JP2011176034A - Method of manufacturing flexible printed board and etching processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a flexible printed board by which metal residues between wiring lines are removed through an inexpensive and easy process without performing side etching of a copper layer and even a microwiring processed article has sufficient insulation reliability, and also to provide the printed wiring board obtained by the manufacturing method. <P>SOLUTION: The method of manufacturing the flexible printed board is characterized by maintaining an oxygen concentration in an etching processing atmosphere at 2 vol.% or below in a process of forming a copper wiring pattern by performing etching processing on a copper coating layer formed at least on one surface of an insulator film without interposing an adhesive. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a flexible printed circuit board used for a flexible printed circuit board to be a substrate for electronic components such as TAB tape and COF tape, and a copper wiring pattern (hereinafter referred to as a wiring pattern) on the copper coating layer of the flexible printed circuit board. It is related with the etching method of the copper coating layer used when forming a case. More specifically, by performing an etching process on the two-layer flexible printed circuit board with atmosphere control suitable for the copper coating layer constituting the wiring pattern, a wiring pattern having sufficient insulation reliability can be obtained even in a fine wiring processed product. It is a manufacturing method of the flexible printed circuit board which can be formed.

  In general, a flexible printed circuit board used for the production of a flexible printed wiring board is a three-layer flexible printed circuit board (for example, see Patent Document 1) in which a copper foil serving as a conductor layer is bonded onto an insulator film using an adhesive. The two-layer flexible printed circuit board can be broadly classified into a two-layer flexible printed circuit board in which a copper coating layer serving as a conductor layer is directly formed on an insulating film by a dry plating method or a wet plating method without using an adhesive.

  By the way, with the recent increase in the density of electronic devices, a wiring board whose wiring width and wiring pitch are reduced has been demanded. In manufacturing, when a flexible printed circuit board is manufactured by etching a conductor layer composed of a copper foil formed on an insulating film as a substrate according to a desired wiring pattern to form a wiring portion, Since side etching of excessive etching of the side surfaces of the wiring portion occurs, there is a problem that the cross-sectional shape of the wiring portion tends to be a trapezoid with a wide base. Therefore, in order to satisfy such a demand, a two-layer flexible printed circuit board is now becoming mainstream instead of a conventional three-layer flexible printed circuit board on which a copper foil is bonded.

  In the production of this two-layer flexible printed board, an electrolytic copper plating method is usually employed as a means for forming a copper coating layer having a uniform thickness on an insulator film. Then, in order to perform the electrolytic copper plating, a thin metal layer is formed on the insulator film on which the electrolytic copper plating film is applied to impart conductivity to the entire surface, and the electrolytic copper plating process is performed on the metal layer. Is common (see, for example, Patent Document 2). Further, in order to obtain a thin metal layer on the insulator film, a dry plating method such as a vacuum deposition method or an ion plating method is used.

Under such circumstances, the adhesion between the insulator film and the copper coating layer is very weak because a fragile layer such as CuO or Cu ₂ O is formed at the interface, and thus is required for a flexible printed circuit board. In order to maintain the adhesive strength with the copper coating layer, a nickel-chromium alloy layer is provided as a base metal layer between the insulator film and the copper coating layer (see Patent Document 3).

By the way, normally, in the formation of a wiring pattern using a subtractive method on a two-layer plated substrate such as a two-layer flexible printed circuit board, for example, a chloride obtained by dissolving ferric chloride (FeCl ₃ ) in water as an etchant. Etching is performed using a ferric solution or a cupric chloride solution in which cupric chloride (CuCl ₂ · 2H ₂ O) is dissolved in water and an appropriate amount of hydrochloric acid is added. In the etching process using these etching solutions, there may be a case where an etching residue of a base metal layer such as a nickel-chromium alloy is generated between the wirings after the etching process, and a sufficient etching result may not be obtained.

  Furthermore, in recent flexible printed wiring boards, the wiring pitch is becoming narrower as the wiring pattern is further densified, and the use of high voltage is required as the functionality is increased. ing. As a result, insulation reliability required for the flexible printed wiring board to be used has become important, and a constant temperature and humidity bias test (HHBT) or the like is performed as an index of this characteristic.

