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EP0037535B1 - Plating bath for depositing coatings of gold and gold alloys - Google Patents

Plating bath for depositing coatings of gold and gold alloys Download PDF

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Publication number
EP0037535B1
EP0037535B1 EP81102316A EP81102316A EP0037535B1 EP 0037535 B1 EP0037535 B1 EP 0037535B1 EP 81102316 A EP81102316 A EP 81102316A EP 81102316 A EP81102316 A EP 81102316A EP 0037535 B1 EP0037535 B1 EP 0037535B1
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EP
European Patent Office
Prior art keywords
gold
bath
acid
potassium
alloy
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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.)
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Application number
EP81102316A
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German (de)
French (fr)
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EP0037535A2 (en
EP0037535A3 (en
Inventor
Wolfgang Dipl.Chem. Zilske
Werner Chem. Ing. Kuhn
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Evonik Operations GmbH
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Degussa GmbH
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Priority to AT81102316T priority Critical patent/ATE6527T1/en
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Publication of EP0037535A3 publication Critical patent/EP0037535A3/en
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/62—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of gold

Definitions

  • the invention relates to a gold bath for the electrodeposition of high-gloss and ductile gold alloy coatings based on potassium cyanoaurate (III), which contains an acid, at least one of the alloy metals cobalt, nickel, indium, tin, zinc or cadmium in the form of water-soluble salts and a complexing agent contains a pH of less than 3.
  • III potassium cyanoaurate
  • the majority of gold coatings are deposited today from weakly acidic electrolytes that operate in the pH range from 3.5 to 5. They contain the gold in the form of potassium dicyanoaurate (I), KAu (CN), and as a buffer salts of weak inorganic or organic acids such as phosphates, citrates or phosphonates.
  • the properties of the deposited layers are strongly influenced by adding metal salts, especially nickel, cobalt or indium. These baths are obtained under conditions in which 0.2 to 0.5% of Ni or Co are also deposited, coatings which are shiny, have a hardness of 150 to 180 HV and have good resistance to mechanical abrasion. From about 5 ⁇ m, these coatings are practically non-porous. They are characterized by good electrical conductivity and low contact resistance.
  • the coatings from these baths also have considerable disadvantages.
  • Your ductility is low. With slight mechanical deformation, cracks form. They contain a relatively large amount (approx. 1%) of non-metallic impurities, which presumably lead to malfunctions in low-voltage electrical contacts. Presumably also because of these impurities, the contact resistance does not remain constant during thermal loading and affects the function of electrical devices.
  • the content of the alloy metal in the coating is strongly dependent on the current density and the pH value, so that the working conditions must be kept within narrow limits in order to obtain coatings of constant quality.
  • the average current density is limited to about 1 A / dm l , the bath temperature must not be higher than 40 ° C, and in most baths the pH must be kept between 3.5 and 4.
  • the layers are often only milky or matt. It is not possible to work at pH values below 3.5, since the KAu (CN) 2 disintegrates at pH 3 with the excretion of gold cyanide, AuCN. Nevertheless, attempts were made to use such baths at pH values below 3 (for example DE-AS No. 1262723, US Pat. No. 2978390), but the results were unsatisfactory.
  • No. 3,598,706 describes a process for the preparation of tetracyano gold (III) acid and a bath on this basis.
  • No. 4168214 describes a hydrochloric acid bath for the pre-gilding of stainless steel, the tetracyano gold (III) complex being formed by reaction of gold (III) chloride with potassium cyanide in the bath and a pH between 0.1 and 1. 5 is set.
  • This bath also contains alloy metals such as nickel, cobalt, tin or indium, and ethylenediamine hydrochloride as a complexing agent.
  • a pure alloy bath for the deposition of gold / tin coatings based on KAu (CN) 4 in the hydrochloric acid medium is claimed in DE-OS No. 2658003.
  • Baths in which the trivalent gold is present have the disadvantage compared to baths based on monovalent gold salts that only a third of the amount of gold is deposited due to the differences in value with the same current densities and times.
  • This disadvantage can only be compensated for by using correspondingly high current densities.
  • Another major disadvantage is the high chloride content in these baths, which causes an unpleasant chlorine development at the anode. If the baths also contain hydrochloric acid, there are also corrosion problems on the systems.
  • potassium cyanoaurate (III) which contains an acid, at least one of the alloy metals cobalt, nickel, indium, tin, zinc or cadmium in the form of water-soluble salts and a complexing agent contains at a pH value of less than 3, which provides high-gloss and ductile coatings even at high current densities and at which no chlorine development occurs.
  • the electrolyte contains, in addition to an amine, an aminocarboxylic acid or phosphonic acid as complexing agent, 20 to 200 g / l of sulfuric acid, phosphoric acid, citric acid or mixtures thereof.
  • a pH range from 0.4 to 2.5 is particularly advantageous.
  • Baths containing 1 to 20 g / l gold in the form of catium cyanoaurate (III), 10 to 200 g / l sulfuric acid, phosphoric acid and / or citric acid, 0.1 to 20 g / l at least one of the alloy metals cobalt, nickel have proven successful , Indium, zinc, tin or cadmium in the form of water-soluble salts and 1 to 100 g / l of an amine, an aminocarboxylic acid or a phosphonic acid, which are able to form a complex with the alloy metal.
  • salts of the acids used such as, for example, potassium dihydrogen phosphate, potassium hydrogen sulfate or potassium citrate.
  • complex shiny gold layers can be deposited over a wide current density range from acidic electrolytes based on the tetracyanoaurate (III) if the baths contain alloy metals and at the same time suitable complexing agents and suitable acids.
  • Alloy metals can be Co, Ni, In, Sn, Zn or Cd.
  • Suitable complexing agents are amines, aminocarboxylic acids or phosphonic acids. If the alloy metals are only added in the form of simple salts, as in the baths known hitherto, the metal distribution in the coating is uneven, since in general the amount of the alloy metal deposited is strongly dependent on the current density.
  • the properties of the deposited layers from the bath according to the invention have particular advantages compared to the coatings from the so-called weakly acidic gold baths.
  • the layers are not only hard and wear-resistant, but also very ductile. They can be deposited in a thin layer with little pores.
  • the contact resistance is low and remains constant even during heat storage.
  • the content of non-metallic impurities is very low.
  • the bath according to the invention is advantageously used in the pH range from 0.4 to 2.5. Both significantly lower and significantly higher pH values lead to the decomposition of the gold complex with the separation of insoluble gold (I) cyanide.
  • the bath is preferably operated at pH values between 0.6 and 2.0.
  • the bath can be used at room temperature, but higher temperatures up to 60 ° C are advantageous to increase the deposition rate.
  • the applicable current density range is extremely wide. Shiny layers are achieved above all with current densities of 0.2 to at least 10 A / dm 2 .
  • the gold content is increased to 8 g / l, the bath is heated to 50 ° C. and the deposition is repeated at a current density of 8 A / dm 2 . 3 gm of gold are now deposited in 10 minutes. The cover is also light yellow and shiny. Approx. 0.5% cobalt is detected in both layers.
  • the copper base of the second sample is dissolved with 3: 1 dilute nitric acid. A ductile gold foil is obtained which does not break even when it is bent.
  • the cobalt complex solution used when preparing the bath becomes like prepared as follows: 47.8 g of CoSO 4 .7H 2 O, corresponding to 10 g of Co, are dissolved in about 600 ml of water with heating, 222 ml of 1-hydroxyethane-1,1-diphosphonic acid are added 60% and made up to 1 liter.
  • An adherent gold layer of 0.2 ⁇ m is deposited on a cathode made of 18Cr8Ni steel in 5 min at a current density of 2 A / dm 2 .
  • the pH is adjusted to 2.0 and the bath is heated to 40 ° C.
  • a current density of 5 A / dm l a 2.5 ⁇ m thick glossy gold layer is deposited on a copper sheet in 10 minutes.
  • Gold contains 0.4% Ni.
  • the pH of the bath is adjusted to 1.8.
  • a shiny, light yellow gold layer of 2 ⁇ m thickness is deposited on a nickel-plated copper sheet in 10 min.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)

