground pattern 21B located around the transmission path 21A. The space between the transmission path 21A and the ground pattern 21B is removed by etching, and the transmission path 21A and the ground pattern 21B are insulated. Figure 3 In the embodiment, the transmission path 21A is formed in a straight line, but may be formed in a curved shape.

[0037] like Figure 2 As shown, the first dielectric layer 11 is provided between the circuit layer 21 and the first conductive layer 31. That is, the circuit layer 21 is provided on the first dielectric layer 11. In other words, the circuit layer 21 is provided above the first conductive layer 31 via the first dielectric layer 11. It should be noted that the circuit layer 21 and the first dielectric layer 11 are bonded via a bonding agent 60. Figure 3 As shown in FIG. 1 , substantially the entire surface of the first conductor layer 31 is composed of the ground pattern 31B except for the first etching portion 31C which becomes the electromagnetic shielding member 50 described later. That is, the first conductor layer 31 is a ground layer.

[0038] The adhesive 60 is preferably an adhesive having excellent flexibility and heat resistance. The adhesive 60 is, for example, an adhesive of various resins such as modified polyphenylene ether, styrene resin, epoxy resin, butyral resin, and acrylic resin.

[0039] The main component of the adhesive 60 is preferably a thermosetting resin. The lower limit of the curing temperature of the thermosetting resin as the main component of the adhesive 60 is preferably 120°C, and more preferably 150°C. The upper limit of the curing temperature of the thermosetting resin as the main component of the adhesive 60 is preferably 250°C, more preferably 230°C, and further preferably 200°C. When the curing temperature of the thermosetting resin as the main component of the adhesive 60 is greater than the above lower limit, the handling of the adhesive 60 is easy. When the curing temperature of the thermosetting resin as the main component of the adhesive 60 is less than the above upper limit, when the adhesive 60 is cured, thermal deformation of the layers bonded by the adhesive 60 can be suppressed. By suppressing the above thermal deformation, the reduction in dimensional accuracy of the high-frequency circuit 10 can be suppressed.

[0040] The lower limit of the relative dielectric constant of the bonding agent 60 is preferably as small as possible, but in order to meet other conditions such as insulation and mechanical strength, 1.5 is considered to be the limit in reality. The upper limit of the relative dielectric constant of the bonding agent 60 is, for example, 3, preferably 2.8, and more preferably 2.6. In addition, when the relative dielectric constant of the bonding agent 60 is less than the above upper limit, the dielectric loss can be suppressed when a high-frequency signal is transmitted through the high-frequency circuit 10.

[0041] like Figure 2 As shown in FIG. 1 , the second dielectric layer 12 is provided between the circuit layer 21 and the second conductor layer 32. That is, the second dielectric layer 12 is provided so that the circuit layer 21 is located between the second dielectric layer 12 and the first dielectric layer 11. Figure 3 As shown, the second conductor layer 32 is composed of a ground pattern 32B over substantially the entire surface except for a high-frequency signal transmission path 32A and a second etching portion 32C serving as an electromagnetic shield 50. That is, the second conductor layer 32 is a ground layer.

[0042] like Figure 2 As shown, on the upper and lower sides of the circuit layer 21, that is, Figure 2 The first conductive layer 31 and the second conductive layer 32 functioning as ground layers are provided on both sides of the high frequency circuit 10 in the Z direction. Therefore, the electromagnetic waves radiated from the transmission path 21A are directed to both sides of the high frequency circuit 10 in the thickness direction, that is, Figure 2 The electromagnetic waves radiated from both sides of the Z direction are shielded by the first conductive layer 31 and the second conductive layer 32 .

[0043] Among the electromagnetic waves radiated from the transmission path 21A, there are Figure 2Electromagnetic waves radiated in a direction parallel to the XY plane. Electromagnetic waves radiated in a direction parallel to the XY plane cannot be shielded by the first conductive layer 31 and the second conductive layer 32, and may leak out of the high-frequency circuit 10 through the first dielectric layer 11 and the second dielectric layer 12. Therefore, the high-frequency circuit 10 of the embodiment has an electromagnetic wave shielding member 50 for shielding electromagnetic waves radiated in a direction parallel to the XY plane. It should be noted that the XY plane is a plane perpendicular to the thickness direction of the high-frequency circuit 10. The Z direction is the thickness direction of the high-frequency circuit 10, which is equivalent to the stacking direction of the multilayer structure of the above-mentioned conductive layer.

