JP3735005B2

JP3735005B2 - Copper alloy having excellent punchability and method for producing the same

Info

Publication number: JP3735005B2
Application number: JP2000108580A
Authority: JP
Inventors: 崇夫平井; 好正大山; 隆行宇佐見
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 1999-10-15
Filing date: 2000-04-10
Publication date: 2006-01-11
Anticipated expiration: 2020-04-10
Also published as: JP2001181757A

Description

【０００１】
【発明の属する技術分野】
本発明は、打抜加工を含む工程により所望の形状に加工されるリードフレーム材、端子・コネクター材、スイッチ材などに適した銅合金とその製造方法に関する。
【０００２】
【従来の技術】
従来より、半導体のリードフレーム材や端子材には、鉄系材料の他、電気・熱伝導性に優れた銅系材料が多く用いられている。銅系材料は、高集積化や小型化が進み放熱性が重視されるようになった半導体機器部材にも用いられている。そして、前記銅系材料がリードフレームに使用される場合は、電気・熱伝導性の他に、貴金属（Ａｇ、Ｐｄなど）や半田のメッキ性および表面平滑性に優れることが要求される。
【０００３】
このような要求に応えるため様々なリードフレーム用銅合金が開発されたが、その多くは淘汰され現在では数種類が用いられているだけである。その中でＣｕ−Ｃｒ−Ｓｎ系合金は高導電性と高強度を兼備する合金として認知され、最も多く使用されている合金の一つである。
【０００４】
【発明が解決しようとする課題】
ところで、リードフレームの成形加工には、通常、打抜加工法またはエッチング加工法が適用されるが、生産性の面から打抜加工法が多用されている。しかし、前記従来のＣｕ−Ｃｒ−Ｓｎ系合金は打抜加工の際に、バリや加工粉が発生してリード間が短絡したり、リードフレームの寸法精度が低下したりする。またバリが発生すると金型のメンテナンスサイクルが短くなり製造コストが高くなる。これらの弊害は特に多ピンリードフレームにおいて大きい。
【０００５】
リードフレームを製造する側としては、大幅な成長を続ける半導体需要に対応するため、より安価なリ−ドフレ−ムをより早く提供する必要があり、そのために如何に打抜加工設備の稼働率を上げるか、如何に打抜不良を減らして製造歩留まりを高めるかが重要な課題になっている。特に需要の多いＣｕ−Ｃｒ−Ｓｎ系合金では打抜加工性の大幅な改善が強く望まれている。本発明の目的は、打抜加工性に優れた銅合金およびその製造方法を提供することにある。
【０００６】
【課題を解決するための手段】
請求項１記載の発明は、Ｃｒを０．２〜０．３５wt％、Ｓｎを０．１〜０．５wt％、Ｚｎを０．１〜０．５wt％、Ｓｉを０．００５〜０．１wt％含み、残部がＣｕおよび不可避的不純物からなる銅合金において、Ｃｕマトリックス中に、各々の最大径が０．１〜１０μｍのＣｒまたはＣｒ化合物の析出相Ａが１×１０^３〜３×１０^５個／ｍｍ^２の個数密度で存在し、且つ各々の最大径が０．００１〜０．０３０μｍのＣｒまたはＣｒ化合物の析出相Ｂが析出相Ａの個数密度の１０倍以上の個数密度で存在することを特徴とする打抜加工性に優れた銅合金である。
【０００７】
請求項２記載の発明は、Ｃｒを０．２〜０．３５wt％、Ｓｎを０．１〜０．５wt％、Ｚｎを０．１〜０．５wt％、Ｓｉを０．００５〜０．１wt％含み、さらにＰｂ０．００１〜０．０６wt％、Ｂｉ０．００１〜０．０６wt％、Ｃａ０．００５〜０．１wt％、Ｓｒ０．００５〜０．１wt％、Ｔｅ０．００５〜０．１wt％、Ｓｅ０．００５〜０．１wt％、希土類元素０．００５〜０．１wt％のうちの１種または２種以上を総量で０．００１〜０．１wt％含み、残部がＣｕおよび不可避的不純物からなる銅合金において、Ｃｕマトリックス中に、各々の最大径が０．１〜１０μｍのＣｒまたはＣｒ化合物の析出相Ａが１×１０^３〜３×１０^５個／ｍｍ^２の個数密度で存在し、且つ各々の最大径が０．００１〜０．０３０μｍのＣｒまたはＣｒ化合物の析出相Ｂが析出相Ａの個数密度の１０倍以上の個数密度で存在することを特徴とする打抜加工性に優れた銅合金である。
【０００８】
請求項３記載の発明は、少なくとも熱間加工および冷間加工を施す、打抜加工性に優れた銅合金の製造方法であって、前記熱間加工前に８８０℃以上９８０℃未満の温度で熱処理を施し、前記冷間加工前または後に３６０〜４７０℃の温度で時効処理を施すことを特徴とする請求項１または２記載の打抜加工性に優れた銅合金の製造方法である。
【０００９】
【発明の実施の形態】
本発明は、特にリードフレーム材に好適な銅合金であるが、打抜加工を含む工程で製造される部材全般、例えば自動車に使用される端子材、民生機器に使用されるコネクター材などにも適用可能である。
【００１０】
本発明の銅合金は、Ｃｕマトリックス中に、打抜加工性を改善するための各々の最大径が０．１〜１０μｍの粗大なＣｒまたはＣｒ化合物の析出相Ａと、強度を確保するための各々の最大径が０．００１〜０．０３０μｍ（１ｎｍ〜３０ｎｍ）の微細なＣｒまたはＣｒ化合物の析出相Ｂを共存させることを骨子として構成されている。
【００１１】
