Stretchable Device

Abstract

This stretchable device (1) comprises: a stretchable base material (11) having a main surface (111); an electronic component (30) provided on the main surface (111) of the stretchable base material (11); first stretchable wiring (21) connected to the electronic component (30); and second stretchable wiring (22) connected to the first stretchable wiring (21), wherein a first end section (211) in the extending direction of the first stretchable wiring (21) is connected to the electronic component (30), and a second end section (212) in the extending direction of the first stretchable wiring (21) is connected to the first end section (221) in the extending direction of the second stretchable wiring (22).

Description

[Technical field]

[0001] The present disclosure relates to stretchable devices. [Background technology]

[0002] Conventionally, there is a stretchable device described in International Publication No. 2009 / 081929 (Patent Document 1). This stretchable device includes an insulating substrate, a first conductor having a land provided on the insulating substrate, a second conductor provided on the land, solder provided individually on the second conductor, and an electronic component having electrode parts that are in independent contact with the solder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2009 / 081929 Summary of the Invention [Problem to be solved by the invention]

[0004] In prior art devices, an end of an electronic component is positioned over the overlapping area of ​​the first conductor and the second conductor, and solder on the second conductor is also positioned over the overlapping area.

[0005] However, when the conventional device having the above structure was evaluated, it was found that the conventional device had low mechanical strength. Upon detailed examination, it was found that when a stretchable base material having stretchability is used as the base material, the stress during stretching is most likely to be concentrated near the interface between the connection member such as solder and the wiring. Therefore, it was found that the conventional device may cause breakage of the wiring or peeling at the interface between the base material and the wiring.

[0006] Therefore, an object of the present disclosure is to provide a stretchable device that can improve mechanical strength. [Means for solving the problem]

[0007] In order to achieve the above object, a stretchable device according to one aspect of the present disclosure includes: A stretchable substrate having a main surface; An electronic component provided on the main surface of the stretchable base material; A first elastic wiring connected to the electronic component; A second elastic wire connected to the first elastic wire, A first end portion in an extension direction of the first elastic wire is connected to the electronic component, A second end portion in an extension direction of the first expandable wire is connected to a first end portion in an extension direction of the second expandable wire. Effect of the Invention

[0008] According to the stretchable device according to an aspect of the present disclosure, it is possible to improve the mechanical strength. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view partially illustrating a stretchable device according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Diagram 3] FIG. 3 is a schematic perspective view showing a stretchable device according to a second embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic plan view partially illustrating a stretchable device according to a second embodiment of the present disclosure. [Diagram 5] FIG. 5 is a graph showing the relationship between stress and elongation of the expandable wiring according to the example. [Figure 6] FIG. 6 is a graph showing the thickness dependency of the relationship between the stretch rate and the resistance value of the expandable wiring according to the example. [Figure 7] FIG. 7 is a schematic perspective view partially illustrating a stretchable device according to an embodiment. [Figure 8A] FIG. 8A is a diagram showing the application shape of the paste. [Figure 8B]FIG. 8B is a diagram showing the application shape of the paste. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. In each embodiment, differences from the previous embodiments will be mainly described. In particular, similar effects due to similar configurations will not be mentioned in each embodiment. Among the components in the following embodiments, components that are not described in the independent claims will be described as optional components. In addition, the size and size ratio of the components shown in the drawings are not necessarily strict. In addition, in each figure, substantially the same configuration is given the same symbol, and duplicated descriptions may be omitted or simplified.

[0011] [First embodiment] (Overall composition) The overall configuration of the stretchable device 1 according to the first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a schematic perspective view partially showing the stretchable device 1. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Note that in Fig. 1, the illustration of a covering layer is omitted.

[0012] In the drawings of this specification, the thickness direction of the stretchable base material is indicated by an arrow T. The "direction perpendicular to the main surface of the stretchable base material" described in the claims corresponds to the T direction. In addition, in this specification, the direction from the main surface of the stretchable base material on which the stretchable wiring is not provided to the main surface of the stretchable base material on which the stretchable wiring is provided is defined as the upper side.

[0013] The stretchable device 1 includes a stretchable base material 11 having a main surface 111, an electronic component 30 provided on the main surface 111 of the stretchable base material 11, a first stretchable wiring 21 connected to the electronic component 30, a second stretchable wiring 22 connected to the first stretchable wiring 21, and a covering layer 50 provided so as to cover the first stretchable wiring 21 and the second stretchable wiring 22. The stretchable device 1 is used, for example, to be attached to a living body and to measure a biosignal.

[0014] Here, "on the main surface of the stretchable substrate" does not mean an absolute direction such as vertically upward as determined by the direction of gravity, but rather means a direction toward the outside of the outside and inside of the stretchable substrate bounded by the main surface of the stretchable substrate. Therefore, "on the main surface of the stretchable substrate" is a relative direction determined by the orientation of the main surface of the stretchable substrate. In addition, "above" an element includes not only a position directly above the element (on) but also a position above the element, i.e., a position above the element through another object or a position above the element with a gap (above).

[0015] The stretchable substrate 11 is a sheet-like or film-like substrate made of a stretchable resin material. Examples of the resin material include thermoplastic polyurethane (TPU). The thickness of the stretchable substrate 11 is not particularly limited, but is preferably 1 mm or less, more preferably 100 μm or less, and even more preferably 50 μm or less, from the viewpoint of not inhibiting the stretching of the surface of the living body when attached to the living body. In addition, the thickness of the stretchable substrate 11 is preferably 1 μm or more. The shape of the stretchable substrate 11 is not particularly limited. In this embodiment, the stretchable substrate 10 is shaped to extend in one direction A when viewed from the thickness direction T.

