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Report from Module Bonding Working Group

Report from Module Bonding Working Group. Salvatore Costa Universit à di Catania and INFN – Sezione di Catania. Outline. Pull Test results Open issues Some peculiar failures. Global review of Module bonding quality that is, Module Pull Test results. # Modules Pull Tested.

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Report from Module Bonding Working Group

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  1. Report fromModule BondingWorking Group Salvatore Costa Università di Catania and INFN – Sezione di Catania

  2. Outline • Pull Test results • Open issues • Some peculiar failures

  3. Global review of Module bonding qualitythat is,Module Pull Test results

  4. # Modules Pull Tested

  5. Mean pull forces

  6. Mean pull forces

  7. StDev/Mean of pull forces

  8. StDev/Mean of pull forces

  9. Open issues

  10. TEC Backplane HV Connection A Bonding and Gantry joined operation Review of established practices in EU and US Preparation for it in Italy

  11. TEC Backplane HV Connection • New DB Interface with new section • v. 6.0 • v. 6.0_US

  12. HV Connection types Connection type inventory: • Conductive Glue dots between gold pad and Sensor (at Gantry) • Conductive Glue reinforcement over gold pad and Sensor (normally at Gantry, occasionally at Bonding) • Bonds without encapsulation (at Bonding) • Bonds with encapsulation (at Bonding) Current established practice: • EU: 1 + 2 + 3 • US: 1 + 4 [existing TOB modules retrofitted] Reason for reinforcement (EU) or encapsulation (US): • Bonds on back are considered at higher risk of being damaged when modules mounted on rods or petals because people’s attention is focused on front and the back may get neglected.

  13. Material and Preparation • Sylgard 186 Silicone Elastomer, 2 part kit, 10:1 mixing ratio (manufacturer: Dow-Corning) • Mixing cups • Mixing sticks • Digital bench scale • Small vacuum chamber or centrifuge for degassing

  14. Dispensing Equipment • Pneumatic glue dispenser with foot pedal and timed pulse option (manufacturer: EFD model: Ultra 1400) www.efd-inc.com • 3ccm syringe barrel and piston (EFD) • Smooth-flow tapered tips, gage 20 (EFD)

  15. Set up Equipment • Base plate (UCSB design), to hold the module on a module carrier upside down • Plastic trowel (UCSB design), to spread the encapsulant over the wirebonds and to keep the height of the encapsulant below the maximum height • Stereo microscope (optional)

  16. Procedure I • Mix encapsulant, degas the mixture and fill syringe • Set pneumatic dispenser to 15 psi and 1 second dispense time • Set module in carrier upside down onto base plate • Dispense a line of encapsulant across the width of the wirebonds

  17. Procedure II • Position the trowel with one leg on the sensor, one leg on the kapton • Spread the encapsulant over all 15 wirebonds by sliding the trowel across the bonds • Once the trowel is past the wirebonds, lift it up and clean it off with a dry tissue paper

  18. Procedure III • Check that all wirebonds are covered completely with the encapsulant (this can be done with or without a stereo microscope) • If necessary apply more silicone and repeat the troweling procedure • Cure for 24 hours with the backside of the module facing up to avoid beading up of the encapsulant

  19. Established EU procedure M.Krammer: no bond encapsulation experience in EU TEC community: use conductive glue reinforcement All tests OK This procedure is now officially requested by TEC to Italy

  20. …Except for R4S modules… …because:

  21. How is Back bonding going? • Aachen: Vibration test of backplane HV bonds: with additional glue near bonds, but bonds bare, in one module some bonds broke, in another module no bonds broke. In modules with encapsulated bonds, none broke. • Strasbourg: Bonded (in hole) 16 modules electrically OK • Vienna: Bonded (in hole) 80 modules previously front-bonded, using special supports that hold module carrier all around: sensors not supportedNo problems. • Hamburg: Not started yet since the backplane jigs are not done before next week. For the last weeks have reinforced the glue connection on the backplane with conductive glue,for some modules where this had not been done before at the Gantries.

  22. Recipe for TEC Mod prod in Italy At the end of the Bonding Meeting, I conveyed its outcome at the Gantry Meeting… • Bari has agreed to use conductive glue under HV pad when assembling modules • Bari has agreed to place conductive glue reinforcement over the “top” of the T-shaped pad • Bonding centers will bond “in the hole” without encapsulation

  23. Some peculiarModule failures

  24. Some recent peculiar Module failures • IV failures: • Affect modules not randomly in time, but in concentrated clusters: • Recently: 5/53 in Aachen, 4/36 in Catania • Had also been seen at least in Catania and Padova in the past. • Seen (in Catania) first TIB module where gold layer on HV pad on back is peeling away. • May drag away the bonds with it • Module will be declared faulty Repair center • Since Sep we see many TIB PA’s where bonds would stick with unusually high parameters, or would not stick at all, in one or more of these locations: • Pads 1-2, 27-30, 738-741, 767-768 • Seen in: Bari, Catania, Padova. • Suspect bad PA metallization in those (symmetric!) spots

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