JP7200980B2 - 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. , the conductive particles are known to exist in a state of being linked or aggregated. For this reason, when the anisotropic conductive film is applied to the connection between the terminals of the IC chip and the terminals of the wiring board, which are narrowed in pitch due to the reduction in weight and size of electronic devices, In some cases, conductive particles that are present in a compacted state can cause a short circuit between adjacent terminals.

Conventionally, as an anisotropic conductive film corresponding to such a narrow pitch, a film in which conductive particles are regularly arranged has been proposed. For example, after forming an adhesive layer on a stretchable film and densely filling a single layer of conductive particles on the surface of the adhesive layer, the film is biaxially stretched until the distance between the conductive particles reaches a desired distance. An anisotropic conductivity obtained by regularly arranging conductive particles, then pressing an insulating adhesive base layer, which is a component of an 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, conductive particles are scattered on the concave-forming surface of a transfer mold having concave portions on the surface, the concave-forming surface is squeegeeed to hold the conductive particles in the concave portions, and an adhesive film having an adhesive layer for transfer is formed thereon. By pressing, the conductive particles are primarily transferred to the adhesive layer, and then the insulating adhesive base layer, which is a component of the anisotropic conductive film, is pressed against the conductive particles attached to the adhesive layer, and the conductive particles are made insulating. An anisotropic conductive film obtained by transferring to an adhesive base layer has also been proposed (Patent Document 2). These anisotropic conductive films generally have an insulating adhesive cover layer laminated on the conductive particle side surface so as to cover the conductive particles.

WO2005/054388 JP 2010-33793 A

However, since the conductive particles tend to agglomerate due to static electricity or the like and become secondary particles, it is difficult for the conductive particles to always exist alone as primary particles. Therefore, 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 fill the entire surface of the stretchable film with the conductive particles in a single layer without defects, 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 "void") is generated, which causes a conduction failure. In addition, in the case of Patent Document 2, when the recesses of the transfer mold are covered with conductive particles having a large particle size, they are removed by a subsequent squeegee, resulting in recesses that do not hold the conductive particles, and the anisotropic conductive film becomes conductive. Particles may "fall out" and cause poor conduction, or 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, or Since the conductive particles located on the bottom side of the recesses are not in contact with the insulating adhesive base layer, they scatter on the surface of the insulating adhesive base layer, impairing the regular arrangement and causing short circuits and poor conduction. There was a problem that

Thus, in Patent Documents 1 and 2, how to control the "missing" and "aggregation" of the conductive particles to be arranged in a regular pattern on the anisotropic conductive film is sufficiently described. The reality 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, the occurrence of short circuits and poor conduction is prevented. An object of the present invention is to provide an anisotropic conductive film that is greatly suppressed.

When arranging the conductive particles at the lattice points of the planar lattice, the present inventors found that "the conductive particles are arranged The present inventors have found that the above object can be achieved by controlling the ratio of lattice points where there is no conductive particles and the ratio of lattice points where conductive particles are aggregated and arranged, and have completed the present invention. In such an anisotropic conductive film, instead of arranging the conductive particles in the recesses of the transfer body, the conductive particles are attached to the tips of the projections of the transfer body having the columnar projections formed on the surface. The present inventors have found that it can be produced by transferring the film using a method of the present invention, and have completed the production method of the present invention.

That is, the present invention provides 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 proportion of lattice points where no conductive particles are arranged with respect to all lattice points of a planar 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 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 the total of voids and aggregation is less than 20%. offer.

Further, in the present invention, the ratio of lattice points where no conductive particles are arranged with respect to all lattice points of a planar lattice pattern assumed in the reference region of the anisotropic conductive film is less than 5%,
Provided is an anisotropic conductive film in which the ratio of lattice points where a plurality of conductive particles are aggregated and arranged to all lattice points of the planar lattice pattern is more than 10% and less than 15%. Again, the sum of shedding and agglomeration is preferably less than 20%.

The present invention also provides the above-described 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 their interface. A manufacturing method comprising the following steps (a) to (e):
<Process (a)>
A step of preparing a transfer body on the surface of which columnar projections corresponding to lattice points of a planar lattice pattern are formed;
<Process (b)>
forming a slightly adhesive layer on at least the top surface of the projections of the transfer body;
<Process (C)>
a step of adhering conductive particles to the slightly adhesive layer on the projections of the transfer body;
<Process (D)>
A step of transferring the conductive particles to the insulating adhesive base layer by overlapping and pressing the insulating adhesive base layer on the surface of the transfer body on which the conductive particles are attached; and <Step (e)>
Provided is a manufacturing method comprising a step of laminating an insulating adhesive cover layer from the conductive particle-transferred surface side on an insulating adhesive base layer to which conductive particles have been transferred.

