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- Title
Effect of Cooling Rate on Growth of the Intermetallic Compound and Fracture Mode of Near-Eutectic Sn-Ag-Cu/Cu Pad: Before and After Aging.
- Authors
Sang Won Jeong; Jong Hoon Kim; Hyuck Mo Lee
- Abstract
Several near-eutectic solders of(l) Sn-3.5Ag, (2) Sn-3.0Ag-0.7Cu, (3) Sn-3.0Ag-1.5Cu, (4) Sn-3.7Ag-0.9Cu, and (5) Sn-6.0Ag-0.5Cu (in wt.% unless specified otherwise) were cooled at different rates after reflow soldering on the Cu pad above 250°C for 60 sec. Three different media of cooling were used to control cooling rates: fast water quenching, medium cooling on an aluminum block, and slow cooling in furnace. Both the solder composition and cooling rate after reflow have a significant effect on the intermetallic compound (IMC) thickness (mainly Cu6Sn5). Under fixed cooling condition, alloys (1), (3), and (5) revealed larger IMC thicknesses than that of alloys (2) and (4). Slow cooling produced an IMC buildup of thicker than 10 µm, while medium and fast cooling produced a thickness of thinner than 5 µm. The inverse relationship between IMC thickness and shear strength was confirmed. All the fast- and medium-cooled joints revealed a ductile mode (fracture surface was composed of the β-Sn phase), while the slow-cooled joints were fractured in a brittle mode (fracture surface was composed of Cu6Sn5 and Cu3Sn phases). The effect of isothermal aging at 130°C on the growth of the IMC, shear strength, and fracture mode is also reported.
- Subjects
EUTECTICS; SOLDER &; soldering; INTERMETALLIC compounds; ISOTHERMAL transformation diagrams; FRACTURE mechanics
- Publication
Journal of Electronic Materials, 2004, Vol 33, Issue 12, p1530
- ISSN
0361-5235
- Publication type
Article
- DOI
10.1007/s11664-004-0095-9