Connection structure

Abstract

A connection structure (1) is provided with: a first substrate (2) having a plurality of first electrodes (12) arranged in a plane direction; a second substrate (4) having a plurality of second electrodes (14) arranged in the plane direction, and disposed at intervals in the thickness direction orthogonal to the plane direction so that the first electrodes (12) and the second electrodes (14) face each other; and an adhesive layer (3) that is interposed between the first base material (2) and the second base material (4), electrically connects the first electrode (12) and the second electrode (14), which face each other in the thickness direction, and adheres the first base material (2) and the second base material (4) to each other. The thickness of the adhesive layer (3) is less than 15 [mu] m. The distance (A) between the first electrodes (12) adjacent to each other in the plane direction is longer than the distance (B) between the first electrodes (12) and the second electrodes (14) facing each other in the thickness direction.

Description

Technical Field

[0001] The present invention relates to a connection structure. Background Art

[0002] Conventionally, a film containing an anisotropic conductive material has been used to join terminals of two wired circuit boards.

[0003] As such a film, for example, a conductive film is proposed, which includes: a binder resin; at least one of a curing agent and a curing accelerator; a flux; and a plurality of solder particles (for example, see Patent Document 1). In Patent Document 1, such a conductive film is used to join a first electrode and a second electrode facing each other in the thickness direction to manufacture a connection structure.

[0004] Specifically, first, a first connection object component having a plurality of first electrodes arranged in a surface direction and a second connection object component having a plurality of second electrodes arranged in a surface direction are prepared. Next, a conductive film is arranged in a manner that covers the surface of the first connection object component provided with the first electrode, and further, the second connection object component is arranged on the surface of the conductive film in a manner that covers the surface of the second connection object component provided with the second electrode. That is, the first electrode and the second electrode are arranged opposite to each other in the thickness direction. Next, the conductive film is heated. As a result, the solder particles contained in the conductive film are melted to form a solder portion that electrically connects the first electrode and the second electrode. Thus, a connection structure is manufactured.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-047590 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In recent years, from the perspective of miniaturization and low height, electrodes have been developed towards narrower pitches, requiring a reduction in mounting thickness. However, for electrodes arranged at narrow pitches, if a thick film is forcibly mounted thinly (by pressure, etc.), the molten solder particles will electrically connect two electrodes adjacent in the surface direction. As a result, there is an undesirable situation in which the two electrodes are short-circuited and reliability is reduced.

[0010] The present invention provides a connection structure which is small in size, low in height and excellent in reliability.

[0011] Means of solving problems

[0012] The present invention [1] is a connection structure, which comprises:

[0013] A first substrate having a plurality of first electrodes arranged in a surface direction;

[0014] a second substrate having a plurality of second electrodes arranged in the surface direction and arranged at intervals in a thickness direction perpendicular to the surface direction so that the first electrode and the second electrode face each other; and

[0015] an adhesive layer interposed between the first substrate and the second substrate, electrically connecting the first electrode and the second electrode facing each other in the thickness direction and bonding the first substrate and the second substrate together,

[0016] The thickness of the adhesive layer is less than 15 μm.

[0017] A distance between the first electrodes adjacent to each other in the plane direction is longer than a distance between the first electrode and the second electrode facing each other in the thickness direction.

[0018] The present invention [2] comprises the connection structure described in the above-mentioned [1], wherein the above-mentioned adhesive layer is a cured product of an anisotropic conductive adhesive film, the above-mentioned anisotropic conductive adhesive film comprises a columnar solder portion and a cured resin, and the above-mentioned columnar solder portion electrically connects the above-mentioned first electrode and the above-mentioned second electrode which are opposite to each other in the above-mentioned thickness direction.

[0019] The present invention [3] includes the connection structure described in [1] or [2] above, wherein the plurality of first electrodes and the plurality of second electrodes are respectively arranged in a dot pattern.

[0020] The present invention [4] includes the connection structure described in [2] above, wherein the anisotropic conductive adhesive film contains solder particles, and the average value of the maximum length of the solder particles is 3 μm or less.

[0021] The present invention [5] comprises the connection structure described in [2] above, wherein the anisotropic conductive adhesive film contains solder particles.

[0022] The average value of the maximum length of the solder particles is 2 μm or less.

[0023] The present invention [6] comprises the connection structure described in [2] above, wherein the anisotropic conductive adhesive film contains solder particles.

[0024] The average value of the maximum length of the solder particles is 1 μm or less.

[0025] The present invention [7] comprises the connection structure described in [2] above, wherein the anisotropic conductive adhesive film contains solder particles.

[0026] The maximum length of the solder particles is 5 μm or less.

[0027] The present invention [8] comprises the connection structure described in [2] above, wherein the anisotropic conductive adhesive film contains solder particles.

[0028] The maximum length of the solder particles is 3 μm or less.

[0029] Effects of the Invention

[0030] In the connection structure of the present invention, since the thickness of the adhesive layer is as thin as less than 15 μm, a low height can be achieved. Moreover, the distance between the first electrodes adjacent in the surface direction is longer than the distance between the first electrode and the second electrode opposite in the thickness direction. Therefore, the electrical connection of the two first electrodes adjacent in the surface direction can be suppressed, and the first electrode and the second electrode opposite in the thickness direction can be reliably electrically connected. Therefore, the reliability is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] [ Figure 1 ] Figure 1 A cross-sectional view showing one embodiment of the connection structure of the present invention.

