Thin ladder development28/3/2006

Targets

• Aiming for 0.1 % X0

• Uniformity over full ladder• Compatibility with wire and bump

bonding• Provision for optical survey• Robust

The story so far…

• Have followed up three different approaches– Unsupported, ladder made purely from

thinned silicon and tensioned.– Fully supported, ladder placed on a self

supporting substrate.– Thin substrate, ladder placed on a

supporting substrate but tensioning still required.

Unsupported Ladders

• Hold silicon detectors at ends and tension

• Use sliding V and flat ceramic block pairs

Rigid base-plate

Annulus block

Tensioning

Glue joint

Glue jointGlue jointGlue joint

Pin

60 μm

Sliding joint

Measure sagitta stability

Silicon sample

Unsupported Ladders

Unsupported Ladders

• Several thin ladders where made and stability found to be good along the length.– Concerns arising are

the there is no strength across the width

– Studies by Glenn Christian at E2V confirmed fears, but no figures have yet been obtained

Profile of Ladder during heating and cooling of the ladder

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

-5 45 95 145 195

Ladder Length (mm)

Rel

ativ

e H

eig

ht

(mm

)

10 degrees C (cooling)

0 degrees C (cooling)

-10 degrees C (cooling)

-20 degrees C (cooling)

-20 degrees C (heating)

-10 degrees C (heating)

0 degrees C (heating)

10 degrees C (heating)

Thin substrate• Tensioned thin substrate ladders

– Attach silicon to substrate using pillars of glue in a pattern of dots• A stiff substrate is used such as beryllium or

carbon fibre• The substrate is strong enough to resist

curling across the ladder caused by imbalances from the detector but not strong enough that it is self supporting along the length, hence requires tension.

TensionSilicon detector

Thin substrate Glue pillar

• Silicon detector can be mounted onto a foam substrate or form a composite by sandwiching the foam.– Structure strong enough across width, may require

tensioning• Foam substrate or foam sandwich

• Microstructure sandwich– Two thin layers of silicon held apart by thin silicon walls

“grown” onto one of the layers of silicon

Thin substrate and foams

Silicon detector

Plain piece of silicon

Silicon detector

Silicon detector

Plain piece of silicon

Foams• Foams currently being

investigated are extremely light weight and made from Carbon or from Silicon Carbide.– Benefits from them are

that as they are lighter they can be made more thick

– The co-efficient of thermal expansion is a close match to silicon

• First results are very promising – Shown right is the profile of 20 micron thick silicon on SiC foam at various temperatures

Photo of an open cell foam structure

Construction

• Now possess a fully automated glue robot.– Will speed up

construction– Allow us higher

quality control on engineering models

– Tested and is simple to use

– I won’t go mental!

Measurement

• Measurement of ladder profiles made using our laser measurement system.– Resolution of 1um– Looking to upgrade

to 0.1um resolution

• Able to compare results with FEA simulation