JP2009176646A - Foil-shaped conductor, wiring member, and manufacturing method of wiring member conductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foil-shaped conductor superior in corrosion resistance such as a gold plating even if the surface layer formed thereof is thin, to provide a wiring member equipped with this foil-shaped conductor, and to provide a manufacturing method of the wiring member. <P>SOLUTION: The foil-shaped conductor is used for a wiring member such as an FFC and an FPC, and has a surface layer (for example, gold) constituted of different kind of metal at least at a part of the surface of a foil-shaped substrate 10 and an intermediate layer (for example, nickel) 11 arranged below the surface layer, and the average crystal grain size of the metal constituting the surface side region in the intermediate layer 11 is 0.001 μm or more and 0.3 μm or less. By making the portion immediately below the surface layer have a fine organization, even if the surface layer is thin less than 0.1 μm, pinholes can be reduced and the foil-shaped conductor is superior in corrosion resistance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention includes FFC (Flexible Flat Cable) and FPC (Flexible Flat Cable).
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring member having a foil-like conductor (Printed Circuits, flexible printed wiring board), a method for manufacturing the wiring member, and a foil-like conductor used for the wiring member.

  Conventionally, FFC and FPC are used as wiring members for connecting and contacting electronic devices. FFC and FPC are generally configured by sandwiching a plurality of foil-like conductors and being integrated with an insulating film. Part of the conductor is exposed and solder is applied to the exposed part. The exposed portion can be brought into contact with the elastic contact piece of the connector. Copper and copper alloys with high conductivity are widely used as the constituent material of the conductor.

  For the purpose of improving the corrosion resistance of the exposed areas, etc., gold plating is applied to the copper surface via nickel plating (Patent Documents 1 and 2), nickel plating is applied to the copper surface, and a rust inhibitor is further applied thereon. (Patent Document 2 Example 3) has been carried out. When direct gold plating is applied to copper, copper and gold are alloyed over time, and there is a risk that the properties (such as corrosion resistance and flexibility) of gold preferable as a contact material may be impaired. Nickel plating is interposed. The gold plating is formed so that the lower limit of the thickness is 0.1 μm (Patent Document 2 Example 3) and the average thickness is about 0.2 μm.

Japanese Unexamined Patent Publication No. 2006-49185 JP 2006-92819 A

For the purpose of cost reduction and the like, it is desired to make the gold plating thin. However, if the gold plating is made thin, particularly less than 0.1 μm, the number of pinholes tends to increase, and the corrosion resistance of the conductor decreases as the number of pinholes increases, and the desired corrosion resistance is not satisfied. For example, a 48 hour salt spray test (e.g. JIS
C 0023 (1998)), corrosion products are formed. In particular, when the surface layer is made of a metal (gold) that is nobler than the base metal (nickel), if there are pinholes in this surface layer, the base metal and the constituent metals of the surface layer are localized in a corrosive environment. A dissimilar metal contact reaction in which the base metal is dissolved at an accelerated rate can occur. Therefore, it is desired to develop a foil-like conductor having few pinholes and excellent corrosion resistance even when the surface layer such as gold plating is thin.

  The present invention has been made in view of the above circumstances, and its object is to provide a foil-like conductor excellent in corrosion resistance even if the surface layer is thin, a wiring member comprising the foil-like conductor, and a method of manufacturing the wiring member. Is to provide.

  If the amount of pinholes in the surface layer such as gold plating provided on the surface of a foil conductor provided on FFC or FPC is small to some extent, apply a sealing agent such as a rust inhibitor onto the pin. The desired corrosion resistance can be satisfied by closing the hole (performing sealing). However, conventionally, the amount of pinholes in the surface layer such as gold plating has been qualitatively evaluated by a salt spray test or the like (visual confirmation of corrosion products), but not quantitatively evaluated. Therefore, the pinhole amount that can maintain the desired corrosion resistance by the sealing treatment has not been clarified. Therefore, the present inventors first evaluated the amount of pinholes quantitatively, found the limit amount of pinholes satisfying the desired anticorrosion, and examined the structure that satisfies this limit amount even when the surface layer is thin In addition, the inventors have found that the base metal (surface region on the intermediate layer) immediately below the surface layer preferably has a specific microstructure. The present invention is based on this finding.

