JP3775273B2

JP3775273B2 - Electromagnetic shielding film

Info

Publication number: JP3775273B2
Application number: JP2001313926A
Authority: JP
Inventors: 直明北川; 勲雄安東
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 2001-10-11
Filing date: 2001-10-11
Publication date: 2006-05-17
Anticipated expiration: 2021-10-11
Also published as: JP2003119577A

Description

【０００１】
【発明の属する技術分野】
本発明は、プラスチック成形品の表面に形成され、電磁波シールド特性、密着性および耐食性に優れる電磁波シールド膜に関する。
【０００２】
【従来の技術】
従来、電気・電子機器や携帯電話などの電波を発信受信する機器には、機器の誤動作を避けるために、筺体のプラスチック成形品やその内側に、電磁波シールド処理を施している。この電磁波シールド処理の方法には、次の方法が知られている。すなわち、(1)プラスチック成形品の中に導電性金属を混入する方法、(2)プラスチック成形品の表面に導電性塗料を塗布する方法、(3)湿式メッキ法により、プラスチック成形品の表面に、金属薄膜を形成する方法、(4)イオン化して成膜するイオンプレーティング法、真空蒸着法などの真空工法により、プラスチック成形品の表面に、金属薄膜を形成する方法である。
【０００３】
湿式メッキ法による成膜では、無電解メッキ法が用いられている。この方法では、クロム酸エッチング、パラジウム触媒付加などを行うため、プラスチック成形品と金属薄膜との密着は強固である。しかし、(1)廃液処理を行う必要がある、(2)処理時間が長い、(3)プラスチック成形品の両面にメッキされる、などの欠点がある。
【０００４】
真空工法は、生産性に優れている。そして、真空工法では、(1)アルミニウム(Al)を2〜3μm形成する方法、(2)銅(Cu)を第１層にニッケル(Ni)などを保護膜として第２層に成膜する方法が一般的である。
【０００５】
しかし、Ａｌを形成する方法は電子銃や抵抗加熱方式では蒸発しないので、フラッシュ蒸着という特殊な方法を用いなければならないという欠点がある。また、Ｃｕを第１層にＮｉを第２層に成膜する方法は、Ａｌを形成する方法が有する上記欠点はないが、融点が高くて蒸発時間が長いＮｉのため生産性が低いという欠点がある。そこで、Ｎｉに替わる膜が、特開平６−１５７７９７号公報や特開平８−２３６９７６号公報に開示されている。
【０００６】
特開平6-157797号公報には、高周波プラズマによりCuを成膜した後に0.05〜2.0μmの錫(Sn)膜を配設した電磁波シールド膜が提案されている。しかしながら、この電磁波シールド膜は、(1)Sn膜が柱状化または針状化し易いため、耐食性が劣る、(2)真空蒸着法により成膜すると、Cu膜とSn膜との密着が悪くなる、という欠点がある。
【０００７】
また、特開平８−２３６９７６号公報には、高周波プラズマによりＣｕを成膜した後に０．１μｍ以上の錫−銀合金膜を配設した電磁波シールド膜が提案されている。しかしながら、この電磁波シールド膜は、特開平６−１５７７９７号公報で提案されている電磁波シールド膜の上記欠点を解決はするが、錫−銀合金膜に含まれる銀のため、コストが高いという問題がある。
【０００８】
【発明が解決しようとする課題】
そこで、本発明は、真空工法を用いて生産性よく成膜され、電磁波シールド特性、密着性および耐食性に優れた低コストの電磁波シールド膜を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記課題を解決するため、本発明の電磁波シールド膜は、プラスチック成形品の表面に形成された第１層被膜および第２層被膜であり、該第１層被膜の材質はCu、第２層被膜の材質は、第１発明によれば、Sn-Cu-Ni合金であり、また、第２発明によれば、Ｓn-Cu-クロム(Cr)合金である。上記プラスチック成形品の材質には、アクリロニトリル-ブタジエン-スチレン樹脂(ABS)、ポリカーボネート(PC)、およびABSとPCの混合樹脂(ABS-PC)を例示することができる。
【００１０】
第１発明および第２発明における第１層被膜は、膜厚が0.3〜4μmであるのが好ましい。
【００１１】
第１発明および第２発明における第２層被膜は、膜厚が０．１〜３μｍであるのが好ましい。また、第１発明および第２発明における第２層被膜のＣｕの含有量がＳｎの含有量に対して３〜２０質量%であるのが好ましく、第１発明における第２層被膜のＮｉの含有量、および第２発明における第２層被膜のＣｒの含有量は、Ｓｎの含有量とＣｕの含有量との和に対して３〜３０質量%であるのが好ましい。
【００１２】
本発明の電磁波シールド膜は、真空工法によって成膜されたものである。
【００１３】
【発明の実施の形態】
第１発明（第２発明）の電磁波シールド膜は、プラスチック成形品の表面に形成された第１層被膜および第２層被膜であり、該第１層被膜の材質はCu、第２層被膜の材質はSn-Cu-Ni合金（Sn-Cu-Cr合金）である。
