TW201319328A - Gold plating solution - Google Patents

Abstract

To provide a cyanide-based gold plating solution, which is capable of producing gold deposits of high levels of hardness and forming excellent bump shape even when a heat treatment is performed. The present invention is drawn to a gold plating solution containing gold cyanide salt, inorganic acid salt, and carboxylate group, and is characterized in that either antimony or antimonid is added to the solution. It is preferable that an antimony concentration is 10-100 mg/L in terms of a metal.

Description

Gold plating solution

The present invention relates to a cyanide gold plating solution, and more particularly to a gold plating solution which can perform gold plating treatment suitable for bump formation and a gold plating method using the gold plating solution.

Gold plating treatment is widely used in industrial fields such as electronics, motor parts, and audio equipment parts because of its excellent electrical characteristics. For example, in the formation of bumps of electrical components such as semiconductors, gold plating treatment which should ensure electrical bonding is often used.

As the gold plating solution used in such gold plating treatment, various kinds of cyanide-based and non-cyanide-based gold plating solutions have been proposed. Since the cyanide gold plating solution is a gold supply source, the stability of the plating solution is high, and the plating conditions are easily controlled, and the plating solution itself is inexpensive. Therefore, it is often used (see Patent Document 1). In addition, a non-cyanide gold plating solution is developed, and a gold salt of sulfite such as gold sodium sulfite is known as a gold supply source (see Patent Document 2).

However, as the gold plating in forming the bumps, in order to achieve good bonding characteristics, gold plating of a certain degree of hardness, particularly high hardness after heat treatment, is required.

Further, the thinness and thinness of the manufactured electrical component are remarkable, and the shape of the bump formed is also small, and recently, bump formation at an angle of several tens of μm has been performed. In the state of forming such tiny bumps, not only before the request The gold plating hardness is described, and a gold plating process which can form a bump shape with high precision is also required. For example, in the state in which the prismatic bumps are formed, it is preferable not to perform the gold plating treatment in which the sides of the corner posts are expanded, and it is required to process the gold plating in accordance with the high linearity of the resist profile.

In this way, a non-cyanide-based gold plating solution is known as a gold plating solution containing a ruthenium compound as a crystal modifier (Patent Document 2). On the other hand, in the cyanide gold plating solution, a cyanide gold plating solution having various compositions is proposed, and it is possible to realize a high hardness gold-plated cyanide gold plating solution after heat treatment, as long as the inventors know The status quo has not yet been proposed.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 05-33148

[Patent Document 2] Japanese Patent Laid-Open No. 64-68489

The present invention is completed in such a condition as a background; a cyanide gold plating solution is provided, and in the case of a cyanide gold plating solution, a gold having a high plating hardness can be treated even in a state of being subjected to heat treatment. Electroplating has the ability to form a good bump shape.

The inventors of the present invention have studied the various kinds of additives with respect to the various cyanide gold plating solutions using the conventional cyanide gold salt as a base. It is thus found that the gold plating solution of the present invention is found.

The gold plating solution of the present invention is a gold plating solution containing a gold cyanide salt, an inorganic salt, and a carboxylate, and is characterized by adding a ruthenium or osmium compound. The cyanide gold plating solution of the present invention is formed by gold plating by a plating treatment by adding ruthenium, and has high hardness after heat treatment. It is presumed that the lanthanoid action of the present invention acts as a precipitation promoter, but also acts as a crystal modifier. Therefore, the bump forming ability, particularly the surface property of the bump surface of the bump, is good. Specifically, in a state where the heat treatment is performed at 100 ° C to 250 ° C for 30 minutes to 2 hours in an inert atmosphere, the Vickers hardness of the gold plating having a thickness of 10 to 50 μm is 60 Hv to 120 Hv. High hardness.

In the present invention, it is preferable that the ruthenium or osmium compound to be added to the gold plating solution has a ruthenium concentration of 10 to 100 mg/L in terms of metal. When it is 10 mg/L or less, there is a tendency to lower the hardness, and when it exceeds 100 mg/L, there is a tendency to lower the formation ability of the bump shape. As the ruthenium compound, bismuth potassium tartrate or ruthenium oxide can be used. Particularly preferred is bismuth potassium tartrate. It can be added as an aqueous solution in a state in which a gold plating solution is added with a crucible.

The gold plating solution of the present invention contains a gold cyanide salt, a mineral acid salt, and a carboxylate salt. However, the gold cyanide salt which is a gold source is not particularly limited. As the gold cyanide salt, potassium cyanide can be used. Next, the cyanide gold salt is preferably 5 to 15 g/L as a gold concentration. When the gold concentration is less than 5 g/L, it is easy to become coarse crystals and the formation ability of the bump shape is lowered, and when it exceeds 15 g/L, it is disadvantageous in terms of cost.

The inorganic acid salt of the present invention contains a buffering agent, and a phosphate (potassium phosphate), a borate or the like can be used. Particularly preferred is potassium phosphate. The inorganic acid salt preferably contains a concentration of 10 to 50 g/L.

Next, the carboxylate of the present invention contains a conductive salt, and potassium citrate can be used. The carboxylate is preferably present in a concentration of from 50 to 200 g/L.

