JP2000204496A - Gold plating solution and plating using the gold plating solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use wider-ranging gold salts free of poisonous cyan as a starting material and to make the gold plating soln. stable and usable over a long period by incorporating specified amts. of a trivalent gold salt, 1,2-ethanediamine, a buffer, an org. brightener and a conductive salt. SOLUTION: This non-cyan gold electroplating soln. contains 5-30 g/l trivalent gold salt as a gold salt and 0.2-3.0 M of 1,2-ethanediamine as a complexing agent and further contains a buffer, org. brightener and conductive salt. Bis(1,2- ethanediamine) gold chloride, gold hydroxide, tetrahydroxogold potassium and chloroauric acid are preferably used as the trivalent gold salt. The buffer preferably contains 0.05-1.0 M of an org. carboxylic acid at 2-6 pK, phosphoric acid, boric acid, or the like, the org. brightener contains 50-10,000 ppm o- phenanthroline, bipyridyl, or the like, and the conductive salt contains 0.05-5.0 M of sulfate ion, hydrochloride ion, nitrate ion, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gold plating solution which does not contain sulfite ions, has excellent solution stability and can be used for a long period of time, and a gold plating method using the same.

[0002]

2. Description of the Related Art Gold plating has been widely used not only for decoration and Western tableware, but also in the field of electronics industry due to its excellent electrical characteristics.

In the past, most of the gold plating solution was a cyanide bath containing toxic potassium potassium cyanide. However, recently, there have been problems in terms of work safety or wastewater treatment, and attacks on resists of semiconductor parts and the like. Due to the problem described above, the demand for a non-cyanide-based gold plating solution is increasing, and various non-cyanide-based gold platings have been proposed.

For example, as a non-cyanide gold plating solution,
As reported in J. Am, Chem, Soc. 1951, vol. 73, P4722, there is one using bis (1,2-ethanediamine) gold chloride as a gold compound. This screw (1,
As the 2-ethanediamine) gold chloride, those obtained by a production method in which chloroauric acid and ethylenediamine (monohydrate) are reacted at room temperature using a solvent (diethyl ether) have been widely known.

The present inventors have proposed a method for producing a new bis (1,2-ethanediamine) gold chloride and a gold plating bath using the bis (1,2-ethanediamine) gold chloride, which has a beautiful appearance by plating. The present inventors have also proposed a plating solution and a method for obtaining a layer.

[0006] Further, among non-cyanide gold plating baths that have been widely used, those using Na ₃ Au (SO ₃ ) ₂ as a gold salt were often found. However, Na ₃ Au (SO ₃ )
_In the gold plating bath using No. ₂ , the sulfite ions in the solution are very unstable, are oxidized by the oxygen generated from the anode and the oxygen in the atmosphere, are cheap, and the concentration naturally decreases. As a result, the stability of the gold complex in the gold plating solution has been reduced, and the physical properties of the electrodeposits have changed and the plating solution has been decomposed.

The present inventors have provided a gold plating solution having a composition which is extremely excellent in solution stability of a gold plating bath and which does not cause change in physical properties of deposited gold or decomposition of the gold plating solution during the operation of gold plating. An electrolytic gold plating solution capable of controlling the hardness, purity, crystal state, etc. of the deposited gold by using a bis (1,2-ethanediamine) gold complex as the gold plating solution,
Advocated and intensively researched.

In this electrolytic gold plating solution, a bis (1,2-ethanediamine) gold complex must always be used as a gold salt, which imposes restrictions on material selection.

[0009]

Therefore, the present inventor has proposed:
A wider range of gold salts can be used as starting materials,
In addition, the present invention provides an electrolytic gold plating solution that can withstand long-term stability and long-term operation, and a plating method using the electrolytic gold plating solution.

[0010]

The inventors of the present invention have made intensive studies on a non-cyanide electrolytic gold plating solution which is more practically practical, and as a result, have found that the gold plating solution according to claim 1 exhibits extremely excellent performance. I found it.

