Anisotropic electrically conductive sheet and method for connecting anisotropic electrically conductive sheet

Abstract

[Problem] To improve the connection reliability of anisotropic electrically conductive sheets. [Solution] An anisotropic electrically conductive sheet 100 comprises a base sheet 103 composed of a rubber-like resilient body of a polymer matrix, and a plurality of electrically conductive portions 104 in which a plurality of electrically conductive particles 107 are linked in the thickness direction of the base sheet 103, wherein: the electrically conductive portions 104 include contacting particles, which are the electrically conductive particles positioned on the surface side of the base sheet 103; the contacting particles have contacting portions that protrude from the surface and are come into conducting contact with an object to be connected; and the base sheet 103 has fillet-shaped holding portions 109 that hold the side surfaces of the contacting portions 107b1.

Description

Anisotropic Conductive Sheet and Connection Method of Anisotropic Conductive Sheet

[0001] The present disclosure relates to an anisotropic conductive sheet and a connection method of 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 and narrower. As an electrical connection member for making electrical conduction connection with the 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 aforementioned semiconductor IC and circuit board, an anisotropic conductive sheet is known. The anisotropic conductive sheet has a conductive portion formed by linking a plurality of conductive particles in the thickness direction of a base sheet made of a rubber-like elastic body of a polymer matrix.

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

[0004] Such an anisotropic conductive sheet can achieve stable electrical conduction connection between connection objects by undergoing compressive deformation. However, in a conventional anisotropic conductive sheet, there is a risk that the conductive particles located on the surface side of the base sheet may fall off due to repeated compressive deformation.

[0005] Therefore, the present disclosure provides a new anisotropic conductive sheet and a connection method of an anisotropic conductive sheet. [[ID=十六]] [[ID=十七]]

[0006] A first aspect of the present disclosure is an anisotropic conductive sheet having a base sheet made of a rubber-like elastic body of a polymer matrix and a plurality of conductive portions in which a plurality of conductive particles are linked in the thickness direction of the base sheet. The conductive portion has contact particles which are the conductive particles located on the surface side of the base sheet. The contact particles have a contact portion that protrudes from the surface and makes electrical conduction contact with a connection object. The base sheet has an anti-drop portion that holds the side surface of the contact portion.

[0007] According to this, the conductive portion includes contact particles having contact portions that protrude from the surface of the base sheet and make electrical contact with the object to be connected, and the base sheet has a fall-prevention portion that holds the sides of the contact portions, so even if the base sheet is repeatedly compressed and deformed, the fall-prevention portion holds the sides of the contact portions, thereby suppressing the fall-off of the contact particles.

[0008] The fall prevention portion has a flared shape extending from the side surface of the contact portion toward the surface of the base sheet and can be a fillet-shaped retaining portion formed within the polymer matrix. This allows the fillet-shaped retaining portion of the polymer matrix to retain the contact particles while following the movement of the contact particles that repeatedly undergo displacement due to compressive deformation.

[0009] The aforementioned anti-detachment portion is an anti-detachment layer laminated on the base sheet and covering the side surface of the contact portion. This allows for the retention of contact particles and provides the anti-detachment layer with various functionalities. These functionalities can, for example, make it suitable as a conductive connecting member for an inspection socket.

[0010] A second aspect of the present disclosure is a method for connecting an anisotropic conductive sheet, comprising the steps of: preparing an anisotropic conductive sheet having a base sheet made of a rubbery elastic body of a polymer matrix; a plurality of conductive parts formed by a chain of conductive particles in the thickness direction of the base sheet; and a thin film coating layer covering the conductive particles on the surface of the base sheet; and forming a rupture opening that exposes the contact portion of the conductive particles to the surface of the base sheet by pressing and contacting the objects to be connected and rupturing the thin film coating layer, wherein the rupture opening functions as a fall prevention part that prevents the conductive particles from falling off the base sheet by contacting the side surface of the conductive particles.

[0011] According to this, since the surface of the base sheet has a thin film coating layer that covers the conductive particles, it is possible to suppress the detachment of conductive particles before use of the anisotropic conductive sheet and prevent foreign matter from adhering to the contact portion. Furthermore, by pressing the object to be connected into contact with the base sheet and breaking the thin film coating layer, a break opening is formed that exposes the contact portion of the conductive particles to the surface of the base sheet. Therefore, even if the contact portion is exposed due to conductive contact with the object to be connected, the detachment of the conductive particles can be suppressed by the break opening. Moreover, even if the base sheet undergoes repeated compression deformation, the detachment prevention portion holds the spherical side surface of the contact portion, thereby suppressing the detachment of the contact particles.

