Dr. Jin Liang, Dr. Nader Dariavach Microstructure & Creep Resistance of Lead-Free Solder under Different Solidification Conditions Dr. Jin Liang, Dr. Nader Dariavach EMC Corp. Dongkai Shangguan Flextronics Corp. Enter speaker notes here. 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA Problem Statement Long term solder joint reliability is one of outmost important concerns for transition to the Pb-Free soldering process. Pb-Free solder metallurgical and processing research: Wettability Creep at various loading and temperature conditions; Low cycle fatigue under various strain rates and temperatures; Deformation and fracture at variable strain rate loading conditions Solidification rate (cooling rate) effects on microstructure and mechanical behavior. The current viable leadfree solders are based on the near-eutectic composition of the Sn-Ag-Cu ternary system with or without additions of other alloying elements. Among the potential candidates to replace Pb-containing solders, ternary Sn-Ag-Cu (SAC) alloys have been considered the most promising substitutes because of their relatively low melting temperature, reasonable wettability, and superior mechanical properties.1-3 However, the solidification characteristics and microstructure and mechanical properties of these alloys are quite different from traditional SnPb solder alloys.4-9 The cooling rate in the reflow process has been found to have a significant effect on the microstructure of SAC alloys during solidification,9,10 although creep behavior was not strongly dependent on the microstructure formation.10 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Ternary Diagram for SAC alloys A projection of the liquidus surfaces for the Sn-Ag-Cu phase diagram showing the ternary eutectic reaction Liquidus surfaces of the Sn-Ag-Cu phase diagram at the Sn-rich corner 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Macrostructure of Pb-free Solder Joints Microstructure of Sn-Ag-Cu solder joint for a chip capacitor. The light etching regions are primary β dendrites, while the grey regions are eutectic Macrostructure of Sn-Ag-Cu solder for a BGA solder ball. The light etching regions are primary β Sn dendrites, while the grey regions are eutectic. Microstructure of Sn-Ag-Cu solder joint for a chip capacitor. Macrostructure of Sn-Ag-Cu solder for a BGA solder ball. 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA Pb-free Creep Samples Alloy: SAC 387 Cast at 300oC Mold size: 4” x 3/8” x 3/8” Sac385 alloy Mold Aluminum Block Water bath Enter speaker notes here. 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Creep samples Casting at Variable Cooling Rates Sample ID Cooling rate, deg./sec. at 250-150oC 5 0.29 1 2.86 2 8.00 3 12.50 4 16.67 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Creep Curves for SAC387 Solder Alloy 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Strain Rate as Function of Stress for the SAC387 Alloy 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Strain Rate as function of Cooling Rate for the SAC387 Alloy 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Microstructure Analysis 0.3 deg/sec 2.9 deg/sec 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

Microstructure Analysis (cont.) 16.7 deg/sec 12.5 deg/sec 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

EDAX Analysis (cooling rate 0.3 deg/sec) 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

EDAX Analysis (cooling rate 8 deg/sec) 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

EDAX Analysis (cooling rate 8 deg/sec) 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

EDAX Analysis (cooling rate 16.5 deg/sec) 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA

2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA Conclusion 2006 Annual Meeting; March 12-16, 2006 — San Antonio, TX, USA