JP2000141079A - Leadless solder alloy - Google Patents
Leadless solder alloyInfo
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- JP2000141079A JP2000141079A JP11250031A JP25003199A JP2000141079A JP 2000141079 A JP2000141079 A JP 2000141079A JP 11250031 A JP11250031 A JP 11250031A JP 25003199 A JP25003199 A JP 25003199A JP 2000141079 A JP2000141079 A JP 2000141079A
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- JP
- Japan
- Prior art keywords
- weight
- solder alloy
- lead
- alloy
- free solder
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、無鉛はんだ合金、
特に詳しくは、延性が改善されたＳｎ-Ｂｉ２元系無鉛
はんだ合金に関する。The present invention relates to a lead-free solder alloy,
More particularly, it relates to a Sn-Bi binary lead-free solder alloy with improved ductility.
【０００２】[0002]
【従来の技術】ＪＩＳ Ｚ ３２８２では電気・電子工
業関係用として、４２重量％Ｓｎ−５８重量％Ｂｉ共晶
はんだ（記号：Ｈ４２Ｂｉ５８Ａ）が規定されている。
文献（Binary Alloy Phase Diagrams, Ed by B.T.Massa
lski et al, vol.2(1996)）では、Ｓｎ−Ｂｉ２元系合
金の共晶組成は４３重量％Ｓｎ−５７重量％Ｂｉ（以
下、「Ｓｎ−５７Ｂｉ」と記載）であることから、この
Ｓｎ−５８Ｂｉの組成をもつはんだは、低融点(溶融温
度：１３９℃）であり、電子用はんだとして多く用いら
れているＳｎ−３７Ｐｂ共晶はんだ（溶融温度：１８３
℃）に比べて、より低温で電子部品を実装することが可
能である。2. Description of the Related Art JIS Z 3282 specifies a 42% by weight Sn-58% by weight Bi eutectic solder (symbol: H42Bi58A) for use in the electric and electronic industries.
Literature (Binary Alloy Phase Diagrams, Ed by BTMassa
According to lski et al, vol. 2 (1996), the eutectic composition of the Sn-Bi binary alloy is 43% by weight Sn-57% by weight Bi (hereinafter referred to as "Sn-57Bi"). The solder having the composition of Sn-58Bi has a low melting point (melting temperature: 139 ° C.), and is a Sn-37Pb eutectic solder (melting temperature: 183) which is often used as an electronic solder.
C), it is possible to mount electronic components at a lower temperature.
【０００３】はんだ付け作業温度の低温化は、電子部品
への熱的負荷をより小さくすることができ、より信頼性
の高い回路基板の製造が可能となる。また、はんだ付け
作業をより低温で行うことは、溶融はんだの酸化による
ドロス生成量の低減を可能とし、作業性を改善できる利
点をも持ち合わせている。[0003] Reducing the soldering operation temperature can reduce the thermal load on the electronic components, and can produce a more reliable circuit board. Performing the soldering operation at a lower temperature also has the advantage of reducing the amount of dross generated due to oxidation of the molten solder and improving the workability.
【０００４】しかしながら、論文(例えば、日本金属学
会誌，ｖｏｌ．５７（１９９３），４５５−４６２）等
で報告されているように、Ｓｎ−Ｂｉ共晶はんだは延性
に乏しいという欠点がある。電子部品の発熱あるいは使
用環境の温度変化によって部品や基板が熱膨張・収縮を
繰り返すため、はんだ接合部には繰返し応力と歪みが発
生し、これによる熱疲労から、はんだにクラックが発生
することがある。熱疲労によるはんだ付け部の剥離は、
電気的な導通を阻害し、電子機器がその機能を果たせな
くなる一因となってしまう。[0004] However, as reported in a paper (eg, Journal of the Japan Institute of Metals, vol. 57 (1993), 455-462), the Sn-Bi eutectic solder has a drawback of poor ductility. Due to the heat generated by the electronic components or the temperature change of the usage environment, the components and the board repeatedly undergo thermal expansion and contraction, so that repeated stress and distortion are generated at the solder joints, and solder fatigue may cause cracks in the solder due to thermal fatigue. is there. The peeling of the soldered part due to thermal fatigue
This hinders electrical continuity and causes electronic devices to fail to perform their functions.
【０００５】したがって、はんだには、その延性により
はんだ接合部に発生する応力と歪みを緩和し、クラック
等の発生を抑制するように機能することが求められる。
つまりはんだが良好な延性を有することは、接合部の熱
疲労特性を向上させる上で必要不可欠な特性となる。[0005] Therefore, it is required that the solder functions to relieve the stress and strain generated in the solder joint due to its ductility and to suppress the occurrence of cracks and the like.
That is, the fact that the solder has good ductility is an indispensable property for improving the thermal fatigue property of the joint.
【０００６】Ｓｎ−Ｂｉ系のはんだの延性を改善させる
ための技術として、従来から第３成分を添加するものが
あった。例えば、特開平８−２５２６８８号公報、特開
平１０−５２７９１号公報およびＪ．Ｅｌｅｃｔｒｏ
ｎ．Ｍａｔｅｒ．，ｖｏｌ．２６（１９９７），９５４
−９５８に示すＡｇの添加によって組織の微細化を図る
もの、特開平７−４００７９号公報に示すＳｂの添加に
よってＳｎのβ相からα相への変態抑制を図るもの、特
開平８−１５０４９３号公報に示すＩｎを添加するもの
等である。[0006] As a technique for improving the ductility of Sn-Bi based solder, there has been a technique in which a third component is conventionally added. For example, JP-A-8-252688, JP-A-10-52791 and J.P. Electro
n. Mater. , Vol. 26 (1997), 954
Japanese Patent Application Laid-Open No. 8-150493 discloses a method of miniaturizing the structure by adding Ag shown in -958, a method of suppressing the transformation of Sn from β phase to α phase by adding Sb shown in JP-A-7-40079, and JP-A-8-150493. It is the one to which In shown in the gazette is added.
【０００７】[0007]
【発明が解決しようとする課題】ところが、特開平８−
２５２６８８号公報、特開平８−１５０４９３号公報等
のようにＡｇやＩｎを添加する場合、ＡｇやＩｎは高価
な金属であることから、その添加量が多いときには、は
んだ合金のコスト上昇が避けられず、さらにＩｎの場合
は希少金属であるためその供給性にも問題がある。特
に、特開平８−１５０４９３号公報に示す技術では、数
重量％以上のＩｎの添加によりＳｎ−Ｂｉ−Ｉｎ３元系
合金を目指すものであり、そのコスト上昇は著しいもの
となる。また、特開平８−２５２６８８号公報、特開平
１０−５２７９１号公報等に示すようなＡｇの添加を本
発明者が追試したが、Ａｇの添加による延性の改善効果
は見られず、場合によっては逆に延性を損なう結果とな
った。SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. 8-
When Ag or In is added as in JP-A-252688, JP-A-8-150493, etc., since Ag or In is an expensive metal, an increase in the cost of the solder alloy can be avoided when the addition amount is large. In addition, since In is a rare metal, there is a problem in its supply property. In particular, the technique disclosed in Japanese Patent Application Laid-Open No. 8-150493 aims at a Sn-Bi-In ternary alloy by adding In of several weight% or more, and the cost increase is remarkable. Further, the inventors of the present invention have repeated the addition of Ag as disclosed in JP-A-8-252688, JP-A-10-52791, etc., but the effect of improving the ductility due to the addition of Ag is not seen. Conversely, ductility was impaired.
