Hiroshi Nishikawa's research while affiliated with Osaka University and other places

Publications (261)

Article
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In recent years, solid-state bonding has attracted attention for various electronic packaging applications as an alternative to conventional solders. Surface-nanostructured materials enable solid-state bonding without complex surface modifications and operate at a low bonding temperature and pressure. Therefore, in this study, molecular dynamics si...
Article
To meet the increasing demand for thermal stability in electronic packaging required for next-generation power modules, transient liquid phase (TLP) bonding of Cu/In system is concerned owing to its high remelting temperature and high strength. In this study, a novel TLP bonding method using In-coated Cu sheet was designed for high-temperature die...
Article
Full-text available
The metallization process has received significant attention in the electronic industry. It is one of the best method to enhance bonding strength via interfacial reaction between the back side metallization layer of the SiC chip and an insert material while facilitating superior electrical and thermal conductivity along with excellent chemical resi...
Article
In 3D packaging, an increase in the solder bump density and reductions in solder-bump height are the roadblocks to using gel or liquid fluxes for the soldering process. Fluxless soldering has become a popular technology, and the formic acid (FA) atmosphere soldering is one of the most promising fluxless soldering techniques. In this study, the effe...
Article
Full-text available
Nanoparticle sintering is considered a promising alternative bonding method to Pb-based soldering for the attachment of components in high-temperature electronic devices. However, the technology still poses certain challenges, such as the difficulty in controlling the joint thickness and the generation of voids owing to solvent evaporation. In this...
Article
With the trends of miniaturization and high density of electronic packaging, there has been an urgent demand to open up lead-free solders with high strength and ductility. In this study, a ZrO2-reinforced Sn1.0Ag0.5Cu composite solder was designed. First, surface modification on ZrO2 was conducted with ball milling-pyrolysis method. Subsequently, N...
Article
Sn-58Bi, an eutectic alloy, has been explored for use as a low-temperature lead-free solder alloy. However, the properties of Sn-Bi alloys as well as those of their joints need to be improved significantly so that these alloys can be applicable for practical use. In particular, two drawbacks need to be addressed: the intrinsic brittleness of Bi and...
Article
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The low melting temperature In-48Sn alloy is a promising candidate for flexible devices. However, the joint strength of the In-48Sn alloy on the Cu substrate was low due to the rapid diffusion of Cu into the In-rich alloy. In this study, the effect of the addition of xCu (x = 2.0 and 8.0 wt.%) on wettability, interfacial reaction, and mechanical st...
Article
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This study investigated the effects of the manufacturing process on the microstructure of nanoporous copper (NPC) produced using cold-rolled Mn–30 at.% Cu and Mn–40 at.% Cu precursor sheets. NPC was prepared by chemically dealloying these precursor sheets in a 4% HCl aqueous solution. The initial Mn–Cu alloys were homogenous solid solutions with go...
Article
Transient liquid phase (TLP) bonding technology attracts great attention as it can produce a full intermetallic compound (IMC) bonding structure for high-temperature applications. In this study, the Cu–Sn TLP bonding is investigated based on the microstructural and mechanical analyses of a sandwiched structure of Cu/Sn-3.5 wt% Ag/Cu under thermal c...
Article
Background Cu-Cu direct bonding is a promising technology to construct a temperature resistant bonding structure for emerging power devices and vehicle electronics. The main challenge is the ease oxidation of Cu and slow solid-state atomic diffusion at the bonding surface. Methods In this study, nanocrystalline Cu is constructed on the bonding sur...
Article
Sintered silver paste is a popular material for die attachment technology in power electronics. However, using traditional nano-silver paste when fabricating sintered joints has intrinsic material problems that cannot be overcome, such as the high cost of nano-silver particles and their potential health hazards. In this study, a novel micro-silver...
Article
Thermal conductivity of a Ag sintered joint was measured using the steady-state comparison method. The results showed that with the increasing sintering temperature, the thermal conductivity increased from 126.3 to 228.5 W/m·K and the corresponding porosity of the Ag sintered joint decreased from 23.4% to 8.4%. However, except for the porosity, the...
Article
Full-text available
In order to omit the step of removing organic items in Cu–Cu joint with Cu paste and improve the interface of the Cu–Cu bonding, a novel method based on cold spray deposition and subsequent oxidation–reduction process was proposed to achieve solid-state Cu–Cu joint with cheap micro-sized Cu particles at low temperature with different applied pressu...
