HK1261541B - Anisotropic electroconductive film - Google Patents

Description

Anisotropic conductive film

Technical Field

The present invention relates to an anisotropic conductive film.

Background Art

Anisotropic conductive films, which consist of conductive particles dispersed in an insulating resin binder, are widely used when mounting electronic components such as IC chips on wiring boards. With the narrowing of bump pitches associated with high-density mounting of electronic components, there is a strong demand for anisotropic conductive films to improve the ability to capture conductive particles on the bumps and prevent short circuits between adjacent bumps.

To meet these requirements, proposals have been made to arrange the conductive particles in an anisotropic conductive film in a grid-like pattern, with the arrangement axis tilted relative to the longitudinal direction of the anisotropic conductive film. In this case, the conductive particles are spaced at a predetermined ratio (Patent Documents 1 and 2). Furthermore, proposals have been made to link the conductive particles to form a locally dense region to accommodate narrower pitches (Patent Document 3).

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent No. 4887700;

Patent Document 2: Japanese Patent Application Laid-Open No. 9-320345;

Patent Document 3: Japanese Patent Application Publication No. 2002-519473.

Summary of the Invention

Problems to be solved by the invention

When conductive particles are arranged in a simple grid pattern, as described in Patent Documents 1 and 2, the bump layout is determined by the inclination angle of the arrangement axis or the distance between the conductive particles. Therefore, when the bumps are arranged at narrow pitches, the distance between the conductive particles must be reduced, making short circuits difficult to avoid. Furthermore, increasing the number density of conductive particles increases the manufacturing cost of the anisotropic conductive film.

On the other hand, if the distance between the conductive particles is not reduced, there is a concern that a sufficient number of conductive particles may not be captured by the terminals.

Furthermore, the method of forming a locally dense region of conductive particles by linking conductive particles is not preferred because the risk of short circuit increases when a plurality of linked conductive particles simultaneously enter the gaps between bumps.

Therefore, an object of the present invention is to provide an anisotropic conductive film that can accommodate bumps with narrow pitches and that can reduce the number density of conductive particles compared to conventional anisotropic conductive films.

Solutions to Problems

The inventors discovered that when units of conductive particles spaced apart from each other and arranged in a specific manner are repeatedly arranged on the entire surface of an anisotropic conductive film, sparse and dense regions of conductive particles can be formed on the entire surface of the film. Therefore, narrow-pitch bumps can be connected in dense regions of the sparse regions, and the conductive particles are also separated from each other in the dense regions, thereby reducing the risk of short circuits. Furthermore, the presence of the sparse regions can reduce the number density of conductive particles in the entire film, which led to the present invention.

That is, the present invention provides an anisotropic conductive film in which conductive particles are arranged in an insulating resin binder, wherein:

A repeating unit of conductive particles is formed by repeatedly arranging conductive particle rows in which conductive particles having different numbers of conductive particles are arranged in parallel and spaced apart from each other.

Effects of the Invention

According to the anisotropic conductive film of the present invention, the individual conductive particles are not arranged in a simple lattice shape, but the repeating units of the conductive particles with a specific particle configuration are repeatedly arranged, so that a sparse area of conductive particles can be formed in the film, so the anisotropic conductive film as a whole can suppress the increase in the number density of the conductive particles. Therefore, it is possible to suppress the increase in manufacturing costs accompanying the increase in the number density of the conductive particles. In addition, generally, if the number density of the conductive particles increases, the thrust required to press the clamp during anisotropic conductive connection also increases. However, according to the anisotropic conductive film of the present invention, by suppressing the increase in the number density of the conductive particles, the increase in the thrust required to press the clamp during anisotropic conductive connection is also suppressed, thereby preventing electronic components from being deformed due to anisotropic conductive connection. In addition, the pressing clamp does not require excessive thrust, thereby stabilizing the thrust of the pressing clamp, and thus the quality of the conductive characteristics of the electronic components of the anisotropic conductive connection is stable.

On the other hand, the anisotropic conductive film of the present invention forms repeating units that form densely packed conductive particles, allowing for connection of narrowly pitched bumps. Furthermore, the conductive particles are separated from each other within the repeating units, preventing short circuits even when the repeating units span gaps between terminals.

BRIEF DESCRIPTION OF THE DRAWINGS

[ FIG. 1A] FIG. 1A is a plan view showing the arrangement of conductive particles in an anisotropic conductive film 1A of the embodiment.

[ FIG. 1B] FIG. 1B is a cross-sectional view of an anisotropic conductive film 1A of the embodiment. [ FIG.

[ Fig. 2] Fig. 2 is a plan view of an anisotropic conductive film 1B of the embodiment.

[ Fig. 3] Fig. 3 is a plan view of an anisotropic conductive film 1C according to the embodiment.

[ Fig. 4] Fig. 4 is a plan view of an anisotropic conductive film 1D according to an embodiment.

[ Fig. 5] Fig. 5 is a plan view of an anisotropic conductive film 1E according to the embodiment.

[ Fig. 6] Fig. 6 is a plan view of an anisotropic conductive film 1F according to the embodiment.

[ Fig. 7] Fig. 7 is a plan view of an anisotropic conductive film 1G according to an embodiment.

[ Fig. 8] Fig. 8 is a plan view of an anisotropic conductive film 1H according to the embodiment.

[ Fig. 9] Fig. 9 is a plan view of an anisotropic conductive film 1I according to an embodiment.

[ Fig. 10] Fig. 10 is a plan view of an anisotropic conductive film 1J of the embodiment.

[ Fig. 11] Fig. 11 is a plan view of an anisotropic conductive film 1K according to an embodiment.

[ Fig. 12] Fig. 12 is a cross-sectional view of an anisotropic conductive film 1a according to an embodiment.

[ Fig. 13] Fig. 13 is a cross-sectional view of an anisotropic conductive film 1b of an embodiment.

[ Fig. 14] Fig. 14 is a cross-sectional view of an anisotropic conductive film 1c according to an embodiment.

[ Fig. 15] Fig. 15 is a cross-sectional view of an anisotropic conductive film 1d according to an embodiment.

[ Fig. 16] Fig. 16 is a cross-sectional view of an anisotropic conductive film 1e according to an embodiment.

DETAILED DESCRIPTION

Hereinafter, the anisotropic conductive film of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or equivalent components.

<Overall Structure of Anisotropic Conductive Film>

FIG1A is a plan view showing the arrangement of conductive particles in an anisotropic conductive film 1A according to an embodiment of the present invention, and FIG1B 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 the surface of an insulating resin binder 3 or in the vicinity thereof, and an insulating adhesive layer 4 is laminated thereon.

Furthermore, 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

Conductive particles 2 can be appropriately selected from known conductive particles used in anisotropic conductive films. Examples include metal particles of nickel, copper, silver, gold, palladium, and the like; and metal-coated resin particles obtained by coating the surface of resin particles such as polyamide and polybenzoguanamine with a metal such as nickel. The size of the conductive particles is preferably 1 to 30 μm, more preferably 1 μm to 10 μm, and even more preferably 2 μm to 6 μm.

The average particle size of the conductive particles 2 can be measured using an imaging or laser particle size distribution analyzer. Alternatively, the average particle size can be determined by observing the anisotropic conductive film from above and measuring the particle size. In this case, preferably 200 or more particles are measured, more preferably 500 or more particles are measured, and even more preferably 1000 or more particles are measured.

The surfaces of the conductive particles 2 are preferably coated with an insulating coating or insulating particle treatment. This coating is easily removed from the surface of the conductive particles 2 and does not hinder anisotropic conductive connection. Alternatively, protrusions may be provided on the entire or a portion of the surface of the conductive particles 2. The height of the protrusions is preferably within 20% of the conductive particle diameter, and more preferably within 10%.

