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

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

Gluing and grease test program on C-foams stavelets ~20 mm ~150 mm Glass pieces loaded with glue and or grease and various patterns 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 Glued holding bar Procurements: - Glass pieces (20x40 mm 2 )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/cm 3, 0.5g/cm 3 et 0.9g/cm 3 - 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

Assembly jig allowing to glue the aluminum ends, but also the dummy glass modules Features to reference the dummy glass modules Area to glue gleass fiducial marks Stavelet Jig Designs 4

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

Glass Pieces Under fabrication Dummy Glass Modules with Fiducial Marks Glass pieces for Jig References 6

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

Pictures of the Foams under a Microscope Carbon Foam 0.25g/cm3 – No Parylene POCOFoam 0.55g/cm3 – No Parylene 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) Magnification x µm 8

Set-up – 1 st 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) HV HV GND Foam sample 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

® Parylene® CoatingInsulation to contactBreakdown Voltages [V] No 0 5 µmYes550 (over 10 microns) 20 µmYes1100 (over 40 microns) Comments: The coated (5-20 microns) foams does not release any visible carbon dust. Set-up pictures and Results 10

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

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 HV HV GND Foam sampleInsulating shims (~400µm) Plastic stiffener Clamp 12

Set-up Pictures and Results with Shims ® Parylene® CoatingBreakdown Voltages [V]Equivalent insulation for 300µm air + coating No1100 (over 800µm air) 400 V 5 µm2400 (over 10 µm microns air) 1050 V 20 µm3300V (over 40 µm microns air) 1500 V 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 µm Parylene® 13

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

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

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