Multisized nanoparticles (MPs) are widely employed as electronic materials to form conductive patterns, benefitting from their excellent sintering properties and mechanical reliability. However, due to the lack of effective detection methods for the real-time sintering process, it is difficult to reveal the sintering behavior during the MPs sintering process. In this work, a molecular dynamics method is used to track the trajectory of silver atoms. The melting behavior of a single nanoparticle (SP) is first discussed. The structural evolution of equally sized nanoparticles (EPs) and unequally sized nanoparticles (UPs) during the sintering process is analyzed alongside morphology changes. It is proposed that the UPs sintering process benefits from the wetting behavior of small-sized nanoparticles on the surface of large-sized nanoparticles, and the sintering angle (θ) is proposed as an index to estimate the sintering result of UPs. Based on the works above, three basic sintering modes and one advanced sintering mode in the MP sintering process are analyzed emphatically in this paper, and the roles of different-sized nanoparticles in MPs are concluded from simulation and experimental results. This work provides theoretical support for conductive ink composition design and sintering process optimization.

Inkjet printing of high-viscosity (up to 10⁵ mPa·s) nanosilver inks is an interesting emerging technology to achieve the 3D fully printed fabrication of electronic products. The highly viscous force of the ink makes it impossible to achieve droplet ejection with the traditional piezoelectric-driven drop-on-demand inkjet method. In this study, a pneumatic needle jetting valve is adopted to provide sufficient driving force. A large number of high-viscosity inkjet printing tests are carried out, and the jetting behavior is recorded with a high-speed camera. Different jetting states are determined according to the recorded images, and the causes of their formation are revealed. Additionally, the effects of the operating pressure, preload angle, and fluid pressure on jetting states are elucidated. Furthermore, the jetting phase diagram is obtained with the characterization of the Reynolds number and the printable region is clarified. This provides a better understanding of high-viscosity inkjet printing and will promote the application of high-viscosity inkjet printing in 3D fully printed electronic products.

The non-uniform temperature field in laser sintering critically affects conductive silver paste performance, yet its quantitative relationship with sintering mechanisms remains unclear. This study addresses this issue by proposing effective sintering temperature (T_a) and effective sintering time (S_a) as metrics to link laser parameters and sintering temperature field with sintering performance. Through full-factorial experiments, finite element simulation, and in situ thermal monitoring, it was revealed that (1) Increasing laser power and reducing laser scanning speed effectively reduce resistivity. For example, at 10 W and 0.1 mm/s, the resistivity reached 6.81 μΩ·cm, which was 88.9% lower than the value of 61.11 μΩ·cm at 2 W and 0.5 mm/s. (2) The resistivity exhibits a threshold effect in its reduction across low-power (5 W) ranges. (3) The action of laser sintering parameters on sintering performance through T_a and S_a. The resistivity decreases are correlated with T_a, exceeding the exothermic peaks (T₁ = 196 °C and T₂ = 232 °C). Unlike prior qualitative analyses, this work quantifies how non-uniform temperature fields govern sintering through T_a and S_a, offering a quantitative method to analyze the temperature field’s effect on sintering performance.