JP6797535B2 - Manufacturing method of anisotropic conductive film and anisotropic conductive film - Google Patents

Description

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

The pillar array structure provided with a plurality of micrometer-sized metal columns can be expected to have various applications such as battery electrodes and anisotropic conductive films. Various methods have been proposed as a method for producing such a pillar array structure.

As one of the methods, there is a method of forming a fine hole pattern array in a resist pattern by a photolithography method or an electron beam lithography method, and filling the hole pattern array with a metal by a plating method to obtain a pillar array structure.

However, such a method has a problem that it is difficult to form a resist pattern having a high aspect ratio (ratio to the depth diameter), and it is difficult to produce a hole pattern array having a high aspect ratio.

Further, as another method, there is a method of patterning an aluminum anodized film (Patent Document 3). In this method, an aluminum substrate is anodized in an acidic aqueous solution to form a porous anodic oxide film (porous alumina layer).

Then, a resist mask is formed on the porous alumina layer, and wet etching is performed on the resist mask to form a microhole (opening pattern) array in the porous alumina layer appearing at the opening of the resist mask.

Since the porous alumina layer is etched with a uniform width from the surface to the bottom surface, a microhole array having an opening pattern with a high aspect ratio can be obtained.

By filling this microhole array with metal, it is possible to obtain a pillar array structure containing metal columns with a high aspect ratio.

Japanese Unexamined Patent Publication No. 2008-055556 Special Table 2013-506309 Japanese Unexamined Patent Publication No. 2010-407454 Japanese Unexamined Patent Publication No. 2013-057102

However, when the depth of the macrohole array formed on the porous alumina layer is 10 μm or more, or the aspect ratio exceeds 5, it is difficult to fill the bottom of the microhole with metal by conventional techniques such as sputtering and vapor deposition. In addition, there is a problem that the height of the formed pillars (metal pillars) also varies.

Therefore, there is a problem that a pillar array structure including a metal column having a high aspect ratio similar to that of the macrohole array cannot be obtained.

Therefore, it is an object of the present invention to provide a method for producing an anisotropic conductive film including a pillar array structure having a metal column having a higher aspect ratio, and an anisotropic conductive film .

According to one aspect of the following disclosure, a step of forming a porous alumina layer by anodizing the surface of an aluminum substrate, a step of forming a resist pattern on the surface of the porous alumina layer, and a step of performing wet etching to perform the resist pattern. A step of selectively dissolving and removing the porous alumina layer of the portion not covered with the metal to form an opening pattern, a step of performing replacement plating on the aluminum substrate exposed at the bottom of the opening pattern, and a step of the replacement plating. A step of forming a metal column that fills the inside of the opening pattern and an overflow layer that covers the upper part of the porous alumina layer and connects the metal columns to each other by performing electrolytic plating later, and the aluminum substrate and the porous alumina layer. A method for producing an anisotropic conductive film having a step of removing the metal column, a step of embedding the metal column in an insulator, and a step of removing the overflow layer is provided.

According to still another aspect, a sheet body made of an insulating material and a plurality of metal columns embedded in the sheet body and penetrating in the thickness direction of the sheet body are provided on the side surface of the metal column. Provides an anisotropic conductive film characterized in that streaky grooves extending in the thickness direction are formed.

Further, according to the method for producing an anisotropic conductive film from the above viewpoint, the anisotropic conductive film contains a large number of metal columns having a high aspect ratio at a fine pitch, and the anisotropic conductive film having a low contact pressure and low resistance is obtained. can get.

