JP2013080735A - Copper foil for printed wiring board having excellent productivity and laminate sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for a printed wiring board capable of manufacturing a circuit having a cross section shape which is suitable for finer pitches and whose skirt is small with excellent manufacturing efficiency and to provide a laminate sheet using the same.SOLUTION: A copper foil for a printed wiring board includes: a copper foil base material; and a coating layer which covers at least a part of the surface of the copper foil base material and includes one kind or more selected from the group consisting of Au, Pt, Pd and Mo. In the coating layer, the amount of deposited A is 650 μg/dmor less, the amount of deposited Pt is 650 μg/dmor less, the amount of deposited Pd is 400 μg/dmor less and the amount of deposited Mo is 1000 μg/dmor less. When a circuit having a prescribed width and a prescribed pitch is formed, and a cupric chloride solution whose cupric chloride concentration is 2.0M and hydrochloric acid concentration is 0-4.5M or a ferric chloride solution whose cupric chloride concentration is 3.2M and hydrochloric acid concentration is 0-1.0M is injected at 50°C with a pressure of 0.2 MPa to perform etching, time until the bottom width becomes a half of the circuit pitch is shorter than a case where the coating layer is not formed by 1 second or more.

Description

  The present invention relates to a copper foil for a printed wiring board and a laminated board using the same, and more particularly to a copper foil for a flexible printed wiring board and a laminated board using the same.

  Printed wiring boards have made great progress over the last half century and are now used in almost all electronic devices. In recent years, with the increasing needs for miniaturization and higher performance of electronic devices, higher density mounting of components and higher frequency of signals have progressed, and conductor patterns have become finer (fine pitch) and higher frequency than printed circuit boards. Response is required.

  A printed wiring board is made by bonding an insulating substrate to a copper foil, or depositing a Ni alloy or the like on the insulating substrate and then forming a copper layer by electroplating to form a copper-clad laminate, and then etching the copper foil or copper layer surface. In general, it is manufactured through a process of forming a conductor pattern. Therefore, good etching properties are required for the copper foil or copper layer for printed wiring boards.

  As a technique for improving the etching property, for example, Patent Document 1 includes a silver-based coating layer made of silver or a silver-palladium alloy on a bonding surface with an insulating base material that is a constituent material of a copper-clad laminate. An invention relating to a copper foil with a silver-based coating layer is disclosed.

JP 2005-101398 A

  However, in order to form a precise circuit of a level required in recent years for a high-density mounting substrate, it is not sufficient that the etching property of the copper foil is simply good. That is, the etching property required in recent years means that the metal derived from the surface treatment does not remain in the insulating part between the circuits and that the circuit is less skirted. If metal remains in the insulating part between the circuits, a short circuit occurs between the circuits. In the etching for forming the circuit, the circuit is etched from the upper surface to the lower side (insulating substrate side), and the cross section of the circuit becomes a trapezoid. If the difference between the upper and lower bases of the trapezoid (hereinafter referred to as “tailing”) is small, the space between circuits can be narrowed, and a high-density wiring board can be obtained. If the skirting is large, the circuit is short-circuited if the space between the circuits is narrowed, so that a high-density mounting substrate cannot be manufactured.

  On the other hand, the invention disclosed in Patent Document 1 forms a coating layer made of a noble metal on the roughened surface of the copper foil, so it does not suppress side etch, and a circuit with a small tail is provided. It may be difficult to produce well.

  Etching proceeds in the thickness direction and the planar direction of the copper base material. At this time, if the etching time is long, the etching proceeds in the planar direction of the copper base material, so that the circuit cross-sectional area is reduced. There's a problem. In order to suppress such etching in the planar direction, a method of performing anisotropic etching with priority in the thickness direction or a method of shortening the etching time by forming a circuit using a thin copper substrate is considered. It is done.

  However, in the former method, the etching time becomes long, and in the latter method, there is a possibility that the circuit cross-sectional area decreases and the conductor resistance increases.

