JP4475282B2 - Electroless gold plating solution and electroless gold plating method - Google Patents
Electroless gold plating solution and electroless gold plating method Download PDFInfo
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Description
本発明は、無電解金めっき液及び無電解金めっき方法に関する。 The present invention relates to an electroless gold plating solution and an electroless gold plating method.
従来の高温、高アルカリ性無電解金めっき液に代わって、中性及び低温で使用可能な無電解金めっき液が近年開発されている。かかる無電解金めっき液は、めっき可能なレジストや電子部品の使用範囲を広げることを目的として開発されたものであるが、既存の製品ではめっき液の安定性が不充分であり、付きまわり性にも劣っている。 In recent years, electroless gold plating solutions that can be used at neutral and low temperatures have been developed in place of conventional high-temperature, highly alkaline electroless gold plating solutions. This electroless gold plating solution was developed for the purpose of expanding the range of use of resists and electronic components that can be plated. However, existing products have insufficient plating solution stability and throwing power. Also inferior.
このような安定性低下の原因としては、（１）無電解金めっき自体の安定性が不充分であること、及び（２）めっき処理による不純物金属混入により安定性が低下すること、の２つが想定されており、これらの観点からめっき液を改良する試みがなされている。 There are two reasons for such a decrease in stability: (1) the stability of electroless gold plating itself is insufficient, and (2) the stability is reduced due to impurity metal contamination by the plating process. It is assumed that attempts have been made to improve the plating solution from these viewpoints.
例えば、特許文献１には、シアン化合物を使用することなく、中性付近で無電解金めっきを実現するために、還元剤としてアスコルビン酸を使用することが開示されている。 For example, Patent Document 1 discloses using ascorbic acid as a reducing agent in order to realize electroless gold plating near neutrality without using a cyanide compound.
また、めっき処理による不純物金属混入の抑制や液安定性向上のために、メルカプトベンゾチアゾール系化合物の金属隠蔽剤を添加することが、特許文献２及び特許文献３に開示されている。 In addition, Patent Document 2 and Patent Document 3 disclose that a metal masking agent of a mercaptobenzothiazole-based compound is added for the purpose of suppressing impurity metal contamination by plating and improving liquid stability.
更に、特許文献４には、無電解金めっき液に還元剤としてヒドラジン化合物（１０〜３０ｇ／Ｌ）を使用することが開示され、この浴は上記のアスコルビン酸浴と比較して低濃度で実用的な析出速度が得られるとされている。 Furthermore, Patent Document 4 discloses that a hydrazine compound (10 to 30 g / L) is used as a reducing agent in an electroless gold plating solution, and this bath is practically used at a lower concentration than the above ascorbic acid bath. It is said that a typical deposition rate can be obtained.
また、めっき処理による不純物金属混入の抑制や液安定性向上のためベンゾトリアゾール系化合物の金属隠蔽剤を添加する改良がなされており、この隠蔽剤の管理範囲は広く（３〜１０ｇ／Ｌ）実用的であることが、特許文献５に開示されている。 In addition, the metal masking agent of the benzotriazole compound has been improved to suppress impurity metal contamination by plating and to improve liquid stability, and the management range of this masking agent is wide (3 to 10 g / L). This is disclosed in Patent Document 5.
一方、特許文献６には、還元剤にチオ尿素またはフェニル系化合物を使用する方法が開示されており、チオ尿素は低濃度で金を還元できることが示されている。
しかしながら、上記従来技術のめっき液には以下のような問題点が存在していた。すなわち、アスコルビン酸による還元は還元効率が低く、実用析出速度を確保するために、アスコルビン酸ナトリウム濃度を６０〜１００ｇ／Ｌと過剰に配合するため、めっき液の安定性が低下していた。 However, the following problems existed in the above-described conventional plating solutions. That is, the reduction with ascorbic acid has a low reduction efficiency, and the sodium ascorbate concentration is excessively blended with 60 to 100 g / L in order to secure a practical precipitation rate, so that the stability of the plating solution was lowered.
また、メルカプトベンゾチアゾール系化合物の金属隠蔽剤は、使用管理範囲が非常に狭く（０．１〜５ｐｐｍ）、作業の効率が低く、添加量が多くなると、付きまわり不良が発生するという問題があった。 In addition, the metal concealing agent of the mercaptobenzothiazole compound has a problem that the use management range is very narrow (0.1 to 5 ppm), the work efficiency is low, and if the addition amount is large, a throwing-out defect occurs. It was.
一方、還元剤としてヒドラジン化合物を使用すると、この浴はアスコルビン酸浴と比較して低濃度で実用的な析出速度を得られるものの、ヒドラジン化合物自体の安定性が低く、液の安定性が確保できないという問題があった。また、めっき処理による不純物金属混入の抑制や液安定性向上のためベンゾトリアゾール系化合物の金属隠蔽剤を添加する改良がなされているが、上記のように還元剤自体の安定性が低いため、結果的に安定性向上が不十分で実用化が困難である。 On the other hand, when a hydrazine compound is used as the reducing agent, this bath can obtain a practical precipitation rate at a lower concentration than the ascorbic acid bath, but the stability of the hydrazine compound itself is low and the stability of the liquid cannot be ensured. There was a problem. In addition, the metal masking agent of the benzotriazole-based compound has been improved for the purpose of suppressing impurity metal contamination by plating treatment and improving the liquid stability, but the result is that the reducing agent itself has low stability as described above. In particular, the stability improvement is insufficient and practical application is difficult.
また、チオ尿素化合物及びフェニル化合物の両方の還元剤を配合した無電解金めっき液は、チオ尿素の副生成物をフェニル化合物系還元剤で還元し、液安定性を向上せしめたものであるが、チオ尿素の副生成物を完全に元の還元剤にもどすことが困難であり、この残留副生成物がめっきの付きまわり不良や不安定化の原因となり、充分な安定性を保持できない場合があった。また、フェニル化合物系還元剤は、中性（ｐＨ７〜７．５）において還元力が少ないため実用的な析出速度を得ることができず、弱アルカリ性領域（ｐＨ９．０付近）においては、皮膜外観が悪くめっき中に液が分解する問題があった。 In addition, the electroless gold plating solution containing both the thiourea compound and the phenyl compound reducing agent is obtained by reducing the by-product of thiourea with a phenyl compound reducing agent to improve the liquid stability. However, it is difficult to completely return the thiourea by-product to the original reducing agent, and this residual by-product may cause poor adhesion and instability of the plating and may not maintain sufficient stability. there were. In addition, since the phenyl compound reducing agent has a reducing power at neutrality (pH 7 to 7.5), a practical deposition rate cannot be obtained, and in the weakly alkaline region (around pH 9.0), the appearance of the film However, there was a problem that the solution was decomposed during plating.