[0044] In the high-frequency circuit 10 involved in the embodiment, the electromagnetic waves radiated in the Z direction are shielded by the first conductive layer 31 and the second conductive layer 32. The electromagnetic waves radiated in the direction parallel to the XY plane are shielded by the electromagnetic wave shield 50. Therefore, it is possible to effectively prevent the electromagnetic waves radiated from the transmission path 21A from leaking outside the high-frequency circuit 10. As a result, it is possible to suppress the influence of the leakage electromagnetic waves on other peripheral circuits.

[0045] The electromagnetic wave shielding member 50 is configured to function as a shielding wall around the transmission path 21A to shield electromagnetic waves passing through the first dielectric layer 11 and the second dielectric layer 12. Figure 1 As shown, the electromagnetic wave shield 50 is formed so as to surround the transmission path 21A in a plan view.

[0046] like Figure 2 As shown, the electromagnetic wave shielding member 50 is formed by providing a grounded conductor on the inner surface of the hole penetrating the first dielectric layer 11 and the second dielectric layer 12. Since the grounded conductor exists in a manner surrounding the transmission path 21A, it is possible to shield the electromagnetic waves passing through the first dielectric layer 11 and the second dielectric layer 12. The grounded conductor here is the conductor 53, 54 described later. It should be noted that in Figure 1 The transmission path 21A is not surrounded by the electromagnetic wave shielding member 50. This is simply because, when drawing, Figure 1 The transmission path 21A is omitted on the lower side, and the electromagnetic wave shielding member 50 is omitted. Therefore, the electromagnetic wave shielding member 50 can actually completely surround the transmission path 21A.

[0047] like Figure 7 As shown in FIG. 1 , the conventional shielding via 102 is generally circular in a top view. Therefore, in order to shield the leakage electromagnetic wave, it is necessary to densely arrange a plurality of shielding vias 102 in a manner of surrounding the signal transmission path 101. Figure 1 In the illustrated embodiment, the electromagnetic wave shielding member 50 is formed into a shape elongated in a direction surrounding the transmission path 21A instead of a circular shape, so that leakage electromagnetic waves can be effectively shielded by a small number of electromagnetic wave shielding members 50 .

[0048] Figure 4 and Figure 5 A method for manufacturing the high-frequency circuit 10 according to the embodiment is shown. Figure 4 In step S11 shown, as an example of a substrate, a fluororesin substrate with copper on both sides is prepared. The fluororesin substrate with copper on both sides includes a fluororesin substrate constituting the second dielectric layer 12, copper constituting the circuit layer 21, and copper constituting the second conductor layer 32. It should be noted that the material of the substrate is not limited to fluororesin.

[0049] In step S12 , through holes 41 penetrating the circuit layer 21 , the second dielectric layer 12 , and the second conductor layer 32 are formed at the positions of the transmission paths 21A and 32A.

[0050] In step S13, the inside of the through hole 41 is filled with a conductor by plating. Thus, a via 40 is formed to electrically connect the transmission path 21A and the transmission path 32A. The transmission path 32A functions as an external connection terminal for the transmission path 21A, for example. It should be noted that the inner surface of the through hole 41 can also be covered by plating, and the remaining space is filled with synthetic resin.

[0051] In step S14 , the circuit layer 21 and the second conductor layer 32 of the double-sided copper-coated fluororesin substrate are etched to form the transmission path 21A of the circuit layer 21 and the transmission path 32A of the second conductor layer 32 .

[0052] In step S15, a single-sided fluororesin substrate is bonded to the circuit layer 21 side. The single-sided fluororesin substrate includes a fluororesin substrate constituting the first dielectric layer 11 and copper constituting the first conductor layer 31. In step S15, the first dielectric layer 11 and the circuit layer 21 are bonded to each other via a bonding agent 60. The bonding agent 60 is, for example, an adhesive sheet. The adhesive sheet is used for bonding between substrate layers. The adhesive sheet has insulation and bonding properties.

[0053] In step S21 after step S15, Figure 5 As shown, the portions of the first conductive layer 31 and the second conductive layer 32 where the electromagnetic shield 50 is formed are removed by etching. Hereinafter, the portion of the first conductive layer 31 where the electromagnetic shield 50 is formed, that is, the portion removed by etching, is referred to as a first etching portion 31C. The portion of the second conductive layer 32 where the electromagnetic shield 50 is formed, that is, the portion removed by etching, is referred to as a second etching portion 32C.

