WO2011122643A1 - プリント配線板用銅箔及びそれを用いた積層体 - Google Patents
プリント配線板用銅箔及びそれを用いた積層体 Download PDFInfo
- Publication number
- WO2011122643A1 WO2011122643A1 PCT/JP2011/057892 JP2011057892W WO2011122643A1 WO 2011122643 A1 WO2011122643 A1 WO 2011122643A1 JP 2011057892 W JP2011057892 W JP 2011057892W WO 2011122643 A1 WO2011122643 A1 WO 2011122643A1
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- WIPO (PCT)
- Prior art keywords
- copper foil
- copper
- etching
- printed wiring
- coating layer
- Prior art date
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/14—Metallic material, boron or silicon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/14—Metallic material, boron or silicon
- C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
- C23C14/165—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon by cathodic sputtering
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/09—Use of materials for the conductive, e.g. metallic pattern
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/03—Conductive materials
- H05K2201/0332—Structure of the conductor
- H05K2201/0335—Layered conductors or foils
- H05K2201/0355—Metal foils
Definitions
- the present invention relates to a copper foil for a printed wiring board and a laminate using the same, and more particularly to a copper foil for a flexible printed wiring board and a laminate using the same.
- a printed wiring board is generally manufactured through a process of forming a laminated body by bonding an insulating substrate to copper foil and then forming a conductor pattern on the copper foil surface by etching. Therefore, good etching properties are required for the copper foil for printed wiring boards.
- FIG. 4 shows an enlarged photograph of the circuit surface showing an example in which “sagging” occurs during copper circuit formation and the copper circuit is short-circuited in the vicinity of the resin substrate.
- Patent Document 1 discloses a surface treatment in which a metal or alloy layer having a slower etching rate than copper is formed on a copper foil on the etching surface side.
- the metal or alloy includes Ni, Co, and alloys thereof.
- the etching solution penetrates from the resist coating side, that is, from the surface of the copper foil, so if there is a metal or alloy layer with a slow etching rate directly under the resist, the etching of the copper foil portion in the vicinity is suppressed. Since the etching of the copper foil portion of the metal film progresses, the “sag” is reduced, and a circuit with a more uniform width can be formed. This makes it possible to form a sharper circuit compared to the prior art, and a great progress has been made. It can be said that there was.
- Patent Document 2 a Cu thin film having a thickness of 1000 to 10,000 mm is formed, and an Ni thin film having an etching rate slower than that of copper having a thickness of 10 to 300 mm is formed on the Cu thin film.
- the thickness of the surface treatment layer As for the former, it is necessary to reduce the thickness of the surface treatment layer as much as possible in order to shorten the etching removal time as much as possible, and to remove it cleanly.
- the underlying copper layer is oxidized (discolored, so it is commonly called “yake”), due to poor resist coatability (uniformity, adhesion), excessive etching of interfacial oxide during etching, etc.
- defects such as etching property in pattern etching, short circuit, and controllability of the width of the circuit pattern occur, so that improvement is required or replacement with other materials is required.
- Ni or Co may adversely affect electronic devices due to its magnetism.
- the present invention has an object to provide a copper foil for a printed wiring board, which has good etching properties when forming a circuit pattern, is suitable for fine pitch, and has excellent magnetism, and a laminate using the same. To do.
- the inventors have provided a coating layer containing any one or more of platinum, palladium, and gold at a predetermined metal adhesion amount on the non-adhesive surface side with the resin of the copper foil.
- a circuit having an inclination angle of 80 ° or more on the side surface of the circuit can be formed. As a result, it is possible to form a circuit that can sufficiently cope with the recent miniaturization and high density of the circuit.
- 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 and a coating layer comprising a deposition amount of platinum 1050 ⁇ g / dm 2 or less in the coating layer, the adhesion amount of palladium 600 [mu] g / dm 2 or less, the printed wiring board copper deposition amount of gold is 1000 [mu] g / dm 2 or less It is a foil.
- the adhesion amount of platinum in the coating layer is 20 to 400 ⁇ g / dm 2
- the adhesion amount of palladium is 20 to 250 ⁇ g / dm 2
- the adhesion amount of gold is 20 ⁇ 400 ⁇ g / dm 2 .
- the adhesion amount of platinum in the coating layer is 50 to 300 ⁇ g / dm 2
- the adhesion amount of palladium is 30 to 180 ⁇ g / dm 2
- the adhesion amount of gold Is 50 to 300 ⁇ g / dm 2 .
- the printed wiring board is a flexible printed wiring board.
