Gold plating method, composition for gold plating, and plating solution

Abstract

Provided are: a gold plating method for achieving soft gold plating; a composition for gold plating; and a plating solution. The gold plating method is performed using a plating solution comprising: a gold sulfite salt; and at least one among thiosulfate ions and trithionic acid ions.

Description

Gold plating method, gold plating composition and plating solution

[0001] The present disclosure relates to a gold plating method, a gold plating composition, and a plating solution.

[0002] Japanese Patent Laid-Open Publication No. 2006-322037 (Patent Document 1) discloses a gold plating solution. This gold plating solution contains sodium gold sulfite or its ethylenediamine complex at a gold concentration of 5 to 20 g / L, sodium sulfite at 10 to 100 g / L, and a thallium compound at a thallium concentration of 1 to 50 ppm, and also contains 0.1 to 50 g / L of potassium sulfite. This plating solution is said to be suitable for gold plating processes for bump formation. Patent Document 1 discloses that gold plating is often used to ensure electrical bonding in the formation of bumps in semiconductor electrical elements, etc., and that gold plating that does not have a very high hardness after heat treatment is required to achieve good bonding characteristics.

[0003] Japanese Patent Application Laid-Open No. 2000-319016 (Patent Document 2) discloses a method for producing a sodium gold sulfite solution. This method comprises the steps of: (a) preparing Na(AuCl ４ (b) reacting an aqueous solution of barium aurate with sodium sulfite to produce sodium gold sulfite and additional by-products; and (c) recovering the sodium gold sulfite solution. Patent Document 2 discloses that this sodium gold sulfite solution is useful for use in gold electroplating baths and can be used in applications requiring pure, soft gold plating films.

[0004] JP 2006-322037 A JP 2000-319016 A

[0005] As disclosed in Patent Documents 1 and 2, gold plating that is not very hard, i.e., soft gold plating, is sometimes desired for applications such as electrical elements.

[0006] The present disclosure has been made in view of the above circumstances, and its object is to provide a gold plating method, a gold plating composition, and a plating solution that can achieve soft gold plating.

[0007] To achieve the above object, the gold plating method according to the present disclosure performs gold plating using a plating solution containing gold sulfite and at least one of thiosulfate ions and trithionate ions.

[0008] To achieve the above object, the gold plating composition according to the present disclosure contains a gold sulfite salt and at least one of a thiosulfate ion and a trithionate ion.

[0009] In order to achieve the above object, the gold plating composition according to the present disclosure contains a sulfite and at least one of a thiosulfate and a trithionate.

[0010] In order to achieve the above object, the gold plating composition according to the present disclosure contains a bisulfite and at least one of a thiosulfate and a trithionate.

[0011] To achieve the above object, the plating solution for gold plating according to the present disclosure contains a gold sulfite salt and at least one of a thiosulfate ion and a trithionate ion.

[0012] According to the present disclosure, it is possible to provide a gold plating method, a gold plating composition, and a plating solution that realize soft gold plating.

[0013] A gold plating method, a gold plating composition, and a plating solution according to an embodiment of the present disclosure will be described.

[0014] In the plating method according to this embodiment, gold plating is performed using a plating solution containing gold sulfite and at least one of thiosulfate ions and trithionate ions.

[0015] The gold plating composition according to this embodiment contains a gold sulfite salt and at least one of a thiosulfate ion and a trithionate ion.

[0016] The gold plating composition according to this embodiment contains a sulfite and at least one of a thiosulfate and a trithionate.

[0017] The gold plating composition according to this embodiment contains a bisulfite and at least one of a thiosulfate and a trithionate.

[0018] The gold plating solution according to this embodiment (hereinafter, sometimes simply referred to as a plating solution) contains a sulfite and at least one of a thiosulfate and a trithionate.

[0019] The plating method according to this embodiment can achieve soft gold plating. The gold plating composition according to this embodiment and the plating solution according to this embodiment can achieve the plating method according to this embodiment, and as a result, soft gold plating can be achieved. Note that in this embodiment, gold plating refers to plating containing gold, and is not limited to gold alone. In this embodiment, gold plating may be any plating containing gold, and includes plating containing gold and metal elements other than gold.

