JP4445046B2 - Lead-free solder alloy - Google Patents
Lead-free solder alloy Download PDFInfo
- Publication number
- JP4445046B2 JP4445046B2 JP04114798A JP4114798A JP4445046B2 JP 4445046 B2 JP4445046 B2 JP 4445046B2 JP 04114798 A JP04114798 A JP 04114798A JP 4114798 A JP4114798 A JP 4114798A JP 4445046 B2 JP4445046 B2 JP 4445046B2
- Authority
- JP
- Japan
- Prior art keywords
- lead
- solder alloy
- free solder
- weight
- alloy
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Description
【0001】
【発明の属する技術分野】
本発明は、新規な無鉛はんだ合金の組成に関するものである。
【0002】
【発明が解決しようとする課題】
はんだ合金の従来からの組成において鉛ははんだ合金の特性を決定するものとして非常に有効に機能する。錫の融点232℃は、鉛との共晶によって183℃まで降下させることができるので、熱に弱い電子部品の組立用はんだとして広く用いられており、従来でははんだ合金素材として鉛は不可避であるとされていた。しかしながら、近年はんだにおける鉛の毒性が問題になっている。即ち、はんだ付けを行なう作業環境、はんだ付けされた物品を使うときの使用環境、およびはんだを廃棄するときの地球環境などを考慮すると、毒性の強い重金属である鉛の使用を回避するのが好ましい。
【0003】
また、環境維持を阻害する金属として鉛以外に規定されたものとして、アンチモン、カドミウム、砒素、ベリリウム、テルル、水銀などがあるが、鉛の場合と同様にこれらを含まないはんだ合金がより好ましい。
【0004】
ところで、上記各有害金属を用いることなくはんだ合金を組成する場合であっても、合金自体が相手の接合物に対してヌレ性を有していることが不可欠である。そして、錫はヌレ性が良好な金属である。本発明では、錫を基材として鉛などの有害金属を回避したはんだ合金を開示することを目的とする。
【0005】
【課題を解決するための手段】
本発明では、上記目的を達成するための新規なはんだ合金として、Cu0.1〜2重量%、Ge0.001〜1重量%、Ga0.001〜2重量%、残部Snからなる組成を採用した。また、より好ましい組成として、Cu0.3〜0.7重量%、Ge0.005〜0.1重量%、Ga0.005〜0.2重量%、残部Snとした。この成分中、錫は融点が232℃であり、接合母材に対するヌレを得るために必須の金属である。ところが、錫のみでははんだ付けに適した温度を得ることができないだけでなく、結晶組織が柔らかく機械的強度が十分に得られない。従って、銅を加えて合金自体を固溶強化する。銅は錫に0.7%加えると、融点が227℃の共晶合金となる。また、はんだ付け中に母材の銅表面から銅が溶出するという銅食われを抑制する機能も果たすと共に、はんだ付け界面における銅濃度差を小さくして、脆い化合物層の成長を遅らせる機能も果たす。ゲルマニウムは融点が936℃であり、Sn−Cu合金中には微量しか溶解せず、凝固するときに結晶を微細化する機能を有すると共に、結晶粒界に出現して結晶の粗大化を防止する。また、合金溶解時の酸化物生成を抑える機能も有する。ただし、1重量%を超えて添加するとコストが高くつくばかりでなく、過飽和状態になって均一に拡散しないので、実益はない。ガリウムは融点が30℃であり、Cuよりも原子半径がわずかに小さいので、接合時の拡散ヌレが速くなり、接合強度が向上する。ただし、2重量%を超えて添加した場合には固相温度が下がりすぎるために、信頼性に悪影響を及ぼすし、コスト面でも問題がある。好ましい範囲として示した請求項2の組成は、コストと添加効率の両面を考慮したものである。
【0006】
次に、上記手段の組成物に対して、さらにBi0.05〜5重量%、好ましくは0.3〜3重量%を加えるという手段を採用した。ここで、ビスマスを添加した分だけ残部であるSnの重量配分が減少することはいうまでもない。ビスマスは融点が271℃であり、錫にある程度固溶して結晶の強度を上げる機能を有している。また、融点を下げる働きがある。ただし、多く入れすぎると合金が脆くなり、またSn−Biの低い融点をもった組織が析出して、信頼性に悪影響を与えることになる。従って、これらを考慮して上限を定めた。
【0007】
さらに、In0.05〜5重量%、好ましくは0.5〜3重量%を加える手段も採用したが、インジウムは融点が157℃であり、合金の融点を下げる働きがある。また、物性として軟質な金属であるから、合金にしなやかさを与えることになる。