  Therefore, the present invention is to provide a copper foil for printed wiring boards and a laminate using the copper foil, which can produce a circuit having a small cross-sectional shape suitable for fine pitching and having a good manufacturing efficiency. And

  As a result of intensive studies, the present inventors have found that when a trace amount of noble metal is deposited as a layer on the etched surface of the copper foil, the bottom of the formed circuit is reduced, thereby enabling the formation of a high-density mounting substrate. I found out. Such a configuration is based on a completely different idea from the configuration in which the coating layer made of the noble metal described in Patent Document 1 is formed on the roughened surface of the copper foil, and the effect is also greatly different. . Furthermore, it has been found that by depositing a small amount of noble metal as a layer on the etched surface of the copper foil in this way, the etching time is shortened and the circuit manufacturing efficiency is improved.

The present invention completed on the basis of the above knowledge is selected from the group consisting of a copper foil base material and at least a part of the surface of the copper foil base material and made of Au, Pt, Pd and Mo in one aspect. and a least one of the containing coating layer, the adhesion amount of Au in the coating layer is 650μg / dm ² or less, the adhesion amount of Pt is 650μg / dm ² or less, the adhesion amount of Pd is 400 [mu] g / dm ² or less, Mo An aqueous solution of cupric chloride having a deposition amount of 1000 μg / dm ² or less, forming a circuit having a predetermined width and a predetermined pitch, a cupric chloride concentration of 2.0 M, and a hydrochloric acid concentration of 0 to 4.5 M; Or, when etching by spraying an aqueous cupric chloride solution having a ferric chloride concentration of 3.2 M and a hydrochloric acid concentration of 0 to 1.0 M at a pressure of 0.2 MPa at 50 ° C., the bottom width of the circuit Is the time until the circuit pitch becomes half of the circuit pitch. It is a copper foil for printed wiring boards that is shorter by 1 s or more than when no coating layer is formed.

  In one embodiment of the copper foil for printed wiring board according to the present invention, the coating layer further contains one or more of Co, Ni, Cr, Sn, V, and Zn.

  In another embodiment of the copper foil for printed wiring boards according to the present invention, a layer containing any one or more of Co, Ni, Cr, Sn, V and Zn between the surface of the coating layer or the copper foil. Is provided.

  In another aspect, the present invention is a laminate of the copper foil of the present invention and a resin substrate.

  In still another aspect, the present invention is a laminate including a copper layer and a resin substrate, the laminate including the coating layer of the present invention that covers at least a part of the surface of the copper layer.

  In one embodiment of the laminate according to the present invention, the resin substrate is a polyimide substrate.

  In yet another aspect, the present invention is a printed wiring board made from the laminate of the present invention.

  According to another aspect of the present invention, a step of preparing a rolled copper foil or an electrolytic copper foil composed of the copper foil of the present invention, and the copper foil and the resin substrate with the coating layer of the copper foil as an etching surface And a step of etching the laminate with an aqueous ferric chloride solution or an aqueous cupric chloride solution to remove unnecessary portions of copper to form a copper circuit. A method for forming a circuit.

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil for printed wiring boards which can manufacture the circuit of the cross-sectional shape with small footing suitable for fine pitch production with favorable manufacturing efficiency, and a laminated board using the same can be provided. .

It is the outline | summary of the calculation method of the etching factor (EF) using the surface photograph of a part of circuit pattern, the schematic diagram of the cross section of the width direction of the circuit pattern in the said part, and this schematic diagram. 22 is a circuit photograph of Example 24. 10 is a circuit photograph of Comparative Example 11.

