Enhanced copper micro/nano-particle mixed paste sintered at low temperature for 3D interconnects

Dai, Yuan; Ng, Mei Zhen; Anantha, P Chandrakasan; Lin, Yiding; Li, Z. G.; Gan, Chee Lip; Tan, Chuan Seng

doi:10.1063/1.4954966

Cited by 44 publications

(15 citation statements)

References 27 publications

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“…In fact, such crack propagation was observed for the Cu films prepared from AEP–Cu NPs and AB–Cu NPs after the environmental stability experiments. In contrast, the mixing of micrometer‐sized Cu particles with nanometer‐sized Cu NPs in the composite ink could prevent the sintered Cu film from cracking and improved the packing density . As a result, the sintered Cu film from the composite ink showed high stability even after storage in the humid environment.…”

Section: Resultsmentioning

confidence: 99%

“…More recently, besides low‐temperature sintering of Cu‐based inks, ensuring the durability of sintered Cu films to safeguard their environmental stability and mechanical flexibility has become the most important task from a practical standpoint . The mechanical properties of sintered Cu films on flexible substrates are an important factor of their practical application to flexible devices.…”

Section: Introductionmentioning

confidence: 99%

“…The mechanical properties of sintered Cu films on flexible substrates are an important factor of their practical application to flexible devices. Unfortunately, nanoparticle‐based inks cause many problems regarding mechanical cracking in the joints of sintered nanoparticle films, which result in low durability of sintered copper films under repetitive bending. Some approaches have been proposed to increase the mechanical durability of the sintered copper film by mixing other fillers such as carbon nanotubes (CNTs) and nanowires (NWs) .…”

Section: Introductionmentioning

confidence: 99%

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Contribution of Ligand Oxidation Products to High Durability of Copper Films Prepared from Low‐Sintering‐Temperature Copper Ink on Polymer Substrates

2017

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In electronic printing, ensuring high durability of sintered copper films on flexible substrates to obtain environmental stability and mechanical flexibility has become the most important task from a practical standpoint. In the study reported here, the authors develop solution synthesis of 2‐amino‐2‐ethyl‐1,3‐propanediol (AEP)‐protected copper nanoparticles (AEP–Cu NPs) with sizes of 3–8 nm in ethylene glycol, where the Cu NPs are stabilized via the metallacyclic coordination stability of the AEP ligands. The sintered Cu film exhibits a resistivity of 50 μΩ cm−1 after heating at 150 °C under a nitrogen atmosphere. Most importantly, the resulting Cu films on the polyethylene terephthalate (PET) substrates show excellent durability in terms of bending and adhesion without requiring any additives like nanotubes and nanowires. Furthermore, the authors successfully demonstrated the high environmental stability of the resulting Cu film even after it is exposed to harsh environmental conditions (RH 80%, 60 °C) for 1 month. The environmental durability is further improved by utilizing a composite ink of AEP–Cu NPs with copper microflakes. It is experimentally proven that oxidation products from AEP ligands originating in the sintering process contributed to the high durability of sintered copper films on flexible substrates.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Contribution of Ligand Oxidation Products to High Durability of Copper Films Prepared from Low‐Sintering‐Temperature Copper Ink on Polymer Substrates

2017

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“…The influences of the ink solvent, the solid fraction of the ink, the drying treatment, and the sintering parameters affect the crack formation. Dai et al reported a mixed paste of Cu micro- and nanoparticles to prevent cracking and achieved an improved packing density [ 123 ]. The particle mixture of two different sizes reduced the porosity of the micro-paste and resolved the cracking issue in the nano-paste.…”

Section: Formulation Designs In Cu-based Mixed Inks/pastesmentioning

confidence: 99%

Surface and Interface Designs in Copper-Based Conductive Inks for Printed/Flexible Electronics

Tomotoshi

Kawasaki

2020

Nanomaterials

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Silver (Ag), gold (Au), and copper (Cu) have been utilized as metals for fabricating metal-based inks/pastes for printed/flexible electronics. Among them, Cu is the most promising candidate for metal-based inks/pastes. Cu has high intrinsic electrical/thermal conductivity, which is more cost-effective and abundant, as compared to Ag. Moreover, the migration tendency of Cu is less than that of Ag. Thus, recently, Cu-based inks/pastes have gained increasing attention as conductive inks/pastes for printed/flexible electronics. However, the disadvantages of Cu-based inks/pastes are their instability against oxidation under an ambient condition and tendency to form insulating layers of Cu oxide, such as cuprous oxide (Cu2O) and cupric oxide (CuO). The formation of the Cu oxidation causes a low conductivity in sintered Cu films and interferes with the sintering of Cu particles. In this review, we summarize the surface and interface designs for Cu-based conductive inks/pastes, in which the strategies for the oxidation resistance of Cu and low-temperature sintering are applied to produce highly conductive Cu patterns/electrodes on flexible substrates. First, we classify the Cu-based inks/pastes and briefly describe the surface oxidation behaviors of Cu. Next, we describe various surface control approaches for Cu-based inks/pastes to achieve both the oxidation resistance and low-temperature sintering to produce highly conductive Cu patterns/electrodes on flexible substrates. These surface control approaches include surface designs by polymers, small ligands, core-shell structures, and surface activation. Recently developed Cu-based mixed inks/pastes are also described, and the synergy effect in the mixed inks/pastes offers improved performances compared with the single use of each component. Finally, we offer our perspectives on Cu-based inks/pastes for future efforts.

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“…Current additive manufacturing technologies, such as inkjet printing, microextrusion, and powder bed fusion are hardly optimized for high‐resolution (smaller than 30 µm) printing of common metals with a high melting point such as copper, gold, and platinum. Therefore, metal nanoparticle inks and pastes have been used for manufacturing of functional and flexible devices in complex shapes. However, the geometry and properties of printed objects are constrained by the liquid wetting or porosity caused by the postprinting thermal sintering step.…”

mentioning

confidence: 99%

Printing Functional 3D Microdevices by Laser‐Induced Forward Transfer

Luo

Pohl

et al. 2016

Small

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Slender, out-of-plane metal microdevices are made in a new spatial domain, by using laser-induced forward transfer (LIFT) of metals. Here, a thermocouple with a thickness of 10 µm and a height of 250 µm, consisting of platinum and gold pillars is demonstrated. Multimaterial LIFT enables manufacturing in the micrometer to millimeter range, i.e., between lithography and other 3D printing technologies.

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Enhanced copper micro/nano-particle mixed paste sintered at low temperature for 3D interconnects

Cited by 44 publications

References 27 publications

Contribution of Ligand Oxidation Products to High Durability of Copper Films Prepared from Low‐Sintering‐Temperature Copper Ink on Polymer Substrates

Contribution of Ligand Oxidation Products to High Durability of Copper Films Prepared from Low‐Sintering‐Temperature Copper Ink on Polymer Substrates

Surface and Interface Designs in Copper-Based Conductive Inks for Printed/Flexible Electronics

Printing Functional 3D Microdevices by Laser‐Induced Forward Transfer

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