Wiring board, electronic device including wiring board, and method for manufacturing wiring board

Abstract

Provided is a wiring board in which bonding strength of a pattern formed on a base material thereof is improved. A wiring board 200 comprises: a base material 100 having a first surface 101 including a first direction (a direction parallel to a Y axis); and a plurality of conductor patterns 210 formed on the first surface 101 of the base material 100. The first surface 101 of the base material 100 contains a fluororesin preferentially oriented in the first direction. In a plan view, the plurality of conductor patterns 210 each include a first end part 221, a second end part 222, and a wiring part 225 electrically connecting the first end part 221 and the second end part 222. The wiring part 225 has one or more linear regions extending linearly, and is formed so that the extension direction of a longest linear region is substantially perpendicular to the first direction (the direction parallel to the Y axis) of the base material, the longest linear region having the longest extension length among the linear regions in the wiring board.

Description

Wiring board, electronic device using wiring board, and method for manufacturing wiring board

[0001] The present invention relates to a wiring board with improved bonding reliability, an electronic device using the wiring board, and a method for manufacturing the wiring board.

[0002] In recent years, with the increase in the volume of information and communication, the transmission signals in information and communication devices have become larger in capacity and faster. As a result, the wiring boards mounted on information and communication devices must be able to handle high-frequency signals, and wiring boards are required to have properties such as a low dielectric constant to improve transmission efficiency and a low dielectric loss tangent to enable reduction in transmission loss.

[0003] One example of an insulating material having such electrical properties is a fluororesin material such as polytetrafluoroethylene (PTFE). Fluororesin not only has extremely small values ​​of dielectric constant and dielectric loss tangent, but also has properties such as heat resistance and elastic modulus that are suitable for use as a wiring board material. Therefore, attempts have been made to achieve low-loss signal transmission in extremely high frequency ranges by using wiring boards that use fluororesin as the base material.

[0004] Wiring boards require extremely fine patterns, such as conductors, to be formed with high precision on the surface or inside of the board. Therefore, in order to improve the reliability of wiring boards, it is essential to ensure a certain level of bonding strength between the substrate and the conductor pattern.

[0005] Patent Document 1 discloses a fluororesin printed circuit board including an insulating layer made of at least one layer of nonwoven fabric formed by fusion bonding fluororesin short fibers randomly oriented in both the longitudinal and transverse directions, the insulating layer being substantially made of fluororesin, and a conductor layer having a desired pattern bonded to at least one surface of the insulating layer by thermocompression bonding. According to this fluororesin printed circuit board, the randomly oriented fluororesin short fibers are wrapped around minute protrusions on the back surface of the conductor layer by thermocompression bonding, thereby exerting a strong anchor effect, thereby improving the peel strength of the conductor layer.

[0006] The fluororesin printed circuit board described in Patent Document 1 is produced by fusing fluororesin short fibers, and therefore the surface of the substrate is rough when viewed microscopically. From this perspective, the anchoring effect described above can be expected, improving the peel strength of the conductive layer. On the other hand, if the substrate surface is rough, the surface roughness of the conductive layer along the rough substrate increases, resulting in a problem of deterioration in electrical characteristics, particularly for high-frequency transmission signals, due to the skin effect.

[0007] Patent Document 2 discloses a fluororesin film whose melting curve has an endothermic peak at a predetermined position and has a specific relationship between film thickness and haze value. This fluororesin film has a linear expansion coefficient of 100 ppm / °C or less in the X and Y directions of the film at 30°C to 250°C, achieving both excellent electrical and physical properties. However, even with this film, there is still room for improvement in the bonding strength with conductive materials such as copper foil.

[0008] JP 2002-076544 A International Publication No. 2022 / 071237

[0009] In view of the above circumstances, the invention described in the claims of this application aims to provide a wiring board having improved bonding strength of a pattern formed on a base material and excellent reliability, an electronic device using the wiring board, and a method for manufacturing the wiring board.

[0010] A wiring board according to one aspect of the present invention is a wiring board comprising a substrate having a first surface including a first direction and a plurality of conductor patterns formed on the first surface of the substrate, wherein the first surface of the substrate contains a fluororesin preferentially oriented in the first direction, and the plurality of conductor patterns each include, in a planar view, a first end, a second end, and a wiring portion electrically connecting the first end and the second end, and the wiring portion has one or more linear regions extending in a straight line, and when the linear region having the greatest extension length within the wiring board is defined as a longest linear region, the extension direction of the longest linear region is formed so as to be approximately perpendicular to the first direction of the substrate. A wiring board according to another aspect of the present invention is a wiring board including a substrate having a first surface including a first direction and a plurality of conductor patterns formed on the first surface of the substrate, wherein the first surface of the substrate includes a fluororesin, and the plurality of conductor patterns each include, in a plan view, a first end, a second end, and a wiring portion electrically connecting the first end and the second end, and the wiring portion has one or more linear regions extending linearly, and when the linear region having the longest extension length in the wiring board is defined as a longest linear region, in a cross section of the substrate perpendicular to the first surface of the substrate, a refractive index of a cross section of the substrate perpendicular to the extension direction of the longest linear region is greater than a refractive index of a cross section of the substrate parallel to the extension direction of the longest linear region.An electronic device according to another aspect of the present invention is characterized by comprising any of the above wiring boards and an electronic component connected to the first end.Furthermore, a method for manufacturing a wiring board according to one aspect of the present invention includes preparing a fluororesin sheet containing a fluororesin, orienting the fluororesin sheet so that a first direction in the plane of the sheet is a direction in which fluororesin molecules are preferentially oriented, and forming a plurality of conductor patterns on a surface of the sheet, wherein the plurality of conductor patterns each include, in a planar view, a first end, a second end, and a wiring portion electrically connecting the first end and the second end, the wiring portion having one or more linear regions extending linearly, and forming the wiring board such that the extension direction of the linear region having the longest extension length is approximately perpendicular to the first direction.

[0011] 1A is a schematic diagram of a wiring board 200 according to a first embodiment of the present invention. FIG. 1A is a schematic diagram of the surface of the wiring board 200 on which a conductor pattern 210 is formed, viewed from vertically above, and FIG. 1B is a schematic diagram showing a cross section of the wiring board 200 viewed from the lateral direction of the base material. FIG. 1B is a schematic diagram of the surface of the wiring board 200 according to a second embodiment of the present invention on which a conductor pattern 210 is formed, viewed from vertically above. FIG. 1C is a schematic diagram of the surface of the wiring board 200 according to a third embodiment of the present invention on which a conductor pattern 210 is formed, viewed from vertically above. FIG. 1D is a schematic diagram of the surface of the wiring board 200 according to a fourth embodiment of the present invention on which a conductor pattern 210 is formed, viewed from vertically above. FIG. 1E is a schematic diagram of the surface of the wiring board 200 according to a fifth embodiment of the present invention on which a conductor pattern 210 is formed, viewed from vertically above. FIG. 1F is a schematic diagram of the wiring board 200 according to a sixth embodiment of the present invention. 6( a) is a schematic diagram of the surface of the wiring board 200 on which the conductor pattern 210 is formed, viewed from vertically above, and FIG. 6( b) is a schematic diagram showing a cross section of the wiring board 200 viewed from the lateral direction of the substrate. FIG. 6( b) is a schematic diagram of the wiring board 200 according to a seventh embodiment of the present invention, and is a diagram explaining the refractive index of the cross section of the substrate 100 constituting the wiring board 200. FIG. 6( a) is a schematic diagram of the wiring board 200 according to an eighth embodiment of the present invention. FIG. 6( b) is a schematic diagram of the wiring board 200 according to a ninth embodiment of the present invention, and a perspective view of an electronic device 300. FIG. 6( a) is a schematic diagram of an endoscope 400, which is an example of the electronic device 300 according to a tenth embodiment of the present invention. FIG. 6( b) is a schematic diagram of the electronic device 300 according to an eleventh embodiment of the present invention. FIG. 6( b) is a schematic diagram of the wiring board 200 according to a thirteenth embodiment of the present invention. FIG. 6( b) is a schematic diagram of the wiring board 200 according to a fourteenth embodiment of the present invention.

[0012] The following describes embodiments of the wiring board according to the invention as claimed in the present application, an electronic device using such a wiring board, and a method for manufacturing a wiring board. The embodiments described below do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. Furthermore, each embodiment and example can be freely combined within the scope that does not lose the technical significance of the present invention.

[0013] (Example 1) (First Embodiment) Figure 1 is a schematic diagram of a wiring board 200 according to a first embodiment of the present invention. Figure 1(a) is a schematic diagram of the surface of the wiring board 200 on which a conductor pattern 210 is formed, viewed from vertically above, and Figure 1(b) is a schematic diagram showing a cross section of the wiring board 200, viewed from the lateral direction of the base material. The wiring board 200 according to the present invention can be used, for example, as a flexible wiring board that transmits signals between two electronic components.

[0014] The wiring board 200 includes a substrate 100 containing fluororesin and a conductor pattern 210 (P １ In this specification, in order to distinguish the conductor pattern 210 from other conductor patterns, the conductor pattern is referred to as P ｎ (n: natural number) The substrate 100 has a first surface 101, and the fluororesin constituting the substrate 100 is preferentially oriented in at least the first surface 101 in the direction indicated by the Y axis of the Cartesian coordinate system shown in the drawing.

[0015] Conductor pattern 210 (P １ ) is formed on the first surface 101 of the substrate 100, and has a first end portion 221 at one end and a second end portion 222 at the other end in a plan view (i.e., when viewed from the thickness direction of the substrate indicated by the Z axis in the drawing). １ ) further includes a wiring portion 225 , which is formed as a conductive path that electrically connects the first end portion 221 and the second end portion 222 .

[0016] The wiring portion 225 has a "linear region" that extends linearly. When an imaginary straight line located on the first surface 101 of the substrate 100 is defined as an imaginary straight line 1000, the "linear region" refers to a region of the wiring portion 225 that is configured with a constant wiring width, is disposed on any imaginary straight line 1000 on the first surface 101, and extends in a direction parallel to the imaginary straight line 1000. In other words, the wiring portion in the linear region has a shape that is approximately symmetrical with respect to the imaginary line corresponding to the linear region. The extension length of the linear region refers to the length of the region of the conductor pattern on the imaginary line corresponding to the linear region. For example, in the embodiment of FIG. 1, the conductor pattern 210 (P １The entire length of the wiring portion 225 of the conductor pattern 210 (P １ The wiring portion 225 of the conductor pattern 210 (P) has a constant wiring width over its entire length, is disposed on the imaginary straight line 1000, and extends parallel to the imaginary straight line 1000. １ ) has a linear region with an extension length indicated by A in FIG. 1(a).

[0017] As will be described later, when the wiring substrate 200 has a plurality of conductor patterns and / or when one conductor pattern has a plurality of extension directions, the wiring substrate 200 includes a plurality of straight line regions. If the straight line region having the longest extension length among the plurality of straight line regions is defined as the "longest straight line region," the extension direction of the longest straight line region is formed so as to be approximately perpendicular to the first direction of the base material 100.

[0018] In the embodiment of FIG. 1, a wiring substrate 200 includes a conductor pattern 210 (P １ ), the longest linear area of ​​the wiring board 200 is 210 (P １ ) is a linear region of the wiring portion 225. The direction of extension of the longest linear region is the X-axis direction in the figure, that is, it is approximately perpendicular to the first direction (Y-axis direction in the figure), which is the direction in which the fluororesin on the first surface 101 of the substrate 100 is preferentially oriented. The direction in which the longest linear region extends is also referred to as the "second direction" in this specification. The wiring board 200 having the above configuration improves the bonding strength between the specific conductor pattern formed on the substrate and the substrate, and can provide excellent reliability.

[0019] While promoting efforts to control various mechanical properties of wiring boards by controlling the molecular orientation of fluororesin, the present inventors discovered that the bonding strength of a conductor pattern having a specific configuration can be controlled by the orientation of the fluororesin on the substrate surface. For example, they found that the peel strength of a rectangular conductor pattern can be increased by approximately 40% when the long side of the conductor pattern is oriented perpendicular to the preferred orientation of the fluororesin on the substrate surface compared to when the long side is oriented parallel to the preferred orientation. In other words, they found that even for two conductor patterns with the same width, when these conductors extend in mutually perpendicular directions, the peel strength of a specific conductor pattern can be controlled, for example, by 1.3 times or more relative to the other conductor pattern, depending on the relationship between their extension directions and the orientation of the fluororesin on the substrate surface.