ここで、最大径とは、析出相が球状の場合はその径、楕円状の場合は長径、棒状の場合は最大長さである。本発明者らはこのＣｒを含む銅合金系について研究を行い、成分の子細な限定と製造条件の最適化により理想的なＣｒまたはＣｒ化合物の析出状態を達成できることを知見し、実用性に優れた銅合金を得たものである。本発明の銅合金は、粗大なＣｒまたはＣｒ化合物を析出させるために熱間加工前に８８０℃以上９８０℃未満で熱処理を施し、さらに微細なＣｒまたはＣｒ化合物を析出させるために３６０〜４７０℃での時効処理を施すことにより最適に製造される。
【００１２】
以下に本発明銅合金の合金成分の限定理由について説明する。従来、Ｃｕ中にＣｒを添加する場合は、Ｃｒの析出硬化のみを期待しており、Ｃｕマトリックス中に分散するＣｒまたはＣｒ化合物の析出相の各々の大きさは最大径が０．００１〜０．０３０μｍであり、最大径が０．１〜１０μｍの粗大な析出相は殆ど存在していなかった。本発明は、添加したＣｒは析出硬化のみならず、打抜加工性の改善効果も有するため、その成分範囲を子細に限定する必要があることを見出してなされたものである。
【００１３】
本発明において、Ｃｒ量が０．２wt％未満では、熱間加工前の熱処理を９８０℃近辺の高温で行っても、粗大な析出相Ａは殆ど析出せず打抜加工性は改善されない。逆にＣｒ量が０．３５wt％を超えると鋳造の凝固時にＣｒが晶出物として生成する。この晶出Ｃｒも打抜加工の際に破壊の起点になり得るため、打抜加工に有効と言えなくもないが、晶出物故に疎に分散し、その大きさも粗大に（１０μｍより大きく）なりがちである。即ち、０．３５wt％を超えてＣｒを添加しても、添加量に見合った効果が得られないばかりでなく、１０μｍを超える大きさのＣｒ晶出物は、工具の磨耗を早め金型の寿命を短くする点でも不適当である。以上の観点からＣｒの含有量は０．２〜０．３５wt％とした。
【００１４】
本発明は、前述のように、ＣｒまたはＣｒ化合物の粗大な析出相Ａと微細な析出相Ｂを共存させることを骨子としている。前記粗大な析出相Ａは破壊の起点となって打抜加工性を改善するが、その最大径が０．１μｍに満たない析出相は破壊の起点になり得ないため、本発明の目的とする打抜加工性を改善することができない。逆に最大径が１０μｍを超える析出相は、打抜用金型の寿命を縮めるため好ましくない。従って各々の最大径が０．１〜１０μｍの析出相Ａが適量分散している状態が理想的である。
【００１５】
前記粗大な析出相Ａの個数密度が１×１０^３個／ｍｍ^２未満では、前記打抜加工性が改善されず、３×１０^５個／ｍｍ^２を超えると析出相Ａが増加した分、析出相Ｂが減少して強度特性が低下する。従って、析出相Ａの個数密度は１×１０^３〜３×１０^５個／ｍｍ^２に規定する。一方、ナノメートルレベルで析出する微細な析出相Ｂは強度特性を改善する。その個数密度は、析出相Ａの個数密度の少なくとも１０倍以上でないと必要な強度特性が得られない。逆に、微細な析出相Ｂが多くなると、打抜加工性を改善する粗大な析出相Ａの個数密度が低下し、充分な打抜加工性が得られなくなる。本発明は、Ｃｒの含有量のみならず、ＣｒまたはＣｒ化合物の析出相Ａと析出相Ｂのそれぞれの大きさと個数密度を限定することにより、打抜加工性を改善した銅合金である。
【００１６】
Ｓｎは材料の強度特性を高める効果を有する。その含有量が０．１wt％未満ではその効果が充分に得られず、０．５wt％を超えると導電率が大幅に低下する。従ってＳｎの含有量は０．１〜０．５wt％とする。
【００１７】
ＺｎはＳｎメッキやハンダメッキの耐熱剥離性、耐マイグレーション性を改善する効果を有する。特にリードフレームや端子として使用する場合は、実装後の半田付部の経時劣化が重視されるため、Ｚｎの添加は不可欠である。その含有量が０．１wt％未満では充分な効果が得られず、０．５wt％を超えて含有させてもその量に見合った効果が得られないばかりか、導電率が低下する。従ってＺｎの含有量は０．１〜０．５wt％とする。
【００１８】
Ｐｂ、Ｂｉ、Ｃａ、Ｓｒ、Ｔｅ、Ｓｅ、希土類元素も打抜加工性を改善する添加元素である。これら元素は、Ｃｕマトリックス中への固溶量が小さく、Ｃｕマトリックス中に分散し、ＣｒまたはＣｒ化合物と同じように破壊の起点になって打抜加工性を改善する。しかしながら、これら元素は鋳造性や熱間加工性などの製造性を損なう元素であり、その添加量は厳密に管理する必要がある。Ｐｂ、ＢｉはＣｕマトリックス中に殆ど固溶せず、従って打ち抜き加工性の改善効果は大きい。Ｐｂ、Ｂｉはそれぞれ０．００１wt％以上の添加量から打ち抜き加工性の改善効果が認められるが、反面、製造性への悪影響も大きく、０．０６wt％を超えて添加すると、正常に製造することができなくなる。Ｃａ、Ｓｒ、Ｔｅ、Ｓｅ、希土類元素は、それぞれ０．００５wt％以上の添加量から打ち抜き加工性の改善効果が現れ、０．１wt％を超えて添加すると、鋳造加工性や熱間加工性が損なわれる。依って、これら元素を各々１種添加する場合の添加量は上述の通りとし、２種以上添加する場合の総量は０．００１〜０．１wt％とした。
【００１９】
次に銅合金に含まれるＳｉについて説明する。Ｓｉは、その微量添加によりＣｒ−Ｓｉ化合物を形成してＣｒを析出し易くする。その結果析出相Ａの個数密度が増加し、打抜加工性が大幅に改善される。その含有量が０．００５wt％未満ではＣｒ−Ｓｉ化合物が殆ど形成されず、０．１wt％を超えると析出相Ａが増加しすぎ、その分、析出相Ｂが減少して強度特性が低下する。またＳｉの固溶量が増えて導電率が低下する。Ｓｉは、Ｃｒ3 Ｓｉとして存在するように、原子比でＣｒ：Ｓｉ＝３：１になるように添加するのが好ましい。