[0032] [ Figure 2 ] Figure 2 A~ Figure 2 E shows an embodiment of a method for manufacturing a connection structure; Figure 2 A shows a first step of preparing a first substrate and a second substrate; Figure 2 B shows the second step of preparing the anisotropic conductive adhesive film; Figure 2 C shows a third step of laminating the first substrate, the anisotropic conductive adhesive film and the second substrate; Figure 2 D shows a fourth step of thermocompression bonding the first substrate and the second substrate to the anisotropic conductive adhesive film; Figure 2 E shows a fifth step of forming an adhesive layer for soldering the first substrate and the second substrate to the anisotropic conductive adhesive film.

[0033] [ Figure 3 ] Figure 3 A top view of the first substrate is shown.

[0034] [ Figure 4 ] Figure 4 A top view of the second substrate is shown.

[0035] [ Figure 5 ] Figure 5 A~ Figure 5 C is a schematic diagram showing a columnar solder portion in the bonding layer; Figure 5A shows the following mode: when the distance between the adjacent first electrodes in the surface direction is longer than the distance between the first electrode and the second electrode facing each other in the thickness direction, the electrical connection between the two adjacent first electrodes is suppressed, and the first electrode and the second electrode facing each other in the thickness direction are electrically connected; Figure 5 B shows the following mode: when the distance between the first electrodes adjacent in the plane direction is shorter than the distance between the first electrode and the second electrode opposite in the thickness direction, the first electrode and the second electrode opposite in the thickness direction are electrically connected, and the columnar solder portions adjacent in the plane direction are electrically connected; Figure 5 C shows the following method: when the distance between adjacent first electrodes in the surface direction is shorter than the distance between the first electrode and the second electrode opposite to each other in the thickness direction, the first electrode and the second electrode opposite to each other in the thickness direction are not electrically connected, but the two adjacent first electrodes are electrically connected. DETAILED DESCRIPTION

[0036] Reference Figure 1 One embodiment of the connection structure of the present invention will be described in detail.

[0037] exist Figure 1 In the figure, the up-down direction on the paper is the up-down direction (thickness direction). In addition, the upper side on the paper is the upper side (one side in the thickness direction), and the lower side on the paper is the lower side (the other side in the thickness direction). In addition, the left-right direction and the depth direction on the paper are the plane directions orthogonal to the up-down direction. Specifically, according to the direction arrows in each figure.

[0038] like Figure 1 As shown, the connection structure 1 includes: a first substrate 2; a second substrate 4 disposed at a distance in the thickness direction; and an adhesive layer 3 interposed between the first substrate 2 and the second substrate 4 .

[0039] In other words, the connection structure 1 includes, in order toward one side in the thickness direction, a first substrate 2, an adhesive layer 3, and a second substrate 4. More specifically, the connection structure 1 includes: a first substrate 2; an adhesive layer 3 directly disposed on the upper surface (one surface in the thickness direction) of the first substrate 2; and a second substrate 4 directly disposed on the upper surface (one surface in the thickness direction) of the adhesive layer 3.

[0040] Below, refer to Figure 2 A~ Figure 2 E describes in detail the method for manufacturing the connection structure 1. It should be noted that in this method, an anisotropic conductive adhesive film is used to manufacture the connection structure 1, and the details will be described later. That is, the adhesive layer 3 in the connection structure 1 obtained by this method is a cured product of the anisotropic conductive adhesive film.

[0041] <Method for Manufacturing Connected Structure>

[0042] The manufacturing method of the connection structure comprises: a first step of preparing a first substrate 2 and a second substrate 4; a second step of preparing an anisotropic conductive adhesive film 5; a third step of stacking the first substrate 2, the anisotropic conductive adhesive film 5 and the second substrate 4; a fourth step of thermally pressing the first substrate 2 and the second substrate 4 to the anisotropic conductive adhesive film 5; and a fifth step of forming an adhesive layer 3 for soldering the first substrate 2 and the second substrate 4 to the anisotropic conductive adhesive film 5.

[0043] [1st step]

[0044] In the first step, if Figure 2 As shown in A, a first substrate 2 and a second substrate 4 are prepared.

[0045] The first substrate 2 has a flat plate shape.

[0046] The first substrate 2 includes: a first wired circuit board 11 and a plurality of first electrodes 12 arranged in the surface direction of the first wired circuit board 11. In other words, the first substrate 2 includes: the first wired circuit board 11; and a plurality of first electrodes 12 provided on the surface (one surface in the thickness direction) of the first wired circuit board 11.

[0047] The first wired circuit board 11 is formed of an insulating material.

[0048] The thickness of the first wired circuit board 11 is, for example, not less than 5 μm, and not more than 1000 μm.

[0049] The first electrode 12 is formed of metal.

[0050] Reference Figure 3 In the plan view of the first substrate 2 shown, the first electrodes 12 are arranged in a dot pattern on the first substrate 2 .

[0051] Specifically, the first electrode 12 has a circular shape in plan view. In addition, the plurality of first electrodes 12 are arranged evenly in the surface direction.

[0052] When the first electrodes 12 are arranged in a dot pattern, electrical connection between two adjacent first electrodes 12 in the plane direction can be suppressed, and the first electrode 12 and the second electrode 14 facing each other in the thickness direction can be reliably electrically connected. As a result, reliability can be improved.

[0053] The thickness of the first electrode 12 is, for example, 0 μm or more, preferably 0.001 μm or more, and, for example, 5 μm or less. When the surface of the first substrate 2 coincides with the surface of the first electrode 12 , the thickness of the first electrode 12 is 0 μm.

