Nano-Structured Cu/W Brazing Fillers for Advanced Joining Applications

Moszner, Frank; Cancellieri, Claudia; Becker, Christoph; Chiodi, Mirco; Janczak‐Rusch, Jolanta; Jeurgens, Lars P. H.

doi:10.17265/2161-6221/2016.9-10.003

Cited by 9 publications

(7 citation statements)

References 19 publications

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“…Our research team envisages another class of nanostructured filler materials, namely, hybrid nanolaminates, for selective bonding at reduced temperatures, which may tackle some of the aforementioned limitations of emerging nano-joining methods. ,,− The nanolaminates (also referred to as nanomultilayers; NMLs) are composed of a stack of alternating nanolayers (NLs) of a metal or an alloy ( here : eutectic Ag–Cu 40at.% ) and a chemically inert barrier material (a nitride, oxide, or refractory metal; here AlN). Such hybrid NML systems can be easily produced as a coating or as a foil by (reactive) magnetron sputtering with accurate control of the NL thickness, modulation periodicity, chemical composition, in-plane texture, and growth stress ,,, Figure a,b show cross-sectional and planar scanning electron microscopy (SEM) micrographs of the type of hybrid nanolaminate addressed in the present study, which is composed of alternating NLs of an Ag–Cu 40at.% alloy and an AlN barrier.…”

Section: Introductionmentioning

confidence: 99%

Tailoring Fast Directional Mass Transport of Nano-Confined Ag–Cu Alloys upon Heating: Effect of the AlN Barrier Thickness

Araullo‐Peters

Cancellieri

Chiodi

et al. 2019

ACS Appl. Mater. Interfaces

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This study addresses the phase stability and atomic mobility of Ag–Cu40at.% nano-alloys confined by AlN in a nanomultilayered configuration during thermal treatment. To this end, nanomultilayers (NMLs) with a fixed Ag–Cu40at.% nanolayer thickness of 8 nm and a AlN barrier nanolayer with variable thickness of 4, 8, or 10 nm were deposited by magnetron sputtering on sapphire substrates and subsequently isothermally annealed for 5 or 20 min in air in the range of 200–500 °C. The microstructure of the as-deposited and heat-treated NMLs was analyzed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. Annealing of the thicker AlN barrier layers at T > 300 °C leads to the formation of an interconnected network of line-shaped Cu(O) protrusions on the annealed NML surface. The well-defined outflow pattern of Cu(O) originates from the thermally induced surface cracking of the top AlN barriers with subsequent fast mass transport of Cu along the Cu/AlN interfaces toward the surface cracks. The thinnest (i.e., 4 nm thick) AlN barrier layers exhibit a relatively open grain boundary structure and act as nanoporous membranes upon heating, resulting in the formation of a dense and homogenous distribution of Cu(O) and Ag droplets on the NML surface. These findings demonstrate that the microstructure (i.e., layer thicknesses, interface coherency, and texture) of hybrid nanolaminates can be tuned to provide defined pathways for fast, directional transport of the confined metal to the surface at relatively low temperatures, which might open new routes for low-temperature bonding of micro- and nano-scaled systems.

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Section: Introductionmentioning

confidence: 99%

Tailoring Fast Directional Mass Transport of Nano-Confined Ag–Cu Alloys upon Heating: Effect of the AlN Barrier Thickness

Araullo‐Peters

Cancellieri

Chiodi

et al. 2019

ACS Appl. Mater. Interfaces

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“…Actually, such size-dependent materials stabilities are known to be vital to the high performance and long-term service of a wide range of nanotechnologies. On one hand, the intrinsically higher mobility of electrons (holes) and/or ions (ion vacancies) in the metastable nanostructured systems can be exploited for high performance electronic devices and device integration at lower temperatures. , On the other hand, stable thin films and multilayered microstructures can be utilized to achieve smooth optical/electrical response and extended device lifetimes. , A fundamental understanding and engineering know-how of mass transport phenomena in metal/ceramic thin films and NMLs is needed to adjust their optical performances and electrical conductivities for photonics or electronics applications.…”

