JP4570948B2 - Sn-plated strip of Cu-Zn alloy with reduced whisker generation and method for producing the same - Google Patents
Sn-plated strip of Cu-Zn alloy with reduced whisker generation and method for producing the same Download PDFInfo
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Description
本発明は、ウィスカーの発生が抑制されたＣｕ−Ｚｎ系合金のＳｎめっき条及びその製造方法に関する。 The present invention relates to a Cu-Zn alloy Sn plating strip in which the generation of whiskers is suppressed, and a method for manufacturing the same.
ＪＩＳ−Ｃ２６００およびＣ２６８０等の黄銅に代表されるＣｕ−Ｚｎ系合金は、りん青銅、ベリリウム銅、コルソン合金等と比較するとばね性が劣るものの、廉価なため、コネクタ用素材として広く使用されている。この場合、コネクタとして接触抵抗や熱安定性を得るために、Ｃｕ−Ｚｎ系合金条にＳｎめっきを施すことが多い。
Ｃｕ−Ｚｎ系合金のＳｎめっき条は、Ｓｎの優れたはんだ付け性、耐食性、電気接続性を生かし、主として民生用のコネクタ接点、自動車電装用ワイヤーハーネスをはじめとする端子、コネクタ等の様々な電気、電子部品に大量に使われている。
Cu-Zn alloys represented by brass such as JIS-C2600 and C2680 are widely used as connector materials because they are less expensive than phosphor bronze, beryllium copper, Corson alloy, etc., but are inexpensive. . In this case, in order to obtain contact resistance and thermal stability as a connector, the Cu—Zn alloy strip is often plated with Sn.
The Sn-plated strip of Cu-Zn alloy utilizes Sn's excellent solderability, corrosion resistance, and electrical connectivity, mainly for consumer connector contacts, various terminals such as automobile electrical wiring harnesses, connectors, etc. Used in large quantities in electrical and electronic parts.
Ｃｕ−Ｚｎ系合金のＳｎめっきでは、通常、Ｓｎめっきに先立ちＣｕ下地めっきを施す。これは、Ｃｕ下地めっきを施さない或いは施してもＣｕ下地めっき層が薄い場合、リフロー処理の際に、母材中のＺｎがＳｎめっき表面にＺｎ濃化層を形成し、はんだ付け性が低下するためである。即ち、Ｃｕ下地層はＺｎの拡散を抑制する効果を持つからである。
特許文献１の実施例に示されるようにＣｕ−Ｚｎ系合金のリフローＳｎめっきのＣｕ下地めっきは０．５μｍ以上が施されていた。
As shown in the example of Patent Document 1, Cu underplating of reflow Sn plating of a Cu—Zn-based alloy was performed with a thickness of 0.5 μm or more.
Ｃｕ−Ｚｎ系合金のＳｎめっき条は、一般的に連続めっきラインにおいて、次の工程で製造される。Ｃｕ−Ｚｎ系合金条を、前処理として脱脂、酸洗した後に、電気めっき法により、Ｃｕ下地めっき層を形成した後、Ｓｎめっき層を形成する。電気めっき後のＳｎめっき条には、Ｓｎめっき層を溶融させるリフロー処理を施すことが多い。
また、Ｓｎめっき材を常温に放置すると、Ｓｎめっき表面からＳｎの単結晶が成長することが知られている。このＳｎの単結晶は、ウィスカーと呼ばれるものであり、電子部品内の回路の短絡を引き起こすことがある。ウィスカーは、電着時に生ずるＳｎめっき皮膜の内部応力が原因で発生する。したがって、リフロー処理でＳｎを溶融させ皮膜の内部応力を除去することは、ウィスカーの発生を抑制する手段として有効である。
A Sn-plated strip of Cu-Zn alloy is generally manufactured in the following process in a continuous plating line. After degreasing and pickling the Cu—Zn-based alloy strip as a pretreatment, a Cu undercoat layer is formed by electroplating, and then an Sn plating layer is formed. In many cases, the Sn plating strip after electroplating is subjected to a reflow treatment for melting the Sn plating layer.
Further, it is known that when a Sn plating material is left at room temperature, a single crystal of Sn grows from the Sn plating surface. This single crystal of Sn is called a whisker and may cause a short circuit of a circuit in the electronic component. Whisker is generated due to the internal stress of the Sn plating film generated during electrodeposition. Therefore, melting Sn by reflow treatment to remove the internal stress of the coating is effective as a means for suppressing the occurrence of whiskers.
