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Copper azide with high density was successfully synthesized by in-situ reaction of nanoporous copper (NPC) precursor with HN3 gaseous. NPC with pore size of about 529 nm has been prepared by electroless plating using polystyrene (PS) as templates. The copper shells thickness of NPC was controlled by adjusting the PS loading amount. The effects of copper shell on the morphology, structure and density of copper azide were investigated. The conversion increased from 87.12% to 95.31% when copper shell thickness decrease from 100 to 50 nm. Meanwhile, the density of copper azide prepared by 529 nm NPC for 24 h was up to 2.38 g/cm3. The hollow structure of this NPC was filled by swelling of copper azide which guaranteed enough filling volume for keeping the same shape as well as improving the charge density. Moreover, HNS-IV explosive was successfully initiated by copper azide with minimum charge thickness of 0.55 mm, showing that copper azide prepared has excellent initiation performance, which has more advantages in the application of miniaturized explosive systems.

A series of large-area, flexible and transparent ultraviolet (UV) photodetectors (PDs) based on Ag nanowire (NW)@ZnO nanorods (NRs) are fabricated by an inexpensive, facile and effective approach. These Ag NW@ZnO NRs are successfully synthesized using a two-step method in an oil bath with a high surface-to-volume ratio and good crystallinity. The PDs are fabricated by drop-coating with different drop-coating times on the surface of polyethylene terephthalate (PET) coupled with Au electrodes. By optimizing the cross-linked network of Ag NW@ZnO NRs, PD2 with a size greater than 25 mm exhibits excellent photoresponse under UV light illumination of 365 nm (1.3 mW cm−2) with a bias of 5 V: a high sensitivity of over 103, and a much shorter rise/decay time of 2.6 s/2.3 s. Simultaneously, the detector exhibits an average transmittance of more than 70% in the visible light region, as well as good flexibility and excellent mechanical stability under a bending angle of 120 degrees over 1000 circles bending. These integral advantages have significant potential for practical applications and mass production.

This article presents a thermal control design method for a surface acoustic wave (SAW) device. We designed a heat-dissipation structure and packaging scheme to solve three key issues observed in SAW devices using anisotropic crystals as piezoelectric substrates in acoustofluidics (e.g., lithium niobate): SAW chip cracking caused by thermal stress, SAW chip cracking caused by mismatched thermal expansion coefficients of the packaging materials, and enhancement of the structural strength and stability of the SAW chip. This study establishes the physical model of the designed structure and the relationship between the steady-state working temperature and the physical properties of the material. By comparing these physical properties and numerical calculations, we identified nanosilver adhesive as the most effective bonding material between the SAW chip and the heat sink. In addition to designing and fabricating, we also evaluated our SAW devices experimentally. The results not only confirmed that the abovementioned three key problems were solved but also demonstrated the significant enhancement of the stability of the SAW device.

High interfacial resistance and uncontrollable lithium (Li) dendrite are major challenges in solid-state Li-metal batteries (SSLMBs), as they lead to premature short-circuiting and failure of SSLMBs. Here, we report the synthesis of a composite anode comprising a three-dimensional LiCux nanowire network host infiltrated with Li (Li* anode) with low interfacial impedance and superior electrochemical performance. The Li* anode is fabricated by dissolving Cu foil into molten Li followed by solidification. The Li* anode exhibits good wettability with Li6.4La3Zr1.4Ta0.6O12 (LLZTO) and high mechanical strength, rendering low Li*/LLZTO interfacial impedance, homogeneous deposition of Li, and suppression of Li dendrites. Consequently, the Li* anode-based symmetric cells and full cells with LiNi0.88Co0.1Al0.02O2 (NCA), LiFePO4 (LFP), and FeF2 cathodes deliver remarkable electrochemical performance. Specifically, the Li*/LLZTO/Li* symmetrical cell achieves a remarkably long cycle lifetime of 10 000 h with 0.1 mA·cm-2; the Li*/LLZTO/NCA full cell maintains capacity retention of 73.4% after 500 cycles at 0.5C; and all-solid-state Li*/LLZTO/FeF2 full cell achieves a reversible capacity of 147 mAh·g-1 after 500 cycles at 100 mA·g-1. This work demonstrates potential design tactics for an ultrastable Li*/garnet interface to enable high-performance SSLMBs.

The strip formation process on a glass surface in 3D printing of viscous droplets is presented with the relevant strip characteristics modelled. PEDOT:PSS polymer inks at different viscosities are used. It is found that unlike the symmetric circulation flow developed by a single droplet deposition, strip-printing by multiple droplets is achieved by the coalescence of droplets spreading unequally in different directions. Whereas the liquid viscous cohesion retards the flow in the direction aligning with the centre line of the coalesced droplets, the side spreading driven by liquid surface tension fills up the space on the target surface along the bridge between two coalesced droplets. When the deposition distance or space of two consecutive droplets is set at greater than a critical value, this flow inequality results in strips of scallop shape. With a deposition distance below the critical value, the strips formed tend to have parallel edges and the strip width increases with a decrease in the deposition distance. However, if the distance is set below a saturate level at which the liquid surface tension cannot withstand the deposited liquid volume, bulges are detrimentally formed randomly along the printed strips. Because of the viscous retardation to the spreading of drop liquid, the strips printed using a higher viscosity ink is narrower than that of a lower viscosity. Based on the strip formation process, the relevant characteristics of the printed strips are mathematically modelled using dimensional analysis. The developed models are found in good agreement with the experimental data and can be used to guide the selection of the operating parameters for strips with desired characteristics.