Article
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To develop a lead-free solder with high strength and ductility, a novel interface was designed between the tetra-needle-like ZnO whisker (T-ZnOw) and Sn1.0Ag0.5Cu solder matrix. First, surface modification of T-ZnOw was conducted using a pyrolysis method based on self-assembly to deposit NiO nanoparticles densely and evenly on the whisker surface....
Preprint
Full-text available
Nanoparticle sintering is considered a promising alternative bonding method to Pb- based soldering for the attachment of components in high-temperature electronic devices. However, the technology still poses certain challenges, such as difficulty controlling joint thickness and the generation of voids owing to solvent evaporation. In this study, a...
Article
It is well known that composites of nano-ZrO2 and nano-NiO have many advantageous properties that can be harnessed in a variety of applications. However, the state-of-the-art methods for producing these nanocomposites are often cumbersome and expensive. Therefore, in the current study, we introduced a new method for the synthesis of NiO/ZrO2 nanoco...
Article
Full-text available
Electromigration (EM) is considered as a serious issue that threatens the reliability of electronic packaging. For the long-term reliability of the application of pure silver thin films, it is important to investigate its EM effect; however, there are limited studies focused on this aspect. In this study, the EM of a silver thin film deposited on a...
Article
Full-text available
With the ever-reducing sizes of electronic devices, the problem of electromigration (EM) has become relevant and requires attention. However, only the EM behavior of Sn–Ag solders within the solder joint structure has been focused on thus far. Therefore, in this study, a thin metallic film composed of Sn–3.5Ag (wt.%) was subjected to a current dens...
Article
In order to improve the mechanical properties after thermal aging of an Sn-45Bi-2.6Zn (SBZ) alloy, which we had proposed in a previous study, in this study, we prepared Sn-Bi-Zn-In alloys and investigated the effects of the addition of In and Zn on their microstructure and mechanical properties before and after thermal aging. We found that the addi...
Article
High-entropy alloy (HEA) FeCoNiCu (FCNC) can be potentially employed in electronic packaging because it contains commonly used substrate metals. However, its microstructure, thermal stability, corrosion behavior, and wettability toward Sn-3.0Ag-0.5Cu (SAC305, wt.%) solder have never been examined in detail, especially in terms of the microstructure...
Article
Full-text available
The In-48Sn eutectic alloy has emerged as a favorable solder for flexible electronic devices, owing to its low operating temperature. However, the low strength of In-48Sn eutectic alloy compared with that of other commercial solders affects the product life and limits its use in the device applications. Herein, we studied the effects of xCu additio...
Article
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Silver (Ag) microparticle sintering bonding is a promising die-attach method for power device packaging. In this study, an ultrasonic-assisted bonding method that bonds chestnut-burr-like Ag microparticles rapidly at low temperatures is reported. Robust joints with an average shear strength of 36.2 MPa were achieved under ~ 240 °C (actual) 7 MPa in...
Article
As Cu is appearing to be a promising alternative for Au in wire bonding applications the corrosion behavior of the Cu/Al intermetallic compounds (IMCs) is becoming a concern. In this study, the corrosion behavior of Cu/Al IMC layers in NaCl solution is investigated. Among Cu9Al4, CuAl and CuAl2 IMCs only CuAl IMC appears to be corroded. The surface...
Article
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Wide bandgap (WBG) power devices have been attracting increasing attention for next-generation electronic applications. Cu–Cu bonding has been developed to accommodate the high temperature and current characteristics encountered in WBG semiconductors service conditions. In this study, we demonstrate and optimize a pressureless Cu–Cu bonding method...
Article
Full-text available
Alloys with melting points < 150 °C are required for the development of flexible consumer devices. While the eutectic In–48Sn alloy is a promising candidate for these applications, its low tensile strength and low creep resistance during solid-state aging are of concern. The addition of Ag can address this issue to some extent; however, the effect...
Article
Full-text available
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Article
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Fluxes have a negative impact on the environment; as a result, fluxless soldering has become a promising method in electronic packaging. However, detailed studies on fluxless soldering are very rare, especially those involving the use of electroless nickel immersion gold (ENIG) substrate under formic acid (FA) atmosphere that can effectively reduce...
Article
Nowadays, several joining processes are proposed as alternatives to high-Pb-containing solders. There are many reports on bonding techniques using metal nanoparticles, and there has been an increasing focus on developing solid-state bonding interconnection processes based on sintering, such as bonding techniques using Ag or Cu nanoparticles. Howeve...