According to the first aspect of the present invention, a gold salt, 1,2-
An electrolytic gold plating solution comprising ethanediamine, a buffer, an organic brightener, and a conductive salt, comprising a trivalent gold salt as a source of 5 g / l to 30 g / l gold, and a 0.2 M to 3.0 M gold salt. A non-cyanide electrolytic gold plating solution comprising: 1,2-ethanediamine.

The gold salt is used as a supply source of gold, and a general trivalent gold salt can be used.
The reason for using this trivalent gold salt is that it does not include sulfite ions and takes into account the long-term solution stability exceeding the conventionally used gold sulfite plating solution and the properties of the plating film formed. This is because the result of the study was that the best balance was obtained.

The trivalent gold salt referred to here is bis (1,2)
-Ethanediamine) any one or two of gold trichloride, gold hydroxide, potassium tetrahydroxogold, and chloroauric acid
It is particularly desirable to use more than one species. This is because these trivalent gold salts are hardly deteriorated as a gold plating solution over a long period of time, and have been found to be particularly excellent in long-term solution stability. Therefore, these contents are described in claim 2.

The content as gold is in the range of 5 to 30 g / l. If the lower limit is 5 g / l or less, the deposition rate of gold is too low to be suitable for actual operation, and the upper limit of 30 g / l is the limit of the soluble amount. Therefore, as long as the amount of gold is within the solubility limit, the larger the amount, the higher the deposition rate. Therefore, a value corresponding to the target operating condition can be selected and used within this range.

1,2-ethanediamine is used as a complexing agent. This 1,2-ethanediamine sulfate is added in the range of 0.2 to 3.0M. Lower limit 0.1
If it is less than M, the effect as a complexing agent will not be exhibited, and if it exceeds the upper limit of 3.0 M, it will not be dissolved. By using this 1,2-ethanediamine, gold is converted into bis (1,
The situation is the same as when a 2-ethanediamine) gold complex is used, and non-cyanide electrolytic gold plating showing stability that does not easily decompose is obtained. Even when bis (1,2-ethanediamine) gold trichloride, which is a kind of bis (1,2-ethanediamine) gold complex, is used, a more stable gold plating solution can be obtained by adding 1,2-ethanediamine. It becomes.

As the potassium salt of an inorganic acid, potassium sulfate, potassium chloride, potassium nitrate and the like can be used. These are substances added to fulfill the function as a conductive salt when used as an electrolytic solution. The added amount is 1 to 1
It is preferable to add in the range of 00 g / l. If the lower limit is 1 g / l or less, it is difficult to secure sufficient conductivity as a plating solution, and if the upper limit is 100 g / l or more, it will not be dissolved in the solution.

It is desirable to use one or more of the organic carboxylic acid phosphoric acid and boric acid having a pK value of 2 to 6 described in claim 3 as the buffering agent. It is desirable that the molarity be in the range of 0.05M to 1.0M. Here, the organic carboxylic acid having a pK value of 2 to 6 specifically includes citric acid, acetic acid, succinic acid,
Lactic acid, tartaric acid, and the like, as well as those having a buffering action such as phosphoric acid and boric acid are used. The buffering function plays a role in suppressing the fluctuation of the pH of the non-cyanide electrolytic gold plating solution. Even when one or two or more drugs are used, the added amount is 0.05M to 1.
It is preferably in the range of 0M. If the lower limit value is 0.05M or less, it does not sufficiently play a role as a buffer, and if the upper limit value is 1.0M or more, the effect as a buffer does not increase.

Further, as the organic brightener, one or more kinds of heterocyclic compounds such as O-phenanthroline, bipyridyl and derivatives thereof can be used. And, the amount of addition is preferably in the range of a total concentration of 50 ppm to 10000 ppm. Such a broad concentration range is indicated because the solubility of these organic brighteners varies depending on the solution pH. If the lower limit value is 50 ppm or less, it does not sufficiently serve as a brightener, and if the upper limit value is 10000 ppm or more, the effect of improving gloss is not improved.

