The requirements for wafer-level packaging (WLP) are becoming more and more stringent both from a sustainability perspective and process performance. For instance, there is a demand for continuous process improvement for within die uniformity (WID) and operating in a low acid environment for copper pillar plating. Antagonistic these requests are; however, we must devise novel ECP techniques and additive designs to meet such ambitious targets. The additives consist of an accelerator, suppressor, and leveler. The systematic use of Linear Sweep Voltammetry (LSV) aided the study of the electrochemical response to screen the additives and determine the Wagner number (Wa) in the current density region of interest. In addition, the rigorous use of the Design of Experiment (DOE) enabled us to determine the concentrations for combining this new leveler and suppressor with the accelerator. Owing to designing the right leveler and suppressor, we controlled the free acid concentration at 10% (100 g/L) while maintaining the WID below 2.5% and controlling the within-feature (WIF) less than 1µm (~2.0%), using a deposition rate of approximately 2.0 µm/min, to various wafer patterns with various aspect ratios and layouts. Lastly, the resulting film properties are as crucial as ECP performance. SIMS studies support a deficient level of inclusion in the copper film with a total impurity of 3.1 ppm, including C, O, N, S, and Cl. Therefore, when studied with a solder cap, the Kirkendall void performance was outstanding based on minimal voids post 10X reflow cycles and high-temperature storage. The shear stress test measuring the bonding between the copper and its pad on the wafer is 18.4 gf/mil2.