Anisotropic conductive elastic material containing conductive balls and a method for producing the same

Abstract

The present invention relates to a stretchable anisotropic conductive film containing conductive balls and a method for manufacturing the same. The stretchable anisotropic conductive film according to the present invention includes a stretchable base material and conductive balls inserted and aligned in the stretchable base material.

Description

Technical Field

[0001] The present invention relates to a stretchable anisotropic conductive film containing conductive balls and a method for manufacturing the same.

Background Art

[0002] Recently, with the development of stretchable electrodes and device structures, stretchable electronic devices have evolved into high-resolution integrated circuits. When applying the electrical interfaces used in existing electronic devices to the interfaces between stretchable devices, problems such as peeling and cracking occur. To solve this problem, research has been conducted on ACF (Anisotropic Conductive Film) having electrical conductivity in the thickness direction.

[0003] In order to form a stable interface between stretchable devices and avoid technical defects, the adhesive layer of ACF requires high toughness and stable adhesive force. However, the conventional adhesive layer of ACF does not have sufficient toughness or adhesive force. In addition, the particles responsible for conductivity are irregularly arranged in the adhesive layer, making it difficult to form a high-resolution electrical interface between circuits having fine intervals and widths. In order to form a connection between devices, high pressure, temperature, and time are required. Therefore, it is necessary to develop an ACF that solves such problems and is excellent in both stretchability and conductivity.

[0004] The background art described above is what the inventor retained or acquired in the process of deriving the disclosure of this specification, and it cannot necessarily be said to be publicly known technology that was publicly disclosed to the general public before this application.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to solve the above-described problems, the present invention provides a stretchable anisotropic conductive film that can be manufactured quickly and easily at low temperature and low pressure, and a method for manufacturing the same.

[0006] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those of ordinary skill in the art from the following description.

Means for Solving the Problems

[0007] The stretchable anisotropic conductive film according to the present invention includes a stretchable base material and conductive balls inserted and aligned in the stretchable base material.

[0008] The stretchable base material according to one embodiment can include a heat-firable rubber grafted with maleic anhydride containing at least any one heat-firable rubber selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS), styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), polyurethane (PU)-based rubber, and polyolefin (PO)-based rubber.

[0009] The conductive ball according to one embodiment includes at least any one particle selected from the group consisting of PS (Polystyrene), PU (Polyurethane), PE (Polyethylene), PP (Polypropylene), PB (Polybutylene), Nylon, and styrene-divinyl benzene, and the particle can be coated with at least any one selected from the group consisting of gold (Au), nickel (Ni), silver (Ag), copper (Cu), aluminum (Al), palladium (Pd), chromium (Cr), titanium (Ti), tin (Sn), and molybdenum (Mo).

[0010] The diameter of the conductive ball according to one embodiment is 1 μm to 100 μm, the interval between the conductive balls is 1 μm to 100 μm, the pitch is 2 μm to 200 μm, and the diameter of the conductive ball and the interval between the conductive balls may be 2:1 to 1:2.

[0011] The thickness of the stretchable base material according to one embodiment may be 40% to 70% of the diameter of the conductive ball.

[0012] The stretchable base material according to one embodiment has a constant overall physical property, and the conductive balls are inserted and aligned in a direction perpendicular to the surface of the stretchable anisotropic conductive film so that both surfaces of the stretchable anisotropic conductive film are energized, and 30% to 60% of the external surface can be exposed outside the stretchable base material.

[0013] The method for manufacturing a stretchable anisotropic conductive film according to the present invention includes a step of manufacturing a mold patterned with a pattern including recesses, a step of arranging conductive balls on the mold, a step of coating a stretchable base material on the mold on which the conductive balls are arranged, and a step of removing the mold.

[0014] The step of manufacturing the mold according to one embodiment can be performed by a photolithography, nanoimprint, soft lithography, block copolymer lithography, or capillary lithography process.

[0015] The step of manufacturing the mold according to one embodiment includes a step of preparing a UV curable polymer, a step of positioning a photomask on the UV curable polymer and irradiating with UV for patterning, and a step of washing the patterned UV curable polymer to obtain a patterned mold, and the UV curable polymer can include at least any one selected from the group consisting of PEG-DA (Polyethylene glycol diacrylate), epoxy acrylate, polyester acrylate, polyurethane acrylate, and silicone acrylate.

[0016] The step of irradiating UV for patterning according to an embodiment is patterned with a hard gel in which the UV curable polymer is cured and a soft gel that is not cured, and the soft gel forms the concave portion, and the depth of the concave portion may be 10% to 30% of the diameter of the conductive ball.

[0017] The step of irradiating UV for patterning according to an embodiment irradiates UV for 1 second to 10 seconds, the distance between the UV curable polymer and the UV light source is 8 cm to 16 cm, and the UV intensity is 2 mW / cm 2 ~20 mW / cm 2 and may be.

[0018] The step of disposing the conductive ball according to an embodiment rubs the conductive ball on the mold, the conductive ball adheres to the concave portion, and the adhesive force of the concave portion may be 1 nN to 90 nN.

