Programmable Line Width and Ground Plane for Thin Film Module Package
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
This article describes a method of having wiring lines for the thin film module (TFM) package, with more than one resistance level, within the same plane-pair. The method achieves increased wirability by decreasing line resistance and allowing multi-drop nets. One possible design for the high wiring density requirements results in signal lines with a center to center distance of 25.5 mm. The 8 mm wide lines have a resistance of Ro = 4.09 L/cm which limits distortionless signal propagation to about 15 cm for a two-point net (one driver and one receiver). The maximum length Lmax for these kinds of lossy unterminated lines is proportional to 2Zo/Ro . Reducing the resistance, for example, to Ro = 2.18 L/cm results in distortionless propagation for 1max of over 24 cm.