FIG. 1 is a cross-sectional view showing a state in which a resist mask is formed on a porous alumina layer in the method for manufacturing a pillar array structure according to the first embodiment. FIG. 2 is a cross-sectional view showing a structure obtained by wet-etching the structure of FIG. FIG. 3 is a cross-sectional view showing a state in which the structure of FIG. 2 is subjected to replacement plating. 4 (a) to 4 (c) are scanning electron micrographs showing the effect on the aperture pattern and the metal column when the replacement plating time is too long. FIG. 5 is a cross-sectional view showing a state in which the structure of FIG. 3 is electrolytically plated to form a metal column and an overflow layer. 6 (a) to 6 (c) are views showing an example of a metal column in which a plurality of metals are laminated. FIG. 7 is a cross-sectional view showing a pillar array structure obtained by removing the aluminum substrate and the porous alumina layer from the structure of FIG. 8 (a) and 8 (b) are scanning electron micrographs of the microhole array according to Experimental Example 1. FIG. 9 is a scanning electron micrograph showing the precipitated zinc according to Experimental Example 1. FIG. 10 is a scanning electron micrograph of the pillar array structure 5 produced in Experimental Example 1. 11 (a) and 11 (b) are cross-sectional views showing the manufacturing method of the anisotropic conductive film according to the second embodiment in the order of steps (No. 1). 12 (a) and 12 (b) are cross-sectional views showing the method for producing the anisotropic conductive film according to the second embodiment in the order of steps (No. 2). 13 (a) is a cross-sectional view showing an anisotropic conductive film obtained from the structure of FIG. 12 (b), and FIG. 13 (b) is also a perspective view.

The inventors of the present application have investigated and examined various methods for reliably filling a high aspect ratio microhole array with metal from the bottom.

As a result, if the aluminum substrate at the bottom of the microhole array is subjected to replacement plating and then electroplating using the aluminum substrate as the electrode, even a microhole array with an extremely high aspect ratio can be reliably plated from the bottom. It was found that metal can be filled in.

That is, according to the present invention, for example, even a microhole having a depth of 100 μm or more and an aspect ratio of 5 or more can be filled with metal from the bottom.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First Embodiment)
FIG. 1 is a cross-sectional view showing a state in which a resist mask is formed on a porous alumina layer in the method for manufacturing a pillar array structure according to the present embodiment.

In the method for manufacturing the pillar array structure of the present embodiment, first, an aluminum substrate 1 having a porous alumina layer 2 formed on its surface is formed.

The porous alumina layer 2 is a film made of a porous material having a structure in which fine pores extending in a direction perpendicular to the film surface are densely packed. The porous alumina layer 2 can be obtained most simply by anodizing the aluminum substrate 1 in an acidic electrolytic solution, and has a feature that pores having a uniform diameter are formed perpendicular to the film surface. Have.

The formed pores form independent pores, and the diameter of the pores can be appropriately adjusted in the range of 5 to 800 nm and the interval can be appropriately adjusted in the range of 10 to 1000 nm by the chemical conversion voltage at the time of anodizing.

Further, after anodizing, the diameter of the pores can be enlarged by immersing in a soluble etchant such as phosphoric acid.

The thickness of the porous alumina layer 2 is proportional to the chemical conversion time and can be adjusted in the range of 0.1 μm to 5 mm.

In addition, by optimizing the conditions at the time of anodizing, it is possible to obtain a structure in which the pores are regularly arranged in a wide range. In the porous alumina layer in which the pores are regularly arranged, the pore shape and the pore diameter are made uniform as the pore arrangement is regularized, and the orthogonality of the pores is improved.

Such regular pores are obtained by removing parts of the less regular structure formed in the early stages of anodization.

Specifically, after anodizing for a certain period of time to regularize the pore arrangement, the oxide film is selectively removed by appropriate etching, and anodizing is performed again under the same conditions from the surface to the bottom. A porous alumina layer 2 having regular pores is obtained.

In this case, the shape and diameter of the pores are uniform, and the structure is linearly continuous in the film thickness direction. That is, the length of the pores and the thickness of the porous alumina layer 2 are substantially the same.

