WO2022085464A1

WO2022085464A1 - Conductive film having gold layer

Info

Publication number: WO2022085464A1
Application number: PCT/JP2021/037072
Authority: WO
Inventors: 敬之野坂; 昌利後藤; 英希薩摩
Original assignee: セーレン株式会社; 敬之野坂; 昌利後藤; 英希薩摩
Priority date: 2020-10-20
Filing date: 2021-10-06
Publication date: 2022-04-28
Also published as: JPWO2022085464A1; CN116096942A; KR20230091902A

Abstract

[Problem] The present invention addresses the problem of obtaining a conductive film in which the migration of copper into a gold layer is suppressed, discoloration of the gold layer over time is suppressed, and cracks in the gold layer do not occur due to bending. Furthermore, a conductive film having excellent corrosion resistance can be obtained. [Solution] The conductive film is formed by laminating a copper layer, a nickel layer, and a gold layer on one surface of an insulating film substrate in this order, the conductive film being characterized in that the thickness of the nickel layer is 0.05-0.2 μm. The arithmetic average roughness (Ra) of the surface of the copper layer on the side in which the nickel layer is laminated is preferably 0.02 μm or less.

Description

Conductive film with gold layer

The present invention relates to a conductive film. More specifically, the present invention relates to a conductive film in which a gold layer is laminated on the surface and the bending resistance and corrosion resistance of the gold layer are improved while suppressing the migration of copper to the gold layer.

With the miniaturization and weight reduction of electronic devices, flexible printed substrates in which circuits are formed on the surface of flexible films are being used. Highly conductive copper is often used for circuits formed on the film surface. Further, for the purpose of protecting the circuit surface made of copper and lowering the contact resistance, a layer made of gold is laminated on the copper surface. When a layer made of gold is directly laminated on the surface of copper, there is a problem that migration of copper occurs over time and copper accumulates on the surface of the gold layer, causing discoloration and an increase in contact resistance value.

In order to solve this problem, an intermediate layer made of nickel, tin, etc. is provided. However, as a result of providing the intermediate layer, new problems such as cracks on the surface of the layer made of gold due to bending and pinholes, which reduce corrosion resistance, have been presented. Is required to be resolved.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2009-176646) is characterized in that the average crystal grain size of a metal constituting a surface side region under a surface layer made of gold or the like is 0.001 to 0.3 μm. A foil-like conductor provided with an intermediate (nickel) layer is proposed. It is said that this makes the area directly under the surface layer smooth and makes it difficult for pinholes to be formed in the surface layer, but the thickness of the intermediate layer cannot be made sufficiently thin, so that the bending resistance is inferior.

JP 2009-176646

An object of the present invention is to solve the above-mentioned problems and to provide a conductive film having improved bending resistance and corrosion resistance of the gold layer while suppressing the migration of copper to the gold layer. ..

The conductive film of the present invention is a conductive film in which a metal layer composed of a copper layer, a nickel layer, and a gold layer is laminated in this order on one surface of an insulating film base material, and the thickness of the nickel layer is high. It is a conductive film characterized by having a thickness of 0.05 to 0.2 μm.

According to this, it is possible to obtain a conductive film in which cracks do not occur in the gold layer even when it is bent, while suppressing the migration of copper to the gold layer.

In the copper layer, it is preferable that the arithmetic mean roughness Ra of the surface of the copper layer on the side where the nickel layer is laminated is 0.02 μm or less. According to this, the corrosion resistance of the conductive film can be enhanced.

It is preferable that the arithmetic mean roughness Ra of the surface of the gold layer is 0.03 μm or less. According to this, the corrosion resistance of the conductive film can be further improved.

The thickness of the copper layer is preferably 1 to 5 μm.
It is preferable to provide a resin layer having an elongation rate of 200 to 2000% on the surface of the insulating film opposite to the surface on which the metal layer is provided.

It is preferable that a film made of at least one organic pore-treating agent selected from the group consisting of heterocyclic compounds, thiol compounds, and amine compounds is formed on the surface of the gold layer. It is desirable to seal a pinhole that is so small that it cannot be visually recognized.

It is preferable that the insulating film base material is made of a polyimide resin. According to this, it is possible to obtain a conductive film having excellent heat resistance.
The thickness of the insulating film substrate is preferably 4 to 25 μm.

According to the present invention, it is possible to obtain a conductive film in which the gold layer is not cracked due to bending while suppressing discoloration with time. Further, a conductive film having excellent corrosion resistance can be obtained.

It is a schematic diagram which shows the method of the bending resistance test of this invention.

The conductive film of the present invention has a metal layer consisting of a copper layer, a nickel layer, and a gold layer on one surface of an insulating film base material, and a copper layer, a nickel layer, and gold on the insulating film base material. It is laminated in the order of layers. That is, the conductive film of the present invention has a layer structure of "insulating film base material / copper layer / nickel layer / gold layer", and one outermost layer is a gold layer.

