Conductive film with gold layer

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

[Technical Field]

[0001] The present invention relates to a conductive film, and more particularly to a conductive film having a gold layer laminated on its surface, which has improved flex resistance and corrosion resistance while suppressing copper migration into the gold layer. [Background technology]

[0002] As electronic devices become smaller and lighter, flexible printed circuit boards (FPCBs), in which circuits are formed on the surface of a flexible film, are increasingly being used. Highly conductive copper is often used for the circuits formed on the film surface. Furthermore, a gold layer is often laminated on the copper surface to protect the copper circuit surface and reduce contact resistance. When a gold layer is directly laminated on the copper surface, copper migration occurs over time, causing copper to accumulate on the surface of the gold layer, resulting in problems such as discoloration and increased contact resistance.

[0003] To solve this problem, an intermediate layer made of nickel, tin, etc. has been provided, but the provision of the intermediate layer has presented new problems, such as cracks or pinholes occurring on the surface of the gold layer due to bending, which reduces corrosion resistance, and solutions to these problems are needed.

[0004] For example, Patent Document 1 (JP 2009-176646 A) proposes a foil conductor that has an intermediate (nickel) layer beneath a surface layer made of gold or the like, characterized in that the average crystal grain size of the metal that makes up the surface region is 0.001 to 0.3 μm. This makes the surface directly below the surface layer smooth and prevents pinholes from forming in the surface layer, but it results in poor bending resistance because the thickness of the intermediate layer cannot be made sufficiently thin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2009-176646 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to solve the above-mentioned problems and provide a conductive film in which the gold layer has improved flex resistance and corrosion resistance while suppressing copper migration into the gold layer. [Means for solving the problem]

[0007] The conductive film of the present invention is a conductive film comprising metal layers, including a copper layer, a nickel layer, and a gold layer, laminated in this order on one surface of an insulating film substrate, The copper layer has a thickness of 1 to 5 μm, The thickness of the nickel layer is 0.05 to 0.2 μm. The thickness of the gold layer is 0.05 μm or less. The conductive film is characterized by the above.

[0008] This makes it possible to obtain a conductive film that suppresses copper migration into the gold layer and that does not cause cracks in the gold layer even when bent.

[0009] The copper layer preferably has an arithmetic mean roughness Ra of 0.02 μm or less on the surface thereof on which the nickel layer is laminated, thereby improving the corrosion resistance of the conductive film.

[0010] The arithmetic mean roughness Ra of the gold layer surface is preferably 0.03 μm or less, which can further improve the corrosion resistance of the conductive film.

[0011] The copper layer includes a copper vapor deposition layer formed by a vapor deposition method and / or a copper plating layer formed by an electrolytic copper plating method using a copper plating bath containing a brightener. is preferred. It is preferable to provide a resin layer having an elongation percentage of 200 to 2000% on the surface of the insulating film opposite to the surface on which the metal layer is provided.

[0012] It is preferable that a film made of at least one organic sealing agent selected from the group consisting of heterocyclic compounds, thiol compounds, and amine compounds is formed on the surface of the gold layer, thereby sealing pinholes that are too small to be visible to the naked eye.

[0013] The peel strength between the insulating film substrate and the metal layer is 0.6 kgf / 15 mm 2 It is preferable that this is equal to or greater than this. The insulating film substrate preferably has a thickness of 4 to 25 μm. [Effects of the Invention]

[0014] According to the present invention, a conductive film can be obtained that is free from cracks in the gold layer due to bending while suppressing discoloration over time, and further has excellent corrosion resistance. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing a method for testing bending resistance according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The conductive film of the present invention has a metal layer consisting of three layers, a copper layer, a nickel layer, and a gold layer, laminated on one surface of an insulating film substrate in this order. That is, the conductive film of the present invention has a layer structure of "insulating film substrate / copper layer / nickel layer / gold layer," with one outermost layer being the gold layer.

[0017] 1. Insulating film substrate The conductive film of the present invention is based on an insulating film substrate. A film made of a synthetic resin is preferably used as the insulating film substrate. The synthetic resin is not particularly limited, but examples thereof include polyimide resin, polyester resin, polypropylene resin, polyvinyl chloride resin, and polycarbonate resin. Among these, an insulating film substrate made of a polyimide resin is preferred because it can provide a conductive film with excellent heat resistance.

[0018] The thickness of the insulating film substrate is not particularly limited, but the lower limit is preferably 2 μm, more preferably 3 μm, and particularly preferably 4 μm. The upper limit is preferably 100 μm, more preferably 50 μm, even more preferably 25 μm, and particularly preferably 13 μm. If the thickness of the insulating film substrate is within this range, a conductive film with appropriate flexibility can be obtained. Desirably, the thickness of the insulating film substrate is 4 to 25 μm.

