JP2024030661A - Wire-like circuit board, device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire-like circuit board which is appropriate to be applied to a stretchable device and has flexibility, a device and a manufacturing method thereof.

SOLUTION: A circuit board is configured by winding a thin film substrate to which a circuit layer consisting of a thin film covering an elastic body film and including a conductive circuit portion is applied, swell is formed on a surface of the circuit layer in a length direction in such a manner that the swell is flattened when the circuit board is stretched in the length direction, and a device using the circuit board is also provided. A manufacturing method of the circuit board includes the steps of: applying a load so as to separate opposed two short sides of the rectangular elastic body film from each other while restricting them in a width direction and performing elastic deformation in a uniaxial direction; applying the circuit layer consisting of the conductive thin film while covering the elastic body film; and forming the swell on the surface of the circuit layer in the uniaxial direction by cancelling the load, and performing winding in mutually reverse directions from two long sides of the elastic body film.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a stretchable wire-shaped circuit board, a device, and a method for manufacturing the same.

Electronic devices that can be comfortably worn on the body are required for health monitoring and sensory sharing systems, and the central circuitry of these devices is required to be highly functional, compact, and lightweight.

For example, Patent Document 1 discloses a spiral circuit device in which a circuit layer is formed on a sheet material and then spirally wound. The spirally wound circuit is extremely advantageous in terms of volume and weight characteristics compared to conventional circuits, and can be applied to smaller, lighter, and more multifunctional circuit devices in aerospace technology and the like.

Special Publication No. 2006-527484

In order to use the above-described spiral circuit device in a wearable device, a degree of freedom in deformation is required, and in particular, stretchability in the direction of the winding axis (lengthwise direction) is required. In addition, in order to process a deformable spiral circuit device into a thinner wire shape, it is also necessary to limit the use of adhesives to bond between spiral layers as much as possible, which increases the volume and weight of the spiral circuit device. .

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a stretchable wire-shaped circuit board and device suitable for application to stretchable devices, and the manufacture thereof. The purpose is to provide a method.

The circuit board according to the present invention is a wire-shaped circuit board having stretchability, and is wound with a thin film board provided with a circuit layer made of a thin film covering an elastic film and having a conductive circuit portion. The circuit layer is characterized in that undulations are formed on the surface of the circuit layer along the longitudinal direction, and the undulations are flattened when stretched in the longitudinal direction. According to this feature, it is possible to have stretchability in the direction of the winding axis (lengthwise direction) without sacrificing its small size and light weight, and is suitable for application to stretchable devices.

Further, the device according to the present invention is a device using a stretchable wire-shaped circuit board, in which a functional element is placed on a circuit layer made of a thin film covering an elastic film and having a conductive circuit portion. The applied thin film substrate is wound, and undulations are formed on the surface of the circuit layer along the longitudinal direction, and the undulations are flattened when stretched in the longitudinal direction. According to this feature, it is possible to have stretchability in the direction of the winding axis (lengthwise direction) without sacrificing its small size and light weight, and is suitable for application to stretchable devices.

The above-described invention may be characterized by including two parallel winding portions wound in opposite directions from two opposite sides of the rectangular elastic membrane. According to this feature, the circuit density can be increased and it is suitable for application to stretchable devices.

Furthermore, the method for manufacturing a circuit board according to the present invention is a method for manufacturing a wire-shaped circuit board having stretchability, in which two opposing short sides of a rectangular elastic film are restrained in the width direction and spaced apart from each other. a step of applying a load to elastically deform the elastic film in a uniaxial direction; a step of applying a circuit layer made of a conductive thin film to cover the elastic film; and a step of releasing the load and deforming the elastic film along the uniaxial direction. The method is characterized in that it includes the steps of forming undulations on the surface of the circuit layer and winding the elastic film from two long sides in opposite directions. According to these characteristics, it is possible to easily obtain a circuit board that is stretchable in the direction of the winding axis (lengthwise direction) without sacrificing its small size and light weight, and is suitable for application to stretchable devices. It is.