そこで、チオ尿素化合物、フェニル化合物の両方の還元剤を配合した無電解金めっき液が提案されており（特開平３−１０４８７７号公報）、このめっき液によれば、チオ尿素の副生成物がフェニル化合物系還元剤で還元されるため、液安定性が向上することが可能になる。また、この浴にベンゾトリアゾール系化合物の金属隠蔽剤を添加することが提案されており（特開平９−１５７８５９号公報）、このめっき液によれば、不純物金属混入の抑制や液安定性向上を図り、従来浴に比べて安定性を向上させることが可能になる。 Thus, an electroless gold plating solution containing both thiourea compound and phenyl compound reducing agents has been proposed (JP-A-3-104877). According to this plating solution, a by-product of thiourea is produced. Since it is reduced with a phenyl compound-based reducing agent, the liquid stability can be improved. In addition, it has been proposed to add a metal masking agent of a benzotriazole-based compound to this bath (Japanese Patent Laid-Open No. 9-1557859). According to this plating solution, the suppression of impurity metal contamination and the improvement of the liquid stability are proposed. As a result, the stability can be improved as compared with the conventional bath.
しかしながら、安定性が更に高く、中性且つ低温で実用的な析出速度を発揮するめっき液が求められているのが現状である。そこで、本発明の目的は、ｐＨ６〜８程度の中性領域において液温６０〜８０℃程度の低温でも、充分な金の析出速度を発揮する無電解金めっき液であって、めっき液の安定性が特に優れた無電解金めっき液を提供することにある。本発明の目的は、また、かかる無電解金めっき液を用いた無電解金めっき方法を提供することにある。 However, at present, there is a demand for a plating solution that is more stable, neutral, and exhibits a practical deposition rate at low temperatures. Accordingly, an object of the present invention is an electroless gold plating solution that exhibits a sufficient gold deposition rate even at a low temperature of about 60-80 ° C. in a neutral region of about pH 6-8, It is to provide an electroless gold plating solution having particularly excellent properties. Another object of the present invention is to provide an electroless gold plating method using such an electroless gold plating solution.
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、特定の還元剤と重金属塩を含む無電解金めっき液により、上記目的が達成可能であることを見出し、本発明を完成させた。 As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by an electroless gold plating solution containing a specific reducing agent and a heavy metal salt, and completed the present invention. I let you.
すなわち、本発明の無電解金めっき液は、金塩と、下記一般式（Ｉ）で表される還元剤と、重金属塩と、を含むことを特徴とするものである。 That is, the electroless gold plating solution of the present invention includes a gold salt, a reducing agent represented by the following general formula (I), and a heavy metal salt.
［式中、Ｒ１は水酸基又はアミノ基を示し、Ｒ２、Ｒ３及びＲ４はそれぞれ独立に水酸基、アミノ基、水素原子又はアルキル基を示す。］
[Wherein, R 1 represents a hydroxyl group or an amino group, and R 2 , R 3 and R 4 each independently represents a hydroxyl group, an amino group, a hydrogen atom or an alkyl group. ]
本発明の無電解金めっき液は、金塩と組み合わせる還元剤を上記一般式（Ｉ）で表される化合物とし、重金属塩を併用したことから、ｐＨ６〜８程度の中性領域において液温６０〜８０℃程度の低温でも、充分な金の析出速度を発揮するのみならず、めっき液の安定性が特に優れるようになる。 The electroless gold plating solution of the present invention uses a reducing agent combined with a gold salt as a compound represented by the above general formula (I) and also uses a heavy metal salt, so that the solution temperature is 60 in a neutral region of about pH 6-8. Even at a low temperature of about ˜80 ° C., not only a sufficient gold deposition rate is exhibited, but also the stability of the plating solution becomes particularly excellent.
上記本発明の無電解金めっき液は、錯化剤を更に含むことが好ましく、ｐＨ緩衝剤を更に含むことが好ましく、金属イオン隠蔽剤を更に含むことが好ましい。すなわち、本発明の無電解金めっき液は、錯化剤、ｐＨ緩衝剤及び金属イオン隠蔽剤のうち少なくとも１つを更に含むことが好ましい。かかる成分を含有することにより、めっき液の安定性が更に優れるようになる。 The electroless gold plating solution of the present invention preferably further includes a complexing agent, preferably further includes a pH buffer, and preferably further includes a metal ion concealing agent. That is, it is preferable that the electroless gold plating solution of the present invention further includes at least one of a complexing agent, a pH buffering agent, and a metal ion concealing agent. By containing such a component, the stability of the plating solution is further improved.
そして、重金属塩は、タリウム塩、鉛塩、砒素塩、アンチモン塩、テルル塩及びビスマス塩からなる群より選ばれる少なくとも１つの重金属塩であることが好ましく、重金属塩はタリウム塩であることが特に好ましい。また、重金属塩としては重金属無機化合物塩又は重金属有機錯体塩が良く、無電解金めっき液は、重金属塩に由来する重金属が１〜１００ｐｐｍとなるように重金属塩を含有することが好適である。重金属塩が上記化合物である場合又は上記濃度である場合には、金の析出速度及びめっき液の安定性が更に優れるようになる。 The heavy metal salt is preferably at least one heavy metal salt selected from the group consisting of a thallium salt, a lead salt, an arsenic salt, an antimony salt, a tellurium salt and a bismuth salt, and the heavy metal salt is particularly a thallium salt. preferable. The heavy metal salt is preferably a heavy metal inorganic compound salt or a heavy metal organic complex salt, and the electroless gold plating solution preferably contains a heavy metal salt so that the heavy metal derived from the heavy metal salt is 1 to 100 ppm. When the heavy metal salt is the above compound or at the above concentration, the deposition rate of gold and the stability of the plating solution are further improved.
本発明の無電解金めっき液においては、還元剤が、下記一般式（ＩＩ）で表される還元剤であることが好ましい。一般式（ＩＩ）で表される還元剤を用いることによりめっき液の安定性が高まると共に、金の析出速度を向上させることが可能になる。 In the electroless gold plating solution of the present invention, the reducing agent is preferably a reducing agent represented by the following general formula (II). By using the reducing agent represented by the general formula (II), it is possible to improve the stability of the plating solution and improve the deposition rate of gold.
［式中、Ｒ２１は水酸基又はアミノ基を示し、Ｒ２２は水素原子又は炭素数１〜４のアルキル基を示す。］
[Wherein, R 21 represents a hydroxyl group or an amino group, and R 22 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ]
本発明の無電解金めっき液は、ｐＨが５〜１０であることが好ましい。無電解金めっき液のｐＨが上記範囲である場合は、様々な被めっき体に対して中性且つ低温で無電解金めっきが可能なることから、めっき可能なレジストや電子部品の使用範囲を広げることが可能になる。 The electroless gold plating solution of the present invention preferably has a pH of 5-10. When the pH of the electroless gold plating solution is in the above range, it is possible to perform electroless gold plating on various objects to be plated at neutral and low temperatures. It becomes possible.
本発明は、また、ｐＨ６〜８、液温６０〜８０℃における金の析出速度が０．２〜１．０μｍ／時であり、０．３６ｄｍ２／Ｌのめっき負荷で６５℃において１時間めっきを行った後に室温で１日放置したときの異常析出成分が０％であることを特徴とする無電解金めっき液を提供する。 In the present invention, the deposition rate of gold at a pH of 6 to 8 and a liquid temperature of 60 to 80 ° C. is 0.2 to 1.0 μm / hour, and plating is performed at 65 ° C. for 1 hour at a plating load of 0.36 dm 2 / L. The electroless gold plating solution is characterized in that the abnormal precipitation component is 0% when left at room temperature for 1 day after performing the above.
