Understanding Molecular Properties of Bismarck Brown R and Its Effects on the Electroreduction of Copper Ions at a Polarized Interface: Toward Void-Free Filling of Microvia

= 6.95%), indicative of a superior bottom-up filling performance. Electroplating experiments validate that void-free, dense copper filling of microvias is achieved exclusively in the presence of BBR. Furthermore, BBR modulates the preferred crystallographic orientation of the copper coating from (200) to (111). This work provides a comprehensive molecular-level understanding of BBR as a high-performance additive and offers an effective strategy for void-free microvia filling in advanced PCB manufacturing.