Electroless gold plating solution

Abstract

The present invention provides a non-electrolytic gold plating solution which is less likely to cause dissolution of copper from a copper raw material when forming a gold plating film on a substrate such as a nickel film, or a method for manufacturing a non-electrolytic gold plating film or a method for manufacturing an electronic component using the same. The solution to the problem is a non-electrolytic gold plating solution containing a water-soluble gold salt and a condensed ring compound having a nitrogen atom in the ring. Examples of the condensed ring compound include a condensed ring compound having two or more atoms other than carbon atoms in the ring, or a condensed ring compound condensed from a benzene ring or a pyridine ring and a hetero five-membered ring having a nitrogen atom. The condensed ring compound can have a substituent such as an alkyl group having a carbon number of 1 to 6, a mercapto group, a hydroxyl group, a carboxyl group, a nitro group, a halogen group, and the like.

Description

Technical Field

[0001] This invention relates to an electroless gold plating solution. Furthermore, this invention relates to an electroless gold plating solution preparation composition for preparing the electroless gold plating solution, or a method for manufacturing an electroless gold plating film using the electroless gold plating solution, or a method for manufacturing electronic components. Background Technology

[0002] In the plating of connectors and other parts used in electronic components such as printed circuit boards, as a process to prevent corrosion of the connectors and to perform wire bonding, solder bonding, etc., the method of stacking a gold film on an electroless nickel plating film on a copper base material uses the following processes: a process of applying a displacement gold plating on an electroless nickel plating film (ENIG, Electroless Nickel Immersion Gold); a process of applying a displacement gold plating on an electroless nickel plating film with an electroless palladium film in between (ENEPIG, Electroless Nickel Electroless Palladium Immersion Gold); a process of applying a displacement gold plating on an electroless nickel plating film and further applying a reduction gold plating on top to increase the gold film thickness (ENEAG, Electroless Nickel Electroless Autocatalytic Gold), etc.

[0003] The substitution gold plating used in the above processes involves the metal substrate becoming ions and dissolving in the gold plating solution. The electrons released are then transferred to the gold ions, causing the gold ions to become gold and precipitate on the surface of the substrate metal, thus forming a gold film.

[0004] Since gold deposition in displacement gold plating involves the substitution of gold ions with the substrate metal, the gold will not react further once the substrate metal surface is covered with gold, making it difficult to achieve a thick gold film. Therefore, it is known to add a reducing agent to a displacement-type electroless gold plating solution to induce a gold reduction reaction in the solution and form a gold plating film, thereby reducing the proportion of gold film formed due to the displacement reaction (displacement-reduction gold plating) (e.g., Patent Document 1, Patent Document 2).

[0005] To achieve good bonding strength in wire bonding and solder bonding, the gold plating solution must have good adhesion to the base metal. Various improvements are made to the gold plating solution based on this principle.

[0006] Patent Document 3 describes a displacement gold plating solution applicable to the surface of a nickel film on a copper surface for displacement gold plating (ENIG process). This displacement gold plating solution contains a nitrogen-containing aliphatic compound or a nitrogen-containing heterocyclic compound as a gold deposition inhibitor. The gold deposition inhibitor in Patent Document 3 suppresses partial and excessive etching or corrosion of the substrate metal caused by the displacement reaction with the substrate metal (nickel) during gold plating. The gold plating film formed by the displacement gold plating solution of Patent Document 3 is considered to have excellent adhesion to the substrate metal.

[0007] Patent document 4 describes a displacement gold plating solution containing polyethylene glycol, amidosulfuric acid, and amidosulfonate as corrosion inhibitors and applicable to the ENEPIG process. It is considered to have a fast gold deposition rate and small variation in the thickness of the deposited film.

[0008] In processes such as ENIG, ENEPIG, and ENEAG, a nickel or palladium film is formed on top of the copper substrate, and a replacement gold plating film is then formed on top of these films. Ideally, the copper will not be exposed on the substrate with the gold plating film, and no copper will dissolve into the replacement gold plating solution.

[0009] However, in actual mass production of printed circuit boards, copper is still present even though the amount of exposed copper is small, due to the presence of undeposited portions of the nickel and palladium films on the substrate or structural problems (such as poor dry film formation). Therefore, copper will gradually accumulate in the gold plating solution.