【００２０】
次に、数有る元素の中から、特にＳｉを選定した理由について述べる。先ず、本願発明の目的からして、Ｃｒと化合物を作ることが必要条件であり、Ｃｒと化合物を作る元素としては、Ｓｉの他に、Ｐ、Ｓ、Ｏ、Ｇｅ、Ｐt が挙げられる。このうちＰ、Ｓ、Ｏは非金属元素のためＣｒとの結合力が非常に強く、溶解鋳造中に化合物が生成してしまうため、その分散状態は実質上制御不可能である。またＧｅおよびＰt は溶解し難いうえ、高価なため実用的でない。このようなことから、あらゆる面で最も効果的なＳｉを選定した。
【００２１】
上述した本発明の構成において、所要の特性を好適に発現するためには、その製造方法が重要である。本発明では、打抜加工性を改善する粗大な析出相Ａの個数密度は、熱間加工前の熱処理温度を８８０℃以上９８０℃未満に限定することにより、１×１０^３〜３×１０^５個／ｍｍ^２に制御している。従来、Ｃｕ−Ｃｒ系合金の場合の前記熱間加工前の熱処理温度は９８０℃を超える高温であった。これはＣｒを完全に固溶させることを目的としたためであり、Ｃｒが析出する９８０℃未満の温度で熱処理することはなかった。
【００２２】
前記熱処理温度が９８０℃以上では、最大径０．１〜１０μｍの粗大なＣｒまたはＣｒ化合物の析出相Ａの個数密度が低くなり打抜加工性が改善されない。逆に前記熱処理温度が８８０℃未満では、析出相Ａの個数密度が高くなりすき、その後の工程で析出する０．００１〜０．０３０μｍの析出相Ｂの個数密度が低くなり所要の強度特性が得られなくなる。このような観点から、熱間加工前の熱処理温度は８８０℃以上９８０℃未満とする。特には９１０〜９４０℃が好ましい。
【００２３】
本発明において、強度特性の改善に寄与する微細な析出相Ｂの個数密度は、時効処理温度を３６０〜４７０℃に限定することにより、析出相Ａの個数密度の１０倍以上に制御する。前記時効処理温度が３６０℃未満では析出相Ｂが充分に析出せず、４７０℃を超えると析出相Ｂが粗大化して、いずれの場合も所要の強度特性が得られない。
【００２４】
この時効処理は、熱間加工し、次いで冷間加工したのち施すが、冷間加工中に施しても構わない。この場合は冷間加工後に比較的低温での焼鈍を施して加工歪みを減じておくことが推奨される。前記低温焼鈍をバッチ式焼鈍により施す場合は２００〜４００℃の温度で０．５〜５ｈｒ、走間焼鈍で施す場合は６００〜８００℃の温度で５〜６０秒施すことが好ましい。必要に応じて最終熱処理（時効処理または低温焼鈍）の前または後にテンションレベラーやローラーレベラーなどで矯正加工を行っても差し支えない。
【００２５】
【実施例】
以下に本発明を実施例により詳細に説明する。
（実施例１）
表１に示す本発明規定値内組成の合金を高周波溶解炉にて溶解し、これを厚さ３０ｍｍ、幅１００ｍｍ、長さ１５０ｍｍの鋳塊に鋳造し、この鋳塊を９３０℃で２時間熱処理後、厚さ１１ｍｍまで熱間圧延し、熱間圧延後、直ちに水中に浸漬して速やかに冷却した。次に両面を各１ｍｍづつ面削したのち厚さ０．２５ｍｍに冷間圧延し、この冷間圧延材を不活性ガス雰囲気中で４２５℃で２ｈｒ時効処理した。次いで０．１５ｍｍまで仕上冷間圧延したのち、３００℃で２ｈｒ低温焼鈍処理を施し銅合金板を製造した。
【００２６】
（比較例１）
表１に示す本発明規定値外組成の合金を用いた他は、実施例１と同じ方法により銅合金板を製造した。
【００２７】
実施例１および比較例１で製造した各々の銅合金板から試験片を切り出して、析出相Ａ、Ｂの各個数密度、引張強さ、伸び、導電率、打抜加工性、半田めっき耐熱剥離性を調べた。結果を表２に示す。
【００２８】
前記析出相Ａの個数密度は、試験片を酸性水溶液（６体積％Ｈ_２ＳＯ_４＋７体積％Ｈ_２Ｏ_２）中に３０秒間浸漬してエッチングし、その表面を走査型電子顕微鏡（５００倍）により写真撮影して測定した。析出相Ｂの個数密度は透過型電子顕微鏡を用いて測定した。加速電圧は３００ｋＶに設定した。透過型電子顕微鏡では、試料の厚さにより析出相Ｂの個数が異なって見えることがあるため、各試料毎に厚さの異なる３箇所で測定し、３箇所とも、析出相Ｂの個数密度が析出相Ａの個数密度の１０倍以上の場合のみを「析出相Ｂの個数密度が析出相Ａの個数密度の１０倍以上」とした。それ以外は１０倍未満とした。
【００２９】
引張強さ（ＴＳ）および伸び（Ｅｌ）はＪＩＳＺ２２４１に準じて、また熱・電気の伝導性を示す導電率はＪＩＳＨ００５に準じてそれぞれ測定した。打抜加工性は、金型で角孔（１ｍｍ×５ｍｍ）を多数打抜き、ＦＡＲ（ＦｒａｃｔｕｒｅＡｒｅａＲａｔｉｏ：脆性破断部厚さ比）、バリの高さ、金型磨耗量について調べた。前記金型のダイおよびパンチは超硬合金製で、両者のクリアランスは９μｍ（対板厚比６％）とした。前記ＦＡＲは角孔加工面を観察して脆性破断部の厚さｔを測定し、これを打抜加工前の試験片の厚さＴで除した値（ｔ／Ｔ）を各２０箇所につき求め、その平均値（百分率）で評価した。ＦＡＲは大きいほど打抜加工性に優れる。バリの高さは、角孔縁部のバリの高さを接触式形状測定器で各２０箇所測定し、その平均値で示した。金型摩耗量は触針式輪郭形状測定器を使用してパンチの先端面の初期断面積Ｓと１００万回打抜加工後の断面積ｓの差（Ｓ−ｓ）を求め評価した。半田めっき耐熱剥離性は、試験片にロジン系フラックスを塗布し、２３０℃の共晶半田（Ｐｂ−６３wt％Ｓｎ合金）浴中に５秒間浸漬して半田を付着させ、これを１５０℃で１０００時間大気加熱したのち、１８０度に密着曲げし、次いで曲げ戻し、曲げ戻し部分の半田の剥離有無を目視観察して評価した。
【００３０】
【表１】

