1：Experimental Design and Method Selection

A UV fs Laser Ablation Ionization Mass Spectrometry (LIMS) approach was used for chemical depth profiling of SnAg solder bumps. The methodology included the use of a fs-laser beam at 258 nm for ablation and ionization, with an optical microscope system for precise sample positioning.

2：Sample Selection and Data Sources

SnAg films and bumps were prepared galvanostatically on blanket and patterned Cu-seeded Si wafer coupons. The plating bath composition and parameters were carefully controlled to achieve the desired alloy composition.

3：List of Experimental Equipment and Materials

Potentiostat/galvanostat PGSTAT128N (Metrohm Autolab, Switzerland), rotating disk electrode (RDE), Pt wire anode, Ag/AgCl (3 M KCl) double junction electrode (Metrohm, Switzerland), UV fs laser system (Clark-MXR Inc., U.S.A.), SEM (Zeiss Gemini SEM, Hitachi S-3000N SEM), AFM (FlexAFM V5+, Nanosurf AG, Switzerland).

4：Experimental Procedures and Operational Workflow

The experiment involved the electrochemical deposition of SnAg films and bumps, followed by LIMS measurements for depth profiling. A 2D raster approach was used for layer-by-layer ablation and analysis, with data acquisition for each laser shot.

5：Data Analysis Methods

Data analysis included the determination of relative sensitivity coefficients (RSCs) for Sn and Ag from a certified reference material, and the conversion of 2D-binned data into three-dimensional representations to trace element distributions.