GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Persis S. Drell

GLAST LAT Project Monthly Review, November 3, 2004

Tracker Subsystem P. S. Drell 1

GLAST Large Area Telescope:GLAST Large Area Telescope:

Tracker SubsystemTracker SubsystemWBS 4.1.4WBS 4.1.4

Persis S. DrellStanford Linear Accelerator CenterLAT Deputy Project Manager

[email protected]

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope



OutlineOutline

• Technical Status- last month’s accomplishments– Issues identified and closure plans– Status of flight hardware

• Cost and Schedule Status– Tower A Schedule– Delivery schedule for Tower B—Tower 16



Accomplishments and Issues Identified in Tower Accomplishments and Issues Identified in Tower A FabricationA Fabrication

• Tracker Tray Fabrication– Bias circuit bonding problem resolved

• MRB 10/1/04– Flight tray production restarted 10/4/04

• Tray Production Status (Plyform + INFN)– >90 bare trays (no converter or bias circuits) produced– Converter production

• Tiles for Tower A at Plyform etched in Turin, primed in Plyform• Tiles for Tower B and beyond being etched and primed at

GSFC– Delivery rate plan of 300 tiles/week

– 21 trays completed with converter and bias circuit through T/V• 1 failure

– 2 tiles had primer delaminate from converter foils (Turin process)– Cause under investigation

• 3 others show bubbles (before T/V)– Disposition under discussion



Tray Production Status (example)Tray Production Status (example)

Mid Trays - total

0

5

10

15

20

25

30

35

40

45

time

tra

ys

BP-FH-Mid

ESPI-FH-Mid

CP-FH_Mid

TVAC-FH-Mid

Mid Trays - differential rate

0

2

4

6

8

10

12

14

16

18

20

time

tra

ys

BP-FH-Mid

ESPI-FH-Mid

CP-FH_Mid

TVAC-FH-Mid

FLIGHT TRAYS SUMMARY

10T-VAC done

20Panel with payload

56ESPI done

73Bare Panel

Qty-FHProduction Step



Issues Identified in Tower A FabricationIssues Identified in Tower A Fabrication

• Tower A Tray Assembly Status (G&A)– Anomaly found in assembly: missing connections on MCM

• WORK IS STOPPED– 1 tray with MCMs bonded (but no SSDs yet) found to have a

problem with no bias from the MCM to the two center ladder attachment points on the bias circuit.

– One caused by resistor badly soldered on MCM– Cause of other is not yet known

– 6 more MCMs of 32 tested in Pisa have at least 1 missing bias or HV connection

• 18+ tested at SLAC do not show any problem– Currently applying all available resources in Pisa and at

SLAC to determine root cause

– G&A work is ~ 1 week behind nominal Tower A fabrication schedule at this point



MCM and Bias CircuitMCM and Bias Circuit



Issues Identified in Tower A FabricationIssues Identified in Tower A Fabrication

• Other Issues for Tower A– In Tower 0, identified interference between connector on

MCM and sidewall on many trays• New MCM bonding procedures finalized to ensure

connector stay clear– Critical hardware for Tower A assembly in work

• Impacted by SLAC shutdown• Pulled work from shops and sent outside to complete

• Flight cables for Tower A a critical problem



Issues Identified in Flight Cable ProductionIssues Identified in Flight Cable Production

• Two technical issues identified:– Separations between barrel plating and internal layers.– Bubbles in adhesive holding connector to cable



Path forward with Tracker Flex CablesPath forward with Tracker Flex Cables

• Parlex– CAP developed for plating process

• Early tests validated new process• Coupon tests on cables with new plating process so far test

acceptable– Process problems in cable assembly under discussion

• Bubbles in the adhesive between the flex and the Omnetics connectors.