- a step of preparing a rolled copper foil or an electrolytic copper foil composed of the copper foil according to the present invention, and a lamination of the copper foil and the resin substrate using the coating layer of the copper foil as an etching surface Forming an electronic circuit including a step of forming a body and a step of etching the laminate using an aqueous ferric chloride solution or an aqueous cupric chloride solution to remove unnecessary portions of copper to form a copper circuit Is the method.
- the present invention is a laminate of a copper foil and a resin substrate according to the present invention.
- FIG. 1 Another aspect of the present invention is a laminate including a copper layer and a resin substrate, the laminate including a coating layer according to the present invention that covers at least a part of the surface of the copper layer.
- the resin substrate is a polyimide substrate.
- the present invention is a printed wiring board made of the laminate according to the present invention.
- a copper foil for a printed wiring board which has good etching properties when forming a circuit pattern, is suitable for fine pitch, and has excellent magnetism, and a laminate using the copper foil.
- 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.
- 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.
- a copper alloy such as a copper alloy, a Corson copper alloy to which Ni, Si and the like are added.
- a copper alloy foil is also included.
- the thickness of the copper foil base material that can be used in the present invention is not particularly limited, and may be appropriately adjusted to a thickness suitable for a printed wiring board.
- the thickness can be about 5 to 100 ⁇ m.
- it is 30 ⁇ m or less, preferably 20 ⁇ m or less, and typically about 5 to 20 ⁇ m.
- the copper foil base material used in the present invention is not particularly limited, but for example, a material not subjected to roughening treatment may be used.
- the surface is generally roughened by special plating with irregularities on the order of ⁇ m, 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.
- the roughening process process is abbreviate
- a coating layer is formed on at least a part of the surface of the copper foil base opposite to the adhesive surface with the insulating substrate (circuit formation planned surface side).
- the coating layer contains at least one of platinum, palladium, and gold.
- the amount of platinum deposited is 1050 ⁇ g / dm 2 or less, more preferably 20 to 400 ⁇ g / dm 2 , and even more preferably 50 to 300 ⁇ g / dm 2. preferable.
- the adhesion amount of palladium is 600 ⁇ g / dm 2 or less, more preferably 20 to 250 ⁇ g / dm 2 , and even more preferably 30 to 180 ⁇ g / dm 2. preferable.
- the adhesion amount of gold is 1000 ⁇ g / dm 2 or less, more preferably 20 to 400 ⁇ g / dm 2 , and even more preferably 50 to 300 ⁇ g / dm 2. preferable.
- Adhesion amount of platinum coating layer 1050 ⁇ g / dm 2 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, adverse effect on the initial etching of respectively Effect.
- 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 one selected from the group consisting of a platinum group metal, gold, and silver having an etching rate lower than that of 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.
- 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.
- 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.
- 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.
- a prepreg in which a base material such as glass cloth is impregnated with a resin and the resin is cured to a semi-cured state is prepared. 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.
- a polyimide film or a polyester film and a copper foil can be bonded using an epoxy or acrylic adhesive (three-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
- a laminating method in which a thermoplastic polyimide is applied to the substrate, a copper foil is overlaid thereon, and heated and pressed.
- 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.
- PWB printed wiring boards
- 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 the resist pattern formed by development is immersed in an etching solution.
- the coating layer composed of one type selected from the group consisting of platinum group metal, gold, and silver that suppresses etching is located near the resist portion on the copper foil, and etching of the copper foil on the resist side
- the etching of the copper circuit pattern proceeds substantially vertically by the etching of the copper away from the coating layer at a rate faster than the rate at which the vicinity of the coating layer is etched.
- unnecessary portions of copper can be removed, and then the etching resist can be peeled and removed to expose the circuit pattern.
- the etching rate of the coating layer is sufficiently smaller than that of copper, so that the etching factor is improved.
- 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.
- a heat-resistant layer may be formed in advance on the surface of the copper foil base before forming the coating layer.
- Example 1 Examples 1-33
- rolled copper foils Nikko Metal C1100 having a thickness of 12 or 17 ⁇ m were prepared.
- the surface roughness (Rz) of the rolled copper foil was 0.7 ⁇ m.
- a non-roughened electrolytic copper foil having a thickness of 9 ⁇ m was prepared as a copper foil base material of Examples 22 to 24, a non-roughened electrolytic copper foil having a thickness of 9 ⁇ m was prepared.
- the surface roughness (Rz) of the electrolytic copper foil was 1.5 ⁇ m.
