1. UK ATLAS Stave materials research
Glasgow, Liverpool, QMUL, RAL, UK Astronomy Technology Centre
11th November 2010
ATLAS upgrade week. R. Bates

2. ATLAS upgrade week. R. Bates
Contents
Update on thermal measurements
Discussion on hybrid model
Glues, face sheets etc
Foams
Update on FEA
Mechanical
Foams and plans
11th November 2010
ATLAS upgrade week. R. Bates

3. Cross-section of stave/module
* - interface between tape and CFRP considered co-cured
† - no glue on vertical interface between foam and honeycomb
honeycomb
Asic: silicon
tra-duct 2902
hybrid: polyimide / Cu (layers and vias)
C-channel
CFRP
Dow Corning SE4445
epolite 5313
Sensor: silicon
bus tape: polyimide / Cu / Al / composite
hysol or co-cured*
facing: CFRP
Pocofoam
fluid film X Y
S/S cooling pipe
Hysol
Hysol+BN †
11th November 2010
ATLAS upgrade week. R. Bates

4. ATLAS upgrade week. R. Bates
Thermal measurements
Aim :
To measure all the materials with accuracy for FEA
To understand material variations due to product batch, preparation and irradiation exposure
Hybrid
CFRP
Foams
In plane of Poco and Allcomp as function of temperature
BN loaded Hysol glue
Before and after irradiation
11th November 2010
ATLAS upgrade week. R. Bates

5. Hybrid
Unit hybrid cell: 9.6 X x 12.0 Z
0.5 no Cu.
Asic Land
hybrid centre line
7.7
2.2
2.95
3.7
hybrid edge
digital side of asic
1.05 Z X
Thermal Vias: 3 rows (7+6+7).
Pitch: 1.0 X, Z.
(land to GND plane).
7.5
analogue side of asic
Cu 15
Bond Ply 50
Cu/Kapton/Cu 18/50/18
Layer
1 Top (Asic Lands)
2 Signal (tracks)
3 Power (~solid)
4 Ground (~solid)
5 Shield (solid) (under review)
Resist (~Kapton) 25
Via 150mm o/dia, Plated 10mm Cu
(20 posns)
ASIC: Silicon 300
Glue: Tra-duct ~100, 50% area
Complex structure under chips with thermal vias through Kapton and glue layers
Ground and shield layers spread ASIC heat.
Measured R = 11 C/W for 8x8 cm region
Calculated R = 10.8 C/W for 8x8 cm region
Kapton conductivity change from 0.16 to 0.12 k/mW → R increases to ~20 C/W
Factor two change in conductivity changes chip temperature by 3.2oC
11th November 2010
ATLAS upgrade week. R. Bates

6. ATLAS upgrade week. R. Bates
CFRP - Measurements
Measurements (20oC)
Kx: 144 (±20) W/m-K
Ky: 0.96 & 1.3 W/m-K
Kz: 294 (±20) W/m-K
(1/K) dK/dT = % / degree (x and y). Slope plausible but unsubstantiated
11th November 2010
ATLAS upgrade week. R. Bates

7. ATLAS upgrade week. R. Bates
CFPR - Calculations
In-plane: Kx = 160, Kz = 319 W/m-K
From FEA model of cylindrical carbon fibre + resin.
Ideal fibre geometry, conductivity = 800 W/mK
Fibre fraction, fv, ~0.6 (from Young's modulus measurements)
Kresin = 0.21 W/m-K (take Hysol/epoxy. Lack data for polycyanate).
Through-plane: Ky = need an update here?
Effective Ky very sensitive to glue thickness, g (for even moderate fibre transverse K).
Centre of fibre: g = h (ply) * [0.5 - √ (f/p)] ≈ 4µm for 70µm thick sheet and fv = 0.7
Our K13D2U/RS3 u/d pre-preg specified at 70% fibre fraction (60% from Mitsubishi's Dialed brochure).
… important that we get a reliable measure of the face sheet modulus
fibre
r = 94%
(f=70%)
11th November 2010
ATLAS upgrade week. R. Bates