＜Arrangement of Conductive Particles＞

(Repeating unit)

The arrangement of the conductive particles 2 in the anisotropic conductive film 1A, when viewed from above, forms a repeating unit 5 consisting of rows of conductive particles 2p, 2q, and 2r and individual conductive particles 2s arranged side by side, repeated vertically and horizontally (in the X and Y directions) across the entire surface of the anisotropic conductive film 1A. The polygon formed by sequentially connecting the centers of the conductive particles forming the outer shape of the repeating unit 5 forms a triangle. Furthermore, the anisotropic conductive film of the present invention may, as desired, include regions where no conductive particles are arranged.

Each conductive particle array 2p, 2q, and 2r has conductive particles 2 arranged in a straight line with intervals when viewed from above. Furthermore, the number of conductive particles constituting each of the conductive particle arrays 2p, 2q, and 2r gradually varies, and the conductive particle arrays 2p, 2q, and 2r are arranged in parallel. By repeatedly arranging the particles in such a manner that the conductive particle arrays 2p, 2q, and 2r each have gradually varying numbers of particles, the number density of the conductive particles is locally sparse. Therefore, even if slight misalignment occurs when the anisotropic conductive film is attached to an electronic component, a stable number of conductive particles can be easily captured in any bump constituting the bump array. This is effective when continuous anisotropic conductive connections are made. Specifically, if a simple lattice arrangement results in slight misalignment when the anisotropic conductive film is attached to an electronic component, the number of captured particles can easily become scattered, particularly at the bump ends, depending on the presence or extent of misalignment. To prevent this scattering, the lattice arrangement is designed to be angled relative to the long side of the film (Patent Document 1, etc.). However, if the bump width or the distance between bumps is further narrowed, the effect of tilting the grid arrangement will be limited. In contrast, in the present invention, the number density of conductive particles is sparse within the range of the bump length, so that conductive particles can be captured at any position within the range of the bump length. In other words, a bump is simultaneously generated with positions where conductive particles are captured and positions where they are not captured. Therefore, if the shape (area) of the bumps in any bump arrangement is the same, the number of conductive particles captured by the bumps can be stabilized by appropriately setting the repetition interval of the repeating unit. Therefore, even if there is a slight misalignment in the attachment of the anisotropic conductive film, the capture state of the conductive particles in the bump arrangement of each connector when the connectors are continuously manufactured on the production line will be easily stabilized. In addition, by simultaneously generating positions where conductive particles are captured and positions where they are not captured on a bump, it is expected that the inspection labor after the anisotropic conductive connection will be reduced or quality management will be improved. For example, by simultaneously generating locations where conductive particles are trapped and locations where they are not trapped within a single bump, it is easier to compare consecutively produced connections during indentation inspection after anisotropic conductive connection. Furthermore, the presence or absence of misalignment when the anisotropic conductive film is temporarily attached to the electronic component during the anisotropic conductive connection process can be compared between consecutively produced connections, making it easier to identify improvements to the connection system.

The configuration of the conductive particles 2 in the repeating unit 5 is such that a part of the conductive particles 2 constituting the repeating unit 5 occupies a part of the vertices of each regular hexagon when regular hexagons are arranged side by side without gaps. Alternatively, the configuration is such that the vertices of the regular triangle when regular triangles are arranged side by side without gaps overlap with the conductive particles constituting the repeating unit 5. In other words, the remaining configuration of the conductive particles that regularly omit the predetermined lattice points from the configuration of the conductive particles present at each lattice point of the hexagonal lattice arrangement becomes the repeating unit 5. If the conductive particles 2 are configured at the lattice points of the hexagonal lattice arrangement in this way, the particle configuration of the repeating unit 5 can be easily identified and easily designed. In addition, as described later, the configuration of the conductive particles in the repeating unit is not limited to the configuration based on the hexagonal lattice, and can be based on the regular lattice, or on a configuration in which regular polygons of more than octagon are arranged side by side vertically and horizontally, and the sides of adjacent regular polygons overlap each other.

(How the repeating unit is repeated)

More specifically, the repetition of repeating unit 5 in the anisotropic conductive film 1A shown in Figure 1A involves repeating in the X direction, with the repeating unit 5 spaced apart from the particles within the repeating unit 5. Furthermore, in the Y direction, repeating unit 5B and repeating unit 5, which are inverted about the Y-axis of symmetry, are repeated alternately at intervals. In this case, it is preferable that the position of the long-side edge of the anisotropic conductive film, when projecting the polygon formed by sequentially connecting the centers of the conductive particles forming the repeating unit's outer shape, onto the short side of the anisotropic conductive film, partially overlap with the same position of the repeating unit adjacent to the repeating unit. This is because the width direction of the terminals of electronic components typically corresponds to the long side direction of the anisotropic conductive film. Therefore, overlapping the polygons forming the repeating unit's outer shape as described above increases the probability that the terminals of the electronic component will capture the conductive particles. Alternatively, the long and short side directions of the anisotropic conductive film can be reversed. This is because the terminal layout may require some switching.

In addition, when considering the repeating unit of the conductive particle 2, the unit of the combined repeating unit 5 and the reversed repeating unit 5B can also be regarded as the repeating unit of the conductive particle, but in the present invention, the repeating unit is a unit formed by multiple conductive particle columns arranged in parallel, preferably the smallest unit repeated vertically and horizontally.

(Size of repeating unit)

The size of the anisotropic conductive film of the repeating unit 5 or the distance between the repeating units is preferably determined based on the width of the bumps of the electronic component connected by the anisotropic conductive film 1A or the size of the gap between the bumps.

For example, when the connection target has a non-micro-pitch, the size of the anisotropic conductive film in the long-side direction of the repeating unit 5 is preferably smaller than the width of the bump or the length of the narrower of the gaps between the bumps. Even with this size, the repeated arrangement of the repeating unit 5 allows the bumps to capture the minimum number of conductive particles required for connection. Furthermore, the number of conductive particles not involved in the connection can be reduced, thereby reducing the cost of the anisotropic conductive film. Furthermore, by slanting the sides of the polygons that form the outer shape of the repeating unit 5 toward the short sides of the anisotropic conductive film 1A, stable connection performance can be achieved regardless of the location of the cutout of the long anisotropic conductive film.

When the connection target is not a fine pitch, the distance between adjacent repeating units 5 and 5B in the longitudinal direction of the anisotropic conductive film is preferably shorter than the gap between bumps of the electronic component connected by the anisotropic conductive film.

On the other hand, when the connection target has a fine pitch, it is preferable that the size of the repeating units 5 and 5B in the longitudinal direction of the anisotropic conductive film be set to a size that spans the gap between the bumps.

Regarding the boundary between micro pitch and non-micro pitch, as an example, a bump width of less than 30 μm can be considered micro pitch, while a bump width of 30 μm or greater can be considered non-micro pitch.

As described above, when the size of the repeating unit 5 is determined based on the connection target, the number of conductive particles constituting the repeating unit 5 is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. Generally, it is desirable to capture 3 or more, and particularly 10 or more, conductive particles between opposing terminals connected by anisotropic conductive connection. To this end, when the repeating unit is sandwiched between the opposing terminals, the indentation of one repeating unit can confirm that the required number of conductive particles has been captured.

(Specific deformation mode of repeating unit)

In the present invention, the arrangement of the conductive particles 2 in the repeating unit 5, or the vertical and horizontal repetition pitch of the repeating unit 5, can be appropriately modified according to the shape or spacing of the terminals to be connected by the anisotropic conductive connection. Therefore, compared to a case where the conductive particles 2 are arranged in a simple lattice pattern, the anisotropic conductive film as a whole can achieve higher capture efficiency with a smaller number of conductive particles.

