In Case You Missed It
Component Inspection
“Advancements in PCB Components Recognition Using WaferCaps: A Data Fusion and Deep Learning Approach”
Authors: Dmitrii Starodubov, et. al.
Abstract: As technology advances and becomes more complex, the demand for automated solutions to verify the quality and origin of components assembled on printed circuit boards (PCBs) is skyrocketing. This paper proposes an innovative approach to detecting and classifying microelectronic components with impressive accuracy and reliability, paving the way for a more efficient and safer electronics industry. The authors’ approach introduces significant advancements by integrating optical and x-ray imaging, overcoming the limitations of traditional methods that rely on a single imaging modality. This method uses a novel data fusion technique that enhances feature visibility and detectability across various component types, crucial for densely packed PCBs. By leveraging the novel capsule network, the authors’ system improves spatial hierarchy and dynamic routing capabilities, leading to robust and accurate classifications. The authors employ decision-level fusion across multiple classifiers trained on different representations – optical, x-ray, and fused images – enhancing accuracy by synergistically combining their predictive strengths. This comprehensive method directly addresses challenges surrounding concurrency, reliability, availability, and resolution in component identification. Through extensive experiments, the authors demonstrate that their approach not only significantly improves classification metrics but also enhances the learning and identification processes of PCB components, achieving a total accuracy of 95.2%. (Electronics, May 2024, https://doi.org/10.3390/electronics13101863)
Conformal Coating
“Conformal Coating Testing in Various Test Environments”
Authors: Prabjit Singh, et. al.
Abstract: Conformal coatings have traditionally been tested by determining the mean time to failure of conformally coated hardware exposed to corrosive test environments. This test approach has serious shortcomings: The test temperatures are most often too high. At these high temperatures, the conformal coating properties may be quite different from those at the application temperatures. In addition, the times to failure are unacceptably long, extending into many months. Overcoming these shortcomings is an iNEMI-championed test that involves exposing conformally coated thin films of copper and silver to sulfur vapors at 40o-50oC in flowers of sulfur (FoS) chamber and using the corrosion rates of the coated metal thin films as a measure of the corrosion protection capabilities of the conformal coatings. The test temperatures are similar to the application temperatures, the test durations are no more than a week and can be conducted under various temperature and humidity conditions. The purpose of this work was to determine if testing in the industry-standard mixed-flowing gas corrosion chamber would give similar results as those using the FoS chamber. Acrylic, fluorinated acrylate, and atomic layer deposition conformal coatings were tested in three environments: flowers of sulfur (FoS), mixed-flowing gas (MFG), and iodine vapor. The performance of the coatings tested in the FoS and MFG corrosion chambers were quantitatively similar. The iodine vapor test results were in qualitative agreement with the FoS and MFG test results. In addition, the authors present early results pointing to the utility of terahertz-frequency imaging as a technique for measuring conformal-coating thickness nondestructively. (Journal of Surface Mount Technology, April 2024, https://doi.org/10.37665/smt.v37i1.48)
Dielectrics
“Aramid Nanofiber and Boron Nitride Nanosheet Composite Films for Mechanical and Dielectric Insulation Application”
Authors: Nan Li, et. al.
Abstract: In this work, the authors enhanced the mechanical and dielectric insulation properties of the aramid nanofiber (ANF) film only by mixing a small amount of two-dimensional boron nitride nanosheets (BNNSs) (0.09 wt %), which were in situ introduced as the assistor of aramid splitting. The composite nanofilm exhibited a tensile stress of 282MPa and a dielectric breakdown strength of 100.7kV·mm–1, which increased by 55.8 and 149.3%, respectively. These improvements may be attributed to the introduction of BNNSs, which made the films denser and more horizontally ordered, as well as the enhanced interfacial interactions between individual ANFs. Meanwhile, the ANF/BNNS film also shows high thermal stability, self-extinguishing properties, and excellent chemical stability simultaneously. This work provides a strategy to enhance the mechanical and dielectric insulation properties of ANF-based nanocomposites. (ACS Applied Nano Materials, April 2024, https://doi.org/10.1021/acsanm.3c05821)
Solder Joint Reliability
“The Role of Microstructure in the Thermal Fatigue of Solder Joints”
Authors: J. W. Xian, et. al.
Abstract: Thermal fatigue is a common failure mode in electronic solder joints, yet the role of microstructure is incompletely understood. Here, the authors quantify the evolution of microstructure and damage in Sn-3Ag-0.5Cu joints throughout a ball grid array (BGA) package using EBSD mapping of localized subgrains, recrystallization and heavily coarsened Ag3Sn. The authors then interpret the results with a multiscale modeling approach that links from a continuum model at the package/board scale through to a crystal plasticity finite element model at the microstructure scale. The authors measure and explain the dependence of damage evolution on the β-Sn crystal orientation(s) in single and multigrain joints, and the coefficient of thermal expansion (CTE) mismatch between tin grains in cyclic twinned multigrain joints. The authors further explore the relative importance of the solder microstructure versus the joint location in the array. The results provide a basis for designing optimum solder joint microstructures for thermal fatigue resistance. (Nature, May 2024, https://doi.org/10.1038/s41467-024-48532-6)
