Multilayer Sunken Gold PCB

What is ENIG PCB?
同意する (エレクトロレスニッケルイマージョンゴールド), also known as gold immersion (AU), electroless Ni/AU, or soft gold, is a metal plating process used in the manufacture of printed circuit boards (プリント基板) to prevent copper oxidation and improve touch and through-hole plating.