A tin or tin alloy plating solution includes: (A) a soluble salt containing at least a stannous salt; (B) an acid selected from an organic acid and an inorganic acid or a salt thereof; (C) a surfactant; and (D) a leveling agent. In addition, the surfactant contains polyoxyethylene polyoxypropylene alkylamine, an alkyl group of the polyoxyethylene polyoxypropylene alkylamine is C.sub.aH2.sub.a+1 (where a is 12 to 18). Further, in a case where a number of a functional group of polyoxypropylene of the polyoxyethylene polyoxypropylene alkylamine is set as p and a number of a functional group of polyoxyethylene of the polyoxyethylene polyoxypropylene alkylamine is set as q, the sum of p and q (p+q) is 8 to 21, and a ratio of p to q (p/q) is 0.1 to 1.6.

A tin or tin alloy plating solution includes: (A) a soluble salt containing at least a stannous salt; (B) an acid selected from an organic acid and an inorganic acid or a salt thereof; (C) a surfactant; and (D) a leveling agent. In addition, the surfactant contains polyoxyethylene polyoxypropylene alkylamine, an alkyl group of the polyoxyethylene polyoxypropylene alkylamine is C.sub.aH2.sub.a+1 (where a is 12 to 18). Further, in a case where a number of a functional group of polyoxypropylene of the polyoxyethylene polyoxypropylene alkylamine is set as p and a number of a functional group of polyoxyethylene of the polyoxyethylene polyoxypropylene alkylamine is set as q, the sum of p and q (p+q) is 8 to 21, and a ratio of p to q (p/q) is 0.1 to 1.6.

A tin-plated product contains: a substrate 10 of copper or a copper alloy; an underlying layer 12 of nickel which is formed on the surface of the substrate 10; and an outermost layer 14 containing tin, the outermost layer 14 being formed on the surface of the underlying layer 12, the outermost layer 14 being composed of a copper-tin alloy layer 14a of a large number of crystal grains of a copper-tin alloy, tin layers 14b of tin having an average thickness of 0.01 to 0.20 micrometers, and a plurality of copper-nickel-tin alloy layers 14c of a copper-nickel-tin alloy, each of the tin layers 14b being formed in a corresponding one of recessed portions between adjacent two of the crystal grains of the copper-tin alloy on the outermost surface of the copper-tin alloy layer, the copper-nickel-tin alloy layers 14c being arranged on the side of the underlying layer 12 in the copper-tin alloy layer 14a so as to be apart from each other.

A metal porous body includes a flat plate shape and having continuous pores, a framework of the metal porous body including an alloy layer containing nickel and at least one of chromium and tin, a cobalt layer being formed on a surface of the alloy layer.

On a base member made of copper or a copper alloy, a zinc-nickel alloy layer including zinc and nickel, and a tin layer made of tin alloy are laminated in this order: the zinc-nickel alloy layer has a thickness of 0.1-5 μm inclusive and has a nickel content of 5-50 mass % inclusive, the tin layer has a zinc concentration of 0.6-15 mass % inclusive, and, under an oxide layer which is the outermost layer, a metal zinc layer, having a zinc concentration of 5-40 at % inclusive and a thickness of 1-10 nm inclusive in SiO.sub.2 conversion, is formed on the tin layer.

Described herein is an aqueous composition including tin ions and at least one compound of formula I ##STR00001## wherein X.sup.1 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O or S or a C.sub.5 to C.sub.12 aromatic moiety, R.sup.11 is a copolymer of ethylene oxide and a further C.sub.3 to C.sub.6 alkylene oxide, wherein the content of ethylene oxide is from 5 to 30% by weight, R.sup.11 is selected from H, R.sup.11, R.sup.40, R.sup.13, R.sup.14 are (a) independently selected from H, R.sup.11, R.sup.40, or (b) may together form a divalent group X.sup.13; X.sup.13 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O, S or NR.sup.43; R.sup.40 is H or a linear or branched C.sub.1-C.sub.20 alkyl, R.sup.43 is selected from H, R.sup.11 and a linear or branched C.sub.1-C.sub.20 alkyl.

Described herein is an aqueous composition including tin ions and at least one compound of formula I ##STR00001## wherein X.sup.1 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O or S or a C.sub.5 to C.sub.12 aromatic moiety, R.sup.11 is a copolymer of ethylene oxide and a further C.sub.3 to C.sub.6 alkylene oxide, wherein the content of ethylene oxide is from 5 to 30% by weight, R.sup.11 is selected from H, R.sup.11, R.sup.40, R.sup.13, R.sup.14 are (a) independently selected from H, R.sup.11, R.sup.40, or (b) may together form a divalent group X.sup.13; X.sup.13 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O, S or NR.sup.43; R.sup.40 is H or a linear or branched C.sub.1-C.sub.20 alkyl, R.sup.43 is selected from H, R.sup.11 and a linear or branched C.sub.1-C.sub.20 alkyl.

The present invention provides an aqueous composition comprising tin ions and at least one compound of formula I wherein X.sub.1 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O or S or a C.sub.5 to C.sub.12 aromatic moiety, R.sup.11 is a copolymer of ethylene oxide and a further C.sub.3 to C.sub.6 alkylene oxide, wherein the content of ethylene oxide is from 5 to 30% by weight, R.sup.12 is selected from H, R.sup.11, R.sup.40, R.sup.13, R.sup.14, are (a) independently selected from H, R.sup.11, R.sup.40, or (b) may together form a divalent group X.sup.13; X.sup.13 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O, S or NR.sup.43; R.sup.40 is H or a linear or branched C.sub.1-C.sub.20 alkyl, R.sup.43 is selected from H, R.sup.11 and a linear or branched C.sub.1-C.sub.20 alkyl.

##STR00001##

The present invention provides an aqueous composition comprising tin ions and at least one compound of formula I wherein X.sub.1 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O or S or a C.sub.5 to C.sub.12 aromatic moiety, R.sup.11 is a copolymer of ethylene oxide and a further C.sub.3 to C.sub.6 alkylene oxide, wherein the content of ethylene oxide is from 5 to 30% by weight, R.sup.12 is selected from H, R.sup.11, R.sup.40, R.sup.13, R.sup.14, are (a) independently selected from H, R.sup.11, R.sup.40, or (b) may together form a divalent group X.sup.13; X.sup.13 is selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, which may optionally be interrupted by O, S or NR.sup.43; R.sup.40 is H or a linear or branched C.sub.1-C.sub.20 alkyl, R.sup.43 is selected from H, R.sup.11 and a linear or branched C.sub.1-C.sub.20 alkyl.

##STR00001##

A plating solution containing a leveler is brought into contact with silica particles with an average particle diameter of 500 μm or less to remove impurities from the plating solution.