JP6962404B2 - Anisotropic conductive film - Google Patents

Description

The present invention relates to an anisotropic conductive film.

An anisotropic conductive film in which conductive particles are dispersed in an insulating resin binder is widely used when mounting electronic components such as IC chips on a wiring board or the like. In such an anisotropic conductive film, , It is known that conductive particles exist in a state of being connected or aggregated. Therefore, when the anisotropic conductive film is applied to the connection between the terminal of the IC chip and the terminal of the wiring board, which are narrowed in pitch due to the weight reduction and miniaturization of the electronic device, they are connected or aggregated in the anisotropic conductive film. In some cases, the conductive particles present in this state may cause a short circuit between adjacent terminals.

Conventionally, as an anisotropic conductive film corresponding to such a narrowing of pitch, a film in which conductive particles are regularly arranged in a film has been proposed. For example, an adhesive layer is formed on a stretchable film, conductive particles are densely filled on the surface of the adhesive layer with a single layer, and then the film is biaxially stretched until the distance between the conductive particles reaches the desired distance. The conductive particles are regularly arranged, and then the insulating adhesive base layer, which is a component of the anisotropic conductive film, is pressed against the conductive particles, and the conductive particles are transferred to the insulating adhesive base layer to obtain anisotropic conductivity. A film has been proposed (Patent Document 1). Further, the conductive particles are sprayed on the transfer type concave portion forming surface having the concave portion on the surface, the concave portion forming surface is squeezed to hold the conductive particles in the concave portion, and the adhesive film on which the adhesive layer for transfer is formed is formed. The conductive particles are first transferred to the adhesive layer by pressing, and then the insulating adhesive base layer, which is a component of the anisotropic conductive film, is pressed against the conductive particles adhering to the adhesive layer to insulate the conductive particles. An anisotropic conductive film obtained by transferring to an adhesive base layer has also been proposed (Patent Document 2). In these anisotropic conductive films, an insulating adhesive cover layer is generally laminated on the surface on the conductive particle side so as to cover the conductive particles.

WO2005 / 054388 Japanese Unexamined Patent Publication No. 2010-33793

However, since the conductive particles are easily aggregated by static electricity or the like to become secondary particles, it is difficult for the conductive particles to always exist alone as primary particles. Therefore, the techniques of Patent Document 1 and Patent Document 2 have the following problems. That is, in the case of Patent Document 1, it is difficult to densely fill the entire surface of the stretchable film with conductive particles in a single layer without defects, and the conductive particles are packed in the stretchable film in an aggregated state, which may cause a short circuit. There is a problem that an unfilled region (so-called “missing”) occurs, which causes poor continuity. Further, in the case of Patent Document 2, when the transfer type recess is covered with conductive particles having a large particle diameter, the recess is removed by a squeegee thereafter to generate a recess that does not hold the conductive particles, and the anisotropic conductive film is conductive. If the particles "pull out" and cause poor continuity, or if a large number of small conductive particles are pushed into the recesses, the conductive particles will agglomerate when transferred to the insulating adhesive base layer. Since the conductive particles located on the bottom side of the recess are not in contact with the insulating adhesive base layer, they are scattered on the surface of the insulating adhesive base layer, the regular arrangement is impaired, and it causes a short circuit or poor continuity. There was a problem of particles.

As described above, in Patent Documents 1 and 2, it is sufficient to control how to control the “missing” and “aggregation” of the conductive particles that should be arranged in a regular pattern on the anisotropic conductive film. The fact is that it is not taken into consideration.

An object of the present invention is to solve the above-mentioned problems of the prior art, and from the viewpoint of "missing" and "aggregation" of conductive particles that should be arranged in a regular pattern, short circuits and poor conduction may occur. It is to provide a greatly suppressed anisotropic conductive film.

When arranging the conductive particles at the lattice points of the planar lattice, the present inventor refers to the "lattice points where the conductive particles are not arranged" with respect to all the lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film. The present invention has been found that the above object can be achieved by controlling "the ratio of the lattice points in which the conductive particles are aggregated and arranged" and "the direction in which the conductive particles are aggregated". Has been completed. Further, in such an anisotropic conductive film, the conductive particles are not arranged in the concave portions of the transfer body, but the conductive particles are attached to the tips of the convex portions of the transfer body in which the columnar convex portions are formed on the surface. We found that it can be produced by transferring the particles, and completed the production method of the present invention.

That is, the present invention is an anisotropic conductive film having a structure in which conductive particles are arranged at lattice points of a planar lattice pattern on an insulating adhesive base layer.
The ratio of the lattice points where the conductive particles are not arranged to all the lattice points of the plane lattice pattern assumed in the reference region of the anisotropic conductive film is less than 20%.
An anisotropic conductive film in which the ratio of lattice points in which a plurality of conductive particles are agglutinated and arranged to all the lattice points of the plane lattice pattern is 15% or less, and the total of omission and agglutination is 25% or less. offer.

In the preferred anisotropic conductive film of the present invention, the ratio of the lattice points where the conductive particles are not arranged to all the lattice points of the plane lattice pattern assumed in the reference region of the anisotropic conductive film is 15% or less. ,
The ratio of the lattice points in which a plurality of conductive particles are aggregated and arranged to all the lattice points of the plane lattice pattern is 10% or less.
Provided is an anisotropic conductive film in which conductive particles arranged in agglomeration are aggregated in the plane direction of the anisotropic conductive film. Again, the total loss and agglutination is preferably 25% or less.

