Authors:

Diego Jimenez Rivera

Date Created:

Not specified

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About Paper:

Lead (Pb)-based solders had traditionally been used in the microelectronics and defense industries due to their favorable melting temperatures, wettability, and low cost; however, as increasing studies highlight lead's detriment on public and environmental health as well as supranational legislation restricting the use of lead-based materials in electronics, industry and research shifted towards lead-free solders, with Sn-Ag-Cu and Sn-Bi alloys rising in prominence. Concerns over high melting temperatures in Sn-Ag-Cu-based alloys and high strain rate dependence on flow strength in Sn-Bi-based alloys with respect to modern microelectronic applications prompted research into higher order elemental additions to further improve material properties. While mechanical testing of SAC 305 (Sn-Ag-Cu based) shows that the alloy exhibits decreased strength when aged when compared to as- reflow,?Innolot?(enhanced Sn-Ag-Cu based) contrastingly exhibits increased strength when aged. Such behaviors may be attributed to differences and evolution of microstructures during reflow and aging. This work seeks to link microstructure evolution to mechanical properties in these solders and improve performance through tailored aging heat treatments. CALPHAD simulations were conducted using Thermo- Calc(R) software to determine equilibrium phase fractions and precipitation behavior?and were compared to experimental results obtained from?Differential Scanning Calorimetry (DSC) and Scanning?Electron Microscopy (SEM) image analysis. This combination of thermal and microstructural analysis revealed microstructural evolution of the as-reflow structure and evolution of precipitates as a function of temperature and composition. The results of this and subsequent projects will ultimately contribute to a guide?for solder selection in aerospace and defense. Keywords: [no keywords provided]

Source:

Purdue University / 2025

Topics:

No topics listed

Co-authors:

Diego Jimenez Rivera