JP6260312B2 - Anisotropic conductive film and manufacturing method thereof - Google Patents

Description

  The present invention relates to an anisotropic conductive film and a method for producing the same.

  Anisotropic conductive films are widely used for mounting electronic components such as IC chips. Recently, from the viewpoint of application to high mounting density, improvement of conduction reliability and insulation, improvement of mounting conductive particle capture rate For the purpose of reducing manufacturing costs, etc., a two-layer anisotropic conductive film in which conductive particles for anisotropic conductive connection are arranged in a single layer on an insulating adhesive layer has been proposed (Patent Document 1). .

  In this anisotropic conductive film having a two-layer structure, conductive particles are arranged uniformly at predetermined intervals by biaxially stretching the transfer layer after conductive particles are arranged in a single layer and closely packed in the transfer layer. After forming a transfer layer, the conductive particles on the transfer layer are transferred to an insulating resin layer containing a thermosetting resin and a polymerization initiator, and the transferred conductive particles contain a thermosetting resin. However, it is manufactured by laminating another insulating resin layer that does not contain a polymerization initiator (Patent Document 1).

Japanese Patent No. 4778938

  However, since the anisotropic conductive film having a two-layer structure in Patent Document 1 uses an insulating resin layer that does not contain a polymerization initiator, the conductive particles are evenly arranged at predetermined intervals in a single layer. Nevertheless, a relatively large resin flow is likely to occur in the insulating resin layer that does not contain the polymerization initiator due to heating during anisotropic conductive connection, and the conductive particles also easily flow along the flow. For this reason, problems such as a decrease in the mounting conductive particle capture rate, the occurrence of short circuits, and a decrease in insulation have occurred.

  The object of the present invention is to solve the above-mentioned problems of the prior art, in a multilayer structure anisotropic conductive film having conductive particles arranged in a single layer, good conduction reliability, good insulation. And good mounting conductive particle capture rate.

  The present inventors fixed or temporarily fixed the conductive particles by arranging the conductive particles in a single layer on the photopolymerizable resin layer, and then irradiating with ultraviolet rays inclined from at least two directions, and further fixing or temporarily fixing the conductive particles. That the anisotropic conductive film obtained by laminating a heat or photocation, anion or radical polymerizable resin layer on the temporarily fixed conductive particles has a configuration capable of achieving the object of the present invention. The headline and the present invention have been completed.

That is, the present invention is an anisotropic conductive film having a first connection layer and a second connection layer formed on one side thereof,
The first connection layer is a photopolymerization resin layer;
The second connection layer is a heat or photocation, anion or radical polymerizable resin layer;
Conductive particles for anisotropic conductive connection are arranged in a single layer on the one surface of the first connection layer,
The anisotropic property characterized in that the curing rate of a portion relatively close to the other surface of the first connection layer in the region near the conductive particles of the first connection layer is lower than the cure rate of the one surface of the first connection layer. An electrically conductive film is provided.

  The second connection layer is preferably a thermopolymerizable resin layer using a thermal polymerization initiator that starts a polymerization reaction by heating, but photopolymerization using a photopolymerization initiator that starts a polymerization reaction by light. May be a conductive resin layer. A thermal / photopolymerizable resin layer in which a thermal polymerization initiator and a photopolymerization initiator are used in combination may be used. Here, the second connection layer may be limited to a thermopolymerizable resin layer using a thermal polymerization initiator in production.

  The anisotropic conductive film of the present invention has a third connection layer having substantially the same configuration as the second connection layer on the other surface of the first connection layer for the purpose of preventing warpage of the joined body such as stress relaxation. It may be. That is, you may have the 3rd connection layer which consists of a heat | fever or a photocation, an anion, or a radically polymerizable resin layer in the other surface of a 1st connection layer.

  The third connection layer is preferably a thermopolymerizable resin layer using a thermal polymerization initiator that initiates a polymerization reaction by heating, but photopolymerization using a photopolymerization initiator that initiates a polymerization reaction by light. May be a conductive resin layer. A thermal / photopolymerizable resin layer in which a thermal polymerization initiator and a photopolymerization initiator are used in combination may be used. Here, the third connection layer may be limited to a thermopolymerizable resin layer using a thermal polymerization initiator in production.

  Moreover, this invention is a manufacturing method of the above-mentioned anisotropic conductive film, Comprising: The following processes (A)-(C) which form a 1st connection layer by one-step photopolymerization reaction, or a 1st connection layer The manufacturing method which has process (AA)-(DD) mentioned later which forms is formed by a two-stage photopolymerization reaction is provided.

(When the first connection layer is formed by a one-step photopolymerization reaction)
Step (A)
Arranging the conductive particles in a single layer on the photopolymerizable resin layer;
Process (B)
A step of causing a photopolymerization reaction by irradiating the photopolymerizable resin layer in which the conductive particles are arranged at an inclination from at least two directions to form a first connection layer having the conductive particles fixed on the surface; and Process (C)
The process of forming the 2nd connection layer which consists of a heat | fever or a photocation, an anion, or a radically polymerizable resin layer in the electrically conductive particle side surface of a 1st connection layer.

(When the first connection layer is formed by a two-step photopolymerization reaction)
Process (AA)
Arranging the conductive particles in a single layer on the photo-radical polymerizable resin layer;
Process (BB)
A step of forming a temporary first connection layer in which conductive particles are temporarily fixed on the surface by irradiating the photopolymerizable resin layer in which the conductive particles are arranged with an ultraviolet ray inclined at least from two directions. ;
Process (CC)
Forming a second connection layer comprising a thermal cation, anion, or radical polymerizable resin layer on the surface of the temporary first connection layer on the conductive particle side; and step (DD)
A step of forming a first connection layer by subjecting the temporary first connection layer to a photopolymerization reaction by irradiating ultraviolet rays from the side opposite to the second connection layer, and finally curing the temporary first connection layer.

