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

3. 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

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

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

6. 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

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

8. 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

9. 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

10. 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

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

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

13. 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.