- Examples 31 to 33 8 ⁇ m thick metalizing CCL (Nikko Metal Machinus, copper layer side Ra 0.01 ⁇ m, tie coat layer metal adhesion amount Ni 1780 ⁇ g / dm 2 , Cr 360 ⁇ g / dm 2 ) was 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.
- 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.
- a polyimide film was bonded to the Ni layer and Cr layer forming side surface of the copper foil base material by the following procedure.
- (1) Using an applicator on a copper foil of 7 cm ⁇ 7 cm, Ube Industries U Varnish-A (polyimide varnish) was applied to a dry body to a thickness of 25 ⁇ m.
- (2) The resin-coated copper foil obtained in (1) is dried at 130 ° C. for 30 minutes in an air dryer.
- Imidization at 350 ° C. for 30 minutes in a high-temperature heating furnace with a nitrogen flow rate set to 10 L / min.
- Circuit shape by etching Ten circuits were printed by a photosensitive resist coating and exposure process on the surface on which the coating layer of copper foil was formed, and an etching process for removing unnecessary portions of the copper foil was performed under the following conditions.
- the etching factor is the distance of the length of sagging from the intersection of the vertical line from the upper surface of the copper foil and the resin substrate, assuming that the circuit is etched vertically when sagging at the end (when sagging occurs) Is a ratio of a to the thickness b of the copper foil: b / a, and the larger the value, the larger the inclination angle, and the etching residue does not remain and the sagging is small. It means to become.
- 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.
- the inclination angle ⁇ 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 ⁇ m, and an etching factor of 12 points, its standard deviation, and an average value of the inclination angle ⁇ were adopted as a result.
- Example 2 Comparative Examples 1 to 3: Blank material
- Rolled copper foils having a thickness of 12 ⁇ m, 17 ⁇ m, and 9 ⁇ m were prepared, and polyimide films were bonded in the same procedure as in Example 1.
- 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 4 to 6
- a rolled copper foil having a thickness of 12 ⁇ m was prepared, and a polyimide film was bonded in the same procedure as in Example 1.
- each layer of Au, Pd and / or Pt was formed on the copper foil surface by sputtering in the same manner as in Example 1, and a circuit was formed by etching.
- the measurement results of Examples 1 to 3 are shown in Tables 1 to 4.
- the cross-sectional shape of the circuit is not exactly a trapezoid whose hypotenuse is a straight line.
- Tables 2 and 4 the inclination angles of the circuits of the example and the comparative example are described, but this is a value calculated by the definition formula shown in FIG.