As the conductive salt for imparting conductivity, as described in claim 5, a compound containing any of sulfate ion, hydrochloric acid ion and nitrate ion is used. That is,
A means for moving and supplying 1,2-ethanediamine and conductive ions using a compound of 1,2-ethanediamine is the most efficient and economical. Therefore, one or two or more compounds of 1,2-ethanediamine are used,
Further, it is preferable to add the conductive ions in a total molar concentration of 0.05 M to 5.0 M. This lower limit value is 0.05M
In the following, it is difficult to secure sufficient conductivity as a plating solution, and if the upper limit value is 5.0 M, the plating solution will not be dissolved in the solution.

It is also possible to add any of sulfate ion, hydrochloric acid ion and nitrate ion in the form of sulfuric acid, hydrochloric acid and nitric acid, but such addition may be used as a means for adjusting pH. Deemed desirable.

A sixth aspect of the present invention provides a method for plating using the non-cyanide electrolytic gold plating solution according to the first to fifth aspects, wherein the solution has a pH of 2 to 6 and a solution temperature of 40 to 70 ° C.
Under the conditions described above, and a current density of 0.1 to 3.0 A / dm ² .

Here, the pH value of the solution is in the range of pH 2 to 6, and within this range, no abnormality occurs in the appearance of the deposited gold plating layer. When the pH needs to be adjusted, it is preferable to adjust the pH using an inorganic acid salt such as sulfuric acid, hydrochloric acid, and nitric acid which does not affect the properties of the plating solution, or an organic carboxylic acid such as acetic acid, formic acid, and benzoic acid.

The reason why the temperature of the plating solution is set to a temperature of 40 to 70 ° C. is that when the plating temperature is lower than the lower limit, the deposition rate is slow and is not suitable for actual operation. This is because the life is shortened.

The current density during the electrolysis is 0.1 to 3.0 A / d
The range of m ² is a range in which good properties can be imparted to the deposited gold plating layer in consideration of the pH value and the solution temperature of the plating solution.

By using the above gold plating solution and gold plating method, it is possible to obtain a deposited gold having low hardness while having fine crystal grains and excellent long-term stability, as compared with the case of using a conventional electrolytic gold plating solution. It can be used for a long time. Since the crystal structure obtained by the plating method according to the present invention has a high purity of precipitated gold, a low-hardness gold plating layer having a low intragranular transition density and close to bulk gold even with fine crystal grains can be obtained.

This is, for example, Na ₃ Au (SO ₃ ) ₂
In the gold plating bath using, the sulfur contained in the plating solution is precipitated in the deposited gold, so that the same effect as when the deposited gold is dispersed is obtained, and a hard crystal structure is obtained even if the crystal grains are large. In addition, compared with the case where the electrolytic gold plating solution according to the present invention is used, deterioration of the plating solution such as gold deposition occurs in a short time, and stable operation for a long period is difficult.

In the conventional plating method using a plating solution, very fine bump plating cannot be performed with high precision, and the gold deposition surface after plating becomes rough, and the bump shape becomes irregular. was there. By adopting the gold plating solution and the gold plating method according to the present invention, it is possible to obtain a gold plating layer in which gold is finely deposited.
It is possible to form a gold plating layer with high precision also on the bumps of I, and it is possible to reduce the running cost of the gold plating solution.

Table 1 shows the results of the long-term stability test when the electrolytic gold plating solution according to the present invention was used. In Table 1, the stability was 10 g / l after applying a current of 15000 coulombs to 1 liter of non-cyanide electrolytic gold plating solution.
When gold was used as the gold, the deposition stability (deposition rate, deposition variation, precipitation hardness, etc.) of the gold plating layer was evaluated.

[0029]

[Table 1]

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The non-cyanide electrolytic gold plating solution and the plating method using the plating solution according to the present invention will be described below in more detail with reference to the embodiments considered to be optimal.

First Embodiment: Bis (1,1) used for a gold salt
2-ethanediamine) gold trichloride has a reaction temperature of 3
Obtained at 0 ° C. by the following reaction. The reaction temperature at this time is 15 ~
60 ° C. is preferred. If the temperature is lower than 15 ° C., the reaction does not proceed sufficiently and the yield is lowered. If the temperature is higher than 60 ° C., a reduction reaction of gold ions occurs, and gold fine particles are generated.

