BTeV Pixel Substrate

C. M. LeiNovember 2001

Design Spec. Exposed to >10 Mrad Radiation Exposed to Operational Temp about –15C Under Ultra-high Vacuum, 10E-4 torr or better Serve as a Dimensionally Stable Support Serve as a Heat Sink to remove heat 60W

(0.5W/cm^2)

Material Spec.

Rad-Hardness and Low Rad Length Low Out-gassing Rate Light and Stiff High Thermal k and Low cte

Design Approach Address Cooling Needs First Heat Removed Basically by

Conduction to Coolant: Q = k*A* T/ L

Maximize k*A while Keeping Thickness L Small

Design Types

Cooling Tubes Array with Added Substrate (Fuzzy C Design)

Cooling Chamber as Substrate (Beryllium Design)

Cooling Tubes Array with Added Substrate

Need Manifolds and many Joints Need to build up Substrate on Array Allow Porous Substrate – Low Rad L Seamless Tubing Array Generate a Temp Drop across the

Array/Substrate Interface Effective Heat Transfer Area limited

Cooling Chamber as Substrate

Need to Machine Integral Cooling Channels

Need to make a Large-Surface Quality Joint at the Interface

Huge Area for Heat Transfer Wall = Substrate, Min. Thickness Allow Smaller Temp Drop due to 1 less

Joint Impedance

Material Choices

Material K, in-plane K, out-of-plane cte, in-plane cte, out-of-plane Rad L E DensityW/m-K W/m-K ppm/K ppm/K cm Gpa g/cc

Be 145.0 145.0 11.6 11.6 35.4 290.0 1.85AlBeMet 210.0 210.0 13.9 13.9 16.1 200.0 2.10diamond 1500.0 1800.0 1.8 1.8 12.0 896.6 3.27Aluminum 237.0 237.0 23.4 23.4 8.9 69.0 2.76

C-C 185.0 25.0 2.0 2.0 19.0 4.8 2.25C-fiber composite, uni-tape 520.0 0.8 -1.1 0.2 25.0 606.0 1.87SiC 300.0 300.0 2.2 2.2 8.0 460.0 3.21pyrolitic graphite 400.0 3.5 0.5 6.5 19.4 20.0 2.20peek 0.2 0.2 4.7 4.7 35.0 3.6 1.32CoolPoly RS012 (PPS) 10.0 10.0 10.0 20.0 21.0 1.70

SiC foam, 8% packing ratio 11.0 11.0 2.2 2.2 99.0 2.8 0.26RVC foam (vitreous C), 3% pr 0.5 0.5 2.2 2.2 854.0 0.1 0.05poco-foam, 25% pr 80.0 150.0 2.5 2.5 76.0 20.7 0.56fuzzy C, 5% pr, 100% contact 55.0 1.0 1.0 406.7 50.0 0.11

Glassy C 5.0 5.0 3.0 3.0 25.9 30.0 1.65peekBeAl

Fuzzy Carbon Design All Carbon Heat Exchanger - Non-permeable Leak-tight

Glassy Carbon Tubing, Manifold and Joints Tubing Flattened in Cooling Area and Bonded together to

form a Stiffened Array Radial high k Carbon fibers bonded to Array with Intimate

Carbon Joint Pixel Sensors to be supported directly by fuzzy carbon

fibers Leak-tight Carbon Joints Toughened by Resin mixed with

Carbon Nanotubes (Preferred, Regular Epoxy may be allowed to use)

Radial Fintubing Array

Top View

Bottom View

Ovalized Tubing Array

Ovalized C tubing precursor fuses together for greater stiffness

Monolayer of C fiber applied to ovalized tube array

Carbon Coupon

Toughening and fuzzy C interface not illustrated here

Coupon Test Article

Al ManifoldWith epoxy joints

C ManifoldWith C joints

Problems Before Tubing and Joint Broken Many fibers not in contact with Tubing

Small diameter thin wall tubing Tubing Array used as the sole Support Brittle carbonized joint between tubing

and manifold (just good for sealing purpose)

Prospective Solutions Use larger diameter, thicker wall tubing, and

fused together to form a solid cooling array Use C superstructures next to cooling array and

connect them to manifolds to form a rectangular back-frame support

Toughen the manifold/tubing joints with carbonized resin or regular epoxy

Radial C fibers are sure in contact with tubing by forming a solid cooling array

Be Substrate Design

4X 0.5-mm-Deep Channels Cooling Strips along the Channels Overall Thickness 3.066 mm Ave. Rad L per Plane = 0.33%

Be Substrate – Bottom Plate

Be Substrate – Top Plate

Be Substrate – Assembly

Flow Test on Be Substrate

@ 960 cc/min

Loading on Bond Area

Coolant Contact Area = 8.9 in^2For P = 80 psi, F = 710 lbf

Bonding Area = 5.8 in^2Tensile Stress in Bond = 122 psi

If Peeling occurs, (assume all forces acting on 1 line)PIW =150

Choices of Structural AdhesivesVendor Loctite 3M Ciba-Geigy Ciba-Geigy Bacon Emerson

Adhesive Hysol EA9394 DP460 off-whiteAradite 2011 TDR 1100 LCA-48 Eccobond 285Activator BA105