  The foil-like conductor of the present invention comprises a surface layer made of a different metal and an intermediate layer disposed under the surface layer on at least a part of the surface of the foil-like substrate. The surface layer is made of at least one metal selected from gold, a gold alloy, a platinum group metal, and a platinum group metal alloy. The intermediate layer is made of at least one metal selected from nickel, nickel alloy, tin, and tin alloy. The intermediate layer has an average crystal grain size of the metal constituting the surface side region of not less than 0.001 μm and not more than 0.3 μm. The foil conductor of the present invention having the above configuration is excellent in corrosion resistance even if the surface layer is thin, and the cost can be reduced by making the surface layer thin. Hereinafter, the present invention will be described in more detail.

  The base material is a foil that constitutes the main part of the conductor of the present invention, and has high conductivity, high ductility, moderate strength, and easy coating with other metals (Cu) and Cu alloys The one consisting of is preferred. Examples of the Cu alloy include a Cu—Ni alloy, a Cu—Sn alloy, a Cu—Zn alloy, and a Cu—Ag alloy. The base material may be selected according to the use of the conductor of the present invention. For example, when the conductor of the present invention is used for FFC, a thin wire such as a flat wire, and when used for FPC, a metal foil can be used. A coated wire or coated foil in which nickel, tin, or an alloy thereof is coated on the surface of these wire or metal foil, for example, a plated wire can also be used as a substrate. Examples of the coated wire and the coated foil include those obtained by coating a wire or foil made of copper or a copper alloy after plating or the like and then rolling. As for the thickness of a base material, 0.01-0.05 mm is mentioned, More specifically, FFC is 0.025-0.050 mm, FPC is about 0.018 mm. The conductor of the present invention has a surface layer and an intermediate layer on at least a part of the longitudinal direction of such a substrate.

  Specific constituent metals of the surface layer include gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), and alloys of these metals. Examples of the Au alloy include so-called hard gold such as Au-Co alloy and Au-Ni alloy. Examples of the platinum group metal alloy include a Pd—Ni alloy. The surface layer may be a single layer, or may be a plurality of layers made of different metals selected from the above metals, for example, a laminated structure including an Au alloy layer on an Au layer.

  Since the surface layer is composed of a relatively expensive metal, it is preferable to reduce the thickness in consideration of cost reduction, and the thickness (total thickness in the case of multiple layers) is less than 0.1 μm, particularly 0.05 μm. The following is preferable, and 0.01 μm or more is preferable in consideration of securing contact resistance with a connector or the like. The thicknesses of the surface layer and the intermediate layer described later can be adjusted by forming conditions (for example, when forming by plating, plating time, current density, etc.). Since the conductor of the present invention has a specific structure in the intermediate layer below the surface layer as described later, the pinhole amount is small even if the thickness of the surface layer is reduced to less than 0.1 μm (specifically, By performing sealing treatment with a pinhole ratio of 3% or less, sufficient corrosion resistance can be obtained with respect to the salt spray test (48 hours). Further, the conductor of the present invention is equivalent to the pinhole ratio (about 1%) of a conventional conductor in which the thickness of the gold plating is 0.1 μm or more by controlling the thickness of the surface layer and the structure state of the intermediate layer, Or it can be less (1% or less).