[0016] The electronic component 30 is, for example, a capacitor component, an inductor component, or an IC (semiconductor integrated circuit). The type of electronic component 30 is not particularly limited. The shape of the electronic component 30 is not particularly limited, but is rectangular in this embodiment. The electronic component 30 is arranged so that the longitudinal direction is parallel to the extension direction of the stretchable base material 11 (hereinafter referred to as "direction A"). External electrodes 31 are provided on both ends of the electronic component 30 in direction A.

[0017] The first elastic wire 21 is a member having a function of relieving stress applied to the elastic device 1. The first elastic wire 21 is formed of an elastic conductive material. For example, a metal foil such as silver, copper, or nickel may be used as the conductive material, or a mixture of a metal powder such as silver, copper, or nickel and an elastomer resin such as an epoxy resin, a urethane resin, an acrylic resin, or a silicone resin may be used. The first elastic wire 21 preferably has a larger Young's modulus than the second elastic wire 22. The shape of the first elastic wire 21 is not particularly limited, but in this embodiment, it is formed to extend in one direction. Specifically, the first elastic wire 21 is formed so that the extension direction is parallel to the A direction.

[0018] A first end 211 in the extension direction of the first elastic wire 21 is connected to the electronic component 30. Specifically, the first end 211 in the extension direction of the first elastic wire 21 is connected to an external electrode 31 on one side of the electronic component 30 via a connection member 40. The connection member 40 is, for example, solder, a conductive adhesive, or the like.

[0019] The length L1 of the first elastic wire 21 in the extension direction is preferably, for example, 0.2 mm or more and 5 mm or less. In this specification, the length L1 does not include the overlapping portion with the second elastic wire 22. The width W1 of the first elastic wire 21 in the direction perpendicular to the extension direction is preferably, for example, 0.2 mm or more and 3.2 mm or less. The thickness t1 of the first elastic wire 21 in the T direction is preferably, for example, 10 μm or more and 30 μm or less.

[0020] The second elastic wire 22 is a wire that mainly transmits and receives biosignals and the like. The second elastic wire 22 is formed of an elastic conductive material. For the conductive material, for example, a metal foil such as silver, copper, or nickel may be used, or a mixture of a metal powder such as silver, copper, or nickel and an elastomer resin such as an epoxy resin, a urethane resin, an acrylic resin, or a silicone resin may be used. The shape of the second elastic wire 22 is not particularly limited, but in this embodiment, it is formed to extend in one direction. Specifically, the second elastic wire 22 is formed so that the extension direction is parallel to the A direction. That is, the extension direction of the second elastic wire 22 is parallel to the extension direction of the first elastic wire 21. In this application, "parallel" is not limited to a strict parallel relationship, and also includes a substantial parallel relationship in consideration of the range of practical variations.

[0021] The first end 221 in the extension direction of the second elastic wire 22 is connected to the second end 212 in the extension direction of the first elastic wire 21. Specifically, the first end 221 in the extension direction of the second elastic wire 22 is stacked on the second end 212 in the extension direction of the first elastic wire 21 and connected to the second end 212 in the extension direction of the first elastic wire 21. However, without being limited thereto, the second end 212 in the extension direction of the first elastic wire 21 may be stacked on the first end 221 in the extension direction of the second elastic wire 22 and connected to the first end 221 in the extension direction of the second elastic wire 22. The length L3 in the A direction of the portion (overlap portion) 22P of the second elastic wire 22 overlapping with the first elastic wire 21 is preferably, for example, 0.1 mm or more and 1 mm or less.

[0022] The length L2 of the second elastic wire 22 in the extension direction is preferably, for example, three times or more the length L1. In this specification, the length L2 does not include the overlapping portion with the first elastic wire 21. In addition, as shown in FIG. 7 described later, when there are multiple electronic components 30 and one second elastic wire 22 is connected to multiple electronic components 30, L2 is the length to the midpoint between adjacent electronic components 30 in the extension direction of the second elastic wire 22. The width W2 in the direction perpendicular to the extension direction of the second elastic wire 22 is preferably, for example, 0.2 mm or more and 3.2 mm or less. The thickness t2 of the second elastic wire 22 in the T direction is preferably, for example, 10 μm or more and 30 μm or less.

[0023] In this embodiment, there are two sets of expandable wirings each composed of a first expandable wiring 21 connected to an external electrode 31 of an electronic component 30 and a second expandable wiring 22 connected to the first expandable wiring 21, each set corresponding to one of the two external electrodes 31 provided at both ends of the electronic component 30 in the A direction.

[0024] The covering layer 50 protects the first elastic wire 21 and the second elastic wire 22 from the external environment. The covering layer 50 is, for example, a potting resin. The covering layer 50 is preferably a resin material having elasticity, for example, ionomer resin, polyester resin, styrene resin, olefin resin, epoxy resin, urethane resin, acrylic resin, or silicone resin, and more preferably urethane resin. The covering layer 50 does not need to be provided, but it is preferable that it covers at least the connection portion between the first elastic wire 21 and the electronic component 30.

