JP2011210987A - Copper foil for printed wiring board and layered body which have superior etching property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for a printed wiring board and a layered body which have superior initial etching property, are suitable for fine-pitch fabrication, and form a circuit having a cross-section of an approximately trapezoidal shape with a small difference between its lower base and its upper base.SOLUTION: The copper foil for the printed wiring board includes a copper foil base material and a coating layer which covers at least a part of a surface of the copper foil base material, and includes at least one kind among platinum, palladium and gold, wherein ∫f(x)dx/∫g(x)dx≤15 [the definite integrals of f(x) and g(x) over 0≤x≤1.0] is satisfied, where f(x) represents a distribution of atom concentration (%) of gold, platinum and/or palladium in a depth direction (x: unit nm) from a surface obtained by analysis in the depth direction by the XPS, and g(x) represents a distribution of atom concentration (%) of copper.

Description

  The present invention relates to a copper foil and a laminate for a printed wiring board excellent in etching properties, and particularly relates to a copper foil and a laminate for a flexible printed wiring board.

  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 laminate, and then etching the conductor pattern on the copper foil or copper layer surface. In general, it is manufactured through a process of forming. For this reason, the copper foil or copper layer for printed wiring boards is required to have adhesion and etching properties with an insulating substrate.

  The adhesiveness here means that the formed circuit does not peel from the insulating substrate. For this reason, the roughening process which forms an unevenness | corrugation in the adhesion surface side with the resin of copper foil or a copper layer, and processes, such as Ni plating and chromate, are further performed as needed. Alternatively, from the viewpoint of the skin effect and the like, a method of directly performing a chromate treatment or the like on a copper foil without performing a roughening treatment is also known (Patent Document 1).

  Etchability means that no metal derived from the surface treatment remains in the insulating portion between the circuits, and that the circuit tailing is small. 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 top and bottom of the trapezoid (hereinafter referred to as “tailing”) is small, the space between the 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. Here, FIG. 5 shows an enlarged photograph of the circuit surface showing an example in which tailing occurs during the formation of the copper circuit and the copper circuit is short-circuited in the vicinity of the resin substrate.

  Etching proceeds in two directions: the thickness of the copper foil or copper layer and the plane. Since the etching rate in the plate thickness direction is lower than that in the plane direction, the circuit cross section becomes trapezoidal. For this reason, in order to obtain a circuit with a small footing, the thickness of the copper foil or the copper layer may be reduced to shorten the etching time (Patent Document 2).

  In addition, there is a method of forming a metal having a slower etching rate than copper or an alloy layer thereof on the etching surface side of the copper foil in order to reduce the bottoming (Patent Documents 3 and 4). These candidate metals are Ni, Co and the like. A layer of several tens of nanometers formed by adhering a large amount of these to the etching surface of the copper foil or copper layer suppresses the lateral etching of the upper part of the circuit and forms a circuit with a small tail.

  As the circuit pitch of the printed circuit board becomes finer, the circuit interval also becomes smaller, so the circuit tailing must be small. According to Non-Patent Document 1, the circuit width (L, the unit is μm) and the circuit interval (S, the unit is μm) tend to decrease year by year, and the flexible printed wiring board has L / S = 25 / in 2012. It will reach 25. In order to cope with the fine pitch of the wiring circuit, the thickness of the copper foil must be reduced in order to reduce the bottom of the circuit. However, since the handling at the time of manufacture becomes difficult when the thickness of the copper foil is reduced, it is said that the limit of the wiring pattern that can be handled by the electrolytic copper foil or the rolled copper foil is L / S = 25/25. Even if a metal layer such as Ni or Co is formed on the etched surface of the copper foil, it is expected that it is difficult to cope with such a circuit pattern.

  Further, a method of imparting conductivity by depositing a nickel alloy or the like on a resin film such as polyimide by sputtering and then performing copper plating (metalizing method) is suitable for forming a fine wiring pattern. Since this method can easily change the thickness of the copper layer formed by plating, it is a material suitable for fine wiring circuit. However, since it takes time to form the copper layer, there is a problem that the manufacturing cost is high.

