WO2016098789A1 - Cyanogen-free gold electroplating liquid and gold electroplating method - Google Patents

Abstract

Provided is a cyanogen-free gold electroplating liquid with which conventional gold electroplating liquids comprising cyanogen-based compounds can be replaced, the cyanogen-free gold electroplating liquid being characterized by containing components (a) through (c): (a) is a monovalent metal complex represented by general formula (I) (where in general formula (I), R₁ is hydrogen or an optionally branched C1-4 alkyl group optionally having mercapto groups, R₂ is hydrogen or an optionally branched C1-4 alkyl group, R₃ is hydrogen, an optionally branched C1-4 alkyl group, a hydroxyalkyl group, or an optionally branched C1-4 carboxyalkyl group optionally having mercapto groups, and n is an integer of 1 to 10); (b) is an electrolyte; and (c) is a crystal modifier selected from metals.

Description

Norcyan electrolytic gold plating solution and gold plating method

The present invention relates to a nocyan electrolytic gold plating solution and a gold plating method.

Gold plating films have long been used not only for decorative purposes and tableware, but also because they have excellent chemical stability and electrical conductivity and low mechanical hardness. For example, bump electrode formation, wire bonding, solder balls It is also widely used in the electronic industry field such as bonding pad surface treatment.

The gold plating solutions used in the past were mostly cyanide solutions containing toxic potassium gold cyanide, but recently there are problems with work safety and wastewater treatment, and attacks on resists for semiconductor components, etc. Due to these problems, demands for non-cyanide gold plating solutions are increasing, and various nocyanide gold platings have been proposed. As such a gold plating solution, for example, there are many reports using gold (I) sodium sulfite as a gold salt (for example, Patent Documents 1 and 2).

However, in a gold plating solution using gold (I) sodium sulfite, sulfite ions in the solution are easily oxidized by oxygen generated from the anode or oxygen in the atmosphere, and the concentration naturally decreases. As a result, the stability of the gold complex in the gold plating solution was lowered, causing a problem that the physical properties of the electrodeposited material were changed and the plating solution was decomposed.

Also, as another gold plating solution, for example, a gold plating solution using a hydantoin derivative as a complexing agent has been reported (Patent Document 3). However, since the plating solution has low stability, the cost is high, and the performance of the film does not reach that of the cyan solution, practical use is limited. Therefore, it is desired to develop a practical nocyanide gold plating solution that is excellent in solution stability and has the same plating film characteristics as the cyan solution.

Recently, a monovalent gold complex was obtained by using 6-aminopenicillanic acid, thiopronin or the like as a complexing agent, and a gold plating solution using this was also reported (Patent Document 4). However, the electrolytic plating solution disclosed therein contains sodium chloroaurate, 6-aminopenicillanic acid, citric acid, bipyridyl, and PEG200, and although gold plating can be performed, the current efficiency, the deposited gold film It was not practical in terms of hardness, purity, precipitated crystal state, and the like.

Japanese Patent Laid-Open No. 11-61480 JP 2011-184734 A US Patent Application Publication No. 2003/111353 International Publication No. 2014/10301

Therefore, the present inventors have made it a problem to provide a nocyan electrolytic gold plating solution that can be used in place of an electrolytic gold plating solution containing a cyanide compound that has been used so far.

As a result of diligent research to solve the above-mentioned problems, the present inventors have obtained a practical non-cyanide electrolytic gold plating solution by combining a monovalent gold complex having a specific structure with an electrolyte and a metal crystal modifier. The present invention has been completed.

That is, the present invention provides the following components (a) to (c):
(A) Monovalent gold complex represented by the following general formula (I)

(In the formula (I), R ₁ represents hydrogen or a mercapto group which may be branched or optionally branched alkyl group 1 to 4; R ₂ is hydrogen or branched. R ₃ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, and R ₃ may have hydrogen, an optionally branched alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, or a mercapto group. And optionally represents a carboxyalkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10.)
(B) Electrolyte (c) A non-cyanide gold plating solution containing a metal crystal modifier selected from metals.

Further, the present invention is a method for the nocyan electrolysis gold plating of a member to be plated, characterized in that the member to be plated is electroplated in the above-mentioned nocyan electrolytic gold plating solution.

The non-cyanide electrolytic gold plating solution of the present invention is extremely stable, has not changed even for one year after preparation, and hardly changes the physical properties of the deposited gold or decomposes the gold plating solution during the gold plating operation.

Also, the gold plating film obtained by the gold plating method using the non-cyanide gold plating solution of the present invention has a beautiful appearance, a dense crystal structure, and excellent solderability and wire bonding properties. Moreover, since the current efficiency of the present invention is 90% or more, it is practical. Moreover, according to the non-cyanide gold plating method of the present invention, it is possible to control the hardness, purity, crystal state, and the like of the gold plating obtained.

