US20140054175A1

US20140054175A1 - Acidic aqueous composition for semiglossy tin plating and member having semiglossy tin plating film

Info

Publication number: US20140054175A1
Application number: US13/781,108
Authority: US
Inventors: Yoshinori Kusunoki; Shinya Akamatsu
Original assignee: Yuken Industry Co Ltd
Current assignee: Yuken Industry Co Ltd
Priority date: 2012-08-24
Filing date: 2013-02-28
Publication date: 2014-02-27
Also published as: JP2014040650A; CN103628099A

Abstract

An acidic aqueous composition for semiglossy tin electroplating has a water-soluble tin (II)-containing substance and a surfactant. The surfactant includes a surfactant (A) comprising N,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane. The surfactant (A) the number of carbon atoms of the alkyl group that bonds to N ranges from 14 to 18. The weight-average molecular weight of the surfactant (A) ranges from 300 to 1500.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an acidic aqueous composition for tin electroplating.
In the present disclosure, the term “tin plating” denotes electroplating which can form a film consisting of tin and impurities.
2. Description of the Related Art
Tin plating films are widely used in contact sections and solder connections in electric and electronic components such as semiconductor chip components, crystal oscillators, capacitors, connector pins, lead frames, printed circuit boards and the like. Tin plating films include films having gloss, films lacking gloss, and semiglossy films that lie in between. In the present disclosure, the term “semigloss” denotes glossiness G_s(60°) ranging from 10 to less than 200 (specifically, as measured using a measurement device IG-331 by Horiba Ltd., likewise hereafter), at an incidence angle of 60°, according to JIS 28741: 1997 (ISO 2813: 1994). In the present disclosure, a glossiness G_s(60°) ranging from 20 to less than 150 corresponds to instances of good semi-gloss, and a glossiness G_s(60°) ranging from 30 to less than 100 corresponds to instances of particularly good semi-gloss.
Patent Document 1 discloses a tin or tin-alloy electroplating solution that contains (1) a reaction product obtained by reacting glutaraldehyde and at least one compound selected from hydrocarbon compounds containing a hydroxyl group, in the presence of an acid, and (2) at least one compound selected from amine compounds, and describes an example wherein a tin plating film obtained through electroplating for 90 minutes at 0.1 A/dm², using such a plating solution (liquid temperature: 20° C.), has a semiglossy appearance.
Patent Document 2 discloses a tin plating solution that contains a stannous salt, a compound such as gluconic acid or the like, and a surfactant, and describes an example wherein a tin plating film obtained through electroplating for 5 minutes to 20 minutes at 1 A/dm²to 4 A/dm², using such a plating solution (liquid temperature: 30° C. to 55° C.), has a semiglossy appearance.

Patent Document 1: Japanese Patent Application Publication No. 2008-266757A
Patent Document 2: Japanese Patent Application Publication No. S57-63689A

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provides an acidic aqueous composition for semiglossy tin plating that allows forming, with excellent productivity, a semiglossy tin plating film of stable quality.
One or more embodiments of the present invention provides a member that has a semiglossy tin plating film formed out of the abovementioned acidic aqueous composition for semiglossy tin plating.
Embodiments of the present invention include the following.
(1) An acidic aqueous composition for semiglossy tin electroplating, which contains a water-soluble tin (II)-containing substance and a surfactant,
wherein said surfactant includes a surfactant (A) comprising N,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane.
(2) The acidic aqueous composition for semiglossy tin electroplating according to (1), wherein in the surfactant (A) the number of carbon atoms of the alkyl group that bonds to N ranges from 14 to 18.
(3) The acidic aqueous composition for semiglossy tin electroplating according to (1), wherein the weight-average molecular weight of the surfactant (A) ranges from 300 to 1500.
(4) The acidic aqueous composition for semiglossy tin electroplating according to (1), wherein the content of the water-soluble tin (II)-containing substance in tin content equivalent ranges from 5 g/L to 200 g/L and the content of the surfactant (A) ranges from 0.5 g/L to 40 g/L.
(5) The acidic aqueous composition for semiglossy tin electroplating according to (1), further containing an organic sulfonic acid compound.
(6) The acidic aqueous composition for semiglossy tin electroplating according to (5), wherein the content of the organic sulfonic acid compound in organic sulfonic acid content equivalent ranges from 50 g/L to 300 g/L.
(7) A member, comprising: a member to be plated; and a semiglossy tin plating film that is formed on at least part of the surface of the member to be plated, by electroplating of the acidic aqueous composition for semiglossy tin electroplating according to any one of (1) to (6).
(8) The member according to (7), wherein the semiglossy tin plating film in the member is electroplated under a condition of current density of 5 A/dm²or higher.
(9) The member according to (7), wherein the semiglossy tin plating film of the member has a ratio of 8 or less of glossiness G_s(60°) measured in accordance with JIS 28741: 1997 (ISO 2813: 1994) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to the glossiness G_s(60°) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm².
(10) The member according to (7), wherein the semiglossy tin plating film in the plating member has a ratio of 1.3 or less of arithmetical mean roughness Ra measured according to JIS B0601:2001 (ISO 4287:1997) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to the arithmetical mean roughness Ra of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm².
(11) The member according to (7), wherein the semiglossy tin plating film in the plating member has a ratio of 1.5 or less of root mean square roughness Rq measured according to JIS B0601:2001 (ISO 4287:1997) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to the root mean square roughness Rq of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm².
(12) The member according to (7), wherein the semiglossy tin plating film in the member has a thickness ranging from 1 μm to 5 μm.
(13) The member according to (7), wherein the semiglossy tin plating film in the member is formed by electroplating with a current density ranging from 5 A/dm²to 15 A/dm², and a ratio (before/after) of a value of zero crossing time (unit: seconds) of the member as measured in a solderability test by a balance method according to JIS C60068-2-54: 2009 (IEC60068-2-54: 2006) after an environment test of standing for 8 hours in an environment at 105° C. and relative humidity of 100%, with respect to the value measured before the environment test, is 2.1 or less.
(14) The member according to (7), wherein the member to be plated is an electronic component.
(15) The member according to (14), wherein the electronic component includes one or more selected from the group consisting of resistors, variable resistors, capacitors, filters, inductors, thermistors, crystal oscillators, switches, connectors, lead wires, printed circuit boards, and semiconductor integrated circuits and modules.
The acidic aqueous composition for semiglossy tin plating according to one or more of the above-described embodiments allows forming a semiglossy tin plating film of stable quality with excellent productivity. The member having a semiglossy tin plating film formed using such an acidic aqueous composition for semiglossy tin plating exhibits excellent homogeneity in surface properties such as semiglossy appearance, solder wettability and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating plating deposition states of tin plating films obtained by electroplating at dissimilar current densities, using a plating solution 1 obtained in an example;

