throughholes

Throughholes, in the context of printed circuit boards, refer to holes drilled through the board to accept the leads of through-hole components. Most through-hole work uses plated through-hole (PTH) technology, where the hole is copper-plated to provide a conductive path between copper planes and to anchor the component lead. Components with leads that pass through the board, such as radial and axial types, are inserted and then soldered on the opposite side.

Hole sizes vary with lead diameter and component type. Finished hole diameters for small through-hole components typically range from about 0.8 to 1.0 millimeters, with larger leads requiring bigger holes, sometimes up to several millimeters for power devices. The drilling and plating process must ensure accurate alignment, adequate plating thickness, and reliable solderability across many holes.

The assembly process commonly uses drilling, plating, and then soldering, often by wave soldering or manual soldering. Through-hole components provide strong mechanical anchoring, making boards resistant to vibration and mechanical stress. They also simplify geometry for connectors and for vintage or high-rereliability designs.

Compared with surface-mount technology, through-hole construction generally results in lower interconnection density and larger board area, and can be more labor-intensive. However, it remains favored for high-reliability applications, hobbyist projects, power electronics, and boards requiring robust mechanical support or easier manual prototyping. Many modern boards use a mix of through-hole and surface-mount components to balance density, performance, and robustness.