4 is a diagram showing a polarization curve measured in Test Example 1. FIG. 4 is a SEM photograph of a gold plating film deposited in Example 2. 4 is a SEM photograph of a gold plating film deposited in Example 3. 4 is a SEM photograph of a gold plating film deposited in Example 4. 6 is a SEM photograph of gold bumps formed in Example 5. It is a figure which shows the result of the solder ball joint shear strength of test example 2, and the failure mode. It is a figure which shows the fracture | rupture mode in wire bonding pull strength measurement. It is a figure which shows the result of the wire bonding strength of Test Example 2. 4 is a SEM photograph of a gold plating film deposited in Example 7.

In this specification, the non-cyanide gold plating solution does not contain a cyanide compound such as potassium gold cyanide used in conventional gold plating solutions.

The following general formula (I) of the component (a) used in the nocyan electrolytic gold plating solution of the present invention

In which R ₁ is hydrogen or a mercapto group and may be branched or an alkyl group having 1 to 4 carbon atoms, preferably hydrogen, methyl group, ethyl group Propyl group, isopropyl group, butyl group, isobutyl group, mercaptomethyl group (—CH ₂ —SH), more preferably hydrogen or methyl group. R ₂ is hydrogen or an optionally branched alkyl group having 1 to 4 carbon atoms, preferably hydrogen, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, more preferably hydrogen, Indicates a methyl group. Further, R ₃ represents hydrogen, an optionally branched alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, or a mercapto group, and optionally branched carboxy group having 1 to 4 carbon atoms. Alkyl group, preferably hydrogen, methyl group, carboxymethyl group, carboxyethyl group, hydroxyethyl group, isocarboxyethyl group (—CH (CH ₃ ) —COOH), mercaptocarboxymethyl group (—CH (SH) —COOH) 2-mercapto-isocarboxyethyl group (—CH (CH ₂ SH) —COOH), more preferably a carboxymethyl group and hydrogen. Furthermore, n represents an integer of 1 to 10, preferably an integer of 3 to 6, more preferably 4. Here, n represents the number of monomers formed of the monovalent gold complex.

The monovalent gold complex represented by the above general formula (I) is, for example, a trivalent gold aqueous solution containing tetrachloride gold (III) acid ion or a monovalent gold salt aqueous solution of sodium gold sulfite in the following general formula. (II)

(Wherein X represents hydrogen, ammonium ion or metal, preferably alkali metal such as sodium or potassium, alkaline earth metal such as calcium or magnesium, ammonium ion, silver, tin, antimony, germanium, lead) Bismuth, cobalt, indium, mercury, nickel, zinc, more preferably hydrogen, sodium, potassium, R ₁ to R ₂ are the same as above, and R ₃ ′ is the same as R ₃ above Or an alkyl group, a hydroxyalkyl group or a carboxyalkyl group represented by R ₃ , wherein the above X (excluding hydrogen) is substituted with 1 to 5 moles of gold salt, preferably 3 Add to 3.5-fold mol, adjust the pH to 3 or less by adding an acidic substance if necessary, and then stir well. It can be prepared.

Examples of the compound represented by the general formula (II) include thiopronin, 2-mercaptoacetamide, N- (2-mercaptoethionyl) glycine, N- (2-mercaptoacetyl) glycine, N- (2-hydroxyethyl). ) -2-mercaptoacetamide or N- (2-mercapto-1-oxopropyl) glycine and sodium, potassium and tin salts thereof.

The trivalent gold aqueous solution containing the tetrachloride gold (III) acid ion described above can be prepared by, for example, dissolving gold in aqua regia or dissolving sodium chloroaurate sodium salt in pure water. it can. Moreover, the monovalent gold salt aqueous solution of sodium gold sulfite can be prepared by, for example, dissolving gold in aqua regia to bring the pH to 8 or more and reacting gold hydroxide to be separated with sodium sulfite. .

The acidic substance used for adjusting the pH is not particularly limited, and examples thereof include carboxylic acids such as acetic acid, citric acid, lactic acid, and tartaric acid, carbonic acid, and phosphoric acid.

Since the monovalent gold complex prepared as described above is prepared under the condition of pH 3 or less, it does not dissolve and becomes a precipitate. Therefore, the monovalent gold complex can be purified by a known purification means such as filtration using a membrane filter or the like, or centrifugation. Moreover, the purification degree can be increased by performing these purification means twice or more.

In order to increase the degree of purification of the monovalent gold complex, for example, the monovalent gold complex obtained by filtration and centrifugation once is added to water, and the pH of this aqueous solution is adjusted to potassium hydroxide, sodium hydroxide or the like. An alkaline substance is added and adjusted to about 5 to dissolve the monovalent gold complex. Next, the above acidic substance is added to this aqueous solution to adjust the pH to 3 or less to reprecipitate the monovalent gold complex. By repeating this one or more times, the purity of the monovalent gold complex can be increased.

