HK1205364B - Anisotropic-conductive-film manufacturing method and anisotropic conductive film - Google Patents

Description

Method for manufacturing anisotropic conductive film and anisotropic conductive film

Technical Field

The present invention relates to a method for manufacturing an anisotropic conductive film and an anisotropic conductive film.

Background

Anisotropic conductive films are widely used for mounting electronic components such as IC chips, and in recent years, from the viewpoint of application to high-density mounting, in order to improve connection reliability and insulation, improve particle capture efficiency, reduce manufacturing cost, and the like, an 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).

The anisotropic conductive film is produced as follows. That is, first, conductive particles are held at the opening of a transfer mold having an opening, and an adhesive film having an adhesive layer for transfer formed thereon is pressed from above, so that the conductive particles are primarily transferred onto the adhesive layer. Next, a polymer film, which is a component of the anisotropic conductive film, is pressed against the conductive particles attached to the adhesive layer, and the conductive particles are secondarily transferred to the surface of the polymer film by heating and pressurizing. Next, an adhesive layer is formed on one surface of the conductive particles of the polymer film subjected to the secondary transfer of the conductive particles so as to cover the conductive particles, thereby forming an anisotropic conductive film.

Documents of the prior art

Patent document

Patent document 1: japanese patent application No. 2010-33793.

Disclosure of Invention

Problems to be solved

However, in the anisotropic conductive film of patent document 1 produced using a transfer mold having an opening, improvement of connection reliability, insulation property, and particle capturing efficiency of the anisotropic conductive film may be expected to some extent as long as primary transfer and secondary transfer are smoothly advanced, but in general, a film having relatively weak adhesion is used as an adhesive film for primary transfer in order to facilitate secondary transfer, and a contact area between conductive particles and the adhesive film is reduced. Therefore, when the primary transfer operation-the secondary transfer operation is performed, there may occur problems such as occurrence of conductive particles that are not subjected to the primary transfer, peeling of the conductive particles from the adhesive film after the primary transfer, or positional deviation of the conductive particles on the adhesive film, and the overall operation efficiency may be lowered.

On the other hand, if the adhesive force of the adhesive film is enhanced to some extent to stably hold the conductive particles on the adhesive film in order to perform the primary transfer operation more rapidly and smoothly, the secondary transfer to the polymer film becomes difficult; if the film properties of the polymer film are enhanced in order to avoid this problem, the on-resistance of the anisotropic conductive film increases, and the on-reliability also decreases. Thus, in the case of using a transfer mold having an opening as an anisotropic conductive film, since it is the actual situation that the primary transfer and the secondary transfer do not always proceed smoothly, there is still a strong demand for an anisotropic conductive film to achieve good connection reliability, good insulation properties, and good particle capture efficiency at the same time.

An object of the present invention is to solve the above problems of the prior art, in which an anisotropic conductive film exhibiting good connection reliability, good insulation, and good particle capture efficiency can be manufactured when an anisotropic conductive film in which conductive particles are arranged in a single layer is manufactured by a transfer mold having an opening.

Means for solving the problems

The inventor finds that: in the case of using a transfer mold having an opening as an anisotropic conductive film, the above object can be achieved by using a light-transmitting material as a transfer mold, transferring the conductive particles directly in a monolayer arrangement from the transfer mold onto an insulating resin layer constituting the anisotropic conductive film without temporarily transferring the conductive particles onto an adhesive film at a first time, transferring the insulating resin layer in a central region between adjacent conductive particles so that the thickness of the insulating resin layer is thinner than the thickness of the insulating resin layer in the vicinity of the conductive particles, and irradiating ultraviolet rays through the light-transmitting transfer mold.

That is, the present invention provides a method for manufacturing an anisotropic conductive film having a 3-layer structure in which a 1 st connection layer is sandwiched between a 2 nd connection layer and a 3 rd connection layer, which are mainly composed of an insulating resin, the method including the following steps (a) to (F).

< Process (A) >

And disposing conductive particles in the opening of the light-transmissive transfer mold having the opening, and allowing the photopolymerizable insulating resin layer formed on the release film to face the surface of the transfer mold having the opening.

< Process (B) >

And a step of pressing the photopolymerizable insulating resin layer from the side of the release film into the opening by applying pressure to the photopolymerizable insulating resin layer from the side of the release film, and transferring the conductive particles to the surface of the photopolymerizable insulating resin layer, thereby forming a 1 st connection layer, the 1 st connection layer having a structure in which the conductive particles are arranged in a single layer in the planar direction of the photopolymerizable insulating resin layer, and having a structure in which the thickness of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles is smaller than the thickness of the photopolymerizable insulating resin layer in the vicinity of the conductive particles.

< Process (C) >

And irradiating the 1 st connection layer with ultraviolet rays from the light-transmitting transfer mold side.

< Process (D) >

And removing the release film from the 1 st connection layer.

< Process (E) >

And a step of forming a 2 nd connecting layer mainly composed of an insulating resin on a surface of the 1 st connecting layer opposite to the light-transmissive transfer mold.

< step (F) >

And a step of forming a 3 rd connection layer mainly composed of an insulating resin on the surface of the 1 st connection layer opposite to the 2 nd connection layer.

The present invention also provides a connection method for anisotropically and electrically connecting a 1 st electronic component and a 2 nd electronic component with the anisotropic conductive film obtained by the above-mentioned production method, wherein the anisotropic conductive film is temporarily bonded to the 2 nd electronic component from the 3 rd connection layer side thereof, the 1 st electronic component is mounted on the temporarily bonded anisotropic conductive film, and thermocompression bonding is performed from the 1 st electronic component side; the invention also provides an anisotropic conductive connection structure obtained by the connection method.

The present invention further provides an anisotropic conductive film having a 3-layer structure in which a 1 st connection layer is sandwiched between a 2 nd connection layer and a 3 rd connection layer, which are mainly composed of an insulating resin, wherein the boundary between the 1 st connection layer and the 3 rd connection layer has undulations, the 1 st connection layer has a structure in which conductive particles are arranged in a single layer in the planar direction on the 3 rd connection layer side of the insulating resin layer, and the thickness of the insulating resin layer in the central region between adjacent conductive particles is thinner than the thickness of the insulating resin layer in the vicinity of the conductive particles.

The anisotropic conductive film preferably has the following configuration: the 1 st connecting layer is a thermal or photo radical polymerization type resin layer containing an acrylate compound and a thermal or photo radical polymerization initiator, or a layer obtained by thermally or photo radical polymerization of the layer; or a layer of a thermally or photocationically or anionically polymerizable resin containing an epoxy compound and a thermal or photocationically or anionically polymerizable initiator, or a layer obtained by thermally or photocationically polymerizing or anionically polymerizing the layer. Also preferred is a scheme in which conductive particles are extruded into the 3 rd connecting layer. Further preferably, in the 1 st connection layer, a curing rate of the 1 st connection layer in a region between the conductive particles and the 2 nd connection layer side surface of the 1 st connection layer is lower than a curing rate of the 1 st connection layer in a region between mutually adjacent conductive particles. And the lowest melt viscosity of the 1 st joining layer is preferably higher than the lowest melt viscosity of each of the 2 nd joining layer and the 3 rd joining layer. It is also preferable that the ratio of the lowest melt viscosity of the 1 st joining layer to the lowest melt viscosity of each of the 2 nd joining layer and the 3 rd joining layer is 1:4 to 400.