[0012] A third aspect of this disclosure is an electrical device comprising an anisotropic conductive sheet according to the first aspect as a conductive connecting member.

[0013] By incorporating an anisotropic conductive sheet, in which conductive particles are less likely to fall off, as a conductive connecting member, the operational reliability of electrical equipment can be improved.

[0014] A fourth aspect of the present disclosure is an inspection socket comprising a socket body having electrodes and a conductive connecting member housed in the socket body for electrically connecting the electrodes and an object to be inspected, wherein the conductive connecting member is an anisotropic conductive sheet according to the first aspect.

[0015] According to this method, the shedding of conductive particles from the anisotropic conductive sheet can be suppressed, thereby improving the durability of the conductive connection member of the inspection socket.

[0016] According to this disclosure, it is possible to suppress the shedding of conductive particles from an anisotropic conductive sheet.

[0017] 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 another embodiment. Figure 2 is a partially enlarged cross-sectional view showing the connection between the anisotropic conductive sheet of the first embodiment and the object to be connected. Figure 3 is a partially enlarged cross-sectional view illustrating variations of the fillet-shaped retaining portion formed on the polymer matrix, which is the first embodiment of the anti-detachment portion. Figure 4A is a partially enlarged cross-sectional view showing the anisotropic conductive sheet of the second embodiment, and Figure 4B is an explanatory diagram for illustrating variations of the anti-detachment layer. Figure 5A is a cross-sectional view showing the state of the anisotropic conductive sheet of the second embodiment before it makes electrical contact with the object to be connected, and Figure 5B is a cross-sectional view showing the state after it has made electrical contact with the object to be connected. Figure 6 is a partially enlarged cross-sectional view showing the anisotropic conductive sheet of the third embodiment. Figure 7A is a cross-sectional view showing the state of the anisotropic conductive sheet of the third embodiment before it makes electrical contact with the object to be connected, and Figure 7B is a cross-sectional view showing the state after it has made electrical contact with the object to be connected.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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."

[0022] 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.

[0023] 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.

[0024] In this disclosure, the terms "surface," "plane," and "planar" used for sheet-like members such as anisotropic conductive sheets and base sheets refer to the X-Y plane of the sheet-like member, excluding the end faces of the peripheral edges of the sheet-like member.

[0025] 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.

[0026] 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, contacts, terminals, electrodes, conductive layers, etc. of those electrical components. The anisotropic conductive sheet is provided in electrical equipment. Examples of electrical equipment include, but are not limited to, industrial equipment, home appliances, vehicles, etc.

[0027] 1. First Embodiment [Figures 1 to 3]

[0028] (1) Structure of the anisotropic conductive sheet 100

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The base sheet 103 has the rubber elasticity of a polymer matrix. 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.).

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 under 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 member used in a test socket for testing semiconductor ICs.

[0039] 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. It is preferable that tolerances that may occur due to such electrical connections can be absorbed by the anisotropic conductive sheet 100. 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. And 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.

[0040] Furthermore, if the thickness of the base sheet 103 is 0.3 mm or more and 1.5 mm or less, breakage due to the compression load can be avoided, and it has durability that enables use even in applications that repeatedly receive a compression load. It is possible to achieve thinning of the above-described connection structure and obtain a compression deformation amount that enables conductive connection with preferable specifications.

[0041] Note that the thickness of the base sheet 103 can be formed with a uniform thickness as a whole on condition that it has the exemplified predetermined thickness, but the thickness may be different depending on the part. Also, the thickness may be made different between the conductive connection region 105 and the outer region 106. In this case, for example, the outer region 106 can be made thicker than the conductive connection region 105, whereby deformation of the outer region 106 can be suppressed more than that of the conductive connection region 105, and the ease of handling of the anisotropic conductive sheet 100 can be improved. Therefore, the thickness of the outer region 106 may be thicker than the above-described predetermined thickness.