FIG. 1 is a perspective view of a wire-shaped circuit board as an embodiment of the present invention. FIG. 3 is a perspective view showing a cross section along the longitudinal direction of the same circuit board. It is an enlarged view of the same cross section. FIG. 3 is a perspective view showing steps of a first method for manufacturing a circuit board. It is a perspective view which shows the process of the 2nd manufacturing method of a circuit board. It is a photograph which shows the process of the 3rd manufacturing method of a circuit board. FIG. 3 is a perspective view showing dimension symbols of a circuit board in a manufacturing test. It is a graph showing whether a scroll shape is formed or not depending on the initial length and width in the first manufacturing test. It is a list of the manufacturing conditions and the scroll width of the obtained circuit board in the second manufacturing test.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A wire-shaped circuit board, a device using the same, and a method for manufacturing the same, which is one embodiment of the present invention, will be described below with reference to FIGS. 1 to 6.

As shown in FIG. 1, the circuit board 1 has a wire shape as a whole by winding the thin film substrate 2 around a winding axis extending in the longitudinal direction. In this embodiment, there are two winding axes A1 and A2, thereby forming two parallel winding portions R1 and R2.

Referring to FIG. 2 and FIG. 3(a) together, the winding portions R1 and R2 are multilayer bodies formed by the thin film substrate 2, and the inner surface of each layer has undulations 3 along the winding axes A1 and A2. is formed. In other words, the undulations 3 are formed such that the ridges 3a and valleys 3b thereof revolve around the winding axes A1 and A2 on a plane perpendicular to the winding axes A1 and A2. The thin film substrate 2 has a two-layer structure including an elastic film 5 and a circuit layer 4 covering the elastic film 5. The circuit layer 4 is formed by a thin film having a conductive circuit portion.

Here, as shown in FIG. 3(b), when the circuit board 1 is stretched in the longitudinal direction (in the left-right direction on the paper), the undulations 3 are flattened and the height difference between the ridges 3a and valleys 3b is reduced. Further, when the stretching force is released, the circuit board 1 returns to the shape with a large difference in height of the undulations 3 as shown in FIG. 2A due to the elasticity of the elastic film 5.

In other words, even though the circuit layer 4 does not have excellent elasticity like the elastic film 5, it forms the undulations 3 along the longitudinal direction, so that the undulations 3 are suppressed when stretched in the longitudinal direction. It can be followed by flattening. Therefore, the circuit board 1 can be stretched by applying a load in the longitudinal direction, and can be returned to its original shape by releasing the load. For example, the wire-shaped circuit board 1 can be made into stretchable wiring.

Moreover, the circuit board 1 can be made into a stretchable device such as a bend detection device, a photovoltaic device, a light emitting device, etc. by incorporating necessary functional elements with the circuit layer 4 having a predetermined configuration.

For example, the material used for the conductive circuit portion of the circuit layer 4 is required to be able to follow the deformation of the thin film substrate 2. For example, when constructing a pressure sensor as a device using the circuit board 1, a conductive polymer material such as PEDOT:PSS, which is a polythiophene-based conductive polymer, is suitably used. In addition, conductive polymer materials, luminescent elastic materials, organic luminescent materials, and the like may be used in the case of making a light emitting element. Furthermore, in the case of stretchable wiring, a liquid metal material or the like may be used. Furthermore, in the case of a photovoltaic device, applications of conductive polymer materials, gold, organic semiconductor materials for organic thin film solar cells such as P3HT/PCBM, and liquid metal materials are considered.

Next, a method for manufacturing such a circuit board 1 will be explained.

[First manufacturing method]
As shown in FIG. 4(a), first, a rectangular elastic membrane 5 is prepared, and both ends in the longitudinal direction are fixed with jigs 11 so that the two opposing short sides are restrained in the width direction. do. As the elastic film 5, for example, a silicone elastomer such as PDMS (polydimethylsiloxane) can be suitably used.

As shown in FIG. 5B, while restraining the short sides of the elastic membrane 5 in the width direction with the jig 11, a load is applied to separate the two jigs 11 from each other, and the elastic membrane 5 is It is elastically deformed so as to be stretched in a uniaxial direction (elastic deformation step). Then, the circuit layer 4 is applied so as to cover the elastic film 5 while maintaining its elastic deformation (circuit layer application step). The circuit layer 4 is a film body that can form the undulations 3 due to its flexibility, and is, for example, a conductive thin film in which a conductive circuit portion is added to an insulating film such as Parylene (registered trademark) or fluororesin. be. A thin film substrate 2 is obtained by applying a circuit layer 4 to an elastic film 5. Note that, before forming the circuit layer 4, it is preferable to apply O ₂ plasma or the like to improve the bondability between each layer. When the circuit layer 4 is made into a multilayer structure, it is also preferable to perform plasma treatment in the same manner.

