JPH08222300A - Anisotropic conductive film and its manufacture - Google Patents

Abstract

PURPOSE: To lengthen the service life of an anisotropic conductive film by preventing fall-off of conductive metallic bodies from the anisotropic conductive film. CONSTITUTION: An anisotropic conductive film is composed of a high polymer film 1 having a large number of through holes bored in the thickness direction and conductive metallic bodies 2 embedded in the through holes of the high polymer film 1. In the anisotropic conductive film where both ends of the conductive metallic bodies 2 are formed in projecting electrode parts 2e and 2f projecting from both surfaces of the high polymer film 1, one end opening of the through holes of the high polymer film 1 is a net-like opening covered with a net part 1a formed from a part of the high polymer film 1. The net part 1a of this net-like opening is positioned inside the conductive metallic bodies 2, and the high polymer film 1 and the conductive metallic bodies 2 are integrally formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive film having conductivity in the film thickness direction and insulating property in the film surface direction, and a method for producing the same.

[0002]

2. Description of the Related Art With recent improvements in performance and miniaturization of electric and electronic products, fine wiring of electronic circuits is being advanced. Therefore, the wire bonding method and the TAB method (Tape Automated
In place of the Bonding method), wiring using an anisotropic conductive film is adopted (Japanese Patent Laid-Open No. 3-182083).
No.

The anisotropic conductive film has a structure in which a large number of conductive metal bodies are embedded in a polymer film, and both ends of the conductive metal body project from both sides of the polymer film. . That is, as shown in the cross-sectional view of FIG. 6 (A), the polymer film 1e has a large number of through holes formed in the thickness direction, and the conductive metal body 2c is embedded in the through holes. In addition, both ends of the conductive metal body 2c are formed into substantially hemispherical projecting electrode portions, and the projecting electrode portions at both ends project from both surfaces of the polymer film 1e. The large number of conductive metal bodies 2c are separated by a constant interval (pitch) so as not to contact each other.
By adopting such a configuration, the anisotropic conductive film is electrically connected in the thickness direction and electrically insulated in the film surface direction. In this anisotropic conductive film, since it is a required characteristic to reduce the insulation distance in the film surface direction, it is preferable to reduce the outer diameter of the protruding electrode portion of the conductive metal body 2c. .

Further, as shown in FIG. 6B, which is an enlarged cross-sectional view of the X portion of FIG. 6A, the protruding electrode portions 2g and 2h at both ends of the conductive metal body 2c are made of the conductive metal body 2c. In order to prevent the claw portion 2 from being detached, the outer diameter thereof is formed to be larger than the inner diameter of the opening of the through hole of the polymer film 1e.
equipped with k.

Conventionally, an anisotropic conductive film provided with such a conductive metal body having a protruding electrode portion is manufactured as shown in FIG. That is, first, FIG.
As shown in (a), the polymer film 1e is formed on the conductive support 3a. As the conductive support 3a, a metal film such as copper foil is usually used. Then, as shown in FIG. 4B, the polymer film 1e is irradiated with a laser 4 through a mask (not shown) to form through holes in the film thickness direction. The mask has an arrangement pattern of conductive metal bodies of an anisotropic conductive film. Next, as shown in FIG. 3C, the conductive support 3a is etched from the through holes of the polymer film 1e to form recesses at locations corresponding to the through holes of the conductive support 3a. To form. For the etching process, for example, a solution that dissolves the conductive support 3a is used. Then, as shown in FIG. 3D, electroplating is performed using the conductive support 3a as an electrode to deposit the conductive metal in the through holes of the polymer film 1e to form the conductive metal body 2c. At this time, by projecting and growing the conductive metal body 2c from both surfaces of the polymer film 1e, a protruding electrode portion having an outer diameter larger than the inner diameter of the opening of the through hole is formed. Then, by removing the conductive support 3a, an anisotropic conductive film having a large number of conductive metal bodies 2c embedded in the polymer film 1e is obtained as shown in FIG.

[0006]

According to the above conventional manufacturing method, an anisotropic conductive film in which a conductive metal body having a protruding electrode portion having a claw portion is embedded in a polymer film can be manufactured. However, the performance of the product manufactured by this conventional manufacturing method is insufficient. That is,
In the anisotropic conductive film obtained by the above conventional manufacturing method, the shape of the protruding electrode portion on the side of the conductive support is formed unevenly, and in particular, the height is uneven. Therefore, the anisotropic conductive film manufactured by the conventional manufacturing method has a problem that the reliability of electrical connection is poor. In addition, since the shape of the protruding electrode portion on the side of the conductive support is a flat and substantially hemispherical shape, the thickness of the claw portion becomes thin and is easily chipped. For this reason, the conductive metal body is likely to fall off from the anisotropic conductive film, resulting in a problem that performance is rapidly deteriorated. As a method of forming the claw portion thickly, there is a method of sufficiently etching the conductive support to form a large concave portion, but when the concave portion is formed large, the outer diameter of the protruding electrode portion becomes larger than necessary. Therefore, in the obtained anisotropically conductive film, it is not possible to achieve a sandwiching pitch of the conductive metal body, and the insulating property in the film surface direction deteriorates.

The present invention has been made in view of the above circumstances, and is an anisotropic conductive film capable of improving the reliability of electrical connection, preventing the conductive metal body from falling off, and achieving a narrow pitch. The purpose is to provide the manufacturing method.