[0010] Because copper accumulates in the gold plating solution, problems such as reduced corrosion resistance and peeling of the gold film can occur due to increased plating speed and decreased coverage of the gold plating film. These issues can sometimes hinder mass production. In such cases, the gold plating solution must be replaced frequently, leading to increased costs.

[0011] As printed circuit boards and other materials become more complex and denser, they tend to accumulate copper. Therefore, it is hoped that a technology can be developed to suppress copper accumulation.

[0012] [Existing technical documents]

[0013] [Patent Literature]

[0014] Patent Document 1: Japanese Patent Application Publication No. 2001-107259

[0015] Patent Document 2: Japanese Patent Application Publication No. 2000-219973

[0016] Patent Document 3: Japanese Patent Application Publication No. 2000-144441

[0017] Patent document 4: Japanese Patent No. 6521553. Summary of the Invention

[0018] [The problem that the invention aims to solve]

[0019] The present invention was developed in view of the above-mentioned prior art. The object of the present invention is to provide an electroless gold plating solution that does not easily produce copper leaching from copper raw materials when forming a gold plating film on a substrate such as a nickel film. In addition, the object of the present invention is to provide a method for manufacturing an electroless gold plating film using the electroless gold plating solution or a method for manufacturing electronic components.

[0020] [Technical means used to solve the problem]

[0021] In order to solve the above-mentioned problems, the inventors conducted careful research and found that by adding a condensed ring compound containing nitrogen atoms in the ring to an electroless gold plating solution, it can be made to be extremely difficult to produce copper leaching from the copper raw material, thus completing the present invention.

[0022] That is, the present invention provides an electroless gold plating solution containing: a water-soluble gold salt, and a condensed ring compound having a nitrogen atom in the ring.

[0023] Furthermore, the present invention provides a composition for preparing an electroless gold plating solution, which is used to prepare an electroless gold plating solution by adding water and water-soluble gold salt, the composition for preparing the electroless gold plating solution containing the aforementioned condensed ring compound.

[0024] Furthermore, the present invention provides a method for manufacturing an electroless gold plating film, which uses the aforementioned electroless gold plating solution to manufacture the electroless gold plating film.

[0025] Furthermore, the present invention provides a method for manufacturing an electronic component having an electroless gold plating film manufactured by the aforementioned method for manufacturing an electroless gold plating film.

[0026] Furthermore, the present invention provides a method for manufacturing an electronic component, comprising the following steps: forming an electroless gold plating film using the aforementioned electroless gold plating solution.

[0027] [The effects of the invention]

[0028] According to the present invention, an electroless gold plating solution is provided that does not easily produce copper leaching from copper raw materials when forming a gold plating film on a substrate such as a nickel film.

[0029] The electroless gold plating solution of this invention does not easily cause copper leaching from the copper raw material, and copper does not easily accumulate in the plating solution. Therefore, the aforementioned problems caused by copper accumulation will not occur, and the number of times the plating solution needs to be replaced can be reduced (extending the life of the plating solution).

[0030] In mass production, the use of the electroless gold plating solution of the present invention can suppress the cost of expensive gold plating solutions and improve productivity. Detailed Implementation

[0031] The present invention is described below, but the present invention is not limited to the following embodiments and can be implemented in any modified form.

[0032] Electroless gold plating solution

[0033] The electroless gold plating solution of the present invention contains: a water-soluble gold salt, and a condensed ring compound having a nitrogen atom in the ring.

[0034] Water-soluble gold salts are used as the gold source for the electroless gold plating solution of the present invention. There are no particular limitations as long as the gold salt is sufficiently stable in the plating solution, easily soluble in water, and suitable as the gold source for the plating solution.

[0035] Specifically, examples include gold cyanide salts, gold chloride salts, gold sulfite salts, and gold thiosulfate salts. Gold cyanide salts (gold (I) cyanide salts and gold (III) cyanide salts) are preferred, and gold (I) cyanide salts are particularly preferred.

[0036] There are no particular limitations on the relative cations that form the above salts; examples include alkali metal ions and ammonium ions. Examples of alkali metal ions include potassium ions, sodium ions, and lithium ions.

[0037] Among water-soluble gold salts, potassium gold cyanide (I) is the most preferred from the perspectives of plating speed and stability.

[0038] Water-soluble gold salts can be used alone or in combination with two or more.

