The rising cost of silver poses significant economic pressure on the electronics industry. Silver-coated copper powder has attracted attention as a cost-effective alternative to pure silver powder. This review establishes a full-chain analysis framework of “preparation–structure–performance–application”. It systematically discusses the synthesis routes, microstructure, performance limits, and failure mechanisms of silver-coated copper powder, and integrates first-principles calculations to reveal the physical nature of interfacial bonding. This work proposes a shift from coating engineering to interfacial engineering, providing a reference direction for future sustainable electronic materials. Quantitatively, optimized silver-coated copper powder achieves a volume resistivity on the order of 10−5 Ω·cm—comparable to pure silver-based products—while reducing material costs by approximately 70
Ovonic threshold switches (OTS), first reported by Ovshinsky over five decades ago, have re-emerged as the selector for high-density 3D cross-point non-volatile memory, where they are stacked in series with phase-change or resistive memory cells (1S1R) to suppress sneak-path leakage. Moreover, the recent discovery of a memory effect in OTS—whereby the device state depends on the history of the applied voltage—has drawn growing attention to selector-only memory. As the cross-point pitch shrinks below 20 nm and stacked decks multiply, the conformality, composition uniformity, and low thermal budget provided by atomic layer deposition (ALD)—but not by physical vapor deposition (PVD)—become essential. This review summarizes chalcogenide ALD for OTS, organized around the surface chemistry rather than by material system. The germanium, antimony, tellurium, selenium, and sulfur precursors compatible with surface-limited growth in the 60–170 °C back-end-of-line (BEOL) window are first surveyed. Reactivity-enhancement strategies, including methanol and ammonia co-injection, the discrete feeding method (DFM), super-cycle composition control, and plasma activation, are reviewed. These strategies have extended ALD from binary films to quaternary Ge–As–Se–Te and Ge–Sb–Se–Te selectors approaching PVD performance. Alternative chemistries (SnSe, van der Waals Te) and the etch-free patterning enabled by area-selective deposition of Ge2Sb2Te5 and sacrificial ALD of Sb2Te3 are also discussed. Finally, ALD and PVD OTS devices are compared in threshold voltage, off-current, switching speed, drift and endurance, and open challenges—doping, sulfide processes, uniformity, and precursor cost—are outlined.
Cu-core balls were electroplated with a 4 µm Ni layer, followed by SAC 305 electroplating, to fabricate Cu-core solder balls (CCSBs) with enhanced electrical performance and stable standoff height for 2.5-dimensional (2.5D) packaging. These CCSBs were bonded onto organic solderability preservative (OSP)-finished FR-4 printed circuit boards (PCBs) via reflow (300 s), laser (5 s), and IPL (10–16 s) soldering at 250 °C. Reflow soldering produced thicker Cu6Sn5 intermetallic compound (IMC) layers due to prolonged thermal exposure ( 300 s). In contrast, IPL and laser-assisted bonding produced comparatively thinner IMC layers due to their considerably shorter processing times. The IMC layer thickness at the CCSB joint interface was governed by interdiffusion between the SAC 305 solder and OSP-finished Cu pad, highlighting the strong influence of soldering energy source and processing time on the IMC layer growth kinetics. Conventional reflow soldering yielded IMC layers with 2.62 μm thickness, 2.3 and 2.2 times that of the IMC layers yielded via IPL soldering (1.15 μm) and laser- assisted bonding, respectively. The high-speed shear strength of IPL-soldered CCSB joints increased with increasing IPL pulse number, reaching a maximum of 736 gf at 36 pulses. The high-speed shear strength followed the order of IPL soldering (736.2 gf) > laser-assisted bonding (667.8 gf) > reflow soldering (397.5 gf).
Functional materials are central to high-performance chemical and biological sensors because their physicochemical properties directly govern sensitivity, selectivity, response speed, and operational stability. Rapid advances in nanostructured metal oxides, carbon-based materials, two-dimensional materials, polymers, and hybrid composites have driven major improvements in sensing performance for environmental monitoring, healthcare diagnostics, industrial safety, and food quality control. This review summarizes recent progress in sensing materials, with emphasis on how nanostructuring, surface functionalization, defect engineering, and hybridization enhance sensor behavior. Major material classes are briefly categorized according to their key features, advantages, and representative applications. Recent developments in sensitivity enhancement, selectivity improvement, response kinetics, stability, and flexible or wearable sensing platforms are also discussed. Emerging directions, including AI/ML-assisted materials design, self-powered sensors, multimodal sensing, and sustainable materials, are highlighted. Finally, key challenges such as reproducibility, scalable manufacturing, real-world reliability, and cost-performance trade-offs are critically examined. Overall, this review outlines a rational design framework for functional sensing materials toward robust, practical, and scalable next-generation sensor technologies.
Nanometer-thick membranes, including extreme ultraviolet (EUV) pellicles, require temporary protection during wet-based Si bulk etching. This sacrificial layer must shield the target membrane from the Si etchant and be removable after membrane fabrication. Here, sputtered Cu is introduced as a sacrificial protection layer for Mo₂C-based membrane fabrication. Cu exhibited strong resistance to a 30 wt