[0025] According to the stretchable device 1, the first end 211 in the extension direction of the first stretchable wire 21 is connected to the electronic component 30, and the second end 212 in the extension direction of the first stretchable wire 21 is connected to the first end 221 in the extension direction of the second stretchable wire 22. Therefore, when viewed from a direction perpendicular to the main surface 111 of the stretchable base material 11, the end of the electronic component 30 does not overlap the connection portion between the first stretchable wire 21 and the second stretchable wire 22. Furthermore, the connection member 40 connecting the electronic component 30 and the first stretchable wire 21 can also be arranged so as not to overlap the connection portion between the first stretchable wire 21 and the second stretchable wire 22. This allows different members to be arranged in stages from the end of the electronic component 30 toward the second stretchable wire 22. As a result, the stress that may be concentrated at the connection portion between the electronic component 30 and the first stretchable wire 21 can be dispersed from the end of the electronic component 30 toward the second stretchable wire 22, thereby mitigating the concentration of the stress. As a result, the mechanical strength of the stretchable device 1 can be improved.

[0026] (Tensile load ratio) It is preferable that the stretchable device 1 satisfies the following formulas (1) and (2). In the following description, the stretching direction is parallel to the A direction. σ1≦Allowable stress of first elastic wiring σ1 max (1) σ2≦Allowable stress of second elastic wiring σ2 max (2) however, σ1=(δ×E1×S2×E2) / (L1×S2×E2+L2×S1×E1) ···(3) σ2=(δ×E1×S1×E2) / (L1×S2×E2+L2×S1×E1) ···(4) δ: Total displacement of the first elastic wire 21 and the second elastic wire 22 L1: Length of the first elastic wire 21 in the elastic direction (direction A) L2: Length of the second elastic wire 22 in the elastic direction S1: Cross-sectional area of ​​the first elastic wiring 21 in a cross section perpendicular to the elastic direction (width W1 of the first elastic wiring 21 × thickness t1) S2: Cross-sectional area of ​​the second elastic wiring 22 in a cross section perpendicular to the elastic direction (width W2 of the second elastic wiring 22 × thickness t2) E1: Elastic modulus of the first elastic wiring 21 E2: Elastic modulus of the second elastic wiring 22

[0027] The above σ1 means the tensile load acting on the first elastic wire 21 when a displacement amount δ is applied to the entire first elastic wire 21 and the second elastic wire 22. The above σ2 means the tensile load acting on the second elastic wire 22 when a displacement amount δ is applied to the entire first elastic wire 21 and the second elastic wire 22. In other words, satisfying the above formulas (1) and (2) means that each of the first tensile load ratio and the second tensile load ratio calculated by the following formula is 1 or less. First tensile load ratio=(tensile load σ1 acting on the first elastic wiring 21) / (allowable stress σ1 of the first elastic wiring 21) max ) Second tensile load ratio=(tensile load acting on the second elastic wire 22 σ2) / (allowable stress of the second elastic wire 22 σ2 max )

[0028] Here, the derivation of the above formulas (3) and (4), which are calculation formulas for the tensile load σ1 and the tensile load σ2, will be described. When a displacement amount δ is applied to the entire first elastic wire 21 and the second elastic wire 22, the load F applied to the first elastic wire 21 and the second elastic wire 22 is expressed by the following formula. F=δ / [{L1 / (E1×S1)}+{L2 / (E2×S2)}]

[0029] The tensile load σ1 and the tensile load σ2 are derived using the above load F according to the following formula. σ1=F / S1=(δ / S1)×{(E1×S1×E2×S2) / (L1×S2×E2+L2×S1×E1)}=(δ×E1×S2×E2) / (L1×S2×E2+L2×S1×E1) σ2=F / S2=(δ / S2)×{(E1×S1×E2×S2) / (L1×S2×E2+L2×S1×E1)}=(δ×E1×S1×E2) / (L1×S2×E2+L2×S1×E1)

[0030] As can be seen from the above formulas (3) and (4), the tensile load σ1 and the tensile load σ2 can be adjusted by adjusting the elastic modulus E1, E2, the length L1, L2 in the stretch direction, the cross-sectional area S1, S2, and the length L3 of the portion where the first stretchable wiring 21 and the second stretchable wiring 22 overlap with each other of the first stretchable wiring 21 and the second stretchable wiring 22. When the length of each member of the first stretchable wiring 21 and the second stretchable wiring 22 in the extension direction is a predetermined length, the length L1, L2 of the first stretchable wiring 21 and the second stretchable wiring 22 in the stretch direction can be adjusted by adjusting the length of the portion where the first stretchable wiring 21 and the second stretchable wiring 22 overlap with each other.

[0031] The calculation of the tensile load σ1 and the calculation of the tensile load σ2 are shown for one of the two sets of expandable wires, but the calculation is similar for the other set. That is, δ, L1, L2, S1, S2, E1, and E2 can be defined for each of the two sets of expandable wires.

[0032] The allowable stress σ1 of the first elastic wiring 21 in the above formula (1) max is the stress at the maximum elongation of the first elastic wire 21. The allowable stress σ1 of the first elastic wire 21 max For example, after cutting out the first elastic wire 21 at a predetermined length in the extension direction, the relationship between the elongation and stress of the first elastic wire 21 (stress-strain diagram) is measured, and the stress at which the first elastic wire 21 breaks may be determined. The allowable stress σ2 of the second elastic wire 22 in the above formula (2) max is the stress at the maximum elongation of the second elastic wire 22. The allowable stress σ2 of the second elastic wire 22 max For example, after cutting out the second elastic wire 22 to a predetermined length in the extension direction, the relationship between the elongation and stress of the second elastic wire 22 is measured, and the stress at which the second elastic wire 22 breaks may be determined.

