JP2016205967A - Method for determining quality of polyimide film, copper-clad laminate sheet using polyimide film and method for manufacturing flexible wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for determining the quality of a polyimide film for flexible wiring boards for manufacturing a flexible wiring board having a small warp and torsion, a high yield thereby and high productivity.SOLUTION: The method for determining the quality of a polyimide film is used for a flexible wiring board having a metal layer laminated on the polyimide film. The polyimide film has MD and TD directions orthogonal in the flat surface thereof. In the polyimide film, an orientation angle of molecules in a plane showing the maximum orientation being the maximum value obtained by measuring orientation in the flat surface is 0 degree or more and 30 degrees or less in the absolute value of a difference between the TD and MD directions of the polyimide film, and a surface orientation degree ratio of the front to the rear of the polyimide film is less than 1.0.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for determining pass / fail of a polyimide film used for a chip on film (COF), a flexible printed circuit (FPC), and the like, and a copper-clad laminate using the polyimide film The present invention relates to a manufacturing method of a flexible wiring board (FCCL: Flexible Copper Clad Laminate).

  Flexible wiring boards take advantage of their freely bendable properties, such as wiring parts that require bending of moving parts of hard disk read / write heads and printer heads, and small gaps in small electronic devices such as mobile phones and liquid crystal display devices. Widely used in industry for electronic parts, optical parts, packaging materials, etc. The flexible wiring board to be used is generally a wiring process using a subtractive method or semi-additive method for a flexible copper-clad laminate with a laminated structure consisting of a copper layer and a resin film such as a polyimide film. It is made with.

  The subtractive method, which is one of the wiring processing methods, is a method of removing unnecessary portions other than wiring by etching the copper layer of the copper-clad laminate. Specifically, after forming a photoresist layer on the surface of the copper layer of the copper clad laminate, the photoresist layer is subjected to patterning to expose the surface of the copper layer other than the portion to be left as the conductor wiring. The exposed portion of the copper layer is selectively removed using an etching solution that dissolves copper to form a conductor wiring, and then washed with water. Then, tin plating etc. are given to wiring as needed, and after tin plating, a solder resist is apply | coated and hardened in a required part, a solder resist film is formed, and a flexible wiring board is completed. Electronic components such as semiconductor elements are mounted on the completed flexible wiring board to form a circuit device.

  Thus, in the process of manufacturing the flexible wiring board, heat is applied to the copper-clad laminate by curing by a solder resist method or the like. Here, the copper clad laminate is a laminate of a copper layer and a resin film, and both the copper layer and the resin film undergo expansion and contraction due to heat and wiring processing. Further, since the copper layer and the resin film are made of different materials, there is a difference in expansion / contraction. For this reason, warpage and twisting behavior due to the difference between the expansion and contraction are problematic.

  In addition, in general, the thickness of the resin film is larger in the flexible wiring board. Moreover, since copper is selectively removed from the surface of the flexible wiring board after wiring processing, the area occupied by the resin film is larger than the area occupied by copper. Therefore, the influence of the expansion and contraction of the resin film is relatively larger than that of the metal film layer. The warp and twist of the resin film itself, and those factors after the resin film is heated are the copper layer and the resin layer described above. This is a major cause of defects rather than warping and twisting due to the difference in expansion and contraction of the material.

  The cause of this warp and twist is due to stretching or baking at a high temperature during the manufacturing process of the polyimide film used for the resin film. The resin film that has undergone these processes is the orientation of molecular chains in the resin film width direction and Internal stress due to distortion occurs, and as a result, it appears as warping and twisting.

  The warping and twisting of the resin film is related to the alignment of the wiring pattern when connecting the flexible wiring board and an electronic component such as a semiconductor element by reducing the wiring pitch of the flexible wiring board. It is becoming strict to meet the required accuracy with progress.

  Therefore, Patent Document 1 proposes a method for producing a resin film that reduces twisting with respect to a polyimide film that is a raw material of a copper-clad laminate. However, the polyimide film of Patent Document 1 only uses the orientation strengths of 45 degrees and 135 degrees as an index, and does not mention the orientation angle related to twist. In addition, warpage and twist affect not only the orientation angle but also the difference between the front and back, and furthermore, when processed into a copper clad laminate, the twist is amplified by the difference between the internal stress of copper and the internal stress of the resin film, This scope of management is insufficient. This is because the wiring width required in recent years is about 10 to 15 μm, and a flexible wiring board that does not warp or twist is strongly demanded.

  In particular, in an electronic device such as a liquid crystal display, there is a tendency that the wiring length drawn by the flexible wiring board increases due to the increase in size and thickness. Due to this increase in wiring length, in the assembly process of electronic equipment, when an electrode on a flexible wiring board is connected to an electrode that is not on another flexible wiring board, an electrode accompanying warping or twisting of the flexible wiring board. The alignment time between each other has increased, and the productivity reduction in the electronic device assembly process has become a problem.

  The background of these times is also a factor, and in order to cope with the wiring width specifications required in recent years, it is necessary to adjust parameters for each lot of copper clad laminates. Such parameter adjustment for each lot has various adverse effects such as labor for process adjustment, raw material loss at the time of adjustment, deterioration of product quality variation, and yield reduction. Therefore, when a flexible wiring board that has not been studied for warping and twisting is used in recent small electronic devices, there is a problem in that the yield decreases and the productivity becomes a flexible wiring board.

JP 2014-093317 A

  An object of the present invention is to provide a polyimide film quality determination method that can produce a flexible wiring board with high yield and high yield because warpage and twist are small in the polyimide film quality determination method. And

  The present inventors diligently studied about a polyimide film which is a resin film used as a raw material for a copper-clad laminate in a copper-clad laminate production process that is one of the production processes of a flexible wiring board. As a result, the orientation of the polyimide film used in the copper-clad laminate is evaluated by a predetermined apparatus, and a flexible wiring board is manufactured using the polyimide film whose orientation is limited to a predetermined range as the resin film of the copper-clad laminate. As a result, it was discovered that the warping and twisting of the flexible wiring board was small. Therefore, the polyimide film manufactured by the polyimide film quality determination method using the orientation of the polyimide film is found to have a high yield and high productivity of copper-clad laminates and flexible wiring boards, completing the present invention. It came to do.

