KR102315943B1 - Composition, use thereof and method for electrodepositing gold containing layers - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to a composition and method for electrodepositing a gold-containing layer using the composition, and to the use of a mercapto-triazole compound as an anti-immersion additive. The composition contains a mercapto-triazole compound which acts as an anti-immersion additive. The compositions and methods are suitable for depositing functional or hard gold or gold alloys that can be applied in the industry as contact materials for electrical connectors for high reliability applications.

Description

Composition for electrodeposition of a gold-containing layer, use and method thereof

The present invention relates to a composition of the present invention and a method therefor for electrodepositing a gold containing layer using the composition. The composition of the present invention contains a mercapto-triazole compound which acts as an anti-immersion additive. The compositions and methods are suitable for depositing functional or hard gold or gold alloys that can be applied in the industry as contact materials for electrical connectors for high reliability applications.

Hard gold or gold alloys of cobalt and nickel are widely used as contact materials in electrical connectors for high reliability applications. Therefore, a connector having a hard gold end layer is electroplated onto an electrically conductive metal layer, for example on a nickel substrate such as nickel plated on copper. Typically, a connector is part of a larger electrical device or wire. Selective electroplating techniques are used to deposit a layer of gold or gold alloy only on the contact area of the connector, without plating the rest of the electrical circuit. This selective plating technique significantly reduces the material cost of the connector by limiting the plating area of gold and other precious metals such as palladium and palladium-nickel alloys.

Since gold is a precious metal that is typically plated on connectors made of less precious metals, the problem of gold displacement arises. Gold displacement is the deposition of gold by an exchange reaction. When the surface to be gold plated is, for example, a nickel surface, the displacement reaction is thought to occur as follows:

2 Au ⁺ + Ni ⁰ → 2 Au ⁰ + Ni ²⁺

(wherein the precious gold metal displaces the less precious nickel). Metal deposition by this exchange or displacement reaction is also called immersion reaction or immersion plating.

On the other hand, this problem occurs on the surface of a portion or region of the substrate that is not to be plated, and thus the functional surface of the electronic component, ie, the connector, is not electrically connected while being electroplated. Also, an immersion reaction may occur, for example, when electroplating is interrupted during idle time. The connector surface is then left in the gold deposition bath for a period of time without being electrically connected.

In both cases, the gold layer is deposited on the non-connected surface by an immersion reaction. Thus, the gold layer is deposited by an immersion reaction in the undesired regions of the substrate. This immersion gold deposition is undesirable because it consumes more gold than is needed to coat connectors and other electronic components, thus consuming excess gold and increasing manufacturing costs.

A layer of gold deposited on portions of printed circuit lines, connectors or other electronic devices that are not desirable to be plated can also cause defects in the substrate, resulting in defective end products. Therefore, the gold layer must be removed later, which is laborious, time consuming and expensive.

In addition, the gold layer formed by the immersion reaction has low adhesion to its lower surface. If a portion of the immersed gold layer peels off from the surface underneath it, misconnecting separate circuit lines or other contact metals, there is a risk of a short circuit.

Also, the problem of gold immersion increases with the aging of the gold electrolyte.

Gold immersion can be reduced by improving the design of the plating equipment. However, this requires high cost to redesign and manufacture new equipment parts.

European patent EP 2 309 036 B1 discloses a hard gold plating bath which reduces the gold displacement reaction. The effect is due to the mercapto-tetrazole compound contained in the plating bath. However, the reduction of the gold displacement response is still insufficient. Further, EP 2 309 036 B1 does not mention an increase in gold displacement with progressive aging of the gold deposition bath.

Accordingly, there is still a need to suppress gold immersion reactions in electrodeposition baths for functional pure gold and gold alloy layers.

It is, therefore, an object of the present invention to provide a composition and method for electrodepositing a gold containing layer while further reducing the gold immersion reaction.

Another object of the present invention is to provide a method for reducing the gold immersion reaction that increases during the lifetime of a gold electrodeposition composition.

These objects are achieved by the following compositions and methods.

An electroplating composition comprising:

(i) one or more sources of gold ions, and

(ii) at least one mercapto-triazole having the formula (I) or (II):

(wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are as defined below).

The mercapto-triazole or salt thereof according to (ii) above significantly reduces or almost inhibits the gold immersion reaction when the gold-containing layer is electrodeposited.

A method comprising the steps of:

(i) providing an electroplating composition as defined above;

(ii) contacting the substrate with the composition; and

(iii) depositing gold or a gold alloy on the substrate by applying an electric current between the substrate and one or more anodes.

The method is suitable for electrodepositing a gold-containing layer on a substrate. This method significantly reduces or almost inhibits the gold immersion reaction.

A method comprising the steps of:

(i) providing a used gold or gold alloy electroplating composition;

(ii) adding a mercapto-triazole as defined above to the gold or gold alloy electroplating composition used, and

(iii) contacting the substrate with the composition; and

(iv) depositing gold or a gold alloy on the substrate by applying an electric current between the substrate and one or more anodes.

The method is suitable for regenerating used gold or gold alloy electroplating compositions where the gold immersion reaction has reached a level that prevents the effective operation and deposition of a suitable gold or gold alloy layer. This method significantly reduces or almost inhibits the gold immersion reaction.

1 shows the thickness of a gold alloy layer deposited from an electroplating bath containing different mercaptoazole compounds by an immersion reaction.
2 shows the thickness of a gold alloy layer deposited from an electroplating bath containing different mercapto triazole compounds by an immersion reaction.

The present invention relates to an electroplating composition comprising:

(i) one or more sources of gold ions, and

(ii) at least one mercapto-triazole having the formula (I) or (II):

(Wherein, R ¹ , R ⁴ are independently of each other hydrogen, linear or branched, saturated or unsaturated (C ₁ -C ₂₀ ) hydrocarbon chain, (C ₈ -C ₂₀ ) aralkyl group; substituted or unsubstituted phenyl group, naph a tyl group or a carboxyl group;

R ² , R ³ , R ⁵ , R ⁶ are independently of each other —SX, hydrogen, linear or branched, saturated or unsaturated (C ₁ -C ₂₀ ) hydrocarbon chain, (C ₈ -C ₂₀ ) aralkyl group; a substituted or unsubstituted phenyl group, a naphthyl group, or a carboxyl group;

X is hydrogen, a (C ₁ -C ₄ ) alkyl group or a counter ion selected from alkali metal ions, calcium ions, ammonium ions and quaternary amines;

at least one of R ² and R ³ is -SX and at least one of R ⁵ and R ⁶ is -SX).