As shown in FIG. 5C, the load applied to the jig 11 is maintained while the load applied to the jig 11 is released as shown in FIG. Then, winding portions R1 and R2 are formed in the central portion of the thin film substrate 2 in the longitudinal direction that is not restrained by the jig 11. The winding portions R1 and R2 are wound in opposite directions from two opposite sides (long sides) of the rectangular elastic film 5 so that the elastic film 5 of the thin film substrate 2 faces outside. Hereinafter, the shape including the winding portions wound in opposite directions from the two long sides will be referred to as a "scroll shape". Furthermore, undulations 3 are formed on the surface of the circuit layer 4 along the long sides of the elastic film 5 . In this way, the circuit board 1 can be obtained. Note that by cutting in the longitudinal direction between the winding parts R1 and R2, a wire-shaped circuit board having one winding part can also be obtained.

In such a manufacturing method, the amount of stretching depends on the elastic limit of the elastic membrane 5, so it can be relatively large, and the conditions for forming the wound portion can be easily adjusted.

Note that, as shown in FIG. 2(d), when a load is applied in the direction of separating the two jigs 11 from each other from a state where no load is applied to the jigs 11, the restraint of the short sides by the jigs 11 is reduced. Therefore, the winding portions R1 and R1 are spread out to make the entire thin film substrate 2 flat, as shown in FIG. Moreover, the undulations 3 become smaller and disappear when a sufficient load is applied.

[Second manufacturing method]
As shown in FIG. 5, the circuit board 1 having a scroll shape can also be obtained by other manufacturing methods.

First, as shown in FIG. 3A, a pre-stretched thin film substrate 2' is prepared, on which a pre-stretched circuit layer 4' is provided so as to cover the rectangular elastic film 5. At this time, no load is applied to the elastic membrane 5. Then, similarly to the first manufacturing method, both ends in the longitudinal direction are fixed with jigs 11 so that the two opposing short sides of the rectangular pre-stretched thin film substrate 2' are restrained in the width direction.

Next, as shown in FIG. 2B, while restraining the short sides of the unstretched thin film substrate 2' in the width direction with the jig 11, a load is applied so as to separate the two jigs 11 from each other. A thin film substrate 2 is obtained by deforming the thin film substrate 2' so as to stretch it in one longitudinal direction. At this time, the elastic membrane 5 undergoes elastic deformation, and the unstretched circuit layer 4' is expanded by plastic deformation to become the circuit layer 4. The pre-stretched circuit layer 4' has dimensions such that it becomes the circuit layer 4 when stretched, and is formed using a material that can maintain its thin film shape even when plastically deformed. As a material for the unstretched circuit layer 4', for example, parylene can be suitably used. Furthermore, the material used for the conductive circuit portion of the unstretched circuit layer 4' is required to be able to follow the deformation of the unstretched thin film substrate 2'. For example, the above-mentioned conductive polymer materials, luminescent elastic materials, organic luminescent materials, liquid metal materials, gold, organic semiconductor materials, and the like can be suitably used.

Finally, as shown in FIG. 3C, when the load applied to the jig 11 is released, winding portions R1 and R2 are formed in the longitudinal center portion of the thin film substrate 2 that is not restrained by the jig 11. . The winding portions R1 and R2 are wound in opposite directions from the opposite two sides (long sides) of the rectangular elastic film 5 so that the elastic film 5 of the thin film substrate 2 faces outward, forming a scroll shape. obtain. Furthermore, undulations 3 are formed on the surface of the circuit layer 4 along the long sides of the elastic film 5 . In this way, the circuit board 1 can be obtained.

Furthermore, when a load is applied in a direction that separates the two jigs 11 from each other from a state where no load is applied to the jig 11, as shown in FIG. 2(c), as shown in FIG. , the thin film substrate 2 is stretched. At this time, since the short sides are restrained by the jig 11, the wound portions R1 and R1 are expanded to make the entire thin film substrate 2 flat. Moreover, the undulations 3 become smaller and disappear when a sufficient load is applied.

