JP7401798B2 - Anisotropic conductive film - Google Patents

Description

The present invention relates to an anisotropic conductive film.

Anisotropic conductive films in which conductive particles are dispersed in an insulating resin binder are widely used when mounting electronic components such as IC chips on wiring boards and the like. In anisotropic conductive films, as the pitch of bumps becomes narrower due to the high-density mounting of electronic components, there is a strong need to improve the ability of the bumps to capture conductive particles and to avoid short circuits between adjacent bumps. .

In response to these demands, it has been proposed to arrange the conductive particles in an anisotropic conductive film in a lattice-like arrangement, and to make the arrangement axis inclined with respect to the longitudinal direction of the anisotropic conductive film (patent patent). Literature 1, Patent Literature 2).

Patent No. 4887700 Japanese Patent Application Publication No. 9-320345

As described in Patent Documents 1 and 2, when conductive particles are arranged in a simple lattice shape, the bump layout corresponds to the inclination angle of the arrangement axis and the distance between the conductive particles. Therefore, when the pitch of the bumps becomes narrow, the distance between the conductive particles must be reduced, the number density of the conductive particles increases, and the manufacturing cost of the anisotropic conductive film increases.

In addition, in order to narrow the distance between conductive particles and avoid short circuits, it is necessary to suppress the conductive particles from being washed away by the resin flow of the insulating resin binder during anisotropic conductive connection. There are also restrictions on the design of the insulating resin binder.

Therefore, an object of the present invention is to provide a film that can accommodate narrow pitch bumps and that has a lower number density of conductive particles than conventional anisotropic conductive films.

The present inventor did not arrange the conductive particles in a simple lattice-like arrangement in a plan view of an anisotropic conductive film, but instead arranged the conductive particles vertically and horizontally by repeating polygonal units consisting of a plurality of conductive particles, and The inventors have discovered that the above-mentioned problem can be solved by making the sides of the rectangle obliquely intersecting the longitudinal direction or the transverse direction of the anisotropic conductive film, and have conceived the present invention.

That is, the present invention is an anisotropic conductive film in which conductive particles are arranged in an insulating resin binder,
In plan view, polygonal repeating units formed by sequentially connecting the centers of multiple conductive particles are arranged repeatedly,
The polygon of the repeating unit provides an anisotropic conductive film having sides obliquely intersecting the longitudinal direction or the transverse direction of the anisotropic conductive film.

According to the anisotropic conductive film of the present invention, the individual conductive particles are not arranged in a simple lattice-like arrangement, but repeating units formed by a plurality of conductive particles are repeatedly arranged, so that the distance between the conductive particles is Narrow areas exist uniformly throughout the film. Further, since the polygon of the repeating unit has sides obliquely intersecting the longitudinal direction or the transverse direction of the anisotropic conductive film, the conductive particles are highly captured in the bumps. Therefore, it is possible to connect narrow pitch bumps without causing short circuits.

On the other hand, according to the anisotropic conductive film of the present invention, portions where the distance between conductive particles is widened are uniformly present throughout the film, so that the number density of conductive particles in the entire anisotropic conductive film can be increased. Therefore, it is possible to suppress an increase in manufacturing costs due to an increase in the number density of conductive particles. Moreover, by suppressing an increase in the number density of conductive particles, it is also possible to suppress an increase in the thrust force required for the pressing jig during anisotropic conductive connection. Therefore, the pressure applied from the pressing jig to the electronic component during anisotropic conductive connection can be reduced, and deformation of the electronic component can be prevented.

FIG. 1A is a plan view illustrating the arrangement of conductive particles in an anisotropic conductive film 1A of an example. FIG. 1B is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1A of the example. FIG. 1C is a cross-sectional view of the anisotropic conductive film 1A of the example. FIG. 2A is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Ba of the example. FIG. 2B is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Bb of the example. FIG. 3A is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Ca of the example. FIG. 3B is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Cb of the example. FIG. 4A is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Da of the example. FIG. 4B is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Db of the example. FIG. 5A is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Ea of the example. FIG. 5B is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1Eb of the example. FIG. 6 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1F of the example. FIG. 7 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1G of the example. FIG. 8 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1H of the example. FIG. 9 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1I of the example. FIG. 10 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1J of the example. FIG. 11 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1K of the example. FIG. 12 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1L of the example. FIG. 13 is a plan view illustrating the arrangement of conductive particles in the anisotropic conductive film 1M of the example. FIG. 14 is a cross-sectional view of the anisotropic conductive film 1a of the example. FIG. 15 is a cross-sectional view of the anisotropic conductive film 1b of the example. FIG. 16 is a cross-sectional view of the anisotropic conductive film 1c of the example. FIG. 17 is a cross-sectional view of the anisotropic conductive film 1d of the example. FIG. 18 is a cross-sectional view of the anisotropic conductive film 1e of the example.

Hereinafter, the anisotropic conductive film of the present invention will be explained in detail with reference to the drawings. Note that in each figure, the same reference numerals represent the same or equivalent components.

<Overall structure of anisotropic conductive film>
FIG. 1A is a plan view showing the arrangement of conductive particles in an anisotropic conductive film 1A according to an example of the present invention, and FIG. 1C is a cross-sectional view thereof.
This anisotropic conductive film 1A has a structure in which conductive particles 2 are arranged in a single layer on or near the surface of an insulating resin binder 3, and an insulating adhesive layer 4 is laminated thereon.

Note that the anisotropic conductive film of the present invention may have a structure in which the insulating adhesive layer 4 is omitted and the conductive particles 2 are embedded in the insulating resin binder 3.

<Conductive particles>
As the conductive particles 2, those used in known anisotropic conductive films can be appropriately selected and used. Examples include metal particles such as nickel, copper, silver, gold, and palladium, and metal-coated resin particles in which the surface of resin particles such as polyamide and polybenzoguanamine is coated with a metal such as nickel. The size of the conductive particles arranged is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 10 μm or less, and still more preferably 2 μm or more and 6 μm or less.

The average particle diameter of the conductive particles 2 can be measured using an image-type or laser-type particle size distribution analyzer. The particle diameter may be determined by observing the anisotropic conductive film in plan view and measuring the particle diameter. In that case, preferably 200 or more, more preferably 500 or more, even more preferably 1000 or more are measured.

The surface of the conductive particles 2 is preferably coated with an insulating coat, an insulating particle treatment, or the like. Such a coating should be easily peeled off from the surface of the conductive particles 2 and should not interfere with the anisotropic conductive connection. Furthermore, protrusions may be provided on the entire surface or a part of the surface of the conductive particles 2. The height of the protrusions is preferably within 20%, preferably within 10%, of the conductive particle diameter.

<Arrangement of conductive particles>
1A to 7 below, examples of arrangement of repeating units when the polygonal repeating unit 5 is a trapezoid will be described as an example.
The arrangement of the conductive particles 2 in a plan view of the anisotropic conductive film 1A shown in FIG. It is repeated in two directions (X direction, Y direction), and is arranged on one surface (that is, the entire surface) of the anisotropic conductive film 1. Note that the anisotropic conductive film of the present invention can have regions where conductive particles are not arranged, if necessary.