Next, a resist pattern 3 having etching resistance is formed on the porous alumina layer 2 formed by anodizing as shown in the figure. A porous alumina layer is exposed in the opening 3a of the resist pattern 3. The shape of the opening 3a is the same as the planar shape of the desired pillar array structure.

As the material of the resist pattern 3, a material having excellent water resistance and acid resistance and having sufficient adhesion to the alumina film can be used. For example, chloroprene rubber, butadiene rubber, aculonitrile butadiene rubber, acrylic adhesive. , Cellulose acetate and the like can be used as a masking agent.

In such a resist pattern 3, for example, a resist agent is applied to the surface of a stamper having a predetermined pattern shape, the stamper is pressed against the surface of the porous alumina layer 2, and the resist agent on the surface of the stamper is transferred to the porous alumina layer 2. It can be formed by doing. According to this method, it is possible to repeatedly use the stamp once prepared, to form a pattern at low cost, and to prevent the masking agent from penetrating into the pores of the porous alumina layer.

Further, instead of the above method, the resist pattern 3 may be formed by coating a photoresist film and patterning by a photolithography method or an electron beam lithography method. FIG. 2 is obtained by etching the structure of FIG. It is sectional drawing which shows the structure.

Next, as shown in FIG. 2, the porous alumina layer 2 exposed in the opening 3a of the resist pattern 3 is selectively removed by performing wet etching.

As the etchant, an aqueous phosphoric acid solution or a mixed solution of chromic acid and phosphoric acid can be used. When immersed in such an etchant, the etchant invades into the pores of the porous alumina layer 2 exposed in the opening 3a, and uniform dissolution of the pore wall proceeds from the upper part to the bottom of the porous alumina layer 2.

As a result, even if the porous alumina layer 2 is thick, only the portion of the porous alumina layer 2 exposed to the opening 3a can be selectively removed, so that the opening pattern (microhole) 2a having a high aspect ratio is provided. A microhole array is obtained.

At this time, the porous alumina layer 2 under the opening 3a is completely dissolved and removed, the aluminum substrate 1 is exposed at the bottom of the opening pattern 2a, and etching in the depth direction is stopped. As a result, an opening pattern 2a having a uniform depth according to the film thickness of the porous alumina layer 2 is formed.

The opening pattern 2a formed in this way has streaky irregularities extending in the film thickness direction of the porous alumina layer 2 on its side surface. The streaky unevenness reflects the shape of the pores of the porous alumina layer 2.

After that, if the metal is deposited by electroplating using the aluminum substrate 1 as an electrode, it is considered possible to fill the metal from the bottom of the opening pattern 2a.

However, it has been found that it is difficult to fill the metal even if the surface of the aluminum substrate 1 is electrolytically plated. This is because an insulating natural oxide film exists on the surface of the aluminum substrate 1 and inhibits the growth of the plating film.

A method of removing the natural oxide film of the aluminum substrate 1 can be considered in order to enable electrolytic plating.

Therefore, in order to remove the natural oxide film of the aluminum substrate 1 and deposit zinc 4 as a seed for electrolytic plating on the bottom of the opening pattern 2a, a substitution is made in contact with an alkaline solution (sodium hydroxide aqueous solution) containing zinc ions for a predetermined time. It was decided to perform plating.

FIG. 3 is a cross-sectional view showing a state in which the structure of FIG. 2 is subjected to replacement plating.

As shown in FIG. 3, by performing replacement plating, zinc 4 which is kept in a conductive state with the aluminum substrate 1 and becomes a seed for metal precipitation by subsequent electroplating is deposited on the bottom of the opening pattern 2a.

When contacted with an alkaline solution containing zinc ions, the natural oxide film of the aluminum substrate 1 is dissolved and aluminum is exposed, and replacement plating with zinc ions proceeds. Then, zinc 4 which is a conductive layer when electrolytic plating is performed is deposited on the bottom of the opening pattern 2a.

