Resin multilayer substrate and electronic apparatus

Abstract

This resin multilayer substrate is less likely to fracture when bent. A resin multilayer substrate (100) comprises a laminated substrate (1) and a plurality of conductor layers (21, 22). The laminated substrate (1) has a plurality of resin layers (11, 12). In the laminated substrate (1), the plurality of resin layers (11, 12) are laminated. The plurality of conductor layers (21, 22) overlap the plurality of resin layers (11, 12) in the lamination direction of the plurality of resin layers (11, 12). The resin multilayer substrate (100) has a boundary surface (B1) including the interface (31) between two resin layers (11, 12) adjacent to each other in the lamination direction among the plurality of resin layers (11, 12). The interface (31) includes: a first interface (311); and a second interface (312) having an adhesion strength lower than that of the first interface (311), and having an adhesion strength lower than that of the interfaces between the conductor layers and the resin layers that are in contact with each other among the plurality of resin layers (11, 12) and the plurality of conductor layers (21, 22).

Description

Resin Multilayer Substrate and Electronic Device

[0001] The present invention generally relates to a resin multilayer substrate and an electronic device, and more particularly to a resin multilayer substrate having a plurality of resin layers and an electronic device including the resin multilayer substrate.

[0002] Patent Document 1 discloses a signal transmission line including a laminate formed by laminating a plurality of resin layers.

[0003] Patent Document 1 discloses that the signal transmission line is bent and used.

[0004] International Publication No. 2017 / 130731

[0005] In the signal transmission line disclosed in Patent Document 1, depending on the thickness of the laminate, when the bending radius is reduced, the bent portion may break.

[0006] An object of the present invention is to provide a resin multilayer substrate and an electronic device that are less likely to break when bent.

[0007] A resin multilayer substrate according to an aspect of the present invention includes a laminated substrate and a plurality of conductor layers. The laminated substrate has a plurality of resin layers. In the laminated substrate, the plurality of resin layers are laminated. The plurality of conductor layers overlap the plurality of resin layers in the lamination direction of the plurality of resin layers. The resin multilayer substrate has a boundary surface including an interface between two adjacent resin layers in the lamination direction among the plurality of resin layers. The interface includes a first interface and a second interface. The second interface has a lower adhesion strength than the first interface and a lower adhesion strength than an interface between a resin layer and a conductor layer that are in contact with each other among the plurality of resin layers and the plurality of conductor layers.

[0008] A resin multilayer substrate according to one aspect of the present invention comprises a laminated substrate and a plurality of conductive layers. The laminated substrate has a plurality of resin layers. The plurality of resin layers are laminated in the laminated substrate. The plurality of conductive layers overlap the plurality of resin layers in the lamination direction of the plurality of resin layers. The resin multilayer substrate has an interface including the interface of two resin layers that are adjacent in the lamination direction of the plurality of resin layers. The interface includes a first interface to which the two resin layers are fixed and a second interface to which the two resin layers are in contact and not fixed. The surface roughness of the surface of one of the two resin layers corresponding to the second interface is smaller than the surface roughness of the surface of the one resin layer corresponding to the first interface when the two resin layers are peeled off at the first interface.

[0009] An electronic device according to one aspect of the present invention comprises a resin multilayer substrate according to the above aspect and a hinge device. The resin multilayer substrate includes the second interface in a portion that undergoes plastic deformation due to the movement of the hinge device.

[0010] The resin multilayer substrate and electronic device according to the above embodiment of the present invention are less prone to fracture when the resin multilayer substrate is bent.

[0011] Figure 1 is a plan view of a resin multilayer substrate according to Embodiment 1. Figure 2 is a cross-sectional view of the same resin multilayer substrate taken along line II-II in Figure 1. Figure 3 is a cross-sectional view of the same resin multilayer substrate taken along line III-III in Figure 1. Figure 4 is a cross-sectional view of a resin multilayer substrate according to Modification 1 of Embodiment 1. Figure 5 is a cross-sectional view of a resin multilayer substrate according to Modification 2 of Embodiment 1. Figure 6 is a cross-sectional view of the main part of an electronic device equipped with the same resin multilayer substrate in an unfolded state. Figure 7 is a cross-sectional view of the main part of an electronic device equipped with the same resin multilayer substrate in a folded state. Figure 8 is a cross-sectional view of a resin multilayer substrate according to Embodiment 2. Figure 9 is a cross-sectional view of a resin multilayer substrate according to Modification 1 of Embodiment 2. Figure 10 is a cross-sectional view of a resin multilayer substrate according to Modification 2 of Embodiment 2. Figure 11 is a plan view of a resin multilayer substrate according to Embodiment 3. Figure 12 is a cross-sectional view of the same resin multilayer substrate taken along line XII-XII in Figure 11. Figure 13 is a cross-sectional view of the same resin multilayer substrate taken along line XIII-XIII in Figure 11. Figure 14 is a cross-sectional view of the same resin multilayer substrate taken along the line XIV-XIV in Figure 11. Figure 15 is a cross-sectional view of the same resin multilayer substrate taken along the line XV-XV in Figure 11. Figure 16 is a cross-sectional view of a resin multilayer substrate according to modification 1 of Embodiment 3. Figure 17 is a cross-sectional view of a resin multilayer substrate according to modification 2 of Embodiment 3, corresponding to the cross-section taken along the line XII-XII in Figure 11. Figure 18 is a cross-sectional view of the same resin multilayer substrate, corresponding to the cross-section taken along the line XIII-XIII in Figure 11. Figure 19 is a cross-sectional view of the same resin multilayer substrate, corresponding to the cross-section taken along the line XV-XV in Figure 11. Figure 20 is a plan view of a resin multilayer substrate according to Embodiment 4. Figure 21 is a cross-sectional view of the same resin multilayer substrate taken along the line XXI-XXI in Figure 20. Figure 22 is a cross-sectional view of the same resin multilayer substrate taken along the line XXII-XXII in Figure 20. Figure 23 is a cross-sectional view of a resin multilayer substrate according to modification 1 of Embodiment 4. Figure 24 is a cross-sectional view of a resin multilayer substrate according to modification 2 of Embodiment 4. Figure 25 is another cross-sectional view of a resin multilayer substrate according to a modified example 2 of Embodiment 4.

[0012] Embodiments 1 to 4 will be described below with reference to the drawings. The drawings referenced in Embodiments 1 to 4 below are schematic diagrams, and the size and thickness of the components shown in the drawings do not necessarily reflect the actual dimensions, nor do the ratios of size and thickness between components necessarily reflect the actual dimensional ratios. Furthermore, each drawing defines and represents a Cartesian coordinate system with three mutually orthogonal axes: the X, Y, and Z axes. The X, Y, and Z axes are all virtual axes, and the arrows indicating "X," "Y," and "Z" in the drawings are merely for illustrative purposes and do not represent actual objects.

[0013] (Embodiment 1) The resin multilayer substrate 100 according to Embodiment 1 will be described with reference to Figures 1 to 3.

[0014] (1) The resin multilayer substrate 100 according to Embodiment 1 comprises a laminated substrate 1 and a plurality of (two in the example of Figure 2) conductive layers 21, 22, as shown in Figures 2 and 3. The laminated substrate 1 has a plurality of (two in the example of Figure 2) resin layers 11, 12. The plurality of resin layers 11, 12 are laminated in the laminated substrate 1. The plurality of conductive layers 21, 22 overlap the plurality of resin layers 11, 12 in the lamination direction of the plurality of resin layers 11, 12. The resin multilayer substrate 100 has an interface B1. The interface B1 includes the interface 31 of two adjacent resin layers 11, 12 in the lamination direction among the plurality of resin layers 11, 12.

[0015] The resin multilayer substrate 100 is used, for example, in electronic devices. The electronic device is, for example, a foldable communication device. The communication device is, for example, a mobile phone (e.g., a smartphone), but is not limited to mobile phones; it may also be, for example, a notebook computer, a wearable device, etc. The communication device is not limited to a foldable communication device.

[0016] Hereinafter, each component of the resin multilayer substrate 100 according to this embodiment will be described with reference to the drawings.

[0017] (1.1) Laminated substrate As shown in Figure 1, when the laminated substrate 1 is not bent, the width direction is along the Y-axis direction, and the length along the X-axis direction is longer than the width direction. The laminated substrate 1 may have a shape other than a laminated substrate.

[0018] As shown in Figures 2 and 3, the laminated substrate 1 has a plurality of (two in the illustrated example) resin layers 11 and 12, and the plurality of resin layers 11 and 12 are laminated together.

[0019] The thickness direction of the laminated substrate 1 is the stacking direction of the multiple resin layers 11 and 12. Hereinafter, the resin layers 11 and 12 may be referred to as the first resin layer 11 and the second resin layer 12, respectively. The first resin layer 11 has a first main surface 111 and a second main surface 112. The second resin layer 12 has a third main surface 121 and a fourth main surface 122.

[0020] Each of the multiple resin layers 11 and 12 contains, for example, a thermoplastic resin. The thermoplastic resin is, for example, a liquid crystal polymer. The thermoplastic resin is not limited to a liquid crystal polymer, but may also be, for example, PTFE (polytetrafluoroethylene). In this embodiment, the first resin layer 11 and the second resin layer 12 are self-adhered, and no adhesive layer is interposed between the first resin layer 11 and the second resin layer 12. In this embodiment, the second main surface 112 of the first resin layer 11 and the fourth main surface 122 of the second resin layer 12 are self-adhered. In the laminated substrate 1, the material of the first resin layer 11 and the material of the second resin layer 12 are the same, and the first resin layer 11 and the second resin layer 12 are directly joined together.

[0021] The thickness of each of the multiple resin layers 11 and 12 is, for example, 10 μm or more and 120 μm or less.

[0022] (1.2) Multiple Conductor Layers As shown in Figures 2 and 3, the resin multilayer substrate 100 comprises multiple (two in the example of Figure 2) conductor layers 21 and 22. Each of the multiple conductor layers 21 and 22 is electrically conductive. The material of each of the multiple conductor layers 21 and 22 includes, for example, copper. Hereinafter, for the sake of explanation, conductor layer 21 may be referred to as the first conductor layer 21 and conductor layer 22 as the second conductor layer 22.

[0023] The first conductor layer 21 is laminated on the first main surface 111 of the first resin layer 11. The second conductor layer 22 is laminated on the third main surface 121 of the second resin layer 12. In this embodiment, the first conductor layer 21 is the ground electrode, and the second conductor layer 22 is the signal line.

[0024] In the following, the first conductor layer 21 may be referred to as the ground electrode 21, and the second conductor layer 22 may be referred to as the signal line 22. The signal line 22 is a high-frequency signal line through which a high-frequency signal is transmitted. The frequency of the high-frequency signal is, for example, 1 GHz or higher. The frequency of the high-frequency signal is not limited to 1 GHz or higher, but may be less than 1 GHz. The resin multilayer substrate 100 of this embodiment is designed so that the impedance of the signal line 22 is 50 Ω. In this embodiment, the multilayer substrate 1, the signal line 22, and the ground electrode 21 constitute a microstrip line.

[0025] The signal line 22 is formed in a predetermined pattern. In this embodiment, the signal line 22 is linear (see Figure 1). The signal line 22 is formed, for example, by patterning a metal foil (e.g., copper foil) attached to the third main surface 121 of the second resin layer 12.

[0026] The signal line 22 has a line width in the Y-axis direction and a thickness in the stacking direction of the multiple resin layers 11 and 12. In this embodiment, as shown in Figure 1, the line width of the signal line 22 is narrower than the width of the laminated substrate 1 in the Y-axis direction. As shown in Figures 2 and 3, the thickness of the signal line 22 is thinner than the thickness of each of the multiple resin layers 11 and 12. The thickness of the signal line 22 is, for example, 3 μm or more and 40 μm or less.

[0027] The ground electrode 21 is formed on the first main surface 111 of the first resin layer 11. The ground electrode 21 is formed in a predetermined pattern. In this embodiment, the ground electrode 21 is elongated. The ground electrode 21 is formed by patterning a metal foil (for example, copper foil) attached to the first main surface 111 of the first resin layer 11.

[0028] As shown in Figures 2 and 3, the ground electrode 21 overlaps the signal line 22 in the stacking direction of the multiple resin layers 11 and 12. The conductor layer 21 (ground electrode 21) and the conductor layer 22 (signal line 22) overlap the multiple resin layers 11 and 12 in a plan view from the stacking direction of the multiple resin layers 11 and 12, and the ground electrode 21 overlaps the signal line 22 in a plan view from the stacking direction of the multiple resin layers 11 and 12.

[0029] The ground electrode 21 is adjacent to the signal line 22 in the stacking direction of the multiple resin layers 11 and 12. The statement "the ground electrode 21 is adjacent to the signal line 22 in the stacking direction of the multiple resin layers 11 and 12" means that the ground electrode 21 and the signal line 22 are spaced apart in the stacking direction of the multiple resin layers 11 and 12, without any other conductors being placed between them.

[0030] In this embodiment, as shown in Figure 3, the width of the ground electrode 21 is wider than the width of the signal line 22 in the width direction (direction parallel to the Y-axis) of the signal line 22. The thickness of the ground electrode 21 is, for example, 3 μm or more and 40 μm or less.

[0031] As shown in Figures 2 and 3, the resin multilayer substrate 100 has an interface B1. The interface B1 includes the interface 31 of two adjacent resin layers 11 and 12 in the stacking direction among the plurality of resin layers 11 and 12. At interface B1, the interface 31 includes a first interface 311 and a second interface 312, as shown in Figure 2. The adhesion strength of the two resin layers 11 and 12 at the second interface 312 is lower than the adhesion strength of the two resin layers 11 and 12 at the first interface 311. Furthermore, the adhesion strength of the second interface 312 is lower than that of the interfaces between resin layers and conductor layers that are in contact with each other among the plurality of resin layers 11 and 12 and the plurality of conductor layers 21 and 22. More specifically, the adhesion strength of the first resin layer 11 and the second resin layer 12 at the second interface 312 is lower than the adhesion strength of the first resin layer 11 and the first conductor layer 21, and lower than the adhesion strength of the second resin layer 12 and the second conductor layer 22. Adhesion strength is evaluated by a peel test. In the resin multilayer substrate 100 according to Embodiment 1, when a peel test is performed, delamination occurs between the first resin layer 11 and the second resin layer 12 at the second interface 312, and then cohesive failure occurs near the first interface 311. The peel test is, for example, a 90-degree peel strength test (IPC-TM-650 2.4.9). Furthermore, "cohesive failure" means that the failure occurs inside the two resin layers 11 and 12, rather than at the interface 31 between the two resin layers 11 and 12. In Figure 2, the first interface 311 is shown with a thick line, and the second interface 312 is shown with a thin line. The first interface 311 has relatively high adhesion strength at interface 31. The second interface 312 has relatively low adhesion strength at interface 31.

