A mechanical probe station is used to physically acquire signals from the internal nodes of a semiconductor device. The probe station utilizes manipulators which allow the precise positioning of thin needles on the surface of a semiconductor device. If the device is being electrically stimulated, the signal is acquired by the mechanical probe and is displayed on an oscilloscope. The mechanical probe station is often used in the failure analysis of semiconductor devices.
There are two types of mechanical probes: active and passive. Passive probes usually consist of a thin tungsten needle. Active probes utilize a FET device on the probe tip in order to significantly reduce loading on the circuit.
Source: Wikipedia
