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Test of HV Prototype Boards for LHCb Outer Tracker

Test of HV Prototype Boards for LHCb Outer Tracker. NIKHEF, Amsterdam The Netherlands 2003-10-16. HV Boards. x 32. Johanson Capacitors PCB Embedded. Working HV = 1,600V Mass Production: 1,950. Test items: Leakage Current Capacitance Micro-cracks inside Caps. Experimental Setup.

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Test of HV Prototype Boards for LHCb Outer Tracker

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  1. Test of HV Prototype Boards for LHCb Outer Tracker NIKHEF, Amsterdam The Netherlands 2003-10-16

  2. HV Boards x 32 Johanson Capacitors PCB Embedded Working HV = 1,600V Mass Production: 1,950 • Test items: • Leakage Current • Capacitance • Micro-cracks inside Caps

  3. Experimental Setup HV to gnd net on HV boards may contributes to the measured leakage currents!

  4. Experimental Setup (cont.) HV = 2kV, Thermal Cycling = 20oC ~73oC, Time = 24days, 15 boards are tested

  5. Temperature Cycling • Temperature Cycle: 20oC 45 min. 20oC 73oC 15 min. 73oC 45 min. 73oC 20oC 15 min. • Relative Humidity, not controlled, but kept low when temperature goes down Due to unknown error of the temperature control system

  6. Leakage Currents Leakage currents of 15 boards are logged, as well as the temperature and relative humidity

  7. One Thermal Cycle Left: with gnd net on HV board connected Right: only 32 output pins of capacitors connected Contribution from HV to gnd net on HV board: ~1nA@T=20oC and ~10nA@T=73oC

  8. Correlation with Temperature and RH Spread at T=73oC (T=20oC) is caused by time needed to warm up (cool down) the capacitors inside PCB Not sensitive to RH anymore

  9. Spikes • It is highly suspected that: •  T goes down to <0oC due to unknown error; • ice formed on the board surface; • T goes up to 0oC, ice turns to be water to make board surface conductive • current spike occurs

  10. Leakage current at T=20oC Ileak of each board ↓ < 2nA, including the component from HV to gnd net on HV boards

  11. Capacitance Measurement • 480 Capacitors 479: ~30pF less than before 1: 187pF, 2/3 of other capacitors • A crack found under microscope

  12. Summary • Ileak of each board < 2nA after 24-day HV-on • 1 of 480 channels of capacitors has merely been broken by 24-day thermal cycling. • Micro-cracks could be detected by thermal cycling, although cycling conditions should be optimized by further study.

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