[0032] The resin multilayer substrate 100 according to Embodiment 1 can be bent, for example, as shown in Figure 4. Figure 4 is a cross-sectional view of the resin multilayer substrate 100 according to Modification 1 of Embodiment 1. With respect to the resin multilayer substrate 100 according to Modification 1 of Embodiment 1, components that are the same as those in the resin multilayer substrate 100 according to Embodiment 1 (see Figures 1 to 3) are denoted by the same reference numerals and their descriptions are omitted. In the resin multilayer substrate 100 according to Modification 1, the interface 31 included in the interface B1 includes a second interface 312a instead of the second interface 312 of the resin multilayer substrate 100 according to Embodiment 1. In the resin multilayer substrate 100 according to Modification 1, the first resin layer 11 and the second resin layer 12 are fixed at the first interface 311, and the first resin layer 11 and the second resin layer 12 are peeled off at the second interface 312a. The second interface 312a is in contact with the surface 112a in the first resin layer 11 that corresponds to the second interface 312a, and with the surface 122a in the second resin layer 12 that corresponds to the second interface 312a, but they are not fixed together. In addition, the resin multilayer substrate 100 according to Modification 1 may have a void between a part of the surface 112a of the first resin layer 11 and a part of the surface 122a of the second resin layer 12.

[0033] Figure 5 is a cross-sectional view of a resin multilayer substrate 100 according to Modification 2 of Embodiment 1. The resin multilayer substrate 100 according to Modification 2 is substantially the same as the resin multilayer substrate 100 according to Modification 1, and differs from the resin multilayer substrate 100 according to Modification 1 in that it is not bent, although it may be formed by bending the resin multilayer substrate 100 according to Modification 1. With respect to the resin multilayer substrate 100 according to Modification 2 of Embodiment 1, components that are the same as those in the resin multilayer substrate 100 according to Modification 1 of Embodiment 1 (see Figure 4) are denoted by the same reference numerals and their description is omitted. In the resin multilayer substrate 100 according to Modification 2, the surface roughness of the surface 112a corresponding to the second interface 312a in the first resin layer 11 is smaller than the surface roughness of the surface corresponding to the first interface 311 in the second main surface 112 of the first resin layer 11 when the laminated substrate 1 is peeled off at the first interface 311. The surface roughness is the arithmetic mean roughness Ra. The arithmetic mean roughness Ra is defined in ISO 4287-1997. The arithmetic mean roughness Ra can be measured, for example, with a microscope or a laser displacement meter.

[0034] In the modified example 2, the resin multilayer substrate 100 undergoes cohesive failure near the first interface 311 when a peel test is performed. The peel test is, for example, a 90-degree peel strength test (IPC-TM-650 2.4.9). "Cohesive failure" means that the failure occurs within the two resin layers 11, 12, rather than at the interface 31 between two adjacent resin layers 11, 12 in the stacking direction of the multiple resin layers 11, 12.

[0035] The resin multilayer substrate 100 according to Embodiment 1 may further comprise at least one of a first resist layer (not shown) disposed on a first main surface 101 of the laminated substrate 1 and a second resist layer (not shown) disposed on a second main surface 102 of the laminated substrate 1. The first main surface 101 of the laminated substrate 1 includes the first main surface 111 of the first resin layer 11. The first resist layer is disposed to cover a part of the first main surface 101 of the laminated substrate 1 and the first conductor layer 21. The second main surface 102 of the laminated substrate 1 includes the third main surface 121 of the second resin layer 12. The second resist layer is disposed to cover a part of the second main surface 102 of the laminated substrate 1 and the second conductor layer 22.

[0036] (2) Method for manufacturing a resin multilayer substrate In the method for manufacturing a resin multilayer substrate 100 according to Embodiment 1, for example, the first step, the second step, and the third step are performed in the order of the first step, the second step, and the third step.

[0037] In the first step, a first single-sided copper-clad film and a second single-sided copper-clad film are prepared. The first single-sided copper-clad film is a single-sided copper-clad film in which a ground electrode 21 is formed on the first main surface 111 of the first resin layer 11. The second single-sided copper-clad film is a single-sided copper-clad film in which a signal line 22 is formed on the third main surface 121 of the second resin layer 12.

[0038] In the second step, the regions corresponding to the first interface 311 on the second main surface 112 of the first resin layer 11 of the first single-sided copper-clad film and the fourth main surface 122 of the second resin layer 12 of the second single-sided copper-clad film are roughened or altered by surface treatment. In the surface treatment, plasma discharge treatment is performed on the regions corresponding to the first interface 311 on the second main surface 112 of the first resin layer 11 and the third main surface 121 of the second resin layer 12. In the second step, for example, the regions corresponding to the second interface 312 on the second main surface 112 of the first resin layer 11 and the fourth main surface 122 of the second resin layer 12 are covered with a mask and surface treatment is performed so that surface treatment is not performed on the regions corresponding to the second interface 312.

[0039] In the third step, the first single-sided copper-clad film and the second single-sided copper-clad film are stacked and pressed while heated to form the resin multilayer substrate 100. The adhesion strength between the first resin layer 11 and the second resin layer 12 is higher at the first interface 311, which corresponds to the area where surface treatment was performed in the second step, and lower at the second interface 312, which corresponds to the area where surface treatment was not performed. In the manufacturing method of the resin multilayer substrate 100, the first single-sided copper-clad film and the second single-sided copper-clad film prepared in the first step are sheets of a size that allows for the formation of a large number of resin multilayer substrates 100.

[0040] (3) Electronic equipment equipped with a resin multilayer substrate The electronic equipment 700 is, for example, foldable and, as shown in Figures 6 and 7, comprises a resin multilayer substrate 100, a hinge device 705, and a plurality of (two in the example of Figure 6) base plates 706. In the electronic equipment 700, the hinge device 705 is provided to allow the electronic equipment 700 to be transformed between an unfolded state (see Figure 6) and a folded state (see Figure 7). The hinge device 705 includes a fixing member 750 and a plurality of (two in the example of Figure 6) rotating members 751 that are connected to the fixing member 750 and are rotatable. The plurality of base plates 706 correspond one-to-one with the plurality of rotating members 751. Each of the plurality of base plates 706 is connected to a corresponding rotating member 751 from the plurality of rotating members 751 and is rotatable. The resin multilayer substrate 100 is arranged across the plurality of base plates 706. Therefore, the shape of the resin multilayer substrate 100 changes between the state in which the electronic device 700 is unfolded (see Figure 6) and the state in which the electronic device 700 is folded (see Figure 7). The electronic device 700 is, for example, a foldable communication device. The communication device is, for example, a mobile phone (e.g., a smartphone), but is not limited to a mobile phone; it may also be, for example, a notebook personal computer, a wearable device (e.g., a smartwatch), etc.

[0041] The resin multilayer substrate 100 shown in Figures 6 and 7 is a resin multilayer substrate 100 according to Modification 2, and the portion that undergoes plastic deformation due to the movement of the hinge device 705 includes the second interface 312a. In the electronic device 700, the resin multilayer substrate 100 may be the resin multilayer substrate 100 according to Embodiment 1.

[0042] (4) The resin multilayer substrate 100 according to Embodiment 1 includes a laminated substrate 1 and a plurality of conductor layers 21 and 22. The laminated substrate 1 has a plurality of resin layers 11 and 12. In the laminated substrate 1, the plurality of resin layers 11 and 12 are laminated. The plurality of conductor layers 21 and 22 overlap the plurality of resin layers 11 and 12 in the lamination direction of the plurality of resin layers 11 and 12. The resin multilayer substrate 100 has an interface B1. The interface B1 includes an interface 31 between two adjacent resin layers 11 and 12 in the lamination direction among the plurality of resin layers 11 and 12. The interface 31 includes a first interface 311 and a second interface 312. The second interface 312 has a lower adhesion strength than the first interface 311 and a lower adhesion strength than the interface between the resin layer and the conductor layer that are in contact with each other among the plurality of resin layers 11 and 12 and the plurality of conductor layers 21 and 22.

[0043] According to the above configuration, when the resin multilayer substrate 100 is bent, breakage of the resin multilayer substrate 100 is unlikely to occur. More specifically, according to the above configuration, when the resin multilayer substrate 100 is bent at a portion including the second interface 312, the two resin layers 11 and 12 are likely to peel off at the second interface 312, so breakage of the resin multilayer substrate 100 is unlikely to occur. Further, according to the above configuration, it is possible to improve the bending resistance without reducing the number of layers of the plurality of resin layers 11 and 12 in the portion including the second interface 312. Further, according to the above configuration, since the first resin layer 11 and the second resin layer 12 are fixed at the second interface 312, it is possible to improve the reproducibility of the shape and characteristics of the resin multilayer substrate 100 during manufacturing.

[0044] Further, in the resin multilayer substrate 100 according to Embodiment 1, the two resin layers 11 and 12 include a first resin layer 11 and a second resin layer 12. The first resin layer 11 has a first main surface 111 and a second main surface 112. The second resin layer 12 has a third main surface 121 and a fourth main surface 122. The plurality of conductor layers 21 and 22 include a first conductor layer 21 laminated on the first main surface 111 of the first resin layer 11 and a second conductor layer 22 laminated on the third main surface 121 of the second resin layer 12. In the laminated substrate 1, the material of the first resin layer 11 and the material of the second resin layer 12 are the same. In the laminated substrate 1, the first resin layer 11 and the second resin layer 12 are directly joined.

[0045] According to the above configuration, an adhesive need not be interposed between the first resin layer 11 and the second resin layer 12.

[0046] In addition, in the resin multilayer substrate 100 according to the first modification examples 1 and 2 of the first embodiment, the two resin layers 11 and 12 are peeled off at the second interface 312a.

[0047] According to the above configuration, the resin multilayer substrate 100 according to the first modification examples 1 and 2 is difficult to break.

[0048] In addition, in the resin multilayer substrate 100 according to the first embodiment, the plurality of conductor layers 21 and 22 include the signal line 22.

[0049] According to the above configuration, the loss of the signal line 22 can be reduced, and it is not necessary to change the shape and arrangement of the signal line 22, and it is possible to suppress the deterioration of characteristics without widening the width of the bent portion in the resin multilayer substrate 100.

[0050] In addition, in the resin multilayer substrate 100 according to the first embodiment, the plurality of conductor layers 21 and 22 further include a ground electrode 21 that overlaps the signal line 22 in the stacking direction of the plurality of resin layers 11 and 12.

[0051] According to the above configuration, a microstrip line can be formed by the multilayer substrate 1, the signal line 22, and the ground electrode 21.

[0052] In addition, in the resin multilayer substrate 100 according to the first embodiment, the multilayer substrate 1 is long. The second interface 312 is formed over the entire length in the width direction of the multilayer substrate 1.

[0053] According to the above configuration, the resin multilayer substrate 100 is difficult to break.

[0054] In addition, in the resin multilayer substrate 100 according to the first modification example 1 of the first embodiment, the multilayer substrate 1 is bent, and the bent portion includes the second interface 312a.

[0055] According to the above configuration, the resin multilayer substrate 100 is difficult to break.

[0056] Furthermore, the resin multilayer substrate 100 according to the modified example 1 of Embodiment 1 comprises a laminated substrate 1 and a plurality of conductive layers 21, 22. The laminated substrate 1 has a plurality of resin layers 11, 12. In the laminated substrate 1, a plurality of resin layers 11, 12 are laminated. The plurality of conductive layers 21, 22 overlap the plurality of resin layers 11, 12 in the lamination direction of the plurality of resin layers 11, 12. The resin multilayer substrate 100 has an interface B1. The interface B1 includes the interface 31 of two adjacent resin layers 11, 12 in the lamination direction of the plurality of resin layers 11, 12. The interface 31 includes a first interface 311 to which the two resin layers 11, 12 are fixed, and a second interface 312a to which the two resin layers 11, 12 are in contact and not fixed. In one of the two resin layers 11 and 12, the surface roughness of the surface 112a corresponding to the second interface 312a in one resin layer 11 is smaller than the surface roughness of the surface corresponding to the first interface 311 in one resin layer 11 when the two resin layers 11 and 12 are peeled off at the first interface 311.

[0057] With the above configuration, the resin multilayer substrate 100 is less likely to break when bent. More specifically, with the above configuration, the two resin layers 11 and 12 are not fixed to each other at the second interface 312a, so the resin multilayer substrate 100 is less likely to break. Furthermore, with the above configuration, it is possible to improve bending resistance in the portion including the second interface 312a without reducing the number of resin layers 11 and 12.

[0058] Furthermore, the electronic device 700 according to Embodiment 1 includes a resin multilayer substrate 100 and a hinge device 705. The resin multilayer substrate 100 includes a second interface 312a of the resin multilayer substrate 100 in a portion that undergoes plastic deformation due to the movement of the hinge device 705.

[0059] According to the above configuration, when the resin multilayer substrate 100 is bent in the electronic device 700, the resin multilayer substrate 100 is less likely to break.

[0060] (Embodiment 2) The resin multilayer substrate 100A according to Embodiment 2 will be described with reference to Figure 8. With respect to the resin multilayer substrate 100A according to Embodiment 2, components that are the same as those in the resin multilayer substrate 100 according to Embodiment 1 (see Figures 1 to 3) are denoted by the same reference numerals and their description is omitted.

[0061] (1) Resin multilayer substrate Embodiment 2 The resin multilayer substrate 100A according to Embodiment 1 includes a laminated substrate 1A instead of the laminated substrate 1 of the resin multilayer substrate 100 according to Embodiment 1. The laminated substrate 1A has a plurality of (four in the example of Figure 8) resin layers 11 to 14. In the laminated substrate 1A, the plurality of resin layers 11 to 14 are laminated. The resin multilayer substrate 100A according to Embodiment 2 includes the laminated substrate 1A and a plurality of (five in the example of Figure 8) conductive layers 21A to 25A.

