PIM: Components, Material, Handling & Testing

New connector surfaces look and feel very smooth, but the picture changes quickly when viewed under a microscope. The atomic lattice size of metals is often no more than 25 Angstroms (0.0000025 mm) wide. Machined metal surfaces will never have such a degree of smoothness. Metallic surfaces look indeed very rough under high magnification. That causes surfaces of mated connectors to touch only at a few spots, called asperities. Tightening connectors applies localized pressure to these asperities, which causes them to deform. Deformations increases the contact area, but it is still limited to some load-bearing areas, so called a-spots. They add up, but their overall area is still by several orders of magnitude smaller than the apparent contact surface of connectors.