【００１４】
第１層被膜は、材質がCuである。それは、比抵抗が小さく、安価であるからである。
【００１５】
第１層被膜の膜厚が0.3μm未満では、充分な電磁波シールド特性が得られず、また、第１層被膜自体の構造が粗になって耐食性が著しく低下する。一方、第１層被膜の膜厚が4μmを超えると、電磁波シールド特性は塊状の金属銅と同等であるが、密着性が低下する。すなわち、成膜後に、自然剥離したりテープ剥離試験で剥離したりする可能性が高くなる。それは、膜応力が高くなるからである。さらに第１層被膜の膜厚が4μmを超えると、成膜に時間がかかって生産性が低下する。
【００１６】
第１層被膜のプラスチック成形品に対する密着力に応じて適宜、プラスチック成形品と第１層被膜との間にアンダーコートを塗布してもよい。
【００１７】
第２層被膜において、Ｃｕは、次の(1)〜(3)の作用を発揮する。すなわち、(1)電磁波シールド膜として必要な低比抵抗を実現する。(2)錫ウイスカーの発生を抑える。(3)融点が３００℃以下の共晶（Ｓｎ−Ｃｕ）を作って簡単に早く蒸発させる。第２層被膜のＣｕの含有量がＳｎの含有量に対して３質量%未満では、上記Ｃｕの作用を充分発揮させることが困難である。一方、第２層被膜のＣｕの含有量がＳｎの含有量に対して２０質量％を超えると、融点が高くなって、蒸発時間が長くなり、生産性が低下してしまう。
【００１８】
第２層被膜において、Ni(Cr)は、耐食性、特に耐酸化性を向上させる。この理由は、次の(1)〜(3)のように考えられる。すなわち、(1)Ni(Cr)の蒸発量は、融点が高いためSn-Cuと比較すると少ないが、成膜時間とともに増す。(2)そのため、Ni濃度(Cr濃度)は、成膜初期には、つまり第２層被膜の第１層被膜側では低く、第２層被膜の表面に近くなるほど高くなる、(3)このようなNi(Cr)の濃度勾配が耐酸化性の向上、つまり耐食性の向上に大きく寄与する。
【００１９】
第２層被膜においてSn-CuにNiを添加すると、単味のNiを成膜する従来の場合と比較して、Niが蒸発しやすくて生産性が上がる。また、Sn-CuにCrを添加しても、単味のCrを成膜する場合と比較して、Crが蒸発しやすくて生産性が上がる。このようにNi(Cr)が蒸発しやすくなる理由は、次の(1)、(2)のように考えられる。すなわち、(1)融点の高いＮｉ、Ｃｒを融点の低いＳｎ−Ｃｕ合金に微量添加すると、Ｓｎ−Ｃｕ−Ｎｉ（Ｃｒ）合金の融点がかなり下がる。(2)そのため、微量添加した高融点のNi(Cr)もSn-Cuが蒸発している最中に徐々に蒸発し、Sn-Cu-Ni合金(Sn-Cu-Cr合金)として成膜される。
【００２０】
第２層被膜のＮｉの含有量（Ｃｒの含有量）がＳｎの含有量とＣｕの含有量との和の３質量%未満では、上記Ｎｉ（Ｃｒ）の作用を充分発揮させることが困難である。さらにいえば、電磁波シールド膜外観の一部に青白いＳｎ−Ｃｕ合金色が表れ、その部分の耐食性はＳｎ−Ｃｕ合金並みに低下する。なお、Ｓｎ−Ｃｕ合金の耐食性は比較的高いが、単味で成膜した従来のＮｉと同等である。一方、第２層被膜のＮｉの含有量（Ｃｒの含有量）がＳｎの含有量とＣｕの含有量との和の３０質量%を超えると、Ｓｎ−Ｃｕ−Ｎｉ合金（Ｓｎ−Ｃｕ−Ｃｒ合金）の融点が上がりすぎるため、合金成分を蒸発させる電子ビームの出力では融点の高いＮｉ（Ｃｒ）が蒸発しきらず、蒸発源のまま残ってしまう。さらにいえば、Ｎｉ（Ｃｒ）はＣｕと比較して比抵抗が高いので第２層被膜そのものの抵抗値が上がり、電磁波シールド特性が低下する。
【００２１】
第２層被膜の膜厚が0.1μm未満では、ピンホールが多くなり第１層被膜のCuが腐食する恐れがある。また、付きまわりが悪い部分が生じたり隅に付きがない部分が生ずる可能性がある。一方、第２層被膜の膜厚が3μmを超えると、膜応力が強くなって密着性が低下するだけでなく、成膜に時間がかかって生産性が低下する。
【００２２】
本発明の電磁波シールド膜を成膜するには、例えば、プラスチック成形品を基材とし、前処理を適宜施した後に、真空槽に入れる。そして、プラスチック成形品の表面に、第１層被膜および第２層被膜を、各々所望の組成・膜厚になるように、真空工法により成膜する。
【００２３】
【実施例】
［実施例１］
プラスチック成形品として、ABS製の携帯電話筺体を用いた。洗浄なしで電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを100g充填し、5分間で1μm成膜した。この後、1ハース当たりSn-5質量%Cu合金を35gおよびNiを7g充填し、プラスチック成形品を自公転させて2分間で0.6μｍ成膜した。このように成膜したプラスチック成形品に対して、外観観察、テープ剥離試験、腐食試験および膜抵抗値測定を行った。ここで、テープ剥離試験は、96hrの耐湿試験の前および後において行った。腐食試験は、24hrの塩水噴霧試験である。また、膜抵抗値測定は、携帯電話筺体のピン間抵抗を上記腐食試験の前および後において行った。第１層被膜および第２層被膜の材質および膜厚、並びにこの試験で得られた結果を表１に示す。
【００２４】
［実施例２］
