WO2010024099A1

WO2010024099A1 - Hard gold plating liquid

Info

Publication number: WO2010024099A1
Application number: PCT/JP2009/063931
Authority: WO
Inventors: 理恵菊池; 新吾渡邊
Original assignee: 日本エレクトロプレイテイング・エンジニヤース株式会社
Priority date: 2008-08-25
Filing date: 2009-08-06
Publication date: 2010-03-04
Also published as: TWI495766B; KR20110034683A; CN102131962B; KR101275886B1; JP2010077527A; TW201022483A; CN102131962A; US20110127168A1; JP5513784B2

Abstract

A hard gold plating liquid which enables selective partial plating and is suitable for electronic components such as connectors. The hard gold plating liquid contains a soluble gold salt or gold complex, a conductive salt and a chelating agent, and is characterized by also containing an aromatic compound having one or more nitro groups such as one selected from the group consisting of nitrobenzoic acids, dinitrobenzoic acids and nitrobenzene sulfonic acids. The hard gold plating liquid is also characterized by additionally containing at least one metal salt selected from cobalt salts, nickel salts and silver salts, or alternatively an organic additive of a polyethylene imine.

Description

Hard gold plating solution

The present invention relates to a hard gold plating technique, and more particularly to a hard gold plating solution for performing hard gold plating and hard gold alloy plating suitable for forming contact materials for electronic devices such as connectors. The hard gold plating in the present application refers to either hard gold plating or hard gold alloy plating, and a plating solution for performing hard gold plating is referred to as a hard gold plating solution.

Conventionally, gold plating has been used for electronic devices and electronic parts for reasons such as excellent electrical properties and corrosion resistance of gold, and has been widely used for applications that protect the surface of connection terminals such as electronic parts. Gold plating is used as a surface treatment for electronic components such as electrode terminals of semiconductor elements, leads formed on resin films, and connectors for connecting electronic devices.

Electronic parts such as connectors for connecting electronic devices use gold plating as a surface treatment, but they require hard gold plating because their properties require corrosion resistance, friction resistance, and electrical conductivity. There are many. As this hard gold plating, hard gold alloy plating such as gold-cobalt alloy plating and gold-nickel alloy plating has been known for a long time (Patent Document 1, Patent Document 2).

For electronic parts such as connectors, copper or copper alloy is generally used as the material. However, when performing hard gold plating, usually nickel plating is applied to the surface of copper or copper alloy, Hard gold plating is applied to the surface of the nickel plating.

When carrying out hard gold plating on such electronic parts such as connectors, a partial plating process is required so that hard gold plating is applied only to necessary parts. That is, it is necessary that the hard gold plating is applied only to a necessary portion, and the hard gold plating is not deposited on an unnecessary portion. The reason for this is that if hard gold plating is applied to the unnecessary part of the connector, the solder will crawl up on the unnecessary part when soldering to make an electrical connection. This is because the typical characteristics deteriorate. Furthermore, if it does not precipitate in unnecessary parts, the amount of gold to be used can be suppressed, so that the amount of gold can be reduced. In response to such a requirement, a technique has been proposed in which hard gold plating can be selectively performed only on necessary portions (for example, Patent Document 3).

The gold-cobalt alloy plating solution in this prior art deposits a gold alloy plating film only at a desired location on an electronic component such as a connector, and suppresses the deposition at an unnecessary location, thereby producing a hard gold system. Plating can be performed.

German Patent No. 1111987 JP-A-60-155696 JP 2008-45194 A

By the way, in recent electronic parts, gold or gold alloy plating is very often applied to a portion requiring electrical connection because of its excellent material characteristics. There are various target parts, and although a hard gold plating solution capable of selective partial plating is required, there are few types of such hard gold plating solutions. In other words, there is a demand for a new hard gold plating solution capable of selective partial plating as proposed in Patent Document 3.

The present invention has been made in the background as described above, and an object of the present invention is to provide a hard gold plating solution that can be selectively subjected to partial plating and is suitable for electronic parts such as connectors.