The electroplating composition is suitable for electrodepositing a gold-containing layer on a substrate. The gold-containing layer may be a pure gold layer or a gold alloy layer. Preferably, the gold-containing layer is a gold alloy layer. More preferably, the gold-containing layer is a gold alloy layer used as a so-called functional or hard gold layer. Functional or hard gold layers have high mechanical stability and are therefore particularly resistant to mechanical wear. Therefore, the gold layer and especially the gold alloy layer are suitable for use in electrical connectors.

The mercapto-triazole or salt thereof according to (ii) above significantly reduces or almost inhibits the gold immersion reaction when the gold-containing layer is electrodeposited.

In one embodiment, X is a counter ion, preferably selected from alkali metal ions, wherein the alkali metal ions are selected from sodium ions, potassium ions and lithium ions.

In another embodiment, the substituent of the substituted phenyl or naphthyl group of ^{R 1} , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ _{is a branched or unbranched (C 1} -C ₁₂ ) alkyl group, branched or unbranched (C ₂ -C ₂₀ ) alkylene group, branched or unbranched (C ₁ -C ₁₂ ) alkoxy group; independently selected from a hydroxyl group, and a halogen. In another embodiment, the halogen is selected from chlorine and bromine.

In solution, the mercapto triazole of formula (I) can exist in two tautomeric forms.

Therefore, formula (I) includes both tautomeric forms. Tautomeric forms are particularly ^{relevant when R 1} is an H atom.

In a preferred embodiment, the at least one mercapto-triazole is

R ¹ , R ⁴ are each independently hydrogen or a linear (C ₁ -C ₄ ) alkyl group,

R ² , R ³ , R ⁵ , R ⁶ are each independently —SX, hydrogen or a linear (C ₁ -C ₄ ) alkyl group;

X is hydrogen, a methyl group, an ethyl group, or a counter ion selected from sodium ion and potassium ion;

At ^{least one of R 2} and R ³ is -SX and at least one of R ⁵ and R ⁶ is -SX

It has the formula (I) or (II).

In another preferred embodiment, at least one mercapto-triazole is

R ¹ , R ⁴ are each independently hydrogen, a methyl group or an ethyl group,

R ² , R ³ , R ⁵ , R ⁶ are each independently -SX, hydrogen, a methyl group or an ethyl group,

X is hydrogen, sodium ion or potassium ion;

At ^{least one of R 2} and R ³ is -SX and at least one of R ⁵ and R ⁶ is -SX

It has the formula (I) or (II).

In another preferred embodiment, at least one mercapto-triazole is

R ¹ , R ⁴ are each independently hydrogen or a methyl group,

R ² , R ³ , R ⁵ , R ⁶ are each independently —SX, hydrogen or a methyl group,

X is hydrogen, sodium ion or potassium ion;

At ^{least one of R 2} and R ³ is -SX and at least one of R ⁵ and R ⁶ is -SX

It has the formula (I) or (II).

In a more preferred embodiment, the at least one mercapto-triazole ^{has the formula (I), wherein R 1} , R ² , R ³ and X have the meanings as defined above.

In a more preferred embodiment, the at least one mercapto-triazole is 5-mercapto-1,2,3-triazole; 4,5-dimercapto-1,2,3-triazole; 5-mercapto-1,2,4-triazole; 3-mercapto-1,2,4-triazole; 3,5-dimercapto-1,2,4-triazole; 3-mercapto-4-methyl-1,2,4-triazole; 5-phenyl-1H-1,2,4-triazole-3-thiol and salts thereof.

In a more preferred embodiment, the at least one mercapto-triazole is 5-mercapto-1,2,3-triazole; 4,5-dimercapto-1,2,3-triazole; 5-mercapto-1,2,4-triazole; 3-mercapto-1,2,4-triazole; 3,5-dimercapto-1,2,4-triazole and salts thereof.

In a more preferred embodiment, the at least one mercapto-triazole is 5-mercapto-1,2,3-triazole; 3-mercapto-4-methyl-1,2,4-triazole; 5-phenyl-1H-1,2,4-triazole-3-thiol; 3-mercapto-1,2,4-triazole and salts thereof.

In a more preferred embodiment, the at least one mercapto-triazole is selected from 5-mercapto-1,2,3-triazole and salts thereof. The mercapto-triazole compound is commercially available or can be prepared by methods well known in the art.

In one embodiment, the at least one mercapto-triazole has a concentration in the electroplating composition in the range of 1 mg/L to 1 g/L. Preferably, the concentration is less than 1 g/l. More preferably, the concentration is from 1 mg/L to 900 mg/L, more preferably from 1 mg/L to 500 mg/L, even more preferably from 5 mg/L to 100 mg/L, still more preferably 20 mg/L to 100 mg/L. If the concentration of the one or more mercapto-triazoles is too high, the electrodeposition of the gold-containing layer is completely prevented, or the electrodeposited gold or gold alloy layer does not adhere sufficiently to the surface of the substrate.

The addition of one or more mercapto-triazoles to the gold or gold alloy electroplating composition inhibits the gold immersion reaction without compromising the gold alloy appearance. In addition, the functional properties of the gold or hard gold layer, such as contact resistance and hardness, are not impaired. The contact resistance is kept to the required low level, and the gold layer is sufficiently hard for commercial electrical contact to electronic devices. Furthermore, by adding at least one mercapto-triazole according to the invention to the gold or gold alloy electroplating composition, the advantageous functional properties of high wear resistance of the gold or hard gold layer, in particular the hard gold layer, are also not impaired.