(Copper foil base material)
Although there is no restriction | limiting in particular in the form of the copper foil base material which can be used for this invention, Typically, it can use with the form of rolled copper foil or electrolytic copper foil. In general, the electrolytic copper foil is produced by electrolytic deposition of copper from a copper sulfate plating bath onto a drum of titanium or stainless steel, and the rolled copper foil is produced by repeating plastic working and heat treatment with a rolling roll. Rolled copper foil is often used for applications that require flexibility.
In addition to high-purity copper such as tough pitch copper and oxygen-free copper, which are usually used as conductor patterns for printed wiring boards, for example, Sn-containing copper, Ag-containing copper, Cr, Zr or Mg are added as the copper foil base material. It is also possible to use a copper alloy such as a copper alloy, a Corson copper alloy to which Ni, Si and the like are added. In addition, when the term “copper foil” is used alone in this specification, a copper alloy foil is also included.

  There is no restriction | limiting in particular also about the thickness of the copper foil base material which can be used for this invention, What is necessary is just to adjust to the thickness suitable for printed wiring boards suitably. For example, it can be set to about 5 to 100 μm. However, for the purpose of forming a fine pattern, it is 30 μm or less, preferably 20 μm or less, and typically about 5 to 20 μm.

  Although the copper foil base material used for this invention is not specifically limited, For example, you may use what does not perform a roughening process. Conventionally, the surface is generally roughened by special plating with irregularities on the order of μm, and the physical anchor effect provides adhesion to the resin. A smooth foil is considered to have good characteristics, and a roughened foil may work in a disadvantageous direction. Moreover, since the roughening process process is abbreviate | omitted if it does not perform a roughening process, there exists an effect of economical efficiency and productivity improvement.

(1) Structure of coating layer The coating layer is formed in at least one part of the surface on the opposite side (circuit formation plan side) of the copper foil base material with the insulating substrate. The coating layer contains one or more selected from the group consisting of Au, Pt, Pd, and Mo. Examples of the metal other than Au, Pt, Pd, and Mo include one or more selected from the group consisting of Co, Ni, Cr, Sn, V, and Zn. When a small amount of noble metal is attached to the etched surface of the copper foil in this way, the bottom of the formed circuit is reduced. As a result, even if the copper foil is not thin, it is possible to form a circuit with a small trailing edge, and thus a high-density mounting substrate can be formed. The thickness of the coating layer is 0.1 to 3.0 nm, preferably 0.5 to 2.0 nm for Au, Pt, and Pd, and 0.1 to 10 nm, preferably 0.5 to 5.0 nm for Mo. is there. If the thickness of the coating layer is less than 0.1 nm, the etching promoting effect is insufficient and an etching time comparable to that of the blank material is required. On the other hand, if Au, Pt, and Pd are 3.0 nm, and Mo is more than 10 nm, the initial etching property may be deteriorated. If the thickness of the uppermost layer covering Au, Pt, Pd, and Mo exceeds 3.0 nm, the initial etching property may be deteriorated and an etching time as long as the blank material may be required, so 3.0 nm or less is preferable.

(2) Identification of coating layer The coating layer can be identified by the presence of each detected peak by performing argon sputtering from the surface layer with a surface analyzer such as XPS or AES and performing chemical analysis in the depth direction.

(3) Adhesion amount When the coating layer contains Au, the adhesion amount of Au is 650 μg / dm ² or less, preferably 40 to 650 μg / dm ² , more preferably 70 to 420 μg / dm ² . When the coating layer contains Pt, the adhesion amount of Pt is 650 μg / dm ² or less, preferably 40 to 650 μg / dm ² , more preferably 70 to 420 μg / dm ² . If the coating layer containing Pd is the amount of adhesion of Pd is 400 [mu] g / dm ² or less, preferably 20~400μg / dm ^2, more preferably 50~240μg / dm ^2. When the coating layer contains Mo, the adhesion amount of Mo is 1000 μg / dm ² or less, preferably ²⁰ to 1000 μg / dm ² , and more preferably 40 to 600 μg / dm ² . Adhesion amount of Au in the coating layer is 650μg / dm ^2, more than the amount deposited of Pt of the coating layer is 650μg / dm ² than the coating weight is 400 [mu] g / dm ² than the Pd coating layer, and the adhesion of Mo in the coating layer If the amount is more than 1000 μg / dm ² , the initial etching property is deteriorated. Therefore, although the etching acceleration effect is estimated to be exhibited, the total time required for etching becomes equal to or more than that of the blank material.

