JP6398596B2 - Two-layer flexible wiring board and flexible wiring board using the same - Google Patents

Description

  The present invention relates to a two-layer flexible wiring board in which a part of a copper layer is deposited by a copper electroplating method to improve folding resistance, and a flexible wiring board using the two-layer flexible wiring board.

A flexible wiring board is widely used for a portion requiring refraction or bending of an electronic device such as a read / write head of a hard disk or a printer head, or a refraction wiring in a liquid crystal display, taking advantage of its flexibility.
For manufacturing such a flexible wiring board, a method for wiring a flexible wiring board (copper-clad laminated board, also referred to as FCCL: Flexible Copper Clad Lamination) in which a copper layer and a resin layer are laminated using a subtractive method or the like. Is used.

  This subtractive method is a method of removing unnecessary portions by chemically etching the copper layer of the flexible wiring board. That is, a resist is provided on the surface of the copper layer of the flexible wiring board to be left as the conductor wiring, and unnecessary portions of the copper layer are selectively removed through chemical etching treatment and water washing with an etching solution corresponding to copper. Thus, the conductor wiring is formed.

By the way, the flexible wiring board (FCCL) can be classified into a three-layer FCCL board (hereinafter referred to as a three-layer FCCL) and a two-layer FCCL board (referred to as a two-layer FCCL).
The three-layer FCCL has a structure (copper foil / adhesive layer / resin film) in which an electrolytic copper foil or a rolled copper foil is bonded to a base (insulating layer) resin film. On the other hand, the two-layer FCCL has a structure (copper layer or copper foil / resin film) in which a copper layer or copper foil and a resin film substrate are laminated.

The two-layer FCCL is roughly divided into three types.
That is, FCCL (commonly known as a metalizing substrate) formed by sequentially plating a base metal layer and a copper layer on the surface of a resin film, FCCL (commonly referred to as a cast substrate) in which an insulating layer is formed by applying a resin film varnish to a copper foil, And FCCL (commonly referred to as a laminate substrate) in which a resin film is laminated on a copper foil.

FCCL, which is formed by sequentially plating the base metal layer and the copper layer on the surface of the metalizing substrate, ie, the resin film, can reduce the thickness of the copper layer and has high smoothness at the interface between the polyimide film and the copper layer. Compared with cast substrate, laminate substrate, or three-layer FCCL, it is suitable for fine wiring.
For example, the thickness of the copper layer of the metalizing board can be freely controlled by dry plating and electroplating, whereas the thickness of the cast board, laminate board or three-layer FCCL is limited by the copper foil used. Will be.

Moreover, about copper foil used for the wiring of a flexible wiring board, for example, the method of performing heat processing (refer patent document 1) to copper foil, or the method of performing a rolling process (refer patent document 2) WHEREIN: Improvements are being made.
However, these methods relate to the processing of the copper foil itself used for the cast substrate and the laminate substrate of the three-layer FCCL rolled copper foil and the electrolytic copper foil and the two-layer FCCL.

In addition, the MIT refraction resistance test (Folding Endurance Test) standardized by “JIS C-5016-1994” or “ASTM D2176” is used industrially for the evaluation of the folding resistance of the copper foil.
In this test, evaluation is performed based on the number of refractions until the circuit pattern formed on the test piece breaks, and the greater the number of refractions, the better the folding resistance.

JP-A-8-283886 JP-A-6-269807

The substrate for two-layer flexible wiring targeted by the present invention is a plating substrate in which a metal layer composed of a seed layer and a copper plating layer formed on at least one surface of a resin film base material without an adhesive is sequentially formed. However, it is difficult to improve the folding endurance by subjecting only the copper plating layer to heat treatment or rolling as disclosed in the prior art documents. It was desired.
In view of such a situation, the present invention provides a two-layer flexible wiring board and a flexible wiring board excellent in folding resistance.

  In order to solve the above problems, the present inventors have intensively studied the bending resistance of a copper layer formed on a polyimide resin layer by plating, and as a result, the change in crystal orientation and the crystallite diameter before and after the folding resistance. The effect of the increase on the folding resistance test result was confirmed, and the present invention was achieved.