The monovalent gold complex prepared as described above may be used as it is. For example, a purified monovalent gold complex is added to water in an amount such that the gold ion is 50 to 100 g / L, and the pH of the aqueous solution is adjusted. A syrup in which a monovalent gold complex is dissolved by adding an alkaline substance such as potassium hydroxide or sodium hydroxide to about pH 5 may be used.

The content of the monovalent gold complex of component (a) in the nocyan electrolytic gold plating solution of the present invention is not particularly limited, but is, for example, in the range of 2 to 30 g / L, preferably 4 to 16 g / L as gold ions. . When the amount of gold is less than 2 g / L, the deposition rate of gold is slow and may not be suitable for actual operation. When the amount exceeds 30 g / L, the cost increases and industrial utility may be lost.

Further, the electrolyte of the component (b) used in the non-cyanide gold plating solution of the present invention is not particularly limited, and examples thereof include potassium salts, sodium salts and ammonium salts of inorganic acids or organic acids. Examples of the inorganic acid or organic acid include sulfuric acid, formic acid, carbonic acid, nitric acid, phosphoric acid, citric acid, acetic acid, lactic acid, succinic acid, glycolic acid, and tartaric acid, with sulfuric acid or formic acid being preferred. These electrolytes can be used alone or in combination of two or more.

The content of the component (b) electrolyte in the non-cyanide gold plating solution of the present invention is not particularly limited, but is, for example, 0.01 to 10 mol / L, preferably 0.1 to 1 mol / L. If the electrolyte is less than 0.01 mol / L, it may be difficult to ensure sufficient conductivity as a plating solution, and if it exceeds 10 mol / L, the effect as an electrolyte may not increase.

Further, the crystal modifier selected from the metal of component (c) used in the nocyan electrolytic gold plating solution of the present invention is not particularly limited as long as it has a crystal adjusting action. For example, thallium, antimony, arsenic, bismuth , Tin, lead, indium, tellurium, cerium, selenium, cobalt, nickel and the like. Of these, thallium, antimony, bismuth, and tin are preferable. One or more kinds of crystal modifiers selected from these metals can be used. Moreover, it is preferable to add the crystal modifier selected from a metal as metal salts, such as formic acid, a sulfuric acid, tartaric acid, and methanesulfonic acid, to the nocyan electrolytic gold plating solution of this invention.

The content of the crystal modifier selected from the metal of component (c) in the nocyan electrolytic gold plating solution of the present invention is not particularly limited, but is, for example, 1 to 1000 ppm, preferably 5 ppm to 100 ppm.

In addition to the components (a) to (c), the nocyan electrolytic gold plating solution of the present invention further includes components (d) and (e).
(D) pH buffer (e) It is preferable to contain one or two selected from the group consisting of crystal modifiers selected from sulfur-containing compounds.

The pH buffering agent of the component (d) is not particularly limited as long as it has a pH buffering action, and examples thereof include inorganic acids, organic carboxylic acids, organic phosphoric acids, pyridinesulfonic acids and their potassium salts, sodium salts, An ammonium salt etc. are mentioned. Examples of the pH buffering agent include inorganic acids such as phosphoric acid, carbonic acid and boric acid, organic carboxylic acids such as ethylenediaminetetraacetic acid (EDTA), nitrosotriacetic acid (NTA), citric acid and tartaric acid, 1-hydroxyethane- Organic phosphoric acids such as 1,1-diphosphonic acid (HEDP), 1,1,1-nitrotris (methylphosphonic acid) (ATMP), ethylenediaminetetramethylenephosphonic acid (EDTMP), 3-pyridinesulfonic acid, 2-pyridinesulfonic acid Pyridinesulfonic acid such as 5-methyl-3-pyridinesulfonic acid and 4-hydroxypyridine-3-sulfonic acid, and potassium salts, sodium salts, ammonium salts thereof and the like, preferably EDTA. These pH buffering agents can be used alone or in combination of two or more.

The content of the pH buffering agent of component (d) in the non-cyanide electrolytic gold plating solution of the present invention is not particularly limited. For example, it is 0.5 to 10 mol, preferably 1 to 1 mol with respect to 1 mol of gold ions in the gold plating solution. 2 mmol. By adding the pH buffering agent of component (d), the pH of the solution becomes stable, so that the gold complex is stabilized and the deposition uniformity of plating is improved. And the external appearance of the obtained gold plating is brighter and precipitation becomes uniform. Furthermore, the stability of the liquid can be ensured even when plating is performed for a long time.

The crystal modifier selected from the sulfur-containing compound of the component (e) is not particularly limited as long as it is a sulfur-containing compound having a crystal adjusting action. For example, thiosulfuric acid and thiophosphoric acid and their potassium salts, sodium salts, ammonium Examples thereof include salts and organic compounds having both a mercapto group and a carboxy group. Among these crystal modifiers selected from these sulfur-containing compounds, thiosulfuric acid, thiosalicylic acid, thioglycolic acid, 4-mercaptobenzoic acid, and 3-mercaptopropionic acid are preferable, and thiosulfuric acid and thiosalicylic acid are preferable. One or more crystal modifiers selected from these sulfur-containing compounds can be used.