  However, when an etching residue of a base metal layer such as a nickel-chromium alloy is generated when the two-layer plated substrate is etched using the previous etching solution, a constant temperature and humidity bias test (High Temperature High Humidity) (Bias Test, hereinafter referred to as HHBT) may cause a short circuit between adjacent wiring lines due to the etching residue of the nickel-chromium alloy layer, resulting in a defective product without high insulation resistance. It was happening.

  Therefore, as one of means for realizing good insulation reliability, there is a method of removing the remainder of the base metal layer component between the wirings described above. For example, Patent Document 4 discloses that after etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, one or more of an alkaline etching solution such as an acidic etching solution containing hydrochloric acid or a potassium permanganate solution is used. It has been proposed to dissolve the etching residue of the nickel-chromium alloy by processing in combination. In this case, the etching residue of the nickel-chromium alloy can be removed by a method with less side etching of the wiring.

JP-A-6-132628 Japanese Patent Laid-Open No. 8-139448 JP-A-6-120630 JP 2005-23340 A

  However, when an etching process is performed using a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, in the spray etching process in which air is mixed such that the etching solution is sprayed using a nozzle or the like, Nickel-chromium alloy residues may be observed. In particular, it is often found not in a fine wiring portion but in a portion having no wiring pattern (hereinafter sometimes referred to as a rough portion) or a wiring portion having a relatively wide pitch.

  Furthermore, when a selective removal process (also referred to as a selective etching process) of the nickel-chromium alloy is performed in the presence of the residue of the underlying alloy layer, etching is performed under conditions that cleanly remove the portion where the residue is seen. As a result, the nickel-chromium alloy, which is the underlying alloy layer under the lead called “smudge”, is also etched excessively, resulting in floating of the lead, and inducing the occurrence of migration when the HHBT test or the like is performed. Result.

  In addition, if nickel-chromium alloy is selectively removed under conditions that do not cause “smearing” under the leads, the removal of residues other than wiring parts such as rough parts becomes insufficient, which also reduces insulation reliability. Resulting in.

  In view of such circumstances, the present invention solves the conventional problems in the production of a two-layer flexible printed circuit board, can uniformly remove metal residue between wirings, and has sufficient insulation reliability even in a fine wiring processed product. The manufacturing method of the flexible printed circuit board which provides the flexible printed wiring board which has, and the etching processing method of a copper coating layer are provided.

  In order to solve the above-mentioned problems, the present inventor has intensively studied the etching method of the flexible printed circuit board, and as a result, injects an etching solution using a spray nozzle in the air so far, and entrains air. In the case where the etching process is performed, it is found that the residue increases at the place where the bubbles touch the surface, and further, the oxygen contained in the air greatly contributes to the formation of the residue, and the present invention has been achieved. .

  That is, according to one aspect of the present invention, the oxygen concentration in the etching atmosphere in the step of etching the copper coating layer formed on at least one surface of the insulator film without using an adhesive to form a copper wiring pattern is 2 It is a manufacturing method of a flexible printed circuit board maintained at a volume% or less.

  Moreover, the copper coating layer of the flexible printed circuit board which concerns on 1st invention is the structure laminated | stacked in order of the nickel alloy layer and the copper layer from the insulator film side, and the film thickness 3 formed by the dry-type plating method on the insulator film It is a base metal layer of a nickel-chromium alloy containing 5 to 24% by weight of chromium of ˜40 nm, and a copper layer having a thickness of 10 nm to 35 μm formed on the base metal layer.

  Further, the step of etching the copper coating layer according to the first invention is performed by a selective removal liquid that selectively removes the underlying metal layer after forming the copper wiring pattern by etching the copper layer of the copper coating layer. It is characterized by including a removal process of the base metal layer, and the etching process of the copper layer is performed using a ferric chloride solution or a cupric chloride solution containing hydrochloric acid as an etching solution. It is what.

  Another aspect of the present invention is characterized in that an oxygen concentration in an etching atmosphere is maintained at 2% by volume or less in a method for etching with a chemical solution of a laminate having a structure in which a copper layer is laminated on a nickel alloy layer. In the etching method, the nickel alloy layer is a nickel-chromium alloy containing 5 to 24% by weight of chromium having a film thickness of 3 to 40 nm, and the chemical used for etching is ferric chloride solution or hydrochloric acid containing hydrochloric acid. It is a dicopper solution.