[0054] In addition, in the plane direction, the distance (pitch) between adjacent first electrodes 12 is, for example, 3 μm or more, preferably 5 μm or more, and, for example, 500 μm or less, preferably 100 μm or less.

[0055] The above distance (pitch) is the same as a distance A (described later) between first electrodes 12 adjacent to each other in the surface direction.

[0056] The distance (pitch) between first electrodes 12 adjacent in the plane direction (distance A between first electrodes 12 adjacent in the plane direction) is longer than the distance B between the first electrode 12 and second electrode 14 facing each other in the thickness direction, as will be described in detail later.

[0057] The second substrate 4 has a flat plate shape.

[0058] The second base material 4 includes: a second wiring circuit board 13; and a plurality of second electrodes 14 arranged in the surface direction of the second wiring circuit board 13. In other words, the second base material 4 includes: a second wiring circuit board 13; and a plurality of second electrodes 14 provided on the surface (the other surface in the thickness direction) of the second wiring circuit board 13.

[0059] The second wired circuit board 13 is formed of, for example, an insulating material or a semiconductor material.

[0060] The thickness of the second wired circuit board 13 is, for example, not less than 5 μm, and not more than 1000 μm.

[0061] The second electrode 14 is formed of metal.

[0062] Reference Figure 4 In the plan view of the second substrate 4 shown in FIG. 1 , the second electrode 14 is arranged in a dot pattern on the second substrate 4 .

[0063] Specifically, the second electrode 14 has a circular shape in plan view. In addition, the plurality of second electrodes 14 are arranged evenly in the plane direction.

[0064] When the second electrode 14 is arranged in a dot pattern, electrical connection between two adjacent first electrodes 12 can be suppressed in the plane direction, and the first electrode 12 and the second electrode 14 facing each other in the thickness direction can be reliably electrically connected. As a result, reliability can be improved.

[0065] The thickness of the second electrode 14 is, for example, 0 μm or more, preferably 0.001 μm or more, and, for example, 5 μm or less. When the surface of the second substrate 4 coincides with the surface of the second electrode 14 , the thickness of the second electrode 14 is 0 μm.

[0066] In addition, the distance (pitch) between the second electrodes 14 adjacent to each other in the plane direction is the same as the distance (pitch) between the first electrodes 12 adjacent to each other in the plane direction described above.

[0067] [Step 2]

[0068] In the second step, if Figure 2 As shown in B, an anisotropic conductive adhesive film 5 is prepared.

[0069] In order to prepare the anisotropic conductive adhesive film 5 , first, an anisotropic conductive adhesive film composition is prepared.

[0070] The anisotropic conductive adhesive film composition contains solder particles 6 and a curable resin.

[0071] Taking environmental adaptability into consideration, the solder material forming the solder particles 6 may include a lead-free solder material (lead-free solder material). Specifically, as the solder material, for example, tin and tin alloys may be included. As the tin alloy, for example, tin-bismuth alloy (Sn-Bi), tin-silver-copper alloy (Sn-Ag-Cu) and tin-silver alloy (Sn-Ag) may be included. As the solder material, preferably tin-silver-copper alloy (Sn-Ag-Cu) and tin-silver alloy (Sn-Ag) may be included.

[0072] The content of tin in the tin-bismuth alloy is, for example, 10% by mass or more, preferably 25% by mass or more, and for example, 50% by mass or less, preferably 45% by mass. In addition, the content of bismuth in the tin-bismuth alloy is, for example, 50% by mass or more, preferably 55% by mass or more, and for example, 90% by mass or less, preferably 75% by mass or less.

[0073] In addition, the content ratio of tin in the tin-silver-copper alloy is, for example, 90% by mass or more, preferably 95% by mass or more. In addition, the content ratio of silver in the tin-silver-copper alloy is, for example, 10% by mass or less, preferably 5% by mass or less. In addition, the content ratio of copper in the tin-silver-copper alloy is, for example, 1% by mass or less, preferably 0.5% by mass or less.

[0074] In addition, the content of tin in the tin-silver alloy is, for example, 90% by mass or more, preferably 95% by mass or more. In addition, regarding the content of silver in the tin-silver alloy, for example, silver is 10% by mass or less, preferably 5% by mass or less.

[0075] The melting point of the solder material (ie, the melting point of the solder particles 6 ) is, for example, 260° C. or less, preferably 235° C. or less, and for example, 100° C. or more, preferably 130° C. or more. The melting point is determined by differential scanning calorimetry (DSC) (the same applies hereinafter).

[0076] The shape of the solder particles 6 is not particularly limited, and examples thereof include spherical, plate-like, and needle-like shapes. The shape of the solder particles 6 is preferably spherical. Figure 2 In B, the shape of the solder particle 6 is shown as a spherical shape, but the shape of the solder particle 6 is not limited to this.

[0077] The average value of the maximum length of the solder particles 6 (in the case of spherical particles, the average particle size D 50 ) is, for example, less than 15 μm, preferably less than 10 μm, more preferably less than 5 μm, and from the viewpoint of small-sized and low-height, further preferably less than 3 μm, particularly preferably less than 2 μm, and most preferably less than 1 μm. The average value of the maximum length is measured using a laser diffraction scattering particle size distribution meter. In addition, the average value of the maximum length can be adjusted by classification.

[0078] The maximum length of the solder particles 6 (in the case of a spherical shape, the maximum particle diameter D max ) is, for example, 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less from the viewpoint of small-sized and low-height. The maximum length is measured using a laser diffraction scattering particle size distribution meter. In addition, the average value of the maximum length can be adjusted by classification.

