JP3900116B2

JP3900116B2 - Surface-treated copper foil for electronic circuit board and manufacturing method thereof

Info

Publication number: JP3900116B2
Application number: JP2003200904A
Authority: JP
Inventors: 宗男小平; 元佐々木; 保之伊藤
Original assignee: Hitachi Cable Ltd
Current assignee: Hitachi Cable Ltd
Priority date: 2003-07-24
Filing date: 2003-07-24
Publication date: 2007-04-04
Anticipated expiration: 2023-07-24
Also published as: JP2005042139A

Description

【０００１】
【発明の属する技術分野】
本発明は、表面処理銅箔及びその製造方法に関し、更に詳しくは、樹脂密着性、耐変色性が良好で電子回路基板用途に適した電子回路基板用の表面処理銅箔及びその製造方法に関するものである。
【０００２】
【従来の技術】
銅箔は、現在、電子回路基板の分野で大量に使用されている。例えば、ガラスエポキシ基材と熱プレスされたり、接着剤付きのポリイミドフィルムとラミネートされたり、あるいはポリイミドワニスを塗布後キュアにより基板とされたりして、プリント配線板の基本的な構成要素となる。この際、銅箔と樹脂との間の密着性を向上させるため、銅箔にはいわゆるトリート処理と称する表面粗化処理が施される。銅箔には電解銅箔と圧延銅箔があるが、表面粗化処理についてはいずれも同様の方法がとられる。すなわち銅イオンを含有する電解液中で銅箔を陰極電解し、銅箔表面に樹枝状や米粒状の銅電着層を形成する。最適な表面状態を得るため電解液中には微量の塩素イオン、ゼラチンあるいは複数の金属イオンが共添されることがある。このようにして形成された凹凸を持った銅電着層は樹脂などと接着されるときアンカー効果により密着性を向上させることになる。
【０００３】
電子回路基板として利用する場合、さらに樹脂密着性を向上させるため、一般に、クロメート処理が施される（例えば、特許文献１参照）。クロメート膜の優れたバリア効果により、耐変色性も大幅に向上する。従来、上記のクロメート処理は無水クロム酸等の６価クロムを含む処理液に浸漬する、あるいは陰極電解することで行なわれてきた。この時形成されるクロメート皮膜は、３価クロムと６価クロムを含む複合酸化物と考えられている。
【０００４】
【特許文献１】
特開２０００−１６５０３７号
【０００５】
【発明が解決しようとする課題】
しかしながら、近年、環境保護の動きが活発化する中で、６価クロムに対する規制が厳しくなり、６価クロムを含まないクロメート皮膜を有する表面処理銅箔が望まれている。
【０００６】
一方、３価クロムのクロメート皮膜を形成する試薬が市販されている。しかし、これらは自動車用途を前提としており、電子回路基板用途には適当でない。例えば、これら市販試薬の場合、下地Ｚｎめっきを２μｍ以上必要とするが、電子回路基板用途ではクロメート処理、樹脂フィルム貼付け後にめっき工程やエッチング工程があるため、Ｚｎ層が厚いと顕著な酸浸蝕が起こるため、樹脂密着性が低下してしまう。
【０００７】
従って、本発明の目的は、有害物質である６価クロムを含有することなく、樹脂密着性および耐変色性に優れた電子回路基板用の表面処理銅箔及びその製造方法を提供することである。
【０００８】
【課題を解決するための手段】
前記課題を解決するため本発明者らが鋭意検討した結果、特定の組成を有するクロメート処理液に浸漬して所定の膜厚のクロメート処理膜を形成することによって、薄い下地Ｚｎめっき層上に６価クロムを含まない３価クロメート膜を形成することが可能であることを見出し、本発明を完成させた。
【０００９】
即ち、本発明の電子回路基板用の表面処理銅箔は、表面粗化処理された銅箔上に、順に、亜鉛めっき膜、クロメート処理膜が形成された表面処理銅箔において、前記亜鉛めっき膜厚が３ｎｍ以上１４０ｎｍ未満であり、前記クロメート処理膜が３価クロメート処理を施すことにより形成されたものであり、かつその膜厚が１ｎｍ以上４０ｎｍ以下であることを特徴とする。
【００１１】
表面粗化処理された前記銅箔を、無酸素銅にジルコニウムを０．０１５〜０．０３wt％配合した銅合金とすることができる。
【００１２】
表面粗化処理された前記銅箔を、タフピッチ銅とすることもできる。
【００１３】
