2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) is a kind of organic semiconductor materials with high carrier concentrations. In this work, we reported the thermoelectric performances of C8-BTBT under isotropic compressive strain of 5%. The results indicate that the figure of merit (zT) for N-type C8-BTBT could be improved by 17.6% and strain engineering plays an important role in the regulation strategy for thermoelectric materials.

In this study, effects of different yttrium (Y) contents ranging from 0 to 2.5 wt% on the microstructure and tension/compression asymmetry of as‐extruded Mg–5.5Zn–0.6Zr alloys are investigated. The influence of Y on improving the tension/compression yield strength is been studied. The results show that the volume fractions of the microscale I (Mg3YZn6) and W (Mg3Zn3Y2) phases remarkably increase with Y addition. Simultaneously, the nanoscale MgZn and Mg–Zn–Y phases uniformly precipitate during extrusion. Benefiting from the pinning of second phases, the microstructure is strikingly refined from 16.3 to 5.5 μm. Among them, the Y element promotes grain refinement most effectively when the Y content is 2.0 wt%. Second phase strengthening and fine‐grain strengthening enhance the hardening rate and suppress twinning, which leads to the improvement of the tension/compression asymmetry. Specifically, yield strength of 231 MPa and ultimate tensile strength of 312 MPa are achieved with 2.5 wt% Y addition. The relative increment is about 33.0% and 65.3% compared to the unmodified alloy, respectively. In addition, the tensile yield strength to compressive yield strength ratio (TYS/CYS) is reduced from 1.30 to 1.09.

O_2 plasma treatment is a useful way to increase adhesion strength between polymer resins and adhered substrates in electronic packaging areas. However, a low adhesion strength of polymer adhesives on the adhered surfaces is a critical issue for anisotropic conductive film (ACF) joint reliability, especially when it comes to moisture-induced effects. This paper discusses the effects of oxygen plasma treatment (100W 20mTorr 3min) on the wettability and reliability of solder ACFs joints on Au/Ni metal electrodes. We carried out the surface analysis using surface energy, AFM, XPS, FTIR and joint resistances, peel adhesion strength, and reliability. By using the contact angle and surface energy, the un-wetted solder joining was explained from a spontaneous wettability to a hindered wettability, as a reason for poor electrical performance and reliability after oxygen treatment. Although the resin and electrode adhesion was increased, it was proven that the solder part played a more important role in determining joint reliability and mechanical property.

Electrically conductive adhesives (ECAs) are mainly used in IC packaging, LED packaging and other electronic industry to replace the traditional soldering and lead-free solders, therefore, there is a constant need to improve the electrical conductive and mechanical property of ECAs. In this study, the electrical resistivity and shear strength of the modified nano-Ag coated Cu particles in ECA was investigated and compromised, in terms of filler contents, curing temperature and curing time. The conductive mechanism of the modified nano-Ag coated Cu particles in ECA was discussed as the filler content increased. Finally, the filler content was optimized by 23.5 vol% and 170 °C 100 min curing condition was selected to obtain the compromised property (5.159 × 10−6 Ω cm 6.121 MPa), which is better than the previous one (4.99 × 10−6 Ω cm, 4.406 MPa) at 200 °C. The tested data, as well as the failure mode and fracture interfaces, were carried out in this study.

In the present work, an ultrasonic assisted squeeze casting method is proposed for processing wrought aluminum alloys. A frame-shaped part was fabricated to verify the feasibility of ultrasonic assisted squeeze casting technology. The results show that a 2024 alloy part with a complex shape and good surface quality can be produced by the proposed ultrasonic assisted squeeze casting method. As the ultrasonic power increasing, the microstructures of the squeeze cast parts were clearly refined, and the coarse polygonal or dendritic structures evolved to fine and equiaxed grains. Mechanical properties, such as strength and plasticity, were also improved significantly as the ultrasonic power increasing. When the ultrasonic power was 1.8 kW, the UTS, YS and elongation to fracture were 372 MPa, 246 MPa and 8.5%, which were improved by 20.8%, 21.2% and 84.8%, respectively, compared to a conventional squeeze cast part. Finally, the effect of ultrasonic vibration on mold-filling and solidification was analyzed.

A new type of Ag nanoparticle (NP) paste for rapid sintering was prepared by controlling the thickness of the NP capping agent. The Ag NP paste was combined with a rapid thermo-compression (RTC) method to form a reliable Cu–Cu joint. The shear strengths of the Cu/Ag NP/Cu joints were 46.8 MPa and 90.7 MPa after sintering at 300 °C for only 5 s and 20 s, respectively. The sintering sequence phenomenon was observed, and the differences in microstructure between the pressure-assisted and pressureless joints were investigated. Robust bonding at the lattice level between the Ag NPs and Cu substrate was observed by high-resolution transmission electron microscopy, and this bonding contributed to the high shear strength obtained under rapid sintering conditions. A commercially acceptable alternative solution to achieving reliable Cu–Cu joint formation was obtained, especially for thermo-sensitive devices.