[0039] The concentration of water-soluble gold salts in the electroless gold plating solution (the total concentration when two or more water-soluble gold salts are used together) is not particularly limited, but in gold equivalents, it is preferably 0.1 g / L or more, particularly preferably 0.3 g / L or more, and especially preferably 0.5 g / L or more. Furthermore, it is preferably 5 g / L or less, particularly preferably 4 g / L or less, and especially preferably 3 g / L or less.

[0040] When the concentration of water-soluble gold salt is above the lower limit mentioned above, the plating speed can be significantly increased. When the concentration of water-soluble gold salt is below the upper limit mentioned above, the stability of the plating solution is easily maintained.

[0041] A condensed ring compound having a nitrogen atom in its ring is not particularly limited as long as it is a condensed ring compound (a compound in which two or more rings share two or more atoms and are bonded together) and has a nitrogen atom in its ring (that is, any one or more of the atoms constituting the ring is a nitrogen atom). Hereinafter, "a condensed ring compound having a nitrogen atom in its ring" will sometimes be referred to as a "specific condensed ring compound".

[0042] By including a specific condensation ring compound in the electroless gold plating solution, the dissolution of copper in the electroless gold plating solution can be suppressed even when there is an exposed portion of the copper raw material during electroless gold plating.

[0043] This can be presumably due to the strong hydrophobicity of certain condensation ring compounds, which firmly form a protective layer on the copper surface to prevent copper leaching.

[0044] Examples of specific condensed ring compounds include condensed ring compounds formed by the condensation of a benzene ring or a pyridine ring with a hetero five-membered ring having a nitrogen atom.

[0045] A particular condensed ring compound is preferably composed of two or more non-carbon atoms in the ring. Since a particular condensed ring compound has at least one nitrogen atom in the ring, in other words, it is preferably composed of two or more nitrogen atoms in the ring, or has a nitrogen atom and non-carbon and non-nitrogen atoms. Examples of non-carbon and non-nitrogen atoms include sulfur atoms, oxygen atoms, phosphorus atoms, etc.

[0046] A particular condensed ring compound has a hetero pentagonal ring with a nitrogen atom, preferably having two or more non-carbon atoms in the hetero pentagonal ring.

[0047] Specifically, examples include: cases with 2 nitrogen atoms, cases with 3 nitrogen atoms, cases with 1 nitrogen atom and 1 sulfur atom, cases with 1 nitrogen atom and 1 oxygen atom, cases with 2 nitrogen atoms and 1 sulfur atom, and cases with 2 nitrogen atoms and 1 oxygen atom.

[0048] A certain condensed ring compound has at least one nitrogen atom in its molecule, but may have two nitrogen atoms, three nitrogen atoms, four nitrogen atoms, or even more than five nitrogen atoms.

[0049] Certain condensed ring compounds may also have nitrogen-containing substituents such as amino, alkylamine, and nitro groups. In this case, the term "nitrogen atom present in the molecule" is not limited to nitrogen atoms in the ring; the nitrogen atoms contained in these substituents are also equivalent to "nitrogen atoms present in the molecule".

[0050] Examples of specific structures of certain condensed ring compounds include compounds having the following skeletons (basic skeletons): indole skeleton, isoindole skeleton, benzimidazole skeleton, indazole skeleton, purine skeleton, benzothiazole skeleton, benzothiazole skeleton, benzotriazole skeleton, quinoline skeleton, isoquinoline skeleton, quinoxaline skeleton, quinazoline skeleton, cinnoline skeleton, phthalazine skeleton, pyrazolopyridine skeleton, and triazolopyridine skeleton.

[0051] A specific condensed ring compound having the above structure (basic skeleton) may or may not have substituents.

[0052] When substituents are present, specific examples of substituents include: alkyl groups having 1 to 6 carbon atoms, mercapto groups, hydroxyl groups, carboxyl groups, nitro groups, halogen groups, etc.

[0053] Specific examples of alkyl groups include: methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc.

[0054] Specific examples of the halogen group include fluorine group, chlorine group, bromine group, iodine group, and the like.

[0055] When the above-mentioned substituents are present, the hydrophobicity of the specific condensation ring compound becomes stronger, so a protective layer for copper leaching protection can be formed more effectively, making the inhibition effect of copper leaching more significant.

[0056] When a specific condensed ring compound is a condensed ring compound formed by the condensation of a benzene ring or a pyridine ring with a hetero five-membered ring having a nitrogen atom, the substituents can be bonded to the benzene ring or the pyridine ring, or to the hetero five-membered ring having a nitrogen atom. Multiple substituents can each be bonded to the benzene ring or the pyridine ring, or to the hetero five-membered ring having a nitrogen atom.

