JP5170681B2

JP5170681B2 - Electric aluminum plating solution and aluminum plating film

Info

Publication number: JP5170681B2
Application number: JP2008259192A
Authority: JP
Inventors: 裕之星
Original assignee: Hitachi Metals Ltd
Current assignee: Hitachi Metals Ltd
Priority date: 2008-10-06
Filing date: 2008-10-06
Publication date: 2013-03-27
Anticipated expiration: 2028-10-06
Also published as: JP2010090414A

Description

本発明は、電気アルミニウムめっき液およびそれを使用しためっき方法と生成した被膜に関する。 The present invention relates to an electroaluminum plating solution, a plating method using the same, and a produced coating.

アルミニウムの電析電位は水素発生の電位よりも卑であるため、水溶液からアルミニウムを電析することは不可能である。従って、電気アルミニウムめっき液としては非水溶媒を用いためっき液が多く研究されてきた。非水溶媒としてはテトラヒドロフラン、トルエンなどが知られているが、引火性が強いという問題点があるため、殆ど実用化されていない。このような中で安全且つ低コストなめっき液として、特許文献１などにはジメチルスルホンを溶媒とした低温溶融塩電気めっき液が報告されている。
特開２００４−７６０３１号公報 Since the electrodeposition potential of aluminum is lower than the potential for hydrogen generation, it is impossible to deposit aluminum from an aqueous solution. Therefore, many electroplating solutions using a non-aqueous solvent have been studied as an electroaluminum plating solution. Tetrahydrofuran, toluene and the like are known as non-aqueous solvents, but they are hardly put into practical use due to the problem of strong flammability. Under such circumstances, a low-temperature molten salt electroplating solution using dimethyl sulfone as a solvent is reported in Patent Document 1 as a safe and low-cost plating solution.
JP 2004-76031 A

しかしながら、このめっき液から生成したアルミニウムめっき膜は不純物として塩素と硫黄を含有し、被膜の硬化、電気抵抗の増大、反射率の低下などを引き起こすという欠点がある。特に、被膜が硬く脆いためめっき後の曲げ加工等による変形によって被膜に剥離や亀裂が生じる。また、被膜中に塩素を含有しているため、時間の経過とともに素地の腐食を引き起こす可能性がある。柔らかい被膜または素地の腐食を引き起こしにくい被膜を形成するには、得られる被膜中に不純物、特に塩素と硫黄を含まないめっき液を用いることが望ましい。このめっき液を用いた被膜の高純度化については電流密度を上げるかめっき温度を下げる方法が考えられる。いずれもアルミニウムめっき膜とそのめっき液の反応を緩慢にすることで不純物の取り込み量を減らしているが、反応そのものを防止できないため微量ながら不純物は存在し、アルミニウムめっき膜の各種物性値に影響を与えている。 However, the aluminum plating film produced from this plating solution contains chlorine and sulfur as impurities, and has the drawback of causing hardening of the film, an increase in electrical resistance, a decrease in reflectance, and the like. In particular, since the coating is hard and brittle, peeling or cracking occurs in the coating due to deformation caused by bending after plating. Moreover, since chlorine is contained in the coating, it may cause corrosion of the substrate over time. In order to form a soft coating or a coating that does not easily corrode the substrate, it is desirable to use a plating solution that does not contain impurities, particularly chlorine and sulfur. A method for increasing the current density or lowering the plating temperature can be considered for increasing the purity of the coating using this plating solution. In both cases, the amount of impurities incorporated is reduced by slowing the reaction between the aluminum plating film and its plating solution. However, since the reaction itself cannot be prevented, impurities are present in trace amounts, affecting various physical property values of the aluminum plating film. Giving.

本発明は、アルミニウムめっき液に添加物を加えることによってめっき液とめっき膜の反応を防止し、被膜を高純度化することで被膜の延性を向上させ、めっき後の加工が可能なめっき膜を形成することを目的とする。 The present invention prevents the reaction between the plating solution and the plating film by adding an additive to the aluminum plating solution, improves the ductility of the coating by increasing the purity of the coating, and provides a plating film that can be processed after plating. The purpose is to form.