本発明は、更に、無電解金めっき液中に被めっき体を浸漬して該被めっき体表面に金被膜を形成させる無電解金めっき方法において、無電解金めっき液は上記本発明の無電解金めっき液であることを特徴とする無電解金めっき方法を提供する。かかる方法においては、無電解金めっき液のｐＨを６〜８とすることが好ましく、金被膜の形成を液温６０〜８０℃の無電解めっき液で行うことが好ましい。かかる方法を適用することにより、様々な被めっき体に対して中性且つ低温で無電解金めっきが可能となる。 The present invention further relates to an electroless gold plating method in which a body to be plated is immersed in an electroless gold plating solution to form a gold film on the surface of the body to be plated. An electroless gold plating method characterized by being a gold plating solution. In such a method, the pH of the electroless gold plating solution is preferably 6 to 8, and the gold film is preferably formed with an electroless plating solution having a liquid temperature of 60 to 80 ° C. By applying this method, it is possible to perform electroless gold plating on various objects to be plated at neutral and low temperatures.
本発明によれば、ｐＨ６〜８程度の中性領域において液温６０〜８０℃程度の低温でも、充分な金の析出速度を発揮する無電解金めっき液であって、めっき液の安定性が特に優れた無電解金めっき液を提供することが可能になる。また、かかる無電解金めっき液を用いた無電解金めっき方法を提供することが可能になる。 According to the present invention, an electroless gold plating solution that exhibits a sufficient gold deposition rate even at a low temperature of about 60 to 80 ° C. in a neutral region of about pH 6 to 8, and the stability of the plating solution is high. It becomes possible to provide a particularly excellent electroless gold plating solution. It is also possible to provide an electroless gold plating method using such an electroless gold plating solution.
本発明の無電解金めっき液は、上述のように、必須成分として、金塩、還元剤及び重金属塩を含有している、先ず、かかる必須成分の実施の形態について説明する。 As described above, the electroless gold plating solution of the present invention contains a gold salt, a reducing agent, and a heavy metal salt as essential components. First, an embodiment of the essential component will be described.
（金塩）
本発明の無電解金めっき液に使用可能な金塩としては、シアン系金塩及び非シアン系金塩が挙げられる。シアン系金塩としては、シアン化第一金カリウム及びやシアン化第二金カリウムが例示でき、非シアン系金塩としては、塩化金酸塩、亜硫酸金塩、チオ硫酸金塩、チオリンゴ酸金塩が例示可能である。金塩は１種のみ用いてもよく、２種以上を組み合わせて用いてもよい。
(Gold salt)
Examples of the gold salt that can be used in the electroless gold plating solution of the present invention include cyan gold salts and non-cyan gold salts. Examples of cyanide gold salts include potassium primary cyanide and potassium secondary gold cyanide. Examples of non-cyanide gold salts include chloroaurate, goldsulfite, gold thiosulfate, gold thiomalate. Salts can be exemplified. Only 1 type may be used for gold salt and it may use it in combination of 2 or more type.
金塩としては、亜硫酸金塩及びチオ硫酸金塩が好ましく、その含有量としては金として１〜１０ｇ／Ｌの範囲であることが好ましい。金の含有量が１ｇ／Ｌ未満であると、金の析出反応が低下し、１０ｇ／Ｌを超えると、めっき液の安定性が低下すると共に、めっき液の持出により金消費量が多くなるため経済的に好ましくない。含有量は、２〜５ｇ／Ｌの範囲とすることがより好ましい。 As the gold salt, gold sulfite and gold thiosulfate are preferable, and the content thereof is preferably in the range of 1 to 10 g / L as gold. If the gold content is less than 1 g / L, the gold precipitation reaction decreases, and if it exceeds 10 g / L, the stability of the plating solution decreases and the amount of gold consumed increases due to the removal of the plating solution. Therefore, it is not preferable economically. The content is more preferably in the range of 2 to 5 g / L.
（還元剤）
本発明の無電解金めっき液において用いる還元剤は、下記一般式（Ｉ）で表される化合物（以下「化合物Ｉ」という。）である。
(Reducing agent)
The reducing agent used in the electroless gold plating solution of the present invention is a compound represented by the following general formula (I) (hereinafter referred to as “Compound I”).
化合物Ｉにおける、Ｒ１は水酸基又はアミノ基、Ｒ２、Ｒ３及びＲ４はそれぞれ独立に水酸基、アミノ基、水素原子又はアルキル基であるが、アルキル基としては、直鎖又は分岐状の炭素数１〜６のアルキル基が好ましく、直鎖又は分岐状の炭素数１〜４のアルキル基（メチル基、エチル基、ｔ−ブチル基等）がより好ましい。 In compound I, R 1 is a hydroxyl group or an amino group, and R 2 , R 3 and R 4 are each independently a hydroxyl group, an amino group, a hydrogen atom or an alkyl group, and the alkyl group is a linear or branched carbon. A C1-C6 alkyl group is preferable, and a linear or branched C1-C4 alkyl group (a methyl group, an ethyl group, t-butyl group, etc.) is more preferable.
化合物Ｉの具体例としては、例えばフェノール、ｏ−クレゾール、ｐ−クレゾール、ｏ−エチルフェノール、ｐ−エチルフェノール、ｔ−ブチルフェノール、ｏ−アミノフェノール、ｐ−アミノフェノール、ヒドロキノン、カテコール、ピロガロール、メチルヒドロキノン、アニリン、ｏ−フェニレンジアミン、ｐ−フェニレンジアミン、ｏ−トルイジン、ｐ−トルイジン、ｏ−エチルアニリン、ｐ−エチルアニリン等が挙げられ、これらの１種又は２種以上を用いることができる。 Specific examples of compound I include, for example, phenol, o-cresol, p-cresol, o-ethylphenol, p-ethylphenol, t-butylphenol, o-aminophenol, p-aminophenol, hydroquinone, catechol, pyrogallol, methyl Hydroquinone, aniline, o-phenylenediamine, p-phenylenediamine, o-toluidine, p-toluidine, o-ethylaniline, p-ethylaniline and the like can be used, and one or more of these can be used.
めっき液の安定性及び金の析出速度の観点からは、化合物Ｉは、下記一般式（ＩＩ）で表される化合物（以下「化合物ＩＩ」という。）であることが好ましい。 From the viewpoint of the stability of the plating solution and the deposition rate of gold, the compound I is preferably a compound represented by the following general formula (II) (hereinafter referred to as “compound II”).
化合物ＩＩにおいて、Ｒ２１は水酸基又はアミノ基、Ｒ２２は水素原子又は炭素数１〜４のアルキル基（メチル基、エチル基、ｔ−ブチル基等）である。化合物ＩＩの具体例としては、ｐ−フェニレンジアミン、メチルヒドロキノン、ヒドロキノン等が挙げられる。 In Compound II, R 21 is a hydroxyl group or an amino group, and R 22 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, t-butyl group, etc.). Specific examples of compound II include p-phenylenediamine, methylhydroquinone, hydroquinone and the like.
