SNAP CCD Packaging R

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SNAP CCD Packaging RD

• 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

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SNAP Focal Plane
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Approximate SNAP CCD Dimensions
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SNAP 4-Side Buttable CCD Design
Exploded View of Package
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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

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Experience with Large Format CCD Cameras
QUEST II 112 CCD Large Area Camera For the
Palomar Schmidt Camera
QUEST I 16 CCD Camera for the Venezuelan Schmidt
Camera
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CCD Package for the QUEST II Camera
Packaged and tested 376 CCDs at Yale to select
the 112 best devices for the Palomar-QUEST Camera
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Thermal Expansion Data for SNAP CCD Candidate
Packaging Materials
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Thermal Expansion Data for SNAP CCD Candidate
Packaging Materials

• Guillaume Curve1

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SNAP 4-side Buttable CCD Finite Element Analysis

• Quarter Model Without Boundary Constraints or
  Elements Shown

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SNAP 4-side Buttable CCD Finite Element Analysis
Quarter Model Showing Boundary Constraints
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SNAP 4-side Buttable CCD Finite Element Analysis

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

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SNAP 4-side Buttable CCD Finite Element Analysis
Selected Result from Dan Chengs Finite Element
Analysis (LBL
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SNAP 4-side Buttable CCD Finite Element Analysis
Deformation in Z-axis (m) for Invar/AlN Case
(293oK to 153oK)-Diagonal Section View from
Center to Corner
1 um out-of-plane
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SNAP 4-side Buttable CCD Finite Element Analysis
Deformation in Z-axis (m) for Molybdenum/AlN Case
(293oK to 153oK)-Diagonal Section View From
Center to Corner
18 um
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SNAP 4-side Buttable CCD Finite Element Analysis
Summary of Finite Element Analysis Results
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SNAP 4-Side Buttable CCD Design
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SNAP 4-Side Buttable CCD Design

• Sectional View

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SNAP 4-Side Buttable CCD Design

• Aluminum Nitride Substrate-Top View

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SNAP 4-Side Buttable CCD Design

• Aluminum Nitride Substrate-Bottom View

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SNAP 4-Side Buttable CCD Design

• Circuit Board-Bottom View

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SNAP 4-Side Buttable CCD Design

• Circuit Board-Top View

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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.
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SNAP 4-Side Buttable CCD Assembly Sequence

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

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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

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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

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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

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Open Questions

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

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Mounting CCD Package on Molybdenum Focal Plane

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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