[0019] The step of air blowing can be further included after the step of disposing the conductive ball according to an embodiment.

[0020] The step of removing the mold according to an embodiment peels off the stretchable base material, and the stretchable base material can be inserted with the conductive balls and aligned.

Effects of the Invention

[0021] The present invention can provide a stretchable anisotropic conductive film manufactured quickly and simply at low temperature and low pressure and a manufacturing method thereof.

[0022] Specifically, the manufacturing method of the stretchable anisotropic conductive film according to the present invention can provide a quick and simple manufacturing method of a stretchable anisotropic conductive film that does not require a thermocompression bonding process such as high temperature and pressure. In addition, the size and interval of a desired pattern can be set to arrange particles in various forms, and conductive balls of various sizes can be used for manufacturing a stretchable anisotropic conductive film without designing a new mold.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0024] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, various changes may be made to the embodiments, and the scope of the patent application is not limited or restricted by such embodiments. It should be understood that all changes, equivalents, or alternatives to the embodiments are included in the scope of the rights.

[0025] The terms used in the embodiments are for illustrative purposes only and are not to be construed as intended to limit. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "including" or "having" indicate the presence of the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should not be construed as precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0026] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the technical field to which this embodiment belongs. Commonly used pre-defined terms should be interpreted as having a meaning consistent with their meaning in the context of the related art, and should not be interpreted in an ideal or overly formal sense unless clearly defined herein.

[0027] Also, in the description with reference to the accompanying drawings, regardless of the reference numerals in the drawings, the same components are given the same reference numerals, and duplicate descriptions thereof are omitted. In the description of the embodiments, when it is determined that a specific description of related known technologies would unnecessarily obscure the gist of the embodiments, the detailed description thereof is omitted. Also, in describing the components of the embodiments, terms such as first, second, A, B, (a), (b), etc. can be used. These terms are for distinguishing the components from other components, and do not limit the essence, order, or sequence of the components. When it is mentioned that any component is "connected", "coupled", or "joined" to another component, it should be understood that the component is directly connected or joined to the other component, but there may be additional components "connected", "coupled", or "joined" between each component.

[0028] Components that include functions common to the components included in any of the embodiments will be described using the same names in other embodiments. Unless otherwise stated, the descriptions provided in any of the embodiments will also apply to other embodiments, and specific descriptions within overlapping ranges will be omitted.

[0029] Hereinafter, the stretchable anisotropic conductive film of the present invention and its manufacturing method will be specifically described with reference to embodiments and drawings. However, the present invention is not limited to these embodiments and drawings.

[0030] The stretchable anisotropic conductive film according to the present invention includes a stretchable base material; and conductive balls inserted and aligned within the stretchable base material.

[0031] The stretchable anisotropic conductive film (S-ACF) according to the present invention is excellent in stretchability, that is, elasticity, and is suitable for flexible electronic devices by changing together with the deformation of the substrate. It has excellent adhesion and is applicable to electronic devices, can firmly bond the interfaces of different members to each other, includes regularly arranged conductive balls, can maintain uniform and constant conductivity, and can freely control the regions where the conductive balls are arranged, so it can be utilized in various fields.

[0032] FIG. 1 is a schematic diagram of a stretchable anisotropic conductive film according to an embodiment of the present invention. Referring to FIG. 1, the conductive balls 10 are inserted and aligned within the stretchable base material 20, and an electric current flows vertically through the exposed portions of the conductive balls 10, providing a stretchable anisotropic conductive film 100 with a vertical conduction path where no electric current flows horizontally due to the non-conductive stretchable base material 20.

[0033] According to one embodiment, the stretchable substrate can include a heat-firable rubber grafted with maleic anhydride, which includes at least any one heat-firable rubber selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS), styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), polyurethane (PU)-based rubber, and polyolefin (PO)-based rubber.

[0034] The stretchable substrate has excellent elasticity, a high elongation rate, and low conductivity, and can form a stretchable anisotropic conductive film so that electricity flows only at desired positions.

[0035] The heat-firable rubber grafted with maleic anhydride is excellent in flexibility and elasticity and is suitable as a material for the stretchable substrate. The heat-firable rubber grafted with maleic anhydride can form a chemical bond with other members such as a target substrate to form a stable adhesion even at low temperature and low pressure. The heat-firable rubber may preferably be styrene-ethylene-butylene-styrene, but is not limited to those listed above.

[0036] The maleic anhydride may be 1% by weight or more of the heat-firable rubber. When maleic anhydride is included in the content within the above range, there is an effect of providing a sufficient number of bond-forming sites compared to the adhesion area.

[0037] According to one embodiment, the conductive ball includes at least any one particle selected from the group consisting of PS (Polystyrene), PU (Polyurethane), PE (Polyethylene), PP (Polypropylene), PB (Polybutylene), Nylon, and styrene-divinyl benzene, and the particle may be coated with at least any one selected from the group consisting of gold (Au), nickel (Ni), silver (Ag), copper (Cu), aluminum (Al), palladium (Pd), chromium (Cr), titanium (Ti), tin (Sn), and molybdenum (Mo).

