SNAP CCD Packaging

1
SNAP CCD Packaging Testing

• CCD Packaging
• CCD Testing Characterization
• CCD Radiation Testing
• A collaborative effort between LBL and Yale
• LBL Chris Bebek, John Bercovitz, John Emes,
• Don Groom, Steve Holland, Armin Karcher,
• Bill Kolbe, Hakeem Oluseyi, Natalie Roe,
• Guobin Wang
• Yale Charlie Baltay, Will Emmet, Tom Hurteau,
• Dave Rabinowitz, Andy Szymkowiak

C. Baltay SNAP Collaboration Meeting May 19, 2004
2
CCD Packaging - Requirements

• CCD pattern consistent with NIR array
• Mechanical Rigidity, Thermal Stability
• Temperature range 100o C to 150o C
• CCD Flatness tolerance 10 microns
• CCD package thickness tolerance 10 microns
• Thermal Conductivity
• Heat generated by CCD electronics on package
  1 watt
• Thermal resistance to back plate should be lt 1o
  C/watt
• Substrate should be opaque to photons not to see
  traces on back of substrate
• Electrical Connections
• 74 contact pads on CCD
• Will read out 65 of these in the 1st prototype
  package. Number may change if we put more
  electronics on package

3
Approximate SNAP CCD Dimensions
4
SNAP Focal Plane
5
SNAP 4-Side Buttable CCD Design
Exploded View of Package
6
Thermal Expansion Data for SNAP CCD Candidate
Packaging Materials
7
SNAP 4-side Buttable CCD Finite Element Analysis

• Isometric View of Deformation in Z-axis (Invar
  36/Aln Package)

8
SNAP 4-side Buttable CCD Finite Element Analysis
Selected Result from Dan Chengs Finite Element
Analysis (LBL)
9
SNAP 4-side Buttable CCD Finite Element Analysis
Summary of Finite Element Analysis Results
10
SNAP 4-Side Buttable CCD Design

• Sectional View

11
SNAP 4-Side Buttable CCD Design

• Aluminum Nitride Substrate-Top View

12
SNAP 4-Side Buttable CCD Design

• Aluminum Nitride Substrate-Bottom View

13
SNAP 4-Side Buttable CCD Design

• Circuit Board-Bottom View

14
SNAP 4-Side Buttable CCD Design

• Circuit Board-Top View

15
SNAP 4-Side Buttable CCD Assembly Sequence

• Step 1 Bump-bond CCD to AlN Substrate flow
  Epotek 301-2 between
• components (50 um space)

Developed in consultation with Michael Lesser,
University of Arizona.
16
SNAP 4-Side Buttable CCD Assembly Sequence

• Step 2 Glue Wirebond Circuit Board Subassembly
  to CCD/AlN

17
SNAP 4-Side Buttable CCD Assembly Sequence

• Step 3 Subassembly from Step 2 to Invar 36 Base
• Precision-ground spacers set overall thickness to
  within /-5 um during bonding
• Thickness of Hysol EA9361 is sufficient to absorb
  all tolerances

18
SNAP 4-Side Buttable CCD Design
19
Package Prototypes

• Mechanical Mockup to test thermal properties,
  glues, flatness, etc.
• Prototype 1
• Test as many features of design and assembly
  procedures as possible
• Serve as package for testing first batch of CCDs
• Invar pads will be fabbed at Yale, shipped to
  Lesser
• Circuit boards to be processed and assembled at
  Yale then shipped to Lesser
• Contract with Mike Lesser at the Imaging
  Technologies Laboratories for procuring the AlN
  substrate with the required traces and bump
  bonding and assembly of the whole package

20
(No Transcript)
21
(No Transcript)
22
SNAP 4-Side Buttable CCD Assembly Sequence

• Step 3 (contd) Precision-ground spacers set
  overalthickness to within /-5 um during
  bonding
• Thickness of Hysol EA9361 is sufficient to
  absorb all tolerances

23
SNAP 4-Side Buttable CCD
Mechanical Prototype Thickness and Flatness
Measurements Following Immersion in Liquid
Nitrogen (all dimensions in mm)
Prototype 1
Prototype 2
Prototype 3
Range 7.219-7.222 mm 3um spread
Range 7.214-7.220 mm 6 um spread
Range 7.211-7.218 mm 7 um spread
24
Open Questions

• Invar pad to Moly back plate attachments
• Assembly procedure of CCDs into detector array
• Electronics on package
• Electrical connections

