Chunqing Wang

Harbin Institute of Technology | HIT · School of Materials Science and Engineering

Tin (Sn), as the matrix of most lead-free solders, plays a primary role in stress absorption during the service of small-scale solder joints under cryogenic environment. The Sn grain orientation would produce a strong effect on the cryogenic mechanical stability of solder joints due to the anisotropy of Sn with a body-centered tetragonal structure....

Exact prediction of lifespans of solder interconnects is critical for designing reliable solar photovoltaic systems that operate for a long time across a wide range of temperatures in low earth orbit, but pertinent prediction methodology has rarely been investigated. Here, a systematic approach for analyzing the fatigue life of the solder interconn...

A method of decreasing the ductile–brittle transition temperature (DBTT) of Sn-3.5Ag solder by aging treatment has been found to allow the solder to serve at lower temperatures. Charpy impact tests under various temperatures (from −150°C to 20°C) were performed on Sn-3.5Ag solder after 150°C aging treatment, and the morphology of second-phase parti...

Black phosphorus (BP) has attracted much attention as a promising anode material for lithium-ion batteries. However, poor environmental stability, large volume expansion, and irreversible solid-electrolyte interphase (SEI) have limited its practical applications. Herein, an electrode-coating method was adopted to spin-coat the amorphous TiOx precur...

The inherent ductile-to-brittle transition (DBT) of body-centered tetragonal Sn at cryogenic temperatures restricts the use of Sn-based solders in the interconnection of cryogenic electronics, but little is known about the deformation behaviors accompanying with the transition and the underlying transition mechanism. In this work, the deformation f...

Black phosphorus (BP) is an attractive anode material for advanced lithium-ion batteries due to its intrinsic layered structure, high electrical conductivity and large theoretical capacity. However, the formation of an unstable solid-electrolyte interphase (SEI) and electrode pulverization caused by volume expansion during the lithiation-delithiati...

Detailed comprehensive comparison of temperature variations of ductility over common solders forms the sound basis of designing reliable solder joints that operate across a wide range of low temperatures, but the cryogenic fracture mechanism needs further investigation so far. Here, we investigate fracture behaviors of typical solders at different...

With the application of wide bandgap semiconductors for high power electronics, the joints are inevitably faced with a trade-off between withstanding high temperature environments and remaining low bonding temperatures. In this study, a full Cu3Sn intermetallic compounds layer with thickness of 40 μm, which can survive at 679 °C, were obtained betw...

In this work, intrinsic and p-type ZnO nanowires (NWs) have been synthesized. Pure intrinsic ZnO nanowires have been fabricated by direct oxidation method with an aspect ratio of 271.3. Sb-doped ZnO nanowires were uniformly grown on Si substrates by chemical vapor deposition (CVD) with diameters ranging from 0.5 to 5 μm and lengths ranging from 100...

Low temperature nanojoining and high temperature service in the microelectronic packaging technology has received much focused attention. Here, we suggest a facile thermal decomposition method for preparation of Cu10Sn3 nanoparticles (NPs) with high bulk melting point (640 °C) by using common organic salts, oleylamine (OLA), and oleic acid (OA). Th...

Sn–Pb eutectic alloy is widely applied to the deep-space electronics that work under cryogenic environments, but little is known about its responses to the mechanical loading at cryogenic temperatures. In this work, a comprehensive investigation about the deformation and fracture behaviors as well as constitutive relations of the eutectic alloy at...

As a single-phase multiferroic oxide, BiFeO3 (BFO) is suitable for applications such as magnetoelectric memories, sensors and actuators. However, BFO suffers from high leakage current density and small magnetization. And the BFO in film form is apt to react with Pt bottom electrode during the thermal treatment. In addition, its required high proces...

Cu3Sn intermetallic compound as an interconnecting material has great prospect in power electronic device applications due to its high melting temperature. However, the intermetallic compound is essentially brittle, and hard to be transferred. In this study, Cu3Sn thin films have been successfully transferred by means of laser-induced forward trans...