また、本発明の電子回路基板用の表面処理銅箔の製造方法は、銅イオンを含む電解液中で銅箔表面を陰極電解により粗化した後、順に、亜鉛めっき、クロメート処理を施す表面処理箔の製造方法において、前記亜鉛めっきをその膜厚が３ｎｍ以上１４０ｎｍ未満となるように形成し、前記クロメート処理を、３価クロムイオンを１．４ｍｇ／Ｌ以上７０ｍｇ／Ｌ未満、弗化物イオンを０．８ｍｇ／Ｌ以上４０ｍｇ／Ｌ未満、硝酸を２．５ｍｇ／Ｌ以上１２５ｍｇ／Ｌ未満含有する組成の水溶液に浸漬して行うことを特徴とする。
【００１５】
【発明の実施の形態】
以下、本発明の表面処理銅箔及びその製造方法の実施形態について説明する。
【００１６】
まず、本発明の表面処理銅箔として使用される銅箔としては、ＣＯＦ(Chip on Film)用途の場合、樹脂接合時およびチップアセンブリ時に高温に曝され、素地銅箔に高い耐熱性が要求されることから、無酸素銅にジルコニウムを０．０１５〜０．０３wt％配合した銅合金（日立電線株式会社製「ＨＣＬ−０２Ｚ」）が好適である。この銅合金とすることで、高い導電性を維持したまま耐熱性のよい表面処理銅箔を得ることが可能となる。また、ＦＰＣ（Flexible Printed Circuits）用途の場合は、高い屈曲性が要求されることから、タフピッチ圧延銅箔とすることが好ましい。このタフピッチ圧延銅箔は、樹脂フィルム貼付け時の加熱で容易に軟化し、圧延上がりに比べ屈曲性が向上するため、最適である。
【００１７】
上記銅箔には樹脂との密着性を向上させるために粗化めっき処理が施されるが、めっき膜の均一性を向上させるため、予め前処理として電解脱脂処理、酸洗処理を行なう。次いで、銅めっき液中で銅箔を陰極として所定の電流密度でめっき処理を施し、銅箔の表面に突起状の銅電着物からなる粗化処理層を形成して銅箔の表面に粗化めっき処理を行なう。
【００１８】
次に、粗化めっき処理を施した銅箔の表面に、クロメート処理に先んじで、亜鉛めっき処理、又はニッケルめっき処理及び亜鉛めっき処理を施す。下地の亜鉛めっき膜厚は３ｎｍ以上１４０ｎｍ未満が望ましい。３ｎｍ未満ではクロメート処理に伴う亜鉛の消失が無視できなくなる。１４０ｎｍ以上では樹脂張り合わせ後のめっき工程あるいはエッチング工程で酸などによる亜鉛溶出が顕著になり、樹脂密着性が低下する。また、亜鉛めっき層と下地銅箔の間にニッケルめっき層を設けると、樹脂フィルム貼付け時の加熱でＺｎ−Ｃｕ合金層が形成されず、耐酸性、樹脂密着性が低下するのを防止できる。ニッケルめっき膜厚は３ｎｍ以上１４０ｎｍ未満が望ましい。３ｎｍ未満ではバリア効果が乏しく、Ｃｕ−Ｚｎ合金層の形成を防げない。１４０ｎｍ以上では、回路パターンエッチング時にＮｉがエッチングされずに残ってしまう。
【００１９】
その後、所定の濃度のクロメート処理液によりクロメート処理を施す。クロメート処理液としては、６価クロムイオンを含まず、３価クロムイオン１．４ｍｇ/Ｌ以上７０ｍｇ/Ｌ未満、フッ素イオン０．８ｍｇ/Ｌ以上４０ｍｇ／Ｌ未満、硝酸２．５ｍｇ／Ｌ以上１２５ｍｇ／Ｌ未満含有する水溶液が望ましい。これら濃度値未満の場合、クロメート処理膜がほとんど形成されない。これら濃度値以上では下地亜鉛の溶解消失が起こり、下地亜鉛が溶解消失するとクロメート膜も形成されない。上記濃度範囲においては、形成されるクロメート処理膜の厚さが濃度に正比例するので、クロメート処理膜の厚さをこれら成分濃度で制御することができる。クロメート処理膜厚は処理時間に依存せず、１秒未満の浸漬でも１０分の浸漬でも形成されるクロメート処理膜の厚さは同じである。クロメート処理膜の膜厚は、上記濃度範囲において、１ｎｍ以上４０ｎｍ以下とすることができる。また、上記クロメート処理液中の３価クロムイオンは硫酸クロムで、フッ素イオンは弗化水素ナトリウムあるいは弗化水素アンモニウムで供給することが望ましい。なお、本処理にともなう下地亜鉛の溶解は実質的に無視できる程度である。
【００２０】
【実施例】
以下、本発明の実施例について説明する。
【００２１】
【実施例１】
（３価クロメート処理液組成の最適範囲）
板厚１８μｍの圧延銅箔を用意し、表１に示す条件で前処理（脱脂、酸洗）を行った後、表２に示す条件で粗化めっき処理を行い、更に、表３に示す条件でＺｎめっきを施した。次いで、表４に示す条件で３価クロムイオン及び弗化物イオンの濃度を変化させて３価クロメート処理を施した。その後、ＦＲ−５相当ガラス・エポキシ樹脂含浸基材にサンプルの粗化面側を積層し銅張積層板とした。次にエッチングにより銅箔幅１ｍｍとしＪＩＳＣ６４８１に準拠し、接着強度を測定した。このときの接着強度が、０．８Ｎ/ｍｍ以上の試料を○、０．５以上０．８未満を△、０．５未満を×で判定した。更に、１０％ＨＣｌ水溶液に室温で１時間浸漬したのち、同様に密着性評価を行なった。また、積層前の表面処理銅箔を３００℃×１０分、大気加熱することで、変色試験を行った。目視観察で変色のないものを○、変色ありを×と判定した。
【００２２】
【表１】

