Design of 60 GHz contactless probe system for RDL in passive silicon interposer

A probe design for detecting discontinuities of a redistribution layer (RDL) on TSV silicon interposer is presented in this paper. The probe is a 60 GHz contactless system based on a quarter-wavelength directional coupler, using the capacitive coupling effects between two signal traces. The probes consists of one ground plane and one signal trace embedded in BCB, low dielectric constant insulator. The length, width, and thickness of the contactless probe are 749.3 um, 100.584 um, and 10.414 um, respectively. A time-domain reflectometery (TDR) pulse with 10 ps rise time makes it possible to obtain high resolution. A variation of the probe´s TDR signal through two capacitance coupling effects indicates the location of the open or short circuit fault where RDL has. Reaching a peak and dip of the probe´s TDR signal represents the open and short circuit sites, respectively.