Plated Through Hole (PTH)

What Is a Plated Through Hole (PTH)?

A plated through hole (PTH) is a hole drilled through the entire thickness of a PCB that has been plated with copper on its interior barrel surface. The copper plating creates an electrical connection between all copper layers in the board stackup — from the top layer through every internal layer to the bottom layer. Plated through holes serve two primary functions: as vias that allow signal and power traces to transition between routing layers, and as component mounting holes where through-hole component leads are inserted and soldered.

The manufacturing process for PTH involves mechanical drilling, cleaning the hole walls, activating the dielectric surface with a catalyst, depositing a thin initial copper layer through electroless plating, and then building up the copper thickness through electrolytic plating. The quality of the plated barrel depends on the drill accuracy, hole wall condition, plating chemistry, and the via's aspect ratio (depth-to-diameter ratio). Plated through holes are the simplest and most cost-effective via type, as they are created in a single drilling and plating cycle regardless of the number of layers they traverse.

Efficient Through-Hole Via Utilization

While plated through holes are inexpensive to manufacture, they consume routing space on every layer of the board — including layers where the via's electrical connection is not needed. In dense designs, this layer-spanning footprint can create routing congestion that limits overall board density. Physics-driven AI layout tools optimize via utilization by analyzing which layer transitions each signal requires and recommending the most space-efficient via strategy — using standard PTH where appropriate and flagging opportunities for blind or buried vias where the routing density benefits justify the additional manufacturing cost.

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