JP6217422B2 - 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 them with an inclined ultraviolet ray, and further fixing or temporarily fixing the conductive particles. The present inventors have found that an anisotropic conductive film obtained by laminating a heat or photocation, anion, or radical polymerizable resin layer on a conductive particle has a configuration capable of achieving the above-described object of the present invention. It came to complete.

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,
Regarding the curing rate of the first connection layer, an anisotropic conductive film characterized in that a region having a curing rate lower than the curing rate of one side is present obliquely in the thickness direction of the first connection layer I will provide a.

  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 the process (AA)-(DD) mentioned later which forms is formed by two-stage photoradical polymerization reaction is provided.

(When the first connection layer is formed by a one-step photopolymerization reaction)
Process (A)
Arranging the conductive particles in a single layer on the photopolymerizable resin layer;
Process (B)
A step of forming a first connection layer in which conductive particles are fixed on the surface by subjecting the photopolymerizable resin layer in which the conductive particles are arranged to a photo-radical polymerization reaction by irradiating with ultraviolet rays; and a step (C )
The process of forming the 2nd connection layer which consists of a heat | fever or photocationic or anion polymerizable resin layer, or a heat | fever or radical photopolymerizable resin layer in the 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 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 causing photo-radical polymerization reaction by irradiating the photopolymerizable resin layer in which the conductive particles are arranged with tilting ultraviolet rays;
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 first connection layer is cured with light irradiation obliquely, a region having a cure rate lower than the cure rate on the surface of the second connection layer is inclined in the thickness direction of the first connection layer. Exist in line. As a result, in the anisotropic conductive connection, the region of low curing rate and the direction of flow of the conductive particles can be aligned in the oblique direction, so that a short-circuit can be generated without impairing the initial conduction characteristics and conduction reliability. It can be greatly suppressed.

  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 a photocation, an anion, or the like on one side of a first connection layer 2 composed of a photopolymerized resin layer obtained by photopolymerizing a photopolymerizable resin layer. It has a structure in which a second connection layer 3 made of a radical 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 it is polymerized, it becomes difficult for the resin to flow even when heated at the time of anisotropic conductive connection, so the occurrence of a short circuit can be greatly suppressed, thus improving the conduction reliability and insulation, and the mounting particle capture 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 a polyfunctional (meth) acrylate for at least a part of the acrylic monomer in order to make the adhesive 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. You may use together similarly to a 2nd connection layer and a 3rd connection layer.

  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 may further contain an epoxy compound and a heat, photocation, or 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. If the degree of biting is too small, the mounting conductive particle trapping rate tends to decrease, and if it is too large, the conduction resistance tends to increase. Therefore, it is preferably 10 to 90% of the average particle diameter of the conductive particles, more preferably. 20 to 80%.

  In addition, since light irradiation is performed obliquely in the first connection layer 2, the region having a curing rate lower than the curing rate of the surface of the first connection layer on the second connection layer side is the thickness of the first connection layer. It exists obliquely in the direction. 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, curing tends to be poor, and if too much, the product life tends to decrease. 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, light is irradiated by inclining ultraviolet rays (UV) from the conductive particle side to the photopolymerizable resin layer 31 in which the conductive particles 4 are arranged using an LED light source or the like. The first connection layer 2 having the conductive particles 4 fixed on the surface is formed by a polymerization reaction. As a result, as shown in FIG. 3B, the curing rate of the skewed first connection layer portion 2X located between the conductive particles 4 and the outermost surface of the first connection layer 2 is determined between the adjacent conductive particles 4. It can be made lower than the curing rate of the first connection layer portion 2Y in the region located at. At the time of irradiation, ultraviolet rays may be irradiated in a pulse shape as necessary, or a shutter may be provided for irradiation. By doing so, the curability of the back side of the particles is surely lowered, the pushing at the time of joining is facilitated, the flow direction of the conductive particles can be aligned in the oblique direction, and a plurality of conductive particles are excessively connected. Can be prevented, and occurrence of a short circuit can be suppressed.

  To irradiate with ultraviolet rays is to irradiate the photopolymerizable resin layer 31 with ultraviolet rays at an inclination angle θ. The inclination angle θ is 0 ° <θ <90 °, preferably 30 ° ≦ θ ≦ 60 °. In this case, it is preferable to incline in the direction orthogonal to the longitudinal direction of the anisotropic conductive film. If it does in this way, the direction of flow of conductive particles and the longitudinal direction of a bump (namely, width direction of an anisotropic conductive film) can be made to correspond. In this case, the left half of the photopolymerizable resin layer in the longitudinal direction of the anisotropic conductive film is masked, and the right half is irradiated by inclining ultraviolet rays so as to flow toward the right side of the anisotropic conductive film. Then, it is preferable that the right half is masked, and the left half is irradiated with an ultraviolet ray inclined so that a flow occurs toward the left side of the anisotropic conductive film.

(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 radical photopolymerizable resin layer.

(Manufacturing method for carrying out two-stage photoradical polymerization 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 a photoradical polymerization reaction by inclining ultraviolet rays (UV) from the conductive particle side, and is applied to the surface. A temporary first connection layer 20 in which the conductive particles 4 are temporarily fixed is formed. As a result, as shown in FIG. 7B, the curing rate of the skewed temporary first connection layer portion 2X located between the conductive particles 4 and the outermost surface of the temporary first connection layer 20 is determined as the conductive particles 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 between the four.

(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 photoradical polymerization reaction. 20 is fully cured to form the first connection layer 2. Thereby, the anisotropic conductive film 1 of FIG. 9B can be obtained. The ultraviolet irradiation in this step is preferably performed from a direction perpendicular to the temporary first connection layer. 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.