  The initiator used in forming the second connection layer in the step (CC) is limited to the thermal polymerization initiator in terms of product life as an anisotropic conductive film, connection and stability of the connection structure. This is to prevent adverse effects from occurring. That is, in the case where the first connection layer is irradiated with ultraviolet rays in two stages, the second connection layer may be limited to a thermosetting curable one due to restrictions on the process. In addition, when performing two-step irradiation continuously, since it can form by the process substantially the same as one step | paragraph, the equivalent effect can be anticipated.

  Moreover, this invention is a manufacturing method of the anisotropic conductive film which has the 3rd connection layer of the structure similar to a 2nd connection layer in the other surface of a 1st connection layer, Comprising: The above process (A ) To (C), after the step (C), the production method having the following step (Z), or after the step (DD) in addition to the above steps (AA) to (DD), The manufacturing method which has the following processes (Z) is provided.

Step (Z)
The process of forming the 3rd connection layer which consists of a heat | fever or a photocation, an anion, or a radically polymerizable resin layer in the surface opposite to the electroconductive particle side of a 1st connection layer.

  Furthermore, this invention is a manufacturing method of the anisotropic conductive film which has the 3rd connection layer of the structure substantially the same as the 2nd connection layer on the other surface of the 1st connection layer, Comprising: A manufacturing method having the following step (a) prior to step (A) in addition to A) to (C), or the following steps prior to step (AA) in addition to the above steps (AA) to (DD) The manufacturing method which has a process (a) is provided.

Step (a)
A step of forming a third connection layer comprising a heat or photocation, anion or radical polymerizable resin layer on one surface of the photopolymerizable resin layer.

  In the step (A) or the step (AA) of the production method having the step (a), the conductive particles may be arranged in a single layer on the other surface of the photopolymerizable resin layer.

  In the case where the third connection layer is provided in such a process, it is preferable that the polymerization initiator is limited to a thermal reaction for the reasons described above. However, if the second and third connection layers containing the photopolymerization initiator are provided by a method that does not adversely affect the product life and connection after the first connection layer is provided, the photopolymerization initiator containing the photopolymerization initiator can be obtained. There is no particular limitation on the production of the anisotropic conductive film along the gist.

  An embodiment in which either the second connection layer or the third connection layer of the present invention functions as a tack layer is also included in the present invention.

  In addition, the present invention provides a connection structure in which the first electronic component is anisotropically conductively connected to the second electronic component using the anisotropic conductive film described above.

  The anisotropic conductive film of the present invention has a first connection layer made of a photopolymerization resin layer, and a second connection layer made of a heat or photocation, anion, or radical polymerizable resin layer formed on one surface thereof. Furthermore, conductive particles for anisotropic conductive connection are arranged in a single layer on the surface of the first connection layer on the second connection layer side. For this reason, the conductive particles can be firmly fixed to the first connection layer. In addition, since the irradiation of ultraviolet rays is performed at an inclination from at least two directions, the region below the conductive particles (back side) in the first connection layer is not sufficiently irradiated with ultraviolet rays due to the presence of the conductive particles. The curing rate is lowered. In other words, in the region near the conductive particles of the first connection layer, the portion of the first connection layer that is relatively closer to the other surface of the first connection layer than the curing rate of one side (second connection layer side surface) of the first connection layer. Low cure rate. As a result, the region below the back (back side) of the conductive particles in the first connection layer exhibits good pushability, and as a result, good conduction reliability, insulation, and mounting conductive particle capture rate can be realized. In addition, the conductive particle vicinity area | region of a 1st connection layer means the area | region of 0.2 to 5 times the width of the conductive particle diameter surrounding a conductive particle. The region where the curing rate of the first connection layer resin layer is relatively low preferably exists only in the first connection layer. This is to prevent the conductive particles from shifting in directions other than the connecting direction at the time of initial pressing during connection.

  In addition, when an anisotropic conductive connection utilizes heat, it becomes the method similar to the connection method of a normal anisotropic conductive film. In the case of using light, the connection tool may be pushed in until the reaction is completed. Even in this case, the connection tool or the like is often heated to promote resin flow and particle indentation. Moreover, what is necessary is just to carry out similarly to the above also when using heat and light together.

FIG. 1 is a cross-sectional view of the anisotropic conductive film of the present invention. Drawing 2 is an explanatory view of the manufacturing process (A) of the anisotropic conductive film of the present invention. FIG. 3A is an explanatory diagram of the production process (B) of the anisotropic conductive film of the present invention. FIG. 3B is an explanatory diagram of the production process (B) of the anisotropic conductive film of the present invention. FIG. 4A is an explanatory diagram of the production process (C) of the anisotropic conductive film of the present invention. FIG. 4B is an explanatory diagram of the production process (C) of the anisotropic conductive film of the present invention. FIG. 5 is a cross-sectional view of the anisotropic conductive film of the present invention. FIG. 6 is an explanatory view of the production process (AA) of the anisotropic conductive film of the present invention. FIG. 7A is an explanatory diagram of the production process (BB) of the anisotropic conductive film of the present invention. FIG. 7B is explanatory drawing of the manufacturing process (BB) of the anisotropic conductive film of this invention. FIG. 8A is explanatory drawing of the manufacturing process (CC) of the anisotropic conductive film of this invention. FIG. 8B is explanatory drawing of the manufacturing process (CC) of the anisotropic conductive film of this invention. FIG. 9A is explanatory drawing of the manufacturing process (DD) of the anisotropic conductive film of this invention. FIG. 9B is an explanatory diagram of the production process (DD) of the anisotropic conductive film of the present invention.

<< anisotropic conductive film >>
Hereinafter, a preferable example of the anisotropic conductive film of the present invention will be described in detail.

  As shown in FIG. 1, the anisotropic conductive film 1 of the present invention has heat or photocations, anions or radicals on one side of a first connection layer 2 made of a photopolymerized resin layer obtained by photopolymerizing a photopolymerized resin layer. It has a structure in which a second connection layer 3 made of a polymerizable resin layer is formed. On the surface 2a of the first connection layer 2 on the second connection layer 3 side, the conductive particles 4 are arranged in a single layer, preferably evenly arranged for anisotropic conductive connection. Here, “equal” means a state in which the conductive particles are arranged in the plane direction. This regularity may be provided at regular intervals.

