Anisotropically conductive sheet and method for manufacturing anisotropically conductive sheet

Abstract

[Problem] To enhance connection reliability of an anisotropically conductive sheet. [Solution] An anisotropically conductive sheet 100 comprises a base sheet 103 composed of a polymer matrix and a plurality of conductive parts 104 each including a plurality of magnetic, electrically conductive particles 107 aligned in a chain in the thickness direction of the base sheet 103. The plurality of conductive parts 104 are disposed in the base sheet 103 at regular intervals based on a predetermined design arrangement without relying on magnetic repulsion between the electrically conductive particles 107. Each of the conductive parts 104 is formed by aligning two or more electrically conductive particles 107 in a linear chain in the thickness direction of the base sheet 103.

Description

Anisotropic Conductive Sheet and Method for Manufacturing Anisotropic Conductive Sheet

[0001] The present disclosure relates to an anisotropic conductive sheet and a method for manufacturing an anisotropic conductive sheet.

[0002] In order to meet the requirements of miniaturization and high integration, the semiconductor IC and the circuit board have a large number of connection terminals and connection contacts arranged at a narrow pitch, and the pitch distance between them tends to become narrower. As an electrical connection member for making electrical conduction connection with connection terminals and connection contacts arranged at such a narrow pitch, and as an inspection electrical connection member for testing the electrical conductivity and durability of the semiconductor IC and the circuit board described above, an anisotropic conductive sheet is known. As an example, an anisotropic conductive sheet is known in which one conductive particle is arranged in the thickness direction of a base sheet made of a polymer matrix (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2015-026584

[0004] However, in the conventional anisotropic conductive sheet, on the premise of a structure in which one conductive particle is arranged within the thickness of the base sheet, it is not possible to increase the thickness of the anisotropic conductive sheet beyond the height of one conductive particle.

[0005] Therefore, the present disclosure provides a new anisotropic conductive sheet and a method for manufacturing the same.

[0006] A first aspect of the present disclosure is an anisotropic conductive sheet having a base sheet made of a polymer matrix and a plurality of conductive portions in which a plurality of conductive particles exhibiting magnetism are chained in the thickness direction of the base sheet, the plurality of conductive portions being arranged on the base sheet at regular intervals based on a predetermined design arrangement, and each of the conductive portions being formed by two or more of the conductive particles being chained in series in the thickness direction of the base sheet.

[0007] According to this, a conductive portion can be realized in which conductive particles are arranged at regular intervals based on a predetermined design arrangement in the planar direction of the base sheet. Furthermore, since two or more of the conductive particles are linked in series in the thickness direction of the base sheet in each conductive portion, the thickness of the anisotropic conductive sheet can be increased. As a result, the anisotropic conductive sheet can reduce the compressive load during use. The anisotropic conductive sheet can achieve a compression amount that can absorb the tolerances of the connected object. The anisotropic conductive sheet can achieve durability that makes it less likely to break or other problems even after being compressed and used many times.

[0008] A second aspect of the present disclosure is a method for manufacturing an anisotropic conductive sheet, comprising the steps of: forming a conductive particle layer in which a plurality of first conductive particles are positioned and fixed at regular intervals based on a predetermined design arrangement; forming a polymer liquid film layer consisting of a liquid polymer matrix containing magnetic second conductive particles so as to cover the conductive particle layer; applying a magnetic field to the polymer liquid film layer to cause the positioned first conductive particles to function as a magnetic field forming medium, thereby orienting at least one of the second conductive particles on top of each of the first conductive particles; and curing the polymer liquid film layer in which the second conductive particles are oriented.

[0009] According to this, it is possible to obtain an anisotropic conductive sheet having conductive portions in which conductive particles are arranged one by one at regular intervals based on a predetermined design arrangement, and in which two or more of the conductive particles are chained in series in each conductive portion in the thickness direction of the base sheet.

[0010] In the above manufacturing method, the first conductive particles, which are positioned and fixed at regular intervals, function as a magnetic field forming medium, and one second conductive particle can be placed for each first conductive particle. Therefore, in an anisotropic conductive sheet in which two or more conductive particles are linked in the thickness direction of the base sheet, the multiple conductive particles forming individual conductive parts do not branch out, and can be linked in series along the thickness direction (a direction perpendicular to the plane of the base sheet). Thus, even in an anisotropic conductive sheet having multiple conductive parts arranged at regular intervals, where each conductive part is a link of two or more conductive particles, the conductive parts do not short-circuit with each other, and each conductive part functions as an independent conductive path, thereby improving connection reliability. Furthermore, the thickness of the anisotropic conductive sheet can be increased, and as a result, an anisotropic conductive sheet with the above-mentioned effects and advantages can be obtained.

[0011] According to this disclosure, the connection reliability of anisotropic conductive sheets can be improved.

[0012] Figure 1A is a perspective view of the anisotropic conductive sheet according to one embodiment, and Figure 1B is a perspective view of the anisotropic conductive sheet according to one embodiment. Figure 1 is a partially enlarged cross-sectional view showing the connection of the anisotropic conductive sheet to the object to be connected. Figure 3A is a partially enlarged cross-sectional view illustrating a method for manufacturing the anisotropic conductive sheet of Figure 2, Figure 3B is an explanatory diagram showing the process following 3A, and Figure 3C is a partially enlarged cross-sectional view showing the process following 3B. Figure 4A is a partially enlarged cross-sectional view showing a manufacturing method of a modified example, and Figure 4B is a partially enlarged cross-sectional view showing a manufacturing method of another modified example. Figure 5A is a partially enlarged cross-sectional view showing a manufacturing method of a modified base sheet, and Figure 5B is a partially enlarged cross-sectional view of a modified base sheet obtained through the process following 5A.