- Examples 1 to 33 In each of Examples 1 to 33, 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.
- FIG. 2 shows a photograph of a circuit formed in Example 27 and a cross-sectional photograph thereof.
- Comparative Examples 1 to 6 were blank materials each having an untreated copper foil surface, and a circuit having a rectangular cross section could not be formed.
- the adhesion amount is 1050 ⁇ g / dm 2 than platinum deposition amount of palladium 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.
- FIG. 3 shows a photograph of a circuit formed in Comparative Example 6.
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- Metallurgy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Microelectronics & Electronic Packaging (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing Of Printed Circuit Boards (AREA)
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- ing And Chemical Polishing (AREA)
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Abstract
Description
本発明に用いることのできる銅箔基材の形態に特に制限はないが、典型的には圧延銅箔や電解銅箔の形態で用いることができる。一般的には、電解銅箔は硫酸銅めっき浴からチタンやステンレスのドラム上に銅を電解析出して製造され、圧延銅箔は圧延ロールによる塑性加工と熱処理を繰り返して製造される。屈曲性が要求される用途には圧延銅箔を適用することが多い。
銅箔基材の材料としてはプリント配線板の導体パターンとして通常使用されるタフピッチ銅や無酸素銅といった高純度の銅の他、例えばSn入り銅、Ag入り銅、Cr、Zr又はMg等を添加した銅合金、Ni及びSi等を添加したコルソン系銅合金のような銅合金も使用可能である。なお、本明細書において用語「銅箔」を単独で用いたときには銅合金箔も含むものとする。
銅箔基材の絶縁基板との接着面の反対側(回路形成予定面側)の表面の少なくとも一部には、被覆層が形成されている。被覆層は、白金、パラジウム、及び、金のいずれか1種以上を含んでいる。被覆層が白金で構成されている場合は、白金の付着量が1050μg/dm2以下であり、20~400μg/dm2であるのがより好ましく、50~300μg/dm2であるのが更により好ましい。被覆層がパラジウムで構成されている場合は、パラジウムの付着量が600μg/dm2以下であり、20~250μg/dm2であるのがより好ましく、30~180μg/dm2であるのが更により好ましい。被覆層が金で構成されている場合は、金の付着量が1000μg/dm2以下であり、20~400μg/dm2であるのがより好ましく、50~300μg/dm2であるのが更により好ましい。被覆層の白金の付着量が1050μg/dm2、被覆層のパラジウムの付着量が600μg/dm2、及び、被覆層の金の付着量が1000μg/dm2を超えると、それぞれ初期エッチング性に悪影響を及ぼす。
本発明に係るプリント配線板用銅箔は、スパッタリング法により形成することができる。すなわち、スパッタリング法によって銅箔基材の表面の少なくとも一部を、被覆層により被覆する。具体的には、スパッタリング法によって、銅箔のエッチング面側に銅よりもエッチングレートの低い白金族金属、金、及び、銀からなる群から選択される1種からなる被覆層を形成する。被覆層は、スパッタリング法に限らず、例えば、電気めっき、無電解めっき等の湿式めっき法で形成してもよい。
本発明に係る銅箔を用いてプリント配線板(PWB)を常法に従って製造することができる。以下に、プリント配線板の製造方法の例を示す。
積層体に回路パターンを形成するために用いるエッチング液に対しては、被覆層のエッチング速度は、銅よりも十分に小さいためエッチングファクターを改善する効果を有する。エッチング液は、塩化第二銅水溶液、又は、塩化第二鉄水溶液等を用いることができるが、特に塩化第二鉄水溶液が有効である。微細回路はエッチングに時間が掛かるが、塩化第二鉄水溶液の方が塩化第二銅水溶液よりもエッチング速度が早いためである。また、被覆層を形成する前に、あらかじめ銅箔基材表面に耐熱層を形成しておいてもよい。
(銅箔への被覆層の形成)
実施例1~21及び25~30の銅箔基材として、厚さ12又は17μmの圧延銅箔(日鉱金属製C1100)を用意した。圧延銅箔の表面粗さ(Rz)は0.7μmであった。また、実施例22~24の銅箔基材として、厚さ9μmの無粗化処理の電解銅箔を用意した。電解銅箔の表面粗さ(Rz)は1.5μmであった。さらに、実施例31~33として、厚さ8μmのメタライジングCCL(日鉱金属製マキナス、銅層側Ra0.01μm、タイコート層の金属付着量Ni1780μg/dm2、Cr360μg/dm2)を用意した。
・装置:バッチ式スパッタリング装置(アルバック社、型式MNS-6000)
・到達真空度:1.0×10-5Pa
・スパッタリング圧:0.2Pa
・逆スパッタ電力:100W