Effects of the invention

The invention provides a method for manufacturing an anisotropic conductive film having a 3-layer structure in which a 1 st connection layer is sandwiched between an insulating 2 nd connection layer and an insulating 3 rd connection layer. In this manufacturing method, when an anisotropic conductive film is formed by using a transfer mold having an opening, conductive particles are directly transferred from a transfer mold to a photopolymerizable insulating resin layer constituting the anisotropic conductive film, which is the 1 st connecting layer, without being once transferred to an adhesive film, and the conductive particles are arranged in a single layer. The thickness of the photopolymerizable insulating resin layer at the center between adjacent conductive particles is made thinner than the thickness of the photopolymerizable insulating resin layer in the vicinity of the conductive particles (in other words, the conductive particles are made to protrude from the 1 st connecting layer) and then transferred. When the projection is arranged on the 3 rd connection layer side and the 3 rd connection layer is arranged on the side of a wiring board or the like on which an electronic component such as an IC chip is mounted, the particle capturing efficiency can be improved. By further irradiating ultraviolet rays through the light-transmitting transfer mold, the photopolymerizable insulating resin layer holding the conductive particles and serving as the 1 st connecting layer can be photo-cured while being held on the transfer mold, and the curing rate of the part of the photopolymerizable insulating resin layer in which ultraviolet rays are blocked by the conductive particles can be relatively reduced. This prevents excessive movement of the conductive particles in the planar direction, improves the press-fitting property, and realizes good connection reliability, good insulation property, and good particle capture efficiency.

Drawings

Fig. 1A is an explanatory view of step (a) of the method for producing an anisotropic conductive film of the present invention.

Fig. 1B is an explanatory view of the step (a) of the method for manufacturing an anisotropic conductive film of the present invention.

Fig. 2A is an explanatory view of step (B) of the method for producing an anisotropic conductive film of the present invention.

Fig. 2B is an explanatory view of the step (B) of the method for manufacturing an anisotropic conductive film of the present invention.

Fig. 3 is an explanatory view of step (C) of the method for producing an anisotropic conductive film of the present invention.

Fig. 4 is an explanatory view of step (D) of the method for producing an anisotropic conductive film of the present invention.

Fig. 5 is an explanatory view of step (E) of the method for producing an anisotropic conductive film of the present invention.

Fig. 6 is a cross-sectional view of the anisotropic conductive film of the present invention obtained in step (F) of the method for manufacturing an anisotropic conductive film of the present invention.

Fig. 7 is a partial sectional view of an anisotropic conductive film obtained by the manufacturing method of the present invention.

Fig. 8 is a cross-sectional view of the anisotropic conductive film of the present invention.

Detailed Description

Method for producing anisotropic conductive film

The method for producing the anisotropic conductive film of the present invention will be described in detail below for each step.

Next, an example of the method for producing an anisotropic conductive film of the present invention will be described. The manufacturing method comprises the following steps (A) to (F). The following description will be made for each step.

< Process (A) >

As shown in fig. 1A, conductive particles 4 are disposed in an opening 21 of a light transmissive transfer mold 20 in which the opening 21 is formed. As shown in fig. 1B, the photopolymerizable insulating resin layer 10 is formed on a release film 22 such as a polyethylene terephthalate film subjected to a release treatment, so as to face the surface of the transfer mold 20 having the opening 21 formed therein.

The transparency of the transfer mold 20 refers to the property of transmitting ultraviolet rays. The level of transmission is not particularly limited, and from the viewpoint of rapid photopolymerization, it is preferable that the ultraviolet transmittance (measurement wavelength: 365nm, optical path length: 1.0cm) when measured by a spectrophotometer be 70% or more.

The transfer mold 20 is obtained by forming an opening in a transparent inorganic material such as ultraviolet-transmitting glass or an organic material such as polymethacrylate by a known opening forming method such as photolithography (phototopography). Such a transfer mold 20 may be in the form of a plate or a roll.

The opening 21 of the transfer mold 20 contains conductive particles inside thereof. The shape of the opening 21 may be, for example: a polygonal column such as a cylindrical column or a quadrangular column, or a pyramid such as a quadrangular pyramid.

The openings 21 are preferably arranged in a regular pattern such as a lattice pattern or a staggered pattern.

From the viewpoint of the balance between the improvement of transferability and the retention of conductive particles, the ratio of the average particle diameter of the conductive particles 4 to the depth of the openings 21 (= the average particle diameter of the conductive particles/the depth of the openings) is preferably 0.4 to 3.0, and more preferably 0.5 to 1.5.

From the viewpoint of the balance between ease of storage of the conductive particles, ease of press-fitting of the insulating resin, and the like, the ratio of the diameter of the opening 21 to the average particle diameter of the conductive particles 4 (= opening diameter/average particle diameter of conductive particles) is preferably 1.1 to 2.0, and more preferably 1.3 to 1.8.

The diameter and depth of the opening 21 of the transfer mold 20 can be measured by a laser microscope.

The method of accommodating the conductive particles 4 in the openings 21 of the transfer mold 20 is not particularly limited, and a known method can be used. For example, the surface of the opening-forming surface of the transfer mold 20 may be wiped with a brush, a blade, or the like after spreading or coating the dried conductive particle powder or a dispersion obtained by dispersing the powder in a solvent.

< Process (B) >

Next, as shown in fig. 2A, pressure is applied to the photopolymerizable insulating resin layer 10 from the side of the release film 22 to press the photopolymerizable insulating resin into the opening 21, thereby allowing the conductive particles 4 to be embedded and transferred to the surface of the photopolymerizable insulating resin layer 10. As a result, as shown in fig. 2B, a 1 st connection layer is formed, the 1 st connection layer having a structure in which the conductive particles 4 are arranged in a single layer in the planar direction of the photopolymerizable insulating resin layer 10, wherein the thickness t1 of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles 4 is thinner than the thickness t2 of the photopolymerizable insulating resin layer in the vicinity of the conductive particles 4.

Here, the thickness t1 of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles 4 is too thin relative to the thickness t2 of the photopolymerizable insulating resin layer in the vicinity of the conductive particles 4, and therefore, the conductive particles 4 tend to move excessively during anisotropic conductive connection, and too thick tends to decrease the press-in property, and the particle capture efficiency may be decreased, and therefore, 0.2 to 0.8 is preferable, and 0.3 to 0.7 is more preferable.

In addition, the absolute thickness of the photopolymerizable insulating resin layer thickness t1 is preferably 0.5 μm or more because it may be difficult to form the 1 st interconnect layer. If the thickness is too large, the insulating resin layer is difficult to be removed from the connection region when anisotropic conductive connection is performed, and conduction failure may occur, and therefore, it is preferably 6 μm or less.

The central region between adjacent conductive particles 4 means: a region of a small thickness in the photopolymerizable insulating resin layer 10 including an intermediate point of a distance between adjacent conductive particles; the vicinity of the conductive particles 4 means: a position near a line segment tangent to the conductive particle 4 in the layer thickness direction of the 1 st connecting layer 1.

The adjustment to such a numerical range can be performed by adjusting the aperture diameter, aperture depth, conductive particle diameter, aperture interval, pressure value, composition of the photopolymerizable insulating resin, and the like.

As shown in fig. 8, the thickness of the resin layer containing the conductive particles greatly varies in the planar direction, and as a result, when the resin layer is present so as to be blocked, the thickness of the insulating resin layer between the conductive particles 4 can be substantially 0. Substantially 0 means: the insulating resin layers containing conductive particles are in a state of being independent of each other. In this case, in order to achieve good connection reliability, good insulation, and good particle capture efficiency, the shortest distance L between a perpendicular line passing through the center of the conductive particle 4 and a position where the thickness of the insulating resin layer is thinnest can be controlled¹、L²、L³、L⁴… is preferably performed. I.e. the shortest distance L¹、L²、L³、L⁴… becomes longer, the amount of resin in the 1 st connecting layer 1 becomes relatively large, the productivity is improved, and the flow of the conductive particles 4 can be suppressed. And the shortest distance L¹、L²、L³、L⁴… becomes shorter, the amount of resin in the 1 st connecting layer 1 becomes relatively smaller, and the distance between particles can be easily controlled. In other words, the positional alignment accuracy of the conductive particles can be improved. Preferred shortest distance L¹、L²、L³、L⁴… is preferably larger than 0.5 times but less than 1.5 times the particle diameter of the conductive particles 4.