[0038] The conductive balls can form a stretchable anisotropic conductive film having conductivity at least on the surface and selectively having conductivity in a region. The conductive balls are inserted into and aligned with the stretchable substrate. That is, the conductive balls may be in a form driven into the stretchable substrate, or may be regularly arranged and aligned.

[0039] The "alignment" means that a plurality of conductive balls are arranged at the same interval or an interval having a specific regularity. That is, when any one of the conductive balls is inserted into the stretchable substrate, the other conductive balls are positioned at a predetermined distance, and the other conductive balls may also be arranged at a predetermined distance from the other conductive balls. The conductive balls may be aligned in any one of a lattice type, a honeycomb type, a linear type, and a square type, but are not limited thereto and may be arranged in various forms as needed.

[0040] The conductive balls are preferably entirely metal particles or particles coated with a metal material on the surface and are spherical. Preferably, the conductive balls may have a core-shell structure including a core containing an insulating polymer; and a shell containing a metal. In the case of the core-shell structure, conductive balls of uniform size can be utilized for the stretchable anisotropic conductive film, the weight of the stretchable anisotropic conductive film can be reduced, the weight of the device can be reduced, and the effect of reducing production costs can be achieved.

[0041] According to one embodiment, the diameter of the conductive balls is 1 μm to 100 μm, the interval between the conductive balls is 1 μm to 100 μm, the pitch is 2 μm to 200 μm, and the diameter of the conductive balls and the interval between the conductive balls may be 2:1 to 1:2.

[0042] The diameter of the conductive ball is preferably 1 μm to 80 μm; 1 μm to 60 μm; 1 μm to 40 μm; 1 μm to 20 μm; 2 μm to 80 μm; 2 μm to 60 μm; 2 μm to 40 μm; 2 μm to 20 μm; 5 μm to 80 μm; 5 μm to 60 μm; 5 μm to 40 μm; or 5 μm to 20 μm.

[0043] When the diameter of the conductive ball is less than 1 μm, in order to arrange the conductive balls in the stretchable substrate, when rubbing, the conductive balls are not rolled and are swept as they are, resulting in a problem that it is difficult to form a particle assembly. When it exceeds 100 μm, there is a problem with the resolution.

[0044] Each individual conductive ball may have the same diameter. When using conductive balls having the same diameter, since there is no step in the height direction of the stretchable anisotropic conductive film, a separate bump layer for anisotropic conduction is not required.

[0045] The interval between the conductive balls indicates the closest distance between the end of one conductive ball and the end of the other conductive ball. The interval between the conductive balls is preferably 1 μm to 80 μm; 1 μm to 60 μm; 1 μm to 40 μm; 1 μm to 20 μm; 2 μm to 80 μm; 2 μm to 60 μm; 2 μm to 40 μm; 2 μm to 20 μm; 5 μm to 80 μm; 5 μm to 60 μm; 5 μm to 40 μm; or 5 μm to 20 μm.

[0046] The pitch of the conductive balls indicates the distance from the center of one conductive ball to the center of the other conductive ball. The pitch of the conductive balls is preferably 2 μm to 160 μm; 2 μm to 120 μm; 2 μm to 80 μm; 2 μm to 40 μm; 4 μm to 160 μm; 4 μm to 120 μm; 4 μm to 80 μm; 4 μm to 40 μm; 10 μm to 160 μm; 10 μm to 120 μm; 10 μm to 80 μm; or 10 μm to 40 μm, and a stretchable anisotropic conductive film with a fine pitch can be provided.

[0047] When the intervals and pitches of the conductive balls are less than the above ranges, there is a problem that the arrays cannot be properly formed. The closer the intervals of the conductive balls are, the more likely contact phenomena such as electrostatic attraction between the conductive balls occur during the rubbing process, resulting in cross-talk, and in some cases, the conductive balls are densely arranged and difficult to arrange in the desired pattern. When the conductive balls are aligned with intervals and pitches within the above ranges, the performance such as conductivity and resolution becomes constant within all areas of the stretchable anisotropic conductive film due to the regular array in units of particle diameter, and thus, an accurate design of electrode interconnection becomes possible. The intervals and pitches of the conductive balls can be adjusted according to the arrangement form, the diameter of the conductive balls, and the application field of the stretchable anisotropic conductive film.

[0048] The diameter of the conductive balls and the intervals between the conductive balls may preferably be 2:1 to 2:3; 2:1 to 1:1; 2:1 to 3:2; 3:2 to 1:1; 3:2 to 2:3; 3:2 to 1:2; 1:1 to 2:3; 1:1 to 1:2; or 2:3 to 1:2.

[0049] According to an embodiment, the thickness of the stretchable base material may be 40% to 70% of the diameter of the conductive balls.

[0050] When the thickness of the stretchable base material is less than 40% of the diameter of the conductive balls, there are problems that the arrays of the conductive balls cannot be sufficiently formed, or the thickness of the stretchable base material is too thin and the adhesion to the surface of the electrode substrate is not sufficient. When it exceeds 70%, there is a problem with energization because the stretchable base material covers the surface of the conductive balls and the conductive balls are not exposed.