これに対して、Ｓｎめっき材を電気、電子部品のコネクタ等に使用する場合、接点部ではめっき表面に局部的な応力が加わり、Ｓｎめっき皮膜内部には歪が発生するため、従来、耐ウィスカー性が良好とされてきたリフローＳｎめっき条であっても微小なウィスカーが発生することがある。近年、電子、電気部品の回路数増大により、回路に電気信号を供給するコネクタの多極化が進んでいる。このため端子間の間隔が狭くなり、従来は問題にならなかったような微小なウィスカーでも回路の短絡を引き起こす危険性が生じてきた。このような背景により、従来、耐ウィスカー性が良好とされてきたリフローＳｎめっき条に対し、さらなるウィスカーの制御が求められるようになった。
本発明の目的は、ウィスカーの発生が抑制されたＣｕ−Ｚｎ系合金のリフローＳｎめっき条を提供することにある。
On the other hand, when the Sn plating material is used for a connector of an electric or electronic component, local stress is applied to the plating surface at the contact portion, and distortion is generated inside the Sn plating film. Even if the reflow Sn plating strip has been considered to have good properties, fine whiskers may occur. In recent years, with the increase in the number of electronic and electrical components, the number of connectors for supplying electrical signals to circuits has been increasing. For this reason, the space | interval between terminals narrows and the danger which causes the short circuit of a circuit has arisen even if it was a micro whisker which was not a problem conventionally. Due to such a background, further whisker control has been required for reflow Sn plating strips that have been considered to have good whisker resistance.
An object of the present invention is to provide a reflow Sn plating strip of a Cu—Zn alloy in which the generation of whiskers is suppressed.
本発明者等は、Ｃｕ−Ｚｎ系合金のリフローＳｎめっき条に対し、ウィスカー発生を抑制する方策を鋭意研究し、Ｓｎめっき表面にＺｎを濃化させるとウィスカーが抑制されることを知見した。しかし、上述したように、Ｓｎめっき表面にＺｎが濃化すると、はんだ付け性が低下する。そこで、本発明者等は、ウィスカー発生の抑制と良好なはんだ付け性が両立するＺｎ濃化状態を探索し、これを見出すことに成功した。同時に、この適度なＺｎ濃化状態を得るための製造条件として、母材表面の性状、Ｃｕ下地めっき厚、Ｓｎめっき厚、リフロー処理での加熱条件を明らかにすることができた。 The present inventors diligently studied a measure for suppressing the generation of whiskers with respect to the reflow Sn plating strip of the Cu—Zn alloy, and found that whisker is suppressed when Zn is concentrated on the Sn plating surface. However, as described above, when Zn is concentrated on the Sn plating surface, the solderability is deteriorated. Therefore, the present inventors have searched for and found a Zn-concentrated state in which suppression of whisker generation and good solderability are compatible. At the same time, as manufacturing conditions for obtaining this appropriate Zn enriched state, it was possible to clarify the properties of the surface of the base material, the Cu base plating thickness, the Sn plating thickness, and the heating conditions in the reflow treatment.
即ち、本発明は以下のとおりである。
（１）平均濃度で２０〜４０質量％のＺｎを含有する銅合金を母材として、表面から母材にかけてＳｎ相、Ｓｎ−Ｃｕ合金相、Ｃｕ相の各層でめっき皮膜が構成され、該Ｓｎ相の最表層のＺｎ濃度が３〜３５質量％であることを特徴とする、ウィスカー発生が抑制されたＣｕ−Ｚｎ系合金のＳｎめっき条。
That is, the present invention is as follows.
(1) A copper alloy containing 20 to 40% by mass of Zn at an average concentration is used as a base material, and a plating film is composed of Sn phase, Sn—Cu alloy phase, and Cu phase layers from the surface to the base material. A Sn-plated strip of Cu-Zn alloy with suppressed whisker generation, wherein the Zn concentration of the outermost layer of the phase is 3 to 35 mass%.