  The pinhole ratio was determined by preparing an electrochemical measurement cell using a foil conductor and a specific electrolyte, and evaluating the current value associated with the dissolution reaction of the metal in the electrolyte as the pinhole amount. Let the amount be the proportion of the surface layer. Specifically, when a foil-like conductor is immersed in an electrolyte and applied to this conductor while changing its potential, the change in current caused by oxidation of the metal exposed from the pinhole in the electrolyte is measured. Based on this measurement result, the pinhole amount (area) is calculated, and the pinhole amount (area) / surface layer area is defined as the pinhole ratio. The electrolyte solution does not substantially react with the constituent metal of the surface layer, and is an acid solution with a specific concentration that easily reacts with the metal exposed from the pinhole (mainly the constituent metal of the intermediate layer), specifically, 2 to 7M. Use sulfuric acid or hydrochloric acid. Gold, gold alloy, platinum group metal, and platinum group metal alloy do not substantially react with such an electrolyte, and nickel, nickel alloy, tin, and tin alloy react (dissolve). I have confirmed. Moreover, the pinhole of the surface layer communicates with the intermediate layer and reaches the base material, and the base material may be exposed, but copper and copper alloy react with the above electrolyte and intermediate layers such as nickel In order to obtain the same current change as that of the constituent metals, it is possible to quantify such pinholes by using the electrochemical measurement cell.

  Specific constituent metals of the intermediate layer include nickel (Ni), Ni alloy, tin (Sn), and Sn alloy. Examples of the Ni alloy include a Ni—P alloy, a Ni—Bi alloy, a Ni—Sn alloy, and a Ni—Co alloy. Examples of the Sn alloy include lead-free solder such as Sn—Ag alloy and Sn—Bi alloy. Sn-Ag alloys and Sn-Bi alloys are unlikely to produce Sn whiskers. An intermediate layer, a single layer, or a plurality of layers made of different metals selected from the above metals may be used. For example, a multilayer structure including a Ni layer on a Sn layer may be used.

  The thickness of the intermediate layer (in the case of a plurality of layers, the total thickness) is preferably 0.5 μm or more and 5 μm or less, and more preferably 1.0 μm or more and 2.0 μm or less. When the thickness of the intermediate layer is 0.5 μm or more, pinholes in the intermediate layer itself are reduced, and the base material existing under the intermediate layer is difficult to be exposed. Therefore, it can suppress that the characteristic of a surface layer deteriorates because a surface layer is directly formed on the exposed base material and both form an alloy. On the other hand, when the thickness of the intermediate layer is 5 μm or less, it is possible to prevent the intermediate layer from being peeled off due to stress at the time of fitting between the wiring member having the conductor of the present invention and the connector.

  The most characteristic feature of the conductor of the present invention is that the average crystal grain size of the constituent metal in at least the surface side region in the intermediate layer is 0.001 μm or more and 0.3 μm or less. A more preferable range is 0.01 μm or more and 0.20 μm or less. When the intermediate layer is a single layer, the surface side region is the region from the boundary between the surface layer and the intermediate layer to half the thickness of the intermediate layer in the thickness direction of the intermediate layer. The layer immediately below. It is preferable that the average crystal grain size satisfies the above range over the entire intermediate layer. When the average crystal grain size is less than 0.001 μm, the hardness of the surface of the intermediate layer increases, and when the wiring member having the conductor of the present invention is inserted into the connector or pulled out from the connector, the intermediate layer cannot be sufficiently deformed, There is a risk of contact failure. On the other hand, when the average crystal grain size exceeds 0.3 μm, pinholes are easily formed as the surface layer becomes thinner. In the conductor of the present invention, by controlling the average crystal grain size of the surface side region of the intermediate layer in contact with the surface layer within the above range, the state immediately below the surface layer becomes dense and smooth, and the surface layer is formed thereon Thus, it is considered that pinholes are hardly formed in the surface layer. Details of the method for measuring the average crystal grain size will be described later.

  Examples of the method for forming the surface layer and the intermediate layer include plating methods such as electrolytic plating and electroless plating, and vapor deposition methods (dry process) such as a CVD method and a PVD method. The formation method can be appropriately selected depending on the type of metal. For example, gold and nickel can be formed by electrolytic plating, and Ni-P alloy can be formed by electroless plating. The plating usually contains impurities such as C, S, and O. Therefore, when each of the above layers is formed by a plating method, the above impurities are allowed to be contained (however, the total is 0.1% by mass or less).