[0051] When the thickness ratio of the stretchable base material is formed within the above range, a part of the conductive balls is exposed from the surface of the stretchable base material, and high conductivity can be obtained when the stretchable anisotropic conductive film is pressure-bonded to other members such as a target substrate.

[0052] The thickness of the stretchable base material may be 1 μm to 50 μm, but is not limited within the above range.

[0053] According to one embodiment, the stretchable substrate has uniform physical properties throughout, and the conductive balls are inserted and aligned in a direction perpendicular to the surface of the stretchable anisotropic conductive film so that both sides of the stretchable anisotropic conductive film are energized, and 30% to 60% of the external surface may be exposed outside the stretchable substrate.

[0054] In a conventional stretchable anisotropic conductive film, the conductive balls are exposed to the outside through hot press and come into contact with other members such as a target substrate to form conductivity. The stretchable substrate of the stretchable anisotropic conductive film that has undergone the hot press process undergoes a development phenomenon in which the conductive balls are pressed while being in close contact with the conductive balls and the conductive balls are exposed to the outside, resulting in a difference in physical properties depending on the position, so that it is not uniform as a whole, and the stretchable substrate can be deformed before hot press. Here, the physical properties mean elongation rate, toughness, etc. On the other hand, since the stretchable anisotropic conductive film according to the present invention is formed by coating the stretchable substrate on the conductive balls without a hot press process, the stretchable substrate is not deformed, so regardless of the position of the conductive balls inserted into the stretchable substrate, the physical properties of the entire part of the stretchable substrate are constant.

[0055] The stretchable anisotropic conductive film can form a vertical conduction path that is energized through the vertically inserted conductive balls. The conductive balls are exposed outside the upper and lower portions of the stretchable substrate. When the conductive balls are exposed outside the upper and lower portions of the stretchable substrate, the current flowing from the member in contact with one surface of the stretchable anisotropic conductive film can be made to flow to another member in contact with the other surface of the stretchable anisotropic conductive film.

[0056] The exposed outer surface includes all of the upper and lower surfaces where the conductive balls are exposed. Preferably, 30% to 50%; 30% to 40%; 40% to 60%; 40% to 50%; or 50% to 60% of the outer surface of the conductive balls may be exposed to the outside of the upper and lower surfaces of the stretchable substrate. When the outer surface of the conductive balls is exposed within the mentioned range, excellent conductivity can be ensured because the connection resistance is low while minimizing the step of the stretchable anisotropic conductive film.

[0057] The stretchable anisotropic conductive film according to the present invention may have a stress of 10 MPa or less, 8 MPa or less, or 5 MPa or less when stretched at a stretch ratio of 100%. When having a stress within the mentioned range when stretched at a stretch ratio of 100%, the stretchable anisotropic conductive film has excellent stretchability and excellent conduction stability without a decrease in conductivity even when there is a physical stimulus. Further, the stretchable anisotropic conductive film according to the present invention may have a stress of 10 MPa or less when stretched at a stretch ratio of 200%.

[0058] The method for manufacturing a stretchable anisotropic conductive film according to the present invention includes the steps of manufacturing a mold patterned with a pattern including recesses; disposing conductive balls on the mold; coating a stretchable substrate on the mold on which the conductive balls are disposed; and removing the mold.

[0059] The method for manufacturing a stretchable anisotropic conductive film according to the present invention can provide a fine pitch stretchable anisotropic conductive film excellent in stretchability and conductivity quickly and simply at low temperature and low pressure.

[0060] FIG. 2 is a schematic view of a method for manufacturing a stretchable anisotropic conductive film according to an embodiment of the present invention. Referring to FIG. 2, after manufacturing a mold 30 patterned with a pattern including recesses, conductive balls 10 are arranged on the patterned mold 30. A stretchable base material 20 is coated on the patterned mold 30 on which the conductive balls 10 are arranged, and the conductive balls 10 inserted on the stretchable base material 20 can be obtained, and the patterned mold 30 is removed by peeling it off, thereby manufacturing a stretchable anisotropic conductive film.

[0061] The conventional method for manufacturing a stretchable anisotropic conductive film uses a thermocompression bonding method, while the method for manufacturing a stretchable anisotropic conductive film according to the present invention can easily manufacture a stretchable anisotropic conductive film with a fine pitch under low-temperature and low-pressure conditions by arranging conductive balls on a mold and then coating a stretchable base material.

[0062] Here, since the characteristics of the conductive balls and the stretchable base material are the same as those described above, the following description is omitted.

[0063] According to an embodiment, the step of manufacturing the mold can be performed in a photolithography, nanoimprint, soft lithography, block copolymer lithography, or capillary lithography process.

[0064] The process in which the step of manufacturing the mold is performed is not particularly limited, but preferably, it may be performed in a photolithography process.

