Space transformer connector characterization for a wafer test system

Standard connections from the probe head to the PCB for vertical type probe cards in wafer test are individual separate wires in space transformers (STs), traditionally used for device pitches 80 mu m and above for quick turn inexpensive solutions compared to multilayer ceramic substrates. There are inherent signal integrity issues using separate wires in controlling impedance, bandwidth, and cross-talk of STs and probe cards. A method of wiring that includes parallel pairs and twisted pairs is proposed and electrical characterization was performed to establish predictive specifications on the test cards.