プラスチック成形品として、ABS-PC製の携帯電話筺体を用いた。この成形品はCuとの密着が悪いので、アンダーコートを塗布した。この後に、電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを100g充填し、5分間で1μm成膜した。この後、1ハース当たりSn-10質量%Cu合金を35gおよびNiを10g充填し、プラスチック成形品を自公転させて2分間で0.6μｍ成膜した。このように成膜したプラスチック成形品に対して、外観観察、テープ剥離試験、腐食試験および膜抵抗値測定を実施例１と同様に行った。それらの結果は実施例１と同様であった。
【００２５】
［参考例１］
プラスチック成形品として、ABS製の携帯電話筺体を用いた。洗浄なしで電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを100g充填し、5分間で1μm成膜した。この後、1ハース当たりSn-5質量%Cu合金を35gおよびNiを15g充填し、プラスチック成形品を自公転させて、実施例１と同様0.6μmの膜厚に成膜した。その結果、第２層被膜の蒸着時間は5分で、実施例１より長くかかった。また、蒸発後のハースを観察すると、蒸発しきらなかったNiが残っていた。
【００２６】
［参考例２］
プラスチック成形品として、ABS製の携帯電話筺体を用いた。洗浄なしで電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを180g充填し、15分間で4μm成膜した。この後、1ハース当たりSn-5質量%Cu合金を35gおよびNiを7g充填し、プラスチック成形品を自公転させて0.6μｍ成膜した。このように成膜したプラスチック成形品を観察すると、該成形品の端部で基材(ABS)と第１層被膜(Cu)との間が剥離していた。
【００２７】
［実施例３］
プラスチック成形品として、ABS製の携帯電話筺体を用いた。洗浄なしで電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを100g充填し、5分間で1μm成膜した。この後、1ハース当たりSn-5質量%Cu合金を35gおよびCrを7g充填し、プラスチック成形品を自公転させて2分間で0.6μｍ成膜した。このように成膜したプラスチック成形品に対して、外観観察、テープ剥離試験、腐食試験および膜抵抗値測定を実施例１と同様に行った。第１層被膜および第２層被膜の材質および膜厚、並びにこの試験で得られた結果を表１に示す。
【００２８】
［実施例４］
プラスチック成形品として、ABS-PC製の携帯電話筺体を用いた。この成形品はCuとの密着が悪いので、アンダーコートを塗布した。この後に、電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを100g充填し、5分間で1μm成膜した。この後、1ハース当たりSn-10質量%Cu合金を35gおよびCrを10g充填し、プラスチック成形品を自公転させて2分間で0.6μｍ成膜した。このように成膜したプラスチック成形品に対して、外観観察、テープ剥離試験、腐食試験および膜抵抗値測定を実施例１と同様に行った。それらの結果は実施例３と同様であった。
【００２９】
［参考例３］
プラスチック成形品として、ABS製の携帯電話筺体を用いた。洗浄なしで電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを100g充填し、5分間で1μm成膜した。この後、1ハース当たりSn-5質量%Cu合金を35gおよびCrを15g充填し、プラスチック成形品を自公転させて、実施例３と同様0.6μmの膜厚に成膜した。その結果、第２層被膜の蒸着時間は5分で、実施例３より長くかかった。また、蒸発後のハースを観察すると、蒸発しきらなかったCrが残っていた。
【００３０】
［参考例４］
プラスチック成形品として、ABS製の携帯電話筺体を用いた。洗浄なしで電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを180g充填し、15分間で4μm成膜した。この後、1ハース当たりSn-5質量%Cu合金を35gおよびCrを7g充填し、プラスチック成形品を自公転させて２分間で0.6μm成膜した。このように成膜したプラスチック成形品を観察すると、該成形品の端部で基材(ABS)と第１層被膜(Cu)との間が剥離していた。
【００３１】
［従来例］
プラスチック成形品として、ABS製の携帯電話筺体を用いた。洗浄なしで電子ビーム方式のイオンプレーティング装置に設置した。次に、真空度5×10^-3Paまで排気した後、Arガスを3.2×10^-2Paまで導入した。この状態で高周波出力1.0kwで励起放電を起こし、5分間放電させて、プラスチック成形品表面を洗浄した。続けて、1ハース当たりCuを100g充填し、5分間で1μm成膜した。この後、Niを充填し、プラスチック成形品を自公転させて、15分間で0.3μｍ成膜した。このように成膜したプラスチック成形品に対して、外観観察、テープ剥離試験、腐食試験および膜抵抗値測定を実施例１と同様に行った。第１層被膜および第２層被膜の材質および膜厚、並びにこの試験で得られた結果を表１に示す。
【００３２】
【表１】