Various methods can be employed to set the thickness of the insulating resin layer between the conductive particles 4 to substantially 0 within a range not impairing the effects of the present invention. For example, the following may be employed: a method of scraping the surface of the photopolymerizable insulating resin layer 10 formed in the step (B) to the surface of the transfer mold 20 with a squeegee (squeegee) or the like.

As shown in fig. 8, the conductive particles 4 may be buried in the 1 st connection layer 1. The degree of burying, such as shallow burying or deep burying, varies depending on the viscosity of the material at the time of forming the 1 st connecting layer, the shape, size, etc. of the opening of the transfer mold in which the conductive particles are arranged, and particularly can be controlled by the relationship between the base diameter of the opening and the opening diameter. For example, the base diameter is preferably 1.1 times or more and less than 2 times the conductive particle diameter, and the opening diameter is preferably 1.3 times or more and less than 3 times the conductive particle diameter.

The conductive particles 4' may be present in the 3 rd connection layer 3 as shown by a dotted line in fig. 8 within a range not to impair the effect of the present invention. The ratio of the number of conductive particles to the total number of conductive particles present in the 3 rd connecting layer 3 is preferably 1 to 50%, more preferably 5 to 40%. Particularly if the number of the conductive particles 4 in the 1 st connection layer 1 is substantially the same as the number of the conductive particles 4' in the 3 rd connection layer 3, adjacent particles exist in mutually different resin layers, and therefore, connection of a plurality of conductive particles can be suppressed, while also expecting an effect that a high conductive particle density can be locally achieved. The invention therefore also comprises the following solutions: for the particles arranged in a plane, conductive particles adjacent to an arbitrary conductive particle exist and are arranged in a layer different from the arbitrary conductive particle.

The conductive particles 4' are made to exist in the 3 rd connecting layer 3, which is generated as follows: in addition to the conductive particles accommodated inside the openings of the transfer mold, the operation of forming the 1 st connection layer and, subsequently, the operation of forming the 3 rd connection layer 3 were performed in a state where the conductive particles were present on the surface of the transfer mold. Since it is practically inevitable that the conductive particles are present on the surface of the transfer mold other than the openings in a predetermined number or more, the occurrence of defective products is reduced as long as the adverse effect of impairing the product performance does not occur, which contributes to the improvement of the yield.

< Process (C) >

Next, as shown in fig. 3, the 1 st connecting layer 1 is irradiated with ultraviolet rays from the side of the light-transmissive transfer mold 20. This makes it possible to polymerize and cure the photopolymerizable insulating resin 10 constituting the 1 st connecting layer 1, to stably hold the conductive particles 4 in the 1 st connecting layer 1, and to relatively reduce the curing rate of the photopolymerizable insulating resin in the region 1X under the conductive particles 4 where ultraviolet rays are blocked by the conductive particles 4, as compared with the curing rate in the surrounding region 1Y, thereby making it possible to improve the press-fit property of the conductive particles 4 at the time of anisotropic conductive connection. In this way, when anisotropic conductive connection is performed, it is possible to prevent the conductive particles from being displaced (in other words, to improve the particle capture efficiency), improve the press-fitting property of the conductive particles, reduce the on-resistance value, and realize good on-reliability.

The ultraviolet irradiation conditions may be appropriately selected from known conditions.

Here, the curing ratio is a value defined as a reduction ratio of a functional group (e.g., vinyl group) contributing to polymerization. Specifically, if the amount of vinyl groups present after curing is 20% of that before curing, the cure rate is 80%. The amount of vinyl groups present can be determined by characteristic absorption analysis of vinyl groups by infrared absorption spectroscopy.

The curing rate of the region 1X thus defined is preferably 40 to 80%, and the curing rate of the region 1Y is preferably 70 to 100%.

It is also preferred that the lowest melt viscosity of the 1 st tie layer 1 as measured by rheometer is higher than the lowest melt viscosity of each of the 2 nd tie layer 2 and the 3 rd tie layer 3. Specifically, the numerical value of [ minimum melt viscosity (mpa.s) of the 1 st connecting layer 1) ]/[ minimum melt viscosity (mpa.s) of the 2 nd connecting layer 2 or the 3 rd connecting layer 3] is preferably 1 to 1,000, more preferably 4 to 400, because when it is too low, the particle capturing efficiency tends to decrease and the probability of short circuit occurrence tends to increase, and when it is too high, the conduction reliability tends to decrease. Further, regarding the respective preferred minimum melt viscosities, since the particle capture efficiency tends to decrease if the viscosity is too low and the on-resistance value tends to increase if the viscosity is too high, 100-; in the latter case, if too low, the resin tends to bleed out when rolled, and if too high, the on-resistance value tends to increase, so 0.1 to 10000 mPa.s is preferable, and 1 to 1000 mPa.s is more preferable.

< Process (D) >

Next, as shown in FIG. 4, the release film 22 is removed from the 1 st connecting layer 1. The method of removal is not particularly limited.

< Process (E) >

Next, as shown in fig. 5, a 2 nd connecting layer 2 mainly composed of an insulating resin is formed on the surface of the 1 st connecting layer 1 opposite to the light transmissive transfer mold 20.

The 2 nd connection layer 2 is a layer located on the surface of the 1 st connection layer 1 on which the conductive particles 4 do not protrude, and is generally a layer disposed on the side of a terminal such as a bump of an IC chip that must be aligned with high positional accuracy. Since the region 1X of the 1 st connection layer 1 in which the curing rate between the conductive particles 4 and the 2 nd connection layer 2 is low is lower than the curing rate of the other regions 1Y, the conductive particles are easily excluded at the time of anisotropic conductive connection, and since the conductive particles are surrounded by the region 1Y in which the curing rate is high, unintended movement is less likely to occur. Therefore, the position deviation of the conductive particles can be prevented (in other words, the particle capture efficiency can be improved), the press-in property of the conductive particles can be improved, the on-resistance value can be reduced, and good on-reliability can be realized.

The thickness of the 2 nd connecting layer 2 is preferably 5 to 20 μm, more preferably 8 to 15 μm, because when it is too thin, conduction failure may occur due to insufficient resin filling, and when it is too thick, resin bleeding may occur during pressure bonding, and the pressure bonding apparatus may be contaminated.

< step (F) >

Next, as shown in fig. 6, the 3 rd connecting layer 3 mainly composed of an insulating resin is formed on the surface (surface on which conductive particles protrude) of the 1 st connecting layer 1 opposite to the 2 nd connecting layer 2, thereby obtaining the anisotropic conductive film 100. As a result, the boundary between the 1 st and 3 rd connection layers is in a wavy or undulating shape. By adopting a shape having undulations in the layer existing in the film in this manner, the probability of an increase in the contact area mainly with the bump at the time of bonding can be increased, and as a result, the adhesive strength can be expected to be improved. In addition, by having such undulation, a state in which particles are present in the 3 rd connecting layer 3 can be easily obtained. This is due to: in the process of providing the 3 rd connection layer 3, particles present in the undulating, unrumped portions in the 1 st connection layer 1 move into the 3 rd connection layer 3.

The 3 rd connecting layer 3 is generally disposed on the terminal side where relatively high alignment accuracy is not required, such as a solid (ベタ) electrode on the wiring board. The 3 rd connection layer 3 is disposed on the side of the 1 st connection layer 1 from which the conductive particles 4 protrude. Therefore, in the anisotropic conductive connection, the conductive particles 4 of the 1 st connection layer 1 directly collide with an electrode such as a wiring board and deform, and therefore, even if the insulating resin flows during the anisotropic conductive connection, the insulating resin is hard to move to an unintended position. Therefore, the position deviation of the conductive particles can be prevented (in other words, the particle capture efficiency can be improved), the press-in property of the conductive particles can be improved, the on-resistance value can be reduced, and good on-reliability can be realized.

When the layer thickness of the 3 rd connecting layer 3 is too small, a defective bonding may occur when temporarily bonded to the 2 nd electronic component, and when it is too large, the on-resistance tends to increase, and therefore, it is preferably 0.5 to 6 μm, more preferably 1 to 5 μm.