[0019] The insulating property of the insulating film substrate is not particularly limited, but the preferred resistance value is 1×10 14 It is Ω / □ or more.

[0020] 2. Copper layer A copper layer is laminated on one surface of the insulating film substrate, and the copper layer is in contact with the insulating film substrate. 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. If the thickness of the copper layer is within this range, sufficient conductivity is ensured, and a conductive film with excellent flexibility can be obtained. Desirably, the thickness of the copper layer is 1 to 5 μm.

[0021] The method for forming the copper layer is not particularly limited, but preferably includes forming the copper layer on an insulating film substrate by a known deposition method such as vacuum deposition, forming the copper layer using a sputtering method, or forming the copper layer by a known electrolytic copper plating method.

[0022] The copper layer may be composed of multiple layers formed by two or more different methods. For example, the first copper layer may be a copper vapor-deposited layer formed on an insulating film substrate by vapor deposition, and the second copper layer may be a copper plated layer formed on the first copper layer by copper electroplating. This allows a copper layer of the desired thickness to be obtained efficiently.

[0023] 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, and the combined thickness of the first copper layer and the second copper layer should be the above-mentioned copper layer thicknesses. In addition, when the copper layer has a first copper layer and a second copper layer, 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.

[0024] The arithmetic mean roughness Ra of the surface of the copper layer is preferably 0.02 μm or less, and more preferably 0.01 to 0.02 μm. If Ra is within this range, the thicknesses of the nickel layer and gold layer formed thereon will be more uniform, pinholes in the surface (gold) layer will be suppressed, and corrosion resistance will be improved.

[0025] The arithmetic mean roughness Ra can be measured using a device such as a scanning confocal laser microscope (for example, manufactured by Olympus Corporation, trade name "LEXT OLS30-SU") according to a method in accordance with JIS B 0601:2001.

[0026] To set the arithmetic mean roughness Ra of the copper layer within the above range, it is preferable to use a copper film formation method such as vacuum deposition, sputtering, or electrolytic copper plating containing a brightener as the method for forming the copper layer.

[0027] 3. Nickel layer A nickel layer is laminated on the surface of the copper layer (the side opposite the insulating film substrate, between the copper layer and the gold layer). It is essential 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, and preferably 0.07 μm or more. The upper limit of the thickness is 0.2 μm, and preferably 0.15 μm or less, and more preferably 0.12 μm or less. If the thickness of the nickel layer is within this range, it is possible to suppress the occurrence of cracks in the gold layer, which will be described later, when the conductive film is bent while suppressing copper migration.

[0028] Furthermore, in the present invention, since the thickness of the nickel layer is extremely thin, the effect of keeping the arithmetic mean roughness of the copper layer surface small makes it possible to form not only the nickel layer but also the gold layer in a uniformly thin shape.

[0029] 4. Gold layer A gold layer is laminated on the surface of the nickel layer (the outermost layer, opposite the copper layer). The thickness of the gold layer is preferably 0.05 μm or less, more preferably 0.04 μm or less. If the thickness of the gold layer is within the above range, low contact resistance can be achieved while keeping costs down. There is no particular lower limit for the thickness of the gold layer, but it is preferably 0.02 μm or more, more preferably 0.03 μm or more.

[0030] The arithmetic mean roughness Ra of the gold layer surface is preferably 0.03 μm or less. If the arithmetic mean roughness Ra of the gold layer surface is 0.03 μm or less, a conductive film with excellent corrosion resistance can be obtained. Note that the arithmetic mean roughness Ra of the gold layer surface is the mean roughness of the surface not in contact with the nickel layer (the outermost surface of the conductive film).

[0031] In the present invention, since the thickness of the nickel layer and the gold layer is extremely thin, the arithmetic mean roughness Ra of the gold layer surface can be kept within the above range (0.03 μm or less) by setting the arithmetic mean roughness of the copper layer surface to 0.02 μm or less. Furthermore, it is also preferable to form the gold layer by employing a gold film formation method such as vacuum deposition, sputtering, or electroplating with a brightener, because this easily keeps the arithmetic mean roughness Ra of the gold layer surface within the above range.

[0032] In addition to the arithmetic mean roughness Ra of the gold layer surface being 0.03 μm or less, it is preferable from the viewpoint of corrosion resistance that a film of an organic sealing agent be formed on the surface of the gold layer (the outermost surface of the conductive film). Generally, the surface of the gold layer obtained by electroplating may have tiny pinholes that are too small to be visible to the naked eye, and therefore it is desirable to perform a treatment to seal these.

