Wiring board and method for manufacturing a wiring board

Abstract

A wiring substrate (10) comprises a substrate (11) and a mesh wiring layer (20) disposed on the substrate (11) and including a plurality of wirings (21, 22). The substrate (11) has a transmittance of 85% or more for light rays with a wavelength of 400 nm or more and 700 nm or less. The wirings (21, 22) include a surface roughness Ra, and the surface roughness Ra is 100 nm or less.

Description

Technology Field

[0001] Embodiments of the present disclosure relate to a wiring board and a method for manufacturing a wiring board. Background Technology

[0002] Currently, portable devices such as smartphones and tablets are undergoing advancements in high functionality, miniaturization, thinning, and weight reduction. To utilize multiple communication bands, these portable devices require multiple antennas corresponding to each band. For example, portable devices are equipped with multiple antennas, such as a telephone antenna, a WiFi (Wireless Fidelity) antenna, a 3G (Generation) antenna, a 4G (Generation) antenna, an LTE (Long Term Evolution) antenna, a Bluetooth (registered trademark) antenna, and an NFC (Near Field Communication) antenna. However, with the miniaturization of portable devices, the space available for mounting antennas is limited, thereby narrowing the freedom of antenna design. Furthermore, since antennas are housed within a limited space, radio wave sensitivity cannot necessarily be fully satisfied.

[0003] For this reason, a film antenna that can be mounted on the display area of ​​a mobile terminal device has been developed. This film antenna is a transparent antenna in which an antenna pattern is formed on a transparent substrate, and the antenna pattern is formed by a mesh-like conductive mesh layer consisting of a conductive part as a part forming an opaque conductive layer and a plurality of openings as a non-forming part. Prior art literature

[0004] Japanese Patent Publication No. 2011-66610, Japanese Patent No. 5636735, Specification of Japanese Patent No. 5695947

[0005] In conventional film antennas, a mesh wiring layer (conductive mesh layer) is mounted on a transparent substrate. In particular, in recent years, high-frequency electromagnetic waves have been used in film antennas. When high-frequency electromagnetic waves are used, the number of times electrons pass through the grain boundaries of the metal constituting the mesh wiring layer per unit time increases, making it difficult for current to flow, and there is a risk that transmission loss will increase.

[0006] The present embodiment provides a wiring board and a method for manufacturing a wiring board that can suppress the difficulty of current flowing through a mesh wiring layer.

[0007] A wiring substrate according to the present embodiment is a wiring substrate and comprises a substrate and a mesh wiring layer disposed on the substrate and including a plurality of wirings, wherein the substrate has a transmittance of 85% or more for light rays with a wavelength of 400 nm or more and 700 nm or less, and the wiring includes a surface roughness Ra, wherein the surface roughness Ra is 100 nm or less.

[0008] In the wiring substrate according to the present embodiment, the wiring comprises a metal crystal, and the area average particle size of the metal crystal may be 300 nm or more.

[0009] In the wiring board according to the present embodiment, the line width of the wiring may be 0.1 μm or more and 5.0 μm or less.

[0010] In the wiring board according to the present embodiment, the mesh wiring layer may be an antenna.

[0011] In the wiring board according to the present embodiment, the wiring may include gold, silver, copper, platinum, tin, aluminum, iron, or nickel.

[0012] In the wiring board according to the present embodiment, the dielectric loss tangent of the board may be 0.002 or less.

[0013] In the wiring board according to the present embodiment, the thickness of the board may be 5㎛ or more and 200㎛ or less.

[0014] In the wiring substrate according to the present embodiment, the substrate may include a cycloolefin polymer or a polynorbornene polymer.

[0015] In the wiring substrate according to the present embodiment, the mesh wiring layer may exist only in a part of the substrate.

[0016] In the wiring substrate according to the present embodiment, the surface roughness Ra may be 90 nm or less.

[0017] The method for manufacturing a wiring board according to the present embodiment is a method for manufacturing a wiring board, comprising a process of preparing a substrate and a process of forming a mesh wiring layer including a plurality of wirings on the substrate, wherein the substrate has a transmittance of 85% or more for light rays with a wavelength of 400 nm or more and 700 nm or less, and the wiring includes a surface roughness Ra, and the surface roughness Ra is 100 nm or less.

[0018] In the method for manufacturing a wiring board according to the present embodiment, the wiring comprises a metal crystal, and the area average particle size of the metal crystal may be 300 nm or more.

[0019] In the method for manufacturing a wiring board according to the present embodiment, the line width of the wiring may be 0.1 μm or more and 5.0 μm or less.

[0020] In the method for manufacturing a wiring board according to the present embodiment, the mesh wiring layer may be an antenna.

[0021] In the method for manufacturing a wiring board according to the present embodiment, the wiring may include gold, silver, copper, platinum, tin, aluminum, iron, or nickel.

[0022] In the method for manufacturing a wiring board according to the present embodiment, the dielectric loss tangent of the board may be 0.002 or less.

[0023] In the method for manufacturing a wiring board according to the present embodiment, the thickness of the board may be 5㎛ or more and 200㎛ or less.

[0024] In the method for manufacturing a wiring substrate according to the present embodiment, the substrate may include a cycloolefin polymer or a polynorbornene polymer.

[0025] In the method for manufacturing a wiring board according to the present embodiment, the mesh wiring layer may exist only in a part of the substrate.

[0026] In the method for manufacturing a wiring board according to the present embodiment, the surface roughness Ra may be 90 nm or less.

[0027] According to an embodiment of the present disclosure, it is possible to suppress the difficulty of current flowing within the mesh wiring layer. Brief explanation of the drawing

[0028] FIG. 1 is a plan view illustrating a wiring board according to one embodiment. FIG. 2 is an enlarged plan view illustrating a wiring board according to one embodiment (enlarged view of part II of FIG. 1). FIG. 3 is an enlarged plan view illustrating a wiring board according to one embodiment (enlarged view of part III of FIG. 2). FIG. 4 is a cross-sectional view illustrating a wiring board according to one embodiment (cross-sectional view along line VI-VI of FIG. 3). FIG. 5 is a cross-sectional view illustrating a wiring board according to one embodiment (cross-sectional view along line VV of FIG. 3). FIG. 6 is a cross-sectional view illustrating the first direction wiring and the second direction wiring. FIG. 7 is a cross-sectional view showing an enlarged portion of the first direction wiring and the second direction wiring (enlarged view of part VII of FIG. 6). FIGS. 8a to 8e are cross-sectional views illustrating a method for manufacturing a wiring board according to one embodiment. FIGS. 9a to 9e are cross-sectional views illustrating a method for manufacturing a wiring board according to one embodiment. FIG. 10 is a plan view illustrating an image display device according to one embodiment. FIG. 11 is a plan view illustrating a wiring board according to Examples 1 to 2 and Comparative Example 1. Specific details for implementing the invention

[0029] First, an embodiment will be described with reference to FIGS. 1 to 10. FIGS. 1 to 10 are drawings illustrating the present embodiment.