Further, the present invention is the above-mentioned method for producing an anisotropic conductive film, wherein the following steps (a) to (e):
<Process (a)>
A step of preparing a transfer body in which convex portions corresponding to lattice points of a planar lattice pattern are formed on the surface;
<Process (b)>
A step of forming at least the top surface of the convex portion of the transfer body as a slightly adhesive layer;
<Process (c)>
A step of adhering conductive particles to the slightly adhesive layer of the convex portion of the transfer body;
<Process (d)>
A step of transferring the conductive particles to the insulating adhesive base layer by superimposing and pressing the insulating adhesive base layer on the surface of the transfer body on the side to which the conductive particles are attached; and <Step (e)>.
Provided is a manufacturing method including a step of laminating an insulating adhesive cover layer from a conductive particle transfer surface side on an insulating adhesive base layer on which conductive particles are transferred.

Further, the present invention provides a connection structure in which the terminals of the first electronic component and the terminals of the second electronic component are anisotropically conductively connected by the anisotropic conductive film of the present invention.

In the anisotropic conductive film of the present invention, the ratio of "lattice points where conductive particles are not arranged" to all the lattice points of the plane lattice pattern assumed in the reference region is set to less than 20%, and "plurality of conductivity" is set. The ratio of "lattice points where particles are agglomerated and arranged" is set to 15% or less, and the total of omission and agglomeration is set to 25% or less. Therefore, when the anisotropic conductive film of the present invention is applied to the anisotropic conductive connection, a good initial conduction resistance value and good conduction reliability after aging can be realized, and the occurrence of a short circuit can be suppressed. Further, it is excellent in economy not only for COG but also for electronic components having a sufficiently large bump area and distance, such as FOG.

In the preferred anisotropic conductive film of the present invention, the ratio of "lattice points where conductive particles are not arranged" to all the lattice points of the plane lattice pattern assumed in the reference region is set to 15% or less, and moreover, "plurality". The ratio of "lattice points where the conductive particles are aggregated and arranged" is set to 10% or less, and the conductive particles which are aggregated and arranged are aggregated in the plane direction of the anisotropic conductive film. There is. Therefore, when the anisotropic conductive film of the present invention is applied to the anisotropic conductive connection, a good initial conduction resistance value and good conduction reliability after aging can be realized, and the occurrence of a short circuit can be suppressed.

Further, in the method for producing an anisotropic conductive film of the present invention, a transfer body in which columnar convex portions corresponding to lattice points of a planar lattice pattern are formed on the surface is used and formed on the top surface of the convex portions. After the conductive particles are attached to the fine adhesive layer, the conductive particles are transferred to the insulating adhesive base layer. Therefore, the ratio of "lattice points on which conductive particles are not arranged" to all the lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film is set to 15% or less, and the ratio to all the lattice points of the planar lattice pattern is set to 15% or less. It is possible to set the ratio of "lattice points in which a plurality of conductive particles are aggregated and arranged" to 10% or less, and to agglomerate the agglomerated and arranged conductive particles in the plane direction of the anisotropic conductive film. can. Therefore, the manufacturing method of the present invention can economically produce an anisotropic conductive film, and if this anisotropic conductive film is used, the IC chip having a narrow pitch and the wiring board can be short-circuited. It is possible to make an anisotropic conductive connection while greatly suppressing the occurrence of poor continuity.

FIG. 1 is a cross-sectional view of the anisotropic conductive film of the present invention. FIG. 2 is a perspective perspective view of the anisotropic conductive film of the present invention. FIG. 3A is a process explanatory view of the manufacturing method of the present invention. FIG. 3B is a process explanatory view of the manufacturing method of the present invention. FIG. 3C is a process explanatory view of the manufacturing method of the present invention. FIG. 3D is a process explanatory view of the manufacturing method of the present invention. FIG. 3E is a process explanatory view of the manufacturing method of the present invention. FIG. 3F is a process explanatory view of the manufacturing method of the present invention, and at the same time, is a schematic cross-sectional view of the anisotropic conductive film of the present invention.

The anisotropic conductive film of the present invention has a structure in which an insulating adhesive base layer and an insulating adhesive cover layer are laminated, and conductive particles are arranged at lattice points of a plane lattice pattern in the vicinity of their interfaces. The ratio of the lattice points where the conductive particles are not arranged to all the lattice points of the plane lattice pattern assumed in the reference region of the anisotropic conductive film is less than 20%, and a plurality of lattice points to all the lattice points of the plane lattice pattern. The ratio of the lattice points where the conductive particles of the above are aggregated and arranged is 15% or less, and the total of omission and aggregation is 25% or less. Hereinafter, the anisotropic conductive film of the present invention will be described in detail with reference to the drawings.

<Animolic conductive film>
As shown in FIGS. 1 (cross-sectional view) and 2 (planar perspective view), in the anisotropic conductive film 10 of the present invention, the insulating adhesive base layer 11 and the insulating adhesive cover layer 12 are laminated, and they are laminated. It has a structure in which conductive particles 13 are arranged at lattice points of a plane lattice pattern (dotted line in FIG. 2) in the vicinity of the interface. In FIGS. 1 and 2, the plane lattice pattern is assumed along the longitudinal direction of the anisotropic conductive film 10 and the direction orthogonal to the longitudinal direction (minor direction), but the entire planar lattice pattern is assumed with respect to the longitudinal direction and the lateral direction. May be assumed to be tilted. Here, the arrow A indicates a position where the conductive particles are not arranged at the lattice points of the plane lattice, that is, a position where the so-called conductive particles are “missing”. The arrow B indicates a position where the conductive particles are in contact with each other and aggregated.