[0054] like Figure 3As shown, the first etching portion 31C and the second etching portion 32C are formed so as to surround the periphery of the transmission path 21A. In the first etching portion 31C, the first dielectric layer 11 is exposed. In the second etching portion 32C, the second dielectric layer 12 is exposed.

[0055] In step S22, a first hole 51 and a second hole 52 for the electromagnetic wave shielding member 50 are formed on the first dielectric layer 11 and the second dielectric layer 12 by laser processing. The laser processing is performed from both sides of the substrate. That is, the first hole 51 in the first dielectric layer 11 is formed by irradiating the first dielectric layer 11 exposed by the first etching processing part 31C with laser. In other words, the first hole 51 is formed to penetrate the first conductor layer 31. The laser irradiated to the first dielectric layer 11 scans along the first etching processing part 31C surrounding the transmission path 21A. As a result, the first hole 51 surrounding the transmission path 21A is formed in the first dielectric layer 11. The first hole 51 is an elongated long hole surrounding the transmission path 21A when viewed from above. Therefore, in this embodiment, through a single first hole 51, the transmission path 21A can be surrounded on the first dielectric layer 11 side.

[0056] Laser processing can easily form a long and narrow hole by laser scanning, and is therefore preferred for forming the first hole 51 according to the embodiment. It should be noted that the first hole 51 formed in the first dielectric layer 11 does not need to be single, but may be divided into a plurality of holes.

[0057] The first hole 51 is formed so as not to penetrate the ground pattern 21B of the circuit layer 21 but to penetrate the first dielectric layer 11 and the layer of the bonding agent 60. In addition, the first hole 51 formed by laser processing has a larger opening as it approaches the first etching portion 31C on the laser irradiation side, and a smaller opening as it approaches the circuit layer 21. That is, the first hole 51 has a shape that tapers toward the inner front end on the circuit layer 21 side, i.e., a tapered shape, in the depth direction of the first hole 51. In other words, the first hole 51 has a larger opening as it is farther from the circuit layer 21. Since the laser is irradiated from the first etching portion 31C side, the energy of the laser is absorbed in the first dielectric layer 11 on the side close to the first etching portion 31C. The energy reaching the side away from the first etching portion 31C becomes smaller. By utilizing this point, the first hole 51 having a tapered shape can be formed. The laser output used for laser processing is adjusted to an appropriate size so as to form a tapered shape without penetrating the ground pattern 21B.

[0058] The second hole 52 in the second dielectric layer 12 is formed by irradiating the second dielectric layer 12 exposed by the second etching portion 32C with laser. In other words, the second hole 52 is formed to penetrate the second conductor layer 32. The laser irradiated to the second dielectric layer 12 is scanned along the second etching portion 32C surrounding the transmission path 21A. As a result, the second hole 52 surrounding the transmission path 21A is formed in the second dielectric layer 12. The second hole 52 is an elongated hole surrounding the transmission path 21A when viewed from above. Therefore, in the present embodiment, the transmission path 21A can be surrounded on the second dielectric layer 12 side by a single second hole 52.

[0059] Laser processing can easily form an elongated hole by laser scanning, and is therefore preferred for forming the second hole 52 according to the embodiment. It should be noted that the second hole 52 formed in the second dielectric layer 12 does not need to be a single hole, but may be divided into a plurality of holes.

[0060] like Figure 1 As shown, the second hole 52 includes: a first hole portion 52A extending along the length direction of the transmission path 21A on one side in the width direction of the transmission path 21A; and a second hole portion 52B extending along the length direction of the transmission path 21A on the other side in the width direction of the transmission path 21A. The first hole portion 52A and the second hole portion 52B are arranged at a position sandwiching the transmission path 21A. In addition, the second hole 52 includes a third hole portion 52C connecting the first hole portion 52A and the second hole portion 52B. The third hole portion 52C connects the first hole portion 52A and the second hole portion 52B at one end side in the length direction of the first hole portion 52A and the second hole portion 52B, and constitutes a single second hole 52 as a whole. It should be noted that a hole portion connecting the first hole portion 52A and the second hole portion 52B may also exist at the other end side in the length direction of the first hole portion 52A and the second hole portion 52B. The width direction of the transmission path 21A is Figure 1 The width direction is Figure 1 The other side in the width direction is Figure 1 The length direction of the transmission path 21A is Figure 1 Y direction. Figure 1 Although the case where the planar shape of the third hole portion 52C is a curved shape is exemplified, it may be a linear shape.

