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The Ternary Eutectic of Sn-Ag-Cu Solder Alloys



Kil-Won Moon, William J. Boettinger, Ursula R. Kattner, Frank S. Biancaniello, C A. Handwerker


New measurements using precision thermal analysis and existing experimental data for the Sn-Ag-Cu system are summarized. For Sn-Ag-Cu alloys, the location of the ternary eutectic involving L, Sn, Ag3Sn, and Cu6Sn5 phases in the Sn-rich corner is of critical interest. From the thermal analysis, the ternary eutectic is located at a composition of (3.57 plus or minus 0.05) mass % Ag and (0.9 plus or minus 0.04) mass % Cu at a temperature of (217.2 plus or minus 0.2) degrees C (2 sigma). A thermodynamic calculation of the Sn-rich part of the diagram from the three constituent binary systems and the available ternary data using the CALPHAD method is conducted. The best fit to the experimental data is 3.66 mass % Ag and 0.91 mass % Cu at a temperature of 216.3 degrees C. Finally, using the assessed ternary thermodynamics, solidification paths and freezing ranges will be presented for various solder compositions.
Proceedings Title
Proceedings of the Surface Mount Technology Association
Conference Dates
September 1, 2000
Conference Title
SMTA International Conference


Pb-free solder, phase diagram, Sn-Ag-Cu solder, ternary eutectic, thermal analysis


Moon, K. , Boettinger, W. , Kattner, U. , Biancaniello, F. and Handwerker, C. (2000), The Ternary Eutectic of Sn-Ag-Cu Solder Alloys, Proceedings of the Surface Mount Technology Association (Accessed May 27, 2024)


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Created September 1, 2000, Updated February 17, 2017