The electroplating composition further comprises (i) one or more sources of gold ions. The source of gold ions may be selected from a source of gold (I) ions and a source of gold (III) ions. The source of gold (I) ions may be selected from the group of gold (I) salts comprising gold cyanide compounds, gold thiosulfate compounds, gold sulfite compounds, and gold (I) halides. The gold cyanide compound may be an alkali gold cyanide such as potassium gold cyanide or sodium gold cyanide; and ammonium gold cyanide. The gold thiosulfate compound may be selected from alkali gold thiosulfates such as trisodium gold thiosulfate or tripotassium gold thiosulfate. Gold sulfite compounds include alkali gold sulfites such as sodium gold sulfite or potassium gold sulfite; and ammonium gold sulfite. The gold (I) halide may be gold (I) chloride. The source of gold (III) ions may be a gold (III) halide such as gold (III) trichloride. Preferably, the gold ion source is an alkali gold cyanide compound such as potassium gold cyanide or sodium gold cyanide. More preferably, the source of gold ions is potassium gold cyanide such as potassium dicyanoaurate (I) or potassium tetracyanoaurate (III); or sodium gold cyanide, such as sodium dicyanoaurate (I) or sodium tetracyanoaurate (III). More preferably, the source of gold ions is potassium dicyanoaurate (I) or potassium tetracyanoaurate (III). Potassium gold cyanide has better solubility than other gold compounds.

In one embodiment wherein the gold alloy layer deposited from the electroplating composition of the present invention is a hard gold layer, the source of gold ions is preferably a gold cyanide compound, more preferably potassium gold cyanide or sodium gold cyanide and such as alkali gold cyanide; or ammonium gold cyanide. When the source of gold ions is a gold cyanide compound, electrodeposition of a functional or hard gold alloy layer with a high gold content is most possible. In this case, the gold ion is contained in the electroplating composition in the form of a gold-cyanide complex, preferably as an alkali ion-gold-cyanide complex, more preferably as a potassium ion-gold-cyanide complex, which It is particularly suitable for electrodepositing a hard gold alloy layer having a gold content. This is because gold compounds other than gold-cyanide complexes, alkali ion-gold-cyanide complexes or potassium ion-gold-cyanide complexes are less stable at high current densities, and therefore contain gold from electrolytes used at high current densities. This also applies to the electrodeposition of layers.

In one embodiment, the at least one source of gold ions has a concentration in the electroplating composition in the range of 1 g/l to 50 g/l, preferably in the range of 5 g/l to 50 g/l, more preferably is in the range of 10 g/l to 50 g/l, more preferably in the range of 5 g/l to 30 g/l, even more preferably in the range of 5 g/l to 20 g/l, still more preferably in the range of 10 g/l to 20 g/l. The tendency of the electroplating composition to deposit gold by an immersion reaction increases with the concentration of gold contained in the composition.

In one embodiment, the electroplating composition may further comprise a complexing agent for gold ions. Complexing agents for gold ions include alkali metal cyanides such as potassium cyanide, sodium cyanide and ammonium cyanide; thiosulfuric acid and its salts, such as sodium thiosulfate, potassium thiosulfate and ammonium thiosulfate; sulfurous acid and salts thereof such as potassium sulfite, ammonium sulfite, carboxylic acids such as sorbic acid; hydroxy carboxylic acids such as citric acid and malonic acid; aminocarboxylic acids such as ethylenediamine tetraacetic acid, iminodiacetic acid, nitrilotriacetic acid, 1,2-diaminocyclohexane tetraacetic acid, bis-2-amino ethylether tetraacetic acid, and diethylene triamine pentaacetic acid; inorganic acids such as phosphoric acid, sulfuric acid, and boric acid; 1-hydroxyethane-1,1-diphosphonic acid, 1-hydroxyethane-1,2-diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethyl phosphonic acid, hexamethylene diaminotetramethyl phosphonic acid and such phosphonic acids; and salts of the above-mentioned acids such as alkali metal salts and alkaline earth metal salts; preferably sodium and potassium salts; amines such as tetraethylenepentaamine, triethylenetetraamine, triethylamine, diethylenetriamine and ethylenediamine. Complexing agents may also function as conductive salts.

In one embodiment where the source of gold ions is an alkali gold cyanide compound, the complexing agent is preferably not a cyanide compound, more preferably not an alkali metal cyanide.

In one embodiment, the complexing agent has a concentration in the electroplating composition in the range of 1 g/l to 200 g/l, preferably in the range of 1 g/l to 100 g/l, more preferably 10 g/l to 50 g/l.

In one embodiment, the electroplating composition may further comprise one or more sources of alloying metal ions. The metal of the alloying metal ion is selected from cobalt, nickel and iron. Gold-cobalt, gold-nickel and gold-iron alloys belong to hard gold alloys.

The hard gold alloy deposit has a gold content in the range of 99.00 mass % to less than 99.90 mass %. The content of alloying metals cobalt, nickel and/or iron may range from less than 0.03 mass % to greater than 0.3 mass % for hard gold alloys (ASTM B488-11, Section 7). Alloying metals impart the highest hardness and highest wear resistance to gold alloys required for industrial applications such as contact materials in electrical connectors for high reliability applications (ASTM B488-11, Appendix X1). At the same time, hard gold alloys maintain high electrical conductivity which is also important for their use in electrical connectors. In contrast, gold deposits having a gold content of 99.90 mass % or higher have low hardness (ASTM B488-11, Sections 4 and 7), low wear resistance, and thus are not suitable for use in electrical connectors.

The alloying metal ion is selected from cobalt (II) ions, nickel (II) ions, iron (II) ions and iron (III) ions. Sources of alloying metal ions are cobalt carbonate, cobalt sulfate, cobalt gluconate, cobalt potassium cyanide, cobalt bromide, cobalt chloride, nickel chloride, nickel bromide, nickel sulfate, nickel tartrate, nickel phosphate, nickel nitrate, nickel sulfamate, iron chloride, iron bromide, iron citrate, iron fluoride, iron iodide, iron nitrate, iron oxalate, iron phosphate, iron pyrophosphate, iron sulfate and iron acetate.

