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B. Donakowski UCB/SSL 1FIELDS iCDR – MEP Mechanical
SPP FIELDS MEPMain Electronics Package
Mechanical Packaging
Bill [email protected]
UCB/SSLMAVEN PFDPU
Flight UnitSPP MEP
Baseline Design
SPP MEPEM Hardware
B. Donakowski UCB/SSL 2FIELDS iCDR – MEP Mechanical
Agenda
• Requirements• Design Overview• Interlocking Frame Design Details• Daughter Board Details• Thermal Design• FEM Design Analysis• Mass Properties• Vibration Testing • Ongoing Issues
B. Donakowski UCB/SSL 3FIELDS iCDR – MEP Mechanical
MEP Functional Requirements
• Provide Packaging for 9 different Board Assemblies in common box– LNPS1, LNPS2, MAGo, MAGi, RFS/DCB, DFB, AEB (2x), TDS
• Modular box arrangement allows individual boxes to be built up independently and taken apart a/r
• Design/Coordinate/Fab Box Frames with responsible groups– UCB/MN/LASP/GSFC
• .060” thick Aluminum walls for Radiation Shielding • One plane mounting interface to Spacecraft• Adequate Structure Integrity (Strength, Dynamics)• Optimal thermal path to Spacecraft• Electrical Ground to S/C
B. Donakowski UCB/SSL 4FIELDS iCDR – MEP Mechanical
MEP Project Requirements
• Requirements per EDTRD, 7434-9039• Analysis/Design
– Materials selection, dynamics analysis, structural analysis, venting, EMI/EMC, grounding
• Testing/Verification– Mass Properties, Vibration, TVAC, Bakeout,
Cleanliness
B. Donakowski UCB/SSL 5FIELDS iCDR – MEP Mechanical
MEP Box Overview
Attach surface to Spacecraft Panel
10”6.85”
8.25”
B. Donakowski UCB/SSL 6FIELDS iCDR – MEP Mechanical
MEP Box Overview
6x Skewers
MEP Overview• 9 Separate Cards sharing common Frame
details• Bolted to S/C on one Box face
10x Attach feet to S/C(every other Frame)#8 Fasteners
(no shear panels)
Box Size: 9.4” wide x 6.5” Tall x 8.0” long
Connectors on 3 sides of box
B. Donakowski UCB/SSL 7FIELDS iCDR – MEP Mechanical
MEP Typ Box Frame Assy
Frame Instrument Connectors
EMI Shield
Mounting Surface to Spacecraft
Intrabox Connectors
Screws and Custom Inserts at PCB perimeter
Card PWA6.2” x 9.2”
Daughter Board (DCB, DFB, TDS)
2X Center Posts
B. Donakowski UCB/SSL 8FIELDS iCDR – MEP Mechanical
Box Machined Open Frame Design
Box Frame walls .060”
Multiple PCB attach screws to Frame to increase PWB stiffness and provide good thermal conduction path
Machined 6061 T6 Al Alloy Machined Frame.85” Pitch (Frame to Frame)
Feet for attachment to S/C
LNPS Boxes are 5-sided
6X Skewers (#8 Threaded Rod)(OPEN)
B. Donakowski UCB/SSL 9FIELDS iCDR – MEP Mechanical
Interlocking Frames Design
Individual Frames bolted together with 6X skewers
Detail showing Frame Interlocking
Features
Each Box can be Pulled From Stack
B. Donakowski UCB/SSL 10FIELDS iCDR – MEP Mechanical
Daughter Board Details
• DB Module to be designed/built by SSL• Large Chip (RJEX4000 CCGA) at Center• Used on DCB, TDS, DFB
Custom threaded tool thru threaded inserts applies gentle force at corners to remove DB from MB
4X Custom Tools
EM Hardware built and working well
B. Donakowski UCB/SSL 11FIELDS iCDR – MEP Mechanical
Thermal Design• S/C environment is hot
– Testing Operational: -25 to +60– Testing Survival: -30 to +65
• (Temps at baseplate)
• Boards screwed to Frames at perimeter• 2X Screws at PCB center to EMI shield w/ integral posts• Attachment frame wet mounted to S/C (CHO-SEAL, APL Provided)• All Exterior Walls painted with Black Paint (Aeroglaze Z307)• Black Anodize Interior Walls• Alodine 600 Treatment at Box interfaces (to PCB, SC, other Frames)
S/C
S/C
S/C
PCB screwed to EMI Shield (2x)
Baseplate
B. Donakowski UCB/SSL 12FIELDS iCDR – MEP Mechanical
PWB Thermal Design
• Consider entire heat path• Component To Board
