High-Density Interconnect (HDI) PCBs have become the backbone of modern electronics — powering everything from smartphones and wearables to 5G base stations, medical devices, and automotive control systems. Their finer lines, smaller vias, and higher wiring density allow engineers to pack more functionality into less space. But this complexity also means that not every PCB manufacturer is equipped to produce HDI boards reliably. Choosing the wrong supplier can lead to delayed