Abstract

In the electro industry, there are needed acid gold alloy baths which give glossy, ductile coatings, operate at high current densities, and contain little non-metallic impurities. This is attained by a bath based on potassium cyanoaurate (III) and an acid whereby the bath contains at least one of the alloying metals cobalt, nickel, indium, tin, zinc, or cadmium in the form of a water soluble salt, together with an amine, an aminocarboxylic acid, or a phosphonic acid and has a pH of below 3.

Description

Die Erfindung betrifft ein Goldbad zur galvanischen Abscheidung hochglänzender und duktiler Goldlegierungsüberzüge auf der Basis von Ka- liumcyanoaurat(III), das eine Säure, mindestens eines der Legierungsmetalle Kobalt, Nickel, Indium, Zinn, Zink oder Cadmium in Form wasserlöslicher Salze und einen Komplexbildner bei einem pH-Wert von weniger als 3 enthält.The invention relates to a gold bath for the electrodeposition of high-gloss and ductile gold alloy coatings based on potassium cyanoaurate (III), which contains an acid, at least one of the alloy metals cobalt, nickel, indium, tin, zinc or cadmium in the form of water-soluble salts and a complexing agent contains a pH of less than 3.

In der Elektrotechnik wird der überwiegende Teil der Goldüberzüge heute aus schwach sauren Elektrolyten abgeschieden, die im pH-Bereich von 3,5 bis 5 arbeiten. Sie enthalten das Gold in Form von Kaliumdicyanoaurat(I), KAu(CN), und als Puffer Salze von schwachen anorganischen oder organischen Säuren wie Phosphate, Citrate oder Phosphonate. Durch Zusätze von Metallsalzen, vor allem des Nickels, Kobalts oder Indiums, werden die Eigenschaften der abgeschiedenen Schichten stark beeinflusst. Man erhält aus diesen Bädern unter Bedingungen, bei denen 0,2 bis 0,5% Ni oder Co mitabgeschieden werden, Überzüge, die glänzend sind, eine Härte von 150 bis 180 HV haben und eine gute Beständigkeit gegen mechanischen Abrieb aufweisen. Ab etwa 5 µm sind diese Überzüge praktisch porenfrei. Sie zeichnen sich durch gute elektrische Leitfähigkeit und niedrigen Kontaktwiderstand aus.In electrical engineering, the majority of gold coatings are deposited today from weakly acidic electrolytes that operate in the pH range from 3.5 to 5. They contain the gold in the form of potassium dicyanoaurate (I), KAu (CN), and as a buffer salts of weak inorganic or organic acids such as phosphates, citrates or phosphonates. The properties of the deposited layers are strongly influenced by adding metal salts, especially nickel, cobalt or indium. These baths are obtained under conditions in which 0.2 to 0.5% of Ni or Co are also deposited, coatings which are shiny, have a hardness of 150 to 180 HV and have good resistance to mechanical abrasion. From about 5 µm, these coatings are practically non-porous. They are characterized by good electrical conductivity and low contact resistance.