還元剤の含有量は、めっき液の全容量を基準として０．５〜５０ｇ／Ｌが好ましい。還元剤の含有量が、０．５ｇ／Ｌ未満であると、実用的な析出速度を得るのが困難になる。５０ｇ／Ｌを超えると、めっき液の安定性を確保できなくなる傾向にある。還元剤の含有量は、２〜１０ｇ／Ｌとすることがより好ましい。 The content of the reducing agent is preferably 0.5 to 50 g / L based on the total capacity of the plating solution. When the content of the reducing agent is less than 0.5 g / L, it is difficult to obtain a practical deposition rate. If it exceeds 50 g / L, the stability of the plating solution tends not to be ensured. The content of the reducing agent is more preferably 2 to 10 g / L.
（重金属塩）
本発明においては、上述した金塩と還元剤との組み合わせに重金属塩を添加したことが大きな特徴である。重金属塩を添加することにより、ｐＨ６〜８程度の中性領域において液温６０〜８０℃程度の低温でも、実用上充分な金の析出速度（０．２μｍ／時以上）が可能になる。すなわち、重金属塩は析出速度促進剤として機能する。また、従来技術では不可能であった優れためっき液安定性も得られるようになる。
(Heavy metal salt)
In the present invention, a major feature is that a heavy metal salt is added to the combination of the gold salt and the reducing agent described above. By adding a heavy metal salt, a practically sufficient gold deposition rate (0.2 μm / hour or more) is possible even at a low temperature of about 60 to 80 ° C. in a neutral region of about pH 6 to 8. That is, the heavy metal salt functions as a deposition rate accelerator. In addition, excellent plating solution stability, which was impossible with the prior art, can be obtained.
析出速度を更に促進する観点からは、重金属塩は、タリウム塩、鉛塩、砒素塩、アンチモン塩、テルル塩及びビスマス塩からなる群より選ばれる少なくとも１つであることが好ましい。 From the viewpoint of further promoting the deposition rate, the heavy metal salt is preferably at least one selected from the group consisting of thallium salt, lead salt, arsenic salt, antimony salt, tellurium salt and bismuth salt.
タリウム塩としては、硫酸タリウム塩、塩化タリウム塩、酸化タリウム塩、硝酸タリウム塩等の無機化合物塩、マロン酸二タリウム塩等の有機錯体塩が挙げられ、鉛塩としては、硫酸鉛塩、硝酸鉛塩等の無機化合物塩、酢酸鉛等の有機錯体塩が挙げられる。 Examples of the thallium salt include inorganic compound salts such as thallium sulfate salt, thallium chloride salt, thallium oxide salt, and thallium nitrate salt, and organic complex salts such as dithallium malonate salt. Lead salts include lead sulfate salt, nitric acid salt, and the like. Examples include inorganic compound salts such as lead salts and organic complex salts such as lead acetate.
また、砒素塩としては、亜砒酸塩、砒酸塩、三酸化砒素等の無機化合物塩や有機錯体塩が挙げられ、アンチモン塩としては、酒石酸アンチモニル塩等の有機錯体塩、塩化アンチモン塩類、オキシ硫酸アンチモン塩、三酸化アンチモン等の無機化合物塩類が挙げられる。 Arsenic salts include inorganic compound salts such as arsenite, arsenate, and arsenic trioxide, and organic complex salts. Antimony salts include organic complex salts such as antimony tartrate, antimony chloride salts, and antimony oxysulfate. And inorganic compound salts such as salts and antimony trioxide.
そして、テルル塩としては、亜テルル酸塩、テルル酸塩等の無機化合物塩や有機錯体塩が挙げられ、ビスマス塩としては、硫酸ビスマス（ＩＩＩ）、塩化ビスマス（ＩＩＩ）、硝酸ビスマス（ＩＩＩ）等の無機化合物塩、しゅう酸ビスマス（ＩＩＩ）等の有機錯体塩が挙げられる。 Examples of tellurium salts include inorganic compound salts and organic complex salts such as tellurite and tellurate. Examples of bismuth salts include bismuth sulfate (III), bismuth chloride (III), and bismuth nitrate (III). And an inorganic complex salt such as bismuth (III) oxalate.
本発明においては、重金属化合物塩として、タリウム塩（好ましくは、タリウム無機化合物塩又はタリウム有機錯体塩）を用いることが特に好ましい。 In the present invention, it is particularly preferable to use a thallium salt (preferably a thallium inorganic compound salt or a thallium organic complex salt) as the heavy metal compound salt.
上述した重金属塩は１種又は２種以上を用いることができるが、その添加量の合計はめっき液全容量を基準として１〜１００ｐｐｍが好ましく、１〜１０ｐｐｍがより好ましい。１ｐｐｍ未満では、析出速度向上効果が充分でない場合があり、１００ｐｐｍを超す場合はめっき液安定性が悪くなる傾向にある。 Although the heavy metal salt mentioned above can use 1 type (s) or 2 or more types, 1-100 ppm is preferable on the basis of the plating solution total capacity, and 1-10 ppm is more preferable. If it is less than 1 ppm, the effect of improving the deposition rate may not be sufficient, and if it exceeds 100 ppm, the stability of the plating solution tends to deteriorate.
本発明の無電解金めっき液は、上述した金塩、還元剤及び重金属塩に加えて、錯化剤、ｐＨ緩衝剤及び金属イオン隠蔽剤の少なくとも一つを含有することが好ましく、これらの全てを含有することがより好ましい。以下、かかる成分について説明する。 The electroless gold plating solution of the present invention preferably contains at least one of a complexing agent, a pH buffering agent and a metal ion concealing agent in addition to the above-described gold salt, reducing agent and heavy metal salt. It is more preferable to contain. Hereinafter, such components will be described.
（錯化剤）
本発明の無電解金めっき液には、錯化剤を含有させることが好ましく、当該成分を含有せしめることにより、金イオン（Ａｕ＋）が安定的に錯体化されて、Ａｕ＋の不均化反応（３Ａｕ＋＝Ａｕ３＋＋２Ａｕ）の発生を低下させ、液が安定に保たれるという効果が得られる。錯化剤は、１種のみを用いてもよく２種類以上を組み合わせて用いてもよく、好適な錯化剤としては、シアン系錯化剤及び／又は非シアン系錯化剤が挙げられる。
(Complexing agent)
The electroless gold plating solution of the present invention preferably contains a complexing agent. By containing the component, gold ions (Au + ) are stably complexed, and Au + is disproportionated. The generation of the reaction (3Au + = Au 3+ + 2Au) is reduced, and the effect that the liquid is kept stable is obtained. Only one type of complexing agent may be used, or two or more types may be used in combination, and suitable complexing agents include cyan complexing agents and / or non-cyanide complexing agents.
シアン系錯化剤としては、シアン化ナトリウム、シアン化カリウム等のシアン塩が挙げられ、非シアン系錯化剤としては亜硫酸塩、チオ硫酸塩、チオリンゴ酸塩が挙げられる。 Examples of the cyanate complexing agent include cyanate salts such as sodium cyanide and potassium cyanide, and examples of the non-cyanide complexing agent include sulfite, thiosulfate, and thiomalate.