Furthermore, the present invention provides a connection structure in which terminals of a first electronic component and terminals of a 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 no conductive particles are arranged" to all lattice points of the planar lattice pattern assumed in the reference area is set to less than 20%, and the planar lattice pattern The ratio of grid points where a plurality of conductive particles are aggregated to all grid points is set to 15% or less, and the total of voids and aggregation is set to less than 20%. Therefore, when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, good initial conductivity (initial conduction resistance value) and good conduction reliability after aging can be achieved, and short circuits can occur. can also be suppressed. Moreover, it is economical not only for COG, but also for electronic components with sufficiently large bump areas and distances, such as FOG.

In the preferred anisotropic conductive film of the present invention, the ratio of "lattice points where no conductive particles are arranged" to all lattice points of a planar lattice pattern assumed in an arbitrary reference area is set to less than 5%, and The ratio of "lattice points where a plurality of conductive particles are aggregated and arranged" is set to more than 10% and less than 15%. Therefore, when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, a good initial conduction resistance value and good conduction reliability after aging can be achieved, and short circuits can be suppressed.

In addition, in the method for producing an anisotropic conductive film of the present invention, a transfer body having a surface formed with columnar projections corresponding to lattice points of a planar lattice pattern is used, and the projections are formed on the top surface of the projections. After the conductive particles are attached to the slightly tacky layer, the conductive particles are transferred to the insulating adhesive base layer. For this reason, the ratio of "lattice points where no conductive particles are arranged" to all lattice points of a planar lattice pattern assumed in an arbitrary reference region of the anisotropic conductive film is set to less than 5%, and all lattices of the planar lattice pattern The ratio of "lattice points where a plurality of conductive particles are aggregated and arranged" to the points can be more than 10% and less than 15%. Therefore, in the production method of the present invention, an anisotropic conductive film can be produced economically. Anisotropic conductive connection can be achieved while greatly suppressing the occurrence of poor conduction.

FIG. 1 is a cross-sectional view of the anisotropic conductive film of the present invention. FIG. 2A is a plan perspective view of the anisotropic conductive film of the present invention. FIG. 2B is a partially enlarged plan perspective view of the anisotropic conductive film of the present invention. FIG. 3A is a process explanatory diagram of the manufacturing method of the present invention. FIG. 3B is a process explanatory diagram of the manufacturing method of the present invention. FIG. 3C is a process explanatory diagram of the manufacturing method of the present invention. FIG. 3D is a process explanatory diagram of the manufacturing method of the present invention. FIG. 3E is a process explanatory diagram of the manufacturing method of the present invention. FIG. 3F is a schematic cross-sectional view of the anisotropic conductive film of the present invention, as well as a process explanatory view of the manufacturing method 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 their interface. 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%, and a plurality of lattice points with respect to all lattice points of the planar lattice pattern The ratio of lattice points where the conductive particles are aggregated is 15% or less, and the total of voids and aggregation is less than 20%. 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 FIGS. 2A and 2B (plan perspective views), the anisotropic conductive film 10 of the present invention is formed by laminating an insulating adhesive base layer 11 and an insulating adhesive cover layer 12. , and conductive particles 13 are arranged at lattice points of a planar lattice pattern (dotted lines in FIGS. 2A and 2B) near their interfaces. In FIGS. 1, 2A, and 2B, the planar lattice pattern is assumed along the longitudinal direction of the anisotropic conductive film 10 and the direction perpendicular thereto (lateral direction). It may be assumed that the whole is tilted with respect to Here, the arrow A indicates a position where the conductive particles are not arranged at the grid point of the planar grid, that is, a position where the conductive particles are "missing". The arrow B indicates the position where the conductive particles are in contact with each other and aggregated (connected), and the arrow C indicates the position where the conductive particles are aggregated without contact with each other. Here, "non-contact aggregation" means that the conductive particles are close to each other within a range not exceeding 25% of the average particle size of the conductive particles.