A new phase-transformation-induced path to spontaneous formation of extreme nanograin structure is reported. In-situ-heating-mode-microscopy exhibited a substantial grain-growth of Cu6Sn5. During cooling, the grain-growth continued, but it spontaneously switched to grain-refinement mode on phase transformation through ∼180 °C from η-Cu6Sn5 to η’-Cu...

Cu 10 Sn 3 intermetallic compound (IMC) nanoparticles (NPs) were synthesized by one-step thermal decomposition method with low cost. The in-situ formed metal amide in the presence of LiN(iPr) 2 can be reduced and thermally decomposed into metal NPs, and then the Cu 10 Sn 3 NPs were obtained, which have an average diameter of 65 nm and good oxidatio...

The sintering mechanism of multiphase ceramic film—made of alumina, mullite and aluminum nitride—fabricated by water vapor-assisted sintering on Cr/WCu substrate was investigated. The multiphase ceramic film and interfacial reaction layer between ceramic film and Cr/WCu substrate were examined to reveal their microstructure by relevant test methods...

Reliable measurements of the kinetics of β → α allotropic transformation in Sn-based solder underlie the design and development of advanced interconnects for low-temperature electronics. In this paper, a highly-accessible and buoyancy-based method, but different from common dilatometry, was developed to consistently detect a change of the transform...

The atomic structure, interfacial charge distribution, bonding nature, and interfacial electronic states of a 4H–SiC/TiN interface are systematically investigated to understand the Ohmic contact formation mechanisms of TiN to 4H–SiC. The experiment results clearly demonstrate that the well-arranged TiN (111)-oriented lattice planes are parallel to...

In this paper, a novel capacitor-inductor integrated structure was proposed. The dielectric material BaTiO3 (BTO) and ferromagnetic material Ni0.5Zn0.5Fe2O4 (NZFO) was prepared by sol-gel method. Phase composition and morphology of the thin films were characterized by XRD, SEM and AFM. The effect of annealing temperature on film crystallinity, surf...

In order to obtain Ag nanoparticles (NPs) sintered Cu–Cu joints with better mechanical properties in a relative short time and under a suitable pressure, a laser sintering process and a novel paste prepared by mixed Ag NPs (19 and 62 nm in diameters) were utilized and studied. The results indicated that joints with low porosities were fabricated wi...

A novel Cobalt-free perovskite dense oxygen permeable membrane with the composition Pr0.6Sr0.4Cu0.2Fe0.8O3-δ (PSCF) is designed and evaluated in this work. The XRD results reveal that the perovskite-type PSCF materials exhibit typical orthorhombic structure without any impurity phases. And PSCF powder exhibits excellent chemical stability in CO2 du...

Though copper nano-pillars (CNPs) filled in anodic aluminum oxide (AAO) film has been developed for many years, the high pore-filling percentage in AAO is still a bottleneck. We have demonstrated a new electrodeposition method to fill CNPs in AAO without the seed layer which is required in the traditional electrodeposition process. CNPs with unifor...

Functional materials for flexible and wearable smart devices have attracted much attention in recent years. This paper describes structure and properties of uniquely prepared, functional interconnectable nanoparticles (NPs) of Cu6Sn5 intermetallic compound that can allow 3D flexible packaging and nanocircuits. In situ TEM analysis confirms that siz...

Recently, nanosilver pastes have emerged as one of the most promising high temperature bonding materials for high frequency and high power applications, which provide an effective lead-free electronic packaging solution instead of high-lead and gold-based solders. Although nanosilver pastes can be sintered at lower temperature compared to bulk silv...

Spalling of intermetallic compounds is a common and detrimental phenomenon in the wetting reaction between Sn-based solders and under-bump metallizations; however, it is still not clear whether spalling will appear in solid-state aging. Here, the solid-state spalling of Ag-Sn intermetallic compounds at the interface between an eutectic Sn-Pb solder...

Unpredictable Kirkendall void formation at the interface of circuit interconnections underlies degradation in electronics, yet there is a lack of effective approaches to curb the amount of these voids. In this paper, we developed a modified strain-anneal method to tailor grain size distributions in the copper substrate of interconnections by inhomo...

