TWI568865B - Layer 2 flexible wiring substrate and manufacturing method thereof, and two-layer flexible wiring board and manufacturing method thereof - Google Patents

Description

Two-layer flexible wiring substrate and manufacturing method thereof, and two-layer flexible wiring board and manufacturing method thereof

The present invention relates to a two-layer flexible wiring substrate and a method for producing the two-layer flexible wiring substrate, in which a copper layer is partially deposited by a copper plating method to improve folding resistance, and a two-layer flexible wiring. Board and its manufacturing method.

The flexible wiring board is widely used for a bent or bent portion of an electronic device such as a hard disk read/write head or a printer head, and a meandering wiring in a liquid crystal display.

For the manufacture of the related flexible wiring board, a method of using a flexible wiring board in which a copper layer and a resin layer are laminated by using a removal method or the like (also referred to as a flexible copper clad laminate, FCCL: Flexible) can be used. Copper Clad Lamination) for wiring processing.

This removal method generally refers to a method of chemically etching a copper layer of a copper clad laminate to remove unnecessary portions. In other words, in the copper layer of the flexible wiring substrate, a resist is provided on the surface of the portion where the conductor wiring remains, and chemical etching treatment and water washing using an etching solution corresponding to copper are required to selectively remove the copper layer. Partially, the conductor wiring is formed.

The flexible wiring board (FCCL) can be classified into a three-layer flexible wiring board (hereinafter referred to as a three-layer FCCL) and a two-layer flexible wiring board (referred to as a two-layer FCCL).

The three-layer FCCL is adhered to the resin film of the substrate (insulating layer) with an electrolytic copper foil or Structure of rolled copper foil (copper foil/adhesive layer/resin film). On the other hand, the two-layer FCCL is a structure in which a copper layer or a copper foil is laminated with a resin film substrate (a copper layer or a copper foil/resin film).

Further, the above two layers of FCCL are roughly classified into three types.

In other words, FCCL (collectively referred to as a metallized substrate) formed by sequentially plating a base metal layer and a copper layer on the surface of a resin film, and a varnish coated with a resin film on a copper foil to form an insulating layer, FCCL (generalally referred to as a cast substrate) And FCCL (commonly referred to as laminated substrate) for copper foil laminated resin film.

The metal-plated substrate, that is, the FCCL formed by sequentially plating the underlying metal layer and the copper layer on the surface of the resin film, can form a thin film of the copper layer and have high smoothness at the interface between the polyimide film and the copper layer. Therefore, it is suitable for fine patterning of wiring as compared with a cast substrate, a build-up substrate, or a 3-layer FCCL.

The reason for this is that, for example, the copper layer of the metal plating substrate is freely controlled by the dry plating method and the plating method, and the copper used is affected by the thickness of the cast substrate, the laminated substrate, or the three-layer FCCL. The thickness of the foil is limited.

In the copper foil used for the wiring of the flexible wiring board, for example, a method of heat-treating a copper foil (see Patent Document 1) or a method of performing a rolling process (see Patent Document 2) , can improve the folding resistance.

However, these methods are related to the copper foil or electrolytic copper foil of the three-layer FCCL, the cast substrate in the two-layer FCCL, and the copper foil itself used for the laminated substrate.

In addition, in the evaluation of the folding endurance of the copper foil, the MIT Folding Endurance Test based on "JIS C-5016-1994" or the "ASTM D2176" standard is used industrially.

In this test, the number of times of bending until the circuit pattern formed on the test piece was broken was evaluated, and the larger the number of times of bending, the more excellent the folding endurance.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 8-283886

Patent Document 2: Japanese Patent Laid-Open No. Hei 6-269807

The two-layer flexible wiring board and the two-layer flexible wiring board which are the object of the present invention are formed by sequentially forming a seed layer and a copper plating layer which are not formed by an adhesive on at least one surface of the resin film substrate. The plated substrate of the metal layer is therefore difficult to improve the folding resistance by merely performing the heat treatment or the rolling process of the copper plating layer as disclosed in the prior art documents. Therefore, a method of manufacturing a plated substrate having excellent folding resistance is desired for a plated substrate.

In view of the above, the present invention provides a two-layer flexible wiring board excellent in folding resistance, a method for producing the same, a two-layer flexible wiring board, and a method for manufacturing the same.

In order to solve the above problems, the present inventors have conducted intensive studies on the folding resistance of a copper layer formed on a polyimide film by a plating method, and as a result, (200) a preferentially oriented sputtering material is used, and then borrowed. From the copper plating, the influence of the change in the crystal orientation before and after the folding endurance test on the folding endurance test results was confirmed, and the present invention has been completed.

According to a first aspect of the invention, there is provided a substrate for a two-layer flexible wiring, wherein the metal laminate includes a base metal made of a nickel-containing alloy without using an adhesive on the surface of the resin film substrate. a layer having a copper layer on the surface of the underlying metal layer, wherein the metal laminated body measured by an electron backscatter diffraction method (EBSD) has a thickness of 0.4 μm from the surface of the resin film substrate The ratio of the crystal ratio OR ₁₁₁ of the crystal 111 orientation in the range of 111 to the crystal ratio of the 001 orientation OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less, and the orientation index of the (111) plane of the copper layer is 1.2 or more. And the difference in crystal orientation ratio [(200)/(111)] of the copper layer obtained before and after the implementation of the folding endurance test prescribed in JIS C-5016-1994 is d [(200)/(111)] It is 0.03 or more.

According to a second aspect of the invention, the substrate for a two-layer flexible wiring according to the first aspect of the invention, wherein the thickness of the underlying metal layer is from 3 nm to 50 nm.

According to a third aspect of the invention, the two-layer flexible wiring board according to the first aspect of the invention, wherein the copper layer has a thickness of 5 μm to 12 μm.

According to a fourth aspect of the present invention, in the second aspect of the invention, the copper layer is formed by a copper thin film layer formed on the surface of the underlying metal layer and formed by electroplating copper. The copper plating layer is formed on the surface of the copper thin film layer, and the electroplated copper layer is in a thickness range of 10% or more of the film thickness from the surface thereof in the direction of the resin film substrate, and the cycle is reversed by periodically performing the short-time potential inversion ( Periodic Reverse) The current is formed by electroplating copper.

According to a fifth aspect of the invention, the two-layer flexible wiring board according to the fourth aspect of the invention, wherein the base metal layer and the copper thin film layer are formed by a dry plating method.

According to a sixth aspect of the present invention, in the second aspect of the invention, the resin film substrate is selected from the group consisting of a polyimide film, a polyamide film, and a polyester film. At least one or more resin films of a polytetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a liquid crystal polymer film.

The manufacturer of the two-layer flexible wiring board according to the seventh aspect of the present invention In the method for producing a two-layer flexible wiring board according to the first to sixth aspects of the invention, the method of forming a base metal layer and a substrate by dry plating on the surface of the resin film substrate without using an adhesive A copper thin film layer is formed on the surface of the metal layer, and a copper plating film is formed on the surface of the copper thin film layer by a copper plating method, wherein the ambient gas formed by the dry plating method is an argon-nitrogen mixed gas. The electroplated copper layer is a thickness range of 10% or more of the thickness of the electroplated copper layer from the surface of the electroplated copper layer in the direction of the resin film substrate, and the copper plating method is performed by periodically performing a reverse current of a short time potential inversion. form.

The two-layer flexible wiring board according to the eighth aspect of the present invention is a wiring layer provided with a metal laminated body on the surface of the resin film substrate without using an adhesive, and the metal laminated body includes a base metal layer made of a nickel-containing alloy, And a copper layer provided on the surface of the underlying metal layer, wherein the metal laminated body has a range of 0.4 μm from the surface of the resin film substrate as measured by an electron backscatter diffraction method (EBSD) 111 crystal orientation of the crystalline fraction contained ₁₁₁ OR 001 with respect to the ratio of crystal orientation ratio of ₀₀₁ OR (OR ₁₁₁ / OR ₀₀₁₎ of 7 or less, (111) crystalline orientation degree of the copper layer index of 1.2 or more, and in The difference in the crystal orientation ratio [(200)/(111)] of the above copper layer obtained before and after the implementation of the folding endurance test (the folding endurance test specified in JIS C-5016-1994) is d [(200)/(111) ] is 0.03 or more.

According to a ninth aspect of the present invention, in the second aspect of the invention, the thickness of the underlying metal layer is from 3 nm to 50 nm.

According to a tenth aspect of the invention, the two-layer flexible wiring board of the eighth aspect of the invention, wherein the copper layer has a thickness of 5 μm to 12 μm.

According to a tenth aspect of the present invention, the two-layer flexible wiring board of the eighth to tenth invention, wherein the copper layer is formed of a copper thin film layer formed on the surface of the underlying metal layer and formed on the surface of the copper thin film layer. An electroplated copper layer from which the electroplated copper layer is applied The thickness range of 10% or more of the film thickness in the direction of the resin film substrate is formed by periodically performing electroplating of a reverse current in a short-time potential inversion.

According to a twelfth aspect of the invention, the two-layer flexible wiring board of the eleventh invention, wherein the base metal layer and the copper thin film layer are formed by a dry plating method.

According to a thirteenth aspect of the invention, the two-layer flexible wiring board of the eighth aspect of the invention, wherein the resin film substrate is selected from the group consisting of a polyimide film, a polyamide film, a polyester film, and a poly At least one or more resin films of a tetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a liquid crystal polymer film.