JP 2006-222185 A JP 2000-269619 A JP-A-6-81172 JP 2002-176242 A

2009 Japan Packaging Technology Roadmap Printed Wiring Board

  According to the method of forming a circuit from a copper foil (subtractive method), with the conventional thickness, the etching in the plane direction proceeds until the etching in the thickness direction of the copper foil is completed, and the cross-sectional shape with a large tailing is obtained. Only a circuit can be obtained. Since the current concentrates on the upper surface of the circuit with a narrow width, heat is generated and there is a possibility of disconnection in some cases.

  In order to reduce the bottom of the circuit cross section, the thickness of the copper foil may be reduced and the etching time may be shortened. However, the thinner the copper foil, the more difficult it is to handle in the CCL manufacturing process, which adversely affects product yield. Further, when the copper layer is thin as in Patent Document 2, the cross-sectional area of the circuit is reduced, so that there is a possibility that a necessary amount of conductivity cannot be ensured.

  The technique of providing a Ni, Co layer or the like on the etched surface of the copper foil may not be able to cope with the narrow pitch of circuit patterns that are expected to advance in the future. In the prior art, it is necessary to attach a large amount of these metals. However, since these metal layers have ferromagnetism, there is a possibility of adversely affecting electronic devices. Therefore, it is necessary to remove these layers by soft etching after circuit formation etching and resist removal, which increases the number of manufacturing steps.

  When a Ni, Co layer or the like is provided on the etched surface of the copper foil base material, these layers are usually inferior in initial etchability because the corrosion rate by the etchant is slower than the copper component of the copper foil base material. As a result, the etching solution may enter between the copper foil base material and the resist, and the resist may be peeled off. This causes a decrease in circuit linearity. Moreover, since the time required for etching becomes long, the production efficiency is lowered.

  Then, this invention makes it a subject to provide the copper foil and laminated body for printed wiring boards which are excellent in initial stage etching property, and can form the circuit of a cross-sectional shape with small footing suitable for fine pitch formation.

  Conventionally, in order to form a fine pitch circuit by a subtractive method, it has been necessary to reduce the thickness of the copper foil. In addition, in order to form a circuit having a cross-sectional shape with a small skirt, it is necessary to deposit a large amount of ferromagnetic Ni or Co on the etched surface of the copper foil to form a layer having a thickness of several tens of nm. However, as a result of intensive studies, the present inventors have found that the tailing of the formed circuit is reduced when a small amount of noble metal is attached to the etched surface of the copper foil. At this time, since the noble metal layer is very thin, the noble metal layer moderately diffuses with the copper of the copper foil base material due to the thermal history during production. Furthermore, the copper atoms that have reached the vicinity of the outermost layer by this diffusion are oxidized by heating in the atmosphere or the resist drying step, and copper oxide is generated. 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. Therefore, the initial etching property is excellent and the linearity is superior to the circuit formed by the conventional technique. 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. Moreover, since these noble metal elements are extremely small in addition to having no ferromagnetism like Ni and Co, it is expected that they will not have an effect on electronic devices.

  In one aspect, the present invention completed on the basis of the above knowledge covers at least a part of the surface of the copper foil base material and the copper foil base material, and any one or more of platinum, palladium, and gold F (x) is the atomic concentration (%) of gold, platinum and / or palladium in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS. When the atomic concentration (%) of copper is g (x), it is a copper foil for printed wiring boards that satisfies ∫f (x) dx / ∫g (x) ≦ 15 in the interval [0, 1.0]. .

  In one embodiment of the copper foil for printed wiring boards according to the present invention, when heat treatment equivalent to polyimide curing is performed, the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS. When the atomic concentration (%) of gold, platinum and / or palladium is f (x) and the atomic concentration (%) of copper is g (x), 区間 f (x) in the interval [0, 1.0] It satisfies dx / (g (x) ≦ 3.

  In another embodiment of the copper foil for printed wiring boards according to the present invention, when heat treatment equivalent to polyimide curing is performed, the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS ), The atomic concentration (%) of gold, platinum and / or palladium is f (x) and the atomic concentration (%) of copper is g (x). ≦ ∫f (x) dx / ∫g (x) ≦ 3 is satisfied.

  In yet another embodiment of the copper foil for printed wiring board according to the present invention, the copper foil for printed wiring board is subjected to a heat treatment equivalent to polyimide curing, and is obtained from a depth direction analysis from the surface by XPS. If the atomic concentration (%) of gold, platinum and / or palladium in the depth direction (x: unit nm) is f (x) and the atomic concentration (%) of copper is g (x), the interval [0 , 1.0], ∫f (x) dx / ∫g (x) ≦ 3 is satisfied.