We demonstrate a facile bonding process for combining silicon and quartz glass wafers by a two-step wet chemical surface cleaning. After a post-annealing at 200 °C, strong bonding interfaces with no defects or microcracks were obtained. On the basis of the detailed surface and bonding interface characterizations, the bonding mechanism was explored...

We develop a cost-effective vacuum ultraviolet (VUV) irradiation in air combined with an in situ bonding process. The whole bonding process does not require high vacuum environments. Strong bonding strengths for Si/Si, Si/glass, and glass/glass pairs were achieved with the assistance of annealing at 200°C. There was no crack or defect at the bondin...

Unpredictable Kirkendall void formation at the interface of circuit interconnections underlies degradation in electronics, yet there is a lack of effective approaches to curb the amount of these voids. Here we developed a strain-anneal method to tailor grain size distributions in the copper substrate of interconnections, and demonstrate quantitativ...

We demonstrate a facile bonding method for combining Si/Si, Si/quartz, and quartz/quartz wafers at room temperature (∼25 °C) using a one-step O2/CF4/H2O plasma treatment. The bonding strengths were significantly improved by adding a small amount of CF4 into the oxygen plasma, such that reliable and tight bonding was obtained after storage in ambien...

Understanding the thermal evolution mechanisms of metal nanoparticles (NPs) at the quantum-dot-scale is arrestive and meaningful for utilization of nanomaterials. Herein, an interesting fusion evolution phenomenon of Ag-Cu NPs induced by in-situ TEM high-energy electron beam illumination has been observed and investigated. It turned out that a rapi...

In this paper, we have investigated a laser-assisted fast nano-Ag sintering process for die attach in power electronic applications. The effects of laser power, irradiation time, and load on microstructure and shear performance of the bonded samples are presented. Moreover, samples sintered by a hotplate were also studied as a comparison. The resul...

Room-temperature direct bonding is an attractive approach to combine dissimilar wafers avoiding any thermal stress by a difference of thermal expansion coefficients. In this paper, we investigate a room-temperature bonding process using fluorine containing plasma activation and propose a mechanism model to address the roles of fluorine. Details of...

A thermal stress model for dissimilar wafer bonding is developed based on theoretical as well as finite element methods. To ensure no facture, sliding or debonding during thermal treatments, two requirements are taken into account in our model, i.e., (1) thermal stress smaller than the fracture strength of the bonded wafers and (2) the deformation...

Wafer bonding, also termed as “direct bonding” or “wafer direct bonding”, has one of the main advantages for its ability to integrate dissimilar materials in various areas of microelelctronics, optoelectronics, micro/nanoelectromechanical systems (M/NEMS). Silicon is the most extensively used material for semiconductor industry. To meet demands on...

Low temperature nanojoining has been identified as a challenging nanotechnology in the construction of nanoscale structures as well as microelectronic devices. Herein, three kinds of Ag-Cu nanopastes have been designed by mixing different organics with the Ag-Cu nanocrystalline particles synthesized in our previous work. The mechanical properties o...

A series of CuSn reactions were studied for the electroless plating of Sn onto Cu microparticles. The Cu microparticles were more temperature-sensitive than the planar Cu substrate when electrolessly plated with Sn. The coordination ligand (L) thiourea complexing agent played a key role in the interface reaction between the inner Cu core and the ou...

High-temperature-stable Cu3Sn-based joints were selectively fabricated using electric current-assisted bonding process within an extremely short time (~200 ms) and under a low pressure of 0.08 MPa in a Cu/Sn/Cu interconnection system at ambient temperature. The experimental results showed that the imposed electric current density (~104 A/cm2) resul...

We report the synthesis of Bi0.9La0.1Fe0.95Mn0.05O3 (BLFMO) films with enhanced multiferroic properties and without second phase using Ba0.7Sr0.3Ti0.95Co0.05O3 (BSTCO) film as a buffer layer. Sol–gel processes were used to prepare the crystallized BLFMO/BSTCO films, in which magnetic domains were observed and no impurity phase was detected. We foun...

We report the synthesis of Bi0.9 La0.1 Fe0.95 Mn0.05 O3 (BLFMO) films with enhanced multiferroic properties and without second phase using Ba0.7Sr0.3Ti0.95Co0.05O3 (BSTCO) film as a buffer layer. Sol–gel processes were used to prepare the crystallized BLFMO/BSTCO films, in which magnetic domains were observed and no impurity phase was detected. We...