In one embodiment, the at least one alloying metal ion source has a concentration in the electroplating composition in the range of 0.001 g/l to 5 g/l, preferably in the range of 0.05 g/l to 2 g/l, more preferably preferably in the range from 0.05 g/l to 1 g/l.

In one embodiment, the electroplating composition may further include a complexing agent for alloying metal ions. Complexing agents for alloying metal ions include sulfurous acid and salts thereof such as potassium sulfite, ammonium sulfite, carboxylic acids such as sorbic acid; hydroxy carboxylic acids such as citric acid and malonic acid; amino carboxylic acids such as ethylenediaminetetraacetic acid, iminodiacetic acid, nitrilotriacetic acid, 1,2-diamino cyclohexane tetraacetic acid, bis-2-amino ethylether tetraacetic acid, diethylene triamine pentaacetic acid; inorganic acids such as phosphoric acid, sulfuric acid, boric acid, and thiosulfuric acid; 1-hydroxyethane-1,1-diphosphonic acid, 1-hydroxyethane-1,2-diphosphonic acid, aminotrimethylenephosphonic acid, ethylenediaminetetramethylphosphonic acid, hexamethylene diaminotetramethylphosphonic acid and such phosphonic acids; and salts of the above-mentioned acids such as alkali metal salts and alkaline earth metal salts; preferably sodium and potassium salts; amines such as tetraethylenepentaamine, triethylenetetraamine, triethylamine, diethylenetriamine and ethylenediamine. Complexing agents may also function as conductive salts.

The complexing agent for alloying metal ions may have a concentration in the electroplating composition in the range of 1 to 200 g/l, preferably in the range of 20 to 150 g/l. When the same complexing agent is used for the gold ion and the alloying metal ion, the concentration of the complexing agent is the sum of the concentrations required for the gold ion and the alloying metal ion.

In one embodiment, the electroplating composition may further comprise one or more brightening agents. The at least one brightener is selected from pyridine and quinoline compounds. The pyridine and quinoline compounds are selected from substituted pyridine and substituted quinoline compounds. Preferably, the substituted pyridine and substituted quinoline compounds are selected from mono- or dicarboxylic acids, mono- or disulfonic acids, mono- or dithiol substituted pyridines, quinolines, pyridine derivatives or quinoline derivatives. The pyridine or quinoline derivatives may be substituted at one or more positions with the same or different substituents. More preferably, the pyridine derivative or the quinoline derivative is selected from derivatives substituted at the 3-position of the pyridine ring. More preferably, the pyridine derivative or quinoline derivative is selected from pyridine or quinoline carboxylic acid, pyridine or quinoline sulfonic acid, and pyridine or quinoline thiol. More preferably, the pyridine or quinoline carboxylic acid is selected from their respective esters and amides. More preferably, the pyridine or quinoline carboxylic acid is pyridine-3-carboxylic acid (nicotinic acid), quinoline-3-carboxylic acid, 4-pyridine carboxylic acid, nicotinic acid methyl ester, nicotinamide, nicotinic acid diethyl amide, pyridine -2,3-dicarboxylic acid, pyridine-3,4-dicarboxylic acid and pyridine-4-thioacetic acid. More preferably, the pyridine or quinoline sulfonic acid is selected from 3-pyridinesulfonic acid, 4-pyridinesulfonic acid and 2-pyridinesulfonic acid. Most preferably, the at least one brightening agent is selected from pyridine-3-carboxylic acid (nicotinic acid), nicotinamide and 3-pyridinesulfonic acid.

The at least one brightener may have a concentration in the electroplating composition in the range from 0.5 g/l to 10 g/l, preferably in the range from 1 g/l to 10 g/l.

The brightener advantageously causes the deposition of a bright gold layer over a wide current density range of 2 A/dm 2 to 100 A/dm 2 .

In one embodiment, the electroplating composition may further comprise one or more acids. Preferably, the at least one acid is an organic or inorganic acid. More preferably, the at least one acid is selected from phosphoric acid, citric acid, malic acid, oxalic acid, formic acid and polyethylene amino acetic acid. One or more acids are used to adjust the pH value of the electroplating composition. One or more acids may also function as complexing agents and/or as conductive salts.

The one or more acids may have a concentration in the electroplating composition in the range of 1 g/L to 200 g/L.

In one embodiment, the electroplating composition may further comprise one or more alkali compounds. One or more alkali compounds are used to adjust the pH value of the electroplating composition. The at least one alkali compound is selected from hydroxides, sulfates, carbonates, phosphates, hydrogen phosphates and other salts of sodium, potassium and magnesium. Preferably, the at least one alkali compound is selected from KOH, NaOH, K ₂ CO ₃ , Na ₂ CO ₃ , K ₂ HPO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ and mixtures thereof.

In one embodiment, the electroplating composition is an acidic electroplating composition. The electroplating composition will have a pH value of less than 7, more preferably less than 5, still more preferably 1 to 6, even more preferably 3 to 6, even more preferably 3.5 to 5.5, even more preferably 3.5 to 4.5. can

In one embodiment where the gold alloy layer deposited from the electroplating composition of the present invention is a hard gold layer, the electroplating composition is preferably an acidic electroplating composition. When the electrodeposition composition is acidic, electrodeposition of a functional or hard gold alloy layer having a high gold content is most possible.

In one embodiment, the electroplating composition may include additional additives such as surfactants and/or crystal refiners.

The invention also relates to a method comprising the steps of:

(i) providing an electroplating composition as defined above;

(ii) contacting the substrate with the composition; and

(iii) depositing a gold-containing layer on the substrate by applying an electric current between the substrate and at least one anode.

The method is suitable for electrodepositing a gold-containing layer on a substrate. The method uses the electroplating composition of the present invention containing at least one mercapto-triazole or a salt thereof as an anti-immersion additive. This method significantly reduces or almost inhibits the gold immersion reaction. Therefore, the method of the present invention significantly reduces gold consumption and increases the lifetime of the gold or gold alloy electroplating composition. The gold-containing layer may be a pure gold layer or a gold alloy layer, preferably a gold alloy layer, more preferably a hard gold layer.