[0008]

In order to achieve the above object, the present invention provides a polymer film having a large number of through holes formed in the thickness direction, and a polymer film embedded in the through holes of the polymer film. And a conductive metal body, both ends of the conductive metal body is an anisotropic conductive film formed on the protruding electrode portion protruding from both sides of the polymer film, the through hole of the polymer film One end opening of which is a net-like opening covered by a net formed from a part of the polymer film, and the net of the net-like opening is located inside the conductive metal body and is electrically conductive with the polymer film. An anisotropic conductive film integrated with a metal body is defined as a first gist.

A second aspect of the present invention is a method for producing an anisotropic conductive film including the following steps (a) to (g). (A) A laminated film in which a polymer film is laminated on an uneven rough surface of a conductive film, and the polymer film bites into the concave portion of the uneven rough surface of the conductive film at the joint portion thereof, and both are in close contact with each other. Step of preparing. (B) When a laser is applied to the surface of the polymer film of the laminated film in the thickness direction to form a through hole only in the polymer film, unevenness of the conductive film located under the polymer film A step of forming a net by the remaining polymer film portion by leaving the above-mentioned polymer film portion that bites into the concave portion of the rough surface to form one end opening of the through hole into a net-like opening. (C) A conductive metal is deposited in the through-holes of the polymer film by an electroplating method using the conductive film as an electrode to form a conductive metal body continuous in the thickness direction. The other end corresponding to the other end of the through hole of
A step of forming a protruding electrode portion protruding from the other end opening of the through hole. (D) A step of forming a conductive layer on the protruding electrode portion at the other end opening of the through hole. (E) A step of removing the conductive film of the laminated film and exposing the end face of the conductive metal body on one end side from the mesh of the one end opening of the through hole of the polymer film. (F) Exposing one end side of the conductive metal body formed in the through hole of the polymer film by electroplating using the conductive layer formed on the protruding electrode portion at the other end opening of the through hole as an electrode A step of depositing a conductive metal on the end face and forming one end of the conductive metal body on a protruding electrode portion protruding from the entire opening of the one end of the through hole. (G) A step of removing the conductive layer formed on the protruding electrode portion at the other end opening of the through hole.

[0010]

That is, in the anisotropic conductive film of the present invention, one end of the through hole of the polymer film is a net-like opening covered with a net portion formed from a part of the polymer film. The projection electrode portion of the conductive metal body projects from the entire mesh-shaped opening, and the mesh portion of the polymer film is located inside the conductive metal body, which is a special structure. As a result, the polymer film and the conductive metal body are integrated,
Since the conductive metal body is in a state of being physically bonded to the polymer film even if the protruding electrode portion is not provided with a claw portion, it does not fall off.

Further, the anisotropic conductive film having the above-mentioned special structure can be produced by the method for producing the anisotropic conductive film of the present invention. That is, a laminated film in which a polymer film is closely formed on the rough surface of the conductive film is prepared. Then, by irradiating the polymer film of the laminated film with a laser, leaving a polymer film portion that has dented in the recesses of the rough surface of the conductive film, one end of the through hole is reticulated. To form. Then, by electroplating, a conductive metal body is formed in the through holes of the polymer film, and a conductive metal is further deposited from the mesh of the mesh opening so that the metal mesh is projected from the whole mesh opening of the through hole. A protruding electrode portion of a conductive metal body is formed on the. As a result, the mesh portion of the polymer film comes to be positioned inside the conductive metal body, and both are integrated.

The method for producing the anisotropic conductive film of the present invention is a method for forming the protruding electrode portions on both sides of the polymer film by electroplating, one by one. This makes it possible to make the formation conditions of the protruding electrode portions uniform,
The protruding electrode portion has a uniform shape with uniform height, and the surface thereof is also a glossy smooth surface.

The reason why the protruding electrode portions are formed on both sides of the polymer film in this way is as follows. That is, in the method of forming the protruding electrode portion, when the drawbacks of the conventional manufacturing method were examined in detail, it was found that the shape of the protruding electrode portion formed on the conductive support side was non-uniform.
The present inventors have found out that the etching treatment rate for the conductive support differs depending on the location, so that the shape of the formed recess becomes non-uniform. Further, the shape of the protruding electrode portion becomes a flattened substantially hemispherical protruding electrode portion, and the thickness of the claw portion becomes thin because the etching progresses easily in the interface direction between the conductive support and the polymer film. Therefore, they have also found out that the inner shape of the recess formed in the conductive support is a flat hemisphere having a shallow depth and a wide width. Therefore, as a result of repeated research based on these findings, as described above, if the protruding electrode portions at the both ends are separately formed one by one by the electroplating method, the forming conditions of the protruding electrode portions can be made uniform. It has been found that the shape of the protruding electrode portion becomes uniform and the heights thereof can be made uniform.

Next, the present invention will be described in detail.

FIG. 1 shows an example of the anisotropic conductive film of the present invention. In the figure, (A) is a cross-sectional view of the anisotropic conductive film of the present invention, and (B) is X of the above (A).
It is an expanded sectional view of a part. As shown in FIG. 1 (A), in this anisotropic conductive film, the polymer film 1 has a large number of through holes, and the conductive metal body 2 is embedded in the through holes.
Both ends of the conductive metal body 2 are formed in substantially hemispherical protruding electrode portions protruding from both surfaces of the polymer film. Then, as shown in the enlarged cross-sectional view of FIG. 1 (B), the through hole of the polymer film 1 has a continuous inner diameter from the upper opening (the other end opening) to the lower opening (the one end opening) in the drawing. The taper is formed to be small, and the outer diameters (bottom surface diameters) of the protruding electrode portions 2e and 2f of the conductive metal body are also formed.
Is approximately the same as the corresponding inner diameter of the opening. And
One end opening of the through hole of the polymer film 1 is a net-like opening covered with a net portion 1a formed by using a part of the polymer film, and the net portion 1a is formed of the conductive metal body 2. The protruding electrode portion 2f is formed so as to project in the state of being located inside (downward in the drawing), and the polymer film 1 and the conductive metal body 2 are physically bonded and integrated. Therefore, in this anisotropic conductive film, the conductive metal body 2 does not fall off from the polymer film 1. Further, since it is not necessary to form the claw portion, the protruding electrode portions 2e and 2f of the conductive metal body 2 can be formed to be small so as to have an outer diameter substantially the same as the inner diameter of the corresponding opening. It is possible. Therefore, it is possible to achieve a narrow pitch between the conductive metal bodies 2 and to improve the insulating property in the film surface direction of the anisotropic conductive film.