[0061] The second hole 52 has a length dimension L in a direction surrounding the transport path 21A and a width dimension W in a direction orthogonal to the direction of the length dimension L. The length dimension L of the second hole 52 is greater than the width dimension W. The length dimension L is preferably greater than 5 times the width dimension W. The length dimension L is more preferably greater than 10 times the width dimension W, further preferably greater than 15 times the width dimension W, and further preferably greater than 20 times the width dimension W.

[0062] In the embodiment, the first hole 51 has the same shape as the second hole 52 when viewed from above. The first hole 51, like the second hole 52, includes: a first hole portion extending along the length direction of the transmission path 21A on one side in the width direction of the transmission path 21A; and a second hole portion extending along the length direction of the transmission path 21A on the other side in the width direction of the transmission path 21A. In addition, the first hole 51 includes a third hole portion connecting the first hole portion and the second hole portion. Like the second hole 52, a single first hole 51 is formed by the first hole portion, the second hole portion, and the third hole portion.

[0063] The first hole 51, like the second hole 52, has a length dimension L in a direction surrounding the transport path 21A and a width dimension W in a direction orthogonal to the direction of the length dimension L. The length dimension L of the first hole 51 is larger than the width dimension W. The length dimension L is preferably larger than 5 times the width dimension W. The length dimension L is more preferably larger than 10 times the width dimension W, further preferably larger than 15 times the width dimension W, and further preferably larger than 15 times the width dimension W.

[0064] The second hole 52 is formed so as to penetrate the second dielectric layer 12 instead of the ground pattern 21B of the circuit layer 21. In addition, the second hole 52 formed by laser processing has a larger opening as it is closer to the second etching processing portion 32C on the laser irradiation side, and a smaller opening as it is closer to the circuit layer 21. That is, the second hole 52 has a shape that becomes narrower toward the front end on the inner side on the circuit layer 21 side, that is, a tapered shape, in the depth direction of the second hole 52. In other words, the second hole 52 has a larger opening as it is farther away from the circuit layer 21.

[0065] The first hole 51 and the second hole 52 are provided at the same position when the high-frequency circuit 10 is viewed from above. Therefore, assuming that the first hole 51 and the second hole 52 are formed to penetrate the ground pattern 21B, the first hole 51 and the second hole 52 are connected to form a single hole. In this case, in the high-frequency circuit 10, the portion within the range surrounded by the first hole 51 and the second hole 52, that is, the portion where the transmission path 21A exists, is separated from the portion outside the range surrounded by the first hole 51 and the second hole 52. It should be noted that in the following description, the first hole 51 and the second hole 52 are sometimes collectively represented as holes 51 and 52.

[0066] In the embodiment, the first hole 51 on the first dielectric layer 11 side and the second hole 52 on the second dielectric layer 12 side are divided by the ground pattern 21B. Therefore, the two holes 51 and 52 are not connected. That is, in the high-frequency circuit 10 of the embodiment, the holes 51 and 52 penetrate the first dielectric layer 11 and the second dielectric layer 12, and there are partially connected parts in the thickness direction of the high-frequency circuit 10, that is, in the Z direction, and no completely through hole is formed. Therefore, even if the holes 51 and 52 surrounding the transmission path 21A are formed, the part where the transmission path 21A exists can be prevented from being separated.

[0067] It should be noted that, in the embodiment, the first hole 51 and the second hole 52 are provided at the same position when the high-frequency circuit 10 is viewed from above, but the first hole 51 and the second hole 52 may be provided at different positions when the high-frequency circuit 10 is viewed from above. For example, the second hole 52 may be formed to surround the transmission path 21A on the inner circumference or outer circumference of the first hole 51 surrounding the transmission path 21A. In this case, the ground pattern 21B of the circuit layer 21 and the second dielectric layer 12 exist in the portion where the first hole 51 is formed. The ground pattern 21B of the circuit layer 21 and the first dielectric layer 11 exist in the portion where the second hole 52 is formed. As a result, the thickness of the high-frequency circuit 10 can be prevented from being locally reduced in the portion where the first hole 51 or the second hole 52 is formed. In addition, in this case, the planar shape of the first hole 51 and the planar shape of the second hole 52 may be the same or different. The length dimension L of the first hole 51 and the length dimension L of the second hole 52 may be the same or different. The width dimension W of the first hole 51 and the width dimension W of the second hole 52 may be the same or different.