[0020] That is, the fluororesin on the first surface 101 of the base material 100 of the wiring board 200 is given an orientation so that it is preferentially oriented in a certain direction, and a specific conductor pattern 210 (P １ By forming the extending direction of the fluororesin layer 10 so as to be approximately perpendicular to the direction in which the fluororesin is preferentially oriented, it is possible to provide a wiring board with excellent reliability.

[0021] As the specific conductor pattern, the longest linear region of the wiring portion in the wiring substrate 200 is selected as a region having a configuration in which the improvement of its bonding strength contributes to the reliability of the wiring substrate. This is because a conductor pattern having an extending region over a long distance is most susceptible to internal (e.g., internal stress due to mismatch of Young's modulus or thermal expansion) and / or external (e.g., external stress due to contact with transportation system components) stress during and after manufacturing, and therefore the bonding strength with the substrate has a relatively large effect on the reliability of the wiring substrate.

[0022] The mechanism by which the bonding strength of a conductor pattern can be controlled by the orientation direction of the substrate surface is believed to be, for example, as follows. In this specification, molecular orientation (sometimes simply referred to as orientation) refers to a state in which polymer molecular chains are aligned in a certain direction to form a molecular structure that is nearly linear. In a component such as a sheet, membrane, or substrate made of such a polymer, when viewed macroscopically, the state in which the molecular chains are aligned (molecular chain axis direction) is biased in one direction is said to be preferentially oriented in a specific direction. In other words, the molecular chain axis direction possessed by the largest number of molecules among the molecules constituting the component can be considered the component's preferential orientation. A component that is preferentially oriented in a specific direction in this way has anisotropic physical properties resulting from molecular orientation. Examples of such physical properties include tensile strength, linear expansion coefficient, and / or refractive index. The present inventors have confirmed that the destruction mode when the conductor pattern 210 is peeled from the substrate 100 described in the present specification includes a mode in which the substrate 100 itself undergoes material destruction. In light of the above, when the material constituting the first surface 101 of the substrate 100 is preferentially oriented in the first direction of the first surface 101 and the longest linear region of the conductor pattern extends parallel to the first direction, peeling between the substrate 100 and the conductor pattern 210 can be achieved by peeling the material of the substrate 100 along that orientation. That is, this can be achieved with a relatively small force that exceeds the intermolecular force. In contrast, when the longest linear region of the conductor pattern 210 extends in a direction substantially perpendicular to the first direction of the first surface 101 of the substrate 100, peeling between the substrate 100 and the conductor pattern 210 requires peeling the material of the substrate 100 in a direction perpendicular to the orientation. More specifically, a relatively large force is required to sever the molecular chains of the material at the peeling location of the substrate 100, i.e., to break the covalent bonds within the molecules, which is thought to improve the bonding strength between the substrate 100 and the conductor pattern 210.

[0023] The bond strength between the substrate and the conductor pattern can be evaluated based on the value measured in accordance with the method for measuring the peel strength of flexible printed wiring boards described in Japanese Industrial Standard JIS C 5016-1994. The peel test can be performed using an autograph (AGS-X manufactured by Shimadzu Corporation) by peeling the conductor pattern at a speed of 50 mm / min in a direction forming an angle of 90 degrees with respect to the conductor pattern-removed surface of the substrate 100, and measuring the peel strength (N / mm) measured by the autograph.

[0024] The first surface 101 of the substrate 100 preferably contains a fluororesin as a main component. Here, "main component" refers to the component that occupies the largest amount in the composition, and this also applies hereinafter unless otherwise specified. From the viewpoint of electrical properties, the proportion of the fluororesin in the first surface 101 is preferably 90 wt % or more, more preferably 95 wt % or more, even more preferably 99.5 wt % or more, and particularly preferably 99.8 wt % or more. Furthermore, the substrate 100 may contain a fluororesin as a main component.

[0025] The fluororesin may be, for example, polytetrafluoroethylene (hereinafter referred to as PTFE) as the main component. PTFE may be a homopolymer of tetrafluoroethylene (hereinafter referred to as TFE), or may be modified PTFE containing other monomers. Examples of monomers other than TFE contained in the modified PTFE include ethylene, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and perfluoroalkyl vinyl ether (PAVE), and the modified PTFE may contain one or more of these monomers in combination. Furthermore, the fluororesin may be primarily composed of polyvinylidene fluoride (PVDF), perfluoroalkoxyalkane (PFA), which is a copolymer of TFE and PPVE, perfluoroethylenepropene copolymer (FEP), which is a copolymer of TFE and HFP, or ethylene-tetrafluoroethylene copolymer (ETFE), which is a copolymer of ethylene and TFE. From the viewpoint of electrical properties, a homopolymer of TFE is preferable. The polymer constituting the substrate 100 may include PE (polyethylene), PP (polypropylene), PA (polyamide), POM (polyacetal, polyoxymethylene), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), PEEK (polyether ether ketone), LCP (liquid crystal polymer), etc. These materials, depending on impurities and thickness, can provide a flexible substrate 100 and a flexible wiring board using the same.

[0026] The main surface of the substrate 100 is the surface with the largest area that is in a front-back relationship. As such main surfaces, the substrate 100 has a first surface 101 and a second surface 102 that is in a front-back relationship with the first surface 101. FIG. 1( a) is a plan view of the first surface 101 of the substrate 100. Note that the ordinal numbers such as "first" for the first surface 101 and "second" for the second surface 102 do not indicate an order but are simply used to distinguish between the two surfaces. Unless otherwise specified, other ordinal numbers in this specification are also based on this concept.

[0027] Directions are defined based on the first surface 101 of the substrate 100. Note that, if the first surface 101 and the second surface 102 are parallel, each direction may be defined based on the second surface 102. In this specification, it is basically assumed that the first surface 101 and the second surface 102 are parallel, but this does not mean that the first surface 101 and the second surface 102 are parallel at a geometric level. In this specification, one direction in the extension plane of the first surface 101 is defined as the X direction, a direction perpendicular to the X direction in the extension plane of the first surface 101 is defined as the Y direction, and a direction perpendicular to both the X direction and the Y direction is defined as the Z direction. The first surface 101 of the substrate 100 includes a bonding interface with the conductor pattern 210.

[0028] Although not shown, the wiring substrate 200 may further include a second layer on the surface opposite to the first surface 101 of the substrate 100. The second layer may have the same configuration as the substrate 100, or may include another layer on the surface opposite to the bonding surface with the substrate 100. The second layer preferably contains a fluororesin preferentially oriented in a direction parallel to the first surface 101 of the substrate 100 and substantially perpendicular to the first direction.

[0029] In this specification, a conductor pattern refers to a conductor configured to form a specific shape in a planar view. The conductor pattern 210 on the first surface 101 of the substrate 100 has a first end 221 used as an input terminal (or output terminal) for an electrical signal in a planar view, a second end 222 used as an output terminal (or input terminal) for an electrical signal, and a wiring portion 225 electrically connecting the first end 221 and the second end 222. These input terminals and / or output terminals are, for example, called pads or fingers, and are regions for electrical connection with various electronic components such as connectors, plugs, passive components, sensors, semiconductor components, or other wiring boards. Alternatively, they may be, for example, called via lands or through-hole lands, and may be regions for stable connection with vias or through-holes that form electrical connections between the conductor pattern on the first surface 101 and the conductor patterns of other conductor layers when the wiring board 200 includes other conductor layers. In this specification, when the wiring substrate 200 includes curved and / or bent portions, it is advisable to check the conductor pattern 210 and other configurations after placing it in a stretched state on a surface plate.

[0030] In this embodiment, the first end 221 and the second end 222 are substantially circular, but the shapes of the first end 221 and the second end 222 are not limited to this, and there are no particular limitations on the shapes of the first end 221 and the second end 222. The end width of the first end 221 and the second end 222 is preferably formed to be 1.15 times or more larger than the wiring width. Here, the wiring width is the length of the wiring portion in a direction perpendicular to the direction in which electrical energy such as an electrical signal flows (hereinafter referred to as the transmission direction) in a planar view. The end width is the maximum end length in a direction parallel to the wiring width in a planar view.

[0031] The wiring portion 225 serves as a conductive path for transmitting electrical energy such as an electrical signal. In a linear region of the wiring portion 225, the direction of transmission can also be considered to be linear.

[0032] If there is only one conductor pattern 210 in the wiring substrate 200, and the shape of the conductor pattern 210 is L-shaped in plan view with two straight line regions, and there is a difference in the extension lengths of the two straight line regions, the straight line region with the longer extension length is the longest straight line region. If there are multiple conductor patterns 210 in one wiring substrate 200, the straight line region of each of the multiple conductor patterns 210 with the longest extension length is the longest straight line region. It is preferable that the extension direction of the longest straight line region is formed so as to be approximately perpendicular to the first direction of the base material 100.

[0033] The conductor pattern 210 described above can be composed of a first metal layer 211 formed directly on the first surface 101 of the substrate 100, as shown in FIG. 1B. This first metal layer 211 preferably contains copper from the viewpoints of electrical conductivity and processability. Alternatively, the first metal layer 211 may contain a conductive material such as gold, silver, nickel, aluminum, titanium, or tungsten.

[0034] Here, "substantially perpendicular" in this specification means that the included angle θ between the extension direction of the longest linear region and the first direction is greater than 67.5 degrees and less than 112.5 degrees. Furthermore, this included angle θ is preferably closer to 90 degrees. The included angle θ is preferably greater than 80 degrees and less than 100 degrees, and more preferably greater than 85 degrees and less than 95 degrees.

[0035] As a result of improving the bonding strength between the substrate 100 and the conductor pattern 210 as described above, the wiring board 200 according to the present invention can have a relative dielectric constant εr of 2.3 or less, preferably 2.1 or less, at 30 GHz and 22° C., and a dielectric loss tangent tanδ of 0.001 or less, more preferably 0.0003 or less, and particularly preferably 0.0001 or less. Furthermore, even at 50 GHz and 110 GHz, the relative dielectric constant εr at 22° C. can be 2.3 or less, preferably 2.1 or less, and a dielectric loss tangent tanδ of 0.001 or less, more preferably 0.0003 or less, and particularly preferably 0.0001 or less. Furthermore, the wiring board 200 can have a relative permittivity εr of 2.3 or less, preferably 2.1 or less, at 22°C even at 250 GHz and 300 GHz, and a dielectric loss tangent tanδ of 0.001 or less, more preferably 0.0003 or less, and particularly preferably 0.0001 or less, thereby providing a wiring board with extremely excellent electrical properties. The relative permittivity εr and dielectric loss tangent tanδ can be measured using a general measuring device, but measurements in the high-frequency range, such as 250 GHz and 300 GHz, can be performed using the Fabry-Perot method, which is a type of open-type resonator method. When measuring electrical properties using the Fabry-Perot method, it is preferable to use a measurement environment with a temperature of 25°C ±3°C and a relative humidity of approximately 60% or less. The relative permittivity εr and dielectric dissipation factor tanδ of the wiring board 200 described in the present application were measured by the Fabry-Perot method, and it was found that the relative permittivity εr was 2.3 or less and the dielectric dissipation factor tanδ was 0.001 or less at 250 GHz and 22°C. Similarly, it was confirmed that the relative permittivity εr was 2.3 or less and the dielectric dissipation factor tanδ was 0.001 or less at 300 GHz and 22°C. Furthermore, at any frequency in the range of 250 GHz to 300 GHz at 22°C, the relative permittivity εr of the substrate described in the present application was 2.3 or less and the dielectric dissipation factor tanδ was 0.001 or less.

