Electrical Characteristics of Copper/Polyimide Thin-Film Multilayer Interconnects

A multilayer substrate Containing two-chip emitter-coupled logic (ECL) ring oscillator circuits was fabricated and tested to determine the static and dynamic electrical characteristics of the copper/polyimide thin-film multilayer (TFML) interconnections between chips. The circuit oscillated at 122 MHz without delay lines; delay lines in the circuit enabled measurement of 88 ps/cm propagation delay and -28 dB crosstalk between adjacent parallel lines. The measured electrical characteristics agreed with predictions obtained from static electrical models and SPICE simulations of the interconnections. The ring oscillator circuit has general applications for determining dynamic electrical characteristics of a variety of packaging structures, such as co-fired ceramic single-chip packages and tape-automated-bonding (TAB) leadframes.