<First connection layer 2>
Since the first connection layer 2 constituting the anisotropic conductive film 1 of the present invention is a photopolymerized resin layer obtained by photopolymerizing a photopolymerizable resin layer such as a photocation, anion or radical polymerizable resin layer, Particles can be immobilized. In addition, since the resin is difficult to flow even when heated at the time of anisotropic conductive connection because it is polymerized, the occurrence of a short circuit can be greatly suppressed, thus improving conduction reliability and insulation, and capturing mounted conductive particles. The rate can also be improved. The particularly preferable first connection layer 2 is a photo radical polymerization resin layer obtained by photo radical polymerization of a photo radical polymerizable resin layer containing an acrylate compound and a photo radical polymerization initiator. Hereinafter, the case where the 1st connection layer 2 is a radical photopolymerization resin layer is demonstrated.

(Acrylate compound)
As the acrylate compound serving as the acrylate unit, a conventionally known photoradical polymerizable acrylate can be used. For example, monofunctional (meth) acrylate (here, (meth) acrylate includes acrylate and methacrylate), and bifunctional or more polyfunctional (meth) acrylate can be used. In the present invention, it is preferable to use polyfunctional (meth) acrylate for at least a part of the acrylic monomer in order to make the photo-radically polymerizable resin thermosetting.

  If the content of the acrylate compound in the first connection layer 2 is too small, the viscosity difference from the second connection layer 3 tends to be difficult, and if it is too large, the curing shrinkage tends to be large and workability tends to decrease. Preferably it is 2-70 mass%, More preferably, it is 10-50 mass%.

(Photo radical polymerization initiator)
As a radical photopolymerization initiator, it can be used by appropriately selecting from known radical photopolymerization initiators. Examples include acetophenone photopolymerization initiators, benzyl ketal photopolymerization initiators, and phosphorus photopolymerization initiators.

  If the amount of the radical photopolymerization initiator used is too small relative to 100 parts by mass of the acrylate compound, the radical photopolymerization will not proceed sufficiently, and if too large, it will cause a decrease in rigidity, so preferably 0.1 to 25 masses. Part, more preferably 0.5 to 15 parts by mass.

(Conductive particles)
The conductive particles can be appropriately selected from those used in conventionally known anisotropic conductive films. For example, metal particles such as nickel, cobalt, silver, copper, gold, and palladium, metal-coated resin particles, and the like can be given. Two or more kinds can be used in combination.

  The average particle size of the conductive particles is too small to absorb the variation in the height of the wiring and tends to increase the resistance, and if it is too large, it tends to cause a short circuit, preferably 1 to 10 μm, More preferably, it is 2-6 micrometers.

  If the amount of such conductive particles in the first connection layer 2 is too small, the number of trapped conductive particles is reduced and anisotropic conductive connection becomes difficult. The number is preferably 50 to 50000 per square mm, more preferably 200 to 30000.

  For the first connection layer 2, a film forming resin such as a phenoxy resin, an epoxy resin, an unsaturated polyester resin, a saturated polyester resin, a urethane resin, a butadiene resin, a polyimide resin, a polyamide resin, or a polyolefin resin is used in combination as necessary. be able to. Similarly, the second connection layer 3 and the third connection layer 5 may be used together.

  If the layer thickness of the first connection layer 2 is too thin, the mounting conductive particle trapping rate tends to decrease, and if it is too thick, the conduction resistance tends to increase, so that it is preferably 1.0 to 6.0 μm, more preferably. Is 2.0 to 5.0 μm.

  The first connection layer 2 can further contain an epoxy compound and heat, a photocation or an anionic polymerization initiator. In this case, as will be described later, the second connection layer 3 is also preferably a heat or photocation or anion polymerizable resin layer containing an epoxy compound and heat or a photocation or anion polymerization initiator. Thereby, delamination strength can be improved. The epoxy compound and the heat or photocation or anion polymerization initiator will be described in the second connection layer 3.

  In the first connection layer 2, as shown in FIG. 1, the conductive particles 4 bite into the second connection layer 3 (in other words, the conductive particles 4 are exposed on the surface of the first connection layer 2. Is preferred. This is because when all the conductive particles are buried in the first connection layer 2, there is a concern that the resistance conduction is increased. The degree of biting is preferably 10 to 90%, more preferably 20 to 80% of the average particle diameter of the conductive particles, from the viewpoint of improving the mounting conductive particle capture rate and reducing the conduction resistance.

  Moreover, in the 1st connection layer 2, rather than the hardening rate of the single side | surface (2nd connection layer side surface) (1st connection layer part 2Y) of the 1st connection layer 2, out of the electroconductive particle vicinity area | region of the 1st connection layer 2 It is preferable that the curing rate of the portion (first connection layer portion 2X) that is relatively close to the other surface (outermost surface 2b) of the first connection layer 2 is low. As a result, the first connection layer portion 2X is easily removed during the thermocompression bonding of the anisotropic conductive connection, and the conduction reliability is improved. Here, the curing rate is a numerical value defined as a vinyl group reduction ratio, the curing rate of the first connection layer portion 2X is preferably 40 to 80%, and the curing rate of the first connection layer portion 2Y is preferably 70 to 100%.

  The radical photopolymerization at the time of forming the first connection layer 2 may be performed in one step (that is, one time of light irradiation), but may be performed in two steps (that is, two times of light irradiation). Good. In this case, the second-stage light irradiation is performed from the other surface side of the first connection layer 2 in an oxygen-containing atmosphere (in the atmosphere) after the second connection layer 3 is formed on one surface of the first connection layer 2. It is preferable. Thereby, it can be expected that the radical polymerization reaction is oxygen-inhibited, the surface concentration of the uncured component is increased, and tackiness can be improved. In addition, since the polymerization reaction is complicated by performing the curing in two stages, it can be expected that the fluidity of the resin and particles can be precisely controlled.

