Alkoxylated β-Naphthol as an Additive for Tin Plating from Chloride and Methane Sulfonic Acid Electrolytes

Journal article, 2018

Beta-naphthol was one of the first additives introduced for smooth and homogeneous
tin electrodeposition. Although it can be oxidized under the plating conditions, forming either
1,2-napthoquinone or polymeric materials based on naphthioxides, it is still in use. In this work,
an investigation of its more stable form, alkoxylated beta-naphthol (ABN), on tin plating is undertaken.
For this purpose, chloride based (pH ~5) and methane sulfonic acid (MSA, pH ~0.5) electrolytes,
including ABN, were prepared. Reaction kinetics were studied by polarization, Tafel measurements,
and cyclic voltammetry. Tin electrodeposits were obtained on flat brass substrates. Surface
morphology and preferred crystal orientation were studied by Scanning Electron Microscopy (SEM)
and X-ray Diffraction (XRD). In both studied electrolytes ABN acts as an inhibitor but in the case of
the chloride electrolyte it is more pronounced. In the MSA electrolyte this effect was overlaid by the
presence of tin-citrate complexes. In the chloride-based electrolyte, ABN has a grain refining effect,
while in the MSA electrolyte an increase of ABN concentration leads to a slight enlargement of the
average grain size. X-ray analysis shows a constant decrease of the (101) intensity with increasing
concentration of ABN for the sample deposited from both baths.