[0033] The first tensile load ratio being 1 or less means that the tensile load σ1 acting on the first elastic wire 21 is less than the allowable stress σ1 of the first elastic wire 21. maxThis means that the selected configuration of the first expandable wire 21 is smaller than the allowable stress σ2 of the second expandable wire 22. In other words, this means that the first expandable wire 21 does not break and the mechanical strength of the first expandable wire 21 is sufficient. Similarly, the second tensile load ratio being 1 or less means that the tensile load σ2 acting on the second expandable wire 22 is smaller than the allowable stress σ2 of the second expandable wire 22. max That is, if the selected configuration of the second elastic wire 22 is used, the second elastic wire 22 does not break and the mechanical strength of the second elastic wire 22 is sufficient.

[0034] By satisfying the above formulas (1) and (2), the first tensile load ratio and the second tensile load ratio are each equal to or less than 1, so that it is possible to prevent each of the first and second elastic wires 21 and 22 from breaking. In addition, by satisfying the above formulas (1) and (2), it is possible to determine the shape and material of the first and second elastic wires 21 and 22 corresponding to the displacement amount δ. Therefore, the displacement amount δ is within a range in which the stretchable device 1 does not break.

[0035] More preferably, the following formula is further satisfied. σ1≦0.80×allowable stress σ1 of the first elastic wiring 21 max σ2≦0.80×allowable stress σ2 of the second elastic wiring 22 max According to this configuration, breakage of the first elastic wire 21 and the second elastic wire 22 can be more reliably suppressed.

[0036] Even more preferably, the following formula is further satisfied: σ1≦0.50×allowable stress σ1 of the first elastic wiring 21 max σ2≦0.50×allowable stress σ2 of the second elastic wiring 22 max According to this configuration, breakage of the first elastic wire 21 and the second elastic wire 22 can be suppressed even more reliably.

[0037] (Other preferred configurations) Preferably, a connection member 40 that connects the electronic component 30 and the first elastic wire 21 is further provided, and the connection member 40 does not overlap the first end 221 in the extension direction of the second elastic wire 22 when viewed from a direction (T direction) perpendicular to the main surface 111 of the elastic base material 11. According to this configuration, for example, when the connection member 40 is solder, it is possible to suppress the thermal effect on the second elastic wire 22 when the connection member 40 is formed.

[0038] Preferably, the solder leach resistance of the first elastic wire 21 is higher than the solder leach resistance of the second elastic wire 22. Solder leach is a phenomenon in which metals in the elastic wire dissolve into solder, causing the volume of the elastic wire to decrease. According to this configuration, when the connection member 40 is solder, the connection reliability between the first elastic wire 21 and the connection member 40 can be improved.

[0039] As an example of a method for evaluating the solder leach resistance, for example, the expandable wiring is immersed in molten solder, and a graph is created showing the relationship between the immersion time and the amount of metal dissolved in the expandable wiring. Then, the greater the slope of the graph, the easier it is for solder to leach, i.e., the lower the solder leach resistance can be evaluated.

[0040] Preferably, the solubility (chemical attack) of the first elastic wire 21 in resin is smaller than the solubility (chemical attack) of the second elastic wire 22 in resin. With this configuration, even if the covering layer 50 is, for example, a potting resin and covers at least the connection portion between the electronic component 30 and the first elastic wire 21, the material of the first elastic wire 21 can be prevented from dissolving in the covering layer 50.

[0041] The solubility of the expandable wiring in the resin can be evaluated based on, for example, JIS K 7114:2001 (ISO 175:1999). In this test method, a test piece is completely immersed in a test liquid at a specified temperature for a specified time. The mass of the test piece is measured before immersion, and after removal from the test liquid and drying if necessary. It can be evaluated that the greater the change in mass, the greater the solubility in the test liquid (the greater the chemical attack).

[0042] Preferably, the length L1 in the extension direction of the first elastic wire 21 is shorter than the length L2 in the extension direction of the second elastic wire 22. According to this configuration, even if the first elastic wire 21 is harder than the second elastic wire 22, the influence on the elasticity of the stretchable device 1 can be suppressed.

[0043] Preferably, the Young's modulus (elastic modulus) of the first elastic wire 21 is greater than the Young's modulus (elastic modulus) of the second elastic wire 22. With this configuration, the first elastic wire 21 can be made harder than the second elastic wire 22. Therefore, the hardness can be softened stepwise from the end of the electronic component 30 toward the second elastic wire 22. As a result, the stress that may be concentrated in the connection portion between the electronic component 30 and the first elastic wire 21 can be further alleviated.

[0044] Preferably, the thickness t1 of the first elastic wire 21 is greater than the thickness t2 of the second elastic wire 22. With this configuration, the solder erosion resistance of the first elastic wire 21 can be further improved. In addition, the allowable stress σ1 of the first elastic wire 21 can be further improved. max Since the first tensile load ratio can be further reduced, the clearance between the electronic component 30 and the elastic base material 11 can be increased, so that the filling of the coating layer 50 into the clearance can be improved.