The present invention is characterized in that a hard gold plating solution containing a soluble gold salt or gold complex, a conductive salt, and a chelating agent contains an aromatic compound having one or more nitro groups. Selective partial plating treatment by hard gold plating when an aromatic compound having one or more nitro groups is contained in a hard gold plating solution containing a soluble gold salt or gold complex, a conductive salt, and a chelating agent. Is possible.

The hard gold plating solution according to the present invention preferably contains at least one metal salt of a cobalt salt, a nickel salt, and a silver salt. With these metal salts, the plating film can be made into a gold alloy and the film can be hardened.

The hard gold plating solution according to the present invention may contain a polyethyleneimine organic additive instead of a metal salt such as a cobalt salt, a nickel salt, or a silver salt. As the polyethyleneimine, those having various molecular weights can be used, and any structure such as a linear structure or a branched structure can be used. With this organic additive, the plating film is hardened in the same manner as the addition of the metal salt.

In the hard gold plating solution according to the present invention, a soluble gold salt or a gold complex can be used as the gold ion source. Specifically, potassium potassium cyanide, potassium potassium cyanide, ammonium gold cyanide, potassium chloride gold, potassium chloride chloride, sodium chloride chloride, sodium chloride chloride, thiosulfuric acid Gold potassium, sodium gold thiosulfate, potassium gold sulfite, sodium gold sulfite, and combinations of two or more thereof can be used. Particularly preferable is potassium gold cyanide.

The gold concentration in the hard gold plating solution of the present invention is preferably in the range of 1 g / L to 20 g / L in terms of gold. If it is less than 1 g / L, it becomes difficult to process at a high current density, and high-speed plating tends to be difficult. If the amount exceeds 20 g / L, the amount of gold taken out from the plating solution (a slight amount of plating solution is attached to the connector to be plated, etc., and is taken out to the next process. For example, several drops of plating solution are taken out. This is because the higher the gold concentration, the greater the amount of gold lost from the plating solution), which increases the manufacturing cost. A more preferable gold salt concentration is 2 g / L to 16 g / L in terms of gold.

When the hard gold plating solution according to the present invention contains a cobalt salt, a soluble cobalt compound can be used as the cobalt source. For example, cobalt sulfate, cobalt chloride, cobalt carbonate, cobalt sulfamate, cobalt gluconate, and combinations of two or more thereof can be used. Preferably, it is an inorganic cobalt salt, especially cobalt sulfate.

The concentration of this cobalt salt in the plating solution is preferably in the range of 0.05 g / L to 10 g / L in terms of cobalt. If it is less than 0.05 g / L, the amount of eutectoid of cobalt in the plating film decreases, and it becomes difficult to improve the hardening of the hard gold plating. Moreover, when it exceeds 10 g / L, it will become the tendency for stability of a plating solution to fall. A more preferable cobalt salt concentration is 0.1 g / L to 3 g / L in terms of cobalt.

When the hard gold plating solution according to the present invention contains a nickel salt, a soluble nickel compound can be used as the nickel source. For example, nickel sulfate, nickel chloride, nickel carbonate, nickel sulfamate, nickel gluconate, and combinations of two or more thereof can be used. Particularly preferred is nickel sulfate.

The concentration of this nickel salt in the plating solution is preferably in the range of 0.05 g / L to 30 g / L in terms of nickel. If it is less than 0.05 g / L, the amount of eutectoid of nickel in the plating film is lowered, and the hard gold plating tends to be hardened. Moreover, when it exceeds 30 g / L, it will become the tendency for stability of a plating solution to fall. A more preferable nickel concentration is 0.1 g / L to 20 g / L in terms of nickel.

When the hard gold plating solution according to the present invention contains a silver salt, a soluble silver compound can be used as the silver source. For example, silver cyanide and its salt, silver chloride, silver carbonate, silver nitrate and combinations of two or more thereof can be used. Particularly preferred is silver cyanide.

The concentration of this silver salt in the plating solution is preferably in the range of 0.05 g / L to 100 g / L in terms of silver. If it is less than 0.05 g / L, the amount of silver eutectoid in the plating film decreases, and it becomes difficult to improve the hardening of the hard gold plating. Moreover, when it exceeds 100 g / L, it will become the tendency for stability of a plating solution to fall. A more preferable silver concentration is 0.1 g / L to 50 g / L in terms of silver.

