High-Speed Flex-Circuit Chip-to-Chip Interconnects

• Published in: IEEE transactions on advanced packaging Vol. 31; no. 1; pp. 82 - 90
• Main Authors: Braunisch, H., Jaussi, J.E., Mix, J.A., Trobough, M.B., Horine, B.D., Prokofiev, V., Daoqiang Lu, Baskaran, R., Meier, P.C.H., Dong-Ho Han, Mallory, K.E., Leddige, M.W.
• Format: Journal Article
• Language: English
• Published: Piscataway, NY IEEE 01-02-2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Bandwidth; Channels; Chip-to-chip interconnects; Circuit testing; CMOS; CMOS technology; Connectors; Crosstalk; Design. Technologies. Operation analysis. Testing; Electrical resistance measurement; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; flex-circuit; High speed; high-speed connectors; high-speed input/output (I/O); Integrated circuit interconnections; Integrated circuits; low-loss substrates; Noise levels; Ribbons; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Test vehicles; Timing; Vehicles; Voltage; Connector; High performance; Chip-to-chip interconnects; high-speed connectors; Prototype; Bit error rate; flex-circuit; High-speed integrated circuits; Crosstalk; Flip-chip; Durability; Contact resistance; high-speed input/output (I/O); low-loss substrates; Interconnection; Flexible structure; Complementary MOS technology; Electronic packaging; Integrated circuit; Insertion loss; CMOS integrated circuits; Reliability; High frequency
• ISSN: 1521-3323; 1557-9980
• DOI: 10.1109/TADVP.2007.909451

High-speed chip-to-chip interconnect utilizing flex-circuit technology is investigated for extending the lifetime of copper-based system-level channels. Proper construction of the flex ribbon is shown to improve the raw bandwidth over standard FR-4 boards by about three times. Active testing results from a 130-nm CMOS test vehicle show the potential of up to two times higher data rates. The next-generation test vehicle with 90-nm CMOS circuits gives improved voltage and timing margins at 20 Gb/s. In an interconnect limited case a channel with 36 in (91.4 cm) of flex runs at 18.2 Gb/s data rate at a bit-error ratio (BER) of better than 10 -12 . The channel includes two 90-nm CMOS test chips, two organic flip-chip package substrates, and two flex connectors; crosstalk is not included in this experiment. High-speed connector solutions, including results from a ldquosplit socketrdquo assembly test vehicle, are discussed in detail. The characterization of two top-side flex connector prototypes demonstrates their basic durability and good high-frequency performance. Samples survive 100 mating cycles at an average contact resistance of less than 30 mOmega, adequate for high-speed signaling. Measured differential insertion loss is less than 1.5 dB up to 10 GHz and less than 3.5 dB up to 20 GHz. Near-end and far-end crosstalk measurements indicate that the connectors exceed crosstalk specifications.