[0079] The surface of the solder particle 6 is generally covered with an oxide film formed of an oxide of the solder material. The thickness of the oxide film is, for example, not less than 1 nm, and not more than 20 nm.

[0080] The content ratio of the solder particles 6 relative to the anisotropic conductive adhesive film composition is, for example, 10 volume % or more, preferably 15 volume % or more, and for example, 50 volume % or less, preferably 40 volume % or less.

[0081] The solder particles 6 can be used alone or in combination of two or more.

[0082] As the curable resin, for example, a thermosetting resin can be mentioned. As the thermosetting resin, for example, an epoxy resin (for example, a bisphenol A type epoxy resin), a urea-formaldehyde resin, a melamine resin, a diallyl phthalate resin, a silicone resin, a phenolic resin, a thermosetting acrylic resin, a thermosetting polyester, a thermosetting polyimide and a thermosetting polyurethane can be mentioned. As the curable resin, preferably an epoxy resin is mentioned.

[0083] The curable resin is liquid at 25°C or solid at 25°C.

[0084] When the curable resin is solid at 25° C., the softening point of the curable resin is, for example, 50° C. or higher, preferably 80° C. or higher, and for example, 230° C. or lower, preferably 200° C. or lower. The softening point can be measured by a thermomechanical analyzer.

[0085] The content ratio of the curable resin relative to the anisotropic conductive adhesive film composition is, for example, 10 volume % or more, preferably 20 volume % or more, and for example, 90 volume % or less, preferably 85 volume % or less.

[0086] The curable resins may be used alone or in combination of two or more.

[0087] The anisotropic conductive adhesive film composition may contain a thermoplastic resin as necessary.

[0088] Thermoplastic resins are used to form the anisotropic conductive adhesive film composition into a sheet shape. Examples of thermoplastic resins include phenoxy resins, polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymers, etc.), acrylic resins, polyesters, polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide (nylon (registered trademark)), polycarbonates, polyacetals, polyethylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyallyl sulfone, thermoplastic polyimide, thermoplastic polyurethane, polyaminobismaleimide, polyamideimide, polyetherimide, bismaleimide triazine resin, polymethylpentene, fluororesins, liquid crystal polymers, olefin-vinyl alcohol copolymers, ionomers, polyarylates, acrylonitrile-ethylene-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, and butadiene-styrene copolymers. As the thermoplastic resin, preferably, an acrylic resin and a phenoxy resin are mentioned.

[0089] The content ratio of the thermoplastic resin relative to the anisotropic conductive adhesive film composition is, for example, 5 volume % or more, preferably 10 volume % or more, and for example, 80 volume % or less, preferably 70 volume % or less.

[0090] The thermoplastic resins can be used alone or in combination of two or more.

[0091] Furthermore, the anisotropic conductive adhesive film composition contains flux as necessary.

[0092] The flux is a component for removing an oxide film (an oxide film formed of an oxide of the solder material) on the surface of the solder particles 6 .

[0093] As the material of the flux, for example, organic acid salts can be mentioned. As the organic acid salts, for example, organic acids, hydroxyquinoline derivatives and metal carbonyl acid salts can be mentioned. As the organic acid, for example, aliphatic carboxylic acids and aromatic carboxylic acids can be mentioned. As the aliphatic carboxylic acid, for example, aliphatic dicarboxylic acids can be mentioned. As the aliphatic dicarboxylic acids, specifically, adipic acid, malic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid and sebacic acid can be mentioned. As the aromatic carboxylic acid, for example, benzoic acid, 2-phenoxybenzoic acid, phthalic acid, diphenylacetic acid, trimellitic acid and pyromellitic acid can be mentioned. As the material of the flux, preferably, organic acids can be mentioned. As the material of the flux, more preferably, malic acid can be mentioned.

[0094] The melting point of the flux is, for example, 250°C or lower, preferably 180°C or lower, more preferably 160°C or lower, and for example, 100°C or higher, preferably 120°C or higher, more preferably 130°C or higher.

[0095] The shape of the flux is not particularly limited, and examples thereof include plate-like, needle-like, and spherical shapes. The flux may also be dissolved in a known solvent.

[0096] The content ratio of the flux relative to the anisotropic conductive adhesive film composition is, for example, 0.1 volume % or more, preferably 1 volume % or more, and for example, 50 volume % or less, preferably 20 volume % or less.

[0097] The fluxes may be used alone or in combination of two or more.

[0098] Furthermore, the anisotropic conductive adhesive film composition may contain additives (for example, a curing agent, a curing accelerator, and a silane coupling agent) as necessary.

[0099] In addition, when preparing the anisotropic conductive adhesive film composition, the solder particles 6, the curable resin, the thermoplastic resin mixed as needed, the flux mixed as needed, and the additives mixed as needed are mixed. Thus, the anisotropic conductive adhesive film composition is prepared. In addition, the anisotropic conductive adhesive film composition can also be mixed with a known solvent to prepare the anisotropic conductive adhesive film composition as a varnish.

[0100] Next, in order to prepare the anisotropic conductive adhesive film 5 , the anisotropic conductive adhesive film composition (varnish of the anisotropic conductive adhesive film composition) is applied onto one surface in the thickness direction of the release liner 7 , and then dried as necessary.

[0101] The release liner 7 is a film for covering and protecting the anisotropic conductive adhesive film 5. The release liner 7 has a film shape.