[0045] Preferably, the viscosity of the material of the first elastic wire 21 is greater than the viscosity of the material of the second elastic wire 22. According to this configuration, the thickness t1 of the first elastic wire 21 can be made greater than the thickness t2 of the second elastic wire 22 more reliably.

[0046] Preferably, the first stretchable wire 21 is made of a thermosetting material, the second stretchable wire 22 is made of a thermoplastic material, and the first end 221 in the extension direction of the second stretchable wire 22 is laminated on the second end 212 in the extension direction of the first stretchable wire 21. According to this configuration, even when stress is applied to the stretchable device 1, interfacial peeling between the first stretchable wire 21 and the second stretchable wire 22 can be suppressed, and the mechanical strength of the stretchable device 1 can be further improved.

[0047] [Second embodiment] Hereinafter, the stretchable device 1A according to the second embodiment will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a schematic perspective view of the stretchable device 1A. Fig. 4 is a schematic plan view partially showing the stretchable device 1A. Specifically, Fig. 4 is a view of the lower right part of the paper surface of Fig. 3 as viewed from above. The stretchable device 1A differs from the stretchable device 1 according to the first embodiment in the configurations of the electronic components, the first stretchable wiring, and the second stretchable wiring.

[0048] 3 and 4, in this embodiment, the electronic component 30A has a square prism shape. A plurality of external electrodes 32 are provided on the outer periphery of the lower surface of the electronic component 30A.

[0049] There are a plurality of first and second elastic wires 21 and 22, and there are a plurality of sets of elastic wires each composed of a first elastic wire 21 connected to the electronic component 30A and a second elastic wire 22 connected to the first elastic wire 21. Specifically, one first elastic wire 21 is connected to one external electrode 32 of the electronic component 30A, and one second elastic wire 22 is connected to the one first elastic wire 21. And there are a plurality of sets of elastic wires each composed of the one first elastic wire 21 and the one second elastic wire 22 corresponding to each external electrode 32.

[0050] According to the above configuration, since there are multiple sets of the stretchable wirings, the stress that may be concentrated at the connection portion between the electronic component 30A and the first stretchable wiring 21 can be further alleviated, and the mechanical strength of the stretchable device 1A can be further improved.

[0051] Preferably, when viewed from a direction (T direction) perpendicular to the main surface 111 of the stretchable base material 11, each of the first stretchable wires 21 in the set of multiple stretchable wires is arranged on the periphery of the electronic component 30A so as to be radial with respect to the center C of the electronic component 30A, and in two sets of stretchable wires adjacent to each other along the periphery of the electronic component 30A, the angle between the extension direction of the first stretchable wire 21 in one set of stretchable wires and the extension direction of the first stretchable wire 21 in the other set of stretchable wires is greater than 0° and less than or equal to 90°.

[0052] Specifically, as shown in Fig. 4, the first elastic wires 21 in the first elastic wire set P1, the second elastic wire set P2, and the third elastic wire set P3 are disposed on the periphery of the electronic component 30A so as to be radial with respect to the center C of the electronic component 30A. In the first elastic wire set P1 and the second elastic wire set P2 adjacent to each other along the periphery of the electronic component 30A, the angle θ1 between the extension direction of the first elastic wire 21 in the first elastic wire set P1 and the extension direction of the first elastic wire 21 in the second elastic wire set P2 is greater than 0° and less than or equal to 90°. In a set P2 of second expandable wirings and a set P3 of third expandable wirings adjacent to each other along the outer periphery of the electronic component 30A, the angle θ2 between the extension direction of the first expandable wirings 21 in the set P2 of second expandable wirings and the extension direction of the first expandable wirings 21 in the set P3 of third expandable wirings is greater than 0° and less than or equal to 90°.

[0053] In this embodiment, in the multiple second expandable wires 22 connected to the external electrode 32 provided on one side of the outer periphery of the electronic component 30A when viewed from the T direction, the extension directions of the second expandable wires 22 are parallel to each other, but may be arranged at an angle to each other.

[0054] According to the above configuration, each of the first stretchable wirings 21 in the set of the plurality of stretchable wirings is disposed on the outer periphery of the electronic component 30A so as to be radial with respect to the center C of the electronic component 30A, so that the inter-wire pitch WP can be made different from the inter-electrode pitch EP. In addition, the periphery of the electronic component 30A can be covered with the first stretchable wiring 21 which is softer than the electronic component 30A. Therefore, even if a tensile stress is applied to the stretchable device 1A, the stress which may be concentrated on the connection portion between the electronic component 30A and the first stretchable wiring 21 can be further alleviated. In addition, even if a tensile stress is applied to the stretchable device 1A from any direction, the shear deformation of the most affected portion can be reduced, and the durability of the stretchable device 1A can be improved.

[0055] Note that each embodiment is an example, and the present disclosure is not limited to each embodiment. Also, each drawing is an example of components, and does not limit the shape. Also, partial replacement or combination of configurations shown in different embodiments is possible.

[0056] In the embodiment, there are a plurality of pairs of the first expandable wiring connected to the electronic component and the second expandable wiring connected to the first expandable wiring, but it is sufficient that there is at least one pair of expandable wirings.

[0057] Example 1 The elongation with respect to stress was measured for the first and second expandable wires. FIG. 5 is a graph showing the relationship of the elongation with respect to stress for the first and second expandable wires. Graph G1 shows the results for the first expandable wire. Graph G2 shows the results for the second expandable wire.