That is, the first of the present invention is a method for determining the quality of the polyimide film used for a flexible wiring board in which a metal layer is laminated on the polyimide film, wherein the polyimide film is composed of an aromatic diamine and 3,3 ′. The polyimide film has an imide bond composed of -4,4'-diphenyltetracarboxylic dianhydride, and the thermal expansion coefficient in the TD direction of the polyimide film is 10 ppm / K or more and 16 ppm / K or less. The polyimide film has an MD direction and a TD direction orthogonal to each other, and the polyimide film measures the orientation in the plane, and the orientation angle of molecules in the plane showing the maximum orientation which is the maximum value is the polyimide film. The absolute value of the difference in the TD direction or MD direction of the film is 0 degree or more and 30 degrees or less, and the polyimide film is Quality determination method of the polyimide film surface orientation ratio of the front and back being defined is less than 1.0.
Surface orientation degree ratio of front and back: The surface orientation of each polyimide film surface is measured on the laminated surface (A) and non-laminated surface (B) of the metal layer in the polyimide film, and the in-plane distribution of orientation on each surface Is converted into an ellipse to calculate the ellipticity (ellipticity = maximum orientation corresponding to the major axis of the ellipse / minimum orientation corresponding to the minor axis of the ellipse). Let the rate (A) be the surface orientation degree ratio of the front and back.

  A second aspect of the present invention is the polyimide film quality determination method according to the first aspect, wherein the orientation is measured by optical evaluation using birefringence.

  The third of the present invention is a step of laminating a polyimide film screened through the pass / fail judgment method according to the first or second invention, and a base metal layer and a copper layer on one surface of the polyimide film. And a method for producing a copper clad laminate.

  4th of this invention is a manufacturing method of a flexible wiring board including the process of performing wiring processing on the copper clad laminated board manufactured by the manufacturing method as described in 3rd invention.

  A fifth aspect of the present invention is the method for manufacturing a flexible wiring board according to the fourth aspect, wherein the wiring processing is performed by a subtractive method or a semi-additive method.

  According to the quality determination method of the present invention, the copper-clad laminate using the polyimide film that has been judged good and the flexible wiring board using the copper-clad laminate are suppressed in warping and twisting, and the assembly process of the electronic device In this case, the alignment becomes easy, the yield is high, and the productivity can be improved.

It is typical sectional drawing of the copper clad laminated board of this invention. It is a front view of one specific example of the roll-to-roll sputtering apparatus which is one embodiment of the dry plating of the present invention. It is a front view of one specific example of the roll-to-roll electroplating apparatus which is one Embodiment of the wet plating of this invention. It is a schematic diagram at the time of warpage and twist evaluation of the copper clad laminate of the present invention.

  Hereinafter, embodiments of the present invention will be described. The polyimide film quality determination method according to the present invention is such that, as a polyimide film, the in-plane molecular orientation angle indicating the maximum orientation, which is the maximum in-plane orientation, is the absolute difference between the TD direction and the MD direction of the polyimide film. This is a polyimide film quality determination method in which the value is 0 degree or more and 30 degrees or less, and the surface orientation degree ratio, which is the ratio of the front and back molecular orientations, is less than 1.0. Moreover, the manufacturing method of the flexible wiring board which concerns on this invention is a manufacturing method using the polyimide film screened through the quality determination method, Comprising: As shown in FIG. 1, it laminates | stacks copper on the one surface side of a resin film A flexible copper-clad laminate forming step and a method of manufacturing a flexible wiring board including a step of etching copper to form a copper wiring.

(1) Copper-clad laminate First, a copper-clad laminate, which is a premise for manufacturing a flexible wiring board, will be described. Copper-clad laminates used in the production of flexible wiring boards are "copper foil / adhesive layer / resin film" in which electrolytic copper foil or rolled copper foil is bonded to an insulating resin film as a base layer using an adhesive. A copper-clad laminate having a three-layer structure (hereinafter also referred to as a three-layer copper-clad laminate) and a “copper layer or copper foil / resin film” in which a copper layer or copper foil and a resin film are directly joined. It can be classified into a copper clad laminate having a structure (hereinafter also referred to as a copper clad laminate).

  The copper-clad laminate targeted by the present invention can be further divided into the following three types. That is, a copper clad laminate (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, and a copper clad laminate obtained by applying a resin film varnish to a copper foil to form an insulating layer. (Commonly called cast substrate) and copper-clad laminate (commonly called laminate substrate) obtained by laminating a resin film on copper foil.

  Among these, the metallizing substrate can make the copper layer thin, and the smoothness of the interface between the resin film and the copper layer or the base metal layer is high, so the cast substrate, the laminate substrate, or the three-layer copper-clad laminate It is suitable for miniaturization of wiring pitch compared to

  On the other hand, in cast substrates, laminate substrates, or three-layer copper-clad laminates, the surface roughness on the resin film side of the copper foil surface is increased in order to improve the adhesion due to the anchor effect at the interface between the resin film and the copper foil. Therefore, the smoothness of the interface between the resin film and the copper foil cannot be expected. Therefore, it is desirable that the copper-clad laminate according to the present invention is a copper-clad laminate and a metalizing substrate is used.

(2) Metalizing board Next, the metalizing board which is one embodiment of the present invention is explained. FIG. 1 is a schematic cross-sectional view showing an example of a metallizing substrate (copper-clad laminate 6).
The base metal layer 2, the copper thin film layer 3, and the copper electroplating layer 4 are laminated in order from the resin film 1 side on at least one surface of the resin film 1 using the polyimide film, and the copper layer 5 includes the copper thin film layer 3 and the copper electric layer. And a plating layer 4.

  The base metal layer 2 is formed on the surface of the resin film 1 mainly by a dry plating method such as a vapor deposition method or a sputtering method. Here, the base metal layer 2 ensures reliability such as adhesion and heat resistance between the resin film 1 and the copper layer 5. Therefore, it is preferable that the material of the base metal layer 2 is any one of nickel, chromium, or an alloy containing these as a main component. In particular, a nickel-chromium alloy is suitable in consideration of adhesion strength and ease of etching during wiring production.

  The nickel-chromium alloy used for the base metal layer 2 desirably has a chromium content of 15% by mass or more and 22% by mass or less, whereby excellent corrosion resistance and migration resistance can be obtained. Among these, nickel / chromium alloy of 20% by mass chromium is distributed as a nichrome alloy and can be easily obtained as a sputtering target of the magnetron sputtering method. Further, chromium, vanadium, titanium, molybdenum, cobalt, or the like may be added to an alloy containing nickel or chromium. Further, a plurality of nickel-chromium alloy thin films having different chromium concentrations may be laminated to form a base metal layer having a concentration gradient with respect to the nickel-chromium alloy.