– Stop work issued—QA visit tomorrow supported by tracker personnel

– Delivery schedule continues to be unreliable– Project Manager to visit next week

– Option: If new process has good coupons, consider getting bare cables and assemble at company of our choosing

• Investigations underway• Current proposal to install cables in hand (with original plating

process or with adhesive bubbles) if necessary to stay on schedule for Tower A assembly – Tower A will have lien to be resolved at a later time



Alternate sources for tracker flex cablesAlternate sources for tracker flex cables

• Developing alternate source for full length cables• PO at Titan with 12/1 delivery to produce 5 C4 cables• Will proceed with QA source inspection if looks viable

• Developing option of 2 short cables with ‘rigid-flex’ joint• Need to validate design• New drawings in process

– Anticipate flight order with alternate source by 12/15



Alternate sources for tracker flex cablesAlternate sources for tracker flex cables



Issues Identified in MCM ProductionIssues Identified in MCM Production

• 343 units delivered to SLAC– 325 through burn in and final test at SLAC– Need 686 for 18 towers + electronics group– Production at Teledyne currently stopped

• MCM Issues– Pitch adaptor

• 13.5% drop out at MIP 1 due to broken traces (visual inspection)

• Brittle Ni plating cracks easily in bend region, sometimes also cracking Cu

• Two new pitch adaptor concepts in work to eliminate problem– Option 1: masking over bend radius– Option 2: selective plating process for Ni plating

» New designs to be qualified when production at Teledyne resumes (scheduled for 11/15)

• New electrical test fixture in test for detecting broken traces




• MCM Issues (cont.)– MCM Leakage Current Problem

• 8 boards have developed low resistance between layers 7 and 8 (120 V potential difference) of the multilayer board during burn-in.

• Destructive Physical Analysis in process at Goddard and CALCE to determine root cause

– Moisture during lamination or reflow, contamination, and conductive filament growth are all possibilities.

• In case it is moisture, a pre-reflow bake has been added. Prepreg will be vacuum dried if more PWBs are made.

• The problems seem clustered, so we are holding PWBs from the same panels as failed boards

• The MCMs failed 2, 3.5, 4, 6, 10, 20, and 75 hours into our 168 hour burn-in where about 350 others did not fail giving hope that the burn-in catches almost all the problems.

– Data readback errors• Some MCMs are too sensitive to clock duty factor during burn-in

– Related to quality of clock received by GTRC– Problem mitigated by changing termination resistor on cables




• MCM Conformal Coating Problems– Issues identified in QA with peeling, contamination and bubbles– A full inspection of all units has been completed.

• CC got into many connectors. – They will be carefully cleaned

• CC is lifting in small areas near components.– 200 thermal cycles did not make the lifting worse.– 3 vacuum cycles on 4 MCMs did not make lifting worse– The risk involved in reworking them may be greater than in using

them as is.

• CC is thin or missing on sides of many components– Due to spraying from only one direction– Mostly on non-conductive sides of “tall” components– Not clear if rework is practical. (CC could end up too thick.)

– MRB 10AM 11/3/04• In parallel, manufacturing process is being improved to prevent these

problems on future units.




• Restart of MCM Flight Production– Need improved ESD and PWB bake-out

• Waiting for final quote– Implement conformal coat process improvments– Pitch adapter re-qualification program– MC restart MRR at Teledyne anticipated 11/15/04



Flight Hardware Drawings StatusFlight Hardware Drawings Status

• Top/Bottom Tray Panels (including flexures)– All drawings complete and released.

• Interface Hardware– All complete and released.

• Mid Tray Panels– Some rework and improvements of the drawings to reflect

as-built condition are in work.• Tray Assembly (Bonding MCMs + Ladders to tray panels)

– All complete and released.• Sidewall Drawings

– All complete and released.• Heat Straps

– Complete and released.



Flight Hardware Drawings StatusFlight Hardware Drawings Status

• Flex-Circuit Cables– All complete and released. Drawing revision to match as

built in progress• Top Mount Cable Retainer and Alignment Hardware

– All complete and released.• Tower Assembly Drawing

– Complete and in release cycle• Electronics, including SSDs, MCMs, Bias Circuits, ASICs, etc.:

all complete and released.– Ladder drawing revised to match as built.