According to a fourteenth aspect of the present invention, there is provided a method for producing a two-layer flexible wiring board according to the eighth to thirteenth aspects of the present invention, wherein the method is to form a film on the surface of the resin film substrate without using an adhesive but by dry plating. Forming a copper thin film layer on the surface of the metal layer and the base metal layer, and forming a copper plating film on the surface of the copper thin film layer by a copper plating method to form a metal laminated body as a wiring, wherein dry plating is performed The ambient gas at the time of film formation is an argon-nitrogen mixed gas, and the electroplated copper layer is a thickness range of 10% or more from the surface of the electroplated copper layer in the direction of the resin film substrate to the thickness of the electroplated copper layer, and the short-time potential is periodically performed. An inverted periodic reverse current is formed by electroplating copper.

The effects of the first to seventh inventions are as follows. According to the two-layer flexible wiring board of the present invention, when the wiring for the flexible wiring board is used, the folding endurance can be remarkably improved, and an industrially remarkable effect can be obtained. The two-layer flexible wiring of the present invention is used. The substrate is a wiring device in which a metal laminate is provided on the surface of the resin film substrate without an adhesive, and the metal laminate includes a base metal layer made of a nickel-containing alloy and a copper layer on the surface of the base metal layer. In the metal laminated body measured by the electron backscatter diffraction method (EBSD), the crystal ratio of the crystal 111 in the range of 0.4 μm from the surface of the resin film substrate to the crystallization ratio OR ₁₁₁ of the orientation 001 is OR The ratio of ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less, and the (111) crystal orientation index of the copper layer is 1.2 or more, and is performed before and after the folding endurance test (the folding endurance test prescribed in JIS C-5016-1994) The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] of the obtained copper layer was 0.03 or more.

The effects of the eighth to fourteenth inventions are as follows. According to the flexible wiring board of the present invention, the folding resistance of the substrate can be remarkably improved, and an industrially remarkable effect can be achieved. The flexible wiring board of the present invention forms Ni on the surface of the resin film by vapor deposition or sputtering. a metal layer such as Cr or Cu or an alloy layer, and then a copper layer is laminated by a plating method, an electroless plating method, or a combination thereof to form a metal laminate which is a formed wiring, and is subjected to electron backscatter diffraction. The ratio of the crystal ratio OR _{111 of the} orientation of the crystal 111 contained in the range of 0.4 μm from the surface of the resin film substrate to the crystal ratio OR ₀₀₁ of the 001 orientation in the metal laminate measured by the method (EBSD) (OR) ₁₁₁ /OR ₀₀₁ ) is 7 or less, and the (111) crystal orientation index of the copper layer is 1.2 or more, and the copper layer obtained before and after the folding endurance test (the folding endurance test specified in JIS C-5016-1994) is performed. The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] is shown to be 0.03 or more.

1‧‧‧ Polyimine film (resin film substrate)

2‧‧‧Base metal layer

3‧‧‧ copper film layer

4‧‧‧Electroplated copper layer

5‧‧‧ copper layer

6‧‧‧2 layers of flexible wiring substrate

7‧‧‧Metal laminate

10‧‧‧Wind-type sputtering device

12‧‧‧ frame

13‧‧‧Rolling roll

14‧‧‧Roller

15a, 15b, 15c, 15d‧‧‧ Sputtered cathode

16a‧‧‧Advance roll

16b‧‧‧Back feed roller

17a‧‧‧Tensile roller

17b‧‧‧ tension roller

18‧‧‧ winding roller

20‧‧‧(winding type continuous electricity) plating device

21‧‧‧ plating bath

22‧‧‧Rolling roll

23‧‧‧Reverse Roller

24a~24t‧‧‧Anode

26a~26k‧‧‧Power supply roller

28‧‧‧ plating solution

28a‧‧‧liquid level of plating solution

29‧‧‧ winding roller

F‧‧‧ Polyimine film (resin film substrate)

F2‧‧‧ Polyimide film with copper film layer (resin film substrate with copper film layer)

S‧‧‧2 layer flexible wiring substrate

Fig. 1 is a schematic cross-sectional view showing a two-layer flexible wiring substrate produced by a metal plating method.

2 is a schematic view showing a wound sputter apparatus for forming a base metal layer and a copper thin film layer of a two-layer flexible wiring substrate.

3 is a winding type in which electroplating is performed in the production of a two-layer flexible wiring substrate. A schematic view of a continuous plating apparatus of the mode.

Fig. 4 is a view schematically showing time and current density of a PR current in the present invention.

Fig. 5 is a schematic cross-sectional view showing a two-layer flexible wiring board produced by the metal plating method used in the present invention.

6 is a schematic view showing a wound sputter apparatus for forming a base metal layer and a copper thin film layer on a two-layer flexible wiring board used in the two-layer flexible wiring board of the present invention.

FIG. 7 is a schematic view showing a winding type continuous plating apparatus which performs electroplating in the production of a two-layer flexible wiring board used in the two-layer flexible wiring board of the present invention.

Fig. 8 is a view schematically showing time and current density of a PR current in the present invention.

1. First embodiment (1) Two-layer flexible wiring substrate

First, the two-layer flexible wiring board of the present invention will be described.

The two-layer flexible wiring board of the present invention has a laminated structure in which a metal layer of a base metal layer and a copper layer are sequentially laminated on at least one surface of a resin film substrate such as a polyimide film. The laminate is composed of a copper thin film layer and an electroplated copper layer.

Fig. 1 is a schematic view showing a cross section of a two-layer flexible wiring board 6 produced by a metal plating method.

The resin film substrate 1 is a polyimide film, and the polyimide film 1 is used. On at least one side, a base metal layer 2, a copper thin film layer 3, and an electroplated copper layer 4 are laminated in this order from the polyimide film 1 side. The copper thin film layer 3 and the electroplated copper layer 4 constitute the copper layer 5, and the copper layer 5 and the underlying metal layer 2 are combined to form a laminated structure of the metal laminated body 7.

As the resin film substrate 1 to be used, in addition to the polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyphenylene sulfide film, or a polyethylene naphthalate film can also be used. , liquid crystal polymer film, and the like.

In particular, from the viewpoint of mechanical strength, heat resistance and electrical insulation, a polyimide film is particularly preferred.

Further, it is preferable to use the above-mentioned resin film substrate having a film thickness of 12.5 to 75 μm.

The underlying metal layer 2 is used to ensure reliability such as adhesion between a resin film substrate and a metal layer such as copper, and heat resistance. Therefore, the material of the underlying metal layer is selected from nickel, chromium, or any of these alloys. However, in consideration of the adhesion strength and the ease of etching during wiring production, a nickel-chromium alloy is preferable.

The composition of the nichrome alloy is preferably 15% by weight or more and 22% by weight or less or less, and it is preferred to improve corrosion resistance and migration resistance.

Among them, a nickel-chromium alloy having a chromium content of 20% by weight is distributed as a nickel-chromium alloy, and can be easily obtained as a sputtering target of a magnetron sputtering method. Further, chromium, vanadium, titanium, molybdenum, cobalt, or the like may be added to the nickel-containing alloy.

Further, a film of a plurality of nickel-chromium alloys having different chromium concentrations may be laminated to form a base metal layer having a concentration gradient of a nickel-chromium alloy.

The film thickness of the underlying metal layer 2 is preferably from 3 nm to 50 nm.

When the film thickness of the underlying metal layer is less than 3 nm, the adhesion between the polyimide film and the copper layer cannot be ensured, so that corrosion resistance and migration resistance are inferior. On the other hand, if the base metal When the film thickness of the layer exceeds 50 nm, it is difficult to sufficiently remove the underlying metal layer when the wiring process is performed by the removal method. When the removal of the underlying metal layer is insufficient, problems such as migration between wirings may occur.

The copper thin film layer 3 is mainly composed of copper, and the copper thin film layer preferably has a film thickness of 10 nm to 1 μm.

When the film thickness of the copper thin film layer is less than 10 nm, the conductivity at the time of forming the copper plating layer by the plating method cannot be ensured, and the appearance at the time of plating is poor. When the film thickness of the copper thin film layer exceeds 1 μm, there is no problem in the quality of the two-layer flexible wiring substrate, but there is a problem in that productivity is poor.

The base metal layer 2 and the copper thin film layer 3 are formed by a dry plating method as will be described later, and the copper layer 4 may be formed by a wet plating method.

In addition, the obtained flexible wiring board 6 must be measured from the surface of the resin film substrate 1 to a thickness of 0.4 μm of the metal laminate 7 by an electron backscatter diffraction method (EBSD). 111 crystal orientation of the obtained crystalline fraction ₁₁₁ with respect to the ratio of the crystalline OR 001 OR ₀₀₁ of the orientation ratio (OR ₁₁₁ / OR ₀₀₁₎ of 7 or less.

If the ratio of the crystal orientation ratio OR _{111 of the 111-} direction to the crystal ratio OR ₀₀₁ of the 001 orientation (OR ₁₁₁ /OR ₀₀₁ ) exceeds 7, the bottom width B, the top width T, and the height C of the cross-sectional shape of the wiring pattern. The etching factor (F _E ) obtained by the following formula (1) is less than 5, and a cross-sectional shape of an unsuitable wiring pattern is formed in the open-type narrow-pitch wiring in which the bottom width is widened and the top width is narrowed.

In other words, in order to ensure the insulation with the adjacent wiring patterns, the pitch of the wiring patterns (the distance between the centers of the wirings), it is necessary to ensure the interval between the wiring patterns and also the width of the bottom portion of the cross section of the wiring pattern, when the sectional shape of the wiring pattern When opening to the bottom, considering the width of the bottom, it is not suitable for narrow spacing.

In the flexible wiring substrate of the present invention which satisfies the azimuth ratio of the crystal, the printed wiring board having a narrow pitch of the wiring pattern can be obtained even if the wiring process is performed by the removal method.