The gold-containing layer may be deposited on the entire surface of the substrate or on a portion of the surface of the substrate. Depositing a metal layer on a portion of the surface of a substrate is also referred to as selectively depositing or plating a metal layer. Thus, the gold-containing layer can be selectively electroplated onto the substrate.

The selective plating may be performed by a known method such as a masking method, a spot plating method, or a brush plating method. The masking method involves the use of a mask that covers a portion of the substrate surface that is not plated. In the spot plating method, only a portion of the substrate to be metallized is electrically connected, thereby plated. The brush plating method applies a brush-covered anode locally to an area of a substrate to be plated, the brush containing a metal plating solution.

In both cases of metal deposition over the entire surface of the substrate or selective metal deposition, the electrically conductive surface of the substrate or a portion of the substrate surface is contacted with the electroplating composition of the present invention. A surface of the substrate or a portion of the substrate surface is electrically connected as a cathode. A voltage is applied between the cathode and the one or more anodes so that a current flow is supplied to the substrate surface or a portion of the substrate surface.

The current density of the current flow is from 0.05 A/dm to 100 A/dm, preferably from 1 A/dm to 50 A/dm, more preferably from 1 A/dm to 40 A/dm, further Preferably it may range from 5 A/dm2 to 40 A/dm2, even more preferably from 5 A/dm2 to 20 A/dm2. By applying a higher current density during the electrodeposition of the gold-containing layer, the deposition rate is advantageously increased, thereby increasing the productivity of the electrodeposition method.

The plating time may vary. The amount of time depends on the desired thickness of the gold-containing layer on the substrate. The thickness of the gold-containing layer ranges from 0.01 μm to 5 μm, preferably from 0.05 μm to 3 μm, more preferably from 0.05 μm to 1.5 μm.

During plating, the electroplating composition of the present invention can be maintained at a temperature in the range of 40 °C to 70 °C.

During plating, the electroplating composition of the present invention may not be moved or agitated. Agitation may be effected by mechanical movement of the aqueous plating bath, for example by shaking, stirring or continuous pumping of liquid, or essentially by sonication or by elevated temperature or by purging the aqueous plating bath with an inert gas or simply with air. It can be carried out by supplying gas such as

The method of electrodepositing a gold-containing layer on a substrate may further comprise a pretreatment step prior to contacting the substrate with the electroplating composition of the present invention. The pretreatment step is activation of the substrate surface, typically using an acid or a fluoride containing acid.

The method of electrodepositing a gold-containing layer on a substrate may include an additional plating step prior to contacting the substrate with the electroplating composition of the present invention. A further plating step deposits an additional metal layer on the substrate prior to electrodepositing the gold or gold alloy layer on the substrate. The metal of the further metal layer may be selected from iron, nickel, nickel-phosphorus alloys, copper, palladium, silver, cobalt and alloys thereof, preferably nickel, nickel-phosphorus alloys, and copper. Plating methods for the above-mentioned metals are known in the art.

In one embodiment, the substrate plated with the gold-containing layer, ie, the gold or gold alloy layer, is an electrically conductive material. The electrically conductive material may be a metal. The metal may be any metal capable of undergoing a gold immersion reaction. The metal may be selected from iron, nickel, nickel-phosphorus alloys, copper, palladium, silver, cobalt and alloys thereof. Preferably the substrate is made of iron or copper and covered with a layer of nickel.

In one embodiment, the substrate plated with the gold containing layer is an electrical connector. Preferably, the substrate is a contact interface of an electrical connector. More preferably, the board is a plug connector. This board may be a printed circuit board, a wire or part of an electrical device.

The invention also relates to a method comprising the steps of:

(i) providing a used gold or gold alloy electroplating composition;

(ii) adding a mercapto-triazole as defined above to the gold or gold alloy electroplating composition used, and

(iii) contacting the substrate with the composition; and

(iv) depositing gold or a gold alloy on the substrate by applying an electric current between the substrate and one or more anodes.

The method is suitable for regenerating used gold or gold alloy electroplating compositions. Meanwhile, the electroplating composition used may be an aged gold or gold alloy electroplating composition. As used herein, aged electroplating composition means a composition already used for electroplating, where the gold immersion reaction has reached a level that prevents the effective operation and deposition of a suitable gold or gold alloy layer. The criterion for evaluating the degree of aging is the deposition rate by the immersion reaction. For freshly prepared gold or gold alloy electroplating baths, the deposition rate is about 5 nm/5 min metal at 60°C. The deposition rate increases with the lifetime of the electroplating bath. When the deposition rate reaches 80-100 nm/5 min metal at 60° C., the gold or gold alloy electroplating bath should normally be replaced. Even when deposition rates reach 20-40 nm/5 min metal at 60° C., gold or gold alloy electroplating baths may no longer be suitable for industrial plating applications, as the immersion reaction already causes high gold losses. In contrast, the method of the present invention significantly reduces or substantially inhibits the gold immersion reaction in the aged gold or gold alloy electroplating composition. Therefore, the method of the present invention regenerates the aged gold or gold alloy electroplating composition and significantly increases the lifetime of the gold or gold alloy electroplating composition.

The invention also relates to a method comprising the steps of:

(i) providing an aged gold or gold alloy electroplating composition;

(ii) adding a mercapto-triazole as defined above to the aged gold or gold alloy electroplating composition, and

(iii) contacting the substrate with the composition; and

(iv) depositing gold or a gold alloy on the substrate by applying an electric current between the substrate and one or more anodes.

The thickness of the gold layer can be measured by x-ray fluorescence (XRF) known in the art. XRF thickness measurements use characteristic fluorescent radiation emitted from samples (substrates, deposits) excited by x-rays. By evaluating the strength and assuming the layered structure of the sample, the layer thickness can be calculated.

On the other hand, the electroplating composition used may be a gold or gold alloy electroplating composition that has not been used for some time in the electroplating process. Unused means that the gold or gold alloy electroplating composition is not electrically connected and no gold or gold alloy is electrodeposited from the composition. It has also been observed that the problem of gold immersion plating increases while the gold or gold alloy electrodeposition composition is not used in the electroplating process. The addition of the mercapto-triazoles of the present invention to a gold or gold alloy electrodeposition composition that has temporarily stopped working also significantly reduces or substantially inhibits the gold dipping reaction when the composition is again working.

