Local Support R&D Update

1. Local Support R&D Update ATLAS Pixel Upgrade Meeting April 9, 2008 M. Cepeda, S. Dardin, M. Garcia-Sciveres, M. Gilchriese and R. Post LBNL W. Miller and W. Miller iTi C. Daly, B. Kuykendall, H. Lubatti University of Washington

2. Module Dimensions for Studies • Have defined multi-chip and single-chip dimensions(two alternatives) as basis for studies. • Assumption is that multi-chip used for outer layers and single-chip used for innermost layer(s). Exact break in radius is TBD. • See backup for more information • Also basis for understanding possible cost reductions in bump deposition and flip-chip (not discussed here) Optimize module size assuming 6” planar sensor wafers

3. Outer Stave Concept • Staves for outer barrel layers for multi-chip modules. • Based on foam, thin carbon-fiber facings AND flex-cable laminated to stave under modules (bus-cable) • Bus-cable routes power, signals, HV to end-of-stave cards. Studies started to see if this works electrically. • Bus-cable worst case thermally • If bus-cable concept bad…revert to “Type I cables” • Modules on both sides (staggered for coverage) • Connector from module to connector on bus-cable • Dimensions shown for CO2(thicker for C3F8) CARBON FOAM

4. Outer Layer Layout Example

5. Double-Outer Layer Concept • Support two outer layers of staves from single shell? • Doesn’t look impossible • Obviously lots of details…… Composite shell and inner support rings combine assembly into one unit

6. Sensors Heating • From Dawson et al. (radiation task force) and temperature parameterization of Unno • Figure is for 6000 fb-1 • Table except 1016 assumes 6000 fb-1. Short strips are at about 30 cm • W/cm2 shown in table

7. FEA Thermal Model • Pixel Arrangement • Modules alternate top to bottom, total 5 modules • Take an array of 3 on top to obtain reasonable symmetry in heat spreading for middle module, leaving two on the bottom Inputs for thermal runaway calculations VG 7

8. Pixel Thermal Model-Baseline • Thermal Solution • Carbon foam core K=6W/mK • Peak Differential Temperature Center Module • 7.63ºC Cooling Tube Inner Wall Reference Temperature 0ºC VG 8

9. Thermal Performance - I • Include detector heating (worst case shown is for total fluence of about 1016. Best case shown is for R ~ 16 cm(and 6000 fb-1). • “Baseline” parameters assumed in thermal model – see backup • Looks promising for outer layers. Need higher K’s for 1016 (see next page) unless assume colder fluid(<-30) than current C3F8 Remember need to include effect of T from pressure drops

10. 10 5 0 -5 -10 Peak Sensor Temperature-(C) -15 -20 baseline foam 6 W/mK -25 foam=15W/mK foam=15W/mK, CC=250/25/250 -30 foam=15W/mK, Cable=200W/mK -35 -35 -30 -25 -20 -15 -10 -5 0 Coolant Tube Inner Wall Temperature-(C) Thermal Performance - II • Results below all for 1016 fluence and changes in stave-component K values. • Need to optimize for 1016. Different designs for inner(most) and outer layers • Unless CO2. Note CO2 also significantly lower in radiation length Higher K foam Carbon-carbon facings CVD diamond facings No bus cable Combinations….. Note that these studies also apply to 2cm wide stave with single pipe that is more likely at innermost R

11. Pixel Monolithic Structure Alternating: Inner and Outer Layer Older module dimensions used for this study VG 11

12. Thermal FEA-Based on 0.6W/cm2 Foam K=10 W/mK Differential from silicon to coolant wall is 10.6˚C. Need improvement to prevent thermal runaway with C3F8….to be studied VG 12

13. Thermally Conducting Foam Update • Obtained additional foam samples – three vendors • Made additional small thermal prototypes and measured (see backup for details). Preliminary results. Average Tmax at 0.64W/cm2 on one side Old prototype, shown last meeting New results, new samples * Have 2 other higher density and K samples from Koppers

14. Foam Mechanical Properties • Important to measure mechanical properties of foam • Being done at University of Washington • Allcomp 1 results – see presentation at meeting link at http://phyweb.lbl.gov/atlaswiki/index.php?title=ATLAS_Upgrade_RandD_-_Mechanical_Studies#Pixel_Upgrade_Support.2FCooling_Structure_Studies

15. Outlook • Optimize thermal performance, radiation length, mechanical properties combining foam(s), facing materials and support. Likely to result in different inner and outer staves. Monolithic still option for innermost layer. • Biggest impact on radiation length is choice of coolant… • Starting on disks. Layout not as easy as barrel…..particularly in case of two-part system, one inside support tube • Overall layout issues and electrical interfaces that drive layout – started some work on this (with UCSC, SLAC, OSU, SMU..) • Thermally conducting, carbon foam continues to look promising. Multiple vendors interested (are there more?). Need to optimize and get more samples of what we want. Vendors willing to develop lower density.