本発明では、主にジメチルスルホンとアルミニウムハロゲン化物からなる溶融塩にメチル基を持つアンモニウム塩を添加することによってめっき膜への不純物の取り込みを防止し、高純度のアルミニウムめっき膜を作製した。この添加剤を使用することでめっき液とめっき膜の反応を防止し、高純度の被膜を得ることができる。更に、電流過剰によるヤケを防止する効果もあり、電流密度を高く設定できるようになる。 In the present invention, an ammonium salt having a methyl group is added to a molten salt mainly composed of dimethylsulfone and an aluminum halide to prevent impurities from being taken into the plating film, thereby producing a high-purity aluminum plating film. By using this additive, the reaction between the plating solution and the plating film can be prevented, and a high-purity film can be obtained. Furthermore, there is an effect of preventing burns due to excessive current, and the current density can be set high.

アルミニウム源として使用するアルミニウムハロゲン化物としては、塩化アルミニウム、臭化アルミニウム等の無水塩が使用できる。めっき液中のアルミニウムハロゲン化物濃度は、ジメチルスルホン10molに対して、1.5〜4.0molが好ましい。特に好ましくは2.0〜3.0molである。アルミニウムハロゲン化物濃度が1.5molを下回ると黒い被膜が形成され、めっき効率が低下する。一方、4.0molを上回るとめっき膜の未析等の欠陥はなくなるが、液抵抗が高くなり発熱するようになる。処理温度は85℃〜95℃が好ましい。温度が85℃未満になると、粘度が高くなると共に液抵抗が上昇しめっき液の分解を生じる。一方、95℃を超えるとめっき膜とめっき液の反応が活性化することによりめっき膜中への不純物取り込み量が多くなる。電流密度は2.0〜7.5A/dm²が好ましい。特に好ましくは3.0〜5.0A/dm²である。電流密度が2A/dm²未満になると成膜速度が低下するためめっき液とめっき膜の反応が相対的に速くなり、めっき膜中の不純物が増加する。一方、7.5A/dm²を超えるとヤケが顕著となるとともにアンモニウム塩の分解が生じ、分解成生物が被膜中に取り込まれる。 As the aluminum halide used as the aluminum source, anhydrous salts such as aluminum chloride and aluminum bromide can be used. The aluminum halide concentration in the plating solution is preferably 1.5 to 4.0 mol with respect to 10 mol of dimethyl sulfone. Most preferably, it is 2.0-3.0 mol. When the aluminum halide concentration is less than 1.5 mol, a black film is formed and the plating efficiency is lowered. On the other hand, when the amount exceeds 4.0 mol, defects such as undeposited plating film disappear, but the liquid resistance increases and heat is generated. The treatment temperature is preferably 85 ° C to 95 ° C. When the temperature is less than 85 ° C., the viscosity increases and the liquid resistance increases, causing decomposition of the plating solution. On the other hand, when the temperature exceeds 95 ° C., the reaction between the plating film and the plating solution is activated, and the amount of impurities taken into the plating film increases. The current density is preferably 2.0 to 7.5 A / dm ² . Particularly preferably 3.0~5.0A / dm ^2. When the current density is less than 2 A / dm ² , the deposition rate decreases, so the reaction between the plating solution and the plating film becomes relatively fast, and impurities in the plating film increase. On the other hand, when it exceeds 7.5 A / dm ² , burns become prominent and ammonium salts are decomposed, and decomposition products are taken into the film.