【００２３】
【表２】

【００２４】
【表３】

【００２５】
【表４】

【００２６】
表４より、実施例１−１〜１−３に示すように、３価クロムイオンを１．４ｍｇ／Ｌ以上７０ｍｇ／Ｌ未満、弗化物イオンを０．８ｍｇ／Ｌ以上４０ｍｇ／Ｌ未満、硝酸を２．５ｇ／Ｌ以上１２５ｍｇ／Ｌ未満含有するクロメート処理液を使用すれば、樹脂密着性および耐変色性に優れた表面処理銅箔が得られることが判明した。なお、比較例１−１でこれら特性が劣る理由は、クロメート膜厚が薄いためである。また、比較例１−２では、クロメート処理中に亜鉛皮膜が全て溶解、消失してしまい、クロメート膜が形成されないため、樹脂密着性および耐変色性が低下したものと考えられる。
【００２７】
【実施例２】
（亜鉛めっき厚の最適範囲）
実施例１と同様に、表１、表２に示す条件で前処理、粗化めっき処理を施した。次に、表５に示すように亜鉛めっき厚を変化させて亜鉛めっきを行った後、実施例１−３の条件（膜厚４０ｎｍ）で３価クロメート処理を施した。また、一部のサンプルについて亜鉛めっき前にニッケルめっき処理を施した。このニッケルめっきはワット浴を使用して行った。サンプルの評価方法は、実施例１と同様である。
【００２８】
【表５】