[0013] The following describes embodiments relating to one aspect of this disclosure. The following embodiments are not intended to unduly limit the scope of the claims of this disclosure, and not all of the configurations described in these embodiments are necessarily essential solutions indispensable to one aspect of this disclosure.

[0014] In the following description, terms indicating directions such as "up," "down," "left," and "right" are used for explanatory purposes only and do not limit the structure, method of use, or manner of use of the present invention unless otherwise specified. Terms such as "first" and "n" (where n is a natural number) following "first" as described herein and in the claims are used as identifying terms to distinguish different elements and do not indicate any particular order or superiority.

[0015] The terms used in the following description are for the sole purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Components in any aspect described herein and in the claims are intended to include plural forms unless the context explicitly indicates otherwise.

[0016] The term "and / or" refers to and is intended to include any one or more of the related enumerated elements and all possible combinations thereof. For example, "A or B" means "A, B, or both A and B." "A," "B," and "both A and B" each satisfy "A or B."

[0017] The terms “including” and “equipped with” as used herein and in the claims identify the presence of features, actions, elements, and steps. However, they are used in a manner that does not exclude the presence or addition of one or more other features, actions, elements, steps, and / or groups thereof.

[0018] As used in this disclosure, the terms “connection,” “contact,” “lamination,” “formation,” “support,” “arrangement,” and “adhesion” may include not only direct but also indirect aspects (configuration, structure), unless otherwise contradictory. Specifically, this may include indirect connection, contact, lamination, formation, support, arrangement, and adhesion of a second element to a first element.

[0019] In this disclosure, the terms "surface" and "plane" used with respect to sheet-like members refer to the X-Y plane of a sheet-like member, excluding the end faces of the peripheral edges of the sheet-like member.

[0020] All embodiments and optional embodiments included in this disclosure may be combined to form new embodiments. Furthermore, all technical features and optional technical features included in this disclosure can be combined to form new technical features.

[0021] The anisotropic conductive sheet relating to this disclosure is an electrical connecting member that electrically connects multiple objects to be connected. "Objects to be connected" includes "first objects to be connected" and "second objects to be connected." "First objects to be connected" and "second objects to be connected" may each be one or more "electrical components." Examples of combinations of first objects to be connected and second objects to be connected as electrical components include, but are not limited to, circuit boards to circuit boards, semiconductor ICs to circuit boards, and semiconductor ICs to test sockets for testing semiconductor ICs. Examples of objects that the anisotropic conductive sheet directly contacts include, but are not limited to, the contacts, terminals, electrodes, conductive layers, etc. of those electrical components.

[0022] 1. Structure of anisotropic conductive sheet [Figures 1-3]

[0023] As shown in Figure 1, the anisotropic conductive sheet 100 includes, as an example, an elastic connector portion 101 and an outer frame portion 102.

[0024] Elastic connector portion 101: The elastic connector portion 101 has a base sheet 103 formed of a sheet-shaped polymer matrix. Multiple conductive portions 104 are formed on the base sheet 103. The circular dot shapes shown in Figures 1A and 1B are conductive portions 104, and all conductive portions 104 have the same structure unless otherwise specified.

[0025] Base sheet 103: The base sheet 103 is formed from a solid polymer matrix. The polymer matrix is ​​a molded body formed by the curing of a liquid polymer material. An electrically insulating rubber-like elastic material is used for the polymer matrix. Thermosetting rubbers and thermoplastic elastomers can be used as the material. Specifically, examples include natural rubber, silicone rubber, isoprene rubber, butadiene rubber, acrylonitrile butadiene rubber, 1,2-polybutadiene, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene-propylene rubber, chlorosulfone rubber, polyethylene rubber, acrylic rubber, epichlorohydrin rubber, fluororubber, urethane rubber, styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, ester-based thermoplastic elastomer, urethane-based thermoplastic elastomer, amide-based thermoplastic elastomer, vinyl chloride thermoplastic elastomer, fluorinated resin thermoplastic elastomer, ion-crosslinked thermoplastic elastomer, etc. As will be described later, when heat curing occurs in a mold, thermosetting rubber is preferred as the polymer matrix, and among these, silicone rubber and fluororubber, which have high heat resistance, are more preferred.

[0026] The polymer matrix forming the base sheet 103 has rubber elasticity. The hardness of the polymer matrix, which is an indicator of its rubber elasticity, is preferably 15 to 70 on the A hardness scale, measured using a Type A durometer in accordance with JIS K6253. By setting the hardness of the polymer matrix to 15 to 70 on the A hardness scale, an anisotropic conductive sheet 100 that can be used as a standard in a variety of applications can be obtained. On the other hand, if the A hardness is lower than 15, the elastic connector portion 101 becomes too soft, which may lead to insulation failure due to bending or breakage. If the A hardness is higher than 70, the compressive load on the elastic connector portion 101 becomes too large, which may cause deformation such as warping in the object to be connected (circuit board, socket housing of inspection socket, etc.).

[0027] The planar shape of the base sheet 103 can be a shape that corresponds to the conductive connection area between a first connection target and a second connection target to which the anisotropic conductive sheet 100 is electrically connected to each other. Figure 1 shows a rectangular shape as an example, but it is not limited to this, and other polygons, circles, combinations of polygons and circles may also be used. For example, when the anisotropic conductive sheet 100 is used for electrical connection between a test socket and a test target (semiconductor IC, etc.) or for electrical connection between circuit boards, the base sheet 103 can be a shape and size that corresponds to the test area of ​​the test socket or the connection area between circuit boards.

