Wiring board

Abstract

This wiring board comprises a first base material having a first main surface, a second base material having a second main surface, a first wire disposed on the first main surface, and a second wire disposed on the second main surface. The first main surface and the second main surface are in contact with each other. The first base material and the second base material are in connection with each other. The first wire and the second wire are opposed to each other in the thickness direction of the first base material and are electrically connected to each other.

Description

wiring board

[0001] The present disclosure relates to a wiring substrate.

[0002] A conventional wiring board is described in Japanese Patent Laid-Open Publication No. 7-94861 (Patent Document 1). This wiring board is formed by forming a heat-adhesive insulating resist on a first substrate and a second substrate, forming an electrode pattern on the insulating resist, and pressing the electrode patterns of the substrates together while facing each other, and then heat-adhering the resist around the electrode patterns while they are pressed together. In this manner, the wiring board has two layers of insulating resist between the first substrate and the second substrate. The first substrate and the second substrate are connected via the two layers of insulating resist.

[0003] Japanese Patent Application Publication No. 7-94861

[0004] However, in the conventional wiring board, there is a problem that the wiring board becomes thick because two layers of insulating resist are present between the first substrate and the second substrate.

[0005] Therefore, an object of the present disclosure is to provide a wiring board that can be made thinner.

[0006] In order to achieve the above object, a wiring board according to one aspect of the present invention comprises: a first substrate having a first main surface; a second substrate having a second main surface; a first wiring arranged on the first main surface; and a second wiring arranged on the second main surface, wherein the first main surface and the second main surface are in contact with each other and the first substrate and the second substrate are connected, and the first wiring and the second wiring are electrically connected opposite each other in the thickness direction of the first substrate.

[0007] According to the wiring board according to one aspect of the present invention, it is possible to achieve a thinner wiring board.

[0008] FIG. 1 is an exploded perspective view of a wiring board according to a first embodiment of the present invention. FIG. 2 is an exploded plan view of the wiring board. FIG. 3 is a plan view of the wiring board. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3. FIG. 5 is a cross-sectional view taken along line V-V of FIG. 3. FIG. 6A is a cross-sectional view illustrating a method for manufacturing a wiring board. FIG. 6B is a cross-sectional view illustrating a method for manufacturing a wiring board. FIG. 7 is a cross-sectional view of a wiring board according to a second embodiment of the present invention. FIG. 8A is a cross-sectional view illustrating a method for manufacturing a wiring board. FIG. 8B is a cross-sectional view illustrating a method for manufacturing a wiring board. FIG. 9 is a plan view of a wiring board according to a third embodiment of the present invention. FIG. 10 is a cross-sectional view taken along line X-X of FIG. 9. FIG. 11 is a cross-sectional view of a wiring board according to a fourth embodiment of the present invention. FIG. 12 is a cross-sectional view of a wiring board according to a fifth embodiment of the present invention. FIG. 13 is a cross-sectional view of a first modified example of the wiring board according to the fifth embodiment. FIG. 14 is a cross-sectional view of a second modified example of the wiring board according to the fifth embodiment. FIG. 15 is a cross-sectional view of a wiring board according to a sixth embodiment. FIG. 16 is a plan view of a wiring board according to a seventh embodiment. FIG. 17 is a cross-sectional view taken along line XVII-XVII of FIG. 16. Fig. 18 is a cross-sectional view of a wiring board according to an eighth embodiment, Fig. 19 is a cross-sectional view of a wiring board according to a ninth embodiment, and Fig. 20 is a cross-sectional view of a wiring board according to a tenth embodiment.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each embodiment, differences from those described previously will be mainly described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment. Among the components in the following embodiments, components not described in independent claims will be described as optional components. Furthermore, the size and size ratios of components shown in the drawings are not necessarily strict. Furthermore, in each figure, substantially identical components are assigned the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0010] [First Embodiment] (Structure) The structure of a wiring board according to a first embodiment will be described with reference to Figures 1, 2, 3, 4, and 5. Figure 1 is an exploded perspective view of a wiring board according to a first embodiment of the present invention. Figure 2 is an exploded plan view of the wiring board. Figure 3 is a plan view of the wiring board. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3. Figure 5 is a cross-sectional view taken along line V-V in Figure 3.

[0011] In the drawings in this specification, the arrow Z indicates a direction parallel to the thickness direction of the first substrate and extending from the first main surface to the third main surface of the first substrate. The thickness direction may include both the forward Z direction and the reverse Z direction. In this embodiment, the thickness direction of the second substrate is also parallel to the Z direction. Furthermore, the arrow X indicates a direction parallel to the extension direction of the first substrate and extending from a position on the first substrate that is far from the second substrate to a position on the first substrate that is close to the second substrate. The extension direction of the first substrate may include both the forward X direction and the reverse X direction. In this embodiment, the extension directions of the first wiring, the second substrate, and the second wiring are also parallel to the X direction. The X direction and the Z direction are perpendicular to each other, and the direction perpendicular to the X direction and the Z direction is the Y direction. When arranged in the order of X, Y, and Z, a right-handed system is formed.

[0012] The wiring board 100 includes a first substrate 10 having a first main surface 11, a second substrate 20 having a second main surface 21, a first wiring 31 arranged on the first main surface 11, and a second wiring 32 arranged on the second main surface 21. The wiring board 100 is used for circuit connection with, for example, a printed circuit board or a flexible substrate.

[0013] The first substrate 10 is a support material such as a film made of a stretchable resin material. The first substrate 10 is in the form of a sheet or film. The first substrate 10 has a first main surface 11 and a third main surface 12 located on opposite sides of each other.

