Gold plating method, gold plating composition and plating solution

Abstract

The present invention provides a gold plating method, a gold plating composition, and a plating solution that realize soft gold plating. The gold plating method is carried out using a plating solution that contains gold sulfite and at least one of thiosulfate ions and trithionate ions.

Description

[Technical field]

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

[0002] Japanese Patent Application Laid-Open No. 2006-322037 (Patent Document 1) discloses a gold plating solution. This gold plating solution contains sodium gold sulfite or its ethylenediamine complex with a gold concentration of 5 to 20 g / L, sodium sulfite with 10 to 100 g / L, and a thallium compound with a thallium concentration of 1 to 50 ppm, and also contains potassium sulfite with 0.1 to 50 g / L. It is said that this plating solution can perform gold plating suitable 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, and that gold plating that does not have a very high hardness after heat treatment is required to achieve good bonding characteristics.

[0003] JP 2000-319016 A (Patent Document 2) discloses a method for producing sodium gold sulfite solution. This production method comprises the steps of (a) reacting Na(AuCl4) with sodium hydroxide and barium hydroxide to produce barium aurate and additional by-products, (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, thereby producing sodium gold sulfite in solution form. 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 a pure and soft gold plating film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-322037 A [Patent Document 2] JP 2000-319016 A Summary of the Invention [Problem to be solved by the invention]

[0005] As disclosed in Patent Documents 1 and 2, there are cases where gold plating that is not very hard, that is, soft, is desired for applications such as electric elements.

[0006] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a gold plating method, a gold plating composition, and a plating solution that realize soft gold plating. [Means for solving the problem]

[0007] In order to achieve the above object, the gold plating method according to the present disclosure comprises: Gold plating is carried out using a plating solution containing gold sulfite and at least one of thiosulfate ions and trithionate ions.

[0008] In order to achieve the above object, the gold plating composition according to the present disclosure comprises: The gold sulfite salt includes 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 comprises: The sulfite includes 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 comprises: The acid salts include bisulfite and at least one of thiosulfate and trithionate.

[0011] In order to achieve the above object, the present disclosure provides a plating solution for gold plating, The gold sulfite salt includes at least one of a thiosulfate ion and a trithionate ion. Effect of the Invention

[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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, may be simply referred to as a plating solution) contains a sulfite and at least one of a thiosulfate and a trithionate.

[0019] According to the plating method of this embodiment, soft gold plating can be realized. According to the gold plating composition of this embodiment and the plating solution of this embodiment, the plating method of this embodiment can be realized, and as a result, soft gold plating can be realized. In this embodiment, gold plating refers to plating containing gold, and is not limited to gold alone. In this embodiment, gold plating may be 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] In the plating method according to the present embodiment, a gold plating composition containing a gold sulfite salt such as sodium gold sulfite and at least one of thiosulfate ions and trithionate ions may be used. An example of the gold plating composition (plating solution composition) is a gold plating solution.

[0022] An example of this plating solution for gold plating 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 (additive for gold plating) described later. In this embodiment, the concept of the term plating solution includes a plating replenisher for use by adding 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 prepares this plating solution and performs 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 salt 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. The second composition will be described in detail 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, and 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, and arsenic. 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 as a bath make-up solution, its specific gravity is 2.0 Bh or more and 22.0 Bh or less, preferably 3.3 Bh or more and 19.9 Bh or less, and more preferably 4.1 Bh or more and 17.8 Bh or less.

[0030] When the plating solution is for electrolytic plating, 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 bath solution, its specific gravity is 0.2 Bh or more and 14.3 Bh or less, preferably 0.4 Bh or more and 13.0 Bh or less, and more preferably 0.6 Bh or more and 11.8 Bh or less.

[0032] When the plating solution is for electroless plating, 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 ion may come from a thiosulfate salt, such as sodium thiosulfate, ammonium thiosulfate, potassium thiosulfate, calcium thiosulfate.