[0062] (1.1) Laminated Substrate The thickness direction of the laminated substrate 1A is the stacking direction of the multiple resin layers 11 to 14. Hereinafter, resin layers 11, 12, 13, and 14 may be referred to as the first resin layer 11, the second resin layer 12, the third resin layer 13, and the fourth resin layer 14, respectively. In the laminated substrate 1A, the multiple resin layers 11 to 14 are arranged in the order of the first resin layer 11, the second resin layer 12, the third resin layer 13, and the fourth resin layer 14. The first resin layer 11 has a first main surface 111 and a second main surface 112. The second resin layer 12 has a third main surface 121 and a fourth main surface 122. The third resin layer 13 has a fifth main surface 131 and a sixth main surface 132. The fourth resin layer 14 has a seventh main surface 141 and an eighth main surface 142.

[0063] Each of the multiple resin layers 11 to 14 contains, for example, a thermoplastic resin. The thermoplastic resin is, for example, a liquid crystal polymer. The thermoplastic resin is not limited to a liquid crystal polymer, but may also be, for example, PTFE (polytetrafluoroethylene). In this embodiment, the first resin layer 11 and the second resin layer 12 are self-adhered, and no adhesive layer is interposed between the first resin layer 11 and the second resin layer 12. In this embodiment, the second main surface 112 of the first resin layer 11 and the fourth main surface 122 of the second resin layer 12 are self-adhered. In the laminated substrate 1A, the material of the first resin layer 11 and the material of the second resin layer 12 are the same, and the first resin layer 11 and the second resin layer 12 are directly joined. Also in this embodiment, the second resin layer 12 and the third resin layer 13 are self-adhered, and no adhesive layer is interposed between the second resin layer 12 and the third resin layer 13. In this embodiment, the third main surface 121 of the second resin layer 12 and the sixth main surface 132 of the third resin layer 13 are self-adhered in a region that does not overlap with the conductor layer 23A. In the laminated substrate 1A, the material of the second resin layer 12 and the material of the third resin layer 13 are the same, and the second resin layer 12 and the third resin layer 13 are directly joined. Also in this embodiment, the third resin layer 13 and the fourth resin layer 14 are self-adhered, and there is no adhesive layer interposed between the third resin layer 13 and the fourth resin layer 14. In this embodiment, the fifth main surface 131 of the third resin layer 13 and the eighth main surface 142 of the fourth resin layer 14 are self-adhered. In the laminated substrate 1A, the material of the third resin layer 13 and the material of the fourth resin layer 14 are the same, and the third resin layer 13 and the fourth resin layer 14 are directly joined.

[0064] The thickness of each of the multiple resin layers 11 to 14 is, for example, 10 μm or more and 120 μm or less.

[0065] As shown in Figure 8, when the laminated substrate 1A is not bent, it has a long shape in which the width is in the direction along the Y-axis and the length in the direction along the X-axis is longer than the width. The laminated substrate 1A may have a shape other than a long shape.

[0066] (1.2) Multiple Conductive Layers Each of the multiple conductive layers 21A to 25A is electrically conductive. The material of each of the multiple conductive layers 21A to 25A includes, for example, copper. The multiple conductive layers 21A to 25A are formed on the laminated substrate 1A. The multiple conductive layers 21A to 25A include a first conductive layer 21A laminated on the first main surface 111 of the first resin layer 11, a second conductive layer 22A laminated on the second main surface 112 of the first resin layer 11, a third conductive layer 23A laminated on the third main surface 121 of the second resin layer 12, a fourth conductive layer 24A laminated on the fifth main surface 131 of the third resin layer 13, and a fifth conductive layer 25A laminated on the seventh main surface 141 of the fourth resin layer 14. In this embodiment, the first conductor layer 21A is a ground electrode (first ground electrode), and the fifth conductor layer 25A is a ground electrode different from the first ground electrode (second ground electrode). In this embodiment, the third conductor layer 23A includes a ground electrode 230A (third ground electrode 230A). The third conductor layer 23A further includes a signal line (not shown) that is separated from the ground electrode 230A in the Y-axis direction. The multiple conductor layers 21A to 25A overlap the multiple resin layers 11 to 14 in the stacking direction of the multiple resin layers 11 to 14. The multiple conductor layers 21A to 25A overlap the multiple resin layers 11 to 14 in a plan view from the stacking direction of the multiple resin layers 11 to 14.

[0067] Hereinafter, the first conductor layer 21A may be referred to as the first ground electrode 21A, the fifth conductor layer 25A as the second ground electrode 25A, the ground electrode 230A as the third ground electrode 230A, the second conductor layer 22A as the fourth ground electrode 22A, and the fourth conductor layer 24A as the fifth ground electrode 24A.

[0068] The above signal line is, for example, a high-frequency signal line through which a high-frequency signal is transmitted. The frequency of the high-frequency signal is, for example, 1 GHz or higher. The frequency of the high-frequency signal is not limited to 1 GHz or higher, but may be, for example, less than 1 GHz. The resin multilayer substrate 100A in this embodiment is designed so that the impedance of the above signal line is 50 Ω. In this embodiment, the multilayer substrate 1A, the first ground electrode 21A, the above signal line, and the second ground electrode 25A constitute a strip line.

[0069] The signal line and the third ground electrode 230A are each formed in a predetermined pattern. In this embodiment, the signal line is linear. The signal line and the third ground electrode 230A are formed, for example, by patterning a metal foil (for example, copper foil) attached to the third main surface 121 of the second resin layer 12.

[0070] The signal line has a line width in the Y-axis direction and a thickness in the stacking direction of the multiple resin layers 11 to 14. In this embodiment, the line width of the signal line is narrower than the width of the laminated substrate 1A in the Y-axis direction. The thickness of the signal line and the third ground electrode 230A is thinner than the thickness of each of the multiple resin layers 11 to 14. The thickness of the signal line and the third ground electrode 230A is, for example, 3 μm or more and 40 μm or less.

[0071] The first ground electrode 21A and the second ground electrode 25A overlap the signal line in the stacking direction of the multiple resin layers 11 to 14. The first ground electrode 21A and the second ground electrode 25A overlap the signal line in a plan view from the stacking direction of the multiple resin layers 11 to 14.

[0072] The first ground electrode 21A is formed on the first main surface 111 of the first resin layer 11. The first ground electrode 21A is formed in a predetermined pattern. In this embodiment, the first ground electrode 21A is elongated.

[0073] In this embodiment, the first ground electrode 21A is formed by patterning a metal foil (for example, copper foil) attached to the first main surface 111 of the first resin layer 11. In the width direction of the signal line, the width of the first ground electrode 21A is wider than the width of the signal line. The thickness of the first ground electrode 21A is, for example, 3 μm or more and 40 μm or less.

[0074] The second ground electrode 25A is formed on the seventh main surface 141 of the fourth resin layer 14. The second ground electrode 25A is formed in a predetermined pattern. In this embodiment, the second ground electrode 25A is elongated.

[0075] In this embodiment, the second ground electrode 25A is formed by patterning a metal foil (for example, copper foil) attached to the seventh main surface 141 of the fourth resin layer 14. In the width direction of the signal line, the width of the second ground electrode 25A is wider than the width of the signal line. The thickness of the second ground electrode 25A is, for example, 3 μm or more and 40 μm or less.

[0076] In this embodiment, the fourth ground electrode 22A is formed by patterning a metal foil (for example, copper foil) attached to the second main surface 112 of the first resin layer 11. The thickness of the fourth ground electrode 22A is, for example, 3 μm or more and 40 μm or less.

[0077] In this embodiment, the fifth ground electrode 24A is formed by patterning a metal foil (for example, copper foil) attached to the fifth main surface 131 of the third resin layer 13. The thickness of the fifth ground electrode 24A is, for example, 3 μm or more and 40 μm or less.

[0078] The resin multilayer substrate 100A has multiple (three in Figure 8) interface surfaces B1, B2, and B3 that are spaced apart in the stacking direction of the multiple resin layers 11 to 14. The outer edges of each of the three interface surfaces B1, B2, and B3 are the same as the outer edge of the multilayer substrate 1A. The three interface surfaces B1, B2, and B3 are arranged in the order of interface surface B1, interface surface B2, and interface surface B3 from the first resin layer 11 side in the stacking direction of the multiple resin layers 11 to 14. Interface surface B1 includes the interface 31 of two adjacent resin layers 11 and 12 in the stacking direction of the multiple resin layers 11 to 14. Interface surface B2 includes the interface 32 of two adjacent resin layers 12 and 13 in the stacking direction of the multiple resin layers 11 to 14. Interface surface B3 includes the interface 33 of two adjacent resin layers 13 and 14 in the stacking direction of the multiple resin layers 11 to 14.

[0079] The interface 31 included in the interface B1 includes a first interface 311 and a second interface 312. The adhesion strength between the first resin layer 11 and the second resin layer 12 at the second interface 312 is lower than the adhesion strength between the first resin layer 11 and the second resin layer 12 at the first interface 311. Furthermore, the adhesion strength of the second interface 312 is lower than that of the interfaces between the resin layers and conductor layers that are in contact with each other among the plurality of resin layers 11 to 14 and the plurality of conductor layers 21A to 25A.

[0080] The interface B1 further includes a third interface 313 between the first resin layer 11 and the second conductor layer 22A. The adhesion strength between the first resin layer 11 and the second resin layer 12 at the second interface 312 of interface 31 is lower than the adhesion strength between the first resin layer 11 and the second conductor layer 22A. The adhesion strength between the first resin layer 11 and the second resin layer 12 at the second interface 312 is lower than the adhesion strength between the first resin layer 11 and the second conductor layer 22A at the third interface 313. The adhesion strength between the first resin layer 11 and the second resin layer 12 at the second interface 312 is lower than the adhesion strength between the second resin layer 12 and the third conductor layer 23A. Furthermore, the adhesion strength between the first resin layer 11 and the second resin layer 12 at the second interface 312 is lower than the adhesion strength between the third resin layer 13 and the third conductor layer 23A. Furthermore, the adhesion strength between the first resin layer 11 and the second resin layer 12 at the second interface 312 is lower than the adhesion strength between the fourth resin layer 14 and the fourth conductor layer 24A. Also, the adhesion strength between the first resin layer 11 and the second resin layer 12 at the second interface 312 is lower than the adhesion strength between the fourth resin layer 14 and the fifth conductor layer 25A. The adhesion strength is evaluated by a peel test. When a peel test is performed on the resin multilayer substrate 100A, delamination occurs between the first resin layer 11 and the second resin layer 12 at the second interface 312, followed by cohesive failure near the first interface 311. The peel test is, for example, a 90-degree peel strength test (IPC-TM-650 2.4.9). "Cohesive failure" means that the failure occurs within two adjacent resin layers, rather than at the interface between two adjacent resin layers among the multiple resin layers 11 to 14. In Figure 8, the first interface 311 and the third interface 313, which have relatively high adhesion strength at interface B1, are shown with thick lines, while the second interface 312, which has relatively low adhesion strength at interface B1, is shown with a thin line.

[0081] The interface 33 included in the interface B3 includes a first interface 331 and a second interface 332. The second interface 332 has lower adhesion strength than the first interface 331. Furthermore, the second interface 332 has lower adhesion strength than the interfaces between the resin layers 11-14 and the conductor layers 21A-25A that are in contact with each other.

[0082] The interface B3 further includes a third interface 333 between the third resin layer 13 and the fourth conductor layer 24A. The adhesion strength between the third resin layer 13 and the fourth resin layer 14 at the second interface 332 of interface 33 is lower than the adhesion strength between the third resin layer 13 and the fourth conductor layer 24A at the third interface 333 between the third resin layer 13 and the fourth conductor layer 24A. Also, the adhesion strength between the third resin layer 13 and the fourth resin layer 14 at the second interface 332 is lower than the adhesion strength between the third resin layer 13 and the third conductor layer 23A. The adhesion strength between the third resin layer 13 and the fourth resin layer 14 at the second interface 332 is lower than the adhesion strength between the fourth resin layer 14 and the fifth conductor layer 25A. Also, the adhesion strength between the third resin layer 13 and the fourth resin layer 14 at the second interface 332 is lower than the adhesion strength between the second resin layer 12 and the third conductor layer 23A. Furthermore, the adhesion strength between the third resin layer 13 and the fourth resin layer 14 at the second interface 332 is lower than the adhesion strength between the second resin layer 12 and the second conductor layer 22A. Also, the adhesion strength between the third resin layer 13 and the fourth resin layer 14 at the second interface 332 is lower than the adhesion strength between the first resin layer 11 and the second conductor layer 22A, and lower than the adhesion strength between the first resin layer 11 and the first conductor layer 21A. The adhesion strength is evaluated by a peel test. When a peel test is performed on the resin multilayer substrate 100A, delamination occurs between the third resin layer 13 and the fourth resin layer 14 at the second interface 332, and then cohesive failure occurs near the first interface 321. The peel test is, for example, a 90-degree peel strength test (IPC-TM-650 2.4.9). "Cohesive failure" means that the failure occurs within two adjacent resin layers, rather than at the interface between two adjacent resin layers among the multiple resin layers 11 to 14. In Figure 8, the first interface 331 and the third interface 333, which have relatively high adhesion strength at interface B3, are shown with thick lines, while the second interface 332, which has relatively low adhesion strength at interface B3, is shown with a thin line.

[0083] The resin multilayer substrate 100A can be bent, for example, as shown in Figure 9. Figure 9 is a cross-sectional view of the resin multilayer substrate 100A according to Modification 1 of Embodiment 2. With respect to the resin multilayer substrate 100A according to Modification 1 of Embodiment 2, components that are the same as those in the resin multilayer substrate 100A according to Embodiment 2 (see Figure 8) are denoted by the same reference numerals and their description is omitted. In the resin multilayer substrate 100A according to Modification 1, the first resin layer 11 and the second resin layer 12 are fixed at the first interface 311, and the first resin layer 11 and the second resin layer 12 are separated at the second interface 312a. In the resin multilayer substrate 100 according to Modification 1, the interface 31 includes the first interface 311 and the second interface 312a formed by the separation of the first resin layer 11 and the second resin layer 12 at the second interface 312. At the second interface 312a, the surface 112a in the first resin layer 11 corresponding to the second interface 312a and the surface 122a in the second resin layer 12 corresponding to the second interface 312a are in contact but not fixed. Furthermore, the resin multilayer substrate 100A shown in Figure 9 has a second interface 332a formed by the delamination of the third resin layer 13 and the fourth resin layer 14 at the second interface 332 (see Figure 8). At the second interface 332a, the surface 131a in the third resin layer 13 corresponding to the second interface 332a and the surface 142a in the fourth resin layer 14 corresponding to the second interface 332a are in contact but not fixed. Note that the resin multilayer substrate 100A according to Modification 1 may have a void between a part of the surface 112a of the first resin layer 11 and a part of the surface 122a of the second resin layer 12. Furthermore, the resin multilayer substrate 100A according to Modification 1 may have a void between a part of the surface 132a of the third resin layer 13 and a part of the surface 142a of the fourth resin layer 14.