The invention also relates to a method comprising the steps of:

(i) providing a gold or gold alloy electroplating composition that is temporarily inoperative;

(ii) adding a mercapto-triazole as defined above to a temporarily inoperative gold or gold alloy electroplating composition, and

(iii) contacting the substrate with the composition; and

(iv) depositing gold or a gold alloy on the substrate by applying an electric current between the substrate and one or more anodes.

The invention also relates to a substrate electroplated with a gold-containing layer obtainable by one of the methods of the invention.

The present invention also relates to the use of the inventive mercapto-triazoles as anti-dipping additives in electrodeposition compositions, preferably in electrodeposition compositions for gold-containing layers.

The electroplating compositions and methods of the present invention significantly reduce or substantially inhibit the gold immersion reaction. Thus, gold is not deposited in undesired areas of the substrate surface. This saves money as loss of gold and production of defective end products are minimized. In addition, the lifetime of the gold or gold alloy electroplating composition is significantly increased.

In contrast to the triazole compounds of the present invention, the tetrazole compounds are significantly less effective in reducing the gold immersion reaction. In addition, the tetrazole compound exhibits low stability in gold or gold alloy electroplating compositions, resulting in high consumption of the tetrazole compound, malfunction due to an increase in the concentration of decomposition products during processing, and thus a decrease in the lifespan of the gold electrolyte.

Example

Example 1

A copper panel electroplated with nickel was used as the substrate. The substrate was pretreated by rinsing with water, oxidative activation (UniClean 675, from Atotech Deutschland GmbH) at room temperature (ca. 20° C.) for 15 seconds, followed by rinsing again with water and then with deionized water.

Copper panel A was subjected to a freshly prepared gold-cobalt alloy plating bath (Aurocor HSC, 15 g) further containing 500 mg/L of sodium salt of 5-mercapto-1,2,3-triazole as an anti-immersion additive. /L gold, pH 4.5, from Atotech Deutschland GmbH). Electroplating was performed with shaking at a current density of 10 A/dm 2 and a temperature of 60° C. for a time of 150 seconds.

After plating, the substrate was completely covered with a layer of high hardness, bright, uniform and sufficiently adherent gold-cobalt alloy having a thickness of 5 μm.

Example 2

A copper panel electroplated with nickel and pretreated as described in Example 1 was used as the substrate. To mask the unplated areas, half of the substrate area was covered with tesa tape.

Copper panel B was contacted with an aged gold-cobalt alloy plating bath (Aurocor HSC, 15 g/L gold, pH 4.5, from Atotech Deutschland GmbH) containing no mercapto triazole compound.

Copper panels C to F were subjected to a freshly prepared gold-cobalt alloy plating bath (Aurocor HSC, 15 g) each containing 500 mg/L of a mercapto triazole compound or a mercapto tetraazole compound as schematically shown in Table 1. /L gold, pH 4.5, from Atotech Deutschland GmbH).

During contact with the gold-cobalt alloy plating bath, copper panels B to F were not electrically connected. Therefore, metal deposition by electroplating was not possible. 50 ml of a gold-cobalt alloy plating bath containing each mercapto azole compound was used for each panel. The gold-cobalt alloy plating bath was maintained at a temperature of 60° C. and agitated constantly at 400 rpm (revolutions per minute). The contact of each panel was carried out for 5 minutes.

After the panel was brought into contact with each gold-cobalt alloy plating bath, the thickness of the gold alloy layer deposited by the immersion reaction was measured by XRF. The results are summarized in Table 1 below and are shown in FIG. 1 .

Generally, a gold alloy layer was deposited on the portion of the substrate panel that was not covered with tape, whereas the gold alloy was not deposited on the portion of the substrate panel that was covered with the tape. From the gold alloy bath containing the mercapto triazole according to the invention, only a minimum thickness gold alloy layer was deposited by means of an immersion reaction. In contrast, from a gold alloy bath containing no mercapto azole compound or containing a comparable mercapto tetrazole compound, a significantly higher layer thickness gold alloy layer was deposited by the immersion reaction. In addition, comparative compound D caused unwanted precipitation in the gold alloy bath. In contrast to the triazole compound of the present invention, the tetrazole compound exhibits low stability in the gold alloy electrolyte, so that the high consumption of the tetrazole compound, malfunction due to increased concentration of decomposition products during processing, and thus the lifetime of the gold electrolyte causes a decrease Therefore, the mercapto triazole compound of the present invention significantly reduces or almost inhibits the gold immersion reaction.

Example 3

A copper panel electroplated with nickel and pretreated as described in Example 1 was used as the substrate.

The aged gold-cobalt alloy electroplating bath (Aurocor HSC, Atotech Deutschland GmbH) was first treated with activated carbon at 60° C. for 30 min.

In step 1, the gold plating bath was maintained at 60° C. and the substrates were immersed in the gold plating bath for different periods of time without electrical connection. After 30 seconds in the bath, no gold was deposited on the substrate. However, after 2 min and after 3 min, a gold layer was deposited on the substrate by an immersion reaction.

In a subsequent step 2, 25 mg/L of sodium salt of 5-mercapto-1,2,3-triazole was added to the gold plating bath and again the substrate was immersed in the gold plating bath for different periods without electrically connecting the substrate. After 30 seconds, 2 minutes, 3 minutes, and even 5 minutes of contact with the gold plating bath, no gold was deposited on the substrate by the immersion reaction.

Accordingly, the mercapto triazole compound of the present invention significantly reduces or almost inhibits the gold immersion reaction in the aged gold or gold alloy electroplating composition. Therefore, the mercapto triazole compound of the present invention regenerates the aged gold or gold alloy electroplating composition, and significantly increases the lifetime of the gold or gold alloy electroplating composition.

Example 4

On day 1, Example 3 was repeated with the same results. After step 2, the bath was left for 1 day without being used for plating.

On day 2, the substrate was again contacted with the gold plating bath according to step 1 of Example 3. After 3 minutes in the bath, no gold was deposited on the substrate. However, after 5 min, a gold layer was deposited on the substrate by an immersion reaction.