【００３１】
【表２】

【００３２】
表２より明らかなように、本発明例のＮｏ．１〜７はいずれも優れた打抜加工性を示し、また半田めっき耐熱剥離性も良好に維持された。これに対し、Ｃｒ量が少ない比較例のＮｏ．８は析出相Ａが少ないため打抜加工性が劣った。Ｓｎ量の多いＮｏ．９は導電率が低く、Ｃｒ量の多いＮｏ．１０はパンチが著しく磨耗した。Ｓｉ量の多いＮｏ．１１は析出相Ａの個数密度が高くなり、その分、析出相Ｂの個数密度が低下して強度特性が劣り、導電率も低下した。Ｔｅ、Ｐｂの多いＮｏ．１２およびＢｉの多いＮｏ．１３はいずれも熱間圧延中に割れが生じ正常に製造できなかった。
【００３３】
（実施例２）
表１に示した本発明規定値内組成のＮｏ．２の合金を用い、熱間圧延前の熱処理および冷間圧延後の時効処理を請求項３記載の本発明規定値内の条件で種々に変化させた他は、実施例１と同じ方法により銅合金板を製造した。
【００３４】
（比較例２）
熱間圧延前の熱処理または冷間圧延後の時効処理を請求項３記載の本発明規定値外の条件とした他は、実施例２と同じ方法により銅合金板を製造した。
【００３５】
実施例２および比較例２で製造した各々の銅合金板から試験片を切り出し、実施例１と同じ方法により種々特性を調査した。製造条件を表３に、調査結果を表３、４に示す。
【００３６】
【表３】

