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GLAST LAT Project Gamma-ray Large Area Space Telescope October 1st, 2004 TART recommendations implementation and qualification program results Alessandro Brez INFN - Pisa [email protected] GLAST LAT Tracker Anomaly Resolution Team 1 GLAST LAT Project October 1st, 2004 Agenda Summary of the TART recommendations and their implementation Peel test results Test articles description Thermo-vacuum test results Conclusions GLAST LAT Tracker Anomaly Resolution Team 2 GLAST LAT Project October 1st, 2004 TART recommendation 1 Qualification program The qualification program has addressed the recommendations of the TART: Main activities: 1. 2. 3. 4. Tests and analysis of the materials and their compatibility to 3M2216 Revision of the assembly procedures and of the assembly environment Construction of 3 tests articles to test different solutions implementing the new procedures in a improved environment Thermo-vacuum tests of the test articles GLAST LAT Tracker Anomaly Resolution Team 3 GLAST LAT Project October 1st, 2004 TART recommendation 2 Tungsten surface preparation Recommendation: Etch the tiles surfaces by MIL-HDBK-961B process (degrease + acid bath) and prime with BR-127 Test 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 GLAST LAT Tracker Anomaly Resolution Team 4 GLAST LAT Project October 1st, 2004 Tungsten preparation: GSFC results Verify 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 GLAST LAT Tracker Anomaly Resolution Team 5 GLAST LAT Project October 1st, 2004 Tungsten preparation: GSFC analysis of W tiles Analysis Performed by: Debbie Thomas, Code 541/ Swales, 301-286-8577 Stringers Figure 3. Cross section of tungsten foil showing “stringers” of included material.~ 200X Included Material Figure 5. SEM photograph of included material. EDS revealed very high carbon, low tungsten content in included material as opposed to tungsten base material GLAST LAT Tracker Anomaly Resolution Team 6 GLAST LAT Project October 1st, 2004 Tungsten 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 observed The anomalies can be related with the synterization process used for W tiles The thick W tiles are from a W alloy (kulite alloy K1750) to have smooth and machinable tiles GLAST LAT Tracker Anomaly Resolution Team 7 GLAST LAT Project October 1st, 2004 Peel test of sand blasted tiles First action: W sand blasting : controlled and uniform roughness of the tiles Qualification test: peel test material 1N/mm~6lb/inch F sand paper Al oxide sand blasting 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 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 The debonding pattern at 1mm roughness was better: At Ra=0.5m film left on Kapton At Ra=1.0m film left part on Kapton and part on W Tray MID 48 assembled with sand blasted tiles gave acceptable results GLAST LAT Tracker Anomaly Resolution Team 8 GLAST LAT Project October 1st, 2004 Peel tests of Turin etched tiles 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. 4 tests have been performed with etched and primed tiles Results: 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/mm In 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 Conclusions (qualitative) The adhesion of the 3M2216 to the W tiles was generally good The adhesion of the 3M2216 to the Kapton was often bad need of comparison tests of abraded and unabraded Kapton foils GLAST LAT Tracker Anomaly Resolution Team 9 GLAST LAT Project October 1st, 2004 TART recommendation 3 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/mm Peel strenght of abraded samples = 3.5N/mm 0.35N/mm GLAST LAT Tracker Anomaly Resolution Team 10 GLAST LAT Project October 1st, 2004 TART recommendation 4,5 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 GLAST LAT Tracker Anomaly Resolution Team 11 GLAST LAT Project October 1st, 2004 TART recommendation 6 Grounding of Tungsten tiles Test article 2 Test article 2 Planarity 170m Planarity 224m A wire sticks out from the tray after gluing Grounded tile MCM front Not grounded tile MCM front Aluminum gold plated 55m wires Test article 2 Planarity 139m A wire sticks out from the tray after gluing Conclusions: The system does not guarantee the tiles grounding The vacuum extracts the wires to the edge of the tray, very dangerous! The wires seem to compromise the final planarity of the tray MCM front GLAST LAT Tracker Anomaly Resolution Team 12 GLAST LAT Project October 1st, 2004 Do we need W tiles grounding? GFSC primed W tile 0.06mm 3M2216 film (cured 15h at 40oC) Al base A Any buildup charge will disappear in few seconds I 1.4 1.2 V 1 C=6nF R=~1GW at 1V t~6s Giga-Ohm Keythley 467 0.8 Breakdown to 1.4KW 0.6 0.4 0.2 0 0 100 200 300 400 500 600 Volts GLAST LAT Tracker Anomaly Resolution Team 13 GLAST LAT Project October 1st, 2004 TART recommendation 7,8 Process cleanliness, QA control A detailed list of manufacturing rules have been dictated. These rules have been incorporated in INFN-LAT-MECH-007-01 INFN 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 results 2. Kapton preparation 3. Adhesive preparation and deposition with hardness tests GLAST LAT Tracker Anomaly Resolution Team 14 GLAST LAT Project October 1st, 2004 TART recommendation 9 Non use of grid blasted tungsten The 0.1mm sand blasted tiles are no more flat. We cannot use them in any case segregated TART recommendation 10 Bond joint compression steel vacuum chucks tray A possible cause of bubbles: The Kapton is hold flat by Bias circuit the tool during adhesive curing. A local depression of 3M2216 the tray surface (50m or more) could cause a bridge effect Proposed 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. GLAST LAT Tracker Anomaly Resolution Team 15 GLAST LAT Project October 1st, 2004 TART recommendation 11 Alternate 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 GLAST LAT Tracker Anomaly Resolution Team 16 GLAST LAT Project October 1st, 2004 TART recommendation 12 Examine 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 GLAST LAT Tracker Anomaly Resolution Team 2443Hz, first ladder resonance mode 17 GLAST LAT Project October 1st, 2004 Test articles Test article #1 MID045 #2 MID042 #3 MID049 To etching Y Y Y Primer Y Y N RT 35oC 35oC Cure temp. An operator error in top bias circuit assembly caused a misalignment of the bias circuit and a not perfect adhesion Notes Thermo-vacuum cycles (P<10-2mBar, min P=50bar) 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 GLAST LAT Tracker Anomaly Resolution Team 18 GLAST LAT Project Top faces behavior October 1st, 2004 Very good results of bias circuit adhesion on face sheet up to 75oC GLAST LAT Tracker Anomaly Resolution Team 19 GLAST LAT Project October 1st, 2004 Bottom face #3 NO primer 60oC development of a Ø25mm delamination 65oC debonding over 3 whole tiles 70oC one more tile debonded Perfect clean W tile Very good and uniform 3M2216 film on bias circuit Very good adhesion to the previous glue layer (no Frecot55 pollution) GLAST LAT Tracker Anomaly Resolution Team 20 GLAST LAT Project October 1st, 2004 Bottom face #1 primer RT Temp start N. bubbles 0 45 1 50 1 55 8 GLAST LAT Tracker Anomaly Resolution Team 60 8 65 8 70 10 75 11 21 GLAST LAT Project October 1st, 2004 Bottom face #2 primer 35oC The best result in terms of n. of little bubbles and temperature stability Temp start N. bubbles 3 45 3 50 3 55 3 60 3 GLAST LAT Tracker Anomaly Resolution Team 65 3 70 5 75 5 22 GLAST LAT Project October 1st, 2004 TART qualification program indications 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 Used Plyform clean room, clean Process clenliness 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 GLAST LAT Tracker Anomaly Resolution Team 23