The content of the crystal modifier selected from the sulfur-containing compound of the component (e) in the nocyan electrolytic gold plating solution of the present invention is not particularly limited, but is, for example, 0.0001 to 0.025 mol / L, preferably 0.001. ~ 0.01 mol / L. In addition, by adding a crystal modifier selected from the sulfur-containing compound of component (e), nanoholes are not recognized even in SEM observation of gold plating.

Furthermore, components such as surfactants, brighteners and other additives may be added to the nocyan electrolytic gold plating solution of the present invention within a range not impairing the effects of the present invention.

Still further, the non-cyanide electrolytic gold plating solution of the present invention is a non-cyanide by adjusting the kind and amount of metal added as a crystal adjusting agent selected from the metals of component (c) and the pH of the non-cyanide gold plating solution. It can also be used as an electrolytic alloy plating solution.

Specifically, for example, when thallium is added as the component (c) to the non-cyanide gold plating solution of the present invention, it is almost pure gold soft gold. On the other hand, when antimony is added as the component (c), pure gold is easily formed at 10 ppm and pH 7 or less, soft gold is formed, and a gold / antimony alloy is easily formed at 20 ppm and pH 7 or more, and the hardness is increased. When tin is added, it becomes a gold / tin alloy.

The pH of the above-described nocyan electrolytic gold plating solution of the present invention is not particularly limited, but is, for example, 3 to 14, preferably 5 to 8. For pH adjustment, an alkaline substance such as potassium hydroxide, sodium hydroxide, or ammonia, or an acidic substance such as sulfuric acid, citric acid, or acetic acid may be used as appropriate.

The non-cyanide gold plating solution of the present invention can be produced by adding the above components to water and stirring, and adjusting the pH as necessary.

The non-cyanide electrolytic gold plating solution of the present invention described above can be used for electrolytic gold plating. Specifically, electrolytic gold plating can be performed by electrolyzing a member to be plated in the nocyan electrolytic gold plating solution of the present invention. The member to be plated used for the electrolytic gold plating is not particularly limited, and examples thereof include a wafer, a printed wiring board, a connector of an electronic component device, and a lead frame. Although the raw material of these to-be-plated members is not specifically limited, For example, nickel, copper, gold | metal | money etc. are mentioned.

The conditions for electrolytic gold plating using the non-cyanide electrolytic gold plating solution of the present invention are not particularly limited. For example, the solution temperature is 20 to 80 ° C. and the current density is 0.1 to 6 A / dm ² .

The plated member subjected to electrolytic gold plating as described above has a beautiful appearance, improved corrosion resistance, and excellent solderability and wire bonding. Moreover, since the gold purity of the film can be adjusted depending on the composition of the gold plating solution and the plating conditions, it is possible to control softness and hardness.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Reference example 1
Preparation of monovalent gold complex syrup:
An aqueous solution containing 0.15M thiopronin, 0.50M acetic acid and 0.05M sodium chloroaurate was stirred at 20 ° C for 10 hours to form a monovalent gold complex. In addition, since the pH of this aqueous solution is 3 or less, the produced | generated monovalent gold complex does not melt | dissolve but is a microparticle. Next, this aqueous solution was filtered with a 0.4 μm membrane filter to isolate a monovalent gold complex. The gold recovery rate in this operation was 99.9%. It is already known that the structure of this monovalent gold complex is a tetramer structure represented by the following formula (III) (Carrie A. Simpson et al., Inorganic Chemistry 2010, 49 (23), 10858 -10866).

 

The monovalent gold complex obtained above was poured into water, potassium hydroxide was added to adjust the pH to 5, and the monovalent gold complex was dissolved. Subsequently, the pH was adjusted to 3 or lower again by the above operation to produce a precipitate, which was further purified by filtration. This operation was repeated twice, and finally a monovalent gold complex purified to a purity of 98% or more (confirmed by NMR) was obtained.

The monovalent gold complex purified as described above was poured into water and adjusted to pH 5 with potassium hydroxide to prepare a monovalent gold complex syrup containing 100 g / L of gold ions.

Reference example 2
Preparation of monovalent gold complex:
An aqueous solution containing 0.05 M thiopronin and 0.05 M sodium gold sulfite was stirred at 20 ° C. for 10 hours to form a monovalent gold complex. By adjusting the pH of this aqueous solution to 3 or less with acetic acid, the produced monovalent gold complex was precipitated. Next, the monovalent gold complex was isolated by filtering the aqueous solution through a 0.4 μm membrane filter. The gold recovery rate in this operation was 99.9%.

