JP6035678B2 - Method for manufacturing flexible wiring board and flexible wiring board - Google Patents

Description

  The present invention relates to a method for manufacturing a flexible wiring board in which a part of a copper layer is deposited by a copper electroplating method to improve folding resistance, and the 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 by utilizing its flexibility.

  For the production of such a flexible wiring board, a flexible wiring board (flexible copper clad laminate, also referred to as FCCL: Flexible Copper Clad Lamination) in which an ultrathin copper layer (corresponding to a copper thin film layer described later) and a resin layer are laminated is used. A method of wiring processing using a semi-additive method or the like is used.

  In this semi-additive method, a resist layer is formed on the base metal layer and the ultrathin copper layer of the copper clad laminate, the resist layer is patterned by photolithography, and the resist layer where the wiring is to be formed is removed. Copper plating is applied to the opening where the ultrathin copper layer obtained is exposed to form a wiring. After the wiring is formed, the resist is removed, and the ultrathin copper layer and the base metal layer are chemically etched to remove the ultrathin copper layer and the base metal layer portion. That is, without forming a resist on the surface of the copper layer of the flexible wiring board where conductor wiring is to be formed, copper is deposited by electrolytic copper plating, and an etching solution corresponding to the ultrathin copper layer and the underlying metal layer is used. Through the chemical etching process and washing with water, unnecessary portions of the ultrathin copper layer and the base metal layer are selectively removed to form a conductor wiring.

  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 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.

For the evaluation of the folding resistance of the copper foil, an MIT refraction resistance test (Folding Endurance Test) standardized by JIS C-5016-1994 or ASTM D2176 is industrially used.
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 flexible wiring board targeted by the present invention is a plating substrate in which a metal layer composed of a base metal layer and a copper plating layer formed on an at least one surface of a resin film base material without an adhesive is sequentially formed. It is difficult to improve the folding resistance by subjecting only the copper plating layer as disclosed in the technology to improve the folding resistance, and in addition to the copper wiring formation, a flexible wiring board manufacturing method with excellent folding resistance Was desired.

  In view of such a situation, the present invention provides a flexible wiring board excellent in folding resistance and a manufacturing method thereof.

  In order to solve the above-mentioned problems, the present inventors diligently studied the folding resistance of a copper layer formed on a polyimide resin layer by a plating method, and as a result, the change in crystal orientation before and after the folding resistance was tested. The influence on the results was confirmed, and the present invention was achieved.

According to a first aspect of the present invention, a base metal layer made of a nickel alloy is formed 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 is formed by a semi-additive method. In the method of manufacturing a flexible wiring board, after forming a copper thin film layer constituting a part of the copper layer on the surface of the base metal layer formed by the dry plating method, a resist layer is disposed at a place where no wiring is provided. Copper electroplating from the surface of the copper electroplating layer in the direction of the polyimide film when the copper electroplating layer constituting the remaining portion excluding the copper thin film layer of the copper layer is subjected to copper electroplating by a semi-additive method. In the thickness range of 10% or more and less than 100% of the layer thickness, the copper electroplating method using Periodic Reverse current that periodically performs short-time potential reversal. Thus, the difference in crystal orientation ratio [(200) / (111)] before and after the MIT fold resistance test specified in JIS C-5016-1994 of the obtained copper electroplating layer was formed. A flexible wiring board manufacturing method is characterized in that a flexible wiring board having d [(200) / (111)] of 0.03 or more is formed .

According to a second aspect of the present invention, the thickness of the copper electroplating layer formed by a copper electroplating method using a periodic reverse current that periodically reverses the potential for a short time in the first invention is It is the manufacturing method of the flexible wiring board characterized by being the thickness range of 10% or more and 30% or less of the film thickness of a copper electroplating layer from the surface to a polyimide film direction.

  3rd invention of this invention is equipped with the base metal layer which consists of a nickel alloy on the surface of a polyimide film without an adhesive agent, and the copper layer which consists of a copper thin film layer and a copper electroplating layer on the surface of the said base metal layer A flexible wiring board having a wiring of a laminated structure, wherein the copper electric plate is formed with a thickness range of 10% or more and 30% or less of the film thickness of the copper electroplating layer from the surface of the copper electroplating layer to the polyimide film direction. A copper electroplating layer having fewer grain boundaries than the layer on the polyimide film side is provided on the surface side of the plating layer, and the crystal orientation ratio before and after the MIT fold resistance test specified in JIS-C-5016-1994 [(200) / (111)] has a copper layer having a difference d [(200) / (111)] of 0.03 or more.

