text: Source:
  Fretting also occurs on virtually all electrical connectors subject to motion (e.g. a printed circuit board connector plugged into a backplane, i.e. SOSA/VPX).  Commonly most board to board (B2B) electrical connectors are especially vulnerable if there is any relative motion present between the mating connectors.  A mechanically rigid connection system is required to hold both halves of a B2B motionless (often impossible). Wire to board (W2B) connectors tend to be immune to fretting because the wire half of the connector acts as a spring absorbing relative motion that would otherwise transfer to the contact surfaces of the W2B connector. Very few exotic B2B connectors exist that address fretting by: 1) incorporating springs into the individual contacts or 2) using a Chinese finger trap design to greatly increase the contact area. A connector design that contacts all 4-sides of a square pin instead of just one or 1 or 2 can delay the inevitable fretting some amount.  Keeping contacts clean and lubricated also offers some longevity.
  Contact fretting can change the impedance of a B2B connector from milliohms to ohms in just minutes when vibration is present. The relatively soft and thin gold plating used on most high quality electrical connectors is quickly worn through exposing the underlying alloy metals and with fretting debris the impedance rapidly increases. Somewhat counterintuitively, high contact forces on the mated connector pair (thought to help lower impedance and increase reliability) can actually make the rate of fretting even worse.