For example, in addition to the repetitive pattern shown in FIG1A , the repeating unit 5 may be repeated in a staggered arrangement, as in the anisotropic conductive film 1B shown in FIG2 . In a staggered arrangement, the effect of resin flow on the conductive particles during anisotropic conductive connection of electronic components differs between the bumps located in the center of the staggered arrangement and those located on the outer sides. Furthermore, the risk of short circuits also differs between the bumps located in the center of the staggered arrangement and those located on the outer sides. Therefore, the shape of the repeating unit 5 can be appropriately changed to adjust the flow of resin.

The arrangement of the conductive particles 2 in the repeating unit 5 can also be appropriately changed according to the shape of the terminal to be connected to the anisotropic conductive connection or the spacing between the terminals. For example, as in the anisotropic conductive film 1C shown in FIG3 , the number of conductive particles constituting the conductive particle column 2p in a repeating unit 5 can be gradually increased or decreased, or individual conductive particles 2s can be repeatedly arranged along with the repetition of the repeating unit 5. Furthermore, in the three parallel rows of conductive particle columns in a repeating unit, the number of conductive particles constituting the central column can be greater or less than the number of conductive particles constituting the two side columns. For example, as in the anisotropic conductive film 1D shown in FIG4 , in each repeating unit 5, a conductive particle column 2p with four conductive particles 2 arranged along the long side of the anisotropic conductive film, a conductive particle column 2q with two conductive particles arranged, a conductive particle column 2r with three conductive particles arranged, and one conductive particle 2s are arranged side by side. By increasing or decreasing the number of conductive particles in the rows of conductive particles arranged side by side within a repeating unit, the repeating unit's outer shape becomes a complex polygonal shape, making it easier to connect to radial bump arrays (so-called fan-out bumps). The arrangement of conductive particles within a repeating unit is represented by the number of conductive particles in the rows that make up the repeating unit. For example, if the repeating unit shown in Figure 4 is represented as [4-2-3-1], variations of this repeating unit include [4-1-4-1], [4-3-1-2], [3-2-2-1], [4-1-2-3], and [4-2-1-3]. Combinations of these arrangements are also possible. For example, [4-2-3-1-2-1-4-3] is an example.

Furthermore, the distances between conductive particles within a conductive particle column, that is, the distances between conductive particle columns arranged side by side within a repeating unit, can be the same or different. For example, as in the anisotropic conductive film 1E shown in FIG5 , the repeating unit 5 can be formed into a rhombus shape, with conductive particles 2 arranged in the center. In this repeating unit, a conductive particle column 2m consisting of five conductive particles, a conductive particle column 2n consisting of two conductive particles, a conductive particle column 2o consisting of three conductive particles, a conductive particle column 2p consisting of two conductive particles, and a conductive particle column 2q consisting of five conductive particles are arranged side by side, and the distances between conductive particles in conductive particle columns 2m and 2q, the distances between conductive particles in conductive particle columns 2n and 2p, and the distances between conductive particles in conductive particle column 2o are different. In the case of [4-3-2-1] as previously described, the arrangement of the conductive particles in the center of column 3 can also be omitted. This is because the risk of short circuits can be further reduced.

In the above-mentioned anisotropic conductive films 1A, 1B, 1C, 1D, and 1E, the arrangement of the conductive particles 2 within the repeating units 5 and 5B exists at the lattice points of the hexagonal lattice. However, as long as the conductive particle columns 2p are arranged in parallel, an arrangement based on a square lattice can also be made as shown in the anisotropic conductive film 1F in Figure 6.

The anisotropic conductive film 1G shown in FIG7 has a repeating unit 5 consisting of two rows of conductive particles 2p and 2q, and a repeating unit 5B in which the arrangement axis of the conductive particles in the repeating unit 5 is rotated by 60°, which are repeatedly arranged over the entire film surface. In this manner, a single repeating unit and a repeating unit in which the repeating unit is rotated by a predetermined angle may be used in combination.

As the shape of the repeating unit, the polygon formed by the conductive particles that are sequentially connected to form its outer shape can also be a regular polygon. It is thus easy to identify the configuration of the conductive particles, so it is preferred. In this case, each conductive particle that forms the repeating unit may not exist at the lattice points of the 6-square lattice or the square lattice. For example, the outer shape of the repeating unit 5 can be formed into a regular octagon as in the anisotropic conductive film 1H shown in Figure 8. In this case, the conductive particles that constitute the outer shape of the repeating unit are arranged at the vertices of the regular octagon of the lattice in which the sides of the adjacent regular octagons overlap as shown in the dotted lines. Conductive particles can also be arranged at the vertices of a regular dodecagon or a regular polygon above a regular dodecagon. In addition, a repeating unit whose outer shape becomes a roughly regular polygon above an octagon can also be formed by arranging conductive particles at the lattice points of the 6-square lattice or the square lattice. For example, the repeating unit 5 of the anisotropic conductive film 1I shown in FIG9 is formed by conductive particles 2 arranged at the lattice points of a square lattice, forming an octagon that is symmetrical in both the longitudinal and transverse directions of the anisotropic conductive film.

Furthermore, the rows of conductive particles arranged side by side in a repeating unit do not necessarily need to be parallel to each other and can also be arranged radially. For example, as in the anisotropic conductive film 1J shown in FIG10 , a repeating unit 5 having rows of conductive particles 2m, 2n, 2o, 2p, and 2q arranged radially can be repeatedly arranged vertically and horizontally. In this case, the conductive particles 2 do not need to be located at the lattice points of a hexagonal lattice or a square lattice.

(Orientation of the edges of the repeating unit)

In the aforementioned anisotropic conductive film, for example, in the anisotropic conductive film 1A shown in FIG1A , the sides of the triangle 5x formed by sequentially connecting the centers of the conductive particles that form the outer shape of the repeating unit 5 are obliquely intersecting the longitudinal or transverse direction of the anisotropic conductive film 1A. Consequently, a tangent line L1 circumferentially tangent to a conductive particle 2a in the longitudinal direction of the anisotropic conductive film passes through a conductive particle 2b adjacent to the conductive particle 2a in the longitudinal direction of the anisotropic conductive film. Furthermore, a tangent line L2 circumferentially tangent to a conductive particle 2a in the transverse direction of the anisotropic conductive film passes through a conductive particle 2c adjacent to the conductive particle 2a in the transverse direction of the anisotropic conductive film. Generally, in anisotropic conductive connection, the long side direction of the anisotropic conductive film becomes the short side direction of the bump. Therefore, when the side of the polygon 5x of the repeating unit 5 is obliquely intersected with the long side direction or short side direction of the anisotropic conductive film 1A, it is possible to prevent multiple conductive particles from being arranged side by side in a straight line along the edge of the bump. This can avoid the phenomenon that multiple conductive particles arranged side by side in a straight line aggregate and detach from the terminal, thereby not contributing to conduction, thereby improving the capture property of the conductive particles 2.

In addition, when the long side direction of the anisotropic conductive film becomes the short side direction of the bump during anisotropic conductive connection, the polygon 5x formed by the conductive particles constituting the outer shape of the repeating unit 5 does not necessarily have to have all its sides oblique to the long side direction or short side direction of the anisotropic conductive film. However, from the perspective of the capture ability of the conductive particles, it is preferred that more than two sides, and more preferably more than three sides, be oblique to the long side direction or short side direction of the anisotropic conductive film.