[Number 1] F _E = 2 × C / (BT). . . (1)

The etching solution for a copper layer used for wiring processing by the removal method is not limited to an aqueous solution or a special chemical solution containing iron chloride, copper chloride, and copper sulfate which is specially prepared to cope with a narrow pitch, even if it is used in general. A commercially available etching solution containing a ferric chloride aqueous solution having a specific gravity of 1.30 to 1.45 and/or a copper chloride aqueous solution having a specific gravity of 1.30 to 1.45, and a cross-sectional shape of the wiring pattern may also have a bottom width B value and a top width. The etching factor (F _E ) obtained by the equation (1) between T and height C is 5 or more.

In addition, even if the flexible wiring substrate is etched, the crystal orientation ratio of the wiring thickness range from 0.4 μm on the surface of the resin film substrate does not change.

(2) Film forming method of base metal layer and copper thin film layer

The base metal layer and the copper thin film layer are preferably formed by dry plating.

Examples of the dry plating method include a sputtering method, an ion plating method, a cluster ion beam method, a vacuum vapor deposition method, a CVD method, etc., but in the dry plating method, from the viewpoint of composition control of the underlying metal layer and the like Preferably, the sputtering method is used.

The film formation by sputtering on the resin film substrate can be carried out by using a known sputtering apparatus, and the formation of a film on a long resin film substrate can be carried out by using a known winding method. If the roll-type sputtering device is used, it can be used in long strips. The base metal layer and the copper thin film layer are continuously formed on the surface of the imide film.

Fig. 2 is an example of a wound sputter apparatus.

The wound sputter apparatus 10 is provided with a rectangular parallelepiped casing 12 that houses most of its components.

The frame 12 may have a cylindrical shape, and its shape is not limited as long as the pressure is reduced to a range of 10 ^-4 Pa to 1 Pa.

In the casing 12, a take-up roll 13 for supplying a polyimide film F as a long-length resin film substrate, a roll roll 14, sputtering cathodes 15a, 15b, 15c, and 15d, a feed roll 16a, and a rear feed are provided. The roll 16b, the tension roll 17a, the tension roll 17b, and the winding roll 18.

The winding roller 13, the can roller 14, the feed roller 16a, and the winding roller 18 are provided with power generated by a servo motor. The winding roller 13 and the winding roller 18 are controlled by the torque of the powder clutch or the like to maintain the tension balance of the polyimide film F.

The surfaces of the tension rolls 17a and 17b are finished by plating hard chrome, and are provided with a tension sensor.

The sputter cathodes 15a-15d are arranged in a direction opposite to the can roller 14 by a magnetron cathode type. The size of the polyimide film F of the sputtering cathodes 15a to 15d in the width direction may be wider than the width of the long resin film polyimide film F.

The polyimide film F is transported in a roll-type sputtering apparatus 10 as a wound vacuum film forming apparatus, and is formed into a film by sputtering cathodes 15a to 15d opposed to the tube roll 14 Film layer of polyimide film F2.

The can roller 14 is finished by plating hard chromium on the surface thereof, and the refrigerant and/or the heating agent supplied from the outside of the casing 12 is circulated therein to be adjusted to a substantially constant temperature.

When the base metal layer and the copper thin film layer are formed by using the wound sputtering apparatus 10, a target having a composition of the underlying metal layer is mounted in the sputtering cathode 15a, and A copper target is attached to each of the sputtering cathodes 15b to 15d, and a vacuum gas is exhausted in a device in which the winding roller 13 is provided with a polyimide film, and a sputtering gas such as argon gas is introduced, and the inside of the device is maintained at 1.3. Pa or so.

As an example, it is preferable to use an argon-nitrogen mixed gas as the sputtering atmosphere gas, and the nitrogen blending is preferably 1% by volume or more and 12% by volume or less. However, it is necessary to pay attention to the fact that it is unique to the device such as the shape of the wound sputtering apparatus. The possibility of influence.

For example, it is sufficient to appropriately check the sputtering ambient gas while confirming the ratio of the crystal ratio OR ₁₁₁ of the 111-direction orientation of the obtained metal laminate to the crystallization ratio OR ₀₀₁ of the 001 orientation.

In addition, when the blend ratio of the nitrogen of the argon-nitrogen mixed gas is more than 12% by volume, when the obtained metal laminate is used for wiring such as a flexible wiring board, the heat resistance of the wiring may be lowered, which is not preferable. . Further, although an example of an ambient gas that is sputtered using an argon-nitrogen mixed gas is shown, the sputtering ambient gas is not limited to the argon-nitrogen mixed gas as long as the target crystal state can be achieved.

Moreover, the crystal alignment of the copper thin film layer is also affected by the sputtering ambient gas.

If the sputtering atmosphere is only argon, the (111) plane of the face-centered cubic lattice structure can be observed in the crystallized Wilson index of the copper film layer obtained by X-ray diffraction, but almost or completely observed. It is less than the (200) plane of the face-centered cubic lattice and the surface equivalent to the 001 orientation in the EBSD.

Here, when nitrogen gas is added to the argon gas of the sputtering ambient gas, the (200) plane of the face-centered cubic lattice and the surface corresponding to the 001 orientation of the EBSD can be observed in the copper thin film layer.

When wiring is processed using such conditions and plating conditions described later, cloth can be realized. A flexible wiring substrate having a small difference between the widths of the top and the bottom of the wire.

(3) Electroplated copper layer and film forming method thereof

The electroplated copper layer is formed by electroplating. The thickness of the electroplated copper layer is preferably from 1 μm to 20 μm.

Here, the plating method used is electroplating using an insoluble anode in a plating bath of copper sulfate. Further, the composition of the copper plating bath to be used may be a high-throw copper sulfate plating bath used for through-hole plating or the like of a commonly used flexible wiring board.

3 is an example of a wound continuous plating apparatus (hereinafter referred to as a plating apparatus 20) that can be used to manufacture the two-layer flexible wiring board of the present invention.

The polyimide film F2 of the copper-film-coated layer obtained by forming the base metal layer and the copper thin film layer is wound up from the take-up roll 22, and is continuously immersed in the plating solution 28 in the plating tank 21, while continuing Ground transportation. In addition, 28a means the liquid level of the plating solution.

The polyimide film F2 with a copper film layer is formed by forming a copper layer on the surface of the metal film by electroplating while being immersed in the plating solution 28, and forming a copper layer having a predetermined film thickness to form a metallized resin. The two layers of the flexible wiring board S of the film substrate are wound around the winding roller 29. Further, the transport speed of the polyimide film F2 with a copper film layer is preferably in the range of several m to several tens of m/min.

Specifically, the polyimide film F2 with a copper film layer is wound up from the take-up roll 22, and the plating liquid 28 immersed in the plating tank 21 via the power supply roller 26a. The polyimide film F2 which has entered the copper film layer in the plating tank 21 is reversed in the conveyance direction via the reverse roller 23, and is pulled out to the outside of the plating tank 21 by the power supply roller 26b.

Thus, the polyimide film F2 with a copper film layer is repeatedly immersed in the plating solution (20 times in FIG. 3), and the polyimide film F2 in the copper film layer is repeatedly applied. A copper layer is formed on the metal film.

A power source (not shown) is connected between the power supply roller 26a and the anode 24a.

A plating circuit is formed by the power supply roller 26a, the anode 24a, the plating solution, and the polyimide film F2 with a copper film layer and the above-mentioned power source. Further, the insoluble anode does not require a special anode, and may be a known anode in which the surface of the insoluble anode is coated with a conductive ceramic. Further, a mechanism for supplying copper ions to the plating solution 28 is provided outside the plating tank 21.

The supply of copper ions to the plating solution 28 is carried out by using a copper oxide aqueous solution, a copper hydroxide aqueous solution, a copper carbonate aqueous solution or the like. Alternatively, a method of supplying a small amount of iron ions to the plating solution and dissolving the oxygen-free copper balls to supply copper ions. The copper supply method can use any of the above methods.

The current density at the time of plating, as it enters the downstream direction from the anode 24a, the current density rises stepwise, and the maximum current density is reached from the anodes 24o to 24t.

By increasing the current density in this manner, discoloration of the copper layer can be prevented. In particular, when the thickness of the copper layer is thin, the copper layer is likely to be discolored when the current density is high. Therefore, the current density in the plating is preferably 0.1 A in addition to the reverse current of the PR current to be described later. /dm ² ~8A/dm ² . When the current density is high, the appearance of the electroplated copper layer is poor.

In order to manufacture the two-layer flexible wiring board of the present invention, a PR current is formed from the surface of the thickness of the plated copper layer in a range of 10% or more.

When the PR current is used, the reverse current can be added to the current of 1 to 9 times the forward current.

As the reverse current time ratio, it is preferably about 1 to 10%.

Further, the period in which the PR current flows through the next reverse current is preferably 10 msec or more, more preferably 20 msec to 300 msec.

Figure 4 shows schematically the time and current density of the PR current.

Further, the plating voltage may be appropriately adjusted so that the current density described above can be achieved.

When the two-layer flexible wiring board of the present invention is produced by the winding type continuous plating apparatus, the number of anodes flowing through the PR current is sufficient as long as the PR current flows through one or more anodes from the downstream side of the transport path. It is determined by how the ratio of the range of the film formed by the PR current from the surface of the electroplated copper layer toward the polyimide film side is determined. That is, the PR current flows at least at the anode 24t, and the PR current flows through the anode 24s, the anode 24r, and the anode 24q as necessary.

Further, the PR current may flow through all the anodes, but since the price of the rectifier for the PR current is high, the manufacturing cost increases. Therefore, in the two-layer flexible wiring substrate of the present invention, when a PR current is formed from the surface of the electroplated copper layer in the direction of the polyimide phase by 10% of the film thickness, the folding resistance test (JIS) is performed. C-5016-1994) The difference d [(200)/(111)] of the crystal orientation ratio [(200)/(111)] of the copper layer before and after the implementation is 0.03 or more, and therefore, it is expected that the folding endurance can be improved. Test (MIT test).