8. Pocofoams Thermal conductivity measured with 2 apparatuses
Guard Box (2mm Al)
Guard Heaters (2 top, 2 bottom)
Sample
clamped to isolated heater
Guard thermistor
4 spring-loaded thermistors contact sample
Sample thermally shorted to guard
~ 1-d heat flow along sample and guard (when temperatures balanced)
Heat sink is floor of chamber
Thermal conductivity measured with 2 apparatuses
TIM apparatus
1x1x2cm cube with heater attached to top surface, cooled via lower copper block, PT100’s glued along edge, in air.
TTC apparatus
Thin samples surrounded by thermal shield, housed in vacuum tank
T1 (RTD 1)
T2 (RTD 2)
Heater
Lower Cu bar ΔL
Poco foam
Cooling block
Plastic insulating supports
DUT
H2O
Electrical
Heaters
(V,I measured)
Water cooled
Cu block
Al thermal
shield
PT100s
RTD1
RTD2
RTD3
11th November 2010
ATLAS upgrade week. R. Bates

9. ATLAS upgrade week. R. Bates
Pocofoams
kX, (W/mK)
Density, (gcm-3)
Poco08
TIM 71
135
0.56
TTC
54.5
57.5
Poco09 43 55
0.41 51
53.5
Slight temperature dependence on conductivity (6% fall in Poco08 for -30C to 20C)
Large difference between the two measurements techniques (up to 15%)
11th November 2010
ATLAS upgrade week. R. Bates

10. ATLAS upgrade week. R. Bates
Allcomp foam
Density = 0.39 gcm-3.
Thermal conductivity increases with temperature
ΔT =50°C
23% increase for x
17.5% increase for y
y plane conductivities are twice the values found in x plane.
At 20oC
Ky = 110 W/mK
Kx = 55 W/mK
11th November 2010
ATLAS upgrade week. R. Bates

11. ATLAS upgrade week. R. Bates
BN loaded Hysol 9396
Conductivty measured by TIM tower and Line Source Thermal Conductivity Probe method
Two methods gave different results.
Measured different BN in TIM tower – still different results
Could it be technique or sample preparation?
Black triangles : LSTCP, Goodfellows BN, particle size : 10um
Purple Squares : TIM, Goodfellows BN, particle size : 10um
Red diamonds : TIM, SCT Japanese BN
11th November 2010
ATLAS upgrade week. R. Bates

12. BN loaded Hysol 9396 – after irradiation
29% K increase
13 samples made and 9 irradiated to 3 fluences: 0.5, 1, 1.5 x 1015 cm-2 1MeV neq
Measurements show increase in conductivity with fluence.
The 0.5 and 1.0 x 1015 cm-2 neq points lie further from the line than 1.5 x 1015 cm-2 neq data suggesting that the thermal conductivity rises and then falls as a function of dose.
11th November 2010
ATLAS upgrade week. R. Bates

13. ATLAS upgrade week. R. Bates
CGL7018 and ER2074
26MeV protons from Karlsruhe
CGL7018 (compliant) and Elctrolube ER2074 (filled epoxy).
ER2074 showed 20% increase in conductivity
11th November 2010
ATLAS upgrade week. R. Bates

14. ATLAS upgrade week. R. Bates
CTE of BN loaded Hysol 9396
Vishay P3 strain indicator with Vishay CEA UW-120 strain gauges, imbedded at centre point of glue layer
Class-A PT100 for temperature measurements
Must correct for thermal output strain from gauge itself ~10% of expected value
% BN
20C,µm/m/oC
-40C,µm/m/oC
-40C/20C
71.8
63.1
88% 10
63.2
52.8
84% 20
50.9
39.6
78% 30
39.1
27.1
69%
c.f. Bill Miller 76+/-7 µm/m/C for Hysol 9396 and
60 µm/m/C for a mixture of Hysol and 30% boron nitride by weight
11th November 2010
ATLAS upgrade week. R. Bates