1. 1. Insulating film base material The conductive film of the present invention is based on an insulating film base material. As the insulating film base material, a film made of a synthetic resin is preferably used. The synthetic resin is not particularly limited, and examples thereof include a polyimide resin, a polyester resin, a polypropylene resin, a polyvinyl chloride resin, and a polycarbonate resin. Among them, an insulating film base material made of a polyimide resin is preferable because a conductive film having excellent heat resistance can be obtained.

The thickness of the insulating film base material is not particularly limited, but the lower limit is preferably 2 μm, more preferably 3 μm, and particularly preferably 4 μm. The upper limit of the thickness is preferably 100 μm, more preferably 50 μm, still more preferably 25 μm, and particularly preferably 13 μm. When the thickness of the insulating film base material is within this range, a conductive film having appropriate flexibility can be obtained. Desirably, the thickness of the insulating film substrate is 4 to 25 μm.

The insulating property of the insulating film base material is not particularly limited, but a preferable resistance value is 1 × 10 ¹⁴ Ω / □ or more.

2. 2. Copper layer A copper layer is laminated on one surface of the insulating film base material, and the copper layer is in contact with the insulating film base material. The thickness of the copper layer is not particularly limited, but the lower limit is preferably 0.5 μm, more preferably 1 μm, and particularly preferably 1.5 μm. The upper limit of the thickness is preferably 8 μm, more preferably 6 μm, and particularly preferably 5 μm. When the thickness of the copper layer is within this range, sufficient conductivity can be ensured and a conductive film having excellent flexibility can be obtained. Desirably, the thickness of the copper layer is 1 to 5 μm.

The method for forming the copper layer is not particularly limited, but is preferably formed on an insulating film substrate by a known vapor deposition method such as a vacuum vapor deposition method, formed by a sputtering method, or a known electrolytic copper plating method. And the like.

The copper layer may be composed of a plurality of layers formed by two or more different methods. For example, the first copper layer has a copper vapor deposition layer formed on an insulating film base material by a vapor deposition method, and the second copper layer is a copper plating layer formed on the first copper layer by an electrolytic copper plating method. Can have. As a result, a copper layer having a desired thickness can be efficiently obtained.

The thickness of the first copper layer is preferably 0.1 to 2.0 μm, and the thickness of the second copper layer is preferably 0.5 to 5.0 μm. It is better to have a layer thickness. Further, the arithmetic mean roughness Ra of the copper layer surface is the roughness of the surface of the second copper layer in contact with the nickel layer when the first copper layer and the second copper layer are provided.

With respect to the surface of the copper layer, its arithmetic mean roughness Ra is preferably 0.02 μm or less, and more preferably 0.01 to 0.02 μm. When Ra is within this range, the thickness of the nickel layer and the gold layer formed on the nickel layer and the gold layer becomes more uniform, pinholes in the surface (gold) layer can be suppressed, and corrosion resistance can be improved. ..

The arithmetic mean roughness Ra shall be measured by a method compliant with JIS B 0601: 2001 using a device such as a scanning confocal laser scanning microscope (for example, manufactured by Olympus Corporation, trade name "LEXT OLS30-SU"). Can be done.

In order to keep the arithmetic mean roughness Ra of the copper layer within the above range, it is preferable to adopt a vacuum vapor deposition method, a sputtering method, or a copper film forming method by electrolytic copper plating containing a brightener as a method for forming the copper layer.

3. 3. Nickel layer A nickel layer is laminated on the surface of the copper layer (on the opposite side of the insulating film base material, between the copper layer and the gold layer). It is important that the thickness of the nickel layer is 0.05 to 0.2 μm. That is, the lower limit of the thickness is 0.05 μm, preferably 0.07 μm or more. The upper limit of the thickness is 0.2 μm, preferably 0.15 μm or less, and more preferably 0.12 μm or less. When the thickness of the nickel layer is within this range, it is possible to suppress the occurrence of cracks in the gold layer described later when the conductive film is bent while suppressing the migration of copper.

Further, in the present invention, since the thickness of the nickel layer is extremely thin, the effect of suppressing the arithmetic mean roughness of the copper layer surface to a small value makes it possible to form not only the nickel layer but also the gold layer uniformly and thinly. There is.

4. Gold layer A gold layer is laminated on the surface of the nickel layer (opposite to the copper layer, the outermost layer). The thickness of the gold layer is preferably 0.05 μm or less, more preferably 0.04 μm or less. When the thickness of the gold layer is not more than the above range, the cost can be suppressed and a low contact resistance value can be realized. The lower limit of the thickness of the gold layer is not particularly limited, but is preferably 0.02 μm or more, and more preferably 0.03 μm or more.

The arithmetic mean roughness Ra of the surface of the gold layer is preferably 0.03 μm or less. When the arithmetic mean roughness Ra of the surface of the gold layer is 0.03 μm or less, a conductive film having excellent corrosion resistance can be obtained. The arithmetic mean roughness Ra of the surface of the gold layer is the average roughness of the surface of the surface (outermost surface of the conductive film) that is not in contact with the nickel layer.