[0084] Figure 10 is a cross-sectional view of a resin multilayer substrate 100A according to Modification 2 of Embodiment 2. The resin multilayer substrate 100A according to Modification 2 is substantially the same as the resin multilayer substrate 100A according to Modification 1, and differs from the resin multilayer substrate 100A according to Modification 1 in that it is not bent, although it may be formed by bending the resin multilayer substrate 100A according to Modification 1. With respect to the resin multilayer substrate 100A according to Modification 2 of Embodiment 2, components that are the same as those in the resin multilayer substrate 100A according to Modification 1 of Embodiment 2 (see Figure 9) are denoted by the same reference numerals and their description is omitted. In the resin multilayer substrate 100A according to Modification 2, the surface roughness of the surface 112a corresponding to the second interface 312a in the first resin layer 11 is smaller than the surface roughness of the surface corresponding to the first interface 311 in the second main surface 112 of the first resin layer 11 when the laminated substrate 1A is peeled off at the first interface 311. The surface roughness is the arithmetic mean roughness Ra. The arithmetic mean roughness Ra is defined in ISO 4287-1997. The arithmetic mean roughness Ra can be measured, for example, with a microscope or a laser displacement meter.

[0085] In the modified example 2, the resin multilayer substrate 100A undergoes cohesive failure near the first interface 311 during a peel test. The peel test is, for example, a 90-degree peel strength test (IPC-TM-650 2.4.9).

[0086] The resin multilayer substrate 100A according to Embodiment 2 may further include at least one of a first resist layer (not shown) disposed on the first main surface 101 of the laminated substrate 1A and a second resist layer (not shown) disposed on the second main surface 102 of the laminated substrate 1A. The first main surface 101 of the laminated substrate 1A includes the first main surface 111 of the first resin layer 11. The second main surface 102 of the laminated substrate 1A includes the seventh main surface 141 of the fourth resin layer 14. The first and second ends of the signal line are each led out to the first main surface 101 or the second main surface 102 of the laminated substrate 1A by an interlayer connecting conductor.

[0087] (2) Method for manufacturing a resin multilayer substrate In the method for manufacturing the resin multilayer substrate 100A of this embodiment, for example, the first step, the second step, and the third step are performed in the order of the first step, the second step, and the third step.

[0088] In the first step, a double-sided copper-clad film, a first single-sided copper-clad film, a second single-sided copper-clad film, and a third single-sided copper-clad film are prepared. The double-sided copper-clad film is a copper-clad film in which a first conductor layer 21A is formed on the first main surface 111 of the first resin layer 11 and a second conductor layer 22A is formed on the second main surface 112. The first single-sided copper-clad film is a single-sided copper-clad film in which a third conductor layer 23A is formed on the third main surface 121 of the second resin layer 12. The second single-sided copper-clad film is a single-sided copper-clad film in which a fourth conductor layer 24A is formed on the fifth main surface 131 of the third resin layer 13. The third single-sided copper-clad film is a single-sided copper-clad film in which a fifth conductor layer 25A is formed on the seventh main surface 141 of the fourth resin layer 14.

[0089] In the second step, the region corresponding to the first interface 311 on the second main surface 112 of the first resin layer 11 of the double-sided copper-clad film and the fourth main surface 122 of the second resin layer 12 of the first single-sided copper-clad film is roughened or altered by surface treatment. In the surface treatment, for example, plasma discharge treatment is performed on the region corresponding to the first interface 311 on the second main surface 112 of the first resin layer 11 and the fourth main surface 122 of the second resin layer 12. In the second step, the region corresponding to the second interface 312 is covered with a mask and surface treatment is performed so that surface treatment is not performed on the region corresponding to the second interface 312 on the second main surface 112 of the first resin layer 11 and the fourth main surface 122 of the second resin layer 12. Also in the second step, the region corresponding to the first interface 331 on the fifth main surface 131 of the third resin layer 13 of the second single-sided copper-clad film and the eighth main surface 142 of the fourth resin layer 14 of the third single-sided copper-clad film is roughened or altered by surface treatment. In the surface treatment, plasma discharge treatment is performed on the region corresponding to the first interface 331 on the fifth main surface 131 of the third resin layer 13 and the eighth main surface 142 of the fourth resin layer 14. In the second step, the region corresponding to the second interface 332 is covered with a mask and surface treatment is performed on the region corresponding to the second interface 332 on the fifth main surface 131 of the third resin layer 13 and the eighth main surface 142 of the fourth resin layer 14, so that surface treatment is not performed on that region.

[0090] In the third step, a resin multilayer substrate 100A is formed by stacking a double-sided copper-clad film, a first single-sided copper-clad film, a second single-sided copper-clad film, and a third single-sided copper-clad film, and pressing them while heating. The adhesion strength between the first resin layer 11 and the second resin layer 12 is higher at the first interface 311 corresponding to the area where surface treatment was performed in the second step, and lower at the second interface 312 corresponding to the area where surface treatment was not performed. Similarly, the adhesion strength between the third resin layer 13 and the fourth resin layer 14 is higher at the first interface 331 corresponding to the area where surface treatment was performed in the second step, and lower at the second interface 332 corresponding to the area where surface treatment was not performed. In the manufacturing method of the resin multilayer substrate 100A, the double-sided copper-clad film, the first single-sided copper-clad film, the second single-sided copper-clad film, and the third single-sided copper-clad film prepared in the first step are sheets of a size that allows for the formation of a large number of resin multilayer substrates 100A.

[0091] (3) Electronic device having a resin multilayer substrate The resin multilayer substrate 100A may be used, for example, in place of the resin multilayer substrate 100 in the electronic device 700 (see Figures 6 and 7) described in Embodiment 1. The resin multilayer substrate 100A may be housed in the casing of an electronic device different from the electronic device 700.

[0092] (4) The resin multilayer substrate 100A according to the second embodiment comprises a laminated substrate 1A and a plurality of conductive layers 21A to 25A. The laminated substrate 1A has a plurality of resin layers 11 to 14. The plurality of resin layers 11 to 14 are laminated in the laminated substrate 1A. The plurality of conductive layers 21A to 25A overlap the plurality of resin layers 11 to 14 in the lamination direction of the plurality of resin layers 11 to 14. The resin multilayer substrate 100A has an interface surface B1 that includes the interface 31 of two adjacent resin layers 11 and 12 among the plurality of resin layers 11 to 14 in the lamination direction. The interface 31 includes a first interface 311 and a second interface 312. The second interface 312 has lower adhesion strength than the first interface 311 and lower adhesion strength than the interface between the resin layers and conductive layers that are in contact with each other among the plurality of resin layers 11 to 14 and the plurality of conductive layers 21A to 25A.

[0093] According to the above configuration, when the resin multilayer substrate 100A is bent, fracture of the resin multilayer substrate 100A is less likely to occur. More specifically, according to the above configuration, when the resin multilayer substrate 100A is bent in the portion including the second interface 312, the two resin layers 11 and 12 are more likely to separate at the second interface 312, so fracture of the resin multilayer substrate 100A is less likely to occur. Furthermore, according to the above configuration, it is possible to improve bending resistance without reducing the number of resin layers 11 to 14 in the portion including the second interface 312. In addition, according to the above configuration, since the resin layer 11 and the resin layer 12 are fixed at the second interface 312, it is possible to improve the reproducibility of the shape and characteristics of the resin multilayer substrate 100A during manufacturing.

[0094] Furthermore, in the resin multilayer substrate 100A according to Embodiment 2, the interface B1 further includes a third interface 313 between a smaller conductor layer 22A interposed between two resin layers 11 and 12 from among the plurality of conductor layers 21A to 25A and one of the resin layers 11 and 12. The adhesion strength of the third interface 313 is greater than the adhesion strength of the second interface 312.

[0095] According to the above configuration, when the resin multilayer substrate 100A is bent, fracture of the resin multilayer substrate 100A is less likely to occur, and delamination at the third interface 313 between the conductive layer 22A and the resin layer 11 is less likely to occur.

[0096] Furthermore, the resin multilayer substrate 100A according to Embodiment 2 has a plurality of interface surfaces B1, B2, and B3, including interface surface B1. The plurality of interface surfaces B1, B2, and B3 are separated in the stacking direction of the plurality of resin layers 11 to 14. Interface surface B3 includes the interface 33 of two adjacent resin layers 13 and 14 in the stacking direction among the plurality of resin layers 11 to 14. Interface 33 includes a first interface 331 and a second interface 332. The second interface 332 has lower adhesion strength than the first interface 331 and also lower adhesion strength than the interface between the resin layers and conductor layers that are in contact with each other among the plurality of resin layers 11 to 14 and the plurality of conductor layers 21A to 25A.

[0097] According to the above configuration, when the resin multilayer substrate 100A is bent, fracture of the resin multilayer substrate 100A is less likely to occur.

[0098] Furthermore, in the resin multilayer substrate 100A according to modified examples 1 and 2 of Embodiment 2, the two resin layers 11 and 12 are delaminated at the second interface 312a.

[0099] According to the above configuration, the resin multilayer substrate 100A is less likely to break.

[0100] Furthermore, in the resin multilayer substrate 100A according to modified examples 1 and 2 of Embodiment 2, the two resin layers 13 and 14 are delaminated at the second interface 332a.

[0101] According to the above configuration, the resin multilayer substrate 100A is less likely to break.

[0102] Furthermore, in the resin multilayer substrate 100A according to Embodiment 2, the plurality of conductor layers 21A to 25A include signal lines.

[0103] According to the above configuration, signal line loss can be reduced, and there is no need to change the shape and arrangement of the signal lines. Furthermore, it is possible to suppress a decrease in performance without widening the width of the bendable portion in the resin multilayer substrate 100A.

[0104] Furthermore, in the resin multilayer substrate 100A according to Embodiment 2, the plurality of conductor layers 21A to 25A further include ground electrodes 21A and 25A that overlap with signal lines in the stacking direction of the plurality of resin layers 11 to 14.

[0105] According to the above configuration, a strip line can be formed using a laminated substrate 1A, a signal line, and two ground electrodes 21A and 25A.

[0106] Furthermore, in the resin multilayer substrate 100A according to Embodiment 2, the laminated substrate 1A is elongated. The second interface 312 is formed along the entire length in the width direction of the laminated substrate 1A.

[0107] According to the above configuration, the resin multilayer substrate 100A is less likely to break.

[0108] Furthermore, in the resin multilayer substrate 100A according to Embodiment 2, the second interface 312 is formed along the entire length in the width direction of the laminated substrate 1A.

[0109] According to the above configuration, the resin multilayer substrate 100A is less likely to break.

[0110] Furthermore, the resin multilayer substrate 100A according to the modified example 1 of Embodiment 2 includes a second interface 312a in the curved portion.

[0111] According to the above configuration, the resin multilayer substrate 100A is less likely to break in the bent portion.

[0112] Furthermore, the resin multilayer substrate 100A according to the modified example 2 of Embodiment 2 comprises a laminated substrate 1A and a plurality of conductive layers 21A to 25A, as shown in Figure 10. The laminated substrate 1A has a plurality of resin layers 11 to 14. The plurality of resin layers 11 to 14 are laminated in the laminated substrate 1A. The plurality of conductive layers 21A to 25A overlap the plurality of resin layers 11 to 14 in the lamination direction of the plurality of resin layers 11 to 14. The resin multilayer substrate 100A has an interface surface B1 that includes the interface 31 of two adjacent resin layers 11 and 12 in the lamination direction of the plurality of resin layers 11 to 14. The interface 31 includes a first interface 311 to which the two resin layers 11 and 12 are fixed, and a second interface 312a to which the two resin layers 11 and 12 are in contact and not fixed. In one of the two resin layers 11 and 12, the surface roughness of the surface 112a corresponding to the second interface 312a in one resin layer 11 is smaller than the surface roughness of the surface corresponding to the first interface 311 in one resin layer 11 when the two resin layers 11 and 12 are peeled off at the first interface 311.

[0113] According to the above configuration, when the resin multilayer substrate 100A according to the modified example 2 is bent, the resin multilayer substrate 100A is less likely to break. More specifically, according to the above configuration, when the resin multilayer substrate 100A is bent in the portion including the second interface 312a, the two resin layers 11 and 12 are not fixed to each other at the second interface 312a, so the resin multilayer substrate 100A is less likely to break. Furthermore, according to the above configuration, it is possible to improve bending resistance in the portion including the second interface 312a without reducing the number of resin layers 11 and 12.

[0114] Furthermore, the electronic device according to Embodiment 2 includes a resin multilayer substrate 100A instead of the resin multilayer substrate 100 in the electronic device 700 according to Embodiment 1 (see Figures 6 and 7). The resin multilayer substrate 100A includes a second interface 312a of the resin multilayer substrate 100A in which it undergoes plastic deformation due to the movement of the hinge device 705 (see Figures 6 and 7).

[0115] According to the above configuration, when the resin multilayer substrate 100A is bent in the electronic device according to Embodiment 2, the resin multilayer substrate 100A is less likely to break.

[0116] (Embodiment 3) The resin multilayer substrate 100B according to Embodiment 3 will be described with reference to Figures 11 to 15. With respect to the resin multilayer substrate 100B according to Embodiment 3, components that are the same as those in the resin multilayer substrate 100A according to Embodiment 2 (see Figure 8) are denoted by the same reference numerals and their description is omitted.