Further, the coating layer may include Co and Ni, deposition amount of Co is at 300 [mu] g / dm ² or less, preferably 50~250μg / dm ^2. The coating weight of Ni is at 300 [mu] g / dm ² or less, preferably 50~250μg / dm ^2. When the coating amount of Co and Ni on the coating layer is more than 300 μg / dm ² , the initial etching property is deteriorated. Therefore, although the etching acceleration effect is estimated to be exhibited, the total time required for etching is equal to or more than that of the blank material. Become.

(4) Etching time The copper foil for printed wiring boards according to the present invention forms a circuit having a predetermined width and a predetermined pitch, and has a cupric chloride concentration of 2.0 M and a hydrochloric acid concentration of 0 to 4.5 M. When etching by spraying a cupric chloride aqueous solution or a cupric chloride aqueous solution having a ferric chloride concentration of 3.2 M and a hydrochloric acid concentration of 0 to 1.0 M at a pressure of 0.2 MPa at 50 ° C. The time until the bottom width of the circuit becomes half of the circuit pitch is 1 s or more shorter than the case where the coating layer is not formed. As described above, the copper foil for a printed wiring board according to the present invention has a small amount of noble metal deposited as a layer on the etched surface of the copper foil, so that the etching time is shortened and the circuit manufacturing efficiency is improved. Furthermore, since the etching time is short, the progress of etching in the planar direction is suppressed, and there is an advantage that the cross-sectional area of the circuit increases. Here, the principle of shortening the etching time by depositing a small amount of noble metal as a layer on the etching surface of the copper foil will be described. Since the noble metal remaining on the back side of the resist reduces the etching solution, corrosion proceeds in the thickness direction of the copper base material. At this time, a local battery effect is manifested between the coating layer and the copper substrate (the copper substrate is oxidized at a position corresponding to the circuit bottom in order to supply electrons for etching solution reduction to the coating layer) . That is, since the corrosion of the copper base at the position corresponding to the circuit bottom proceeds with the effect of the etching solution and the local battery effect, the circuit can be formed in a shorter time than when the coating layer is not formed.

In cupric chloride etching,
^{Cu + Cu 2+ + 2Cl - →} 2CuCl ↓
_{^{CuCl ↓ + Cl - → CuCl 2}} -
The two-stage reaction takes place. Etching proceeds when Cl ⁻ is coordinated to the insoluble salt CuCl produced and the insoluble salt is dissolved [complex (CuCl ₂ ⁻ ) is generated]. Hydrochloric acid Cl ^- is added to facilitate the dissolution of insoluble salts as a source of. For this reason, if the hydrochloric acid concentration is low, the etching time will be longer if the blank material is not subjected to surface treatment, but the surface-treated copper foil according to the present invention requires a shorter etching time than the blank material. It becomes.

  In order to enhance the rust prevention effect or prevent the resist from being peeled off from the copper base material during etching, the outermost layer on the coating layer is further made of any one of Co, Ni, Cr, Sn, V, and Zn. A layer containing at least one kind and / or a rust prevention treatment layer composed of a silane treatment layer can be formed. Further, in order to further suppress oxidation due to heat treatment between the coating layer and the copper foil, one or more of Co, Ni, Cr, Sn, V and Zn as an underlayer having oxidation resistance is included. A layer may be formed.

(Manufacturing method of copper foil)
The copper foil for printed wiring boards according to the present invention can be formed by a sputtering method. That is, at least a part of the surface of the copper foil base material is coated with the coating layer by a sputtering method. Specifically, a layer made of one or more selected from the group consisting of Au, Pt, Pd, and Mo having a lower etching rate than copper is formed on the etching surface side of the copper foil by sputtering. The coating layer is not limited to the sputtering method, and may be formed by, for example, a wet plating method such as electroplating or electroless plating. At this time, the coating layer may be formed by adding one or more selected from the group consisting of Co, Ni, Cr, Sn, V, and Zn.
Moreover, it is preferable that the copper foil for printed wiring boards which concerns on this invention removes an oxide film etc. by a well-known means as a pretreatment before performing a sputtering process.

