| The impending adoption of Pb-free solder by the microelectronics industry demands that a better understanding of these systems be attained. The industry has indicated a selection of near eutectic SnAgCu as the Pb-free system of choice. The near-eutectic ternary Sn-Ag-Cu alloys yield three phases upon solidification: beta-Sn and two intermetallic compounds, Ag3Sn and Cu6Sn5. A distinct need exists to understand the formation of these intermetallic compounds in the bulk Sn and at solder/metallization interfaces. Only then can those in the field begin to model the impact of these details of microstructure of solder joints on package reliability.; This thesis focuses on the preparation of Pb-free; near eutectic Sn-Ag-Cu solder alloys in a highly controlled environment and the analysis of the microstructure of these materials. All samples contained 3.9 weight percent Ag, while the Cu concentration was varied. The specimens were subjected to a predefined thermal profiles using Differential Scanning Calorimeter. The microstructural properties of the specimens were examined using metallographic sectioning, optical microscopy techniques, and SEM microprobe analysis. The effect of Cu concentration and cooling rate on the microstructure and solidification temperature was delineated. It was observed that variations in the Cu concentration resulted in profound changes in the morphology of Ag3Sn primary precipitates. |