  The curing rate in the first stage of the first connection layer portion 2X in the two-stage photoradical polymerization is preferably 10 to 50%, and the curing ratio in the second stage is preferably 40 to 80%. The curing rate in the first stage of the one connection layer portion 2Y is preferably 30 to 90%, and the curing rate in the second stage is preferably 70 to 100%.

  Further, when the photoradical polymerization reaction at the time of forming the first connection layer 2 is performed in two stages, only one type can be used as the radical polymerization initiator, but two types with different wavelength bands for starting the radical reaction can be used. The radical photopolymerization initiator is preferably used for improving tackiness. For example, IRGACURE 369 (BASF Japan Co., Ltd.) that initiates a radical reaction with light having a wavelength of 365 nm from an LED light source, and IRGACURE 2959 (BASF) that initiates a radical reaction with light from a high-pressure mercury lamp light source. Japan) is preferably used in combination. As described above, since the bonding of the resin is complicated by using two different curing agents, it becomes possible to more precisely control the behavior of the thermal flow of the resin at the time of connection. This is because, when the anisotropic conductive connection is pushed in, the particles are easily subjected to a force in the thickness direction, but the flow in the surface direction is suppressed, so that the effect of the present invention is more easily manifested.

  Further, the minimum melt viscosity when measured with the rheometer of the first connection layer 2 is higher than the minimum melt viscosity of the second connection layer 3, specifically, [the minimum melt viscosity of the first connection layer 2 (mPa The numerical value of s)] / [minimum melt viscosity (mPa · s) of the second connection layer 3] is preferably 1 to 1000, more preferably 4 to 400. In addition, each preferable minimum melt viscosity is 100-100000 mPa * s about the former, More preferably, it is 500-50000 mPa * s. About the latter, Preferably it is 0.1-10000 mPa * s, More preferably, it is 0.5-1000 mPa * s.

The first connection layer 2 is formed on a photo radical polymerizable resin layer containing a photo radical polymerizable acrylate and a photo radical polymerization initiator by a film transfer method, a mold transfer method, an ink jet method, an electrostatic adhesion method, or the like. Conductive particles can be attached by a technique, and ultraviolet rays can be irradiated from the conductive particle side, the opposite side, or both sides. In particular, it is preferable to irradiate ultraviolet rays only from the conductive particle side from the viewpoint that the curing rate of the first connection layer portion 2X can be suppressed relatively low.
<Second connection layer 3>

  The second connection layer 3 is a heat or photocation, anion or radical polymerizable resin layer, preferably a heat or photocation or anion polymerizable resin layer containing an epoxy compound and a heat or photocation or anion polymerization initiator, or It consists of a heat or photo radical polymerizable resin layer containing an acrylate compound and a heat or photo radical polymerization initiator. Here, the formation of the second connection layer 3 from the thermopolymerizable resin layer means that the polymerization reaction of the second connection layer 3 does not occur due to the ultraviolet irradiation when the first connection layer 2 is formed. And desirable in terms of quality stability.

  When the second connection layer 3 is a heat, photocation or anion polymerizable resin layer, it can further contain an acrylate compound and a heat or photo radical polymerization initiator. Thereby, the 1st connection layer 2 and delamination strength can be improved.

(Epoxy compound)
When the second connection layer 3 is a heat or photocation or anion polymerizable resin layer containing an epoxy compound and a heat or photocation or anion polymerization initiator, the epoxy compound has two or more epoxy groups in the molecule. Preferred are compounds or resins having These may be liquid or solid.

(Thermal cationic polymerization initiator)
As the thermal cationic polymerization initiator, those known as the thermal cationic polymerization initiator of the epoxy compound can be adopted, for example, those which generate an acid capable of cationically polymerizing the cationic polymerizable compound by heat. Iodonium salts, sulfonium salts, phosphonium salts, ferrocenes, and the like can be used, and aromatic sulfonium salts exhibiting good potential with respect to temperature can be preferably used.

  If the amount of the thermal cationic polymerization initiator is too small, curing tends to be poor, and if it is too much, product life tends to decrease. Therefore, it is preferably 2 to 60 masses per 100 mass parts of the epoxy compound. Part, more preferably 5 to 40 parts by weight.

(Thermal anionic polymerization initiator)
As the thermal anionic polymerization initiator, those known as the thermal anionic polymerization initiator of the epoxy compound can be employed. For example, a base capable of anionic polymerization of the anionic polymerizable compound is generated by heat, and is publicly known. Aliphatic amine compounds, aromatic amine compounds, secondary or tertiary amine compounds, imidazole compounds, polymercaptan compounds, boron trifluoride-amine complexes, dicyandiamide, organic acid hydrazides, etc. can be used. An encapsulated imidazole compound showing good potential with respect to temperature can be preferably used.

  If the amount of the thermal anionic polymerization initiator is too small, it tends to be poorly cured, and if it is too much, the product life tends to decrease. Therefore, it is preferably 2 to 60 masses per 100 parts by mass of the epoxy compound. Part, more preferably 5 to 40 parts by weight.

(Photocationic polymerization initiator and photoanionic polymerization initiator)
A well-known thing can be used suitably as a photocationic polymerization initiator or photoanion polymerization initiator for epoxy compounds.

(Acrylate compound)
When the second connection layer 3 is a heat or photo radical polymerizable resin layer containing an acrylate compound and a heat or photo radical polymerization initiator, the acrylate compound is appropriately selected from those described for the first connection layer 2 Can be used.

(Thermal radical polymerization initiator)
Further, examples of the thermal radical polymerization initiator include organic peroxides and azo compounds, but organic peroxides that do not generate nitrogen that causes bubbles can be preferably used.

  If the amount of the thermal radical polymerization initiator used is too small, curing will be poor, and if it is too large, the product life will be reduced. Therefore, the amount is preferably 2 to 60 parts by weight, more preferably 5 to 40 parts per 100 parts by weight of the acrylate compound. Part by mass.

(Photo radical polymerization initiator)
As a radical photopolymerization initiator for the acrylate compound, a known radical photopolymerization initiator can be used.