The plating bath used for replacement plating is a strong alkali containing sodium hydroxide or the like because it is necessary to dissolve the natural oxide film of the aluminum substrate 1.

However, the alkaline solution may corrode not only the natural oxide film (aluminum oxide) on the surface of the aluminum substrate 1, but also the aluminum substrate 1 and the porous alumina layer 2.

Therefore, in the present embodiment, it has been found that zinc 4 serving as a conductive layer can be precipitated without dissolving the porous alumina layer 2 by performing a short-time treatment on the replacement plating under appropriate conditions.

Specifically, replacement plating is performed under the following conditions.

The concentration range of the plating bath is 1 to 30 [g / liter] for zinc oxide (optimal concentration: 6.5 [g / liter]) and 10 to 50 [g / liter] for sodium hydroxide (optimal concentration: 35 [g / liter]). g / liter]).

The temperature of the plating bath may be 10 to 30 [° C.] (optimum temperature 20 [° C.]).

The contact time with the plating bath may be 20 to 90 [seconds] (optimum time 60 [seconds]).

It is not necessary to perform the replacement plating so as to cover the entire bottom surface of the opening pattern 2a with zinc, and it is sufficient if zinc 4 conducting with the aluminum substrate 1 is deposited even on a part of the opening pattern 2a.

If the replacement plating time is too short than the above time, the precipitation of zinc 4 may be insufficient at the bottom of a part of the opening pattern 2a. Further, if the replacement plating time is too long, the aluminum substrate 1 at the bottom of the opening pattern 2a will be corroded.

FIG. 4A is a scanning electron micrograph of a cross section of the aluminum substrate 1 and the opening pattern 2a near the bottom when the replacement plating time is long, and FIG. 4B is a scanning electron micrograph showing the resulting metal column. It is a micrograph, and FIG. 4 (c) is a scanning electron micrograph of the tip of the metal column of FIG. 4 (b) enlarged.

As shown in FIG. 4A, if the replacement plating time is too long, the aluminum substrate 1 of the opening pattern 2a melts, and as a result, the bottom portion of the opening pattern 2a expands.

When such dissolution occurs, as shown in FIGS. 4 (b) and 4 (c), a metal column having a diameter of the tip portion larger than that of the other portions is formed.

As another condition of the replacement plating, it is preferable to perform the etching of the porous alumina layer 2 and before the porous alumina layer 2 is dried.

After etching the porous alumina layer 2 and before drying, the inner wall of the opening pattern 2a is kept hydrophilic, so that the aqueous solution containing zinc oxide and sodium hydroxide can surely penetrate the opening pattern deep into 2a. Because.

A surfactant may be added in order to improve the wettability of the aqueous solution containing zinc oxide and sodium hydroxide to the porous alumina layer 2 and to improve the permeability to the fine opening pattern 2a.

In the above description, substitution plating with zinc has been described as an example, but the present embodiment is not limited to this, and an alkaline or acidic aqueous solution containing metal ions having a standard electrode potential higher than that of aluminum in addition to zinc is used. Replacement plating can also be performed. When the aluminum substrate 1 is immersed in such a plating bath, the natural oxide film on the surface of the aluminum substrate 1 is dissolved by an acid or an alkali, and after the aluminum is exposed, the substitution plating proceeds, as in the case of replacement plating with zinc. A conductive layer (seed layer) for electrolytic plating can be obtained.

FIG. 5 is a cross-sectional view showing a state in which the structure of FIG. 3 is electrolytically plated to form a metal column and an overflow layer.

After the replacement plating, as shown in FIG. 5, a current is passed through the aluminum substrate 1 to perform electrolytic plating, so that the inside of the opening pattern 2a is filled with metal to form a metal column 5a.

This electrolytic plating is performed by applying a DC voltage to the aluminum substrate 1 in a plating bath containing metal ions such as Ni.