Since the thickness of the nickel layer and the gold layer is extremely thin in the present invention, the arithmetic average roughness Ra of the surface of the copper layer is set within the above range (0.) by setting the arithmetic average roughness of the copper layer surface to 0.02 μm or less. It can be stored in (03 μm or less). Further, the gold layer can be formed by adopting a vacuum vapor deposition method, a sputtering method, a gold film forming method by electroplating containing a brightener, etc., so that the arithmetic mean roughness Ra of the surface of the gold layer can be easily kept within the above range. It is preferable because it can be stored.

In addition to setting the arithmetic mean roughness Ra of the gold layer surface to 0.03 μm or less, it is resistant to the formation of a film with an organic sealing treatment agent on the surface of the gold layer (outermost surface of the conductive film). It is preferable from the viewpoint of corrosiveness. In general, the surface of the gold layer obtained by the electrogold plating method may have minute pinholes that cannot be visually recognized, and it is desirable to perform a treatment for sealing these.

The organic sealing treatment agent is preferably one or a combination of a plurality of types selected from the group consisting of heterocyclic compounds, thiol compounds, and amine compounds. Of these, thiol compounds are preferable. Specific examples thereof include triazinethiol and mercaptobenzothiazole.

The thickness of the film formed by the organic sealing treatment agent is not particularly limited, but is preferably 0.01 μm or less.

5. Other Layers In the present invention, a resin layer having excellent flexibility and high elongation can be provided on the other surface of the insulating film base material (the surface opposite to the surface on which the metal layer is provided). In that case, the layer structure of the conductive film of the present invention is "resin layer / insulating film base material / copper layer / nickel layer / gold layer".

The resin layer is preferably made of a resin film having a high elongation rate, and the lower limit is preferably 200%, more preferably 500%, and particularly preferably 1000%. The upper limit of the elongation rate is not particularly limited, but is preferably 2000%, more preferably 1500%, and particularly preferably 1300%.

By providing a resin layer made of a resin film having a high elongation rate, the bending resistance of the conductive film of the present invention is further improved, and metal cracks are generated even in a bending test under stricter conditions (the curvature of the bent portion is small). It can be suppressed.

Examples of the type of the resin film include polyester, polyurethane, polyolefin, polyamide and the like. The thickness of the resin is preferably about 10 to 100 μm, more preferably 20 to 50 μm.

6. Adhesion, bending resistance, corrosion resistance, suppression of copper migration In the conductive film of the present invention, the metal layer composed of the copper layer, the nickel layer, and the gold layer adheres to the insulating film base material. In the peel strength test for evaluating the property, the peel strength is preferably 0.6 kgf / 15 mm ² or more. That is, in the present invention, the adhesiveness between the conductive film base material and the copper layer in contact with the base material is good.

Here, the peel strength test follows the following procedure. First, the conductive film is cut into a length of 50 mm and a width of 5 mm to prepare a sample. Masking is performed so as to expose a length of 3 mm at the center of the sample in the length direction. Copper nail (Showa Electric Wire Cable System Co., Ltd.) is used on the exposed 3 mm x 5 mm sample surface (gold layer surface) using solder paste (manufactured by Senju Metal Industry Co., Ltd .; trade name "ECO SOLDER PASSE L20-BLT5-T7F"). With the head of a copper thin flat rivet M3 × 20) manufactured by the company attached, heat treatment is performed at 250 ° C. for 2 minutes.

For the heat treatment, for example, a constant temperature dryer (manufactured by Advantech Toyo Co., Ltd .; trade name "DRA630DA") or the like can be used. After the heat treatment, the sample is cooled to room temperature, folded in half at the position where the copper nail is connected, and the sample and the copper nail are pulled in the opposite directions with a tensile strength tester to measure the peel strength. As the tensile strength tester, for example, a digital load meter SV-55 manufactured by Imada Seisakusho Co., Ltd. is used. The tensile speed is 25 mm / min.

The conductive film of the present invention is less likely to cause cracks in the gold layer in the bending resistance test. A schematic diagram showing the method of the bending resistance test is shown in FIG. The conductive film 1 is cut into a sample having a length of 100 mm and a width of 30 mm, bent so that the conductive layer (metal layer 3) of the conductive film 1 is on the outside, and a PET film 4 (Toray Industries, Inc.) having a thickness of 163 μm is bent between them. The bent portion 8 has a curvature of 82 μm by sandwiching the mirror 38S10 and 125S10).

The sample (conductive film 1) bent with the PET film 4 sandwiched between them is placed on a horizontal workbench 7 as shown in FIG. A 2.0 kg weight 5 is placed on the sample at the position shown in FIG. 1 via a slide glass 6 and allowed to stand for 1 second so that a predetermined load is applied to the bent portion 8. After removing the weight 5, the bent portion 8 is observed with a microscope or the like to confirm the occurrence of cracks. This method is referred to as evaluation method 1.