【0010】
【発明の実施の形態】
以下、本発明の組成を有するはんだ合金の物性を表に示す。
【表1】
【0011】
この実験例からも明らかなように、発明の範囲外である比較例と比べても、全てのサンプルが強度的に満足いくものである。なお、従来のSn−Pb共晶はんだ合金では、ほぼ同じ条件において強度は約4〜5Kgf/mm2 であり、これと比較すると強度的に劣るサンプルも見られるが、極端に低いものはなく、電子部品の実装に十分適用可能である。
【0012】
伸びについては、従来の共晶はんだ合金は10〜30%の範囲にあり、これらの範囲を超えるものは良好な伸び率であると考えられる。なお、サンプル3、6、7および9ははんだ試料の作成工程において冷却時間を短縮するために急冷したので、組織が細かくなり、硬くなったことが原因であると考えられる。従って、通常の時間で冷却を行った場合には組織は何れもより柔らかくなり、10%以上の伸び率を示すものと推測される。
【0013】
なお、サンプル8については結果の確認ができなかったので、数値は記入されていない。
【0014】
ところで、融点を2つの温度で示しているが、低いほうが固相温度であり、高いほうが液相温度を示す。一般的にこれらの温度差が小さいほうがはんだ付け後のはんだ固化中における部品の移動がなく、安定している一方、温度差が大きいほうは冷却後のはんだ付け部分に柔軟性があり、疲労破壊の機会が小さいということができる。何れが優れているかという点については一義的に決定できるものではなく、はんだ付け製品の用途などに応じて適宜サンプルから適正な温度差を有するはんだ合金を採用する。
【0015】
はんだ付けにおいて重要な性質であるヌレ性については、今回試験の対象としていないが、一般にRMAタイプのフラックスが銅板に対するヌレが良好である。従って、このフラックスを採用することによってヌレの良好性を確保することができる。何れにしても、主要組成である錫自体がヌレ性の良好な金属であり、相当重量%が錫である場合にはヌレ性についての欠陥は基本的には生じないものと推測される。
【0016】
【発明の効果】
本発明のはんだ合金は、有害重金属とされる鉛を組成としていないので、環境に悪影響を与えることはなく、従来のはんだ合金とほぼ同様の物性を示すことができる。従って、従来の鉛はんだ合金に十分代替することができるはんだ合金を提供することが可能となった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel lead-free solder alloy composition.
[0002]
[Problems to be solved by the invention]
In the conventional composition of solder alloys, lead functions very effectively as determining the properties of the solder alloy. Since the melting point of 232 ° C. of tin can be lowered to 183 ° C. by eutectic with lead, it is widely used as a solder for assembling heat-sensitive electronic components, and conventionally, lead is inevitable as a solder alloy material. It was said. However, the toxicity of lead in solder has become a problem in recent years. That is, it is preferable to avoid the use of lead, which is a highly toxic heavy metal, in consideration of the working environment where soldering is performed, the usage environment when using soldered articles, the global environment when discarding solder, etc. .
[0003]
In addition to lead as a metal that inhibits environmental maintenance, there are antimony, cadmium, arsenic, beryllium, tellurium, mercury and the like, but a solder alloy not containing these is more preferable as in the case of lead.