[0033] The organic sealing agent is preferably one or a combination of compounds selected from the group consisting of heterocyclic compounds, thiol compounds, and amine compounds. Among these, thiol compounds are preferred. Specific examples include triazine thiol and mercaptobenzothiazole.

[0034] There are no particular restrictions on the thickness of the film formed by the organic sealing agent, but it is preferably 0.01 μm or less.

[0035] 5. Other layers In the present invention, a resin layer having excellent flexibility and high elongation can be provided on the other side of the insulating film substrate (the side opposite to the side on which the metal layer is provided). In this case, the layer structure of the conductive film of the present invention is "resin layer / insulating film substrate / copper layer / nickel layer / gold layer."

[0036] The resin layer is preferably made of a resin film having a high elongation percentage, and the lower limit of the elongation percentage is preferably 200%, more preferably 500%, and particularly preferably 1000%. The upper limit of the elongation percentage is not particularly limited, but is preferably 2000%, more preferably 1500%, and particularly preferably 1300%.

[0037] By providing a resin layer made of a resin film with high elongation, the flex resistance of the conductive film of the present invention is further improved, and the occurrence of metal cracks can be suppressed even in flex tests under more severe conditions (small curvature of the bent portion).

[0038] The types of the resin film include polyester, polyurethane, polyolefin, polyamide, etc. The thickness of the resin is preferably about 10 to 100 μm, more preferably 20 to 50 μm.

[0039] 6. Adhesion, bending resistance, corrosion resistance, copper migration suppression In a peel strength test for evaluating the adhesion between the metal layer consisting of the three layers of the copper layer, the nickel layer, and the gold layer and the insulating film substrate, the conductive film of the present invention has a peel strength of 0.6 kgf / 15 mm. 2 That is, in the present invention, the adhesiveness between the conductive film substrate and the copper layer in contact with the substrate is good.

[0040] The peel strength test was performed according to the following procedure. First, the conductive film was cut into a length of 50 mm and a width of 5 mm to prepare a sample. The center of the sample was masked so that a 3 mm length was exposed. The head of a copper nail (Showa Electric Cable Systems Co., Ltd., copper thin flat rivet M3 x 20) was attached to the exposed 3 mm x 5 mm sample surface (surface of the gold layer) using solder paste (Senju Metal Industry Co., Ltd., product name "ECO SOLDER PASTE L20-BLT5-T7F"), and heat treatment was performed at 250°C for 2 minutes.

[0041] For the heat treatment, a constant temperature dryer (manufactured by Advantec Toyo Co., Ltd.; product name "DRA630DA") can be used, for example. 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 copper nail are pulled in opposite directions using a tensile strength tester to measure the peel strength. For example, a digital load meter SV-55 manufactured by Imada Seisakusho Co., Ltd. is used as the tensile strength tester. The pulling speed is 25 mm / min.

[0042] The conductive film of the present invention is resistant to cracks in the gold layer during a bending resistance test. A schematic diagram illustrating the bending resistance test method is shown in Figure 1. Conductive film 1 was cut into a length of 100 mm and a width of 30 mm to prepare a sample, and the conductive layer (metal layer 3) of conductive film 1 was folded so that it faced outward. A 163 μm-thick PET film 4 (a laminate of Lumirror 38S10 and 125S10 manufactured by Toray Industries, Inc.) was sandwiched between the film and the folded portion 8, resulting in a curvature radius of 82 μm.

[0043] The sample (conductive film 1) folded with the PET film 4 sandwiched between them is placed flat on a horizontal workbench 7 as shown in Figure 1. A 2.0 kg weight 5 is placed on top of the sample via a glass slide 6 in the position shown in Figure 1, so that a specified load is applied to the folded portion 8, and the sample is left to stand for one second. After removing the weight 5, the folded portion 8 is observed with a microscope or the like to check for the occurrence of cracks. This method is referred to as Evaluation Method 1.

[0044] In addition, the thickness of the PET film was changed to 100 μm, and the specimen was bent to a curvature radius of 50 μm. The same procedure was followed, and the occurrence of cracks was confirmed in the same manner. This method is designated as Evaluation Method 2.

[0045] In addition, the same procedure as above was carried out except that the PET film was not sandwiched and the bent part of the sample had a curvature radius of 0 μm, and then the occurrence of cracks was confirmed in the same manner. This method is referred to as Evaluation Method 3.

[0046] In each of the above evaluation methods 1, 2 and 3, the degree of cracking is checked according to the following criteria. 〇: No cracks △: Fine cracks ×: Fracture level cracks observed.

