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78 PCB007 MAGAZINE I NOVEMBER 2018 Article by Maria Nikolova, Confesol Rodriguez, Kesheng Feng, Carmichael Gugliotti, William Bowerman, Jim Watkowski and Bob Wei MACDERMID ENTHONE Introduction Electroplating copper solutions are used in many industrial applications, such as anti- corrosion and decorative coatings, and in the electronics industry for the manufacturing of electronic devices. Aqueous sulfuric acid cop- per baths are particularly useful for the fab- rication of printed circuit boards (PCBs) and semiconductors. Copper, having better electri- cal conductivity than any metal except silver, is the metal of choice since copper metalliza- tion allows for smaller features application. In- terconnect features are features such as blind microvias (BMV), trenches, and through-holes (THs) that are formed in a dielectric substrate. They are metallized, preferably with copper, to render the interconnect electrically conduc- tive. During circuit fabrication, copper is elec- troplated over selected portions of the surface of the PCB, into blind vias and trenches and onto the walls of THs passing between the sur- faces of the circuit board base material. The walls of the THs are metallized to provide con- ductivity between the circuit layers of the PCB. The conductive deposits should be of a uni- form plating thickness. Vias and trenches pro- vide conductive connections between circuit board innerlayers. For semiconductor fabrica- tion, copper is electrodeposited over a surface of a wafer with various features such as vias and trenches. Copper-filled vias and trenches ensure a good conductivity between the semi- conductor device layers. Thus, in many PCB and semiconductor fabrication processes, elec- troplating has been adopted by the industry as the primary deposition means for copper met- allization [1–2] . The trend of portability combined with in- creased functionality of electronic devices has driven the miniaturization of PCBs. Smaller device sizes and increased circuit density re- quire decreasing the dimensions of intercon- nect features and increasing their density. The conventional multilayer PCBs with TH inter- connects are not always the optimal solution. Sequential build-up technologies that utilize blind vias have been developed for high-densi-

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