[0102] The release liner 7 is, for example, a plastic substrate (plastic film). Examples of the plastic substrate include polyester sheets (polyethylene terephthalate (PET) sheets), polyolefin sheets (e.g., polyethylene sheets, polypropylene sheets), polyvinyl chloride sheets, polyimide sheets, and polyamide sheets (nylon sheets). The surface (one surface in the thickness direction) of the release liner 7 may be subjected to a surface treatment such as silicone treatment.

[0103] The thickness of the release liner 7 is, for example, not less than 1 μm, and not more than 100 μm.

[0104] As drying conditions, the drying temperature is, for example, 40° C. or higher, and for example, 100° C. or lower. The drying time is, for example, 1 minute or longer, and for example, 60 minutes or less.

[0105] Thus, the anisotropic conductive adhesive film 5 is prepared on one surface of the release liner 7 in the thickness direction.

[0106] Such anisotropic conductive adhesive film 5 has a film shape (including a sheet shape) having a predetermined thickness.

[0107] The anisotropic conductive adhesive film 5 is formed of an anisotropic conductive adhesive film composition containing solder particles 6 and a curable resin. Therefore, the anisotropic conductive adhesive film 5 contains solder particles 6 and a curable resin. Specifically, the anisotropic conductive adhesive film 5 contains a curable resin and solder particles 6 dispersed in the curable resin.

[0108] From the viewpoint of reducing the height, the thickness of the anisotropic conductive adhesive film 5 is, for example, less than 15 μm, preferably 10 μm or less, more preferably less than 10 μm, further preferably 5 μm or less, and for example, 1 μm or more.

[0109] In this way, the anisotropic conductive adhesive film 5 is prepared.

[0110] [Step 3]

[0111] In the third step, if Figure 2 As shown in C, the first substrate 2, the anisotropic conductive adhesive film 5, and the second substrate 4 are stacked.

[0112] Specifically, the first substrate 2 and the second substrate 4 are brought close to the anisotropic conductive adhesive film 5, and the first substrate 2 and the second substrate 4 are brought into contact with the anisotropic conductive adhesive film 5. More specifically, in the thickness direction, one surface of the first substrate 2 in the thickness direction is brought into contact with the other surface of the anisotropic conductive adhesive film 5 in the thickness direction, and one surface of the second substrate 4 in the thickness direction is brought into contact with one surface of the anisotropic conductive adhesive film 5 in the thickness direction, so that the first electrode 12 and the second electrode 14 are opposed to each other.

[0113] In this way, the first substrate 2 , the anisotropic conductive adhesive film 5 , and the second substrate 4 are stacked, and a stacked body 8 is manufactured.

[0114] [Step 4]

[0115] In the fourth step, if Figure 2 As shown in D, the first substrate 2 and the second substrate 4 are thermally pressed together with the anisotropic conductive adhesive film 5 .

[0116] Specifically, while the laminated body 8 is heated, the first substrate 2 and the second substrate 4 are pressed toward the anisotropic conductive adhesive film 5 (thermocompression bonding).

[0117] The temperature of the thermocompression bonding is a temperature lower than the melting point of the solder particles 6. Specifically, the temperature of the thermocompression bonding is, for example, lower than 100° C., preferably lower than 80° C., and for example, higher than 40° C., and preferably higher than 60° C. In addition, the pressure of the thermocompression bonding is, for example, higher than 0.001 MPa, preferably higher than 0.005 MPa, and more preferably higher than 0.01 MPa, and for example, lower than 10 MPa, preferably lower than 5 MPa, and more preferably lower than 1 MPa.

[0118] Thus, the first electrode 12 of the first substrate 2 is embedded in the anisotropic conductive adhesive film 5, and one surface of the first substrate 2 in the thickness direction is covered by the anisotropic conductive adhesive film 5. In addition, the second electrode 14 of the second substrate 4 is embedded in the anisotropic conductive adhesive film 5, and the other surface of the second substrate 4 in the thickness direction is covered by the anisotropic conductive adhesive film 5.

[0119] [Step 5]

[0120] In the fifth step, if Figure 2 As shown in E, the adhesive layer 3 for soldering the first substrate 2 and the second substrate 4 to the anisotropic conductive adhesive film 5 is formed.

[0121] Specifically, the stacked body 8 is heated.

[0122] The heating temperature is a temperature equal to or higher than the melting point of the solder particles 6. Specifically, the heating temperature is, for example, 100°C or higher, preferably 130°C or higher, more preferably 200°C or higher, and for example, 400°C or lower, preferably 350°C or lower, more preferably 300°C or lower.

[0123] By such heating, the solder particles 6 melt. The melted solder particles 6 aggregate (self-aggregate) between the first electrode 12 and the second electrode 14 facing each other in the thickness direction to form a columnar solder portion 15. On the other hand, the curable resin in the anisotropic conductive adhesive film 5 is driven out by the self-aggregated solder particles 6 and moves to the periphery of the columnar solder portion 15. Then, the curable resin is thermally cured to become a cured resin 16 that bonds the first substrate 2 and the second substrate 4.

[0124] It should be noted that, as described above, most of the melted solder particles 6 are used to form the columnar solder portion 15, but a portion of the melted solder particles 6 and / or unmelted solder particles 6 are sometimes not used to form the columnar solder portion 15, but remain dispersed in the curable resin. In this case, the cured resin 16 includes a portion of the melted solder particles 6 and / or unmelted solder particles 6.

[0125] Thus, the adhesive layer 3 including the columnar solder portion 15 and the cured resin 16 is formed.