(“Release” of conductive particles)
In the anisotropic conductive film of the present invention, “lattice points where no conductive particles are arranged” (A in FIG. 2A) for all lattice points of a planar lattice pattern assumed in an arbitrary reference region of the anisotropic conductive film (percentage of lattices with missing conductive particles) is set to less than 5%, preferably 4% or less, more preferably 1% or more and 4% or less. As a result, when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, good initial conduction resistance and good conduction reliability after aging can be achieved, and the occurrence of short circuits can be suppressed.

(Planar lattice pattern)
Planar grid patterns include orthorhombic grids, hexagonal grids, square grids, rectangular grids, and parallel grids. Among them, a hexagonal lattice capable of close packing is preferable.

Here, as the reference region of the anisotropic conductive film, it is possible to select the entire surface of the anisotropic conductive film, but usually the following relational expression (A) of the plane central portion of the anisotropic conductive film, preferably It is preferable to select, as the reference area, a substantially rectangular area composed of sides X and Y that satisfy the relational expression (1) and the relational expressions (2) and (3).

In addition, when applying to c-connection that can take a relatively large connection area, it is possible to reduce the amount 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 numerical value of "X+Y" is also preferably a numerical value in the vicinity of 100D to 400D, and finally 400D.

In 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 with an image type particle size distribution meter. It may be measured from surface observation. Further, the side Y is a straight line within a range of less than ±45° with respect to the longitudinal direction of the anisotropic conductive film (see FIG. 2A), 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 made similar or approximate to the shape of the bump against which the conductive particles are pressed. It is possible to economically and stably perform anisotropic conductive connection. In other words, by setting the minimum side of the reference region to be 5 times or more the diameter of the conductive particles, even if the conductive particles are misaligned, missing, or close to each other within this range, any The anisotropic conductive connection can be ensured because the particles are trapped by the bumps and are not excessively agglomerated in the inter-bump spaces.

The reason why the minimum side is 5 times or more the diameter of the conductive particles is that, in general, the particles are larger than the average particle diameter of the conductive particles in order to ensure trapping on at least one side of the bump to be anisotropically conductively connected. Moreover, the space between the bumps should preferably be at least twice the average particle size of the conductive particles for the purpose of preventing short circuits. In other words, when focusing on a circular conductive particle that serves as a reference, the length (that is, 5D) obtained by adding the length (4D) four times the diameter to the average particle diameter D of this conductive particle is the diameter This is because it is considered that the above requirements can be satisfied if no unexpected defects occur within the concentric circles. Another reason is that the minimum distance between bumps when the pitch is fine is, for example, less than four times the diameter of the conductive particles.

(aggregation of conductive particles)
Further, in the anisotropic conductive film of the present invention, the ratio of grid points (arrows B and C in FIG. 2A) where a plurality of conductive particles are aggregated and arranged with respect to all grid points of the planar grid pattern is 15. % or less is preferable, it may be more than 10% and less than 15%, and if it is 11% or more and 14% or less, there is no practical problem. When the ratio of 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 conductivity and conduction reliability after aging are realized. It is possible to further suppress the occurrence of short circuits. Here, the state in which the conductive particles are aggregated means not only the case where the conductive particles are directly connected as shown by the arrow B in FIG. 2A, but also the conductive particles are directly connected to each other as shown by the arrow C in FIG. Also included are none but very close to each other. The adjacent distance is preferably within 25% of the average particle size of the conductive particles. In addition, the degree of aggregation of the conductive particles with respect to one lattice point may be that more than two conductive particles are linked in a chain, but from the viewpoint of suppressing short circuits, the smaller the aggregation, the better. It is preferred that the conductive particles do not agglomerate.

In the present invention, the direction of aggregation of the conductive particles that are aggregated and arranged (usually, the direction of the line connecting the centers of gravity of the two aggregated conductive particles) is deviated in the thickness direction, and arrows B and arrows in FIG. Like C, it becomes a direction inclined to the plane direction of the anisotropic conductive film. The degree of inclination is preferably 5 to 45°, more preferably 10 to 40° so as not to impede the pushing during connection. It should be noted that the reason why such an inclination occurs is that if it exists at the end of the bump at the time of connection, it can be captured by only one side (overlapping without inclination affects pushing). be). There is no particular problem even if the aggregation is horizontal.