  The film thickness of the base metal layer 2 is desirably 3 to 50 nm. If the film thickness of the base metal layer 2 is less than 3 nm, the adhesion between the resin film 1 made of a polyimide film and the copper layer 5 cannot be maintained, and the corrosion resistance and migration resistance may be inferior. On the other hand, if the thickness of the base metal layer 2 exceeds 50 nm, it may be difficult to sufficiently remove the base metal layer 2 when wiring processing is performed by a subtractive method or a semi-additive method. Thus, when the removal of the base metal layer 2 is insufficient, there is a concern about problems such as migration between wirings.

  Similar to the base metal layer 2, the copper thin film layer 3 is formed on the surface of the base metal layer 2 mainly by a dry plating method such as vacuum deposition, sputtering, or ion plating. The copper thin film layer 3 is mainly composed of copper, and the film thickness is desirably 10 nm or more and 1 μm or less. When the film thickness of the copper thin film layer 3 is less than 10 nm, it becomes difficult to ensure conductivity when a copper electroplating layer 4 described later is formed by an electroplating method, which leads to poor appearance during electroplating. Even if the film thickness of the copper thin film layer 3 exceeds 1 μm, there is no problem in the quality of the copper-clad laminate, but 1 μm or less is desirable because it causes a problem of lowering productivity.

  As for the film thickness of the copper layer 5 which combined the copper electroplating layer 4 and the copper thin film layer 3, 12 micrometers or less are desirable. When the film thickness of the copper layer 5 exceeds 12 μm, chemical etching wiring processing (wiring processing such as a subtractive method) to a flexible wiring board having a wiring pitch of 50 μm or less becomes difficult. Moreover, although the electrical conductivity as a flexible wiring board will fall, so that the film thickness of the copper layer 5 becomes thin, if this film thickness shall be 5 micrometers or more, it will become a flexible wiring board with sufficient electroconductivity.

  The polyimide film used for the resin film 1 is an aromatic polyimide film. Since the characteristics of the polyimide film are governed by an imide compound comprising an aromatic diamine and an aromatic acid anhydride, in the method for producing a flexible wiring board according to the present invention, the polyimide film is composed of an aromatic diamine and 3,3′- It contains an imide compound composed of 4,4-diphenyltetracarboxylic dianhydride. Aromatic diamines include diaminobenzenes such as paraphenylenediamine. For example, “UPILEX (registered trademark, manufactured by Ube Industries)” is known as a polyimide film having such an imide bond. “Upilex®” film is readily available on the market.

  The polyimide film is a polyimide film having a thermal expansion coefficient in the TD direction of 10 ppm / K or more and 16 ppm / K or less by stretching. When the thermal expansion coefficient is in such a range, warping and twisting of the flexible wiring board can be suppressed. In addition, the thermal expansion coefficient in this specification means the thermal expansion coefficient when the temperature is increased at a rate of 5 ° C./min within the range of 50 ° C. to 200 ° C.

  The thickness of a polyimide film should just be the thickness which can keep a shape as a softness | flexibility and a film, and thickness 10 micrometers-50 micrometers are desirable.

(3) Manufacturing method of metallizing substrate Next, the manufacturing method of the metalizing substrate which is one Embodiment of this invention is demonstrated. As an example of a manufacturing method of a metalizing substrate, it is manufactured through the following three steps (a) to (c).

(A) Dehydration step: A dehydration treatment is performed on a polyimide film used as a resin film.
(B) Dry plating process: A base metal layer is formed on at least one surface of a dehydrated polyimide film by a dry plating method such as sputtering, and a copper thin film layer is formed on the surface of the base metal layer by a dry plating method. To do.
(C) Wet plating process: Copper electroplating by a wet plating method such as an electroplating method in an aqueous copper sulfate solution on the surface of the copper thin film layer of the resin film with a copper thin film layer on which the base metal layer and the copper thin film layer are formed. Is deposited.

  Hereinafter, a method for manufacturing the metalizing substrate will be described in detail.

(A) Dehydration process It is preferable to dehydrate the polyimide film used for the metalizing substrate before performing dry plating described below. If this dehydration is insufficient, moisture will be taken into the base metal layer and oxidized, and sufficient chemical etching cannot be performed when a flexible wiring board using the subtractive method is produced.

  For this reason, there is a problem that the insulation reliability of the obtained flexible wiring board is lowered due to the fact that the base metal layer remains undissolved between the edges of the wiring and between the wirings, and a metal component called an etching residue remains.

Since the polyimide film is wound in a roll shape, the dehydration process is continuously performed while the polyimide film is conveyed by roll-to-roll. The method of the dehydration treatment is not particularly limited, and a known method such as a method of heating in the air or in a reduced pressure atmosphere using a heating device such as a heater, a method of performing plasma treatment or ion beam treatment in a reduced pressure atmosphere, or the like may be used. Good.
Using these methods, dehydration treatment is performed so that wrinkles are not generated in the polyimide film.

(B) Dry plating process In order to form a base metal layer or a copper thin film layer on a polyimide film, for example, a roll-to-roll sputtering apparatus shown in FIG. 2 may be used. The dry plating method is not limited to this sputtering, and vacuum deposition, ion plating, or the like may be used.

The roll-to-roll sputtering apparatus 10 shown in FIG. 2 has a structure in which most of its constituent elements are housed in a rectangular parallelepiped chamber 12. The shape of the chamber 12 is not limited to the rectangular parallelepiped shape of FIG. 2, and may be other shapes such as a cylindrical shape as long as a reduced pressure state of about 10 ⁻⁴ Pa to 1 Pa can be maintained.

  Inside this chamber 12, an unwinding roll 13 from which a resin film F1 made of a polyimide film is drawn, a free roll 11 that rotates following the conveyance of the resin film F1, and a can roll 14 that winds and cools the resin film F1 around the outer peripheral surface. A magnetron cathode type sputtering cathode 15, a front feed roll 16a and a rear feed roll 16b provided adjacent to the can roll 14, tension rolls 17a and 17b equipped with a tension sensor, a base metal layer and a copper thin film layer are formed. A take-up roll 18 is provided for winding the resin film F <b> 2 in a roll shape.

