Developing a highly efficient leveler in acid copper electroplating solution is one of the primary tasks necessary for achieving superconformal filling of microvias and interconnections in printed circuit boards (PCBs). Two triethylenediamine-based Gemini levelers, both with terminal quaternary ammonium groups, are synthesized and
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Developing a highly efficient leveler in acid copper electroplating solution is one of the primary tasks necessary for achieving superconformal filling of microvias and interconnections in printed circuit boards (PCBs). Two triethylenediamine-based Gemini levelers, both with terminal quaternary ammonium groups, are synthesized and named as GL
1 (C8) after reaction of triethylenediamine with 1,8-dichlorooctane and GL
2 (C6 with two C–O linkages) after triethylenediamine with 1,2-bis(2-chloroethoxy) ethane. Electrochemical experiments indicate that at 100 rpm and 1000 rpm GL
2 combines with a suppressor and accelerator to exhibit greater potential difference of 23 mV than GL
1 in 9 mV for Cu
2+ reduction, demonstrating that GL
2 has a stronger synergistic convection-dependent adsorption (CDA) effect. Microvias copper electroplating experiments confirm that acid copper electroplating solution containing GL
2 achieve more effective superconformal void-free filling as it results in FP = 96.1%, while the solution containing GL
1 results in FP = 70%. Theoretical calculations indicate that adsorption energy of GL
2 is −1037.54 kJ·mol
−1, which is lower than GL
1 (−1019.06 kJ·mol
−1). GL
2 displays lower electron density compared to GL
1, which facilitates its displacement by accelerator at the bottom. The lower adsorption energy of GL
2 suggests the weaker adsorption ability and the stronger CDA behavior.
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