Materials for constructing No. 1, No. 2 and No. 3 connecting layers and electroconductive particles

As described above, the anisotropic conductive film 100 shown in fig. 6 obtained by the manufacturing method of the present invention has a 3-layer structure in which the 1 st connecting layer 1 is sandwiched between the 2 nd connecting layer 2 and the 3 rd connecting layer 3 mainly composed of an insulating resin. The 1 st connection layer 1 has the following structure: the conductive particles 4 are aligned in a single layer in the planar direction so as to protrude toward the 3 rd connecting layer 3 side of the photopolymerizable insulating resin layer 10, according to the opening pattern of the transfer mold used in manufacturing the anisotropic conductive film 100. In this case, the conductive particles are preferably arranged in a regular uniform state at regular intervals in the plane direction. Also has the following structure: the thickness t1 of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles 4 is thinner than the thickness t2 of the photopolymerizable insulating resin layer in the vicinity of the conductive particles 4. Therefore, the conductive particles 4 which are not present between the terminals to be connected and are not used exhibit the behavior shown in fig. 7. That is, by heating and pressing at the time of anisotropic conductive connection, the relatively thin insulating resin layer between the conductive particles 4 is fused, and the conductive particles 4 are covered, thereby forming the covering layer 1 d. Thereby, occurrence of short circuit can be greatly suppressed.

< connection layer 1 >

As the photopolymerizable insulating resin layer 10 constituting the 1 st connecting layer 1, a known insulating resin layer can be suitably used. For example, there may be employed: a thermally or photoradically polymerizable resin layer containing an acrylate compound and a thermal or photoradically polymerizable initiator, or a layer obtained by thermally or photoradically polymerizing the resin layer; or a layer obtained by thermal or photo cationic or anionic polymerization of a thermal or photo cationic or anionic polymerization type resin layer containing an epoxy compound and a thermal or photo cationic or anionic polymerization initiator.

Among them, the photopolymerizable insulating resin layer 10 constituting the 1 st connecting layer 1 may be a thermal radical polymerization type resin layer containing an acrylate compound and a thermal radical polymerization initiator, and preferably a photo radical polymerization type resin layer containing an acrylate compound and a photo radical polymerization initiator. In this way, the photo-radical polymerizable resin layer can be irradiated with ultraviolet rays to be photo-radical polymerized, thereby forming the 1 st connecting layer 1.

< acrylic acid ester Compound >

As the acrylate compound used for the photopolymerizable insulating resin layer 10 constituting the 1 st joining layer 1, a conventionally known radical polymerizable acrylate can be used. For example, monofunctional (meth) acrylates (herein, (meth) acrylates include acrylates and methacrylates), and polyfunctional (meth) acrylates having two or more functions can be used. In the present invention, in order to make the adhesive thermosetting, it is preferable to use a polyfunctional (meth) acrylate for at least a part of the acrylic monomer.

Examples of monofunctional (meth) acrylates are: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-methylbutyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, 2-methylhexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-butylhexyl (meth) acrylate, isooctyl (meth) acrylate, isoamyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, phenoxy (meth) acrylate, phenylglycidyl (meth), N-nonyl (meth) acrylate, n-decyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, morpholin-4-yl (meth) acrylate, and the like. Examples of difunctional (meth) acrylates are: bisphenol F-EO-modified di (meth) acrylate, bisphenol A-EO-modified di (meth) acrylate, polypropylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, tricyclodecane dimethylol di (meth) acrylate, dicyclopentadiene (meth) acrylate, and the like. Examples of trifunctional (meth) acrylates are: trimethylolpropane tri (meth) acrylate, trimethylolpropane PO-modified (meth) acrylate, isocyanuric acid EO-modified tri (meth) acrylate, and the like. Examples of the tetrafunctional or higher (meth) acrylate include: dipentaerythritol penta (meth) acrylate, pentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetraacrylate, and the like. In addition, polyfunctional urethane (meth) acrylates can also be used. Specific examples thereof include: m1100, M1200, M1210, M1600 (manufactured by Toyo Synthesis Co., Ltd.), AH-600, AT-600 (manufactured by Kyoeisha Co., Ltd.), and the like.

In the photopolymerizable insulating resin layer 10 constituting the 1 st joining layer 1, when the content of the acrylate compound is too small, the minimum melt viscosity difference with the 2 nd joining layer 2 tends to be difficult to form, and when too large, curing shrinkage tends to increase, and workability tends to decrease, and therefore, 2 to 70% by mass is preferable, and 10 to 50% by mass is more preferable.

< photo radical polymerization initiator >

The photo radical polymerization initiator can be suitably selected from known photo radical polymerization initiators and used. Examples thereof include: acetophenone-based photopolymerization initiator, benzyl ketal-based photopolymerization initiator, phosphorus-based photopolymerization initiator, and the like. Specifically, the acetophenone-based photopolymerization initiator includes: 2-hydroxy-2-cyclohexylacetophenone (IRGACURE184, manufactured by BASF Japan), α -hydroxy- α, α' -dimethylacetophenone (DAROCUR1173, manufactured by BASF Japan), 2-dimethoxy-2-phenylacetophenone (IRGACURE651, manufactured by BASF Japan), 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (DAROCUR2959, manufactured by BASF Japan), 2-hydroxy-1- {4- [ 2-hydroxy-2-methyl-propionyl ] -benzyl } phenyl } -2-methyl-propan-1-one (IRGACURE127, manufactured by BASF Japan), and the like. Examples of the benzyl ketal photopolymerization initiator include: benzophenone, fluorenone, dibenzosuberone, 4-aminobenzophenone, 4 '-diaminobenzophenone, 4-hydroxybenzophenone, 4-chlorobenzophenone, 4' -dichlorobenzophenone and the like. 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (IRGACURE369, manufactured by BASF Japan) can also be used. Examples of the phosphorus-based photopolymerization initiator include: bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide (IRGACURE819, manufactured by BASF japan corporation), (2,4, 6-trimethylbenzoyl-diphenylphosphine oxide (DAROCURE TPO, manufactured by BASF japan corporation), and the like.

The amount of the photo radical polymerization initiator used is preferably 0.1 to 25 parts by mass, more preferably 0.5 to 15 parts by mass, because if the amount is too small, photo radical polymerization tends to be insufficient, and if it is too large, rigidity may be reduced.

< thermal radical polymerization initiator >

Examples of the thermal radical polymerization initiator include: organic peroxides, azo compounds, and the like, and organic peroxides that do not generate nitrogen that causes air bubbles can be preferably used.

Examples of the organic peroxide include: methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, acetylacetone peroxide, 1-bis (t-butylperoxy) 3,3, 5-trimethylcyclohexane, 1-bis (t-butylperoxy) cyclohexane, 1-bis (t-hexylperoxy) 3,3, 5-trimethylcyclohexane, 1-bis (t-hexylperoxy) cyclohexane, 1-bis (t-butylperoxy) cyclododecane, isobutyl peroxide, lauroyl peroxide, succinic peroxide, 3,5, 5-trimethylhexanoyl peroxide, benzoyl peroxide, octanoyl peroxide, stearoyl peroxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, ethyl-n-propyl peroxydicarbonate, methyl ethyl peroxydicarbonate, ethyl-n-propyl peroxydicarbonate, ethyl-propyl peroxydicarbonate, ethyl peroxydicarbonate, and ethyl, Di-2-methoxybutyl peroxydicarbonate, bis- (4-tert-butylcyclohexyl) peroxydicarbonate, (alpha, alpha-bis-neodecanoylperoxy) diisopropylbenzene, cumyl peroxyneodecanoate, octyl peroxyneodecanoate, hexyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, 2, 5-dimethyl-2, 5-bis (2-ethylhexanoylperoxy) hexane, 1,3, 3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-hexyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3-methylpropionate, tert-butyl peroxy-4-tert-butylcyclohexyl) peroxydicarbonate, tert-butyl peroxypivalate, tert-butyl, T-butyl peroxylaurate, t-butyl peroxy-3, 5, 5-trimethylhexanoate, t-hexyl peroxyisopropylmonocarbonate, t-butyl peroxyisopropylcarbonate, 2, 5-dimethyl-2, 5-bis (benzoylperoxy) hexane, t-butyl peracetate, t-hexyl perbenzoate, t-butyl perbenzoate, and the like. The organic peroxide may be used as a redox polymerization initiator by adding a reducing agent thereto.