  Among these, the unwinding roll 13, the can roll 14, the front feed roll 16 a, and the take-up roll 18 are provided with servo motors that are rotation driving means. Further, each of the unwinding roll 13 and the winding roll 18 maintains the tension balance of the resin film being conveyed by torque control using a powder clutch or the like. The outer surfaces of the free rolls 11a and 11b, the can roll 14 and the tension rolls 17a and 17b are finished with hard chrome plating.

  A refrigerant and a heating medium supplied from the outside of the chamber 12 circulate inside the can roll 14, and the outer peripheral surface of the can roll 14 can be adjusted to a substantially constant temperature. Sputtering cathodes 15 a to 15 d are arranged facing the outer peripheral surface of the can roll 14. The dimensions of the sputtering cathodes 15a to 15d in the width direction of the outer peripheral surface of the can roll 14 are preferably larger than the width of the resin film F1.

(C) Wet Plating Step Next, the copper electroplated layer is formed by the wet plating method on the resin film F2 with the copper thin film layer on which the copper thin film layer is formed by the dry plating method. Examples of the apparatus for performing the wet plating method include an apparatus for performing electroplating using an insoluble anode in a plating bath such as copper sulfate. In addition, the composition of the copper plating bath to be used may be a commonly used high-throw copper sulfate plating bath for printed wiring boards.

  FIG. 3 shows a roll-to-roll electroplating apparatus 20 (hereinafter also referred to as electroplating apparatus 20) as a specific example of such an electroplating apparatus. The electroplating apparatus 20 is configured to perform plating in the electroplating tank 21 by continuously transporting a resin film F2 with a copper thin film layer obtained by forming a base metal layer and a copper thin film layer in a roll-to-roll manner. A copper electroplating layer is formed on the surface of the metal thin film by electroplating while being immersed in the plating solution 28 by repeating the immersion in the solution 28 and the non-immersion state. Thereby, the copper clad laminated board S in which the copper layer of the predetermined | prescribed film thickness was formed can be produced. In addition, the conveyance speed of the resin film F2 with a copper thin film layer has the preferable range of several m-several dozen m / min.

If it demonstrates concretely, the resin 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 resin film F2 with a copper thin film layer that has entered the plating solution 28 is pulled up above the plating solution surface 28a after the conveying direction is reversed by the reversing roll 23.
An anode 24a and an anode 24b are respectively provided at positions facing the resin film F2 with a copper thin film layer that runs on the transport path immediately before and immediately after the reversal by the reversing roll 23. A voltage is applied between each anode and a power supply roll. For example, an electroplating circuit is configured by the power supply roll 26a, the anode 24a, a plating solution, a resin film F2 with a copper thin film layer, and a power source.
Thereby, an electroplating process is given to the surface of the resin film F2 with a copper thin film layer.

  That is, by 11 power supply rolls 26a to 26k and 10 reversing rolls 23, the resin film F2 with a copper thin film layer is immersed in the plating solution 28 several times and in a non-immersed state (total of 10 times in FIG. 3). Repeatedly, a copper layer is gradually formed on the copper thin film layer of the resin film F2 with a copper thin film layer, and the copper-clad laminate S is formed. The copper-clad laminate S whose direction of conveyance has been reversed by the final reversing roll 23 passes through the power supply roll 26k and is then wound around the winding roll 29. As the insoluble anode constituting each anode, a known one whose surface is coated with a conductive ceramic can be used.

  A mechanism for supplying copper ions to the plating solution 28 is provided outside the electroplating tank 21. It is preferable to supply the copper ions to the plating solution 28 with a copper oxide aqueous solution, a copper hydroxide aqueous solution, a copper carbonate aqueous solution or the like. Or the method of adding a trace amount iron ion in a plating solution, melt | dissolving an oxygen-free copper ball | bowl, and supplying copper ion may be used.

The current density during electroplating is preferably increased stepwise from the anode 24a to the downstream in the transport direction so that the maximum current density is obtained from the anodes 24q to 24t.
Thus, discoloration of the copper layer can be prevented by increasing the current density. Further, since the color change tends to occur in the current density is high and the copper layer when the thickness of the copper layer is thin, the current density in the plating 0.1~8A / dm ² is preferred. When this current density is higher than 8 A / dm ^2, there is a possibility that a poor appearance of the copper electroplating layer may occur.

  As described above, a copper electroplating layer is formed to obtain a metallized substrate of a copper-clad laminate. The obtained metallizing substrate is cut with a slitter to a width suitable for wiring processing.

(4) Manufacturing method of flexible wiring board Next, the manufacturing method of the flexible wiring board which concerns on this invention is demonstrated in detail. First, as a wiring processing method of a flexible wiring board with a fine wiring pitch, the following is known as a subtractive method.

  In the metalizing substrate cut to a width suitable for wiring processing, a photoresist film is formed on the surface of the copper layer, and this photoresist film is exposed and developed to form a desired pattern. Next, using the formed photoresist pattern as a mask, the exposed copper layer is etched to form a wiring pattern composed of a copper layer and a base metal layer having a shape substantially similar to the photoresist pattern. Next, the photoresist layer is peeled off with an alkaline solution or the like. After stripping and removing the photoresist layer, tin plating is performed as necessary, and a solder resist film is formed to produce a flexible wiring board.

In the photoresist film forming step of forming a photoresist film, a liquid photoresist is applied to the surface of the copper layer by a known coating method such as screen printing, and is heated and dried after coating.
When the liquid photoresist is heated and dried, the copper clad laminate is also heated and subjected to heat treatment.
The drying conditions for the liquid photoresist are a temperature range of 100 ° C. to 150 ° C. and a drying time of 5 minutes or more.

  The photoresist film may be a dry film type photoresist (dry film) laminated on the surface of the copper layer. When laminating a dry film resist, it is pressure-contacted at a temperature of 100 ° C. to 150 ° C. for several seconds or more by a known laminating method. Although it is instantaneous, heat treatment to be heated is performed on the copper clad laminate even when laminating a dry film resist.

  Next to the photoresist film forming step is an exposure step. In the exposure process, the photoresist film formed on the surface of the copper layer of the copper clad laminate is irradiated with ultraviolet rays through a photomask having a predetermined pattern in order to form a wiring pattern on the copper layer. Then, an exposed portion is formed.

The exposure process is followed by a development process. In the developing process, the exposed photoresist is dissolved and removed with a developing solution to form a photoresist pattern having openings.
The developing step is performed by showering the developer with an alkaline solution such as a sodium carbonate aqueous solution or a triethanolamine aqueous solution at a temperature of 30 ° C. to 50 ° C., for example.