Reference example 3
Preparation of electrolytic gold plating solution:
An aqueous solution containing 50 ml / L of monovalent gold complex syrup prepared in Reference Example 1 (5 g / L as gold ion) and 65 g / L of tripotassium citrate monohydrate was prepared, and the pH of this aqueous solution was adjusted to potassium hydroxide. The solution adjusted to 7.2 was used as an electrolytic gold plating solution.

Reference example 4
Electrolytic gold plating:
The copper test piece was subjected to generally known pretreatment such as electrolytic degreasing, soft etching, and acid treatment, and then electrolytic nickel plating was performed. Immediately thereafter, the electrolytic gold plating solution prepared in Reference Example 3 was used to perform gold plating on a test piece plated with nickel on copper. The size of the plated portion of the test piece was 2 cm × 2 cm, and the area of the anode was 1.5 to 2.0 times the plating area. The anode was an insoluble titanium anode with iridium oxide as a coating layer, and the distance from the test piece (as a cathode) was about 6 cm. Electrolytic gold plating was performed for 2 minutes in a plating tank made of heat-resistant vinyl chloride having a capacity of 100 ml while maintaining a liquid temperature of 60 ° C. and stirring at a current density of 0.4 A / dm ² .

The appearance after gold plating was gold. Further, when the gold plating was observed by SEM, it was a smooth surface having a regular shape. However, the cathode current efficiency (hereinafter referred to as current efficiency) in electrolytic gold plating was calculated from “actual precipitation amount / theoretical precipitation amount × 100%” and was 30%. Moreover, when plating was performed for a long time, it turned out that an external appearance tends to become red and the pH of a plating solution falls gradually.

Example 1
Electrolytic gold plating:
An aqueous solution containing 40 ml / L of monovalent gold complex syrup prepared in Reference Example 1 (4 g / L as gold ions), 44 g / L of potassium sulfate, and 24.4 ppm of thallium formate (20 ppm as thallium ions) was prepared. The solution was adjusted to 6.2 with potassium hydroxide as an electrolytic gold plating solution.

When this electrolytic gold plating solution was subjected to electrolytic gold plating under the same plating conditions as in Reference Example 4, the appearance after gold plating was gold. When the current efficiency in electrolytic gold plating was calculated in the same manner as in Reference Example 4, it was 90% or more. However, when plating was performed for a long time, although not as much as in Reference Example 4, the appearance was likely to be red, and the pH of the plating solution gradually decreased.

Test example 1
Electrochemical measurement:
Polarization curves obtained by electrochemical measurements of the electrolytic gold plating solution obtained in Example 1 (added with 20 ppm thallium) and the electrolytic gold plating solution prepared in Reference Example 3 (without adding thallium) are shown in FIG. It has been found that the addition of thallium, a metal as a crystal modifier, shifts the polarization curve to the right, making polarization much easier. The current efficiency of the electrolytic gold plating solution to which thallium was added was about 100%, which was about twice that of the electrolytic gold plating solution to which thallium was not added.

Example 2
Electrolytic gold plating:
An aqueous solution containing 50 ml / L of monovalent gold complex syrup prepared in Reference Example 1 (5 g / L as gold ions), 42 g / L of potassium formate, 24.4 ppm of thallium formate (20 ppm as thallium ions), and 7.31 g / L of EDTA. A solution prepared by adjusting the pH of this aqueous solution to 7.4 with potassium hydroxide was used as an electrolytic gold plating solution.

The electrolytic gold plating solution was subjected to electrolytic gold plating in the same manner as in Reference Example 4. As a result, the appearance after gold plating was brighter than those obtained in Reference Example 4 and Example 1. When the current efficiency in electrolytic gold plating was calculated in the same manner as in Reference Example 4, it was 90% or more. Furthermore, the pH of the plating solution was stable even after plating for a long time. However, when the gold plating film was observed with an SEM, nanoholes were slightly observed, although not as much as in Reference Example 4 (FIG. 2).

Example 3
Electrolytic gold plating:
Monovalent gold complex syrup 50 ml / L prepared as in Reference Example 1 (5 g / L as gold ion), potassium formate 42 g / L, thallium formate 24.4 ppm (20 ppm as thallium ion), EDTA 7.31 g / L, thiosalicylic acid 1 An aqueous solution containing 0.54 g / L was prepared, and the pH of this aqueous solution was adjusted to 7.4 with potassium hydroxide to obtain an electrolytic gold plating solution.

The electrolytic gold plating solution was subjected to electrolytic gold plating in the same manner as in Reference Example 4. As a result, the appearance after gold plating was brighter than those obtained in Reference Example 4 and Example 2. When the current efficiency in electrolytic gold plating was calculated in the same manner as in Reference Example 4, it was 95% or more. Further, when the gold plating film was observed by SEM, nanoholes observed in the gold plating film obtained in Example 2 were not recognized (FIG. 3).