[0028] In this case, if the outermost group of conductive parts 104 arranged on the base sheet 103 is considered the outer edge, the inner portion surrounded by that outer edge can be understood as the conductive connection area 105. The conductive connection area 105 can be, for example, 5 mm x 5 mm or larger and 300 mm x 300 mm or smaller. If the conductive connection area 105 is between 5 mm square and 300 mm square, most semiconductor ICs can be placed inside the conductive connection area 105, and electrical connections can be made without strict positioning accuracy. Furthermore, connections between circuit boards can often be handled if the conductive connection area 105 is of that size.

[0029] The size of the outer region 106 of the conductive connection region 105 where the conductive portion 104 is absent is not particularly limited and can be any size depending on the object to which the anisotropic conductive sheet 100 is connected. When the conductive connection region 105 elastically deforms due to pressure contact with the object to be connected, the outer frame portion 102 is subjected to tension toward the conductive connection region 105. However, because the outer region 106 is interposed between the conductive connection region 105 and the outer frame portion 102, the outer region 106 can absorb the tension by stretching and deforming, so that the outer frame portion 102 does not unintentionally shift position.

[0030] Furthermore, if the anisotropic conductive sheet 100 lacks an outer frame portion 102 (not shown), it can have an outer region 106, allowing the anisotropic conductive sheet 100 to be handled without foreign matter such as finger oils or dust adhering to the conductive portion 104.

[0031] The anisotropic conductive sheet 100 allows for more reliable conductive contact between the connected objects and the conductive portion 104, as well as between the linked conductive particles 107, by compressing and deforming the base sheet 103 between the objects to be connected, thereby obtaining a stable conductive connection with low resistance. To enable such compressive deformation of the base sheet 103, it is preferable that the base sheet 103 has a predetermined thickness. The thickness of the base sheet 103, excluding the outer frame portion 102, can be, for example, 0.1 mm to 3.0 mm, more preferably 0.3 mm to 1.5 mm.

[0032] If the lower limit of the thickness of the base sheet 103 is less than 0.1 mm, the base sheet 103 may be prone to fracture due to compressive load. If the lower limit of the thickness of the base sheet 103 is 0.1 mm or more, fracture due to compressive load can be suppressed, and if the lower limit is 0.3 mm or more, fracture due to compressive load can be avoided while ensuring the durability required for applications that are repeatedly subjected to compressive load. An example of an application that is repeatedly subjected to compressive load is an electrical connection component used in a test socket for testing semiconductor ICs.

[0033] Furthermore, for example, when a circuit board is pressed into contact with the anisotropic conductive sheet 100, causing the anisotropic conductive sheet 100 to compress and deform, the circuit board may bend. There may also be errors in the thickness dimensions of each circuit board. It is preferable that the anisotropic conductive sheet 100 can absorb tolerances in the pressing dimensions that may occur due to such electrical connections. On the other hand, the base sheet 103 is designed to have a compressive deformation amount that enables a conductive connection with desirable specifications in terms of resistance and compressive load. If the upper limit of the thickness of the base sheet 103 is in the range of 1.5 mm to 3.0 mm, it is possible to absorb the aforementioned tolerances while being relatively thin, without impairing the desirable compressive deformation amount as much as possible. If the upper limit of the thickness of the base sheet 103 is 1.5 mm or less, it is possible to make the connection structure, including the anisotropic conductive sheet 100 and the object to be connected, thinner, and to obtain a compressive deformation amount that enables a conductive connection with even more desirable specifications.

[0034] Furthermore, if the thickness of the base sheet 103 is between 0.3 mm and 1.5 mm, fracture due to compressive load can be avoided, it has durability that allows it to be used even in applications subjected to repeated compressive loads, the aforementioned connection structure can be made thinner, and a compressive deformation amount that enables conductive connection with desirable specifications can be obtained.

[0035] The thickness of the base sheet 103 can be uniform overall, provided that it has the predetermined thickness exemplified, but the thickness may vary depending on the part. Furthermore, the thickness of the conductive connection region 105 and the outer region 106 may differ. In this case, for example, the outer region 106 can be thicker than the conductive connection region 105, thereby suppressing deformation of the outer region 106 more than the conductive connection region 105, and thus improving the ease of handling of the anisotropic conductive sheet 100. Therefore, the thickness of the outer region 106 may be thicker than the predetermined thickness mentioned above.

[0036] Conductive portion 104: The conductive portion 104 is formed by a chain of multiple conductive particles 107 exhibiting magnetism, arranged in series in the thickness direction of the base sheet 103. As shown in Figure 2, the conductive portion 104 is exemplified by two conductive particles 107 arranged in series, but it may also consist of one or three or more. The direction in which the multiple conductive particles 107 are arranged in series is perpendicular to the surface of the base sheet 103, and being arranged in series means that the multiple conductive particles 107 are stacked in that perpendicular direction. Therefore, it does not include overlapping conductive particles 107 that branch out.

