The corrosion characteristics and solderability of immersion tin coatings on copper

Abstract

Immersion tin is widely used as a lead free surface finish in the printed circuit board technology. Tin prevents the underlying copper from corrosion and preserves its solderability during a long storage and lead-free assembly processes. Investigated immersion tin coatings were deposited on copper foil from thiourea-type baths with hydrochloric acid addition (SnHCl coatings) or methanesulfonic acid addition (SnMSA coatings). Obtained coatings were investigated in the as deposited state and after aging (4 h at 155 8C, in air). The scanning electron microscopy studies revealed differences in structure of tin samples deposited from different baths. Results of polarization and impedance investigations indicated that as deposited SnHCl coatings had better corrosion resistance in 0.5 M NaCl solution than SnMSA coatings. The aging resulted in the improvement of the corrosion resistance of thinner coatings (0.2 and 0.5 mm thick SnHCl and 0.3 mm thick SnMSA), which were thoroughly converted into Sn-Cu intermetallic (IMC) phases. In contrary, thicker coatings exhibited some worsening of the corrosion resistance upon aging. The solderability of all as-deposited tin coatings was acceptable, but decreased after aging, especially for thinner coatings, showing the through conversion into Sn-Cu IMC phases.

Electrodeposition, Characterization, and Corrosion Behavior of CoCrFeMnNi High-Entropy Alloy Thin Films

“…It is difficult to evaluate the EIS data for Cu electrodes, as results are subject to various interpretations. However, the linear aspect of the Nyquist plot suggests a semi-infinite diffusion type for the Cu electrode [29]. The Warburg impedance considers the diffusion of oxygen and diffusion of corrosive species The corrosion behavior, corrosion mechanisms, and adsorption phenomena of the films formed on the surface of the CoCrFeMnNi alloy coating sample in artificial seawater solution were studied by electrochemical impedance spectroscopy (EIS).…”

“…EIS data were examined utilizing equivalent electrical circuits, as shown in Figure 7. (as Cl − ) to the copper surface and/or diffusion process of soluble copper compounds (CuCl2 − ) from the surface into the solution [29][30][31][32][33]. The appearance of diffusion is also considered in the Bode diagram (phase angle vs. log f), where the phase angle amounts around (−45)/(−50°).…”

“…It is difficult to evaluate the EIS data for Cu electrodes, as results are subject to various interpretations. However, the linear aspect of the Nyquist plot suggests a semi-infinite diffusion type for the Cu electrode [29]. The Warburg impedance considers the diffusion of oxygen and diffusion of corrosive species (as Cl − ) to the copper surface and/or diffusion process of soluble copper compounds (CuCl 2 − ) from the surface into the solution [29][30][31][32][33].…”

Surface coverage characterization of tinplates after post‐treatment processes

“…For this process, the content of stannous ion and sulfate ion should be strictly defined. Besides, the complexing agent and stabilizer should also be considered [18]. In addition, the content of tin, ferrous ion and sludge should also be strictly controlled.…”

Contact tinning: A millennia‐old plating technology

“…Thus, a final polishing step was no longer necessary. Nevertheless, because of their simplicity, during the last decades contact and displacement tinning have regained some favour to coat the inner surface of plumbing tubes as a protection against corrosive waters or for spot-coating printed circuit boards to facilitate the soldering of interconnecting wires (Araźna and Bielinski 2009;Araźna 2013;Araźna et al 2013;Huttunen-Saarivirta 2002;Welter and N'Guyen 2005).…”