This arrangement of conductive particles 2 is such that the conductive particles are placed at some of the vertices of regular triangles when regular triangles are lined up without gaps (or at the vertices of regular hexagons when regular hexagons are lined up without gaps). You can also see things. In other words, it can be said to be an arrangement in which conductive particles at predetermined lattice points are regularly removed from an arrangement in which conductive particles are present at each lattice point of a hexagonal lattice. Therefore, the vertices of the trapezoid of the repeating unit 5 made up of the conductive particles 2a, 2b, 2c, and 2d are part of a regular hexagon formed by combining regular triangles, and are located at the lattice points of the hexagonal lattice. When the trapezoid is inverted around one side 2a, 2b, the sides 2c, 2d overlap the sides 2g, 2h of the adjacent trapezoid repeating unit (i.e., the repeating unit consisting of conductive particles 2e, 2f, 2g, 2h). .

When considering the repeating unit of conductive particles 2, as shown in FIG. 1B, a regular hexagonal repeating unit 5x consisting of conductive particles 2p, 2q, 2r, 2s, 2t, and 2u has one side in the X direction. Although it can be seen as repeating in the Y direction without overlapping sides or vertices, in the present invention, a repeating unit is a polygon consisting of four or more conductive particles, and It is preferable to consider it as the smallest unit polygon that is repeated in the vertical and horizontal directions of the anisotropic conductive film without overlapping the sides of the rectangle.

Each side of the trapezoid of the repeating unit 5 (FIG. 1A) is oblique to the longitudinal direction and the lateral direction of the anisotropic conductive film 1A. Thereby, the external tangent L1 of the conductive particle 2a in the longitudinal direction of the anisotropic conductive film passes through the conductive particle 2b adjacent to the conductive particle 2a in the longitudinal direction of the anisotropic conductive film. Further, an external tangent L2 of the conductive particle 2a in the transverse direction of the anisotropic conductive film passes through the conductive particle 2d adjacent to the conductive particle 2a in the transverse direction of the anisotropic conductive film. Generally, at the time of anisotropic conductive connection, the longitudinal direction of the anisotropic conductive film is the short direction of the bump, so the sides of the polygon of the repeating unit 5 are the longitudinal direction or the short direction of the anisotropic conductive film 1A. If they are diagonal, it is possible to prevent multiple conductive particles from lining up in a straight line along the edge of the bump, and as a result, the multiple conductive particles that are lined up in a straight line will come loose from the terminal and no longer contribute to conduction. Since this phenomenon can be avoided, the ability to capture the conductive particles 2 can be improved.

In addition, in the present invention, all sides of the repeating unit do not necessarily have to be oblique to the longitudinal direction or lateral direction of the anisotropic conductive film, but the lateral direction of each bump is anisotropic conductive film. In the case of the longitudinal direction of the film, each side of the repeating unit is preferably obliquely intersecting the longitudinal direction or the lateral direction of the anisotropic conductive film from the viewpoint of capturing the conductive particles.

On the other hand, when the arrangement pattern of the bumps is radial (so-called fan-out bumps), it is preferable that the polygon forming the repeating unit has sides in the longitudinal direction or the lateral direction of the anisotropic conductive film. That is, in order to prevent the bumps to be connected from shifting their positions due to thermal expansion, the arrangement pattern of the bumps may be arranged radially (for example, Japanese Patent Laid-Open No. 2007-19550, Japanese Patent Laid-Open No. 2015-232660, etc.). ), in that case, the angles formed by the longitudinal direction of each bump and the longitudinal and lateral directions of the anisotropic conductive film gradually change. Therefore, even if the polygonal sides of the repeating unit 5 are not diagonal to the longitudinal direction or the transverse direction of the anisotropic conductive film, the repeating unit 5 can be aligned with the longitudinal edges of the individual bumps arranged radially. The sides of a polygon are diagonal. Therefore, it is possible to avoid a phenomenon in which most of the conductive particles hanging on the edge of the bump during anisotropic conductive connection are not captured by the bump, and the ability to capture the conductive particles is reduced.

On the other hand, the radial arrangement pattern of bumps is usually formed symmetrically. Therefore, from the point of view of making it easy to confirm the quality of the connection state by the indentation after anisotropic conductive connection, it is preferable that the polygon forming the repeating unit 5 have sides in the longitudinal direction or the width direction of the anisotropic conductive film. In particular, the polygon forming the repeating unit 5 has sides in the longitudinal direction or the lateral direction of the anisotropic conductive film, and is symmetrical with the axis of symmetry being the lateral direction or the longitudinal direction of the anisotropic conductive film. It is preferable that the repeating units 5 are repeatedly arranged in the longitudinal direction or the lateral direction of the anisotropic conductive film. For example, like the anisotropic conductive film 1Ba shown in FIG. 2A, the trapezoid of the repeating unit 5 is a trapezoid having an axis of symmetry in the transverse direction of the anisotropic conductive film, and the base and top sides are the longitudinal sides of the anisotropic conductive film. Alternatively, the bottom and top sides of a similar trapezoidal repeating unit may be parallel to the width direction of the anisotropic conductive film, as in the anisotropic conductive film 1Bb shown in FIG. 2B.

In the present invention, the arrangement of the conductive particles 2 in the repeating unit 5 and the repeating pitch in the vertical and horizontal directions of the repeating unit 5 can be changed as appropriate depending on the shape and pitch of the terminals to be connected in the anisotropic conductive connection. Therefore, compared to the case where the conductive particles 2 are arranged in a simple lattice-like arrangement, high trapping performance can be achieved with a smaller number of conductive particles in the anisotropic conductive film as a whole. For example, in order to increase the number density of conductive particles in the longitudinal direction of the anisotropic conductive film 1Ba, as shown in FIG. 3A, a trapezoidal repeating unit 5 is used. is repeated as it is in the width direction of the anisotropic conductive film, and in the longitudinal direction of the anisotropic conductive film, a trapezoidal repeating unit 5 is formed, and the trapezoidal repeating unit is inverted about the axis in the longitudinal direction of the film. It is also possible to arrange the shape repeating units 5B alternately. In this case, as in the anisotropic conductive film 1Da shown in FIG. 4A, a trapezoidal repeating unit 5 and a repeating unit 5B having an inverted shape are alternately repeated also in the width direction of the anisotropic conductive film. Good too.

Similarly, in order to increase the number density of conductive particles in the width direction of the anisotropic conductive film 1Bb, an anisotropic conductive film 1Cb shown in FIG. In the longitudinal direction of the anisotropic conductive film, a trapezoidal repeating unit 5 is repeated in its shape. It is also possible to alternately repeat the repeating units 5B whose shape is inverted about the axis. Further, as in the anisotropic conductive film 1Db shown in FIG. 4B, a repeating unit 5 and a repeating unit 5B having an inverted shape are alternately repeated in both the longitudinal and transverse directions of the anisotropic conductive film. You can also use it as

Furthermore, in contrast to the above-described anisotropic conductive film 1Ca, in order to reduce the number density of the anisotropic conductive film in the transverse direction, the repeating units 5 and 5B are different from each other, as in an anisotropic conductive film 1Ea shown in FIG. 5A. The interval between the repeating rows in the longitudinal direction of the anisotropic conductive film may be increased, and in order to reduce the number density in the longitudinal direction of the anisotropic conductive film, repeating units 5 may be used as in the anisotropic conductive film 1Eb shown in FIG. 5B. , 5B, the interval between the repeating rows in the width direction of the anisotropic conductive film may be increased.