[0037] Multiple conductive parts 104 are arranged at "regular intervals based on a predetermined design arrangement." An example of this is shown in Figure 1. In the particle arrangement in Figure 1A, multiple conductive parts 104 are arranged on the base sheet 103 at the intersections of a square lattice. In the particle arrangement in Figure 1B, multiple conductive parts 104 are arranged on the base sheet 103 in a staggered arrangement. "Regular intervals based on a predetermined design arrangement" means that the distance between adjacent conductive parts 104 is controlled based on a predetermined design value, and that this is substantially equal spacing. That is, among the multiple conductive parts 104 arranged on the base sheet 103, the distance between any two arbitrarily selected adjacent conductive parts 104 is always a constant interval based on a predetermined design value. The regular interval can be the straight-line distance (center-to-center distance) connecting the center of one conductive part 104 and the center of the other conductive part 104 that are exposed on the surface of the base sheet 103. Alternatively, it can be defined as the straight-line distance (distance between outer edges) connecting the outer edge of one conductive portion 104 and the outer edge of the other conductive portion 104 that are exposed on the surface of the base sheet 103.

[0038] Here, "regular spacing based on a predetermined design arrangement" includes both configurations in which all conductive parts 104 on the base sheet 103 are arranged at equal intervals based on a single design value, and configurations in which the base sheet 103 is divided into multiple regions, and the conductive parts 104 are regularly arranged in each region based on a single design value that is different from each other. In contrast, configurations in which multiple conductive parts 104 are arranged randomly and the spacing between adjacent conductive parts 104 is irregular or non-uniform are excluded from the scope of "regular spacing based on a predetermined design arrangement" in this specification and the claims.

[0039] The number and arrangement of the conductive parts 104 are not limited to the embodiment shown in Figure 1. For example, the planar shape of the elastic connector part 101 and the conductive connection area 105 shown in Figure 1 is a square, but their planar shapes can also be other polygons or circles, and the number and arrangement of the conductive parts 104 can be changed accordingly. However, the square shape shown in Figure 1 is preferable because any conductive part 104 can make conductive contact with any object that can be connected inside the square, regardless of the shape and arrangement of the conductive connection parts (connection terminals, contact parts, etc.) of the object to be connected.

[0040] As described above, the plurality of conductive portions 104 are arranged at regular intervals. That is, any two adjacent conductive portions 104 are arranged at the same pitch distance. The "pitch distance" as referred to in the present specification and the claims means the distance D between the centers of gravity of adjacent conductive particles 107 observed when the anisotropic conductive sheet 100 is viewed in a plan view (see FIG. 2). The distance D between the centers of gravity can be 0.02 mm or more and 0.5 mm or less. If the distance D between the centers of gravity is within this range, while suppressing a short circuit between adjacent conductive portions 104, it is also possible to cope with electrical connection (narrow pitch connection) to terminals or contacts that have been narrowed in pitch with the miniaturization, high-density mounting, and multi-pinning of the semiconductor IC and circuit board which are the connection objects. On the other hand, if the distance between the centers of gravity is less than 0.02 mm, there is a risk that adjacent conductive portions 104 will short-circuit during the manufacturing process. Also, if the distance between the centers of gravity exceeds 0.5 mm, there is a risk that it will not be possible to cope with narrow pitch connection to the connection object. In order to more surely suppress the short circuit and cope with narrow pitch connection described above, it is more preferable that the distance between the centers of gravity be 0.02 mm or more and 0.3 mm or less. By setting the distance between the centers of gravity to 0.3 mm or less, a narrow pitch connection that is difficult to achieve with metal contacts such as pogo pins and leaf springs becomes possible from the viewpoints of manufacturing constraints, durability of repeated use, and manufacturing cost.

[0041] The number of the plurality of conductive portions 104 is preferably 10 or more and 500 or less per 1 mm

[0042] , ,

[0041] , , , ２ ,

[0043] In this range, it is possible to realize a narrow pitch connection with high connection reliability that can cope with the miniaturization, high-density mounting, and multi-pinning of the semiconductor IC and circuit board which are the connection objects.

[0042] As shown in FIG. 2, when focusing on the stacked structure of the conductive particles 107, each conductive portion 104 is constituted by a multi-layer structure, that is, a stacked structure of a plurality of conductive particle layers 108. The multi-layer structure is a first conductive particle layer 108a formed by first conductive particles 107a and a second conductive particle layer 108b formed by second conductive particles 107b.

[0043] Among them, the second conductive particle 107b constitutes the "contact particle". That is, the "contact particle" is a conductive particle 107 having a contact portion 107b1 that protrudes from the first surface 103a of the base sheet 103 and makes electrical contact with the connection object.

[0044] The first conductive particle layer 108a and the second conductive particle layer 108b have different orientation methods of the conductive particles 107. Also, the plurality of conductive particles 107 forming the first conductive particle layer 108a are arranged simultaneously in the same process. The plurality of conductive particles 107 forming the second conductive particle layer 108b are also arranged simultaneously in the same process. This point will be described in the later manufacturing method.

[0045] The plurality of conductive portions 104 are formed with a uniform height H along the thickness direction of the base sheet 103. The "uniform height" of the conductive portion as referred to in this specification and the claims means not only that the heights are the same, but may also include substantially the same height. "Substantially the same height" may include cases where there is a difference in height within a range of 20% of the average particle diameter of the conductive particles 107. This point will be further described with respect to the conductive particles 107 later.