(Printed wiring board manufacturing method)
A printed wiring board (PWB) can be manufactured according to a conventional method using the copper foil according to the present invention. Below, the example of the manufacturing method of a printed wiring board is shown.

  First, a laminated body is manufactured by bonding a copper foil and an insulating substrate. The insulating substrate on which the copper foil is laminated is not particularly limited as long as it has characteristics applicable to a printed wiring board. For example, paper base phenolic resin, paper base epoxy resin, synthetic fiber for rigid PWB Use cloth base epoxy resin, glass cloth / paper composite base epoxy resin, glass cloth / glass non-woven composite base epoxy resin, glass cloth base epoxy resin, etc., use polyester film, polyimide film, etc. for FPC I can do things.

  In the case of the rigid PWB, a prepreg is prepared by impregnating a base material such as a glass cloth with a resin and curing the resin to a semi-cured state. It can be carried out by superposing a copper foil on the prepreg from the opposite surface of the coating layer and heating and pressing.

  In the case of a flexible printed wiring board (FPC), a polyimide film or a polyester film and a copper foil can be bonded using an epoxy or acrylic adhesive (three-layer structure). In addition, as a method without using an adhesive (two-layer structure), a polyimide varnish (polyamic acid varnish), which is a polyimide precursor, is applied to a copper foil and heated to form an imidization or on a polyimide film. There is a laminating method in which a thermoplastic polyimide is applied to the substrate, a copper foil is overlaid thereon, and heated and pressed. In the casting method, it is also effective to apply an anchor coating material such as thermoplastic polyimide in advance before applying the polyimide varnish.

  The laminate according to the present invention can be used for various printed wiring boards (PWB) and is not particularly limited. For example, from the viewpoint of the number of layers of the conductor pattern, the single-sided PWB, double-sided PWB, and multilayer PWB ( It is applicable to rigid PWB, flexible PWB (FPC), and rigid flex PWB from the viewpoint of the type of insulating substrate material. Further, the laminate according to the present invention is not limited to the above-described copper-clad laminate obtained by attaching a copper foil to a resin, and is a metalizing material in which a copper layer is formed on the resin by sputtering or plating. Also good.

A resist is applied to the surface of the coating layer formed on the copper foil of the laminate produced as described above, the pattern is exposed with a mask, and developed to form a resist pattern.
Subsequently, the coating layer exposed at the opening of the resist pattern is removed using a reagent. As the reagent, one containing hydrochloric acid, sulfuric acid or nitric acid as a main component is preferably used for reasons such as availability. Since the noble metal layer is very thin, it diffuses moderately with the copper of the copper foil base material due to the thermal history at the time of manufacture, and the copper atoms that have reached the vicinity of the outermost layer by this diffusion are heated in the atmosphere or in the resist drying process. Is oxidized to produce copper oxide. Since the copper oxide in the noble metal / copper alloy layer formed by diffusion is easily dissolved by an acid, the noble metal is removed at the same time. Therefore, even a noble metal layer having corrosion resistance can be easily removed from the exposed portion of the opening of the resist pattern.
Next, the laminate is immersed in an etching solution. At this time, the coating layer containing any one or more of platinum, palladium, and gold that suppresses etching is located near the resist portion on the copper foil, and the etching of the copper foil on the resist side is performed by this coating layer. Etching of the copper circuit pattern proceeds substantially vertically by etching of the copper in a portion away from the coating layer at a speed faster than the speed at which the vicinity is etched. Thus, unnecessary portions of copper can be removed, and then the etching resist can be peeled and removed to expose the circuit pattern.
With respect to the etching solution used for forming the circuit pattern on the laminate, the etching rate of the coating layer is sufficiently smaller than that of copper, so that the etching factor is improved. As the etching solution, a cupric chloride aqueous solution, a ferric chloride aqueous solution, or the like can be used.
In addition, a heat-resistant layer may be formed in advance on the surface of the copper foil base before forming the coating layer.

