JP2016085985A - Anisotropically conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropically conductive film having regularly arrayed conductive particles and arranged so that the occurrence of a short or conduction failure is reduced largely.SOLUTION: An anisotropically conductive film comprises: an insulating adhesive base layer; and conductive particles disposed at lattice points of a two-dimensional lattice pattern on an insulating adhesive base layer. As to the anisotropically conductive film, the percentage of lattice points where no conductive particle is disposed to all of lattice points of a two-dimensional lattice pattern supposed in a reference region is less than 20%; the percentage of lattice points where agglomerates of conductive particles are disposed to all the lattice points of the two-dimensional lattice pattern is 15% or less; and vacancies and the agglomerates account for less than 25% in total.SELECTED DRAWING: Figure 1

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 the conductive particles exist in a connected or aggregated state. For this reason, 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 is narrowed with the reduction in weight and size of the electronic device, the anisotropic conductive film is connected or aggregated in the anisotropic conductive film. In some cases, short-circuiting may occur between adjacent terminals due to the conductive particles present in the above state.

  Conventionally, an anisotropic conductive film corresponding to such a narrow pitch has been proposed in which conductive particles are regularly arranged in the film. For example, an adhesive layer is formed on a stretchable film, and conductive particles are densely packed in a single layer on the surface of the adhesive layer, and then this film is biaxially stretched until the distance between the conductive particles reaches a desired distance. Anisotropic conductivity obtained by regularly arranging conductive particles and then pressing the insulating adhesive base layer, which is a component of the anisotropic conductive film, against the conductive particles and transferring the conductive particles to the insulating adhesive base layer A film has been proposed (Patent Document 1). In addition, an adhesive film in which conductive particles are dispersed on the surface of a transfer type recess having a recess on its surface, the recess forming surface is squeezed to hold the conductive particles in the recess, and an adhesive film for transfer is formed thereon. Press and transfer the conductive particles to the adhesive layer for primary transfer, and then press the insulating adhesive base layer that is a component of the anisotropic conductive film against the conductive particles attached 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). About these anisotropic conductive films, the insulating adhesive cover layer is generally laminated | stacked on the conductive particle side surface so that a conductive particle may be covered.

WO2005 / 054388 JP 2010-33793 A

  However, since the conductive particles easily aggregate to secondary particles due to static electricity or the like, it is difficult for the conductive particles to always exist alone as primary particles. For this reason, the following problems arise in the techniques of Patent Document 1 and Patent Document 2. That is, in the case of Patent Document 1, it is difficult to densely pack conductive particles with a single layer without defects on the entire surface of the stretchable film, and the conductive particles are packed into 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 may cause poor conduction. 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 subsequent squeegee to generate a recess that does not hold the conductive particles, and the anisotropic conductive film is electrically conductive. If the particles "drop out" causes poor conduction, and conversely, if a large number of small conductive particles are pushed into the recesses, the conductive particles may aggregate 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, the conductive particles are scattered on the surface of the insulating adhesive base layer, the regular arrangement is impaired, and this causes a short circuit and poor conduction. There was a problem.

  As described above, in Patent Documents 1 and 2, it is sufficient as to how to control “dropping” and “aggregation” of conductive particles to be arranged in a regular pattern on an anisotropic conductive film. The fact is that they are not considered.

  An object of the present invention is to solve the above-described problems of the prior art, and from the viewpoint of “missing” and “aggregation” of conductive particles to be arranged in a regular pattern, the occurrence of short circuits and poor conduction is prevented. It is to provide a highly suppressed anisotropic conductive film.

  When arranging conductive particles at the lattice points of the planar lattice, the present inventor made “the lattice points where the conductive particles are not disposed” with respect to all the lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film. ”And“ ratio of lattice points where conductive particles are aggregated and arranged ”, and at least some of the aggregated conductive particles are shifted in the thickness direction of the anisotropic conductive film. As a result of the arrangement, the inventors have found that the above-described object can be achieved, and have completed the present invention. Further, such an anisotropic conductive film does not dispose the conductive particles in the concave portions of the transfer body, but causes the conductive particles to adhere to the tips of the convex portions of the transfer body in which columnar convex portions are formed on the surface. Thus, the inventors have found that it can be produced by transferring, and completed the production method of the present invention.

