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1 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU Chassis
Mechanical Design and Development
Bill Donakowski
Mechanical Engineer
UCB/SSL
2 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisRequirements
• Functional– Provide Mechanical Packaging for 4 EFW electronic boards in one card cage box– BEB/DFB/DCB/LVPS Boards– Allow removal of each board layer separately– Provide structure and attachment to S/C– All access to test points following board installation into box
• Structural– Positive strength margins– First natural frequency greater than 50 Hz
• Radiation Shielding– External walls to have .35” equivalent thickness Aluminum– LOS requirement from outside to boards
• Venting– Allow proper venting on ascent
• Thermal– Alodined Box attach face is conductively attached to S/C Panel 5– All other outer surfaces black anodized to radiatively couple to inside of S/C– Temperature range: -35° C to +65° C (preliminary)
• EMI Shielding– Provide metal shielding between each board layer
3 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU Chassis Design Description
• Standard card-cage design– Standard 6U format circuit boards (160mm x 230mm)
– Similar to THEMIS
– Aluminum 6061 T6 panels bolted together
– gaps prevented at panel interface by step in edges
• Separate layers for individual boards to slide into box– Each card layer consists of PCB, wedgelocks, connectors, and EMI shield
– Cards held in place by wedgelocks on sides and fasteners on front panels
– Each panel can be removed by unscrewing bolts, loosening wedgelocks, and sliding out
• Separate, removable radiation shield over connectors and cables– Installed for testing and at integration to S/C
– Aluminum 6061-T6
4 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisOverview
LVPS
DFB
DCB
BEB
REMOVABLE RADIATION SHIELD
HOLES FOR BOLTING TO S/C PANEL #5 (10-32 bolts)
ALL CABLES TO S/C MATE TO FRONT OF BOX
TOTAL MASS: CBE 8.3 Kg
10”
VENT3.5”
7.5”
4.2”
5 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisOverview
WEDGELOCKS ON EACH BOARD EDGE
(manuf: CALMARK)
EACH BOARD CAN BE REMOVED INDIVIDUALLY
(without removing others)
6 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisOverview
REMOVABLE RADIATION SHIELD
(INSTALLED FOLLOWING BOX INTEGRATION ONTO S/C)
BACKPLANE CONNECTOR ACCESS PANEL TO TEST POINTS ON BOARDS
8 x ATTACH BOLTS
(8-32)
7 3-4 Sept. 2008 EFW INST+SOC PDR
RBSP ChassisRadiation Shielding
• All external aluminum panels provide shielding– .35” thickness
– Interlocking steps to prevent any gaps at connections
• Removable Radiation Shield covers connectors and cables on front of box– Radiation Shield installs following box installation onto S/C
– Provides .35” equivalent thickness radiation shielding line of sight to boards
Volume for cable run to S/C
EMI SHIELDS BETWEEN LAYERS
( 3 SHIELDS)
8 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisRadiation Scheme for Cables
• Radiation LOS Maze allows simple cable runs
.90”
Pass-thru for cables to S/C
9 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisAnalysis
• Structural– Thick wall sections for radiation shielding makes for very robust box– Preliminary strength analysis strength margins > .7 on yield (100G)
• Venting– Volumetric analysis to confirm– Vent size 1 in2 for every 1 ft3 Volume– Size vent accordingly
Preliminary FEM output
Showing Von Mises Stresses
10 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisStatus
• ICD drawing submitted to APL – Overall box geometry
– Cable routing
– Keep-out zones to allow radiation shield installation on S/C
• Individual Board ICDs completed– Showing connectors, board geometry
– Allowing electrical components layouts to begin
• Mechanical Box detailing ongoing– Weight relieving of .35” walls to be implemented where possible
11 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU ChassisIssues and Concerns
• Thick walled construction produces rapid mass gain if box grows
12 3-4 Sept. 2008 EFW INST+SOC PDR
IDPU Chassis (backup)Materials
• 6061-T6 Aluminum Alloy– Yield Strength: 37,000 psi
– Ultimate Tensile Strength: 42,000 psi
• Delrin– Ultimate Tensile Strength: 8,000 psi