  In yet another embodiment of the copper foil for printed wiring board according to the present invention, the copper foil for printed wiring board is subjected to a heat treatment equivalent to polyimide curing, and is obtained from a depth direction analysis from the surface by XPS. If the atomic concentration (%) of gold, platinum and / or palladium in the depth direction (x: unit nm) is f (x) and the atomic concentration (%) of copper is g (x), the interval [0 , 1.0], 0.05 ≦ ∫f (x) dx / ∫g (x) ≦ 3 is satisfied.

In yet another embodiment of a copper foil for printed wiring boards according to the present invention, the amount of deposition of platinum 1050μg / dm ² or less in the coating layer, the adhesion amount of palladium 600 [mu] g / dm ² or less, the adhesion amount of gold 1000 μg / dm ² or less.

In still another embodiment of the copper foil for printed wiring board according to the present invention, the adhesion amount of platinum in the coating layer is 15 to 1050 μg / dm ² , the adhesion amount of palladium is 10 to 600 μg / dm ² , and the adhesion of gold The amount is 10 to 1000 μg / dm ² .

In still another embodiment of the copper foil for printed wiring board according to the present invention, the adhesion amount of platinum in the coating layer is 20 to 400 μg / dm ² , the adhesion amount of palladium is 20 to 250 μg / dm ² , and the adhesion of gold. The amount is 20 to 400 μg / dm ² .

  In yet another embodiment of the copper foil for printed wiring board according to the present invention, the printed wiring board is a flexible printed wiring board.

  In another aspect of the present invention, a step of preparing a copper foil according to the present invention, a step of producing a laminate of a copper foil and a resin substrate using the copper foil coating layer as an etching surface, and a coating layer After forming the circuit pattern with resist, the coating layer exposed at the opening of the circuit pattern is removed, and then unnecessary portions of copper are removed by etching using a ferric chloride aqueous solution or a cupric chloride aqueous solution. And a step of forming a copper circuit.

  In one embodiment of the method for forming an electronic circuit according to the present invention, the coating layer exposed in the opening is removed with a reagent mainly composed of hydrochloric acid, sulfuric acid or nitric acid.

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

  In still another aspect, the present invention is a laminate including a copper layer and a resin substrate, the laminate including the coating layer according to 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 of the laminate according to the present invention.

  According to the present invention, it is possible to provide a copper foil for a printed wiring board and a laminate that are excellent in initial etching property and suitable for fine pitch formation and capable of forming a circuit having a cross-sectional shape with a small skirt.

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. It is a density | concentration profile of the depth direction by XPS of the copper foil before the heat processing of Example 13. FIG. It is the density | concentration profile of the depth direction by XPS of the copper foil which concerns on the heat processing of Example 13. FIG. 10 is a photograph showing a circuit formed by Comparative Example 4. It is an enlarged photograph of the circuit surface which shows the example which produced tailing at the time of copper circuit formation, and the copper circuit short-circuited near the resin substrate.

(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 at least one of platinum, palladium, and gold.
In addition, on the adhesive surface side of the copper foil base material with the insulating substrate, for the purpose of improving the adhesiveness with the insulating substrate, for example, another coating layer composed of an intermediate layer and a surface layer laminated in order from the copper foil base material surface May be formed. In this case, the intermediate layer preferably contains at least one of Ni, Mo, Ti, Zn, Co, V, Sn, Mn, Nb, Ta, and Cr, for example. The intermediate layer may be composed of a single metal, for example, preferably composed of any one of Ni, Mo, Ti, Zn, Co, Nb, and Ta. The intermediate layer may be made of an alloy, for example, preferably made of an alloy of at least any two of Ni, Zn, V, Sn, Mn, Cr and Cu.

