Adhesive film for circuit connection, connection structure and method for manufacturing the same

Abstract

A thermosetting adhesive film for circuit connection according to the present invention contains solder particles having an average particle diameter of 1-30 μm with the particle diameter having a CV value of 20% or less. A ratio of the thickness of the adhesive film for circuit connection to the average particle diameter of the solder particles is more than 1.0 and less than 1.5. Assuming that the solder particles have a melting point of Tm°C, the curing rate at Tm°C is 80% or more when heating is performed at a rate of temperature rise of 10°C / minute under a nitrogen atmosphere.

Description

[Technical Field]

[0001] The present invention relates to an adhesive film for circuit connection, as well as a connection structure and a method for producing the same. [Background technology]

[0002] Methods for mounting liquid crystal driver ICs on glass panels for liquid crystal displays can be broadly divided into two types: chip-on-glass (COG) mounting and chip-on-flex (COF) mounting. In COG mounting, for example, a film-like circuit connection adhesive (hereinafter referred to as "circuit connection adhesive film") is used to bond the liquid crystal driver IC directly to the glass panel. On the other hand, in COF mounting, for example, the liquid crystal driver IC is bonded to a flexible tape with metal wiring, and then these are bonded to the glass panel using a circuit connection adhesive film.

[0003] As LCD displays have become increasingly high-definition in recent years, the pitch and area of ​​the metal bumps, which serve as circuit electrodes for LCD driver ICs, have become increasingly narrow. This creates the risk of conductive particles in the adhesive leaking between adjacent circuit electrodes and causing short circuits. This tendency is particularly pronounced in COG mounting. Furthermore, if conductive particles leak between adjacent circuit electrodes, the number of conductive particles trapped between the metal bumps and the glass panel decreases, potentially increasing the connection resistance between the opposing circuit electrodes and causing poor connection.

[0004] To solve these problems, a method has been proposed in which a plurality of insulating particles (child particles) are attached to the surface of a conductive particle (mother particle) to form a composite particle (insulating-coated conductive particle). For example, Patent Document 1 proposes a method in which spherical resin particles are attached to the surface of a conductive particle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4773685 Summary of the Invention [Problem to be solved by the invention]

[0006] The main object of the present invention is to provide an adhesive film for circuit connection that can ensure sufficient insulation between adjacent electrodes while ensuring a sufficient capture rate of conductive particles without using the insulating coated conductive particles described above. [Means for solving the problem]

[0007] One aspect of the present invention relates to an adhesive film for circuit connection shown in [1] below.

[0008] [1] A thermosetting adhesive film for circuit connection, containing solder particles having an average particle size of 1 to 30 μm and a CV value of the particle size of 20% or less, wherein the ratio of the thickness of the adhesive film for circuit connection to the average particle size of the solder particles is greater than 1.0 and less than 1.5, and the melting point of the solder particles is T m °C, T when heated at a rate of 10 °C / min under a nitrogen atmosphere. m An adhesive film for circuit connection having a cure rate of 80% or more at ℃.

[0009] The adhesive film for circuit connection according to the above aspect can ensure sufficient insulation between adjacent electrodes while ensuring a sufficient capture rate of conductive particles (solder particles). Here, the "capture rate" refers to the ratio of the number of conductive particles (solder particles) captured per unit area of ​​the connection location to the number of conductive particles (solder particles) per unit area of ​​the adhesive film for circuit connection.

[0010] Recently, with the development of a new technology called micro LED, circuit components with low electrode heights have come into use. When using such circuit components, the total height of the connected electrodes may be smaller than the particle diameter of the conductive particles used in the circuit connection adhesive. The inventors have found that even when using a circuit connection adhesive (e.g., a circuit connection adhesive film) containing the above-described insulating-coated conductive particles to manufacture such connection structures, it is difficult to achieve both a sufficient capture rate and sufficient insulation. On the other hand, the circuit connection adhesive film of the above aspect can ensure sufficient insulation between adjacent electrodes while ensuring a sufficient capture rate of conductive particles (solder particles), even when the total height of the connected electrodes is smaller than the particle diameter of the conductive particles.

[0011] The adhesive film for circuit connection on the side surface may be any of the adhesive films for circuit connection shown in [2] to [6] below.

[0012] [2] The adhesive film for circuit connection according to [1], which contains a polymerizable compound and a thermal polymerization initiator.

[0013] [3] The adhesive film for circuit connection according to [2], wherein the polymerizable compound is a cationically polymerizable compound, and the thermal polymerization initiator is a thermal cationic polymerization initiator.

[0014] [4] The adhesive film for circuit connection according to [3], wherein the polymerizable compound comprises at least one selected from the group consisting of alicyclic epoxy compounds and oxetane compounds.

[0015] [5] The adhesive film for circuit connection according to any one of [1] to [4], wherein the melting point of the solder particles is 280° C. or lower.

[0016] [6] An adhesive film for circuit connection according to any one of [1] to [5], which is used to bond a first circuit member having a first electrode and a second circuit member having a second electrode, and to electrically connect the first electrode and the second electrode to each other, wherein the sum of the height of the first electrode and the height of the second electrode is smaller than the average particle diameter of the solder particles.

[0017] Another aspect of the present invention relates to a connection structure shown in [7] below.

[0018] [7] A connection structure comprising: a first circuit member having a first electrode; a second circuit member having a second electrode electrically connected to the first electrode; and a connection portion electrically connecting the first electrode and the second electrode to each other via a solder layer and bonding the first circuit member and the second circuit member together, wherein the connection portion comprises a cured product of the adhesive film for circuit connection according to any one of [1] to [6].

[0019] The connection structure of the above-mentioned side may be the connection structure shown in [8] below.

[0020] [8] The connection structure according to [7], wherein the sum of the height of the first electrode and the height of the second electrode is smaller than the average particle diameter of the solder particles.

[0021] Another aspect of the present invention relates to a method for producing a connection structure as shown in [9] below.

[0022] [9] A method for manufacturing a connection structure, comprising: placing an adhesive film for circuit connection according to any one of [1] to [6] between a surface of a first circuit member having a first electrode, the surface having the first electrode, and a surface of a second circuit member having a second electrode, the surface having the second electrode; and heating a laminate including the first circuit member, the adhesive film for circuit connection, and the second circuit member while pressing the laminate in the thickness direction of the laminate, thereby electrically connecting the first electrode and the second electrode to each other via a solder layer and bonding the first circuit member and the second circuit member.

[0023] The method for manufacturing the connection structure of the above aspect may be the method shown in

[10] below.

[0024]

[10] The method for manufacturing a connection structure according to [9], wherein the sum of the height of the first electrode and the height of the second electrode is smaller than the average particle diameter of the solder particles. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide an adhesive film for circuit connection that can ensure a sufficient capture rate of conductive particles (solder particles) while also ensuring sufficient insulation between adjacent electrodes. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection. [Figure 2] FIG. 2 is a schematic plan view showing an example of the arrangement of conductive particles in the adhesive film for circuit connection of FIG. [Figure 3] FIG. 3 is a schematic plan view showing an example of the arrangement of conductive particles in the adhesive film for circuit connection of FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of a substrate used in the production of the adhesive film for circuit connection of FIG. [Figure 5] FIG. 5 is a diagram showing a modified example of the cross-sectional shape of the recess in the base body of FIG. [Figure 6] FIG. 6 is a diagram showing a state in which solder particles are arranged in the recesses of the base of FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view showing one step in the method for producing the adhesive film for circuit connection of FIG. [Figure 8] FIG. 8 is a schematic cross-sectional view showing one step in the method for producing the adhesive film for circuit connection of FIG. [Figure 9] FIG. 9 is a schematic cross-sectional view showing one embodiment of a connection structure. [Figure 10]FIG. 10 is a schematic cross-sectional view showing one embodiment of a method for manufacturing a connection structure. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following describes embodiments of the present invention. However, the present invention is not limited to the following embodiments. The materials exemplified below may be used singly or in combination, unless otherwise specified. When multiple substances corresponding to each component are present in the composition, the content of each component refers to the total amount of the multiple substances present in the composition, unless otherwise specified. Numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of a numerical range in another stage. In numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. In this specification, "(meth)acrylate" refers to at least one of acrylate and its corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl."

[0028] <Adhesive film for circuit connection> The adhesive film for circuit connection in one embodiment is a thermosetting adhesive film and contains, as conductive particles, solder particles having an average particle size of 1 to 30 μm and a CV value of the particle size of 20% or less. Here, "for circuit connection" means that it is used for connecting circuit components (for example, mounting light-emitting elements). The adhesive film for circuit connection may or may not have anisotropic conductivity. That is, the adhesive film for circuit connection may be an anisotropically conductive adhesive film or a non-anisotropically conductive (for example, isotropically conductive) adhesive film. Here, "anisotropically conductive" means that it is conductive in the direction of pressure application and maintains insulation in the direction of no pressure application. Hereinafter, an adhesive film for circuit connection in one embodiment will be described with reference to FIG. 1.

[0029] Figure 1 is a diagram showing a schematic longitudinal section of an adhesive film for circuit connection according to one embodiment. The "longitudinal section" refers to a section (thickness direction section) that is approximately perpendicular to the main surface of the adhesive film for circuit connection. The adhesive film for circuit connection 10 shown in Figure 1 is composed of a thermosetting adhesive film 1 and solder particles 2 disposed in the adhesive film 1.

[0030] The adhesive film 1 comprises a first adhesive layer 3 and a second adhesive layer 4 provided on the first adhesive layer 3. The first adhesive layer 3 is a layer onto which solder particles 2 are transferred in a manufacturing method of an adhesive film for circuit connection 10, which will be described later.

[0031] The solder particles 2 are arranged near the boundary S between the first adhesive layer 3 and the second adhesive layer 4, and the boundary S is located in the space between adjacent solder particles 2, 2. In FIG. 1, the surface of the solder particle 2 (the surface on the second adhesive layer 4 side) is exposed from the surface of the first adhesive layer 3, but the solder particle 2 may be entirely embedded in the first adhesive layer 3.

[0032] In the longitudinal cross section of the adhesive film for circuit connection 10, adjacent solder particles are spaced apart and aligned in the horizontal direction. In other words, in its longitudinal cross section, the adhesive film for circuit connection 10 is composed of a central region 10a in which solder particles 2 spaced apart from adjacent solder particles are aligned in the horizontal direction, and surface regions 10b and 10c in which solder particles 2 are substantially absent. Here, "lateral direction" refers to a direction approximately parallel to the main surface of the adhesive film for circuit connection (the left-right direction in FIG. 1). The fact that adjacent solder particles are aligned in the horizontal direction and spaced apart can be confirmed, for example, by observing the longitudinal cross section of the adhesive film for circuit connection using a scanning electron microscope or the like.