錯化剤としては、亜硫酸塩、チオ硫酸塩が好ましく、錯化剤の含有量は、めっき液の全容量を基準として１〜２００ｇ／Ｌが好ましい。錯化剤の含有量が１ｇ／Ｌ未満であると、金錯化力が低下し安定性を低下する傾向にある。また、２００ｇ／Ｌを超えると、めっき液の安定性が向上するが、液中に再結晶が発生し経済的に負担となる。錯化剤の含有量は、２０〜５０ｇ／Ｌとすることがより好ましい。 As the complexing agent, sulfites and thiosulfates are preferable, and the content of the complexing agent is preferably 1 to 200 g / L based on the total capacity of the plating solution. When the content of the complexing agent is less than 1 g / L, the gold complexing power tends to be low and the stability tends to be low. On the other hand, if it exceeds 200 g / L, the stability of the plating solution is improved, but recrystallization occurs in the solution, resulting in an economical burden. The content of the complexing agent is more preferably 20 to 50 g / L.
（ｐＨ緩衝剤）
本発明の無電解金めっき液には、ｐＨ緩衝剤を含有させることが好ましく、当該成分を含有せしめることにより、析出速度を所望の値に調整することができ、ｐＨ等を一定に保つこともできる。ｐＨ緩衝剤は、１種のみを用いてもよく２種類以上を組み合わせて用いてもよい。好適なｐＨ緩衝剤としては、リン酸塩、酢酸塩、炭酸塩、硼酸塩、クエン酸塩、硫酸塩等が挙げられ、これらの中では、硼酸塩及び／又は硫酸塩が特に好ましい。
(PH buffer)
The electroless gold plating solution of the present invention preferably contains a pH buffering agent, and by adding the component, the deposition rate can be adjusted to a desired value, and the pH and the like can be kept constant. it can. Only one type of pH buffer may be used, or two or more types may be used in combination. Suitable pH buffering agents include phosphates, acetates, carbonates, borates, citrates, sulfates, etc. Among these, borates and / or sulfates are particularly preferable.
錯化剤の含有量は、めっき液の全容量を基準として１〜１００ｇ／Ｌが好ましい。錯化剤の含有量が１ｇ／Ｌ未満であると、ｐＨの緩衝効果がなくめっき浴の状態が変化する場合があり、１００ｇ／Ｌを超えると、めっき液中で再結晶化が進行する傾向にある。錯化剤の含有量は、２０〜５０ｇ／Ｌの範囲とすることがより好ましい。 The content of the complexing agent is preferably 1 to 100 g / L based on the total capacity of the plating solution. If the content of the complexing agent is less than 1 g / L, there may be no pH buffering effect and the state of the plating bath may change. If it exceeds 100 g / L, recrystallization tends to proceed in the plating solution. It is in. The content of the complexing agent is more preferably in the range of 20 to 50 g / L.
（金属イオン隠蔽剤）
本発明の無電解金めっき液には、金属イオン隠蔽剤を含有させることが好ましく、当該成分を含有せしめることにより、以下の効果が得られる。すなわち、作業中にめっき装置の錆や金属破片等の持込み等による不純物の混入や、被めっき物の付きまわり不足による下地金属のめっき液中への混入などによって、銅、ニッケル、鉄などの不純物イオンが混入し、めっき液の異常反応が進行して、めっき液の分解が発生した場合に、このような異常反応を抑制することが可能になる。
(Metal ion concealing agent)
The electroless gold plating solution of the present invention preferably contains a metal ion concealing agent, and the following effects can be obtained by including the component. That is, impurities such as copper, nickel, iron, etc. due to contamination of the plating equipment during work by bringing in rust, metal fragments, etc. or contamination of the base metal into the plating solution due to insufficient coverage of the object to be plated When the ions are mixed and the abnormal reaction of the plating solution proceeds and the decomposition of the plating solution occurs, such an abnormal reaction can be suppressed.
金属イオン隠蔽剤としては、ベンゾトリアゾール系化合物を用いることができ、かかる化合物としては、ベンゾトリアゾールナトリウム、ベンゾトリアゾールカリウム、テトラヒドロベンゾトリアゾール、メチルベンゾトリアゾール、ニトロベンゾトリアゾール等が例示できる。 As the metal ion masking agent, a benzotriazole-based compound can be used, and examples of such a compound include benzotriazole sodium, benzotriazole potassium, tetrahydrobenzotriazole, methylbenzotriazole, nitrobenzotriazole and the like.
金属イオン隠蔽剤の含有量は、めっき液の全容量を基準として０．５〜１００ｇ／Ｌが好ましい。金属イオン隠蔽剤の含有量が０．５ｇ／Ｌ未満であると、不純物の隠蔽効果が少なく、充分な液安定性を確保できない傾向にある。一方、１００ｇ／Ｌを超えると、めっき液中に再結晶化が生じる場合がある。コスト及び効果を考慮すると、金属イオン隠蔽剤の含有量は、２〜１０ｇ／Ｌとすることがより好ましい。 The content of the metal ion concealing agent is preferably 0.5 to 100 g / L based on the total capacity of the plating solution. When the content of the metal ion concealing agent is less than 0.5 g / L, the effect of concealing impurities is small, and sufficient liquid stability tends not to be ensured. On the other hand, if it exceeds 100 g / L, recrystallization may occur in the plating solution. In consideration of cost and effect, the content of the metal ion concealing agent is more preferably 2 to 10 g / L.
（無電解金めっき液のｐＨ）
本発明の無電解金めっき液のｐＨは５〜１０であることが好ましい。無電解金めっき液のｐＨが５未満であると、めっき液の金錯化剤である亜硫酸塩や、チオ硫酸塩が分解し、毒性の亜硫酸ガスが発生するおそれがある。また、ｐＨが１０を超えると、めっき液の安定性が低下する傾向にある。無電解金めっき液のｐＨは、６〜８がより好ましく、７〜８が更に好ましい。
(PH of electroless gold plating solution)
The pH of the electroless gold plating solution of the present invention is preferably 5-10. If the pH of the electroless gold plating solution is less than 5, the sulfite or thiosulfate that is the gold complexing agent of the plating solution may be decomposed to generate toxic sulfite gas. Moreover, when pH exceeds 10, it exists in the tendency for stability of a plating solution to fall. The pH of the electroless gold plating solution is more preferably 6-8, and still more preferably 7-8.
（無電解金めっき方法）
次に、本発明の無電解金めっき方法について説明する。本発明の無電解金めっき方法は、上述した本発明の無電解金めっき液中に被めっき体を浸漬して該被めっき体表面に金被膜を形成させることを特徴とするものである。
(Electroless gold plating method)
Next, the electroless gold plating method of the present invention will be described. The electroless gold plating method of the present invention is characterized in that a body to be plated is immersed in the electroless gold plating solution of the present invention described above to form a gold film on the surface of the body to be plated.
