Vertical-flexure CCD module:Vertical-flexure CCD module:Thermal and Dynamic FEAThermal and Dynamic FEA

Bruce C. Bigelow

University of Michigan

Department of Physics

10/28/04

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Vertical-flexure CCD moduleVertical-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

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CCD module FEACCD module FEA

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CCD module FEACCD module FEA

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CCD module FEACCD module FEA

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Vertical-flexure module FEAVertical-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

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CCD module FEA - elementsCCD module FEA - elements

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Vertical-flexure module FEAVertical-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)

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CCD module FEA – node couplesCCD module FEA – node couples

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CCD module FEA – frame stressCCD module FEA – frame stress

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

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CCD module FEA – Invar stressCCD module FEA – Invar stress

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

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CCD module FEA - elementsCCD module FEA - elements

Max distortion of Invar base (CCD mounting surface) is 0.1 micron

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Vertical-flexure module FEAVertical-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.

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CCD module FEA - DynamicCCD module FEA - Dynamic

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CCD module FEA - DynamicCCD module FEA - Dynamic

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CCD module FEA - DynamicCCD module FEA - Dynamic

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Vertical flexure CCD moduleVertical 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