It is also possible to fill the opening pattern 2a with metal by forming the plating seed layer by a dry process such as a sputtering method or a thin film deposition method as in the prior art. However, in the conventional method, when the depth of the opening pattern 2a increases and the aspect ratio exceeds 5, it is difficult to completely fill the bottom of the opening pattern 2a with metal.

On the other hand, according to the present embodiment, the metal is precipitated from the bottom of the opening pattern 2a as the filling of the metal seeded with zinc 4 precipitated by the replacement plating proceeds, so that the opening pattern 2a has a high aspect ratio. Even so, the bottom can be reliably filled with metal.

Even after the opening pattern 2a is filled with metal, electrolytic plating is continuously performed to cover the upper part of the porous alumina layer 2 and to form an overflow layer 5b connecting the metal columns 5a to each other.

The metals that can be filled by the electrolytic plating of the present embodiment are Ti, V, Cr, Mn, Fe, Co, Zn, Ga, As, Ru, Rh, Pd, Ag when an aqueous solution-based plating bath is used. , Cd, Dc, In, Sn, Sb, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po and the like. When a non-aqueous plating bath is used, Li, Be, Na, Mg, Al, K, Ca, Rb, Sr, Cs, Ba, Fr, and Ra can be filled.

Further, the metal column 5a in which at least two or more metals are laminated may be formed by exchanging the plating bath while filling the inside of the opening pattern 2a with metal.

6 (a) to 6 (c) are views showing an example of a metal column 5a in which a plurality of metals are laminated.

FIG. 6A is a cross-sectional view showing the structure of a metal column 5a in which two types of metals are laminated. Further, FIG. 6B is a cross-sectional view showing the structure of the metal column 5a in which three types of metals are laminated. Further, FIG. 6C is a cross-sectional view showing a structure in which two types of metals are alternately laminated in three layers.

Based on such a method, for example, as shown in FIG. 5 (c), a composite having excellent functionality using Ni having excellent mechanical strength in the central portion and Au having low contact resistance at both upper and lower ends. A metal column 5a having a structure can also be obtained.

FIG. 7 is a cross-sectional view showing a pillar array structure 5 obtained by removing the aluminum substrate 1 and the porous alumina layer 2 from the structure of FIG.

After the metal columns 5a and the overflow layer 5b are formed, the aluminum substrate and the porous alumina layer 2 are removed as shown in FIG.

Here, the aluminum substrate 1 and the porous alumina layer 2 can be removed by immersing the structure of FIG. 5 in an alkaline solution such as an aqueous sodium hydroxide solution. At the same time, the resist film 3 is removed.

As a result, the pillar array structure 5 of the present embodiment is completed. The height of the metal column 5a of the pillar array structure 5 obtained here corresponds to the film thickness of the porous alumina layer 2, and is controlled in the range of 0.1 μm to 5 mm by changing the anodizing time. Can be done.

Since the film thickness of the porous alumina layer 2 formed by anodizing has a substantially uniform thickness over a wide area, according to the present embodiment, for example, the height variation within a range of several centimeters is 5% or less. A pillar array structure 5 having a metal column 5a is obtained.

Further, the diameter and pitch of the metal column 5a can be controlled by changing the size and pitch of the opening 3a of the resist pattern 3.

Further, if the shape of the resist pattern 3 is changed, the opening pattern 2a can be formed not only as a columnar microhole but also as an align and space pattern, and various microstructures can be formed.

Further, on the side surface of the metal column 5a of the pillar array structure 5 obtained by the present embodiment, a streak-like uneven structure in the height direction reflecting the structure of the pores of the porous alumina layer 2 is formed.

When the metal column 5a having such irregularities is applied to the anisotropic conductive film, the adhesion between the metal column 5a and the resin sheet is improved, and defects such as pulling out of the metal column 5a are less likely to occur.

(Experimental Example 1)
In Experimental Example 1, a pillar array structure 5 made of a metal column 5a made of nickel having a high aspect ratio was produced.