[0057] The number of the above-mentioned substituents in a particular condensed ring compound may be one, two, three, or four or more.

[0058] When there are multiple substituents, the same substituent can be present in multiple locations, or different types of substituents can be present.

[0059] Specific compound names for certain condensed ring compounds include: benzimidazole, 1-methylbenzimidazole, 2-methylbenzimidazole, 2-mercaptobenzimidazole, 2-aminobenzimidazole, 1,2,3-benzotriazole, 5-methyl-1H-benzotriazole, 1-methyl-1H-benzotriazole, carboxybenzotriazole, hydroxybenzotriazole, carboxyhydroxybenzotriazole, nitrobenzotriazole, 1-aminobenzotriazole, 2-aminobenzothiazole, 1H-1,2,3-triazolidine, 3-aminoquinoline, 5-aminoindole, etc.

[0060] A specific condensation ring compound may be used alone or in combination with two or more compounds.

[0061] The concentration of the specific condensation ring compound in the electroless gold plating solution (the total concentration when two or more specific condensation ring compounds are used together) is not particularly limited, but is preferably 0.1 ppm or more, particularly preferably 0.5 ppm or more, and especially preferably 2 ppm or more. Furthermore, it is preferably 1000 ppm or less, particularly preferably 500 ppm or less, and especially preferably 100 ppm or less.

[0062] When the concentration of the specific condensed ring compound is above the lower limit mentioned above, the effect of inhibiting copper dissolution is easily and fully exerted. When the concentration of the specific condensed ring compound is below the upper limit mentioned above, costs can be suppressed, and in addition, the precipitation of components exceeding the solubility can be prevented.

[0063] The electroless gold plating solution of the present invention may contain chelating agents. The function of the chelating agent is to prevent the precipitation of metals such as nickel, copper, palladium, iron, chromium, lead, and cobalt accumulated in the plating tank and to dissolve them stably during the operation of the electroless gold plating solution.

[0064] There are no particular limitations as long as the chelating agent is a chelating agent that is formulated with metals such as nickel, copper, palladium, iron, chromium, lead, and cobalt and is stably soluble in water. However, chelating agents with good chelating properties relative to metals such as nickel, copper, and palladium are preferred.

[0065] Preferred chelating agents include: chelating agents having an imine diacetic acid structure within the molecule, and chelating agents having a methylene phosphonic acid structure.

[0066] These chelating agents exhibit good chelating properties compared to nickel, copper, palladium, etc.

[0067] Examples of chelating agents having an intramolecular imine diacetic acid structure include: ethylenediaminetetraacetic acid, aziridine triacetic acid, hydroxyethyl ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, dicarboxymethylglutamic acid, propanediaminetetraacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, and other carboxylic acids or their salts.

[0068] Chelating agents having a methylene phosphonic acid structure include, for example, aminotrimethylene phosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylene phosphonic acid, diethylenetriaminepentamethylene phosphonic acid, hexamethylenediaminetetramethylene phosphonic acid, and other phosphonic acids or their salts.

[0069] Among the chelating agents mentioned above, from the viewpoint of chelating properties or cost, ethylenediaminetetraacetic acid, azirmonotriacetic acid, aminotrimethylenephosphonic acid, and ethylenediaminetetraacetic acid are particularly preferred.

[0070] Chelating agents can be used alone or in combination of two or more.

[0071] The concentration of the chelating agent in the electroless gold plating solution (the total concentration when two or more chelating agents are used together) is not particularly limited, but is preferably 0.5 g / L or more, particularly preferably 1 g / L or more, and especially preferably 2 g / L or more. Furthermore, it is preferably 30 g / L or less, particularly preferably 20 g / L or less, and especially preferably 10 g / L or less.

[0072] When the concentration of the chelating agent is above the lower limit mentioned above, it achieves a sufficient chelating effect and easily prevents abnormal precipitation of metal accumulated in the plating bath. When the concentration of the chelating agent is below the upper limit mentioned above, it is cost-effective and, in addition, prevents the precipitation of components exceeding the solubility.

[0073] The electroless gold plating solution of the present invention may further contain a buffer. The buffer has the function of stabilizing the pH of the electroless gold plating solution. As long as it has this function, the type of buffer is not particularly limited, whether it is an organic compound or an inorganic compound, and it can be appropriately adjusted with acid, alkali or salt for use.