[0058] As shown in FIG. 5, the first expandable wire broke at an elongation of about 7%. The stress at this time was about 16 MPa. That is, the allowable stress of the first expandable wire was about 16 MPa. The second expandable wire broke at an elongation of about 17%. The stress at this time was about 3 MPa. That is, the allowable stress of the second expandable wire was about 3 MPa.

[0059] The relationship between the thickness of the first expandable wire and the expansion rate until the first expandable wire breaks was measured. Fig. 6 is a graph showing the thickness dependency of the relationship between the expansion rate and resistance value of the first expandable wire.

[0060] As shown in Fig. 6, it was found that the expansion rate until breakage increases as the thickness of the first expandable wire increases. This is considered to be because the tensile load acting on the first expandable wire decreases as the thickness of the first expandable wire increases, and the first tensile load ratio decreases.

[0061] Example 2 The range of the tensile load F that the stretchable device can use without breaking was calculated. Note that the following calculation is an example, and the range of the tensile load F that the stretchable device can use without breaking may vary depending on the material and shape of the stretchable base material, the material and shape of the first and second stretchable wirings, the number and arrangement of electronic components, etc.

[0062] Assuming that the stretch rate is ε%, the tensile load F that the stretch device 1 can use without breaking is calculated by the following formula. The stretch rate ε can be defined, for example, as the ratio of the above-mentioned displacement δ to the entire length of the stretchable base material before stretching. The tensile load that the stretchable device 1 can withstand without breaking is F = E × (ε / 100) × S however, E: Combined elastic modulus (combined elastic coefficient) of the elastic base material 11, the first elastic wiring 21, and the second elastic wiring 22 S: Cross-sectional area of ​​the stretchable base material 11 in a cross section perpendicular to the stretching direction

[0063] Fig. 7 is a schematic perspective view partially showing a stretchable device 1B according to Example 2. As shown in Fig. 7, in the stretchable device 1B, a wiring / component group in which a second stretchable wiring 22, a first stretchable wiring 21, an electronic component 30, and a first stretchable wiring 21 are connected in this order is repeatedly connected along the A direction. A plurality of such repeatedly connected wiring / component groups exist in a direction perpendicular to the A direction. In Fig. 7, the stretching direction is indicated by an arrow.

[0064] The dashed line of the region AR in FIG. 7 indicates a virtual line connecting the midpoints between adjacent electronic components 30. Although the region AR is depicted as being square in FIG. 7, the region AR is not necessarily square. The center of gravity of the region AR overlaps with the electronic component 30 when viewed from the T direction. The area of ​​the region AR is the value obtained by dividing the area of ​​the entire substrate by the number of electronic components 30. When the region AR is ε EX When the material is stretched at a stretch rate of , the composite elastic modulus of this occupied range is E EX , the cross-sectional area of ​​the cross section perpendicular to the stretching direction is S EX Then, the load dF of this occupied range is calculated by the following formula. dF=EEX ×ε EX ×S EX

[0065] The area of ​​the AR region is 10 mm 2 , expansion / contraction ratio ε EX was assumed to be 20%. The elastic modulus (elastic modulus, Young's modulus) of the stretchable base material, the first stretchable wire, and the second stretchable wire in the region AR, the cross-sectional area in the cross section perpendicular to the stretching direction, the length in the stretching direction, and the composite elastic modulus are shown in Table 1. The composite elastic modulus was roughly calculated from the elastic modulus, cross-sectional area, and length of each member. The stretchable base material was assumed to be thermoplastic polyurethane (TPU). In FIG. 7, the length in the stretching direction of the first stretchable wire 21 is the sum of the length L1a and the length L1b. The length in the stretching direction of the second stretchable wire 22 is the sum of the length L2a and the length L2b. The length in the stretching direction of the stretchable base material is the sum of the length L1a, the length L1b, the length L2a, and the length L2b.

[0066] [Table 1]

[0067] Cross-sectional area S EX When is approximated as the cross-sectional area of ​​the stretchable substrate, the load dF is calculated as follows: dF=E EX ×ε EX ×S EX = 14MPa × 0.2 × (4 × 10 -1 mm 2 )=1.12N The total area of ​​the stretchable device 1B is 100 mm 2 In this case, the load is 10 times greater, so the maximum tensile load F that the stretchable device can withstand without breaking is calculated to be 10 N.

[0068] Example 3 A paste was used as the material for the first expandable wiring, and the relationship between the viscosity of the paste and the thickness of the first expandable wiring was investigated. Since the shape of the first expandable wiring is island-shaped, it can be printed using a metal mask, and a paste with thixotropy, i.e., paste viscosity, can be increased by adding a thixotropic agent can be used. The paste was printed using a metal mask to form the first expandable wiring.

[0069] FIG. 8A is a diagram showing the applied shape of paste M1 to which a thixotropic agent is not added. FIG. 8B is a diagram showing the applied shape of paste M2 to which a thixotropic agent is added. As shown in FIG. 8A, in the case of paste M1 to which a thixotropic agent is not added, the paste spreads and has a thickness of about 25 μm. As shown in FIG. 8B, in the case of paste M2 to which a thixotropic agent is added, the paste does not spread and has a thickness of about 50 μm. It was found that the thickness of the first expandable wiring can be increased in the case of paste M2 to which a thixotropic agent is added to increase the viscosity.