かかる方法においては、無電解金めっき液のｐＨは５〜１０が好ましく、６〜８がより好ましく、７〜８が更に好ましい。また、金被膜の形成を液温６０〜８０℃の無電解めっき液で行うことが好ましく、液温は６５℃〜８０℃とすることがより好ましい。 In such a method, the pH of the electroless gold plating solution is preferably 5 to 10, more preferably 6 to 8, and still more preferably 7 to 8. Further, the gold film is preferably formed with an electroless plating solution having a solution temperature of 60 to 80 ° C., and the solution temperature is more preferably 65 to 80 ° C.
次に、実施例により本発明を具体的に説明するが、本発明はこれによって制限されるものではない。 Next, although an Example demonstrates this invention concretely, this invention is not restrict | limited by this.
［試料の作成］
めっき試験用サンプルには３ｃｍ×３ｃｍ×０．３ｍｍの圧延銅板を使用し、表面の錆や有機物等を除去するために、酸性脱脂であるＺ−２００（ワールドメタル株式会社製、商品名）に４５℃で３分間処理した。更に、余分な界面活性剤を除去するために湯洗（４５℃、純水）を１分間実施した。その後、水洗処理を１分間行った。更に、表面の形状を均一化するために、過硫酸アンモニウム溶液（１２０ｇ／Ｌ）に室温で３分間浸漬処理するソフトエッチング処理を行った。その後、水洗処理を１分間行った。次いで、表面の酸化銅を除去するために硫酸（１０％）に室温で１分間浸漬処理を行い、その後、水洗処理を１分間行った後、置換パラジウムめっきであるＳＡ−１００（日立化成工業株式会社製、商品名）に室温で５分間浸漬処理を行った。その後、水洗処理を１分間行った。
[Sample preparation]
A 3cm x 3cm x 0.3mm rolled copper plate is used for the plating test sample, and Z-200 (trade name, manufactured by World Metal Co., Ltd.), which is acidic degreasing, is used to remove rust and organic matter on the surface. Treated at 45 ° C. for 3 minutes. Furthermore, in order to remove excess surfactant, hot water washing (45 degreeC, pure water) was implemented for 1 minute. Then, the water washing process was performed for 1 minute. Furthermore, in order to make the shape of the surface uniform, a soft etching treatment was performed in which the substrate was immersed in an ammonium persulfate solution (120 g / L) for 3 minutes at room temperature. Then, the water washing process was performed for 1 minute. Next, in order to remove the copper oxide on the surface, it was immersed in sulfuric acid (10%) at room temperature for 1 minute, then washed with water for 1 minute, and then replaced with SA-100 (Hitachi Chemical Co., Ltd.). The company-made product name) was immersed for 5 minutes at room temperature. Then, the water washing process was performed for 1 minute.
次に、無電解Ｎｉ−Ｐめっき液であるＮＩＰＳ−１００（日立化成工業株式会社製、商品名）に８５℃で、２５分間浸漬処理をしてニッケル−リンのめっき皮膜を５μｍ程度に行い、水洗処理を１分間行った後、置換金めっき液であるＨＧＳ−５００（日立化成工業株式会社製、商品名）に８５℃で、１０分間浸漬処理して、０．０５〜０．１μｍ程度の膜厚の金めっき膜を形成させて水洗処理を１分間行い、更に、以下の無電解金めっきを行って評価した。また、無電解金めっき液の評価用めっき槽には、ポリプロピレン製の樹脂槽を使用した。 Next, an immersion treatment is performed at 85 ° C. for 25 minutes in NIPS-100 (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is an electroless Ni—P plating solution, and a nickel-phosphorous plating film is formed to about 5 μm. After washing with water for 1 minute, it was immersed in HGS-500 (trade name, manufactured by Hitachi Chemical Co., Ltd.) which is a displacement gold plating solution at 85 ° C. for 10 minutes, and was about 0.05 to 0.1 μm. A gold plating film having a thickness was formed and washed with water for 1 minute, and further evaluated by performing the following electroless gold plating. Moreover, the resin tank made from a polypropylene was used for the plating tank for evaluation of an electroless gold plating solution.
［金めっき液安定性評価方法］
（金めっき液安定性評価用実験槽の洗浄方法）
[Gold plating solution stability evaluation method]
(Cleaning method of the experimental tank for gold plating solution stability evaluation)
金めっき液安定性評価方法には、ＰＰ（ポリプロピレン製）樹脂製の１Ｌビーカーをめっき槽として使用した。また、槽内に付着している不純物を除去するために、実験前に槽内を王水（１：３＝硝酸：塩酸、５０％に純水で希釈）で６時間以上、常温で洗浄した後、水洗、純水洗を順次、充分行い、８０℃で乾燥して実験に使用した。 In the gold plating solution stability evaluation method, a 1 L beaker made of PP (polypropylene) resin was used as a plating tank. In order to remove impurities adhering to the tank, the inside of the tank was washed with aqua regia (1: 3 = nitric acid: hydrochloric acid, diluted to 50% with pure water) for 6 hours or more at room temperature before the experiment. Thereafter, washing with water and washing with pure water were sufficiently carried out successively, dried at 80 ° C. and used for the experiment.
（金めっき液安定性評価方法）
金めっき液安定性は、３条件に分類して評価した。まず（１）上記めっき槽を使用して、めっき前に液温度を６５℃に設定して１時間放置した時の金めっき液の安定性を評価した。次に（２）昇温後０．３６ｄｍ２／Ｌのめっき負荷で１時間（６５℃）めっき処理した。次いで（３）そのめっき液を自然冷却し、室温で金めっき液を１日放置し、異常析出物がめっき槽の底面を覆う面積の割合（槽内異常析出発生面積（％））、すなわち異常析出成分（％）でめっき液安定性を評価した。なお、評価基準は表１に示す通りである。
(Gold plating solution stability evaluation method)
The gold plating solution stability was classified into three conditions and evaluated. First, (1) using the above plating tank, the stability of the gold plating solution was evaluated when the solution temperature was set to 65 ° C. and left for 1 hour before plating. Next, (2) after the temperature rise, plating was performed for 1 hour (65 ° C.) with a plating load of 0.36 dm 2 / L. Next, (3) the plating solution is naturally cooled, the gold plating solution is allowed to stand at room temperature for one day, and the ratio of the area where the abnormal deposit covers the bottom of the plating tank (abnormal deposition occurrence area (%) in the tank), that is, abnormal The plating solution stability was evaluated by the precipitation component (%). The evaluation criteria are as shown in Table 1.
［皮膜外観及びめっき付き回り不良評価方法］
めっき外観、めっき付き回り不良については、電気金めっき皮膜（０．５μｍ相当）に近い外観を標準とした。また、めっき付き回り性につては、めっき端部を顕微鏡（２０〜５０倍相当）で目視観察して評価した。
[Film appearance and plating failure evaluation method]
As for the plating appearance and plating failure, the appearance close to an electrogold plating film (corresponding to 0.5 μm) was standard. In addition, the plating endurance was evaluated by visually observing the plating end with a microscope (equivalent to 20 to 50 times).
