Presentation on theme: "A vertical-flexure CCD module Bruce C. Bigelow University of Michigan Department of Physics 10/7/04."— Presentation transcript:
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
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.).
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
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.
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
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