アンモニウム塩としては、塩化トリメチルアンモニウム（トリメチルアミン塩酸塩）、塩化ジメチルアンモニウム（ジメチルアミン塩酸塩）、塩化モノメチルアンモニウム（モノメチルアミン塩酸塩）等が使用できるが、添加量に対する効果が大きいのは塩化ジメチルアンモニウム、塩化トリメチルアンモニウムである。めっき液中のアンモニウム塩の濃度は、ジメチルスルホン10mol、アルミニウムハロゲン化物1.5〜4.0molに対して0.01〜0.20molが好ましく、0.01〜0.10molが更に好ましい。アンモニウム塩の濃度が0.01mol未満になると被膜の高純度化の効果が期待できなくなる。一方、0.20molを超えると効果が飽和すると共に、アンモニウム塩による水分持込によりめっきができなくなる。また、これらのめっき液に更に塩化テトラメチルアンモニウムを添加することによってめっき液の抵抗が減少し、高電流密度でのめっきが可能となる。このとき塩化テトラメチルアンモニウムはジメチルスルホン10molに対して0.75molまで添加することが可能である。添加量が0.75molを超えるとめっき膜が生成しなくなる。 As the ammonium salt, trimethylammonium chloride (trimethylamine hydrochloride), dimethylammonium chloride (dimethylamine hydrochloride), monomethylammonium chloride (monomethylamine hydrochloride) and the like can be used. , Trimethylammonium chloride. The concentration of the ammonium salt in the plating solution is preferably 0.01 to 0.20 mol, more preferably 0.01 to 0.10 mol with respect to 10 mol of dimethyl sulfone and 1.5 to 4.0 mol of aluminum halide. If the ammonium salt concentration is less than 0.01 mol, the effect of increasing the purity of the coating cannot be expected. On the other hand, when the amount exceeds 0.20 mol, the effect is saturated and plating cannot be performed due to moisture brought in by the ammonium salt. Further, by adding tetramethylammonium chloride to these plating solutions, the resistance of the plating solution is reduced, and plating at a high current density becomes possible. At this time, tetramethylammonium chloride can be added up to 0.75 mol per 10 mol of dimethylsulfone. When the addition amount exceeds 0.75 mol, no plating film is generated.

本発明を用いれば、ジメチルスルホン溶媒系電気めっきにより純度の高いアルミニウムめっき膜を得ることができる。 By using the present invention, a highly pure aluminum plating film can be obtained by dimethylsulfone solvent-based electroplating.

次に本発明を実施例によって具体的に説明するが、これら実施例により本発明が限定されるものではない。 EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

本発明の電解アルミニウムめっき液について、その一例を以下に述べる。被めっき物にはどのような素材を用いてもめっき可能であるが、本発明では20mm×20mm×0.5mmtの純度99.99%の無酸素銅板を使用した。まず、試料表面の酸化膜等を取り除くため、16ml/L硫酸水溶液で表面を研磨した後、水洗し、温風にて十分に乾燥した。 An example of the electrolytic aluminum plating solution of the present invention will be described below. Although any material can be used for the object to be plated, an oxygen-free copper plate having a purity of 99.99% of 20 mm × 20 mm × 0.5 mmt is used in the present invention. First, in order to remove the oxide film and the like on the sample surface, the surface was polished with a 16 ml / L sulfuric acid aqueous solution, washed with water, and sufficiently dried with warm air.

（比較例１）
無水塩化アルミニウムとジメチルスルホンが3：10のモル比となるようにアルミニウムめっき液を建浴した。陽極には純度99.99％のAl板を使用し、陰極に試料を設置して110℃にて4.5A/dm²の電流密度で60min間通電した。その結果、図１に示すような白色のアルミニウムめっき膜が生成した。WDX分析の結果、この被膜に不純物として含まれる塩素の濃度は0.3wt%、硫黄の濃度は0.4wt%であった。また、この被膜のビッカース硬さは226Hvであり、純アルミニウムの値（37Hv）に比べて約6倍大きな値となっている。 (Comparative Example 1)
The aluminum plating solution was erected so that the molar ratio of anhydrous aluminum chloride and dimethyl sulfone was 3:10. An aluminum plate with a purity of 99.99% was used for the anode, a sample was placed on the cathode, and current was applied at 110 ° C. at a current density of 4.5 A / dm ² for 60 minutes. As a result, a white aluminum plating film as shown in FIG. 1 was produced. As a result of WDX analysis, the concentration of chlorine contained as an impurity in the coating was 0.3 wt%, and the concentration of sulfur was 0.4 wt%. The Vickers hardness of this film is 226 Hv, which is about 6 times larger than that of pure aluminum (37 Hv).