(Circuit shape on the copper foil surface of the printed wiring board)
As described above, the circuit on the copper foil surface of the printed wiring board formed by etching from the coating layer side is not usually formed with two long side surfaces perpendicular to the insulating substrate. From the surface of the foil downward, that is, toward the resin layer, it is formed so as to spread toward the end (generation of sagging). Thus, the two long side surfaces each have an inclination angle θ with respect to the surface of the insulating substrate. It is important to reduce the circuit pitch as much as possible for miniaturization (fine pitch) of the circuit pattern that is currently required. However, if this inclination angle θ is small, the sagging increases accordingly, The pitch becomes wider. In addition, the inclination angle θ is usually not completely constant in each circuit and circuit. If the variation in the inclination angle θ is large, the circuit quality may be adversely affected. Accordingly, the circuit on the copper foil surface of the printed wiring board formed by etching from the coating layer side has two long side surfaces each having an inclination angle θ of 65 to 90 ° with respect to the insulating substrate surface, In addition, it is desirable that the standard deviation of tan θ in the same circuit is 1.0 or less. The etching factor is preferably 1.5 or more, and more preferably 2.5 or more when the circuit pitch is 50 μm or less.

  EXAMPLES Examples of the present invention will be described below, but these are provided for better understanding of the present invention and are not intended to limit the present invention.

(Example 1: Examples 1 to 24)
(Formation of coating layer)
As the copper foil base material of Examples 1 to 24, a rolled copper foil (C1100 manufactured by JX Nippon Mining & Metals) having a thickness of 8 or 17 μm was prepared.

The thin oxide film adhering to the surface of the copper foil is removed by reverse sputtering, and the target of Au, Pt, Pd, Mo, Ni, Co, Cr, Sn, Zn, V, or an alloy thereof is subjected to the following apparatus and conditions. The coating layer was formed on the plated copper layer surface by sputtering. The simple substance of the various metals used for sputtering used the thing of purity 3N. Moreover, NiV (V is 7 mass%), NiZn (Zn is 20 mass%), NiSn (Sn is 20 mass%), etc. were used as specific alloy targets. In the order of film formation, one of Au, Pd, Pt, and Mo was formed, and a layer made of at least one of Co, Ni, Cr, Sn, V, and Zn was used.
-Equipment: Batch type sputtering equipment (ULVAC, Model MNS-6000)
・ Achieving vacuum: 1.0 × 10 ⁻⁵ Pa
・ Sputtering pressure: 0.2 Pa
・ Reverse sputtering power: 50W
・ Reverse sputtering time: 300 seconds ・ Sputtering power: 50 W
Film formation rate: About 0.2 μm of film was formed for each target for a fixed time, the thickness was measured with a three-dimensional measuring device, and the sputtering rate per unit time was calculated.
-Equipment: Batch type sputtering equipment (ULVAC, Model MNS-6000)
・ Achieving vacuum: 1.0 × 10 ⁻⁵ Pa
・ Sputtering pressure: 0.2 Pa

The thin oxide film previously attached to the copper foil substrate surface under the following conditions is removed by reverse sputtering on the copper foil substrate surface on the opposite side of the surface on which the coating layer is formed, and Ni and Cr alone are removed. A Ni layer and a Cr layer were sequentially formed by sputtering a layer target. The thicknesses of the Ni layer and the Cr layer were changed by adjusting the film formation time.
-Equipment: Batch type sputtering equipment (ULVAC, Model MNS-6000)
・ Achieving vacuum: 1.0 × 10 ⁻⁵ Pa
・ Sputtering pressure: 0.2 Pa
・ Reverse sputtering power: 100W
·target:
For Ni layer = Ni (purity 3N)
For Cr layer = Cr (purity 3N)
・ Sputtering power: 50W
Film formation rate: About 0.2 μm of film was formed for each target for a fixed time, the thickness was measured with a three-dimensional measuring device, and the sputtering rate per unit time was calculated.

