Post on 21-Jan-2016
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