When the hard gold plating solution according to the present invention contains a polyethyleneimine organic additive, the concentration of the organic additive in the plating solution is preferably 0.1 g / L to 300 g / L. If it is less than 0.1 g / L, the hardening of the hard gold plating tends to be impossible to improve, and if it exceeds 300 g / L, the stability of the plating solution tends to be lowered. A more preferred concentration is 1 g / L to 200 g / L.

As the conductive salt in the hard gold plating solution of the present invention, either an organic compound or an inorganic compound can be used. Examples of the organic compound include citric acid, tartaric acid, adipic acid, malic acid, succinic acid, lactic acid, Examples include carboxylic acids such as benzoic acid and salts thereof, and compounds containing phosphonic acid groups and salts thereof. Inorganic compounds include alkali metal salts such as phosphoric acid, sulfurous acid, nitrous acid, nitric acid, sulfuric acid, ammonium salts, and cyanide. Examples include alkali and ammonium cyanide. A combination of two or more of these can also be used.

The concentration of the conductive salt in the plating solution is preferably in the range of 0.1 g / L to 300 g / L. A more preferred concentration is 1 g / L to 200 g / L.

As a chelating agent in the hard gold plating solution of the present invention, a carboxyl group-containing compound such as citric acid, potassium citrate, sodium citrate, tartaric acid, oxalic acid and succinic acid, a phosphonic acid group or a salt thereof is contained in the molecule. The phosphonic acid group containing compound etc. which have can be used. As the phosphonic acid group-containing compound, for example, aminotrimethylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid and the like have a plurality of phosphonic acid groups in the molecule. Compounds or their alkali metal or ammonium salts are included. Moreover, nitrogen compounds, such as ammonia, ethylenediamine, and triethanolamine, can also be used with a carboxyl group-containing compound as an auxiliary chelating agent. A chelating agent can also use 2 or more types of combinations.

The concentration of this chelating agent in the plating solution is preferably in the range of 0.1 g / L to 300 g / L. When the amount is less than 0.1 g / L, the chelating action tends not to work, and when the amount exceeds 300 g / L, the chelating solution tends not to be dissolved. A more preferred concentration is 1 g / L to 200 g / L.

As the aromatic compound having one or more nitro groups in the hard gold plating solution of the present invention, dinitrobenzoic acid, nitrobenzoic acid, and nitrobenzenesulfonic acid can be used. When these aromatic compounds are added to the plating solution, selective partial plating treatment is possible, and precipitation of hard gold plating on unnecessary portions is effectively suppressed.

The concentration of the aromatic compound having one or more nitro groups in the plating solution is preferably in the range of 0.01 g / L to 30 g / L. If it is less than 0.01 g / L, deposition of gold alloy plating on unnecessary portions tends to occur. On the other hand, if it exceeds 30 g / L, the plating deposition amount is excessively suppressed as a whole, and it becomes difficult to perform hard gold plating on a necessary portion. A more preferred concentration is 0.05 g / L to 15 g / L.

The hard gold plating solution in the present invention can contain a pH adjusting agent, a buffering agent and the like in addition to the above basic composition. As the pH adjuster, alkali metal hydroxides such as potassium citrate and potassium hydroxide, or acidic substances such as citric acid and phosphoric acid can be used. As the buffer, citric acid, tartaric acid, oxalic acid, succinic acid, phosphoric acid, sulfurous acid, or a salt thereof can be used.

The above-described hard gold plating solution according to the present invention preferably has a plating solution pH of 3 or more as a plating treatment condition, and is preferably performed at a solution temperature of 5 ° C. to 90 ° C. If the pH is less than 3, cyan gas is likely to be generated. More preferable plating conditions are pH 4 or more and a liquid temperature of 20 ° C. to 70 ° C. About the current density at the time of a plating process, the applicable range is wide and it can select an optimal current density value according to conditions, such as a plating target object, a plating apparatus, and a plating solution flow rate. The hard gold plating solution according to the present invention is particularly applicable to high current density plating treatment conditions such as high-speed plating treatment.

According to the hard gold plating solution according to the present invention, it is possible to perform hard gold plating only on necessary portions of electronic parts such as connectors. In particular, when hard gold plating is performed on the surface of the base plated with nickel, it is possible to selectively perform partial plating.