[0035] The trithionate ion may result 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 electrolytic plating, 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 for the plating to be soft. 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 or more and 2.50 mg / L or less, preferably 0.13 mg / L or more and 2.19 mg / L or less, which makes it easier to produce 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 or more and 4.00 mg / L or less, preferably 0.20 mg / L or more and 3.68 mg / L or less. This makes it easier for the plating to become soft.

[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, for example, when visually observed, the plating surface appears glossy.

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

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

[0043] In the sulfitation step, the gold hydroxide may be sulfitized using a first composition containing a sulfite salt. In the sulfitation step, the gold hydroxide may be sulfitized using a second composition containing a bisulfite salt. In the sulfitation step, the gold hydroxide may be sulfitized using the first composition and the second composition.

[0044] The first composition preferably contains a sulfite, a thiosulfate, and a trithionate. This makes it easier for the plating to be soft. As an example, the first composition may be obtained by a first heating treatment step in which a sulfite is heated. The first heating treatment step will be described later.

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

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

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

[0048] In the first heating treatment step, a heating treatment may be performed in which the sulfite is heated to 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, a salt capable of generating thiosulfate ions (thiosulfate) and a salt capable of generating trithionate ions (trithionate) are generated from the sulfite by the heating treatment. When the heating treatment in the first heating treatment step is performed at 40°C or higher and 60°C or lower, the heating time is sufficient to be 100 hours or higher and 200 hours or lower. 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, in terms of thiosulfate ions, preferably from 1 ppm to 300 ppm, more preferably from 10 ppm to 1500 ppm.

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

[0053] In the second heating process, 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 process, the bisulfite is decomposed by the heating treatment to generate a salt capable of generating a thiosulfate ion (thiosulfate) and a salt capable of generating a trithionate ion (trithionate). When the heating treatment in the second heating process is performed at 40°C or higher and 60°C or lower, the heating time is sufficient to be 100 hours or higher and 200 hours or lower. When the heating temperature in the second heating process is lower than 40°C, the heating time is preferably 10 days or longer.

[0054] An example of the sulfite is sodium sulfite. The sulfite may also be potassium sulfite, ammonium sulfite, magnesium sulfite, or calcium hydrogen sulfite.

[0055] An example of a sulfite is sodium bisulfite. Other examples of bisulfite include potassium bisulfite, ammonium bisulfite, magnesium bisulfite, and calcium hydrogen bisulfite. In this embodiment, the concept of sodium bisulfite includes sodium disulfite (Na2S2O5) and sodium hydrogen sulfite (NaHSO3) obtained by hydrolysis of sodium disulfite, and when simply described as sodium bisulfite or sodium bisulfite (Na2S2O5), it 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 capable of generating thiosulfate ions. The thiosulfate may also be other salts capable of generating thiosulfate ions, such as thiosulfate, sodium thiosulfate, ammonium thiosulfate, magnesium thiosulfate, and potassium thiosulfate.

[0057] The trithionate may be, for example, sodium trithionate capable of generating trithionate ions. The trithionate may be potassium trithionate, ammonium trithionate, magnesium trithionate, calcium trithionate, or another salt capable of generating trithionate ions. EXAMPLES

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

[0059] The gold plating process of Experimental Example 1-14 shown in Table 1 was carried out as described below, forming gold-plated bumps, which were then evaluated.

[0060] [Table 1]

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

[0062] First, barium gold hydroxide (Ba[Au(OH)4]2) was produced using chloroauric acid (HAuCl4), barium hydroxide (Ba(OH)2), and sodium hydroxide.