[0046] Conductive particle 107: The conductive particle 107 is a particulate conductive substance exhibiting magnetism. The conductive particle 107 is preferably a magnetic conductive filler. Examples of the material of the magnetic conductive filler include, but are not limited to, nickel, cobalt, iron, ferrite, or alloys thereof. The shape of the magnetic conductive filler is spherical, particularly a true spherical shape. By using a true spherical shape, it is possible to easily make the height H of the conductive portion 104 uniform. Further, the magnetic conductive filler may be a good electrical conductivity metal, a resin, a ceramic coated with a magnetic conductor, or a magnetic conductor coated with a good electrical conductivity metal. Examples of the good electrical conductivity metal include gold, silver, platinum, aluminum, copper, iron, palladium, chromium, stainless steel, etc.

[0047] The average particle size of the conductive particles 107 is preferably 1 μm to 200 μm, and more preferably 5 μm to 100 μm, in that it is easy to form a chain state by applying a magnetic field and can efficiently form a conductor. In this specification and in the claims, "average particle size" means the particle size at which the cumulative frequency is 50% in the volume-based cumulative frequency distribution curve measured using a laser diffraction particle size distribution analyzer (D ５０ ) means.

[0048] It is preferable that the conductive particles 107 have as narrow a particle size distribution as possible. For example, the particle size distribution of conductive particles 107 is such that the cumulative frequencies in the volume-based cumulative frequency distribution curve measured using a laser diffraction particle size distribution analyzer are 10%, 50%, and 90%, respectively, for particle size D １０ , D ５０ , D ９０ Using this, the particle size distribution calculated from the following equation (1) can be set to be between 0.55 and 1.45. Particle size distribution = (D ９０ -D １０ ) / D ５０ ... (1) By using conductive particles 107 with such a particle size distribution, when the number of stacked conductive particles 107 (number of stacked conductive particle layers 108) is set to the same number for multiple conductive parts 104, it becomes easy to form the height H of the conductive parts 104 to a uniform height.

[0049] Outer frame portion 102: The outer frame portion 102 can be formed as a part with various functionalities. Examples of these functionalities include maintaining the shape of the elastic connector portion 101, improving the handling of the anisotropic conductive sheet 100, positioning the anisotropic conductive sheet 100 relative to the object to be connected, and waterproofing to prevent moisture from entering the elastic connector portion 101. The material and shape of the outer frame portion 102 can be selected according to these functionalities.

[0050] Examples of materials for the outer frame 102 include metal, thermoplastic resin, resin film, silicone rubber, and combinations of two or more of these materials. For the aforementioned shape retention and handling properties, the outer frame 102 can be made of metal, specifically iron, stainless steel, copper, aluminum, and alloys containing these materials. Alternatively, a rigid resin film can be used, specifically polyimide film, polyetherimide film, polycarbonate film, polyethylene naphthalate film, etc. For the aforementioned waterproofing properties, the outer frame 102 can be made of silicone rubber with waterproof ribs. Although the positioning function is not shown in the illustration, the outer frame 102 can be provided with waterproof ribs made of silicone rubber with rubber-like elasticity. For the aforementioned positioning function, the outer frame 102 can be provided with positioning holes or positioning protrusions.

[0051] 2. Method for manufacturing the anisotropic conductive sheet 100

[0052] The method for manufacturing the anisotropic conductive sheet 100 will be explained with reference to Figure 3.

[0053] Formation of the first conductive particle layer 108a [Figure 3A]: A support member 109 for forming the anisotropic conductive sheet 100 is prepared, and a particle holding portion 110 is formed on the support member 109.

[0054] The support member 109 can be made of a resin film as an example. The particle holding portion 110 has the function of positioning and fixing the first conductive particles 107a constituting the first conductive particle layer 108a one by one at regular intervals based on a predetermined design arrangement. The particle holding portion 110 can hold one first conductive particle 107a and is detachable from the first conductive particle 107a when the support member 109 is peeled off from the anisotropic conductive sheet 100. Such a particle holding portion 110 can be made of an adhesive layer, a magnetic layer, as an example.

[0055] The adhesive layer can be formed on the support member 109 by printing or coating a liquid adhesive at regular intervals based on a predetermined design arrangement as shown in Figure 1, for example, and in a size that adheres only one first conductive particle 107a. The magnetic layer can be formed on the support member 109 by printing or coating a liquid magnetic ink containing magnetic particles at regular intervals as shown in Figure 1, for example, and in a size that magnetically adheres only one first conductive particle 107a. In this case, the particle holding portion 110 is formed as an island-shaped coating layer in which a large number of dots are dispersed at the same spacing distance.

[0056] Next, the first conductive particles 107a are attached to each individual particle-holding portion 110. The first conductive particles 107a can be attached to each particle-holding portion 110, for example, by scattering them. Specifically, the first conductive particles 107a scattered on each adhesive layer adhere to the first conductive particles 107a, and the first conductive particles 107a scattered on each magnetic layer adhere due to magnetic force. As a result, the first conductive particle layer 108a is formed, as shown in Figure 3A.

[0057] Formation of the second conductive particle layer 108b [Figure 3B]: A liquid polymer composition containing the second conductive particles 107b in a liquid polymer matrix is ​​prepared. The liquid polymer composition can be, as an example, a liquid silicone rubber containing the aforementioned magnetic conductive filler.

[0058] The support member 109 is placed in a molding die, and the liquid silicone rubber is applied in a thin film to form a thin polymer liquid film layer 111 that covers the support member 109 and the first conductive particle layer 108a. The surface of the thin polymer liquid film layer 111 is flattened to a plane using a squeegee or the like, and its film thickness is formed to be substantially the same height as the thickness of the base sheet 103.

