阅读说明：本技术 柔性基板及可拉伸电子装置 (Flexible substrate and stretchable electronic device ) 是由 陈镇鹏 于 2020-03-25 设计创作，主要内容包括：本申请公开一种柔性基板,包括导线、基底和覆盖在导线上的封装层,其中,所述导线设置于所述基底上,由导电材料构成,其中,所述导线夹设于所述封装层和所述基底之间；所述基底上设有多个与所述导线间隔设置的孔,所述孔用于降低基底弯曲或者拉伸时所述导线与所述基底的结合面处受到的拉伸应力。本申请实还进一步公开了一种可拉伸电子装置,包括前述柔性基板。(The application discloses a flexible substrate, which comprises a lead, a substrate and an encapsulation layer covering the lead, wherein the lead is arranged on the substrate and is made of a conductive material, and the lead is clamped between the encapsulation layer and the substrate; the substrate is provided with a plurality of holes which are arranged at intervals with the lead, and the holes are used for reducing the tensile stress on the joint surface of the lead and the substrate when the substrate is bent or stretched. The application still further discloses a stretchable electronic device, which comprises the flexible substrate.)

1. A flexible substrate comprising a conductive line, a substrate, and an encapsulation layer covering the conductive line,

the lead is arranged on the substrate and made of a conductive material, wherein the lead is clamped between the packaging layer and the substrate;

the substrate is provided with a plurality of holes which are arranged at intervals with the lead, and the holes are used for reducing the tensile stress on the joint surface of the lead and the substrate when the substrate is bent or stretched.

2. The flexible substrate of claim 1, wherein the conductive traces are disposed on the substrate in a curved shape, the curved shape being a concave-convex variation along a first direction and a second direction, the first direction and the second direction being 180 °;

the hole is provided at a side convex in the first direction and at a position concave in the second direction.

3. The flexible substrate of claim 2, wherein the hole comprises a major axis and a minor axis when the hole is shaped with unequal dimensions in two perpendicular directions;

the long axis direction is parallel to a third direction which is perpendicular to the first direction and the second direction;

the long axis direction is parallel to the first direction and the second direction.

4. The flexible substrate of claim 1, wherein the shape of the hole is one or more of a pill shape, a rectangle, a circle, a triangle.

5. The flexible substrate of claim 1, wherein the type of the hole is one or both of a through hole that pierces the base, a blind hole that does not pierce the base.

6. The flexible substrate as claimed in claim 1, wherein the wire has a curved shape of U-shape, Z-shape, horseshoe shape and other single pattern or mixed pattern having equal stretching effect.

7. The flexible substrate of claim 6, wherein the conductive material constituting the conductive wire is one or more of a metal material, a carbon nanomaterial, a conductive polymer, and an ionic conductor material.

8. The flexible substrate of any one of claims 1-7, wherein a plurality of rigid islands are further disposed on the substrate, the rigid islands being disposed on the substrate at intervals, and functional devices are disposed on the rigid islands and connected to the conductive wires for receiving electrical signals transmitted through the conductive wires.

9. The flexible substrate of claim 8, wherein the elastic modulus of the rigid island is greater than the elastic modulus of the base, and the rigid island is maintained in a non-stretched state when the base and the conductive wires are in a stretched state, so that the functional devices disposed on the rigid island can work normally.

10. A stretchable electronic device comprising the flexible substrate of any one of claims 1-9.

11. A stretchable electronic device according to claim 10, characterized in that the stretchable electronic device is a flexible display device or a biomimetic camera or a stretchable catheter or a brain signal acquisition device.

Technical Field

The present application relates to the field of wire technology, and in particular, to a flexible substrate and a stretchable electronic device.

Background

The stretchable electronic device has wide application prospects in the fields of biomedicine, flexible display, intelligent wearing and the like due to the extensibility of the stretchable electronic device.