Examples of the azo compound include: 1, 1-azobis (cyclohexane-1-carbonitrile), 2 ' -azobis (2-methyl-butyronitrile), 2 ' -azobisbutyronitrile, 2 ' -azobis (2, 4-dimethylvaleronitrile), 2 ' -azobis (2, 4-dimethyl-4-methoxyvaleronitrile), 2 ' -azobis (2-amidino-propane) hydrochloride, 2 ' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] hydrochloride, 2 ' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ]), 2,2 ' -azobis [ 2-methyl-N- (1, 1-bis (2-hydroxymethyl) -2-hydroxyethyl) propionamide ], 2 ' -azobis [ 2-methyl-N- (2-hydroxyethyl) propionamide ], 2 ' -azobis (2-methyl-propionamide) dihydrate salt, 4 ' -azobis (4-cyano-pentanoic acid), 2 ' -azobis (2-hydroxymethylpropionitrile), dimethyl 2,2 ' -azobis (2-methylpropionate) (dimethyl 2,2 ' -azobis (2-methylpropionate)), cyano-2-propylazoformamide, and the like.

When the amount of the thermal radical polymerization initiator used is too small, curing is poor, and when it is too large, the product life is reduced, so that it is preferably 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, per 100 parts by mass of the acrylate compound.

< epoxy Compound >

The photopolymerizable insulating resin layer 10 constituting the 1 st connecting layer 1 may be composed of: a layer of a thermally or photocationically or anionically polymerizable resin containing an epoxy compound and a thermal or photocationically or anionically polymerizable initiator, or a layer obtained by thermally or photo-radically polymerizing the resin.

When the photopolymerizable insulating resin layer 10 constituting the 1 st joining layer 1 contains a thermal cationic polymerization resin containing an epoxy compound and a thermal cationic polymerization initiator, the epoxy compound is preferably a compound or a resin having 2 or more epoxy groups in the molecule. They may be liquid or solid. Specific examples thereof include: glycidyl ethers obtained by reacting epichlorohydrin with polyhydric phenols such as bisphenol a, bisphenol F, bisphenol S, hexahydrobisphenol a, tetramethylbisphenol a, diallylbisphenol a, hydroquinone, catechol, resorcinol, cresol, tetrabromobisphenol a, trihydroxybiphenyl, benzophenone, bisresorcinol, bisphenol hexafluoroacetone, tetramethylbisphenol a, tetramethylbisphenol F, tris (hydroxyphenyl) methane, bitoltibenol, phenol novolac (phenol novolac), cresol novolac (cresol novolac); or polyglycidyl ethers obtained by reacting epichlorohydrin with an aliphatic polyhydric alcohol such as glycerol, neopentyl glycol, ethylene glycol, propylene glycol, butylene glycol (チレングリコール), hexylene glycol, polyethylene glycol, or polypropylene glycol; glycidyl ether esters obtained by reacting a hydroxycarboxylic acid such as p-hydroxybenzoic acid or β -hydroxynaphthoic acid with epichlorohydrin; or polyglycidyl esters obtained from polycarboxylic acids such as phthalic acid, methyl phthalate, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, endomethylenetetrahydrophthalic acid, endomethylenehexahydrophthalic acid, trimellitic acid, and polymerized fatty acids; glycidyl amino glycidyl ethers derived from aminophenols, aminoalkylphenols; glycidyl amino glycidyl esters derived from aminobenzoic acid; glycidylamines obtained from aniline, toluidine, tribromoaniline, xylylenediamine, diaminocyclohexane, diaminomethylcyclohexane, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylsulfone, or the like; known epoxy resins such as epoxidized polyolefins. An alicyclic epoxy compound such as 3, 4-epoxycyclohexenylmethyl-3 ', 4' -epoxycyclohexene carboxylate can also be used.

< thermal cationic polymerization initiator >

As the thermal cationic polymerization initiator, a compound known as a thermal cationic polymerization initiator for an epoxy compound can be used, for example, an initiator which generates heat to generate an acid capable of cationically polymerizing a cationically polymerizable compound, and a known iodine can be usedOnium salts, sulfonium salts,Salts, ferrocenes, etc., aromatic sulfonium salts showing good potential for temperature can be preferably used. Preferable examples of the thermal cationic polymerization initiator include: diphenyl iodideHexafluoroantimonate and diphenyl iodideHexafluorophosphate and diphenyl iodideHexafluoroborate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroborate. Specific examples thereof include: SP-150, SP-170, CP-66 and CP-77 manufactured by ADEKA; CI-2855 and CI-2639 manufactured by Nippon Caoda corporation; サンエイド SI-60 and SI-80 manufactured by Sanxin chemical industry; CYRACURE-UVI-6990, UVI-6974, and the like, manufactured by Union Carbide (ユニオンカーバイド).

When the amount of the thermal cationic polymerization initiator to be incorporated is too small, thermal cationic polymerization tends to be insufficiently carried out, and when it is too large, rigidity may be lowered, so that it is preferably 0.1 to 25 parts by mass, more preferably 0.5 to 15 parts by mass, per 100 parts by mass of the epoxy compound.

< thermal anionic polymerization initiator >

As the thermal anionic polymerization initiator, a compound known as a thermal anionic polymerization initiator of an epoxy compound can be used, for example, an initiator which generates heat to generate a base capable of anionically polymerizing an anionic polymerizable compound, and known aliphatic amine compounds, aromatic amine compounds, secondary or tertiary amine compounds, imidazole compounds, polythiol compounds, boron trifluoride-amine complexes, dicyandiamide, organic acid hydrazide and the like can be used, and an encapsulated imidazole compound having a good potential for temperature can be preferably used. Specifically, they include NOVACURE (ノバキュア) HX3941HP manufactured by Asahi Kasei E-Materials (Asahi Kasei イーマテリアルズ) (strain) and the like.

When the amount of the thermal anionic polymerization initiator is too small, curing tends to be poor, and when too large, the product life tends to be reduced, and therefore, the amount is preferably 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, based on 100 parts by mass of the epoxy compound.

< cationic photopolymerization initiator and anionic photopolymerization initiator >

As the photocationic polymerization initiator or photocationic polymerization initiator for epoxy compounds, known ones can be suitably used.

< conductive particles >

The conductive particles 4 constituting the 1 st connecting layer 1 can be appropriately selected from those used in conventionally known anisotropic conductive films. Examples thereof include: metal particles of nickel, cobalt, silver, copper, gold, palladium, or the like, resin particles coated with a metal, or the like. More than 2 kinds may be used in combination.

The average particle diameter of the conductive particles 4 is preferably 1 to 10 μm, more preferably 2 to 6 μm, because it is impossible to cope with variations in wiring height and the on-resistance tends to be high, and when it is too large, it tends to cause short-circuiting. The average particle diameter can be measured by a conventional particle size distribution measuring apparatus.

The presence amount of the conductive particles 4 in the 1 st connection layer 1 is too small, the particle capturing efficiency is lowered, the anisotropic conductive connection is difficult, and the short circuit is likely to occur if it is too large, and therefore, it is preferably 50 to 40000 per 1 square mm, more preferably 200 to 20000.

< other ingredients in the No. 1 connecting layer >

The 1 st connecting layer 1 may be formed of a film-forming resin such as a phenoxy resin, an epoxy resin, an unsaturated polyester resin, a saturated polyester resin, a polyurethane resin, a butadiene resin, a polyimide resin, a polyamide resin, or a polyolefin resin, if necessary.

