tart recommendations implementation and qualification program results alessandro brez infn - pisa

GLAST LAT Project October 1st, 2004

GLAST LAT Tracker Anomaly Resolution Team 1

TART recommendations implementation and qualification program results

Alessandro BrezINFN - Pisa

[email protected]

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



AgendaAgenda

Summary of the TART recommendations and their implementation

Peel test results

Test articles description

Thermo-vacuum test results

Conclusions



TART recommendation 1 TART recommendation 1 Qualification program Qualification program

The qualification program has addressed the recommendations of the TART:

Main activities:

1. Tests and analysis of the materials and their compatibility to 3M22162. Revision of the assembly procedures and of the assembly

environment3. Construction of 3 tests articles to test different solutions

implementing the new procedures in a improved environment4. Thermo-vacuum tests of the test articles



TART recommendation 2 TART recommendation 2 Tungsten surface preparation Tungsten surface preparation

Recommendation:Etch the tiles surfaces by MIL-HDBK-961B process (degrease + acid bath) and prime with BR-127Test the results with peel tests

Actions:2 processes have been investigated:

GSFC adopted MIL-HDBK-961B and primed the tiles with BR-127

Vaiarelli (Venaria, Turin) Company process + Plyform BR-127 priming



Tungsten preparation: GSFC resultsTungsten preparation: GSFC resultsVerify BR-127 Primer Material and Process with lap shear strength tests using 3M2216 and EA9309

Good results close or better than manufacturer declared values with Al 6061 samples and 0.7mm W tiles

Check Cleanliness of 100m W Etched per Modified MIL-HNBK-961B

Some silicone contamination on 0.1mm tiles (bags?), no contamination from etched surfaces after 120oC heating

Evaluate HF Etch on 100m W Very poor peel tests results (~1lb/inch=0.17N/mm). HF etching abandoned

Evaluate Kapton Surface Preparation: tests with abraded and unabraded kapton samples

Tests in progress

Generate Bell test samples Plyfrom style to compare sand blasted tiles results

Tests in progress

Evaluate ammonium biflouride etch on 100m W

Some 2216 started to fail cohesively but specimens tore in W due to rough edges.Specimens have to be re-made with smooth edges



Tungsten preparation: GSFC analysis of W tilesTungsten preparation: GSFC analysis of W tiles Analysis Performed by: Debbie Thomas, Code 541/ Swales, 301-286-8577

Figure 3. Cross section of tungsten foil showing “stringers” of included material.~ 200X

Stringers

Figure 5. SEM photograph of included material. EDS revealed very high carbon, low tungsten content

in included material as opposed to tungsten base material

Included Material



Tungsten preparation: GSFC analysis of W tilesTungsten preparation: GSFC analysis of W tiles

Figure 6. The photograph on the left was taken on the metallograph (~ 200X) and the one on the right was taken on the SEM. Both show an unusual expansion of the base material

(compare the photo on the left to the one in Figure 3 taken at the same magnification).

No clear conclusions.The 120oC bakeout did not reveal extrusion of material from the W tiles.Delamination of the W tiles themselves never observedThe anomalies can be related with the synterization process used for W tilesThe thick W tiles are from a W alloy (kulite alloy K1750) to have smooth and machinable tiles



material Thickness (mm)

Al 1.6

Hysol 934A ~0.1

W 0.1

3M2216 ~0.1

Kapton 0.1

Hysol 934A ~0.1

Al 0.6

First action:W sand blasting : controlled and uniform roughness of the tilesQualification test: peel test

sand paper

roughness Ra (um) 0.45 0.5 0.87 0.88 0.95

peel strenght (N/mm) 1.7 2.2 2.8 2.7 2.9

Al oxide sand blasting

The debonding pattern at 1mm roughness was better:At Ra=0.5m film left on KaptonAt Ra=1.0m film left part on Kapton and part on W

Tray MID 48 assembled with sand blasted tiles gave acceptable results

F

1N/mm~6lb/inch

Peel test of sand blasted tilesPeel test of sand blasted tiles



Peel tests of Turin etched tilesPeel tests of Turin etched tiles

4 tests have been performed with etched and primed tilesResults: in 1 case the adhesive layer was left part on W, part on bias circuit. Peel strength=2.1N/mm, comparable with the sand blasted tiles taking into account the different adhesive thickness. In 3 cases there was a complete failure on the Kapton side with rather low and disperse peel strength values (from 0.2 to 1.4 N/mm)

3 tests have been performed with etched tiles without primer.In 2 cases the failure was on kapton side, peel strength=0.8,0.9N/mmIn 1 case some of the adhesive, in the central part of the tile, was left on bias circuit.Observed a non uniform glue thickness. Strange pattern. Peel strength=1.4N/mm

The sand blasted coupons were cured at RT in normal atmosphere with a not quantified mechanical pressure. Bond thickness 0.1mm. The Kapton foils were not abraded.The etched coupons were cured at RT in a vacuum bag. Bond thickness ~60m. The Kapton foils were abraded.

Conclusions (qualitative)The adhesion of the 3M2216 to the W tiles was generally goodThe adhesion of the 3M2216 to the Kapton was often bad need of comparison tests of abraded and unabraded Kapton foils



TART recommendation 3 TART recommendation 3 Bias circuit preparation Bias circuit preparation

•Roughen surface with Scotch Brite pads until sheen is removed•Clean (acetone wipe + IPA wipe)•Bake 60oC for 12hours•Clean (acetone wipe + IPA wipe)•Wait 30 min•Bond

The process has been implemented in Plyform (INFN_LAT_MECH_008_2)

After the ambiguous results of peel the tests 2 sets of peel tests coupons have been prepared with abraded and unabraded kapton foils glued on Al specimens with 3M2216.