In this study, medical Mg–xZn (x = 3, 6, 9 wt%) alloys were successfully prepared by a novel technique, semi-solid powder moulding. The effects of Zn content and temperature (580, 590, 600 ℃) on the relative density, microstructure, microhardness and degradation behaviour were studied. The microstructure evolution and refinement mechanism during the forming process were analysed. The results show as the temperature and Zn content increase, the relative density and microhardness gradually increase. When the temperature is 600 ℃, the relative density of Mg–3Zn, Mg–6Zn and Mg–9Zn is 92.3%, 97.2% and 97.8%, respectively. The corresponding microhardness is 101.2 HV, 105.6 HV and 106.3 HV, respectively. The prepared Mg–Zn alloys have fine microstructure with equiaxed grains, which consists of α-Mg matrix and second phase of MgZn2 with a few of Mg4Zn7 and Mg2Zn11. As Zn content increases, the amount of second phase increases, and the microstructure becomes uneven at the Zn content of 9 wt%. Pseudo-transgranular liquation cracking is one of the grain refinement mechanisms. As the Zn content increases, the corrosion rate decreases firstly and then increases. Mg–6Zn prepared at 600 ℃ has the lowest corrosion rate of 4.8 mm/year after 9 days of dynamic immersion. Both the porosity and second phase influence the corrosion rate, but the porosity is the main factor controlling the degradation. Mg–6Zn alloy is the best composition based on the properties and microstructures. The main components of corrosion products are Mg (OH)2, hydroxyapatite and a small amount of MgO and CaCO3, which shows a good biocompatibility. Semi-solid powder moulding shows a fantastic potential to prepare medical Mg alloys.

A low-temperature sintered silver paste was used for the metallization of tempered glass, which was used to prepare vacuum-tempered glass by soldering with Sn96.5Ag3Cu0.5 paste (SAC305). The effects of the glass content and the sintering temperature on the microstructures, shear strengths, and fracture mechanisms of the bondlines were investigated in detail. The microstructure of the thick silver film and its interface with the tempered glass was characterized. The dissolution and precipitation behaviors of silver in Bi–B–Zn glass were also analyzed. Bi4B2O9 crystals were detected in the microstructure of the thick silver film when the joining temperature was increased above 450 °C, which can strengthen the silver film and the interface with the tempered glass. After soldering at 450 °C for 10 min, an excellent bondline was formed using the low-temperature sintered paste, which had a shear strength of 42.3 ± 2.4 MPa and a leak rate of 7.2 ± 0.4 × 10–3 Pa.cm3/s. The sintered paste had a composition of 80 wt.% silver and 20 wt.% glass powder. Furthermore, heat transfer tests revealed that the vacuum tempered glass had excellent thermal insulation properties. The results showed that the low-temperature sintered silver paste combined with soldering was an effective method to prepare vacuum-tempered glass.

Catalysts with high stability and efficient electrocatalytic properties are urgently explored to improve sluggish kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in Li-O2 batteries. In this paper, exquisitely designed bifunctional catalyst comprising Co3O4 nanospheres embedded in NiO nanosheet arrays on carbon cloth as a freestanding cathode is reported. The unique hierarchical structure facilitates the continuous oxygen diffusion and the transport of Li+. Moreover, benefitting from the synergetic effect between NiO and Co3O4, the interface charge transfer kinetics was greatly enhanced. As a result, Li-O2 cells based on the integrated NiO/Co3O4/CC electrode present an improved overpotential of 1.1 V, a high discharge capacity of 8000 mAh g−1 at 200 mA g−1 and an enhanced cycle stability of 130 cycles under a restricted capacity at 500 mAh g−1 were reached.

This paper presents a novel die attach material for power device packaging based on transient liquid phase (TLP) bonding. Through two-step electroless plating, the Cu@Sn@Ag particles were prepared, and realize interconnection with Cu Substrates after being compressed into preform. Due to the large specific surface area of the core–shell particles, the reflow time can be reduced to 15 min at a low temperature of 250 °C under a pressure of 3 MPa to form high-remelting-point intermetallic compounds (IMCs), which can withstand a high temperature of at least 475 °C. Due to the protection of the Ag coating, the Cu@Sn@Ag particles exhibited excellent oxidation resistance, and the bonding process can be carried out in the atmosphere. Then, the service reliability of the bondlines was evaluated in harsh environments, such as high temperature and humidity, high temperature storing, and thermal shock. The average resistivity of the bondlines was increased from 4.6 ± 1.4 to 8.5 ± 3.8 µΩ cm after being stored at high temperature (85 °C) and high humidity (85% RH) environment for 14 days. After storing at 300 °C for 15 days, the porosity of bondline increased from 6.8 to 10.8%, and the average shear strength decreased from 30.5 ± 6.3 to 22.3 ± 5.6 MPa. After thermal shock between − 40 and 125 °C for 500 cycles, the bonding rate decreased from 99.9 to 84.2%. Moreover, the short-circuit time of electrochemical migration under 60 V voltage was extended to 145 s. The bondline based on the novel core–shell particles exhibited excellent performance as a die attach material under harsh environments.

Cu-to-Cu interconnection has drawn increasing attention as the bump pitch is decreasing continuously. Cu-to-Cu interconnections exhibit excellent mechanical, electrical, and thermal properties without forming IMCs, which usually degrade the interconnect reliability due to their brittle nature. In this paper, Cu-to-Cu interconnection can be realized at 150 °C for 10 min under a pressure of 3 MPa. The microstructure of the nanoporous Cu coarsened significantly and the interfaces of the bondline can not be distinguished clearly after bonding at 250 °C for 30 min under a pressure of 3 MPa. The microstructure was more densified along the bonding interface than the rest part, and the degree of densification was increased with the increasing bonding temperature and pressure. The average resistivity, thermal conductivity, and shear strength of the bondlines were determined to be 4.12 μΩ cm, 176.49 W m−1 K−1, and 18.78 MPa, respectively. After aging at 200 °C for 300 h, the shear strength was increased by 44.5% due to the increased densification rate brought by the diffusion of Cu atoms, which confirmed the Cu–Cu interconnection reliability during long-term service.