【０００８】Ｓｂによる変態抑制は、特開平７−４００
７９号公報に係る出願前からの公知技術であり(例え
ば、高信頼度マイクロソルダリング技術，（１９９
１），ｐ４４に記述あり）、またＳｂは、環境基本法に
基づく水質汚濁に係わる環境基準の中で要監視項目とな
っており、その点ではんだ合金の添加元素として用いる
のは好ましくない。さらに特開平７−４００７９号公報
ではＧａを必須の第４成分元素としているが、発明者ら
はＧａがたとえ少量であっても大幅にはんだ付け性を損
なうという実験結果を得ており、Ｇａの添加自体に問題
がある。[0008] Transformation suppression by Sb is disclosed in JP-A-7-400.
No. 79, which is a well-known technique before the filing of the application (for example, a highly reliable micro soldering technique, (199)
1), p44), and Sb is an item to be monitored in the environmental standards for water pollution based on the Basic Environmental Law, and it is not preferable to use it as an additional element in the solder alloy in that respect. Further, in Japanese Patent Application Laid-Open No. 7-40079, Ga is used as an essential fourth component element. However, the inventors have obtained an experimental result that even if the amount of Ga is small, the solderability is greatly impaired. There is a problem with the addition itself.
【０００９】本発明は、上記実状に鑑みてなされたもの
であり、無鉛はんだ合金であるＳｎ−Ｂｉ共晶はんだと
同等レベルのはんだ付け性および機械的強度を有しなが
ら、安価でかつ延性を改善した高信頼性のＳｎ−Ｂｉ２
元系無鉛はんだ合金を提供することを課題としている。The present invention has been made in view of the above situation, and has low cost and ductility while having the same level of solderability and mechanical strength as Sn-Bi eutectic solder which is a lead-free solder alloy. Improved high reliability Sn-Bi2
It is an object to provide an original lead-free solder alloy.
【００１０】[0010]
【課題を解決するための手段】本発明の無鉛はんだ合金
は、２５重量％以上５５重量％以下のＢｉを含有し、残
部がＳｎと不可避不純物とからなることを特徴とする。
つまり本発明の無鉛はんだ合金は、ＳｎとＢｉとの組成
割合を適正なものとすることにより、はんだの延性を改
善するものである。A lead-free solder alloy according to the present invention is characterized in that it contains Bi in an amount of 25% by weight or more and 55% by weight or less, with the balance being Sn and unavoidable impurities.
That is, the lead-free solder alloy of the present invention improves the ductility of the solder by adjusting the composition ratio of Sn and Bi to an appropriate ratio.
【００１１】本発明の無鉛はんだ合金が延性に優れてい
るのは、以下の理由によるものと考えられる。Ｓｎ−Ｂ
ｉ２元系合金は共晶組成がＳｎ−５７Ｂｉである。これ
に対して本発明の無鉛はんだ合金は、Ｂｉの組成割合が
２５〜５５重量％であることから、凝固の過程で、まず
Ｓｎが初晶として析出し、その後共晶相であるＳｎ−Ｂ
ｉが析出する。この初晶ＳｎとＳｎ−Ｂｉ共晶との存在
割合がはんだの延性に影響を与える。It is considered that the lead-free solder alloy of the present invention has excellent ductility for the following reasons. Sn-B
The eutectic composition of the binary alloy is Sn-57Bi. On the other hand, in the lead-free solder alloy of the present invention, since the composition ratio of Bi is 25 to 55% by weight, Sn is first precipitated as a primary crystal in the process of solidification, and then Sn-B, which is a eutectic phase.
i precipitates. The proportion of the primary crystal Sn and the Sn-Bi eutectic affects the ductility of the solder.
【００１２】図５に、Ｂｉの組成割合に対するはんだ組
織中の初晶ＳｎとＳｎ−Ｂｉ共晶の存在比率（組織中の
面積比）について示す。Ｓｎ−４０Ｂｉ付近は、両相が
組織の断面観察においてほぼ１：１の割合で存在してい
る。このような状態の場合が最も延性に優れており、Ｓ
ｎまたはＳｎ−Ｂｉのいずれかが多くなるにつれてはん
だの延性が低下する。したがって本発明の無鉛はんだ合
金では、Ｂｉの組成割合を２５〜５５重量％とすること
によって、延性に富むはんだ合金が得られるのである。FIG. 5 shows the ratio of the primary crystal Sn and the Sn-Bi eutectic in the solder structure to the composition ratio of Bi (area ratio in the structure). In the vicinity of Sn-40Bi, both phases are present at a ratio of approximately 1: 1 in cross-sectional observation of the structure. Such a state is most excellent in ductility, and S
As either n or Sn—Bi increases, the ductility of the solder decreases. Therefore, in the lead-free solder alloy of the present invention, by setting the composition ratio of Bi to 25 to 55% by weight, a solder alloy having high ductility can be obtained.
【００１３】また、本発明の無鉛はんだ合金は、固相線
が共晶組成の溶融温度とほぼ同じ温度にあるため、溶融
特性においても、共晶組成のＳｎ−５７Ｂｉ合金と比較
してそれ程劣るものではなく、Ｓｎ−Ｂｉ共晶はんだ合
金と同等レベルの溶融特性を示すものとなる。In addition, since the solidus of the lead-free solder alloy of the present invention is at substantially the same temperature as the melting temperature of the eutectic composition, the melting characteristics are also inferior to those of the eutectic Sn-57Bi alloy. However, it does not show the same melting characteristics as the Sn-Bi eutectic solder alloy.
【００１４】なお、本発明の無鉛はんだ合金では、共晶
組成から外れているため、固相線と液相線に囲まれた溶
融温度範囲を有している。このことは、部品を基板に搭
載してリフロー熱源によって一括はんだ付けする実装プ
ロセスにおいて有利に働く。多数搭載されている電子部
品を均一に加熱することは困難であり、例えばチップ部
品では部品両端の電極間で加熱ムラが生じると、一方の
電極のはんだが先に溶融し、溶融したはんだの表面張力
により部品が持ち上げられるいわゆるチップ立ち不良が
起こる場合がある。これを抑制するためには、はんだ合
金に溶融温度範囲を持たせることが有効であり、本発明
の無鉛はんだ合金は、このチップ立ち等のはんだ付け不
良の抑制が可能で、共晶組成付近のＳｎ−Ｂｉ合金より
安定したはんだ付け品質が確保できるという利点をも有
する。The lead-free solder alloy of the present invention has a melting temperature range surrounded by a solidus line and a liquidus line because it is out of the eutectic composition. This is advantageous in a mounting process in which components are mounted on a board and are collectively soldered by a reflow heat source. It is difficult to uniformly heat a large number of mounted electronic components.For example, in the case of chip components, if heating unevenness occurs between the electrodes at both ends of the components, the solder on one electrode melts first and the surface of the molten solder A so-called chip standing defect in which a component is lifted by tension may occur. In order to suppress this, it is effective to give the solder alloy a melting temperature range, and the lead-free solder alloy of the present invention can suppress poor soldering such as chip standing, and has a near eutectic composition. There is also an advantage that a more stable soldering quality can be ensured than the Sn-Bi alloy.