[0014] The first substrate 10 has a recess 14 on the first main surface 11 (see FIG. 4 ). The recess 14 exists at least in a region 70 where the first substrate 10 and the second substrate 20 overlap when viewed from the Z direction. The recess 14 corresponds to a portion of the first main surface 11 where the first substrate is recessed in the Z direction (i.e., the thickness direction of the first substrate 10). Therefore, the inner surface of the recess 14 can also be interpreted as a surface forming the recess in the first main surface 11. The first main surface 11 may be composed of the inner surface of the recess 14 and a flat surface other than the recess 14. The recess 14 may extend along the X direction. There may be multiple recesses 14. Each of the multiple recesses 14 may be arranged parallel to one another along the Y direction. In this embodiment, the third main surface 12 is an exposed surface.

[0015] Examples of materials for the first substrate 10 include thermoplastic resins. Specifically, the material for the first substrate 10 is a stretchable resin material, such as styrene resin, olefin resin, epoxy resin, urethane resin, acrylic resin, and / or silicone resin. More specifically, examples include thermoplastic polyurethane (TPU) and polyethylene (PE). The resin material preferably has a softening point. Specifically, a softening point of 90 degrees or higher is more preferable. This facilitates contact between the first main surface 11 of the first substrate 10 and the second main surface 21 of the second substrate 20.

[0016] The first substrate 10 is stretchable. The stretchability of the first substrate 10 reduces the risk of breakage due to expansion and contraction during use of the wiring substrate 100. The thickness of the first substrate 10 is not particularly limited, but from the viewpoint of not inhibiting expansion and contraction of the surface of the living body when attached to the living body, it is preferably 160 μm or less, and more preferably 80 μm or less. Furthermore, the thickness of the first substrate 10 is preferably 40 μm or more.

[0017] The second substrate 20 has a second main surface 21 and a fourth main surface 22 located on opposite sides to each other. When viewed from the Z direction, the X-direction end of the second substrate 20 overlaps with the X-direction end of the first substrate 10. More specifically, the reverse X-direction end of the second substrate 20 overlaps with the forward X-direction end of the first substrate 10. The second main surface 21 faces the first main surface 11. In this embodiment, the fourth main surface 22 is an exposed surface. Note that the fourth main surface 22 does not have to be exposed.

[0018] In this embodiment, the second substrate 20 is a substrate different from the first substrate 10, and may be, for example, a rigid substrate or a flexible substrate. For example, a rigid substrate may be a glass-epoxy substrate made by impregnating layers of glass fiber cloth with epoxy resin. For example, a flexible substrate may be made of polyimide, a plastic with excellent heat resistance.

[0019] The first substrate 10 and the second substrate 20 are connected by contacting the second main surface 21 of the second substrate 20 with the first main surface 11 of the first substrate 10 (see FIG. 3 ). This allows the wiring substrate 100 to be made thinner. In other words, the first substrate 10 and the second substrate 20 are connected by direct contact without the need for an insulating resist, so the overall thickness of the device can be made thinner by the amount of the insulating resist compared to conventional contact via an insulating resist. Furthermore, since the insulating resist is no longer required, printing of the insulating resist is also no longer necessary. This reduces the manufacturing costs and man-hours for the wiring substrate.

[0020] Preferably, the first main surface 11 of the first substrate 10 and the second main surface 21 of the second substrate 20 are in contact with and bonded to each other. The bonding may be, for example, thermocompression bonding, welding, fusion bonding, etc. In the region 70 where the first substrate 10 and the second substrate 20 overlap, it is sufficient that at least a portion of the first main surface 11 and the second main surface 21 are in contact with and bonded to each other.

[0021] Here, "adhesion" means the ability to withstand a tensile force of 20 N. Evaluation of the adhesive strength between the first substrate 10 and the second substrate 20 can be performed based on JIS K 6849. "Adhesion through contact" means that the first main surface 11 of the first substrate 10 and the second main surface 21 of the second substrate 20 are directly attached to each other without the use of another member such as an adhesive.

[0022] Therefore, the first substrate 10 and the second substrate 20 come into contact with each other through surface contact between the first main surface 11 and the second main surface 21, thereby improving the connection strength between the first substrate 10 and the second substrate 20. Note that the method for bringing the first main surface and the second main surface into contact is not particularly limited, but for example, the first substrate 10 and the second substrate 20 may be connected to the side surfaces of the first substrate 10 and the second substrate 20 via another member, so that the first main surface and the second main surface come into contact with each other.

[0023] If the position of the interface between the first main surface 11 and the second main surface 21 cannot be determined in the contact region between the first main surface 11 and the second main surface 21, the interface is defined as the portion where an extended surface extending from a non-overlapping surface of the first main surface 11 that does not overlap with the second main surface 21 to be flush with the non-overlapping surface overlaps with the contact region between the first main surface 11 and the second main surface 21. As shown in FIG. 5 , the extended surface 11b of the flat surface 11a (non-overlapping surface) of the first main surface 11 located in the region where the first main surface 11 and the second main surface 21 do not contact is defined as the interface between the first main surface 11 and the second main surface 21. In other words, the extended surface 11b is a surface that is substantially flush with the flat surface 11a in the contact region between the first substrate 10 and the second substrate 20. It goes without saying that the extended surface is a virtual surface. This also applies to the following embodiments.

[0024] The first wiring 31 is disposed on the first main surface 11 of the first substrate 10. At least in the region 70 where the first substrate 10 and the second substrate 20 overlap, the first wiring 31 has a shape that extends in one direction. Specifically, the first wiring 31 may extend along the X direction. There may be a plurality of first wirings 31. The plurality of first wirings 31 may be arranged parallel to one another along the Y direction. The shape of the first wiring 31 is not particularly limited.

[0025] The first wiring 31 is made of a conductive material. The conductive material may be, for example, a metal foil such as silver, copper, or nickel, or a mixture of a metal powder such as silver, copper, or nickel and an elastomer resin such as an epoxy resin or a silicone resin. The first wiring 31 is preferably stretchable.