[0042] Conductive portion 104: The conductive portion 104 is formed by a plurality of conductive particles 107 exhibiting magnetism being chained in series in the thickness direction of the base sheet 103. As shown in FIG. 2, the conductive portion 104 exemplifies two conductive particles 107 chained in series, but it may be one or three or more. The direction in which the plurality of conductive particles 107 are chained in series is the direction perpendicular to the surface of the base sheet 103, and being chained in series means a state in which the plurality of conductive particles 107 are stacked in that perpendicular direction. Therefore, overlapping of the conductive particles 107 where the plurality of conductive particles 107 branch is not included.

[0043] The plurality of conductive portions 104 are arranged at "regular intervals based on a predetermined design arrangement". An example thereof is shown in FIG. 1. The particle arrangement in FIG. 1A is one in which a plurality of conductive portions 104 are arranged at the intersection positions of a lattice on the base sheet 103. The particle arrangement in FIG. 1B is one in which a plurality of conductive portions 104 are arranged in a staggered pattern on the base sheet 103. "Regular intervals based on a predetermined design arrangement" means that the separation distance between adjacent conductive portions 104 is controlled based on a predetermined design value and is substantially equidistant. That is, among the plurality of conductive portions 104 arranged on the base sheet 103, the separation distance between any two arbitrarily selected adjacent conductive portions 104 all have a constant interval based on a predetermined design value. The regular interval can be the straight-line distance (distance between centroids) connecting the center of one conductive portion 104 and the center of the other conductive portion 104, which are exposed on the surface of the base sheet 103. Also, it can be 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, which are exposed on the surface of the base sheet 103.

[0044] Here, "regular intervals based on a predetermined design arrangement" includes both a configuration in which all the conductive portions 104 on the base sheet 103 are arranged at equal intervals based on a single design value, and a configuration in which the base sheet 103 is divided into a plurality of regions and the conductive portions 104 are regularly arranged based on mutually different single design values for each region. In contrast, a configuration in which the plurality of conductive portions 104 are randomly arranged and the separation distance between adjacent conductive portions 104 is irregular or non-uniform is excluded from the scope of "regular intervals based on a predetermined design arrangement" in this specification and the claims.

[0045] The arrangement of the multiple conductive parts 104 may be formed by magnetic field orientation. In this case, a liquid polymer matrix containing conductive particles 107 is applied to a molding die, and a magnetic field is applied to the upper surface of the polymer matrix with the molding die open, thereby oriented the conductive particles 107 by the magnetic field. As a result, adjacent conductive particles 107 are dispersed by magnetic repulsion, and adjacent conductive parts 104 can be dispersed and arranged in the planar direction of the base sheet 103 without contacting each other. The multiple conductive parts 104 of the anisotropic conductive sheet 100 may be arranged in such an irregular and random manner.

[0046] 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.

[0047] Adjacent conductive portions 104 can be formed at a predetermined pitch distance. In this specification and in the claims, "pitch distance" means the distance D between the centroids of adjacent conductive particles 107 as observed when viewing the anisotropic conductive sheet 100 in plan view (see Figure 2). The centroid distance D can be 0.02 mm or more and 0.5 mm or less. If the centroid distance D is within this range, it is possible to suppress short circuits between adjacent conductive portions 104 while also accommodating electrical connections (narrow-pitch connections) to terminals or contacts that have been narrowed in pitch due to the miniaturization, high-density mounting, and multi-pinning of semiconductor ICs and circuit boards, which are the objects to be connected. On the other hand, if the centroid distance is less than 0.02 mm, there is a risk that adjacent conductive portions 104 may short circuits during the manufacturing process. Also, if the centroid distance exceeds 0.5 mm, there is a risk that it will not be possible to accommodate narrow-pitch connections with the objects to be connected. To more reliably suppress the short circuits and accommodate narrow-pitch connections as described above, it is preferable to set the distance between the centers of gravity to 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, it becomes possible to achieve narrow-pitch connections that are difficult to realize with metal contacts such as pogo pins or leaf springs from the standpoint of manufacturing constraints, durability for repeated use, and manufacturing costs. The pitch distance between adjacent conductive parts 104 can be applied to both cases: when they are arranged at regular intervals based on the predetermined design arrangement shown in Figure 1, and when they are arranged randomly by the magnetic repulsion of the conductive particles 107.

[0048] The number of conductive parts 104 is 1 mm ２ It is preferable to set the number of pins between 10 and 500. Within this range, it is possible to achieve highly reliable narrow-pitch connections that can accommodate the miniaturization, high-density mounting, and multi-pin configuration of semiconductor ICs and circuit boards that are the objects to be connected.