  In order to make the intermediate layer have a fine structure as described above, for example, when the intermediate layer is formed by a plating method, a plating bath containing a brightener may be used. Here, since the conductor of the present invention is further provided with a surface layer on the intermediate layer, a brightener mainly for the purpose of improving the decorative property is not necessary in forming the intermediate layer. However, the conductor of the present invention dare to use a brightening agent to make the intermediate layer a fine structure for the purpose of reducing pinholes in the surface layer. For example, when nickel-based plating such as nickel or nickel alloy is performed, various types of nickel-based plating that are used as a primary brightener and a secondary brightener can be used. Even with the primary brightener alone, the crystal grains can be refined and a semi-glossy appearance can be obtained. However, when both the primary brightener and the secondary brightener are used, the crystal grains are more easily refined and a smooth surface is obtained. Obtained and has high gloss. When only the secondary brightener is used, the application range of the current density is small. Specific primary brighteners include saccharin, vinyl sulfonic acid, sodium 1,3,6 naphthalene trisulfonate, and specific secondary brighteners include 2-butyne 1,4 diol, propargyl alcohol, and coumarin. It is done. For example, when tin-based plating such as tin plating or tin-plated alloy is performed, specific brighteners are synthesized from aromatic organic amines, aliphatic aldehydes and ketones in the presence of an acid or alkali catalyst, aromatic aldehydes. And ketones. Alternatively, one method for miniaturizing the intermediate layer without using a brightener is to use a pulse plating method (a method in which energization and pause of high current density are repeated in milliseconds). On the other hand, when the intermediate layer is formed by a vapor deposition method, it is possible to adjust the film forming conditions so that the conditions are close to rapid solidification. For example, in the case of the sputtering method, the substrate is cooled, or the voltage during sputtering is increased. By using these specific plating baths or by controlling the plating conditions and vapor deposition conditions, the entire intermediate layer can be made into a fine structure composed of uniform fine particles.

  The foil-shaped conductor of the present invention comprises a wiring member such as FFC or FPC, that is, a foil-shaped conductor and an insulating coating layer that covers the foil-shaped conductor so that a part of the foil-shaped conductor is exposed from the insulating coating layer. It is suitable for a conductor of a wiring member having a connection region that can be electrically connected. In the wiring member of the present invention, the conductor is composed of the foil-shaped conductor of the present invention, and the connection region in the foil-shaped conductor is easily corroded in a corrosive environment, so that the intermediate layer and the surface layer are provided to enhance the corrosion resistance.

  By further applying a sealing agent on the surface layer to obtain a conductor having a sealing film, the corrosion resistance can be further improved. In particular, since the surface layer of the connection region is provided on the intermediate layer made of a fine structure as described above, even if the thickness is less than 0.1 μm, there are few pinholes, for example, a salt spray test ( 48 hours). Various organic materials can be used as the sealing agent. Water-soluble or oil-based ones can be coated by simply immersing the foil-like conductor in the sealing agent, or those that can be coated by immersing the sealing agent in the sealing agent and conducting an electric current treatment, etc. It is good to select suitably from. When the wiring member of the present invention is used for connection or contact of electronic equipment, it is not preferable that the electrical resistance on the surface of the member is large. Therefore, a sealing agent having a high anticorrosion effect even if the film thickness is thin is preferable. Examples of such a sealing agent include water-soluble thiol-based organic substances.

The said wiring member of this invention can be manufactured with this invention manufacturing method which comprises the following processes.
(1) A step of preparing a pre-material comprising a foil-like base material and an insulating coating layer covering the base material so that a part of the surface of the base material is exposed from the insulating coating layer.
(2) A step of forming an intermediate layer in a region exposed from the insulating coating layer in the base material of the pre-material.
(3) A step of forming a surface layer on the intermediate layer. In this step, by using a specific plating bath as described above, or by controlling the plating conditions and vapor deposition conditions, the average crystal grain size of the metal constituting the surface side region in the intermediate layer is 0.001 μm or more and 0.3 μm or less. To do.