[0026] The first wiring 31 is disposed in the first recess 14 of the first substrate 10. The first wiring 31 may be disposed on the first main surface 11 so as to be fitted into the first recess 14. This can also be interpreted as the first wiring 31 being disposed within the first recess 14 and extending along the first recess 14. Furthermore, one first wiring 31 is disposed in one first recess 14. That is, each of the multiple first wirings 31 may be disposed separately in each of the multiple first recesses 14. With this structure, the first substrate 10 is present between two first wirings 31 adjacent to each other in the Y direction. This ensures insulation between the two adjacent first wirings 31. From the viewpoint of thinning the entire wiring board, the thickness of the first wiring 31 is preferably 30 μm or less.

[0027] The second wiring 32 is disposed in the first recess 14 of the first substrate 10. At least in the region 70 where the first substrate 10 and the second substrate 20 overlap, the second wiring 32 has a shape that extends in one direction. Specifically, the second wiring 32 may extend along the X direction. There may be multiple second wirings 32. The multiple second wirings 32 may be arranged parallel to each other in the Y direction. The shape of the second wiring 32 is not particularly limited.

[0028] The second wiring 32 is made of a conductive material. The conductive material may be, for example, a metal foil such as silver, copper, or nickel, or a mixture of a metal powder such as silver, copper, or nickel and an elastomer resin such as an epoxy resin or a silicone resin. Preferably, the second wiring 32 is stretchable.

[0029] The first wiring 31 and the second wiring 32 are electrically connected to face each other in the Z direction (thickness direction of the first base material). Specifically, the first wiring 31 and the second wiring 32 are electrically connected by direct contact. Note that the first wiring 31 and the second wiring 32 may be electrically connected via a conductive member disposed between the first wiring 31 and the second wiring 32.

[0030] Preferably, the second wiring 32 may be in contact with the first wiring 31 arranged in the first recess 14. In this case, the first wiring 31 and the second wiring 32 may be in contact with each other at the first recess 14 in a cross-sectional view. On the other hand, the first main surface 11 and the second main surface 21 may be in contact with each other on the flat surface of the first main surface 11 (see FIG. 4 ). In such a structure, in a cross-sectional view, the interface between the first wiring 31 and the second wiring 32 and the interface between the first main surface 11 and the second main surface 21 are located on different planes. By having the interface between the first wiring 31 and the second wiring 32 and the interface between the first substrate 10 and the second substrate 20 located on different planes in a cross-sectional view, the strength against peeling at the adhesive surfaces of the first substrate 10 and the second substrate 20 can be improved.

[0031] As shown in FIG. 4 , in the region 70 where the first substrate 10 and the second substrate 20 overlap, the multiple second wirings 32 are arranged side by side in the Y direction. Preferably, the ratio L1 / L2 of the width L1 of each second wiring 32 to the width L2 between two adjacent second wirings 32 in the Y direction is 1 or greater and 20 or less. When the L1 / L2 ratio is 20 or less, insulation between two adjacent second wirings 32 can be suitably ensured. Furthermore, by ensuring a sufficient contact area between the first main surface 11 and the second main surface 21, the connection strength between the first substrate 10 and the second substrate 20 can be improved. When the L1 / L2 ratio is 1 or greater, larger second wirings 32 can be ensured, thereby reducing the electrical resistance of the second wirings 32. It is sufficient that at least two second wirings 32 adjacent to each other in the Y direction among the multiple second wirings 32 satisfy the above-described configuration, and preferably, it is sufficient that all second wirings 32 satisfy the above-described configuration. Similarly, it is more preferable that the width of the first wiring 31 and the distance between two adjacent first wirings 31 also satisfy the above relationship.

[0032] Here, the width L1 of the second wiring 32 is the size in a direction perpendicular to the direction in which the second wiring 32 extends when viewed from the Z direction. In other words, the width L1 of the second wiring 32 is the size of the second wiring 32 in the Y direction. The width L1 of the second wiring 32 is the maximum value of the width of the second wiring 32. If it is difficult to measure the maximum value of the second wiring 32, the average value of the width of the second wiring 32 is taken as L1. The width of the first wiring 31 may be the same as the width L1 of the second wiring 32.

[0033] Similarly, the width L2 between two adjacent second wirings 32 in the Y direction is defined as the shortest distance in the Y direction between the two adjacent second wirings 32. If it is difficult to measure the shortest distance in the Y direction between the second wirings 32, the average value of the width between the two adjacent second wirings 32 in the Y direction is defined as L2.

[0034] The average value refers to the average value of the measurement values ​​obtained by measuring the width of one second wiring 32 at three different locations along the extension direction (X direction) in the area where the first substrate 10 and the second substrate 20 overlap.

[0035] 3 , when viewed from the thickness direction (Z direction) of the first substrate, in a region 70 where the first substrate 10 and the second substrate 20 overlap, the plurality of second wirings 32 are arranged side by side in the Y direction. In the region 70, the ratio S1 / S2 of the area S1 of a region 71 (hereinafter referred to as the first region 71) where the second wirings 32 exist to the area S2 of a region 72 (hereinafter referred to as the second region 72) between two second wirings 32 adjacent in the Y direction is preferably 1 or more and 20 or less.

[0036] Here, the first region 71 is a region of one second wiring 32 in the region 70 where the first substrate 10 and the second substrate 20 overlap, as viewed from the Z direction. The second region 72 is a region between two first regions 71 adjacent to each other in the Y direction, as viewed from the Z direction. In FIG. 3 , the first region 71 and the second region 72 are shown hatched for convenience. The first region 71 and the second region 72 may each have a rectangular shape. The lengths of the first region 71 and the second region 72 in the X direction are the same. Note that the shapes of the first region 71 and the second region 72 are not limited to rectangular.

[0037] When the ratio S1 / S2 is 20 or less, insulation between two adjacent second wirings 32 can be suitably ensured. Also, the contact area between the first main surface 11 and the second main surface 21 can be ensured. This improves the connection strength between the first substrate 10 and the second substrate 20. Also, when the ratio S1 / S2 is 1 or more, larger second wirings 32 can be arranged, and therefore the electrical resistance of the second wirings 32 can be reduced.

