Copper sintering has gained great attention as a die-attach technology for power electronics because of its potential cost effectiveness and high reliability under harsh working conditions. However, the mechanism of how the intrinsic pores within such sintered joints influence the thermal and electrical properties still needs further investigation. The evolution of pores within such sintered joints is difficult for in-situ observation during the sintering process and reliability tests, while the porosity level greatly affects the thermal and electrical properties. In this work, four two-dimensional (2D) models with various random pore structures were established based on the Quartet Structure Generation Set (QSGS) algorithm. Then, finite element method (FEM) simulations were conducted to simulate the heat and current conduction in the sintered materials. Subsequently, the distribution of temperature as well as the electric potential in the porous sintered materials were further discussed. Lastly, both the thermal and the electrical conductivities were calculated, followed by a concluded parabolic relationship of thermal and electrical conductivities with the porosity. These findings offer insights into optimizing and predicting copper sintered joint performance and accelerate the wide application of copper sintering.

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Driven by the need for improved quality, energy efficiency, and visual innovation, display technology has evolved from CRT to Mini LED. However, the transfer process in Mini LED assembly poses challenges in precision. This study addressed the displacement issue during the transfer process by investigating the synergistic effects of solder and functional organic chemicals. Through the Mini LED assembly process, with the Mini LED size measuring 150 μm (length) ∗ 100 μm (width) ∗ 70 μm (thickness), polyamide was identified as a facilitator for precise alignment, which enhanced self-alignment capabilities by 68.8 % and improved the accuracy on self-aligned distance from 12.5 μm to 21.1 μm in Mini LED packaging. Through the powder coalescence approach, further extensive analysis using XPS, SEM, FTIR, and DSC reveals the synergistic effects. It supports the proposed three-dimensional polyamide-tin ion coordination interfacial network construction mechanism that facilitates solder-to-solder self-alignment and coalescence. This study provides insight into such a polymer-metal ion 3D coordination network for Mini LED precise alignment, which is promising for mass production.@en

Micro LED displays offer superior performance compared to traditional LCD and OLED displays. However, challenges in transfer technology, such as high throughput and scalability, must be addressed. Among various mass transfer techniques, stamp transfer and laser-assisted transfer are widely used for Micro LED assembly. The laser-assisted transfer technique enables high-speed and accurate transfer. Anisotropic conductive film (ACF) is commonly used for its energy absorption properties during chip transfer. However, during the subsequent thermocompression bonding process, the ACF film needs to be ruptured, which adds no value to the bonding process. To address limitations, we have developed a polymer-reinforced solder paste that demonstrates high effectiveness in absorbing impact energy during chip dropping, providing performance comparable to ACF-like materials for die receiving. It also possesses typical solder paste characteristics, enabling the formation of reliable solder joints between the chip and substrate. This material facilitates streamlined manufacturing process and providing opportunities for chip rework in subsequent stages.@en

Micro LED display technology has been spotlighted as the most promising technology compared to LCD and OLED. Its excellent advantages include higher brightness, self-illumination, higher resolution, lower power consumption, faster response, higher integration, higher stability, thinner thickness, longer life, etc. In terms of the unique benefits, it is attracting increasing attention from industries. With the commercialization of Micro LED technology, the following hurdles are identified: wafer manufacturing, full color, bonding, and mass transfer. Among them, mass transfer is so far considered as the most severe bottleneck. Several mass transfer technologies have emerged, including fine picking and placing, roll printing, laser transferring, and fluid self-assembly, which aim to solve the mass transfer problems. However, the aforementioned first 3 types of technologies still rely on the pick-and-place process, which is limited when the Micro LED die dimension shrinks to smaller scales due to processability and equipment precision. Fluidity self-assembly, on the other hand, will not be constrained by the Micro LED size and machine accuracy in the mass transfer process, which received increasing attention from researchers. In the self-assembly of component level, gravitational attraction, magnetic /electromagnetic fields, and capillary force are considered the mainstream force to facilitate the assembly process. Therefore, the component self-assembly becomes a prospective substitute for the Micro LED mass transfer solution, which overcomes the problems of the trade-off between throughput and the placement accuracy of the pick-and-place technology.@en