FIG. 2 is a diagram illustrating a plating deposition state of a tin plating film obtained by electroplating at dissimilar current densities, using a plating solution 2 obtained in an example;

FIG. 3 is a diagram illustrating a plating deposition state of a tin plating film obtained by electroplating at dissimilar current densities, using a plating solution 3 obtained in an example;

FIG. 4 is a diagram illustrating a plating deposition state of a tin plating film obtained by electroplating at dissimilar current densities, using a plating solution 4 obtained in an example;

FIG. 5 is a diagram illustrating a plating deposition state of a tin plating film obtained by electroplating at dissimilar current densities, using a plating solution 5 obtained in an example;

FIG. 6 is a diagram illustrating a plating deposition state of a tin plating film obtained by electroplating at dissimilar current densities, using a plating solution 6 obtained in an example;

FIG. 7 is a diagram illustrating a plating deposition state of a tin plating film obtained by electroplating at dissimilar current densities, using a plating solution 7 obtained in an example; and

FIG. 8 is a diagram illustrating a plating deposition state of a tin plating film obtained by electroplating at dissimilar current densities, using a plating solution 8 obtained in an example.

DETAILED DESCRIPTION

In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention.
1. Acidic Aqueous Composition for Tin Plating
One or more embodiments of the present invention provides an acidic aqueous composition for semiglossy tin electroplating that contains a water-soluble tin (II)-containing substance and a surfactant, wherein the surfactant contains N,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane. A tin plating film having a semiglossy appearance can be obtained, even under conditions of current density of 5 A/dm²or higher, when using such a composition. Therefore, the plating rate can be increased, and productivity enhanced, as compared with instances of semiglossy tin plating according to conventional techniques. When such a composition is used, surface characteristics such as appearance of the tin plating film, solder wettability and so forth do not readily fluctuate for a current density lying within a wide range, from 5 A/dm²to 15 A/dm². Therefore, the obtained tin plating film has excellent homogeneity in surface properties, even in cases where current density is likely to exhibit variability, for instance in cases of barrel plating, or when the surface that is to be plated in the member to be plated is a rugged surface.
(1) Water-Soluble Tin (II)-Containing Substance
The acidic aqueous composition for tin plating according to one or more embodiments of the present invention (hereafter also referred to as “plating solution”) contains a water-soluble tin (II)-containing substance. The “water-soluble tin (II)-containing substance” denotes a substance that comprises one, two or more substances selected from the group consisting of divalent tin cations (Sn²⁺) and water-soluble substances that contain divalent tin cations.
Examples of starting-material substances (also referred to as “tin (II) sources”) that provide a water-soluble tin (II)-containing substance to a plating solution include inorganic stannous acid salts such as stannous sulfate, stannous chloride, and stannous fluoroborate; stannous alkanol sulfonates such as stannous isethionate; stannous alkane sulfonates such as stannous methanesulfonate and stannous ethanesulfonate; aromatic stannous sulfonates such as stannous phenolsulfonate and stannous cresolsulfonate; and stannous carboxylates such as stannous citrate and stannous acetate. The foregoing may be used singly or in combinations of a plurality of types.
According to one or more embodiments of the present invention, the content of the water-soluble tin (II)-containing substance in tin content equivalent in the plating solution ranges from 5 g/L to 200 g/L, and according to one or more embodiments of the present invention, ranges from 30 g/L to 100 g/L. If the content of the water-soluble tin (II)-containing substance is excessively low, tin plating may not be deposited. On the other hand, if the content of the water-soluble tin (II)-containing substance is excessively high, the plating throwing power may drop on account of the increased viscosity of the plating solution. If the blending amount of the tin (II) source is excessively high, the plating solution comprises then both the water-soluble tin (II)-containing substance, in a dissolved state in the plating solution, and the tin (II) source in a solid state in the plating solution. In that case, the content of water-soluble tin (II)-containing substance in the plating solution depends on the solubility of the tin (II) source.
(2) Surfactant
The plating solution according to one or more embodiments of the present invention contains a surfactant. The surfactant comprises an N,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane. In the present disclosure, this surfactant is referred to as “surfactant (A)”. According to one or more embodiments of the present invention, the alkyl group that bonds to N in the surfactant (A) has 14 carbon atoms to 18 carbon atoms.
According to one or more embodiments of the present invention, the weight-average molecular weight of the surfactant (A) ranges from 300 to 1500, and according to one or more embodiments of the present invention, ranges from 500 to 1300, and according to one or more embodiments of the present invention, ranges from 900 to 1000, in terms of preventing the cloud point of the surfactant (A) from dropping down to the plating temperature range and in terms of using a surfactant (A) that has good defoamability. According to one or more embodiments of the present invention, the number of consecutive oxyethylene groups in the polyoxyethylene moiety of the surfactant (A) is 3 or more, from the viewpoint of stably bringing out the functionality of the surfactant, and according to one or more embodiments of the present invention, is 30 or less, from the viewpoint of using a surfactant (A) that has good defoamability.
Through the use of the surfactant (A), the plating solution according to one or more embodiments of the present invention allows obtaining a semiglossy tin plating film having the below-described superior characteristics. From the viewpoint of stably eliciting such an effect, according to one or more embodiments of the present invention, the content of the surfactant (A) ranges from 0.5 g/L to 40 g/L, and according to one or more embodiments of the present invention, from 1 g/L to 20 g/L and according to one or more embodiments of the present invention, from 2 g/L to 10 g/L.
The plating solution according to one or more embodiments of the present invention may contain surfactants other than the surfactant (A). In terms of obtaining more stably the abovementioned semiglossy tin plating film having excellent characteristics, however, according to one or more embodiments of the present invention, the plating solution contains no other surfactant. If other surfactants are used, according to one or more embodiments of the present invention, the total content thereof is smaller than the content of the surfactant (A), and according to one or more embodiments of the present invention, ¼ or less of the content of the surfactant (A), and according to one or more embodiments of the present invention, 1/10 or less of the content of the surfactant (A).
(3) Electrolyte Component