("Detachment" of conductive particles)
In the anisotropic conductive film of the present invention, the ratio of "lattice points where conductive particles are not arranged" (A in FIG. 2) to all the lattice points of the plane lattice pattern assumed in the reference region of the anisotropic conductive film. (Ratio of lattices from which conductive particles are missing) is set to 15% or less, preferably 10% or less, and more preferably 6 to 10%. As a result, when the anisotropic conductive film of the present invention is applied to the anisotropic conductive connection, good initial conduction resistance and good conduction reliability after aging can be realized, and the occurrence of short circuit can be suppressed.

(Plane grid pattern)
Examples of the plane lattice pattern include an orthorhombic lattice, a hexagonal lattice, a square lattice, a rectangular lattice, and a parallel lattice. Of these, a hexagonal grid that can be packed most densely is preferable.

Here, it is possible to select the entire surface of the anisotropic conductive film as the reference region of the anisotropic conductive film, but usually, the following relational expression (A) at the center of the plane of the anisotropic conductive film is preferable. It is preferable to select a substantially square region including sides X and sides Y satisfying the relational expressions (1) and the relational expressions (2) and (3) as a reference region.

When applied to a FOG connection in which a relatively large connection area can be obtained, it is possible to reduce the abundance of conductive particles in the film. In such a case, as shown below, X and The value of Y is preferably increased, preferably 20D or more, and the value of "X + Y" is also preferably a value in the vicinity of 100D to 400D, and finally 400D.

In the formulas (A) and (1) to (3), D is the average particle size of the conductive particles. The average particle size of the conductive particles can be measured by an image-type particle size distribution meter. It may be measured from the surface observation. Further, the side Y is a straight line in a range of less than ± 45 ° with respect to the longitudinal direction of the anisotropic conductive film (see FIG. 2), and the side X is a straight line perpendicular to the side Y.

By defining the reference region in this way, the reference region can be made similar to or approximate to the shape of the bump on which the conductive particles are pressed, and as a result, the allowable range of deviation of the conductive particles from the planar lattice pattern is increased. This makes it possible to economically and stably perform anisotropic conductive connections. In other words, by making the smallest side of this reference region 5 times or more the diameter of the conductive particles, even if the conductive particles are misaligned, missing, or close to each other within the range assumed within this range, any one of them. Since it is not captured by the bumps of the above and is not excessively aggregated in the space between the bumps, the anisotropic conductive connection can be surely performed.

The reason why the smallest side is set to 5 times or more the conductive particle size is generally larger than the average particle size of the conductive particles in order to ensure capture on at least one side of the bump to be anisotropically conductively connected. This is because it is necessary to provide a space between bumps that is preferably at least twice the average particle size of the conductive particles for the purpose of preventing short circuits. In other words, when focusing on the circular conductive particles that serve as a reference, the diameter (that is, 5D) is the average particle diameter D of the conductive particles plus four times the diameter (4D). This is because it is considered that the above requirements can be satisfied if unexpected defects do not occur within the concentric circles. Another reason is that the minimum distance between the bumps in the case of a fine pitch is, for example, less than four times the diameter of the conductive particles.

(Agglutination of conductive particles)
Further, in the anisotropic conductive film of the present invention, the ratio of the lattice points (B in FIG. 2) in which a plurality of conductive particles are aggregated and arranged with respect to all the lattice points of the planar lattice pattern is preferably 10% or less. It is 9% or less, and 5 to 9% as a range where there is no problem in practical use. When the ratio of the cohesive arrangement lattice points is within this range, even when the anisotropic conductive film of the present invention is applied to the anisotropic conductive connection, better initial conductivity and conduction reliability after aging are realized. It can be done, and the occurrence of short circuits can be further suppressed. Here, the degree of aggregation of the conductive particles with respect to one lattice point is preferably small from the viewpoint of suppressing short circuits, and preferably does not exceed two.

(Arrangement of conductive particles)
It is preferable that 11 or more conductive particles are continuously arranged in a direction perpendicular to the longitudinal direction of the film, and more preferably 13 or more conductive particles are continuously arranged. This is because if the conductive particles are missing in the longitudinal direction of the bump, the anisotropic conductive connection may be hindered. In this case, it is preferable that all three rows continuous along the longitudinal direction of the film satisfy the above conditions, and it is more preferable that all five rows satisfy the above conditions. As a result, the number of conductive particles captured by the bump can be increased to a certain level or more, and stable anisotropic conductive connection can be performed.

When the conductive particles are agglutinated, the number of pairs of the two conductive particles connected is preferably three or less, more preferably two or less, and even more preferably 1 around the two agglutinated conductive particles. Less than one. This is because if two agglomerated conductive particles are densely present, it causes a short circuit.

Further, it is preferable that four or more conductive particles are continuous in the longitudinal direction of the film and four or more continuous particles are not continuous in the direction perpendicular to the longitudinal direction of the film, and any of four or more conductive particles are continuous. It is more preferable that the missing parts are not adjacent to each other via the conductive particles that become one or more lattice points, and it is preferable that any of four or more consecutive missing parts are transmitted through the conductive particles that become two or more lattice points. It is even more preferable that they are not adjacent to each other. There is no problem in the intersection of such gaps even if up to three rows intersect for the gap in one direction at the same time. This is because if the defects are not more continuous, they will be captured by the bumps by the conductive particles in the vicinity.

It is generally not preferable that there are a plurality of regions where continuous defects intersect in the vicinity, but if the number of conductive particles is equal to or greater than the number of the missing regions, the stability of the anisotropic conductive connection can be improved. Is no problem. Specifically, there is no practical problem as long as one or more conductive particles in which two are connected are present on the 7 × 7 matrix centered on the missing region.