Although cationic epoxy was optimized for low-melting SnBi58 solder ACF joints with the lowest coefficient of thermal expansion (CTE) in terms of reliability, cationic epoxy also showed a faster curing property than any other types of adhesives. In fact, solder joint shapes at 250 degrees C bonding are very different from those shapes at 200 degrees C bonding. In this paper, four adhesive film types were investigated in terms of Sn-3Ag-0.5Cu solder ACF joint shapes on the electrical performances and reliability in a pressure cooker test (PCT). Thermal stability of adhesive films was tested to be first. Resin curing speeds were measured in a 250 degrees C isothermal mode differential scanning calorimetry, resin viscosities were checked by a parallel-plate rheometer, and adhesive thermomechanical properties, such as modulus and CTE, were characterized. Then, four different types of ACF resins containing the same weight percentages of Sn-3Ag-0.5Cu solders were assembled by the same thermocompression bonding parameter (250 degrees C 10s 2MPa on bump) on a 500-mu m-pitch flex-on-board (FOB) application, and different solder joint morphologies were verified. Various bonded solder ACFs joints were compared in terms of solder wetting areas, electrical performances by a four-point-probe method, and the reliability of PCT (121 degrees C 100% humidity 2atm) for 120 h. This paper aims at optimizing the best adhesive film candidate for SAC305 solder ACF joints of FOB application.

A composite silver nanoparticle (AgNP) ink was prepared by mixing the small AgNPs (10 nm in diameter), large AgNPs (50 nm in diameter), ethylene glycol, and deionized water at a mass ratio of 4:2:3:51. By spraying a sodium hydroxide solution, the AgNP pattern printed on the polyethylene terephthalate film surface can be sintered at room temperature with a minimum electric resistivity of 12.11 mu Omega.cm, 0.7 times smaller than that sintered at 150 degrees C. Our study confirmed that OH- ions can partially replace citrates on AgNP surfaces at room temperature, resulting in the loss of the encapsulated density of citrates. Such loss can induce the particle agglomeration, cause the sintering necks to form, and finally create the three-dimensional conductive networks. This research is of great importance to the rapid manufacturing of low-cost, low-environmental-impact and high-performance flexible printed circuits. (C) 2018 Elsevier B.V. All rights reserved.

In this study, a composite citrate-encapsulated AgNP ink was designed and synthesized. The ink was then printed on PET films to create the AgNP patterns by using an inkjet printing method. After that, the AgNP patterns were sprayed by the NaCl solution. Based on the experiments, the excellent sintering performance for AgNP patterns were obtained by NaCl treatment. The Cl- ions were confirmed to be able to partially replace citrates on AgNP surfaces, resulting the agglomeration of AgNPs at room temperature.

For the development of electronic packaging products, the mixture of micron-filler and nano-filler was adopted to improve the electronic property of conductive adhesive. The porpose of the addition of micron-filler and nano-filler is to achieve a higher conductive property, so that the perfect conductive adhesive could be obtained by the optimized conductive fillers. The conductive filler composed of Cu powders coated by nano-Ag layer and silver nanowire and resin matrix were mixed to fabricate conductive adhesive. The conductive filler composed of Cu powder coated by nano-Ag layer and silver nanowire could reduce the bulk resistivity and percolation threshold of conductive adhesive. When the conductive adhesive was cured at 170° for 60min using Cu powder coated by nano-Ag layer and silver nanowire as conductive filler and the content of filler was 60wt.%, the bulk resistivity of the newly formed conductive adhesive was low to $6.53\times 10- 5 \Omega \cdot$ cm, while the shear strength of the adhesive was 5.36MPa.

Micron sizes solder metallurgical joints have been applied in a thin film application of anisotropic conductive film and benefited three general advantages, such as lower joint resistance, higher power handling capability, and reliability, when compared with pressure based contact of metal conductor balls. Recently, flex-on-board interconnection has become more and more popular for mobile electronic applications. However, crack formation of the solder joint crack was occurred at low temperature curable acrylic polymer resins after bonding processes. In this study, the mechanism of SnBi58 solder joint crack at low temperature curable acrylic adhesive was investigated. In addition, SnBi58 solder joint cracks can be significantly removed by increasing the storage modulus of adhesives instead of coefficient of thermal expansion. The first approach of reducing the amount of polymer rebound can be achieved by using an ultrasonic bonding method to maintain a bonding pressure on the SnBi58 solder joints cooling to room temperature. The second approach is to increase storage modulus of adhesives by adding silica filler into acrylic polymer resins to prevent the solder joint from cracking. Finally, excellent acrylic based SnBi58 solder joints reliability were obtained after 1000 cycles thermal cycling test.

