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,

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

15Electronics 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