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Published byAmanda Hodge Modified over 9 years ago
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Test of HV Prototype Boards for LHCb Outer Tracker NIKHEF, Amsterdam The Netherlands 2003-10-16
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HV Boards Johanson Capacitors PCB Embedded Working HV = 1,600V Mass Production: 1,950 Test items: Leakage Current Capacitance Micro-cracks inside Caps x 32
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Experimental Setup HV to gnd net on HV boards may contributes to the measured leakage currents!
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Experimental Setup (cont.) HV = 2kV, Thermal Cycling = 20 o C ~73 o C, Time = 24days, 15 boards are tested
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Temperature Cycling Temperature Cycle: 20 o C 45 min. 20 o C 73 o C 15 min. 73 o C 45 min. 73 o C 20 o C 15 min. Relative Humidity, not controlled, but kept low when temperature goes down Due to unknown error of the temperature control system
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Leakage Currents Leakage currents of 15 boards are logged, as well as the temperature and relative humidity
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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=20 o C and ~10nA@T=73 o C
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Correlation with Temperature and RH Spread at T=73 o C (T=20 o C) is caused by time needed to warm up (cool down) the capacitors inside PCB Not sensitive to RH anymore
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Spikes It is highly suspected that: T goes down to <0 o C due to unknown error; ice formed on the board surface; T goes up to 0 o C, ice turns to be water to make board surface conductive current spike occurs
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Leakage current at T=20oC I leak of each board ↓ < 2nA, including the component from HV to gnd net on HV boards
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Capacitance Measurement 480 Capacitors 479: ~30pF less than before 1: 187pF, 2/3 of other capacitors A crack found under microscope
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Summary I leak 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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