[0074] Specific examples of buffers include: adipic acid, benzyl acid, citric acid, malic acid, succinic acid, formic acid, acetic acid, lactic acid, malonic acid, phthalic acid, oxalic acid, tartaric acid, glycine, glutamic acid, glutamate, iminodiacetic acid, dehydroacetic acid, maleic acid, fumaric acid, and other carboxylic acids or their salts; ethylenediamine, hydroxylamine, ethanolamine, diethanolamine, triethanolamine, and other amine compounds or their salts; and boric acid, phosphoric acid, pyrophosphate, phosphorous acid, thiosulfate, sulfurous acid, nitric acid, sulfuric acid, hydrochloric acid, thiocyanate, and other inorganic acids or their salts.

[0075] Preferred buffers include acids containing atoms with intermediate oxidation states, or salts thereof. Additionally, compounds with potentials intermediate between oxidizing and reducing agents can be listed.

[0076] Preferred buffers include: phosphorous acid or its salts, sulfurous acid or its salts, etc. Examples of salts of phosphorous acid or sulfurous acid include: lithium salts, sodium salts, potassium salts, magnesium salts, calcium salts, barium salts, ammonium salts, etc.

[0077] Based on the reason that insoluble salts are not easily formed in the plating solution, the most preferred buffers include sodium sulfite, potassium sulfite, and sodium phosphite.

[0078] Buffers can be used alone or in combination with two or more.

[0079] The concentration of the buffer in the electroless gold plating solution (the total concentration when two or more buffers are used together) is not particularly limited, but is preferably 1 g / L or more, more preferably 2 g / L or more, and especially preferably 3 g / L or more. Furthermore, it is preferably 300 g / L or less, more preferably 200 g / L or less, and especially preferably 100 g / L or less.

[0080] When the concentration of the buffer is above the lower limit mentioned above, it is easy to achieve a sufficient buffering effect. When the concentration of the buffer is below the upper limit mentioned above, it is cost-effective and can prevent the precipitation of components exceeding the solubility.

[0081] The electroless gold plating solution of the present invention mainly maintains pH stability through the aforementioned buffer. The ideal pH range is preferably 4 or higher, more preferably 4.5 or higher, and especially preferably 5 or higher. Furthermore, it is preferably 8 or lower, more preferably 7.5 or lower, and especially preferably 7 or lower.

[0082] When the pH is above the lower limit mentioned above, water-soluble gold salts can exist stably in the liquid. When the pH is below the upper limit mentioned above, the resist on the substrate is not easily eroded.

[0083] The electroless gold plating solution of the present invention can be a displacement-type electroless gold plating solution, a reduction-type electroless gold plating solution, or a displacement-reduction-type electroless gold plating solution.

[0084] When using a reduced-type electroless gold plating solution or a replacement reduced-type electroless gold plating solution, the reducing agents contained in the electroless gold plating solution of the present invention can be listed as follows: ascorbic acid, isoascorbic acid, glyoxylic acid, formic acid, thioglycolic acid, formamidinesulfinic acid, and aspartic acid. Organic acids such as tartaric acid and their salts; inorganic acids such as hypophosphoric acid and their salts; thioureas such as 1-allyl-2-thiourea, 1-allyl-3-(2-hydroxyethyl)-2-thiourea, 1,3-diethyl-2-thiourea, trimethylthiourea, 1,3-dimethylthiourea, 1-acetylthiourea, N-allylthiourea, ethylenethiourea, and N-methylthiourea; hydrazine derivatives such as thiosemicarbazide, hydrazine, p-hydrazinebenzenesulfonic acid, isonicotinamide hydrazine, and hydrazine sulfate; boron compounds such as dimethylaminoborane, trimethylaminoborane, sodium borohydride, potassium borohydride, diethylaminoborane, and triethylaminoborane; aldehydes such as formaldehyde and acetaldehyde; hydroxylamine; and hydroquinone.

[0085] From the viewpoint of the stability of the plating solution, ascorbic acid or its salts, or thiourea, are particularly preferred among the reducing agents mentioned above.

[0086] Reducing agents can be used alone or in combination with two or more.

[0087] The concentration of the reducing agent in the electroless gold plating solution (the total concentration when two or more reducing agents are used together) is not particularly limited, but is preferably 0.01 g / L or more, particularly preferably 0.05 g / L or more, and especially preferably 0.2 g / L or more. Furthermore, it is preferably 50 g / L or less, particularly preferably 20 g / L or less, and especially preferably 5 g / L or less.