[0004]
By the way, even when a solder alloy is composed without using the above-mentioned toxic metals, it is indispensable that the alloy itself has a wetting property with respect to the mating joint. And tin is a metal with good wettability. It is an object of the present invention to disclose a solder alloy that uses tin as a base material and avoids harmful metals such as lead.
[0005]
[Means for Solving the Problems]
In the present invention, a composition composed of 0.1 to 2% by weight of Cu, 0.001 to 1% by weight of Ge, 0.001 to 2% by weight of Ga, and the remaining Sn is adopted as a novel solder alloy for achieving the above object. Further, as a more preferable composition, Cu 0.3 to 0.7% by weight, Ge 0.005 to 0.1% by weight, Ga 0.005 to 0.2% by weight, and the balance Sn were used. Among these components, tin has a melting point of 232 ° C., and is an essential metal for obtaining wetness with respect to the bonding base material. However, not only tin cannot obtain a temperature suitable for soldering, but also the crystal structure is soft and sufficient mechanical strength cannot be obtained. Accordingly, copper is added to strengthen the alloy itself. When 0.7% of copper is added to tin, it becomes a eutectic alloy having a melting point of 227 ° C. It also functions to suppress copper erosion that copper elutes from the copper surface of the base metal during soldering, and also serves to delay the growth of fragile compound layers by reducing the difference in copper concentration at the soldering interface. . Germanium has a melting point of 936 ° C., dissolves only a small amount in the Sn—Cu alloy, has a function of refining the crystal when solidified, and appears at the grain boundary to prevent the crystal from becoming coarse. . It also has a function of suppressing oxide formation when the alloy is dissolved. However, if it is added in excess of 1% by weight, not only is the cost high, but it is supersaturated and does not diffuse uniformly, so there is no practical benefit. Gallium has a melting point of 30 ° C. and has an atomic radius slightly smaller than that of Cu, so that diffusion diffusion at the time of bonding becomes faster and bonding strength is improved. However, if added in excess of 2% by weight, the solid phase temperature is too low, which adversely affects reliability and has a problem with cost. The composition of claim 2 shown as a preferred range takes into consideration both the cost and the addition efficiency.
[0006]
Next, a means of adding 0.05 to 5% by weight, preferably 0.3 to 3% by weight of Bi to the composition of the above means was adopted. Here, it goes without saying that the weight distribution of the remaining Sn is reduced by the amount of addition of bismuth. Bismuth has a melting point of 271 ° C. and has a function of increasing the strength of the crystal by being dissolved in tin to some extent. It also has the function of lowering the melting point. However, if too much is added, the alloy becomes brittle, and a structure having a low melting point of Sn—Bi precipitates, which adversely affects reliability. Therefore, the upper limit was set in consideration of these.
[0007]
Furthermore, although means for adding 0.05 to 5% by weight of In, preferably 0.5 to 3% by weight was also employed, indium has a melting point of 157 ° C., and serves to lower the melting point of the alloy. Moreover, since it is a soft metal as a physical property, it gives flexibility to the alloy.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The physical properties of the solder alloy having the composition of the present invention are shown in the table below.
[Table 1]
[0011]
As is clear from this experimental example, all the samples are satisfactory in strength as compared with the comparative example which is outside the scope of the invention. In addition, in the conventional Sn—Pb eutectic solder alloy, the strength is about 4 to 5 kgf / mm 2 under almost the same conditions, and some samples are inferior in strength compared to this, but there are no extremely low ones, It is sufficiently applicable to mounting electronic components.
[0012]
Regarding the elongation, the conventional eutectic solder alloys are in the range of 10 to 30%, and those exceeding these ranges are considered to have good elongation. Samples 3 , 6, 7 and 9 were rapidly cooled in order to shorten the cooling time in the solder sample preparation process, and it is considered that the cause was that the structure became fine and hard. Therefore, when cooling is performed in a normal time, all the structures become softer and it is estimated that the elongation rate is 10% or more.
[0013]
Since the result of Sample 8 could not be confirmed, no numerical value is entered.