[0068] In the laser processing for forming the holes 51 and 52, it is preferable to use a laser that is suitable for hole processing of dielectrics such as synthetic resins such as fluororesins, but is not suitable for hole processing of metals that are conductors, that is, materials with high reflectivity. Such a laser is, for example, a carbon dioxide (CO2) laser. Even if the carbon dioxide laser is irradiated on a material with high reflectivity such as copper, the laser will be reflected, making it difficult to perform processing. Therefore, when a carbon dioxide laser is used, it is easy to form the first hole 51 that penetrates the first dielectric layer 11 or the second hole 52 that penetrates the second dielectric layer 12, and the penetration of the ground pattern 21B composed of copper is avoided.

[0069] In the embodiment, the first and second conductive layers 31 and 32 made of copper, which are not suitable for laser processing using a carbon dioxide laser, have first and second etching portions 31C and 32C formed before laser processing. Therefore, the first and second dielectric layers 11 and 12 can be laser processed.

[0070] In addition, when a laser which is also suitable for metal processing is used to form the holes 51 and 52 , it is desirable to appropriately adjust the laser output or the laser output time so as not to penetrate the ground pattern 21B.

[0071] In step S23 , conductors 53 and 54 are formed on the inner surfaces of holes 51 and 52 and first and second etching portions 31C and 32C by plating. Figure 2 The conductor 53 is provided in contact with the inner surface of the first hole 51 as a whole, and the conductor 53 has a cylindrical portion having an outer peripheral shape corresponding to the inner peripheral shape of the first hole 51. Similarly, the conductor 54 is also provided in contact with the inner surface of the second hole 52 as a whole, and the conductor 54 has a cylindrical portion having an outer peripheral shape corresponding to the inner peripheral shape of the second hole 52. The conductors 53 and 54 may be formed only on the surface of the inner surface of the holes 51 and 52 and the first etching process part 31C and the second etching process part 32C, or may be formed so as to completely fill the inner side of the holes 51 and 52 and the first etching process part 31C and the second etching process part 32C. The inner side of the conductors 53 and 54 may be filled with a dielectric such as a synthetic resin, or may be filled with a conductor such as a conductive paste.

[0072] The conductor 53 electrically connects the ground pattern 21B of the circuit layer 21 to the ground pattern 31B of the first conductor layer 31. Therefore, the conductor 53 and the ground patterns 21B and 31B have the same potential, and thus become a ground conductor constituting the first ground conductor. The conductor 53 as a ground conductor is provided in the first hole 51 surrounding the periphery of the transmission path 21A, and thus functions as an electromagnetic wave shield 50 surrounding the periphery of the transmission path 21A. The conductor 53 as a ground conductor can shield electromagnetic waves radiated through the first dielectric layer 11.

[0073] The conductor 54 electrically connects the ground pattern 21B of the circuit layer 21 and the ground pattern 32B of the second conductor layer 32. Therefore, the conductor 54 and the ground patterns 21B and 32B have the same potential, and thus become a ground conductor constituting the second ground conductor. The conductor 54 as a ground conductor is arranged in the second hole 52 surrounding the transmission path 21A, and thus functions as an electromagnetic wave shield 50 surrounding the transmission path 21A. The conductor 54 as a ground conductor can shield electromagnetic waves radiated through the second dielectric layer 12.

[0074] As described above, the holes 51 and 52 for forming the conductors 53 and 54 are tapered. Therefore, it is easy to find plating defects that occur during the plating process for forming the conductors 53 and 54. The conductors 53 and 54 need to be formed so as to be in contact with the ground pattern 21B. However, sometimes the plating solution cannot fully enter the fine holes 51 and 52, and a plating defect portion 90 (see FIG. 1 ) that is a defect portion of the conductors 53 and 54 is generated on the inner side of the holes 51 and 52. Figure 6 ).

[0075] In the plating completion inspection, it is desirable to observe the holes 51 and 52 using a microscope or the like to check whether there is a plating defect 90. If the holes 51 and 52 are not tapered but straight, even if there is a plating defect 90 on the inner side of the holes 51 and 52, the plating defect 90 on the inner side will be hidden by the conductors 53 and 54 near the front side of the holes 51 and 52, making it difficult to find the plating defect 90. In contrast, if the holes 51 and 52 are straight, even if there is a plating defect 90 on the inner side of the holes 51 and 52, the conductors 53 and 54 near the front side of the holes 51 and 52 will be hidden, making it difficult to find the plating defect 90. Figure 6 As shown, when the holes 51 and 52 are tapered, the plating defective portion 90 can be found as long as it exists on the back side of the holes 51 and 52 by observing from the front side of the holes 51 and 52.

