Journal of Electronic Materials

, Volume 35, Issue 1, pp 81–88 | Cite as

Characterizing metallurgical reaction of Sn3.0Ag0.5Cu composite solder by mechanical alloying with electroless Ni-P/Cu under-bump metallization after various reflow cycles

  • Li-Yin Hsiao
  • Szu-Tsung Kao
  • Jenq-Gong Duh
Article
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Accepted:

Abstract

Electroless Ni-P/Cu under-bump metallization (UBM) is widely used in electronics packaging. The Sn3.0Ag0.5Cu lead-free composite solder pastes were produced by a mechanical alloying (MA) process doped with Cu6Sn5 nanoparticles. In this study, the detailed interfacial reaction of Sn3.0Ag0.5Cu composite solders with EN(P)/Cu UBM was investigated after reflow. A field-emission scanning electron microscope (FESEM) was employed to analyze the interfacial morphology and microstructure evolution. The intermetallic compounds (IMCs) formed at the interface between the Sn3.0Ag0.5Cu composite solders and EN(P)/Cu UBM after one and three reflows were mainly (Ni1−x,Cux)3Sn4 and (Cu1−y,Niy)6Sn5. However, only (Ni1−x,Cux)3Sn4 IMC was observed after five reflows. The elemental distribution near the interfacial region was evaluated by an electron probe microanalyzer (EPMA) as well as field-emission electron probe microanalyzer (FE-EPMA). Based on the observation and characterization by FESEM, a EPMA, and an FE-EPMA, the reaction mechanism of interfacial phase transformation between Sn3.0Ag0.5Cu composite solders and EN(P)/Cu UBM after various reflow cycles was discussed and proposed.

Key words

Electroless Ni-P under-bump metallization (UBM) Sn3.0Ag0.5Cu composite solder intermetallic compound phase transformation 
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Copyright information

© TMS-The Minerals, Metals and Materials Society 2006

Authors and Affiliations

  • Li-Yin Hsiao
    • 1
  • Szu-Tsung Kao
    • 1
  • Jenq-Gong Duh
    • 1
  1. 1.Department of Materials Science and EngineeringNational Tsing Hua UniversityHsinchuTaiwan

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