A first invention of the present invention is a two-layer flexible wiring board having a laminated structure in which a base metal layer made of a nickel alloy is not provided on the surface of a polyimide film and a copper layer is provided on the surface of the base metal layer. The copper layer is composed of a copper thin film layer provided on the surface of the base metal layer and a copper electroplating layer provided on the surface of the copper thin film layer, and has a folding resistance defined in JIS C-5016-1994. The difference d [(200) / (111)] in the crystal orientation ratio [(200) / (111)] of the copper layer obtained before and after the test is 0.03 or more, and the (111) plane of the copper layer is A double-layer flexible wiring board having a crystal orientation degree index of 1.2 or more and a crystallite diameter of 300 nm or more.

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

According to a third aspect of the present invention, the copper layer in the first and second aspects is composed of a copper thin film layer provided on the surface of the base metal layer and a copper electroplating layer provided on the surface of the copper thin film layer, A double-layer flexible wiring board having a crystallite diameter of 200 nm to 400 nm in a thickness range of 10% or more of the thickness of the copper electroplating layer from the surface of the copper layer toward the polyimide film. .

  A fourth invention of the present invention is a two-layer flexible wiring board characterized in that the surface roughness of the copper layer in the first to third inventions is an arithmetic average roughness Ra of 0.2 μm or less. .

According to a fifth aspect of the present invention, there is provided a flexible wiring board in which a base metal layer made of a nickel alloy is provided on the surface of a polyimide film without using an adhesive and a wiring having a laminated structure including a copper layer on the surface of the base metal layer The copper layer is composed of a copper thin film layer provided on the surface of the base metal layer and a copper electroplating layer provided on the surface of the copper thin film layer, and is a folding resistance test defined in JIS-P-8115. The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] of the copper layer obtained before and after the execution of the step is 0.03 or more, crystal orientation index in 111) plane, a flexible wiring board, characterized in that the crystallite diameter of 1.2 or more and 300nm or more.

According to a sixth aspect of the present invention, the copper layer in the fifth aspect is composed of a copper thin film layer provided on the surface of the underlying metal layer and a copper electroplating layer provided on the surface of the copper thin film layer, and the surface of the copper layer. From the thickness of the copper electroplating layer in the polyimide film direction to a thickness range of 10% or more, the crystallite diameter is 200 nm to 400 nm .

Seventh aspect of the present invention, the surface roughness of the copper layer in the invention of the fifth and sixth, a flexible wiring board, characterized in that at 0.2μm or less in terms of arithmetic average roughness Ra.

  It has a laminated structure with a base metal layer made of a nickel alloy on the surface of a polyimide film and a copper layer provided on the surface of the base metal layer, and has a folding resistance defined in JIS C-5016-1994. The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] of the copper layer obtained before and after the performance test is 0.03 or more, and the (111) plane of the copper layer According to the substrate for a two-layer flexible wiring according to the present invention showing that the crystal orientation degree index at 1.2 is 1.2 or more and the crystallite diameter is 300 nm or more, the folding resistance of the substrate is remarkably improved, and it is industrially remarkable. It has a great effect.

It is a cross-sectional schematic diagram of the board | substrate for two-layer flexible wiring produced by the metalining method. It is a schematic diagram showing a roll-to-roll sputtering apparatus for forming a base metal layer and a copper thin film layer of a two-layer flexible wiring board. It is a schematic diagram which shows the continuous plating apparatus of the roll-to-roll system which performs electroplating in manufacture of the board | substrate for 2 layer flexible wiring. It is the figure which showed typically the time and current density of PR current in this invention.

(1) Two-layer flexible wiring board 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 base metal layer and a copper layer are sequentially laminated on at least one surface of a polyimide film without using an adhesive, and the copper layer includes a copper thin film layer and a copper thin film layer. It is comprised by the copper electroplating layer.

FIG. 1 is a schematic view showing a cross section of a substrate 6 for a two-layer flexible wiring manufactured by a metalining method.
A polyimide film is used for the resin film substrate 1, and the base metal layer 2, the copper thin film layer 3, and the copper electroplating layer 4 are sequentially formed and laminated on at least one surface of the polyimide film from the polyimide film side. The copper thin film layer 3 and the copper electroplating layer 4 constitute a copper layer 5.