［無電解金めっき液の作製及び評価］
（実施例１〜４）
表２に示す組成になるように実施例１〜４の無電解金めっき液を作製し、上述した評価方法に基づいて評価を行った。なお、実施例１〜４は、還元剤であるヒドロキノン濃度を３ｇ／Ｌに一定にして実験を行った。また、析出速度促進剤である重金属塩として硝酸タリウムとして用い、実施例１〜４の無電解金めっき液におけるＴｌ（タリウム）イオンは、それぞれ１、３、５、１０ｐｐｍとなるようにした。
[Production and evaluation of electroless gold plating solution]
(Examples 1-4)
The electroless gold plating solutions of Examples 1 to 4 were prepared so as to have the compositions shown in Table 2, and evaluated based on the evaluation method described above. In Examples 1 to 4, the concentration of hydroquinone, which is a reducing agent, was fixed to 3 g / L, and experiments were conducted. Moreover, it used as thallium nitrate as a heavy metal salt which is a precipitation rate accelerator, and Tl (thallium) ions in the electroless gold plating solutions of Examples 1 to 4 were 1, 3, 5, and 10 ppm, respectively.
析出速度、皮膜外観、めっき付き回り不良及び金めっき液安定性について表２にまとめて示すが、タリウムイオン濃度が１ｐｐｍで析出速度の増加が見られ、未添加浴との比較で約２倍の析出速度向上が確認できた。また、めっき皮膜の外観は均一なレモンイエローで、付き回り不良の発生もなく良好であった。また、めっき中やめっき後の金めっき液安定性も良好であった。更に、タリウムイオンの含有量が３、５、１０ｐｐｍになるにしたがって、析出速度は増加し、１０ｐｐｍの添加で０．３６μｍ／時の析出速度（未添加時の約３倍）を示した。しかも、めっき皮膜の外観は均一なレモンイエローで、析出速度の増加に伴うめっき付き回り不良の発生もなく良好であった。また、めっき中やめっき後の液安定性も良好であった。 Table 2 summarizes the deposition rate, film appearance, plating failure, and stability of the gold plating solution. The deposition rate increased when the thallium ion concentration was 1 ppm, approximately twice that of the unadded bath. An improvement in deposition rate was confirmed. Further, the appearance of the plating film was uniform lemon yellow, and it was good without occurrence of poor attachment. Also, the stability of the gold plating solution during and after plating was good. Furthermore, as the thallium ion content became 3, 5, and 10 ppm, the deposition rate increased, and the addition rate of 10 ppm showed a deposition rate of 0.36 μm / hour (about three times that when no addition was made). Moreover, the appearance of the plating film was uniform lemon yellow, and it was good without the occurrence of defective plating with the increase in the deposition rate. Also, the liquid stability during and after plating was good.
（実施例５〜８）
表３に示す組成になるように実施例５〜８の無電解金めっき液を作製し、上述した評価方法に基づいて評価を行った。実施例５〜８は、還元剤であるヒドロキノン濃度を更に多い５ｇ／Ｌに一定にして実験を行った。また、析出速度促進剤である重金属塩として硝酸タリウムとして用い、実施例５〜８の無電解金めっき液におけるＴｌ（タリウム）イオンは、それぞれ１、３、５、１０ｐｐｍなるようにした。
(Examples 5 to 8)
Electroless gold plating solutions of Examples 5 to 8 were prepared so as to have the compositions shown in Table 3, and evaluated based on the evaluation method described above. In Examples 5 to 8, experiments were conducted with the concentration of hydroquinone as a reducing agent being kept constant at 5 g / L. Moreover, it used as thallium nitrate as a heavy metal salt which is a deposition rate accelerator, and Tl (thallium) ions in the electroless gold plating solutions of Examples 5 to 8 were 1, 3, 5, and 10 ppm, respectively.
析出速度、皮膜外観、めっき付き回り不良及び金めっき液安定性について表３にまとめて示すが、タリウムイオン濃度が１ｐｐｍで析出速度の増加が見られ、実施例１と同様に未添加浴（比較例４）との比較で約２倍の析出速度向上が確認できた。また、めっき皮膜の外観は均一なレモンイエローで、めっき付き回り不良の発生もなく良好であった。また、めっき中やめっき後の金めっき液安定性も良好であった。更に、タリウムイオンの含有量が３、５、１０ｐｐｍになるにしたがって、析出速度は増加し、ヒドロキノン５ｇ／Ｌ、タリウム１０ｐｐｍ、ｐＨ７．５の条件で０．５６μｍ／時の析出速度（未添加時の約３から４倍）を示した。しかも、めっき皮膜の外観は均一なレモンイエローで、析出速度の増加に伴うめっき付き回り不良の発生もなく良好であった。また、めっき中やめっき後の液安定性も良好であった。 The deposition rate, film appearance, plating failure, and gold plating solution stability are summarized in Table 3. As shown in Table 1, an increase in the deposition rate was observed when the thallium ion concentration was 1 ppm. Compared with Example 4), it was confirmed that the deposition rate was improved about twice. Also, the appearance of the plating film was uniform lemon yellow, and it was good without the occurrence of defects with plating. Also, the stability of the gold plating solution during and after plating was good. Further, as the thallium ion content becomes 3, 5, and 10 ppm, the deposition rate increases, and the deposition rate of 0.56 μm / hr under conditions of hydroquinone 5 g / L, thallium 10 ppm, pH 7.5 (when not added) About 3 to 4 times greater). Moreover, the appearance of the plating film was uniform lemon yellow, and it was good without the occurrence of defective plating with the increase in the deposition rate. Also, the liquid stability during and after plating was good.
（実施例９〜１２）
表４に示す組成になるように実施例９〜１２の無電解金めっき液を作製し、上述した評価方法に基づいて評価を行った。金めっき液組成は、実施例５〜８と同様に、還元剤であるヒドロキノンを５ｇ／Ｌ、ｐＨを液安定性の良い７．５で、析出速度促進剤としてタリウムイオンを１、３、５、１０ｐｐｍの条件で、めっき温度を８０℃で実験を行った。
(Examples 9 to 12)
The electroless gold plating solutions of Examples 9 to 12 were prepared so as to have the compositions shown in Table 4, and evaluated based on the evaluation method described above. As in Examples 5 to 8, the gold plating solution composition is 5 g / L of hydroquinone as a reducing agent, pH is 7.5 with good liquid stability, and thallium ions are 1, 3, 5 as a deposition rate accelerator. The experiment was conducted at a plating temperature of 80 ° C. under the condition of 10 ppm.
析出速度、皮膜外観、めっき付き回り不良及び金めっき液安定性について表４にまとめて示すが、めっき温度を８０℃にすると析出速度は更に速くなり、１．０ｐｐｍの添加で約０．５μｍ／時の析出速度を示した。また、更に添加量を多くすると１０．０ｐｐｍの添加で１．１５μｍ／時の実用析出速度を示した。また、めっき外観については、実施例９〜１２の条件ではすべて、均一なレモンイエローの外観を示し、めっき付き回り不良や、析出ムラの発生もなく良好な結果であった。金めっき液の安定性については、めっき前、めっき中、めっき後、めっき後（１日以上）も良好な結果であった。 The deposition rate, film appearance, plating failure, and gold plating solution stability are summarized in Table 4. When the plating temperature is 80 ° C., the deposition rate is further increased, and the addition of 1.0 ppm is about 0.5 μm / The deposition rate at the time was shown. Further, when the addition amount was further increased, a practical precipitation rate of 1.15 μm / hour was exhibited with addition of 10.0 ppm. As for the plating appearance, all of the conditions of Examples 9 to 12 showed a uniform lemon yellow appearance, which was a good result with no defective plating around and no occurrence of precipitation unevenness. Regarding the stability of the gold plating solution, good results were obtained before plating, during plating, after plating, and after plating (1 day or more).