Hereinafter, embodiments of the present invention will be described.

First Embodiment: In this embodiment, the results of investigating the plating characteristics of a hard gold plating solution of a gold-cobalt alloy will be described.

In this Example 1, the result of examining the electrodeposition characteristics by conducting a hull cell test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups will be described. The composition of the hard gold plating solution was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Cobalt sulfate 3.6 g / L (0.76 g / L in terms of cobalt)
Citric acid 150g / L
Potassium hydroxide 20g / L
Dinitrobenzoic acid 1g / L, 5g / L
pH 4.4
Liquid temperature 60 ℃

The hull cell test uses a commercially available hull cell tester (manufactured by Yamamoto Kakin Tester Co., Ltd.), and the substrate to be plated is nickel-plated (thickness 70 mm, width 100 mm, thickness 0.3 mm) on a brass hull cell plate. 10 μm) was used on both sides. The plating treatment time was 30 seconds, and the energization current was 3A. During the plating process, the plating solution was vigorously stirred.

Hull cell evaluation was performed by measuring the plating film thickness of nine places of the plated hull cell plate. Nine locations on this Hull cell plate are the portion about 2 cm above the bottom of the Hull cell plate that touches the inner bottom surface of the Hull cell tester (the portion that has been immersed in the plating solution). Selected. Moreover, the plating film thickness was measured with a fluorescent X-ray film thickness measuring instrument (manufactured by SII Nanotechnology Co., Ltd.). The approximate current density value at each of the nine points (Nos. 1 to 9) where the film thickness was measured is 1 is 0.3 A / dm ² , No. 1 2 is 1 A / dm ² , No. ² 3 is 2 A / dm ² , No. 3 4 is 3 A / dm ² , No. 4 5 is 4 A / dm ² , No. 5 6 is 5.5 A / dm ² , No. 6 7 is 7.5 A / dm ² , No. 7 8 is 10 A / dm ² , No. 8 9 was 13.5 A / dm ² . This hull cell evaluation was performed on both the surface of the hull cell plate subjected to plating and the back surface thereof. Table 1 shows the results of measuring the film thickness at each point. The nine current density values described above indicate the current density on the front side of the hull cell plate, and the current density value on the back side of the hull cell plate is unknown. On the back side of the hull cell plate, the current density value is considerably lower than that on the front side.

Table 1 also shows the results of a blank hard gold plating solution to which dinitrobenzoic acid is not added for comparison. The numbers 1 to 9 shown in Table 1 indicate the measurement points at nine locations on the Hull cell plate, and the results of the hyphen row are the results of the blank hard gold plating solution. 1 g / L, 5 g / L Are the results of the hard gold-based plating solution containing dinitrobenzoic acid at that concentration (the same applies to the table of film thickness measurement results of the hull cell plate shown below). As can be seen from the results of the film thickness measurement on the surface of the Hull cell plate, it was found that the addition of dinitrobenzoic acid sharply decreased the plating film thickness on the low current density side. Further, it was found that when the addition amount is 5 g / L, plating on the low current density side is further suppressed. Further, in the case of the blank, hard gold plating was also performed on the back side of the hull cell plate, but it was found that when dinitrobenzoic acid was added, the back side was hardly plated.

In Example 2, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 2 is the same as that of Example 1, except that nitrobenzoic acid is used instead of dinitrobenzoic acid of Example 1. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. Table 2 shows the results of measuring the film thickness at each point according to Example 2.

As can be seen from the results shown in Table 2, when nitrobenzoic acid was added, it was found that the plating film thickness on the low current density side sharply decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzoic acid was added, the Hull cell plate was hardly plated on the back side.

In this Example 3, nitrobenzenesulfonic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 3 is the same as that of Example 1, except that nitrobenzenesulfonic acid is used instead of dinitrobenzoic acid of Example 1. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. Table 3 shows the results of measuring the film thickness at each point according to Example 3.

As can be seen from the results shown in Table 3, when nitrobenzenesulfonic acid was added, it was found that the plating film thickness on the low current density side rapidly decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzenesulfonic acid was added, the Hull cell plate was hardly plated on the back side.

