Effects of Minor Ni Doping on Microstructural Variations and Interfacial Reactions in Cu/Sn-3.0Ag-0.5Cu-xNi/Au/Ni Sandwich Structures

Authors: Yu, Chi-Yang¹; Lee, Tae-Kyu²; Tsai, Michael²; Liu, Kuo-Chuan²; Duh, Jenq-Gong³

Source: Journal of Electronic Materials, Volume 39, Number 12, December 2010 , pp. 2544-2552(9)

Publisher: Springer

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Abstract:

The effects of Ni doping on microstructural variations and interfacial reactions in Cu/Sn-3.0Ag-0.5Cu-xNi/Au/Ni sandwich structures were investigated. The sandwich structures, i.e., Cu/Sn-3.0Ag-0.5Cu/Au/Ni and Cu/Sn-3.0Ag-0.5Cu-0.1Ni/Au/Ni (wt.%), were reflowed and isothermally aged at 150°C for 500 h. The behavior of Ni and Cu migration in the solders before and after aging was investigated using field-emission electron probe microanalysis (FE-EPMA), and the microstructure evolution of the solders with Ni doping was investigated. It was observed that Ni migrated to the board Cu-side, while Cu tended to migrate toward the Ni/Au package side, and two different types of (Cu,Ni)₆Sn₅ intermetallic compounds (IMCs), one with 19.8 at.% to 23.4 at.% Ni and the other with 1.3 at.% to 6.4 at.% Ni content, were found. Regarding interfacial reactions, it was identified that the local Ni and Cu concentrations affected the formation of (Cu,Ni)₆Sn₅. Redistribution of Ni and Cu was correlated with the formation mechanism of interfacial (Cu,Ni)₆Sn₅.

Keywords: Pb-free solders; soldering; Ni doping; packaging; interfacial reaction

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11664-010-1372-4

Affiliations: 1: Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan 2: Interconnect Technology Team, Manufacturing Technology Group, Cisco Systems, Inc., San Jose, CA, USA 3: Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan, Email: jgd@mx.nthu.edu.tw

Publication date: 2010-12-01