<Measurement of adhesion amount>
The coating amount of the coating layer was measured by dissolving about 50% of the copper layer in a solution of a 50 mm × 50 mm copper layer surface mixed with HNO ₃ (2 wt%) and HCl (5 wt%). The metal concentration was quantified with an ICP emission spectroscopic analyzer (SFC-3100, manufactured by SII Nanotechnology Co., Ltd.), and the amount of metal per unit area (μg / dm ² ) was calculated.

A polyimide film with an adhesive (Nikkan Kogyo, CISV1215) was bonded to the Ni layer and Cr layer forming side surfaces of the copper foil base material under the conditions of pressure 7 kgf / cm ² , 160 ° C., 40 minutes.

(Circuit shape by etching)
Etching was performed under the following conditions by printing 10 21 μm or 33 μm wide circuits on the surface of the copper foil with the surface treatment layer formed thereon by a photosensitive resist coating and exposure process, and removing unnecessary portions of the copper foil. .

<Etching conditions>
Etching was performed using a spray etching apparatus under the following conditions.
-Liquid composition Each of the following two systems of etchants was evaluated.
(1) Cupric chloride (2.0M) + hydrochloric acid (1.5M, 3.0M, 4.5M)
(2) Ferric chloride (3.2M) + hydrochloric acid (0M, 1.0M)
・ Spray pressure: 0.2MPa
・ Liquid temperature: 50 ℃
(30 μm pitch circuit formation (in the case of 8 μm thick copper foil))
・ Resist L / S = 21μm / 9μm
-Finished circuit bottom (bottom) width: 15 μm
-Confirmation of etching end point: Etching was carried out at several levels by changing the time, and it was confirmed by an optical microscope that no copper remained between the circuits.
After the etching, the resist was peeled off by being immersed in an aqueous NaOH solution (100 g / L) at 45 ° C. for 1 minute.
(40 μm pitch circuit formation (in the case of 17 μm thick copper foil))
・ Resist L / S = 33μm / 7μm
-Finished circuit bottom (bottom) width: 20 μm
-Confirmation of etching end point: Etching was carried out at several levels by changing the time, and it was confirmed by an optical microscope that no copper remained between the circuits.
After the etching, the resist was peeled off by being immersed in an aqueous NaOH solution (100 g / L) at 45 ° C. for 1 minute.

<Etching factor measurement conditions>
The etching factor is the distance of the length of the sag from the intersection of the vertical line from the copper layer and the resin substrate, assuming that the circuit is etched vertically when sag is widened (when sag occurs). In the case of a, the ratio of a to the thickness b of the copper layer is shown as b / a. As this value is larger, the inclination angle becomes larger, the etching residue does not remain, and the sagging is reduced. Means that. FIG. 1 shows a surface photograph of a part of a circuit pattern, a schematic diagram of a cross section in the width direction of the circuit pattern at the part, and an outline of a method for calculating an etching factor using the schematic diagram. This a was measured by SEM observation from above the circuit, and the etching factor (EF = b / a) was calculated. By using this etching factor, it is possible to easily determine whether the etching property is good or bad. The measurement range was a circuit length of 600 μm, and an etching factor of 12 points, its standard deviation and an average value were adopted as a result.

(Example 2: Example 25)
As Example 25, a 17 μm-thick rolled copper foil (Nikko Metal C1100) was prepared. After removing the oxide of the copper layer by the procedure of Example 1 to form a Pd layer, a NiV layer was formed by sputtering. Thereafter, the etching property and the like were evaluated by the procedure of Example 1.

(Example 3: Comparative Examples 1 and 11)
As Comparative Examples 1 and 11, 8 or 17 μm thick rolled copper foil (Nikko Metal C1100) was prepared. Next, 10 circuits were printed on the copper layer by a photosensitive resist coating and exposure process, and an etching process for removing unnecessary portions of the copper layer was performed.