[0049] As shown in Figure 2, each conductive part 104, focusing on the laminated structure of the conductive particles 107, is composed of a multilayer structure, that is, a laminated structure of multiple conductive particle layers 108. This multilayer structure consists of a first conductive particle layer 108a made of the first conductive particle 107a and a second conductive particle layer 108b made of the second conductive particle 107b.

[0050] Of these, the second conductive particle 107b constitutes a "contact particle." That is, the "contact particle" is a conductive particle 107 that has a contact portion 107b1 that protrudes from the first surface 103a of the base sheet 103 and makes electrical contact with the object to be connected. As shown in Figure 3, the base sheet 103 has a fillet-shaped holding portion 109 that serves as a "fall prevention portion" that holds the side surface (spherical side surface) of the contact portion 107b1.

[0051] The fillet-shaped retaining portion 109 is formed from the surface layer of the polymer matrix and has a shape that widens from the spherical side surface of the contact portion 107b1 of the second conductive particle 107b toward the first surface 103a of the base sheet 103. The fillet-shaped retaining portion 109 is formed in a conical shape that surrounds the spherical side surface of the second conductive particle 107b around its entire circumference. The upper end of the fillet-shaped retaining portion 109 is an open edge that exposes the second conductive particle 107b.

[0052] Having such a fillet-shaped holding portion 109 allows the fillet-shaped holding portion 109, which is made of a rubber-like elastic material, to follow the movement of the second conductive particles 107b, which are repeatedly displaced in the thickness direction of the base sheet 103 due to compression deformation, and to hold the second conductive particles 107b.

[0053] The fillet-shaped retaining portion 109 can be formed in various forms, as shown in Figure 3. Figure 3 shows the outlines S1, S2, S3, and S4 of the first surface 103a of the base sheet 103 including the fillet-shaped retaining portion 109.

[0054] The second conductive particle 107b is prone to falling off if it protrudes from the base sheet 103 beyond a length L1 equal to 50% of its diameter. However, even when the height position of the first surface 103a of the base sheet 103 is located below the center C of the second conductive particle 107b, as shown by the first outline S1, for example, the fillet-shaped retaining portion 109 extends beyond the center C of the second conductive particle 107b and covers the spherical side surface of the contact portion 107b1, thereby suppressing the detachment of the second conductive particle 107b.

[0055] In the anisotropic conductive sheet 100, the presence of second conductive particles 107b having contact portions 107b1 protruding from the first surface 103a of the base sheet 103 makes it difficult to form a uniform height on the first surface 103a of the base sheet 103. For example, even if the design specifies that a liquid polymer matrix should be applied and cured at a height level exceeding the center C of the second conductive particles 107b, as shown by the second outline S2, third outline S3, and fourth outline S4, in reality, areas may be formed lower than the design height, as shown by the first outline S1. However, even if such areas with lower heights occur unintentionally, the fillet-shaped retaining portion 109 can suppress the detachment of the second conductive particles 107b.

[0056] The first surface 103a of the base sheet 103, including the fillet-shaped retaining portion 109, can be formed to have a second outline S2, a third outline S3, and a fourth outline S4, in addition to the first outline S1. The fillet-shaped retaining portion 109 shown by the fourth outline S4 is most advantageous for preventing detachment because it exposes the second conductive particles 107b the least. On the other hand, the fillet-shaped retaining portion 109 shown by the third outline S3 and the second outline S2 effectively prevents detachment by covering the substantially central area of ​​50% of the diameter of the second conductive particles 107b, while also allowing for a wider contact area of ​​the contact portion 107b1. This enables conductive connection even when the object to be connected is tilted or contacted at an angle, while accommodating those contact angles.

[0057] Multiple conductive portions 104 are formed with a uniform height H along the thickness direction of the base sheet 103. As used herein and in the claims, "uniform height" of a conductive portion includes not only identical heights but also substantially identical heights. "Substantially identical heights" may include cases where the height difference is within 20% of the average particle size of the conductive particles 107. This point will be further explained in the later section on the conductive particles 107.