[0117] (1) Resin multilayer substrate Embodiment 3 The resin multilayer substrate 100B according to Embodiment 2 includes a laminated substrate 1B instead of the laminated substrate 1A of the resin multilayer substrate 100A according to Embodiment 2. The laminated substrate 1B has a plurality of resin layers 11 to 15 (five in the example of Figure 12), as shown in Figures 12 to 15. The plurality of resin layers 11 to 15 are laminated in the laminated substrate 1B. The resin multilayer substrate 100B according to Embodiment 3 includes a laminated substrate 1B and a plurality of conductive layers 21B to 25B (five in the example of Figure 12), as shown in Figure 12. The resin multilayer substrate 100B also includes a plurality of first connecting conductors 41 (for example, eight), a plurality of second connecting conductors 42 (for example, eight), a plurality of third connecting conductors 43 (for example, eight), a plurality of fourth connecting conductors 44 (for example, eight), and a plurality of fifth connecting conductors 45 (eight in the example of Figure 11). Furthermore, as shown in Figure 14, the resin multilayer substrate 100B includes a plurality (for example, eight) sixth connecting conductors 51, a plurality (for example, eight) seventh connecting conductors 52, a plurality (for example, eight) eighth connecting conductors 53, a plurality (for example, eight) ninth connecting conductors 54, and a plurality (eight in the example of Figure 11) tenth connecting conductors 55.

[0118] (1.1) Laminated Substrate As shown in Figures 12 to 15, the thickness direction of the laminated substrate 1B is the stacking direction of the multiple resin layers 11 to 15. Hereinafter, resin layers 11, 12, 13, 14, and 15 may be referred to as the first resin layer 11, the second resin layer 12, the third resin layer 13, the fourth resin layer 14, and the fifth resin layer 15, respectively. In the laminated substrate 1B, the multiple resin layers 11 to 15 are arranged in the order of the first resin layer 11, the second resin layer 12, the third resin layer 13, the fourth resin layer 14, and the fifth resin layer 15. The first resin layer 11 has a first main surface 111 and a second main surface 112. The second resin layer 12 has a third main surface 121 and a fourth main surface 122. The third resin layer 13 has a fifth main surface 131 and a sixth main surface 132. The fourth resin layer 14 has a seventh main surface 141 and an eighth main surface 142. The fifth resin layer 15 has a ninth main surface 151 and a tenth main surface 152.

[0119] Each of the multiple resin layers 11 to 15 contains, for example, a thermoplastic resin. The thermoplastic resin is, for example, a liquid crystal polymer. The thermoplastic resin is not limited to a liquid crystal polymer, but may also be, for example, PTFE (polytetrafluoroethylene). In this embodiment, the first resin layer 11 and the second resin layer 12 are self-adhered, and no adhesive layer is interposed between the first resin layer 11 and the second resin layer 12. In this embodiment, the second main surface 112 of the first resin layer 11 and the fourth main surface 122 of the second resin layer 12 are self-adhered. In the laminated substrate 1B, the material of the first resin layer 11 and the material of the second resin layer 12 are the same, and the first resin layer 11 and the second resin layer 12 are directly joined. Also in this embodiment, the second resin layer 12 and the third resin layer 13 are self-adhered, and no adhesive layer is interposed between the second resin layer 12 and the third resin layer 13. In this embodiment, the third main surface 121 of the second resin layer 12 and the sixth main surface 132 of the third resin layer 13 are self-adhered. In the laminated substrate 1B, the material of the second resin layer 12 and the material of the third resin layer 13 are the same, and the second resin layer 12 and the third resin layer 13 are directly joined. Also in this embodiment, the third resin layer 13 and the fourth resin layer 14 are self-adhered, and there is no adhesive layer interposed between the third resin layer 13 and the fourth resin layer 14. In this embodiment, the fifth main surface 131 of the third resin layer 13 and the eighth main surface 142 of the fourth resin layer 14 are self-adhered. In the laminated substrate 1B, the material of the third resin layer 13 and the material of the fourth resin layer 14 are the same, and the third resin layer 13 and the fourth resin layer 14 are directly joined. Furthermore, in this embodiment, the fourth resin layer 14 and the fifth resin layer 15 are self-adhered, and no adhesive layer is interposed between the fourth resin layer 14 and the fifth resin layer 15. In this embodiment, the seventh main surface 141 of the fourth resin layer 14 and the tenth main surface 152 of the fifth resin layer 15 are self-adhered. In the laminated substrate 1B, the material of the fourth resin layer 14 and the material of the fifth resin layer 15 are the same, and the fourth resin layer 14 and the fifth resin layer 15 are directly joined together.

[0120] The thickness of each of the multiple resin layers 11 to 15 is, for example, 10 μm or more and 120 μm or less.

[0121] As shown in Figures 11 to 13, when the laminated substrate 1B is not bent, it has a long shape in which the width is in the direction along the Y-axis and the length in the direction along the X-axis is longer than the width. The laminated substrate 1B may have a shape other than long.

[0122] (1.2) Multiple Conductor Layers As shown in Figure 12, multiple (five in the example of Figure 12) conductor layers 21B to 25B are formed on the laminated substrate 1B. Each of the multiple conductor layers 21B to 25B is conductive. The material of each of the multiple conductor layers 21B to 25B includes, for example, copper. The multiple conductor layers 21B to 25B include a first conductor layer 21B laminated on the first main surface 111 of the first resin layer 11, a second conductor layer 22B laminated on the third main surface 121 of the second resin layer 12, a third conductor layer 23B laminated on the fifth main surface 131 of the third resin layer 13, a fourth conductor layer 24B laminated on the seventh main surface 141 of the fourth resin layer 14, and a fifth conductor layer 25B laminated on the ninth main surface 151 of the fifth resin layer 15. In this embodiment, the first conductor layer 21B is the ground electrode (first ground electrode). Furthermore, in this embodiment, the fifth conductor layer 25B is a ground electrode (second ground electrode) different from the first ground electrode. Also, in this embodiment, as shown in Figures 11 to 14, the third conductor layer 23B includes a ground electrode 232B (third ground electrode 232B), a ground electrode 233B (fourth ground electrode 233B), and a signal line 231B. Also, in this embodiment, the second conductor layer 22B is a ground electrode (fifth ground electrode), and the fourth conductor layer 24B is a ground electrode (sixth ground electrode).

[0123] Hereinafter, the first conductor layer 21B may be referred to as the first ground electrode 21B, the fifth conductor layer 25B as the second ground electrode 25B, the ground electrode 232B as the third ground electrode 232B, and the ground electrode 233B as the fourth ground electrode 233B. Also, the second conductor layer 22B may be referred to as the fifth ground electrode 22B, and the fourth conductor layer 24B as the sixth ground electrode 24B. The signal line 231B is a high-frequency signal line through which a high-frequency signal is transmitted. The frequency of the high-frequency signal is, for example, 1 GHz or higher. The frequency of the high-frequency signal is not limited to 1 GHz or higher, but may be less than 1 GHz. The resin multilayer substrate 100B of this embodiment is designed so that the impedance of the signal line 231B is 50 Ω. In this embodiment, the multilayer substrate 1B, the first ground electrode 21B, the signal line 231B, and the second ground electrode 25B constitute a strip line.

[0124] The signal line 231B, the third ground electrode 232B, and the fourth ground electrode 233B are conductive. The material of the signal line 231B, the third ground electrode 232B, and the fourth ground electrode 233B includes, for example, copper. The signal line 231B, the third ground electrode 232B, and the fourth ground electrode 233B are each formed in a predetermined pattern. As shown in Figures 11 and 14, the third ground electrode 232B is adjacent to the signal line 231B in the width direction of the signal line 231B. "The third ground electrode 232B is adjacent to the signal line 231B in the width direction of the signal line 231B" means that the third ground electrode 232B and the signal line 231B are spaced apart without any other conductors being placed between them in the width direction of the signal line 231B. The fourth ground electrode 233B is adjacent to the signal line 231B in the width direction of the signal line 231B. "The fourth ground electrode 233B is adjacent to the signal line 231B in the width direction of the signal line 231B" means that the fourth ground electrode 233B and the signal line 231B are spaced apart without any other conductors being placed between them in the width direction of the signal line 231B. In this embodiment, the signal line 231B is linear. The signal line 231B, the third ground electrode 232B, and the fourth ground electrode 233B are formed, for example, by patterning a metal foil (e.g., copper foil) attached to the fifth main surface 131 of the third resin layer 13.

[0125] The signal line 231B has a line width in the Y-axis direction and a thickness in the stacking direction of the plurality of resin layers 11 to 15. In this embodiment, the line width of the signal line 231B is narrower than the width of the laminated substrate 1B in the Y-axis direction. The thickness of the signal line 231B, the third ground electrode 232B, and the fourth ground electrode 233B is thinner than the thickness of each of the plurality of resin layers 11 to 15. The thickness of the signal line 231B, the third ground electrode 232B, and the fourth ground electrode 233B is, for example, 3 μm or more and 40 μm or less.

[0126] The first ground electrode 21B and the second ground electrode 25B overlap the signal line 231B in the lamination direction of the multiple resin layers 11 to 15. The first ground electrode 21B and the second ground electrode 25B overlap the signal line 231B in a plan view from the lamination direction of the multiple resin layers 11 to 15.

[0127] Each of the first ground electrode 21B and the second ground electrode 25B is conductive. The material of each of the first ground electrode 21B and the second ground electrode 25B includes, for example, copper.

[0128] The first ground electrode 21B is formed on the first main surface 111 of the first resin layer 11. The first ground electrode 21B is formed in a predetermined pattern. In this embodiment, the first ground electrode 21B is elongated.

[0129] In this embodiment, the first ground electrode 21B is formed by patterning a metal foil (for example, copper foil) attached to the first main surface 111 of the first resin layer 11. In the width direction of the signal line 231B, the width of the first ground electrode 21B is wider than the width of the signal line 231B. The thickness of the first ground electrode 21B is, for example, 3 μm or more and 40 μm or less.

[0130] The second ground electrode 25B is formed on the ninth main surface 151 of the fifth resin layer 15. The second ground electrode 25B is formed in a predetermined pattern. In this embodiment, the second ground electrode 25B is elongated.

[0131] In this embodiment, the second ground electrode 25B is formed by patterning a metal foil (for example, copper foil) attached to the ninth main surface 151 of the fifth resin layer 15. In the width direction of the signal line 231B, the width of the second ground electrode 25B is wider than the width of the signal line 231B. The thickness of the second ground electrode 25B is, for example, 3 μm or more and 40 μm or less.

[0132] In this embodiment, the fifth ground electrode 22B is formed by patterning a metal foil (for example, copper foil) attached to the third main surface 121 of the second resin layer 12. The thickness of the fifth ground electrode 22B is, for example, 3 μm or more and 40 μm or less.

[0133] In this embodiment, the sixth ground electrode 24B is formed by patterning a metal foil (for example, copper foil) attached to the seventh main surface 141 of the fourth resin layer 14. The thickness of the sixth ground electrode 24B is, for example, 3 μm or more and 40 μm or less.

[0134] (1.3) Multiple Connecting Conductors As shown in Figures 12 and 14, the multiple first connecting conductors 41 penetrate the first resin layer 11 and are connected to the first ground electrode 21B. The multiple second connecting conductors 42 penetrate the second resin layer 12 and are connected to the fifth ground electrode 22B. The multiple third connecting conductors 43 penetrate the third resin layer 13 and are connected to the third ground electrode 232B. The multiple fourth connecting conductors 44 penetrate the fourth resin layer 14 and are connected to the sixth ground electrode 24B. The multiple fifth connecting conductors 45 penetrate the fifth resin layer 15 and are connected to the second ground electrode 25B. In this embodiment, the multiple first connecting conductors 41 and the multiple second connecting conductors 42 correspond one-to-one, and the corresponding first connecting conductors 41 and second connecting conductors 42 overlap and are connected to each other in the lamination direction of the multiple resin layers 11 to 15.

[0135] In this embodiment, a plurality of first connecting conductors 41 and a plurality of second connecting conductors 42 connect the first ground electrode 21B and the fifth ground electrode 22B. In this embodiment, a plurality of third connecting conductors 43 connect the fifth ground electrode 22B and the third ground electrode 232B. In this embodiment, a fourth connecting conductor 44 connects the third ground electrode 232B and the sixth ground electrode 24B. In this embodiment, a fifth connecting conductor 45 connects the sixth ground electrode 24B and the second ground electrode 25B. The plurality of first connecting conductors 41 are spaced apart in the direction along the length of the signal line 231B. The length of the signal line 231B is the direction along the signal line 231B, perpendicular to the width direction (line width direction) of the signal line 231B, and is the direction in which the signal is transmitted on the signal line 231B. The plurality of second connecting conductors 42 are spaced apart in the direction along the length of the signal line 231B. Furthermore, the multiple third connecting conductors 43 are arranged spaced apart in the direction along the length of the signal line 231B. Also, the multiple fourth connecting conductors 44 are arranged spaced apart in the direction along the length of the signal line 231B. Also, the multiple fifth connecting conductors 45 are arranged spaced apart in the direction along the length of the signal line 231B (see Figure 11). In this embodiment, the multiple second connecting conductors 42, the multiple third connecting conductors 43, the multiple fourth connecting conductors 44, and the multiple fifth connecting conductors 45 overlap in the lamination direction of the multiple resin layers 11 to 15, but they do not have to overlap in the lamination direction of the multiple resin layers 11 to 15. Also, the number of second connecting conductors 42, third connecting conductors 43, fourth connecting conductors 44, and fifth connecting conductors 45 may be the same or different.

[0136] As shown in Figure 14, the multiple sixth connecting conductors 51 penetrate the first resin layer 11 and are connected to the first ground electrode 21B. The multiple seventh connecting conductors 52 penetrate the second resin layer 12 and are connected to the fifth ground electrode 22B. The multiple eighth connecting conductors 53 penetrate the third resin layer 13 and are connected to the fourth ground electrode 233B. The multiple ninth connecting conductors 54 penetrate the fourth resin layer 14 and are connected to the sixth ground electrode 24B. The multiple tenth connecting conductors 55 penetrate the fifth resin layer 15 and are connected to the second ground electrode 25B. In this embodiment, the multiple sixth connecting conductors 51 and the multiple seventh connecting conductors 52 correspond one-to-one, and the corresponding sixth connecting conductors 51 and seventh connecting conductors 52 overlap and are connected to each other in the stacking direction of the multiple resin layers 11 to 15.