[0033] The shortest distances (d11 and d21 in FIG. 1 ) from the surface of the solder particle 2 to the surface of the adhesive film for circuit connection 10 (the surface 3a of the first adhesive layer 3 opposite the second adhesive layer 4 side and the surface 4a of the second adhesive layer 4 opposite the first adhesive layer 3 side) may be 0.05 to 1.5 μm. When the shortest distances d11 and d21 are 0.05 μm or more, the adhesive resin can be effectively filled between the circuit components after pressure-bonding, which tends to improve the insulation of the circuit. When the shortest distances d11 and d21 are 1.5 μm or less, the flow of conductive particles during pressure-bonding is suppressed, which tends to achieve high particle capture. The shortest distances d11 and d21 may be 0.1 μm or more or 0.2 μm or more, or 1.4 μm or less or 1.2 μm or less. The shortest distances d11 and d21 may be the same or different.

[0034] 2 and 3 are plan views schematically illustrating exemplary arrangements of solder particles 2 in a circuit-connecting adhesive film 10. As shown in FIGS. 2 and 3, at least a portion of the multiple solder particles 2 may be arranged in a predetermined pattern when viewed from above the circuit-connecting adhesive film. In FIG. 2, the solder particles 2 are arranged regularly and at approximately equal intervals across the entire area of ​​the circuit-connecting adhesive film 10. However, as shown in FIG. 3, for example, the solder particles 2 may be arranged so that, when viewed from above the circuit-connecting adhesive film, a region 10d in which the multiple solder particles 2 are regularly arranged and a region 10e in which the solder particles 2 are substantially absent are regularly formed. The position and number of the solder particles 2 can be determined, for example, depending on the shape, size, and pattern of the electrodes to be connected. The fact that at least a portion of the multiple solder particles are arranged in a predetermined pattern can be confirmed, for example, by observing the circuit-connecting adhesive film from above the main surface of the circuit-connecting adhesive film using an electron microscope or the like.

[0035] The ratio (monodispersion rate) at which the solder particles 2 are present in a state where they are separated from other solder particles 2 (monodispersed state) is preferably 90.0% or more, and may be 93.0% or more, 95.0% or more, 97.0% or more, or 98.0% or more. The upper limit of the monodispersion rate is 100%. The higher the monodispersion rate, the more likely it is that a connection structure with excellent insulation reliability will be obtained. Such a dispersed state can be achieved by using a substrate on which the solder particles 2 are arranged in a predetermined array in the manufacturing method of the adhesive film 10 for circuit connection described below.

[0036] The adhesive film 10 for circuit connection has a thickness that is more than 1.0 times but less than 1.5 times the average particle diameter of the solder particles 2. That is, the ratio of the thickness of the adhesive film 10 for circuit connection to the average particle diameter of the solder particles 2 is more than 1.0 and less than 1.5. The ratio of the thickness of the adhesive film 10 for circuit connection to the average particle diameter of the solder particles 2 may be 1.4 or less, 1.3 or less, 1.2 or less, or 1.1 or less, from the viewpoint of further improving the capture rate of the solder particles 2 between opposing electrodes and further improving the insulation resistance between adjacent electrodes. That is, the ratio of the thickness of the adhesive film 10 for circuit connection to the average particle diameter of the solder particles 2 may be more than 1.0 but less than 1.4, more than 1.0 but less than 1.3, more than 1.0 but less than 1.2, or more than 1.0 but less than 1.1. The thickness of the adhesive film 10 for circuit connection is equal to the thickness of the adhesive film 1.

[0037] The thickness of the adhesive film 10 for circuit connection may be, for example, 2.0 μm or more, 3.0 μm or more, or 4.0 μm or more, and may be 10.0 μm or less, 8.0 μm or less, or 6.0 μm or less, or may be 2.0 to 10.0 μm, 3.0 to 8.0 μm, or 4.0 to 6.0 μm.

[0038] The circuit connecting adhesive film 10 has a melting point of the solder particles of T m °C, T when heated at a rate of 10 °C / min under a nitrogen atmosphere. mThe curing rate at ℃ is 80% or more. Generally, in the manufacture of connection structures using solder particles, the solder is melted to connect circuit components, and then the sealing resin is cured. Therefore, the melting point of the solder particles is usually lower than the curing temperature of the adhesive component. However, if the thickness of the adhesive film 10 for circuit connection is less than 1.5 times the average particle diameter of the conductive particles, the amount of adhesive component will be small relative to the amount of conductive particles. Therefore, when solder particles are used as conductive particles, the insulation may be reduced (e.g., short circuits may be more likely to occur) due to solder diffused into the adhesive film 1 by thermocompression bonding during connection. On the other hand, in the adhesive film 10 for circuit connection having the above curing properties, the adhesive film 1 cures before the solder particles 2 melt by thermocompression bonding during connection, suppressing the diffusion of solder. Therefore, sufficient insulation between adjacent electrodes is ensured even when the thickness of the adhesive film 10 for circuit connection is less than 1.5 times the average particle diameter of the conductive particles. T under the above conditions m From the viewpoint of improving the insulation between adjacent electrodes, the cure rate at ° C. may be 85% or more, 90% or more, or 95% or more, or may be 100%.

[0039] The curing rate of the adhesive film 10 for circuit connection (T when heated at a temperature increase rate of 10°C / min in a nitrogen atmosphere) m The cure rate (curing rate at 50°C) can be determined from the calorific value measured using a differential scanning calorimeter. Specifically, the calorific value of the adhesive film 10 for circuit connection is measured using a differential scanning calorimeter at a temperature rise rate of 10°C / min in a nitrogen (N2) atmosphere, and the calorific value (Q1) from 50°C until the adhesive film 10 for circuit connection is completely cured is calculated as the calorific value (Q2) from 50°C until the melting point T m After determining the amount of heat generated (Q2) up to 100°C, the cure rate can be calculated by substituting the determined value into the following formula (A). When determining Q1, the adhesive film 10 for circuit connection is considered to be completely cured when the rate of change of the differential curve (DDSC curve) of the DSC curve obtained in the measurement is 0.01 [W·g°C] or less. Curing rate (%)=Q2 / Q1×100 (A)

[0040] A circuit connection adhesive film 10 having the above-mentioned curing rate can be easily produced by a person skilled in the art, for example, by using a compound having a cyclic ether group as a thermosetting component, selecting the type of polymerization initiator, adjusting the amount of the initiator, etc.

[0041] The adhesive film 10 for circuit connection having the above-mentioned characteristics is suitable for use in bonding a first circuit member having a first electrode and a second circuit member having a second electrode, and for electrically connecting the first electrode and the second electrode to each other. In particular, the adhesive film 10 for circuit connection contains solder particles as conductive particles, and has a thickness that is more than 1.0 times but less than 1.5 times the average particle diameter of the solder particles 2, and is therefore suitable for use in mounting at low pressures (for example, 5 MPa or less, based on the area of ​​either the first or second circuit member, whichever has the smaller bonding area).

[0042] The adhesive film 10 for circuit connection can ensure sufficient insulation between adjacent electrodes while ensuring a sufficient capture rate of conductive particles (solder particles). This effect is particularly pronounced when the total height of the electrodes to be connected (the total height of the first electrode and the second electrode) is smaller than the average particle diameter of the solder particles. Furthermore, the adhesive film 10 for circuit connection tends to achieve a sufficiently low connection resistance.

[0043] The adhesive film 1 and the solder particles 2 will be described in detail below.

[0044] (adhesive film) The adhesive film 1 is, for example, an insulating adhesive film made of a non-conductive material (such as an insulating resin). The first adhesive layer 3 and second adhesive layer 4 that make up the adhesive film 1 are each made of a thermosetting adhesive composition. Hereinafter, the adhesive composition that makes up the first adhesive layer 3 may be referred to as the "first adhesive composition," and the adhesive composition that makes up the second adhesive layer 4 may be referred to as the "second adhesive composition."

[0045] The adhesive compositions (first adhesive composition and second adhesive composition) contain at least a thermosetting component. The thermosetting component is a component that is flowable at the time of connection and hardens when heated. The adhesive composition may contain a polymerizable compound and a thermal polymerization initiator as the thermosetting component. From the viewpoint of achieving a more excellent effect of reducing connection resistance, the polymerizable compound may be a cationically polymerizable compound, and the thermal polymerization initiator may be a thermal cationic polymerization initiator.

[0046] [Cationic polymerizable compounds] The cationically polymerizable compound may be a compound having a cyclic ether group, from the viewpoint of further improving the effect of reducing connection resistance and achieving more excellent connection reliability. Among compounds having a cyclic ether group, when at least one selected from the group consisting of alicyclic epoxy compounds and oxetane compounds is used, the effect of reducing connection resistance tends to be further improved. The cationically polymerizable compound may contain both an alicyclic epoxy compound and an oxetane compound, from the viewpoint of easily obtaining a desired melt viscosity.

[0047] The alicyclic epoxy compound can be used without any particular limitation as long as it is a compound having an alicyclic epoxy group (for example, an epoxycyclohexyl group). Commercially available alicyclic epoxy compounds include CELLOXIDE 8010 (trade name, bi-7-oxabicyclo[4.1.0]heptane, manufactured by Daicel Corporation), as well as EHPE3150, EHPE3150CE, CELLOXIDE 2021P, and CELLOXIDE 2081 (trade name, manufactured by Daicel Corporation). These compounds may be used alone or in combination of two or more.

[0048] The oxetane compound can be any compound having an oxetanyl group without any particular limitation. Commercially available oxetane compounds include, for example, ETERNACOLL OXBP (trade name: 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl, manufactured by Ube Industries, Ltd.), OXSQ, OXT-121, OXT-221, OXT-101, and OXT-212 (trade names, manufactured by Toagosei Co., Ltd.). These compounds may be used alone or in combination.

[0049] As the compound having a cyclic ether group, an epoxy compound other than an alicyclic epoxy compound may be used. Specifically, for example, an epoxy compound having an aromatic hydrocarbon group, such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin (for example, a product name "jER1010" manufactured by Mitsubishi Chemical Corporation), may also be used. The epoxy compound having an aromatic hydrocarbon group may be used in combination with an alicyclic epoxy compound, from the viewpoint of further improving the effect of reducing connection resistance and achieving more excellent connection reliability.

[0050] [Thermal cationic polymerization initiator] The thermal cationic polymerization initiator is, for example, a compound (thermal latent cation generator) that can generate an acid or the like by heating to initiate polymerization. The thermal cationic polymerization initiator may be a salt compound composed of a cation and an anion. The thermal cationic polymerization initiator is, for example, BF4 - , BR4 - (R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups), PF6 - , SbF6 - , AsF6 - and onium salts such as sulfonium salts, phosphonium salts, ammonium salts, diazonium salts, iodonium salts, anilinium salts, and pyridinium salts, each of which has an anion such as any of the above. These may be used alone or in combination of two or more.

[0051] From the viewpoint of rapid curing, the thermal cationic polymerization initiator may be, for example, a salt compound having an anion containing boron as a constituent element. Examples of such salt compounds include BF4 - or BR4 - (R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups). An anion containing boron as a constituent element is BR4 - and more specifically, tetrakis(pentafluorophenyl)borate.