  As a conventional FFC conductor, after applying nickel plating to the copper wire, it is sandwiched by the insulating film so that a part of the drawn and rolled rolled wire is exposed from the insulating film, and the exposed portion is plated with gold. There is something that has been given. In this conductor, since nickel plating is rolled, it is difficult to control the average crystal grain size of nickel plating within the range of 0.001 to 0.3 μm after rolling. In contrast, the wiring member of the present invention is not subjected to plastic working such as rolling after the formation of the intermediate layer as described above. Therefore, by controlling the formation conditions of the intermediate layer, the average crystal grain size is 0.001 to 0.3 μm. Can range.

  Since the foil conductor of the present invention has few pinholes even if the surface layer is thin, the wiring member of the present invention including the conductor of the present invention is excellent in corrosion resistance. The manufacturing method of the wiring member of the present invention can manufacture the wiring member of the present invention having excellent corrosion resistance.

  An FFC having a foil-like conductor in which nickel plating (intermediate layer) and gold plating (surface layer) are formed in sequence on a substrate is prepared, and the pinhole ratio of the surface layer is measured and the salt spray test is evaluated. It was.

  Here, samples with different intermediate layer structures were produced by changing the plating conditions as follows. First, a pre-sample that was sandwiched between insulating films (insulating coating layers) in a state where a plurality of base materials were juxtaposed was prepared. The base material is a copper flat wire (JIS H 3100 tough pitch copper) with a thickness of 0.035 mm and a width of 0.3 mm, and these base materials are arranged in parallel with a distance of 100 cores so as not to contact each other. The two sides of the film are sandwiched between insulating films, and the adhesive applied to the bonding surface of the film is pressed or melted to bond the films together to electrically insulate the base materials and produce a pre-material that integrates 100 cores. did. Examples of the insulating film include a polyester resin, and examples of the adhesive include a thermoplastic resin and a thermosetting resin, and commercially available products can be used. Here, as one insulating film, a plurality of windows (width: size that exposes 100 cores, length: 5 mm) are provided at equal intervals in the longitudinal direction of the film, and the other insulating film has no window. Each one was used so that one side of the 100-core substrate was exposed from each window.

  The prepared pre-material was subjected to the following treatments, and then appropriately cut to prepare a sample. Each sample has one window, and a part of the 100-core substrate is exposed from the window. Here, the pre-material is a sample that is appropriately cut into a desired length after sealing treatment using equipment that can perform various treatments such as plating with the hoop material (long material). Each treatment such as plating may be performed after cutting a pre-material.

Immersion degreasing → Electrolytic degreasing → Soft etching → Acid activity → Ni plating → Au strike plating → Au—Co plating → sealing treatment Washing is performed between the above steps (the same applies to sample No. 200 described later).

The conditions of each process excluding the Ni plating process are shown below.
Immersion degreasing was performed using NG-30 (manufactured by Kizai Co., Ltd.) at 40 g / L, 50 ° C. for 1 minute.
Electrolytic degreasing was performed using EBR (manufactured by Chuo Chemical Co., Ltd.): 35 g / L + sulfuric acid: 200 g / L at 45 ° C. and a current density of 5 A / dm ² .
Soft etching was performed using Actan 97 (manufactured by Meltex); Actan 97A: 90 g / L, Actan 97B: 150 g / L at room temperature for 30 seconds.
The acid activity was performed using sulfuric acid at 100 g / L, 40 ° C., for 10 seconds.
Au strike plating was performed using acid strike (manufactured by Nippon Kogyo Kagaku Co., Ltd.) as a gold plating solution at an Au concentration of 1.0 g / L, 40 ° C., and a current density of 0.7 A / dm ² × 7 seconds.
Au-Co plating is Aurobrite-HS2 (manufactured by Japan High Purity Chemical Co., Ltd.) as a gold plating solution, Au concentration: 8 g / L, Co concentration: 0.2 g / L, 50 ° C, current density 1A / dm ² × 14 Went in seconds.
The total target plating thickness of Au strike plating and Au—Co plating was 0.05 μm (50 nm).
Sealing treatment was performed by using CT-3 (manufactured by Nikko Metal Co., Ltd.) and dipping for 30 seconds at 40 ° C. (the thickness of the sealing treatment film: about 20 mm, a known method using an Auger electron spectrometer) Measured by).