[0038] Preferably, in the Z direction, the distance D1 from the first wiring 31 to the third main surface 12 of the first substrate 10 is smaller than the distance D2 from the interface between the first substrate 10 and the second substrate 20 to the third main surface 12 of the first substrate 10 (see FIG. 4 ). The distance D1 refers to the minimum value between the first wiring 31 and the third main surface 12, and the distance D2 refers to the minimum value between the interface between the first substrate 10 and the second substrate 20 and the third main surface 12. This allows the shape of the third main surface 12 of the first substrate 10 to be made flatter. Preferably, the distance D2 is equal to or greater than the sum of the thicknesses of the first wiring 31 and the second wiring 32. Furthermore, by reducing the distance D1, the thickness of the first substrate 10 in the portion overlapping with the first wiring 31 as viewed from the Z direction can be reduced. It is expected that the stretchability of the substrate in the portion overlapping with the wiring as viewed from the Z direction will be reduced. According to the above structure, the thickness of the base material can be reduced in the portion where a decrease in stretchability is expected, so if the first base material 10 has stretchability, the stretchability of the first base material 10 becomes good.

[0039] (Manufacturing Method) Next, a manufacturing method of the exemplary wiring substrate 100 will be described with reference to FIGS. 6A and 6B.

[0040] 6A , a plurality of first wirings 31 are formed on the first main surface 11 of the first substrate 10. Similarly, a plurality of second wirings 32 are formed on the second main surface 21 of the second substrate 20. The first substrate 10 and the second substrate 20 are overlapped so that the first wirings 31 and the second wirings 32 face each other in the Z direction (i.e., the thickness direction of the substrates). Then, the overlapped first substrate 10 and the second substrate 20 are thermocompression bonded together. This may be performed, for example, by pressing a heater against the third main surface 12 of the first substrate 10.

[0041] As shown in FIG. 6B , pressure and heat from the heater cause the first substrate 10 to flow into spaces where no wiring is present, such as spaces between multiple wirings adjacent to each other in the Y direction. The flowing first substrate 10 contacts the second substrate 20 while covering the first wiring 31 and the second wiring 32. This results in thermocompression bonding between the first main surface 11 of the first substrate 10 and the second main surface 21 of the second substrate 20, with the first wiring 31 and the second wiring 32 being positioned in the first recess 14. Because the first substrate 10 has a softening point, it tends to flow easily when heated, making it easier to contact the second substrate 20. In other words, a first substrate 10 with a softening point is suitable for thermocompression bonding. Furthermore, because the first substrate 10 has thermoplastic properties, it is also suitable for thermocompression bonding. Note that the thermocompression bonding method is not particularly limited; for example, another heater may be pressed against the fourth main surface 22 of the second substrate 20.

[0042] Second Embodiment (Structure) Next, a second embodiment will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view of a wiring board 100A according to the second embodiment. Fig. 7 corresponds to Fig. 4 of the first embodiment. The wiring board 100A according to the second embodiment differs from the wiring board 100 according to the first embodiment in the structure of the second base material 20A.

[0043] 7 , the second substrate 20A has a second main surface 21 and a fourth main surface 22 located on opposite sides. The first substrate 10 has a first recess 14 on the first main surface 11, and the second substrate 20A has a second recess 24 on the second main surface 21. The first wiring 31 is disposed in the first recess 24, and the second wiring 32 is disposed in the second recess 24. One first wiring 31 is disposed in one first recess 14. One second wiring 32 is disposed in one second recess 24.

[0044] According to the above configuration, the first wiring 31 is disposed in the first recess 14, so that the first substrate 10 exists between two first wirings 31 adjacent to each other in the Y direction. This makes it possible to ensure insulation between two adjacent first wirings 31. Similarly, the second wiring 32 is disposed in the second recess 24, so that the second substrate 20A exists between two second wirings 32 adjacent to each other in the Y direction. This makes it possible to ensure insulation between two adjacent second wirings 32.

[0045] In the above-described structure, recesses 14, 24 are provided in the first substrate 10 and the second substrate 20A, respectively, and wiring 31, 32 are arranged in the recesses 14, 24. This allows the thickness of the first substrate 10 and the second substrate 20A to be further reduced, thereby enabling the wiring board to be made even thinner.

[0046] The second substrate 20A is a substrate having the same elasticity as the first substrate 10, such as a thermoplastic resin. Specifically, examples of thermoplastic resins include thermoplastic polyurethane (TPU) and polyethylene (PE). Thermoplastic resins have a softening point, e.g., a softening point of 90°C or higher. The second substrate 20A is preferably in the form of a sheet or film. The thickness of the second substrate 20A is not particularly limited, but is preferably 160 μm or less, and more preferably 80 μm or less, to avoid inhibiting the elasticity of the surface of the living body when attached to the living body. Furthermore, the thickness of the second substrate 20A is preferably 40 μm or more. The second substrate 20A is preferably made of the same material as the first substrate. Using the same material as the first substrate 10 allows for a more uniform amount of elasticity across the entire wiring substrate. The first substrate 10 and the second substrate 20A may be made of different materials.

[0047] Furthermore, according to the present embodiment, similarly to the first embodiment, the distance between the second wiring 32 and the fourth main surface 22 of the second substrate 20A can also be reduced for the second substrate 20A. In other words, the thickness of the second substrate 20A at the portion overlapping with the second wiring 32 when viewed from the Z direction can be reduced, and therefore, if the second substrate 20A has stretchability, the stretchability of the second substrate 20A is improved.

