PCB implementation techniques and evaluations for 10 Gbit/s high-speed signal transmission

Abstract

Conventionally, inner layer wires using via holes that have large losses are not intended for high-speed electrical signal transmission in 10 Gbit/s printed-circuit boards (using the 7-GHz evaluation standard bandwidth), so only dedicated surface wires are used. However, surface wiring has a two-dimensional wiring layout and is not suited to high-density packaging. Therefore, to transmit high-speed signals by using inner layer wiring that allows high-density packaging, we designed and fabricated prototypes of extremely small via stub structures on a printed-circuit board by using a low-dielectric-constant and low-dielectric-tangent material and quantitatively evaluated the improvement in the transmission losses. Our results showed that the use of a low-dielectric-constant and low-dielectric-tangent material can double the transmission distance to 130 mm (from about 60 mm using FR-4 material). In addition, by using blind via holes and making the stubs as small as possible, via losses can be decreased by about 8 dB (for the 7-GHz band and with stub length reduced from 1.89 to 0.25 mm) compared to through-via holes. Based on this result, we demonstrated inner layer transmission of 10 Gbit/s signals in the board with high-density packaging. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 88(7): 39–49, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20152