In this manufacturing direction, the amount of plastic deformation depends on the plastic deformability of the unstretched circuit layer 4', and therefore tends to be smaller than in the first manufacturing method described above. On the other hand, when applying the unstretched circuit layer 4', no load is required on the jig 11, and manufacturing is easy.

[Third manufacturing method]
As shown in FIG. 6, it is also possible to manufacture a circuit board 1 having a length exceeding 1 m, for example.

First, as shown in FIG. 3A, a release agent is deposited on the surface of a disc-shaped base, and a pre-stretched thin film substrate 2' is deposited thereon in the same manner as in the second manufacturing method. Furthermore, a spiral cut was made in the pre-stretched thin film substrate 2'.

Here, a silicon wafer with a diameter of 8 inches was used as a base, and Cytop 809M was used as a release agent to form a film by spin coating. Further, as the elastic film 5 of the pre-stretched thin film substrate 2', the main ingredient of Sylgard 184 and a curing agent were mixed at a ratio of 5:1, and the mixture was coated to a thickness of about 50 μm and cured. Furthermore, Parylene C was formed into a film with a thickness of 4 μm as the unstretched circuit layer 4' of the unstretched thin film substrate 2'. Further, the width of the spiral cut was approximately 5 mm.

Next, as shown in FIG. 4B, a part of the unstretched thin film substrate 2' is peeled off from the outer circumferential side, and a tensile load is applied to stretch it. When the load on the stretched portion is released, winding portions R1 and R2 are formed on the thin film substrate 2 at the peeled and stretched portion, resulting in a circuit board 1 having a scroll shape. Here, a length of about 3 cm of the unstretched thin film substrate 2' was peeled off, stretched to a length of about 5 cm to form the thin film substrate 2, and the load was released.

Furthermore, as shown in FIG. 2(c), peeling and stretching were sequentially and repeatedly performed from the outside of the spiral to obtain a circuit board 1 having a long continuous scroll shape.

As described above, by the structure in which the thin film substrate 2 is wound, it is possible to obtain the circuit board 1 which can be stretchable in the direction of the winding axis (lengthwise direction) without impairing its small size and light weight. Moreover, since such a circuit board 1 is wire-shaped and has stretchability in the length direction, it is suitable for application to a stretchable device and can be obtained relatively easily.

Next, the results of actually manufacturing a circuit board using the second manufacturing method described above will be explained using FIGS. 7 to 9.

[First manufacturing test]
It was confirmed under a plurality of manufacturing conditions whether a wire-shaped circuit board 1 having a scroll shape could be obtained when the thin film substrate 2 was manufactured by a manufacturing method similar to the second manufacturing method described above.

First, as shown in FIG. 7, a rectangular unstretched thin film substrate 2' having an initial length L and a width W between the jigs 11 was prepared. That is, both short sides of the unstretched thin film substrate 2' provided with the elastic film 5 and the unstretched circuit layer 4' covering the elastic film 5 were restrained by the jig 11. The elastic film 5 was formed to a thickness of 55 μm using Sylgard (registered trademark) 184 Erastomer kit (manufactured by The Dow Chemical Company) by mixing the main agent and curing agent at a ratio of 5:1. I got it. The pre-stretched circuit layer 4' was obtained by forming Parylene C (PARYLENE is a registered trademark) on the elastic film 5 to a thickness of 4 μm.

Next, a load is applied to separate the two jigs 11 from each other, and the unstretched thin film substrate 2' is stretched until the distance between the jigs 11 becomes 1.8 times the initial length L. The front circuit layer 4' was plastically deformed to obtain a thin film substrate 2 (see FIG. 5(b)). Furthermore, the load that caused the jigs 11 to be spaced apart was released, and it was observed whether the thin film substrate 2 took on a scroll shape.

FIG. 8 shows the observed results. Here, "〇" indicates that a scroll shape was obtained, and "x" indicates that a scroll shape was not obtained. It can be seen that there is a condition for the combination of width and initial length that provides a scroll shape.

[Second manufacturing test]
When a circuit board 1 having a scroll shape was manufactured by a manufacturing method similar to the second manufacturing method described above, the width of the scroll-shaped portion (scroll width) was measured.