Die Überzüge aus diesen Bädern weisen allerdings auch erhebliche Nachteile auf. Ihre Duktilität ist gering. Bei leichter mechanischer Verformung bilden sich Risse. Sie enthalten relativ viel (ca. 1%) nichtmetallische Verunreinigungen, die vermutlich zu Funktionsstörungen bei elektrischen Schwachstromkontakten führen. Vermutlich auch auf Grund dieser Verunreinigungen bleibt bei thermischer Belastung der Kontaktwiderstand nicht konstant und beeinträchtigt die Funktion elektrischer Geräte.However, the coatings from these baths also have considerable disadvantages. Your ductility is low. With slight mechanical deformation, cracks form. They contain a relatively large amount (approx. 1%) of non-metallic impurities, which presumably lead to malfunctions in low-voltage electrical contacts. Presumably also because of these impurities, the contact resistance does not remain constant during thermal loading and affects the function of electrical devices.

Der Gehalt des Legierungsmetalls im Überzug ist stark von der Stromdichte und dem pH-Wert abhängig, so dass die Arbeitsbedingungen in engen Grenzen gehalten werden müssen, um Überzüge mit gleichbleibender Qualität zu erhalten. Die mittlere Stromdichte ist auf etwa 1 A/dml begrenzt, die Badtemperatur darf nicht höher als 40°C sein, und bei den meisten Bädern muss der pH-Wertzwischen 3,5 und 4 gehalten werden. Bei pH 4 sind die Schichten oft nur noch milchigglänzend oder schon matt. Bei pH-Werten unter 3,5 kann nicht gearbeitet werden, da das KAu(CN)2 bei pH 3 unter Ausscheidung von Goldcyanid, AuCN, zerfällt. Trotzdem wurde versucht, solche Bäder bei pH-Werten unter 3 zu benutzen (z.B. DE-AS Nr. 1262723, US-PS Nr. 2978390), die Ergebnisse waren jedoch nicht befriedigend.The content of the alloy metal in the coating is strongly dependent on the current density and the pH value, so that the working conditions must be kept within narrow limits in order to obtain coatings of constant quality. The average current density is limited to about 1 A / dm l , the bath temperature must not be higher than 40 ° C, and in most baths the pH must be kept between 3.5 and 4. At pH 4, the layers are often only milky or matt. It is not possible to work at pH values below 3.5, since the KAu (CN) 2 disintegrates at pH 3 with the excretion of gold cyanide, AuCN. Nevertheless, attempts were made to use such baths at pH values below 3 (for example DE-AS No. 1262723, US Pat. No. 2978390), but the results were unsatisfactory.

Es wurde auch versucht, mit Bädern im sauren Bereich zu arbeiten, die den Komplex des dreiwertigen Goldes mit Kaliumcyanid, das Kaliumtetracyanoaurat (111), KAu(CN)4 enthalten.Attempts have also been made to work with acidic baths containing the trivalent gold complex with potassium cyanide, the potassium tetracyanoaurate (111), KAu (CN) 4 .

In der US-PS Nr. 3598706 wird ein Verfahren zur Herstellung der Tetracyanogold(III)säure und ein Bad auf dieser Basis beschrieben. In der US-PS Nr. 4168214 wird ein salzsaures Bad zur Vorvergoldung von Edelstahl beschrieben, wobei der Tetracyanogold(III)komplex durch Umsetzung von Gold(III)chlorid mit Kaliumcyanid im Bad entsteht und ein pH-Wert zwischen 0,1 und 1,5 eingestellt wird. Dieses Bad enthält ausserdem Legierungsmetalle, wie Nickel, Kobalt, Zinn oder Indium, und Äthylendiaminhydrochlorid als Komplexbildner. Ein reines Legierungsbad zur Abscheidung von Gold/Zinn-Überzügen auf der Basis von KAu(CN)4 im salzsauren Medium wird in der DE-OS Nr. 2658003 beansprucht.No. 3,598,706 describes a process for the preparation of tetracyano gold (III) acid and a bath on this basis. No. 4168214 describes a hydrochloric acid bath for the pre-gilding of stainless steel, the tetracyano gold (III) complex being formed by reaction of gold (III) chloride with potassium cyanide in the bath and a pH between 0.1 and 1. 5 is set. This bath also contains alloy metals such as nickel, cobalt, tin or indium, and ethylenediamine hydrochloride as a complexing agent. A pure alloy bath for the deposition of gold / tin coatings based on KAu (CN) 4 in the hydrochloric acid medium is claimed in DE-OS No. 2658003.

