A vertical-flexure CCD module

1. A vertical-flexure CCD module Bruce C. Bigelow University of Michigan Department of Physics 10/7/04

2. Vertical-flexure CCD module Objectives: • Accommodate thermal mismatch between Invar/Moly • Invar CCD package • Invar filter frame • Moly TZM flexure frame • Moly TZM mosaic base-plate • Provide maximum volume/area for CRIC chip, output PCB • Provide for +/- 15 micron focal plane flatness spec. • Provide zero (minimum) thermal stress at operating T. • Provide discrete filter and aperture stop for each CCD • Use only mechanical (fastener) assembly methods

3. Vertical-flexure CCD module

4. Vertical-flexure frame Fabrication steps: • Start with a block of TZM • Finish outside dimensions to spec • Grind top and bottom flat to spec • Machine/EDM back side (mounting pads, chip pocket) • Machine/EDM front side (flexures, cut-outs) • Measure flatness of flexure tops vs. mounting pads, touch-up pads to bring into spec. (if necessary) • Make one flexure low (for 3-point definition) • NOTE: Frame can be oversized (by ~20 microns) relative to CCD package, in order to have zero thermal stress at operating temperature (but then stressed at room temp.).

5. Vertical-flexure frame

6. AlN/Invar package Fabrication steps: • Grind and polish AlN package to flatness spec • Index and bond CCD to AlN package • BACK side of AlN package provides flatness, height references for focal plane • Index and bond CCD/AlN package to Invar base • Package is (fairly) insensitive to Invar base dimensions, but alignment is important for mosaic geometry

7. AlN/Invar package

8. CCD module Assembly steps: • Index back side of AlN package to flexures • Mount CCD package to frame with M2 screws • Using non-contact height sensor, measure height and flatness of CCD relative to reference surface • If out of spec., note orientation of CCD to flexure frame, remove CCD from frame, touch-up frame mounting pads, re-assemble and re-measure.

9. Vertical-flexure CCD module

10. Keyence Sensor Optical (non-contact) profilometer with 1 micron resolution, with coaxial, confocal camera, www.world.keyence.com

11. CCD filter and aperture Assembly steps: • Start with Invar filter frame • Drop in aperture plate (select aperture by mosaic position) • Bond filter into frame, capturing aperture plate • Frames index to top surface of AlN package • Note vent holes in filter frame

12. Vertical-flexure CCD module

13. Vertical-flexure CCD module

14. Vertical-flexure CCD module

15. Electronics PCBs: • CRIC/aux board slightly changed from HDH geometry • Flexible geometry for pocket in Invar base • Output board is larger than HDH geometry • Minimal frame dimensions require FEA, thermal analysis

16. CRIC/aux board

17. Output PCB

18. Vertical-flexure CCD module

19. Vertical-flexure CCD module

20. Vertical-flexure CCD module

21. CCD module 3x3 mosaic 43.16mm pitch

22. CCD module 3x3 mosaic

23. New CCD module Conclusions: • A new CCD module design has been presented • Utilizes a vertical-flexure Moly carrier • Assembly method for meeting the mosaic height and flatness specs seems feasible • No supporting analysis yet, but straight-forward • Width, depth, and thickness of TZM flexures needed - FEA • Thermal analysis needed - FEA