[0036] To summarize the above, the wiring board 200 of the present invention can be, for example, a wiring board 200 comprising a substrate 100 having a first surface 101 including a first direction and a plurality of conductor patterns 210 formed on the first surface 101 of the substrate 100, wherein the first surface 101 of the substrate 100 contains a fluororesin preferentially oriented in the first direction, and the plurality of conductor patterns 210 each include, in a planar view, a first end 221, a second end 222, and a wiring portion 225 that electrically connects between the first end and the second end, and the wiring portion 225 has one or more linear regions that extend linearly, and the wiring board 200 can be formed so that the extension direction of the linear region having the longest extension length within the wiring board 200 is approximately perpendicular to the first direction of the substrate 100.

[0037] According to the wiring board 200 of the present invention as described above, it is possible to provide a wiring board having excellent electrical characteristics and improved bonding strength of the specific conductor pattern 210 formed on the base material 100.

[0038] In the embodiment shown in FIG. 1 , a wiring board 200 in which a conductor pattern 210 is formed only on the first surface 101 of the substrate 100 is described as an example. However, the present invention can also be applied to a wiring board 200 in which a conductor pattern is also formed on the second surface 102. In this case, it is preferable that the direction in which the longest linear region of the conductor pattern in the wiring board 200 extends is approximately perpendicular to a first direction on the first surface 101 that includes the bonding interface with the longest linear region. In addition to the above, it is more preferable that the direction in which the longest linear region of the conductor pattern formed on the second surface 102 of the substrate 100 extends is approximately perpendicular to a first direction on the second surface 102 (the direction in which the fluororesin on the second surface 102 is preferentially oriented). In this case, the conductor pattern formed on the first surface 101 and the conductor pattern formed on the second surface 102 may be electrically connected via a through hole. A wiring board 200 having conductor patterns on both the first surface 101 and the second surface 102 of the substrate 100 has two layers of conductor patterns. However, the present invention can also be applied to a wiring board 200 having, for example, three layers of conductor patterns, by further disposing a new substrate on the second surface 102 and forming a conductor pattern on the new substrate. In this case, the new substrate may be bonded via an adhesive layer such as a bonding sheet. By expanding this, the present invention can be applied to a wiring board 200 having multiple layers of conductor patterns, and the definition of the longest straight line region in the wiring board 200 is the same as that described above for such a wiring board 200.

[0039] In the embodiment shown in FIG. 1 , the wiring board 200 includes a substrate 100 and a pattern formed on the first surface 101. Here, the term "pattern" as used herein is not limited to a conductor pattern made of a conductor, but may also include an insulator pattern made of an insulator having a specific shape when viewed perpendicularly from the first surface 101. Examples of insulator patterns include patterns made of a protective layer formed on the surface of the substrate, such as solder resist or coverlay. The wiring board 200 may also include a pattern serving as a protective layer (not shown) on the first surface 101 side of the substrate 100. Examples of protective layers include coatings such as solder resist and coverlay. It is preferable that such an insulator pattern be formed directly on the first surface 101 of the substrate 100. In other words, the first surface 101 of the substrate 100 may include a bonding interface with the insulator pattern. The wiring board 200 may also include a support layer on the second surface 102 side of the substrate 100. This support layer may be a glass epoxy resin in which glass fibers are impregnated with epoxy resin, which is used for rigid substrates, and by providing such a support layer on the second surface side of base material 100, wiring board 200 can be used for rigid substrates. The support layer may be a single layer, or multiple layers may be laminated.

[0040] An example of a method for manufacturing the wiring substrate 200 according to the present invention as described above is as follows. First, a fluororesin sheet containing a fluororesin is prepared, and the fluororesin sheet is oriented so that a first direction of the fluororesin sheet in the plane of the sheet corresponds to a direction in which the fluororesin molecules are preferentially oriented. Then, a plurality of conductor patterns are formed on the surface of the oriented fluororesin sheet. The plurality of conductor patterns can be formed so as to include, in a plan view, a first end portion 221, a second end portion 222, and a wiring portion 225 that electrically connects the first end portion 221 and the second end portion 222. Furthermore, the wiring portion 225 can have one or more linear regions that extend linearly, and can be formed so that the extension direction of the linear region having the longest extension length in the wiring substrate 200 is approximately perpendicular to the first direction.

[0041] Methods for imparting orientation to a fluororesin sheet include extrusion, rolling, and / or stretching of the fluororesin material. When the shape of the material to be processed is stretched in a certain direction by these means, the molecular chains that make up the material also approach an alignment that is stretched in the same direction.

[0042] The oriented fluororesin sheet may serve as the first surface 101 of the substrate 100 in FIG. 1 . A member preferentially oriented in a specific direction, such as the oriented fluororesin sheet, exhibits anisotropy of physical properties within its plane. Such anisotropy of physical properties may be such that the tensile strength of the member in the specific direction is greater than the tensile strength of the member in a direction generally perpendicular to the specific direction. Alternatively, the linear expansion coefficient of the member in the specific direction is smaller than the tensile strength of the member in a direction generally perpendicular to the specific direction. Specifically, the tensile strength of the member in the specific direction may be at least 1.5 times, or even at least 2.0 times, greater than the tensile strength of the member in a direction generally perpendicular to the specific direction. The tensile strength of such a member can be measured in accordance with JIS K7127. Furthermore, the linear expansion coefficient of the member in the specific direction may be at least 50 ppm / °C smaller, or at least 80 ppm / °C smaller, than the linear expansion coefficient of the member in a direction generally perpendicular to the specific direction. And / or, the linear expansion coefficient of the member in the specific direction may be half or less of the linear expansion coefficient of the member in a direction substantially perpendicular to the specific direction. The linear expansion coefficient of such a member can be calculated from the results of measurement in a temperature range of 30°C to 250°C by mechanical thermal analysis (TMA method) in accordance with ISO 11359-2. In this embodiment, a member having the above-mentioned anisotropy in tensile strength and / or linear expansion coefficient can be selected as the material constituting the first surface 101 of the substrate 100. A method for forming a conductor pattern on the surface of an oriented fluororesin sheet can be formed by directly superimposing a thin metal film such as copper foil on the fluororesin sheet and, for example, pressing it. However, the method for forming the conductor pattern 210 is not limited to this method. For example, a metal film (first metal layer 211) may be grown on the fluororesin sheet (first surface 101 of the substrate 100) by other means such as plating. In addition, the first metal layer 211 can be further nickel-plated, and then gold-plated on top of the nickel plating. This treatment can prevent oxidation and corrosion in the areas where it is applied, allowing good solderability to be maintained for a long period of time.As described above, by understanding and controlling the positional relationship between the first direction of the first surface 101 of the base material 100 and the direction in which the longest linear region of the conductor pattern 210 extends, it is possible to obtain a wiring substrate 200 with improved bonding strength between the base material 100 and the conductor pattern 210. The mounting design of the substrate can be implemented to achieve the above configuration.

[0043] According to the method for manufacturing the wiring board 200 of the present invention as described above, it is possible to manufacture a wiring board 200 that has excellent electrical properties and has improved bonding strength of the specific conductor pattern 210 formed on the base material 100.

[0044] The fluororesin sheet may be primarily composed of PTFE. In this case, an example of a method for manufacturing the wiring substrate 200 according to the present invention is as follows. First, a fluororesin sheet (hereinafter referred to as a PTFE sheet) made of a film of PTFE is prepared. The PTFE sheet can be produced by, for example, passing PTFE resin through an extrusion die while applying pressure. Next, the PTFE sheet is oriented so that a first direction of the PTFE sheet in the sheet plane corresponds to the direction in which PTFE molecules are preferentially oriented. Then, a conductor pattern 210 is formed on the surface of the oriented PTFE sheet. This conductor pattern 210 can be formed to include, in a plan view, a first end 221, a second end 222, and a wiring portion 225 that electrically connects the first end 221 and the second end 222. Furthermore, within each wiring portion 225 of this conductor pattern 210, the extension direction of the linear region having the greatest extension length (longest linear region) can be formed so as to be approximately perpendicular to the first direction of the base material.

[0045] Methods for imparting orientation to a PTFE sheet include extrusion, rolling, and / or stretching of PTFE, but it is particularly preferable for the orientation process to include stretching. Stretching is preferably carried out at a temperature lower than the crystalline melting temperature of PTFE. It is known that under these conditions, a unique microporous structure consisting of nodes and fibrils, in which fibrils are preferentially aligned in the direction of greatest orientation, can be obtained. An appropriate combination of extrusion, rolling, and stretching is suitable for obtaining fibrous or film-like resin materials with a high degree of orientation. The structure with a unique microstructure consisting of nodes and fibrils obtained by stretching PTFE is called expanded PTFE, expanded PTFE, or expanded PTFE. In the process of preparing this oriented PTFE sheet, if the direction with the greatest stretch ratio is defined as the first stretching direction, the first direction of the first surface 101 of the substrate 100 is preferably formed parallel to this first stretching direction. Here, the stretching ratio refers to the rate of change in dimension of the sheet in the stretching direction before and after stretching.

[0046] A process of compressing the PTFE sheet in the thickness direction may also be included. In this process, the PTFE sheet may be a single sheet, multiple sheets may be stacked, or sheets of other materials may be stacked and compressed. When stacking and compressing, however, it is preferable to position the oriented PTFE sheet on the front side so that it forms the bonding surface with the conductor pattern. The oriented PTFE sheets may also be stacked so that their preferential orientations (molecular chain axis direction) intersect with each other. In this compression process, the PTFE sheet can be sandwiched and pressure applied using a press, for example. Alternatively, the PTFE sheet can be continuously pressed by passing it between one or more pairs of rolls. The temperature during compression can be, for example, 40°C or higher and 340°C or lower. The pressure during compression is adjusted appropriately based on the thickness and density of the substrate to be obtained; for example, in the case of a press, the pressure can be in the range of 5 MPa to 400 MPa.

[0047] Next, a process for forming a conductor pattern 210 on the oriented PTFE sheet is performed. First, a first metal layer 211 is formed directly on the oriented PTFE sheet of the conductor pattern 210. The surface of the oriented PTFE sheet on which the first metal layer 211 is formed corresponds to the first surface 101 of the substrate 100 in the wiring board 200 according to the present invention. In other words, the first surface 101 includes a bonding interface with the conductor pattern 210. The first metal layer 211 can be formed on the first surface 101 of the substrate 100, for example, by overlapping a rolled copper foil with the PTFE sheet at a temperature of 340°C and a pressure of 10 MPa and applying pressure to bond them together. This process may be performed simultaneously with the process for compressing the PTFE sheet. The process for forming the first metal layer 211 can also be performed by plating, vapor deposition, sputtering, or the like instead of using rolled copper foil. The conductor pattern 210 configured to form a specific shape can be formed by a subtractive method in which a portion of the first metal layer 211 is removed by etching or the like and the remaining metal layer region is used as the conductor pattern 210, or an additive method in which a metal layer is built up only in a portion of the conductor pattern 210 using the first metal layer 211 as a power supply layer for plating. By applying a known method such as photolithography to control the portion of the conductor pattern 210 in these processes, the shape and extension direction of the conductor pattern 210 can be controlled with high precision. The conductor pattern 210 obtained by the above process can be formed to include, in a plan view, a first end 221, a second end 222, and a wiring portion 225 that electrically connects the first end 221 and the second end 222. Furthermore, within each wiring portion of the conductor pattern 210, the extension direction of the linear region having the longest extension length (longest linear region) is formed so as to be approximately perpendicular to the first direction of the substrate 100. When forming the conductor pattern 210 on the substrate as described above, the fluororesin sheet that forms the first surface of the substrate 100 may be oriented in accordance with the desired conductor pattern design, or the conductor pattern may be designed in accordance with the orientation of the first surface of the substrate. From the viewpoint of productivity, the former is preferred because it can also be applied to the design of the imposition of the substrate.

[0048] According to the method for manufacturing the wiring board 200 of the present invention as described above, it is possible to manufacture a wiring board 200 that has excellent electrical properties and has improved bonding strength of the specific conductor pattern 210 formed on the base material 100.

[0049] Second Embodiment Next, another embodiment of the present invention will be described. Figure 2 is a schematic view of the surface of a wiring substrate 200 according to a second embodiment of the present invention, on which a conductor pattern 210 is formed, as viewed from vertically above. In the following other embodiments, components having the same reference numerals as those in the first embodiment are the same as those in the first embodiment, and therefore their description may be omitted.