The exemption of Pb-bearing automobile electronics in the End of Life Vehicle (ELV) directive has recently expired, bring an urgent need to find Pb-free alloys that can maintain good performance under high-temperature and vibration conditions for automobile application. In this study, a new lead-free solder, Sn-0.7Cu-0.2Cr (wt.%) alloy, was developed. To evaluate the thermomechanical reliability of the new solder alloy in automobile electronics, a thermal shock test was performed. The results show that the presence of Cr in solder inhibits the growth of interfacial Cu3Sn layer and the formation of Kirkendall voids, which effectively improves the joint reliability under intense thermal shock condition compared with the commercial SAC305 and SC07 solders. Specifically, the shear strength of the Sn-0.7Cu-0.2Cr/Cu solder joints was higher by 23% and 44% than that of SAC305 and SC07 solder joints after 2000 cycles of thermal shock at 1 m/s shear speed.

3-D mask with a vacuum filtration system allows efficient fabrication of complex Ag nanowire patterns with clear edges.

The mechanism and morphological evolution of a thermal interface material prepared by pressureless sintering of a paste containing bimodal silver nanoparticles (AgNPs) were investigated. A high thermal conductivity (232 Wm -1 K -1 ) was obtained from the material sintered at 250 °C for 30 min. These results could be ascribed to decrease of the defect densities and sintered densities of the sintered structures.

Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous studies have discussed the influence of Ag on the interfacial intermetallic compound (IMC) thickness. However, because IMC growth is the joint result of multiple factors, such characterizations do not reveal the actual role of Ag. In this study, changes in interfacial IMCs after Ag introduction were systemically and quantitatively characterized in terms of coarsening behaviors, orientation evolution, and growth kinetics. The results show that Ag in the solder alloy affects the coarsening behavior, accelerates the orientation concentration, and inhibits the growth of interfacial IMCs during solid–state aging. The inhibition mechanism was quantitatively discussed considering the individual diffusion behaviors of Cu and Sn atoms, revealing that Ag inhibits interfacial IMC growth primarily by slowing the diffusion of Cu atoms through the interface.

An effective method for inhibiting the growth of interfacial intermetallic compounds during solid-state aging has been proposed in this study. Pre-tinned Cu substrates containing oriented interfacial Cu6Sn5 grains were prepared and reacted with a low-Ag Pb-free solder. The results show that the initial oriented interfacial grains were retained after the subsequent reflow. In addition, the presence of the oriented grains accelerated their orientation concentration and significantly affected the ultimate orientation distribution range during solid-state aging. As a result, the growth of the interfacial intermetallic compounds was inhibited due to the slower diffusion of Sn species through the solder/substrate interface.

The effects of Ag content on the interfacial reactions between Sn–Ag–Cu (SAC) solders and Cu substrates during soldering were studied based on an experiment in which the liquid solder is removed after a long exposure time. This removal of the solder allows for the capture and visualization of the interfacial IMCs formed during soldering and avoids the influence of Cu6Sn5 precipitated from the solder matrix during cooling. The results showed that a Cu6Sn5 scallop type layer with round grains having a strong texture was formed at the interface of the SAC solders/Cu systems. The addition of Ag decreased the IMC/liquid SAC solder interfacial energy and improved the wettability of the solder on the Cu. In addition to the reaction energy, the interfacial microstructure also affected the interfacial IMC growth extent. By changing the growth environment near the interface, Ag affected the orientation of Cu6Sn5 grains formed at the interface, leading to the evolution of a microstructure that generates more Cu6Sn5 grain boundaries at the interface. Consequently, under the same reflow conditions, SAC solders with a higher Ag content in contact with the Cu substrate form thicker IMCs interfacial layers.

The formation process and mechanism of the Sn3.5Ag/Cu solder bump during induction heating were investigated to elucidate the basic characteristics of the induction heating soldering process. During induction heating, solder balls quickly melted from the surface to the center, which could be utilized to prepare solder bumps of controlled height. Cu6Sn5 grains with a round scallop shape were generated at the interface as soon as the solder ball was wetted on the Cu substrate. With prolonged heating time, the uniform morphology of the interfacial Cu6Sn5 grains was transformed to a special morphology in which scallop-shaped grains occupy the central area of the interface, surrounded by prismatic grains. Numerous bulk Cu6Sn5 grains were precipitated and regularly distributed in the solder matrix, which affected the hardness and shear strength of the solder bumps.

A study was performed on the precipitation behavior of Cu6Sn5 during the solidification of Sn-based solders/Cu joints and its effect on the growth of interfacial intermetallic compounds (IMCs). During cooling, Cu in molten solder precipitates in the form of Cu6Sn5 both within the solder matrix and at the interface. The precipitation at the interface can greatly affect the interfacial IMC morphology and thickness but cannot change the interfacial IMC orientation. In general, additional Cu6Sn5 will precipitate at the solder/Cu interface when the Cu content is increased in the molten solder during soldering and when the cooling rate decreases during solder solidification. If the Cu content in the molten solder is sufficiently high, during cooling, the precipitated Cu6Sn5 will develop a prismatic morphology with the exposed surface indexed as (10-10) along the [0 0 0 1] direction of the existing Cu6Sn5 grains at the interface. (c) 2013 Elsevier B.V. All rights reserved.