[0020] The gold plating method, gold plating composition, and plating solution according to this embodiment will be described in detail below.

[0021] The plating method according to this embodiment may use a gold plating composition containing a gold sulfite salt such as sodium gold sulfite and at least one of thiosulfate ions and trithionate ions. One example of the gold plating composition (plating solution composition) is a gold plating solution.

[0022] An example of this gold plating solution is a plating solution containing gold sulfite and at least one of thiosulfate ions and trithionate ions. The plating solution may contain thiosulfate ions and trithionate ions. The plating solution may further contain another gold plating composition (gold plating additive) described below. In this embodiment, the concept of the term "plating solution" includes a plating replenisher solution that is added to a plating solution in use. The plating solution may be a solution such as an aqueous solution. The plating method according to this embodiment involves preparing this plating solution and performing gold plating using this plating solution. The plating method according to this embodiment may include a preparation step of preparing this plating solution and a plating step of performing gold plating using this plating solution.

[0023] The gold plating composition (gold plating additive) may be a first composition containing a sulfite and at least one of a thiosulfate salt that generates thiosulfate ions and a trithionate salt that generates trithionate ions. For example, the first composition may contain a sulfite salt, thiosulfate ions, and trithionate ions. Details of the first composition will be described later.

[0024] The gold plating composition (gold plating additive) may be a second composition containing a bisulfite and at least one of a thiosulfate and a trithionate. For example, the second composition may contain a bisulfite, a thiosulfate, and a trithionate. Details of the second composition will be described later.

[0025] That is, the plating solution may contain, in addition to a gold sulfite such as sodium gold sulfite, thiosulfate ions, and trithionate ions, a sulfite other than gold sulfite such as sodium sulfite, or a bisulfite such as sodium bisulfite.

[0026] The plating solution may contain other additives such as complexing agents, buffers, crystal modifiers, brighteners, alloy metal salts, reducing agents, and surfactants. Examples of complexing agents include sulfites, EDTA, NTA, and amine compounds. Examples of buffers include various inorganic acid salts and various organic acid salts. Examples of crystal modifiers include salts of thallium, lead, bismuth, antimony, arsenic, and the like. Examples of brighteners include amine compounds and aromatic compounds. Examples of alloy metal salts include salts of cobalt, nickel, iron, and silver. Examples of reducing agents include SBH, DMAB hydrazine, hydroquinone, thiourea, and ascorbate. Examples of surfactants include anionic surfactants, cationic surfactants, and amphiphilic surfactants.

[0027] The pH of the plating solution is 6.0 to 10.0, preferably 7.0 to 9.0, and can be adjusted by adding sodium hydroxide or sodium bisulfite.

[0028] The specific gravity of the plating solution, when evaluated in Baume scale (heavy Baume scale), is 0.2 Bh or more and 33.3 Bh or less.

[0029] When the plating solution is for electrolytic plating, particularly when it is a make-up solution, its specific gravity is 2.0 Bh to 22.0 Bh, preferably 3.3 Bh to 19.9 Bh, and more preferably 4.1 Bh to 17.8 Bh.

[0030] When the plating solution is for electrolytic plating, and particularly when it is a replenisher, its specific gravity is 12.0 Bh or more and 33.3 Bh or less.

[0031] When the plating solution is for electroless plating, particularly when it is a make-up solution, its specific gravity is 0.2 Bh to 14.3 Bh, preferably 0.4 Bh to 13.0 Bh, and more preferably 0.6 Bh to 11.8 Bh.

[0032] When the plating solution is for electroless plating, and particularly when it is a replenisher, its specific gravity is 12.0 Bh or more and 33.3 Bh or less.

[0033] The gold sulfite may be an alkali gold sulfite such as the above-mentioned sodium gold sulfite or ammonium gold sulfite. When the gold sulfite is an alkali gold sulfite, sodium gold sulfite or potassium gold sulfite is particularly preferred.

[0034] The thiosulfate ions may be derived from thiosulfates such as sodium thiosulfate, ammonium thiosulfate, potassium thiosulfate, calcium thiosulfate.

[0035] The trithionate ion may be from a trithionate salt such as sodium trithionate, ammonium trithionate, potassium trithionate, calcium trithionate.

