Electrical performance analysis of fine line on high density package substrate

This paper presents the electrical characterization of fine line design. For this kind of very thin and narrow fine lines in high density substrate, the trace is no longer lossless or low-loss transmission line and the characteristic impedance is also varying with frequency. This phenomenon on high density substrate will lead to different design guideline from conventional one. In this paper, the electrical performance of the micro-strip line (MSL) with coupling trace, Co-Planar Waveguide (CPW) and Grounded Co-Planar Waveguide (GCPW) three transmission line designs will be analyzed and discussed. For fine pitch fabrication quality control, it is better to keep thick-width-aspect-ratio larger than 1.5. As a result the trace is designed to 3um thick and 2um wide. Impedance, conductor loss, cross-talk and eye diagram for 10mm long trace will be analyzed in this paper. Proper design of line pitch of GCPW to have good signal integrity performance is then demonstrated.