(Particle area occupancy)
Further, the particle area occupancy of all the conductive particles existing in the reference region of the anisotropic conductive film with respect to the area of the reference region is such that the bump size and the distance between bumps are relatively large, such as FOG connection. Is usually 0.15% or more, preferably 0.35% or more, and more preferably 1.4% or more. In this case, the upper limit is preferably 35% or less, more preferably 32% or less. Further, when the bump size and the distance between bumps are relatively small (for example, COG connection), it is more preferably 15 to 35%, and particularly preferably 16 to 20%. Within this range, even when the anisotropic conductive film of the present invention is applied to the anisotropic conductive connection, better initial conductivity and conduction reliability after aging can be realized, and short circuits are further generated. Can be suppressed. Here, the particle area occupancy rate is the ratio of the area occupied by all the conductive particles existing in the reference region to the area S of the reference region. ^{The area occupied by all the conductive particles is represented by (R / 2) 2} × π × n when the average particle diameter of the conductive particles is R and the number of conductive particles is n. Therefore, the particle area occupancy (%) = [{(R / 2) ² × π × n} / S] × 100.

By the way, when the average particle diameter of the conductive particles is 2 μm, the number density is 500 particles / mm ² (0.0005 ^{particles / μm 2} ), X = Y = 200D, and X + Y = 400D, the calculated particle area occupancy is It becomes 0.157%. When the average particle diameter of the conductive particles is 3 μm, the number density is 500 particles / mm ² (0.0005 ^{particles / μm 2} ), X = Y = 200D, and X + Y = 400D, the calculated particle area occupancy is 0. It becomes 35325%. When the average particle diameter of the conductive particles is 3 μm, the number density is 2000 particles / mm ² (0.002 ^{particles / μm 2} ), X = Y = 200D, and X + Y = 400D, the calculated particle area occupancy is 1. It will be 413%. Further, when the average particle diameter of the conductive particles is 30 μm, the number density is 500 particles / mm ² (0.0005 ^{particles / μm 2} ), X = Y = 200D, and X + Y = 400D, the calculated particle area occupancy rate is It will be 35.325%.

(Conductive particles)
As the conductive particles, those used in known anisotropic conductive films can be appropriately selected and used. For example, metal-coated resin particles in which the surface of metal particles such as nickel, copper, silver, gold, and palladium, and resin particles such as polyamide and polybenzoguanamine are coated with a metal such as nickel can be mentioned. The average particle size is preferably 1 to 30 μm, more preferably 1 to 10 μm, and even more preferably 2 to 6 μm from the viewpoint of handleability during production. As described above, the average particle size can be measured by an image-type or laser-type particle size distribution meter.

The abundance of conductive particles in the anisotropic conductive film depends on the lattice pitch of the planar lattice pattern and the average particle size of the conductive particles, and is usually 300 to 40,000 particles / mm ² .

(Distance between adjacent grid points)
Further, the distance between adjacent lattice points in the planar lattice pattern assumed for the anisotropic conductive film is preferably larger than 0.5 times, more preferably 1 time or more, and further preferably 1 to 1 times the average particle size of the conductive particles. It is 20 times. Within this range, even when the anisotropic conductive film of the present invention is applied to the anisotropic conductive connection, better initial conductivity and conduction reliability after aging can be realized, and short circuits are further generated. Can be suppressed.

(Insulating adhesive base layer)
As the insulating adhesive base layer 11, those used as the insulating adhesive base layer in a known anisotropic conductive film can be appropriately selected and used. For example, a photoradical polymerizable resin layer containing an acrylate compound and a photoradical polymerization initiator, a thermal radical polymerizable resin layer containing an acrylate compound and a thermal radical polymerization initiator, and heat containing an epoxy compound and a thermal cationic polymerization initiator. A cationically polymerizable resin layer, a thermally anionic polymerizable resin layer containing an epoxy compound and a thermal anionic polymerization initiator, or a cured resin layer thereof can be used. Further, in these resin layers, a silane coupling agent, a pigment, an antioxidant, an ultraviolet absorber and the like can be appropriately selected and contained, if necessary.

The insulating adhesive base layer 11 is formed by forming a coating composition containing a resin as described above by a coating method and drying it, further curing it, or forming a film by a method known in advance. can do.

The thickness of such an insulating adhesive base layer 11 is preferably 1 to 30 μm, more preferably 2 to 15 μm.

(Insulating adhesive cover layer)
As the insulating adhesive cover layer 12, those used as the insulating adhesive cover layer in a known anisotropic conductive film can be appropriately selected and used. Further, those formed from the same material as the insulating adhesive base layer 11 described above can also be used.

The insulating adhesive cover layer 12 is formed by forming a coating composition containing a resin as described above by a coating method and drying it, further curing it, or forming a film by a method known in advance. can do.

The thickness of such an insulating adhesive cover layer 12 is preferably 1 to 30 μm, more preferably 2 to 15 μm.

Further, an insulating filler such as silica fine particles, alumina, or aluminum hydroxide may be added to the insulating adhesive base layer 11 and the insulating adhesive cover layer 12, if necessary. The blending amount of the insulating filler is preferably 3 to 40 parts by mass with respect to 100 parts by mass of the resin constituting the layer. As a result, even if the insulating adhesive layer 10 is melted during the anisotropic conductive connection, it is possible to prevent the conductive particles 2 from being unnecessarily moved by the melted resin.