As the resin film substrate 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, a liquid crystal polymer film, or the like can be used.
In particular, a polyimide film is preferable from the viewpoint of mechanical strength, heat resistance, and electrical insulation.
Furthermore, the said resin film board | substrate whose film thickness is 12.5-75 micrometers can be used preferably.

  The base metal layer 2 ensures reliability such as adhesion and heat resistance between the resin film substrate and a metal layer such as copper. Therefore, the material of the base metal layer is any one selected from nickel, chromium, or an alloy thereof, but a nickel / chromium alloy is suitable in consideration of adhesion strength and ease of etching during wiring production. ing.

The composition of the nickel-chromium alloy is desirably 15% by weight or more and 22% by weight or less of chromium, and an improvement in corrosion resistance and migration resistance can be expected.
Of these, nickel / chromium alloy of 20% by weight chromium is distributed as a nichrome alloy and is easily available as a sputtering target for the magnetron sputtering method. Further, chromium, vanadium, titanium, molybdenum, cobalt, or the like may be added to the alloy containing nickel.
Furthermore, a plurality of nickel-chromium alloy thin films having different chromium concentrations may be laminated to form a base metal layer having a nickel-chromium alloy concentration gradient.

The film thickness of the base metal layer 2 is desirably 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 maintained, and the corrosion resistance and migration resistance are poor. On the other hand, if the thickness of the base metal layer exceeds 50 nm, it may be difficult to sufficiently remove the base metal layer when wiring processing is performed by the subtractive method. If the removal of the underlying metal layer is insufficient, there is a concern about problems such as migration between wirings.

The copper thin film layer 3 is mainly composed of copper, and the film thickness is desirably 10 nm to 1 μm.
When the film thickness of the copper thin film layer is less than 10 nm, the conductivity when the copper electroplating layer is formed on the copper thin film layer by the electroplating method cannot be ensured, leading to an appearance defect during electroplating. Even if the film thickness of the copper thin film layer exceeds 1 μm, the quality problem of the two-layer flexible wiring board does not occur, but the productivity is inferior.

(2) Film formation method for base metal layer and copper thin film layer The base metal layer and the copper thin film layer are preferably formed by a dry plating method.
Examples of the dry plating method include a sputtering method, an ion plating method, a cluster ion beam method, a vacuum evaporation method, a CVD method, and the like. From the viewpoint of controlling the composition of the underlying metal layer, the sputtering method is preferable.
The sputtering film formation on the resin film substrate can be performed with a known sputtering apparatus, and the film formation on the long resin film substrate can be performed with a known roll-to-roll sputtering apparatus. it can. If this roll-to-roll sputtering apparatus is used, a base metal layer and a copper thin film layer can be continuously formed on the surface of a long polyimide film.

FIG. 2 is an example of a roll-to-roll sputtering apparatus.
The roll-to-roll sputtering apparatus 10 includes a rectangular parallelepiped casing 12 that accommodates most of its components.
The casing 12 may have a cylindrical shape, and the shape is not limited as long as it can maintain a reduced pressure in a range of 10 ⁻⁴ Pa to 1 Pa.
Inside this housing 12, a polyimide film F, which is a long resin film substrate, is supplied with an unwinding roll 13, a can roll 14, sputtering cathodes 15a, 15b, 15c, 15d, a front feed roll 16a, and a rear feed roll. 16b, a tension roll 17a, a tension roll 17b, and a winding roll 18.

The unwinding roll 13, the can roll 14, the front feed roll 16a, and the take-up roll 18 are provided with power by a servo motor. The unwinding roll 13 and the winding roll 18 are configured so that the tension balance of the polyimide film F is maintained by torque control using a powder clutch or the like.
The tension rolls 17a and 17b are finished with hard chrome plating and provided with a tension sensor.
The sputtering cathodes 15a to 15d are of a magnetron cathode type and are arranged to face the can roll 14. The width direction dimension of the polyimide film F of the sputtering cathodes 15a to 15d only needs to be wider than the width of the polyimide film F.