[0048] Preferably, the first main surface 11 and the second main surface 21 are in contact and bonded. Preferably, the first wiring 31 and the second wiring 32 are in contact facing each other in the Z direction. Preferably, in a cross-sectional view, the interface between the first wiring 31 and the second wiring 32 and the interface between the first main surface 11 and the second main surface 21 are located on the same plane. That is, the contact surfaces between the wirings and the contact surfaces between the substrates are located on the same plane. By aligning the interfaces, the amount of expansion and contraction on the first substrate 10 side and the second substrate 20A side can be made closer to uniform. Note that the interface between the first wiring 31 and the second wiring 32 and the interface between the first main surface 11 and the second main surface 21 do not have to be located on the same plane.

[0049] (Manufacturing Method) Next, a manufacturing method of the wiring substrate 100A will be described with reference to FIGS. 8A and 8B.

[0050] 8A , a plurality of first wirings 31 are formed on the first main surface 11 of the first substrate 10. Similarly, a plurality of second wirings 32 are formed on the second main surface 21 of the second substrate 20A. The first substrate 10 and the second substrate 20A are overlapped in the Z direction so that the first wirings 31 and the second wirings 32 face each other. Then, heaters are pressed against the third main surface 12 of the first substrate 10 and the fourth main surface 22 of the second substrate 20A, respectively, and the first substrate 10 and the second substrate 20A are heated by the heaters.

[0051] As shown in FIG. 8B , due to the application of pressure and heat by the heater, the first substrate 10 flows between two adjacent first wirings 31. Furthermore, the second substrate 20A flows between two adjacent second wirings 32. The flowing first substrate 10 and second substrate 20A come into contact with each other while covering the first wirings 31 and second wirings 32. This results in thermocompression bonding between the first main surface 11 of the first substrate 10 and the second main surface 21 of the second substrate 20A. The first wirings 31 are disposed in the first recesses 14, and the second wirings 32 are disposed in the second recesses 24. Because the first substrate 10 and the second substrate 20A have softening points, they tend to flow easily when heated and come into contact with each other. In other words, they are suitable for thermocompression bonding. Furthermore, the first substrate 10 and the second substrate 20A have thermoplastic properties, making them similarly suitable for thermocompression bonding.

[0052] Third Embodiment Next, a wiring board 100B according to a third embodiment will be described with reference to Fig. 9 and Fig. 10. Fig. 9 is a plan view of the wiring board according to the third embodiment. Fig. 10 is a cross-sectional view taken along the line X-X in Fig. 9. The wiring board 100B according to the third embodiment differs from the wiring board 100 according to the first embodiment in that an insulating layer 40 is provided.

[0053] 10 , at least a portion of the first wiring 31 arranged on the first main surface 11 of the first base material 10 is covered with an insulating layer 40. Preferably, a portion of the first main surface 11 located between two adjacent first wirings 31 is also covered with the insulating layer 40. Covering the first wiring 31 with the insulating layer 40 suppresses the intrusion of moisture into the first wiring 31 from the outside, and further prevents short-circuiting of the first wiring 31.

[0054] When viewed from the thickness direction (Z direction) of the first base material, the insulating layer 40 may extend along the X direction. The thickness of the insulating layer 40 is not particularly limited, but in order to suppress moisture penetration and achieve a thin structure, the thickness of the insulating layer 40 is preferably 40 μm or more and 80 μm or less.

[0055] The material of the insulating layer 40 may be an insulating material based on acrylic oligomer or urethane acrylate. The insulating layer 40 is preferably made of a low-water-absorbent insulating resin such as silicone resin, acrylic resin, olefin resin, modified urethane resin, vinyl chloride resin, polyester, polyamide, polyolefin, polyethylene, or polypropylene, or a low-water-absorbent insulating layer containing a paraxylylene-based polymer. The insulating layer 40 is in the form of a sheet or film.

[0056] Fourth Embodiment Next, a wiring board 100C according to a fourth embodiment will be described with reference to Fig. 11. Fig. 11 is a cross-sectional view of the wiring board according to the fourth embodiment. Fig. 11 corresponds to Fig. 10 of the third embodiment. The wiring board 100C according to the fourth embodiment differs from the wiring board 100 according to the first embodiment in that a covering layer 60 is provided.

[0057] 11 , at least a portion of the first wiring 31 is covered with a coating layer 60. Preferably, the first main surface 11 located between two adjacent first wirings 31 is also covered with the coating layer 60. This makes it possible to suppress the intrusion of moisture from the outside into the first wiring 31. When viewed from the thickness direction (Z direction) of the first base material, the coating layer 60 extends along the X direction. The thickness of the coating layer 60 is not particularly limited, but from the viewpoint of achieving both suppression of moisture intrusion and thinning, the thickness of the coating layer 60 is preferably 40 μm or more and 80 μm or less.

[0058] The material of the covering layer 60 is not particularly limited, but may be, for example, a laminate. Examples of laminate materials include an adhesive-type stretchable film, highly adhesive crystal gel, and an ultra-thin PDMS sheet. Using such materials improves the biocompatibility of the wiring substrate. For example, when using the wiring substrate 100C so that the covering layer 60 comes into contact with a living body, the covering layer 60's affinity for living tissue can reduce the possibility of the living body experiencing a foreign body reaction or rejection. The covering layer 60 is in the form of a film or sheet.

[0059] Fifth Embodiment A wiring board 100D according to a fifth embodiment will be described with reference to Fig. 12. Fig. 12 is a cross-sectional view of the wiring board according to the fifth embodiment. Fig. 12 corresponds to Fig. 10 of the third embodiment. The wiring board 100D according to the fifth embodiment differs from the wiring board 100 according to the first embodiment in that a thermoplastic sheet 50 is provided.

[0060] 12 , at least a portion of the first wiring 31 is covered with a thermoplastic sheet 50, and the thermoplastic sheet 50 is in contact with and adhered to the first main surface 11. Specifically, the first main surface 11 located between adjacent first wirings 31 is also covered with the thermoplastic sheet 50. This prevents moisture from penetrating into the first wiring 31. Furthermore, the connection strength between the thermoplastic sheet 50 and the first wiring 31 is improved, allowing the first wiring 31 to be firmly fixed to the first substrate 10.