Ni plating was performed under the following conditions.
(Sample No.1)
Composition of plating solution Nitric acid sulfamate: 450 g / L, Boric acid: 35 g / L, Ni chloride: 10 g / L, NSF-X (Nippon Chemical Industry Co., Ltd.): 5 mL / L
Energizing condition Current density 5A / dm ² x 1 min (target plating thickness: 1μm)

(Sample No.2)
The same plating solution as that used for sample No. 1 was used, and the current supply conditions were a current density of 5 A / dm ² × 2 minutes (target plating thickness: 2 μm).

(Sample No. 3)
The same plating solution as that used for sample No. 1 was used, and the current supply conditions were a current density of 10 A / dm ² × 30 seconds (target plating thickness: 1 μm).

(Sample No. 101)
In the plating solution used for sample No. 1, a plating solution that does not contain brightener (NSF-X) was used, and the energization condition was a current density of 10 A / dm ² × 30 seconds (target plating thickness: 1 μm). .

(Sample No.102)
In the plating solution used for sample No. 1, a plating solution that does not contain brightener (NSF-X) was used, and the energization condition was set to a current density of 20 A / dm ² × 30 seconds (target plating thickness: 2 μm). .

(Sample No. 200)
This sample was obtained by applying nickel plating (thickness 5 μm) to a copper wire (JIS H 3100 tough pitch copper) with a diameter of φ0.58 mm, drawing the wire to a diameter of φ0.117 mm, and using a rolling roll 0.035 mm in thickness × 3 mm in width Using a rolled wire rod flattened as a base material, a 100-core long material is produced using this base material and the insulating film with a window described above, and immersion degreasing → electrolytic degreasing → soft etching A sample was prepared by sequentially performing treatments of → acid activity → Au strike plating → Au—Co plating → sealing treatment, and then cutting appropriately. This sample No. 200 has one window like the sample No. 1 and the like, and a part of the 100-core base material is exposed from the window. The nickel plating of sample No. 200 was performed using Ni sulfamate as a plating solution (without using a brightener). In Au strike plating and Au-Co plating, the same plating solution as that of sample No. 1 was used, the plating time was lengthened, and the total target plating thickness was set to 0.1 μm.

  For each of the obtained samples No. 1 to 3, 101, 102, 200, the thickness of nickel plating, the thickness of gold plating, the average crystal grain size of nickel plating, the pinhole ratio of gold plating, and the salt spray test were evaluated. The results are shown in Table 1.

The thickness of the gold plating was measured using a commercially available fluorescent X-ray film thickness meter, and the thickness of the nickel plating and the average crystal grain size of the nickel plating were measured using the FIB-SIM image of each sample. The FIB-SIM image is a FIB (Focused) with a protective material (material: Pt) placed on the surface layer of each sample.
It is an image obtained by observing a cross section obtained by Ion Beam processing with SIM (Scanning Ion Microscopy). FIG. 1 shows a FIB-SIM image (10,000 times) of each sample (excluding No. 200). In each sample shown in FIG. 1, in order from the lower side, region 10 represents a base material (copper flat wire), region 11 represents an intermediate layer (nickel plating), and region 12 represents a protective material. The surface layer (gold plating) exists between the region 11 and the region 12.