【００３７】
【表４】

【００３８】
表３、４より明らかなように、本発明例のＮｏ．２１〜２８はいずれも優れた打抜加工性を示し、また半田めっき耐熱剥離性も良好に維持された。これに対し、比較例のＮｏ．２９は熱間圧延前の熱処理温度が高いため析出相Ａが殆ど存在せず、打抜加工性が劣った。比較例のＮｏ．３０は熱間圧延前の熱処理温度が低いため析出相Ａの個数密度が高くなりすぎ、その分、析出相Ｂの個数密度が低くなり強度特性が低下した。粗大な析出相Ａが多い割りには打抜加工性が劣った。これは打抜加工性の改善にはある程度の強度が必要なためである。比較例のＮｏ．３１は時効処理温度が低いため、固溶元素が多くなり導電率が低下した。比較例のＮｏ．３２は時効処理温度が６３０℃と高かったため析出相Ｂが殆ど確認されず、そのため強度が低く、打抜加工性にも劣った。また固溶元素が多いため導電率も低めであった。この試験片では微細な析出相Ｂに代わって、やや成長した最大径が０．０４〜０．０７μｍの析出相が多数観察された。
【００３９】
【発明の効果】
以上に述べたように、本発明の銅合金は、Ｃｕ−Ｃｒ系合金のＣｕマトリックス中に、各々の最大径が０．１〜１０μｍのＣｒまたはＣｒ化合物の析出相Ａを１×１０^３〜３×１０^５個／ｍｍ^２の個数密度で存在させて打抜加工性を改善し、また各々の最大径が０．００１〜０．０３０μｍのＣｒまたはＣｒ化合物の析出相Ｂを析出相Ａの個数密度の１０倍以上の個数密度で存在させて強度特性を改善したもので、微細に打抜加工される多ピン・狭ピッチのリードフレームを始め、プレスにより打抜加工される端子・コネクター、スイッチ、リレー材など導電材料全般に適用して生産性の向上が図れる。また本発明の銅合金は熱間加工前に８８０℃以上９８０℃未満の温度で熱処理し、冷間加工前または後に３６０〜４７０℃の温度で時効処理することにより容易に製造できる。依って、工業上顕著な効果を奏する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a copper alloy suitable for a lead frame material, a terminal / connector material, a switch material and the like, which are processed into a desired shape by a process including punching, and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, in addition to iron-based materials, copper-based materials having excellent electrical and thermal conductivity have been used for semiconductor lead frame materials and terminal materials. Copper-based materials are also used in semiconductor device members that have become highly integrated and miniaturized, and heat dissipation has become important. When the copper-based material is used for a lead frame, it is required to have excellent plating properties and surface smoothness of noble metals (Ag, Pd, etc.) and solder in addition to electrical / thermal conductivity.
[0003]
A variety of lead frame copper alloys have been developed to meet these requirements, many of which have been discouraged and currently only a few are used. Among them, a Cu—Cr—Sn alloy is recognized as an alloy having both high conductivity and high strength, and is one of the most frequently used alloys.
[0004]
[Problems to be solved by the invention]
Incidentally, a punching method or an etching method is usually applied to the forming process of the lead frame, but the punching method is frequently used from the viewpoint of productivity. However, when the conventional Cu—Cr—Sn alloy is punched, burrs and processing powder are generated, and the leads are short-circuited or the dimensional accuracy of the lead frame is reduced. In addition, when burrs occur, the mold maintenance cycle is shortened and the manufacturing cost is increased. These adverse effects are particularly significant in multi-pin lead frames.
[0005]
Lead frame manufacturers need to provide cheaper lead frames more quickly in order to meet the growing demand for semiconductors. An important issue is how to increase the manufacturing yield by reducing punching defects. In particular, a drastic improvement in punching workability is strongly desired for Cu-Cr-Sn alloys, which are in great demand. An object of the present invention is to provide a copper alloy having excellent punchability and a method for producing the same.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, Cr is 0.2 to 0.35 wt%, Sn is 0.1 to 0.5 wt%, Zn is 0.1 to 0.5 wt%, and Si is 0.005 to 0.1 wt%. %, With the balance being Cu and inevitable impurities, in the Cu matrix, each of the precipitated phases A of Cr or Cr compound having a maximum diameter of 0.1 to 10 μm is 1 × 10 ^{3 to} 3 × 10 ^5. present in a number density of pieces / mm ^2, and the maximum diameter of each is present at 10 or more times the number density of the number density of the precipitate phase B is precipitation phase a of Cr or a Cr compound of 0.001~0.030μm It is a copper alloy excellent in punching processability characterized by this.
[000 7 ]
According to the second aspect of the present invention, Cr is 0.2 to 0.35 wt%, Sn is 0.1 to 0.5 wt%, Zn is 0.1 to 0.5 wt%, and Si is 0.005 to 0.1 wt%. Pb 0.001 to 0.06 wt%, Bi 0.001 to 0.06 wt%, Ca 0.005 to 0.1 wt%, Sr 0.005 to 0.1 wt%, Te 0.005 to 0.1 wt%, Se0 .005 to 0.1 wt%, rare earth element 0.005 to 0.1 wt% of one or two or more in a total amount of 0.001 to 0.1 wt% with the balance being Cu and inevitable impurities In the alloy, the precipitation phase A of Cr or Cr compound having a maximum diameter of 0.1 to 10 μm is present in the Cu matrix at a number density of 1 × 10 ^{3 to} 3 × 10 ⁵ pieces / mm ² , and Precipitation phase of Cr or Cr compound having a maximum diameter of 0.001 to 0.030 μm There is an excellent copper alloy stamping properties, characterized in that present at 10 or more times the number density of the number density of the precipitation phase A.
[000 8 ]
The invention according to claim 3 is a method for producing a copper alloy having excellent punching workability, at least performing hot working and cold working, at a temperature of 880 ° C. or more and less than 980 ° C. before the hot working. heat treatment, a manufacturing method according to claim 1 or 2 stamping with excellent copper alloy, wherein the performing aging treatment at a temperature of three hundred and sixty to four hundred seventy ° C. in the cold working before or after.
[00 09 ]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a copper alloy particularly suitable for a lead frame material. However, the present invention is applicable to all members manufactured in a process including punching, for example, a terminal material used for automobiles and a connector material used for consumer equipment. Applicable.
[001 0 ]
The copper alloy of the present invention has a coarse precipitate phase A of coarse Cr or Cr compound having a maximum diameter of 0.1 to 10 μm for improving the punching workability in the Cu matrix, and for ensuring strength. The essence is that fine Cr or Cr compound precipitation phases B each having a maximum diameter of 0.001 to 0.030 μm (1 nm to 30 nm) coexist.
[0011]
Here, the maximum diameter is the diameter when the precipitated phase is spherical, the long diameter when it is elliptical, and the maximum length when it is rod-shaped. The present inventors have studied the copper alloy system containing Cr, and found that it is possible to achieve an ideal precipitation state of Cr or Cr compound by finely limiting the components and optimizing the production conditions. A copper alloy is obtained. The copper alloy of the present invention is subjected to heat treatment at 880 ° C. or more and less than 980 ° C. before hot working in order to precipitate coarse Cr or Cr compound, and further 360 to 470 ° C. in order to precipitate fine Cr or Cr compound. It is optimally manufactured by aging treatment at
[001 2 ]
The reasons for limiting the alloy components of the copper alloy of the present invention will be described below. Conventionally, when Cr is added to Cu, only the precipitation hardening of Cr is expected, and the maximum diameter of each of the precipitated phases of Cr or Cr compound dispersed in the Cu matrix is 0.001 to 0. There was almost no coarse precipitate phase having a maximum diameter of 0.1 to 10 μm. The present invention has been made by finding that the added Cr has an effect of improving not only the precipitation hardening but also the punching workability, so that it is necessary to limit the component range in detail.
[0013]