[0047] The corrosion resistance of the conductive film of the present invention can be evaluated in accordance with the neutral salt spray test method of JIS Standard 2371: 2015. That is, using an ISO-type salt spray tester (for example, STP-90VR manufactured by Suga Test Instruments Co., Ltd.), treatment is carried out for 48 hours at a spray temperature of 35°C and an air saturation temperature of 47°C using a 5% sodium chloride aqueous solution (pH 6.8) as the spray liquid.

[0048] After the treatment, the gold layer surface of the sample is visually observed, and the degree of corrosion is evaluated according to the following criteria. 〇: No change in metallic luster on the gold layer surface △: The metallic luster of the gold layer surface decreased, but no pinholes were observed. ×: Pinholes occurred on the gold layer surface.

[0049] The conductive film of the present invention suppresses copper migration into the gold layer. Methods for evaluating this property include measuring discoloration and contact resistance before and after an accelerated heat treatment test. The accelerated heat treatment is performed at 260°C for 15 minutes. The samples before and after the accelerated heat treatment are subjected to SCI color measurement using a colorimeter (e.g., a spectrophotometer CM-2600d manufactured by Konica Minolta Japan, Inc.), and the color difference (ΔE) is calculated and evaluated. A color difference (ΔE) of 3.0 or less can be considered to have effectively suppressed copper migration.

[0050] Similarly, the copper migration suppression effect can be evaluated by measuring the contact resistance of the sample before and after the accelerated test. The contact resistance (mΩ) was measured by preparing two gold-plated jigs measuring 30 mm x 30 mm x 10 mm and weighing 50 g, and measuring 900 mm 2The two jigs are placed side by side on the sample surface, with the surface that has the area of ​​1 mm facing down, and the resistance (mΩ) between the two jigs can be measured using a milliohm high tester (such as the 3540 manufactured by Hioki E.E. Corporation). It is preferable that the contact resistance be 3.0 mΩ or less both before and after the accelerated test.

[0051] 7. Conductive film manufacturing method The method for producing a conductive film of the present invention includes, in this order, a first step of forming a copper layer on one side of an insulating film substrate by vapor deposition, a second step of forming a nickel layer on the surface of the copper layer by electroplating, and a third step of forming a gold layer on the surface of the nickel layer by electroplating.

[0052] In the first step, a copper layer is formed on one surface of the insulating film substrate. Examples of methods for forming the copper layer include vapor deposition and electroless copper plating. Among these, vapor deposition is preferred. For the vapor deposition, known vapor deposition devices and methods can be used.

[0053] Prior to forming the copper layer, the surface of the insulating film substrate may be pretreated and modified by plasma treatment, ion irradiation treatment, etc. The surface of the copper layer formed in the first step is preferably smooth, and its arithmetic mean roughness Ra is preferably 0.02 μm or less. If a vapor deposition method is used to form the copper layer, a copper layer with high surface smoothness can be formed.

[0054] In the first step, a copper layer may be formed by electrolytic copper plating following the vapor deposition process. This allows the copper layer to be formed thicker more efficiently. In this case, a second copper layer formed by electrolytic copper plating is laminated on the surface of the copper layer formed by vapor deposition. Therefore, it is preferable that the arithmetic mean roughness Ra of the surface of the second copper layer is 0.02 μm or less.

[0055] In order to achieve an arithmetic mean roughness Ra of 0.02 μm or less on the surface of the second copper layer by electrolytic copper plating, it is preferable to employ a method such as adding a specific plating treatment agent to the plating bath, among which there is a plating treatment agent called a brightener.

[0056] Examples of plating treatment agents include organic sulfur compounds such as bis(3-sulfopropyl)disulfide disodium, 2,5-dimercapto-1,3,4-thiadiazole, 3-mercapto-1-propanesulfonic acid, and N,N-dimethyldithiocarbamic acid (3-sulfopropyl) ester.

[0057] Further examples of plating treatment agents include organic nitrogen compounds such as phenazine compounds, safranine compounds, polyalkyleneimines, thiourea derivatives, and polyacrylic acid amides. Organic nitrogen compounds are thought to be effective as leveling agents for forming a uniform copper layer.

[0058] These organic sulfur compounds and organic nitrogen compounds may be used alone or in combination with each other. In addition to these, nonionic polyether polymer surfactants such as polyethylene glycol and polyoxyethylene polyoxypropylene copolymers, water-soluble polymer compounds such as dextrin and glycerin may also be blended and used. More preferred examples 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.

[0059] In the present invention, commercially available plating additives can also be used. In particular, commercially available compounds containing organic sulfur compounds and / or organic nitrogen compounds appropriately blended with polymeric surfactants and the like can also be used.