On the other hand, when the bumps are arranged in a radial pattern (so-called fanout bumps), the polygons forming the repeating units preferably have sides in the long or short direction of the anisotropic conductive film. Specifically, to prevent the bumps to be connected from being misaligned due to thermal expansion of the base material on which the bumps are provided, the bumps are sometimes arranged in a radial pattern (e.g., Japanese Patent Application Publication Nos. 2007-19550 and 2015-232660). In these cases, the angle formed between the long side of each bump and the long side of the anisotropic conductive film gradually changes. Therefore, even if the sides of the polygons of the repeating unit 5 are not arranged obliquely with respect to the long or short side of the anisotropic conductive film, the sides of the polygons of the repeating units 5 and 5B intersect obliquely with the long side edges of the radially arranged bumps. This prevents the phenomenon in which most of the conductive particles at the edges of the bumps are not captured by the bumps during anisotropic conductive connection, thus reducing the capture efficiency of the conductive particles. On the other hand, the radial arrangement pattern of the bumps is usually formed bilaterally symmetrically. Therefore, from the perspective of easily confirming the quality of the connection state based on the indentation after the anisotropic conductive connection, it is preferred that the polygon constituting the outer shape of the repeating unit 5 has a side in the long side direction or the short side direction of the anisotropic conductive film. Therefore, for example, when the repeating unit is a triangle like the anisotropic conductive film 1A shown in Figure 1A, it is preferred to configure it so that one side 5a of the triangle constituting the outer shape of the repeating unit 5 is parallel to the long side direction or the short side direction of the anisotropic conductive film, as in the anisotropic conductive film 1K shown in Figure 11. In addition, it is also possible to have a side 5a parallel to the long side direction of the anisotropic conductive film and a side 5b parallel to the short side direction, as in the repeating unit 5 of the anisotropic conductive film 1H shown in Figure 8.

Furthermore, the arrangement of the conductive particles in the present invention is not limited to the illustrated arrangement of repeating units. For example, the illustrated arrangement can be tilted. This also includes a 90° tilt, i.e., a method in which the long and short sides of the film are reversed. Furthermore, the spacing between the repeating units 5 or the spacing between the conductive particles within a repeating unit can be varied.

＜Closest distance between conductive particles＞

The closest inter-particle distance of the conductive particles, whether between adjacent conductive particles within the repeating unit 5 or between adjacent conductive particles between repeating units 5, is preferably more than 0.5 times the average conductive particle size. The distance between repeating units 5 is preferably longer than the distance between adjacent conductive particles within the repeating unit 5. If the 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 according to the bump shape or the bump spacing. For example, when the bump width is 200μm and the gap between the bumps is 200μm, when there is at least one conductive particle on either the bump width or the gap between the bumps, the distance between the conductive particles is made less than 400μm. From the perspective of making the capture of conductive particles reliable, it is preferably less than 200μm.

＜Number density of conductive particles＞

From the perspective of reducing the manufacturing cost of the anisotropic conductive film and preventing excessive thrust from being required by the pressing jig used for anisotropic conductive connection, when the average particle size of the conductive particles is less than 10 μm, the number density of the conductive particles is preferably 50,000 particles/ ^mm² or less, more preferably 35,000 particles/ ^mm² or less, and even more preferably 30,000 particles/ ^mm² or less. On the other hand, if the number density of the conductive particles is too low, there is a concern that the terminals may not be sufficiently captured by the conductive particles, resulting in poor conduction. Therefore, the number density is preferably 300 particles/ ^mm² or more, more preferably 500 particles/ ^mm² or more, and even more preferably 800 particles/ ^mm² or more.

When the average particle size of the conductive particles is 10 μm or greater, the number of particles is preferably 15 or ^greater , more preferably 50 or ^greater , and even more preferably 160 or ^greater . This is because as the conductive particle size increases, the area occupied by the conductive particles also increases. For the same reason, the number of particles is preferably 1800 or ^less , more preferably 1100 or ^less , and even more preferably 800 or ^less .

Furthermore, the number density of the conductive particles may not be within the above-mentioned number density range in a local area (for example, 200 μm×200 μm).

<Insulating resin adhesive>

As the insulating resin binder 3, a suitable selection of known thermopolymerizable compositions, photopolymerizable compositions, and photothermal polymerizable compositions used as insulating resin binders in anisotropic conductive films can be used. Examples of thermopolymerizable compositions include thermoradical polymerizable resin compositions containing an acrylate compound and a thermal radical polymerization initiator; thermocationic polymerizable resin compositions containing an epoxy compound and a thermal cationic polymerization initiator; and thermoanionic polymerizable resin compositions containing an epoxy compound and a thermal anionic polymerization initiator. Examples of photopolymerizable compositions include photoradical polymerizable resin compositions containing an acrylate compound and a photoradical polymerization initiator. In particular, multiple polymerizable compositions may be used in combination if no problems arise. Examples of combined use include the combination of a thermocationic polymerizable composition and a thermoradical polymerizable composition.

Here, the photopolymerization initiator may contain multiple photopolymerization initiators that react to light of different wavelengths. This allows different wavelengths to be used for photocuring the resin constituting the insulating resin layer during the manufacture of the anisotropic conductive film and for photocuring the resin used to bond electronic components during anisotropic connection.

When insulating resin binder 3 is formed using a photopolymerizable composition, all or part of the photopolymerizable compound contained in insulating resin binder 3 can be photocured by photocuring during the manufacture of the anisotropic conductive film. This photocuring maintains or fixes the arrangement of conductive particles 2 in insulating resin binder 3, offering the potential for suppressing short circuits and improving capture. Furthermore, by adjusting the photocuring conditions, the viscosity of the insulating resin layer during the anisotropic conductive film manufacturing process can be adjusted.

The amount of the photopolymerizable compound in the insulating resin adhesive 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 too much photopolymerizable compound increases the thrust required for press-fitting during anisotropic conductive connection.

On the other hand, the thermopolymerizable composition contains a thermopolymerizable compound and a thermopolymerizable initiator. However, the thermopolymerizable compound may also function as a photopolymerizable compound. Furthermore, the thermopolymerizable composition may contain a photopolymerizable compound separately from the thermopolymerizable compound and a photopolymerizable initiator. Preferably, the thermopolymerizable compound and the photopolymerizable initiator are separately from the thermopolymerizable compound. For example, a thermal cationic polymerization initiator may be used as the thermopolymerizable initiator, an epoxy resin may be used as the thermopolymerizable compound, a photoradical initiator may be used as the photopolymerizable initiator, and an acrylate compound may be used as the photopolymerizable compound. The insulating adhesive 3 may also comprise a cured product of any 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 difunctional or higher-functional (meth)acrylate monomers.

In addition, the epoxy compound used as the polymerizable compound preferably forms a three-dimensional network structure and imparts good heat resistance and adhesion, and is used in combination with a solid epoxy resin and a liquid epoxy resin. Here, a solid epoxy resin refers to an epoxy resin that is solid at room temperature. In addition, a liquid epoxy resin refers to an epoxy resin that is liquid at room temperature. In addition, room temperature refers to the temperature range of 5 to 35°C as specified in JIS Z8703. In the present invention, two or more epoxy compounds can be used in combination. In addition, an oxetane compound can also be used in combination in addition to the epoxy compound.

The solid epoxy resin is not particularly limited as long as it is compatible with the liquid epoxy resin and is solid at room temperature. Examples thereof include bisphenol A epoxy resin, bisphenol F epoxy resin, multifunctional epoxy resin, dicyclopentadiene epoxy resin, novolac-benzaldehyde epoxy resin, biphenyl epoxy resin, and naphthalene epoxy resin. These can be used alone or in combination of two or more. Among these, bisphenol A epoxy resin is preferably used.

The liquid epoxy resin is not particularly limited as long as it is liquid at room temperature. Examples thereof include bisphenol A epoxy resin, bisphenol F epoxy resin, novolac-benzaldehyde epoxy resin, and naphthalene epoxy resin. These can be used alone or in combination of two or more. In particular, bisphenol A epoxy resin is preferably used from the viewpoints of film adhesion and flexibility.

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

The amount of the thermal radical polymerization initiator used is preferably 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, based on 100 parts by mass of the (meth)acrylate compound, because curing may be poor if too little, and product life may be shortened if too much.

As the thermal cationic polymerization initiator, a known initiator for thermal cationic polymerization of epoxy compounds can be used. For example, iodonium salts, sulfonium salts, quaternary phosphonium salts, ferrocenes, etc. that generate oxygen by heat can be used. In particular, aromatic sulfonium salts that show good latency with respect to temperature can be preferably used.

