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This study investigates the use of nanocrystalline Cu (NC-Cu) to suppress interfacial voids in low-temperature Cu-Cu bonding for 3D IC packaging. We quantitatively compared the void characteristics of electrodeposited NC-Cu (grain size ~89.3 nm) and (111)-oriented nanotwinned Cu (NT-Cu, ~621.8 nm) bonded at 200 °C. Plan-view STEM-HAADF analysis revealed that NC-Cu achieved a much lower void area ratio (1.8%) than NT-Cu (4.0%), attributed to its high grain boundary density, which enhances atomic diffusion and grain boundary migration. At 250 °C, typical Ostwald ripening was observed, with fewer but larger voids. However, a rise in total void area fraction suggests a competing mechanism-possibly new void nucleation at grain boundaries triggered by residual defects from the electroplating process. These results highlight the superior void-mitigating capability of NC-Cu under low thermal budgets.
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http://dx.doi.org/10.3390/ma18163725 | DOI Listing |
ACS Omega
September 2025
Materials and Manufacturing Directorate, AFRL/RXEE, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433, United States.
This study addresses a critical limitation in direct bonded copper (DBC) materials used in power electronics by introducing a copper-zirconium (Cu/Zr) alloy interposing layer at the copper-ceramic interface. This novel design aims to mitigate mechanical stress induced by mismatched material properties, such as the coefficient of thermal expansion (CTE) and elastic modulus, during thermal cycling. The key findings of this study are (1) thermal fatigue improvement: Test samples with the Cu/Zr interface layer (Cu-Cu/Zr-AlN) three times enhanced thermal fatigue resistance, surviving 30 thermal cycles from -55 to 300 °C before delamination, while standard DBC substrates without the Cu/Zr layer failed after just 10 cycles, indicating a performance improvement with the Cu/Zr alloy, (2) durability projections: Based on the Coffin-Manson model, if the upper temperature is capped at 150 °C, the Cu-Cu/Zr-AlN substrates are projected to survive approximately 1372 cycles, underscoring their potential for long-term reliability, and (3) stress mitigation: The Cu/Zr alloy layer bridges the CTE disparity between copper and ceramic, reducing mechanical stress and improving structural integrity across a broad temperature range (-55 to 300 °C).
View Article and Find Full Text PDFNanoscale Adv
August 2025
Department of Physics, Jeonbuk National University Jeonju 54896 Republic of Korea
The chemical and atomic structures of Cu-, Ni-, or CuNi-embedded MXene (TiCT , T = O or OH) nanosheet catalysts are examined by using various characterization methods to demonstrate the chemical origin of their composition-dependent evolution. The results of combined X-ray spectroscopy studies and the electrochemical test reveal that Cu ions in (Cu or CuNi):MXene remain active having a +1 valence and form metallic Cu-Cu bonds to enhance the catalytic activity for nitrate reduction. By contrast, Ni ions in (Ni or CuNi):MXene tend to remain bound to O as in NiO staying inactive, and, furthermore, hinder the catalytic activity of Cu when co-doped on MXene.
View Article and Find Full Text PDFLangmuir
August 2025
Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan.
Cyanoacrylate-based instant adhesives, commonly known as super glues, are widely used across various fields owing to their high adhesive performance and rapid curing. However, the molecular-level understanding of their interfacial bonding mechanism remains limited. In this study, we investigated the adhesion behavior of ethyl cyanoacrylate (ECA) on typical inorganic surfaces such as Au, Cu, CuO, AlO, and SiO using periodic density functional theory (DFT) calculations.
View Article and Find Full Text PDFMaterials (Basel)
August 2025
Institute of Pioneer Semiconductor Innovation, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan.
This study investigates the use of nanocrystalline Cu (NC-Cu) to suppress interfacial voids in low-temperature Cu-Cu bonding for 3D IC packaging. We quantitatively compared the void characteristics of electrodeposited NC-Cu (grain size ~89.3 nm) and (111)-oriented nanotwinned Cu (NT-Cu, ~621.
View Article and Find Full Text PDFSci Rep
August 2025
Department of Chemical and Materials Engineering, National Central University, No. 300, Zhongda Rd., Zhongli District, Taoyuan City, 32001, Taiwan, ROC.
Cu-Cu direct bonding using electroplated ultrafine-grain Cu (107.24 nm) was studied in air at 110-150 °C. Unstable grain boundaries enabled ultrafast grain growth across the bonding interface, analyzed via coincidence site lattice (CSL) boundaries using EBSD.
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