In Example 4, the results of examining the electrodeposition characteristics of a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups will be described. The composition of the gold-cobalt alloy hard gold plating solution was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Cobalt sulfate 3.6 g / L (0.76 g / L in terms of cobalt)
Citric acid 150g / L
Potassium hydroxide 20g / L
Dinitrobenzoic acid 0.5 g / L, 1.0 g / L,
1.5 g / L, 2.0 g / L,
3.0g / L, 5.0g / L
pH 4.4
Liquid temperature 60 ℃

In the high-speed partial plating test, a brass plate subjected to nickel plating (10 μm thickness) was used as an object to be plated. In order to confirm the deposition selectivity of the gold plating film, it was liquid-tightly sealed with silicon packing so that a circular portion having a diameter of 9 mm was exposed. However, a groove (width 2 mm, length 20 mm, depth 3 mm) extending from one end of the circular exposed portion was formed between the nickel plating and the silicon packing mask. When the plating solution is jetted onto an exposed circular portion that is not masked with silicon packing, plating is formed in the circular portion, and the plating solution passes through the gap formed in the groove portion and is discharged from the end side of the groove portion. It has come to be. Since this groove portion has a mask above it, it becomes a low current density portion during electrolysis as compared with a circular exposed portion without a mask. Therefore, when plating is performed by this high-speed partial plating apparatus, it is an ideal plating process that only the circular portion is plated and the groove portion is not plated.

Plating conditions were adjusted to a flow rate of 15 L / min and a current density of 50 A / dm ² to form a gold-cobalt alloy plating film having a thickness of 0.5 μm.

When the plating state when the concentration of dinitrobenzoic acid in the plating solution was changed was observed in appearance, it was found that as the amount of dinitrobenzoic acid added increased, the groove portion was not plated.

Therefore, for the test samples plated at various concentrations, the plating film thickness at four locations in the groove portion was measured, and the average plating film thickness was investigated. The results are shown in Table 4. This plating film thickness was measured with a fluorescent X-ray film thickness measuring instrument (manufactured by SII Nanotechnology Inc.).

From the results shown in Table 4, when the concentration of dinitrobenzoic acid in the plating solution increases, the plating process proceeds selectively to the circular plating part of the substrate, and the groove part of the unnecessary part of the plating process is not plated. It has been found.

Second Embodiment: In this embodiment, the results of investigating the plating characteristics of a hard gold plating solution of a gold-nickel alloy will be described.

In this Example 5, dinitrobenzoic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Nickel sulfate 9g / L (2g / L in terms of nickel)
Citric acid 150g / L
Potassium hydroxide 20g / L
Dinitrobenzoic acid 1g / L, 5g / L
pH 4.4
Liquid temperature 60 ℃

Halcell test conditions and evaluation were the same as in Example 1. Table 5 shows the results of measuring the film thickness at each point according to Example 5.

Table 5 also shows the results of a blank hard gold plating solution to which dinitrobenzoic acid is not added for comparison. As can be seen from the results shown in Table 5, when nitrobenzoic acid was added, the plating film thickness on the low current density side was abruptly reduced as in the case of the first embodiment. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. In the case of the blank, hard gold plating was also performed on the back side of the hull cell plate, but it was found that when dinitrobenzoic acid was added, the back side was hardly plated.

In Example 6, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 6 is the same as that of Example 5 except that nitrobenzoic acid is used instead of dinitrobenzoic acid of Example 5. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. Table 6 shows the results of measuring the film thickness at each point according to Example 6.

As can be seen from the results shown in Table 6, when nitrobenzoic acid was added, the plating film thickness on the low current density side was abruptly decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzoic acid was added, the Hull cell plate was hardly plated on the back side.

In this Example 7, nitrobenzenesulfonic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 7 is the same as that of Example 5, except that nitrobenzenesulfonic acid is used instead of dinitrobenzoic acid of Example 5. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. Table 7 shows the results of measuring the film thickness at each point according to Example 7.

As can be seen from the results shown in Table 7, it was found that when nitrobenzene sulfonic acid was added, the plating film thickness on the low current density side rapidly decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzenesulfonic acid was added, the Hull cell plate was hardly plated on the back side.