[0050] The wiring board 200 according to the second embodiment has a conductor pattern 210 (P １ ) and the conductor pattern 210 (P ２ ) and the conductor pattern 210 (P １ ) linear region and the conductor pattern 210 (P ２ ) extend parallel to each other, but otherwise the same configuration as in the first embodiment can be adopted.

[0051] Conductor pattern 210 (P １ , P ２ ) has a wiring portion 225 having a linear region with an extension length indicated by A in FIG. 2 (hereinafter, this may be expressed as a linear region with an extension length of A). Here, the conductor pattern 210 having the longest linear region is P １ and P ２ Therefore, the second direction for the wiring board 200 according to the second embodiment is the direction in which the X axis extends. Furthermore, the first direction, which is the preferentially oriented direction on the first surface 101 of the base material 100 of the wiring board 200, is a direction substantially perpendicular to the second direction, and is therefore the direction in which the Y axis extends. １ The wiring width of the linear region of the conductor pattern 210 (P ２ ) is smaller than the wiring width of the straight line region of the extension length A, the longest straight line region is the conductor pattern 210 (P １) is selected. That is, when there are multiple linear regions with the longest extension length in the conductor pattern formed on the first surface 101 of the substrate 100, the linear region with the smallest wiring width among them can be selected as the longest linear region. By selecting in this manner, it is possible to improve the bonding strength between the substrate and a specific conductor pattern that has a region with a configuration that has a relatively small bonding area with the first surface 101 and whose improved bonding strength contributes to the reliability of the wiring board.

[0052] The wiring board 200 according to the second embodiment has a conductor pattern having the longest linear region (extension length A) with the longest extension length in the wiring board 200, which is formed as a first conductor pattern 210 (for example, P １ ), the first conductor pattern 210 (P １ ) and adjacent to the first conductor pattern 210 (P １ ) along the second conductor pattern 210 (for example, P ２ For example, the second conductor pattern 210 (P ２ The total extension length of the linear regions of the first conductor pattern 210 (P) is preferably 50% or more of the total extension length of the longest linear region, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more. １ The second conductor pattern 210 (P) extends parallel to the direction in which the longest linear region of the ２ When the total extension length of the linear regions of the plurality of adjacent conductor patterns 210 is 90% or more, bonding reliability can be maintained in more regions without the need for a new structure such as an adhesive to improve reliability, which is preferable. Furthermore, it is preferable that the wiring board 200 does not include a conductor pattern on the first surface 101 of the base material 100 in a region sandwiched between the wiring portions 225 of the plurality of adjacent conductor patterns 210 that does not have a linear region that is approximately parallel to the extension direction of the longest linear region. This structure suppresses uneven internal and / or external stresses acting on each of the plurality of adjacent conductor patterns 210, making it easier to achieve improved bonding reliability, resulting in a wiring board with improved reliability.

[0053] In addition, the second conductor pattern 210 (P ２ ) the linear region with the longest extension length is the first conductor pattern 210 (P １ ) and extends parallel to the longest linear region. ２ Among the linear regions of the wiring board 200, the extension length of the linear region having the longest extension length is preferably 50% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more of the extension length of the longest linear region. By configuring the first direction of the first surface 101 of the base material 100 and the extension directions of the plurality of linear regions including the longest linear region to be substantially perpendicular to each other in this manner, the bonding strength between the first surface of the base material 100 and the conductor pattern 210 can be improved in a plurality of regions of the wiring board 200 that are likely to affect bonding reliability, thereby providing a highly reliable wiring board.

[0054] Furthermore, since the first surface 101 of the base material 100 of the wiring board 200 described in the present application contains a fluororesin, which is a material having an extremely small dielectric constant and dielectric loss tangent, it is also suitable for use as a high-frequency circuit board. For this reason, the impedance in the longest linear region of the conductor pattern 210 of the wiring board 200 described in the present application is preferably 40 Ω or more and 130 Ω or less, and more preferably 40 Ω or more and 60 Ω or less.

[0055] Furthermore, the wiring width in the longest linear region of the conductor pattern 210 of the wiring board 200 described in the present invention is preferably 1 micrometer to 1000 micrometers, more preferably 10 micrometers to 400 micrometers, and particularly preferably 40 micrometers to 200 micrometers. In the case of a stripline structure, the wiring width is preferably 10 micrometers to 400 micrometers, and more preferably 40 micrometers to 200 micrometers. In such a configuration, the area of ​​the bonding interface between the substrate 100 and the conductor pattern 210 is small, making it difficult to ensure bonding strength. However, according to the configuration described in the present invention, the bonding strength between the longest linear region of the conductor pattern 210 and the substrate 100 can be improved. Because of this effect, it is possible to reduce the width of the conductor pattern 210 without reducing the reliability of the wiring board 200, and it is possible to form multiple conductor patterns 210 (e.g., P １ and P ２ ) can be arranged at a high density, which contributes to miniaturizing the wiring board 200 and adding more functions by increasing the number of conductor patterns 210 without changing the size of the wiring board 200.

[0056] According to the wiring board 200 of the present invention, a plurality of conductor patterns 210 having linear regions extending parallel to each other can be provided, and a first conductor pattern 210 (P １ ) and the substrate 100, and further, １ ) along the second conductor pattern 210 (P ２ ) also has a first conductor pattern 210 (P １ ) can improve the bonding strength with the substrate 100 at a level equivalent to that of the conventional method.

[0057] Third Embodiment Next, another embodiment of the present invention will be described. Fig. 3 is a schematic diagram showing the surface of a wiring board 200 according to a third embodiment of the present invention, on which a conductor pattern 210 is formed, as viewed from above.

[0058] The wiring board 200 according to the third embodiment has a conductor pattern 210 (P １ ) and the conductor pattern 210 (P １ ) extending in a direction different from the direction in which the longitudinal direction of the conductor pattern 210 (P ３ 3, the conductor pattern 210 (P ３ ) is illustrated. As in the other embodiments, the imaginary straight line 1000 is an imaginary straight line drawn on the first surface in order to identify a linear region, and is not provided as a component of the wiring substrate 200.

[0059] Conductor pattern 210 (P １ ) has a wiring portion 225 having a linear region with an extension length A, and the conductor pattern 210 (P ３ ) has a wiring portion 225 having a linear region with an extension length A'. Here, the relationship between the extension lengths is A>A', so the conductor pattern 210 having the longest linear region is P １ Therefore, the second direction for the wiring substrate 200 according to the third embodiment is the direction in which the X-axis extends. Furthermore, the first direction, which is the direction in which the fluororesin is preferentially oriented on the first surface 101 of the base material 100 of the wiring substrate 200, is a direction substantially perpendicular to the second direction, and is therefore the direction in which the Y-axis extends.

[0060] In the conductor pattern 210, the range in which the bonding strength must be ensured is larger than the length of the linear region. １ ) is the linear region of length A of conductor pattern 210 of wiring board 200 that has the longest distance of bonding to base material 100, and is therefore the region with the highest risk of leading to a decrease in reliability, such as peeling of the conductor pattern. Therefore, by arranging conductor pattern 210 on base material 100 so that the direction in which the longest linear region extends is approximately perpendicular to the first direction in which first surface 101 of base material 100 is preferentially oriented, the bonding strength between the longest linear region and base material 100 is improved, and the reliability of wiring board 200 as a whole can be improved.

[0061] (Fourth embodiment) Next, another embodiment of the present invention will be described. Fig. 4 is a schematic diagram of a surface of a wiring board 200 according to a fourth embodiment of the present invention, on which a conductor pattern 210 is formed, as viewed from above. The wiring board 200 according to this embodiment has a conductor pattern 210 (P ４ ) P ４ The conductor pattern 210 of this embodiment differs from the other embodiments in that it has a plurality of linear regions, but otherwise can have the same configuration as the other embodiments described above. ４ The conductor pattern 210 in FIG. 1 shows an example of a conductor pattern having a linear region with an extension length B, a linear region with an extension length C, and a linear region with an extension length D. Here, the relationship between the extension lengths of the linear regions is B>C>D, so the longest linear region is the conductor pattern 210 (P ４ ) is a linear region of length B in the wiring board 200 according to the fourth embodiment. Therefore, the second direction for the wiring board 200 according to the fourth embodiment is the direction in which the X-axis extends. Furthermore, the first direction, which is the direction in which the fluororesin is preferentially oriented on the first surface 101 of the substrate 100 of the wiring board 200, is a direction approximately perpendicular to the second direction, and is therefore the direction in which the Y-axis extends. Thus, the concept of the present invention can be applied to a wiring board 200 having a conductor pattern 210 that is curved in a planar view. That is, when the conductor pattern 210 includes multiple linear regions, improving the bonding strength of the longest linear region with the substrate increases the bonding strength of the region in the conductor pattern 210 that is longest in length and that is bonded to the substrate, thereby improving the reliability of the entire wiring board 200.

[0062] Fifth Embodiment Next, another embodiment of the present invention will be described. Fig. 5 is a schematic diagram of a surface of a wiring board 200 according to a fifth embodiment of the present invention, on which a conductor pattern 210 is formed, as viewed from above. The wiring board 200 according to this embodiment has the same conductor pattern 210 (P １ ) and this conductor pattern 210 (P １ ) and is used as a reference potential. ５) and the other points, the present embodiment differs from the other embodiments, but can otherwise have the same configuration as the other embodiments described above. Note that in this specification, the reference potential refers to, for example, a ground voltage such as ground, or a power supply voltage.

[0063] Conductor pattern 210 (P １ ) had a linear region with an extension length A (not shown in FIG. 5). ５ ) has a linear region equal to or longer than the extension length A, the longest linear region in the wiring board 200 is selected based on the conductor pattern 210 (P ５ ) is not taken into consideration. ５ ) The solid pattern used for the reference potential, as exemplified by the solid pattern shown in FIG. 1, has a relatively larger bonding area with the first surface 101 of the substrate 100 compared to the wiring portion, which is a conductive path that transmits electrical signals, and therefore can ensure sufficient bonding strength.

[0064] Therefore, the conductor pattern having the longest straight line region in the wiring substrate 200 according to the fifth embodiment is the conductor pattern 210 (P １ ), and the second direction of the wiring board 200 according to the fifth embodiment is the direction in which the X-axis extends. Furthermore, the first direction, which is the direction in which the fluororesin is preferentially oriented on the first surface 101 of the base material 100 of the wiring board 200, is a direction approximately perpendicular to the second direction, and is therefore the direction in which the Y-axis extends. In this way, the concept of the present invention can also be applied to a wiring board 200 that includes a conductor pattern used as a reference potential. By configuring the conductor pattern having the longest linear region to be surrounded by the conductor pattern used as a reference potential, as in this embodiment, noise can be suppressed, and the wiring board can be particularly preferably used as a high-frequency wiring board.

[0065] Sixth Embodiment Next, another embodiment of the present invention will be described. Fig. 6 is a schematic diagram of a wiring board 200 according to a sixth embodiment of the present invention. Fig. 6(a) is a schematic diagram of the surface of the wiring board 200 on which a conductor pattern 210 is formed, viewed from vertically above, and Fig. 6(b) is a schematic diagram showing a cross section of the wiring board 200, viewed from the lateral direction of the base material.

[0066] The wiring board 200 according to the sixth embodiment has the conductor pattern 210 (P １ The wiring board 200 according to the sixth embodiment is different from the wiring board 200 according to the other embodiments in that a support layer 115 is provided on the second surface 102 side of the base material 100, but otherwise can have the same configuration as the other embodiments described above.

[0067] The substrate 100 of the wiring board 200 according to the sixth embodiment has a support layer 115 at least on the second surface 102 side. Such a support layer may also be provided on the first surface 101 side. The support layer 115 may be, for example, a carrier sheet or other structure that mechanically supports the substrate. While the first surface 101 of the substrate 100 is made of a fluororesin, the support layer 115 may contain a crystalline polymer other than fluororesin, a fluororesin, or the same material as the first surface. The material of the support layer 115 can be appropriately selected depending on the physical properties required of the wiring board. Furthermore, when the support layer 115 includes a layer primarily composed of a fluororesin, the support layer 115 may be imparted with an orientation different from that of the first surface 101 of the substrate.