The polyimide film F is transported through a roll-to-roll sputtering apparatus 10 which is a roll-to-roll vacuum film forming apparatus, and is formed by sputtering cathodes 15 a to 15 d facing the can roll 14, with a copper thin film layer. Processed into a polyimide film F2.
The surface of the can roll 14 is finished with hard chrome plating, and a coolant or a heating medium supplied from the outside of the housing 12 circulates inside the can roll 14 to be adjusted to a substantially constant temperature.

When the base metal layer and the copper thin film layer are formed using the roll-to-roll sputtering apparatus 10, the target having the composition of the base metal layer is attached to the sputtering cathode 15a, and the copper target is attached to the sputtering cathodes 15b to 15d. The inside of the apparatus in which the polyimide film is set on the unwinding roll 13 is evacuated, and then the inside of the apparatus is held at about 1.3 Pa by introducing a sputtering gas such as argon.
Further, after forming the base metal layer by sputtering, the copper thin film layer may be formed by vapor deposition.

(3) Copper electroplating layer and film forming method The copper electroplating layer is formed by electroplating. The thickness of the copper electroplating layer is desirably 1 μm to 20 μm.
Here, the electroplating method used is to perform electroplating using an insoluble anode in a copper sulfate plating bath containing iron ions, and the composition of the copper plating bath used is a commonly used printed wiring board. High throw copper sulfate plating bath may be used.

FIG. 3 is an example of a roll-to-roll continuous electroplating apparatus (hereinafter referred to as a plating apparatus 20) that can be used in the production of the two-layer flexible wiring board according to the present invention.
A polyimide film F2 with a copper thin film layer obtained by forming a base metal layer and a copper thin film layer is unwound from the unwinding roll 22 and continuously immersed in the plating solution 28 in the electroplating tank 21. It is conveyed to. Incidentally, 28a indicates the surface of the plating solution.
The polyimide film F2 with a copper thin film layer is formed by depositing a copper layer on the surface of the metal thin film by electroplating while being immersed in the plating solution 28, and after forming a copper layer with a predetermined thickness, the metallized resin The film is wound around a winding roll 29 as a two-layer flexible wiring substrate S which is a film substrate. In addition, the conveyance speed of the polyimide film F2 with a copper thin film layer has the preferable range of several m-several dozen m / min.

If it demonstrates concretely, the polyimide film F2 with a copper thin film layer will be unwound from the unwinding roll 22, and will be immersed in the plating solution 28 in the electroplating tank 21 through the electric power feeding roll 26a. The copper thin film layer-attached polyimide film F2 that has entered the electroplating tank 21 is reversed in the conveying direction through the reversing roll 23, and is drawn out of the electroplating tank 21 by the power supply roll 26b.
Thus, while the polyimide film F2 with a copper thin film layer repeats immersion in a plating solution a plurality of times (10 times in FIG. 3), a copper layer is formed on the metal thin film of the polyimide film F2 with a copper thin film layer. It is.

A power source (not shown) is connected between the power supply roll 26a and the anode 24a.
An electroplating circuit is configured by the power supply roll 26a, the anode 24a, the plating solution, the polyimide film F2 with a copper thin film layer, and the power source.
The anode is preferably an insoluble anode. The insoluble anode does not require a special one, and may be a known anode whose surface is coated with a conductive ceramic. A mechanism for supplying copper ions to the plating solution 28 is provided outside the electroplating tank 21.

  The copper ions are supplied to the plating solution 28 using an aqueous copper oxide solution, an aqueous copper hydroxide solution, an aqueous copper carbonate solution, or the like. Alternatively, there is a method in which a small amount of iron ions is added to the plating solution to dissolve the oxygen-free copper balls and supply the copper ions. Any of the above methods can be used as a method for supplying copper.

The current density during plating is increased stepwise from the anode 24a toward the downstream in the transport direction so that the maximum current density is reached at 24t from the anode 24o.
Thus, discoloration of the copper layer can be prevented by increasing the current density. In particular, when the current density is high when the copper layer is thin, discoloration of the copper layer is likely to occur. Therefore, the current density during plating is 0.1 A / dm ^{2 to} 8 A except for the reverse current of Periodic Reverse current described later. / Dm ² is desirable. When the current density is increased, a poor appearance of the copper electroplating layer occurs.