15. notes/actions/references
FEA numbers
Item
Material
K x / y / z [W/m-K]
thickness [mm]
additional info.
notes/actions/references
Asic
silicon
see Table (1)
0.3
asic to hybrid
tra-duct-2902
2.99
0.1
50% area coverage!
Future alternative: non-conductive glue (thinner)
hybrid
Cu/polyimide
64/???/64
Kxz neglecting land, taking Affolder dims, inc.shield layer.
hybrid to sensor
epolite
0.23
2mm stay-clear (guard region)
K from Glasgow measurement.
Sensor
Temperature dependence included
sensor to bus
DC SE4445(a)
1.26
0.2
glue pattern (a) aligned ~ Z
K optimistic? Glasgow to measure.
bus tape
PolyI/Cu/Al
34 / 0.24 / 34
0.17
Al 25um, 100%.
Cu (16% area) neglected
Measurements to support
bus to facing
Hysol
0.21
Omit if co-cured tape (preferred build).
Facing
CFRP
150/1/300
(Eng. dwgs 0.27mm too big).
Ky need more understanding
Facing to honeycomb
glue assumed 100% absorbed
Honeycomb
Air
0.025
as drawn
Facing to Pocofoam
Hysol+BN
1.63
Foam
Pocofoam
43/55/43
Gla.Poco (but Kx,y = 52 in Gla.TCC)
P’foam to Pipe
allows for pipe-foam gaps
Cooling Pipe
S/Steel 316L
see Table (2)
0.22
3.18 o/d
Temp dep included. Poss.alternatives: Titanium, 2mm dia.
Fluid film
CO2
htc = W/m2K
Need input
11th November 2010
ATLAS upgrade week. R. Bates

16. Attempt to measure change in foam conductivity under force
Heat
Tufnol™ frame
(2mm thick)
Shear force sample
Stainless steel finger
(30x10x1mm)
Force
0/90/0 K13D2U/RS3 face sheet (0.18mm thick)
1 cm2 Pocofoam Block
(thickness TBA)
Also measuring conductivity as apply a compressive force through sample under test in TIM tower
11th November 2010
ATLAS upgrade week. R. Bates

17. ATLAS upgrade week. R. Bates
Mechanical
Mechanical tests on foams in
Compression
Tension
Shear
Modulus of skins and
sandwiches just started
Will use strain gauges
Foam core vs. corrugated CFRP core
Double cantilever beam tests to look at bond strength to the CFRP skins
Sorry no results yet to show.
11th November 2010
ATLAS upgrade week. R. Bates

18. Tested using modified Tensile Jig
Using linear variable differential transformer to measure strain
11th November 2010
ATLAS upgrade week. R. Bates

19. Pocofoam Results Density gcm-3 Poco08 0.56 Poco09 0.41
Direction
Poco 08
Poco 09
Tensile modulus GPa
Tensile strength MPa
Compressive modulus MPa
Compressive strength MPa X
1.1
0.59
146 ± 27
1.55± 0.18
71 ± 14
0.82 ± 0.17 Y
1.3
0.61
119 ± 32
1.53 ± 0.28
64 ± 8.2
0.75 ± 0.13 Z
3.8
2.48
232 ± 42
1.5 ± 0.35
81 ± 27
0.83 ± 0.21
Density gcm-3
Poco
Poco
12/09/2010
11th November 2010
LBL Stave Mechanics 19

20. Poco shear modulus Used non-contact Video method X : 933 ± 32 MPa
Y : 868 ± 25 MPa
Z : 1796 ± 121 MPa
11th November 2010

21. Allcomp foam in compression
Tested foam along three axes
Tested between three and four samples for each axes.
Mean
Min value
11th November 2010
12/09/2010
LBL Stave Mechanics 21

22. Summary FEA to understand thermal and mechanical aspects of stave
Lots of data for thermal quantities
Still a few things to check, including more radiation tests
CTE measurements to do
Mechanical measurements progressing
CFRP and sandwich modulus outstanding
Modulus of foams loaded with glue
Measurements on materials
To check data for FEA
Understand radiation effects
For QA/QC during production
Questions to be addressed
New fillers for glue
Different foams being investigated
Under questions to be addressed
More work on understanding correlations between density and thermal and mechanical properties of Pocofoam
need to understand the spread better.
22nd April 2010

23. Back-up slides
11th November 2010

24. Two methods Line Source Thermal Conductivity Probe method (Liverpool)‏
TIM tower (Glasgow and QMUL)
Measure conductivity between
surfaces (as a function of thickness)
Line Source Thermal Conductivity Probe method (Liverpool)‏
Transient method
Infinite long wire to heat
sample surrounding wire
Measure sample temperature
(R change of heating wire)‏
K = thermal diffusivity
Lambda = thermal conductivity

25. ATLAS upgrade week. R. Bates
Results so far
SE4486
0.19
Hysol EA9396
1.64 ± 0.13
BN 30% loaded Hysol
1.47 ± 0.08
CGL7018
1.53 ± 0.05
Dow Corning SE4486
0.21 compared with book value of 0.22
Araldite
Thermal conductivity compared to theoretical predictions
Data prefer A29 indicating BN powder forms long chains enhancing thermal conductivity
22nd April 2010
ATLAS upgrade week. R. Bates

26. ATLAS upgrade week. R. Bates
WP7 8/3/2010: impact on runaway power of halving component conductivities.
- Baseline Runaway Power from full FEA.
- Effect of changing conductance from FEA of initial T and slope of runaway curve + analytic formula.
25% reduction in runaway power if facing Kx halved
11th November 2010
ATLAS upgrade week. R. Bates

27. ATLAS upgrade week. R. Bates
Components involved in lateral (X) conduction (heat flow from nether regions towards the pipe)
Layer f(Area) t[mm] K[W/m-K] Conductance
(top down) (f × t × K)
Asics - Si ~ (but segmented)
Hybrid - Cu
Sensor
Tape (FEA) ~0
Tape (Al) < < 6
CFRP
H’comb(FEA) ~0
Ultracore < ? < 6? (pocofoam contact problematic)
(not the whole story)
11th November 2010
ATLAS upgrade week. R. Bates

28. ATLAS upgrade week. R. Bates
FEA: Model CFRP without 90o layer by retaining thickness but K(x,y,z) = (148, 1.3, 294) => (0.87, 1.95, 294)
sLHC
FEA runaway curves, for 0.3W/Asic
Tmax
Ttyp
Avoid tedious plotting of runaway curve:
2 FEA points: T distribution at Qref = 0, 0.01
Q(runaway) ~ l/slope (l from Analytic model)
Model - is based on zero T variation across sensor, so use a typical node (Tmax => runaway ~5% earlier).
- tends to underestimate runaway power by 5-10% (but adequate for design purposes)
2-point FEA + analytic.
Power at runaway
0.3W/chip 0.15 W/chip
Baseline
No 90o layer
11th November 2010
ATLAS upgrade week. R. Bates

29. ATLAS upgrade week. R. Bates
A Design Guideline? WP7 suggestion (last week): “ Optimise (tailor) design for a factor 2 runaway headroom ” In the analytic model, Sensor Temperature rise and Runaway power depend on: R - thermal resistance (sensor-to-fluid, ~ common to hybrid and sensor heat in Stave concept) Tc - fluid temperature (heat sink – fixed T) Qh – hybrid heat …and Eg , taken to be 1.2 eV. SO: Find R for a given design (from quick FEA). Fix runaway power at 2mW/mm2(0C) => Sensor temperature at zero leakage current. (analytic model eqs 18-19) Subtract temperature rise due to hybrid heat (R.Qh) => the corresponding fluid temperature:
- Removing the 90o CFRP layer increases the thermal resistance (and dependence on ASIC power) by 50%.
- If the ASIC power is small, the increase in R is less important*
Caveats:
Off-sensor (e.g. DCDC) heat ignored
Convection ignored
FEA model input imperfect (e.g. glue coverage, K of tape)
Formulae slightly pessimistic (5-10% in terms of runaway power).
* Beware d.s. interpretation!
ABC130??
ABC250 as designed
ABC250 actual
11th November 2010
ATLAS upgrade week. R. Bates

30. Mechanical measurements
Stress/Strain graphs under tensile and compression
Use of non-contact Video or LVDT (linear variable differential transformer) to obtain strain
Video camera measures strain
Load cell
Testpiece
Linear bearing frame
Video camera 2
Testometric
Testing machine