An Air Coplanar Wafer Probe

Abstract

A new wafer probe is presented based on using coplanar waveguide in air. The transmission line is called air coplanar waveguide, and the probe an air coplanar probe (ACP). The probe consists of a coaxial connector, a short piece of coaxial cable and finally the air coplanar waveguide which is formed into a probe tip. This air coplanar tip is made of beryllium copper (BeCu) and allows in excess of 500,000 contact cycles. Both the coaxial cable and air coplanar waveguide are very low loss allowing the ACP to have less than 1 dB insertion loss at 40 GHz. The flexible air coplanar waveguide exhibits high mechanical compliance and repeatable measurements for non planar DUT surfaces. For example either surface irregularities up to 25 um high, or 10 degrees of surface non-planarity cause less than -30 dB error in measured data up to 40 GHz. The air coplanar waveguide also allows better viewing of the contact pads of the DUT than previously attainable with wafer probes. A discussion will be included on the development of the probe and examples of it in use.