In order to manufacture the two-layer flexible wiring board according to the present invention, the copper electroplating layer is formed using a PR current in a range of 10% or more from the surface of the film thickness.
In the case of using a periodic reverse current (hereinafter also referred to as a PR current), it is preferable to add a current that is 1 to 9 times as large as the positive current.
The reversal current time ratio is preferably about 1 to 10%.
Further, the period in which the reversal current next to the PR current flows is desirably 10 milliseconds or more, and more desirably 20 milliseconds to 300 milliseconds.
FIG. 4 schematically shows the time and current density of the PR current.
In addition, what is necessary is just to adjust a plating voltage suitably so that the above-mentioned current density is realizable.

In order to manufacture the two-layer flexible wiring board according to the present invention with a roll-to-roll continuous electroplating apparatus (hereinafter referred to as a plating apparatus 20), a PR current is allowed to flow at one or more anodes from the downstream side of the conveyance path. The number of anodes through which the PR current flows is determined by the ratio of the range in which the PR current is formed from the surface of the copper electroplating layer to the polyimide film side. That is, at least the anode 24t causes a PR current to flow, and if necessary, the PR current flows to the anode 24s, the anode 24r, and the anode 24q.
Although a PR current may be supplied to all the anodes, a manufacturing cost increases because a rectifier for PR current is expensive. Therefore, in the two-layer flexible wiring board according to the present invention, if 10% of the film thickness is formed with a PR current in the polyimide direction from the surface of the copper electroplating layer, a fold resistance test (JIS C-5016-1994). The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] of the copper layer is 0.03 or more before and after the execution of the above, and as a result, the folding resistance test (MIT Improvement of the test).

  The reason why copper electroplating using a PR current is desirable is that when the current is reversed, the copper crystallite diameter of the copper electroplating layer can be about 300 nm or more, and the grain boundaries can be reduced. This is because the starting point of the generated crack can be reduced.

Furthermore, by adding iron ions to the copper plating solution, orientations other than (111) that are easily soluble are preferentially dissolved, and crystals of (111) orientation can be grown.
The concentration of iron ions contained in the copper plating solution is preferably 0.1 to 20 g / liter in total of divalent and trivalent ions.
Iron ions change in a circulatory manner from trivalent to divalent and from divalent to trivalent in the course of copper plating. Therefore, if the iron ion concentration exceeds 20 g / liter, the consumption of iron ions is increased, which is not economical, and the copper plating layer is easily dissolved. On the other hand, when the iron ion concentration is less than 0.1 g / liter, preferential growth of (111) oriented crystals cannot be expected.

In general, in the electroplating method, the deposited copper is affected by the surface of the substrate to be copper-plated, but if 10% or more of the film thickness from the surface of the copper electroplating layer is formed by PR current, the grain boundary Can be controlled. Therefore, if 10% or more of the film thickness from the surface of the copper electroplating layer of the two-layer flexible wiring board is a crystal that matches the folding resistance, an effect on the folding resistance of the copper electroplating layer can be obtained. The object of the present invention can be achieved.
In addition, when adjusting the thickness of the copper layer of the obtained two-layer flexible wiring board by chemical polishing or the like, a layer formed with a PR current of 10% or more of the film thickness from the surface of the copper layer after polishing is used. If it remains, the effect of the present invention can be exhibited.

(4) Features of the copper electroplating layer A feature of the copper layer in the two-layer flexible wiring board of the present invention is that it shows a (111) crystal orientation index of copper of 1.2 or more. In this state, the crystal becomes slippery in the MIT folding resistance test (JIS C-5016-1994). The copper layer of the flexible wiring board of the present invention includes (200), (220), and (311) orientations in addition to the (111) orientation, of which the (111) orientation occupies most of the crystal orientation. The degree index is 1.20 or more.

A further feature is that the difference in crystal orientation ratio [(200) / (111)] before and after the MIT folding resistance test (JIS C-5016-1994) is 0.03 or more. In this state, it is considered that the crystal slipped due to the MIT folding resistance test and recrystallization occurred.
For the glossiness of the surface, a glossy film is preferable so that unevenness on the surface does not cause a notch.