For the "island bridge" structure of the stretchable electronic devices that are currently mainstream, ductility is achieved mainly by deformation of the metal interconnection wires. However, due to the difference in the properties of the materials of the conductive wire and the encapsulation layer, the bonding strength between the conductive wire and the encapsulation layer is generally weak, and thus, the conductive wire and the encapsulation layer are easily separated from each other at the bonding surface during the stretching process, thereby reducing the performance and the service life of the stretchable electronic device.

Disclosure of Invention

In order to solve the foregoing problems, an embodiment of the present invention provides a flexible substrate and a stretchable electronic device, so as to solve the problem of interface separation occurring in the conventional stretchable electronic device due to a large stress at a joint of a conductive wire and a substrate during a stretching process.

In a first aspect, an embodiment of the present application provides a flexible substrate, including a conductive line, a substrate, and an encapsulation layer covering the conductive line, where the conductive line is disposed on the substrate and made of a conductive material, and the conductive line is sandwiched between the encapsulation layer and the substrate; the substrate is provided with a plurality of holes which are arranged at intervals with the lead, and the holes are used for reducing the tensile stress on the joint surface of the lead and the substrate when the substrate is bent or stretched.

In one embodiment, the conductive wires are disposed on the substrate in a curved shape, the curved shape is concave-convex variation along a first direction and a second direction, and the first direction and the second direction form an angle of 180 degrees; the hole is provided on a side convex in the first direction and at a position concave in the second direction. The tensile stress at the interface of the conductive material and the substrate can be reduced as much as possible by perforating the conductive material in close proximity thereto.

In one embodiment, when the hole is shaped with unequal dimensions in two perpendicular directions, the hole comprises a major axis and a minor axis; the long axis direction is parallel to a third direction which is perpendicular to the first direction and the second direction; the long axis direction is parallel to the first direction and the second direction.

In one embodiment, the shape of the aperture is one or more of a pill shape, a rectangle, a circle, a triangle. The flexible substrate with different tensile stresses in a stretching state can be designed according to different action sizes of the holes with different shapes.

In one embodiment, the type of the hole is one or both of a through hole that is punched through the substrate, a blind hole that is not punched through the substrate. The flexible substrate with different tensile stress in a stretching state can be designed according to different action sizes of different types of holes.

In one embodiment, the curved shape of the conducting wire is U-shaped, Z-shaped, horseshoe-shaped, and other single patterns or mixed patterns with equivalent stretching effects. The flexible substrate with function differentiation can be designed by arranging the patterns of the conductive material according to different patterns.

In one embodiment, the conductive material forming the conductive wire is one or more of a metal material, a carbon nanomaterial, a conductive polymer, and an ionic conductor material. The flexible substrate with more function differentiation can be designed according to the difference of the conductive performance and the tensile performance of different materials.

In an embodiment, the substrate is further provided with a plurality of rigid islands, the rigid islands are arranged on the substrate at intervals, and the rigid islands are provided with functional devices, and the functional devices are connected with the wires and used for receiving the electrical signals transmitted through the wires.

In one embodiment, the elastic modulus of the rigid island is greater than that of the stretchable substrate, so that when the stretchable substrate and the conductive wires are in a stretched state, the rigid island is still in a non-stretched state to enable functional devices disposed on the rigid island to work normally.

In a second aspect, an embodiment of the present application provides a stretchable electronic device, which includes the foregoing flexible substrate.

In one embodiment, the stretchable electronic device is a flexible display device or a bionic camera or a stretchable catheter or a brain signal acquisition device.

