A tin alloy plating solution includes a soluble tin salt, a soluble salt of a metal more noble than tin, and a sulfide compound represented by General Formula (1). In the General Formula (1), (A) is a hydrocarbon group including no oxygen atom and having 1 to 2 carbon atoms, or (A) is a hydrocarbon group including one or more oxygen atoms and having 2 to 6 carbon atoms. The metal which is more noble than tin is preferably silver, copper, gold or bismuth.

As a tin-silver plating solution that contains a source of tin ions; a source of silver ions (Ag.sup.+); and an organic additive including a silver (Ag) complexing agent, a tin carrier, and a crystal grain refiner is provided, in the case of performing high-speed plating using the plating solution, the generation of whiskers is diminished, the composition of silver ions (Ag.sup.+) in the tin-silver plating solution is uniformly maintained, and thus a uniform silver composition in the formed tin-silver solder bumps can be achieved.

As a tin-silver plating solution that contains a source of tin ions; a source of silver ions (Ag.sup.+); and an organic additive including a silver (Ag) complexing agent, a tin carrier, and a crystal grain refiner is provided, in the case of performing high-speed plating using the plating solution, the generation of whiskers is diminished, the composition of silver ions (Ag.sup.+) in the tin-silver plating solution is uniformly maintained, and thus a uniform silver composition in the formed tin-silver solder bumps can be achieved.

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 (OCH.sub.2CHR.sup.41).sub.mOR.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.4N(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 (OCH.sub.2CHR.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 (OCH.sub.2CHR.sup.41).sub.mOR.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.4N(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 (OCH.sub.2CHR.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.

The present disclosure relates to methods of monitoring the concentrations of silver ion and complexing agent in tin-silver (SnAg) electrodeposition solutions, and analysis and process control using such methods. Methods can include adding a precipitating agent to an electrodeposition solution including at least tin ions, silver ions, and complexing agent to cause a reaction between at least a portion of the precipitating agent and substantially all of the silver ions (to precipitate silver ions as a precipitant); adding a metallic salt to the electrodeposition solution to cause a reaction with substantially all of the remaining precipitating agent; measuring the endpoint of the silver ion back titration; further adding metallic salt to cause a further reaction with the complexing agent; and measuring the endpoint of the complexing agent titration.

The present disclosure relates to methods of monitoring the concentrations of silver ion and complexing agent in tin-silver (SnAg) electrodeposition solutions, and analysis and process control using such methods. Methods can include adding a precipitating agent to an electrodeposition solution including at least tin ions, silver ions, and complexing agent to cause a reaction between at least a portion of the precipitating agent and substantially all of the silver ions (to precipitate silver ions as a precipitant); adding a metallic salt to the electrodeposition solution to cause a reaction with substantially all of the remaining precipitating agent; measuring the endpoint of the silver ion back titration; further adding metallic salt to cause a further reaction with the complexing agent; and measuring the endpoint of the complexing agent titration.

This tin or tin-alloy plating liquid contains (A) a soluble salt including at least a stannous salt; (B) an acid selected from an organic acid and an inorganic acid, or a salt thereof; (C) a surfactant; (D) a leveling agent; and (E) an additive, wherein the surfactant is a compound (C1) represented by Formula (1) and/or a compound (C2) represented by Formula (2).

##STR00001##

In Formulas (1) and (2), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 1 to 3, and m and n are different from each other.

This tin or tin-alloy plating liquid contains (A) a soluble salt including at least a stannous salt; (B) an acid selected from an organic acid and an inorganic acid, or a salt thereof; (C) a surfactant; (D) a leveling agent; and (E) an additive, wherein the surfactant is a compound (C1) represented by Formula (1) and/or a compound (C2) represented by Formula (2).

##STR00001##

In Formulas (1) and (2), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 1 to 3, and m and n are different from each other.

An apparatus for continuous simultaneous electroplating of two metals having substantially different standard electrodeposition potentials (e.g., for deposition of SnAg alloys) comprises an anode chamber for containing an anolyte comprising ions of a first, less noble metal, (e.g., tin), but not of a second, more noble, metal (e.g., silver) and an active anode; a cathode chamber for containing catholyte including ions of a first metal (e.g., tin), ions of a second, more noble, metal (e.g., silver), and the substrate; a separation structure positioned between the anode chamber and the cathode chamber, where the separation structure substantially prevents transfer of more noble metal from catholyte to the anolyte; and fluidic features and an associated controller coupled to the apparatus and configured to perform continuous electroplating, while maintaining substantially constant concentrations of plating bath components for extended periods of use.