Further, after changing the thickness of the PET film to 100 μm so that the bent portion of the sample has a curvature of a radius of 50 μm, the same method as described above is performed, and then the occurrence of cracks is confirmed by the same method. This method is referred to as evaluation method 2.

In addition, the same method as above was performed except that the bent portion of the sample had a curvature of 0 μm without sandwiching the PET film, and then the occurrence of cracks was confirmed by the same method. This method is referred to as evaluation method 3.

In each of the

above evaluation methods

1, 2 and 3, the cracking condition is confirmed according to the following criteria.
〇: No cracks occur △: Fine cracks are present ×: Cracks at the tear level are present.

The corrosion resistance of the conductive film of the present invention can be evaluated in accordance with JIS standard 2371: 2015 neutral salt spray test method. That is, using an ISO type salt spray tester (for example, STP-90VR manufactured by Suga Test Instruments Co., Ltd.), a 5% sodium chloride aqueous solution (pH 6.8) was used as a spray liquid, and the spray liquid temperature was 35 ° C. and the air saturation temperature was 47. The treatment is carried out at ° C for a test time of 48 hours.

The surface of the gold layer of the treated sample is visually observed, and the degree of corrosion is evaluated according to the following criteria.
〇: No change in metallic luster on the surface of the gold layer △: Metallic luster on the surface of the gold layer decreased, but no pinholes occurred ×: Pinholes occurred on the surface of the gold layer.

The conductive film of the present invention suppresses the migration of copper to the gold layer. Examples of the method for evaluating this characteristic include discoloration before and after the accelerated test by heat treatment and measurement of contact resistance value. As an accelerated test, heat treatment is performed at 260 ° C. for 15 minutes. Each sample before and after the accelerated test is color-measured by the SCI method with a colorimeter (for example, a spectrocolorimeter CM-2600d manufactured by Konica Minolta Japan Co., Ltd.), and a color difference (ΔE) is calculated and evaluated. When the color difference (ΔE) is 3.0 or less, it can be evaluated that the migration of copper is effectively suppressed.

Similarly, the migration suppressing effect of copper can be evaluated by measuring the contact resistance value of the samples before and after the accelerated test. For the contact resistance value (mΩ), prepare two gold-plated jigs with a contact resistance value (mΩ) of 30 mm × 30 mm × 10 mm and a mass of 50 g, and place them side by side on the sample surface so that the surface with an area of 900 mm ² is facing down and an interval of 1 mm is opened. .. The resistance value (mΩ) between the two jigs can be measured with a milliohm high tester (such as 3540 manufactured by Hioki Electric Co., Ltd.). The contact resistance value is preferably 3.0 mΩ or less both before and after the accelerated test.

7. Method for manufacturing a conductive film The method for manufacturing a conductive film of the present invention includes a first step of forming a copper layer on one surface of an insulating film substrate by a vapor deposition method and a nickel layer on the surface of the copper layer by an electroplating method. The second step of forming a gold layer on the surface of the nickel layer by an electroplating method is included in this order.

In the first step, a copper layer is formed on one surface of the insulating film base material. Examples of the method for forming the copper layer include a vapor deposition method and a copper film forming method by electroless copper plating. Of these, the vapor deposition method is preferable. As the vapor deposition method, a known vapor deposition apparatus and method can be adopted.

Prior to forming the copper layer, the surface of the insulating film base material may be pretreated and modified by plasma treatment, ion irradiation treatment, or the like. The surface of the copper layer formed by the first step is preferably smooth, and its arithmetic mean roughness Ra is preferably 0.02 μm or less. If a thin-film deposition method is used to form the copper layer, a copper layer having high surface smoothness can be formed.

In the first step, a copper layer may be further formed by using an electrolytic copper plating method following the vapor deposition method. According to this, the thickness of the copper layer can be formed thicker more efficiently. In this case, the second copper layer by the electrolytic copper plating method is laminated on the surface of the copper layer formed by the vapor deposition method. Therefore, it is preferable that the arithmetic mean roughness Ra of the surface of the second copper layer is 0.02 μm or less.

In order to reduce the arithmetic mean roughness Ra of the surface of the second copper layer by the electrolytic copper plating method to 0.02 μm or less, it is necessary to adopt a method such as adding a specific plating treatment agent to the plating bath. preferable. Some of such plating treatment agents are called brighteners.

As the treatment agent for plating, bis (3-sulfopropyl) disulfide disodium, 2,5-dimercapto-1,3,4-thiadiazole, 3-mercapto-1-propanesulfonic acid, N, N-dimethyldithiocarbamic acid ( Examples include organic sulfur compounds such as 3-sulfopropyl) esters.

Further, examples of the treatment agent for plating include organic nitrogen compounds such as phenazine compounds, safranin compounds, polyalkyleneimines, thiourea derivatives, and polyacrylic acid amides. The organic nitrogen compound is considered to have an effect as a leveling agent for forming a uniform copper layer.

