Researchers at the National Institute of Standards and Technology (NIST) have published a peer-reviewed perspective paper identifying critical polymer science deficiencies in advanced semiconductor packaging and proposing a measurement-driven framework to address them - with direct implications for the reliability of sensors and electronic control units (ECUs) in harsh automotive environments.
Background
As transistor scaling reaches its physical limits, the industry faces key challenges in packaging, ranging from mechanical stress and distortion to electrical interference, environmental effects, and failure mechanisms - and polymer-based packaging materials, once viewed as little more than a means to encase a chip, have emerged as important factors for reliability, performance, and cost.
The automotive environment places these materials under particularly severe strain. Car parts must handle extreme temperatures ranging from -40°C to +150°C, constant vibration, moisture, and long service lifespans. Degradation factors in automotive electronics can be categorized into thermal, electrical, mechanical, chemical, electromagnetic, radiation, humidity, and dust loads, among which high temperature, moisture, and mechanical vibration carry the most relevance - each altering the thermal, mechanical, electrical, and chemical behavior of packaging materials and influencing the performance and lifetime of an electronic component.
At the polymer level, the failure modes are well-documented. Coefficient of thermal expansion (CTE) mismatch in polymer-based packaging materials is widely acknowledged as a primary contributor to temperature-induced drift in sensors, and experimental findings indicate that moisture ingress at the packaging interface can induce plastic deformation in these materials, exacerbating nonlinear drift in long-term bias. This degradation primarily leads to delamination, bond wire failure, and cracks in substrates, encapsulation, and solder joints, while combined thermal and humidity loads result in adhesion failure of moulding compounds as well as the "popcorning" effect in electronic packages.
Details
The NIST perspective - developed from a workshop titled "Materials and Metrology Needs for Advanced Semiconductor Packaging Strategies," held at the 35th annual Electronics Packaging Symposium in Binghamton, NY, on September 5, 2024 - outlines critical challenges and opportunities related to polymer-based "soft" materials in advanced semiconductor packaging, with emphasis on polymer science, measurement science (metrology), and the strategic development of Research-Grade Test Materials (RGTMs).
The paper was co-authored by researchers at NIST, North Carolina State University, the National Renewable Energy Laboratory, ASE, Intel, Innocentrix, and Binghamton University. It was published as R. Tao et al., "Material Needs and Measurement Challenges for Advanced Semiconductor Packaging: Understanding the Soft Side of Science," in IEEE Transactions on Components, Packaging and Manufacturing Technology, Vol. 15, No. 10, pp. 2071-2082, 2025 (DOI: 10.1109/TCPMT.2025.3603484).
Central to the framework is the RGTM concept. NIST is pioneering research-grade test materials (RGTMs) - open, nonproprietary polymer systems that serve as benchmarks, allowing researchers across industry, academia, and government to compare results, improve reproducibility, and feed reliable data into computer models. "RGTMs are key," said Christopher Soles, NIST materials scientist and co-project leader. "By providing shared, transparent materials, we can accelerate innovation across the entire ecosystem."
The paper also underscores the importance of predictive modeling. "Modeling without metrology is imagination," stated co-author William Chen, Chair of the IEEE's Heterogeneous Integration Roadmap for semiconductors. Reproducible data are described as critical for building reliable simulations and enabling digital twins in thermoset manufacturing, with robust metrology enabling faster materials screening and supporting the deployment of new materials from research into production.
These efforts, led by the NIST CHIPS team, aim to advance the fundamental understanding of structure-property-processing relationships, promote standardized guidelines and innovative methods for material characterization, and emphasize the need for close collaboration among materials scientists, process engineers, and metrology experts - as well as cross-sector partnerships among industry, academia, and government.
The polymer types under scrutiny span the core materials used in automotive-grade electronics packages. Epoxies, silicones, and polyimides encapsulate chips, connect them to circuit boards, and keep them running reliably; as the industry shifts toward 3D heterogeneous integration, where multiple chips are stacked or linked in three dimensions, the demands on these materials are rapidly escalating - and unlike metals or ceramics, polymers are time- and temperature-sensitive, absorbing moisture and changing shape under stress, which can cause chips to warp, signals to degrade, or connections to fail over years of operation.
Outlook
With some new packaging materials taking 10 to 25 years to reach production, the authors stress that early, collaborative work is essential - and that bridging the gap between polymer science and semiconductor engineering could accelerate innovation while strengthening supply chain resilience. For the automotive sector specifically, where AEC-Q100 qualification standards already mandate thermal cycling, moisture sensitivity, and mechanical stress testing, the NIST measurement infrastructure could provide the validated material data needed to qualify next-generation encapsulants against those protocols. Traditional packaging materials, many of which have not changed significantly in decades, now face new performance demands in applications including 5G/6G communications, artificial intelligence, and high-performance computing - requirements that closely mirror those imposed by ADAS and electrified powertrain platforms in modern vehicles.
