【公開日：2024.10.22】【最終更新日：2024.10.22】
課題データ / Project Data
課題番号 / Project Issue Number
22KU0046
利用課題名 / Title
In-situ high voltage transmission electron microscope study of the intermetallic compounds (IMCs) formed between Ga-based alloys and Cu-based substrates.
利用した実施機関 / Support Institute
九州大学 / Kyushu Univ.
機関外・機関内の利用 / External or Internal Use
外部利用/External Use
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）マテリアルの高度循環のための技術/Advanced materials recycling technologies（副 / Sub）次世代ナノスケールマテリアル/Next-generation nanoscale materials
キーワード / Keywords
Low temperature solder, Gallium, intermetallic compounds (IMCs), transmission electron microscopy
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
Kazuhiro Nogita
所属名 / Affiliation
The University of Queensland Mechanical and Mining Engineering
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
Xin Fu Tan,Qichao Hao
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
Kazuhiro Yasuda,Hiroshi Maeno
利用形態 / Support Type
（主 / Main）技術補助/Technical Assistance（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
The requirement to reduce soldering
temperature for lower power consumption, lower costs and environmental friendly
processing has attracted wide attention among the electrical packaging
industry. To decrease the soldering temperature, liquid Ga is a promising
candidate due to its near room temperature melting point of 29.76℃ and
non-toxic property. Liquid Ga can react with the Cu substrate to form a solid
solder joint by forming intermetallic compounds like CuGa2 and Cu9Ga4
with solidus temperatures of 254℃ and 466℃ . However, the formation of
intermetallic compounds (IMCs) between Ga with Cu substrate, which is
conventional substrate in electronic devices, is slow limiting the application
of Ga based soler alloys. This research proposed a new method for accelerating
the formation of the IMCs layer by electrically plating a layer of Ag on the Cu
based substrate. The results show that the IMCs layer is much thicker after
introducing an Ag layer compared to pure Cu based substrate. Therefore, this
method is worth detailed investigation of both morphology and phases of the
IMCs layer and to check the stability of these IMCs. These can provide
information the further improvement.
Therefore,
the aims of this experiment are:
・ To study the morphology of phases
at the substrate interface and to identify the phases formed between GaSn or Ga
and the substrate when a layer of electrically plated Ag is present between the
solder and the substrate.
・ To study the morphology change
of the IMCs during heating from 30℃ to 260℃ (20℃ every step).
・ To study the diffraction
patterns of the IMCs phases from 30℃ to 260℃ (20℃ every step).
実験 / Experimental
1.1 Sample fabrication:The intermetallic joints between couples of Ga/Cu(Ag plated), Ga13.5
wt%Sn/Cu(Ag plated) and Ga/Cu6Ni(Ag plated) were fabricated at 150ºC for 2h.
The excess Ga/Ga13.5%Sn were removed by 10% HCl. The samples were mounted in
resin and polished before a focused ion beam (FIB) technique was used for
preparing the high voltage transmission electron microscopy (HV-TEM) lamellar
samples. All FIB samples’ thickness is controlled as 500nm.The Sample 1 and Sample 2：
Sample 1 and Samples 2 are Ga13.5wt%Sn/Cu(Ag), and the interface
between the substrate and the IMC layer were selected for preparing the TEM
samples (Fig.1).
Sample 3
Sample 3 is Ga/Cu(Ag), and the interface between the substrate and
the IMC layer was selected for preparing the TEM sample (Fig.2).
Sample 4 and Sample 5:Sample 4 and Sample 5 were cut from the
Ga/Cu6Ni(Ag) interface at two different areas. Sample 4 is from the edge
reaction area where Ga was fully consumed during the reaction with the
substrate, and Sample 5 is from an area with excess Ga (Fig.3).
1.2 In-situ heating high voltage
transmission electron microscopy (HV-TEM)The samples were placed on a heating TEM holder. Sample 1 of Ga13.5wt%Sn/Cu(Ag),
Sample 3 of Ga/Cu(Ag), and Sample 5 of Ga/Cu6Ni(Ag) were heated from 30℃ to
200 ℃. Images and diffraction patterns were taken every 20℃. The
microstructure and diffraction patterns of Sample 2 Ga13.5wt%Sn/Cu(Ag) and
Sample 4 of Ga/Cu6Ni(Ag) were checked at room temperature before and after
heating to 200℃.
結果と考察 / Results and Discussion
The researchers conducted experiments by taking images and
diffraction patterns of the interface of the samples at different temperatures
ranging from 30 ℃ to 200 ℃ with a 20℃ interval. The Ga/Cu(Ag) couple was the easiest system for these experiments
and it consists of three main layers: Cu substrate, Cu-rich IMC layer, and
Ag-rich IMC layer (Fig.4). It was confirmed that all plated Ag had reacted and
formed a layer of IMCs above the Cu-rich IMC layer, and this Ag IMCs layer
appeared to be more porous than the Cu-rich IMC layer.
As the heating began, each IMC layer was observed to examine changes
in morphology and phase transformation. It was found that the morphology of the
phases remained relatively stable before the temperature reached 160 ℃. Fig.4
illustrates the morphology of the whole Sample 3 Ga/Cu(Ag) at different
temperatures, including 40℃, 140 ℃, at the beginning of 160℃, holding at
160℃ for a while, at the beginning of 180℃, and holding at 180 ℃ for a
while. The IMC layer near the Cu substrate side remained stable before 160℃,
and the Cu9Ga4 layer began to grow at 160℃ between the
Cu substrate and the IMC layer interface. At 180℃, the Cu9Ga4
layer at the interface between the Cu-rich IMC layer continued to grow, and the
morphology of the Ag-rich IMC layer also changed. It was observed that some
Ag-rich IMCs appeared to have dissolved, leaving thin film areas like cavities.
For the Cu6Ni(Ag)/Ga sample, the same
phenomenon was observed at 160℃, that the Cu9Ga4 IMC
layer at the interface began to grow significantly and Ag IMCs dissolved when
temperature is high (Fig.5).
The phase transformation phenomenon was
also found for the Ga13.5wt%Sn/Cu(Ag) system. After introducing Sn into the
system, the composition of the IMCs become more complicated and further EDS and
XRD experiments will be combined with these HV-TEM results to confirm the phases.
図・表・数式 / Figures, Tables and Equations
Fig.1 Sample 1 and Sample 2 of Ga13.5wt%Sn /Cu(Ag) 150ºC 2h.
Fig.2 Sample 3 of Ga/Cu(Ag) 150ºC 2h.
Fig.3 Sample 4 and Sample 5 of Ga/Cu6Ni(Ag) 15º0C 2h.
Fig.4 Morphology change of Sample 3 of Ga/Cu (Ag).
Fig.5 Morphology change of Sample 5 of Ga/Cu6Ni (Ag).
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
Funding: This work was supported by The University of Queensland, Australia [Knowledge Exchange & Translation fund 2021002690]; Nihon Superior Co., Ltd, Japan [2016001895, 2021002341]; Australian Research Council, Australia [LP180100595]; and Walter and Eliza Hall Travelling Scholarship.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件