Compared with the prior art, in the embodiment of the application, the tensile stress of the lead and the base at the joint surface when the lead is in the stretching state is reduced by digging the hole on the base of the flexible substrate, so that the probability of separation of the joint surface of the lead and the base is reduced, and the stretching performance and the service life of the stretchable electronic device applying the flexible substrate are further improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a flexible substrate disclosed in an embodiment of the present application;

fig. 2 is a schematic structural diagram of an island bridge structure in the flexible substrate shown in fig. 1;

FIG. 3 is a schematic cross-sectional view at I-I of the flexible substrate shown in FIG. 1;

FIG. 4 is a schematic top view of the island bridge structure of FIG. 1 at one conductive line;

FIG. 5 is a normal stress diagram of the wire-substrate interface of the wire of FIG. 4 at a 25% elongation;

FIG. 6 is a schematic top view of the island bridge structure of FIG. 1 at another conductive line;

fig. 7 is a diagram of the normal stress at the wire-substrate interface of the wire of fig. 6 when a 25% elongation is achieved.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The structure and operation of the wires in the stretchable electronic device will be described in detail with reference to the accompanying drawings.

The extensible flexible inorganic electronic has certain flexibility and extensibility while keeping the functions of the traditional silicon-based electronic system, is rapidly developed and widely applied, is particularly made into a stretchable electronic device in the fields of biomedicine, intelligent wearable equipment, flexible display, health care and military, and has wide application prospect. Currently, the stretching function of stretchable electronic devices is mainly achieved by "bridges" in "island bridge structures". Wherein, the island refers to each rigid island in the stretchable electronic device, and the rigid island is provided with a functional device, such as a pixel packaging layer body in the stretchable display screen, a camera in the stretchable bionic camera, and the like; the bridge refers to a wire having a stretching effect formed by a conductive material through deformation, that is, a stretchable wire, such as a U-shaped wire, a Z-shaped wire, or the like. Therefore, in the island bridge structure, the stretchable wire is the weakest link in the stretching effect of the stretchable electronic device, and the extensibility of the stretchable electronic device under stretching deformation is the key for improving the overall extensibility and reliability of the structure.

Please refer to fig. 1, which is a schematic structural diagram of a flexible substrate according to an embodiment of the present disclosure. As shown in fig. 1, the flexible substrate 10 includes a base 11, a plurality of wires 12, a plurality of rigid islands 13, and an encapsulation layer 14 covering each wire 12.

The plurality of wires 12 and the plurality of rigid islands 13 are disposed on the substrate 11. The plurality of rigid islands 13 are disposed on the substrate 11 at intervals, and functional devices, such as a pixel encapsulation layer in a stretchable display screen, a camera in a stretchable bionic camera, etc., are disposed on the rigid islands 13. The functional devices on the rigid islands 13 are connected to the wires 12 and form a power supply circuit through the wires 12, that is, the wires 12 are disposed on the spacing areas between adjacent rigid islands 13, and the functional devices on each rigid island 13 are powered through the wires 12, so that the functional devices are independently packaged on each rigid island 13 and powered through the wires 12.

Further, the spacing region between adjacent rigid islands 13 on the substrate 11 is a stretchable region, and the conductive wires 12 are disposed on the stretchable region. Therefore, when the substrate 11 is pulled by an external force, the wires 12 disposed on the stretchable region can deform with the change of the stretchable region, so that the flexible substrate 10 has a stretchable property, during which the wires 12 continuously provide reliable electrical signals for the functional devices on the rigid islands 13. Meanwhile, since the functional devices on the rigid islands 13 are independently encapsulated and the rigid islands 13 are not changed along with the stretching of the substrate 11, the functional devices on the rigid islands 13 are not affected by an external force under the stretching condition, so that the structural stability of the functional devices and the effectiveness of the encapsulation layer can be maintained.

Specifically, the base 11 is made of an elastic material, such as low-modulus polydimethylsiloxane, elastic polyimide, polyurethane, etc., and the present embodiment is not particularly limited thereto as long as it can satisfy the stretchability required for the design of the flexible substrate 10. The rigid islands 13 are made of a material with a high elastic modulus, such as polyimide, silicone rubber with a high elastic modulus, polymethyl methacrylate, etc., but the present embodiment is not particularly limited thereto, as long as the tensile properties required for the design of the flexible substrate 10 can be satisfied.