  Following the development process is a chemical etching process. After the photoresist pattern is formed, the copper-clad laminate is processed into a wiring pattern in this chemical etching process. The etchant preferably has a composition capable of etching a copper layer or a base metal layer (hereinafter also referred to as a metal film layer).

  As an etching solution to be used, for example, a cupric chloride aqueous solution or a ferric chloride aqueous solution is used. As the processing conditions, for example, the etching process is performed by spraying an etching solution under the conditions of a temperature of 40 to 50 ° C., a shower pressure of 0.1 to 0.7 MPa, and a processing time of 20 to 120 seconds. At this time, the underlying metal layer is also etched away. Moreover, you may add a base metal layer removal process by shower-injecting base metal layer removal agents, such as permanganate aqueous solution, as needed.

  When the wiring pattern is formed through this chemical etching process, the photoresist pattern is stripped in the photoresist stripping process. In the photoresist stripping step, the photoresist pattern is dissolved and removed with an alkaline solution such as an aqueous sodium hydroxide solution.

  After the photoresist removal step, the chemical solution is removed by washing with water, and then dried by draining with an air knife or the like. The chemical etching process and the photoresist stripping process are performed continuously.

  Thereafter, a tin plating step and a solder resist film forming step are performed as necessary. In the tin plating step, a tin plating layer is formed on the surface of the copper layer wiring formed by the chemical etching step by a known electroless tin plating method. After the tin plating step, the chemical solution is removed by washing with water, and then dried by draining with an air knife or the like. After drying, the process proceeds to the next solder resist film forming step.

  In the solder resist film forming step, a predetermined pattern of the solder resist is printed on the wiring pattern by screen printing. As the solder resist, polyimide (made by Hitachi Chemical Co., Ltd .: SN-9000) or urethane (made by Nippon Polytech Co., Ltd .: NPR-3300) can be used, both of which are hardened by heating. is there.

After the solder resist printing, the solder resist is heated and cured.
The heat curing conditions of the solder resist are heated to a temperature range of 100 ° C to 150 ° C. Even with solder resist heat curing, the copper clad laminate is subjected to heat treatment.

  Through the above steps, the product is completed as a flexible wiring board product. And if necessary, it is cut into a size that facilitates mounting of electronic components.

(5) Polyimide film quality determination method Next, a polyimide film quality determination method according to an embodiment of the present invention will be described. The polyimide film that can be used for the copper-clad laminate and the flexible wiring board of the above embodiment is (I) measuring the orientation in the plane, and the orientation angle of the molecules in the plane showing the maximum orientation, which is the maximum value, The absolute value of the difference in the TD direction or MD direction of the polyimide film is 0 degree or more and 30 degrees or less, and (II) the front and back surface orientation ratio is less than 1.0. In the present specification, the orientation means a parameter representing the arrangement of molecular chains in the film plane, such as a refractive index in optical evaluation. By setting the polyimide film in which molecular chains are arranged in a certain direction in such a range, warpage and twist of a copper-clad laminate or a flexible wiring board using the polyimide film can be reduced.

  In addition, the surface orientation degree ratio of the front and back means the surface orientation of each polyimide film surface on the laminated surface (A) and the non-laminated surface (B) of the metal layer of the polyimide film, and the orientation on each surface. The in-plane distribution is converted into an ellipse to calculate an ellipticity (ellipticity = maximum orientation corresponding to the major axis of the ellipse / minimum orientation corresponding to the minor axis of the ellipse). B) / Ellipticity (A) is the ratio of the front and back surface orientation degrees.

(I) Method for Measuring Molecular Orientation Angle in the Plane of Polyimide Film In the method for measuring the molecular orientation angle in the plane of the polyimide film, first, the orientation in the plane of the polyimide film is measured. The method for measuring the orientation of the polyimide film includes X-ray diffraction, infrared spectroscopy, laser Raman spectroscopy, which directly evaluates molecular orientation, polarization measurement, optical evaluation such as birefringence, and electrical properties such as dielectric constant. A method for evaluating molecular orientation indirectly such as thermal measurement such as mechanical measurement, thermal expansion coefficient measurement, mechanical measurement such as tensile test, and orientation evaluation by ultrasonic waves can be used. As will be described later, from the viewpoint of the need to determine the surface orientation ratio between the front and back surfaces, it is preferable to determine the orientation using infrared spectroscopy or optical evaluation utilizing birefringence, and in particular, birefringence from the viewpoint of measurement accuracy. It is most preferable to use optical evaluation using

  The optical evaluation using birefringence includes optical evaluation by spectroscopic ellipsometry, for example. Spectroscopic ellipsometry is a method of irradiating a sample surface with linearly polarized light at a certain angle and evaluating optical constants such as refractive index from the amplitude ratio and phase difference of elliptically polarized light of the reflected light interacting with the sample surface or bulk. . When the orientation is large, the measured refractive index becomes large. The alignment of molecular chains in the sample plane can be evaluated by changing the measurement angle in the plane at regular intervals and measuring the refractive index (orientation) in all directions (360 degrees) of the sample plane.

  When the refractive index (orientation) of the polyimide film surface is measured by spectroscopic ellipsometry, the irradiation angle is about 70 ° to 80 ° when the normal direction of the polyimide film surface is 0 °. preferable. This is because linearly polarized light mainly interacts with the polyimide film surface if it is about 70 to 80 degrees. Moreover, it is preferable to measure the wavelength of the polarized light irradiated to the polyimide film surface in a visible region (about 400 nm to 700 nm). Spectral ellipsometry can be measured by using, for example, VASE manufactured by JA Woollam, SE2000 manufactured by Semilab, or the like.

  When measuring the molecular orientation by spectroscopic ellipsometry, when measuring the bulk of the polyimide film, the irradiation angle is about 40 to 70 degrees when the normal direction of the polyimide film surface is 0 degree. Linearly polarized light can be transmitted through the polyimide film and measured in a bulk state.

  The quality determination method of the polyimide film of the present invention measures the orientation in all directions in the plane of the polyimide film by any one of the above methods, and obtains the maximum orientation which is the maximum value. The method for obtaining the maximum orientation is not particularly limited. For example, the orientation in all directions (360 degrees) in the plane of the polyimide film at every predetermined angle (for example, 10 degrees to 30 degrees) in the plane of the film. Is measured, and the in-plane distribution of orientation is converted into an ellipse. The maximum orientation can be obtained from the major axis of the ellipse converted into the ellipse.