The reason why the copper plating of the PR current is preferably used is that if the current is reversed, the copper crystal grain size of the electroplated copper layer can be set to about 200 nm or more, and the grain boundary can be reduced, so that the crack origin at the grain boundary can be reduced. .

In the case of the general plating method, the copper deposited by the plating is affected by the surface of the copper-plated substrate. However, if the PR current is formed from the surface of the electroplated copper layer by 10% or more of the film thickness, the grain boundary can be controlled. The effect of the folding resistance of the electroplated copper layer can be obtained. Therefore, the two-layer flexible wiring board has a film thickness of 10% or more from the surface of the electroplated copper layer, and when it is a crystal which conforms to the folding endurance, the effect of the folding resistance of the electroplated copper layer can be obtained. The problem to be solved by the present invention.

(4) Characteristics of electroplated copper layer

The copper layer of the flexible wiring substrate of the present invention is characterized by a (111) crystal orientation index of copper of 1.2 or more. In this state, in the MIT folding test (JIS C-5016-1994), the crystal was easily slid. Further, in the copper layer of the flexible wiring substrate of the present invention, in addition to the (111) alignment, (200), (220), and (311) alignment are also included, but (111) alignment is dominant. The crystal orientation index is shown to be 1.20 or more.

Further, a crystal state in which the difference in crystal alignment ratio [(200)/(111)] before and after the MIT folding endurance test (JIS C-5016-1994) was 0.03 or more was achieved. In this state, by performing the MIT folding test, it was confirmed that the crystal slipped and caused recrystallization.

The glossiness of the surface is preferably a gloss film in order to prevent the surface unevenness from becoming a notch.

In addition, the larger the average crystal grain size, the better, but it is necessary to pay attention to the etching of the copper layer when the copper-clad laminate substrate is subjected to wiring processing on the flexible wiring substrate by the removal method.

When the aqueous solution of ferric chloride is used for etching the copper layer by the removal method, the crystal grain size of the copper layer may not be affected. However, when the grain boundary of the crystal grains of the copper layer is etched, the crystal grain size affects the shape of the wiring. The average crystal grain size is preferably about 200 nm to 400 nm. The reason is that when it is 200 nm or less, there are many grain boundaries, and it is easy to cause a crack which is a fracture origin, and it is set to 400 nm or less in order to maintain the smoothness of a metal surface. Further, the surface roughness Ra is preferably 0.2 μm or less in order not to cause cracks which are the starting points of the fracture.

In other words, the copper plating layer of the flexible wiring substrate of the present invention is obtained by the film formation method described above, and the (111) crystal orientation index is 1.2 or more, and the crystal orientation ratio before and after the MIT folding test is [(200)/ The difference between (111)] is 0.03 or more. In addition, the crystallographic alignment of the electroplated copper layer can be known from the Wilson symmetry index of the X-ray diffraction.

Further, the copper crystal of the electroplated copper layer obtained by the above method has a dynamic recrystallization effect at room temperature during the meandering. The average crystal grain size after the folding endurance test tends to be about 100 nm to 200 nm due to recrystallization.

It is considered that the film formation by electroplating copper does not cause dynamic recrystallization at normal temperature. However, in the flexible wiring board of the present invention, the electroplated copper layer causes dynamic recrystallization at normal temperature, and as a result, it is difficult to break the sample when performing a zigzag test such as the MIT test. The average crystal grain size and dynamic recrystallization at normal temperature can be observed by cross-sectional SIM image.

The crystal orientation of the electroplated copper layer formed by the electroplating method is affected by the crystal orientation of the copper thin film layer, but the electroplated copper layer and the copper thin film layer have different crystal orientations. For example, even if the (200) plane is not observed in the crystal orientation of the copper thin film layer and the surface corresponding to the 001 orientation in the EBSD, the (111) plane can be observed in the crystal orientation of the electroplated copper layer.

Still another feature of the flexible wiring board of the present invention is a crystal orientation of a copper thin film layer of a resin film with a copper thin film layer and an electroplated copper layer provided on the copper thin film layer by electroplating copper, and a resin thin film. The film thickness range of the substrate surface of 0.4 μm is different by the electron backscatter diffraction method (EBSD); and the film thickness range of the copper plating layer from the surface of the resin film substrate to 0.4 μm is borrowed. The relationship between the bottom width B of the sectional shape of the wiring and the width T of the top portion is changed by the difference in the azimuth ratio of the crystal measured by the electron backscatter diffraction method (EBSD).

In other words, the metal laminate of the flexible wiring substrate of the present invention has a crystal thickness range of 0.4 μm from the surface of the resin film substrate, and crystal orientation of the crystal 111 is measured by an electron backscatter diffraction method (EBSD). The ratio of the ratio OR ₁₁₁ to the crystal ratio of the 001 orientation OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less.

In addition, when such a metal laminate is used as a wiring, if the wiring is processed by the removal method, the cross-sectional shape can be obtained from the bottom width B, the top width T, and the copper film thickness C by the following formula (2). The effect of the obtained etching factor (F _E ).

[Number 2] F _E = 2 × C / (BT). . . (2)

That is, when the etching factor (F _E ) is 5 or more, the effect that the bottom width B value and the top width T are close values is shown.

Further, in order to measure the crystal orientation of the metal laminate, a known electron backscatter diffraction method (EBSD) can be used.

In the flexible wiring board of the present invention, it is possible to confirm the orientation of the crystal 111 measured by the electron backscatter diffraction method (EBSD) from the surface of the resin film substrate to a thickness of 0.4 μm. The ratio of the crystal ratio OR ₁₁₁ to the crystal ratio of the 001 orientation OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less.

In addition, the metal laminate includes the underlying metal layer, but since the thickness of the underlying metal layer is extremely thin to 3 to 50 nm, there is almost no influence on the measurement result of the crystal orientation obtained by the electron backscatter diffraction method (EBSD). The measurement result can be obtained substantially in accordance with the crystal state in the copper layer of the copper thin film layer and the electroplated copper layer.

The metal layered body having a film thickness range of 0.4 μm from the surface of the resin film substrate, which is one of the characteristics of the flexible wiring substrate of the present invention, is obtained by electron backscatter diffraction (EBSD). An example of a method in which the ratio of the crystal orientation ratio OR ₁₁₁ of the 111 orientation to the crystal ratio of the 001 orientation OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less is as follows, and the base metal layer and the copper thin film layer are sputter-deposited. The ambient gas uses an argon-nitrogen mixed gas containing a ratio of nitrogen of 1% by volume to 12% by volume, and the current density is set to 1 A/dm in the range of the electroplated copper layer from the surface of the copper thin film layer to the film thickness of 1 μm to 2.5 μm. ² film formation method.

As a result of the MIT folding endurance test of the flexible wiring board, the wiring width was deteriorated as a result of deterioration.

In the folding endurance test according to JIS C-5016-1994, the wiring width is 1 mm, but for the flexible wiring board used for the curved wiring in the liquid crystal display, the wiring width is 50 μm or less, and further converted into high definition. The wiring width is 25 μm or less. Even in a flexible wiring board which is processed into a flexible wiring board having a wiring width of 1 mm and which can achieve sufficient folding resistance, if the wiring width is 50 μm or less, sufficient folding resistance may not be achieved.

Of course, in the flexible wiring board having a wiring width of 1 mm and the flexible wiring substrate having insufficient folding resistance, even if the wiring width is 50 μm or less, insufficient folding resistance is obtained as a result.

Therefore, when the relationship between the cross-sectional shape of the wiring and the folding endurance is evaluated by the flexible wiring board having a wiring width of 50 μm or less, the etching factor (F _E ) which is close to the top width T of the wiring is more than 5 It can be observed that its folding endurance is improved.

2. Second embodiment (1) Two-layer flexible wiring substrate

First, a two-layer flexible wiring board used in the two-layer flexible wiring board of the present invention will be described.

The two-layer flexible wiring board has a laminated structure in which a base metal layer and a copper layer are sequentially laminated on at least one surface of a resin film substrate such as a polyimide film, without using an adhesive, and the copper layer is sequentially laminated. It consists of a copper film layer and an electroplated copper layer.

5 is a schematic cross-sectional view showing a two-layer flexible wiring board 6 produced by a metal plating method, and is also a cross section of a wiring portion of the two-layer flexible wiring board of the present invention. Figure.

The resin film substrate 1 is made of a polyimide film, and at least one surface of the polyimide film 1 is formed by laminating the base metal layer 2, the copper film layer 3, and the copper plating from the polyimide film 1 side. Layer 4. Further, the copper thin film layer 3 and the electroplated copper layer 4 constitute a copper layer 5, and the copper layer 5 and the underlying metal layer 2 are contained to form a metal laminate 7.

As the resin film substrate 1 to be used, in addition to the polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, or the like may be used. Liquid crystal polymer film and the like.

In particular, from the viewpoint of mechanical strength, heat resistance and electrical insulation, a particularly preferred polyimide film.

Further, the above-mentioned resin film substrate having a film thickness of 12.5 to 75 μm can be preferably used.

The base metal layer 2 is a metal layer that ensures reliability such as adhesion between the resin film substrate and a metal layer such as copper and heat resistance. Therefore, the material of the underlying metal layer is selected from any one selected from the group consisting of nickel, chromium, and the like. However, in consideration of the adhesion strength and the easiness of etching during wiring production, a nickel-chromium alloy is preferable.

The composition of the nichrome alloy is preferably 15% by weight or more and 22% by weight or less, and it is desired to improve corrosion resistance and migration resistance.