(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 13 or more conductive particles are more preferably 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, the above conditions are preferably satisfied in all three continuous rows along the longitudinal direction of the film, and more preferably in all five rows. As a result, the number of conductive particles captured by the bumps can be kept above a certain level, and stable anisotropic conductive connection can be achieved.

When the conductive particles are agglomerated, it is preferable that there are three or less sets of two-linked conductive particles around the two agglomerated conductive particles, more preferably two or less, and even more preferably one. less than or equal to This is because the presence of two aggregated conductive particles in a dense manner may cause a short circuit. It is preferable that the number of the two aggregated conductive particles satisfy the above conditions and that the number of the particles is not more than three consecutively in one direction of arrangement.

In addition, it is preferable that 4 or more continuous conductive particles in the longitudinal direction of the film and 4 or more continuous conductive particles in the direction perpendicular to the longitudinal direction of the film do not intersect. It is more preferable that one missing is not adjacent via conductive particles that become one or more lattice points, and any four or more consecutive missings are two or more lattice points through conductive particles. even more preferably not adjacent. There is no problem in crossing up to three rows of missing lines in one direction at the same time. This is because if the chipping is not continuous any more, it will be captured by the bump by the conductive particles in its vicinity.

It should be noted that it is generally not preferable to have a plurality of regions in the vicinity where such continuous missing regions intersect, but the stability of the anisotropic conductive connection can be improved by arranging the conductive particles in the same number or more as the missing regions. is no problem.

Further, as shown in FIG. 2B, the distance L between the grid point P1 where the agglomerated conductive particles 13 are arranged and the center P2 of the circle inscribed with the agglomerated conductive particles 13 is the distance L of the conductive particles. It is preferably 25% or less of the average particle size from the viewpoint of suppressing short circuits.

(Particle area occupation ratio)
Furthermore, the particle area occupancy ratio of all the conductive particles present in the area of an arbitrary reference region of the anisotropic conductive film is the same as in FOG connection, where the bump size and the distance between bumps are relatively large. For this, 0.15% or more, preferably 0.35% or more, more preferably 1.4% or more is effective. In this case, the upper limit is preferably 35% or less, more preferably 32% or less. Further, when the bump size or the distance between bumps is relatively small (for example, COG connection), it is more preferably 15 to 35%, particularly preferably 20 to 25%. Within this range, even when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, better initial conductivity and conduction reliability after aging can be achieved, and the occurrence of short circuits is further reduced. can be suppressed. Here, the particle area occupancy ratio is the ratio of the area occupied by all the conductive particles existing within the reference area to the area S of any reference area. The area occupied by all the conductive particles is represented by (R/2) ² ×π×n, where R is the average particle diameter of the conductive particles and n is the number of the conductive particles. Therefore, the particle area occupation ratio (%)=[{(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, the calculated particle area occupation ratio is 0.157%. When the average particle diameter of the conductive particles is 3 μm, the number density is 500/mm ² (0.0005/μm ² ), X=Y=200D, and X+Y=400D, the calculated particle area occupation ratio is 0. 35325%. When the average particle diameter of the conductive particles is 3 μm, the number density is 2000/mm ² (0.002/μm ² ), X=Y=200D, and X+Y=400D, the calculated particle area occupation ratio is 1. 413%. Further, when the average particle diameter of the conductive particles is 30 μm, the number density is 500/mm ² (0.0005/μm ² ), X=Y=200D, and X+Y=400D, the calculated particle area occupation ratio is 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 obtained by coating the surfaces of resin particles such as polyamide and polybenzoguanamine with a metal such as nickel. Also, the average particle size thereof is preferably 1 to 30 μm, more preferably 1 to 10 μm, particularly preferably 2 to 6 μm, from the viewpoint of handling during production. The average particle size can be measured with an image-type or laser-type particle size distribution meter, as described above.

The amount of conductive particles present 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 40000 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, still more preferably 1 to Twenty times. Within this range, even when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, better initial conductivity and conduction reliability after aging can be achieved, and the occurrence of short circuits is further reduced. can be suppressed.

(insulating adhesive base layer)
As the insulating adhesive base layer 11, one used as an insulating adhesive base layer in known anisotropic conductive films 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 a thermal polymerizable resin layer containing an epoxy compound and a thermal cationic polymerization initiator. A cationically polymerizable resin layer, a thermally anionically polymerizable resin layer containing an epoxy compound and a thermally anionic polymerization initiator, or the like, or a cured resin layer thereof can be used. In addition, these resin layers can contain silane coupling agents, pigments, antioxidants, ultraviolet absorbers, and the like by appropriately selecting them as necessary.

