Vertical-flexure CCD module: Thermal and Dynamic FEA

1
Vertical-flexure CCD moduleThermal and Dynamic
FEA

• Bruce C. Bigelow
• University of Michigan
• Department of Physics
• 10/28/04

2
Vertical-flexure CCD module

• Objectives
• Accommodate Moly-Invar CTE mismatch with
  vertical flexure Moly CCD mount (see previous
  presentation)
• Demonstrate acceptable thermal stresses for
  package over survival temperature range
• Demonstrate acceptable modal performance for
  package

3
CCD module FEA
4
CCD module FEA
5
CCD module FEA
6
Vertical-flexure module FEA

• Analyses
• Neglect AlN, silicon from models (TZM and Invar
  only)
• No pre-stress of package at room temp
• TZM Flexure geometry (not optimized)
• Blade thickness 0.4 mm (0.016)
• Blade width 8 mm (0.32)
• Blade effective length 4 mm (0.16)
• Thermal
• Simple delta-T -160K, constant CTEs
• Frame constrained for zero mounting stress
• Dynamic
• Mounting pads constrained
• TZM Flexure to Invar joint nodes coupled

7
CCD module FEA - elements
8
Vertical-flexure module FEA

• Analyses
• Thermal
• Simple DT -160K, constant CTEs
• Frame constrained for zero base stress at
  mounting
• Flexures and Invar base interface nodal
  deflections coupled at centerline to simulate
  single screw constraints (very conservative
  neglects screw head constraint)
• Z constraints coupled at top of Invar surface
  (worst case)

9
CCD module FEA node couples
10
CCD module FEA frame stress
Max stress in flexures 132 MPa 19,410 PSI
(TZM Sy 860 MPa)
11
CCD module FEA Invar stress
Max stress in Invar 5.6 MPa 812 PSI (Invar Sy
300 MPa)
12
CCD module FEA - elements
Max distortion of Invar base (CCD mounting
surface) is 0.1 micron
13
Vertical-flexure module FEA

• Analyses
• Dynamic
• Modal analysis, reduced (Householder) modal
  extraction
• TZM - Invar interface nodal deflections coupled
  as in thermal case
• First 10 frequencies
• SET TIME/FREQ
• 1 3279.8
• 2 3458.6
• 3 3955.8
• 4 5009.2
• 5 6928.7
• 6 7684.2
• 7 8830.7
• 8 9707.0
• 9 12753.
• 10 13239.

14
CCD module FEA - Dynamic
15
CCD module FEA - Dynamic
16
CCD module FEA - Dynamic
17
Vertical flexure CCD module

• Conclusions
• Thermal and dynamic FEA presented
• Low thermal stresses demonstrated with
  non-optimized TZM flexures
• High resonant frequencies demonstrated with
  non-optimized TZM flexures
• Optimal flexure dimensions still TBD for minimal
  stress and maximum first resonance