[0088] When the concentration of the reducing agent is above the lower limit mentioned above, stable plating precipitation is obtained. When the concentration of the reducing agent is below the upper limit mentioned above, it is cost-effective, and the plating solution exhibits excellent stability.

[0089] The electroless gold plating solution of the present invention may further contain: a metal ion sequestering agent, a surfactant, a crystallization modifier, etc.

[0090] When impurity metals are mixed into the electroless gold plating solution, metal ion blocking agents can remove their influence.

[0091] Surfactants play a role in controlling the wetting properties of electroless gold plating solutions.

[0092] Crystallization modifiers have the function of controlling the crystal structure of the electroless gold plating film that has been deposited.

[0093] [Composition for preparing electroless gold plating solution]

[0094] The present invention also relates to a composition for preparing an electroless gold plating solution, which is used to prepare an electroless gold plating solution by adding water and water-soluble gold salt, the composition for preparing the electroless gold plating solution containing the aforementioned specific condensed ring compound.

[0095] Water-soluble gold salts, an essential component of the electroless gold plating solution of the present invention, are extremely expensive and are usually traded at market price. Furthermore, storing water-soluble gold salts in an aqueous solution is not economical, and storing them in an aqueous solution can reduce the performance of the plating solution.

[0096] Therefore, water-soluble gold salts are preferably stored separately in an undissolved state and added to an aqueous solution containing other ingredients (which may be all or part of the ingredients contained in the electroless gold plating solution) when the electroless gold plating solution is to be used.

[0097] The composition for preparing the electroless gold plating solution of the present invention contains the aforementioned specific condensed ring compound, and may contain the aforementioned chelating agent, buffer, metal ion blocking agent, surfactant, crystallization modifier, and reducing agent as required.

[0098] The form of the composition for preparing the electroless gold plating solution of the present invention is not limited, and it may be in powder or aqueous solution form.

[0099] In the case of an aqueous solution, the concentration of a specific condensed ring compound can be set to be higher than that of the specific condensed ring compound in the aforementioned electroless gold plating solution. When it is to be used as an electroless gold plating solution, water is added further (to dilute the concentration of the specific condensed ring compound).

[0100] The electroless gold plating solution of the present invention can be prepared by adding water-soluble gold salt, or water-soluble gold salt and water, to the composition for preparing the electroless gold plating solution of the present invention.

[0101] The composition for preparing the electroless gold plating solution of the present invention can be a composition that does not contain all or part of other components of the electroless gold plating solution (chelating agents, buffers, metal ion blocking agents, surfactants, crystallization modifiers, reducing agents, etc.). In other words, these components, like water-soluble gold salts or water, can be added separately to the composition for preparing the electroless gold plating solution when preparing the electroless gold plating solution.

[0102] [Method for manufacturing electroless gold plating coating]

[0103] The present invention also relates to a method for manufacturing an electroless gold plating film, which uses the aforementioned electroless gold plating solution to manufacture the electroless gold plating film.

[0104] The process for applying the method of manufacturing the electroless gold plating film of the present invention is not particularly limited, and can be applied to processes such as the following: a process of forming an electroless gold plating film on top of an electroless nickel film formed on a copper raw material (ENIG); a process of forming an electroless palladium film on top of an electroless nickel film formed on a copper raw material, and further forming an electroless gold plating film on top of it (ENEPIG); a process of forming a displacement gold plating film on top of an electroless nickel film formed on a copper raw material, and further forming a reduction gold plating film on top of it (ENEAG), etc.

[0105] According to the method for manufacturing the electroless gold plating film of the present invention, even if there are a few exposed copper portions due to undeposited nickel film or poor dry film formation, the dissolution of copper from these exposed portions can be suppressed. Therefore, in the method for manufacturing the electroless gold plating film of the present invention, problems caused by copper accumulation in the electroless gold plating solution are less likely to occur, and the number of times the electroless gold plating solution needs to be replaced can be reduced, thereby improving production efficiency.

[0106] When forming the electroless gold plating film according to the manufacturing method of the present invention, the thickness of the electroless gold plating film (the thickness measured by the method described in the following embodiments) is not particularly limited, but is preferably 0.005 μm or more, more preferably 0.01 μm or more, and especially preferably 0.02 μm or more. Furthermore, it is preferably 1 μm or less, more preferably 0.7 μm or less, and especially preferably 0.5 μm or less.