In the present invention, when the Cr content is less than 0.2 wt%, even if the heat treatment before hot working is performed at a high temperature around 980 ° C., the coarse precipitate phase A hardly precipitates and the punching workability is not improved. Conversely, if the Cr content exceeds 0.35 wt%, Cr is produced as a crystallized product during casting solidification. Since this crystallized Cr can also be a starting point of fracture during punching, it cannot be said that it is effective for punching, but it is sparsely dispersed because of the crystallized material, and its size is coarse (greater than 10 μm). It tends to be. That is, even if adding Cr exceeding 0.35 wt%, not only an effect commensurate with the added amount is not obtained, but the Cr crystallized material having a size exceeding 10 μm accelerates the wear of the tool. It is also unsuitable for shortening the service life. From the above viewpoint, the Cr content is set to 0.2 to 0.35 wt%.
[0014]
As described above, the present invention is based on the coexistence of coarse precipitate phase A and fine precipitate phase B of Cr or Cr compound. The coarse precipitated phase A serves as a starting point for fracture and improves the punching workability. However, a precipitated phase whose maximum diameter is less than 0.1 μm cannot serve as a starting point for fracture, and is therefore an object of the present invention. The punching processability cannot be improved. Conversely, a precipitated phase having a maximum diameter exceeding 10 μm is not preferable because it shortens the life of the punching die. Accordingly, it is ideal that the precipitated phase A having a maximum diameter of 0.1 to 10 μm is dispersed in an appropriate amount.
[0015]
If the number density of the coarse precipitate phase A is less than 1 × 10 ³ pieces / mm ² , the punching processability is not improved, and if it exceeds 3 × 10 ⁵ pieces / mm ² , the amount of the precipitate phase A increases. The precipitated phase B is reduced and the strength characteristics are lowered. Therefore, the number density of the precipitated phase A is defined as 1 × 10 ^{3 to} 3 × 10 ⁵ pieces / mm ² . On the other hand, the fine precipitate phase B precipitated at the nanometer level improves the strength characteristics. If the number density is not at least 10 times the number density of the precipitated phase A, the required strength characteristics cannot be obtained. On the contrary, when the number of fine precipitated phases B increases, the number density of coarse precipitated phases A that improve the punching processability is lowered, and sufficient punching processability cannot be obtained. The present invention is a copper alloy with improved punchability by limiting not only the Cr content but also the size and number density of each of the precipitated phase A and the precipitated phase B of Cr or Cr compound.
[0016]
Sn has the effect of increasing the strength properties of the material. If the content is less than 0.1 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.5 wt%, the conductivity is greatly lowered. Therefore, the Sn content is 0.1 to 0.5 wt%.
[0017]
Zn has an effect of improving the heat-resistant peelability and migration resistance of Sn plating or solder plating. In particular, when used as a lead frame or a terminal, addition of Zn is indispensable because deterioration with time of the soldered portion after mounting is emphasized. If the content is less than 0.1 wt%, a sufficient effect cannot be obtained. Even if the content exceeds 0.5 wt%, not only an effect commensurate with the amount cannot be obtained, but also the conductivity decreases. Accordingly, the Zn content is 0.1 to 0.5 wt%.
[0018]
Pb, Bi, Ca, Sr, Te, Se, and rare earth elements are also additive elements that improve the punching processability. These elements have a small amount of solid solution in the Cu matrix and are dispersed in the Cu matrix, and become the starting point of fracture in the same manner as Cr or Cr compounds, thereby improving the punching workability. However, these elements are elements that impair the manufacturability such as castability and hot workability, and the amount of addition must be strictly controlled. Pb and Bi are hardly dissolved in the Cu matrix, so that the punching workability is greatly improved. Pb and Bi have an effect of improving the punching workability from the added amount of 0.001 wt% or more, respectively, but on the other hand, the adverse effect on the manufacturability is great, and if added over 0.06 wt%, it should be manufactured normally. Can not be. Ca, Sr, Te, Se, and rare earth elements each have an effect of improving the punching workability when added in an amount of 0.005 wt% or more. When added in excess of 0.1 wt%, casting workability and hot workability are improved. Damaged. Therefore, the addition amount when one of these elements is added is as described above, and the total amount when adding two or more of these elements is 0.001 to 0.1 wt%.
[0019]
For Si contained in the following in the copper alloy will be described. Si makes it easy to precipitate Cr by forming a Cr-Si compound by adding a small amount thereof. As a result, the number density of the precipitated phase A increases, and the punching processability is greatly improved. When the content is less than 0.005 wt%, almost no Cr—Si compound is formed. When the content exceeds 0.1 wt%, the precipitated phase A increases excessively, and the precipitated phase B decreases correspondingly and the strength characteristics deteriorate. . Moreover, the solid solution amount of Si increases and the conductivity decreases. Si is preferably added so that the atomic ratio is Cr: Si = 3: 1 so that it exists as Cr3 Si.
[0020]
Next, the reason why Si was selected from among a number of elements will be described. First, for the purpose of the present invention, it is a necessary condition to make a compound with Cr, and as elements for making a compound with Cr, there are P, S, O, Ge, and Pt in addition to Si. Among these, P, S, and O are non-metallic elements and therefore have a very strong bonding force with Cr, and a compound is generated during melt casting, so that the dispersion state thereof is substantially uncontrollable. Ge and Pt are not practical because they are difficult to dissolve and are expensive. For these reasons, Si that was most effective in all aspects was selected.
[0021]
In the above-described configuration of the present invention, the manufacturing method is important in order to properly develop the required characteristics. In the present invention, the number density of the coarse precipitate phase A that improves the punching processability is limited to 1 × 10 ^{3 to} 3 × 10 ⁵ by limiting the heat treatment temperature before hot working to 880 ° C. or more and less than 980 ° C. The number is controlled to pieces / mm ² . Conventionally, the heat treatment temperature before the hot working in the case of a Cu—Cr alloy was a high temperature exceeding 980 ° C. This was for the purpose of completely dissolving Cr, and no heat treatment was performed at a temperature lower than 980 ° C. at which Cr was precipitated.
[0022]
When the heat treatment temperature is 980 ° C. or higher, the number density of coarse Cr or Cr compound precipitation phase A having a maximum diameter of 0.1 to 10 μm is lowered, and the punching processability is not improved. On the contrary, if the heat treatment temperature is less than 880 ° C., the number density of the precipitated phase A tends to increase, and the number density of the precipitated phase B of 0.001 to 0.030 μm that precipitates in the subsequent process decreases, resulting in the required strength characteristics. It can no longer be obtained. From such a viewpoint, the heat treatment temperature before hot working is set to 880 ° C. or more and less than 980 ° C. 910-940 degreeC is especially preferable.