The purity of the gold plating film obtained in Examples 1, 2, and 3 was confirmed by ICP analysis after dissolving the gold plating film with a gold release agent and found to be 99.9% or more. Therefore, it was found that the gold plating films obtained in Examples 1, 2, and 3 were pure gold. Further, when the hardness of the gold film was confirmed, the hardness of the gold plating film was measured with a load of 5 g using an MVK-G3 Vickers hardness tester (manufactured by AKASHI). The Vickers hardness of the gold plating films obtained in Examples 1, 2, and 3 is 110 HV or less, and is 60 to 70 HV after 30 minutes of annealing at 300 ° C., which is required for pure gold plating films of electronic products. It has been shown to have good performance.

Example 4
Electrolytic gold plating:
Monovalent gold complex syrup prepared in Reference Example 1 40 ml / L (4 g / L as gold ion), 44 g / L potassium sulfate, potassium antimony tartrate (10 ppm as antimony ion), 7.31 g / L EDTA, 10 g trisodium citrate / L, an aqueous solution containing 0.77 g / L of thiosalicylic acid, and the pH of this aqueous solution adjusted to 6.2 with potassium hydroxide was used as the electrolytic gold plating solution.

When this electrolytic gold plating solution was subjected to electrolytic gold plating in the same manner as in Reference Example 4, the appearance of the gold plating film was brighter than that obtained in Reference Example 4 and was obtained in Example 3. The appearance was brighter than the gold plating film. When the current efficiency in electrolytic gold plating was calculated in the same manner as in Reference Example 4, it was 95% or more. Further, when the gold plating film was observed by SEM, it was found that the crystals were dense and had a smooth surface (FIG. 4). Further, although the purity of gold was slightly lowered, the Vickers hardness was increased to 170 HV, and after annealing at 300 ° C. for 30 minutes, it was 80 to 90 HV.

Example 5
Micro bump formation:
Using the electrolytic gold plating solution prepared in Example 4, bump plating of the semiconductor wafer was performed. Gold plating was performed on a resist-patterned wafer (plating base material was sputtering gold) at a current density of 0.4 A / dm ² and a liquid temperature of 60 ° C. for 40 minutes. When the resist was peeled off after plating and the surface was observed, fine gold bumps (width: 10 μm, height: about 10 μm) as shown in FIG. 5 were formed. Since the gold bumps grew straight up, it was found that this electrolytic gold plating solution did not attack the resist.

Comparative Example 1
Electrolytic gold plating:
Using an electrolytic pure gold plating solution SKYGOLD S-10 (manufactured by JCU) as a commercial product of cyan gold plating, the liquid temperature is 60 ° C., and the current density is 0.3 A / dm ² for 2 minutes (thickness 0.35 μm). ) Electrolytic gold plating was performed.

Comparative Example 2
Electrolytic gold plating:
Sodium gold sulfite (10 g / L as gold ion), sodium sulfite 80 g / L, thallium sulfate (20 ppm as thallium ion), ethylenediamine 10 g / L, EDTA 4 g / L, disodium hydrogen phosphate 20 g / L, 3,5-dinitro An aqueous solution containing 1 g / L of benzoic acid was prepared, and the pH of this aqueous solution was adjusted to 8.0 with potassium hydroxide was used as an electrolytic gold plating solution. Using this liquid, electrolytic gold plating was performed for 70 seconds (film thickness 0.35 μm) while stirring at a liquid temperature of 60 ° C. and a current density of 0.5 A / dm ² .

Test example 2
Physical property measurement:
(1) Solder ball joint shear strength and fracture mode The solder ball joint shear strength and fracture mode of the gold plating films obtained with the solutions of Examples 3 and 4 and Comparative Examples 1 and 2 were compared (FIG. 6).
Solder ball bondability was evaluated by M705 (Sn-3.0Ag-0.5Cu) 0.76mmφ solder ball (manufactured by Senju Metal Industry), flux 529D (paste: Senju Metal Industry), and reflow RF- Use 430-M2 (manufactured by Pulse), solder at a top temperature of 260 ° C and a retention time of about 32 seconds above the melting point, and then use a bond tester 4000HS (manufactured by ARCTEK) to share at a shear rate of 40 mm / s. Tested. The film thickness of the gold plating evaluated was all (Ni 5.0 μm / Au 0.35 μm).
The fracture mode was evaluated by the ratio of the remaining area of the solder balls on the fracture surface. It was evaluated that the bondability was strong when there was no interfacial fracture and there were many remaining solder balls, and it was evaluated that the bondability was weak when there was no remaining solder balls and the interface was broken. As shown in FIG. 6, with 20 samples, the solder joint strengths of Example 3 and Example 4 of the present invention were equivalent to those of Comparative Example 1 and Comparative Example 2, and the fracture mode was almost free from interface fracture. . On the other hand, the cyan gold plating solution of Comparative Example 1 and the gold sulfite gold plating solution of Comparative Example 2 are slightly more likely to have a little solder residue, and there are cases of interface breakdown. There was nothing.