図２はこの試料を180度折り曲げた後の外観を示している。(a)は折り曲げた試料の外観である。(a)において矢印で示した部分の表面の拡大像を(b)に、断面写真を(c)に示す。不純物により皮膜の延性が低下したため、クラックを生じているのがわかる。 FIG. 2 shows the appearance after the sample is bent 180 degrees. (a) is the appearance of the bent sample. An enlarged image of the surface of the portion indicated by the arrow in (a) is shown in (b), and a cross-sectional photograph is shown in (c). It can be seen that cracks are generated because the ductility of the film is reduced by the impurities.

（比較例２）
めっき温度を90℃とした以外は比較例１と同様にしてめっきを行った。その結果、図３に示すように試料エッジに副反応によるヤケを生じるとともに、被膜は強烈な硫黄臭を発した。この被膜の塩素濃度は0.2wt%、硫黄濃度は0.2wt%であった。また、ビッカース硬さは186Hvであり、純アルミニウムの5倍近い値を示している。 (Comparative Example 2)
Plating was performed in the same manner as in Comparative Example 1 except that the plating temperature was 90 ° C. As a result, as shown in FIG. 3, the sample edge was burned due to side reactions, and the coating emitted a strong sulfur odor. This coating had a chlorine concentration of 0.2 wt% and a sulfur concentration of 0.2 wt%. The Vickers hardness is 186 Hv, which is nearly 5 times that of pure aluminum.

（実施例１）
比較例２と同じ組成のめっき液にジメチルスルホン10mol当たりジメチルアミン塩酸塩を0.1molを添加し、それ以外は比較例２と同じ条件でめっきを行った。その結果、図４に示すような白色のアルミニウム被膜が得られ、図３に示すヤケは抑制された。この被膜の不純物濃度をWDX分析により測定した結果を図５に示す。横軸はメチル基の数、縦軸は不純物としてめっき膜中に含まれる塩素と硫黄の濃度を示している。塩素濃度は0.1wt%未満、硫黄濃度は0.1wt%であった。図６はビッカース硬さ測定結果を示しており、図５と同様に横軸にはメチル基の数、縦軸にはビッカース硬さをとってある。ビッカース硬さは52Hvであり、純アルミニウムとほぼ同等の硬さとなった。図７は図２と同様にして試料を180度折り曲げた後の外観を示している。被膜が柔らかく延性に富むため、図２のようなクラックは認められなかった。 Example 1
Plating was performed under the same conditions as in Comparative Example 2 except that 0.1 mol of dimethylamine hydrochloride was added per 10 mol of dimethylsulfone to the plating solution having the same composition as Comparative Example 2. As a result, a white aluminum film as shown in FIG. 4 was obtained, and the discoloration shown in FIG. 3 was suppressed. The result of measuring the impurity concentration of this film by WDX analysis is shown in FIG. The horizontal axis indicates the number of methyl groups, and the vertical axis indicates the concentration of chlorine and sulfur contained in the plating film as impurities. The chlorine concentration was less than 0.1 wt% and the sulfur concentration was 0.1 wt%. FIG. 6 shows the measurement results of Vickers hardness, and the horizontal axis represents the number of methyl groups and the vertical axis represents Vickers hardness, as in FIG. The Vickers hardness was 52Hv, which was almost equivalent to that of pure aluminum. FIG. 7 shows the appearance after the sample is bent 180 degrees as in FIG. Since the film was soft and rich in ductility, no cracks as shown in FIG. 2 were observed.