[0058] Conductive particles 107: Conductive particles 107 are particulate conductive material exhibiting magnetism. Preferably, conductive particles 107 are magnetic conductive fillers. Examples of materials for 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, especially perfectly spherical. Using a perfectly spherical shape makes it easier to uniformly adjust the height H of the conductive part 104. Furthermore, the magnetic conductive filler may be a metal, resin, or ceramic coated with a magnetic conductor, or a magnetic conductor coated with a metal. Examples of metals with good electrical conductivity include gold, silver, platinum, aluminum, copper, iron, palladium, chromium, and stainless steel.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] (2) Method for manufacturing the anisotropic conductive sheet 100

[0064] A method for manufacturing an anisotropic conductive sheet 100 will be described below. As an example, a manufacturing method for forming a dispersion pattern of multiple conductive parts 104 by magnetic field orientation will be described.

[0065] A liquid polymer composition containing conductive particles 107 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.

[0066] A thin polymer film layer is formed by applying a liquid polymer composition in a thin film form to a support member such as a resin film. The polymer film layer can be formed by painting, printing, or the like. The thin polymer film layer is flattened to a plane on its surface, for example, by using a squeegee, and its film thickness is formed to be substantially the same height as the thickness of the base sheet 103.

[0067] Then, when a magnetic field is applied along the thickness direction of the support member, the magnetic conductive fillers dispersed in the polymer liquid film layer are oriented to form a series chain. This forms a conductive particle layer 108. Adjacent magnetic conductive fillers are spaced apart due to magnetic repulsion.

[0068] In the magnetic field orientation process described above, the surface of the polymer liquid film layer is open and not held down by a jig such as a molding die. 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 open makes it easier for the magnetic conductive filler to move, and makes it easier to stack the first conductive particles 107a and the second conductive particles 107b in a series chain.

[0069] Next, the polymer liquid film layer is cured. In the example above, the polymer liquid film layer is liquid silicone rubber, so it is cured by heating. Even at this stage of heat curing, 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 molding die has a support member attached to it. This support member 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.

[0070] 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. On the first surface 103a of the base sheet 103 formed in this way, the tops of the second conductive particles 107b are exposed, 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 considering molding shrinkage according to the material used for the polymer liquid film layer, or considering the thickness of the polymer liquid film layer. 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.

[0071] On the other hand, on the second surface 103b of the base sheet 103 from which the support member has been removed, the lower top of the first conductive particle 107a is exposed, thereby forming a contact portion 107a1 (first contact portion). 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.

[0072] (3) How to use the anisotropic conductive sheet 100 [Figure 2]

[0073] 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.

[0074] (4) Operation and effects of the embodiment

[0075] The anisotropic conductive sheet 100 can improve the reliability of the connection to the objects 200 and 300.

[0076] The conductive portion 104 includes a second conductive particle 107b, which is a "contact particle" having a contact portion 107b1 that protrudes from the first surface 103a (plane) of the base sheet 103 and makes electrical contact with the object to be connected 300. The base sheet 103 has a fillet-shaped retaining portion 109 that prevents the contact portion 107b1 from falling off by holding the spherical side surface of the contact portion 107b1. Therefore, even if the base sheet 103 undergoes repeated compression deformation, the fillet-shaped retaining portion 109 holds the spherical side surface of the contact portion 107b1, thereby suppressing the detachment of the second conductive particle 107b.

[0077] The fillet-shaped retaining portion 109 is formed in the polymer matrix in a flared shape from the spherical side surface of the contact portion 107b1 toward the first surface 103a. As a result, the fillet-shaped retaining portion 109, which is made of a rubbery elastic polymer matrix, can follow the movement of the second conductive particle 107b, which is repeatedly displaced by the compressive deformation of the object to be connected 300, and retain it.

[0078] In the anisotropic conductive sheet 100, each conductive portion 104 is formed by two conductive particles 107 linked in series in the thickness direction of the base sheet 103, so the thickness of the anisotropic conductive sheet 100 (elastic connector portion 101, base sheet 103) can be increased. For this reason, the anisotropic conductive sheet 100 can reduce the compressive load during use.

[0079] 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.

[0080] 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.

[0081] 2. Second Embodiment [Figures 4 and 5]

[0082] The second embodiment differs from the first embodiment in the configuration of the base sheet 103 of the anisotropic conductive sheet 120 and the method of connecting the anisotropic conductive sheet 120 based thereon. The other configurations and manufacturing methods of the anisotropic conductive sheet 120 are the same as in the first embodiment, and the functions and effects based thereon are also the same. Therefore, redundant explanations will be omitted, and the differences will be explained in detail.