16. Backup

17. 2x2 module & stave layouts M. Garcia-Sciveres

18. 2 options • “Small chip” • “Big chip” • Boundary between “small” and “big” is determined by the 6” sensor wafer layout that must be compatible with bump bonding (will become clear later) • “Small” chip has also a more natural number of rows & columns, but this is probably a minor issue for chip design.

19. Parameters Normal col. width x row height = 250um x 50um

20. “Small” 4-chip module 34.8 37.5 Flex down to chip w-bonds 0.2 Active 32.8 x 32.8 34.8 Pixel orientation 15.0 Flex pigtail (connector plugs into page) 10.0 (vertical inter-chip gap 0.1mm)

21. “Big” 4-chip module 37.1 39.9 Flex down to chip w-bonds 0.2 Active 35.8 x 35.1 37.8 Pixel orientation 15.0 Flex pigtail (connector plugs into page) 10.0 (vertical inter-chip gap 0.1mm)

22. Loaded module stiffener flex 1.0 mm connector sensor chips glue Reduced scale 20 position connector would be used. Replace 10.22 dimension by 6.52

23. “Small” module outer stave Module on back 38.4 26.8 34.8 … 986mm End of stave card serving 8 modules (half a stave) along Z Can serve one face only (top or bottom) => 4 cards per stave Or can be a wrap-around end of stave card and serve both faces => 2 cards per stave. This way identical staves (including bus cable) design can be used over a wide radial range: 4 cards/stave at lower radius and 2 wrap-around cards per stave at higher radius

24. “Big” module outer stave Module on back 39.9 29.8 37.8 … 946mm End of stave card serving 7 modules (half a stave) along Z (or 8 modules for 1082mm active length) Can serve one face only (top or bottom) => 4 cards per stave Or can be a wrap-around end of stave card and serve both faces => 2 cards per stave. This way identical staves (including bus cable) design can be used over a wide radial range: 4 cards/stave at lower radius and 2 wrap-around cards per stave at higher radius

25. “Small” sensor 6 inch wafer • Active area = 7508 mm^2 • Sensor tiles shown with darker line • Wafer scale flip chip compatible. Chips shown with lighter line. • The name “small” 2x2 tile comes from the wafer layout. • A slightly larger chip and therefore larger 2x2 tile is possible, but only 6 such “large” 2x2 tiles will fit on a 6” wafer.

26. “Big” sensor 6 inch wafer • Active area = 7539 mm^2 • Sensor tiles shown with darker line • Wafer scale flip chip compatible. Chips shown with lighter line. • OPTION to make 4 6-chip modules per wafer instead of 6 4-chip modules.

27. “Small” single chip module • Using same chip as 4-chip module (hence “small”) • Active edge sensor • 2-side abuttable format active 16.4 16.2 18.7 16.2

28. “Big” single chip module • Using same chip as 4-chip module (hence “small”) • Active edge sensor • 2-side abuttable format active 17.9 17.4 19.9 17.7

29. Stave Concepts and FEA W. Miller and W. Miller

30. Pixel Activities Analysis Analyze foam structure for inner Pixel Layer steady state chip heating and thermal runaway Thermal runaway evaluation covers different foam and facing thermal conductivities Design Layout Preliminary stages of evaluating packaging for layers at 16cm and 21cm radius Testing Thermal solutions to compare with LBNL stave/carbon foam core thermal tests Evaluation embraces several foam core thermal conductivities VG 30

31. Pixel Stave Structure • Stave Analysis- 1 meter length • In the near future an effort will be underway to assess structural aspects of stave concept for pixels • For now focusing on thermal effects • Pixel sensor is 34.85 mm by 34.85 mm • Pixel chip footprint, 4 total, is 38.4 mm by 38.4mm • Assumed pixel heat load is 0.6W/cm2 • Small diameter cooling tube (presumes CO2) • Steps in process • 1st Order thermal analysis of sandwich structure (conductive carbon foam core) • Several solutions made for thermal runaway • Looks workable without CVD diamond sandwich facings • This model is still being evaluated