(2) Wire bonding strength The wire bonding strengths of the gold plating films obtained with the solutions of Examples 3 and 4 and Comparative Examples 1 and 2 were compared.
Wire bonding strength is measured by using a gold wire φ18μm (manufactured by GMH), hitting and mounting the wire with bonder HW27U-HF (manufactured by Panasonic), and measuring pull strength using pull tester BT-14 (manufactured by DAGE). (Fracture modes (5 levels A to E) in the pull strength measurement are shown in FIG. 7. A and E fail). The film thickness of the gold plating evaluated was all (Ni 5.0 μm / Au 0.35 μm). The measurement results of Examples 3 and 4 and Comparative Examples 1 and 2 were all B (pass). As for wire bonding strength, as shown in FIG. 8, the gold plating solutions of Example 3 and Example 4 of the present invention are significantly different from the cyan gold plating solution of Comparative Example 1 and the gold sulfite gold plating solution of Comparative Example 2. Not as good.

From the above measurement results, the gold plating film obtained with the gold plating solutions of Examples 3 and 4 is almost the same as the gold plating film obtained with the cyan bath of Comparative Example 1 and the sulfite bath of Comparative Example 2 that have been used conventionally. It has the characteristics required for electrical components at or above. Therefore, it was found that the present invention can be used in place of an electrolytic gold plating solution containing a cyanide compound.

Example 6
Electrolytic gold plating:
50 ml / L of monovalent gold complex syrup prepared in Reference Example 1 (5 g / L as gold ion), 42 g / L of potassium formate, bismuth methanesulfonate (20 ppm as bismuth), 7.31 g / L of EDTA, and 0.1 mg of thioglycolic acid. An aqueous solution containing 46 g / L was prepared, and the pH of this aqueous solution was adjusted to 7.4 with potassium hydroxide was used as an electrolytic gold plating solution.

When this electrolytic gold plating solution was subjected to electrolytic gold plating in the same manner as in Reference Example 4, the appearance after gold plating was brighter than Reference Example 4. When the current efficiency in electrolytic gold plating was calculated in the same manner as in Reference Example 4, it was 90% or more.

Example 7
Electrolytic gold plating:
An aqueous solution containing 50 ml / L of monovalent gold complex syrup prepared in Reference Example 1 (5 g / L as gold ions), 42 g / L of potassium formate, tin sulfate (100 ppm as tin), 5.8 g / L of EDTA, A solution prepared by adjusting the pH of this aqueous solution to 7.4 with potassium hydroxide was used as an electrolytic gold plating solution.

A test piece plated with nickel on copper was put into this electrolytic gold plating solution, and the mixture was lightly stirred at a liquid temperature of 60 ° C. and a current density of 1 A / dm ² to perform electrolytic gold plating for 3 minutes. The appearance after plating was bright and bright gold. When observed by SEM, the surface morphology was fairly smooth, and the interface of crystal grains was not visible at all compared to Examples 3 and 4 (FIG. 9). When the current efficiency in electrolytic gold plating was calculated in the same manner as in Reference Example 4, it was 40%. When the gold purity of the film was confirmed, the composition was a gold alloy of 99.4% gold and 0.6% tin.

Example 8
Electrolytic gold plating:
Monovalent gold complex syrup prepared in Reference Example 1 80 ml / L (8 g / L as gold ion), potassium sulfate 44 g / L, tin sulfate (100 ppm as tin), EDTA 7.31 g / L, thiosalicylic acid 1.54 g / L An aqueous solution containing the solution was prepared, and the pH of this aqueous solution was adjusted to 7.4 with potassium hydroxide was used as the electrolytic gold plating solution.

The electrolytic gold plating solution was subjected to electrolytic gold plating in the same manner as in Reference Example 4. As a result, the appearance after gold plating was brighter than those obtained in Reference Example 4 and Example 1. When the current efficiency in electrolytic gold plating was calculated in the same manner as in Reference Example 4, it was 90%. When the gold purity of the film was confirmed, the composition was a gold alloy of 99.2% gold and 0.8% tin.

Example 9
Preparation of electrolytic gold plating solution:
An aqueous solution containing 0.15M 2-mercaptoacetamide and 0.05M chloroauric acid generated from the hydrolysis of 2,4-thiazolidinedione was stirred at 20 ° C. for 10 hours to form a monovalent gold complex. In addition, since the pH of this aqueous solution is 3 or less, the produced | generated monovalent | monohydric complex does not melt | dissolve but becomes a precipitate. Next, this aqueous solution was filtered with a 0.4 μm membrane filter to isolate a monovalent gold complex. The gold recovery rate in this operation was 99.9%. The structure of the monovalent gold complex was confirmed by NMR to be a structure represented by the formula (IV) (n is 1 to 10). This monovalent gold complex can be used in an electrolytic gold plating solution as in the above examples.

