Development of a printed circuit based transmission channel between high-speed chips

With today's advancing semiconductor technologies, it has become possible to process and transfer data at high speeds in a short time. Advanced technology products, such as radar, satellite, mobile phone, and computer, also hosts several sub-systems; those products contain complex architectures consisting of high-speed chips in telecommunication, defense, space, and aviation industries. In electronic products operating at high frequencies; the power loss of the transmitted signal, reflections in the transmission line, cross talk, electromagnetic propagation, and the parameters that affect the signal quality, such as noise on the signal, may cause the design to fail or operate with low performance. Printed circuit boards, which form the entire electronic system architecture's backbone, are vital in system stability and reliability. This study aims to develop a printed circuit-based, slot-pass test platform to perform fast and cost-effective high-bandwidth chips' tests under development. Within this study's scope, 5 Gbps multi-channel interface design for high-speed chips, system-level S-parameter modeling of the high-speed interface, calibration and measurement techniques with Vector Network Analyzer (VNA), modeling of factors affecting signal quality on the printed circuit board, and measurements were carried out. In order to verify the design, three configurations of printed circuit boards were manufactured complying with IPC-Class 3 requirements. Design and production consist of a backplane board that provides a slot connector and RF connector interface for the chip carrier board, a chip carrier board, and a test board with 5 SMA connector inputs required for VNA measurements. The chip carrier board consists of 100 µm wide, 15 µm thick, 50Ω impedance controlled, 96 channel microstrip line on FR408 dielectric substrate. The channel has a signal reflection below -10 dB (S11) and -1.72 dB insertion loss (S21) at 2.5 GHz frequency bandwidth for a 77.45 mm microstrip transmission line. The insertion loss is -3.53 dB when 1 meter long, RF cable with 6 GHz bandwidth support is added to the channel output. The measured near-end cross talk (S31) on the signal line is below -10 dB, and the measured far-end cross talk is below -20 dB. The aggressive channel causing cross-talk is coupled to the silent signal line 7.5 mm in length with a 0.2 mm air gap. The measurement bandwidth is set to 2.5 GHz.