【００１５】[0015]
【発明の実施の形態】〈無鉛はんだ合金の製造〉本発明
の無鉛はんだ合金は、当該分野における通常の溶融手段
により調整することが可能である。例えば、重量で秤取
ったＳｎおよびＢｉを加熱中の容器に入れて溶融させれ
ばよい。この場合、部分的に合金を用いてもよい。これ
らの金属は従来のいずれの溶融技術を用いても溶融で
き、当該金属をすべて液体になるまで加熱した後、適当
な型に流し込んで冷却し製造される。DESCRIPTION OF THE PREFERRED EMBODIMENTS <Manufacture of lead-free solder alloy> The lead-free solder alloy of the present invention can be adjusted by a usual melting means in the art. For example, Sn and Bi weighed by weight may be put in a container being heated and melted. In this case, an alloy may be partially used. These metals can be melted using any conventional melting technique, and are manufactured by heating all of the metals until they become liquid and then pouring them into a suitable mold and cooling.
【００１６】本発明の無鉛はんだ合金は、適当な方法に
より、線状、棒状、リボン、ワイヤ、粉末、球状など、
用途に応じ様々な形状にすることができる。また、急冷
法等を用いることにより、リボンや粉末などの作製も可
能である。さらにまた、線状のはんだの芯にロジン等の
フラックスを入れたやに入りはんだとして用いることも
可能であり、粉末状のはんだにフラックス等を混合混練
してはんだペーストとして用いることも可能である。ま
た、接合用のみならず、電子部品およびプリント配線板
の電極表面処理用のはんだとしても利用可能である。[0016] The lead-free solder alloy of the present invention can be obtained by a suitable method such as wire, rod, ribbon, wire, powder, and sphere.
Various shapes can be made according to the application. Also, by using a quenching method or the like, it is possible to produce a ribbon or powder. Furthermore, it is also possible to use flux such as rosin in the core of a linear solder and use it as a cored solder, and it is also possible to mix and knead flux and the like with powdered solder and use it as a solder paste. . In addition, it can be used not only for bonding but also as a solder for electrode surface treatment of electronic components and printed wiring boards.
【００１７】〈ＳｎとＢｉとの２成分のみからなる無鉛
はんだ合金〉本発明の無鉛はんだ合金の場合、ＳｎとＢ
ｉとの２つの合金成分からなる無鉛はんだ合金とするこ
とができる。その場合のＳｎとＢｉとの割合は、前述し
たように、ＳｎとＢｉとの合計を１００重量％とした際
にＢｉが２５重量％以上５５重量％以下とする。この範
囲が、はんだの機械的強度、濡れ性、および溶融特性を
損なわずに、延性を改善できる範囲だからである。本発
明の無鉛はんだ合金に求められるこれらの特性を総合的
に考慮し、また後述する本発明者の試験の結果を勘案す
れば、Ｂｉを４０重量％以上５０重量％未満とするのが
より望ましい。<Lead-free solder alloy consisting of only two components Sn and Bi> In the case of the lead-free solder alloy of the present invention, Sn and B
A lead-free solder alloy consisting of two alloy components i. In this case, as described above, the ratio of Sn and Bi is set to 25% by weight or more and 55% by weight or less when the total of Sn and Bi is 100% by weight. This is because this range can improve ductility without impairing the mechanical strength, wettability, and melting properties of the solder. Considering these characteristics required for the lead-free solder alloy of the present invention comprehensively, and considering the results of the tests of the present inventors described below, it is more preferable that Bi be 40% by weight or more and less than 50% by weight. .
【００１８】また、試験結果から判断すれば、Ｂｉが４
０重量％〜４５重量％の範囲が、最もはんだの延性に優
れる範囲であるといえる。前述したように、初晶Ｓｎと
Ｓｎ−Ｂｉ共晶との存在比が１：１となる組成領域で最
もよい延性を示す。組織観察の結果、高延性を示す合金
は、初晶ＳｎをＳｎ−Ｂｉ共晶がネットワーク状に取り
囲む組織を呈し、初晶ＳｎとＳｎ−Ｂｉ共晶との境界で
すべりが起こっていることが明らかとなった。つまり、
Ｂｉの含有割合が約４０重量％で初晶ＳｎとＳｎ−Ｂｉ
共晶との存在比が概ね１：１となり、Ｂｉの含有割合が
４０重量％付近のものが最も延性が高くなる。Also, judging from the test results, Bi is 4
It can be said that the range of 0% to 45% by weight is the range in which the ductility of the solder is most excellent. As described above, the best ductility is exhibited in a composition region in which the abundance ratio of primary crystal Sn and Sn-Bi eutectic is 1: 1. As a result of microstructure observation, the alloy exhibiting high ductility exhibits a structure in which Sn-Bi eutectic surrounds primary Sn in a network form, and slip may occur at the boundary between primary crystal Sn and Sn-Bi eutectic. It became clear. That is,
When the Bi content is about 40% by weight and the primary crystal Sn and Sn-Bi
The one having an abundance ratio with eutectic of about 1: 1 and having a Bi content of around 40% by weight has the highest ductility.
【００１９】ＳｎとＢｉとの２成分のみからなる無鉛は
んだ合金とするメリットの１つは、ＳｎおよびＢｉのい
ずれも比較的安価であり、高価な第３成分を添加してい
ないため、はんだ合金自体が安価である点にある。そし
て、もう１つのメリットは、組成管理が極めて容易にな
る点にある。合金は多元化するにつれてその組成管理が
難しく、特に添加成分割合が小さいほどその管理が困難
になる。つまり、ＳｎとＢｉとの２成分のみからなる無
鉛はんだ合金では、組成管理面での煩雑さが解消され
る。One of the advantages of using a lead-free solder alloy comprising only two components, Sn and Bi, is that both Sn and Bi are relatively inexpensive and do not contain an expensive third component. It is inexpensive. Another merit is that the composition management becomes extremely easy. As alloys become more diversified, it becomes more difficult to control the composition of the alloy, and in particular, the smaller the proportion of added components, the more difficult it is to control. That is, in the case of a lead-free solder alloy consisting of only two components, Sn and Bi, the complexity of composition management is eliminated.
【００２０】〈Ｃｕを微量添加した無鉛はんだ合金〉本
発明の無鉛はんだ合金では、延性を改善するために、微
量のＣｕを添加した無鉛はんだ合金とすることが望まし
い。Ｃｕを微量添加した場合、添加したＣｕは、Ｃｕ−
Ｓｎ系金属間化合物の形でＳｎ−Ｂｉ共晶中に微細に分
散する。この共晶中の微細な金属間化合物は、上述した
初晶ＳｎとＳｎ−Ｂｉ共晶との境界ですべりを生じ易く
する。このことから、Ｃｕを微量添加したＳｎ-Ｂｉ２
元系無鉛はんだ合金では、延性がより向上する。<Lead-free solder alloy containing a small amount of Cu> In the lead-free solder alloy of the present invention, it is desirable to use a lead-free solder alloy containing a small amount of Cu in order to improve ductility. When a trace amount of Cu is added, the added Cu is Cu-
Finely dispersed in the Sn-Bi eutectic in the form of Sn-based intermetallic compound. The fine intermetallic compound in the eutectic tends to cause slip at the boundary between the primary crystal Sn and the Sn-Bi eutectic. From this, Sn-Bi2 with a small amount of Cu added
In the original lead-free solder alloy, the ductility is further improved.