 

Example 10
Electrolytic gold plating:
An aqueous solution containing 0.15 M N- (2-mercaptoethionyl) glycine and 0.05 M chloroauric acid generated by hydrolysis of rhodanine-3-acetic acid was stirred at 20 ° C. for 10 hours to form a monovalent gold complex. It was. In addition, since the pH of this aqueous solution is 3 or less, the produced | generated monovalent | monohydric complex does not melt | dissolve but becomes a precipitate. Next, this aqueous solution was filtered with a 0.4 μm membrane filter to isolate a monovalent gold complex. The gold recovery rate in this operation was 99.9%. The structure of the monovalent gold complex was confirmed by NMR to be a structure represented by the formula (V) (n is 1 to 10).

 

The monovalent gold complex of the above formula (V) was made into a syrup in the same manner as in Reference Example 1, and this was replaced with the monovalent gold complex syrup used in Example 1 to prepare an electrolytic gold plating solution. When electrolytic gold plating is performed with this electrolytic gold plating solution, a similar gold plating film is obtained.

Example 11
Preparation of electrolytic gold plating solution ::
An aqueous solution containing 0.15M N- (2-hydroxyethyl) -2-mercaptoacetamide and 0.05M chloroauric acid formed from the hydrolysis of 2,4-thiazolidinedione and 2-aminoethanol was stirred at 20 ° C. for 10 hours. And a monovalent gold complex was produced. In addition, since the pH of this aqueous solution is 3 or less, the produced | generated monovalent | monohydric complex does not melt | dissolve but becomes a precipitate. Next, this aqueous solution was filtered with a 0.4 μm membrane filter to isolate a monovalent gold complex. The gold recovery rate in this operation was 99.9%. The structure of the monovalent gold complex was confirmed by NMR to be a structure represented by the formula (VI) (n is 1 to 10). This monovalent gold complex can be used in an electrolytic gold plating solution as in the above examples.

 

The non-cyanide electrolytic gold plating solution of the present invention is practical and can be used in place of the electrolytic gold plating solution containing a cyanide compound that has been used so far.

more than

Claims (11)

1. The following components (a) to (c)
   (A) Monovalent gold complex represented by the following general formula (I)
   

   

   
   (In the formula (I), R ₁ represents hydrogen or a mercapto group which may be branched or optionally branched alkyl group 1 to 4; R ₂ is hydrogen or branched. R ₃ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, and R ₃ may have hydrogen, an optionally branched alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group, or a mercapto group. And optionally represents a carboxyalkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10.)
   (B) Electrolyte (c) A cyanide electrolytic gold plating solution containing a crystal modifier selected from metals.
2. The monovalent gold complex represented by the general formula (I) of the component (a) is one in which R ₁ in the formula (I) is hydrogen, R ₂ is a methyl group, R ₃ is a carboxymethyl group, and n is 4. The nocyan electrolytic gold plating solution according to claim 1.
3. The non-cyanide electrolytic gold plating solution according to claim 1, wherein the electrolyte of component (b) is one or more selected from the group consisting of potassium salts, sodium salts, and ammonium salts of inorganic or organic acids.
4. The metal of the crystal modifier selected from the metals of component (c) is selected from the group consisting of thallium, antimony, arsenic, bismuth, tin, lead, indium, germanium, gallium, tellurium, cerium, selenium, cobalt and nickel The norcyan electrolytic gold plating solution according to claim 1, which is a seed or two or more.
5. In addition, components (d) and (e)
   5. The non-cyanide gold plating solution according to claim 1, comprising (d) a pH buffer (e) one or two selected from the group consisting of crystal modifiers selected from sulfur-containing compounds.
6. The pH buffer of component (d) is one or more selected from the group consisting of inorganic acids, organic carboxylic acids, organic phosphoric acids, pyridinesulfonic acids, and potassium, sodium and ammonium salts thereof. Item 6. A non-cyanide gold plating solution according to item 5.
7. The sulfur-containing compound of the crystal modifier selected from the sulfur-containing compounds of component (e) is composed of thiosulfuric acid and thiophosphoric acid and their potassium, sodium, ammonium, and organic compounds having both mercapto and carboxy groups. The nocyan electrolytic gold plating solution according to claim 5, which is one or more selected from the group.
8. The non-cyanide gold plating solution according to any one of claims 1 to 7, wherein the pH is 3 to 14.
9. 9. A method for non-cyanide electrolytic gold plating of a member to be plated, comprising subjecting the member to be plated to electrolytic plating in the non-cyanide electrolytic gold plating solution according to any one of claims 1 to 8.
10. 10. The method for non-cyanide electroplating of a member to be plated according to claim 9, wherein the temperature of the solution during electroplating is 20 to 80 ° C. and the current density is 0.1 to 6 A / dm ² .
11. A gold-plated member obtained by the nocyan electrolytic gold plating method for a member to be plated according to claim 9 or 10.
    

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