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

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

(insulating adhesive cover layer)
As the insulating adhesive cover layer 12, one used as an insulating adhesive cover layer in known anisotropic conductive films can be appropriately selected and used. A layer 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 applying a coating composition containing a resin as described above and drying it, further curing it, or forming it into a film in advance by a known method. can do.

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

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

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

<Production 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 interface. explain. This manufacturing method has the following steps (a) to (e). Each step will be described in detail with reference to the drawings. Note that the present invention is not particularly limited to this manufacturing method.

(Process (a))
First, as shown in FIG. 3A, a transfer member 100 is prepared on the surface of which columnar projections 101 corresponding to lattice points of a planar lattice pattern are formed. This column contains a cone. It is preferably 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 conductively connected. It is preferably 2 times or more and less than 4 times. Further, the width (width at half height) of the projections 101 is preferably 1.4 to 3.6 times the average particle size of the conductive particles. If the height and width are within these ranges, an effect is obtained in which excessive falling-off does not occur and the falling-out occurs only sporadically.

Furthermore, the convex portion 101 has a substantially flat top surface to which the conductive particles can stably adhere.

*Specific example of the transfer body The transfer body to be prepared in this step (a) can be prepared using a known method. It can be prepared by coating and curing. Specifically, by cutting a flat metal plate, a transfer body master is also prepared in which recesses corresponding to the protrusions are formed, and a resin composition constituting the transfer body is applied to the recessed surface of this master, After curing, a transfer body is obtained by separating from the master.

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

*Slightly Adhesive Layer of Transfer Body The slightly adhesive layer 102 is a layer that exhibits adhesive strength that can temporarily hold the conductive particles until the conductive particles are transferred to the insulating adhesive base layer that constitutes the anisotropic conductive film. It is formed on at least the top surface of the convex portion 101 . Therefore, the entire protrusion 101 may be slightly sticky. The thickness of the slightly adhesive layer 102 can be appropriately determined according to the material of the slightly adhesive layer 102, the particle size of the conductive particles, and the like. Further, the term "slightly sticky" means that the adhesive force is weaker than that of the insulating adhesive base layer when the conductive particles are transferred onto the insulating adhesive base layer.

A slightly adhesive layer used in known anisotropic conductive films can be applied to such a slightly adhesive layer 102 . For example, it can be formed by applying a silicone adhesive composition or an adhesive layer made of the same material as 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 adhered to the slightly adhesive layer 102 of the projections 101 of the transfer body 100 . Specifically, the conductive particles 103 are sprayed from above the convex portions 101 of the transfer member 100, and the conductive particles 103 that have not adhered to the slightly adhesive layer 102 are blown away using a blower. In this case, in some of the convex portions 101, conductive particles adhere to the side surfaces of the convex portions 101 due to the action of static electricity or the like with a certain frequency, and moreover, the conductive particles cannot be removed by a blower.

In addition, the direction of the surface may be reversed from that of 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 attaching only the conductive particles necessary for arrangement to the top surface of the projection in this way, it becomes easier to collect and reuse the conductive particles, and it is also more economical than the method of filling the openings with the conductive particles and taking them out. Become. In addition, in the case of the method of filling the opening with the conductive particles and taking them out, there is a concern that the conductive particles that are not filled are likely to be subjected to unnecessary stress.

In FIG. 3C, the width of the slightly adhesive layer 102 on the convex portion 101 on the left half is adjusted to be narrower than the width of the slightly adhesive layer 102 on the convex portion 101 on the right half. As a result, as shown in FIG. 3C, the left half and the right half may have different aggregation modes of the conductive particles 103 .

(Process (d))
Next, as shown in FIG. 3D, an insulating adhesive base layer 104 to constitute an anisotropic conductive film is superimposed and pressed on the surface of the transfer body 100 to which the conductive particles 103 are attached, thereby increasing the insulating properties. Conductive particles 103 are transferred to one side of adhesive base layer 104 (FIG. 3E). In this case, it is preferable that the transfer body 100 is overlapped with the insulating adhesive base layer 104 and pressed so that the projections 101 of the transfer body 100 face downward. By blowing downward, the conductive particles that are not adhered to the top surface of the projection can be easily removed.