In addition, the larger the crystallite diameter, the better. However, it should be noted that it also affects the etching of the copper layer when the flexible wiring board is processed into a flexible wiring board by the subtractive method.
When using an aqueous ferric chloride solution for etching the copper layer in the subtractive method, the crystallite size of the copper layer may not affect, but when etching the grain boundaries of the crystal grains of the copper layer, The crystallite diameter also affects the shape of the wiring. The crystallite size is preferably about 200 nm to 400 nm. If it is 200 nm or less, there are many crystal grain boundaries, and cracks that are the starting points of fracture are likely to occur, and the reason why it is 400 nm or less is to maintain the smoothness of the metal surface.

  In addition, the copper layer of the flexible wiring board of the present invention is obtained by the above-described method for forming a copper layer, and the difference in crystal orientation ratio [(200) / (111)] before and after the MIT folding resistance test is 0.03 or more. And a copper layer having the characteristics that the crystallite diameter is 300 nm or more. The crystal orientation and crystallite diameter of the copper electroplating layer can be known from an X-ray diffractometer.

Furthermore, the copper crystal of the copper layer obtained by the above method has a dynamic recrystallization effect at room temperature during refraction. The average crystallite size after the bending resistance test tends to be about 100 nm to 200 nm by recrystallization.
In general, it has been considered that a copper electroplated film does not dynamically recrystallize at room temperature. However, since the flexible wiring substrate of the present invention is dynamically recrystallized at room temperature, it is difficult to cut the sample when a refraction test such as the MIT test is performed. The average crystal grain size of the copper layer and dynamic recrystallization at room temperature can be observed with a cross-sectional SIM image.

Next, the arithmetic surface roughness Ra is preferably 0.2 μm or less.
When the surface roughness Ra exceeds 0.2 μm, even if the difference in crystal orientation ratio [(200) / (111)] before and after the MIT bending resistance test is 0.03 or more, the effect of improving the bending resistance is small. . Therefore, it is desirable that the difference in the crystal orientation ratio [(200) / (111)] before and after the MIT bending resistance test is 0.03 or more and the arithmetic surface roughness Ra is 0.2 μm or less.
Naturally, when the surface of the copper layer is polished by chemical polishing or the like, the arithmetic surface roughness Ra of the surface of the copper layer after chemical polishing may be 0.2 μm or less.

(5) Flexible wiring board The flexible wiring board according to the present invention is manufactured by performing wiring processing on the two-layer flexible wiring board according to the present invention by a subtractive method.
Etching solution used for etching process to process copper electroplating layer etc. into wiring is not limited to aqueous solution or special chemical solution containing ferric chloride, cupric chloride and copper sulfate with special blending, general A commercially available etching solution containing a ferric chloride aqueous solution having a specific gravity of 1.30 to 1.45 or a cupric chloride aqueous solution having a specific gravity of 1.30 to 1.45 can be used.

  The surface of the wiring is subjected to tin plating, nickel plating, gold plating, or the like as required, and the surface is covered with a known solder resist or the like. And electronic parts, such as a semiconductor element, are mounted and an electronic device is formed.

Hereinafter, the present invention will be described in more detail using examples.
The polyimide film with a copper thin film layer was produced using a roll-to-roll sputtering apparatus 10.
A nickel-20 wt% chromium alloy target for forming a base metal layer is mounted on the sputtering cathode 15a, and a copper target is mounted on the sputtering cathodes 15b to 15d, respectively, and a polyimide film (Kapton registered trademark Toray DuPont Co., Ltd.) After vacuuming the inside of the apparatus in which the product was set, argon gas was introduced and the inside of the apparatus was held at 1.3 Pa to produce a polyimide film with a copper thin film layer. The film thickness of the base metal layer (nickel-chromium alloy) was 20 nm, and the film thickness of the copper thin film layer was 200 nm.

  The obtained polyimide film with a copper thin film layer was subjected to copper electroplating using a plating apparatus 20 to form a copper electroplating layer. The plating solution is a copper sulfate aqueous solution having a pH of 1 or less, and the anodes 24o to 24t are set to have the maximum current density (excluding the reversal current of the PR current) unless otherwise specified. The current density was adjusted to 8.5 μm.