Moreover, like the anisotropic conductive film 1F shown in FIG. 6, the repetition pitch in the Y direction of the repeat unit 5 may be increased with respect to the arrangement of the conductive particles of the anisotropic conductive film 1A shown in FIG. 1A. In the arrangement of the conductive particles 2 shown in FIG. 1A, each conductive particle 2 overlaps with one of the vertices of a regular hexagon when the regular hexagons are arranged without any gaps, but in the arrangement of the conductive particles 2 shown in FIG. This differs from the arrangement of the conductive particles shown in FIG. 1A in that not all the conductive particles are located at the vertices of a regular hexagon when the regular hexagons are arranged without gaps.

Furthermore, as in the anisotropic conductive film 1G shown in FIG. Repeating units may be arranged. Further, the repeating pitch of the repeating units 5 in the X direction may be changed as appropriate, and a single conductive particle or a separate repeating unit may be arranged between the repeating pitches in the X direction.

Like the anisotropic conductive film 1H shown in FIG. 8, the trapezoidal repeating unit 5 or the repeating unit 5B which is an inverted version of the trapezoidal repeating unit 5 is repeated in the transverse direction or the longitudinal direction of the anisotropic conductive film. A single row of conductive particles 2p may be arranged between the row of the anisotropic conductive film in the width direction of the repeating unit 5B and the row of the anisotropic conductive film of the repeating unit 5B in the width direction. As a result, the conductive particles 2 are arranged in an orthorhombic lattice, and a single conductive particle 2p is present at the center of the unit lattice. In order to reduce the number density of conductive particles when the conductive particles are arranged in an orthorhombic lattice, the repeating unit 5 itself may be formed into a rhombus shape as in an anisotropic conductive film 1I shown in FIG. By arranging the conductive particles 2 in an orthorhombic lattice shape as shown in FIGS. 8 and 9, the conductive particles 2 are present in the longitudinal direction, the transverse direction of the anisotropic conductive film, and in a direction inclined thereto. Therefore, it becomes easier to improve the trapping property of conductive particles and suppress short circuits at the time of anisotropic conductive connection.

In addition, as in the anisotropic conductive film 1J shown in FIG. A rectangular lattice-like arrangement of rhombic repeating units 5B reversed in the transverse direction may be arranged so that the lattice points do not overlap. An anisotropic conductive film 1K shown in FIG. 11 has the same particle arrangement as the anisotropic conductive film 1J shown in FIG. Also good.

The repeating unit is not limited to an arrangement in which the conductive particles occupy a part of the vertices of a regular hexagon (that is, the lattice points of a hexagonal lattice) when regular triangles are arranged without gaps. The conductive particles may occupy part of the lattice points of the square lattice. For example, the figure shows an arrangement in which a trapezoidal repeating unit 5 similar to the arrangement of conductive particles shown in FIG. It can be formed on the lattice points of a square lattice like the anisotropic conductive film 1L shown in 12.

Further, the number of vertices forming the polygon of the repeating unit is not limited to four, but may be five or more, six or more, or seven or more. However, in order to make the shape of the repeating unit easier to recognize in the design and production process of manufacturing the anisotropic conductive film, it is preferable that the number of vertices of the repeating unit be an even number.

The shape of the polygon forming the repeating unit may or may not be a regular polygon, but from the viewpoint of making the shape of the repeating unit easier to recognize, a shape with an axis of symmetry is preferable. In this case, each conductive particle constituting the repeating unit does not need to be present at the lattice points of the hexagonal lattice or the square lattice. For example, like the anisotropic conductive film 1M shown in FIG. 13, the repeating unit 5 may be constructed from conductive particles located at the vertices of a regular octagon. The polygonal shape of the repeating unit is determined by the shape of the bumps or terminals to be anisotropically conductively connected, the pitch, the inclination angle of the bumps or terminals in the longitudinal direction of the anisotropic conductive film with respect to the longitudinal direction of the film, and the insulation in the anisotropic conductive film. It can be determined as appropriate depending on the resin composition of the plastic binder.

Note that the arrangement of the conductive particles in the present invention is not limited to the illustrated arrangement of repeating units, and may be, for example, an arrangement in which the illustrated repeating units are arranged at an angle. In this case, a configuration in which the film is tilted by 90 degrees, that is, a configuration in which the longitudinal direction and the lateral direction of the film are interchanged, is also included. Further, the interval between repeating units or the interval between conductive particles within the repeating unit may be changed.

<Shortest distance between conductive particles>
The shortest interparticle distance of the conductive particles is preferably 0.5 times or more the average particle diameter of the conductive particles, both between adjacent conductive particles within a repeating unit and between adjacent conductive particles between repeating units. If this distance is too short, short circuits are likely to occur due to contact between the conductive particles. The upper limit of the distance between adjacent conductive particles is determined depending on the bump shape and bump pitch. For example, when the bump width is 200 μm and the inter-bump space is 200 μm, and at least one conductive particle is present in either the bump width or the inter-bump space, the shortest distance between the conductive particles is less than 400 μm. From the viewpoint of ensuring the ability to capture conductive particles, the thickness is preferably less than 200 μm.

<Number density of conductive particles>
The number density of the conductive particles is determined from the viewpoint of suppressing the manufacturing cost of the anisotropic conductive film and preventing the thrust required for the pressing jig used for anisotropic conductive connection from becoming excessively large. When the average particle diameter of the particles is less than 10 μm, it is preferably 50,000 particles/mm ² or less, more preferably 35,000 particles/mm ² or less, and even more preferably 30,000 particles/mm ² or less. On the other hand, if the number density of the conductive particles is too small, there is a concern that the conductive particles will not be sufficiently captured by the terminal, resulting in poor continuity, so it is preferably 300 particles/mm ² or more, and more preferably 500 particles/mm ² or more. , more preferably 800 pieces/mm ² or more.

Further, when the average particle diameter of the conductive particles is 10 μm or more, it is preferably 15 particles/mm ² or more, more preferably 50 particles/mm ² or more, and even more preferably 160 particles/mm ^{2 or} more. This is because as the diameter of the conductive particles increases, the area ratio occupied by the conductive particles also increases. For the same reason, it is preferably 1800 pieces/mm ² or less, more preferably 1100 pieces/mm ² or less, and even more preferably 800 pieces/mm ² or less.

Note that the number density of the conductive particles may deviate from the above-mentioned number density locally (for example, 200 μm×200 μm).

