P. Béné, F. Cadoux, A. Clark, D. Ferrère , C. Husi , M. Weber University of Geneva

1. IBL Stave Loading Status IBL General Week - 11, 12 February 2010 P. Béné, F. Cadoux, A. Clark, D. Ferrère, C. Husi, M. Weber University of Geneva • Summary of the activities at UniGe: • Stavelet program for thermal interface investigation • Electrical insulation of module versus stave

2. Stavelet – Loading with glue/grease test program • Purpose of the tests – glue versus grease: • Selection of candidates according to past experiences, thermal performances, viscosity, … • Evaluation of weight versus area • Optimization of the glue/grease dispensing technique (no glue overlap between the 2 chips) • Thickness uniformity and placement accuracy – XYZ metrology • Robustness to thermal cycling – XYZ metrology • Rework ability? •  Removal and evaluation of time and risk for this operation •  Inspection of neighboring module edges •  Inspection of remaining surface •  loading again • Does the use of Parylene® coating make a change? • Practical use • Independent tests to the stavelet program: • Radiation hardness of the glue and grease samples – Thermal performances, consistency… • Glue and grease mechanical and thermal characterizations • Others… 2

3. Gluing and grease test program on C-foams stavelets Glass pieces loaded with glue and or grease and various patterns ~20 mm Glued holding bar Glued holding bar ~150 mm Glass references: • Glued on the 2 sides • Height > glass thickness • - Hole for XY metrology • - Top surface for Z plane NB: Assembly of the 3 washers as much as possible in the same plane • Procurements: • Glass pieces (20x40 mm2)1 or 2 mm thick to be cut by a diamond tip  CERN stroe + cutting UniGe • C-foams to be coated with parylen. 1 or the 2 sides?  Samples to be cut at UniGe + Comelec (coating) – C-foam in 0.25 g/cm3, 0.5g/cm3 et 0.9g/cm3 • Holding bars made of aluminum or plastic to be butt joined to the C-foam  UniGe • Mechanical washers to be made & glued  UniGe • Glue and grease candidates  To be discussed with Marseille and IBL stave WG • Jigs to handle and load the glass pieces on this stavelet  To be made by UniGe with the corresponding threads for the holding bars and placement accuracy • Tungsten wires for the rework with glue 3

4. StaveletJig Designs Assembly jig allowing to glue the aluminum ends, but also the dummy glass modules Area to glue gleassfiducial marks Features to reference the dummy glass modules 4

5. Stavelet assembly jig StaveletJigs Features for dummy module assembly references Stavelet jigs for metrology, thermal cycling, storage 5

6. Glass Pieces Under fabrication 20 Dummy Glass Modules with Fiducial Marks 40 10 Glass pieces for Jig References 10 6

7. Carbon Foam Electrical Insulation using Parylene® Coating – Investigation for IBL Stave • Concerns: • Carbon foams are electrical conductive materials • IBL module require an electrical insulation for the FEI4 backplane but as well as for the detector HV • Depending of the detector technology the potential at a distance of 300µm from the foam can be as high as 1000V. • Bare foams can easily release carbon dust that could cumulate and be oriented into the electric field and therefore reduce the insulating distance • Proposal is to use of a thin coating like Parylene® allowing: • To prevent electrical problems and limiting the thermal resistance • To contain and avoid releasing carbon dusts 7

8. Pictures of the Foams under a Microscope POCOFoam 0.55g/cm3 – No Parylene Carbon Foam 0.25g/cm3 – No Parylene 500 µm 500 µm 500 µm 500 µm Magnification x100 POCOFoam 0.55g/cm3 – 5 µm Parylene POCOFoam 0.55g/cm3 – 20 µm Parylene NB: No coating was made for carbon foam 0.25 (No sample available) 8

9. Set-up – 1st Testing Step - Cupper foils were directly in contact with the foam samples - 3 samples tested for the resistivity (non coated, 5µm and 20µm) - 2 samples tested for HV insulation (5µm and 20µm) Clamp insulator HV Foam sample HV GND insulator Clamp Tested samples: POCOFoam ® Test setup: Coated foam samples clamped between 2 cupper foils and connected to the 2 HV polarities Pressure to the coated surface: Unknown but not null 9

10. Set-up pictures and Results Comments: The coated (5-20 microns) foams does not release any visible carbon dust. 10

11. Pictures after Electrical Breakdown NB: Breakdown possibly occurred where the clamps were applying the highest pressure 11

12. Second Testing Step with Shims • Electrical insulation in a new test conditions: • With 400µm gap between the cupper and the foam • Various samples: non-coated, 5µm and 20µm Clamp Plastic stiffener HV Foam sample Insulating shims (~400µm) HV GND Plastic stiffener Clamp 12

13. Set-up Pictures and Results with Shims NB: - Safety factor should be applied to the limit to get guaranty on long term QA - Considering a safety factor , the current design is acceptable with 10-20 µm Parylene® 13

14. Pictures – Copper after Electrical Breakdown 5 µm Parylene 20 µm Parylene 14

15. Additional Comment Si-detector backplane Edge chipping and Si-debris often seen pointing in all directions Observed during SCT production and QA Stave coating is clearly an advantage in such a case even for backplane/edge voltage like 100V 15

16. Summary • Stavelet Program • - Goal is to test various thermal interfaces to evaluate the practicality for loading, the thermal stability, the weight, the rework-ability • Thermal evaluation of a selected grease interface will be done with dedicated thermal set-up • Time scale: ~3 months • Module to stave electrical insulation • - Parylene® coating have been made on POCOFoam samples: 5, 10 and 20 microns • Coating almost invisible under the microscope • No carbon dust release when touching the samples with the fingers • In IBL condition with ~300µm gap from the sensor edge to the stave it will be risky to operate it without an insulating coating. • The preliminary recommendations from this test is to coat the stave with 10 to 20µm Parylene®. • Remaining question: Is this 10 to 20µm enough when considering the aging, and the radiations • Stave loading concept • Close connection between CPPM and UniGe • Common concept with a cradle and a manipulator • Progress to be made with a nominal stave design 16