In Case You Missed It

Assembly Reliability

“Reliability Analysis and Parameter Optimization of Board-Level BGA Packaging Structures under Thermal-Drop Impact Load”

Authors: Yanxi Sun, et al.

Abstract: This study investigates the reliability of a board-level BGA package structure when subjected to simultaneous thermal and drop impact loads. The investigation encompasses the effects of dimensional parameters on the stress and fatigue life of solder balls. The findings of this study provide a theoretical foundation for enhancing the reliability of BGA package structures under the sequential coupling of thermal-drop impact loads. In this work, a three-dimensional finite element model of a board-level BGA package structure is established, and numerical calculations are performed based on thermal-drop impact load sequence coupling. The effects of chip thickness, solder ball height, diameter and array on its temperature field distribution, solder ball stress and average impact life are investigated. Optimization schemes were designed using Taguchi quadrature and surface response method. The optimal combination of structural parameters to minimize solder ball peeling stress was obtained by mathematical-statistical analysis and regression analysis. (Soldering & Surface Mount Technology, vol. 37, no. 4, June 2026; https://www.emerald.com/ssmt/article-abstract/37/4/308/1256208/Reliability-analysis-and-parameter-optimisation-of)

Chip Stacking

“Die-to-Wafer Hybrid Bonding Technology Down to 1μm Pitch for Multi-Die Stacking Integration”

Authors: Melissa Najem, et al.

As Moore’s Law reaches physical limits, the semiconductor industry is increasingly relying on 3D stacking to enhance performance and energy efficiency. Die-to-wafer (D2W) technology addresses a critical bottleneck in AI accelerator design: interconnect density and bandwidth. Here, the authors demonstrate a functional test vehicle utilizing D2W hybrid bonding with pitches down to 1μm. By vertically stacking device layers with ultra-fine pitches, the technology shortens interconnect paths, significantly increasing data transfer speeds while reducing power consumption. Achieving a 1μm pitch requires engineering very precise alignment accuracy, the primary challenge for the D2W building block. Additionally, the wafer reconstruction process involving inter-die gap filling (IDGF) demanded optimized chemical mechanical planarization (CMP) to ensure compatibility with subsequent vertical interconnects. Electrical characterization of daisy-chain structures confirmed expected performance and yields for pitches ranging from 5μm down to 2μm. While the yield at 1μm is limited by the alignment accuracy of existing bonding tools, the team anticipates significant improvements with the introduction of next-generation tools featuring 0.5μm (3σ) alignment capabilities. This demonstration serves as a transitional proof of concept, laying the groundwork for a second-generation test vehicle. The immediate next steps include integrating the D2W technology with vertical interconnections – specifically high-density through-silicon vias (HD TSV) and through-oxide vias (TOV) – facilitated by the intermediate inter-die gap filling (IDGF) process step. (IEEE Electronic Components and Technology Conference, April 2026; https://www.leti-cea.com/cea-tech/leti/english/Pages/What’s-On/Press%20release/Die-to-Wafer-Hybrid-Bonding-Press-Release.aspx)

Circularity

“From Biotechnological Residues to Biodegradable Printed Circuit Boards: Aspergillus Niger Mycelium as a Structural Support Material”

Authors: Nina Oehlsen, et al.

Abstract: The electronics industry urgently seeks sustainable, biodegradable alternatives to conventional substrates for printed circuit boards (PCBs) to reduce the environmental impact of electronic waste and CO₂ emissions. Here, the authors introduce a biobased, plastic-like material derived from Aspergillus niger mycelium, Animat_RT. This material is produced from residual biomass generated in industrial citric acid production, offering a circular-economy approach. The raw mycelial biomass, consisting of spherical pellets, is processed via mold casting and air-drying, consolidating the pellets into a dense, plastic-like monolith (1.23g cm⁻³).

When formed into sheets, Animat_RT serves as a viable substrate for low-complexity PCB fabrication, permitting direct ink writing and manual soldering of electronic components. Although its electrical properties are lower than those of FR-2, a common, low-cost PCB laminate made of paper bonded with a phenolic resin, it remains suitable for low-frequency and proof-of-concept applications and, on average, has 56% lower embodied carbon. The mycelium boards disintegrate in water, allowing recovery of operative electronic components, whose functionality was demonstrated by resoldering them onto a conventional PCB. The material exhibits high mechanical performance, with compressive strengths of up to 121MPa, a flexural modulus of 2.3GPa, and a flexural strength of 30 MPa. It is fully biodegradable (ISO 20200), redispersible in water, has low flammability, and favorable thermal insulation properties (0.21W (mK)⁻¹). Heat treatment at 120°C enhances the mechanical properties, improves water resistance, and slows biodegradation. This study demonstrates the first use of biotechnology–derived A. niger mycelium as a biodegradable substrate for PCBs, addressing circularity and end-of-life challenges in electronics. (Cleaner Materials, vol. 21, no. 100416, September 2026, https://www.sciencedirect.com/science/article/pii/S2772397626000511)

Sensors

“Tactile Perception through Fluid–Solid Interaction”

Authors: Arman Goshtasbi, et al.

Abstract: Soft tactile sensors elevate robotic touch through enhanced flexibility and adaptability, yet most existing designs depend on embedded electronics that are susceptible to interference and environmental limitations. In this work, the authors leverage fluid–solid interactions to develop a class of soft tactile sensors that operate entirely without electronics at the sensing site. The sensor comprises a fluid-filled elastomeric channel connected to only two external pressure sensors. Touching different regions of the elastomeric surface displaces the viscous fluid, producing distinct pressure patterns that encode both touch position and force. These signals are decoded through a machine learning framework that integrates feature extraction, soft clustering, and adaptive neuro-fuzzy inference to achieve accurate localization and force estimation. We validate this concept through single-point touch localization and force estimation in a linear (1D) sensor and extend the same sensing principle to 2D tactile mapping by routing the channel across the surface using space-filling curves, while maintaining the same minimal hardware setup. This simple approach remains effective in environments where conventional electronic sensors often fail, such as underwater or in the presence of magnetic interference. (Nature Communications, Apr. 29, 2026, vol. 17, no. 5784, https://www.nature.com/articles/s41467-026-72497-3)End of article content