<Insulating resin binder>
As the insulating resin binder 3, thermally polymerizable compositions, photopolymerizable compositions, photothermal polymerizable compositions, etc., which are used as insulating resin binders in known anisotropic conductive films, are appropriately selected and used. can do. Among these, thermally polymerizable compositions include thermally radically polymerizable resin compositions containing an acrylate compound and a thermally radical polymerization initiator, thermally cationically polymerizable resin compositions containing an epoxy compound and a thermally cationic polymerization initiator, and epoxy compounds. Examples of photopolymerizable compositions include photoradical polymerizable resin compositions containing an acrylate compound and a photoradical polymerization initiator. can be given. If no particular problem arises, multiple types of polymerizable compositions may be used in combination. Examples of combined use include a combination of a thermally cationically polymerizable composition and a thermally radically polymerizable composition.

Here, a plurality of types of photopolymerization initiators that react to light of different wavelengths may be included. As a result, the wavelength used for photo-curing of the resin constituting the insulating resin layer during the production of anisotropic conductive film and photo-curing of the resin for bonding electronic components together during anisotropic conductive connection can be changed. Can be used differently.

When the insulating resin binder 3 is formed using a photopolymerizable composition, all or part of the photopolymerizable compound contained in the insulating resin binder 3 is removed by photocuring during production of the anisotropic conductive film. can be photocured. This photocuring maintains or fixes the arrangement of the conductive particles 2 in the insulating resin binder 3, and is expected to suppress short circuits and improve trapping. Furthermore, by adjusting the photocuring conditions, the viscosity of the insulating resin layer in the process of manufacturing the anisotropic conductive film can be adjusted.

The amount of the photopolymerizable compound in the insulating resin binder 3 is preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably less than 2% by mass. This is because if the amount of the photopolymerizable compound is too large, the thrust required for pushing during anisotropic conductive connection increases.

On the other hand, the thermally polymerizable composition contains a thermally polymerizable compound and a thermal polymerization initiator, but as the thermally polymerizable compound, one that also functions as a photopolymerizable compound may be used. Further, the thermally polymerizable composition may contain a photopolymerizable compound separately from the thermally polymerizable compound, and may also contain a photopolymerizable initiator. Preferably, a photopolymerizable compound and a photopolymerization initiator are contained separately from the thermally polymerizable compound. For example, a thermal cationic polymerization initiator is used as a thermal polymerization initiator, an epoxy resin is used as a thermally polymerizable compound, a photoradical initiator is used as a photopolymerization initiator, and an acrylate compound is used as a photopolymerizable compound. The insulating binder 3 may include cured products of these polymerizable compositions.

As the acrylate compound used as the thermally or photopolymerizable compound, conventionally known thermally polymerizable (meth)acrylate monomers can be used. For example, monofunctional (meth)acrylate monomers and polyfunctional (meth)acrylate monomers having more than two functionalities can be used.

Further, the epoxy compound used as the polymerizable compound forms a three-dimensional network structure and imparts good heat resistance and adhesiveness, and it is preferable to use a solid epoxy resin and a liquid epoxy resin together. Here, the solid epoxy resin means an epoxy resin that is solid at room temperature. Moreover, liquid epoxy resin means an epoxy resin that is liquid at room temperature. Further, normal temperature means a temperature range of 5 to 35° C. as defined in JIS Z 8703. In the present invention, two or more types of epoxy compounds can be used in combination. Further, in addition to the epoxy compound, an oxetane compound may be used in combination.

The solid epoxy resin is not particularly limited as long as it is compatible with the liquid epoxy resin and solid at room temperature, and includes bisphenol A epoxy resin, bisphenol F epoxy resin, polyfunctional epoxy resin, dicyclopentadiene epoxy resin, Examples include novolak phenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, etc., and one type among these can be used alone or two or more types can be used in combination. Among these, it is preferable to use bisphenol A type epoxy resin.

The liquid epoxy resin is not particularly limited as long as it is liquid at room temperature, and examples include bisphenol A epoxy resin, bisphenol F epoxy resin, novolac phenol epoxy resin, naphthalene epoxy resin, and one type from these. These can be used alone or in combination of two or more. In particular, from the viewpoint of film tackiness, flexibility, etc., it is preferable to use bisphenol A type epoxy resin.

Among thermal polymerization initiators, examples of thermal radical polymerization initiators include organic peroxides and azo compounds. In particular, organic peroxides that do not generate nitrogen, which causes bubbles, can be preferably used.

The amount of thermal radical polymerization initiator used is preferably 2 to 60 parts by mass, more preferably 2 to 60 parts by mass, based on 100 parts by mass of the (meth)acrylate compound, since too little will result in poor curing, and too much will shorten the product life. It is 5 to 40 parts by mass.

As the thermal cationic polymerization initiator, those known as thermal cationic polymerization initiators for epoxy compounds can be used. For example, iodonium salts, sulfonium salts, phosphonium salts, ferrocenes, etc. that generate acid when heated can be used. In particular, aromatic sulfonium salts that exhibit good temperature-dependent latency can be preferably used.

The amount of thermal cationic polymerization initiator used is preferably 2 to 60 parts by mass per 100 parts by mass of the epoxy compound, since too little tends to result in poor curing, and too much tends to shorten the product life. parts, more preferably 5 to 40 parts by weight.

As the thermal anionic polymerization initiator, commonly used and known ones can be used. For example, organic acid dihydrazide, dicyandiamide, amine compound, polyamide amine compound, cyanate ester compound, phenolic resin, acid anhydride, carboxylic acid, tertiary amine compound, imidazole, Lewis acid, Brønsted acid salt, polymercaptan curing agent , urea resin, melamine resin, isocyanate compound, blocked isocyanate compound, etc., and one type among these can be used alone or two or more types can be used in combination. Among these, it is preferable to use a microcapsule-type latent curing agent which has a core of a modified imidazole and whose surface is coated with polyurethane.

It is preferable that the thermopolymerizable composition contains a film-forming resin. The film-forming resin corresponds to, for example, a high molecular weight resin having an average molecular weight of 10,000 or more, and preferably has an average molecular weight of about 10,000 to 80,000 from the viewpoint of film-forming properties. Examples of the film-forming resin include various resins such as phenoxy resin, polyester resin, polyurethane resin, polyester urethane resin, acrylic resin, polyimide resin, butyral resin, and these may be used alone or in combination of two or more types. It may also be used. Among these, phenoxy resin is preferably used from the viewpoint of film formation state, connection reliability, etc.

The thermally polymerizable composition may contain an insulating filler in order to adjust the melt viscosity. Examples of this include silica powder and alumina powder. The size of the insulating filler is preferably a particle diameter of 20 to 1000 nm, and the blending amount is preferably 5 to 50 parts by mass per 100 parts by mass of a thermally polymerizable compound (photopolymerizable compound) such as an epoxy compound. .

Furthermore, fillers different from the above-mentioned insulating fillers, softeners, accelerators, anti-aging agents, colorants (pigments, dyes), organic solvents, ion catcher agents, etc. may be contained.

Additionally, stress relaxation agents, silane coupling agents, inorganic fillers, etc. may be added as necessary. Examples of stress relaxation agents include hydrogenated styrene-butadiene block copolymers, hydrogenated styrene-isoprene block copolymers, and the like. Further, examples of the silane coupling agent include epoxy type, methacryloxy type, amino type, vinyl type, mercapto sulfide type, and ureide type. Further, examples of inorganic fillers include silica, talc, titanium oxide, calcium carbonate, magnesium oxide, and the like.