【００２１】微量とは、具体的には、合金全体を１００
重量％とした場合の、０．４重量％以下である。実質的
な延性向上効果を得るためには、０．０１重量％以上の
Ｃｕ添加をすることが望ましい。逆に０．５重量％以上
添加する場合、添加したＣｕは初晶として晶出し、粗大
粒子となって合金中に分散することで、かえって合金の
延性が失われることとなる。実験の結果明らかになった
ことであるが、合金中のＣｕ含有割合が０．１重量％程
度のときが延性の改善効果が最も大きい。したがって、
より望ましいＣｕの含有割合は０．０５重量％以上０．
２重量％以下となる。The term “trace amount” refers to, specifically, 100%
0.4% by weight or less in the case of weight%. In order to obtain a substantial ductility improving effect, it is desirable to add 0.01% by weight or more of Cu. Conversely, when 0.5% by weight or more is added, the added Cu is crystallized as a primary crystal, becomes coarse particles and is dispersed in the alloy, so that the ductility of the alloy is rather lost. As is evident from the results of experiments, the effect of improving ductility is greatest when the Cu content in the alloy is about 0.1% by weight. Therefore,
A more desirable content ratio of Cu is 0.05% by weight or more.
It becomes 2% by weight or less.
【００２２】ここで、第３の成分を上記のような微量添
加した場合であっても、Ｓｎ−Ｂｉ合金は、２元系の特
性をそのまま維持する。したがって、微量の他成分を添
加した合金であっても、２元系合金というのを妨げるも
のではない。そこで、本明細書においては、このような
合金をも、Ｓｎ-Ｂｉ２元系無鉛はんだ合金という。Here, even when the third component is added in such a small amount as described above, the Sn-Bi alloy maintains the characteristics of the binary system as it is. Therefore, even an alloy to which a small amount of another component is added does not prevent a binary alloy. Therefore, in the present specification, such an alloy is also referred to as a Sn-Bi binary lead-free solder alloy.
【００２３】〈Ｉｎを微量添加した無鉛はんだ合金〉本
発明の無鉛はんだ合金では、はんだ表面の腐食を抑制し
電気化学的信頼性を向上するために、微量のＩｎを添加
した無鉛はんだ合金とすることが望ましい。Ｉｎは、酸
化しやすい金属であり、Ｉｎを添加した合金では、その
表面にＩｎ酸化物の被膜が形成される。この酸化物皮膜
は、一種の不動態膜となり、はんだの表面の腐食が防止
される。したがって、微量のＩｎを添加したＳｎ-Ｂｉ
２元系無鉛はんだ合金は、電子部品等の接合に用いられ
る場合の電気化学的信頼性が向上する。<Lead-free solder alloy containing a small amount of In> In the lead-free solder alloy of the present invention, a lead-free solder alloy containing a small amount of In is used in order to suppress the corrosion of the solder surface and improve the electrochemical reliability. It is desirable. In is a metal that is easily oxidized. In an alloy containing In, an In oxide film is formed on the surface of the alloy. This oxide film becomes a kind of passivation film, and the corrosion of the solder surface is prevented. Therefore, Sn-Bi with a small amount of In added
The binary lead-free solder alloy has improved electrochemical reliability when used for joining electronic components and the like.
【００２４】また、Ｓｎ−Ｂｉ系はんだ合金によりＣｕ
系材料からなる部材を接合する場合、はんだとＣｕ系材
料との界面には、硬くて脆いＣｕ−Ｓｎ系金属間化合物
の層が形成される。Ｉｎを添加した場合、そのＩｎは、
Ｃｕ−Ｓｎ系金属間化合物中に固溶したりまたＣｕ−Ｉ
ｎ系金属間化合物を形成することにより、Ｃｕ−Ｓｎ系
金属間化合物層の成長を抑制するように作用する。この
ことから、Ｉｎを添加したＳｎ-Ｂｉ２元系無鉛はんだ
合金では、接合における強度的信頼性の向上をも図るこ
とができる。In addition, Cu-Cu is formed by Sn-Bi solder alloy.
When joining members made of a system material, a hard and brittle Cu-Sn system intermetallic compound layer is formed at the interface between the solder and the Cu material. When In is added, the In is
Solid solution in Cu-Sn intermetallic compound or Cu-I
The formation of the n-based intermetallic compound acts to suppress the growth of the Cu-Sn-based intermetallic compound layer. From this, in the Sn-Bi binary lead-free solder alloy to which In is added, it is possible to improve the strength and reliability in bonding.
【００２５】微量とは、具体的には、合金全体を１００
重量％とした場合の、１重量％以下である。実質的な電
気化学的信頼性の向上効果を得るためには、０．０１重
量％以上のＩｎ添加をすることが望ましい。逆に１重量
％を超えて添加する場合、Ｉｎが極めて高価な材料であ
るため、はんだ合金自体のコストが上昇し、また、２元
系であることの特性が失われる結果となる。合金コスト
等と信頼性向上効果とを総合的に勘案すれば、より望ま
しいＩｎの含有割合は０．０１重量％以上０．０５重量
％以下となる。[0025] The term "trace amount" means that the total amount of the alloy is 100%.
1% by weight or less in the case of weight%. In order to obtain a substantial effect of improving the electrochemical reliability, it is desirable to add 0.01% by weight or more of In. Conversely, if the addition exceeds 1% by weight, the cost of the solder alloy itself increases because In is an extremely expensive material, and the characteristics of being a binary system are lost. When the alloy cost and the effect of improving the reliability are comprehensively considered, a more desirable content ratio of In is 0.01% by weight or more and 0.05% by weight or less.
【００２６】なお、Ｉｎの添加は、上記Ｃｕの添加とと
もに行うことができる。両者を添加したＳｎ-Ｂｉ２元
系無鉛はんだ合金は、延性向上の効果と電気化学的信頼
性向上の効果の２つの効果が得られるものとなる。ま
た、本Ｓｎ-Ｂｉ２元系無鉛はんだ合金は、他の特性向
上のために、既に公知の技術に従い、他の合金元素を微
量添加することを妨げるものではない。例えばＮｉ、Ｚ
ｎ、Ｆｅ、Ｇｅ等の添加による引張強度の改善、Ｐ等の
添加による耐酸化特性の向上等を挙げることができる。The addition of In can be performed together with the addition of Cu. The Sn-Bi binary lead-free solder alloy to which both are added provides two effects, an effect of improving ductility and an effect of improving electrochemical reliability. In addition, the present Sn-Bi binary lead-free solder alloy does not prevent the addition of trace amounts of other alloy elements in accordance with a known technique in order to improve other properties. For example, Ni, Z
Improvement of tensile strength by addition of n, Fe, Ge and the like, improvement of oxidation resistance by addition of P and the like can be given.