In the bending resistance test, a test pattern of JIS-C-5016-1994 was formed by a subtractive method using ferric chloride as an etching solution, and evaluated according to the same standard.
The crystal orientation of the copper electroplating layer before and after the folding resistance test was measured by X-ray diffraction using Wilson's orientation degree index.

In order to perform electroplating using a PR current from the surface of the copper electroplating layer to a film thickness range of 10%, a PR current was passed through the anode 24t to produce a two-layer flexible wiring board of Example 1. The iron ion concentration was 5 g / liter.
The (111) crystal orientation index of the copper electroplating layer before the MIT fold resistance test is 1.34, and the crystal orientation ratio represented by the X-ray orientation index before and after the MIT fold resistance test [(200) / (111) ], The sample of Example 1 having a crystallite diameter of 383 nm and an arithmetic surface roughness Ra of 0.06 μm obtained a good result of 349 times in the MIT folding resistance test.

The crystal orientation of the copper electroplating layer before the MIT folding resistance test is (111) crystal orientation degree index of 1.36, and electroplating is performed using a PR current from the surface of the copper electroplating layer to a film thickness range of 40%. For this purpose, the same procedure as in Example 1 was conducted except that a PR current was passed through the anodes 24r to 24t, and a two-layer flexible wiring board of Example 2 was produced.
Example in which the difference in crystal orientation ratio [(200) / (111)] expressed by the X-ray orientation index before and after the MIT folding resistance test is 0.05, the crystallite diameter is 363 nm, and the arithmetic surface roughness Ra is 0.18 μm. Sample 2 gave good results of 247 in the MIT fold resistance test.

The crystal orientation of the copper electroplating layer before the MIT bending resistance test was (111) crystal orientation degree index of 1.37, and the electric current was measured using PR current from the surface of the copper electroplating layer to a film thickness range of 40%. In order to perform the plating, a PR current was passed through the anodes 24r to 24t, and the same procedure as in Example 1 was performed except that the iron ion concentration was changed to 0.1 g / liter, and a two-layer flexible wiring board of Example 3 was produced. .
Example in which the difference in crystal orientation ratio [(200) / (111)] expressed by the X-ray orientation index before and after the MIT folding resistance test is 0.05, the crystallite diameter is 327 nm, and the arithmetic surface roughness Ra is 0.20 μm. The sample of 3 obtained a result of 180 times in the MIT folding resistance test.

(Comparative Example 1)
The crystal orientation of the copper electroplating layer before the MIT folding resistance test is (111) crystal orientation degree index of 0.98, and electroplating using PR current from the surface of the copper electroplating layer to a film thickness range of 8%. Thus, a PR layer was passed through the anode 24t, and the anode current density was changed to 80% of Example 1, and the same procedure as in Example 1 was performed to produce a two-layer flexible wiring board of Comparative Example 1. .
Comparative example in which the difference in crystal orientation ratio [(200) / (111)] expressed by the X-ray orientation index before and after the MIT body foldability test is 0.02, the crystallite diameter is 280 nm, and the arithmetic surface roughness Ra is 0.15 μm. Sample No. 1 was a result in which the improvement effect of 135 times was not observed in the MIT folding resistance test.

(Comparative Example 2)
The crystal orientation of the copper electroplating layer before the MIT bending resistance test is (111) crystal orientation degree index is 0.85, and electroplating is performed with PR current from the surface of the copper electroplating layer to a film thickness range of 5%. Therefore, a substrate for two-layer flexible wiring of Comparative Example 2 was produced in the same manner as in Example 1 except that a PR current was passed through the anode 24t and the current density of the anode was changed to 50% of Example 1.
Comparative example in which the difference in crystal orientation ratio [(200) / (111)] expressed by the X-ray orientation degree index before and after the MIT folding resistance test is 0.01, the crystallite diameter is 195 nm, and the arithmetic surface roughness Ra is 0.16 μm. The sample of 2 was a result in which the improvement effect of 83 times was not seen in the MIT folding resistance test.