These organic sulfur compounds and organic nitrogen compounds may be used alone or in combination of both. In addition to these, nonionic polyether-based polymer surfactants such as polyethylene glycol and polyoxyethylene polyoxypropylene copolymer, and water-soluble polymer compounds such as dextrin and glycerin may be blended and used. You can also.
More preferable ones include a combination of an organic nitrogen compound and a surfactant, and a combination of an organic sulfur compound, an organic nitrogen compound and a surfactant.

In the present invention, commercially available additives for plating treatment can also be used. In particular, organic sulfur compounds and / or organic nitrogen compounds mixed with a polymer surfactant or the like as appropriate are commercially available, and they can also be used.

Commercially available products of such plating treatment agents include the trade name "COSMO S-MU" (manufactured by Daiwa Special Co., Ltd.) and the trade name "KOTAC MU" (manufactured by Daiwa Special Co., Ltd.) as additives for glossy copper plating. Examples include the product name "COSMO S-1" (manufactured by Yamato Special Co., Ltd.) and the product name "KOTAC 1" (manufactured by Yamato Special Co., Ltd.).

In addition, the product name "Top Lucina SF Base WR" (manufactured by Okuno Pharmaceutical Industry Co., Ltd.), the product name "Top Lucina SF-QB" (manufactured by Okuno Pharmaceutical Industry Co., Ltd.), and the product name "Top Lucina SF-Leveler-Z" (Okuno Pharmaceutical Co., Ltd.) (Manufactured by Kogyo Co., Ltd.), product name "DAINCOPPER LS004R" (manufactured by Daiwa Kasei Co., Ltd.), product name "DAINCOPPER LS004S" (manufactured by Daiwa Kasei Co., Ltd.) and the like can also be mentioned.

All of the above-mentioned commercial products can be used in combination of 2 to 3 products.
For example, the above-mentioned "Top Lucina SF Base WR", "Top Lucina SF-QB" and "Top Lucina SF-Leveler-Z" are combinations that can be mixed and used.
Further, the above-mentioned "DAINCOPPER LS004R" and "DAINCOPPER LS004S" are combinations that can be mixed and used.
Further, the above-mentioned "KOTAC MU" and "KOTAC 1" are combinations that can be mixed and used.

Following the first step, a second step of forming a nickel layer on the surface of the copper layer is carried out. The nickel layer is formed by a known electroplating method. As described above, it is important that the thickness of the nickel layer is 0.05 to 0.2 μm. Each condition of the electrolytic nickel plating method in the second step is not particularly limited and may be set within a range in which a nickel layer having a desired thickness can be formed. As general conditions, the temperature of the plating solution can be 20 to 60 ° C., the current density can be 0.5 to 5.0 A / dm ² , and the processing time can be 5 to 300 sec.

Further, following the second step, a third step of forming a gold layer on the surface of the nickel layer is carried out. A known electroplating method is also adopted for forming the gold layer. The arithmetic mean roughness Ra of the surface of the gold layer is preferably 0.03 μm or less. According to this, the corrosion resistance can be improved. Each condition of the electrogold plating method in the third step is not particularly limited and may be set within a range in which a gold layer having a desired thickness can be formed. As general conditions, the temperature of the plating solution can be 40 to 60 ° C., the current density can be 0.1 to 3.0 A / dm ² , and the processing time can be 5 to 300 sec.

Following the third step, a step of contacting the surface of the gold layer with a treatment liquid in which an organic sealing treatment agent is dissolved may be carried out. As a result, a film made of the organic sealing treatment agent is formed on the surface of the gold layer, and fine pinholes can be sealed.

The organic sealing treatment agent is preferably one or a combination of a plurality of types selected from the group consisting of heterocyclic compounds, thiol compounds, and amine compounds. Of these, thiol compounds are preferable. Specific examples thereof include alkylthiols, alkyldisulfides, triazinethiols, and mercaptobenzothiazoles.

Examples of the solvent for dissolving the organic sealing treatment agent include water, alcohols and the like. A surfactant or the like may be added to disperse the organic sealing treatment agent. Examples of such surfactants include polyoxyethylene nonylphenyl ether and the like.

A commercially available product can also be used as the organic sealing treatment agent dispersed with a surfactant or the like. Examples of such commercially available products include EL-8000B (manufactured by Nikkei Seisei Co., Ltd.), CT-3 (manufactured by JX Nippon Mining & Metals Co., Ltd.), KG-230 (manufactured by JX Nippon Mining & Metals Co., Ltd.) and the like.

When the commercially available product is used, it is preferably used by diluting it to a concentration of 20 to 100 mL / L and bringing it into contact with the surface of the gold layer.

The first step, the second step, and the third step may be continuously carried out. The step of contacting the treatment liquid in which the organic sealing treatment agent is dissolved may also be continuously carried out following the third step. Further, a washing step and a drying step may be appropriately carried out between each of these steps.