[0052] From the viewpoint of storage stability, the thermal cationic polymerization initiator may be a salt compound having a cation represented by the following formula (I) or (II). [ka] [ka]

[0053] In formula (I), R 1 and R 2 each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an organic group containing a substituted or unsubstituted aromatic hydrocarbon group, and R 3 represents an alkyl group having 1 to 6 carbon atoms.

[0054] The salt compound having the cation represented by formula (I) may be an aromatic sulfonium salt compound (aromatic sulfonium salt-type thermal acid generator) from the viewpoint of achieving both storage stability and low-temperature activity. 1 and R 2 At least one of the above may be an organic group containing a substituted or unsubstituted aromatic hydrocarbon group. The anion in the salt compound having the cation represented by formula (I) may be an anion containing antimony as a constituent element, such as hexafluoroantimonate (hexafluoroantimonic acid).

[0055] Specific examples of compounds having a cation represented by formula (I) include 1-naphthylmethyl-p-hydroxyphenylsulfonium hexafluoroantimonate (manufactured by Sanshin Chemical Industry Co., Ltd., SI-60 base agent).

[0056] In formula (II), R 4 and R 5 each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an organic group containing a substituted or unsubstituted aromatic hydrocarbon group, and R 6 and R 7 are each independently an alkyl group having 1 to 6 carbon atoms.

[0057] The salt compound (quaternary ammonium salt-type thermal acid generator) having a cation represented by formula (II) is resistant to substances that can cause curing inhibition in cationic curing, and may be, for example, an anilinium salt compound. 4 and R 5 At least one of the groups may be an organic group containing a substituted or unsubstituted aromatic hydrocarbon group. Examples of the anilinium salt compound include N,N-dialkylanilinium salts such as N,N-dimethylanilinium salt and N,N-diethylanilinium salt. The anion in the salt compound having the cation represented by formula (II) may be an anion containing boron as a constituent element, such as tetrakis(pentafluorophenyl)borate.

[0058] The compound having the cation represented by formula (II) may be an anilinium salt having an anion containing boron as a constituent element. Commercially available products of such salt compounds include CXC-1821 (trade name, manufactured by King Industries).

[0059] From the viewpoint of ensuring the formability and curability of the adhesive film, the content of the thermal cationic polymerization initiator may be, for example, 0.1 to 20 parts by mass, 1 to 18 parts by mass, 3 to 15 parts by mass, or 5 to 12 parts by mass per 100 parts by mass of the cationically polymerizable compound. The content of the thermal cationic polymerization initiator in the first adhesive composition (based on 100 parts by mass of the cationically polymerizable compound in the first adhesive composition) may be within the above-mentioned range, and the content of the thermal cationic polymerization initiator in the second adhesive composition (based on 100 parts by mass of the cationically polymerizable compound in the second adhesive composition) may also be within the above-mentioned range.

[0060] The content of the thermosetting component (e.g., the total content of the polymerizable compound and the thermal polymerization initiator) may be, for example, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, based on the total mass of the adhesive composition, from the viewpoint of ensuring the curability of the adhesive film. The content of the thermosetting component may be, for example, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less, based on the total mass of the adhesive composition, from the viewpoint of ensuring the formability of the adhesive film. From these viewpoints, the content of the thermosetting component may be, for example, 5 to 70% by mass, 10 to 60% by mass, 15 to 50% by mass, or 20 to 40% by mass, based on the total mass of the adhesive composition. The content of the thermosetting component in the first adhesive composition (based on the total mass of the first adhesive composition) may be within the above-mentioned range, and the content of the thermosetting component in the second adhesive composition (based on the total mass of the second adhesive composition) may be within the above-mentioned range. Similarly, below, the content of each component contained in the adhesive composition (based on the total mass of the adhesive composition) can be rephrased as the content of the thermosetting component in the first adhesive composition (based on the total mass of the first adhesive composition), or as the content of the thermosetting component in the second adhesive composition (based on the total mass of the second adhesive composition).

[0061] [Other ingredients] The adhesive compositions (first adhesive composition and second adhesive composition) may further contain, in addition to the thermosetting component, for example, a thermoplastic resin, a filler, a coupling agent, and the like.

[0062] The thermoplastic resin contributes to improving the film-forming properties of the adhesive film. Examples of thermoplastic resins include phenoxy resin, polyester resin, polyamide resin, polyurethane resin, polyester urethane resin, acrylic rubber, and epoxy resin (solid at 25°C). Examples of the phenoxy resin include fluorene-type phenoxy resin and bisphenol A-bisphenol F copolymer-type phenoxy resin. These may be used alone or in combination.

[0063] From the viewpoint of resin removal properties during mounting, the weight average molecular weight (Mw) of the thermoplastic resin may be, for example, 5,000 to 200,000, 10,000 to 100,000, 20,000 to 80,000, or 40,000 to 60,000. Mw refers to a value measured by gel permeation chromatography (GPC) and converted using a calibration curve based on standard polystyrene.

[0064] The content of the thermoplastic resin may be, for example, 1 mass % or more, 5 mass % or more, 10 mass % or more, or 20 mass % or more, and may be 70 mass % or less, 60 mass % or less, 50 mass % or less, or 40 mass % or less, or may be 1 to 70 mass %, 5 to 60 mass %, 10 to 50 mass %, or 20 to 40 mass %, based on the total mass of the adhesive composition.

[0065] Examples of the filler include non-conductive fillers (e.g., non-conductive particles). The filler may be either an inorganic filler or an organic filler. Examples of the inorganic filler include inorganic fine particles such as metal oxide fine particles such as silica fine particles, alumina fine particles, silica-alumina fine particles, titania fine particles, and zirconia fine particles; and metal nitride fine particles. Examples of the organic filler include organic fine particles such as silicone fine particles, methacrylate-butadiene-styrene fine particles, acrylic-silicone fine particles, polyamide fine particles, and polyimide fine particles. These may be used alone or in combination. Examples of the filler include silica fine particles. The content of the filler may be, for example, 0.1 to 10 mass % based on the total mass of the adhesive composition.

[0066] Examples of coupling agents include silane coupling agents (e.g., γ-glycidoxypropyltrimethoxysilane) having an organic functional group such as a (meth)acryloyl group, a mercapto group, an amino group, an imidazole group, or an epoxy group, silane compounds such as tetraalkoxysilane, tetraalkoxytitanate derivatives, and polydialkyltitanate derivatives. These may be used alone or in combination. By including a coupling agent in the adhesive composition, the adhesive properties can be further improved. The content of the coupling agent may be, for example, 0.1 to 10% by mass based on the total mass of the adhesive composition.

[0067] The adhesive compositions (first adhesive composition and second adhesive composition) may further contain other additives as other components, such as softeners, accelerators, anti-degradants, colorants, flame retardants, thixotropic agents, etc. The content of the other additives may be, for example, 0.1 to 10% by mass based on the total mass of the adhesive composition.

[0068] The first adhesive composition and the second adhesive composition may contain the same components as each other, or may contain different components.

[0069] The thickness d1 of the first adhesive layer 3 (the distance indicated by d1 in FIG. 1) may be, for example, 0.5 μm or more, 1.0 μm or more, or 2.0 μm or more, from the viewpoint of the transferability of the solder particles 2 during the production of the adhesive film for circuit connection 10. The thickness d1 of the first adhesive layer 3 may be, for example, 5.0 μm or less, 4.0 μm or less, or 3.0 μm or less, from the viewpoint of being able to capture the solder particles more efficiently during connection. From these viewpoints, the thickness d1 of the first adhesive layer 3 may be, for example, 0.5 to 5.0 μm, 1.0 to 4.0 μm, or 2.0 to 3.0 μm.

[0070] The thickness d2 of the second adhesive layer 4 (the distance indicated by d2 in FIG. 1) may be set appropriately depending on the height of the electrodes of the circuit member to be connected, etc. From the viewpoint of being able to sufficiently fill the space between the electrodes and seal the electrodes and obtain better connection reliability, the thickness d2 of the second adhesive layer 4 may be, for example, 0.5 μm or more, 1.0 μm or more, or 2.0 μm or more, or 10 μm or less, 5.0 μm or less, 4.0 μm or less, or 3.0 μm or less, or may be 0.5 to 10 μm, 0.5 to 5.0 μm, 1.0 to 4.0 μm, or 2.0 to 3.0 μm.

[0071] The thickness d1 of the first adhesive layer 3 and the thickness d2 of the second adhesive layer can be determined, for example, by sandwiching the circuit connection adhesive film 10 between two pieces of glass (thickness: approximately 1 mm), pouring in a resin composition consisting of 100 g of bisphenol A type epoxy resin (trade name: jER811, manufactured by Mitsubishi Chemical Corporation) and 10 g of a curing agent (trade name: Epomount Curing Agent, manufactured by Refine Tech Co., Ltd.), polishing the cross section using a polishing machine, and measuring using a scanning electron microscope (SEM, trade name: SE-8020, manufactured by Hitachi High-Tech Science Corporation).

[0072] (solder particles) The solder particles have a melting point lower than the connection temperature, for example. Therefore, the solder particles melt and adhere to the electrodes by thermocompression bonding during connection, thereby electrically connecting the opposing electrodes. The melting point of the solder particles may be, for example, 280°C or lower, 220°C or lower, 180°C or lower, 160°C or lower, or 140°C or lower, from the viewpoint of enabling mounting at low temperatures. The melting point of the solder particles is, for example, 100°C or higher.

[0073] From the viewpoint of achieving both connection strength and a low melting point, the solder particles may contain at least one selected from the group consisting of tin, a tin alloy, indium, and an indium alloy.

[0074] Examples of tin alloys that can be used include In—Sn alloys, In—Sn—Ag alloys, Sn—Au alloys, Sn—Bi alloys, Sn—Bi—Ag alloys, Sn—Ag—Cu alloys, Sn—Cu alloys, etc. Specific examples of these tin alloys include the following: ·In-Sn (In52 mass%, Sn48 mass%, melting point 118℃) ·In-Sn-Ag (In20% by mass, Sn77.2% by mass, Ag2.8% by mass, melting point 175℃) Sn-Bi (Sn 43% by mass, Bi 57% by mass, melting point 138°C) Sn-Bi-Ag (Sn 42% by mass, Bi 57% by mass, Ag 1% by mass, melting point 139°C) Sn-Ag-Cu (Sn 96.5% by mass, Ag 3% by mass, Cu 0.5% by mass, melting point 217°C) Sn-Cu (Sn 99.3% by mass, Cu 0.7% by mass, melting point 227°C) ·Sn-Au (Sn21.0% by mass, Au79.0% by mass, melting point 278℃)

[0075] Examples of indium alloys that can be used include In-Bi alloys, In-Ag alloys, etc. Specific examples of these indium alloys include the following. In-Bi (In 66.3 mass%, Bi 33.7 mass%, melting point 72°C) In-Bi (In 33.0 mass%, Bi 67.0 mass%, melting point 109°C) In-Ag (In 97.0 mass%, Ag 3.0 mass%, melting point 145°C) The above-mentioned indium alloy containing tin is classified as a tin alloy.