Bäder, in denen das Gold dreiwertig vorliegt, haben gegenüber den Bädern auf der Basis von einwertigen Goldsalzen den Nachteil, dass auf Grund der Wertigkeitsunterschiede bei gleichen Stromdichten und Zeiten nur ein Drittel der Goldmenge abgeschieden wird. Dieser Nachteil kann nur durch Anwendung entsprechend hoher Stromdichten ausgeglichen werden. Das ist aber bei den bisher bekannten Bädern nicht möglich, da dann die abgeschiedenen Schichten matt und rauh werden, so dass dickere Überzüge wirtschaftlich nicht herstellbar sind. Ein weiterer wesentlicher Nachteil ist der hohe Chloridgehalt in diesen Bädern, wodurch eine unangenehme Chlorentwicklung an der Anode auftritt. Enthalten die Bäder noch zusätzlich Salzsäure, so treten ausserdem noch Korrosionsprobleme an den Anlagen auf.Baths in which the trivalent gold is present have the disadvantage compared to baths based on monovalent gold salts that only a third of the amount of gold is deposited due to the differences in value with the same current densities and times. This disadvantage can only be compensated for by using correspondingly high current densities. However, this is not possible with the previously known baths, since the deposited layers then become matt and rough, so that thicker coatings cannot be produced economically. Another major disadvantage is the high chloride content in these baths, which causes an unpleasant chlorine development at the anode. If the baths also contain hydrochloric acid, there are also corrosion problems on the systems.

Es war daher Aufgabe der vorliegenden Erfindung, ein Goldbad zur galvanischen Abscheidung von Goldlegierungsüberzügen auf der Basis von Kaliumcyanoaurat(lll), das eine Säure, mindestens eines der Legierungsmetalle Kobalt, Nickel, Indium, Zinn, Zink oder Cadmium in Form wasserlöslicher Salze und einem Komplexbildner bei einem pH-Wert von weniger als 3 enthält, zu finden, das auch bei hohen Stromdichten hochglänzende und duktile Überzüge liefert und bei dem keine Chlorentwicklung auftritt.It was therefore an object of the present invention to provide a gold bath for the electrodeposition of gold alloy coatings based on potassium cyanoaurate (III) which contains an acid, at least one of the alloy metals cobalt, nickel, indium, tin, zinc or cadmium in the form of water-soluble salts and a complexing agent contains at a pH value of less than 3, which provides high-gloss and ductile coatings even at high current densities and at which no chlorine development occurs.

Diese Aufgabe wurde erfindungsgemäss dadurch gelöst, dass im Elektrolyten neben einem Amin, einer Aminocarbonsäure oder Phosphonsäure als Komplexbildner als Säure 20 bis 200 g/I Schwefelsäure, Phosphorsäure, Citronensäure oder Gemische davon enthalten sind. Besonders vorteilhaft ist ein pH-Bereich von 0,4 bis 2,5.This object was achieved according to the invention in that the electrolyte contains, in addition to an amine, an aminocarboxylic acid or phosphonic acid as complexing agent, 20 to 200 g / l of sulfuric acid, phosphoric acid, citric acid or mixtures thereof. A pH range from 0.4 to 2.5 is particularly advantageous.

Bewährt haben sich Bäder, die 1 bis 20 g/I Gold in Form von Katiumcyanoaurat(III), 10 bis 200 g/1 Schwefelsäure, Phosphorsäure und/oder Citronensäure, 0,1 bis 20 g/I mindestens eines der Legierungsmetalle Kobalt, Nickel, Indium, Zink, Zinn oder Cadmium in Form wasserlöslicher Salze und 1 bis 100 g/I eines Amins, einer Aminocarbonsäure oder einer Phosphonsäure enthalten, die mit dem Legierungsmetall einen Komplex zu bilden vermögen. Vorteilhaft ist ausserdem die Zugabe von Salzen der verwendeten Säuren, wie beispielsweise Kaliumdihydrogenphosphat, Kaliumhydrogensulfat oder Kaliumcitrat. Vorzugsweise arbeitet man bei Temperaturen von 40 bis 60° C und Stromdichten von 0,1 bis 20 A/dm2.Baths containing 1 to 20 g / l gold in the form of catium cyanoaurate (III), 10 to 200 g / l sulfuric acid, phosphoric acid and / or citric acid, 0.1 to 20 g / l at least one of the alloy metals cobalt, nickel have proven successful , Indium, zinc, tin or cadmium in the form of water-soluble salts and 1 to 100 g / l of an amine, an aminocarboxylic acid or a phosphonic acid, which are able to form a complex with the alloy metal. It is also advantageous to add salts of the acids used, such as, for example, potassium dihydrogen phosphate, potassium hydrogen sulfate or potassium citrate. Preferably one works at temperatures from 40 to 60 ° C and current densities from 0.1 to 20 A / dm 2 .