The insulating resin binder 3 can be formed by forming a coating composition containing the above-mentioned resin into a film by a coating method and drying it, further curing it, or by forming it into a film in advance by a known method. The insulating resin binder 3 may be obtained by laminating resin layers as necessary. Further, the insulating resin binder 3 is preferably formed on a release film such as a polyethylene terephthalate film that has been subjected to release treatment.

(Viscosity of insulating resin binder)
The minimum melt viscosity of the insulating resin binder 3 can be determined as appropriate depending on the method of manufacturing the anisotropic conductive film. For example, when manufacturing an anisotropic conductive film, conductive particles are held in a predetermined arrangement on the surface of an insulating resin binder and the conductive particles are pushed into the insulating resin binder. In order to enable molding, it is preferable that the minimum melt viscosity of the resin is 1100 Pa·s or more. Further, as will be described later, a recess 3b may be formed around the exposed portion of the conductive particles 2 pushed into the insulating resin binder 3 as shown in FIG. From the viewpoint of forming a recess 3c directly above the conductive particles 2 pushed into the conductive particles 3, the minimum melt viscosity is preferably 1500 Pa·s or more, more preferably 2000 Pa·s or more, still more preferably 3000 to 15000 Pa·s, especially It is 3000 to 10000 Pa·s. This minimum melt viscosity can be determined using, for example, a rotary rheometer (manufactured by TA instruments), with a heating rate of 10°C/min, a constant measuring pressure of 5 g, and a measuring plate with a diameter of 8 mm. I can do it. Further, when performing the step of pressing the conductive particles 2 into the insulating resin binder 3 at preferably 40 to 80°C, more preferably 50 to 60°C, from the viewpoint of forming the recesses 3b or 3c as described above, 60°C As for the viscosity of Preferably it is 10,000 Pa·s or less.

By making the viscosity of the resin constituting the insulating resin binder 3 high as described above, when using the anisotropic conductive film, the conductive particles 2 can be sandwiched between opposing objects to be connected such as electronic components. When heating and pressurizing the anisotropic conductive film, it is possible to prevent the conductive particles 2 in the anisotropic conductive film from being washed away by the flow of the molten insulating resin binder 3.

(Thickness of insulating resin binder)
The thickness La of the insulating resin binder 3 is preferably 1 μm or more and 60 μm or less, more preferably 1 μm or more and 30 μm or less, and still more preferably 2 μm or more and 15 μm or less. Furthermore, in relation to the thickness La of the insulating resin binder 3 and the average particle diameter D of the conductive particles 2, the ratio thereof (La/D) is preferably 0.6 to 10. If the thickness La of the insulating resin binder 3 is too large, the conductive particles are likely to be displaced during anisotropic conductive connection, and the ability to capture the conductive particles at the terminal is reduced. This tendency is remarkable when La/D exceeds 10. Therefore, La/D is preferably 8 or less, more preferably 6 or less. On the other hand, if the thickness La of the insulating resin binder 3 is too small and La/D is less than 0.6, it becomes difficult to maintain the conductive particles in a predetermined particle dispersion state or in a predetermined arrangement by the insulating resin binder 3. Become. In particular, when the terminal to be connected is a high-density COG, the ratio (La/D) between the layer thickness La of the insulating resin binder 3 and the particle diameter D of the conductive particles 2 is preferably 0.8 to 2.

(Embedding mode of conductive particles in insulating resin binder)
There is no particular restriction on the embedded state of the conductive particles 2 in the insulating resin binder 3, but when an anisotropic conductive connection is made by sandwiching an anisotropic conductive film between opposing parts and applying heat and pressure, As shown in FIGS. 14 and 15, the conductive particles 2 are partially exposed from the insulating resin binder 3, and the tangential plane 3p of the surface 3a of the insulating resin binder 3 in the center between adjacent conductive particles 2 is A recess 3b is formed around the exposed portion of the conductive particles 2, or as shown in FIG. It is preferable that a recess 3c be formed with respect to a tangential plane 3p similar to the above, and that undulations be present on the surface of the insulating resin binder 3 directly above the conductive particles 2. The presence of the recesses 3b shown in FIGS. 14 and 15 prevents the flattening of the conductive particles 2 that occurs when the conductive particles 2 are sandwiched between opposing electrodes of electronic components and heated and pressurized. The resistance received from the insulating resin binder 3 is reduced compared to the case where there is no recess 3b. Therefore, the conductive particles 2 are easily sandwiched between the opposing electrodes, and the conduction performance is also improved. In addition, among the resins constituting the insulating resin binder 3, since the depressions 3c (Fig. 16) are formed on the surface of the resin directly above the conductive particles 2, the heat and pressure are increased compared to the case where there are no depressions 3c. The pressure at the time becomes easier to concentrate on the conductive particles 2, and the conductive particles 2 are easily held between the electrodes, thereby improving conduction performance.

From the point of view of making it easier to obtain the effects of the above-mentioned recesses 3b and 3c, the ratio between the maximum depth Le of the recess 3b (FIGS. 14 and 15) around the exposed portion of the conductive particles 2 and the average particle diameter D of the conductive particles 2. (Le/D) is preferably less than 50%, more preferably less than 30%, even more preferably 20 to 25%, and the maximum The ratio (Ld/D) between the diameter Ld and the average particle diameter D of the conductive particles 2 is preferably 100% or more, more preferably 100 to 150%, and the depression 3c in the resin directly above the conductive particles 2 (Fig. 16 The ratio (Lf/D) between the maximum depth Lf of ) and the average particle diameter D of the conductive particles 2 is preferably greater than 0, preferably less than 10%, and more preferably less than 5%.

Note that the diameter Lc of the exposed portion of the conductive particles 2 can be equal to or less than the average particle diameter D of the conductive particles 2, and is preferably 10 to 90% of the particle diameter D. The conductive particles 2 may be exposed at one point on the top 2t, or the conductive particles 2 may be completely buried in the insulating resin binder 3 and the diameter Lc may be zero.

(Position of conductive particles in the thickness direction of the insulating resin binder)
In order to make it easier to obtain the effect of the recess 3b described above, the ratio (Lb /D) (hereinafter referred to as embedding rate) is preferably 60% or more and 105% or less.

<Insulating adhesive layer>
In the anisotropic conductive film of the present invention, an insulating adhesive layer 4 having a different viscosity and adhesiveness from the resin constituting the insulating resin binder 3 is laminated on the insulating resin binder 3 on which the conductive particles 2 are arranged. You can leave it there.

When the above-described depressions 3b are formed in the insulating resin binder 3, as in the anisotropic conductive film 1d shown in FIG. It may be laminated on the surface opposite to the surface on which the recess 3b is formed, as in the anisotropic conductive film 1e shown in FIG. 18. The same applies to the case where the insulating resin binder 3 has a recess 3c. The lamination of the insulating adhesive layer 4 fills the space formed by the electrodes and bumps of the electronic component and improves adhesiveness when anisotropically conductive connecting the electronic component using the anisotropic conductive film. I can do it.