In addition to the abovementioned components, the plating solution according to one or more embodiments of the present invention contains a component (hereafter also referred to as “electrolyte component”) for increasing the electroconductivity of the plating solution. The type of the electrolyte component is not particularly limited. Examples thereof include acids inorganic acids such as sulfuric acid, hydrochloric acid, boric acid, and fluoroboric acid; organic sulfonic acids such as alkanol sulfonic acids, e.g., isethionic acid, alkane sulfonic acids, e.g., methanesulfonic acid, and aromatic sulfonic acids, e.g., phenolsulfonic acid; and carboxylic acids such as acetic acid, citric acid, malic acid, tartaric acid or the like, as well as ammonium salts, sodium salts, potassium salts or the like of the foregoing acids. The above acids and salts may be used singly or in combinations of a plurality to types thereof. According to one or more embodiments of the present invention, among the foregoing are organic sulfonic acids and/or salts of organic sulfonic acids.
The content of the electrolyte component is not limited, but is to be appropriately set on the basis of, for instance, the current density during plating. In an example of the content range, the free-acid equivalent content ranges from 50 g/L to 300 g/L.
(4) Other Components
The plating solution according to one or more embodiments of the present invention may contain, for instance, a known brightening agent, brightening auxiliary agent, antioxidant, defoaming agent and the like. In a case where the plating solution contains a brightening agent and a brightening auxiliary agent, the content of the foregoing components should remain within a range such that the appearance of the tin plating film obtained from the plating solution according to one or more embodiments of the present invention is not glossy but remains semiglossy. The brightening agent and the brightening auxiliary agent decompose and/or polymerize on account of the acid contained in the plating solution, and/or due to electrolysis for electroplating. As a result, the content of the above-mentioned components decreases as the total time of the plating process increases. Moreover, byproducts of such decomposition and/or polymerization accumulate in the plating solution, and, as a result, the stability of the plating solution decreases, and plating defects are brought about through adhesion of such byproducts to the member to be plated. According to one or more embodiments of the present invention, therefore, the plating solution contains substantially no brightening agent or brightening auxiliary agent.
An antioxidant that the plating solution according to one or more embodiments of the present invention may contain, as the case may require, is an antioxidant for suppressing oxidation of tin (II) ions in the plating solution according to one or more embodiments of the present invention. Examples of such antioxidants include catechol, hydroquinone and the like. The content of the antioxidant is not limited, but in an example, ranges from 0.05 g/L to 20 g/L, and according to one or more embodiments of the present invention, from 0.1 g/L to 15 g/L. Examples of the defoaming agent include organic defoaming agent such as polyoxyethylene-polyoxypropylene block polymers, higher aliphatic alcohols, acetylene alcohols, polyalkoxylates and the like, as well as silicone-based defoaming agents.
(5) Solvent and pH
The solvent of the plating solution according to one or more embodiments of the present invention has water as a main component. Examples of solvents other than water that may be mixed in include organic solvents having high solubility in water such as alcohols, ethers, and ketones. In such a case, the ratio of the organic solvent, according to one or more embodiments of the present invention, is no greater than 10 vol % with respect to the entire solvent, from the viewpoint of high stability of the entire plating solution and of easing the waste treatment load.
The plating solution according to one or more embodiments of the present invention is acidic. In a form according to one or more embodiments of the present invention, the solution is strongly acidic, and the pH thereof is ordinarily 1 or less. When incorporating the above-described electrolyte component, the plating solution can be set to a desired pH through adjustment of the amount of acid that is added.
2. Plating Condition
The plating conditions of the plating solution are not particularly limited. Instances of the various conditions are set out below.
(1) Current Density
The current density of the plating solution according to one or more embodiments of the present invention can be set to 5 A/dm²or higher. Plating abnormal deposition occurs, and glossiness decreases dramatically in affected portions, when the current density is set to 5 A/dm²or higher in conventional semiglossy tin plating solutions. In the plating solution according to one or more embodiments of the present invention, by contrast, the appearance of the obtained plating film can be rendered semiglossy even if the current density is set to 5 A/dm²or higher, and there can be obtained a tin plating film having a particularly good semiglossy appearance (glossiness) G_s(60°) smaller than 100) even with a current density of 15 A/dm². That is, the plating solution according to one or more embodiments of the present invention allows increasing current density beyond that in conventional plating solutions, and allows increasing, in proportion, the deposition rate of the plating film. Therefore, the plating solution according to one or more embodiments of the present invention allows enhancing the productivity of plating film formation beyond that of a conventional plating solution.
In a specific example, there can be achieved a ratio of or less for the ratio of glossiness G_s(60°), measured in accordance with JIS 28741: 1997 (ISO 2813: 1994), of the semiglossy tin plating film obtained using the plating solution according to one or more embodiments of the present invention in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to the ratio of the glossiness G_s(60°) in a semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm². In a case where an amine-based surfactant, for instance polyoxyethylene polyoxypropylene tallow amine is used instead of the surfactant (A) contained in the plating solution according to one or more embodiments of the present invention, a plating film can be obtained that has semiglossiy appearance (glossiness G_s(60°) equal to or greater than 150) close to the gloss of a glossy film, at a low current density (5 A/dm²), while at a high current density (15 A/dm²) there is obtained plating film having matte appearance. A plating film having good semiglossy appearance cannot thus be obtained for a wide current density range of 5 A/dm²to 15 A/dm², as is the case in the plating solution according to one or more embodiments of the present invention.
The plating solution according to one or more embodiments of the present invention that allows obtaining a plating film of semiglossy appearance within this wide current density range elicits the following advantageous effects.
Firstly, the obtained tin plating film has excellent homogeneity in surface properties, even in cases where current density exhibits readily variability within one batch. Specific examples of such instances include, for instance, cases where multiple members to be plated are plated by barrel plating, or cases where the surface to be plated of the member to be plated is a rugged surface.
Secondly, the obtained tin plating film has excellent homogeneity in surface properties, even in cases where current density exhibits readily variability between batches. Specific examples of such instances include, for instance, a case where the shapes and/or total count of the members to be plated that are fed to barrel plating fluctuate between batches.
(2) Plating Temperature