[0137] In this embodiment, multiple sixth connecting conductors 51 and multiple seventh connecting conductors 52 connect the first ground electrode 21B and the fifth ground electrode 22B. In this embodiment, multiple eighth connecting conductors 53 connect the fifth ground electrode 22B and the fourth ground electrode 233B. In this embodiment, the ninth connecting conductor 54 connects the fourth ground electrode 233B and the sixth ground electrode 24B. In this embodiment, the tenth connecting conductor 55 connects the sixth ground electrode 24B and the second ground electrode 25B. Multiple sixth connecting conductors 51 are spaced apart along the length of the signal line 231B. Multiple seventh connecting conductors 52 are spaced apart along the length of the signal line 231B. Multiple eighth connecting conductors 53 are spaced apart along the length of the signal line 231B. Multiple ninth connecting conductors 54 are spaced apart along the length of the signal line 231B. Furthermore, the multiple tenth connecting conductors 55 are spaced apart in the direction along the length of the signal line 231B (see Figure 11). In this embodiment, the multiple seventh connecting conductors 52, the multiple eighth connecting conductors 53, the multiple ninth connecting conductors 54, and the multiple tenth connecting conductors 55 overlap in the lamination direction of the multiple resin layers 11 to 15, but they do not have to overlap in the lamination direction of the multiple resin layers 11 to 15. Also, the number of seventh connecting conductors 52, eighth connecting conductors 53, ninth connecting conductors 54, and tenth connecting conductors 55 may be the same or different.

[0138] Each of the multiple first connecting conductors 41, multiple second connecting conductors 42, multiple third connecting conductors 43, multiple fourth connecting conductors 44, multiple fifth connecting conductors 45, multiple sixth connecting conductors 51, multiple seventh connecting conductors 52, multiple eighth connecting conductors 53, multiple ninth connecting conductors 54, and multiple tenth connecting conductors 55 is electrically conductive. Each of the multiple first connecting conductors 41, multiple second connecting conductors 42, multiple third connecting conductors 43, multiple fourth connecting conductors 44, multiple fifth connecting conductors 45, multiple sixth connecting conductors 51, multiple seventh connecting conductors 52, multiple eighth connecting conductors 53, multiple ninth connecting conductors 54, and multiple tenth connecting conductors 55 includes, for example, copper, copper-tin alloy, and resin.

[0139] The plurality of first connecting conductors 41 and the plurality of sixth connecting conductors 51 are formed, for example, by filling the plurality of first via holes and the plurality of sixth via holes formed in the first resin layer 11 with a conductive paste containing copper, a low melting point metal (e.g., tin), and resin, while each of the plurality of first via holes and the plurality of sixth via holes formed in the first resin layer 11 is blocked by a portion of the first conductor layer 21B made of a metal foil (copper foil) of a first predetermined pattern, and then heating the paste. The plurality of second connecting conductors 42 and the plurality of seventh connecting conductors 52 are formed, for example, by filling the plurality of second via holes and the plurality of seventh via holes formed in the second resin layer 12 with a conductive paste containing copper, a low melting point metal (e.g., tin), and resin, while each of the plurality of second via holes and the plurality of seventh via holes formed in the second resin layer 12 is blocked by a portion of the second conductor layer 22B made of a metal foil (copper foil) of a second predetermined pattern, and then heating the paste. The plurality of third connecting conductors 43 and the plurality of eighth connecting conductors 53 are formed, for example, by filling the plurality of third via holes and the plurality of eighth via holes formed in the third resin layer 13 with a conductive paste containing copper, a low melting point metal (e.g., tin), and resin, and heating it, while each of the plurality of third via holes and the plurality of eighth via holes formed in the third resin layer 13 is blocked by a portion of the third conductor layer 23B made of a third predetermined pattern of metal foil (copper foil). The plurality of fourth connecting conductors 44 and the plurality of ninth connecting conductors 54 are formed, for example, by filling the plurality of fourth via holes and the plurality of ninth via holes formed in the fourth resin layer 14 with a conductive paste containing copper, a low melting point metal (e.g., tin), and resin, and heating it, while each of the plurality of fourth via holes and the plurality of ninth via holes formed in the fourth resin layer 14 is blocked by a portion of the fourth conductor layer 24B made of a fourth predetermined pattern of metal foil (copper foil). The multiple fifth connecting conductors 45 and the multiple tenth connecting conductors 55 are formed, for example, by filling the multiple fifth via holes and the multiple tenth via holes formed in the fifth resin layer 15 with a conductive paste containing copper, a low melting point metal (e.g., tin), and resin, and heating it, with each of the multiple fifth via holes and the multiple tenth via holes formed in the fifth resin layer 15 being blocked by a portion of the fifth conductor layer 25B made of a fifth predetermined pattern of metal foil (copper foil).

[0140] The resin multilayer substrate 100B has multiple (four in Figures 12 to 14) interface surfaces B11, B12, B13, and B14 that are spaced apart in the stacking direction of the multiple resin layers 11 to 15. The outer edges of each of the four interface surfaces B11, B12, B13, and B14 are the same as the outer edge of the multilayer substrate 1B. In the stacking direction of the multiple resin layers 11 to 15, the four interface surfaces B11, B12, B13, and B14 are arranged in the order of interface surface B11, interface surface B12, interface surface B13, and interface surface B14 from the first resin layer 11 side. Interface surface B11 includes the interface 31 of two adjacent resin layers 11 and 12 in the stacking direction of the multiple resin layers 11 to 15. Interface surface B12 also includes the interface 32 of two adjacent resin layers 12 and 13 in the stacking direction of the multiple resin layers 11 to 15. Furthermore, the interface B13 includes the interface 33 (see Figures 14 and 15) of two adjacent resin layers 13 and 14 in the stacking direction among the multiple resin layers 11 to 15. Also, the interface B14 includes the interface 34 of two adjacent resin layers 14 and 15 in the stacking direction among the multiple resin layers 11 to 15.

[0141] The interface 32 included in the interface B12 includes a first interface 321 and a second interface 322. The adhesion strength between the second resin layer 12 and the third resin layer 13 at the second interface 322 is lower than the adhesion strength between the second resin layer 12 and the third resin layer 13 at the first interface 321. Furthermore, the adhesion strength of the second interface 322 is lower than that of the interfaces between the resin layers and conductor layers that are in contact with each other among the plurality of resin layers 11 to 15 and the plurality of conductor layers 21B to 25B.

[0142] The interface B12 further includes a third interface 323 between the second resin layer 12 and the second conductor layer 22B. The adhesion strength between the second resin layer 12 and the third resin layer 13 at the second interface 322 of interface 322 is lower than the adhesion strength between the first resin layer 11 and the first conductor layer 21B. The adhesion strength between the second resin layer 12 and the third resin layer 13 at the second interface 322 is lower than the adhesion strength between the second resin layer 12 and the second conductor layer 22B at the third interface 323. The adhesion strength between the second resin layer 12 and the third resin layer 13 at the second interface 322 is lower than the adhesion strength between the third resin layer 13 and the third conductor layer 23B. Furthermore, the adhesion strength between the second resin layer 12 and the third resin layer 13 at the second interface 322 is lower than the adhesion strength between the fourth resin layer 14 and the fourth conductor layer 24B. Furthermore, the adhesion strength between the second resin layer 12 and the third resin layer 13 at the second interface 322 is lower than the adhesion strength between the fifth resin layer 15 and the fifth conductor layer 25B.

[0143] Furthermore, the interface B12 further includes a fourth interface 324 between the connecting conductors (second connecting conductor 42, seventh connecting conductor 52) penetrating the second resin layer 12 and the second conductor layer 22B. The adhesion strength of the fourth interface 324 is greater than that of the second interface 322.

[0144] The interface 34 included in the interface B14 includes a first interface 341 and a second interface 342. The adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 is lower than the adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the first interface 341. Furthermore, the adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 is lower than the adhesion strength between the resin layers and conductor layers that are in contact with each other among the multiple resin layers 11 to 15 and the multiple conductor layers 21B to 25B.

[0145] The interface B14 further includes a third interface 343 between the fourth resin layer 14 and the fourth conductor layer 24B. The adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 of interface 34 is lower than the adhesion strength between the first resin layer 11 and the first conductor layer 21B. The adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 is lower than the adhesion strength between the second resin layer 12 and the second conductor layer 22B at the third interface 323 between the second resin layer 12 and the second conductor layer 22B. The adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 is lower than the adhesion strength between the third resin layer 13 and the third conductor layer 23B. Furthermore, the adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 is lower than the adhesion strength between the fourth resin layer 14 and the fourth conductor layer 24B. Furthermore, the adhesion strength between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 is lower than the adhesion strength between the fifth resin layer 15 and the fifth conductor layer 25B.

[0146] Furthermore, the interface B14 further includes a fourth interface 344 between the connecting conductors (fourth connecting conductor 44, ninth connecting conductor 54) penetrating the fourth resin layer 14 and the fourth conductor layer 24B. The adhesion strength of the fourth interface 344 is greater than that of the second interface 342.

[0147] Adhesion strength is evaluated by a peel test. When a peel test is performed on the resin multilayer substrate 100B, delamination occurs between the second resin layer 12 and the third resin layer 13 at the second interface 322 included in interface 32, and between the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 included in interface 34. Subsequently, cohesive failure occurs near the first interface 321 included in interface 32 or near the first interface 341 included in interface 34. The peel test is, for example, a 90-degree peel strength test (IPC-TM-650 2.4.9). "Cohesive failure" means that the failure occurs within two adjacent resin layers, rather than at the interface between two adjacent resin layers among the multiple resin layers 11 to 15. In Figures 12 to 15, among the first interface 321, second interface 322, third interface 323, and fourth interface 324 included in interface B12, the first interface 321, third interface 323, and fourth interface 324, which have relatively high adhesion strength, are shown with thick lines, while the second interface 322, which has relatively low adhesion strength, is shown with a thin line. Similarly, in Figures 12 to 15, among the first interface 341, second interface 342, third interface 343, and fourth interface 344 included in interface B14, the first interface 341, third interface 343, and fourth interface 344, which have relatively high adhesion strength, are shown with thick lines, while the second interface 342, which has relatively low adhesion strength, is shown with a thin line. Furthermore, since the adhesion strength of interface B11 is higher than that of the second interface 322, interface B11 is shown with a thick line in Figures 12 to 15. Furthermore, since the adhesion strength of interface B13 is higher than that of the second interface 322, interface B13 is shown with a thick line in Figures 14 and 15.

[0148] The resin multilayer substrate 100B can be bent, for example, as shown in Figure 16. Figure 16 is a cross-sectional view of the resin multilayer substrate 100B according to Modification 1 of Embodiment 3. With respect to the resin multilayer substrate 100B according to Modification 1 of Embodiment 3, components that are the same as those in the resin multilayer substrate 100B according to Embodiment 3 (see Figures 11 to 15) are denoted by the same reference numerals and their description is omitted. In the resin multilayer substrate 100B according to Modification 1, the second resin layer 12 and the third resin layer 13 are peeled off at the second interface 322 (see Figure 12) included in the interface 32 before the resin multilayer substrate 100B is bent, and the fourth resin layer 14 and the fifth resin layer 15 are peeled off at the second interface 342 (see Figure 12) included in the interface 34 before the resin multilayer substrate 100B is bent. In the resin multilayer substrate 100B according to Modification 1, the interface B12 has a second interface 322a formed by the delamination of the second resin layer 12 and the third resin layer 13 at the second interface 322 (see Figure 12). At the second interface 322a, the surface 121a in the second resin layer 12 corresponding to the second interface 322a and the surface 132a in the third resin layer 13 corresponding to the second interface 322a are in contact but are not fixed. Also, in the resin multilayer substrate 100B according to Modification 1, the interface B14 has a second interface 342a formed by the delamination of the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342. At the second interface 342a, the surface 141a in the fourth resin layer 14 corresponding to the second interface 342a and the surface 152a in the fifth resin layer 15 corresponding to the second interface 342a are in contact but are not fixed. Furthermore, the resin multilayer substrate 100B according to Modification 1 may have a void between a part of the surface 122a of the second resin layer 12 and a part of the surface 132a of the third resin layer 13. Also, the resin multilayer substrate 100B according to Modification 1 may have a void between a part of the surface 141a of the fourth resin layer 14 and a part of the surface 152a of the fifth resin layer 15.

[0149] Figures 17-19 are cross-sectional views of a resin multilayer substrate 100B according to Modification 2 of Embodiment 3. The resin multilayer substrate 100B according to Modification 2 is substantially the same as the resin multilayer substrate 100B according to Modification 1, and differs from the resin multilayer substrate 100B according to Modification 1 in that it is not bent, although it may be formed by bending the resin multilayer substrate 100B according to Modification 1. With respect to the resin multilayer substrate 100B according to Modification 2 of Embodiment 3, components that are the same as those in the resin multilayer substrate 100B according to Modification 1 of Embodiment 3 (see Figure 16) are denoted by the same reference numerals and their description is omitted. In the resin multilayer substrate 100B according to Modification 2, the surface roughness of the surface 121a corresponding to the second interface 322a on the third main surface 121 of the second resin layer 12 is smaller than the surface roughness of the surface corresponding to the first interface 321 on the third main surface 121 of the second resin layer 12 when the second resin layer 12 and the third resin layer 13 are peeled off at the first interface 321. Surface roughness is defined as the arithmetic mean roughness Ra. The arithmetic mean roughness Ra is specified in ISO 4287-1997. The arithmetic mean roughness Ra can be measured, for example, with a microscope or a laser displacement meter.

[0150] When a peel test is performed on the resin multilayer substrate 100B, cohesive failure occurs at at least one of the locations near the first interface 321 and the first interface 341. The peel test is, for example, a 90-degree peel strength test (IPC-TM-650 2.4.9). Furthermore, "cohesive failure" means that the failure occurs within the resin layers of the multiple resin layers 11-15, rather than at the interface between two adjacent resin layers in the lamination direction.

[0151] The resin multilayer substrate 100B according to Embodiment 3 may further include at least one of a first resist layer (not shown) disposed on the first main surface 101 of the laminated substrate 1B and a second resist layer (not shown) disposed on the second main surface 102 of the laminated substrate 1B. The first main surface 101 of the laminated substrate 1B includes the first main surface 111 of the first resin layer 11. The second main surface 102 of the laminated substrate 1B includes the ninth main surface 151 of the fifth resin layer 15. The first and second ends of the signal line 231B are each led out to the first main surface 101 or the second main surface 102 of the laminated substrate 1B by an interlayer connecting conductor. The interlayer connecting conductor is formed in the same manner as the first connecting conductor 41, the sixth connecting conductor 51, the fifth connecting conductor 45, the tenth connecting conductor 55, etc.