A soft body area sensor network presents a promising direction in wearable devices to integrate on-body sensors for physiological signal monitoring and flexible printed circuit boards (FPCBs) for signal conditioning/readout and wireless transmission. However, its realization currently relies on various sophisticated fabrication approaches such as lithography or direct printing on a carrier substrate before attaching to the body. Here, we report a universal fabrication scheme to enable printing and room-temperature sintering of the metal nanoparticle on paper/fabric for FPCBs and directly on the human skin for on-body sensors with a novel sintering aid layer. Consisting of polyvinyl alcohol (PVA) paste and nanoadditives in the water, the sintering aid layer reduces the sintering temperature. Together with the significantly decreased surface roughness, it allows for the integration of a submicron-thick conductive pattern with enhanced electromechanical performance. Various on-body sensors integrated with an FPCB to detect health conditions illustrate a system-level example.

With the rapid development of the third-generation semiconductor materials, an appropriate high-temperature-resistant die attach material has become one of the bottlenecks to fully exploit the excellent properties of the third-generation semiconductor power devices. At the same time, a low-bonding temperature is always the pursuit goal of packaging engineers to reduce the thermal residual stress in electronic devices. In this paper, a low-temperature bonding method was proposed to address the above-mentioned issue based on In infiltrating the nanoporous Cu. In, as a low melting point metal, can significantly reduce the bonding temperature, and the nanoporous Cu structure can provide a very large specific surface area, which greatly increases the consumption rate of In. Furthermore, the formed Cu-In IMCs with high-remelting temperature can withstand the high operating temperature. The microstructures of the bondlines before and after bonding were studied in detail. The results show that the bondline can completely consume the low melting point In, within 10 min at 165 °C under a pressure of 0.75 MPa. When the bonding temperature was further increased to 310 °C, the bondline was composed of η-Cu2In and δ-Cu7In3 phases, whose melting points were more than 600 °C. The average electrical resistivity was determined to be 5.53 ± 0.65 μΩ cm, and the thermal conductivities were 144.33 W m−1 K−1, 139.24 W m−1 K−1 and 129.79 W m−1 K−1 at 30 °C, 150 °C and 300 °C, respectively. The average shear strength were 19.09 ± 3.4 MPa, 20.47 ± 4.6 MPa and 30.73 ± 5.2 MPa at 30 °C, 250 °C, 310 °C, respectively. These results indicate that the nanoporous Cu infiltrated with In could meet the requirements of electrical, thermal conduction, and mechanical support as a die attachment for high-power devices.

P2O5–V2O5–ZnO (PVZ) glass was prepared by the melt-quenching method and displayed its excellent properties including the low glass transition temperature (Tg = 387 °C), the moderate coefficient of thermal expansion of 6.48 × 10–6/°C and the excellent thermal stability (ΔT) of 198 °C. Both IR and Raman spectroscopy results indicated the units of VO2, VO3, (VO3)n chain structure increased with the increasing of V2O5 content, which resulting in the reduction of Tg and the increase of ΔT. A lead-free silver paste incorporated with different glass content was sintered on the Al2O3 ceramic substrate from 500 to 650 °C. The resistivity of the silver thick film increased with the increasing of the PVZ glass content, but the adhesion between the silver thick film and the Al2O3 substrates was obviously improved. The silver paste with 1 wt% glass showed a low resistivity (3.13 μΩ cm) and a high shear strength (40.47 MPa) after sintering at 650 °C for 10 min. The results suggested these improvements were attributed to the significant effect of PVZ glass on the densification of the silver thick film and the formation of the silver particles embedded in glass and AlPO4 reaction product. Hence, the PVZ glass exhibits tremendous potential application in nontoxic lead-free low temperature sintered silver paste for the Al2O3 ceramic metallization.

Ultrasonic-assisted brazing (28.8 kHz, 180 W) was introduced to achieve high-quality joints between Ti–6Al–4V alloy and ZrO2 ceramic with Al-5wt.%Si brazing filler in air. The interfacial microstructure of intermetallic compounds (IMCs) and the phase constitution of joints ultrasonic-assisted brazed at 700 °C for different ultrasonic time were investigated in detail using a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer and X-ray diffractometer. When the ultrasonic time was 20s, the average shear strength of the joint reached a maximum value of 90.68MPa and two important types of IMCs Ti(Al,Si)3 and Ti7Al5Si12 formed at the interface between the Ti–6Al–4V and the filler. Ultrasonic played a vital role in the formation of Si segregation regions at the interface near the Ti–6Al–4V and in the centre of the joint. A change in the Ti molar fraction, resulting from the cavitation effect of ultrasonic on the surface of Ti–6Al–4V, increased the chemical potential gradient of Si across the joint. Meanwhile, driven by the ultrasonic standing wave field in the liquid Al-5wt.%Si filler, Si atoms moved to the ultrasonic antinode-plane spontaneously. Ultrasonic-assisted brazing proved to be an effective method of joining Ti–6Al–4V and ZrO2 with Al-5wt.%Si filler.

The phase-transformation-induced damage of Cu6Sn5 is an emerging reliability issue in the manufacturing of 3D ICs. Although the retarded phase transformation from η-Cu6Sn5 to η′-Cu6Sn5 at room temperature can produce a large expansion in volume, how the transformation stress threatens the joint reliability during usage is poorly understood. In this paper, the evolution characteristics of quenched η-Cu6Sn5 bumps were observed during ageing at 25 °C for 1–40 d Due to the retarded phase transformation, η′-Cu6Sn5 whiskers spontaneously nucleated and grew on the surfaces of η-Cu6Sn5 bumps. The orientation relationship between the two phases favourable for whisker growth was confirmed, and two necessary conditions for whisker formation were discussed. In addition, the potential harmfulness of whisker growth was analysed. The study will help expose the phase-transformation-induced damage of Cu6Sn5 during room-temperature ageing and may reduce the failure risk of entire Cu6Sn5 intermetallic joints in future large-scale applications of 3D ICs.

A Z-scheme photocatalytic system has been widely called for to solve water pollution problems. However, the mechanism for the degradation of pollutants with a Z-scheme photocatalyst has so far been ambiguous. In this work, an efficient all solid-state BiOI/Pt/g-C3N4 photocatalyst was conceived and fabricated based on the Fermi level matched principle. The morphology, structure and chemical composition were characterized in detail. The degradation rate for phenol over as-prepared BiOI/1% Pt/g-C3N4 was 6.0, 2.3 and 1.8 times higher than those of pristine g-C3N4, BiOI/g-C3N4 and Pt/BiOI, respectively. Furthermore, the highest degradation rate constant (0.0514 min−1) for tetracycline hydrochloride (TCH) could be achieved with BiOI/1% Pt/g-C3N4. Notably, the outstanding degradation performance was ascribed to unobstructed photogenerated charge separation and transfer resulting from the appropriate interfacial interaction of Pt/g-C3N4 and BiOI/g-C3N4, which was verified by the results of electron spin resonance studies, reactive oxidation species scavenger experiments, and work function analysis. Characterization results from fresh and used photocatalyst samples, and cyclic degradation and toxicity experiments demonstrated the extremely high stability and low toxicity of BiOI/1% Pt/g-C3N4. Accordingly, the comprehensive degradation mechanism based on photophysical and photochemical processes was investigated in depth. The rationally designed all solid-state photocatalyst has prospects for environmental remediation.

This paper presents a novel die attach material based on Cu@Sn@Ag particles, in which the outermost Ag layer prevents the oxidation of the Sn layer and expedites the consumption of the low-melting point Sn phase. The die attach material can be reflowed at 250 °C for 15 min under a pressure of 3 MPa in the atmosphere, subsequently, the bondline can sustain a much higher temperature up to 480 °C. The results show that the Sn phase was totally transformed into Cu3Sn and Ag3Sn intermetallic compounds (IMCs) after reflow. Moreover, the Cu particles were evenly distributed in the Cu3Sn and Ag3Sn IMCs. After Cu@Sn@Ag particles were heated at 250 °C for 6 h, the average mass increased only by 2.8%, which indicates that the oxidation resistance property of Cu@Sn@Ag particles is excellent. The average electrical resistivity of the bondline was 4.6 µΩ cm, and the thermal conductivities were 159.97 W m−1 K−1, 142.71 W m−1 K−1, 137.28 W m−1 K−1 at 30 °C, 150 °C, 300 °C, respectively. The average shear strengths of the bondline were 25.8 MPa and 19.7 MPa at 30 °C and 400 °C, respectively. The coefficient of thermal expansion of the bondline was measured to be 15.77 × 10–6/°C. This novel paste shows great potential in die attachment in power device packaging.

Drop coalescence is central to diverse processes involving microfluidics in industrial, engineering, and scientific realms and has attracted much attention in recent years. Here, the effect of temp...

In this work, three-dimensional ZnS/reduced graphene oxide/polypyrrole ternary composites were synthesized. The as-prepared composites are investigated as electrode materials for supercapacitors and lithium-ion batteries. For the application of supercapacitor in three electrode system, its discharge specific capacitance and energy density at 1 A/g are 1175.8 F/g and 80.0 Wh/kg after 5000 cycles, respectively. Meanwhile, its cycle stability at 1 A/g is up to 151% during 5000 loops. For the application of lithium-ion battery, its discharge specific capacitance and energy density at 100 mA/g can be up to 1446.9 mAh/g and 955.6 Wh/kg after 200 cycles, respectively. The cycle stability of the ternary composite is up to 157% at 100 mA/g during 200 loops. The excellent electrochemical performance of the composites could be ascribed to the three-dimensional structure which facilitates the penetration of the electrolyte and the insertion/extraction process of Li+ and the synergistic effect between organic and inorganic materials. The results indicate that the ZnS/reduced graphene oxide/polypyrrole composite are promising electrode materials for high-performance supercapacitors and lithium-ion batteries.

Metal aerogels are a new material class with unique properties, including lightweight, high surface area, high reactivity, and high electrical conductivity, making them highly attractive in various applications, such as sensing, thermal insulation, energy generation/storage, and catalytic conversion. A novel flexible preformed film has been produced from the AgNW aerogel to realize the flexible integration among complex structures in this work. As the AgNW forming bulk 3D networks in the aerogel has excellent flexibility, stability and high reactivity and conductivity, the proposed preformed film can enable the interconnection between metals like Cu or Ag through self-sintering without additional flux or solders. According to the experimental data, reliable and flux-free bonds can be achieved between components with If-shaped, V-shaped, round-shaped or step-shaped structures through the preformed AgNW aerogel film, with a high shear strength over 30 MPa, a low electrical resistivity less than 4.5 J.1g.cm and a large thermal conductivity attaining 110 W/m*K, if proper temperature and stress were applied. Meanwhile, these flexible preformed films can also provide ultra-high electromagnetic shielding effect over 75 dB in the frequency range of 8–12 GHz, and be further combined with PDMS to serve as a flexible circuit with a high electrical conductivity over 1.4*106 S/m. In summary, this work provides novel approaches to realize the adaptive interconnection between complex structures and provide new material classes for electromagnetic shielding and flexible circuit, which may enable the extended usage of metal aerogel materials in flexible electronics and packaging.

The fast development of highly integrated circuit packaging electronics generates electromagnetic pollution, causing harmful effects on the performance of the facility and the health of human. Thus, there is an increasing demand for electromagnetic interference (EMI) shielding materials. Metals are traditional EMI shielding materials with extremely high EMI shielding effectiveness (SE) because of their high electrical conductivity. However, the disadvantages of metals, including high density, poor corrosion resistance and poor workability, restrict their use. At present, carbon materials (such as graphene, CNF, and CNTs) are widely used to prepare EMI materials because of their high flexibility and conductivity. However, the complex synthesis process of carbon-based fillers and poor dispersion limit their application. Recently, silver nanowires are considered excellent fillers for the preparation of EMI materials due to their excellent conductivity, dispersibility and flexibility. Herein, we prepared silver nanowire aerogels by the method of freeze casting and freeze drying. The aerogel has an ultralow density below 5 mg/cm3 and the porosity is as high as 99.3%. The conductivity of aerogels is further enhanced with the treatment of NaCl solution. The EMI SE of the aerogel approaches 75.2 dB at a thickness of 4 mm due to the interconnected three-dimensional network structure and excellent conductivity of 28368 S/m.