The plating temperature is not particularly limited. Ordinarily, the plating temperature ranges from 20° C. to 60° C. According to one or more embodiments of the present invention, the control range of the plating temperature is set to about 5° C., since temperature fluctuations may result in changes in plating appearance.
(3) Cumulative Current Amount
The cumulative current amount is not particularly limited. If the cumulative current amount is excessively small, a concern arises in that the base metal, which comprises nickel or the like, may fail to be sufficiently covered and in that solder wettability may fail to be enhanced. On the other hand, an excessively large cumulative current amount is disadvantageous in economic terms. The range of cumulative current amount is to be appropriately set with the above considerations in mind.
3. Member Having a Tin Plating Film
A member (hereafter also referred to as “tin plating member”) in which a semiglossy tin plating film is formed on at least part of the surface of a member to be plated can be produced by performing electroplating in a state where the member to be plated is in contact with the plating solution according to one or more embodiments of the present invention.
The type of the member to be plated is not particularly limited, so long as at least part of the surface thereof has conductivity. Examples of such members include electronic components. Specific examples of electronic components include resistors, variable resistors, capacitors, filters, inductors, thermistors, crystal oscillators, switches, connectors, lead wires, printed circuit boards, and semiconductor integrated circuits and modules. In a case where the member to be plated is an electronic component, the electronic component may include one, two or more types selected from the group consisting of these electronic components.
The thickness of the plating film on the member to be plated is not particularly limited, but according to one or more embodiments of the present invention, ranges from 1 μm to 5 μm. If the thickness in the plating film is excessively small, there increases the likelihood of occurrence of portions at which the plating film fails locally to form properly. On the other hand, an excessively large thickness of the plating film is not only disadvantageous in economic terms, but results also in an increased likelihood of detachment of the plating film off the member to be plated.
In the semiglossy tin plating film of the plating member according to one or more embodiments of the present invention, a ratio of 8 or less can be achieved for the ratio of glossiness G_s(60°) measured in accordance with JIS 28741: 1997 (ISO 2813: 1994) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm²with respect to the ratio of the glossiness G_s(60°) of the film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm². If the above ratio is 8 or less, the glossiness G_s(60°) of the semiglossy tin plating film in the plating member according to one or more embodiments of the present invention is not readily affected by fluctuations in the plating conditions, in particular fluctuations in current density. Accordingly, appearance is highly homogeneous, and quality exhibits likewise high homogeneity, as described below. According to one or more embodiments of the present invention, the ratio is 6 or less, and according to one or more embodiments of the present invention, 4 or less, and according to one or more embodiments of the present invention, 2 or less.
An overview of the glossiness measurement method according to the abovementioned standard (JIS 28741: 1997 (ISO 2813: 1994)) follows next.
A light beam of a prescribed aperture angle is caused to strike a sample surface at a prescribed incidence angle. A light beam of prescribed aperture angle that is reflected in the specular reflection direction is measured using a photoreceiver.
The incidence optical system is made up of a light source, a first aperture, a first convex lens disposed between the light source and the first aperture, and a second convex lens disposed between the first aperture and the sample. The first aperture is positioned at the focal point of the second convex lens. The first aperture and the first lens may be omitted in a case where a light source filament is disposed at the position of the first aperture. The acceptance optical system is made up of a third convex lens, a second aperture and a photoreceiver, in this order from the sample.
The optical systems are disposed in such a manner that when a mirror surface is positioned at the position of the sample, the image at the first aperture forms a sharp image at the center of the second aperture. The optical axes of the incidence and acceptance sides intersect at the sample plane.
The incidence angle θ is the angle formed by the normal to the sample and a line that joins the center of the first aperture and the center of the second convex lens (principal point of a lens). The acceptance angle is set to incidence angle θ±0.1° in a case where the incidence angle θ is set to 60°±0.2°. The aperture angles of the light source image (angle at which the image of the first aperture spreads at the position of the third lens) include an angle α₁′ of 0.75°±0.10° in the incidence plane and an angle β₁′ of 2.5°±0.1° in the vertical plane. The aperture angles of the photoreceiver (angle at which the third lens spreads at the position of the third lens) include an angle α₂of 4.4°±0.1° in the incidence plane and an angle β₂of 11.7°±0.2° in the vertical plane.
A non-polarizing light source is used as the light source. The light source and photoreceiver that are ordinarily used correspond to a combination of standard light (standard illuminant) D₆₅and spectral luminous efficiency V (λ) (color-matching function y (λ) in the XYZ color system). The readings of the instrument used to measure the reflected light beam must be proportional within a range of 1% of the maximum scale value of the light beam that strikes the photoreceiver. The width of the area of the sample irradiated by the light source, in the direction perpendicular to the incidence plane, must ordinarily be 10 mm or greater.
The mirror-surface glossiness at the prescribed incidence angle 0 at a glass surface having a constant value of refractive index of 1.567, over the entire visible wavelength range, is taken as a reference value of 100% with respect to which other values are expressed. The specular reflectivity ρ₀(60°) is 0.1001 in a case where the incidence angle θ is 60°.
The description of the measurement results include the value of the mirror-surface glossiness and the device used for measurement.
Observation of the surface of the tin plating member according to one or more embodiments of the present invention reveals that the grain size distribution of plating metal, as observed in surface sections, varies little for a current density ranging from 5 A/dm²to 15 A/dm²during electroplating. In conventional tin plating solutions, it is observed that the metal crystal that makes up the plating film formed out of the plating solution tends to become coarser when current density increases. In the plating solution according to one or more embodiments of the present invention, however, the crystalline state of the metal that constitutes the plating film formed out of the plating solution is not readily influenced by fluctuations in current density.
In the semiglossy tin plating film of the plating member according to one or more embodiments of the present invention, accordingly, fluctuations of the following parameters relating to peak heights and valley depths of the roughness-profile do not readily exhibit in-plane fluctuation upon measurement of the surface roughness of the surface made up of the film.
(i) arithmetical mean roughness Ra in JIS B0601:2001 (corresponding standard: ISO 4287:1997)