The amount of the thermal cationic polymerization initiator used tends to be insufficient in curing if too little, and tends to be shortened in product life if too much. Therefore, the amount is preferably 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, based on 100 parts by mass of the epoxy compound.

As thermal anionic polymerization initiators, commonly used known initiators can be used. Examples include organic acid dihydrazides, dicyandiamide, amino compounds, polyamideamine compounds, cyanate compounds, phenolic resins, acid anhydrides, carboxylic acids, tertiary amino compounds, imidazoles, Lewis acids, Brønsted acid salts, polythiol curing agents, urea resins, melamine resins, isocyanate compounds, and blocked isocyanate compounds. These can be used alone or in combination of two or more. Among these, microcapsule-type latent curing agents comprising a modified imidazole core coated with polyurethane are preferred.

The thermopolymerizable composition preferably contains a film-forming resin. The film-forming resin is, for example, a high molecular weight resin having an average molecular weight of 10,000 or more. From the perspective of film formation, the average molecular weight is preferably about 10,000 to 80,000. Examples of the film-forming resin include phenoxy resins, polyester resins, polyurethane resins, polyester polyurethane resins, acrylic resins, polyimide resins, butyral resins, and the like. These resins may be used alone or in combination of two or more. Among these, phenoxy resins are preferably used appropriately from the perspectives of film formation and connection reliability.

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

Furthermore, fillers other than the above-mentioned insulating fillers, softeners, accelerators, antioxidants, colorants (pigments, dyes), organic solvents, ion trapping agents, and the like may be contained.

In addition, as needed, stress buffers, silane coupling agents, inorganic fillers, etc. can also be mixed. Examples of stress buffers include hydrogenated styrene butadiene block copolymers and hydrogenated styrene isoprene block copolymers. In addition, examples of silane coupling agents include epoxy, methacryloyloxy, amino, vinyl, mercapto/sulfide, and urea compounds. In addition, examples of inorganic fillers include silica, talc, titanium oxide, calcium carbonate, and magnesium oxide.

The insulating resin adhesive 3 can be formed by forming a coating composition containing the above-mentioned resin into a film by coating and drying or further curing it, or by pre-forming it into a film by a known method. The insulating resin adhesive 3 can also be obtained by laminating resin layers as needed. In addition, the insulating resin adhesive 3 is preferably formed on a release film such as a polyethylene terephthalate film that has been subjected to a release treatment.

(Viscosity of insulating resin adhesive)

The minimum melt viscosity of the insulating resin binder 3 can be appropriately determined based on factors such as the anisotropic conductive film manufacturing method. For example, in a method for manufacturing an anisotropic conductive film in which conductive particles are retained in a predetermined arrangement on the surface of an insulating resin binder and then press-fitted into the insulating resin binder, the minimum melt viscosity of the resin of the insulating resin binder is preferably 1100 Pa·s or higher to facilitate film formation. Furthermore, as described later, when recesses 3b are formed around the exposed portions of the conductive particles 2 pressed into the insulating resin binder 3 as shown in FIG12 or FIG13 , or recesses 3c are formed directly above the conductive particles 2 pressed into the insulating resin binder 3 as shown in FIG14 , the minimum melt viscosity is preferably 1500 Pa·s or higher, more preferably 2000 Pa·s or higher, even more preferably 3000 to 15000 Pa·s, and particularly preferably 3000 to 10000 Pa·s. As an example, the minimum melt viscosity can be determined using a rotational rheometer (manufactured by TA Instruments) at a temperature increase rate of 10°C/minute, a constant measuring pressure of 5g, and a measuring plate with a diameter of 8mm. Furthermore, when the step of press-fitting the conductive particles 2 into the insulating resin binder 3 is preferably performed at 40-80°C, more preferably 50-60°C, then, similarly to the above description, from the perspective of forming the recesses 3b or 3c, the lower limit of the viscosity at 60°C is preferably 3000 Pa·s or higher, more preferably 4000 Pa·s or higher, and even more preferably 4500 Pa·s or higher. The upper limit is preferably 20000 Pa·s or lower, more preferably 15000 Pa·s or lower, and even more preferably 10000 Pa·s or lower.

By making the viscosity of the resin constituting the insulating resin adhesive 3 high as described above, it is possible to prevent the conductive particles 2 in the anisotropic conductive film from flowing due to the flow of the molten insulating resin adhesive 3 when the conductive particles 2 are clamped between opposing connection objects such as electronic components and heated and pressurized when the anisotropic conductive film is used.

(Thickness of insulating resin adhesive)

The thickness La of the insulating resin adhesive 3 is preferably between 1 μm and 60 μm, more preferably between 1 μm and 30 μm, and even more preferably between 2 μm and 15 μm. Furthermore, the ratio (La/D) of the thickness La of the insulating resin adhesive 3 to the average particle size D of the conductive particles 2 is preferably between 0.6 and 10. If the thickness La of the insulating resin adhesive 3 is too large, the conductive particles may become easily misaligned during anisotropic conductive connection, reducing the ability of the terminals to capture the conductive particles. This tendency is pronounced when La/D exceeds 10. Therefore, La/D is preferably 8 or less, and more preferably 6 or less. Conversely, if the thickness La of the insulating resin adhesive 3 is too small, such that La/D is less than 0.6, it becomes difficult for the insulating resin adhesive 3 to maintain the conductive particles in a predetermined dispersion or arrangement. In particular, when the terminals are connected using high-density COG, the ratio (La/D) of the thickness La of the insulating resin adhesive 3 to the particle size D of the conductive particles 2 is preferably between 0.8 and 2.

(Method of embedding conductive particles in insulating resin adhesive)

The embedding state of the conductive particles 2 in the insulating resin adhesive 3 is not particularly limited. However, when an anisotropic conductive connection is made by sandwiching an anisotropic conductive film between opposing components and applying heat and pressure, it is preferable to partially expose the conductive particles 2 from the insulating resin adhesive 3, as shown in Figures 12 and 13 , and to form recesses 3b around the exposed portions of the conductive particles 2 relative to a tangent plane 3p taken along the insulating resin adhesive surface 3a at the center between adjacent conductive particles 2. Alternatively, as shown in Figure 14 , recesses 3c are formed relative to the same tangent plane 3p in the portion of the insulating resin adhesive directly above the conductive particles 2 pressed into the insulating resin adhesive 3, thereby creating undulations on the surface of the insulating resin adhesive 3 directly above the conductive particles 2. The presence of recesses 3b as shown in Figures 12 and 13 reduces the resistance experienced by the conductive particles 2 from the insulating resin adhesive 3 compared to a case without recesses 3b, as opposed to flattening of the conductive particles 2 that occurs when the conductive particles 2 are sandwiched between opposing electrodes of electronic components and subjected to heat and pressure. This facilitates the holding of the conductive particles 2 between the opposing electrodes, further improving conductivity. Furthermore, by forming recesses 3c (Figure 14) on the surface of the resin immediately above the conductive particles 2 within the resin constituting the insulating resin binder 3, the pressure during heating and pressing is more easily concentrated on the conductive particles 2, compared to a case without recesses 3c. This allows the conductive particles 2 to be more easily held between the electrodes, thereby improving conductivity.

In order to facilitate the effects of the recesses 3 b and 3 c described above, the ratio (Le/D) of the maximum depth Le of the recesses 3 b ( FIG. 12 and FIG. 13 ) around the exposed portion of the conductive particles 2 to the average particle diameter D of the conductive particles 2 is preferably less than 50%, more preferably less than 30%, and even more preferably 20 to 25%. The ratio (Ld/D) of the maximum diameter Ld of the recesses 3 b ( FIG. 12 and FIG. 13 ) around the exposed portion of the conductive particles 2 to the average particle diameter D of the conductive particles 2 is preferably 100% or more, more preferably 100 to 150%. The ratio (Lf/D) of the maximum depth Lf of the recesses 3 c ( FIG. 14 ) in the resin directly above the conductive particles 2 to the average particle diameter D of the conductive particles 2 is preferably greater than 0, and preferably less than 10%, and more preferably less than 5%.