[0070] In addition, a sample with a first elastic wire having a thickness of 10 μm and a sample with a first elastic wire having a thickness of 50 μm were prepared. Then, for each sample, the solder thickness and the number of reflows were variously changed to evaluate the solder leaching resistance. The solder thickness was changed to 20 μm, 50 μm, 80 μm, 110 μm, and 140 μm. The number of reflows was changed to 1 time, 2 times, 3 times, 4 times, and 5 times. Solder leaching was confirmed in the sample with the first elastic wire having a thickness of 10 μm, but solder leaching was not confirmed in the sample with the first elastic wire having a thickness of 50 μm. It was found that the solder leaching resistance was improved by increasing the thickness of the first elastic wire.

[0071] Example 4 The relationship between the stacking order of the first and second stretchable wires and interfacial peeling was investigated. Specifically, it was investigated whether the behavior of interfacial peeling occurs differently when the first end of the second stretchable wire is stacked on the second end of the first stretchable wire as shown in FIG. 2 and when the second end of the first stretchable wire is stacked on the first end of the second stretchable wire. A thermosetting material was used as the material of the first stretchable wire. A thermoplastic material was used as the material of the second stretchable wire. Table 2 shows the results when the first end of the second stretchable wire is stacked on the second end of the first stretchable wire. Table 3 shows the results when the second end of the first stretchable wire is stacked on the first end of the second stretchable wire. In Tables 2 and 3, for example, a numerical value such as "0.16 N / mm" means the tensile load per unit width at the time of interfacial peeling.

[0072] [Table 2]

[0073] [Table 3]

[0074] As shown in Tables 2 and 3, when a thermosetting material was used as the material of the first stretchable wire and a thermoplastic material was used as the material of the second stretchable wire, cohesive failure occurred when the first end of the second stretchable wire was laminated on the second end of the first stretchable wire, and interfacial peeling occurred when the second end of the first stretchable wire was laminated on the first end of the second stretchable wire. Cohesive failure is a state in which the interface between the first stretchable wire and the second stretchable wire is not peeled off, but rather fracture occurs inside either the first stretchable wire or the second stretchable wire. It was found that when a thermosetting material was used as the material of the first stretchable wire and a thermoplastic material was used as the material of the second stretchable wire, interfacial peeling was suppressed and mechanical strength was improved by laminating the first end of the second stretchable wire on the second end of the first stretchable wire.

[0075] The present disclosure includes the following aspects. <1> A stretchable substrate having a main surface; An electronic component provided on the main surface of the stretchable base material; A first elastic wiring connected to the electronic component; A second elastic wire connected to the first elastic wire, A first end portion in an extension direction of the first elastic wire is connected to the electronic component, A stretchable device, wherein a second end portion in an extension direction of the first stretchable wire is connected to a first end portion in an extension direction of the second stretchable wire. <2> Satisfy the following formula: <1> The stretchable device according to claim 1 . σ1≦Allowable stress of the first elastic wiring σ2≦Allowable stress of second elastic wiring however, σ1=(δ×E1×S2×E2) / (L1×S2×E2+L2×S1×E1) σ2=(δ×E1×S1×E2) / (L2×S1×E1+L1×S2×E2) δ: Total displacement of the first stretchable wiring and the second stretchable wiring L1: Length of the first elastic wiring in the elastic direction L2: Length of the second elastic wiring in the elastic direction S1: Cross-sectional area of ​​the first elastic wiring in a cross section perpendicular to the elastic direction S2: Cross-sectional area of ​​the second elastic wiring in a cross section perpendicular to the elastic direction E1: Elastic modulus of the first elastic wiring E2: Elastic modulus of the second elastic wiring <3> Furthermore, the following formula is satisfied: <2> The stretchable device according to claim 1 . σ1≦0.80×allowable stress of first elastic wiring σ2≦0.80×allowable stress of second elastic wiring <4> Furthermore, the following formula is satisfied: <2> The stretchable device according to claim 1 . σ1≦0.50×allowable stress of first elastic wiring σ2≦0.50×allowable stress of second elastic wiring <5> Further comprising a connection member that connects the electronic component and the first elastic wiring, When viewed from a direction perpendicular to the main surface of the stretchable base material, the connection member does not overlap with a first end portion in an extension direction of the second stretchable wire. <1> from <4> 13. The stretchable device according to claim 12, <6> The first elastic wire and the second elastic wire each exist in plurality, There are a plurality of sets of stretchable wirings each composed of the first stretchable wiring connected to the electronic component and the second stretchable wiring connected to the first stretchable wiring, <1> from <5> 13. The stretchable device according to claim 12, <7> When viewed from a direction perpendicular to the main surface of the stretchable base material, each of the first stretchable wires in the set of the plurality of stretchable wires is disposed on the outer periphery of the electronic component so as to be radial with respect to the center of the electronic component; In two sets of the stretchable wiring adjacent to each other along the outer periphery of the electronic component, the angle between the extension direction of the first stretchable wiring in one set of the stretchable wiring and the extension direction of the first stretchable wiring in the other set of the stretchable wiring is greater than 0° and less than 90°. <6> The stretchable device according to claim 1 . <8> The solder leach resistance of the first elastic wiring is higher than the solder leach resistance of the second elastic wiring. <1> from <7> 13. The stretchable device according to claim 12, <9> The solubility of the first elastic wire in resin is lower than the solubility of the second elastic wire in resin. <1> from <8> 13. The stretchable device according to claim 12, <10> The length of the first expandable wire in the extension direction is shorter than the length of the second expandable wire in the extension direction. <1> from <9> 13. The stretchable device according to claim 12, <11> The Young's modulus of the first elastic wire is greater than the Young's modulus of the second elastic wire. <1> from <10> 13. The stretchable device according to claim 12, <12> The thickness of the first elastic wire is greater than the thickness of the second elastic wire. <1> from <11> 13. The stretchable device according to claim 12, <13> The viscosity of the material of the first elastic wire is greater than the viscosity of the material of the second elastic wire. <1> from <12> 13. The stretchable device according to claim 12, <14> The first elastic wire is made of a thermosetting material, The second elastic wire is made of a thermoplastic material, A first end portion in an extension direction of the second elastic wire is laminated on a second end portion in an extension direction of the first elastic wire. <1> from <13> 13. The stretchable device according to claim 12, [Explanation of symbols]

