Spring Contact
A helical compression component provides a temporary electrical connection between a test fixture and a target circuit board. A pogo pin resides within a non-conductive barrel and maintains pressure against a contact point through internal mechanical resistance. This assembly allows for rapid testing cycles on production lines where traditional soldering prevents efficient diagnostics.
The contact tip geometry determines the penetration depth into the surface finish of pads and vias. Proper operation depends on the spring force overcoming the oxidation layer on copper surfaces during the touchdown event.
Alignment Constraint
Precision guidance ensures that the tip centers on the intended target pad during the descent of the fixture. If a pogo pin deflects during contact, the resulting lateral force causes uneven wear on the plunger barrel and intermittent signal transmission. Designers specify a capture range based on the diameter of the probe and the clearance afforded by the surrounding solder mask.
These limits define the tolerance stackup for high density interconnects where pads remain close to ground planes.
Wear Mechanism
Fatigue occurs after repeated compression cycles as the internal spring undergoes plastic deformation. Material selection for the plunger coating dictates the resistance to friction and electrical degradation over the life of the test probe. Gold plating prevents oxidation at the interface while nickel serves as a hard barrier to reduce cratering of the substrate metal.
Consistent maintenance protocols involve periodic replacement of probes to prevent false negatives caused by increased contact resistance.