  In addition, when carrying out photo radical polymerization in two steps, the anisotropic conductive film 100 of FIG. 5 can be obtained by implementing the following processes (Z) after a process (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 1-3, Comparative Example 1
Conductive particles are arranged according to the operation of Example 1 (equal arrangement of conductive particles) of Japanese Patent No. 4778938, and the first connection layer and the second connection layer are laminated according to the composition (parts by mass) shown in Table 1. An anisotropic conductive film having a two-layer structure 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. Further, ultraviolet rays having a wavelength of 365 nm and an integrated light amount of 4000 mJ / cm ² from the LED light source are orthogonal to the longitudinal direction of the anisotropic conductive film from the conductive particle side to the radical photopolymerizable resin layer at the angles shown in Table 1. By irradiating in the direction, the first connection layer having conductive particles fixed on the surface was formed. In Comparative Example 1, ultraviolet rays were irradiated from the conductive particle side to the photoradical polymerizable resin layer at an angle of 90 °.

(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, as described below, “mounting conductive particle capture efficiency”, “direction of conductive particles during anisotropic conductive connection”, “initial conduction resistance”, “conduction after aging” Resistance ”and“ Short occurrence rate ”were tested and evaluated. The obtained results are shown in Table 1.

"Mounting conductive particle capture rate"
At the time of mounting, the ratio of the amount of particles actually captured after heating and pressing to the theoretical amount of particles existing on the bumps of the connection structure sample body before heating and pressing was determined. The amount of particles was counted using an optical microscope. Practically 50% or more is desirable.

"Direction of conductive particles during anisotropic conductive connection"
The conductive particles captured by the bumps after the anisotropic conductive connection were observed with an optical microscope, and it was investigated whether the uniformity of the flow direction was obtained by the inclination of the LED. A group of two or more connected conductive particles is counted as 100 units (a total of 200 particles), and among these, those that are aligned in 70% or more are defined as “uniform”, and those that are less than that are defined as “random”. .

"Initial conduction resistance"
The conduction resistance value of the connection structure sample was measured using a digital multimeter (Agilent Technology Co., Ltd.).

"Continuation resistance after aging"
After the connection structure sample was left in a high-temperature and high-humidity environment at 85 ° C. and 85% RH for 500 hours, the conduction resistance was measured using a digital multimeter (Agilent Technology Co., Ltd.). Practically, it is desirable that it is 4Ω or less.

"Short incidence"
The short-circuit occurrence rate of the comb tooth TEG pattern in the 7.5 μm space was determined. If it is practically 100 ppm or less, it can be judged that the insulation is good.

  From Table 1, the anisotropic conductive films of Examples 1 to 3 were subjected to UV irradiation at the time of production, so that the mounting conductive particle capture rate was not only slightly improved but also different from that of Comparative Example 1. It can be seen that the direction of the flow of the conductive particles during the isotropic conductive connection can be made uniform. As a result, it can be seen that the occurrence rate of the short circuit can be greatly reduced as compared with the comparative example.

  The anisotropic conductive film of the present invention comprises a first connection layer obtained by photoradical polymerization of a photoradically polymerizable resin layer, and a heat or photocation or anion polymerizable resin layer, or preferably an acrylate compound and heat or photoradical polymerization. It has a two-layer structure in which a second connection layer composed of a thermal or photoradical polymerizable resin layer containing an initiator is laminated, and furthermore, on the second connection layer side surface of the first connection layer, The conductive particles for anisotropic conductive connection are arranged in a single layer. And the area | region which has a hardening rate lower than the hardening rate of one side (2nd connection layer side surface) regarding the hardening rate of a 1st connection layer exists diagonally in the thickness direction of a 1st connection layer. For this reason, in the anisotropic conductive connection, the direction of flow of the conductive particles can be made uniform. Therefore, good conduction reliability, insulation, and mounting conductive particle capture rate are shown.

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 (16)

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,
Regarding the curing rate of the first connection layer, an anisotropic conductive film characterized in that a region having a curing rate lower than the curing rate of one side is present obliquely in the thickness direction of the first connection layer .   The anisotropic conductive film according to claim 1, 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.   The anisotropic conductive film according to claim 2, wherein the first connection layer further contains an epoxy compound and a heat, photocation, or 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 The anisotropic conductive film according to claim 1, which is a radical photopolymerizable resin layer.   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 4.   The anisotropic conductive film according to any one of claims 1 to 5, wherein the conductive particles are biting into the second connection layer.   The anisotropic conductive film in any one of Claims 1-6 whose minimum melt viscosity of a 1st connection layer is higher than the minimum melt viscosity of a 2nd connection layer. It is a manufacturing method of the anisotropic conductive film of Claim 1, Comprising: The following processes (A)-(C):
Process (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 by inclining ultraviolet rays to form a first connection layer having the conductive particles fixed on the surface; and step (C)
The manufacturing method which has the process of forming the 2nd connection layer which consists of a heat | fever or photocationic or anion polymerizable resin layer, or a heat | fever or radical photopolymerizable resin layer in the conductive particle side surface of a 1st connection layer.   The production method according to claim 8, wherein the ultraviolet irradiation in the step (B) is performed from the side where the conductive particles of the photopolymerizable resin layer are arranged. It is a manufacturing method of the anisotropic conductive film of Claim 1, 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 a surface by irradiating the photopolymerizable resin layer in which the conductive particles are arranged with a tilted ultraviolet ray for photopolymerization reaction;
Process (CC)
Forming a second connection layer comprising a thermal cation or thermal anion polymerizable resin layer or a thermal radical polymerizable resin layer on the conductive particle side surface of the temporary first connection layer; 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 10 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 8, 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. 9. The manufacturing method according to claim 8, wherein prior to step (A), the following 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 10, 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 10, wherein, prior to step (AA), the following step (a):
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 1-7.

Images