(Example 4: Comparative Examples 2 to 10)
As Comparative Examples 2 to 10, 8 μm-thick rolled copper foil (Nikko Metal C1100) was prepared, and a surface treatment layer composed of various metals was formed on the copper layer surface by sputtering in the same procedure as in Example 1 and etched. A circuit was formed.
Each test condition and measurement result of Examples 1-4 are shown in Tables 1-3.
2 and 3 show circuit photographs of Example 24 and Comparative Example 11, respectively.

<Evaluation>
In each of Examples 1 to 25, the etching factor is larger than that of the blank material (Comparative Example 1 or 11) under any condition, and the etching time until the circuit bottom width becomes half the circuit pitch is 1 s or shorter. It was.
Although Comparative Examples 2 to 10 had a higher etching factor than the blank material (Comparative Example 1), the etching time until the bottom width of the circuit became half the circuit pitch was equal or longer. Moreover, these etching factors are low when compared with the Examples.
Moreover, as the hydrochloric acid concentration becomes thinner, the time until the etching of the surface-treated copper foil according to the example is shorter than that of the blank material. For example, comparing Example 1 with Comparative Example 1, when the hydrochloric acid concentration is 4.5 M, Comparative Example 1 is 33 seconds and Example 1 is 30 seconds (the difference is 3 seconds). On the other hand, when the hydrochloric acid concentration is 1.5M, Comparative Example 1 is 53 seconds, and Example 1 is 45 seconds (the difference is 8 seconds). For this reason, it can be seen that, for example, Example 1 is shorter than Comparative Example 1 even when the hydrochloric acid concentration of the etching solution is OM, the time to completion of etching is shortened by at least 8 seconds.

Claims (8)

A copper foil base material, and a coating layer that covers at least a part of the surface of the copper foil base material and includes at least one selected from the group consisting of Au, Pt, Pd, and Mo,
The adhesion amount of Au in the coating layer is 650μg / dm ² or less, the adhesion amount of Pt is 650μg / dm ² or less, the adhesion amount of Pd is 400 [mu] g / dm ² or less, the adhesion amount of Mo is at 1000 [mu] g / dm ² or less,
A circuit having a predetermined width and a predetermined pitch is formed, an aqueous cupric chloride solution having a cupric chloride concentration of 2.0 M and a hydrochloric acid concentration of 0 to 4.5 M, or a ferric chloride concentration of 3.2 M, And when the aqueous solution of cupric chloride having a hydrochloric acid concentration of 0 to 1.0 M is jetted and etched at a pressure of 0.2 MPa at 50 ° C., the time until the bottom width of the circuit becomes half of the circuit pitch, A copper foil for a printed wiring board that is shorter than the case where the coating layer is not formed by 1 s or more.   The copper foil for printed wiring boards according to claim 1, wherein the coating layer further contains at least one of Co, Ni, Cr, Sn, V, and Zn.   The copper foil for printed wiring boards of Claim 1 or 2 provided with the layer containing any 1 or more types of Co, Ni, Cr, Sn, V, and Zn between the surface of the said coating layer or copper foil.   The laminated body of the copper foil and resin substrate in any one of Claims 1-3. A laminate of a copper layer and a resin substrate,
The laminated body provided with the coating layer in any one of Claims 1-3 which coat | covers at least one part of the surface of the said copper layer.   The laminate according to claim 4 or 5, wherein the resin substrate is a polyimide substrate.   The printed wiring board which used the laminated body in any one of Claims 4-6 as a material. A step of preparing a rolled copper foil or an electrolytic copper foil composed of the copper foil according to claim 1;
A step of producing a laminate of the copper foil and the resin substrate using the coating layer of the copper foil as an etching surface;
Etching the laminate with an aqueous ferric chloride solution or an aqueous cupric chloride solution to remove unnecessary portions of copper to form a copper circuit;
A method of forming an electronic circuit comprising: