JP2000345359A - Electroless gold plating solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a gold plating film high in purity and to improve the stability of a plating soln. by allowing the soln. to contain a water soluble metal salt which does not contain cyanide, at least one kind among nitrate, thiosulfate and amino acid and one or more kinds among an aromatic nitroso compd., ascorbic acid and a salt thereof. SOLUTION: As water soluble metal salt which does not contain cyanide, sodium gold chloride, or the like, is examplified. For maintaining the stability of the soln., as a complexing agent, in addition to sulfite and thiosulfate, an amino acid is used. As the amino acid, ethylenediaminetetraacetic acid is cited, and its using concn. is preferably controlled to 0.01 to 0.40 mol/l. For maintaining the stability of the soln. and improving the color tone of precipitates, an aromatic nitroso compd., for instance, a nitrosonaphthol is used, and its using concn. is suitably controlled to 50 to 3000 ppm. Then, for efficiently precipitating gold from the soln., ascorbic acid, the Na salt thereof, or the like, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless gold plating solution containing no cyanide and stable for a long time.

[0002]

2. Description of the Related Art Conventionally, miniaturization of electrodes, wiring, and the like has been carried out with the miniaturization and high performance of electronic devices. Then, it is effective to apply a metal coating to the electrical contact portion of the electronic component by electro-noble metal plating having corrosion resistance and excellent electrical characteristics. For example, in order to electrically connect a circuit of a printed board and a semiconductor chip, the connection portion is plated with gold. On the other hand, in recent years, due to the high integration of electronic components and the rapid development of packaging technology, when gold plating for bonding is performed on electrically independent fine parts, electroless gold plating is generally used instead of electroplating. It has come to be. The gold plating solution used in the above electroless gold plating method is gold (I) gold (II)
A compound containing a cyanide as a complexing agent of I) and a boride such as dimethylamine borane (DMBA) as a reducing agent is known (JP-A-50-3743). However, this plating solution contains a large amount of cyanide ions, and poses a problem in safety at the time of operation and at the time of disposal of a waste solution and in environmental safety. Further, when a material to be plated via a positive type organic resist is used, there has been a problem that a resist pattern changes or peeling occurs. Therefore, there has been an increasing demand for a non-cyanide electroless gold plating solution containing no cyanide as a metal salt, a complexing agent and an additive. Examples of the electroless gold plating solution containing no cyanide ion include electroless gold using chloroaurate, gold sulfite or gold thiosulfate as metal salts, and sulfite and thiosulfate as complexing agents. Plating solution (JP-A-64-52083), electroless gold plating solution using thiocyanate (JP-A-62-1983)
174384) and an electroless gold plating solution using a thiocyanate and a sulfite (Japanese Patent Application Laid-Open No. 9-71871) are known. However, the conventional non-cyanide gold plating solution has a slow plating rate, requires a large amount of a reducing agent, cannot provide a sufficient thickness, and has a short period of time due to lack of stability of the plating solution. , Productivity or technical characteristics were not sufficiently satisfied.

[0003]

According to the present invention, a gold plating solution containing no cyanide ion is practically applicable on an industrial scale and can form a highly pure gold plating film. Another object of the present invention is to provide an electroless gold plating solution having low toxicity and excellent plating solution stability.

[0004]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, as a result, a complexing agent such as a water-soluble gold salt and a sulfite which does not contain a cyanide ion, ascorbic acid And at least one selected from amino acids and at least one selected from aromatic nitroso compounds to a low-toxic electroless gold plating solution comprising a reducing agent comprising The inventors have found that the bath stability is remarkably improved as compared with the electrolytic gold plating solution, and that the deposition rate and the appearance of the deposited film are also improved, thereby completing the present invention. That is, the present invention provides: (1) (a) a water-soluble gold salt containing no cyanide;
(B) sulfite, (c) thiosulfate, (d) at least one kind of amino acid, (e) aromatic nitroso compound, and (f) at least one kind selected from ascorbic acid and a salt thereof. Electroless gold plating solution characterized by the following. (2) (d) 0.01 to 0.40 mol / l of amino acid
The electroless gold plating solution according to claim 1, wherein (e) the aromatic nitroso compound is contained in an amount of 50 to 3000 p.
2. The electroless gold plating solution according to claim 1, wherein the electroless gold plating solution contains pm, and (4) the pH of the plating solution is adjusted to 6.0 to 7.0. A gold plating solution.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The water-soluble cyanide-free gold salt (a) used in the present invention includes, for example, sodium chloroaurate, sodium gold sulfite, potassium gold sulfite, ammonium gold sulfite, thiosulfate And water-soluble gold salts such as sodium gold and gold potassium thiosulfate. The concentration of the water-soluble gold salt used is 0.0 in the electroless gold plating solution.
12 to 0.024 mol / l, preferably 0.06 to
It is used in the range of 0.018 mol / l. 0.012
If the concentration is less than mol / l, the plating deposition rate becomes slow, and the color tone of the deposits is undesirably reduced. Also,
If it is 0.024 mol / l or more, the bath stability is undesirably reduced.

In the gold plating solution of the present invention, in order to maintain the stability of the plating solution, in addition to the sulfite of component (b) and the thiosulfate of component (c), the amino acid of component (d) is used as a complexing agent. At least one kind is used. Examples of the amino acid include ethylenediaminetetraacetic acid and its sodium salt, potassium salt, ammonium salt, nitrilotriacetic acid and its sodium salt, potassium salt, ammonium salt, iminodiacetic acid, glycine, cysteine, and aspartic acid. The above-mentioned amino acids form a complex with gold ions in the plating solution to function to stably retain these components in the solution, thereby contributing to the stability of the solution. The concentration of the amino acid used is 0.01 to 0.01% in the electroless gold plating solution.
0.40 mol / l, preferably 0.05 to 0.20 m
It is used in the range of ol / l. When the concentration is 0.01 mol / l or less, the effect of the stability of the liquid is not sufficiently exhibited.
The use of 0 mol / l or more improves the stability of the solution, but is not economically preferable.

In the present invention, at least one aromatic nitroso compound is used as the component (e) in order to maintain the stability of the liquid and improve the color tone of the precipitate. Examples of the aromatic nitroso compound include nitrosonaphthol, 4-nitroso-1-naphthol, 1-nitroso-2
-Naphthol, cupron and neotaproin. The aromatic nitroso compound forms a complex with excess gold ions at the reaction interface and contributes to the stability of the liquid. Also,
With a plating solution to which an aromatic nitroso compound is added, the appearance of the plating film becomes particularly good when the plating film is thickened. The concentration of the aromatic nitroso compound used in the electroless gold plating solution is 50 to 3000 ppm, preferably 1 to 3 ppm.
It is used in the range of 00 to 1000 ppm. 50 ppm
The following is not preferable because the stability of the liquid is lowered.
When the content is more than 00 ppm, the deposition rate decreases, which is not preferable.

Further, in the present invention, ascorbic acid and sodium ascorbate are used as the component (f) in order to efficiently deposit gold from the plating solution. The concentration of ascorbic acid and sodium ascorbate used in the electroless gold plating solution is in the range of 10 to 50 g / l, preferably 20 to 35 g / l. 10g
/ L or less, the effect of depositing gold is low, and the use of 50 g / l or more is not economically preferable because the effect is the same.

The pH of the plating solution of the present invention is appropriately adjusted with sulfuric acid or sodium hydroxide as long as the components of the plating solution do not decompose during use. Particularly preferred pH is 6-7. When electroless gold plating is performed using the plating solution of the present invention, the bath temperature of the plating bath is set at 50%.
It is preferably carried out at -80 ° C. If the bath temperature is lower than 50 ° C., the deposition rate is low, and if the bath temperature is higher than 80 ° C., the plating bath is decomposed, which is not preferable.

[0010]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

Example 1 (Composition of plating solution) Gold sodium sulfite 0.012 mol / l sodium sulfite 0.07 mol / l sodium thiosulfate 0.01 mol / l nitrilotriacetic acid 0.05 mol / l neocuproin 200 ppm ascorbic acid 0.25 mol / L of the above plating solution with sulfuric acid and sodium hydroxide
H was adjusted to 7.0, and at a solution temperature of 60 ° C., a copper plate previously plated with electroless nickel
As a result of immersion for a minute, a bright golden gold film having a thickness of 0.43 μm was obtained.

Example 2 Gold sodium sulfite 0.012 mol / l Sodium sulfite 0.07 mol / l Sodium thiosulfate 0.01 mol / l Glycine 0.05 mol / l Kuperone 100 ppm Ascorbic acid 0.25 mol / l And sodium hydroxide
H was adjusted to 7.0, and at a solution temperature of 60 ° C., a copper plate previously plated with electroless nickel
As a result of immersion for one minute, a glossy golden gold film having a thickness of 0.61 μm was obtained.

Comparative Example 1 A copper plate was plated in the same manner as in Example 2 except that glycine was removed from Example 2, and as a result, a satisfactory gold film was not obtained because the plating solution was decomposed during plating. Was.

Comparative Example 2 A copper plate was plated in the same manner as in Example 2 except that cupperon was removed from Example 2, and as a result, a plating solution was decomposed during plating and a satisfactory gold film was not obtained. Was.

Comparative Example 3 A copper plate was plated in the same manner as in Example 2 except that glycine and cupperon were omitted, and as a result, a satisfactory gold film was obtained by the decomposition of the plating solution during plating. I couldn't.