  By using the manufacturing method of the flexible printed circuit board according to the present invention and the etching method of the present invention, the metal residue between the wirings in the two-layer flexible printed circuit board can be removed, thereby obtaining a fine wiring having higher insulation reliability. And has an industrially significant effect.

  When producing a two-layer flexible substrate, the insulator film of the base material is activated by modifying the surface of the insulator film by hydrazine treatment or plasma treatment, etc., and good with the underlying metal layer provided immediately above the insulator film Is connected. Since the bonding strength obtained by this treatment is strong, it is considered that a peel strength that can withstand practical use is developed as a two-layer flexible substrate.

  However, after the wiring pattern is formed by etching, in the space portion between the leads, the metal component of the extremely small amount of the underlying metal layer that is directly bonded to the insulator film after etching and the subsequent cleaning process However, it is thought that it will remain in the surface layer part of an insulator film. Therefore, the present inventors presume that the metal component remaining in the surface layer is one of the causes of migration when a constant temperature and humidity bias test (HHBT) is performed.

The present invention is described in detail below.
The present invention provides a two-layer flexible printed circuit board in which a base metal layer is formed directly on at least one surface of an insulator film without using an adhesive, and a copper coating layer is formed by laminating a copper layer on the base metal layer. In the production, when the wiring pattern was formed, an etching treatment with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid was performed in an atmosphere having a low oxygen concentration. It comprises an etching treatment for treating with a chromium alloy selective removal solution.

1. At the time of wiring pattern formation, that is, when wiring is formed by etching using a ferric chloride solution or a cupric chloride solution containing hydrochloric acid in an oxygen atmosphere of about 21% contained in the air, The nickel-chromium alloy that forms the underlying metal layer that appears on the surface after removing the copper layer forms a passive film under the influence of oxygen that is subsequently touched, resulting in local stagnation of the etching and the ferric chloride solution. In the etching process using a cupric chloride solution, further etching does not proceed. When the residue is removed with a nickel-chromium selective removing solution, a part of the nickel-chromium alloy layer existing under the copper lead may be excessively etched to expose the copper. When the HHBT test is performed in this state, migration in which copper elutes occurs and the migration resistance is extremely lowered.

  In order to prevent such a situation, the atmosphere at the time of etching the copper coating layer is controlled. When wiring formation is performed using a ferric chloride solution or a cupric chloride solution as an etching solution, the atmosphere is preferably set to an oxygen concentration of 2% or less. It is also desirable to perform the same atmosphere when selectively removing the nickel-chromium alloy of the underlying metal layer remaining after the etching of the copper layer.

2.2-layer flexible printed circuit board 2-1. Insulator film Insulator film used as an insulating substrate material in the present invention is a polyimide film, polyamide film, polyester film, polytetrafluoroethylene film, polyphenylene sulfide film, polyethylene naphthalate from the viewpoint of heat resistance. At least one kind of thermosetting resin film selected from a polymer film and a liquid crystal polymer film is preferred. Among these, a polyimide film and a polyamide film are particularly preferable films in that they are suitable for applications that require high-temperature connection in solder reflow or the like.

  Moreover, the thing of 8-75 micrometers can be used conveniently for the film thickness of this insulator film. In order to reduce the coefficient of thermal expansion, an inorganic material such as glass fiber or CNT (carbon nanotube) may be appropriately added to the resin film.

2-2. Base metal layer The material of the base metal layer formed on the insulator film is one metal selected from Ni, Cu, Mo, Ta, Ti, V, Cr, Fe, Co, and W, or two kinds An alloy composed of the above is preferable because it has high corrosion resistance, high adhesion, and heat resistance. Note that an oxide of the base metal layer may be stacked over the base metal layer.

  Furthermore, it is preferable that the film thickness of the base metal layer of the printed wiring board of this invention is 3-50 nm. If the thickness of the underlying metal layer is less than 3 nm, it is not preferable because an etching solution infiltrate when forming the wiring so that the wiring peel strength floats and the wiring peel strength significantly decreases. Moreover, since it will become difficult to etch if the film thickness becomes thicker than 50 nm, it is not preferable.