Among them, a nickel-chromium alloy having a chromium content of 20% by weight is distributed as a nickel-chromium alloy, and can be easily obtained as a sputtering target of a magnetron sputtering method. Further, chromium, vanadium, titanium, molybdenum, cobalt, or the like may be added to the nickel-containing alloy.

Further, a film of a plurality of nickel-chromium alloys having different chromium concentrations may be laminated to form a base metal layer having a concentration gradient of a nickel-chromium alloy.

The film thickness of the underlying metal layer 2 is preferably from 3 nm to 50 nm.

When the film thickness of the underlying metal layer is less than 3 nm, the adhesion between the polyimide film and the copper layer cannot be ensured, and the corrosion resistance and migration resistance are inferior. On the other hand, when the film thickness of the underlying metal layer exceeds 50 nm, it is difficult to sufficiently remove the underlying metal layer when the wiring process is performed by the removal method. When the removal of the underlying metal layer is insufficient, problems such as migration between wirings may occur.

The copper thin film layer 3 is mainly composed of copper, and the copper thin film layer preferably has a film thickness of 10 nm to 1 μm.

When the film thickness of the copper thin film layer is less than 10 nm, the conductivity at the time of forming a copper plating layer by electroplating on the copper thin film layer cannot be ensured, resulting in poor appearance at the time of plating. When the film thickness of the copper thin film layer exceeds 1 μm, there is no problem in the quality of the two-layer flexible wiring substrate, but there is a problem in that productivity is poor.

The base metal layer 2 and the copper thin film layer 3 are formed by dry plating as will be described later, and the copper layer 4 may be formed by wet plating.

In addition, the obtained flexible wiring board 6 must be measured from the surface of the resin film substrate 1 to a thickness of 0.4 μm of the metal laminated body 7 by an electron backscatter diffraction method (EBSD). 111 crystal orientation of ₁₁₁ relative to the crystalline fraction than the crystalline OR 001 OR ₀₀₁ of the orientation ratio (OR ₁₁₁ / OR ₀₀₁₎ of 7 or less.

When the crystal orientation of the crystalline fraction 111 ₁₁₁ OR 001 crystal orientation with respect to the ratio of the proportion of OR ₀₀₁ (OR ₁₁₁ / OR ₀₀₁₎ more than 7, the width B of the cross-sectional shape by the bottom wiring pattern top width and height T C, When the etching factor (F _E ) obtained by the following formula (3) is less than 5, the slit-shaped narrow-pitch wiring having a wide bottom width and a narrow top width is formed into a cross-sectional shape of an unsuitable wiring pattern.

In other words, in order to ensure the insulation from adjacent wiring patterns, the pitch between the wiring patterns (the distance between the centers of the wirings) must be ensured. The width of the bottom portion of the cross section of the wiring pattern must be considered. When the cross-sectional shape of the wiring pattern is opened toward the bottom, the width of the bottom is taken into consideration, and the narrow pitch is not suitable.

By wiring the flexible wiring substrate which satisfies the azimuth ratio of the crystal by the removal method, a flexible wiring board having a narrow pitch of the wiring pattern can be obtained.

In addition, even if the etching process is performed as a resin film substrate having a metal laminate, the orientation ratio of the crystal in the film thickness range from 0.4 μm on the surface of the resin film substrate does not change.

[Number 3] F _E = 2 × C / (BT). . . (3)

(2) Film forming method of base metal layer and copper thin film layer

The base metal layer and the copper thin film layer are preferably formed by dry plating.

Examples of the dry plating method include a sputtering method, an ion plating method, a cluster ion beam method, a vacuum vapor deposition method, a CVD method, and the like. However, in the dry plating method, composition control from a seed layer or the like is performed. From the viewpoint of consideration, sputtering is preferred.

In order to form a film by sputtering on a resin film substrate, it is possible to form a film by using a known sputtering apparatus, and it is possible to form a film on a long resin film substrate by using a known roll type sputtering apparatus. When the wound sputter apparatus is used, the underlying metal layer and the copper thin film layer can be continuously formed on the surface of the elongated polyimide film.

Fig. 6 is an example of a wound sputtering apparatus.

The wound sputter apparatus 10 is provided with a rectangular parallelepiped frame 12 that accommodates most of its components.

The frame 12 may have a cylindrical shape, and its shape is not limited as long as the pressure is reduced to a range of 10 ^-4 Pa to 1 Pa.

In the casing 12, a take-up roll 13 for supplying a polyimide film F as a long-length resin film substrate, a roll roll 14, sputtering cathodes 15a, 15b, 15c, and 15d, a feed roll 16a, and a rear feed are provided. The roll 16b, the tension roll 17a, the tension roll 17b, and the winding roll 18.

The winding roller 13, the can roller 14, the feed roller 16a, and the winding roller 18 are provided with power generated by a servo motor. The winding roller 13 and the winding roller 18 perform torque control by a powder clutch or the like to maintain the tension balance of the polyimide film F.

The tension rolls 17a and 17b are finished by surface-plating hard chrome, and are provided with a tension sensor.

The sputter cathodes 15a-15d are arranged in a direction opposite to the can roller 14 by a magnetron cathode type. The size of the polyimide film F of the sputtering cathodes 15a to 15d in the width direction may be larger than the width of the elongated resin film polyimide film F.

The polyimide film F is transported in a roll-type sputtering apparatus 10 as a wound vacuum film forming apparatus, and is formed into a film by sputtering cathodes 15a to 15d opposed to the roll 14 Film layer of polyimide film F2.

The can roller 14 is finished by finishing hard chromium plating, and the refrigerant and/or the heating agent supplied from the outside of the casing 12 to the inside thereof are adjusted to a substantially constant temperature.

When the underlying metal layer and the copper thin film layer are formed by using the wound sputtering apparatus 10, a target having a composition of a base metal layer is mounted in the sputtering cathode 15a, and a copper target is respectively mounted on the sputtering cathodes 15b to 15d. After the vacuum is exhausted in the apparatus in which the take-up roll 13 is provided with a polyimide film, a sputtering gas such as argon gas is introduced, and the inside of the apparatus is maintained at about 1.3 Pa.

Alternatively, the copper thin film layer may be formed by a vapor deposition method after the underlying metal layer is formed by sputtering.

The sputtering atmosphere gas when the base metal and the copper are sputtered on the resin film substrate is preferably an argon-nitrogen mixed gas, and the nitrogen blending ratio is 1% by volume or more and 12% by volume or less, but it is necessary to pay attention to the determination. The possibility of intrinsic influence of the device such as the shape of the wound sputter device.

For example, as long as the ratio of the crystal ratio OR _{111 of the} orientation of the metallized resin film crystal 111 obtained on the resin film substrate to the final plating is determined with respect to the crystal ratio OR ₀₀₁ of the 001 orientation, the sputtering atmosphere is appropriately examined. Just fine.

In addition, when the blend ratio of nitrogen of the argon-nitrogen mixed gas is more than 12% by volume, when the obtained metal laminate is used for wiring such as a flexible wiring board, the heat resistance of the wiring may be lowered, which is not preferable. . Further, although an example of an ambient gas which is sputtered with an argon-nitrogen mixed gas is shown, the sputtering ambient gas is not limited to the argon-nitrogen mixed gas as long as the target crystal state can be achieved.

Further, the crystal alignment of the copper thin film layer is also affected by the sputtering atmosphere.

If the sputtering ambient gas is only argon, the (111) plane of the face-centered cubic lattice structure can be observed in the Wilson orientation index of the crystal obtained by X-ray diffraction of the copper thin film layer, but almost or completely The (200) plane of the face-centered cubic lattice and the face corresponding to the 001 orientation in the EBSD were not observed.

Here, when nitrogen gas is added to the argon gas of the sputtering ambient gas, the (200) plane of the face-centered cubic lattice and the surface corresponding to the 001 orientation of the EBSD can be observed in the copper thin film layer.

With such conditions and plating conditions to be described later, a flexible wiring board having a small difference in width between the top and the bottom of the wiring can be realized.

(3) Electroplated copper layer and film forming method thereof

The electroplated copper layer is formed by electroplating. The thickness of the electroplated copper layer is preferably from 1 μm to 20 μm.

Here, the plating method used is electroplating using an insoluble anode in a plating bath of copper sulfate. Further, the composition of the copper plating bath to be used may be a highly uniform copper sulfate plating bath used for through-hole plating or the like of a commonly used flexible wiring board.

FIG. 7 is an example of a wound continuous plating apparatus (hereinafter referred to as a plating apparatus 20) that can be used to manufacture a two-layer flexible wiring board used in the wiring board of the present invention.

The polyimide film F2 of the copper-clad film layer obtained by forming the base metal layer and the copper thin film layer is wound up from the take-up roll 22, and is continuously immersed in the plating solution 28 in the plating tank 21, while continuing Ground transportation. In addition, 28a means the liquid level of the plating solution.

The polyimide film F2 with a copper film layer is formed by forming a copper layer film on the surface of the metal film by plating, and forming a copper layer having a predetermined film thickness, thereby forming a metallized resin. The two layers of the flexible wiring substrate S of the film substrate are wound around the winding roller 29. Further, the transport speed of the polyimide film F2 with a copper film layer is preferably in the range of several m to several tens of m/min.

Specifically, the polyimide film F2 with a copper film layer is taken up from the take-up roll 22, and the plating liquid 28 in the plating tank 21 is immersed via the power supply roller 26a. The polyimide film F2 which has entered the copper film layer in the plating tank 21 is reversed in the conveyance direction via the reverse roller 23, and is pulled out to the outside of the plating tank 21 by the power supply roller 26b.

Thus, during the impregnation of the plating solution (20 times in FIG. 7) of the polyimine film F2 having the copper film layer repeatedly, the metal film of the polyimide film F2 with the copper film layer is applied. A copper layer is formed.

A power source (not shown) is connected between the power supply roller 26a and the anode 24a.