[0036] The plating solution may have a gold concentration of 0.50 g / L or more and 20.0 g / L or less. When the plating solution is used for electroplating, the gold concentration of the plating solution is preferably 5.0 g / L or more and 20.0 g / L or less, and more preferably 10.0 g / L or more and 16.0 g / L or less.

[0037] The plating solution may contain thiosulfate ions in an amount of 0.02 mg / L to 4.00 mg / L, preferably 0.03 mg / L to 3.55 mg / L. This makes it easier to produce soft plating. In this embodiment, when simply referring to "ppm," it means "ppm by mass."

[0038] The plating solution may contain trithionate ions in an amount of 0.10 mg / L to 2.50 mg / L, preferably 0.13 mg / L to 2.19 mg / L, which facilitates soft plating.

[0039] The plating solution preferably contains thiosulfate ions and trithionate ions. The plating solution may contain thiosulfate ions and trithionate ions in a total amount of 0.20 mg / L to 4.00 mg / L, preferably 0.20 mg / L to 3.68 mg / L. This facilitates soft plating.

[0040] By making the plating soft as described above, the plating surface becomes smooth. In other words, the surface roughness of the plating surface becomes small. In this case, when visually observed, for example, the plating surface becomes glossy.

[0041] The plating process may be, for example, electrolytic gold plating. In this case, the plating conditions are a current density of 0.1 A / dm ２ 2.0A / dm or more ２ The liquid temperature is preferably 40°C or higher and 80°C or lower. The current density is more preferably 0.2 A / dm ２ 1.0A / dm or more ２ The liquid temperature is more preferably 50°C or higher and 70°C or lower.

[0042] The preparation step may include a sulfiting step of sulfiting gold hydroxide to prepare a plating solution. An example of gold hydroxide is the hydroxide of barium and gold, Ba[Au(OH) ４ ] ２ (tetrahydroxide barium gold (III) acid, hereinafter sometimes referred to as barium gold hydroxide).

[0043] In the sulfiting step, gold hydroxide may be sulfited using a first composition containing a sulfite, or a second composition containing a bisulfite, or the gold hydroxide may be sulfited using both the first and second compositions.

[0044] The first composition preferably contains a sulfite, a thiosulfate, and a trithionate. This makes it easier to produce soft plating. For example, the first composition may be obtained by a first heat treatment step in which a sulfite is heat-treated. The first heat treatment step will be described later.

[0045] The first composition may contain 95.0% by mass or more of sulfite, with the remainder being thiosulfate, trithionate, and impurities.

[0046] The first composition may contain thiosulfate in an amount of preferably 1 ppm or more and 3000 ppm or less, and more preferably 10 ppm or more and 1500 ppm or less, in terms of thiosulfate ions.

[0047] The first composition may contain trithionate in an amount of preferably 1 ppm to 3000 ppm, more preferably 10 ppm to 1500 ppm, in terms of trithionate ions.

[0048] In the first heating treatment step, a heating treatment may be performed in which the sulfite is heated to a temperature of 28°C or higher and 60°C or lower, preferably 40°C or higher and 60°C or lower. In the first heating treatment step, the heating treatment produces a salt capable of generating thiosulfate ions (thiosulfate) and a salt capable of generating trithionate ions (trithionate). When the heating treatment in the first heating treatment step is performed at a temperature of 40°C or higher and 60°C or lower, a heating time of 100 hours or higher and 200 hours or lower is sufficient. When the heating temperature in the first heating treatment step is lower than 40°C, the heating time is preferably 10 days or longer.

[0049] The second composition preferably contains a bisulfite, a thiosulfate, and a trithionate. For example, the second composition may be obtained by a second heat treatment step in which the bisulfite is heat treated.

[0050] The second composition may contain 95.0% by mass or more of bisulfite, with the remainder being thiosulfate ions, trithionate ions, and impurities.

[0051] The second composition may contain thiosulfate in an amount of preferably 1 ppm or more and 300 ppm or less, and more preferably 10 ppm or more and 1500 ppm or less, in terms of thiosulfate ions.

[0052] The second composition may contain trithionate in an amount of preferably 1 ppm to 3000 ppm, more preferably 10 ppm to 1500 ppm, in terms of trithionate ions.