– All components dissipating more than 50 mW should be looked at by thermal engineer
• Thermal / Ground / Power Planes– Board dissipated power needs to travel to the frame via
conduction in thermal (or ground) planes, then to the frame• Board Mounting to Box
– Need a good path from thermal planes to standoffs / box lip /
– 2 Oz Copper Layers
B. Donakowski UCB/SSL 13FIELDS iCDR – MEP Mechanical
MEP FEM Dynamic Analysis and Test
Component Requirement Analysis Test Results Remarks
Box Structure
Fn > 100 Hz 600 Hz 450 Hz
TBD
-MEP EM Hardware(w/ dummy masses)-February 2014 (w/ EM PWAs installed)
Mother Board (DCB)
Adequate (2X) Separation from Structure
195 Hz 210 Hz (MAVEN)
235 Hz (DFB)
• MAVEN Board similar in design
• DFB test run by LASP on EM (NOV 2014)
Daughter Board (DCB)
Adequate (2X) Separation from MB
850 Hz TBD Sine Survey Test February 2015
Modal Analysis, Axis Perpendicular to PCBs
B. Donakowski UCB/SSL 14FIELDS iCDR – MEP Mechanical
FEM Analysis
• PCB/Spacers/EMI Shield Assy
• Fixed at Perimeters (to Frame)
• Fn=195 Hz
• Entire MEP Box Assy• (PCBs/Frames)• Fixed at Attach Feet (to S/C)• Fn > 600 Hz
B. Donakowski UCB/SSL 15FIELDS iCDR – MEP Mechanical
Mass Properties
• Current Masses (Measured EM Units)
Component CBE Mass (Kg)
DCB .495
RFS .100
TDS .435
DFB .437
AEB1 .362
AEB2 .362
MEP Chassis 3.202
LNPS1 .900
LNPS2 .620
Internal (Box to Box) Harnessing .229
MEP BOX CBE TOTAL 7.142 Kg
(NTE MASS: 7.856 Kg)
B. Donakowski UCB/SSL 16FIELDS iCDR – MEP Mechanical
MEP Status and Schedule
• EM Hardware– All Mechanical hardware fabrication complete– Hardware In-house and part of box build-up
• Required Design Changes for FLIGHT (not incorporated in EM design)
– Change in connectors due to survival heater scheme change • All Drawing changes complete
– Increase in TDS Box width due to component height increases below board• All Drawing Changes complete
– DCB and DFB request for taller components below DFB Board• Design under evaluation/ Appears to be simple change
• EM Testing– Fit checks of Frames/Weighing PWA– Verification of flatness on bottom of frames– Some limited Thermal Vac Testing, January 2015– If hardware allows, vibration (sine sweep) test, February 2015
B. Donakowski UCB/SSL 17FIELDS iCDR – MEP Mechanical
MEP Status and Schedule
• S/C Interface– MICD produced
• No outstanding issues with APL
– SSL has approved APL’s baseline spacecraft panel inserts design
B. Donakowski UCB/SSL 18FIELDS iCDR – MEP Mechanical
MEP Concerns
• Machining Details Critical– Fit of Frames to each other– Frame Flatness and coplanarity at interface to Spacecraft panel
• Final Assy needs to preclude preloading/warping frames
Full inspection of machined parts and adequate assembly tooling should alleviate potential fit
problems on Flight Build
B. Donakowski UCB/SSL 19FIELDS iCDR – MEP Mechanical
Backup Slides
B. Donakowski UCB/SSL 20FIELDS iCDR – MEP Mechanical
Electronics Board Layout Control Drawing
Drawing Maintained by SSLDistributed to Electronics DesignersMain Document for Design Consistency between EE and ME aspects
B. Donakowski UCB/SSL 21FIELDS iCDR – MEP Mechanical
Connectors Fastening
UCB Custom Connector Nutplate
• Easier than nuts to assemble • no need to get wrench to hold nuts
during jackpost torquing• Standoffs can be removed one-by-
one
D-Connector
OTS Jackposts
Spiralock tapped holes
Desirement: Allow Jackposts to be Removed from outside of Box without opening box
Material: 6061 T6 Aluminum
B. Donakowski UCB/SSL 22FIELDS iCDR – MEP Mechanical
PCB Attach Method
• Custom UCB designed insert• Stainless Steel, Silver Plated• Spiralock Threads provide
Locking Device• Insert soldered to PCB Traces• UCB will provide to outside
groups