[0126] From the viewpoint of reducing the height, the thickness of the adhesive layer 3 is less than 15 μm, preferably 10 μm or less, more preferably less than 10 μm, further preferably 5 μm or less, and for example, 1 μm or more.

[0127] In this way, the connection structure 1 is manufactured.

[0128] <Connection structure>

[0129] like Figure 2 As shown in E, the connection structure 1 includes: a first substrate 2; a second substrate 4 arranged with a gap in the thickness direction so that the first electrode 12 and the second electrode 14 face each other; and an adhesive layer 3 interposed between the first substrate 2 and the second substrate 4 .

[0130] The adhesive layer 3 includes a columnar solder portion 15 and a cured resin 16 .

[0131] The adhesive layer 3 bonds the first substrate 2 and the second substrate 4. Specifically, the adhesive layer 3 is bonded to the surface of the first substrate 2 excluding the first electrode 12. In addition, the adhesive layer 3 is bonded to the surface of the second substrate 4 excluding the second electrode 14.

[0132] The columnar solder portion 15 electrically connects the first electrode 12 and the second electrode 14 facing each other in the thickness direction. The columnar solder portion 15 has a columnar shape (specifically, a cylindrical shape) and is disposed between the first electrode 12 and the second electrode 14 to contact them.

[0133] The thickness (height) of the columnar solder portion 15 is, for example, greater than or equal to 1 μm, or preferably greater than or equal to 3 μm, and, for example, less than or equal to 10 μm, or preferably less than or equal to 5 μm.

[0134] The thickness of the columnar solder portion 15 is equal to a distance B (described later) between the first electrode 12 and the second electrode 14 that face each other in the thickness direction.

[0135] The thickness of the adhesive layer 3 is equal to the sum of the thickness of the first electrode 12 , the thickness of the second electrode 14 , and the thickness of the columnar solder portion 15 .

[0136] In the connection structure 1 , a distance A between adjacent first electrodes 12 in the plane direction (hereinafter sometimes referred to as distance A) is longer than a distance B between the first electrode 12 and the second electrode 14 facing each other in the thickness direction (hereinafter sometimes referred to as distance B).

[0137] That is, the distance A and the distance B satisfy the following formula (1).

[0138] A>B (1)

[0139] Thus, electrical connection between two adjacent first electrodes 12 can be suppressed, and the first electrode 12 and the second electrode 14 facing each other in the thickness direction can be reliably electrically connected. As a result, reliability can be improved.

[0140] Specifically, the distance A is the same as the distance (pitch) between the first electrodes 12 adjacent to each other in the above-mentioned plane direction, and is specifically 3 μm or more, preferably 5 μm or more, and for example, 500 μm or less, preferably 100 μm or less.

[0141] The distance B is the same as the thickness of the columnar solder portion 15. Specifically, it is 1 μm or more, preferably 3 μm or more, and for example, 10 μm or less, preferably 5 μm or less.

[0142] The difference between the distance A and the distance B (distance A-distance B) is, for example, 1 μm or more, preferably 5 μm or more, and, for example, 499 μm or less, preferably 100 μm or less.

[0143] The ratio of the distance B to the distance A (distance B / distance A) is, for example, not less than 0.01, preferably not less than 0.1, and, for example, less than 1, preferably not more than 0.8.

[0144] The thickness of the connection structure 1 is, for example, 50 μm or more, and for example, 1000 μm or less.

[0145] <Effects>

[0146] In the connection structure 1, the thickness of the adhesive layer 3 is as thin as less than 15 μm. Therefore, a low height can be achieved. In addition, in the connection structure 1, the distance A is longer than the distance B. That is, in the connection structure 1, the distance A and the distance B satisfy the above formula (1). Therefore, Figure 5 As shown in A, electrical connection between two adjacent first electrodes 12 can be suppressed, and the first electrode 12 and the second electrode 14 facing each other in the thickness direction can be reliably electrically connected. As a result, reliability can be improved.

[0147] On the other hand, in the connection structure 1, when the distance A and the distance B do not satisfy the above formula (1), in other words, when the distance A and the distance B satisfy the following formula (2), Figure 5 As shown in FIG. 1B , the first electrode 12 and the second electrode 14 facing each other in the thickness direction are electrically connected, and the columnar solder portions 15 adjacent to each other in the plane direction are electrically connected (that is, two adjacent first electrodes 12 are electrically connected). Alternatively, Figure 5 As shown in C, the first electrode 12 and the second electrode 14 facing each other in the thickness direction are not electrically connected, but two adjacent first electrodes 12 are electrically connected. In any of these cases, since the two adjacent first electrodes 12 are electrically connected, the two first electrodes 12 are short-circuited, and reliability is reduced.

[0148] A≤B (2)

[0149] In particular, from the viewpoint of increasing the density of circuits (narrowing the pitch of electrodes), the distance A tends to be shorter than the distance B.

[0150] On the other hand, in the connection structure 1, by reducing the thickness of the adhesive layer 3 (specifically, less than 15 μm), the distance A can be made longer than the distance B, and as a result, the reliability can be improved.

[0151] <Modification>

[0152] In the modification, the same reference numerals are used for the same components and processes as those in the first embodiment, and detailed description thereof is omitted. In addition, the modification can have the same effects as those in the first embodiment except for special descriptions. Furthermore, the first embodiment and the modification can be appropriately combined.

