Nano-metal materials have received considerable attention because of their promising performance in wide bandgap semiconductor packaging. In this study, molecular dynamics (MD) simulation was performed to simulate the nano-Cu sintering mechanism and the subsequent mechanical behaviors. Hybrid sintering, comprising nanosphere (NS) and nanoflake (NF), was performed at temperatures from 500 to 650 K. Furthermore, shear and tensile simulations were conducted with constant strain rates on the sintered structure at multiple temperatures. Subsequently, the extracted mechanical properties were correlated with the sintering behavior. The results revealed that the mechanical properties of the nano-Cu sintered structure could be improved by tuning material composition and increasing the sintering temperature. We established a relationship between the sintered microstructure and mechanical response. The shear modulus and shear strength of the sintered structure with NF particles increased to 41.20 and 3.51 GPa respectively. Furthermore, the elastic modulus increased to 55.60, and the tensile strength increased to 4.88 GPa. This result provides insights into the preparation phase of nano-Cu paste for sintering technology.

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In the rapidly evolving era of information and intelligence,microelectronic devices are pivotal across various fields, such as mobile devices, big data computing, electric vehicles, and aerospace. However, the electrical performance of these devices often suffers due to residual stress from microelectronic manufacturing. This issue is compounded by the additional thermal stress that accumulates during device operation. Therefore, it is essential to understand, characterize, and control this residual stress to ensure the reliability and efficiency of microelectronic devices. Raman spectroscopy emerges as an invaluable tool for nondestructive, fast, noncontact, and precise testing of micro-scale mechanics, significantly aiding in stress and strain analysis within microelectronic manufacturing. This article aims to provide a thorough overview of the theory and application beyond a mere compilation of recent advances. Theoretically, it critically evaluates existing models that describe the Raman-stress relation. Practically, it explores the application of Raman spectroscopy in researching residual stress in various components, including substrate materials, epitaxial films, and packaging. Through a detailed examination of current applications, it highlights the significance of Raman spectroscopy in understanding micro-scale mechanics. Finally, it offers both theoretical and practical insights into the future developments of Raman-stress detection technology.@en

Nano-copper sintering is one of new die-attachment and interconnection solutions to realize the wide bandgap semiconductor power electronics packaging with benefits on high temperature, low inductance, low thermal resistance and low cost. Aiming to assess the high-temperature reliability of sintered nano-copper die-attachment and interconnection, this study characterized the mechanical properties of sintered nano-copper particles using the high-temperature nanoindentation tests. The results showed that: firstly, the hardness and indentation modulus of the sintered nano-copper particles increased rapidly when the loading rate increased below 0.2 mN·s⁻¹ and then stabilized, and decreased with increased applied load up to 30 mN. Next, by extracting the yield stress and strain hardening index, a plastic stress–strain constitutive model at room temperature for sintered nano-copper particles was obtained. Finally, the high temperature nanoindentation tests were performed at 140 ˚C–200 ˚C on the sintered nano-copper particles prepared under different assisted pressures, which showed that a high assisted pressure resulted in the reduced temperature sensitivity of hardness and indentation modulus. The creep tests indicated that high operation temperature resulted in a high steady-state creep rate, which negatively impacted the creep resistance of sintered nano-copper particles, while the higher assisted pressure could improve the creep resistance.

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This paper studied the behaviors of sintering between Ag nanoparticle (NP) and nanoflake (NF) in the same size by molecular dynamics simulation. Before the sintering simulation, the melting simulation of NF was carried out to calculate the melting points of NFs and investigate the thermostability of NF. The Lindemann index and potential energy showed that the melting points of NF were significantly size-dependent. During the heating process, the sharp corner of NF transformed to the round corner and could bend spontaneously lower than melting points. In sintering simulation, the sintering process of NF-NP showed a metastable stage before equilibrium. Under low sintering temperature (500 K), the degree of plasticity sintering mechanism of NF-NP was more prominent, which generated more defects, such as amorphous atoms, dislocations, and stacking faults, than NP-NP. The sintered products of NF-NP also presented a better neck size and shrinkage than NP-NP in the same size. A new sintering behavior was observed: NF was bent toward the NP during the sintering. The bending curvature of NF increased as the thickness or the length/width decreased. For the NF with the ratio of length/width to thickness of 5:1, bending could further significantly facilitate neck growth. At 700 K, the plasticity mechanism dominated both the sintering processes of NF-NP and NP-NP. And NF-NP showed a larger diffusivity than NP-NP. At last, we investigated the effects of crystal misorientation, and found that a tilted grain boundary generated in the neck. The NF had the trend of rotation to decrease the crystal misorientation.

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