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• Interfacial reactions at Sn-3.0Ag-0.5Cu/thin-Au/Pd/Ni(P) solder joints were probed. • Effects of Pd layer structure on these reactions probed for various reflow times. • P in the Pd layer strongly affected interfacial reactions during reflow. • Pd layer structure affected interfacial reactions and microstructure evolution. Herein, we investigated the interfacial reactions of crystalline Pd (pure Pd) and amorphous Pd (Pd(P)) layers in thin electroless-Ni electroless-Pd immersion-Au (thin-ENEPIG) surface-finished printed circuit board with Sn-3.0Ag-0.5Cu (SAC305) solder joints reflowed at 260 °C for 10–180 s. After 20 s reflow, a thick (Pd,Au)Sn 4 IMC was formed at the interface of the pure Pd joint, while thick AuSn 4 and thin (Pd,Au)Sn 4 IMCs were formed at the interface of the Pd(P) joint. After 30 s reflow, needle-type (Cu,Ni) 6 Sn 5 IMC was mainly formed at the top-side interface of the pure Pd joint, while scallop-type (Cu,Ni) 6 Sn 5 IMC was formed at the top-side interface of Pd(P) joints. Finally, the top-side (Cu,Ni) 6 Sn 5 IMC of the pure Pd and the top- and bottom-side (Cu,Ni) 6 Sn 5 IMCs of the Pd(P) joints coarsened with increasing reflow time up to 180 s. In the results of top-view SEM micrographs, the (Cu,Ni) 6 Sn 5 IMCs on the Pd(P) joint were larger than those on the pure Pd joint for reflow times of 30–180 s. Therefore, P in the Pd layer was concluded to significantly affect the interfacial reactions and IMC morphology of the SAC 305 solder with ENEPIG joints during reflow reactions. [ABSTRACT FROM AUTHOR]

Silver nanowire (AgNW) network is known for its low percolation threshold, high conductivity and good flexibility, therefore, considered one of the best candidates for fabrication of flexible and transparent electrodes. However, a general approach to make the AgNWs-based electrodes, an overcoating of nanowire dispersion onto a transparent polymer, should make an issue of poor mechanical stability, mainly caused by low adhesion between the nanowires and polymer. In addition, a thin insulating layer of polyvinylpyrrolidone (PVP) formed on the surface of AgNWs deteriorates the conductivity of their network, which means that a post-processing such as high temperature annealing is essentially needed. Here we employed a plasma treatment with an inert gas to remove the residual PVP layer, so that the conductivity could be enhanced without employing any high temperature processing. Interestingly, the optical transmittance in the wavelength near 400 nm was also increased, resulting in more neutral coloration of the electrode. An inverted layer processing made the nanowires to be partially buried at the surface of colorless polyimide (cPI), so that the enhancement of mechanical stability and connectivity with overlying materials were simultaneously achieved. [ABSTRACT FROM AUTHOR]

High heat-endurance bonding between Cu Ni was investigated by hybrid transient liquid phase sintering bonding. By simultaneously adding Cu and Ni to SAC305, the IMC was stably formed, and the bonding strength of hybrid TLPS joint was the highest. It is expected to be used for SiC die attachment of power module packaging. [Display omitted] • Novel hybrid transient liquid phase sintering bonding is developed for Cu Ni bonding. • Fast and stable ternary (Cu,Ni)-Sn IMCs were formed by hybrid transient liquid phase sintering bonding. • Electron probe micro-analyzer was used for investigating the atomic distribution of TLPS joints. A novel approach to copper-nickel bonding was investigated by hybrid transient liquid phase sintering (TLPS) method. Hybrid bonding material containing copper, nickel, and Sn-3.0Ag-0.5Cu (SAC305) and an organic solvent was fabricated to form a fast and stable ternary Cu Ni Sn intermetallic compound (IMC) joint between Cu to Ni joint. The atomic distribution was analyzed by an electron probe micro-analyzer, showing full IMC formation of the hybrid TLPS joint. In addition, by simultaneously adding Cu and Ni to SAC305, the IMC was stably formed, and the bonding strength of hybrid TLPS joint was the highest. [ABSTRACT FROM AUTHOR]

• We prepare Sn-coated Cu particles of different diameters as a micro paste. • We use the paste to bond a dummy chip and a DBC substrate. • The bonding is carried out via transient liquid-phase sintering (TLPS) technology. • The paste affords a high shear strength value of ~40 MPa. • Our approach is suitable for power electronics packaging and allied applications. Cu paste has been considered as a promising substitute for Ag paste for high-temperature-endurable chip-bonding applications, particularly for power electronics packaging, because it is cheaper than Ag. However, the primary disadvantage of using Cu paste is its possible oxidation during the handling and bonding process. In this context, to overcome the oxidation problem of the Cu sinter paste and to exploit the advantages of transient liquid-phase sintering (TLPS) bonding technology, we prepare Sn-coated Cu micro paste in this study, and we evaluate its feasibility as a die-attach material for power electronics packaging. We first prepare various Sn-coated Cu powders under various plating conditions, and we successfully perform TLPS bonding with Sn-coated Cu paste at a relatively low bonding temperature and a short bonding time. During the TLPS bonding, Sn is completely consumed, and the resulting bonded joint is composed of the Cu–Sn intermetallic compounds and remnant Cu particles. The TLPS-bonded joints exhibit relatively high shear strength values of ~40 MPa, and all fractures mainly occur at the chip-side interfaces irrespective of the Cu particle size. We believe that our findings can contribute to the use of Sn-coated Cu paste as an alternative bonding technology for power electronics applications. [ABSTRACT FROM AUTHOR]

Ag particles have been attractive candidates for highly reliable interconnections in electronic packages due to an absence of IMCs, high melting temperature, and high electrical and thermal conductivity. We fabricated various Ag-nanoparticle (NP) pastes containing different epoxy/binder percent weight (epoxy: 4.5, 9.0, 13.5, and 18 wt%) to investigate the effect on the bonding strength and electrical performance of multilayer ceramic capacitor (MLCC) components. MLCC joints were obtained by stencil printing Ag NP pastes on an Al 2 O 3 substrate with Cu electrodes followed by pressureless bonding at 250 °C for 15 min. When using Ag NP pastes containing higher epoxy compositions, more residues were identified while the other organic additives, such as the binder and dispersant, were removed by debinding during the bonding process. The Ag NP-18 wt% epoxy paste showed bonding strength approximately 8.6 times that of the paste containing 4.5 wt% epoxy. However, the electrical resistivity of MLCC components of 18 wt% epoxy paste showed an electrical resistance of 3.5 Ω, which was about 1.8 times that with the 4.5 wt% epoxy paste. We designed Ag NP pastes with varying epoxy ratio, and studied their chemical, bonding, and electrical characteristics for the development of advanced interconnection. • Ag nanoparticle paste containing epoxy was fabricated for pressureless MLCC bonding. • Robust bonding strength, 44.59 MPa, was achieved with Ag NP-epoxy (18 wt%) paste. • Epoxy filled voids and covered the circuit, deteriorating electrical conductance. • Moderate electrical and mechanical characteristics were achieved with 13.5 wt% epoxy. [ABSTRACT FROM AUTHOR]