(Lamination of insulating adhesive base layer and insulating adhesive cover layer, embedding of conductive particles)
When the insulating adhesive base layer 11 and the insulating adhesive cover layer 12 are laminated with the conductive particles 13 interposed therebetween, it can be carried out by a known method. In this case, the conductive particles 13 are present near the interface between these layers. Here, "existing near the interface" means that a part of the conductive particles bites into one layer and the rest bites into the other layer. Further, the conductive particles may be embedded in the insulating adhesive base layer. In this case, it can be formed without laminating the insulating adhesive cover layer.

<Manufacturing of anisotropic conductive film>
Next, the method for producing an anisotropic conductive film of the present invention having a structure in which an insulating adhesive base layer and an insulating adhesive cover layer are laminated and conductive particles are arranged at lattice points of a planar lattice pattern in the vicinity of their interfaces. To explain. This manufacturing method has the following steps (a) to (e). Each process will be described in detail with reference to the drawings. The present invention is not particularly limited to this production method.

(Process (a))
First, as shown in FIG. 3A, a transfer body 100 in which a convex portion 101 corresponding to a lattice point of a planar lattice pattern is formed on the surface is prepared. Here, as the shape of the convex portion 101, a columnar shape (for example, a cylinder, a triangular prism, a square column, a hexagonal column, etc.), a substantially columnar shape, a hemispherical shape, a truncated cone shape, a prismatic trapezoidal shape, or the like can be mentioned. The height of the convex portion 101 can be determined according to the terminal pitch to be anisotropically conductively connected, the terminal width, the space width, the average particle size of the conductive particles, etc. It is preferably 1.2 times or more and less than 2 times. The width of the convex portion 101 (width at half height) is preferably 1.4 times or more and 3.6 times or less the average particle size of the conductive particles. If this height and width are within these ranges, it is possible to obtain the effect of avoiding continuous dropouts and omissions.

Further, the convex portion 101 has a flat top surface at a level at which conductive particles can be stably attached.

* Specific example of transfer material The transfer material to be prepared in this step (a) can be prepared by using a known method. For example, a metal plate is processed to prepare a master, and a curable resin is applied thereto. It can be prepared by applying and curing. Specifically, a flat metal plate is cut to create a transfer master master in which recesses corresponding to the convex portions are formed, and a resin composition constituting the transfer body is applied to the recess-forming surface of the master. After curing, the transfer material is obtained by pulling it away from the master.

(Process (b))
Next, as shown in FIG. 3B, at least the top surface of the convex portions 101 of the transfer body 100 in which a plurality of convex portions 101 are formed in a plane lattice pattern on the surface is designated as the microadhesive layer 102.

* Slightly adhesive layer of transfer material The slightly adhesive layer 102 is a layer exhibiting adhesive strength capable of temporarily holding conductive particles until the conductive particles are transferred to the insulating adhesive base layer constituting the anisotropic conductive film. Yes, it is formed on at least the top surface of the convex portion 101. Therefore, the entire convex portion 101 may be slightly adhesive. The thickness of the fine adhesive layer 102 can be appropriately determined according to the material of the fine adhesive layer 102, the particle size of the conductive particles, and the like. Further, "slightly adhesive" means that the adhesive force is weaker than that of the insulating adhesive base layer when the conductive particles are transferred to the insulating adhesive base layer.

As such a slightly adhesive layer 102, the slightly adhesive layer used in a known anisotropic conductive film can be applied. For example, it can be formed by applying an adhesive layer made of the same material as the silicone-based adhesive composition, the insulating adhesive base layer, or the insulating adhesive cover layer to the top surface of the convex portion 101.

(Process (c))
Next, as shown in FIG. 3C, the conductive particles 103 are attached to the slightly adhesive layer 102 of the convex portion 101 of the transfer body 100. Specifically, the conductive particles 103 may be sprayed from above the convex portion 101 of the transfer body 100, and the conductive particles 103 that have not adhered to the fine adhesive layer 102 may be blown off using a blower. In this case, the conductive particles adhere to the side surface of some of the convex portions 101 due to the action of static electricity or the like at a certain frequency, and cannot be removed by the blower.

The direction of the surface may be reversed from FIG. 3C, and the top surface of the protrusion may be attached to the surface on which the conductive particles are spread all over. This is because unnecessary stress is not applied to the conductive particles. By adhering only the conductive particles necessary for arrangement to the top surface of the protrusion in this way, the conductive particles can be easily collected and reused, which is more economical than the method of filling the openings with the conductive particles and taking them out. Become. In the case of the method of filling the opening with the conductive particles and taking them out, there is a concern that unnecessary stress is likely to be applied to the unfilled conductive particles.

(Process (d))
Next, as shown in FIG. 3D, the surface of the transfer body 100 on the side to which the conductive particles 103 are attached is pressed with the insulating adhesive base layer 104 that should form the anisotropic conductive film in an overlapping manner to provide insulating properties. Conductive particles 103 are transferred to one side of the adhesive base layer 104 (FIG. 3E). In this case, it is preferable to press the transfer body 100 on the insulating adhesive base layer 104 so that the convex portion 101 faces downward. This is to make it easier to remove the conductive particles that are not attached to the top surface of the convex portion by blowing downward.

(Process (e))
As shown in FIG. 3F, the insulating adhesive cover layer 105 is laminated on the insulating adhesive base layer 104 to which the conductive particles 103 are transferred from the conductive particle transfer surface side. As a result, the anisotropic conductive film 200 of the present invention can be obtained.

In the anisotropic conductive film 200, when a plurality of conductive particles are arranged at one lattice point of the plane lattice pattern, they are arranged in contact with each other in the horizontal direction. This is to prevent an excessive decrease in the particle number density.