[0068] In the wiring substrate 200 according to the sixth embodiment, the conductor pattern 210 (P １ ) has the longest linear region, and the second direction of the wiring board 200 is the direction in which the X axis extends. The first direction, which is the direction in which the fluororesin is preferentially oriented on the first surface 101 of the base material 100 of the wiring board 200, is a direction substantially perpendicular to the second direction, and is therefore the direction in which the Y axis extends. In the wiring board 200 according to the sixth embodiment, the conductor pattern 210 (P １ The first surface 101 of the substrate 100 on which the first layer 115 is formed is preferentially oriented in the first direction. On the other hand, there is no such limitation on the orientation imparted to the support layer 115, and an orientation different from the first direction may be provided.

[0069] In the wiring board 200 according to the sixth embodiment, a preferential orientation is provided in at least the first direction with respect to the first surface 101 of the base material 100 on which the conductor pattern 210 is directly formed, and therefore such wiring board 200 can provide a wiring board that has excellent electrical properties and improved bonding strength of the specific conductor pattern 210 formed on the base material 100. Furthermore, by providing the support layer 115, it is possible to improve the processability of the wiring board and control the rigidity of the wiring board itself.

[0070] Seventh Embodiment Next, another embodiment of the present invention will be described. Fig. 7 is a perspective view of a wiring board similar to the wiring board 200 described in the first embodiment. As described above, for this wiring board 200, the first direction is the direction in which the Y axis extends, and the second direction is the direction in which the X axis extends.

[0071] In the seventh embodiment, in a cross section of the substrate 100 perpendicular to the first surface 101 of the substrate 100, the refractive index of the fluororesin constituting the first surface 101 of the substrate 100 in a cross section parallel to the preferential orientation direction of the fluororesin is greater than the refractive index in a cross section perpendicular to the preferential orientation direction. This is because optical anisotropy occurs due to the arrangement of the fluororesin molecules, i.e., orientation. When the refractive index is large, the reflectance also increases, and the substrate appears relatively bright. On the other hand, when the refractive index is small, the reflectance also decreases, and the substrate appears relatively dark. When this is applied to the wiring board 200 shown in FIG. 7 , the extension direction of the longest linear region of the conductor pattern 210 is parallel to the extension direction of the X-axis, and the cross section of the first surface 101 of the substrate 100 perpendicular to the extension direction of the longest linear region of this conductor pattern 210 (i.e., the plane of cutting the first surface 101 in the YZ plane) is referred to as a second cross section CS. ２ The cross section of the first surface 101 of the substrate 100 perpendicular to the direction substantially perpendicular to the X-axis (for example, the direction in which the Y-axis extends in FIG. 7) (i.e., the plane in which the first surface 101 is cut by the ZX plane) is defined as the first cross section CS １ When this is done, the first cross section CS １ The refractive index of the second cross section CS ２ That is, in the wiring substrate 200 according to the present invention, the refractive index of the second cross section CS２ The first cross section CS １ The other configurations may be the same as those of the other embodiments described above.

[0072] In addition, when the main component of the first surface 101 of the substrate 100 in this embodiment is PTFE, in the cross section of the substrate 100 perpendicular to the first surface 101 of the substrate 100, the cross section of the first surface 101 of the substrate 100 perpendicular to the extending direction of the longest linear region of the conductor pattern 210 on the first surface 101 of the substrate 100 is referred to as a third cross section CS ３ (not shown), and the cross section of the first surface 101 of the substrate 100 perpendicular to the direction in which the longest linear region extends is called the fourth cross section CS ４ (not shown), the fourth cross section CS ４ The refractive index of the third cross section CS ３ At this time, the refractive index of the third cross section CS ３ and the fourth cross section CS ４ The difference in refractive index is preferably 0.01 or more, more preferably 0.02 or more, and particularly preferably 0.03 or more. It is believed that a large difference in refractive index indicates that the structural state of the PTFE molecules on the first surface 101 of the substrate 100 is such that a high proportion of molecules are preferentially oriented in a specific direction. Therefore, the improvement in bonding strength according to the present invention can be effectively achieved.

[0073] The refractive index can be measured in accordance with Japanese Industrial Standard JIS K 0062. From a substrate or a wiring board containing a substrate, a measurement sample including a cross section cut parallel to the direction in which the longest linear region extends and perpendicular to the extending surface of the substrate in a planar view is cut using a razor or the like, and a measurement sample including a cross section cut perpendicular to the direction in which the longest linear region extends and perpendicular to the extending surface of the substrate in a planar view is cut. These cross sections serve as the observation surfaces. If necessary, resin sealing may be performed, and the observation surface may be obtained by polishing the cross section. The refractive index of the sample is measured by irradiating light with a wavelength of 589 nm through this observation surface and observing the critical refraction angle. The refractive index of the sample in a specific direction can be measured by using a polarized lens in the eyepiece. An Abbe refractometer manufactured by Atago can be used as a measuring instrument. In this specification, the refractive index values ​​measured for the observation surface in accordance with Japanese Industrial Standard JIS K 0062 may be referred to as the refractive index of each cross section. If the observation surface (cross section) is not optically uniform, i.e., if it has optically different regions, the refractive index is measured in a region including the first surface 101 of the substrate 100. By measuring in this manner, the molecular structure state of the substrate 100 in the vicinity of the bonding interface between the conductor pattern and the substrate 100 can be more accurately identified.

[0074] Furthermore, when the main component of the first surface 101 of the substrate 100 in this embodiment is PTFE, the first surface 101 of the substrate 100 preferably exhibits a first endothermic peak in the temperature range of 339°C to 355°C and a second endothermic peak in the temperature range of 370°C to 390°C in a crystalline melting curve obtained by differential scanning calorimetry (DSC) measured during a temperature rise process at a temperature rise rate of 10°C. This first endothermic peak is derived from the PTFE material, while the second endothermic peak is a peak specific to PTFE that has been strongly oriented. The present inventors' observations have revealed that this second melting energy is larger than the strength of the oriented state. The melting energy of a crystal can be calculated from the area of ​​the endothermic peak of the crystal melting curve obtained by DSC, and the ratio of the first melting energy calculated from the first endothermic peak to the second melting energy calculated from the second endothermic peak ("first melting energy" to "second melting energy") is preferably 3:1 to 30:1, and more preferably 4:1 to 25:1. Here, a peak is referred to when the curve takes an extreme value, and a shoulder is referred to when the curve does not take an extreme value. In this specification, a shoulder is not considered to be a peak in a DSC crystal melting curve.

[0075] DSC can be performed in accordance with JIS K 7122 using a DSC3200 manufactured by NETZSCH JAPAN. A measurement sample of 5 mg to 10 mg is cut from the first surface 100 of the substrate 100. The measurement sample can be clamped to an aluminum pan to prevent the effects of thermal shrinkage. Using data obtained during a temperature increase from room temperature to 400°C at a heating rate of 10°C / min, the baseline of the obtained crystalline melting curve (DSC curve) can be adjusted and the heat of transition determined in accordance with JIS K 7122, and the melting energy can be calculated from the peak area. If the baseline of the DSC curve is approximately linear, the point where the DSC curve leaves the baseline is taken as the 300°C point, and the point where the DSC curve returns to the baseline is taken as the 360°C point. By connecting these two points with a straight line, the area of ​​the first endothermic peak between 339°C and 355°C can be calculated. Similarly, the peak area can be calculated by connecting the 370° C. point and the 390° C. point on the DSC curve with a straight line, and using this as the baseline for the second endothermic peak between 370° C. and 390° C. From the peak areas calculated in this way, the first melting energy, the second melting energy, and the ratio between them can be determined.

[0076] When the above-described difference in refractive index depending on the orientation direction is applied to the sixth embodiment, in a cross section of the substrate 100 perpendicular to the first surface 101 of the substrate 100, the cross section of the first surface 101 of the substrate 100 perpendicular to the direction in which the longest linear region extends (second direction) is defined as a first cross section, and the cross section of the first surface 101 of the substrate 100 perpendicular to the first direction, which is approximately orthogonal to the second direction, is defined as a second cross section. The refractive index of the first cross section is greater than the refractive index of the second cross section, and the first cross section appears brighter than the second cross section. Furthermore, when the cross section of the support layer 115 perpendicular to the second direction and adjacent to the first cross section is defined as a third cross section, the refractive index of the first cross section is preferably greater than the refractive index of the third cross section. Therefore, the first cross section preferably appears brighter than the third cross section. By configuring the wiring board 200 in this manner, the bonding strength between the longest linear region of the conductor pattern 210 and the substrate 100 is improved, and a wiring board 200 can be obtained in which deviations in physical properties due to the orientation occurring on the oriented surface are suppressed.

[0077] The substrate 100 may be composed of multiple layers (not shown). In this case, the wiring board 200 may include the substrate 100 including a first layer having a first surface and a second layer formed on the first layer, and a plurality of conductor patterns 210 formed on the first surface 101 of the substrate 100. The first layer and the second layer may contain fluororesin, and the plurality of conductor patterns 210 may each include, in a plan view, a first end 221, a second end 222, and a wiring portion 225 electrically connecting the first end 221 and the second end 222. The wiring portion 210 may have one or more linear regions extending linearly. In this case, the refractive index of the cross section of the first layer perpendicular to the extension direction of the linear region having the longest extension length (longest linear region) in a cross section of the substrate 100 perpendicular to the first surface of the substrate 100 may be greater than the refractive index of the cross section of the second layer perpendicular to the extension direction. It is preferable that the first layer and the second layer share a bonding interface with each other. When the main component of the first layer and the second layer having the first surface 101 of the substrate 100 is PTFE, in the cross section of the substrate 100 perpendicular to the first surface 101 of the substrate 100, the cross section of the first layer of the substrate 100 perpendicular to the extending direction of the longest linear region of the conductor pattern 210 on the first surface 101 of the substrate 100 is referred to as a fifth cross section CS ５ (not shown), and the cross section of the second layer of the base material 100 perpendicular to the extending direction is called a sixth cross section CS ６ (not shown), the sixth cross section CS ６ The refractive index of the fifth cross section CS ５ At this time, the refractive index of the fifth cross section CS ５ and sixth section CS ６ The difference in refractive index between the two is preferably 0.01 or more, more preferably 0.02 or more, and particularly preferably 0.03 or more. A higher refractive index makes the surface appear relatively brighter, and a lower refractive index makes the surface appear relatively darker. Therefore, the above relationship can be confirmed by observing a cross section perpendicular to the direction of extension of the longest linear region of the conductor pattern under a microscope in one field of view. The cross section is preferably observed using reflected light from the microscope.

[0078] In addition, in the wiring board, in a cross section of the base material perpendicular to the first surface of the base material, the refractive index of the cross section of the first layer parallel to the extension direction of the linear region having the longest extension length can be smaller than the refractive index of the cross section of the second layer parallel to the extension direction. Furthermore, when the main components of the first layer and the second layer having the first surface 101 of the base material 100 are PTFE, in the cross section of the base material 100 perpendicular to the first surface 101 of the base material 100, the cross section of the first layer of the base material 100 perpendicular to the extension direction of the longest linear region of the conductor pattern 210 on the first surface 101 of the base material 100 is referred to as a seventh cross section CS ７ (not shown), and the cross section of the second layer of the base material 100 perpendicular to the extending direction is called an eighth cross section CS ８ (not shown), the seventh cross section CS ７ The refractive index of the eighth cross section CS ８ At this time, the refractive index of the seventh cross section C ７ and eighth section CS ８ The difference in refractive index between the conductor pattern 210 and the substrate 100 is preferably 0.01 or more, more preferably 0.02 or more, and particularly preferably 0.03 or more. By providing the wiring board 200 with such a configuration, the bonding strength between the longest linear region of the conductor pattern 210 and the substrate 100 is improved, and further, by providing the substrate with multiple layers made of fluororesin that are differently oriented based on the extending direction of the longest linear region as described above, it is possible to obtain a wiring board 200 in which the physical properties such as the tensile properties and the thermal expansion coefficient of the entire substrate 100 are controlled while maintaining excellent electrical properties.