（２）平均濃度で２０〜４０質量％のＺｎを含有する銅合金に対して、以下の処理を順次施すことを特徴とする、ウィスカー発生が抑制されたＣｕ−Ｚｎ系合金のＳｎめっき条の製造方法、
ａ．母材の表面から深さ方向に０．１μｍの位置でのＺｎ濃度を、１０〜４０質量％に調整するための表層の除去
ｂ．厚み０．１〜０．４μｍのＣｕ下地めっき
ｃ．厚み０．５〜２．０μｍのＳｎめっき
ｄ．加熱時間ｔ（秒）および加熱温度Ｔ（℃）を次式の範囲に調整することを特徴とするリフロー処理
ｔ＞５、Ｔ＞２５０、Ｔ＜−１４ｔ＋６７０。
(2) A copper alloy containing 20 to 40% by mass of Zn at an average concentration is subjected to the following treatment in order, and the Sn-plated strip of Cu—Zn alloy with suppressed whisker generation Production method,
a. Removal of surface layer for adjusting Zn concentration at a position of 0.1 μm in the depth direction from the surface of the base material to 10 to 40% by mass b. Cu base plating with a thickness of 0.1 to 0.4 μm c. Sn plating with a thickness of 0.5 to 2.0 μm d. Reflow treatment characterized by adjusting the heating time t (seconds) and the heating temperature T (° C.) to the range of the following formula: t> 5, T> 250, T <−14t + 670.
本発明によれば、ウィスカーの発生が抑制された、Ｃｕ−Ｚｎ系合金のリフローＳｎめっき材を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the reflow Sn plating material of a Cu-Zn type alloy by which generation | occurrence | production of the whisker was suppressed can be provided.
本発明について、以下詳細に説明する。
本発明のＳｎめっきが対象とする銅合金母材は２０〜４０質量％のＺｎを含有するＣｕ−Ｚｎ系合金である。また、Ｚｎ以外の合金元素として、強度を改善する目的でＳｎ、Ａｇ、Ｐｂ、Ｆｅ、Ｎｉ、Ｍｎ、Ｓｉ、Ａｌ、Ｔｉから選択された１種以上の元素を合計で１０質量％以下含有でき、この濃度範囲であれば本発明の効果は得られる。
The present invention will be described in detail below.
The copper alloy base material targeted by the Sn plating of the present invention is a Cu—Zn-based alloy containing 20 to 40% by mass of Zn. Further, as an alloy element other than Zn, it can contain a total of 10% by mass or less of one or more elements selected from Sn, Ag, Pb, Fe, Ni, Mn, Si, Al, and Ti for the purpose of improving the strength. In this concentration range, the effect of the present invention can be obtained.
（１）めっきの構造
本発明のＳｎめっきの基本的な構造は、従来のＣｕ下地リフローＳｎめっきと同様、表面から母材にかけてＳｎ相、Ｓｎ−Ｃｕ合金相、Ｃｕ相の各層で構成される。本発明の特徴は、Ｓｎ相の最表層に適度な濃度のＺｎを濃化させることにある。
Ｓｎめっき層に局部的な応力が負荷されると、めっき表面にウィスカーが発生する。Ｓｎめっき最表層のＺｎには、このウィスカー発生を抑制する作用がある。これは、ＺｎがＳｎめっき層の局部的に応力の高い場所に拡散、凝集することで、応力を緩和するためと推測される。
(1) Structure of plating The basic structure of Sn plating of the present invention is composed of layers of Sn phase, Sn-Cu alloy phase, and Cu phase from the surface to the base material, as in the case of conventional Cu underlayer reflow Sn plating. . A feature of the present invention is that Zn having an appropriate concentration is concentrated on the outermost surface layer of the Sn phase.
When local stress is applied to the Sn plating layer, whiskers are generated on the plating surface. Zn on the outermost surface of the Sn plating has an effect of suppressing the generation of whiskers. This is presumably because Zn diffuses and agglomerates in places with high stress locally in the Sn plating layer to relieve stress.