Furthermore, the diameter Lc of the exposed portion of the conductive particles 2 can be set to be less than or equal to the average particle diameter D of the conductive particles 2, preferably 10 to 90% of the average particle diameter D. A single point of the top 2t of the conductive particle 2 may be exposed, or the conductive particle 2 may be completely buried in the insulating resin binder 3 so that the diameter Lc is zero.

(Position of Conductive Particles in the Thickness Direction of the Insulating Resin Adhesive)

In order to facilitate the effect of the above-mentioned recess 3b, the ratio (Lb/D) of the distance Lb to the deepest part of the conductive particle 2 from the tangent plane 3p of the surface 3a of the insulating resin adhesive in the center portion between adjacent conductive particles 2 (hereinafter referred to as the embedding amount) to the average particle diameter D of the conductive particles 2 (hereinafter referred to as the 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 viscosity or tackiness different from that of the resin constituting the insulating resin adhesive 3 may be laminated on the insulating resin adhesive 3 having the conductive particles 2 arranged thereon.

When the insulating resin adhesive 3 is formed with the aforementioned recessed portion 3b, the insulating adhesive layer 4 can be laminated on either the surface of the insulating resin adhesive 3 having the recessed portion 3b, as in the anisotropic conductive film 1d shown in FIG15 , or on the surface opposite the surface having the recessed portion 3b, as in the anisotropic conductive film 1e shown in FIG16 . The same applies when the insulating resin adhesive 3 is formed with the recessed portion 3c. By laminating the insulating adhesive layer 4, when anisotropic conductive film is used to connect electronic components anisotropically, gaps formed by the electrodes or bumps of the electronic components can be filled, thereby improving adhesion.

Furthermore, when insulating adhesive layer 4 is laminated on insulating resin adhesive 3, regardless of whether insulating adhesive layer 4 is on the surface where recesses 3b and 3c are formed, it is preferred that insulating adhesive layer 4 be located on the side of the first electronic component, such as the IC chip (in other words, insulating resin adhesive 3 be located on the side of the second electronic component, such as the substrate). This prevents unintended movement of conductive particles, thereby improving capture. Furthermore, typically, the first electronic component, such as the IC chip, is positioned on the pressing jig side, and the second electronic component, such as the substrate, is positioned on the stage side. After the anisotropic conductive film and the second electronic component are temporarily pressed together, the first and second electronic components are officially pressed together. However, due to the size of the thermal compression bonding area of the second electronic component, the first and second electronic components may be officially pressed together after the anisotropic conductive film and the first electronic component are temporarily bonded together.

As the insulating adhesive layer 4, an adhesive layer used as an insulating adhesive layer in a known anisotropic conductive film can be appropriately selected and used. The insulating adhesive layer 4 can also use the same resin as the insulating resin adhesive 3 mentioned above to adjust the viscosity to a lower level. The greater the difference in the minimum melt viscosity between the insulating adhesive layer 4 and the insulating resin adhesive 3, the easier it is to use the insulating adhesive layer 4 to fill the gaps formed by the electrodes or bumps of the electronic components, thereby expecting the effect of improving the adhesion between the electronic components. In addition, the greater the difference, the smaller the amount of movement of the resin constituting the insulating resin adhesive 3 during the anisotropic conductive connection, so the capture of the conductive particles on the terminal becomes easier to improve. In actual use, the minimum melt viscosity ratio of the insulating adhesive layer 4 to the insulating resin adhesive 3 is preferably greater than 2, more preferably greater than 5, and even more preferably greater than 8. On the other hand, if this ratio is too large, there is a concern that the resin will be squeezed out or blocked when the long anisotropic conductive film is made into a roll, so in actual use, it is preferably less than 15. More specifically, the preferred 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, and particularly 100 to 2000 Pa·s.

The insulating adhesive layer 4 can be formed by coating a coating composition containing the same resin as that forming the insulating resin binder 3 and then drying or curing it, or by forming it into a film in advance using a known method.

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

In addition, the minimum melt viscosity of the entire anisotropic conductive film that combines the insulating resin adhesive 3 and the insulating adhesive layer 4 also depends on the ratio of the thickness of the insulating resin adhesive 3 and the insulating adhesive layer 4, but in actual use it can be less than 8000 Pa·s. In order to facilitate the filling between the bumps, it can also be 200 to 7000 Pa·s, and preferably 200 to 4000 Pa·s.

If necessary, an insulating filler such as silica particles, alumina, or aluminum hydroxide may be added to the insulating resin binder 3 or the insulating adhesive layer 4. The amount of the insulating filler is preferably 3 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the resin constituting these layers. This prevents the conductive particles from being wasted due to the melting of the anisotropic conductive film during anisotropic conductive connection.

<Method for Manufacturing Anisotropic Conductive Film>

A method for producing an anisotropic conductive film includes, for example, preparing a transfer mold for arranging conductive particles in a predetermined arrangement, filling the concave portion of the transfer mold with conductive particles, and then covering the concave portion with an insulating resin adhesive 3 formed on a release film. Pressure is applied to press the conductive particles 2 into the insulating resin adhesive 3, thereby transferring the conductive particles 2 to the insulating resin adhesive 3. Alternatively, an insulating adhesive layer 4 is further laminated on the conductive particles 2. In this manner, an anisotropic conductive film 1A can be obtained.

Alternatively, an anisotropic conductive film can be produced by filling the recesses of a transfer mold with conductive particles, then covering them with an insulating resin binder. The conductive particles are then transferred from the transfer mold to the surface of the insulating resin binder, and the conductive particles on the insulating resin binder are then pressed into the insulating resin binder. The amount of conductive particles embedded (Lb) can be adjusted by adjusting the pressure and temperature during this press-in process. Furthermore, the shape and depth of the recesses 3b and 3c can be adjusted by adjusting the viscosity, speed, and temperature of the insulating resin binder during press-in. For example, the viscosity of the insulating resin binder during press-in is preferably at least 3000 Pa·s, more preferably at least 4000 Pa·s, and even more preferably at least 4500 Pa·s, and the upper limit is preferably at most 20000 Pa·s, more preferably at most 15000 Pa·s, and even more preferably at most 10000 Pa·s. This viscosity is preferably achieved at 40-80°C, more preferably 50-60°C. More specifically, when manufacturing an anisotropic conductive film 1a having a recessed portion 3b as shown in FIG12 on the surface of the insulating resin adhesive, it is preferred that the viscosity of the insulating resin adhesive when the conductive particles are pressed in is 8000 Pa·s (50 to 60°C), while when manufacturing an anisotropic conductive film 1c having a recessed portion 3c as shown in FIG14, the viscosity of the insulating resin adhesive when the conductive particles are pressed in can be 4500 Pa·s (50 to 60°C).

Furthermore, in addition to filling the concave portions with the conductive particles, a transfer mold may also be formed by applying a slight adhesive to the top surfaces of the convex portions to allow the conductive particles to adhere to the top surfaces.

These transfer molds can be produced by utilizing or applying known techniques such as machining, photolithography, and printing.

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

＜Rolled body＞

For continuous connection of electronic components, the anisotropic conductive film is preferably provided as a film roll wound on a reel. The length of the film roll may be at least 5 m, and preferably at least 10 m. While there is no particular upper limit, from the perspective of shipping handling, the length is preferably 5000 m or less, more preferably 1000 m or less, and even more preferably 500 m or less.