[0083] The anisotropic conductive sheet 120 has a thin film coating layer 103c on the first surface 103a of the base sheet 103 that covers the second conductive particles 107b of the conductive portion 104. The thin film coating layer 103c is formed as the surface layer portion of a polymer matrix located in the projection region obtained by projecting the second conductive particles 107b onto the first surface 103a. As an example, the polymer matrix of the second embodiment can be silicone rubber, which is a rubber-like elastic material. The thin film coating layer 103c functions as a "detachment prevention portion" that suppresses the detachment of the second conductive particles 107b.

[0084] As shown in Figure 4, the thickness t1 of the thin film coating layer 103c is formed such that the thinnest part is 10 μm or less. If the thinnest part is 10 μm or less, the thin film coating layer 103c can be reliably broken by compressive deformation due to pressing contact with the object to be connected 300, thereby exposing the contact portion 107b1. On the other hand, if the thinnest part exceeds 10 μm, although breaking is possible, the compressive load required for breaking becomes high, which may cause distortion in the object to be connected 300. Furthermore, if the thinnest part exceeds 30 μm, it becomes impossible to break within the range of acceptable compressive load.

[0085] Next, the method for connecting the anisotropic conductive sheet 120 will be explained. As shown in Figure 5A, when the object to be connected 300 is pressed into contact with the thin film coating layer 103c, as shown in Figure 5B, the thin film coating layer 103c is compressed and deformed, causing it to break and expose the contact portion 107b1. When the thin film coating layer 103c breaks, a first break opening 103d is formed on the first surface 103a of the base sheet 103, exposing the contact portion 107b1. This first break opening 103d is a portion that exposes the contact portion 107b1 and holds the second conductive particle 107b, and is a concept that includes a circular or irregularly shaped break edge that forms the opening after breaking, and a portion that overlaps with the second conductive particle 107b outside the break edge in a plan view of the base sheet 103. The first fracture opening 103d contacts the spherical side surface of the second conductive particle 107b and holds it in place, functioning as a fall prevention part to suppress its detachment from the base sheet 103. In this way, the anisotropic conductive sheet 120 of the second embodiment can be electrically connected to the object to be connected.

[0086] According to the second embodiment, since the base sheet 103 has a thin film coating layer 103c that covers the second conductive particles 107b, it is possible to suppress the detachment of the second conductive particles 107b before use of the anisotropic conductive sheet 120, and it is also possible to prevent foreign matter from adhering to the contact portion 107b1.

[0087] Furthermore, by pressing the object to be connected 300 into contact with the thin film coating layer 103c and breaking it, a first broken opening 103d is formed that exposes the contact portion 107b1 of the second conductive particle 107b to the first surface 103a of the base sheet 103. Therefore, even if the contact portion 107b1 is exposed due to conductive contact with the object to be connected 300, the first broken opening 103d can prevent the second conductive particle 107b from falling off. Moreover, even if the base sheet 103 undergoes repeated compression deformation, the thin film coating layer 103c, acting as a fall prevention part, holds the spherical side surface of the contact portion 107b1, thereby preventing the second conductive particle 107b from falling off.

[0088] 3. Third Embodiment [Figures 6 and 7]

[0089] The third embodiment differs from the first embodiment in the configuration of the anisotropic conductive sheet 130 and the method of connecting the anisotropic conductive sheet 130 based thereon. The other configurations and manufacturing methods of the anisotropic conductive sheet 130 are the same as in the first embodiment, and the functions and effects based thereon are also the same. Therefore, redundant explanations will be omitted, and the differences will be explained in detail.

[0090] As shown in Figure 6A, the anisotropic conductive sheet 130 has a thin film coating layer 131 that covers the first surface 103a of the base sheet 103. The thin film coating layer 131 is formed as a "detachment prevention layer" that suppresses the detachment of the second conductive particles 107b.

[0091] The maximum thickness t2 of the thin film coating layer 131 can be set to 10% to 20% of the diameter L2 of the second conductive particle 107b, as shown in Figure 6B. If the maximum thickness t2 of the thin film coating layer 131 is within this range, it can function as a fall-prevention layer while suppressing an increase in resistance.

[0092] The thin film coating layer 131 shown in Figure 6A is formed such that the first surface 103a of the base sheet 103 is positioned above the center of the second conductive particle 107b and below its upper vertex, and the thin film coating layer 131 is formed to cover the first surface 103a. Therefore, the thinnest part of the thin film coating layer 131 is thinner than the maximum value range of the thickness t2. However, it is also possible to form the first surface 103a at substantially the same height as the upper vertex of the second conductive particle 107b. In this case, the thin film coating layer 131 can be formed by laminating it from the upper vertex of the second conductive particle 107b within the range of the thickness t2.