Next, the method for producing the anisotropic conductive film of the present invention comprises the steps (a) to (g).
These steps will be described step by step with reference to the drawings.

In the step (a), the polymer film 1 is formed on the rough surface of the conductive film 3 as shown in FIG. 2 (a).
In the step of preparing a laminated film in which b is laminated and the polymer film 1b bites into the concave portion of the rough surface of the conductive film 3 at the joint portion, and the two are in close contact with each other.

That is, as shown in FIG. 4, which is an enlarged cross-sectional view of the above-mentioned laminated film, the conductive film 3 has an uneven rough surface, and the polymer film 1b is laminated on this uneven rough surface. Then, on the joint surface 7 of this laminated film, the lower part of the polymer film 1b bites into the concave portion of the rough surface of the conductive film 3, and they are in close contact with each other in a meshed state.

As the material for the polymer film 1b,
There is no particular limitation as long as it exhibits insulating properties,
For example, a thermoplastic resin such as a polyimide resin, a polyester resin, a polyethylene resin, an epoxy resin or a thermosetting resin can be used. Among these, insulation,
A polyimide resin, which has excellent properties such as heat resistance and abrasion resistance, is preferable.

The conductive film 3 is not particularly limited, and examples thereof include a conductive film made of metal such as copper foil. The surface roughness of the rough surface of the conductive film 3 is 5 mm in measurement length and 0.8 in cutoff value.
In the measurement of mm, it is shown by the center line average roughness Ra and is usually 0.2 to 6.3 μm, preferably 0.4 to
The thickness is 3.2 μm, particularly preferably 0.8 to 1.6 μm. Further, the maximum height Rmax of the rough surface having irregularities is usually 0.8 to 25 μm, preferably 1.6 to 18 μm, and particularly preferably 3.2 to 12.5 μm.

The method of closely forming the polymer film 1b on the conductive film 3 is not particularly limited, and a method of extrusion-molding the material for forming the polymer film 1b on the conductive film 3 or previously Polymer film 1b
There is a method of forming a layer and sticking it on the conductive film 3 by a method such as pressure bonding. Moreover, you may use a commercial item for such a laminated film. Examples of commercially available products include flexible printed wiring boards (FP
An example is a copper clad laminate for C). And since a part of the polymer film is formed in the net portion, there is no adhesive layer,
Moreover, a copper-clad laminate for FPC using an electrolytic copper foil is preferable. Further, the thickness of the polymer film 1b is preferably 5 to 200 μm, and particularly preferably 10 to 100 μm from the viewpoint of hole diameter accuracy of the through holes. The thickness of the conductive film 3 is usually 5 μm or more, preferably 5 μm or more.
The thickness is 100 μm, particularly preferably 10 to 50 μm.

Next, as shown in FIG. 2 (b), in the step (b), the surface of the polymer film 1b of the laminated film is irradiated with a laser 4 in the thickness direction to expose only the polymer film 1b. When the through hole is formed, the remaining polymer is formed by leaving a portion of the polymer film 1b which bites into the concave and convex rough surface of the conductive film 3 located below the polymer film 1b. It is a step of forming a mesh portion in the film 1b portion and forming one end opening of the through hole into a mesh opening.

That is, as shown in the enlarged cross-sectional view of the laminated film of FIG. 5, an arrangement pattern of conductive metal bodies is formed on the polymer film 1b formed on the rough surface of the conductive film 3. A laser 4 is radiated through a mask (not shown), and a through hole is formed while leaving the portion 1a of the polymer film 1b that has digged into the concave portion of the rough surface of the conductive film 3. Then, in the joint surface 7, the remaining portion 1a of the polymer film 1b becomes a net portion, the exposed convex portion of the rough surface of the conductive film 3 becomes a mesh, and one end of the through hole is a net-like opening. Is formed. Thus, the mesh-like openings of the through holes can be formed by keeping the depth of the through holes constant by adjusting the laser output and the number of shots. In addition,
The conductive film 3 is not processed during the drilling by the laser. The inner shape of the through hole formed by this laser irradiation is the opening on the laser irradiation side (the other end opening).
To the opening on the joint surface 7 side, the inner diameter becomes a taper shape that continuously decreases.

As the above laser, a laser used in general laser processing can be applied, but preferably,
It is an excimer laser. The conditions of this excimer laser are as follows. First, as a laser medium,
KrF (oscillation wavelength 248 nm), ArF (193 nm)
And the like, and preferably KrF. The oscillation frequency is usually 1 to 1000 Hz, particularly preferably 300 to 600 Hz. The energy density is usually 0.1 to 10 J / cm ² , preferably 0.2 to 6 J.
/ Cm ² , and particularly preferably 0.5 to 1 J / cm ² . The number of shots varies depending on the thickness of the polymer film and the processing energy density, but 50 to 200 shots are preferable from the viewpoint of cross-sectional shape accuracy and processing time.