That is, the present invention is an anisotropic conductive film 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 near the interface between them. ,
The ratio of lattice points where conductive particles are not arranged with respect to all lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film is less than 20%,
An anisotropic conductive film in which a ratio of lattice points where a plurality of conductive particles are aggregated and arranged with respect to all lattice points of the planar lattice pattern is 15% or less, and a total of omission and aggregation is less than 25%. provide.

Further, 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 in an insulating adhesive base layer,
The ratio of lattice points where conductive particles are not arranged with respect to all lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film is less than 10%,
The ratio of lattice points where a plurality of conductive particles are aggregated and arranged with respect to all lattice points of the planar lattice pattern is 15% or less,
Provided is an anisotropic conductive film in which at least some of the conductive particles arranged in an agglomerated manner are arranged obliquely in the thickness direction of the anisotropic conductive film. Again, the sum of omission and aggregation is preferably less than 25%.

Moreover, this invention is a manufacturing method of the above-mentioned anisotropic conductive film, Comprising: The following processes (i)-(e):
<Process (I)>
Preparing a transfer body having columnar convex portions corresponding to lattice points of a planar lattice pattern 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 attaching 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 pressing the insulating adhesive base layer on the surface of the transfer body on which the conductive particles are adhered; 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 to an insulating adhesive base layer to which conductive particles are transferred.

  Furthermore, this invention provides the connection structure in which the terminal of the 1st electronic component and the terminal of the 2nd electronic component were anisotropically conductive-connected by the anisotropic conductive film of this invention.

  In the anisotropic conductive film of the present invention, the ratio of “lattice points where no conductive particles are arranged” with respect to all lattice points of the planar lattice pattern assumed in the reference region is set to less than 20%. The ratio of “lattice points at which particles are aggregated and arranged” is set to 15% or less, and the sum of omission and aggregation is set to less than 25%. For this reason, when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, it is possible to realize a good initial conduction resistance and good conduction reliability after aging, and to suppress the occurrence of a short circuit. Further, not only COG but also an electronic component having a sufficiently large bump area and distance, such as FOG, is excellent in economic efficiency.

  In a preferred anisotropic conductive film of the present invention, the ratio of “lattice points where no conductive particles are arranged” to all lattice points of the planar lattice pattern assumed in the reference region is set to less than 10%, The ratio of “lattice points where conductive particles are aggregated and arranged” is set to 15% or less, and at least some of the conductive particles arranged in an aggregate are slanted in the thickness direction of the anisotropic conductive film. It is arranged with a gap. For this reason, when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, it is possible to realize a good initial conduction resistance and good conduction reliability after aging, and to suppress the occurrence of a short circuit.

  Further, in the method for producing an anisotropic conductive film of the present invention, a transfer body having columnar convex portions corresponding to lattice points of a planar lattice pattern formed on the surface is used, and formed on the top surface of the convex portions. After the conductive particles are attached to the slightly adhesive layer, the conductive particles are transferred to the insulating adhesive base layer. Therefore, the ratio of “lattice points where no conductive particles are arranged” to the total lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film is less than 10%, The ratio of “lattice points where a plurality of conductive particles are aggregated and arranged” is set to 15% or less, and at least some of the conductive particles arranged in an aggregated manner are arranged in the thickness direction of the anisotropic conductive film. They can be arranged obliquely. Therefore, in the manufacturing method of the present invention, an anisotropic conductive film can be manufactured economically advantageously, and if the anisotropic conductive film is used, a narrow pitch IC chip and a wiring board can be short-circuited or electrically connected. Anisotropic conductive connection is possible while greatly suppressing the occurrence of defects.

FIG. 1 is a cross-sectional view of the anisotropic conductive film of the present invention. FIG. 2 is a plan perspective view of the anisotropic conductive film of the present invention. FIG. 3A is a process explanatory diagram of the production method of the present invention. FIG. 3B is a process explanatory diagram of the production method of the present invention. FIG. 3C is a process explanatory diagram of the production method of the present invention. FIG. 3D is a process explanatory diagram of the production method of the present invention. FIG. 3E is a process explanatory diagram of the production method of the present invention. FIG. 3F is a process explanatory view of the production method of the present invention, and at the same time, 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 planar lattice pattern in the vicinity of the interface between them. The ratio of lattice points where no conductive particles are arranged to all lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film is less than 20%. The ratio of the lattice points where the conductive particles are aggregated is 15% or less, and the total of omission and aggregation is less than 25%. Hereinafter, the anisotropic conductive film of the present invention will be described in detail with reference to the drawings.

<Anisotropic conductive film>
As shown in FIG. 1 (cross-sectional view) and FIG. 2 (plan view), the anisotropic conductive film 10 of the present invention has an insulating adhesive base layer 11 and an insulating adhesive cover layer 12 laminated. In the vicinity of the interface, the conductive particles 13 are arranged at lattice points of a planar lattice pattern (dotted lines in FIG. 2). In FIG. 1 and FIG. 2, the planar lattice pattern is assumed along the longitudinal direction of the anisotropic conductive film 10 and the direction orthogonal to the longitudinal direction (short direction). May be assumed to be inclined. Here, the arrow A indicates a position where the conductive particles are not arranged at the lattice points of the planar lattice, that is, a position where the so-called conductive particles are “missed”. An arrow B indicates a position where the conductive particles are aggregated in a non-contact manner. Here, “non-contact agglomeration” means that the conductive particles are close to each other within a range not exceeding 50% of the average particle diameter of the conductive particles.

("Omitted" conductive particles)
In the anisotropic conductive film of the present invention, the ratio of “lattice points where no conductive particles are arranged” (A in FIG. 2) to all lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film. The (ratio of the lattice from which the conductive particles are missing) is set to less than 10%, preferably 6% or less. Thereby, when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, a good initial conduction resistance and good conduction reliability after aging can be realized, and the occurrence of a short circuit can also be suppressed.

(Plane lattice pattern)
Examples of the planar lattice pattern include an orthorhombic lattice, a hexagonal lattice, a square lattice, a rectangular lattice, and a parallel lattice. Among these, a hexagonal lattice that can be close packed 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, preferably Is preferably selected as a reference area from a substantially square area composed of side X and side Y that satisfies relational expression (1) and relational expressions (2) and (3).

  In addition, when applied to FOG connection that can take a relatively large connection area, it is possible to reduce the abundance of conductive particles in the film. In such a case, as shown below, X and It is preferable to increase the value of Y, preferably 20D or more, and the value of “X + Y” is preferably a value in the vicinity of 100D to 400D, and finally 400D.

  In the formulas (A) and (1) to (3) and the above formula, D is the average particle diameter of the conductive particles. The average particle diameter of the conductive particles can be measured by an image type particle size distribution meter. You may measure from surface observation. 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 area in this way, the reference area can be similar to or approximate to the shape of the bump against which the conductive particles are pressed, and as a result, the allowable range of deviation from the planar lattice pattern of the conductive particles is increased. Thus, the anisotropic conductive connection can be made economically and stably. In other words, by setting the minimum side of the reference region to 5 times or more the diameter of the conductive particle, even if there is a displacement, omission, or proximity of the conductive particle within the range assumed within this range, either Therefore, the anisotropic conductive connection can be surely performed.

  The reason why the minimum side is 5 times or more the conductive particle diameter is generally larger than the average particle diameter of the conductive particles in order to ensure capture on at least one side of the bumps connected anisotropically. In addition, it is necessary to provide a space between the bumps that is preferably twice or more the average particle diameter of the conductive particles for the purpose of preventing short circuit. In other words, when attention is paid to a circular conductive particle serving as one reference, the length (ie, 5D) obtained by adding the length (4D) four times the diameter to the average particle diameter D of the conductive particles is the diameter. This is because it is considered that the above requirement can be satisfied if no unexpected failure occurs within the concentric circle. Moreover, it is also because the minimum distance between bumps in the case of a fine pitch is less than four times the conductive particle diameter as an example.

(Condensation of conductive particles)
In the anisotropic conductive film of the present invention, the ratio of lattice points (B in FIG. 2) in which a plurality of conductive particles are aggregated to all lattice points of the planar lattice pattern is preferably 15% or less. More preferably, it is 11% or less, and still more preferably 9% or less. If the ratio of the aggregated lattice points is within this range, even when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, better initial conduction and conduction reliability after aging are realized. 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 smaller from the viewpoint of short circuit suppression, and preferably not more than two.

  In addition, as an aspect of aggregation of the conductive particles, as indicated by an arrow B in FIGS. 1 and 2, at least some of the conductive particles that are aggregated are not in contact with each other. Arranged obliquely in the thickness direction. Here, “displaced diagonally” means that they are separated obliquely in a cross-sectional view. Thereby, the state which does not inhibit pushing at the time of a connection is realizable. Furthermore, when the conductive particles arranged obliquely in the thickness direction are viewed in plan, the conductive particles appear to partially overlap each other as shown in FIG. Thereby, even if resin flow occurs at the time of connection, anisotropic conductive connection can be realized with any of the conductive particles. It should be noted that there is no particular problem even if the aggregation is horizontal.

  In addition, the distance between the conductive particles (aggregation distance) arranged so as to be shifted in the thickness direction is preferably 25 to 50%, more preferably 30 to 45% of the average particle diameter of the conductive particles. If it is this range, even if it exists in a terminal edge part at the time of a connection, the effect that it becomes easy to avoid the contact with the electrically-conductive particle which exists between terminals can be implement | achieved. Thus, by finding a condition that does not adversely affect the connection, it is possible to reduce restrictions due to manufacturing conditions and to achieve both performance and productivity.

(Disposition 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 it is more preferable that 13 or more conductive particles are continuously arranged. This is because if conductive particles are missing in the longitudinal direction of the bump, the anisotropic conductive connection may be hindered. In this case, it is preferable to satisfy the above condition in all three rows that are continuous along the longitudinal direction of the film, and it is more preferable to satisfy the above condition in all five rows. As a result, the number of conductive particles captured by the bumps can be made a certain value or more, and stable anisotropic conductive connection can be performed. The row along the longitudinal direction satisfies the above condition if five or more conductive particles overlap in the direction perpendicular to the longitudinal direction.

  When the conductive particles are agglomerated, it is preferable that there are 3 or less, more preferably 2 or less, and still more preferably 1 around the aggregated conductive particles. Or less. This is because if two agglomerated conductive particles are present densely, a short circuit occurs.

  Moreover, it is preferable that the lack of conductive particles is such that four or more continuous particles in the longitudinal direction of the film do not intersect with four or more continuous ones in the direction perpendicular to the longitudinal direction of the film. It is more preferable that the omission is not adjacent through the conductive particles that become one or more lattice points, and any omission that is four or more continuous passes through the conductive particles that become two or more lattice points. Even more preferably, they are not adjacent. There is no problem with such missing intersections even if up to three rows intersect simultaneously for one direction missing. This is because if the missing portions are not continuous any more, the bumps are captured by the nearby conductive particles.

  In general, it is not preferable that there are a plurality of regions where the continuous missing portions are present in the vicinity as described above, but the stability of the anisotropic conductive connection is improved if the number of conductive particles is equal to or more than the number of the missing regions. There is no problem. There may be two conductive particles aggregated adjacent to each other in a region where continuous missing portions intersect.

(Particle area occupancy)
Furthermore, the particle area occupancy ratio of all the conductive particles existing in the area of the reference area of the anisotropic conductive film is relatively large in the bump size and the distance between the bumps as in the FOG connection. Is usually 0.15% or more, preferably 0.35% or more, more preferably 1.4% or more. In this case, the upper limit is preferably 35% or less, and more preferably 32% or less. Also, when the bump size and the distance between bumps are relatively small (for example, COG connection), it is preferably 35% or less, more preferably 32% or less, still more preferably 25% or less, and particularly preferably 18-23%. . Within this range, even when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, better initial conduction and conduction reliability after aging can be realized, and the occurrence of short-circuiting is further increased. Can be suppressed. Here, the particle area occupation ratio is a 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 expressed by (R / 2) ² × π × n where the average particle diameter R of the conductive particles is n and the number of conductive particles is n. Accordingly, the particle area occupancy (%) = [{(R / 2) ² × π × n} / S] × 100.

Incidentally, when the average particle diameter of the conductive particles is 2 μm, the number density is 500 / mm ² (0.0005 / μm ² ), X = Y = 200D, and X + Y = 400D, 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 0.00. 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. 413%. In addition, 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, 35.325%.

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

The abundance of the conductive particles in the anisotropic conductive film depends on the lattice pitch of the planar lattice pattern and the average particle diameter 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 the average particle diameter of the conductive particles, more preferably 1 time or more, and still more preferably 1 to 1. 20 times. Within this range, even when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, better initial conduction and conduction reliability after aging can be realized, and the occurrence of short-circuiting is further increased. Can be suppressed.