In the embodiment of the present application, in the process of implementing the stretching function of the flexible substrate 10, because the elastic modulus at the rigid island 13 is much greater than the elastic modulus of the substrate 11, the functional device on the rigid island 13 can receive the influence of the stretching force as little as possible, and thus the functional device on the rigid island 13 can be protected, i.e., the package structure of the functional device and the elements in the package structure are prevented from being damaged when the substrate 11 is pulled, and the flexible substrate 10 can be ensured to stably work in the stretching process by continuously receiving the electrical signal through the wire 12.

Please refer to fig. 2, which is a schematic structural diagram of an island bridge structure in the flexible substrate shown in fig. 1. As shown in fig. 2, the island-bridge structure is composed of a wire 12, a rigid island 13, and an encapsulation layer 14 overlying the wire 12.

The conductive lines 12 are disposed in the spacing regions between the adjacent rigid islands 13, i.e., the stretchable regions on the substrate 11, and the conductive lines 12 are divided into row conductive lines and column conductive lines according to the distribution direction of the conductive lines on the substrate 11, wherein the row conductive lines are disposed on the substrate 11 along a first direction, the column conductive lines are disposed on the substrate 11 along a second direction, and the row conductive lines and the column conductive lines are disposed perpendicular to each other, i.e., the first direction and the second direction are perpendicular to each other.

Specifically, each wire is used to connect either the functional device anode or cathode on the rigid island 13 to provide power for proper operation of the elements within the functional device. Thus, the number of row conductors and column conductors on the substrate 11 is the same. In order to allow reliable connection of the wires 12 to the functional devices on the rigid island 13, at least part of the wires 12 extend onto the rigid island 13.

Further, wires 12 are connected to an external control chip and are used to transmit electrical signals to the functional devices on each rigid island 13 under the control of the external chip. When the row and column conductors to which the cathodes and anodes of the functional devices on rigid islands 13 are connected are energized, the functional devices begin to operate, thereby effecting control of the functional devices on each rigid island 13.

Further, the conducting wire 12 disposed on the substrate 11 may be only a single direction, such as a conducting wire applied in a stretchable catheter, or may have a plurality of conducting wires in different directions based on the difference of the substrate 11, such as a conducting wire applied in a stretchable bionic camera, which is not particularly limited in this embodiment.

Specifically, the conductive wire 12 (curved shape shown in fig. 3) includes any one or more of the following conductive materials: metal materials, carbon nanomaterials, conductive polymers, ion conductor materials, and the like. If the conductive material is a metal material, it can be a conductive wire made of metal with better conductivity, such as gold, silver, copper, aluminum, molybdenum, chromium, etc., or a metal conductive wire made of alloy metal with conductivity meeting the design requirements; if the conductive material is a metal nano material, the conductive material can be a wire made of metal nano materials such as metal nanowires, nano particles, nano sheets, nano belts and the like; if the wire is made of carbon nano-materials, the wire can be made of carbon nano-materials such as graphene, multilayer graphite, carbon nanotubes, carbon nanobelts and the like. If the conductive material is a liquid metal material, the conductive material can be a lead made of gallium-containing alloy; alternatively, the conductive material may be made of a conductive polymer, an ion conductor material, or the like, which is not particularly limited in the embodiment of the present application.

Please refer to fig. 3, which is a schematic cross-sectional view at I-I of the flexible substrate shown in fig. 1. As shown in fig. 3, the package layer 14, the wires 12 and the substrate 11 are sequentially disposed therein.

The package layer 14, the wires 12 and the substrate 11 are stacked, that is, the wires 12 are sandwiched between the package layer 14 and the substrate 11.

Specifically, unlike conventional conductive wires, the conductive wires 12 are generally patterned or curved, such as U-shaped, horseshoe-shaped, Z-shaped, etc., to improve the stretchability of the conductive wires 12. Therefore, the encapsulation layer 14 and the substrate 11 are arranged to provide protection for the wires 12 of the wires 12. The material of the encapsulation layer 14 and the substrate 11 may be the same or different elastic materials according to the requirement, such as low modulus polydimethylsiloxane, elastic polyimide, polyurethane, and the like, which is not specifically limited in this embodiment of the application.

