Electrodeposition of Sn–In Alloys Involving Deep Eutectic Solvents

Round 1

Reviewer 1 Report

Line 43-45: Sn-Ag and Sn-Cu has higher melting point (>200 ^oC) point but Sn-Bi and Sn-In has lower Mp (<180^oC). It would be better to include the exact BPs of these alloys here. Please update the referencing system, now the manuscript has both numeric (1,2,3) and roman numbering. Please change them to numeric only. Line 47: Please explain a bit more about Tin whisker (what is it? why it’s a problem?etc). This would be helpful for general audience. Line 54: Please include, why Sn-In alloy is suitable to make connection by soldering in assembly of integrated circuits and micromodules? What are the operating temperatures for ILEG-In and ILEG-Sn system? Its hard to see the dimension bar in the micrographs. Please include visible bars. Its hard to conclude that (in line 269) “As In:Sn molar ratio of salts in the electrolyte increased (higher In content) the constituent particles seem to lose their tetragonal shape” only with only one ratio change ( from equimolar to 3.33) at a constant applied current. Did authors try other combinations of concentration (different ratios of In:Sn) while holding the applied current constant? I guess, the author tried In:Sn ratio of 2. If still the shape of particles changes while increasing In:Sn ratio, then author needs to explain the reasons behind this. How many experiments were done for each data point? (fig 4) Need error bars with all graphs. Also, In content increases with ratio of In:Sn and temp. Author must do regression analysis to see if there is any linear relationship. Fig 5, What is the point of putting same SEM images with different magnification (a and b) ? Also, put clear dimension bar on the SEM image. Author suggested PC approach generated slightly decreased particle size. Need to add a) compared to what and b) by what extent. (Figure 7) How many times each experiment performed (n value)? , Needs error bar and linear analysis. Author should explain more why the In content decrease as applied current decreases? On the corrosion study, I suggest the following : a) Include bode plots to get more clear idea about the resistance of film b) Authors have the data of Rc and Rf values with respect to time. Its important to check if there any dependency / linearity between immersion time and Rct/Rf values. From line 399 to 403, author says between 144-360 h Nyquist diameter increase (that means RCT value should increase) and its due to re-passivation. But the table says otherwise (RCT values consistently decrease from 0-360h). Author must solve this contradiction. Author must include the scope of future work in the conclusion section.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript presents the studies on electroeposition of Sn-In alloys. Though, the results are well-presented, I would mention following issues that has to be considered:

The signal at ca. 0.1 V in CV (Figure 1) has been assigned oxidation of Sn2+ to Sn4+. If so, why such signal is not present for pure SnCl2 and is visible only for aloys? Figure 4 represents the influence on various proces paramaters on In content. Can authors add some more experimental points? It is a little bit superficial to give conclusiosn based on only 3 points. The editing issue: there are errors in numbers of references.

 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The Authors reported electrochemical deposition of Sn-In alloys from DES solutions.
The topic of manuscript is within the scope of the journal and the obtained results can be interesting for the readers, it cannot be recommended for publication in the present form for the following reasons.

- introduction section should be rearranged. In the present form is definetely too long and too general. I don't thinkt that so much information not directly related to the present work should be provided.
- the results of CV measurements should be discussed with respect to the existing literature as well as short summary of this part of the manuscript is needed in my opinion.
- in my opinion there is no direct connection between first part of the manuscript discussing the electrochemical deposition of Sn and In on vanadium surface with the second part on fabrication and characterization of Sn-In alloys galvanostatically depositied on Cu plates in two-electrode system. I wonder it the first part is really necessary.
- how was the thickness of deposits verified?
- the trends shown in Figure 4 should be discussed with respect to the reduction potentials of both components.
- the Authors stated that "To improve the operation parameters during Sn-In alloy deposition, pulsed current (PC) has been also applied." But it is not clear what parameters were considered? What was the real motivation for using pulsed electrodeposition?
- page 8 (lines 290-300). I don't think that it is necessary to provide so much literature information not used for the discussion of the obtained results
- if I understand correctly, XRD pattern of the deposit obtained at one particular conditions is shown in FIgure 7. Did you observe any effect of electrodeposition conditions on the phase composition of the deposits?
- Figure 7 caption - information about inset should be also provided
- Page 10 lines 340-341 - the Authors stated that "The electrodeposition has been carried out on Ti substrate". Did you observe any effect of type of the substrate (Cu, Ti) on the composition, morphology and properties (e.g. melting point) of the deposit?
- I think that in general electrodeposition conditions should be correlated with the composition (In to Sn ratio, phase composition), morphology and properties (melting point, corrosion behavior) of the deposits. The lack of this correlation is the main drawback of the manuscript in my opinion.

Therefore I cannot recommend the manuscript for publication in Coatings in the present form.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Authors did a good job on following most of my suggestions and answering questions and I recommend this paper to be published in the present form. 

Reviewer 2 Report

Authors have addressed all issue raised in previous review.

Reviewer 3 Report

Now, the manuscript is acceptable