TRANSMISSION PROPERTIES OF VARIOUS STYLES OF PRINTED WIRING BOARDS

This paper presents some experimental results concerning the pulse transmission properties of fine line printed conductors (e.g., width = 8 mils, spaces = 9 mils) on various styles of circuit packs (CPS). The pulse transmission properties include the characteristic impedance, the propagation delay, the rise time, the bandwidth, and the intra‐layer and interlayer pulse crosstalk. A simplified theoretical model is presented which leads directly to some basic crosstalk equations. Theoretical results are developed to extend the application of the experimental crosstalk results to arbitrary pulse signals, periodic signals, and random signals. Also, theoretical scaling laws are developed to extend the crosstalk results to conductor spaces in the range of 7 to 40 mils. The crosstalk results are very important, since they tend to limit the packaging density of printed conductors on the CP styles by limiting the coupled length and spacing of parallel conductors. The results can be incorporated into computer‐aided designs which can analyze routed CPS to detect potential crosstalk problems before the CP routing is finalized for manufacture. Other applications include CP selection, crosstalk estimation, electrical characterization of CPS and backplanes, estimation of conductor capacitance and inductance, and effects of various dielectrics. The results are applicable to general styles of printed wiring boards. In particular, they apply directly to all styles of CPS in the BELLPAC™ apparatus housing—a modular packaging system for packaging electronic equipment in the Bell System. © 1979 The Bell System Technical Journal