(ii) maximum height Rz in JIS B0601:2001 (corresponding standard:ISO 4287:1997)
(iii) maximum height Rz_JISin JIS B0601:2001 (corresponding standard: ISO 4287:1997)
(iv) root mean square roughness Rq in JIS B0601:2001 (corresponding standard: ISO 4287:1997)
As regards the relationship between current density in the plating process time and surface roughness of the semiglossy tin plating film in the plating member according to one or more embodiments of the present invention, the semiglossy tin plating film has a ratio of 1.4 or less of Ra (units: μm) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to the Ra (units: μm) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm². If the above ratio is 1.4 or less, the surface roughness of the semiglossy tin plating film in the plating member according to one or more embodiments of the present invention is not readily affected by fluctuations in the plating conditions, in particular fluctuations in current density. Accordingly, appearance is highly homogeneous, and quality exhibits likewise high homogeneity, as described below. According to one or more embodiments of the present invention, the above ratio is 1.3 or less.
According to one or more embodiments of the present invention, the semiglossy tin plating film in the plating member has a ratio of 1.5 or less of Rq (units: μm) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to the Rq (units: μm) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm². If the above ratio is 1.5 or less, the surface roughness of the semiglossy tin plating film in the plating member according to one or more embodiments of the present invention is not readily affected by fluctuations in the plating conditions, in particular fluctuations in current density. Accordingly, appearance is highly homogeneous, and quality exhibits likewise high homogeneity, as described below. According to one or more embodiments of the present invention, the above ratio is 1.3 or less.
According to one or more embodiments of the present invention, the semiglossy tin plating film in the plating member has a ratio of 1.3 or less of Ry (units: μm) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to the Ry (units: μm) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm². If the above ratio is 1.3 or less, the surface roughness of the semiglossy tin plating film in the plating member according to one or more embodiments of the present invention is not readily affected by fluctuations in the plating conditions, in particular fluctuations in current density. Accordingly, appearance is highly homogeneous, and quality exhibits likewise high homogeneity, as described below. According to one or more embodiments of the present invention, the above ratio is 1.2 or less, and according to one or more embodiments of the present invention, 1.1 or less.
As described above, the glossiness G_s(60°) does not vary easily with current density, and hence surface properties, such as solder wettability, are not readily influenced by current density. In the tin plating member according to one or more embodiments of the present invention, the ratio (before/after) of zero crossing time (units: seconds) before and after a high-temperature high-humidity environment test may be of 2.1 or less for a current density during electroplating that ranges from 5 A/dm²to 15 A/dm². The above ratio, according to one or more embodiments of the present invention, is 1.9 or less, and according to one or more embodiments of the present invention, is 1.7 or less, for a current density during electroplating that ranges from 5 A/dm²to 15 A/dm². The method of measuring the zero crossing time will be described below in detail.
In the present disclosure, the zero crossing time denotes the time, after start of the test, at which the force exerted on a test piece by a solder bath becomes 0, i.e., the time, from test start, at which the pulling force on account of wetting of the test piece by solder equals the expulsion force exerted by solder on the test piece, as measured in a solderability test according to JIS C60068-2-54: 2009 (IEC60068-2-54: 2006), by a balance method.
An overview of the solderability test according to the abovementioned standard (JIS C60068-2-54: 2009 (IE060068-2-54: 2006)) follows next.
The standard prescribes a test method of solderability of component terminals having arbitrary shapes. The specimen to be tested is suspended from a high-sensitivity balance (typically a spring system), and is immersed edgewise to a prescribed depth in a bath of molten solder at a given temperature. The resultant of the vertical forces of buoyancy and surface tension acting upon the immersed specimen is detected and is converted, by a signal converter, to an electric signal which is continuously recorded as a function of time on a computer or a high-speed chart recorder. The recording may be compared with that of a perfectly wetted specimen of the same nature and dimensions. In the standard there is tested a stationary mode the purpose whereof is to assess the solderability of a particular site on the specimen.
The size of the solder bath is such that no portion of the specimen is less than 15 mm from the wall, and the depth of the bath is not less than 15 mm. The material of the solder bath used in the test should be resistant to molten solder.
The specimen undergoes essentially no pre-treatment, but may be cleaned by immersion in a neutral organic solvent at room temperature.
After mounting the specimen in a suitable holder, the prescribed surface portion is immersed in flux at room temperature. The specimen is taken out of the flux, and thereafter excess flux is immediately drained off by standing the specimen vertically on clean filter paper for 1 s to 5 s.
The specimen is then suspended vertically 20 mm±5 mm above the surface of the solder in the solder bath, which is kept at a prescribed temperature, for 30 s±15 s, to allow most of the flux solvent to evaporate, and the specimen to dry off, before initiating the test. During drying, the recorder is adjusted to the zero point, and immediately before the test, oxides are removed from the surface of the solder using a blade of suitable material.
The terminal of the specimen is then immersed at a speed of 5 mm/s±1 mm/s to 20 mm/s±1 mm/s to the specified depth in the molten solder, is held in this position for a specified time and is then pulled up. The time of immersion of the specimen to the prescribed depth may be set to 0.2 seconds or less after the specimen starts making contact with the molten solder.
The time sequence of the test is as follows.
1) Flux coating time: 0 seconds, duration: about 5 seconds
2) Excessive flux drain time: about 10 seconds, duration: 1 second to 5 seconds
3) Time of specimen suspension on the solder bath: about 15 seconds
4) Preheating time: about 20, seconds, duration 30 seconds±15 seconds
5) Time oxide wiping off the solder surface: about 60 seconds
6) Test start time: about 65 seconds, duration: 1 second to 5 seconds
7) Solder immersion time: up to 70 seconds, duration: 5 seconds
In the above sequence, “time” is the elapsed time from flux coating, and “duration” denotes the duration of the respective procedure.
The following items should be specified. If there is prescribed a test by the balance method for defining a test by a balance method.
a) Degreasing time (if necessary)
b) Ageing method (if necessary)
c) Solder alloy composition
d) Flux type
e) Test temperature
f) Portion to be tested in the specimen
g) Immersion depth
h) Immersion time
i) Immersion rate
j) Parameters to be measured from the recording
k) Acceptable values for these parameters
Embodiments of the present invention are explained next based on examples, but the present invention is not limited to these examples.

