Status report of Resistive Strips

PreparationAtsuhiko Ochi,

Kobe University

16/04/2014 MM PCB WG mtg@ CERN

Large size resistive strip production• 2013 October

– First trial to make a large size sample • 870mm x 425mm trapezoidal shape• 8 foils are produced• Provided as a MSW resistive strips

• 2014 March– Second trial

• Same size as first trial• 3 foils are produced

• 2014 April– Third trial

• 50cm x 40cm rectangle shape• 2 foils are produced• Provided as a new test chamber

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Micro scorpic pictures of strips

• Recent rectangle foil– Strip width: 0.35mm– Gap width: 0.1mm

• Foils are attached on PET film– To avoid the damage of the

sputtered carbon pattern, by bending the foil

50 μm polyimide foil

PET FILM

Sputtered pattern

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Resistivity check

• Resistivity from HV source bar

• Line resistivity : 15MΩ/cm• Carbon sputter thickness:

310 nm

5 10 15 20 25 30 35(cm)

0 10.1 15.5 17 18.1 19.6 23.6 27

10 9.5 11.5 12.6 13.8 15.4 14.7 18.2

20 9.5 12 12.7 14.3 15.7 14.2 17

30 9.4 8.9 12.9 14 16 17.8 21.9

40 9.5 12.3 13.5 14.5 16.2 18.8 23.4

47(cm)

11.2 14.1 17.4 18.8 22.9 25.8 30.9

x

Y

100 1000 100000.1

1

10

100

1000

10000

Max

Min

Preliminary

Cupper thickness [Ǻ]

Surf

ace

Resi

stivi

ty [M

Ω/s

q.]

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Problem in liftoff process• It is not easy to remove the wide

resist pattern (correspond to non resistive pattern)– Long exposure in NaOH liquid may

cause the damage to sputtered patterns

• This is more critical for outside of the pattern– Currently, we have masked outside

area by tape and other sheet by hand

– However, it is time and cost consuming

Sputtered carbon

Substrate (polyimide)

resist

On the liftoff process

NaOH

Sputtered carbon

Substrate (polyimide)

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Request for new pattern- Dummy resistive coating -

• Can we put dummy resistive coating around the resistive strip pattern with < 5mm gap?– Do we have to consider the mesh attachment and O-ring

attachment ?

Resistive strip pattern

Dummy resistive coating16/04/2014 A. Ochi, MM PCB WG 6

Feasibility for Module-0

• Technical challenging– There are more than 2m long foils!– 16 types 64 foils needed– Are there resistivity variability for different sputtering

batch ?• It should be checked.

– Fast sputtering method should be developed for reducing the cost.• Currently: 6 hours/batch• Next trial: 2.5hours/batch, using multiple sputtering target• Shorter time available ?

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Summary and prospects

• Currently, resistive foils production using sputtering is succeeded for large foils.

• To reduce the process and the cost, dummy sputtering is needed.

• 2.2m long foils can be made!• Discussion of the cost should be started.

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