The inner diameter of the opening (the other end opening) of the through hole on the laser irradiation side is usually 10 to 100 μ from the viewpoint of the insulation distance in the film surface direction of the anisotropic conductive film.
m, preferably 15 to 50 μm, particularly preferably 20.
Is about 40 μm. The inner diameter of the one-end opening (mesh-shaped opening) of the through hole is usually 7 to 100 μm, preferably 1
It is in the range of 2 to 50 μm, particularly preferably 17 to 40 μm. The distance (pitch) between the through holes is usually 1
It is 5 to 200 μm, preferably 30 to 100 μm, and particularly preferably 40 to 80 μm.

Next, in the step (c), as shown in FIG. 2 (c), a conductive metal is formed in the through hole of the polymer film 1b by an electroplating method using the conductive film 3 as an electrode. To form a conductive metal body 2a continuous in the thickness direction, and the other end of the conductive metal body corresponding to the other end of the through hole projects from the other end opening of the through hole. Is a step of forming.

The electroplating method is not particularly limited, and a usual method can be applied. The conductive metal to be deposited is not particularly limited, but gold, which has excellent conductivity, is preferable. The formation of the conductive metal body 2a by the electroplating method will be described by taking the electroplating using gold as an example.

That is, first, as shown in FIG. 3C, a resist layer 4 is formed on the back surface of the conductive film 3 if necessary. This is to prevent the conductive metal from depositing on the back surface of the conductive film 3.
The resist layer 4 is preferably an ultraviolet curable resist layer because of its resistance to plating solution, and specific examples thereof include those formed from a plating resist for printed boards. The resist layer 4 is formed as follows. That is, on the rotating plate of the spin coater, the laminated film is placed with the conductive film side up,
This is rotated and an appropriate amount of liquid resist is dropped. Then, after applying a resist so that the film thickness becomes uniform, it is dried (usually 25 ° C. × 15 minutes) and irradiated with ultraviolet rays to be cured. The thickness of the resist layer 4 is usually 1 to
50 μm, preferably 2 to 20 μm, particularly preferably 5
Is about 15 μm.

Next, after performing cleaning treatment and activation treatment (acid cleaning treatment) as necessary, electro gold plating is performed.

The above-mentioned cleaning treatment is carried out for the purpose of removing foreign matters in the through holes, and ultrasonic cleaning is usually employed.

The activation treatment is for removing the oxide film formed on the surface of the conductive film 3 by washing with an acid. Examples of the acid used for the above acid washing include hydrochloric acid, sulfuric acid and phosphoric acid, preferably hydrochloric acid. Generally, the acid cleaning treatment is performed by immersing the laminated film in the acidic solution.

In the electro gold plating, for example, the entire laminated film is immersed in the electro gold plating solution, the conductive film 3 is used as an electrode, and the electro gold plating solution is electrically conducted to penetrate the polymer film 1b. This is done by depositing gold in the holes. As a result, a conductive metal is deposited in the through hole to form a rod-shaped conductive metal body 2a along the inner shape of the through hole, and the conductive metal body 2a continues to grow and the through hole is opened. And the other end of the conductive metal body 2a serves as a protruding electrode portion. The formation of the protruding electrode portion is performed until the outer diameter thereof is substantially the same as the inner diameter of the other end opening of the through hole and is sufficiently high. As the above-mentioned electro gold plating solution,
Cyan bath, acidic bath, etc. can be mentioned. Among these, it is preferable to use an acidic bath for reasons of plating rate and uniform electrodeposition. Further, an additive may be used in the electrogold plating solution. This additive includes In, Tl,
Examples thereof include trace metals such as As, Sb, Se, Te and Ti, and organic substances containing nitrogen. As the current density of the electric gold plating, typically, 0.1~20A / dm ^2, preferably 0.1 to 10 A / dm ^2, particularly preferably 0.1
Is about 5 A / dm ² . The processing time is, for example, 1 A
In the case of / dm ² , it is 0.21 μm / min. The temperature condition is usually 10 to 85 ° C, preferably 20 to 85 ° C.
The temperature is 85 ° C, particularly preferably 40 to 80 ° C. Further, it is preferable to stir the electrogold plating solution during the electrogold plating treatment. Examples of the agitation method include air agitation, ultrasonic agitation, rocking agitation, and propeller agitation, but the agitation method using both agitation agitation and ultrasonic agitation is preferable.

The size of the protruding electrode portion thus formed is appropriately determined by the inner diameter of the through hole of the polymer film 1a and the like, but generally the height is usually 5 μm.
m or more, preferably 5 to 100 μm, particularly preferably 5
Is about 40 μm. Further, its shape is also preferably a substantially hemispherical shape like the mushroom head shown in FIG.

Next, the step (d) is a step of forming the conductive layer 5 on the protruding electrode portion of the other end opening of the through hole of the polymer film 1b, as shown in FIG. 2 (d). This conductive layer 5 is used for the conductive metal body 2 in the step (f) described later.
It serves as a cathode of the electrolytic plating method when forming the protruding electrode portion on the other end side of a. The method for forming the conductive layer 5 is not particularly limited, but examples thereof include an electroless plating method, and an electroless copper plating method is preferable. By this electroless copper plating method, a continuous conductive layer 5 as shown in the figure can be formed.