• Ready for release



Status of Parts & Materials from SLACStatus of Parts & Materials from SLAC

Item Status IssuesMCMs ~40 will be hand carried to Italy

Sunday for Tower BResolution of conformal coat issues have delayed shipment

Flex-Circuit Cables No complete flight sets in hand Production problem at Parlex

In discussion with alternate vendors

Ti Corner Brackets & Flexures

Flight order complete

Bottom-tray closeouts

Flight order complete

Interface cones & studs

The Tower-A set is ready and the remainder is in fab

Threads on some studs are out of spec. Return to AMT for rework. Nytemp patch will be run-in.

Hex nut In hand




Item Status IssuesShims Enough in hand for Tower A,

but working on Ni plating

Top Tray Corner Brackets

Two tower sets on-hand. CMM inspection this week

Sidewall Prepreg Italy purchased enough already for at least 2 or 3 towers. Rest is in shipment

Ti Sidewall washers

Sufficient quantities are in Italy

Sidewall Fasteners All are except for bottom tray are in hand and verified

Cytec BR-127 Primer

A large quantity was shipped last week and arrived okay

Bias Circuits Plenty in Italy for tray mass production to begin

CR released. Coupon via plating thickness issue resolved




Item Status IssuesHeat straps Tower A set plus spares are in

Italy. Balance at SLAC. CMM and ship to INFN.

Locktite 401 for heat straps

Being shipped to Italy

Solithane (for locking screws)

Being shipped to Italy, will ship to INFN next week

Nusil silicone adhesives

Sufficient quantities now in Italy

Aeroglaze paint and primer

Sufficient quantities now in Italy

Honeycomb Full flight order is in Italy

Carbon Carbon for Tray Closeouts

Full flight order is in Italy

Flex Cable Foam Compression Pads

Placing order. Ship to INFN next week.

INFN to perform 1st article fit check.

M2.5 x 100 deg Replacement units being ordered Original order has wrong head



Status of GSE from SLACStatus of GSE from SLAC

Item Status IssuesVibration Fixture (Grid Simulator)

Ten units received and CMM inspected.

Adding insert for electrical grounding

Inner Shipping Container

Tower-A container is on-hand and is being proof tested

Cable Holding Plate In hand and being proof tested this week. Will ship with all associated H/W.

Static Test Grid Simulator

In Italy, already used for Tower A

Lifting Fixture One is in hand and proof tested. 2 more will also be made for use in Italy.

Outer Shipping Container

1st article is at SLAC Needs drop test qualification performed. Outsource test due to SLAC stand-down.




Item Status IssuesCable Bending Tool Production models in fab

Tools for Cone Alignment and Extraction

Enough tools are in hand for Tower A assembly in Italy. Improved stud socket in fab.

EGSE Sets 4 sets are in Italy. One more for T/V testing is under test at SLAC prior to shipping.

Long EGSE Cables for T/V Test

1 set delivered to Italy. 2 more are in work

C0 Cables for Stacked Tray Tests

Enough in hand for Tower A Remaining test sets in Italy will be equipped with reject cables

Breakout Boxes for Tray Testing

2 are in Italy ~10 more in fab at SLAC




Item Status IssuesTransport Environmental monitors

Pisa has nine units

ESD wrap for inner container

Order placed. Ship to INFN next week.

Desiccant pads (for inner container

On hand at SLAC. Ship to INFN this week



PMCS Schedule & Cost VariancePMCS Schedule & Cost Variance

• September: Schedule variance decreased from -$736k to -$575k on total $15,274 BCWI– Schedule has actually degraded due to work stoppage at

Teledyne– Improvement in PMCS comes from receiving prepreg used

for sidewalls– Keep in mind most of Tracker assembly work is in Italy and

not tracked by this schedule variance calculation• Cumulative Cost Variance: -$456k

– Large payment made to Teledyne for MCM’s received before work stoppage



Schedule Status: Tower A CampaignSchedule Status: Tower A Campaign

• The Tracker team is focused on delivery of Tower A to I&T

– Updated plan: Tower A ships 12/16/04



Schedule Status: Tower Delivery ScheduleSchedule Status: Tower Delivery Schedule

• Updated plan:– Start production 10/4– Plyform produces 4 trays/day starting 11/1– G&A going to 2 shifts

• Extra CMM• Extra Wire bonder

• Tower 13,14 arrive in May

Documents

GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 Persis S. Drell