32. 34.85 38.4 34.85 Basic Model Parameters-Baseline • Core • Carbon foam, 6 W/mK • Facing • Resin Composite, 0.14mm thick, 110, 1, 110 (X,Y,Z) W/mK • Cable • Includes adhesive for bonding to chips and from cable to composite facing • 2mils Al and 0.7mils of copper, plus adhesives, total compressed thickness=114microns • Calculated: Kt=0.38W/mK and K (in-plane)=83W/mK Sensor Chip heat 0.6W/cm2

33. FEA Thermal Model • Pixel Arrangement • Modules alternate top to bottom, total 5 modules • Take an array of 3 on top to obtain reasonable symmetry in heat spreading for middle module, leaving two on the bottom Inputs for thermal runaway calculations VG 33

34. Pixel Thermal Model-Baseline • Thermal Solution • Carbon foam core K=6W/mK • Peak Differential Temperature Center Module • 7.63ºC Cooling Tube Inner Wall Reference Temperature 0ºC VG 34

35. Pixel Thermal Model Very High FoamConductivity alters peak differential by 3.58ºC • Thermal Solution • Carbon foam core K=100W/mK • Peak Differential Temperature Center Module • 4.05ºC VG 35

36. Thermal Runaway-Baseline 1*1016 fluence makes -25ºC impractical without design changes to sandwich material maheup

37. 10 5 0 -5 -10 Peak Sensor Temperature-(C) -15 -20 baseline foam 6 W/mK -25 foam=15W/mK foam=15W/mK, CC=250/25/250 -30 foam=15W/mK, Cable=200W/mK -35 -35 -30 -25 -20 -15 -10 -5 0 Coolant Tube Inner Wall Temperature-(C) Thermal Runaway with Possible Mod’s • Results show increasing conductivity of foam and facing thermal conductivity improve situation noticeably • Thermal solution with CVD diamond facing still under evaluation, all indications is that it may be overkill Fluence of 1*1016

38. Design Layouts-In Process • Beginnings of 210mm and 160mm layers Composite shell and inner support rings combine assembly into one unit

39. Design Layouts-In Process • Space between adjacent staves is very tight, suggesting that the stave support from the rings may best engage area between module dead-spaces

40. Design Layouts-In Process • First option for 1m length is three support rings, one in middle which will provide the Z-restraint and the two at the ends reacting out gravitational effects, but allowing slip in Z Ring locations

41. Carbon Foam Thermal Tests Following slides provide background on carbon foam thermal conductivity VG 41

42. FEA Model Primary Objective Compare FEA results with LBNL thermal tests of foam core structures Difficulty lies in assigning material properties There are four solids, with three thermal interfaces on each side of the mid-plane Thermal interface thermal resistance becomes an assumption, as well as the thickness Water coolant Flow results in turbulent flow and very high convection coefficient, less problematic than thermal interface resistance Expect small variations in coolant temperature from test to test VG 42

43. Solution With FEA Model Material Properties Heater heat loads, 8.38W Silicon heater, 148 W/mK, 0.28mm thick Silicon heater adhesive, SE4445, 0.6 W/mK, 0.004in thick, two places YSH70 open cloth fabric, one layer, 0.6 W/mK, 0.14mm YSH70 adhesive, 1.55 W/mK, 0.002in Foam properties varied, from 6 to 30 W/mK Al cooling tube, 180 W/mK, 2.8mm OD and 2.19mm ID Water, convective film coefficient, 66,000 W/m2K, 1.0L/min Set 20.25ºC on inner tube wall K13D2U facing, 1 W/mK, 0.28mm thick K13D2U adhesive, 1.55 W/mK, 0.002in thick VG 43

44. Pixel Prototype Components Tube with CGL7018 YSH-70 and K13D2U glued to foam Tube in foam with CGL7018 VG 44

45. LBNL Thermal Test Set-Up Silicon heater VG 45

46. Thermal Solutions for Single Tube Tests Double heater Single heater

47. Prototype Details

48. Old Results Note if CO2 used as coolant then reference temperature could be about -30C. Thus delta T of 10 => T of -20C. * * FE-I3 normal Max. spec FE-I4 goal * Includes sensors & power conv. But not cables.

49. Old Results Table • All relative to 20C water temperature, would be slightly lower if referenced to power off temperature.

50. New Prototypes • Identical width, thickness and adhesives to older prototype (Allcomp 1) but shorter in length (7.4 cm). • YSH-70 facings on both sides. • Heater only on one side. Compare at 0.64 W/cm2 • IR and water flow same as older prototoype(1.0 l/min)