【００３３】
表１から次のことが分かる。すなわち、実施例１および実施例３について、従来例と比較して、保護膜としての第２層被膜の成膜時間が大きく短縮され、生産性が向上している。また、耐食性も向上している。
【００３４】
【発明の効果】
本発明によれば、生産性よく成膜され、電磁波シールド特性、密着性および耐食性に優れた低コストの電磁波シールド膜を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic wave shielding film which is formed on the surface of a plastic molded article and is excellent in electromagnetic wave shielding characteristics, adhesion and corrosion resistance.
[0002]
[Prior art]
Conventionally, devices that transmit and receive radio waves, such as electric / electronic devices and mobile phones, have been subjected to electromagnetic wave shielding treatment on the plastic molded product of the casing and the inside thereof in order to avoid malfunction of the device. The following method is known as the electromagnetic wave shielding method. That is, (1) a method of mixing a conductive metal into a plastic molded product, (2) a method of applying a conductive paint to the surface of the plastic molded product, and (3) a wet plating method on the surface of the plastic molded product. A method of forming a metal thin film, and (4) a method of forming a metal thin film on the surface of a plastic molded article by a vacuum method such as an ion plating method for ionization to form a film or a vacuum deposition method.
[0003]
In film formation by a wet plating method, an electroless plating method is used. In this method, since chromic acid etching, palladium catalyst addition, and the like are performed, adhesion between the plastic molded product and the metal thin film is strong. However, there are drawbacks such as (1) it is necessary to perform waste liquid treatment, (2) the treatment time is long, and (3) plating is performed on both surfaces of the plastic molded product.
[0004]
The vacuum method is excellent in productivity. In the vacuum method, (1) a method of forming aluminum (Al) in a thickness of 2 to 3 μm, (2) a method of forming copper (Cu) in the first layer and nickel (Ni) as a protective film in the second layer Is common.
[0005]
However, since the method of forming Al does not evaporate by an electron gun or a resistance heating method, there is a disadvantage that a special method called flash vapor deposition must be used. In addition, the method of forming Cu on the first layer and Ni on the second layer does not have the above-mentioned drawbacks of the method of forming Al, but has the disadvantage of low productivity due to Ni having a high melting point and a long evaporation time. There is. Therefore, a film replacing Ni is disclosed in JP-A-6-157797 and JP-A-8-236976 .
[0006]
Japanese Laid-Open Patent Publication No. 6-157797 proposes an electromagnetic wave shielding film in which a Cu film is formed by high-frequency plasma and then a 0.05 to 2.0 μm tin (Sn) film is disposed. However, this electromagnetic wave shielding film, (1) Sn film is easily columnar or needle-like, so the corrosion resistance is inferior, (2) When deposited by vacuum deposition, the adhesion between the Cu film and the Sn film is poor, There is a drawback.
[0007]
JP-A-8-236976 proposes an electromagnetic wave shielding film in which a tin-silver alloy film having a thickness of 0.1 μm or more is disposed after Cu is formed by high-frequency plasma. However, although this electromagnetic wave shielding film solves the above-mentioned drawbacks of the electromagnetic wave shielding film proposed in JP-A-6-157797, there is a problem that the cost is high because of silver contained in the tin-silver alloy film. is there.
[0008]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a low-cost electromagnetic shielding film which is formed with high productivity using a vacuum method and is excellent in electromagnetic shielding characteristics, adhesion and corrosion resistance.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the electromagnetic wave shielding film of the present invention is a first layer film and a second layer film formed on the surface of a plastic molded product, and the material of the first layer film is Cu, and the second layer film According to the first invention, the material is a Sn—Cu—Ni alloy, and according to the second invention, it is a Sn—Cu—chromium (Cr) alloy. Examples of the material of the plastic molded article include acrylonitrile-butadiene-styrene resin (ABS), polycarbonate (PC), and a mixed resin of ABS and PC (ABS-PC).
[0010]
The first layer film in the first and second inventions preferably has a film thickness of 0.3 to 4 μm.
[0011]