In order to better study the damage effect of nanosecond pulsed laser on PIN photodiodes, a two-dimensional axisymmetric model and heat source model of nanosecond irradiation photodiodes were established according to the theory of heat conduction, and the factors of thermal physical parameters changing with temperature were considered. The finite element COMSOL Multiphysics software was used to simulate the temperature field distribution of PIN photodiodes irradiated by nanosecond pulse lasers. The research results show that the temperature change trend of the target surface under different energy densities is consistent, and there is a phenomenon of energy ac-cumulation. From the center of the irradiation to the edge of the target, the temperature gradually weakens and dis-tributes in a gradient. and the temperature rise rate of the target is directly proportional to the increase in energy density. It is found that the melting damage of the photodiode is reached. The range of energy density is, 144.01mJ/cm2 ~ 175.58 mJ/cm2 , The research results provide a theoretical basis for the research field of laser damage to materials.

The laser ablation micro thruster uses the target vapor or plasma jet generated by the laser ablation working fluid to obtain the reaction impulse and thrust. The working mode of the laser micro thruster is divided into two types, reflection type and transmission type. In this paper, the influence of plasma treatment on the bonding force between ablation layer and transparent layer is studied in transmission mode, and the influence of different kinds of substrate materials on the mechanical properties of laser ablation is studied. The results show that the surface activity of the PET transparent substrate is greatly improved by the formation of N-C=O or C=O active groups after plasma treatment, and the interlayer bonding force of the target band is increased by about 50%. Thus the peeling of the ablation layer and the transparent layer around the ablation pit after laser ablation target zone is eliminated. The light transmittance of PET substrate material is better than that of PI substrate material. In the case of the same thickness of ablation layer, the single pulse impulse and specific impulse of PET substrate target band are better than that of PI substrate material target band. The punching is better than the PI base material target tape. The optimization of target parameters provides guidance for further application of laser propulsion.

Model tests were performed to investigate the lateral earth pressure acting on the retaining structure adjacent to both natural ground (NG) and composite foundation (CFRLP), which were supported with rigid-flexible and long-short piles. Two testing procedures, namely, applying a load to the foundation and rotating the retaining structure along its toe, were considered. The results indicate that the additional lateral earth pressure acting on the retaining structure adjacent to the CFRLP is less than that of the NG in the depth of the reinforcement area strengthened by flexible piles. Compared with NG, the CFRLP yielded a smaller normalized height of application of the lateral earth pressure, suggesting that the CFRLP blocked the horizontal diffusion of the load and had a strong ability to transfer the surcharge load to the deep soil. When rotating the retaining structure, the lateral earth pressure acting on the upper part of the retaining structure experienced limited reduction once the displacement at the top of the retaining structure was greater than 8 mm, whereas the pressure acting on the lower part of the retaining structure continued to decrease with increasing displacement. In addition, a three-dimensional finite element model (FEM) was used to investigate the influence of the pile parameter and the wall-soil friction angle on the additional lateral earth pressure.

Soda lime tempered glass was successfully joined by a Bi-B-Zn lead-free low-melting glass with a composition of 35Bi2O3-50H3BO3-15ZnO (mol%). The Bi-B-Zn glass exhibited a glass transition temperature (Tg), softening point (Td) and crystallization temperature (Tc) of 346 ℃, 364 ℃and 448 ℃ respectively. The wettability of the glass on tempered glass substrate was investigated, and a contact angle of less than 13.94° was obtained when the temperature was raised to above 470 ℃ in open atmosphere. The microstructural evolution, interfacial bonding mechanism and mechanical properties of the joint at different joining temperatures were investigated. The diffusion bonding between Bi-B-Zn glass solder and tempered glass was achieved. The crystals of Bi4B2O9 were detected in the joint when the joining temperature was higher than 450 ℃. The shear strength and Vickers hardness of the joint reached 35.14 ± 1.89 MPa and 191.55 ± 13.93 MPa, respectively. The effects of the fractions and size of Bi4B2O9 on the shear strength were evaluated, and the fracture mechanism at the interface was also clarified.

In this study, ultrasonic-assisted soldering was applied to join a Ta alloy with the light structural material of a Mg alloy. The effects of the ultrasonication time on the microstructure and mechanical properties of the Ta/Sn/Mg joints were investigated. The results showed that molten Sn could wet the substrates of Mg and Ta without flux under the effect of ultrasonic vibration and that the maximum shear strength of the joint was approximately 27 MPa. A large amount of Mg entered into the Sn with the effect of ultrasonic vibration and was present in molten Sn in the form of both solute and primary Mg2Sn phases. During the cooling of the joint, the supersaturated Mg solute was precipitated at the area close to the Ta sheet by way of the growth of the primary Mg2Sn phase and the nucleation of Mg2Sn on the Ta surface and in the Sn matrix. Finally, a large amount of Mg2Sn formed at the substrate/solder interface and in the Sn matrix, and the Mg2Sn at the Ta/solder interface increased the interfacial strength. With an increase in the ultrasonication time, the number of Mg2Sn phases in soldering seam was increased, but the nucleated Mg2Sn at the Ta/solder interface decreased, which resulted in a gradual decrease in the strength of the Ta/solder interface.

