1. ATLAS ITK WP3 WP3 Bi-weekly meeting 29-09-2016
Nixon Yu, Sinead Farrington, Ankush Mitra

2. Content
Preliminary result of “high-cycle” thermal testing of thermo-mechanical (TM) module.
TM thermal cycles plans for Oct 2016 and forward.
Cold box development/ modification update.

3. Visual inspection result
1. Preliminary result of “high-cycle” thermal testing of thermo-mechanical (TM) module.
Background and recap
Glasgow TM3 was subjected to thermal cycling.
Each cycle goes from 18C to -37C and back to 18C. Hybrid heater not bonded or used.
Low %RH and good vacuum maintained during thermal cycles.
Metrology performed before and after cycle 1. (Steve Liverpool)
Metrology performed after cycle 32. (Nixon, Ankush and Birmingham)
Metrology done at 2 different places! See discussion (p.7)
Visual inspection result
Frequent visual inspection between cycles.
No signs of mechanical failure, i.e. no sensor breakage, no glue failure, no wirebond failures.

4. Metrology method (recap)
Smart scope measurements performed on surface of sensor and surface of hybrids. Points shown in right photo.
Module in test frame, but not on vacuum chuck. i.e. only supported at the sensor outer edges.
Hybrid measurement on fiducials if available, others are on solder resist layer.
Sensor measurement on Al pads.

5. Metrology point names 0 1 2… …9 10 X positions
Sensor; Left Hybrid; ABC edge
Hybrid; Left Hybrid, ABC edge
Hybrid; Left Hybrid, inner edge
Sensor; Left Hybrid, inner edge
Sensor; Right Hybrid; inner edge
Hybrid; Right Hybrid, inner edge
Hybrid; Right Hybrid, ABC edge
Sensor; Right Hybrid, ABC edge …
…9 10
X positions

6. Result
Step increases range from 0um to about 50um

7. Discussion (1) Measured step increases range from 0um to about 50um.
Initial reason for this measurement is to identify potential change in glue shape/ hence possible glue failure, by monitoring any changes in the sensor-to-hybrid step height.
However if the 50um of change purely comes from glue height increase, considering the original spec is from 120um to 140um, this is potentially a serious problem, and can impact on the mechanical integrity, thermal and electrical performance.
It is important to re-examine the methodology to understand this 50um increase.

8. Discussion (2) Possible reason for this observation Next steps
Different smart scope used. Original metrology at Liverpool, post thermal cycle metrology at Birmingham. “Between-systems” error, optical focus measurements at Liverpool, laser measurement at Birmingham.
Module tilt. Not completely identical points measured (XY deviation at the 0.1mm to 1mm level).
Possible change in hybrid thickness. Polyimide layer could absorb moisture, and may lead to thickening. True glue height change is unknown.
Next steps
Re-examine Glasgow TM3 at Liverpool (Sven is helping). Remove inter-system error.
Perform all future metrology with same smart scope, preferably with same run program.
Further numerical analysis on measured result (Ankush).
Include some hybrids in thermal cycling in the next batch of runs. (hybrids only, not glued onto any sensors). Gives better estimate to true glue height change.

9. 2. TM thermal cycles plans for Oct 2016 and forward.
Thermal cycle candidate:
Cambridge failed electrical TM
Failed electrical Si sensor; Epolite; TM hybrids v1.2; Triduct; glass ABCs; ABC to sensor fully bonded.
Hybrid heater not used, module-to-testframe power not bonded.
Comments: some epolite seepage under right hybrid inner edge.
TM hybrid request:
Several TM v1.2 hybrids needed. Will be thermal cycled with Cambridge Failed electrical.
Thickness measurement with micrometer to monitor any potential thickening after thermal cycle.
Need a micometer!

10. 2. TM thermal cycles plans for Oct 2016 and forward.
Thermal cycle profile:
Same profile used for every cycle.
30C (not 18) to -37C, max cooling/heating rate. Explore effect of warm environment
Profile ok? Any comments?
Metrology/ thermal cycle schedule:
Pre-cycling metrology (this Friday at Birmingham)
Pre-cycling thermal imaging?? (Question to Graham and QM)
Thermal cycles can begin from next week.
Max cycles 20 per week; Monday to Thursday nights, 5 cycles per night (maybe 4 max with new wider temp range).
Possible 40 cycles done in 2 weeks time.
Note: This may halt development/ modification process on the cold jig.
Book more metrology sessions at Birmingham, preferable on Fridays (no thermal cycles over Friday nights).
More frequent metrology sessions at the earlier stage would better.

11. Important reminder: thermal cycle profile for future modules can change, depending on what we want to study. Possible next set of thermal test after the Cambridge failed electrical module: Thermal cycling modules with power boards, incorporating with thermal imaging (QM) to identify glue pattern. Use thermal imaging pre and post thermal cycling to identify changes in glue pattern.

12. 3. Vacuum chucks for electrical test in cold box
Recap:
Warwick test jig chucks: unknown electrical noise performance. Possible break down of the test frame solder mask layer, shorting HV bias to test frame ground.
Berkeley chucks: Unknown thermal performance due to the insulated insert.
Immediate solutions:
Add a sheet of isolation between vac-chuck to test frame, e.g. Kapton
Investigation required:
Compare electrical noise performance of the 2 chuck designs. Perform at RAL (need to organise this). High voltage safety more critical.
Compare cooling/heating rate and efficiency of Berkeley chuck at Warwick.
Can Warwick have a Berkeley chuck?
Please note modification may be needed to add the vacuum seal.

13. 4. General cold test jig development/ modification
Would like to incorporate electronic flow sensor or flow switch, as well as electronic vacuum gauge/ or switch. So these measurements can be used as interlocks.
Currently analogue gauges and a webcam is used.
Flow sensor/ flow switch (nominal N2 flow 6 to 8 sL/min), good drying rate and cooling rate.
Vacuum gauge for vacuum chucks(nominal at bar, fail at -0.9bar)
Using these sensors as interlock to switch off power or cooling will be faster than temperature or %RH interlock.
Does anyone have any suggestions for suitable electronic sensors, with reasonable cost.

14. End