[0063] The first composition was produced as follows: Sodium sulfite (Na2SO3, manufactured by Air Water Performance Chemical Inc., specification: industrial use, purity 97% or more) was kept in an atmosphere of 50°C for 168 hours (first heat treatment), and this was used as the 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 the LC measurement, Shimadzu Corporation's Prominence UFLC was used as the measurement device. The column used for 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. The mobile phase A was acetonitrile / water / formic acid = 10 / 90 / 0.1. The mobile phase B was acetonitrile / 100 mM ammonium formate = 10 / 90. 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 (measurement target) was dissolved in ultrapure water to 10 mg / mL to prepare the measurement sample. The amount of the measurement sample injected into the LC was 5 μL.

[0067] For the MS measurement, a Triple TOF 5600+ manufactured by AB SCIEX was used as the measurement device. The ionization method was ESI, and the IonSpray Voltage Floating was 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 thiosulfate ion peak (peak at approximately 7.5 minutes) was calculated.

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

[0070] The second composition was prepared as follows: Anhydrous sodium bisulfite (Na2S2O5, manufactured by Air Water Performance Chemicals, Inc., specification: industrial use, purity 97% or more) was kept in an atmosphere of 50°C for 168 hours (second heat treatment), and this was used as the 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 measured as a standard 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 found to be 5 ppm, and the trithionate ions were found to be 230 ppm. Moreover, the thiosulfate ions in the second composition were found to be 650 ppm, and the trithionate ions were found to be 2190 ppm.

[0073] Next, a plating solution containing sodium gold sulfite (Na3Au(SO3)2) was prepared as follows.

[0074] Sodium gold sulfite was produced from barium gold hydroxide as follows. That is, 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 barium gold 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 produce 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 described as "proportion (%) of the first composition." In addition, the ratio (mass%) of the second composition to the total amount of sodium bisulfite and the second composition in the second aqueous solution is described as "proportion (%) of the second composition."

[0077] The plating solution prepared as described above 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 the first aqueous solution," "Trithionate ions (mg / L) derived from the first aqueous solution," "Thiosulfate ions (mg / L) derived from the second aqueous solution," and "Trithionate ions (mg / L) derived from the second aqueous solution" indicate the 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 was increased by the concentration shown in Table 1 ("Additional thiosulfate ions" in Table 1).

[0078] Then, the test substrate was gold plated using the above plating solution.

[0079] The plating process was carried out as follows. The test substrate had a resist patterned on the surface of a silicon wafer 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 solution was stirred while plating was performed 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 the sodium sulfite and sodium bisulfite used in Experimental Examples 1-12 were used.

[0081] (Experimental Example 14) In Experimental Example 14, a gold plating process 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 the sodium sulfite and sodium bisulfite 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 subjected to a heat treatment. The heat treatment was performed at 300°C for 30 minutes. The Vickers hardness and surface roughness (Ra) of the gold plating surface (bump surface) after the heat treatment were then measured, and the appearance was observed using an optical microscope (presence or absence of nodules). These results are shown in Table 1. In Table 1, "hardness (HV)" refers to the Vickers hardness of the gold plating surface after 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). In this example, the Vickers hardness was measured using a micro Vickers hardness tester (manufactured by Mitutoyo Corporation, model: HM-200) in accordance with the Japanese Industrial Standard JIS Z 2244:2009, with a test force of 10 gf (98.07 mN) and a holding time of 10 seconds.

[0084] In this embodiment, 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 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 determined to be absent ("absent" in Table 1) when such nodules were not confirmed.

[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 amount 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 realized. When the total amount 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, and the hardness could not be measured appropriately.

[0087] When the total amount of thiosulfate ions and trithionate ions in the plating solution is between 0.20 mg / L and 4.00 mg / L, the plating solution should contain between 0.02 mg / L (0.03 mg / L) and 4.00 mg / L (3.55 mg / L) of thiosulfate ions and between 0.10 mg / L (0.13 mg / L) and 2.50 mg / L (2.19 mg / L).