The aluminum substrate 1 having a purity of 99.9% was electropolished in a mixed solution of perchloric acid and ethanol. Then, anodic oxidation was carried out for 10 hours under the conditions of a 0.3 M aqueous oxalic acid solution, a bath temperature of 17 ° C. and a chemical conversion voltage of 40 V to obtain a porous alumina layer 2 having a film thickness of 80 μm.

Next, a stamp made of polydimethylsiloxane having a pattern in which circular recess patterns having a diameter of 10 μm were arranged in a grid pattern at a pitch of 30 μm was prepared on the porous alumina layer 2. Then, a chloroprene rubber thin film was formed on the surface of the stamp by a dip coating method, and a resist pattern 3 made of chloroprene rubber was transferred to the surface of the porous alumina layer 2.

Next, the above sample was immersed in a mixed solution of chromic acid (1.8 wt%) and phosphoric acid (6 wt%) at a bath temperature of 50 ° C. for 20 minutes to expose the porous alumina layer in the opening 3a. 2 was selectively dissolved and removed.

As a result, as shown in FIGS. 8A and 8B, a microhole array having an opening pattern 2a as a circular microhole was obtained.

Next, the obtained sample was immersed in an aqueous solution of zinc oxide (0.65 wt%) and sodium hydroxide (3.3 wt%) at a bath temperature of 20 ° C. for 60 seconds to bring zinc to the bottom of the opening pattern 2a. 4 was precipitated.

By this treatment, as shown in FIG. 9, it was confirmed that zinc 4 was deposited on the bottom of the opening pattern 2a.

Then, the sample was subjected to nickel plating in a nickel plating bath with a constant voltage of −1.4 V applied to the aluminum substrate 1, the opening pattern 2a was filled with nickel, and then nickel was deposited on the sample surface. ..

Finally, by immersing the sample in an aqueous solution of sodium hydroxide (10 wt%), the aluminum base metal and the alumina portion were dissolved and removed to obtain a pillar array structure 5 made of nickel.

FIG. 10 is a scanning electron micrograph of the pillar array structure 5 produced in Experimental Example 1.

As shown in FIG. 10, it was confirmed that the pillar array structure 5 composed of the metal columns 5a having a high aspect ratio and having a uniform height can be obtained.

(Second Embodiment)
In this embodiment, a method for producing an anisotropic conductive film using a pillar array structure will be described.

11 (a) to 13 (a) are diagrams showing the manufacturing method of the anisotropic conductive film according to the present embodiment in the order of steps.

FIG. 11A is a cross-sectional view showing a pillar array structure 50 used in the method for producing an anisotropic conductive film according to the present embodiment.

As shown in FIG. 11 (a), in the present embodiment, the pillar array structure manufactured by the method described with reference to FIGS. 1 to 7 is used.

However, in the pillar array structure 50 of the present embodiment, a stopping layer 5c made of a material having etching resistance to the etchant against the overflow layer 5 is formed between the metal columns 5a and the overflow layer 5b.

Such a stopping layer 5c can be produced by exchanging the plating bath in the middle of electrolytic plating, as described with reference to FIG. 6C.

For example, when the metal column 5a and the overflow layer 5b are nickel, gold or the like can be used as the stopping layer 5d.

Further, as the pillar array structure 50 used for manufacturing the anisotropic conductive film, a metal column 5a having a diameter of about 2 μm, a pitch of about 5 μm, and a height of about 100 μm can be used.

Next, as shown in FIG. 11B, the covering sheet 7 is mounted on the metal column 5a of the pillar array structure 50.

The coating sheet 7 has a PET (polyethylene terephthalate) resin film 7a constituting the main body of the sheet, a PDMS (polymethylsiloxane) film 7b coated on the surface of the PET resin film 7a, and the surface tension of the PDMS film 7b. It has a mold release treatment layer 7c that has been subjected to a reduction treatment.