  The thickness of the nickel plating was measured over the entire area of the FIB-SIM image shown in FIG. Sample No. 200 is rolled after nickel plating, so the thickness distribution is thick in the nickel plating (the central part and the vicinity of the edge are thick, and the gap between the central part and the edge is thin). Table 1 shows the range of the thinnest part.

The average crystal grain size of nickel plating is measured as follows. In each FIB-SIM image shown in FIG. 1, a straight line with a length of 5 μm is drawn parallel to the surface of the substrate (copper flat wire), and the number of grain boundaries existing on this straight line is measured. The obtained value is defined as the crystal grain size in this image. Then, the crystal grain size is determined for any three cross-sectional FIB-SIM images in each sample, and the average of these crystal grain sizes is taken as the average crystal grain size.
Crystal grain size = 5μm ÷ (number of grain boundaries measured + 1)

  The pinhole ratio was measured as follows by using a sample and an electrolyte solution and constituting a three-electrode electrochemical measurement cell. The cell includes a container into which an electrolytic solution is injected, a reference electrode and a counter electrode immersed in the electrolytic solution, and a measurement target (sample), and one end of each electrode and the measurement target (one end of each conductor) is a potentiostat / Connected to a galvanostat device (commercially available). Here, 5M sulfuric acid is used as the electrolyte, Ag / AgCl is used as the reference electrode, and Pt is used as the counter electrode. The apparatus is set in the potentiostat mode, and the potential is swept in the oxidation direction at a sweep rate of 1 mV / s. The device is connected to a control device (not shown) having input means, storage means, calculation means, comparison means, judgment means, display means, etc., and potential sweep, measurement result (potential-current curve) Can be obtained automatically.

  When there is a pinhole in the surface layer, as the potential applied to the object to be measured increases, the metal exposed from the pinhole (mainly nickel here) is oxidized in the electrolyte, causing current to flow. Then, the surface of this metal becomes passivated and the current becomes small. As a result, a potential-current curve (anodic polarization curve) having a peak is obtained. Since this peak current depends on the amount of metal exposed from the pinhole, that is, the amount (area) of the pinhole, the pinhole can be quantified by measuring the peak current. Therefore, the peak current of each sample is measured.

  On the other hand, a plurality of metal plates (here, having the same composition as nickel constituting the intermediate layer) made of metal exposed from the pinhole (mainly the constituent metal of the intermediate layer) are prepared, and a part of each plate is prepared. A plurality of samples (hereinafter referred to as control samples) having different exposed areas (contact areas with the electrolytic solution) are prepared by exposing and masking with an epoxy resin. Use these control samples to create an electrochemical measurement cell, measure changes in current under the same conditions (same electrolyte, same concentration, same sweep speed) as the measurement target, and obtain correlation data between peak current and exposed area To do. Then, the peak current of each sample is collated with the acquired correlation data, and the exposed area corresponding to the current value in the correlation data is evaluated as the pinhole area. Then, the area of the pinhole / the area of the surface layer (here, the total area of the portions exposed from the window in the foil conductor) is defined as the pinhole ratio.

  In the salt spray test, the test time was 48 hours in accordance with JIS C 0023 (1998), and the surface of the foil conductor was visually confirmed and evaluated. The results are shown in Table 1.

  As shown in FIG. 1, sample Nos. 1 to 3 using a plating solution containing a brightener consist of uniform fine particles not only on the surface side area but also on the entire surface of the intermediate layer (nickel plating). It can be seen that it is composed. On the other hand, for example, Samples Nos. 101 and 102 show that the intermediate layer 11 has large particles that follow the crystal of the substrate 10.