・スパッタリング電力:50W
・成膜速度:各ターゲットについて一定時間約0.2μm成膜し、3次元測定器で厚さを測定し、単位時間当たりのスパッタレートを算出した。
上記実施例のうち、実施例28~30については、以下のターゲットを用いた。
・ターゲット:Au-50質量%Pd、Pt-50質量%Pd、Au-50質量%Pt
・装置:バッチ式スパッタリング装置(アルバック社、型式MNS-6000)
・到達真空度:1.0×10-5Pa
・スパッタリング圧:0.2Pa
・逆スパッタ電力:100W
・ターゲット:
Ni層用=Ni(純度3N)
Cr層用=Cr(純度3N)
・スパッタリング電力:50W
・成膜速度:各ターゲットについて一定時間約0.2μm成膜し、3次元測定器で厚さを測定し、単位時間当たりのスパッタレートを算出した。
(1)7cm×7cmの銅箔に対しアプリケーターを用い、宇部興産製Uワニス-A(ポリイミドワニス)を乾燥体で25μmになるよう塗布。
(2)(1)で得られた樹脂付き銅箔を空気下乾燥機で130℃30分で乾燥。
(3)窒素流量を10L/minに設定した高温加熱炉において、350℃30分でイミド化。
被覆層のAu,Pd、Ptの付着量測定は、王水で表面処理銅箔サンプルを溶解させ、その溶解液を希釈し、原子吸光分析法で行った。
銅箔の被覆層が形成された面に感光性レジスト塗布及び露光工程により10本の回路を印刷し、さらに銅箔の不要部分を除去するエッチング処理を以下の条件で実施した。
・塩化第二鉄水溶液:(37wt%、ボーメ度:40°)
・液温:50℃
・スプレー圧:0.25MPa
(50μmピッチ回路形成)
・レジストL/S=33μm/17μm
・仕上がり回路ボトム(底部)幅:25μm
・エッチング時間:10~130秒
(30μmピッチ回路形成)
・レジストL/S=25μm/5μm
・仕上がり回路ボトム(底部)幅:15μm
・エッチング時間:30~70秒
・エッチング終点の確認:時間を変えてエッチングを数水準行い、光学顕微鏡で回路間に銅が残存しなくなるのを確認し、これをエッチング時間とした。
エッチング後、45℃のNaOH水溶液(100g/L)に1分間浸漬させてレジストを剥離した。
エッチングファクターは、末広がりにエッチングされた場合(ダレが発生した場合)、回路が垂直にエッチングされたと仮定した場合の、銅箔上面からの垂線と樹脂基板との交点からのダレの長さの距離をaとした場合において、このaと銅箔の厚さbとの比:b/aを示すものであり、この数値が大きいほど、傾斜角は大きくなり、エッチング残渣が残らず、ダレが小さくなることを意味する。図1に、回路パターンの一部の表面写真と、当該部分における回路パターンの幅方向の横断面の模式図と、該模式図を用いたエッチングファクターの計算方法の概略とを示す。このaは回路上方からのSEM観察により測定し、エッチングファクター(EF=b/a)を算出した。このエッチングファクターを用いることにより、エッチング性の良否を簡単に判定できる。さらに、傾斜角θは上記手順で測定したa及び銅箔の厚さbを用いてアークタンジェントを計算することにより算出した。これらの測定範囲は回路長600μmで、12点のエッチングファクター、その標準偏差及び傾斜角θの平均値を結果として採用した。
12μm厚、17μm厚及び9μm厚の圧延銅箔を準備し、それぞれ例1と同じ手順でポリイミドフィルムを接着した。次に反対面に感光性レジスト塗布及び露光工程により10本の回路を印刷し、さらに銅箔の不要部分を除去するエッチング処理を例1の条件で実施した。
12μm厚の圧延銅箔を準備し、例1と同じ手順でポリイミドフィルムを接着した。次に、銅箔表面に例1と同様にAu、Pd及び/又はPtの各層をスパッタリングで形成し、エッチングで回路を形成した。
例1~3の各測定結果を表1~4に示す。
(実施例1~33)
実施例1~33ではいずれもエッチングファクターが大きく且つバラツキもなく、矩形方に近い断面の回路を形成することができた。
図2に、実施例27により形成された回路の写真およびその断面写真を示す。
比較例1~3は、それぞれ銅箔表面が未処理であるブランク材であり、矩形方の断面の回路を形成することができなかった。
比較例4~6では、白金の付着量が1050μg/dm2超、パラジウムの付着量が600μg/dm2超、又は、金の付着量が1000μg/dm2超であるために、矩形方の断面の回路を形成することができなかった。ここで、例として、図3に、比較例6により形成された回路の写真を示す。
Claims (9)
- 銅箔基材と、該銅箔基材の表面の少なくとも一部を被覆し、且つ、白金、パラジウム、及び、金のいずれか1種以上を含む被覆層とを備え、
前記被覆層における白金の付着量が1050μg/dm2以下、パラジウムの付着量が600μg/dm2以下、金の付着量が1000μg/dm2以下であるプリント配線板用銅箔。 - 前記被覆層における白金の付着量が20~400μg/dm2、パラジウムの付着量が20~250μg/dm2、金の付着量が20~400μg/dm2である請求項1に記載のプリント配線板用銅箔。
- 前記被覆層における白金の付着量が50~300μg/dm2、パラジウムの付着量が30~180μg/dm2、金の付着量が50~300μg/dm2である請求項2に記載のプリント配線板用銅箔。
- プリント配線板はフレキシブルプリント配線板である請求項1~3のいずれかに記載のプリント配線板用銅箔。
- 請求項1~4のいずれかに記載の銅箔で構成された圧延銅箔又は電解銅箔を準備する工程と、
前記銅箔の被覆層をエッチング面として該銅箔と樹脂基板との積層体を作製する工程と、
前記積層体を塩化第二鉄水溶液又は塩化第二銅水溶液を用いてエッチングし、銅の不必要部分を除去して銅の回路を形成する工程と、
を含む電子回路の形成方法。 - 請求項1~4のいずれかに記載の銅箔と樹脂基板との積層体。
- 銅層と樹脂基板との積層体であって、
前記銅層の表面の少なくとも一部を被覆する請求項1~4のいずれかに記載の被覆層を備えた積層体。 - 前記樹脂基板がポリイミド基板である請求項6又は7に記載の積層体。
- 請求項6~8のいずれかに記載の積層体を材料としたプリント配線板。
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