The interfacial reactions between Cu and Al during ultrasonic welding were investigated, focusing on the effect of Pd in Pd-coated Cu and Pd-alloyed Cu (0.3 wt% and 2 wt% PdCu). For Pd-coated Cu–Al bonding, it is found that Pd layer would act as diffusion barrier layer at the interface, and intermetallic compounds (IMCs) formed at Pd-free location for as-welded condition. As annealing time increases, Cu atoms and Al atoms bypassed the fractured Pd layer to form IMCs at the interface. Combining experimental observations, a model of Pd diffusion barrier effect was first proposed at the Pd-coated Cu–Al interface. For Pd-alloyed Cu–Al bonding, Pd can promote the atomic diffusion of active elements and accelerate the formation of IMCs, and excessive 2 wt% Pd addition can lead to the appearance of voids and cracks at interface, which is destructive for reliable interconnection structure. The thickness of the interfacial IMCs for pure Cu and 0.3 wt% PdCu at different heat treatment conditions has a linear relationship with the square root of time, which means that the growth of IMCs is controlled by volume diffusion. The diffusion activation energy of IMCs for 0.3 wt% PdCu (46.08 kJ/mol, 52.88 kJ/mol, and 65.35 kJ/mol for Cu9Al4, CuAl and CuAl2 respectively) was smaller than that for pure Cu (60.24 kJ/mol, 58.12 kJ/mol, and 82.94 kJ/mol for Cu9Al4, CuAl and CuAl2 respectively). Furthermore, the percentage of Cu9Al4 in the whole IMC decreased for 0.3 wt% PdCu, which can reduce the halogen corrosion from epoxy molding compound (EMC) during the reliability test of highly accelerated temperature and humidity stress testing (HAST).

A new die attach material prepared by pressing micro-sized Sn-coated Ag powders as a preform is proposed for high-temperature power device packaging. The Sn-coated Ag powders were completely transformed into Ag3Sn with a melting point of 480°C after bonding at 250°C for 10 min, subsequently producing a bondline which can sustain a much higher temperature than the processing temperature. The detailed microstructural analysis indicates that a fine-grained full Ag3Sn bondline with high-density twin boundaries can be formed in a short reflow time, which contributes to the improved performance of the full Ag3Sn bondline, with an average shear strength of 37.5 MPa at 400°C. Nano-indentation testing showed that the average hardness and elasticity modulus of the prepared full Ag3Sn bondline were 3.1 ± 0.26 GPa and 84.56 ± 6.13 GPa, respectively. The electrical resistivity was measured to be 11.42 μΩ cm. The shear strength at 400°C was kept above 20 MPa after aging at 200°C for 200 h due to the thermostability of Ag3Sn microstructure in the bondlines.

In this study, the nanoporous copper (NPC) sheets were fabricated by dealloying Cu40Al60 precursor alloy in 1.45 mol/L dilute hydrochloric acid solution under water bath at 80 °C for 12 h. The NPC sheets had a typical homogeneous ligament-pore microstructure with the average pore size of 320 nm. The NPC sheet was sandwiched between two Cu substrates with Sn3.0Ag0.5Cu (SAC305) solder paste. The melted solder infiltrated the NPC sheets and reacted with the Cu ligaments rapidly. A Cu/Cu-Sn IMCs/Cu interconnection can be achieved after reflow at 240 °C for 10 min under a pressure of 5 MPa. The average shear strength of the bondlines was 37.68 MPa, and the maximum shear strength can reach up to 57.38 MPa. The average resistivity of the bondlines was measured to be 13.38 μΩ·cm. At last, the evolution of microstructure, Vickers hardness and shear strength of the bondlines during aging test at 200 °C for 15 days were characterized. The bondline can be fabricated at a low temperature but can service at a much higher temperature with a high re-melting point, which can provide a new die attach method for high temperature power device packaging.

A new Pb-free Ag paste containing a Bi2O3-B2O3-ZnO glass frit was developed for Al2O3 substrate metallization. First, Bi2O3-B2O3-ZnO glass frits with various compositions and glass transition temperatures (Tg) of 322 °C–440 °C were synthesized by using a traditional melt-quenching method. Then, silver pastes containing different contents of the glass frit were sintered on an Al2O3 substrate at temperatures ranging from 450 °C to 600 °C. The glass frit content and the sintering temperature had significant impacts on the electrical resistivity and shear strength of the product. The experimental results indicated that the silver film formed from the paste containing 7 wt.% glass frit and sintered at 600 °C for 15 min had a low electrical resistivity of 2.5 μΩ cm and a high strength of 28.5 MPa. These properties resulted from the formation of a stable glass network that supported the Ag network. Furthermore, ZnAl2O4 was observed to form close to the interface of the Al2O3 substrate, which could improve the shear strength. Moreover, the Bi-based glass frit could be a suitable substitute for Pb-based glass frits in the preparation of environmentally friendly silver pastes for forming thick Ag films on Al2O3 substrates.

In this study, composite solder pastes with different sizes of Sn and Cu particles were prepared. A large fraction of solid/liquid interfacial contacts adjusted by the Cu particle sizes contributed to an ultra-rapid metallurgical reaction at a high in-situ temperature of 437.1 °C under ultrasonic waves. Thus, the sole IMC of high-melting-point Cu3Sn joints with a tiny proportion of residual Cu were obtained in air at 250 °C for 10 s under the ultrasonic-assisted transient liquid phase (TLP). The intermetallic joints exhibited the average shear strength of 49.96 MPa at ambient temperature. In particular, a promising shear strength of 46.54 MPa was obtained at the high temperature of 350 °C, which exhibits significant potential for the high temperature electronic devices.

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.

A silver (Ag) composite paste was fabricated based on Ag nanoparticles (NPs) and Ag microflakes (MFs). Robust interconnections were achieved after sintering in the temperature range of 150–225 °C. The shear strengths of the Ag MF + NP joints before and after thermal shock from − 50 to 150 °C for 1000 cycles were 155.7 ± 14.5 MPa and 78.4 ± 20.8 Mpa, respectively. The results show that the Ag composite paste not only has similar sintering properties to the Ag NP pastes but also exhibited superior mechanical reliability due to the addition of the Ag MFs. In addition, the sintered properties of different Ag pastes were discussed in terms of the coating organics, thermal behaviour and microstructure. The fracture modes after the shearing tests were analysed in detail. The Ag composite paste provides a potential solution for high-temperature applications.