[0059] Then, when a magnetic field is applied along the thickness direction of the support member 109, as shown in Figure 3B, the magnetic conductive filler (second conductive particle 107b) dispersed in the polymer liquid film layer 111 is oriented to stack and chain on top of the first conductive particle 107a. At this time, the first conductive particle 107a functions as a magnetic field forming medium (magnetic pin). Therefore, one magnetic conductive filler can be oriented on top of one first conductive particle 107a. This forms the second conductive particle layer 108b.

[0060] In the magnetic field orientation process described above, the surface of the polymer liquid film layer 111 is open and not pressed down by any member. That is, instead of performing magnetic field orientation in a closed space with the upper and lower molds of the molding die closed, applying a magnetic field with the surface of the polymer liquid film layer 111 open makes it easier for the magnetic conductive filler to move and to be laminated in a series chain on top of the first conductive particles 107a.

[0061] Curing treatment of polymer liquid film layer 111 [Figure 3C]: Next, the polymer liquid film layer 111 is cured. In the above example, the polymer liquid film layer 111 is liquid silicone rubber and is cured by heating. Even at this point of heat curing treatment, the upper surface of the polymer liquid film layer 111 remains open. In this way, a base sheet 103 made of solid silicone rubber is formed, and an anisotropic conductive sheet 100 can be obtained. The anisotropic conductive sheet 100 removed from the mold has a support member 109 attached to it. This support member 109 may remain attached as a "film sheet" to protect the anisotropic conductive sheet 100 until it is actually used, or it may be peeled off.

[0062] As described above, the anisotropic conductive sheet 100 is formed by leaving the surface of the polymer liquid film layer 111 open and orienting the magnetic conductive filler in a magnetic field, which is then cured. In the resulting base sheet 103, the upper tops of the second conductive particles 107b are exposed on the first surface 103a, thereby forming a contact portion 107b1 (second contact portion). The height to which the contact portion 107b1 is exposed and protrudes from the first surface 103a can be adjusted by considering the molding shrinkage according to the material used for the polymer liquid film layer 111, or by considering the thickness of the polymer liquid film layer 111. By having the exposed contact portion 107b1, the anisotropic conductive sheet 100 can obtain a highly reliable conductive connection to the object to be connected.

[0063] On the other hand, on the second surface 103b of the base sheet 103 from which the support member 109 has been peeled off, the lower top of the first conductive particle 107a is exposed, forming a contact portion 107a1 (first contact portion). The lower top of the first conductive particle 107a is exposed because the particle holding portion 110 of the support member 109 peels off from the first conductive particle 107a. In addition, a recess corresponding to the shape of the particle holding portion 110 is formed around the exposed contact portion 107a1. A conductive connection portion 201, which protrudes from the surface of the object to be connected 200 (described later), can fit into this recess. In this case, the shape of the particle holding portion 110 can be a shape corresponding to the shape of the conductive connection portion 201. By having the exposed contact portion 107a1, the anisotropic conductive sheet 100 can obtain a highly reliable conductive connection to the object to be connected.

[0064] 3. How to use the anisotropic conductive sheet 100 [Figure 2]

[0065] As shown in Figure 2, when the anisotropic conductive sheet 100 is placed on the first connection target 200, the contact portion 107a1 of the first conductive particle 107a comes into contact with the conductive connection portion 201. Then, when the second connection target 300 is pressed into contact with the base sheet 103, the contact portion 107b1 of the second conductive particle 107b comes into contact with the conductive connection portion 301. The anisotropic conductive sheet 100 is compressed and deformed by the first connection target 200 and the second connection target 300, and they are electrically connected via a plurality of conductive portions 104. Here, the combination of the first connection target 200 and the second connection target can be circuit board to circuit board, semiconductor IC to circuit board, semiconductor IC to semiconductor IC, etc. Also, the conductive connection portion 201 and the conductive connection portion 301 can be contacts, connection terminals, electrodes, conductive layers, etc.

[0066] 4. Operation and Effects of the Embodiments

[0067] The anisotropic conductive sheet 100 can improve the reliability of the connection to the objects 200 and 300.

[0068] During the manufacturing of the anisotropic conductive sheet 100, the first conductive particles 107a that form the conductive portion 104 are oriented without relying on magnetic repulsion between the first conductive particles 107a. As a result, the anisotropic conductive sheet 100 can have conductive portions 104 in which one first conductive particle 107a is arranged at regular intervals based on a predetermined design arrangement. Furthermore, since each conductive portion 104 is formed by at least two conductive particles 107 linked in series in the thickness direction of the base sheet 103, the thickness of the anisotropic conductive sheet 100 (elastic connector portion 101, base sheet 103) can be increased compared to the case of an anisotropic conductive sheet in which there is only one second conductive particle 107 without lamination. As a result, the anisotropic conductive sheet 100 can reduce the compressive load during use.

[0069] During use, the anisotropic conductive sheet 100 is subjected to compressive deformation by the pressure contact between the first object to be connected 200 and the second object to be connected 300. This causes strain in either the first object to be connected 200 or the second object to be connected 300, resulting in tolerances. However, as mentioned above, the anisotropic conductive sheet 100 can be made thicker, and its compressive deformation (elastic deformation) can absorb the different tolerances that may arise depending on the objects to be connected 200 and 300.

[0070] As mentioned above, the anisotropic conductive sheet 100 can be made thicker, thus achieving durability that makes it less prone to breakage or other problems even when subjected to compression and deformation many times during use.

[0071] According to the above manufacturing method, an anisotropic conductive sheet 100 can be obtained which has a plurality of conductive portions 104 in which conductive particles 107 are arranged one by one at regular intervals based on a predetermined design arrangement, and in which two conductive particles 107 are linked in series in each conductive portion 104 in the thickness direction of the base sheet 103.