[0023]
In the present invention, the number density of the fine precipitated phase B contributing to the improvement of the strength characteristics is controlled to 10 times or more of the number density of the precipitated phase A by limiting the aging treatment temperature to 360 to 470 ° C. If the aging treatment temperature is less than 360 ° C., the precipitated phase B does not sufficiently precipitate, and if it exceeds 470 ° C., the precipitated phase B becomes coarse, and in either case, the required strength characteristics cannot be obtained.
[0024]
The aging treatment is performed after hot working and then cold working, but may be performed during the cold working. In this case, it is recommended that annealing is performed at a relatively low temperature after cold working to reduce the working distortion. When the low temperature annealing is performed by batch annealing, it is preferably performed at a temperature of 200 to 400 ° C. for 0.5 to 5 hours, and when it is performed by running annealing, it is preferably performed at a temperature of 600 to 800 ° C. for 5 to 60 seconds. If necessary, straightening may be performed with a tension leveler or roller leveler before or after the final heat treatment (aging treatment or low-temperature annealing).
[0025]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
An alloy having a composition within the specified values of the present invention shown in Table 1 is melted in a high-frequency melting furnace and cast into an ingot having a thickness of 30 mm, a width of 100 mm, and a length of 150 mm. Then, it hot-rolled to thickness 11mm, and after hot rolling, it immediately immersed in water and cooled rapidly. Next, both sides were chamfered by 1 mm and then cold-rolled to a thickness of 0.25 mm, and the cold-rolled material was aged at 425 ° C. for 2 hours in an inert gas atmosphere. Next, after finish cold rolling to 0.15 mm, a low temperature annealing treatment was performed at 300 ° C. for 2 hours to produce a copper alloy sheet.
[0026]
(Comparative Example 1)
A copper alloy plate was produced by the same method as in Example 1 except that the alloy having a composition outside the specified value of the present invention shown in Table 1 was used.
[0027]
A test piece was cut out from each copper alloy plate manufactured in Example 1 and Comparative Example 1, and the number density, tensile strength, elongation, conductivity, punching workability, solder plating heat-resistant peeling of each of the precipitated phases A and B I examined the sex. The results are shown in Table 2.
[0028]
The number density of the precipitated phase A is determined by immersing the test piece in an acidic aqueous solution (6 vol% H ₂ SO ₄ +7 vol% H ₂ O ₂ ) for 30 seconds and etching the surface, and scanning the surface with a scanning electron microscope (500 times). ) Was taken and measured. The number density of the precipitated phase B was measured using a transmission electron microscope. The acceleration voltage was set to 300 kV. In the transmission electron microscope, the number of precipitated phases B may appear different depending on the thickness of the sample. Therefore, the number density of the precipitated phases B is measured at three locations with different thicknesses for each sample. Only when the number density of the precipitated phase A was 10 times or more, the number density of the precipitated phase B was 10 times or more of the number density of the precipitated phase A. Otherwise, it was less than 10 times.
[0029]
Tensile strength (TS) and elongation (El) were measured according to JISZ2241, and conductivity indicating thermal and electrical conductivity was measured according to JISH005. For punching workability, a number of square holes (1 mm × 5 mm) were punched with a mold, and FAR (Fracture Area Ratio: brittle fracture portion thickness ratio), burr height, and die wear amount were examined. The die and punch of the mold were made of cemented carbide, and the clearance between them was 9 μm (vs. thickness ratio 6%). The FAR measures the thickness t of the brittle fracture portion by observing the square hole processed surface, and obtains a value (t / T) obtained by dividing this by the thickness T of the test piece before punching processing for each of 20 locations. The average value (percentage) was evaluated. The larger the FAR, the better the punching processability. The height of burrs was measured by measuring the height of burrs at the edge of the square hole with 20 contact-type shape measuring instruments, and showing the average value. The die wear amount was evaluated by determining the difference (S−s) between the initial cross-sectional area S of the punch tip surface and the cross-sectional area s after one million punching operations using a stylus type contour shape measuring instrument. For solder plating heat-resistant peelability, a rosin-based flux is applied to a test piece and immersed in a 230 ° C. eutectic solder (Pb-63 wt% Sn alloy) bath for 5 seconds to attach the solder. After atmospheric heating for an hour, the film was tightly bent at 180 degrees, then bent back, and evaluated by visually observing whether or not the solder was peeled off at the bent back portion.
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
As is apparent from Table 2, No. of the present invention example. All of Nos. 1 to 7 showed excellent punching workability, and the solder plating heat-resistant peelability was maintained well. On the other hand, the comparative example No. No. 8 had poor precipitation workability because of a small amount of precipitated phase A. No. with a large amount of Sn. 9 conductivity rather low, C r large amount of No. In No. 10, the punch was significantly worn. No. with a large amount of Si. In No. 11, the number density of the precipitated phase A was increased, and the number density of the precipitated phase B was lowered accordingly, the strength characteristics were inferior, and the conductivity was also lowered. No. with a lot of Te and Pb. No. 12 and Bi rich No. No. 13 was cracked during hot rolling and could not be produced normally.
[0033]
(Example 2)
No. of the composition within the specified value of the present invention shown in Table 1. In the same manner as in Example 1, except that the heat treatment before hot rolling and the aging treatment after cold rolling were variously changed under the conditions specified in the present invention according to claim 3, An alloy plate was produced.
[0034]
(Comparative Example 2)
Except that the present invention defined value outside the conditions according to claim 3, wherein the aging treatment after the heat treatment or cold rolling before hot rolling, to produce a copper alloy sheet by the same method as in Example 2.
[003 5 ]
Test pieces were cut out from the respective copper alloy plates produced in Example 2 and Comparative Example 2, and various characteristics were investigated by the same method as in Example 1. The production conditions are shown in Table 3, and the survey results are shown in Tables 3 and 4.
[003 6 ]
[Table 3]