Please refer to fig. 4, which is a schematic top view of a conductive line in the island bridge structure shown in fig. 1. As shown in fig. 4, the wires 12 in such a wire site are of U-shaped design and are sandwiched between the encapsulation layer 14 and the substrate 11.

Further, when the device is stretched, the U-shape of the U-shaped conductive line sandwiched between the encapsulation layer 14 and the substrate 11 changes according to the stretching ratio of the flexible substrate 10, thereby achieving the stretching effect and continuously providing the electrical signals for the functional devices in the rigid islands 13.

Through research, due to the difference in properties of the conductive material, the encapsulation layer and the base material, which form the conductive wires, the overall strength of the conductive wires and the base material after being bonded is generally weak, and therefore, the conductive wires and the base material are easily separated at the bonding surface during the stretching process, thereby affecting the normal operation of the flexible substrate 10.

FIG. 5 is a diagram of the normal stress at the wire-substrate interface of the wire of FIG. 4 when a 25% elongation is achieved. As shown in fig. 5, the magnitude of the tensile stress at this point is represented by the lightness of color in the image, the darker the color indicates the greater the tensile stress at this point, and the lighter the color indicates the lesser the tensile stress at this point. It can be seen that in the diagram of fig. 5, the maximum position of the tensile stress is concentrated near the position where the two semicircles are tangent, where the value of the tensile stress is 20.4MPa, and the minimum position of the tensile stress is concentrated near the inflection point position of the inner circle of the semicircles, where the value of the tensile stress is 5.5 MPa.

In the embodiment of the present application, when the stretching ratio of the wire in fig. 4 is increased to 25%, the maximum tensile stress at the position of the wire and the substrate reaches 20.4MPa, and when the flexible substrate 10 is in a stretched state for a long time, the wire 12 and the substrate 11 may be separated at the joint surface due to a large tensile stress, so that the normal operation of the flexible substrate 10 is affected.

Please refer to fig. 6, which is a schematic top view of another conductive line in the island bridge structure shown in fig. 1. As shown in fig. 6, the wires 12 of such wires are of U-shaped design in a curved shape and are sandwiched between the encapsulation layer 14 and the substrate 11. The substrate 11 is provided with a plurality of holes 15 located on the periphery of the conductive material, the plurality of holes 15 are used for reducing tensile stress applied to a joint surface of the lead 12 and the substrate 11 when the substrate 11 is in a bent or stretched state, and the holes 15 are in shapes with different sizes in the transverse and longitudinal directions.

Specifically, in the embodiment of the present application, the conductive line 12 has a curved shape that varies in a concave-convex manner along a first direction and a second direction, and the first direction and the second direction form an angle of 180 °; the hole 15 is provided on the side convex in the first direction and at a position concave in the second direction. Further, in the embodiment of the present application, when the hole 15 has a shape with unequal dimensions in two perpendicular directions, the hole 15 includes a major axis and a minor axis; the long axis direction is parallel to a third direction which is perpendicular to the first direction and the second direction; in the hole on the side of the conductive material recessed in the second direction, the long axis direction is parallel to the first direction and the second direction. In the embodiment of the application, each hole 15 is in the shape of a capsule with different sizes in the horizontal and vertical directions, and is vertically arranged on the side where the conducting wire 12 protrudes outwards; the wires 12 are transversely arranged on the inward concave side.

Further, in this embodiment of the application, the plurality of holes 15 disposed on the substrate 11 may be through holes, blind holes, or hybrid holes, where the through holes are holes punched through the substrate 11, the blind holes are holes not punched through the substrate 11, and the hybrid holes include both through holes and blind holes, which is not specifically limited in this embodiment of the application.

