Vertical-flexure CCD module: Thermal and Dynamic FEA Bruce C. Bigelow University of Michigan Department of Physics 10/28/04

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

CCD module FEA

CCD module FEA

CCD module FEA

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

CCD module FEA - elements

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)

CCD module FEA – node couples

CCD module FEA – frame stress Max stress in flexures – 132 MPa – 19,410 PSI (TZM Sy = 860 MPa)

CCD module FEA – Invar stress Max stress in Invar – 5.6 MPa – 812 PSI (Invar Sy = 300 MPa)

CCD module FEA - elements Max distortion of Invar base (CCD mounting surface) is 0.1 micron

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.

CCD module FEA - Dynamic

CCD module FEA - Dynamic

CCD module FEA - Dynamic

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