[0053] In the second heating treatment step, a heating treatment may be performed in which the bisulfite is heated to 28°C or higher and 60°C or lower, preferably 40°C or higher and 60°C or lower. In the second heating treatment step, the heating treatment decomposes the bisulfite to produce a salt capable of generating thiosulfate ions (thiosulfate) and a salt capable of generating trithionate ions (trithionate). When the heating treatment in the second heating treatment step is performed at 40°C or higher and 60°C or lower, a heating time of 100 hours or higher and 200 hours or lower is sufficient. When the heating temperature in the second heating treatment step is lower than 40°C, the heating time is preferably 10 days or longer.

[0054] An example of a sulfite is sodium sulfite. Other sulfites include potassium sulfite, ammonium sulfite, magnesium sulfite, and calcium hydrogen sulfite.

[0055] An example of a sulfite is sodium bisulfite. Other examples of the bisulfite include potassium bisulfite, ammonium bisulfite, magnesium bisulfite, and calcium hydrogen bisulfite. In this embodiment, the concept of sodium bisulfite includes sodium disulfite (Na ２ S ２ O ５ ) and sodium hydrogen sulfite (NaHSO ) which is the product of hydrolysis of sodium disulfite. ３ ), and simply sodium bisulfite or sodium bisulfite (Na ２ S ２ O ５) includes sodium disulfite, sodium hydrogen sulfite, and a mixture of sodium disulfite and sodium hydrogen sulfite.

[0056] The thiosulfate may be, for example, sodium thiosulfate, which can generate thiosulfate ions. The thiosulfate may also be other salts that generate thiosulfate ions, such as thiosulfate, sodium thiosulfate, ammonium thiosulfate, magnesium thiosulfate, and potassium thiosulfate.

[0057] The trithionate may be, for example, sodium trithionate, which can generate trithionate ions. The trithionate may also be potassium trithionate, ammonium trithionate, magnesium trithionate, calcium trithionate, or another salt that can generate trithionate ions.

[0058] The gold plating method, gold plating composition, and plating solution according to this embodiment will be described below with reference to examples.

[0059] Gold plating treatment of Experimental Example 1-14 shown in Table 1 was carried out as follows, and gold-plated bumps were formed and evaluated.

[0060]

[0061] (Experimental Example 1-12) In Experimental Example 1-12, gold plating was performed on a test substrate as follows.

[0062] First, chloroauric acid (HAuCl ４ ) and barium hydroxide (Ba(OH) ２ ) and sodium hydroxide to prepare barium gold hydroxide (Ba[Au(OH) ４ ] ２ ) was manufactured.

[0063] The first composition was prepared as follows: ２ SO ３ (manufactured by Air Water Performance Chemicals Inc., specifications: industrial grade, purity 97% or more) was kept in an atmosphere of 50°C for 168 hours (first heat treatment), and this was used as a first composition.

[0064] When sodium sulfite and the first composition were measured (analyzed) by liquid chromatography (LC-TOFMS), thiosulfate ions and trithionate ions were detected in the first composition.

[0065] Here, the measurement of sodium sulfite and the first composition by LC-TOFMS was carried out as follows.

[0066] For LC measurements, a Shimadzu Prominence UFLC was used as the measurement device. The column used during this measurement was an Intrade Organic Acid (2.0 mm x 150 mm, 3.0 μm). The column temperature during this measurement was 40°C. Acetonitrile / water / formic acid = 10 / 90 / 0.1 was used as mobile phase A. Acetonitrile / 100 mM ammonium formate = 10 / 90 was used as mobile phase B. The measurement profile was changed in the following order: A:B = 100:0 (0 min), A:B = 100:0 (1 min), A:B = 0:100 (7 min), and A:B = 0:100 (10 min). The flow rate of the mobile phase was 0.2 mL / min. The sample to be measured (the substance to be measured) was dissolved in ultrapure water to a concentration of 10 mg / mL to prepare the measurement sample. The amount of the measurement sample injected into the LC was 5 μL.

[0067] The MS measurement was performed using a Triple TOF 5600+ manufactured by AB SCIEX. The ionization method was ESI, and the IonSpray Voltage Floating was set to 4.5 kV (negative mode) and 5.5 kV (positive mode). The mass range was m / z 50-1500.