Three-dimensional (3D) nano-hierarchical Ni nanomace (Ni NM) array was fabricated on copper substrate by only one step with electroplating method, the unique structure was covered with Au film (Ni/Au NM) without changing its morphology and in the following step, it was sintered with silver nanoparticle (Ag NP) paste. The structure of Ni NM array an...

Three-dimensional (3D) nanohierarchical Ni nanomace (Ni NM) array was fabricated on copper substrate by only one step with electroplating method, the unique structure was covered with Au film (Ni/Au NM) without changing its morphology, and in the following step, it was sintered with silver nanoparticle (Ag NP) paste. The structure of the Ni NM arra...

The actuation of microsize liquid metal droplets on an open solid surface with laser offset heating is reported in this work. The process allows the droplets to move towards the laser beam center. The analysis of the actuations showed that the droplets were predominantly driven by the thermally induced wettability alteration on the solid; in contra...

Ultrafine Ag–Cu nanoparticles (NPs) have been synthesized by a rapid one-step reduction within only 10 min. Effects of temperature and dispersants on the phases and morphology of Ag–Cu NPs were investigated. Results showed that citric acid exhibited an advantageous nature to avoid the formation of Cu2O and form uniform morphology over PVP. The aver...

All the time, longer life is a goal for Low Earth Orbit Satellite (LEO). LEO has short orbit period (about 97min), so it will experience thermal shock for approximately 5500 times per year. Long and frequent thermal recycling becomes a big challenge to the reliability of these systems, particularly to the reliability of solar cell interconnections....

Hydrophilic bonding is commonly used in the wafer bonding field. Water management is of great importance to obtain good bonding quality over the entire bonded pairs. However, current wafer bonding equipments do not have the function of regulating the surface humidity prior to bonding. It is difficult to make a quantitative study on the role of mois...

In this paper, we propose an facile one-step reduction approach free of microwave-assisted heating or water-bath heating to synthesize Ag-Cu nanoparticles (NPs). Results showed that fcc Ag-Cu NPs with an ultra-fine average size of 9 nm were achieved and expected to sinter at about 330 °C which is much lower than the eutectic temperature of bulk Ag-...

As the integrated circuit and semiconductor industry developing rapidly, traditional micro-joining technology can not meet the new high-power devices challenge. Due to the size effect, nano-materials can offer low-temperature connection and high-temperature service property, which may be a promising approach for the high-power application. In the i...

Ultra-long silver nanowires (AgNWs) could be an ideal material to replace the commercial used indium tin oxide in highly conductive and transparent electrodes field. In this report, AgNWs with mean length of 102 μm and even 268 μmhave been synthesized through a rapid and one-step polyol method within only 40 min. The effective synthesis was contrib...

In this study, Ag–Cu nano-particles (NPs) with face-centered cubic crystal structure have been synthesized through a facile one-step approach. The statistical design of experiment has been employed to optimize the process parameters and find significant factors that affect the particle size of Ag–Cu NPs. Results showed that the reaction temperature...

One-dimensional multiferroic nanostructures have received a great deal of recent attention. This paper presents the synthesis of Ba0.7Sr0.3TiO3 (BSTO) and Ni0.8Zn0.2Fe2O4 (NZFO) co-reinforced Bi0.9La0.1Fe0.95Mn0.05O3 (BLFMO) nanotubes with one closed end. The aim was to obtain one-dimensional multiferroics with higher ferroelectric and magnetic pro...

Copper (Cu) nanoparticle (NP) paste has emerged as a promising choice for future high power electronics. However, the application of CuNP paste is generally limited because of its easy oxidation and complex processing parameters such as high sintering temperature (∼400 °C) and necessary protection atmosphere. Although capping CuNPs with a stable la...

During the past few decades, silicon carbide (SiC) has emerged as the most promising wide-bandgap semiconductor for high-temperature, high-frequency, and high-power applications. All its attractive properties depend critically on and are often limited by the formation of Ohmic contacts to SiC. Although impressive progress has been made, improvement...