NaAuCl 4 + 2en → Au (e
n) 2 Cl3 + NaCl

Using the bis (1,2-ethanediamine) gold trichloride thus obtained, a non-cyanide electrolytic gold plating solution was built up. The composition of the non-cyanide electrolytic gold plating solution is as follows.

Bis (1,2-ethanediamine) gold trichloride (as gold) 10 g / l 1,2-ethanediamine sulfate 100 g / l Buffer (citric acid) 50 g / l Organic brightener (o-phenanthroline) 100 ppm

Using this gold plating solution, a test pattern was subjected to gold plating under the following plating conditions.

PH value 3.50 Plating solution temperature 60 ° C. Current density 1.0 A / dm ² Electrolysis time 75 min

The physical properties of the gold plating layer formed under the above conditions were measured, and the results are shown in Table 2. As can be seen from Table 2, the Vickers hardness of the gold plating layer is 66.7 on average. The life of the electrolytic gold plating solution is 35 in terms of energizing time.
00 hours.

Second Embodiment Gold hydroxide was used as the gold salt. Then, the gold concentration was adjusted to 8 g / l. The composition of the non-cyanide electrolytic gold plating solution is as follows.

Gold hydroxide (as gold) 8 g / l 1,2-ethanediamine dihydrochloride 80 g / l Buffer (boric acid) 30 g / l Organic brightener (2,2-bipyridyl) 400 ppm

Using this gold plating solution, a test pattern was subjected to gold plating under the following plating conditions.

PH value 4.30 Plating solution temperature 55 ° C. Current density 1.2 A / dm ² Electrolysis time 75 min

The physical properties of the gold plating layer formed under the above conditions were measured, and the results are shown in Table 2. As can be seen from Table 2, the Vickers hardness of the gold plating layer is 72.1 on average. The life of the electrolytic gold plating solution is 34 in terms of energizing time.
50 hours.

Third Embodiment: As the gold salt, potassium tetrahydroxogold was used. And the gold concentration is 10 g /
l. The composition of the non-cyanide electrolytic gold plating solution is as follows.

Potassium tetrahydroxogold (as gold) 10 g / l 1,2-ethanediamine disulfate 120 g / l Buffer (boric acid) 50 g / l Organic brightener (2,2-bipyridyl) 1200 ppm

Using this gold plating solution, a test pattern was subjected to gold plating under the following plating conditions.

PH value 3.60 Plating solution temperature 65 ° C. Current density 1.5 A / dm ² Electrolysis time 75 min

The physical properties of the gold plating layer formed under the above conditions were measured, and the results are shown in Table 2. As can be seen from Table 2, the Vickers hardness of the gold plating layer is 73.0 on average. The life of the electrolytic gold plating solution is 33
00 hours.

Fourth Embodiment: Chloroauric acid was used for the gold salt. Then, the gold concentration was adjusted to 10 g / l. The composition of the non-cyanide electrolytic gold plating solution is as follows.

Chloroauric acid (as gold) 10 g / l 1,2-ethanediamine disulfate 150 g / l Buffer (boric acid) 40 g / l Organic brightener (2,2-bipyridyl) 1000 ppm

Using this gold plating solution, a test pattern was subjected to gold plating under the following plating conditions.

PH value 3.60 Plating solution temperature 60 ° C. Current density 1.2 A / dm ² Electrolysis time 75 min

The physical properties of the gold plating layer formed under the above conditions were measured, and the results are shown in Table 2. As can be seen from Table 2, the Vickers hardness of the gold plating layer is 70.5 on average. The life of the electrolytic gold plating solution is 31 in terms of energizing time.
00 hours.

Fifth Embodiment: As the gold salt, potassium tetrahydroxo and chloroauric acid were used. Then, the total gold concentration was adjusted to 10 g / l. The composition of the non-cyanide electrolytic gold plating solution is as follows.