[0030] Each drawing shown below is illustrated schematically. Therefore, the size and shape of each part are appropriately exaggerated to facilitate understanding. Furthermore, it is possible to implement the design by making appropriate modifications within the scope of not deviating from the technical concept. Additionally, in each drawing shown below, the same reference numerals are assigned to identical parts, and some detailed descriptions may be omitted. Furthermore, numerical values ​​such as dimensions and material names of each component described in this specification are examples of embodiments and are not limited thereto, and may be appropriately selected and used. In this specification, terms specifying shapes or geometric conditions, such as parallel, orthogonal, and perpendicular, are to include substantially identical states in addition to their strict meanings.

[0031] In addition, in the following embodiments, "X direction" is a direction parallel to one side of the substrate. "Y direction" is a direction perpendicular to the X direction and parallel to the other side of the substrate. "Z direction" is a direction perpendicular to both the X direction and the Y direction and parallel to the thickness direction of the wiring substrate. In addition, "surface" refers to the surface on the positive side of the Z direction, which is the surface on which wiring is provided relative to the substrate. "Back side" refers to the surface on the negative side of the Z direction, which is the surface opposite to the surface on which wiring is provided relative to the substrate.

[0032] [Composition of the wiring board]

[0033] With reference to FIGS. 1 to 7, the configuration of a wiring board according to the present embodiment will be described. FIGS. 1 to 7 are drawings illustrating a wiring board according to the present embodiment.

[0034] As illustrated in FIG. 1, the wiring board (10) according to the present embodiment is disposed on, for example, a display of an image display device. The wiring board (10) comprises a transparent substrate (11) and a mesh wiring layer (wiring pattern area) (20) disposed on the substrate (11). Additionally, a power supply unit (40) is electrically connected to the mesh wiring layer (20).

[0035] Among these, the substrate (11) is approximately rectangular in shape when viewed in a planar view, with its length direction parallel to the Y direction and its short direction parallel to the X direction. The substrate (11) is transparent and approximately flat, and its thickness is generally approximately uniform. The length L1 of the substrate (11) in the length direction (Y direction) can be selected, for example, in a range of 2 mm or more and 300 mm or less, and preferably in a range of 100 mm or more and 200 mm or less. The length L2 of the substrate (11) in the short direction (X direction) can be selected in a range of 2 mm or more and 300 mm or less, and preferably in a range of, for example, 50 mm or more and 100 mm or less. Additionally, the corners of the substrate (11) may each be rounded.

[0036] The material of the substrate (11) may be a material having transparency in the visible light region and electrical insulation. In this embodiment, the material of the substrate (11) is polyethylene terephthalate, but is not limited thereto. As the material of the substrate (11), it is preferable to use an organic insulating material such as a polyester resin such as polyethylene terephthalate, an acrylic resin such as polymethyl methacrylate, a polycarbonate resin, a polyimide resin, a polyolefin resin such as a cycloolefin polymer, or a cellulose resin such as triacetylcellulose. Alternatively, as the material of the substrate (11), an organic insulating material such as a cycloolefin polymer (e.g. ZF-16 manufactured by Nippon Zeon Co., Ltd.) or a polynorbornene polymer (manufactured by Sumitomo Bakelite Co., Ltd.) may be used. Additionally, as the material of the substrate (11), glass, ceramics, etc. may be appropriately selected depending on the application. Additionally, although an example in which the substrate (11) is composed of a single layer has been shown, it is not limited to this and may have a structure in which multiple substrates or layers are stacked. Also, the substrate (11) may be in the form of a film or a plate. Therefore, the thickness of the substrate (11) is not particularly limited and can be appropriately selected according to the application, but as an example, the thickness (Z direction) T1 (see FIG. 4 and FIG. 5) of the substrate (11) can be in the range of, for example, 5 μm or more and 200 μm or less.

[0037] In addition, the dielectric loss tangent of the substrate (11) may be 0.002 or less, and preferably 0.001 or less. In addition, there is no specific lower limit for the dielectric loss tangent of the substrate (11), but it may be greater than 0. By having the dielectric loss tangent of the substrate (11) within the above range, the loss of gain (sensitivity) associated with the transmission and reception of electromagnetic waves can be reduced, especially when the electromagnetic waves (e.g., millimeter waves) transmitted and received by the mesh wiring layer (20) are high frequency. In addition, the lower limit for the dielectric loss tangent of the substrate (11) is not specifically limited. The dielectric constant of the substrate (11) is not specifically limited, but may be 2.0 or more and 10.0 or less.

[0038] The dielectric loss tangent of the substrate (11) can be measured in accordance with IEC 62562. Specifically, first, a test specimen is prepared by cutting out a portion of the substrate (11) where the mesh wiring layer (20) is not formed. Alternatively, the substrate (11) on which the mesh wiring layer (20) is formed may be cut out, and the mesh wiring layer (20) may be removed by etching or the like. The dimensions of the test specimen are set to a width of 10 mm to 20 mm and a length of 50 mm to 100 mm. Next, the dielectric loss tangent is measured in accordance with IEC 62562. The dielectric constant and dielectric loss tangent of the substrate (11) may also be measured in accordance with ASTM D150.

[0039] Additionally, the substrate (11) may have a transmittance of visible light (light with a wavelength of 400 nm or more and 700 nm or less) of 85% or more, and preferably 90% or more. Additionally, there is no specific upper limit for the transmittance of visible light of the substrate (11), but for example, it may be 100% or less. By setting the transmittance of visible light of the substrate (11) to the above range, the transparency of the wiring substrate (10) can be increased, making it easier to see the display (91) (described later) of the image display device (90). Also, visible light refers to light with a wavelength of 400 nm to 700 nm. In addition, the statement that the transmittance of visible light is 85% or higher means that when the absorbance of the substrate (11) is measured using a known spectrophotometer (e.g., a spectrometer manufactured by Nihon Bunko Co., Ltd.: V-670), the transmittance is 85% or higher in the entire wavelength range of 400 nm to 700 nm.