【００２９】
表５より、実施例２−１〜２−３に示す亜鉛めっき厚が３ｎｍ以上１４０ｎｍ未満の条件で、良好な評価結果が得られることが判った。なお、比較例２−１では亜鉛めっき厚が薄いのでクロメート処理で溶解、消失してしまい、クロメート膜が形成されなかったため特性が出なかったものと考えられる。また、比較例２−２では、亜鉛めっき厚が厚いため、Ｃｕ−Ｚｎ合金層の酸浸蝕で樹脂密着性が悪くなったと考えられる。また、実施例２−４に示すように、亜鉛めっき前にニッケルめっきを施すことで、亜鉛めっき厚が比較例２−２と同条件でも良好な樹脂密着性を示すことが判明した。これは樹脂貼り付け時の加熱時にバリア膜として働き、Ｚｎ−Ｃｕ合金層の形成を防ぐためと推定される。
【００３０】
【発明の効果】
本発明の電子回路基板用の表面処理銅箔は、亜鉛めっき膜厚を３ｎｍ以上１４０ｎｍ未満とし、クロメート処理膜を３価クロムで構成しかつその膜厚を１ｎｍ以上４０ｎｍ以下としているので、クロメート処理膜が有害物質である６価クロムを含有することなく耐変色性に優れたものとなる。また、亜鉛めっき膜厚を薄く形成しているので、エッチング工程による顕著な酸浸蝕を防止でき樹脂密着性に優れたものとすることができる。
【００３２】
更に、表面粗化処理された銅箔を無酸素銅にジルコニウムを０．０１５〜０．０３wt％配合した銅合金とすることにより、高い導電性を維持したまま耐熱性のよい表面処理銅箔を得ることが可能となるので、ＣＯＦ(Chip on Film)用途として好適なものとなる。
【００３３】
また、表面粗化処理された銅箔をタフピッチ銅とすることにより、樹脂フィルム貼付け時の加熱で容易に軟化し、圧延上がりに比べ屈曲性が向上するため、ＦＰＣ（Flexible Printed Circuits）用途として好適なものとなる。
【００３４】
また、本発明の電子回路基板用の表面処理銅箔の製造方法は、クロメート処理を、３価クロムイオンを１．４ｍｇ／Ｌ以上７０ｍｇ／Ｌ未満、弗化物イオンを０．８ｍｇ／Ｌ以上４０ｍｇ／Ｌ未満、硝酸を２．５ｍｇ／Ｌ以上１２５ｍｇ／Ｌ未満含有する組成の水溶液に浸漬して行なっているので、薄い下地亜鉛めっき膜上に６価クロムを含まない３価クロメート膜を形成することが可能となり、これによって樹脂密着性および耐変色性に優れた表面処理銅箔を提供することが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface-treated copper foil and a method for producing the same, and more particularly relates to a surface-treated copper foil for an electronic circuit board suitable for use in an electronic circuit board and a method for producing the same. It is.
[0002]
[Prior art]
Copper foil is currently used in large quantities in the field of electronic circuit boards. For example, it is heat-pressed with a glass epoxy base material, laminated with a polyimide film with an adhesive, or coated with a polyimide varnish and then made into a substrate by curing to become a basic component of a printed wiring board. At this time, in order to improve the adhesion between the copper foil and the resin, the copper foil is subjected to a surface roughening treatment called a so-called treating treatment. The copper foil includes an electrolytic copper foil and a rolled copper foil, and the same method is used for the surface roughening treatment. That is, the copper foil is subjected to cathodic electrolysis in an electrolytic solution containing copper ions to form a dendritic or rice granular copper electrodeposition layer on the copper foil surface. In order to obtain an optimum surface state, a trace amount of chlorine ions, gelatin or a plurality of metal ions may be co-added to the electrolytic solution. When the copper electrodeposition layer having irregularities formed in this manner is bonded to a resin or the like, the adhesion is improved by the anchor effect.
[0003]
When used as an electronic circuit board, chromate treatment is generally performed to further improve resin adhesion (see, for example, Patent Document 1). Due to the excellent barrier effect of the chromate film, discoloration resistance is also greatly improved. Conventionally, the above chromate treatment has been performed by dipping in a treatment solution containing hexavalent chromium such as chromic anhydride, or by cathodic electrolysis. The chromate film formed at this time is considered to be a composite oxide containing trivalent chromium and hexavalent chromium.
[0004]
[Patent Document 1]
JP 2000-165037 A
[Problems to be solved by the invention]
However, in recent years, as the trend of environmental protection has been activated, regulations on hexavalent chromium have become stricter, and a surface-treated copper foil having a chromate film not containing hexavalent chromium has been desired.
[0006]
On the other hand, a reagent for forming a trivalent chromium chromate film is commercially available. However, these are premised on automobile use and are not suitable for electronic circuit board use. For example, in the case of these commercially available reagents, the base Zn plating needs to be 2 μm or more. However, since there are a plating process and an etching process after the chromate treatment and the resin film pasting in the electronic circuit board application, if the Zn layer is thick, remarkable acid erosion occurs. As a result, the resin adhesion is reduced.