[0107] Above the aforementioned lower limit, the performance as a coating can be fully utilized. Furthermore, below the aforementioned upper limit, it is cost-effective.

[0108] As a side note, the term "coating" is not limited to a uniformly flat membrane; membranes with pores or granular portions are also called "coatings." The term "coating" is synonymous with "layer."

[0109] The temperature of the electroless gold plating solution used in the manufacturing method of electroless gold plating film is preferably 10°C or higher, more preferably 15°C or higher, and especially preferably 20°C or higher. Furthermore, it is preferably 100°C or lower, more preferably 95°C or lower, and especially preferably 90°C or lower.

[0110] Furthermore, the time (plating time) for forming the electroless gold plating film using the manufacturing method of electroless gold plating film is preferably 0.5 minutes or more, more preferably 1 minute or more, and especially preferably 2 minutes or more. It is also preferably 240 minutes or less, more preferably 120 minutes or less, and especially preferably 60 minutes or less.

[0111] When the temperature or plating time of the electroless gold plating solution is within the above-mentioned range, it is easy to form a film thickness within the aforementioned range.

[0112] Manufacturing methods for electronic components

[0113] The present invention also relates to a method for manufacturing an electronic component having an electroless gold plating film manufactured by the aforementioned method for manufacturing an electroless gold plating film.

[0114] Furthermore, the present invention also relates to a method for manufacturing an electronic component, comprising the following steps: forming an electroless gold plating film using the aforementioned electroless gold plating solution.

[0115] [Example]

[0116] The present invention is illustrated in more detail by providing examples and comparative examples, but the present invention is not limited to these examples without departing from its spirit.

[0117] As a side note, "ppm" means "mass ppm" unless otherwise specified.

[0118] [Preparation of Electroless Gold Plating Solution]

[0119] Examples 1 to 18, Comparative Examples 1 to 6

[0120] In a base solution A prepared by dissolving each component in ion-exchanged water at the concentrations shown below, the nitrogen-containing condensed ring compounds or comparative compounds shown in Table 1 were dissolved at a concentration of 10 ppm relative to the overall electroless plating solution, and the pH was adjusted to 6.5 to prepare the electroless gold plating solutions of Examples 1 to 18 and Comparative Examples 1 to 6. Note that when adjusting the pH, an aqueous solution of sodium hydroxide is used to increase the pH, and sulfuric acid is used to decrease the pH.

[0121] <Base Fluid A>

[0122] Potassium gold(I) cyanide 2g / L

[0123] Potassium citrate 30g / L

[0124] Examples 19 to 20

[0125] In a base solution B prepared by dissolving each component in ion-exchanged water at the concentrations shown below, the nitrogen-containing condensed ring compounds shown in Table 1 were dissolved at a concentration of 10 ppm relative to the overall electroless plating solution, and the pH was adjusted to 6.5 to prepare the electroless gold plating solutions of Examples 19 and 20. Note that when adjusting the pH, an aqueous solution of sodium hydroxide is used to increase the pH, and sulfuric acid is used to decrease the pH.

[0126] <Base Fluid B>

[0127]

[0128] Examples 21 to 22

[0129] In a base solution C prepared by dissolving each component in ion-exchanged water at the concentrations shown below, the nitrogen-containing condensed ring compounds shown in Table 1 were dissolved at a concentration of 10 ppm relative to the overall electroless plating solution, and the pH was adjusted to 6.5 to prepare the electroless gold plating solutions of Examples 21 and 22. Note that when adjusting the pH, an aqueous solution of sodium hydroxide was used to increase the pH, and sulfuric acid was used to decrease the pH. The electroless gold plating solutions using base solution C are reduced electroless plating solutions.

[0130] <Base Fluid C>

[0131] Potassium gold(I) cyanide 2g / L

[0132] Potassium citrate 30g / L

[0133] Sodium ascorbate 2g / L

[0134] [Table 1]

[0135]

[0136] [Assessment of Copper Leaching]

[0137] The electroless gold plating solutions prepared in each embodiment and comparative example were heated to 85°C. After immersing three 2.0cm×2.5cm copper plates in 100mL of the electroless gold plating solution, the electroless gold plating solution was cooled to room temperature.

[0138] Note that the copper plates used should be treated as shown in Table 2 before being immersed in the electroless gold plating solution.