【００２７】[0027]
【実施例】以下に、本発明の無鉛はんだ合金の特性を評
価するために、種々の組成のＳｎ−Ｂｉ系無鉛はんだ合
金を調製し、種々の試験を行い、それらの特性の評価を
行った。以下に、実施例として示す。EXAMPLES In order to evaluate the characteristics of the lead-free solder alloy of the present invention, Sn-Bi-based lead-free solder alloys having various compositions were prepared, various tests were performed, and the characteristics were evaluated. . The following is an example.
【００２８】〈実施例１：Ｂｉの含有割合によるはんだ
合金の特性評価〉純度９９．９％以上のＳｎおよびＢｉ
を用いて、これらを種々の割合で混合し、各種組成のＳ
ｎ−Ｂｉ２元系無鉛はんだ合金を調製した。それぞれ、
Ｂｉが３０重量％のものを実施例１−１と、Ｂｉが４０
重量％のものを実施例１−２と、Ｂｉが４５重量％のも
のを実施例１−３と、Ｂｉが５０重量％のものを実施例
１−４と、Ｂｉが５５重量％のものを実施例１−５とし
た。Example 1 Evaluation of Solder Alloy Properties Based on Bi Content Ratio Sn and Bi with a purity of 99.9% or more
These are mixed at various ratios to obtain S of various compositions.
An n-Bi binary lead-free solder alloy was prepared. Respectively,
Example 1-1 having a Bi content of 30% by weight,
Wt.% Of Example 1-2, Bi of 45 wt.% Of Example 1-3, Bi of 50 wt.% Of Example 1-4, and Bi of 55 wt.%. Example 1-5 was set.
【００２９】また同時に、上記実施例の無鉛はんだ合金
との性能比較を行うため、それらと異なる組成の合金を
も調製した。これらをそれぞれ、Ｂｉが５７重量％のも
のを比較例１−１と、Ｂｉが２０重量％のものを比較例
１−２と、Ｂｉが１０重量％のものを比較例１−３と、
Ｂｉが５重量％のものを比較例１−４と、Ｂｉが３重量
％のものを比較例１−５と、Ｂｉが１重量％のものを比
較例１−６と、そしてＢｉを含まないＳｎだけのものを
比較例１−７とした。At the same time, alloys having compositions different from those of the lead-free solder alloys of the above-mentioned examples were also prepared in order to compare their performance. These are respectively Comparative Example 1-1 having 57% by weight of Bi, Comparative Example 1-2 having 20% by weight of Bi, and Comparative Example 1-3 having 10% by weight of Bi.
Comparative Example 1-4 with Bi at 5% by weight, Comparative Example 1-5 with Bi at 3% by weight, Comparative Example 1-6 with Bi at 1% by weight, and no Bi The thing only with Sn was set as Comparative Example 1-7.
【００３０】これら実施例および比較例の無鉛はんだ合
金に対して、機械的特性および濡れ性について、試験を
行って評価した。また、溶融温度については、文献（Bi
naryAlloy Phase Diagrams, Ed by B.T.Massalski et a
l, vol.2(1996)）に記載されているデータにより考察し
た。The lead-free solder alloys of these examples and comparative examples were tested and evaluated for mechanical properties and wettability. For the melting temperature, refer to the literature (Bi
naryAlloy Phase Diagrams, Ed by BTMassalski et a
1, vol. 2 (1996)).
【００３１】機械的特性は、引張試験を行ない強さ（最
大引張強さ）と伸び（破断伸び）を求めて評価した。引
張試験片は、金型鋳造した２０×１５×６０（ｍｍ）の
インゴットから、機械加工により図６に示す形状に成形
した。試験片は、１つのインゴットから３本採取した。
機械加工後、加工による歪みを除去するために、５０℃
で２４時間の熱処理を行い、その後１週間以上室温にて
放置してから、引張試験に供した。引張試験における歪
み速度は、はんだ接合部での状態を再現するため１×１
０-4ｓ-1とし、試験温度は室温（２５℃）および１２５
℃で、それぞれｎ数を３としてこれらの平均を求めた。The mechanical properties were evaluated by performing a tensile test to determine the strength (maximum tensile strength) and elongation (elongation at break). The tensile test piece was formed into a shape shown in FIG. 6 by machining from a 20 × 15 × 60 (mm) ingot cast by a mold. Three test pieces were collected from one ingot.
After machining, 50 ° C to remove distortion due to machining
For 24 hours, and then allowed to stand at room temperature for one week or more, and then subjected to a tensile test. The strain rate in the tensile test was 1 × 1 to reproduce the state at the solder joint.
0 −4 s −1 , and the test temperature was room temperature (25 ° C.) and 125 ° C.
At 0 ° C., the average of these was determined with n being 3 for each.
【００３２】はんだの濡れ性は、広がり試験（ＪＩＳ
Ｚ ３１９７）を行い、広がり率を求めて評価した。広
がり率（単位：％）は、次の（１）式より求めた。The wettability of the solder is measured by a spread test (JIS
Z 3197) and the spread rate was determined and evaluated. The spread rate (unit:%) was obtained from the following equation (1).
【００３３】 Ｓ＝（Ｄ−Ｈ）／Ｄ×１００ （１）式 Ｄ：試験前のはんだを球形とみなしたときの高さ Ｈ：試験後のはんだの高さ 広がり試験に用いたはんだの形状は円板状（φ６ｍｍ×
ｔ２ｍｍ）であり、基板にはＣｕを、フラックスは市販
品（千住金属：Ｐ０−Ｚ−７）を用いた。雰囲気は大
気、加熱温度は液相線温度＋５０℃の条件で行った。S = (DH) / D × 100 (1) Formula D: Height when solder before test is regarded as spherical H: Height of solder after test Shape of solder used in spread test Is a disk (φ6mm ×
t2 mm), Cu was used for the substrate, and a commercially available flux (Senju Metal: P0-Z-7) was used. The atmosphere was air and the heating temperature was the condition of the liquidus temperature + 50 ° C.
【００３４】下記表１に、各実施例および比較例の無鉛
はんだ合金の、機械的特性、濡れ性、および溶融特性に
関する試験データを示す。そして、表２には、表１のデ
ータについて評価を行った評価結果を示す。評価結果に
おいて、◎は極めて良好、○は良好、△は普通、×は不
良を意味する。Table 1 below shows test data on mechanical properties, wettability, and melting properties of the lead-free solder alloys of Examples and Comparative Examples. Table 2 shows the evaluation results obtained by evaluating the data in Table 1. In the evaluation results, ◎ means extremely good, は means good, △ means normal, and × means bad.
【００３５】[0035]
【表１】 [Table 1]
【００３６】[0036]
【表２】 [Table 2]
【００３７】これらの特性についてわかりやすく表すた
めに、図１にＳｎ−Ｂｉ２元系無鉛はんだ合金の室温で
の引張特性を、図２にＳｎ−Ｂｉ２元系無鉛はんだ合金
の１２５℃での引張特性を、図３にＳｎ−Ｂｉ２元系無
鉛はんだ合金の広がり率を、図４にＳｎ−Ｂｉ２元系無
鉛はんだ合金の固相線、液相線温度および溶融範囲を、
それぞれグラフの形式で図示する。FIG. 1 shows the tensile properties of the Sn—Bi binary lead-free solder alloy at room temperature, and FIG. 2 shows the tensile properties of the Sn—Bi binary lead-free solder alloy at 125 ° C. FIG. 3 shows the spread rate of the Sn-Bi binary lead-free solder alloy, and FIG. 4 shows the solidus temperature, liquidus temperature and melting range of the Sn-Bi binary lead-free solder alloy.
