Lowering temperature of Cu sinter bonding under low-pressure in ambient air by in-situ generation and reduction of Cu₂O nanoparticles

Oba, Miwa; Matsuda, Tomoki; Dougakiuchi, Masashi; Okubo, Shio; Kambara, Makoto

doi:https://doi.org/10.1007/s10854-025-14352-7

Lowering temperature of Cu sinter bonding under low-pressure in ambient air by in-situ generation and reduction of Cu₂O nanoparticles

Oba, Miwa; Matsuda, Tomoki; Dougakiuchi, Masashi et al.

Journal of Materials Science: Materials in Electronics, 2025, 36(291)

Number of Access:449（2025-08-14 15:06 Counts）

Identifier to cite or link to this item: https://hdl.handle.net/11094/100256

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Title	Lowering temperature of Cu sinter bonding under low-pressure in ambient air by in-situ generation and reduction of Cu₂O nanoparticles
Creator	CreatorName Oba, Miwa
	NRID 1000030756333 1000030756333 ORCID 0000-0002-3978-0118 0000-0002-3978-0118 researchmap permalink tomokimatsuda tomokimatsuda Scopus Author ID 56430312900 56430312900 CreatorName Matsuda, Tomoki
	CreatorName Dougakiuchi, Masashi
	CreatorName Okubo, Shio
	NRID 1000080359661 1000080359661 researchmap permalink pme305 pme305 CreatorName Kambara, Makoto
Description	This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s10854-025-14352-7.
Abstract	Cu sinter bonding has emerged as a promising technology for highly reliable electronic packaging due to its low cost and excellent electrical and thermal conductivity. However, Cu particles are prone to oxidation, and their sinterability decreases significantly at lower temperatures, requiring high-pressure or controlled atmospheric conditions at elevated temperatures. This study investigated reducing the bonding temperature of Cu sinter bonding under low bonding pressure in ambient air by utilizing the in-situ oxidation and subsequent reduction of the Cu surface, leading to the formation of Cu nanoparticles. Slightly oxidized Cu particles were prepared through a plasma flash evaporation process under an Ar–H₂ plasma, followed by vacuum refrigeration. These particles were used to facilitate surface reactions with polyethylene glycol (PEG400) during the bonding process. We found that the prepared particles contributed to lowering the reduction temperature through the temporary formation of Cu₂O nanoparticles. These nanoparticles, precipitating above 160 °C from Cu complexed with PEG400, were subsequently reduced to Cu nanoparticles. The generated Cu nanoparticles acted as bridges among Cu fine particles, enhancing sinterability. Consequently, Cu–Cu sinter bonding was achieved at 220 °C under 0.3 MPa in ambient air, forming a sufficiently sintered Cu layer. This approach offers a pathway for low-temperature, low-pressure bonding suitable for industrial-scale applications.
Publisher	Springer Science and Business Media LLC
Source Title	Journal of Materials Science: Materials in Electronics
Volume (Issue)	36(291)
Date of Issued	2025-02-10
Language	English
Handle URL	https://hdl.handle.net/11094/100256
PISSN	09574522
eISSN	1573482X
Relation.isVersionOf	DOI (Publisher Version) https://doi.org/10.1007/s10854-025-14352-7
Access Rights	embargoed access
CopyRight	The full-text file will be made open to the public on 10 February 2026 in accordance with the publisher's policy.
oaire:version	Accepted Manuscript
Category	学術雑誌論文 Journal Article

Resource Type	journal article
Local Type	Journal Article
DCTERMS.bibliographicCitation	Journal of Materials Science: Materials in Electronics. 2025, 36(291)
DC.title	Lowering temperature of Cu sinter bonding under low-pressure in ambient air by in-situ generation and reduction of Cu₂O nanoparticles
DC.creator	Oba, Miwa
	Matsuda, Tomoki
	Dougakiuchi, Masashi
	Okubo, Shio
	Kambara, Makoto
DC.publisher	Springer Science and Business Media LLC
DC.language' scheme='DCTERMS.RFC1766	English
DCTERMS.issued' scheme='DCTERMS.W3CDTF	2025-02-10
DC.identifier	https://doi.org/10.1007/s10854-025-14352-7
DC.description	This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s10854-025-14352-7.
DCTERMS.abstract	Cu sinter bonding has emerged as a promising technology for highly reliable electronic packaging due to its low cost and excellent electrical and thermal conductivity. However, Cu particles are prone to oxidation, and their sinterability decreases significantly at lower temperatures, requiring high-pressure or controlled atmospheric conditions at elevated temperatures. This study investigated reducing the bonding temperature of Cu sinter bonding under low bonding pressure in ambient air by utilizing the in-situ oxidation and subsequent reduction of the Cu surface, leading to the formation of Cu nanoparticles. Slightly oxidized Cu particles were prepared through a plasma flash evaporation process under an Ar–H₂ plasma, followed by vacuum refrigeration. These particles were used to facilitate surface reactions with polyethylene glycol (PEG400) during the bonding process. We found that the prepared particles contributed to lowering the reduction temperature through the temporary formation of Cu₂O nanoparticles. These nanoparticles, precipitating above 160 °C from Cu complexed with PEG400, were subsequently reduced to Cu nanoparticles. The generated Cu nanoparticles acted as bridges among Cu fine particles, enhancing sinterability. Consequently, Cu–Cu sinter bonding was achieved at 220 °C under 0.3 MPa in ambient air, forming a sufficiently sintered Cu layer. This approach offers a pathway for low-temperature, low-pressure bonding suitable for industrial-scale applications.
DC.rights	The full-text file will be made open to the public on 10 February 2026 in accordance with the publisher's policy.
DC.format	100256
citation_title	Lowering temperature of Cu sinter bonding under low-pressure in ambient air by in-situ generation and reduction of Cu₂O nanoparticles
citation_author	Oba, Miwa
	Matsuda, Tomoki
	Dougakiuchi, Masashi
	Okubo, Shio
	Kambara, Makoto
citation_publisher	Springer Science and Business Media LLC
citation_language	English
citation_date	2025-02-10
citation_journal_title	Journal of Materials Science: Materials in Electronics
citation_volume	36
citation_issue	291
citation_doi	https://doi.org/10.1007/s10854-025-14352-7
citation_public_url	https://hdl.handle.net/11094/100256

Lowering temperature of Cu sinter bonding under low-pressure in ambient air by in-situ generation and reduction of Cu₂O nanoparticles

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