[0040] In this embodiment, the mesh wiring layer (20) is composed of an antenna pattern area that functions as an antenna. In FIG. 1, the mesh wiring layer (20) is formed in a plurality (3) on the substrate (11), each corresponding to a different frequency band. That is, the plurality of mesh wiring layers (20) have a length (length in the Y direction) L. aThey are different from each other and each has a length corresponding to a specific frequency band. In addition, the lower the corresponding frequency band, the longer the length L of the mesh wiring layer (20). a When the wiring board (10) is placed on the display (91) of the image display device (90) (see FIG. 10 described later), each mesh wiring layer (20) may correspond to any of the following: a telephone antenna, a WiFi antenna, a 3G antenna, a 4G antenna, a 5G antenna, an LTE antenna, a Bluetooth (registered trademark) antenna, an NFC antenna, etc. Additionally, the mesh wiring layer (20) may not exist on the entire surface of the board (11), but may exist only in a part of the area on the board (11).

[0041] Each mesh wiring layer (20) is approximately rectangular in shape when viewed in a planar view. Each mesh wiring layer (20) has its length direction parallel to the Y direction and its short direction parallel to the X direction. The length L of each mesh wiring layer (20) in the length direction (Y direction) a The width W of each mesh wiring layer (20) in the short direction (X direction) can be selected, for example, from a range of 3mm or more to 100mm or less. a It can be selected, for example, within a range of 1 mm or more and 10 mm or less. In particular, the mesh wiring layer (20) may be a millimeter wave antenna. If the mesh wiring layer (20) is a millimeter wave antenna, the length L of the mesh wiring layer (20) a It can be selected in the range of 1 mm or more and 10 mm or less, more preferably 1.5 mm or more and 5 mm or less.

[0042] The mesh wiring layer (20) is formed with metal wires in a grid shape or a net shape and has a repeating pattern in the X direction and Y direction. That is, the mesh wiring layer (20) has a pattern shape composed of a part extending in the X direction (second direction wiring (22)) and a part extending in the Y direction (first direction wiring (21)).

[0043] As illustrated in FIG. 2, each mesh wiring layer (20) includes a plurality of first-direction wirings (antenna wirings) (21) that function as antennas, and a plurality of second-direction wirings (antenna connection wirings) (22) that connect the plurality of first-direction wirings (21). Specifically, the plurality of first-direction wirings (21) and the plurality of second-direction wirings (22) are integrated as a whole to form a grid shape or a mesh shape. Each first-direction wiring (21) extends in a direction corresponding to the frequency band of the antenna (length direction, Y direction), and each second-direction wiring (22) extends in a direction orthogonal to the first-direction wiring (21) (width direction, X direction). The first-direction wiring (21) has a length L corresponding to a predetermined frequency band. a By having the length of the mesh wiring layer (20) described above (see FIG. 1), it primarily functions as an antenna. Meanwhile, the second direction wiring (22) serves to suppress problems such as the first direction wiring (21) being disconnected or the first direction wiring (21) and the feed unit (40) not being electrically connected by connecting the first direction wiring (21) to each other.

[0044] As illustrated in FIG. 3, in each mesh wiring layer (20), a plurality of openings (23) are formed by being surrounded by adjacent first-direction wiring (21) and adjacent second-direction wiring (22). Additionally, the first-direction wiring (21) and the second-direction wiring (22) are arranged at equal intervals from each other. That is, a plurality of first-direction wirings (21) are arranged at equal intervals from each other, and their pitch P1 can be, for example, in the range of 0.01 mm or more and 1 mm or less. Additionally, a plurality of second-direction wirings (22) are arranged at equal intervals from each other, and their pitch P2 can be, for example, in the range of 0.01 mm or more and 1 mm or less. In this way, since a plurality of first-direction wirings (21) and a plurality of second-direction wirings (22) are each arranged at equal intervals, there is no variation in the size of the opening (23) within each mesh wiring layer (20), making it difficult to see the mesh wiring layer (20) with the naked eye. In addition, the pitch P1 of the first-direction wiring (21) is equal to the pitch P2 of the second-direction wiring (22). Because of this, each opening (23) is approximately square in shape when viewed in a planar view, and a transparent substrate (11) is exposed from each opening (23). Because of this, by increasing the area of ​​each opening (23), the transparency of the entire wiring substrate (10) can be increased. In addition, the length L3 of one side of each opening (23) can be, for example, in the range of 0.01 mm or more and 1 mm or less. Additionally, each first direction wiring (21) and each second direction wiring (22) are orthogonal to each other, but are not limited to this and may intersect at an acute or obtuse angle. Furthermore, while it is preferable that the shape of the opening (23) be the same shape and size across the entire surface, it is not necessary to make it uniform across the entire surface, such as by changing it depending on the location.

[0045] As illustrated in FIG. 4, each first direction wiring (21) has a cross-section (X-direction cross-section) perpendicular to its length direction that is approximately rectangular or approximately square in shape. In this case, the cross-sectional shape of the first direction wiring (21) is approximately uniform along the length direction (Y-direction) of the first direction wiring (21). Also, as illustrated in FIG. 5, the cross-sectional shape (Y-direction cross-section) perpendicular to the length direction of each second direction wiring (22) is approximately rectangular or approximately square in shape, and is approximately identical to the cross-sectional shape (X-direction cross-section) of the first direction wiring (21) described above. In this case, the cross-sectional shape of the second direction wiring (22) is approximately uniform along the length direction (X-direction) of the second direction wiring (22). The cross-sectional shapes of the first direction wiring (21) and the second direction wiring (22) do not necessarily have to be approximately rectangular or approximately square in shape. The cross-sectional shape of the first direction wiring (21) and the second direction wiring (22) may be, for example, a roughly trapezoidal shape in which the surface side (Z direction plus side) is narrower than the back side (Z direction minus side), or a shape in which the sides located on both sides in the longitudinal direction are curved.

[0046] In the present embodiment, the line width W1 of the first direction wiring (21) (length in the X direction, see FIG. 4) and the line width W2 of the second direction wiring (22) (length in the Y direction, see FIG. 5) are not particularly limited and can be appropriately selected according to the application. For example, the line width W1 of the first direction wiring (21) can be selected from a range of 0.1 μm or more and 5.0 μm or less, and it is preferable to make it 0.2 μm or more and 2.0 μm or less. In addition, the line width W2 of the second direction wiring (22) can be selected from a range of 0.1 μm or more and 5.0 μm or less, and it is preferable to make it 0.2 μm or more and 2.0 μm or less. In addition, the height H1 (length in the Z direction, see FIG. 4) of the first direction wiring (21) and the height H2 (length in the Z direction, see FIG. 5) of the second direction wiring (22) are not particularly limited and can be appropriately selected according to the application, for example, can be selected in the range of 0.1 μm or more and 5.0 μm or less, and it is preferable to make it 0.2 μm or more and 2.0 μm or less.