ＺｎのＳｎめっき層表面への濃化は、リフロー処理での加熱においてＺｎが拡散することによって生ずる。Ｓｎめっき最表層のＺｎ濃度が３質量％未満では、ウィスカーの発生を抑制する効果が認められない。Ｓｎめっき最表層のＺｎ濃度が３５質量％を超えると、材料のはんだ付け性が著しく劣化するため好ましくない。したがって、Ｓｎめっき最表層のＺｎ濃度は、３〜３５質量％とする。より好ましいＳｎめっき最表層のＺｎ濃度は、５〜１５質量％である。ここで、Ｓｎめっき最表層のＺｎ濃度とは、ＧＤＳ（グロー放電発光分析）により分析した、表面から深さ方向に０．０１μｍの位置でのＺｎ濃度である。
なお、本発明の効果は、Ｓｎ相最表層のＺｎを上記範囲に濃化させれば発揮されるので、リフロー後のＳｎ相、Ｓｎ−Ｃｕ合金相、Ｃｕ相の厚みは、特に限定されない。同様に、電着時の厚みおよびリフロー条件によっては、Ｃｕ相の全てがＳｎ−Ｃｕ合金相に変化する（Ｃｕ層が残留しない）こともあるが、本発明はＣｕ相が残留しない状態をも含むものである。
Concentration of Zn on the surface of the Sn plating layer is caused by diffusion of Zn during heating in the reflow process. When the Zn concentration of the outermost layer of Sn plating is less than 3% by mass, the effect of suppressing the generation of whiskers is not recognized. If the Zn concentration of the outermost layer of Sn plating exceeds 35% by mass, the solderability of the material is significantly deteriorated, which is not preferable. Therefore, the Zn concentration of the outermost layer of Sn plating is 3 to 35% by mass. The Zn concentration of the outermost Sn plating outer layer is more preferably 5 to 15% by mass. Here, the Zn concentration of the outermost layer of Sn plating is the Zn concentration at a position of 0.01 μm in the depth direction from the surface, analyzed by GDS (glow discharge emission analysis).
In addition, since the effect of this invention is exhibited if Zn of Sn phase outermost layer is concentrated in the said range, the thickness of the Sn phase after reflow, Sn-Cu alloy phase, and Cu phase is not specifically limited. Similarly, depending on the thickness and reflow conditions during electrodeposition, all of the Cu phase may change to a Sn—Cu alloy phase (the Cu layer does not remain), but the present invention also has a state in which no Cu phase remains. Is included.
（１）製造方法
上記めっきの構造は、めっきを施す母材表層のＺｎ濃度、Ｃｕ下地めっきの厚み、Ｓｎめっきの厚みおよびリフロー条件の４つを適正範囲に調整することにより得られる。
ａ．めっきを施す母材表層のＺｎ濃度
Ｃｕ−Ｚｎ系合金を母材としＳｎめっきした材料では、加熱により母材中のＺｎがＳｎめっき層へ拡散する。後述するリフロー条件で加熱した場合、母材表層のＺｎ濃度が１０質量％未満であると、Ｓｎめっき最表層のＺｎ濃度が３質量％よりも低くなり、母材表層のＺｎ濃度が４０質量％を超えると、Ｓｎめっき最表層のＺｎ濃度が３５質量％を超える。したがって、母材に用いる銅合金の表層のＺｎ濃度を１０〜４０質量％に調整する必要がある。ここで、母材表層のＺｎ濃度とは、ＧＤＳにより分析した、表面から深さ方向に０．１μｍの位置でのＺｎ濃度である。
(1) Manufacturing method The plating structure can be obtained by adjusting the Zn concentration of the surface layer of the base material to be plated, the thickness of the Cu base plating, the thickness of the Sn plating, and the reflow conditions within an appropriate range.
a. Zn concentration in surface layer of base material to be plated In a material plated with Sn using a Cu-Zn alloy as a base material, Zn in the base material diffuses into the Sn plating layer by heating. When heated under reflow conditions to be described later, if the Zn concentration of the base metal surface layer is less than 10% by mass, the Zn concentration of the outermost Sn plating layer is lower than 3% by mass, and the Zn concentration of the base metal surface layer is 40% by mass. When exceeding, Zn density | concentration of Sn plating outermost layer will exceed 35 mass%. Therefore, it is necessary to adjust the Zn concentration of the surface layer of the copper alloy used for the base material to 10 to 40% by mass. Here, the Zn concentration in the surface layer of the base material is the Zn concentration at a position of 0.1 μm in the depth direction from the surface, analyzed by GDS.