[0139] [Table 2]

[0140]

[0141] The electroless gold plating solution, prepared at room temperature, was accurately measured to 100 mL in a volumetric flask and homogenized by stirring. The copper concentration was then quantified and the amount of copper leaching was assessed using an ICPS-7510 plasma optical emission spectrophotometer (manufactured by Shimadzu Corporation). The results are presented in Table 1.

[0142] [Fabrication of Coated Laminates]

[0143] Copper foil was attached to a glass cloth epoxy material (FR-4), and an opening with a diameter of φ0.5mm was created using solder resist. The resulting substrate (40mm × 40mm × 1mm) was used as the substrate to be plated, and the plating laminate was fabricated according to the steps in Table 3. In the electroless gold plating, the electroless gold plating solution prepared in each embodiment was used.

[0144] [Table 3]

[0145]

[0146]

[0147] [Determination of gold plating film thickness]

[0148] The thickness of the gold plating in the fabricated plating stack was determined using a fluorescence X-ray spectrophotometer (FT-150, Hitachi High-Tech Science, Inc.). The results are presented in Table 1.

[0149] [Evaluation of the appearance of the gold plating]

[0150] The plating openings of the fabricated plating laminate were observed using an optical microscope at 10x magnification. A uniform, golden color was considered "normal," while an orange or brown color, or an uneven color, was considered "defective." The results are presented in Table 1.

[0151] The electroless gold plating solution of the present invention, containing a specific condensation ring compound, exhibits almost no copper leaching and can form a high-quality gold plating layer.

[0152] [Industry applicability]

[0153] Since the electroless gold plating solution of the present invention contains a specific condensation ring compound, it is not easy to produce copper leaching from copper raw materials when forming a gold plating film on a substrate such as a nickel film. Therefore, it can be widely used to form gold plating films for the connection terminals of electronic components.

Claims

1. A method for suppressing the leaching of copper from a displacement-type electroless gold plating solution, comprising suppressing the leaching of copper from the displacement-type electroless gold plating solution when forming a displacement-type electroless gold plating film on a copper raw material using a displacement-type electroless gold plating solution, wherein, An electroless gold plating film is formed using an electroless gold plating solution containing: a water-soluble gold salt and a condensed ring compound having a nitrogen atom in the ring.

2. The method according to claim 1, wherein, The condensed ring compound is a condensed ring compound formed by the condensation of a benzene ring or a pyridine ring with a hetero pentagonal ring containing a nitrogen atom.

3. The method according to claim 1 or 2, wherein, The condensed ring compound is a condensed ring compound having two or more atoms other than carbon in the ring.

4. The method according to claim 1 or 2, wherein, The condensed ring compound is a condensed ring compound having one or more substituents selected from the group consisting of alkyl, mercapto, hydroxyl, carboxyl, nitro and halogen groups having 1 to 6 carbon atoms.

5. The method according to claim 1 or 2, wherein the displacement-type electroless gold plating solution further contains a chelating agent.

6. The method according to claim 5, wherein, The chelating agent contains one or more chelating agents selected from the group consisting of chelating agents having an imine diacetic acid structure within the molecule and chelating agents having a methylene phosphonic acid structure.

7. The method according to claim 1 or 2, wherein the displacement-type electroless gold plating solution further contains a buffer.

8. The method according to claim 7, wherein, The buffer contains one or more compounds selected from the group consisting of sulfurous acid, phosphorous acid, and their salts.

9. A composition for preparing a substitution-type electroless gold plating solution, used to prepare a substitution-type electroless gold plating solution for use in any one of claims 1 to 8 by adding water and a water-soluble gold salt, the composition for preparing the substitution-type electroless gold plating solution containing a condensed ring compound as described in any one of claims 1 to 8.

10. The composition for preparing the substitution-type electroless gold plating solution according to claim 9, wherein it is in powder form.

11. A method for manufacturing a displacement-type electroless gold plating film, wherein the displacement-type electroless gold plating film is manufactured by using the method described in any one of claims 1 to 8.

12. A method for manufacturing an electronic component, wherein, The electronic component has a displacement-type electroless gold plating film manufactured by the manufacturing method of the displacement-type electroless gold plating film as described in claim 11.

13. A method for manufacturing an electronic component, comprising the following steps: forming a displacement-type electroless gold plating film by using the method of any one of claims 1 to 8.

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