  If the amount of the radical photopolymerization initiator used is too small, curing will be poor, and if it is too large, the product life will be reduced. Therefore, the amount is preferably 2 to 60 parts by weight, more preferably 5 to 40 parts per 100 parts by weight of the acrylate compound. Part by mass.

(Third connection layer 5)
The anisotropic conductive film having the two-layer structure in FIG. 1 has been described above, but the third connection layer 5 may be formed on the other surface of the first connection layer 2 as shown in FIG. Thereby, the effect that it becomes possible to control the fluidity | liquidity of the whole layer more precisely is acquired. Here, the third connection layer 5 may have the same configuration as the second connection layer 3 described above. That is, the third connection layer 5 is made of a heat or photocation, anion, or radical polymerizable resin layer, like the second connection layer 3. The third connection layer 5 may be formed on the other surface of the first connection layer after the second connection layer is formed on one surface of the first connection layer. Before the second connection layer is formed, the third connection layer 5 may be formed. The third connection layer may be formed in advance on the other surface (the surface on which the second connection layer is not formed) of one connection layer or a photopolymerizable resin layer that is a precursor thereof.

<< Method for Manufacturing Anisotropic Conductive Film >>
Examples of the method for producing an anisotropic conductive film of the present invention include a production method for carrying out a one-stage photopolymerization reaction and a production method for carrying out a two-stage photopolymerization reaction.

<Production method for carrying out one-step photopolymerization reaction>
An example in which the anisotropic conductive film of FIG. 1 (FIG. 4B) is produced by photopolymerization in one step will be described. This production example has the following steps (A) to (C).

(Process (A))
As shown in FIG. 2, the conductive particles 4 are arranged in a single layer on the photopolymerizable resin layer 31 formed on the release film 30 as necessary. The method for arranging the conductive particles 4 is not particularly limited, and a method using a biaxial stretching operation for the unstretched polypropylene film of Example 1 of Japanese Patent No. 4778938, or a mold disclosed in JP 2010-33793 A is used. The method used can be adopted. The degree of arrangement is preferably two-dimensionally separated from each other by about 1 to 100 μm in consideration of the size of the connection target, conduction reliability, insulation, mounting conductive particle capture rate, and the like.

(Process (B))
Next, as shown in FIG. 3A, the photopolymerizable resin layer 31 in which the conductive particles 4 are arranged is irradiated with ultraviolet rays (UV) inclined from at least two directions from the conductive particle side using an LED light source or the like. By doing so, a photopolymerization reaction is performed to form the first connection layer 2 on the surface of which the conductive particles 4 are fixed. As a result, as shown in FIG. 3B, the first connection layer portion 2X in the region located between the conductive particles 4 and the outermost surface of the first connection layer 2 (in other words, the back side of the conductive particles of the first connection layer). The curing rate of the portion) can be made lower than the curing rate of the first connection layer portion 2Y in the region located between the conductive particles 4 adjacent to each other. In other words, in the first connection layer 2, the first connection layer 2 in the region near the conductive particles of the first connection layer 2 is harder than the curing rate of the first connection layer portion 2 Y of the first connection layer 2 on the second connection layer side. The curing rate of the portion (first connection layer portion 2X) that is relatively close to the other surface (outermost surface 2b) of the connection layer 2 can be reduced. By doing in this way, the hardening rate of the back side part of the 1st connection layer of a conductive particle becomes low reliably, it becomes easy to push in at the time of joining, and it also becomes possible to prevent a flow of conductive particles.

  The directions in “inclined from at least two directions” are directions intersecting each other, and these directions may not be in the same plane. In the case of two directions, it is preferable to incline axisymmetrically in a plane perpendicular to the photopolymerizable resin layer 31. The inclination angle θ is preferably 0 ° <θ ≦ 90 °, more preferably 30 ° ≦ θ ≦ 60 ° with respect to the photopolymerizable resin layer 31. The plurality of directions preferably have the same inclination angle, but may have different inclination angles. For example, there is a case where one inclination angle θ is 30 ° and the other inclination angle θ is 60 °, or one is 90 ° and the other is 30 °. Thus, by irradiating with light inclined from two or more directions, the first connection layer portion 2X, which is a region having a relatively low curing rate, can be localized on the back side portion of the conductive particles. Further, the position of the first connection layer portion 2X can be controlled by making the inclination angles in the two directions asymmetric.

(Process (C))
Next, as shown in FIG. 4A, the second connection layer 3 made of heat, photocation, anion, or radical polymerizable resin layer is formed on the surface of the first connection layer 2 on the conductive particle 4 side. As a specific example, the second connection layer 3 formed on the release film 40 by a conventional method is placed on the surface of the first connection layer 2 on the conductive particle 4 side, and thermocompression-bonded to such an extent that excessive thermal polymerization does not occur. Then, by removing the release films 30 and 40, the anisotropic conductive film of FIG. 4B can be obtained.

In addition, the anisotropic conductive film 100 of FIG. 5 can be obtained by implementing the following processes (Z) after a process (C).
(Process (Z))
A third connection layer made of a heat, photocation, anion, or radical polymerizable resin layer is formed on the opposite surface of the first connection layer on the conductive particle side, preferably in the same manner as the second connection layer. Thereby, the anisotropic conductive film of FIG. 5 can be obtained.

  Moreover, the anisotropic conductive film 100 of FIG. 5 can also be obtained by performing the following process (a) prior to the process (A) without performing the process (Z).

(Process (a))
This step is a step of forming a third connection layer made of heat, photocation, anion, or radical polymerizable resin layer on one side of the photopolymerizable resin layer. Subsequent to the step (a), the anisotropic conductive film 100 of FIG. 5 can be obtained by carrying out the steps (A), (B) and (C). However, in the step (A), the conductive particles are arranged in a single layer on the other surface of the photopolymerizable resin layer.

(Manufacturing method that performs a two-stage photopolymerization reaction)
Next, an example of producing the anisotropic conductive film of FIG. 1 (FIG. 4B) by photopolymerization in two steps will be described. This production example includes the following steps (AA) to (DD).