一方、母材であるＣｕ−Ｚｎ系合金は、溶解・鋳造で製造したインゴットを必要に応じて熱間圧延した後、冷間圧延と焼鈍を繰り返して条に加工される。Ｃｕ−Ｚｎ系合金の焼鈍では、脱Ｚｎ現象が生じることが知られている。脱Ｚｎ現象とは、焼鈍においてＣｕ−Ｚｎ系合金が高温に熱せられた際に、蒸気圧の低いＺｎが気相中に逃散しＣｕ−Ｚｎ系合金表面のＺｎ濃度が低下する現象である。したがって、Ｃｕ−Ｚｎ系合金表面のＺｎ濃度を上記範囲に調整するためには、焼鈍で生じた脱Ｚｎ層を除去することが必要である。この除去方法としては、回転式バフを用いる機械研磨、腐食液を用いる化学研磨等がある。 On the other hand, a Cu—Zn-based alloy as a base material is processed into a strip by repeatedly performing cold rolling and annealing after hot rolling an ingot produced by melting and casting as necessary. It is known that the removal of Zn occurs when annealing Cu—Zn alloys. The Zn removal phenomenon is a phenomenon in which when the Cu—Zn alloy is heated to a high temperature during annealing, Zn having a low vapor pressure escapes into the gas phase and the Zn concentration on the surface of the Cu—Zn alloy decreases. Therefore, in order to adjust the Zn concentration on the surface of the Cu—Zn-based alloy to the above range, it is necessary to remove the Zn-free layer generated by annealing. As this removal method, there are mechanical polishing using a rotary buff, chemical polishing using a corrosive liquid, and the like.
本発明では、Ｓｎめっきに供される直前のＣｕ−Ｚｎ系合金表面のＺｎ濃度を、上記範囲に調整することが肝要であり、そのための手段や工程順序は特に限定されない。例えば、コネクタ用のＣｕ−Ｚｎ系合金は、焼鈍後に冷間圧延を施した調質状態でＳｎめっきに供されることが多いが、この場合、脱Ｚｎ層除去の研磨は、冷間圧延前（焼鈍直後）に行っても良いし、冷間圧延後（めっき直前）に行っても良い。 In the present invention, it is important to adjust the Zn concentration on the surface of the Cu—Zn-based alloy immediately before being subjected to Sn plating to the above range, and means and process order for that purpose are not particularly limited. For example, a Cu—Zn-based alloy for connectors is often used for Sn plating in a tempered state after cold rolling after annealing. In this case, polishing for removing the Zn-free layer is performed before cold rolling. It may be performed (immediately after annealing) or after cold rolling (immediately before plating).
ｂ．Ｃｕ下地めっき厚
Ｃｕ−Ｚｎ系合金にＳｎめっきする場合、母材からＳｎめっき層へのＺｎの拡散を抑制するため、Ｃｕを下地めっきすることが一般的である。後述するリフロー条件で加熱した場合、Ｃｕ下地めっきの厚みが０．１μｍ未満であると、Ｓｎめっき層へのＺｎの拡散を十分に抑制することができず、Ｓｎめっき最表層のＺｎ濃度が３５質量％を超える。Ｃｕ下地めっきの厚みが０．４μｍを超えると、Ｓｎめっき層へのＺｎの拡散が進行せず、Ｓｎめっき最表層のＺｎ濃度が３質量％に満たない。したがって、Ｃｕ下地めっきの厚みは、０．１〜０．４μｍとする。
b. Cu Underplating Thickness When Sn plating is applied to a Cu-Zn alloy, it is common to undercoat Cu to suppress the diffusion of Zn from the base material to the Sn plating layer. When heated under reflow conditions described later, if the thickness of the Cu undercoat is less than 0.1 μm, the diffusion of Zn into the Sn plating layer cannot be sufficiently suppressed, and the Zn concentration of the outermost surface of the Sn plating is 35. Exceeds mass%. When the thickness of the Cu base plating exceeds 0.4 μm, the diffusion of Zn into the Sn plating layer does not proceed, and the Zn concentration of the outermost layer of Sn plating is less than 3% by mass. Therefore, the thickness of the Cu base plating is 0.1 to 0.4 μm.
ｃ．Ｓｎめっき厚
Ｓｎめっきの厚みが０．５μｍ未満では、後述するリフロー条件で加熱した場合、Ｓｎめっき最表層のＺｎ濃度が３５質量％を超え、はんだ付け性が劣化する。Ｓｎめっきの厚みが２．０μｍを超えると、後述するリフロー条件で加熱した場合、Ｓｎめっき最表層のＺｎ濃度が３質量％に満たない。したがって、Ｓｎめっきの厚みは０．５〜２．０μｍとする。
c. Sn plating thickness When the thickness of Sn plating is less than 0.5 μm, when heated under reflow conditions described later, the Zn concentration of the outermost layer of Sn plating exceeds 35 mass%, and solderability deteriorates. When the thickness of the Sn plating exceeds 2.0 μm, the Zn concentration of the outermost layer of the Sn plating is less than 3% by mass when heated under reflow conditions described later. Therefore, the thickness of Sn plating shall be 0.5-2.0 micrometers.