This electroless copper plating will be specifically described. That is, first, if necessary, an acid cleaning treatment is performed. The method described above can be applied to this acid cleaning treatment. And, the electroless plating catalyst which becomes the precipitation nucleus of the electroless plating,
A catalyst process, which is a process of depositing on the object to be plated, is performed. Palladium is usually used as the electroless plating catalyst, and its deposition is performed by physical adsorption.
The condition for this catalyst processing is that the temperature is usually 1
It is 0 to 50 ° C., preferably 15 to 40 ° C., particularly preferably 20 to 30 ° C., and the time is usually 0.5 to 20 minutes, preferably 1 to 10 minutes, particularly preferably 1 to 5 minutes.
Then, accelerator processing is performed. This accelerator treatment is an acid cleaning treatment. The conditions are as follows: dipping in dilute sulfuric acid or dilute hydrochloric acid, and the temperature is usually 10 to 50 ° C., preferably 20 to 50 ° C., and particularly preferably 35 to 45 ° C. The time is usually 0.5 to 10 minutes, preferably 2 to 3 minutes. Then, the laminated film is immersed in an electroless copper plating solution to perform electroless copper plating. Examples of the electroless copper plating solution include those containing copper sulfate, a chelating agent, a reducing agent, and a pH adjusting agent as main components. Examples of the chelating agent include ethylenediaminetetraacetic acid (EDTA), examples of the reducing agent include formaldehyde, and examples of the pH adjusting agent include sodium hydroxide. As a condition of this electroless copper plating treatment, the temperature is usually 30 to 6
5 ° C, preferably 40-60 ° C, particularly preferably 48-
55 ° C. And the processing time is usually 1 to 60 minutes,
It is preferably 2 to 20 minutes, particularly preferably 3 to 10 minutes.

As shown in FIG. 2D, it is preferable to form a resist layer 6 on the conductive layer 5. This is to prevent the conductive metal from depositing on the conductive layer 5 during the electroplating process in the step (f) described later. The formation of the resist layer 6 can be performed by the same method as described above, and the conditions such as the forming material and the thickness thereof are also the same.

Next, in the step (e), as shown in FIG. 3 (e), the conductive film 3 is removed from the laminated film, and the end face of the conductive metal body 2a on one end side is meshed with a mesh-shaped opening. It is a process of exposing from. The method of removing the conductive film 3 is not particularly limited. For example, when the conductive film 3 is a conductive metal such as copper foil, a method of using an etching solution that dissolves the conductive metal can be used. This etching solution is used for the conductive film 3
It is appropriately determined depending on the type of the solution, and examples thereof include cupric chloride solution and ferric chloride solution. Also,
When the resist layer 4 is formed, it is necessary to remove it along with the removal of the conductive film 3. For this removal, a method using an etching solution that dissolves the resist layer 4 can be used. The etching solution for dissolving the resist layer 4 is appropriately determined depending on the type of the resist layer 4, and examples thereof include a solution of toluene, ketone, cellosolve, etc., and a commercially available exclusive stripping solution.

Next, in the step (f), as shown in FIG. 3 (f), an electroplating method is used in which the conductive layer 5 formed on the protruding electrode portion at the other end opening of the through hole is used as an electrode. , Depositing a conductive metal on the exposed end surface of one end side of the conductive metal body 2a formed in the through hole of the polymer film 1b,
This is a step of forming one end of the conductive metal body 2a on the protruding electrode portion projecting from the entire one end opening of the through hole.

The formation of the protruding electrode portion by this electroplating method can be performed in the same manner as in the above step (c). By this step (f), as shown in FIG. 3 (f), a protruding electrode portion protruding from the back surface (the surface opposite to the laser irradiation surface) of the polymer film 1b is formed with a uniform shape and a sufficient height. It becomes possible to do. Further, unlike the conventional method, the inner shape of the recess formed by etching on the conductive support is not transferred to form the protruding electrode portion surface, so that the surface of the protruding electrode portion has high smoothness, The reliability of the electrical connection becomes extremely excellent.

Next, the step (g) is a step of removing the conductive layer 5 formed on the protruding electrode portion at the other end opening of the through hole. The removal of the conductive layer 5 can also be performed by the same method as in the step (e) described above, and the removal of the resist layer 6 when the resist layer 6 is formed can be performed in the same manner as described above. it can.

Through the above steps (a) to (g), an anisotropic conductive film as shown in FIG. 3 (g) can be obtained. In the figure, 1
Indicates a polymer film, and 2 indicates a conductive metal body having both ends formed on the protruding electrode portions. Further, in this invention,
From the viewpoint of reliability of electrical connection, the shape of the protruding electrode portion is preferably a substantially hemispherical shape, but the shape is not limited to this.

Next, the formation of the conductive layer in the step (d) and the electroplating method in the step (f) can be carried out by a method different from the above-mentioned method. As another method of this, there is a spray electroplating method. That is, FIG.
As shown in, the conductive support (conductive layer) 10 is brought into contact with the protruding electrode portion on the other end side of the conductive metal body 2a formed in the through hole of the polymer film 1b to make it a cathode, Further, using the spray nozzle 11 as an anode, the electroplating solution 12 is sprayed from the spray nozzle 11 to the surface of the polymer film 1b (the surface where the mesh openings are formed) opposite to the side of the protruding electrode portion. Then, the conductive metal is deposited on the end surface of the conductive metal body 2a exposed from the mesh of the through-hole net-like openings, and the protruding electrode portion is formed. According to the spray electroplating method, the process of forming the conductive layer and the process of forming the resist layer formed thereon are simplified, so that the manufacturing efficiency is improved.