[0060] Commercially available products of such plating treatment agents include bright copper plating additives such as "COSMO S-MU" (manufactured by Daiwa Tokushu Co., Ltd.), "KOTAC MU" (manufactured by Daiwa Tokushu Co., Ltd.), "COSMO S-1" (manufactured by Daiwa Tokushu Co., Ltd.), and "KOTAC 1" (manufactured by Daiwa Tokushu Co., Ltd.).

[0061] Other examples include the product name "TOP LUCINA SF BASE WR" (manufactured by Okuno Chemical Industries Co., Ltd.), the product name "TOP LUCINA SF-QB" (manufactured by Okuno Chemical Industries Co., Ltd.), the product name "TOP LUCINA SF-LEVELER Z" (manufactured by Okuno Chemical Industries Co., Ltd.), the product name "DAINCOPPER LS004R" (manufactured by Yamato Chemical Industries Co., Ltd.), and the product name "DAINCOPPER LS004S" (manufactured by Yamato Chemical Industries Co., Ltd.).

[0062] Any of the above-mentioned commercially available products can be used in combination of two or three 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. Furthermore, the above-mentioned "DAINCOPPER LS004R" and "DAINCOPPER LS004S" are a combination that can be used in combination. Furthermore, the above-mentioned "KOTAC MU" and "KOTAC 1" are a combination that can be used in combination.

[0063] Following the first step, a second step is carried out in which a nickel layer is formed on the surface of the copper layer. The nickel layer is formed by a known electroplating method. As mentioned above, it is essential that the thickness of the nickel layer is 0.05 to 0.2 μm. The conditions for the electroplating method in the second step are not particularly limited, and may be set within a range in which a nickel layer of the desired thickness can be formed. Typical conditions include a plating solution temperature of 20 to 60°C and a current density of 0.5 to 5.0 A / dm 2 The processing time can be 5 to 300 seconds.

[0064] Furthermore, following the second step, a third step is carried out in which a gold layer is formed on the surface of the nickel layer. A known electroplating method is also used to form the gold layer. The arithmetic mean roughness Ra of the gold layer surface is preferably 0.03 μm or less. This can improve corrosion resistance. The conditions for the electroplating method in the third step are not particularly limited, and may be set within a range in which a gold layer of the desired thickness can be formed. Typical conditions include a plating solution temperature of 40 to 60°C and a current density of 0.1 to 3.0 A / dm 2 The processing time can be 5 to 300 seconds.

[0065] The third step may be followed by a step of contacting the surface of the gold layer with a treatment solution containing an organic sealing agent, thereby forming a film of the organic sealing agent on the surface of the gold layer and sealing fine pinholes.

[0066] The organic sealing agent is preferably one or a combination of compounds selected from the group consisting of heterocyclic compounds, thiol compounds, and amine compounds. Among these, thiol compounds are preferred. Specific examples include alkyl thiols, alkyl disulfides, triazine thiols, and mercaptobenzothiazoles.

[0067] Examples of solvents that dissolve the organic sealing agent include water and alcohols. A surfactant may be added to disperse the organic sealing agent. Examples of such surfactants include polyoxyethylene nonylphenyl ether.

[0068] Commercially available products can also be used as the organic sealing agent dispersed with a surfactant, etc. Examples of such commercially available products include EL-8000B (manufactured by Nisshin Seiki Co., Ltd.), CT-3 (manufactured by JX Nippon Mining & Metals Corporation), and KG-230 (manufactured by JX Nippon Mining & Metals Corporation).

[0069] When using the commercially available product, it is preferably diluted to a concentration of 20 to 100 mL / L and then brought into contact with the surface of the gold layer.

[0070] The first, second, and third steps may be carried out continuously. The step of contacting the treatment liquid containing the organic sealing agent may also be carried out continuously after the third step. Furthermore, a water-washing step or a drying step may be carried out as appropriate between these steps.

[0071] When a resin layer having a high elongation rate is provided on the other surface of the insulating film substrate (the surface opposite to the surface on which the metal layer is provided), the step of forming the resin layer can be performed by attaching or laminating a resin film to the insulating film substrate before the first to third steps of providing each metal layer on the insulating film substrate. Alternatively, the step can be performed by attaching or laminating a resin film to the surface of the insulating film substrate opposite to the surface on which the metal layer is provided after providing each metal layer on the insulating film substrate. [Example]

[0072] The present invention will be described below with reference to examples, but the present invention is not limited to these examples in any way.