Filler 24LV

Curing Temp C 20 20 20 82 100 25Curing Time hrs 2

Work Life minutesViscosity cp 160000 80000 45000 13000 25

Modulus Msi 0.396Gravity 1.36 1.75 2.18

Hardness Shore D 77 80 95Glass TT C 193

Tensile Strength psi 6675 4800 9100Lap Shear St. psi 4200 4500 2560 3820 2000

T-peel PIW 5 50 28Elongation % 1.66 9 3.6

CTE ppm/C 55.6 59 85 25Thermal K W/M-K 0.331 0.015 1.22

outgassing TML 0.848CVCM 0.002

suggested by Axsys, Hysol Hardric Peregrine

FEA on Be Substrate

Heat Load from ROC = .5 W/cm^2 Heat Load from Sensor = .025 W/cm^2

Constant Coolant Temp = -15C Coolant Pressure = 40 psi Convective film Coef. = 2000 W/m^2*C Radiation Effect Ignored (< 1%) Surrounding Temp = 20C

Temp Profile

3.8C

Coolant Temp = -15C

Temp Profile

Coolant Temp = -15C

3.8C

Temp Profile

Displacement UY

UY = 0 at 4 corners

.071

Displacement UX

UX = 0 this side

.018

Displacement UZ

.025 mm

UZ = 0 this side

Resultant Stresses

(16,710 psi)

Be Sy = 240 MPa

Resultant Stresses in Epoxy Layers

(5,550 psi)

Stresses can be lowered significantlyIf epoxy with lower E is used.

E = 1 Msi

Resultant Stresses in ROC

(5,440 psi)

Sy = 120 MPa

Resultant Stresses in Sensor

(5,470 psi)

Sy = 120 MPa

Temp Profile of 8-chip Module

Coolant Temp = -15C

In this model, bump bonds between ROC & sensor are added.Kapton HDI cable with epoxy are also added.

Results of temperatures, displacements and stressesAre somewhat similar and less because of smaller size of model.

Temp Profile on ROC

Resultant Stresses in HDI Cable

(290 psi)

Tensile stress of Kapton= 24,000 psi

Resultant Stresses in Bump Bonds

Bump bonds (0.01mm DIA, 0.01mm high) were modeled with Beam Elements

Min Principle Stress = -104 Mpa (15,000 psi) Max Principle Stress = +189 Mpa (27,400 psi)

Tensile Strength of Indium = 1.6 Mpa ~13.7 Mpa (?)

Stresses can be reduced significantly if 0.5mm wide epoxy can be glued around the ROC

Reinforced Min Principle Stress = -71 Mpa (10,300 psi) Reinforced Max Principle Stress = +44 Mpa (6,380 psi)

Resultant Stresses in Reinforced Epoxy

(4.600 psi)

(0.5mm wide epoxy around ROC perimeter)

FEA Conclusions on Be Substrate

For h = 2000, Temperature Distribution OK For T = 35C, Thermal Displacements OK Stresses on Epoxy is High Stresses on Bump Bond is not Acceptable

Displacements and Stresses can be reduced if Smaller T allowed

Choices of Thermal Conductive Epoxy

Vendor Master Bond Master Bond Emerson & C Emerson & C Emerson & C Emerson & C Emerson & C NeumannAdhesive EP21 EP21Stycast 2850KTStycast 2850KTStycast 2850FT-FRStycast 2850FTStycast 2850FT NEE001Activator TDCAOHT TCHT-1 24LV 9 9 9 24LV

Filler

Curing Temp C 20 20 25 25 25 25 25Curing Time hrs 24 40 12 20 20 20 12

Work Life minutes 75 45 30 45 45 45 30Viscosity cp <60000 <60000 22000 174000 80000 58000 5600

Modulus Msi 0.39 0.47Gravity 2.7 2.8 2.33 2.29 2.19

Hardness Shore D 92 94 92 96 92Bond Strength psi (8700} {10200} 3300

Glass TT C 40 68 86 68

CTE ppm/C 36 19 24.3 20.3 21 35 39Thermal K W/M-K 1.44 1.44 2.29 2.68 1.23 1.25 1.02 0.24

outgassing TML 0.55% 0.34% 0.25% 0.39%CVCM 0.02% 0.01% 0.01% 0.00%

Vendor Tra-Con Tra-Con Tra-Con Tra-Con Tra-Con Tra-ConAdhesive 2151 2154Supertherm2004Supertherm2005Supertherm2009 816H01Activator

Filler a-alumina boron nitrile

Curing Temp C 25 25 25 25 25 25Curing Time hrs 24 24 24 24 24 24

Work Life minutes 90 45 180 45 90 180Viscosity cp 40000 33000 33000 33000 460000 5000

Modulus MsiGravity 2.3 2.3 2.3 2.3 1.7 1.3

Hardness Shore D 90 90 90 90 80 80Bond Strength psi 7500 2000

Glass TT C 60 48 48 48 54

CTE ppm/C 26 26 26 26 19 40Thermal K W/M-K 0.95 0.88 1.01 1.06 2.7 2

outgassing TML pass NASA pass NASA pass NASA 0.60%CVCM 0.02%

strength @65C

Thermal Cycle Test

After 5 cycles between –15C and 20C, all 3 epoxies stay OK.

Other Tubing-Array Designs

Rad L % of Designs

Thickness per Plane in mm

tubing wall coolant substrate C-CBe 1.13 fuzzy C 0.15 0.58 0.90 pocofoam 0.20 0.29 1.45 pocofoam+cc 0.10 0.53 1.32 0.10

Rad L % per Plane

tubing wall coolant substrate C-C TotalBe 0.32% 0.33%fuzzy C 0.06% 0.08% 0.02% 0.16%pocofoam 0.08% 0.04% 0.19% 0.31%pocofoam+cc 0.03% 0.07% 0.17% 0.05% 0.33%

Future Plans

Run Thermal Test and verify effective h with cooling-strip effect included

Try to lower coolant temp to –10C or so Evaluate and Select Epoxies Do Thermal Cyclic Test on Si Dummies

with Bump-Bond Do Bump-bonds Testing Works on other Designs