（実施例２）
比較例２と同じ組成のめっき液にジメチルスルホン10mol当たりトリメチルアミン塩酸塩を0.1molを添加し、それ以外は比較例２と同じ条件でめっきを行った。その結果、図８に示すような白色のアルミニウム被膜が得られ、図３に示すヤケは抑制された。この被膜の塩素濃度は0.1wt%未満、硫黄濃度も0.1wt%未満と非常に純度の高いアルミニウム被膜を得ることができた。この被膜のビッカース硬さは55Hvであり、純アルミニウムとほぼ同等の硬さとなった。 (Example 2)
Plating was performed under the same conditions as in Comparative Example 2 except that 0.1 mol of trimethylamine hydrochloride was added per 10 mol of dimethylsulfone to the plating solution having the same composition as in Comparative Example 2. As a result, a white aluminum film as shown in FIG. 8 was obtained, and the discoloration shown in FIG. 3 was suppressed. The coating had a chlorine concentration of less than 0.1 wt% and a sulfur concentration of less than 0.1 wt%, and an aluminum coating with very high purity could be obtained. The Vickers hardness of this film was 55 Hv, which was almost the same as that of pure aluminum.

（実施例３）
比較例２と同じ組成のめっき液にジメチルスルホン10mol当たりモノメチルアミン塩酸塩を0.1molを添加し、それ以外は比較例２と同じ条件でめっきを行った。その結果、図９に示すような白色のアルミニウム被膜が得られ、図３に示すヤケは抑制された。この被膜の塩素濃度は0.1wt%、硫黄濃度も0.1wt%であった。この被膜のビッカース硬さは116Hvと実施例１、２に比べると硬いものの、蒸着により生成したアルミニウム被膜とほぼ同等の硬さとなった。 (Example 3)
Plating was carried out under the same conditions as in Comparative Example 2 except that 0.1 mol of monomethylamine hydrochloride was added per 10 mol of dimethylsulfone to the plating solution having the same composition as in Comparative Example 2. As a result, a white aluminum coating as shown in FIG. 9 was obtained, and the discoloration shown in FIG. 3 was suppressed. This coating had a chlorine concentration of 0.1 wt% and a sulfur concentration of 0.1 wt%. The Vickers hardness of this coating was 116 Hv, which was hard compared to Examples 1 and 2, but was almost the same as the aluminum coating produced by vapor deposition.

（比較例３）
比較例２と同じ組成のめっき液にジメチルスルホン10mol当たり塩化アンモニウムを0.1molを添加し、それ以外は比較例２と同じ条件でめっきを行った。その結果、図１０に示すような白色のアルミニウム被膜が得られ、図３に示すヤケは抑制された。この被膜の塩素濃度は0.1wt%、硫黄濃度は0.1wt%未満であり、実施例１〜３と同等レベルの高純度被膜であったが、ビッカース硬さは178Hvと純アルミニウム約5倍の硬さを示した。 (Comparative Example 3)
Plating was performed under the same conditions as in Comparative Example 2 except that 0.1 mol of ammonium chloride was added per 10 mol of dimethylsulfone to the plating solution having the same composition as in Comparative Example 2. As a result, a white aluminum film as shown in FIG. 10 was obtained, and the discoloration shown in FIG. 3 was suppressed. The coating had a chlorine concentration of 0.1 wt% and a sulfur concentration of less than 0.1 wt%, and was a high-purity coating of the same level as in Examples 1 to 3, but the Vickers hardness was 178 Hv, which was about 5 times as hard as pure aluminum. Showed.

（比較例４）
比較例２と同じ組成のめっき液にジメチルスルホン10mol当たり塩化テトラメチルアンモニウムを0.1molを添加し、それ以外は比較例２と同じ条件でめっきを行った。その結果、図１１に示すような白色のアルミニウム被膜が得られたものの、めっき膜はアンモニア臭を発していた。添加したアンモニウム塩が分解し、被膜中に取り込まれたためと考えられる。この被膜の塩素濃度は0.4wt%、硫黄濃度は0.3wt%であり、無添加の場合よりもめっき膜純度は低下した。また、ビッカース硬さは250Hvと純アルミニウム約5倍の硬さを示した。 (Comparative Example 4)
Plating was performed under the same conditions as in Comparative Example 2 except that 0.1 mol of tetramethylammonium chloride per 10 mol of dimethyl sulfone was added to the plating solution having the same composition as in Comparative Example 2. As a result, a white aluminum film as shown in FIG. 11 was obtained, but the plating film emitted an ammonia odor. This is probably because the added ammonium salt was decomposed and incorporated into the film. This coating had a chlorine concentration of 0.4 wt% and a sulfur concentration of 0.3 wt%, and the purity of the plated film was lower than when no additive was added. The Vickers hardness was 250 Hv, about 5 times as high as pure aluminum.