Specifically, in the embodiment of the present application, the holes disposed on the substrate 11 may be rectangular, circular, or other hole shapes capable of playing a same role, or may be a mixture of a plurality of different hole shapes, besides the pill shape shown in fig. 6, which is not specifically limited in the embodiment of the present application.

Further, in the embodiment of the present application, the holes disposed on the substrate 11 may be punched at random positions or disposed according to different pattern shapes of the conductive wires 12, in addition to the arrangement of the positions of the holes shown in fig. 6, which is not specifically limited in the embodiment of the present application.

Further, in the embodiment of the present application, the arrangement pattern or the curve shape of the conductive wires 12 may be a Z-shape, a horseshoe-shape, or other single pattern or mixed pattern with equal stretching effect, besides the U-shape shown in fig. 6, which is not specifically limited in the embodiment of the present application.

Optionally, in this embodiment of the application, in addition to the plurality of holes 15 disposed on the substrate 11, a hole may also be dug in the encapsulation layer 14, and the hole disposed on the encapsulation layer 14 may be a through hole or a blind hole, which is not specifically limited in this embodiment of the application. Further, the holes disposed on the packaging layer 14 may be rectangular, circular, triangular or other holes that can play a role in a similar way to the pill shape shown in fig. 6, which is not specifically limited in the embodiments of the present application.

FIG. 7 is a diagram of the normal stress at the wire-substrate interface of the wire of FIG. 6 when a 25% elongation is achieved. As shown in fig. 7, the magnitude of the tensile stress at this point is represented by the lightness of color in the image, the darker the color indicates the greater the tensile stress at this point, and the lighter the color indicates the lesser the tensile stress at this point. It can be seen that the maximum tensile stress position in the diagram of fig. 7 is still concentrated near the position where the two semicircles are tangent, where the tensile stress value is 10.7MPa, and the tensile stress at several positions drops to 0 MPa.

In the embodiment of the present application, when the elongation of the wire in fig. 6 is increased to 25%, the maximum tensile stress at the position of the wire 12 and the substrate 11 reaches only 10.7MPa, and the maximum tensile stress is reduced by nearly 50% compared with the structure at the position of the wire shown in fig. 4. Therefore, when the flexible substrate 10 to which the lead structure shown in fig. 6 is applied is in a stretched state, the probability that the bonding surface of the flexible substrate 10 is separated can be reduced due to the small tensile stress existing between the lead 12 and the base 11, and the tensile property and the service life of the flexible substrate 10 are improved.

Further, in the embodiment of the present application, the conductive line shown in fig. 6 may be fabricated by a template method, an etching method, or a local hydrophobic treatment.

Specifically, the template method is to pour a solution on a mold and then add a thermal evaporation solvent, so as to realize a packaging layer of the wire. Therefore, the present proposal can be realized only by making a mold having a pattern at the lead as shown in fig. 6.

Specifically, the etching method is to fabricate a complete substrate, and then form a specific pattern at the conducting wire position as shown in fig. 6 by etching, so as to implement the present disclosure.

Specifically, the partial hydrophobic treatment is to inject a hydrophobic treatment solution to the surface of a specific position of a mold by using a micro-capillary injector, so as to obtain a mold with controllable partial hydrophobic property, and then the mold with the pattern at the conducting wire as shown in fig. 6 can be manufactured, so that the proposal can be realized.

Compared with the prior art, in the embodiment of the application, the tensile stress at the joint surface of the lead 12 and the base 11 when the lead 12 is in the tensile state is reduced by digging a hole on the base of the lead, so that the probability of separation of the joint surface of the conductive material and the base is reduced, and the tensile property and the service life of the flexible substrate using the lead are further improved.

The flexible substrate and the stretchable electronic device disclosed in the embodiments of the present application are described in detail above, and the principles and embodiments of the present application are explained herein by applying specific examples, and the above description of the embodiments is only used to help understand the method and the core ideas of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.