The second layer coating in the first and second inventions preferably has a thickness of 0.1 to 3 μm. Further, the Cu content of the second layer coating in the first invention and the second invention is preferably 3 to 20% by mass relative to the Sn content , and the Ni content of the second layer coating in the first invention The amount and the Cr content of the second layer coating in the second invention are preferably 3 to 30% by mass with respect to the sum of the Sn content and the Cu content .
[0012]
The electromagnetic wave shielding film of the present invention is formed by a vacuum method.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The electromagnetic wave shielding film of the first invention (second invention) is a first layer coating and a second layer coating formed on the surface of a plastic molded product, and the material of the first layer coating is Cu, and the second layer coating The material is Sn-Cu-Ni alloy (Sn-Cu-Cr alloy).
[0014]
The material of the first layer coating is Cu. This is because the specific resistance is small and inexpensive.
[0015]
When the film thickness of the first layer coating is less than 0.3 μm, sufficient electromagnetic wave shielding characteristics cannot be obtained, and the structure of the first layer coating itself becomes rough and the corrosion resistance is remarkably lowered. On the other hand, when the film thickness of the first layer coating exceeds 4 μm, the electromagnetic wave shielding characteristics are equivalent to the massive metallic copper, but the adhesion is lowered. That is, after film formation, the possibility of natural peeling or peeling by a tape peeling test increases. This is because the film stress increases. Furthermore, when the film thickness of the first layer coating exceeds 4 μm, it takes time to form the film and the productivity is lowered.
[0016]
An undercoat may be applied between the plastic molded product and the first layer coating as appropriate according to the adhesion of the first layer coating to the plastic molded product.
[0017]
In the second layer coating, Cu exhibits the following actions (1) to (3). That is, (1) a low specific resistance required as an electromagnetic wave shielding film is realized. (2) Suppress the generation of tin whiskers. (3) Eutectic (Sn—Cu) with a melting point of 300 ° C. or less is made and evaporated easily and quickly. When the content of Cu in the second layer coating is less than 3% by mass with respect to the content of Sn, it is difficult to sufficiently exert the effect of the Cu. On the other hand, when the content of Cu in the second layer coating exceeds 20% by mass with respect to the content of Sn , the melting point becomes high, the evaporation time becomes long, and the productivity is lowered.
[0018]
In the second layer coating, Ni (Cr) improves corrosion resistance, particularly oxidation resistance. The reason is considered as follows (1) to (3). That is, (1) The amount of evaporation of Ni (Cr) is small compared to Sn—Cu because of its high melting point, but increases with the film formation time. (2) Therefore, the Ni concentration (Cr concentration) is low at the initial stage of film formation, that is, on the first layer film side of the second layer film, and increases as it approaches the surface of the second layer film. (3) Ni (Cr) concentration gradient greatly contributes to improvement of oxidation resistance, that is, improvement of corrosion resistance.
[0019]
When Ni is added to Sn—Cu in the second layer coating, the Ni is easily evaporated and productivity is increased as compared with the conventional case of forming simple Ni. Further, even if Cr is added to Sn—Cu, compared to the case where a simple Cr film is formed, Cr is easily evaporated and productivity is increased. The reason why Ni (Cr) easily evaporates can be considered as follows (1) and (2). That is, (1) When a small amount of Ni or Cr having a high melting point is added to a Sn—Cu alloy having a low melting point, the melting point of the Sn—Cu—Ni (Cr) alloy is considerably lowered. (2) Therefore, Ni (Cr) with a high melting point added in a small amount gradually evaporates while Sn-Cu evaporates, and is formed as a Sn-Cu-Ni alloy (Sn-Cu-Cr alloy). The
[0020]