2-3. Copper layer A copper layer is formed using a sputtering apparatus in which a copper target is mounted on a sputtering cathode. At this time, the base metal layer and the copper layer are preferably formed continuously in the same vacuum chamber. When the base metal layer is formed, the film is taken out into the atmosphere, and when a copper layer is formed using another sputtering apparatus, it is necessary to sufficiently perform dehydration before film formation.

  In addition, when a copper layer is formed by a dry plating method and then a copper layer is formed on the copper layer by a wet plating method, for example, an electroless copper plating process is performed. By forming a copper layer, even if the insulator film has coarse pinholes, the entire surface of the substrate is covered with a good conductor by covering the film exposed surface, thereby preventing the influence of pinholes. Is. Note that the thickness of the plated copper layer by the electroless copper plating solution should be such that defects on the substrate surface can be repaired by pinholes and not dissolved by the electrolytic copper plating solution when the electrolytic copper plating process is performed. What is necessary is just to be 0.01-1.0 micrometer.

  In the dry plating method, resistance heating vapor deposition, ion plating vapor deposition, sputtering vapor deposition, or the like can be used. Although it is possible to form a copper coating layer only by the dry plating method, it is relatively thick to form a copper layer by the wet plating method after forming the copper layer by the dry plating method. Suitable for forming a film.

  In the flexible printed circuit board of the present invention, a copper layer formed on a base metal layer may be formed by laminating a copper layer formed by a dry plating method and a wet plating method on the copper layer to form a copper layer. it can. The thickness of the layer formed by combining the copper layer formed by the dry plating method and the copper layer formed by the wet plating method on the copper layer is preferably 10 nm to 35 μm. When the thickness is less than 10 nm, the copper layer formed by the dry plating method becomes thin, so that it is difficult to supply power in the subsequent wet plating process, which is not preferable. Moreover, when it becomes thicker than 35 micrometers, since productivity falls, it is unpreferable.

3. Hereinafter, a method for producing a flexible printed board according to the present invention will be described in detail.
In the present invention, as described above, a commercially available thermosetting selected from a polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a liquid crystal polymer film. An insulator film, which is a film, is subjected to a pretreatment for dehydration treatment, and a base metal layer is directly formed on at least one surface without using an adhesive as described above, and copper having a desired thickness is formed on the base metal layer. A layer is formed to form a copper coating layer.

3-1. The insulator film to be used usually contains moisture. Before the base metal layer is formed by dry plating, the insulator film is dehydrated by air drying or vacuum drying to remove moisture present in the insulator film. It needs to be removed. If this is insufficient, the adhesion with the underlying metal layer is impaired.

  Furthermore, it is possible to modify the insulator film surface after the dehydration treatment. As a method for forming the modified layer, chemical treatment with chemicals or physical treatment such as plasma treatment, corona discharge, ultraviolet irradiation treatment, etc. can be employed, but it is not limited to any of them.

3-2. Formation of the base metal layer When forming the base metal layer by a dry plating method, for example, when forming the base metal layer using a winding type sputtering apparatus, an alloy target having the composition of the base metal layer is used as the cathode for sputtering. Installing. Specifically, after evacuating the inside of the sputtering apparatus in which the film is set, Ar gas is introduced to hold the inside of the apparatus at about 1.3 Pa, and an insulator film attached to a winding / unwinding roll in the apparatus While transporting at a speed of about 3 m / min, power is supplied from a sputtering DC power source connected to the cathode to start sputtering discharge, and a base metal layer is continuously formed on the film. By this film formation, a base metal layer having a desired film thickness is formed on the film.

3-3. Formation of a copper layer Similarly, a copper layer can be formed by a dry plating method using a sputtering apparatus in which a copper target is mounted on a sputtering cathode. In addition, when forming the above-mentioned base metal layer and copper layer using a dry plating method, it is preferable to form continuously in the same vacuum chamber.

  In addition, a copper layer having a further thickness may be formed on the copper layer using a wet plating method. In that case, when the formation of the copper layer is performed only by an electrolytic copper plating process, a wet plating method such as an electroless copper plating process as a primary plating and an electrolytic copper plating process as a secondary plating may be combined.

