A silver nanoparticle sintering method is promising for the fabrication of flexible electronics. An ultrasonic-assisted sintering process is presented to obtain conductive patterns with low resistivity on a paper-based substrate. Compared to the conventional hot-pressing sintering process, the proposed method can efficiently fabricate densified microstructures with better electrical properties at low temperature and pressure. In particular, the effects of ultrasonic effective time, entry time, and amplitude were systematically analyzed. It was found that lower resistivity preferred larger ultrasonic amplitude. The ultrasonic effective time happened during the first 3 min of the entire sintering process, which implied that the ultrasonic synergetic effect occurred at the very beginning stage of the sintering process. Additionally, better conductivity of the sintered patterns was obtained when the ultrasonic entry time was shorter. The mechanism of the synergetic effect of ultrasonic sintering was also discussed in terms of vibration and cyclic stress perspectives. The proposed ultrasonic-assisted sintering method is believed to provide insights for the fabrication of flexible electronics.

Through-silicon-via (TSV) filling with optimum electrodeposition parameters is still a challenge in the industry, especially for via with different depths. Herein, the effects of via depth on optimum current density and filling patterns were investigated. It was found that the deeper the via, the lower the optimum current density. At low current density (4 mA cm−2), the via depth only affects the size of the defect, but does not change the filling pattern. However, at medium current density (7 mA cm−2), the filling pattern changes from super-conformal filling to sub-conformal filling with the increase of via depth, the pinch-off position remaining constant at a depth of about 70 µm from the top surface. Simulations of the TSV filling process using COMSOL modeling software revealed that the local concentration of additives, which is affected by the via depth, determine the morphology of the electrodeposition, matching well the experimental results.

This work demonstrates the dynamic through-silicon-via (TSV) filling process through staged electrodeposition experiments at different current densities. Different morphologies corresponding to TSV filling results can be obtained by controlling the applied current density. Specifically, a low current density (4 mA/cm2) induces seam defect filling, a medium current density (7 mA/cm2) induces defect-free filling, and a high current density (10 mA/cm2) induces void defect filling. Analysis of the filling coefficient indicates that the effect of current density on the TSV filling models is triggered by the coupling effect of consumption and diffusion of additives and copper ions. Further, the morphological evolution of plating reveals that the local deposition rate is affected by the geometrical characteristics of the plating.

Highly stretchable, flexible, and sensitive strain sensors have promising applications in motion detection—especially multifunctional strain sensors that can detect stretching, bending, compression and twisting. Herein, this study presents a graphene and glycerol solution-based multifunctional sensor with ultra-high stretchability and sensitivity. Owing to the self-lubrication and fluidity of the graphene-glycerol solution, the strain sensors display super stretchability up to 1000%, a maximum gauge factor up to 45.13, and excellent durability for over 10,000 cycles. In addition, the sensor can also rapidly respond to small strains (1%, 5%, 10%) and different stretching rates (12.5%/s, 25%/s, 50%/s, and 100%/s). More impressively, the sensors can measure up to 50 kPa pressure and 180° twisting without any damage. Furthermore, the strain sensors demonstrate their applicability in scenarios involving motion detection, such as that for finger bending, wrist rotating, touching, and drinking water.

Through-silicon via (TSV) filling by electrochemical deposition is still a challenge for 3D IC packaging, and three-component additive systems (accelerator, suppressor, and leveler) were commonly used in the industry to achieve void-free filling. However, models considering three additive systems and the current density effect have not been fully studied. In this paper, a novel three-component model was developed to study the TSV filling mechanism and process, where the interaction behavior of the three additives (accelerator, suppressor, and leveler) were considered, and the adsorption, desorption, and consumption coefficient of the three additives were changed with the current density. Based on this new model, the three filling types (seam void, ‘V’ shape, and key hole) were simulated under different current density conditions, and the filling results were verified by experiments. The effect of the current density on the copper ion concentration, additives surface coverage, and local current density distribution during the TSV filling process were obtained. Based on the simulation and experimental results, the diffusion–adsorption–desorption–consumption competition behavior between the suppressor, the accelerator, and the leveler were discussed. The filling mechanisms under different current densities were also analyzed.