[0073] [Various physical property tests] (1) Peel strength test (adhesion evaluation) The conductive film was cut into a 50 mm long and 5 mm wide specimen. The center of the specimen was masked to expose a 3 mm long section. The exposed 3 mm x 5 mm specimen surface (surface of the gold layer) was then heat-treated at 250°C for 2 minutes with the head of a copper nail (Showa Electric Cable Systems Co., Ltd., copper thin flat rivet M3 x 20) attached using solder paste (manufactured by Senju Metal Industry Co., Ltd., product name "ECO solder paste L20-BLT5-T7F"). The heat treatment was performed using a constant temperature dryer (manufactured by Advantec Toyo Co., Ltd., product name "DRA630DA").

[0074] After the heat treatment, the sample was cooled to room temperature, folded in half at the location where the copper nail was attached, and the peel strength was measured by pulling the sample and the copper nail in opposite directions using a tensile strength tester. A digital load meter (manufactured by Imada Seisakusho Co., Ltd., product name "SV-55") was used as the tensile strength tester. The pulling speed was 25 mm / min.

[0075] (2) Bending resistance test A schematic diagram illustrating the method for the bending resistance test carried out in this example is shown in Figure 1. Conductive film 1 was cut into a length of 100 mm and a width of 30 mm to prepare a sample, and the conductive layer (metal layer 3) of conductive film 1 was folded so that it faced outward, and a 163 μm thick PET film 4 (a laminate of Lumirror 38S10 and 125S10 manufactured by Toray Industries, Inc.) was sandwiched between the film and the folded portion 8 so that the radius of curvature was 82 μm.

[0076] The sample (conductive film 1) folded with the PET film 4 sandwiched between them was placed flat on a horizontal workbench 7 as shown in Figure 1. A 2.0 kg weight 5 was placed on top of the sample via a glass slide 6 in the position shown in Figure 1, and the sample was left to stand for 1 second so that a predetermined load was applied to the folded portion 8. After removing the weight 5, the folded portion 8 was observed with a microscope (product name "Digital Microscope VHX-5000"; manufactured by Keyence Corporation) to confirm the occurrence of cracks. This method was designated Evaluation Method 1.

[0077] In addition, the thickness of the PET film was changed to 100 μm, and the same procedure was followed as above, except that the bent portion of the sample was bent to a curvature radius of 50 μm. The occurrence of cracks was then confirmed using the same method (this method was designated Evaluation Method 2).

[0078] In addition, the same procedure as above was carried out except that the PET film was not sandwiched and the bent portion of the sample had a curvature radius of 0 μm, and then the occurrence of cracks was confirmed in the same manner (this procedure was designated as Evaluation Method 3). Evaluation Method 3 was carried out only in Examples 4 and 5.

[0079] In each of the above evaluation methods 1, 2 and 3, the degree of cracking was confirmed according to the following criteria. 〇: No cracks △: Fine cracks ×: Fracture level cracks present.

[0080] (3) Corrosion resistance test In accordance with the neutral salt spray test method of JIS Standard 2371:2015, an ISO-type salt spray tester (manufactured by Suga Test Instruments Co., Ltd., product name "STP-90VR") was used, and the test was carried out for 48 hours at a spray liquid temperature of 35°C and an air saturation temperature of 47°C using a 5% sodium chloride aqueous solution (pH 6.8).

[0081] After the treatment, the gold layer surface of the sample is visually observed, and the degree of corrosion is evaluated according to the following criteria. 〇: No change in metallic luster on the gold layer surface △: The metallic luster of the gold layer surface decreased, but no pinholes were observed. ×: Pinholes occurred on the gold layer surface.

[0082] (4) Copper migration suppression effect (presence or absence of discoloration) An accelerated heat treatment test was performed at 260°C for 15 minutes. The samples before and after the accelerated heat treatment were subjected to SCI color measurement using a spectrophotometer (manufactured by Konica Minolta Japan, Inc., product name "CM-2600d"), and the color difference (ΔE) was calculated and evaluated.

[0083] (5) Copper migration suppression effect (change in contact resistance value) The copper migration suppression effect was evaluated by measuring the contact resistance of the samples before and after the accelerated heat treatment test. The contact resistance (mΩ) was measured using two gold-plated jigs measuring 30 mm x 30 mm x 10 mm and weighing 50 g. 2 The two jigs were placed side by side on the sample surface with the surface with the area of ​​1 mm facing downwards, and the resistance (mΩ) between the two jigs was measured using a milliohm high tester (manufactured by Hioki E.E. Corporation, product name "3540").

[0084] (6) Arithmetic mean roughness The arithmetic mean roughness Ra was measured using a scanning confocal laser microscope (manufactured by Olympus Corporation, trade name "LEXT OLS30-SU") according to a method in accordance with JIS B 0601:2001.

[0085] (7) Elongation measurement method The elongation of the resin layer was calculated using the following formula from the elongation length until the resin layer broke using a tensile strength tester, where Lo was the sample length (mm) before the test and L was the sample length (mm) at break.