[0079] According to the configuration of the wiring board 200 of this embodiment, a fluororesin material that has been given a strong orientation that causes a difference in refractive index is arranged on the first surface 101 of the substrate 100, and by determining the relative positional relationship with the direction in which the longest linear region extends as described above, a highly reliable wiring board can be obtained in which the bonding strength between the conductor pattern 210 and the substrate 100 is improved.

[0080] Eighth Embodiment Next, another embodiment of the present invention will be described. FIG. 8 is a schematic diagram of a wiring board 200 according to an eighth embodiment of the present invention. FIG. 8(a) is a schematic diagram of the surface of the wiring board 200 on which a conductor pattern is formed, viewed from vertically above. The wiring board 200 has one end 230 and the other end 231. FIG. 8(b) is a schematic diagram showing a cross section of the wiring board 200 viewed from the lateral direction of the base material 100. FIGS. 8(c), 8(d), and 8(e) are schematic diagrams of a portion of one end 230 of the wiring board 200 in FIG. 8(a), on which each conductor pattern is formed, viewed from the Z direction (vertically above). FIG. 8(f) is a schematic diagram of the A-A cross section of the laminate of FIGS. 8(c), 8(d), and 8(e). That is, Figures 8(c), 8(d), and 8(e) are exploded views showing the surfaces on which the respective conductor patterns are formed, while Figure 8(f) is a cross-sectional view of the wiring board 200 in which these are integrated. Similarly, Figure 8(g) is a schematic diagram of the B-B cross section of the laminate of Figures 8(c), 8(d), and 8(e). Figure 8 shows via lands 240, which are conductor patterns provided on the substrate 100, and vias 245, which are conductor patterns that provide electrical continuity between the substrates. The vias 245 may be filled with a conductive material or a non-conductive material. In Figure 8, the vias 245 indicate the positions of the vias.

[0081] In this embodiment, the wiring board 200 includes a conductor pattern 210 on the first surface 101 of the substrate 100 in a plan view, and a conductor pattern (e.g., a ground pattern) used as a reference potential formed around the conductor pattern 210. The wiring board 200 also includes a first end 221 (via land 240) used as a terminal for an electrical signal in a plan view, a second end 222 (not shown) also used as a terminal for an electrical signal, and a wiring portion 225 electrically connecting the first end 221 and the second end 222. The conductor pattern 210 is preferably a signal transmission pattern that transmits an electrical signal. The conductor pattern used as the reference potential is preferably electrically connected to a conductor pattern used as a reference potential of another layer via a via. The wiring board 200 in this embodiment also includes a conductor pattern (e.g., a solid ground) used as a reference potential on the second surface 102, which is opposite the first surface 101 of the substrate 100. The first surface 101 of the substrate 100 may further include a substrate 100' (dielectric layer) via an adhesive layer. Furthermore, the substrate 100′ has a conductor pattern (e.g., a solid ground) used as a reference potential on the surface opposite to the bonding surface with the first surface 101 of the substrate 100, and a pad electrically connected to the first end 221 via a via. Other configurations can be similar to those of the other embodiments described above. The conductor pattern used as a reference potential in this embodiment may have a plurality of openings regularly arranged so that the conductor pattern has a mesh shape. The opening shapes of such a plurality of openings may be shapes with a longitudinal direction, such as a diamond or rectangle. In this case, it is preferable to form the conductor pattern used as a reference potential so that the longitudinal direction of the openings in the conductor pattern is approximately perpendicular to the direction in which the fluororesin on the first surface 101 of the substrate 100 is preferentially oriented. This configuration can provide a wiring board that combines flexibility and bonding reliability between the conductor pattern used as a reference potential and the substrate 100.

[0082] In the wiring board 200 according to the eighth embodiment, a conductor pattern used as a reference potential is disposed around the conductor pattern 210, thereby suppressing the generation of noise such as electromagnetic interference (EMI), and providing a highly reliable wiring board 200. Furthermore, by arranging the two conductor patterns 210 in parallel along the longitudinal direction, the wiring board 200 can also be suitably used for differential transmission.

[0083] Ninth Embodiment Next, another embodiment of the present invention will be described. FIG. 9( a) is a schematic diagram of a wiring board 200 according to a ninth embodiment of the present invention. The wiring board 200 according to the ninth embodiment shows nine conductor patterns 210 formed on a first surface 101 of a rectangular substrate 100 in a plan view. As shown in the figure, a pair of short sides of the rectangular substrate 100 are referred to as a first side 121 and a second side 122, respectively, and a pair of long sides are referred to as a third side 123 and a fourth side 124, respectively. The remaining configurations can be similar to those of the other embodiments described above. Also, FIGS. 9( b) and 9( c) are perspective views each showing a portion of an electronic device 300 in which an electronic component is connected to a first end 221 side of the wiring board 200 in FIG. 9( a). Note that, in this specification, a side refers to a line segment that includes vertices at both ends as a zero-dimensional "portion."

[0084] The conductor pattern 210 on the first surface 101 of the substrate 100 has a first end portion 221 (also referred to as the "first terminal") that is used as a terminal for an electrical signal in a planar view, a second end portion 222 (also referred to as the "second terminal") that is also used as a terminal for an electrical signal, and a wiring portion 225 that electrically connects the first end portion 221 and the second end portion 222.

[0085] In the wiring board 200 according to the ninth embodiment, the extension direction (second direction) of the longest linear region of the conductor pattern 210 is a direction parallel to the third side 123 (or the fourth side 124) (the direction in which the X-axis extends in the drawing). The first direction in the base material 100 is a direction substantially perpendicular to the second direction, and is therefore set to be the direction in which the Y-axis extends in the drawing. The length of the third side 123 (or the fourth side 124) is preferably longer than the length of the first side 121 (or the second side 122). While the wiring board 200 in FIG. 9 is rectangular, this is not a limitation, and the edges may be chamfered. Furthermore, the wiring board 200 has an outer shape with a constant width, is disposed on an imaginary straight line 1000 (not shown in FIG. 9 ) located on the first surface 101 of the base material 100, and includes a portion extending parallel to the imaginary straight line 1000. When the ratio of the extension length of wiring substrate 200 that satisfies the above relationship to the fixed width of wiring substrate 200 is defined as the aspect ratio of wiring substrate 200, the aspect ratio of wiring substrate 200 is preferably 2 or more, more preferably 10 or more, and particularly preferably 50 or more. When wiring substrate 200 includes a three-dimensional shape such as a curved portion and / or a bent portion and / or is flexible, the above-described configuration makes it possible to obtain wiring substrate 200 that is reliable over a long length, and therefore the aspect ratio of wiring substrate 200 is preferably 10 or more, and particularly preferably 50 or more.

[0086] From the viewpoint of the accuracy of the formation of the conductor pattern, the aspect ratio of the wiring substrate 200 may be set to 1000 or less, or may be set to 500 or less. With such a configuration, the bonding strength between the longest linear region of the conductor pattern 210 and the base material 100 can be improved over the entire length, and further, the same effect of improving the bonding strength can be obtained in linear regions extending parallel to the longest linear region.

[0087] Furthermore, in the wiring board 200, multiple first end portions 221 are arranged along the first edge 121. Furthermore, the extension direction of the longest linear region within the wiring board 200 can be configured to be approximately perpendicular to the first edge of the wiring board. Furthermore, multiple second end portions 222 are preferably arranged along the second edge 122. Note that "arranged along the edge" refers to the absence of wiring portions of other conductor patterns between the edge and the terminal. In this wiring board 200, multiple first end portions 221 are arranged up to the edge of the first edge 121, and multiple second end portions 222 are arranged up to the edge of the second edge 122. By inserting each edge into a connector 335 or the like, electrical signals can be transmitted. The multiple conductor patterns 210 in the wiring board 200 according to the ninth embodiment can be particularly suitable as multiple signal transmission patterns and can also be used as a replacement for multiple transmission cables. The wiring board 200 according to this embodiment can include two or more regions within its plane having different flexural moduli. For example, the region of the wiring substrate 200 that includes components may be formed to have a higher flexural modulus than the transmission region. This configuration allows the wiring substrate 200 to be positioned by freely deforming the transmission region while improving the bonding reliability between the wiring substrate 200 and the components. Furthermore, the linear region of the conductor pattern 210 that spans the boundary between the two regions with different flexural moduli is preferably the longest linear region. The longest linear region is preferably formed so as to be approximately perpendicular to the first direction, which is the direction in which the fluororesin on the first surface 101 of the substrate 100 is preferentially oriented. This configuration improves the bonding strength between the substrate and the conductor pattern in the region where loads tend to concentrate when external stress is applied to the wiring substrate 200, resulting in a highly reliable wiring substrate.

[0088] 9(b) and 9(c) are perspective views showing an example of one end side of an electronic device 300 according to an embodiment of the present invention. The electronic device 300 in FIG. 9(b) can be configured, for example, with a wiring substrate 200, a first electronic component 310 electrically connected via the wiring substrate 200, and a second electronic component 320 (not shown). The first electronic component 310 and / or the second electronic component 320 can be, for example, a rigid substrate on which an electronic element 333 and a connector 335 are mounted. Alternatively, a configuration may be adopted in which components such as the electronic element 333 are provided directly on the wiring substrate 200, as shown in FIG. 9(c).

[0089] In the electronic device 300 as described above, for example, the first end 221 side of the conductor pattern 210 of the wiring board 200 is inserted into the connector 335 on the first electronic component 310 side and electrically connected, and the second end 222 (not shown) side of the conductor pattern 210 of the wiring board 200 is inserted into the connector 335 on the second electronic component 320 side and electrically connected, thereby making it possible to transmit and / or receive electrical signals between the first electronic component 310 and the second electronic component 320.

[0090] 9(b), an I-shaped wiring board 200 is used to enable electrical connection between two electronic components, but the electronic device 300 may also be configured with three or more electronic components, and electrical connections between the respective electronic components may be made using the wiring board 200 according to the present invention. For example, the wiring board 200 may be T-shaped, and electrical connections between three electronic components may be made using the wiring board 200. Note that regardless of the shapes of the wiring board 200 or the base material 100, the longest linear region of the conductor pattern 210 may be determined using the same method as described above.

[0091] The electronic device 300 according to the present invention can be applied to, for example, digital cameras and smartphones. The internal space of digital cameras, smartphones, and the like is limited, and the wiring board is often folded and placed, making it susceptible to physical stress due to bending. Even in such cases, the wiring board 200 according to the present invention can contribute to improving the reliability of the electronic device 300 because of the good bonding strength between the conductor pattern 210 and the substrate 100.

[0092] Tenth Embodiment Next, another embodiment of the present invention will be described. By making the I-shaped wiring board 200 as shown in FIG. 8 and / or FIG. 9 long and flexible, the wiring board 200 according to the present invention can be disposed inside a catheter tube and can be used for electrical connections in medical devices such as an endoscope 400, which is an example of an electronic device 300. For example, it can also be used as a component to replace a coaxial cable for an endoscope. FIG. 10 is a schematic diagram of an endoscope 400 equipped with a wiring board 200 according to a tenth embodiment of the present invention. As shown in FIG. 10( a), the endoscope 400 has an operation unit 405, an insertion tube 408 extending from the operation unit 405, and an imaging unit 410 located at the end of the insertion tube. The operation unit 408 is further connected to an image processing device 401 via a communication cable 403. The insertion tube 408 incorporates a signal transmission unit that transmits signals between the imaging unit 410 and the image processing device 401. FIG. 10( b) is a cross-sectional view of the insertion tube 408 taken along the line C-C, illustrating the internal configuration of the insertion tube 408. In FIG. 10 , the insertion tube further includes a tube for passing a medicinal solution or the like, but may also have a multi-lumen structure with multiple compartments. A wiring board 200 according to a tenth embodiment of the present invention is used for the signal transmission section. In applications where electrical signals are transmitted unidirectionally or bidirectionally from one end of the wiring board 200 to the other, the wiring board 200 can be configured such that the first direction in which the first surface 101 of the substrate 100 bonded to the conductor pattern 210 is preferentially oriented is substantially perpendicular to the extension direction of the insertion tube (catheter tube) containing the wiring board 200. The wiring board 200 according to the present invention may also be flexible and may be capable of flexibly deforming in accordance with the bending motion of the insertion section and the internal configuration of the insertion tube 408. Even in applications involving such physical deformation, the wiring board 200 according to the present invention maintains high reliability due to the excellent bonding strength between the conductor pattern 210 and the substrate 100. In the medical field, more non-invasive treatments are required, and it is expected that medical devices will transmit an increasing amount of information and will have more channels in the future. The use of the wiring board 200 according to the present invention makes it possible to accommodate such multi-channelization.