(Process (AA))
As shown in FIG. 6, the conductive particles 4 are arranged in a single layer on the photopolymerizable resin layer 31 formed on the release film 30 as necessary. The method for arranging the conductive particles 4 is not particularly limited, and a method using a biaxial stretching operation for the unstretched polypropylene film of Example 1 of Japanese Patent No. 4778938, or a mold disclosed in JP 2010-33793 A is used. The method used can be adopted. The degree of arrangement is preferably two-dimensionally separated from each other by about 1 to 100 μm in consideration of the size of the connection target, conduction reliability, insulation, mounting conductive particle capture rate, and the like.

(Process (BB))
Next, as shown in FIG. 7A, the photopolymerizable resin layer 31 in which the conductive particles 4 are arranged is irradiated with ultraviolet rays (UV) inclined from at least two directions from the conductive particle side to cause a photopolymerization reaction. The temporary first connection layer 20 in which the conductive particles 4 are temporarily fixed is formed on the surface. As a result, as shown in FIG. 7B, the curing rate of the temporary first connection layer portion 2X in the region located between the conductive particles 4 and the outermost surface of the temporary first connection layer 20 is set to the conductive particles 4 adjacent to each other. It can be made lower than the curing rate of the temporary first connection layer portion 2Y in the region located therebetween. In other words, in the first connection layer 20, the conductivity of the temporary first connection layer 20 is higher than the curing rate of one surface (second connection layer side surface) of the temporary first connection layer 20 (temporary first connection layer portion 2Y). The hardening rate of the part (provisional 1st connection layer part 2X) relatively close to the other surface (outermost surface 2b) of the temporary 1st connection layer 20 among particle | grain vicinity area | regions can be made low.

(Process (CC))
Next, as shown in FIG. 8A, the second connection layer 3 made of a thermal cation, anion, or radical polymerizable resin layer is formed on the surface of the temporary first connection layer 20 on the conductive particle 4 side. As a specific example, the second connection layer 3 formed on the release film 40 by a conventional method is placed on the surface of the first connection layer 2 on the conductive particle 4 side, and thermocompression-bonded to such an extent that excessive thermal polymerization does not occur. Then, the temporary anisotropic conductive film 50 of FIG. 8B can be obtained by removing the release films 30 and 40.

(Process (DD))
Next, as shown in FIG. 9A, by using an LED light source or the like, the temporary first connection layer 20 is irradiated with ultraviolet rays from the side opposite to the second connection layer 3 to cause a photopolymerization reaction. Is hardened to form the first connection layer 2. Thereby, the anisotropic conductive film 1 of FIG. 9B can be obtained. The irradiation with ultraviolet rays in this step is preferably performed from a direction perpendicular to the temporary first connection layer 20. Moreover, it is preferable to irradiate through a mask so that the curing rate difference between the first connection layer portions 2X and 2Y does not disappear, or to provide a difference in the amount of irradiation light depending on the irradiation site.

  When photopolymerization is performed in two stages, the anisotropic conductive film 100 in FIG. 5 can be obtained by performing the following step (Z) after the step (DD).

(Process (Z))
A third connection layer made of a heat, photocation, anion, or radical polymerizable resin layer is formed on the opposite surface of the first connection layer on the conductive particle side, preferably in the same manner as the second connection layer. Thereby, the anisotropic conductive film of FIG. 5 can be obtained.

  Moreover, the anisotropic conductive film 100 of FIG. 5 can also be obtained by performing the following process (a) prior to the process (AA) without performing the process (Z).

(Process (a))
This step is a step of forming a third connection layer made of heat, photocation, anion, or radical polymerizable resin layer on one side of the photopolymerizable resin layer. Subsequent to the step (a), the anisotropic conductive film 100 of FIG. 5 can be obtained by performing the steps (AA) to (DD). However, in the step (AA), the conductive particles are arranged in a single layer on the other surface of the photopolymerizable resin layer. In this case, it is preferable to apply a thermal polymerization initiator as a polymerization initiator used in forming the second connection layer. In the case of a photopolymerization initiator, there is a concern that the product life as an anisotropic conductive film, connection, and stability of the connection structure may be adversely affected in the process.

<< Connection structure >>
The anisotropic conductive film thus obtained is preferably applied when anisotropically conductively connecting a first electronic component such as an IC chip or IC module and a second electronic component such as a flexible substrate or a glass substrate. can do. The connection structure thus obtained is also part of the present invention. Note that the first connection layer side of the anisotropic conductive film is disposed on the second electronic component side such as a flexible substrate, and the second connection layer side is disposed on the first electronic component side such as an IC chip. It is preferable from the point of improving the property.

  Hereinafter, the present invention will be specifically described by way of examples.

Examples 1-6, Comparative Examples 1-2
The conductive particles are arranged in accordance with the operation of Example 1 of Japanese Patent No. 4778938, and the difference in the two-layer structure in which the first connection layer and the second connection layer are laminated according to the formulation (parts by mass) shown in Table 1. An anisotropic conductive film was prepared.

(First connection layer)
Specifically, first, a mixed solution of an acrylate compound, a radical photopolymerization initiator, and the like was prepared using ethyl acetate or toluene so that the solid content was 50% by mass. This mixed solution is applied to a polyethylene terephthalate film having a thickness of 50 μm so as to have a dry thickness of 5 μm, and dried in an oven at 80 ° C. for 5 minutes, whereby radical photopolymerization that is a precursor layer of the first connection layer is performed. A functional resin layer was formed.

Next, conductive particles (Ni / Au plating resin particles, AUL704, Sekisui Chemical Co., Ltd.) having an average particle diameter of 4 μm are arranged in a single layer with a separation of 4 μm from the obtained photoradical polymerizable resin layer. I let you. Furthermore, the surface of the conductive particles is irradiated to the radical photopolymerizable resin layer from the LED light source with ultraviolet light having a wavelength of 365 nm and an integrated light amount of 4000 mJ / cm ² from the LED light source in the direction and angle shown in Table 1. Formed a first connection layer.