Article
A comprehensive study of the interfacial reactions between Zn-added Sn58Bi solder alloys and electroless Ni/immersion Au (ENIG) substrates during reflow and solid-state thermal aging was conducted. The shear strengths of these samples were tested before and after aging. Zn first reacted with Au forming AuZn₃ intermetallic compounds (IMCs) that deta...
Article
Growth of an intermetallic compound (IMC) plays a critical role in the reliability of flip-chip solder joints. It has been found that IMC growth is accelerated on the anode and inhibited on the cathode during electromigration (EM), although there are discrepancies in the relevant literature. In this study, Cu/Sn3.0Ag0.5Cu/Cu solder joints were exam...
Article
Formic acid, which can provide efficient reduction for most solders, is widely used in fluxless soldering. In this study, to establish a reliable fluxless soldering process, a formic acid atmosphere was used to reduce the oxides of Sn-3.0Ag-0.5Cu solders and Cu substrates. The wetting behavior of Sn-Ag-Cu solder balls on Cu pads under a formic acid...
Article
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Recently, there have been moves to replace Si power devices with SiC ones, which will require new materials with higher thermal conductivity for power module assemblies owing to their higher operating temperatures. Al wire bond interconnections suffer from a mismatch in the coefficient of thermal expansion (CTE) between the SiC chip and the wire ma...
Article
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Package-on-Package (PoP) is a popular technology for fabricating chipsets of accelerated processing units. However, the coefficient of thermal expansion mismatch between Si chips and polymer substrates induces thermal warpage during the reflow process. As such, the reflow temperature and reliability of solder joints are critical aspects of PoP. Alt...
Article
The intermetallic compound (IMC) produced through an interfacial reaction between Sn-0.7wt.%Cu-0.2wt.%Cr (SC-Cr) solder and a Cu substrate was evaluated at 100 °C, 125 °C, and 150 °C for 1000 h and after ten reflows. The comparable study on the interfacial reaction for Sn-0.7wt.%Cu (SC07) and Sn-3.0wt.%Ag-0.5wt.%Cu (SAC) with a Cu substrate was als...
Article
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High-entropy alloys (HEAs) are promising materials for next-generation applications because of their mechanical properties, excellent high-temperature stability, and resistance against oxidation and corrosion. Although many researchers have investigated high-temperature HEA applications, few have considered low-temperature applications. Here we dem...
Chapter
Soldering is the major micro-joining process for assembling printed circuit boards of electronic products and is an important method of joining two metals without melting of base metals. In light of the remarkable progress in recent years in electronic products, the micro-joining process represented in soldering to incorporate devices and component...
Chapter
This chapter describes a novel low-temperature Au–Au bonding method using nanoporous Au–Ag powder and vacuum ultraviolet irradiation in the presence of oxygen gas (VUV/O3) pretreatment. The nanoporous powder, which was fabricated by dealloying Ag–Au alloy sheet, was used to form the bump structure on the Au substrate by simple filling process, whil...
Article
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Low silver (Ag) solder alloys e.g., SAC 105 (Sn–1.0Ag–0.5Cu) have attracted a great deal of attention recently due to economic concerns and improved in impact resistance as compared to other SAC solder with higher silver content. This work studies the influence of addition of minor zinc (0.1–0.5 wt%) to SAC105 on the interfacial structure between s...
Article
Recently the new SiC power device provides the possibility to develop the next-generation power conversion circuit with high efficiency and high power density. The SiC power device can operate with significant lower power loss and higher operating temperature, which contributes to miniaturization and higher performance of power modules. To assemble...
Article
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The effects of 0.5 wt% In as well as 0.5 wt% In and 1 wt% Zn double (In & Zn) additions to eutectic Sn58Bi alloy on the microstructure and mechanical properties were investigated. Newly designed In & Zn-added Sn58Bi alloy showed much finer microstructure than eutectic Sn58Bi and In-added Sn58Bi alloys. The elongation improvements of 36% and 41% bef...
Article
The grain sizes and grain orientations of Sn and Bi phases in Sn-58Bi alloy are investigated. We find that the grain size of Bi is larger than that of Sn. Tensile test and two-dimensional simulation reveal that the ductility and yield stress decrease upon Bi coarsening after 504 h of thermal aging at 80 ∘ C, and that thermal stress is crowed on the...
Article
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High-entropy alloys (HEAs) are well known for their excellent high-temperature stability, mechanical properties, and promising resistance against oxidation and corrosion. However, their low-temperature applications are rarely studied, particularly in electronic packaging. In this study, the interfacial reaction between a Sn-3.0Ag-0.5Cu solder and F...