When a resin layer having a high elongation rate is provided on the other surface of the insulating film base material (the surface opposite to the surface on which the metal layer is provided), the step of forming the resin layer is the insulating film base material. Prior to the first to third steps of providing each metal layer, a resin film can be attached to or laminated with an insulating film base material in advance. Alternatively, after each metal layer is provided on the insulating film base material, the resin film is attached or laminated on the surface opposite to the surface on which the metal layer of the insulating film base material is provided. Can be done.

The present invention will be described below by way of examples, but the present invention is not limited by these examples.

[Various physical property tests]
(1) Peeling strength test (adhesion evaluation)
The conductive film was cut into a length of 50 mm and a width of 5 mm to prepare a sample. Masking is performed so that the length of 3 mm is exposed at the center of the sample in the length direction, and solder paste (manufactured by Senju Metal Industry Co., Ltd .; trade name " ECO solder paste L20-BLT5-T7F ") with the head of a copper nail (copper thin flat rivet M3 x 20 manufactured by Showa Densen Cable System Co., Ltd.) attached, heat treatment at 250 ° C for 2 minutes. Was carried out. A constant temperature dryer (manufactured by Advantech Toyo Co., Ltd .; trade name "DRA630DA") was used for the heat treatment.

After the heat treatment, the sample was cooled to room temperature, folded in half at the position where the copper nail was connected, and the sample and the copper nail were pulled in the opposite directions with a tensile strength tester to measure the peel strength. As the tensile strength tester, a digital load meter (manufactured by Imada Seisakusho Co., Ltd., trade name "SV-55") was used. The tensile speed was 25 mm / min.

(2) Bending resistance test FIG. 1 shows a schematic diagram showing the method of the bending resistance test carried out in this example. The conductive film 1 is cut into a sample having a length of 100 mm and a width of 30 mm, bent so that the conductive layer (metal layer 3) of the conductive film 1 is on the outside, and a PET film 4 (Toray Industries, Inc.) having a thickness of 163 μm is bent between them. The bent portion 8 has a curvature with a radius of 82 μm by sandwiching the mirror 38S10 and 125S10).

The sample (conductive film 1) bent with the PET film 4 sandwiched between them was placed on a horizontal workbench 7 as shown in FIG. A 2.0 kg weight 5 was placed on the sample at the position shown in FIG. 1 via a slide glass 6 and allowed to stand for 1 second so that a predetermined load was applied to the bent portion 8. After removing the weight 5, the bent portion 8 was observed with a microscope (trade name "Digital Microscope VHX-5000"; manufactured by KEYENCE CORPORATION), and the occurrence of cracks was confirmed. This method was used as evaluation method 1.

Further, the same method as above was performed except that the thickness of the PET film was changed to 100 μm so that the bent portion of the sample had a curvature with a radius of 50 μm, and then the occurrence of cracks was confirmed by the same method (. This method was used as evaluation method 2).

In addition, the same method as above was performed except that the bent portion of the sample had a curvature of 0 μm without sandwiching the PET film, and then the occurrence of cracks was confirmed by the same method (this method was used. Evaluation method 3). The evaluation method 3 was performed only in Examples 4 and 5.

In each of the

above evaluation methods

1, 2 and 3, the cracking condition was confirmed according to the following criteria.
〇: No cracks occur △: Fine cracks are present ×: Cracks at the tear level are present.

(3) Corrosion resistance test Compliant with JIS standard 2371: 2015 neutral salt spray test method, using ISO type salt spray tester (manufactured by Suga Test Instruments Co., Ltd., trade name "STP-90VR"), 5% An aqueous sodium chloride solution (pH 6.8) was used as a spray solution, and the treatment was performed at a spray solution temperature of 35 ° C. and an air saturation temperature of 47 ° C. for a test time of 48 hours.

(4) Copper migration suppression effect (presence or absence of discoloration)
As an accelerated test by heat treatment, heat treatment was carried out at 260 ° C. for 15 minutes. The samples before and after the accelerated test were measured by the SCI method using a spectrocolorimeter (manufactured by Konica Minolta Japan Co., Ltd., trade name "CM-2600d"), and the color difference (ΔE) was calculated and evaluated.

(5) Copper migration suppression effect (change in contact resistance value)
The effect of suppressing copper migration was evaluated by measuring the contact resistance values of the samples before and after the accelerated test by the heat treatment described above. For the contact resistance value (mΩ), prepare two gold plating jigs with a contact resistance value (mΩ) of 30 mm × 30 mm × 10 mm and a mass of 50 g, and place them side by side on the sample surface so that the surface with an area of 900 mm ² is facing down and an interval of 1 mm is opened. The resistance value (mΩ) between the two jigs was measured with a milliohm high tester (manufactured by Hioki Electric Co., Ltd., trade name "3540").

(6) Arithmetic Mean Roughness Arithmetic Mean Roughness Ra is measured by a method based on JIS B 0601: 2001 using a scanning confocal laser scanning microscope (manufactured by Olympus Co., Ltd., trade name "LEXT OLS30-SU"). bottom.