[0007]
Accordingly, an object of the present invention is to provide a surface-treated copper foil for an electronic circuit board excellent in resin adhesion and discoloration resistance without containing hexavalent chromium which is a harmful substance, and a method for producing the same. .
[0008]
[Means for Solving the Problems]
As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, a chromate treatment film having a predetermined film thickness is formed by dipping in a chromate treatment solution having a specific composition. The inventors have found that it is possible to form a trivalent chromate film containing no valent chromium, and have completed the present invention.
[0009]
That is, the surface-treated copper foil for an electronic circuit board of the present invention is the surface-treated copper foil in which a zinc-plated film and a chromate-treated film are formed in this order on the surface-roughened copper foil. The thickness is 3 nm or more and less than 140 nm, the chromate treatment film is formed by performing trivalent chromate treatment, and the film thickness is 1 nm or more and 40 nm or less.
[0011]
The copper foil subjected to the surface roughening treatment can be made into a copper alloy in which 0.015 to 0.03 wt% of zirconium is blended with oxygen-free copper.
[0012]
The copper foil subjected to the surface roughening treatment may be tough pitch copper.
[0013]
Moreover, the manufacturing method of the surface treatment copper foil for electronic circuit boards of this invention is a surface treatment which, after roughening the copper foil surface by cathodic electrolysis in an electrolytic solution containing copper ions, in order, galvanizing and chromate treatment In the foil manufacturing method, the galvanizing is formed so that the film thickness is 3 nm or more and less than 140 nm, the chromate treatment is performed using trivalent chromium ions at 1.4 mg / L or more and less than 70 mg / L, and fluoride ions. It is characterized by being immersed in an aqueous solution having a composition containing 0.8 mg / L or more and less than 40 mg / L and nitric acid containing 2.5 mg / L or more and less than 125 mg / L.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the surface-treated copper foil and the manufacturing method thereof according to the present invention will be described.
[0016]
First, as the copper foil used as the surface-treated copper foil of the present invention, in the case of COF (Chip on Film) application, it is exposed to high temperatures during resin bonding and chip assembly, and the base copper foil is required to have high heat resistance. Therefore, a copper alloy (“HCL-02Z” manufactured by Hitachi Cable, Ltd.) in which 0.015 to 0.03 wt% of zirconium is added to oxygen-free copper is preferable. By using this copper alloy, it becomes possible to obtain a surface-treated copper foil with good heat resistance while maintaining high conductivity. Moreover, in the case of FPC (Flexible Printed Circuits) use, since a high flexibility is required, it is preferable to use a tough pitch rolled copper foil. This tough pitch rolled copper foil is optimal because it is easily softened by heating at the time of application of the resin film, and the flexibility is improved as compared with rolling up.
[0017]
The copper foil is subjected to a roughing plating process in order to improve the adhesion to the resin. In order to improve the uniformity of the plating film, an electrolytic degreasing process and a pickling process are performed in advance as pretreatments. Next, plating is performed at a predetermined current density using a copper foil as a cathode in a copper plating solution, and a roughening treatment layer made of protruding copper electrodeposits is formed on the surface of the copper foil to roughen the surface of the copper foil. Plating is performed.
[0018]