[0065] According to an embodiment, the step of manufacturing the mold includes: preparing a UV curable polymer; positioning a photomask on the UV curable polymer and irradiating with UV for patterning; and washing the patterned UV curable polymer to obtain a patterned mold. The UV curable polymer may include at least any one selected from the group consisting of PEG-DA (Polyethylene glycol diacrylate), epoxy acrylate, polyester acrylate, polyurethane acrylate, and silicone acrylate.

[0066] FIG. 3 is a schematic diagram of the step of manufacturing a mold in a method for manufacturing a stretchable anisotropic conductive film according to an embodiment of the present invention. Referring to FIG. 3, a UV curable polymer 40 can be prepared by coating, and after positioning a photomask 50 thereon, irradiating with UV can obtain a mold 30 patterned in a desired pattern.

[0067] In the step of preparing the UV curable polymer, the UV curable polymer can be coated on a wafer. The wafer is not particularly limited, and one selected from a silicon wafer, glass, and a metal substrate may be used. Preferably, it may be a silicon wafer.

[0068] The wafer can be chemically surface-treated for stable bond formation with the UV-curable polymer. When peeling the photomask with the UV-curable polymer via chemical surface treatment, the UV-curable polymer may not be peeled off from the wafer. The surface treatment can be performed by treating with oxygen plasma at 100 W to 300 W for 1 minute to 5 minutes and then treating with a silane compound solution. The silane compound may preferably be TMSPMA (3-(Trimethoxysilyl)propyl methacrylate). The silane compound solution treatment may be performed at a temperature of 50°C to 80°C for 30 minutes to 2 hours.

[0069] The step of preparing the UV-curable polymer can be coating a solution in which the UV-curable polymer and a photoinitiator are mixed on the surface-treated wafer. The coating may include at least any one selected from the group consisting of spray coating, spin coating, dip coating, screen coating, knife coating, kiss coating, gravure coating, bar coating, screen printing, and spray-mist spray coating, and preferably may be spin coating.

[0070] The photomask can have circular patterns aligned in various forms. The patterns may be aligned in any one of the arrangement forms of lattice type, honeycomb type, linear type, and square type, but are not limited thereto, and may be arranged in various forms as required. The photomask can be patterned by arranging a pattern of a desired shape where conductive balls are finally arranged.

[0071] The UV-curable polymer is not limited to those mentioned above, and preferably has low extensibility and low adhesion to the substrate. The UV-curable polymer can be patterned by UV irradiation because the part exposed to UV is cured and the part not exposed to UV is not cured.

[0072] According to one embodiment, in the step of irradiating with UV for patterning, the UV curable polymer is turned into a cured hard gel and an uncured soft gel, the soft gel forms the concave portion, and the depth of the concave portion may be 10% to 30% of the diameter of the conductive ball.

[0073] For the UV curable polymer, the portion exposed to UV is cured to form a hard gel, while the portion not exposed to UV is not cured and forms a soft gel. It can be cured into a desired pattern by a photomask, and the patterned form may be recessed. This is caused by the difference in refractive index between the cured UV curable polymer and the uncured UV curable polymer. The concave pattern may have an adhesive force due to the viscoelastic polymer at the interface of the UV curable polymer.

[0074] When the depth of the concave portion is less than 10% of the diameter of the conductive ball, there is a problem that the conductive balls are not sufficiently arranged. When it exceeds 30%, when forming the film, the stretchable substrate covers the upper part of the conductive ball, and there are problems that the upper part of the conductive ball is not open or the film thickness is not appropriate. When the depth ratio of the concave portion is formed within the above range, a stretchable anisotropic conductive film excellent in stretchability and conductivity can be manufactured by appropriately exposing the surface of the conductive ball.

[0075] According to one embodiment, in the step of irradiating with UV for patterning, UV is irradiated for 1 second to 10 seconds, the distance between the UV curable polymer and the UV light source is 8 cm to 16 cm, and the UV intensity is 2 mW / cm 2 ~20 mW / cm 2 and it may be so.

[0076] The UV irradiation time is preferably 1 second to 8 seconds; 1 second to 6 seconds; 1 second to 4 seconds; 1 second to 3 seconds; 3 seconds to 10 seconds; 3 seconds to 8 seconds; 3 seconds to 6 seconds; 3 seconds to 5 seconds; 4 seconds to 10 seconds; 4 seconds to 8 seconds; or 4 seconds to 6 seconds, and it may be so.

[0077] The distance between the UV curable polymer and the UV light source is preferably 8 cm to 14 cm; 8 cm to 12 cm; 8 cm to 10 cm; 10 cm to 16 cm; 10 cm to 14 cm; 10 cm to 12 cm; 12 cm to 16 cm; or 12 cm to 14 cm.

