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Strengthening mechanisms of Cu/SACZ/Al micro-connection joints with solid-state bonding

Guisheng Gan, Hao Yang, Jie Luo, Yongchong Ma, Jiajun Zhang, Xin Liu, Qiao He, Leqi Li, Dayong Cheng

Microelectronics International

ISSN: 1356-5362

Article publication date: 27 January 2025

Issue publication date: 12 February 2025

15

Abstract

Purpose

The purpose of this study was to investigate the effects of aging time on the microstructure, mechanical properties and fracture morphology of Cu/Zn160%SAC0307/Al solder joints produced through solid-state bonding.

Design/methodology/approach

Zn particles with a size of 1 µm and Sn-0.3Ag-0.7Cu (SAC0307) particles ranging from 20 to 38 µm were used to achieve Cu/Al micro-connections using ultrasonic assistance at a temperature of 180 °C, followed by aging treatment at 150 °C to enhance the quality of Cu/Al joints. Scanning electron microscopy was used for observing and analyzing the solder seam, interface microstructure, and fracture morphology. The structural composition was determined using energy dispersive spectroscopy, while a PTR-1102 bonding tester was used to measure the average shear strength.

Findings

The results indicated that the intermetallic compounds formed at the interface between Cu substrates and solder metal primarily consisted of smooth Cu5Zn8. The Al-side interface mainly comprises an Al-Sn-Zn solid solution, with Zn-Sn-Cu phases forming between SAC0307 particles at 180 °C. During the aging process, atomic diffusion was accelerated, leading to improved connection quality. The shear strength of the joints initially increased before decreasing as aging time progressed; it peaked at 32.92 MPa after 24 h – an increase of 76.8% compared to as-received joints. After reaching stability at 96 h, there was still a notable increase in shear strength by 48.4% relative to as-received joints.

Originality/value

This study further explores the strengthening mechanisms associated with solid-state bonded Cu/SACZ/Al joints through aging processes. Joints created via solid-state bonding demonstrate superior reliability compared to traditional soldered connections. It is anticipated that insights gained from this research will contribute valuable knowledge toward developing low-temperature soldering methodologies for heterogeneous materials.

Keywords

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant Nos. 62274020 and 61974013), as well as the Scientific and Technological Research Program of the Chongqing Municipal Education Commission (Nos. KJZD-K202101101 and KJZD-M202301102).

Citation

Gan, G., Yang, H., Luo, J., Ma, Y., Zhang, J., Liu, X., He, Q., Li, L. and Cheng, D. (2025), "Strengthening mechanisms of Cu/SACZ/Al micro-connection joints with solid-state bonding", Microelectronics International, Vol. 42 No. 1, pp. 1-14. https://doi.org/10.1108/MI-08-2024-0260

Publisher

:

Emerald Publishing Limited

Copyright © 2025, Emerald Publishing Limited

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