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SPP FIELDS MEP Main Electronics Package Preliminary Design Review Bill Donakowski

SPP FIELDS MEP Main Electronics Package Preliminary Design Review Bill Donakowski billd@ssl.berkeley.edu. UCB/SSL 13/14 NOVEMBER 2013. SPP MEP Baseline Design. MAVEN PFDPU Flight Unit. SPP MEP Prototype Unit. B. Donakowski. MEP PDR Overview. Requirements Challenges

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SPP FIELDS MEP Main Electronics Package Preliminary Design Review Bill Donakowski

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  1. SPP FIELDS MEP Main Electronics Package Preliminary Design Review Bill Donakowski billd@ssl.berkeley.edu UCB/SSL 13/14 NOVEMBER 2013 SPP MEP Baseline Design MAVEN PFDPU Flight Unit SPP MEP Prototype Unit B. Donakowski

  2. MEP PDR Overview • Requirements • Challenges • Design Overview • Design Heritage • Interlocking Frame Design • Board Layout Control Drawing • Daughter Board Details • Connectors Fastening • Thermal Design • FEM Dynamics Analysis • Vibration Testing • Mass Properties • Spacecraft Mounting • Ongoing Issues B. Donakowski

  3. 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

  4. 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

  5. MEP Challenges • Provide common module for different boards • Differing functions, connectors, and organizations (UCB/LASP/MN/GSFC) • Box will be located in hot environment, must get heat out of box as much as possible (Thermal environment: baseline 65 C) • Modular Frames must fit well together into final structural/thermal package • All frames must be in-plane for proper interface to Spacecraft Panel • Limited Mass • Column Grid Arrays require conformance to Steinberg requirements (separation of first natural frequencies of PWB and structure) B. Donakowski

  6. MEP Box Overview 9 Individual Boxes 6.85” 10” Attach surface to Spacecraft Panel 8.25” 10 X #8 Fasteners B. Donakowski

  7. MAVEN Design Heritage Connectors on 3 sides of box Top EMI Shield over Card-Card Harnesses Connectors on 3 sides of box Box Vents Box Vents 6x Skewers (no shear panels) 2 Shear Panels 10x Attach feet to S/C (every other Frame) #8 Fasteners S/C Bracket 2x Skewers Box Size: 8.1” Wide x 6.2” Tall x 9.3” Long Box Size: 8.25” wide x 6.85” Tall x 10.0” long SPP FIELDS Electronics Box • 9 Separate Cards sharing common Frame details • Bolted to S/C on one Box face MAVEN Electronics Box • 11 Separate Cards sharing common Frame details • Bolted to S/C Bracket on one Box face B. Donakowski

  8. MEP Typ Box Frame Assy Frame Instrument Connectors Intrabox Connectors EMI Shield Card PWB Screws and Custom Inserts at PCB perimeter Daughter Board (DCB, DFB, TDS) Mounting Surface to Spacecraft B. Donakowski

  9. Box Machined Frame Design Prototype Frame Box Frame walls .060” (OPEN) 6X Skewers (#8 Threaded Rod) Multiple PCB attach screws to Frame to increase PWB stiffness and provide good thermal conduction path Feet for attachment to S/C 7 Open Framed Boxes Machined 6061 T6 Al Alloy Machined Frame .85” Pitch (Frame to Frame) 2 5-sided Framed Boxes (LNPS) B. Donakowski

  10. Interlocking Frames Design Detail showing Frame Interlocking Features Each Box can be Pulled From Stack Individual Frames bolted together with 6X skewers B. Donakowski

  11. Electronics Board Layout Control Drawing Drawing Maintained by UCB Distributed to Electronics Designers Controlling Document for Design Consistency between EE and ME aspects B. Donakowski

  12. 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 B. Donakowski

  13. Daughter Board Details • DB Module to be designed/built by SSL • Large Chip (RJEX4000 CCGA) at Center • Used on DCB, TDS, DFB 4X Custom Tools Custom threaded tool thru threaded inserts applies gentle force at corners to remove DB from MB Prototype Hardware B. Donakowski

  14. Connectors Fastening Desirement: Allow Jackposts to be Removed from outside of Box without opening box OTS Jackposts UCB Custom Connector Nutplate D-Connector Material: 6061 T6 Aluminum • Easier than nuts to assemble • no need to get wrench to hold nuts during jackpost torquing • Standoffs can be removed one-by-one Spiralock tapped holes B. Donakowski

  15. Thermal Design • S/C environment is hot—testing at 65 C • Boards screwed to Frames at perimeter • 2X Screws at PCB center to EMI shield w/ integral posts • Attachment frame wet mounted to S/C (TBC) • All Exterior Surfaces painted with electrically conductive Black Paint (Aeroglaze Z307) • Black Anodize Interior Surfaces • Alodine 600 Treatment at Box interfaces (to PCB, SC, other Frames) S/C S/C PCB screwed to EMI Shield (2x) S/C B. Donakowski

  16. Thermal Considerations: Center of PCB • EMI Shield with integral posts to PCB • provide conductive path from center of PCB • Shield screwed to Frames at perimeter Screws at perimeter to frame Integral Posts at Center (fastened to PCB) B. Donakowski

  17. 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 / wedge locks etc • 2 Oz Copper Layers • Layouts to be reviewed by thermal engineer B. Donakowski

  18. MEP FEM Dynamics Analysis • Requirements • Project: MEP Box First Natural Frequency > 100 Hz • Easy to achieve • Project: PWB First Natural Frequency > 150 Hz • Analysis: 190 Hz • Steinberg Design: First Natural Frequency separation of 2X between individual PCB Assys and Entire Box (2 X 195 Hz = 390 Hz) B. Donakowski

  19. MEP FEM Dynamics 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) • Predict Fn > 500 Hz • Preliminary FEM Runs Encouraging • Fn > 100 Hz • Separation of 2X between PCB and Overall Structure • More detailed analysis required • With completed LNPSs design • Vibration testing of Prototype frames B. Donakowski

  20. Vibration Testing • Vibration Testing Performed 01 Nov 2013 • Sine Survey Performed • X Axis first mode: 376 Hz (perpendicular to PCBs) • Predict: > 500 Hz • Prototype Hardware First Mode frequency Lower than FEM predicts • Required 2X frequency separation close • Further analysis required B. Donakowski

  21. Mass Properties • Current Estimate: 7.397 Kg • Continengency (20%): 1.479 Kg • Current Best Estimate: 8.876 Kg • (Intrabox Cables included, S/C cables not included) B. Donakowski

  22. Spacecraft Mounting +Y Interior Panel B. Donakowski

  23. Ongoing Issues • EMI shielding of cables on top of Box TBD • Separate Aluminum EMI Shield • Wrapping individual cables with proper shielding • FEM • Verify adequate frequency separation between box structure and PWAs • Further analysis and test required • Continue coordination with outside groups design efforts • LASP/MN: PWA (Connectors, EMI Standoffs, Dynamics, Structural Properties) • GSFC: Box Frame (Interface Geometry to other Frames, Dynamics, Structural Properties) • Grounding strap interface (APL to provide straps) B. Donakowski

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