[0078] The UV intensity is preferably 2 mW / cm 2 ~18 mW / cm 2 ; 2 mW / cm 2 ~14 mW / cm 2 ; 2 mW / cm 2 ~10 mW / cm 2 ; 2 mW / cm 2 ~6 mW / cm 2 ; 4 mW / cm 2 ~20 mW / cm 2 ; 4 mW / cm 2 ~18 mW / cm 2 ; 6 mW / cm 2 ~14 mW / cm 2 ; 6 mW / cm 2 ~10 mW / cm 2 ; 8 mW / cm 2 ~20 mW / cm 2 ; 8 mW / cm 2 ~18 mW / cm 2 ; 8 mW / cm 2 ~14 mW / cm 2 ; or 8 mW / cm 2 ~10 mW / cm 2 ; may be.

[0079] When irradiating with UV under the above conditions, the photoreaction of the UV curable polymer can proceed smoothly, and the conductive ball can be smoothly adhered to form a recess having a depth such that the surface of the conductive ball is exposed to the stretchable substrate clearly.

[0080] According to one embodiment, the step of disposing the conductive ball is to rub the conductive ball on the mold so that the conductive ball adheres to the recess, and the adhesive force of the recess may be 1 nN to 90 nN.

[0081] Figure 4 is a schematic diagram of a step of arranging conductive balls and a step of coating a stretchable base material in a method for manufacturing a stretchable anisotropic conductive film according to an embodiment of the present invention. Referring to Figure 4, the elastic member 60 may be used to rub in order to arrange the conductive balls 10 on the patterned mold 30, and the stretchable base material 20 may be coated on the mold 30 on which the conductive balls 10 are arranged to form a stretchable anisotropic conductive film.

[0082] The concave pattern formed by the uncured UV curable polymer has an adhesive force due to the viscoelastic polymer at the interface of the UV curable polymer. The rubbing can embed the conductive balls into the stamp of the elastic member by arranging the conductive balls in the concave portions having the adhesive force, and the conductive balls can be arranged by rubbing them into the patterned mold.

[0083] The elastic member serves to hold the conductive ball, and more specifically, it can directly contact the conductive ball and perform the role of rubbing on the recess pattern formed in the mold. The elastic member may include at least any one selected from the group consisting of PDMS (polydimethylsiloxane), PUA (polyurethane acrylate), PMMA (polymethyl methacrylate), PB (polybutadiene), PU (polyurethane), SBR (styrenebutadiene rubber), PVDF (polyvinylidene fluoride), PVDF-TrFE (poly(vinylidenefluorideco-trifluoroethylene)), PS (polystyrene), SBS PEDGA (poly(ethylene glycol)diacrylate), SBS (ploy(styrene-butadiene-styrene)), SEBS (poly(styreneethylene-butylene-styrene)), and SIS (poly(styrene-isoprene-styrene)). By reciprocating a predetermined distance one or more times in one direction of the patterned mold, the elastic member can place the conductive ball in the recess of the patterned mold.

[0084] The conductive ball can be adhered by the adhesion force formed in the recess. The adhesion force is preferably 1 nN to 70 nN; 1 nN to 50 nN; 1 nN to 30 nN; 1 nN to 10 nN; 10 nN to 90 nN; 10 nN to 70 nN; 10 nN to 50 nN; 10 nN to 30 nN; 30 nN to 90 nN; 30 nN to 70 nN; 30 nN to 50 nN; 50 nN to 90 nN; or 50 nN to 70 nN. When the adhesion force is less than 1 nN, the adhesion force is weak, the conductive ball is not adhered and is easily blown away, or the conductive balls are not properly arranged, making it difficult to manufacture a highly arranged anisotropic conductive film. When it exceeds 90 nN, when peeling the stretchable substrate, the conductive ball is inserted into the stretchable substrate and not transferred to the film, remaining in the mold.

[0085] According to one embodiment, it further includes the step of arranging the conductive balls; and then the step of air blowing.

[0086] In addition to the soft gel of the recess pattern, the mold in which the conductive balls are arranged may also have conductive balls in the hard gel. In order to remove the conductive balls not arranged on the pattern, air blowing can be used to blow away the conductive balls not arranged on the pattern. The conductive balls formed in the recess may not be blown away even when air blowing is performed due to the adhesion force.

[0087] The step of coating the stretchable substrate on the mold in which the conductive balls are arranged can expose the conductive balls and coat the stretchable substrate. That is, it can be adjusted so that the coated stretchable substrate does not cover all the conductive balls and then coated. The coating may include at least any one selected from the group consisting of spray coating, spin coating, dip coating, screen coating, knife coating, kiss coating, gravure coating, bar coating, screen printing, and spray-mist spray coating, and preferably may be spin coating.

[0088] The extensible substrate may be coated in a solution state diluted in a solvent. If the concentration of the solution is too high or the coating speed is too slow, all the conductive balls will be covered and the surface of the conductive balls will not be exposed, making it difficult to form the target member and conductivity. If the concentration is too low or the coating speed is too fast, the extensible substrate coating will become too thin and the adhesion part with the target member will not contact sufficiently. Therefore, it is necessary to perform the coating considering the concentration and speed.

[0089] The solvent can be removed by heat treatment at a temperature of 50°C to 80°C for 1 minute to 10 minutes.

[0090] According to one embodiment, the step of removing the mold peels the extensible substrate, and the extensible substrate can be inserted with the conductive balls and aligned.

