材料に関する洞察が新しい高速エレクトロニクスを可能にする(Material insights enable new, high-speed electronics)

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2024-02-26 デラウェア大学 (UD)

電子機器の需要がますます高まる中、新しい高速伝送技術の開発に向けて、薄くて柔軟で丈夫な回路基板が必要とされています。デラウェア大学とDuPontの研究者らが行った新しい研究では、高速電子アプリケーションに適した複合材料を提案し、材料の結合方法や新しい材料の作成手法についての洞察が示されました。この研究は、将来の高速電子機器のニーズに適した革新的な材料の開発を促すものとなっています。

<関連情報>

次世代マイクロエレクトロニクスへの応用に向けたポリイミド-シリカ複合材料と結節銅の接着特性評価と強化 Adhesion Characterization and Enhancement between Polyimide-Silica Composite and Nodulated Copper for Applications in Next-Generation Microelectronics

Sagar M. Doshi, Alexander Barry, Alexander Schneider, Nithin Parambil, Catherine Mulzer, Mobin Yahyazadehfar, Aref Samadi-Dooki, Benjamin Foltz, Keith Warrington, Richard Wessel, Lei Zhang, Christopher Simone, Gregory S. Blackman, Mark A. Lamontia, and John W. Gillespie Jr.
ACS Applied Materials & Interfaces  Published:January 3, 2024
DOI:https://doi.org/10.1021/acsami.3c14434

Abstract

材料に関する洞察が新しい高速エレクトロニクスを可能にする(Material insights enable new, high-speed electronics)

As the need for high-speed electronics continues to rise rapidly, printed wiring board (PWB) requirements become ever-more demanding. A typical PWB is fabricated by bonding dielectric films such as polyimide to electrically conductive copper foil such as rolled annealed (RA) copper and is expected to become thinner, flexible, durable, and compatible with high-frequency 5G performance. Polyimide films inherently feature a higher coefficient of thermal expansion (CTE) than copper foils; this mismatch causes residual thermal stresses. To attenuate the mismatch, silica nanoparticles may be used to reduce the CTE of PI. A nodulated copper surface can be used to enhance the Cu/PI adhesion by additional bonding mechanisms that could include a type of mechanical bonding, which is a focus of this study. In this investigation, a 90° peel test was used to measure the peel strength in copper/polyimide/copper laminates containing nodulated copper and polyimide reinforced with 0, 20, and 40 wt % silica nanoparticles. The influence of silica nanoparticles on the peel strength was quantitatively evaluated. Laminates incorporating polyimide films lacking silica nanoparticles had a ∼3.75× higher peel strength compared with laminates reinforced with 40% silica. Their failure surfaces were analyzed by using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy to identify the mode of failure and to understand bonding mechanisms. The key bonding mechanism, mechanical interlocking, was achieved when the polyimide surrounded or engulfed the copper nodules when the laminate was created. Post-testing failure surface analysis revealed the presence of copper on the polyimide side and polyimide on the copper side, indicating mixed mode failure. An analytical model was developed to determine the impact of applied pressure, temperature, and time on the polyimide penetration and mechanical interlocking around the copper nodules. The model was validated by measuring the peel strength on another set of specimens fabricated using increased temperature and pressure that showed a 3× increase in peel strength compared to lower temperature/pressure processing conditions. This enhanced adhesion resulted from the lower polymer material viscosity at higher temperatures, which fosters deeper and more complete penetration around the copper nodules during processing at higher pressures for longer durations. The methodology of combining peel testing, viscosity and CTE measurement, SEM/EDX, surface chemical analysis, and penetration depth calculation developed herein enables the calculation of the desired processing parameters to enhance functionality and improve adhesion.

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