（実施例４）
実施例１と同じ組成のめっき液にジメチルスルホン10mol当たり塩化テトラメチルアンモニウムを0.75mol添加し、それ以外は実施例１と同じ条件でめっきを行った。比較例４において塩化テトラメチルアンモニウムは硬さ低下に寄与しないことを示したが、図６に示すようにジメチルアミン塩酸塩などのアンモニウム塩と併用しても被膜は硬くならない。一方、図１２に示すように定電流電解における端子間電圧は実施例１よりも低下しており、電流を高く設定でき消費電力も減らすことができる。 Example 4
Plating was performed under the same conditions as in Example 1 except that 0.75 mol of tetramethylammonium chloride was added per 10 mol of dimethylsulfone to the plating solution having the same composition as in Example 1. In Comparative Example 4, it was shown that tetramethylammonium chloride does not contribute to the decrease in hardness. However, as shown in FIG. 6, the coating does not become hard even when used in combination with an ammonium salt such as dimethylamine hydrochloride. On the other hand, as shown in FIG. 12, the voltage between the terminals in constant current electrolysis is lower than that in Example 1, so that the current can be set higher and the power consumption can be reduced.

添加剤未使用時の電気アルミニウムめっき膜外観（めっき温度110℃）External appearance of electroplated aluminum film when no additives are used (plating temperature 110 ° C) 180°折り曲げ試験後のめっき膜外観Appearance of plating film after 180 ° bending test 添加剤未使用時の電気アルミニウムめっき膜外観（めっき温度90℃）External appearance of electroplated aluminum film when no additives are used (plating temperature 90 ° C) ジメチルアミン塩酸塩0.1mol添加後の電気アルミニウムめっき膜外観External appearance of electroplated aluminum film after addition of 0.1 mol of dimethylamine hydrochloride 添加したアンモニウム塩が有するメチル基の数とめっき膜中不純物濃度の関係Relationship between the number of methyl groups in the added ammonium salt and the impurity concentration in the plating film 添加したアンモニウム塩が有するメチル基の数とめっきビッカース硬さの関係Relationship between the number of methyl groups in the added ammonium salt and plating Vickers hardness ジメチルアミン塩酸塩0.1mol添加後の180°折り曲げ試験後のめっき膜外観Appearance of plating film after 180 ° bending test after addition of 0.1 mol of dimethylamine hydrochloride トリメチルアミン塩酸塩0.1mol添加後の電気アルミニウムめっき膜外観External appearance of electroplated aluminum film after addition of 0.1 mol of trimethylamine hydrochloride モノメチルアミン塩酸塩0.1mol添加後の電気アルミニウムめっき膜外観External appearance of electroplated aluminum film after addition of 0.1 mol of monomethylamine hydrochloride 塩化アンモニウム0.1mol添加後の電気アルミニウムめっき膜外観External appearance of electroplated aluminum film after addition of 0.1 mol of ammonium chloride 塩化テトラメチルアンモニウム0.1mol添加後の電気アルミニウムめっき膜外観External appearance of electroplated aluminum film after addition of 0.1 mol of tetramethylammonium chloride 塩化テトラメチルアンモニウム、ジメチルアミン塩酸塩併用時の端子間電圧の変化Changes in terminal voltage when using tetramethylammonium chloride and dimethylamine hydrochloride together

Claims

An electroaluminum plating solution comprising 1.5 to 4.0 mol of an aluminum halide per 10 mol of dimethylsulfone and 0.01 to 0.20 mol of an ammonium salt having 1 to 3 methyl groups.

Electric aluminum containing 1.5 to 4.0 mol of aluminum halide per 10 mol of dimethylsulfone, 0.01 to 0.20 mol of ammonium salt having 1 to 3 methyl groups and 0.75 mol or less of tetramethylammonium chloride Plating solution.

The aluminum plating film | membrane produced | generated using the electric aluminum plating solution of Claim 1 or 2.