Next, the surface of the copper foil subjected to the roughening plating treatment is subjected to zinc plating treatment, nickel plating treatment and zinc plating treatment prior to chromate treatment. The thickness of the underlying galvanized film is preferably 3 nm or more and less than 140 nm. If it is less than 3 nm, the disappearance of zinc accompanying the chromate treatment cannot be ignored. If it is 140 nm or more, zinc elution due to an acid or the like becomes remarkable in the plating step or etching step after resin bonding, and the resin adhesion is lowered. Moreover, when a nickel plating layer is provided between the zinc plating layer and the base copper foil, the Zn—Cu alloy layer is not formed by heating at the time of pasting the resin film, and it is possible to prevent acid resistance and resin adhesion from deteriorating. The nickel plating film thickness is desirably 3 nm or more and less than 140 nm. If the thickness is less than 3 nm, the barrier effect is poor and the formation of the Cu—Zn alloy layer cannot be prevented. If it is 140 nm or more, Ni remains without being etched during circuit pattern etching.
[0019]
Thereafter, chromate treatment is performed with a chromate treatment solution having a predetermined concentration. The chromate treatment solution does not contain hexavalent chromium ions, trivalent chromium ions 1.4 mg / L or more and less than 70 mg / L, fluorine ions 0.8 mg / L or more and less than 40 mg / L, nitric acid 2.5 mg / L or more and 125 mg. An aqueous solution containing less than / L is desirable. When the concentration is less than these, the chromate-treated film is hardly formed. Above these concentration values, dissolution of the base zinc occurs, and when the base zinc dissolves and disappears, no chromate film is formed. In the above concentration range, the thickness of the chromate treatment film to be formed is directly proportional to the concentration, so that the thickness of the chromate treatment film can be controlled by the concentration of these components. The chromate treatment film thickness does not depend on the treatment time, and the thickness of the chromate treatment film formed by immersion for less than 1 second or 10 minutes is the same. The film thickness of the chromate treatment film can be 1 nm or more and 40 nm or less in the above concentration range. Further, it is desirable that the trivalent chromium ion in the chromate treatment liquid is supplied by chromium sulfate and the fluorine ion is supplied by sodium hydrogen fluoride or ammonium hydrogen fluoride. The dissolution of the base zinc accompanying this treatment is substantially negligible.
[0020]
【Example】
Examples of the present invention will be described below.
[0021]
[Example 1]
(Optimal range of trivalent chromate treatment liquid composition)
A rolled copper foil having a plate thickness of 18 μm was prepared, and after pretreatment (degreasing and pickling) under the conditions shown in Table 1, roughening plating treatment was performed under the conditions shown in Table 2, and further, conditions shown in Table 3 Zn plating was performed. Next, trivalent chromate treatment was performed by changing the concentrations of trivalent chromium ions and fluoride ions under the conditions shown in Table 4. Thereafter, the roughened surface side of the sample was laminated on the FR-5 equivalent glass / epoxy resin impregnated base material to obtain a copper-clad laminate. Next, the copper foil width was set to 1 mm by etching, and the adhesive strength was measured according to JIS C6481. At this time, a sample having an adhesive strength of 0.8 N / mm or more was evaluated as ◯, 0.5 or more and less than 0.8 as Δ, and less than 0.5 as ×. Further, after being immersed in a 10% HCl aqueous solution at room temperature for 1 hour, the adhesion evaluation was performed in the same manner. Moreover, the discoloration test was done by heating the surface-treated copper foil before lamination to the air at 300 ° C. for 10 minutes. It was determined that there was no discoloration by visual observation, and that there was no discoloration was evaluated as x.
[0022]
[Table 1]