[0014]
By the way, although melting | fusing point is shown by two temperature, the lower one is a solid phase temperature, and the higher one shows a liquid phase temperature. Generally, the smaller the temperature difference is, the more stable the parts are not moved during solidification after soldering, while the larger the temperature difference is, the more flexible the soldered part after cooling and fatigue failure It can be said that the opportunity is small. Which is superior cannot be uniquely determined, and a solder alloy having an appropriate temperature difference from the sample is appropriately employed depending on the use of the soldered product.
[0015]
The wetting property, which is an important property in soldering, is not the subject of this test, but generally the RMA type flux has good wetting on the copper plate. Therefore, by adopting this flux, it is possible to ensure good wetting. In any case, it is presumed that when the tin itself, which is the main composition, is a metal with good wettability, and a considerable weight% is tin, defects with respect to wettability basically do not occur.
[0016]
【The invention's effect】
Since the solder alloy of the present invention does not contain lead, which is a harmful heavy metal, it does not adversely affect the environment and can exhibit substantially the same physical properties as conventional solder alloys. Therefore, it has become possible to provide a solder alloy that can sufficiently replace the conventional lead solder alloy.
Claims (6)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP04114798A JP4445046B2 (en) | 1998-02-06 | 1998-02-06 | Lead-free solder alloy |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP04114798A JP4445046B2 (en) | 1998-02-06 | 1998-02-06 | Lead-free solder alloy |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH11221695A JPH11221695A (en) | 1999-08-17 |
JP4445046B2 true JP4445046B2 (en) | 2010-04-07 |
Family
ID=12600316
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP04114798A Expired - Lifetime JP4445046B2 (en) | 1998-02-06 | 1998-02-06 | Lead-free solder alloy |
Country Status (1)
Country | Link |
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JP (1) | JP4445046B2 (en) |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4039653B2 (en) * | 1999-11-01 | 2008-01-30 | 千住金属工業株式会社 | Sn alloy for lead plating |
DE60142387D1 (en) † | 2001-03-01 | 2010-07-29 | Senju Metal Industry Co | Lead-free solder paste |
KR100885543B1 (en) | 2004-10-22 | 2009-02-26 | 엠케이전자 주식회사 | Pb-free solder alloy |
JP5115915B2 (en) * | 2005-03-17 | 2013-01-09 | 株式会社タムラ製作所 | Lead-free solder, processed solder, solder paste and electronic component soldering board |
JP2007160401A (en) * | 2005-11-15 | 2007-06-28 | Hitachi Metals Ltd | Solder alloy, solder ball, and solder joint using the same |
WO2007081006A1 (en) | 2006-01-16 | 2007-07-19 | Hitachi Metals, Ltd. | Solder alloy, solder ball and solder joint using same |
CN100366378C (en) * | 2006-01-24 | 2008-02-06 | 昆山成利焊锡制造有限公司 | Leadless soft soldering material |
JP4673860B2 (en) * | 2007-02-02 | 2011-04-20 | 象印マホービン株式会社 | Pb / Sb-free solder alloys, printed wiring boards, and electronic equipment products |
CN102909481A (en) | 2007-07-13 | 2013-02-06 | 千住金属工业株式会社 | Lead-free solder for vehicle, and in-vehicle electronic circuit |
US8888932B2 (en) | 2007-07-18 | 2014-11-18 | Senju Metal Industry Co., Ltd. | Indium-containing lead-free solder for vehicle-mounted electronic circuits |
CN101780608B (en) * | 2010-04-12 | 2011-09-21 | 天津市恒固科技有限公司 | SnAgCu series lead-free solder containing Si and Ge |
EP3870389A1 (en) * | 2018-10-24 | 2021-09-01 | Alpha Assembly Solutions Inc. | Low temperature soldering solutions for polymer substrates, printed circuit boards and other joining applications |
-
1998
- 1998-02-06 JP JP04114798A patent/JP4445046B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPH11221695A (en) | 1999-08-17 |
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