[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 other than the Vickers hardness of the plated surface are as follows. The surface roughness (Ra) of the plated surface is good if it is, for example, 82 nm or more and 220 nm or less. In this embodiment, the surface roughness (Ra) of the plated surface in the experimental examples other than Experimental Example 14 was in the range of 82 nm or more and 220 nm or less, which was good. And, in the experimental examples other than Experimental Example 14, the formation of significant nodules (lumps) on the plated surface was not confirmed. Thus, the plated surface (plated surface) had a necessary and sufficient smoothness.

[0090] In Experimental Example 14, as described above, the unevenness of the plating surface was significant, and nodules were observed. In Experimental Example 14, the unevenness of the plating surface was significant, so that the surface roughness (Ra) could not be measured by the method for measuring surface roughness 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] Note that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited thereto, and may be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

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

Claims

1. The method includes a plating step of performing gold plating using a plating solution containing sodium gold sulfite, thiosulfate ions, and trithionate ions, The plating solution is Contains gold at 0.50 g / L or more and 20.0 g / L or less; Contains thiosulfate ions in an amount of 0.03 mg / L or more and 3.55 mg / L or less; Contains 0.13 mg / L or more and 2.19 mg / L or less of trithionate ion; A gold plating method comprising the steps of: providing a solution containing thiosulfate ions and trithionate ions in a total amount of 0.20 mg / L or more and 3.68 mg / L or less.

2. A gold plating method as described in claim 1, wherein the plating solution further contains thallium ions.

3. A gold plating method as described in claim 1 or 2, wherein the pH of the plating solution is 7.0 or higher and 9.0 or lower.

4. 2. The gold plating method according to claim 1, further comprising a sulfiting step of sulfiting gold hydroxide to prepare the plating solution.

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

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

7. The method further includes a second heat treatment step of heat treating the bisulfite to obtain a second composition containing the bisulfite and at least one of a thiosulfate and a trithionate; 5. The gold plating method according to claim 4, wherein in the sulfiting step, the gold hydroxide is sulfitized using the second composition.

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

9. A gold plating method as described in claim 1 or 2, wherein the plating solution contains 9 g / L or more and 11 g / L or less of gold.

10. A gold plating method as described in claim 1 or 2, wherein the specific gravity of the plating solution is 0.2 Bh or more and 33.3 Bh or less.

11. Sodium gold sulfite having a content of 0.50 g / L or more and 20.0 g / L or less as gold; Thiosulfate ions of 0.03 mg / L or more and 3.55 mg / L or less; and 0.13 mg / L or more and 2.19 mg / L or less of trithionate ion; A gold plating composition having a total amount of thiosulfate ions and trithionate ions of 0.20 mg / L or more and 3.68 mg / L or less.

12. The gold plating composition of claim 11, further comprising thallium ions.

13. A gold plating composition as described in claim 11 or 12, having a pH of 7.0 or more and 9.0 or less.

14. The gold plating composition according to claim 11 or 12, comprising 9 g / L or more and 11 g / L or less of sodium gold sulfite as gold.

15. The gold plating composition according to claim 11 or 12, having a specific gravity of 0.2 Bh or more and 33.3 Bh or less.

16. Sodium gold sulfite having a content of 0.50 g / L or more and 20.0 g / L or less as gold; Thiosulfate ions of 0.03 mg / L or more and 3.55 mg / L or less; and 0.13 mg / L or more and 2.19 mg / L or less of trithionate ion; A plating solution for gold plating, wherein the total amount of thiosulfate ions and trithionate ions is 0.20 mg / L or more and 3.68 mg / L or less.

17. The plating solution for gold plating according to claim 16, further comprising thallium ions.

18. A plating solution for gold plating as described in claim 16 or 17, having a pH of 7.0 or more and 9.0 or less.

19. A plating solution for gold plating as described in claim 16 or 17, containing 9 g / L or more and 11 g / L or less of sodium gold sulfite as gold.

20. A plating solution for gold plating as described in claim 16 or 17, having a specific gravity of 0.2 Bh or more and 33.3 Bh or less.