The National Institute of Standards and Technology (NIST) has published a major perspective paper identifying critical deficiencies in polymer-based materials used to package semiconductors in automotive sensors and electronic control units (ECUs). The paper sets out a framework to address these gaps through standardized test materials, new metrology methods, and shared material property databases.
The paper, "Material Needs and Measurement Challenges for Advanced Semiconductor Packaging: Understanding the Soft Side of Science," was published in IEEE Transactions on Components, Packaging and Manufacturing Technology in 2025 by researchers from NIST, North Carolina State University, the National Renewable Energy Laboratory, Intel, ASE Group, and Binghamton University. The work builds on a NIST-organized workshop held at the 35th annual Electronics Packaging Symposium in Binghamton, New York, on September 5, 2024, where industry, academic, and government experts identified shared priorities for polymer materials and measurement science in advanced semiconductor packaging.
Background
Polymer-based packaging compounds-including epoxies, silicones, and polyimides-now account for more than 99% of the global electronics packaging market, having displaced hermetic ceramic and glass enclosures from the 1970s onward. In automotive applications, these materials must maintain performance over lifespans exceeding 15 years under extreme temperature cycling, vibration, and moisture ingress-demands that far exceed those of commercial or consumer electronics.
Automotive-grade semiconductors must typically operate across a temperature range of -40°C to 150°C, and qualification standards such as AEC-Q100 (for integrated circuits) mandate extensive stress testing to simulate years of in-vehicle operation. The shift toward electrified powertrains and autonomous driving platforms is intensifying these requirements as ECUs and sensor clusters multiply and take on increasingly safety-critical functions. As transistor scaling approaches physical limits, the industry is transitioning toward 3D heterogeneous integration-stacking or linking multiple chips in three dimensions-which further escalates mechanical and thermal demands on polymer encapsulants.
Details
The NIST paper identifies several interconnected failure pathways in polymer packaging particularly relevant to harsh automotive environments. Unlike metals or ceramics, polymers are time- and temperature-sensitive, absorbing moisture and changing shape under stress, with these behaviors capable of causing chips to warp, signals to degrade, or connections to fail over years of operation.
At the materials level, a key concern is coefficient of thermal expansion (CTE) mismatch between silicon dies and epoxy moulding compounds. The CTE of silicon dies typically falls between 2 and 3 ppm/°C, while that of unfilled epoxy resin can exceed 80 ppm/°C-a disparity that drives warpage and interconnect fatigue under repeated thermal cycling. Research also confirms that moisture ingress at polymer packaging interfaces can induce plastic deformation in encapsulant materials, exacerbating nonlinear drift in long-term sensor bias.
To address these gaps, the NIST CHIPS team is developing Research-Grade Test Materials (RGTMs): open, nonproprietary polymer systems that provide transparent benchmarks for cross-sector comparison. "By providing shared, transparent materials, we can accelerate innovation across the entire ecosystem," said Christopher Soles, NIST materials scientist and co-project leader on the initiative. The paper also notes that new metrology tools-spanning advanced rheology, spectroscopy, and in-situ stress measurement-are being refined to track how polymers cure, shrink, and deform during manufacturing, all of which directly affect long-term device reliability. "Modeling without metrology is imagination," stated co-author William Chen, Chair of the IEEE Heterogeneous Integration Roadmap for semiconductors.
The framework identifies three priorities agreed upon at the 2024 workshop: rebuilding U.S.-based supply chains for packaging materials, creating shared databases of polymer material properties to enable predictive digital twin modeling, and advancing measurement standards that allow results to be reproduced and compared across organizations.
Outlook
The path from fundamental polymer research to production-ready automotive packaging materials is lengthy. The NIST authors note that some new packaging materials take between 10 and 25 years to reach volume production, making early and collaborative work across industry, academia, and government essential. On the infrastructure side, the CHIPS for America National Advanced Packaging Manufacturing Program (NAPMP) Advanced Packaging Piloting Facility-awarded $1.1 billion in January 2025 and expected to be located at Arizona State University Research Park in Tempe, Arizona-is projected to be operational by 2028 and will provide a manufacturing-like R&D environment for testing new polymer materials and packaging architectures. For automotive Tier-1 suppliers and OEM procurement teams, the NIST framework signals a forthcoming shift toward standardized polymer qualification protocols that could reshape material sourcing specifications and long-term supplier qualification programs.