A plating circuit is formed by the power supply roller 26a, the anode 24a, the plating solution, and the polyimide film F2 with a copper film layer and the above-mentioned power source. Further, the insoluble anode does not require a special anode, and may be a known anode coated with a conductive ceramic. Further, a mechanism for supplying copper ions to the plating solution 28 is provided outside the plating tank 21.

The supply of copper ions to the plating solution 28 is carried out by using a copper oxide aqueous solution, a copper hydroxide aqueous solution, a copper carbonate aqueous solution or the like. Alternatively, a method of supplying a small amount of iron ions to the plating solution and dissolving the oxygen-free copper balls to supply copper ions. The copper supply method can use any of the above methods.

The current density in the plating, as it goes downstream from the anode 24a into the transport direction, the current density rises stepwise, reaching a maximum current density from the anode 24o to 24t.

By increasing the current density in this manner, discoloration of the copper layer can be prevented. In particular, when the thickness of the copper layer is thin, the copper layer is likely to be discolored when the current density is high. Therefore, the current density in the plating is preferably 0.1 A in addition to the reverse current of the PR current to be described later. /dm ² ~8A/dm ² . When the current density is high, the appearance of the electroplated copper layer is poor.

In order to manufacture the two-layer flexible wiring board of the present invention, a PR current is formed from a surface of a film thickness of the electroplated copper layer in a range of 10% or more.

When the PR current is used, the reverse current can be added to the current of 1 to 9 times the forward current.

As the reverse current time ratio, it is preferably about 1 to 10%.

Further, the period in which the PR current flows through the next reverse current is preferably 10 msec or more, more preferably 20 msec to 300 msec.

Fig. 8 schematically shows the time and current density of the PR current.

Further, the plating voltage can be appropriately adjusted to achieve the above current density.

When the two-layer flexible wiring board used in the present invention is produced by the winding type continuous plating apparatus, the PR current flows through one or more anodes from the downstream side of the transport path, and the PR current flows. The number of anodes is determined by how the ratio of the surface of the electroplated copper layer is formed by the PR current on the side of the polyimide film side. That is, the PR current flows at least at the anode 24t, and the PR current flows through the anode 24s, the anode 24r, and the anode 24q as necessary.

Further, the PR current may flow through all the anodes, but since the price of the rectifier for the PR current is high, the manufacturing cost increases. Therefore, in the two-layer flexible wiring substrate of the present invention, when a PR current is formed from the surface of the electroplated copper layer in the direction of the polyimide phase by 10% of the film thickness, the folding resistance test (JIS) is performed. C-5016-1994) The difference d [(200)/(111)] of the crystal orientation ratio [(200)/(111)] of the copper layer before and after the implementation is 0.03 or more, and therefore, the result is expected to improve the folding endurance test. (MIT test).

The reason why the copper plating of the PR current is preferably used is that if the current is reversed, the copper crystal grain size of the electroplated copper layer can be set to about 200 nm or more, and the grain boundary can be reduced, so that the crack origin at the grain boundary can be reduced. .

In the case of the general plating method, the copper deposited by the plating is affected by the surface of the copper-plated substrate. However, if the PR current is formed from the surface of the electroplated copper layer by 10% or more of the film thickness, the grain boundary can be controlled. The effect of the folding resistance of the electroplated copper layer can be obtained. Therefore, when the two-layer flexible wiring substrate is a crystal having a folding resistance from 10% or more of the thickness of the surface of the electroplated copper layer, the folding resistance to the electroplated copper layer can be obtained, and the cost can be obtained. The problem to be solved by the invention.

(4) Characteristics of electroplated copper layer

The copper layer of the two-layer flexible wiring board of the present invention is characterized by copper of 1.2 or more. (111) crystal orientation index. In this state, in the MIT folding test (JIS C-5016-1994), the crystal was apt to slide. Further, in the copper layer of the flexible wiring substrate of the present invention, in addition to the (111) alignment, (200), (220), and (311) alignment are also included, but (111) alignment is dominant. The crystal orientation index is shown to be 1.20 or more.

Further, a crystal state in which the difference in crystal alignment ratio [(200)/(111)] before and after the MIT folding endurance test (JIS C-5016-1994) was 0.03 or more was achieved. In this state, by performing the MIT folding test, it was confirmed that the crystal slipped and caused recrystallization.

The glossiness of the surface is preferably a gloss film in order to prevent the surface unevenness from becoming a notch.

In addition, the larger the average crystal grain size, the better, but it is necessary to pay attention to the etching of the copper layer when the copper-clad laminate substrate is subjected to wiring processing on the flexible wiring substrate by the removal method.

When the aqueous solution of ferric chloride is used for etching the copper layer by the removal method, the crystal grain size of the copper layer may not be affected. However, when the grain boundary of the crystal grains of the copper layer is etched, the crystal grain size affects the shape of the wiring. The average crystal grain size is preferably about 200 nm to 400 nm. The reason is that when it is 200 nm or less, there are many grain boundaries, and it is easy to cause a crack which is a fracture origin, and it is set to 400 nm or less in order to maintain the smoothness of a metal surface. Further, the surface roughness Ra is preferably 0.2 μm or less in order not to cause cracks which are the starting points of the fracture.

That is, the copper layer of the flexible wiring board of the present invention is a copper layer having the following characteristics: obtained by the film formation method of the above copper layer, and the (111) crystal orientation index is 1.2 or more, and before and after the MIT folding test The difference in crystal orientation ratio [(200)/(111)] is 0.03 or more. In addition, the crystallographic alignment of the electroplated copper layer can be known from the Wilson symmetry index of the X-ray diffraction.

Further, the copper crystal of the copper layer obtained by the above method has a dynamic recrystallization effect at room temperature during the meandering. The average crystal grain size after the folding endurance test tends to be about 100 nm to 200 nm due to recrystallization.

It is generally believed that the film produced by electroplating copper does not undergo dynamic recrystallization at normal temperature. However, in the flexible wiring board of the present invention, dynamic recrystallization is caused at normal temperature, and as a result, it is difficult to break the sample when performing a tortuous test like the MIT test. The average crystal grain size of the copper layer and dynamic recrystallization at normal temperature can be observed by a cross-sectional SIM image.

Further, the flexible wiring board of the present invention is characterized in that the crystal orientation of the copper thin film layer of the metal thin film-attached resin film and the plating of the metal thin film of the metal thin film are from 0.4 μm from the surface of the resin thin film substrate. The film thickness range is different by the electron backscatter diffraction method (EBSD); and the film thickness range from the surface of the resin film substrate to 0.4 μm after plating copper, by electron backscattering The relationship between the bottom width B of the cross-sectional shape of the wiring and the top width T changes depending on the orientation ratio of the crystal measured by the EBSD method.

The metal laminate of the flexible wiring board of the present invention has a crystal thickness range of a crystal 111 orientation measured by an electron backscatter diffraction method (EBSD) from a surface of the resin film substrate to a film thickness range of 0.4 μm. _The ratio of the crystal ratio OR ₀₀₁ of _{111 to 001} (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less.

Further, when such a metal laminate is used as a wiring, if the wiring is processed by the removal method, the cross-sectional shape can be obtained from the bottom width B, the top width T, and the copper film thickness C by the following formula (4). The effect of the obtained etching factor (F _E ).

[Number 4] F _E = 2 × C / (BT). . . (4)

That is, when the etching factor (F _E ) is 5 or more, the effect that the bottom width B value and the top width T are close to each other is obtained.

Further, in order to measure the crystal orientation of the metal laminate, a known electron backscatter diffraction method (EBSD) can be used.

In the flexible wiring board of the present invention, it is confirmed that the crystal 111 orientation crystal measured by the electron backscatter diffraction method (EBSD) in the metal laminate having a film thickness range from 0.4 μm on the surface of the resin film substrate The ratio of the ratio OR ₁₁₁ to the crystal ratio of the 001 orientation OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less.

Further, as one of the features of the flexible wiring board of the present invention, a metal laminate having a film thickness range of 0.4 μm from the surface of the resin film substrate is obtained by electron backscatter diffraction (EBSD). An example of a method in which the ratio of the crystal orientation ratio OR ₁₁₁ of the 111-direction to the crystal ratio of the 001 orientation OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less is as follows, when the substrate for the two-layer flexible wiring is produced, the substrate is used. An atmosphere of a metal layer and a copper thin film layer is formed by sputtering, and an argon-nitrogen mixed gas containing nitrogen in a ratio of 1% by volume to 12% by volume is used, and the surface of the copper plating layer is from the surface of the copper thin film layer to a film thickness of 1 μm. A film formation method in which the current density is set to 1 A/dm ² in the range of 2.5 μm.

As a result of the MIT folding endurance test of the flexible wiring board, the result of the wiring width change was deteriorated.

In the folding endurance test according to "JIS C-5016-1994", the wiring width is 1 mm, but for the flexible wiring board used for the curved wiring in the liquid crystal display, the wiring width is 50 μm or less, and further converted into High-definition wiring width of 25μm or less. Even in a flexible wiring board having a wiring width of 1 mm for testing, and a flexible wiring board capable of achieving sufficient folding resistance, if the wiring width is 50 μm or less, sufficient resistance may not be achieved. Folding.

Of course, in the flexible wiring board having a wiring width of 1 mm and the folding resistance is insufficient, even if the wiring width is 50 μm or less, insufficient folding resistance is obtained as a result.

Therefore, when the relationship between the cross-sectional shape of the wiring and the folding endurance is evaluated by the flexible wiring board having a wiring width of 50 μm or less, the etching factor (F _E ) which is close to the top width T of the wiring is more than 5 It can be observed that the folding resistance is improved.

The two-layer flexible wiring board of the present invention is produced by wiring a two-layer flexible wiring board by a removal method.