[0076] The solder particles may contain at least one selected from the group consisting of an In-Bi alloy, an In-Sn alloy, an In-Sn-Ag alloy, an Sn-Au alloy, an Sn-Bi alloy, an Sn-Bi-Ag alloy, an Sn-Ag-Cu alloy, and an Sn-Cu alloy, from the viewpoint of obtaining higher reliability during high-temperature high-humidity tests and thermal shock tests.

[0077] The tin alloy or indium alloy may be selected depending on the application of the solder particles (temperature during use), etc. For example, when using solder particles for low-temperature fusion, if an In-Sn alloy or an Sn-Bi alloy is used, fusion can be achieved at 150°C or less. If a material with a high melting point, such as an Sn-Ag-Cu alloy or an Sn-Cu alloy, is used, high reliability can be maintained even after exposure to high temperatures.

[0078] The solder particles may contain one or more elements selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, P, and B. When the solder particles contain Ag or Cu, the melting point of the solder particles can be lowered to about 220°C, and the bonding strength with the electrode is further improved, making it easier to obtain better electrical conductivity reliability.

[0079] The Cu content of the solder particles is, for example, 0.05 to 10 mass%, or may be 0.1 to 5 mass%, or 0.2 to 3 mass%. A Cu content of 0.05 mass% or more facilitates achieving better solder connection reliability. Furthermore, a Cu content of 10 mass% or less facilitates achieving solder particles with a low melting point and excellent wettability, which in turn facilitates improving connection reliability at the joints formed by the solder particles.

[0080] The Ag content of the solder particles is, for example, 0.05 to 10 mass%, and may be 0.1 to 5 mass%, or 0.2 to 3 mass%. When the Ag content is 0.05 mass% or more, better solder connection reliability is easily achieved. When the Ag content is 10 mass% or less, the solder particles tend to have a low melting point and excellent wettability, which results in good connection reliability at the joints formed by the solder particles.

[0081] The solder particles may have a flat portion on a portion of their surface. When such solder particles are used, the flat portion of the solder particles contacts an electrode, ensuring a wide contact area between the flat portion and the electrode. Furthermore, when connecting an electrode made of a material that is easily wettable and spreadable with another electrode made of a material that is difficult to wet and spreadable with solder, the flat portion of the solder particles can be positioned on the latter electrode side, thereby enabling a favorable connection between the two electrodes. The surface of the solder particles other than the flat portion may be spherically crown-shaped. That is, the solder particles may have a flat portion and a spherically crown-shaped curved portion. Specifically, the solder particles may have a shape in which a flat portion of diameter B is formed on a portion of the surface of a sphere having diameter A. When such solder particles are used, better electrical conductivity and insulation reliability are likely to be achieved.

[0082] When a solder particle has a shape of a sphere having a diameter A on which a flat portion having a diameter B is formed as a part of the surface, from the viewpoint of realizing better conductivity reliability and insulation reliability, the ratio of the diameter B of the flat portion to the diameter A of the solder particle (B / A) is, for example, more than 0.01 and less than 1.0 (0.01

[0083] ​When a quadrilateral circumscribing the projection image of a solder particle is created by two pairs of parallel lines, and the distances between opposite sides are X and Y (where Y < X), the ratio of Y to X (Y / X) may be greater than 0.8 and less than or equal to 1.0 (0.8 < Y / X ≤ 1.0), and may also be greater than 0.8 and less than 1.0 or between 0.81 and 0.99. Such solder particles can be said to be closer to spherical particles. When the solder particles have a shape closer to a sphere, there is a tendency for the solder particles to be easily accommodated in the concave portions of the substrate in the manufacturing method described later. Also, when the solder particles have a shape closer to a sphere, when electrically connecting between a plurality of opposing electrodes via a solder layer, unevenness in contact between the solder particles and the electrodes is less likely to occur, and a stable connection tends to be obtained. The projection image of the solder particle can be obtained, for example, by observing an arbitrary solder particle with a scanning electron microscope. When obtaining Y / X, draw two pairs of parallel lines on the obtained projection image, place one pair of parallel lines at the position where the distance between the parallel lines is minimized, and place the other pair of parallel lines at the position where the distance between the parallel lines is maximized. Perform this operation on 300 solder particles and calculate the average value of Y / X, and use this as the Y / X of the solder particles.

[0084] The average particle diameter of the solder particles is 1 to 30 μm. From the viewpoint of easily obtaining excellent conductivity, the average particle diameter of the solder particles may be 2 μm or more or 4 μm or more. From the viewpoint of easily obtaining better connection reliability to electrodes of a micro size, the average particle diameter of the solder particles may be 25 μm or less or 20 μm or less. From these viewpoints, the average particle diameter of the solder particles may be 2 to 25 μm or 4 to 20 μm.

[0085] The average particle diameter of the solder particles can be measured using various methods according to the size. For example, methods such as dynamic light scattering method, laser diffraction method, centrifugal sedimentation method, electrical sensing zone method, resonant mass measurement method, etc. can be used. Furthermore, a method of measuring the particle size from an image obtained by an optical microscope, an electron microscope, etc. can be used. Specific devices include flow type particle image analyzers, Microtrac, Coulter counters, etc. Note that the particle diameter of a solder particle that is not spherical may be the diameter of a circle circumscribing the solder particle in an SEM image.

[0086] The CV value of the solder particle diameter is 20% or less. The CV value of the solder particle diameter is a value calculated by dividing the standard deviation of the solder particle diameter by the average particle diameter and multiplying the result by 100. It is a parameter that indicates the degree of variation in the solder particle diameter. A small CV value of the solder particle diameter means that the solder particle diameter has little variation. The standard deviation of the solder particle diameter can be measured using the same method as the method for measuring the average solder particle diameter described above. From the viewpoint of achieving better electrical conductivity reliability and insulation reliability, the CV value of the solder particle diameter may be 10% or less, 9% or less, 8% or less, 7% or less, or 5% or less. The lower limit of the CV value of the solder particle diameter is not particularly limited and may be, for example, 0.1% or more, 1% or more, or 2% or more. That is, the CV value of the solder particle diameter may be 0.1 to 20%, 1 to 10%, 2 to 9%, 2 to 8%, etc.

[0087] The content of solder particles may be, for example, 40% by mass or more, 50% by mass or more, or 60% by mass or more, based on the total mass of the adhesive film for circuit connection, from the viewpoint of further improving conductivity. The content of solder particles may be, for example, 80% by mass or less, 75% by mass or less, or 70% by mass or less, based on the total mass of the adhesive film for circuit connection, from the viewpoint of easily suppressing short circuits. From these viewpoints, the content of solder particles may be, for example, 40 to 80% by mass, 50 to 75% by mass, or 60 to 70% by mass, based on the total mass of the adhesive film for circuit connection.

[0088] The particle density of the solder particles in the circuit connecting adhesive film 10 is set to 100 particles / mm 3 in order to obtain a stable connection resistance. 2 More than 1000 pieces / mm 2 More than 3000 pieces / mm 2 or more than 5000 pieces / mm 2 The particle density of the solder particles in the adhesive film 10 for circuit connection may be 100,000 particles / mm 3 or more from the viewpoint of improving the insulation between adjacent electrodes. 2Below, 70000 pieces / mm 2 Below, 50000 pieces / mm 2 or less than 30,000 pieces / mm 2 It may be the following:

[0089] <Method of manufacturing an adhesive film for circuit connection> The adhesive film 10 for circuit connection can be produced, for example, by a method including the following steps: preparing a substrate having a plurality of solder particles 2 arranged on its surface (e.g., a substrate having a plurality of recesses on its surface, with solder particles 2 arranged in at least some of the recesses) (preparation step); providing a first adhesive layer 3 on the surface of the substrate (e.g., the surface on which the recesses are formed) to transfer the solder particles to the first adhesive layer 3 (transfer step); and providing a second adhesive layer 4 on one surface of the first adhesive layer 3 (lamination step). According to this method, by using a substrate on which solder particles have already been arranged in a predetermined arrangement, it is possible to obtain an adhesive film 10 for circuit connection having the predetermined arrangement and an excellent monodispersity rate.

[0090] A method for producing an adhesive film 10 for circuit connection will be described below with reference to FIGS. 4 to 8. FIG. 4 is a diagram schematically showing a longitudinal section of a substrate used in the method for producing an adhesive film 10 for circuit connection. FIG. 5 is a diagram showing a modified example of the cross-sectional shape of the recesses of the substrate of FIG. 4. FIG. 6 is a cross-sectional view schematically showing a state in which solder particles 2 are arranged in the recesses of the substrate of FIG. 4. FIG. 7 is a cross-sectional view schematically showing an example of a preparation step. FIG. 8 is a cross-sectional view schematically showing an example of a transfer step. In the method described below, a substrate having a plurality of recesses on its surface and having solder particles 2 arranged in at least some of the plurality of recesses is used as the substrate. However, the present invention is not limited to such a substrate. For example, a substrate having support portions (needles, etc.) on its surface to which solder particles can be fixed can also be used.

[0091] (preparation process) In the preparation step, first, a substrate 6 having a plurality of recesses 7 on its surface is prepared (see FIG. 4). The substrate 6 has a plurality of recesses 7. The recesses 7 are regularly arranged, for example, in a predetermined pattern (for example, a pattern corresponding to the electrode pattern of a circuit component). When the recesses 7 are arranged in a predetermined pattern, the solder particles 2 are transferred to the first adhesive layer in the predetermined pattern. Therefore, an adhesive film 10 for circuit connection is obtained in which the solder particles 2 are regularly arranged in the predetermined pattern (such as the pattern shown in FIGS. 2 and 3).

[0092] The recess 7 of the base 6 may be formed in a tapered shape, for example, as shown in Figure 4, with the opening area increasing from the bottom 7a of the recess 7 toward the surface 6a of the base 6. That is, the width of the bottom 7a of the recess 7 (width a in Figure 4) may be narrower than the width of the opening of the recess 7 (width b in Figure 4). The size of the recess 7 (width a, width b, volume, taper angle, depth, etc.) can be set depending on the size of the desired solder particles and the position of the solder particles in the adhesive film for circuit connection. For example, the width of the opening of the recess 7 (width b) may be larger than the maximum particle diameter of the solder particles 2, but less than twice the maximum particle diameter of the solder particles.

[0093] The shape of the recess 7 in the longitudinal section of the base 6 (cross-sectional shape of the recess 7) may be, for example, any of the shapes shown in (a) to (h) of Figure 5. In all of the cross-sectional shapes shown in (a) to (h) of Figure 5, the width of the opening of the recess 7 (width b) is the maximum width in the cross-sectional shape. This makes it easier to remove the solder particles placed in the recess 7, improving workability.

[0094] The shape of the opening of the recess 7 may be circular, elliptical, triangular, rectangular, polygonal, or the like.

[0095] The recesses 7 in the substrate 6 can be formed by known methods such as lithography, machining, etc. These methods allow the size and shape of the recesses to be freely designed.

[0096] Materials that can be used to form the base 6 include, for example, inorganic materials such as silicon, various ceramics, glass, metals such as stainless steel, and organic materials such as various resins. As will be described later, in the manufacturing method of this embodiment, the solder particles 2 can be arranged in the recesses 7 of the base 6 by forming the solder particles 2 in the recesses 7 of the base 6. In this case, the base 6 may have heat resistance that does not change at the melting temperature of the fine particles used to form the solder particles 2.

[0097] Next, solder particles 2 are placed (housed) in at least some (partially or entirely) of the plurality of recesses 7 of the base 6 (see FIG. 6).

[0098] The method for arranging the solder particles 2 is not particularly limited. The arrangement method may be either a dry method or a wet method. For example, the solder particles 2 are arranged on the surface 6a of the base 6, and then the surface 6a of the base 6 is rubbed with a squeegee or a slightly adhesive roller to remove excess solder particles 2 and arrange the solder particles 2 in the recesses 7. If the width b of the opening of the recesses 7 is greater than the depth of the recesses 7, the solder particles may protrude from the opening of the recesses 7. Using a squeegee removes the solder particles protruding from the opening of the recesses 7. Other methods for removing excess solder particles include blowing compressed air or rubbing the surface 6a of the base 6 with a nonwoven fabric or a bundle of fibers. These methods use weaker physical force than a squeegee and are therefore preferred for handling easily deformable particles (e.g., solder particles).

[0099] In the method for producing an adhesive film 10 for circuit connection, the solder particles 2 may be formed in the recesses 7 of the substrate 6, thereby disposing the solder particles 2 in the recesses 7. Specifically, as shown in FIG. 7, for example, fine particles 8 for forming the solder particles 2 are placed in the recesses 7, and then the fine particles 8 placed in the recesses 7 are fused to form the solder particles 2 in the recesses 7. The fine particles 8 placed in the recesses 7 coalesce upon melting and become spherical due to surface tension. At this time, the molten metal conforms to the shape of the bottom 7a of the recesses 7 at the contact point. Therefore, for example, if the bottom 7a of the recesses 7 has a flat shape as shown in FIG. 7, the solder particles 2 will have a flat portion 2a on part of their surface.

[0100] The fine particles 8 only need to be able to be contained in the recesses 7, and may have a large variation in particle size distribution or may have an irregular shape.

[0101] One method for melting the particles 8 accommodated in the recesses 7 is to heat the particles 8 to a temperature equal to or higher than the melting point of the material (solder) that forms the particles. Due to the influence of an oxide film, the particles 8 may not melt, wet, spread, or coalesce even when heated to a temperature equal to or higher than the melting point. For this reason, the particles 8 are exposed to a reducing atmosphere, the oxide film on the surfaces of the particles 8 is removed, and then the particles 8 are heated to a temperature equal to or higher than the melting point of the particles 8, thereby melting the particles 8, causing them to wet, spread, and coalesce. From a similar perspective, the particles 8 may be melted in a reducing atmosphere.

[0102] The method for creating a reducing atmosphere is not particularly limited as long as it can achieve the above-mentioned effects, and examples include methods using hydrogen gas, hydrogen radicals, formic acid gas, etc. For example, the microparticles 8 can be melted in a reducing atmosphere by using a hydrogen reduction furnace, a hydrogen radical reduction furnace, a formic acid reduction furnace, or a conveyor furnace or continuous furnace thereof. These devices may be equipped with a heating device, a chamber filled with an inert gas (nitrogen, argon, etc.), a mechanism for evacuating the chamber, etc., within the furnace, which makes it easier to control the reducing gas. Furthermore, if the chamber can be evacuated, voids can be removed by reducing the pressure after the microparticles 8 have melted and coalesced, resulting in solder particles 2 with even better connection stability.

[0103] The profile of the reduction of the fine particles 8, the melting conditions, the temperature, the atmosphere adjustment in the furnace, etc. may be set appropriately taking into consideration the melting point of the fine particles 8, the particle size, the size of the recesses, the material of the base 6, and the like.

[0104] According to the above method, solder particles 2 of approximately uniform size can be formed regardless of the material and shape of the particles 8. Furthermore, since the size and shape of the solder particles 2 depend on the amount of particles 8 accommodated in the recesses 7, the shape of the recesses 7, etc., the size and shape of the solder particles 2 can be freely designed by designing the recesses 7 (adjusting the size, shape, etc. of the recesses), and solder particles having a desired particle size distribution (solder particles with an average particle size of 1 to 30 μm and a CV value of the particle size of 20% or less) can be easily prepared.

[0105] The above method is particularly suitable when the solder particles 2 are indium-based solder particles. That is, although indium-based solder can be deposited by plating, it is difficult to deposit in particulate form, and it is a soft material that is difficult to handle. However, the above method uses indium-based solder fine particles as a raw material, making it easy to produce indium-based solder particles with a substantially uniform particle size.

[0106] After the solder particles 2 are placed in the recesses 7, the base 6 can be handled with the solder particles 2 placed (housed) in the recesses 7. For example, when the base 6 is transported or stored with the solder particles 2 placed (housed) in the recesses 7, deformation of the solder particles 2 can be prevented. Furthermore, since the solder particles 2 are easily removed when placed (housed) in the recesses 7, deformation of the solder particles 2 when they are recovered or subjected to surface treatment can also be easily prevented.

[0107] (Transfer process) In the transfer step, the first adhesive layer 3 is provided on the surface of the base 6 (the surface on which the recesses 7 are formed), and the solder particles 2 are transferred to the first adhesive layer 3 (see FIG. 8).

[0108] Specifically, first, a first adhesive layer 3 is formed on a support 11 to obtain a laminated film 12. Then, the surface 6a of the substrate 6 on which the recesses 7 are formed (the surface of the substrate 6) is opposed to the surface of the laminated film 12 on the first adhesive layer 3 side (the surface of the first adhesive layer 3 opposite the support 11), bringing the substrate 6 and the first adhesive layer 3 close together (see (a) of FIG. 8). Next, the laminated film 12 and the substrate 6 are bonded together to bring the first adhesive layer 3 into contact with the surface 6a of the substrate 6 (the surface on which the recesses 7 are formed), and the solder particles 2 are transferred to the first adhesive layer 3. This results in a particle transfer layer 13 comprising the first adhesive layer 3 and solder particles 2 at least partially embedded in the first adhesive layer 3 (see (b) of FIG. 8). In this case, as shown in (b) of Figure 8, if the bottom of the recess 7 is flat, the solder particle 2 will have a flat portion 2a corresponding to the shape of the bottom of the recess 7, and will be placed in the first adhesive layer 3 with the flat portion 2a facing away from the support 11.

[0109] The first adhesive layer 3 can be formed using a varnish composition (varnish-like first adhesive composition) prepared by dissolving or dispersing the components of the first adhesive layer 3 in an organic solvent by stirring, mixing, kneading, or the like. Specifically, the first adhesive layer 3 can be formed, for example, by applying the varnish composition to a support 11 (e.g., a substrate that has been subjected to a release treatment) using a knife coater, roll coater, applicator, comma coater, die coater, or the like, and then volatilizing the organic solvent by heating. At this time, the thickness of the final first adhesive layer can be adjusted by adjusting the amount of varnish composition applied.

[0110] The organic solvent used in preparing the varnish composition is not particularly limited as long as it has the property of being able to dissolve or disperse each component substantially uniformly. Examples of such organic solvents include toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, and butyl acetate. These organic solvents can be used alone or in combination of two or more. The stirring, mixing, or kneading in preparing the varnish composition can be carried out using, for example, a mixer, a grinder, a three-roll mill, a ball mill, a bead mill, a homodisper, or the like.

[0111] The support 11 is not particularly limited as long as it has heat resistance sufficient to withstand the heating conditions used to volatilize the organic solvent. The support 11 may be a plastic film or a metal foil. Examples of the support 11 that may be used include substrates (e.g., films) made of oriented polypropylene (OPP), polyethylene terephthalate (PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, polyimide, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, and liquid crystal polymer.

[0112] The heating conditions for volatilizing the organic solvent from the varnish composition applied to the substrate can be appropriately set depending on the organic solvent used, etc. The heating conditions may be, for example, 40 to 120°C for 0.1 to 10 minutes.

[0113] A portion of the solvent may remain unremoved in the first adhesive layer 3. The content of the solvent in the first adhesive layer 3 may be, for example, 10 mass % or less based on the total mass of the first adhesive layer 3.

[0114] Examples of methods for bonding the laminated film 12 and the substrate 6 include hot pressing, roll lamination, vacuum lamination, etc. Lamination can be carried out under temperature conditions of 0 to 80°C, for example.

[0115] In the transfer process, the first adhesive layer 3 may be formed by applying the varnish composition directly to the substrate 6, but by using a laminated film 12 as in the above method, it becomes easier to obtain a particle transfer layer 13 in which the support 11, the first adhesive layer 3, and the solder particles 2 are integrated.

[0116] (Lamination process) In the lamination step, a second adhesive layer 4 is provided on the surface of the first adhesive layer 3 opposite the support 11 (the side to which the solder particles 2 have been transferred). This results in an adhesive film 10 for circuit connection as shown in FIG.

[0117] The second adhesive layer 4 can be provided on the first adhesive layer 3 in the same manner as the method for providing the first adhesive layer 3 on the substrate 6, except that a varnish composition (varnish-like second adhesive composition) prepared by dissolving or dispersing the components of the second adhesive layer 4 in an organic solvent by stirring, mixing, kneading, or the like is used instead of the varnish-like first adhesive composition. That is, the second adhesive layer 4 may be provided on the first adhesive layer 3 by laminating the first adhesive layer 3 with a laminate film obtained by forming the second adhesive layer 4 on a support, or the second adhesive layer 4 may be provided on the first adhesive layer 3 by directly applying the varnish-like second adhesive composition to the first adhesive layer 3.

[0118] In the lamination process, after peeling off the support 11, a second adhesive layer 4 may be provided on the surface on which the support 11 was provided, but by providing the second adhesive layer 4 on the surface opposite the support 11 as in the above method, it is expected that the adhesive film for circuit connection can be attached to the circuit component with improved adhesion and peeling during connection can be suppressed.

[0119] The method for producing an adhesive film for circuit connection of the present invention has been described above using the adhesive film for circuit connection 10 and its production method as an example, but the present invention is not limited to the above embodiment.

[0120] For example, the adhesive film 1 in the adhesive film for circuit connection 10 may consist of only the first adhesive layer 3, or may further comprise other adhesive layers in addition to the first adhesive layer 3 and the second adhesive layer 4.

[0121] <Connection structure and method for manufacturing the same> A connection structure (circuit connection structure) using the above-mentioned adhesive film 10 for circuit connection as a connection material and a method for producing the same will be described below.

[0122] Fig. 9 is a schematic cross-sectional view showing one embodiment of a connection structure. As shown in Fig. 9, connection structure 100 includes first circuit board 21 and a first circuit member 23 having first electrodes 22 formed on main surface 21a of first circuit board 21, second circuit board 24 and a second circuit member 26 having second electrodes 25 formed on main surface 24a of second circuit board 24, and connecting portion 27 that electrically connects first electrode 22 and second electrode 25 to each other via solder layer 30 and bonds first circuit member 23 and second circuit member 26 together.

[0123] The first circuit member 23 and the second circuit member 26 may be the same or different. The first circuit member 23 and the second circuit member 26 may be a glass or plastic substrate on which circuit electrodes are formed; a printed wiring board; a ceramic wiring board; a flexible wiring board; an IC chip such as a driver IC; or the like. The first circuit board 21 and the second circuit board 24 may be formed from inorganic materials such as semiconductors, glass, and ceramics; organic materials such as polyimide and polycarbonate; or composites such as glass / epoxy. The first circuit board 21 may be a plastic substrate. The first circuit member 23 may be, for example, a plastic substrate (a plastic substrate made of an organic material such as polyimide, polycarbonate, polyethylene terephthalate, or cycloolefin polymer) on which circuit electrodes are formed, and the second circuit member 26 may be, for example, an IC chip such as a driver IC. The plastic substrate on which electrodes are formed may be a plastic substrate on which a display area is formed by, for example, a pixel driving circuit such as an organic TFT or a plurality of organic EL elements R, G, and B are regularly arranged in a matrix.

[0124] The first electrode 22 and the second electrode 25 may be electrodes containing metals such as gold, silver, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, aluminum, molybdenum, and titanium, or oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), and indium gallium zinc oxide (IGZO). The first electrode 22 and the second electrode 25 may be electrodes formed by laminating two or more of these metals, oxides, and the like. Electrodes formed by laminating two or more of these metals, oxides, and the like may have two or more layers, or three or more layers. The first electrode 22 and the second electrode 25 may be circuit electrodes or bump electrodes. In FIG. 9, the first electrode 22 is a circuit electrode, and the second electrode 25 is a bump electrode.

[0125] The total height of the first electrode 22 and the second electrode 25 may be smaller than the average particle diameter of the solder particles 2 in the adhesive film for circuit connection used to form the connection portion 27. The total height may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, less than 4 μm, less than 3 μm, less than 2 μm, or less than 1 μm. The height of the first electrode 22 (e.g., the height of the circuit electrode) may be, for example, 0.05 to 5.0 μm, 0.1 to 4.0 μm, or 0.5 to 3.0 μm. The height of the second electrode 25 (e.g., the height of the bump electrode) may be, for example, 0.5 to 25.0 μm, 2.0 to 15.0 μm, or 5.0 to 10.0 μm.

[0126] The connection portion 27 is a cured product of the adhesive film 10 for circuit connection. The connection portion 27 has, for example, a first region 28 located on the first circuit member 23 side in the direction in which the first circuit member 23 and the second circuit member 26 face each other (hereinafter referred to as the "facing direction") and containing a cured product of the first adhesive layer 3, a second region 29 located on the second circuit member 26 side in the facing direction and containing a cured product of the second adhesive layer 4, a solder layer 30 interposed between the first electrode 22 and the second electrode 25 to electrically connect the first electrode 22 and the second electrode 25, and solder particles 2 located between adjacent electrodes. The solder particles 2 may be in a molten state in the connection portion 27. The connection portion 27 does not have to have two distinct regions between the first region 28 and the second region 29, and may, for example, include a region in which the first adhesive layer 3 and the second adhesive layer 4 are cured in a mixed state.

[0127] Examples of connection structures include micro LED display devices such as a color display in which a plastic substrate on which minute LED elements (light-emitting elements) are regularly arranged is connected to a drive circuit element that is a driver for displaying images, and a touch panel in which a plastic substrate on which minute LED elements are regularly arranged is connected to a position input element such as a touchpad. The connection structure may also be an organic EL display device in which the LED elements are organic EL elements. The connection structure can also be applied to various monitors such as smartphones, tablets, televisions, vehicle navigation systems, and wearable devices; furniture; home appliances; and everyday items.

[0128] 10 is a schematic cross-sectional view showing one embodiment of a method for manufacturing a connection structure 100. (a) and (b) of FIG. 10 are schematic cross-sectional views showing each step. As shown in FIG. 10, the method for manufacturing the connection structure 100 includes: placing the above-described adhesive film for circuit connection 10 between the surface of the first circuit member 23 on which the first electrode 22 is provided and the surface of the second circuit member 26 on which the second electrode 25 is provided; and heating a laminate including the first circuit member 23, the adhesive film for circuit connection 10, and the second circuit member 26 while pressing the laminate in the thickness direction of the laminate, thereby electrically connecting the first electrode 22 and the second electrode 25 to each other via the solder layer 30 and bonding the first circuit member 23 and the second circuit member 26 together.

[0129] Specifically, first, a first circuit member 23 having a first circuit board 21 and a first electrode 22 formed on the main surface 21a of the first circuit board 21, and a second circuit member 26 having a second circuit board 24 and a second electrode 25 formed on the main surface 24a of the second circuit board 24 are prepared.

[0130] Next, the first circuit member 23 and the second circuit member 26 are arranged so that the first electrode 22 and the second electrode 25 face each other, and the adhesive film for circuit connection 10 is placed between the first circuit member 23 and the second circuit member 26. For example, as shown in FIG. 10(a), the adhesive film for circuit connection 10 is laminated onto the first circuit member 23 so that the first adhesive layer 3 faces the main surface 21a of the first circuit board 21. Next, the second circuit member 26 is placed on the first circuit member 23 on which the adhesive film for circuit connection 10 has been laminated so that the first electrode 22 on the first circuit board 21 and the second electrode 25 on the second circuit board 24 face each other.

[0131] 10(b), a laminate formed by stacking a first circuit member 23, a circuit connection adhesive film 10, and a second circuit member 26 in this order is heated while being pressed in the thickness direction of the laminate, thereby thermocompression-bonding the first circuit member 23 and the second circuit member 26 to each other. At this time, as indicated by the arrows in FIG. 10(b), the flowable uncured thermosetting components contained in the first adhesive layer 3 and the second adhesive layer 4 flow to fill the gaps between adjacent electrodes (the gaps between the first electrodes 22 and the gaps between the second electrodes 25) and are cured by the heating. Furthermore, by being heated while being pressed, the solder particles 2 melt and gather between the first electrode 22 and the second electrode 25 to form a solder layer 30. The solder layer 30 is then fixed between the first electrode 22 and the second electrode 25 by cooling. As a result, the first electrode 22 and the second electrode 25 are electrically connected to each other via the solder layer 30 (the molten and solidified solder particles 2), and the first circuit member 23 and the second circuit member 26 are bonded to each other, resulting in the connection structure 100 shown in Figure 9.

[0132] The heating temperature during connection may be any temperature at which the solder particles can melt (for example, a temperature higher than the melting point of the solder particles), and may be, for example, 130 to 260°C. The pressure to be applied is not particularly limited as long as it does not damage the adherend, and may be, for example, a chip area-equivalent pressure of 0.1 to 50 MPa, or 40 MPa or less, or 0.1 to 40 MPa. The heating and pressurizing time may be in the range of 0.5 to 300 seconds. [Example]

[0133] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0134] <Preparing ingredients> In the examples and comparative examples, the following materials were used as the adhesive film materials.

[0135] (A: Cationic polymerizable compound) A1: Celloxide 8010 (bi-7-oxabicyclo[4.1.0]heptane, manufactured by Daicel Corporation) A2: ETERNACOLL OXBP (4,4'-bis[3-ethyl-3-oxetanyl]methoxymethyl]biphenyl, manufactured by Ube Industries, Ltd. A3: jER1010 (bisphenol A solid epoxy resin, manufactured by Mitsubishi Chemical Corporation)

[0136] (B: Thermal cationic polymerization initiator (thermal latent cation generator)) B1: CXC-1821 (quaternary ammonium salt-type thermal acid generator, manufactured by King Industries)

[0137] (C: Thermoplastic resin) C1: P-1 (fluorene-type phenoxy resin synthesized by the method described below) C2: YP-70 (bisphenol A / bisphenol F copolymer phenoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd.)

[0138] [Synthesis of P-1] 45 g of 4,4'-(9-fluorenylidene)-diphenol (Sigma-Aldrich Japan Co., Ltd.) and 50 g of 3,3',5,5'-tetramethylbiphenol diglycidyl ether (YX-4000H, Mitsubishi Chemical Corporation) were dissolved in 1000 mL of N-methylpyrrolidone in a 3000 mL three-neck flask equipped with a Dimroth condenser, a calcium chloride tube, and a PTFE stirrer connected to a stirring motor to form a reaction solution. 21 g of potassium carbonate was added to the reaction solution, which was then heated to 110 °C with a mantle heater and stirred. After stirring for 3 hours, the reaction solution was added dropwise to a beaker containing 1000 mL of methanol, and the resulting precipitate was collected by suction filtration. The collected precipitate was washed three times with 300 mL of methanol to obtain 75 g of phenoxy resin P-1.

[0139] The molecular weight of the phenoxy resin P-1 was then measured using a Tosoh high-performance liquid chromatograph GP8020 (column: Gelpak GL-A150S and GLA160S, Hitachi Chemical Co., Ltd.; eluent: tetrahydrofuran; flow rate: 1.0 ml / min). The results, calculated in terms of polystyrene, were Mn=15769, Mw=38045, and Mw / Mn=2.413.

[0140] (D: Filler) D1: Aerosil R805 (hydrolysis product of trimethoxyoctylsilane and silica (silica fine particles), manufactured by Evonik Industries AG, diluted with an organic solvent to a non-volatile content of 10% by mass) D2: Surface-treated silica particles (hydrolysis product of silica and bis(trimethylsilyl)amine)

[0141] (E: Coupling agent) E1: KBM-403 (γ-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0142] <Preparation of the substrate> Substrate (A) (PET film, thickness: 55 μm), substrate (B) (PET film, thickness: 54 μm), and substrate (C) (PET film, thickness: 57 μm) each having a plurality of recesses on the surface were prepared.

[0143] The recesses of the base (A) were truncated cones with an opening area that expanded toward the surface of the base (when viewed from above the opening, the center of the bottom and the center of the opening were the same), with an opening diameter of 4.3 μmφ, a bottom diameter of 4.0 μmφ, and a depth of 4.0 μm. The multiple recesses of the base (A) were formed in a regular triangular array at intervals of 6.2 μm (the distance between the centers of each bottom) so that there were 29,000 recesses per 1 mm square.