[0068] In this measurement, before measuring the object to be measured (sodium sulfite or the first composition), sodium thiosulfate (10 mg / mL, concentration as a measurement sample) was first measured as a reference substance, and the area (S1) of the peak of thiosulfate ions (peak at approximately 7.5 minutes) was determined.

[0069] Next, the object to be measured was measured, and the area (S21) of the thiosulfate ion peak (peak at approximately 7.5 minutes) and the area (S22) of the trithionate ion peak (peak at approximately 8.5 minutes) were determined. Then, the mass of thiosulfate ion in the object to be measured (sodium sulfite and the first composition) was determined based on the concentration of the reference substance, area S1, the concentration of the object to be measured, and area S21. Similarly, the mass of trithionate ion in the object to be measured was determined based on the concentration of the reference substance, area S1, the concentration of the object to be measured, and area S21. From these results, the thiosulfate ion concentration in sodium sulfite was determined to be 3 ppm, and the trithionate ion concentration was 1 ppm. Furthermore, the thiosulfate ion concentration in the first composition was determined to be 54 ppm, and the trithionate ion concentration was 460 ppm.

[0070] The second composition was prepared as follows: anhydrous sodium bisulfite (Na ２ S ２ O ５ , manufactured by Air Water Performance Chemicals Inc., specifications: industrial grade, purity 97% or more) was held in an atmosphere of 50°C for 168 hours (second heat treatment), and this was used as a second composition.

[0071] When sodium bisulfite and the second composition were measured (analyzed) by liquid chromatography (LC-TOFMS) in the same manner as in the case of sodium sulfite and the first composition, thiosulfate ions and trithionate ions were detected in the second composition.

[0072] In this measurement, before measuring the object to be measured (anhydrous sodium bisulfite or the second composition), sodium thiosulfate was first measured as a reference substance, and the masses of thiosulfate ions and trithionate ions in each object to be measured were determined based on the measurement results. From these results, the thiosulfate ions in anhydrous sodium bisulfite were determined to be 5 ppm, and the trithionate ions were determined to be 230 ppm. Furthermore, the thiosulfate ions in the second composition were determined to be 650 ppm, and the trithionate ions were determined to be 2190 ppm.

[0073] Next, sodium gold sulfite (Na ３ Au(SO ３ ) ２A plating solution containing 1,2-dimethyl-3,4-trimethylsilyl methylcellulose was prepared.

[0074] Sodium gold sulfite was produced from gold barium hydroxide as follows. Specifically, sodium gold sulfite was prepared by adding an aqueous solution of sodium sulfite and the first composition (hereinafter referred to as the first aqueous solution), an aqueous solution of sodium bisulfite and the second composition (hereinafter referred to as the second aqueous solution), and a complexing agent (EDTA.2Na) to gold barium hydroxide, stirring the mixture, and filtering the precipitate (barium sulfate). Thallium formate was added to this sodium gold sulfite, and sodium thiosulfate was further added to adjust the pH to prepare a plating solution.

[0075] The concentration of the first aqueous solution (total concentration of sodium sulfite and the first composition) was 126 g / L, and the concentration of the second aqueous solution (total concentration of sodium bisulfite and the second composition) was 84 g / L.

[0076] The ratio of sodium sulfite to the first composition in the first aqueous solution was changed for each experimental example, as shown in Table 1. Similarly, the ratio of sodium bisulfite to the second composition in the second aqueous solution was changed for each experimental example, as shown in Table 1. In Table 1, the ratio (mass%) of the first composition to the total amount of sodium sulfite and the first composition in the first aqueous solution is referred to as the "proportion (%) of the first composition." Furthermore, the ratio (mass%) of the second composition to the total amount of sodium bisulfite and the second composition in the second aqueous solution is referred to as the "proportion (%) of the second composition."

[0077] The plating solution prepared as described above generally had a thallium ion concentration of 10 mg / L, contained 10 g / L of gold ions in the solution, had a pH of 8.0, and had a specific gravity of 4.5 Bh. In Table 1, the items "Thiosulfate ions (mg / L) derived from first aqueous solution," "Trithionate ions (mg / L) derived from first aqueous solution," "Thiosulfate ions (mg / L) derived from second aqueous solution," and "Trithionate ions (mg / L) derived from second aqueous solution" indicate concentrations in the plating solution. In preparing the plating solution, a predetermined amount of sodium thiosulfate was added to the plating solution for each experimental example so that the concentration of thiosulfate ions in the plating solution would increase by the concentration shown in Table 1 ("Additional thiosulfate ions" in Table 1).