[0086] (Number 1) Elongation rate (%) = 100 × (L-Lo) / Lo

[0087] A 20 mm x 5 mm resin film for the resin layer was masked with tape (trade name "No. 642", manufactured by Teraoka Seisakusho) so that a central 5 mm x 5 mm area remained. Using a tensile strength tester, the two masked tape areas were pinched and pulled in opposite directions to measure the time until the resin film broke, and L was calculated from the tensile speed. In this test, the Lo value was 5. For the tensile strength test, a digital load meter (manufactured by Imada Seisakusho Co., Ltd., trade name "SV-55") was used, and the tensile speed was 30 mm / min.

[0088] [Example 1] A copper-deposited film manufactured by Toray KP Films Co., Ltd. (a thick copper film deposited on Kapton 100V manufactured by DuPont-Toray Co., Ltd.) with a 1.5 μm thick copper layer formed by vapor deposition on one surface of a 25 μm thick polyimide resin film used as an insulating film substrate was acid-washed in a 50 mL / L aqueous solution of sulfuric acid 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.

[0089] Next, nickel electroplating was carried out to form a nickel layer on the surface of the copper layer. The nickel plating bath contained 200 g / L of nickel sulfate hexahydrate, 60 g / L of trisodium citrate dihydrate, pH 5.5, and temperature 40°C. The nickel electroplating conditions were a current density of 3.0 A / dm 2 The treatment time was 15 seconds, and the anode used was Anodek 100 (manufactured by Nisshin Seiki Co., Ltd.) The thickness of the obtained nickel layer was 0.12 μm.

[0090] Next, electrolytic gold plating was performed to form a gold layer on the surface of the nickel layer, obtaining a conductive film. The gold plating bath used was Eco Gold 24 (manufactured by Nisshin Seiki Co., Ltd., gold concentration 8.0 g / L). The plating bath temperature was 40°C, and the current density was 0.32 A / dm 2 for 15 seconds using an Anode DEC 100 (manufactured by Nisshin Seiki Co., Ltd.) The thickness of the gold layer obtained was 0.031 μm, and the arithmetic mean roughness Ra of the gold layer surface was 0.025 μm.

[0091] Next, the conductive film with the gold layer formed thereon was immersed in a 50 mL / L aqueous solution of an organic sealing agent, trade name "EL-8000B" (manufactured by Nisshin Seiki Co., Ltd.; thiol compound), at a treatment temperature of 40°C for 16 seconds.

[0092] The obtained conductive film was evaluated and measured for adhesion in a peel strength test, corrosion resistance in a bending test, and corrosion resistance in a salt spray test. The results are shown in Table 1.

[0093] [Example 2] A conductive film was obtained in the same manner as in Example 1, except that the gold electroplating treatment time was 22.5 seconds and the gold layer thickness was 0.046 μm. The arithmetic mean roughness Ra of the gold layer surface was 0.026 μm. The evaluation and measurement results are shown in Table 1.

[0094] [Example 3] A copper-deposited film manufactured by Toray KP Films Co., Ltd. (a thick film of copper deposited on Kapton 100V manufactured by DuPont-Toray Co., Ltd.) was used as an insulating film substrate. The film had a 12.5 μm-thick polyimide resin film on one surface of which a 0.3 μm-thick copper layer was formed by vapor deposition. The film was then acid-washed with a 50 mL / L aqueous solution of sulfuric acid at 20°C for 30 seconds.

[0095] This was subjected to electrolytic copper plating to form a copper layer with a thickness of 1.99 μm. The copper plating bath contained 200 g / L of copper sulfate pentahydrate, 55 mL / L of sulfuric acid, 20 mL / L of a soft copper film forming agent (trade name "CU-SOFT", manufactured by JCU Corporation), and 85 mg / L of sodium chloride, and the plating bath temperature was set to 40°C. The electrolytic copper plating conditions were 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.

[0096] Next, electrolytic nickel plating was carried out 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 The treatment time was 69.4 seconds, and the thickness of the resulting nickel layer was 0.11 μm.

[0097] Furthermore, electrolytic gold plating and film formation using an organic sealing agent were carried out under the same conditions as in Example 1, forming a gold layer with a thickness of 0.033 μm and an arithmetic mean surface roughness Ra of 0.118 μm. The evaluation and measurement results are shown in Table 1.

[0098] [Example 4] A copper-deposited film manufactured by Toray KP Films Co., Ltd. (a thick film of copper deposited on Kapton 100V manufactured by Toray DuPont Co., Ltd.) was used as an insulating film substrate. The film had a 4 μm-thick polyimide resin film on one surface of which a 0.3 μm-thick copper layer was formed by vapor deposition. The film was then acid-washed in a 50 ml / L aqueous solution of sulfuric acid at 20°C for 30 seconds.

