AVS 71 Session MN-ThP: MEMS and NEMS Poster Session

The study explores the challenges and opportunities in 3D printing continuous fiber-reinforced polymers, with a focus on Polylactic Acid-Stainless Steel Fiber (PLA-SSF) composites. Statistical analysis of the printed parts highlighted deviations from design specifications, especially in acute angles and tight radii, emphasizing the need for optimized printing parameters and tooling paths. Fiber migration and excess polymer deposition were identified as key factors influencing geometric distortions, particularly at smaller radii and more acute angles. The study also developed a curvature bending stiffness (CBS) testing methodology to assess the mechanical performance of PLA-SSF composites, comparing them with neat PLA, nylon with short carbon fibers (Onyx), and nylon with continuous carbon fibers (Onyx-cCF). Results showed that PLA-SSF composites exhibited the highest CBS, with stiffness increasing linearly as radii decreased from 20 mm to 3 mm. PLA and PLA-SSF samples failed by tensile fracture, while Onyx samples deformed without fracturing. By employing statistical techniques, the study achieved a robust analysis of the printability and mechanical performance. The non-parametric Kruskal-Wallis test allows for the comparison of medians across multiple groups, such as different materials or different geometries, providing a reliable way to assess differences in mechanical performance without relying on normal distribution assumptions. Moreover, regression analysis is valuable for modeling relationships between printing parameters and outcomes such as dimensional accuracy or mechanical performance. This technique helps optimize printing parameters to achieve better results. Further, the Wilcoxon Signed-Rank Test, a nonparametric method, is useful for comparing as-printed dimensions with designed dimensions, especially when data does not follow a normal distribution. It provides a robust way to assess deviations from design specifications. The findings highlight the geometric limitations of 3D printing continuous fiber-reinforced polymers and suggest that adjusting printing speeds and tooling paths can mitigate distortions. This work provides critical insights into optimizing the printability and mechanical performance of reinforced polymer composites for advanced manufacturing applications. Moreover, the findings not only provide insights into improving the geometric accuracy and mechanical properties of 3D-printed composites but also suggest potential applications in structural health monitoring and sensor technologies. This work contributes to advancing the understanding of reinforced polymer composites for high-performance manufacturing applications.

The material properties of glass such as low dielectric constant and loss, low roughness, adjustable coefficient of thermal expansion (CTE), and low electrical conductivity at high frequencies make it a desired material for high function radio frequency (RF) device interposers.¹ Through glass vias (TGV) are a key technology for incorporating 3D integration techniques into RF devices as a way of improving device performance, increasing I/O per unit volume, simplifying design and assembly, and allowing for a more compact system. Vias are typically filled with copper (Cu) to form an electrical connection from one surface to another. Although TGVs are a promising technology, they are subject to thermo-mechanical reliability challenges due to the interaction between glass and Cu during thermal cycling. The thermal mismatch between copper (CTE_Cu= 16.7e^-6/°C) and glass (CTE_glass= 3.4-9.0e^-6/°C) can cause reliability issues, such as glass fractures, Cu protrusion, and Cu via sliding and delamination which are difficult failure mechanisms to predict.

In this work, Corning SG3.4 glass was bonded to an Si carrier with vias fabricated of diameters 30 um, 50 um, and 75 um in both square and hexagonal arrays with three different pitches being investigated 120 um, 160 um, 200 um. These samples were tested in various methods to study the mechanical and thermomechanical stability of Cu filled TGVs. For thermomechanical stability, the vias were filled with Cu through an electrochemical depTosition (ECD) process with a 30 nm platinum seed layer. The variation in TGV geometry was studied to determine the yield strength of glass for the different TGV geometries and densities. This was used to develop optimal design and process parameters for future TGV applications in RF devices. The Cu filled TGV samples were heated in a reflow oven which allows for controlled ramp rates and dwell times while keeping the substrates in an inert environment. Observed fractures and Cu protrusion was recorded to determine yield strength. Mechanical stability was studied through various flexure method tests to understand how the glass performed with the various via densities. This work demonstrates novel design and process parameters for reliability of through glass vias for future generation RF devices. Different via geometries and densities were analyzed to determine the yield strength of a glass interposer, relieving stress and reliability issues within RF devices.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2025-04604A

¹K. Pan et al., 2021 IEEE 71st Electronic Components and Technology Conference (ECTC), pp. 1660-1666, doi: 10.1109/ECTC32696.2021.00263.

Recently identified as extremely promising candidates for next-generation nanoelectromechanical systems (NEMS), magnetic 2D materials are particularly well suited to applications where magnetic ordering and mechanical motion are tightly coupled, such as sensors and spintronics. The high area-to-volume ratio of suspended 2D resonators makes them highly sensitive to magnetic phase transitions through strain change detected by mechanical properties such as resonance frequency and dissipation.

We explore the coupling of magnetic ordering to nanomechanical response as a function of external conditions, including temperature and magnetic field. Theoretical modeling is done using Landau phase transition theory to analyze the magnetic behavior. The theory used focuses on the dynamic regime and does not rely on assumptions of small deflections, which makes it suitable for more general applications under extreme conditions. The model is also tested against experimental data obtained on CrBr₃ and FePS₃ nanodrums.

This work provides the basis for further development of improved NEMS sensors and actuators that use phase transitions to enhance performance.