  The present invention provides a flexible wiring board obtained by a semi-additive method 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 copper thin film layer is provided on the surface of the base metal layer. 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 -5016-1994 is 0 0.03 or more, and the thickness of the copper layer is 5 μm to 12 μm. The copper layer includes a copper thin film layer formed on the surface of the base metal layer and the copper layer. It is comprised from the copper electroplating layer formed into a film on the surface of a thin film layer. In addition, the copper electroplating layer is formed by copper electroplating with a periodic reverse current that periodically performs a short-time potential reversal within a thickness range of 10% or more of the film thickness from the surface to the polyimide film direction. It is characterized by being.

  As a method for obtaining a flexible wiring board, a metal layer such as Ni, Cr, Cu or an alloy layer is formed on the polyimide film surface by vapor deposition or sputtering as in the present invention, and then a wiring pattern is obtained by a semi-additive method. In a flexible wiring board, in the step of forming a copper wiring by an electroplating method, an electroless plating method or a combination of both, the crystal orientation ratio obtained before and after the MIT fold resistance test (JIS C-5016-1994) [( 200) / (111)] is laminated on the polyimide film surface with a copper layer having a difference of 0.03 or more, whereby a flexible wiring board with improved folding resistance is obtained.

It is a cross-sectional schematic diagram of the substrate for flexible wiring. 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 a flexible wiring board. It is the figure which showed typically the time and current density of PR current in this invention.

  In the method for producing a flexible wiring board of the present invention, a wiring pattern is formed on a two-layer flexible wiring board by a semi-additive method. A copper layer serving as wiring is formed by the copper thin film layer and the copper electroplating layer of the two-layer flexible wiring board.

(1) Two-layer flexible wiring board First, a two-layer flexible wiring board used in the 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 and the copper thin film layer 3 are sequentially formed and laminated on at least one surface of the polyimide film from the polyimide film side.

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 thickness of a film is 25-75 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 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 thickness of the base metal layer 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 semi-additive 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 by the electroplating method cannot be ensured, leading to an appearance defect during electroplating. Even if the film thickness of the copper foil film layer exceeds 1 μm, there is no problem in quality of the two-layer flexible wiring board, but there is a problem that 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 deposition method, a CVD method, and the like. From the viewpoint of controlling the composition of the underlying metal layer, the sputtering method is desirable.

  To form a film on a resin film substrate by sputtering, the film can be formed by a known sputtering apparatus. To form a film on a long resin film substrate, use a known roll-to-roll sputtering apparatus. Can do. If this roll-to-roll sputtering apparatus is used, a base metal layer and a copper foil 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 which is the long resin film substrate 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.
Further, the copper thin film layer has a surface formed by a dry plating method and copper is added by a wet plating method to 0.4 to 4 μm.
It may be completed by thickening. Here, the wet plating method includes an electroless copper plating method and a copper electroplating method, and can be appropriately selected.

(3) Fabrication of wiring forming resist A resist layer of a portion where a wiring is to be formed is formed by a known photolithography method in which a resist layer such as a dry film resist is formed on a substrate on which a copper thin film layer is formed, and exposure and development are performed. The layer is removed and an opening is provided. The thickness of the resist layer may be 1 to 3 μm thicker than the film thickness of the copper electroplating layer described later. If the resist layer is approximately the same as the thickness of the copper electroplating layer, copper electroplating may protrude from the opening where the wiring is formed by copper electroplating, and the wiring cannot be formed. It becomes difficult to form a layer.

(4) Copper electroplating layer and film forming method The copper electroplating layer is formed by electroplating. The thickness of the copper electroplating layer is desirably 5 μm to 18 μm. Here, the electroplating method to be used is to perform electroplating using an insoluble anode or a soluble anode in a copper sulfate plating bath, and the composition of the copper plating bath to be used is for 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 for manufacturing the flexible wiring board according to the present invention.