(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) Atomic concentration on the surface of the coating layer The coating layer according to the present invention has an atomic concentration of gold, platinum and / or palladium in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS. (%) Is f (x) and the atomic concentration (%) of copper is g (x). In the interval [0, 1.0],) f (x) dx / ∫g (x) ≦ 15 Fulfill. In the case of a coating layer formed by a normal surface treatment, the atomic concentration g (x) of copper is extremely small in the above formula, so that ∫f (x) dx / ∫g (x) is infinite. However, since the coating layer according to the present invention has a very small amount of precious metal attached, copper is appropriately diffused, and ∫f (x) dx / ∫g (x) does not become infinite. It is as follows. In this way, the presence of copper in the above-described ratio in the coating layer formed of a very small amount of noble metal enables the oxide formed thereby to be dissolved with an acid, thereby providing a corrosion-resistant noble metal layer. However, it can be easily removed from the exposed portion of the opening of the resist pattern.

  In addition, when heat treatment equivalent to polyimide curing (nitrogen atmosphere, 350 ° C., 2 hours heating) was performed, gold, platinum in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS, and If the atomic concentration (%) of palladium is f (x) and the atomic concentration (%) of copper is g (x), 区間 f (x) dx / ∫g in the interval [0, 1.0] It is preferable to satisfy (x) ≦ 3. As described above, the coating layer according to the present invention has ∫f (x) dx / ∫g (x) of 15 or less before heat treatment, and the upper limit is higher than that after heat treatment. If the thermal history of the manufacturing process is received, noble metal atoms on the surface of the copper foil diffuse to the copper foil side, so that ∫f (x) dx decreases and ∫g (x) dx increases. Therefore, ∫f (x) dx / ∫g (x) is smaller than that before the heat treatment, and ∫f (x) dx / ∫g (x) ≦ 3. Further, if ∫f (x) dx / ∫g (x) exceeds 3, the initial etching property is lowered, which is not preferable. Furthermore, in order to obtain good etching properties which are the effects of the present invention, a certain level of noble metal atom concentration is required. Therefore, when a heat treatment equivalent to polyimide curing is performed, it is preferable that 0.05 ≦ ∫f (x) dx / ∫g (x) ≦ 3 is satisfied in the interval [0, 1.0].

Moreover, it is the copper foil for printed wiring boards by which the heat processing equivalent to a polyimide hardening was performed, Comprising: The gold | metal | money, platinum, and / or of the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS Assuming that the atomic concentration (%) of palladium is f (x) and the atomic concentration (%) of copper is g (x), in the interval [0, 1.0], に お い て f (x) dx / ∫g (x ) ≦ 3 is preferably satisfied.
Furthermore, it is more preferable that 0.05 ≦ ∫f (x) dx / ∫g (x) ≦ 3 is satisfied in the interval [0, 1.0].

(4) When the deposition amount covering layer is composed of platinum, the amount of deposition of platinum is at 1050μg / dm ² or less, more preferably from 15~1050μg / dm ^2, in 20~400μg / dm ² Even more preferably. If the coating layer is composed of palladium is in the amount of deposition of palladium 600 [mu] g / dm ² or less, more preferably from 10~600μg / dm ^2, further that a 20~250μg / dm ² from preferable. If the coating layer is composed of gold is the amount of adhesion of gold 1000 [mu] g / dm ² or less, more preferably from 10~1000μg / dm ^2, further that a 20~400μg / dm ² from preferable. When the coating amount of platinum in the coating layer is less than 15 μg / dm ² , the coating amount of palladium in the coating layer is less than 10 μg / dm ² , and the deposition amount of gold in the coating layer is less than 10 μg / dm ² , the effect is obtained. not enough. On the other hand, the amount of adhered 1050μg / dm ² of the platinum coating layer, the coating layer coating weight of 600 [mu] g / dm ² of palladium, and, when the amount of deposition of the gold of the coating layer is more than 1000 [mu] g / dm ^2, respectively initial etch resistant Adversely affect.

  In addition, a base layer may be provided between the copper foil base material and the coating layer from the viewpoint of heat discoloration resistance as long as the initial etching property is not adversely affected. As the underlayer, nickel, nickel alloy, cobalt, silver, and manganese are preferable. The method for providing the underlayer may be either a dry method or a wet method.

  Further, a chromium layer or a chromate layer and / or a silane treatment layer can be further formed on the coating layer in order to enhance the rust prevention effect. Moreover, in order to suppress the oxidation by heat processing further between the coating layer and copper foil, you may form the base layer which has oxidation resistance.