In addition, when the insulating adhesive layer 4 is laminated on the insulating resin binder 3, regardless of whether the insulating adhesive layer 4 is on the surface where the recesses 3b and 3c are formed, the insulating adhesive layer 4 is laminated on the IC chip, etc. (In other words, the insulating resin binder 3 is preferably located on the second electronic component side such as a substrate). By doing so, it is possible to avoid unwanted movement of the conductive particles, and it is possible to improve the trapping performance. Note that normally, the first electronic component such as an IC chip is placed on the pressing jig side, the second electronic component such as a board is placed on the stage side, and after the anisotropic conductive film is temporarily bonded to the second electronic component, the first electronic component is The component and the second electronic component are finally bonded together, but depending on the size of the thermocompression bonding area of the second electronic component, the anisotropic conductive film may be temporarily attached to the first electronic component, and then the first electronic component and the second electronic component are bonded together. Final crimp the parts.

As the insulating adhesive layer 4, those used as insulating adhesive layers in known anisotropic conductive films can be appropriately selected and used. The insulating adhesive layer 4 may be made of the same resin as the insulating resin binder 3 described above, but the viscosity thereof is adjusted to be lower. The greater the difference in the minimum melt viscosity between the insulating adhesive layer 4 and the insulating resin binder 3, the easier it is to fill the spaces formed by the electrodes and bumps of electronic components with the insulating adhesive layer 4, which increases the bonding between electronic components. It can be expected to have the effect of improving sex. Furthermore, the larger this difference is, the smaller the amount of movement of the resin constituting the insulating resin binder 3 during anisotropic conductive connection becomes, and thus the ability to capture conductive particles at the terminal is more likely to be improved. Practically speaking, the minimum melt viscosity ratio between the insulating adhesive layer 4 and the insulating resin binder 3 is preferably 2 or more, more preferably 5 or more, still more preferably 8 or more. On the other hand, if this ratio is too large, resin may ooze out or block when a long anisotropic conductive film is wound. Therefore, it is preferably 15 or less for practical purposes. More specifically, the preferable minimum melt viscosity of the insulating adhesive layer 4 satisfies the above ratio and is 3000 Pa·s or less, more preferably 2000 Pa·s or less, particularly 100 to 2000 Pa·s.

The insulating adhesive layer 4 can be formed by forming a coating composition containing a resin similar to the resin forming the insulating resin binder 3 by a coating method and drying it, by further curing it, or by using a known method in advance. It can be formed by forming it into a film using the following method.

The thickness of the insulating adhesive layer 4 is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 15 μm or less.

In addition, the minimum melt viscosity of the entire anisotropic conductive film including the insulating resin binder 3 and the insulating adhesive layer 4 depends on the ratio of the thicknesses of the insulating resin binder 3 and the insulating adhesive layer 4, but in practice may be 8000 Pa·s or less, and may be 200 to 7000 Pa·s, preferably 200 to 4000 Pa·s, in order to facilitate filling between bumps.

Furthermore, insulating filler such as silica fine particles, alumina, aluminum hydroxide, etc. may be added to the insulating resin binder 3 and the insulating adhesive layer 4 as necessary. The blending amount of the insulating filler is preferably 3 parts by mass or more and 40 parts by mass or less based on 100 parts by mass of the resin constituting these layers. Thereby, even if the anisotropic conductive film melts during anisotropic conductive connection, unnecessary movement of the conductive particles by the melted resin can be suppressed.

<Method for manufacturing anisotropic conductive film>
As a method for manufacturing an anisotropic conductive film, for example, a transfer mold for arranging conductive particles in a predetermined arrangement is manufactured, conductive particles are filled in the recesses of the transfer mold, and then a release film is formed on top of the conductive particles. The conductive particles 2 are transferred onto the insulating resin binder 3 by applying pressure and forcing the conductive particles 2 into the insulating resin binder 3. Alternatively, an insulating adhesive layer 4 is further laminated on the conductive particles 2. In this way, an anisotropic conductive film 1A can be obtained.

In addition, after filling the concave portions of the transfer mold with conductive particles, an insulating resin binder is placed over the concave portions of the transfer mold, and the conductive particles are transferred from the transfer mold to the surface of the insulating resin binder, thereby insulating the conductive particles on the insulating resin binder. An anisotropic conductive film may be manufactured by pressing the film into a polyurethane resin binder. The amount of conductive particles embedded (Lb) can be adjusted by the pressing force, temperature, etc. during this pressing. Further, the shape and depth of the recesses 3b and 3c can be adjusted by adjusting the viscosity of the insulating resin binder during pressing, the pressing speed, temperature, etc. For example, the lower limit of the viscosity of the insulating resin binder when the conductive particles are pressed is preferably 3000 Pa.s or more, more preferably 4000 Pa.s or more, still more preferably 4500 Pa.s or more, and the upper limit is preferably 20000 Pa.s. Hereinafter, it is more preferably 15,000 Pa·s or less, still more preferably 10,000 Pa·s or less. Further, such a viscosity is preferably obtained at a temperature of 40 to 80°C, more preferably 50 to 60°C. More specifically, when manufacturing the anisotropic conductive film 1a having the indentations 3b shown in FIG. When manufacturing the anisotropic conductive film 1c having the recesses 3c shown in FIG. 60° C.) is preferable.

In addition to the transfer mold in which the concave portions are filled with conductive particles, a type in which a slight adhesive is applied to the top surface of the convex portion so that the conductive particles adhere to the top surface may be used.

These transfer molds can be manufactured using or applying known techniques such as machining, photolithography, and printing.

Further, as a method for arranging the conductive particles in a predetermined arrangement, a method using a biaxially stretched film, etc. may be used instead of a method using a transfer mold.

<Wrapping body>
Since the anisotropic conductive film is continuously used for connecting electronic components, it is preferable to form a film-wrapped body wound around a reel. The length of the film wrapping body may be at least 5 m, preferably at least 10 m. Although there is no particular upper limit, from the point of view of handling of shipped items, the length is preferably 5000 m or less, more preferably 1000 m or less, and even more preferably 500 m or less.

The film wrapping body may be made by connecting anisotropic conductive films shorter than the entire length with a connecting tape. A plurality of connection points may exist, and they may exist regularly or randomly. The thickness of the connecting tape is not particularly limited as long as it does not interfere with performance, but if it is too thick, it will affect resin extrusion and blocking, so it is preferably 10 to 40 μm. Further, the width of the film is not particularly limited, but is, for example, 0.5 to 5 mm.

According to the film-wrapped body, a continuous anisotropic conductive connection can be made and it can contribute to cost reduction of the connecting body.

<Connection structure>
The anisotropic conductive film of the present invention connects a first electronic component such as an FPC, an IC chip, or an IC module to a second electronic component such as an FPC, a rigid substrate, a ceramic substrate, a glass substrate, or a plastic substrate by heat or light. It can be preferably applied when making anisotropic conductive connections. It is also possible to stack IC chips or IC modules and connect the first electronic components to each other in an anisotropic conductive manner. The thus obtained connected structure and its manufacturing method are also part of the present invention.