[0047] FIG. 6 illustrates a cross-section in the width direction (X direction, Y direction) of a first direction wiring (21) and a second direction wiring (22). The first direction wiring (21) and the second direction wiring (22) each have a surface (24a), a back surface (24b), and two sides (24c, 24d). Among these, the surface (24a) is located on the side (Z direction plus side) where the first direction wiring (21) and the second direction wiring (22) are visible to an observer during use. The back surface (24b) is on the opposite side of the surface (24a) and is located on the substrate (11) side (Z direction minus side). Additionally, the two sides (24c, 24d) are located between the surface (24a) and the back surface (24b) and are located on both sides in the width direction (X direction, Y direction) of the first direction wiring (21) and the second direction wiring (22), respectively. In this case, the surface (24a) and the side (24c, 24d) are each approximately orthogonal, and the back surface (24b) and the side (24c, 24d) are each approximately orthogonal, but are not limited to this and may intersect at an acute or obtuse angle. Also, the surface (24a), the back surface (24b), and the side (24c, 24d) are each extended in a straight line, but are not limited to this and the surface (24a), the back surface (24b), or the side (24c, 24d) may each be curved.

[0048] FIG. 7 is a schematic diagram showing an enlarged view of the vicinity of the surface (24a) of the first direction wiring (21) and the second direction wiring (22). As shown in FIG. 7, the size of the crystal grains appearing in the cross-section in the width direction (X direction, Y direction) of the first direction wiring (21) and the second direction wiring (22) can be measured by the EBSD method.

[0049] The EBSD method is a method for analyzing crystal grains based on the electron beam diffraction pattern (hereinafter also referred to as the EBSD pattern) obtained when an electron beam is irradiated onto a sample from a direction significantly inclined with respect to the surface of the sample using a scanning electron microscope (hereinafter also referred to as SEM). As a measuring device, for example, a combination of a Schottky field emission scanning electron microscope and an EBSD detector can be used. As an EBSD detector, for example, an OIM (Orientation Imaging Microscopy) detector manufactured by TSL Solutions, Inc. can be used.

[0050] As a pretreatment prior to the EBSD method, cross-sectional processing of the sample may be performed using the FIB (Focused Ion Beam) method. Additionally, as a pretreatment prior to the FIB method, carbon may be applied to the sample surface as a protective film of 200 nm or more. This protective film may be composed of components such as Pt, PtPd, or Os, and either the sputtering method or the deposition method may be used to apply the protective film. The protective film is intended to prevent damage to the surface of the processed area during processing by the FIB method, and the film thickness of the protective film can be appropriately adjusted according to the processing conditions. As for the FIB device used for the FIB method, any device equipped with a system capable of picking up from any location, including micro-sampling, may be used; for example, the Hitachi High Technologies NB5000 may be used. Furthermore, the thickness of the finished film formed by thin-film processing of the cross-section of the observation area shall be 300 nm or more, and the degree of thickness is not an issue. The finished width of the thin-film formed by thin-film processing of the cross-section of the observation area may be, for example, 30 μm. Although it relies on the system installed in the FIB device, a wider finishing width is more efficient.

[0051] An example of the conditions of a scanning electron microscope used in the EBSD method is as follows.

[0052] · Observation magnification: 30,000x (based on 120mm × 90mm for x1 magnification)

[0053] · Acceleration voltage: 15kV

[0054] · Working distance: 15mm

[0055] · Sample inclination angle: 70 degrees

[0056] An example of the conditions for the interpretation of a decision by the EBSD method is as follows.

[0057] · Step size: 25nm

[0058] Interpretation conditions:

[0059] The following analysis is performed using the decision orientation analysis software OIM (Ver7.3) manufactured by TSL Solutions Co., Ltd.

[0060] If the number of crystal grains appearing in the measurement area to be analyzed is less than 100, images may be acquired at multiple locations on the cross-section of the sample while shifting the measurement area, and by connecting the multiple images obtained, an image showing 100 or more crystal grains may be generated.

[0061] Data with a Confidence Index (CI value) of less than or equal to a predetermined value, as defined in the crystal orientation analysis software OIM (Ver7.3) manufactured by TSL Solutions Co., Ltd., is excluded, and the analysis is performed. For example, data with a CI value of 0.2 or less is excluded. By doing so, the influence of substrates present on the front and back surfaces of the sample, protective films used in pretreatment, grain boundaries present on the cross-section of the sample, or amorphous materials can be excluded. As another method, locations with a contrast of a certain level or higher in the image quality are considered as crystals, and data extraction is performed. Twin grain boundaries are disregarded, and only normal grain boundaries are counted.

[0062] The area average particle size of the metal crystal (29) included in the first direction wiring (21) and the second direction wiring (22) may be 300 nm or more, and it is preferable that it be 400 nm or more. In addition, there is no particular upper limit for the area average particle size of the metal crystal (29), but for example, it may be 1000 nm or less. Since the area average particle size of the metal crystal (29) is 300 nm or more, as described later, the density of the metal crystal (29) is relatively lowered, so the total area of ​​the grain boundary is reduced, electron diffusion at the grain boundary is reduced, and the difficulty of current flow can be suppressed, thereby reducing the transmission loss of electromagnetic waves.

[0063] Also, the particle size d of the metal crystal (29) p For example, the size of the metal crystal (29) when viewed from a cross-section such as that of FIG. 7, in other words, the size of the metal crystal (29) observed when the first direction wiring (21) and the second direction wiring (22) are observed from a direction parallel to the length direction of the first direction wiring (21) and the second direction wiring (22), and the diameter of a circle with the same area may be used. Strictly speaking, the area average particle size of the metal crystal (29) is the particle size d for all metal crystals (29) included in the first direction wiring (21) and the second direction wiring (22). p The average value is calculated by investigating it. However, considering the size of the metal crystal (29), the particle size d of the metal crystal (29) within the first direction wiring (21) and the second direction wiring (22) p The particle size d of the metal crystal (29) in a quantity expected to show the overall trend of p The average value may be investigated and used as the area average particle size of the metal crystal (29). For example, the particle size d of 5 to 50 or more metal crystals (29) per length of 3 μm to 30 μm in the longitudinal direction of the first direction wiring (21) and the second direction wiring (22). pYou can investigate the average value and use it as the area average particle size of the metal crystal (29).

[0064] The location for measuring the area average particle size of the metal crystal (29) is a location spaced apart from the end of the measurement surface, such as the cross-section of the first direction wiring (21) and the second direction wiring (22), if the size required for measurement is narrower than the measurement surface. For example, if the position in the width direction of the first direction wiring (21) and the second direction wiring (22) can be measured, the measurement is taken at a location near the center spaced apart from the end in the width direction by a length of at least 10% of the width of the first direction wiring (21) and the second direction wiring (22). If the position in the thickness direction of the first direction wiring (21) and the second direction wiring (22) can be measured, the measurement is taken at a location near the center spaced apart from the end in the thickness direction by a length of at least 10% of the thickness of the first direction wiring (21) and the second direction wiring (22). Additionally, as described above, several points may be measured and their average value may be used as the area average particle size.

