What Is an Axial Lead?

An axial lead is connection configuration used on many electric and electronic parts and components designed for through-board or carrier mounting. It locates a part's leads or wires axially, or in a straight line, with one exiting the component at either end. Common examples of axial lead configurations include carbon resistors, electrolytic capacitors, fuses, and light emitting diodes (LEDs). The leads are typically fairly long to allow for easy installation in most printed circuit board (PCB) layouts. Generally, the leads are solid, single strand wire although some heavy current axial lead components, such as fuses and capacitors, feature stranded or braided leads.

Twin lead electronic components designed for flat mounting through holes in a PCB generally feature one of two lead configurations — radial and axial. Radial lead components have both leads located on one side of a component, typically closely positioned next to each other. The axial lead configuration locates the leads on opposite sides of the component in a straight line, or axially, with the component body. Axial lead configurations are found on a wide range of components including carbon and wire wound resistors, electrolytic capacitors, and diodes. Batteries, fuses, and lamps such as LEDs are also presented in axial lead configurations.

The leads or wires on axial lead components are typically made fairly long to accommodate as many PCB layouts as possible. The norm, however, with most boards is to keep the holes for a component as close together as possible meaning the majority of the lead is usually trimmed and discarded after soldering. If the holes are too close to mount the component flat, it may be inserted vertically through one hole with the opposite lead bent down next to it. Typically, however, axial components are mounted horizontally to the printed circuit board.

The leads on smaller electronic axial lead components are typically made of a solid, single core wire. Heavy duty components designed to carry large currents may be equipped with multistrand leads terminated with bolt down lugs. These are typically encountered on components such as heavy fuse links which lock into insulating carriers with their two leads bolted down onto bus bars or connections on other components. Several types of heavy duty capacitors in high load direct current (DC) applications also feature braided or stranded axial leads. This type of stranded or braided lead is usually made from fairly fine cored copper wire capable of carrying the large current loads involved.