The etching liquid used for etching processing such as wiring plating of an electroplated copper layer is not limited to an aqueous solution or a special chemical solution containing a specific ratio of ferric chloride, copper chloride, and copper sulfate, and ferric chloride generally having a specific gravity of 1.30 to 1.45 may be used. A commercially available etching solution of an aqueous solution and/or a copper chloride aqueous solution having a specific gravity of 1.30 to 1.45.

On the wiring surface, tin plating, nickel plating, gold plating, or the like is applied to a desired portion by a known plating method as needed, and the surface is covered with a known solder resist or the like. Next, electronic components such as semiconductor elements are mounted to form an electronic device. Further, in the two-layer flexible wiring board of the present invention, the characteristic crystal structure does not change during the process such as tin plating or the coating with the solder resist.

[First Embodiment]

Hereinafter, the two-layer flexible wiring board of the present invention will be described in more detail using the first embodiment.

Using the wound sputter apparatus 10 as shown in Fig. 2, a polyimide film F2 with a copper film layer was produced as follows.

First, the nickel-20 weight for forming the underlying metal layer 2 is mounted on the sputter cathode 15a. A % chromium alloy target was used to mount a copper target on the sputter cathodes 15b to 15d.

Next, as a resin film substrate F, a polyethyleneimine film (registered trademark Kapton, manufactured by Toray-DuPont Co., Ltd.) having a thickness of 38 μm was used, and the inside of the apparatus provided with the film was evacuated, and then a sputtering gas was introduced to cause a device. The polyimine film F2 having a copper film layer was produced while maintaining the inside at 1.3 Pa. The thickness of the underlying metal layer (nickel-chromium alloy) 2 was 20 nm, and the thickness of the copper thin film layer 3 was 200 nm.

The obtained copper film layer-attached polyimide film F2 was subjected to electroplating of copper to form a copper plating layer 4 by using a plating apparatus 20 as shown in FIG. The plating solution 28 is a copper sulfate aqueous solution having a pH of 1 or less, and the anode 24o to 24t is set to have a maximum current density (in addition to the reverse current of the PR current) unless otherwise specified, and the current density is adjusted to finally cause the copper plating layer 4 to be plated. The film thickness was 8.5 μm.

In the folding endurance test, the test liquid of "JIS C-5016-1994" was formed by using the ferric chloride in the etching solution, and was evaluated according to the same standard; the test piece was a test piece having a wiring width of 50 μm (hereinafter, The test piece (50 μm) and the test piece having a wiring width of 20 μm (hereinafter referred to as a test piece of 20 μm) were evaluated in accordance with "JIS C-5016-1994".

The crystal orientation of the electroplated copper layer before and after the folding endurance test was measured by X-ray diffraction using a Wilson orientation index.

For the metal laminate, the orientation and orientation ratio of the copper crystal was measured by the EBSD method. The measurement results were classified into a range from the surface side of the resin film substrate to a film thickness of 0.4 μm and a range in which the film thickness exceeded 0.4 μm.

The measurement conditions of the electron backscatter diffraction method (EBSD) used in the first embodiment are as follows.

[Measurement conditions of electron backscatter diffraction method (EBSD)]

The diffraction apparatus was measured using an Oxford Accumulator (HKL Channel 5) under the conditions of an acceleration voltage of 15 kV and a measurement procedure of 0.05 μm. Further, the ratio of the (111) plane alignment of crystal grains is a crystal grain which is aligned in the range of ±15° in the normal direction of the (111) plane by the area occupancy ratio in the measurement range.

The etching liquid used in the wiring process by the removal method was an aqueous solution of ferric chloride (specific gravity: 1.35, temperature: 45 ° C).

[Embodiment 1 in the first embodiment]

The sputtering gas (sputtering atmosphere) was set to a mixed gas of argon and 5 vol% nitrogen of 1.3 Pa.

The current density of the anodes 24a to 24f formed in the copper layer from the surface of the copper thin film layer to the film thickness of 1.5 μm is 1 A/dm ² or less, and as a result, the metal laminated body is 0.4 μm from the surface of the resin film substrate. The film thickness range, the ratio of the crystal ratio OR ₁₁₁ of the crystal 111 orientation measured by the electron backscatter diffraction method (EBSD) to the crystal ratio OR ₀₀₁ of the 001 orientation (OR ₁₁₁ /OR ₀₀₁ ) was 0.7.

The two-layer flexible wiring substrate of Example 1 was produced by plating with a PR current from the surface of the plated copper layer 4 to a film thickness of 10% and flowing a PR current through the anode 24t. The ratio of the negative current time at this time was set to 10% to obtain a plating film.

The (111) crystal orientation index of the electroplated copper layer before the MIT folding test was 1.34.

The MIT folding endurance sample of Example 1 having a crystal orientation ratio [(200)/(111)] represented by an X-ray alignment index before and after the MIT folding test was 0.04 in a test piece having a wiring width of 1 mm. When it was 895 times, the test piece was 78 times in 50 μm, and the test piece was 50 times in 20 μm, good results were obtained.

The etching factor was 6.3 in the test piece at 50 μm and 6.3 in the test piece at 20 μm.

[Embodiment 2 in the first embodiment]

A two-layer flexible wiring board was produced in the same manner as in Example 1 except that the sputtering atmosphere was a mixed gas of argon and 1% by volume of nitrogen. The film thickness range of the metal laminate from the surface of the resin film substrate to 0.4 μm, the crystal ratio of the crystal 111 orientation obtained by the electron backscatter diffraction method (EBSD) OR ₁₁₁ relative to the 001 orientation, OR ₀₀₁ The ratio (OR ₁₁₁ /OR ₀₀₁ ) is 3.3.

The (111) crystal orientation index of the electroplated copper layer before the MIT folding test was 1.34.

The MIT folding endurance sample of Example 2 having a crystal orientation ratio [(200)/(111)] represented by the X-ray alignment index before and after the MIT folding resistance test was a test having a wiring width of 1 mm. The film was 851 times, the test piece was 69 times in 50 μm, and the test piece was 45 times in 20 μm, that was, good results were obtained.

The etching factor was 5.3 in the test piece at 50 μm and 5.5 in the test piece at 20 μm.

(Comparative Example 1 of the first embodiment)

A two-layer flexible wiring board was produced in the same manner as in Example 1 except that only argon gas was used as the sputtering atmosphere.

The ratio of the crystal ratio OR ₁₁₁ of the crystal 111 orientation measured by the electron backscatter diffraction method (EBSD) to the crystal ratio OR ₀₀₁ of the 001 orientation (OR ₁₁₁ /OR ₀₀₁ ) was 7.3.

The (111) crystal orientation index of the electroplated copper layer before the MIT folding test was 1.20.

The difference between the crystal orientation ratio [(200)/(111)] expressed by the X-ray alignment index before and after the MIT folding test was 0.03.

The sample of Comparative Example 1 having the above characteristics exhibited folding endurance, 541 times in the test piece having a wiring width of 1 mm, 27 times in the test piece at 50 μm, and 20 times in the test piece at 20 μm, that is, the wiring width was 50 μm or less. As a result of poor performance, the results were clearly inferior to the first embodiment of the present invention.

The etching factor was 3.9 in the test piece at 50 μm, and 4.1 in the test piece at 20 μm.

Table 1 summarizes the wiring shapes (bottom width B, top width T, and copper film thickness C) in the first embodiment of the first embodiment and the comparative example of the first embodiment, in which the wiring width is 20 μm and 50 μm, and the sputtering environment. Gas, calculated etch factor F _E and MIT folding test results.

Etch factor calculation formula F _E =C×2/(BT)

[Second Embodiment]

Hereinafter, the two-layer flexible wiring board of the present invention will be described in more detail using the second embodiment.

The resin film substrate was produced by using a wound sputter apparatus 10 using a copper film layer of a polyimine film.

A nickel-20% by weight chromium alloy target for forming a base metal layer is attached to the sputtering cathode 15a, and a copper target is attached to each of the sputtering cathodes 15b to 15d, and a polyethylene film having a thickness of 38 μm is provided on the resin film substrate. Amine film (registered trademark Kapton, After vacuum evacuation in the apparatus of Toray-DuPont Co., Ltd., the inside of the apparatus was maintained at 1.3 Pa to produce a polyimide film having a copper film layer. The thickness of the base metal layer (nickel-chromium alloy) was 20 nm, and the thickness of the copper thin film layer was 200 nm.

The polyimine film of the obtained copper thin film layer was subjected to electroplating copper using a plating apparatus 20 to form a copper plating layer. The plating solution is a copper sulfate aqueous solution having a pH of 1 or less, and the anode is 24 m to 24 t, unless otherwise specified, and the maximum current density (except for the reverse current of the PR current) is set, and the current density is adjusted to finally make the thickness of the electroplated copper layer. It is 8.5 μm.

The folding endurance test was carried out by using a ferric chloride as an etching solution, and a test pattern of "JIS C-5016-1994" was formed by a removal method, and evaluated according to the same standard; a test piece having a wiring width of 50 μm was used for the test piece (below) In addition, the test piece (50 μm) and the test piece having a wiring width of 20 μm (hereinafter referred to as a test piece of 20 μm) were evaluated in accordance with "JIS C-5016-1994".

The crystal orientation of the electroplated copper layer before and after the folding endurance test was measured by X-ray diffraction using a Wilson orientation index.

For the metal laminate, the orientation and orientation ratio of the copper crystals were determined by the EBSD method. The measurement results were classified into a range from the surface side of the resin film substrate to a film thickness of 0.4 μm and a range in which the film thickness exceeded 0.4 μm.

The measurement conditions of the electron backscatter diffraction method (EBSD) used in the second embodiment are as follows.