[0065] Additionally, as shown in FIG. 7, the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) may be 100 nm or less, and is preferably 90 nm or less. Furthermore, there is no specific lower limit for the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22), but it may be, for example, 5 nm or more. Since the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) is 100 nm or less, as described later, electrons flow mainly on the surface of the first direction wiring (21) and the second direction wiring (22) due to the skin effect, particularly in high-frequency electromagnetic waves. For this reason, the smoother the surface, that is, the smaller the surface roughness Ra, the lower the transmission loss of electromagnetic waves can be reduced. The surface roughness Ra is an arithmetic mean roughness measured using a non-contact illuminance meter. As a non-contact illuminance meter, the Keyence VK-X250 laser microscope (control unit) can be used.

[0066] Here, the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) refers to the surface roughness Ra of the outer surface of the first direction wiring (21) and the second direction wiring (22), specifically the surface roughness Ra of the surface (24a) of the first direction wiring (21) and the second direction wiring (22). Additionally, while it is preferable that the entire surface of the surface (24a) satisfy the above range, it is not limited to this, and the surface roughness Ra of a part of the surface (24a) may satisfy the above range. The location for measuring the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) is a location on the surface (24a) that is spaced apart from the end in the width direction. For example, it is measured at a location close to the center that is spaced apart from the end in the width direction by a length of at least 10% of the width of the first direction wiring (21) and the second direction wiring (22). Also, it may be 1 point, but it may be measured as several points and the average value may be used.

[0067] In addition, in the present embodiment, as described above, it is preferable that (i) the area average particle size of the metal crystal (29) included in the first direction wiring (21) and the second direction wiring (22) is 300 nm or more, and (ii) the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) is 100 nm or less. However, it is not limited to this, and it is sufficient to satisfy only one of the conditions (i) or (ii).

[0068] The materials of the first direction wiring (21) and the second direction wiring (22) may be conductive metal materials. In this embodiment, the materials of the first direction wiring (21) and the second direction wiring (22) are copper, but are not limited thereto. The materials of the first direction wiring (21) and the second direction wiring (22) may be metal materials (including alloys) such as gold, silver, copper, platinum, tin, aluminum, iron, and nickel. Additionally, the first direction wiring (21) and the second direction wiring (22) may be plating layers formed by electroplating.

[0069] Additionally, as illustrated in FIGS. 4 and 5, an adhesive layer (15) is formed on the substrate (11). The adhesive layer (15) enhances the adhesion between the substrate (11) and the first direction wiring (21) and the second direction wiring (22), and is formed over approximately the entire surface of the substrate (11). The adhesive layer (15) is made of an insulating film. As a material for this adhesive layer (15), for example, a colorless transparent resin such as an acrylic resin including polymethyl (meth)acrylate and polyethyl (meth)acrylate, and their modified resins and copolymers, a polyester, a polyvinyl resin including polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, and polyvinyl butyral, and their copolymers, a polyurethane, an epoxy resin, a polyamide, and a chlorinated polyolefin may be used. Additionally, the thickness of the adhesive layer (15) can be appropriately set in the range of 10 nm or more and 800 nm or less. Additionally, the adhesive layer (15) only needs to be formed on at least the mesh wiring layer (20) on the surface of the substrate (11).

[0070] An adhesive layer (16) is formed on the adhesive-easy layer (15). This adhesive layer (16) is located between the first direction wiring (21) and the second direction wiring (22) and the adhesive-easy layer (15). The adhesive layer (16) enhances the adhesion between the substrate (11) and the first direction wiring (21) and the second direction wiring (22), and is formed with a planar shape identical to that of the first direction wiring (21) and the second direction wiring (22). That is, the adhesive layer (16) has a grid shape or a mesh shape when viewed in a planar view. As the material for this adhesive layer (16), metal oxides such as titanium, titanium oxide, nickel, nickel oxide, indium-zinc oxide (IZO), and indium-tin oxide (ITO) can be used. Additionally, the thickness of the adhesion layer (16) can be selected from a range of 10 nm or more and 100 nm or less. Also, the adhesion layer (16) does not necessarily have to be provided.

[0071] Additionally, a protective layer (17) is formed on the surface of the substrate (11) to cover the first direction wiring (21), the second direction wiring (22), and the adhesive layer (15). The protective layer (17) protects the first direction wiring (21) and the second direction wiring (22) and is formed over approximately the entire surface of the substrate (11). As the material for the protective layer (17), colorless transparent insulating resins such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, acrylic resins and their modified resins and copolymers, polyester, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, polyvinyl butyral, polyvinyl resins and their copolymers, polyurethane, epoxy resin, polyamide, and chlorinated polyolefin may be used. Additionally, the thickness of the protective layer (17) can be selected from a range of 0.3 μm or more and 10 μm or less. Additionally, the protective layer (17) may be formed to cover at least the mesh wiring layer (20) of the substrate (11).

[0072] The overall opening ratio At of the mesh wiring layer (20) can be set to a range of, for example, 87% or more and less than 100%. By setting the overall opening ratio At of the wiring board (10) to this range, the conductivity and transparency of the wiring board (10) can be secured. In addition, the opening ratio refers to the ratio (%) of the area of ​​the opening region (an area where metal parts such as the first direction wiring (21) and the second direction wiring (22) do not exist and the substrate (11) is exposed) that occupies a unit area of ​​a predetermined region (for example, the entire mesh wiring layer (20)).

[0073] Referring again to FIG. 1, the power supply section (40) is electrically connected to the mesh wiring layer (20). This power supply section (40) is made of a conductive thin plate-like member with a roughly rectangular shape. The length direction of the power supply section (40) is parallel to the X direction, and the short direction of the power supply section (40) is parallel to the Y direction. Additionally, the power supply section (40) is positioned at the length direction end (the end on the Y-direction negative side) of the substrate (11). The material of the power supply section (40) may be a metal material (including alloys) such as gold, silver, copper, platinum, tin, aluminum, iron, nickel, etc. When the wiring board (10) is embedded in the image display device (90) (see FIG. 10), this power supply section (40) is electrically connected to the wireless communication circuit (92) of the image display device (90). Additionally, the power supply unit (40) is provided on the surface of the substrate (11), but is not limited thereto, and part or all of the power supply unit (40) may be located outside the periphery of the substrate (11). Additionally, by forming the power supply unit (40) flexibly, the power supply unit (40) may be able to go around the side or back side of the image display device (90) and be electrically connected from the side or back side.