Then, step 2 of Example 3 was performed. Even after 5 minutes of contact with the gold plating bath, no gold was deposited on the substrate by the immersion reaction.

Thus, the addition of the mercapto-triazole compound of the present invention to a gold or gold alloy electrodeposition composition that has temporarily stopped working also significantly reduces or substantially inhibits the gold immersion reaction when the composition is put back into operation.

Example 5

A copper panel electroplated with nickel was used as the substrate. Copper panels were electroplated with nickel and pretreated as summarized in Table 2 below. The copper panels were rinsed with water after each process step listed in Table 2. To mask the unplated areas, half of the substrate area was covered with tesa tape.

Copper panel G was contacted with an aged gold-cobalt alloy plating bath (Aurocor SC, 4 g/L gold, pH 4.5, from Atotech Deutschland GmbH) containing no mercapto triazole compound.

Copper panels H to M were subjected to aged gold-cobalt alloy plating baths (Aurocor SC, 4 g/L gold, pH 4.5, each containing 50 mg/L of mercaptotriazole compound as schematically shown in Table 3) from Atotech Deutschland GmbH).

During contact with the gold-cobalt alloy plating bath, the nickel-coated, pre-treated copper panels G to M were not electrically connected. Therefore, metal deposition by electroplating was not possible. 50 ml of a gold-cobalt alloy plating bath containing each mercapto triazole compound was used for each panel. The gold-cobalt alloy plating bath was maintained at a temperature of 60° C. and agitated constantly at 400 rpm (revolutions per minute). The contact of each panel was carried out for 5 minutes.

After the panel was brought into contact with each gold-cobalt alloy plating bath, the thickness of the gold alloy layer deposited by the immersion reaction was measured by XRF. The results are summarized in Table 3 below and shown in FIG. 2 .

The thickness of the gold-cobalt layer (panel G) deposited from the plating bath containing no mercapto triazole compound was found in Example 2, because the gold concentration in the plating bath in Example 5 was significantly lower than in Example 2. (Panel B) was lower. The thickness of the gold-cobalt layer (panel H) deposited from the plating bath containing 5-mercapto-1,2,3-triazole was determined by: 5-mercapto-1,2, in the plating bath in Example 5; Since the concentration of 3-triazole was significantly lower than in Example 2, it was higher than in Example 2 (Panel C).

Generally, a gold alloy layer was deposited on the portion of the substrate panel that was not covered with tape, whereas the gold alloy was not deposited on the portion of the substrate panel that was covered with the tape. From a gold alloy bath containing mercapto triazole according to the present invention, a gold alloy layer of minimum thickness was deposited by an immersion reaction. In contrast, from a gold alloy bath containing no mercapto triazole compound or containing a comparable amino modified mercapto triazole compound, a significantly higher layer thickness gold alloy layer was deposited by the immersion reaction. Therefore, the mercapto triazole compound of the present invention significantly reduces the gold immersion reaction.

Example 6

Effect of mercapto-triazole compounds on deposition rate, hardness and adhesion of deposited gold layer

A copper panel electroplated with nickel and pretreated as described in Example 1 was used as the substrate.

First, as described in Example 5, the immersion reaction of the aged gold-cobalt alloy plating bath (Aurocor HSC, 15 g/L gold, pH 4.5, manufactured by Atotech Deutschland GmbH) was measured.

Copper panel N was plated by immersion reaction from the fraction of the plating bath containing no mercapto triazole compound. A copper panel P was plated by an immersion reaction from a fraction of the plating bath containing 25 mg/L of the sodium salt of 5-mercapto-1,2,3-triazole. The gold-cobalt alloy layer deposited on panel N by the immersion reaction had a thickness of 82±6 nm and on panel P of 10±4 nm.

Thereafter, unless otherwise stated in subsequent paragraphs, the same aged gold-cobalt alloy plating bath was used to electrodeposit the gold-cobalt alloy layer onto the panel. The deposition rate, hardness and adhesion of the deposited alloy layer were measured. Electrodeposition was performed as described in Example 1.

Deposition rate:

Copper panels Q1 to Q4 were plated from individual fractions of an aged plating bath containing no mercapto triazole compound. Copper panels R1 to R4 were plated from individual fractions of aged plating baths containing 25 mg/L of sodium salt of 5-mercapto-1,2,3-triazole. The current density was varied between 5 and 20 A/dm 2 , as schematically shown in Table 4 below. The thickness of the electrodeposited gold-cobalt alloy layer was measured by XRF. The results are summarized in Table 4.

In the absence or presence of mercapto-triazole, the deposition rates of gold-cobalt alloys from the aged plating baths were approximately the same. Thus, the presence of the mercapto-triazole according to the invention in the gold electrodeposition bath did not affect the deposition rate.

Hardness:

Copper panels S were plated from a fraction of the aged plating bath containing no mercapto triazole compound. Copper panels T were plated from a fraction of the aged plating bath containing 25 mg/L of the sodium salt of 5-mercapto-1,2,3-triazole. Electroplating was performed for 150 seconds at a current density of 15 A/dm 2 to obtain a gold-cobalt alloy layer with a thickness of about 5 μm. Fischer Technology, Inc. Using the XRF-SDD (X-ray Fluorescence-Silicon Drift Detector) instrument of the Fischerscope X-RAY XDRL made of the product, the hardness of the gold-cobalt alloy layer was measured by a Vickers hardness test. The gold-cobalt alloy layer electrodeposited on panel S had a hardness of 180±10 HV 0.001 and on panel T a hardness of 178±10 HV 0.001.

In the absence or presence of mercapto-triazole, the hardness of the gold-cobalt alloy layers deposited from the aged plating baths was approximately the same. Thus, the presence of the mercapto-triazole according to the invention in the gold electrodeposition bath did not affect the hardness of the deposited gold-containing layer.

Adhesion:

To measure the adhesion, a freshly prepared gold-cobalt alloy plating bath (Aurocor HSC, 15 g/L gold, pH 4.5, manufactured by Atotech Deutschland GmbH) was used. The negative effect on the adhesion of the electrodeposited gold-containing layer is best detectable when the deposition is performed using freshly prepared gold or gold alloy plating baths, which have only a low immersion response, and This is because it usually has good adhesion.