[Measurement conditions of electron backscatter diffraction method (EBSD)]

The diffraction apparatus was measured using an Oxford Accumulator (HKL Channel 5) under the conditions of an acceleration voltage of 15 kV and a measurement procedure of 0.05 μm. Moreover, the ratio of the (111) plane alignment of the crystal grains is calculated along the area occupancy ratio of the measurement range (111) The grain in the normal direction of the surface is ±15°.

[Embodiment 1 in the second embodiment]

The sputtering ambient gas was set to a mixed gas of 1.3 Pa of argon and 5 vol% of nitrogen.

In the electroplated copper layer, the current density of the anodes 24a to 24f which are formed in the copper layer from the surface of the copper thin film layer to the film thickness of 1.5 μm is 1 A/dm ² or less, in order to use the PR current from the surface of the electroplated copper layer to 10 Since the plating was performed in the range of the film thickness of %, the PR current was passed through the anode 24t, and the two-layer flexible wiring board of Example 1 was produced. The ratio of the negative current time at this time was set to 10%.

In the film thickness range from 0.4 μm to the surface of the resin film substrate of the metal laminate formed of electroplated copper, the crystal ratio OR _{111 of the} orientation of the crystal 111 obtained by the electron backscatter diffraction method (EBSD) is relative to 001. The ratio of the orientation crystal ratio OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) was 0.7.

The (111) crystal orientation index of the electroplated copper layer before the MIT folding test was 1.35.

The difference between the crystal orientation ratio [(200)/(111)] expressed by the X-ray alignment index before and after the MIT folding endurance test was 0.04.

The sample of Example 1 showed the above-mentioned characteristics. In the MIT folding endurance test, 545 times when the wiring width was 1 mm, 78 times in the test piece 50 μm, and 50 times in the test piece 20 μm, that is, good results were obtained respectively. the result of.

Further, the etching factor was 6.3 in the test piece of 50 μm, and was also 6.3 in the test piece of 20 μm.

[Embodiment 2 in the second embodiment]

In addition to the sputtering ambient gas is set to a mixture of argon and 1% by volume of nitrogen A flexible wiring board was produced in the same manner as in Example 1 except for the body.

The ratio of the crystallographic ratio OR ₁₁₁ of the crystal 111 orientation obtained by the electron backscatter diffraction method (EBSD) to the crystal ratio of the 001 orientation OR ₀₀₁ from the surface of the resin film substrate to the film thickness range of 0.4 μm. (OR _111/ OR ₀₀₁ ) is 3.3.

The (111) crystal orientation index of the electroplated copper layer before the MIT folding test was 1.34.

In addition, the MIT folding endurance sample of Example 2 having a difference in crystal orientation ratio [(200)/(111)] represented by the X-ray alignment index before and after the MIT folding test was a test having a wiring width of 1 mm. The film was 851 times, the test piece was 69 times in 50 μm, and the test piece was 45 times in 20 μm, that was, good results were obtained.

The etching factor was 5.3 in the test piece at 50 μm and 5.5 in the test piece at 20 μm.

(Comparative Example 1 of the second embodiment)

A flexible wiring board was produced in the same manner as in Example 1 except that only argon gas was used as the sputtering atmosphere.

The ratio of the crystal ratio OR ₁₁₁ of the crystal 111 orientation measured by the electron backscatter diffraction method (EBSD) to the crystal ratio OR ₀₀₁ of the 001 orientation (OR ₁₁₁ /OR ₀₀₁ ) was 7.3.

The (111) crystal orientation index of the electroplated copper layer before the MIT folding test was 1.20.

The difference between the crystal orientation ratio [(200)/(111)] expressed by the X-ray alignment index before and after the MIT folding test was 0.03.

The sample of Comparative Example 1 having the above characteristics had a folding endurance. In the MIT folding endurance test, 541 times were displayed when the wiring width was 1 mm, 27 times in the test piece 50 μm, and 20 times in the test piece 20 μm, that is, the display efficiency was not Good result, result It is apparent that it is inferior to Embodiment 1 of the present invention.

Further, the etching factor was 3.9 in the test piece at 50 μm, and 4.1 in the test piece at 20 μm.

Table 2 summarizes the wiring shapes (bottom width B, top width T, and copper film thickness C) in the second embodiment of the second embodiment and the second embodiment in which the wiring width is 20 μm and 50 μm, and the sputtering environment gas, calculation Etching factor F _E and MIT folding test results.

Etch factor calculation formula F _E =C×2/(BT)

Claims (16)

A two-layer flexible wiring board is a wiring provided on a surface of a resin film substrate without an adhesive, and includes a base metal layer made of a nickel-containing alloy and the base metal. The surface of the layer is provided with a copper layer; and the orientation of the crystal 111 included in the range from the surface of the resin film substrate to 0.4 μm in the metal laminate as measured by an electron backscatter diffraction method (EBSD) The ratio of the crystal ratio OR ₁₁₁ to the crystal ratio of the 001 orientation OR ₀₀₁ (OR ₁₁₁ /OR ₀₀₁ ) is 7 or less, and the (111) crystal orientation index of the above copper layer is 1.2 or more, and the folding endurance test is performed. The folding resistance test prescribed in JIS C-5016-1994) The difference d [(200)/(111)] of the crystal orientation ratio [(200)/(111)] of the above-mentioned copper layer obtained before and after the implementation is 0.03 or more. The two-layer flexible wiring board according to the first aspect of the invention, wherein the base metal layer has a thickness of 3 nm to 50 nm. The two-layer flexible wiring board according to the first aspect of the invention, wherein the copper layer has a thickness of 5 μm to 12 μm. The two-layer flexible wiring board according to the second aspect of the invention, wherein the copper layer has a film thickness of 5 μm to 12 μm. The two-layer flexible wiring board according to any one of claims 1 to 4, wherein the copper layer is formed by a copper thin film layer formed on the surface of the underlying metal layer and formed by electroplating copper. The electroplated copper layer is formed on the surface of the copper thin film layer, and the electroplated copper layer is subjected to periodic short-time potential inversion in a thickness range of 10% or more in thickness from the surface of the resin film substrate. The periodic reverse current is formed by electroplating copper. a two-layer flexible wiring substrate according to claim 5, wherein the base The bottom metal layer and the copper thin film layer described above are formed by dry plating. The two-layer flexible wiring board according to any one of claims 1 to 4, wherein the resin film substrate is selected from the group consisting of a polyimide film, a polyamide film, and a polyester film. At least one or more resin films of a polytetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a liquid crystal polymer film. A method for producing a two-layer flexible wiring substrate according to any one of claims 1 to 7, which is a method of manufacturing a substrate for a flexible film substrate. Forming a base metal layer by dry plating, forming a copper thin film layer on the surface of the base metal layer, and forming a copper plating film by electroplating copper on the surface of the copper thin film layer; The ambient gas when the film is formed by the dry plating method is an argon-nitrogen mixed gas, and the plated copper layer is formed on the surface of the plated copper layer in the direction of the resin film substrate by 10% or more of the thickness of the plated copper layer. In the thickness range, it is formed by a copper plating method in which a periodic reverse current of a short-time potential inversion is periodically performed. A two-layer flexible wiring board, which is a flexible wiring board in which a wiring of a metal laminated body is provided on a surface of a resin film substrate without an adhesive, the metal laminated body including a base metal layer composed of a nickel-containing alloy, and The surface of the base metal layer is provided with a copper layer, and the metal laminated body measured by an electron backscatter diffraction method (EBSD) is included in a range from 0.4 μm from the surface of the resin film substrate. 111 crystal orientation of ₁₁₁ relative to the crystalline fraction than the crystalline OR 001 OR ₀₀₁ of the orientation ratio (OR ₁₁₁ / OR ₀₀₁₎ of 7 or less, (111) crystalline orientation degree of the copper layer index of 1.2 or more, and the folding The difference between the crystal orientation ratio [(200)/(111)] of the above copper layer obtained before and after the performance test (the folding endurance test specified in JIS C-5016-1994) is d [(200)/(111)] It is 0.03 or more. The two-layer flexible wiring board of claim 9, wherein the underlying metal layer has a film thickness of 3 nm to 50 nm. The two-layer flexible wiring board of claim 9, wherein the copper layer has a film thickness of 5 μm to 12 μm. A two-layer flexible wiring board according to claim 10, wherein the copper layer has a film thickness of 5 μm to 12 μm. The two-layer flexible wiring board according to any one of claims 9 to 12, wherein the copper layer is formed of a copper thin film layer formed on the surface of the base metal layer, and is formed on the surface of the copper thin film layer. The electroplated copper layer is formed by a periodic reverse current in which a short-time potential inversion is periodically performed in a thickness range of 10% or more of the film thickness in the direction from the surface of the resin film substrate. Formed by electroplating copper. The two-layer flexible wiring board of claim 13, wherein the base metal layer and the copper thin film layer are formed by a dry plating method. The two-layer flexible wiring board according to any one of claims 9 to 12, wherein the resin film substrate is selected from the group consisting of a polyimide film, a polyamide film, a polyester film, and a poly At least one or more resin films of a tetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a liquid crystal polymer film. A method for producing a two-layer flexible wiring board according to any one of claims 9 to 15, which is characterized in that the surface of the resin film substrate is not via an adhesive. Forming a base metal layer by dry plating, forming a copper thin film layer on the surface of the base metal layer, and forming a copper plating film on the surface of the copper thin film layer by a copper plating method; The ambient gas at the time of film formation by the dry plating method is an argon-nitrogen mixed gas, and the plated copper layer is a thickness of 10% or more of the thickness of the plated copper layer from the surface of the plated copper layer in the direction of the resin film substrate. In the range, it is formed by a copper plating method in which a periodic reverse current of a short-time potential inversion is periodically performed.