[003 7 ]
[Table 4]

[003 8 ]
As is apparent from Tables 3 and 4, No. of the present invention example. All of Nos. 21 to 28 showed excellent punching workability, and the solder plating heat-resistant peelability was also kept good. In contrast, No. of the comparative example. 2 9 is absent most precipitation phase A for the heat treatment temperature before hot rolling is high and poor stamping properties. Comparative Example No. No. 30 had a low heat treatment temperature before hot rolling, so that the number density of the precipitated phase A was too high, and accordingly, the number density of the precipitated phase B was lowered and the strength characteristics were lowered. Although there were many coarse precipitate phases A, the punching workability was inferior. This is because a certain degree of strength is required to improve the punching workability. Comparative Example No. No. 31 has a low aging treatment temperature, so that the amount of solid solution elements increased and the conductivity decreased. Comparative Example No. In No. 32, the aging treatment temperature was as high as 630 ° C., so almost no precipitated phase B was confirmed, so that the strength was low and the punching workability was poor. Moreover, since there are many solid solution elements, electrical conductivity was also low. In this test piece, in place of the fine precipitate phase B, a number of precipitated phases having a slightly grown maximum diameter of 0.04 to 0.07 μm were observed.
[00 39 ]
【The invention's effect】
As described above, the copper alloy of the present invention, Cu-Cr system during the Cu matrix of the alloy, 1 × ¹⁰ 3 to precipitation phase A of each maximum diameter of 0.1~10μm of Cr or a Cr compound ~ It is made to exist at a number density of 3 × 10 ⁵ pieces / mm ² to improve the punching workability, and the precipitation phase B of Cr or Cr compound having a maximum diameter of 0.001 to 0.030 μm is added to the precipitation phase A. The strength characteristics are improved by being present at a number density more than 10 times the number density, including multi-pin, narrow pitch lead frames that are finely punched, terminals and connectors that are punched by a press, Productivity can be improved by applying to all conductive materials such as switches and relay materials. The copper alloy of the present invention can be easily manufactured by heat treatment at a temperature of 880 ° C. or more and less than 980 ° C. before hot working and aging treatment at a temperature of 360 to 470 ° C. before or after cold working. Therefore, there is an industrially significant effect.

Claims

Contains 0.2 to 0.35 wt% of Cr, 0.1 to 0.5 wt% of Sn, 0.1 to 0.5 wt% of Zn, 0.005 to 0.1 wt% of Si, the balance being Cu and inevitable In a copper alloy composed of mechanical impurities, the precipitation phase A of Cr or Cr compound having a maximum diameter of 0.1 to 10 μm in each Cu matrix has a number density of 1 × 10 ^{3 to} 3 × 10 ⁵ pieces / mm ^2. Punching process, characterized in that a Cr or Cr compound precipitation phase B having a maximum diameter of 0.001 to 0.030 μm exists at a number density of 10 times or more of the number density of the precipitation phase A. Excellent copper alloy.

0.2 to 0.35 wt% of Cr, 0.1 to 0.5 wt% of Sn, 0.1 to 0.5 wt% of Zn, 0.005 to 0.1 wt% of Si, and further Pb0.001 0.06 wt%, Bi 0.001 to 0.06 wt%, Ca 0.005 to 0.1 wt%, Sr 0.005 to 0.1 wt%, Te 0.005 to 0.1 wt%, Se 0.005 to 0.1 wt%, In a copper alloy containing one or more of 0.005 to 0.1 wt% of rare earth elements in a total amount of 0.001 to 0.1 wt%, with the balance being Cu and inevitable impurities, in the Cu matrix, Precipitation phase A of Cr or Cr compound having a maximum diameter of 0.1 to 10 μm exists at a number density of 1 × 10 ^{3 to} 3 × 10 ⁵ pieces / mm ² , and each maximum diameter is 0.001 to 0.001. Precipitation phase B of 0.030 μm Cr or Cr compound is number density of precipitation phase A Stamping excellent in copper alloy being present in more than 10 times the number density.

A method for producing a copper alloy excellent in punching workability, which is subjected to at least hot working and cold working, wherein heat treatment is performed at a temperature of 880 ° C. or more and less than 980 ° C. before the hot working, and the cold working The method for producing a copper alloy having excellent punchability according to claim 1 or 2 , wherein the aging treatment is performed at a temperature of 360 to 470 ° C before or after.