Each is shown in the form of a graph.
【００３８】図１および図２から明らかなように、Ｂｉ
の含有割合が２５重量％以上５５重量％以下の無鉛はん
だ合金は、Ｂｉ５７重量％という共晶組成の無鉛はんだ
合金に比べて、格段に延性が改善されていることが判
る。伸びは、Ｂｉ量が３０重量％と４５重量％との間の
領域で極大になり、特に、Ｂｉが４０〜４５重量％付近
の組成の合金は、室温での伸びは１１０％を超え、１２
５℃では３００％以上伸びても破断しない。As is apparent from FIGS. 1 and 2, Bi
It can be seen that a lead-free solder alloy having a content of 25% by weight or more and 55% by weight or less has significantly improved ductility as compared with a lead-free solder alloy having a eutectic composition of Bi 57% by weight. The elongation is maximized in the region where the amount of Bi is between 30% by weight and 45% by weight. In particular, alloys having a composition with a Bi content of about 40 to 45% by weight have an elongation at room temperature of more than 110% and 12%.
At 5 ° C., it does not break even if it extends 300% or more.
【００３９】また図３から、本発明の無鉛はんだ合金
は、濡れ性においても、共晶組成の無鉛はんだ合金より
優れていることが判る。FIG. 3 also shows that the lead-free solder alloy of the present invention is superior to the lead-free solder alloy having a eutectic composition in terms of wettability.
【００４０】さらに図４から、本発明の無鉛はんだ合金
は、溶融特性についても、共晶組成の無鉛はんだ合金と
同等レベルであることが確認でき、共晶組成付近の無鉛
はんだ合金の利点であるはんだ付け作業温度の低温化を
阻害するものではないことが判る。また、本発明の無鉛
はんだ合金は、いずれも溶融範囲を有しており、チップ
立ち等のはんだ付け不良を抑制可能であることも明らか
である。なお、溶融範囲が大きい場合には、「はんだの
溶け分かれ」現象により、はんだ接合部の組織が不均一
になって、充分な特性が得られない場合があるため、Ｂ
ｉ量を４０重量％以上とすることがより好ましい。Further, from FIG. 4, it can be confirmed that the lead-free solder alloy of the present invention has the same melting characteristics as the lead-free solder alloy having the eutectic composition, which is an advantage of the lead-free solder alloy having a eutectic composition. It can be seen that this does not hinder the lowering of the soldering operation temperature. Further, it is clear that all of the lead-free solder alloys of the present invention have a melting range and can suppress soldering defects such as chip standing. If the melting range is large, the structure of the solder joint may become uneven due to the phenomenon of "solder melting and splitting", and sufficient characteristics may not be obtained.
More preferably, the i amount is 40% by weight or more.
【００４１】上記結果を総合的に判断すれば、Ｓｎ−Ｂ
ｉ２元系無鉛はんだ合金において、Ｂｉの含有割合は、
２５重量％以上５５重量％以下とするのがよく、その範
囲の中でも４０重量％以上５０重量％未満とするのが望
ましく、さらに、４０重量％以上４５重量％以下とする
のがより望ましいことが確認できる。If the above results are comprehensively determined, Sn-B
In the binary lead-free solder alloy, the content ratio of Bi is:
The content is preferably from 25% by weight to 55% by weight, more preferably from 40% by weight to less than 50% by weight, and more preferably from 40% by weight to 45% by weight. You can check.
【００４２】〈実施例２：Ｃｕ添加効果の評価〉純度９
９．９％以上のＳｎ、ＢｉおよびＣｕを用いて、これら
を種々の割合で混合し、各種組成のＳｎ−Ｂｉ２元系無
鉛はんだ合金を調製した。そして、Ｂｉを４０重量％含
有し、Ｃｕを含有しないもの、それぞれ０．０５重量
％、０．１重量％、０．２重量％、０．３重量％含有す
るものを、それぞれ実施例２−１〜実施例２−５とし
た。また、Ｂｉを４５重量％含有し、Ｃｕを含有しない
もの、０．３重量％含有するものを、それぞれ実施例２
−６および実施例２−７とし、Ｂｉを５０重量％含有
し、Ｃｕを含有しないもの、０．３重量％含有するもの
を、それぞれ実施例２−８および実施例２−９とした。<Example 2: Evaluation of the effect of adding Cu> Purity 9
Using 9.9% or more of Sn, Bi and Cu, these were mixed at various ratios to prepare Sn-Bi binary lead-free solder alloys of various compositions. Then, those containing 40% by weight of Bi and not containing Cu, and those containing 0.05% by weight, 0.1% by weight, 0.2% by weight and 0.3% by weight, respectively, of Example 2- 1 to Example 2-5. Further, those containing 45% by weight of Bi and not containing Cu, and those containing 0.3% by weight of Bi were used in Example 2 respectively.
-6 and Example 2-7, those containing 50% by weight of Bi, not containing Cu, and those containing 0.3% by weight were called Example 2-8 and Example 2-9, respectively.
【００４３】また同時に、上記実施例の無鉛はんだ合金
との性能比較を行うため、それらと異なる組成の合金を
も調製した。そして、Ｂｉを４０重量％含有し、Ｃｕを
０．５重量％、１重量％、２重量％含有するものを、そ
れぞれ比較例２−１〜比較例２−３とし、Ｂｉを４５重
量％含有し、Ｃｕを０．５重量％含有するものを比較例
２−４とした。さらに、Ａｇ添加の効果を確認すべく、
Ｂｉを４０重量％含有しＡｇを０．３重量％含有するも
の、および、Ｂｉを４０重量％含有しＣｕおよびＡｇを
それぞれ０．３重量％含有するものを調製し、それらを
それぞれ比較例２−５、比較例２−６とした。At the same time, alloys having compositions different from those of the lead-free solder alloys of the above-mentioned examples were also prepared in order to compare their performance. Those containing 40% by weight of Bi and 0.5% by weight, 1% by weight, and 2% by weight of Cu were referred to as Comparative Examples 2-1 to 2-3, respectively, and contained 45% by weight of Bi. And what contained 0.5 weight% of Cu was made into Comparative Example 2-4. Furthermore, in order to confirm the effect of Ag addition,
A composition containing 40% by weight of Bi and 0.3% by weight of Ag, and a composition containing 40% by weight of Bi and containing 0.3% by weight of Cu and Ag, respectively, were prepared. -5 and Comparative Example 2-6.
【００４４】これら実施例および比較例の無鉛はんだ合
金に対して、機械的特性を評価すべく引張試験を行い、
強さ（最大引張強さ）と伸び（破断伸び）を求めた。引
張試験片および引張試験の要領、条件については、上記
実施例１に示すものと同様とした。A tensile test was performed on the lead-free solder alloys of these examples and comparative examples to evaluate mechanical properties.