When the photopolymerizable insulating resin layer 10 constituting the 1 st joining layer 1 is a layer obtained by radical photopolymerization of a radical photopolymerization type resin layer containing an acrylate compound and a radical photopolymerization initiator, it is preferable that the photopolymerizable insulating resin layer 10 further contains an epoxy compound and a thermal cationic polymerization initiator. In this case, as described later, it is preferable that the 2 nd connecting layer 2 and the 3 rd connecting layer 3 are also formed of a thermal cationic polymerization type resin layer containing an epoxy compound and a thermal cationic polymerization initiator. This can improve the interlayer peel strength.

In the 1 st connection layer 1, as shown in fig. 6, the conductive particles 4 are preferably pushed into the 3 rd connection layer 3 (in other words, the conductive particles 4 are exposed on the surface of the 1 st connection layer 1). This is because if the conductive particles are completely buried in the 1 st connecting layer 1, there is a possibility that the conduction reliability is lowered due to the insufficient exclusion of the insulating resin layer. When the degree of intrusion is too small, the particle capturing efficiency tends to be low, and when too large, the on-resistance tends to be high, and therefore, the average particle diameter of the conductive particles is preferably 10 to 90%, more preferably 20 to 80%.

< 2 nd connection layer and 3 rd connection layer >

Both the 2 nd connecting layer 2 and the 3 rd connecting layer 3 are mainly formed of an insulating resin. The insulating resin can be appropriately selected from known insulating resins. The same material as the photopolymerizable insulating resin layer 10 of the 1 st connecting layer 1 may be used.

The 3 rd connection layer 3 is located on the conductive particle 4 side of the 1 st connection layer 1, and is generally a layer disposed on the terminal side of a bump or the like of an IC chip that must be aligned with high positional accuracy. The 2 nd connecting layer 2 is generally a layer disposed on the side of a terminal such as a solid electrode of a glass substrate, which does not require high alignment accuracy.

The thickness of the layer 3 of the 3 rd connecting layer 3 is preferably 5 to 20 μm, more preferably 8 to 15 μm, because when it is too thin, conduction failure may occur due to insufficient resin filling, and when it is too thick, resin bleeding may occur at the time of crimping, and the crimping apparatus may be contaminated. On the other hand, if the layer thickness of the 2 nd connecting layer 2 is too small, a defective bonding may occur when temporarily bonding to the 2 nd electronic component, and if it is too thick, the on-resistance value tends to increase, and therefore, it is preferably 0.5 to 6 μm, and more preferably 1 to 5 μm.

Use of Anisotropic conductive film

The anisotropic conductive film thus obtained can be preferably used when the 1 st electronic component such as an IC chip or an IC module and the 2 nd electronic component such as a flexible substrate or a glass substrate are anisotropically and electrically connected by heat or light. The connection structure thus obtained is also part of the present invention. In this case, it is preferable to temporarily attach the anisotropic conductive film to the 2 nd electronic component such as a wiring board from the 2 nd connection layer side, mount the 1 st electronic component such as an IC chip on the temporarily attached anisotropic conductive film, and perform thermocompression bonding from the 1 st electronic component side, from the viewpoint of improving connection reliability. In the case of optical connection, thermocompression bonding may be used in combination.

Examples

The present invention will be described more specifically with reference to examples.

Examples 1 to 6

According to the compounding composition shown in table 1, a mixed solution was prepared from acrylic ester and a photo radical polymerization initiator using ethyl acetate or toluene so that the solid content was 50 mass%. This mixed solution was applied to a release-treated polyethylene terephthalate film (release PET film) having a thickness of 50 μm so as to have a dry thickness of 5 μm, and dried in an oven at 80 ℃ for 5 minutes, thereby forming a photo radical polymerization type insulating resin layer to be a 1 st connection layer.

Next, a glass ultraviolet-transmitting transfer mold having cylindrical openings of 5.5 μm in diameter and 4.5 μm in depth at a pitch of 9 μm in length and width was prepared, and conductive particles of 4 μm in average particle size were contained in each opening (Ni/Au plated resin particles, AUL704, manufactured by waterlogging chemical Co., Ltd.). The insulating resin layer for the 1 st connection layer was opposed to the opening-formed surface of the transfer mold, and conductive particles were pressed into the insulating resin layer by applying pressure from the release film side under conditions of 60 ℃ and 0.5 MPa. This results in an insulating resin layer in which the thickness t1 (see fig. 2B) of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles is thinner than the thickness t2 (see fig. 2B) of the photopolymerizable insulating resin layer in the vicinity of the conductive particles. Table 1 shows the results of measuring the thickness t1 of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles and the thickness t2 of the photopolymerizable insulating resin layer in the vicinity of the conductive particles using an electron microscope. The ratio of t1 to t2 [ t1/t2] was calculated and the results are also shown.

Then, the insulating resin layer of photo-radical polymerization type was irradiated from the side of the ultraviolet-transmitting transfer mold with a cumulative light amount of 4000mL/cm at a wavelength of 365nm²Thereby forming a 1 st connection layer having conductive particles fixed to the surface thereof.

Subsequently, the peeled PET film adhered to the 1 st connection layer was peeled off to expose the 1 st connection layer.

Next, a mixed solution of the thermosetting resin and the latent curing agent was prepared with ethyl acetate or toluene so that the solid content was 50 mass%. This mixed solution was coated on a release PET film having a thickness of 50 μm so that the dry thickness was 12 μm, and dried in an oven at 80 ℃ for 5 minutes, thereby forming a 2 nd connecting layer. A3 rd connection layer having a dry thickness of 3 μm was formed by the same operation.

The 2 nd connecting layer formed on the peeled PET film was laminated on the exposed surface of the 1 st connecting layer obtained above at 60 ℃ under 0.5MPa, and the laminate was removed from the transfer mold. The 3 rd connecting layer was similarly laminated on the 1 st connecting layer conductive particle-protruding surface of the removed laminate, thereby obtaining an anisotropic conductive film.

Comparative example 1

A radical photopolymerization type insulating resin layer was formed as a precursor layer of the 1 st interconnect layer in the same manner as in example 1.

Next, a glass ultraviolet-transmitting transfer mold having cylindrical openings of 5.5 μm in diameter and 4.5 μm in depth at a pitch of 9 μm in length and width was prepared, and conductive particles of 4 μm in average particle size were contained in each opening (Ni/Au plated resin particles, AUL704, manufactured by waterlogging chemical Co., Ltd.). The insulating resin layer for the 1 st connection layer was opposed to the opening-formed surface of the transfer mold, and the conductive particles were transferred to the surface of the insulating resin layer by applying pressure from the side of the release film under relatively weak conditions of 40 ℃ and 0.1 MPa. The film to which the conductive particles are transferred is removed, and the conductive particles are completely pressed into the insulating resin layer, thereby flattening the surface of the resin layer.

Then, the photo radical polymerization type insulating resin layer having conductive particles embedded therein was irradiated from the ultraviolet ray transmitting transfer mold side with a light having a wavelength of 365nm and a cumulative light amount of 4000mL/cm²Thereby forming a flat 1 st connection layer.

Subsequently, the peeled PET film adhered to the 1 st connection layer was peeled off to expose the 1 st connection layer.

An anisotropic conductive film was obtained by laminating a 3 rd connecting layer having a thickness of 3 μm and a 2 nd connecting layer having a thickness of 12 μm, which were prepared in the same manner as in example 1, to the 1 st connecting layer.

Comparative example 2

The resin composition for the first connection layer in table 1 used the same components as in example 1, and conductive particles were uniformly dispersed, and from the resulting mixture, a conductive particle-containing resin film having a thickness of 6 μm was produced. The conductive particles were present in the conductive particle-containing resin film in an amount of 20000 per 1 mm square, and the 2 nd connecting layer having a thickness of 12 μm, which was prepared in the same manner as in example 1, was attached to the film at 60 ℃ and 0.5MPa, thereby preparing an anisotropic conductive film having a two-layer structure.