Next, as shown in FIG. 12A, the undiluted solution of silicone rubber is poured into the space between the pillar array structure 50 and the covering sheet 7. Then, the silicone rubber is cured to form the resin sheet 6.

Then, as shown in FIG. 12B, the overflow layer 5b is removed up to the stopping layer 5c by wet etching.

Next, the coating sheet 7 is peeled off from the metal column 5a and the resin sheet 6 to obtain the anisotropic conductive film 10 shown in FIGS. 13 (a) and 13 (b).

The anisotropic conductive film 10 has a structure in which a metal column 5a is embedded in a resin sheet 6 made of an elastic body, and when electrodes are brought into contact with the upper and lower surfaces of the resin sheet 6, conduction in the vertical direction is obtained. be able to.

In the conventional anisotropic conductive film, conductive particles are dispersed in an elastic resin matrix, and the conductive particles come into contact with each other at a pressure-applied portion and conduct in the thickness direction. .. However, there is a problem that the contact resistance between particles is large and the resistance value becomes high unless a relatively high pressure is applied, so that it cannot be used for highly sensitive measurement.

On the other hand, since the anisotropic conductive film 10 of the present embodiment conducts with the metal column 5a penetrating the resin sheet 6, a low resistance value can be obtained even if contact is made with a low contact pressure, and the measurement is more sensitive. Can be done.

Further, since the height uniformity of the metal column 5a is high, the reliability is excellent without causing a problem such as local poor continuity.

Further, the metal column 5a embedded in the anisotropic conductive film 10 has streaky irregularities on its side surface and is more firmly bonded to the resin sheet 6, so that the pin can be pulled out due to bending or the like. It is less likely to cause troubles such as squeezing and has excellent durability.

Therefore, the anisotropic conductive film 10 of the present embodiment can be suitably used for, for example, testing a semiconductor device.

1 ... Aluminum substrate, 2 ... Porous alumina layer, 3 ... Resist pattern, 4 ... Zinc (precipitate), 5, 50 ... Pillar array structure, 5a ... Metal column, 5b ... Overflow layer, 5c ... Stopping layer, 6 ... Resin sheet, 7 ... coating sheet, 10 ... anisotropic conductive film.

Claims (6)

The process of forming a porous alumina layer by anodizing the surface of the aluminum substrate,
A step of forming a resist pattern on the surface of the porous alumina layer and
A step of performing wet etching to selectively dissolve and remove the porous alumina layer in the portion not covered by the resist pattern to form an opening pattern.
The step of performing replacement plating on the aluminum substrate exposed at the bottom of the opening pattern, and
A step of forming a metal column that fills the inside of the opening pattern and an overflow layer that covers the upper part of the porous alumina layer and connects the metal columns by performing electrolytic plating after the replacement plating.
The step of removing the aluminum substrate and the porous alumina layer, and
The process of embedding the metal pillar in the insulation and
The step of removing the overflow layer and
A method for producing an anisotropic conductive film, which comprises. The method for producing an anisotropic conductive film according to claim 1, wherein the insulating material is made of a resin or a metal oxide. The step of embedding the metal column in the insulator is
The process of arranging the covering sheet on the metal column and
A step of infiltrating the resin into the gap between the coating sheet and the overflow layer,
The method for producing an anisotropic conductive film according to claim 1, wherein the anisotropic conductive film is produced. A sheet made of insulating material and
It has a plurality of metal columns embedded in the sheet body and penetrating in the thickness direction of the sheet body.
A streak-like groove extending in the thickness direction is formed on the side surface of the metal column.
An anisotropic conductive film characterized in that zinc is contained at one end of the metal column. The anisotropic conductive film according to claim 4 , wherein the metal columns are arranged at a constant pitch. The anisotropic conductive film according to claim 4 or 5 , wherein the diameter of the metal column is 10 μm or less, and the height of the metal column is 100 μm or more.