In Case You Missed It
Substrate Materials
“Designing a Filler Material to Reduce Dielectric Loss in Epoxy-Based Substrates for High-Frequency Applications”
Authors: Ilkan Calisir, et. al.
Abstract: In response to the demand for epoxy-based dielectric substrates with low dielectric loss in high-frequency and high-speed signal transmission applications, this work presents a surface-engineered filler material. Utilizing ball-milling, surface-modified aluminum flakes containing organic (stearic acid) and inorganic (aluminum oxide) coatings are developed. Incorporation of the filler into the epoxy matrix results in a significant increase in dielectric permittivity, εr, by nearly five times (from 4.3 to 21.2) and nearly an order of magnitude reduction in dielectric loss, tan δ, (from 0.037 to 0.005) across the 1-10GHz frequency range. Extension of this method to glass fabric-reinforced epoxy-based substrates, resembling widely used FR-4 in printed circuit boards, exhibits minimal permittivity variation (4.5 to 5.4) and considerable reductions in dielectric loss (from 0.04 to 0.01) within the same frequency range. These enhancements are attributed to improved filler dispersion and suppression of electron transport facilitated by double-layer coatings on the flake surface under varying electric fields. The findings highlight the potential of surface-modified aluminum flakes as a promising filler material for high-frequency and high-speed substrate applications requiring low-loss. (RSC Advances, January 2025, https://doi.org/10.1039/D4RA07419J)
Thermal Crosstalk
“Impact of Thermal Crosstalk on Dependent Failure Rates of Multilayer Ceramic Capacitors Undergoing Lifetime Testing”
Authors: Pedram Yousefian, et. al.
Abstract: Several research studies have investigated the degradation of BaTiO3-based dielectric capacitor materials, focusing on the impact of composition, defect chemistry and microstructural design to limit the electromigration of oxygen vacancies under electric fields at finite temperatures. Electromigration can be a dominant mechanism that controls failure rates in the individual multilayer ceramic capacitor (MLCC) components in testing the reliability of failures with highly accelerated lifetime testing (HALT) to determine the mean time to failure of MLCCs surface mounted onto printed circuit boards (PCBs). Conventional assumptions often consider these failures as independent, with no interaction between components on the PCB. This study employs a physics of failure (PoF) approach to closely examine transient degradation and its impact on MLCC reliability, emphasizing thermal crosstalk and its influence on dependent and independent failure rates. Finite element analysis thermal modeling and infrared thermography were used to assess the impact of circuit layout and component spacing on heat dissipation and thermal crosstalk under various electrical stress conditions. The study distinguishes between dependent and independent failures under a HALT, quantified through a β′ factor reflecting common cause failures due to thermal crosstalk. Through a series of experimental and statistical analyses, the β′ factor is evaluated with respect to temperature, voltage, and component spacing. These insights highlight the importance of understanding the nature of the data in reliability testing of MLCCs and optimizing the layout design of high-density circuits to mitigate dependent failures, improving overall reliability and informing better design and packaging strategies. (Journal of Applied Physics, January 2025, https://doi.org/10.1063/5.0245201)
Thermal Management
“Cooling Methods for a Typical Printed Circuit Board Assembly in Spacecraft: Simulation and Experiment”
Authors: Sheng Wang, et. al.
Abstract: In this work, cooling methods for a typical spacecraft circuit board assembly are investigated. The power dissipation of the assembly is more than 100W, and the max heat dissipation of a component is 16W, making it very difficult to cool the assembly. According to the packaging characteristics and heat dissipation of the components on the circuit board, cooling methods such as potting brackets, cooling springs and cooling blocks are used, and the effects of various cooling methods are analyzed. Through simulation and experimental research, it is proven that the power components in the printed circuit board assembly meet the requirements of temperature derating, which provides a reference for the thermal design of spacecraft electronics equipment. (Electronics, January 2025, https://doi.org/10.3390/electronics14020314)
Wearable Electronics
“Revolutionizing Wearable Technology: Advanced Fabrication Techniques for Body-Conformable Electronics”
Authors: Ruilai Wei, et. al.
Abstract: With the increasing demand for wearable electronic products, the need is pressing to develop electronic devices that seamlessly conform to the contours of the human body while delivering excellent performance and reliability. Traditional rigid electronic fabrication technologies fall short of meeting these requirements, necessitating the exploration of advanced flexible fabrication technologies that offer new possibilities for designing and fabricating flexible and stretchable electronic products, particularly in wearable devices. Over time, the continuous development of innovative fabrication techniques has ushered in significant improvements in the design freedom, lightweight, seamless integration and multifunctionality of wearable electronics. Here, the authors provide a comprehensive overview of the advancements facilitated by advanced fabrication technology in wearable electronics. It specifically focuses on key fabrication methods, including printed electronics fabrication, soft transfer, 3-D structure fabrication and deformation fabrication. By highlighting these advancements, it sheds light on the challenges and prospects for further development in wearable electronics fabrication technologies. The introduction of advanced fabrication technologies has revolutionized the landscape of wearable/conformable electronics, expanding their application domains, streamlining system complexity associated with customization, manufacturing and production, and opening new avenues for innovation and development of body-conformable electronics. (NPJ Flexible Electronics, December 2024, https://doi.org/10.1038/s41528-024-00370-8)