[0061] Examples of materials for the thermoplastic sheet 50 include thermoplastic resins. Specifically, examples include thermoplastic polyurethane (TPU) and polyethylene (PE). The thermoplastic sheet 50 is in the form of a sheet or film. From the viewpoint of reducing the overall thickness of the wiring board, the thickness of the thermoplastic sheet 50 is preferably 160 μm or less. The materials of the thermoplastic sheet 50 and the first substrate 10 may be the same or different.

[0062] 13 is a cross-sectional view of a first modified example of the wiring board according to the fifth embodiment. As shown in Fig. 13, the thermoplastic sheet 50A covers the first wiring 31, contacts and adheres to the first main surface 11, and also contacts and adheres to the second wiring 32. This increases the connection strength between the thermoplastic sheet 50A and the second wiring 32.

[0063] Alternatively, the thermoplastic sheet 50A may be spaced apart from the second wiring 32. In the cross-sectional view shown in FIG. 13 , a gap may be provided between the thermoplastic sheet 50A and the second wiring 32. More specifically, in the region where the first substrate 10 and the second substrate 20 overlap, the edge of the thermoplastic sheet 50A and the edge of the second wiring 32 may be spaced apart from each other via a gap. This can also be interpreted as the thermoplastic sheet 50A being spaced apart from the connection portion between the first wiring 31 and the second wiring 32. This structure can prevent the thermoplastic sheet 50A from deforming or flowing due to heat, such as during thermocompression bonding, and from affecting the connection portion between the first wiring 31 and the second wiring 32. In other words, by separating the thermoplastic sheet 50A from the second wiring 32, the possibility that the thermoplastic sheet 50A will interfere with the connection between the wirings is reduced, thereby further improving the connection reliability between the wirings.

[0064] Preferably, when viewed from the thickness direction (Z direction) of the first substrate, in the region where the first substrate 10 and the second substrate 20 overlap, an edge 81 in the extension direction of the first substrate 10 is located further outward in the extension direction of the first substrate 10 than an edge 82 in the extension direction of the first wiring 31. Specifically, the first substrate 10 has another edge 85 on the opposite side of the extension direction from the edge 81, and the edge 81 is farther away from the other edge 85 than the edge 82. This prevents the first wiring 31 from being exposed from the first substrate 10, and the first wiring 31 can be protected by the first substrate 10.

[0065] [Second Modification] Figure 14 is a cross-sectional view of a second modification of the wiring board according to the fifth embodiment. As shown in Figure 14, the thermoplastic sheet 50B covers the first wiring 31, contacts and adheres to the first main surface 11, and also contacts and adheres to the second wiring 32 and the second substrate 20. That is, the thermoplastic sheet 50B may be sandwiched between the first substrate 10 and the second substrate 20 and contact and adhere to both the first main surface 11 and the second main surface 21. This increases the connection strength between the thermoplastic sheet 50B and the second substrate 20. Furthermore, the adhesive strength between the first substrate 10 and the second substrate 20 may also be improved. In this structure, the thermoplastic sheet 50B may have the same thickness as the second wiring 32. More specifically, the thermoplastic sheet 50B may have the same thickness as the second wiring 32, at least in the region where the first substrate 10 and the second substrate 20 overlap. At this time, the thermoplastic sheet 50B does not need to be in contact with the second wiring 32.

[0066] The thickness of the thermoplastic sheet may be smaller than that of the second wiring 32 as shown in Fig. 13, or may be equal to that of the second wiring 32 as shown in Fig. 14. Alternatively, from the viewpoint of placing greater importance on protecting the wiring, the thermoplastic sheet may have a thickness larger than that of the second wiring 32.

[0067] 13 and 14, the thickness of the thermoplastic sheet does not necessarily have to be uniform across the X direction. For example, the thermoplastic sheet may have a smaller thickness in the region where the first substrate 10 and the second substrate 20 overlap than in other regions. More specifically, the thermoplastic sheet may have a smaller thickness in a portion proximal to the connection between the first wiring 31 and the second wiring 32. That is, the thermoplastic sheet may have a smaller thickness in the region where multiple components overlap. This allows the overall thickness of the wiring board to be reduced in the region where multiple components overlap, thereby enabling the wiring board to be made thinner.

[0068] Furthermore, the thermoplastic sheet as described above may also be provided on the second substrate 20 that is overlaid on the first substrate 10. That is, the second substrate may include a thermoplastic sheet that covers the second wiring 32 and is in contact with and adhered to the second main surface 21. The thermoplastic sheet covering the second wiring 32 may be in contact with and adhered to the first wiring 31. Alternatively, the thermoplastic sheet covering the second wiring 32 may be separated from the first wiring 31. Covering each of the first wiring 31 and the second wiring 32 with a thermoplastic sheet can provide the effects of suppressing moisture penetration into each wiring and improving the adhesive strength between the wiring and the base material.

[0069] Wiring having a portion covered by a covering member such as the thermoplastic sheet, insulating layer, and / or coating layer described above does not necessarily have a uniform thickness. The wiring may have different thicknesses in the overlapping portion that overlaps with the covering member and the non-overlapping portion that does not overlap with the covering member. Such "overlapping portion" and "non-overlapping portion" may also be referred to as "covered portion" and "non-covered portion," respectively. For example, the wiring may have a smaller thickness in the overlapping portion than in the non-overlapping portion. In other words, the thickness of the wiring in the non-overlapping portion may be greater than the thickness of the wiring in the overlapping portion. In the overlapping portion, the wiring is suitably protected by the covering member and can adhere more suitably to the substrate, allowing it to have a relatively small thickness. Having a small wiring thickness allows for a thinner wiring board.