A film roll can also be connected with a connecting tape to anisotropic conductive films shorter than the full length. The connecting points can be multiple, regularly spaced, or randomly arranged. The thickness of the connecting tape is not particularly limited as long as it does not impair performance. However, excessive thickness can affect resin extrusion and cause clogging, so it is preferably 10 to 40 μm. The film width is not particularly limited, but is, for example, 0.5 to 5 mm.

The film package enables continuous anisotropic conductive connection and can contribute to cost reduction of the connection body.

＜Connection structure＞

The anisotropic conductive film of the present invention is preferably used for anisotropically conductively connecting a first electronic component such as an FPC, IC chip, or IC module to a second electronic component such as an FPC, rigid substrate, ceramic substrate, glass substrate, or plastic substrate using heat or light. Furthermore, IC chips or IC modules can be stacked to anisotropically conductively connect the first electronic components. The resulting connection structure and its manufacturing method also form part of the present invention.

As a method for connecting electronic components using anisotropic conductive film, for example, from the perspective of improving connection reliability, it is preferable to temporarily adhere the interface of the anisotropic conductive film on the side near the conductive particles in the thickness direction to a second electronic component such as a wiring substrate placed on a stage. The temporarily adhered anisotropic conductive film is then thermally compressed from the first electronic component side using a pressing jig to the first electronic component, which carries an IC chip. Similar electronic component connection can also be achieved using light curing.

In addition, when it is difficult to temporarily adhere an anisotropic conductive film to a second electronic component such as a wiring substrate due to the size of the connection area of the second electronic component such as a wiring substrate, the anisotropic conductive film is temporarily adhered to the first electronic component of the IC chip carried on the stage, and then the first electronic component and the second electronic component are thermally pressed together.

Example

Experimental Examples 1 to 8

(Fabrication of anisotropic conductive film)

Regarding anisotropic conductive films used for COG connection, the effects of the resin composition of the insulating resin binder and the arrangement of the conductive particles on film forming ability and conduction characteristics were investigated as follows.

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

[Table 1]

Next, a mold was prepared so that the conductive particles were arranged as shown in Table 2 when viewed from above, with the center-to-center distance between the closest conductive particles in the repeating unit being 6 μm. Molten pellets of a known transparent resin were poured into the mold, cooled, and solidified, forming a resin mold with recesses arranged as shown in Table 2. In Experiment 8, the conductive particles were arranged in a hexagonal lattice (32,000 particles/ ^mm² ), with one of the lattice axes tilted 15° relative to the longitudinal direction of the anisotropic conductive film.

Metal-coated resin particles (Sekisui Chemical Co., Ltd., AUL703, average particle size 3μm) were prepared as conductive particles. These particles were then filled into the recesses of a resin mold, covered with the insulating resin adhesive described above, and bonded by pressing at 60°C and 0.5 MPa. The insulating resin adhesive was then peeled from the mold, and the conductive particles on the insulating resin adhesive were pressed (pressing conditions: 60-70°C, 0.5 MPa) to press the insulating resin adhesive into the film. Films were produced in which the conductive particles were embedded in the insulating resin adhesive in the manner shown in Table 2. In this case, the embedding state of the conductive particles was controlled by the pressing conditions. As a result, in Experiment 4, the film shape failed to be maintained after the conductive particles were pressed into the film. However, in the other Experiments, films with embedded conductive particles were successfully produced. Observation under a metallurgical microscope revealed recesses around the exposed portions of the embedded conductive particles or directly above them, as shown in Table 2. In addition, in each of Experimental Example 4, both the concave portions around the exposed portions of the conductive particles and the concave portions directly above the conductive particles were observed. However, Table 4 shows the measured values of the most clearly observed concave portions for each Experimental Example.

An anisotropic conductive film with two resin layers was produced by laminating an insulating adhesive layer on the side of the conductive particle-embedded film where the conductive particles were to be pressed. However, in Experiment 4, the film shape was not maintained after the conductive particles were pressed in, so subsequent evaluation was not performed.

(evaluate)

The anisotropic conductive film of each experimental example was measured for (a) initial on-resistance and (b) conduction reliability as follows. The results are shown in Table 2.

(a) Initial on-resistance

The anisotropic conductive film of each experimental example was sandwiched between a glass substrate on a stage and an IC for conducting characteristics evaluation on the side of a pressing tool. The pressing tool then applied heat and pressure (180°C, 5 seconds) to produce the various connected products for evaluation. The pressing tool's thrust was varied in three stages: low (40 MPa), medium (60 MPa), and high (80 MPa), resulting in three types of connected products for evaluation.

Here, the IC for conducting characteristic evaluation and the glass substrate have corresponding terminal patterns and dimensions as follows: When connecting the IC for evaluation and the glass substrate, the long side direction of the anisotropic conductive film and the short side direction of the bumps are aligned.

IC for conducting characteristics evaluation

Dimensions: 1.8 x 20.0 mm

Thickness 0.5mm

Bump specifications: size 30×85μm, distance between bumps 50μm, bump height 15μm.

Glass substrate (ITO wiring)

Glass material: 1737F manufactured by CORNING

Dimensions: 30×50mm

Thickness 0.5mm

Electrode ITO wiring.

The initial on-resistance of the obtained connection product for evaluation was measured and evaluated based on the following three-stage evaluation criteria.

Evaluation criteria for initial on-resistance (In actual use, if it is less than 2Ω, there is no problem)

A: less than 0.4Ω

B: 0.4Ω or more and less than 0.8Ω

C: 0.8Ω or more.

(b) Conductivity reliability

The connection for evaluation prepared in (a) was placed in a thermostat at 85°C and 85% RH for 500 hours for reliability testing. Subsequent on-resistance was measured in the same manner as the initial on-resistance and evaluated according to the following three-stage evaluation criteria.

Evaluation criteria for conduction reliability (in actual use, if it is less than 5Ω, there is no problem)

A: less than 1.2Ω

B: 1.2Ω or more and less than 2Ω

C: 2Ω or more.

[Table 2]

Table 2 shows that in Experiment 4, where the minimum melt viscosity of the insulating resin adhesive was 800 Pa·s, it was difficult to form a film with recessed portions of the insulating resin adhesive near the conductive particles. On the other hand, in Experiments 1 through 7, where the minimum melt viscosity of the insulating resin adhesive was 1500 Pa·s or higher, it was possible to form protrusions near the conductive particles in the insulating resin adhesive by adjusting the conditions for embedding the conductive particles. The resulting anisotropic conductive films exhibited excellent conductive properties for COG applications. Furthermore, compared to Experiment 8, which employed a hexagonal lattice arrangement, Experiments 1 through 7, where the conductive particle density was low, demonstrated that anisotropic conductive connections could be made with lower pressure.

(c) Short circuit rate

Using the anisotropic conductive films of Experimental Examples 1 to 3 and 5 to 8 and the following evaluation IC for short-circuit rate, evaluation connections were obtained under connection conditions of 180°C, 60 MPa, and 5 seconds. The number of short circuits in the obtained evaluation connections was measured, and the ratio of the measured number of short circuits to the number of terminals of the evaluation IC was calculated as the short-circuit rate.

IC for evaluating short-circuit rate (7.5μm gap comb-tooth TEG (test element group)):

Dimensions: 15×13mm

Thickness 0.5mm

Bump specifications: size 25×140μm, bump distance 7.5μm, bump height 15μm.

A short circuit of less than 50 ppm is ideal for practical use, and all of the anisotropic conductive films of Experimental Examples 1 to 3 and 5 to 8 had a short circuit of less than 50 ppm.

In addition, in each of the experimental examples except for experimental example 4, the number of conductive particles captured per bump was measured, and in each of the experimental examples, 10 or more conductive particles were captured.

Experimental Examples 9-16

(Fabrication of anisotropic conductive film)

Regarding anisotropic conductive films used in FOG connections, the effects of the resin composition of the insulating resin binder and the arrangement of the conductive particles on film forming ability and conduction characteristics were investigated as follows.