[0093] Eleventh Embodiment Next, another embodiment of the present invention will be described. Fig. 11 is a schematic diagram of a wiring board 200 according to an eleventh embodiment of the present invention. In the wiring board 200 according to the eleventh embodiment, a conductor pattern 210 (P ６ 11 ) has an extension length indicated by E in Fig. 11 is the longest linear region. The direction of this longest linear region is parallel to the X-axis in the drawing, and this direction is the second direction, so the substrate 100 used has a first direction in the substrate 100 that is parallel to the Y-axis in the drawing.

[0094] The electronic device according to this embodiment may be configured with a wiring board 200 and multiple components (e.g., electronic elements). The wiring board includes multiple conductor patterns, each of which includes a first end 221, a second end 222, and a wiring portion 225 electrically connecting the first end 221 and the second end 222. The first end 221 and / or the second end 222 may be electrically connected to multiple components (e.g., electronic elements). In this embodiment, the first end 221 may serve as an interface for transmitting and receiving signals to and from the outside. Examples of the electronic elements include memory elements, sensors, logic elements, and other semiconductor elements.

[0095] The wiring board 200 according to the eleventh embodiment can be used, for example, as a substrate for a computer component (e.g., SSD, etc.) In the field of electronic devices that require large capacity and high speed transmission, a decrease in reliability due to heat generation is an issue, but even in an environment where heat is applied to the wiring board 200, the wiring board 200 according to the present invention can ensure good bonding strength between the base material 100 and the conductor pattern 210, thereby contributing to improving the reliability of the electronic device.

[0096] Twelfth Embodiment Next, another embodiment of the present invention will be described. The wiring board 200 according to the twelfth embodiment differs from the wiring board 200 according to the other embodiments in that the wiring board 200 is used or provided in a rolled form. However, the other configurations can be the same as those of the other embodiments described above.

[0097] The wiring substrate 200 of this embodiment can be bent or curved, and is, for example, a flexible substrate. This substrate can be provided and stored in a rolled form, making it suitable for use in devices in which wiring substrates are supplied and / or stored in rolled form. As with the other examples, this embodiment is also formed so that the extension direction of the longest linear region of the wiring substrate 200 and the direction in which the fluororesin on the first surface 101 of the substrate 100 is preferentially oriented are substantially perpendicular. This embodiment further includes a configuration in which the axial direction of the roll winding is substantially parallel to the direction in which the fluororesin on the first surface 101 of the substrate 100 is preferentially oriented. That is, the extension direction of the longest linear region of the wiring substrate 200 and the axial direction of the roll winding are substantially perpendicular to each other.

[0098] When using the wiring substrate 200 wound into a roll, a large tensile stress may be applied to the wiring substrate in the feed direction of the wiring substrate, i.e., in a direction perpendicular to the winding axis, due to differences in feeding and storing speeds within the device, the application of tension to prevent sagging, the weight of the wiring substrate, and other factors. In particular, a conductor pattern having a longest linear region parallel to the feed direction of the wiring substrate and the substrate below it will be subjected to increased stress depending on the length of the longest linear region. In this embodiment, even when a conductor pattern subjected to such increased stress is included, the conductor pattern is formed on the substrate 100 so as to be approximately perpendicular to the direction in which the fluororesin on the first surface 101 of the substrate 100 is preferentially oriented, thereby providing a wiring substrate 200 with improved reliability.

[0099] The wiring board 200 of this embodiment can be applied to wiring boards that can be bent or curved, such as flexible boards. The wiring board 200 of this embodiment can also be fixed or used in a bent or curved state. In this case, the wiring board 200 includes a bent region including a bent or curved portion and a flat, non-bent region that does not include a bent or curved portion. The bent region preferably includes the longest linear region of the wiring board 200. This configuration ensures bonding strength between the substrate 100 and the longest linear region of the conductor pattern 210 in regions of the wiring board 200 where stress is likely to concentrate, thereby improving the reliability of the wiring board 200. Furthermore, the first surface 101 of the substrate 100 of the wiring board 200 of this embodiment is preferably formed so as to be located on the inner periphery of the bent region. Due to the material properties of substrates containing fluororesin, it is difficult to ensure mechanical strength, and bending results in greater deformation on the inner periphery. For this reason, the reliability of the joint between the substrate and the conductor pattern on the inner side of the bending region where the deformation amount is large is likely to be disadvantageous. However, by adopting the above-described configuration, the reliability of the joint between the substrate and the conductor pattern can be improved, and a wiring board with better reliability can be provided.

[0100] (Thirteenth Embodiment) Next, another embodiment of the present invention will be described. FIG. 12( a) is a schematic diagram of a wiring board 200 according to a thirteenth embodiment of the present invention. In the wiring board 200 according to the thirteenth embodiment, a conductor pattern 210 is formed on the first surface 101 of the substrate 100 in a plan view, and a protective layer (a pattern made of an insulator) 250 having a plurality of opening regions 251 is further formed thereon. In FIG. 12( a), the conductor pattern 210 is covered by the protective layer 250, and a portion of it is visible in the opening region 251. As shown in the figure, a pair of short sides of the rectangular substrate 100 are referred to as a first side 121 and a second side 122, respectively, and a pair of long sides are referred to as a third side 123 and a fourth side 124, respectively. The remaining configurations can be similar to those of the other embodiments described above. FIG. 12( b) is a modified example of this embodiment in which the shape of the protective layer 250 is different from that of FIG. 12( a).

[0101] A wiring board 200 according to a thirteenth embodiment will be described below with reference to FIG. 12( a). Examples of the protective layer 250 include solder resist and coverlay. An opening region 251 of the protective layer 250 is located on a first end 221 and / or a second end 222 of the conductor pattern 210, and the first end 221 and / or the second end 222 are exposed in the opening region 251 for connection to, for example, other components. In the wiring board 200 including such a protective layer 250, the vicinity of the opening region 251 forms a boundary between regions of different thicknesses and mechanical strengths of the wiring board, and therefore stress tends to concentrate therein, becoming a starting point for peeling, and thus requiring higher bonding reliability with the substrate. In particular, in order to further improve the bonding reliability between base material 100 and protective layer 250, it is preferable that protective layer 250 be formed so that the longitudinal direction (the direction in which the Y axis in the drawing extends) of opening region 251 thereof is approximately parallel to the direction in which the fluororesin on first surface 101 of base material 100 is preferentially oriented (the direction in which the Y axis in the drawing extends). Forming wiring substrate 200 in this manner improves the bonding strength between protective layer 250 and base material 100 in the direction in which the longitudinal direction of opening region 251 of protective layer 250 is likely to peel off from base material 100 (the direction in which the X axis in the drawing extends), and this is preferable because wiring substrate 200 can be formed as a substrate with improved reliability overall. In particular, when 80% or more of the total area of ​​the linear regions of the conductor pattern on the first surface 101 of the base material 100 of the wiring board 200 is covered and protected by the protective layer 250, and / or when it is considered that ensuring the bonding reliability between the protective layer 250 and the base material 100 contributes more to improving the reliability of the entire wiring board 200 than the bonding reliability between the conductor pattern 210 and the base material 100, it is preferable to form the wiring board 200 so that the longitudinal direction of the opening region 251 and the direction in which the fluororesin on the first surface 101 of the base material 100 is preferentially oriented have the above-mentioned relationship.

[0102] In the wiring substrate 200 of this embodiment shown in FIG. 12( b ), the shape of the opening region 251 is different from that shown in FIG. 12( a ). In FIG. 12( b ), the longitudinal direction of the opening region 251 of the protective layer 250 is the direction along which the X-axis in the figure extends. Based on the same concept as above, the first direction, which is the direction in which the fluororesin on the first surface 101 of the base material 100 is preferentially oriented, is preferably formed so that it is the direction along which the X-axis in the figure extends, which is approximately parallel to the longitudinal direction of the opening region 251 of the protective layer 250. The wiring substrate 200 formed in this manner has improved bonding strength between the base material 100 and the protective layer 250, which can suppress damage to the conductor pattern due to peeling of the protective layer 250, thereby improving the reliability of the substrate as a whole.

[0103] (Fourteenth Embodiment) Next, another embodiment of the present invention will be described. Fig. 13(a) is a schematic diagram of a wiring board 200 according to a fourteenth embodiment of the present invention. Fig. 13(a) is a schematic diagram of the surface of the wiring board 200 on which a pattern is formed, viewed from vertically above. The wiring board 200 includes a conductor pattern 210 (not shown). The wiring board 200 also includes a protective layer 250 having an opening region 251 on the conductor pattern 210. Fig. 13(b) is a schematic diagram of the surface of the wiring board 200 on which a pattern of a partial region indicated by 260 in Fig. 13(a) is formed, viewed from vertically above. Fig. 13(c) is a modified example of Fig. 13(b). The conductor pattern 210 (P ７ ) has a cross shape and is exposed in an opening region 251 of the protective layer 250. ７ ) is an alignment mark used for positioning, etc., during the manufacturing process of the wiring substrate 200, which differs from the wiring substrate 200 of the other embodiments. However, other configurations can be the same as those of the other embodiments described above.

[0104] The wiring board 200 in this embodiment has a conductor pattern 210 (P ７ ) is provided. ７) includes a power supply line 270 for forming an electroplated layer. This power supply line 270 is drawn out in the direction of the X-axis in the drawing. In the wiring board 200 of this embodiment, it is preferable that the direction in which the power supply line 270 is drawn out is approximately perpendicular to the direction in which the fluororesin on the first surface 101 of the base material 100 is preferentially oriented. In this embodiment, the preferential orientation direction is the direction in which the Y-axis in the drawing extends.

[0105] As described above, when it is particularly required to improve the bonding reliability between the substrate and alignment marks used for positioning or the like in the manufacturing process of wiring board 200, or power supply lines 270 that are wiring for supplying power for forming an electrolytic plating layer, wiring board 200 can be configured so that the longitudinal direction of these structures is approximately perpendicular to the direction in which the fluororesin on first surface 101 of substrate 100 is preferentially oriented. The reliability of the alignment marks is an important factor that directly affects yield, and if the power supply wiring is not drawn accurately without breaks, it can lead to plating defects and have a significant impact on productivity. Therefore, improving the bonding strength of these structures is important for improving the reliability of the wiring board.

[0106] (Example 2) (Fifteenth embodiment) Next, an embodiment in another example of the present invention will be described. Using FIG. 1 as an example, a wiring board 200 in this embodiment comprises a substrate 100 having a first surface 101 and a conductor pattern 210. As in embodiment 1 of example 1, the conductor pattern 210 is formed on the first surface 101 of the substrate 100, and in a plan view (i.e., when viewed from the thickness direction of the substrate indicated by the Z axis in the figure), comprises a first end 221 at one end and a second end 222 at the other end. The conductor pattern 210 (P １ ) includes a wiring portion 225 , which is formed as a conductive path that electrically connects the first end portion 221 and the second end portion 222 .