In this Example 8, as in Example 4, the electrodeposition characteristics were examined by conducting a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups. Will be described. The composition of the gold-nickel alloy hard gold plating solution was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Nickel sulfate 9g / L (2g / L in terms of nickel)
Citric acid 150g / L
Potassium hydroxide 20g / L
Dinitrobenzoic acid 0.5 g / L, 1.0 g / L,
1.5 g / L, 2.0 g / L,
3.0g / L, 5.0g / L
pH 4.4
Liquid temperature 60 ℃

The test sample, equipment, plating conditions, etc. for the high-speed partial plating test were the same as in Example 4.

In Example 8 as well, when the plating state when the concentration of dinitrobenzoic acid in the plating solution was changed was observed in appearance, as the amount of dinitrobenzoic acid added increased, the groove portion was not plated. Turned out to be.

In this Example 8, the results of investigating the average plating film thickness of the groove portions as in Example 4 are shown in Table 8. This film thickness investigation was performed in the same manner as in Example 4 above.

From the results of Table 8, as in Example 4 above, when the concentration of dinitrobenzoic acid in the plating solution increases, the plating process proceeds selectively to the circular plating part of the substrate, and the unnecessary part of the plating process is obtained. It was found that the groove was not plated.

Third Embodiment: In this embodiment, the results of investigating the plating characteristics of a hard gold plating solution of gold-silver alloy will be described.

In this Example 9, dinitrobenzoic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Silver cyanide 10g / L (8g / L in terms of silver)
Potassium cyanide 50g / L
Dinitrobenzoic acid 1g / L, 5g / L
pH 12
Liquid temperature 20 ℃

Halcell test conditions and evaluation were the same as in Example 1. Table 9 shows the results of measuring the film thickness at each point according to Example 9.

Table 9 also shows the results of a blank hard gold plating solution to which dinitrobenzoic acid is not added for comparison. As can be seen from the results shown in Table 9, when nitrobenzoic acid was added, the plating film thickness on the low current density side was abruptly reduced as in the case of the first embodiment. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank case, it was found that when dinitrobenzoic acid was added, there was almost no plating treatment on the back side of the hull cell plate.

In Example 10, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 10 is the same as that of Example 9, except that nitrobenzoic acid is used instead of dinitrobenzoic acid of Example 10. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. In Table 10, the result of having measured the film thickness of each point in Example 10 is shown.

As can be seen from the results shown in Table 10, when nitrobenzoic acid was added, it was found that the plating film thickness on the low current density side rapidly decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzoic acid was added, the Hull cell plate was hardly plated on the back side.

In this Example 11, nitrobenzenesulfonic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 11 is the same as that of Example 9, except that nitrobenzenesulfonic acid is used instead of dinitrobenzoic acid of Example 9. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. In Table 11, the result of having measured the film thickness of each point in Example 11 is shown.

As can be seen from the results shown in Table 11, when nitrobenzenesulfonic acid was added, it was found that the plating film thickness on the low current density side rapidly decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzenesulfonic acid was added, the Hull cell plate was hardly plated on the back side.

In this Example 12, as in Example 4, the electrodeposition characteristics were examined by conducting a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups. Will be described. The composition of the gold-silver alloy hard gold plating solution was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Silver cyanide 10g / L (8g / L in terms of silver)
Potassium cyanide 50g / L
Dinitrobenzoic acid 0.5 g / L, 1.0 g / L,
1.5 g / L, 2.0 g / L,
3.0g / L, 5.0g / L
pH 12
Liquid temperature 20 ℃

Also in this Example 12, when the plating state when the concentration of dinitrobenzoic acid in the plating solution was changed was observed in appearance, as the amount of dinitrobenzoic acid added increased, the groove portion was not plated. Turned out to be.

In this Example 12, the results of investigating the average plating film thickness of the groove portions as in Example 4 are shown in Table 12. This film thickness investigation was performed in the same manner as in Example 4 above.

From the results of Table 12, as in Example 4 above, when the concentration of dinitrobenzoic acid in the plating solution increases, the plating process proceeds selectively to the circular plating part of the substrate, and the unnecessary part of the plating process is obtained. It was found that the groove was not plated.