(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 coating layer made of at least one of platinum, palladium, and gold having an etching rate lower than that of copper is formed on the etching surface side of the copper foil by a sputtering method. 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.

(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. 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, an aqueous solution of cupric chloride, an aqueous solution of ferric chloride, or the like can be used, but an aqueous solution of ferric chloride is particularly effective. This is because the fine circuit takes time to etch, but the ferric chloride aqueous solution has a higher etching rate than the cupric chloride aqueous solution. If the initial etchability is poor due to low concentration of Fe ^{3+ in} ferric chloride aqueous solution or Cu ²⁺ in cupric chloride, a solution that pre-dissolves the noble metal exposed in the opening It may be removed with. As a solution for dissolving the noble metal, there is “AURUM” manufactured by Kanto Chemical Co., Ltd. containing hydrochloric acid and iodine. However, when these liquids are used excessively, the liquid wraps around the back side of the resist and dissolves the processing layer.
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 line pattern shape on the copper foil surface of the printed wiring board)
As described above, each line pattern of the circuit on the copper foil surface of the printed wiring board formed by etching from the coating layer side does not have two long side surfaces formed vertically on the insulating substrate. Usually, it is formed so as to spread from the surface of the copper foil downward, that is, toward the resin layer. 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 pitch of the line pattern as much as possible for the finer circuit pattern (currently required), but if this inclination angle θ is small, the tailing will increase accordingly. The line pattern pitch becomes wider. In addition, the inclination angle θ is usually not completely constant within each line pattern and line pattern. If the variation in the inclination angle θ is large, the circuit quality may be adversely affected. Therefore, each line pattern of the circuit on the copper foil surface of the printed wiring board formed by etching from the coating layer side has an elongated angle θ of 65 to 90 ° with respect to the two long side surfaces with respect to the insulating substrate surface. And the standard deviation of tan θ in the same circuit is preferably 1.0 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 on copper foil)
As a base material in Examples 1 to 18, rolled copper foil (Nikko Metal C1100) having a thickness of 12 μm was prepared. The surface roughness (Rz) of the rolled copper foil was 0.7 μm. Moreover, as a copper foil base material of Examples 19 to 21, a non-roughened electrolytic copper foil (Nikko Metal JTC foil) having a thickness of 9 μm was prepared. The surface roughness (Rz) of the adhesion surface of the electrolytic copper foil to the resin was 1.5 μm. Further, as a base material of Examples 22 to 24, a metalizing CCL having a thickness of 8 μm (Nikko Metal Machinus, copper layer side Ra 0.01 μm, tie coat layer metal adhesion amount Ni 1780 μg / dm ² , Cr 360 μg / dm ² ). Prepared.

The thin oxide film adhering to the surface of the copper foil was removed by reverse sputtering, and a target of Au, Pt and / or Pd was sputtered with the following apparatus and conditions to form a coating layer. The thickness of the coating layer was changed by adjusting the film formation time. The simple substance of the various metals used for sputtering used the thing of purity 3N.
-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
・ 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.
For Examples 16 to 18, the following targets were used.
Target: Au-50 mass% Pd, Pt-50 mass% Pd, Au-50 mass% Pt

The thin oxide film previously attached to the surface opposite to the coating layer was removed from the copper foil provided with the coating layer by reverse sputtering, and a Ni layer and a Cr layer were sequentially formed. 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.

  A heat treatment (a nitrogen atmosphere, 350 ° C., 2 hours heating) simulating polyimide curing was applied to a part of the copper foil produced by the above procedure.

On the surface of the Ni layer and Cr layer forming side of the heat treated copper foil or unheated copper foil base material, a polyimide film with an adhesive (CISV1215, manufactured by Nikkan Kogyo Co., Ltd.) is heated at a pressure of 7 kgf / cm ² at 160 ° C. for 40 minutes. Was laminated. Some copper foil was laminated | stacked with the polyimide film in the said procedure, after hold | maintaining at 350 degreeC for 2 hours by nitrogen atmosphere.

<Measurement of adhesion amount>
The adhesion amount of Au, Pd, and Pt in the coating layer was measured by atomic absorption spectrometry by dissolving the surface-treated copper foil sample with aqua regia, diluting the solution.