[0023]
[Table 2]

[0024]
[Table 3]

[0025]
[Table 4]

[0026]
From Table 4, as shown in Examples 1-1 to 1-3, trivalent chromium ions are 1.4 mg / L or more and less than 70 mg / L, fluoride ions are 0.8 mg / L or more and less than 40 mg / L, nitric acid When a chromate treatment solution containing 2.5 g / L or more and less than 125 mg / L is used, it has been found that a surface-treated copper foil excellent in resin adhesion and discoloration resistance can be obtained. The reason why these characteristics are inferior in Comparative Example 1-1 is that the chromate film thickness is thin. Further, in Comparative Example 1-2, it is considered that the zinc adhesion was completely dissolved and disappeared during the chromate treatment, and the chromate film was not formed.
[0027]
[Example 2]
(Optimum range of zinc plating thickness)
Similar to Example 1, pretreatment and roughening plating were performed under the conditions shown in Tables 1 and 2. Next, as shown in Table 5, after galvanizing by changing the galvanizing thickness, trivalent chromate treatment was performed under the conditions of Example 1-3 (film thickness 40 nm). Some samples were subjected to nickel plating before galvanization. This nickel plating was performed using a Watt bath. The sample evaluation method is the same as in Example 1.
[0028]
[Table 5]

[0029]
From Table 5, it turned out that a favorable evaluation result is obtained on the conditions whose zinc plating thickness shown to Examples 2-1 to 2-3 is 3 nm or more and less than 140 nm. In Comparative Example 2-1, since the galvanized thickness was thin, it was dissolved and disappeared by the chromate treatment, and the chromate film was not formed. Moreover, in Comparative Example 2-2, since the zinc plating thickness is thick, it is considered that the resin adhesion deteriorated due to acid erosion of the Cu—Zn alloy layer. In addition, as shown in Example 2-4, it was found that by applying nickel plating before zinc plating, the zinc plating thickness shows good resin adhesion even under the same conditions as in Comparative Example 2-2. This is presumed to function as a barrier film at the time of heating at the time of resin pasting to prevent the formation of a Zn-Cu alloy layer.
[0030]
【The invention's effect】
Since the surface-treated copper foil for an electronic circuit board of the present invention has a zinc plating film thickness of 3 nm or more and less than 140 nm, the chromate treatment film is composed of trivalent chromium, and the film thickness thereof is 1 nm or more and 40 nm or less. The film has excellent discoloration resistance without containing hexavalent chromium which is a harmful substance. Moreover, since the galvanized film thickness is formed thin, remarkable acid erosion due to the etching process can be prevented and the resin adhesion can be improved.
[0032]
Furthermore, the surface-treated copper foil having good heat resistance while maintaining high conductivity can be obtained by making the copper foil subjected to surface roughening treatment into a copper alloy in which 0.015 to 0.03 wt% of zirconium is mixed with oxygen-free copper. Therefore, it is suitable for COF (Chip on Film) applications.
[0033]
In addition, the surface roughened copper foil is made tough pitch copper, so it is easily softened by heating when a resin film is applied, and its flexibility is improved compared to rolling up, so it is suitable for FPC (Flexible Printed Circuits) applications. It will be something.
[0034]
In the method for producing a surface-treated copper foil for an electronic circuit board according to the present invention, the chromate treatment is carried out with a trivalent chromium ion of 1.4 mg / L or more and less than 70 mg / L, and a fluoride ion of 0.8 mg / L or more and 40 mg. Less than / L and nitric acid is immersed in an aqueous solution having a composition containing 2.5 mg / L or more and less than 125 mg / L, a trivalent chromate film not containing hexavalent chromium is formed on a thin base galvanized film. Thus, it becomes possible to provide a surface-treated copper foil excellent in resin adhesion and discoloration resistance.

Claims

In the surface-treated copper foil for an electronic circuit board in which a galvanized film and a chromate-treated film are sequentially formed on the surface-roughened copper foil,
The galvanized film thickness is 3 nm or more and less than 140 nm,
A surface-treated copper foil for an electronic circuit board, wherein the chromate-treated film is formed by performing trivalent chromate treatment and has a film thickness of 1 nm to 40 nm.

Surface roughening-treated the copper foil, treated copper for electronic circuit board according to claim 1 Symbol mounting, characterized in that the zirconium oxygen-free copper is 0.015～0.03Wt% compounded copper alloy Foil.

Surface roughening-treated the copper foil, treated copper foil for electronic circuit board according to claim 1 Symbol mounting characterized in that it is a tough pitch copper.

In the method for producing a surface-treated copper foil for an electronic circuit board that is subjected to galvanization and chromate treatment in order after the surface of the copper foil is roughened by cathodic electrolysis in an electrolytic solution containing copper ions,
The galvanizing is formed so that the film thickness is 3 nm or more and less than 140 nm, and the chromate treatment is carried out by adding trivalent chromium ions to 1.4 mg / L or more and less than 70 mg / L, and fluoride ions to 0.8 mg / L or more. A method for producing a surface-treated copper foil for an electronic circuit board, which is performed by immersing in an aqueous solution having a composition containing less than 40 mg / L and nitric acid of 2.5 mg / L or more and less than 125 mg / L.