(Comparative Example 3)
The crystal orientation of the copper electroplating layer before the MIT folding resistance test is (111) crystal orientation degree index of 1.06, and electroplating using PR current from the surface of the copper electroplating layer to a film thickness range of 9%. Thus, a PR layer was passed through the anode 24t, and the anode current density was changed to 90% of Example 1, and the same procedure as in Example 1 was performed to produce a two-layer flexible wiring board of Comparative Example 3. .
Comparative example in which the difference in crystal orientation ratio [(200) / (111)] expressed by the X-ray orientation index before and after the MIT body foldability test is 0.02, the crystallite diameter is 190 nm, and the arithmetic surface roughness Ra is 0.11 μm. The sample of 3 was a result in which the improvement effect of 141 times was not seen in the MIT folding resistance test.

1 Polyimide film (resin film substrate)
DESCRIPTION OF SYMBOLS 2 Base metal layer 3 Copper thin film layer 4 Copper electroplating layer 5 Copper layer 6 Two-layer flexible wiring board 10 Roll-to-roll sputtering apparatus 12 Housing 13 Unwinding roll 14 Can rolls 15a, 15b, 15c, 15d Sputtering cathode 16a Front feed roll 16b Rear feed rolls 17a, 17b Tension roll 18 Winding roll 20 Roll-to-roll type continuous plating apparatus 21 Electroplating tank 22 Unwinding roll 23 Reversing rolls 24a-24t Anode 26a-26k Feeding roll 28 Plating Liquid 28a Plating liquid level 29 Winding roll F Resin film substrate (polyimide film)
F2 Polyimide film with copper thin film layer (resin film substrate with copper thin film layer)
S 2 layer flexible wiring board

Claims (7)

In the substrate for a two-layer flexible wiring having a laminated structure in which a base metal layer made of a nickel alloy is not provided on the surface of the polyimide film and a copper layer is provided on the surface of the base metal layer,
The copper layer is composed of a copper thin film layer provided on the surface of the base metal layer and a copper electroplating layer provided on the surface of the copper thin film layer, and
The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] of the copper layer obtained before and after the execution of the folding resistance test specified in JIS C-5016-1994 is A substrate for two-layer flexible wiring, characterized by being 0.03 or more, a crystal orientation index in the (111) plane of the copper layer being 1.2 or more, and a crystallite diameter of 300 nm or more.   The board | substrate for 2 layers flexible wiring of Claim 1 whose film thickness of the said copper layer is 5 micrometers-12 micrometers. The copper layer is composed of a copper thin film layer provided on the surface of the base metal layer and a copper electroplating layer provided on the surface of the copper thin film layer,
The crystallite diameter is 200 nm to 400 nm in a thickness range of 10% or more of the film thickness of the copper electroplating layer in the polyimide film direction from the surface of the copper layer. Two-layer flexible wiring board.   4. The substrate for two-layer flexible wiring according to claim 1, wherein the surface roughness of the copper layer is an arithmetic average roughness Ra of 0.2 μm or less. 5. In a flexible wiring board provided with a base metal layer made of a nickel alloy without using an adhesive on the surface of the polyimide film, and a wiring having a laminated structure including a copper layer on the surface of the base metal layer,
The copper layer is composed of a copper thin film layer provided on the surface of the base metal layer and a copper electroplating layer provided on the surface of the copper thin film layer, and
The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] of the copper layer obtained before and after the execution of the bending resistance test specified in JIS-P-8115 is 0. 0.03 or more, a crystal orientation degree index in the (111) plane of the copper layer is 1.2 or more, and a crystallite diameter is 300 nm or more. The copper layer is composed of a copper thin film layer provided on the surface of the base metal layer and a copper electroplating layer provided on the surface of the copper thin film layer,
6. The flexible wiring board according to claim 5, wherein a crystallite diameter is 200 nm to 400 nm in a thickness range of 10% or more of the thickness of the copper electroplating layer in a direction from the surface of the copper layer to the polyimide film. .   7. The flexible wiring board according to claim 5, wherein a surface roughness of the copper layer is an arithmetic average roughness Ra of 0.2 μm or less.