Examples 3 to 4 Using the same plating solution as in Example 2, a plating solution having a pH of 6.0 and 7.0 was adjusted with sulfuric acid and sodium hydroxide. The copper plate subjected to plating and displacement gold plating was immersed for 60 minutes, and the evaluation results of gold deposition rate, bath stability and appearance of the deposited gold plating film are shown in Table 1.

Comparative Examples 4 to 5 Using the same plating solution as in Example 2, a plating solution having a pH of 8.0 and 9.0 was adjusted with sulfuric acid and sodium hydroxide. The copper plate subjected to plating and displacement gold plating was immersed for 60 minutes, and the evaluation results of gold deposition rate, bath stability and appearance of the deposited gold plating film are shown in Table 1.

[0018]

[Table 1]

Example 5 Gold Sodium Sulfite 0.012 mol / l Sodium Sulfite 0.07 mol / l Sodium Thiosulfate 0.01 mol / l Glycine The concentration described in Table 2 Neocuproin 200 ppm Ascorbic acid 0.25 mol / l P with sulfuric acid and sodium hydroxide
H was adjusted to 7.0, and at a solution temperature of 60 ° C., a copper plate previously plated with electroless nickel
Table 2 shows the results of the immersion for one minute.

[0020]

[Table 2]

As shown in Table 2, the glycine concentration was 0.05
When it is in the range of mol / l to 0.10 mol / l (Examples 5-2 to 5-4), the bath stability is good, the deposition rate of gold is high, and it is possible to obtain a glossy golden gold film. did it.
However, when the glycine concentration was less than 0.005 mol / l (Example 5-1), the deposition rate of gold was low, a dark gold-colored gold film was formed, and bath decomposition occurred after plating. When the glycine concentration was 0.30 mol / l or more (Example 5-
5) Although the bath stability and the deposition rate of gold were high, a reddish brown and uneven deposition film was obtained. As is clear from the results of Example 5, it was found that the addition of the amino acid was effective also in bath stability, gold deposition rate and appearance of the gold film.

Example 6 Gold sodium sulfite 0.012 mol / l Sodium sulfite 0.07 mol / l Sodium thiosulfate 0.01 mol / l Aspartic acid 0.08 mol / l Cupron Concentration described in Table 3 Ascorbic acid 0.25 mol / l The above plating solution is p-pulped with sulfuric acid and sodium hydroxide.
H was adjusted to 7.0, and at a solution temperature of 60 ° C., a copper plate previously plated with electroless nickel
Table 3 shows the results of the immersion for one minute.

[0023]

[Table 3]

As shown in Table 3, the couperone concentration was 50-1.
000 ppm (Examples 6-1 to 6-
4) The bath stability was good, the deposition rate of gold was high, and a glossy golden gold film could be obtained. However, when the cupron concentration was less than 50 ppm (Example 6-1), the deposition rate of gold was low, a dark gold-colored gold film was formed, and bath decomposition occurred after plating. When the couperone concentration was 1000 ppm or more (Example 6-5), the bath stability and the deposition rate of gold were high, but a reddish brown and uneven deposition film was obtained. As is clear from the results of Example 6, it was found that the addition of the aromatic nitroso compound was effective also in bath stability, gold deposition rate and appearance of the gold film.

[0025]

According to the present invention, an electroless electroless system comprising a cyanide-free water-soluble gold salt, a sulfite and a thiosulfate as a complexing agent, and ascorbic acid and a salt thereof as a reducing agent has a very low toxicity. By adding at least one selected from amino acids and at least one selected from aromatic nitro compounds to the gold plating solution, the bath stability is significantly improved as compared with the conventional non-cyanide electroless gold plating solution. Further, there is an effect that the deposition rate and the appearance of the deposited film are also improved. Further, since the plating solution of the present invention does not contain cyanide, it is effective in terms of workability of electroless gold plating work and safety in waste liquid treatment.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideo Honma 8-1-60 Isogo-ku, Yokohama-shi, Kanagawa F-term (reference) 4K022 AA42 BA03 DA01 DB01 DB04 DB07 DB08

Claims (4)

[Claims] (1) (a) a water-soluble cyanide-free gold salt, (b) a sulfite, (c) a thiosulfate, (d) at least one kind of amino acid, (e) an aromatic nitroso compound, and (f) A) an electroless gold plating solution comprising at least one selected from ascorbic acid and salts thereof; 2. The method according to claim 2, wherein (d) the amino acid is 0.01 to 0.40 mo.
The electroless gold plating solution according to claim 1, wherein the electroless gold plating solution contains 1 / l. 3. The method according to claim 1, wherein (e) the aromatic nitroso compound is used in an amount of 50 to 30.
The electroless gold plating solution according to claim 1, which contains 00 ppm. 4. The electroless gold plating solution according to claim 1, wherein the pH of the plating solution is adjusted to 6.0 to 7.0.