Es wurde überraschenderweise gefunden, dass aus sauren Elektrolyten auf der Basis des Tetra- cyanoaurat(III)komplexes glänzende Goldschichten über einen weiten Stromdichtebereich abgeschieden werden können, wenn die Bäder Legierungsmetalle und gleichzeitig geeignete Komplexbildner und geeignete Säuren enthalten. Legierungsmetalle können Co, Ni, In, Sn, Zn oder Cd sein. Geeignete Komplexbildner sind Amine, Aminocarbonsäuren oder Phosphonsäuren. Werden die Legierungsmetalle nur in Form einfacher Salze, wie in den bisher bekannten Bädern, zugegeben, so ist die Metallverteilung im Überzug ungleichmässig, da im alltemeinen die Menge des mitabgeschiedenen Legierungsmetalls stark von der Stromdichte abhängt. Überraschend zeigte sich nun, dass bei Verwendung der genannten Komplexbildner die Mitabscheidung praktisch unabhängig von der Stromdichte wird, so dass bei optimaler Wahl von Goldgehalt, pH-Wert und Badtemperatur die Überzüge einen konstanten Legierungsmetallgehaltaufweisen. In anderen bekannten Bädern ist diese Unabhängigkeit im allgemeinen nicht gegeben.It has surprisingly been found that complex shiny gold layers can be deposited over a wide current density range from acidic electrolytes based on the tetracyanoaurate (III) if the baths contain alloy metals and at the same time suitable complexing agents and suitable acids. Alloy metals can be Co, Ni, In, Sn, Zn or Cd. Suitable complexing agents are amines, aminocarboxylic acids or phosphonic acids. If the alloy metals are only added in the form of simple salts, as in the baths known hitherto, the metal distribution in the coating is uneven, since in general the amount of the alloy metal deposited is strongly dependent on the current density. Surprisingly, it has now been found that when using the complexing agents mentioned, the co-deposition becomes practically independent of the current density, so that the coatings have a constant alloy metal content when the gold content, pH value and bath temperature are optimally selected. This independence is generally not given in other known baths.

Dadurch wird die Anwendung hoher Stromdichten möglich und somit können Abscheidungsraten erreicht werden, wie sie bei den bekannten schwach sauren Goldbädern im pH-Bereich zwischen 3,5 und 5 üblich sind.This makes it possible to use high current densities and thus deposition rates can be achieved, as are customary in the known weakly acidic gold baths in the pH range between 3.5 and 5.

Die Verwendung der genannten Komplexbildner und der genannten Säuren in galvanischen Bädern ist an sich bekannt, jedoch war nicht zu erwarten, dass die Kombination dieser Substanzen unter den gegebenen Bedingungen die Mitabscheidung der Legierungsmetalle so stark steuern, da die Stabilität der Komplexe mit den genannten Metallen bei pH-Werten unter 3 normalerweise gering ist.The use of the complexing agents mentioned and the acids mentioned in galvanic baths is known per se, but it was not to be expected that the combination of these substances under the given conditions would control the co-deposition of the alloy metals to such an extent that the stability of the complexes with the metals mentioned would pH values below 3 is usually low.

Besondere Vorteile weisen die Eigenschaften der abgeschiedenen Schichten aus dem erfindungsgemässen Bad im Vergleich zu den Überzügen aus den sogenannten schwach sauren Goldbädern auf. Die Schichten sind nicht nur hart und verschleissfest, sondern auch sehr duktil. Sie können bereits in dünner Schicht porenarm abgeschieden werden. Der Kontaktwiderstand ist niedrig und bleibt auch bei der Wärmelagerung konstant. Der Gehalt an nichtmetallischen Verunreinigungen ist sehr gering.The properties of the deposited layers from the bath according to the invention have particular advantages compared to the coatings from the so-called weakly acidic gold baths. The layers are not only hard and wear-resistant, but also very ductile. They can be deposited in a thin layer with little pores. The contact resistance is low and remains constant even during heat storage. The content of non-metallic impurities is very low.

Bäder gemäss der Erfindung enthalten:

  • 1 bis 20 g/I Gold als KAu(CN)4
  • 10 bis 200 g/I Phosphorsäure, Schwefelsäure oder Gemische davon, Citronensäure, Phosphate, Sulfate
  • 0,1 bis 20 g/I eines Legierungsmetalls, das Co, Ni, In, Sn, Zn, Cd sein kann
  • 1 bis 100 g/I eines Amins, einer Aminocarbon-oder Phosphonsäure
Baths according to the invention contain:
  • 1 to 20 g / l gold as KAu (CN) 4
  • 10 to 200 g / l phosphoric acid, sulfuric acid or mixtures thereof, citric acid, phosphates, sulfates
  • 0.1 to 20 g / l of an alloy metal, which can be Co, Ni, In, Sn, Zn, Cd
  • 1 to 100 g / l of an amine, an aminocarbon or phosphonic acid

Das KAu(CN)4 wird auf bekannte Weise durch Umsetzung von AuCl3 mit KCN hergestellt und aus der Mutterlauge kristallisiert. Dabei erhält man ein Salz, das nur noch wenig Chlorid enthält. Die Menge der im Bad enthaltenen Säure ist nicht kritisch. Bei höheren Gehalten wird eine bessere Leitfähigkeit erreicht. Ein Teil der Phosphorsäure kann auch als KH2PO4 zugegeben werden, wenn durch die Säure allein zu niedrige pH-Werte erreicht würden. Für die Gruppen der geeigneten Komplexbildner werden nachfolgend beispielhaft eine Reihe von Verbindungen genannt:

  • Amine:
  • Äthylendiamin
  • Tetraäthylenpentamin
  • Triäthylamin
  • Diäthylentriamin
  • Triäthylentetramin
  • Aminocarbonsäuren:
  • Nitrilotriessigsäure
  • Äthylendiamintetraessigsäure
  • 1,2-Diaminocyclohexantetraessigsäure
  • Bis-2-Aminoäthyläthertetraessigsäure
  • Diäthylentriaminpentaessigsäure
  • Phosphonsäuren:
  • 1-Hydroxyäthan-1,1-diphosphonsäure
  • Aminotrimethylenphosphonsäure
  • Äthylendiamintetramethylphosphonsäure
The KAu (CN) 4 is prepared in a known manner by reacting AuCl 3 with KCN and crystallized from the mother liquor. This gives you a salt that contains very little chloride. The amount of acid contained in the bath is not critical. At higher levels, better conductivity is achieved. Some of the phosphoric acid can also be added as KH 2 PO 4 if the acid alone would cause the pH values to be too low. For the groups of suitable complexing agents, a number of compounds are mentioned below by way of example:
  • Amines:
  • Ethylenediamine
  • Tetraethylene pentamine
  • Triethylamine
  • Diethylene triamine
  • Triethylene tetramine
  • Aminocarboxylic acids:
  • Nitrilotriacetic acid
  • Ethylenediaminetetraacetic acid
  • 1,2-diaminocyclohexanetetraacetic acid
  • Bis-2-aminoethyl ether tetraacetic acid
  • Diethylenetriaminepentaacetic acid
  • Phosphonic acids:
  • 1-hydroxyethane-1,1-diphosphonic acid
  • Aminotrimethylenephosphonic acid
  • Ethylenediaminetetramethylphosphonic acid

Das erfindungsgemässe Bad wird vorteilhafterweise im pH-Bereich von 0,4 bis 2,5 angewendet. Sowohl wesentlich niedrigere als auch wesentlich höhere pH-Werte führen zur Zersetzung des Goldkomplexes unter Abscheidung von unlöslichem Gold(I)cyanid. Vorzugsweise wird das Bad bei pH-Werten zwischen 0,6 und 2,0 betrieben. Das Bad kann bei Raumtemperatur benutzt werden, doch sind höhere Temperaturen bis 60° C zur Erhöhung der Abscheidungsrate vorteilhaft. Der anwendbare Stromdichtebereich ist ausserordentlich breit. Es werden glänzende Schichten vor allem bei Stromdichten von 0,2 bis mindestens 10 A/dm2 erzielt.The bath according to the invention is advantageously used in the pH range from 0.4 to 2.5. Both significantly lower and significantly higher pH values lead to the decomposition of the gold complex with the separation of insoluble gold (I) cyanide. The bath is preferably operated at pH values between 0.6 and 2.0. The bath can be used at room temperature, but higher temperatures up to 60 ° C are advantageous to increase the deposition rate. The applicable current density range is extremely wide. Shiny layers are achieved above all with current densities of 0.2 to at least 10 A / dm 2 .

Die Erfindung soll anhand der folgenden Beispiele näher erläutert werden.The invention is illustrated by the following examples.

Beispiel 1:Example 1:

Ein Bad wird durch Auflösen folgender Bestandteile hergestellt:

  • 75 g Phosphorsäure 85%ig werden in 500 ml destilliertem Wasser verdünnt. Dann werden 50 ml einer Kobaltkomplexlösung und 3,5 g KAu(CN)4, gelöst in Wasser, zugegeben. Das Bad wird mit Wasser auf ca. 900 ml aufgefüllt, der pH-Wert mit Kalilauge auf 1,5 eingestellt und zum Schluss wird mit Wasser auf 1 I ergänzt. Das Bad wird auf 25° C erwärmt. Auf einer Kathode aus Kupferblech wird bei einer Stromdichte von 2 A/dm2 in 20 min eine hellgelbe, glänzende Goldschicht von 1,2 µm Dikke abgeschieden.
A bath is made by dissolving the following components:
  • 75 g of 85% phosphoric acid are diluted in 500 ml of distilled water. Then 50 ml of a cobalt complex solution and 3.5 g of KAu (CN) 4 , dissolved in water, are added. The bath is made up to approx. 900 ml with water, the pH is adjusted to 1.5 with potassium hydroxide solution and the mixture is finally made up to 1 l with water. The bath is heated to 25 ° C. A light yellow, shiny gold layer of 1.2 µm thick is deposited on a copper sheet cathode at a current density of 2 A / dm 2 in 20 min.

Nun wird der Goldgehalt auf 8 g/I erhöht, das Bad auf 50°C erwärmt und die Abscheidung bei einer Stromdichte von 8 A/dm2 wiederholt. Es werden nun in 10 min 3 gm Gold abgeschieden. Der Überzug ist ebenfalls hellgelb und glänzend. In beiden Schichten wird ca. 0,5% Kobalt nachgewiesen. Von der zweiten Probe wird die Kupferunterlagemit3:1 verdünnter Salpetersäure aufgelöst. Es wird eine duktile Goldfolie erhalten, die auch beim Knicken nicht bricht. Die beim Ansatz des Bades verwendete Kobaltkomplexlösung wird wie folgt hergestellt: 47,8 g CoSO4·7H2O, entsprechend 10 g Co, werden unter Erwärmen in ca. 600 ml Wasser gelöst, 222 ml 1-Hydroxyäthan-1,1- diphosphonsäure 60% zugesetzt und auf 1 I aufgefüllt.Now the gold content is increased to 8 g / l, the bath is heated to 50 ° C. and the deposition is repeated at a current density of 8 A / dm 2 . 3 gm of gold are now deposited in 10 minutes. The cover is also light yellow and shiny. Approx. 0.5% cobalt is detected in both layers. The copper base of the second sample is dissolved with 3: 1 dilute nitric acid. A ductile gold foil is obtained which does not break even when it is bent. The cobalt complex solution used when preparing the bath becomes like prepared as follows: 47.8 g of CoSO 4 .7H 2 O, corresponding to 10 g of Co, are dissolved in about 600 ml of water with heating, 222 ml of 1-hydroxyethane-1,1-diphosphonic acid are added 60% and made up to 1 liter.

