1. Equipment for Assembly – UK Experiences
Ian Wilmut mostly based on material from Martin Gibson

2. Process steps to describe
Holding a stave during the build
Attaching daughter boards
Gluing modules
Glue patterns, mixing etc.
Wire bonding a stave
Dimensioning scheme
Things we still need to do

3. Stave(let) Frames Intended to hold the stave(let) in position
Provides “standard” frame of reference
Allows cross referencing between the two sides of the stave
Allows for wirebonding of stave without removal from the frame
Aim is to have very few frames (i.e. 2 or less per site)
Can be skinned to provide protection to stave

4. Stavelet frame detail

5. Frame for stave 250

6. Working drawing soon to be passed out for comment to wire bonders, electrical testers etc. Frame has top and bottom covers and the entire frame sits in an insulated box for testing purposes .

7. Daughter boards
Daughter boards exist for 250nm objects for power and HCC
Stave extensions required if we use DC-DC convertors (no image)
Daughter boards hopefully have no long term future in final staves as they make build process more complex
To date we have mounted daughter boards with double sided tape or Araldite – all boards were placed by hand.

8. Daughter Boards

9. Module mounting
Process has been described lots of times before, so I’ll try and talk through this quickly.
Basic principal is to drive a microscope to a known position and optically position a module to the centre of this location (twice per module to get rotation and location)
Design goal has been to position modules “as well as possible”

10. Overall setup

11. Overall photo of the installation
Overall photo of the installation. Shows laser, illuminated strip for pin holes, prototype stavelet frame and one bridge structure

12. Detail of one bridge structure sitting over a prototype stavelet frame

13. Two bridge structures sitting adjacent to each other at the correct spacing. one can see the Y and the combined X and theta adjusters

14. Original concept and working sketch of bridge structure
Top view of placement jig
Y adjustment
X and Theta adjustment

15. Detail of the optics

16. Detail of Z axis laser

17. Typical laser spot giving 1 micron sensitivity in y

18. Wire bonding a stave
It seems we never photographed stave/stavelet wire bonding process
This is not an efficient process – the set up is slow for very few bonds.
However, it does not take long to fully bond a stave – but this is not a well controlled process and is a high risk part of the build.

19. Gluing modules Two glues are discussed.
SE4445, lots of history – poor adhesive
IRS2125, very unexceptional room temperature epoxy
We would like to avoid 4445 if possible, but have no strong preference to an alternative.
At the moment we are most concerned with thin parallel glue layers.

20. Original glue pattern running at right angle to the surface features before module mounting

21. Explanation for the change in direction of the adhesive pattern
New approach to applying adhesive to address the question of non flat stave(let) surface
Features run in
this direction
Old approach
New approach
Rotate pattern by 90 degrees and use wide spreader

22. New style adhesive pattern made with 450g load no spacers

23. Comparison of SE4445 and 2125 flexible epoxy

24. Old and new pattern
Old mask pattern
New mask pattern

25. Two test plates to show the theory after fabricating a ceramic substrate with typical bumps as seen on the stave. Old style adhesive only contacts on the high spots. New technique gives a flatter adhesive surface and hence better contact.
No contact
contact
Old mask pattern with contact only at high spots
New mask pattern with uniform contact
View at shallow angle to show areas of contact between gel and glass plate

26. Dimensioning scheme I have talked about this before.
Nothing has changed
But we still need to get this right.
Stave 250 should use a sensible dimensioning scheme (as detailed in talk last year)
Using HV pads as dimensional references is not ideal as they get covered with modules.

27. Additional HV separation Modifications for 130nm modules
We recognise the need to lengthen the path in air between sensors for HV protection.
Most sensible solution seems to be kapton “walls” between sensors.
Walls have been prototyped but not fitted
Modifications for 130nm modules
Has been doodled and looks to be a simple modification
Will not be advanced until we finalise 130nm module design.

28. Fabrication of Kapton isolator for inter-module electrical isolation
After removal of side 1
and slicing
Removal of base
Final item with a 2mm edge
Store in a box and wait to see if it relaxes

29. Current design being worked on
Symmetric hybrids
Design required for asymmetric hybrids

30. First go with 4445 and new spring loaded jig
Addendum – 6th Sept 2012
First go with 4445 and new spring loaded jig
MDG stavelet
(Not flat)
Small spacers
Very old frame
Glass ‘detector’
Ceramic sheet (flexible)

31. Footprint of silicon vacuum cup hardly visible visible
Vacuum cups and edge support probably not all in a plane
Footprint of silicon vacuum cup very visible
Good contact around edges less so in the middle
New adhesive pattern

32. Adhesive gap data Adhesive gap 107 microns Adhesive gap 93 microns
Uniformity of gap indicates tha the conformal jig is working
in Z but the lack of uniform spreading means more fettling!