  In Examples 1 to 3, ultraviolet rays were applied to the photo-radical polymerizable resin layer from the conductive particle side from two directions each having an angle of 60 ° and an included angle of 60 ° within a vertical plane. In Example 4, the photoradical polymerizable resin layer was irradiated with ultraviolet rays from two directions in which an angle of 60 ° and 30 ° and an included angle of 90 ° were formed in a vertical plane from the conductive particle side. In Example 5, the photoradical polymerizable resin layer was irradiated from the conductive particle side with ultraviolet rays from two directions at an angle of 90 ° and 30 ° and an included angle of 60 ° in a vertical plane. In Example 6, the photoradical polymerizable resin layer was irradiated with ultraviolet rays from the conductive particle side from two directions, ie, a 90 ° direction and a 60 ° angle and a included angle of 30 ° within a vertical plane. In Comparative Example 1, ultraviolet rays were irradiated at an angle of 90 ° from the back surface of the photoradical polymerizable resin layer (the surface on the side where the conductive particles are not arranged). In Comparative Example 2, on the contrary, the photoradical polymerizable resin layer was irradiated with ultraviolet rays in one direction at 90 ° from the conductive particle side.

(Second connection layer)
A liquid mixture of a thermosetting resin and a latent curing agent was prepared with ethyl acetate or toluene so that the solid content was 50% by mass. This mixed solution was applied to a polyethylene terephthalate film having a thickness of 50 μm so as to have a dry thickness of 12 μm, and dried in an oven at 80 ° C. for 5 minutes to form a second connection layer.

(Anisotropic conductive film)
An anisotropic conductive film was obtained by laminating the first connection layer and the second connection layer thus obtained so that the conductive particles were inside.

(Connection structure sample)
Using the obtained anisotropic conductive film, an IC chip (bump size 30 × 85 μm: bump height 15 μm, bump pitch 50 μm) of 0.5 × 1.8 × 20.0 mm is 0.5 × Temporarily attached to a glass wiring board (1737F) manufactured by Corning with a size of 50 × 30 mm under conditions of 50 ° C., 5 MPa, and 1 second, and further mounted and connected under conditions of 180 ° C., 80 MPa, and 5 seconds. A structural sample body was obtained.

(Test evaluation)
About the obtained connection structure sample body, “the thickness ratio (%) at which the curing rate of the first connection layer is 90% or more”, “the ratio of conductive particles on the bump edge (%)”, “bump The “average distance between conductive particles (μm) in the plane” and “the behavior of the conductive particles in the bump plane at the time of connection” were examined as described below. The obtained results are shown in Table 1.

“Thickness ratio (%) of 90% or more of the first connection layer”
A portion where the cross section of the first connection layer is exposed by cross-sectional polishing from the connection structure sample body, the presence or absence of a vinyl group in the vicinity of the exposed conductive particles is IR-measured, and the curing rate with respect to the total thickness is 90% or more The thickness ratio was determined.

“Percentage of conductive particles on bump edge (%)”
When creating the connection structure sample body, the number of conductive particles on the bump edge (the outer edge of the bump 6 μm wide) at the time of temporary attachment is counted using an optical microscope, and it exists on the same outer edge after mounting. The number of conductive particles was counted, and the ratio of the number of conductive particles after mounting to the number of conductive particles at the time of temporary attachment was determined.

“Average distance between conductive particles in the bump plane (μm)”
For 100 conductive particles in the bump plane of the connection structure sample body, the distance between the conductive particles was measured using an optical microscope, and the arithmetic average of the measurement results was obtained to obtain the average distance between the conductive particles.

  From Table 1, about the anisotropic conductive film of Examples 1-6, it hardens | cures in the area | region (1st connection layer surface direction on the opposite side to a 2nd connection layer) of the 1st connection layer in the area | region below the electroconductive particle adjacent area | region. Since the ratio of the thickness where the rate is 90% or more is 20 to 90%, in order to prevent the displacement of the conductive particles during mounting, in other words, it is pushed in well while suppressing the movement in the plane direction. As a result, it can be seen that the distance between the conductive particles on the bump is difficult to change, and the ratio of the conductive particles flowing out of the bump from the bump edge is greatly reduced. From this, it can be seen that good conduction reliability, good insulating properties, and good mounting conductive particle capture rate can be realized.

  On the other hand, for the anisotropic conductive film of Comparative Example 1, since the entire first connection layer has a curing rate of 90% or more, it cannot be pushed in well while suppressing movement in the plane direction. As a result, it can be seen that the distance between the conductive particles on the bumps is increased, and the ratio of the conductive particles flowing out of the bumps from the bump edges is greatly increased. The anisotropic conductive film of Comparative Example 2 was irradiated with ultraviolet rays from the direction of 90 ° (vertical direction) from the conductive particle side instead of ultraviolet irradiation from two directions. Since the rate of curing is less than 10% and is too small, it cannot be pushed in well while suppressing the movement in the plane direction as compared with Examples 1 to 3, and as a result, the conductivity on the bumps It can be seen that the distance between the particles has increased, and the rate at which the conductive particles have flowed out of the bump from the bump edge has been greatly increased.

  The anisotropic conductive film of the present invention has a two-layer structure in which a first connection layer made of a photopolymerization resin layer and a second connection layer made of a heat or photocation, anion or radical polymerizable resin layer are laminated. Furthermore, conductive particles for anisotropic conductive connection are arranged in a single layer on the surface of the first connection layer on the second connection layer side. Moreover, the curing rate of the portion relatively close to the other surface of the first connection layer in the region near the conductive particles of the first connection layer, rather than the cure rate of one surface (second connection layer side surface) of the first connection layer. Is low. For this reason, favorable conduction | electrical_connection reliability, insulation, and a mounting conductive particle capture rate are shown. Therefore, it is useful for anisotropic conductive connection of an electronic component such as an IC chip to a wiring board. The wiring of such electronic parts is being narrowed, and the present invention particularly exhibits its effect when it contributes to such technical progress.

