Researchers at the National Institute of Standards and Technology (NIST) have published a comprehensive framework for advancing polymer-based semiconductor packaging materials, with direct implications for the reliability of automotive sensors and electronic control units (ECUs) operating in harsh under-hood and exterior environments.
Background
Polymer-based packaging materials, once viewed as little more than a means to encapsulate or bond chips, have emerged as critical factors in reliability, performance, and cost. The shift is consequential for the automotive sector, where the proliferation of electrified powertrains and sensor-heavy advanced driver-assistance systems (ADAS) architectures is driving demand for packaging materials that can withstand broader temperature ranges, vibration, and chemical exposure.
As the industry moves toward 3D heterogeneous integration-where multiple chips are stacked or linked in three dimensions-demands on these materials are escalating rapidly. Unlike metals or ceramics, polymers are time- and temperature-sensitive, absorbing moisture and changing shape under stress. These behaviors can cause chips to warp, signals to degrade, or connections to fail over years of operation.
Reliable advanced microelectronic packaging has become a top priority across multiple semiconductor growth markets, including automotive, industrial, and cloud-based computing. In the automotive context, engine-bay ECUs routinely face conditions including operating temperatures exceeding 125°C in under-hood positions, combined with repeated cold-start thermal cycling, mechanical vibration, and exposure to hydraulic fluids, oils, and cleaning agents.
Key Framework Details
The NIST perspective builds on insights from a NIST-organized workshop, "Materials and Metrology Needs for Advanced Semiconductor Packaging Strategies," held at the 35th annual Electronics Packaging Symposium in Binghamton, New York, on September 5, 2024. It 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).
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 accelerate the development, qualification, and adoption of next-generation packaging materials.
NIST is also pioneering RGTMs: open, nonproprietary polymer systems that serve as benchmarks. Unlike commercial "black box" materials, RGTMs allow researchers across industry, academia, and government to compare results, improve reproducibility, and feed reliable data into computational models.
NIST materials scientist Christopher Soles, co-project leader, stated that "by providing shared, transparent materials, we can accelerate innovation across the entire ecosystem", according to the NIST announcement.
The framework addresses established engineering polymers-including epoxies, silicones, and polyimides-that serve as die encapsulants, underfills, and structural adhesives within chip packages. Encapsulating materials must exhibit chemical stability, hydrophobic characteristics, suitable thermomechanical properties, electrical insulation, thermal stability, and specific dielectric performance. For automotive-grade sensor and ECU packaging, these requirements are compounded by the need to survive AEC-Q100-mandated temperature cycling from -40°C to +125°C (Grade 1) or -40°C to +150°C (Grade 0) in safety-critical applications.
Electronic devices incorporate a wide range of materials-metals, composites, polymers, and ceramics-making thermal expansion a persistent source of damage. A prime example is shear strain in solder joints, where mechanical stresses arise from mismatches in coefficients of thermal expansion (CTE) between adjacent materials. The NIST framework's emphasis on structure-property-processing relationships aims to give materials formulators quantitative tools to engineer lower-CTE polymer systems that remain dimensionally stable through cold starts and prolonged thermal cycling.
Outlook
With some new packaging materials taking 10 to 25 years to reach production, the authors stress that early, collaborative work is essential. The framework's call for shared property databases and standardized metrology protocols is particularly time-sensitive as automakers accelerate electrification programs and introduce domain- and zone-based electrical architectures that increase both the number and thermal load of semiconductor packages per vehicle.
NIST's identified priorities include rebuilding U.S.-based supply chains for packaging materials, creating shared databases of material properties, and advancing measurement standards. The perspective also distills key insights from a panel discussion with industry experts, emphasizing close collaboration among materials scientists, process engineers, and metrology specialists. It further highlights the importance of cross-sector partnerships among industry, academia, and government to address pressing challenges in packaging materials and processes.
Automotive Tier 1 suppliers and polymer compounders are expected to engage with NIST's RGTM program as a route to accelerating qualification timelines for new high-temperature encapsulants and underfill formulations, with compliance pathways likely to inform future revisions to AEC-Q100 and related industry standards.