[0152] In the resin multilayer substrate 100B according to Modification 2 of Embodiment 3, in a plan view from the stacking direction of the multiple resin layers 11 to 15, for example, the length of the second interface 312a in the X-axis direction is 10 mm or more and 20 mm or less, and the length of the second interface 312a in the Y-axis direction is 5 mm or more and 10 mm or less. Also, in the resin multilayer substrate 100B according to Modification 2 of Embodiment 3, in a plan view from the stacking direction of the multiple resin layers 11 to 15, the distance between the second interface 312a and the second connecting conductor 42 in the X-axis direction is 200 μm or more and 400 μm or less, and the distance between the second interface 312a and the seventh connecting conductor 52 in the X-axis direction is 200 μm or more and 400 μm or less. Furthermore, in the resin multilayer substrate 100B according to the modified example 2 of Embodiment 3, in a plan view from the stacking direction of the plurality of resin layers 11 to 15, the distance between the second interface 342a and the fourth connecting conductor 44 in the X-axis direction is 200 μm or more and 400 μm or less, and the distance between the second interface 342a and the ninth connecting conductor 54 in the X-axis direction is 200 μm or more and 400 μm or less.

[0153] (2) Method for manufacturing a resin multilayer substrate In the method for manufacturing the resin multilayer substrate 100B of this embodiment, for example, the first step, the second step, and the third step are performed in the order of the first step, the second step, and the third step.

[0154] In the first step, a first single-sided copper-clad film, a second single-sided copper-clad film, a third single-sided copper-clad film, a fourth single-sided copper-clad film, and a fifth single-sided copper-clad film are prepared. The first single-sided copper-clad film is a single-sided copper-clad film in which a first conductor layer 21B is formed on the first main surface 111 of the first resin layer 11, and a plurality of first via holes and a plurality of sixth via holes are formed in the first resin layer 11, which are closed by the first conductor layer 21B. The second single-sided copper-clad film is a single-sided copper-clad film in which a second conductor layer 22B is formed on the third main surface 121 of the second resin layer 12, and a plurality of second via holes and a plurality of seventh via holes are formed in the second resin layer 12, which are closed by the second conductor layer 22B. The third single-sided copper-clad film is a single-sided copper-clad film in which a third conductor layer 23B is formed on the fifth main surface 131 of the third resin layer 13, and a plurality of third via holes and eighth via holes, which are closed by the third conductor layer 23B, are formed in the third resin layer 13. The fourth single-sided copper-clad film is a single-sided copper-clad film in which a fourth conductor layer 24B is formed on the seventh main surface 141 of the fourth resin layer 14, and a plurality of fourth via holes and a plurality of ninth via holes, which are closed by the fourth conductor layer 24B, are formed in the fourth resin layer 14. Furthermore, the fifth single-sided copper-clad film is a single-sided copper-clad film in which a fifth conductor layer 25B is formed on the ninth main surface 151 of the fifth resin layer 15, and a plurality of fifth via holes and a plurality of tenth via holes, which are closed by the fifth conductor layer 25B, are formed in the fifth resin layer 15.

[0155] In the second step, the surfaces of the first, second, third, fourth, and fifth single-sided copper-clad films that increase the adhesion strength with the single-sided copper-clad film to be adhered are roughened or altered by surface treatment, while surfaces that decrease the adhesion strength are not treated. In the surface treatment, for example, plasma discharge treatment is performed on the region corresponding to the first interface 321 on the third main surface 121 of the second resin layer 12 of the second single-sided copper-clad film and the sixth main surface 132 of the third resin layer 13 of the third single-sided copper-clad film, respectively. However, the region corresponding to the second interface 322 on the third main surface 121 of the second resin layer 12 and the sixth main surface 132 of the third resin layer 13 is covered with a mask and the surface treatment is performed so that the surface treatment is not performed on the region corresponding to the second interface 322 on the third main surface 121 of the second resin layer 12 and the sixth main surface 132 of the third resin layer 13. Furthermore, plasma discharge treatment is performed on the region corresponding to the first interface 341 on the seventh main surface 141 of the fourth resin layer 14 and the tenth main surface 152 of the fifth resin layer 15, respectively. However, the region corresponding to the second interface 342 is covered with a mask before surface treatment is performed on the region corresponding to the second interface 342 on the seventh main surface 141 of the fourth resin layer 14 and the tenth main surface 152 of the fifth resin layer 15, respectively.

[0156] In the third step, a resin multilayer substrate 100B is formed by stacking and pressing a first single-sided copper-clad film, in which conductive paste is filled into each of the multiple first via holes and multiple sixth via holes; a second single-sided copper-clad film, in which conductive paste is filled into each of the multiple second via holes and multiple seventh via holes; a third single-sided copper-clad film, in which conductive paste is filled into each of the multiple third via holes and multiple eighth via holes; a fourth single-sided copper-clad film, in which conductive paste is filled into each of the multiple fourth via holes and multiple ninth via holes; and a fifth single-sided copper-clad film, in which conductive paste is filled into each of the multiple fifth via holes and multiple tenth via holes.

[0157] (3) The resin multilayer substrate 100B of the electronic device equipped with a resin multilayer substrate may be used, for example, in place of the resin multilayer substrate 100 in the electronic device 700 (see Figures 6 and 7) described in Embodiment 1.

[0158] (4) Effect The resin multilayer substrate 100B according to Embodiment 3 comprises a laminated substrate 1B and a plurality of conductive layers 21B to 25B. The laminated substrate 1B has a plurality of resin layers 11 to 15. The plurality of resin layers 11 to 15 are laminated in the laminated substrate 1B. The plurality of conductive layers 21B to 25B overlap the plurality of resin layers 11 to 15 in the lamination direction of the plurality of resin layers 11 to 15. The resin multilayer substrate 100B has an interface surface B12 that includes the interface 32 of two adjacent resin layers 12 and 13 among the plurality of resin layers 11 to 15 in the lamination direction. The interface 32 includes a first interface 321 and a second interface 322. The second interface 322 has lower adhesion strength than the first interface 321 and lower adhesion strength than the interface between the resin layers and conductive layers that are in contact with each other among the plurality of resin layers 11 to 15 and the plurality of conductive layers 21B to 25B.

[0159] According to the above configuration, when the resin multilayer substrate 100B is bent, fracture of the resin multilayer substrate 100B is less likely to occur. More specifically, according to the above configuration, when the resin multilayer substrate 100B is bent in the portion including the second interface 322, the two resin layers 12 and 13 are easily separated at the second interface 322, so fracture of the resin multilayer substrate 100B is less likely to occur. Furthermore, according to the above configuration, it is possible to improve bending resistance without reducing the number of resin layers 11 to 15 in the portion including the second interface 322. In addition, according to the above configuration, since the resin layer 12 and the resin layer 13 are fixed at the second interface 322, it is possible to improve the reproducibility of the shape and characteristics of the resin multilayer substrate 100B during manufacturing.

[0160] Furthermore, in the resin multilayer substrate 100B according to Embodiment 3, the interface B12 further includes a third interface 323 between the conductive layer 22B and one of the two resin layers 12 and 13. The conductive layer 22B is interposed between two of the multiple conductive layers 21B to 25B and is smaller than the two resin layers 12 and 13. The adhesion strength of the third interface 323 is greater than the adhesion strength of the second interface 322.

[0161] According to the above configuration, when the resin multilayer substrate 100B is bent, fracture of the resin multilayer substrate 100B is less likely to occur, and delamination at the third interface 323 between the conductive layer 22B and the resin layer 12 is less likely to occur.

[0162] Furthermore, in the resin multilayer substrate 100B according to Embodiment 3, the interface B12 further includes a fourth interface 324 between the connecting conductors (second connecting conductor 42, seventh connecting conductor 52) penetrating the second resin layer 12 and the second conductor layer 22B. The adhesion strength of the fourth interface 324 is greater than that of the second interface 322.

[0163] With the above configuration, since the interface B12 includes the fourth interface between the connecting conductors (second connecting conductor 42, seventh connecting conductor 52) and the second conductor layer 22B, it is possible to suppress the delamination of the adhering portion starting from the delamination portion.

[0164] Furthermore, the resin multilayer substrate 100B according to Embodiment 3 has a plurality of interface surfaces B11, B12, B13, and B14, including interface surface B12. The plurality of interface surfaces B11, B12, B13, and B14 are separated in the stacking direction of the plurality of resin layers 11 to 15. Interface surface B14 includes the interface 34 of two adjacent resin layers 14 and 15 in the stacking direction among the plurality of resin layers 11 to 15. Interface 34 includes a first interface 341 and a second interface 342. The second interface 342 has lower adhesion strength than the first interface 341 and also lower adhesion strength than the interface between the resin layers and conductor layers that are in contact with each other among the plurality of resin layers 11 to 15 and the plurality of conductor layers 21B to 25B.

[0165] According to the above configuration, when the resin multilayer substrate 100B is bent, fracture of the resin multilayer substrate 100B is less likely to occur.

[0166] Furthermore, in the resin multilayer substrate 100B according to modified examples 1 and 2 of Embodiment 3, the two resin layers 12 and 13 are delaminated at the second interface 312a.

[0167] According to the above configuration, the resin multilayer substrate 100B is less likely to break.

[0168] Furthermore, in the resin multilayer substrate 100B according to Embodiment 3, the two resin layers 14 and 15 are delaminated at the second interface 342a.

[0169] According to the above configuration, the resin multilayer substrate 100B is less likely to break.

[0170] Furthermore, in the resin multilayer substrate 100B according to Embodiment 3, the plurality of conductor layers 21B to 25B include signal lines 231B.

[0171] According to the above configuration, the loss of the signal line 231B can be reduced, and there is no need to change the shape and arrangement of the signal line 231B. Furthermore, it is possible to suppress a decrease in performance without widening the width of the bendable portion in the resin multilayer substrate 100B.

[0172] Furthermore, in the resin multilayer substrate 100B according to Embodiment 3, the plurality of conductor layers 21B to 25B further include ground electrodes 21B and 25B that overlap the signal line 231B in the stacking direction of the plurality of resin layers 11 to 15.

[0173] According to the above configuration, a strip line can be formed using the laminated substrate 1B, the signal line 231B, and the two ground electrodes 21B and 25B.

[0174] Furthermore, in the resin multilayer substrate 100B according to Embodiment 3, the laminated substrate 1B is elongated. In the resin multilayer substrate 100B according to Embodiment 3, the second interface 322 is formed along the entire length in the width direction of the laminated substrate 1B.

[0175] According to the above configuration, the resin multilayer substrate 100B is less likely to break.

[0176] Furthermore, similar to the resin multilayer substrate 100B according to Embodiment 3, in the resin multilayer substrate 100B according to Modifications 1 and 2 of Embodiment 3, the second interface 322a is formed along the entire length in the width direction of the laminated substrate 1B.

[0177] According to the resin multilayer substrate 100B of the modified examples 1 and 2 of Embodiment 3, the resin multilayer substrate 100B is less prone to breakage.

[0178] Furthermore, in the resin multilayer substrate 100B according to the modified example 1 of Embodiment 3, the laminated substrate 1B is curved, and the curved portion includes the second interface 322a.

[0179] According to the above configuration, the resin multilayer substrate 100B is less likely to break.

[0180] Furthermore, the resin multilayer substrate 100B according to the modified example 2 of Embodiment 3 comprises a laminated substrate 1B and a plurality of conductive layers 21B to 25B. The laminated substrate 1B has a plurality of resin layers 11 to 15. In the laminated substrate 1B, the plurality of resin layers 11 to 15 are laminated. The plurality of conductive layers 21B to 25B overlap the plurality of resin layers 11 to 15 in the lamination direction of the plurality of resin layers 11 to 15. The resin multilayer substrate 100B has an interface surface B12 that includes the interface 32 of two adjacent resin layers 12 and 13 among the plurality of resin layers 11 to 15 in the lamination direction of the plurality of resin layers 11 to 15. The interface 32 includes a first interface 321 to which the two resin layers 12 and 13 are fixed, and a second interface 322a to which the two resin layers 13 and 14 are in contact and not fixed. The surface roughness of the surface 112a corresponding to the second interface 322a in one of the two resin layers 12 and 13 is smaller than the surface roughness of the surface corresponding to the first interface 321 in one of the resin layers 12 when the two resin layers 12 and 13 are peeled off at the first interface 321.

[0181] According to the above configuration, when the resin multilayer substrate 100B is bent, fracture of the resin multilayer substrate 100B is less likely to occur. More specifically, according to the above configuration, when the resin multilayer substrate 100B is bent in the portion including the second interface 322a, the two resin layers 12 and 13 are not fixed to each other at the second interface 322a, so fracture of the resin multilayer substrate 100B is less likely to occur. Furthermore, according to the above configuration, it is possible to improve bending resistance in the portion including the second interface 322a without reducing the number of resin layers 11 to 15.

[0182] Furthermore, the electronic device according to Embodiment 3 includes a resin multilayer substrate 100B instead of the resin multilayer substrate 100 in the electronic device 700 according to Embodiment 1 (see Figures 6 and 7). The resin multilayer substrate 100B includes a second interface 322 of the resin multilayer substrate 100B in which it undergoes plastic deformation due to the movement of the hinge device 705 (see Figures 6 and 7).

[0183] According to the above configuration, when the resin multilayer substrate 100B is bent in the electronic device according to Embodiment 3, the resin multilayer substrate 100B is less likely to break.

[0184] (Embodiment 4) The resin multilayer substrate 100C according to Embodiment 4 will be described with reference to Figures 20 to 22. With respect to the resin multilayer substrate 100C according to Embodiment 4, components that are the same as those in the resin multilayer substrate 100B according to Embodiment 3 (see Figures 11 to 15) are denoted by the same reference numerals and their description is omitted.

[0185] (1) In the resin multilayer substrate 100C according to the fourth embodiment of the configuration, as shown in Figures 21 and 22, the interface surface B12 of the laminated substrate 1B includes a plurality of first interfaces 321 including a first interface 321, and a plurality of second interfaces 322 including a second interface 322. In the resin multilayer substrate 100C, the plurality of first interfaces 321 and the plurality of second interfaces 322 are arranged in the longitudinal direction of the signal line 231B.