Example 1

(1) Preparation of a Plating Solution
Plating solutions Nos. 1 to 8 were prepared that contained 50 g/L of a water-soluble tin (II)-containing substance in tin content equivalent, 5 g/L of a surfactant given in Table 1, 120 ml/L of methanesulfonic acid of 70% methanesulfonic acid (i.e. 84 g/L of methanesulfonic acid) as an electrolyte component, and water as a solvent. Plating solutions Nos. 7 and 8, contained 50 mg/L of benzothiazole was incorporated as a brightening agent. The weight-average molecular weight in Table 1 is a value for the surfactant.

TABLE 1

		Appearance
		of high-
	Weight-	current

average

Glossiness G_s(60°)

density

Plating	Additive	molecular	Portion	Portion	Portion		portion
solution	component such	weight of	of 5	of 10	of 15	Glossiness	(anomalous
No.	as surfactant	surfactant	A/dm²	A/dm²	A/dm²	ratio	deposition)

1	N, N′, N′-	930	78	75	49	1.6	No
	polyoxyethylene-
	N-alkyl-(C14-
	18)1,3-
	diaminopropane
2	Polyoxyethylene	1150	178	39	6	30	No
	polyoxypropylene
	tallow amine
3	Polyoxyethylene	1350	114	71	7	16	Yes
	palm oil
	alkylamine
4	Polyoxypropylene	1000	120	19	1	120	No
	polyoxyethylene
	alkyl (C8-C18)
	amine
5	Polyoxyethylene	700	19	0	0	Not	Yes
	(β-naphthyl ether					calculable
6	Polyoxyethylene	560	194	92	21	9	Yes
	paracumyl phenyl
	ether
7	Polyoxyalkylene	1300	57	12	6	10	No
	polycyclic
	phenyl ether +
	benzothiazole
8	Polyoxyethylene	560	155	43	15	10	No
	paracumyl phenyl
	ether +
	benzothiazole

(2)Plating process

Electroplating was carried out, under the below-described plating conditions, using the obtained plating solutions 1 to 8.
Plating bath: Hullcell (registered trademark), water tank (by YAMAMOTO-MS Co., Ltd.)
Member to be plated: steel sheet (length 65 mm, width 100 mm, thickness 0.2 mm)
Current density: 1 A/dm²to 20 A/dm²(varying depending on the position, with respect to the anode, of the surface to be plated of the member to be plated)
Plating temperature: 45° C. (control range: ±1° C.)
Cumulative current amount: 5A, 60 seconds
Agitation: Agitation by stirrer tip (750 rpm)
(3) Measurement of Glossiness
Glossiness G_s(60°) at an incidence angle of 60° was measured, according to JIS 28741: 1997 (ISO 2813: 1994), in each tin plating member obtained as a result of the above-described plating process, at a portion at which the current density was 5 A/dm², at a portion at which the current density was 10 A/dm², and at a portion at which the current density was 15 A/dm². The device used for measurement was IG-331, by Horiba, Ltd. The measurement results are given in Table 1. The glossiness G_s(60°) of the member to be plated was likewise measured. However, the glossiness G_s(60°), which exceeded 200, lay in a non-measurable range.
There was worked out the ratio of the glossiness G_s(60°) of the obtained portion for which the current density was 15 A/dm²with respect to the glossiness G_s(60°) of the obtained portion for which the current density was 5 A/dm²(glossiness ratio). The results are given in Table 1.
(4) Observation of the High-Current Density Portion
The appearance of the portion at which the current density was 15 A/dm²or higher was observed for each tin plating member that was obtained in accordance with the above-described plating process. The occurrence or not of anomarouls deposition was checked. The results are given in Table 1.
(5) Observation of the Plating Deposition State
The plating deposition state at the portions corresponding to current density of 5 A/dm², 10 A/dm²and 15 A/dm²was observed using a scanning electron microscope for each tin plating member obtained in accordance with the above-described plating process. The results are illustrated in FIGS. 1 to 8. The capture angle in the figures denotes the angle formed by the incidence direction of the electron beam and the normal of the plating film.
(6) Measurement of the Surface Roughness of the Plating Surface
The surface roughness of the surface made up of the plating film, at the portions of current density 5 A/dm², 10 A/dm²and 15 A/dm², was measured, using a surface roughness meter (ultra-deep color 3D shape measuring microscope VK-9500, by Keyence Corporation) in the respective tin plating members obtained in accordance with the above-described plating process. A ratio of the result at 15 A/dm²with respect to the result at 5 A/dm²was calculated for each of the following seven measurement items.
Ra: arithmetical mean roughness according to JIS B0601:1994 (which corresponds to the arithmetical mean roughness Ra in JIS B0601:2001 (corresponding standard: ISO 4287:1997))
Ry: maximum height according to JIS B0601:1994 (which corresponds to maximum height Rz in JIS B0601:2001 (corresponding standard: ISO 4287:1997))
Rz: ten-point height according to JIS B0601:1994 (which corresponds to maximum height Rz_JISin JIS B0601:2001 (corresponding standard: ISO 4287:1997))
RMS: root mean square roughness RMS according to JIS B0601:1994 (which corresponds to root mean square roughness Rq in JIS B0601:2001 (corresponding standard: ISO 4287:1997))
tp: material ratio for each sampling length of 50% cutoff level, according to JIS B0601:1994 (related to material ratio Rmr (c) over the entire evaluation length in JIS B0601:2001 (corresponding standard: ISO 4287:1997))
Sm: mean spacing of profile irregularities according to JIS B0601:1994 (which corresponds to the mean width RSm of roughness profile elements in JIS B0601:2001 (corresponding standard: ISO 4287:1997))
S: mean spacing between local peaks according to JIS B0601:1994
The evaluation results are given Table 2.