When the Ni content (Cr content) of the second layer coating is less than 3% by mass of the sum of the Sn content and the Cu content, it is difficult to sufficiently exert the above-described effect of Ni (Cr). is there. More specifically, a bluish Sn—Cu alloy color appears on a part of the outer appearance of the electromagnetic wave shielding film, and the corrosion resistance of that portion is reduced to the same level as that of the Sn—Cu alloy. In addition, although the corrosion resistance of Sn-Cu alloy is comparatively high, it is equivalent to the conventional Ni formed into a simple film. On the other hand, when the Ni content (Cr content) of the second layer coating exceeds 30 mass% of the sum of the Sn content and the Cu content , the Sn—Cu—Ni alloy (Sn—Cu—Cr) Since the melting point of the alloy) is too high, Ni (Cr) having a high melting point is not completely evaporated at the output of the electron beam for evaporating the alloy components, and remains as an evaporation source. Furthermore, since Ni (Cr) has a higher specific resistance than Cu, the resistance value of the second layer coating itself is increased, and the electromagnetic shielding characteristics are deteriorated.
[0021]
If the film thickness of the second layer coating is less than 0.1 μm, the number of pinholes increases and the Cu of the first layer coating may corrode. In addition, there is a possibility that a part with poor attachment occurs or a part with no corner is attached. On the other hand, when the film thickness of the second layer film exceeds 3 μm, not only the film stress becomes strong and the adhesion is lowered, but also the film formation takes time and the productivity is lowered.
[0022]
In order to form the electromagnetic wave shielding film of the present invention, for example, a plastic molded product is used as a base material, and after pretreatment is appropriately performed, the film is placed in a vacuum chamber. And a 1st layer film and a 2nd layer film are formed into a film by the vacuum construction method so that it may become a desired composition and film thickness on the surface of a plastic molded product.
[0023]
【Example】
[Example 1]
An ABS mobile phone housing was used as a plastic molded product. It was installed in an electron beam ion plating apparatus without cleaning. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 100 g of Cu was filled per hearth, and a film having a thickness of 1 μm was formed in 5 minutes. Thereafter, 35 g of Sn-5 mass% Cu alloy per hearth and 7 g of Ni were filled, and the plastic molded product was revolved to form a film of 0.6 μm in 2 minutes. Appearance observation, a tape peeling test, a corrosion test, and a film resistance measurement were performed on the plastic molded product thus formed. Here, the tape peeling test was performed before and after the 96 hr moisture resistance test. The corrosion test is a 24 hr salt spray test. In addition, the membrane resistance value was measured before and after the corrosion test for the inter-pin resistance of the cellular phone housing. Table 1 shows the material and film thickness of the first layer coating and the second layer coating, and the results obtained in this test.
[0024]
[Example 2]
As a plastic molded product, an ABS-PC mobile phone housing was used. Since this molded article had poor adhesion to Cu, an undercoat was applied. Thereafter, it was installed in an electron beam type ion plating apparatus. Next, after evacuating to a vacuum degree 5 × 10 ^-3 Pa, Ar gas was introduced until 3.2 × 10 ^-2 Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 100 g of Cu was filled per hearth, and a film having a thickness of 1 μm was formed in 5 minutes. Thereafter, 35 g of Sn-10 mass% Cu alloy per hearth and 10 g of Ni were filled, and the plastic molded product was revolved to form a film of 0.6 μm in 2 minutes. Appearance observation, tape peeling test, corrosion test, and film resistance measurement were performed on the plastic molded article thus formed in the same manner as in Example 1. The results were the same as in Example 1.
[0025]
[Reference Example 1]
An ABS mobile phone housing was used as a plastic molded product. It was installed in an electron beam ion plating apparatus without cleaning. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 100 g of Cu was filled per hearth, and a film having a thickness of 1 μm was formed in 5 minutes. Thereafter, 35 g of Sn-5 mass% Cu alloy per hearth and 15 g of Ni were filled, and the plastic molded product was revolved to form a film having a thickness of 0.6 μm as in Example 1. As a result, the deposition time of the second layer coating was 5 minutes, which was longer than that of Example 1. Further, when the hearth after evaporation was observed, Ni that could not be evaporated remained.
[0026]
[Reference Example 2]