[0091] The extensible substrate is coated in a form in which the conductive balls are inserted and aligned in the extensible substrate, and the anisotropic conductive film with extensibility can be manufactured by peeling from the mold.

[0092] In the conventional process, in order to expose the conductive balls and impart conductivity, it is difficult to manufacture a fine pitch while performing a hot press process, and high temperature and high pressure conditions are required. However, the manufacturing method of the anisotropic conductive film with extensibility according to the present invention uses a method of manufacturing a patterned mold, arranging conductive balls thereon, coating an extensible substrate, and then peeling it, so that a fine pitch anisotropic conductive film with extensibility of 20 μm or less can be manufactured in a low temperature and low pressure process.

[0093] Hereinafter, the present invention will be described in more detail by embodiments.

[0094] However, the following embodiments are for illustrating the present invention, and the content of the present invention is not limited by the following embodiments.

[0095] Embodiment

[0096] Manufacture of an extensible anisotropic conductive film

[0097] (1) Chemical surface treatment of a silicon wafer

[0098] For the formation of a stable bond between a PEG-DA (Poly(ethylene glycol) diacrylate) layer, which is a UV-curable polymer, and a silicon wafer, the silicon wafer was treated with TMSPMA (3-(Trimethoxysilyl)propyl methacrylate). After the silicon wafer was treated with oxygen plasma (200 W, 2 min) to form hydroxyl groups on the surface, it was immersed in a TMSPMA solution diluted with ethanol (3 wt% in EtOH) at 60 °C for 1 hour and then taken out, rinsed with ethanol, and dried with an air blow.

[0099] (2) Formation of a UV-curable polymer pattern

[0100] A solution (PEG-DA:HOMPP = 9:1) in which PEG-DA, the main material of the polymer, and HOMPP (2-Hydroxy-2-methylpropiophenon), its photoinitiator, were mixed together was spin-coated (30 seconds, 1000 rpm) on a silicon wafer treated with TMSPMA. Next, UV curing was performed with a photomask designed according to the pattern. The PEG-DA part blocked by the chromium pattern of the photomask cannot receive UV and is not cured, while the transparent part can receive UV and is thus cured. The shape of the PEG-DA pattern is a concave shape rather than a right-angled form, which is caused by the refractive index difference between the cured PEG-DA and the uncured PEG-DA. Next, after peeling the photomask from the PEG-DA layer, in order to remove the uncured liquid PEG-DA in the part where the chromium pattern was present, it was rinsed with toluene while spin-coating (30 seconds, 2000 rpm). Next, heat treatment (60 °C, 5 minutes) was performed to remove the remaining toluene. In the case of the formed concave pattern, there was an adhesive force due to the viscoelastic polymer at the interface of the uncured PEG-DA.

[0101] Figure 5 is an SEM image of the patterned mold according to an embodiment of the present invention. Referring to Figure 5, a cross-section of the patterned mold having a form in which the uncured part is recessed after UV irradiation can be confirmed, and conductive balls can be adhered to the concave pattern.

[0102] (3) Conductive ball arrangement and stretchable substrate coating

[0103] Conductive balls (20, 10, 5, 2.5 μm) sized to fit the formed pattern were embedded in the PDMS stamp, rubbed against the PEG-DA layer with the concave pattern to arrange the conductive balls, and then the conductive balls without the pattern were removed by blowing them away with an air blower. Thanks to the adhesion of the concave pattern, the conductive balls in the pattern are not blown away even by a strong wind. Next, since the conductive balls were not all covered, an SEBS-g-MA solution diluted in toluene at an appropriate concentration was spin-coated to form a film only in the center of the conductive balls. The remaining toluene was removed by heat treatment (60 °C, 5 minutes).

[0104] Figure 6 is an OM image of the mold with conductive balls arranged in (a) and an SEM image of the cross-section of the stretchable anisotropic conductive film in (b) according to an embodiment of the present invention. Referring to Figure 6(a), it can be confirmed that the conductive balls are satisfactorily adhered to the mold in a certain pattern, and referring to Figure 6(b), it can be confirmed that a stretchable anisotropic conductive film in which the conductive balls are inserted into the stretchable substrate was manufactured.

[0105] Test Example

[0106] The stretchable anisotropic conductive film of the embodiment was transferred between two electrode circuits and thermocompression bonded at 80 °C for 10 minutes (0.1 MPa) and used as an electrical interface. The electrode circuit was formed by five lines numbered 1 to 5. IV measurement was performed for performance testing.

[0107] In the case of the electrode circuit, Au sputtering (20 mA, 300 s DC magnetron sputter) was performed on a PET substrate using a metal mask to form the electrode circuit. After thermocompression bonding the stretchable anisotropic conductive film of the embodiment between two electrode circuits, liquid metal was thinly applied to the end of the lower electrode, liquid metal was thinly applied to the end of the upper electrode, a conductive tape was attached, and then liquid metal was thinly applied to the end again. Then, an IV chip was brought into contact with each end. In the case of the IV measurement conditions, with 1 mA as the compliance, a voltage was applied from 0 to 2 V to measure the current value.