[0153] In the above description, the adhesive layer 3 is a cured product of an anisotropic conductive adhesive film. However, the adhesive layer 3 is not particularly limited as long as it is a layer that electrically connects the first electrode 12 and the second electrode 14 and bonds the first substrate 2 and the second substrate 4. For example, it can be a cured product of an anisotropic conductive adhesive paste.

[0154] The anisotropic conductive adhesive paste contains, for example, the solder particles 6 , the curable resin, and an activator (for example, carboxylic acid).

[0155] When anisotropic conductive adhesive paste is used, columnar solder portions 15 electrically connecting the first electrode 12 and the second electrode 14 are formed, and the curable resin is cured to become the cured resin 16 , thereby bonding the first substrate 2 and the second substrate 4 , as in the fifth step.

[0156] In the above description, the first electrodes 12 and the second electrodes 14 are arranged in a dot pattern, but the arrangement of the first electrodes 12 and the second electrodes 14 is not limited thereto.

[0157] In the above description, the first electrode 12 and the second electrode 14 have a circular shape in plan view, but the shapes of the first electrode 12 and the second electrode 14 are not limited thereto, and may be, for example, a rectangular shape in plan view.

[0158] In the above description, the second substrate 4 has a flat plate shape, but the shape of the second substrate 4 is not limited thereto, and may be a shape of a chip component (eg, mini / microLED).

[0159] In the above description, in the third step, the first substrate 2 and the second substrate 4 are brought close to the anisotropic conductive adhesive film 5 and brought into contact with the anisotropic conductive adhesive film 5. However, it is also possible that the anisotropic conductive adhesive film 5 is first arranged on one surface in the thickness direction of the first substrate 2 (the surface provided with the first electrode 12), and then the second substrate 4 is arranged on one surface in the thickness direction of the anisotropic conductive adhesive film 5 so that the first electrode 12 and the second electrode 14 are opposed. In addition, before the second substrate 4 is arranged, a surface treatment (for example, surface treatment by coating a silica filler) may be performed on one surface in the thickness direction of the anisotropic conductive adhesive film 5.

[0160] In the above description, the fourth step and the fifth step are implemented as different steps, but the fourth step and the fifth step may be implemented simultaneously. In such a case, the thermocompression bonding is performed with the pressure in the fourth step and the temperature in the fifth step.

[0161] In addition, in the above description, in the fourth step, the first substrate 2 and the second substrate 4 are thermally pressed together with the anisotropic conductive adhesive film 5. In particular, when the second substrate 4 is a chip component, the connection structure 1 can be manufactured by reflow soldering or vacuum reflow soldering without performing thermal pressing.

[0162] Example

[0163] Next, the present invention is described based on examples and comparative examples, but the present invention is not limited to the following examples. It should be noted that "parts" and "%" are mass references unless otherwise specified. In addition, the specific numerical values ​​such as the mixing ratio (containing ratio), physical property values, parameters, etc. used in the following description can replace the corresponding upper limit values ​​(values ​​defined as "below", "less than / lower than") or lower limits (values ​​defined as "above", "greater than / higher than") of the mixing ratios (containing ratios), physical property values, parameters, etc. corresponding to them recorded in the above-mentioned "Specific Implementation Methods".

[0164] <Details of ingredients>

[0165] The trade names and abbreviations of the components used in each Example and each Comparative Example are described in detail.

[0166] jER828: Bisphenol A epoxy resin, epoxy equivalent 184 ~ 194g / eq, liquid at room temperature (25 ° C), manufactured by Mitsubishi Chemical Corporation

[0167] ARUFON UH-2170: Acrylic resin (styrene acrylic polymer containing hydroxyl groups), solid at room temperature (25°C), manufactured by Toagosei Co., Ltd.

[0168] Solder particle A: (96.5 mass% Sn-3.5 mass% Ag alloy, melting point 221°C, spherical, particle size D 50 : 3μm, maximum particle size D max : 12μm, oxygen concentration: 1100ppm)

[0169] Solder particles B: Solder particles (96.5 mass% Sn-3.0 mass% Ag-0.5 mass% Cu alloy, melting point 217-219°C, spherical, particle size D 50 : 3 μm, oxygen concentration 1100 ppm) and the solder particles obtained by classification have a particle size D 50 : 2μm, maximum particle size D max :4.6μm

[0170] Solder particles C: Solder particles (96.5 mass% Sn-3.0 mass% Ag-0.5 mass% Cu alloy, melting point 217-219°C, spherical, particle size D 50 : 3 μm, oxygen concentration 1100 ppm) and the solder particles obtained by classification have a particle size D 50 : 1μm, maximum particle size D max :2.9μm

[0171] <Manufacturing of Connected Structure>

[0172] Example 1

[0173] [1st step]

[0174] A first substrate was prepared. The first substrate had a cylindrical first electrode having a diameter of 15 μm and a thickness of 1 μm, and a distance A between adjacent first electrodes was 15 μm.

[0175] A second substrate was prepared separately. The second substrate had a cylindrical second electrode with a diameter of 15 μm and a thickness of 1 μm, and the distance between adjacent second electrodes was 15 μm.

[0176] [Step 2]

[0177] An anisotropic conductive adhesive film was prepared. Specifically, first, 50 parts by mass of jER828 as a thermosetting resin, 50 parts by mass of ARUFON UH-2170 as a thermoplastic resin, 150 parts by mass of solder particles A, and 20 parts by mass of malic acid as a flux were added to methyl ethyl ketone (MEK) and mixed. Thus, an anisotropic conductive adhesive film composition (solid content concentration 50% by mass) was prepared.