[0043]

As described above, in the anisotropic conductive film of the present invention, one end of the through hole of the polymer film is formed into a net-like opening, and the protruding electrode portion of the conductive metal body is projected from the net-like opening. The net portion is located inside the conductive metal body. Therefore, the conductive metal body and the polymer film are integrated, and the conductive metal body does not fall off. Therefore, the anisotropic conductive film of the present invention maintains excellent performance for a long time. Further, since it is not necessary to form the claw portion on the protruding electrode portion, the protruding electrode portion can be formed small, and the pitch between the conductive metal bodies can be narrowed. The insulating property of the flexible film in the film surface direction is improved.

Further, the method for producing an anisotropic conductive film of the present invention is carried out by irradiating a laser beam onto the above-mentioned polymer film of a laminated film in which a polymer film is closely formed on an uneven rough surface of the conductive film. The conductive film is formed in a mesh-like opening by forming one end of the through hole by forming a mesh-like opening by leaving a polymer film portion that has digged into the concave and convex rough surface of the conductive film. In this manufacturing method, the body is formed and the end of the conductive metal body is projected from the entire mesh-shaped opening to form a protruding electrode portion. As a result, the mesh portion of the polymer film comes to be positioned inside the conductive metal body, and an anisotropic conductive film in which both are integrated can be manufactured.

Further, in the method for producing the anisotropic conductive film of the present invention, the protruding electrode portions on both surfaces of the polymer film are formed by electroplating one by one in separate steps. As a result, the shape of the protruding electrode portions on both ends of the conductive metal body of the obtained anisotropic conductive film is uniform and the heights are uniform. Further, like the conventional manufacturing method, the rough inner surface of the recess formed in the conductive support by etching is not transferred to the surface of the protruding electrode portion, and the surface of the protruding electrode portion becomes a glossy smooth surface, The contact performance of this protruding electrode portion is high.
From these facts, the anisotropic conductive film obtained by the present invention has extremely excellent electrical connection reliability. The method for producing the anisotropic conductive film of the present invention is a simple method that does not require special equipment or a special device, and thus can be easily carried out. Further, if a method such as a spray electroplating method is adopted, it is possible to improve the manufacturing efficiency.

Next, examples will be described together with comparative examples.

[0047]

Example 1 That is, first, a laminated film (Espanex, manufactured by Nippon Steel Chemical Co., Ltd.) as shown in FIG.
Prepared. In this laminated film, a polyimide film 1b having a thickness of 25 μm is formed on a rough surface of a rolled copper foil 3 having a thickness of 35 μm. The roughened surface of the rolled copper foil 3 has a surface roughness Ra of 1.0 μm and a maximum surface roughness Rm.
ax is 12.3 μm.

Next, the polyimide film 1b of the laminated film is perforated by an excimer laser by the above-described method as shown in FIG. 2 (b), and a square having a vertical and horizontal pitch of 45 μm and a side of 30 mm. A large number of through holes each having an opening inner diameter of 30 μm on the laser irradiation surface side were bored in the region (2). The conditions for laser processing are as follows.

Excimer laser device: Excimer laser processing device, manufactured by Nissin Electric Co., Ltd. Laser medium: KrF (oscillation wavelength 248 nm) Oscillation frequency: 300 Hz Processing energy density: 1.2 J / cm ² Number of shots: 220 shots

The laminated film was observed with a scanning electron microscope (750 times). As a result, the inner diameter of the one end opening (opening on the bonding surface side) of the through hole of the polyimide film 1b was 17 μm, and the inner shape was tapered. In addition, at one end of the through hole, an average of 23 convex tip ends of the uneven rough surface of the copper foil 3 is exposed per through hole, and a part of the polyimide film is present in the concave portion of the uneven rough surface. It remained and formed the mesh part. The size of the mesh of this mesh portion was 2 to 5 μm. FIG. 9 shows a photograph of a state in which one end opening of the through hole of this polyimide film 1b is formed as a mesh opening.

Next, as shown in FIG. 2C, the copper foil 3
A UV-curable resist layer 4 (Eagle NT-90, Shipley Far East Co., Ltd.) having a thickness of 8 μm is formed on the back surface of the substrate, ultrasonic cleaning is performed for 60 seconds, and then activation treatment (acid cleaning treatment) is performed. It carried out for 30 seconds using the hydrochloric acid of 10 volume% concentration. Then, using the copper foil 3 as an electrode, an electro-gold plating process was performed by the above-described method, and the conductive metal body 2a having the other end formed on the protruding electrode portion was formed in the through hole of the polymer film 1b. The height of the protruding electrode portion of the conductive metal body 2a is 7 μm. In addition, the conditions of the above-mentioned electro gold plating are as follows.

Electrolytic gold plating solution composition: potassium gold cyanide 8 g / l acid gold plating additive 500 ml / l (Orchid GS-21, manufactured by Metalworking Technology Laboratory Co., Ltd.) Temperature: 60 ° C. Stirring: Swing stirring and super Combined use with sonic agitation Current density: 1 A / dm ² Hour: 190 minutes

Then, as described above, an acid cleaning treatment, a catalyst treatment, an accelerator treatment, and an electroless copper plating treatment are performed, and as shown in FIG. The copper conductive layer 5 was formed. The conditions for each of the above processes are as follows.