(7) Elongation rate measurement method The elongation rate of the resin layer was calculated by the following formula from the elongation length until the resin layer broke by a tensile strength tester. Lo was the sample length before the test (mm), and L was the sample length at break (mm).

(Number 1)
Growth rate (%) = 100 × (L-Lo) / Lo

A single resin film for a resin layer of 20 mm x 5 mm was masked with tape (trade name "No. 642", manufactured by Teraoka Seisakusho) so that the center of 5 mm x 5 mm remained, and the two masked locations were masked with a tensile strength tester. By pinching the tape portion of No. 1 and pulling it in the opposite direction, the time until the resin film broke was measured, and L was calculated from the numerical value of the tensile speed. In the case of this test, the Lo value is 5. As a tensile strength test, a digital load meter (manufactured by Imada Seisakusho Co., Ltd., trade name "SV-55") was used, and the tensile speed was set to 30 mm / min.

[Example 1]
A copper vapor-deposited film manufactured by Toray KP Film Co., Ltd. (manufactured by Toray DuPont Co., Ltd.) in which a copper layer having a thickness of 1.5 μm is formed on one surface of a polyimide resin film having a thickness of 25 μm as an insulating film base material. Copper 100 V with a thick film vapor-deposited) was acid-washed with an aqueous solution of sulfuric acid 50 mL / L at 20 ° C. for 30 seconds. The arithmetic mean roughness Ra of the copper layer surface was measured and found to be 0.014 μm.

Next, electrolytic nickel plating was performed to form a nickel layer on the surface of the copper layer. In the nickel plating bath, nickel sulfate hexahydrate was 200 g / L, trisodium citrate dihydrate was 60 g / L, the pH was 5.5, and the temperature was 40 ° C. The conditions for electrolytic nickel plating were a current density of 3.0 A / dm ² , a processing time of 15 seconds, and an Anodec 100 (manufactured by Nikkei Seisei Co., Ltd.) as the anode. The thickness of the obtained nickel layer was 0.12 μm.

Next, electrogold plating was carried out to form a gold layer on the surface of the nickel layer, and a conductive film was obtained. As the gold plating bath, Eco Gold 24 (manufactured by Nikkei Seisei Co., Ltd., gold concentration 8.0 g / L) was used. Anodec 100 (manufactured by Nikkei Seisei Co., Ltd.) was used as the anode at a plating bath temperature of 40 ° C. and a current density of 0.32 A / dm ² for 15 seconds. The thickness of the obtained gold layer was 0.031 μm, and the arithmetic mean roughness Ra of the surface of the gold layer was 0.025 μm.

Next, as an organic sealing treatment agent, a conductive film having a gold layer formed in a 50 mL / L aqueous solution of the trade name "EL-8000B" (manufactured by Nikkei Seisei Co., Ltd .; thiol compounds) was placed at a treatment temperature of 40 ° C. Soaked for 16 seconds.

Regarding the obtained conductive film, adhesion by peel strength test, bending resistance test, corrosion resistance by salt spray test, and discoloration and contact resistance value before and after accelerated test by heat treatment were evaluated as the effect of suppressing copper migration. The results of the measurements are shown in Table 1.

[Example 2]
In electrogold plating, a conductive film was obtained in the same manner as in Example 1 except that the treatment time was 22.5 seconds and the thickness of the gold layer was 0.046 μm. The arithmetic mean roughness Ra on the surface of the gold layer was 0.026 μm. Table 1 shows the results of each evaluation / measurement.

[Example 3]
A copper vapor-deposited film manufactured by Toray KP Film Co., Ltd. (Toray DuPont Co., Ltd.) in which a copper layer with a thickness of 0.3 μm is formed on one surface of a polyimide resin film having a thickness of 12.5 μm as an insulating film base material. A thick film of copper vapor-deposited on 100 V of DuPont manufactured by the company) was acid-washed with an aqueous solution of 50 mL / L of sulfuric acid at 20 ° C. for 30 seconds.

This was subjected to electrolytic copper plating to make the thickness of the copper layer 1.99 μm. As the copper plating bath, 200 g / L of copper sulfate pentahydrate, 55 mL / L of sulfuric acid, 20 mL / L of soft copper film forming agent (trade name "CU-SOFT", manufactured by JCU Co., Ltd.), and sodium chloride. The plating bath temperature was set to 40 ° C. using one containing 85 mg / L. The conditions for electrolytic copper plating were 150 seconds at a current density of 3.0 A / dm ² . The arithmetic mean roughness Ra of the copper layer surface was measured and found to be 0.085 μm.

Next, electrolytic nickel plating was performed to form a nickel layer on the surface of the copper layer. The electrolytic nickel plating bath was the same as in Example 1, and the current density was 0.6 A / dm ² and the processing time was 69.4 seconds. The thickness of the obtained nickel layer was 0.11 μm.

Further, film formation by electrogold plating and an organic sealing treatment agent was carried out under the same conditions as in Example 1 to form a gold layer having a thickness of 0.033 μm and a surface arithmetic mean roughness Ra of 0.118 μm. bottom. Table 1 shows the results of each evaluation / measurement.