<Measurement by XPS>
The operating conditions of XPS when creating the depth profile of the coating layer are shown below.
・ Device: XPS measuring device (ULVAC-PHI, Model 5600MC)
・ Achieving vacuum: 3.8 × 10 ⁻⁷ Pa
X-ray: Monochromatic AlKα or non-monochromatic MgKα, X-ray output 300 W, detection area 800 μmφ, angle between sample and detector 45 °
Ion beam: ion species Ar ⁺ , acceleration voltage 3 kV, sweep area 3 mm × 3 mm, sputtering rate 2.0 nm / min (SiO ₂ conversion)

(Circuit shape by etching)
The etched surface of the copper foil was degreased with acetone and immersed in sulfuric acid (100 g / L) for 30 seconds to remove the surface contamination and the oxide layer. Next, a liquid resist (manufactured by Tokyo Ohka Kogyo Co., Ltd., OFPR-800LB) was dropped onto the etching surface using a spin coater and dried. The resist thickness after drying was adjusted to 1 μm. After that, 10 circuits are printed by the exposure process, the noble metal layer at the opening of the resist pattern is removed with dilute sulfuric acid (90 g / L), and the etching process for removing unnecessary portions of the copper foil is performed under the following conditions: did.

<Etching conditions>
-Ferric chloride aqueous solution: (37 wt%, Baume degree: 40 °)
・ Liquid temperature: 50 ° C
・ Spray pressure: 0.25 MPa
(50 μm pitch circuit formation)
・ Resist L / S = 33μm / 17μm
-Finished circuit bottom (bottom) width: 25 μm
Etching time: 10 to 130 seconds (30 μm pitch circuit formation)
・ Resist L / S = 25μm / 5μm
-Finished circuit bottom (bottom) width: 15 μm
-Etching time: 30 to 70 seconds-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 dipping in a 45 ° C. aqueous NaOH solution (100 g / L) for 1 minute.

<Etching factor measurement conditions>
The etching factor is the length of the skirt from the intersection of the perpendicular from the copper foil top surface and the resin substrate, assuming that the circuit is etched vertically when the edge is etched (when skirting occurs) When the distance is a, the ratio of a to the thickness b of the copper foil: b / a is shown. The larger the value, the larger the inclination angle, and no etching residue remains, and the bottom It means that pull becomes small. 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. Furthermore, the inclination angle θ was calculated by calculating the arc tangent using a and the thickness b of the copper foil measured in the above procedure. The measurement range was a circuit length of 600 μm, and an etching factor of 12 points, its standard deviation, and an average value of the inclination angle θ were adopted as a result.

(Example 2: Comparative Example 1: Blank material)
A rolled copper foil having a thickness of 12 μm was prepared, and a polyimide film was bonded in the same procedure as in Example 1. Next, 10 circuits were printed on the opposite surface by a photosensitive resist coating and exposure process, and an etching process for removing unnecessary portions of the copper foil was performed under the conditions of Example 1.

(Example 3: Comparative Examples 2 to 4)
A rolled copper foil having a thickness of 12 μm was prepared, and surface treatment was performed in accordance with the procedure of Example 1, and etching treatment was performed.

(Example 4: Comparative Example 5)
Ni plating was performed on one side of a rolled copper foil having a thickness of 12 μm under the following conditions, and then surface treatment by sputtering was performed on the opposite side according to the procedure of Example 1. A polyimide film was adhered to this copper foil by the procedure of Example 1 so that the Ni-plated surface became an etched surface, and a circuit was formed by etching.
・ Ni: 30g / L
-PH: 3.0
・ Temperature: 50 ℃
・ Current density: 35 A / dm ²
-Time: 5 seconds Each measurement result of Examples 1-4 is shown in Tables 1-4.

<Evaluation>
(Examples 1 to 24)
In each of Examples 1 to 24, the etching factor was large and there was no variation, and a circuit having a cross section close to a rectangular shape could be formed.
In FIG. 2, the density | concentration profile of the depth direction by XPS of the copper foil before the heat processing of Example 13 is shown. In FIG. 3, the density | concentration profile of the depth direction by XPS of the copper foil which concerns on the heat processing of Example 13 is shown.