(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 have been transferred from the conductive particle-transferred surface side. Thereby, the anisotropic conductive film 200 of the present invention is obtained.

<Connection structure>
The anisotropic conductive film of the present invention is provided between terminals (e.g. bumps) of a first electronic component (e.g. IC chip) and terminals (e.g. bumps, pads) of a second electronic component (e.g. wiring board). The so-called COG (chip on glass) or FOG (film connection structures such as (on glass) can be provided.

The present invention will be specifically described below.

Example 1
A nickel plate having a thickness of 2 mm was prepared, and cylindrical concave portions (inner diameter of 6 μm, depth of 8 μm) were formed in a tetragonal lattice pattern to obtain a transfer master master. The center-to-center distance between adjacent recesses was 8 μm.
Therefore, the density of recesses was 16000/mm ² .

The obtained transfer body master was coated with 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.), and a photopolymerization initiator (IRGACURE 184, BASF Japan Co., Ltd.) A photopolymerizable resin composition containing 2 parts by mass was coated on a PET (polyethylene terephthalate) film to a dry thickness of 30 μm, dried at 80° C. for 5 minutes, and then exposed to a high-pressure mercury lamp. A transfer member was produced by irradiating 1000 mJ of light.

The transfer body is peeled off from the master, wound around a stainless steel roll with a diameter of 20 cm so that the convex portion 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, a weak adhesive composition containing 30 parts by mass of Nippon Steel & Sumikin Chemical Co., Ltd.) is brought into contact with an adhesive sheet impregnated with a nonwoven fabric, and the weak adhesive composition is attached to the top surface of the convex part. , a slightly 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 size of 4 μm on the surface of this transfer body, the conductive particles that are not adhered to the slightly adhesive layer are removed by blowing. Removed.

A sheet-shaped thermosetting insulating adhesive film (phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical (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 Industry Co., Ltd.) 2 parts by mass, and silica fine particles (Aerosil RY200, Japan Aerosil Co., Ltd.), a film formed from an insulating adhesive composition containing 20 parts by mass) is 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. rice field.

On the conductive particle-transferred surface of the obtained insulating adhesive base layer, another sheet-like insulating adhesive film (phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.) having a thickness of 15 μm was applied as a transparent insulating adhesive cover layer. )) 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 Insulating adhesive composition containing A film formed from ) was superimposed and laminated at a temperature of 60° C. and a pressure of 2 MPa. An anisotropic conductive film was thus obtained.

Example 2
An anisotropic conductive film was obtained by repeating Example 1 except that the amount of the conductive particles dispersed and the number of times of blowing were doubled.

Example 3
The cylindrical recesses of the transfer member master have an inner diameter of 4.5 μm and a depth of 7.5 μm, the distance between the centers of adjacent recesses is 6 μm, the density of the recesses is 28000/mm ² , and the conductive particles having an average particle diameter of 4 μm are substituted. An anisotropic conductive film was obtained by repeating Example 1 except that conductive particles (AUL703, Sekisui Chemical Co., Ltd.) having an average particle size of 3 μm were used.

Example 4
An anisotropic conductive film was obtained by repeating Example 3 except that the amount of the conductive particles dispersed and the number of times of blowing were doubled.

Comparative example 1
Example 1 is repeated except that the depth of the recesses of the transfer member master is 4.4 μm, the inner diameter of the recesses 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 . An anisotropic conductive film was thus obtained.

Comparative example 2
Conductive particles having a depth of 3.3 μm, an inner diameter of 3.3 μm, a distance between the centers of adjacent recesses of 4.2 μm, a density of 57000 pieces/mm ² of recesses, 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 size of 3 μm (AUL703, Sekisui Chemical Co., Ltd.) were used instead.

<Evaluation>
(“Disconnection” 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 Co., Ltd.). 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 in the planar lattice pattern. rice field. Table 1 shows the results obtained.

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

(Particle area occupation ratio)
Based on the average particle diameter of the conductive particles and the density of the concave portions of the transfer member master (=the density of the convex portions of the transfer member), the particle area occupancy was calculated, taking into consideration the "missing" and "aggregation" of the conductive particles. . Table 1 shows the results obtained.