[0070] Sixth Embodiment Next, a wiring board 100E according to a sixth embodiment will be described with reference to Fig. 15. Fig. 15 is a cross-sectional view of the wiring board according to the sixth embodiment. The wiring board 100E according to the sixth embodiment differs from the wiring board 100B according to the third embodiment in that a covering layer 60 is further provided.

[0071] 15 , the insulating layer 40 is covered with a covering layer 60. The covering layer 60 is made of a material different from that of the insulating layer 40. When viewed from the thickness direction (Z direction) of the first base material, the covering layer 60 extends along the X direction.

[0072] This can prevent deterioration of the insulating layer 40 and leakage of components contained in the insulating layer 40. Preferably, the covering layer 60 is bonded to the insulating layer 40 via an adhesive. Alternatively, the covering layer 60 may be bonded to the second substrate 20.

[0073] The covering layer 60 may be, for example, a laminate. The covering layer 60 may be made of, for example, a hydrocarbon-based material, a urethane gel tape, or a silicone elastomer. Such a material improves the biocompatibility of the wiring substrate. For example, when the wiring substrate 100E is used so that the covering layer 60 comes into contact with a living body, the covering layer 60 has affinity for living tissue, which can prevent the living body from experiencing a foreign body reaction or rejection. Furthermore, from the viewpoint of achieving both improved biocompatibility and a thinner wiring substrate, the thickness of the covering layer 60 is preferably 20 μm or more and 80 μm or less.

[0074] Seventh Embodiment Next, a wiring board 100F according to a seventh embodiment will be described with reference to Fig. 16 and Fig. 17. Fig. 16 is a plan view of the wiring board according to the seventh embodiment. Fig. 17 is a cross-sectional view taken along line XVII-XVII of Fig. 16. The wiring board 100F according to the seventh embodiment differs from the wiring board 100E according to the sixth embodiment in that an electronic component 90 and a resist 80 are provided.

[0075] 16 and 17 , a resist 80 is disposed between the first substrate 10 and the second substrate 20 in the thickness direction (Z direction) of the first substrate. Specifically, the resist 80 is in contact with the first main surface 11 and the second main surface 21. Furthermore, the resist 80 is not present between the first main surface 11 and the first wiring 31, and the resist 80 is not present between the second main surface 21 and the second wiring 32. For example, the resist may be disposed so as to be in contact with both the first main surface 11 and the second wiring 32 disposed on the second main surface 21. This allows the space between the first substrate 10 and the second substrate 20 to be filled with the resist 80, thereby preventing foreign matter from adhering to the first wiring 31 from the outside.

[0076] The material of the resist 80 is not particularly limited, but examples thereof include liquid epoxy solder resist, alkaline development type solder resist, UV curing type solder resist, thermosetting type solder resist, etc. The shape of the resist 80 is not particularly limited, but it may be in the form of a film or a sheet.

[0077] The electronic component 90 is electrically connected to the second wiring 32. There is no particular limitation on the number of second wirings 32 electrically connected to the electronic component 90, and the electronic component 90 may be connected to one or more second wirings 32. There is no particular limitation on the type of electronic component 90, and examples include inductors and capacitors. There is no particular limitation on the number of electronic components 90. A large number of electronic components 90 may be mounted as necessary.

[0078] Eighth Embodiment Next, a wiring board 100G according to an eighth embodiment will be described with reference to Fig. 18. Fig. 18 is a cross-sectional view of the wiring board according to the eighth embodiment. Fig. 18 corresponds to Fig. 4 of the first embodiment. The wiring board 100G according to the eighth embodiment differs from the wiring board 100 according to the first embodiment in the width of the first wiring 31A.

[0079] 18 , the first wiring 31A and the second wiring 32 are in contact with each other. In a region 70 where the first substrate 10 and the second substrate 20 overlap, the width L3 of the first wiring 31A is smaller than the width L1 of the second wiring 32. This increases the contact area between the first substrate 10 and the second wiring 32, improving the connection strength between the first substrate 10 and the second wiring 32.

[0080] Here, the width L3 of the first wiring 31A is the size in the direction perpendicular to the direction in which the first wiring 31A extends when viewed from the Z direction. In other words, the width L3 of the first wiring 31A is the size of the first wiring 31A in the Y direction. The width L3 of the first wiring 31A is the maximum width of the first wiring 31A. If it is difficult to measure the maximum width of the first wiring 31A, the average width of the first wiring 31A is taken as L3.

[0081] Here, the width L1 of the second wiring 32 is the size in the direction perpendicular to the direction in which the second wiring 32 extends when viewed from the Z direction. In other words, the width L1 of the second wiring 32 is the size of the second wiring 32 in the Y direction. The width L1 of the second wiring 32 is the maximum value of the width of the second wiring 32. If it is difficult to measure the maximum value of the second wiring 32, the average value of the width of the second wiring 32 is taken as L1.

[0082] The average value refers to the average value of the measurement values ​​obtained by measuring the width of one first wiring 31A at three different locations along the extension direction (X direction) in the area where the first substrate 10 and the second substrate 20 overlap.

[0083] Ninth Embodiment Next, a wiring board 100H according to a ninth embodiment will be described with reference to Fig. 19. Fig. 19 is a cross-sectional view of the wiring board according to the ninth embodiment. Fig. 19 corresponds to Fig. 4 of the first embodiment. The wiring board 100H according to the ninth embodiment differs from the wiring board 100 according to the first embodiment in the shape of the third main surface 12.

[0084] As shown in FIG. 19 , the first substrate 10 is in contact with and bonded to the second substrate 20. The first substrate 10 covers the first wiring 31 and the second wiring 32. The third main surface 12 of the first substrate 10, which is located on the opposite side of the first main surface in contact with the first wiring 31, has an uneven shape. This increases the surface area of ​​the third main surface 12 of the first substrate 10, improving the heat dissipation of the first wiring 31. Furthermore, when the first substrate 10 and the second substrate 20 are thermocompression-bonded during the manufacture of the wiring board, the heater comes into contact with the convex portions of the third main surface 12, allowing heat to be applied intensively to the convex portions of the first substrate 10. This allows for rapid thermocompression bonding.