The strength (maximum tensile strength) and elongation (elongation at break) were determined. The conditions and conditions of the tensile test piece and the tensile test were the same as those described in Example 1 above.
【００４５】この試験の結果として、下記表３に、各実
施例および比較例の無鉛はんだ合金の機械的特性（強さ
および伸び）に関する試験データを示す。また、機械的
特性についてわかりやすく表すために、Ｂｉを４０重量
％含有した場合におけるＣｕの含有量と引張強さおよび
伸びとの関係を、図７に、グラフの形式で図示する。As a result of this test, Table 3 below shows test data relating to the mechanical properties (strength and elongation) of the lead-free solder alloys of Examples and Comparative Examples. FIG. 7 is a graph showing the relationship between the Cu content and the tensile strength and elongation when Bi is contained at 40% by weight in order to clearly show the mechanical properties.
【００４６】[0046]
【表３】 [Table 3]
【００４７】表３および図７から明らかなように、Ｓｎ
−Ｂｉ２元系合金へのＣｕ添加量を制御することによ
り、Ｃｕ無添加の場合に比べて，機械的強度に影響を与
えず、格段に延性が改善されることが判る。例えば，Ｂ
ｉを４０重量％含有した合金においては、Ｃｕ添加割合
は０．１重量％程度にした場合に最も延性が改善され、
室温での伸びはＣｕ無添加の場合の約１．４倍に達する
ことが明らかとなった。しかし、Ｃｕ添加割合が大きす
ぎると、逆に延性改善効果は失われることが判る。例え
ば、Ｃｕ添加割合を０．５重量％以上にすると、Ｃｕ無
添加の場合よりも伸びが小さくなり，延性が損なわれて
いる。As is clear from Table 3 and FIG.
It can be seen that by controlling the amount of Cu added to the -Bi binary alloy, the ductility is remarkably improved without affecting the mechanical strength as compared with the case where Cu is not added. For example, B
In an alloy containing 40% by weight of i, the ductility is most improved when the Cu addition ratio is about 0.1% by weight,
It was found that the elongation at room temperature reached about 1.4 times that in the case where Cu was not added. However, if the Cu content is too high, the ductility improving effect is lost. For example, when the Cu addition ratio is 0.5% by weight or more, the elongation is smaller than that in the case where Cu is not added, and the ductility is impaired.
【００４８】上記結果を総合的に判断すれば、Ｓｎ−Ｂ
ｉ２元系無鉛はんだ合金において、Ｃｕを０．４重量％
以下の割合で含有することで、延性改善の効果が得られ
ることが確認できる。また、より改善効果の大きいＣｕ
の含有割合は、０．０５重量％以上０．２重量％以下で
あることも確認できる。If the above results are comprehensively determined, Sn-B
0.4% by weight of Cu in i-based lead-free solder alloy
It can be confirmed that the effect of improving the ductility can be obtained by containing at the following ratio. In addition, Cu having a greater improvement effect
Can be confirmed to be 0.05% by weight or more and 0.2% by weight or less.
【００４９】なお、比較例２−５および比較例２−６の
ものは、Ａｇによる特性改善を意図した前述の従来技術
に示されている合金である。しかし、それぞれ実施例２
−１、実施例２−５と比較して判るように、延性改善効
果は認められないばかりか、逆に延性を損なう結果とな
った。したがって、Ｓｎ−Ｂｉ２元系無鉛はんだ合金に
おいては、高延性を確保するためには、Ａｇの添加を避
けるべきであると判断できる。The alloys of Comparative Examples 2-5 and 2-6 are the alloys disclosed in the above-mentioned prior art, which are intended to improve the characteristics by Ag. However, in Example 2
-1, As can be seen from comparison with Example 2-5, not only the effect of improving ductility was not recognized, but also the result that ductility was impaired. Therefore, it can be determined that the addition of Ag should be avoided in the Sn-Bi binary lead-free solder alloy in order to ensure high ductility.
【００５０】〈実施例３：Ｉｎ添加効果の評価〉純度９
９．９％以上のＳｎ、Ｂｉ、ＣｕおよびＩｎを用いて、
これらを種々の割合で混合し、各種組成のＳｎ−Ｂｉ２
元系無鉛はんだ合金を調製した。そして、Ｂｉを４０重
量％、Ｃｕを０．１重量％含有し、Ｉｎを含有しないも
の、それぞれ０．１重量％、０．５重量％含有するもの
を、それぞれ実施例３−１〜実施例３−３とした。ま
た、Ｂｉを４５重量％、Ｃｕを０．０５重量％含有し、
Ｉｎそれぞれ０．１重量％、０．５重量％含有するもの
を、それぞれ実施例３−４〜実施例３−５とした。Example 3 Evaluation of In-addition Effect Purity 9
Using 9.9% or more of Sn, Bi, Cu and In,
These are mixed at various ratios to obtain Sn-Bi2 of various compositions.
An original lead-free solder alloy was prepared. Examples 3-1 to Example 3 each containing 40% by weight of Bi and 0.1% by weight of Cu and not containing In, and containing 0.1% by weight and 0.5% by weight of In, respectively. 3-3. It also contains 45% by weight of Bi and 0.05% by weight of Cu,
In each containing 0.1% by weight and 0.5% by weight of In were respectively referred to as Examples 3-4 to 3-5.
【００５１】上記実施例のはんだ合金に対して、電気化
学的信頼性を評価するための試験を行った。試験は、以
下の要領にて行った。まず、基板( ＪＩＳ２型くし歯基
板、材質：ＦＲ−４、ピッチ間隔：０．３１８ｍｍ)
に、水溶性フラックス(ＷＦ２０５０：千住金属製)を塗
布し、９０℃で３０秒間の予備加熱を行なった後、２２
０℃で溶融した各はんだ浴槽に基板を５秒間浸漬し、は
んだ付けした。本試験では、はんだ合金の電気化学的信
頼性を評価することを目的としているため、はんだ付
後、超音波水洗→流水洗浄→金ブラシ洗浄→イソプロパ
ノールで超音波洗浄→乾燥の手順で基板を洗浄し、フラ
ックス残渣を除去した。この試料に、８５℃、相対湿度
８５％の雰囲気中で１０００時間、直流のバイアス電圧
１６Ｖを印加した。A test for evaluating the electrochemical reliability was performed on the solder alloy of the above embodiment. The test was performed as follows. First, a substrate (JIS2 type comb substrate, material: FR-4, pitch interval: 0.318 mm)
Was coated with a water-soluble flux (WF2050: manufactured by Senju Metal Co., Ltd.) and preheated at 90 ° C. for 30 seconds.
The substrate was immersed for 5 seconds in each solder bath melted at 0 ° C. and soldered. Since the purpose of this test is to evaluate the electrochemical reliability of the solder alloy, after soldering, the board is cleaned in the order of ultrasonic water washing → running water washing → gold brush washing → ultrasonic washing with isopropanol → drying Then, the flux residue was removed. A direct current bias voltage of 16 V was applied to this sample in an atmosphere at 85 ° C. and a relative humidity of 85% for 1000 hours.