ｄ．リフロー条件
Ｓｎめっき最表層のＺｎ濃度が本発明の範囲となるリフロー条件を以下に示す。加熱温度が２５０℃未満では、母材からＳｎめっき層へのＺｎの拡散が十分でなく、Ｓｎめっき最表層のＺｎ濃度が３質量％に満たない。加熱温度が６００℃を超えると、Ｚｎの拡散が著しくなるため、Ｓｎめっき最表層のＺｎ濃度が３５質量％を超えるばかりでなく、母材が再結晶し、軟化するため、材料に必要な機械的強度が得られない。したがって、リフロー処理での加熱温度は２５０〜６００℃とする。
また、加熱時間が５秒未満では、Ｓｎめっき層が溶融されず、リフロー光沢がえられないだけでなく、Ｓｎめっき層へのＺｎの拡散が十分でなく、Ｓｎめっき最表面のＺｎ濃度が３質量％に満たない。加熱時間が３０秒を超えると、Ｚｎの拡散が著しくなるため、Ｓｎめっき最表面のＺｎ濃度が３５質量％を超える。したがって、リフロー処理での加熱時間は５〜３０秒とする。
さらに、Ｓｎめっき層へのＺｎの拡散は、温度と時間の両因子の関係によって決定されるので、リフローの温度を、Ｔ＜−１４ｔ＋６７０の範囲に限定する。すなわち、リフロー処理条件は、図１の斜線の範囲である。ここで、Ｔは加熱温度（℃）、ｔは加熱時間（秒）を表す。
d. Reflow conditions The reflow conditions under which the Zn concentration of the outermost layer of Sn plating falls within the scope of the present invention are shown below. When the heating temperature is less than 250 ° C., Zn is not sufficiently diffused from the base material to the Sn plating layer, and the Zn concentration of the outermost layer of Sn plating is less than 3% by mass. When the heating temperature exceeds 600 ° C., the diffusion of Zn becomes significant, so that not only the Zn concentration of the outermost layer of Sn plating exceeds 35% by mass, but also the base material recrystallizes and softens, so that the necessary machine for the material Strength cannot be obtained. Therefore, the heating temperature in the reflow process is set to 250 to 600 ° C.
In addition, when the heating time is less than 5 seconds, the Sn plating layer is not melted and reflow gloss is not obtained, and Zn is not sufficiently diffused into the Sn plating layer, and the Zn concentration on the outermost surface of the Sn plating is 3 Less than mass%. When the heating time exceeds 30 seconds, the diffusion of Zn becomes remarkable, so that the Zn concentration on the outermost surface of the Sn plating exceeds 35% by mass. Therefore, the heating time in the reflow process is 5 to 30 seconds.
Furthermore, since the diffusion of Zn into the Sn plating layer is determined by the relationship between the temperature and time factors, the reflow temperature is limited to the range of T <−14t + 670. That is, the reflow processing condition is within the hatched range in FIG. Here, T represents the heating temperature (° C.), and t represents the heating time (seconds).
表１に示されるＣｕ−Ｚｎ系合金（厚さ０．２ｍｍ）を供試材として用いた。表１にはＧＤＳで分析した、表面から深さ方向に０．１μｍの位置でのＺｎ濃度も示してある。母材表層のＧＤＳ分析データの一例として、図２に発明例Ｎｏ．１および比較例Ｎｏ．１１のチャートを示す。 A Cu—Zn alloy (thickness 0.2 mm) shown in Table 1 was used as a test material. Table 1 also shows the Zn concentration at a position of 0.1 μm in the depth direction from the surface, analyzed by GDS. As an example of the GDS analysis data of the base material surface layer, FIG. 1 and Comparative Example No. 1 11 charts are shown.
各供試材を脱脂、酸洗した後、表１に示す条件でめっきおよびリフロー処理した。表２、表３にめっき浴の組成を示す。ＣｕおよびＳｎめっき厚みの調整は、電着時間を変えることで行った。 Each sample material was degreased and pickled, and then plated and reflowed under the conditions shown in Table 1. Tables 2 and 3 show the composition of the plating bath. Adjustment of Cu and Sn plating thickness was performed by changing the electrodeposition time.
