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<p>Advanced electronic packaging necessitates Cu/Al joints featuring low-temperature bonding, high performance, and ideal isothermal aging reliability. Nevertheless, elevated processing temperatures, excessive growth of brittle intermetallic compounds (IMCs) and Kirkendall voids remain critical challenges. To address this gap, we developed a synergistic strategy combining a SAC307 + Zn composite interlayer with ultrasonic-assisted solid-state bonding at 180&#xa0;°C. With a marginal ultrasonic-induced temperature-increment of 8&#xa0;°C, we fabricated Cu/Al joints with a peak shear strength of 42.1&#xa0;MPa. Subjected to isothermal aging at 150&#xa0;°C for 312&#xa0;h, it exhibited long-term isothermal aging reliability, maintaining a stable shear strength of ~ 24&#xa0;MPa. The Zn particles drove the transformation of Cu<sub>6</sub>Sn<sub>5</sub> into the thermodynamically stable Cu<sub>5</sub>Zn<sub>8</sub> phase, mitigating internal stresses from brittle transitions. Furthermore, the Cu<sub>5</sub>Zn<sub>8</sub> layer maintained an ultrafine grain size of only 0.85&#xa0;μm. No obvious Kirkendall void clusters were detected during aging within the resolution limits of the present observations. Moreover, ultrasonication facilitated the formation of an Al-Zn solid solution at the Al-side interface. The fracture mode transitioned from a weak interfacial failure between Zn particles to a ductile fracture within Sn matrix after aging, indicating that the metallurgical bonding is highly robust and surpasses the strength of Sn. Ultimately, this study provides a low-temperature, highly reliable joining strategy for advanced electronic packaging.</p>

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Low-temperature Cu/Al solid-state bonding with SAC307 + Zn composite interlayer: achieving robust long-term isothermal aging reliability via ultrasonic-assistance

  • 期刊论文

  • 发表日期：

    2026年6月28日

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  • Guisheng Gan,
  • Fangliang Li,
  • Mingli Geng,
  • Jiajun Zhang,
  • Yunfei Du,
  • Donghua Yang,
  • Hao Pan

摘要

Advanced electronic packaging necessitates Cu/Al joints featuring low-temperature bonding, high performance, and ideal isothermal aging reliability. Nevertheless, elevated processing temperatures, excessive growth of brittle intermetallic compounds (IMCs) and Kirkendall voids remain critical challenges. To address this gap, we developed a synergistic strategy combining a SAC307 + Zn composite interlayer with ultrasonic-assisted solid-state bonding at 180 °C. With a marginal ultrasonic-induced temperature-increment of 8 °C, we fabricated Cu/Al joints with a peak shear strength of 42.1 MPa. Subjected to isothermal aging at 150 °C for 312 h, it exhibited long-term isothermal aging reliability, maintaining a stable shear strength of ~ 24 MPa. The Zn particles drove the transformation of Cu6Sn5 into the thermodynamically stable Cu5Zn8 phase, mitigating internal stresses from brittle transitions. Furthermore, the Cu5Zn8 layer maintained an ultrafine grain size of only 0.85 μm. No obvious Kirkendall void clusters were detected during aging within the resolution limits of the present observations. Moreover, ultrasonication facilitated the formation of an Al-Zn solid solution at the Al-side interface. The fracture mode transitioned from a weak interfacial failure between Zn particles to a ductile fracture within Sn matrix after aging, indicating that the metallurgical bonding is highly robust and surpasses the strength of Sn. Ultimately, this study provides a low-temperature, highly reliable joining strategy for advanced electronic packaging.