Stave Assembly (module mounting and stave 250)

1. Stave Assembly (module mounting and stave 250) Ian Wilmut (RAL)

2. Martin Gibson • Martin has been developing the module mounting system at RAL for the last three years – everything we have so far comes from his input. • Martin died on Tuesday 20th August from Oesophageal cancer • Module mounting activities will continue at RAL picking up where Martin left off. • We hope we can continue to do as good a job as he always did • We are all very sad about this – and are only now really appreciating just how much he knew, and just what we have lost. • We have all struggled to find words to express our sadness, all I can say is “Martin we miss you”

3. I will talk about • Recap on how the module mounting works • Hopefully very quick • Stave 250 • Where we stand today • What we had to do to get here • How module mounting is going without Martin • Glue patterns and cupped sensors changing shape • Plans for stave 250 (in the context of module mountuing) • Plans for the longer term • 130nm modules • Pixel disk module mounting • Problems we have encountered

4. Module mounting system

5. Module mounting process • I have discussed this lots of times before… • Last upgrade week (https://indico.cern.ch/getFile.py/access?contribId=73&sessionId=12&resId=1&materialId=slides&confId=233533) • Upgrade week before that (videos) (https://indico.cern.ch/conferenceDisplay.py?confId=158040) 10:10 on Wednesday • Probably the week before that as well • Rather than re-cap the whole process in minute detail here is a “cartoon” explanation of what is happening.

6. We have a stage with a camera that can move in x and y Y stage X stage In plan view

7. As the X axis of the stage isn’t very straight we have laser line to correct things Y stage X stage LASER

8. Into this we insert a stave in a frame (eachstave stays in the frame for the whole build) Y stage X stage LASER

9. The frame has a series of fecucials that can be found and a co-ordinate system placed with Y stage X stage LASER

10. We can now survey the stave and understand where it is in the frame using feducials or pads on the bus Y stage X stage LASER Note: we don’t yet know enough about bus tapes and accumulation of errors to understand what the criterion for QA of bus or bus to stave will be – so for now we will just collect as much data as we can.

11. We can then park the camera out of the way Y stage X stage LASER

12. The module can then be picked up on to a vacuum chuck Close up side view of 1 module

13. The chuck is rotationally compliant in the X and Y axis. Close up side view of 1 module

14. The compliance is used to orientate the module to match the local stave shape with small feet which reference the surface Close up side view of 1 module

15. The chuck is part of a larger bridge which has lead screws to move the module in the X and Y axis and provides rotation in Z

16. We can then place the bridge over the frame (key into the table) Y stage X stage LASER

17. Move the camera to where the 1st corner of the sensor should be Y stage X stage LASER

18. Move the module so the feducial is in the centre of the field of view (in the right place) Y stage X stage LASER

19. Rotate the module into the correct place Move the camera to where the 2nd module feducial should be Y stage X stage LASER

20. Park the camera and remove the bridge Y stage X stage LASER

21. Apply the glue to the stave & reinstate the bridge Y stage X stage LASER

22. Stave 250

23. Stave 250 summary Stave 250 (DC-DC) Module mounting • Received broken • Repaired • Retested • Installed in frame • Test connected to infrastructure • Ready for mounting (just as soon as we are happy with the glue) • 5 flat test plates to “flat” stave • 3 psudo bowed modules to “flat” stave • 2 real bowed sensors to stave • Lots of “removed” test pieces where we didn’t let the glue set.

24. Stave 250 repair • Stave 250 was built in the US between Brookhaven and LBL • It was packed and shipped from LBL • When it was received at RAL it had been “smashed” on one end • We have instigated a repair by flooding the core with epoxy (West G-flex 650) • The core was then thermally imaged and cycled top see if any damage was evident.

