Controlling the Amount of Copper Formate Shells Surrounding Cu Flakes via Wet Method and Thermo-Compression Sinter Bonding between Cu Finishes in Air Using Flakes

Round 1

Reviewer 1 Report

1.    In section 2.4 Characterization, the authors have mentioned the test temperature and heating rate for the TG-DSC test, but they should also provide the test atmosphere, especially the oxygen content, which would affect the degree of oxidation. Without this information, the readers cannot judge whether the TG-DSC results are reliable and valid.

2. In section 3.1 Characteristics of Cu particles after surface treatment, the authors stated that “Before the surface treatment (Fig. 3(a)), the Cu particles exhibited a gradual weight increase from 156 °C owing to oxidation.” However, from Figure 3(a), this statement seems to be questionable. From the figure, it can be seen that the Cu particles had already started to oxidize before 156 °C, and the weight increase between 156 °C and 220 °C was not significant. The authors should describe more accurately the oxidation behavior of Cu particles at different temperatures, and provide corresponding explanations and analyses.
3. In section 3.1 Characteristics of Cu particles after surface treatment, the author mentioned that "The copper formate layer eventually decomposed at approximately 220 °C", but from Figure 3 (b), it can be seen that the actual complete decomposition temperature should be 250 °C. The authors explain the reasons for this bias.
4. In section 3.2 Bond-line microstructures, the authors stated that “sinter-bonding was achieved even by 1 min bonding, and the density in bond-line gradually increased with increasing time.” This statement needs to be supported by statistical data of density. The authors should provide the density values or density distribution maps at the bond-line, so that they can show more clearly the effect and mechanism of sinter-bonding.
5. In section 3.2 Bond-line microstructures, the authors stated that “When the bonding time was increased to 3 and 5 min, oxidation gradually advanced on the exposed Cu surfaces, but the degree of sintering by interdiffusion between Cu particles and between the Cu finish/Cu particle interfaces increased significantly, resulting in a gradual reduction in porosity at the bond line.”, but in Figure 4, the dashed lines blocked the pores at the bond line. The authors should redraw Figure 4, so that the pores at the bond line can be clearly observed and compared with other regions. This would make it more intuitive to show the change of porosity at the bond line.
6. In section 3.2 Bond-line microstructures, the authors stated that “The 3-min-bonding bond-line at 300 °C (Fig. 5(b)) presented a near-full-density microstructure, and the distribution of Cu oxide layers at interfaces between particles and at the Cu finish/Cu flakes interfaces were also observed.” They should provide more convincing data to illustrate the oxidation phenomenon of Cu. The authors should provide the detection of Cu oxide layer. This would make it more objective to evaluate the influence of Cu oxide layer on sinter-bonding performance.
7. In section 3.2 Bond-line microstructures, the authors stated that “In the subsequent 5-min-bonding bond line, the Cu oxide phase slightly expanded with the intensified oxidation of the particles.” They should add statistical data of oxide layer ratio to better illustrate the oxidation process. The authors should provide the oxide layer ratio at the 5-min-bonding bond line, and compare it with that at the 3-min-bonding bond line. This would make it clearer to show the trend of oxide layer expansion with increasing time.
8. The author should compare the strength with other copper pastes(such as IEEE TRANSACTIONS ON POWER ELECTRONICS, 2022, 37(2), Journal of Materials Research and Technology , 2022, 18: 859-871, Applied Surface Science 603 (2022) 154422), composite copper pastes (such as, Journal of Materials Science & Technology, 145 (2023) 56–65, Contents lists available, copper films (IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, 2023, 13(6)), etc. to reflect the advantages of this article.

No

Author Response

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled, “Controlling the amount of copper formate shells surrounding Cu flakes by wet method and thermo-compression sinter-bonding between Cu finishes in air using flakes” to Metals. We appreciate the time and effort dedicated by the reviewers and the editor toward evaluating this manuscript and providing valuable feedback. We are also grateful to the reviewers and editor for thoughtful and insightful comments. We carried out additional experiments and analyses to address the comments of reviewers. Also, we revised the manuscript according to the suggestions provided by the reviewers, and the changes are marked in red.