  The polyimide film F2 with a copper thin film layer obtained by forming a base metal layer and a copper thin film layer and then formed with a resist layer pattern is unwound from the unwinding roll 22 and is plated in the electroplating tank 21. It is continuously conveyed while being repeatedly dipped in.

  The polyimide film F2 with a copper thin film layer is a metallized resin film after a copper layer is formed on the surface of the metal thin film by electroplating while being immersed in a plating solution, and a copper layer having a predetermined thickness is formed. The substrate is wound around a winding roll 29 as a two-layer flexible wiring substrate S which is a 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 14a.

  An electroplating circuit is configured by the power supply roll 26a, the anode 14a, the plating solution, the polyimide film F2 with a copper thin film layer, and the power source. 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 is provided outside the electroplating tank 21.

  In the case of an insoluble anode, copper ions are supplied to the plating solution 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. In the case of a soluble anode, a phosphorus-containing copper ball is used for the anode, and copper ions are also supplied.

  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 obtained at the anodes 24m to 24r.

Thus, discoloration of the copper layer can be prevented by increasing the current density. In particular, when the current density is high when the thickness of 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 reversal current of the PR 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 flexible wiring board according to the present invention, it is formed using a PR current in a range of 10% or more from the surface of the film thickness of the copper electroplating layer.
When using a PR current, the reversal current is preferably 1 to 9 times the positive current.
The reversal current time ratio is preferably about 1 to 10%.
Further, the period during which the next reversal current of the PR current is applied 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 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 may be passed through one or more anodes from the downstream side of the transport 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, a PR current flows at least in the anode 24r, and a PR current flows in the anode 24q, the anode 24p, and the anode 24o as necessary.
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 flexible wiring board according to the present invention, if 10% of the film thickness is formed with a PR current from the surface of copper electroplating in the polyimide direction, before and after the implementation of the folding resistance test (JIS C-5016-1994). Since the difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] of the copper layer can be 0.03 or more, as a result, the folding resistance test (MIT test) is improved. Can be expected.

  The reason why copper electroplating using a PR current is desirable is that when the current is reversed, the copper crystal grain size of the copper electroplating layer can be about 200 nm or more, and the grain boundaries can be reduced. This is because the starting point of cracking can be reduced.

  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 Therefore, if 10% or more of the film thickness from the surface of the copper electroplating layer of the 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.

  After the copper electroplating layer is formed, the resist can be removed with an alkaline aqueous solution such as a caustic soda solution, and the copper thin film layer and the base metal layer can be removed for a known semi-additive solution such as a ferric chloride aqueous solution. An etchant may be used.

(5) Features of the copper electroplating layer The copper layer of the flexible wiring board of the present invention is characterized by the crystal orientation ratio before and after the MIT fold resistance test (JIS C-5016-1994) [(200) / (111)]. Difference d [(200) / (111)] is 0.03 or more. In such a 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.
Further, the copper layer of the flexible wiring board of the present invention is obtained by the above-described copper layer deposition method, and the difference d [(200 ) in the crystal orientation ratio [(200) / (111)] before and after the MIT fold resistance test. ) / (111)] is 0.03 or more. The crystal orientation of the copper electroplating layer can be determined from the Wilson orientation degree index of X-ray diffraction.

  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 crystal grain 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 board 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.

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-d, respectively, and a polyimide film (Kapton registered trademark, manufactured by Toray DuPont, Inc.) ) Was evacuated, and argon gas was introduced to keep the inside of the apparatus 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.

  A dry film resist layer is formed on the obtained polyimide film with a copper thin film layer, exposed and developed, and after patterning the resist layer, copper electroplating is performed using the plating apparatus 20 to form a copper electroplated wiring layer. did. The plating solution is a copper sulfate aqueous solution having a pH of 1 or less, and the anodes 24m to 24r have the maximum current density (except for the reversal current of the PR current) unless otherwise specified. The current density was adjusted to 8.5 μm. Thereafter, after removing the resist, the base metal layer was dissolved using ferric chloride as an etching solution to obtain a wiring board.

