Multilayer PCBs are printed circuit boards that achieve high-density wiring by stacking multiple conductive and insulating layers, and electrically connecting these layers with through-holes and vias. They are indispensable for the miniaturization, higher performance, and enhanced functionality of electronic devices, characterized by improved wiring density, enhanced noise immunity, and ease of impedance control. They are adopted in a wide range of fields, including smartphones, PCs, servers, automotive ECUs, and industrial control equipment. In the manufacturing process, techniques such as conductor pattern formation, insulating layer lamination, drilling, through-hole plating, and etching are employed. The build-up method is frequently used, especially for achieving higher density.