Copper panels U1 to U2 were plated from individual fractions of a freshly prepared plating bath containing no mercapto triazole compound. Copper panels V1 to V2 were plated from individual fractions of a freshly prepared plating bath containing 50 mg/L of sodium salt of 5-mercapto-1,2,3-triazole.

Copper panels U1 and V1 were first brought into contact with their respective plating baths for 5 minutes without being electrically connected. Accordingly, in the case of panel V1, mercapto-triazole was adhered to the nickel surface of the panel. Thereafter, a gold-cobalt alloy layer was electrodeposited on the panel by electroplating the copper panels U1 and V1 from each plating bath at 5 A/dm 2 for 72 seconds. The adhesion of the gold-cobalt alloy layer to the panel surface was measured by bending test and tape test. The bending test was performed as follows: The part of the panel to be tested was bent once at an angle of 90°. Adhesion was considered good when no air bubbles were formed in the deposited gold layer or when the flakes of the deposited gold layer did not peel from the bent area. For the tape test, tesa tape 4102 having an adhesive strength of about 6 N/cm was adhered to the gold-cobalt plated panel and then removed from the panel surface. If the tape did not remove some or all of the gold-cobalt layer, the adhesion was as good as at least 6 N/cm, which was considered good. In contrast, when the tape removed some or all of the gold-cobalt layer, the adhesion was insufficient.

The above bending test and tape test showed that the adhesion of the gold-cobalt alloy layer to the nickel surface of panels U1 and V1 was almost the same and was good.

Copper panels U2 and V2 were first brought into contact with their respective plating baths, and a thin gold-cobalt layer (first gold-cobalt layer) having a thickness of 0.1 to 0.2 mu m was electrodeposited. Thereafter, the plated copper panels were brought into contact with each plating bath for 10 seconds without being electrically connected. Thus, for panel V2, mercapto-triazole was adhered to the surface of the deposited gold-cobalt layer. A second gold-cobalt alloy layer was then electrodeposited on the panels by electroplating the copper panels U2 and V2 from their respective plating baths at 5 A/dm 2 for 72 seconds. The adhesion of the second gold-cobalt alloy layer to the surface of the first gold-cobalt layer was measured by the bending test and the tape test as described above.

The above bending test and tape test showed that the adhesion of the second gold-cobalt alloy layer to the surface of the first gold-cobalt layer of panels U2 and V2 was almost equal and good.

In the absence or presence of mercapto-triazole, the adhesion of the gold-cobalt alloy layer deposited from the freshly prepared plating bath was approximately the same. Thus, the presence of the mercapto-triazole according to the invention in the gold electrodeposition bath did not affect the adhesion of the deposited gold-containing layer.

Claims (12)

An acidic electroplating composition comprising:
(i) one or more sources of gold ions, and
(ii) at least one mercapto-triazole having the formula (I) or (II):

(Wherein, R ¹ , R ⁴ are independently of each other hydrogen, linear or branched, saturated or unsaturated (C ₁ -C ₂₀ ) hydrocarbon chain, (C ₈ -C ₂₀ ) aralkyl group; substituted or unsubstituted phenyl group, naph a tyl group or a carboxyl group;
R ² , R ³ , R ⁵ , R ⁶ are independently of each other —SX, hydrogen, linear or branched, saturated or unsaturated (C ₁ -C ₂₀ ) hydrocarbon chain, (C ₈ -C ₂₀ ) aralkyl group; a substituted or unsubstituted phenyl group, a naphthyl group, or a carboxyl group;
X is hydrogen, a (C ₁ -C ₄ ) alkyl group or a counter ion selected from alkali metal ions, calcium ions, ammonium ions and quaternary amines;
at least one of R ² and R ³ is -SX and at least one of R ⁵ and R ⁶ is -SX)
includes,
The acidic electroplating composition, wherein the at least one mercapto-triazole has a concentration in the acidic electroplating composition in the range of 1 mg/L to 1 g/L. 2. The method of claim 1, wherein the at least one mercapto-triazole is
R ¹ , R ⁴ are each independently hydrogen or a linear (C ₁ -C ₄ ) alkyl group,
R ² , R ³ , R ⁵ , R ⁶ are each independently —SX, hydrogen or a linear (C ₁ -C ₄ ) alkyl group;
X is hydrogen, a methyl group, an ethyl group, or a counter ion selected from sodium ion and potassium ion;
at least one of R ² and R ³ is -SX and at least one of R ⁵ and R ⁶ is -SX;
An acidic electroplating composition having formula (I) or (II). The acidic electroplating composition according to claim 1, wherein the at least one mercapto-triazole has a concentration in the range of 1 mg/L to 900 mg/L. The acidic electroplating composition of claim 1, further comprising one or more sources of alloying metal ions, wherein the metal of the alloying metal ions is selected from cobalt, nickel and iron. The acidic electroplating composition of claim 1, further comprising a complexing agent for gold ions. The acidic electroplating composition according to claim 1, further comprising at least one brightening agent selected from pyridine and quinoline compounds. The acidic electroplating composition according to claim 1, having a pH value of 1-6. A method comprising the steps of:
(i) providing an acidic electroplating composition according to any one of claims 1 to 7;
(ii) contacting the substrate with the composition; and
(iii) depositing gold or a gold alloy on the substrate by applying an electric current between the substrate and the one or more anodes. 9. The method of claim 8, wherein the substrate is iron, nickel, copper or an alloy thereof. 9. The method of claim 8, wherein the substrate is an electrical connector. A method comprising the steps of:
(i) providing a used gold or gold alloy electroplating composition;
(ii) adding a mercapto-triazole as defined in claim 1 or 2 to the used gold or gold alloy electroplating composition for regeneration, and
(iii) contacting the substrate with the composition; and
(iv) depositing gold or a gold alloy on the substrate by applying an electric current between the substrate and the one or more anodes. 3. Acidic electroplating composition according to claim 1 or 2, wherein mercapto-triazole is used as an anti-immersion additive.

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