<Connection structure>
In the anisotropic conductive film of the present invention, between a terminal (for example, a bump) of a first electronic component (for example, an IC chip) and a terminal (for example, a bump, a pad) of a second electronic component (for example, a wiring board). The so-called COG (chip on glass) and FOG (film) in which short circuits and poor continuity are suppressed by being placed in the first or second electronic component side by thermocompression bonding to form an anisotropic conductive connection. A connection structure such as on glass) can be provided.

Hereinafter, the present invention will be specifically described.

Example 1
A nickel plate having a thickness of 2 mm was prepared, and a columnar recess (inner diameter 6 μm, depth 7 μm) was formed in a four-sided lattice pattern to prepare a transfer master. The distance between the centers of the adjacent recesses was 8 μm. Therefore, the density of the recesses was 16000 pieces / mm ² .

60 parts by mass of phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.), 29 parts by mass of acrylate resin (M208, Toa Synthesis Co., Ltd.), photopolymerization initiator (IRGACURE184, BASF Japan) on the obtained transfer master. Co., Ltd. A photopolymerizable resin composition containing 2 parts by mass is applied onto a PET (polyethylene terephthalate) film so that the drying thickness is 30 μm, dried at 80 ° C. for 5 minutes, and then 1000 mJ with a high-pressure mercury lamp. A transcript was prepared by irradiating with light.

The transfer material is peeled off from the master, wrapped around a stainless steel roll with a diameter of 20 cm so that the convex part is on the outside, and while rotating this roll, 70 parts by mass of epoxy resin (jER828, Mitsubishi Chemical Co., Ltd.) and phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.) A fine pressure-sensitive adhesive composition containing 30 parts by mass is brought into contact with a pressure-sensitive adhesive sheet impregnated in a non-woven fabric, and the fine pressure-sensitive adhesive composition is adhered to the top surface of the convex portion. A slightly adhesive layer having a thickness of 1 μm was formed to obtain a transcript.

Conductive particles having an average particle diameter of 4 μm (nickel-plated resin particles (AUL704, Sekisui Chemical Co., Ltd.)) are sprayed on the surface of this transfer body, and then blown to obtain conductive particles that do not adhere to the fine adhesive layer. Removed.

A sheet-like heat-curable insulating adhesive film (phenoxy resin (YP-50, Nippon Steel & Sumitomo Metal Chemical Co., Ltd.) with a thickness of 5 μm, which is an insulating adhesive base layer, is attached to the transfer material to which the conductive particles are attached. Co., Ltd.) 60 parts by mass, epoxy resin (jER828, Mitsubishi Chemical Co., Ltd.) 40 parts by mass, cationic curing agent (SI-60L, Sanshin Chemical Industry Co., Ltd.) 2 parts by mass, and silica fine particles (Aerodil RY200, A film formed from an insulating adhesive composition containing 20 parts by mass of Nippon Aerodil Co., Ltd.) is pressed at a temperature of 50 ° C. and a pressure of 0.5 MPa to transfer conductive particles to the insulating adhesive base layer. rice field.

Another sheet-like insulating adhesive film with a thickness of 15 μm as a transparent insulating adhesive cover layer on the conductive particle transfer surface of the obtained insulating adhesive base layer (phenoxy resin (YP-50, Nippon Steel & Sumitomo Metal Corporation) )) Insulating adhesive composition containing 60 parts by mass of epoxy resin (jER828, Mitsubishi Chemical Corporation) and 2 parts by mass of cationic curing agent (SI-60L, Sanshin Chemical Industry Co., Ltd.) The film formed from the above was laminated, and laminated at a temperature of 60 ° C. and a pressure of 2 MPa. As a result, an anisotropic conductive film was obtained.

Example 2
An anisotropic conductive film was obtained by repeating Example 1 except that the amount of the conductive particles sprayed and the number of blowers were doubled as compared with the case of Example 1.

Example 3
The columnar recesses of the transfer master have an inner diameter of 4.5 μm, the distance between the centers of adjacent recesses is 6 μm, the density of the recesses is 28,000 / mm ² , and the conductivity has an average particle diameter of 3 μm instead of conductive particles having an average particle diameter of 4 μm. An anisotropic conductive film was obtained by repeating Example 1 except that particles (AUL703, Sekisui Chemical Co., Ltd.) were used.

Example 4
An anisotropic conductive film was obtained by repeating Example 3 except that the amount of the conductive particles sprayed and the number of blowers were doubled as compared with the case of Example 3.

Comparative Example 1
Example 1 is repeated except that the depth of the recesses of the transfer master is 4.4 μm, the inner diameter of the recesses is 4.8 μm, the distance between the centers of the adjacent recesses is 5.6 μm, and the density of the recesses is 32000 pieces / mm ^2. As a result, an anisotropic conductive film was obtained.

Comparative Example 2
Conductive particles with a recess depth of 3.3 μm, an inner diameter of the recess 3.6 μm, a distance between adjacent recess centers 4.2 μm, a recess density of 57,000 / mm ² , and an average particle diameter of 4 μm. An anisotropic conductive film was obtained by repeating Example 1 except that conductive particles having an average particle diameter of 3 μm (AUL703, Sekisui Chemical Co., Ltd.) were used instead.

<Evaluation>
("Pulling out" and "aggregation" of conductive particles)
With respect to the anisotropic conductive films of Examples 1 to 4 and Comparative Examples 1 and 2, a 1 cm square area was observed with an optical microscope (MX50, Olympus Co., Ltd.) from the transparent insulating adhesive cover layer side, and it was assumed. Investigate the ratio of lattice points to which no conductive particles are attached to all lattice points (missing [%]) and the ratio of lattice points to which two or more conductive particles are aggregated to all lattice points. rice field. The results obtained are shown in Table 1.