Section: Introductionmentioning

confidence: 99%

Maskless Patterning of Metal Outflow in Alternating Metal/Ceramic Multiple Nanolayers by Femtosecond Laser Irradiation

et al. 2019

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In this work, solid-state metal transport from internal metal nanolayers onto the surface of metal/ceramic nanomultilayers (NMLs) has been directed in a controlled way by femtosecond (fs) laser irradiation and subsequent low-temperature thermal annealing. Laser-irradiation-induced modifications of the NML microstructures and stress states can be limited within the first few top nanolayers due to the focused laser energy input at the metal/ceramic interface by exploiting the local plasmonic effect. Accompanied laser peening can further refine the crystallites and introduce compressive stress at the laser-irradiated region, which reduces the activation energies for vacancy formation and migration of metal atoms in the nanoconfinement. Patterned Cu surface nanostructures (outflow) appear selectively along the laser path after air annealing at temperatures down to 360 °C. For the solid-state diffusion of Cu in confinement, in-plane metal transport along the Cu–AlN interfaces is much faster than the outward short-circuit diffusion of Cu across the AlN barrier layers. Localized metal outflow is accompanied by the collapse and sintering of the remaining AlN barrier layers, under the influence of the acting capillary forces, which may further accelerate the metal transport. This laser-induced maskless patterning of metal outflow is applicable not only in Cu/AlN NMLs but also in Ag/AlN NMLs, assisted by subsequent low-temperature annealing.

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“…A more extensively studied system is the Cu/W NML, where W serves as the diffusion barrier between the Cu layers. With the use of this multilayer, the formation of a joint similar to the mechanism of a diffusion bonding was observed at 750°C [28]. The study of its thermal behaviour revealed the degradation of the multilayer structure, transforming into a spheroidised nanocomposite at 700°C [29].…”

Section: Introductionmentioning

confidence: 86%

Synthesis, characterisation and thermal behaviour of Cu-based nano-multilayer

et al. 2020

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Cu/AlN–Al2O3 nano-multilayer (NML) was deposited by magnetron sputtering method on 42CrMo4 steel samples, starting with a 15 nm AlN–Al2O3 layer and followed by 200 alternating layers of 5 nm thick Cu and 5 nm thick AlN–Al2O3 layers. The microstructure and thermal behaviour of the as-deposited and heat-treated multilayer was studied. Starting from about 400 °C, extensive coarsening of Cu nanocrystallites and the migration of Cu within the multilayer were observed via solid-state diffusion. Part of the initial Cu even formed micron-sized reservoirs within the NML. Due to increased temperature and to the different heat expansion coefficients of Cu and the AlN–Al2O3, the latter cracked and Cu appeared on the top surface of the NML at around 250 °C. Below 900 °C, the transport of Cu to the top surface of the NML probably took place as a solid-state flow, leading to faceted copper micro-crystals. However, above 900 °C, the Cu micro-crystals found on the top of the NML have rounded shape, so they were probably formed by pre-melting of nano-layered Cu due to its high specific surface area in the NML. Even if the Cu crystals appear on the top surface of the NML via solid-state flow without pre-melting, the Cu crystals on the top surface of the NML can be potentially used in joining applications at and above 250 °C.

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Nano-Structured Cu/W Brazing Fillers for Advanced Joining Applications

Cited by 9 publications

References 19 publications

Tailoring Fast Directional Mass Transport of Nano-Confined Ag–Cu Alloys upon Heating: Effect of the AlN Barrier Thickness

Tailoring Fast Directional Mass Transport of Nano-Confined Ag–Cu Alloys upon Heating: Effect of the AlN Barrier Thickness

Maskless Patterning of Metal Outflow in Alternating Metal/Ceramic Multiple Nanolayers by Femtosecond Laser Irradiation

Synthesis, characterisation and thermal behaviour of Cu-based nano-multilayer

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