1. HB RM prototypes
Ianos Schmidt
Aug 17, 2017

2. Overview
Six sets (3 odd + 3 even) of HB prototype mechanics were produced at Iowa, five were carried to CERN.
These HB prototypes are relatively crude
Many missing features and shortcuts taken to expedite design and production in time for Testbeam
RM’s however do have representations of most major components and features to maximize what can be learned from them
Many small problems were identified during assembly
All were correctable and was able to make the four RM’s for which we had components

3. Card packs and Card order
HE RM
HB RM
Control card
Control card
HE and HB card-packs were made identical in card order and card spacing (allows testing of HB RM’s in HE backplanes)
Note however that HB RM’s are wider

4. Card-pack
Some issues, but card-packs went together with only a little difficulty once main problems corrected
Missing pocket for QIE thermal pads on back side of plates.
Pocket added to all plates taken to CERN
Interference with large cap
corrected
Perpendicularity and flatness spec of top/bottom edges of cooling plates not met.
Sacrifice to complete production on time.
Unfortunately made assembly a bit more difficult, and impacts heat transfer

5. Card-pack cont. Pelt. transistor Control card transistor
Fibers (and maybe JTAG cables) can be connected after card-pack assembly.
Bend radius look reasonable
Not sure where to put thermal pads on control cards. Pads placed to reasonably support board sandwich b/t cooling plates
Same thickness thermal pads on top and bottom of boards
Pelt. transistor
Control card transistor

6. Mounting board and flex cables
Mounting boards:
Fit well in the thermal assembly
Masking the areas that contact metal with Kapton tape was very tedious
-> Protective coatings/masks/layers should be part of PCB manufacturing
Flex cables (mounting board end):
Connection to board was easy and does not appear to be stressed
Flex cable stiffeners interfered with the assembly by ~0.7mm
-> Required careful trimming and inspection, and insulation of edges from metal
Trimmed un-trimmed
Trimmed

7. Insufficient gap width to wrap around board
Fingers too short to allow multiple bends without damage
Fingers too short to allow multiple bends without damage
Insufficient gap width to wrap around board

8. Flex cables!(card-pack end)
Impossible to connect the shortest “finger”
Second shortest connection almost impossible, was destroyed on RM#1
Connections very difficult to make,
~20 min/connection!
Multiple twists and bends forced into a small area
Insufficient gap width to reach other side of board
Fingers too short to allow multiple bends without damage

9. Connected flex cables
Despite difficulties, managed to connect most of them!

10. ODU
In general ODU fit well into RM assembly, but is not without issues:
Fiber bend radius much too tight for many fibers
- Supporting fibers during gluing could help
Will evaluate increasing angle b/t cookie and patch panel (now 90 degrees).
Cookie skewed by force from fibers, does not want to line up well with SiPM packages
- May need to introduce screws between cookie and cold assembly and/or change alignment scheme
Fibers rub on some parts of the ODU/RM covers. Primarily at support for JTAG adapter board.
- Expect to change adapter board and/or support piece.
Not parallel
Fibers rub at JTAG adapter board support
Tight bend radius

11. Assembled RM (without covers)

12. Fit in RBX Backplane and RM’s fit into RBX. No conflicting features
Features for clamping/extracting hardware were included in the prototype, however due to time constraints hardware components were not produced.
Worries confirmed:
- Spring fingers for pressing RM against RBX baseplate made insertion of RM’s into RBX very difficult
Alignment with backplane connectors hard to achieve, risks damage to connectors.
RBX does not have good provisions for aligning RM’s
RBX’s are not exactly flat. May not have good thermal contact even with finger springs and clamping hardware.
Look forward to seeing RM temperatures.
would also like a measurement of DC-DC cooling plate temperatures
Much more work needed!
Location for RM clamp

13. Summary Six sets of mechanics produces although not ideal
Problems discovered during assembly were corrected
Four RM’s assembled
Very useful in identifying where additional work is needed
Particular concern is thermal contact with RBX and difficulty inserting RM’s
Much more to be learned from these prototypes
Much more work to do

14. Backup

16. Thermal assembly

17. HB RBX
Megatile cables and source tubes go through RBX