An ABS mobile phone housing was used as a plastic molded product. It was installed in an electron beam ion plating apparatus without cleaning. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 180 g of Cu per 1 hearth was filled, and a 4 μm film was formed in 15 minutes. Thereafter, 35 g of Sn-5 mass% Cu alloy per hearth and 7 g of Ni were filled, and the plastic molded product was revolved to form a film of 0.6 μm. When the plastic molded product thus formed was observed, the substrate (ABS) and the first layer coating (Cu) were separated at the end of the molded product.
[0027]
[Example 3]
An ABS mobile phone housing was used as a plastic molded product. It was installed in an electron beam ion plating apparatus without cleaning. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 100 g of Cu was filled per hearth, and a film having a thickness of 1 μm was formed in 5 minutes. Thereafter, 35 g of Sn-5 mass% Cu alloy per hearth and 7 g of Cr were filled, and the plastic molded product was revolved to form a film of 0.6 μm in 2 minutes. Appearance observation, tape peeling test, corrosion test, and film resistance measurement were performed on the plastic molded article thus formed in the same manner as in Example 1. Table 1 shows the material and film thickness of the first layer coating and the second layer coating, and the results obtained in this test.
[0028]
[Example 4]
As a plastic molded product, an ABS-PC mobile phone housing was used. Since this molded article had poor adhesion to Cu, an undercoat was applied. Thereafter, it was installed in an electron beam type ion plating apparatus. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 100 g of Cu was filled per hearth, and a film having a thickness of 1 μm was formed in 5 minutes. Thereafter, 35 g of Sn-10 mass% Cu alloy per hearth and 10 g of Cr were filled, and the plastic molded product was revolved to form a film of 0.6 μm in 2 minutes. Appearance observation, tape peeling test, corrosion test, and film resistance measurement were performed on the plastic molded article thus formed in the same manner as in Example 1. The results were the same as in Example 3.
[0029]
[Reference Example 3]
An ABS mobile phone housing was used as a plastic molded product. It was installed in an electron beam ion plating apparatus without cleaning. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 100 g of Cu was filled per hearth, and a film having a thickness of 1 μm was formed in 5 minutes. Thereafter, 35 g of Sn-5 mass% Cu alloy per hearth and 15 g of Cr were filled, and the plastic molded product was revolved to form a film having a thickness of 0.6 μm as in Example 3. As a result, the deposition time of the second layer coating was 5 minutes, which was longer than that of Example 3. Further, when the hearth after evaporation was observed, Cr that could not be evaporated remained.
[0030]
[Reference Example 4]
An ABS mobile phone housing was used as a plastic molded product. It was installed in an electron beam ion plating apparatus without cleaning. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 180 g of Cu per 1 hearth was filled, and a 4 μm film was formed in 15 minutes. Thereafter, 35 g of Sn-5 mass% Cu alloy per hearth and 7 g of Cr were filled, and the plastic molded product was revolved to form a film of 0.6 μm in 2 minutes. When the plastic molded product thus formed was observed, the substrate (ABS) and the first layer coating (Cu) were separated at the end of the molded product.
[0031]
[Conventional example]
An ABS mobile phone housing was used as a plastic molded product. It was installed in an electron beam ion plating apparatus without cleaning. Next, after evacuating to a vacuum degree of 5 × 10 ⁻³ Pa, Ar gas was introduced to 3.2 × 10 ⁻² Pa. In this state, excitation discharge was generated at a high frequency output of 1.0 kw, and the discharge was performed for 5 minutes to clean the surface of the plastic molded product. Subsequently, 100 g of Cu was filled per hearth, and a film having a thickness of 1 μm was formed in 5 minutes. Thereafter, Ni was filled, and the plastic molded product was revolved and a film of 0.3 μm was formed in 15 minutes. Appearance observation, tape peeling test, corrosion test, and film resistance measurement were performed on the plastic molded article thus formed in the same manner as in Example 1. Table 1 shows the material and film thickness of the first layer coating and the second layer coating, and the results obtained in this test.
[0032]
[Table 1]