[0099] This was subjected to electrolytic copper plating to a copper layer thickness of 3.13 μm. The copper plating bath contained 220 g / L of copper sulfate pentahydrate, 35 ml / L of sulfuric acid, 5 ml / L of a bright copper plating additive (trade name "COSMO S-MU", manufactured by Daiwa Tokushu Co., Ltd.), 2 ml / L of a bright copper plating additive (trade name "COSMO S-1", manufactured by Daiwa Tokushu Co., Ltd.), and 170 mg / L of sodium chloride, and the plating temperature was 35°C. The electrolytic copper plating conditions were a current density of 3.0 A / dm 2 The arithmetic mean roughness of the copper layer surface was Ra 0.019 μm.

[0100] Next, electrolytic nickel plating was carried out 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 The treatment time was 56 seconds, and the thickness of the resulting nickel layer was 0.07 μm.

[0101] Furthermore, electrolytic gold plating and film formation using an organic sealing agent were carried out under the same conditions as in Example 1, forming a gold layer with a thickness of 0.046 μm and an arithmetic mean surface roughness Ra of 0.025 μm. The evaluation and measurement results are shown in Table 1.

[0102] [Example 5] For the conductive film obtained under the same conditions as in Example 4, a 30 μm thick polyurethane resin film (product name "UH-203", manufactured by Nihon Matai Co., Ltd.) was attached to the side of the insulating film substrate opposite the side on which the metal layer was provided, and the two were bonded together by placing a 5 kg weight on a 100°C hot plate (product name "HT-1000", manufactured by AS ONE Corporation) for 10 seconds. The elongation of the polyurethane resin film used in this experiment was 1300%. The evaluation and measurement results for the obtained conductive film are shown in Table 1.

[0103] [Comparative Example 1] A conductive film was obtained in the same manner as in Example 1, except that the nickel electroplating treatment time was 69.4 seconds and the nickel layer thickness was 0.61 μm. The arithmetic mean roughness Ra of the gold layer surface was 0.026. The evaluation and measurement results are shown in Table 1.

[0104] Comparative Example 2 A conductive film was obtained in the same manner as in Example 1, except that the nickel electroplating treatment time was 1.0 second and the nickel layer thickness was 0.012 μm. The arithmetic mean roughness Ra of the gold layer surface was 0.017. The evaluation and measurement results are shown in Table 1.

[0105] [Table 1] [Industrial Applicability]

[0106] The conductive film of the present invention can be used as a grounding conductive film. By wrapping it around an elastic material, it can be made into a gasket, which can be sandwiched inside the housing of an electronic device to be used as a countermeasure against electromagnetic interference. It can block noise generated by the electronic device itself as well as external noise that affects the electronic device. Because it is in film form, it can also be used as an electrical connection member for electrical circuits formed on flexible substrates, such as in wearable devices. [Explanation of symbols]

[0107] 1.Conductive film 2.Insulating film substrate 3. Metal layer 4.PET film 5. Weight 6. Glass slides 7. Workbench 8. Bending section

Claims

1. A conductive film comprising metal layers, each consisting of a copper layer, a nickel layer, and a gold layer, laminated in this order on one surface of an insulating film substrate, wherein the copper layer has a thickness of 1 to 5 μm, the nickel layer has a thickness of 0.05 to 0.2 μm, and the gold layer has a thickness of 0.05 μm or less.

2. The conductive film according to claim 1 , wherein the copper layer has an arithmetic mean roughness Ra of 0.02 μm or less on the surface thereof on which the nickel layer is laminated.

3. The conductive film according to claim 1 , wherein the gold layer has an arithmetic mean roughness Ra of 0.03 μm or less.

4. A conductive film as described in claim 1, characterized in that the copper layer includes a copper vapor deposition layer formed by a vapor deposition method and / or a copper plating layer formed by an electrolytic copper plating method using a copper plating bath containing a brightener.

5. 2. The conductive film according to claim 1, further comprising a resin layer having an elongation of 200 to 2000% on the surface of the insulating film substrate opposite to the surface on which the metal layer is provided.

6. 2. The conductive film according to claim 1, wherein a film made of at least one organic sealing agent selected from the group consisting of heterocyclic compounds, thiol compounds, and amine compounds is formed on the surface of the gold layer.

7. The conductive film according to claim 1, wherein the peel strength between the insulating film substrate and the metal layer is 0.6 kgf / 15 mm 2 or more.

8. 2. The conductive film according to claim 1, wherein the insulating film substrate has a thickness of 4 to 25 μm.

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