[0072] According to the above manufacturing method, the first conductive particle layer 108a is not formed by magnetic field orientation. When the first conductive particles 107a are oriented in a magnetic field to form the first conductive particle layer 108a, the magnetic repulsion between adjacent first conductive particles 107a results in uneven spacing between adjacent first conductive particles 107a, causing the first conductive particles 107a to be randomly arranged. Therefore, it is not possible to form the conductive portion 104 at regular intervals based on the design arrangement (regular arrangement intervals based on the design concept). In this manufacturing method, the first conductive particles 107a are not oriented in a magnetic field, but rather particle holding portions 110 are formed on the support member 109 at regular intervals, and the first conductive particles 107a are attached thereto. As a result, it is possible to form the first conductive particle layer 108a in which the first conductive particles 107a are arranged at regular intervals based on a predetermined design arrangement, without relying on magnetic repulsion between the conductive particles 107a.

[0073] According to the manufacturing method described above, first conductive particles 107a, which are positioned and fixed at regular intervals based on a predetermined design arrangement, can function as a magnetic field forming medium, and one second conductive particle 107b can be placed for each first conductive particle 107a. Therefore, in an anisotropic conductive sheet 100 in which two or more conductive particles 107 are linked in the thickness direction of the base sheet 103, the multiple conductive particles 107 do not branch out and link in parallel, but can be linked in series along the thickness direction (a direction perpendicular to the plane of the base sheet 103).

[0074] Therefore, even if the conductive sheet 100 has multiple conductive parts 104 arranged at regular intervals based on a predetermined design arrangement, and each conductive part 104 is an anisotropic conductive sheet 100 in which two or more conductive particles 107 are linked together, adjacent conductive parts 104 do not short-circuit with each other, and each conductive part 104 functions as an independent conductive path, thereby improving connection reliability.

[0075] Furthermore, according to the above manufacturing method, the thickness of the anisotropic conductive sheet 100 (elastic connector portion 101, base sheet 103) can be increased, thereby obtaining an anisotropic conductive sheet 100 having the aforementioned effects and benefits.

[0076] 5. Modified examples of the embodiment [Figure 4]

[0077] (1) In the above embodiment, an example was described in which the particle holding portion 110 is formed in a dot or island shape corresponding to the arrangement of the conductive portion 104. However, as shown in Figure 4A, for example, the particle holding portion 112 can also be formed on the entire surface of the support member 109. Such a particle holding portion 112 can be formed on the support member 109 by printing or coating a liquid adhesive. The particle holding portion 112 is formed as a coating layer formed on the portion of the support member 109 corresponding to the conductive connection region 105 having a plurality of conductive portions 104.

[0078] To attach the first conductive particles 107a to the particle-holding portion 112 at regular intervals based on a predetermined design arrangement (see Figure 1), a mask is prepared with holes formed at regular intervals through which one first conductive particle 107a can pass. This mask is placed on the support member 109, and the mask is attached to the particle-holding portion 112 with one first conductive particle 107a held in each hole of the mask. Once the first conductive particles 107a have adhered to the particle-holding portion 112 through all the holes, the mask is removed. This allows the first conductive particles 107a to be attached to the particle-holding portion 112 at regular intervals based on a predetermined design arrangement.

[0079] (2) In the above embodiment, a method of scattering and adhering the first conductive particles 107a to the particle holding portion 110 which is made of an adhesive layer or a magnetic layer was illustrated. However, it is also possible to position the particle holding portion 110 which is made of an adhesive layer or a magnetic layer facing downwards, provide a vibrating plate below it, and use the vibrating plate to bounce the first conductive particles 107a upwards and adhere them to the particle holding portion 110. This makes it possible to prevent the first conductive particles 107a from adhering to the surface of the support member 109 other than the particle holding portion 110.

[0080] (3) In the above embodiment, a method of attaching the first conductive particles 107a to the particle holding portion 110 formed on the support member 109 was illustrated, but as shown in Figure 4B, the first conductive particle layer 108a can be formed by inkjet printing. This makes it easy to form a first conductive particle layer 108a having the first conductive particles 107a arranged at regular intervals based on various design arrangements. In this case, an inkjet ink composition containing an adhesive composition and the first conductive particles 107a is prepared, and a printed layer is formed on the support member 109 at predetermined regular intervals using an inkjet printer, thereby forming a first conductive particle layer 108a in which the cured layer of the adhesive composition serves as the particle holding portion 113.

[0081] (4) In the above embodiment, an example was shown in which the base sheet 103 is a single-layer molded body, but as shown in Figure 5, the base sheet 103 can also be a multi-layer molded body. The base sheet 103 shown in Figure 5B has a first sheet layer 114 and a second sheet layer 115. The second sheet layer 115 is the single-layer molded body base sheet 103 described above.

[0082] The first sheet layer 114 has a plurality of first conductive portions 104a, each consisting of two first conductive particles 107a and two second conductive particles 107b linked in series. The second sheet layer 115 has a plurality of second conductive portions 104b, each having one third conductive particle 107c. Each conductive portion 104 of the base sheet 103 is formed by linking one first conductive portion 104a with one second conductive portion 104b linked in series. The material forming the second sheet layer 115 is the same as that forming the first sheet layer 114.

