DE10007325A1 - Acid bath for galvanically depositing glossy gold and gold alloy layers contains gold and optionally one or more alloying elements in dissolved form as well as an organic compound as brightening agent - Google Patents

Abstract

Acid bath contains gold and optionally one or more alloying elements in dissolved form as well as an organic compound as brightening agent. Acid bath contains gold and optionally one or more alloying elements in dissolved form as well as an organic compound as brightening agent. The brightening agent is a compound of the formula: R-SOmH; m = 3 or 4; R = up to 20C alkyl; and when m = 4, R = up to 10C aryl or heteroaryl which can be substituted by 1-14C alkyl.

Description

The invention relates to an acidic bath for galvanic Ab separation of shiny gold and gold alloy layers and a gloss additive for this.

Galvanic gold baths usually contain gold and ge if necessary one or more alloying elements in dissolved most form.

Such electrolytes are mainly based on gold cyanide complex. It is necessary to use these electrolytes of inorganic and / or organic acids and buffers salt to a weak to moderately acidic pH put.

So shiny gold or gold alloy from such baths layers are deposited, these contain usual Certain inorganic or organic compounds conditions as so-called "gloss additives".

A typical, very frequently used gloss additive is as described for example in DE 23 55 581, the verb dung pyridine-3-sulfonic acid.

Such additions move or expand the working area rich, i.e. the range of applicable current density in which a shiny gold plating is deposited toward higher Current densities. The use of higher current densities in turn allows separation at a higher speed.

On the other hand, the working area of such gold baths also depends on the pH of the electrolyte. The following applies: that at higher pH the working range (applicable Current density range), but at the same time the current  yield and thus increased the separation speed becomes.

It was therefore an object of the invention to optimize the Working conditions and the separation performance of such acidic gold baths in the sense that one a maximum current density working range at possible minimal negative influence by pH Changes and on the other hand a maximum current efficiency and Separation speed is achieved.

Surprisingly, it has now been found that this can be achieved if such acid baths for the deposition of shiny gold layers as a further additive to shine at least one compound of general formula I.

R-SO _m -H (I)

is added in which
m the numbers 3 or 4 and
R is a straight or branched chain or cyclic alkyl group with up to 20 C atoms and in the case of m = 4 also an aryl or hetero ryl group with up to 10 C atoms, which may be one or more times with straight or branched chains Alkyl groups with 1 to 14 C atoms can be substituted,
means.

The invention thus relates to an acidic bath for the galvanic deposition of shiny gold and gold alloy layers, containing gold and optionally one or more alloying elements in dissolved form and at least one organic compound as an additive, characterized in that the bath has at least one additional additive least a compound of the general formula

R-SO _m -H (I)

contains what
m the numbers 3 or 4 and
R is a straight or branched chain or cyclic alkyl group with up to 20 C atoms and in the case of m = 4 also an aryl or hetero ryl group with up to 10 C atoms, which may be one or more times with straight or branched chains Alkyl groups with 1 to 14 C atoms can be substituted,
means.

The gloss additives according to formula I are selected compounds genes from the classes of alkyl sulfonates and alkyl, Aryl or heteroaryl sulfates. In formula I means if m stands for the numbers 3 or 4, R is a straight or ver branched or cyclic alkyl group with up to 20 C- Atoms. If m stands for the number 4, then R can also be one Aryl or heteroaryl group with up to 10 C atoms, these one or more times with straight or ver branched chain alkyl groups with 1 to 14 carbon atoms substituted can be.

The compounds of formula I are known per se and are either commercially available or readily available Standard processes can be produced.

These compounds are sufficiently water-soluble and with compatible with the electroplating bath. The compounds have surfactant properties, the corresponding effect with a Total number of carbon atoms is less than 4, and with a total number of C atoms of more than 20 in general mean there is no longer sufficient solubility.  

Preferred gloss additives are compounds of the formula I in which R for straight or branched chain or cyclic Al alkyl groups with 5 to 12 carbon atoms and especially for ver branched chain alkyl groups having 6 to 10 carbon atoms.

Typical gloss additives according to the invention are
Pentyl sulfonate
Pentyl sulfate
Hexyl sulfonate
Hexyl sulfate
Heptyl sulfonate
Heptyl sulfate
Octyl sulfonate
Octyl sulfate
Nonyl sulfonate
Nonyl sulfate
Decyl sulfonate
Decyl sulfate
Dodecyl sulfonate
Dodecyl sulfate
Cyclohexyl sulfonate
Cyclohexyl sulfate
and their isomers.

These compounds can also be in the form of their salts gene.

Branched-chain and short-chain connections are suitable due to the less pronounced tendency to foam in processes and systems in which there is a strong foam dung disturbs, e.g. B. in air-moving electrolytes in the Drum processing in high-speed plants separation (spraying systems) and in systems for selective Deposition, such as B. diving cells.