  The polyimide film quality determination method of the present invention obtains the maximum orientation of the polyimide film, and the difference between the orientation angle of the molecules in the plane showing the maximum orientation and the TD direction (Transverse Direction) or MD direction (Machine Direction) of the polyimide film. An absolute value of 0 degrees or more and 30 degrees or less is used as a pass / fail criterion. If it is such a range, the curvature and twist of the copper clad laminated board and flexible wiring board using the said polyimide film can be made small. The MD direction means the flow direction (winding direction) in which the film is biaxially stretched during the production of the polyimide film and the film is stretched, and the TD direction is the MD direction that is the film flow direction. Means the direction perpendicular to

(II) Calculation method of front and back surface orientation degree ratio In the calculation method of front and back surface orientation degree ratio in the polyimide film quality determination method, first, as described above, the laminated surface (A) of the polyimide film metal layer, and non- The surface orientation of each polyimide film surface is measured with the laminate surface (B). The surface orientation can be measured by using an optical evaluation method using birefringence similar to that described above. Then, the in-plane distribution of orientation on each surface is converted into an ellipse to obtain an ellipticity (maximum orientation corresponding to the ellipse major axis / minimum orientation corresponding to the ellipse minor axis). The ellipticity of the laminated surface (A) and the non-laminated surface (B) of the metal layer is calculated, respectively, and the ellipticity (B) / ellipticity (A), which is the ratio of the ellipticity of both the front and back surfaces, is calculated. The ellipticity (B) / ellipticity (A) is less than 1.0 as the pass / fail criterion. If it is such a range, the curvature and twist of the copper clad laminated board and flexible wiring board using the said polyimide film can be made small.

(6) Flexible wiring board Relative to the metalizing substrate according to one embodiment of the present invention, the polyimide film is thicker, and the flexible wiring board after wiring processing has a smaller area occupied by metal than the film area. In addition, the influence of the polyimide film is greater than that of the metal film layer. Furthermore, as described above, there is a heating step when processing a flexible wiring board, and when a polyimide film is heated, warping and twisting tend to become remarkable. In order to suppress this, it is effective to perform a pass / fail judgment method for the polyimide film and limit it within a predetermined management range. Therefore, if it is the copper clad laminated board manufactured using the polyimide film screened through the said quality determination method of a polyimide film, the curvature and twist of a metalizing board and a flexible wiring board using the same can be suppressed.

  The warping and twisting properties of polyimide films are due to the rigidity and thermal properties of the molecular chain, and these properties are governed by the imide compound formed by the aromatic acid anhydride and aromatic diamine that constitute the molecular chain. The predetermined numerical range of the quality determination method includes an imide compound composed of an aromatic diamine and 3,3′-4,4-diphenyltetracarboxylic dianhydride, and has a thermal expansion coefficient in the TD direction by stretching. It is unique to polyimide films that are 10 ppm / K or more and 16 ppm / K or less, and in the case of different types of imide compounds, warpage and twisting can be suppressed even if values within the above ranges of both dimensional change rates are shown. The effect may not be obtained. In addition, the thermal expansion coefficient in this specification means the thermal expansion coefficient when the temperature is increased at a rate of 5 ° C./min within the range of 50 ° C. to 200 ° C.

  Examples of the different kinds of imide compounds include imide compounds composed of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride. As a polyimide film containing this imide compound, Kapton (registered trademark, manufactured by Toray DuPont Co., Ltd.) is known and can be easily obtained in the market.

  Although the metallizing substrate has been described above as being processed into a flexible wiring board by a subtractive method, a metalizing substrate having a thickness of 1 to 2 μm as a copper electroplating layer, which is a preferable range in the present invention, is semi-additive. Even if it is processed into a flexible wiring board by the method, the effect of suppressing warpage and twisting is sufficiently exerted and does not particularly hinder.

  Hereinafter, the manufacturing method of the flexible wiring board of this invention is demonstrated still in detail based on an Example. In addition, this invention is not limited to this Example.

Example 1
<Manufacture of copper-clad laminate>
Low-CTE (linear expansion coefficient) grade polyimide film (thickness: 35 μm, manufactured by Ube Industries, Ltd .: Upilex 35 SGA) is laminated on one side of the resin film by sputtering and electroplating, and 8 μm is laminated. A sample of the board was made. The polyimide film contains an imide bond composed of an aromatic diamine and 3,3′-4,4′-diphenyltetracarboxylic dianhydride, and the thermal expansion coefficient in the TD direction of the polyimide film is 10 ppm. / K or more and 16 ppm / K or less (coefficient of thermal expansion when the temperature is raised at a rate of 5 ° C./min within the range of 50 ° C. to 200 ° C.).

  The polyimide film used was SE2000 manufactured by Semilab, and the polyimide film was irradiated with linearly polarized light, and the refractive index was determined by the reflected light. The measurement was performed over 360 degrees at intervals of 30 degrees in the plane of the polyimide film. The incident angle of linearly polarized light was measured at two angles (bulk) of 65 degrees and 70 degrees when the normal direction of the film surface was 0 degree. The wavelength of linearly polarized light was 400 nm to 700 nm. Of the measured refractive indexes, the refractive index at a wavelength of 486 nm is used as the orientation, and the average in-plane distribution at two points is converted into an ellipse, and the maximum orientation from the major axis of the ellipse (in Table 1, expressed as the orientation angle (degree)). ) The absolute value of the difference between the orientation angle of molecules in the plane showing the maximum orientation of the polyimide film and the TD direction was 14 degrees, and the absolute value of the difference between the orientation angle and the MD direction was 76 degrees.

  Moreover, the surface orientation degree ratio (represented as the difference between the front and back of the orientation in Table 1) of each polyimide film surface between the laminated surface of the metal layer and the non-laminated surface was measured. Except that the irradiation angle is 80 degrees and 75 degrees when the normal direction of the film surface is 0 degrees, the refractive index is oriented in the same manner as described above, and the in-plane distribution on the polyimide film surface and the back surface is converted into an ellipse. The ratio (maximum orientation corresponding to the ellipse major axis / minimum orientation corresponding to the ellipse minor axis) was determined. The surface orientation degree ratio of the polyimide film (represented as the difference between the front and back orientations in Table 1) was 0.9 on the non-laminated surface (B) / laminated surface of the metal layer (A).

  The polyimide film was heat-treated at 150 ° C. for 1 minute in a chamber maintained at a vacuum degree of 0.01 to 0.1 Pa. This polyimide film is untreated on the laminated surface.