25. We had some quite big holes to fill!

26. We drilled holes along the end… 1 2 3 4 5 6 789 10 11 12

27. Which looked a bit like this 11 12

28. We then injected glue through the holes 11 12

29. Filling of extra holes Small amount of surface flue where the masking allowed a little build up Smaller crack on rear completely filled

30. It was set up at QMUL and thermally imaged with warm water Graham Beck, QMUL 1st August 2013

31. Thermal Cycling (first 5 cycles – next 5 are similar): - about 45 mins/cycle- Red line is thermocouple taped to End of Stave region (CFRP) Then thermally cycled Graham Beck, QMUL for WP3/5, 29 April 2013

32. 10cm interval IR - 3D images (damaged side, before cycling) Graham Beck, QMUL 1st August 2013

33. Before/After IR of damaged end Water bath and ambient are slightly different temperature before and after (try harder in future!) Maximum T rise of surface above ambient ~ 10 degrees (above pipe) - This is constant within a degree along stave length (0.5C asymmetry due to water cooling along length) and wrt before/after cycling. Graham Beck, QMUL 1st August 2013

34. Stave 250 • We concluded it was well enough repaired to consider attaching modules. • We can’t be certain that its thermal performance has been reduced, but we consider its performance to be adequate for real modules • We also found a number of faults with the stave that were addressed through this process, • some have been fixed • Holes • “shorts” • some have been accommodated • Non straight closeout • Offset HV lines • some we think we can live with • Non flat core • Non flat EOS

35. Lessons learned on stave production • The edges are not straight • If this is always going to be the case we need to change the handling tooling • Glue filets are a problem (see image) • We need to pack more robustly • Glue used to attach power bus seems to have fibres in it that lower open circuit resistances. • We still have off shaped we don’t understand Bad Good

36. Gluing down modules

37. Challenges • Up until 2 months ago only Martin had ever glued modules at RAL • We thought what we needed to do was to extend Martins work mounting hogged modules to mounting cupped ones… • In doing this we have learned a lot about 4445 and glue patterns. • Most unexpectedly we have discovered that modules made with dramatically bowed sensors change shape when attached to the module mounting tooling.

38. Original glue pattern • Glue pattern intended to push air towards perimeter of module • Used to date with film of 75 or 150 microns • Stavelet modules all use this pattern with glue layers of ~100µm

39. Flat “sensor” to flat stave • Pattern was altered to allow for more space in the middle to allow for cupped sensor • Worked well with flat plate • This is a 50µm glue layer

40. With psudo bowed sensors it also seemed to work OK • 2 layers of film stacked to simulate module surface • 2 layers of film for this test

41. But it isn’t consistent

42. And…

43. And a failed electrical • Seen through a clear stave (sheet of plexiglass/Perspex) • Looks quite good here • But this was • Placed with vacuum & left for 1 hour • Vac released and inspected • Looked very bad • Jig replaced with no vac for 1 hour • Re-inspected and looked like this • So we are now wondering what effect the vaccum has on the module shape

44. The pick up chuck

45. Sensor shape • One specific challenge is that the module change shape when attached to the vac chuck.

46. 250 Plans • We will not mount any electrical modules until we have placed 3 failed electricals in a row with good coverage • We will ten place one “mechanical grade” module with a FZ1 sensor to a stavelet • Only then start with modules on stave 250

47. Longer term plans • Stave 250 & module mounting • Use stave 250 as a proving ground for the process & collect data on method of all modules • At the end of 250 formulate improvements to system • Iterate design for 130 stave (4 module bridges) • Post 130 stavelets build enough bridges for full stave • Pixels • We are starting to look at extending this system for pixel disks – very provisional • We are starting to produce full drawing sets for the kit we presently have, and also the future iterations

48. Extras

49. Detector epoxy S Canfer, STFC 12/9/13

50. Status • A low modulus adhesive is required to bond detectors • An epoxy has been formulated at RAL • Low viscosity • Very low Tg (approx -40°C) • Very low stiffness at ambient temperature • Low tear strength above Tg (potential for reworking) • Cure currently 50°C for 24 hrs, should be possible to reduce this temperature