FIG. 9 shows the thickness of the elastic membrane 5, the thickness of the unstretched circuit layer 4', the length and width of the unstretched thin film substrate 2', and the ratio (maximum strain) at which the unstretched thin film substrate 2' is stretched. The scroll width when changed is shown. Note that the maximum strain ε indicates that the initial length L is expanded until the total length becomes L×(1+ε/100%). For example, when the maximum strain ε is 100%, the initial length L is set to 2×L when expanded.

No. For Nos. 1 to 27, the following conditions were used. The elastic film 5 was prepared by mixing the Sylgard 184 Erastomer kit at a ratio of 5:1 of base material and curing agent, and had a Young's modulus of 1.37 MPa. Further, as the pre-stretched circuit layer 4', Parylene C was used with a thickness of 4 μm as described above. Note that the Young's modulus of the unstretched circuit layer 4' is 1.8 GPa.

No. 28 and 29 are examples in which the elastic membrane 5 is made of a mixed material and the pre-stretched thin film substrate 2' is made into a multilayer structure. The elastic film 5 was prepared by mixing the base agent (a) and curing agent (b) of Sylgard 184 Erastomer kit with the A agent (c) and B agent (d) of Ecoflex 00-30 (manufactured by Smoothon). The mixing ratio was (a):(b):(c):(d)=40:1:82:82. Note that Young's modulus was 86 kPa. In addition, the thin film substrate 2' before stretching has a four-layer structure of Parylene C → diX-SR (diX is a registered trademark: manufactured by KISCO Corporation) → Parylene C → Cytop 809M (Cytop is a registered trademark: manufactured by AGC Chemicals Company). did. Both Parylene layers had a thickness of 0.2 μm and a Young's modulus of 1.8 GPa. diX-SR is No. No. 28 has a thickness of 1 μm. In No. 29, the thickness was 0.8 μm, and the Young's modulus was 4.0 GPa. Cytop 809M had a thickness of 0.3 μm and a Young's modulus of 1.3 GPa.

As shown in these figures, the circuit board 1 having a scroll shape could be manufactured under various conditions. The scroll width tended to become smaller as the thickness of the unstretched thin film substrate was smaller, the width W of the unstretched thin film substrate was smaller, and the maximum strain ε was larger.

Although embodiments according to the present invention and modifications based thereon have been described above, the present invention is not necessarily limited thereto, and those skilled in the art will be able to understand that it deviates from the gist of the present invention or the scope of the appended claims. Various alternative embodiments and modifications may be found without having to do so.

1 Circuit board 2 Thin film board 2' Thin film board before stretching 3 Waviness 4 Circuit layer 4' Circuit layer before stretching 5 Elastic film 11 Jig R1, R2 Winding part

Claims (5)

A wire-shaped circuit board having stretchability,
A thin film substrate provided with a circuit layer made of a thin film having a conductive circuit portion covering an elastic film is wound, and undulations are formed on the surface of the circuit layer along the longitudinal direction. A wire-shaped circuit board characterized in that the undulations become flat when stretched in a direction. 2. The wire-shaped circuit board according to claim 1, further comprising two parallel winding portions wound in opposite directions from two opposite sides of the rectangular elastic film. A device using a stretchable wire-shaped circuit board,
A thin film substrate provided with a functional element is wound on a circuit layer consisting of a thin film covering an elastic film and having a conductive circuit portion, and the surface of the circuit layer is undulated along the longitudinal direction. A device using a wire-shaped circuit board, characterized in that the undulations are flattened when stretched in the longitudinal direction. 4. The device according to claim 3, comprising two parallel winding portions wound in opposite directions from two opposing sides of the rectangular thin film substrate. A method for manufacturing a wire-shaped circuit board having stretchability, the method comprising:
applying a load so as to constrain two opposing short sides of the rectangular elastic membrane in the width direction and separating them from each other, thereby elastically deforming the rectangular elastic membrane in a uniaxial direction;
applying a circuit layer made of a conductive thin film to cover the elastic film;
A wire characterized in that it includes the step of releasing the load to form undulations on the surface of the circuit layer along the uniaxial direction, and winding the elastic film from two long sides in opposite directions. A method of manufacturing a circuit board.