DESCRIPTION OF SYMBOLS 1,100 Anisotropic conductive film 2 1st connection layer 2X, 2Y 1st connection layer part 3 2nd connection layer 4 Conductive particle 5 3rd connection layer 30, 40 Release film 20 Temporary 1st connection layer 31 Photopolymerizable resin Layer 50 Temporary anisotropic conductive film

Claims (17)

An anisotropic conductive film having a first connection layer and a second connection layer formed on one side thereof,
The first connection layer is a photopolymerization resin layer;
The second connection layer is a heat or photocation, anion or radical polymerizable resin layer;
Conductive particles for anisotropic conductive connection are arranged in a single layer on the one surface of the first connection layer,
The curing rate of the back side portion of the conductive particles relatively close to the other surface of the first connection layer in the region near the conductive particles of the first connection layer is lower than the cure rate of the one surface and the other surface of the first connection layer. An anisotropic conductive film characterized by that. An anisotropic conductive film having a first connection layer and a second connection layer formed on one side thereof,
The first connection layer is a photopolymerization resin layer;
The second connection layer is a heat or photocation, anion or radical polymerizable resin layer;
Conductive particles for anisotropic conductive connection are provided on the one surface of the first connection layer at regular intervals in the plane direction of the anisotropic conductive film,
The curing rate of the back side portion of the conductive particles relatively close to the other surface of the first connection layer in the region near the conductive particles of the first connection layer is lower than the cure rate of the one surface and the other surface of the first connection layer.
An anisotropic conductive film characterized by that. The anisotropic conductive film according to claim 1 or 2 , wherein the first connection layer is a photo radical polymerization resin layer obtained by photo radical polymerization of a photo radical polymerizable resin layer containing an acrylate compound and a photo radical polymerization initiator. First connection layer, further, et epoxy compound and heat or light cation or anisotropic conductive film according to claim 3, wherein containing the anionic polymerization initiator. The second connection layer is a heat containing an epoxy compound and heat or a photocation or anion polymerization initiator, or a heat or photocation or anion polymerizable resin layer, or a heat containing an acrylate compound and a heat or radical polymerization initiator, or It is a radical photopolymerizable resin layer, The anisotropic conductive film in any one of Claims 1-4 . The second connection layer is a heat or photocation or anion polymerizable resin layer containing an epoxy compound and heat or a photocation or anion polymerization initiator, and further contains an acrylate compound and a heat or photoradical polymerization initiator. The anisotropic conductive film according to claim 5 . Conductive particles, an anisotropic conductive film according to any one of claims 1 to 6 which bite into the second connecting layer. The anisotropic conductive film according to any one of claims 1 to 7 , wherein the minimum melt viscosity of the first connection layer is higher than the minimum melt viscosity of the second connection layer. It is a manufacturing method of the anisotropic conductive film of Claim 1 or 2 , Comprising: The following processes (A)-(C):
Step (A)
Arranging the conductive particles in a single layer on the photopolymerizable resin layer;
Process (B)
A step of causing a photopolymerization reaction by irradiating the photopolymerizable resin layer in which the conductive particles are arranged at an inclination from at least two directions to form a first connection layer having the conductive particles fixed on the surface; and Process (C)
The manufacturing method which has the process of forming the 2nd connection layer which consists of a heat | fever or a photocation, an anion, or a radically polymerizable resin layer in the electrically conductive particle side surface of a 1st connection layer. The manufacturing method of Claim 9 which performs the ultraviolet irradiation of a process (B) from the side in which the electrically conductive particle of the photopolymerizable resin layer arranged. It is a manufacturing method of the anisotropic conductive film of Claim 1 or 2 , Comprising: The following processes (AA)-(DD):
Process (AA)
Arranging the conductive particles in a single layer on the photopolymerizable resin layer;
Process (BB)
A step of forming a temporary first connection layer in which conductive particles are temporarily fixed on the surface by irradiating the photopolymerizable resin layer in which the conductive particles are arranged with an ultraviolet ray inclined at least from two directions. ;
Process (CC)
Forming a second connection layer comprising a thermal cation, anion, or radical polymerizable resin layer on the surface of the temporary first connection layer on the conductive particle side; and step (DD)
The manufacturing method which has a process which carries out photopolymerization reaction by irradiating a temporary 1st connection layer by irradiating an ultraviolet-ray from the opposite side to a 2nd connection layer, and main-hardens a temporary 1st connection layer, and forms a 1st connection layer. The manufacturing method of Claim 11 which performs the ultraviolet irradiation of a process (BB) from the side in which the electrically conductive particle of the photopolymerizable resin layer arranged. The manufacturing method according to claim 9 , wherein after the step (C), the following step (Z):
Step (Z)
The manufacturing method which has the process of forming the 3rd connection layer which consists of a heat | fever or a photocation, an anion, or a radically polymerizable resin layer in the surface opposite to the electroconductive particle side of a 1st connection layer. 10. The manufacturing method according to claim 9 , wherein the following step (a) is performed prior to step (A).
Step (a)
A step of forming a third connection layer comprising a heat or photocationic, anionic or radically polymerizable resin layer on one side of the photopolymerizable resin layer; in step (A), on the other side of the photopolymerizable resin layer; A manufacturing method in which conductive particles are arranged in a single layer. The manufacturing method according to claim 11 , wherein after the step (DD), the following step (Z):
Step (Z)
The manufacturing method which has the process of forming the 3rd connection layer which consists of a heat | fever or a photocation, an anion, or a radically polymerizable resin layer in the surface opposite to the electroconductive particle side of a 1st connection layer. The manufacturing method according to claim 11 , wherein the following step (a) is performed prior to step (AA).
Step (a)
A step of forming a third connection layer made of heat, photocation, anion, or radical polymerizable resin layer on one side of the photopolymerizable resin layer; and in step (AA), on the other side of the photopolymerizable resin layer A manufacturing method in which conductive particles are arranged in a single layer. The connection structure which anisotropically connected the 1st electronic component to the 2nd electronic component with the anisotropic conductive film in any one of Claims 1-8 .

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