  Here, the electroless copper plating treatment is used as the primary plating because, when dry plating is performed by vapor deposition, coarse pinholes may be formed, and there may be places where the resin film is exposed on the surface. This is because an electroless copper plating layer is formed on the entire surface of the substrate to cover the film exposed surface and make the entire surface of the substrate a good conductor so that it is not affected by pinholes. In addition, the electroless plating solution used in electroless plating is a reduction deposition type in which the contained metal ions have autocatalytic properties and are reduced by a reducing agent such as hydrazine, sodium phosphinate, formalin, etc. However, in view of the gist of the present invention, the purpose is to improve the conductivity of the exposed portion of the insulator film exposed by the pinhole generated in the underlying metal layer. An electroless copper plating solution that is good and has relatively good workability is optimal.

  In addition, the thickness of the copper plating layer by the electroless copper plating treatment as the primary plating can repair defects by pinholes on the substrate surface, and when performing the copper electroplating treatment as the secondary plating described later, The thickness may be such that it is not dissolved by the plating solution, and is preferably in the range of 0.01 to 1.0 μm.

Next, the electrolytic copper plating process is performed as the secondary plating on the electroless copper plating layer in order to form a copper layer having a desired thickness.
In this way, according to the copper layer formed on the base metal layer, a flexible printed circuit board that is not affected by various pinholes generated during the formation of the base metal layer and has good adhesion to the conductor layer can be obtained. Is possible. In addition, the wet copper plating process performed in this invention should just employ | adopt the conditions in the wet copper plating method by a conventional method for both primary and secondary.

3-4. Formation of wiring pattern Using the two-layer flexible printed board according to the present invention as described above, a flexible printed wiring board is obtained by individually forming a wiring pattern on at least one surface of the two-layer flexible printed board. In addition, via holes for interconnecting wiring layers can be formed at predetermined positions and used for various purposes.

More specifically, the wiring pattern is formed by the following process.
(A) A high-density wiring pattern is individually formed on at least one surface of a flexible printed board (also referred to as a flexible sheet).
(B) A via hole penetrating the wiring layer and the flexible sheet is formed in the flexible sheet on which the wiring pattern (also referred to as a wiring layer) is formed.
(C) In some cases, the via hole is filled with a conductive substance to make the hole conductive.

  As a method for forming such a wiring pattern, a conventionally known method such as photoetching can be used. For example, a two-layer flexible printed board having a base metal layer and a copper coating layer made of a copper layer formed on at least one side is prepared. Then, after screen printing or laminating a dry film on the copper layer to form a photosensitive resist film, exposure and development are performed for patterning. Next, the copper coating layer is selectively removed by etching with an etching solution, and then the resist is removed to form a predetermined wiring pattern.

  Specifically, first, the copper layer of the two-layer flexible printed board is etched with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid. Etching treatment of the copper layer uses an etching device that sprays a ferric chloride solution or a cupric chloride solution containing hydrochloric acid like a shower, and etches so that the oxygen concentration in the atmosphere in the device is 2% by volume or less. Keep inside the device. The etching apparatus used in the present invention is a known etching apparatus that injects an etching solution like a shower, as long as the atmosphere can be controlled, and includes a nitrogen generator to reduce the oxygen concentration in the atmosphere, or a nitrogen gas or argon The oxygen concentration is adjusted by flowing an inert gas such as a gas. A gas mainly composed of an inert gas whose oxygen concentration is controlled to 2% by volume or less may be flowed.

  Thereafter, the obtained two-layer flexible printed board is treated with a nickel-chromium alloy selective removal solution. As this nickel-chromium alloy selective removal liquid, a liquid having a component composition composed of a permanganate and an acidic oxidant is used. Known international publications WO / 2009/8273 or WO / 2009/34764 are known. The solution of the component composition described in the gazette can be used.

  Furthermore, in the selective removal process using a solution containing a permanganate, manganese or the like, which is a solution component, may adhere to the etched surface after the process and form a metal compound such as an oxide. . In order to remove this, treatment with an organic acid aqueous solution such as oxalic acid or ascorbic acid having reducibility, or a commercially available manganese residue remover used to remove manganese residues in alkaline permanganate etchants Good.

  As described above, if the method for producing a flexible printed board of the present invention is used, there is no occurrence of penetration into the nickel-chromium alloy layer under the leads, and a nickel-chromium residue between the wirings or in the rough portion is generated. Therefore, it is possible to carry out fine wiring processing.