リフロー後の供試材について、Ｓｎめっき最表層のＺｎ濃度をＧＤＳにより分析した。表１に、供試材のＳｎめっき表面から深さ方向に０．０１μｍの位置におけるＺｎ濃度を示す。Ｓｎめっき表層のＧＤＳ分析データの一例として、図３に発明例Ｎｏ．１および比較例Ｎｏ．１１のチャートを示す。 About the test material after reflow, the Zn density | concentration of Sn plating outermost layer was analyzed by GDS. Table 1 shows the Zn concentration at a position of 0.01 μm in the depth direction from the Sn plating surface of the test material. As an example of the GDS analysis data of the Sn plating surface layer, FIG. 1 and Comparative Example No. 1 11 charts are shown.
各供試材について、ウィスカーの長さおよびはんだ付け性を、次の方法で評価した。
（１）ウィスカー長さ
供試材表面に、直径が０．７ｍｍの球状の圧子（ステンレス製）を１５０ｇの荷重で負荷したまま室温で７日間放置し、めっき表面の圧子接点部にウィスカーを発生させた。発生したウィスカーを電子顕微鏡で観察し、各供試材で最も長く成長したウィスカーの長さが、１０μｍ以下の供試材は評価○とし、１０μｍを超えた材料は評価×とした。
About each test material, the length of the whisker and solderability were evaluated by the following method.
(1) Whisker length A spherical indenter (made of stainless steel) with a diameter of 0.7 mm is left on the surface of the test material with a load of 150 g for 7 days at room temperature, and whiskers are generated at the indenter contacts on the plating surface. I let you. The generated whisker was observed with an electron microscope. The length of the whisker that grew the longest in each specimen was 10 μm or less, and the specimen exceeding 10 μm was evaluated as “Good”.
（２）はんだ付け性
供試材を脱脂後、フラックスとして２５質量％ロジン−７５質量％エタノールを塗布し、はんだ付けを行った（はんだ組成：６０質量％Ｓｎ−４０質量％Ｐｂ）。はんだの付着面積が８０％以上の場合を「良好」とし、付着面積が８０％未満の場合を「不良」と評価した。
本発明例および比較例の評価結果を表４に示す。
(2) Solderability After degreasing the test material, 25 mass% rosin-75 mass% ethanol was applied as a flux and soldering was performed (solder composition: 60 mass% Sn-40 mass% Pb). The case where the adhesion area of the solder was 80% or more was evaluated as “good”, and the case where the adhesion area was less than 80% was evaluated as “bad”.
Table 4 shows the evaluation results of the inventive examples and the comparative examples.
本発明例Ｎｏ．１〜１０は、いずれもＳｎめっき最表層のＺｎ濃度が本発明の範囲内であるため、ウィスカーの長さが１０μｍ以下であり、また良好なはんだ付け性を示した。
一方、比較例Ｎｏ．１１は母材表層のＺｎ濃度が低すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも低く、１０μｍを超えるウィスカーが発生した。比較例Ｎｏ．１２は母材表層のＺｎ濃度が高すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも高く、はんだ付け性が劣った。
Invention Example No. In Nos. 1 to 10, since the Zn concentration of the outermost layer of Sn plating is within the range of the present invention, the length of whiskers is 10 μm or less, and good solderability is exhibited.
On the other hand, Comparative Example No. In No. 11, since the Zn concentration of the surface layer of the base material was too low, the Zn concentration of the outermost layer of Sn plating was lower than the range of the present invention, and whiskers exceeding 10 μm were generated. Comparative Example No. In No. 12, since the Zn concentration of the surface layer of the base material was too high, the Zn concentration of the outermost layer of Sn plating was higher than the range of the present invention, and the solderability was inferior.
比較例Ｎｏ．１３、１４はＣｕ下地めっきが薄すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも高く、はんだ付け性が劣った。比較例Ｎｏ．１５、１６はＣｕ下地めっきが厚すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも低く、１０μｍを超えるウィスカーが発生した。 Comparative Example No. In Nos. 13 and 14, since the Cu base plating was too thin, the Zn concentration of the outermost layer of Sn plating was higher than the range of the present invention, and the solderability was inferior. Comparative Example No. In Nos. 15 and 16, since the Cu base plating was too thick, the Zn concentration of the outermost Sn plating layer was lower than the range of the present invention, and whiskers exceeding 10 μm were generated.