[0178] Next, the anisotropic conductive adhesive film composition was applied onto a release liner to form a coating film, and then dried at 80° C. for 5 minutes. Thus, an anisotropic conductive adhesive film was prepared.

[0179] [Step 3]

[0180] The first substrate, the anisotropic conductive adhesive film and the second substrate are stacked. Specifically, the anisotropic conductive adhesive film is transferred to one surface of the first substrate in the thickness direction (the surface provided with the first electrode). Next, a silica filler (trade name "HIPRESICA", manufactured by UBE EXSYMO Co., Ltd.) with a diameter of ΦS = 5μm is applied to one surface of the anisotropic conductive adhesive film in the thickness direction. After removing the excess silica filler with a blower, the second substrate is arranged in a manner that the first electrode and the second electrode are opposite to each other. Thus, a laminate having the first substrate, the anisotropic conductive adhesive film and the second substrate in sequence in the thickness direction is manufactured.

[0181] [Step 4 and Step 5]

[0182] The laminate was heated at 260° C. for 1 minute while applying a pressure of 10 kPa in the thickness direction. Thus, a columnar solder portion and a cured resin were formed to produce a connection structure. It should be noted that the distance B between the first electrode and the second electrode facing each other in the thickness direction measured by a microscope was 7 μm.

[0183] Examples 2 to 7 and Comparative Examples 1 to 4

[0184] A connection structure was manufactured based on the same steps as in Example 1. The formula of the anisotropic conductive adhesive composition and the thickness of the anisotropic conductive adhesive film were changed according to Table 1. It should be noted that in Example 3, in the third step, a silica filler with a diameter of ΦS = 10 μm was applied to one surface of the anisotropic conductive adhesive film in the thickness direction. In addition, in Comparative Example 2, a silica filler with a diameter of ΦS = 15 μm was applied.

[0185] <Evaluation>

[0186] [reliability]

[0187] (The Creation of the Bridge)

[0188] The connection structures of each embodiment and each comparative example were observed using an X-ray transmission observation device (SMX-100, manufactured by SHIMADZU Corporation) to observe the presence or absence of a bridge connecting adjacent first electrodes. The generation of the bridge was evaluated based on the following criteria. The results are shown in Table 1.

[0189] {Benchmark}

[0190] ○: No bridge was observed.

[0191] ×: A bridge was observed.

[0192] (Conduction of the counter electrode)

[0193] For the connection structures of each embodiment and each comparative example, the connection structures were polished until the connection portion formed by the anisotropic conductive adhesive film and the cross section of the connection portion could be confirmed, and then the columnar solder portion was observed. The conduction of the opposing electrodes was evaluated based on the following criteria. The results are shown in Table 1.

[0194] {Benchmark}

[0195] ◯: Connection between the first electrode and the second electrode by the columnar solder portion was observed.

[0196] ×: No connection between the first electrode and the second electrode by the columnar solder portion was observed.

[0197] [Table 1]

[0198]

[0199] It should be noted that the above invention is provided as an exemplary embodiment of the present invention, but this is only an example and is not to be construed as limiting. Modifications of the present invention that are obvious to those skilled in the art are within the scope of the claims.

[0200] Industrial Applicability

[0201] The connection structure of the present invention is suitable for use in the production of semiconductor devices.

[0202] Description of Reference Numerals

[0203] 1Connection structure

[0204] 21st base material

[0205] 3 Adhesive layer

[0206] 4. Second base material

[0207] 5Anisotropic conductive adhesive film

[0208] 111st electrode

[0209] 12 Second electrode

[0210] 13 Columnar solder part

[0211] 14. Curing resin

Claims

1. A connection structure comprising: A first substrate having a plurality of first electrodes arranged in a surface direction; a second substrate having a plurality of second electrodes arranged in the surface direction and arranged at intervals in a thickness direction orthogonal to the surface direction so that the first electrode and the second electrode face each other; and an adhesive layer interposed between the first substrate and the second substrate, electrically connecting the first electrode and the second electrode facing each other in the thickness direction and bonding the first substrate and the second substrate together, The thickness of the adhesive layer is less than 15 μm, A distance between the first electrodes adjacent to each other in the plane direction is longer than a distance between the first electrode and the second electrode facing each other in the thickness direction.

2. The connection structure according to claim 1, wherein: The adhesive layer is a cured product of an anisotropic conductive adhesive film. The anisotropic conductive adhesive film includes a columnar solder portion and a cured resin, and the columnar solder portion electrically connects the first electrode and the second electrode that are opposed to each other in the thickness direction.

3. The connection structure according to claim 1 or 2, wherein: The plurality of first electrodes and the plurality of second electrodes are respectively arranged in a dot pattern.

4. The connection structure according to claim 2, wherein: The anisotropic conductive adhesive film includes solder particles. The average value of the maximum length of the solder particles is 3 μm or less.

5. The connection structure according to claim 2, wherein: The anisotropic conductive adhesive film includes solder particles. The average value of the maximum length of the solder particles is 2 μm or less.

6. The connection structure according to claim 2, wherein: The anisotropic conductive adhesive film includes solder particles. The average value of the maximum length of the solder particles is 1 μm or less.

7. The connection structure according to claim 2, wherein: The anisotropic conductive adhesive film includes solder particles. The maximum length of the solder particles is 5 μm or less.

8. The connection structure according to claim 2, wherein: The anisotropic conductive adhesive film includes solder particles. The maximum length of the solder particles is 3 μm or less.

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