The use of the further gloss additive according to the invention in acidic baths for the galvanic deposition of shine the gold and gold alloy layers are more convenient wise in a concentration range of 0.01 to 10 g / l. Baths according to the invention which are particularly advantageous are those which Gloss additive according to formula I in a concentration of 0.1 up to 5 g / l included.  

By using the compounds of the invention Compounds of formula I as a further gloss additive in gal Vanian gold baths of otherwise usual composition the applicable current density is unexpectedly Work area significantly expanded and at the same time the Electricity yield and the separation performance sometimes drastic increased.

To produce the gold baths according to the invention, from many common and commercially available galvanic, weak acidic gold baths, in which the appropriate amount of compound of formula I added becomes. The qualitative and quantitative composition of the like gold baths is the specialist from literature and practice well known and therefore does not require a more detailed He purification. In any case, these contain gold in dissolved form Form, starting from gold salts or gold complex salts, where mainly used in gold cyanide complexes. Wei The baths can also be alloyed in the form of dissolved Contain salts or complex salts. Furthermore, the Baths inorganic and / or organic acids de salts and, if appropriate, buffer and conductive salts, around which Adjust pH and conductivity. To shine, Deposition of smooth gold layers is regularly organic contain chemical compounds, mostly surfactant properties have and act as brighteners. A typical and be pyridine-3-sulfonic acid is the most common such brightener.

Furthermore, conventional gloss additives also come
Nicotinic acid,
Nicotinamide,
3- (3-pyridyl) acrylic acid
3- (4-imidazolyl) acrylic acid
3-pyridylhydroximethanesulfonic acid
Pyridine
Picolin
Quinoline sulfonic acid
3-aminopyridine
2,3-diamino pyridine
2,3-di- (2-pyridyl) pyrazine
2- (pyridyl) -4-ethanesulfonic acid
1- (3-sulfopropyl) pyridinium betaine
1- (3-sulfopropyl) isoquinolinium betaine
and their salts and derivatives. The galvanic gold baths according to the invention typically contain approximately
0.1-50 g / l gold as a gold cyanide complex
0-50 g / l alloy metals such as iron, cobalt, nickel, indium, silver, copper, cadmium, tin, zinc, bismuth, arsenic, antimony as salt or complex salt
10-200 g / l citric acid / citrate as buffer and / or conductive salts
0.1-10 g / l pyridine-3-sulfonic acid as a brightener
0.1-5 g / l compound of the formula I as a further gloss additive according to the invention,
wherein the pH of the bath is adjusted to 3 to 6, preferably 4 to 5.

The use of the gloss additive according to the invention brings about a A number of practical advantages. So under otherwise unchanged conditions the separation performance clearly be increased. Because of the wider work area the fine tuning of the way of working is less critical, whereby the risk of sudy deposition is significantly reduced is decorated.

But it can also with higher pH values with unchanged Work area. So that's it too possible to increase the separation performance.

Alternatively, a low gold content can also be used constant separation performance can be used. The The advantages are the lower carry-over electrolyte adhering to the goods and in the lower one Capital commitment.

example 1

In a gold-cobalt electrolyte with
10 g / l gold in the form of potassium gold (I) cyanide
0.5 g cobalt as cobalt sulfate
100 g / l citric acid
3 g / l pyridine-3-sulfonic acid
adjusted to pH 4.2 with potassium hydroxide
a working range of up to 3 A / dm ^{2 is} achieved in a Hull cell (test conditions: platinized titanium anode, temperature 50 ° C, duration 2 mm, movement 500 rpm by means of a magnetic stirring bar 25 mm) with a cell current of 2 A. The current yield at 3 A / dm ² is 48%; the separation speed is 0.98 µm / min.

By adding 1 g / l nonyl sulfate, the maximum applicable current density is increased to over 5 A / dm ² . This corresponds to a widening of the work area by over 66%.

When the pH is then raised to 4.4, a working range of up to 4 A / dm ^{2 is} achieved; the separation rate is 1.05 µm / min.

At pH 4.6 the working range extends to 3 A / dm ² and a deposition speed of 1.15 µm / min is achieved.

Example 2

In a gold-nickel electrolyte with
10 g / l gold in the form of potassium gold (I) cyanide
0.7 g of nickel in the form of nickel sulfate
100 g / l citric acid
3 g / l pyridine-3-sulfonic acid
adjusted to pH 4.2 with potassium hydroxide
a maximum current density of 3 A / dm ² is achieved on pre-nickel-plated sheets of size 25 × 40 mm (test setup: 1 liter beaker, platinum-coated titanium anode, bath movement 200 rpm using a magnetic stirring bar 60 mm, movement of goods 5 cm / s). The cathodic current yield at 3 A / dm ² is 52% and the deposition rate is 1.0 µm / min.

The addition of 0.5 g / l decyl sulfate increases the maximum applicable current density to over 7 A / dm ² . At 7 A / dm ² the current yield is still 26%, the separation performance increases to 1.18 µm / min. This corresponds to a speed increase of 18%.