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

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

  The thickness of the 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 known anisotropic conductive films can be appropriately selected and used. Moreover, what was formed from the same material as the insulating adhesive base layer 11 demonstrated previously can also be used.

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

  Furthermore, 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 as necessary. It is preferable that the compounding quantity of an insulating filler shall be 3-40 mass parts with respect to 100 mass parts of resin which comprises those layers. Thereby, even if the insulating adhesive layer 10 melts at the time of anisotropic conductive connection, it is possible to prevent the conductive particles 2 from moving unnecessarily with the melted resin.

(Lamination of insulating adhesive base layer and insulating adhesive cover layer, embedding of conductive particles)
In addition, when laminating the insulating adhesive base layer 11 and the insulating cover layer 12 with the conductive particles 13 interposed therebetween, it can be performed by a known method. In this case, the conductive particles 13 are present near the interface between these layers. Here, “existing in the vicinity of the interface” indicates that part of the conductive particles bites into one layer and the remaining part bites into the other layer. Further, the conductive particles may be embedded in the insulating adhesive base layer. In this case, the insulating adhesive cover layer can be formed without being laminated.

<Manufacture 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 the interface between them. Will be explained. This manufacturing method includes the following steps (a) to (e). The process will be described in detail with reference to the drawings. The present invention is not particularly limited to this manufacturing method.

(Process (I))
First, as shown in FIG. 3A, a transfer body 100 is prepared in which columnar convex portions 101 corresponding to lattice points of a planar lattice pattern are formed on the surface. Here, the columnar shape is a columnar shape or a prismatic shape (a triangular prism, a quadrangular prism, a hexagonal prism, etc.). This columnar shape includes a cone. Preferably it is cylindrical. The height of the convex portion 101 can be determined according to the terminal pitch, terminal width, space width, average particle diameter of the conductive particles, etc. to be anisotropically conductive, but the average particle diameter of the conductive particles used Preferably they are 2 times or more and less than 4 times. Further, the width of the convex portion 101 (width at half height) is preferably 0.7 to 1.3 times the average particle diameter of the conductive particles. If the height and width are within these ranges, the effect of avoiding the occurrence of continuous dropout and dropout is obtained.

  Furthermore, the convex portion 101 has a flat top surface at a level that allows the conductive particles to adhere stably.

* Specific examples of transfer body The transfer body 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 to it. It can be applied and cured. Specifically, a flat metal plate is cut to create a transfer body master in which recesses corresponding to the protrusions are formed, and a resin composition constituting the transfer body is applied to the recess forming surface of the master, After curing, a transfer body is obtained by pulling away from the master.

(Process (b))
Next, as shown in FIG. 3B, at least the top surface of the convex portion 101 of the transfer body 100 having a plurality of convex portions 101 formed on the surface in a planar lattice pattern is used as a slightly adhesive layer 102.

* Slightly-adhesive layer of the transfer body The slightly-adhesive layer 102 is a layer showing an adhesive force capable of temporarily holding conductive particles until the conductive particles are transferred to the insulating adhesive base layer constituting the anisotropic conductive film. Yes, and formed on at least the top surface of the convex portion 101. Therefore, the whole convex part 101 may be slightly adhesive. The thickness of the slightly adhesive layer 102 can be appropriately determined according to the material of the slightly adhesive layer 102, the particle diameter 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, a slightly adhesive layer used in a known anisotropic conductive film can be applied. For example, it can be formed by applying a pressure-sensitive adhesive layer of the same material as the silicone-based pressure-sensitive 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, 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 portions 101 of the transfer body 100, and the conductive particles 103 that have not adhered to the slightly adhesive layer 102 may be blown off using a blower. In this case, in some of the convex portions 101, the conductive particles adhere to the side surfaces due to the action of static electricity or the like with a certain frequency, and it cannot be removed by the blower.

  Note that the direction of the surface may be reversed from FIG. 3C, and the top surface of the protrusion may be attached to the surface where the conductive particles are spread all over. This is because unnecessary stress is not applied to the conductive particles. By attaching only the conductive particles necessary for the arrangement to the top surface of the projection, it becomes easier to collect and reuse the conductive particles, and to be more economical than the method of filling and taking out the conductive particles in the opening. Become. In the case of the method of filling and removing the conductive particles in the opening, there is a concern that unnecessary stress is easily applied to the conductive particles that are not filled.