Potassium tetrahydroxogold (as gold) 5 g / l Chloroauric acid (as gold) 5 g / l 1,2-ethanediamine disulfate 120 g / l Buffer (dipotassium hydrogen phosphate) 30 g / l Organic brightener (2,2-bipyridyl) 400ppm

Using this gold plating solution, a test pattern was subjected to gold plating under the following plating conditions.

PH value 6.0 Plating solution temperature 45 ° C. Current density 1.0 A / dm ² Electrolysis time 75 min

The physical properties of the gold plating layer formed under the above conditions were measured, and the results are shown in Table 2. As can be seen from Table 2, the Vickers hardness of the gold plating layer is 67.0 on average. The life of the electrolytic gold plating solution is 32 in terms of energizing time.
80 hours.

In order to compare the performance of the non-cyanide electrolytic gold plating solution according to the present invention with that of a conventional non-cyanide electrolytic gold plating solution, gold plating using Na ₃ Au (SO ₃ ) ₂ as a gold salt was carried out, and a bath similar to the above was prepared. The test pattern was plated with gold to make a comparative example. The composition of a conventional non-cyanide gold plating solution is as follows.

Na ₃ Au (SO ₃ ) ₂ (as Au) 10 g / l Na ₂ SO ₃ 20 g / l Na 2 HPO 4 20 g / l thallium 0.01 g / l

Using this solution, a test pattern was plated with gold under the following conditions.

PH value 7.5 Plating solution temperature 65 ° C. Current density 0.5 A / dm ² Electrolysis time 60 min

The life of the gold plating solution produced under the above conditions and the physical properties of the gold plating layer were measured, and the results are shown in Table 1 as a conventional non-cyanide gold plating solution. As can be seen from Table 2, the Vickers hardness of the gold plating layer is 75.1 on average. Further, the life of the conventional electrolytic gold plating solution was 1000 to 2000 hours in terms of the energizing time. This has a shorter life than the non-cyanide electrolytic gold plating solution according to the present invention.

[0063]

[Table 2]

[0064]

By using the non-cyanide gold plating solution according to the present invention, it is possible to provide a gold plating solution which is extremely excellent in solution stability and does not cause change in physical properties of deposited gold or decomposition of the gold plating solution during the operation of gold plating. This has made it possible to reduce the operating cost of this electrolytic gold plating.

Claims (6)

[Claims] 1. An electrolytic gold plating solution comprising a gold salt, 1,2-ethanediamine, a buffer, an organic brightener, and a conductive salt, comprising a trivalent gold as a supply source of 5 g / l to 30 g / l. A non-cyanide electrolytic gold plating solution comprising: a gold salt; and 0.2 M to 3.0 M 1,2-ethanediamine. 2. The trivalent gold salt is characterized by using one or more of bis (1,2-ethanediamine) gold chloride, gold hydroxide, potassium tetrahydroxogold and chloroauric acid. The non-cyanide electrolytic gold plating solution according to claim 1. 3. The buffer contains one or more of organic carboxylic acids, phosphoric acids and boric acids having a pK value of 2 to 6, and has a total molar concentration of 0.05 M to 1.
The non-cyanide electrolytic gold plating solution according to claim 1 or 2, wherein the electroless gold plating solution is 0M. 4. An organic brightener comprising one or more of o-phenanthroline, bipyridyl, an o-phenanthroline derivative and a bipyridyl derivative, and having a total concentration of 50 ppm to 10,000 ppm.
The non-cyanide electrolytic gold plating solution according to any one of claims 1 to 3, wherein 5. The conductive salt is a compound containing any one of a sulfate ion, a hydrochloric acid ion and a nitrate ion, using one or more of the compounds, and having a total molar concentration of 0.05M. The non-cyanide electroless gold plating solution according to claim 1, wherein the plating solution has a concentration of up to 5.0 M. 6. A plating method using the non-cyanide electrolytic gold plating solution according to claim 1, wherein the current density is 0.about.6 under the conditions of a solution pH of 2 to 6 and a solution temperature of 40 to 70 ° C. A non-cyanide electrolytic gold plating method for performing electrolysis under a condition of 1 to 3.0 A / dm ² .