[0074] [Method for manufacturing a wiring board]

[0075] Next, a method for manufacturing a wiring board according to the present embodiment will be described with reference to FIGS. 8a to 8e and FIGS. 9a to 9e. FIGS. 8a to 8e and FIGS. 9a to 9e are cross-sectional views illustrating a method for manufacturing a wiring board according to the present embodiment.

[0076] First, as illustrated in FIG. 8a, a substrate (11) is prepared, and an easy-to-adhesion layer (15) and an adhesion layer (16) are sequentially formed over approximately the entire surface of the substrate (11). As a method for forming the easy-to-adhesion layer (15), a roll coat, gravure coat, gravure reverse coat, micro gravure coat, slot die coat, die coat, knife coat, inkjet coat, dispenser coat, kiss coat, or spray coat may be used. Additionally, as a method for forming the adhesion layer (16), a deposition method, a sputtering method, or a plasma CVD method may be used.

[0077] Next, as illustrated in FIG. 8b, a conductive layer (51) is formed on the adhesion layer (16), covering approximately the entire surface of the substrate (11). In this embodiment, the thickness of the conductive layer (51) is 200 nm. However, it is not limited to this, and the thickness of the conductive layer (51) can be appropriately selected from a range of 10 nm or more and 1000 nm or less. In this embodiment, the conductive layer (51) is formed by sputtering using copper. As a method for forming the conductive layer (51), a plasma CVD method may be used.

[0078] Next, as shown in FIG. 8c, a photocurable insulating resist (52) is applied to the adhesion layer (16), which is approximately the entire surface of the substrate (11). As for this photocurable insulating resist (52), an organic resin such as an epoxy resin may be used.

[0079] Next, a transparent mold (53) for imprinting having a convex portion (53a) is prepared (Fig. 8d), and the mold (53) and the substrate (11) are brought close together so that a photocurable insulating resist (52) is spread between the mold (53) and the substrate (11). Subsequently, light irradiation is performed from the side of the mold (53) to cure the photocurable insulating resist (52), thereby forming an insulating layer (54). By doing so, a trench (54a) having a shape in which the convex portion (53a) is transferred is formed on the surface of the insulating layer (54). The trench (54a) has a planar shape pattern corresponding to the first direction wiring (21) and the second direction wiring (22).

[0080] After that, by peeling the mold (53) off the insulating layer (54), the insulating layer (54) with the cross-sectional structure shown in FIG. 8e is obtained. It is preferable that the direction in which the mold (53) is peeled off from the insulating layer (54) be in the Y direction, where the longer first direction wiring (21) is extended.

[0081] In this way, by forming a trench (54a) on the surface of the insulating layer (54) by an imprint method, the shape of the trench (54a) can be made fine. Furthermore, the insulating layer (54) may be formed by a photolithography method, not limited to this. In this case, a resist pattern is formed by a photolithography method to expose a conductive layer (51) corresponding to the first direction wiring (21) and the second direction wiring (22).

[0082] At this time, there may be residue of insulating material remaining at the bottom of the trench (54a) of the insulating layer (54). For this reason, the residue of insulating material is removed by performing wet treatment using an organic solvent such as a permanganate solution or N-methyl-2-pyrrolidone, or dry treatment using oxygen plasma.

[0083] In this way, by removing the residue of the insulating material, a trench (54a) with an exposed conductive layer (51) can be formed as shown in FIG. 9a.

[0084] Next, as illustrated in FIG. 9b, the trench (54a) of the insulating layer (54) is filled with a conductor (55). In this embodiment, the conductive layer (51) is used as a seed layer, and the trench (54a) of the insulating layer (54) is filled with copper using an electroplating method. Additionally, the conductor (55) has a planar shape corresponding to the first direction wiring (21) and the second direction wiring (22).

[0085] In this way, when filling the trench (54a) with a conductor (55) using an electroplating method, for example, by appropriately adjusting the plating solution used for electroplating, (i) the area average particle size of the metal crystal (29) included in the conductor (55) (first direction wiring (21) and second direction wiring (22)) can be made 300 nm or more, and / or (ii) the surface roughness Ra of the conductor (55) (first direction wiring (21) and second direction wiring (22)) can be made 100 nm or less. For example, when a conductor (55) is made of copper and a copper sulfate bath with copper sulfate as the main component is used as the plating solution, by appropriately adjusting various components such as copper sulfate, sulfuric acid, and a brightener containing a surfactant, the crystal growth rate can be suppressed, and consequently, the area average particle size of the metal crystal (29) contained in the conductor (55) can be increased, thereby suppressing the surface roughness Ra of the conductor (55). In this way, when a plating solution with copper sulfate as the main component is used, compared to when a general plating solution with copper cyanide as the main component is used, the area average particle size of the metal crystal (29) contained in the conductor (55) can be increased, and the outer surface of the conductor (55) can be made smooth.

[0086] Next, as illustrated in FIG. 9c, the insulating layer (54) is removed. In this case, the insulating layer (54) on the substrate (11) is removed by performing a wet treatment using an organic solvent such as a permanganate solution or N-methyl-2-pyrrolidone, or by performing a dry treatment using oxygen plasma.

[0087] Next, as illustrated in FIG. 9d, the conductive layer (51) and the adhesion layer (16) on the surface of the substrate (11) are removed. At this time, the conductive layer (51) and the adhesion layer (16) are etched so that the surface of the substrate (11) is exposed by performing a copper etching treatment using a copper etching solution such as an aqueous solution of ferric chloride, an aqueous solution of copper(II) chloride, an aqueous solution of ammonium peroxodisulfate, an aqueous solution of sodium peroxodisulfate, sulfuric acid, or hydrogen peroxide. Additionally, a blackened layer may be formed on the surface of the conductor (55) (first direction wiring (21) and second direction wiring (22)).

[0088] After that, as illustrated in FIG. 9e, a protective layer (17) is formed to cover the adhesive layer (15), the conductor (55), and the adhesion layer (16) on the substrate (11). As a method for forming the protective layer (17), roll coating, gravure coating, gravure reverse coating, micro gravure coating, slot die coating, die coating, knife coating, inkjet coating, dispenser coating, kiss coating, spray coating, screen printing, offset printing, and flexographic printing may be used.

[0089] In this way, a wiring board (10) having a substrate (11) and a mesh wiring layer (20) disposed on the substrate (11) is obtained (Fig. 9e). In this case, the mesh wiring layer (20) includes a first direction wiring (21) and a second direction wiring (22). At this time, a power supply section (40) may be formed by a part of the conductor (55). Alternatively, a flat power supply section (40) may be prepared separately and electrically connected to the mesh wiring layer (20).

[0090] [Operation of the present embodiment]

[0091] Next, the operation of the wiring board formed by this configuration will be explained.