TABLE 2

	Ra	Ry	Rz

ratio

(15 A/

Plating

Ra (μm)

dm²/

Ry (μm)

dm²/

Rz (μm)

dm²/

solution	5	10	15	5A/	5	10	15	5A/	5	10	15	5A/
No.	A/dm²	A/dm²	A/dm²	dm²)	A/dm²	A/dm²	A/dm²	dm²)	A/dm²	A/dm²	A/dm²	dm²

1	0.84	0.99	1.09	1.30	9.04	9.29	9.13	1.01	6.67	6.38	7.82	1.17
2	0.92	1.12	1.49	1.62	9.82	17.21	14.34	1.46	8.09	10.19	11.40	1.41
3	0.87	0.96	1.49	1.71	7.24	9.00	28.89	3.99	6.02	6.84	13.41	2.23
4	0.67	0.83	1.29	1.93	4.84	9.34	12.02	2.48	4.14	5.87	9.14	2.21
5	1.18	1.61	1.81	1.53	11.15	13.39	15.65	1.40	8.41	10.46	14.56	1.73
6	0.79	0.95	1.49	1.89	9.01	9.00	23.28	2.58	6.34	6.40	12.15	1.92
7	0.90	1.38	1.64	1.82	5.95	21.61	20.62	3.47	5.47	13.59	13.88	2.54
8	0.92	1.24	1.48	1.61	9.58	12.16	16.93	1.77	6.78	8.40	12.81	1.89

RMS

ratio

tp ratio

Plating

RMS (μm)

(15 A/

tp (%)

(15 A/dm²/

solution	5	10	15	dm²/5	5	10	15	5
No.	A/dm²	A/dm²	A/dm²	A/dm²)	A/dm²	A/dm²	A/dm²	A/dm²)

1	1.13	1.22	1.42	1.26	19.14	28.91	51.86	2.71
2	1.27	1.58	2.11	1.66	23.93	1.86	92.82	3.88
3	1.11	1.26	2.85	2.57	22.41	74.71	58.50	2.61
4	0.85	1.06	1.66	1.95	33.74	37.26	54.15	1.60
5	1.54	2.02	2.41	1.56	58.11	32.42	88.59	1.52
6	1.05	1.22	2.28	2.17	58.30	70.95	86.38	1.48
7	1.10	2.06	2.20	2.00	39.55	76.56	95.31	2.41
8	1.19	1.60	2.07	1.74	39.40	86.67	90.92	2.31

Sm ratio

S ratio

Plating

Sm (μm)

(15 A/dm²/

S (mm)

(15 A/dm²/

solution	5	10	15	5	5	10	15	5
No.	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²)

1	13.54	14.92	17.90	1.32	5.98	7.05	5.93	0.99
2	15.13	14.67	17.93	1.19	5.88	5.16	4.81	0.82
3	13.98	16.48	16.13	1.15	5.27	5.43	5.49	1.04
4	12.87	14.86	16.36	1.27	5.74	4.80	4.54	0.79
5	14.57	17.53	16.45	1.13	4.75	4.49	4.37	0.92
6	12.61	16.63	16.89	1.34	5.93	5.63	5.59	0.94
7	13.78	16.51	16.63	1.21	5.51	5.63	5.85	1.06
8	13.77	16.05	15.32	1.11	4.74	5.74	5.87	1.24

Example 2

(1) Plating Process

Plating was carried out under the below-described plating conditions using the plating solutions 1, 2, 5 and 6 prepared in Example 1. The substrate to be plated was an open-frame printed board, in which electrolytic nickel plating (sulfamic acid bath, 1 μm) was formed on wiring comprising C1020, and which was then cleaned and activated in accordance with known methods, to yield test pieces for evaluation of zero crossing time. The average thickness of the tin plating film in the test pieces was 3 μm.
Current density: 5 A/dm², 10 A/dm²or 15 A/dm²
Plating temperature: 45° C. (control range: ±1° C.)
Cumulative current amount: 300 A·sec/dm²
Other plating conditions: stirred plating (stirrer revolutions 500 rpm), with rocking, (cathode rocker, 5 m/minute)
(2) Measurement of Zero Crossing Time (Before Environment Test)
A solderability test by the balance method according to JIS C60068-2-54: 2009 (IEC60068-2-54: 2006) was carried out using each of the plurality of test pieces for zero crossing time measurement of dissimilar plating solutions and/or current densities, obtained in accordance with the above-described plating process. Specifically, the surface of the test pieces was cleaned and the test pieces were immersed for 2 seconds in the below-described flux. Thereafter, the test pieces were taken out of the flux, and the drooping residual solution on the surface of the test pieces was removed. The test pieces, with the oxide film on the surface thereof removed, were quickly immersed, after droop-removal, in the solder bath, to carry out the test thereby. After start of the immersion of the test pieces in the solder bath, the zero crossing time was worked out as the time that it took for the force of the solder bath acting on the test pieces to reach 0 (time elapsed from test start until wetting begins). The zero crossing time is substantially identical to the test time that it takes a recorded signal trace to intersect a zero balance point in a device for measuring a wetting curve, as prescribed in MIL STD-883 METHOD 2022. The test conditions and so forth were as follows.
Used device: SAT-5100, by RHESCA Corporation
Solder: M7005, by Senju Metal Industry Co., Ltd.
Solder composition: Sn-3.0 wt %, Ag-0.5 wt %, balance Cu
Solder temperature: 245° C.±5° C.
Flux: ES-1061, by Senju Metal Industry Co., Ltd.
Immersion speed of test piece: 2 mm/second
Immersion depth of test piece: 1 mm
Immersion time of test piece: 5 seconds
The measurement results for the zero crossing time of each test piece are given in Table 3.
(3) Measurement of Zero Crossing Time (after Environment Test)
The plurality of types of test pieces for zero crossing time measurement obtained in accordance with the above-described plating process were kept in a high-temperature high-humidity environment, at 105° C. and at a relative humidity of 100%, for 8 hours. After the environment test, the zero crossing time of the test pieces was measured as described above. The measurement results for the zero crossing time of each test piece are given in Table 2. The ratio of the zero crossing time before and after the environment test was worked out for each test piece out on the basis of the respective measurement results (after test/before test). The results are given in Table 3.