[Acid cleaning treatment] Acid: 10% by volume concentration hydrochloric acid Time: 2 minutes

[Catalyst Treatment] Catalyst solution composition: Palladium catalyst solution 40 ml / l (Catalyst C, manufactured by Okuno Chemical Industries Co., Ltd.) 15% by volume hydrochloric acid Temperature: 25 ° C. Time: 2 minutes

[Accelerator treatment] Accelerator treatment liquid: 100 ml / l hydrochloric acid Temperature: 35 ° C. Time: 2 minutes

[Electroless Copper Plating] Electroless Copper Plating Solution: Copper Copper 2.6 g / l (OPC Copper H, Okuno Chemical Industries Co., Ltd.) Temperature: 55 ° C. Time: 10 minutes

Next, the UV-curable resist layer 4 formed on the back surface of the copper foil 3 was dissolved and removed by using a solvent (Eagle NT-90, manufactured by Shipley Far East Co., Ltd.), and then, as shown in FIG. 2 (d). As shown, on the copper conductive layer 5 formed on the protruding electrode portion, a thickness of 8 is formed by the method described above.
μm UV curable resist layer 6 (Eagle NT-9
0, manufactured by Shipley Far East Co., Ltd.) was formed. Also,
As shown in FIG. 3E, the copper foil 3 was dissolved and removed with a cupric chloride solution. Then, as shown in FIG.
The above-described electro-gold plating treatment is performed to deposit a conductive metal on the exposed end surface of the conductive metal body 2a on one end side (lower side in the drawing), and the height is 6 μm and the outer diameter is the same as the inner diameter of the mesh opening of the through hole. Substantially the same protruding electrode portions were formed. The conditions of this electro gold plating treatment are the same as those described above.

Then, the copper conductive layer 5 and the resist layer 6 were removed in the same manner as described above to prepare an anisotropic conductive film as shown in FIG. 2 (g).

The shape of the protruding electrode portions formed on both ends of the conductive metal body of the anisotropic conductive film of Example 1 thus obtained was evaluated using a metallurgical microscope. As a result, the protruding electrode portion was formed in a substantially hemispherical shape like a mushroom head, and the surface was a glossy and smooth surface. In addition, the shape of each protruding electrode portion was formed uniformly, and in particular, the height was uniform. Next, the anisotropic conductive film was connected to a probe for measuring electric resistance and a circuit substrate, and the reliability of the electrical connection was evaluated. As a result, the reliability of the electrical connection was excellent. In addition, the conductive metal body did not fall off during this evaluation.

[0061]

Example 2 The conductive metal body was formed so that the other end thereof would serve as a protruding electrode portion by the above-mentioned spray electro-gold plating method. That is, in the same manner as in Example 1, by the steps (a), (b), (c), and (e), a conductive metal having the other end serving as a protruding electrode portion in the through hole of the polyimide film 1b. Formed body 2a. The end surface of the conductive metal body 2a on the one end side is exposed from the mesh of the mesh openings of the through holes. Then, as shown in FIG. 8, the conductive support (titanium-
Platinum electrode plate 10 is brought into contact with the above-mentioned protruding electrode portion, and this is used as the cathode of the electro-gold plating method, and the spray nozzle 11 is used as the anode, with respect to the film surface of the polyimide film 1b on the exposed end surface side of the conductive metal body 2a. The gold plating solution was sprayed.

Then, one end of the conductive metal body 2a is formed on the protruding electrode portion (height 6 μm) by this electroplating by spraying.
m) to form the desired anisotropic conductive film.

The shape of the protruding electrode portions formed on both ends of the conductive metal body of the anisotropic conductive film of Example 2 thus obtained was evaluated in the same manner as in Example 1. As a result, the protruding electrode portion was formed in a substantially hemispherical shape like a mushroom head, and the surface was a glossy and smooth surface. In addition, the shape of each protruding electrode portion was formed uniformly, and in particular, the height was uniform. Next, the anisotropic conductive film was evaluated for reliability of electrical connection in the same manner as in Example 1. As a result, the reliability of electrical connection was excellent. In addition, the conductive metal body did not fall off during this evaluation. Further, in this example, since the spray electroplating method was adopted, the step of forming the conductive layer and the step of forming the resist layer formed on the conductive layer were simplified, and the manufacturing efficiency was improved.

[0064]

[Comparative Example] An anisotropic conductive film was produced in the same manner as the conventional production method. That is, first, the same laminated film as in Example 1 as shown in FIG. 7A is prepared, and then FIG.
As shown in FIG. 5, the polyimide film 1e was irradiated with the excimer laser 4 through a mask (not shown) to form through holes in the film thickness direction. The conditions of this excimer laser and the size of the through holes are the same as in Example 1.
Next, as shown in FIG. 3C, the copper foil 3a was etched from the through holes of the polyimide film 1e to form recesses at locations corresponding to the through holes of the copper foil 3a. The etching solution used for this etching treatment is a solution containing hydrogen peroxide solution (30% by weight) and sulfuric acid (3% by weight). The state of the concave portion of the copper foil 3a formed by this etching treatment is shown in the micrograph (100 times) of FIG. As is clear from this photograph, the shape of the recess formed in the copper foil 3a was not uniform. Next, as shown in FIG. 3D, electroplating was performed using the copper foil 3a as an electrode to deposit gold in the through hole of the polymer film 1e to form the conductive metal body 2c. The conditions for this electrogold plating are the same as in Example 1. By this electroplating, the conductive metal bodies 2c were projected and grown from both surfaces of the polyimide film 1e to form a protruding electrode portion having an outer diameter larger than the inner diameter of the opening of the through hole. Then,
The copper foil 3a was removed to obtain an anisotropic conductive film in which a large number of conductive metal bodies 2c were embedded in the polyimide film 1e, as shown in FIG.