As a method for connecting electronic components using an anisotropic conductive film, for example, the interface of the anisotropic conductive film on the side where conductive particles are nearby in the film thickness direction is temporarily attached to a second electronic component such as a wiring board. However, it is preferable to mount a first electronic component such as an IC chip on the temporarily pasted anisotropic conductive film and to bond it by thermocompression from the first electronic component side, from the viewpoint of improving connection reliability. Further, connection can also be made using photocuring. In addition, in this connection, from the point of view of connection work efficiency, it is preferable that the longitudinal direction of the terminal of the electronic component is aligned with the transverse direction of the anisotropic conductive film.

Experimental example 1 to experimental example 8
(Preparation of anisotropic conductive film)
Regarding the anisotropic conductive film used for COG connection, the effects of the resin composition of the insulating resin binder and the arrangement of the conductive particles on the film forming ability and conduction properties were investigated as follows.

First, resin compositions for forming an insulating resin binder and an insulating adhesive layer were prepared using the formulations shown in Table 1. In this case, the minimum melt viscosity of the resin composition was adjusted according to the conditions for preparing the insulating resin composition. The resin composition forming the insulating resin binder was coated on a PET film with a thickness of 50 μm using a bar coater, and dried in an oven at 80° C. for 5 minutes to form an insulating layer on the PET film with a thickness of La shown in Table 2. A synthetic resin binder layer was formed. Similarly, an insulating adhesive layer was formed on the PET film with the thickness shown in Table 2.

Next, a mold was produced so that the conductive particles were arranged as shown in Table 2 in plan view, and the distance between the centers of the nearest conductive particles in the repeating unit was 6 μm. Pellets of a known transparent resin were poured into the mold in a molten state, and then cooled and solidified to form a resin mold having concavities arranged as shown in Table 2. Here, in Experimental Example 8, the conductive particles were arranged in a hexagonal lattice arrangement (number density: 32,000 particles/mm ² ), and one of the lattice axes was inclined by 15 degrees with respect to the longitudinal direction of the anisotropic conductive film. .

As the conductive particles, metal-coated resin particles (Sekisui Chemical Co., Ltd., AUL703, average particle diameter 3 μm) were prepared, the conductive particles were filled into the recesses of the resin mold, and the above-mentioned insulating resin binder was covered. , 60° C., and 0.5 MPa. Then, the insulating resin binder is peeled off from the mold, and the conductive particles on the insulating resin binder are pressed into the insulating resin binder by applying pressure (pressing conditions: 60 to 70°C, 0.5 MPa). A film was prepared in which conductive particles were embedded in a binder in the state shown in Table 2. In this case, the embedded state of the conductive particles was controlled by the indentation conditions. As a result, in Experimental Example 4, the film shape was not maintained after the conductive particles were pushed in, but in other Experimental Examples, films in which conductive particles were embedded were able to be produced. Upon observation using a metallurgical microscope, depressions were observed around the exposed portion of the embedded conductive particles or directly above the embedded conductive particles as shown in Table 2. In addition, in each experimental example except Experimental Example 4, both the dents around the exposed part of the conductive particles and the dents directly in front of the conductive particles were observed, but in Table 4, the dents were most clearly observed for each experimental example. Measured values of what was observed are shown.

An anisotropic conductive film having two resin layers was produced by laminating an insulating adhesive layer on the side of the film in which conductive particles were embedded. However, in Experimental Example 4, the film shape was not maintained after the conductive particles were pushed in, so subsequent evaluation was not performed.

(evaluation)
For the anisotropic conductive film of each experimental example, (a) initial conduction resistance and (b) conduction reliability were measured as follows. The results are shown in Table 2.

(a) Initial conduction resistance The anisotropic conductive film of each experimental example was sandwiched between the glass substrate on the stage and the IC for evaluating conduction characteristics on the pressing tool side, and heated and pressed with the pressing tool (180°C, 5 seconds). ) to obtain each connection for evaluation. In this case, three types of connected objects for evaluation were obtained by changing the thrust force by the pressing tool to three levels: low (40 MPa), medium (60 MPa), and high (80 MPa).

Here, the IC for evaluating conductivity characteristics and the glass substrate have corresponding terminal patterns, and the sizes are as follows. Furthermore, when connecting the evaluation IC and the glass substrate, the longitudinal direction of the anisotropic conductive film and the lateral direction of the bumps were aligned.

IC for evaluating continuity characteristics
External size 1.8 x 20.0mm
Thickness 0.5mm
Bump specifications Size: 30 x 85 μm, distance between bumps: 50 μm, bump height: 15 μm

Glass substrate (ITO wiring)
Glass material Corning 1737F
External size 30x50mm
Thickness 0.5mm
Electrode ITO wiring

The initial conduction resistance of the obtained evaluation connection was measured and evaluated using the following three-level evaluation criteria.
Evaluation criteria for initial conduction resistance (in practice, there is no problem if it is less than 2Ω)
A: Less than 0.4Ω B: 0.4Ω or more and less than 0.8Ω C: 0.8Ω or more

(b) Continuity Reliability A reliability test was carried out by placing the evaluation connection manufactured in (a) in a constant temperature bath at a temperature of 85°C and a humidity of 85% RH for 500 hours, and the subsequent continuity resistance was the same as the initial continuity resistance. was measured and evaluated using the following three-level evaluation criteria.

Evaluation criteria for continuity reliability (in practice, there is no problem if it is less than 5Ω)
A: Less than 1.2Ω B: 1.2Ω or more and less than 2Ω C: 2Ω or more

Table 2 shows that in Experimental Example 4 in which the minimum melt viscosity of the insulating resin layer was 800 Pa·s, it was difficult to form a film having depressions in the insulating resin binder near the conductive particles. On the other hand, in an experimental example in which the minimum melt viscosity of the insulating resin binder was 1500 Pa·s or more, it was found that by adjusting the conditions when embedding the conductive particles, a convex portion could be formed near the conductive particles of the insulating resin binder. It can be seen that the anisotropic conductive film has good conduction properties for COG. Furthermore, it can be seen that in Experimental Examples 1 to 7, in which the number density of conductive particles is lower than that in Experimental Example 8 with a hexagonal lattice arrangement, anisotropic conductive connections can be made at a lower pressure.

(c) Short-circuit occurrence rate The anisotropic conductive films of Experimental Examples 1 to 3 and 5 to 8 were used, and the following short-circuit occurrence rate evaluation IC was used to evaluate the connection conditions at 180°C, 60 MPa, and 5 seconds. A connection object for evaluation was obtained, the number of shorts in the obtained connection object for evaluation was measured, and a short occurrence rate was determined as a ratio of the measured number of shorts to the number of terminals of the evaluation IC.

IC for evaluating short circuit occurrence rate (comb toothed TEG (test element group) with 7.5 μm space: external size 15 x 13 mm
Thickness 0.5mm
Bump specifications Size 25 x 140μm, distance between bumps 7.5μm, bump height 15μm

It is practically preferable that the short circuit is less than 50 ppm, and the anisotropic conductive films of Experimental Examples 1 to 3 and 5 to 8 were all less than 50 ppm.