  And as shown in Table 1, sample Nos. 1 to 3 in which the average crystal grain size of the constituent metal of the intermediate layer is 0.001 to 0.3 μm, the thickness of the surface layer (gold plating) is as thin as less than 0.1 μm. However, pinholes are as small as 3% or less, and it can be seen that sufficient corrosion resistance is exhibited even in the salt spray test (48 hours). On the contrary, when the average crystal grain size is more than 0.3 μm (Sample No. 200), it can be seen that the pinhole ratio is not lowered unless the thickness of the surface layer (gold plating) is 0.1 μm or more. It can also be seen that if the pinhole ratio is 3% or less, a foil-like conductor having sufficient corrosion resistance can be obtained by performing the sealing treatment. Furthermore, it can be seen that in sample Nos. 1 to 3, the pinhole ratio tends to be smaller as the average crystal grain size of the constituent metal of the intermediate layer is smaller. When the obtained sample Nos. 1 to 3 were inserted into the connector and pulled out from the connector, the intermediate layer could be sufficiently deformed.

  In addition, this invention is not limited to the above-mentioned embodiment, It can change suitably in the range which does not deviate from the summary of this invention. For example, the composition and thickness of the surface layer and the intermediate layer, the average crystal grain size can be changed, and the composition of the substrate can be changed. Further, in forming the intermediate layer, when a pulse plating method is used or a vapor deposition method is used without using a brightener, the vapor deposition conditions may be controlled to form a fine structure. Furthermore, the intermediate layer may have a multilayer structure of tin plating and nickel plating. In addition, a pair of insulating films sandwiching the base material is used to produce a long material in which the entire surface of the base material is exposed from the window portion, and the base material exposed from the window portion in the long material. Cut the material so that the exposed base material is placed at the end of the cut piece, and wire the insulation reinforcing material placed at the end of the cut piece so as to contact one surface of the base material It is good also as a member. Alternatively, the conductor of the present invention can also be used as an FPC conductor.

  The foil conductor of the present invention can be suitably used for an FPC or FFC conductor. The wiring member of the present invention can be suitably used for connection wiring and contact wiring for electronic devices. The manufacturing method of the wiring member of the present invention can be used for manufacturing the wiring member of the present invention.

It is a FIB-SIM image (micrograph) of sample No.1-3,101,102.

Explanation of symbols

  10 Base material 11 Intermediate layer 12 Protective material

Claims (6)

A foil-shaped conductor comprising a surface layer composed of a different metal and an intermediate layer disposed under the surface layer on at least a part of the surface of the foil-shaped substrate,
The surface layer is made of at least one metal selected from gold, a gold alloy, a platinum group metal, and a platinum group metal alloy,
The intermediate layer is made of at least one metal selected from nickel, nickel alloy, tin, and tin alloy, and the average crystal grain size of the metal constituting the surface side region in the intermediate layer is 0.001 μm or more and 0.3 μm or less. A foil-like conductor characterized by being.   2. The foil conductor according to claim 1, wherein the surface layer has a thickness of less than 0.1 μm and a pinhole ratio of 3% or less. A wiring member comprising a foil-shaped conductor and an insulating coating layer covering the foil-shaped conductor so that a part of the foil-shaped conductor is exposed from the insulating coating layer and can be electrically connected. There,
The foil conductor is composed of the foil conductor according to claim 1 or 2,
The wiring region, wherein the connection region in the foil-shaped conductor includes an intermediate layer and a surface layer.   4. The wiring member according to claim 3, further comprising a sealing treatment film on the surface layer. Providing a foil-like base material and an insulating coating layer covering the base material so as to sandwich the base material, and preparing a pre-material in which a part of the surface of the base material is exposed from the insulating coating layer;
Forming an intermediate layer made of at least one metal selected from nickel, a nickel alloy, tin, and a tin alloy in a region exposed from the insulating coating layer in the base material of the pre-material,
Forming a surface layer made of at least one metal selected from gold, a gold alloy, a platinum group metal, and a platinum group metal alloy on the intermediate layer,
A method for producing a wiring member, wherein an average crystal grain size of a metal constituting a surface side region in the intermediate layer is 0.001 μm or more and 0.3 μm or less.   6. The method for manufacturing a wiring member according to claim 5, wherein the surface side region in the intermediate layer is formed by a plating method using a plating bath containing a brightener.