In addition, the maximum distance (aggregation distance) between the agglomerated conductive particles was measured and also shown in Table 1. The "aggregation" direction was the horizontal direction of the anisotropic conductive film.

(Particle area occupancy)
The particle area occupancy was calculated from the average particle size of the conductive particles and the concave density of the transfer master (= convex density of the transfer), taking into consideration the “missing” and “aggregation” of the conductive particles. The results obtained are shown in Table 1.

(Initial conduction resistance)
Using the anisotropic conductive films of Examples and Comparative Examples, an IC chip having a space between bumps of 12 μm, a height of 15 μm, and a gold bump of 30 × 50 μm, and a glass substrate provided with wiring having a space of 12 μm were obtained. An anisotropic conductive connection was made under the conditions of 180 ° C., 60 MPa, and 5 seconds to obtain a connection structure. The initial conduction resistance value of the obtained connection structure was measured using a resistance measuring device (Digital Multimeter 7565, Yokogawa Electric Co., Ltd.). The results obtained are shown in Table 1. It is desirable that it is 0.5Ω or less.

(Conduction reliability)
The connection structure used for measuring the initial conduction resistance value was put into an aging tester set at a temperature of 85 ° C. and a humidity of 85%, and the conduction resistance value after being left for 500 hours was set to the same as the initial conduction resistance value. It was measured. The results obtained are shown in Table 1. It is desired that it is 5Ω or less.

(Short occurrence rate)
The same connection structure used for the initial conduction resistance was created, and the presence or absence of short circuits between adjacent wires was investigated. The results obtained are shown in Table 1. It is desirable that the short circuit occurrence rate is 50 ppm or less.

From the results in Table 1, it was found that the connection structure using the anisotropic conductive film of Examples 1 to 4 showed good results for each evaluation item of initial conduction resistance, conduction reliability, and short circuit occurrence rate. Recognize.

On the other hand, in the case of the anisotropic conductive films of Comparative Examples 1 and 2, although the ratio of “missing” of the conductive particles was small, the ratio of “aggregation” was too high, so that the evaluation of the short-circuit occurrence rate was low.

Example 5
A transfer body was prepared in the same manner as in Example 2 except that the distance between the centers of adjacent recesses was adjusted in order to use a transfer master having a recess density of 500 pieces / mm ^{2, and an anisotropic conductive film was further prepared.} .. With respect to the obtained anisotropic conductive film, “missing” and “aggregation” of the conductive particles were measured in the same manner as in Example 2, and the particle area occupancy was further calculated. As a result, the “missing” and “aggregation” of the conductive particles were equivalent to those in Example 2. The particle area occupancy was 0.6%.

Further, the obtained anisotropic conductive film is placed between the glass substrate (ITO solid electrode) and the flexible wiring substrate (bump width: 200 μm, L (line) / S (space) = 1, wiring height 10 μm). An anisotropic conductivity was obtained under the conditions of 180 ° C., 80 MPa, and 5 seconds so that the pinching and connection bump length would be 1 mm, and a connection structure for evaluation was obtained. For the obtained connection structure, the "initial conduction resistance value" and the "conduction reliability" after being put into a constant temperature bath at a temperature of 85 ° C. and a humidity of 85% RH for 500 hours are measured by a digital multimeter (34401A, Agilent). -Measure the conduction resistance by the 4-terminal method with a current of 1A using (Technology Co., Ltd.), and in the case of "initial conduction resistance value", it is good if the measured value is 2Ω or less, and if it exceeds 2Ω. It was evaluated as defective, and in the case of "conductivity reliability", the case where the measured value was 5Ω or less was evaluated as good, and the case where the measured value was 5Ω or more was evaluated as defective. As a result, all the connection structures of Example 5 were evaluated as "good". Moreover, when the "short occurrence rate" was measured in the same manner as in Example 2, good results were obtained as in Example 2.

Example 6
A transfer body was prepared in the same manner as in Example 2 except that the distance between the centers of adjacent recesses was adjusted in order to use a transfer master having a recess density of 2000 pieces / mm ^{2, and an anisotropic conductive film was further prepared.} .. With respect to the obtained anisotropic conductive film, “missing” and “aggregation” of the conductive particles were measured in the same manner as in Example 2, and the particle area occupancy was further calculated. As a result, the “missing” and “aggregation” of the conductive particles were equivalent to those in Example 2. The particle area occupancy was 2.4%.

Further, the obtained anisotropic conductive film was sandwiched between the glass substrate and the flexible wiring substrate in the same manner as in Example 5, and the anisotropic conductive film was connected to obtain a connection structure for evaluation. When the "initial conduction resistance value", "conduction reliability", and "short-circuit occurrence rate" were evaluated for the obtained connection structure in the same manner as in Example 5, good results were obtained for all of them.

In the preferred anisotropic conductive film of the present invention, the ratio of "lattice points where conductive particles are not arranged" to all the lattice points of the planar lattice pattern assumed in the reference region is set to 15% or less, and the planar lattice pattern The ratio of "lattice points in which a plurality of conductive particles are aggregated and arranged" to all the lattice points is 10% or less. Further, the conductive particles arranged in agglutination are in contact with each other in the plane direction of the anisotropic conductive film and are agglutinating. Therefore, when the anisotropic conductive film of the present invention is applied to the anisotropic conductive connection, good initial conductivity and good conduction reliability after aging can be realized, and the occurrence of short circuit can be suppressed, so that the narrowness is narrowed. This is useful when the pitched IC chip and the wiring board are anisotropically conductively connected.

