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Design and test of a prototype of a flex cable for high speed transmission

Design and test of a prototype of a flex cable for high speed transmission. Jan Buytaert ( CERN), Daniel Esperante, Pablo Vázquez, Jevgenij Visniakov (USC). What we have done. Design of the cable. What we can do.

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Design and test of a prototype of a flex cable for high speed transmission

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  1. Design and test of a prototype of aflex cable for high speed transmission Jan Buytaert (CERN), Daniel Esperante, Pablo Vázquez, Jevgenij Visniakov (USC)

  2. Whatwehave done • Design of the cable VELO Upgrade 24.6.2011

  3. Whatwe can do • MeasuretheS-parameters of decoupledlineswith a VNA HP8719D (13.5 GHz) in Santiago • Helpwithmanpowertomeasure in otherlabs VELO Upgrade 24.6.2011

  4. Cable designgoals • Toprovethatisfeasibletobuild a highspeedflex cable in CERN labs • as no companieswerefoundto produce longerthan 55 cm (> 65 cm needed) • Characterizethetransmissionlines (31 in total) • Test transmissionthrough a fine pitch connector • Molex 5024304410 VELO Upgrade 24.6.2011

  5. Cable divided in areasfordifferentstudies • Area 1: effect of a miniature fine pitch connector • This area is cut-off in two pieces • Area 2: parameters of decoupled strip-lines • Area 3: parameters of edge coupled differential striplines • Area 4: effect of viasongnd traces • Area 5: lengthdependance: 0, 56, 75, 100 cm Area 1 (6 lines) Area 1 (6 lines) Area 2 (6 lines) Area 3 (10 lines) 270 mm SMA connectors onbothends Area 4 (5 lines) Area 5 (4 lines) 570 mm (pyraluxwidth – handlingmargin) VELO Upgrade 24.6.2011

  6. Cable profile • Edge coupled differential striplines separated with gnd traces • Made out of 2 foils of pyralux AP- PLUS AP7229R • Dielectric Constant = 3.4 • Dissipation Factor (Loss tangent) = 0.002 • Z iscalculatedwith Rogers MWI-2010 toolwhichdoes not includeGnd traces overstimation (~ 5-10% ?) TOP G Dg1 Wd1 D Wd2 Dg2 G SIGNAL 18 um 500 um Gnd S+ S- Gnd BOTTOM VELO Upgrade 24.6.2011

  7. Area 1: miniature fine pitch (400 um) connector • Twogroups of 3 lines, onegroup per side of theconnector • (L1, L2, L3) = (L4, L5, L6) • L1, L2: S+ and S- match the pitch of the connector (L1 = L10 in Area3) • crosstalk and impedance • insertion loss of connector • L3: S+ and S- twice the pitch of the connector (L3 = L3 in Area 3) VELO Upgrade 24.6.2011

  8. Area 2: decoupled striplines • (L1,L2), (L3,L4) and (L5,L6) are 3 pairs for differential transmission • Impedance, crosstalk, bit error rate (BER) • decoupled (area 2) versus coupled (area 3) transmission lines • (L3,L4) and (L5,L6): parameter ‘Wd’ VELO Upgrade 24.6.2011

  9. Area 3: coupled differential striplines • L1-L3: distance signal to signal ‘D’ • L3-L5: distance signal to gnd ‘Dg’ • L3, L6: width of signal ‘Wd’ (D=500) • L7-L9: width of signal ‘Wd’ (D=250) • L10: D=400 um VELO Upgrade 24.6.2011

  10. Area 4: striplines without vias on gnd traces • L1-L5 = L1-L5 of Area 3 (whitoutviasongnd traces) • No vias gnd traces width ‘G’ = 300um VELO Upgrade 24.6.2011

  11. TOP groundlayer VELO Upgrade 24.6.2011

  12. SIGNAL layer Grid to avoid delamination Lines are routedturningleft – righttoequalizeall trace lengths VELO Upgrade 24.6.2011

  13. DRILL layer VELO Upgrade 24.6.2011

  14. BOTTOM groundlayer Openingson top/bottomlayerstoallowqualityevaluation: gluing, etching… of traces (and cutting-off) VELO Upgrade 24.6.2011

  15. Detail: end of transmissionlines • Surface mount SMA and find pitch connectors mounted directly on signal layer to avoid vias on signal traces • 4 viascloseto SMA connector and 1 viaevery 10 mm ongnd traces toimprovegroundconnection VELO Upgrade 24.6.2011

  16. Detail: fine pitch molexconnector VELO Upgrade 24.6.2011

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