25
Moly Interface Plate

• Monolithic EDM (spark erosion) construction
• 0.75mm thick flexures
• Notch cutouts to eliminate in-plane torsion
  constraint
• Tapped holes for M3 mount to cold-plate

26
Moly Interface Plate

• Monolithic EDM (spark erosion) construction
• 0.75mm thick flexures
• Notch cutouts to eliminate in-plane torsion
  constraint
• Tapped holes for M3 mount to cold-plate
• Thermal resistance 10oc/watt

27
Individual Molybdenum Mounting Scheme
4-side Buttable CCD Package
Molybdenum Mounting Plate (1 CCD per Plate)
28
Individual Mounting Scheme (cont'd)
Thermo-mechanical Behavior of Molybdenum Mount
from 293oK to 153oK
Thermal Resistance 0.44oc/watt
Quarter model of CCD with 2.9 Oz.force at mount
point
293 oK to 153 oK 7 um relative displacement at
each mount point This results in a force of 2.9
ounces at each corner of the CCD package
Von Mises Stresses in Silicon CCD
29
CCD Modular Mounting Scheme
Molybdenum Mounting Plate (9 CCDs per Plate)
4-side Buttable CCD Package (1 of 9)
30
CCD Modular Mounting Scheme (cont'd)
Steady-state Thermal Model of Molybdenum Plate
(Quarter model) with Heat Load of 0.2 W per CCD
Boundary Temp 153.0 oK
Max. Temp 153.8 oK
31
CCD Testing and Characterization at Yale

• Modification of Leech electronics now complete
• Large test dewar ready with 10 inch diameter
  window
• Will allow us to test 9 CCDs at a time
• This will be important both for testing large
  numbers of CCDs, and to test simultaneous
  operation of a 3x3 CCD array (crosstalk, etc. )
• Testing to start soon
• Well understood SARNOFF CCDs (from
  Palomar-QUEST)
• Small LBL CCDs we have at Yale
• The real thing

32
CCD Test Lab 2 at Yale Showing Modified Leech
Electronics
33
CCD Test Lab 1 at Yale
34
Test Dewar in Lab

• Test dewar to read out multiple cold CCDs for
  SNAP CCD testing and
• characterization (dewar has 10 inch diameter top
  window)

35
CCD Radiation Testing at Yale

• We now have a beam line assigned to SNAP for CCD
  testing at the Yale Tandem Heavy Ion Accelerator
• Plan to irradiate CCDs while cold could
  actually read out CCD during the exposure
• Dewar for cooling CCDs with feed through
  connections, etc., has been designed and built at
  Yale
• Starting to understand details of intensities,
  exposure times, etc. Have designed and are now
  building scattering chamber
• Plan to get some test beam in June, 2004
• Can schedule beam time after July, 2004

36
The SNAP Beam Line at the Yale Tandem Accelerator
37
Test Dewar for Radiation Tests

• Dewar to allow the CCD to be read out cold during
  irradiation at the
• Yale Tandem Accelerator

38
The Radiation Environment for the Next Generation
Space Telescope
From a document by J. Barth, J. Isaacs and C.
Poivey
Unshielded
100 mils Aluminum Shielding
Protons/cm2/7 years
Protons/cm2/7 years
Proton Energy (Mev)
Proton Energy (Mev)
39
Radiation Exposures at the Yale Tandem Heavy Ion
Accelerator

• Beam from Accelerator
• 1010 to 1013 protons/sec, 5 to 40 Mev
• Up to 1012 alphas/sec, 5 to 60 Mev
• Up to 1012 heavy ions/sec, up to 400 Mev/ion

25 micron gold foil target (0.05 grams/cm2)

• Scattered beam
• 3x103 to 3x106 protons/cm2/sec at 10 Mev
• 107 to 1010 Protons/cm2/hour

30o
30o
CCD
Flux Meas
Faraday Cup
40
SNAP CCD Radiation Testing Setup
Copper Cold Head
Target Manipulator
Beam In
4-Side Buttable CCD
Beam Dump
Scattering Chamber
Electronic Feedthroughs
Source Insertion
CCD Test Dewar
Valve/Vacuum Pump Out
Standard 25 Liter LN2 Dewar
Scattering Chamber Plan View
41
Radiation Dose in 250µ Thick CCD
250µm thick Si 0.06 grams/cm2 1 rad 6x107
Mev/gram
Rads/1011protons/cm2
Energy Loss Mev/gr/cm2