Peel strenght of unabraded samples = 1.1N/mm 0.5N/mmPeel strenght of abraded samples = 3.5N/mm 0.35N/mm



TART recommendation 4,5 TART recommendation 4,5 Tungsten bonding Tungsten bonding

The recommendation describes in details the W tile bond process and the preparation of the adhesive with degassing.

The recommendations have been implemented

INFN_LAT_MECH_009_02 Adhesive preparation

INFN_LAT_MECH_006_02 Tungsten and bias circuit bonding



TART recommendation 6TART recommendation 6Grounding of Tungsten tilesGrounding of Tungsten tiles

MCM front

MCM front

MCM front

Grounded tile

Not grounded tile

Test article 2

Planarity 224mA wire sticks out from the tray after gluing

Aluminum gold plated 55m wires

Test article 2

Planarity 170m

Test article 2

Planarity 139mA wire sticks out from the tray after gluing

Conclusions:The system does not guarantee the tiles groundingThe vacuum extracts the wires to the edge of the tray, very dangerous!The wires seem to compromise the final planarity of the tray



Do we need W tiles grounding?Do we need W tiles grounding?GFSC primed W tile

0.06mm 3M2216 film (cured 15h at 40oC)Al base

A

Keythley 467

V

I

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 100 200 300 400 500 600

Volts

Gig

a-O

hmBreakdownto 1.4KC=6nF

R=~1G at 1V~6s

Any buildup charge will disappear in few seconds



TART recommendation 7,8TART recommendation 7,8Process cleanliness, QA controlProcess cleanliness, QA control

A detailed list of manufacturing rules have been dictated.These rules have been incorporated in INFN-LAT-MECH-007-01INFN personnel made detailed revision of all the Istruzioni di Lavoro (Work Instructions) and will directly overlook the construction of the first trays. The real main effort to satisfy the request of a clean area insulated from the rest of the Plyform activities, has been the purchase of a clean-tent dedicated to GLAST tray assembly.The tent will be ready to work on October 4th.Mandatory inspection points have

been introduced:1. Tile cleanliness and priming

with routinely peel results2. Kapton preparation3. Adhesive preparation and

deposition with hardness tests



TART recommendation 9TART recommendation 9Non use of grid blasted tungsten Non use of grid blasted tungsten

The 0.1mm sand blasted tiles are no more flat.We cannot use them in any case segregated

steel vacuum chucks

trayBias circuit3M2216

A possible cause of bubbles:The Kapton is hold flat by the tool during adhesive curing. A local depression of the tray surface (50m or more) could cause a bridge effectProposed solution:

Add a compliant pad between tool and bias circuit to compensate the tray irregularities.A suitable material has not found up to now.The test of this solution will be addressed again if needed.

TART recommendation 10 TART recommendation 10 Bond joint compressionBond joint compression



TART recommendation 11TART recommendation 11Alternate bond cure protocolAlternate bond cure protocol

Cure the 3M2216 adhesive at 35oC in a oven for 18hours

Pro:•Better controlled cure cycle.•The whole cure cycle is under vacuum.•At the beginning the adhesive is more fluid + higher temperature => better outgassing

Contra:•Possible deformation of the tray due to CTE mismatch

2 test articles have been produced at 35oC



TART recommendation 12TART recommendation 12Examine bonding integrity of the EM towerExamine bonding integrity of the EM tower

Only one tray of the EM tower is representative:The TOP TRAY has the W thin tiles + the final version of the bias circuit, with the continuous Cu layer insulated by a smooth Kapton layer.The TOP EM tray is equipped with dummy ladders After the optical inspection, taping the tray and the ESPI test, we had NO evidence of defects

726Hz, first tray resonance mode

1251Hz, Second tray resonance mode

2443Hz, first ladder resonance mode



Test articlesTest articles

Test temp. (oC) 45 oC 50 oC 55 oC 60 oC 65 oC 70 oC 75 oC

Test duration (h) 1h10’ 3h 12h 3h 3h 3h 3h

Thermo-vacuum cycles (P<10-2mBar, min P=50bar)

Test article #1 MID045 #2 MID042 #3 MID049

To etching Y Y Y

Primer Y Y N

Cure temp. RT 35oC 35oC

Notes An operator error in top bias circuit assembly caused a misalignment of the bias circuit and a not perfect adhesion



Top faces behaviorTop faces behavior

Very good results of bias circuit adhesion on face sheet up to 75oC



Bottom face #3 NO primerBottom face #3 NO primer

60oC development of a Ø25mm delamination 65oC debonding over 3 whole tiles70oC one more tile debonded

Perfect clean W tileVery good and uniform 3M2216 film on bias circuitVery good adhesion to the previous glue layer (no Frecot55 pollution)



Bottom face #1 primer RTBottom face #1 primer RT

Temp start 45 50 55 60 65 70 75N. bubbles 0 1 1 8 8 8 10 11



Bottom face #2 primer 35Bottom face #2 primer 35ooCC

Temp start 45 50 55 60 65 70 75N. bubbles 3 3 3 3 3 3 5 5

The best result in terms of n. of little bubbles and temperature stability



TART qualification program TART qualification program indicationsindications

The best results have been obtained with the configuration

Tungsten preparation To etching + BR-127

Bias circuit Abraded and baked

Grounding of W tiles NO

Process clenlinessUsed Plyform clean room, clean tent for production

Cure cycle T=35C for 18h min.

These options + the specific procedures to match the TART recommendations are included in the LAT-DS-01584 procedure

tart recommendations implementation and qualification program results alessandro brez infn - pisa

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