(initial conduction resistance)
Using the anisotropic conductive films of Examples and Comparative Examples, an IC chip having gold bumps of 30 μm×50 μm with a height of 15 μm and a space between bumps of 12 μm, and a glass substrate provided with wiring with a space of 12 μm. Anisotropic conductive connection was performed under 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 Corporation). Table 1 shows the results obtained. It is desired to be 0.5Ω or less.

(Continuity reliability)
The connection structure used for measuring the initial conduction resistance value is placed in an aging tester set at a temperature of 85 ° C. and a humidity of 85%, and the conduction resistance value after leaving for 500 hours is measured in the same manner as the initial conduction resistance. It was measured. Table 1 shows the results obtained. It is desired to 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 short-circuiting between adjacent wirings was examined. Table 1 shows the results obtained. It is desired that the short circuit occurrence rate is 50 ppm or less.

From the results in Table 1, the connection structures 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 occurrence rate. Understand.

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 "cohesion" was too high, so the occurrence rate of shorts greatly exceeded 50 ppm.

Example 5
A transfer member was prepared in the same manner as in Example 2, except that the distance between the centers of adjacent concave portions was adjusted in order to use a transfer master having a concave portion density of 500/mm ² , and an anisotropic conductive film was also prepared. . Regarding 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 area occupation ratio of the particles was calculated. As a result, the "loosening" and "aggregation" of the conductive particles were the same as in Example 2. Moreover, the particle area occupation ratio was 0.7%.

In addition, the obtained anisotropic conductive film was placed between a glass substrate (ITO solid electrode) and a flexible wiring substrate (bump width: 200 μm, L (line)/S (space)=1, wiring height: 10 μm). Anisotropic conduction was performed under the conditions of 180° C., 80 MPa, and 5 seconds so that the connection bump length was 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 placed in a constant temperature chamber at a temperature of 85 ° C. and a humidity of 85% RH for 500 hours were measured with a digital multimeter (34401A, Agilent Technology Co., Ltd.) is used to measure the conduction resistance by the 4-terminal method at a current of 1A. In the case of "conductivity reliability", a measured value of 5Ω or less was evaluated as good, and a measured value of 5Ω or more was evaluated as defective. As a result, all of the connection structures of Example 5 were evaluated as "good". Moreover, 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 member was prepared in the same manner as in Example 2, except that the distance between the centers of adjacent concave portions was adjusted to use a transfer master having a concave portion density of 2000/mm ² , and an anisotropic conductive film was also prepared. . Regarding 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 area occupation ratio of the particles was calculated. As a result, the "loosening" and "aggregation" of the conductive particles were the same as in Example 2. Moreover, the particle area occupation ratio was 2.7%.

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

In the preferred anisotropic conductive film of the present invention, the ratio of "lattice points where no conductive particles are arranged" to all lattice points of a planar lattice pattern assumed in an arbitrary reference area is set to less than 5%, and The ratio of "lattice points where a plurality of conductive particles are aggregated and arranged" to all lattice points of the planar lattice pattern is more than 10% and less than 15%. Therefore, when the anisotropic conductive film of the present invention is applied to anisotropic conductive connection, good initial conductivity and good conduction reliability after aging can be achieved, and the occurrence of short circuits can be suppressed. It is useful for anisotropically conductive connection between a pitched IC chip and a wiring substrate.

REFERENCE SIGNS LIST 10, 200 Anisotropic conductive film 11, 104 Insulating adhesive base layer 12, 105 Insulating adhesive cover layer 13, 103 Conductive particles 100 Transfer body 101 Projection 102 Slight adhesive layer A Conductive particles are not arranged at lattice points Position (position where conductive particles are missing)
B Position where the conductive particles contact each other and agglomerate C Position where the conductive particles agglomerate without contact P1 Lattice point where the agglomerated conductive particles are arranged P2 Center of a circle inscribed with the agglomerated conductive particles L distance between P1 and P2

Claims (18)

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 planar lattice pattern assumed for the reference region of the anisotropic conductive film always has lattice points where no conductive particles are arranged and lattice points where the conductive particles are aggregated and arranged,
The reference region is the following relational expressions (A), (2) and (3) of the plane central portion of the anisotropic conductive film:

It is a substantially rectangular region consisting of sides X and sides Y that satisfy, where D is the average particle size of the conductive particles, and the sides Y are in the range of less than ±45° with respect to the longitudinal direction of the anisotropic conductive film is a straight line, side X is a straight line perpendicular to side Y,
The ratio of lattice points where no conductive particles are arranged to all lattice points of the planar lattice pattern is less than 20%,
The ratio of lattice points where a plurality of conductive particles are aggregated and arranged with respect to all the lattice points of the planar lattice pattern is 15% or less, and a set of two connected conductive particles around the two aggregated conductive particles is 3 or less, and
The sum of shedding and aggregation is less than 20% ,
Regarding aggregation of the conductive particles, there are 3 or less pairs of conductive particles that are connected to each other around the two aggregated conductive particles, and regarding lack of conductive particles, 4 or more continuous in the longitudinal direction of the anisotropic conductive film. An anisotropic conductive film in which four or more continuous defects in a direction perpendicular to the longitudinal direction of the anisotropic conductive film do not intersect . The proportion of lattice points where no conductive particles are arranged with respect to all lattice points of a planar lattice pattern assumed in an arbitrary reference region of the anisotropic conductive film is less than 5%,
2. The anisotropic conductive film according to claim 1, wherein a ratio of grid points where a plurality of conductive particles are aggregated to all grid points of the planar grid pattern is more than 10% and less than 15%. The reference region is the following relational expressions (1) to (3) of the plane central portion of the anisotropic conductive film:

It is a substantially rectangular region consisting of sides X and sides Y that satisfy, where D is the average particle size of the conductive particles, and the sides Y are in the range of less than ±45° with respect to the longitudinal direction of the anisotropic conductive film 3. The anisotropic conductive film according to claim 1, wherein the side X is a straight line perpendicular to the side Y. The anisotropic anisotropic film according to any one of claims 1 to 3 , wherein the area occupancy of all the conductive particles in the area of any reference region of the anisotropic conductive film is 0.15% or more. conductive film. 5. The anisotropic conductive film according to claim 4 , wherein a particle area occupancy of all conductive particles present in the area of any 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 conductive particles have an average particle size of 1 to 30 µm. 7. The anisotropic conductive film according to any one of claims 1 to 6 , wherein the distance between adjacent lattice points of the planar lattice pattern is larger than 0.5 times the average particle diameter of the conductive particles. The anisotropic conductive film according to any one of claims 1 to 7 , wherein the direction of aggregation of the conductive particles that are aggregated and arranged is inclined with respect to the planar direction of the anisotropic conductive film. The distance between the lattice point where the agglomerated conductive particles are arranged and the center of the circle in which the agglomerated conductive particles are inscribed is 25% or less with respect to the average particle diameter of the conductive particles. 9. The anisotropic conductive film according to any one of 8 . The anisotropic conductive film according to any one of claims 1 to 9 , wherein the conductive particles are metal particles or metal-coated resin particles. 11. The anisotropic conductive film according to any one of claims 1 to 10 , wherein in the planar lattice pattern, 11 or more conductive particles are continuously arranged in a direction perpendicular to the longitudinal direction of the anisotropic conductive film. 11. The anisotropic conduction according to any one of claims 1 to 11 , wherein in the planar lattice pattern, 11 or more conductive particles are continuously arranged in each of three continuous rows along the longitudinal direction of the anisotropic conductive film. the film. 13. The anisotropic conductive film according to any one of claims 1 to 12 , wherein the aggregated conductive particles are not in contact with each other. The anisotropic conductive film according to any one of claims 1 to 13 , wherein the planar lattice pattern comprises an orthorhombic lattice, a hexagonal lattice, a square lattice, a rectangular lattice, or a parallel lattice. An anisotropic conductive film according to any preceding claim, wherein an insulating adhesive cover layer is laminated to an insulating adhesive base layer. The insulating adhesive base layer comprises 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 an epoxy compound and thermal cationic polymerization initiation. 16. The anisotropic according to any one of claims 1 to 15 , which is a thermal cationically polymerizable resin layer containing an epoxy compound and a thermal anionic polymerization initiator, or a cured resin layer thereof. conductive film. A connection structure in which a terminal of a first electrical component and a terminal of a second electrical component are anisotropically conductively connected by the anisotropic conductive film according to any one of claims 1 to 16 . Manufacture of a connection structure in which a terminal of a first electrical component and a terminal of a second electrical component are anisotropically conductively connected via the anisotropic conductive film according to any one of claims 1 to 16 . Method.

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