Specifically, resin compositions for forming an insulating resin binder and an insulating adhesive layer were prepared according to the formulations shown in Table 3, and an anisotropic conductive film was produced using these compositions in the same manner as in Experimental Example 1. The arrangement of the conductive particles and the center-to-center distances of the closest conductive particles in this case are shown in Table 4. In Experimental Example 16, the conductive particles were arranged in a hexagonal lattice (number density of 15,000 particles/ ^mm² ), with one of the lattice axes tilted 15° relative to the longitudinal direction of the anisotropic conductive film.

During the anisotropic conductive film production process, after the conductive particles were pressed into the insulating resin binder, the film shape was not maintained in Experimental Example 12, but it was maintained in the other Experimental Examples. Therefore, the embedded state of the conductive particles in the anisotropic conductive films of Experimental Examples other than Experimental Example 12 was observed and measured using a metallographic microscope for subsequent evaluation. Table 4 shows the embedded state of the conductive particles in each Experimental Example. Similar to Table 2, the embedded state shown in Table 4 represents the measurement values obtained for each Experimental Example, where the recessed portion of the insulating resin binder was most clearly observed.

(evaluate)

The anisotropic conductive film of each experimental example was measured for (a) initial on-resistance and (b) conduction reliability as follows. The results are shown in Table 4.

(a) Initial on-resistance

The anisotropic conductive films obtained in each experimental example were cut into 2mm x 40mm pieces and sandwiched between an FPC for conducting performance evaluation and a glass substrate. Heat and pressure were applied (180°C, 5 seconds) using a 2mm tool width to produce each evaluation connection. The pressing force of the tool was varied in three stages: low (3MPa), medium (4.5MPa), and high (6MPa), resulting in three types of evaluation connections. The on-resistance of the resulting evaluation connections was measured in the same manner as in Experimental Example 1, and the measured values were evaluated in three stages according to the following criteria.

Evaluation FPC:

Terminal pitch 20μm

Terminal width/inter-terminal gap 8.5μm/11.5μm

Polyimide film thickness (PI) / copper foil thickness (Cu) = 38/8, Sn plating.

Alkali-free glass substrate:

Electrode ITO wiring

Thickness 0.7mm.

Evaluation criteria for initial on-resistance

A: less than 1.6Ω

B: 1.6Ω or more and less than 2.0Ω

C: 2.0Ω or more.

(b) Conductivity reliability

The connected product for evaluation prepared in (a) was placed in a thermostat at 85°C and 85% RH for 500 hours. The subsequent on-resistance was measured in the same manner as the initial on-resistance, and the measured values were evaluated in three stages according to the following criteria.

Evaluation criteria for conduction 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 Experiment 12, where the minimum melt viscosity of the insulating resin binder was 800 Pa·s, it was difficult to form a film having recessed portions. On the other hand, in Experiment 12, where the minimum melt viscosity of the insulating resin layer was 1500 Pa·s or higher, it was found that by adjusting the conditions for embedding the conductive particles, recessed portions could be formed near the conductive particles in the insulating resin binder. The resulting anisotropic conductive film exhibited excellent conduction characteristics for FOG applications.

(c) Short circuit rate

The number of short circuits in the evaluation connection object after the initial on-resistance measurement is counted, and the short circuit incidence rate is calculated from the measured short circuit number and the number of gaps in the evaluation connection object. If the short circuit incidence rate is less than 100 ppm, there is no problem in practical use.

The short circuit occurrence rate of any of Experimental Examples 9 to 11 and 13 to 16 was less than 100 ppm.

In addition, in each of the experimental examples except for experimental example 12, the number of conductive particles captured per bump was measured, and in each case, 10 or more conductive particles were captured.

[Table 3]

[Table 4]

Label Description

1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1a, 1b, 1c, 1d, 1e anisotropic conductive film; 2, 2a, 2b, 2c, 2s conductive particles; 2m, 2n, 2o, 2p, 2q, 2r conductive particle array; 2t top of conductive particle; 3 insulating resin binder; 3a surface of insulating resin binder; 3b, 3c recessed portion; 3P tangent plane; 4 insulating adhesive layer; 5, 5B repeating unit; 5a side parallel to the long side of the anisotropic conductive film; 5b side parallel to the short side of the anisotropic conductive film; 5x polygon formed by sequentially connecting the centers of the conductive particles constituting the outer shape of the repeating unit; D average particle size; L1, L2 external tangent line; La thickness of insulating resin binder; Lb embedding amount of conductive particles ; Lc is the diameter of the exposed part of the conductive particle; Ld is the maximum diameter of the recess; Le, Lf are the maximum depths.

Claims (21)

1. An anisotropic conductive film, wherein conductive particles are disposed in an insulating resin adhesive, wherein, The repeating units of conductive particles are arranged repeatedly with a repeating interval between them. Each repeating unit is composed of a column of conductive particles with different numbers of conductive particles arranged side by side and spaced apart. The distance between conductive particles within a single conductive particle column differs from that between conductive particle columns arranged side-by-side with different numbers of conductive particles within a repeating unit. 2. The anisotropic conductive film as claimed in claim 1, wherein the repeating units are arranged across the entire surface of the anisotropic conductive film. 3. The anisotropic conductive film as described in claim 1 or 2, wherein the number of conductive particles forming parallel conductive particle columns in the repeating unit gradually differs. 4. The anisotropic conductive film as claimed in claim 1 or 2, wherein, in the three columns of conductive particles arranged side by side in the repeating unit, the number of conductive particles constituting the central conductive particle column is more or less than the number of conductive particles constituting the two side conductive particle columns. 5. The anisotropic conductive film as claimed in claim 1 or 2, wherein each side of the polygon formed by the centers of the conductive particles that are sequentially connected to form the shape of repeating units is obliquely intersecting the long side direction or the short side direction of the anisotropic conductive film. 6. The anisotropic conductive film as claimed in claim 1 or 2, wherein the polygon formed by the centers of the conductive particles that are sequentially connected to form the shape of repeating units has a side parallel to the long side direction or the short side direction of the anisotropic conductive film. 7. The anisotropic conductive film as claimed in claim 1 or 2, wherein, in the repeating unit, the columns of conductive particles are parallel to each other. 8. The anisotropic conductive film as claimed in claim 1 or 2, wherein individual conductive particles are repeatedly configured together with the repeating unit. 9. The anisotropic conductive film as claimed in claim 1 or 2, wherein, within the repeating unit, the closest distance between adjacent conductive particles is more than 0.5 times the average particle size of the conductive particles. 10. The anisotropic conductive film as claimed in claim 1 or 2, wherein the conductive particles constituting the repeating unit are arranged from the conductive particles present in each grid point of the hexagonal or square grid, with predetermined grid points omitted in a regular manner. 11. The anisotropic conductive film as claimed in claim 1 or 2, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 12. The anisotropic conductive film of claim 3, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 13. The anisotropic conductive film of claim 4, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 14. The anisotropic conductive film of claim 5, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 15. The anisotropic conductive film of claim 6, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 16. The anisotropic conductive film of claim 7, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 17. The anisotropic conductive film of claim 8, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 18. The anisotropic conductive film of claim 9, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 19. The anisotropic conductive film of claim 10, wherein an insulating adhesive layer with a viscosity or tackiness different from that of the resin constituting the insulating resin adhesive is laminated on the insulating resin adhesive on which the conductive particles are disposed. 20. A connection structure for anisotropically conductively connecting a first electronic component and a second electronic component via an anisotropic conductive film as described in any one of claims 1 to 19. 21. A method for manufacturing a connection structure, wherein a connection structure for a first electronic component and a second electronic component is manufactured by hot-pressing an anisotropic conductive film between them, wherein the anisotropic conductive film is the anisotropic conductive film according to any one of claims 1 to 19.