1 SPP FIELDS MEP Main Electronics Package Peer Review Bill Donakowski UCB/SSL 18 NOV 2014 MAVEN PFDPU Flight Unit SPP MEP Baseline

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SPP FIELDS MEPMain Electronics Package

Peer Review

Bill [email protected]

UCB/SSL18 NOV 2014 MAVEN PFDPU

Flight UnitSPP MEP

Baseline Design

B. Donakowski

SPP MEPEM Hardware

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MEP PDR Overview

• Requirements• Design Heritage• Design Overview• Interlocking Frame Design Details• Daughter Board Details• Thermal Design• FEM Design Analysis• Mass Properties• Vibration Testing • Ongoing Issues18 NOV 2014 B. Donakowski

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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/C18 NOV 2014 B. Donakowski

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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

18 NOV 2014 B. Donakowski

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MEP Box Overview

Attach surface to Spacecraft Panel

18 NOV 2014

10”6.85”

8.25”

B. Donakowski

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MAVEN Design Heritage

6x Skewers

Top EMI Shield over Card-Card Harnesses

S/C Bracket

Box Vents

Connectors on 3 sides of box

MAVEN Electronics Box• 11 Separate Cards sharing common Frame

details• Bolted to S/C Bracket on one Box face

Box Size: 8.1” Wide x 6.2” Tall x 9.3” Long

SPP FIELDS Electronics Box• 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

2x Skewers

Connectors on 3 sides of box

B. Donakowski

2 Shear Panels

18 NOV 2014

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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)

18 NOV 2014 B. Donakowski

2X Center Posts

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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. Donakowski18 NOV 2014

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Interlocking Frames Design

Individual Frames bolted together with 6X skewers

Detail showing Frame Interlocking

Features

Each Box can be Pulled From Stack


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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 wellB. Donakowski18 NOV 2014

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Thermal Design

• S/C environment is hot—testing at 75 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 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/CPCB screwed to EMI Shield (2x)


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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


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MEP FEM Dynamic Analysis


Component Requirement Analysis Test Results RemarksBox Structure Fn > 100 Hz 600 Hz 450 Hz MEP EM HardwareMother 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 DEC 2014

Modal Analysis, Axis Perpendicular to PCBs

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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


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Mass Properties• Current Estimate: 7.081 Kg• Contingency (20%): 1.416 Kg

• Current Best Estimate: 8.497 Kg

– (Intrabox Cables included, S/C cables not included)


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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

– LASP request for taller components below DFB Board• Design under evaluation/ Appears to be simple change

• Final FEM Analysis– December 2014

• EM Testing– Fit checks of Frames/Weighing PWA– Some limited Thermal Vac Testing, December 2014– If hardware allows, vibration (sine sweep) test, January 2014


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MEP Status and Schedule• S/C Interface

– SSL has approved APL’s baseline spacecraft panel inserts design


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Backup Slides


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Electronics Board Layout Control Drawing

Drawing Maintained by SSLDistributed to Electronics DesignersMain Document for Design Consistency between EE and ME aspects


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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


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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


Documents

1 SPP FIELDS MEP Main Electronics Package Peer Review Bill Donakowski UCB/SSL 18 NOV 2014 MAVEN PFDPU Flight Unit SPP MEP Baseline