  Furthermore, in order to further increase the density of the wiring, it is preferable to prepare a two-layer flexible substrate having a copper coating layer formed on both sides, apply a wiring mask pattern on both sides, and form a wiring pattern on both sides of the substrate. . Whether or not the entire wiring pattern is divided into the number of wiring areas depends on the distribution of the wiring density of the wiring pattern. For example, the wiring pattern is divided into a high-density wiring area having a wiring width and a wiring interval of 50 μm or less, and the like. In consideration of the thermal expansion difference from the printed circuit board and the convenience in handling, the size of the wiring board to be divided may be set to about 10 to 65 mm and divided appropriately.

As a method for forming the via hole, a conventionally known method can be used. For example, a via hole penetrating the wiring pattern and the flexible sheet is formed at a predetermined position of the wiring pattern by laser processing, photoetching, or the like. The diameter of the via hole is preferably reduced within a range that does not hinder the conductivity in the hole, and is usually 100 μm or less, preferably 50 μm or less.
This via hole is filled with a conductive metal such as copper by plating, vapor deposition, sputtering, etc., or a conductive paste is press-fitted and dried using a mask having a predetermined opening pattern to make the inside of the hole conductive. To make electrical connection between layers. Copper, gold, nickel or the like is used as the conductive metal.

Hereinafter, the present invention will be described in more detail with reference to examples.
The nickel-chromium alloy layers in the examples and comparative examples used an insulator film polyimide film (manufactured by Toray DuPont, film thickness 25 μm, hereinafter referred to as PI), and a 20 wt% chromium-nickel alloy target (hereinafter referred to as PI) Sumitomo Metal Mining Co., Ltd.) and a thickness of 20 to 30 nm by a direct current sputtering method.

Furthermore, the copper layer was formed in the range of 100-120 nm by the direct current | flow sputtering method on the polyimide film, the copper layer was formed in thickness of 8 micrometers by the electroplating method, and the copper polyimide board | substrate was produced and it was set as the test material. The commercially available etching liquid CH-1920 (made by MEC Co., Ltd.) was used for the selective removal process of a nickel-chromium alloy layer.

  Using the etching conditions shown in Table 1, the copper polyimide substrate was prepared as an entire surface etching substrate of the copper coating layer and a 30 μm pitch insulation reliability test specimen, and as a nickel-chromium alloy layer removal treatment, After immersion for 1 minute in a CH-1920 (MEC Co., Ltd.) solution at a liquid temperature of 40 ° C., the solution was taken out and washed with water for 20 seconds.

  The degree of dissolution of the nickel-chromium alloy layer is described in Table 2 as “No residue” when the nickel-chromium alloy is dissolved over the entire surface, and “No residue” when a residue that can be confirmed by microscopic observation is observed. did. In addition, if a nickel-chromium alloy residue is confirmed, the etching time is extended until no residue is found, and the substrate is further immersed in a 2% oxalic acid aqueous solution at 40 ° C. for 1 minute and then washed with water for 20 seconds. did.

  In addition, in order to quantitatively analyze the residual metal component on the film surface, which was evaluated as “No residue”, each sample was dissolved in a solution composed of 5 ml of nitric acid and 1 ml of hydrogen peroxide using a microwave decomposition apparatus. The metal component in each obtained solution was quantitatively analyzed with an inductively coupled plasma ion source mass spectrometer. Table 2 shows the residual amounts of nickel and chromium.

Insulation reliability is achieved by applying a voltage of 60 V between the terminals in an atmosphere where electroless Sn plating is applied to the wiring processed to a pitch of 30 μm and the temperature is maintained at 85 ° C. and humidity of 85%. It evaluated by measuring. The pass / fail judgment is “○” when the insulation resistance continuously shows 10 ⁶ Ω or more in continuous measurement for 1000 hours: “Pass”, and “X” when the resistance value is less than 10 ⁶ Ω: Passed. The resistance value did not become less than 10 ⁶ Ω but decreased from the initial value and greatly fluctuated.