[0144] The recesses of the substrate (B) were truncated cones with an opening area that expanded toward the surface of the substrate (when viewed from above the opening, the center of the bottom and the center of the opening were the same), with an opening diameter of 3.3 μmφ, a bottom diameter of 3.0 μmφ, and a depth of 3.0 μm. The recesses were formed in a regular triangular array with an interval of 6.2 μm (the distance between the centers of each bottom) so that there were 29,000 recesses per 1 mm square.

[0145] The recesses of the substrate (C) were truncated cones with an opening area that expanded toward the surface of the substrate (when viewed from above the opening, the center of the bottom and the center of the opening were the same), with an opening diameter of 5.3 μmφ, a bottom diameter of 5.0 μmφ, and a depth of 5.0 μm. The recesses were formed in a regular triangular array with an interval of 6.2 μm (the distance between the centers of each bottom) so that there were 29,000 recesses per 1 mm square.

[0146] <Examples 1 to 8 and Comparative Examples 1 to 6> Anisotropic conductive adhesive films of Examples 1 to 8 and Comparative Examples 1 to 6 were produced using the method described below, each comprising an adhesive film having the composition shown in Table 1 and conductive particles disposed in the adhesive film. Note that, as step (a), step (a1) was performed in Examples 1 to 5, Comparative Examples 1 to 3, and Comparative Example 5, step (a2) was performed in Example 6, step (a3) ​​was performed in Example 7 and Comparative Example 4, step (a4) was performed in Example 8, and step (a5) was performed in Comparative Example 6.

[0147] (Process (a): Preparation process) [Step (a1): Preparation and Arrangement of Solder Particles (Type: F1, Average Particle Diameter: 4.0 μm)] 100 g of Sn-Bi solder particles (manufactured by 5N Plus, melting point 138°C, Type 8) were immersed in distilled water and ultrasonically dispersed. The resulting solution was then leveled and the floating solder particles were collected. This process was repeated to collect 10 g of solder particles. The average particle diameter of the resulting solder particles was 1.0 μm, and the CV value of the particle diameter was 42%. The resulting solder particles (average particle diameter: 1.0 μm, CV value of the particle diameter: 42%) were then placed on the surface of the substrate (A) where the recesses were formed. The surface of the substrate (A) where the recesses were formed was then rubbed with a low-tack roller to remove excess solder particles, leaving only the solder particles within the recesses. The substrate with the solder particles placed within the recesses was then placed in a hydrogen radical reduction furnace (manufactured by Shinko Seiki Co., Ltd., hydrogen plasma reflow device). After evacuation, hydrogen gas was introduced into the furnace and filled with hydrogen gas. The temperature inside the furnace was then adjusted to 120°C, and hydrogen radicals were irradiated for 5 minutes. The hydrogen gas inside the furnace was then removed by evacuating it, and the furnace was heated to 145°C. Nitrogen was then introduced into the furnace to return it to atmospheric pressure, and the temperature inside the furnace was then lowered to room temperature to form solder particles. This provided a substrate with conductive particles (solder particles) arranged in the recesses for use in step (b2).

[0148] Using the same procedure separately, solder particles were produced, and the obtained solder particles were recovered from the recesses by tapping the back side of the recesses of the substrate. The solder particles had a flat portion on a part of their surfaces, and it was confirmed that the ratio (B / A) of the diameter B of the flat portion to the diameter A of the solder particles was 0.35. Also, when a quadrilateral circumscribing the projection image of the solder particles was created by two pairs of parallel lines, and the distances between the opposing sides were set as X and Y (where Y < X), it was confirmed that Y / X was 0.93. Further, when the average particle diameter and the C.V. value of the particle diameters of the solder particles were measured, the average particle diameter was 4.0 μm and the C.V. value of the particle diameters was 7.9%. The average particle diameter, B / A, and Y / X of the solder particles were values measured by observing 300 solder particles with SEM after cutting out the particle transfer layer produced in step (b) into a 10 cm × 10 cm size and subjecting the surface on which the solder particles were arranged to Pt sputtering.

[0149] [Step (a2): Production and Arrangement of Solder Particles (Type: F1, Average Particle Diameter: 3.0 μm)] Except for using substrate (B) instead of substrate (A), solder particles were formed in the same manner as in step (a1), and a substrate with conductive particles (solder particles) arranged in the recesses, which was to be used in step (b2), was prepared.

[0150] Using the same procedure separately, solder particles were produced, and the obtained solder particles were recovered from the recesses by tapping the back side of the recesses of the substrate. The solder particles had a flat portion on a part of their surfaces, and it was confirmed that the ratio (B / A) of the diameter B of the flat portion to the diameter A of the solder particles was 0.40. Also, when a quadrilateral circumscribing the projection image of the solder particles was created by two pairs of parallel lines, and the distances between the opposing sides were set as X and Y (where Y < X), it was confirmed that Y / X was 0.93. Further, when the average particle diameter and the C.V. value of the particle diameters of the solder particles were measured, the average particle diameter was 3.0 μm and the C.V. value of the particle diameters was 8.8%. The average particle diameter, B / A, and Y / X of the solder particles were values measured by observing 300 solder particles with SEM after cutting out the particle transfer layer produced in step (b) into a 10 cm × 10 cm size and subjecting the surface on which the solder particles were arranged to Pt sputtering.

[0151] [Process (a3): Production and Arrangement of Solder Particles (Type: F1, Average Particle Diameter: 5.0 μm)] Solder particles were formed in the same manner as in process (a1), except that substrate (C) was used instead of substrate (A), and a substrate with conductive particles (solder particles) disposed in the recesses, which was to be used in process (b2), was prepared.

[0152] Solder particles were separately produced by the same operation, and the obtained solder particles were recovered from the recesses by tapping the back side of the recesses of the substrate. It was confirmed that the solder particles had a flat portion on a part of the surface, and the ratio (B / A) of the diameter B of the flat portion to the diameter A of the solder particles was 0.44. Also, when a quadrilateral circumscribing the projection image of the solder particles was created by two pairs of parallel lines, and the distances between the opposing sides were set as X and Y (where Y < X), it was confirmed that Y / X was 0.93. Further, when the average particle diameter and the C.V. value of the particle diameter of the solder particles were measured, the average particle diameter was 5.0 μm and the C.V. value of the particle diameter was 7.6%. The average particle diameter, B / A, and Y / X of the solder particles were values measured by SEM observation of 300 solder particles after cutting out the particle transfer layer produced in process (b) into a 10 cm × 10 cm size and subjecting the surface on which the solder particles were disposed to Pt sputtering.

[0153] [Process (a4): Production and Arrangement of Solder Particles (Type: F2, Average Particle Diameter: 4.0 μm)] Solder particles were formed in the same manner as in process (a1), except that Sn - Ag - Cu solder fine particles (manufactured by Mitsui Mining & Smelting Co., Ltd., melting point 219°C, ST - 3) were used instead of Sn - Bi solder fine particles, the temperature before irradiating hydrogen radicals in the hydrogen radical reduction furnace was changed from 120°C to 200°C, and the heating temperature after removing hydrogen gas in the furnace was changed from 145°C to 225°C, and a substrate with conductive particles (solder particles) disposed in the recesses, which was to be used in process (b2), was prepared.

[0154] By performing the same operation separately, solder particles were produced, and the obtained solder particles were recovered from the recess by tapping the back side of the recess of the substrate. It was confirmed that the solder particles had a flat portion on a part of the surface, and the ratio (B / A) of the diameter B of the flat portion to the diameter A of the solder particles was 0.35. Further, when a quadrilateral circumscribing the projection image of the solder particles was created by two pairs of parallel lines, and the distances between the opposing sides were set as X and Y (where Y < X), it was confirmed that Y / X was 0.93. Also, when the average particle diameter and the C.V. value of the particle diameter of the solder particles were measured, the average particle diameter was 4.0 μm, and the C.V. value of the particle diameter was 7.9%. The average particle diameter, B / A, and Y / X of the solder particles were values measured by observing 300 solder particles with SEM after cutting out the particle transfer layer produced in step (b) into a 10 cm × 10 cm size and performing Pt sputtering on the surface where the solder particles were arranged.

[0155] [Step (a5): Preparation and Arrangement of Conductive Particles (Type: F3, Average Particle Diameter: 3.9 μm)] As the conductive particles, conductive particles (type: F3, average particle diameter: 3.9 μm, C.V. value of particle diameter: 3.0%, specific gravity: 2.7) in which a nickel layer with a thickness of 0.15 μm was formed on the surface of a core (particle) made of plastic (crosslinked polystyrene) were prepared, and these were arranged on the surface of the substrate (A) where the recess was formed. Next, the surface of the substrate (A) where the recess was formed was rubbed with a micro-adhesive roller to remove excess conductive particles, and the conductive particles were arranged only inside the recess. The average particle diameter and the C.V. value of the particle diameter of the conductive particles were values measured by observing 300 conductive particles with SEM after cutting out the particle transfer layer produced in step (b) described later into a 10 cm × 10 cm size and performing Pt sputtering on the surface where the conductive particles were arranged.

[0156] (Step (b): Transfer Step) [Step (b1): Preparation of the First Adhesive Layer] A resin solution was obtained by mixing the components shown as X1 or X2 in Table 1 with an organic solvent (2-butanone) in the amounts (units: parts by mass, solid content) shown in Table 1. Next, this resin solution was applied to a 38 μm thick PET film that had been treated with a silicone release agent, and dried with hot air at 60°C for 3 minutes to produce a first adhesive layer on the PET film with the thickness shown in Tables 2 to 4.

[0157] [Step (b2): Transfer of conductive particles] The first adhesive layer formed on the PET film in step (b1) was placed opposite the substrate with conductive particles arranged in the recesses in step (a), and the conductive particles were transferred to the first adhesive layer, thereby obtaining a particle transfer layer.

[0158] (Process C: Lamination process) [Step (c1): Preparation of second adhesive layer] A resin solution was obtained by mixing the components shown as X1 or X2 in Table 1 with an organic solvent (2-butanone) in the amounts (units: parts by mass, solid content) shown in Table 1. Next, this resin solution was applied to a 50 μm thick PET film that had been treated with a silicone release agent, and dried with hot air at 60°C for 3 minutes to produce a second adhesive layer on the PET film with the thickness shown in Tables 2 to 4.

[0159] [Step (c2): Lamination of the second adhesive layer] The particle transfer layer produced in step (b) and the second adhesive layer produced in step (c1) were bonded together at a temperature of 50°C. This resulted in an anisotropically conductive adhesive film. The thickness of the anisotropically conductive adhesive film and the ratio r of the thickness of the anisotropically conductive adhesive film to the average particle diameter of the conductive particles are shown in Tables 2 to 4.