< evaluation >

The planar direction uniform alignment of the conductive particles in the obtained anisotropic conductive film is described as "having an application (presence)" when the planar uniform alignment is formed, and is described as "not having an application (absence)" in addition to the above. When the thickness of the insulating resin layer in the vicinity of the conductive particles is larger than the thickness of the insulating resin layer in the intermediate region between the conductive particles (including the layer thickness 0), the thickness is described as an increase (presence) in the insulating resin layer in the vicinity of the conductive particles, and the thickness is described as none (absence) in the other cases. The results are shown in Table 1. The number of constituent layers of the anisotropic conductive film is also shown.

Using the obtained anisotropic conductive film, an IC chip (bump size 30X 85 μm, bump height 15 μm, bump pitch 50 μm) having a size of 0.5X 1.8X 20.0mm was mounted on a glass wiring board (1737F) manufactured by コーニング having a size of 0.5X 50X 30mm under conditions of 180 ℃ and 80MPa for 5 seconds to obtain a connection structure sample. When the cross section of the connection structure sample body connecting portion was observed by an electron microscope, as shown in fig. 7, it was confirmed that the insulating resin layer existed around the conductive particles.

As described below, the obtained connection structure sample was evaluated for "minimum melt viscosity", "particle capture efficiency", "conduction reliability", and "insulation" in a test. The results obtained are shown in table 1.

"minimum melt viscosity"

The lowest melt viscosity of each of the 1 st and 2 nd connecting layers constituting the sample body of the joint structure was measured using a rotary rheometer (TA Instruments) under a temperature rise rate of 10 ℃/min and a measurement pressure of 5g constant, and a diameter of a measurement plate of 8 mm.

"particle Capture efficiency"

The ratio of "the amount of particles actually trapped in the connection structure sample bump after heating and pressurizing (after actual mounting)" to "the theoretical amount of particles present in the connection structure sample bump before heating and pressurizing" is determined by the following mathematical expression. In practice, 40% or more is desirable.

Particle capture efficiency (%) =

{ [ number of particles on bump after heating and pressurizing ]/[ number of particles on bump before heating and pressurizing ] } × 100

"conduction reliability"

The connection structure sample was placed in a high-temperature and high-humidity environment at 85 ℃ and 85% RH, and the initial and after 500 hours, the on-resistance values were measured. In practical applications, it is desirable that the resistance value is 10 Ω or less even after 500 hours have elapsed.

Insulation "

The short-circuit occurrence rate of the comb TEG pattern was determined at a distance of 7.5. mu.m. In practice, it is preferably 100ppm or less.

[ Table 1]

As is clear from table 1, the anisotropic conductive films of examples 1 to 6 each showed practically preferable results in terms of evaluation items of particle capture efficiency, conduction reliability, and insulation property. From the results of examples 1 to 4, it is understood that if the 1 st, 2 nd and 3 rd connection layers are all the same curing system, the layers thereof are reacted with each other, and the conductive particle penetration property is somewhat lowered, and the on-resistance value tends to be increased. It is also found that the first connection layer 1 is a cationic polymerization system, and the heat resistance is improved as compared with a radical polymerization system, and therefore, the conductive particles still have a slightly decreased indentation property, and the on-resistance tends to be increased.

In contrast, in the anisotropic conductive film of comparative example 1, in the 1 st connecting layer, the thickness of the insulating resin layer in the central region between adjacent conductive particles is not reduced from the thickness of the insulating resin layer in the vicinity of the conductive particles, and therefore the on-resistance performance is greatly reduced. The conventional anisotropic conductive film of comparative example 2 having a two-layer structure had a problem in that the electron capture efficiency was greatly lowered and the insulating property was also deteriorated.

Examples 7 to 8

As shown in table 2, anisotropic conductive films were produced in the same manner as in example 1 except that the conditions of pressurization on the self-release film side were adjusted so that the ratio [ t1/t2] of the thickness t1 (see fig. 2B) of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles to the thickness t2 (see fig. 2B) of the photopolymerizable insulating resin layer in the vicinity of the conductive particles was set to table 2 when forming the first connection layer 1.

< evaluation >

The anisotropic conductive film obtained was evaluated for the uniform alignment of the conductive particles in the planar direction in the same manner as in example 1. The results obtained are shown in Table 2. The number of constituent layers of the anisotropic conductive film is also shown.

Using the obtained anisotropic conductive film, a connection structure sample was obtained in the same manner as in example 1. When the cross section of the connecting portion of the connection structure sample was observed with an electron microscope, as shown in fig. 7, it was confirmed that the insulating resin layer existed around the conductive particles.

The obtained connection structure sample was evaluated for "minimum melt viscosity", "particle capture efficiency", and "insulation" in the same manner as in example 1, as described below. The "on reliability" was evaluated by the test as described below. The results obtained are shown in Table 2.

"conduction reliability"

The connection structure sample was placed in a high-temperature and high-humidity environment at 85 ℃ and 85% RH, and taken out at intervals of 100 hours to confirm the increase in the on-resistance. The time when the on-resistance exceeded 50 Ω was regarded as the time when the failure occurred. In practice, it is desirable that the time is 1000 hours or more.

[ Table 2]

As is clear from the results in table 2, good results were obtained in each of the items of conduction reliability, insulation properties, and particle capture efficiency by setting the ratio [ t1/t2] of the thickness t1 of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles to the thickness t2 (see fig. 2B) of the photopolymerizable insulating resin layer in the vicinity of the conductive particles to 0.2 to 0.8. Further, as the value of [ t1/t2] becomes smaller, the insulation property tends to be improved in particular.

Examples 9 to 20

As shown in table 3, when forming the 1 st connection layer, an anisotropic conductive film was produced in the same manner as in example 1 except that the conditions of pressurization on the self-release film side were adjusted so that the ratio [ t1/t2] of the thickness t1 (see fig. 2B) of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles to the thickness t2 (see fig. 2B) of the photopolymerizable insulating resin layer in the vicinity of the conductive particles in table 2 was set, and that the surface of the 1 st connection layer was wiped by a known wiping method, for example, a squeegee or the like after forming the 1 st connection layer as necessary.

< evaluation >

The planar direction uniform alignment of the conductive particles in the obtained anisotropic conductive film is described as "having an application (presence)" when the planar uniform alignment is formed, and is described as "not having an application (absence)" in addition to the above. When the thickness of the insulating resin layer in the vicinity of the conductive particles is larger than the thickness of the insulating resin layer in the intermediate region between the conductive particles (including the layer thickness 0), the thickness is described as being increased (existing) in the vicinity of the conductive particles, and the thickness is described as being absent (absent) in the other cases. The results are shown in table 1 or table 2. The number of constituent layers of the anisotropic conductive film is also shown.

In examples 9 to 20, the ratio of the conductive particles present in the 3 rd connecting layer among all the conductive particles was measured by an optical microscope to obtain an area of 200. mu. m.times.200. mu.m, and the results are shown in Table 3. The influence of the proportion of the conductive particles present in the 3 rd connecting layer was confirmed. The case where the value of the ratio is 0 is the case where the conductive particles are present only in the 1 st connection layer, and the case where the value of the ratio is 1 is the case where the conductive particles are present only in the 3 rd connection layer 3.

Using the obtained anisotropic conductive film, a connection structure sample was obtained in the same manner as in example 1. When the cross section of the connecting portion of the connection structure sample was observed with an electron microscope, as shown in fig. 7, it was confirmed that the insulating resin layer existed around the conductive particles.

The obtained connection structure sample was evaluated for "minimum melt viscosity", "particle capture efficiency", and "insulation" in the same manner as in example 1, as described below. The "on reliability" was evaluated by the test as described below. The results obtained are shown in Table 3.