[0085] 19 , when viewed from the Z direction, the third main surface 12 has a convex shape in a region overlapping with the first wirings 31, and a concave shape in a region between two adjacent first wirings 31. In other words, the third main surface 12 is formed along the first wirings 31 and the second main surface 21 between the two adjacent first wirings 31.

[0086] Tenth Embodiment Next, a wiring board 100I according to a tenth embodiment will be described with reference to Fig. 20. Fig. 20 is a cross-sectional view of the wiring board according to the tenth embodiment. Fig. 20 corresponds to Fig. 4 of the first embodiment. The wiring board 100I according to the tenth embodiment differs from the wiring board 100 according to the first embodiment in the size and number of second wirings 32A.

[0087] As shown in FIG. 20 , the multiple first wirings 31 and one second wiring 32A are electrically connected to face each other in the thickness direction (Z direction) of the first base material. That is, among the multiple first wirings 31 arranged on the first main surface 11, at least two first wirings 31 may be electrically connected to the same second wiring 32A. Specifically, the width of the second wiring 32A in the Y direction is greater than the width of the first wiring 31 in the Y direction, and two or more first wirings 31 are connected to one second wiring 32A. The second wiring 32A may extend in the Y direction so as to be mutually connected to each of the multiple first wirings 31 arranged in parallel in the Y direction. Adjacent multiple first wirings 31 are spaced apart from each other. This reduces the number of second wirings 32A relative to the multiple first wirings 31, increasing the design flexibility of the wiring substrate 100I.

[0088] A portion of the first substrate 10 is disposed between each of the adjacent first wirings 31 and contacts the second wirings 32A. This ensures insulation between the adjacent first wirings 31. The form of connection between the first wirings 31 and the second wirings 32A is not particularly limited. For example, the plurality of second wirings may be electrically connected to one first wiring. In this case, it is preferable that the second substrate 20 is made of the same material as the first substrate 10.

[0089] The present disclosure is not limited to the above-described embodiments, and design modifications are possible within the scope of the present disclosure. For example, the features of the first to tenth embodiments may be combined in various ways.

[0090] 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H, 100I Wiring board 10 First substrate 11 First main surface 11a Flat surface 11b Extended surface 12 Third main surface 20, 20A Second substrate 21 Second main surface 22 Fourth main surface 31 31A First wiring 32 32A Second wiring 40 Insulating layer 50, 50A, 50B Thermoplastic sheet 60 Covering layer 70 Region where first substrate and second substrate overlap 71 Region of second wiring 72 Region between two adjacent second wirings 80 Resist 81 Edge of first substrate 82 Edge of first wiring 85 Other edge 90 Electronic component L1 Width of second wiring L2 Width between second wirings L3 Width of the first wiring D1 Distance from the first wiring to the third main surface D2 Distance from the interface between the first substrate and the second substrate to the third main surface X Extension direction of the first substrate Z Thickness direction of the first substrate

Claims

1. A first substrate having a first major surface; a second substrate having a second major surface; A first wiring disposed on the first main surface; A second wiring disposed on the second main surface; Equipped with the first main surface and the second main surface are in contact with each other, and the first base material and the second base material are connected to each other; the first wiring and the second wiring are electrically connected to each other in a thickness direction of the first base material, Further, an insulating layer is provided to cover at least a portion of the first wiring, The wiring board, wherein the insulating layer overlaps the second base material when viewed in the thickness direction.

2. the first base material has a first recess in the first main surface; The wiring board according to claim 1 , wherein the first wiring and the second wiring are disposed in the first recess.

3. the first wiring and the second wiring are opposed to each other in the thickness direction and in contact with each other; The wiring board according to claim 1 , wherein an interface between the first wiring and the second wiring and an interface between the first main surface and the second main surface are located on different planes.

4. the first substrate has a third major surface; The wiring board according to claim 1 , wherein a distance from the first wiring to the third main surface in the thickness direction is smaller than a distance from an interface between the first base material and the second base material to the third main surface.

5. 2. The wiring board according to claim 1, wherein the first substrate has a first recess in the first main surface, the second substrate has a second recess in the second main surface, the first wiring is disposed in the first recess, and the second wiring is disposed in the second recess.

6. The wiring board according to claim 1 , further comprising a cover layer covering at least a portion of the insulating layer, the cover layer being made of a material different from that of the insulating layer.

7. 2. The wiring board according to claim 1, wherein in a region where the first substrate and the second substrate overlap when viewed from the thickness direction, an edge of the first substrate in the extension direction is located outside an edge of the first wiring in the extension direction of the first substrate.

8. The wiring board according to claim 1 , further comprising a resist disposed between the first base material and the second base material in the thickness direction.

9. 2. The wiring board according to claim 1, wherein in a region where the first substrate and the second substrate overlap, the second wirings are arranged side by side, and a ratio L1 / L2 of a width L1 of the second wirings to a width L2 between two adjacent second wirings is 1 or more and 20 or less.

10. The wiring board according to claim 1 , wherein in a region where the first base material and the second base material overlap, a width L3 of the first wiring is smaller than a width L1 of the second wiring.

11. the first substrate has a third major surface; The wiring board according to claim 1 , wherein the third main surface has an uneven shape.

12. The wiring board according to claim 1 , wherein the plurality of first wirings and one of the second wirings are electrically connected to each other while facing each other in the thickness direction.

13. The wiring board according to claim 12 , wherein a portion of the first base material is disposed between each of the plurality of adjacent first wirings and in contact with the second wiring.

14. The wiring board according to claim 1 , wherein at least the first substrate of the first substrate and the second substrate has a softening point.