[0078] Then, the test substrate was subjected to gold plating treatment using the above plating solution.

[0079] The plating process was carried out as follows: The test substrate had a silicon wafer on the surface coated with a patterned resist so that bumps of 60 μm square (thickness: 14 μm to 17 μm) could be formed. The current density was 0.5 A / dm ２ The plating solution was stirred at a temperature of 60° C. The plating process was carried out for 48 minutes.

[0080] Experimental Example 13 In Experimental Example 13, gold plating was performed on a test substrate in the same manner as in Experimental Example 1, except that sodium sulfite and sodium bisulfite from different lots from those used in Experimental Examples 1-12 were used.

[0081] Experimental Example 14 In Experimental Example 14, gold plating was performed on a test substrate in the same manner as in Experimental Example 1, except that sodium sulfite and sodium bisulfite from different lots from those used in Experimental Examples 1-12 and 13 were used.

[0082] After plating in each experimental example, the resist was removed from the test substrate. The test substrate was then heat-treated. The heat treatment was carried out at 300°C for 30 minutes. The Vickers hardness and surface roughness (Ra) of the gold-plated surface (bump surface) after the heat treatment were measured, and the appearance (presence or absence of nodules) was observed using an optical microscope. These results are all shown in Table 1. In Table 1, "hardness (HV)" refers to the Vickers hardness of the gold-plated surface after the heat treatment, and "Ra (nm)" refers to the surface roughness (Ra).

[0083] In this example, the Vickers hardness was measured using a micro Vickers hardness tester (manufactured by Mitutoyo Corporation, model: HM-200). The Vickers hardness was measured in accordance with Japanese Industrial Standard JIS Z 2244:2009 using the micro Vickers hardness tester (manufactured by Mitutoyo Corporation, model: HM-200), with a test force of 10 gf (98.07 mN) and a holding time of 10 seconds.

[0084] In this example, a nodule is a type of uneven structure formed on the plating surface, and is a protrusion on the plating surface that is approximately circular in a front view of the plating surface. A nodule is a structure that protrudes from the plating surface. When nodules are formed on the plating surface, the tops of the nodules are often rounded (spherical). The presence or absence of nodules was determined to be present ("present" in Table 1) when nodules with a long side of 3 μm or more were confirmed, and otherwise determined to be absent ("absent" in Table 1).

[0085] In Table 1, the item "Total of thiosulfate ions and trithionate ions (mg / L)" indicates the total amount of thiosulfate ions and trithionate ions in 1 L of plating solution. Also, in Table 1, the item "Total of thiosulfate ions (mg / L)" indicates the total amount of thiosulfate ions in 1 L of plating solution. Similarly, in Table 1, the item "Total of trithionate ions (mg / L)" indicates the total amount of trithionate ions in 1 L of plating solution.

[0086] As shown in Table 1, in the experimental examples (Experimental Examples 3, 4, 6-11, and 13) in which the total concentration of thiosulfate ions and trithionate ions in the plating solution was 0.20 mg / L or more and 4.00 mg / L or less (3.68 mg / L or less), the Vickers hardness (hardness in Table 1) of the gold plating surface after heat treatment was 60 Hv or less, and a sufficiently soft and good gold plating film was achieved. When the total concentration of thiosulfate ions and trithionate ions was less than 0.20 mg / L or more than 4.00 mg / L, the Vickers hardness of the plating surface exceeded 60 Hv. In Experimental Example 14, the plating surface was significantly uneven, making it impossible to properly measure the hardness.

[0087] When the total amount of thiosulfate ions and trithionate ions in the plating solution is 0.20 mg / L or more and 4.00 mg / L or less, it appears that the plating solution may contain thiosulfate ions in an amount of 0.02 mg / L or more (0.03 mg / L or more) and 4.00 mg / L or less (3.55 mg / L or less) and trithionate ions in an amount of 0.10 mg / L or more (0.13 mg / L or more) and 2.50 mg / L or less (2.19 mg / L or less).