（比較例１〜４）
表５に示す組成になるように比較例１〜４の無電解金めっき液を作製し、上述した評価方法に基づいて評価を行った。比較例１、２、３及び４にはそれぞれ、還元剤としてヒドロキノンを０、１、３及び５ｇ／Ｌ添加して金めっきを行った。
(Comparative Examples 1-4)
The electroless gold plating solutions of Comparative Examples 1 to 4 were prepared so as to have the compositions shown in Table 5, and evaluated based on the evaluation method described above. Comparative Examples 1, 2, 3 and 4 were subjected to gold plating by adding hydroquinone as a reducing agent at 0, 1, 3 and 5 g / L, respectively.
析出速度、皮膜外観、めっき付き回り不良及び金めっき液安定性について表５にまとめて示すが、還元剤であるヒドロキノンを添加しない場合は、１時間めっき液中に浸漬しても、ほとんど金膜厚の増加がなく、析出が進行しない結果となった。一方、還元剤としてヒドロキノンを添加した場合、析出膜厚が除々に増加し、ヒドロキノン５ｇ／Ｌで０．１５２μｍ／時（未添加時の約２．５倍）の析出膜厚を得ることができた。 Table 5 summarizes the deposition rate, film appearance, plating failure, and stability of the gold plating solution. When hydroquinone as a reducing agent is not added, even if immersed in the plating solution for 1 hour, it is almost a gold film. There was no increase in thickness, and precipitation did not proceed. On the other hand, when hydroquinone is added as the reducing agent, the deposited film thickness gradually increases, and a deposited film thickness of 0.152 μm / hour (about 2.5 times that when no additive is added) can be obtained at 5 g / L hydroquinone. It was.
また、比較例２〜４の条件では、めっき皮膜の外観は均一なレモンイエローで、付き回り不良の発生もなく良好であった。また、めっき中やめっき後の液安定性も良好であった。しかし、析出速度が実用的な無電解金めっき液（約０．２〜１．０μｍ／時、又はこれ以上）と比較して析出速度が遅い結果となった。このためパッケージ基板等のワイヤボンディング基板には、生産性が悪く問題であることがわかった。 Moreover, on the conditions of Comparative Examples 2-4, the external appearance of the plating film was uniform lemon yellow, and it was good without the occurrence of a dipping failure. Also, the liquid stability during and after plating was good. However, the deposition rate was slower than that of a practical electroless gold plating solution (about 0.2 to 1.0 μm / hour or more). For this reason, it has been found that wire bonding substrates such as package substrates are problematic because of poor productivity.
（比較例５〜８）
表６に示す組成になるように比較例５〜８の無電解金めっき液を作製し、上述した評価方法に基づいて評価を行った。析出速度、皮膜外観、めっき付き回り不良及び金めっき液安定性について表６にまとめて示すが、金めっき液のｐＨを１ＮのＮａＯＨを使用して、それぞれ８、９、１０と変化させると、ｐＨ９の条件で析出速度が著しく増加し、約０．８μｍ／時を示した。しかし、ｐＨ９と１０の条件では、めっき液が非常に不安定で昇温中に、めっき槽内で異常析出が発生して通常に使用することが困難な結果となった。またｐＨ８．０の条件（比較例５）でも、めっき後１日経過すると、めっき槽内の一部に異常析出が発生する結果となった。
(Comparative Examples 5 to 8)
Electroless gold plating solutions of Comparative Examples 5 to 8 were prepared so as to have the compositions shown in Table 6, and evaluated based on the evaluation method described above. Table 6 summarizes the deposition rate, film appearance, plating failure, and gold plating solution stability. When the pH of the gold plating solution is changed to 8, 9, and 10 using 1N NaOH, Under the condition of pH 9, the deposition rate increased remarkably and showed about 0.8 μm / hour. However, under the conditions of pH 9 and 10, the plating solution was very unstable and abnormal precipitation occurred in the plating tank during the temperature rise, resulting in difficulty in normal use. Further, even under the condition of pH 8.0 (Comparative Example 5), abnormal deposition occurred in a part of the plating tank after 1 day from the plating.
更に、めっき外観については、ｐＨ８の条件ではレモンイエローの均一な表面であったが、ｐＨ９と１０については赤褐色の外観不良になる結果となった。また、めっき付き回り性については、比較例５、６、７の条件では問題無い結果となった。比較例８については、比較例６と同様にｐＨ９．０で、めっき温度を８０℃で実験したが、めっき外観が赤褐色で悪く、液安定性は６５℃と比較して更に悪くなり、めっき前に液中の金イオンの消費が多く、析出速度が６５℃の条件と変わらない結果となった。 Further, the plating appearance was a uniform surface of lemon yellow under the condition of pH 8, but the results of red and brown appearance were poor at pH 9 and 10. In addition, with regard to the wraparound property with plating, there was no problem under the conditions of Comparative Examples 5, 6, and 7. As for Comparative Example 8, the experiment was conducted at pH 9.0 and the plating temperature of 80 ° C. as in Comparative Example 6, but the plating appearance was poor reddish brown and the liquid stability was further deteriorated compared to 65 ° C. In addition, the consumption of gold ions in the liquid was large, and the deposition rate was the same as that at 65 ° C.
以上の結果から本発明の無電解金めっき液は、重金属塩の添加によって、還元剤であるヒドロキノンの析出効率を高めることが可能となり、しかも、実用的な析出速度（０．２〜１．０μｍ／時）が得られ、安定性と均一なレモンイエローの皮膜外観を有する無電解金めっきが可能であることがわかった。また、液のｐＨが中性付近（６〜８）で、かつ低い温度条件（６０〜８０℃）で使用可能なため、金めっき液の安定性が低く、大量生産が不可能なため実用化されていなかった中性での無電解金めっきが可能となり、適用できる材料や電子部品等の範囲は大幅に拡大される。 From the above results, the electroless gold plating solution of the present invention can increase the deposition efficiency of hydroquinone, which is a reducing agent, by adding a heavy metal salt, and also has a practical deposition rate (0.2 to 1.0 μm). It was found that electroless gold plating having a stable and uniform lemon yellow film appearance is possible. Also, since the pH of the solution is near neutral (6-8) and can be used under low temperature conditions (60-80 ° C), the gold plating solution is low in stability and cannot be mass-produced. The neutral electroless gold plating that has not been performed becomes possible, and the range of applicable materials and electronic parts is greatly expanded.
Claims (14)
前記無電解金めっき液は、請求項１〜１１のいずれか一項に記載の無電解金めっき液であることを特徴とする無電解金めっき方法。 In the electroless gold plating method of immersing the object to be plated in an electroless gold plating solution to form a gold film on the surface of the object to be plated,
The electroless gold plating solution according to any one of claims 1 to 11, wherein the electroless gold plating solution is an electroless gold plating method.
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