Plated Through Holes

Plated Through Holes (PTH) are fundamental interconnect structures in multilayer printed circuit boards (PCBs), particularly critical in High-Density Interconnect (HDI) substrates. These are precisely drilled holes that penetrate through multiple PCB layers, then undergo a comprehensive electroplating process where copper is deposited along the hole walls to establish reliable electrical continuity between different conductive layers. The plating process typically involves electroless copper deposition followed by electrolytic copper plating to achieve the required thickness and conductivity. PTHs enable three-dimensional routing of electrical signals in complex electronic assemblies, supporting miniaturization and increased functionality in modern electronic devices.

PTHs function by creating conductive pathways through insulating PCB substrate materials. After mechanical or laser drilling creates holes through the PCB stack-up, the hole walls undergo surface preparation and activation. Electroless copper deposition establishes a thin conductive seed layer, followed by electrolytic copper plating that builds up the required copper thickness. This creates continuous conductive barrels that connect copper traces on different layers, allowing electrical signals and power to pass vertically through the PCB structure while maintaining mechanical integrity.