In addition, when the number of conductive particles captured per bump was measured for each of the experimental examples except for Experimental Example 4, 10 or more conductive particles were captured in all cases.

Experimental examples 9 to 16
(Preparation of anisotropic conductive film)
Regarding the anisotropic conductive film used for FOG connection, the effects of the resin composition of the insulating resin binder and the arrangement of the conductive particles on the film forming ability and conduction properties were investigated as follows.

That is, a resin composition for forming an insulating resin binder and an insulating adhesive layer was prepared with the formulation shown in Table 3, and an anisotropic conductive film was produced using these in the same manner as in Experimental Example 1. Table 4 shows the arrangement of the conductive particles and the distance between the centers of the nearest conductive particles in this case. In Experimental Example 16, the conductive particles were arranged in a hexagonal lattice arrangement (number density: 15,000 particles/mm ² ), and one of the lattice axes was inclined at 15 degrees with respect to the longitudinal direction of the anisotropic conductive film.

In the process of creating this anisotropic conductive film, the film shape was not maintained in Experimental Example 12 after the conductive particles were pushed into the insulating resin binder, but the film shape was maintained in the other experimental examples. Therefore, the embedded state of the conductive particles in the anisotropic conductive films of the experimental examples other than Experimental Example 12 was observed and measured using a metallurgical microscope, and the subsequent evaluations were performed. Table 4 shows the embedded state of conductive particles in each experimental example. Similar to Table 2, the embedding conditions shown in Table 4 are the measured values of the insulating resin binder in which the dents were most clearly observed in each experimental example.

(evaluation)
For the anisotropic conductive film of each experimental example, (a) initial conduction resistance and (b) conduction reliability were measured as follows. The results are shown in Table 4.

(a) Initial conduction resistance The anisotropic conductive film obtained in each experimental example was cut to 2 mm x 40 mm, sandwiched between an FPC for evaluating conduction characteristics and a glass substrate, and heated and pressed at 180°C using a tool width of 2 mm. , 5 seconds) to obtain each connected object for evaluation. In this case, three types of connectors for evaluation were obtained by changing the thrust force by the pressing tool to three levels: low (3 MPa), medium (4.5 MPa), and high (6 MPa). The conduction resistance of the obtained evaluation connection was measured in the same manner as in Experimental Example 1, and the measured values were evaluated in three stages based on the following criteria.

Evaluation FPC:
Terminal pitch 20μm
Terminal width/space between terminals 8.5μm/11.5μm
Polyimide film thickness (PI)/copper foil thickness (Cu) = 38/8, Sn plating

Non-alkali glass substrate:
Electrode ITO wiring thickness 0.7mm

Evaluation criteria for initial conduction resistance A: Less than 1.6Ω B: 1.6Ω or more and less than 2.0Ω C: 2.0Ω or more

(b) Continuity reliability The evaluation connection manufactured in (a) was placed in a constant temperature bath at a temperature of 85°C and a humidity of 85% RH for 500 hours, and the subsequent continuity resistance was measured in the same manner as the initial continuity resistance. The values were evaluated in three stages based on the following criteria.

Evaluation criteria for continuity reliability A: Less than 3.0Ω B: 3.0Ω or more and less than 4Ω C: 4.0Ω or more

Table 4 shows that in Experimental Example 12 where the minimum melt viscosity of the insulating resin layer was 800 Pa·s, it was difficult to form a film with depressions. On the other hand, in an experimental example in which the minimum melt viscosity of the insulating resin layer was 1500 Pa·s or more, it was found that by adjusting the conditions when embedding the conductive particles, it was possible to form depressions in the vicinity of the conductive particles in the insulating resin binder. It can be seen that the oriented conductive film has good conduction properties for FOG.

(c) Short-circuit occurrence rate The number of short-circuits of the evaluation connection whose initial conduction resistance was measured was measured, and the short-circuit occurrence rate was determined from the measured number of shorts and the number of gaps of the evaluation connection. There is no practical problem if the short circuit occurrence rate is less than 100 ppm.
In both Experimental Examples 9 to 11 and 13 to 16, the short circuit occurrence rate was less than 100 ppm.

In addition, when the number of conductive particles captured per bump was measured for each of the experimental examples except for Experimental Example 12, 10 or more conductive particles were captured in all cases.

1A, 1Ba, 1Bb, 1Ca, Cb, 1Da, Db, 1Ea, Eb, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1a, 1b, 1c, 1d, 1e Anisotropic conductive film 2, 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2p, 2q, 2r, 2s, 2t, 2u Conductive particles 3 Insulating resin binder 4 Insulating adhesive layer 5, 5B Repeat unit

Claims (12)

An anisotropic conductive film in which conductive particles are arranged in an insulating resin binder,
In plan view, polygonal repeating units formed by sequentially connecting the centers of multiple conductive particles are arranged repeatedly,
When regular triangles are arranged without gaps, the vertices of the regular triangles and the conductive particles that make up the repeating unit overlap,
There is one or more regular triangular regions in which no conductive particles are arranged between the repeating units that are arranged repeatedly,
The polygon of the repeating unit has sides obliquely intersecting the longitudinal direction or the transverse direction of the anisotropic conductive film,
Single conductive particles or separate repeating units are arranged between the repeating units,
Anisotropy in which, when a polygon constituting a repeating unit is inverted around one side of the polygon, one side of the polygon of the repeating unit after inversion overlaps with one side of the repeating unit that was adjacent to it before inversion. conductive film. The anisotropic conductive film according to claim 1, wherein the repeating units are arranged on one surface of the anisotropic conductive film. The anisotropic conductive film according to claim 1 or 2, wherein the repeating unit is trapezoidal. The anisotropic conductive film according to any one of claims 1 to 3, wherein each side of the polygon forming the repeating unit is oblique to the longitudinal direction or the transverse direction of the anisotropic conductive film. The anisotropic conductive film according to any one of claims 1 to 3, wherein the polygon forming the repeating unit has sides in the longitudinal direction or the transverse direction of the anisotropic conductive film. The anisotropic conductive film according to any one of claims 1 to 5 , wherein the repeating unit forms part of a regular polygon. The anisotropic conductive film according to any one of claims 1 to 5, wherein the arrangement of the conductive particles constituting the repeating unit overlaps with the vertices of a hexagon when regular hexagons are arranged without gaps. The anisotropic conductive film according to any one of claims 1 to 7 , further comprising an insulating adhesive layer laminated thereon. The anisotropic conductive film according to any one of claims 1 to 8 , wherein the repeating units are repeated in both the vertical direction and the horizontal direction when the anisotropic conductive film is viewed in plan. 10. The anisotropic conductive film according to claim 9 , wherein the shortest distance between repeating units in the longitudinal direction, the transverse direction, or both directions is longer than the distance between adjacent conductive particles within the repeating unit. A connected structure in which a first electronic component and a second electronic component are anisotropically conductively connected by the anisotropic conductive film according to any one of claims 1 to 10 . A method for manufacturing a connection structure of a first electronic component and a second electronic component by thermocompression bonding the first electronic component and the second electronic component via an anisotropic conductive film, the method comprising: A method for producing a connected structure using the anisotropic conductive film according to any one of claims 1 to 10 .

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