This paper presents a fabrication method for high-temperature-resistant bondlines based on Cu@Ag@Sn multilayer core–shell hybrid microspheres in which a Ag layer was adopted to accelerate the consumption of a Sn layer. The phase transformation and microstructural evolution during the bonding process were investigated in detail. After the microspheres were heated at 250 °C for 20 min under a pressure of 0.5 MPa, the bondline could withstand high operation temperatures of up to 480 °C. After reflowing at 250 °C for just 5 min, the outer low-melting-point Sn layer was completely consumed. After 20 min, the bondline was composed of Ag3Sn and Cu3Sn intermetallic compounds with a dispersion of Cu microspheres. The average shear strengths of the resulting bondlines were 39.9 and 31.9 MPa at room temperature and at 400 °C, respectively.

In this paper, a novel high-sensitivity optical sensor based on cascaded two Fabry-Perot interferometers (FPIs) has been investigated theoretically and experimentally. In order to improve the sensitivity, the two FP interferometers were designed with slightly different free spectrum ranges (FSRs) to produce Vernier effect. The experimental results showed that the sensitivity of the sensor is 23,794.6 nm/RIU for the wavelength interrogation and 4602.3 dB/RIU for the intensity interrogation, much higher than that of the conventional sensors for the bulk refractive index (RI) sensing. Finally, the reaction between Streptomycin monoclonal antibody and Streptomycin-BSA was measured, showing a great potential for low-cost and portable systems in biochemical sensing.

In the application of electronic products, it is critical for conductive adhesives to ensure high electrical conductivity and good adhesion reliability. In this study, isotropic conductive adhesives (ICAs) with high conductivity and low percolation threshold can be achieved by making full use of the synergistic effect of micron spherical and flaky silver-coated copper (Cu@Ag) conductive fillers. The flaky Cu@Ag powder prepared by electroless plating was chosen as the main conductive filler, and the spherical core-shell structure Cu@Ag powder was used as an auxiliary conductive filler to be dispersed in the flaky Cu@Ag particles, providing more possibilities for building a large number of conductive bridges. In this study, the Cu@Ag powder was synthesized to eliminate the disadvantages of Cu oxidation and Ag electrochemical migration, while making the ICAs low cost and favourable conductivity. Furthermore, the curing parameters were optimized for the matrix resin in corresponding experiments. The results showed that a combination of spherical and flaky Cu@Ag powders in ICAs could not only significantly reduce the percolation threshold and the bulk resistivity but also increase the shear strength compared with the single component. In particular, the bulk resistivity of the optimum sample was 1.95×10-3 Ω·cm, and the shear strength was 22.69 MPa when the filler content was only 60 wt%. Hence, the ICAs filled with spherical and flaky Cu@Ag will pave the way for high-performance and low-cost ICAs in the electronics packaging industry.

It is a tradeoff between bandwidth and resolution for the on chip Fourier transform spectrometer. To solve this problem, a single ring filter enhanced on chip Fourier transform spectrometer was proposed recently. In this paper, the performance of the cascaded double-ring enhanced Fourier transform on chip spectrometer was investigated theoretically. The cascaded two tunable Micro-ring resonators forms a large narrow band filter with a larger free spectral range (FSR) than the single ring, which reduces the requirement of the Fourier transform spectrometer spectral resolution. The spectrum of the input is retrieved by the Fourier transform algorithm with dispersion correction. The cascaded doublering enhanced Fourier transform spectrometer has a high resolution (0.3 nm) and a large bandwidth (1500nm-1600nm). The fabrication process is compatibility with CMOS process. It can be easily integrated with other silicon-based optical devices.

In this paper, a thermo-optic tuning optical waveguide sensor system based on a cascaded double micro-ring resonator is investigated. The system consists of a micro-ring resonator with the microheater as a reference ring and a micro-ring resonator with removing the upper cladding layers as a sensing ring, combined with a microfluidic control. The refractive index change of the sample is measured by the electric power change of the microheater. The experimental results show that the sensitivity of the thermo-optic tuning is 34.231 W/RIU (refractive index units), and the measurement range is 4.325 × 10−3 RIU, almost eight times larger than that of the cascaded double micro-ring resonator without thermo-optic tuning for the intensity interrogation.

The smart solder has been developed for the geometry control by the external magnetic field, which could be attractive for the application in the electronic packaging industry. However, the knowledge about the smart solder is still in a preliminary stage. In this paper, for the soldering of smart solder under an external magnetic field, the effect of Ni content and magnetic field on the wetting and spreading of solder was studied by melting the smart solder balls on a polished copper plate. The mechanism of magnetic field was analyzed for the wetting and spreading process of smart solders. The interfacial IMC between the smart solder and the copper plate was studied. The influence of the magnetic field on the interface morphology and phase of the IMC was analyzed. The mechanical properties, interface IMC and fracture morphology of copper soldering were compared with and without magnetic field, and the effect of magnetic field on the soldering joint was comprehensively analyzed.

As a bulk micromachining technology, the metal assisted chemical etching (MACE) is attractive for the application of silicon via fabrication, which is an important technology to realize the 3D stacked chip electrical interconnection in integrated circuit. In this paper, silver is used as catalyst to make an anisotropic wet etching of silicon bulk. The effect of the dimension of Ag nanoparticles (NP) on TSV holes is discussed. In the experiments, the etching rate could be about 10 μm/min, and the aspect ratio could reach around 100 with the Ag NP catalyst. When the average diameter of silver particles increases from 19nm to 43nm, the average diameter of corrosion holes also increases from about 20nm to about 45nm. The MaCE shows the possibility of a low-cost wet etching technology to achieve a high-aspect-ratio nano size silicon via.