10,200 Anisotropic conductive film 11,104 Insulating adhesive base layer 12,105 Insulating adhesive cover layer 13,103 Conductive particles 100 Transfer material 101 Convex part 102 Fine adhesive layer A Position where conductive particles are missing from lattice points B Position where conductive particles are in contact with each other and aggregated at the lattice point

Claims (21)

An anisotropic conductive film having a structure in which conductive particles are arranged at lattice points of a planar lattice pattern on an insulating adhesive base layer.
In all the lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film, there are lattice points in which conductive particles are not arranged and lattice points in which a plurality of conductive particles are aggregated and arranged. Must exist,
The ratio of the lattice points where the conductive particles are not arranged to all the lattice points of the plane lattice pattern assumed in the reference region of the anisotropic conductive film is 15% or less.
The ratio of the lattice points in which a plurality of conductive particles are aggregated and arranged with respect to all the lattice points of the plane lattice pattern is 10% or less.
The ratio of the lattice points where the conductive particles are not arranged to all the lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film and the plurality of conductive particles to all the lattice points of the planar lattice pattern are aggregated. An anisotropic conductive film having a total of 25% or less with the ratio of the arranged lattice points. The anisotropic conductive film according to claim 1, wherein the conductive particles arranged in agglutination are aggregated in the plane direction of the anisotropic conductive film. The following relational expressions (A), (2) and (3):

It is a substantially rectangular region consisting of sides X and sides Y that satisfy the conditions, where D is the average particle diameter of the conductive particles, and the side Y is in the range of less than ± 45 ° with respect to the longitudinal direction of the anisotropic conductive film. The anisotropic conductive film according to claim 1 or 2 , wherein the side X is a straight line and the side X is a straight line perpendicular to the side Y. The following relational expressions (1) to (3):

It is a substantially rectangular region consisting of sides X and sides Y that satisfy the conditions, where D is the average particle diameter of the conductive particles, and the side Y is in the range of less than ± 45 ° with respect to the longitudinal direction of the anisotropic conductive film. The anisotropic conductive film according to any one of claims 1 to 3 , wherein the side X is a straight line and the side X is a straight line perpendicular to the side Y. The anisotropic conductive film according to any one of claims 1 to 4 , wherein the particle area occupancy of all the conductive particles existing in the reference region of the anisotropic conductive film is 15 to 35%. The anisotropic conductive film according to any one of claims 1 to 5 , wherein the average particle size of the conductive particles is 1 to 10 μm. The reference region is the following relational expression in the center of the plane of the anisotropic conductive film:

It is a substantially rectangular region consisting of sides X and sides Y that satisfy the conditions, where D is the average particle diameter of the conductive particles, and the side Y is in the range of less than ± 45 ° with respect to the longitudinal direction of the anisotropic conductive film. The anisotropic conductive film according to any one of claims 1 to 3 , wherein the side X is a straight line and the side X is a straight line perpendicular to the side Y. The anisotropic conductive film according to claim 7 , wherein the particle area occupancy of all the conductive particles existing in the area with respect to the area of an arbitrary reference region of the anisotropic conductive film is 0.15% or more. The anisotropic conductive film according to claim 7 or 8 , wherein the average particle size of the conductive particles is 1 to 30 μm. The anisotropic conductive film according to any one of claims 1 to 9 , wherein the distance between adjacent lattice points of the planar lattice pattern is 1 to 20 times the average particle size of the conductive particles. The anisotropic conductive film according to any one of claims 1 to 10 , wherein the conductive particles are metal particles or metal-coated resin particles. The anisotropic conductive film according to any one of claims 1 to 11 , wherein in the plane lattice pattern, 11 or more conductive particles are continuously arranged in a direction perpendicular to the longitudinal direction of the anisotropic conductive film. The anisotropic conductive film according to claim 12 , wherein in the plane lattice pattern, 11 or more conductive particles are continuously arranged in each of three consecutive rows along the longitudinal direction of the anisotropic conductive film. The anisotropic conductive film according to any one of claims 1 to 13 , wherein when the conductive particles are aggregated, the number of pairs of the two conductive particles connected is three or less around the two aggregated conductive particles. When the conductive particles are missing, four or more continuous missing particles in the longitudinal direction of the anisotropic conductive film and four or more continuous missing particles in the direction perpendicular to the longitudinal direction of the anisotropic conductive film do not intersect. The anisotropic conductive film according to any one of claims 1 to 13. The anisotropic conductive film according to any one of claims 1 to 15 , wherein the planar lattice pattern is an orthorhombic lattice, a hexagonal lattice, a square lattice, a rectangular lattice, or a parallel lattice. The anisotropic conductive film according to any one of claims 1 to 16 , wherein an insulating adhesive cover layer is further laminated on the insulating adhesive base layer. The anisotropic conductive film according to claim 17, which has a structure in which conductive particles are arranged at lattice points of a planar lattice pattern in the vicinity of the interface between the insulating adhesive base layer and the insulating adhesive cover layer. The anisotropic conductive film according to any one of claims 1 to 18 , wherein the conductive particles arranged in agglutination are in contact with each other in the plane direction of the anisotropic conductive film and are agglomerated. A connection structure in which a terminal of a first electronic component and a terminal of a second electronic component are anisotropically conductively connected by the anisotropic conductive film according to any one of claims 1 to 19. The anisotropic conductive film according to any one of claims 1 to 19 is arranged between the terminal of the first electronic component and the terminal of the second electronic component, and the first electronic component side or the second electron is placed. A method for manufacturing a connection structure, in which the components are main-cured by thermocompression bonding and anisotropically conductively connected.

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