[0088] In Table 1, Experimental Examples 1-14 are classified into Examples 1-9 and Comparative Examples 1-5 based on the above Vickers hardness results.

[0089] The evaluation results for the plating surface other than the Vickers hardness are as follows. The surface roughness (Ra) of the plating surface is good if it is, for example, between 82 nm and 220 nm. In this example, the surface roughness (Ra) of the plating surface in all experimental examples except for Experimental Example 14 was in the range of 82 nm to 220 nm, which was good. Furthermore, in all experimental examples except for Experimental Example 14, no significant formation of nodules (lumps) was confirmed on the plating surface. Thus, the plating surface (plating surface) had the necessary and sufficient smoothness.

[0090] In Experimental Example 14, as described above, the unevenness of the plated surface was significant, and nodules were observed. In Experimental Example 14, the unevenness of the plated surface was significant, so that the surface roughness (Ra) could not be measured using the surface roughness measurement method adopted in this example.

[0091] As shown by the above experimental examples, it was found that soft gold plating can be achieved if the plating solution contains predetermined amounts of thiosulfate ions and trithionate ions.

[0092] As described above, a gold plating method, a gold plating composition, and a plating solution that realize soft gold plating can be provided.

[0093] It should be noted that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited to these, and can be modified as appropriate within the scope of the purpose of the present disclosure.

[0094] The present disclosure is applicable to gold plating methods, gold plating compositions, and plating solutions.

Claims

1. A gold plating method in which gold plating is performed using a plating solution containing gold sulfite and at least one of thiosulfate ions and trithionate ions.

2. The gold plating method according to claim 1, wherein the plating solution contains thiosulfate ions and trithionate ions.

3. The gold plating method according to claim 2, wherein the plating solution contains thiosulfate ions and trithionate ions in a total amount of 0.20 mg / L or more and 4.00 mg / L or less.

4. The gold plating method according to any one of claims 1 to 3, further comprising a sulfiting step of sulfiting gold hydroxide to prepare the plating solution.

5. The gold plating method according to claim 4, further comprising a first heating step of heating a sulfite to obtain a first composition containing sulfite and at least one of thiosulfate and trithionate, wherein in the sulfiting step, the gold hydroxide is sulfited using the first composition.

6. The gold plating method according to claim 5, wherein the first composition comprises a thiosulfate and a trithionate.

7. The gold plating method according to claim 4, further comprising a second heating step of heating the bisulfite to obtain a second composition containing the bisulfite and at least one of a thiosulfate and a trithionate, wherein the second composition is used in the sulfiting step to sulfite the gold hydroxide.

8. The gold plating method according to claim 7, wherein the second composition comprises a thiosulfate and a trithionate.

9. A gold plating method according to any one of claims 1 to 3, wherein the gold sulfite is sodium sulfite.

10. A gold plating composition comprising a gold sulfite salt and at least one of thiosulfate ions and trithionate ions.

11. The gold plating composition of claim 10, comprising thiosulfate ions and trithionate ions.

12. A gold plating composition comprising a sulfite and at least one of a thiosulfate and a trithionate.

13. The gold plating composition of claim 12, comprising a thiosulfate and a trithionate.

14. A gold plating composition comprising a bisulfite and at least one of a thiosulfate and a trithionate.

15. The gold plating composition of claim 14, comprising a thiosulfate and a trithionate.

16. A plating solution for gold plating, comprising a gold sulfite salt and at least one of a thiosulfate ion and a trithionate ion.

17. The gold plating solution according to claim 16, which contains thiosulfate ions and trithionate ions.

18. The plating solution for gold plating according to claim 17, which contains thiosulfate ions and trithionate ions in a total amount of 0.20 mg / L or more and 4.00 mg / L or less.

19. The plating solution for gold plating according to any one of claims 16 to 18, containing thiosulfate ions in an amount of 0.20 mg / L or more and 4.00 mg / L or less.

20. The plating solution for gold plating according to any one of claims 16 to 18, containing 0.10 mg / L or more and 2.50 mg / L or less of trithionate ions.

21. The plating solution for gold plating according to claim 19, which contains 0.10 mg / L or more and 2.50 mg / L or less of trithionate ions.

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