[0076] 1, 1A, 1B: Stretchable device 11: Stretchable base material 111: Main surface 21: 1st telescopic wiring 211: First end of the first elastic wiring 212: Second end of the first elastic wiring 22: 2nd telescopic wiring 221: First end of second elastic wiring 222: Second end of the second elastic wiring 30, 30A: Electronic components 31, 32: External electrode 40: Connection parts 50: Covering layer C: Center L1: Length of the first elastic wiring L2: Length of the second elastic wiring P1, P2, P3: Elastic wiring set t1: Thickness of the first elastic wiring t2: Thickness of the second elastic wiring W1: Width of the first elastic wiring W2: Width of the second elastic wiring

Claims

1. A stretchable substrate having a main surface; An electronic component provided on the main surface of the stretchable base material; A first elastic wiring connected to the electronic component; A second elastic wire connected to the first elastic wire, A first end portion in an extension direction of the first elastic wire is connected to the electronic component, A second end portion in an extension direction of the first expandable wire is connected to a first end portion in an extension direction of the second expandable wire, A stretchable device that satisfies the following formula: σ1≦Allowable stress of first elastic wiring σ2≦Allowable stress of second elastic wiring however, σ1=(δ×E1×S2×E2) / (L1×S2×E2+L2×S1×E1) σ2=(δ×E1×S1×E2) / (L2×S1×E1+L1×S2×E2) δ: Total displacement of the first elastic wire and the second elastic wire L1: Length of the first elastic wire in the elastic direction L2: Length of the second elastic wire in the elastic direction S1: Cross-sectional area of ​​the first elastic wire in a cross section perpendicular to the elastic direction S2: Cross-sectional area of ​​the second elastic wire in a cross section perpendicular to the elastic direction E1: Elastic modulus of the first elastic wiring E2: Elastic modulus of the second elastic wiring

2. The stretchable device according to claim 1 , further satisfying the following formula: σ1≦0.80×allowable stress of the first elastic wiring σ2≦0.80×allowable stress of second elastic wiring

3. The stretchable device according to claim 1 , further satisfying the following formula: σ1≦0.50×allowable stress of the first elastic wiring σ2≦0.50×allowable stress of second elastic wiring

4. Further comprising a connection member that connects the electronic component and the first elastic wiring, The stretchable device according to claim 1 , wherein the connection member does not overlap with a first end portion of the second stretchable wire in an extension direction when viewed from a direction perpendicular to the main surface of the stretchable base material.

5. There are a plurality of the first elastic wires and a plurality of the second elastic wires, The stretchable device according to claim 1, wherein there are a plurality of sets of stretchable wirings each including the first stretchable wiring connected to the electronic component and the second stretchable wiring connected to the first stretchable wiring.

6. When viewed from a direction perpendicular to the main surface of the stretchable base material, each of the first stretchable wires in the set of the plurality of stretchable wires is disposed on the outer periphery of the electronic component so as to be radial with respect to the center of the electronic component; 6. The stretchable device according to claim 5, wherein an angle between an extension direction of the first stretchable wire in one set of stretchable wires and an extension direction of the first stretchable wire in the other set of stretchable wires is greater than 0° and less than 90°.

7. The stretchable device according to claim 1 , wherein a solder leach resistance of the first stretchable wiring is higher than a solder leach resistance of the second stretchable wiring.

8. The stretchable device according to claim 1 , wherein a solubility of the first stretchable wiring in a resin is lower than a solubility of the second stretchable wiring in a resin.

9. The stretchable device according to claim 1 , wherein a length of the first stretchable wire in an extension direction is shorter than a length of the second stretchable wire in an extension direction.

10. The stretchable device according to claim 1 , wherein a Young's modulus of the first stretchable wire is greater than a Young's modulus of the second stretchable wire.

11. The stretchable device according to claim 1 , wherein a thickness of the first stretchable wire is greater than a thickness of the second stretchable wire.

12. The stretchable device according to claim 1 , wherein a viscosity of a material of the first stretchable wire is greater than a viscosity of a material of the second stretchable wire.

13. The first elastic wire is made of a thermosetting material, The second elastic wire is made of a thermoplastic material, The stretchable device according to claim 1 , wherein a first end portion in an extension direction of the second stretchable wire is stacked on a second end portion in an extension direction of the first stretchable wire.

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