Influence of Cylindrical Cells Surface Cleaning by Means of Laser Ablation on Wedge Wire Bonding Process

Round 1

Reviewer 1 Report

The paper is devoted to improving the properties of the surface for forming a wire connection. The authors use a laser marker to clean the surface and remove surface contaminants. The authors show the effect of laser cleaning modes on the mechanical properties of wire bonding. In this work, detailed studies of the formed wire connection using electron microscopy and elemental analysis are carried out. 

However, for greater clarity and versatility of perception, instead of percentages in the value of the power of the laser setup, it is recommended to write the value of the energy density at which the cleaning process took place, or at least the average power. This will allow you to understand the mechanisms of laser cleaning and navigate the choice of laser systems for such tasks. The paper can be published in its current form.

Author Response

Thank you for reviewing our paper. We are very pleased that you found it interesting.

In regards to your recommendation:

"However, for greater clarity and versatility of perception, instead of percentages in the value of the power of the laser setup, it is recommended to write the value of the energy density at which the cleaning process took place, or at least the average power. This will allow you to understand the mechanisms of laser cleaning and navigate the choice of laser systems for such tasks. The paper can be published in its current form."

Response: Since the percentages are the value set on the machine we would like to keep this unchanged. It is not really clearly specified by the machine / software manufacturer how the power in watts is influenced by this parameter (if it’s average power or the peak power). We believe this is more true to the factual trials conducted in this research.

Reviewer 2 Report

The paper considers an interesting topic. It presents an experimental study and attempts to clear some knowledge gaps in ultrasonic bonding and hat certainly a high scientific value. The study is correctly designed and technically sound. The article is without doubt interesting for the readers and certainly fulfills the aims and scope of the journal.
The introduction provides general explanation of the technological problem and address the scientific topic, namely the limited studies on surface cleaning of nickel plated steel used for cylindrical battery shell production in the aluminum wire bonding process. Although, the last paragraph in the introduction is not really completed. Please specify here the scientific problem more precisely. Also, it is advisable to explain your methodological approach accordingly.
Section 2 presents the materials used in the study, the welding equipment and parameters, followed by laser clearing equipment and parameters, the preparation of cross section samples as well as the equipment used for SEM and EDS. At the end of this section an explanation of the shear test is given. The methodological approach is consistent. However, some details concerning the laser cleaning process, i.e. the process parameter, are missing or imprecise. The abbreviation “TC” is not denoted and the impulse frequency is not specified. Please check also the consistency of data (lens size, focus, pulse duration, frequency and travel speed) for all three (four? 0%?) power sets and clearly state if they were kept unchanged in all three tests sets (20%, 40% and 80%). It is advisable here to present additionally the impulse spots in a proper magnification. Also, please check if the pictures on fig. 1 and 3 are not already published, otherwise please refer them.     
In section 3 the results from investigation of the substrate surface using light microscopy, SEM and EDS subsequently, followed by SEM and EDS examination of the weld cross section and finally the results from shear tests. Already at the first investigation the experiments with 20% power set are assumed as irrelevant and correctly excluded from the study. Although the quality of the images from SEM and EDS is not perfect, they achieve the essence of the results.
As reader, I find the denotation 0% instead uncleaned really unattractive to nasty.
It could be useful to denote the non-cleaned and cleaned areas on fig. 6 to 8. Also the scale on these pictures is not really visible. The SEM and EDS investigations indicate that the both set of power (40% and 80%) ensure a high quality of the joint. Although, by the 40% contrary to 80% samples some voids on the material interface are observed. On this place it is advisable to mark the voids, e.g. with arrows and probably quantify them if applicable (check lines 190-192). The shear test shows an obvious improvement in weld seam strength after cleaning.
In the last section the conclusions are well supported by the results and discussions. It is only a suggestion to limit the conclusions to the considered ultrasonic joining process parameters. It could also be advantageous to specify the power in watts instead of in percent.

Author Response

Thank you for reviewing our article. Your input was very helpful in inproving the quality of the presented paper and most of your recommendations have been inplemented. 

In regards to your feedback:

"Although, the last paragraph in the introduction is not really completed. Please specify here the scientific problem more precisely. Also, it is advisable to explain your methodological approach accordingly."

Response: Thank you for this remark. This paragraph indeed seamed to end without proper conclusion and has been expanded by posing a question about feasibility of laser cleaning using low cost, multi-purpose laser marker to conduct the laser cleaning of battery cells.

"However, some details concerning the laser cleaning process, i.e. the process parameter, are missing or imprecise. The abbreviation “TC” is not denoted and the impulse frequency is not specified."

Response: The abbreviation “TC” has not been clearly specified by the software manufacturer and therefore we would not like to assume its meaning. Impulse frequency parameter has been added to the table.

"Please check also the consistency of data (lens size, focus, pulse duration, frequency and travel speed) for all three (four? 0%?) power sets and clearly state if they were kept unchanged in all three tests sets (20%, 40% and 80%). It is advisable here to present additionally the impulse spots in a proper magnification."

Response: Parameters of lens size and laser source switching frequency has been added to the tables. Methodology of sample collection has been clarified – samples were laser cleaned and the immediately wire bonded (within one minute) on the adjacent wire bonder. Samples were prepared in one go, without change to cleaning area location in relation to the laser source or the focus height.

"Also, please check if the pictures on fig. 1 and 3 are not already published, otherwise please refer them."

Response: This has been verified and indeed figure 2 (b) has been used in one of the previous articles. Proper reference has been added to that figure.

"As reader, I find the denotation 0% instead uncleaned really unattractive to nasty."

Response: This has been changed in the text and figure titles.

"It could be useful to denote the non-cleaned and cleaned areas on fig. 6 to 8. Also the scale on these pictures is not really visible."

Response: The scale has been enlarged. For 40 % and 80% cleaned sample the areas have been marked.

"On this place it is advisable to mark the voids, e.g. with arrows and probably quantify them if applicable (check lines 190-192)."

Response: Since the voids vary throughout the samples we tried showcasing areas more affected by the cleaning process / with more defects. Due to this fact we would like to remain with more qualitive analysis of those areas.

"It is only a suggestion to limit the conclusions to the considered ultrasonic joining process parameters."

Response: This has been corrected.

"It could also be advantageous to specify the power in watts instead of in percent."

Response: Since the percentages are the value set on the machine we would like to keep this unchanged. It is not really clearly specified by the machine / software manufacturer how the power in watts is influenced by this parameter (if it’s average power or the peak power). We believe this is more true to the factual trials conducted in this research.