TABLE 3

							Ratio
							(before/after) of

	Zero crossing	Zero crossing	zero crossing time
	time (sec) before	time (sec) after	before and after
Plating	environment test	environment test	environment test

solution	5	10	15	5	10	15	5	10	15
No.	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²	A/dm²

1	0.28	0.30	0.30	0.49	0.51	0.47	1.7	1.7	1.6
2	0.28	0.29	0.27	0.48	0.50	0.65	1.7	1.7	2.4
5	0.29	0.30	0.28	0.67	0.68	0.70	2.3	2.3	2.5
6	0.30	0.28	0.30	0.64	0.57	0.47	2.2	2.0	1.6

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

What is claimed is:

1. An acidic aqueous composition for semiglossy tin electroplating, comprising:

a water-soluble tin (II)-containing substance; and

a surfactant,

wherein said surfactant comprises a surfactant (A) comprising N,N′,N′-polyoxyethylene-N-alkyl-1,3-diaminopropane.

2. The acidic aqueous composition for semiglossy tin electroplating according to claim 1, wherein, in said surfactant (A), the number of carbon atoms of the alkyl group that bonds to N ranges from 14 to 18.

3. The acidic aqueous composition for semiglossy tin electroplating according to claim 1, wherein the weight-average molecular weight of said surfactant (A) ranges from 300 to 1500.

4. The acidic aqueous composition for semiglossy tin electroplating according to claim 1, wherein the content of said water-soluble tin (II)-containing substance in tin content equivalent ranges from 5 g/L to 200 g/L and the content of said surfactant (A) ranges from 0.5 g/L to 40 g/L.

5. The acidic aqueous composition for semiglossy tin electroplating according to claim 1, which contains an organic sulfonic acid compound.

6. The acidic aqueous composition for semiglossy tin electroplating according to claim 5, wherein the content of said organic sulfonic acid compound ranges from 50 g/L to 300 g/L in organic sulfonic acid content equivalent.

7. A member, comprising:

a member to be plated; and

a semiglossy tin plating film that is formed on at least part of the surface of said member to be plated, by electroplating of acidic aqueous composition for semiglossy tin electroplating comprising:

a water-soluble tin (II)-containing substance; and

a surfactant,

8. The member according to claim 7, wherein said semiglossy tin plating film in said member is electroplated under a condition of current density of 5 A/dm²or higher.

9. The member according to claim 7, wherein said semiglossy tin plating film of said member has a ratio of 8 or less of glossiness Gs(60°) measured in accordance with JIS 28741: 1997 (ISO 2813: 1994) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to said glossiness Gs(60°) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm².

10. The member according to claim 7, wherein said semiglossy tin plating film in said plating member has a ratio of 1.3 or less of arithmetical mean roughness Ra measured according to JIS B0601:2001 (ISO 4287:1997) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to said arithmetical mean roughness Ra of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm².

11. The member according to claim 7, wherein said semiglossy tin plating film in said plating member has a ratio of 1.3 or less of root mean square roughness Rq measured according to JIS B0601:2001 (ISO 4287:1997) of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 15 A/dm², with respect to said root mean square roughness Rq of the semiglossy tin plating film obtained in a case of electroplating under conditions of plating temperature of 45° C. and current density of 5 A/dm².

12. The member according to claim 7, wherein said semiglossy tin plating film in said member has a thickness ranging from 1 μm to 5 μm.

13. The member according to claim 7, wherein said semiglossy tin plating film in said member is formed by electroplating with a current density ranging from 5 A/dm²to 15 A/dm², and a ratio (before/after) of a value (unit: seconds) of zero crossing time (unit: seconds) of said member as measured in a solderability test by a balance method according to JIS C60068-2-54: 2009 (IEC60068-2-54: 2006) after an environment test of standing for 8 hours in an environment at 105° C. and relative humidity of 100%, with respect to the value (unit: seconds) measured before the environment test, is 2.1 or less.

14. The member according to claim 7, wherein said member to be plated is an electronic component.

15. The member according to claim 14, wherein said electronic component includes one, two or more types selected from the group consisting of resistors, variable resistors, capacitors, filters, inductors, thermistors, crystal oscillators, switches, connectors, lead wires, printed circuit boards, and semiconductor integrated circuits and modules.

16. The member according to claim 7, wherein, in said surfactant (A), the number of carbon atoms of the alkyl group that bonds to N ranges from 14 to 18.

17. The member according to claim 7, wherein the weight-average molecular weight of said surfactant (A) ranges from 300 to 1500.

18. The member according to claim 7, wherein the content of said water-soluble tin (II)-containing substance in tin content equivalent ranges from 5 g/L to 200 g/L and the content of said surfactant (A) ranges from 0.5 g/L to 40 g/L.

19. The member according to claim 7, which contains an organic sulfonic acid compound.

20. The member according to claim 19, wherein the content of said organic sulfonic acid compound ranges from 50 g/L to 300 g/L in organic sulfonic acid content equivalent.