[0107] The wiring board 200 of this embodiment differs from Embodiment 1 of Example 1 in the following respects. Specifically, the wiring board 200 of this embodiment is preferably formed so that a first direction, which is the direction in which the fluororesin on the first surface 101 of the substrate 100 of the wiring board 200 is preferentially oriented, and a maximum transmission direction of the wiring board 200, which will be described later, are substantially perpendicular to each other. Here, the "maximum transmission direction" refers to the direction in which the transmission direction in each linear region of the wiring portion 225 is considered to be a straight line, and the sum of the extension lengths of multiple linear regions having parallel transmission directions in multiple conductor patterns formed on the first surface 101 of the substrate 100 in the wiring board 200 is the largest. In this case, the wiring board can be formed so that the maximum transmission direction is substantially perpendicular to the first direction. Forming the conductor patterns in this manner makes it possible to provide a wiring board with high overall reliability, even if there are unavoidable design constraints, such as the number and width of conductor patterns, or the substrate size. Furthermore, the wiring board 200 that combines this embodiment with embodiment 1 of Example 1 is more preferable because it can not only improve the bonding strength between the longest linear region of the multiple conductor patterns 210 in the wiring board, which has the greatest impact on reliability, and the base material 100, but also improve the bonding strength between the substrate 100 and the conductor patterns that are most frequently formed in approximately parallel relation on the wiring board 200.

[0108] Regarding the relationship between the extension direction of the longest linear region of the wiring board in other embodiments of the present specification and the first direction of the base material 100, the maximum transmission direction described in this embodiment may be applied instead of the extension direction of the longest linear region, as long as no technical contradiction occurs. Alternatively, this embodiment can be appropriately combined with other embodiments as long as no technical contradiction occurs. A wiring board formed so that the maximum transmission direction is approximately perpendicular to the first direction of the base material 100 can improve the bonding strength of the largest number of conductor patterns in the wiring board, and can provide a wiring board with higher reliability.

[0109] Furthermore, the determination of the maximum transmission direction when the wiring board 200 has multiple linear regions will be described with reference to FIG. 4 . In the wiring board 200 of FIG. 4 , the maximum transmission direction, which is the direction in which the sum of the extension lengths of the multiple linear regions having parallel transmission directions is the largest, is the direction in which the X-axis extends. The maximum transmission direction in the wiring board of FIG. 4 can be determined by comparing the sum of the extension lengths of the linear regions having extension lengths B and D extending in the X-axis direction and the extension length of the linear region having extension lengths C extending in a direction different from the X-axis direction. In the base material 100 of the wiring board 200, the first direction (the direction in which the Y-axis extends in the figure), in which the fluororesin is preferentially oriented, and the maximum transmission direction are preferably approximately perpendicular. By improving the bond strength between the linear regions extending in the maximum transmission direction and the base material, the bond strength between the conductor pattern 210 and the largest number of linear regions can be improved, thereby improving the reliability of the wiring board 200. When there are multiple conductor patterns on the wiring board 200, the extension direction and extension length of the linear regions of all conductor patterns on the first surface 101 of the base material 100 of the wiring board 200 can be confirmed, and the maximum transmission direction can be identified in the same manner as described above.

[0110] In summary, the wiring board 200 according to the present embodiment may be, for example, a wiring board 200 including a substrate 100 having a first surface 101 including a first direction and a plurality of conductor patterns 210 formed on the first surface 101 of the substrate 100, wherein the first surface 101 of the substrate 100 contains a fluororesin preferentially oriented in the first direction, and the plurality of conductor patterns 210 each include, in a plan view, a first end 221, a second end 222, and a wiring portion 225 electrically connecting the first end and the second end, and the wiring portion 225 has one or more linear regions extending linearly, and the maximum transmission direction in which the sum of the extension lengths of the linear regions extending approximately parallel to each other within the wiring board 200 is maximum is approximately perpendicular to the first direction of the substrate 100. The wiring board 200 according to the present invention as described above can provide a wiring board having improved bonding strength of patterns formed on the substrate 100.

[0111] As described above, the wiring board, the electronic device using the wiring board, and the method for manufacturing the wiring board according to the present invention can improve the bonding strength of the pattern formed on the base material of the wiring board.

[0112] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above embodiments within the scope of the same or equivalent to the present invention.

[0113] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and scope of the present invention, all of which are included in the technical concept of the present invention.

[0114] The present disclosure also includes the following invention: A wiring board including a substrate including a first layer having a first surface including a first direction and a second layer having a second direction substantially perpendicular to the first direction, and a plurality of conductor patterns formed on the first surface of the substrate, wherein the first layer of the substrate contains a fluororesin preferentially oriented in the first direction, and the second layer of the substrate contains a fluororesin preferentially oriented in the second direction, and the plurality of conductor patterns each include, in a plan view, a first end, a second end, and a wiring portion electrically connecting the first end and the second end, the wiring portion having one or more linear regions extending linearly, and the wiring board is formed so that the extension direction of the linear region having the longest extension length is substantially perpendicular to the first direction of the substrate. A wiring board comprising: a substrate including a first layer having a first surface and a second layer formed on the first layer; and a plurality of conductor patterns formed on the first surface of the substrate, wherein the first layer and the second layer contain fluororesin, and the plurality of conductor patterns each include, in a planar view, a first end, a second end, and a wiring portion electrically connecting the first end and the second end, the wiring portion having one or more linear regions extending linearly, and the refractive index of a cross section of the first layer perpendicular to an extension direction of the linear region having the longest extension length within the wiring board is greater than the refractive index of a cross section of the second layer perpendicular to the extension direction.

[0115] DESCRIPTION OF SYMBOLS 100, 100'... Base material 101... First surface 102... Second surface 115... Support layer 121... First edge 122... Second edge 123... Third edge 124... Fourth edge 200... Wiring board 210... Conductor pattern 211... First metal layer 221... First end 222... Second end 225... Wiring section 230... One end 231... Other end 240... Via land 245... Via 250... Protective layer 251... Opening area 300... Electronic device 310... First electronic component 320... Second electronic component 333... Electronic element 335... Connector 400... Endoscope 401... Image processing device 403... Communication cable 405... Operation section 408... Insertion tube 410... Imaging section 420... Signal transmission section (wiring board 200) 430... Tube 1000...imaginary line

Claims

1. A wiring board comprising a base material having a first surface including a first direction and a plurality of conductor patterns formed on the first surface of the base material, wherein the first surface of the base material comprises a fluororesin preferentially oriented in the first direction, and the plurality of conductor patterns each include, in a plan view, a first end portion, a second end portion, and a wiring portion electrically connecting the first end portion and the second end portion, and the wiring portion has one or more linear regions extending linearly, and when the linear region having the greatest extension length within the wiring board is defined as the longest linear region, the wiring board is formed so that the extension direction of the longest linear region is approximately perpendicular to the first direction of the base material.

2. The wiring board according to claim 1, wherein, in a cross section of the substrate perpendicular to a first surface of the substrate, a cross section perpendicular to a first direction of the substrate is defined as a first cross section of the substrate, and a cross section parallel to the first direction of the substrate is defined as a second cross section of the substrate, the refractive index of the first cross section of the substrate is smaller than the refractive index of the second cross section of the substrate.

3. The wiring board according to claim 1 or 2, wherein the refractive index of the first cross section of the substrate is smaller than the refractive index of the second cross section of the substrate by 0.01 or more.

4. The wiring board according to any one of claims 1 to 3, wherein the fluororesin is polytetrafluoroethylene.

5. The wiring board according to any one of claims 1 to 4, wherein when the conductor pattern having the longest straight line region is defined as a first conductor pattern, the wiring board further comprises a second conductor pattern adjacent to the first conductor pattern, the straight line region having the longest extension length in the second conductor pattern extends along the longest straight line region of the first conductor pattern, and the extension length of the straight line region having the longest extension length in the second conductor pattern is 70% or more of the extension length of the longest straight line region of the first conductor pattern.

6. A wiring board according to any one of claims 1 to 5, wherein the first surface of the wiring board has a first side, a second side opposite to the first side, and a third side located between the first side and the second side, the length of the third side is longer than the length of the first side, the ratio of the length of the third side to the length of the first side is 2 or more, and the longest linear region extends parallel to the third side of the wiring board.

7. A wiring board according to any one of claims 1 to 6, wherein the plurality of conductor patterns are signal transmission patterns, each of first and second ends of the plurality of signal transmission patterns includes a terminal that is a connection area with other components, the terminals of the plurality of first ends are arranged along a first side of the wiring board, and the extension direction of the longest straight line area is approximately perpendicular to the first side of the wiring board.

8. The wiring board according to any one of claims 1 to 7, wherein the terminals at the plurality of second ends are arranged along a second side of the wiring board.

9. An electronic device using the wiring board according to any one of claims 1 to 8, wherein the plurality of first ends of the wiring board are each arranged on one end side of the wiring board, and the electronic device comprises the wiring board and a first electronic component connected to the plurality of first ends arranged on one end side of the wiring board.

10. The electronic device according to claim 9, wherein the plurality of second ends of the wiring board are each arranged on the other end side of the wiring board, and the electronic device comprises a second electronic component connected to the wiring board and the plurality of second ends arranged on the other end side of the wiring board.

11. A wiring board comprising a substrate having a first surface including a first direction and a plurality of conductor patterns formed on the first surface of the substrate, wherein the first surface of the substrate comprises a fluororesin, and the plurality of conductor patterns each include, in a plan view, a first end, a second end, and a wiring portion electrically connecting the first end and the second end, and the wiring portion has one or more linear regions extending in a straight line, and when the linear region having the greatest extension length within the wiring board is defined as a longest linear region, in a cross section of the substrate perpendicular to the first surface of the substrate, the refractive index of the cross section of the substrate perpendicular to the extension direction of the longest linear region is greater than the refractive index of the cross section of the substrate parallel to the extension direction of the longest linear region.

12. A wiring board according to claim 11, wherein in a cross section of the substrate perpendicular to the first surface of the substrate, the refractive index of the cross section of the substrate perpendicular to the extension direction of the longest linear region is 0.01 or more greater than the refractive index of the cross section of the substrate parallel to the extension direction of the longest linear region.

13. The wiring board according to claim 11 or 12, wherein the fluororesin is polytetrafluoroethylene.

14. A wiring board according to any one of claims 11 to 13, wherein when the conductor pattern having the longest straight line region is defined as a first conductor pattern, the wiring board further comprises a second conductor pattern adjacent to the first conductor pattern, the straight line region having the longest extension length in the second conductor pattern extends along the longest straight line region, and the extension length of the straight line region having the longest extension length in the second conductor pattern is 70% or more of the extension length of the longest straight line region.

15. A wiring board according to any one of claims 11 to 14, wherein the first surface of the wiring board has a first side, a second side opposite to the first side, and a third side located between the first side and the second side, the length of the third side is longer than the length of the first side, the ratio of the length of the third side to the length of the first side is 2 or more, and the longest linear region extends parallel to the third side of the wiring board.

16. A wiring board according to any one of claims 11 to 15, wherein the plurality of conductor patterns are signal transmission patterns, each of first and second ends of the plurality of signal transmission patterns includes a terminal that is a connection area with other components, the terminals of the plurality of first ends are arranged along a first side of the wiring board, and the extension direction of the longest straight line area is approximately perpendicular to the first side of the wiring board.

17. The wiring board according to any one of claims 11 to 16, wherein the terminals at the plurality of second ends are arranged along a second side of the wiring board.

18. An electronic device using a wiring board according to any one of claims 11 to 17, wherein the plurality of first ends of the wiring board are each arranged on one end side of the wiring board, and the electronic device comprises the wiring board and a first electronic component connected to the plurality of first ends arranged on one end side of the wiring board.

19. The electronic device according to claim 18, wherein the plurality of second ends of the wiring board are each arranged on the other end side of the wiring board, and the electronic device comprises a second electronic component connected to the wiring board and the plurality of second ends arranged on the other end side of the wiring board.

20. A method for manufacturing a wiring board, comprising: preparing a fluororesin sheet containing a fluororesin; orienting the fluororesin sheet so that a first direction in the plane of the sheet is a direction in which fluororesin molecules are preferentially oriented; and forming a plurality of conductor patterns on a surface of the sheet, wherein the plurality of conductor patterns each include, in a plan view, a first end, a second end, and a wiring portion electrically connecting the first end and the second end, and the wiring portion has one or more linear regions extending linearly; and forming the linear region having the longest extension length in the wiring board so that the extension direction is approximately perpendicular to the first direction.

21. The method for manufacturing a wiring board according to claim 20, wherein the fluororesin is polytetrafluoroethylene.

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