Ultrasonic treatment is an effective method for size refinement and dispersion of nanomaterials during their synthesis process. However, the quantitative relationship between ultrasonic conditions and particle size in the synthesis of metal nanoparticles has not been fully revealed. In this study, Cu nanoparticles were synthesized via the wet-chemical redox method under ultrasonic treatment, and statistical analysis on the evolution of particle size distribution was carried out. It was found that the particle size decreased exponentially with increasing ultrasonic power. A quantitative model was then proposed to describe the influence of ultrasonic power on the size distribution of metal nanoparticles from the perspective of the competition between the surface energy and the ultrasonic force. A relational expression of Rc∝γ47P-37 was revealed, and it was proved to fit well with the experimental results. Our study provides new experimental basis and theoretical method for understanding the mechanism of ultrasonic-induced size refinement of metal nanoparticles.

The motivation for this work is to combine the ability to enable a common wafer-level flip-chip packaging system to run in a manner of deviation automatic correction. Three parallel kinematic flexure limbs with lever displacement amplifier are designed to construct a 3-RRR XYθ deviation compensator. After a series of kinematics theoretic analyses and dimension optimizations, the mechanism is evaluated. In view of the dynamic coupling linear and angular motion of the 3-RRR compensator are hard to be acquired simultaneously by the common commercial precision displacement sensors, a “coarse-precise” composite visual inspection algorithm is designed to capture the precise motion in XYθ directions at the same time. Then, a series of validation experiments are successfully carried out, including visual inspection test, kinematics characterization, open-loop and closed-loop tracking tests, and flip-chip deviation correction. It indicates that the resolution, absolute positioning accuracy of the developed alignment system are achieved up to 40 nm/10 μrad, 0.3 μm/30 μrad, respectively, and the positioning period under maximum range is kept within two control-cycle. Finally, the accuracy of the alignment system is improved up to 0.3 μm/0.03 mrad, which means that the proposed strategy provides an effective solution for one-step accurate alignment operation of advanced chip packaging.

Flip-chip bonding system has a high demand for both force sensing and control functions to guarantee the high-quality chip interconnection. The motivation of this work is to combine the ability to enable a flip-chip bonding system to run in the manner of active soft-landing interconnection. The developed flexure bonder achieves these properties by designing a flexure force sensing and control mechanism integrated with strain gauge sensing and piezoelectric actuating functions. Firstly, the design, modeling and optimization of the flexure mechanism are presented. Theoretical analyses including force sensing and control working principle demonstration, force-strain model derivation and dynamics response modeling are carried out, respectively. Besides, aiming at highly sensitive force control under high-dynamic working condition, the mechanism is optimized by the multi-objective genetic optimization algorithm. Then, this flexure bonder mechanism is analyzed and evaluated by Finite Element Analysis. Finally, a series of validation experiments including force sensing calibration and performance tests, open- and closed-loop force controlling tests, active soft-landing tests and actual bonding tests are successfully implemented. The experimental results indicate that the operation accuracy of the developed system is improved up to $\pm$ 1 N under 400 N range, the overshoot of active soft-landing is less than 2 N under 6000 N/s loading speed. All the results uniformly confirm that the proposed bonding system can achieve precise force control and satisfactory chip interconnection performance with the proposed active soft-landing bonding strategy.

In light of the fact that tungsten wire is gradually replacing high-carbon steel wire as a diamond cutting line, it is particularly important to study tungsten alloy wire with better strength and performance. According to this paper, in addition to various technological factors (powder preparation, press forming, sintering, rolling, rotary forging, annealing, wire drawing, etc.), the main factors affecting the properties of the tungsten alloy wire are the composition of the tungsten alloy, the shape and size of the powder, etc. Combined with the research results in recent years, this paper summarizes the effects of changing the composition of tungsten materials and improving the processing technology on the microstructure and mechanical properties of tungsten and its alloys and points out the development direction and trend of tungsten and its alloy wires in the future.

A green method for the synthesis of in situ Cu paste is developed. Cu particles are prepared through chemical reduction by selecting a special copper source, reducing agent, and solvent. Then the reaction solution is directly concentrated to obtain an in situ Cu paste. The synthesis of Cu particles and the preparation of Cu paste are conducted simultaneously, and the process of separation, purification, drying, storage, and re-dispersion of powder are reduced. Particles are not directly exposed to air, thus the oxidation of micro/submicron -Cu is effectively prevented, and the agglomeration of particles caused by drying and dispersion operations is simultaneously reduced. Furthermore, the proposed method has a certain universality, and different types of Cu sources can be used to prepare in situ paste with different sizes and morphologies. The entire preparation process is simple, efficient, green, and the yield can reach 99.99%, which breaks through the bottleneck of the application of traditional micro/submicron-Cu materials. Copper acetate-based in situ paste is sintered for 30 min at 260 °C and 2 MPa in a reducing atmosphere. The shear strength, resistivity, and thermal conductivity reach 55.26 MPa, 4.01 × 10 ^–8 Ω·m, and 92.75 W/(m·K), respectively, which could meet the interconnection application of power semiconductor devices.