"conduction reliability"

The connection structure sample was placed in a high-temperature and high-humidity environment at 85 ℃ and 85% RH, and taken out at intervals of 100 hours to confirm the increase in the on-resistance. The time when the on-resistance exceeded 50 Ω was regarded as the time when the failure occurred. In practice, it is desirable that the time is 1000 hours or more.

[ Table 3]

As is clear from the results in table 3, the ratio [ t1/t2] between the thickness t1 of the photopolymerizable insulating resin layer in the central region between the adjacent conductive particles and the thickness t2 (see fig. 2B) of the photopolymerizable insulating resin layer in the vicinity of the conductive particles is 0.2 to 0.8, and good results were obtained for each of the conduction reliability, the insulation property, and the particle trap efficiency. Further, as the value of [ t1/t2] decreases, the insulation property tends to be improved in particular.

Even when the thickness t1 of the photopolymerizable insulating resin layer is 0 (examples 9, 13, and 17), if the thickness t2 of the photopolymerizable insulating resin layer is made thick, preferably larger than an equal multiple of the diameter of the conductive particles but smaller than 3 times, more preferably 1.25 to 2.2 times, good results are obtained in all of the items of conduction reliability, insulation, and particle capture efficiency. It is also found that when the thickness of the photopolymerizable insulating resin layer t2 is increased, the proportion of the conductive particles present in the 3 rd connecting layer among all the conductive particles tends to be increased. It is found that even if the majority of all the conductive particles are present on the 3 rd connecting layer side, the performance of the anisotropic conductive film is not particularly problematic.

Industrial applicability

In the anisotropic conductive film of the present invention having a 3-layer structure in which the 1 st connecting layer is sandwiched between the insulating 2 nd connecting layer and the insulating 3 rd connecting layer, the 1 st connecting layer has a structure in which conductive particles are arranged in a single layer in the planar direction on the 3 rd connecting layer side of the insulating resin layer, and has a structure in which the thickness of the insulating resin layer in the center between adjacent conductive particles is thinner than the thickness of the insulating resin layer in the vicinity of the conductive particles. Therefore, good connection reliability, good insulation, and good particle capture efficiency can be achieved in an anisotropic conductive film in which conductive particles are arranged in a single layer. This makes it possible to use the anisotropic conductive connection between an electronic component such as an IC chip and a wiring board.

Description of the symbols

1 st connection layer

Region of low cure rate in 1X 1 st connection layer

High cure rate region of 1Y 1 st connection layer

2 nd connecting layer

3 rd connecting layer

4 conductive particles

10 photopolymerizable insulating resin layer

20 light-transmitting transfer mold

21 opening

22 Release film

100 anisotropic conductive film.

Claims (17)

1. A method for manufacturing an anisotropic conductive film having a 3-layer structure in which a 1 st connection layer is sandwiched between a 2 nd connection layer and a 3 rd connection layer mainly composed of an insulating resin, the method comprising the following steps (A) to (F):

process (A)

Disposing conductive particles in an opening of a light-transmissive transfer mold having the opening formed therein, and causing a photopolymerizable insulating resin layer formed on a release film to face a surface of the transfer mold having the opening formed therein;

process (B)

A step of forming a 1 st connection layer by pressing the photopolymerizable insulating resin layer into the opening by applying pressure from the side of the release film to transfer the conductive particles to the surface of the photopolymerizable insulating resin layer, the 1 st connection layer having a structure in which the conductive particles are arranged in a single layer in the planar direction of the photopolymerizable insulating resin layer, and having a structure in which the thickness of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles is thinner than the thickness of the photopolymerizable insulating resin layer in the vicinity of the conductive particles;

process (C)

Irradiating the 1 st connection layer with ultraviolet light from the light-transmitting transfer mold side;

process (D)

Removing the release film from the 1 st connection layer;

process (E)

Forming a 2 nd connecting layer mainly composed of an insulating resin on a surface of the 1 st connecting layer opposite to the light transmissive transfer mold; and

procedure (F)

And a step of forming a 3 rd connection layer mainly composed of an insulating resin on the surface of the 1 st connection layer opposite to the 2 nd connection layer.

2. The production process according to claim 1, wherein in the step (B), the thickness of the photopolymerizable insulating resin layer in the central region between adjacent conductive particles is set to a ratio of 0.2 to 0.8 with respect to the thickness of the photopolymerizable insulating resin layer in the vicinity of the conductive particles.

3. The production method according to claim 1 or 2, wherein in the step (D), the curing rate of the 1 st connection layer located in a region between the conductive particles and the 2 nd connection layer side surface of the 1 st connection layer is made lower than the curing rate of the 1 st connection layer located in a region between mutually adjacent conductive particles.

4. The production method according to claim 1 or 2, wherein the lowest melt viscosity of the 1 st joining layer is made higher than the lowest melt viscosity of each of the 2 nd joining layer and the 3 rd joining layer.

5. The production method according to claim 4, wherein a ratio of the lowest melt viscosity of the 1 st joining layer to the lowest melt viscosity of each of the 2 nd joining layer and the 3 rd joining layer is 1:4 to 400.

6. A connection method for connecting a 1 st electronic component and a 2 nd electronic component in an anisotropic conductive manner by using the anisotropic conductive film obtained by the production method according to any one of claims 1 to 5,

the anisotropic conductive film is temporarily attached to the 2 nd electronic component from the 3 rd connection layer side, the 1 st electronic component is mounted on the temporarily attached anisotropic conductive film, and thermocompression bonding is performed from the 1 st electronic component side.

7. The connecting method according to claim 6, wherein the 2 nd electronic component is a wiring substrate, and the 1 st electronic component is an IC chip.

8. An anisotropic conductive connection structure obtained by the connection method according to claim 6 or 7.

9. An anisotropic conductive film having a 3-layer structure in which a 1 st connection layer is sandwiched between a 2 nd connection layer and a 3 rd connection layer mainly composed of an insulating resin,

the boundary of the 1 st connecting layer and the 3 rd connecting layer has undulation,

the 1 st connection layer has a structure in which conductive particles are arranged in a single layer in a plane direction on the 3 rd connection layer side of the insulating resin layer, and the thickness of the insulating resin layer in a central region between adjacent conductive particles is smaller than the thickness of the insulating resin layer in the vicinity of the conductive particles.

10. The acf of claim 9 wherein the 2 nd connection layer is a layer disposed on the side of the terminal that is aligned with a relatively high positional accuracy, and the 3 rd connection layer is a layer disposed on the side of the terminal that is aligned with a relatively low positional accuracy.

11. The acf of claim 9 or 10 wherein the 1 st connecting layer is a thermally or photo radical polymerizable resin layer containing an acrylate compound and a thermal or photo radical polymerization initiator, or a layer obtained by thermally or photo radical polymerization of the layer, or a thermally or photo cationically or anionically polymerizable resin layer containing an epoxy compound and a thermal or photo cationically or anionically polymerization initiator, or a layer obtained by thermally or photo cationically or anionically polymerizing the layer.

12. The acf of claim 9 or 10 wherein the conductive particles are extruded into the 3 rd connection layer.

13. The anisotropic conductive film according to claim 9 or 10, wherein a curing rate of the 1 st connection layer in a region between the conductive particles and the 2 nd connection layer side surface of the 1 st connection layer is lower than a curing rate of the 1 st connection layer in a region between mutually adjacent conductive particles in the 1 st connection layer.

14. The acf of claim 9 or 10 wherein the 1 st connection layer has a lowest melt viscosity that is higher than the lowest melt viscosity of each of the 2 nd and 3 rd connection layers.

15. The acf of claim 14 wherein a ratio of the lowest melt viscosity of the 1 st connection layer to the lowest melt viscosity of each of the 2 nd and 3 rd connection layers is 1:4 to 400.

16. The acf of claim 9 or 10 wherein the insulating resin layer in the central region between adjacent conductive particles is substantially 0 thick.

17. The acf of claim 9 or 10 wherein conductive particles are also present in the 3 rd connection layer.