The disclosure provides a Sn—In electroplating bath that is Pb-free, environmentally safe, operates at room temperature, and does not require changes in existing plating assemblies. Room temperature aging and limited thermal cycling tests show that the electroplated Sn—In alloy film on a Cu substrate effectively mitigates whisker growth.

The disclosure provides a Sn—In electroplating bath that is Pb-free, environmentally safe, operates at room temperature, and does not require changes in existing plating assemblies. Room temperature aging and limited thermal cycling tests show that the electroplated Sn—In alloy film on a Cu substrate effectively mitigates whisker growth.

The present invention provides a high-concentration tin sulfonate aqueous solution, in which a divalent tin ion (Sn.sup.2+) concentration is 360 g/L to 420 g/L, a tetravalent tin ion (Sn.sup.4+) concentration is 10 g/L or less, a free methanesulfonic acid concentration is 40 g/L or less, a Hazen unit color number (APHA) is 240 or less, and a turbidity is 25 FTU or less. This aqueous solution is produced such that stannous oxide powder whose temperature is adjusted to a temperature of 10° C. or lower is added to an aqueous methanesulfonic acid solution having a concentration of 60% by mass to 90% by mass when the aqueous solution circulates in a state of being maintained at the temperature of 10° C. or lower, and the stannous oxide powder is dissolved.

Described herein is an aqueous composition including tin ions and at least one compound of formula I ##STR00001##
where X.sup.1, X.sup.2 are independently selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, R.sup.11 is a monovalent group of formula —(O—CH.sub.2—CHR.sup.41).sub.m—OR.sup.42, R.sup.12, R.sup.13, R.sup.14 are independently selected from H, R.sup.11, and R.sup.40; R.sup.15 is selected from H, R.sup.11, R.sup.40 and —X.sup.4—N(R.sup.21).sub.2, X.sup.4 is a divalent group selected from (a) a linear or branched C.sub.1 to C.sub.12 alkanediyl, and (b) formula —(O—CH.sub.2—CHR.sup.41).sub.o—, R.sup.21 is selected from R.sup.11 and R.sup.40, R.sup.40 is a linear or branched C.sub.1-C.sub.20 alkyl, R.sup.41 is selected from H and a linear or branched C.sub.1 to C.sub.5 alkyl, R.sup.42 is selected from H and a linear or branched C.sub.1-C.sub.20 alkyl, n is an integer of from 1 to 6, m is an integer of from 2 to 250, and o is an integer of from 1 to 250.

Described herein is an aqueous composition including tin ions and at least one compound of formula I ##STR00001##
where X.sup.1, X.sup.2 are independently selected from a linear or branched C.sub.1-C.sub.12 alkanediyl, R.sup.11 is a monovalent group of formula —(O—CH.sub.2—CHR.sup.41).sub.m—OR.sup.42, R.sup.12, R.sup.13, R.sup.14 are independently selected from H, R.sup.11, and R.sup.40; R.sup.15 is selected from H, R.sup.11, R.sup.40 and —X.sup.4—N(R.sup.21).sub.2, X.sup.4 is a divalent group selected from (a) a linear or branched C.sub.1 to C.sub.12 alkanediyl, and (b) formula —(O—CH.sub.2—CHR.sup.41).sub.o—, R.sup.21 is selected from R.sup.11 and R.sup.40, R.sup.40 is a linear or branched C.sub.1-C.sub.20 alkyl, R.sup.41 is selected from H and a linear or branched C.sub.1 to C.sub.5 alkyl, R.sup.42 is selected from H and a linear or branched C.sub.1-C.sub.20 alkyl, n is an integer of from 1 to 6, m is an integer of from 2 to 250, and o is an integer of from 1 to 250.

A tin solution applicable to tin film formation by solid electrolyte deposition, and a method for forming a tin film using the solution are provided. The tin solution contains tin methanesulfonate, methanesulfonic acid, water, an isopropyl alcohol, and a polyethylene-block-poly (ethylene glycol).

A tin solution applicable to tin film formation by solid electrolyte deposition, and a method for forming a tin film using the solution are provided. The tin solution contains tin methanesulfonate, methanesulfonic acid, water, an isopropyl alcohol, and a polyethylene-block-poly (ethylene glycol).

The present invention provides a method for producing an aqueous tin methanesulfonate solution by dissolving tin (II) oxide in an aqueous methanesulfonic acid solution, wherein if A is the number of moles of the tin (II) oxide and B is the number of moles of the methanesulfonic acid, the value of B/2A is within the range of from 1.0 to 1.4. This method for dissolving tin (II) oxide into an aqueous methanesulfonic acid solution is able to achieve a high tin ion concentration.

The present invention provides a method for producing an aqueous tin methanesulfonate solution by dissolving tin (II) oxide in an aqueous methanesulfonic acid solution, wherein if A is the number of moles of the tin (II) oxide and B is the number of moles of the methanesulfonic acid, the value of B/2A is within the range of from 1.0 to 1.4. This method for dissolving tin (II) oxide into an aqueous methanesulfonic acid solution is able to achieve a high tin ion concentration.

Provided is an additive for an electroplating solution, including a compound represented by the following general formula (1):

##STR00001##

where R.sup.1 to R.sup.3 each independently represent a group represented by the following general formula (2), A.sup.1 represents an alkanediyl group having 2 to 4 carbon atoms, and “n” represents 0 or 1:

##STR00002##

where R.sup.4 and R.sup.5 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, A.sup.2 and A.sup.3 each independently represent an alkanediyl group having 2 to 4 carbon atoms, “m” represents an integer of from 1 to 4, and * represents a bonding site.