Properties of ternary Sn-Ag-Bi solder alloys. Part 1: Thermal properties and microstructural analysis
Bismuth additions of 1% to 10% were made to the 96.5Sn-3.5Ag (wt.%) alloy in an effort to develop a Sn-Ag-Bi ternary composition. A DSC evaluation of the melting properties of the 91.84Sn-3.33Ag-4.83Bi composition suggested the appearance of metastable, short-range order in the atomic structure as a result of low temperature, thermal aging. More extensive solid-state aging studies on 91.84Sn-3.33Ag-4.83Bi/Cu couples resulted in the growth of an intermetallic compound layer at the solder/substrate interface comprised of Cu{sub 3}Sn and the Cu{sub 6}Sn{sub 5} sub-layers. The growth kinetics of the total layer thickness (x) as a function of solid-state aging time (t) and temperature (T) were represented by the following expression: x {minus} x{sub o} = A t{sup n} exp({minus}Q/RT) where x{sub o} = 0.57 x 10{sup {minus}6} m; A = 6.22 x 10{sup {minus}3} m/s{sup n}; n = 0.46 {+-} 0.15; and Q = 49 {+-} 8 kJ/mol. TEM analysis of the 91.84Sn-3.33Ag-4.83Bi composition indicated that solid-solution and precipitation strengthening mechanisms were a likely consequence of the Bi additions. Contact angle measurements, Cu/solder/Cu solder joint shear strength tests, and microhardness evaluations were also performed on the Sn-Ag-Bi alloys; those results are reported in Part 2.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 20000473
- Journal Information:
- Journal of Electronic Materials, Vol. 28, Issue 10; Other Information: PBD: Oct 1999; ISSN 0361-5235
- Country of Publication:
- United States
- Language:
- English
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