[0108] Figure 7 is a graph showing the IV measurement results of an electronic device to which the stretchable anisotropic conductive film according to an embodiment of the present invention is applied. Referring to Figure 7, an ohmic curve is shown in the case of the same line such as 1-1, 2-2, 3-3, 4-4, 5-5, while it was confirmed that no current flows when measuring by contacting different lines with each other.

[0109] Although the embodiments have been described as above, those having ordinary knowledge in the art can apply various technical modifications and variations based on the above. For example, the described technology may be executed in an order different from the described method, and / or the components such as the described system, structure, device, circuit, etc. may be combined or assembled in a form different from the described method, or replaced or substituted by other components or equivalents, and appropriate results can still be achieved.

[0110] Therefore, other realizations, other embodiments, and those equivalent to the claims will also fall within the scope of the claims described later.

Claims

1. A stretchable base material, Conductive balls inserted and aligned within the stretchable base material, A stretchable anisotropic conductive film comprising the above.

2. The stretchable base material comprises a heat-firable rubber grafted with maleic anhydride containing at least any one heat-firable rubber selected from the group consisting of styrene-ethylene-butylene-styrene (SEBS), styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), polyurethane (PU)-based rubber, and polyolefin (PO)-based rubber. The stretchable anisotropic conductive film according to Claim 1.

3. The conductive balls contain at least any one particle selected from the group consisting of PS (Polystyrene), PU (Polyurethane), PE (Polyethylene), PP (Polypropylene), PB (Polybutylene), Nylon, and Styrene-divinyl benzene, The particles are coated with at least any one selected from the group consisting of gold (Au), nickel (Ni), silver (Ag), copper (Cu), aluminum (Al), palladium (Pd), chromium (Cr), titanium (Ti), tin (Sn), and molybdenum (Mo). The stretchable anisotropic conductive film according to Claim 1.

4. The diameter of the conductive balls is 1 μm to 100 μm, The interval between the conductive balls is 1 μm to 100 μm, The pitch is 2 μm to 200 μm, The diameter of the conductive balls and the interval between the conductive balls are 2:1 to 1:

2. The stretchable anisotropic conductive film according to Claim 1.

5. The thickness of the stretchable base material is 40% to 70% of the diameter of the conductive balls. The stretchable anisotropic conductive film according to Claim 1.

6. The overall physical properties of the stretchable base material are constant, The conductive balls are inserted and aligned in a direction perpendicular to the surface of the stretchable anisotropic conductive film so that both surfaces of the stretchable anisotropic conductive film are energized, 30% to 60% of the external surface is exposed outside the stretchable base material. The stretchable anisotropic conductive film according to Claim 1.

7. The step of manufacturing a mold patterned with a pattern including recesses, The step of arranging conductive balls in the mold, A step of coating a stretchable substrate on a mold on which the conductive balls are disposed; A step of removing the mold; A method for manufacturing a stretchable anisotropic conductive film, comprising:

8. The method for manufacturing a stretchable anisotropic conductive film according to claim 7, wherein the step of manufacturing the mold is performed by a photolithography, nanoimprint, soft lithography, block copolymer lithography, or capillary lithography process.

9. The step of manufacturing the mold includes: A step of preparing a UV curable polymer; A step of positioning a photomask on the UV curable polymer and irradiating with UV for patterning; A step of washing the patterned UV curable polymer to obtain a patterned mold; Including, The method for manufacturing a stretchable anisotropic conductive film according to claim 7, wherein the UV curable polymer includes at least any one selected from the group consisting of PEG-DA (Polyethylene glycol diacrylate), epoxy acrylate, polyester acrylate, polyurethane acrylate, and silicone acrylate.

10. In the step of irradiating with UV for patterning, the UV curable polymer is patterned with a cured hard gel and an uncured soft gel, The soft gel forms the recess, The method for manufacturing a stretchable anisotropic conductive film according to claim 9, wherein the depth of the recess is 10% to 30% of the diameter of the conductive ball.

11. In the step of irradiating with UV for patterning, UV is irradiated for 1 second to 10 seconds, The distance between the UV curable polymer and the UV light source is 8 cm to 16 cm. The UV intensity is 2 mW / cm ２ to 20 mW / cm ２ The method for manufacturing a stretchable anisotropic conductive film according to claim 9, wherein the method is as described above.

12. The step of disposing the conductive balls includes rubbing the conductive balls on the mold, The conductive balls are adhered to the recesses, The method for manufacturing a stretchable anisotropic conductive film according to claim 7, wherein the adhesive force of the recesses is 1 nN to 90 nN.

13. The method for manufacturing a stretchable anisotropic conductive film according to claim 7, further comprising a step of air blowing after the step of disposing the conductive balls.

14. The step of removing the mold includes peeling off the stretchable substrate, The method for manufacturing a stretchable anisotropic conductive film according to claim 7, wherein the stretchable substrate has the conductive balls inserted therein and aligned.

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