Beispiel 2:Example 2:

Entsprechend Beispiel 1 wird ein Bad aus folgenden Bestandteilen hergestellt:

  • 26,3 ml H3PO4 85%
  • 13,6 ml H2S04 96%
  • 50 ml Kobaltkomplexlösung (wie im Beispiel 1) Das Bad wird wiederum auf 1 I aufgefüllt. Es werden 1,73 g KAu(CN)4 (1 g Au) zugesetzt und der pH-Wert wird mit Schwefelsäure auf 0,6 eingestellt.
According to example 1, a bath is produced from the following components:
  • 26.3 ml H 3 PO 4 85%
  • 13.6 ml H 2 S0 4 96%
  • 50 ml cobalt complex solution (as in Example 1) The bath is again made up to 1 liter. 1.73 g of KAu (CN) 4 (1 g of Au) are added and the pH is adjusted to 0.6 with sulfuric acid.

Auf einer Kathode aus 18Cr8Ni-Stahl wird in 5 min bei einer Stromdichte von 2 A/dm2 eine haftfeste Goldschicht von 0,2 µm abgeschieden.An adherent gold layer of 0.2 µm is deposited on a cathode made of 18Cr8Ni steel in 5 min at a current density of 2 A / dm 2 .

Beispiel 3:Example 3:

1 I Bad wird durch Auflösen folgender Bestandteile in Wasser hergestellt:

  • 25 g KH2PO4
  • 60 g H3PO4 85%
  • 4,2 g NiSO4·7H2O
  • 13,8 g KAu(CN)4 (8 g/I Au)
  • 10 g Äthylendiamin
1 l bath is prepared by dissolving the following components in water:
  • 25 g KH 2 PO 4
  • 60 g H 3 PO 4 85%
  • 4.2 g NiSO 4 .7H 2 O
  • 13.8 g KAu (CN) 4 (8 g / I Au)
  • 10 g ethylenediamine

Der pH-Wert wird auf 2,0 eingestellt und das Bad auf 40° C erwärmt. Bei einer Stromdichte von 5 A/dml wird in 10 min eine 2,5 µm dicke glänzende GoJdschicht auf einem Kupferblech abgeschieden. Im Gold sind 0,4% Ni enthalten.The pH is adjusted to 2.0 and the bath is heated to 40 ° C. At a current density of 5 A / dm l , a 2.5 µm thick glossy gold layer is deposited on a copper sheet in 10 minutes. Gold contains 0.4% Ni.

Beispiel 4:Example 4:

Es werden Abscheidungen aus einem Bad vorgenommen, das folgende Bestandteile enthält:

  • 90 g/I H3PO4 85%
  • 10 g/I H2SO4 96%
  • 6 g/l In2(SO4)3·5H2O
  • 8,6 g/I KAu(CN)4 (5 g/I Au)
  • 9 g/I Äthylendiamintetraessigsäure
Deposits are made from a bath that contains the following components:
  • 90 g / IH 3 PO 4 85%
  • 10 g / IH 2 SO 4 96%
  • 6 g / l In 2 (SO 4 ) 3 · 5H 2 O
  • 8.6 g / I KAu (CN) 4 (5 g / I Au)
  • 9 g / l of ethylenediaminetetraacetic acid

Der pH-Wert des Bades wird auf 1,8 eingestellt. Bei einer Stromdichte von 9 A/dm2 und 50°C Badtemperaturwird in 10 min auf einem vernickelten Kupferblech eine glänzende, hellgelbe Goldschicht von 2 µm Dicke abgeschieden.The pH of the bath is adjusted to 1.8. At a current density of 9 A / dm 2 and 50 ° C bath temperature, a shiny, light yellow gold layer of 2 µm thickness is deposited on a nickel-plated copper sheet in 10 min.