(Comparative Examples 1-5)
Comparative Example 1 was a blank material with an untreated copper foil surface, and a circuit with a rectangular cross section could not be formed.
In Comparative Example 2-4, the adhesion amount of platinum 1050μg / dm ² greater, palladium adhesion amount 600 [mu] g / dm ^2, or greater, for the amount of deposition of the gold is 1000 [mu] g / dm ² greater than the cross section of the rectangular side The circuit could not be formed.
Even in Comparative Example 5 in which the etching surface was plated with Ni, a circuit with a rectangular cross section could not be formed.
FIG. 4 shows a photograph of the circuit formed in Comparative Example 4.

Claims (15)

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 any one or more of platinum, palladium, and gold;
The atomic concentration (%) of gold, platinum and / or palladium in the depth direction (x: unit nm) obtained from analysis of the depth direction from the surface by XPS is f (x), and the atomic concentration of copper (%) Is a copper foil for printed wiring board satisfying ∫f (x) dx / ∫g (x) ≦ 15 in the interval [0, 1.0].   When heat treatment equivalent to polyimide curing was performed, the atomic concentration (%) of gold, platinum and / or palladium in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS was expressed as f (x ) And the atomic concentration (%) of copper is g (x), in the interval [0, 1.0], ∫f (x) dx / ∫g (x) ≦ 3 is satisfied. Copper foil for printed wiring boards.   When heat treatment equivalent to polyimide curing was performed, the atomic concentration (%) of gold, platinum and / or palladium in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS was expressed as f (x ) And the atomic concentration (%) of copper is g (x), claim 0.05 ≦ ∫f (x) dx / ∫g (x) ≦ 3 in the interval [0, 1.0] 2. Copper foil for printed wiring boards according to 2.   A copper foil for printed wiring board that has been subjected to a heat treatment equivalent to polyimide curing, and is made of gold, platinum, and / or palladium in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS. If the atomic concentration (%) is f (x) and the copper atomic concentration (%) is g (x), then 区間 f (x) dx / ∫g (x) ≦ in the interval [0, 1.0] The copper foil for printed wiring boards in any one of Claims 1-3 which satisfy | fills 3. FIG.   A copper foil for printed wiring board that has been subjected to a heat treatment equivalent to polyimide curing, and is made of gold, platinum, and / or palladium in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS. When the atomic concentration (%) is f (x) and the atomic concentration (%) of copper is g (x), 0.05 ≦ ∫f (x) dx / ∫g in the interval [0, 1.0]. The copper foil for printed wiring boards according to claim 4, wherein (x) ≦ 3 is satisfied. The adhesion amount of platinum in the coating layer is 1050μg / dm ² or less, the adhesion amount of palladium 600 [mu] g / dm ² or less, printing according to any one of claims 1 to 5 attached amount of gold is 1000 [mu] g / dm ² or less Copper foil for wiring boards. The adhesion amount of platinum in the coating layer is 15~1050μg / dm ^2, the amount of deposition of palladium 10~600μg / dm ^2, the printed wiring board according to claim 6 adhered amount of gold is 10~1000μg / dm ² Copper foil. The printed wiring board according to claim 7, wherein an adhesion amount of platinum in the coating layer is 20 to 400 μg / dm ² , an adhesion amount of palladium is 20 to 250 μg / dm ² , and an adhesion amount of gold is 20 to 400 μg / dm ^2. Copper foil.   A printed wiring board is a flexible printed wiring board, The copper foil for printed wiring boards in any one of Claims 1-8. Preparing the copper foil according to any one of claims 1 to 9,
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;
After forming a circuit pattern with a resist on the coating layer, the coating layer exposed at the opening of the circuit pattern is removed, and then etching is performed using a ferric chloride aqueous solution or a cupric chloride aqueous solution. Removing unnecessary portions of copper to form a copper circuit;
A method of forming an electronic circuit comprising:   The method according to claim 10, wherein the coating layer exposed to the opening is removed with a reagent mainly composed of hydrochloric acid, sulfuric acid, or nitric acid.   A laminate of the copper foil according to claim 1 and a resin substrate. A laminate of a copper layer and a resin substrate,
The laminated body provided with the coating layer in any one of Claims 1-9 which coat | covers at least one part of the surface of the said copper layer.   The laminate according to claim 12 or 13, wherein the resin substrate is a polyimide substrate.   The printed wiring board which used the laminated body in any one of Claims 12-14 as a material.