With the development of the electronics industry, the heat-resistance of interconnect within the electronic components is becoming more and more prominent for the requirement in the multi-functionality, high-performance and high-density of electronic systems. Therefore, there is an urgent need to develop a kind of connecting material that can achieve interconnection at low temperatures and operate reliably at high temperatures. In this paper, novel composite solder based on micron-sized Sn and Cu metal particles was prepared. For the enhanced metallurgical reaction efficiency, high melting-point solder joints were achieved rapidly under low temperature reflowing conditions. The obtained solder joints have intermetallic compounds (IMC) of skeleton-network structure and accordingly excellent mechanical properties. The shear strength can attain 82 MPa and 40 MPa, respectively, at room temperature and 300 °C. Moreover, the metallurgical reaction process and thermal behavior between microparticles in the composite solder were also studied. The formation mechanism of skeleton IMCs and defects is analyzed, and the influence of process parameters is verified. The above results can be used to complete high performance packaging, and further realize the control and optimization for multi-functional high-density electronics.

The lead-tin solder has already been replaced by the lead-free solders gradually in most industrial applications. However, the reliability of lead-free solder is still a critical problem that must be considered during the design scheme period of electronic product. In this paper, the feasibility of a thermo-electric accelerated test, as well as its corresponding failure mechanism, was discussed to reduce the reliability test duration. The test lifetime, analyzed with the Weibull distributions, revealed an apparently decreased time-to-failure and the cycles-to-failure in the thermo-electric accelerated test, comparing with the one under thermal cycling test. Based on the observation of the microstructure evolution in solder joints, it can be found that the electric current in the reliability test could accelerate the evolution of solder microstructure, without apparently changing the corresponding failure mechanism. Thus, it could be concluded that the thermo-electric test scheme would be a valuable option to achieve highly accelerated reliability test for electronic products.

The ability to remove a deposited drop on a substrate is crucial for self-cleaning materials. Here, an approach to achieve the removal of a deposited droplet by employing the impact of a smaller droplet as remover is reported. The results give visible evidence that with the increase of the impact velocity and the size of the impacting droplet, a deposition-to-rebound transition of droplets could occur. Correspondingly, a map showing the relationship between the states of the impacted droplet and the impacting conditions is depicted. More importantly, the proposed model suggests that this novel deposition-to-rebound transition induced by the impact is ascribed to the production of positive excess energy during the process from maximum spreading to complete retraction, which provides the critical value of spreading factor (β) and equilibrium contact angle (θ) for determining whether the transition occurs.

Highly flexible electromagnetic interference (EMI) shielding material with excellent shielding performance is of great significance to practical applications in next-generation flexible devices. However, most EMI materials suffer from insufficient flexibility and complicated preparation methods. In this study, we propose a new scheme to fabricate a magnetic Ni particle/Ag matrix composite ultrathin film on a paper surface. For a ~2 micro meter thick film on paper, the EMI shielding effectiveness (SE) was found to be 46.2 dB at 8.1 GHz after bending 200,000 times over a radius of ~2 mm. The sheet resistance (Rsq) remained lower than 2.30 Ohm after bending 200,000 times. Contrary to the change in Rsq, the EMI SE of the film generally increased as the weight ratio of Ag to Ni increased, in accordance with the principle that EMI SE is positively related with an increase in electrical conductivity. Desirable EMI shielding ability, ultrahigh flexibility, and simple processing provide this material with excellent application prospects.

This study was devoted to investigating the interactions between graphene sheets (GNSs) and metal nanowires via molecular dynamics simulations. The simulation results indicated that the element type, shape, and size of the nanowires would affect their adhering behavior and help achieve the interesting wrapping, deprivation, and transfer phenomenon of a GNS. An appropriate length–width ratio of the GNS and nanowire contributed to the formation of a helical configuration of GNS out of nanowires under the action of van der Waals interactions. Importantly, some of the GNSs could spontaneously peel off from one nanowire and re-assemble a new spiral core–shell structure on another nanowire. This deprivation and re-assembly was associated with the definite elemental selectivity, which was determined by the adsorption energy of the GNSs on the nanowires. The adsorption energy difference drove the full or partial transfer of the GNSs. This study provides deep insights into the interactions between GNSs and nanowires.

Low temperature soldering has been realized to create a strong metallurgical interconnection between Cu using the self-propagating exothermic reaction by Al–Ni NanoFoil. This technique presents a great potential for electronics integration with a significantly reduced processing temperature (at least 150 °C lower than traditional techniques) and minimal thermal effects to the components. In this study, finite element analysis was performed to predict the temperature profiles across bonding interfaces, which were subsequently correlated with the formation and quality of the bonded structures. It has been revealed that, for nonequilibrium nanosized phases and defects, their formation and distribution were primarily attributed to the solid–liquid interdiffusion and rapid solidification, under the highly transient regime due to a drastic heating/cooling (105–107 °C/s). The preheating and pressure applied to the bonding structure were clearly beneficial to improve the quality of bonding. This was achieved by the thinned solder thickness and the correspondingly improved temperature profiles that enable a sufficient wetting, filling, and interfacial reactions. Through the comparative analysis of the numerical predictions and the experimental results, the solder layers must completely melt across their thickness and have a total heat over 30 K ms on the Cu to ensure robust interconnections with a shear strength of approximately 37 ± 3 MPa and dense continuous bonding interfaces.

Electromagnetic interference protection in optoelectronic devices is challenging because of the dual requirements of optical transmittance and high shielding effectiveness (SE). Herein, we propose a novel silver nanowire (AgNW)/polyethylene terephthalate (PET) multi-layer mesh pattern structure for transparent electromagnetic shielding obtained via laser marking and transfer printing. A three-layer composite shielding film with an optical transmittance of 67.8% exhibits a SE of 44 dB at 10 GHz, which is superior to most of the reported transparent shielding films composed of AgNWs to date. The newly designed multi-layer composite structure can enhance the transparent shielding properties of the shielding film via optimization of the AgNW distribution and the shielding film structure. It is expected that this multi-layer mesh composite structure will have splendid application prospects in electromagnetic shielding films, which require both light transmittance and high SE.