Composition for tin or tin alloy electroplating comprising leveling agent

An aqueous composition comprising tin ions, optionally alloy metal ions selected from the group consisting of silver, indium, and bismuth ions and at least one additive of formula L1a

• or of formula L1b
• wherein
• RL1 is, for each group RL1, independently, selected from the group consisting of —F and a linear or branched C1 to C6 alkyl that comprises one or more F substituents in C1 or C2 position;
• RL2 is a C1 to C6 alkyl, C1 to C6 alkenyl, C5 to C12 aryl, C6 to C15 alkylaryl, C6 to C15 arylalkyl, all of which may be substituted by CN, OH, C1 to C6 alkoxy or halogen;
• RL3 is selected from the group consisting of H, C1 to C6 alkyl, C1 to C6 alkenyl, C1 to C6 alkoxy, halogen, CN, and OH;
• RL4 is, for each RL4 independently, selected from the group consisting of RL1 and RL3;
• RL11, RL12, RL13 are independently selected from the group consisting of RL1 and RL3, with the condition that at least two of RL11, RL12, RL13 are RL1;
• and
• XL1 is
• (a) a divalent group selected from the group consisting of
• (i) a C3 to C5 alkanediyl, and
• (ii) a C3 to C5 alkenediyl,
• or
• (b) forms, together with the adjacent C═C double bond, a C5 to C12 aromatic ring system;
• and
• n is the number of groups RL1 selected from the group consisting of 1, 2 and 3;
• wherein the at least one additive is a fluorinated leveler capable of providing a substantially planar tin or tin alloy layer and filling features on the micrometer scale without substantially forming defects.