[0186] Furthermore, in the resin multilayer substrate 100C according to Embodiment 4, the interface B14 of the laminated substrate 1B includes a plurality of first interfaces 341, including a first interface 341, and a plurality of second interfaces 342, including a second interface 342. In the resin multilayer substrate 100C, the plurality of first interfaces 341 and the plurality of second interfaces 342 are arranged in the longitudinal direction of the signal line 231B.

[0187] In the resin multilayer substrate 100C according to Embodiment 4, the plurality of first interfaces 341 correspond one-to-one with the plurality of first interfaces 321. In the stacking direction of the plurality of resin layers 11 to 15, the plurality of first interfaces 341 overlap with the corresponding first interface 321 among the plurality of first interfaces 321. In the resin multilayer substrate 100C, in a plan view from the stacking direction of the plurality of resin layers 11 to 15, the first ground electrode 21B and the second ground electrode 25B are connected by the first to fifth connecting conductors 41 to 45 and the sixth to tenth connecting conductors 51 to 55, inside the outer circumference of each of the plurality of first interfaces 321.

[0188] The resin multilayer substrate 100C may further include at least one of a first resist layer (not shown) disposed on the first main surface 101 of the laminated substrate 1B and a second resist layer (not shown) disposed on the second main surface 102 of the laminated substrate 1B. The first main surface 101 of the laminated substrate 1B includes the first main surface 111 of the first resin layer 11. The second main surface 102 of the laminated substrate 1B includes the ninth main surface 151 of the fifth resin layer 15. The first and second ends of the signal line 231B are each led out to the first main surface 101 or the second main surface 102 of the laminated substrate 1B by interlayer connecting conductors. The interlayer connecting conductors are formed in the same manner as the first connecting conductor 41, the sixth connecting conductor 51, the fifth connecting conductor 45, the tenth connecting conductor 55, etc.

[0189] (2) Effects The resin multilayer substrate 100C according to Embodiment 4 provides the same effects as the resin multilayer substrate 100B according to Embodiment 3.

[0190] Furthermore, in the resin multilayer substrate 100C according to Embodiment 4, the interface B12 includes a plurality of first interfaces 321, including the first interface 321, and a plurality of second interfaces 322, including the second interface 322. The plurality of second interfaces 322 have lower adhesion strength than the plurality of first interfaces 321, and also lower adhesion strength than the interfaces between the resin layers and conductor layers that are in contact with each other among the plurality of resin layers 11 to 15 and the plurality of conductor layers 21B to 25B. In the resin multilayer substrate 100C, the plurality of first interfaces 321 and the plurality of second interfaces 322 are arranged in the longitudinal direction of the signal line 231B.

[0191] According to the above configuration, the length of the second interface 322 in the longitudinal direction of the signal line 231B can be shortened, and if delamination occurs at the second interface 322 in the resin multilayer substrate 100C, it is possible to prevent the resin multilayer substrate 100C from coming into contact with other components in, for example, electronic equipment. Furthermore, according to the above configuration, since the interface surface B12 includes a plurality of first interfaces 321, and the plurality of first interfaces 321 are spaced apart in the longitudinal direction of the signal line 231B, it is possible to make the first ground electrode 21B and the second ground electrode 25B conductive at a constant interval, which suppresses the reduction of the resonant frequency of unwanted resonances and prevents unwanted resonances from interfering with the usable frequency range.

[0192] The resin multilayer substrate 100C may be bent, for example, as shown in Figure 23. Figure 23 is a cross-sectional view of the resin multilayer substrate 100C according to Modification 1 of Embodiment 4. With respect to the resin multilayer substrate 100C according to Modification 1 of Embodiment 4, components that are the same as those in the resin multilayer substrate 100C according to Embodiment 4 (see Figures 20 to 22) are denoted by the same reference numerals and their description is omitted. In the resin multilayer substrate 100C according to Modification 1, the second resin layer 12 and the third resin layer 13 are peeled off at the second interface 322 (see Figures 21 and 22) included in the interface 32 before the resin multilayer substrate 100C is bent, and the fourth resin layer 14 and the fifth resin layer 15 are peeled off at the second interface 342 (see Figures 21 and 22) included in the interface 34 before the resin multilayer substrate 100C is bent. In the resin multilayer substrate 100C according to Modification 1, the interface B12 has a second interface 322a formed by the delamination of the second resin layer 12 and the third resin layer 13 at the second interface 322 (see Figures 21 and 22). At the second interface 322a, the surface 121a in the second resin layer 12 corresponding to the second interface 322a and the surface 132a in the third resin layer 13 corresponding to the second interface 322a are in contact but not fixed together. Furthermore, in the resin multilayer substrate 100C according to Modification 1, the interface B14 has a second interface 342a formed by the delamination of the fourth resin layer 14 and the fifth resin layer 15 at the second interface 342 (see Figures 21 and 22). At the second interface 342a, the surface 141a in the fourth resin layer 14 corresponding to the second interface 342a and the surface 152a in the fifth resin layer 15 corresponding to the second interface 342a are in contact but not fixed together. The resin multilayer substrate 100C according to Modification 1 may have a void between a part of the surface 121a of the second resin layer 12 and a part of the surface 132a of the third resin layer 13. Furthermore, the resin multilayer substrate 100C according to Modification 1 may have a void between a part of the surface 141a of the fourth resin layer 14 and a part of the surface 152a of the fifth resin layer 15.

[0193] Figures 24 and 25 are cross-sectional views of a resin multilayer substrate 100C according to Modification 2 of Embodiment 4. The resin multilayer substrate 100C according to Modification 2 is substantially the same as the resin multilayer substrate 100C according to Modification 1, and differs from the resin multilayer substrate 100C according to Modification 1 in that it is not bent, although it may be formed by bending the resin multilayer substrate 100C according to Modification 1. With respect to the resin multilayer substrate 100C according to Modification 2 of Embodiment 4, components that are the same as those in the resin multilayer substrate 100C according to Modification 1 of Embodiment 4 (see Figure 23) are denoted by the same reference numerals and their description is omitted. In the resin multilayer substrate 100C according to Modification 2, the surface roughness of the surface 121a corresponding to the second interface 322a on the third main surface 121 of the second resin layer 12 is smaller than the surface roughness of the surface corresponding to the first interface 321 on the third main surface 121 of the second resin layer 12 when the second resin layer 12 and the third resin layer 13 are peeled off at the first interface 321. Surface roughness is defined as the arithmetic mean roughness Ra. The arithmetic mean roughness Ra is specified in ISO 4287-1997. The arithmetic mean roughness Ra can be measured, for example, with a microscope or a laser displacement meter.

[0194] (Other Modifications) Embodiments 1 to 4 described above are merely one of many embodiments of the present invention. Embodiments 1 to 4 described above can be modified in various ways depending on the design, etc., as long as the objective of the present invention is achieved, and may be combined as appropriate.

[0195] Each of the multiple resin layers 11 to 15 may be made of, for example, polyimide (PI) or modified polyimide (Modified-PI). In this case, each of the multiple first connecting conductors 41, multiple second connecting conductors 42, multiple third connecting conductors 43, multiple fourth connecting conductors 44, multiple fifth connecting conductors 45, multiple sixth connecting conductors 51, multiple seventh connecting conductors 52, multiple eighth connecting conductors 53, multiple ninth connecting conductors 54, and multiple tenth connecting conductors 55 may be made of through-hole plating. Alternatively, the first connecting conductor 41 and the second connecting conductor 42 connected to each other may be made of a single through-hole plating, or the sixth connecting conductor 51 and the seventh connecting conductor 52 connected to each other may be made of a single through-hole plating. The material for the through-hole plating is, for example, copper.

[0196] Furthermore, each of the multiple conductive layers 21-22, 21A-25A, and 22B-25B is not limited to layers composed of a part of a metal foil, but may also be a metal layer formed using thin-film formation techniques such as sputtering or vapor deposition. In this case, patterning may be performed using, for example, lithography and etching techniques, laser processing techniques, or the lift-off method.

[0197] 1. Laminated substrate 101 First main surface 102 Second main surface 11 Resin layer (First resin layer) 111 First main surface 112 Second main surface 12 Resin layer (Second resin layer) 121 Third main surface 122 Fourth main surface 13 Resin layer (Third resin layer) 131 Fifth main surface 132 Sixth main surface 14 Resin layer (Fourth resin layer) 141 Seventh main surface 142 Eighth main surface 15 Resin layer (Fifth resin layer) 151 Ninth main surface 152 Tenth main surface 21, 21A, 21B Conductor layer (First conductor layer) 22, 22A, 22B Conductor layer (Second conductor layer) 23A, 23B Conductor layer (Third conductor layer) 231B Signal line 232B Third ground electrode 233B Fourth ground electrode 24A, 24B Conductor layer (4th conductor layer) 25A, 25B Conductor layer (5th conductor layer) 41 1st connecting conductor 42 2nd connecting conductor 43 3rd connecting conductor 44 4th connecting conductor 45 5th connecting conductor 51 6th connecting conductor 52 7th connecting conductor 53 8th connecting conductor 54 9th connecting conductor 55 10th connecting conductor 100, 100A, 100B, 100C Resin multilayer substrate 700 Electronic equipment 705 Hinge device

Claims

1. A resin multilayer substrate comprising: a laminated substrate having a plurality of resin layers, wherein the plurality of resin layers are stacked; and a plurality of conductive layers overlapping the plurality of resin layers in the stacking direction of the plurality of resin layers, wherein the substrate has an interface including the interface of two adjacent resin layers in the stacking direction of the plurality of resin layers, and the interface includes a first interface and a second interface having lower adhesion strength than the first interface and lower adhesion strength than the interface between a resin layer and a conductive layer that are in contact with each other among the plurality of resin layers and the plurality of conductive layers.

2. The interface further includes a third interface between a conductor layer interposed between two of the plurality of conductor layers and smaller than the two resin layers, and one of the two resin layers, wherein the adhesion strength of the third interface is greater than the adhesion strength of the second interface, the resin multilayer substrate according to claim 1.

3. The resin multilayer substrate according to claim 2, wherein the interface further includes a fourth interface between a connecting conductor that penetrates one resin layer and overlaps the conductor layer in the lamination direction and the conductor layer, and the adhesion strength of the fourth interface is greater than that of the second interface.

4. The resin multilayer substrate according to any one of claims 1 to 3, wherein the two resin layers include a first resin layer having a first main surface and a second main surface, and a second resin layer having a third main surface and a fourth main surface, and the plurality of conductor layers include a first conductor layer laminated on the first main surface of the first resin layer, and a second conductor layer laminated on the third main surface of the second resin layer, the material of the first resin layer and the material of the second resin layer are the same, and the first resin layer and the second resin layer are directly joined.

5. The resin multilayer substrate according to any one of claims 1 to 4, wherein the two resin layers are delaminated at the second interface.

6. A resin multilayer substrate according to any one of claims 1 to 5, having a plurality of interface surfaces including the interface surface, wherein the plurality of interface surfaces are spaced apart in the lamination direction of the plurality of resin layers.

7. The resin multilayer substrate according to any one of claims 1 to 6, wherein the plurality of conductor layers include signal lines.

8. The resin multilayer substrate according to claim 7, wherein the interface includes a plurality of first interfaces including the first interface, and a plurality of second interfaces including the second interface, the plurality of second interfaces having lower adhesion strength than the plurality of first interfaces and lower adhesion strength than the interface between the resin layer and the conductor layer that are in contact with each other among the plurality of resin layers and the plurality of conductor layers, and the plurality of first interfaces and the plurality of second interfaces are aligned in the longitudinal direction of the signal line.

9. The resin multilayer substrate according to claim 7 or 8, wherein the plurality of conductor layers further include ground electrodes that overlap the signal lines in the stacking direction of the plurality of resin layers.

10. The resin multilayer substrate according to claim 9, wherein the plurality of conductor layers further include a second ground electrode different from the first ground electrode which is the ground electrode, the second ground electrode faces the first ground electrode via at least two resin layers among the plurality of resin layers that are fixed to the signal line in the stacking direction of the plurality of resin layers, and overlaps the signal line in the stacking direction, and in the stacking direction, the second ground electrode, the signal line and the first ground electrode are arranged in the order of second ground electrode, signal line and first ground electrode.

11. The resin multilayer substrate according to any one of claims 1 to 10, wherein the laminated substrate is elongated, and the second interface is formed along the entire length in the width direction of the laminated substrate.

12. A resin multilayer substrate according to any one of claims 1 to 11, wherein the curved portion includes the second interface.

13. A resin multilayer substrate comprising: a laminated substrate having a plurality of resin layers, wherein the plurality of resin layers are stacked; and a plurality of conductive layers overlapping the plurality of resin layers in the stacking direction of the plurality of resin layers, wherein the substrate has an interface including the interface of two adjacent resin layers in the stacking direction of the plurality of resin layers, the interface includes: a first interface to which the two resin layers are fixed; and a second interface to which the two resin layers are in contact and not fixed; wherein the surface roughness of the surface of one of the two resin layers corresponding to the second interface is smaller than the surface roughness of the surface of the one resin layer corresponding to the first interface when the two resin layers are peeled off at the first interface.

14. The resin multilayer substrate according to claim 13, wherein the interface further includes a third interface to which a conductor layer interposed between two of the plurality of conductor layers and smaller than the two resin layers, and one of the two resin layers, are fixed.

15. The resin multilayer substrate according to claim 13, wherein the interface further includes a fourth interface to which a connecting conductor penetrating the one resin layer and overlapping the conductor layer in the lamination direction is fixed to the conductor layer.

16. A resin multilayer substrate according to any one of claims 12 to 14, having a plurality of interface surfaces including the interface surface, wherein the plurality of interface surfaces are spaced apart in the lamination direction of the plurality of resin layers.

17. The resin multilayer substrate according to any one of claims 13 to 16, wherein the plurality of conductor layers include signal lines.

18. The resin multilayer substrate according to claim 17, wherein the interface includes a plurality of first interfaces including the first interface, and a plurality of second interfaces including the second interface, the plurality of second interfaces having lower adhesion strength than the plurality of first interfaces and lower adhesion strength than the interface between the resin layer and the conductor layer that are in contact with each other among the plurality of resin layers and the plurality of conductor layers, and the plurality of first interfaces and the plurality of second interfaces are aligned in the longitudinal direction of the signal line.

19. An electronic device comprising a resin multilayer substrate according to any one of claims 1 to 18, and a hinge device, wherein the resin multilayer substrate has a portion that is plastically deformed by the movement of the hinge device, the portion of which includes the second interface.

Images