[0092] As illustrated in FIG. 10, a wiring board (10) is embedded in an image display device (90) having a display (91). The wiring board (10) is placed on the display (91). Examples of such an image display device (90) include portable terminal devices such as smartphones and tablets. The mesh wiring layer (20) of the wiring board (10) is electrically connected to a wireless communication circuit (92) of the image display device (90) through a power supply unit (40). In this way, radio waves of a predetermined frequency can be transmitted and received through the mesh wiring layer (20), and communication can be performed using the image display device (90).

[0093] However, especially in the case of high-frequency electromagnetic waves used in recent years, the number of times electrons pass through the grain boundaries of the metal constituting the mesh wiring layer (20) per unit time increases, so it is difficult for current to flow, and there is a concern that transmission loss may increase.

[0094] In contrast, according to the present embodiment, (i) the area average particle size of the metal crystal (29) included in the first direction wiring (21) and the second direction wiring (22) is 300 nm or more, and / or (ii) the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) is 100 nm or less. As a result, the density of the metal crystal (29) is relatively lowered, so the total area of ​​the grain boundary is reduced, electron diffusion at the grain boundary is reduced, and the difficulty of current flow can be suppressed, thereby reducing the transmission loss of electromagnetic waves. In addition, since the surface of the first direction wiring (21) and the second direction wiring (22) is smooth, the transmission loss of electromagnetic waves can be reduced.

[0095] In addition, in recent years, the development of mobile terminal devices for fifth-generation communication, namely 5G (Generation), is underway. When the mesh wiring layer (20) of the wiring board (10) is used, for example, as a 5G antenna (especially a millimeter wave antenna), the radio waves (millimeter waves) transmitted and received by the mesh wiring layer (20) are of a higher frequency compared to the radio waves transmitted and received by, for example, a 4G antenna. Generally, when an alternating current is passed through a wire, as the frequency increases, it becomes difficult for the current to flow in the central part of the wire, and the current flows only on the surface of the wire. This phenomenon, in which current flows only on the surface when an alternating current is passed through a wire, is called the skin effect. Furthermore, skin depth refers to the depth from the surface of the wire where the current is attenuated by 1 / e (approximately 0.37) times with respect to the current on the surface of the wire where current flows most easily. This skin depth δ (see FIG. 6) can generally be calculated by the following formula.

[0096]

[0097] In addition, in the above equation, ω is the angular frequency (=2πf), and μ is the permeability (4π×10⁻⁶ in vacuum). -7 [H / m]), σ is the conductivity of the conductor constituting the wiring (5.8×10⁻⁶ in the case of copper) 7 [S / m]) means. The skin depth δ of the copper wiring is δ=approx. 2.3㎛ when the frequency is 0.8GHz, δ=approx. 1.3㎛ when the frequency is 2.4GHz, δ=approx. 1.0㎛ when the frequency is 4.4GHz, and δ=approx. 0.85㎛ when the frequency is 6GHz. In addition, the radio waves (millimeter waves) transmitted and received by the 5G antenna are high frequency (28GHz to 39GHz) compared to, for example, the radio waves transmitted and received by the 4G antenna, and, for example, when the frequency of the current is 28GHz to 39GHz, δ=approx. 0.3㎛ to approximately 0.4㎛.

[0098] For this reason, the smoother the surface of the mesh wiring layer (20), that is, the smaller the surface roughness Ra, the more the increase in the skin resistance of the wiring is suppressed, and the transmission loss occurring during the transmission and reception of radio waves can be reduced. In contrast, as a comparative example, if the surface roughness Ra of the wiring is large, the skin resistance of the wiring increases, and there is a risk of transmission loss occurring during the transmission and reception of radio waves. In particular, when the radio waves (millimeter waves) transmitted and received by the mesh wiring layer (20) are high frequency, the skin resistance of the first direction wiring (21) and the second direction wiring (22) can be reduced by suppressing the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) to 100 nm or less. For this reason, the flow of current in the mesh wiring layer (20) can be prevented from being hindered by the skin resistance of the first direction wiring (21) and the second direction wiring (22).

[0099] In addition, according to the present embodiment, the line width of the first direction wiring (21) and the second direction wiring (22) is 0.1 μm or more and 5.0 μm or less. By doing so, the first direction wiring (21) and the second direction wiring (22) can be made difficult to see with the naked eye, thereby preventing the visibility of the display (91) from being reduced.

[0100] In addition, in this embodiment, the dielectric loss of the substrate (11) is 0.002 or less, so that the dielectric loss generated during transmission and reception of the radio waves (millimeter waves) transmitted and received by the mesh wiring layer (20) can be reduced, especially when the radio waves (millimeter waves) transmitted and received by the mesh wiring layer (20) are high frequency.

[0101] In addition, according to the present embodiment, the first direction wiring (21) and the second direction wiring (22) are formed of a plating layer, thereby allowing the height H1 of the first direction wiring (21) and the height H2 of the second direction wiring (22) to be increased.

[0102] In addition, according to the present embodiment, since an adhesive-easy layer (15) is formed on the substrate (11), the adhesion between the substrate (11) and the first direction wiring (21) and the second direction wiring (22) can be increased. In addition, since an adhesive layer (16) is formed on the adhesive-easy layer (15), the adhesion between the substrate (11) and the first direction wiring (21) and the second direction wiring (22) can be further increased.

[0103] In addition, according to the present embodiment, a protective layer (17) is formed on the substrate (11) to cover the first direction wiring (21) and the second direction wiring (22), so that the first direction wiring (21) and the second direction wiring (22) can be protected from external impacts, etc.

[0104] In addition, according to the present embodiment, the mesh wiring layer (20) functions as an antenna. The mesh wiring layer (20) serving as an antenna can be placed on the outermost surface of the image display device (90). Because of this, communication performance can be improved compared to the case where the antenna is embedded in the image display device (90). Furthermore, since multiple mesh wiring layers (20) serving as antennas can be placed within the surface of the image display device (90), communication performance can be further improved.

[0105] In particular, when the mesh wiring layer (20) is used as an antenna, the degradation of antenna performance, specifically antenna performance such as S11, can be suppressed. Here, S11 refers to, for example, a value obtained by dividing the power reflected from the input terminal of the antenna by the power incident on the input terminal of the antenna. S11 can be measured, for example, using a network analyzer.

[0106] In addition, in this embodiment, the case where the mesh wiring layer (20) functions as an antenna has been described as an example, but it is not limited to this. The mesh wiring layer (20) may perform functions such as hovering (a function that allows operation without the user directly touching the display), fingerprint authentication, a heater, and noise cutting (shielding). Even in such cases, current can be made to flow easily through the mesh wiring layer (20).