Further, the gold plating solution of the present invention preferably has a pH of 4.0 to 8.0. Since the pH tends to be less than 4.0, there is a tendency to cause decomposition of the gold complex, and when the pH exceeds 8.0, the tendency of uniform electric properties to deteriorate is enhanced. Further, the liquid specific gravity is an index for appropriately maintaining the electrical conductivity of the plating solution, and therefore, the liquid specific gravity is preferably in the range of 10 to 20 ° Be'.

In the state in which the gold plating solution of the present invention is used for electrolytic gold plating treatment, the plating conditions are preferably a current density of 0.1 to 1.0 A/dm ² and a liquid temperature of 40 to 60 °C.

The gold plating solution of the present invention may be appropriately added with an oxidation preventive agent for improving liquid stability, a smoothing agent for improving the smoothness of the precipitate, or a surface tension of the plating solution. Surfactant.

In the state in which the gold plating film is formed by the gold plating solution of the present invention, the gold plating film contains 0.1 to 10 ppm of ruthenium. It is presumed that the lanthanum contained in the coating film has a function of maintaining gold plating in a hardened manner even when heat treatment is performed.

According to the present invention, it is possible to realize gold plating which is high in hardness even in a state in which heat treatment is performed.

Hereinafter, embodiments of the gold plating solution of the present invention will be described based on examples.

In the present embodiment, various compositions of the gold plating solution evaluated are shown in Table 1.

Gold: Potassium Cyanide 锑: Potassium Oxalate

Example 1 is a gold plating solution of the present invention. For comparison, a gold plating solution of ruthenium was added using a ruthenium added (Comparative Example 1). Further, as the gold salt system, potassium cyanide is used. The lanthanum is potassium tarlate, and the lanthanum is added to the gold plating solution using barium sulfate. For the evaluation of various gold plating solutions, the hardness of the gold plating film was measured, and the surface roughness and appearance after the formation of the bumps were observed.

Hardness measurement: The gold plating solution of each of the examples shown in Table 1 was prepared, and a test sample substrate having a 50 μm-angle bump (height 15 μm) was prepared by applying a patterned resist on the surface of the substrate coated with the TiW substrate. Gold plating treatment was performed on various gold plating solutions at a current density of 0.5 A/dm ² and a liquid temperature of 42 ° C.

Next, after the resist was removed, the hardness and the roughness of the surface of the columnar bump were measured and the shape of the bump was observed by a metal microscope. The results are shown in Table 2.

Further, in the measurement of the hardness, various heat treatments were performed for 1, 2, 3, and 4 hours in a nitrogen atmosphere at a heat treatment temperature of 250 ° C, and the Vickers hardness of the gold plating after the heat treatment was measured. For the Vickers hardness measurement, a micro Vickers hardness tester (FM-700: manufactured by Future-tec Co., Ltd.) was used, the weight was 25 g, the load time was 15 seconds, and the five sites were measured, and the average value was used to obtain a hardness value. In addition, the surface roughness Ra was performed using a difference of ‧ surface roughness ‧ fine shape measuring apparatus (Tencor P-16: manufactured by KLA-Tencor Co., Ltd.).

As a result of the results of Table 2, it was found that the hardness of the gold plating solution of Example 1 was 70 Hv or more and the hardness was high. Further, in terms of the surface roughness Ra, it is a practical surface roughness of 300 Å to 3,500 Å which is required by the adhesion characteristics of the bumps. As shown in Fig. 1, the bump of Example 1 was observed by a metal microscope (400 times), and as a result, it was confirmed that the shape and appearance were also good. On the other hand, it was confirmed that Comparative Example 1 could not achieve high hardness after heat treatment and became a hardness of less than 50 Hv.

Next, regarding the gold plating solution of Example 1, the cerium concentration is reviewed. The result will be described. Table 3 shows the composition of each gold plating solution evaluated (Example 1 is also described).

Further, the same bumps as in Example 1 were formed by various gold plating solutions of Table 3, and hardness and surface roughness were evaluated after heat treatment at 250 ° C for 4 hours in a nitrogen atmosphere. The results are shown in Table 4 (the results of Example 1 are also described).

From the results of Table 4, it was found that the gold plating solution of the present invention has a tendency to decrease the hardness after heat treatment to less than 60 Hv when the ruthenium is less than 10 mg/L.

[Industrial Availability]

According to the present invention, it is possible to form a gold plating coating film capable of maintaining high hardness even by heat treatment by a gold plating solution of cyanide, and therefore, it is possible to form a bump suitable for an electric component or the like of a semiconductor.

Figure 1 is a metal microscope photograph of a bump.

Claims (6)

A gold plating solution comprising a gold cyanide salt, a mineral acid salt and a carboxylate salt, characterized in that a ruthenium or osmium compound is added. For example, in the gold plating solution of the first application of the patent scope, the cerium concentration is 10 to 100 mg/L in terms of metal. For example, in the gold plating solution of claim 1 or 2, wherein the gold cyanide salt is 5-15 g/L as the gold concentration, 10-50 g/L of the mineral acid salt, and 50-200 g of the carboxylate salt. /L. For example, the gold plating solution of claim 1 or 2, wherein the pH is 4.0 to 8.0, and the specific gravity of the liquid is 10 to 20 ° Be'. For example, in the gold plating solution of the third item of the patent application, wherein the pH is 4.0 to 8.0, and the specific gravity of the liquid is 10 to 20 ° Be'. A gold electroplating method according to any one of claims 1 to 5, characterized in that the current density is 0.1 to 1.0 A/dm ² and the liquid temperature is 40 to 60 ° C. Electrolytic plating is performed.