  In the bending resistance test, a test pattern of JIS-C-5016-1994 was formed using the above wiring board 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 24r to produce the two-layer flexible wiring board of Example 1.
Sample of Example 1 of the difference between the crystal orientation ratio expressed by X-ray orientation degree index before and after the MIT folding endurance is test [(200) / (111)] is 0.04, well that 536 times with MIT resistance bending resistance test Results were obtained.

In order to perform electroplating using a PR current from the surface of the copper electroplating layer to a film thickness range of 30%, the same procedure as in Example 1 was performed except that a PR current was passed through the anodes 24p to 24r. A two-layer flexible wiring board was produced.
Sample of Example 2 of the difference between the crystal orientation ratio expressed by X-ray orientation degree index before and after the MIT resistance breaking resistance test [(200) / (111)] is 0.09, the good that 736 times with MIT resistance bending resistance test Results were obtained.

(Comparative Example 1)
In order to perform electroplating using PR current from the surface of the copper electroplating layer to a film thickness range of 8%, PR current was passed through the anode 24r, and the current density of the anode was set to 80% of Example 1, It carried out similarly to Example 1 and produced the two-layer flexible wiring board of the comparative example 1.
Crystal orientation ratio expressed by X-ray orientation degree index before and after the MIT resistance breaking resistance test [(200) / (111)] difference of Comparative Example 1 0.02 sample, improvement of 135 times with MIT resistance bending resistance test The result was ineffective.

(Comparative Example 2)
In order to carry out electroplating with a PR current from the surface of the copper electroplating layer to a film thickness range of 5%, the PR current was passed through the anode 24r, and the current density of the anode was changed to 50% of that of the first embodiment. In the same manner as in Example 1, a two-layer flexible wiring board of Comparative Example 2 was produced.
Crystal orientation ratio expressed by X-ray orientation degree index before and after the MIT resistance breaking resistance test [(200) / (111)] difference of Comparative Example 2 0.01 samples, improvement of 83 times in MIT resistance bending resistance test The result was ineffective.

1 Polyimide film (resin film substrate)
2 Substrate metal layer 3 Copper thin film layer 6 Two-layer flexible wiring board 10 Roll-to-roll sputtering device 12 Housing 13 Unwinding roll 14 Can rolls 15a, 15b, 15c, 15d Sputtering cathode 16a Front feed roll 16b Rear feed roll 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-r Anode 26a-k Feeding roll 29 Winding roll F Polyimide film (resin film) substrate)
F2 Polyimide film with copper thin film layer (resin film substrate with copper thin film layer)
S 2 layer flexible wiring board

Claims (2)

In the method of manufacturing a flexible wiring board, 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 by a semi-additive method,
After forming a copper thin film layer that constitutes a part of the copper layer on the surface of the base metal layer formed by dry plating, a resist layer is placed at a place where no wiring is provided and copper electroplating is performed by semi-additive method. 10% or more of the thickness of the copper electroplating layer from the surface of the copper electroplating layer toward the polyimide film when the predetermined thickness is obtained by the copper electroplating layer constituting the remainder excluding the copper thin film layer of the layer, In the thickness range of 30% or less, the copper electroplating layer is formed by a copper electroplating method using Periodic Reverse current that periodically performs a short-time potential reversal, and the obtained copper layer conforms to JIS-C-5016-1994. The difference d [(200) / (111)] of the crystal orientation ratio [(200) / (111)] before and after the implementation of the specified MIT folding resistance test is 0.03 or more. Method of manufacturing a flexible wiring board and forming a reluctance wiring board. A flexible wiring board having a multilayer metal structure comprising a base metal layer made of a nickel alloy on the surface of a polyimide film and a copper layer made of a copper thin film layer and a copper electroplating layer on the surface of the base metal layer Because
From the surface of the copper electroplating layer in the direction of the polyimide film, with a thickness range of 10% to 30% of the thickness of the copper electroplating layer as a boundary, the surface of the copper electroplating layer is crystallized from the layer on the polyimide film side A copper electroplating layer with few grain boundaries is provided, and the difference d [(200) / () in the crystal orientation ratio [(200) / (111)] before and after the MIT fold resistance test specified in JIS-C-5016-1994. 111)] has a copper layer of 0.03 or more.