(Process (d))
Next, as shown in FIG. 3D, the surface of the transfer body 100 on which the conductive particles 103 are attached is pressed against the surface of the insulating adhesive base layer 104 that is to form an anisotropic conductive film, thereby insulating the surface. The conductive particles 103 are transferred onto one surface of the adhesive base layer 104 (FIG. 3E). In this case, it is preferable that the transfer body 100 is pressed over the insulating adhesive base layer 104 so that the convex portion 101 faces downward. This is because the conductive particles that are not adhered to the top surface of the convex portion are easily removed by blowing downward.

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

  In this anisotropic conductive film 200, the conductive particles that remain attached to the side surfaces of the convex portions 101 in the step (c) are those in which the conductive particles 103 are present in the slightly adhesive layer 102 of the convex portions 100. In other words, the conductive particles are aggregated in the thickness direction of the anisotropic conductive film 200. Further, when the conductive particles 103 are not present in the slight adhesion layer 102 of the convex portion 100, the conductive particles that are shifted in the horizontal direction and the thickness direction from the lattice points are arranged.

<Connection structure>
The anisotropic conductive film of the present invention is provided between a terminal (for example, a bump) of a first electronic component (for example, an IC chip) and a terminal (for example, a bump or pad) of a second electronic component (for example, a wiring board). Placed on the first and second electronic components from the first or second electronic component side by thermosetting and anisotropic conductive connection, so-called COG (chip on glass) or FOG (film connection structure such as on glass).

  Hereinafter, the present invention will be specifically described.

Example 1
A nickel plate having a thickness of 2 mm was prepared, and a cylindrical recess (inner diameter: 5 μm, depth: 8 μm) was formed with a tetragonal lattice pattern to obtain a transfer body master. The distance between adjacent recess centers was 8 μm. Therefore, the density of the recesses was 16000 pieces / mm ² .

  On the obtained transfer master, 60 parts by mass of phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.), 29 parts by mass of acrylate resin (M208, Toagosei Co., Ltd.), photopolymerization initiator (IRGCUR184, BASF Japan) Co., Ltd.) A photopolymerizable resin composition containing 2 parts by mass was applied onto a PET (polyethylene terephthalate) film so that the dry thickness was 30 μm, dried at 80 ° C. for 5 minutes, and then with a high-pressure mercury lamp. A transfer body was prepared by irradiating with 1000 mJ light.

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

  After spraying conductive particles (nickel plated resin particles (AUL704, Sekisui Chemical Co., Ltd.)) having an average particle diameter of 4 μm on the surface of the transfer body, the conductive particles are not adhered to the fine adhesion layer by blowing. Was removed.

  From the conductive particle adhering surface, the transfer body on which the conductive particles are attached is transferred to the sheet-like thermosetting insulating adhesive film (phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical) Co., Ltd.) 60 parts by mass, epoxy resin (jER828, Mitsubishi Chemical Co., Ltd.) 40 parts by mass, cationic curing agent (SI-60L, Sanshin Chemical Co., Ltd.) 2 parts by mass, silica fine particle filler (Aerosil RY200, Nippon Aerosil Co., Ltd.) film formed from an insulating resin comprising 20 parts by mass) was pressed at a temperature of 50 ° C. and a pressure of 0.5 MPa to transfer the conductive particles to the insulating adhesive base layer.

  On the conductive particle transfer surface of the obtained insulating adhesive base layer, another insulating adhesive film having a thickness of 15 μm as a transparent insulating adhesive cover layer (phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.) )) 60 parts by mass, epoxy resin (jER828, Mitsubishi Chemical Co., Ltd.) 40 parts by mass, and cationic curing agent (SI-60L, Sanshin Chemical Industry Co., Ltd.) 2 parts by mass. And laminated at a temperature of 60 ° C. and a pressure of 2 MPa. Thereby, an anisotropic conductive film was obtained.

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

Example 3
The cylindrical recess of the transfer master has an inner diameter of 3.8 μm and a depth of 6 μm, the distance between the centers of adjacent recesses is 6 μm, the density of the recesses is 28000 / mm ² , and the average is replaced with conductive particles having an average particle diameter of 4 μm. An anisotropic conductive film was obtained by repeating Example 1 except that conductive particles (AUL703, Sekisui Chemical Co., Ltd.) having a particle diameter of 3 μm were used.

