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Indexed by:期刊论文

Date of Publication:2012-07-01

Journal:MATERIALS SCIENCE AND TECHNOLOGY

Included Journals:SCIE、EI、Scopus

Volume:28

Issue:7

Page Number:837-843

ISSN No.:0267-0836

Key Words:LED; Au-230 at-%Sn eutectic solder; Aging; Reflowing; Alloying

Abstract:Au-30 at-%Sn eutectic alloy was fabricated by sequentially pulse electroplating Au and Sn films on Si chips. Three kinds of Au/Sn/Au triple layer films were prepared in the present work: Au/Sn/Au (6/6/1 mu m) films, Au/Sn/Au (6/6/6 mu m) films and Au/Sn/Au (8/6/1 mu m) films. The microstructure and phase transformation in Au/Sn/Au films during aging and reflow soldering were investigated. For Au/Sn/Au (6/6/1 mu m) films during aging at 100 and 150 degrees C, the layered AuSn/AuSn2/AuSn4 structure formed in the reaction region. Furthermore, the Sn film was completely consumed, and AuSn4 finally transformed into AuSn and AuSn2 after aging at 150 degrees C for 15 h. For Au/Sn/Au (6/6/6 mu m) films during aging at 150 degrees C, the electroplating sequence had an important effect on the formation of Au-Sn phases. An Au5Sn layer was present at the Au II/Sn interface but not at the Au I/Sn interface. For Au/Sn/Au (8/6/1 mu m) films, the micropores that formed preferentially along the Au5Sn/AuSn interface remarkably decreased with increasing reflow temperature from 280 to 310 degrees C. After reflowing for 10 s, the microstructure was not an Au-Sn eutectic; however, after reflowing for 60 s, coarsened primary Au5Sn phase and typical Au-30 at-%Sn eutectic microstructure of fine eutectic phases (AuSn + Au5Sn) formed.