[0093] The thin film coating layer 131 can have various functionalities in addition to its detachment prevention function. For example, by forming the thin film coating layer 131 as a hard layer with a firm surface, it is possible to create a non-adhesive surface layer that reduces the tackiness of the surface of the anisotropic conductive sheet 130, thereby suppressing the adhesion of foreign matter such as dust and providing waterproofing and water repellency. Furthermore, such a thin film coating layer 131 can increase the surface strength of the anisotropic conductive sheet 130 and enhance its heat resistance, weather resistance, and oil resistance. Specifically, the thin film coating layer 131 is preferably a silicone resin layer, which allows for the provision of multifunctional properties such as waterproofing, water repellency, weather resistance, heat resistance, and oil resistance to the surface of the anisotropic conductive sheet 130. Such a thin film coating layer 131 can be formed by painting, printing, or the like.

[0094] Next, the method for connecting the anisotropic conductive sheet 130 will be explained. As shown in Figure 7A, when the object to be connected 300 is pressed into contact with the thin film coating layer 131, as shown in Figure 7B, the thin film coating layer 131 breaks due to the pressing force, exposing the contact portion 107b1. When the thin film coating layer 131 breaks, a second break opening 131a is formed on the surface of the anisotropic conductive sheet 130 (thin film coating layer 131) that exposes the contact portion 107b1. The second break opening 131a is a concept that includes a circular or irregularly shaped break edge that forms an opening after breakage, and a portion that overlaps with the second conductive particle 107b outside the break edge in a plan view of the thin film coating layer 131. The second break opening 131a contacts and holds the spherical side surface of the second conductive particle 107b, and can function as a fall prevention part that suppresses detachment from the base sheet 103. As described above, the anisotropic conductive sheet 130 of the third embodiment can be electrically connected to the object to be connected.

[0095] According to the third embodiment, since the base sheet 103 has a thin film coating layer 131 that covers the second conductive particles 107b, it is possible to suppress the detachment of the second conductive particles 107b before use of the anisotropic conductive sheet 120, and it is also possible to prevent foreign matter from adhering to the contact portion 107b1.

[0096] Furthermore, by pressing the object to be connected 300 into contact with the thin film coating layer 131 and breaking it, a second break opening 131a is formed that exposes the contact portion 107b1 of the second conductive particle 107b to the surface of the anisotropic conductive sheet 130. Therefore, even if the contact portion 107b1 is exposed due to conductive contact with the object to be connected 300, the second break opening 131a can prevent the second conductive particle 107b from falling off. Moreover, even if the base sheet 103 undergoes repeated compression deformation, the thin film coating layer 131 (second break opening 131a), acting as a fall prevention part, holds the spherical side surface of the contact portion 107b1, thereby preventing the second conductive particle 107b from falling off.

[0097] Furthermore, the thin film coating layer 131 can impart to the anisotropic conductive sheet 130 surface properties that combine, in addition to its function of preventing detachment, improved surface strength, non-adhesiveness, waterproofing, water repellency, weather resistance, heat resistance, and oil resistance.

[0098] 4. Modifications of Embodiments

[0099] (1) In the above embodiment, an example was shown in which there are two conductive particles 107 in the conductive part 104, but there may be one or three or more.

[0100] (2) In the above embodiment, an example was shown in which the base sheet 103 has a single-layer structure, but it may also have a multi-layer structure. In this case, a multi-layer base sheet can be obtained by forming a first sheet layer corresponding to the base sheet 103 and laminating a second sheet layer corresponding to the base sheet 103 on top of it. The number of additional layers to be laminated can be two or more. With this, the conductive particles 107 of the first sheet layer and the conductive particles 107 of the second sheet layer can be made of materials and have different properties from each other.

[0101] (3) In the above embodiment, an example was shown in which the thin film coating layer 131 has a single-layer structure, but it may also be a multi-layer structure formed of two or more layers.

[0102] (4) In the above embodiment, an anisotropic conductive sheet 100 with an outer frame portion 102 was illustrated, but a configuration without an outer frame portion 102 is also possible, specifically an anisotropic conductive sheet having only an elastic connector portion 101.