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

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

Comparative Example 2
Conductive particles having a recess depth of 3.3 μm, an inner diameter of the recess of 3.6 μm, a distance between adjacent recess centers of 4.2 μm, a density of the recesses of 57000 / mm ² , and an average particle diameter of 4 μm An anisotropic conductive film was obtained by repeating Example 1 except that conductive particles (AUL703, Sekisui Chemical Co., Ltd.) having an average particle diameter of 3 μm were used instead.

<Evaluation>
("Occurrence" and "aggregation" of conductive particles)
For the anisotropic conductive films of Examples 1 to 4 and Comparative Examples 1 and 2, a 1 cm square area was observed from the transparent insulating adhesive cover layer side with an optical microscope (MX50, Olympus Corporation). The ratio (missing [%]) of lattice points where conductive particles are not attached to the total lattice points and the ratio of lattice points where two or more conductive particles are aggregated to the total lattice points It was. The obtained results are shown in Table 1.

  Further, the maximum distance (aggregation distance) between the aggregated conductive particles was measured and is shown in Table 1 together. 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 diameter of the conductive particles and the density of the recesses on the master of the transfer body (= the density of the protrusions on the transfer body) in consideration of “missing” and “aggregation” of the conductive particles. The obtained results are shown in Table 1.

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

(Conduction reliability)
The connection structure used for the measurement of the initial conduction resistance value is 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 is the same as the initial conduction resistance value. It was measured. The obtained results are shown in Table 1. It is desirable that it be 5Ω or less.

(Short occurrence rate)
The same connection structure as that used for the initial conduction resistance was created, and the presence or absence of a short circuit between adjacent wirings was examined. The obtained results 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, the connection structure using the anisotropic conductive films 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 rate of “aggregation” of the conductive particles was small, the rate of “aggregation” was too high.

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. . About the obtained anisotropic conductive film, the “missing” and “aggregation” of the conductive particles were measured in the same manner as in Example 2, and the particle area occupation ratio was calculated. As a result, “dropping” and “aggregation” of the conductive particles were equivalent to those in Example 2. The particle area occupation ratio was 0.7%.

  The obtained anisotropic conductive film is placed between a glass substrate (ITO solid electrode) and a flexible wiring board (bump width: 200 μm, L (line) / S (space) = 1, wiring height 10 μm). It was sandwiched and anisotropically conductive under the conditions of 180 ° C., 80 MPa, and 5 seconds so that the connection bump length was 1 mm to obtain a connection structure for evaluation. About the obtained connection structure, the "initial conduction resistance value" and the "conduction reliability" after putting it in a thermostat of 85% humidity at a temperature of 85 ° C. for 500 hours were converted into a digital multimeter (34401A, Agilent・ Measure the conduction resistance using the 4-terminal method with a current of 1A using Technology Co., Ltd., and in the case of "Initial conduction resistance value", the measured value is 2Ω or less, and the measured value is better than 2Ω. In the case of “conduction 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”. Further, when the “short-circuit 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 / mm ² , and an anisotropic conductive film was further prepared. . About the obtained anisotropic conductive film, the “missing” and “aggregation” of the conductive particles were measured in the same manner as in Example 2, and the particle area occupation ratio was calculated. As a result, “dropping” and “aggregation” of the conductive particles were equivalent to those in Example 2. Further, the particle area occupation ratio was 2.7%.

  Further, the obtained anisotropic conductive film was sandwiched between a glass substrate and a flexible wiring board in the same manner as in Example 5 to obtain an anisotropic conductive connection to obtain a connection structure for evaluation. The obtained connection structure was evaluated for “initial conduction resistance value”, “conduction reliability”, and “short-circuit occurrence rate” in the same manner as in Example 5. As a result, good results were obtained.

  In the preferable anisotropic conductive film of the present invention, the ratio of “lattice points where no conductive particles are arranged” to the total lattice points of the planar lattice pattern assumed in the reference region is set to less than 10%, and the planar lattice pattern The ratio of “lattice points where a plurality of conductive particles are aggregated and arranged” with respect to all the lattice points is set to 15% or less, and at least some of the conductive particles arranged in an aggregate are anisotropic. The conductive conductive film is disposed obliquely in the thickness direction. For this reason, when the anisotropic conductive film of the present invention is applied to an anisotropic conductive connection, it is possible to realize good initial conduction and good conduction reliability after aging, and the occurrence of a short circuit can be suppressed. This is useful when an anisotropic conductive connection is made between the pitched IC chip and the wiring board.

