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Test of HV Prototype Boards for LHCb Outer Tracker - PowerPoint PPT Presentation

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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

Test of HV Prototype Boards for LHCb Outer Tracker

NIKHEF, Amsterdam

The Netherlands


Hv boards
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
Experimental Setup

HV to gnd net on HV boards may contributes to the measured leakage currents!

Experimental setup cont
Experimental Setup (cont.)

HV = 2kV, Thermal Cycling = 20oC ~73oC,

Time = 24days, 15 boards are tested

Temperature cycling
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

Leakage currents
Leakage Currents

Leakage currents of 15 boards are logged,

as well as the temperature and relative humidity

One thermal cycle
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:

[email protected]=20oC and [email protected]=73oC

Correlation with temperature and rh
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


  • 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

Leakage current at t 20 o c
Leakage current at T=20oC

Ileak of each board ↓

< 2nA, including the component from HV to gnd net on HV boards

Capacitance measurement
Capacitance Measurement

  • 480 Capacitors

    479: ~30pF less than before

    1: 187pF, 2/3 of other capacitors

  • A crack found under microscope


  • 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.