Abstract: Miniature soft probes are used to provide a high speed connection to circuits on a wafer. The probe contains a co-planar line on a soft substrate which provides a flexibility for secure contacts. A miniature coaxial line is directly connected to the coplanar line with a zero degree angle. This configuration makes the probe very small and result in high performance. A planar link between two ground planes eliminates any unwanted odd mode. The probes have high speed and wideband transmission lines with interfaces which have speed in the picoseconds and bandwidths in the hundreds of gigahertz. The probes have multi-functional capabilities, such as high impedance buffering and DC blocking, due to printed circuits which constitute a portion of the probe. The printed circuits are produced by a thin film photolithic process. These probes are best suited for on-wafer tests, diagnostics and measurements as well as interfacing on-wafer circuits with other electronic or electro-optical systems.