【００５２】試験終了後、はんだ表面の組織観察を行な
い、電気化学的信頼性の評価を行なった。評価結果を、
下記表４に示す。また、Ｉｎを添加した場合として、実
施例３−３の試験後のはんだ合金表面の外観を図８
（ａ）に、Ｉｎを添加していない場合として、実施例３
−１の試験後のはんだ合金表面の外観を図８（ｂ）にそ
れぞれ示す。After the test, the structure of the solder surface was observed to evaluate the electrochemical reliability. Evaluation results
It is shown in Table 4 below. FIG. 8 shows the appearance of the surface of the solder alloy after the test of Example 3-3, assuming that In was added.
Example 3 is the case where In is not added to (a).
FIG. 8 (b) shows the appearance of the surface of the solder alloy after the test of -1.
【００５３】[0053]
【表４】 [Table 4]
【００５４】図８（ｂ）に示すように、Ｉｎを添加して
いない場合、試験によりはんだ合金の表面に、腐食生成
物が観察される。これに対し、図８（ａ）に示すよう
に、Ｉｎを微量添加した実施例３−３のはんだ合金は、
試験による腐食生成物は生成されていない。Ｉｎを添加
した他の実施例についても、同様に、腐食生成物は生成
されていなかった。このように腐食生成物が生成されな
いものが、電気化学的信頼性が高いはんだ合金であると
いえる。したがって、上記表４にまとめた結果の様に、
Ｉｎを１重量％以下という微量で含有する場合であって
も、Ｓｎ−Ｂｉ２元系はんだ合金は、電気化学的信頼性
が向上することが確認できる。As shown in FIG. 8B, when In was not added, corrosion products were observed on the surface of the solder alloy by the test. On the other hand, as shown in FIG. 8A, the solder alloy of Example 3-3 to which a small amount of In was added
No corrosion products were generated by the test. Corrosion products were not similarly generated in the other examples to which In was added. Those in which no corrosion product is generated can be said to be a solder alloy having high electrochemical reliability. Therefore, as shown in the results summarized in Table 4 above,
Even when In is contained in a trace amount of 1% by weight or less, it can be confirmed that the Sn-Bi binary solder alloy has improved electrochemical reliability.
【００５５】[0055]
【発明の効果】本発明は、Ｓｎ−Ｂｉ２元系無鉛はんだ
合金を、Ｂｉを２５重量％以上５５重量％以下の組成割
合とするように構成したものである。このような構成と
したことにより、本発明の無鉛はんだ合金は、Ｓｎ−Ｂ
ｉ共晶はんだ合金と同等レベルのはんだ付け性および機
械的強度を有しながら、安価で、かつ延性を大幅に改善
した無鉛はんだ合金となっている。そして本無鉛はんだ
合金を使用してはんだ付けを行ったはんだ接合部は、延
性に富み、熱疲労特性の良好な信頼性のある接合部とな
る。According to the present invention, the Sn-Bi binary lead-free solder alloy is constituted so that the composition ratio of Bi is 25% by weight or more and 55% by weight or less. With such a configuration, the lead-free solder alloy of the present invention has a Sn-B
It is a lead-free solder alloy that is inexpensive and has greatly improved ductility, while having the same level of solderability and mechanical strength as the i-eutectic solder alloy. The solder joints soldered using the present lead-free solder alloy have high ductility and are reliable joints having good thermal fatigue characteristics.
【００５６】またＢｉの含有割合をさらに４０重量％以
上５０重量％未満に限定することで、より延性が高いも
のとなる。また、０．４重量％以下のＣｕを含有させる
ことで、さらに延性を改善することができ、１重量％以
下のＩｎを含有させることで、合金コストの大幅増加な
しに電気化学的信頼性を向上させることが可能となる。Further, by further limiting the Bi content to 40% by weight or more and less than 50% by weight, the ductility becomes higher. Further, by containing 0.4% by weight or less of Cu, the ductility can be further improved, and by containing 1% by weight or less of In, electrochemical reliability can be improved without significantly increasing alloy cost. It can be improved.
【図１】 Ｓｎ−Ｂｉ２元系無鉛はんだ合金の室温での
引張特性を示す図FIG. 1 is a diagram showing the tensile properties of a Sn—Bi binary lead-free solder alloy at room temperature.
【図２】 Ｓｎ−Ｂｉ２元系無鉛はんだ合金の１２５℃
での引張特性を示す図FIG. 2 125 ° C. of Sn—Bi binary lead-free solder alloy
Figure showing tensile properties at
【図３】 Ｓｎ−Ｂｉ２元系無鉛はんだ合金の広がり率
を示す図FIG. 3 is a diagram showing the spread rate of a Sn-Bi binary lead-free solder alloy.
【図４】 Ｓｎ−Ｂｉ２元系無鉛はんだ合金の固相線、
液相線温度および溶融範囲を示す図FIG. 4 shows a solidus of Sn—Bi binary lead-free solder alloy,
Diagram showing liquidus temperature and melting range
【図５】 Ｂｉの含有量に対するはんだ組織中の初晶Ｓ
ｎとＳｎ−Ｂｉ共晶との存在比率を示す図FIG. 5: Primary crystal S in solder structure with respect to Bi content
FIG. 7 is a graph showing the abundance ratio of n and Sn—Bi eutectic.
【図６】 引張試験に供した試験片の形状を示す図FIG. 6 is a view showing the shape of a test piece subjected to a tensile test.
【図７】 Ｃｕを添加したＳｎ−Ｂｉ２元系無鉛はんだ
合金のＣｕ含有量と引張特性との関係を示す図FIG. 7 is a diagram showing the relationship between Cu content and tensile properties of a Sn-Bi binary lead-free solder alloy to which Cu has been added.
【図８】 電気化学的信頼性を確認する試験後のはんだ
合金表面の外観を示す写真FIG. 8 is a photograph showing the appearance of a solder alloy surface after a test for confirming electrochemical reliability.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） // Ｂ２３Ｋ 101:36 (72)発明者 長谷川 英雄 愛知県愛知郡長久手町大字長湫字横道41番 地の１株式会社豊田中央研究所内──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification FI FI Theme Court ゛ (Reference) // B23K 101: 36 (72) Inventor Hideo Hasegawa 41-Cho, Yakumichi, Yoji, Nagakute-cho, Aichi-gun, Aichi 1 Inside Toyota Central Research Laboratory
Claims (4)
含有し、残部がＳｎと不可避不純物とからなることを特
徴とする無鉛はんだ合金。1. A lead-free solder alloy containing Bi in an amount of 25% by weight or more and 55% by weight or less, with the balance being Sn and unavoidable impurities.
５０重量％未満である請求項１に記載の無鉛はんだ合
金。2. The lead-free solder alloy according to claim 1, wherein the Bi content is 40% by weight or more and less than 50% by weight.
る請求項１または請求項２に記載の無鉛はんだ合金。3. The lead-free solder alloy according to claim 1, further comprising 0.4% by weight or less of Cu.
求項１ないし請求項３のいずれかに記載する無鉛はんだ
合金。4. The lead-free solder alloy according to claim 1, further comprising 1% by weight or less of In.
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| JP25106498 | 1998-09-04 | ||
| JP10-251064 | 1998-09-04 | ||
| JP25003199A JP4135268B2 (en) | 1998-09-04 | 1999-09-03 | Lead-free solder alloy |
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