I am including a list of changes. For reasons of clarity, the reviewers’ comments are written in italics, and responses to the reviewers’ comments are highlighted in blue. Please contact me if you need further information. Thank you very much.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled "Controlling the Amount of Copper Formate Shells Surround- 2 ing Cu Flakes by Wet Method and Thermo-Compression Sin- 3 ter-Bonding between Cu Finishes in Air Using Flakes" is presenting new results and convincing experimental data. In the Fig. 5, 5d description is missing from the figure caption. 

Author Response

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled, “Controlling the amount of copper formate shells surrounding Cu flakes by wet method and thermo-compression sinter-bonding between Cu finishes in air using flakes” to Metals. We appreciate the time and effort dedicated by the reviewers and the editor toward evaluating this manuscript and providing valuable feedback. We are also grateful to the reviewers and editor for thoughtful and insightful comments. We carried out additional experiments and analyses to address the comments of reviewers. Also, we revised the manuscript according to the suggestions provided by the reviewers, and the changes are marked in red.

I am including a list of changes. For reasons of clarity, the reviewers’ comments are written in italics, and responses to the reviewers’ comments are highlighted in blue. Please contact me if you need further information. Thank you very much.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Editor of Metals

Greetings

The paper entitled; "Controlling the Amount of Copper Formate Shells Surrounding Cu Flakes by Wet Method and Thermo-Compression Sinter-Bonding between Cu Finishes in Air Using Flakes” is an interesting article that contains exciting experimental and applicable results. Therefore, it can be accepted in your valuable journal after doing some minor revisions which can be summarized as the followings:

1.     The authors did not mention the novelty of their work. Thus, the novelty of this work should be clearly discussed.

2.     The language must be reviewed

3.     It is preferable to write the conclusion better and clearerMinor editing of English language required

Author Response

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled, “Controlling the amount of copper formate shells surrounding Cu flakes by wet method and thermo-compression sinter-bonding between Cu finishes in air using flakes” to Metals. We appreciate the time and effort dedicated by the reviewers and the editor toward evaluating this manuscript and providing valuable feedback. We are also grateful to the reviewers and editor for thoughtful and insightful comments. We carried out additional experiments and analyses to address the comments of reviewers. Also, we revised the manuscript according to the suggestions provided by the reviewers, and the changes are marked in red.

I am including a list of changes. For reasons of clarity, the reviewers’ comments are written in italics, and responses to the reviewers’ comments are highlighted in blue. Please contact me if you need further information. Thank you very much.

Author Response File: Author Response.pdf

Reviewer 4 Report

- It is strongly recommended that the authors provide the necessary explanations for each of the references and avoid providing multiple references for the same sentence.

- It is recommended that the authors add pictures related to the experimental work and sample preparation in the article.

- The authors have explained in the article that: "While the XRD results in Fig. 1(a) indicate only pure Cu peaks .........". Please check the results in Figure 1 again.

- The explanation provided for Figure 6 is not enough and it is not possible to understand the shear strength of the connections well. Please improve your explanation and interpretation.

- It is recommended that the authors make a connection between the microstructure of the connections and their shear strength and interpret the results of the shear strength with the microstructure.

Moderate editing of English language required

Author Response

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled, “Controlling the amount of copper formate shells surrounding Cu flakes by wet method and thermo-compression sinter-bonding between Cu finishes in air using flakes” to Metals. We appreciate the time and effort dedicated by the reviewers and the editor toward evaluating this manuscript and providing valuable feedback. We are also grateful to the reviewers and editor for thoughtful and insightful comments. We carried out additional experiments and analyses to address the comments of reviewers. Also, we revised the manuscript according to the suggestions provided by the reviewers, and the changes are marked in red.

I am including a list of changes. For reasons of clarity, the reviewers’ comments are written in italics, and responses to the reviewers’ comments are highlighted in blue. Please contact me if you need further information. Thank you very much.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

The manuscript can be accepted in the present form.