[0107] In addition, in the present embodiment, the case in which both the first direction wiring (21) and the second direction wiring (22) are described as an example in which (i) the area average particle size of the metal crystal (29) included in the first direction wiring (21) and the second direction wiring (22) is 300 nm or more, and / or (ii) the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) is 100 nm or less is not limited thereto. Only one of the first direction wiring (21) and the second direction wiring (22) may be such that (i) the area average particle size of the metal crystal (29) included in the first direction wiring (21) and the second direction wiring (22) is 300 nm or more, and / or (ii) the surface roughness Ra of the first direction wiring (21) and the second direction wiring (22) is 100 nm or less.

[0108] [Example]

[0109] Next, specific embodiments of the present embodiment will be described.

[0110] (Creation of mesh patterns)

[0111] The wiring boards of the examples and comparative examples were prepared as follows.

[0112] (Example 1)

[0113] A copper mesh pattern was fabricated on a PET film substrate by an electroplating method using a plating solution with copper sulfate as the main component. By doing so, a wiring substrate (100) having a substrate (101) and a mesh wiring layer (102) was obtained (see FIG. 11). In addition, the size of the mesh wiring layer (102) was set to a width of 2 mm × a length of 7.5 mm, and a copper front area (103) with the same width of 2 mm and a length of 1 mm was formed at the end of the length of 7.5 mm. The mesh wiring layer (102) and the copper front area (103) are electrically connected. In addition, a copper front area (ground) (104) with a width of 6 mm or more and a length of 6 mm or more was formed at a width of 1 to 2 mm from the copper front area (103). The mesh wiring layer (102) is grid-like, and the front areas (103, 104) are front (solid). The width of each wire was set to 1 μm in both the width direction and the length direction of the mesh wiring layer (102). In addition, the height of each wire was set to 1 μm, and the pitch of each wire was set to 100 μm. The height of the front area (103, 104) was set to 1 μm.

[0114] (Example 2)

[0115] A wiring board of Example 2 was manufactured in the same manner as Example 1, except that the various components of the plating solution used to manufacture the mesh wiring layer (102) and the front area (103, 104) were different.

[0116] (Comparative Example 1)

[0117] A wiring board of Comparative Example 1 was manufactured in the same manner as Example 2, except that the various components of the plating solution used to manufacture the mesh wiring layer (102) and the front area (103, 104) were different.

[0118] For the wiring substrates (100) of the examples and comparative examples, the area average particle size of the copper crystals and the surface roughness Ra of the wiring were measured, respectively. The area average particle size of the copper crystals was analyzed by the SEM-EBSD method. In addition, the surface roughness Ra of the wiring was measured using a laser microscope (Keyence VK-X250 (control unit), VK-X260 (measurement unit), laser wavelength (408 nm)).

[0119] Using a vector network analyzer (Agilent 8722ES), the G signal of the coaxial cable was connected to a copper front area (104) with a width of 6 mm or more and a length of 6 mm or more, and the S signal was connected to a front area (103) of the mesh pattern end, and the S11 of the mesh wiring layer (102) at 8 to 12 GHz was measured.

[0120] As a result, having a peak of -10dB or less was evaluated as “◎” (excellent), having a peak of -8dB or less was evaluated as “○” (good), and not showing a peak of -8dB or less was evaluated as “×” (poor). The above evaluation results are shown in Table 1.

[0121]

[0122] It is also possible to appropriately combine the plurality of components disclosed in the above embodiments and variations as needed. Alternatively, some components may be deleted from the entire set of components shown in the above embodiments and variations.

Claims

Claim 1 A wiring substrate comprising a substrate and a mesh wiring layer disposed on the substrate and including a plurality of wirings, wherein the substrate has a transmittance of 85% or more for light rays with a wavelength of 400 nm or more and 700 nm or less, the wiring includes a surface roughness Ra, wherein the surface roughness Ra is 100 nm or less, the mesh wiring layer is an antenna having a frequency of radio waves to be transmitted and received of 28 GHz to 39 GHz, and the wiring includes a plurality of metal crystals disposed adjacent to each other through grain boundaries when viewed in cross-section, and the area average grain size of the metal crystals is 300 nm or more. Claim 2 A wiring board according to claim 1, wherein the line width of the wiring is 0.1㎛ or more and 5.0㎛ or less. Claim 3 In claim 1, the wiring comprises a wiring substrate including gold, silver, copper, platinum, tin, aluminum, iron, or nickel. Claim 4 A wiring board according to claim 1, wherein the dielectric loss tangent of the substrate is 0.002 or less. Claim 5 A wiring substrate according to claim 1, wherein the thickness of the substrate is 5㎛ or more and 200㎛ or less. Claim 6 In claim 1, the substrate is a wiring substrate comprising a cycloolefin polymer or a polynorbornene polymer. Claim 7 In claim 1, the mesh wiring layer is a wiring substrate that exists only in a part of the substrate. Claim 8 A wiring substrate according to claim 1, wherein the surface roughness Ra is 90 nm or less. Claim 9 A method for manufacturing a wiring board, comprising a process of preparing a substrate and a process of forming a mesh wiring layer including a plurality of wirings on the substrate, wherein the substrate has a transmittance of 85% or more for light rays with a wavelength of 400 nm or more and 700 nm or less, the wiring has a surface roughness Ra, the surface roughness Ra is 100 nm or less, the mesh wiring layer is an antenna having a frequency of 28 GHz to 39 GHz for transmitting and receiving radio waves, and the wiring includes a plurality of metal crystals arranged adjacent to each other through grain boundaries when viewed in cross-section, and the area average grain size of the metal crystals is 300 nm or more. Claim 10 A method for manufacturing a wiring board according to claim 9, wherein the line width of the wiring is 0.1 μm or more and 5.0 μm or less. Claim 11 In claim 9, the method of manufacturing a wiring board, wherein the wiring comprises gold, silver, copper, platinum, tin, aluminum, iron, or nickel. Claim 12 A method for manufacturing a wiring board according to claim 9, wherein the dielectric loss tangent of the substrate is 0.002 or less. Claim 13 A method for manufacturing a wiring board according to claim 9, wherein the thickness of the substrate is 5㎛ or more and 200㎛ or less. Claim 14 A method for manufacturing a wiring substrate according to claim 9, wherein the substrate comprises a cycloolefin polymer or a polynorbornene polymer. Claim 15 A method for manufacturing a wiring substrate according to claim 9, wherein the mesh wiring layer is present only in a part of the substrate. Claim 16 A method for manufacturing a wiring substrate according to claim 9, wherein the surface roughness Ra is 90 nm or less. Claim 17 delete Claim 18 delete Claim 19 delete Claim 20 delete

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