DESCRIPTION OF SYMBOLS 10,200 Anisotropic conductive film 11,104 Insulating adhesive base layer 12,105 Insulating adhesive cover layer 13,103 Conductive particle 100 Transfer body 101 Convex part 102 Slight adhesion layer A Lattice point from which conductive particle is missing B Conductive Lattice points where particles are aggregated apart from each other

Claims (14)

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 lattice points where conductive particles are not arranged with respect to all lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film is less than 25%,
An anisotropic conductive film in which a ratio of lattice points where a plurality of conductive particles are aggregated and arranged with respect to all lattice points of the planar lattice pattern is 15% or less, and a total of omission and aggregation is less than 25%. An anisotropic conductive film 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 the interface,
The ratio of lattice points where conductive particles are not arranged with respect to all lattice points of the planar lattice pattern assumed in the reference region of the anisotropic conductive film is less than 10%,
The ratio of lattice points where a plurality of conductive particles are aggregated and arranged with respect to all lattice points of the planar lattice pattern is 15% or less,
The anisotropic conductive film according to claim 1, wherein at least some of the conductive particles arranged in an agglomerated manner are arranged obliquely in the thickness direction of the anisotropic conductive film. The reference area is the following relational expressions (A), (2) and (3) at the center of the plane of the anisotropic conductive film:

Where D is the average particle diameter of the conductive particles, and 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, wherein the anisotropic conductive film is a straight line and the side X is a straight line perpendicular to the side Y. The reference areas are the following relational expressions (1) to (3) at the center of the plane of the anisotropic conductive film:

Where D is the average particle diameter of the conductive particles, and 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, wherein the anisotropic conductive film 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 a distance between the conductive particles (aggregation distance) arranged so as to be shifted in the thickness direction is 25 to 50% of an average particle diameter of the conductive particles.   The anisotropic conductive film according to any one of claims 1 to 5, wherein the particle area occupancy ratio of all conductive particles existing in the area of the reference region of the anisotropic conductive film is 25% or less.   The average particle size of the conductive particles is 1 to 10 µm, and the distance between adjacent lattice points of the planar lattice pattern is larger than 0.5 times the average particle size of the conductive particles. Isotropic conductive film. The reference area is the following relational expression of the plane central portion of the anisotropic conductive film:

Where D is the average particle diameter of the conductive particles, and 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, wherein the anisotropic conductive film is a straight line and the side X is a straight line perpendicular to the side Y.   The anisotropic conductive film according to claim 8, wherein the particle area occupancy ratio of all 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 8 or 9, wherein the conductive particles have an average particle diameter of 1 to 30 µm, and the distance between adjacent lattice points of the planar lattice pattern is 0.5 times or more of the average particle diameter of the conductive particles. It is a manufacturing method of the anisotropic conductive film of Claim 1, Comprising: The following processes (a)-(e):
<Process (I)>
Preparing a transfer body having columnar convex portions corresponding to lattice points of a planar lattice pattern formed on the surface;
<Process (b)>
Forming at least the top surface of the convex portion of the transfer body as a slightly adhesive layer;
<Process (C)>
A step of attaching 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 pressing the insulating adhesive base layer on the surface of the transfer body on which the conductive particles are adhered; and <Step (e)>
The manufacturing method which has the process of laminating | stacking an insulating adhesive cover layer from the conductive particle transfer surface side with respect to the insulating adhesive base layer which the conductive particle transferred.   The manufacturing method according to claim 11, wherein the transfer body used in the step (a) is prepared by processing a metal plate to prepare a master, applying a curable resin thereto, and curing it.   The height of the convex portion of the transfer body in step (A) is not less than 2 times and less than 4 times the average particle size of the conductive particles, and the half width of the convex portion is not less than 0.7 times the average particle size of the conductive particles. The production method according to claim 11 or 12, which is 1.3 times or less.   The connection structure in which the terminal of the 1st electronic component and the terminal of the 2nd electronic component were anisotropically conductive-connected by the anisotropic conductive film in any one of Claims 1-10.

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