[Example 4]
A copper vapor-deposited film manufactured by Toray KP Film Co., Ltd. (manufactured by Toray DuPont Co., Ltd.) in which a copper layer having a thickness of 0.3 μm is formed on one surface of a polyimide resin film having a thickness of 4 μm as an insulating film base material. A thick film of copper vapor-deposited on 100 V of Capton) was acid-washed with an aqueous solution of 50 ml / L of sulfuric acid at 20 ° C. for 30 seconds.

This was subjected to electrolytic copper plating to make the thickness of the copper layer 3.13 μm. As a copper plating bath, 220 g / L of copper sulfate pentahydrate, 35 ml / L of sulfuric acid, 5 ml / L of an additive for bright copper plating (trade name "COSMO S-MU", manufactured by Daiwa Special Co., Ltd.), An additive for bright copper plating (trade name "COSMO S-1", manufactured by Daiwa Special Co., Ltd.) was used at 2 ml / L and sodium chloride was 170 mg / L, and the plating temperature was 35 ° C. The conditions for electrolytic copper plating were 336 seconds at a current density of 3.0 A / dm ² . The arithmetic mean roughness of the copper layer surface was Ra 0.019 μm.

Next, electrolytic nickel plating was performed to form a nickel layer on the surface of the copper layer. The electrolytic nickel plating bath was the same as in Example 1, and the current density was 0.38 A / dm ² and the processing time was 56 seconds. The thickness of the obtained nickel layer was 0.07 μm.

Further, film formation by electrogold plating and an organic sealing treatment agent was carried out under the same conditions as in Example 1 to form a gold layer having a thickness of 0.046 μm and a surface arithmetic mean roughness Ra of 0.025 μm. bottom. Table 1 shows the results of each evaluation / measurement.

[Example 5]
Regarding the conductive film obtained under the same conditions as in Example 4, a polyurethane resin film having a thickness of 30 μm (trade name “UH-203”, Japan) was placed on the surface opposite to the surface on which the metal layer of the insulating film substrate was provided. (Mattai Co., Ltd.) was bonded, and a 5 kg weight was placed on a hot plate (trade name "HT-1000", manufactured by AS ONE Co., Ltd.) at 100 ° C. for 10 seconds to bond the two. The elongation rate of the polyurethane resin film used in this experiment was 1300%. Table 1 shows the evaluation / measurement results of the obtained conductive film.

[Comparative Example 1]
A conductive film was obtained in the same manner as in Example 1 except that the treatment time for electrolytic nickel plating was 69.4 seconds and the thickness of the nickel layer was 0.61 μm. The arithmetic mean roughness Ra on the surface of the gold layer was 0.026. Table 1 shows the results of each evaluation / measurement.

[Comparative Example 2]
A conductive film was obtained in the same manner as in Example 1 except that the treatment time for electrolytic nickel plating was 1.0 second and the thickness of the nickel layer was 0.012 μm. The arithmetic mean roughness Ra on the surface of the gold layer was 0.017. Table 1 shows the results of each evaluation / measurement.

The conductive film of the present invention can be used as a conductive film for grounding. It can be wound around an elastic material to form a gasket, which can be sandwiched inside an electronic device housing and used as a countermeasure against electromagnetic interference. It is possible to shield noise generated from the electronic device itself, noise affecting the electronic device from the outside, and the like. Since it has a film shape, it can also be used as an electrical connection member to an electric circuit formed on a flexible base material such as a wearable device.

1. 1. Conductive film 2. Insulating film base material 3. Metal layer 4. PET film 5. Weight 6. Slide glass 7. Workbench 8. Bent part

Claims

A conductive film in which a metal layer composed of a copper layer, a nickel layer, and a gold layer is laminated in this order on one surface of an insulating film base material, and the thickness of the nickel layer is 0.05 to 0.2 μm. A conductive film characterized by being.
The conductive film according to claim 1, wherein the arithmetic average roughness Ra of the surface of the copper layer on the side where the nickel layer is laminated is 0.02 μm or less in the copper layer.
The conductive film according to claim 1 or 2, wherein the arithmetic mean roughness Ra of the surface of the gold layer is 0.03 μm or less.
The conductive film according to any one of claims 1 to 3, wherein the copper layer has a thickness of 1 to 5 μm.
The conductive film according to any one of claims 1 to 4, wherein a resin layer having an elongation rate of 200 to 2000% is provided on a surface of the insulating film opposite to the surface on which the metal layer is provided. ..
The claim is characterized in that a film made of at least one organic pore-treating agent selected from the group consisting of a heterocyclic compound, a thiol compound, and an amine compound is formed on the surface of the gold layer. Item 2. The conductive film according to any one of Items 1 to 5.
The conductive film according to any one of claims 1 to 6, wherein the insulating film base material is made of a polyimide resin.
The conductive film according to any one of claims 1 to 7, wherein the thickness of the insulating film base material is 4 to 25 μm.