Characterizing Metallurgical Reaction of Sn3.0Ag0.5Cu Composite Solder by Mechanical Alloying with Electroless Ni-P/Cu Under-Bump Metallization after Various Reflow Cycles
Authors: Hsiao, Li-Yin; Kao, Szu-Tsung; Duh, Jenq-Gong
Source: Journal of Electronic Materials, Volume 35, Number 1, January 2006 , pp. 81-88(8)
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.
Document Type: Research article
Publication date: 2006-01-01