Example 3

In a gold-iron electrolyte with
10 g / l gold in the form of potassium gold (I) cyanide
0.05 g iron as iron (III) citrate
100 g / l citric acid
3 g / l pyridine-3-sulfonic acid adjusted to pH 4.2 with potassium hydroxide
a maximum current density of 5 A / dm ^{2 is} achieved on sheets of size 25 × 40 mm (conditions see example 2). The cathodic current yield is 31% and the deposition rate is 1.0 µm / min.

By adding 4 g / l hexyl sulfate, the maximum current density that can be used is increased to over 6 A / dm ² . At 6 A / dm ² , the current yield is still 30%; the separation rate increases to 1.16 µm / min. This corresponds to a speed increase of 16%.

Example 4

In a gold-cobalt electrolyte with
10 g / l gold in the form of potassium gold (I) cyanide
0.5 g cobalt as cobalt sulfate
100 g / l citric acid
1 g / l 3- (3-pyridyl) acrylic acid
adjusted to pH 4.2 with potassium hydroxide
a working range of up to 5 A / dm ^{2 is} achieved in a Hull cell (test conditions: platinum-plated titanium anode, temperature 50 ° C., duration 2 min. movement 500 rpm by means of a magnetic stirring bar 25 mm) with a cell current of 2 A. The current yield at 5 A / dm ² is 26%; the separation speed is 0.83 µm / min.

By adding 1.5 g / l octyl sulfate, the maximum applicable current density is increased to over 8 A / dm ² . At 8 A / dm ² , the current yield is still 19%; the separation rate increases to 1.0 µm / min.

Example 5

In the gold-cobalt electrolyte from Example 1, the maximum applicable current density is increased to over 5 A / dm ² by adding 1 g / l hexyl sulfonate. At 5 A / dm ² , the current yield is 35.1%, the separation efficiency increases to 1.13 µm / min. This corresponds to a speed increase of 15%.

Example 6

In the gold-cobalt electrolyte from Example 1, the maximum applicable current density is increased to over 7 A / dm ² by adding 1 g / l octyl sulfonate. At 7 A / dm ² , the current yield is 26.2%, the separation efficiency increases to 1.18 µm / min. This corresponds to a speed increase of 20%.

Example 7 Comparative example

In a gold-cobalt electrolyte (see Example 1)
10 g / l gold in the form of potassium gold (I) cyanide
0.5 g cobalt as cobalt sulfate
100 g / l citric acid
adjusted to pH 4.2 with potassium hydroxide
under the test conditions of Example 1, the flow to the working area and deposition rate by adding octyl sulfate alone, pyridine-3-sulfonic acid alone and both substances together as gloss additives, he averaged. Table 1 shows the result.

The combination of both substances extends the Ar working area drastically and causes a considerable climb separation speed.

Table 1

Claims (6)

1. Acidic bath for the electrodeposition of shiny gold and gold alloy layers containing gold and optionally one or more alloy elements in dissolved form and at least one organic compound as a brightener, characterized in that the bath as a further brightener at least one compound of the general formula
R-SO _m H (I)
contains what
m the numbers 3 or 4 and
R is a straight or branched chain or cyclic alkyl group with up to 20 C atoms and in the case of m = 4 also an aryl or hetero ryl group with up to 10 C atoms, which may be one or more times with straight or branched chains Alkyl groups with 1 to 14 C atoms can be substituted,
means. 2. Galvanic bath according to claim 1, characterized, that there is at least one verb as a further gloss additive contains the formula I, wherein R is a straight or  branched-chain alkyl group with 5 to 12 carbon atoms, preferably a branched chain alkyl group with 6 is up to 10 carbon atoms. 3. Galvanic bath according to claim 1 or 2, characterized featured, that the compounds Pen tyl sulfonate, hexyl sulfonate, heptyl sulfonate, octyl sulfo nat, nonyl sulfonate, decyl sulfonate, dodecyl sulfonate, cy clohexyl sulfonate, pentyl sulfate, hexyl sulfate, heptyl sulfate fat, octyl sulfate, nonyl sulfate, decyl sulfate, dodecyl sulfate fat, cyclohexyl sulfate or their isomers. 4. Galvanic bath according to claims 1 to 3, characterized, that it is 0.01 to 10 g / l, preferably 0.1 to 5 g / l Contains compound of formula I. 5. Use of compounds of the general formula
R-SO _m H (I)
wherein
m the numbers 3 or 4 and
R is a straight-chain or branched-chain or cyclic alkyl group with up to 20 C atoms and in the case of m = 4 also or an aryl or heteroaryl group with up to 10 C-atoms, which may be one or more times with straight or branched chains Alkyl groups with 1 to 14 C atoms can be substituted,
means
as a further gloss additive in acid baths for the galvanic deposition of shiny gold and gold alloy layers, containing gold and optionally one or more alloy elements in dissolved form and at least one organic compound as a gloss additive. 6. Process for the electrodeposition of shiny Gold and gold alloy layers, characterized, that the deposition from a bath according to the claims 1 to 4 at a pH range of 3 to 6, preferably way 4 to 5, takes place.