[0033]
Table 1 shows the following. That is, in Example 1 and Example 3, compared with the conventional example, the film formation time of the second layer film as the protective film is greatly shortened, and the productivity is improved. Moreover, corrosion resistance is also improved.
[0034]
【The invention's effect】
According to the present invention, it is possible to provide a low-cost electromagnetic shielding film which is formed with high productivity and is excellent in electromagnetic shielding characteristics, adhesion and corrosion resistance.

Claims

An electromagnetic wave shielding film comprising a first layer film and a second layer film formed on the surface of a plastic molded article, wherein the material of the first layer film is Cu and the material of the second layer film is a Sn—Cu—Ni alloy.

The second layer coating is 3 to 20 wt% relative to the content of the content of Cu is Sn, 3 to 30 mass relative to the sum of the content and the content of Cu in the content of Sn Ni The electromagnetic wave shielding film according to claim 1, which is%.

An electromagnetic wave shielding film comprising a first layer film and a second layer film formed on the surface of a plastic molded article, wherein the material of the first layer film is Cu and the material of the second layer film is a Sn—Cu—Cr alloy.

The second layer coating has a Cu content of 3 to 20 mass% with respect to the Sn content , and a Cr content of 3 to 30 mass with respect to the sum of the Sn content and the Cu content. The electromagnetic wave shielding film according to claim 3, which is%.

The electromagnetic wave shielding film according to claim 1, wherein the first layer film has a film thickness of 0.3 to 4 μm.

The electromagnetic wave shielding film according to claim 1, wherein the second layer film has a thickness of 0.1 to 3 μm.

The electromagnetic wave shielding film according to any one of claims 1 to 6, wherein the plastic molded article is made of ABS, PC, or ABS-PC.

The electromagnetic wave shielding film according to claim 1, which is formed by a vacuum method.