Thin ladder development 28/3/2006

Targets Aiming for 0.1 % X 0 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 Pin 60 μm Sliding joint Measure sagitta stability Silicon sample

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

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. Tension Silicon 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 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