The shape of the protruding electrode portions formed on both ends of the conductive metal body of the anisotropic conductive film of the comparative example product thus obtained was evaluated by the same method as in Example 1. As a result, the protruding electrode portion on the laser irradiation surface side was formed in a substantially hemispherical shape like a mushroom head, and the surface was a glossy smooth surface. However, the bump electrode portion formed by the concave portion of the copper foil 3a had a non-uniform shape, and in particular, the height was uneven. Then, the thickness of the claw portion was thin, and the inner surface of the concave portion of the copper foil 3a was transferred to the surface of the protruding electrode portion to be a rough surface. Next, the anisotropic conductive film was evaluated for reliability of electrical connection in the same manner as in Example 1. As a result, the reliability of electrical connection was compared with the anisotropic conductive film of Example product. Was inferior. In addition, during this evaluation, it was confirmed that the claw portion of the protruding electrode portion was chipped and the conductive metal body was detached.

[Brief description of drawings]

FIG. 1A is a sectional view of an anisotropic conductive film according to an embodiment of the present invention, and FIG. 1B is an enlarged sectional view of the anisotropic conductive film.

FIG. 2 (a) is a cross-sectional view of a laminated film in which a polymer film is laminated on an uneven rough surface of a conductive film, and FIG. It is sectional drawing which shows the state which perforates a through hole, (c) is sectional drawing which shows the state which forms a conductive metal body in the penetration of the said polymer film, and forms the other end in a protrusion electrode part. FIG. 3D is a sectional view showing a state in which a conductive layer and a resist layer are formed on the protruding electrode portion.

FIG. 3 (e) is a cross-sectional view showing a state in which the conductive film is removed from the laminated film to expose one end side end surface of the conductive metal body, and (f) is the conductive film. It is a sectional view showing a state where one end of a metal object is formed in a projection electrode part, and (g) is a sectional view showing a state where a conductive layer on the projection electrode part and a resist layer formed thereon are removed. is there.

FIG. 4 is an enlarged cross-sectional view of a laminated film used in one example of the method for producing an anisotropic conductive film of the present invention.

FIG. 5 is an enlarged cross-sectional view showing a state in which a through hole is formed by laser in the polymer film of the laminated film.

FIG. 6A is a sectional view of a conventional anisotropic conductive film, and FIG. 6B is an enlarged sectional view of the conventional anisotropic conductive film.

FIG. 7 (a) is a cross-sectional view showing a state in which a polymer film is formed on a conductive support, and FIG. 7 (b) is a laser beam perforating process on the polymer film for penetration. It is sectional drawing which shows the state which forms a hole, (c) is sectional drawing which shows the state which forms a recess in the said electroconductive support body by an etching process, (d) is a through-hole of the said polymer film. It is sectional drawing which shows the state in which the electroconductive metal body was formed, and (e) is sectional drawing which shows the state which removed the said electroconductive support body.

FIG. 8 is a schematic view showing a state in which a protruding electrode portion is formed by a spray electroplating method.

FIG. 9 is a thin film photograph showing a state where through holes are formed in a polymer film of a laminated film.

FIG. 10 is a thin film photograph showing the shape of a recess formed in a copper foil of a laminated film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polymer film 1a Net part 2 Conductive metal body 2e Projection electrode part 2f Projection electrode part

[Procedure amendment]

[Submission date] February 16, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] Figure 9

[Correction method] Change

[Correction content]

[Figure 9]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

[Figure 10]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H05K 1/09 7511-4E H05K 1/09 A (72) Inventor Hideki Shinohara Komaki City, Aichi Prefecture Sotoyama character Utsutsu 3600 Tokai Rubber Industry Co., Ltd.

Claims (3)

[Claims] 1. A polymer film having a large number of through holes formed in the thickness direction, and a conductive metal body embedded in the through holes of the polymer film. Both ends of the conductive metal body. Is an anisotropic conductive film formed on the protruding electrode portions protruding from both sides of the polymer film, wherein one end opening of the through hole of the polymer film is a net formed from a part of the polymer film. Is a mesh-like opening covered with a portion, and the mesh portion of the mesh-like opening is located inside the conductive metal body, and the polymer film and the conductive metal body are integrated with each other. Conductive film. 2. The anisotropic conductive film according to claim 1, wherein the through hole of the polymer film is formed in a tapered shape whose inner diameter continuously decreases from the other end opening to the one end opening. 3. A method for producing an anisotropic conductive film, which comprises the following steps (a) to (g): (A) A laminated film in which a polymer film is laminated on an uneven rough surface of a conductive film, and the polymer film bites into the concave portion of the uneven rough surface of the conductive film at the joint portion thereof, and both are in close contact with each other. Step of preparing. (B) When a laser is applied to the surface of the polymer film of the laminated film in the thickness direction to form a through hole only in the polymer film, unevenness of the conductive film located under the polymer film A step of forming a net by the remaining polymer film portion by leaving the above-mentioned polymer film portion that bites into the concave portion of the rough surface to form one end opening of the through hole into a net-like opening. (C) A conductive metal is deposited in the through-holes of the polymer film by an electroplating method using the conductive film as an electrode to form a conductive metal body continuous in the thickness direction. The other end corresponding to the other end of the through hole of
A step of forming a protruding electrode portion protruding from the other end opening of the through hole. (D) A step of forming a conductive layer on the protruding electrode portion at the other end opening of the through hole. (E) A step of removing the conductive film of the laminated film and exposing the end face of the conductive metal body on one end side from the mesh of the one end opening of the through hole of the polymer film. (F) Exposing one end side of the conductive metal body formed in the through hole of the polymer film by electroplating using the conductive layer formed on the protruding electrode portion at the other end opening of the through hole as an electrode A step of depositing a conductive metal on the end face and forming one end of the conductive metal body on a protruding electrode portion protruding from the entire opening of the one end of the through hole. (G) A step of removing the conductive layer formed on the protruding electrode portion at the other end opening of the through hole.