Fourth Embodiment: In this embodiment, the results of investigating the plating characteristics of a hard gold plating solution containing only gold will be described. Polyethyleneamine was used as an organic additive that contributes to hardening.

In this Example 13, dinitrobenzoic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution containing only gold was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Polyethyleneamine 10g / L
Citric acid 150g / L
Dinitrobenzoic acid 1g / L, 5g / L
pH 7
Liquid temperature 65 ℃

Halcell test conditions and evaluation were the same as in Example 1. Table 13 shows the results of measuring the film thickness at each point according to Example 13.

Table 13 also shows the results of a blank hard gold plating solution to which dinitrobenzoic acid was not added for comparison. As can be seen from the results shown in Table 13, as in the case of the first embodiment described above, it was found that when nitrobenzoic acid was added, the plating film thickness on the low current density side rapidly decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank case, it was found that when dinitrobenzoic acid was added, there was almost no plating treatment on the back side of the hull cell plate.

In Example 14, nitrobenzoic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 14 is the same as that of Example 13, except that nitrobenzoic acid is used instead of dinitrobenzoic acid of Example 13. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. In Table 14, the result of having measured the film thickness of each point in Example 13 is shown.

As can be seen from the results shown in Table 14, it was found that when nitrobenzoic acid was added, the plating film thickness on the low current density side rapidly decreased. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzoic acid was added, the Hull cell plate was hardly plated on the back side.

In Example 15, nitrobenzenesulfonic acid was used as an aromatic compound having one or more nitro groups. The composition of the hard gold plating solution of Example 15 is the same as that of Example 13 except that nitrobenzenesulfonic acid is used instead of dinitrobenzoic acid of Example 9. Further, the Hull cell test conditions and the evaluation thereof were the same as those in Example 1. Table 15 shows the results of measuring the film thickness at each point in Example 15.

As can be seen from the results shown in Table 15, it was found that when nitrobenzenesulfonic acid was added, the plating film thickness on the low current density side decreased rapidly. And when the addition amount was 5 g / L, it turned out that the plating by the side of a low current density is further suppressed. Also, unlike the blank, it was found that when nitrobenzenesulfonic acid was added, the Hull cell plate was hardly plated on the back side.

In Example 16, as in Example 4, the electrodeposition characteristics were examined by performing a high-speed partial plating test using dinitrobenzoic acid as an aromatic compound having one or more nitro groups. Will be described. The composition of the hard gold plating solution was as follows.

Potassium cyanide potassium 12g / L (8g / L in terms of gold)
Polyethyleneamine 10g / L
Citric acid 150g / L
Dinitrobenzoic acid 0.5 g / L, 1.0 g / L,
1.5 g / L, 2.0 g / L,
3.0g / L, 5.0g / L
pH 7
Liquid temperature 65 ℃

In Example 16 as well, when the plating state when the concentration of dinitrobenzoic acid in the plating solution was changed was observed in appearance, as the amount of dinitrobenzoic acid added increased, the groove portion was not plated. Turned out to be.

In this Example 16, the result of investigating the average plating film thickness of the groove portion as in Example 4 is shown in Table 16. This film thickness investigation was performed in the same manner as in Example 4 above.

From the results of Table 16, as in Example 4 above, when the concentration of dinitrobenzoic acid in the plating solution increases, the plating process proceeds selectively to the circular plating part of the substrate, and the unnecessary part of the plating process is obtained. It was found that the groove was not plated.

According to the present invention, it is possible to perform hard gold plating only on a necessary portion of an electronic component such as a connector. In particular, when hard gold plating is performed on the surface of the base plated with nickel, partial plating can be selectively performed.

Claims

In hard gold plating solution containing soluble gold salt or gold complex, conductive salt, chelating agent,
A hard gold plating solution containing an aromatic compound having one or more nitro groups.
The hard gold plating solution according to claim 1, further comprising at least one metal salt of a cobalt salt, a nickel salt, and a silver salt.
The hard gold plating solution according to claim 1, further comprising an organic additive of polyethyleneimine.
The hard gold plating solution according to any one of claims 1 to 3, wherein the aromatic compound is selected from any of nitrobenzoic acid, dinitrobenzoic acid, and nitrobenzenesulfonic acid.