[0160] (Measurement of the distance from the adhesive film surface to the conductive particles) The anisotropic conductive adhesive film was cast using an epoxy resin-based casting resin (manufactured by Refine Tech Co., Ltd., product name: Epomount), and then a cross section of the conductive adhesive film was cut out. The cross section was then observed using a metal FPD / LSI inspection microscope L300ND manufactured by Nikon Solutions Corporation, and the shortest distance from the surface of the first adhesive layer of the anisotropic conductive adhesive film to the surface of the conductive particles and the shortest distance from the surface of the second adhesive layer of the anisotropic conductive adhesive film to the surface of the conductive particles were measured at 10 locations, and the shortest distances d11 and d21 were calculated as the averages of the measurements at 10 locations. The results are shown in Tables 2 to 4.

[0161] [Table 1]

[0162] [Table 2]

[0163] [Table 3]

[0164] [Table 4]

[0165] <Evaluation> (Measurement of the cure rate of anisotropic conductive adhesive film) For each of the anisotropically conductive adhesive films of Examples 1 to 8 and Comparative Examples 1 to 6, DSC measurements were carried out in a nitrogen (N2) atmosphere at a heating rate of 10 ° C. / min using a differential scanning calorimeter (trade name: DSC Q1000) manufactured by PerkinElmer. The calorific value Q when heated from 50 ° C. to 130 ° C. A , the amount of heat generated when heated from 50℃ to 160℃ Q B , the amount of heat generated when heated from 50℃ to 210℃ Q C and the amount of heat generated when heated from 50°C to 300°C Q DFor all anisotropically conductive adhesive films, no increase in heat generation was observed at temperatures above 300°C (the rate of change in the differential curve of the DSC curve (DDSC curve) was 0.01 [W·g°C] or less), so it was determined that the film was completely cured at 300°C (100% curing rate). The obtained heat generation Q A , Q B , Q C and Q D Based on this, the cure rate A (Q A / Q D ×100), cure rate B (Q B / Q D ×100), hardening rate C(Q C / Q D × 100) were calculated, and the results are shown in Tables 5 and 6.

[0166] (Measurement of the monodispersity of conductive particles in anisotropic conductive adhesive film) Using a metallurgical microscope at 200x magnification, the anisotropically conductive adhesive films of Examples 1 to 8 and Comparative Examples 1 to 6 were observed from the first adhesive layer side, the number of conductive particles in the anisotropically conductive adhesive film was measured, and the monodispersity of the conductive particles was calculated according to the following formula: The monodispersity of the conductive particles in the anisotropically conductive adhesive films of Examples 1 to 8 and Comparative Examples 1 to 6 was 98%. Monodispersion rate (%) = (2500 μm 2 Number of monodispersed conductive particles in 2500μm 2 (Number of conductive particles in the container) x 100

[0167] (Evaluation of connection resistance and insulation resistance) [Preparing circuit components] The first circuit component was an electrode-attached substrate (A) consisting of an alkali-free glass substrate (OA-11, manufactured by Nippon Electric Glass Co., Ltd., dimensions: 76 mm × 28 mm, thickness: 0.3 mm) on which Cr (20 nm) / Au (200 nm) electrodes (electrode size: 22 μm × 22 μm, interelectrode spacing: 8 μm) were formed. The second circuit component was a sapphire chip with an array of bump electrodes (dimensions: 0.5 mm × 0.5 mm, thickness: 0.2 mm, bump electrode size: 20 μm × 20 μm, interelectrode spacing: 10 μm, bump electrode thickness: 1.5 μm).

[0168] [Fabrication of connection structure (A)] A connection structure (A) was produced using each of the anisotropically conductive adhesive films of Examples 1 to 8 and Comparative Examples 1 to 6. Specifically, the anisotropically conductive adhesive film was first placed on a first circuit member. Next, a thermocompression bonding apparatus (LD-06, manufactured by Ohashi Manufacturing Co., Ltd.) consisting of a stage made of a ceramic heater and a tool (8 mm x 50 mm) was used to bond the anisotropically conductive adhesive film to the first circuit member at 50°C and 0.98 MPa (10 kgf / cm 2 ) for 2 seconds under the conditions of 0°C / 100°C, the anisotropic conductive adhesive film was attached to the first circuit member, and the release film (PET film) on the side of the anisotropic conductive adhesive film opposite the first circuit member was peeled off. Next, the bump electrodes of the first circuit member were aligned with the circuit electrodes of the second circuit member, and then heating and pressing were started at a temperature of 50°C and a pressure of 1 MPa on a base heated to 30°C. While maintaining a substantially constant pressure (1 MPa), the temperature was raised to 160°C or 230°C at a rate of 1°C / second, thereby attaching the anisotropic conductive adhesive film to the second circuit member, thereby producing a connection structure (A). Note that the temperature indicates the maximum temperature actually measured of the anisotropic conductive adhesive film, and the pressure indicates a value calculated with respect to the chip area of ​​the second circuit member. In Examples 1 to 7 and Comparative Examples 1 to 6, the temperature reached by heating was 160°C, and in Example 8, the temperature reached by heating was 230°C.

[0169] [Evaluation of connection resistance] The connection resistance was evaluated using a four-terminal measurement method. The connection resistance was measured immediately after fabrication of the connection structure (A) and after 250 hours in a high-temperature, high-humidity chamber at 85°C and 85% RH. The connection resistance was measured at four locations and averaged. ADC's 6240B (product name) current generator was used, and ADC's 7461A (product name) digital multimeter was used. A connection resistance of less than 0.2 Ω was rated "S," a connection resistance of 0.2 Ω or greater but less than 0.5 Ω was rated "A," and a connection resistance of 0.5 Ω or greater was rated "D." The results are shown in Tables 5 and 6.

[0170] [Insulation resistance evaluation] The insulation resistance was evaluated using the minimum value of the insulation resistance measured at four points immediately after the production of the connection structure (A) and after treatment for 250 hours in a high-temperature, high-humidity chamber at a temperature of 85°C and a humidity of 85% RH. The insulation resistance meter used was SM7120 (product name) manufactured by Hioki E.E. 10 Ω or more is judged as "S", and the insulation resistance value is 1.0 x 10 9 Ω or more 1.0×10 10 An insulation resistance of less than 1.0 x 10 Ω is rated as "A". 9 A resistance of less than Ω was evaluated as "D." The results are shown in Tables 5 and 6.

[0171] (Evaluation of particle capture rate) [Fabrication of connection structure (B)] Connection structures (B) were produced using the anisotropic conductive adhesive films of Examples 1 to 8 and Comparative Examples 1 to 6. Connection structures (B) were produced in the same manner as connection structures (A), except that an electrode-equipped substrate (B) was prepared as a first circuit member, in which ITO (220 nm) electrodes (electrode size 22 μm × 22 μm, inter-electrode space: 8 μm) were formed on the surface of an alkali-free glass substrate (OA-11, manufactured by Nippon Electric Glass Co., Ltd., outer dimensions: 76 mm × 28 mm, thickness: 0.3 mm), and electrode-equipped substrate (B) was used instead of electrode-equipped substrate (A).

[0172] [Evaluation of particle capture rate] The connection points of the connection structure (B) were observed from the electrode-attached substrate (B) side using a metal FPD / LSI inspection microscope L300ND manufactured by Nikon Solutions Corporation, and the number of captured conductive particles (the number of conductive particles captured between the ITO electrode and the bump electrode (on the bump electrode)) was measured at 25 connection points, and the average number of conductive particles captured per bump electrode (electrode area: 20 μm × 20 μm = 400 μm) (average captured particle number) was calculated. The obtained average captured particle number and the density of conductive particles in the anisotropic conductive adhesive film (29,000 particles / mm 2 ) and the capture rate of conductive particles captured between the electrodes was calculated based on the following formula. A capture rate of conductive particles of 70% or more was rated as "S," a capture rate of conductive particles of 60% or more but less than 70% was rated as "A," a capture rate of conductive particles of 50% or more but less than 60% was rated as "B," and a capture rate of conductive particles of less than 50% was rated as "D." The results are shown in Tables 5 and 6. Conductive particle capture rate (%) = (average number of captured particles / (bump electrode area x density of conductive particles in anisotropic conductive adhesive film)) x 100

[0173] [Table 5]

[0174] [Table 6] [Explanation of symbols]

[0175] 1...adhesive film, 2...solder particles, 3...first adhesive layer, 4...second adhesive layer, 6...base, 7...recess, 10...adhesive film for circuit connection, 21...first circuit board, 22...first electrode (circuit electrode), 23...first circuit member, 24...second circuit board, 25...second electrode (bump electrode), 26...second circuit member, 27...connection portion, 30...solder layer, 100...connection structure.

Claims

1. A thermosetting adhesive film for circuit connection, The solder paste contains solder particles having an average particle size of 1 to 30 μm and a CV value of the particle size of 20% or less, the ratio of the thickness of the adhesive film for circuit connection to the average particle size of the solder particles is greater than 1.0 and less than 1.5; The melting point of the solder particles is T ｍ ° C., T when heated at a temperature rising rate of 10 ° C. / min in a nitrogen atmosphere. ｍ An adhesive film for circuit connection, having a cure rate of 80% or more at °C.

2. The adhesive film for circuit connection according to claim 1 , which contains a polymerizable compound and a thermal polymerization initiator.

3. 3. The adhesive film for circuit connection according to claim 2, wherein the polymerizable compound is a cationically polymerizable compound, and the thermal polymerization initiator is a thermal cationic polymerization initiator.

4. 4. The adhesive film for circuit connection according to claim 3, wherein the polymerizable compound comprises at least one selected from the group consisting of alicyclic epoxy compounds and oxetane compounds.

5. 5. The adhesive film for circuit connection according to claim 1, wherein the melting point of the solder particles is 280° C. or lower.

6. the adhesive is used to bond a first circuit member having a first electrode to a second circuit member having a second electrode, and to electrically connect the first electrode to the second electrode; 6. An adhesive film for circuit connection according to claim 1, wherein the sum of the height of the first electrode and the height of the second electrode is smaller than the average particle diameter of the solder particles.

7. a first circuit member having a first electrode; a second circuit member having a second electrode electrically connected to the first electrode; and a connecting portion electrically connecting the first electrode and the second electrode to each other via a solder layer and bonding the first circuit member and the second circuit member together; A connection structure, wherein the connection portion comprises a cured product of the adhesive film for circuit connection according to any one of claims 1 to 6.

8. The connection structure according to claim 7 , wherein the sum of the height of the first electrode and the height of the second electrode is smaller than the average particle diameter of the solder particles.

9. Placing the adhesive film for circuit connection according to any one of claims 1 to 6 between a surface of a first circuit member having first electrodes, on which the first electrodes are provided, and a surface of a second circuit member having second electrodes, on which the second electrodes are provided; and heating a laminate including the first circuit member, the circuit connection adhesive film, and the second circuit member while pressing the laminate in the thickness direction of the laminate, thereby electrically connecting the first electrode and the second electrode to each other via a solder layer and bonding the first circuit member and the second circuit member.

10. The method for manufacturing a connection structure according to claim 9 , wherein the sum of the height of the first electrode and the height of the second electrode is smaller than the average particle diameter of the solder particles.

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