  Subsequently, a nickel-chromium alloy target containing 20% by mass of chromium and a copper target were used to form a nickel-chromium alloy layer having a thickness of 20 nm and a copper layer having a thickness of 100 nm on the polyimide film surface.

  Thereafter, 180 g / L of sulfuric acid, 80 g / L of copper sulfate, 50 mg / L of chloride ions, and a plating solution to which a predetermined amount of an organic additive is added for the purpose of ensuring the smoothness of the copper plating film, etc. A copper film was formed by electroplating to a thickness of 8 μm under the above plating conditions.

  As described above, the metallized polyimide film substrate according to the embodiment of the present invention has a structure of a sputtered metal thin film 20 nm composed of nickel, chromium and copper, a sputtered copper thin film 100 nm, and a copper plating film 8 μm on a polyimide film 38 μm. A copper clad laminate was obtained.

<Environmental change test>
About the said copper clad laminated body sample, it heat-processed.

  Cut the copper-clad laminate into 10cm squares and leave them at 23 ° C, 50RH% for 3 days or longer, then measure the height of the four corners using Keyence's digital dimension measuring instrument (LS-7030) as shown in Fig. 4. did. In the heating test, after measurement at room temperature, a treatment was performed under conditions of 150 ° C. and 30 minutes and then left at 23 ° C. and 50 RH% for 24 hours.

  It is a polyimide film similar to the polyimide film of Example 1 (thickness: 35 μm Ube Industries, Ltd .: Upilex 35SGA), and the degree of stretching, temperature, and taking position are appropriately changed, and Example 2 and Comparative Examples 1 to 6 A polyimide film was prepared. The polyimide film contains an imide bond composed of an aromatic diamine and 3,3′-4,4′-diphenyltetracarboxylic dianhydride, and the thermal expansion coefficient in the TD direction of the polyimide film is 10 ppm. / K or more and 16 ppm / K or less (coefficient of thermal expansion when the temperature is raised at a rate of 5 ° C./min within the range of 50 ° C. to 200 ° C.).

(Example 2)
Similarly to Example 1, the absolute value of the difference between the orientation angle of the in-plane molecules showing the maximum orientation of the polyimide film and the TD direction or MD direction of the polyimide film (in Table 1, indicated as the orientation angle (degree)) and the degree of surface orientation The ratio (in Table 1, expressed as the difference between the front and back of the orientation) was measured. The absolute value of the difference between the orientation angle of the in-plane molecule showing the maximum orientation and the TD direction is 70 degrees, the absolute value of the difference from the MD direction is 20 degrees, and the surface orientation ratio is non-laminated plane (B) / A copper-clad laminate sample was prepared in the same manner as in Example 1 except that a polyimide film having a metal layer lamination surface (A) of 0.8 was used, and an environmental change test was performed.

(Comparative Example 1)
Similarly to Example 1, the absolute value of the difference between the orientation angle of the in-plane molecules showing the maximum orientation of the polyimide film and the TD direction or MD direction of the polyimide film (in Table 1, indicated as the orientation angle (degree)) and the degree of surface orientation The ratio (in Table 1, expressed as the difference between the front and back of the orientation) was measured. The absolute value of the difference between the orientation angle of the molecules in the plane showing the maximum orientation and the TD direction is 42 degrees, the absolute value of the difference from the MD direction is 48 degrees, and the surface orientation degree ratio is non-laminated plane (B) / A copper-clad laminate sample was prepared in the same manner as in Example 1 except that a polyimide film having a metal layer lamination surface (A) of 0.8 was used, and an environmental change test was performed.

(Comparative Example 2)
Similarly to Example 1, the absolute value of the difference between the orientation angle of the in-plane molecules showing the maximum orientation of the polyimide film and the TD direction or MD direction of the polyimide film (in Table 1, indicated as the orientation angle (degree)) and the degree of surface orientation The ratio (in Table 1, expressed as the difference between the front and back of the orientation) was measured. The absolute value of the difference between the orientation angle of the molecule in the plane showing the maximum orientation and the TD direction is 55 degrees, the absolute value of the difference from the MD direction is 35 degrees, and the surface orientation ratio is non-laminated plane (B) / A copper clad laminate sample was prepared in the same manner as in Example 1 except that a polyimide film having a metal layer lamination surface (A) of 0.9 was used, and an environmental change test was performed.

(Comparative Example 3)
Similarly to Example 1, the absolute value of the difference between the orientation angle of the in-plane molecules showing the maximum orientation of the polyimide film and the TD direction or MD direction of the polyimide film (in Table 1, indicated as the orientation angle (degree)) and the degree of surface orientation The ratio (in Table 1, expressed as the difference between the front and back of the orientation) was measured. The absolute value of the difference between the orientation angle of the molecule in the plane showing the maximum orientation and the TD direction is 13 degrees, the absolute value of the difference from the MD direction is 77 degrees, and the surface orientation ratio is non-laminated plane (B) / A copper clad laminate sample was prepared in the same manner as in Example 1 except that a polyimide film having a metal layer lamination surface (A) of 1.0 was used, and an environmental change test was performed.

(Comparative Example 4)
Similarly to Example 1, the absolute value of the difference between the orientation angle of the in-plane molecules showing the maximum orientation of the polyimide film and the TD direction or MD direction of the polyimide film (in Table 1, indicated as the orientation angle (degree)) and the degree of surface orientation The ratio (in Table 1, expressed as the difference between the front and back of the orientation) was measured. The absolute value of the difference between the orientation angle of the molecule in the plane showing the maximum orientation and the TD direction is 78 degrees, the absolute value of the difference from the MD direction is 12 degrees, and the surface orientation ratio is non-laminated plane (B) / A copper clad laminate sample was prepared in the same manner as in Example 1 except that a polyimide film having a metal layer lamination surface (A) of 1.0 was used, and an environmental change test was performed.

(Comparative Example 5)
Similarly to Example 1, the absolute value of the difference between the orientation angle of the in-plane molecules showing the maximum orientation of the polyimide film and the TD direction or MD direction of the polyimide film (in Table 1, indicated as the orientation angle (degree)) and the degree of surface orientation The ratio (in Table 1, expressed as the difference between the front and back of the orientation) was measured. The absolute value of the difference between the orientation angle of the molecules in the plane showing the maximum orientation and the TD direction is 43 degrees, the absolute value of the difference from the MD direction is 47 degrees, and the surface orientation ratio is non-laminated plane (B) / A copper clad laminate sample was prepared in the same manner as in Example 1 except that a polyimide film having a metal layer lamination surface (A) of 1.0 was used, and an environmental change test was performed.