比較例Ｎｏ．１７はＳｎめっきが薄すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも高く、はんだ付け性が劣った。比較例Ｎｏ．１８はＳｎめっきが厚すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも低く、１０μｍを超えるウィスカーが発生した。 Comparative Example No. Since Sn plating of No. 17 was too thin, Zn density | concentration of Sn plating outermost layer was higher than the range of this invention, and solderability was inferior. Comparative Example No. In No. 18, since the Sn plating was too thick, the Zn concentration of the outermost layer of the Sn plating was lower than the range of the present invention, and whiskers exceeding 10 μm were generated.
比較例Ｎｏ．１９はリフロー時間が短いため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも低く、１０μｍを超えるウィスカーが発生した。比較例Ｎｏ．２０はリフロー時間が長すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも高く、はんだ付け性が劣った。比較例Ｎｏ．２１はリフロー温度が低すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも低く、１０μｍを超えるウィスカーが発生した。比較例Ｎｏ．２４はリフロー温度が高すぎるため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも高く、はんだ付け性が劣った。 Comparative Example No. Since No. 19 had a short reflow time, the Zn concentration of the outermost layer of Sn plating was lower than the range of the present invention, and whiskers exceeding 10 μm were generated. Comparative Example No. Since No. 20 had too long reflow time, Zn density | concentration of Sn plating outermost layer was higher than the range of this invention, and solderability was inferior. Comparative Example No. In No. 21, since the reflow temperature was too low, the Zn concentration in the outermost layer of Sn plating was lower than the range of the present invention, and whiskers exceeding 10 μm were generated. Comparative Example No. In No. 24, since the reflow temperature was too high, the Zn concentration of the outermost layer of Sn plating was higher than the range of the present invention, and the solderability was inferior.
また、比較例Ｎｏ．２２、２３は、Ｔ＜−１４ｔ＋６７０を満足しないため、Ｓｎめっき最表層のＺｎ濃度が本発明の範囲よりも高く、はんだ付け性が劣った。 Comparative Example No. Since 22 and 23 do not satisfy T <−14t + 670, the Zn concentration of the outermost layer of Sn plating was higher than the range of the present invention, and the solderability was inferior.
Claims (1)
ａ．母材の表面から深さ方向に０．１μｍの位置での平均Ｚｎ濃度を、１０〜４０質量％に調整するための表層の除去
ｂ．厚み０．１〜０．４μｍのＣｕ下地めっき
ｃ．厚み０．５〜２．０μｍのＳｎめっき
ｄ．加熱時間ｔ（秒）および加熱温度Ｔ（℃）を次式の範囲に調整することを特徴とするリフロー処理
ｔ＞５、Ｔ＞２５０、Ｔ＜−１４ｔ＋６７０ The manufacturing method of the Sn plating strip of the Cu-Zn type alloy in which the whisker generation | occurrence | production was suppressed characterized by performing the following processes sequentially with respect to the copper alloy containing 20-40 mass% Zn by average density | concentration.
a. Removal of surface layer for adjusting the average Zn concentration at a position of 0.1 μm in the depth direction from the surface of the base material to 10 to 40% by mass b. Cu base plating with a thickness of 0.1 to 0.4 μm c. Sn plating with a thickness of 0.5 to 2.0 μm d. Reflow treatment characterized by adjusting heating time t (seconds) and heating temperature T (° C.) to the range of the following equation: t> 5, T> 250, T <−14t + 670
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| JP2004232014A (en) * | 2003-01-30 | 2004-08-19 | Dowa Mining Co Ltd | COPPER OR COPPER ALLOY MEMBER COATED WITH Sn AND MANUFACTURING METHOD THEREFOR |
| JP2004300524A (en) * | 2003-03-31 | 2004-10-28 | Dowa Mining Co Ltd | Sn-COATED COPPER OR COPPER ALLOY MEMBER AND ITS MANUFACTURING METHOD |
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| JP2004232014A (en) * | 2003-01-30 | 2004-08-19 | Dowa Mining Co Ltd | COPPER OR COPPER ALLOY MEMBER COATED WITH Sn AND MANUFACTURING METHOD THEREFOR |
| JP2004300524A (en) * | 2003-03-31 | 2004-10-28 | Dowa Mining Co Ltd | Sn-COATED COPPER OR COPPER ALLOY MEMBER AND ITS MANUFACTURING METHOD |
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