[0076] In step S24, cover films 71 and 72 are attached to the surfaces of the first conductor layer 31 and the second conductor layer 32 via adhesives 81 and 82. The cover films 71 and 72 are made of, for example, polyimide, and protect the first conductor layer 31 and the second conductor layer 32. By attaching the cover films 71 and 72, the strength of the high-frequency circuit 10 in which the holes 51 and 52 are formed can be ensured.

[0077] It should be noted that the embodiments disclosed this time should be considered as illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the above meaning, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0078] Description of Reference Numerals

[0079] 10: High frequency circuit

[0080] 11: First dielectric layer

[0081] 12: Second dielectric layer

[0082] 21: Circuit layer

[0083] 21A: Transmission path

[0084] 21B: Ground pattern

[0085] 31: First conductor layer

[0086] 31B: Ground pattern

[0087] 31C: First etching processing part

[0088] 32: Second conductor layer

[0089] 32A: Transmission path

[0090] 32B: Ground pattern

[0091] 32C: Second etching processing part

[0092] 40: Via

[0093] 41: Through hole

[0094] 50: Electromagnetic wave shielding parts

[0095] 51: First hole

[0096] 52: Second hole

[0097] 52A: First hole

[0098] 52B: Second hole

[0099] 52C: Third hole

[0100] 53: Conductor, first grounding conductor

[0101] 54: Conductor, second grounding conductor

[0102] 60: Adhesive

[0103] 71: Covering film

[0104] 72: Covering film

[0105] 81: Adhesive

[0106] 82: Adhesive

[0107] 90: Plating defect

[0108] 100: High frequency circuit

[0109] 101: Signal Transmission Path

[0110] 102: Shielding vias

[0111] L: length dimension

[0112] W: Width dimension.

Claims

1. A high frequency circuit having: a first dielectric layer; A circuit layer, provided on the first dielectric layer, having a transmission path for high-frequency signals and a ground pattern arranged around the transmission path; a second dielectric layer, arranged so that the circuit layer is located between the second dielectric layer and the first dielectric layer; and an electromagnetic wave shielding member, which is provided around the transmission path and on the first dielectric layer and the second dielectric layer, The electromagnetic wave shielding component comprises: a first ground conductor formed on an inner surface of one or more first holes, wherein the one or more first holes are formed not to penetrate the ground pattern but to penetrate the first dielectric layer; a second ground conductor formed on an inner surface of one or more second holes, wherein the one or more second holes are formed not to penetrate the ground pattern but to penetrate the second dielectric layer; as well as The bonding agent is provided between the first dielectric layer and the circuit layer, and is provided between the transmission path of the circuit layer and the ground pattern of the circuit layer when viewed from above. The first ground conductor and the second ground conductor are electrically connected to the ground pattern, respectively. The first hole and the second hole are arranged at different positions when viewed from above.

2. The high frequency circuit according to claim 1, wherein: The one or more first holes include one or more first long holes whose length dimension in a direction surrounding the transport path is greater than their width dimension.

3. The high frequency circuit according to claim 1 or 2, wherein: The one or more second holes include one or more second long holes whose length dimension in a direction surrounding the transport path is greater than their width dimension.

4. The high frequency circuit according to claim 1, wherein: The one or more first holes include one or more first long holes whose length dimension in a direction surrounding the transmission path is greater than the width dimension, The one or more second holes include one or more second long holes whose length dimension in the direction surrounding the transmission path is greater than the width dimension, The first long hole and the second long hole respectively have: A first hole portion extending along the length direction of the transmission path on one side in the width direction of the transmission path; A second hole portion extending along the length direction of the transmission path at the other side in the width direction of the transmission path; as well as The third hole portion connects the first hole portion and the second hole portion.

5. The high frequency circuit according to claim 1 or 2, wherein: The first hole and the second hole each have a shape in which the opening becomes larger as the hole is farther away from the circuit layer.

6. The high frequency circuit according to claim 1 or 2, further comprising: a first conductor layer, arranged so that the first dielectric layer is located between the first conductor layer and the circuit layer; and The second conductor layer is configured so that the second dielectric layer is located between the second conductor layer and the circuit layer. The first hole is formed to penetrate the first conductor layer. The second hole is formed to penetrate the second conductor layer.

7. The high frequency circuit according to claim 6, wherein: The first conductor layer is electrically connected to the first ground conductor, The second conductor layer is electrically connected to the second ground conductor.

8. The high frequency circuit according to claim 6, further comprising: The cover film is attached to a surface of at least one of the first conductive layer and the second conductive layer.

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