[0083] To manufacture such a base sheet 103, the first sheet layer 114 is inverted and set in the cavity of a molding die M to form the second sheet layer 115. The molding method for the second sheet layer 115 is the same as the molding method for the base sheet 103 as the first sheet layer 114. In this case, when the second sheet layer 115 is laminated on top of the first sheet layer 114, a laminated molding interface layer 116 is formed between them. The laminated molding interface layer 116 is formed as a bonding interface between the skin layer of the first sheet layer 114 formed during molding and the skin layer of the second sheet layer 115 that adheres to and hardens on the first sheet layer 114. When the base sheet 103 is observed in cross-section, the laminated molding interface layer 116 appears as a linear or strip-like shape, and when comparing the interior of the first sheet layer 114 and the interior of the second sheet layer 115, it can be observed as a region with different refractive indices, etc.

[0084] An anisotropic conductive sheet 100 having a multilayer molded base sheet 103 allows for a greater thickness of the base sheet 103 compared to a single-layer molded base sheet 103.

[0085] Figure 5 shows an example where the third conductive particle 107c of the second sheet layer 115 is one, but it may be two or more. Also, the number of layers in the multilayer molding of the base sheet 103 is not limited to two, and additional sheet layers (third sheet layer, fourth sheet layer, etc.) may be laminated onto the second sheet layer 115.

[0086] (5) In the above embodiment, an anisotropic conductive sheet 100 with an outer frame portion 102 was exemplified, but a configuration without an outer frame portion 102 is also possible, specifically an anisotropic conductive sheet having only an elastic connector portion 101.

[0087] While various embodiments of this disclosure have been described, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novelty and effects of this disclosure. Accordingly, all such modifications are included within the scope of this disclosure.

[0088] For example, any term that appears at least once in the specification or drawings alongside a broader or synonymous term may be replaced with that different term anywhere in the specification or drawings. Furthermore, the configuration and operation of the anisotropic conductive sheets are not limited to those described in the embodiments of this disclosure, and various modifications are possible.

[0089] 100 Anisotropic conductive sheet (first embodiment), 101 Elastic connector part, 102 Outer frame part, 103 Base sheet, 104 Conductive part, 107a First conductive particles, 107a1 Contact part, 107b Second conductive particles, 107b1 Contact part, 107c Third conductive particles, 108a First conductive particle layer, 108b Second conductive particle layer, 109 Support member, 110 Particle holding part, 114 First sheet layer, 115 Second sheet layer, 116 Laminated molding interface layer, 200 First object to be connected, 300 Second object to be connected

Claims

1. An anisotropic conductive sheet comprising a base sheet made of a polymer matrix and a plurality of conductive portions in which a plurality of magnetic conductive particles are linked together in the thickness direction of the base sheet, wherein the plurality of conductive portions are arranged on the base sheet at regular intervals based on a predetermined design arrangement, and each of the conductive portions is formed by a series link of two or more conductive particles in the thickness direction of the base sheet.

2. The anisotropic conductive sheet according to claim 1, wherein the conductive particles include contact particles having contact portions that protrude from the surface of the base sheet and make conductive contact with an object to be connected.

3. The anisotropic conductive sheet according to claim 1, wherein the base sheet is formed as a multilayer molded body comprising at least a first sheet layer and a second sheet layer laminated together, the first sheet layer has a plurality of first conductive portions having one conductive particle each, the second sheet layer has a plurality of second conductive portions having at least one conductive particle each, and each conductive portion is configured such that one second conductive portion is chained in series with respect to one first conductive portion.

4. The anisotropic conductive sheet according to claim 3, wherein the base sheet has a laminated molding interface layer between the first sheet layer and the second sheet layer.

5. The anisotropic conductive sheet according to claim 4, wherein the laminated molding interface layer has a refractive index different from that of the first sheet layer or the second sheet layer.

6. The anisotropic conductive sheet according to claim 4, wherein the laminated molding interface layer includes a first skin layer of the first sheet layer and a second skin layer of the second sheet layer adhering to the skin layer.

7. The anisotropic conductive sheet according to claim 1, further comprising a film sheet that adheres to the base sheet and covers the surface of the base sheet and a plurality of conductive particles exposed on the surface.

8. A method for manufacturing an anisotropic conductive sheet, comprising the steps of: forming a conductive particle layer in which a plurality of first conductive particles are positioned and fixed at regular intervals based on a predetermined design arrangement; forming a polymer liquid film layer consisting of a liquid polymer matrix containing magnetic second conductive particles so as to cover the conductive particle layer; applying a magnetic field to the polymer liquid film layer to cause the positioned first conductive particles to function as a magnetic field forming medium, thereby orienting at least one of the second conductive particles on top of each of the first conductive particles; and curing the polymer liquid film layer in which the second conductive particles are oriented.

9. The method for manufacturing an anisotropic conductive sheet according to claim 8, wherein the step of forming the conductive particle layer is to form the conductive particle layer by attaching and positioning the first conductive particles to particle holding portions corresponding to the regular intervals.

10. The method for manufacturing an anisotropic conductive sheet according to claim 9, wherein the particle holding portion is a magnetic layer that holds the first conductive particles by magnetic force.

11. The method for manufacturing an anisotropic conductive sheet according to claim 9, wherein the particle holding portion is an adhesive layer that adheres the first conductive particles.

12. The method for manufacturing an anisotropic conductive sheet according to claim 9, wherein the particle holding portion is a printed layer containing the first conductive particles.

13. The method for manufacturing an anisotropic conductive sheet according to claim 12, wherein the printing layer is a printing layer of an inkjet printer.

Images