The etching treatment of the copper layer was performed using an etching apparatus in which a 40 ° Baume ferric chloride aqueous solution was sprayed in a shower and the atmosphere in the etching apparatus was an atmosphere in which 99.99% nitrogen gas was flowed. The oxygen concentration in the etching zone was 0% by volume (hereinafter referred to as%).
Under microscopic observation, no nickel-chromium residue was found on the PI surface after etching. The result of the insulation reliability test was “◯”: Passed.

The etching treatment of the copper layer was performed in the same manner as in Example 1 except that the atmosphere in the etching apparatus was a gas flow atmosphere using a mixed gas of 2% oxygen + 98% nitrogen. The oxygen concentration in the etching zone was 2%.
Under microscopic observation, no nickel-chromium residue was found on the PI surface after etching. The result of the insulation reliability test was “◯”: Passed.

The same procedure as in Example 1 was performed except that the nickel-chromium alloy layer was not selectively removed.
Microscopic observation revealed no nickel-chromium residue on the PI surface after etching. The result of the insulation reliability test was “◯”: Passed.

(Comparative Example 1)
The etching was performed in the same manner as in Example 1 except that the etching was performed in a gas flow atmosphere using a mixed gas of 4% oxygen + 96% nitrogen. The oxygen concentration in the etching zone was 4%.
Microscopic observation revealed no nickel-chromium residue on the etched polyimide surface. The result of the insulation reliability test was “Δ”.

(Comparative Example 2)
The etching process was performed in the same manner as in Example 1 except that the etching process was performed in a gas flow atmosphere using a mixed gas of 10% oxygen + 90% nitrogen. The oxygen concentration in the etching zone was 10%.
Microscopic observation showed nickel-chromium residues on the PI surface after etching. The result of the insulation reliability test was “×”: failed.

(Comparative Example 3)
The etching process was performed in the same manner as in Example 1 except that the etching process was performed in an air atmosphere. The oxygen concentration in the etching zone was 20.9%.
Microscopic observation showed nickel-chromium residues on the PI surface after etching. The result of the insulation reliability test was “×”: failed.

  As described above, according to the method for manufacturing a printed wiring board according to the present invention, in particular, the etching method according to the present invention, the ferric chloride solution or hydrochloric acid of the conventional two-layer flexible substrate is contained in a cheap and simple process. The generation of the residue of the base metal layer component due to oxygen during the etching process with the cupric chloride solution is suppressed as much as possible, and a fine wiring having a high insulation resistance can be easily obtained, and the effect is extremely great.

Claims (8)

A method for manufacturing a flexible printed circuit board, comprising:
The oxygen concentration in the etching atmosphere in the step of forming a copper wiring pattern by etching a copper coating layer formed on at least one surface of the insulator film without using an adhesive is maintained at 2% by volume or less. A method for producing a flexible printed board characterized by the above.   The method for producing a flexible printed board according to claim 1, wherein the copper coating layer has a structure in which a nickel alloy layer and a copper layer are laminated in this order from the insulator film side.   The copper coating layer is formed on the insulator film by a dry plating method, and a nickel-chromium alloy base metal layer containing 3 to 40 nm of chromium having a thickness of 3 to 40 nm, and on the base metal layer The method for producing a flexible printed board according to claim 2, wherein the copper layer is a formed copper layer having a thickness of 10 nm to 35 μm. Etching the copper coating layer,
2. The method according to claim 1, further comprising: removing a base metal layer with a selective removing solution that selectively removes the base metal layer after the copper layer of the copper coating layer is etched to form a copper wiring pattern. 4. The method for producing a flexible printed board according to any one of items 1 to 3. An etching solution for etching the copper layer is
The method for producing a flexible printed circuit board according to any one of claims 1 to 4, wherein the solution is a ferric chloride solution or a cupric chloride solution containing hydrochloric acid. In the etching treatment method with a chemical solution of a laminate having a structure in which a copper layer is laminated on a nickel alloy layer,
An etching method characterized by maintaining an oxygen concentration in an atmosphere during the etching process at 2% by volume or less. The nickel alloy layer is
7. The etching method according to claim 6, which is a nickel-chromium alloy containing 5 to 24% by weight of chromium having a thickness of 3 to 40 nm. The chemical solution is
The etching method according to claim 6 or 7, which is a ferric chloride solution or a cupric chloride solution containing hydrochloric acid.