Claims (8)

1. A gold bath for the galvanic deposition of highly lustrous and ductile gold alloy coatings based on potassium cyano-aurate (III), which bath contains an acid, at least one of the alloy metals cobalt, nickel, indium, tin, zinc or cadmium in the form of water-soluble salts and a complex former at a pH of less than 3, characterised in that the electrolyte contains, in addition to an amine, an aminocarboxylic acid or a phosphonic acid as the complex former, from 20 to 200 g/I of sulphuric acid, phosphoric acid, citric acid or mixtures thereof as the acid.
2. A gold bath according to claim 1, characterised in that in addition to the acids, the bath also contains the salts thereof, such as potassium dihydrogen phosphate, potassium hydrogen sulphate or potassium citrate.
3. A gold bath according to claim 1 or 2, characterised in that the bath has a pH of from 0.4 to 2.5.
4. A gold bath according to one of claims 1 to 3, characterised in that the bath contains from 1 to 20 g/I of gold in the form of potassium cyano-aurate (III).
5. A gold bath according to one of claims 1 to 4, characterised in that the bath contains from 0.1 to 20 g/I of at least one of the alloy metals cobalt, nickel, indium, tin, zinc or cadmium in the form of water-soluble salts.
6. A gold bath according to one of claims 1 to 5, characterised in that the bath contains from 1 to 100 g of an amine, an aminocarboxylic acid or phosphonic acid which are capable of forming a complex with the alloy metal.
7. The use of a gold bath according to one of claims 1 to 6 for the deposition of highly lustrous and ductile gold alloy coatings, characterised in that the bath is operated at a temperature of from 40 to 60° C.
8. The use of a gold bath according to one of claims 1 to 7, characterised in that the bath operates at current densities of from 0.1 to 20 A/dm2.
EP81102316A 1980-04-03 1981-03-27 Plating bath for depositing coatings of gold and gold alloys Expired EP0037535B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81102316T ATE6527T1 (en) 1980-04-03 1981-03-27 GALVANIC BATH FOR DEPOSITION OF GOLD AND GOLD ALLOY COATINGS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3012999A DE3012999C2 (en) 1980-04-03 1980-04-03 Bath and process for the galvanic deposition of high-gloss and ductile gold alloy coatings
DE3012999 1980-04-03

Publications (3)

Publication Number Publication Date
EP0037535A2 EP0037535A2 (en) 1981-10-14
EP0037535A3 EP0037535A3 (en) 1981-11-04
EP0037535B1 true EP0037535B1 (en) 1984-03-07

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Country Status (6)

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US (1) US4391679A (en)
EP (1) EP0037535B1 (en)
JP (1) JPS56152989A (en)
AT (1) ATE6527T1 (en)
DE (1) DE3012999C2 (en)
HK (1) HK30986A (en)

Cited By (1)

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DE4040526A1 (en) * 1989-12-19 1991-06-20 H E Finishing Sa Electrocoating bath for gold alloys - using auric cyanide complex and alloy salt of alkyl:sulphonic or hydroxy:alkyl:sulphonic acid

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FR2538816A1 (en) * 1983-01-04 1984-07-06 Omi Int Corp Aq. gold alloy electroplating baths
US4470886A (en) * 1983-01-04 1984-09-11 Omi International Corporation Gold alloy electroplating bath and process
US4559121A (en) * 1983-09-12 1985-12-17 Vac-Tec Systems, Inc. Method and apparatus for evaporation arc stabilization for permeable targets
US4559125A (en) * 1983-09-12 1985-12-17 Vac-Tec Systems, Inc. Apparatus for evaporation arc stabilization during the initial clean-up of an arc target
US4448659A (en) * 1983-09-12 1984-05-15 Vac-Tec Systems, Inc. Method and apparatus for evaporation arc stabilization including initial target cleaning
CH665656A5 (en) * 1983-12-29 1988-05-31 Heinz Emmenegger ACID GOLD BATH AND USE OF THIS BATH IN ELECTROPLASTY.
DE3505473C1 (en) * 1985-02-16 1986-06-05 Degussa Ag, 6000 Frankfurt Electroplating bath for gold-indium alloy coatings
DE3509367C1 (en) * 1985-03-15 1986-08-14 Degussa Ag, 6000 Frankfurt Bath and process for electrodeposition of gold / tin alloy coatings
CA2365749A1 (en) * 2001-12-20 2003-06-20 The Governors Of The University Of Alberta An electrodeposition process and a layered composite material produced thereby
JP2007537358A (en) * 2004-05-11 2007-12-20 テクニック・インコーポレイテッド Electroplating solution for gold-tin eutectic alloy
JP4945193B2 (en) * 2006-08-21 2012-06-06 ローム・アンド・ハース・エレクトロニック・マテリアルズ，エル．エル．シー． Hard gold alloy plating solution
JP5317433B2 (en) * 2007-06-06 2013-10-16 ローム・アンド・ハース・エレクトロニック・マテリアルズ，エル．エル．シー． Acid gold alloy plating solution
US20090114345A1 (en) * 2007-11-07 2009-05-07 Sumitomo Metal Mining Co., Ltd. Method for manufacturing a substrate for mounting a semiconductor element
DE102011114931B4 (en) 2011-10-06 2013-09-05 Umicore Galvanotechnik Gmbh Process for more selective electrolytic deposition of gold or a gold alloy

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DE4040526C3 (en) * 1989-12-19 1998-05-20 H E Finishing Sa Bath for the galvanic deposition of gold alloys

Also Published As

Publication number Publication date
HK30986A (en) 1986-05-09
EP0037535A2 (en) 1981-10-14
EP0037535A3 (en) 1981-11-04
DE3012999A1 (en) 1981-10-15
ATE6527T1 (en) 1984-03-15
DE3012999C2 (en) 1984-02-16
JPS56152989A (en) 1981-11-26
JPH0146597B2 (en) 1989-10-09
US4391679A (en) 1983-07-05

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