[0103] 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.

[0104] 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.

[0105] 100 Anisotropic conductive sheet (first embodiment), 101 Elastic connector part, 102 Outer frame part, 103 Base sheet, 104 Conductive part, 107 Conductive particles, 109 Fillet-shaped retaining part (anti-detachment part), 120 Anisotropic conductive sheet (second embodiment), 130 Anisotropic conductive sheet (third embodiment), 131 Thin film coating layer,

Claims

1. An anisotropic conductive sheet comprising a base sheet made of a rubbery elastic polymer matrix, and a plurality of conductive portions in which a plurality of conductive particles are linked together in the thickness direction of the base sheet, wherein the conductive portions have contact particles which are conductive particles located on the surface side of the base sheet, the contact particles have contact portions that protrude from the surface and make conductive contact with an object to be connected, and the base sheet has anti-detachment portions that hold the sides of the contact portions.

2. The anisotropic conductive sheet according to claim 1, wherein the conductive particles are spherical in shape.

3. The anisotropic conductive sheet according to claim 1, wherein the conductive portion has a structure in which a plurality of conductive particles are linked in series along the thickness direction of the base sheet and are arranged in a single row without branching in the planar direction of the base sheet.

4. The anisotropic conductive sheet according to claim 1, wherein the plurality of conductive portions are arranged at equal intervals in the planar direction of the base sheet, and adjacent conductive portions are dispersed in a non-contact state with each other.

5. The anisotropic conductive sheet according to claim 1, wherein the contact portion protrudes from the surface of the base sheet to a height of less than 50% of the diameter of the contact particle.

6. The anisotropic conductive sheet according to claim 1, wherein the fall prevention portion has a flared shape extending from the side surface of the contact portion toward the surface of the base sheet and is a fillet-shaped retaining portion formed within the polymer matrix.

7. The anisotropic conductive sheet according to claim 1, wherein the fall prevention portion has a first break opening that exposes the contact portion, and the first break opening is formed by the base sheet breaking due to pressure contact with the object to be connected.

8. The anisotropic conductive sheet according to claim 1, wherein the anti-detachment portion is an anti-detachment layer laminated on the base sheet and covering the side surface of the contact portion.

9. The anisotropic conductive sheet according to claim 8, wherein the fall prevention layer has a fillet-shaped retaining portion that widens from the side surface of the contact portion toward the surface of the fall prevention layer.

10. The anisotropic conductive sheet according to claim 8, wherein the fall prevention layer has a second break opening that exposes the contact portion, and the second break opening is formed by the base sheet breaking due to pressure contact with the object to be connected.

11. The anisotropic conductive sheet according to claim 8, wherein the fall prevention layer has a layer thickness of 10% to 20% of the diameter of the contact particles.

12. The anisotropic conductive sheet according to claim 8, wherein the fall prevention layer is non-adhesive.

13. The anisotropic conductive sheet according to claim 8, wherein the anti-detachment layer is a silicone resin layer.

14. A method for connecting an anisotropic conductive sheet, comprising the steps of: preparing an anisotropic conductive sheet having a base sheet made of a rubbery elastic body of a polymer matrix; a plurality of conductive parts formed by a chain of a plurality of conductive particles in the thickness direction of the base sheet; and a thin film coating layer covering the conductive particles on the surface of the base sheet; and forming a fracture opening that exposes the contact portion of the conductive particles to the surface of the base sheet by pressing and contacting the objects to be connected and rupturing the thin film coating layer, wherein the fracture opening functions as a fall prevention part that suppresses detachment from the base sheet by contacting the side surface of the conductive particles.

15. The method for connecting an anisotropic conductive sheet according to claim 14, wherein the thin film coating layer is the surface layer portion of the polymer matrix.

16. The method for connecting an anisotropic conductive sheet according to claim 14, wherein the thin film coating layer is a detachment prevention layer formed by laminating it onto the base sheet.

17. The anisotropic conductive sheet according to claim 14, wherein the conductive particles are spherical in shape.

18. An electrical device comprising an anisotropic conductive sheet as described in any one of claims 1 to 13 as a conductive connecting member.

19. An inspection socket comprising: a socket body having electrodes; and a conductive connecting member housed in the socket body for electrically connecting the electrodes and an object to be inspected, wherein the conductive connecting member is an anisotropic conductive sheet according to any one of claims 1 to 13.

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