(Comparative Example 6)
Similarly to Example 1, the absolute value of the difference between the orientation angle of the in-plane molecules showing the maximum orientation of the polyimide film and the TD direction or MD direction of the polyimide film (in Table 1, indicated as the orientation angle (degree)) and the degree of surface orientation The ratio (in Table 1, expressed as the difference between the front and back of the orientation) was measured. The absolute value of the difference between the orientation angle of the molecule in the plane showing the maximum orientation and the TD direction is 37 degrees, the absolute value of the difference from the MD direction is 53 degrees, and the surface orientation ratio is non-laminated plane (B) / A copper-clad laminate sample was prepared in the same manner as in Example 1 except that a polyimide film having a metal layer lamination surface (A) of 1.1 was used, and an environmental change test was performed.

(Warp / twist test results)
The results are shown in Table 1. Specifically, warpage and twist of each sample after plating and before and after heat treatment were determined. As shown in FIG. 4, the average value of the heights of the four corners and the average value of the heights of the diagonal lines are calculated as warpage, and the absolute value of the difference between the average values of the two diagonal lines is set as the size of the twist. That is, the smaller this value is, the smaller the twist is, and when this value is 0, there is no twist. The values of warpage and torsion are values obtained by dividing based on Example 1.

（表１の配向角（度）には、ＴＤ方向の差の絶対値とＭＤ方向の差の絶対値のうち小さい方の値を記載した。）

(The smaller one of the absolute value of the difference in the TD direction and the absolute value of the difference in the MD direction is described as the orientation angle (degree) in Table 1.)

  From this, the absolute value of the difference between the orientation angle of the molecules in the plane showing the maximum orientation and the TD direction or MD direction of the polyimide film is 0 degree or more and 30 degrees or less, and the surface orientation ratio between the front and back surfaces (in Table 1) The copper-clad laminate according to the example using a polyimide film having an orientation difference of less than 1.0 is indicated before heat treatment (indicated as “initial” in Table 1) and after heat treatment (Table 1). It can be seen that the influence of warping and twisting is small. Therefore, the quality determination method of the polyimide film of the present invention makes it possible to manufacture with improved handling strength in the manufacturing process of the copper clad laminate, while reducing warpage and twist. Therefore, it turns out that the quality determination method of the polyimide film which concerns on this invention is the determination method which can manufacture the copper clad laminated board with the high yield and extremely high productivity.

  On the other hand, the copper-clad laminate in which the orientation angle of the in-plane molecules showing the maximum orientation of the comparative example and the surface orientation ratio of the front and back are laminated is out of the range, warpage and twist before the heat treatment are The values are larger than those of the examples. Therefore, it can be seen that the dimensions of the flexible wiring board greatly change when using a polyimide film whose in-plane molecular orientation angle showing the maximum orientation and front / back surface orientation ratio is out of range.

  Therefore, when a flexible wiring board is manufactured using a polyimide film in which the orientation angle of the molecules in the plane showing the maximum orientation and the surface orientation ratio of the front and back surfaces are not controlled, the warping / twisting of the flexible wiring board It can be inferred that the variation becomes large. Therefore, when compared with the manufacturing method using the polyimide film in which the orientation angle of the in-plane molecules exhibiting the maximum orientation and the surface orientation ratio between the front and back surfaces are within the above range, the orientation angle of the in-plane molecules exhibiting the maximum orientation It can be understood that the manufacturing method using a polyimide film in which the surface orientation degree ratio is not controlled is a manufacturing method with low productivity because it is considered that variations in warpage and twisting increase.

F1 resin film F2 resin film with copper thin film layer S copper clad laminate 1 resin film 2 base metal layer 3 copper thin film layer 4 copper electroplating layer 5 copper layer 6 copper clad laminate 10 roll-to-roll sputtering apparatus 11a, 11b Free roll 12 Chamber 13 Unwinding roll 14 Can rolls 15a to 15d Sputtering cathode 16a Front feed roll 16b Rear feed rolls 17a and 17b Tension roll 18 Winding roll 20 Roll-to-roll electroplating apparatus 21 Electroplating tank 22 Unwinding roll 23 Reversing rolls 24a to 24t Anodes 26a to 26k Power feeding roll 28 Plating solution 28a Plating solution surface 29 Winding roll 30 Warp / twist measurement samples 31 to 34 Height measurement point 35 Warp height

Claims (5)

A method for determining the quality of the polyimide film, which is used for a flexible wiring board in which a metal layer is laminated on a polyimide film,
The polyimide film includes an imide bond composed of an aromatic diamine and 3,3′-4,4′-diphenyltetracarboxylic dianhydride, and the thermal expansion coefficient in the TD direction of the polyimide film is 10 ppm / K or more and 16 ppm. / K or less,
The polyimide film has an MD direction and a TD direction orthogonal to each other in the plane,
The polyimide film measures the orientation in the plane, and the orientation angle of molecules in the plane showing the maximum orientation which is the maximum value is 0 degree or more in absolute value of the difference in the TD direction or MD direction of the polyimide film. 30 degrees or less,
The said polyimide film is a quality determination method of the polyimide film whose surface orientation degree ratio of the front and back defined below is less than 1.0.
Surface orientation degree ratio of front and back: The surface orientation of each polyimide film surface is measured on the laminated surface (A) and non-laminated surface (B) of the metal layer in the polyimide film, and the in-plane distribution of orientation on each surface Is converted into an ellipse to calculate the ellipticity (ellipticity = maximum orientation corresponding to the major axis of the ellipse / minimum orientation corresponding to the minor axis of the ellipse). Let the rate (A) be the surface orientation degree ratio of the front and back.   The quality determination method of the polyimide film of Claim 1 which performs the measurement of the said orientation by optical evaluation using birefringence. A polyimide film screened through the quality determination method according to claim 1 or 2,
The manufacturing method of the copper clad laminated board including the process of laminating | stacking a base metal layer and a copper layer on one surface of the said polyimide film.   The manufacturing method of a flexible wiring board including the process of performing wiring processing on the copper clad laminated board manufactured by the manufacturing method of Claim 3.   The method for manufacturing a flexible wiring board according to claim 4, wherein the wiring processing is performed by a subtractive method or a semi-additive method.

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