In Case You Missed It
Electromagnetic Compatibility
“High-Frequency Modelling of Electrical Machines for EMC Analysis”
Authors: Yerai Moreno, et. al.
Abstract: The trend toward electrification in mobility has led to increased use of silicon carbide (SiC) semiconductors. These semiconductors are more efficient but also present challenges related to electromagnetic interference (EMI) due to their higher voltage derivatives. This paper introduces a new high-frequency impedance model for electrical machines. The proposed model distinguishes itself from existing approaches by being entirely derived from finite element method (FEM) simulations, which include capacitances in the magnetic simulation. This approach achieves a balance between computational efficiency and high accuracy across the entire frequency spectrum, ranging from 100Hz to 50MHz. The model provides valuable insights during the design phase and was rigorously validated using data from 28 samples of an industrial machine. (Electronics, February 2024, https://doi.org/10.3390/electronics13040787)
Package Warpage Analysis
“Warpage Study by Employing an Advanced Simulation Methodology for Assessing Chip Package Interaction Effects”
Authors: Jun-Ho Choy, et. al.
Abstract: A physics-based multi-scale simulation methodology that analyzes die stress variations generated by package fabrication is employed for warpage study. The methodology combines coordinate-dependent anisotropic effective properties extractor with finite element analysis (FEA) engine, and computes mechanical stress globally on a package-scale, as well as locally on a feature-scale. For the purpose of mechanical failure analysis in the early stage of a package design, the warpage measurements were used for the tool’s calibration. Warpage measurements on printed circuit board (PCB), interposer and chiplet samples, during heating and subsequent cooling, were employed for calibrating the model parameters. Warpage simulation results on full package represented by PCB-interposer-chiplets stack demonstrate the overall good agreement with measurement profile. The performed study demonstrates that the developed electronic design automation (EDA) tool and methodology can be used for accurate warpage prediction in different types of IC stacks at early stage of package design. (ISPD ’24: Proceedings of the 2024 International Symposium on Physical Design, March 2024, https://dl.acm.org/doi/abs/10.1145/3626184.3635284)
Solder Fatigue
“Numerical Investigation of Thermal Fatigue Crack Growth Behavior in SAC 305 BGA Solder Joints”
Authors: Rilwan Kayode Apalowo, et. al.
Abstract: This study aims to investigate the reliability issues of microvoid cracks in solder joint packages exposed to thermal cycling fatigue. The specimens are subjected to JEDEC preconditioning level 1 (85°C/85%RH/168 hr.) with five times reflow at 270°C. This is followed by thermal cycling from 0° to 100°C, per IPC-7351B standards. The specimens’ cross-sections are inspected for crack growth and propagation under backscattered scanning electronic microscopy. The decoupled thermomechanical simulation technique is applied to investigate the thermal fatigue behavior. The impacts of crack length on the stress and fatigue behavior of the package are investigated. Cracks are initiated from the ball grid array corner of the solder joint, propagating through the transverse section of the solder ball. The crack growth increases continuously up to 0.25mm crack length, then slows down afterward. The J-integral and stress intensity factor (SIF) values at the crack tip decrease with increased crack length. Before 0.15mm crack length, J-integral and SIF reduce slightly with crack length and are comparatively higher, resulting in a rapid increase in crack mouth opening displacement (CMOD). Beyond 0.25mm crack length, the values significantly decline, that there is not much possibility of crack growth, resulting in a negligible change in CMOD value. This explains the crack growth arrest obtained after 0.25mm crack length. (Soldering & Surface Mount Technology, February 2024, https://doi.org/10.1108/SSMT-08-2023-0049)
Substrate Characteristics
“Investigating the Influence of Substrate Orientation and Temperature on Cu Cluster Deposition”
Authors: Yiwen He, et. al.
Abstract: The crystal orientation and temperature of the substrate are crucial factors that influence clusters deposition and, consequently, the properties of thin films. In this study, the molecular dynamics simulation method was employed to investigate the deposition of Cu55 clusters on Fe(001), Fe(011), and Fe(111) substrates with varying crystal orientations. The incident energies used ranged from 0.1 to 20.0eV/atom, and the substrates were maintained at temperatures of 300, 500 and 800K. Analysis of cluster and substrate atom snapshots, along with the physical properties of clusters, revealed how the crystal orientation of Fe substrates affects the morphology and structure of the cluster at different temperatures. Additionally, specific microscopic mechanisms responsible for these effects were identified. The simulation results demonstrate that the crystal orientation of Fe substrate significantly influences the deposition of Cu55 clusters. The structures of the clusters on the three crystal substrates undergo similar changes as the substrate temperature increases, with the Cu55 clusters on the Fe(111) substrate exhibiting the most significant changes in response to the temperature rise. (Journal of Applied Physics, March 2024, https://doi.org/10.1063/5.0193758)
