Full-Wave Electromagnetic Characterization and Measurement of Wirebond Transitions on High Temperature Co-fired Ceramics (HTCC) and Low Temperature Co-fired Ceramic (LTCC) Substrates For Broadband Package Designs

This paper presents the full-wave electromagnetic characterization and measurement validation up to 50 GHz for single and double wire bond transitions on laminated multilayer ceramic substrates. Microstrips and grounded coplanar waveguides (CPWG) are fabricated on one low temperature co-fired ceramic (LTCC) substrate, having nominal dielectric constants of 6, and on one high temperature co-fired ceramic (HTCC) substrate, having a dielectric constant of 8.8. The transmission lines are designed to have a characteristic impedance of 50 Ohms and have varying gap distances between the two probe-fed ends. The gaps range from 4 mils to 100 mils and are connected by a wire bond. The wire bond shape is found to have a significant impact on RF performance at the higher frequencies. Correlation between measured performance and model simulation is also impacted by wire bond shape. The increased improvement in RF performance for a two-wire bond transition is simulated, measured, quantified and finally extended by simulation for the three-wire bond case. Results demonstrate improvements in performance are rapidly approached after two wire bonds. We extend the simulation models for chip-to-substrate wire bond transitions to quantify maximum package speed based on wire bond length, chip pad size, chip material, and return path configuration. The simulation models include silicon as the chip material, and two different return path configurations: microstrip and differential.