1. Vertical-flexure CCD module: Thermal 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

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