Electrical crosstalk in multilayer ceramic substrates

Abstract

Electrical crosstalk is becoming increasingly important as size shrinks and component densities increase in hybrid circuits. This occurs especially in multilayer thick film circuits. Crosstalk studies at high frequencies apply transverse electromagnetic (TEM) or quasi-TEM mode. However, the TEM mode theory is not applicable at low frequencies and low frequency-crosstalk is still a concern for circuit designers.

In this research, crosstalk equations were derived in a simpler way, which can be used for low frequency applications such as automotive electronics. Test patterns were designed in both single and multilayer substrates in order to study crosstalk parameters such as line separation, line width, ground distance, ground type, and multilayer thickness. The mutual inductance and the mutual capacitance were calculated in order to use them in predicting crosstalk for particular transmission line geometrical structures. A conventional technique was used for the mutual inductance, and a new conformal mapping technique was developed for the mutual capacitance.

Frequency dependence of crosstalk was confirmed by the equations developed. There is good agreement between the experimental mutual inductance and mutual capacitance and the calculated values. Finally, crosstalk prediction ( simulated by combining crosstalk equations with calculated mutual parameters ) fits well with the measured values.